(kuprianov 2011) effects of operating conditions and fuel properties on emission performance and...

8122019 (KUPRIANOV 2011) Effects of Operating Conditions and Fuel Properties on Emission Performance and Combustion hellip

httpslidepdfcomreaderfullkuprianov-2011-effects-of-operating-conditions-and-fuel-properties-on-emission 111

Effects of operating conditions and fuel properties on emission performance and

combustion ef 1047297ciency of a swirling 1047298uidized-bed combustor 1047297red with

a biomass fuel

Vladimir I Kuprianov a Rachadaporn Kaewklum b Songpol Chakritthakul a

a School of Manufacturing Systems and Mechanical Engineering Sirindhorn International Institute of Technology Thammasat University PO Box 22 Thammasat Rangsit Post Of 1047297ce

Pathum Thani 12121 Thailandb Department of Mechanical Engineering Faculty of Engineering Burapha University 169 Long-Hard Bangsaen Road Chonburi 20131 Thailand

a r t i c l e i n f o

Article history

Received 29 October 2009

Received in revised form

10 April 2010

Accepted 15 May 2010

Available online 12 June 2010

Keywords

Swirling 1047298uidized bed

Rice husk

Temperature

Gas concentrations

Combustion ef 1047297ciency

a b s t r a c t

This work reports an experimental study on 1047297ring 80 kgh rice husk in a swirling 1047298uidized-bed

combustor (SFBC) using an annular air distributor as the swirl generator Two NO x emission control

techniques were investigated in this work (1) air staging of the combustion process and (2) 1047297ring rice

husk as moisturized fuel In the 1047297rst test series for the air-staged combustion CO NO and C xH y emissions

and combustion ef 1047297ciency were determined for burning ldquoas-receivedrdquo rice husk at 1047297xed excess air of 40

while secondary-to-primary air ratio (SAPA) was ranged from 026 to 075 The effects of SAPA on CO

and NO emissions from the combustor were found to be quite weak whereas C xH y emissions exhibited

an apparent in1047298uence of air staging In the second test series rice husks with the fuel-moisture content

of 84 to 35 were 1047297red at excess air varied from 20 to 80 while the 1047298ow rate of secondary air was

1047297xed Radial and axial temperature and gas concentration (O2 CO NO) pro1047297les in the reactor as well as

CO and NO emissions are discussed for the selected operating conditions The temperature and gas

concentration pro1047297les for variable fuel quality exhibited signi1047297cant effects of both fuel-moisture and

excess air As revealed by experimental results the emission of NO from this SFBC can be substantiallyreduced through moisturizing rice husk while CO is effectively mitigated by injection of secondary air

into the bed splash zone resulting in a rather low emission of CO and high (over 99) combustion

ef 1047297ciency of the combustor for the ranges of operating conditions and fuel properties

2010 Elsevier Ltd All rights reserved

1 Introduction

For many years rice husk hasbeen an importantenergy resource

in most Asian countries The 1047298uidized-bed combustion technology

with its apparent economical and environmental bene1047297ts is proven

to be the most effective technology for energy production from this

agricultural residue However the combustion of rice husk gener-ally characterized by elevated fuel-N and fuel-ash contents is

accompanied by substantial NO x and CO emissions the rate of those

depends on fuel properties as well as on the design features and

operating conditions of a combustion system used [1e4]

For typical ranges of the bed temperature and excess air in

a 1047298uidized-bed combustion system (combustor or boiler furnace)

burning biomass NO x are known to originate mainly from fuel-N

via homogeneous oxidation of the dominant nitrogenous volatile

species NH3 and HCN to fuel-NO since the contributions of

thermal-NO and prompt-NO are insigni1047297cant [35] The relevant

studies reveal that NO x emissions from the reactor are in a quasi-

linear correlation with fuel-N [467] With rising of the bed

temperature NO x emissions are weakly increased or stay constant

[689] but exhibit a substantial increase with rising excess air inboth conventional and air-staged combustion systems [16e12]

However some studies report insigni1047297cant effects of the air staging

on NO x emissions when burning biomass [18912]

The emission of CO from a biomass-fuelled system is affected by

several operating factors excess air combustion temperature resi-

dence time of reactants fuel-ash content and particle size and also

fueleair mixing conditions During the combustion formation of CO

is known to include several sources CO released with fuel volatiles

oxidation of volatile hydrocarbons by oxygen as well as oxidation of

char-C by O2 H2O and CO2 on the char surface [36] As any other

unburned pollutant CO is effectively controlled (reduced) by Corresponding author Tel thorn66 2 986 9009x2208 fax thorn66 2 986 9112

E-mail address ivlaanovsiittuacth (VI Kuprianov)

Contents lists available at ScienceDirect

Energy

j o u r n a l h o m e p a g e w w w e l s e v i e r c o m l o c a t e e n e r g y

0360-5442$ e see front matter 2010 Elsevier Ltd All rights reserved

doi101016jenergy201005026

Energy 36 (2011) 2038e2048



increasing excess air andor combustion temperature both

enhancing therateof COoxidation to CO2 [18911] Some reductionin

COcan be achieved when1047297ring biomass fuels withlowerash content

[1113] The bubbling 1047298uidization mode seems to be one of the effec-

tive regimes for operating the 1047298uidized-bed combustion systems

[131013] as ensuringthe high intensive mixingof fuel particles and

air in the bed region (promoting CO reduction) the latter being

signi1047297cantly affected by the air distributor design [14] However an

in1047298uence of the air staging on CO emission during the 1047298uidized-bed

combustion of biomass is reported to be rather weak [15]

A large number of research studies have addressed emission

characteristics and combustion ef 1047297ciency for 1047297ring rice husk in

various laboratory-scale 1047298uidized-bed combustion techniques

such as bubbling 1047298uidized-bed vortexing 1047298uidized-bed and circu-

lating 1047298uidized-bed combustors [9e12] Due to moderate bed

temperatures (normally not higher than 850 C) NO x emissions

from the combustors are generally below 180 ppm (on 6 O2 dry

gas basis) while CO emission is found to be elevated up to

800 ppm Combustion ef 1047297ciency of these devices operated at

optimal conditions is reported to be within 96e98 Experimental

results revealed minor effects of the air staging on these emissions

as well as on combustion ef 1047297ciency of the vortexing and circulating

1047298uidized-bed combustors 1047297ring rice husk [912]Recently two novel combustion techniques ensuring fuel

oxidation in a strongly swirled 1047298ow a vortex combustor and

a cyclonic 1047298uidized-bed combustor have been developed and

tested for 1047297ring rice husk [1617] Under optimal operating condi-

tions high (over 99) combustion ef 1047297ciency can be achieved in

these pilot reactors while controlling CO emission below 400 ppm

However NO x emissions from the combustors are reported to be

elevated up to 300 ppm for the vortex combustor [16] or rather

high 350e425 ppm for the cyclonic 1047298uidized-bed combustor [17]

Such substantial NO x emissions are mainly caused by (i) elevated

excess air required for sustaining the strongly swirled gasesolid

1047298ow and (ii) high-temperature conditions in these rice husk-fuel-

led combustors operated with a signi1047297cant heat release rate per

unit volume Effects of the air staging on both emissions andcombustion ef 1047297ciency of the vortex and cyclonic 1047298uidized-bed

combustors are reported to be rather weak It should be noted that

elevated excess air basically leads to lower thermal ef 1047297ciency of

a power plant (or any other energy conversion units) using these

devices mainly due to an increase in the heat loss with waste gas

(affected by a signi1047297cant volume of excessive air) [18]

Kaewklum and Kuprianov [19] have recently reported a pio-

neering study on a laboratory-scale swirling 1047298uidized-bed

combustor (SFBC) 1047297ring rice husk In this innovative combustion

technique a swirling 1047298uidized bed is generated due to the special

design of a primary air distributor used in this combustion tech-

nique as the swirl generator Unlike in the vortexing 1047298uidized-bed

combustor secondaryair in this SFBC is injected into the bed splash

zone ie at a relatively low level above the (primary) air distrib-utor The tangential injection of secondary air sustains the rota-

tional gasesolid 1047298ow in the combustor At optimal excess air

40e60 the burning of rice husk in the SFBC is characterized by

high about 995 combustion ef 1047297ciency while CO and NO emis-

sions can be limited within 150e300 ppm and 170e210 ppm

respectively However no effects of the air staging on emission

performance and combustion ef 1047297ciency of the SFBC have been

addressed in this pioneering study

As can be generally concluded from the literature review

compared to the conventional (ie non-swirling) 1047298uidized-bed

combustors the combustion techniques with a rotational gasesolid

1047298ow ensure higher combustion ef 1047297ciency at minimized CO emis-

sion accompanied however by moderate (for the SFBC) or

elevated (for the vortex combustor) or high (for the cyclonic

1047298uidized-bed combustor) NO x emissions The NO x control in these

high ef 1047297ciency devices 1047297ring rice husk is therefore an issue of

paramount importance

Burning biomass in the form of moisturized fuel which prior to

the combustion can be prepared by adding water to ldquoas-receivedrdquo

fuel is proven to be an effective least-cost NO x emission control

technique as reportedin studies on1047297ring of wood sawdust and rice

husk in a conventional 1047298uidized-bed combustor with a cone-shape

bed [420] Moreover a substantial reduction in the bed tempera-

ture occurring with increasing fuel moisture provides more

favorable operating conditions for preventing undesirable ash-

related problems in the 1047298uidized-bed combustor (eg bed

agglomeration and wall slagging) particularly when 1047297ring high-

alkali biomass fuels [3] Howeverwhen using this conical 1047298uidized-

bed combustor the reduction of NO x emissions has been accom-

panied by a noticeable increase in CO emission and corresponding

deterioration of the combustion ef 1047297ciency Thus selection of the

most appropriate fuel-moisture content should be considered

along with optimization of air supply to the combustion system

This study was aimed at determining the technical feasibility of

an effective control of NO emission during the combustion of rice

husk in the SFBC through air staging of the combustion and fuel

moisturizing Detail analysis of the formation and decomposition of major gaseous pollutants (CO and NO) at different locations in this

reactor for variable operating conditions and fuel properties were

the focus of this work Optimization of the fuel-moisture content

and air supply for minimizing CO and NO emissions from this SFBC

1047297ring moisturized rice husk was also among the main objectives of

this study

2 Materials and methods

21 Experimental facilities

Fig1 depicts the general view of the experimental setup and the

schematic diagram of the SFBC It can be seen in Fig 1a that the

system included the combustor with a start-up burner a cyclonea fuel screw feeder and a blower Additionally Fig 1b provides the

design and geometrical details of the SFBC which was made of 45-

mm-thick steel sheet and covered internally with the 50-mm-thick

refractory

The combustor consisted of a conical (bottom) part1047297lled in with

lsquoroundrsquo quartz sand (with the particle sphericity of 086 and density

of 2650 kgm3) used as the inert bed material and a cylindrical

(upper) part The particle (sieve) size of 05e06 mm and static bed

height of 30 cm were selected to be the main characteristics of the

bed material as those ensuring the stable swirling 1047298uidized-bed

regime Under ldquocoldrdquo operating conditions the minimum 1047298uidiza-

tion velocity of the air-sand bed with these characteristics was

about 08 ms while the minimum velocity of the fully swirling

1047298uidized-bed mode was 13 ms [21]The annular spiral air distributor at the combustor bottom was

made up of eleven blades 1047297xed at an angle of 14 to the horizontal

and served as the swirl generator of primary air (PA) the latter

being supplied by the 25-hp blower The distributor had an annular

air exit with 01 m inner and 025 m outer diameters The distance

between two neighbor blades was variable (in a linear relationship

with radius) thus forming a trapezoidal cross-sectional area of

0012 m2 (total) for the air1047298ow between the blades To stabilize the

swirl motion of the gasesolid bed a steel cone was 1047297xed on the top

of the air distributor as shown in Fig 1b

Primary air was supplied to the air distributor by the blower

through an air pipe of a 01-m inner diameter as shown in Fig 1a

The 1047298owrate of primary air was controlled using a butter1047298y valve

arranged on the air pipe downstream from the blower The

VI Kuprianov et al Energy 36 (2011) 2038e 2048 2039



relationship between the actual air1047298ow rate and valve opening was

developed using a measuring system ldquoTesto-454rdquo (Testo Germany)

with a hot-wire probe The measurement uncertainty in the 1047298ow-

rate of primary air was about 3 as estimated in Appendix A

The screw-type feeder delivered the fuel over the bed at a 06 mlever above the air distributor A three-phase inverter was used to

control the fuel feed rate via changing rotation speed of the screw

feeder As established by repeated calibrations the fuel feed rate

was in a quasi-linear correlation with the rotational speed (rpm) of

the feeder For the fuel feed rates of 30e100 kgh the measurement

accuracy of the fuel feed rate was within the range of 3 to 5

when varying the fuel-moisture content from 84 (in ldquoas-receivedrdquo

fuel) to 40

During the combustor start-up a diesel-1047297red burner from Riello

Burners Co (model ldquoPress G24rdquo) was used to preheat the sand to

the speci1047297ed temperature (of about 700 C) The burner air was

tangentially injected into a splash bed zone at a 05 m level through

the burner inclined at a 30 angle to the horizontal Upon

attaining required bed temperature the burner was turned offwhereas desired fuel supply was ensured by the screw feeder

However the burner fan remained to operate delivering secondary

air (SA) to the SFBC during the combustion tests with the aim to

mitigate CO in the bed splash zone and also to protect the burner

head against overheating and impacts from solids The 1047298owrate of

secondary air was controlled by changing an opening of the burner

fan The measurement uncertainty in the 1047298owrate of secondary air

(estimated by the same method as for the primary air) was found to

be about 4

A ldquoTesto-350XL rdquo gas analyzer (Testo Germany) was used to

measure the temperature and gas concentrations (O2 CO NO and

C xH y) along radial and axial directions in the combustor as well as

at the exit of the ash-collecting cyclone The measurement accu-

racies were 05 for the temperature 5 for CO and C xH y

ranged from 100 to 2000 ppm 10 for CO and C xH y higher than

2000 ppm 5 for NO and 02 vol for O2 Besides Chro-

meleAlumel thermocouples were 1047297xed at different levels in the

reactor for (i) monitoring the temperatures during the combustor

start-up (with the accuracy 1) and (ii) obtaining the axialtemperature pro1047297les For the particular test run the excess air ratio

was quanti1047297ed by Ref [22] using the O2 CO and C xH y concentra-

tions at the cyclone exit with an uncertainty of 2 Afterwards

corresponding percentages of total air (TA) and excess air (EA) were

calculated for each trial

Fly ash was sampled from the ash collector (see Fig 1a) to

quantify the content of unburned carbon in the ash required for

predicting the associated heat loss (as discussed below)

22 The fuels

In order to approach the work objectives two series of experi-

mental tests for (i) variable air staging and (ii) variable fuel prop-erties were carried out in this experimental study Table 1 shows

major fuel properties the ultimate and proximate analyses as well

as the lower heating value (LHV) of rice husk used in the tests at

different secondary-to-primary air ratios (SAPA)

Fig 1 (a) Experimental setup and (b) the laboratory-scale swirling 1047298uidized-bed combustor (SFBC)

Table 1

Ultimate and proximate analyses and lower heating value of rice husk 1047297red in the

SFBC during the experimental tests for variable air staging (W frac14 fuel-moisture

A frac14 fuel-ash VM frac14 volatile matter FC frac14 1047297xed carbon LHV frac14 lower heating value)

Ultimate analysis (wt on ldquoas-

receivedrdquo basis)

Proximate analysis (wt on ldquoas-


C H O N S W A VM FC LHV (kJkg)

4220 458 2784 025 003 92 159 574 155 13600

VI Kuprianov et al Energy 36 (2011) 2038e 20482040



The ultimate analysis and LHV of rice husks1047297red in the test runs

for variable fuel quality are shown in Table 2 Since the variation in

the fuel-moisture content affected all other fuel properties the fuel

ultimate analysis and LHV of moisturized rice husks are provided in

Table 2 on ldquoas-1047297redrdquo basis For the particular fuel option the

constituents of the fuel analysis were calculated using the fuel

properties of ldquoas-receivedrdquo fuel (see Table 2 Option 1) accounting

for the actual fuel-moisture content Afterwards LHV for the

moisturized fuels was determined by Ref [22] using corresponding

fuel ultimate analyses from Table 2

The rice husks used in the two experimental series were quite

similar by their chemical and physical properties on ldquoas-receivedrdquo

basis It can be seen in Tables 1 and 2 that the sulfur content in the

rice husks was quite low For this reason SO 2 was not addressed in

this study The dimensions of ldquoas-receivedrdquo rice husk particles were

about 2 mm wide 05 mm thick and 10 mm long while the particle

density was about 1000 kgm3

23 Experimental planning

231 Tests for variable air staging

During this test series rice husk was burned at the 1047297xed fuel

feed rate 80 kgh and excess air of 40 for four values of SAPA

026 040 056 and 075 In each trial (ie for the particular oper-

ating conditions) CO NO and C xH y emissions were determined

together with the O2 concentration at the cyclone exit The main

goal of this test series was to determine the value (or range) of SA

PA ensuring the minimum of these emissions which could be taken

into consideration in the detailed study (test series) below

232 Tests for variable fuel moisture

Fuel moisture (W) and excess air (EA) were chosen as inde-

pendent variables in this test series while the fuel feed rate in all

trials was adjusted at nearly the same value about 80 kgh as in

previous test series Secondary air was supplied to the SFBC at

a minimum 1047298ow rate Q ba frac14 0024 Nm3s required for reliable

cooling of the start-up burner during the combustion testsThis test series included two groups of trials The1047297rst group was

devoted to the behavior of temperature and gas (O2 CO NO)

concentrations in radial and axial directions in the combustor In

this detailed study 1047297ve rice husks (in Table 2 Options 1e5) were

burned at a similar EA value of about 40 The radial temperature

and gas concentration pro1047297les were obtained for 1047297ve levels ( Z )

above the datum Z frac14 0 (see Fig 1b) However the axial pro1047297les

were plotted using the variables measured at eight levels along the

combustor centerline

In the second group of trials CO and NO emissions from the

combustor were quanti1047297ed for all (six) rice husks in Table 2 which

were burned in the SFBC at the excess air values of about 20 40

60 and 80 Using the emission magnitudes optimal values

(ranges) of both EA and fuel-moisture content were determined

using a cost-based approach as discussed below

For the two test series the heat losses with unburned carbon

quc and owing to incomplete combustion qic were quanti1047297ed

together with combustion ef 1047297ciency by using models provided in

Appendix B Note that the effects of C xH y were taken into account

when determining qic for the tests at variable air staging However

these effects were neglected in the qic for the second test series

when the emission of hydrocarbons was at a rather low level in all

trials

24 A model for optimizing excess air and fuel-moisture content

In this work a cost-based approach [23] was applied to deter-

mine the optimal values (ranges) of excess air and fuel-moisture

content leading to the minimized emission (or ldquoexternalrdquo) costs of

1047297ring rice husk in this SFBC Ignoring the effects of SO2 (as negli-

gible) and CO2 (due to the relatively low speci1047297c ldquoexternalrdquo cost of

carbon dioxide) the corresponding objective function used for the

optimization can be represented as

J ec frac14 Min

P NO x_mNO x

thorn P CO _mCO

(1)

where _mNO x and _mCO are emission rates (calculated by Ref [23])

and P NO x and P CO are speci1047297c ldquoexternalrdquo costs of NO x (as NO2) and

CO respectively

It can be concluded from analysis of the objective function that

with the above assumptions the optimal values of excess air and

fuel-moisture content are solely dependent on the cost ratio

P NO x=P CO while the emission costs are apparently affected by all the

variables in Eq (1)

In every country the (average) emission externalities are

strongly affected by the economic structure and activities Studies

on the externalities of heat and electricity generation reveal

therefore a signi1047297cant diversity of the speci1047297c ldquoexternalrdquo costs For

the EU-27 countries the speci1047297c cost of NO x emissions is reportedto be about 7000 Vt (including impacts on human health

ecosystems crops and materials) [24] whereas for Asian countries

this index seems to be substantially (or signi1047297cantly) lower

[25e27] For instance for neighbor China P NO x frac14 2438 US$=t

(including only dominant costs ie those related to the health

damage and climate change) [25] Unlike for NO x limited data on

the externalities by CO is available in literature As revealed by

some relevant studies P CO rises as P NO x increases However the

ratio of P NO x to P CO (ie P NO x

=P CO) is reported to be within certain

limits ranging basically from 5 to 8 [28e30]

Taking the above into consideration it was decided to consider

two options in this optimization study using (1)

P NO x frac14 3000 US$=t and P CO frac14 600 US$t (ie for P NO x

=P CO frac14 5)

and (2) P NO x frac14 3000 US$=t and P CO frac14 400 US$t (ie forP NO x=P CO frac14 75)

3 Results and discussion

31 Emission and combustion characteristics of SFBC for variable

air staging

311 Emissions

Fig 2 shows the CO NO and C xH y emissions (on 6 O2 dry gas

basis) from the combustor 1047297ring 80 kgh rice husk at different SA

PA ratios when excess air was adjusted at about 40

Asseen in Fig 2a the CO emissionwas weakly in1047298uenced by the

air staging factor With increasing SAPA this emission somewhat

increased from about 360 to 450 ppm staying nevertheless at

Table 2

Ultimate analysis and LHV of rice husks 1047297red in the experimental tests for variable

fuel moisture (W)

Property Fuel sample (Option)

1 2 3 4 5 6

Ultimate analysis (wta)

C 4050 3758 3537 3316 3095 2874

H 407 377 355 333 311 289

O 2869 2663 2506 2349 2193 2036

N 031 029 027 025 024 022

S 003 003 003 002 002 002

W 84 150 200 250 300 350

A 180 1670 1572 1474 1376 1277

LHV (kJkg) 14620 13390 12460 11530 10600 9670

a On ldquoas-receivedrdquo basis for Option 1 on ldquoas-1047297redrdquo basis for Options 2e6




a rather low level basically due to the secondary air injection into

the bed splash zone As can be concluded based on the results from

Ref [12] and present study excess air (or percentage of total air) is

an important factor in controlling the CO emission in this SFBC

whereas SAPA shows quite weak effects

With increasing SAPA within the selected range 026e075 the

NO emission exhibited a slight reduction from about 150 to140 ppm (see Fig 2a) mainly due to the diminishing of the bed

temperature and reduction of the O2 concentration in the bed the

latter being occurred because of the lowering of PA Thus the air

staging does not seem to be an effective measure to control the NO

emission in this combustor 1047297ring rice husk

It can be seen in Fig 2b that at relatively small proportions of

secondary air the C xH y emissions were at a quite low level

However at SAPA gt 04 these emissions showed a signi1047297cant

increase from 120 to 1400 ppm which can be explained by the

sub-stoichiometric conditions in the bed region Under such

conditions more volatiles were carried over from the combustor

bottom causing the above increase in the C xH y emissions Thus

primary air should be supplied to the SFBC at a 1047298ow rate ensuring

the oxidation conditions in the bed ie with some excess withregard to the theoretical (stoichiometric) air For instance at

EA frac14 40 the combustor should be operated at 026 lt SAPA lt 04

(see Fig 2b) for avoiding high C xH y emissions from this SFBC 1047297ring

rice husk As can be generally concluded the lower limit of SAPA is

speci1047297ed with the aim to provide the reliable coolingof the start-up

burner whereas the upper one is selected taking into account that

EA should be somewhat greater than SA

312 Heat losses and combustion ef 1047297ciency

The analyses of 1047298y ashes for unburned carbon for this test series

indicated the high rate of fuel burnout in this conical SFBC

Depending on SAPA the unburned carbon content in the 1047298y ashes

varied from 081 to 24 the minimum value being found at the

highest SAPA ratio

Table 3 shows the heat losses with unburned carbon (quc) and

owing to incomplete combustion (qic) together with the combus-

tion ef 1047297ciency (all as the percentage of LHV) for 1047297ring 80 kgh rice

husk at excess air of about 40 for different values of SAPA An

increase in SAPA led to a noticeable reduction in the heat loss with

unburned carbon basically due to the higher rate of fuel burnout

which waslikelycaused by an increase in the residence time of char

particles in the combustor However the exponential rise of qic can

be explained by the above behavior of CO and C xH y emissions

Due to the opposite trends exhibited by the heat losses the

combustion ef 1047297ciency was found to have a maximum 991 for1047297ring rice husk at SAPA of 04e06 and EA of about 40


fuel moisture

As revealed by the experimental results the temperature and

gas concentrations (O2 CO and NO) in this conical SFBC were rep-

resented by three-dimensional patterns (1047297elds) showing the

effects of combustor hydrodynamics fuel quality and operating

conditions on the radial and axial pro1047297les of the temperature and

chemical species Note that at a given excess air SA raised with

increasing fuel moisture because of the reduction in the theoretical

air while the 1047298owrate of secondary air was 1047297xed at the above

constant value changing from 29 (for ldquoas-receivedrdquo fuel) to 41(for rice husk with the highest moisture content) which resulted in

corresponding diminishing of PA Due to the reduction in the

combustion temperature and also in the theoretical air and PA

the residence time of char particles in the bottomregion of the SFBC

was substantially greater when burning rice husks with higher

moisture content leading to the higher rates of devolatilization and

burnout of fuel particles in this region and thus affecting signi1047297-

cantly the behavior of all variables in the reactor

At EA frac14 40 or higher oxidizing conditions were basically

provided in the combustor bottom which justi1047297ed the ignorance of

C xH y emissions in this test series

321 Radial and axial temperature and gas concentration pro 1047297les

in the SFBC Fig 3 shows the radial temperature and O2 concentration

pro1047297les at 1047297ve levels ( Z ) above the air distributor in the SFBC 1047297ring

80 kgh rice husk at excess air of about 40 for variable fuel prop-

erties (Options 1e5 in Table 2) As seen in Fig 3 the variables

exhibitedquitesimilar behaviorsat different levels ( Z ) above the air

distributor The radial temperature pro1047297les were found to be rather

uniform indicating the highly intensive heat-and-mass transfer

along the radius With increasing fuel moisture (at a 1047297xed excess air

level) the temperature at all points in the combustor volume was

found to be reduced (despite the above increase in the residence

time) because of the apparent in1047298uence of the latent heat of water

evaporation Similar results are reported in some studies on

conventional 1047298uidized-bed and 1047297xed-bed combustion systems

1047297ring biomass fuels with variable fuel moisture [4203132]

Fig 2 Effects of secondary-to-primary air ratio (SAPA) on the (a) CO NO and (b) C xH y emissions from the SFBC 1047297ring rice husk at excess air of 40

Table 3

Heat losses and combustion ef 1047297ciency of the SFBC 1047297ring 80 kgh rice husk at excess

air of 40 for variable secondary-to-primary air ratio

SAPA quc () qic () Combustion ef 1047297ciency ()

026 094 024 988

040 051 035 991

056 047 043 991

075 031 212 976




Z = 267 m

700

800

900

1000

1100

00 02 04 06 08 10

rR

) C deg ( e r u t a r

e p m e T

Z = 267 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2

) l o v ( n o i t a r t

n e c n o c

Z = 217 m

700

800

900

1000

1100

00 02 04 06 08 10

rR

) C deg ( e r u t a r e p m e T

Z = 217 m0

5

10

15

20

00 02 04 06 08 10

rR

O 2

) l o v ( n o i t a r t n e c n o c

Z = 155 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 155 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 101 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 101 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 047 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 047 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2

)

l o v ( n o i t a r t n e c n o c

a b

Fig 3 Radial (a) temperature and (b) O2 concentration pro1047297les at different levels in the SFBC 1047297ring rice husk at excess air of about 40 for variable fuel-moisture content (-)

W frac14 84 () W frac1415 () W frac14 20 (6) W frac1425 and (A) W frac1430




Implementation of air staging seems to have a signi1047297cant impact

on the behavior of gaseous species in both radial and axial direc-

tions Due to the tangential injection of secondary air into the bed

splash zone the radial O2 concentration pro1047297les were characterized

by a positive radial gradient (the most signi1047297cant being observed at

Z frac14 101 m) which resulted in the higher O2 concentration near the

combustor wall than that at the centerline (ie at r R frac14 0)

However the radial gradient of O2 was gradually attenuated along

the bed height Note that the injection of secondary air affected the

radial O2 concentration pro1047297les not only in upper regions of the

reactor but also at levels below the injection point (in Fig 3b see

the pro1047297les at Z frac14 047 m) since the secondary air was injected at

the negative angle In the meantime with increasing the fuel-

moisture content the O2 concentration at all the points across the

combustor was found to be reduced and this reduction was caused

by some physical and chemical factors as addressed below in the

discussion of axial O2 concentration pro1047297les

The axial temperature and O2 concentration pro1047297les in the SFBC

are shown in Fig 4 for the same fuel options and operating

conditions as in Fig 3 At 1047297xed excess air a positive axial temper-

ature gradient was found to occur in the lower part of the reactor

for all the fuels (see Fig 4a) likely due to the diminishing of heat

release in the dense bed (caused by air staging) and (ii) in1047298uence of secondary air injected into the bed splash zone at the ambient

temperature However with higher fuel moisture (ie with dete-

riorating fuel quality) the temperature attained its maximum at

lower levels (Z) above the air distributor which can be explained by

the effects of the residence time The maximum temperature for

burning ldquoas-receivedrdquo rice husk (with W frac14 84) was rather high

about 980 C however it was reduced to 850e860 C when

increasing the fuel-moisture content to 25e30

However with raising fuel moisture the rate of oxygen

consumption in the bottom region of the SFBC ( Z lt 08 m) was

apparently higher which despite the above reduction in the bed

temperature resulted in the lower O2 concentration at all locations

in this region (as seen in Fig 4b) This phenomenon can be

explained by the greater residence time (leading to a higher yield of CO and other combustibles with fuel volatiles) and also greater

contribution of the ldquowetrdquo oxidation of char-C by OH radicals both

leading to higher rates of CO formation and consequently O2

consumption in this region The next region (08 lt Z lt 10 m) was

characterized by a noticeable regaining (rise) of O2 as the response

to secondary air injection However in the freeboard of the

combustor ( Z gt 10 m) the O2 concentration was diminished along

the reactor height at a rather low rate and this reduction was

accompanied by the gradual converging of the axial pro1047297les as all

the tests in Fig 4 for variable fuel moisture were conducted at

(nearly) the same EA

Fig 5 shows the radial CO and NO concentration pro1047297les at

different levels above the air distributor for the same fuels and

operating conditions as in Fig 3 Both CO (Fig 5a) and NO (Fig 5b)

were signi1047297cantly affected by fuel moisture and showed negative

gradients along the radius (different numerically) at all the levels in

the SFBC For the 1047297xed fuel-moisture content due to the effects of

secondary air the CO concentration in the peripheral zone across

the combustor was much lower compared to that at the centerline

thus forming the above radial gradient of CO However the NO

concentration varied weakly along the radius except at Z frac14 047 m

The occurrence of the NO maximum at the centerline indicated

higher rates of both fuel devolatilization and oxidation in the

central zone of the reactor (compared to those at the combustor

wall) despite the uniformity of the temperature and the opposite

trends of the O2 concentration pro1047297les across the SFBC (see Fig 3b)

In the freeboardof the reactor the radial CO and NO gradients were

found to be gradually attenuated with higher Z

Fig 6 depicts the axial CO and NO concentration pro1047297les in this

combustor As seen in Fig 6a the pro1047297les exhibited four sequent

regions along the combustor height With increasing fuel moisture

the CO concentration in the 1047297rst region (0lt Z lt 08 m) was

apparently higher at all the levels above the air distributor

particularly at the centerline (see Fig 5a) mainly due to (i) longerresidence time (leading to greater yield of CO with volatiles) (ii)

lower PA (reducing the rate of CO oxidation) (iii) higher contri-

bution of ldquowetrdquo oxidation of char-C by OH radicals and (iv) lower

bed temperature causing an increase in the COCO2 ratio in the

products of fuel-char oxidation [33]

In the second region (08 lt Z lt 10 m) the CO concentration

along the combustor axis was found to be drastically reduced

mainly due to the effects of secondaryair the greater rate of the CO

reduction being observed at a higher level of fuel moisture (ie at

higher SA) In the third region (10 lt Z lt 18 m) the CO concentra-

tion regained substantial values along the centerline mainly due to

oxidation of unburned hydrocarbons and fuel-C carried over from

the bed region to CO However in the fourth (upper) region the CO

concentration was found to be gradually reduced along thecombustor height likely via homogeneous reaction of CO with

residual O2 and OH [333]

Like for CO four speci1047297c regions can be distinguished in the

axial NO concentration pro1047297les as can be seen in Fig 6b In the 1047297rst

region (0 lt Z lt 08 m) NO was mainly formed from NH3 in volatiles

(a major precursor of NO in biomass combustion) via the fuel-NO

formation mechanism [343435] With increasing fuel moisture

despite the reduction in bed temperature the NO concentration at

the reactor centerline showed a trend to increase at any given Z

mainly due to (i) greater residence time promoting a higher yield

of nitrogenous species with fuel volatiles and (ii) enhanced

a b

500

600

700

800

900

1000

1100

0 1 2 3

Height above air distributor (m)


0

5

10

15

20

0 1 2 3Height above air distributor (m)

O 2


Fig 4 Axial (a) temperature and (b) O2 concentration pro1047297les in the SFBC 1047297ring rice husk at excess air of about 40 for variable fuel-moisture content (-) W frac1484 () W frac1415

(

) Wfrac14

20 (6

) Wfrac14

25 and (A

) Wfrac14

30




Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t n e c n o c

O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m

p p ( n o i t a r t n e c n o c O N

Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab

Fig 5 Radial (a) CO and (b) NO concentration pro1047297les at different levels in the SFBC 1047297ring rice husk at excess air of about 40 for variable fuel-moisture content (-) W frac1484 ()

W frac14 15 () W frac1420 (6) W frac1425 and (A) W frac1430




oxidation of NH3 by OH [36] In the second region (08 lt Z lt 10 m)

the chemical reactions responsible for NO decomposition such as

catalytic reduction of NO by CO on the char surface [3] as well as

reaction of NO with NH3 at oxygen de1047297ciency [34] were predom-

inant This resulted in a signi1047297cant reduction of the NO concen-

tration along the combustor height and the NO reduction was more

apparent when burning rice husks with higher moisture contentsHowever the injection of secondary air promoted a slight increase

in NO in the third region (10 lt Z lt 16 m) of the reactor as a result

of oxidation of the nitrogenous species carried over from the

combustor bottom In the fourth (upper) region the pro1047297les

exhibited some diminishing of the NO concentration along the

reactor height because of the catalytic reduction of NO by CO

occurred however at a rather low rate

322 Emissions

Fig 7 depicts the CO and NO emissions (on 6 O 2 dry gas basis)

from the combustor 1047297ring 80 kgh rice husk at variable EA for the

whole range of fuel moisture (Options 1e6 in Table 2) It can be

concluded from analysis of data in Fig 7a that at EA greater than

40 the CO emission from the SFBC can be controlled ata comparatively low level below 350 ppm regardless of the fuel

quality On the contrary at excess air lower than 40 the CO

emission exhibited quite strong effects of both fuel quality and EA

Note that at EA frac14 20 the CO emission was extremely high

3000e7000 ppm for the whole range of fuel moisture However

with increasing the fuel-moisture content from 84 (in ldquoas-

receivedrdquo rice husk) to 25 the CO emission at this lowest EA

exhibited some reduction roughly from 4000 to 3000 ppm basi-

cally caused by (i) the higher rate of chemical reaction between CO

and OH [333] and (ii) higher rate of CO decomposition in the

freeboard (due to enhanced SA and greater residence time) Similar

trend is reported in some studies on effects of fuel moisture on the

CO emission from the 1047297xed-bed combustion systems [3132]

However with further increase in the fuel-moisture content (from

25 to 35) the CO emission from the SFBC was found to rise from

about 3000 to 7000 ppm likely due to the signi1047297cant contribution

of ldquowetrdquo oxidation of char-C occurred at the lowered combustion

temperatures This trend is in concordance with the behavior of theCO emission during the conventional 1047298uidized-bed combustion of

some biomass fuels with variable moisture [420]

It can be seen in Fig 7b that at EA frac14 40 (the ldquocriticalrdquo value for

the CO emission) the NO emission diminished from about 170 to

130 ppm (or by some 25) when changing the fuel-moisture

content from 84 to 25 A further increase in fuel moisture up to

30e35 resulted in some more emission reduction Note that this

positive result was accompanied by deterioration of combustion

stability (likely caused by inconsistency in fuel properties) which

showed itself by the noticeable time-domain 1047298uctuations of the

temperature and gaseous species particularly in the vicinity of the

fuel injection As revealed by experimental data from this study

through moisturizing of ldquoas-receivedrdquo rice husk the NO emission

from the SFBC can be substantially reduced However thisachievement was accompanied by the conventional effects of EA

leading to the increase in the NO emission with higher EA [16e12]

323 Optimal excess air and fuel-moisture content

Fig 8 shows the emission costs US$ per 1 ton of fuel for 1047297ring

rice husk in the SFBC at variable fuel moisture and excess air pre-

dicted using the above CO and NO emissions and the speci1047297c

ldquoexternalrdquo costs P NO x frac14 3000 US$=t and P CO frac14 600 US$t (ie for

P NO x=P CO frac14 5) At low values of EA the contribution of CO to the

emission costs was predominant whereas the effects of NO were

substantial at higher EA values It can be seen in Fig 8 that the

Fig 6 Axial (a) CO and (b) NO concentration pro1047297les in the SFBC 1047297ring rice husk at excess air of about 40 for variable fuel-moisture content (-) W frac1484 () W frac1415 ()

W frac1420 (6) W frac1425 and (A) W frac1430

Fig 7 Effects of the fuel-moisture content and excess air on the (a) CO and (b) NO emissions from the SFBC 1047297ring 80 kghr rice husk (-) W frac1484 () W frac1415 () W frac1420 (6)

Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35




emission costs were at the minimal value when 1047297ring rice husk

with the fuel-moisture content of 25e

35 at excess air of 40e

50

Switching P NO x=P CO from 5 to 75 (keeping however P NO x

at the

above value) led in effect to nearly the same optimal ranges of fuel

moisture and excess air quanti1047297ed however at different magni-

tudes of the emission costs Thus the optimized variables are not

sensitive to the speci1047297c ldquoexternalrdquo costs P NO x and P CO within their

actual ranges

324 Combustion heat losses and ef 1047297ciency

Table 4 shows the heat losses with unburned carbon quc and

owing to incomplete combustion qic together with the combustion

ef 1047297ciency of the SFBC actual EA values and SAPA ratios for some

selected fuel options

The heat loss with unburned carbon exhibited a rather weak

correlation with fuel moisture showing however the substantialin1047298uence of excess air Unlike quc the heat loss owing to incomplete

combustion was strongly affected by both fuel moisture and excess

air and it was characterized by quite small magnitudes at EAgt 40

Thus an increase in excess air basically resulted in the improve-

ment of the combustion ef 1047297ciency of the SFBC For the fuel range

the highest combustion ef 1047297ciency 992e997 was obtained at

excess air of 40e80 Numerous studies on 1047297ring various biomass

fuels in conventional 1047298uidized-bed combustion systems report

similar trends [1210e1337]

Based on the analysis of both emission characteristics and

combustion ef 1047297ciency and also taking into consideration an

important issue of the combustion stability it can be generally

concluded that the best performance of this SFBC is achievable

when 1047297ring moisturized rice husk with the moisture content of

about 25 at excess air of 40e50 Under these conditions the

major gaseous emissions from the conical SFBC can be controlled

below 350 ppm for CO and within 130e140 ppm for NO (both on

6 O2 dry gas basis) while the combustion ef 1047297ciency is ensured at

a rather high value about 995

4 Conclusions

Combustion and emission characteristics have been experi-

mentally studied on a SFBC 1047297ring 80 kgh rice husk Two NO x

emission control techniques have been investigated in this work

(1) air staging of the combustion process and (2) 1047297ring rice husk as

moisturized fuel

In the test series for variable air staging the combustorhas been

tested with the aim to investigate the behavior of CO NO and C xH yemissions as well as combustion ef 1047297ciency for burning ldquoas-

receivedrdquo rice husk at a 1047297xed excess air value (of about 40) for

variable secondary-to-primary air ratio (SAPA) With increasing

SAPA from 026 to 075 the CO emission from the SFBC ranges from

about 360 to 450 ppm (on 6 O2 dry gas basis) while the NO

emission reduces at a quite low rate from about 150 to 140 ppm

However with higher SAPA C xH y emissions increase from 120 to

1400 ppm the dramatic rise being observed at SAPA gt 04 Thus

the air staging has minor effects on the CO and NO emissions To

avoid elevated C xH y emissions primary air should be supplied to

the combustor at the amount greater than the stoichiometric air

affected by the fuel properties

During the trialsfor variable fuel quality ricehusks with different

fuel moisture contents (of 84e35) have been burned at different

excess air values rangedfrom about 20 to 80 The analysis of radial

and axial CO and NO concentration pro1047297les has shown the occur-

rence of four speci1047297c regions along the combustor height charac-

terized by different rates of formation and decomposition of CO and

NO The highest rates of CO and NO decomposition are found to

occur in the bed splash zone whereas the top region in the

combustor is characterized by small axial gradients of these species

Through moisturizing rice husk the NO emission from this

SFBC can be substantially reduced while the CO emission is

effectively controlled by the secondary air injection into the bed

splash zone The best combustion and emission performance of

the SFBC is achievable when burning moisturized rice husk with

the moisture content of about 25 at excess air of 40e50 For

these optimal operating conditions the CO emission is expected

to be below 350 ppm ensuring high combustion ef 1047297ciency (about

995 maximum) while the NO emission may range from 130 to

140 ppm With increasing the fuel-moisture content to higher

values eg 30e35 the NO emission from the SFBC can be

secured even at lower values below 110 ppm However elevated

fuel moisture may likely result in deterioration of combustion

stability

Acknowledgements

The authors would like to acknowledge the 1047297nancial support

from the Thailand Research Fund (contract No BRG 50800011) The

authors also sincerely thank Dr Kasama Sirisomboon and Mr

Porametr Arromdee for their effective help in experimental tests

Fig 8 Effects of the fuel-moisture content and excess air on the emission costs for

1047297ring rice husk in the SFBC

Table 4

Heat losses and combustion ef 1047297ciency of the SFBC 1047297ring 80 kgh rice husk for

variable fuel-moisture content and excess air

W () EA () SAPA quc () qic () Combustion

ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996




Appendix A Measurement uncertainty in the 1047298owrate of

primary air

The fractional uncertainty in the 1047298owrate of primary air was

estimated by Ref [38]

sPA frac14 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

4s2D thorn s2

V thorn s2R thorn s2

P

q (A1)

where sD is the error in physical measurement of inner diameter of the primary air pipe sV is the measurement error of the velocity

(dependent mainlyon the type of a selected probe) sR is therelative

error associated with imperfect1047297xing of the probe in air1047298ow and sP

is the uncertainty in the velocity pro1047297le across the pipe

AssumingsD frac14 1 sV frac14 15 sR frac14 1 and sP frac14 15(as advised in

Ref [38]) the uncertainty in the 1047298owrate of primary air was

calculated using Eq (A1) to be about 3

Appendix B Determining heat losses and combustion

ef 1047297ciency

In this work the combustion ef 1047297ciency of the SFBC 1047297ring rice

husk was calculated using the the heat-loss method [18]

For this combustor with no ashremoval through thebottompartthe heat loss with unburned carbon quc () was determined by

quc frac14 32866

LHV

C fa

100 C fa

A (B1)

where C fa is the unburned carbon content in the1047298y ash wt and A

is the fuel-ash content wt on ldquoas-receivedrdquo basis

The heat loss owing to incomplete combustion qic () was

quanti1047297ed based on theconcentrations (vol)of COand C xH y (asCH4)

measured in the 1047298ue gas at the cyclone outlet at actual excess air

qic frac14 eth1264 CO thorn 3582 CH4THORN V dgeth100 qucTHORN

LHV (B2)

where V dg is the volume of dry 1047298ue gas at the cyclone outlet Nm3

kg calculated by Refs [1822] using the fuel ultimate analysis onldquoas-receivedrdquo basis and excess air ratio at this point

The combustion ef 1047297ciency of the 1047298uidized-bed combustor hc

() was then determined by

hc frac14 100 ethquc thorn qicTHORN (B3)

References

[1] Natarajan E Nordin A Rao AN Overview of combustion and gasi1047297cation of rice husk in 1047298uidized bed reactors Biomass Bioenergy 199814533e46

[2] Bhattacharya SC Abdul Salam P Sharma M Emissions from biomass energyuse in some selected Asian countries Energy 200025169e88

[3] Werther J Saenger M Hartge EU Ogada T Siagi Z Combustion of agriculturalresidues Prog Energy Combust Sci 2000261e27

[4] Janvijitsakul K Kuprianov VI Similarity and modeling of axial CO and NO

concentration pro1047297les in a 1047298uidized-bed combustor (co-)1047297ring biomass fuelsFuel 2008871574e84

[5] Demirbas A Combustion characteristics of different biomass fuels ProgEnergy Combust Sci 200430219e30

[6] Leckner B Karlsson M Gaseous emissions form circulating 1047298uidized bedcombustion of wood Biomass Bioenergy 19934379e89

[7] Spliethoff H Hein KRG Effect of co-combustion of biomass on emissions inpulverized fuel furnaces Fuel Process Technol 199854189e205

[8] Lyngfelt A Leckner B Combustion of wood-chips in circulating 1047298uidized bedboilers e NO and CO emissions as functions of temperature and air-stagingFuel 1999781065e72

[9] Chyang CS Wu KT Lin CS Emission of nitrogen oxides in a vortexing 1047298uidizedbed combustor Fuel 200786234e43

[10] Armesto E Bahillo A Cabanillas A Veijonen K Otero J Combustion behavior of rice husk in a bubbling 1047298uidised bed Biomass Bioenergy 200223171e9

[11] Kuprianov VI Janvijitsakul K Permchart W Co-1047297ring of sugar canebagasse with rice husk in a conical 1047298uidized-bed combustor Fuel 200685434e42

[12] Fang M Yang L Chen G Shi Z Luo Z Cen K Experimental study on rice huskcombustion in a circulating 1047298uidized bed Fuel Process Technol2004851273e82

[13] Permchart W Kouprianov VI Emission performance and combustion ef 1047297-ciency of a conical 1047298uidized-bed combustor 1047297ring various biomass fuelsBioresour Technol 20049283e91

[14] Sirisomboon K Kuprianov VI Arromdee P Effects of design features oncombustion ef 1047297ciency and emission performance of a biomass-fuelled 1047298uid-ized-bed combustor Chem Eng Process Process Intens 201049270e7

[15] Leckner B Amand LE Lucke K Werther J Gaseous emissions from co-combustion of sewage sludge and coalwood in a 1047298uidized bed Fuel200483477e86

[16] Eaimsa-ard S Kaewkohkiet Y Thianpong C Promvonge P Combustionbehavior in a dual-staging vortex rice husk combustor with snail entry IntCommun Heat Mass Transfer 2008351134e40

[17] Madhiyanon T Lapirattanakun A Sathitruangsak P Soponronnarit S A novelcyclonic 1047298uidized-bed combustor (J-FBC) combustion and thermal ef 1047297-ciency temperature distribution combustion intensity and emission of pollutants Combust Flame 2006146232e45

[18] Basu P Cen KF Jestin L Boilers and burners New York Springer 2000[19] Kaewklum R Kuprianov VI Experimental studies on a novel swirling 1047298uid-

ized-bed combustor using an annular spiral air distributor Fuel20108943

e52

[20] Kouprianov VI Permchart W Emission from a conical FBC 1047297red witha biomass fuel Appl Energy 200374383e92

[21] Kaewklum R Kuprianov VI Douglas PL Hydrodynamics of airesand 1047298ow ina conical swirling 1047298uidized bed a comparative study between tangential andaxial air entries Energy Convers Manage 2009502999e3006

[22] Bezgreshnov AN Lipov YM Shleipher BM Computations of steam boilersMoscow Energoatomizdat 1991 [in Russian]

[23] Kuprianov VI Application of a cost-based method of excess air optimizationfor the improvement of thermal ef 1047297ciency and environmental performance of steam boilers Renew Sustain Energy Rev 20059474e98

[24] Streimikiene D Roos I Rekis J External cost of electricity generation in BalticStates Renew Sustain Energy Rev 200913863e70

[25] Zhang Q Weili T Yumei W Yingxu C External costs from electricity gener-ation of China up to 2030 in energy and abatement scenarios Energy Pol2007354295e304

[26] Hainoun A Almoustafa A Aldin MS Estimating the health damage costs of Syrian electricity generation system using impact pathway approach Energy

201035628e

38[27] Nguyen KQ Internalizing externalities into capacity expansion planning thecase of electricity in Vietnam Energy 200833740e6

[28] Kitou E Horvath A External air pollution costs of telework Int J Life CycleAssess 200813155e65

[29] Wei X Zhang L Zhou H Evaluating the environmental value of pollutants inChina power industry In Proceedings of the international conference onenergy and the environment Shanghai China 2003

[30] Salisdisouk N The concept of integrated resource planning In Proceeding of the workshop on electric power quality safety and ef 1047297ciency of its useselectric power system management Pathum Thani Thailand 1994

[31] Yang YB Shari1047297 VN Swithenbank J Effect of air 1047298ow rate and fuel moisture onthe burning behaviours of biomass and simulated municipal solid wastes inpacked beds Fuel 2004831553e62

[32] Zhao W Li Z Zhao G Zhang F Zhu Q Effect of air preheating and fuel moistureon combustion characteristics of corn straw in a 1047297xed bed Energy ConversManage 2008493560e5

[33] Tillman DA Rossi AJ Kitto WD Wood combustion New York AcademicPress 1981

[34] Winter F Wartha C Hofbauer H NO and N2O formation during thecombustion of wood straw malt waste and peat Bioresour Technol19997039e49

[35] Sun Z Jin M Zhang M Liu R Zhang Y Experimental studies on cotton stalkcombustion in a 1047298uidized bed Energy 2008331224e32

[36] Smart JP Robert PA De Soete GG The formation of nitrous oxide in a large-scale pulverized-coal 1047298ames J Inst Energy 199063131e5

[37] Abu-Qudais M Fluidized-bed combustion for energy production from olivecake Energy 199621173e8

[38] Trembovlya VI Finger ED Avdeeva AA Thermo-technical tests of boiler unitsMoscow Energoatomizdat 1991 [in Russian]




increasing excess air andor combustion temperature both

enhancing therateof COoxidation to CO2 [18911] Some reductionin

COcan be achieved when1047297ring biomass fuels withlowerash content

[1113] The bubbling 1047298uidization mode seems to be one of the effec-

tive regimes for operating the 1047298uidized-bed combustion systems

[131013] as ensuringthe high intensive mixingof fuel particles and

air in the bed region (promoting CO reduction) the latter being

signi1047297cantly affected by the air distributor design [14] However an

in1047298uence of the air staging on CO emission during the 1047298uidized-bed

combustion of biomass is reported to be rather weak [15]

A large number of research studies have addressed emission

characteristics and combustion ef 1047297ciency for 1047297ring rice husk in

various laboratory-scale 1047298uidized-bed combustion techniques

such as bubbling 1047298uidized-bed vortexing 1047298uidized-bed and circu-

lating 1047298uidized-bed combustors [9e12] Due to moderate bed

temperatures (normally not higher than 850 C) NO x emissions

from the combustors are generally below 180 ppm (on 6 O2 dry

gas basis) while CO emission is found to be elevated up to

800 ppm Combustion ef 1047297ciency of these devices operated at

optimal conditions is reported to be within 96e98 Experimental

results revealed minor effects of the air staging on these emissions

as well as on combustion ef 1047297ciency of the vortexing and circulating

1047298uidized-bed combustors 1047297ring rice husk [912]Recently two novel combustion techniques ensuring fuel

oxidation in a strongly swirled 1047298ow a vortex combustor and

a cyclonic 1047298uidized-bed combustor have been developed and

tested for 1047297ring rice husk [1617] Under optimal operating condi-

tions high (over 99) combustion ef 1047297ciency can be achieved in

these pilot reactors while controlling CO emission below 400 ppm

However NO x emissions from the combustors are reported to be

elevated up to 300 ppm for the vortex combustor [16] or rather

high 350e425 ppm for the cyclonic 1047298uidized-bed combustor [17]

Such substantial NO x emissions are mainly caused by (i) elevated

excess air required for sustaining the strongly swirled gasesolid

1047298ow and (ii) high-temperature conditions in these rice husk-fuel-

led combustors operated with a signi1047297cant heat release rate per

unit volume Effects of the air staging on both emissions andcombustion ef 1047297ciency of the vortex and cyclonic 1047298uidized-bed

combustors are reported to be rather weak It should be noted that

elevated excess air basically leads to lower thermal ef 1047297ciency of

a power plant (or any other energy conversion units) using these

devices mainly due to an increase in the heat loss with waste gas

(affected by a signi1047297cant volume of excessive air) [18]

Kaewklum and Kuprianov [19] have recently reported a pio-

neering study on a laboratory-scale swirling 1047298uidized-bed

combustor (SFBC) 1047297ring rice husk In this innovative combustion

technique a swirling 1047298uidized bed is generated due to the special

design of a primary air distributor used in this combustion tech-

nique as the swirl generator Unlike in the vortexing 1047298uidized-bed

combustor secondaryair in this SFBC is injected into the bed splash

zone ie at a relatively low level above the (primary) air distrib-utor The tangential injection of secondary air sustains the rota-

tional gasesolid 1047298ow in the combustor At optimal excess air

40e60 the burning of rice husk in the SFBC is characterized by

high about 995 combustion ef 1047297ciency while CO and NO emis-

sions can be limited within 150e300 ppm and 170e210 ppm

respectively However no effects of the air staging on emission

performance and combustion ef 1047297ciency of the SFBC have been

addressed in this pioneering study

As can be generally concluded from the literature review

compared to the conventional (ie non-swirling) 1047298uidized-bed

combustors the combustion techniques with a rotational gasesolid

1047298ow ensure higher combustion ef 1047297ciency at minimized CO emis-

sion accompanied however by moderate (for the SFBC) or

elevated (for the vortex combustor) or high (for the cyclonic

1047298uidized-bed combustor) NO x emissions The NO x control in these

high ef 1047297ciency devices 1047297ring rice husk is therefore an issue of

paramount importance

Burning biomass in the form of moisturized fuel which prior to

the combustion can be prepared by adding water to ldquoas-receivedrdquo

fuel is proven to be an effective least-cost NO x emission control

technique as reportedin studies on1047297ring of wood sawdust and rice

husk in a conventional 1047298uidized-bed combustor with a cone-shape

bed [420] Moreover a substantial reduction in the bed tempera-

ture occurring with increasing fuel moisture provides more

favorable operating conditions for preventing undesirable ash-

related problems in the 1047298uidized-bed combustor (eg bed

agglomeration and wall slagging) particularly when 1047297ring high-

alkali biomass fuels [3] Howeverwhen using this conical 1047298uidized-

bed combustor the reduction of NO x emissions has been accom-

panied by a noticeable increase in CO emission and corresponding

deterioration of the combustion ef 1047297ciency Thus selection of the

most appropriate fuel-moisture content should be considered

along with optimization of air supply to the combustion system

This study was aimed at determining the technical feasibility of

an effective control of NO emission during the combustion of rice

husk in the SFBC through air staging of the combustion and fuel

moisturizing Detail analysis of the formation and decomposition of major gaseous pollutants (CO and NO) at different locations in this

reactor for variable operating conditions and fuel properties were

the focus of this work Optimization of the fuel-moisture content

and air supply for minimizing CO and NO emissions from this SFBC

1047297ring moisturized rice husk was also among the main objectives of

this study

2 Materials and methods

21 Experimental facilities

Fig1 depicts the general view of the experimental setup and the

schematic diagram of the SFBC It can be seen in Fig 1a that the

system included the combustor with a start-up burner a cyclonea fuel screw feeder and a blower Additionally Fig 1b provides the

design and geometrical details of the SFBC which was made of 45-

mm-thick steel sheet and covered internally with the 50-mm-thick

refractory

The combustor consisted of a conical (bottom) part1047297lled in with

lsquoroundrsquo quartz sand (with the particle sphericity of 086 and density

of 2650 kgm3) used as the inert bed material and a cylindrical

(upper) part The particle (sieve) size of 05e06 mm and static bed

height of 30 cm were selected to be the main characteristics of the

bed material as those ensuring the stable swirling 1047298uidized-bed

regime Under ldquocoldrdquo operating conditions the minimum 1047298uidiza-

tion velocity of the air-sand bed with these characteristics was

about 08 ms while the minimum velocity of the fully swirling

1047298uidized-bed mode was 13 ms [21]The annular spiral air distributor at the combustor bottom was

made up of eleven blades 1047297xed at an angle of 14 to the horizontal

and served as the swirl generator of primary air (PA) the latter

being supplied by the 25-hp blower The distributor had an annular

air exit with 01 m inner and 025 m outer diameters The distance

between two neighbor blades was variable (in a linear relationship

with radius) thus forming a trapezoidal cross-sectional area of

0012 m2 (total) for the air1047298ow between the blades To stabilize the

swirl motion of the gasesolid bed a steel cone was 1047297xed on the top

of the air distributor as shown in Fig 1b

Primary air was supplied to the air distributor by the blower

through an air pipe of a 01-m inner diameter as shown in Fig 1a

The 1047298owrate of primary air was controlled using a butter1047298y valve

arranged on the air pipe downstream from the blower The















fuel) to 40














be about 4


















22 The fuels







Table 1









4220 458 2784 025 003 92 159 574 155 13600



























































trials









J ec frac14 Min

P NO x_mNO x

thorn P CO _mCO

(1)



CO respectively





variables in Eq (1)



















=P CO frac14 5)




air staging

311 Emissions







Table 2


fuel moisture (W)


1 2 3 4 5 6


C 4050 3758 3537 3316 3095 2874

H 407 377 355 333 311 289

O 2869 2663 2506 2349 2193 2036

N 031 029 027 025 024 022

S 003 003 003 002 002 002

W 84 150 200 250 300 350

A 180 1670 1572 1474 1376 1277

LHV (kJkg) 14620 13390 12460 11530 10600 9670




































highest SAPA ratio













fuel moisture




































Table 3




026 094 024 988

040 051 035 991

056 047 043 991

075 031 212 976




Z = 267 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


e p m e T

Z = 267 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


n e c n o c

Z = 217 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 217 m0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 155 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 155 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 101 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 101 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 047 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 047 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2

)


a b


































































































a b

500

600

700

800

900

1000

1100

0 1 2 3



0

5

10

15

20


O 2



(

) Wfrac14

20 (6

) Wfrac14

25 and (A

) Wfrac14

30




Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m


Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab



















322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e



























fuel) to 40














be about 4


















22 The fuels







Table 1









4220 458 2784 025 003 92 159 574 155 13600



























































trials









J ec frac14 Min

P NO x_mNO x

thorn P CO _mCO

(1)



CO respectively





variables in Eq (1)



















=P CO frac14 5)




air staging

311 Emissions







Table 2


fuel moisture (W)


1 2 3 4 5 6


C 4050 3758 3537 3316 3095 2874

H 407 377 355 333 311 289

O 2869 2663 2506 2349 2193 2036

N 031 029 027 025 024 022

S 003 003 003 002 002 002

W 84 150 200 250 300 350

A 180 1670 1572 1474 1376 1277

LHV (kJkg) 14620 13390 12460 11530 10600 9670




































highest SAPA ratio













fuel moisture




































Table 3




026 094 024 988

040 051 035 991

056 047 043 991

075 031 212 976




Z = 267 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


e p m e T

Z = 267 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


n e c n o c

Z = 217 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 217 m0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 155 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 155 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 101 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 101 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 047 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 047 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2

)


a b


































































































a b

500

600

700

800

900

1000

1100

0 1 2 3



0

5

10

15

20


O 2



(

) Wfrac14

20 (6

) Wfrac14

25 and (A

) Wfrac14

30




Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m


Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab



















322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e







































































trials









J ec frac14 Min

P NO x_mNO x

thorn P CO _mCO

(1)



CO respectively





variables in Eq (1)



















=P CO frac14 5)




air staging

311 Emissions







Table 2


fuel moisture (W)


1 2 3 4 5 6


C 4050 3758 3537 3316 3095 2874

H 407 377 355 333 311 289

O 2869 2663 2506 2349 2193 2036

N 031 029 027 025 024 022

S 003 003 003 002 002 002

W 84 150 200 250 300 350

A 180 1670 1572 1474 1376 1277

LHV (kJkg) 14620 13390 12460 11530 10600 9670




































highest SAPA ratio













fuel moisture




































Table 3




026 094 024 988

040 051 035 991

056 047 043 991

075 031 212 976




Z = 267 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


e p m e T

Z = 267 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


n e c n o c

Z = 217 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 217 m0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 155 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 155 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 101 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 101 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 047 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 047 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2

)


a b


































































































a b

500

600

700

800

900

1000

1100

0 1 2 3



0

5

10

15

20


O 2



(

) Wfrac14

20 (6

) Wfrac14

25 and (A

) Wfrac14

30




Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m


Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab



















322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e















































highest SAPA ratio













fuel moisture




































Table 3




026 094 024 988

040 051 035 991

056 047 043 991

075 031 212 976




Z = 267 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


e p m e T

Z = 267 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


n e c n o c

Z = 217 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 217 m0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 155 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 155 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 101 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 101 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 047 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 047 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2

)


a b


































































































a b

500

600

700

800

900

1000

1100

0 1 2 3



0

5

10

15

20


O 2



(

) Wfrac14

20 (6

) Wfrac14

25 and (A

) Wfrac14

30




Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m


Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab



















322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e
















Z = 267 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


e p m e T

Z = 267 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


n e c n o c

Z = 217 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 217 m0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 155 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 155 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 101 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 101 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2


Z = 047 m

700

800

900

1000

1100

00 02 04 06 08 10

rR


Z = 047 m

0

5

10

15

20

00 02 04 06 08 10

rR

O 2

)


a b


































































































a b

500

600

700

800

900

1000

1100

0 1 2 3



0

5

10

15

20


O 2



(

) Wfrac14

20 (6

) Wfrac14

25 and (A

) Wfrac14

30




Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m


Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab



















322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e












































































































a b

500

600

700

800

900

1000

1100

0 1 2 3



0

5

10

15

20


O 2



(

) Wfrac14

20 (6

) Wfrac14

25 and (A

) Wfrac14

30




Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m


Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab



















322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e
















Z = 267 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 267 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m

p p ( n o i t a r t

n e c n o c O N

Z = 217 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 217 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 155 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 155 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0rR

) m


Z = 101 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O C

Z = 101 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

Z = 047 m

0

5000

10000

15000

20000

25000

30000

0 0 0 2 0 4 0 6 0 8 1 0

rR

)

m


O C

Z = 047 m

0

100

200

300

400

500

0 0 0 2 0 4 0 6 0 8 1 0

rR

) m


O N

ab



















322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e





























322 Emissions
















































Wfrac14

25 (A

) Wfrac14

30 and (A

) Wfrac14

35







50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e



















50


at the





actual ranges


























4 Conclusions





moisturized fuel




































stability

Acknowledgements







Table 4




ef 1047297ciency ()

84 17 033 074 204 972

41 026 049 015 994

64 022 041 007 995

76 019 049 008 994

15 17 036 046 173 978

36 030 041 040 992

63 024 050 008 994

89 021 036 005 996

25 18 042 047 134 982

41 033 035 013 995

63 027 029 003 997

83 024 024 003 997

35 16 055 048 242 971

39 042 033 012 995

65 033 026 003 997

84 029 034 005 996





primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e

















primary air




4s2D thorn s2


P

q (A1)









ef 1047297ciency




quc frac14 32866

LHV

C fa

100 C fa

A (B1)







LHV (B2)






References





















e52








201035628e














(kuprianov 2011) effects of operating conditions and fuel properties on emission performance and...

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