effects of oxygen and steam on the ignition and …ieaghg.org/docs/general_docs/5oxy...

Effects of Oxygen and Steam On the Ignition and Flame Propagation Properties of

Demineralized Coal Particles

Shaozeng Sun, Shun Meng, Rui Sun, Dong Wang, Yue Zhang, Huanhuan Xu,

Mo Liu, Yukun Qin Combustion Engineering Research Institute,

Harbin Institute of Technology, ChinaNational Engineering Laboratory for Reducing

Emissions from Coal Combustion, China

Combustion Engineering Research Institute, Harbin Institute of Technology

National Engineering Laboratory for Reducing Emissions from Coal Combustion

Combustion Engineering Research Institute (CERI), Harbin Institute of Technology

National Engineering Laboratory for Reducing Emissions from Coal Combustion (NELRECC)

Outline

Oxy-coal combustion steam system of near-zero emissions Technology BackgroundOxy-coal combustion steam system

Ignition properties of demineralized coal particles Conclusions



Technological Background

Climate warming CCS Technology Improve the efficiency of fossil fuel

usage

New Concepts and Technologies 3rd generation oxy-fuel systems (Hydroxy-Fuel)

CANMET Energy Technology Centre, CanadaChun Zou et al. HUST, China

CES combustion system (water recycle)Clean Energy Systems, Inc., USA

Oxy-coal combustion steam system Harbin Institute of Technology, China

CHINAAMERICA

INDIARUSSIA

JAPAN

GERMANYKOREA

CO

2E

mis

sion

s/G

t

IEA

w/o CO2Capture w CO2Capture



CES combustion system (water recycle)

Advanced Steam Generators [1]

[1] Richards GA, et al. NETL. CO2 and H2O diluted oxy-fuel combustion for zero-emission power.

Water recycle (replacement of flue gas recycle)

Steam moderates the combustion temperatures

Steam is directly heated in the oxy-fuel flame

High pressure high temperature flue gas as a working medium for turbine

Technological Background



Oxy-coal combustion steam system of near-zero emissions

Excess H2O

Advanced Turbine

Storage/EOR

CO2 Recovery

recycled H2O

Water Processor

CO2

O2

Demineralization

Hyper-coal

Grid

Coal

Condenser

Generator

Oxy-coal combustion steam system (OCCSS)Ash-less coal (or syngas) burnswith pure oxygen and water,directly heating the water andgenerating flue gas (a mixture of~90% of steam and ~10% ofCO2) of high temperature andhigh pressure. The mixture, ascompound working media,drives an advanced turbinedirectly. After work is done, themixture is cooled down andsteam is condensed, and liquidwater & high concentration CO2are obtained. In this way lowcost CO2 capture is realized。




Excess H2O

Advanced Turbine

Storage/EOR

CO2 Recovery

recycled H2O

Water Processor

CO2

O2

Demineralization

Hyper-coal

Grid

Coal

Condenser

Generator

Oxy-coal combustion steam system (OCCSS)

Combustion Characteristics： High Temperature High Pressure, High H2O concentration, High O2 concentration

(“Four High” condition)

Turbine requirement: High Temperature,Multi-working fluid (CO2/H2O)



Plant Operating Factors

Hydroxy-Fuel

CES (based on coal

gasification)[1]OCCSS IGCC w

CO2[2]

USC Oxy-fuel [3]

Net Plant Thermal Efficiency 35 50.7 53.4 39 35.4

Emissions of CO2（kg/MWh） 0 0 0 83 83.7

Capital Cost (US $/kW) - 1210 - 1642 1857Cost of Electricity

（$/kWh） - 0.054 - 0.069 0.062


Efficiency comparison

[1]. Marin O., et al. Proc. 28th Intern. Tech. Conf. Coal Util. Fuel Systems, Cl, March, 2003. [2]. EPRI Report, Interim Report #1000316, Dec., 2000.[3]. Dillon D., et al. Proc 7th Intern. Conf. Greenhouse Gas Control Technol, 2005.

OCCSS and CES technologies have distinct advantage over IGCC and USC Oxy-fuel technologies. OCCSS eliminates the coal gasification process and has a higher efficiency.



FuelAsh+H2O+Pure

coal

Air

H2O

Flue gas CO2+N2 Medium

H2O

Boiler

Material flow

Energy

OxygenCO2+H2O

Turbine

CO2/O2/CO

Combustor

发电机

Chemical EnergyWorking enthalpyThermal Energy Mechanical Energy Electric Energy

H2O

H2O

CO2+H2O

Condenser

CO2/O2/CO/SOx/NOx/PM/Heavy Metals

Steam turbine Generator

Ordinary Rankine Cycle

OCCSSAsh+S +

Heavy Metal

Fuel

H2O+Pure coal

Material flow and energy conversion processes

Demineralization

H2O

Condenser

GeneratorMaterial flow

Energy

Flue gasenthalpy

Thermal Energy Mechanical Energy Electric EnergyWorking enthalpy

Chemical Energy



Using demineralized coal → eliminates mineral impurities & pollutant before the combustion

Oxy-fuel guarantees the flue not be diluted by N2 → reduces the difficulties of capturing CO2

Products of combustion (CO2 & steam) → drive the turbine to work Higher parameters leads to higher efficiency.

advantages of high P of steam turbine & high T of GT The boiler that transforms the enthalpies between flue & medium is avoided → lowers

the cost of manufacture. Wall-type heat exchanger (boiler) is with low efficiency & large volume. Expensive materials are needed for higher steam parameters.

High concentration of CO2 are obtained directly by cooling the working medium →lowers the cost of capture

.

Direct Transformation from Chem. Engy. to Working Enth.

The fuel, oxidant, medium for T control & working should be mixed & burns properly for the efficient transformation of energy in the same space.



Combustion Efficiency？

Combustion kinetics

H2O vs. Flame？Ignition, stability, flame propagation

More Clean, Safer？Nitrogen, sulfur

evolution mechanism

The new combustion environment, many scientific issues need to explain

Volatile combustioncoal Devolatilization Char

combustion Burnout and cooling

H2O

Deminera-lized coal

O2/H2O

O2/H2O

char

CH4

H2O

O2H2O

CO

NHi

CO2CO2

char

H2O

H2O H2O CO2NO

CO

H2OH2O H2O

H2O CO2

charO2

CO

CO CO

CO2

CO2

CO2

CO2

H2O

H2O

Demineralized coal combustion at O2/H2O atmosphere



The ignition properties of demineralized coal particles

Schematic diagram of DTF

CCD

Experimental setup



Schematic diagram of particle feeder (1-30g/h)

Experimental approaches

Stepper motor

Reducer

Coupling

Lead rail

Syringe

Glass container

Shaker

Carried gas

Screw rod




HCl-HF-HCl treatment method

Demineralized coal sample Sample

Proximate analysis (air dry basis, wt.%)

Structural parameters

Aad FCad Vadsurface area

SHg(m2/g)pore volumeVHg(cm3/g）

Porosityε(%)

Zhundongcoal 6.09 44.58 49.33 4.36 0.64 44.33

ZD deminerali

zed coal0.34 66.47 33.19 4.40 0.91 52.43

Yimin coal 14.14 47.13 38.73 6.403 0.7493 47.1295

Yimindeminerali

zed coal0.18 45.18 54.64 8.050 1.0273 58.9266

With the HCl-HF-HCl treatment, the mineral matter that embedded in the coal surface or inside the particles breaks down and dissolves in the solution, which makes the pore structure of demineralized coal more complicated. Hg surface area, pore volume and porosity are larger than those of raw coal.




Defination - Ignition temperature

Ignition temperature is determined by a minimum furnace temperature at which ignition cccurs, which is obtained by increasing the furnace temperature


0 2 4 6 8 10620

640

660

680

700

720

Tem

pera

ture

/ ℃

Furnace centerline

Before feedAfter feed

by 0.5 degrees until the ignition of pulverized coal is detected. Furnace centreline temperature is measured and is compared with the blank centreline temperature (with no coal feeding). The separation point of two curves is defined as the ignition position and the corresponding temperature is defined as the ignition temperature.



Defination - ignition delay time The ignition delay time is defined from the

moment that particles are injected into the furnace to critical ignition point. The average particle ignition delay time and luminous area of all the particles were calculated statistically.




Effects of oxygen and steam on the ignition temperature

10 20 30 40 50500

550

600

650

700

750

800

850

900

950 Zhundong demineralized coal Yimin demineralized coal

igni

tion

tempe

ratu

re/℃

Oxygen concentration/%

steam: 30%

10 20 30 40 50580600620640660680700720740760780

Zhungong demineralized coal Yimin demineralized coal

igni

tion

tempe

ratu

re/℃

steam concentration/%

oxygen: 30%




Effects of oxygen concertration on the Ignition

a) 20%O2 b) 30%O2 c) 40%O2 d) 50%O2Ignition phenomena of particles vs. O2 concentration

20 30 40 500

20

40

60

80

100

igni

tion

flam

e are

a/m

m2

igni

tion

delay

tim

e/ms

oxygen concentration/%

0.0

0.5

1.0

1.5

2.0

Oxygen concentration has a significant impact on the ignition of demineralized coal particles. Ignition delay time reduces from 85ms to 9ms . Besides, the change of ignition mode from heterogeneous to non-heterogeneous ignition occurs while oxygen concentration is higher than 20%.




10 20 30 40 50

20

30

40

50

60

70

steam concentration/%

Zhundong demineralized coal Yimin demineralized coal

igni

tion

delay

tim

e /ms

When steam concentration increases from 10% to 30%, steam promotes the ignition of demineralized coal, and the ignition delay time decrease; when steam concentration is higher than 30%, the inhibition effect of steam on the ignition is dominant.

Effects of steam on the Ignition

a)10%H2O b)20%H2O c)30%H2O d)40%H2O e)50%H2OIgnition phenomena of particles vs. H2O concentration




Demineralized coal particle size has little influence on ignition phenomena as the luminous area of individual particles does not change significantly. Ignition delay time increases with the increase of particle size slowly. it is considered that non-heterogeneous ignition is the main ignition mechanism for diameter range of 0-120μm in 30%H2O and 30%O2 condition.

Effects of particle size on the Ignition


<32 32-53 53-80 >800

10

20

30

40

50

60

particle size/μm

igni

tion

time/ms

zhundong Yi min



Oxy-coal combustion steam system (OCCSS) eliminates a costful boiler and avoids un-efficient heat transfer and has a energy conversion efficiency over 50% with potentials of zero cost of CO2 capture, and is a interesting technology to develop.

Ignition delay time reduces from 85ms to 9ms as oxygen concentration increases from 20% to 50%. Besides, the ignition mode change from heterogeneous to non-heterogeneous ignition occurs while oxygen concentration is higher than 20%.

Conclusions



When steam concentration increases from 10% to 30%, steam promotes the ignition of demineralized coal, and the ignition delay time decrease; when steam concentration is higher than 30%, the inhibition effect of steam on the ignition is dominant.

Conclusions



Combustion Efficiency？

Combustion kinetics

H2O vs. Flame？Ignition, stability, flame propagation

More Clean, Safer？Nitrogen, sulfur

evolution mechanism

The new combustion environment, many scientific issues need to explain

Volatile combustioncoal Devolatilization Char

combustion Burnout and cooling

H2O

Deminera-lized coal

O2/H2O

O2/H2O

char

CH4

H2O

O2H2O

CO

NHi

CO2CO2

char

H2O

H2O H2O CO2NO

CO

H2OH2O H2O

H2O CO2

charO2

CO

CO CO

CO2

CO2

CO2

CO2

H2O

H2O

Demineralized coal combustion at O2/H2O atmosphere



Flame propagation velocity of demineralized pulverized coal in O2/H2O atmosphere;

Pyrolysis characteristics of demineralized pulverized coal ; Combustion characteristics of the main combustible

components(CO/H2/CH4 mixture) under “four high” conditions.

The evolution of nitrogen and sulphur related components during combustion under high steam concentration.

Future research



Schematic diagram of pulverized coal clouds combustion bomb(20 L)Maximum pressure : 10Mpa, Initial temperature: 25-220℃

Pressuretransducer

High speed camera

Timer RelaySolenoid valve

Ignitionline

pulverized coal

Coal dispersiongas

Flame propagation of demineralized coal particles Experimental setup

Electrically heated



Ignition Electrodes and control system:

Experimental approaches

High-sensitivity CCD cameraPCO.1200s: frame rate 1000 fps

Maximum Ignition energy: 3kJ

Flame propagation of demineralized coal particles



Flame propagation process of pulverized coal clouds (<100um, 800g/m3)

t=6ms t=8ms

2 4 6 8 10 1210

20

30

40

Flam

e ra

dius

r (m

m)

t (ms)

left right left 45° right 45°

t=2ms t=4ms

Date process method

Flame radius changes in the four directions

maximum pressure maximum pressure increase rate

Explosion time

Flame propagation of demineralized coal particles



Contact UsContact:Shaozeng SUN, Doctor of EngineeringProfessor and Deputy Director, Combustion Engineering Research Institute, Harbin

Institute of TechnologyDirector, National Engineering Laboratory for Reducing Emissions from Coal

CombustionTel: +86 (0)451 86412238Mobile: +86 (0)13503621454Email: [email protected]

Thank you for your attention !



10g of pulverized coal were used in each treatment. In order to dissolve the phosphates and carbonates, the coal sample was treated in a 500ml glass reactor with 200ml 36% HCl in the water bath at 60℃for 3h. The sample was filtered and washed with pure water for 3~5 times to remove the residual chemicals. Then, the sample was put in a 500 ml plastic reactor with 200ml 40% HF in the water bath at 60℃ for 3h. Repeat the filtering and washing in the previous process, then the sample was treated with 36% HCl again. After filtering, the sample was washed with distilled water until there is no Cl- which is measured by AgNO3 solution. Finally, the demineralized coal sample was dried in a calorstat at 40 ℃ for 3h and the demineralized coal sample is obtained.

Source: H Zhang, et al, Journal of Engineering Thermophysics 8 (2009) 699-702

HCl-HF-HCl treatment method

effects of oxygen and steam on the ignition and …ieaghg.org/docs/general_docs/5oxy...

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