stlucia distillers cogeneration report

7/18/2019 StLucia Distillers Cogeneration Report

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TABLE OF CONTENTS

Part/ Section Page

Abstract 2

Introduction 3

Theory of Steam turbines 4

Steam turbine power cycle 4

Steam turbine classification and type 4

Plant system configuration 5

Electrical system layout

!easibility analysis of cogeneration "

Sample data #$

%onclusions ##

&eference #2

Appendi' #()etailed pro*ect analysis #3



Energy )ynamics +imited( SATIS 2$$5 Presentation

ABSTRACT ON COGENERATION SYSTEM AT ST. LUCIA

DISTILLERS&ichard ,unpat- ./Sc/ 01ech/ Eng

This paper is on the addition of a single stage bac pressure turbine to an e'istingdistillery that uses low pressure steam- but generates it at a higher pressure/ The mainconcern in this pro*ect is matching the electrical demand with the process demand- whilenot being connected to the electrical grid whatsoeer 0stand alone system/

A steam turbine was incorporated by retrofitting the steam mains and directing it to theturbine- thereby producing rotational energy resulting in electrical energy beinggenerated/ The steam is then transmitted to process 0low pressure steam/

This pro*ect was attractie as there was an e'isting source of continuous steam supplyfuel costs are minimal and the cost of electricity is relatiely high/ This maes

cogeneration ideal in this application/

6aste oil from ships was the main fuel used in the boilers/ It is obtained at irtually nocost else the ships would hae to pay to dispose of it/ It is treated before being burnt inthe boiler to remoe water content and other impurities that may affect combustion/ 7ereis a classic e'ample where a company is maing use of aailable source of fuel whichwould otherwise be disposed of and contaminate the earth/

The turbine will generate a fi'ed portion of the facility load since- in this case it is a standalone system and the utility will not allow paralleling with the grid/ The turbine willcontrol on electrical demand and any surplus steam will be bypassed to ent/ In this case

a synchronous generator must be used and the gear ratio optimi8ed to produce thema'imum 6 output with the minimum amount of steam flow/ The e'cess steam wasmarginal and it was used to either heat the feedwater or heat the waste oil in order for it to burn properly/

This pro*ect was to highlight the use of waste oil as a primary fuel bearing in mind thattreatment of it was absolutely essential/ The waste oil has a relatiely high calorific aluecompared to the other fuels- which would mae it burn at a slower rate/ 9ne can estimatethe cost of this fuel as being in the icinity of :S;$/3$ per gallon/ ,ien that the cost of electricity was :S;$/2<= 6h- one can foresee significant saings- een if thecogeneration plant was not feeding the entire distillery/ Simple paybac for this pro*ect

was between #/ to 2 years- with *ust generating 5 6 on ma'imum demand/

In conclusion- there is significant potential for tropical islands to mae use of readilyaailable low cost fuel- which would otherwise be disposed gien that the cost of electricity is relatiely high- in effect the cogeneration potential is substantial andsignificant energy saings can be reali8ed/

%ogeneration at St/ +ucia )istillers 2




SATIS 2!

Cogeneration at St. L"cia Di#ti$$er#% An Energ& So$"tion 'or Di#ti$$erie# in t(e

Cari))ean

Ric(ar* G"n+at

Energ& D&na,ic# Li,ite*

-2 Ba*en Poe$$ Street

oo*)roo01 Port%o'%S+ain

Trini*a* an* To)ago

E,ai$ A**re## ric(ar*3energ&*&na,ic#%$ac.co,

The cost of electricity in the %aribbean Islands is rising at an increasing rate and isamongst the highest across the 6estern 7emisphere/ 9nly recently has there been anagreement where most of the %aribbean Islands can get natural gas at an affordable price/

They hae access to other types of fuels such as diesel oil- +P, and heay oil 0>?- whichthey can use on their boilers- 24 hours a day to generate steam for the distillation process/In this particular application- St/ +ucia )istillers inested in the use of waste oil collectedfrom cruise ships and storage facilities at site/ The primary use of the waste oil 0.uner % was as fuel for the main boiler/ &etrofitting the e'isting system with a bacpressureturbine can offer significant energy saings "+ to US4 -51 annually with a simple paybac of to 627 &ear#/

This paper will briefly describe bacpressure steam turbine technology that can beadopted to proide onsite power generation/ The feasibility of using a bac pressuresteam turbine will be ealuated for St/ +ucia )istillers/

-. Intro*"ction

The steam turbine has been in use for the past century and is aailable in irtually anycapacity ranging from a few 0hp 6 to a seeral hundred 0hp 6/ It is highly reliable-needs little maintenance and e'tremely long serice life/ Steam turbines are custom built-hence efficiency and operating characteristics can be optimi8ed for each application/&etrofitting a steam turbine into a facility@s steam system can be done uite easily-minimi8ing installation costs/ 1ost facilities that hae a steam plant usually are unawareof their potential to cogenerate 0PT%/This paper will proide brief theory and operation of steam turbines with particular focuson bacpressure turbines it will analy8e the steam turbine being the preferred choice for electrical production and present sensitiity analysis based on arying plant operatingconditions/ This information can then be used to proide an indication for distilleries andfacilities in the %aribbean to cogenerate- since the cost of electricity is the %aribbeanislands is generally high/





2. T(eor& o' Stea, T"r)ine#

Steam turbines e'tract heat or .tu@s from steam and transform it into rotational energy bye'panding the steam from high to low pressure- resulting in mechanical wor/ Small andintermediate(si8ed steam turbines are used for a wide range of applications- including

power generation- driers for mechanical serices/ 6hen coupled with gears they can beused to drie fans- reciprocating compressors and other classes of low(speed machinery/The largest turbine applications are generator dries in utility and other central power stations/Since steam can be generated with any type of fuel and in some cases- with recoeredheat- #tea, energ& can o'ten )e +ro*"ce* at a 8er& $o co#t/ Industrial steam turbinescan potentially be applied with any high(pressure steam system and the result is low(to(moderate cost power generation with high reliability- low maintenance 0when added toe'isting steam plants- and e9tre,e$& long life/

2.- Stea, T"r)ine Poer C&c$e#

Steam turbines operate on the &anine %ycle/ This cycle can be reduced to four processes typical in a steam system 0refer to Schematic 2 on page <B

#/ .oiler feedwater 0condensate is pressuri8ed and in*ected into the boiler/2/ 6ater is heated and eaporated in the boiler/ The resulting steam may be

superheated to increase its enthalpy and reduce moisture/3/ Steam is e'panded in the turbine to a lower pressure/ A small portion of the steam

thermal energy is used to drie a generator/4/ Steam is condensed by a cooling medium in the condenser/ In a bac(pressure

turbine- e'haust steam is deliered to a remote heating load- where condensationoccurs/

The steam turbine is considered part of a cogeneration system when an applicationinoles the #e:"entia$ use of a #ing$e source of energy for both power generation anduseful thermal energy output/ These applications are broadly classified as either toppingor bottoming cycles/A topping cycle uses a bac(pressure or e'traction turbine as a pressure(reducing ale/As high pressure steam is e'panded to a lower pressure- the turbine generates shaft power/ A bottoming cycle uses e'cess steam- discharged from a high(pressure process- togenerate shaft power/ .ottoming cycles are also used for applications which dischargehigh(temperature e'haust gas- conert it to steam in a heat recoery steam generator 07&S,- and pass it through a steam turbine/

2.2 Stea, T"r)ine C$a##i'ication an* T&+e#

Steam turbines are classified according to their fundamental operating principles- some of which areB

• Cumber of stagesB single or multi stage

• Cumber of alesB single or multi ale





• Steam supplyB saturated or superheated single or multi pressure

• Turbine stage design classB impulse or reaction

• Steam e'haust conditionsB condensing- non(condensing- automatic e'traction-

mi'ed pressure- regeneratie e'traction or reheat

• Types of drien apparatusB mechanical drie or generator drie

1ore focus will now be emphasi8ed on the single(stage- non(condensing steam turbine asit was the preferred choice in this application/

In a single(stage turbine- steam is accelerated through a no88le or cascade of stationeryno88les and guided into the rotating bucets on the turbine wheel to produce power/ Asingle pressure drop occurs between the no88le inlet and the e'it for the last row of blades/ Single(stage turbines are usually limited to si8es of a few thousand hp 06 or less/ 1echanical efficiency will ary between 3$D to ?$D/ The emphasis on the single(stage design is simplicity- dependability and first low cost/

9ther designs are aailable for higher efficiency generally used for higher steam flows/7oweer the cost and comple'ity can be seeral times that of the single(stage design/Steam turbines can be generally classified as either condensing or non(condensing 0bac( pressure/ A condensing turbine operates with an e'haust pressure less than atmosphericor acuum pressure/ .ecause of the ery low e'haust pressure- the pressure drop throughthe turbine is greater and hence more energy can be e'tracted from the steam flow/ Therecan be a ariety of designs with this type such as straight flow or dual flow/ This type of configuration needs a condenser 0either air or water cooled/ .ecause the unused steamenergy is re*ected to atmosphere by the condenser- it is therefore wasted hencecondensing turbines are generally designed with seeral stages to ma'imi8e efficiency/This design therefore adds increased capital and operating cost/

Con(condensing 0bac(pressure turbines operate with an e'haust pressure eual to or ine'cess of atmosphere/ E'haust steam is used for heating- process or other purposes/.ecause all of the unused steam in the power generation process is passed on to the process application and- therefore- not wasted- mechanical efficiency is not a ma*or concern/

!. P$ant S&#te, Con'ig"ration

As shown in Schematic #- the plant has the basic components necessary for theimplementation of a steam turbine/ There is an e'isting 2$$ 7P .oiler capable of

producing ?-"$$ Pounds Per 7our 0PP7- dry saturated steam/ The bac(pressure steamturbine will replace the e'isting pressure reducing ale/ The e'isting distillery uses low pressure steam at #5 PSI,- but generates it at a higher pressure of #5$ PSI,/ %urrently-there is a total loss of condensate from the process- howeer treated water is passedthrough a heat e'changer to transfer heat from the spent wash- a byproduct from thedistillery process/ The temperature of the feedwater entering the deaerator can approach#<$ !/ The feedwater pump raises the pressure of the feedwater to #5$ PSI, and pumpedto the boiler/ The main fuel used in waste oil with similar properties to Co/ ? oil/ The





boiler is euipped with an electric heater to heat the oil so that it can be atomi8ed easilyin the boiler burner/The ma'imum demand for the process is 3-$$$ PP7 low pressure steam with a baseloaddemand of #-?$$ PP7/

Sc(e,atic -% E9i#ting P$ant Sc(e,atic

%ogeneration at St/ +ucia )istillers ?

2$$ 7P.oiler 3-$$$ PP7

!uel Input> ? 9il

Process+oad2-"$$ PP7#5 PSI,

!eedwater

)eaerator 7ot 6ater fromSpent 6ash7eat E'change

1aeup6ater

!eedwater Pump

2$PSI,

#5$PSI,Sat/ Steam

Pressure(

&educingFale




As shown below in Schematic 2- simple retrofit to the e'isting plant can be done toaccommodate the bac(pressure steam turbine/ The steam turbine will replace thee'isting pressure(reducing ale function by creating a pressure drop with useful shaft power/The boiler pressure will be raised from #5$ PSI, to #<5 PSI, allowing the steam turbine

Ggenerator to produce a net power output of 5 6/ This can safely happen- as the .oiler design pressure is 2$$ PSI,/The e'isting deaerator will hae to be replaced to accommodate an increased condensateflow and to operate under pressure at 2$ PSI,/ It will also hae to handle a steam flow of #-$$$ PP7 at a ma'imum to preheat the feedwater up to 225 !/ The feedwater pumps willhae to handle higher temperatures and as a result will need to be replaced/The e'cess steam will be utili8ed for deaerating the feedwater and thereby remoingdissoled gases preheating the fuel oil prior to being sent to the boiler and the minimale'cess being ented to atmosphere/

Sc(e,atic 2% Pro+o#e* P$ant Sc(e,atic

!.- E$ectrica$ S&#te, La&o"t

%ogeneration at St/ +ucia )istillers <

2$$ 7P.oiler 5-55$ PP7

!uel Input> ? 9il

56

Turbine

Process+oad2-"$$ PP7#5 PSI,

.ypass

!eedwater

)eaerator 7ot 6ater fromSpent 6ash7eat E'change

1aeup6ater

!eedwater Pump

2$PSI,

#<5PSI,Sat/ Steam

E'tra steam to preheat fueloil deaerator




As shown on the Electrical System +ayout for the cogeneration system- this is a standalone system with the steam turbine being coupled to a synchronous generator andfeeding baseloads for the distillery/ 6hen the steam turbine generator is out of serice

%ogeneration at St/ +ucia )istillers




Automatic transfer Switch 2 will transfer power from the utility/ 9n normal mode- thesteam turbine generator will proide power to the distillery@s baseload/ 9n emergencymode- the utility will proide power to the entire facility and when both the steam turbinegenerator and the utility are out of serice- the e'isting diesel generator will proide power/

;. Fea#i)i$it& Ana$&#i# o' Cogeneration

In Appendi' #( )etailed Analysis- different scenarios are gien based on if an inductionor synchronous generator was used how steam usage and annual hours of operationwould affect the economics of the pro*ect/ The cost of fuel was estimated at :S ;$/32 per gallon/ This was based on mainly transporting and storage costs/ ,ien the 7igher 7eating Falue 077F of waste oil as #5$-$$$ .tu=gallon- the cost of waste oil wasaeraged to be :S ; 2/#33 per 11.tu/A conseratie boiler efficiency of $D was used in the analysis/ This was assumed

gien the age and the fact that the boiler uses waste oil as the primary fuel- which whenused reuires that the firetubes be clean freuently/!urther in the analysis- calculations were done to find out the cost of producing #-$$$Pounds of steam based on the heat content of steam/ !inally the cost of producingelectricity from the steam turbine was found based on the e'tra steam reuired togenerate 5 6 0##4 hp/ This was then subtracted from the cost of electricity at :S;$/2"=6h to find the net saings/ !rom the client@s record of steam usage it wasestimated that on ma'imum demand- the distillation process reuires 2-"$$ Pounds per hour 0PP7 of steam/

The Sample )ata shown on Page #$ and ## are e'cerpts from the Appendi' I G )etailedPro*ect Analysis showing best and worst cases for the %ogeneration pro*ect using asynchronous or induction generator/ .oth cases will be e'plained referencing the Sample)ata/

:sing a synchronous generator- which was the preferred choice because of use in standalone or paralleling operation- the e'tra steam reuired to generate power is 2-?5$ PP70"#D more reuiring a total of 5-55$ PP7/ The net saings was then obtained and wasconstant for arying annual hours of operation but arying for e'tra steam reuired/ Thiswas used to simulate if the distillery was taen offline- the effect this would hae on the pro*ect economics/ Alternatiely- the annual hours of operation was aried to simulateconditions of aried operating time/

It can be seen intuitiely that when you ma'imi8e on the annual hours of operation andreuire the least amount of surplus steam to generate electricity the pro*ect has the lowest paybac of 02 years/

4.1 SAMPLE DATA

%ogeneration at St/ +ucia )istillers "




S&nc(rono"# Generator O+tion - G based on 5$ wees annual operation and 2-?5$ PP7e'tra steam reuired to generate 5 6 0best case

Ite, Co#t Ann"a$ Sa8ing# Pa&)ac0 6&ear#7

Steam Turbine ,enerator Pacage ; #55-?$

1echanical 6ors 0estimated ; 5$-$$$

Electrical 6ors Pacage ; 5-$$$

Tota$ 4 2-15< 4 -51==2 -.>=

S&nc(rono"# Generator O+tion 2 G based on 25 wees annual operation and 5-55$ PP7e'tra steam reuired to generate 5 6 0worst case


Steam Turbine ,enerator Pacage ; #55-?$


Electrical 6ors Pacage ; 5-$$$

Tota$ 4 2-15< 4 !1<<2 5.<2

The second set of scenarios inoled the use of an induction generator- which was not the preferred choice as induction generators need to be connected to the grid to receiee'citation/ Cote that the cost of the induction generator is less than the synchronous/7oweer the e'tra steam 0#2#D more reuired is higher than with a synchronousgenerator/ This is because the induction generator as well as the turbine has to run at or near 3-$$$ &P1- for 5$ 78/ A four pole synchronous generator in this case will run at#-5$$ &P1 for 5$ 78/ 7oweer the turbine can run at its best efficiency point- which thegear reducer will reduce to #-5$$ &P1/ In other words- the steam turbine can be selectedto tae more .T:@s from the steam and mae more 6h/

In*"ction Generator O+tion - G based on 5$ wees annual operation and 3-5$$ PP7e'tra steam reuired to generate 5 6 0best case


Steam Turbine ,enerator Pacage ; 4-$42


Electrical 6ors Pacage0estimated

; 3$-$$$

Tota$ 4 -5;1;2 4 >!1?< -.=?

%ogeneration at St/ +ucia )istillers #$




Cote that although the capital cost for the induction generator is lower- the annual saingsis smaller since the e'tra steam reuired is substantially higher- which represents a cost/The paybac is actually smaller but does not gie a realistic picture since the electrical bid pacage was not receied as yet and most liely the induction generator wouldreuire paralleling switchgear- which is more e'pensie/ Estimated costs for the

paralleling switchgear was put at :S ;3$-$$$/$$ as compared to standard automatictransfer switchgear at :S ; 5-$$$/$$

In*"ction Generator O+tion 2 G based on 25 wees annual operation and ?-$$$ PP7e'tra steam reuired to generate 5 6 0worst case


Steam Turbine ,enerator Pacage ; 4-$42


Electrical 6ors Pacage0estimated

; 3$-$$$

Tota$ 4 -5;1;2 4 2=1!> ?.>>

It is important to note that a condensing turbine was not considered in the feasibilityanalysis simply because the capital cost and operating cost of the system would proe thefeasibility uneconomical as the condenser would add additional capital and operationalcost/

?. Conc$"#ion#

The following points can be concluded from this paperB

#/ .ac(pressure steam turbine technology is a worthwhile inestment for facilitiesin the %aribbean where the cost of electricity is high fuel costs are low and thereis an e'isting steam system where high pressure steam is generated/

2/ .ac(pressure steam turbines can be easily retrofitted into an e'isting steamsystem/

3/ The increase in steam usage resulting from cogenerating can be substantial- butwill decrease as the steam system si8e increases/ In summary the minimumamount of steam demand necessary for cogeneration should be in the icinity of3-$$$ PP7/

4/ :sing low cost fuel such as waste oil is one method to reali8e tremendoussaings/ 7oweer treatment of the oil to remoe contaminants must beconsidered/

5/ %ogeneration is ideal for implementation into e'isting facilities that haema'imum annual operating hours and the e'tra steam reuired to cogenerate isminimal/

5. Re'erence#

%ogeneration at St/ +ucia )istillers ##




#/ Petchers- Ceil 02$$3 %ombined heating- cooling and power handbooBtechnologies and applicationsB an integrated approach to energyconseration=resource optimi8ation- !airmont Press- 1arcel )eer/

2/ %asten- Sean and [email protected] ThomasB !ree electricity from steam turbine(

generators/3/ Turbo Steam %orporationB The cost of producing electricity/

%ogeneration at St/ +ucia )istillers #2




APPENDI@ -% DETAILED PROECT ANALYSIS

Scenario 1: Use of synchronous generator; varying annual hours of operation

25 30 35 40 45 50weeks

Cost of Fuel (#6 Oil) $0.32 US$/gal.

Heat Cotet of #6 Oil !50"000 tu/gal

Cost of fuel (#6 Oil) 2.!33 $/tu

oile% effi&ie&' 0.00

Cost of stea (oile% eff. of 5*) 2.66+ $/tu

!000 ,ou- of Stea 0.+ tu

Cost e% !000 ls of stea 2.5+ $/tu

1t%a stea flow %e. togee%ate 5 k 2650 ,,H

Cost to %o-u&e ele&t%i&it' $0.006 $/k

1le&t%i&it' ate 0.2 $/k

Sa7igs $0.204 $/k

8ual ou%s of oe%atio 3000 3600 4200 4800 5400 6000ou%s

Cost of power plant $210,680 $210,680 $210,680 $210,680 $210,680 $210,680$

nnual Savings $!","86 $6#,06" $#,#0 $8!,#18 $%6,0%! $106,2$/'ea%

Sile ,a'a&k "&%! "&2% 2&82 2&# 2&1% 1&%'ea%s

Scenario 2: Use of synchronous generator; varying stea' (e'an(; !0 wee) annual operation




oile% effi&ie&' 0.00Cost of stea (oile% eff. of 5*) 2.66+ $/tu



1t%a stea flow %e. togee%ate 5 k 2650 3000 3500 4000 4500 5550 ,,H

Cost to %o-u&e ele&t%i&it' $0.006 $0.0!3 $0.!065 $0.!2!+ $0.!36 $0.!6$/k


Sa7igs $0.204 $0.!+ $0.!35 $0.!63 $0.!53! $0.!2!!$/k


Cost of power plant $210,680 $210,680 $210,680 $210,680 $210,680 $210,680$

nnual Savings $106,2 $101,"#0 $%",!80 $8!,820 $8,060 $61,6#$/'ea% Sile ,a'a&k 1&% 2&08 2&2! 2&#! 2&0 "&#1'ea%s





Scenario ": Use of in(uction generator; varying annual hours of operation

25 30 35 40 45 50weeks





Cost of stea (oile% eff. of 5 *) 2.66+ $/tu



1t%a stea flow %e. to gee%ate 5 k 3500 ,,H

Cost to %o-u&e ele&t%i&it' $0.!065 $/k


Sa7igs $0.!35 $/k

8ual ou%s of oe%atio 3000 3600 4200 4800 5400 6000 ou%s

nnual Savings $#6,%0 $!6,1#8 $6!,!06 $#,86# $8#,222 $%",!80$/'ea%

Cost of power plant $16#,0#2$16#,0#2$16#,0#2$16#,0#2$16#,0#2 $16#,0#2$

Sile ,a'a&k "&!1 2&%2 2&!0 2&1% 1&%! 1&!'ea%s

Scenario #: Use of in(uction generator; varying stea' (e'an(; !0 wee) annual operation





Cost of stea (oile% eff. of 5 *) 2.66+ $/tu



1t%a stea flow %e. to gee%ate 5 k 3500 4000 4500 5000 5500 6000 ,,H

Cost to %o-u&e ele&t%i&it' $0.!065 $0.!2!+ $0.!36 $0.!522 $0.!6+4 $0.!26$/k


Sa7igs $0.!35 $0.!63 $0.!53! $0.!3+ $0.!226 $0.!0+4$/k


nnual Savings $%",!80 $8!,820 $8,060 $0,"00 $62,!#0 $!#,80$/'ea%

Cost of power plant $16#,0#2$16#,0#2$16#,0#2$16#,0#2$16#,0#2 $16#,0#2$

Sile ,a'a&k 1&! 1&%1 2&10 2&"" 2&62 2&%%'ea%s


stlucia distillers cogeneration report

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