modeling and optimization of processes of bioethanol production with mixed integer process...

Modeling and optimization of processes of bioethanol

production with Mixed Integer Process SYNthesizer

MIPSYN

Summer Workshop, Veszprém 2009

Faculty of Chemistry and Chemical EngineeringUniversity of Maribor, Slovenia

Lidija Čuček, Zdravko Kravanja


WHY BIOETHANOL ??

1. Fossil fuels are non-renewable

2. Growing concern about global warming3. Possible disruption in oil supply 4. Alternative to gasoline, renewable energy5. The most important long-term objectives of the European Union and United States in the energy sector are:- Achieving independence of fossil fuel energy supplies- Achieving substantial improvement of energy efficiency of the whole supply chain from production, distribution, to consumption, while minimizing emissions and waste- Achieving 20 % increase in the share of renewable energy (RES) by 2020- The share of renewable energy in all modes of transport has to be at least 10 % by 2020


RAW MATERIALS

Bioethanol can be produced by fermentation of:- Sugars (molasses),- Starchy raw materials (corn, potato)- Lignocellulose (wood, agricultural residues, municipal solid waste)

First-generation biofuels: produced by fermentation of plants containing starch or sugar. This production has a lot of downsides: plants are mainly food crops, affection of the supply of population with food products, limited quantity, affecting biodiversity, may cause more GHG than fossil fuels, using chemicals for plant production, impact on drinking water supply,...

Third-generation biofuels: produced from algae, sigle-celled aquatic organisms.

Second-generation biofuels: produced by fermentation of lignocelluloses (agricultural residues, forestry waste, fast-growing energy crops...). Many technical and economic issues related to their use before 2020.

http://upload.wikimedia.org/wikipedia/commons/8/85/Cornfield_in_South_Africa2.jpg


OUR GOAL

Problems with using bioethanol:- Usage requires modifications to the engines- Consumption in engines is about 51 % higher compared to gasoline- Costs for bioethanol production are very high (investment, costs of raw materials , etc.)

Therefore it is necessary to develop effective, economical and environment friendly technologies of bioethanol production.

Consumption of raw materials, energy and water should be very carefully analyzed, planed and optimized.

Development and application of optimization methods are becoming necessary in the technique.

Goal: Detailed synthesis and optimization of various production processes of bioethanol production from different raw materials.


GENERAL OVERVIEW OF WORK

Modeling and optimization was performed for ethanol

production from:- starchy raw materials (corn, potato), dry milling process- sugars (molasses), direct fermentation- lignocelluloses:

i) from corn stover, acid prehydrolysis and enzymatic hydrolysis

ii) from wheat straw, ammonia fiber explosion (AFEX) and

iii) from wood chips, gasification and subsequent fermentation of the produced syngas

Superstructures of the processes are modeled as MINLP problems, which include both discrete (topology) and continuous variables (operating conditions, dimensions of the process units).

Synthesis was caried out with and without heat integration.

Different alternatives with respect to the separation of solids and liquids and alternatives to the dehydration of ethanol.


STARCH-BASED PROCESS


SUGAR-BASED PROCESS


ACID PREHYDROLYSIS PROCESS


AFEX PROCESS


THERMOCHEMICAL PROCESS


MIPSYN

• The computer package MIPSYN enabled us to optimize the chemical processes

Processes producing fuel ethanol from biomass are biochemical processes.

Completion of MIPSYN’s library PROSLIB with modules for synthesis of the biochemical processes

• package performs MINLP optimization on superstructures for process flowsheet • enables automated execution of simultaneous topology and parameter optimization of processes

Optimization was performed with equation-oriented process synthesizer MIPSYN.

Modified OA/ER algorithm and modeling and decomposititon (M/D) strategy

_.exe


MODUL - WASHER

* ===========================* = W A S H I N G =* ===========================

EQUATIONS WASHWA(WASH,COMPON) TOTAL STREAM OF WASHING WATER WASHCB(WASH,COMPON) COMPONENT BALANCE AT WASHING WASHT(IN,WASH) INLET TEMPERATURE RELATION AT WASHING WASHP(IN,WASH) INLET PRESSURE RELATION AT WASHING WASHSIZE(WASH) SIZE VARIABLE ;

WASHWA(WASH,COMPON)$EXIST(WASH).. F('IN-2',WASH) =E= WASHMIN*WASHFRAC*F('IN-1',WASH);

WASHCB(WASH,COMPON)$EXIST(WASH).. FC('OUT-1',WASH,COMPON) =E= SUM(IN$RELIOB(IN,WASH),FC(IN,WASH,COMPON));

WASHT(IN,WASH)$(RELIOB(IN,WASH)AND EXIST(WASH)).. T('OUT-1',WASH) =E= T(IN,WASH);

WASHP(IN,WASH)$(RELIOB(IN,WASH)AND EXIST(WASH)).. P('OUT-1',WASH) =E= P(IN,WASH);

WASHSIZE(WASH)$EXIST(WASH).. sizes(wash)*SIZE(WASH) =E= AREA(WASH) ;


MODUL – FLOTATION UNIT

* ===========================* = F L O T A T I O N =* ===========================

EQUATIONS FLOTCBH(FLOT) COMPONENT BALANCE FOR HYDROPHOBIC MOLECULE FLOTCBM(FLOT) COMPONENT BALANCE FOR WATER IN TOP FLOTCB(FLOT,COMPON) COMPONENT BALANCE FOR FLOTATION FLOTT(OUT,FLOT) TEMPERATURE RELATION FOR OUT FLOTP(OUT,FLOT) PRESSURE RELATION FOR OUTLET FLOTSIZE(FLOT) SIZE VARIABLE ;

FLOTCBH(FLOT)$EXIST(FLOT).. FC('OUT-1',FLOT,'PROT') =E= FLOTREC*FC('IN-1',FLOT,'PROT');

FLOTCBM(FLOT)$EXIST(FLOT).. FC('OUT-1',FLOT,'WA') =E= FLOTREC*FLOTMOIST*FC('IN-1',FLOT,'PROT');

FLOTCB(FLOT,COMPON)$EXIST(FLOT).. FC('OUT-2',FLOT,COMPON) =E= FC('IN-1',FLOT,COMPON)-FC('OUT-1',FLOT,COMPON);

FLOTT(OUT,FLOT)$(EXIST(FLOT) AND RELIOB(OUT,FLOT)).. T(OUT,FLOT) =E= T('IN-1',FLOT);

FLOTP(OUT,FLOT)$(EXIST(FLOT) AND RELIOB(OUT,FLOT)).. P(OUT,FLOT) =E= P('IN-1',FLOT);

FLOTSIZE(FLOT)$EXIST(FLOT).. sizes(flot)*SIZE(FLOT) =E= F('IN-1',FLOT)*fs*3.6;


MODUL – ADSORBER I * =============================* = A D S O R P T I O N =* =============================

EQUATIONS ADSSIZE(ADS) REQUIRED BED SIZE ADSMBETHO(ADS,COMPON) FLOW BALANCE FOR ETHANOL FOR OUTLET ADSCBOUT(ADS,COMPON) COMPONENT BALANCE FOR OUTLET 2 ADSCBWA(ADS,COMPON) COMPONENT BALANCE FOR NON-ADSORBED WATER ADSCBWAADS(ADS,COMPON) COMPONENT BALANCE FOR ADSORBED WATER ADSTB(ADS) TOTAL BALANCE FOR ADSORBENT ADSCB(ADS,COMPON) ADDITIVE COMPONENT BALANCE IN ADSORBER ADSFCPH(ADS,COMPON) evaluation of FCPH QHPEQ(ADS) ENTHALPY OF STREAM ADSHB(ADS) HEAT BALANCE ADSP1(ADS) PRESSURE RELATION FOR OUTLET 1 ADSP2(ADS) PRESSURE RELATION FOR OUTLET 2 ADST(OUT,ADS) TEMPERATURE RELATION ;

ADSSIZE(ADS)$(EXIST(ADS) AND (NOT MILP)).. SIZE(ADS)*sizes(ads) =E= ADSSATTIME*F('IN-2',ADS)*fs$BATINCLUDE "P_LINEAR.INC" ADS ;

ADSMBETHO(ADS,COMPON)$(EXIST(ADS) AND (ORD(COMPON) EQ 6)).. FC('OUT-1',ADS,COMPON) =E= FC('IN-1',ADS,COMPON);

ADSCBOUT(ADS,COMPON)$(EXIST(ADS) AND (ORD(COMPON) NE 1) AND (ORD(COMPON) NE 6)).. FC('OUT-2',ADS,COMPON) =E= FC('IN-2',ADS,COMPON);

ADSCBWA(ADS,COMPON)$(EXIST(ADS) AND (ORD(COMPON) EQ 1) AND (NOT MILP)).. FC('OUT-1',ADS,COMPON) =E= (1.-ADSREMWA)*FC('IN-1',ADS,COMPON)$BATINCLUDE "P_LINEAR.INC" ADS ;


MODUL – ADSORBER II

ADSCBWAADS(ADS,COMPON)$(EXIST(ADS) AND (ORD(COMPON) EQ 1) AND (NOT MILP)).. FC('OUT-2',ADS,COMPON) =E= ADSREMWA*FC('IN-1',ADS,COMPON)+ FC('IN-2',ADS,COMPON)$BATINCLUDE "P_LINEAR.INC" ADS ;

ADSTB(ADS)$(EXIST(ADS) AND (NOT MILP)).. F('IN-2',ADS)*fs =E= (1./ADSPOT)*ADSREMWA*FC('IN-1',ADS,'WA')*fcs('wa')$BATINCLUDE "P_LINEAR.INC" ADS ;

ADSCB(ADS,COMPON)$EXIST(ADS).. SUM(OUT$RELIOB(OUT,ADS), FC(OUT,ADS,COMPON)) =E= SUM(IN$RELIOB(IN,ADS), FC(IN,ADS,COMPON));

ADSFCPH(ADS,COMPON)$(EXIST(ADS) AND (ORD(COMPON) EQ 1)).. FCPH(ADS)*fcphs(ads) =E= FC('IN-1',ADS,COMPON)*fcs(compon) * DHADS;

QHPEQ(ADS)$(EXIST(ADS) AND (NOT MILP)).. QHP(ADS)*qhps(ads) =E= ADSREMWA* FCPH(ADS)*fcphs(ads)$BATINCLUDE "P_LINEAR.INC" ADS ;

ADSHB(ADS)$(EXIST(ADS) AND (NOT HIFL) AND (NOT HENFL)).. QC(ADS)*qcs(ads) =E= 3600. * NHOUR * 1.0E-9 * QHP(ADS)*qhps(ads);

ADSP1(ADS)$EXIST(ADS).. P('OUT-1',ADS) =E= P('IN-1',ADS);

ADSP2(ADS)$EXIST(ADS).. P('OUT-2',ADS) =E= P('IN-1',ADS);

ADST(OUT,ADS)$(EXIST(ADS) AND RELIOB(OUT,ADS)).. T(OUT,ADS) =E= T('IN-2',ADS);


MODUL – RECTIFIER COLUMN I

* =====================================* = R E C T I F I E R C O L U M N =* =====================================

EQUATIONS RECCB(REC,COMPON) ADDITIVE COMPONENT BALANCE IN RECTIFIER COLUMN RECTOPH(REC,WE) COMPONENT BALANCE FOR HEAVY KEY - TOP RECTOPL(REC,WE) COMPONENT BALANCE FOR LIGHT KEY - TOP RECBOTH(REC,WE) COMPONENT BALANCE FOR HEAVY KEY - BOTTOM RECBOTL(REC,WE) COMPONENT BALANCE FOR LIGHT KEY - BOTTOM RECPT(REC) OUTLET PRESSURE RELATION (TOP) RECPB(REC) OUTLET PRESSURE RELATION (BOTTOM) NTHEOREC(REC) THEORETICAL NUMBER OF TRAYS NACTREC(REC) ACTUAL NUMBER OF TRAYS RECMFTOP(REC,WE) RELATION OF MOL AND MASS FRACTIONS FOR OUT TOP RECANTATOP(REC,WE) ANTOINE EQUATION FOR OUT TOP RECMFBOT(REC,WE) RELATION OF MOL AND MASS FRACTIONS FOR OUT BOTTOM RECANTABOT(REC,WE) ANTOINE EQUATION FOR OUTLET BOTTOM RECMFCL(REC) MOL FRAC IN THE CONDENSED VAPOR FOR LIGHT RECMFCH(REC) MOL FRAC IN THE CONDENSED VAPOR FOR HEAVY RECXC(REC,WE) RELATION OF MOL AND MASS FRACTION IN THE CONDENSER CONDHVREC(REC,WE) HEAT OF VAPORIZATION OF COMPONENTS IN CONDENSER FCPHREC(RECC) evaluation of FCPH IN CONDENSER QCONDREC(RECC) ENTHALPY OF HOT STREAM IN CONDENSER RECCONDHB(RECC) HEAT BALANCE IN CONDENSER REBHVREC(REC,WE) HEAT OF VAPORIZATION OF COMPONENTS IN REBOILER FCPCREC(RECR) evaluation of FCPC IN REBOILER QREBREC(RECR) ENTHALPY OF COLD STREAM IN REBOILER RECREBHB(RECR) HEAT BALANCE IN REBOILER RECSIZE(REC) SIZE VARIABLE ;


MODUL – RECTIFIER COLUMN II

RECCB(REC,COMPON)$EXIST(REC).. SUM(OUT$RELIOB(OUT,REC), FC(OUT,REC,COMPON)) =E= FC('IN-1',REC,COMPON);

RECTOPH(REC,WE)$(EXIST(REC) AND DHKEY(REC,WE) AND (NOT MILP)).. FC('OUT-1',REC,WE) =E= DHREC(REC)*FC('IN-1',REC,WE)$BATINCLUDE "P_LINEAR.INC" REC ;

RECTOPL(REC,WE)$(EXIST(REC) AND DLKEY(REC,WE)).. FC('OUT-1',REC,WE) =E= DLREC(REC)*FC('IN-1',REC,WE);

RECBOTH(REC,WE)$(EXIST(REC) AND DHKEY(REC,WE) AND (NOT MILP)).. FC('OUT-2',REC,WE) =E= (1.-DHREC(REC))*FC('IN-1',REC,WE)$BATINCLUDE "P_LINEAR.INC" REC ;

RECBOTL(REC,WE)$(EXIST(REC) AND DLKEY(REC,WE)).. FC('OUT-2',REC,WE) =E= (1.-DLREC(REC))*FC('IN-1',REC,WE);

RECPT(REC)$EXIST(REC).. P('OUT-1',REC) =E= P('IN-1',REC);

RECPB(REC)$EXIST(REC).. P('OUT-2',REC) =E= P('IN-1',REC);

NTHEOREC(REC)$(EXIST(REC) AND (NOT MILP)).. NTHEO(REC) =E= LOG((DLREC(REC)/(1.-DLREC(REC)))*((1-DHREC(REC))/DHREC(REC)))/LOG(AVEVLT)$BATINCLUDE "P_LINEAR.INC" REC ;

NACTREC(REC)$(EXIST(REC) AND (NOT MILP)).. NACT(REC) =E= (NTHEO(REC)-1.)/TRAYEFF$BATINCLUDE "P_LINEAR.INC" REC ;


MODUL – RECTIFIER COLUMN III

RECMFTOP(REC,WE)$(EXIST(REC) AND (NOT MILP)).. MF('OUT-1',REC,WE)*SUM(WE1, FC('OUT-1',REC,WE1)/MOLWT(WE1)) =E= FC('OUT-1',REC,WE)/MOLWT(WE)$BATINCLUDE "P_LINEAR.INC" REC ;

RECANTATOP(REC,WE)$(EXIST(REC) AND (NOT MILP) AND DLKEY(REC,WE)).. EXP(ANTA(WE)-ANTB(WE)/(ANTC(WE)+ T('OUT-1',REC)*100.)) =E= (P('OUT-1',REC)-DP/2.)*7600.* (MF('OUT-1',REC,'WA')*AVEVLT + MF('OUT-1',REC,'ETHO'))$BATINCLUDE "P_LINEAR.INC" REC ;

RECMFBOT(REC,WE)$(EXIST(REC) AND (NOT MILP)).. MF('OUT-2',REC,WE)*SUM(WE1, FC('OUT-2',REC,WE1)/MOLWT(WE1)) =E= FC('OUT-2',REC,WE)/MOLWT(WE)$BATINCLUDE "P_LINEAR.INC" REC ;

RECANTABOT(REC,WE)$(EXIST(REC) AND (NOT MILP) AND DHKEY(REC,WE)).. EXP(ANTA(WE)-ANTB(WE)/(ANTC(WE)+ T('OUT-2',REC)*100.))* (MF('OUT-2',REC,'WA') + AVEVLT*MF('OUT-2',REC,'ETHO')) =E= (P('OUT-2',REC)+DP/2.)*7600.

$BATINCLUDE "P_LINEAR.INC" REC ;

RECMFCL(REC)$(EXIST(REC) AND (NOT MILP)).. MFC(REC,'ETHO') =E= MF('OUT-1',REC,'ETHO')*(P('OUT-1',REC)-DP/2.)*7600./ EXP(ANTA('ETHO')-ANTB('ETHO')/(ANTC('ETHO')+T('OUT-1',REC)*100.))$BATINCLUDE "P_LINEAR.INC" REC ;

RECMFCH(REC)$EXIST(REC).. MFC(REC,'WA') =E= 1.- MFC(REC,'ETHO') ;


MODUL – RECTIFIER COLUMN IV

RECXC(REC,WE)$(EXIST(REC) AND (NOT MILP)).. XC(REC,WE)*SUM(WE1,MFC(REC,WE1)*MOLWT(WE1)) =E= MFC(REC,WE)*MOLWT(WE)$BATINCLUDE "P_LINEAR.INC" REC ;

CONDHVREC(REC,WE)$(EXIST(REC) AND (NOT MILP)).. DHV('OUT-1',REC,WE) =E= (HV(WE)/MOLWT(WE))* ((TC(WE)-T('OUT-1',REC)*100.)/(TC(WE)-TB(WE)))**NWATSON$BATINCLUDE "P_LINEAR.INC" REC ;

FCPHREC(RECC)$SUM(REC$(ORD(REC) EQ ORD(RECC)), EXIST(REC) AND (NOT MILP)).. fcphs(recc)*FCPH(RECC) =E= SUM(REC$(ORD(REC) EQ ORD(RECC)), F('OUT-1',REC)*fs*REFLUX* SUM(WE, XC(REC,WE)*DHV('OUT-1',REC,WE)))$BATINCLUDE "P_LINEAR.INC" RECC ;

QCONDREC(RECC)$SUM(REC$(ORD(REC) EQ ORD(RECC)), EXIST(REC) AND CONDFL(RECC)).. QHP(RECC)*qhps(recc) =E= fcphs(recc)*FCPH(RECC)*100.*0.01;

RECCONDHB(RECC)$SUM(REC$(ORD(REC) EQ ORD(RECC)), EXIST(REC)).. QC(RECC) =E= 3600.*NHOUR*1.0E-9 * QHP(RECC)*qhps(recc);

REBHVREC(REC,WE)$(EXIST(REC) AND DHKEY(REC,WE) AND (NOT MILP)).. DHV('OUT-2',REC,WE) =E= (HV(WE)/MOLWT(WE))*((TC(WE)-T('OUT-2',REC)*100.)/ (TC(WE)-TB(WE)))**NWATSON$BATINCLUDE "p_linear.inc" REC ;

FCPCREC(RECR)$SUM(REC$(ORD(REC) EQ ORD(RECR)), EXIST(REC) AND (NOT MILP)).. FCPC(RECR)*fcpcs(recr) =E= SUM(REC$(ORD(REC) EQ ORD(RECR)),(F('OUT-1',REC)*fs*REFLUX-F('OUT-2',REC)*fs)* SUM(WE$DHKEY(REC,WE), DHV('OUT-2',REC,WE)))$BATINCLUDE "P_LINEAR.INC" RECR ;


MODUL – RECTIFIER COLUMN IV

QREBREC(RECR)$SUM(REC$(ORD(REC) EQ ORD(RECR)), EXIST(REC) AND EVAPFL(RECR)).. QCP(RECR)*qcps(recr) =E= 100.*0.01*FCPC(RECR)*fcpcs(recr);

RECREBHB(RECR)$SUM(REC$(ORD(REC) EQ ORD(RECR)), EXIST(REC)).. QH(RECR) =E= 3600.*NHOUR*1.0E-9 * QCP(RECR)*qcps(recr);

RECSIZE(REC)$EXIST(REC).. SIZE(REC)*sizes(rec) =E= VOLUME(REC);


INPUT AND OUTPUT FILES

The high level language GAMS (General Algebraic Modeling System) is interface for mathematical modeling with MIPSYN. Input and output files are written in GAMS language.

User has to define (input files):1.) the superstructure (p_struct)2.) all data (datalib.gms)3.) list of chemical components (p_compon)4.) physical properties of components (if component is not defined) (compon)5.) initialization scheme for non-existing modules in process flowsheet (initlib.gms)6.) the additional modules equations (my_model.dat)7.) components and their physical properties (p_dbase.lib).

Output files: p_w.lst (listing file) optimum.res (optimal solution) p_b.res (MINLP iterations)

Gams.lnk


OPTIMIZATION

nSaaQcQcqcqcP /)( 21cchhreacr

rrprodp

ppmax

Product mass flow Price of product

Price of raw material

Raw material mass flow

Utility price

Need of utility

Raw material mass flow (corn, potato, molasses, etc.): 18 kg/sNumber of annual working hours: 8500

Objective: maximizing the profit

Depreciation

Depreciation period

Profit

Investment was estimated by programme Aspen Icarus 2006.5.

Solvers: for NLP suboptimization: local optimizer CONOPT 3, for MILP optimization: optimizer GAMS/CPLEX 10.1.


RESULTS

Annual profit before taxes:

CORNPOTATOES

MOLASSESCORN STOVER

WHEAT STRAWWOOD CHIPS

0

10000

20000

30000

40000

50000

60000

70000

80000

NHI: 1. structure NHI: 2. structure HI: 1. structure HI: 2. structure


RESULTS

Optimal productivity of products:

CORN

POTATOES

MOLASSES

CORN STOVER

WHEAT STRAW

WOOD CHIPS

0 5 10 15 20 25 30

FLUE GAS ACETIC ACID DDGS BIOGAS BIOETHANOL

Mass flow rate /(kg/s)


RESULTS

Annual profit per kg of bioethanol (k€/a):

CORN POTATOES MOLASSES CORN STOVER WHEAT STRAW WOOD CHIPS0

2000

4000

6000

8000

10000

12000

14000

NHI: 1. structureNHI: 2. structureHI: 1. structureHI: 2. structure


RESULTS

Operating costs (k€/a):


10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

RAW MATERIALUTILITY - NHIUTILITY - HIINVESTMENT


RESULTS

Payback period (a):


2

4

6

8

10

12

14

16

NHI: 1. structureNHI: 2. structureHI: 1. structureHI: 2. structure


RESULTS

Efficiency (%):


5

10

15

20

25

30

35

40

45

50

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modeling and optimization of processes of bioethanol production with mixed integer process...

Documents

raw materials bioethanol

plant production

consumption of raw materials

costs of raw materials

energy sector

different raw materials

starchy raw materials

fastgrowing energy crops