Computer-Aided Multiscale Modelling for Chemical Process Engineering

Transcription

1 17 th Europen Symposium on Computer Aided Process Engineesing ESCAPE17 V. Plesu nd P.S. Agchi (Editors) 2007 Elsevier B.V. All rights reserved. 1 Computer-Aided Multiscle Modelling for Chemicl Process Engineering Ricrdo Morles-Rodríguez, Rfiqul Gni * CAPEC, Deprtment of Chemicl engineering Technicl University of Denmrk, DK Lyngby, Denmrk, *rg@kt.dtu.dk Abstrct Chemicl processes re generlly modeled through monoscle pproches, which, while not dequte, stisfy useful role in product-process design. In this cse, use of multi-dimensionl nd multi-scle model-bsed pproch hs importnce in product-process development. A computer-ided frmework for model genertion, nlysis, solution nd implementtion is necessry for the development nd ppliction of the desired model-bsed pproch for productcentric process design/nlysis. This gol is chieved through the combintion of system for model development (ModDev), nd modelling tool (MoT) for model trnsltion, nlysis nd solution. The integrtion of ModDev, MoT nd ICAS or ny other externl softwre or process simultor (using COM-Objects) permits the genertion of different models nd/or process configurtions for purposes of simultion, design nd nlysis. Consequently, it is possible to reduce time nd humn resources in the development nd solution of models. Keywords Multiscle modelling, MoT, ModDev, COM-Object, CAPE-OPEN. 1. Introduction The development of specil mterils nd/or chemicl products s well s brod vriety of scientific nd engineering problems, requires models covering wide spectrum of prtil nd temporl scles. Trditionlly, chemicl

2 2 R. Morles-Rodríguez et l. processes hve been modeled through monoscle pproches, which, while not dequte, nevertheless stisfied useful role in product-process design. Product-centric process design integrtes spects of product evlution into the process design problem. In this cse, use of multi-dimension nd multi-scle model-bsed pproch is beneficil in product-process development nd it bsiclly consists of mthemticl model tht represents complex problem divided into fmily of subproblems tht exists t different scles nd tht cn be orgnized long vrious scles depending on the system nd on the intended use of the model [1]. A flexible computer-ided frmework for model genertion, nlysis, solution nd implementtion will llow the development nd ppliction of the desired model-bsed pproch for product-centric process design/nlysis. This cn be chieved through the integrtion of model generting system (ModDev), nd modelling tool (MoT) for model trnsltion, nlysis nd solution. The combintion of ModDev, MoT nd ICAS [2] or ny other simultors or externl softwre (through stndrd interfce like CAPE-OPEN or specil interfces) permits tht different models nd/or process configurtions cn be simulted very esily nd quickly, reducing time nd humn resources for model development nd solution with lmost zero progrmming effort. Also, this frmework gives the possibility for producing customized simultors for prticulr process. The objective of this pper is to present the modelling frmework, nd through it, the synergy between ModDev nd MoT; together with new modelling fetures such s multiscle modelling nd models needed for specific productcentric process design tht re usully not found in commercil simultors (for exmple, fuel cells, thin-film evportors). The pper will highlight the ppliction of the modelling frmework to generte model equtions using ModDev nd model nlysis/solution through MoT for different non-trivil modelling tsks. The exmples will lso highlight the development of personlized simultors with models generted through ModDev-MoT nd using EXCEL s the simultor executive through COM-Object. 2. Computer-Aided Process Modelling Frmework Nowdys, Computer-Aided Process Modelling Frmeworks which hve become n importnt tool in the development nd solution of process nd product engineering cn be clssified s: generic modelling lnguges nd domin-oriented modelling lnguges. Process modelling lnguges (PML) could be clssified inside of domin-oriented modelling lnguges [3]. PML should be provided with vrying level of grnulrity (multiscle modelling) concepts to enhnce the ccurcy nd prediction of the behviour of some process tht hve to be solved including multiscle phenomen. Multiscle is n essentil pre-requisite for mking full use of dvnces in scientific understnding within engineering pplictions of prcticl interest. Chemicl

3 Computer-Aided Multiscle Modelling for Chemicl Product-Process Design 3 engineers re turning to multiscle modelling to extend trditionl modelling pproches into new ppliction res nd to chieve higher levels of detil nd ccurcy. There is, however, little dvice vilble on the best strtegy to use in constructing multiscle model [4]. Consequently, Computer-Aided Frmework including Multiscle pproch is usully not vilble, nd it is therefore necessry to ssist in the development of these types of models. Furthermore, multiscle pproch fcilittes the discovery nd mnufcture of complex products [5]. The chllenges nd opportunities for multiscle modelling for chemicl process re open nd prtilly tken into ccount in this work. Integrted Computer Aided System (ICAS) is computer-ided tool for modelling developed by Computer Aided Process Engineering Center (CAPEC) t Technicl University of Denmrk. ModDev nd MoT re modelling tools integrted with ICAS; both hve estblished work-flow defined by the computer-ided modelling frmeworks. But, why do we need to use ModDev nd MoT together? Becuse through their interction, model equtions for specific equipment, process or opertion would be developed by ModDev; nd then trnslted, nlyzed nd solved through MoT with lmost zero progrmming effort, nd thereby, producing customized simultors for prticulr process ModDev ModDev [6] is knowledge-bsed modelling system tht is ble to generte process models. It employs grphicl user-interfce to convert the modeller s perception of the process in terms of phenomen, ccumultion, nd constrints, nd ggregtes them to form models of the unit opertion defined in terms of boundries, connections, nd sttes. In ModDev, fundmentl modelling objects re used to crete generic building blocks. The fundmentl modelling objects nd the generic building blocks re then ggregted to form the desired process model. The eqution set representing the process model is then nlyzed nd trnslted for integrtion with solver. The trnslted model my be used s n eqution set in eqution-oriented simultors (MoT) ICAS-MoT Model Test-bed (MoT) [7] is tool within ICAS nd is n eqution bsed modelling/simultion tool nd llows the user to perform simultions of process without hving to write ny source code. The trnslted model cn be solved, fter stisfying mthemticl consistency requirements. After the model equtions hve been successfully solved, the user hs the option to generte COM-object of the model to trnsfer nd use it in externl softwre. COMobject of other models, in this wy, cn lso be used for different terms of model, for exmple, different sets of compound properties, rection kinetics nd

4 4 R. Morles-Rodríguez et l. Fig. 1. Computer-Aided Modelling Frmework behviour equipment sizing dt. On the other hnd, the connection of these COM-Objects with externl softwre or commercil simultor (such s ProSim) cn be done through CAPE-OPEN link. Also, MoT-COM is ble to interct with the ICAS simultion environment generting new unit opertion tht cn be used with other lredy vilble unit opertion models nd used with other ICAS fetures. Furthermore, some of the externl simultors cn operte with EXCEL t the sme time it is working with MoT-COM without dditionl work nd providing high-qulity interction between them (see figure 1) Cse Study In order to illustrte the connection between the different prts ccording to the computer-ided modelling frmework, multiscle model for fuel cell is chosen from the open literture [8]. Multiscle issue cn be seen between sclephenomen connection crried out in the different prts of the fuel cell; for instnce, between the chrge blnce nd mss blnce. The equtions representing the direct methnol fuel-cell re listed in tble 1. In this cse study, use of ModDev to generte the model equtions is not necessry s published model [8] is used. However, ModDev cn lso be used to verify the model. Once the model eqution for the unit hs been derived/generted, MoT is used to mke the trnsltion, nlysis nd solution. As fr s model nlysis is concerned, the degrees of freedom, determintion of the structure of the eqution system, index nlysis, prtitioning nd ordering of the model equtions nd numericl nlysis cn be crried out in this prt. The next step is to solve the model eqution nlyzed in the previous step.

5 Computer-Aided Multiscle Modelling for Chemicl Product-Process Design 5 Tble 1. The DAE model for DMFC in vrious components [8]. Mss Blnce Type Electrode kinetics Anode Cthode Equtions α F 1 F = r1 1 3 k1 exp η θptc exp CH3OH RT K1 η θpt COH RT 3/2 F F p α RT RT p 5 O2 5 = k5 exp ηc 1 exp ηc 0 r dc 1 k A dt τ V LS S ( c c ) ( c c CH ) 3OH CH3OH CH3OH CH3OH CH3OH F Eq. (1) Eq. (2) = Eq. (3) dc LS S CO 1 2 F k A ( c c CO ) ( c c ) 2 CO2 CO2 CO2 dt = τ V Eq. (4) ( ) dc k A A A = c c n r Eq. (5) LS S S S CH3OH M dt CH 3OH CH3OH CH3OH V V V dc LS S S CO k A 2 A = ( c c CO ) + r1 Eq. (6) 2 CO2 dt V V 1 Chrge Blnce Anode Cthode dη 1 = ( icell 6Fr1 ) Eq. (7) dt C M ( icell 6F( r5 nch )) 3OH dη c 1 = + Eq. (8) dt C c Solution of the model for direct methnol fuel cell (tble 1) is presented below. The results re in greement with the experimentl dt, which re indicted by the points (see figure 2) Cell Vol.,V c F CH3OH [mol/m 3 ] Current Density [A/m 2 ] Model 250 Model 500 Fig. 2. Simultion for two methnol feed concentrtion in the fuel cell.

6 6 R. Morles-Rodríguez et l. The second exmple highlights the solution of model equtions for short-pth evportor [9] where model object is generted through MoT for use in EXCEL which is used s visul interfce nd for simultion of different opertionl scenrios. Figure 3 is highlighting the results obtined nd the esy wy to hndle the results (producing the necessry grphics, reports nd so on) obtined from the simultion crried out previously in MoT-EXCEL interction through COM-objects. Fig. 3. Exmple for MoT-Excel Interction 3. Conclusions nd future work The development of Computer-Aided modelling frmework for multiscle modelling is very importnt tool for the development of chemicl process models. It hs been shown tht the combintion nd interction between different computer-ided tools nd externl softwre provide the dditionl modelling/simultion fetures needed for design/nlysis of specific processes nd lso simultneously obtining customized process simultors, while performing the modelling tsks more esily nd efficiently. References 1. E. Németh, R. Lkner, K. M. Hngos nd I. T. Cmeron, ESCAPE-15, Spin, R. Gni, G. Hytoft, C. Jkslnd nd A. K. Jensen, Comp. Chem. Eng., 10 (1997) L. von Wedel, W. Mrqurdt nd R. Gni, Comp.-ided Chem. Eng., vol. 11 (2002) G.D. Ingrm, I.T. Cmeron, K.H. Hngos, Chem. Eng. Sci., 59 (2004) I.T. Cmeron, F.Y. Wng, C.D. Immnuel, F. Stepnek, Chem. Eng. Sci., 60 (2005) A. K. Jensen, PhD thesis, Deprt.ment of chemicl engineering, DTU Lyngby, A. M. Sles-Cruz, PhD thesis, Deprt.ment of chemicl engineering, DTU Lyngby, C. Xu, P.M. Follmnn, L.T. Biegler nd M.S. Jhon, Comp. Chem. Eng., No. 29 (2005) M. Sles-Cruz nd R. Gni,. Chem. Eng. Res. nd Des., No. 7 (2006) 583.