DYNAMIC SIMULATION OF AN EVAPORATOR SYSTEM

Abstract

The present investigation pertains to a study of multiple effect evaporator system for caustic-soda solution feed arrangement. Basically, it deals with the mathematical models for the weighted overall coefficient and also a dynamic model for the aqueous solution in a long tube vertical MTV] evaporator. It also under forward development of heat transfer evaporation of double effect feed includes the parametric effect of temperature, feed concentration, feed flow rate on the vapor flow rate, liquid flow rate and liquor concentration leaving each effect. It also describes the behavior of the variables for various step inputs and thereby determines the most sensitive variable for the purpose of accurate monitoring and precise control. Using the basic theory of heat transfer and two phase flow, a heat transfer model has been developed to calculate heat tvansfer coefficient. The values of heat transfer coefficient calculated by the model have been compared with the experimentally obtained values of Kassatzkin [KM It is found that the predicted values have excellent agreement with the experimental values of Karsatzkin. The maximum deviation is t 2.5%. Using heat transfer coefficients, a weighted heat transfer coefficient has been calculated. Using the equations of solute material balance, overall material balance, energy balance, heat transfer rate and boiling Lt?81)rt.ii. reldtd.'-' a /El '1' tit.;.)6Effeet" - 844144dPTfle'644ePgivesii oitalitkirdifftWati4)! diff-dgential"eclukeiOnEit'fial3efi rsoived 1E14' h6nt-lineake"'algebr:Sie equations have been linadliiWN gjWtiiii-R4liSon'inethod''and then i(-4WWin Liblaiidap6ailoPieib6elio"deterMinelthe.-values of cl illd%- Age al "'of 'unknoohiknoWnitriai r itavelfieh' tralSt e.:1 the • iterative' pif66edure. The ViajluLi of`' (Inkfa:Mk vTA.IbrtiV iSg'en() taken" to be- c' ri4retiti thletleViiajelithl b'et1vdM1 IOW lthetidleiVeY.Values' of Va'riabl.‘-e' la). found feJ igelCe%he-Vrcig3ilcaL '4514 ‘trelithE " h'a-a aprealiCitec? cittfAVit "e. fid rit t rate; and varka241Eidii" rated temperature, feed concentration, and feed rate. The validity of the dynamic model for its applicability to industrial situations has been examined by comparing the predicted values of concentration, liquid flow rate, liquid temperature, vapor flow rate, and steam requirement of each effect in double efifect evaporator against the values reported by Holland (H61. The maximum deviation between the two values has been found to be of the order of 5.8%. An analysis of transient responses has resulted the parametric effect of feed temperature, feed flow rate, and feed concentration on the computed variables. Feed temperature has been found to decrease the liquid flow rate and to increase the vapor rate HowAver, chancres in,feed.flourate,andr2eed concentration ?rovided the-effects contrary to those_observed by Zeed-,temparature. Tn . " 0 '54.1t.study, feelowrate b,eetirt 2pund to 5e.tae moot crucial , one. as a small .change in it leads-to wide divtameo=ances kn steady C Ast 4.44,, statevalues,cfvariablesin,the evaporator.*. 0,4, jr A I • -1:'70:..C5 Uingregression,analycka a Ikrot,orderan-skent equation fol: the.cor.pnad variables has be4n cbtain1A, tgosn step . - changes in the operating yariablec.are L..0,7a,an.„, The apelye.m • o2 resulting•ennression• has.also yieldalT.:Isod,21.o, p:ata• to, be X40 , - • ; „ k '4 most sensitivr. one,This.analyeis has helped in thb,identi2iqatiPP . • • , ,oUtheNariables which should be• closely monitored and ,control lad • • !"..7 !;1•,. OLT hat ,a steady state.operation can be maintained even uhen- a " " • Esp0111 change, in the operating,variable tafte2,, Rlace. vt-0