粗苯精馏过程的模拟计算-

1、收稿日期:2002-12-08作者简介:张艳辉,女,讲师,硕士,主要从事化学工程与工艺方面的研究,联系电话:0351-*粗苯精馏过程的模拟计算张艳辉1王志锋2刘有智3(1、3.山西太原华北工学院化学工程系030051;2.山西太原中科院山西煤炭化学研究所030051摘要以汽液平衡为基础,应用精馏原理建立了粗苯精馏的数学模型,并采用三对角矩阵法、高斯消元法和追赶法对模型进行了模拟计算。通过验证,证明了该模型是可靠的,通用的,从而为确定精馏塔的设计或操作方案提供了定量依据。关键词粗苯精馏汽液平衡模拟计算中图分类号T Q0241.1+1文献标识码A 文章编号1003-6490(200301-00-0

2、40引言煤焦化后的煤气经过抽提可获得粗苯。粗苯中含有苯,甲苯,二甲苯,尤其是苯的含量较高,因此在苯的生产中,焦化苯所占比重较大。在粗苯的分离法中,结晶法比较经典,但噻吩和苯易生成混合结晶。而萃取法因其装置规模小,处理原料的非芳烃含量低,应用不十分广泛。从综合利用的角度出发,工业生产中经常利用粗苯组分的相对挥发度大的特点而采用精馏法分离粗苯。为了便于在生产中分析过程,标定数据,制定合适的设计操作方案,提高设备的生产能力和产品质量,本文对粗苯精馏过程进行了模拟计算。1数学模型的建立1.1模型塔由于实际生产中操作方案的多样性,在建立粗苯精馏分离过程的数学模型时,应先设计一个广泛适用的模型精馏塔,如图

3、1所示 。图1模型精馏塔该塔具有任意板数,可在任意板上设置进料口、侧线汽液相出料口及换热设备。1.2模型方程组第29卷第1期2003年3月化工设计通讯Chemical Engineering Design C ommunications根据精馏原理对模型进行物料衡算和热量衡算得到如下方程:1相平衡方程y i ,j =K i ,j x i ,j 1i C 1j N (12各组分的物料平衡方程第1块板(冷凝器V 2y 1,2-V 1y i ,1-(S 1+L 1x i ,l =0(2第j 块板(2j N -1F j z i ,j +L j -i x i ,j +V j +1y i ,j +1-(L

4、 j +S j x i ,j-(V j +G j y i ,j =0(3第N 块板(再沸器L N -1x i ,N -1-(V N +G N y i ,N -L N x i ,N =0(43热平衡方程第1块板(冷凝器V 2H V2-V 1H V 1-(L 1+S 1H L 1-Q 1(5第j 块板(2j N -1V j +1H VJ +1+jk -2F kHF k+jk -2Qk-Q 1-I j H Lj -jk -2S k HL k-jk -2G k H k -j k -2G k H Vk -V 1H V1=0(6第N 块板(再沸器L N -1H LN -1+Q N -(V N +G N H

5、 V N -L N H LN =0(74分子分数加和式Ci =1x i ,j -1=01j NCi =1y i ,j -1=01j N(82数学模型的计算多参数SH BWR 状态方程同时适用于汽液相,可以较准确地反映烃类及其混合物的热力学数据。在混合规则的基础上,利用此方程确定汽液相的密度、逸度及焓等参数4。2.1各板组成的计算消元后的式(1(4组成了M -K 方程组,对i 组分M -K 方程组可表示为以下三对角矩阵形式:B 1C 1A 2B 2C 2x 2D 2A jB jC jMA N -1 B N -1C N -1A NB Nx 1x 2Mx j M x N -1x ND 1D 2M D

6、 j MD N -1D N含有c 个组分的系统可写出c 个三对角矩阵,然后运用高斯消去法1消去x j -1,再利用追赶法2求出液相组成x i ,j ,汽相组成y i ,j 通过调整平衡常数得到。2.2热负荷的计算将利用SH BWR 状态方程求得的汽液相的焓回归成以下形式:H 01=B 0i +B 1i T100+B 2i T1002+B 3i T1003+B 4i 100T(10把回归焓值和调整的汽液流量代入方程(5(7,即可求得再沸器、冷凝器及各板的热负荷。2.3计算程序的编制58由于计算中部分变量既关于组分又关于塔板,所以采用二维数组来表示。对于逐板计算,用循环来实现,如图2中的K 循环和

7、V 循环。算法中涉及到众多既前后联系又相对独立的变量和计算式,因此采用函数更方便。程序框图如下:3数学模型的验证程序中塔板数是宏定义,可以任意设定进料量、出料量、塔板压力、回流比等。现将文献2提供的数据输入计算程序后,获得了数学模型的计算结果。为了检验模型的合理性,适用性,将模型的计算结果与文献3中的实验值进行比较,结果如表1所示。由表1可以看出,除了塔底苯组成和塔顶二甲苯组成的偏差大于0.001以外,其余均小于0.001,所以模型适合于粗苯精馏。4结论25化工设计通讯第29卷表1粗苯精馏的数模与实验结果的比较塔顶产品组成苯甲苯二甲苯塔底产品组成苯甲苯二甲苯冷凝热负荷,k J再沸器热负荷,k

8、J 051图2计算程序框图本文通过对焦化粗苯精馏过程的模拟计算,可得出如下结论:a.数模检验结果表明,模型具有可靠性及适用性;b.依据通用的模型塔,利用严格法建立数学模型,可解决烃类系统的多元精馏问题,说明模型具有通用性;c.模型模拟了粗苯精馏时的传质、传热情况,为确定精馏塔的设计或操作方案提供了定量依据。C组分数;F进料流率,km ol/h;G侧线气相出料流率,km ol/h;H焓,kcal/km ol;K相平衡常数;x液相组分摩尔分率;L下降液体流率,km ol/h;N塔板数;下标l冷凝器;i某一组分;j某一塔板;F进料;N再沸器;Q传热速率,kcal/h;S侧线液相出料流率,km ol/

9、h;T温度,K;V上升蒸汽流率,km ol/h;y汽相组分摩尔分率;L塔内液相;V塔内汽相;0理想状态。参考文献2沈春谨.处理量5000t/a粗苯精馏装置学士毕业论文.太原机械学院,198635第1期张桃先:粗苯精馏过程的模拟计算Zhejiang Zeguo Chemical Machine Works,Weiling,317523 Abstract:D ouble-roller com m inutor can be used to produce com2 pound fertilizer.N o drying is needed,besides,production can be con

10、ductedunder ambient tem perature.T he process design in reas onable,the techn ologyis feasible.key w ord:double-roller comminutor,design,applicationBursting P ressure P rediction of MultilayeredCylinder&Spherical ShellsX iao Lihua1,Liu X iaoning2(1.Changde Vocational Univer sity,Hunan Changde,41

11、5900;2.Wuhan Vocational Univer sity o f Industry&T ra ffic,Wuhan,430015Abstract:In this article,the in fluence of thickness reduction due to big deform ation for bursting pressure of multilayered cylinder&sphericalshells is analyzed.T he formula of bursting pressure is found.W ith E x peri2m

12、 ents count verification,the distinguishing feature of this formula sh ow,formsim ple,caculation convenience,high precision,fluctuation scope sm all andstable is g ood.T he results is provided reference for techn ology design using.key w ord:multilayered,cylinder&spherical shells,bursting pressu

13、re,caculation formula.C alculation of Diagonal R ound W eakening Coefficient of H oleR einforcem ent on P ressure V esselLi Bingrong(Hunan Chemical Research Institute,Changsha,410007Abstract:T his article describes tw o calculation meth ods for diag onal round weakening coefficient of h olerein forc

14、ement on pressure vessel by means of definite in2tion and approximate calculation.key w ord:hole reinforcem ent,diagonal round w eakening coefficient,calculationDiscussion of R elationship B etw een Function and Aesthetics ofI ndustrial Buildings T ake H unan Biologically Ph arm aceuticalF actory R

15、elocation P roject for E xampleR ao X u an(Hunan chemical&Pharmaceutical Engineering DesignInstitute,Changsha,410007Abstract:Industrial building design must meet the requirement of function at first,then y ou must considerthe organic com position of function,environment,land2scape and aesthetics

16、.key w ords:industrial building,function,aesthet2 ics,h omm izationComp arison of N ew and old Design codes for Oil refuelling Station and Application in P racticeW en WuAbstract:It com pares s ome clauses in new and old de2 sign codes for oil refuelling station,besides,it puts theminto practice.key

17、 w ards:oil refuelling station,code,com pari2 s on,applicationT reatment of W aste G as Discharged by CS2plantU sing E letric Furnace ProcessYin Xianqi(Zhuzhou Bene ficiation Reagent Factory,Zhuzhou,412005Abstract:This article describes the principle and process of treatment of waste gas discharged

18、by CS2plant using electric furnace process.It de2 velops a new way for H2S reuse.It has g ood econom ic and s ocial benefits.key w ords:CS2,amm onium sulfide,H2S purificationA nalog computation of CrudeB enzeneR ecti fication ProcessZh ang Yanhui1,W ang Zhifeng2,Liu Youzhi3(1、3.Chemical Engineering

19、Department o f North ChinaEngineering College,Taiyuan,030051;2.Shanxi CoalChemical Research Instiute o f Chinese Academy o fSciences,Taiyuan,030051Abstract:This article establishes a mathematical m odel for crude benzene rectification by use of rectification principle on the basis of vapor2 liquid b

20、alance.Besides,it makes analog com putation for the m odel by use of triple diag onal matrix method,G aussian elim ination method and pursuit method.Result proves that this m odel is reliable and universal.This m odel will provide a quantative basis for the design or operating scheme determ ina2 tio

21、n of rectification tower.key w ords:crude benzene,rectification,vapor2liquid balance,analog com putationDirect Method of C alculating the Q uantity of F luid P assingthrough a Pipe and calculating the diameter of a pipeH ong Liang,Zh ang T aoxian,Sun R ong,Liu Xiaoning(Wuhan technical college o f in

22、dustry andtransportation,Wuhan,430015Abstract:Up to now,calculating the quantity of fluid flowing throughthe pipe still depends on trial-calculating method,through,this kind ofmethod is inconvenient.Through analyzing,the authors of this paper con2sider it possible to calculate these quantities direc

23、tly by adopting a newRe22Re andRe22Re calculation chart,through which a direct method ofs olving this s ort of problem can be acquired.This new method shares theadvantage of convenient and can supply a reference to the people inv olved inenqineering design.key w ords:pipe calculation of flowing fluid quantity,trial2calculating method,direct method,new calcula2tion chartDiscussion on Biochemical T reatment ofAmm ania2nitroge