MTBE反應(yīng)精餾塔的建模和應(yīng)用
發(fā)布時間：2018-09-04 08:26
【摘要】：反應(yīng)精餾是將化學(xué)反應(yīng)與精餾過程結(jié)合在同一設(shè)備中進行的工藝。由于在反應(yīng)的同時,用精餾的方法將產(chǎn)物移出,從而有利于提高反應(yīng)轉(zhuǎn)化率、降低能耗和投資,正日益得到學(xué)術(shù)和工程界的高度重視,而其中機理建模是整個問題的核心。本文首先建立了反應(yīng)精餾塔的穩(wěn)態(tài)機理模型,模型包括產(chǎn)品質(zhì)量約束、質(zhì)量平衡、相平衡、歸一化方程、能量平衡和反應(yīng)速率方程,即MESHR方程組。其中,為了準(zhǔn)確地計算各理論板的上升氣體量和下降液體量,又避免采用導(dǎo)致二級循環(huán)迭代的逐板計算法,減少計算負(fù)荷,本文改進了等摩爾流假設(shè),利用各板液相潛熱可算的原理,間接求出了上升氣相量和下降液相量,從而使兩次迭代簡化為一次迭代,大大減少了計算量。本文提出了反應(yīng)精餾塔穩(wěn)態(tài)機理模型的求解方法,該方法由于簡化了各級理論板上升氣相量和下降液相量的計算,使得聯(lián)立求解MESHR微分方程組成為可能。其步驟是:1)給定塔頂壓力、回流比、進料狀況和產(chǎn)品要求,進入第一次循環(huán)計算;2)設(shè)定各理論板溫度和液相組成初值,用Wilson方程計算各組分的活度系數(shù);3)計算各組分的相平衡常數(shù)初值;4)計算各理論板氣相組成初值;5)采用MATLAB內(nèi)置的龍格-庫塔算法(ode45算法),求解各理論塔板MESHR方程組,得到修正后的塔板氣液相組成;6)檢驗各理論板組成是否滿足歸一化方程,滿足則輸出結(jié)果,否則調(diào)整各板溫度初值進行二次循環(huán)計算。編制了相應(yīng)MATLAB計算程序,并將其應(yīng)用于Jacobs和Krishna提出的經(jīng)典MTBE案例[80],計算表明本文的計算結(jié)果與文獻值高度一致,說明本文建立的反應(yīng)精餾塔的穩(wěn)態(tài)機理模型以及計算方法是可行的。最后,將模型應(yīng)用于MTBE反應(yīng)精餾塔的操作優(yōu)化,通過模型內(nèi)置的遺傳算法,以進料溫度、塔頂壓力、回流比為優(yōu)化變量,以體系總操作費用為目標(biāo)函數(shù),應(yīng)用于Jacobs案例,發(fā)現(xiàn)當(dāng)回流比為6.5,塔頂壓力為10.7atm,甲醇進料溫度為324K,C4進料溫度為360K時,按年開工8000小時計算,年度總操作費用可降低947.89萬元/年。
[Abstract]:Reactive distillation is a process that combines chemical reaction with distillation process in the same equipment. At the same time, the products are removed by distillation, which is beneficial to increase the conversion rate, reduce energy consumption and investment, which has been paid more and more attention by the academic and engineering circles, and the mechanism modeling is the core of the whole problem. In this paper, the steady-state mechanism model of reaction distillation column is established. The model includes product quality constraint, mass equilibrium, phase equilibrium, normalized equation, energy balance and reaction rate equation, that is, MESHR equation. In order to accurately calculate the rising gas and decreasing liquid volume of each theoretical plate, and to avoid the plate by plate calculation method which leads to two-stage cycle iteration, and to reduce the calculation load, this paper improves the isomolar flow hypothesis. Based on the principle that the latent heat of liquid phase of each plate can be calculated, the amount of rising gas phase and the amount of falling liquid phase are calculated indirectly, so that the two iterations are simplified to one iteration, and the calculation amount is greatly reduced. In this paper, a method for solving the steady-state mechanism model of the reaction distillation column is presented. The method simplifies the calculation of the ascending gas phase and the descending liquid phase of each theoretical plate, which makes it possible to solve the MESHR differential equation simultaneously. The steps are: 1) given top pressure, reflux ratio, feed condition and product requirements, enter the first cycle calculation and 2) set the initial values of each theoretical plate temperature and liquid phase composition. The Wilson equation is used to calculate the activity coefficient of each component. The initial value of phase equilibrium constant of each component is calculated. (4) the initial value of gas phase composition of each theoretical plate is calculated. (5) the Runge-Kutta algorithm (ode45 algorithm) built in by MATLAB is used to solve the MESHR equations of each theoretical tray. The modified gas-liquid composition of trays is obtained to verify whether the composition of each theoretical plate satisfies the normalized equation and the output result is satisfied. Otherwise, the initial temperature of each plate is adjusted for secondary cycle calculation. The corresponding MATLAB calculation program is compiled and applied to the classical MTBE case [80] proposed by Jacobs and Krishna. The calculation results show that the calculated results in this paper are in good agreement with the reference values. The steady-state mechanism model and calculation method of reaction distillation column established in this paper are feasible. Finally, the model is applied to the operation optimization of MTBE reaction distillation column. Through the genetic algorithm built in the model, the feed temperature, top pressure and reflux ratio are taken as the optimization variables, the total operating cost of the system is taken as the objective function, and applied in the case of Jacobs. It is found that when the reflux ratio is 6.5, the top pressure of the tower is 10.7atm, and the feeding temperature of methanol is 324kg / C4 360K, the total operating cost can be reduced by 9.4789 million yuan per year according to the 8000 hours of annual start up.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ053.5
[Abstract]:Reactive distillation is a process that combines chemical reaction with distillation process in the same equipment. At the same time, the products are removed by distillation, which is beneficial to increase the conversion rate, reduce energy consumption and investment, which has been paid more and more attention by the academic and engineering circles, and the mechanism modeling is the core of the whole problem. In this paper, the steady-state mechanism model of reaction distillation column is established. The model includes product quality constraint, mass equilibrium, phase equilibrium, normalized equation, energy balance and reaction rate equation, that is, MESHR equation. In order to accurately calculate the rising gas and decreasing liquid volume of each theoretical plate, and to avoid the plate by plate calculation method which leads to two-stage cycle iteration, and to reduce the calculation load, this paper improves the isomolar flow hypothesis. Based on the principle that the latent heat of liquid phase of each plate can be calculated, the amount of rising gas phase and the amount of falling liquid phase are calculated indirectly, so that the two iterations are simplified to one iteration, and the calculation amount is greatly reduced. In this paper, a method for solving the steady-state mechanism model of the reaction distillation column is presented. The method simplifies the calculation of the ascending gas phase and the descending liquid phase of each theoretical plate, which makes it possible to solve the MESHR differential equation simultaneously. The steps are: 1) given top pressure, reflux ratio, feed condition and product requirements, enter the first cycle calculation and 2) set the initial values of each theoretical plate temperature and liquid phase composition. The Wilson equation is used to calculate the activity coefficient of each component. The initial value of phase equilibrium constant of each component is calculated. (4) the initial value of gas phase composition of each theoretical plate is calculated. (5) the Runge-Kutta algorithm (ode45 algorithm) built in by MATLAB is used to solve the MESHR equations of each theoretical tray. The modified gas-liquid composition of trays is obtained to verify whether the composition of each theoretical plate satisfies the normalized equation and the output result is satisfied. Otherwise, the initial temperature of each plate is adjusted for secondary cycle calculation. The corresponding MATLAB calculation program is compiled and applied to the classical MTBE case [80] proposed by Jacobs and Krishna. The calculation results show that the calculated results in this paper are in good agreement with the reference values. The steady-state mechanism model and calculation method of reaction distillation column established in this paper are feasible. Finally, the model is applied to the operation optimization of MTBE reaction distillation column. Through the genetic algorithm built in the model, the feed temperature, top pressure and reflux ratio are taken as the optimization variables, the total operating cost of the system is taken as the objective function, and applied in the case of Jacobs. It is found that when the reflux ratio is 6.5, the top pressure of the tower is 10.7atm, and the feeding temperature of methanol is 324kg / C4 360K, the total operating cost can be reduced by 9.4789 million yuan per year according to the 8000 hours of annual start up.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ053.5
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