分批蒸馏优化策略与微机控制的研究(Ⅰ)——分批蒸馏的优化策略

本文提出了塔顶累积全回流及变压强综合回流两个分批蒸馏的新操作策略及相应的优化操作法,通过数学模拟和θ收敛计算法求出了二元(乙醇—异丙醇)和多元(正庚烷—正辛烷—正壬烷—正癸烷)物系的数值解.计算结果表明,两种新操作法分别较传统的操作法缩短生产周期30%和50%以上.     

分批蒸馏优化策略与微机控制的研究(Ⅱ)——分批蒸馏的设备与微机控制

本文为前文(Ⅰ)的继续.文中报道了塔釜无存料分批蒸馏塔新结构以及应用微型计算机对三个实验进行四个闭环回路系统的控制,并在此控制系统上取得大量试验数据,证实了理论计算的正确性与微机控制系统的可靠性.     

分批蒸馏优化策略与微机控制的研究(Ⅱ)——分批蒸馏的设备与微机控制

本文为前文(Ⅰ)的继续.文中报道了塔釜无存料分批蒸馏塔新结构以及应用微型计算机对三个实验进行四个闭环回路系统的控制,并在此控制系统上取得大量试验数据,证实了理论计算的正确性与微机控制系统的可靠性.     

分批精馏最小过渡馏分量及过渡馏分脉冲控制法的研究

研究了分批精馏最小过渡馏分量 ,在此基础上针对分批精馏过渡馏分段的特点采用了全回流 全馏出交替进行的脉冲控制法。该法以动态模拟确定了全回流时间 ,统计法确定了全馏出时间。采用正己烷 环己烷物系进行对比实验结果表明 :与传统的恒回流比操作法相比 ,脉冲操作法可明显减少过渡馏分量、缩短操作时间和提高分离效率     

间歇蒸馏的优化操作

本文研究了间歇蒸馏操作的最佳经济收益问题.在二元物系的系统模型中考虑了塔板的持液及冷凝器的持液,并考虑了塔板效率.用多项式拟合相平衡关系.选择回流比作为控制函数,应用最优控制理论导出计算步骤,用数值方法叠代出使经济收益函数最大的回流比函数.将解出的最优操作方案与两种传统的操作方案进行了比较.为检验最优操作方案的可实施性,在一筛板塔上进行了实验,证明优于传统操作.     

浓硝酸的直接合成

工业上由氨的接触氧化以制硝酸,所得产品的浓度,依所用的操作法不同而异,但最高不超过60%左右。工业上根据不使产量过於减低的经济原则,订出各种操作法及产品浓度,可列表如下: 操作法产品中含HNO_3% 常压法(以空气氧化氨)48—50% 常压法(以纯氧化氨)62% 加压法(在8大气压下)58—60% 联合法(在常压下氨的60—62% 接触氧化,在8大气压下NO的氧化及吸收) 上述这些操作法,因为产品是稀硝酸,所以应     

原油常压蒸馏工艺条件优化研究

为了提高原油性质发生较大变化时常压蒸馏装置的经济效益,对常压装置操作条件、产品性质和总体能耗等进行了对比分析及优化。对脱盐温度进行优化试验,确定了最优温度范围130—135℃,提高了电脱盐效率;对导向浮阀塔板和F1型浮阀塔板的流体力学(干板压降和板效率)进行对比计算,改用了压降小,效率高、操作弹性大的高效塔盘导向浮阀塔板,提高了柴油产率,降低了装置能耗;对全塔回流热平衡、热分布进行计算,在常压塔第6层增设一中段回流,回收热量27.52×106k J/h,折合标油全年节约4 880 t。     

逆向蒸馏

采用严格模拟法对多组分蒸馏过程进行了研究。给出了产生逆向蒸馏的3个主要原因,即进料位置不当、进料中关键组分摩尔分数过低以及实际回流比(摩尔比)接近最小回流比。分析了逆向蒸馏的弊端,如进料位置不当所引起的逆向蒸馏,使冷凝器和再沸器能耗分别增加12.76%和12.19%,总计能耗增加达24.95%。提出了避免逆向蒸馏的方法。蒸馏塔设计需分析有无逆向蒸馏现象,逆向蒸馏应予以消除,同时还需进行参数优化,包括塔板数、进料位置、回流比等。而简化法计算结果过于粗糙,只能作为参考而不能作为最终设计的依据。     

蒸馏装置的经济回流比

为了建立蒸馏装置总偿付费用与回流比的关系式,本文首先对蒸馏的回流比与板数的关系式进行了探讨。根据Eduljee关系式建立了便于求解dN/dR的新回流比与板数的关系式: N_m/N=1-B[1-((R-R_m)/(R+1))~β] 并以该式与其它关系式进行了比较,在本文的计算范围该式的最大偏差为±9％。根据我国具体情况找到了蒸馏塔和热交换器的投资费用以及年运转费用与回流比的关系式,从而依据这些投资费用关系式建立了总偿付费用与回流比的关系式,表示如下: C_T=φ(R+1)~(μ/2){[1-B(1-((R-R_m)/(R+1))~β)]~(-1)+(H_sE)/(N_m·h}]+ω(R+1)~ε+Ψ(R+1) 将此式对R进行求导,并使之等于零,在计算机上用试差法就可求得经济回流比R_E的值。     

复杂系统的蒸馏

本文根据特列古保夫的复杂系统蒸馏理论,沿着微分组成及集体组成的方向,对复杂系统(石油)的蒸馏中各个问题,进一步作了广泛的分析,在相平衡、汽化及凝结方面:引伸了特氏表示复杂系统组成的方法,提出了确定各相物理性质的方法;导出了相对挥发度的新关系式,并用以简化特氏原来的相平衡关系;以特氏一次汽化式为例,说明了本文各式求值的具体步骤,指出了由此尚可进一步确定两相物理性质及一次汽化曲线;最后还补充了渐次汽化的计算公式和确定渐次汽化曲线的方法.在复杂系统的精馏方面,采用了新的分离程度表示方法,把特氏的精馏操作线方程式引伸到有惰性气体及侧线存在时的情况;把特氏的立体图解法改为实际可行的逐板计算法;补充了与复杂系统新的分离程度相适应的最小板数计算法及最小回流比估计法.所有这些分析仍旧保留多元理想系统的限制及复杂性,须要利用新的计算工具才便于实际应用.     

Optimal operation of distillation processes under uncertain inflows accumulated in a feed tank

A new method of optimizing the operation of distillation processes with uncertain inflow streams from upstream plants is discussed. The case considered is the streams that will be first accumulated in a tank before feeding to the column. To minimize the total amount of operating energy while keeping a stable column operation under these inflows, a novel decomposed optimization strategy consisting of two steps was used. For an optimal planning of the dynamic operation, a smooth feed flow policy to the column is developed in the first step by stochastic optimization under chance constraints by ensuring a predefined probability of holding the tank level inside the desired range. An easy-to-use method developed computes the maximum reachable probability of holding the constraints so that a feasible solution of the chance constrained problem can be guaranteed. Since the uncertainty in the inflow stream variability is absorbed in the stochastic optimization over the tank, the operation of the dowstream distillation column is deterministic. Therefore, in the second step, the reflux and reboiler duty policies of the column are developed by deterministic dynamic optimization. The optimal overall strategy is obtained by the maximized smoothness of the feed flow to the distillation column. The approach is applied to a pilot column, and the developed operating policies are implemented on the real plant by experiment.     

内部热耦合精馏塔基于非理想物系的最优评价

Internal thermally coupled distillation column(ITCDIC) is a frontier in energy saving distillation research. In this paper, the optimal assessment on the energy saving and the operating cost for ITCDIC of nonideal mixture is explored. An evaluating method is proposed, and the pertinent optimization model is then derived. The ethanol-water system is studied as an illustrative example. The optimization results show that the maximum energy saving in ITCDIC process is about 35% and the maximum operating cost saving in ITCDIC process is about 30%,as compared with a conventional distillation column(CDIC) under the minimum reflux ratio operating; the optimal operating pressure of the rectifying section is found to be around 0.25 MPa; the effects of the feed composition,operating pressure and the heat transfer rate on operation are also found and analyzed. It is revealed that ITCDIC process possesses high energy saving potential and promising economical prospect.     

无累积罐循环全回流间歇精馏三温控制操作

提出了通过塔顶、塔中上以及塔中3个温度控制进行操作状态转换的无累积罐循环全回流间歇精馏控制方法,并以理想物系--乙醇-正丙醇混合物为分离物系进行了实验研究。通过实验确定了温度控制条件为当塔顶温度稳定后且塔顶和塔中上温差为0.3 ℃时变全回流为全采出操作,当塔中温度升高1.0 ℃时停止全采出转为全回流操作。同时还考察了在不同乙醇投料浓度条件下这种操作的运行情况,发现不同投料浓度对塔顶产品平均纯度的影响并不显著,基本能保持在0.99。最后在相同的投料浓度和操作条件下,对比了这种新型控制方式和双温度控制方式,结果表明三温度控制方式比双温度控制方式操作时间减少了23.3 min,分离效率提高了23.95%,产品浓度提高了1.06%,产品收率提高了1.08%。     

二元混合物“全回流”间歇精馏的能耗

介绍了在理想操作条件下，“全回流”间歇精馏二元理想混合物量纲1最小操作总时间的数值计算方法.通过举例计算，比较了在理想操作条件下，“全回流”与部分回流间歇精馏二元理想混合物的能耗，得到了“全回流”间歇精馏适合于相对挥发度小、原料中轻组分的浓度低、塔顶产品中轻组分收率要求高而浓度要求低的分离任务的结论.     

无累积罐循环全回流操作的模拟研究

间歇精馏循环全回流操作是一种具有前景的新型操作方式。文中在循环全回流操作的基础上,首次提出了无累积罐循环全回流新操作方式。通过数学模型对其进行模拟,模拟计算比较了新方式、恒回流比间歇操作和塔顶储罐一次全回流操作3种操作方式。模拟结果表明:无累积罐新操作方式的全回流阶段时间由2个因素决定,全回流开始时精馏塔内的浓度梯度情况和精馏塔内持液的平均浓度。随着全回流-全采出操作的进行,后续循环中的全回流阶段的时间增加,全采出阶段时间减少。当进料浓度低时,新操作方式的分离效率比恒回流比方式高26.4%—30.1%,并通过模拟揭示了新操作方式的特点。研究表明:无累积罐循环全回流操作方式是一种新型高效的分离操作。     

Optimal operation of extractive distillation in different batch configurations

Optimal operations of extractive distillation for regular and middle-vase1 batch columns are presented based on a profit function. Detailed models are used for the rigorous dynamic optimization considering all operational decision variables, including reflux ratio, solvent feed rate, heat duties, and possible product withdrawals during the process. Optimal feed distribution and stream configuration at the middle section of the middle-vessel column are investigated. Separation of a minimum boiling azeotropic binary mixture (acetone and methanol using water as solvent) involving different separation duties and feed compositions is presented as a case study. The pereformanance of the middle-vessel column is signicantly influenced by the middle-section stream configuration, with the best profit when the stream configuration is allowed to vary during the operation. The optimal operating policy for the middle-vessel column involved the feed being charged mainly to the reboiler still with low holdup in the middle vessel during the operation.     

Closed-loop optimal operation of batch distillation columns

Often, the main source of disturbance for a batch distillation system is an upset in the feed to the process. If the operation of a batch column is carried out on the basis of the nominal value of the feed composition, a high degree of uncertainty in the initial conditions to the batch may lead to run the column suboptimally, with a possibly large economic penalty. In this paper, a three-step strategy is proposed for the closed-loop implementation of optimal operating policies for batch rectifiers. First, the optimal reflux rate is calculated off-line for several feed compositions. Then, a correlation is developed off-line between the optimal reflux rate and the composition profile in the column at the end of the startup phase. Finally, the detection of the composition profile is performed on-line during the startup phase, so that the optimal reflux rate can be calculated and implemented in a closed-loop fashion. This allows operating the column optimally even though the actual feed composition is not known. Since the calculations to be performed on-line are straightforward, the computational demand is kept to a minimum. Results for binary and ternary systems indicate that, by using the proposed procedure, the column performance can be improved by as much as 30% with respect to a conventional open-loop optimal strategy.     

Undergraduate design of experiment laboratory on analysis and optimization of distillation column

A two-level full factorial design and/or a central composite design are used to optimize the operation of a distillation column by manipulating three variables: the feed flow rate, the reflux ratio and the steam flow to the reboiler. The response variable of interest is a profit function where the objective of this experiment is to examine the effect of each of the three factors and their interactions on this profit function. This is accomplished in a sieve tray type continuous distillation column operated at ambient pressure to separate a methanol–isopropanol mixture. Students were asked to determine the significant variables and the optimal operating conditions for steam rate, reflux ratio and feed rate such that the profit is maximized. As a result, this experiment not only exposes students to an industrially relevant unit operation but it also helps complement the classroom teaching on design of experiment concepts.     

乙酸甲酯与甲醇共沸物催化精馏水解工艺

以乙酸甲酯与甲醇共沸物为原料,采用阳离子交换树脂为催化剂,研究了乙酸甲酯催化精馏水解工艺。在实验中以捆扎包作为催化剂的装填方式,系统地研究了催化精馏段和提馏段的高度、进料位置、进料中含甲醇、水酯物质的量比、回流进料比和空速等对酯分解率的影响,获得了最佳的工艺条件。分析了传统的水解分离工艺,提出了可行的新工艺。在最佳工艺条件下,新工艺系统的能耗比传统的固定床工艺降低39.99%。