基于传热/传质的乙烯裂解过程脱甲烷塔进料瓶颈识别及流程重构策略

精馏塔进料的组成与温度会影响塔内质量交换和能量利用,不恰当的进料会导致全塔的分离及用能效果变差。针对多进料精馏塔的组合进料问题提出一种识别不合适进料位置的方法,基于塔板的传热温差和传热量、传质浓度差和传质量计算方法提出应用传热/传质复合曲线识别精馏塔进料瓶颈的方法,并将其应用于裂解装置脱甲烷塔进料瓶颈的识别,采用调整进料位置的流程重构策略实现去瓶颈的操作。流程模拟及瓶颈分析结果表明所提出的方法能识别出脱甲烷塔的进料瓶颈,重构流程的方法能实现去瓶颈的操作,并使全塔的传质传热特性、分离效果变好,能耗降低。     

基于传热/传质的乙烯裂解过程脱甲烷塔进料瓶颈识别及流程重构策略

精馏塔进料的组成与温度会影响塔内质量交换和能量利用,不恰当的进料会导致全塔的分离及用能效果变差。针对多进料精馏塔的组合进料问题提出一种识别不合适进料位置的方法,基于塔板的传热温差和传热量、传质浓度差和传质量计算方法提出应用传热/传质复合曲线识别精馏塔进料瓶颈的方法,并将其应用于裂解装置脱甲烷塔进料瓶颈的识别,采用调整进料位置的流程重构策略实现去瓶颈的操作。流程模拟及瓶颈分析结果表明所提出的方法能识别出脱甲烷塔的进料瓶颈,重构流程的方法能实现去瓶颈的操作,并使全塔的传质传热特性、分离效果变好,能耗降低。     

多变量预测控制软件包APC-Hiecon在液化气回收装置上的应用

针对扬子石化公司芳烃厂液化气回收装置脱丁烷塔存在的进料波动大,操作变量多,关联性强等控制难点,使用多变量预测控制软件包APC－Hiecon设计多变量预测控制器来实现对脱丁烷塔的平稳控制并提高分离效果,取得了很好的控制效果和显著的经济效益。     

乙烯装置脱甲烷系统中甲烷分离浅析

对高压脱甲烷系统中甲烷分离进行了讨论.通过对甲烷在脱甲烷系统内的走向分析,讨论了碳二洗涤塔进料温度对乙烯冷剂负荷的影响;将液相甲烷从-140℃甲烷氢分离罐跨线补充至脱甲烷塔回流罐,可降低乙烯损失和乙烯冷剂消耗;最后,以碳二洗涤塔进料温度和跨线流量2个变量进行综合分析,得到了局部最优解.     

精馏塔进料位置图解法探讨

叙述了精馏塔进料位置对全塔效率的影响.认为不在最佳位置进料会导致全塔效率下降,而不是理论塔板数增多;不能用下移进料位置提高塔顶的含量,也不能用上移进料位置提高塔底的含量;工程设计中可在最佳进料位置附近几块塔板的塔圈上增设进料口,操作中可通过改变进料口使塔长期处于最佳工况.     

大庆裂解老区乙烯分离工艺优化探讨

脱甲烷系统是乙烯裂解装置能量消耗的大户。通过分析大庆乙烯装置裂解老区分离流程,在不改变老区分离进料量的前提下,对前冷、脱甲烷塔及脱乙烷塔部分进行工艺优化,将前冷的前两股进料直接进入脱乙烷塔处理,降低脱甲烷塔和脱乙烷塔负荷;重新启用膨胀机、压缩机,并将再生气、燃料气二者合做驱动力,循环利用冷量,进而达到节能降耗的目的。     

ELUXYL工艺吸附进料开关阀故障对生产的影响及对策

ELUXYL工艺技术吸附塔是通过开关阀切换开关来实现进出物料切换控制并完成吸附塔的模拟移动切换。吸附塔开关阀一共有144个,是整个ELUXYL工艺核心重要设备,其工艺特点是开关阀的数量多,开关动作次数多。随着装置运行周期变长开关阀零件损耗,开关阀故障率也明显增加,如此往复必然会对装置生产及PX产品质量造成严重影响,给公司造成损失。基于某厂ELuxyl工艺吸附塔长期运行的开关阀状态情况进行分析并总结经验,主要进行开关阀内部结构磨损造成的故障分析,并列举进料开关阀出现故障后对装置产生的影响,也为同类型吸附装置出现开关阀问题提供借鉴,对长周期装置后续生产的平稳运行提供有效的依据。     

氯甲烷脱二氧化碳连续精馏过程模拟及工程应用

通过Aspen Plus软件对氯甲烷脱二氧化碳连续精馏过程进行模拟,分别考察了理论板数、进料位置、回流比和塔顶采出率对塔釜二氧化碳含量和氯甲烷收率的影响。结果表明:在理论板数为40,第10块塔板位置进料,回流比24(mol/mol),塔顶采出率0.013(mol/mol)时,塔釜氯甲烷产品中二氧化碳摩尔分数为4×10~(-6),氯甲烷收率为99.86%。根据模拟结果,进行填料塔、塔顶冷凝器、塔釜再沸器工程设计,成功应用于实际生产制得高纯度氯甲烷,氯甲烷质量分数大于99.9%,二氧化碳质量分数小于0.0015%。     

多股进料对乙烯精馏塔回流比的影响

降低乙烯装置能量消耗的问题正日益引起人们重视。最近,在决定建设新装置和扩建已有装置的方案过程中常提出一个问题:究竟是S＆W公司的ARS流程还是Lummus公司的低压脱甲烷顺序流程生产成本低。这是一个很复杂的问题,与多种因素有关,本文仅就其中一个问题,即多股进料对乙烯塔能耗的影响进行讨论。     

前脱丙烷预切割分离MTO粗产品工艺的模拟与优化

选择"前脱丙烷"流程对甲醇制烯烃粗产物进行分离。先利用高低塔脱丙烷工艺, 然后经过脱甲烷塔、脱乙烷塔、乙烯精馏塔、丙烯精馏塔, 最终得到聚合级的烯烃产品, 其中脱甲烷工段采用"预切割-油吸收"脱甲烷工艺, 使用耗能较小的中冷分离, 吸收剂选择产自工艺自身的丙烷产品。丙烯精馏工段采用双塔预分流程, 降低塔高。采用Aspen Plus流程模拟软件对脱甲烷工段进行模拟和优化, 选用Radfrac精馏模型和RKS-BM热力学模型进行计算, 对脱甲烷工艺段进料位置、塔板数、回流比进行灵敏度分析, 并确定出丙烷吸收剂的用量和温度, 最终得到纯度为99.98%的乙烯和99.90%的丙烯。     

闭环控制回路多指标性能评价

针对目前基础回路控制器性能评价方法存在直观性差、易读性差和不可溯源的问题,提出一种多指标性能评价方法。采用相对性能指数评价回路的响应和设定值跟踪情况,采用振荡指数指标评价回路振荡情况,采用有效投用率评价控制器的投用情况。仿真与工业应用结果均证实了所提方法的可行性和有效性。     

变工况切换过程的Petri网自主预测与控制

针对变工况切换过程中切换点难以确定且切换准则不完善等问题,以大范围升温过程为例,利用仿人智能控制中"全压-零制动-稳态调节"的控制策略,提出了"预测Petri网",即在Petri网中增加预测器,为Petri网的变迁提供了判断元素。根据"预测-决策-再预测-再决策"的思想,增加切换过程的判断条件,实现了Petri网自主寻优过程。最后在实验室电加热炉装置上实验表明,在切换点不确定的情况下,在线寻找到切换点并增加了切换条件,使系统的切换更为平稳光滑,提升了系统响应速度和稳定性。     

智能阀门定位器控制算法的改进

国内诸多阀门定位器产品使用五步开关控制算法,但在低阀位控制时振荡次数多,高阀位控制时调整时间长,因而对五步开关控制算法进行改进。将改进后算法的控制效果与五步开关控制算法控制效果进行对比,算法改进后调整时间减小1.6s,超调量减小12.8%,实现了更快速准确的阀门定位。     

Optimality-based grid adaptation for input-affine optimal control problems

This paper studies the solution accuracy of direct single-shooting in comparison to the solution of the continuous optimal control problem (OCP). First, a convergence relation between the solution of the nonlinear program and that of continuous OCP is analyzed by means of an exemplary problem. This example reveals that Pontryagin's minimum principle cannot be used as a stopping criterion for optimality-based control grid adaptation. Consequently, a novel grid refinement strategy is introduced, which is rather based on the switching function and thus limited to the class of input-affine OCPs. Grid points are eliminated and inserted such that the approximation of the optimality condition of the OCP, elucidated by the switching function, is improved. The suggested methodology is illustrated and compared to a previously published wavelet-based adaptation approach by means of two reactor optimization problems with different solution characteristics.     

Fast switching electrochromism from colloidal indium tin oxide in tungstate-based thin film assemblies

Layer-by-layer assembly was used to alternately deposit tungstate anions with cationic poly(4-vinylpyridine-co-styrene) to generate electrochromic thin films that transit from transparent to dark blue in their oxidized and reduced states, respectively. Tungstate is a good electrochromic material because it is completely colorless in its deposited state, while most other electrochromic materials exhibit some type of color in the absence of an applied voltage. Despite its advantages, tungstates are plagued by long switching time (>30 s), which is common amongst ceramic electrochromics, due to lack of electrical conductivity in at least one of the two states. In an effort to decrease switching time, indium tin oxide (ITO) nanoparticles were incorporated into these tungstate-based assemblies. In the absence of ITO, these films take 30-60 s to completely switch and exhibit reduced contrast with each switch. ITO-containing films, with ITO in every other bilayer, fully switch in 14 s and do not exhibit the same drift in transmittance with repeated switching. ITO allows these films to maintain electrical conductivity in both states, which is the source of this faster, more stable switching. With further optimization, this combination of fast switching and high contrast makes these films promising for use in smart windows and flexible displays.     

Microbial Responses after Disinfectant Change to Ozone in a Full-Scale Distribution System

Ozone is a promising alternative disinfectant when the concentration of organic carbon is high in the source water. The microbial responses to primary disinfectant change from monochloramine to ozone in a full-scale distribution system were investigated. Several water quality parameters including heterotrophic bacteria and a new parameter, growth potential (GP), were determined from the finished water and at three different distribution system locations before and after switching to ozone for a period of 12 months. The GP assesses the potential of the water to sustain growth of bacteria. The literature suggests that ozonation will result in a higher biodegradable organic carbon concentration and will therefore stimulate bacterial growth. Biodegradable organic carbon concentration (BDOC) and HPC increased but GP decreased after ozonation during the study period. In order to exclude seasonal effects, the data from the same seasons of the previous year were compared in the statistical analyses. Our findings showed that among the water quality parameters, HPC, disinfectant dose and total organic carbon (TOC) concentration showed statistically significant differences between the two years (paired t-test, p<0.05). When ozone was used as primary disinfectant the TOC was 1.5 times higher than when chloarmine was used, but the HPC and disinfectant dose were lower. Thus the switch of the primary disinfectant to ozone did not increase bacterial growth. At the lower dose, the disinfectant dose was effective enough to control bacterial regrowth in the distribution system during the study period.     

Switching of optical-resolution selectivity through the Onsager's reaction field: Chiral recognition of dl-amino acids by hydrophilic/hydrophobic chitosans

Unusual switching of optical-resolution selectivity in chitosan resins is reported. While in hydrophilic chitosan resins, the l -form of amino acids are selectively adsorbed, and in hydrophobic chitosan resins, the d -form was preferred. We found that the adsorption selectivity of the amino acids in the optical-resolution agents is controlled by the hydrophilicity/hydrophobicity or permittivity of the resins, through the Onsager's reaction field. This intriguing selectivity switching is supported by the polarized continuum model calculations. This method provides a promising strategy for switching of optical-resolution preferences by controlling the permittivity of the resins. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48317.     

Optimization of filling process in RTM using a genetic algorithm and experimental design method

In the resin transfer molding (RTM) process, preplaced fiber mat is set up in a mold and thermoset resin is injected into the mold. An important issue in RTM processing is minimizing the cycle time without sacrificing part quality or increasing the cost. In this study, a numerical simulation and optimization process for the filling stage was conducted in order to determine the optimum gate locations. The control volume finite element method (CVFEM), modeled as a 2‐dimensional flow, was used in this numerical analysis along with the coordinate transformation method to analyze a complex 3‐dimensional structure. Experiments were performed to monitor the flow front to validate the simulation results. The results of the numerical simulation corresponded with that of the experimental quite well for every single, simultaneous, and sequential injection procedure. The optimization analysis of the sequential injection procedure was performed to minimize fill time. The complex geometry of an automobile bumper core was chosen. A genetic algorithm was used to determine the optimum gate locations in the 3‐step sequential injection case. Taguchi's experimental design method was also used for determining the pressure contribution of each gate. These results could provide the information on the optimum gate locations and injection pressure in each injection step and predict the filling time and flow front.