气相聚丙烯反应器的研究进展

聚丙烯气相法工艺具有流程简单、操作简便、装置安全性好等优点,是当前聚丙烯工业中应用最为广泛和最有发展潜力的工艺。气相聚合反应器主要包括流化床反应器、立式搅拌床反应器和卧式搅拌床反应器三种形式。本文调研了气相聚合反应器的实验和模拟的研究现状及进展,以期能够为聚丙烯反应器的设计与优化提供理论指导。     

根据气相法工艺标准论JPP工艺与AMOCO工艺在反应部分的比较

聚丙烯工艺包括催化剂单元、反应器单元、粉料分离、脱活、输送单元、挤压造粒单元、粒料输送、包装单元以及公用工程。反应器单元是Horizone工艺和Amoco工艺中的重要组成部分。第一反应器是一卧式带搅拌反应釜,反应器部分填充聚合物粉末,催化剂浆液送至反应器的上游区域并分散至粉料层,丙烯在气相状态下实现连续聚合。本文着重讨论了武汉采用日本JPP公司所用Horizone工艺的聚丙烯生产装置与扬子所采用的Amoco工艺生产装置在反应器单元的不同,并且从工艺的角度上讨论了这种不同的产生原因。     

流动反应器内返混研究

以多釜串联模型为主体,采用示踪法.对不同搅拌速率和不同流体流量下四联釜流动反应器内的返混状况进行了测定,建立了该系统的数学模型.结果表明,搅拌速率及流体流量影响系统返混程度大小,在实际的生产过程中,可以通过调节上述2个可控制的因素,对反应的过程进行控制和调节,使反应向着最有利的方向发展.     

小型热虹吸环流反应器中丙烯环氧化工艺条件

引　言钛硅催化剂 (ＴＳ - 1)上的丙烯与Ｈ2 Ｏ2 环氧化过程是环氧丙烷 (ＰＯ)洁净生产的发展方向[1,2 ] ,但对于环氧化反应器的研究尚很不完备 .该反应是一个强放热的气液固三相反应 ,要实现该反应过程的连续化 ,可以采用搅拌釜式反应器或固定床反应器(滴流床反应器 ) .搅拌釜式反应器主要用于催化剂性能评价 ,由于搅拌釜内物料返混严重 ,反应器体积效率较低 ;固定床反应器是由美国ＡＲＣＯ公司的Ｊｕｂｉｎ[3] 等发明的 ,实际上为多段气液呈并流向下的滴流床反应器 ,该反应器结构复杂 ,操作压力较大 (在 1.2 5ＭＰａ以上 ) ,且为了便于控…     

国内化工信息

燕化公司20万t/年聚丙烯装置一次投料开车成功 从1998年12月15日投催化剂开始,到12月17日产出聚丙烯颗粒料,这标志燕化公司20万t/年聚丙烯新装置一次投料开车成功。 该装置从开工建设到中交仅用了23个月,从中交到开工只用了15天,这些记录都谱写了特大型化工装置设计、建设,开工的新记录,至1998年底生产了5000多t产品。 这套聚丙烯装置是目前我国单线最大的气相法聚丙烯,全世界也只有5套,其技术特点是: （1）采用卧式釜的气相法工艺 其卧式带搅拌的聚合釜是近似柱塞式流动的运行方式,催化剂从一端注入,聚丙烯粉料从另一端流出,相当于串联了3个以上的返混式的操作单元,使用了短路催     

卧式四搅拌二氧化氮气相合成釜设计工艺探讨

通过对卧式二氧化氮气相反应器的工艺参数与工作条件的分析,对于设计压力为1.6MPa的气相反应器来说,在提高反应物的转化率以外,还得确保其反应物停留时间的准确性。对于复合材料的制作的卧式搅拌气相反应器,分析其工况及介质特性,在满足工艺过程的基础上,为设备设计提供可靠依据。     

磁稳定床己内酰胺加氢精制新工艺

对气液固三相搅拌釜反应器与液固磁稳定床反应器串联的己内酰胺加氢精制过程进行了研究,研究了各种操作参数对反应结果的影响,考察了催化剂的稳定性。实验结果表明,采用该工艺可使w(己内酰胺)=30%的水溶液的高锰酸钾值从50s提高到3000s以上,催化剂寿命3200h。与工业上釜式己内酰胺加氢精制工艺相比,催化剂耗量可降低70%。     

搅拌釜式反应器开孔补强的探讨

搅拌釜式反应器的设计过程当中,开孔补强的设计计算问题是最复杂。因为,在搅拌釜式反应器的釜体上需要的开孔数目多而且开孔类型各不相同。本文,通过分析研究搅拌釜式反应器的开孔补强计算方法的选择、开孔直径的判别、开孔补强的判别,提出如何对搅拌釜式反应器进行快速、简便的开孔补强设计计算。     

聚合釜釜型对偏氟乙烯乳液聚合的影响

偏氟乙烯(VDF)乳液聚合工艺的聚合效果关键是取决于VDF单体与水介质中助剂之间的传质效率。为研究较佳的聚合工艺参数,分别采用立式和卧式聚合釜,投入种类和规格相同的原料,在相同的温度和压力等操作条件下,研究较佳的VDF乳液聚合工艺参数。实验结果显示:釜型及搅拌桨形式在很大程度上影响了传质效率,采用卧式聚合釜能以较少的引发剂和乳化剂,得到较快的反应速率、较高的含固质量分数,且乳液稳定性更佳。因此可以认为卧式聚合釜是VDF乳液聚合较佳的聚合设备。     

丙烯连续聚合SPG工艺的工业应用

对中国石油辽河石化公司采用中国石化集团上海工程有限公司自主开发的SPG工艺(即丙烯液相本体与卧式釜气相本体组合式连续聚合工艺)进行了介绍,并与国内聚丙烯生产工艺进行了技术对比。工业生产实践表明,SPG工艺流程设计合理,在催化剂进料、预聚合及液相本体和卧式釜气相聚合组合技术上均有明显特色：各项技术经济指标显示,SPG工艺在聚丙烯工业中具有较好的推广前景。     

Multiple steady states,viscosity, and high conversion in continuous free-radical polymerization

Using existing literature data on the rate of a bulk polymerization of styrene in a batch reaction carried to high conversion, it is mathematically demonstrated that there is a clear possibility of the existence of multiple steady states induced by viscosity effects in isothermal continuous stirred tank reactors. In solutions of high viscosity, the rate of free-radical polymerization increases with conversion, reaching a peak at very high viscosity, then falling off rapidly. Given this sort of behavior, it is demonstrated mathematically that steady-state mass balance solutions are possible at three levels of conversion. The lower and higher steady states are stable while the middle steady-state condition is shown to be necessarily unstable. This multiplicity of steady states with its particular problems of stability is analogous to the much studied phenomena of temperature stability. It is closely related to the problems of concentration stability characteristic of autocatalytic and heterogeneous catalytic reactions. This multiple steady-state problem is qualitatively discussed in relation to reactor stability, control, and optimization.     

Semi-analytical solutions for a Gray-Scott reaction-diffusion cell with an applied electric field

An ionic version of the Gray-Scott chemical reaction scheme is considered in a reaction-diffusion cell, with an applied electric field, which causes migration of the reactant and autocatalyst in a preferred direction. The Galerkin method is used to reduce the governing partial differential equations to an approximate model consisting of ordinary differential equations. This is accomplished by approximating the spatial structure of the reactant and autocatalyst concentrations. Bifurcation analysis of the semi-analytical model is performed by using singularity theory to analyse the static multiplicity and a stability analysis to determine the dynamic multiplicity. The application of the electric field causes variation in the parameter regions, in which multiple steady-state and oscillatory solutions occur. Moreover, as the reactor is not symmetric, reversal of the direction of the electric field can cause bifurcation in the reactor between high and low conversion states. Comparisons with numerical solutions of governing partial differential equations confirms the accuracy and usefulness of the semi-analytical model.     

Analysis of a Two-Phase Perfectly Mixed Reactor under the Condition of a Phase Equilibrium

A mathematical model is formulated for a gas–liquid perfectly mixed flow reactor under the condition that the two-phase flow at the reactor outlet is at thermodynamic equilibrium. The phase equilibrium is calculated using the Redlich–Kwong–Soave equation of state. The set of nonlinear algebraic equations of the model is numerically solved by the efficient algorithm of the homotopy method. The steady-state modes of reactor operation are analyzed for liquid-phase benzene hydrogenation. It is shown that, under isothermal isobaric conditions, there can be a multiplicity of steady-state solutions, which is, on the one hand, due to the nonlinearity of the kinetic law and, on the other, due to the deviation of the properties of the reaction mixture from the properties of an ideal system. The stability of the steady-state solutions is analyzed, and the causes of the multiplicity and instability are explained.     

Autothermal operation of an adiabatic simulated counter current reactor

Periodic operation of several adiabatic fixed beds connected in series is an alternative to conventional steady-state fixed-bed operation or transient reverse flow reactor operation, e.g. to process lean waste gases or to perform efficiently slightly exothermic equilibrium limited reactions. This work explains the periodic operation of a multi-bed reactor network using both a simplified model assuming a true counter current of the phases involved and a more detailed dynamic model. An appropriate expression for relating the switching times and solid phase velocities is applied. The shapes of the thermal waves are studied in a range of relevant switching times. Results of a stability analysis considering both models reveal hysteresis for ignition and extinction of the reactor network. The accompanying regions of multiplicity provide insight in the potential of performing in such reactor networks exothermal reactions for certain ranges of the adiabatic temperature rise.     

The bifurcation behavior of a polyurethane continuous stirred tank reactor

In this work the open-loop nonlinear bifurcation analysis of a continuous stirred tank reactor where polyurethane polymerization reactions take place is carried out. The effect of potential manipulated, disturbance and design variables on the reactor nonlinear behavior is addressed. Moreover, the impact of cascade feedback control on the steady-state multiplicity pattern is also discussed. It is shown that cascade control introduces new nonlinearity patterns increasing closed-loop sensitivity.     

State multiplicity in PFR-separator-recycle polymerization systems

This article explores the non-linear behaviour of isothermal and non-isothermal plug-flow reactor (PFR)-separator-recycle systems, with reference to radical polymerization. The steady-state behaviour of six reaction systems of increasing complexity, from one-reactant first-order reaction to chain-growth polymerization, is investigated. In PFR-separator-recycle systems feasible steady states exist only if the reactor volume exceeds a critical value. For one-reaction systems, one stable steady state is born at a transcritical bifurcation. In case of consecutive-reaction systems, including polymerization, a fold bifurcation can lead to two feasible steady states. The transcritical bifurcation is destroyed when two reactants are involved. In addition, the thermal effects also introduce state multiplicity. When multiple steady states exist, the instability of the low-conversion branch sets a lower limit on the conversion achievable at a stable operating point. A low-density polyethylene process is presented as a real plant example.The results obtained in this study are similar to CSTR-separator-recycle systems. This suggests that the behaviour is dictated by the chemical reaction and flowsheet structure, rather than by the reactor type.     

Polymerization reactor: The influence of “gel effect” in batch and continuous solution polymerization of methyl methacrylate

This article describes the influence of gel effect in the free radical polymerization of methyl methacrylate. A mathematical model has been developed which tries to predict the performance of batch and continuous polymerization reactors under dynamic and steady-state conditions. The influence of diffusion phenomena on the process kinetics (gel effect) is very important. The autoacceleration in the polymerization rate of the batch reactor and the mulitple steady state for the continuous stirred tank reactor (CSTR) are connected with the attainment of critical conditions in the system. Such a model is useful for the design of the reactor and the choice of the control system.     

Study of gas-liquid stirred reactor stability taking into account the temperature influence on gas solubility

The paper is devoted to the dynamic behavior and stability of gas-liquid stirred reactor taking into account the temperature influence on gas solubility. Since the rate of gas-liquid processes is very sensitive to concentration of gas reactant dissolved in liquid, even weak fluctuations of temperature can significantly influence on process pass. There are two cases of temperature influence on gas solubility are possible: (1) the solubility decreases with increasing temperature; (2) the solubility grows with increasing temperature. The first case is typical for majority of gases. The second case occurs more rarely but has a great practical importance. It takes place, for example, for the hydrogenation of many compounds in organic solvents (such as benzene, toluene, isopropyl alcohol and others). A model of gas-liquid process has been developed to demonstrate the stability of gas-liquid reactor. It has been shown that the gas solubility behavior has an influence on the form of heat production curve and therefore on the multiplicity of the steady states. The areas of multiplicity and limit cycles were found and the phenomenon of hysteresis in the reactor was shown. A criterion to determine whether the multiplicity is possible under the given conditions was found. By means of an analysis of a mathematical model the stability of steady states of the reactor was studied.     

The determination of global solutions from local ones in catalytic systems showing steady-state multiplicity

The problem of constructing the steady-state solutions of the global (in the physical space) system, when local steady-state multiplicity is possible, repeats itself on various scales in heterogeneous catalytic reactors. This work presents a qualitative analysis that classifies this relation according to the physical system, the origin of steady-state multiplicity (thermokinetic, isothermal or truly kinetic) and the shape of the rate curve. A systematic approach for drawing the global observable bifurcation set from the local one is presented. The global features of a catalytic wire exposed to uniform conditions are usually identical to the local ones, i.e. inhomogeneities propagate out of the system. The existence of a global gradient in the adiabatic or isothermal heterogeneous plug-flow reactor or in the heterogeneous model of the catalytic pore adds one or even two stationary-front solutions. The latter problem, which accounts for adsorbate and fluid phases, applies only with truly kinetic multiplicity, and has not been considered earlier in the literature.     

气相法聚乙烯工艺冷凝态操作模式的稳定性和动态行为

气相法聚乙烯工艺冷凝态操作模式由于显著提高了循环气移热能力和反应器时空产率,已成为流化床乙烯聚合工艺的主流操作模式。建立了气相法聚乙烯工艺冷凝态操作模式的数学模型,包括流化床反应器模型,多级换热器模型和反应温度、压力以及循环气组成的控制模型。基于此,采用流程模拟方法,计算了系统在反应器温度采用闭环控制时的稳态解;根据系统对小扰动的动态响应特点,定性判断了反应器温度采用开环控制和闭环控制时聚合反应系统的稳定性;考察了系统对1-己烯分压和催化剂进料速率的阶跃响应特性。结果表明,反应器温度采用闭环控制时,聚合反应系统在所考察操作条件下均是稳定的,而采用开环控制时,解曲线被分叉点分割为稳定区域和不稳定区域。反应器温度对1-己烯分压阶跃变化的动态响应表明聚合反应系统存在长、短周期两类振荡,表明冷凝态操作模式下乙烯聚合反应过程是一个多控制回路耦合的复杂过程。