多级串联等体积全混流反应器与平推流反应器的等效性研究——以二级不可逆反应为例

在多级串联全混流反应器中针对二级不可逆反应,推导出第N级串级反应器的出口浓度表达式.为与平推流反应器进行比较,引人反应器的相对效率,在平推流反应器中一定的转化率条件下,考察反应速率常数和反应物初始摩尔比大于1的情况下对串联级数的影响.通过实例计算,得出随着相对效率的增大,串联反应器级数随之增大.而当串联级数达到5时,相...     

膜反应器的理论分析

以化学反应工程的观点,对一级可逆反应的膜反应器进行了理论分析。建立了反应速率和分离速率偶合的联立动力学方程求解方法,得出关于膜反应器的几个基本结论。1.膜反应器能促进反应效果必须具备下列条件:(1)膜的选择性 S_m 要远大于反应平衡常数 K_o 的倒数S_,》K_c~(-1)(2)正反应的速率常数 k 比反应物 R 的分离速率常数 k_R 要大一些。2.膜反应器的理想最大转化率 X_mX_m=1/[1+(S_mK_c)~(-1)]3.当无因次参数 m 为7.9时,膜反应器的相对转化率η为99%,且应该在 m≥7.9附近进行操作。4.膜反应器的各种参数与促进反应效果的最适宜的操作条件有关。通过分析,确定了膜反应器的总转化率有某一个理想的最大值,可得到理想的最大转化率、膜的选择性和平衡常数之间的关系。在设计条件和操作条件下,这种关系对于所研究的膜反应器是有效的。     

求多级串联全混流反应器的出口浓度-1/3级不可逆反应

在多级串联全混流反应器中进行1/3级不可逆反应时,可用作图法和代数法求每一段反应器的出口浓度。但图解法不够精确,代数法又较为繁琐,而且当反应器个数很多时,上述两种方法则无能为力。考虑以上两种方法的不足,就具体实例,寻求了另外一种方法,即依据第N段反应器的出口浓度的表达式,利用C++语言编制程序,通过该程序能够快速求出每一段反应器的出口浓度,结果与代数法计算结果基本一致。该法具有简便、精确、高效以及通用的优点,不仅在多级串联全混流反应器的设计中具有重要应用价值,而且在实际的化学工业生产中也具有重要意义。     

MATLAB在反应器优化设计中的应用

反应器设计过程中,如何确定最佳的操作条件,使得设计方案既满足工艺要求,又能降低设备投资及产品成本是一个非常重要的问题.本文分别采用传统方法和MATLAB优化工具箱中的fminsearch命令,对具有循环操作的平推流反应器、全混流反应器与平推流反应器串联两种反应器进行了优化,得到了最佳的操作条件.与传统方法相比,MATLAB方法简便快捷,结果准确可靠.     

N形折流反应器内颗粒停留时间分布研究

针对磷石膏矿化反应在搅拌反应器中易发生沉积形成死角的缺点,提出颗粒流化状态良好的内置双层导流筒的N形液固折流反应器,采用计算流体力学软件(CFD)模拟得到石膏颗粒在反应器中平均停留时间,并运用多釜串联模型来表达不同外循环量、进出料流量和颗粒不同粒径条件下反应器的返混程度。结果表明:在泵循环流量1.35、3.00、5.00 m~3/h条件下,模拟结果和实验结果吻合较好;反应器级数为1~3,反应器靠近全混流,理论级数、平均停留时间与进出料流量和泵循环流量成反比;磷石膏颗粒粒径越大,平均停留时间越长,粒径100μm的颗粒平均停留时间为71.5 min,而15μm的颗粒只有52.0 min。     

分段组合式厌氧生物反应器流态特性

厌氧生物反应器高效性与稳定性取决于其流态特性的优良,采用示踪剂脉冲刺激响应技术研究了自主研发的分段组合式厌氧生物反应器的流态,以期揭示其高效机理,便于工程化开发与应用。试验结果表明:常负荷下该反应器的流态趋于平推流;以轴向扩散模型表征,不产气与产气工况下的Peclet数分别为7.94和5.66;以多釜串联模型表征,不产气与产气工况下的串联釜数分别为4.55与3.44。高负荷与超高负荷下该反应器的流态趋于全混流,以轴向扩散模型表征,不产气与产气工况下的Peclet数分别为4.02、2.57和3.93、3.77;以多釜串联模型表征,不产气与产气工况下的串联釜数分别为2.66、2.00与2.62、2.51。反应器总死区的平均值为33.58%,其中水力死区的平均值为13.58%。建立了水力死区V_h(%)与容积水力负荷L(m³·m^-3·d^-1)和容积产气速率G(m³·m^-3·d^-1)之间的关联式。值得注意的是,在分段组合式厌氧反应器中,容积产气速率对水力死区的影响小于容积水力负荷。     

全混流反应器的定态操作点的讨论

从全混流反应器的热稳定性的角度讨论了全混流反应器操作点的选择问题，分析了各定态操作点的稳定性。指出应选择稳定的定态点作为操作点，当条件限制了选择范围时，可通过改变传热能力，介质温度达到定态操作点条件的目的。     

全混流反应器的定态操作点的讨论

从全混流反应器的热稳定性的角度讨论了全混流反应器操作点的选择问题，分析了各定态操作点的稳定性。指出应选择稳定的定态点作为操作点，当条件限制了选择范围时，可通过改变传热能力、介质温度达到改善定态操作点条件的目的。     

外环流氨化反应器数学模型及其放大

研究了外环流氨化反应器的流动模型、传质模型和放大规律 .结果表明 ,在工业条件下 ,此反应器中的液相流动接近于全混流 ,传质模型为kGa =0 61W0 3a q1 2a应用此模型已将反应器放大到年产 60kt固体磷酸一铵规模 .     

反应级数对理想反应器组合方式效率的研究

对于不同级数的不可逆反应,研究了其在全混流反应器(CSTR)与平推流反应器(PFR)不同组合方式中的最终转化率。对两种理想流动反应器的不同组合方式,如CSTR+PFR串联、PFR+CSTR串联及CSTR与PFR并联,反应的最终转化率随反应级数的不同而变化。当反应级数为负值时,CSTR与PFR并联组合方式的最终转化率最高;当反应级数为0~1之间的数值时,CSTR+PFR串联组合方式的最终转化率最高;而当反应级数大于1时,PFR+CSTR串联组合方式的最终转化率最高;当反应级数为0时,三种组合方式具有相同的最终转化率;但当反应为一级不可逆反应时,两种反应器串联时的最终转化率相同,并高于两种反应器并联时的最终转化率。     

Optimal design of continuously stirred membrane reactors in series using Michaelis-Menten kinetics with competitive product inhibition: theoretical analysis

Analytical expressions were derived for the optimal design (based on the minimum of the volume of the total number of reactors) of N continuously stirred membrane reactors (CSMRs) performing the enzyme-catalyzed reaction described by Michaelis-Menten kinetics with competitive product inhibition. The influence of membrane selectivity for both substrate and product on the total dimensionless residence time of the reactors (overall volume) was determined. The optimal design of N CSMRs (variable volume reactors) was compared with equal volume membrane reactors required to achieve the same degree of substrate conversion. The effect of kinetic and operating parameters on the performance of membrane reactors was determined. Optimization results show that membrane reactors are superior to continuously stirred tank reactors (CSTRs) in series at a high substrate rejection coefficient and low product rejection coefficient, high substrate conversion and using a small number of reactors. Also a high dimensionless Michaelis-Menten constant, high dimensionless inhibition constant and low substrate concentration in the feed to the first reactor improved the performance of the membrane reactors vs. CSTRs in series. The reduction in total volume of the optimal membrane reactors compared to CSTRs in series was up to 86% for the conditions in this work. A comparison between the optimum and equal volume design of membrane reactors in series showed no major difference in total volume between the two design criteria at a practical range of operating conditions. A volume reduction up to 16% was observed for the conditions in this work.     

Experimental study of the behaviour of an isothermal continuous stirred tank reactor in the course of an autocatalytic reaction

The dynamic behaviour of an isothermal continuous stirred tank reactor and of a two-element series of continuous stirred tank reactors in the course of an autocatalytic reaction of bistrichlormethyl-trisulphide with aniline, in methanol at 20°C, was studied. It was shown that the regime of the continuous stirred tank reactor and of the series is unstable ia a certain region of the conversion of the initial reaction component (bis-trichlormethyl-trisulphide) and that in a certain interval of the reaction mixture feed rate the reactor can operate at a single value of the feed rate in two (the series in three) stable states. The values of the bis-trichlormethyl-trisulphide conversion in steady states, as well as the dependence of the conversion on the period of stabilization of the reactor regime, determined experimentally in a continuous stirred tank reactor and in the series are in good agreement with the values computed from the kinetic data, determined in a discontinuous stirred tank reactor.     

Optimizing reactors selection and sequencing: Minimum cost versus minimum volume

The present investigation targets minimum cost of reactors in series for the case of one single chemical reaction, considering plug flow and stirred tank reactor（s） in the sequence of flow reactors. Using Guthrie＇s cost correlations three typical cases were considered based on the profile of the reaction rate reciprocal versus conversion. Significant differences were found compared to the classical approach targeting minimum total reactor volume.     

生物柴油新反应器及其应用

生物柴油是石化柴油的重要补充.用传统的搅拌釜和管式反应器制备生物柴油,存在反应速率慢、转化率低的问题.从提高反应速率和转化率两方面综述了生物柴油新反应器的研究进展.提高反应速率的反应器包括:微波反应器、空化反应器、旋转床反应器、振荡流反应器、高剪切反应器、静态反应器、微反应器和液液膜反应器.提高转化率的反应器包括:反应/分离器、反应蒸馏反应器和膜反应器.比较了它们的优势和缺陷.提出联合使用几种技术,将强化传质与分离技术进行有效整合,使反应器小型化并缩短工艺流程,以建立适应未来的生产效率高的便携式生物柴油厂.     

泰勒流反应器的流动及反应特性

利用由静态混合器、喷嘴和分气盒组成的新型布气装置在搅拌釜式反应器中诱导生成泰勒流,对反应器流动特性及反应特性进行了实验研究。结果表明,与常规搅拌釜式反应器相比,泰勒流反应器内物料流动更加接近于平推流流型,泰勒流的生成在反应器内构建出局部平推流区域,降低了物料返混程度。反应器反应性能因流动特性改变而得以增强,相同实验条件下,在泰勒流反应器中进行的蔗糖水解反应转化率比在常规搅拌釜式反应器中高出26.7%。在一定操作范围内,局部平推流区域和反应转化率均随搅拌转速或进气量的增加而增大。泰勒流反应器可简化为平推流区和全混流区并联的流动模型,推导出了反应转化率与平推流区域占反应器总体积比率之间的关联关系。     

An analysis of CSTRs in series for solution copolymerization

Continuous copolymerization is used in order to achieve a product of uniform composition. However, it is difficult to attain high conversions without resorting to very high residence times in a single tank. The way to avoid this is to use a series of stirred reactors with addition of one comonomer and initiator to each one after the first. The allowable half-life of the initator is a function of the residence time. When all the reactors are equal in volume so that the residence time is the same in each, it can be shown that the incremental conversion in each successive reactor must decrease in a well-ordered manner. As a specific example, a copolymerization is postulated with total polymer concentration restricted to the region where viscosity is manageable with conventional mixing equipment. Under these conditions the relative reactivity ratios are presumed to be constant and temperature can be held within narrow bounds.     

Experimental study on the optimum performance of an adiabatic MT reactor

The performance of an adiabatic MT reactor has been studied under various experimental conditions, using the reaction between hydrogen peroxide and sodium thiosulphate. Following the M-section, consisting of a CSTR, the T-section was made up of a large number of small stirred tanks in series. The same general condition for optimizing the MT model, that the reaction rate in the M-section be a maximum, is shown to apply when maximizing the conversion for a given residence time as it was shown previously to apply when minimizing the residence time for a given conversion. Very good agreement is shown between theoretical and experimental results, confirming the superior results often obtained with an MT combination as compared with those given by a stirred tank or a tubular reactor under similar conditions. Bi-stable steady states of conversion have been achieved and their effect shown on the performance of the combined reactor.     

Flow visualization and modelling of a filter-press type electrochemical reactor

A study of flow visualization and residence time distribution is provided in order to model the flow between two electrodes in a commercial filter-press reactor, the ElectroSynCell® from Electrocell AB. Flow visualization indicates that both axial and lateral dispersion phenomena occur and a global plug flow behaviour is observed. The flow distribution is asymmetric due to the design of the inlet system in the active zone. The flow throughout the cell is described by a dispersed plug flow model for which the mean residence time and the Pe´clet number are determined. The reaction area and the inlet system are separately analysed by locating conductimetric probes inside the electrochemical cell. The reaction area is also well described by a dispersed plug flow model, and characterized by high dispersion. The inlet system is, respectively, described by a dispersed plug flow model and by a cascade of continuous stirred tank reactors. The high number of reactors in the cascade denotes a quasi plug flow behaviour. The results are confirmed by two cascades of continuously stirred tank reactors in series. The dispersion coefficients obtained throughout the reaction area of the cell are not constant. This shows that the flow is not well established at the entrance of the reaction zone and depends on the entrance conditions.     

Performance characteristics of a cstr containing immobilised enzyme particles

The effects of internal and external substrate diffusion resistances on the performance of a continuous stirred tank reactor are analysed in this work. Both immobilised enzymatic reactions with and without substrate inhibitions are considered. The substrate conversion for the reaction without substrate inhibition is dependent on four dimensionless parameters: the Thiele modulus, the dimensionless Michaelis constant, the mass transfer Nusselt number and β, which represents a combination of particle hold-up, maximum reaction rate, input substrate concentration and substrate residence time in the continuous stirred tank reactor. For the corresponding reaction with substrate inhibition, the effect of the additional dimensionless inhibition constant on the substrate conversion is also very significant. The substrate conversion generally decreases with decrease in dimensionless parameter β, increase in Thiele modulus and decrease in mass transfer Nusselt number. For the reaction with small Thiele modulus, β and strong substrate diffusion resistances, a multireactor system may be needed if a certain desired substrate conversion is required. The single CSTR model can be extended to describe the multireactor system and the effect of the number of reactors on the substrate conversion for a two- or more reactor system is also examined.