活塞流反应器制备生物柴油

为实现连续、高效、稳定的生物柴油制备,本研究以自行设计的活塞流反应器制备生物柴油。同时利用正交实验的方法对制备过程的影响因素进行了较为系统的研究,得到的优化条件为:催化剂质量为油质量的1.2%,物料在活塞流反应器中滞留时间约17 min,床层温度65℃,油醇摩尔比约1∶6。在此优化条件下所得产品甲酯质量分数达96.33%。经减压蒸馏精制后,甲酯质量分数提高到98.62%,其他燃料特性也与德国现行生物柴油标准相符,同时接近甚至优于我国0#车用柴油标准。为生物柴油的大规模工业化应用奠定了良好的基础。     

Influences of heat transport on the determination of reaction rates using the temperature scanning plug flow reactor

The temperature scanning plug flow reactor enables the investigation of reactions over a wide temperature range with a small time exposure. The experimental data that are gained by carrying out a temperature scanning experiment can be used to calculate the reaction rate of each component of the reactant mixture. The temperature scanning experiment has to be carried out in a certain procedure that has to be fulfilled in order to be able to apply the underlying theory. The influence of the heat transfer coefficients on the determination of the reaction rates was investigated. The ammonia synthesis was taken as an example.     

Modeling a dense polymeric catalytic membrane reactor with plug flow pattern

A theoretical study on a tubular membrane reactor assuming isothermal operation, plug flow pattern and using a dense polymeric catalytic membrane is performed. The reactor conversion for an equilibrium gas-phase reaction generically represented by AB is analyzed, considering the influence of the product’s sorption and diffusion coefficients. It is concluded that the conversion of such a reaction can be significantly improved when the overall diffusion coefficient of the reaction product is higher than the reactant’s one and/or the overall sorption coefficient is lower, and for Thiele modulus and contact time values over a threshold. Though a sorption coefficient of the reaction product lower than that of the reactant may leads to a conversion enhancement higher than that one obtained when the reaction product diffusion coefficient is higher than that of the reactant, the contact time value for the maximum conversion is much higher in the first case. In this way, a higher diffusion coefficient for the reaction product should be generally preferable, because it leads to a lower reactor size. The performance of a dense polymeric catalytic membrane reactor depends in a different way on both sorption and diffusion coefficients of reactants and products and then a study of such a system cannot be based only on their own permeabilities. Favorable combinations of diffusion and sorption coefficients can affect positively the reactor’s conversion.     

Transient operation of a catalytic liquid-liquid plug flow reactor for kinetics measurements

A centrifugal partition chromatograph (CPC) was used as a liquid-liquid catalytic reactor for the isomerisation of hexen-3-ol into ethylpropylketone with a water soluble rhodium catalyst. Global mass transfer coefficients were measured and shown to depend on both the nature of the solute and the flow rate. Liquid-liquid partition isotherms were also determined with the CPC using elution chromatography. Finally, a reactor model was derived to account for the experimental results obtained both under stationary and transient (pulse) conditions. A parameter sensitivity evaluation is also presented.     

Residence time distribution of plug flow in a finite packed-bed chemical reactor

The residence time distributions in a finite packed-bed chemical reactor under plug flow conditions have been studied. Analysis was performed upon the well-known axial dispersion model in one dimension. Of paramount importance it was to construct a high order approximate solution to the corresponding initial-boundary value problem which appeared to be extremely convenient for fast numerical calculations. To this purpose singular perturbation techniq were applied using the reciprocal of the Péclet number as a small parameter. An error analysis was subsequently established for the special case of a pulse-function tracer input. The so-called “tailing phenomenon” of the response curve was simulated by an appropriate parameter-depending boundary condition of diffusion type.     

Differentiation criteria study for continuous stirred tank reactor and plug flow reactor

All reactors in reality are not ideal plug flow reactor (PFR) or ideal continuous stirred tank reactor (CSTR). They are difficult to differentiate. This study was to investigate the reactor analysis of PFR and CSTR through tracer response curves, residence time distributions (RTD) and several hydraulic performance indexes. We set up the differentiated value of each index. The tracer response curve showed that our lab-scale CSTR was close to ideal CSTR and got 99.9% recovery. In the RTD curves, the results could significantly recognize the PFR nature of high rate pond (HRP). With hydraulic performance indexes study, every selected index demonstrated that the studied HRP was closer to PFR than the studied CSTR. Based on the lab-scale study results, this study established the cutting point between the PFR and CSTR in each index; we were looking through the different types of reactors in literature and we confirmed the criteria with all literature reactors with the “graphic method”. The method helped us to establish those important values to help us to differentiate the reactor types in practice and to understand the designs better.     

A dynamic model for plug flow reactor state profiles

A dynamic model for state profiles of a plug flow reactor is developed, including multiple fluid and solid phases. The model is based on conservation of reactor state profile moments along the spatial dimension of the reactor. These moments are transformed analytically into a polynomial approximation at each time step. The method is flexible, and low as well as high order numerical schemes are resulted in by appropriate choice of parameters. A significant advantage of the present method is that boundary conditions of the partial differential equation reactor model are implicitly satisfied via the moment transformation, whereas the polynomial profile in the numerical solution does not have to be forced to satisfy the boundary conditions. The method is tested numerically against analytical solutions in three numerically challenging benchmark cases: prediction of breakthrough curve in packed bed adsorbers; simulation of chromatographic separation; and feeding a step impulse in a plug flow dimerization reactor. It is shown that the high resolution methods result in considerably smaller numerical errors than a simple low-order assumption of piecewise continuous solution.     

多级串联等体积全混流反应器与平推流反应器等效性研究——以二级可逆反应为例

在多级串联全混流反应器中,在等温等容条件下给出了二级可逆反应第Ⅳ级反应器的出口浓度表达式.讨论了在相同操作条件下,达到平推流反应器的转化率所需要的等体积串联全混流反应器的级数Ⅳ;主要考察了正反应速率常数k1、平衡常数K、反应物初始浓度之比M、停留时间τ等因素对N的影响,得出了N与正反应速率常数k1、相平衡常数K以及停留...     

Dilute acid hydrolysis of lignocellulosics: An application to medium consistency suspensions of hardwoods using a plug flow reactor

A one-stage process for the high temperature rapid dilute acid hydrolysis of hardwoods, to produce simultaneously furfural and fermentable sugars, is described. A continuous plug flow reactor unit designed to hydrolyse medium consistency wood suspensions (up to 13% w/w in solids) has been operated at capacities up to 90 kg/h, with temperatures ranging from 190°C to 240°C and 20-120 s as residence times. The final products, mainly furfural and sugars, have been analyzed using high performance liquid chromatography. Yields of 15 kg of hexoses (30% of the theoretical potential) and 10 kg of furfural (65% of the theoretical potential) for 100 kg of sawdust (dry basis) have been obtained. Two pseudokinetic modeis were used to simulate the pentosan and hexosan acid hydrolysis reactions. A Flowtran Simulation has been conducted resulting in mass and energy balances for an eventual industrial unit.     

Modelling of a continuous parallel plate plug flow electrochemical reactor: electrowinning of copper

Journal of Applied Electrochemistry - On the basis of copper winning in a sulphuric acid medium this paper presents an original calculation method for the design of a continuous parallel plate...     

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...     

Determination of optimal temperature profile in an OCM plug flow reactor for the maximizing of ethylene production

An optimal temperature profile for achieving the highest amount of ethylene production in a fixed bed plug flow reactor of oxidative coupling of methane (OCM) was determined and analyzed from chemical reactions point of view. A performance index was defined to solve the problem and the optimal temperature profile was found by means of “piecewise linear continuous optimal control by dynamic programming” (PLCOCIDP) algorithm. The performance obtained from the optimal temperature profile was compared with the best isothermal performance of the reactor, gained from optimization calculations. It was concluded that the quantity of ethylene production by applying the optimal temperature profile is about 42% greater than that of the best isothermal performance of the reactor at 1096.3 K. It was also observed that maximization of ethylene production and minimization of carbon dioxide production are interrelated in this system. The effects of total pressure and initial oxygen concentration were studied as well. The optimal temperature profile spread out and its minimum point rose a little with increasing the concentration of oxygen and/or decreasing the total pressure. Moreover, when the total pressure or initial oxygen mole fraction was elevated, the ethylene molar flux increased, however the selectivity of ethylene reduced in case of increasing the oxygen molar flux.     

Determination of global parameters of gas-phase oxidation reactions from heat-evolution rates in a plug flow reactor

We have obtained curves of heat evolution in the process of gas-phase interaction of oxygen with 1,1-dimethylhydrazine, dimethyl formamide, kerosene (T-1 fuel), 1-methyl-1,2-dicyclopropylcyclopropane, n-butyl alcohol, and toluene in a plug flow reactor, with high dilution with nitrogen. The values of the kinetic constants for the processes have been determined using the data obtained. The adequacy of the kinetic models for chemical processes that cause self-ignition of combustible mixtures has been shown by comparing calculation results concerning self-ignition parameters with the available experimental data. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 2, pp. 20–25, March–April, 1998.     

反应路径和反应器网络同步寻优

反应过程优化主要包括反应路径综合和反应器网络综合,反应路径综合研究原料到目标产物的化学转化途径,反应器网络综合的任务在于寻求适宜的反应器类型、尺寸以及反应器单元间的连接关系,并确定各反应器的最优操作条件。传统的研究将二者孤立,文中以功能性催化剂排列为切入点,提出了同步优化反应路径和反应器网络的超级结构法。通过优化生产目标产物反应过程中多种功能性催化剂的排列,得到生产目标产物的最优反应路径,并同步优化得到装填特定功能性催化剂反应器的网络结构。用提出的方法优化设计了对二甲苯的生产工艺流程,得到装填功能性催化剂反应器的网络,与装填单催化剂的反应器相比,等反应时间下,对二甲苯产率提高22.73%,实例验证了方法的有效性。     

Experimental and kinetic modeling study of ethyl butanoate oxidation in a laminar tubular plug flow reactor

This investigation examines the experimental and the kinetic modeling of the oxidation of ethyl butanoate (EB) selected as model molecule for fatty acid ethyl esters (FAEE). New experimental information of EB oxidation was generated from a laminar tubular plug flow reactor (PFR) operating at atmospheric pressure, under dilute conditions, over the temperature range 500–1200 K, with various equivalence ratios ranging from 0.5 to 1.6, and at residence times varying between 0.65 and 1.40 s under STP conditions. Concentration profiles of the reactants, stable intermediates, and final products, identified by GC/MS, were measured by infrared ray absorption and GC/TCD–FID analyses. Experiments of EB oxidation carried out in the tubular PFR were simulated using a detailed chemical kinetic oxidation mechanism (117 species and 1035 reactions) proposed in a previous work [Hakka et al. Int J Chem Kin 2010;42:226] and automatically generated from an improved version of EXGAS software. Globally, good agreement was observed between experimental and simulated results, confirming the validity of the proposed model for EB oxidation. Reaction flux and sensitivity analyses allowed to determine the main reaction pathways involved in the investigated conditions of EB oxidation.     

Characterization of the reaction environment in a filter-press redox flow reactor

The characteristics of a divided, industrial scale electrochemical reactor with five bipolar electrodes (each having a projected area of 0.72 m²) were examined in terms of mass transport, pressure drop and flow dispersion. Global mass transport data were obtained by monitoring the (first order) concentration decay of dissolved bromine (which was generated in situ by constant current electrolysis of a 1 mol dm⁻³ NaBr_(aq)). The global mass transport properties have been compared with those reported in the literature for other electrochemical reactors. The pressure drop over the reactor was calculated as a function of the mean electrolyte flow velocity and flow dispersion experiments showed the existence of slow and fast phases, two-phase flow being observed at lower velocities.     

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。