Modeling and Optimization of Ethane Steam Cracking Process in An Industrial Tubular Reactor with Improved Reaction Scheme

Ethane steam cracking process in an industrial reactor was investigated.An one-demsional(1D)steady-state model was developed firstly by using an improved molecular reaction scheme and was then simulated in Aspen Plus.A comparison of model results with industrial data and previously reported results showed that the model can predict the process kinetics more accurately.In addition,the validated model was used to study the effects of different process variables,including coil outlet temperature(COT),steam-to-ethane ratio and residence time on ethane conversion,ethylene selectivity,products yields,and coking rate.Finally,steady-state optimization was conducted to the operation of industrial reactor.The COT and steam-to-ethane ratio were taken as decision variables to maximize the annual operational profit.

Continuous Production of Biodiesel from Soybean Oil Using Supercritical Methanol in a Vertical Tubular Reactor：I.Phase Holdup and Distribution of Intermediate Product along the Axial Direction

Production of biodiesel with supercritical methanol is a green synthesis process.A study was carried out in a vertical tubular reactor with a length of 3700 mm and a diameter of 20 mm at 275-375°C,15 MPa,and molar ratio of methanol to soybean oil of 40︰1.The phase holdup,intermediate product,yield and axial distribution of methyl ester(ME) were investigated.Methanol and oil were mixed non-uniformly due to the formation of biodiesel and difference in their densities,even when the reaction system was in the supercritical state.From top to bottom,the phase holdup of methanol increased and that of oil decreased.As temperature increased,the concentrations of monoglyceride and diglyceride decreased gradually and the ME yield increased.When the temperature reached 300°C,the critical temperature of the system,the ME yield was 50%.Further increase in temperature led to a sharp in-crease of ME yield.However,at 375°C after 1200 s of reaction time,the decomposition rate of ME was greater than its formation rate,reducing the ME yield.

Synthesis of Biodiesel Using ZrO_2 Polycrystalline Ceramic Foam Catalyst in a Tubular Reactor

With the help of the ceramic foam research efforts and preparation techniques, the ZrO2 polycrystalline ceramic foam catalyst was synthesized, and its characteristics, including the crystal structure, the phase composition, the acid–base properties, and the microstructure, were analyzed by XRD, SEM, Py-IR, and BET techniques. The performance of the ZrO2 polycrystalline ceramic foam catalyst in a tubular reactor was investigated via biodiesel synthesis using S. wilsoniana oil and methanol. The effects of reaction conditions(i.e., reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil) on transesterification efficiency were investigated, and the reaction conditions were optimized using RSM. The optimum reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil were determined to be 290 ℃, 10 MPa, and 4:1, respectively. Under this condition, the FAME content in the product oil reached 98.38%. The performance of the ZrO2 polycrystalline ceramic foam catalyst synthesized in this work for biodiesel synthesis from S. wilsoniana oil with a moisture content of 7.1% and an acid value of 130.697 mg KOH/g was examined, and the FAME content in the product oil was found to be 93% and 97.67%, respectively. The FAME content in the product oil exceeded 97% after five consecutive cycles(12 h per cycle of use) of the catalyst. The proposed catalyst represents a new type of solid catalyst with excellent acid resistance, water resistance, esterification efficiency, and catalytic stability.

Modeling and experimental studies of methyl methacrylate polymerization in a tubular reactor

In this study, rheological examination of the mixture of a tubular reactor in which methyl methacrylate was polymerized has been studied. The n(flow behavior index) value of Power Law Model of mixture contained in the reactor has been determined within the span of 0.3492 to 0.9889 by curve fitting. Employing these numerical data for velocity profile, the reactor has been modeled. Moreover, the functions of the reactor have been compared in the three modes of plug, mixed and laminar flow. The results obtained in this research indicate that the polymethyl methacrylate mixture contained in the reactor is pseudo-plastic. Moreover, as the conversion grows, the velocity profile starts as a parabolic profile and approaches the plug mode; although it never reaches the plug. The other conclusions borne in this study indicate that when the reactor's radius is decreased, the conversion rate grows. However, as decreasing the radius would also reduce the productions rate, this procedure is not economical. Finally, in this modeling, the amount of conversion is equal to 56.47% at the end and according to its laboratory proportion which is 55.88%, it has reached the conclusion that the modeling duly undertaken is applicable and valid.

Computational Modelling of the Hydride Generation Reaction in a Tubular Reactor and Atomization in a Quartz Cell Atomizer

In this study, we present a model whereby the centre of the atomization channel is shown to be the optimal location for the spectrometric data acquisition in a quartz cell atomizer. The study aims to explore the hydride generation technique which is normally coupled with efficient thermal source to apply determination of heavy metals in water samples via spectrometric analysis. The arsenic hydride generation process and the atomization of the generated hydride in a quartz cell atomizer were studied analytically as model case studies. The hydride generation (HG) process was analyzed by adopting two hypotheses, the nascent hydrogen and formation of intermediate hydroboron species, where the results based on the second hypothesis are found to be more realistic for design purposes. Moreover, the release of the generated hydride from the liquid phase and their transport to the gas phase is simulated in a helical tubular section, in which the actual tubular section length required for separation is deduced. The analytical results have been verified experimentally by measuring the signal intensity for the free arsenic atoms against several reaction tube lengths, in which increasing the tubular section length from 12 cm to 100 cm results in signal amelioration by no more than 6.6%. Furthermore, the atomization of the hydride and the distribution of the generated free atoms are deduced in two configurations of tubular quartz atomizers. The results obtained from both studied cases illustrate that a high concentration of the free analyte atoms is generated in the first part of the atomization channel, saturates to a maximum in a position at the atomizer centre, and dissipates at the inside wall of the tubular atomizer before reaching the atomizer outlet edge, which is found to be in total agreement with the current understanding of atomization mechanism in tubular atomizer and emphasizes the fact that the centre of the quartz cell atomizer is the best location for the spectrometric data acquisition.

Preparation of Ethylene Glycol Monoethyl Ether Acetate Using a Tubular Reactor

Ethylene glycol monoethyl ether acetate (EGEA), an excellent solvent, is prepared with ethylene oxide (EO) and ethyl acetate (EA) in a tubular reactor under suitable reaction condition. The single circulation yield can reach 81%. This technology is not only safe but also makes it possible to continuously produce EGEA in industry,with low content of high boiling point by-products.

VLDPE Synthesis by Radical Ethylene Polymerization in Tubular Reactors–Negative Factor or Unrealized Opportunities

This paper presents the results of polymeric deposit analysis in HP recycling system on two ethylene polymerization trains in tubular reactors when using mixed initiation (organic peroxides and oxygen) in the process of various grade production. It is demonstrated that polymers belong to the very low density type (with ρ in 0,860 to 0,900 g/cm3 range), due to ultra high branching. Consideration is given to known processes of that kind polymer production. There discussed the alternatives of different approaches to special process features found. It is stated that 80-year high pressure PE synthesis history has been keeping potential for the development.

Computational simulation of fluid dynamics in a tubular stirred reactor

The flow and concentration fields in a new style tubular stirred reactor were simulated by simulating the fluids dynamics(CFD),in which FLUENT software was used and the standard k-ε model and multiple reference frame(MRF) were adopted. The various values of initial rotating speed and inlet flow rate were adopted. Simulations were validated with experimental residence time distribution(RTD) determination. It is shown that the fluid flow is very turbulent and the flow pattern approaches to the plug flow. The velocity increases from shaft to the end of impeller,and the gradient is enlarged by increasing the rotating speed. Comparison between RTD curves shows that agitation can improve the performance of reactor. As the flow rate increases,the mean residence time decreases proportionally,and the variance of RTD lessens as well. When rotating speed increases to a certain value,the variance of RTD is enlarged by increasing rotating speed,but the mean residence time has no obvious change.

Performance of a tubular oxygen-permeable membrane reactor for partial oxidation of CH_4 in coke oven gas to syngas

A gas-tight BaCo 0.7 Fe 0.2 Nb 0.1 O 3-δ（BCFNO） tubular membrane was fabricated by hot pressure casting.And a membrane reactor with BCFNO tubular membrane and Ag-based sealant was readily constructed and applied to partial oxidation of CH4 in coke oven gas.At 875 ℃,95% of methane conversion,91% of H 2 and as high as 10 ml cm-2·min-1 of oxygen permeation flux were obtained.There was a good match in the coefficient of thermal expansion between Ag-based alloy and BCFNO membrane materials.The tubular BCFNO membrane reactor packed with Ni-based catalysts exhibited not only high activity but also good stability in hydrogen-enriched coke oven gas（COG） atmosphere.

STUDY ON THE PERFORMANCE OF VERTICAL TUBULAR LEACHING REACTOR

Hydrodynamics in vertical tubular leaching reactor was studied in this work. Based on the observation of particle saltation in curved and square return bends, the inclined return bend was developed and examined. For the narrow and wide size distribution particle system, the method for calculating the particle holdup in upflow and downflow tubes was derived on the basis of generalized fluidization equation. The model of unit pressure drop was given and examined by experiments.

大型轴向列管式固定床反应器的设计、制造、运输

通过对大型轴向列管式固定床反应器的列管布置、管板强度计算、支持板结构、管板的焊接及热处理、壳体组装、运输等多方面优化,从设计、制造、运输三方面综合考虑,使大型轴向固定床反应器的本质安全、运行效果达到更高的要求。

Natural gas pyrolysis in double-walled reactor tubes using thermal plasma or concentrated solar radiation as external heating source

The thermal pyrolysis of natural gas as a clean hydrogen production route is examined. The concept of a double-walled reactor tube is proposed and implemented. Preliminary experiments using an external plasma heating source are carried out to validate this concept. The results point out the efficient CH4 dissociation above 1850 K （CH4 conversion over 90%） and the key influence of the gas residence time. Simulations are performed to predict the conversion rate of CH4 at the reactor outlet, and are consistent with experimental tendencies. A solar reactor prototype featuring four independent double-walled tubes is then developed. The heat in high temperature process required for the endothermic reaction of natural gas pyrolysis is supplied by concentrated solar energy. The tubes are heated uniformly by radiation using the blackbody effect of a cavity-receiver absorbing the concentrated solar irradiation through a quartz window. The gas composition at the reactor outlet, the chemical conversion of CH4, and the yield to H2 are determined with respect to reaction temperature, inlet gas flow-rates, and feed gas composition. The longer the gas residence time, the higher the CH4 conversion and H2 yield, whereas the lower the amount of acetylene. A CH4 conversion of 99% and H2 yield of about 85% are measured at 1880 K with 30% CH4 in the feed gas （6 L/min injected and residence time of 18 ms）, A temperature increase from 1870 K to 1970 K does not improve the H2 yield.

高效溶气气浮设备的分析与应用

对高效溶气气浮设备的工艺原理、设计参数及整体设备的组成、性能特点、管式反应器特点、无堵塞溶气释放系统、刮渣排泥系统进行了分析论述。高效溶气气浮设备能够去除污水中的悬浮物、油脂、浊度、有机物等,提高处理后的水质指标,达到回收利用更多废水的效果。

烷基化反应器长周期运行存在问题分析及预防对策

某烷基化装置采用硫酸法烷基化工艺,烷基化反应器是烯烃与异丁烷在浓硫酸催化剂的作用下反应的主要场所,是烷基化装置的核心设备。烷基化反应器的长周期运行直接决定了烷基化装置异辛烷产品的质量和产量。结合装置运行的实际工况,针对烷基化反应器运行存在的问题,分析原因,找出影响烷基化反应器长周期运行的因素,采取相应的措施,保障烷基化反应器长周期运行。

Observer for Linear Distributed-Parameter Systems with Application to Isothermal Plug-Flow Reactor

This paper presents a conception of an exponential observer for a class of linear distributed-parameter systems (DPSs), in which the dynamics are partially unknown. The given distributed-parameter observer ensures asymptotic state estimator with exponentially decay error, based on the theory of C0-semigroups in a Hilbert space. The theoretical observer developed is applied to a chemical tubular reactor, namely the isothermal Plug-Flow reactor basic dynamical model for which measurements are available at the reactor output only. The process is described by Partial differential equations with unknown initial states. For this application, performance issues are illustrated in a simulation study.

管式加肋光催化反应器降解甲醛实验研究

为探究无肋片与有肋片条件下净化甲醛能力及不同浓度甲醛环境下气流速度和辐照度对甲醛降解效果的影响,分别采用无肋片管式光催化反应器和4片直肋管式反应器对甲醛进行波长为254 nm紫外光光催化氧化反应降解试验。结果表明,在反应器内部设置肋片在一定程度上可提高净化甲醛效果。在高浓度甲醛环境下,反应器净化甲醛最佳气流速度为2 m/s;在低浓度甲醛环境时,气流速度为1~2 m/s时,反应器净化甲醛能力无明显区别。而环境中甲醛浓度的变化对辐照度无明显影响。

精细化工过程连续化的研究进展

精细化学品是各行各业的关键组成,具有特定的功能,大多生产过程复杂、需求量相对较小。传统的间歇过程适合此类反应,但在社会的进步过程中,许多弊端不断显现。过程连续化就成为了主要的发展方向。广泛查阅了相关的科技文献,对该领域的发展状况进行了深入的总结分析。在此基础上,提出了连续化研究工作中的关键技术问题,以及未来的发展方向。

超高压自增强厚壁弯管应力分析

超高压管式反应器由经过自增强处理的厚壁直管和厚壁弯管组合而成,自增强厚壁弯管的受力难以通过理论分析得出。基于有限元方法对自增强厚壁弯管的受力情况进行了分析,并将结果与基于平面应变模型的自增强厚壁直管的有限元计算结果进行对比。研究结果表明,厚壁弯管的回转半径对自增强厚壁弯管的受力情况有显著影响,回转半径越大、厚壁弯管的受力情况越接近厚壁直管。以自增强厚壁直管在工作压力下内表面的当量应力幅值为衡量基准,当厚壁弯管回转半径增大到一定值,可以认为自增强厚壁弯管的疲劳性能与厚壁直管基本一致。对于目前国内LDPE/EVA装置中常用规格的厚壁自增强弯管,如果以厚壁直管内表面当量应力幅值的10%作为厚壁弯管当量应力幅值的最大偏差,则回转半径R的取值应大于7D_(o),当偏差为5%时,回转半径R需大于10D_(o)。该研究结果与国外引进的超高压管式反应器设计参数相吻合。

管式反应器内三甲基氯硅烷连续氨化制备六甲基二硅氮烷研究

针对三甲基氯硅烷半连续氨化反应生产效率低下,反应装置容积效率低的问题,设计并制作了三甲基氯硅烷连续氨化生产六甲基二硅氮烷的管式反应装置,探究了液相进料流量和浓度、气液比、循环流量等操作参数对反应装置运行效果的影响。结果表明:在液相进料总流量为9 mL/min,三甲基氯硅烷体积分数为20%,气液物质的量比为1.8,以及循环流量为240 L/h的条件下运行效果较佳,三甲基氯硅烷转化率达到94.91%,生产强度达到348.93 kg/(m^(3)·h)。该反应装置的顺利操作运行为三甲基氯硅烷氨化制备六甲基二硅氮烷提供了新型连续化生产工艺。

VTBR技术处理纤维素乙醇生产废水中试研究

针对纤维素乙醇生产废水,采用新型垂直折流生物处理反应器(VTBR)开展中试试验研究,对系统稳定运行过程中COD、氨氮、SO_(4)^(2-)、沼气产量等指标进行了考察分析。结果表明,VTBR技术可用于对高有机物、高氨氮、高硫酸盐特征的纤维素乙醇生产废水的处理,且处理效果稳定可靠,装置最终出水COD稳定在(2 617.9±442.7) mg/L,氨氮稳定在(75.7±21.4) mg/L,SO_(4)^(2-)稳定在(1 639.6±139.2) mg/L;中试装置COD、氨氮和SO_(4)^(2-)平均去除率分别达到(95.2±1.4)%、(83.1±4.9)%和(62.5±2.9)%;厌氧平均COD容积负荷为(3.5±0.6) kg/(m^(3)·d),好氧平均COD容积负荷为(1.0±0.5) kg/(m^(3)·d),好氧硝化作用平均NH_(4)^(+)-N容积负荷为(0.27±0.05) kg/(m^(3)·d);厌氧系统单位COD平均沼气产率为(0.50±0.08) m^(3)/kg;VTBR生物处理流程各工艺段B/C逐渐降低,好氧出水B/C小于0.15,且污染物为较难生物降解组分。中试结果同时表明,针对纤维素乙醇生产废水,若要满足达标排放的要求,仅靠生化处理较难实现,需进一步组合合理的深度处理技术。