MASS TRANSFER IN THE LIQUID PHASE METHANOL SYNTHESIS PROCESS

The mass transfer characteristics of the liquid phase methanol synthesis process were experimentally investigated using a one-liter, mechanically agitated slurry reactor. The CuO/ZnO/Al₂O₃ catalyst was crushed to -140 mesh and suspended in an inert mineral oil (Witco # 40). The catalyst loading was varied within limits of experimental feasibility. The effects of temperature, pressure, level of oil, impeller speed, and gas flow rate on the overall gas-liquid mass transfer coefficient K_Lia_B were studied

The results obtained using a two-level, half-fractional factorial design of experiments indicated that the impeller speed, feed flow rate, and temperature had significant effects on the mass transfer coefficient at the experimental conditions examined. Correlations were developed for the Sherwood number based on the Reynolds number, the Schmidt number, the reciprocal gas flow number, the gas-liquid viscosity ratio, and the dimensionless temperature. A simplified power-law type approach was also used to correlate the overall gas-liquid mass transfer coefficient with the impeller speed, gas flow rate, and dimensionless temperature.     

MASS TRANSFER CCMPARISON BEIWEEN MECHANICALLY AGITATED SLURRY REACTCR AND LIQUID ENTRAINED REACTOR IN THE METHANOL SYNTHESIS PROCESS

ABSTRACT

The commercial reactor proposed for the liquid phase methanol synthesis process (LPMeCHTM) is a liquid entrained reactor (LER), since it possesses several operational advantages over a mechanically agitated slurry reactor (MASR). This paper discusses in detail the develocment of a correlation for the prediction of the overall gas-liquid mass transfer coefficient (KLiaB) in a LER. The overall mass transfer coefficient experimentally determined for the LER, is compared with the corresponding value obtained for the MASR under nominally identical operating conditions. It was observed that the overall gas-liquid mass transfer coefficient and hence the overall rate of methanol production per unit mass of catalyst, is significantly higher in the LER compared to the MASR at identical operating conditions. In the LER mode, the limitation posed on the system by chemical equilibrium, is alleviated by selective renewal of products thus making the process ideal for the once-through methanol (CIM) This justifies the proposed commercial mode of synthesis of methanol in the liquid entrained reactor.     

超重力场下络合铁法脱硫过程传质模型研究

H_2S是一种有毒有害气体,故天然气在使用之前必须进行脱硫处理。而超重力旋转填料床因其在巨大的剪切力作用下强化了传质,大大增加了设备的生产能力,且装置尺寸远远小于传统塔设备。超重力技术与氧化还原法结合在天然气脱硫领域具有较好的应用价值。因此,建立一个实用可靠的传质系数模型,对超重力技术脱硫的研究具有重要意义。用CH_4和H_2S的混合气模拟含硫天然气,并在某中试装置上用络合铁氧化还原法进行脱硫。根据所得的数据及旋转填料床中气液接触的特性,包括气体流量、液体流量、转子转速对体积传质系数的影响,采用Matlab进行相关数据拟合分析,得到传质系数经验模型。对经验模型进行分析对比,根据超重力装置气液传质的特性对经验模型进行了改进,得到最终的传质系数经验模型。最后,将建立的传质系数经验模型与实验得到的数据进行对比验证。经分析对比,模型与实验数据吻合程度较高,平均偏差仅为0.12%,且该模型可以外推到其他体积与该超重力装置近似的装置,但气体流量应为1~10 m~3/h,液体流量为0.1~1 m~3/h,转速为100~1 500r/min。     

Computer Simulation on Reaction Condition when Vinyl Acetate is Compound by Acetic Acid and Acetylene in Fixed Bed Reactor

Abstract

The macro-dynamics for synthesis of vinyl acetate on Zn(Ac)₂—acticarbon catalyst was studied. Consulting actual plant conditions by means of computer simulation, the parameters and reaction conditions for a fixed bed reactor used to produce vinyl acetate in acetylene method were calculated. The result shows that total heat transfer coefficient between catalyst bed and heat conductive oil could be affected by variety of conditions: catalyst diameter, airspeed, temperature and speed of heat conductive oil, and tube diameter in reactor. Analyzing the principles about how the factors affect the heat conduction, a laboratory reactor was made according to the analogue data. The actual temperature distribution of catalyst bed could inosculate with the analogue results roughly.     

自吸式气-液-液反应器的相分散和传质特性

研究了空气 水 煤油三相体系在自吸式搅拌槽反应器中的相分散和传质特性 ,比较了四种不同搅拌桨的油相分散临界转速、气体吸入临界转速、气体的吸入量、搅拌功率和气液传质系数 ,得到试验条件下的最优桨型为双层六叶涡轮桨 1,并系统研究了液相体积分数对搅拌操作性能和气液传质系数的影响。结果表明 ,随着油相体积分数的增大 ,油相分散临界转速降低 ,气体吸入临界转速不变 ,气体的吸入量减小 ,气液传质系数先降低 ,随后又升高 ,并基本保持不变     

硫磺回收装置加氢还原尾气超重力脱硫工艺技术研究

还原吸收尾气处理工艺广泛应用于硫磺回收装置含硫尾气处理,是减少尾气中SO_2排放最为有效的方法之一。硫磺回收装置加氢还原尾气的显著特点为:压力低,碳硫比高,要求吸收过程硫化氢脱除率高,同时具有吸收选择性。利用超重力技术强化传质及气液接触时间短等特点,将超重力技术应用于加氢尾气脱硫工艺中,考察了转速、气液比、贫液温度、气体流量等操作参数对脱硫性能及CO_2共吸收率的影响。结果表明,超重力技术应用于硫磺回收装置加氢还原尾气脱硫工艺中优势显著。     

黄原胶发酵过程中流变学行为和气液传质的研究

在10L搅拌式发酵罐中,研究了黄原胶发酵的流变学行为和气液传质特征。发酵液呈现典型的假塑性行为,后期发酵液稠度系数K大于20Pa.snn,流变指数n低于0.2,随着胶浓度的提高,搅拌所带来的剪切力不够,使有效搅拌区域减小,发酵液几乎不随搅拌浆而转动。考察了表观粘度ηm、搅拌转速N和通气速率Ug对体积氧传质系数kLa值的影响,将kLa值与转速N和表观粘度ηm进行了无因次关联。实验条件较高搅拌下的高剪切,不仅能提高整体混合,而且能够促进细胞周边分泌的黄原胶粘液层向主体扩散,有利于强化传递。在所研究的气速范围内,通气速率的提高似乎对气液传质的贡献不大。具有较高剪切和较大有效搅拌区域的反应器被认为更适合于黄原胶发酵过程。     

LIQUID PHASE METHANOL SYNTHESIS IN AN ENTRAINED REACTOR—DEVELOPMENT OF A GAS-LIQUID MASS TRANSFER CORRELATION

Abstract

Research on various aspects of the methanol synthesis was performed in a liquid entrained reactor. The catalyst-oil slurry is pumped through the tubular entrained reactor and syngas is fed cocurrently with the upward flow of slurry. The effect of different operating conditions, syngas composition and catalyst loadings on the productivity of methanol, was studied.

The data obtained from the experiments at high catalyst loadings in slurry, was used to develop a gas-liquid mass transfer correlation for the liquid phase methanol synthesis in an entrained reactor. The productivity of methanol in an entrained reactor was then predicted using the developed mass transfer correlation. This predictive model also helps in the design, development, scale-up and commercialization of the liquid phase methanol synthesis process in an entrained reactor.     

新型自旋导流表面曝气反应器性能的研究

应用多层桨自旋导流技术 ,设计了一种新型自旋导流表面曝气反应器。在内径为 15 4mm、液位高度 2 35mm的搅拌槽中 ,测定了自旋导流表面曝气系统的混合时间、搅拌功率和气液传质性能 ,并与Rushton桨与 4 5°上推斜叶透平桨组成的Rushton桨表面曝气系统进行比较。结果表明 ,自旋导流装置能有效改善上层桨和下层桨间流场的耦合 ,提高搅拌桨的操作效率 ,促进反应器内的分散和循环。与Rushton桨表面曝气系统相比较 ,在相同搅拌转速条件下 ,自旋导流表面曝气系统的混合时间更短 ,搅拌功率小 ;在相同功耗条件下 ,自旋导流表面曝气系统的气液传质性能优于Rushton桨表面曝气系统。     

CATALYST EFFECTIVENESS FACTORS UNDER GAS-TO-LIQUID MASS TRANSFER LIMITING REGIME IN LIQUID PHASE METHANOL SYNTHESIS PROCESS

The effectiveness factors of methanol synthesis catalyst were experimentally measured under condition of gas-to-liquid mass transfer limiting regime in the liquid phase methanol synthesis process, where the synthesis catalyst is slurried in an inert liquid phase. The experimental measurements of effectiveness factors were based on an intrinsic methanol synthesis rate per unit mass of catalyst (gmol/kg cat.h) which is not limited by external mass transfer. The experiments were carried out under well-defined conditions of temperature, pressure, syngas feed flow rate, and impeller speed. The experiments were carried out in a 1-L stirred autoclave. The catalyst slurry ratios were varied from 10 g in 550 mL of Witco-40 oil (corresponding to a slurry ratio of 2.2%) to 150 g in 550 mLof Witco-40 oil (corresponding to a slurry ratio of 25.1%). The experimental measurements have been summarized in one single plot as generalized catalyst effectiveness factor as a function of catalyst slurry ratio. The results of this study are extremely significant and practical in their applicability because the data were obtained using commercial methanol catalysts under actual commercial operating conditions of liquid phase methanol synthesis process.     

METHANOL PRODUCTIVITY COMPARISON BETWEEN AN AGITATED SLURRY REACTOR AND AN ENTRAINED REACTOR

ABSTRACT

The effect of various operating conditions including the catalyst loading in slurry, on the productivity of methanol in an agitated slurry reactor were studied. The modeling of the mechanically agitated slurry reactor was performed with the aid of the reaction rate expression and the gas-liquid mass transfer correlation that were developed, to predict the rate of methanol production for any inlet condition

The equilibrium limitation encountered in the liquid phase methanol synthesis process in an agitated slurry reactor can be alleviated by conducting this process in an entrained reactor, where the product methanol formed is continuously flashed out of the system. After developing a kinetic rate expression and a gas-liquid mass transfer correlation, the modeling of the entrained reactor was performed to predict the reactor productivity for any process condition. The rate of methanol production predicted for nominally identical operating conditions in an entrained reactor and in a mechanically agitated slurry reactor are compared with the aid of the computer models developed     

旋转填充床脱除裂解气中酸性气体的冷模实验

用空气和CO2的混合气体模拟裂解气,在旋转填充床中进行酸性气体吸收实验。考察了吸收液流量、吸收液浓度、空气流量、空气中CO2含量、旋转填充床转速和吸收液温度对气相传质系数(KGa)的影响。实验结果表明,KGa为0.2~3.0s-1时,KGa随吸收液流量、吸收液浓度、空气流量、旋转填充床转速和吸收液温度的升高而增大,随空气中CO2含量的增加而减小。用冷模数据推算工业操作条件(约1.5M Pa,50℃)下旋转填充床的吸收效果,预计可将裂解气中酸性气体的体积分数由1.00%降至1×10-6以下。旋转填充床脱除裂解气中酸性气体的效果优于传统的脱除工艺。     

Relationship Between Wetting Properties and Macroscale Hydrodynamics During Forced Gravity Drainage and Secondary Waterflood

Abstract

In order to relate the wetting properties at the pore scale to the macroscale prevailing forces, a series of experiments was performed in vertical porous media under forced gas invasion at various wettability conditions with partially spreading oil. To describe the dynamics of oil recovery in a three-phase flow condition, the downward gas flood experiments were continued by water injection from the bottom. Experimental results obtained in situations where the magnitudes of viscous, capillary, and gravity forces are comparable. We study the transition from flow configurations where the interface is stable with respect to viscous instability to flow configurations where viscous fingering occurs. The results also have been analyzed using a dimensionless number.     

COAL LIQUEFACTION WITH ANTHRACENE OIL. INFLUENCE OF SOLVENT PRETREATMENT,TEMPERATURE, CATALYST AND PRESSURE

ABSTRACT

The effect of solvent pretreatment, temperature, a CoMo/Al₂O₃ catalyst and pressure on coal liquefaction with anthracene oil has been evaluated. The experiments were conducted in a 500 ml autoclave with 10 g of a Spanish subbituminous A coal. 30 g of solvent, 1 hour reaction time and 400 rpm stirring speed. The liquefaction products were fractionated into oils, asphaltenes and preasphaltenes using pentane, toluene and THF as extractive solvents. The behaviour of anthracene oil as coal liquefaction solvent is very much enhanced by prehydrogenating it and by the addition ot an active catalyst. The influence of temperature depends on the operating conditions such as solvent pretreatment, catalyst, pressure etc. The addition of an active catalyst greatly improves conversion and the quality of the liquefaction products and diminishes repotimerization reactions. Hydrogen pressure is essential for coal liquefaction with anthracene oil, although over 16 MPa no further increase in coal conversion is observed.     

Effect of Recycle Gas Composition of the Performance of Fischer-Tropsch Catalyst

Abstract

In this study, the influence of CO₂ and CH₄ on the performance and selectivity of Co-Ru/Al₂O₃ catalyst is investigated by injection of these gases (0–20 vol.% of feed) to the feed stream. The effect of temperature and feed flow rate are also inspected. The results show that low amounts of CO₂ in the feed stream do not change the catalyst activity, but increasing the amount of CO₂ (more than 10 vol.%), causes the CO conversion to decrease and the selectivity of heavy components to increase. Methane acts as an inert gas and does not affect the catalyst performance. Increasing feed flow rate has a negative effect on both CO conversion and heavy component selectivity. By raising the temperature, CO conversion will increase but there are more volatile components in the product. The effect of CO₂ on catalyst deactivation is also investigated and a mechanism is suggested to explain the negative influence of CO₂ on catalyst deactivation.     

Modeling of CO2 capture from gas stream emissions of petrochemical industries by membrane contactor

Abstract

Process optimization of CO₂ removal from natural gas by a polyvinylidene fluoride hollow-fiber membrane contactor is a major goal of many computational fluid dynamics (CFD) simulations in this area. In this study, a 2D CFD model based on mass transfer equation inside the tube, the membrane, and the shell section of a HMFC at steady state and laminar conditions is developed and solved by COMSOL Multiphysics with finite element approach. Simulation results show an excellent agreement with experimental data. The model predicts that higher liquid velocity and membrane porosity results in higher CO₂ removal, because of enhancement of effective diffusion coefficient. Also, taller fiber length results in higher contact area and higher mass transfer of CO₂ from natural gas into distilled water. Although higher temperature will decrease the CO₂ removal.     

Numerical Simulation of V-cone Flow Meter in Product Oil Pipeline of Batch Transportation

Abstract

For product oil pipeline of batch transportation, this article describes the application of a V-cone flow meter in flow rate calculation of mixing oil in a pipeline, analyzes the velocity distribution in the internal flow field of a pipeline, obtains the qualitative relationship between the discharge coefficient of a V-cone flow meter and Reynolds number of mixing oil, and obtains the variation law of skin friction coefficient on the surface of the pipeline. The results show that a V-cone flow meter can overcome the shortcomings of a traditional flow meter. A V-cone flow meter can be used to measure the flow rate of a mixing oil section.     

HYDROCRACKING OF ARABIAN MIX ASPHALTENES IN THE PRESENCE OF MODIFIED RED MUD

ABSTRACT

Asphaltenes precipitated from an Arabian Mix vacuum residue were hydro-cracked in a batch autoclave at 435 and 460°C for 5-90 min. Experiments without catalyst, with modified red mud and with an industrial Co Mo/Al₂0₃ catalyst were compared. The products were fractionated into gas, naphtha, oil, asphaltenes and coke. Feed asphaltenes and several product fractions were characterised by elemental analysis, by average molecular mass and by ¹H n.mr. Due to the hydrogenation activity, both catalysts caused - with similar efficiency - the decrease of coke formation and the increase of quantity and quality of oil.     

The Effect of Temperature and Impeller Speed on Mechanically Induced Gas Flotation (IGF) Performance in Separation of Oil from Oilfield-Produced Water

Abstract

The effect of temperature and impeller speed on the performance of induced gas flotation (IGF) systems for the removal of oil from produced water in different ranges (5–300 g/L) of total dissolved solids (TDS) was investigated in a pilot plant study. Furthermore, it was evaluated whether the IGF pilot plant effluent could reach the 15 mg/L outlet oil content as required by Article VI of the Kuwait Convention for Persian Gulf region, before being discharged to the sea. The results showed that oil removal efficiencies up to 90% could be reached at high temperature (80°C) in just one single flotation cell without adding any chemicals. Flotation unit, however, should be followed by at least one more flotation cell in series in order to guarantee the Kuwait Convention marine pollution discharge standard for the effluent oil content.     

The Mechanism of Paraffin Oxidation

Abstract

Paraffin was mixed with microcrystalline wax at certain temperatures, airflow rate, and time. The catalyst and the catalyst promoter were added, and the oxidation reaction took place. Factors affecting induction period and activation energy, such as the airflow rate, the reaction temperature, the mass of the catalyst, the mass of catalyst promoter, and the reaction time, were also investigated. The induction period and the activation energy could be reduced, and the production's acid number and its saponification number could be improved by increasing the airflow rate and the reaction temperature. The productions can substitute the beeswax.