Effect of governing parameters on pyrolysis of liquefied petroleum gases in the high-temperature heat carrier

Detailed measurements of temperature and product distributions are carried out during the pyrolysis of liquefied petroleum gases in a model reactor where the inlet conditions of the feedstock/heat carrier fast mixing are realized. The developed theoretical process model involves the detailed kinetic scheme that is tested by the reference data and our experiments. The yield of the most valuable product of petrochemistry, ethylene, substantially increased as compared to the conventional furnace-pyrolysis method is the specific feature of the performed experiments results. By the results of the numerical simulation, the effect of temperature, pressure, and residence time in the reactor on the pyrolysis product composition is determined. The calculation results enable to optimize operation conditions for the fast-mixing reactor.     

离子液体催化苯与1-十二烯烷基化的循环反应-分离实验装置

针对酸性氯铝酸盐室温离子液体［BMIM］［AlCl₄］催化苯与1-十二烯烷基化合成十二烷基苯（LAB）反应体系双液相、反应速率高和催化剂对湿气敏感的特点,建立了一套既可间歇操作也可连续操作的强制混合-反应-分离-再循环实验装置.循环物料和离子液体的混合与烷基化反应在一台静态混合反应器中进行,反应后料液和离子液体在一台液-液沉降器中进行分离.运行结果表明,在一定的物料循环和离子液体注入流量范围内,可以实现离子液体催化剂和反应料液的高效、快速混合与分离,催化剂被有效地保留在反应系统内并实现了它的再循环.     

Continuous reaction performances of benzene alkylation with long chain olefins catalyzed by ionic liquid

Based on a compulsive mixing-reacting-separating-recycling small experimental setup,the continuous reaction performances of benzene alkylation with long chain olefins catalyzed by [BMIM]Cl-AlCl₃ ionic liquid were investigated. Three different situations including normal continuous operation mode (reagent materials), sidetrack feeding from different axial positions along the static mixing reactor (reagent materials) and normal continuous alkylation using industrial paraffin and olefins materials were examined. Even under the relatively hypecritical reaction conditions, the single pass conversion of pure 1-dodecene could reach to nearly 100.0%, and the selectivity of 2-phenyl isomer was higher than 37.7%. Although the positions along the reactor for sidetrack feeding were different, the 100.0% single pass conversion of 1-dodecene was also attained before the outlet of the reactor. The refined industrial olefins as raw material could meet with the requirements of continuous alkylation. The influences of impurities such as di-olefins and non-benzene aromatics on the catalytic activity and stability should be studied further. __________ Translated from Chemical Reaction Engineering and Technology, 2006, 22(4): 289–293 [译自: 化学反应工程与工艺]     

生物质热裂解实验和模型研究(英文)

The analysis on the feedstock pyrolysis characteristic and the impacts of process parameters on pyrolysis outcomes can assist in the designing,operating and optimizing pyrolysis processes.This work aims to utilize both experimental and modelling approaches to perform the analysis on three biomass feedstocks—wood sawdust,bamboo shred and Jatropha Curcas seed cake residue,and to provide insights for the design and operation of pyrolysis processes.For the experimental part,the study investigated the effect of heating rate,final pyrolysis temperature and sample size on pyrolysis using common thermal analysis techniques.For the modelling part,a transient mathematical model that integrates the feedstock characteristic from the experimental study was used to simulate the pyrolysis progress of selected biomass feedstock particles for reactor scenarios.The model composes of several sub-models that describe pyrolysis kinetic and heat flow,particle heat transfer,particle shrinking and reactor operation.With better understanding of the effects of process conditions and feedstock characteristics on pyrolysis through both experimental and modelling studies,this work discusses on the considerations of and interrelation between feedstock size,pyrolysis energy usage,processing time and product quality for the design and operation of pyrolysis processes.     

Heterogeneous chain propagation on a quartz surface

Results of experimental and analytical studies of heterogeneous chain processes on quartz are given. A calculation is made of the ignition of an oxyhydrogen mixture in a quartz reactor under conditions of intense heterogeneous negative interaction of chains in the kinetic and diffusion regions. An energy criterion was developed experimentally that allows one to distinguish the range of reactions with an elevated probability of heterogeneous chain propagation on quartz. The possibility of the formation of atoms and radicals on the surface of quartz and conditions for their passage into the bulk are studied. The possibility of passage of hydrogen atoms from a microporous SiO₂ surface into the bulk is analyzed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 3, pp. 42–52, May–June, 2006.     

Producing ethylene and propylene from natural gas via the intermediate synthesis of methyl chloride and its subsequent catalytic pyrolysis

An original two-stage process for producing ethylene and propylene from natural gas via the catalytic pyrolysis of methyl chloride produced by methane catalytic chlorination is investigated. The kinetics of the methyl chloride catalytic pyrolysis on a silicoaluminophosphate catalyst SAPO-34 is studied and the process parameters are determined, yielding selectivities of 45% and 35% for ethylene and propylene, respectively, at 70% conversion of methyl chloride. The kinetics of methane oxidative chlorination is investigated on a catalyst that is a mixture of copper, potassium, and lanthanum chlorides deposited on a carrier. Based on the results from kinetic investigations, the process of methane oxidative chlorination is tested on an experimental setup in reactors of different types, two with fluidized catalyst beds (diameters 400 and 45 mm) and one tubular (diameter 27 mm), and on a pilot setup in a two-stage adiabatic reactor (diameter 800 mm). The process is tested with oxygen supply distributed for each stage at temperatures of 300–320°C at the inlet and 400–420°C at the outlet of the catalyst bed. The selectivity for methyl chloride formation among chloromethanes is 90%. A basic scheme is developed for a chlorine-balanced process of ethylene and propylene production from natural gas, and conditions for conducting methane oxychlorination and methyl chloride pyrolysis reactions in industrial reactors are determined. The process can be implemented at plants that need ethylene to increase deliveries of vinyl chloride and are experienced in working with hydrochloric acid and chlorinated derivatives of hydrocarbons.     

Computational study of convective–diffusive mixing in a microchannel mixer

Scalar mixing due to convection and diffusion in a microchannel mixer is studied using CFD. A method is developed to quantitatively measure the effect of false diffusion on scalar decay rate. This method computes an average false diffusivity from a given numerical solution and it is not limited to any particular numerical scheme. It is found that a range of molecular diffusivity exist in which average false diffusion is smaller than molecular diffusion and scalar decay rates can be computed accurately with CFD in the mixer. This range of molecular diffusivity covers most of the liquid solutions encountered in chemical and biochemical engineering. When effective diffusivity is used, this range can be further expanded. The predicted mixing structures agree well with experimental results in literature. The classical lamellar structures of the baker's transformation are strongly affected by diffusion. The striation doubling process is destroyed by diffusion broadening at very early stage in the mixer. The optimal mixing is achieved at low Re when the mixing mechanism in the mixer is the baker's transformation. At higher Re, secondary flow is generated and the mixing mechanism is the competition of the kinematics of the baker's transformation and the dynamics of the cross sectional flow. Results show that the secondary flow hinders mixing and the scalar decays at lower exponential rates than when the mixing is due to the baker's transformation alone.     

Continuous spin detonation of hydrogen-oxygen mixtures. 1. Annular cylindrical combustors

A comprehensive numerical and experimental study of continuous spin detonation of a hydrogen-oxygen mixture in annular combustors with the components supplied through injectors is performed. In an annular combustor 4 cm in diameter, burning of a hydrogen-oxygen gas mixture in the regime of continuous spin detonation is obtained. The flow structure is considered for varied flow rates of the components of the mixture and the combustor length and shape. The dynamics of the transverse detonation wave is numerically studied in a two-dimensional unsteady statement of the problem with the geometric parameters of the combustors consistent with experimental ones. A comparison with experiments reveals reasonable agreement in terms of the detonation velocity and pressure in the combustor. The calculated size and shape of detonation fronts are substantially different from the experimental data. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 32–45, March–April, 2008.     

An Analysis of Mixing in a Typical Experimental Set‐up to Measure Nnucleation Rates of Precipitation Processes

Mixing in a typical experimental setup to measure nucleation rates in precipitation processes was assessed. To determine these rates as a function of the driving force for concomitant polymorphs, it is necessary to perform these experiments at constant supersaturation. Therefore, the mixing time must be shorter than the time for the first nuclei to appear. For fast precipitation processes complete mixing has to be achieved within milliseconds. The mixing performance of a wide angle Y‐mixer was studied to see whether this is possible. An analysis of characteristic mixing times as a function of the average energy dissipation rate showed that turbulent dispersion of the feed streams determined the rate of the mixing process. The characteristic time for turbulent dispersion was of the same order as an arbitrarily set residence time in the Y‐mixer. However, CFD simulations of the flow showed large variation in the spatial distribution of the dissipation rate and revealed unsatisfying macromixing.     

Reactor development for the ultrapyrolysis process

A new impinging-jet reactor system has been developed for the fast pyrolysis (ultrapyrolysis) of particulate carbonaceous materials. The reactor system serves to promote rapid uniform mixing between a fine particulate heat carrier and a particulate feedstock in order to achieve the high heat transfer rates necessary for fast pyrolysis. Flow visualization experiments in a cold model testing unit indicated that the system performed effectively over a wide range of conditions. A sampling system utilizing isokinetic sampling probes was developed to investigate the small scale solids mixing. The effects of reactor geometry and operating conditions upon the solids mixing are reviewed.     

Mechanism for oxidation of yperite at high temperatures behind shock waves

The model for post-shock oxidation is based on the oxidation kinetics of one of the main intermediate products, chloroethane sulfonic acid. The kinetic constants for decomposition of this substance are calculated based on standard theories. A kinetic scheme for the subsequent reactions is proposed which takes the special conditions behind a shock wave into account (high radical concentrations). A previously developed program is used to calculate the variation in the concentrations of the components during oxidation of chloroethane sulfonic acid in a mixture of methane and air behind a shock wave. The calculations show that useful chemical products can be obtained under these conditions. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 2, pp. 70–74, Mach–April 1999.     

Mass transfer limitations in slurry photocatalytic reactors: Experimental validation

In the present work the existence of mass transfer limitations in slurry, photocatalytic reactors is studied. Experimental validation is made in a flat plate reactor that is part of a recycling system. The reactor is described with a mathematical model previously developed [Ballari et al., 2008a. Chemical Engineering Journal 136, 50], considering a transient, two-dimensional mass balance (TDM). The complete reactor model was developed to show the existence of these effects, which result from the occurrence of concentration gradients in reaction space. They develop when these reactors are operated under some operating conditions whose effects should be always analyzed before assuming the validity of existence of perfect mixing in reaction space. Dichloroacetic acid (DCA) was the adopted model compound. To solve TDM, a kinetic expression for DCA acid was determined before under well mixed conditions [Ballari et al., 2009. Industrial and Engineering Chemistry Research 48(4), 1847]. The studied variables are flow rate, catalyst loading, and irradiation rates. The experimental data agree quite well when they are interpreted in terms of the two-dimensional model (TDM) regardless of the operating mode. The perfect mixing model (PMM), normally employed to describe this and other types of slurry photoreactors, does not have the same level of universal application; i.e. it is restricted to perfect mixing, but in many cases far simpler to use. However, it can be concluded that when the photocatalytic reaction is not fast, employing catalyst loadings below 1 g L^–1, irradiation rates at the reactor wall below 1×10^?6 Einstein cm^?2 s^?1 and good mixing operation (Re>1700) it will be always safe to assume that mass transport limitations in the bulk of the fluid are nonexistent. In a typical batch reactor the above flow conditions are equivalent to very intense mixing. If the catalyst concentration is increased, the mixing conditions should be improved in the same proportion. Within limits, higher solid loadings can be compensated with lower irradiation rates [Ballari et al., 2008a. Chemical Engineering Journal 136, 50]. In addition, with the validated model, additional simulations are shown, operating the reactor under different virtual reactor thicknesses to widen amplitude of the reached conclusions. These findings will be useful in kinetic studies to prevent incursion in certain ranges of experimental conditions that could lead to erroneous interpretation of the obtained kinetic data.     

Numerical study of shock-wave diffraction in variable-section channels in gas suspensions

The problem of shock-wave transition past a backward-facing step in a gas suspension is solved. The calculation method is tested on a similar problem for a pure gas, and good agreement with available experimental and numerical results is reached. The effect of shock-wave intensity, mass load factor of particles in the mixture, and particle size on the flow structure in the gas suspension is determined. It is shown that the greatest difference between the flow pattern in a two-phase mixture and the corresponding flow in a pure gas is observed in the range of times when the characteristic sizes of the structures being formed are commensurable with the scale of the relaxation zones. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 85–95, January–February, 2008.     

Estimating the explosion hazard of aromatic azo compounds

This paper gives the results of temperature measurements at the beginning of fast decomposition of nine commercial azo dyes under heating. The enthalpies of formation of three azo dyes are measured, and the parameters of their explosive transformation are calculated. It is shown that for the flash temperatures obtained using the kinetic parameters of decomposition reactions and calculated heats of explosion of azo dyes, the average deviation from experimental values is 4.5%. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 93–97, September–October, 2008.     

Recycling and Activity Recovery of Chloroaluminate Ionic Liquid as Catalyst for Alkylation of Benzene with 1-Dodecene

Performances of 1-butyl-3-methylimidazolium aluminium chloride ([BMIM]Cl-AlCl3) ionic liquid as catalyst for the alkylation of benzene with long chain olefins were investigated in a continuous operation mode. A small pilot plant with continuous mixing-reacting-separating-recycling functions, equipped with a static mixer reactor, a tube packed with metal Al thread and a combined liquid-liquid settling phase separator, was introduced as an alternative. The results showed that the continuous fast mixing and separation of ionic liquid catalyst from reactant mixture could be synchronously accomplished within a wider flow rate ratio range of the recycling reaction mixture to the ionic liquid catalyst. The recycling of chloroaluminate ionic liquid was realized. ICP-AES detection results of Al content in the reactants proves that in-situ Al compensation to the reaction system may be an important choice to prolong the stable running time of moisture-sensitive ionic liquid [BMIM]Cl-AlCl3 when feedstock inevitably contains trace water. It suggests that the activity of chloroaluminate ionic liquid is recovered under the in-situ Al compensation operation.     

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.     

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。     

Continuous spin detonation of hydrogen-oxygen mixtures. 2. Combustor with an expanding annular channel

A comprehensive numerical and experimental study of continuous spin detonation of a hydrogen-oxygen mixture in an annular combustor with the components supplied through injectors is performed. The hydrogen-oxygen mixture is burned in the regime of continuous spin detonation in an annular combustor 4 cm in diameter with subsequent channel expansion. The flow structure is considered for varied flow rates of the components of the mixture and the counterpressure of the ambient medium. The dynamics of the transverse detonation wave is numerically studied in a two-dimensional unsteady gas-dynamic statement of the problem with the geometric parameters of the combustor consistent with experimental ones. Reasonable agreement with experiments is reached in terms of the shape of detonation fronts, detonation velocity, and height of the wave front. The optimal point of channel expansion beginning is chosen, which ensures the maximum specific impulse in the spin detonation regime. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 3, pp. 95–108, May–June, 2008.