混合-反应结晶过程(Ⅰ)实验

实验研究了半连续结晶器中混合特性与化学特性对反应结晶过程的影响,实验发现,混合特性对产物粒度分布的影响是非单调的,存在转捩点(criticl point),在该点平均粒径或方差为极小。分析表明,转捩点的出现是微观混合与宏观混合共同作用达到平衡的结果。

混合-反应结晶过程(Ⅱ)模型及验证

提出了1个包括3种不同尺度的微观混合、细观湍流分散及宏观返混在内的混合反应结晶过程模型,定量模拟了混合反应结晶过程中混合特性因素对产物平均粒径和方差的影响曲线上出现极小值的现象。对产物粒子粒度分布的模型预测与实验结果吻合良好。

疑似伤寒患者肥达反应检测阳性的探讨

肥达反应是由法国医师FermandWidal在 1896年建立的抗原 -抗体混合反应 (Widalagglutinationtest ,WAT) ,该试验一直用于临床伤寒的辅助诊断或进行流行病学的调查。但是非伤寒沙门菌引起的其他疾病 (疟疾、登革热、粟粒性结核病、心内膜炎、慢性肝病、布鲁杆菌等 )的病人血清抗体也会与伤寒沙门菌抗原发生交叉反应 ,该反应增加了WAT结果的假阳性率 ,降低了WAT特异性[1 ] 。 2 0 0 2年 9月 ,增城市石头村上百村民陆续发热 ,头痛 ,食欲不振和恶心呕吐 ,少数病人有腹痛腹泻 ,住进了医院 ,临床诊断疑似伤寒、副伤寒 ,对 45位病人先后两次抽血采样 ,作细菌学和血清学方面的检验 ,未检出伤寒沙门菌 ,肥达氏反应抗体滴度第一次普遍升高 ,而第二次的抗体滴度显著下降 ,同时作的登革热血清学检查结果呈典型的阳性 ,最后确认为登革热病毒流行病[2 ,3] 。目前对近期流行的SARS病的病人血液作肥达氏检验 ,发现肥达氏抗体滴度也有略微升高 ,这些现象可能是与免疫系统功能紊乱或发生免疫交叉反应以及免疫回忆有关 。

CSTR-ABR工艺在养殖废水处理工程中的应用——以淮南市天顺生态养殖有限公司沼气工程为例

以淮南市天顺生态养殖有限公司沼气工程为例,介绍了沼气工程的概况、工艺技术及流程、工程效果及效益。

Micromixing efficiency in a T-shaped confined impinging jet reactor

Confined impinging jet reactor(CIJR)offers advantages for chemical rapid processes and has become an important new reactor used in the chemical industry.The micromixing efficiency in a T-shaped CIJR for two tubes of inner diameter of 3 mm was studied by using a parallel competing iodide–iodate reaction as the working system.In this work,the effects of different operating conditions,such as impinging velocity and acid concentration,on segregation index were investigated.In addition,the effects of the inner nozzles diameter and the distance L between the jet axis and the top wall of the mixing chamber on the micromixing efficiency were also considered.It is concluded that the best range of L in this CIJR is 6.5–12.5 mm.Based on the incorporation model,the estimated minimum micromixing time tmof CIJR approximately equals to 2×10-4s.These experimental results indicate clearly that CIJR possesses a much better micromixing performance compared with the conventional stirred tank(micromixing time of 2×10-3to 2×10-2s).Hence,it can be envisioned that CIJR has more promising applications in various industrial processes.

Simulation of hydrocarbons pyrolysis in a fast-mixing reactor

Currently, thermal decomposition of hydrocarbons for the production of basic petrochemicals(ethylene, propylene) is carried out in steam-cracking processes. Aside from the conventional method, under consideration are alternative ways purposed for process intensification. In the context of these activities, the method of hightemperature pyrolysis of hydrocarbons in a heat-carrier flow is studied, which differs from previous ones and is based on the ability of an ultra-short time of feedstock/heat-carrier mixing. This enables to study the pyrolysis process at high temperature(up to 1500 K) at the reactor inlet. A set of model experiments is conducted on the lab scale facility. Liquefied petroleum gas(LPG) and naphtha are used as a feedstock. The detailed data are obtained on temperature and product distributions within a wide range of the residence time. A theoretical model based on the detailed kinetics of the process is developed, too. The effect of governing parameters on the pyrolysis process is analyzed by the results of the simulation and experiments. In particular, the optimal temperature is detected which corresponds to the maximum ethylene yield. Product yields in our experiments are compared with the similar ones in the conventional pyrolysis method. In both cases(LPG and naphtha), ethylene selectivity in the fast-mixing reactor is substantially higher than in current technology.

Necessary and Sufficient Conditions for Reactive Azeotropes in Multi-reaction Mixtures in Terms of Elemental Composition

Necessary and sufficient conditions for azeotropy in reactive mixtures are derived in terms of elemental composition, which shows that in the space of elemental compositions, they take the same functional form as the conditions for azeotropy in non-reactive mixtures. The production of methyl tert-butyl ether (MTBE) is taken as an example. It is found that there are a 'pseudo' intermediate-boiling ternary reactive azeotrope at p = 101.325kPa and two 'real' ternary reactive azeotropes at p = 101.325 Pa. The introduced elemental compositions also reduce the dimensionality of the phase diagrams and provide a natural set of variables for visualization of phase behavior.

Numerical simulation of micromixing effect on the reactive flow in a co-rotating twin screw extruder

To control the multicomponent reactions in extrusion, reactive-mixing flow in a co-rotating twin screw extruder was numerically studied in the present paper. Effects of initial species distribution, rotating speed and flow rate on a competitive-parallel reaction were investigated and the relationship between mixing and reactions was discussed from the view of chemical reaction engineering. The simulation results show the studied operational parameters, which determine residence time distribution, earliness of mixing and segregation degree of reactive-mixing flows, affect the local species concentration and reaction time and hence have significant influences on the reaction extent. Orthogonal test was adopted to clarify the significance of operational parameters.The analysis shows that initial species distribution and flow rate are the most important factors in the control of reaction extent, and effect of rotating speed is conditional depending on the micro-mixing status of the fluid.

Theoretical analysis of fluid mixing time in liquid-continuous impinging streams reactor

The mixing time of impact zone in liquid-continuous impinging streams reactor(LISR) is theoretically calculated by empirical model and modern micromixing model of the fluid mixing process, and the variation laws of macromixing time and micromixing time are quantitatively discussed. The results show that under a continuous and stable operating condition, as the paddle speed increases, the macromixing time and micromixing time calculated by the two models both decrease, even in a linkage equilibrium state. Simultaneously, as the paddle speed increases, the results figured by the two models tend to be consistent. It indicates that two models both are more suitable for calculation of mixing time in high paddle speed. Compared with the existing experimental results of this type of reactor, the mixing time computed in the speed of 1500 r/min is closer to it. These conclusions can provide an important reference for systematically studying the strengthening mechanism of LISR under continuous mixing conditions.

Evaluation of a novel hybrid bioartificial liver based on a multi-layer flat-plate bioreactor

AIM: To evaluate the efficacy and safety of a hybrid bioartificial liver (HBAL) system in the treatment of acute liver failure. METHODS: Canine models with acute liver failure were introduced with intravenous administration of D-galactosamine. The animals were divided into: the HBAL treatment group (n = 8), in which the canines received a 3-h treatment of HBAL; the bioartificial liver (BAL) treatment group (n = 8), in which the canines received a 3-h treatment of BAL; the non-bioartificial liver (NBAL) treatment group (n = 8), in which the canines received a 3-h treatment of NBAL; the control group (n = 8), in which the canines received no additional treatment. Biochemical parameters and survival time were determined. Levels of xenoantibodies, RNA of porcine endogenous retrovirus (PERV) and reverse transcriptase (RT) activity in the plasma were detected. RESULTS: Biochemical parameters were significantly decreased in all treatment groups. The TBIL level in the HBAL group was lower than that in other groups (2.19 ± 0.55 mmol/L vs 24.2 ± 6.45 mmol/L, 12.47 ± 3.62 mmol/L, 3.77 ± 1.83 mmol/L, P < 0.05). The prothrombin time (PT) in the BAL and HBAL groups was significantly shorter than the NBAL and control groups (18.47 ± 4.41 s, 15.5 ± 1.56 s vs 28.67 ± 5.71 s, 21.71 ± 3.4 s, P < 0.05), and the PT in the HBAL group was shortest of all the groups. The albumin in the BAL and HBAL groups significantly increased and a significantly higher level was observed in the HBAL group compared with the BAL group (27.7 ± 1.7 g/L vs 25.24 ± 1.93 g/L). In the HBAL group, the ammonia levels significantly decreased from 54.37 ± 6.86 to 37.75 ± 6.09 after treatment (P < 0.05); there were significant difference in ammonia levels between other the groups (P < 0.05). The levels of antibodies were similar before and after treatment. The PERV RNA and the RT activity in the canine plasma were all negative. CONCLUSION: The HBAL showed great efficiency and safety in the treatment of acute liver failure.

Co-pyrolysis characteristics of typical components of waste plastics in a falling film pyrolysis reactor

Waste plastics mainly come from MSW and usually exist in the form of mixed plastics. During the co-pyrolysis process of mixed plastics, various plastic components have different physicochemical properties and reaction mechanisms. Considering the high viscosity and low thermal conductivity of molten plastics, a falling film pyrolysis reactor was selected to explore the rapid co-pyrolysis process of typical plastic components(PP, PE and PS).The oil and gas yields and the compositions of pyrolysis products of the three components under different ratios at pyrolysis temperatures were analyzed to explore the co-pyrolysis characteristics of PP, PE, and PS. The study is of great significance to the recycling of waste plastics.

新型厌氧反应器处理餐厨垃圾浆液的研究

在中试规模、中温(38℃)条件下,研究脉冲-混合厌氧消化反应器(IMD)处理餐厨垃圾浆液的效果。试验结果表明:在负荷4.0 kgVS/(m^3·d)阶段,处理效果最好,VS产气率最高达到1.60 m^3/kgVS,沼气中的甲烷体积分数最高为68.9%;IMD反应器可在负荷6.0 kgVS/(m^3·d)下稳定运行,平均VS产气率为1.25 m^3/kgVS,平均VS去除率为79.11%。与其他厌氧反应器相比,IMD反应器处理餐厨垃圾浆液的容积负荷较高,处理效果较好。

CFD modeling of turbulent reacting flow in a semi-batch stirred-tank reactor

For the mixing-sensitive reactions, both chemical kinetics and mixing conditions of the reactants determine the distributions of products. The direct quadrature method of moments combining with the interaction by exchange with the mean micro-mixing model(DQMOM-IEM) has been validated for the chemical reacting flows in microreactors. Quite encouraging simulation results offer great promise, but the applicability of this method is needed to be explored furthermore, such as in stirred reactors. In this work, the two-environment DQMOM-IEM model was created with C language and used to customize Fluent through the user-defined functions. The mixing effects on the course of parallel competing chemical reactions carried out in a semi-batch single-phase stirred reactor were predicted. The simulation results show that the rising feed velocity enlarges the volume of reaction zone and maximize the yield of the by-product, which also indicates that the feed stream is more difficultly dispersed into the main stream and the zone surrounding feedpipe exit with high turbulent kinetic dissipation rate cannot be efficiently used.

Investigation of Nitration Processes of iso-Octanol with Mixed Acid in a Microreactor

In this paper, the nitration characteristic of alcohols with mixed acid for the synthesis of energetic mate-rials in a stainless steel microreactor was investigated experimentally. The nitration of iso-octanol with HNO3-H2SO4 mixed acid was chosen as a typical model reaction which involved fast and strong exothermic liquid-liquid heterogeneous reaction process. The influences of mixed acid composition, flow rate, organic/aqueous flow ratio and reaction temperature have been investigated. The results indicated that the reaction could be con-ducted safely and stably in the microreactor at 25-40°C, which are enhanced compared to 15°C or below for safe operating conditions in the conventional reactors. Moreover, the 98.2% conversion of iso-octanol could be obtained and no by-products were detected in all cases.

Micromixing Efficiency of Viscous Media in Micro-channel Reactor

Micromixing efficiency of viscous media in Y-type micro-channel reactor was studied by using iodide-iodate test reaction as working system.Experiments were carried out in water-glycerin mixtures with 7 different viscosities.The experimental results showed that segregation index of the micro-channel reactor increases with the decrease of volumetric flow rate and the increase of solution viscosity.Based on the incorporation model,the micromixing time tm of the micro-channel reactor was estimated in the range of 10-4-10-3s at different viscosities,which indicated that the micro-channel reactor possesses a much better micromixing performance compared to the stirred tank(tm=0.02-0.2s).

Micromixing characteristics in a gas-liquid-solid stirred tank with settling particles

The parallel-competing iodide-iodate reaction scheme was used to study the micromixing performance in a multi-phase stirred tank of 0.3 m diameter.The impeller combination consisted of a half elliptical blade disk turbine below two down-pimping wide-blade hydrofoils,identified as HEDT + 2WH_D.Nitrogen and glass beads of100 μm diameter and density 2500 kg-m^(-3) were used as the dispersed phases.The micromixing could be improved by sparging gas because of its additional potential energy.Also,micromixing could be improved by the solid particles with high kinetic energy near the impeller tip.In a gas-solid-liquid system,the gas-liquid film vibration with damping,due to the frequent collisions between the bubbles and particles,led to the decrease of the turbulence level in the liquid and caused eventually the deterioration of the micromixing.A Damping Film Dissipation model is formulated to shed light on the above micromixing performances.At last,the micromixing time t_m according to the incorporation model varied from 1.9 ms to 6.7 ms in our experiments.

Bubble Column Reactor Fluid-dynamic Evaluation at Pilot-plant for Residue and Extra-heavy Crude Oil Upgrading Technology

Bubble column reactors are multiphase contacting devices used in a wide variety of industrial application. Inrtevep S. A. is working on developing technologies to convert heavy and extra-heavy crude oil using this type of reactors. Volumetric gas hold up, flow pattern, average gas bubble size, average interfacial area, RTD （residence time distribution）, dispersion coefficient, Peclet number are important design parameters for a proper scale up of them. Several cold model experiments have been proposed to determine the previously mentioned parameters at atmospheric conditions, using a plexiglas bubble column reactor at pilot plant scale unit （12 cm diameter）. It was also evaluated our own design of internal trays （plates） in the reactor. Air-tap water and air-light oil systems have been used. A wide operating condition range was applied, superficial gas velocity between 0.5-10 cm/s, liquid flowrate between 15-65 I/h. Generally speaking, working without internal trays was found that gas hold up increase along the reactor and it was possible to identify heterogeneous bubble, transition and turbulent flow pattern areas for the air-light oil system. Average gas bubble size increase along the reactor at bubble regime from 2-5 mm but at turbulent regime, stay oscillating between 1-3 mm. Average interfacial area increases exponentially with superficial gas velocity at any reactor height, till 1,412 m2/m3 for the air-light oil system but, at bubble flow regime, the average interfacial area is lower than 100 m2/m3, which negatively impact the reactor performance. Internal trays in the reactor always increase gas hold up at any condition or system used. Residence time distributions curves, Peclet numbers and dispersion coefficients founded, show that this reactor with this kind of design internal trays still tends to be a complete mixing reactor under the operating conditions used.

Low-temperature Synthesis of Belite Cement from Reactive Mixtures Based on Coal Fly Ash

This paper summarizes the selected results of an extensive investigation of application of two methods （hydrothermal and mechanochemical） assisted by calcination for synthesizing belite cement from reactive mixtures （CaO/SiO2 molar ratio of 2） consisting of various waste kinds from fluidized brown coal combustion in Slovakian power plant and CaO addition. Based on XRD diffraction patterns and infrared spectra ofpre-treatment products, the formation of the new profiles corresponding to CSH phases with low degree of ordering as belite precursors after hydrothermal treatment as well as metastables calcium silicates and aluminosilicates in mechanosynthesized products was confirmed. Calcination of hydrothermally treated products led to transformation of CSH phases to wollastonite （CS）, belite and gehlenite phase, whereas creation oft^- and I^-C2S or wollastonite in milled reactive mixture took place. Differences in phase composition of products before and after calcination depend upon waste quality and precursor＇s synthesis conditions. Bottom ash isn＇t suitable as raw material for synthesizing belite phase because of high CaO content fixed in anhydrite form （44.1%）. Coal fly ash with low CaO content in anhydrite form （4.2%） and its mechanochemical or hydrothermal treatment in combination with subsequent heating offer opportunities for the utilization of coal fly ash as raw material for belite production.

Optimization of coproduction of ethyl acetate and n-butyl acetate by reactive distillation

Based on a previous investigation,a simulation model was used for optimization of coproduction of ethyl acetate and n-butyl acetate by reactive distillation.An experimental setup was established to verify the simulated results.The effects of various operating variables,such as ethanol feed location,acetic acid feed location,feed stage of reaction mixture of acetic acid and n-butanol,reflux ratio of ethyl acetate reactive distillation column,and distillate to feed ratio of n-butyl acetate column,on the ethanol/n-butanol conversions,ethyl acetate/n-butyl acetate purity,and energy consumption were investigated.The optimal results in the simulation study are as follows:ethanol feed location,15th stage;acetic acid feed location,eighth stage;feed location of reaction mixture of acetic acid and n-butanol,eighth stage;reflux ratio of ethyl acetate reactive distillation column,2.0;and distillate to feed ratio of n-butyl acetate,0.6.

Growth Response of Bacterial Antagonists in a Mix of Composted Wood Fibre Waste and Millet Seed under Sterile and Non-sterile Conditions

The potential use ofcomposted wood fibre waste （WFW） for the cultivation of bacterial antagonists of Sclerotinia minor was examined with the result that a mix of millet seed （20% w/w） and WFW, suitably amended with nutrients, proved to be an ideal matrix for the growth of some of these bacteria. Densities in terms ofcfu＇s ranged from 8.5 IOgl0 cfu/g dw to 10.5 logl0 cfu/g dw ullder sterile conditions after 14 days incubation. Lower population densities of the antagonists were achieved under non-sterile conditions in the compost： millet mix of between 7.9-9.3 logm cfu/g dw at the same period. However, when applied in a pot （glasshouse） trial to protect against S. minor, the millet seed appeared to stimulate the growth of this pathogen resulting in a high incidence of attack of lettuce plants after 2-3 weeks. Although the percentage of healthy seedlings increased following application of compost mix grown antagonists （at a rate of 5% v/v） when compared to the control treatment, these values were not statistically significant （p〉0.05） in most cases. Therefore, the use of millet seeds cannot be recommended as a nutrient supplement for the bacterial antagonist cultivation, if to be subsequently used to control fungal pathogens in the field.