基于CPFD的流化床数值模拟

流化床的数值模拟在流化床结构设计和放大中有着重要作用,目前得到广泛应用的多种基于CFD的数学模型在工业尺度的计算中存在不同缺陷。本文引入一种基于CPFD理论的方法,对射流流化床和鼓泡流化床分别进行了数值模拟,结果显示该方法能够有效模拟大量颗粒的两相流体系,反映颗粒和流体的真实运动状态。     

SiHCl_3流化床制备粒状多晶硅研究进展

综述了近年来关于三氯氢硅(Si HCl3)流化床制备颗粒状多晶硅工艺技术研究状况,详细介绍了国内外关于颗粒状多晶硅制备流化床设备的设计思路及制备情况,并讨论了反应器制备方法对产品纯度的影响,分析了"热壁流化床"的技术缺陷,"冷壁流化床"的技术优势,对下一步流化床技术发展进行了展望。     

预排气UASB反应器处理味精废水

采用预排气UASB反应器在35℃下处理味精废水,通过预先排除床层产生的大部分气体控制污泥的上浮,使有机污染物的厌氧消化集中在床部完成,同时采取逐步驯化接种污泥和控制适宜的进水碱度等措施,可使厌氧微生物适应较高浓度的味精废水和毒性抑制物,反应器在高负荷下运行.反应器的水力停留时间为2 h～3 h,COD去除率可达70%～80%,COD容积负荷可达40 kg/(m3·d).     

Combination of a Two-Zone Fluidized Bed Reactor with a Pd hollow fibre membrane for catalytic alkane dehydrogenation

The combination of a Pd hollow fibre membrane with a Two-Zone Fluidized Bed Reactor (TZFBR) is described for catalytic dehydrogenation of propane. This configuration aims to combine the in situ catalyst regeneration provided by the TZFBR with the increased conversion that can be achieved with a Pd membrane, which removes hydrogen from the reactor, thus enhancing the reaction rate and in theory allowing even higher than equilibrium conversion. The experiments show that the Pd hollow fibre membrane acts effectively removing hydrogen from the reaction media and that with a Pt–Sn/Al₂O₃ catalyst the TZFBR can achieve steady state operation in spite of the increased coking of the catalyst. However, with this catalyst the quicker coke formation caused by the removal of hydrogen outweighs the beneficial effect of hydrogen removal and the yield achievable for a given feed is lower in the presence of the membrane. A conclusion from these results is that a catalyst with lower coke tendency is needed to apply this combination of Pd membrane and TZFBR.     

环管式反应器中亚甲基蓝的光催化降解反应

采用环管式反应器,以Degussa P25为光催化剂和亚甲基蓝染料为代表性污染物,测定了20℃时亚甲基蓝在P25上的吸附,采用Langmuir等温吸附模型来拟合该实验数据;并测试了反应器中的紫外光分布,同时考察了P25颗粒剂量和空气流量对该三相鼓泡淤浆床反应器中液相光催化降解反应的影响.实验结果表明,最佳的P25光催化剂颗粒和空气流量分别为0.5g/L和800mL/min.     

Oxidation of Benzene to Maleic Anhydride in a Fluidized Bed Reactor

In this project, the selective oxidation of benzene to maleic anhydride (MAN) was studied. Gas phase catalytic oxidation of benzene was carried out in a laboratory scale fluidized bed reactor on six different types of catalysts, which have different compositions. Effects of temperature, flow rates of benzene and air and catalyst type on the reaction selectivity were investigated at atmospheric pressure. The experiments were performed over a temperature range of 325 to 400 °C, a space‐time (W/F_A0) range from 11.28 × 10⁵ to 31.9 × 10⁵ g s mol^–1, and benzene/air mole ratio changes between 0.0109 and 0.0477. It was seen that conversion of benzene to MAN increased with increasing temperature for the catalysts supported by silica gel, aluminum oxide and titanium oxide. From the results it was found that conversion increased with increasing flow rate of air. When the comparison of the catalysts were made, it could be said that catalysts supported by silica gel showed higher MAN conversions. So it can be concluded that catalysts supported by silica gel were more suitable catalysts for benzene oxidation to MAN in a fluidized bed reactor.     

三维电极反应器降解含酚废水研究

用经吸附处理的活性炭粒子构成的三维电极反应器对模拟苯酚废水进行降解处理,探究不同因素对苯酚降解率的影响。试验结果表明,当槽电压U=10 V,主电极间距d=6 cm,初始pH=6.5,支持电解质浓度CNa2SO4=3 g/L,电解初始浓度C苯酚为300 mg/L的模拟苯酚废水,30 min后降解率为84.21%。若应用在873 K下焙烧负载SnO2的优化活性炭粒子电极,催化降解效率可进一步提高10%。     

Manufacture of Granular Polysilicon from Trichlorosilane in a Fluidized‐Bed Reactor

Manufacturing of polysilicon by chemical vapor deposition from SiHCl₃ in a fluidized‐bed reactor was studied. The effects of reaction temperature, H₂/SiHCl₃ ratio, gas velocity, and seed particle loading were evaluated. The outlet gas composition was analyzed by gas chromatography. The physical features of the product particles were determined by scanning electron microscopy and laser particle size analyzer. Well‐grown product particles were obtained. The temperature and H₂/SiHCl₃ ratio significantly affected conversion, yield, and selectivity, which were less affected by gas velocity and seed particle loading at higher temperatures. The surface reaction kinetics determined the product yield only at lower temperatures, and thermodynamic equilibrium was approached at temperatures above 900 °C.     

Mathematical Modeling and Optimization of Combined Steam and Dry Reforming of Methane Process in Catalytic Fluidized Bed Membrane Reactor

Mathematical modeling of the methane-combined reforming process (steam methane reforming–dry reforming methane) was performed in a fluidized bed membrane reactor. The model characterizes multiple phases and regions considering low-density phase, high-density phase, membrane, and free board regions that allow study of reactor performance. It is demonstrated that the combined effect of membrane and reaction coupling provides opportunities to overcome equilibrium limits and helps to achieve higher conversion. Additionally, the influence of key parameters on reactor performance including reactor temperature, reactor pressure, steam to methane feed ratio (S/C), and carbon dioxide to methane feed ratio (CO₂/C) were investigated in the multi-objective genetic algorithm to find the optimal operating conditions. Finally, the process of steam reforming was simulated in selected optimal conditions and the results are compared to those of the combined reforming process. Comparison reveals the superiority of the combined reforming process in terms of methane conversion, catalyst activity, and outlet H₂/CO ratio in the syngas product in being close to unity.     

Optimization of Ammonium Nitrate Thermal Decomposition in a Fluidized Bed Reactor Using Differential Evolution (DE) Method

ABSTRACT

The reactions of alcohols and alkyl halides to synthesize di-ether compounds under phase-transfer catalysis conditions were carried out in an alkaline solution/organic solvent two-phase medium. Accordingly, the concentrations of alkyl halide, di-ether compound, active intermediate (QOR), and hydration number of active intermediate (QOR) were measured during these reactions. The fractional factorial design (FFD) method was first employed to study the effects of single factors and the effects of their interactions on the PTC reaction. The following reaction conditions (or factors) were investigated in the present FFD analysis: amount of alkaline salt, temperature, amount of water, amount of catalyst, volume of organic solvent, and agitation speed. A polynomial model and an analysis of variance table (ANOVA) were developed to connect the reaction conditions and the conversion from statistical results. Plots of the partition coefficient of alcohol between organic and aqueous phase, the concentration of active intermediate (QOR), and the hydration number of active intermediate (QOR) were used to elucidate the reasons for interactions between factors.     

Effect of pH on the Oxidation of Ferrous Ion and Immobilization Technology of Iron Hydr(oxide) in Fluidized Bed Reactor

Abstract

New, efficient, and a cheap method for the removal of ferrous ion from aqueous in a fluidized bed reactor was developed. Different from the adsorption process in the treatment of iron species, the immobilization of iron oxide on support media in a fluidized bed never reaches saturation. Furthermore, the immobilized iron oxide is reusable in catalysis and adsorption. Silica sand (Si) and iron oxide (SiG) were employed as support media to remove Fe(II) from aqueous in a fluidized bed reactor. The oxidation rate of Fe(II) and the immobilization rate of iron oxide are strongly depend on pH value so the variation of solution pH is considered to be the major parameter. Furthermore, the aeration effect on iron removal efficiency is investigated. 97% of total iron was removed at pH 8 in the presence of SiG and 87% of total iron was removed at pH 6 in the presence of Si. When the initial pH was adjusted to 6 and was not adjusted during the reactions, the optimum total iron removal efficiency (97%) was found. The air aeration was provided to keep the dissolved oxygen in constant. Aeration air accelerates the oxidation of ferrous ion, but does not improve the total iron removal efficiency.     

内循环生物流化床处理氮、磷废水的试验研究

采用内循环生物流化床系统,进行处理氮、磷废水的试验研究,通过控制曝气时间和溶解氧浓度,能同时达到脱氮除磷的性能.对于氮、磷废水,进水COD在352～1048 mg·L-1,TN在46.9～76.4 mg·L-1,TP在5.8～14.4 mg·L-1时,COD 、TN、TP去除率分别为92 %、80 %、93 %,出水可达到国家二级排放标准.     

Pyrolysis of Softwood Carbohydrates in a Fluidized Bed Reactor

In the present work pyrolysis of pure pine wood and softwood carbohydrates, namely cellulose and galactoglucomannan (the major hemicellulose in coniferous wood), was conducted in a batch mode operated fluidized bed reactor. Temperature ramping (5 °C/min) was applied to the heating until a reactor temperature of 460 °C was reached. Thereafter the temperature was kept until the release of non-condensable gases stopped. The different raw materials gave significantly different bio-oils. Levoglucosan was the dominant product in the cellulose pyrolysis oil. Acetic acid was found in the highest concentrations in both the galactoglucomannan and in the pine wood pyrolysis oils. Acetic acid is most likely formed by removal of O-acetyl groups from mannose units present in GGM structure.     

序批式活性污泥法处理城市污水试验研究

广州市城市污水具有有机物浓度低,碳、氮、磷比不合理的特点。采用序批式活性污泥法工艺对广州地区城市污水进行了实验研究。结果表明:在污泥负荷为0.14～0.26kg犤BOD5犦/(kg犤MLSS犦·d)时,出水BOD5为5.12～13.6mg/L,CODCr浓度为10.7～32.2mg/L,NH3-N为2.83～9.23mg/L,TP为0.1～0.45mg/L,证明了采用SBR工艺处理碳氮比较低的城市污水是可行的。     

Ozonation of Phenol-Containing Wastewater Using O3/Ca(OH)2 System in a Micro Bubble Gas-Liquid Reactor

The degradation of phenol in aqueous solution was investigated in an integrated process consisting of O₃/Ca(OH)₂ system and a newly developed micro bubble gas-liquid reactor. The effects of operating parameters such as Ca(OH)₂ dosage, reactor pressure, liquid phase temperature, initial phenol concentration and inlet ozone concentration on degradation and mineralization (TOC removal) were studied in order to know the ozonation performance of this new integrated process. It is demonstrated that the degradation and TOC removal efficiency increased with increasing inlet ozone concentration and increasing Ca(OH)₂ dosage before 2 g/L, as well as decreasing initial phenol concentration. The optimum Ca(OH)₂ dosage should exceed Ca(OH)₂ solubility in liquid phase. The reactor pressure and liquid phase temperature have little effects on the removal and TOC removal efficiency. When Ca(OH)₂ dosage exceeded 3 g/L, the degradation and TOC removal of phenol almost reached 100% at 30 and 55 min, respectively. The intensification mechanism of Ca(OH)₂ assisted ozonation was explored through analysis of the precipitated substances. The mechanism for Ca(OH)₂ intensified mineralization of phenol solution is the simultaneous removal of CO₃^2- ions, as hydroxyl radical scavengers, due to the presence of Ca²⁺ ions. Results indicated that the proposed new integrated process is a highly efficient ozonation process for persistent organic wastewater treatment.     

影响光催化超滤膜反应器降解Acid Blue 7的因素研究

设计研制了一种光催化超滤膜反应器,并选用一种颗粒状纳米级TiO2作光催化剂,对染料Acid Blue 7光氧化降解进行了研究。影响染料降解的因素包括：错流速度、催化剂浓度、染料初始浓度、溶液的pH值以及曝气条件。研究结果发现,光催化超滤反应器对染料废水处理具有较高的处理效果,且颗粒状光催化剂能够实现良好分离。     

Bifurcation Analysis of the Fluidized Bed Polyethylene Reactor with Internal Cooler

A mathematical model has been developed to simulate a gas‐phase ethylene polymerization reactor with internal cooler. The model was analyzed to determine the effects of reactor operating conditions on dynamics and stability. The reactor model employed assumed that both the gas and polymer phase in the reactor are well mixed. Comparing the present model to one with external heat exchanger confirms that, in either form, gas‐phase polyethylene reactors are prone to show unstable steady states, limit cycles and excursions toward unacceptably high temperature steady states. It was also observed that, with internal cooler, minor design changes in the cooler area available for heat transfer and in the inlet temperature of the coolant have a significant effect on the low stable steady state range of catalyst feed rates. With internal cooler, the suitable operating range increased with the increase in the area available for heat transfer. This effect is insignificant in the case of a reactor with external heat exchanger. Manipulating the reactor coolant inlet temperature and/or gas velocity can increase the stability range in the reactor with internal cooler as against one with external heat exchanger.     

好氧流化床生物膜反应器中氧传质过程与污水处理效能研究

好氧流化床生物膜反应器(AFBBR)因具有处理效率高、成本低、适用广泛等优点,在污水处理方面具有很好的应用前景。然而,关于该工艺的关键作用机理的研究仍不完善。为了从氧传质性能的角度提高反应器的运行效能,建立了好氧流化床生物膜反应器,并将其用于探究处理城镇生活污水过程中微生物呼吸作用、氧传质机制以及污水处理效果,并解析了微生物呼吸、氧传质性能以及处理效果之间的响应关系。结果表明,当曝气量为150 L/h、温度为20℃时,反应器内微生物耗氧速率(oxygen uptake rate,OUR)、标准氧总传质系数(K_La_s)较其他条件下显著增加;OUR与K_La_s呈现显著线性关系(R²≥0.97);曝气量为150 L/h条件下化学需氧量(COD_Cr)、氨氮、总氮(TN)和总磷(TP)污水处理效果最佳,分别可达96.55%、89.53%、86.20%和83.96%。     

Fluidized bed magnetic ion exchange (MIEX®) as pre-treatment process for a submerged membrane reactor in wastewater treatment and reuse

Magnetic ion exchange (MIEX®) resin can effectively remove significant amounts of organic matter from biologically treated sewage effluent. The MIEX® process has mainly been used as a batch process, which requires a large area for accommodating both contact tank and settling tank in the treatment process. In this study, a fluidized bed MIEX® reactor (a semi-continuous process) was used as a pre-treatment for a submerged membrane. When used as a pre-treatment for a submerged membrane, the fluidized bed MIEX® contactor could remove a significant amount of organic matter in the wastewater (80% removal). This pre-treatment helped to reduce membrane fouling and keep transmembrane pressure low during the membrane operation of 8 h (less than 19 kPa). The regeneration of MIEX® resin (number of regeneration, regeneration time, etc.) did not have any adverse effect on the organic removal by MIEX®.     

Degradation of Triacetone Triperoxide (TATP) Using Mechanically Alloyed Mg/Pd

A heterogenous catalytic system consisting of mechanically alloyed Mg/Pd particles has been used to degrade the peroxide explosive, triacetone triperoxide (TATP). The degradation of the TATP with the Mg/Pd particles (half life of 1.2×10¹ min) was compared to the degradation with microscale Mg particles (half life of 1.7×10³ min) and 10% Pd on activated carbon (half life of 8.7×10² min). Combining the Mg and Pd on carbon (Pd/C) through a mechanical alloying process is shown to produce reactive particles that can be used to degrade TATP. The major product of the degradation of TATP with mechanically alloyed Mg/Pd particles was acetone. A material balance for carbon was also calculated for the degradation reaction with 94±5% (mean±standard deviation) of the TATP carbons accounted for in the production of acetone.