液膜性质的小尺度研究

Structured packing is a good candidate for CO₂ capture process because of its higher mass transfer efficiency and lower pressure drop.Now,the challenging problem of CO₂ capture and storage demands more and more efficiency equipment.The aim of the present study is to investigate the liquid film characteristics under counter current gas phase and throw some insight into the enhancing mechanism of mass transfer performance in structured packing.A high speed digital camera,non-intrusive measurement technique,was used.Water and air were working fluids.Experiments were carried out for different gas/liquid flow rates and different inclination angles.The time-average and instantaneous film widths for each set of flow parameters were calculated.It is shown that the effects of gas phase could be neglected for lower flow rate,and then,become more pronounced at higher flow rate.According to instantaneous film width,three different stages can be distinguished.One is the constant width of liquid film.The second is the slight decrease of film width and the smooth surface.This kind of character will lead to less interfacial area and deteriorate the packing mass transfer performance.For the third stage,the variation of film width shows clearly chaotic behavior.The prediction model was also developed in present work.The predicted and experimental results are in good agreement.     

自养型生物过滤器硝化氧化一氧化氮

Carbon foam-a, kind of new engineering material as packing material was adopted in three biofilters with different pore dimensions and adapted autotrophic nitrite nitrobacteria to investigate the purification of nitric oxide (NO) in a gas stream. The biofilm was developed on the surface of carbon foams using nitrite as its only nitric source. The moisture in the filter was maintained by ultrasonic aerosol equipment which can minimize the thickness of the liquid film. The liquid phase nitrification test was conducted to determine the variability and the potential of performance among the three carbon foam biofilters. The investigation showed that during the NO2--N inlet concentration of 200g·L-1-min-1 to 800g·L-1-min-1, the 24PPC (pores per centimeter) carbon foam biofilter had the greatest potential, achieving the NO--N removal efficiency of 94% to 98%. The 8PPC and 18PPC carbon foam biofilters achieved the NO2--N removal efficiency of 15% to 21% and of 30% to 40%, respectively. The potential for this     

采用增大凝结液滴方法的锥芯超音速旋流分离装置性能研究

To improve the separation performance of a supersonic gas separation device for the treatment of gas mixture with a single heavy component, a novel structure with shorter settlement distance was constructed and a method of droplet enlargement was applied. A series of experiments were carried out in the improved separation device under various conditions, using air-ethanol vapor as the medium and micro water droplets as nucleation centers. The effects of the inlet pressure, temperature and relative humidity, the swirling intensity, and mass flow rate of water on the separation performance were investigated. The separation was improved by increasing the inlet pressure and relative humidity. With the decrease of swirling intensity and mass flow rate of water, the separation efficiency increased first and then decreased. The inlet temperature had a slight effect on the separation. The results showed that the separation performance was effectively improved using the proposed structure and method, and the best separation in this study was obtained with the ethanol removal rate about 55% and dew point depression 27 K. The addition of water had little pollution to the air-ethanol vapor system since the water carry-over rate was within the range of %-0 in most cases.     

多管气升式环流反应器的液体循环

A multi-tube air-lift loop reactor (MT-ALR) is presented in this paper. Based on the energy conservation, a mathematical model describing the liquid circulation flow rate was developed, which was determined by gas velocity, the cross areas of riser and downcomer, gas hold-up and the local frictional loss coefficient. The experimental data indicate that either increase of gas flow rate or reduction of the downcomer diameter contributes to higher liquid circulation rate. The correlation between total and the local frictional loss coefficients was also established.Effects of gas flowrate in two risers and diameter of downcomer on the liquid circulation rate were examined. The value of total frictional loss coefficient was measured as a function of the cross area of downcomer and independent of the gas flow rate. The calculated results of liquid circulation rates agreed well with the experimental data with an average relative error of 9.6%.     

填料塔中碳酸钾/哌嗪混合吸收液脱除CO2的体积传质系数

The process of removing dilute CO2 from air by using me mixtures of K2CO3 and piperazine (PZ) was conducted in a random packed tower at 25℃. The results showed that PZ increased the absorption rate of CO2 into aqueous K2 CO3 much more effectively than MEA or DEA. The volumetric overall mass transfer coefficient (KGa) of dilute CO2 absorption into K2CO3/PZ was measured. The KGa value was evaluated over the ranges of main operating variables: the concentration of CO2 in inlet gas, gas flow rate, liquid loading, CO2 loading in liquid phase, and the concentrations of K2CO3 and PZ. The test showed that KGa could be remarkably improved by increasing liquid loading and the concentration of PZ, and decreasing the concentration of CO2 in inlet gas, as well as the gas flow rate and CO2 loading in liquid phase.     

加压下填料塔中液相轴向反混的研究

Liquid phase axial mixing was measured with the tracer technique in a packed column with inner diameter of 0.15m,in which the structured packing,Mellapak 350Y,was installed.Tap water as the liquid phase flowed down through the column and stagnant gas was at elevated pressure ranging from atmospheric to 2.0MPa.The model parameters of Bo andθwere estimated with the least square method in the time domain.As liquid flow rate was increased,the liquid axial mixing decreased.under our experimental conditions,the effect of pressure on Bo number on single liquid phase was negligible,and eddy diffusion was believed to be the primary cause of axial mixing in liquid phase.     

Spray and mixing characteristics of liquid jet in a tubular gas–liquid atomization mixer

For the design and optimization of a tubular gas–liquid atomization mixer,the atomization and mixing characteristics of liquid jet breakup in the limited tube space is a key problem.In this study,the primary breakup process of liquid jet column was analyzed by high-speed camera,then the droplet size and velocity distribution of atomized droplets were measured by Phase-Doppler anemometry (PDA).The hydrodynamic characteristics of gas flow in tubular gas–liquid atomization mixer were analyzed by computational fluid dynamics (CFD) numerical simulation.The results indicate that the liquid flow rate has little effect on the atomization droplet size and atomization pressure drop,and the gas flow rate is the main influence parameter.Under all experimental gas flow conditions,the liquid jet column undergoes a primary breakup process,forming larger liquid blocks and droplets.When the gas flow rate (Q_g) is less than 127 m~3·h~(-1),the secondary breakup of large liquid blocks and droplets does not occur in venturi throat region.The Sauter mean diameter (SMD) of droplets measured at the outlet is more than 140μm,and the distribution is uneven.When Q_g127 m~3·h~(-1),the large liquid blocks and droplets have secondary breakup process at the throat region.The SMD of droplets measured at the outlet is less than 140μm,and the distribution is uniform.When 127Q_g162 m~3·h~(-1),the secondary breakup mode of droplets is bag breakup or pouch breakup.When 181Q_g216 m~3·h~(-1),the secondary breakup mode of droplets is shear breakup or catastrophic breakup.In order to ensure efficient atomization and mixing,the throat gas velocity of the tubular atomization mixer should be designed to be about 51 m·s~(-1)under the lowest operating flow rate.The pressure drop of the tubular atomization mixer increases linearly with the square of gas velocity,and the resistance coefficient is about 2.55 in single-phase flow condition and 2.73 in gas–liquid atomization condition.     

聚氨酯合成革湿法生产废气中DMF的回收工艺

A new recovery technology is developed to recycle N,N-dimethyl formamide （DMF） in waste gas from wet type polyurethane synthetic leather industry. Given that the concentration of DMF in waste gas was as low as 325.6- 688.3 mg·m^-3, it was necessary to make sure two phases contact adequately and strengthen the mass transfer by increasing contact area and enhancing the turbulence. Therefore, two-stage countercurrent absorption and two-stage fog removing system were introduced into the technology. The top section of the absorption column was filled with structured wire-ripple stainless steel packing BX500, while the lower section with sting-ripple packing CB250Y. Total height of packing material was 6 m. In addition, there were both two-stage fog removing layer and high efficiency liquid distributor at the column top. All the operating parameters, including temperature, pressure, flow rate and liquid position, could be controlled by computers without manual operation, making sure the outlet gas achieved the national emission standard that the DMF concentration should be below 40 mg·m^-3. The whole equipment could recover 237.6 t of DMF each year, with the profit up to CNY 521×10^3.     

Direct extraction of Mo(Ⅵ) from sulfate solution by synergistic extractants in the rotation column

Direct extraction of molybdenum from sulfate solution with synergistic extractants(mixture of D_2EHPA and TBP)was studied in the rotation column. The influence of extractant concentration and initial pH of aqueous phase was studied in the bench scale experiments. The outcomes demonstrated that the synergistic solvent extraction enhances the constancy of the extracted complexes for transfer into the organic phase. In the continuous experiments, the effect of different operating parameters such as speed of agitation, inlet solvent flow rate and inlet aqueous flow rate on the holdup, mean drop size, drop size distribution, slip and characteristic velocities and extraction percentage were examined. Modified correlations were proposed for prediction of hydrodynamic parameters with consideration of reaction extraction condition in the rotation column. Furthermore, these correlations were compared with the experimental data. According to the results, the direct extraction of Mo(Ⅵ) from aqueous solution and sulfuric media with extraction efficiency of 90.4% was obtained at higher rotor speed(240 r·min~(–1) rpm) in this column.     

在高压下规整填料中的流动实验研究

Both distillation performance and hydrodynamic study for backmixing by tracer technique were carried out in a high-pressure packed column with 0.15 m inner diameter over a wide range of operating conditions. Isobutane and n-pentane are employed as test mixture in the distillation experiment and air/water is used for the hydrodynamic study. The column is installed with Mellapak 350Y structured packing and the total packing height is 2.0 m. With the increasing operating pressure, the separation efficiency increases slightly while the F-factor corresponding to the maximum efficiency at each pressure is descending. It is noted that, at all operating pressures, with the increase of F-factor, the packing efficiency is slightly higher up to the flooding point. The application of SRP model to high-pressure distillation gives much lower values of HTUOG than those obtained experimentally. An additional term, the height of mixing unit, is introduced to correct the SRP model and improve its accuracy at high pressure. From the tracer experiments, the height of mixing unit for gas phase was found to be larger than that for the liquid phase. From this viewpoint, it is believed that the gas phase backmixing gives more unfavorable influence on the separation efficiency in comparison with liquid phase.     

生物膜滴滤床内温度及其分布特性对废气净化性能的影响

对不同温度下,陶瓷球填料生物膜滴滤塔净化低浓度有机废气的降解性能以及填料床内温度分布进行了实验研究,实验结果表明：填料床内微生物生长环境温度对微生物酶活性影响很大,从而造成温度对滴滤塔净化性能的显著影响.微生物酶活性最高时的温度为30℃,最高滴滤塔净化性能所对应的温度在30～40℃.在滴滤塔顺流操作条件下,滴滤床内温度沿气液流动方向升高;在进口碳源浓度一定时,滴滤床内沿气液流动方向的温升随着液体流量的减小和气体流量的增大而升高;废气进口浓度及系统操作方式对滴滤床温度分布也有显著影响.     

Measurements and modeling of heat generation in a trickling biofilter for biodegradation of a low concentration volatile organic compound (VOC)

The experimental and theoretical heat generation behavior of a trickling biofilter treating toluene is discussed. The experimental results show that the temperature of the packed bed has a significant effect on the purification performance of the trickling biofilter and that an optimal operation temperature exists between 30 and 40 °C. During the gas–liquid co-current flow, the temperature in the packed bed gradually rises along the direction of the gas and liquid flow due to the exothermic biodegradation of toluene. The temperature rise between the inlet and outlet of the trickling biofilter increases with an increase in the gas flow rate and inlet toluene concentration. In addition, a larger liquid flow rate leads to a smaller temperature rise. The heat generation process occurring in the trickling biofilter is modeled by representing the packed bed as an equivalent set of parallel capillary tubes covered by the biofilm. The temperature profile in the packed bed during the liquid–gas co-current flow is analyzed by simultaneously solving the problem of gas–liquid two-phase flow and heat and mass transfer through the liquid film and biofilm. It is shown that the model agrees well with the experimental data, predicting the variations of the temperature rise between the inlet and outlet of trickling biofilter with the increasing gas and liquid flow rates.     

Removal of Xylene from Waste Gases using Biotrickling Filters

Two identical laboratory‐scale biotrickling filters, filled with different ceramic materials, were operated in order to investigate the removal of xylene from a waste gas stream. The biotrickling filter columns were seeded with pure bacteria identified as Bacillus firmus, which can utilize xylene as the sole carbon and energy source. The purification performance of the biotrickling filters was examined for xylene inlet concentrations C_g ≤ 3000 mg/m³ at different gas flow rates of 0.2 m³/h, 0.6 m³/h, and 1 m³/h, which correspond to gas empty bed residence times (EBRTs) of 84.8 s, 28.3 s, and 17.0 s, respectively. Both biofilters displayed a removal efficiency of no less than 95 % with the inlet xylene less than 3000 mg/m³ at the EBRTs of 84.8 and 28.3 s. When EBRT decreased to 17.0 s, the biofilter filled with ceramic particle type 2 had a better performance. The flow rate of trickling liquid has little effect on the removal efficiencies of the two filters. In the case of uneven distribution of trickling liquid in the packing materials, the performance of the biofilter can be improved by increasing the nitrogen nutrient supplement. Biomass quantity decreases as the depth of packing material increases in both biofilters, but the biofilter filled with ceramic particle type 1 had more alive bacteria per unit mass of packing material than the other.     

有机废气的生化处理实验研究

研究表明，采用国内现有微生物菌种挂膜接种的生物膜料塔净经低浓度有机废气是可行的，初步实验研究结果显示，增加人口气体甲苯浓度和气体流量，同时减小循环液喷淋量，可使甲苯的生化去除量增大，每升体积的生物膜填料对甲苯的生化去除量最大可达１５７．１３ｍｇ／ｈ。由实验结果推断，生物膜填料塔对废气中甲苯的净化去除过程属于传质控制过程，甲苯在生物膜内的降解为一级生化反应过程。     

规整丝网填料旋转填充床的气相压降特性及脱硫性能

采用空气-水体系,对装有4种不同规格规整丝网填料的旋转填充床的压降特性进行了实验研究,考察了转速、气体流量、液体流量等操作参数及填料特性对气相压降的影响规律,并与传统不锈钢波纹丝网填料旋转填充床压降进行了比较. 结果表明,装有规整丝网填料的旋转填充床压降可降低35%~70%. 进一步采用压降较低的规整丝网填料以(NH4)2SO3为吸收剂进行氨法脱硫性能研究,结果表明,随转子转速和(NH4)2SO3浓度增大,SO2脱除率升高;随进气口SO2浓度升高及气液比增大,SO2脱除率降低;SO2脱除率最高可达97%,可满足国家排放标准.     

生物膜填料床内含有生化反应的多相传输模型

废气处理生物膜滴滤塔的多孔填料床内是带有气液两相流动、有机污染物扩散、生物膜内生化反应的复杂生化反应体系.在平行平板理论模型基础上,建立了生物膜多孔填料床内含生化反应的多元多相流动及传输特性的多相混合模型,获得了废气处理生物膜滴滤塔净化效率的理论计算方法.模型的理论预测值与生物膜滴滤塔净化低浓度甲苯废气的实验结果基本吻合.     

Biodegradation of aromatic hydrocarbons in a compost biofilter

Two laboratory‐scale biofilters filled with the same type of packing material were operated at different gas flow rates and influent concentrations of toluene and xylene in order to investigate their performance in treating waste gas streams. The columns contained a mixture of municipal compost as a base material and wood chips as a bulking agent in an 80:20 ratio; the porosity was 54%. Microbial acclimation was achieved by addition of nutrient‐enriched solution along with pollutants for a week by daily mixing and natural aeration. During the start‐up of the systems with inlet concentrations of 20 and 70 ppm for toluene and xylene, respectively, high biomass growth resulted in pressure drops in excess of 2000 Pam^?1. Under steady state conditions, the response of each biofilter to variations in contaminant mass loading was studied by either changing the influent concentration or flow rate of the inlet waste stream. The results show that organic loading rates of up to 110 and 150 gm^?3h^?1 can be handled without any indication of the elimination capacity being saturated. However, maintaining the pressure drop below 1000 Pam^?1 to avoid operational problems, optimal organic loading rates for toluene and xylene of 78 ± 8 and 80 ± 14 gm^?3h^?1 respectively are suggested for an HRT value of 60 s. Under these conditions, elimination capacities of 73 ± 4 and 73 ± 14 gm^?3h^?1 and removal efficiencies of 94 ± 6% and 91 ± 8% were achieved for toluene and xylene, respectively. Copyright © 2003 Society of Chemical Industry     

生物滴滤塔处理甲苯工艺过程的影响因素研究

采用陶粒为填料的生物滴滤塔降解甲苯,实验研究了浓度和气、液体流量对甲苯降解能力的影响,实验结果表明,随着气、液体流量的增大,净化效率降低。对影响气体进出口温差的因素和填料床内液膜温度分布的结果进行实测和分析发现：进口甲苯浓度和液体流量、气体进出口温差成正比,而与气体流量成反比。液膜在填料床内的温度分布是沿塔高先降低后升高。     

An investigation of liquid maldistribution in trickle beds

The influence of liquid maldistribution at the top of the packing on flow characteristics in packed beds of gas and liquid cocurrent downflow (trickle beds) is experimentally investigated. Particular attention is paid to the effect of gas and liquid flow rates on flow development. Tests are made in the trickling and pulsing flow regimes. A uniform, a half-blocked and a quarter-blocked liquid distributor is tested. Packings of various sizes and shapes are employed. Data are presented on pressure drop and liquid holdup as well as trickling to pulsing flow transition. Diagnosis of radial and axial liquid distribution is made by means of conductance probes. The effects of liquid foaming, bed pre-wetting, top-bed material, and blockage midway the bed on liquid distribution are also examined. Overall, liquid waves in the pulsing flow regime have a beneficial effect, promoting uniform liquid distribution in the bed cross section.     

A trickling fibrous-bed bioreactor for biofiltration of benzene in air

A novel trickling fibrous-bed bioreactor was developed for biofiltration to remove pollutants present in contaminated air. Air containing benzene as the sole carbon source was effectively treated with a coculture of Pseudomonas putida and Pseudomonas fluorescens immobilized in the trickling biofilter, which was wetted with a liquid medium containing only inorganic mineral salts. When the inlet benzene concentration (C_gi) was 0·37 g m⁻³, the benzene removal efficiency in the biofilter was greater than 90% at an empty bed retention time (EBRT) of 8 min or a superficial air flow rate of 1·8 m³ m⁻² h⁻¹. In general, the removal efficiency decreased but the elimination capacity of the biofilter increased with increasing the inlet benzene concentration and the air (feed) flow rate. It was also found that the removal efficiency decreased but the elimination capacity increased with an increase in the loading capacity, which is equal to the inlet concentration divided by EBRT. The maximum elimination capacity achieved in this study was ∽11·5 g m⁻³ h⁻¹ when the inlet benzene concentration was 1·7 g m⁻³ and the superficial air flow rate was 3·62 m³ m⁻² h⁻¹. A simple mathematical model based on the first-order reaction kinetics was developed to simulate the biofiltration performance. The apparent first order parameter K_l in this model was found to be linearly related to the inlet benzene concentration (K_l=4·64−1·38 C_gi). The model can be used to predict the benzene removal efficiency and elimination capacity of the biofilter for benzene loading capacity up to ∽30 g m⁻³ h⁻¹. Using this model, the maximum elimination capacity for the biofilter was estimated to be 12·3 g m⁻³ h⁻¹, and the critical loading capacity was found to be 14 g m⁻³ h⁻¹. The biofilter had a fast response to process condition changes and was stable for long-term operation; no degeneration or clogging of the biofilter was encountered during the 3-month period studied. The biofilter also had a relatively low pressure drop of 750 Pa m⁻¹ at a high superficial air flow rate of 7·21 m³ m⁻² h⁻¹, indicating a good potential for further scale up for industrial applications. © 1998 Society of Chemical Industry