Diagnosis of malfunction in fluidized beds is always a very difficult problem for a long time in academic circles and industrial circles. In this paper,we use acoustic sensor to measure the passive acoustic emissions (AE) from a bubbling fluidized bed.By comparison between acoustic and pressure signals,we found that acoustic signals are very sensitive to large particles such as agglomeration and particle sintering occurred in the bed and so on.Analysis of AE mechanism shows that AE measurement mainly stems from particle-chamber collisions and friction.AE measurements are completely non-intrusive and are not subject to erosion, corrosion, or plugging.Therefore, study and measurement of AE in different fluidization conditions will provide many new methods and trains of thought for detecting early deterioration of the fluidization quality.

Due to the pollution of groundwater by methyl tert -butyl ether(MTBE),the United States government in March 2000 interdicted this ether.Ethyl tert -butyl ether (ETBE) outranks MTBE as an octane enhancer since it shows the lower blending Reid vapor pressure, higher octane value and so on.For this reason,the research about the synthesis of ETBE had gained significant momentum over the past few years.In our previous work,the synthesis of ETBE from ethanol(EtOH) and tert -butyl alcohol (TBA) was studied by using cation exchange resin as catalyst via reaction, reactive distillation, reaction with pervaporation.In this work, catalytic reactive distillation coupled with pervaporation is restudied for the synthesis of ethyl tert -butyl ether from EtOH and TBA.A mathematical model for this combined process is developed.The model incorporates complex reaction kinetics,vapor-liquid non-idealities, distillation and pervaporation process.The rapid solution for this model can be obtained by modified overrelexation method.Simulation results are in good agreements with the experimental results.Some operating parameters are also optimized.

The collapse behavior of nano-particle SiO ₂(R972)is investigated in a 35 mm diameter fluidized bed.This powder can be easily and uniformly fluidized via self-aggregation.Collapse experiments indicate that the bed collapse curve of SiO ₂ particles is different from that of Geldart Group A and C particles.By analyzing the collapsing velocity,the bed collapse process can be clearly divided into two stages:a rapid initial sedimentation stage with constant velocity,and a decelerating stage of solids consolidation for the incompletely supended agglomerates.The bed collapse mechanism of agglomerate particulate fluidization is proposed.

Systematic experiments were conducted with FCC particles in a 16m high CFB riser to investigate the solids holdup in a fully developed section of the riser,with superficial gas velocity U _g from 2.0 to 10.3m·s ^-1 and solids circulating rate G _s from 5.4 to 230kg·m ^-2 ·s ^-1 .Of 134 sets of operation conditions employed in the experiments,there were 113 sets of operation conditions under which the gas-solids two-phase flow became fully developed in the upper or even the whole section of the riser.It is found that in a fully developed section of the riser,the average solids holdup ε _s increases linearly with increasing solids circulating rate G _s and decreases with increasing superficial gas velocity U _g,with a trend rather different from that reported in literature.The correlation developed in the paper,for solids holdup in a fully developed section of CFB riser,is in good agreement with the experimental data and also explains the differences among the predicted results of other authors,delineating more clearly the variations of solids holdup in a fully developed section with operation parameters.

In this paper, the global kinetic rate equations of the main and side reactions of ethylene oxide synthesis are studied in a gradientless reactor under industrial operating conditions. The two-dimensional heterogeneous model of fixed-bed reactor is set up for the simulation of industrial reactor. The Crank-Nicholson predicrot-corrector method is used in the integration for the gas phase and the iteration method is used for the solid phase.The accuracy of reactor model,global kinetic equations and heat transfer parameters were tested by comparing the calculated values with industrial actual values.These also show that the other transfer parameters cited in the calculation are suitable.The activity correction factors of the main and side reactions are correlated with time by regression of industrial operation data.The main and side reaction deactivation rates of sliver catalyst of ethylene oxide synthesis are also obtained through further research.The deactivation rates are used to forecasting the suitable time when the catalyst should be replaced and to optimize operating conditions in the later period of catalyst activity.

In a Ф0.5m×8m semicircular jetting fluidized bed with double nozzles using millet as fluidized material, studies of various flow regimes, i.e.,separate jet regime, transition flow regime and jet coalescence regime were carried out.The equations of transition of flow regimes were proposed.Experimental results indicated that penetration depth increased with increasing jet gas velocity,while penetration depth decreased with decreasing nozzle pitch.A relationship of penetration depth and nozzle distance in a large jetting fluidized bed with double nozzles was obtained.With smaller nozzle distance, jet coalescence always occurred and jet coalescence height replaced the penetration depth.Thus,a correlation of jet coalescence height was also presented.Meanwhile, deterministic chaos theory was used to investigate the flow hydrodynamic characteristics in the bed.When p/d 0 is equal to 5.48,the curve of correlation dimension vs .jetting gas velocity showed a maximum increase rate corresponding with complex flow structure.Correlation dimension increased with static bed height.

The models of mass transfer and crystal growth rate in cycling-fluidized crystallization were simulated by means of the theory of Whiteman’s mass transfer film.The experiment results show that within the some conditions,the crystal growth rate in cycling-fluidized crystallization is only related with the physical and chemical properties,the super-saturation level and the diameter of crystal seeds in crystal system, which regularity is that the crystal growth rate is in direct proportion to the diffusivity of solutes,the diameter of crystal seeds,the relative density between solution and the solute and the super-saturation level,and in inverse proportion to the viscosity of solution,the density of crystal,so with them the crystal growth rate in cycling-fluidized crystallization can be easily predicted among wide flow speed ranges by the models.

A mathematical model was built to describe the mass transfer processes and competitive adsorption in a fixed bed packed with activated carbon fibers (ACFs).The orthogonal collocation method was used to simulate the mathematical model in order to predict the breakthrough curves.The effects of competitive equilibrium constants, axial dispersion,intrafiber diffusion and external mass transfer resistance on the breakthrough curves were investigated for weakly-adsorbed and strongly-adsorbed components.The experiments were carried out to remove the phenolic compounds from water.With the equilibrium data and the intrafiber diffusivities obtained from separate experiments in a batch adsorber, axial dispersion coefficient was obtained by fitting the experimental data of breakthrough curves with the theoretical model.The effects of intraparticle and external mass transfer resistances can be negligible for the fixed bed packed with ACFs,and the axial dispersion is confirmed to be the main parameter that controls the adsorption kinetics.A simpler model, based solely on liquid phase mass balance and incorporating local equilibrium with axial dispersion, provides a good description of the process.

A simple pyrolysis method is presented,in which the coal is preheated with flue gas in a fixed bed. The high heat penetration into the packed bed of coal particles is described mathematically with a reaction and transport model. The temperature profiles for the particles,and the transient local distribution of volatile matter are examined under different conditions. The thermal penetration into the packed-bed particles by fluid flow is analyzed. The thermal penetration depth and coal pyrolysis zone moves along the bed with time. Increasing inlet gas temperature tends to enhance the temperature level in the thermal penetration zone and decrease the pyrolysis time. The model results are found to agree the experimental data available in literature.

According to rigorous procedures, an experimental study was carried out to investigate the effects of jet exit velocity, flow direction, fluid subcooling and nozzle diameter on hysteresis of boiling heat transfer with impinging circular submerged jets of highly-wetting liquids. The experimental results showed that incipient boiling point decreased with increasing fluid subcooling and was independent of other factors, and that temperature overshoot enhanced with decreasing jet velocity and fluid subcooling. Corresponding explanations were given in view of boiling mechanism of highly-wetting liquid. At last, several means were listed to decrease or eliminate the hysteresis phenomenon of boiling heat transfer.

A set-up of bubble column slurry reactor of 0.2m diameter and auxiliary equipment for three-phase methanol synthesis was established. For checking the operatability and stability of the unit and appraising the catalyst activity, a hot-flow test was conducted under the condition of 1000h continuous run at temperature range 498K to 525K, pressure range 2.5MPa to 3.1MPa, mass space velocity range 4500L·kg ^-1 ·h ^-1 to 7500 L·kg ^-1 ·h ^-1 , and CO mole fraction of 0.31 in feed gas. According to the characteristics of this reaction system, a mathematical model which includes axial dispersion of liquid, axial distribution of catalyst particle and intrinsic kinetics of gas-phase methanol synthesis was obtained. The agreement between the calculated values of methanol yield and outlet methanol mole fraction from this model and the test values was good. Besides, the data obtained by the verified model under the pressure of 5.0MPa was close to those from US Laporte pilot-plant. It was considered that Chinese C302 type catalyst and liquid paraffin can be used for three-phase methanol synthesis, and that the hot-flow model test was successful.

The fest conditions,construction of the gasification stove,test systems,fundamental principles and test results of the industrialization test on the Underground Coal Gasification of the Tangshan Liuzhuang coal mine are presented in this paper.Survey Radon technology is used to probe the moving velocity and length of the gasification surface, and test data are analysed.The success of the industrialization test indicates that Underground Coal Gasification has made big progress commercial application in china,and it further proves the reasonableness and feasibility of the new technology of long tunnel,large section,and two stages.It is concluded that this technology could be widely used in the aged scrap pit in china.

The synthetic reaction of HDI biuret polyisocyanate was monitored by gel permeation chromatography (GPC). The best reaction process was selected according to the percent age of HDI biuret, and the influence of operation conditions on product was also analysed. The results demonstrated that the method of using steam with hexamethylene diisocyanate (HDI) monomer is the best process.Reaction temperature is controlled at 120?℃ and reaction time is controlled at about 7 hours.

In this paper the rotating packed bed, a new type of absorber, which has high mass-transfer characteristic by means of centrifugal field instead of gravity field, is used to study on stimulated flue gas desulfurization. Based on experimental data,a model of mass-transfer and reaction of the sulfur dioxide chemical absorption in the rotating packed bed reactor is proposed according to the film-theory. It can be used to predict the performance of the total absorption rate and the enhancement factor of the sulfur dioxide and oxygen simultaneous absorption in the rotating packed bed reactor.The prediction of the model is consistent with the experimental result varying operating conditions, and the relative error between experimental result and predicted result is below 12%. Some interesting potential projects of simultaneous absorption of sulfur dioxide and oxygen in the rotating packed bed reactor are also discussed.

X-ray Photoelctron spectroscopy (XPS) is used to study BSA adsorption on polysulfone (PS) membrane in static and dynamic conditions. The atomic compositions from XPS measurement show that the adsorption ratio, which is defined as the number of made of BSA over that of PS in the test scope, increases with the adsorption time, and dynamic adsorption is more severe than static adsorption at the same adsorption time. The fitting spectra indicate that there are chemical interactions with electron transfer between BSA and PS membrane. Further analysis shows that O 2 dissolved in BSA solution also participates in chemical interaction. These results can explain why the fouling of PS membrane by BSA solution is serious.

The activity, specific rate of reaction and usable ratio of inner surface (URIS) for commercial A301 ammonia catalyst were measured in a tube packed bed reactor. The reaction conditions were: pressure of 7.0 , 10.0 and 15.0MPa, temperature of 325—450℃, space velocity of 6000, 8000 and 10000h ^-1 and particle size of 0.6—0.9,1.6—2.5,2.5—3.0, 3.0—4.0 and 4.0—6.7 mm. The outlet ammonia concentration, specific rate and URIS decreased with increasing particle size. URIS of commercial catalyst depended not only on particle size, but also on temperature and catalyst efficiency. Particle size was the most important factor for URIS. With increasing particle size from 0.6—0.9mm to 4.0—6.7mm, URIS of catalyst decreased from 1 to 0.74—0.80. For the same size range of catalyst,URIS depended on temperature and catalyst efficiency. Above the temperature of 350℃,catalyst efficiency and URIS increased with rising temperature. But below 350℃,URIS increased with the decrease of temperature.

Based on electrical capacitance tomography technique, a novel method for flow pattern display and voidage measurement of two-phase flow was proposed. A 12-electrode ECT measurement system was developed. The weighted back projection algorithm was selected as the image reconstruction algorithm to satisfy the requirement of flow pattern display. Combining the principle of Tikhnov regularization theory with the ART(Algebraic Reconstruction Technique) algorithm, a new quantitative image reconstruction algorithm was developed to implement voidage measurement of two-phase flow. Experimental results of gas-liqiud two-phase flow and gas-solid fluidized bed showed that the developed measurement system was successful. The speed of image reconstruction of flow pattern display was greater than 20 frames per second. The maximum error of voidage measurement is less than 5% and the time of voidage measurement is less than 2 seconds.