粉-粒喷动床的基础与应用

开发的粉-粒喷动床是一种新型喷动床.介绍了粉-粒喷动床的特性以及在多种单元操作和化学反应过程中的应用,如,干燥、细粉制备、燃煤烟气脱硫和同时脱除工业/城市垃圾燃烧发电废气中的二氧化硫和氯化氢气体等.     

喷动床装置的设计研究

介绍了喷动床的工作机理、主要零部件以及喷动床的系统设计。针对喷动床进行了较深入的实验研究,结果表明喷动床在用于涂层、造粒等方面具有广阔的发展前景。     

Developments in spouted bed technology

The spouted bed, though originally developed for drying of coarse granular solids, has, over the last decade, proved to be of interest for carrying out a remarkably wide variety of operations. These include not only other diffusional and/or thermal operations such as heating or cooling of solids, drying of solutions and suspensions onto inert bed particles, particle coating, and granulation, but also certain mechanical functions like solids blending, comminution and aerosol collection from a gas stream. The use of spouted bed reactors for several chemical processes — coal carbonization, shale pyrolysis, ore roasting, cement clinker production, and thermal cracking of petroleum — has also received attention. This paper presents a review of the above developments, supplemented in a few cases by recent results of research being carried out at the University of British Columbia. The particular features of a spouted bed which play the key role in each type of application are identified, some new applications are suggested and consideration given to the future industrial potential of individual processes.     

The british coal spouted fluidised bed gasification process

British Coal Corporation has been developing an air-blown spouted fluidised bed gasification process for the production of low calorific value fuel gas. Development of the gasifier at atmospheric pressure for the industrial market has established the commercial basis for a flexible gasification process, which can achieve coal conversion efficiencies of up to 95%. For larger-scale use, a pressurised gasifier is under development as part of an integrated partial gasification combined cycle, coal-fired, electricity generating system. Known as the British Coal Topping Cycle, the system offers significant advantages in terms of improved thermal efficiency, reduced generating costs and low environmental impact. The paper outlines the gasifier development programme for both applications.     

Scale-up examination of spouted bed dryers

Comparison of experimental results with predictions of the main hydrodynamic characteristics used for the sizing of spouted bed dryers are made. Various new equipment constructions are demonstrated together with operating experiences, both with an emphasis on scale-up.     

Multi-dimensional model of a spouted bed

A multi-dimensional model is developed to describe the fluid and particle dynamic behaviour of spouted beds. The position of the spout-annulus interface is determined by a variational analysis. Two-fluid equations are used to represent gas and solids motions in the spout while the vector Ergun equation and soil mechanics equations are employed to describe, respectively, gas and solids behaviour in the annulus. Using numerical finite difference methods, the set of governing equations is solved subject to carefully chosen boundary conditions. The model predictions of key hydrodynamic characteristics are in reasonable agreement with available measured data selected from the literature to represent a wide range of experimental conditions.     

循环喷动流化床颗粒抛射高度的计算

通过对循环喷动流化床顶部封闭空间气体射流及气固运动的理论分析 ,得出了循环喷动流化床中颗粒出循环管后抛射高度的计算方法 ,所得计算结果与实测结果误差小于 8% ,为循环喷动流化床的设计提供理论依据     

Coal gasification in a spouted bed

Low Btu gas has been produced by gasifying coal in a spouted bed reactor. Coal of size 0.8-3.6 mm is fed continuously to a 0.15 m diameter spouted bed of inerts and gasified using mixtures of steam and air. Tests of the process with Western Canadian coals of free swelling index 0, 4 and 7 are reported. Gases of heating value to 3.61 MJ/m³ were produced at coal throughputs of 0.188 kg/m²s with the reactor operating at atmospheric pressure and temperatures to 930°C. Characteristics of the spouted bed gasifier are presented and results compared to commercial moving and fluidized bed systems. A simple mathematical model based on the two-region spouted bed model of Mathur and Lim is used to predict the effect on steam utilization of bed composition, bed height and diameter, and particle size.     

射流喷动流化床实验研究

射流喷动流化床 ,是在喷动床的基础上 ,通入流化气 ,降低喷动床柱体部分的高度 ,提高喷动速度的方法得到 ;作为一种新型流态化装置 ,可用于颗粒物料的干燥和包衣 ,粉状物料的造粒 ;同时可用于悬浮液的干燥。通过射流喷动流化床用于颗粒物料涂敷造粒的试验 ,对射流喷动流化床流型、压降及其影响因素进行了研究     

Particle circulation in a spouted bed

Based on experimental data, a discussion is presented on particle circulation in a spouted bed produced by introducing air in a 100 mm diameter semi-circular, conical-bottom column, provided with a transparent frontal wall.A high speed camera was used to determine particle movement in the bed.Characteristic pictures show the trajectories of the particles in the spout and in the annulus. Comments are presented on the axial and radial particle velocity variation in the two zones of the spouted bed.A relation between particle velocity in the annulus, at a given level, and the minimum spouting velocity is presented. It is thought that this relation may constitute a reasonable basis for an equation of more general use.The experimental data regarding the average bulk velocity of particles in the annulus point to a value equal to that of particles located at a distance of 0.7 – 0.8 R from the axis of the column. This is in contradiction to previous work, where the average bulk velocity of the particles in the annulus was taken equal to that of the particles moving along and in contact with the wall.     

Spouted bed and microwave-assisted spouted bed drying of parboiled wheat

The effect of spouted bed and microwave-assisted spouted bed drying on drying rates of parboiled wheat was investigated. In addition, the effective moisture diffusivities of parboiled wheat were calculated. The drying experiments were performed using 200 g of parboiled wheat, at three different air temperatures (50, 70, 90 °C) and at two different microwave powers (3.5 W/g (db), 7.5 W/g (db)). Microwave-assisted spouted bed drying at microwave power of 3.5 W/g and 7.5 W/g reduced drying time by at least 60% and 85%, respectively compared to spouted bed drying. The effective diffusivity values were in the range of 1.44 × 10^?10–3.32 × 10^?10 in spouted bed drying while they were between 5.06 × 10^?10 and 11.3 × 10^?10 in microwave-assisted spouted bed drying at different experimental conditions.     

The drying of barley malt in the spouted bed dryer

The drying of barley malt was studied in a batch spouted-bed dryer using three inlet air temperatures (60, 80 and 90°C) and three initial masses of malt (25, 30 and 35 kg). One of the conclusions was that the drying can be conducted at higher temperatures than in the classical equipment. A general correlation was obtained through the use of reduced moisture and reduced time. A mathematical model which assumes only an external resistance of diffusion or heat transfer does not apply. Also, the model based on internal water diffusion does not predict the results. A new semi-empirical model based on semi-permeable membranes has been proposed. A method of using batch laboratory drying data to predict the performance of continuous spouted-bed driers has been outlined.     

On the transition from a fixed to a spouted bed

Theory is developed to predict the maximum pressure drop and superficial gas velocity during the onset of spouting. The theory, which is valid for low Reynolds number flows, assumes an approximate form for the gas distribution in the bed from the central injection point. Spouting is predicted to commence when the upwards drag force exerted by the gas balances the weight of particles within the volume enclosed by the gas flow. There is reasonable agreement between the theory and experimental results for the transition and some experimental results for pressure distributions in situations not covered by the theory are presented. In particular, the existence and importance of radial pressure gradients near the injection point are discussed.     

Oxygen-steam gasification of coals in a spouted bed

A bituminous and a sub-bituminous coal from Western Canada have been gasified in oxygen-steam and air-steam mixtures in a 0.30-m diameter, 50 kg coal/h continuous spouted bed reactor. Results are presented to show the effects of the blast composition and reactor temperature on gas heating value and carbon conversion. Operation in the ash agglomeration mode is illustrated, and the role of K₂CO₃ as catalyst explored. Results from a wide range of experimental gasification conditions are compared with predictions of an equilibrium model.     

The maximum spoutable bed heights of fine particles spouted with air

The maximum spoutable bed heights of systems of fine glass spheres spouted with air are studied in flat based semi circular columns of 80 and 152.4 mm diameters using particles with average diameters ranging from 0.3 to 1.3 mm. New correlations are proposed to predict the maximum spoutable bed heights of air spouted fine particle systems. It is concluded that the influence of the column diameter on the maximum spoutable bed height is significantly decreased compared to coarse particle systems and that it further varies with particle size within the fine particle spouting regime. Data reported in the literature agree with the proposed correlations.     

Drying characteristics of a draft tube spouted bed

Using the results of earlier work on the flow pattern of gas and solids in a draft-tube spouted bed, the drying characteristics of such a spouted bed are discussed. Paddy (unpeeled rice) was dried in a 30 cm bed with a 5.5 cm draft tube and temperatures and moisture content of solid and gas phase were measured as a function of drying time at various points in the system. It appears that the (constant) drying rate is determined by the heat transfer in the recirculation zone (just above the air inlet) and in the draft tube. After the short and rapid heating in the tube, the temperature and moisture gradients in the particle equilibrate in the annulus. It is concluded that a draft-tube spouted bed is a promising dryer design for heat-sensitive particles with slow intra-particle mass transfer coefficients.     

Feasibility study of a spouted bed gasification plant

We have studied the feasibility of building a biomass gasification plant with an innovative spouted bed reactor for distributed energy production. The process was simulated using a thermodynamic approach (concentrated parameter model) using LIBPF, a C++ process modelling library. A nominal size of about 100 kW total thermal power was chosen.     

Aerodynamics of a novel rotating jet spouted bed

A novel rotating jet spouted bed (RJSB) is developed and tested. It consists of a rotating air distributor with two radially located spouting air nozzles. The effects of bed height, distributor rotational speed, nozzle diameter and particle properties on the flow characteristics were examined. Various flow regimes were mapped as functions of distributor rotational speed and superficial air velocity for different materials and column dimensions. Empirical correlations were developed for the minimum spouting velocity, peak pressure drop and steady spouting pressure drop.