DRYING OF SOY PULP (OKARA) IN A BED OF INERT PARTICLES

Drying of okara, an insoluble pulp residue waste byproduct of tofu production, was investigated in a continuously moving bed of inert particles subjected to vortex-like motion. The experimental variables in their respective ranges included the mass of Teflon pellets used as inert particles (0.4-1.2 kg), feed rate (0.5-1.4 kg/h), inlet air temperature (100-145°C) and airflow rate (195-271 m³/h). The dryer showed good performance in general and produced dry okara with moisture content ranging from 5 to 33% wb depending upon the operating conditions. The product recovery ranged from 80 to 90% on dry basis in most experiments. The specific water evaporation rate in okara drying increased with increasing of the feed rate and mass of Teflon pellets. However, the specific heat consumption decreased with an increase in the okara feed rate. Results showed that specific heat consumption for okara drying in a bed of inert particles was about 3 to 4 times higher in comparison with that of free water.     

惰性粒子流化床中的悬浮液干燥

用惰性粒子流化床干燥器对混凝土外加剂等5种物料进行了干燥实验研究，提出了计算体积传热系数的关联式．实验结果表明，由于惰性粒子的存在，强化了传热传质，体积传热系数可达3000W·m~(-3)·K~(-1)，但是，床层压力降较高．干燥强度（以蒸出水计）可达50～60kg·m~(-3)·h~(-1)，热效率30％～43％，若提高热风进口温度，后两项指标还可提高.     

DRYING OF TOBACCO PARTICLES IN A MOBILISED BED

ABSTRACT

The drying performance of a novel device capable of mobilising a bed of fibrous materials is evaluated. The drying kinetic of the vegetable product used for this work, cut lamina tobacco particles, was determined from fixed bed experiments. A falling-rate period was observed for the entire drying curve. The results showed that the drying rate is controlled by internal mass transfer mechanism for gas superficial velocities above 0.8 m/ s. The proposed model is based on an effective liquid diffusion coefficient that varies with solids temperature according to an Arrhenius-type relationship. Batch drying experiments were carried out in the mobilised bed apparatus under various conditions of inlet air temperature, humidity and flowrate. Assuming perfect mixing and no internal resistance to heat transfer for the solids, the performance of the mobile bed can be predicted using the proposed internal liquid diffusion model     

DRYING OF GRANULAR PARTICLES IN A MULTISTAGE INCLINED FLUIDIZED BED WITH MECHANICAL VIBRATION

A mathematical model for the drying rate of granular particles in a multistage inclined fluidized bed(IFB) is presented from the standpoint of simultaneous heat and mass transfer, with taking the effect of mechanical vibration added vertically into consideration.

Steady-state distributions for the temperatures and concentrations of the particles and the heating gas, and for the moisture content of the particles are numerically calculated based on the present model. The calculated results show fairly good agreement with the experimental data, which were obtained from the drying experiments of brick particles in a three-stage IFB using comparatively low temperature air(40-60°C) as the heating gas.

It has been found within the range of the experimental conditions employed that, the mechanical vibration added vertically enhances the over-all drying rate of the particles and its effect can be considered equivalent to an increase in the air velocity.     

大颗粒作用下微细粉流态化干燥研究

为了克服湿微细粉易于结团形成“细粉群”、不易流化和干燥的缺点，在微细粉中加入惰性大颗粒物料，由于大颗粒的“搅动”作用，使细粉分散，可提高流化质量，从而提高微细粉的流化干燥热效率．在实验基础上进行了物料衡算和热量衡算，并进行连续干燥热效率的计算．该方法为微细粉的流化干燥提供一条新的途径．     

ECONOMIC CONSIDERATIONS IN FLUIDIZED BED DRYING OF PASTES USING INERT PARTICLES

A fluidized bed of inert particles lpar;packing)--> can be used advantageously for the drying of paste-like materials of high moisture content. Wet pasty material is fed into a fluidized bed of chemically inert coarse particles. The wet material coats the surface of the inert particles. Drying takes place mainly in the thin layer formed on the surface of particles. After reaching a certain moisture content, the dried material film breaks off the surface of the packing particles, and leave the fluidized bed as a fine powder in the exit gas stream.

Experiments were performed using different organic and inorganic materials e.g. raw materials from human and veterinary     

DRYING OF SUSPENSIONS IN A MODIFIED SPOUTED BED DRIER WITH AN INERT PACKING

Authors summarize results of drying experiments carried out in aim to investigate effects of operational and process-conditions on the drying output and the product quality. The studies were performed in a laboratory-size spouted bed drier of a new construction with tangentional air inlet and with an inner conveyor screw maintaining the spouted bed recirculation of the inert particles

Effects of parameters assuring intensive gas-solid contact were studied, such as the inlet air-velocity, the recirculation of inert particles as well as chemical and physical properties of the inert material.

Various chemical suspensions (e.g. fine grain inorganic-salt pulps, waste products), biologically active materials (e.g, suspension of yeast) food products were used in preliminary experiments which showed effectiveness of this dryin5 method. On this basis two rode1 materials (cobalt-carbonate suspension and pulp of zinc--carbonate) were chosen for detailed experiments.

As a result cf these studies main optimal operational and process pszramters.have been obtained.     

DRYING OF TOBACCO PARTICLES IN A MOBILISED BED

The drying performance of a novel device capable of mobilising a bed of fibrous materials is evaluated. The drying kinetic of the vegetable product used for this work, cut lamina tobacco particles, was determined from fixed bed experiments. A falling-rate period was observed for the entire drying curve. The results showed that the drying rate is controlled by internal mass transfer mechanism for gas superficial velocities above 0.8 m/ s. The proposed model is based on an effective liquid diffusion coefficient that varies with solids temperature according to an Arrhenius-type relationship. Batch drying experiments were carried out in the mobilised bed apparatus under various conditions of inlet air temperature, humidity and flowrate. Assuming perfect mixing and no internal resistance to heat transfer for the solids, the performance of the mobile bed can be predicted using the proposed internal liquid diffusion model     

惰性粒子对气液固三相流化结晶粒度分布的影响

引　言换热壁面垢层的形成增加了热阻和流动阻力 ,降低了换热效率 ,严重时可产生局部过热损坏整个换热设备 ,使得设备的维护、检修费用增加 .李修伦、张利斌等[1,2 ] 80年代以来开发出的三相流化床蒸发沸腾换热技术较好地解决了这一问题 ,然而将该技术应用于带有结晶过程的体系 (如卤水蒸发器 )时 ,由于引入的惰性粒子对结晶过程来说为一外来杂质 ,会对晶体的生长产生影响[3] ,而早期的试验也出现过晶粒变小的问题[4 ] .因此有必要对此进行研究 ,为进一步完善和改进三相流化床技术的工业应用提供必要的基础 .1　实验研究1.1　实验装置及流程…     

SIMULATION OF DRYING SUSPENSIONS IN SPOUT-FLUID BEDS OF INERT PARTICLES

In spouted and spout fluid bed dryers, the suspension is spread into the bed of inert particles, covering these particles with a thin layer. As the inert particles circulate, this suspension layer is dried and must become brittle enough to break off by the particle attrition. The powder produced is then carried out by air. Problems with the spout stability, particle agglomeration and powder deposits inside the column should be overcome by controlling the drying operation. The present work is aimed at modeling and simulating the drying of suspensions, such as organic and biological pastes, in conical spout-fluid beds of inert particles. A computer program has been developed combining the air flow and particle circulation models with the mass and energy balances and the drying kinetic equations in order to describe this drying process. The effect of cohesive forces is also incorporated to the fluid flow model. Simulation results are analyzed and compared with experimental data reported in the literature. Implication of these results in drying suspensions is also discussed.     

DRYING OF SUGAR BEET PULP USING A LABORATORY AIR DRIER

ABSTRACT

Drying curves for sugar beet pulp were obtained in a laboratory-scale air drier. Dehydration conditions were: temperatures in the range of 35 to 90 ^°C, air flow velocities of 0.5 to 2.0 m/s, and air moisture content of 0.005 to 0.06 kg water/kg air. Using data from thin layer experiments, a mathematical model was derived to describe the dehydration behaviour under the described conditions. The model was able to predict data obtained from deep bed experiments. Results from this work could be used to develop a design methodology for dryers that operate at relatively low temperatures (<90^°C).     

AMARANTH GRAIN DRYING IN A FLUIDIZED BED

ABSTRACT

An empirical equation as a function of drying time and temperature was developed to calculate the moisture ratio required Tor balch fluidized bed dryers design for amaranth grain drying

The relative deviations of the moisture ratio values calculated with the proposed equation with regard to the experimental ones ranged between 0.014 and 0.095 for a drying air temperature between 60 and 100 ° C, and a grain initial moisture content between 23.5 and 16.6 % wb.     

DRYING OF PULP AND PAPER SLUDGE IN A PULSED FLUID BED DRYER

ABSTRACT

Hydrodynamics and drying kinetics for the pulp and paper primary sludge dried in a pulsed fluid bed dryer with relocated air stream are presented. Batch experiments have indicated that drying of disintegrated sludge to the required 12% moisture content takes place during the first drying period at practically constant material temperature close to the wet bulb temperature with respect to the inlet air conditions. Equations were developed for pressure drop, minimum pulsed-fluidization velocity, dynamic bed height, and volumetric mass transfer coefficient. Continuous experiments under drying conditions determined from the average residence time concept have confirmed that transportation of disintegrated sludge along the dryer follows the plug flow model.

     

EFFECT OF A TEMPERING PERIOD ON DRYING OF CARROT IN A VffiRO-FLUlDIZED BED

ABSTRACT

Drying of diced carrot in a vibrofluidized bed was studied experimentally for various air temperatures, bed heights and size of the cubes. Effect of a tempering period that mav be implemented into ¦ drying cycle was examined with respect to drying kinetics and energy consumption. Although two stage drying with a tempering period increases the overall drying time, it shortens the drying time in a VFB dryer thus reduces energy consumption     

EXPERIMENTAL INVESTIGATIONS OF BEET PULP DRYING IN SUPERHEATED STEAM UNDER PRESSURE

ABSTRACT

Beet pulp drying in superheated steam under pressure makes it possible to save energy in sugar factories. A new concept of a two-stage convective steam drier is presented. To obtain kinetic data on beet pulp drying, an experimental setup was built. Beet pulp samples were dried at steam pressure up to 4 bar and temperature up to 220° C.     

DRYING OF SUSPENSIONS IN A MODIFIED SPOUTED BED DRIER WITH AN INERT PACKING

Authors summarize results of drying experiments carried out in aim to investigate effects of operational and process-conditions on the drying output and the product quality. The studies were performed in a laboratory-size spouted bed drier of a new construction with tangentional air inlet and with an inner conveyor screw maintaining the spouted bed recirculation of the inert particles

Effects of parameters assuring intensive gas-solid contact were studied, such as the inlet air-velocity, the recirculation of inert particles as well as chemical and physical properties of the inert material.

Various chemical suspensions (e.g. fine grain inorganic-salt pulps, waste products), biologically active materials (e.g, suspension of yeast) food products were used in preliminary experiments which showed effectiveness of this dryin5 method. On this basis two rode1 materials (cobalt-carbonate suspension and pulp of zinc--carbonate) were chosen for detailed experiments.

As a result cf these studies main optimal operational and process pszramters.have been obtained.     

DRYING OF PULP AND PAPER SLUDGE IN A PULSED FLUID BED DRYER

Hydrodynamics and drying kinetics for the pulp and paper primary sludge dried in a pulsed fluid bed dryer with relocated air stream are presented. Batch experiments have indicated that drying of disintegrated sludge to the required 12% moisture content takes place during the first drying period at practically constant material temperature close to the wet bulb temperature with respect to the inlet air conditions. Equations were developed for pressure drop, minimum pulsed-fluidization velocity, dynamic bed height, and volumetric mass transfer coefficient. Continuous experiments under drying conditions determined from the average residence time concept have confirmed that transportation of disintegrated sludge along the dryer follows the plug flow model.     

SELF-TUNING CONTROL OF EGG DRYING IN SPOUTED BED USING THE GPC ALGORITHM

ABSTRACT

A spouted bed is used to dry many and different materials ranging from granules to pastes and suspensions. This work presents an implementation and tests of an advanced control strategy on a spouted bed dryer. Water was used as the ideal paste for tests. An adaptive control algorithm GPC (Generalized Predictive Control) was implemented. A microcomputer was used to maintain humidity and temperature set points of air in the dryer by manipulating electric power of heat exchanger and paste feed flow rate. Instrumentation was set-up with different sensors, interface and final control elements for operation. Stability and performance analysis of the control strategy was accomplished. A robust stable controller was obtained which had also encouraged us to extend the investigation of this control strategy to the drying of other pastes.     

SELF-TUNING CONTROL OF EGG DRYING IN SPOUTED BED USING THE GPC ALGORITHM

A spouted bed is used to dry many and different materials ranging from granules to pastes and suspensions. This work presents an implementation and tests of an advanced control strategy on a spouted bed dryer. Water was used as the ideal paste for tests. An adaptive control algorithm GPC (Generalized Predictive Control) was implemented. A microcomputer was used to maintain humidity and temperature set points of air in the dryer by manipulating electric power of heat exchanger and paste feed flow rate. Instrumentation was set-up with different sensors, interface and final control elements for operation. Stability and performance analysis of the control strategy was accomplished. A robust stable controller was obtained which had also encouraged us to extend the investigation of this control strategy to the drying of other pastes.     

SIMULATION OF PLUM DRYING IN DEEP BED

Thin layer air drying of plum was studied. The drying conditions in this study are : dry bulb temperature ranging from 60 to 100 °C, air moisture content ranging from 0.008 to 0.089 kg water/kg dry air and air velocity ranging from 0.5 to 2 1x11s. An exponential model was used to describe the drying curve. The heat and moisture balances on the air were used to calculate the outlet air temperature and its moisture content. The heat balance on the product was used to calculate the product temperature. These equations were used to predict the drying of plum in deep bed. A good agreement between the experimental and calculated product moisture content, the product temperature and the outlet air temperature were obtained