Shan Jing

Silica white obtained from rice husk in a fluidized bed

Abstract In this paper, silica white, which is obtained from rice husk in a fluidized bed, is investigated. First, the experiments are carried out in the cold fluidized bed of 90-mm interior diameter (I.D.). The experimental results show that the ash mixed with a little rice husk can be fluidized when U g is within the range of 0.18–0.316 m/s. Then, the experiments of combustion of rice husk are investigated in the fluidized bed of 84 mm I.D. The experimental results show that the combustion occurs in the dense zone of the fluidized bed. The ash in the dense zone is easily purified to obtain the SiO 2 powder. The quality of silica white sampled from the dense phase zone is higher than that of GB-precipitated silica and approaches that of pyrogenic silica except for specific surface area and iron content.

The hydrodynamic behavior of the liquid–solid circulating fluidized bed ion exchange system for cesium removal

Abstract In this work, experimental studies on the hydrodynamics have been carried out in a cold model liquid–solid circulating fluidized bed (LSCFB) ion exchange system where the riser is operated in the circulating fluidization regime and the downcomer in the state of slow-moving packed bed, with the aim of removing cesium from high radioactive liquid waste. Two circulating fluidization zones, the initial and the fully developed, have been observed. The solids circulation rate can be controlled merely by the primary liquid flow if the auxiliary liquid flow is set to zero and the injection tap is located at the middle of the intersection of the riser and the solid-return pipe. Therefore, it is possible to minimize the number of the liquid feed assemblies (pumps, valves, flow meters, etc.), and this is crucial to the treatment of high radioactive waste. The liquid inevitably leaks through the solid-return pipe in most cases because of the “loosening effect” of the liquid feed flow, and the direction and magnitude of the leakage vary with the operating conditions. The system geometry, including the injection tap location and the riser outlet location, plays a very important role in the hydrodynamics of the LSCFB system.

Compact Pneumatic Pulse-Jet Pump with Venturi-Like Reverse Flow Diverter

Abstract A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter, which consists of a nozzle and diffuser, is designed for lifting and transporting a hazardous fluid through a narrow mounting hole. The pumping performance for a liquid mixture or a liquid-solid mixture is examined in terms of the effects of liquid viscosity, particle mass concentration, lifting height, and compression pressure. Results reveal that the pumping performance of the compact pneumatic pulse-jet pump is controlled by jet inertia and the flow resistance of the riser tube positioned after the diffuser. The capacity of the compact pneumatic pulse-jet pump increases with compression pressure and decreases with liquid viscosity. However, even for a liquid mixture with a high viscosity of 7.38 mPa·s, a pumping capacity of 170.7 L·h −1 was observed. For a liquid mixture, two dimensionless indices of performance were found to be the ratio of Euler numbers Eu out / Eu DV and the suction factor q . As the liquid-solid mixture was lifted to elevation of 6.74 m by the compact pump, the particle size distributions of the liquid-solid mixture in the tank and from the riser tube outlet were determined by a particle size analyzer and found to coincide well.

Thermal Decomposition of Potassium Titanium Hexacyanoferrate(II) Loaded with Cesium in a Fixed Bed Calciner

Abstract The thermal decomposition of potassium titanium hexacyanoferrate(II) (KTiFC) loaded with cesium (referred to as Used Exchanger, or UE) was studied at different flow rate of air in a fixed bed calciner. The calcination process consisted of four stages: ambient temperature—180°C (stage I), 180–250°C (stage II), 250–400°C (stage III), and constant 400°C (stage IV). The most intense reaction occurred in stage II. The rate of thermal decomposition was controlled, depending on the O2 flux, by O2 or CN concentration in different stages. Results from differential thermal analysis (DTA) showed that the calcination reaction of the anhydrous UE was exothermic, with an approximate heat output of 4.6kJ.g-1, which was so large to cause the possible agglomeration of calcined residues. The agglomeration could be avoided by enhancing heat transfer and controlling the O2 flux. It was found that there was no cyanides in the calcined residues and no CN-bearing gases such as HCN and (CN)2 in the off-gas. It seemed that the catalytic oxidation furnace behind the fixed bed calciner could be cancelled.

Improved particle plug valve for Geldart-D powders

Abstract In this paper, experiments are carried out for three Geldart-D powders in the hopper–standpipe systems with a gas-splitting part. Based on these experimental data, the hopper–standpipe system with gas-splitting part, which can increase the maximum pressure drop of the system in a positive gas conveying system by a factor of about 1.7 greater than Particle Plug Valve (PPV), is called “Improved Particle Plug Valve (IPPV)”. Furthermore, the increased pressure drop produced by this technique can be adequately predicted using the calculation procedure developed.

Introduction of particle plug valve

Abstract In this paper, experiments are carried out for three Geldart-D powders in three conical fluidized beds and the hopper–standpipe system. Based on these experimental data, the hopper–standpipe system, which is used to maintain the large pressure drop without the motion of particles when the flow of particles is cut off, is called “particle plug valve (PPV)” and the method for predicting the maximum strength factor of anti-pressure of PPV is given.

Hopper-valve for fine powders in a moving-bed standpipe

In this paper, a new valve for Geldart-A powder, so-called hopper-valve, is presented. The method of its design, the range of operation, and the method of monitoring are also discussed in detail

Application of particle plug valve in a positive dilute gas-conveying system

Abstract Based on the characteristics of particle plug valve (PPV) [Powder Technol. 115 (1), (2001) 8], a series connection of PPVs, which is used in a positive dilute gas-conveying system for feeding Geldart-D powder periodically from a low-pressurized vessel into a high-pressurized vessel is presented, and four modes of operation have been discussed and tested by experiments.

Experimental study on the flooding of fine powders

Based on new experimental findings, not only a new experimental method for measuring the flooding of powder is given but also a flooding number is defined in this paper. Experimental results have shown that the new flooding number has a distinct physical meaning and can quantitatively describe the tendency to flood.