Cooling of Granules in Vibrating, Suspended Bed: Engineering Simulation

Here we suggest an algorithm for calculation of the process parameters and design of a vertical cooler with inclined, gas-permeable blades and with a vibrating, suspended layer of granules on them (Vibrating Fluidized Bed—VFB). The algorithm is based on the use of the equations of heat and material balance, taking into account the influx of moisture into the layer with cold air and dust—as a carryover. Mode entrainment of dust particles and moisture from the VFB is described by using empirical formulas and Π-theorem. To calculate the cooling time of granules a model of the dynamics of a variable mass VFB was built, which linked the geometrical and physical process parameters to a single dependency. An example showed that mass flow of granules of 248 kg/h and a volume flow of air of 646 m3/h with temperature of 30℃ to cool the zeolite granules from 110℃ to 42℃ for 49 s required a vertical apparatus of rectangular shape with four chambers and with volume of 0.2 m3. A comparative analysis of technological parameters of the projected cooler with the parameters of typical industrial apparatuses showed that for all indicators: the cooling time of granules, the flow rate of gas (air) and the heat flow, a 4-chambered, vertical apparatus of rectangular shape with VFB was the most effective.

Combined Removal of Surface Moisture and Dust from Feed Coal for Coal Dry Cleaning with an Air-solid Fluidized Bed

A demonstration plant and a commercial plant employing coal dry cleaning technology with an air-solid fluidized bed were built in China. The operation practice of these two plants shows that the surface moisture and the fines or dust of feed coal must be well controlled as low as possible. For this purpose, a new process of combined removal of surface moisture and dust from feed coal using a vibrated fluidized bed dryer was investigated in a batch test apparatus and a pilot test system. A mathematical model on drying kinetics of coal surface moisture was developed and three empirical formulas of the model coefficient involving the main operating variables were determined based on the test results from the batch test apparatus. The mathematical model shows that the surface moisture retained in coal during drying decreases exponentially with drying time. According to this model, a new divisional heat supply mode, in which the inlet gas of higher temperature was introduced into the fore part of the dryer and the inlet gas of lower temperature into the rear part of the dryer, was employed in the pilot test system. The pilot tests show that 1） the new divisional heat supply mode is effective for lowering down the average temperature and reducing the total heat loss of the outlet gas off the dryer, 2） the moist coal of about 60 g/kg surface moisture contentcan be dried to about 10 g/kg, and simultaneously the fines （〈1mm in diameter） adhering to the surface of coarse coal particles are completely washed off by the gas flow.

Vibrated fluidized bed air classification of moist raw coal

Vibrated fluidized bed air classification is completely different from traditional screening in principle. It extracts fine coal from moist raw coal by entrainment of an ascending airflow in a vibrated fluidized bed. Pilot tests showed that air classification efficiencies varied from 74.85% to 93.84% at cut-size 6, 4, 3, 2, 1, and 0.5 mm when free moisture of coal is in the range of 1.7% to 9.5%, and ash contents of fine coal products were 2%～3% lower than those of the same size fractions in feed, and 4%～10% lower than those of feeds for most cases because of the density differences between coal and waste, which is beneficial to producing lower ash fine coal from raw coal as fuel of blast furnaces or pulverized coal firing boilers. A commercial unit of 100 t/h has been in smooth operation, and several 300～400 t/h units are in plan or construction.

WaveBehaviorofVibratingFluidizedBeds

Experimental data show how vibration energy is imparted to a vibrating fluidized bed (VFB). A new type of sensor was used to measure the wave signals in a VFB. The experimental results show that the vibration energy imparted is through continuous wave propagation in the vibrating fluidized bed. Wave characteristics are affected by the bed properties. A bubble's behavior in the bed is followed by analyzing the wave frequency spectrum.

Characteristic research of regeneration process of particulate filter medium in vibrated fluidized bed

The vibrational fluidized bed is innovatively adopted to regenerate the particulate filter medium for the purification of crude syn-thesis gas from the coal gasification process.Characteristic research of vibrated fluidized beds during dust-containing particulate filter medium regeneration has been carried out.The ideal transport model of particulate filter medium on the distributor is estab-lished and verified by using experiments.The mean residence time of the particulate filter medium can be reduced by 72%from 5.5 to 1.5 min with an increase in the working frequency from 50 to 60 Hz.The thickness of the bed layer is linearly increased with the feeding rate of the particulate filter medium under ideal working conditions.The resistance models of the fluidizing air are built up and validated,and they can be used to calculate the pressure drop of the static bed layer of the particulate filter medium on the flu-idizing air distributor,which is the maximum value of the dynamic bed layer with the same thickness.The fluidizing air makes the mean residence time of the particulate filter medium decrease by 50%and reduces the difference in the particulate mean residence time under different feeding-rate conditions.The regeneration effect of dust-containing filter medium particles in a vibrated fluidized bed is evaluated.Fluidizing air with superficial velocity ranging from 0 to 0.6~0.9 m·s-1 makes the regeneration efficiency increase from 29.41%to 70.59~88.24%.This article provides a reference for the industrial application of a vibrated fluidized bed for the par-ticulate filter medium recycling system.

Progress in developments of dry coal beneficiation

China’s energy supply heavily relies on coal and China’s coal resource and water resource has a reverse distribution.The problem of water shortages restricts the applications of wet coal beneficiation technologies in drought regions.The present situation highlights the significance and urgency of developing dry beneficiation technologies of coal.Besides,other countries that produce large amounts of coal also encounter serious problem of lack of water for coal beneficiation,such as American,Australia,Canada,South Africa,Turkey and India.Thus,dry coal beneficiation becomes the research hot-points in the field of coal cleaning worldwide in recent years.This paper systematically reviewed the promising research efforts on dry coal beneficiation reported in literature in last 5 years and discussed the progress in developments of dry coal beneficiation worldwide.Finally,we also elaborated the prospects and the challenges of the development of dry coal beneficiation.

Influence of bubbles on the segregated stability of fine coal in a vibrated dense medium gas-solid fluidized bed

In this paper,the variation of bubble size and number in the separation process of vibrated fluidized bed as well as the influence of bubble movement on the axial distribution of fine coal in different positions of the bed were studied.The result revealed that the size and number of bubbles is correlated with the fine coal separation effect in the separation process.When the bed is in a uniform and stable fluidized state,the size of bubbles in the separation process was in the range of 1-2.5 cm and the number of bubbles was reduced by nearly 50%,which is helpful to promote the stratification and segregation of fine coal.Thereby,after separation,the ash content of refined coal products of anthracite and 1/3 coking coal was reduced to 12.1% and 23.7% respectively,and the content of refined coal was up to 42.5% and 68.5% respectively,which show that the vibrated fluidized bed has a good separation performance,and can separate efficiently the coal of size−6+1 mm.