Cold Experimental Study On Pressurized Circulating Fluidized Bed

Based on the background of promoting the efficient use of energy,pressurized coal gasification technology reduces the size of the equipment and the compression energy consumption,which is the only way for coal gasification technology to reduce equipment costs,operating costs and achieve the large-scale.The gas-solid flow characteristics and circulation process in the riser of pressurized circulating fluidized bed are more complex than that under atmospheric pressure,the operation law of circulating fluidized bed under pressure could be better mastered by the experimental study,which can provide theoretical basis for the design and operation of pressurized gasification demonstration project.So far,there are few studies on the pressurized circulating fluidized bed,it is necessary to carry out the further study.According to the research contents,a cold-model experimental facility of pressurized circulating fluidized bed was built,the riser was 300 mm and the effective height was 8700 mm,different key components were designed for the experimental researches,including loop seals,upper variable section and exits of the riser.Silica sand with the mean diameter of 0.347 mm and the bulk density of 1435 kg/m3 was used as the bed material.After the debugging work of the experimental facility,the flow behaviors of silica sand along the riser were investigated with different operating parameters(pressure,superficial air velocity and bed inventory)and different structural parameters of key components.The experimental results show that:At the elevated pressure,the apparent solid holdup is lower at the upper part and higher at the bottom part of the riser,the apparent solid holdup increases with increasing the bed inventory and tend to an uniform distribution with the increase of the superficial air velocity;when the bed inventory and superficial air velocity are kept unchanged,the solid holdup at the upper part of the riser increases with the elevated pressure and the variation is apparent at 0.5 MPa.Normal circulation process can be established under different loop seals with the diameters of 150 mm and 200 mm,the solid holdup distribution in the riser can not be changed with the diameter variation of the loop seals,the 150 mm loop seal is better than the 200 mm loop seal and it can establish a better circulation with increasing the height of separator appropriately for small diameter loop seal;the apparent solid holdup at the top of the riser can be increased with an abrupt exit of the riser;in the case of the same circulating flow rate,the new loop seal can provide a relatively high reverse pressure up to 5.47kPa.