Development Of A Novel Drying Technique For Lignite:Integrated Pneumatic Spouted Mobile Bed

There is a large quantity of lignite all over the world, including our country. With the shortage of oil and natural gas resources, as well as over-exploitation of bituminous coal and anthracite resources, development and utilization of lignite is becoming increasingly important. However, lignite blongs to low rank coal, and its utilization is greatly restricted because of its high water contents and low calorific values. It is necessary to upgrade&improve its quality for large-scale development and utilization. DG process developed by DUT is an economic and efficient lignite utilization technique, which can be used to pyrolyze lignite into light oil, gas and carbocoal. An integrated pneumatic-spouted-moving bed drying system with internal heat exchanger is developed in the present work. This new drying system, which appropriately combines pneumatic drying, spouted bed drying and moving bed drying based on experiment study and patent technology, is aimed to achieve the integration of lignite drying, conveying and separating against the background of DG technology.The development of this integrated drying technique includes of mathematical model of integrated pneumatic spouted mobile bed with internal heat exchanger, system resistance model, device structure design, analytical design of the device using Ansys software, and intensity evaluation.In the process of the novel integrated drying technique, lignite is feed in the bottom of pneumatic dryer first, then is raised into the spout-mobile bed by hot air, and separates with air in the spouted bed, then partly-dried lignite fells into the mobile bed with internal heat exchanger to continue the drying process while exhaust air is discharged through top of the spout bed, and dried lignite is unloaded from bottom of the dryer finally. A universal mathematical model is built to design straight pipe dryer in the paper. The model has discussed the varied relationship between the material moisture content during constant rate drying and the particle acceleration during pneumatic transmission, considered the relative Reynolds number of gas-solid two-phase in both transition flow and turbulent flow, and therefore is applicable to general pneumatic drying situations. Compared with the results of single pneumatic dryer, the integrated drying performance, higher thermal efficiency and longer residence time. The main device and subsidiary structure of the integrated dryer have been designed and drawn. The pneumatic dryer and spout mobile bed are connected by bellow expansion joint, and fixed by lug support with stiffening ring respectively. On the bottom of the spout mobile bed, round top and square bottom components are connected to the discharge auger.The pneumatic dryer and spout mobile bed were analytically designed by ANSYS finite element software with various load cases. Stress intensity of device was calculated, linearized, and evaluated. In addition, the device structure was optimized according to analysis design. The study showed that results meet the stress intensity requirements under design condition.