Preparation And Physicochemical Properties Of Sintered Ceramsite Produced From Coal Gangue And Fly Ash

With the acceleration of industrialization,a large number of industrial solid wastes have been produced,such as fly ash,various tailings,desulfurized gypsum,metallurgical slag,etc.The production of building materials produced from solid wastes is the main way of recycling solid waste,which has consumed most of the solid waste resources.But there is still quite a lot of solid waste not fully utilized due to the limited research level about solid waste resources.The demand for oil and natural gas resources is increasing day by day,which leads to the surge in demand for proppant.In this paper,coal gangue and fly ash are used to prepare ceramsite proppant,which is used in oil and natural gas extraction,and the demand is large.Therefore,it is a practical and feasible method for solid waste disposal and recycling.At the same time,it can reduce the pollution caused by the accumulation of these resources to the ecological environment.The low-density and high-strength proppant can also bring promising economic benefits.Based on the predecessors’ use of raw materials such as clay,tailings or sludge to prepare ceramsite,this paper uses coal-based solid waste such as coal gangue and fly ash as the main raw material to prepare sintered ceramsite.This is one of the important ways of high added value utilization of coal gangue and fly ash,and also provides a new way for the basic research and industrial development of ceramsite in China.In this thesis,coal gangue and fly ash are the main raw materials.Through experimental research and optimization of the experimental plan,the ceramsite proppant is successfully sintered and is expected to be used in the process of hydraulic fracturing to extract oil and gas resources.This paper emphasisly explores the influence of preparation process on ceramsite performance,optimizes the process parameters such as material ratio,baking temperature and holding time,and further studies effect of additional components on ceramsite performance,revealing the sintering process and performance improvement mechanism of added components on ceramsite.All the performance indexes of the prepared ceramsite achieved the requirements of the industry standard of ceramsite proppant.The main conclusions are as follows:(1)The optimum experimental ratio of ceramsite prepared from coal gangue and fly ash is 10:10,sintered temperature is 1250 ℃,and holding time is 30 min.With the increase of calcination temperature,the broken rate first decreases and then increases,that is,the cylinder pressure strength first increases and then decreases.The broken rate reaches the lowest value of 8.65% at the cylinder pressure strength of 16 MPa.The formation of mullite phase in ceramsite result to the high cylinder pressure strength.(2)The addition of zirconia/manganese dioxide can effectively reduce the calcination temperature(about 100 ℃),and promote the formation of liquid phase at a lower temperature.(3)The results show that the performance of the obtained ceramsite by adding a small amount of zirconia into coal gangue and fly ash mixtures is excellent when the temperature is 1150 ℃ and zirconia is 6%.The cylinder pressure strength is 16 MPa when the broken rate is 8.73%.(4)The main phase of obtained ceramsite by adding a small amount of manganese dioxide is aluminate minerals,such as calcium feldspar,albite,feldspar,feldspar and labradorite.