Experimental Study On Flowability Of Pulverized Coal In The Storage Bin

In the coming decades, coal will still be dominant in Chinese energy structure. The thermal power plants often involve the pulverized coal storage and transportation. Due to the cohesion and the influence of the gas-solid two-phase flow, pulverized coal is often sticked together between the solid particles. This problem can lead to blanking plug for powder or instability problems. In this thesis, the influence of moisture content, particle size, particle size distribution, wall materials and other factors on flowability of pulverized coal were studied.In this thesis, repose angle measurement, Jenike shear test method, and FT-4composite powder test method were adopted to study the influence of different moisture content and particle size distribution on the flowability of the Fugu bituminous coal and southeastern Shanxi anthracite coal. A serious of parameters were obtained, including the repose angle, internal friction angle, cohesive force, flow function, wall friction, compression ratio, compression density and flow energy.Moisture contents and particle sizes are the two main factors which influence the flowability of pulverized coal. With the particle size segment of the pulverized coal designed for thermal plant, the results show that with the increase of particle size, pulverized coal has good liquidity, wall friction angle is smaller. What’s more, the more uniform pulverized coal particle size is distributed, the better of the liquidity. The higher of fine powder content, the more illiquid of pulverized coal. The influence of moisture content on the two kinds of pulverized coal is consistent. Both of the two kinds of coal have a critical rate of moisture content. Before reaching the critical rate of water, the flowability of pulverized coal becomes difficulty with the increase of moisture content, When moisture content is more than the critical rate of moisture content, the flowability of pulverized coal becomes unstable. When moisture content is more than the critical rate, the flowability of the Fugu bituminous coal turns to better in the moisture content of6%～8%, and5%～6%to the anthracite pulverized coal. The flowability becomes worse and worse after the moisture content is larger than this range.The test results show that pulverized coal repose angle is larger than the internal friction angle by10°～15°, which means that pulverized coal is cohesive powder. The type of coal also has influence on the flowability of pulverized coal. Anthracite has less inner moisture content, because the pore structure is undeveloped, which leads to smaller critical moisture content. Because of anthracite coal combustion difficulties, the anthracite coal particle size used is smaller, which leads to the flowability of the anthracite poor than Fugu bituminous coal.Four kinds of wall material were selected as experimental object, the experimental results show that the wall friction angle of carbon steel is the largest, followed by stainless steel, the aluminum alloy has minimum wall friction angle. It is recommended to use teflon or aluminum alloy as the storage bin wall material or the lining. For Fugu bituminous coal, the best moisture content is8%,6%for Southeastern Shanxi anthracite.Finally, this thesis carried out the design of maximum half top angle and minimum outlet size to the overall pulverized coal according to the experiment results, which could provide guidance for production.