Study On Explosion Venting Of Coal Pulverizing Process In Heat Power Plant

Coal powder pulverizing system is one of the important links in production safety of heat power plant. How to mitigate the risk of fire and explosion accidents in coal powder pulverizing system is the main issue encountered by each heat power plant. Based on the experiment tests and numerical simulation systematic research on the design of explosion venting was conducted. It is of great practical significance to safety production of coal powder pulverizing system of heat power plant.First, three kinds of coal samples were chosed from Lianyungang heat power plant, Shenhai heat power plant and the Second heat power plant in Tongliao, and physical properties and explosion characteristics of the samples were tested. Explosion characteristic consists of maximum explosion pressure, maximum rate of pressure rise and explosion index. The results indicate that explosion pressure, rate of pressure rise and explosion index increased with increasing of coal powder concentration at the beginning, while after coal powder concentration meets a certain degree they all decreased with the raise of coal powder concentration. Based on this characteristic, risk analysis on the typical coal powder pulverizing system was carried out and the primary hot air inlet was thought to be the weakest part of the process line.For explosion venting design, it is necessary to calculate the loading capacity of the primary hot air inlet of the coal mill. Considering the contingency of explosion and material saving, a finite element software of ANSYS10.0 was used to calculate the ultimate loading capacity of the primary hot air inlet from elastically and plastically. Results showed that structural maximum loading capability allowing plastic deformation is ten times of that when only elastic deformation was allowed. Plate thickness and chamber radius of four corners of the duct were also considered to see their influences on the structural loading capacity, and it is found that the maximum loading capacity increases with the increase of plate thickness and chamber radius of four corners of the duct. Calculation results showed that when the plate thickness is 5mm, carrying capacity is 3.2 times as strong as that when plate thickness is 2mm; when the chamber radius of four corners of the duct is 20mm, its loading capacity is 2.8 times as strong as that of 5mm.Different valid explosion venting standards from China, America and Germany were analyzed. Considering Chinese standards are being under revision, the latest German standard, "Pressure venting of dust explosion" VDI3673-2002 was adopted to do explosion venting design in the paper. After calculation, the author gained the venting area of coal mill primary hot air inlet, also studied the factors which influence the venting area, these influence factors involve explosion pressures, volatile content, plate thickness and chamber radius of four corners of the duct. It is found that venting area increases with the increasing of maximum explosion pressure, maximum rate of pressure rise as well as volatile content and it decreases with the raise of structural loading capacity. Under the same condition, when plastic deformation is permitted the venting area needed for the hot air inlet is 200% less than that when only elastic deformation is permitted.