Fuel With Slime Cycle Fluidized Bed Boiler Design And Performance Analysis

Coal sludge is the residue raised during coal washing. Its granularity is fine of less than 0.5mm and it has stronger water-holding property. Due to the high moisture, high viscosity, difficult transportation, and the unstable modality during piling, it is easy to run out when meeting with water and fly upwards when being dried by wind. This caused the dangers larger than that caused by other residues produced by coal washing such as gangue. Along with the gradual development and maturation of circulating fluidized bed combustion technology, various kinds of circulating fluidized bed combustion technology for coal sludge were successively developed in overseas and domestic in allusion to characteristic of coal sludge and that has blazed a effective way to utilize coal sludge. The research and practice about combustion and utilization of coal sludge has indicated that there are two kinds of key technologies, the one is the design of front coal feeding system and the other is the design of combustion equipment for burning coal sludge. The writer has done some research and practice about these two key technologies on the basis of two 75t/h coal sludge fired circulating fluidized bed boiler(CFBB) and designed for Power Plant of LiangZhuang Coal Mine in XinWen.At present, there are two kinds of front coal feeding system — the one is conveyer belt and traditional mechanical screw conveyer, the other is pump-conveying system. Along with the CFBB development to the large scale and gradual enhancement of requirement for safety and high efficient running, the coal sludge feeding system should be suitable in wide range, stable in running, few in repair and simple in system, easy to conveying coal for a long distance and realize the automatic control. This article gives the analysis to the selection and performance of double plunger pump feeding system on the basis of test and research for rheological characteristic of coal sludge.The physical and combustion characteristic of coal sludge is very important to the design and running of coal sludge fired CFBB. This article gives theanalysis on caking combustion and heat explosion characteristics of water-coal mixture on the basis of Liangzhuang coal sludge. And indicates that the combustion characteristic of coal sludge should be fully used during design.In the design of combustion equipment for coal sludge and CFBB, the writer adopted some new technologies and structure, such as feeding large-size coal from the upper of furnace, adopting different specific gravity fluidized bed, special furnace arrangement, volute cyclone separator and etc. This article analyses the feasibility of feeding coal sludge from the upper of furnace and gangue as the initial bed from the lower of furnace; the selection of fluidizing air speed for CFBB according to the suitable coal sludge; the selection of length to width ratio on furnace section and the height of furnace dense zone; introduces the structure, key design points and performance of new high-efficiency volute cyclone separator.The boiler was put into running in November, 2003. Shandong Energy Utilization Detection Center and Shandong Environment Detection Center Station have done the testing for thermal efficiency and pollution emission. The testing results express that the boiler output, efficiency and emission index are all up to or higher than the design requirements, and the performance is at the domestic advanced level. It passed the appraisal for scientific and technological achievement hold by Shandong Science and Technology Department in November, 2004 and won a higher evaluation.