Study On Reforming Scheme Of Pulverizing System Based On The Experiment Of Mixing Lignite In 330MW Coal-fired Boiler

Mixing coal for combustion is one of the application of coal blending technology in power plants.It refers to mixing different types and qualities of coal in a certain proportion to reduce operating costs and the emission of coal pollutants based on ensuring the safety of unit operation.As a results,economic benefits is improved and the need of national environmental protection is satisfied.Therefore,it is a goal for researcher in the field of thermal energy engineering at home and abroad that us search a useful technology for boiler combustion optimization operation,in order to achieve safe,efficient and clean combustion.Hebei jiantou xuanhua thermal power co.,LTD.has two 330MW coal-fired heating units with datong coal and xuandong coal as the designed coals.At present,due to the change of coal market,it is impossible to fully burn the designed coal.So this company has conducted a large proportion of lignite combustion test.It is found that the pulverizing system is a bottleneck which restrictes the further development of lignite blending.In order to further improve the lignite blending ratio and reduce the operation cost of power plant,combining unit characteristics and the experimental problems,this paper relies on current systems and equipment in xuanhua power co.,we carried out feasibility and economic efficiency analysis.Finally,two coal mills were used to replace each change machine,at the same time,the whole of the coal pulverizing system was optimized and changed.After the completion of the coal mill transformation,due to the increase of its grinding capacity,it can truly realize four operations and one preparation during low-load operation,and can carry out planned coal mill maintenance,which reduces the impact of the shutdown maintenance of coal mill on the lignite mixture ratio and generating capacity of the unit.When the normal unit load is less than 250MW,four coal grinders can make the proportion of lignite burning reach 40%,realizing the optimal pulverizing system operation mode of coal blending dynamically adjusted according to the daily load curve.The fuel of fly ash is generally maintained at 1.7%,the boiler efficiency is increased by 0.22%,and the net coal consumption rate is reduced by 0.8g/(kW·h).According to the test results,when the lignite burning proportion is 40%,compared with that without lignite burning,the net coal consumption rate can be increased by 0.2g/(kW·h),and it can be reduced by about lg/(kW·h)after the pulverization system is reformed,and the annual economic benefit can be increased by about 2 million yuan.To sum up,the transformation project of pulverizing system mixed with lignite has achieved the expected purpose and improved the economic efficiency of the whole plant on the premise of ensuring the safe operation of the unit.