Research On Energy-saving Technical Renovation Plan Of Circulating Fluidized Bed Boiler

Boiler is a type of equipment for producing steam,hot water with the specified parameters(temperature,pressure)and quality by utilizing heat energy released by fuel combustion,or other heat energy plus heating water.As a type of energy conversion equipment,the input energy into the boiler includes chemical energy and electrical energy in fuel,heat energy of smoke and steam with high temperature etc.,after the conversion of the boiler the output energy is steam,high temperature water or organic heat carrier with certain capacity of heat energy.Hot water or steam generated by the boiler can not only provide directly heat energy needed for industrial productions and people's life,but also be converted into mechanical energy by a steam power device,or again transformed into electrical energy by a generator.Boiler is a type of key equipment in many industrial production devices,thus how to ensure its safe operation,service life,production capacity and economic benefit etc.is one of the important research topics in the utilization field of boilers.In allusion to the actual production process and the existed problems such as lower thermal efficiency,higher carbon quantity in ash dregs,lower steam-gas pressure and higher smoke discharge temperature etc.of the coal combustion,high temperature and pressure circulating fluidized bed boiler in 500kt/a ammonia synthesis device of Yunnan Tian'an Chemical Co.,Ltd.,the comparatively systemic analyses,researches and partial practices etc.of its energy-saving technical transformation scheme were carried out in this thesis.The main research contents and achievements are as follows:1.Based on the principle and structure of the coal combustion,high temperature and pressure circulating fluidized bed boiler in 500kt/a ammonia synthesis device of Yunnan Tian'an Chemical Co.,Ltd.,and its actual production process and the existed problems were researched,the pertinent technical transformation scheme was put forward as follows:(1)The adiabatic cyclone separator in the existent coal combustion,high temperature and pressure circulating fluidized bed boiler is changed into gas refrigeration cyclone separator,the declined pipes come from the vapor bag in the boiler are set at the intake around the cyclone separator with the membrane wall,the number of pipe rows is increased to 20,and the length of center cylinder is enhanced to 100 mm in the primary length.Therefore,the separate efficiency of the cyclone separator can be improved,the carbon content of fly ash can be reduced largely,and the thermal efficiency of the boiler can be also enhanced.(2)As for the heated surface system(including superheater and economizer)of the coal combustion,high temperature and pressure circulating fluidized bed boiler,the transverse section distance between the higher and lower temperature superheater is adjusted from 105 mm to 95 mm,and the number of the transverse rows is changed from 80 to 89.The pipe diameter of the higher temperature superheater is adjusted from ?38 to ?42,and the number of the longitudinal rows in the economizer is increased for 2 circles.In this way the serious problems of fly ash with the heated rump area caused by the lower smoke speed in the area of the higher and lower temperature superheater can be also solved efficiently,in order to make the convection heat exchange effect be improved and increase the heated area in the superheater.(3)As for the fly ash blowing system of the coal combustion,high temperature and pressure circulating fluidized bed boiler,fly ash blowing with sound wave is changed to fly ash blowing with steam.Therefore,the fly ash blowing effect can be improved to a great extent,the smoke discharge temperature can be changed obviously,and the smoke temperature can be also reduced to about 20°C.(4)As for the dense hearth area system of the coal combustion,high temperature and pressure circulating fluidized bed boiler,the bed surface of its hearth is transformed.By disposing renewedly the bell cover type wind board jelab,the once wind capacity in the operation is reduced to about 45% of the total wind capacity.Through the transformation of the interface position for the twice wind entering hearth,the bed temperature can be improved efficiently,synchronously the twice wind capacity can be increased,and the adjustment ability of the twice wind to fuel can be enhanced.For this reason the burning on the hearth can be optimized,the burning efficiency of the boiler can be enhanced,the once burning rate of the fuel can be improved,and the carbon content of fly ash and lower dregs can be also decreased.2.In allusion to the technical transformation scheme of the coal combustion,high temperature and pressure circulating fluidized bed boiler,by applying “CHEDEFU” boiler thermodynamic calculation software of Xi`an Jiaotong University,all the data of coal combustion,high temperature and pressure circulating fluidized bed boiler were analyzed and calculated by the computer,the analytical results showed that,after the technical transformation of the coal combustion,high temperature and pressure circulating fluidized bed boiler is finished according to the technical transformation scheme,its main data indexes can be obtained to the original design values or better thermal efficiency and economic behavior.Moreover,the trial operation results after about one half of the technical transformation of the coal combustion,high temperature and pressure circulating fluidized bed boiler was finished at present according to the whole technical transformation scheme also validated the correctness of the analytical results made by the computer with the specified software.In this thesis the actual production process and the existed problems of the coal combustion,high temperature and pressure circulating fluidized bed boiler in 500kt/a ammonia synthesis device of Yunnan Tian'an Chemical Co.,Ltd.were researched,and the pertinent technical transformation scheme is being implemented.The obtained research achievements can solve the difficult problems that have chronically plagued its normal production and operation,make full use of the existing resources,enhance its production capacity and product quality with less investment,ensure “safe,steady,long,full and excellent” operation of the production device,and obtain considerable economic and social benefits.