Experimental Study On Hydrodynamics And Structural Arrangements Optimization Of Sunercritical Circulating Fluidized Bed Boilers

As the coal-dominated energy consumption structure and the power generation structure dominated by coal-fired power will not change in the short term,developing the clean coal power generation technology has been an important direction of the energy development strategy in China.Supercritical CFB(SCFB)boiler combines the high combustion efficiency,good fuel flexibility,and low cost emission control of CFB boiler and high efficiency of supercritical steam cycle.Thus,Supercritical CFB boiler has becomes a potential clean coal power generation technology.At present,SCFB boiler is faced with problems such as the flow non-uniformity among parallel cyclones,the particles accumulation in the furnace corners,the lack of secondary air penetration capability,the large width-depth ratio of furnace,no adequate space to arrange heating surfaces.To deal with these problems,polygonal furnace and annular furnace were proposed by Institute of Engineering Thermophysics,Chinese Academy of Sciences.Theoretically,polygonal furace can reduce the particles accumulation in the furnace corners and annular furnace can solve the problems of secondary air penetration and the layout of heating surfaces.But the structure of polygonal furnace and annular furnace are different from the traditional rectangular furnace,understanding the gas-solids flow of polygonal furnace and annular furnace is the basic of their application.Focused on parallel cyclones,polygonal furnace and annular furnace,this dissertation conducted cold-model experiments to study hydrodynamics and structural arrangements optimization.This dissertation studied the effect of the configurations of three parallel cyclones and the structure of furnace corners on the gas-solids distribution uniformity among three parallel cyclones.Results show that the distance between the entrance of the side cyclones and the side walls is the key influencing factor;The rotational direction of the side cyclones and the position of the middle cyclone have little effect;The chamfer of furnace corners can increase the solids into the side cyclones and can be used to reduce the flow non-uniformity;Through the structural arrangements optimization,flow non-uniformity is reduced from 17.6%to 8.2%.This dissertation studied the hydrodynamics of the CFB with polygonal furnace and three cyclones.Results show that the gas-solids flow distribution in polygonal furnace is the same as the rectangular furnace,the axial gas-solids flow distribution presents the 'dense bottom and sparse top' structure and the lateral gas-solids flow distribution presents the 'core-annulus' structure;The solids concentration near the chamfer is not larger than the center of the furnace walls,which proves that the chamfer structure of the polygonal furnace can reduce the solids accumulation in furnace corners.This dissertation studied the effect of the configurations of three parallel cyclones,the structure of the outer annulus corners,and the furnace strucuture on the gas-solids distribution uniformity among six parallel cyclones in annular furnace CFB.Results show that flow non-uniformity in annular furnace CFB is not greater than rectangular furnace CFB;The distance between the entrance of the two side cyclones and the front/rear wall and the distance between the entrance of the two side cyclones and the inner short sidewall are the key influencing factors;The rotational direction of side cyclones does not change the solid circulating rate distributions trend,but in term of uniformity,side cyclones rotating inward is superior to those rotating outward;The position of the middle cyclones and the symmetric modes of the cyclones have little effect;The chamfer of outer annulus corners can increase the solids into the side cyclones and can be used to reduce the flow non-uniformity;Through the structural arrangements optimization,flow non-uniformity is reduced from 34.1%to 9.3%.This dissertation studied the hydrodynamics of the CFB with annular furnace and six cyclones.Results show that the axial gas-solid flow distribution in annular furnace is similar to the rectangular frrnace,but the lateral gas-solids flow distribution presents the 'core-double annulus' structure;The dissertation also studied the structure and layout of suspended heating surfaces in the CFB with annular furnace and six cyclones.Results show that the structure and layout of suspended heating surfaces can influence the gas-solids flow in surfaces zone.Some principles for the design of suspended heating surfaces are achieved.The studies above supply references and bases for the design of the SCFB boiler with polygonal furnace and three parallel cyclones(350 MW)and the design of the SCFB boiler with annular furnace and six parallel cyclones(660MW).