Test And Uncertainty Analysis Of Surface Radiation And Convection Loss For Circulating Fluidized Bed Boiler

Circulating fluidized bed(CFB)boiler has formed different technology schools in the development process,which makes the boiler structure and layout have a certain degree of difference and makes the heat loss have its own characteristics.The current industry standard refers to the loss of heat capacity of the same-capacity pulverized coal furnace and multiplied by the area correction factor to determine the heat loss of the CFB boiler.The current standard doesn't sufficiently consider the above differences and the estimated heat loss referring to the current standard has unknown uncertainties.This dissertation aims to obtain the exact value of heat loss of CFB boiler and to study the difference of heat loss of different CFB boiler.In this dissertation,the heat loss calculation method of CFB boiler at home and abroad is studied through theoretical analysis and field experiment.The main contents of this paper are as follows: the differences and the methods of calculating the heat loss in the field of "Fired Steam Generators Performance Test Codes"(ASME PTC 4-2008)? "Atmospheric Fluidized-Bed Combustion Performance Guidelines"(EPRI-GS-7164)? "In-situ measurements of heat loss through thermal insulation of equipments and pipes—Heat flow meter apparatus and surface temperature method "(GB/T17357-2008).After theoretical analysis,we found that the three standard radiation heat transfer coefficient is very similar.But in the domestic,the calculation of convective heat transfer coefficient by the surface shape and location of the classification method is very complicated.While the two sets of standards in the calculation of convective heat transfer coefficient formula is very simple and practical.Based on a 440t/h CFB boiler field test data,the three standard test results are not very different,but ASME PTC 4-2008 provides a more practical test method and also provides the uncertainty of the test results of the method.Based on the ASME PTC 4-2008 standard,we measured three boilers: a 440 t/h CFB boiler with a high temperature insulation separator(boiler A),a 240 t/h CFB boiler with a steam cooled cyclone separator(boiler B),and a 130t/h CFB boiler with water-cooled square separator(boiler C).After the calculation,we got the three boiler heat loss and its correction value.As the three boilers with different separators,it resulted that the proportion of its various parts of the heat loss there had a big difference.The high-temperature insulation separator in boiler A and the area of the return system accounted for only 16% and 47% of the total heat loss respectively.The air-cooled cyclone separator in boiler B and the area of the return system accounted for only 15% of the heat loss accounted for 36% of the total respectively.The proportion of the heat loss of each part of the boiler C was basically the same proportion of its area.For Boiler A,the heat dissipation loss test value of the boiler system was 0.731%,and the uncertainty was 0.08%.The test result had a high accuracy.However,the heat dissipation loss was 0.432%,which was 0.382% unilaterally and 1.4 g /(kW · h)respectively,according to the national standard and the industry standard estimation method.By studying the influence of the number of measuring points on the uncertainty of the heat loss test results,it can be concluded that the test plan can not only greatly reduce the number of measuring points,but also ensure the test results have high enough accuracy(test results Relative uncertainty is about 10%).