Distributed Parameters Modeling For Evaporation System In A 35MW Oxy-coal Combustion Boiler

Oxygen-enriched combustion technology is one of the most promising large-scale carbon reduction technologies for coal-fired power plants in 21~stt century.In this paper,the first domestic 35MW oxygen-enriched pulverized coal fired boiler was used as the research object.The numerical simulations are calculate by using Fluent software,which is bases on the traditional air case and oxygen-enriched dry/wet flue gas cycle cases,we combined field measurement data with simulation results,and the heating characteristics of the evaporation system are analysis,we carry out the research of the evaporation system modeling.Finally we get the wall heat flux,metal-surface temperature and steam quality corresponding to the different conditions.In this paper,modular modeling method is adopt for evaporation system.The three-dimensional flue gas temperature field and the heat flux distribution of the water wall are calculate by Fluent software;The two-dimensional steady-state thermal conductivity model is uses to calculate the temperature of the outer wall,the inner wall temperature uses as the lumping parameter;The appropriate heat transfer coefficient and the resistance coefficient are select for the steam water side,and the simulation calculation program is writing by C++,which is to calculate the thermal parameters of the working fluid in the water tube under different working conditions.The simulation research on the distribution parameters of the oxygen enriched combustion boiler evaporation system is carries out.The distribution of the flue gas temperature field in the furnace and the distribution of the two-dimensional heat flux in the water wall under different working load conditions are show that:the heat flux is concentrates on the front wall under air combustion conditions,but the heat flux distribution of the oxygen enriched conditions are more uniform,The average heat flux in the furnace of air combustion condition is consistent with the oxygen-enriched wet FGR condition under the same load,but they are higher than the oxygen-enriched dry FGR condition;The oxygen-enriched combustion wall temperature of the main combustion zone is lower than the traditional air condition under the same load.At the oxy-fuel dry FGR80%load,the maximum relative difference of the wall temperature is 2.14%;The distribution of steam quality in the different combustion conditions are show a trend of"high middle and lower on both sides",the vaporization of the starting point advance with the increasing load.It is found that the enrichment of the physical properties caused by the enrichment of the three atoms in the flue gas,the reasonable oxygen-enriched combustion structure can adjust the furnace heat load and the wall temperature distributed well,it can make the furnace side and boiler side parameters response more coordinated.This topic research effectively integrated numerical simulation of the furnace side with thermodynamic of the evaporation side,the model can accurately predict the distribution of thermal parameters of boiler evaporation system,which reveals the unique superiority in revealing the two-dimensional distribution of the thermal parameters of the heating surface,it provides a new supported method for the large–capacity oxy-fuel boiler design,operation and diagnostics.