Numerical Simulation Of 30MW Pre-drying Lignite Oxy-combustion Boiler

With the development of economy,excessive exploitation of the world hard coal, The development and utilization of lignite resources are more and more valued by the whole world.However,The utilization of low rank coal such as lignite will depend on the development of pre-drying and power generation integration technology and the application of clean combustion technology.Compared with traditional combustion, oxy-fuel combustion is considered to be a potential for development of carbon emission reduction technology,These new technologies can improve the efficiency of coal-fired,reduce the impact on the environment and reduce greenhouse gas emissions.In this paper, The numerical simulation of lignite combustion process was made by CFD software.Firstly, The simulation of single burner cold field and fluent sub-model setting was made to compare the effect of lignite kinetic parameters,the models and lignite moisture on the combustion in the furnace;Secondly,The effects of moisture content and oxygen enrichment on pulverized coal ignition,combustion and the change of concentration of the species in the full size boiler were simulated and analyzed.The main results were as follows:A closed rotary airflow was formed in a single burner,Good distribution and mixing created favorable conditions for the adjustment of a plurality of burners,the control of the air distribution and the ignition start-up.Burner hot simulation results showed that the activation energy smaller the chemical reactions faster;Single-rate and two-competing rates devolatilization model was superior to constant-rate model;With increase of lignite moisture,the temperature level inside the burner gradually decreased which influenced pulverized coal ignition and furnace thermal efficiency,and the amount of NO and the intermediate products were reduced.Boiler cold state simulation results showed that multi-burner swirl direction selection was reasonable,distance was moderate,the air can fully develop and interfere with each other.Boiler hot state simulation results were consistent with the results of the single burner under different moisture content;Oxygen-enriched combustion pulverized coal flame was shortened,the combustion rate is accelerated,pulverized coal ignition temperature,NO and SO2 generation was reduced,and CO2 concentration was above 90%;Oxygen-enriched combustion can appear local high temperature,the local high temperature increased with the oxygen concentration increased,and the surrounding flue gas temperature was more uniform.Through above simulation work,can combine combustion theory with numerical simulation better,which can verify new combustion method,improve fuel efficiency, broaden burning use range, improve combustion product composition,and achieve control the combustion process,reduce the combustion process pollutant emissions etc.At the same time,provide theoretical guidance for the optimal design and the reasonable operation of the boiler.