| The flue gas generators,as main devices for industrial heating stations,play a key role in the stable operation of industrial heating stations and the quality of materials for heating materials.In this thesis,the swirling coal-fired flue gas generator was designed to solve the problem of low combustion efficiency,low cleanliness of the flue gas and low output of existing coal-fired flue gas generator.Aiming at the problems existing in the coal-fired flue gas generators,this thesis presented a swirling coal-fired flue gas generator based on hypoxia combustion.The different combustion characteristics of the swirling coal-fired flue gas generator were studied by the method of cold experiment and numerical simulation.The characteristics of the flow field,temperature field,concentration field and particle trajectory of the flue gas generator were studied.Based on the thermodynamic calculation and the actual industrial demand,the structure and size of the flue gas generator were determined.According to the cold state modeling theory,the cold experiment system of the swirl flue gas generator was established.The height combustion chamber of the flue gas generator was 5.5m and the diameter was 1.8m.The experimental results showed that the distribution of the recirculation zone in the flue gas generator was reasonable when the primary air speed was between 9.91 m/s and 13.22 m/s,and this region was favorable for the ignition and burning of pulverized coal particles.When the secondary air ratio decreased,the radius and velocity of the recirculation zone in combustion chamber increased,which was beneficial to improve the combustion efficiency.But when the secondary air ratio was 2/9,the recirculation zone at the outlet of the burner disappeared,and the ignition of the pulverized coal particles may be delayed.The position of the secondary air inlet in the combustion chamber mainly affected the distribution of the flow field in the chamber.When the secondary air outlet position of the combustion chamber was shifted by 0.3m from the top,the axial flow field distribution in the combustion chamber of the flue gas generator was not stable and conducive to the combustion of pulverized coal particles.The numerical simulation showed that the coal particles were mainly burned in the combustion chamber of the flue gas generator under hypoxia condition,and the high temperature zone was near the wall.The temperature near the wall was about 2100 K,which satisfied the requirements of liquid slagging.The numerical simulation for different offset angles of the secondary air showed that the larger the offset angle,the larger the combustion area of the pulverized coal particles and the longer the residence time,which reduced the oxygen and carbon monoxide concentrations at the outlet and improved the combustion efficiency.In the actual operation,the offset angle is not less than 55°.The higher the secondary air ratio,the longer the residence time of the pulverized coal particles in the combustion chamber and the higher the combustion efficiency,which is conducive to improving the overall burning efficiency.When the secondary air ratio is 2/9,the ignition of the pulverized coal particles was delayed.In order to ensure the stability of ignition and combustion efficiency of coal particles,the secondary ratio is 3/8.The simulation results are in agreement with the experimental results.When the height of the combustion chamber cylinder was shortened from 5.5m to 4.0m,the flue gas temperature and nitrogen oxide concentration at the outlet of the combustion chamber were gradually reduced.Besides,the residence time of the pulverized coal particles in the combustion chamber was shortened and the burning rate in the combustion chamber was gradually reduced.When the height of the combustion chamber was 4.5m,the burning efficiency of pulverized coal particles satisfied the industrial requirements under different loads,and the coal-fired flue gas generator had better load regulation ability. |
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