| In recent years, as the emission standard of NOx becomes more and more stringent, reduction of NOx from utility boilers turns into a hot topic. A horizontal bias combustion (HBC) technology is an effective approach to solve the problems of combustion efficiency, flame stability, resistance to slagging and high-temperature corrosion, and low NOx emission of coal combustion. As the key part of the HBC burner, the louver coal concentrator (LCC) has been successfully applied in many large scale pulverized coal boilers. In order to understand the gas-solid flow characteristics in the LCC, exert the role of the flow duct in coal concentrate, and realize low NOx emission of the boiler, some research work has been done in this study. The flow field in a LCC and an elbow was investigated firstly. A reversing LCC was developed and applied in the HBC burner with small oil nozzle for pulverized coal ignition. Finally,in order to solve the problems of combustion instability and high-temperature corrosion of a pulverized coal fired boiler with elbow and twist-plate type burners, some reconstruction was performed based on the numerical simulation and analysis of the moment of momentum.The mean and fluctuating velocities of the air were measured using a constant temperature hot-wire anemometer in a small-scale 2-D LCC model. Then those velocities were simulated by the standard k-ε, realizable k-ε, RNG k-εand Reynolds-stresses models (RSM) with FLUENT. Comparison between the numerical results and the experimental data shows that all four turbulence models can predict the average velocity pretty good, but only the realizable k-εmodel and RSM can give reasonable prediction of the turbulence kinetic energy. The experiment of using glass sphere as the tugged particle was describe, and the flow visualization of flow field in the LCC by using the laser light sheet and the high speed photography (HSP) technology. Experimental results show that there is a particle flow with a higher concentration near the blade of the fuel-rich side in the LCC. During the operation of the real LCC, the pulverized coal particles flow with high concentration impinges on blades of the LCC, and leads to the blades erosion eventually.The gas-solid two phase flow in a LCC was investigated using PDA (particle dynamics analyzer). Gas-solid two phase flow in typical sections, near the blade surface and fuel-rich side exit of the LCC were obtained. The results show that the particle concentrate in the LCC due to the collision between particles and the blade near the blade surface. Blades concentrate particles near the blade and influence little in the zones away from blades. The erosion wall area in fuel-rich side exists between the last blade to 0.7D ("D"is the width of the LCC) away from it and anti-erosion measures should be considered in application.The study on gas-solid two phase flow of the LCC was carried out by numerical simulation with k-εmodel and stochastic particle trajectory model. It was showed that calculation results reliable by comparing experimental results with them. Furthermore, the gas-solid flow field of the LCC was investigated by numerical simulation under the condition of absent blade. The erosion of the blade was predicted using semi-empirical correlation for the erosion ratio. The industrial test of the erosion of the blade was carried out. The results show that the lower part of the blade is eroded heavily. The erosion ratio of the downstream blade is higher than that of upstream. At a blade, the erosion at the back is heavier than at the front.Two corners of the oil gun ( four corners of the oil gun in the double furnace) have to be arranged at fuel-lean side owing to the space constraints when the boiler combustion system combined HBC technology and coal pulverized direct burning technology with small oil nozzle. It will result in the problem of ignition and startup of the boiler and fuel waste. Thus a novel reversing LCC was developed. This concentrator has advantages of simple configuration, easy operation, and is able to change the direction of the fuel-rich and fuel-lean streams under the operation condition of boiler, which achieves ignition and startup of the boiler, and save fuel oil. The optimization of structure of the reversing LCC was performed by numerical simulation. The air velocity of the primary air nozzle of the improved burner in a 300 MWe utility boiler was measured. The ratio of rich and lean air flux meets design requirement, which shows the reversing LCC was reliable.On a scaled model, the gas-solid two phase flow was measured and analyzed at several representative cross sections in the elbow as well as the downstream line of elbow. The problems of combustion instability and high-temperature corrosion of pulverized coal fired boiler were investigated by numerical simulation and analysis of the moment of momentum. Elbow and twisting plate type of burners were used in the boiler, and the reverse moment of momentum was formed at the outlet of the fuel-rich side of the burner. The moment of momentum in the boiler was opposite to the designed tangential circle, and the tangential circle in the boiler was reversed rotation. The reverse moment of momentum at the burner outlet could be eliminated by using louver horizontal bias pulverized coal burner, while the problems of combustion instability and high-temperature corrosion of the boiler were solved, and the combustion efficiency was improved. Accordingly, economic benefit was obviously got.
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