Numerical Simulation Of Kiln With HTAC In Calcining Bauxite

High temperature air combustion ( HTAC ) technology was developed successfully to be a new technology in the nineties in Japan, which possesses energy saving and environment protection. The technology has brought new opportunities for increasing fuel utilization and reducing environment pollution for every country. HTAC is a new type combustion technology, which the air is heated up to more than 800～1000℃through recovering the waste heat of high temperature flue gas exhausted from furnace. The temperature of exhaust is a little higher than its dew point. The high temperature air and gas are ejected into furnace to form stable diffusion combustion. Thus, the utilization of thermal factor is increased. Compared with traditional combustion, the fuel would be saved up to 50%～60%, the equipment size decreased about 30%.In the article, a three-dimension numerical simulation process in a restricted space for studying kiln with HTAC in calcining bauxite is created by a CFD software. K-εturbulent model, PDF non-premixed combustion model, discrete coordinate radiation model are considered in the physical model. Firstly, temperature field and concentration field were analyzed about kiln with HTAC and traditional kiln; besides, the factors, such as air inlet pressure, flow rate of fuel gas, preheated temperature of combustion air, distance between fuel gas jet and air jets, are studied on temperature field in the furnace, concentration field, and NOx emission. The results showed that:1,Compares with the traditional down-draft kiln,the new kiln has good properties such as: Good temperature level, small temperature difference, fuel burning entirely, energy saving.2,Through analyzing the results of numerical simulation about temperature field under different conditions, we can know that the high temperature region and the temperature difference reduces, the temperature uniformity increases with air pressure reducing; as the fuel velocity increasing, the maximum temperature rises, the high temperature area expands and the temperature difference reduces; with the air preheated temperature's increasing, the high temperature region and the temperature difference reduces, temperature uniformity enhances obviously; with the increasing of distance between fuel gas jet and air jets, the maximum temperature and the temperature difference both rise.3,Through analyzing the results of numerical simulation about concentration field under different conditions,we can see that the methane density distribution and the oxygen density distribution is even, the oxygen density reduces and the Carbon dioxide density increases with air pressure reducing; with the increasing of fuel jet velocity, air preheat temperature and distance between fuel gas jet and air jets, the oxygen density reduces and carbon dioxide density is high in the low oxygen concentration region.4,The results of numerical simulation about NOX emissions under different conditions show that the NOX emissions reduces with air inlet pressure increasing. When the air inlet pressure increase from 50 into 100, the nitrogen oxide decrement is the most fast. The NOX concentration increases with the increasing of fuel jet velocity and air preheat temperature.5,By means of the hot tests in the test furnace,the furnace temperature distribution and furnace temperature fluctuation are analyzed in different exchange period,and regenerative body are analyzed.When the exchange period is 450 second,the furnace temperature fluctuation is the highest.When the exchange period is 90 second,the furnace temperature fluctuation is the lowest.