Study Of Diffuse Combustion Process Conditions In Industrial Furnace And Control Of NO_x Emission

The technology of diffuse combustion has significant characteristics of energy saving and environmental protection. It has great significance in enhancing the utilization of energy, improving the air quality, reducing the enterprise production capital and enhancing the competitiveness of enterprises. It is considered one of the new key combustion technologies which has the most development potential in the 21 century in combustion field.In this article, to explore the technology of diffuse combustion in the application of the industrial furnace with exhaust gas auto-circulation, numerical simulation of study the forming conditions on the diffuse combustion technology in the industrial furnace was made by software(FLUENT), and experimental verification.Firstly, the paper verifies the applicability of industrial furnace device with different turbulent models, and compares with the experimental results, and finds the standard k-ε model gets closest to the actual situation and it works well.Simulation of changing of industrial furnace hearth radius in diffuse combustion process was made. It is found that the local high temperature reduced gradually by increasing of hearth radius. The average temperature, exit temperature, maximum temperature all reduce. It shows that the wide chamber of a furnace space has advantages in averaging the temperature of furnace hearth, forming diffuse combustion process, but should not be too large to increase furnace radius. In the study of this paper, the best hearth radius is limited to 180mm- 240 mm.Simulation of the influence in forming diffuse combustion by changing fuel flow was made. It finds that the more fuel flows in, the temperature distributes more uniform. The high temperature of furnace area is mainly distributed in the rear of the hearth. The high temperature area will gradually expand, with the increase of fuel flowing in. Therefore, combustion in the scope of relatively low oxygen and the reaction rate slowly meet the requirements of forming diffuse combustion when the fuel flows slowly.This paper also contrast analysis the influence in forming diffuse combustion in industrial furnace by using backflow fuel gas preheating air with or without backflow channel of fuel gas under different initial air velocity. In both cases, the exit temperature, the maximum temperature in the hearth will decrease and the furnace temperature will rise when increasing the injection rate of high temperature air. It is in line with the formation of the diffuse combustion conditions. When there are no flue gas backflow channel in the furnace hearth, max temperature, outlet temperature and the average temperature were much higher than the presence of flue gas flow channel and NOX generation is also increasing. Visibly, larger initial momentum has effect to the air and fuel mixture of delayed action, and flue gas flow has effect to the high temperature air and fuel of dilution.It is discussed that the change of the arrangement of burner to the formation of diffuse combustion, change the burner arrangement to the traditional decorate style(for gas inlet, middle upper air jet entrance), using 3d simulation explores the fuel nozzle and air nozzle flow field distribution of different spacing. Studies show that when the fuel nozzle and nozzle spacing is different, the temperature field distribution in the chamber of a furnace space changes a lot. As the gas nozzle and air nozzle spacing increases, the furnace temperature gradient, furnace space temperature distribution more uniform. Conform to the basic characteristics of diffuse combustion.