On 2018-08-08 14:48:54
Annealing furnace of natural gas
The inadequate combustion of the annealing furnace using natural gas is due to the insufficient air in the furnace or the poor mixing of air and fuel, which causes incomplete combustion of natural gas. If the combustible components in the fuel are not completely burned in the furnace, it should be called incomplete combustion. There are unburned carbon particles in the ash.
Reducing the heat loss of heating equipment is the main way to improve the heating efficiency. The methods to reduce the heat loss of the trolley furnace are: reducing the heat dissipation of the furnace wall, improving the heat insulation ability of the furnace lining material and reducing its heat storage, increasing the tightness of the furnace, reducing the heat taken away by the transmission parts, the material basket and the material tray, etc.
1. The effective way to reduce the heat dissipation of the annealing furnace series is to reduce the surface area of the furnace first. When other conditions are the same, the heat loss of the furnace is directly proportional to the surface area of the furnace wall. The outer surface of the cylindrical furnace is 14% smaller than that of the box furnace, the outer wall temperature is 10 ℃ lower, which can reduce the heat dissipation of the furnace wall by about 20%, the heat storage of the furnace lining and the unit energy consumption of the processed workpiece by 7%. Therefore, the latest periodic and continuous heating furnaces have been changed to cylindrical ones.
2. The way to reduce the heat storage of furnace lining is to use heat insulation refractory with small mass heat capacity and density. Ceramic fiber, commonly known as aluminum silicate fiber, is an ideal new energy-saving refractory. Because the thermal conductivity of ceramic fiber is small, the temperature of furnace outer wall is much lower than that of heavy brick and light refractory brick in the same furnace, lining size and furnace temperature. The heating time of ceramic fiber lining is only one fifth to one sixth of that of light firebrick and clay lining. When the trolley furnace often operates intermittently, it is obviously advantageous to use ceramic fiber stir lining. On the one hand, the rapid temperature rise of the furnace shortens the auxiliary time; on the other hand, it greatly reduces the heat storage and energy consumption. With ceramic fiber lining, the heating up time of the empty furnace is reduced by one sixth and the combustion is saved by 50%.
3. For various types of heating furnace, the proportion of heat energy required for heating interlayer and material tray is 18% ~ 29%. So it is important to reduce the weight of fixture and material tray to improve the heating efficiency. One of the ways to reduce the weight is to improve the structure of the fixture and the material tray; the other is to select the material reasonably. It has been proved that it is cost-effective to use high-quality heat-resistant steel to make jigs and plates in order to prolong their service life and save energy. For example, Hitachi construction machinery plant in Japan has improved the structure of the material plate of the sealed box furnace, reducing the weight, increasing the number of shaft parts per plate from 200 to 300, saving 20% of the power. 500 kg propane is saved.
The conveyor belt of the continuous trolley furnace is cooled in the atmosphere for many times after it is rotated out of the furnace, and then enters the furnace for heating. By reducing the conveying weight, a large amount of heat energy on the heating conveyor belt can be saved. In this sense, the vibrating bottom furnace, roller bottom furnace and mesh belt furnace for EPS line are superior to the chain plate furnace in energy saving.
The waste heat can make full use of the waste heat of the fuel furnaces which use various fuels. The temperature of the exhaust gas discharged from the trolley furnace shall be at least 50 ℃ higher than the indicated temperature of the furnace. The higher the temperature of the final exhaust gas, the greater the heat loss of the furnace.
A large amount of air is needed in the combustion process of natural gas. The biggest energy saving measure of combustion furnace is to preheat the air by using the heat of fuel gas. For example, when the exhaust gas temperature is 900 ℃, the air fuel ratio is 1:4. The heat loss rate of exhaust gas is 50%. If the exhaust gas is used to preheat the air to 250 ℃, 15% of the fuel can be saved and 22% of the exhaust gas heat can be recovered. Therefore, the higher the air preheating temperature is, the greater the fuel saving rate is.