3. Downward inclination of small furnace
For the melting furnace burning producer gas, the angle between the slope of the small furnace and the horizontal plane constitutes the downward inclination of the air stream, and the angle between the bottom plate of the small furnace and the horizontal plane constitutes the upward inclination of the gas stream. The upward and downward inclination angles constitute the intersection angle of the gas and air streams. The larger the intersection angle of the two streams, the stronger the mixing. The distance between the end of the tongue and the outlet section of the nozzle is the length of the pre-combustion chamber. The longer the pre-combustion chamber, the higher the degree of mixing of gas and air. At the same time, when the air and gas flow and temperature are constant, the degree of mixing is related to the cross-sectional ratio of the horizontal channels of air and gas. The degree of mixing of gas and air in the pre-combustion chamber is also related to the contact area of gas, that is, under the condition of the same cross-sectional ratio of the horizontal channels of air and gas, the degree of mixing of the streams in the flat pre-combustion chamber is relatively high. For flat glass melting furnaces that burn gas from the generator, the pre-combustion chamber of the small furnace mostly adopts a "small intersection angle" long pre-combustion chamber with a tongue protruding, a stable and long flame, a small temperature difference between the fire root and the fire tip, and is easy to control and maintain. The long pre-combustion chamber generally has an air downward inclination angle of 20°~26° and a gas upward inclination angle of 0°~5°, that is, the intersection angle between air and gas is 20°~30°.
In the bottom-fired small furnace structure that burns liquid and natural gas, the downward inclination angle of the slope of the air channel is an important parameter. In order to make the air and oil mist mix evenly and quickly, and to make the flame close to the liquid surface, the downward inclination angle is generally 20°~25°. The nozzle refractory brick allows an upward inclination angle of 5°~12°. The bottom plate of the small furnace has no upward inclination angle, and is generally built into a flat or stepped style, so that the combustion-supporting air can mix with the oil mist as quickly as possible when entering the kiln through the small furnace door, ensuring that there is enough air near the nozzle for the gradually diffused oil mist to be burned, and the flame just passes over the glass liquid surface. The downward inclination angle must be matched with other conditions, such as the aspect ratio of the small furnace, the distance between the small furnace and the burner, the height between the small furnace and the liquid surface, etc., so as to select the most appropriate angle.
4. Horizontal channel of the small furnace
For the melting furnaces of fuel oil, natural gas, and coke oven gas, the air is preheated in the regenerator, rises to the top and turns to enter the horizontal channel of the small furnace. After the airflow angle is changed under the action of the slope roller, it is sprayed into the melting furnace through the nozzle. The horizontal channel of the small furnace serves as a channel for introducing preheated air and a channel for exhausting exhaust gas.
After the air rises from the regenerator to the turning point of the horizontal channel, the flow direction changes, and the airflow is relatively unstable. In order to stabilize the airflow, the horizontal channel must have a certain length, and the increase in length is conducive to the stability of the airflow. In addition, the lengthening of the horizontal channel expands the operating space under the small furnace, which brings greater convenience to the adjustment, assembly and maintenance of the spray gun.
Due to the large temperature fluctuations at the bend and the airflow has a certain erosion on the refractory material, the more erosion-resistant 33# ordinary cast electric fused zirconium corundum refractory bricks are used for masonry here (the rear flat arch and the stack bricks between the heat storage chamber and the slope arch).
5. Small furnace tongue
The "small furnace tongue" is only for the melting furnace burning the generator gas, and it mainly forms a horizontal channel separating the air and gas. The structure and size of the tongue are another important structural factor affecting the mixing degree of air and gas and the flame entering the kiln. The length, thickness and shape of the tongue have an impact on the length, angle, temperature distribution and erosion of the nozzle.
Tongue length: After the other dimensions of the small furnace are fixed, the longer the tongue, the closer the air and gas meeting point is to the nozzle. The horizontal flame melting furnace requires the flame to have sufficient length, direction and rigidity, and generally uses a tongue made of zirconium corundum refractory bricks.
Tongue thickness: After the external dimensions of the small furnace are determined, the thickness of the tongue is related to the distance between the intersection of air and gas, which affects the mixing degree of air and gas and the angle of the flame. Considering the structural strength, the tongue should also have a certain thickness. If it is too thin, it will cause serious fire penetration and aggravate the burning. Generally, the tongue is 250mm thick.
