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Structural Distribution of Small Furnace Parts of Glass Melting Furnace and Configuration of kiln Refractory Bricks

2022-07-04

The structure of the small furnace has a decisive influence on the direction, speed, air-gas mixing degree and flame length of the flame. The preheating temperature of the air-gas and the excess air coefficient determine the flame atmosphere and the flame combustion temperature, so The structure of the small furnace plays an important role in the heat transfer in the kiln and the melting process of the glass.

 

For the melting furnace that burns liquid fuel, natural gas and coke oven gas, the structure of the small furnace is relatively simple, with only the small furnace nozzle and horizontal passage. For the furnace that burns the producer gas, in addition to the nozzle and the horizontal channel, the small furnace also has a pre-combustion chamber, a small furnace tongue, an air riser, and a gas riser.

(1) Discharge port

 

The jet port is also called the flame jet port (as shown in Figure 1). When the flow rate of air (and gas) and the combustion temperature of the flame are constant, the size of the cross-sectional area of the nozzle determines the speed at which the flame is injected into the kiln, and also affects the length of the flame. When the cross-sectional area of the jetting port is constant, the ratio of the length to the height of the jetting port determines the coverage area of the flame on the glass liquid surface.

 

Too large or too small flame speed is not conducive to the normal progress of the melting process. If the speed is too high, the fuel will extend into the small furnace on the opposite side before it can burn completely, and it will burn in the regenerator. . At the same time, if the flame speed is too high, the powder will be brought into the opposite small furnace, which will erode the masonry of each part of the small furnace and block the lattice body. If the flame speed is too small, the flame is fluttering and weak, which is not conducive to the heat transfer to the glass liquid and the batch materials, and it is easy to burn out the nozzle of the small furnace. In order to increase the flame coverage area, it is required to increase the width of the nozzle as much as possible. The cross-sectional area of the ejection port is often in a flat form to meet the coverage area. Usually according to the requirements of the temperature system in the kiln, the width of the nozzle is different. For the furnace with 7 pairs of small furnaces, the width of 1#, 2#, and 6# small furnaces is the same, "the width of the small furnace nozzle is slightly smaller, and the 7# small furnace nozzle is the smallest.

The top of the spout is called the flat spout in front of the small furnace; the walls on both sides of the spout are called small furnace stacks (also called small furnace legs), and below are the small furnace hook bricks. Since the flame is sprayed into the kiln or the high-temperature gas in the kiln is discharged through the nozzle, the flame erosion and the erosion of the flying material cause a bad use environment. Therefore, all parts of the nozzle are built with fused zirconium corundum bricks by the oxidation method.

 

The distance between the ejection port and the liquid surface is generally desired to be as small as possible, so that the flame is close to the liquid surface, which is beneficial to heat transfer. Generally, the distance between the bottom brick of the ejection outlet and the glass liquid surface is 400~600mm.

(2) Pre-combustion chamber

 

For the furnace that burns producer gas, the small furnace space from the end of the tongue to the outer edge of the nozzle is called the pre-combustion chamber. After the preheated air and gas enter from the upper and lower parts of the tongue respectively, they meet in front of the tongue, diffuse and collide with each other to mix, burn to a certain degree, and spray into the kiln at a certain angle. In order to ensure that the gas can be completely burned in the kiln, the pre-combustion chamber plays a very important role, so the length of the pre-combustion chamber (that is, the distance of the mixed combustion of air and gas) also reflects the time of mixed combustion, which is an important structural indicator.

 

For furnaces with side-, top- or bottom-plug lances on the small furnace, the space inside the small furnace is also called the pre-combustion chamber.

 

For furnaces that burn liquid fuel and natural gas through the bottom of the kiln, the space inside the kiln is called the air channel.

 

The pre-combustion chamber (or air passage) is composed of the slope sill, the side wall of the small furnace and the bottom plate of the small furnace. The bottom plate of the small furnace is composed of bottom bricks, cast steel plates or channel steel arranged in an orderly manner; the transverse thrust of the sloping stile is borne by the tie bars between the I-beam columns on both sides of the small furnace. The structure of the pre-chamber is an important factor for the organization of the whole kiln flame. The brickwork of the pre-combustion chamber is in contact with the high temperature flame, so the 33# oxidation method is used for ordinary casting of fused zirconium corundum bricks for the slope and side walls, and the 33# oxidation method is used for the fused zirconium corundum bricks without shrinkage holes for the bottom bricks of the small furnace. The slope and side walls are insulated with zirconium sealing material, high-alumina insulation bricks and insulation coatings from the inside to the outside; the bottom of the small furnace is insulated with zirconium sealing material and high-alumina bricks from the inside to the outside; The water bag is insulated to reduce the operating ambient temperature during inspection and nozzle replacement.

(3) Down angle of small furnace

 

For the furnace that burns the producer gas, the angle between the slope of the small furnace and the horizontal plane constitutes the downward inclination angle of the air stream, and the angle between the bottom plate of the small furnace and the horizontal plane constitutes the upward inclination angle of the gas stream. The up and down angles form the intersection angle where the gas and air streams meet. The larger the angle between the two streams, the stronger the mixing. The distance from the end of the tongue to 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, gas flow and temperature are constant, the mixture will be The degree is related to the cross-sectional ratio of the air and gas horizontal channels. The mixing degree of gas and air in the pre-combustion chamber is also related to the contact area of the gas, that is, in the case of the cross-section ratio of the air and gas horizontal passages, the mixing degree of the streams in the flat pre-combustion chamber is relatively similar. For the flat glass melting furnace that burns the furnace gas, the pre-combustion chamber of the small furnace mostly adopts a "small cross angle" with a tongue protruding, a stable and long flame, a small temperature difference between the fire root and the fire tip, and easy control and maintenance. Long pre-chamber. The long pre-combustion chamber generally has an air down inclination angle of 20° to 26° and a gas up inclination angle of 0° to 5°, that is, the intersection angle of air and gas is 20° to 30°.

 

In the structure of the bottom-fired small furnace for burning liquid and natural gas, the slope of the air passage is an important parameter. In order to make the air and oil mist mix evenly and quickly, and make the flame close to the liquid surface, the down angle is generally 20°~25°. Nozzle allows up angle of 5°~12°. The bottom of the small furnace does not have an upward inclination angle, and is generally built into a flat or stepped type, so that the combustion-supporting air can be mixed with the oil mist as quickly as possible when entering the kiln through the small furnace door, so as to ensure that there is enough air near the nozzle for the gradually diffused oil mist to allow distribution. Burn so that the flame just brushes over the glass. The down 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 of the small furnace and the liquid level, etc., so as to choose the most suitable angle.

(4) Small furnace horizontal channel

For the furnace of fuel oil, natural gas and coke oven gas, the air is preheated by the regenerator, rises to the top and turns into the horizontal channel of the small furnace, and is sprayed into the furnace through the nozzle after changing the air flow angle under the action of the slope drum. The small furnace horizontal channel serves both as a channel for introducing preheated air and a channel for exhausting exhaust gas.

The air rises through the regenerator to the turning point of the horizontal channel. After the flow direction is changed, 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, after the horizontal channel is lengthened, it expands into the operating space under the small furnace, which brings great convenience to the adjustment, assembly and disassembly and maintenance of the spray gun.

Due to the large temperature fluctuation at the turning point and the scouring of the refractory material by the air flow, here (the rear flat dowel and stacking brick between the regenerator and the slope dowel), the more erosion-resistant 33# oxidation method is used. Fused zirconia corundum brick masonry.

(5) Small stove tongue

"Small furnace tongue" is mainly used to form a horizontal channel separating air and gas for the furnace that burns producer gas. The structure and size of the tongue is another important structural factor that affects the mixing degree of air and gas and the flame entering the kiln. The length, thickness and shape of the tongue have an effect on the length, angle, temperature distribution of the flame and the erosion of the nozzle.

The length of the tongue: After the other dimensions of the small furnace are fixed, the longer the tongue is, the closer the air and gas encounter point is to the nozzle. The transverse flame furnace requires the flame to have sufficient length, direction and rigidity, generally using the tongue of zirconium corundum brick.

Tongue thickness: When the size of the small furnace is determined, the thickness of the tongue is related to the distance of the intersection of air and gas, which affects the mixing degree of air and gas and the angle of 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 burning. Generally, the tongue is 250mm thick.


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