Structural analysis of float glass melting furnace
Compared with other flat glass melting furnaces, the float glass melting furnace is not much different in structure. It is a shallow pool cross-flame furnace, but in terms of scale, the scale of the float glass melting furnace is much larger. Although float glass melting furnaces are different from other flat glass melting furnaces, they still have something in common in their structures. The structure of a float glass melting furnace mainly includes: feeding system, melting system, heat source supply system, waste gas waste heat Utilization system, smoke exhaust and air supply system, etc.
The feeding pool is located at the beginning of the furnace and is a small rectangular pool protruding from the outside of the kiln pool and connected to the kiln pool. The feeding port consists of two parts: the feeding pool and the upper retaining wall (front wall). The batch materials are put into the kiln from the feeding port.
1. The size of the feeding tank
Feeding is one of the important links in the melting process. It is related to the melting speed of the batch materials, the hot spot position of the melting zone, the stability of the bubble boundary, and ultimately affects the quality and output of the product. Due to the large melting capacity of the float glass melting furnace, a horizontal flame pool furnace is generally used, with the feeding pool set at the front end of the melting pool. The size of the feeding pool changes with the size of the melting pool, batch state, feeding method and the number of feeding machines. The states of the batch materials include powdery, granular and slurry (currently powdery is generally used); different feeding machines have different feeding methods. Common feeding methods include spiral, ridge, roller, reciprocating, and wrap-in. type, electromagnetic vibration type and inclined blanket type, etc.
(1) The width of the feeding pool using a ridge feeder depends on the number of feeders selected. The length of the feeding pool can be determined according to the process layout and the structural requirements of the front wall.
(2) Inclined carpet feeder has been widely used in the market. Its feeding method is similar to that of ridge feeder, except that the feeding surface is much wider than that of ridge feeder. Therefore, the size of its feeding tank is in the design The size of the feeding tank is not much different from that of the ridge feeder, and is still determined by the width of the melting tank and the requirements of the feeding surface.
With the maturity of glass melting technology and the updating of melting processes, the width of the float glass melting furnace feeding tank is getting larger and larger. Since the heat absorbed by the batch material is proportional to its coverage area, the wider the feeding pool and the larger the coverage area of the batch material, the more conducive to improving thermal efficiency and energy saving, and improving the melting rate. Therefore, in the current design of large float glass melting furnaces, the mode of equal or quasi-equal width of the feeding pool and the melting pool is adopted. As the width of the feeding pool continues to increase, large-scale inclined blanket feeders have also emerged. For a melting furnace with a melting pool and feeding pool width of 11m, two inclined blanket feeders can meet production and technical needs.
Melting Department
The melting section of the float glass melting furnace is where the batch materials are melted and the glass liquid is clarified and homogenized. The front and rear of the melting section are composed of melting zone and clarification zone; the upper and lower parts are divided into upper flame space and lower kiln pool. The upper space is also called the flame space, which is a space filled with flames surrounded by the front wall, the surface of the glass liquid, the large kiln roof and the breast wall of the kiln wall; the lower part of the kiln is composed of the bottom and wall of the tank. That is to say, the function of the melting zone is that the batch materials undergo physical and chemical reactions at high temperatures to form molten glass, while the function of the clarification zone is to quickly and completely discharge the bubbles in the formed molten glass to achieve the required quality of molten glass for production.
1. Flame space
The flame space is filled with hot flame gas supplied from the heat source. The flame gas uses its own heat to melt the batch materials and also radiates to the glass liquid, kiln wall and kiln roof. The flame space should be able to enable complete combustion of the fuel and ensure the supply of heat required for glass melting, clarification and homogenization, and should minimize heat dissipation.
2. Chi kiln
The tank kiln is the place where the batch materials are melted into molten glass and clarified and homogenized. It needs to supply a sufficient amount of completely melted transparent molten glass. In order to ensure that the kiln pool reaches a certain service life, the thickness of the pool wall is generally 250-300mm, and the thickness of the pool bottom varies according to its insulation conditions. The thickness of the pool bottom without insulation tape is generally 300mm.
(1) Front wall structure
The front wall is the front end wall of the flame space of the melting part, spanning the upper part of the feeding tank to block the escape and thermal radiation of hot gas (including flame) at the feeding port at the front end of the melting furnace. Since the front wall is easily damaged by flames and material powder erosion, and is easily deformed during hot air baking in the kiln, most domestic float glass manufacturers currently use L-shaped hanging walls.
Compared with the previous multi-frame ceilings, the L-shaped hanging wall has the characteristics of extending the service life of the front wall, enhancing the energy-saving effect, improving the on-site environment, protecting the feeder, increasing the melting speed, reducing dust flying, and extending the service life of the grid body. In the design process of the front wall, attention should be paid to the reasonable selection of the distance from the center line of the small furnace in the melting part. If the distance is too small, it will accelerate the burning of the front wall, reduce the preheating effect of the batch materials, and increase the burning and clogging of the small furnace; if the distance is too large, it will cause the temperature of the feeding pool to be too low, the material pile will melt, and it will be difficult to move forward. , At present, depending on the fuel and tonnage of domestic float glass production lines, the distance between the front wall and the center line of the small furnace in the melting part generally ranges from 3.2 to 4.3m.
① The front wall of the arched mortar structure. This kind of front wall is composed of two or three layers of mortar and refractory bricks built on the mortar. The bow-shaped opening under the front wall needs to be added with a fire retaining wall to block the flames from spraying out to save fuel. Protect the feeder. The load-bearing capacity of the fire retaining wall is provided by a large water bag across the feeding tank. Knife-shaped refractory bricks are hung on the large water bag to prevent the flame from directly contacting the water bag. Strip bricks are laid on the knife-handle-shaped bricks. The front wall using this structural form is limited by its strand-to-span ratio due to safety factors. The span should not be too large, generally no more than 7m. Even so, the front wall and the firewall are subject to flame damage and alkalinity. It is easy to be damaged by the erosion of the atmosphere. After the firewall and water bag are damaged, they can be hot repaired and replaced. Once the front grille is seriously burned, it can only be repaired coldly with water. Therefore, this front wall structure is being eliminated on float glass melting furnaces and is still used in flat glass melting furnaces other than float glass melting furnaces.
(2) Breast wall structure
Due to the different corrosion conditions and hot repair times of various parts of the float glass melting furnace, in order to separate the most severely damaged parts during hot repair, the breast wall, the large bed and the kiln tank are divided into three separate support parts, and finally the load is transferred to the kiln On the bottom steel structure, the load-bearing capacity of the breast wall is transmitted from the breast wall support plate (cast iron or angle steel) and chin iron to the columns, and finally to the kiln bottom steel structure.
The design of the parapet must ensure sufficient strength under high temperatures, among which hook bricks are a key part. Hook bricks are provided at the bottom of the parapet to block the flames in the kiln and prevent them from passing through and burning the parapet support plate and palm iron. Generally, the breast wall of the melting zone is made of AZS33# fused bricks, the upper gap brick is made of low creep and crack-resistant sintered zircon bricks, and the breast wall of the clarification zone is generally made of high-quality silica bricks.
The height of the breast wall depends on the type and quality of the fuel, melting rate, melting heat consumption, furnace size, heat dissipation, gas layer thickness and other factors.
Theoretically, as long as the corrosion resistance of the refractory materials used for the breast wall is ensured, the breast wall will not become a key part that affects the life of the furnace. However, in actual use, many melting furnaces have shortened the life of the furnace due to the inclination of the breast wall in the melting zone. In some furnaces, breast wall collapse accidents occurred due to untimely discharge of materials in the later period. The main reason is that when the tie bars are tightened after the masonry is completed, the parapet pallet is tilted (high on the outside and low on the inside), causing the parapet to tilt inward; another reason is that after the bricks are tied to the pool wall, the pallet of the parapet is exposed. In the flame space, the pallet is deformed, causing the parapet to tilt inward. In order to reduce or avoid the occurrence of this phenomenon, the design of the furnace breast wall was improved, and the gap bricks were eliminated. The feet of the large breast wall were directly close to the breast wall. layer of zircon bricks, and the hook design of the hook bricks in the melting zone is cancelled. This can avoid the inward tilt of the parapet due to the breakage of the hook bricks due to the quality of the fused AZS hook bricks. In addition, some large furnaces have changed the 50mm thick ordinary carbon steel supporting plate to a 60mm thick medium silicon ductile iron supporting plate, which has also produced good results.
(3) Large structure
The function of the large sill is to form a flame space with the parapet and front wall. At the same time, it can also be used as a medium for the radiation and heat transfer of the flame to the material and the glass liquid, that is, it absorbs the heat released when the fuel is burned and then radiates it to the surface of the glass liquid.
The weight of the large ballast is transmitted from the steel ballast to the steel structure at the bottom of the kiln through the upper iron and the columns.
The level and characteristics of large stocks can be reflected by the stock-to-span ratio. From a thermal point of view, reducing the height of the large furnace can radiate heat to the glass liquid as much as possible. This can be achieved by reducing the height of the breast wall and reducing the strands of the large furnace. However, the height of the breast wall is affected by the structural strength of the small furnace nozzle and the large furnace. Restricted by factors such as; the smaller the stock height, the greater the thrust, and the smaller the heat dissipation. Reducing the stock will increase the horizontal thrust of the stock and increase the instability of the stock. Generally, the span ratio of large float glass melting furnaces is about 1:8. According to the length of the melting part, the large pile can be divided into several sections, usually at least three sections. During masonry construction, the expansion joints reserved between each joint are about 100 to 120 mm, and the expansion joints at the top of the joints at the front and back gables should be wider.
Large piles are generally built with high-quality silica bricks. The shape of the bricks is wedge-shaped, and the transverse joints are built with staggered joints. The size of the mud joints is determined according to the specific requirements of the masonry mud used, generally 1 to 2 mm.
Most of the float glass furnace ballast uses steel ballast and requires air blowing for cooling. The inclined plane extension lines of the steel ballast on both sides need to pass through the center of the arc of the large ballast, and the angle formed by them is the central angle of the large ballast.
The service life of the furnace determines the age of the entire furnace. The weak links in the use of the furnace are holes such as temperature measurement holes and pressure measurement holes, the transverse seams of the furnace bricks (also called head seams), and the seams of each section of the furnace. The head and the side part of the big bow. When the kiln is in normal operation, the pressure inside the kiln is positive, and the various holes in the top of the furnace are easily burned larger and larger due to fire penetration. If the side furnace is not in close enough contact with the steel ballast, it is easy to be washed away and burned by the flames. Therefore, refractory materials with better performance should be used in these places, and sintered zircon bricks are currently used more.
(4) Structure of pool wall and bottom
The kiln pool consists of two parts: the pool wall and the pool bottom. The pool wall and the pool bottom are both built with large bricks. The kiln pool is built on steel structural beams supported by the furnace columns under the kiln. The quality of the entire kiln pool and the quality of the glass liquid it contains are borne by the steel structure supported by the furnace columns below the kiln. The furnace columns of float glass melting furnaces are generally It is a mixed concrete or steel column. On the furnace column, I-beam or H-shaped steel main beams are installed along the length of the kiln. Large float glass melting furnaces generally have four main beams. I-beam secondary beams are installed on the main beams along the vertical direction of the main beams. In the past, when there was no kiln bottom insulation, flat steel was laid directly on the secondary beams, and large clay bricks were laid on the flat steel. At this time, the secondary beams should avoid the joints of the large clay bricks, and there should be 2 flat steels underneath each brick. and 2 secondary beams. At present, thermal insulation technology has been widely used, and the structure of the kiln bottom has also changed accordingly. That is, channel steel is laid on the secondary beam in the direction vertical to the secondary beam. Stacking bricks are laid inside the channel steel. Large clay bricks from the bottom of the pool are laid on the stacking bricks. Before laying the large bricks , weld the movable steel plate support frame on the channel steel, and build an insulation layer between the stacks of bricks and on the support frame. After the pool depth becomes shallower and the kiln bottom is insulated, the temperature of the bottom glass liquid increases and the fluidity increases. In order to reduce the corrosion of the glass liquid on the pool bottom bricks, a protective layer is laid on the large clay bricks, that is, a layer of 25 cm thick is pounded. ㎜ of zirconium ramming material or zirconium corundum ramming material, and then lay a layer of 75㎜ of fused zirconium corundum or sintered zirconium corundum bricks on top.
The pool walls are built on large clay bricks at the bottom of the pool. Because the fuel is burned and the batch materials are melted on the surface of the molten glass in the melting part, the temperature of the molten glass surface reaches above 1450°C, the convection of the molten glass is also strong, and the liquid level fluctuates up and down. Therefore, the corrosion of the pool wall is relatively serious. , especially the pool wall near the glass liquid level line is damaged quickly. In the past, due to the influence of investment costs and other factors, the pool wall often adopted a multi-layer structure, with clay bricks in the lower part, fused mullite bricks in the middle, and fused zirconium steel jade bricks in the upper part. The corrosion of the pool wall of this structure The situation is uneven, that is, the erosion is most severe near the liquid level line. This kind of pool wall has a greater impact on the quality of the glass liquid.
At present, the pool wall of the float glass melting furnace is made of a whole large brick, usually dry-built with vertical joints of knife-handled bricks, and the material is generally AZS33# electric fused brick. This kind of pool wall has no horizontal joints, the material grade is improved, and the erosion rate is slower , has little pollution to the glass liquid, has a long service life, and is widely used. The thickness of the pool wall is reduced from 300mm to 250mm.
As people's expectations for the life of the kiln continue to increase, the pool wall structure is also constantly being explored. After 2000, knife-handle-shaped pool wall bricks were applied and promoted in float glass melting furnaces. The materials are AZS33#, AZS36# fused bricks, and some companies use AZS41# fused bricks. However, AZS41# fused bricks have poor thermal stability and are prone to bursting when baked in the kiln. Therefore, the smaller the thickness of the pool wall, the better the cooling effect of the cooling air. The knife-handle-shaped bricks can be tied twice, and the erosion rate is slow, which greatly extends the life of the pool wall.
Neck, cooling section
The clamping neck is located between the melting part and the cooling part to install the cooling water bag and agitator and isolate the influence of the air flow in the melting part on the glass forming in the cooling part.
Because the low viscosity of the molten glass is not conducive to molding, it must be cooled to reach the viscosity range required for molding, so a cooling section is provided. The cooling section structure is basically the same as the melting section structure, and is also divided into two parts: the upper space and the lower tank kiln. The difference is that the height of the breast wall is lower than the melting section, and the depth of the tank bottom is shallower than the melting section. The cooling method generally adopts natural cooling, which mainly relies on the uniform heat dissipation from the glass liquid surface and the bottom of the pool wall to the outside for slow cooling.
1. Structure of neck and cooling section
(1) The structure of the neck clamp
Since the birth of the float process in China, the commonly used clamping neck structures mainly include low strut structures and suspended wall structures.
① Low wall structure The earliest low wall used in the domestic float glass production line. The span and stock height of the rear gable wall of the melting part, the clamping neck wall of the melting part and the front gable wall of the cooling part are the same or have a very small difference. The breast wall height is not high. Some clamp-neck ballast bricks are placed directly on the pool wall. This can reduce the space opening as much as possible (that is, the clamp-neck structure of the mixer is not used). With the development of technology and the improvement of people's requirements for glass quality, stirrers have gradually begun to be installed at the neck. There are two types of mixers: one is vertical and the other is horizontal. The vertical mixer is inserted through the reserved hole on the top of the clamp neck. This type of mixer does not require the height of the neck breast wall. Horizontal mixers are inserted from the parapets on both sides of the clamping neck and installed in pairs. In this form, no holes are required on the top of the mast, but holes about 300mm high and long enough must be left on the parapets of the clamping neck to facilitate the mixing of the stirrers. of insertion. Therefore, the parapet must be raised. This structure also creates conditions for connecting the large water pipe from the end of the melting part to the chest.
② For the low-pitched wall-mounted breast structure, considering the safety of the armrest, the strand span ratio cannot be too small, so the space opening is relatively large, and the separation effect is not very good, especially with the use of horizontal mixers, the height of the breast wall With the increase, its use effect is even worse, so a clamp-neck structure with a hanging wall appears. In this structure, the strand span ratio can be designed to be larger to increase its safety, and the space separation is achieved by hanging walls. This kind of suspended wall can be produced at home and abroad. The refractory materials used in the suspended wall are mostly high-quality silica bricks and sintered mullite bricks. The shape of the bricks is I-shaped or king-shaped, and the entire wall is made of each brick. Clamp both sides with steel plates.
In addition to the two clamping neck structures mentioned above, various types of clamping neck structures have appeared in recent years, such as U-shaped hanging cranes, double L-shaped hanging cranes, and flat hanging cranes. These neck clamping structures are complex and require relatively high investment. Large, it has been applied and promoted in some domestic high-end glass and pressure-extended glass production lines.
(2) Structure of cooling section
The function of the cooling part is to cool down the molten glass evenly.
The structure of the cooling section is basically the same as that of the melting section, and also includes large piles, piles, breast walls, pool walls, pool bottoms and corresponding steel structures. However, the depth of the pool can be the same as or slightly lower than the melting part, and the large span is slightly smaller than the melting part, so the structure is slightly simpler, but the refractory materials used are different according to the glass quality requirements. The cooling part pool wall of high-end glass and the paving bricks at the bottom of the pool generally use α-βAl2O3 bricks, and the ramming layer under the paving bricks uses α-βAl2O3 ramming material. The foaming index and pollution index of these materials are zero, so It does not pollute the glass liquid. It is better to use high-quality silica bricks for parapets and large ridges.
Small furnace and regenerator
The small furnace and regenerator are the main components of the furnace structure. The structural combinations of the small furnace and regenerator of the float glass melting furnace are divided into two types according to the different fuel types, namely box-shaped combination and semi-box combination. . The furnaces burning fuel and natural gas adopt a box-shaped combination, while the furnaces burning furnace gas adopt a half-box combination. The small furnaces and regenerators of the float glass melting furnace are set up on both sides of the tank kiln and are arranged symmetrically. Depending on the scale of the melting volume, 4 to 10 pairs of small furnaces are installed.
1. Small furnace
(1) Name
Float glass melting furnaces are divided into different types according to the fuel used. The fuel is used to generate furnace gas. Its combustion equipment is called a small furnace, and the small furnace mouth is called a flame outlet. When the fuel is heavy oil or other liquid fuel, a nozzle (i.e. burner) is used, and the small furnace mouth should be called the spout.
(2) The role of the small furnace
The small furnace is an important part of the glass melting furnace. It is a device that preheats, mixes fuel and air, and organizes combustion. It should be able to ensure that the flame has a certain length, brightness, stiffness, sufficient coverage area, no floating or stratification, and it should also meet the required temperature and atmosphere requirements in the kiln.
The gas and air are preheated by the regenerator and enter the pre-combustion chamber through the vertical channel (ascending channel) and horizontal channel respectively. They are mixed and partially burned in the pre-combustion chamber, and are sprayed into the kiln at a certain direction and speed to continue burning. At this time, the gas enters the small furnace on the opposite side. Therefore, the small furnace plays the role of an air channel and a smoke exhaust channel. However, the structure of the small furnace plays an important role in the heat transfer in the kiln and the glass melting process.
At present, most domestic float glass melting furnaces with a production scale of 400t/d or more use 6 pairs of small furnaces, and those with a production scale of 700t/d or more use 7 pairs of small furnaces, with a maximum of 10 pairs of small furnaces. When designing a small furnace, the characteristics of fuel, coal and gas determine the differences in the technical parameters of the small furnace. For example: the ratio of the total area of the nozzle of the small furnace to the area of the melting part and the downward inclination angle of the small furnace slope, etc.
(1) Structure of small furnace
The small furnace consists of a roof, side walls and a pit bottom. The furnace connected to the small furnace and the melting furnace is called the small furnace flat furnace, the furnace connected to the regenerator is called the rear flat furnace, and the middle part of the furnace is the inclined furnace. The wall, the side walls, and the bottom of the pit form a small furnace space. The flat roof of the float glass melting furnace adopts a plug-in structure, which is made into a flat upper and lower arc shape and matches the breast wall of the furnace. The aforementioned measures to prevent the breast wall from tilting inward are to tilt the design surface of the breast wall inward, and directly press the bricks on the side of the large breast wall. It is on the breast wall, so the small furnace and flat lining should also be changed accordingly.
The inclined lining of the small furnace is an important part of the small furnace, and it is also the part that is easily burned. The design of the slanting lining must match the corresponding flat lining structure of the small furnace. The structures of the rear flat wall, side walls and pit bottom are relatively simple, so I will not describe them one by one here.
(2) Structural characteristics of small gas-fired stoves
In addition to the above-mentioned structural differences between a gas-burning stove and an oil-burning stove, the main difference is the stove tongue. Usually the extension length of the small stove tongue is 400~450mm. Generally, the height of the small gas furnace opening is 400 to 500 mm, and the span ratio of the arch is 1:10.
There are currently two types of slanted grilles for small gas-fired furnaces in the regenerator: one is straight-through; the other is trumpet-shaped. The advantages of the straight-through furnace are: the gas emerges from the ascending path in a flat shape and is easy to mix with the combustion air. The mixed gas has less erosion on the side walls of the furnace. The furnace has a simple structure and is easy to construct. The advantage of the trumpet-shaped small furnace is that the trumpet shape forces the flame to spread, which can improve the coverage of the flame and improve the poor maintenance environment caused by the small distance between the gas risers.
2. Regenerator
The regenerator is actually a waste heat recovery device, which is part of the exhaust gas waste heat utilization system. It uses refractory materials as regenerators (called checker bricks) to accumulate part of the heat of the flue gas discharged from the kiln, and is used to heat the inlet gas. The air inside the kiln. When the high-temperature exhaust gas in the kiln flows through the grid body of the regenerator, the checker bricks are heated. In this process, the temperature of the checker bricks gradually increases. The heat stored in the grid body will heat the gas or air flowing through the grid bricks after the flame is turned, thereby ensuring that the flame has a high enough temperature to meet the needs of glass melting. In this process, the temperature of the grid bricks gradually increases. Lower, and so on. Therefore, the function of the regenerator is to transfer the heat contained in the exhaust gas to the air and gas through the absorption and heat storage of the checker bricks, and heat it to a certain temperature to achieve the purpose of saving fuel and reducing costs.
The temperature of the waste gas in the glass melting furnace when it is discharged from the kiln is about 1400~1500℃. The gas can be preheated to 800~1000℃ and the air can be preheated to 1000~1200℃. The temperature of the waste gas when it is discharged from the regenerator is 600℃ Around ℃.
(1) Structure of regenerator
The regenerator is composed of a roof, inner and outer walls, end walls, partition walls, grids and furnace bars. The roof thickness of the float glass furnace regenerator is generally equal to or greater than 350mm, and it is built with high-quality silica bricks. The center angle is 90° to 120°, depending on the specific situation. The thickness of side walls, end walls, and partition walls is generally 580mm. Generally, the lower part is made of low-pore clay bricks, and the middle and upper parts are made of alkaline refractory materials. Some of the upper parts are made of siliceous materials.
(2) The form of the regenerator. In order to improve the heat storage performance and service life of the regenerator, there are many forms of regenerators at home and abroad. However, as far as domestic float glass melting furnaces are concerned, the most common ones are connected structures and partitioned structures. structure, semi-divided structure, connected structure with two small furnaces, two-stage structure, fully connected structure, etc.
The connected structure is that the air regenerator under the small furnace on one side of the furnace is a connected room, and the gas regenerator is also a connected room. Due to the uneven distribution of air flow in this structure, it is easy to cause local overheating and cause the checker bricks to burn out quickly, so it is rarely used now.
The divided structure divides the regenerator into separate units with each furnace. The gases in each chamber cannot be connected. The gas distribution is adjusted by the gates on the branch flues of each chamber. The advantage of this structure is that it is more convenient to adjust gas distribution and to heat repair the lattice body. However, because there are many partition walls, the volume of the lattice body is reduced, the heat exchange area of the lattice body is small, and the thermal efficiency is not high.
The semi-divided structure means that the flue above the furnace bar of the regenerator is separated by each small furnace. The regenerator itself is not separated, and the gas distribution adjustment gate is still on the branch flue.
The connected structure of two small furnaces divides each two small furnaces into one chamber, and each small furnace has a branch flue to adjust the gas distribution of each small furnace. Compared with the separated structure, this structure reduces the number of partitions. The number of walls increases the heat exchange area of the grid body and improves thermal efficiency. However, due to the reduction in the number of partition walls, there will be some impact on the stability of the side walls. In addition, since the two are connected, it brings certain difficulties to the hot repair of the grid body. Two small furnaces must be repaired together, which will seriously affect production. This form of regenerator is currently widely used in large float glass melting furnaces.
The two-section structure refers to dividing a single regenerator into two regenerators, which are separated by partition walls and connected by a vertical channel, that is, the regenerator is divided into two parts, a high temperature zone and a low temperature zone. This structure is mainly used to prevent the gas, liquid and solid transformation of sodium sulfate from corroding the checker bricks, so that this transformation can be carried out in the connecting channel to extend the service life of the checker bricks. Due to the complex structure of this form, it is rarely used nowadays.
The fully connected structure means that the entire regenerator on one side of the furnace is connected into one chamber, and the branch flue is one for each small furnace to adjust the gas distribution of each small furnace. The regenerator of this structure maximizes the heat exchange area of the grid body and has high thermal efficiency. However, since there are no partition walls, the stability of the side walls is poor. If some of the checkered bricks collapse or become blocked, hot repairs will not be possible. Currently, regenerators with this structure are also used in large float glass melting furnaces.
(3) The furnace bar is a refractory material structure that bears the mass of the grid. In fact, it is also an arch structure, but it is made of single arch bricks one by one, with gaps between the bars for ventilation. , so it is called the grate.
Since the grate grate is an arch grate that bears the weight of the grid body (lattice bricks are stacked on top), the top of the grate grate must be leveled. There are two methods for leveling. One is to use ballast bricks to lay flat on the arc of the arch, and the other is to directly use ballast bricks to lay flat on the top and curved below.
The width and height of the grate grate should be determined based on the calculation of the mass of the grate body that the grate bar bears. Generally, the width is not less than 150mm, the height is not less than 300mm, and the spacing between each grate bar is not less than 150mm. In order to increase the stability and integrity of a single furnace bar, two reinforcing rib bricks are usually added to the furnace bar. The refractory material of the grate area is generally built with low porosity clay bricks.
(4) The grid is the heat transfer part of the regenerator and the most important component of the regenerator structure. Whether the structure of the grid body is reasonable not only affects the service life of the regenerator, but also directly affects the heat storage efficiency of the regenerator, which in turn affects the thermal efficiency of the entire furnace. Therefore, the refractory materials that make up the lattice body are required to be able to withstand high temperatures, resist erosion, accumulate a lot of heat, transfer heat quickly, and have good thermal vibration stability, and the entire lattice body is required to have good structural stability.
Flue
(1) Function and classification of flue
The flue is a gas passage. The exhaust gas after the fuel is burned in the kiln goes down from the small furnace to the regenerator, and then is discharged into the atmosphere through the flue and chimney. In addition to exhausting smoke and supplying gas, the flue can also be used to adjust the gas flow and pressure in the kiln by setting gates; the function of the flue is to use its height to generate a certain suction force to overcome the problems of the kiln system, including the chimney itself. The resistance allows air to be sprayed into the kiln at a certain speed and the combustion products can be discharged out of the kiln.
The flue system includes air flue, gas flue, air branch flue, gas branch flue, middle flue, main flue and the flue leading to the waste heat boiler.
(2) Structural form of flue
The upper part of the flue is an arch structure. The central angle of the flue is generally 90°, and the thickness is 230mm. The lower part is a rectangular cross-section, and the height is generally slightly greater than or equal to the width. Since the temperature of the exhaust gas passing through the flue is relatively high (500-600°C), the inner wall is built with refractory clay bricks, the outer wall is built with red bricks, and the bottom is made of concrete. In order to prevent the concrete temperature from being too high, diatomaceous earth insulation bricks are generally laid. The roof and side walls of the above-ground flue or outdoor flue are generally equipped with an insulation layer to prevent excessive temperature drop.
(3) The layout of the flue
① Burning heavy oil or natural gas: The flue of a float glass melting furnace burning heavy oil or natural gas is arranged inside the regenerator, that is, below the kiln pool, and consists of a main flue, branch flues and branch flues. There are flue gas gates and combustion air inlets on the branch flues, air (smoke) gas exchanger gates (commonly known as large gates or reversing gates) on the branch flues, and rotating gates on the main flue. to adjust kiln pressure. There is a gate at the chimney root to adjust the suction force.
② Gas burning: The flue layout of a gas-burning float glass melting furnace is relatively complicated because it has two flues, air and gas, and a gas reversing jump cover.
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