[Author] Wang Guiqin (1958), female, bachelor, smelting engineer, engaged in alumina production technology work.
Since the Shanxi Aluminum Plant clinker burning system was put into operation in 1987, it has been the weak link of the entire production system. In order to meet the needs of production development, the factory improved its operation methods, increased investment in equipment reform, and adopted many new technologies. This article discusses the ways to increase the capacity of kiln kilns in terms of the stability of raw material quality, the stabilization of clinker operation, the improvement of heat exchange efficiency, and the improvement of the feeding system.
1 Overview of the Shanxi Aluminum Plant Burning System The Shanxi Aluminum Plant Burning System is equipped with 6 sets of 4. 5 m×m clinker kilns, which were built in three batches. The sintering method system was put into operation in advance. From 1987 to 1992, it was produced by the pure sintering method. With the successful investment of one step and two steps of the Bayer process, the production process was also transformed into the mixed joint method, resulting in the design and production capacity. Among them, the Bayer process was 660,000 tons. Method 540,000 t. The aim of the original design of the sintering system to achieve production is that the average domestic alumina industry expert verified that the average clinker production capacity can reach an initial target of 55 t/( h?tai).
In recent years, with the development needs of enterprises, the amount of clinker processed by sintering has risen to about 240 t/h, but there is still a certain distance from reaching the standard. The operating rate of the kiln kiln has increased from about 50 in 1995 to 76 in the first half of 1999. It is still excavating its potential, but the rate of increase in the short term is not large. The author infers that it is quite good to be stable at 80-85 in the next few years. According to the operating rate of 85, the production capacity must be up to 56. To improve the clinker kiln operation rate and production capacity, it is more economical to increase production capacity. The capacity of the kiln kiln depends mainly on the kiln drying capacity.
The formula for production capacity is: G = G where: G is the capacity of the kiln, t / ( h? table) F is the surface area in the kiln, the productivity per unit area, 23 to 24 are the average effective diameter of the kiln, m.? station). At the end of 1995, the average capacity of the mixed clinker kiln was around 45 t/(h?tai). In recent years, the clinker kiln system has undergone process modification and operation adjustments to increase the production capacity at the time ().
Time 1H 1999 Production Capacity 2 Main Factors Affecting Taiwan's Production Capacity 2. 1 Clinker Kiln Operation Cycles The clinker kiln driving procedures are: ignition → warming → cutting → production → stable and high yield, even if the temporary shutdown after the kiln to start again Also go through this process. Usually, the warming time takes 3 to 4 hours, and after the feeding, it takes 4 to 8 hours to stabilize the high production. If it is a new brick hanging kiln skin, the low production time is 2 to 3 days. Therefore, the kiln operation cycle is short and the kiln is stopped. Longer time, a greater impact on productivity. Because there is no production during kiln shutdown, production capacity is affected during the period of warming and low production. The operating period of Shanxi Aluminum clinker kiln burning belt is 90-100 d in the first half of the year. In comparison, a kiln has an increase of repair time of about 3 days in 90- to 100-day operation time to reduce production. : Among them: 79 is a high-yield slurry flow rate, m is raw clinker equivalent to non-ferrous smelting □ Light metal ratio is increased once to open the kiln process, and the output is reduced: 62. 5 is the slurry flow during hanging kiln skin, m/h 60 is low production time, h For a clinker kilns body, stable operation depends on the integrity of the mechanism components and the long liner life. According to the production statistics, it can be seen that (), the shortening of the temporary kiln shutdown and the extension of the lining life have created very good conditions for increasing the production capacity at the time of the Taiwanese.
Temporary kiln/burn belt life/capacity/? Taiwan in the first half of 1999 2. 2 raw slurry components raw slurry composition has been basically stabilized at the following level since 1998: w (mesh aperture 125 actual production and slurry moisture have the greatest impact on productivity. Due to w and sintering The temperature is proportional to the relationship, when the slurry is exceeded when the kiln skin is hung, the temperature of the kiln firing zone is increased, and the kiln skin is often forced to reduce the material supply. Low, the shortest burning belt life is only about 10d, so low operating life, production capacity can not be high.
In the combined production process, fluctuations in slurry moisture are inevitable due to the need for water and alkali balance. However, as far as firing is concerned, the lower water content is beneficial to the operation, which helps increase production capacity.
For the same volume of slurry, if the water content is reduced from 41 to 40, the clinker production can be increased. 2. When the moisture content decreases, the heat load of the drying belt decreases. Especially when the drying capacity is insufficient, the moisture content decreases. Kiln production has a significant impact.
2. 3 Kiln Drying Capacity The kiln drying capacity is the key to the kiln productivity. Υ 4. 5 m × m clinker kiln failed to reach the theoretical capacity of 65 t / (h? Taiwan), dry belt capacity is not fully played out is one of the important reasons. In the case of clinker kiln production capacity of 50 t / (h? Taiwan), there are often kiln tailings, crusting and other phenomena, mainly kiln drying conditions are not well controlled, the specific performance of: 1 electric dust The operation rate is low and the kiln dust circulation is insufficient.
2 The kiln heat exchanger lifting plate was not repaired in time, which affected the heat transfer effect.
3 slurry pressure is insufficient, poor atomization.
2.4 The kiln kiln thermal system The rationality and stability of the thermal system is the key to improving the kiln productivity and clinker quality, mainly manifested in the stability of the kiln head temperature, the firing zone temperature and the kiln tail temperature, which is negative by the kiln tail. Pressure, kiln exhaust coefficient, feed uniformity and kiln speed and other parameters. The stable operating conditions must be adjusted according to the characteristics of the equipment and the actual production, such as the front and rear winds, the length of the flame, etc., and should be stable and unified after proper adjustment.
2. Feed pressure and feeding equipment feed pressure is the key to ensure the atomization and range of the slurry after the kiln.
In terms of equipment capabilities, pump pressure and flow are the most important parameters.
If the feed pressure is too low and the slurry has a short range, it will inevitably affect the drying of the slurry by the kiln gas, resulting in a decrease in the heat utilization rate, operation of the phenomenon of skinning, flow, etc., and in severe cases it will be forced to reduce production and even stop the kiln treatment. . The pressure requirement for the inlet slurry of the spray gun of Shanxi Aluminum Plant was 1. 8 M Pa. The previous years had been the simultaneous use of several small spray guns. Now it has been changed to the big spray gun to feed the material. The effect is good. The feed pump is a hardware that increases the production capacity of the kiln. In addition to the pressure and flow, the operating cycle, power consumption, and fuel consumption must be considered. The oil supply pump and diaphragm pump supply pressure is stable, and the energy-saving effect is obvious. It has been adopted by most manufacturers.
3 Ways to increase Taiwan's production capacity According to thermodynamic calculations, the evaporative capacity of the kiln drying zone is 256 kilograms at a well-equipped facility. h) When the slurry moisture is less than 40, the production capacity can reach 60 t/h. From the current production actual point of view, it is feasible to reach 83-85 m. The capacity of the wet long kiln is also related to whether the thermal strength of the firing zone exceeds the critical value. The volumetric heat intensity of the firing zone is generally? h) The stable operation of the lining of the burning zone can be guaranteed without exceeding the heat load on the surface of the firebrick. The effective internal diameter of the sinter kiln in Shanxi Aluminum Plant is 4 m, and its volume heat load is equal to the heat load on the brick surface. It has been determined that the heat consumption of clinker kilns is 4.68×10 M per tonne of clinker. If the capacity requirement of the kiln reaches 60 t/( h?tai), the burning zone volume should be: The method of production capacity at the time of Taiwan-Wang Guiqin burning zone length: This length can be achieved by adjusting the size of the coal injection nozzle and adjusting the amount of front and rear wind.
According to the above calculations, theoretically, it is feasible that the Shanxi Aluminum Plant clinker production capacity can reach 58-60 t/h. In the actual production process, the Shanxi Aluminum Plant clinker kiln has done a lot of work in tapping the potential for production capacity, and some are still conducting research and implementation.
3.1 Improve the comprehensive operation rate of clinker kilns There are many ancillary equipments for clinker kilns, so the maintenance and maintenance of equipment must be done well. The maintenance of the clinker lining is even more important. In recent years, the operating rate has achieved a certain breakthrough (), mainly carried out the following work: 1 The hydraulic gear wheel system has been improved, so that the blower speed control, exhaust smoke machine door is easy to operate and control, the failure rate is greatly reduced.
Lining the quality of masonry, choose suitable fire bricks and matching fire mud. The original wet bricklaying (brick infusion) was changed to dry bricklaying, which shortened the drying time and reduced the occurrence of brick blasting during the warming process due to moisture not completely dried.
In view of the current situation that the refractory bricks are easily cracked and red kiln, the use of special-shaped bricks makes the two rings effectively connected. In order to solve the problem of annulus seams, Shandong Aluminum Co., Ltd. uses a single brick masonry between the two rings to make one large annular seam into two small annular seams. When the thermal expansion performance of the refractory bricks is satisfied, the small annular seams Small size is not easy to damage, it is also a desirable way.
Select firebricks with suitable fire resistance and load softening point for burning zone. Choose a slightly higher w, lower w slurry hanging kiln skin, control the high temperature slowly hanging high temperature kiln skin. The production practice over the past few years has shown that the slurry of the hanging kiln skin is 0.2 times more suitable than normal production conditions, and the 24h kiln skin is basically shaped. After entering the high-yield stable period, it can be obtained.
Effect on Kiln Lifespan Equipment Time Slurry Kiln Skin Normal Production Burning Zone Life / d Kiln (Clay Brick) February 1999 The first layer of high temperature kiln skin is very important. If the first kiln skin is not properly hung, although it can be supplemented, the thickness of the brick is reduced more (about 20 mm/second) in the process of replenishing the kiln, which has a greater impact on the life of the fire brick.
It can be seen from Table 3 that due to the low w during the hanging of the kiln skin in the 4th kiln, under the normal production conditions, the kiln skin is knocked out, and its operating cycle is obviously affected.
In recent years, the aluminum clinker burning belt of aluminum plant has made some attempts in trialing new types of refractory materials. In 1996, the use of high-alumina bricks was tested to achieve a 176-day operating cycle. By comparison, at this stage, the refractory bricks used in the clinker burning zone of the Shanxi Aluminum Plant can be suitable for high-alumina anti-peeling bricks. The rest of the brick linings should be combined with the actual production, and the anti-wear and anti-explosion types should be selected.
3.2 Strictly control the thermal system and improve the existing operating conditions 3. 2. 1 Improve the structure of the coal injection pipe and improve the flexibility of the coal injection pipe.
Dismantle the three-channel coal injection pipe that is not suitable for the single-stage blower of the second-stage kiln and switch to the single-channel coal injection pipe. At the same time, the head of the single-channel coal injection pipe is reconstructed, and it is appropriately extended relative to the original site to reduce the taper angle. The effective flame lengthens and stabilizes the temperature distribution in the kiln to meet the material heating and reaction requirements.
3. 2. 2 Sintering Temperature Control Sintering temperature control Sintering is performed at a positive sintering temperature or slightly downward, if necessary, the temperature is increased by a short time to treat the kiln skin. The three-shift operation must be performed in accordance with diligence, diligence, and diligence. The strict control over the equilibrium temperature of the firing temperature must be strictly controlled.
3. 2. 3 Improve the operating conditions of watching fire and strengthen monitoring methods.
TV watching fire not only improves the labor intensity of the workers, but also makes the operation more flexible. It is advisable to promote and appropriately increase the monitoring function. In actual production, the kiln exhaust gas monitoring and kiln temperature monitoring should also be further improved.
3. 2. 4 Explore the reasonable matching of the next and the second wind in different conditions to make it standardized and stabilized.
According to the length-diameter ratio of the kiln, after groping, it is believed that under the condition of ensuring the maintenance of the kiln skin, it is appropriate to increase the after-wind, and maintaining a relatively high kiln-tail temperature is the development trend of production. The current temperature of the kiln should be controlled at around °C. In 1998, a high-yield test was conducted in the 5th kiln. The flow rate of the slurry was raised to 85m. In the condition of °C, the kiln tail was slightly poured. The material in the kiln did not reach the corresponding temperature in the preheating decomposition zone, and the burning zone had an abrupt burning phenomenon. When the tail temperature was increased to 240 to 260°C, this problem was well solved, and 5 kilns were continuously operated for 72 hours under high production.
3. 3 Reduce raw slurry moisture and enhance drying capacity 3. 3. 1 Reduce raw material moisture (1) Increase the carbon fraction evaporation mother liquor concentration, reduce the non-production water used in the batching and feeding process to enter the slurry system. In the case of system evaporation capacity and alkali consumption allowable, carbon partial evaporation mother liquor concentration upper limit control, so that the raw material moisture as much as possible (2) reduce the amount of silicon slag back to the batch and Bayer red mud solution. Silica residue not only brings the liquid to the raw material system, but also is sent to the slurry tank with a part of the carbon colored smelting light metal stock solution (H reducing the amount of silicon slag is therefore an important factor in reducing the water content of the slurry. Mud cake moisture should be less than 40.
(3) The sintered silicon slag and the Bayer red mud are mixed and filtered, and then the mother liquor is used to evaporate the cake and the ingredients are fed. The excess water contained in the carbon residue slag can be eliminated.
3.3.2 Increase the heat of the kiln gas in the drying zone (1) Extend the flame operation to ensure that the reducing atmosphere required for desulphurization is properly increased and the kiln tail temperature is increased.
(2) New thermal insulation and refractory materials are used to reduce heat loss from the kiln. In 1998, Shandong Aluminum Plant tried a new type of thermal insulation compound brick within 50 m of the kiln body, compared with the original clay brick, the kiln body temperature dropped by an average of 70-80°C, and the surface heat loss of the kiln was reduced by 33.36 kWh per ton of clinker. Standard coal 8. 19 kg.
3.3.3 Strengthen the heat exchange of the drying belt and the degree of slurry atomization The kiln tail lift plate can effectively promote the heat exchange in the kiln. The length of clinker yawing plate area is 8.2 m, and 80 straight plate type lifting plates are evenly distributed. When the kiln capacity reaches about 52 t/( h?tai), the kiln tail is sampled normally. To achieve a capacity of 58-60 t/( h?tai), it should be improved from the following two aspects: (1) The length of the lifting plate area is extended by 1 to 2 m in the direction of the kiln head, increasing by 10 to 20 pieces. The temperature of this part is about 400°C. It is feasible to add lifting plates.
(2) Change the straight plate type lifting plate to a bucket type lifting plate, so as to increase the amount of material to be lifted, which will help increase the temperature.
Appropriate spray gun position and sufficient feed pressure can increase the degree of atomization of raw slurry and enhance the drying effect. In actual production, since the slurry wears on the spray gun faster, the nozzles and spray guns should be regularly checked to maintain their integrity.
3.3.4 Grasping the operation of the dust collection system The kiln dust circulation is generally between 80 and 120, and the kiln dust can enhance the drying capacity, which is also conducive to the stability of the thermal system. Therefore, the effect of dust removal is directly related to the production capacity of the kiln. The operating rate of dust collection facilities before 1995 was only around 80, which was an important reason for the relatively low production capacity at the time of Taiwan. In 1998, the cyclone dust collector was changed from the first stage of 6 sets of rake 3.2 m×6 m to 4 sets of Υ4.0 m×10 m, and the dust collection efficiency was increased to 85. In addition, dust collection system was also used to block the wind. The electric dust collector body was repaired and cleaned in a timely manner, which resulted in a significant increase in dust collection efficiency and an electric dust collection rate of more than 98. The kiln ash returned to a stable and balanced condition, which greatly improved the conditions of the kiln tail and reduced the phenomenon of falling and crusting.
3. 4 update the feed pump to ensure that the slurry flow and pressure feeding is the basic link of the kiln production. The feed pump was originally designed as a centrifugal pump. During use, the flow-through parts wear quickly and the leakage is serious. In 1988, the oil removal pump with the desiliconization process retrofitted was used for 1 kiln feeding. The pump flow rate was 100 m. The kiln was also fed with a similar oil pump. The oil pressure compensation system of the oil-separation pump has been used abnormally due to improper maintenance of the air pressure and defects of its own control circuit, so the flow pulse condition is serious. In addition, the frequency of the pump is increased, and the pump body vibrates and is not easy to maintain.
From 1996 to 1997, two new diaphragm pumps with a flow rate of /h and a pressure of 3.0 M Pa were newly installed at Sanbu Station. Their advantages lie in the complete pressure compensation system, high level of automation, low fuel consumption, and safe and economical operation. . According to production statistics, the yield advantages of the same conditions are shown in Table 5.
8 h slurry flow / m oil pump diaphragm pump nozzle diameter, m m.
Diaphragm pump fuel consumption in addition to the regular replacement of the diaphragm chamber and gearbox mechanical oil (monthly fuel consumption equivalent to 1 200 yuan), the normal operation of the process does not consume oil, and the oil pump oil slurry per m pump consumption is 0. About 10 kg, the fuel consumption of an oil pump is equivalent to RMB 28 000 for the entire month. Based on this calculation, six kiln operations calculated at 85 operating rate, all with a diaphragm pump to replace the oil pump feed, its annual fuel saving value is: 3.5 active research and development outside the kiln drying, preheating and other new technology cement industry cooked Material kiln has reliable experience in the application of kiln decomposition. Alumina clinker firing Because of the drying of high moisture slurry and the high content of alkali in the raw material, the preheating system is easy to crust. At present, this technology still needs further work. In foreign countries, there is also a practice of adding kiln dust to the firing zone to increase production capacity. It is necessary to draw lessons from absorption and to reduce the energy consumption in the sintering process to achieve the purpose of increasing production and efficiency.
4 Conclusions There are many factors that affect clinker production capacity, and it is impossible to achieve good results in any one of the links. Combined with the actual production of Shanxi Aluminum Plant, the author believes that maintaining a high operating rate and stabilizing the thermal system is the basis for high production, and improving the feeding, intensifying drying, and stabilizing the slurry composition is the direction of effort.
[References] Discussion on improving the production capacity of clinker kilns - Wang Guiqin professional manufacturer of anticorrosion equipment - Wenzhou Baoda Anticorrosion Equipment Co., Ltd. All kinds of valves, pipes, fittings and pumps for metallurgical production Completely replaceable products.
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