Introduction to the problems that should be paid attention to when modifying the rotary dryer

The rotary dryer has been modified to greatly increase the production time and reduce coal consumption. However, some manufacturers have not achieved satisfactory results after the transformation. Even the inner lining wear is fast, the head of the lower barrel and the dryer are easy to burn out, and the life of the bag filter is shortened. This results in high maintenance costs and affects normal production. .
Some of the reasons are not caused by technological transformation, and some of the transformation techniques work well (such as the installation of the central X-shaped lifting plate) and have been successfully applied in many manufacturers. Many mining equipment manufacturers now use this technology, and vigorously promote its superiority of high production and low consumption, and increase the sales share of its equipment in the market. The main reason that affects the transformation effect is mainly to focus on the partial transformation of the dryer, without considering the overall balance of the entire drying system.
The selection of ventilation and dust removal equipment is the key to the ventilation effect of the key dryer. It directly affects the output of the Taiwanese production. To achieve high production, it is necessary to choose a dust collector with a large air volume. Ensure that the feeding end of the dryer has a certain negative pressure, and promptly inject the high-temperature gas generated by the burning furnace into the dryer, so that it can rapidly exchange heat with the drying material, discharge it in time, and reduce the concentration of exhaust gas in the body as quickly as possible. The purpose of drying.
Now drying and dust removal generally use bag dust removal, although the original cyclone dust, electrostatic dust removal, etc., although the ventilation effect is good, but the dust concentration generally does not reach GB4915-2004 "cement industry air pollutant discharge standards." The selection of the amount of waste gas to be treated by the bag filter should be based on the size of the dryer model, the type of the structure and the type of the dried material, the level of moisture, and the reasonable selection after the detailed calculation. The output after the modification of the dryer is improved, and the internal resistance is large. Therefore, the original dust collector is generally small, and it is necessary to replace the large-scale dust collector to achieve the effect.
The internal transformation of the dryer is very important. The internal transformation of the dryer is not large, and it is relatively simple. However, it is necessary to understand the structure principle of the dryer, the type of drying materials and the situation of the supporting dust collector, and formulate feasible methods based on the experience of daily summarization. Transformation plan.
The general transformation method of the dryer is as follows:
1. The rotary dryer is equipped with a central X-shaped lifting plate to reduce hot air holes, prolong the material residence time, improve heat exchange efficiency, and reduce the loss of high temperature gas. The installation site can be installed from the middle of the dryer (later it can be) to the head end to install 3~5 sets of lifting plates at a distance of 0.5~1m, each set of 6 X-shaped lifting plates. However, it can not be installed within 3m near the head end (because the material that has just been input has high moisture, high viscosity and low temperature, it is easy to cause adhesion), otherwise it will affect the overall drying efficiency.
2. The rotary dryer removes the spiral conveying blade from the feeding end and changes it to a triangular rib plate. It can be made of 6mm thick steel plate. The height of the short right angle is the same as the height of the feeding end retaining ring, and it is welded firmly. The length of the long right side is 800mm, welded with the inner cylinder of the drying, welded once every 50mm, naturally forming a conical feeder. Its function is to slow down the flow rate of the material in the high temperature zone, fully absorb the heat, increase the heat exchange rate, and reduce the temperature of the front end of the dryer to avoid burning the cylinder and the retaining ring.
3. Rotary dryer to change the feeding tube angle, as long as it does not affect the feeding, the lowering barrel should be raised as much as possible, the upper end is not in contact with the drying machine retaining ring, but it should not be too long to extend into the cylinder. , control the blanking point within 200mm from the retaining ring. In order to prevent the front end from being overheated, the retaining ring and the cylinder are burned out. After the lowering of the blanking pipe is increased, it is beneficial to the circulation of high-temperature gas and prevent the burning of the sliding pipe. The material naturally falls to form a curtain and is in direct contact with the high-temperature gas. The heat exchange rate is increased.
4. Rotary dryer is modified at the end of the machine. The L-shaped lifting plate with the length of the cylinder is about 1/3. Generally, the L-shaped lifting plate is fixed at 90° vertically, and the circumference can be 30° in turn. 90°, 120° angle welding. In this way, the dryer is rotated, the lifting plate is at different space heights, the distribution area of ​​the lifting material is large, and the heat exchange rate is high.
Note that the dryer transformation should be considered comprehensively. If the ventilation is good and the exhaust gas temperature is higher than 100 °C, several sets of X-shaped center lifting plates can be set up. Conversely, the ventilation is poor, the exhaust gas temperature is lower than 70 °C, and several groups should be reduced. X-shaped center lifting plate. Exhaust gas temperature control is very important, too high, on the one hand, it causes high energy consumption, on the other hand, it will burn out the dust bag; if it is too low, it will cause the paste bag, affecting ventilation, the output will drop, the internal components of the dust removal will be seriously corroded, and the maintenance cost is high. The drying material has a fast flow rate and poor quality control. Several sets of X-shaped center lifting plates can be set up, but ventilation and exhaust gas temperature must be considered. If the conditions are not allowed, the number and position of the retaining ring should be set according to the specific conditions. The disadvantage is that the inner cylinder of the front of the retaining ring is easy to wear, and it can be solved by using wear-resistant materials or thick steel plates in this area.
The balance of “wind, fire and material” is the fundamental condition for the high quality and high yield of the dryer. It is to balance the “wind”, “fire” and “material”. First of all, it is necessary to determine the dust removal ventilation, dryer specifications, models and transformation effects, the amount of heat supplied to the furnace, etc. Second, we must strengthen the operation: 1 feeding should be uniform, moisture fluctuations should not be too large. 2 The temperature of the heat source should be adjusted in time, and the furnace temperature and exhaust gas temperature should be stable. 3 Ventilation and dust removal equipment should be operated normally to ensure the air volume and wind pressure are balanced. Only by mastering these points can we achieve "high winds", "big materials" and "big fires" to achieve high yield and low consumption.
According to the above principles, a Φ2.2×14m slag dryer is technically modified. The situation is as follows:
1. The key part of the rotary dryer is to transform 2 parts: 1 The exhaust gas treatment capacity of the dust collector is increased from 20000m3/h to 35000m3/h.2. The internal structure of the dryer is modified, and the X-shaped center lifting plate is added. The feeding spiral blade is transformed into a triangular rib plate, and the L-shaped lifting plate at the end of the machine adjusts the angle.
2. Rotary dryer reference data: burning room temperature 800 ± 50 °C. 1m from the head of the dryer, the temperature of the outer cylinder is 150±10°C, 1m away from the tail of the dryer, the temperature of the outer cylinder is 70±5°C, the temperature of the outer cylinder of the dryer is 75±5°C, the temperature of the exhaust gas before the precipitator 68±5°C (the dryer is not insulated).
3. Statistical comparison of various indicators after 8 months of operation of the rotary dryer.
From the above data comparison (the amount of coal used in the table is physical coal, non-standard coal), Taiwan's production has increased significantly, coal consumption and electricity consumption have dropped significantly, dust emissions have reached the standard, and comprehensive economic benefits are considerable.
Through the analysis of the above problems, combined with the actual transformation and use, it is proved that the rotary dryer will receive good energy-saving effect through reasonable technical transformation. At present, the national policy requires energy conservation and emission reduction in all walks of life. For those who use such dryers, they should actively carry out scientific and technological transformation to achieve the purpose of increasing production, saving energy, reducing emissions and reducing consumption.
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