5000t/d production line kiln head dust collector electric change bag and operation experience
The 5000t/d production line of our group Weishan Company was put into operation in May 2011. The exhaust gas of rotary kiln head is treated by electrostatic precipitator. Its specification model is BS93034/12.5/3×10/0.4, and the original design emission standard is < 50mg/m? (standard). The kiln head exhaust fan specification model is Y4-73-14No31.5F, the treatment air volume is 620000m?/h, the total pressure is 2000Pa, the electric motor model is Y5603-10, and the rated power is 560kW. The local environmental protection department requires the company to implement the flue gas dust control facilities to improve the standard, to ensure that the concentration limit of each flue gas dust pollutant discharge reaches DB37/2373-2013 "Shandong Province Building Materials Industry Air Pollutant Emission Standard" 30mg/m (standard) . From March to June 2014, the dust removal system was technically modified, and the dust was collected to meet new emission standards. However, after running for a period of time, it was found that it had an impact on the coal mill and the dust collection operation of the rotary kiln next to it. After the investigation and analysis, the reason was found, and the existing problems were solved by improving the central control operation method.
2 dust collector renovation program
2.1 Selection of cooling system scheme
The design value of the high temperature resistance of the electric precipitator is the highest flue gas temperature of 400 °C, and after changing to the bag filter, the filter bag material is resistant to the highest flue gas temperature of 240 ° C, and the waste heat generator is put into the bag dust collector when it is put into operation. When the temperature is 110-130 °C, the waste heat power generation is turned off and the rotary kiln has special conditions such as magenta, the temperature of the flue gas of the bag filter will exceed the maximum temperature of the filter bag by 240 °C, so the electrostatic precipitator is changed to the bag filter. A flue gas cooling system is required. The kiln head bag dust removal cooling system of our new kiln adopts air cooler. The 5000t/d production line kiln head air cooler is equipped with 20 11kW cooling fans, and the total electric load is 220kW. The air cooler and its piping have a resistance of 500 to 600 Pa. Considering the transformation of the existing production line, the air cooler plus the inlet and outlet air ducts and their conveying facilities, the whole set of facilities covers a large area, and the space process layout is difficult; the installation of the cooler requires civil construction, the transformation period is long; the equipment investment is relatively high; Increase system resistance and cooling power load; there is also a flue gas cooling scheme to install a flue gas spray cooling system in the grate cooler. Considering that the flue gas cooling device is only activated when the waste heat power generation is not turned on and the rotary kiln process is faulty, the operation rate of the cooling system is very low compared with the operation of the rotary kiln, and the process resistance is not increased, and the process arrangement is easy. Low investment. We chose to use a spray cooling system solution in the grate cooler.
Hour cooler spray cooling system specific process equipment: designed to install 13 two-fluid spray guns in the grate cooler, install 2 on each side of the second section, install 3 on each side of the three sections, and install 3 on the top. When the flue gas exceeds the set temperature of 140 °C, turn on a water pump. If the temperature is higher, turn on the second pump. Below 140 °C, the pump will stop automatically. If the temperature exceeds 170 °C, the cold air valve will automatically open and reduce the speed of the kiln exhaust fan. If necessary, reduce the output of the rotary kiln, and ensure that the temperature of the flue gas in the bag filter is within the suitable temperature range of the filter bag filter. . Install a blow-blocking fan next to the grate cooler. After the kiln system is ignited, start the blow-blocking fan to protect the spray gun atomizing nozzle.
2.2 Dust collector body reconstruction program
1) Keep the ash discharge system, ash hopper, air inlet, air outlet and outer casing.
2) Remove all components such as the top cover of the electric field, the internal rapping and the baffle inside the hopper.
3) The working contents of the newly installed bag filter: 1 install the air distribution plate and the blowing unit; 2 install the clean air box to make the dust collector form a whole; 3 install the air pipe and the exhaust valve; 4 install the filter bag and bag Cage; 5 restore the dismantled insulation system. The casing is composed of a main electric dust removing part casing and a newly installed blowing unit, a net air box (bag changing room), an air outlet pipe, a wind blocking device and the like. The bag filter is composed of several chambers. The side plates of the original electric precipitator and the newly installed blowing unit and wind-shielding device constitute the dust collecting chambers. The upper part of the dust collection chamber is connected with the clean air tank, and the top of each clean air tank is connected with the air outlet pipe through an exhaust valve (12 sets), and the dust remover is arranged by two dust collecting chambers to form a dust collecting whole.
2.3 design selection of bag changing method
Most of the bag dust collectors use the top bag changing method, and the height of the net air chamber is about 800 mm. This method has more access doors at the top. If the maintenance door seal is not well maintained, the probability of air leakage is large. Statistics show that the air leakage rate of the top bag change structure is as high as 16%. Leaking into the cold air will cause the acid-containing flue gas to condense and corrode the cage bone, the flower board and the shell; leakage into the rain will cause the paste bag, and the pressure difference of the bag filter will increase, which will lead to insufficient underpressure of the system. The personnel need to increase the fan speed and increase the power of the fan motor, resulting in waste of energy consumption and resources.
The program has been demonstrated to adopt the structure of indoor bag change, that is, the height of the clean air chamber is 3688mm, and the filter bag and the bag cage are installed and replaced inside, and each room has a double-layer access door (with its own rainproof function) on the side. It can ensure that the structural air leakage rate is less than 2.5% for a long time, especially suitable for negative pressure working conditions, which can effectively solve the problem of high power consumption of the tail exhaust fan caused by air leakage and paste bag.
2.4 Filter bag and bag cage selection
When the waste heat power generation is in normal operation, the temperature of the measuring point of the dust collecting pipe is 110 to 130 °C. Considering that the kiln waste heat power generation system is not started and the waste heat power generation system is shut down under special working conditions, the temperature of the flue gas of the bag filter will increase, and the material with high temperature resistance of 200 °C is Nomex filter material. The filter bag size is Φ160mm×7500mm, and the number is 2640. The bag cage uses a quick-fit two-piece bag cage. The cage bone is coated with silicone anti-corrosion to reduce the corrosion of the bag by the wet flue gas.
2.5 filter bag cleaning mode
Both online cleaning and offline cleaning can be used. Online cleaning mode is generally used during normal operation. When the pressure difference of the filter bag is large, it is necessary to increase the frequency of cleaning, and the mode of off-line cleaning is adopted; when online maintenance is required, the mode of offline cleaning is also adopted.
2.6 kiln head exhaust fan reconstruction program
After the dust collector is changed to the bag, the system resistance will be increased. In order to ensure the balance of the rotary kiln process, the wind pressure is insufficient, and the kiln head exhaust fan and the motor are modified. The civil engineering foundation of the original fan is unchanged, and the fan casing enters and exits the wind. The pipe is unchanged and 1 set of fan rotors is replaced. After the transformation, the fan model is Y4-73-14No30F, the treatment air volume is 620000m3/h, the wind pressure is 3600Pa, and the motor model is YRKK560-8, and the rated power is 1000kW.
2.7 Install an air compressor to meet the bag dust collector for high pressure wind cleaning
The company's kiln system has three air compressors, two for one. After the electric bag is changed, in order to ensure the bag dust collector to use high pressure wind, and to produce other winds, to avoid the shortage of compressed air, balance the wind design, install a model FHOGD-160 air compressor, the host power 160kW, exhaust The amount is 27.5m?/min, and the exhaust pressure is 0.80MPa, which is in parallel with the original three air compressors.
3 production installation and docking period
In March 2014, non-standard pipelines and clean air chambers were produced. On June 5th, the electrostatic precipitator was rebuilt using the kiln stop time, and the demolition and docking installation was completed in 15 days. The kiln was opened on June 21 and the dust collection system was put into operation.
4 dust collection effect after transformation
On July 23-24, 2014, the local environmental protection bureau's environmental monitoring station monitored the kiln head bag dust collector. The monitoring result was 23mg/m? (standard), which met the emission standards. The process parameters of the central control room are shown in Table 1.
5 Problems encountered during operation and measures taken
5.1 Problems in operation
On August 3rd to 7th, 2014, the company stopped the kiln maintenance, and opened the kiln at 17:06 on the 7th. The coal mill started at 18:52. The resistance of the coal bag dust collector increased. The pressure difference between the pre-duster and the pre-duster increased from 2300Pa to 3400Pa. From 1:45 to 1:59, the grinding was stopped. After the grinding, the pressure difference increased to 2669Pa, and the grinding was stopped again after 3:40~3:50. After that, the pressure difference increased, resulting in 4:25~4:30. , 6:04 ~ 6:25 and 9:10 ~ 9:28 stop grinding. The weight of kiln head and kiln tail coal powder warehouse is decreasing, which is reduced from 21t to 14t and 25t to 16t respectively. The shortage of coal is forced to stop the kiln.
5.2 troubleshooting analysis reasons
After inspection, it was found that the pulse valve, cylinder and solenoid valve of the coal dust bag cleaning system were working properly, and the filter bag was the new filter bag that was replaced after the kiln was shut down. In order to strengthen the cleaning effect, an air compressor was opened to increase the pressure of the compressed air for dust collection and cleaning, from 0.4 MPa to 0.55 MPa. After the coal mill is turned on, the dust pressure difference of the coal bag filter is still high, ranging from 2600 to 3000 Pa. The shift duty clerk of the central control room learned that after the rotary kiln was fed, the water supply was low and the water supply was insufficient (the local area had less precipitation, drought and water shortage, and the groundwater level was low). The waste heat power generation failed to open in time, and the kiln head bag dust collector inlet The flue gas temperature exceeds the set temperature of 140 °C, and the flue gas cooling system is automatically opened according to the setting procedure. It is sprayed from 20:20 to 22:20 and sprayed with 60t of water. The coal mill takes hot air from the grate cooler, and enters the coal mill to have more wet flue gas. The coal dust adsorbed outside the filter bag of the coal mill bag is not easy to be removed, and the resistance of the filter bag is increased. The pressure difference between the pre- and post-dusters is as high as 2400-3000Pa. The coal mill has poor ventilation and affects the production time of the coal mill.
5.3 Measures taken
1) Gradually increase the temperature of the dust collector into the coal grinding bag, the grinding temperature is increased from 170 °C to 200 °C, the temperature of the bag filter is increased from 58 °C to 65 °C, and the pressure difference of the bag filter is reduced from 3000Pa to 1800Pa. The hourly production increased from 24t/h to 34t/h.
2) Change the position of the coal mill to take hot air from the grate cooler. There are two positions for the coal mill to take hot air from the grate cooler. One is from the second section of the grate cooler, and the other is from the third section of the grate cooler. The company does not affect the waste heat generation to take hot air, the central control operation takes hot air from the third section, and closes the second section of the hot air valve. After the coal kiln appeared several times after the opening of the kiln, the coal grinding dust bag, the system resistance is large, the coal mill is low in output, and the coal powder can not be guaranteed to the rotary kiln. The company revised the central control operation procedure. After the kiln is opened, the waste heat power generation is not put into normal operation, the flue gas temperature of the kiln head bag filter exceeds the set value, and the cooling system pump opens the spray to cool down. The coal mill takes hot air from the second section of the grate cooler and closes the three-stage hot air valve. The cooling gun inside the grate cooler takes the rear end of the hot air position in the second stage, and the wet flue gas is moved to the rear end by the negative pressure pulled by the kiln head exhaust fan, and does not enter the coal grinding system; the waste heat power generation is normally operated, and the kiln head bag is inserted. When the temperature of the precipitator is <130 °C, the coal mill takes hot air from the third section of the grate cooler.
6 flue gas cooling system and kiln head bag dust collector use
The flue gas cooling system is sensitive, and the temperature of the flue gas entering the kiln head bag remover exceeds the set value, and the pump automatically turns on the spray to cool down. Check the record, during the 4 months of the operation, the pump was turned on more than 100 times, and the opening time was 168h. When the company stopped the kiln maintenance in October, it inspected the filter bag of the kiln head bag filter. There is no paste bag, and the pressure difference is 1000~1100Pa. In the early stage of the reformation of the kiln head electrostatic precipitator in other production lines of our group, the design and installation plan of the flue gas cooling system of the grate cooler was drawn up, and the operating experience of the company was taken. The coal mill took hot air from the grate cooler and avoided the wet smoke. The effect of gas on coal milling.
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