Large bag filter is convenient for environmental protection of cement plants

The production process of the new dry process cement plant generally has more than 50 sets of dust collectors. In addition to the removal of rotary kiln exhaust gas treatment and kiln head coolers, most companies use electrostatic precipitators. With the development of environmental protection and the advancement of bag filter technology, almost all bag cement can be used in the whole process of cement production.

The large-scale high-efficiency bag filter is one of the signs of the development of modern dust removal technology. It has high dust removal efficiency, especially for capturing fine dust. In recent years, the improvement of filter material of bag filter and the optimization of cleaning control and structural performance have provided technical guarantee for the development of bag filter. The baghouse filter for large dry cement kiln tail gas treatment Has gradually become a trend.

Technical characteristics of bag filter 1. Adaptability to changes in kiln conditions Objectively speaking, both electrostatic precipitators and bag filters have high dust-collecting effects, as long as the design is correct and the product quality is excellent. The maintenance operation is reasonable and can guarantee the emission standards set by the state. In comparison, due to the different structure of the equipment and the mechanism of dust removal and cleaning, when the kiln condition is unstable and the thermal parameters deviate from the original design index, the adaptability of the bag filter is stronger.

In actual production, when the amount of exhaust gas or dust concentration entering the electrostatic precipitator exceeds the original design value, the dust removal efficiency will decrease. The kiln exhaust gas cannot always remain within the design specifications. When the amount of feed ( coal ) and the leakage of the system exceed the design specifications, it is possible to make the amount of kiln exhaust gas exceed the standard, so that the dust removal efficiency of the dust collector is lowered and the discharge concentration exceeds the standard. For example, when the amount of exhaust gas entering the electrostatic precipitator is 5%~10% higher than the design index, the dust removal efficiency will be reduced from 99.875% of the original design to 99.83%~99.77%. In this case, if the original design discharge concentration is ≤100mg /m3, the actual emission concentration will rise to 137mg/m3~184mg/m3. Similarly, when the air leakage in the preheater exceeds 2%, the separation efficiency of the preheater is obviously reduced, and the dust concentration of the exhaust gas may increase. This will also cause the dust removal efficiency of the dust collector to decrease and the exhaust gas emission concentration to exceed the standard.

In order to solve the problem that the amount of exhaust gas or dust concentration entering the electrostatic precipitator increases and the dust removal efficiency decreases and the discharge exceeds the standard, it is necessary to increase the plate to increase the area of the sediment plate, which is very difficult for the electrostatic precipitator being used. . The bag filter determines the filter bag filter area according to the selected filter wind speed, and the filter bag filter area is basically not affected by the amount of exhaust gas or the dust concentration. When the amount of exhaust gas entering the bag filter increases, the filtration wind speed increases and the resistance rise speed increases. At this time, only the filter bag cleaning cycle is shortened and the number of cleaning times is increased to meet the dust removal requirement, and the dust removal efficiency is not affected. of.

In addition, in comparison, changes in the temperature and humidity (ie, the nature of the flue gas) entering the precipitator exhaust gas have a greater impact on the electrostatic precipitator. Generally, the temperature of the flue gas entering the electrostatic precipitator is 120 ° C ~ 150 ° C, the humidity is 10% ~ 15%, and the dew point is 50 ° C ~ 60 ° C. Too high or too low are unfavorable to the operation of the electrostatic precipitator. If the temperature is too high and the humidity is too low, the dust will increase in specific resistance, which may cause frequent spark discharge of the electric field, increase of corona current, and decrease of dust removal efficiency. If the temperature is too low and the humidity is too high, it may cause dust to be on the plate and electricity. Adhesion occurs on the halo line, making it difficult to vibrate the ash, which will affect the normal operation of the precipitator.

Bag type dust collectors require a wide range of temperature and humidity changes of exhaust gas, especially due to the application of some new filter materials, such as glass bulky yarn microporous film composite filter materials, etc., the working temperature is 250 ° C (instantaneous up to 280) °C), the temperature requirement is also wider than the electrostatic precipitator. In summary, it can be said that the bag filter is more adaptable to the change of the kiln working condition and the change of the flue gas property than the electric precipitator.

2. Bag filter can capture fine dust With the development of the filter material industry, new products are constantly appearing, and it is possible to choose to meet the filter material that captures fine dust, which greatly improves the dust removal efficiency.

3. Adaptability to environmental protection requirements As people's requirements for the quality of living environment continue to improve, the government will inevitably gradually improve environmental standards. At present, the electrostatic precipitator further reduces the concentration of the outlet only by increasing the area of the sediment plate to improve the efficiency of dust collection and reduce the amount of emissions, which will inevitably increase the volume and investment of the equipment. The bag filter can meet the new emission requirements simply by adjusting the cleaning frequency.

4. Simple and reliable operation and maintenance During the operation of the cement kiln, when the kiln is opened or the abnormal kiln condition is treated, the fuel quantity is increased, the air volume is insufficient or the fuel and air are not mixed uniformly, and when the kiln temperature is too low to make the fuel burn incompletely, It is often possible to produce a large amount of co combustible gas, as well as excessive unburned pulverized coal into the precipitator. In addition, most of the kiln dust collectors are operated under negative pressure, and the air is leaked into the equipment piping. Whether it is an electrostatic precipitator or a bag filter, if there are two kinds of conditions in the above (ie, there are combustible materials and combustion-supporting oxygen in the machine), once there is an open flame, there is also the possibility of explosion. For an electrostatic precipitator, the discharge spark of a high voltage electric field will excite its blast, which is more likely to ignite. Therefore, the kiln tail must be equipped with a co and o2 analyzer to ensure the safe operation of the electrostatic precipitator. For the bag filter, the safety of the electrostatic precipitator is greater because it does not have the condition of generating an open flame. These control requirements do not need to be so strict, so their operation is relatively simple and reliable.

During the long-term operation of the dust collector, some faults will occur, such as electric transformer deformation or displacement, loosening of the cathode wire, disconnection of the wire, excessive electrode ash, damage of the insulated porcelain bottle and bag breakage of the bag filter. For the electrostatic precipitator, once a sudden failure occurs, affecting the operation of the whole machine, it is necessary to stop the offline maintenance. The large bag filter adopts the sub-chamber structure for offline cleaning. For example, the 2000t/d cement kiln kiln large bag dust collector is generally divided into 14~16 rooms, and a certain room fails, and offline maintenance has no effect on the whole machine operation. Only the filtered wind speed increases slightly.

5. Bag filter can be discharged under abnormal conditions. The existing cement kiln mostly uses electric precipitator. The safety requirements of the electrostatic precipitator are 2 kinds of exceeding the standard conditions: coal combustion is incomplete at 1 point kiln, co Exceeding the standard, at this time, the dust is not supplied to the electrostatic precipitator, causing the dust concentration to exceed the standard. However, its time is not long, and the excess emissions are not large enough to be ignored. When the kiln is ignited and the kiln temperature rises to a certain temperature, the combustion is basically normal when the combustion is started, and the electric precipitator is also put into operation. Because the time is very short, there is only soot before the feeding. Even if there is a certain time exceeding the standard, the super standard value is very small (200mg/m3~300mg/m3), and the total amount of emissions can be ignored. 2 During the production process, due to improper operation, the co exceeded the standard and stopped supplying power to the dust collector, causing the dust concentration to exceed the standard. At this time, because the kiln system needs to be adjusted, the operation cannot be stopped, so the power supply to the electrostatic precipitator can only be stopped, which causes the dust concentration to exceed the standard discharge. At this time, the dust concentration exceeds the standard discharge amount.

The dust concentration at the kiln tail is 60g/nm3~80g/nm3, the sedimentation rate of the humidification tower and the electrostatic precipitator shell are 20% and 50%, respectively, and the dust concentration discharged into the atmosphere is 60~80×(1-0.2). ) × (1-0.5) = 24g / nm3 ~ 32g / nm3, the national cement kiln discharge standard is 100mg / nm3, due to improper operation caused by co-standard in the production process, stop the supply of dust to the electrostatic precipitator caused by excessive dust concentration It is 240 to 320 times the discharge of the standard, which is very amazing, and the bag filter can avoid this situation.

The economical comparison of the bag filter has a large resistance, while the electrostatic precipitator has a small resistance. Therefore, many people think that the main fan of the bag filter consumes much more electric power. In fact, in addition to the electric power consumed by the main fan, the electric precipitator also consumes electricity from the high-voltage power supply unit, the electrostatic precipitator insulation heater and the plate rapping. The power consumption of the two is not very different. The initial investment of Class 2 dust collectors is close (the bag filter is about 4% higher than the electrostatic precipitator), and the operating cost and maintenance fee bag filter are higher than the electrostatic precipitator. But the key is also what kind of filter material is used in the bag filter. Some filter materials cost only tens of yuan per square meter, while others are 200 to 300 yuan, which directly affects the initial investment. The service life of filter bags is 1~2 years, and some can reach 3~4 years, which opens a big gap for maintenance costs. In addition, although the electrostatic precipitator and bag filter have high dust removal efficiency, the bag filter is stronger when dealing with fine dust. Therefore, in the current strict environmental protection requirements, the bag filter is used. To be beneficial.

With the continuous improvement of environmental protection technology and the development of environmental protection industry, the design of large bag filter is continuously optimized, the quality of components is improved, the emergence of new high-quality filter materials, and more and more exhaust gas from cement kiln heads and kiln tails. The treatment uses a large bag filter. In addition, according to the current manufacturing level in China, many manufacturers have fully equipped the equipment and strength to produce large bag filters, which can meet the requirements of the cement industry and other industrial production. Looking into the future, bag filters will have an absolute advantage in cement industry equipment applications.