Energy saving and efficiency increasing ash cleani

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Energy saving and efficiency increasing dust removal technology of bag type dust collector

1 reducing the working resistance of bag type dust collector can significantly reduce the energy consumption of the dust collector

pulse ash cleaning is the main method to reduce resistance. The traditional sequential ash removal mode reduces the efficiency due to the interaction between the boxes and the bag columns of the same box. The proposed "jump ash removal" mode is helpful to improve the efficiency of ash removal. Bag filter is a kind of environmental protection equipment with high dust removal efficiency. In recent years, bag filter has been widely used. Especially in the metallurgical industry and power industry, bag type dust collectors have more advantages than other types of dust collectors that have passed the acceptance. With the increasing ability of bag to resist high temperature, the application range of bag filter will be more extensive

the key technology of bag filter is to use bag as a method to filter smoke and dust. The progress of cloth bag can represent the development history of this kind of dust collector. From the initial organic fabric to the existing film coated needle punched polyester fabric, relevant experts have been committed to reducing the filtration resistance of cloth bag and extending its working life. However, no matter how to change the fabric and manufacturing process of the bag, with the extension of the working time of the dust collector, the resistance formed by the smoke and dust passing through the bag gradually increases, and the higher the wind speed required by the dust collector, the greater the dust removal energy consumption. Reducing filtration resistance means saving energy consumption. People have to reduce this resistance with the help of ash removal. It is injected into the inner cavity of the bag with a very short high-pressure air pulse (lasting for about tens of MS), so that the dust attached to the bag wall can obtain a certain acceleration and be stripped of the bag. Of course, this stripping speed is limited by the pulse intensity, and it is impossible for all dust to be stripped out. After the residual dust is impacted by a certain pulse air flow, its adhesion to the cloth bag fabric increases, so it is more difficult to be removed. With the further continuation of working time, the residual dust accumulates more and more on the cloth bag, the cloth bag resistance is also increasing, and the efficiency of pulse dust removal is also getting lower and lower, resulting in a significant increase in the energy consumption of the dust collector and a reduction in the ability of post dust capture. To sum up, measures should be taken to delay the rapid increase of bag working resistance

2 causes of problems and improvement measures

in the process of reducing bag resistance, people have always emphasized the improvement of bag fabric. However, this paper believes that the improvement of ash removal control mode will have a more obvious effect

a dust collector has multiple boxes, and each box has multiple rows of cloth bags. Generally, the box and bag columns are numbered in sequence according to their adjacent positions, and it is also customary to complete the ash removal procedure in the mode of sequence control. That is, once the bag resistance is large, the pressure difference between the front and rear of the box reaches the specified value, the ash will be removed. Each box is cleaned according to the number sequence of the bag column. After all the bags in a box are cleaned, the next box is cleaned according to the number sequence

in fact, the ash removal effect of each row of cloth bags in the box affects each other. According to the author's research, the diameter of the dust filled space cleared by each cloth bag reaches 1 2 m, from the upper part of the bag to the ash outlet of the box, more than 90% of the dust needs more than 30 s of settling time. If the time interval is less than 30 s, at the diameter of 1 There are two rows of cloth bags within 2 m, and some dust removed from one row of bags will be attracted by the filtering action of adjacent bags and attached to the bag wall. At the same time, the dust removed from the adjacent row of bags will also be attracted by the previous row of bags that have been relatively clean and have low resistance, and more will be attached to the wall of this row of bags. If this situation continues, multiple rows of cloth bags in the whole box will affect each other, which will have a significant negative impact on the ash removal of the whole box

at the same time, the air used for ash cleaning will significantly reduce the pressure of the air compressor independently set in the box. It takes a long time for the air pressure to return to normal level. If the dust removal frequency of the box is too high, the air pressure in the bag does not have enough time to be supplemented, so it cannot meet the specified requirements. The acceleration of the bag caused by the pulse air flow is not enough, and the dust attached to the bag wall will not have enough peeling force, which will also seriously affect the dust removal efficiency of the bag. The low dust removal frequency of the box can ensure that the pressure in the air compression bag meets the specified requirements, but it will cause the dust removal cycle of the dust collector bag to take too long, which will also lead to the continuous increase of the working resistance of the bag

in addition, it is also an unreasonable control mode to clean all cloth bags in one box and then clean the dust removal cloth bags in the next box adjacent to it. The following two facts can prove this conclusion

(1) if all the cloth bags in one box are cleaned and then another box is cleaned, the resistance of the cleaned box will be significantly reduced, and the resistance of other boxes will be relatively large. The smoke and gas to be treated will enter the relatively clean box in large quantities along the path with the least resistance, causing serious uneven distribution of air flow, and then the cloth bags of the box will bear more uneven pressure and be damaged in advance

(2) at present, each box of most dust collectors is equipped with an air compressor for ash removal. All air pressure packs are connected in series with pipes and finally connected to an air tank. Due to the large pressure on the pipeline (the ash removal pulse pressure can reach 0.3 MPa), the diameter of the pipeline is generally thin, and the flow of high-pressure air in the pipeline will cause a certain pressure drop. During bag cleaning, due to the large amount of pulse gas, the air pressure in the bag will be significantly reduced, and there is no one-way valve between the boxes to prevent the interaction of the air bags, that is, when the pressure of the air bag of the box decreases significantly, the pressure of the air bag adjacent to the box will also decrease, thereby affecting the ash cleaning effect of each box

in order to solve these problems, the author puts forward the concept of "jumping ash cleaning". Compared with the traditional sequential numbering method, there are other hidden benefits of these Plexiglas components: in the ash removal control software, the ash removal sequence adopts the method of "jumping" between boxes, and also "jumping" between bag column numbers in the box. At the same time, a single box jumps to another box after only completing an appropriate proportion of bag ash removal each time. This control mode reduces the interaction between the cleaned bags. Adjacent boxes also do not affect each other, and the configured air compressor can always be in good condition. In a word, the concept of jump ash removal is not in order, but based on calculation, taking full account of the dispersion range and settlement time of bag dust, the pressure drop value and recovery time of the air bag in the box, the pipeline loss adjacent to the air bag and the interaction and other parameters, and reasonably arranging the jump position to achieve the ultimate goal of reducing the working resistance of the bag and extending the working life of the bag

to sum up, the author believes that the ash cleaning should realize the "jumping" mode: jumping between boxes to maintain the balance of flow configuration and the recovery of air bag pressure, and jumping in the box to maintain the effect of ash cleaning will not affect each other

of course, these two jumps should be mainly between boxes. Because this jump will prolong the time interval between two rows of cloth bags in the same box at the same time, which will reduce the mutual influence of cloth bags in the same box

3 examples

further illustrate the basic concept and steps of "jumping ash removal" with examples. The dust collector has 10 boxes, each box has 5 rows of cloth bags, as shown in Figure 1

after calculation, it is considered that the following control modes are better:

(1) the jumping mode in the box is 1-4-2-5-3

the loading and control of experimental force is completed by the load loading and holding system

(2) the jumping mode between boxes is 1-6-2-7-3-8-4-9-5-10

(3) every time each box is cleaned, 1/5 of the total number of bags in this box will jump to the next box, so that the bag cleaning can be carried out step by step

in 2007, a set of PLC software was compiled in a power plant in Jiaozuo according to the above control mode, and the concept of skip ash removal was initially realized. According to the measurement, the working resistance of the large bag type dust collector that cleans the ash according to this mode remains at 1. 5% for a long time Below 2 kPa, the working resistance is 10% ~ 15% lower than that of another dust remover of the same model in the same place. The bag changing time was also extended by more than 10%. By not changing the hardware facilities, more than 10% of the energy-saving and efficiency increasing results can be achieved only by relying on the jumping characteristics of the ash removal control mode in the software. This example shows that the concept of jumping ash removal has obvious social significance and economic value

4 conclusion

compared with the traditional sequential ash removal mode, the jumping ash removal mode significantly reduces the weight by about 20%, balances the distribution of air flow, maintains the pressure stability of the air compressor, and also reduces the interaction of bags in the box, which has obvious social significance and economic value. However, there are still some key problems to be solved through further research. For example, the number of dust removal each time accounts for 1/5 of the total number of bags in the box. Cycle between the boxes for 5 times to clean all bags of the dust collector. This proportion is not necessarily the best plan. The optimal value can be obtained only after further discussion. This "jumping" method can arouse some interest of industry peers, which has achieved the basic purpose of this paper. (end)

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