My colleagues and I have long been engaged in the dust bag paste bag "cleaning service, encounter a variety of different types of" paste bag "project, the" paste bag "carried out in-depth analysis and research, we will own experience to share with readers with the help of the limited space.
One. What is the "paste bag":
"Paste bag" is a phenomenon and a problem in the use of dust bag, which is one of the reasons for the loss of dust bag. There is no uniform definition in the industry. I think: "paste bag" is in the long run or dust bag outage process, containing high humidity or contact oily substances and filter conditions, dust condensation in the interior and dust bag filter or filter surface adhesion or crust and cannot be effectively removed online cleaning system, which greatly increased the running resistance the phenomenon of.
Paste bag bag, dust tight cover in the surface of the filter bag, the effective filtration area filter reduced air permeability filter decreases sharply, running resistance is high, the fan load increases caused by the increase of energy consumption, serious or even fan overwhelmed and unable to work. At the same time, the pressure drop of the dust bag is very high, which makes the online cleaning system frequent cleaning. It not only needs a lot of compressed air, but also causes serious loss of mechanical strength and shorten the service life of the filter material. Therefore, if the duster bag is often running in the paste condition, the owner will have to pay more cost for the operation of the system. If the bag problem is not solved in a timely and effective way, the owner will have to replace the whole bag.
Two. The reasons for the formation of paste bag:
In the actual condition, factors that may cause the paste bag is more complex, for the specific case, we must from the condition of flue gas and dust collector, filter material, operation control and other related factors were analyzed, in order to understand the real factors inducing the paste bag, in order to avoid and solve the problem.
1. Dew bag:
In general, the operating temperature of the bag filter must be higher than the acid dew point temperature above 25K, and it is safe to operate for the cloth bag. This is mainly to avoid the occurrence of dew. Liquid water is formed when the operating temperature is lower than the dew point. The mixture of liquid water and dust and aggregated on the surface of the filter bag will form a paste bag.
The formula for the dew point:
Ts=186+20lg H2O SO3 +26lg psi PSI
Where TS is the dew point temperature, H2O and SO3 respectively for the PSI psi volume fraction of H2O and SO3.
It can be seen that the higher the content of water and three sulfur dioxide in the flue gas, the higher the dew point temperature. It also means that the temperature of the continuous operation of the dust collector must be higher. Because of the physical and economic constraints of the material of the filter material of the dust bag, the continuous operating temperature of the dust collector must be controlled in a suitable range. If the two are uncoordinated, it will be inevitable. Therefore, water content, SO3 content and operating temperature are the three main factors to determine whether or not to be exposed. The right picture is a photo of the paste bag caused by the acid dew of a filter bag in an industrial garbage incineration dust collector. The precipitator operating temperature stable at 150 degrees Celsius, but the incineration material is the complex composition of the solid, liquid and gas chemical industry waste, so the change of water and sulfide content in flue gas (large water content of 25% or more), the dew point temperature fluctuation is very big. The condensation is inevitable, and the pouch is extremely serious. At the same time, due to the infiltration of acid and long time operation, the dust on the surface of the filter bag gradually crusted, resulting in the loss of the air permeability of the filter bag.
Secondly, the compressed air of pulsing ash is one of the possible causes of condensation. The compressed air temperature is generally far below the operation temperature of the dust collector. At the instant of pulse, low temperature compressed air will make the upper part of the filter bag temperature decrease rapidly. When the temperature is lower than dew point, it will cause condensation on the outer surface of the filter bag. As the compressed air goes down, the air temperature in the bag is less and less. Therefore, the general dust bag in the range of one meter below the scope of the paste phenomenon is more serious.
Thirdly, the air leakage rate of the dust collector is also a possible factor of condensation. The air leakage rate of the general dust collector is about 1 - 2%. But with the extension of running time, the air leakage rate will increase. If it was in the cold north of the winter, the problem became bigger. The higher the air leakage rate is, the greater the effect on the local temperature in the dust collector, and the risk of the bag is getting higher and higher because of the leakage of the filter bag.
In addition, although the dust collector wall is provided with a heat insulation layer, but because the walls are at the forefront of contact with the outside world, it must be compared with other parts of the actual service is low, we found that the degree of outer bag paste dust bag usually near the walls of the much higher than other parts.
2. Adhesive pouch
It is mainly due to the fact that the dust adhesion is relatively large. Although there is no condensation phenomenon, the dust still adhers to the surface of the fiber, and the online cleaning system can not remove it. The reason for the bond pouch may come from the following.
A, the viscosity of the dust itself is relatively large, when it contact with the filter fiber, the intermolecular force is stronger. For example, oil particles, denitrification of ammonium sulfate, desulfurization of the use of lime and so on.
B, although some dust is not sticky, but it is easy to deliquescence, when it was trapped on the surface of the fiber, can absorb the moisture in the air and solution is formed on the surface of the fiber. For example, sugar.
C and some dusts may not be strong in adhesion, but they can absorb moisture in flue gas and recrystallized chemical process, and generate new hard materials or crystals. The crust formed on the surface of filter material. For example, cement clinker, desulphurization product - calcium sulfate.
D, even if the dust itself is not sticky, but if the dust particles, dust and moisture is relatively large, dust easily absorbed on the filter surface, forming a layer of "dust", adhesion is not very strong, but it is difficult to remove. The running time is longer, the more thick dust ". This is likely to happen in a coal-fired power plant, especially for a filter bag that is more than 6 meters in length. A northern power plant once caused the operation resistance of the dust collector to rise from 1500 to 2200Pa in a short time, resulting in the serious situation of the whole line's outage.
3. Structural paste:
We classify all the paste bags caused by the design of the dust remover and the structure of the related components and the paste bags caused by improper operation as structural paste bags.
A, filter material structure and treatment:
Some media due to needling density is not enough, the fiber filter surface is loose, even after the surface treatment of fine dust singeing, but still very easy to enter and reside in the internal filter. The accumulation of dust in a certain degree, and the effect of water vapor in the flue gas, gradually form a blockage from inside to outside. The use of cloth bags in a power plant in the north is less than a year, and the whole batch of cloth bags has to be considered because of this problem.
In addition, some media are not or cannot singeing or pressure light processing, the surface of the filter retains the fiber ends, which provides the "condensation" actually is the dew, dew phenomenon first from the end of fiber. Dust will also first form a dust cluster, when the dust clusters gradually change ambassadors to each other to bridge. A large area of paste is gradually formed. In the waste incineration power plant with pure PTFE filter, if there is no other treatment on the surface, it is often possible to find the stubborn dust crust at the end of the fiber.
In addition, there is no hydrophobicity treatment for the filter material for the condition that the humidity is larger or the acid condensation is dangerous. Pouch is more common.
B, filter bag coordination:
We know that the pulse cleaning is actually using the pulsed airflow and the two air bag on the impact, so that the bag from top to bottom in the zonal deformation, deformation and inertia of the bag and cage bone caused by collision of "avalanche effect" on the surface of the dust layer, so as to remove surface dust. The effect of ash cleaning depends largely on the size of the deformation inertia and the intensity of the collision between the filter bag and the cage bone. In practical applications, due to the fact that the size of the weft in the filter bag is too small or the heat shrinkage degree of the filter material is too large and so on, after a period of time, the filter bag can not be separated from the cage bone. At this time, the deformation of filter bag caused by pulse dust cleaning is very small, and the intensity of the collision between the filter bag and the cage bone is limited, and the surface dust can not be effectively removed. The accumulation of dust on the surface of the filter bag and the consolidation of the dust may cause the paste bag.
Pressure distribution in C and blowpipe:
At present, a large number of dust remover adopts the way of blowing and blowing ash. Each line is responsible for the cleaning of more than a dozen of the bags in the line. A small injection hole or blowout tube with a certain size of the same size is evenly distributed on the blowpipe. A small blow hole or a blowpipe corresponds to a cloth bag. Theoretically speaking, when compressed air moves forward in the blowpipe, the dynamic pressure of gas is gradually transformed into hydrostatic pressure. Such transformation directly causes the compressed air volume of each filter bag of the line is not the same. The effect of ash cleaning is different. The risk of pouch with poor cleaning effect is higher. We have also used several filter bags in the same state to test the air permeability in the same state, and the highest and lowest difference is larger. The objective existence of this situation is indirectly explained.
D, the pressure of injection is not enough:
The general site cleaning pressure can be adjusted. If the ash pressure is not good, the dust removal effect is not good, and dust accumulates on the surface of the filter bag. After a long time, the risk of paste bag is relatively high. If this is the case, there are two possibilities: one is system design constraints, namely the maximum pressure of the system can provide is too small; two is the injection interval is too short, in the first time after the injection, the system pressure has not been restored to the required pressure, began the second pulse.
E, operation error:
1, the pre spraying is not required as required, so that the oil mist in the ignition is directly intruded into the filter material and causes the paste bag.
2. When the switch machine (especially the long - time shutdown), the cleaning operation is not carried out according to the correct procedure.
3. When the boiler appears to burst in the process of accident, the filter bag is not properly handled and remedial operation is not carried out.
PS: how do you deal with a dust bag containing the dust containing the tar fogs?
The gas bag filter processing only containing tar fog is difficult, but the gas in the oil mist and small amounts of dust can be filtered for pi. For example, in the asphalt concrete plant, the flue gas is mainly made of stone drier, and the dust from transport and other exhaust gas is entered into the bag filter. In the mixing machine and unloaded material. The tar fog produced by the heated asphalt concrete also enters the bag type dust collector. In this case, the amount of dust accumulated on the filter cloth is much higher than that of the oil mist, which can prevent the trouble of oil mist adhesion and ensure the stable operation of the bag filter.
In the manufacture of electrodes and molding carbon products, the process of mixing the powder into the hot bonding agent also produces tar fogs. At this time, the bag type dust collector can be used only if the dust is mainly produced during the process of crushing and transportation and only a part of the tar mist is mixed. However, if more should be added before the amount of coke powder into the dust in flue gas adsorption coke fog are satisfactory effect of coal tar tar coke furnace flue gas in the tail groove.
If the gas contains only a small amount of oil mist, it can be treated separately. That is, adding a proper amount of powder on the pipe as a filter aid, the bag filter can be used. After the added dust absorbs the tar fog, it should be used as far as possible to return to the manufacturing process.