This article analyzes the problems that easily occur during the operation of the dust removal system components of the asphalt mixing equipment, and discusses the solutions to the problems in order to quickly deal with the dust removal system problems and reduce the construction progress caused by the dust removal system problems. Environmental pollution. Due to the poor performance of industrial dust removal methods such as gravity dust removal, inertial dust removal, gravity or inertial dust removal, water removal and dust removal, which do not meet the emission standards required by national standards, they have been eliminated by the asphalt mixing equipment industry. The analysis of the configuration method of the dust removal system and the secondary bag dust removal.
1. Common faults of the industrial dust removal system
There are two common failures of the dust removal system: insufficient wind induction and poor dust removal effect. Insufficient air extraction of the dust removal system is mostly manifested by the phenomenon that the combustion end of the drying drum turns out smoke, the combustion effect is poor, the temperature of the material does not go up, and the seals of the mixing building emit smoke. The dust removal effect of the dust removal system is mostly manifested by smoke from the chimney .
2. Failure cause analysis
According to the analysis of the working principle and structural characteristics of the dust removal system, the reasons for the insufficient induced draft are leakage of the duct, dust collector or cold air valve in front of the induced draft fan of the dust removal system; blocked ducts; blocked dust collector; The poor dust removal effect is mainly caused by the dust collector, and specific analysis is required for the cause of the failure.
2.1 Cause analysis of air leakage
When the inlet of the drying drum, the connection flange of the induced air duct, the connection flange of the dust collector, or the cold air valve on the induced air pipe is working normally, if the seal is not tight, the induced fan will be short-circuited, and a large amount of cold air will be extracted from the environment, thus The amount of exhaust gas generated after the burner is combusted is reduced, and the drying drum becomes positive pressure, and smoke is emitted outward. If this is the cause of insufficient induced draft, you can intuitively judge from the magnitude of the induced draft fan current. In this case, the induced draft fan current will be higher than that during normal production.
2.2 Cause analysis of blocked air ducts
The blockage of the induced air duct will cause the resistance of the entire dust removal system to exceed the induced fan pressure, resulting in the induced fan being unable to extract the combustion exhaust gas and pressure relief air from the drying drum and the mixing building, resulting in insufficient induced air. If the asphalt mixing equipment runs for a long time at a small and medium load state and the induced draft fan is always in a small air volume during the operation, due to the low wind speed in the induced draft pipe, dust will accumulate in the horizontal section of the induced draft pipe and eventually block the pipe. If the layout structure of the induced air duct is not reasonable, it will cause local pipe blockage even under normal conditions.
Generally, the induced draft fan of the asphalt mixing equipment is provided with a damper adjusting mechanism. If a problem occurs in the damper adjusting mechanism, it may also lead to poor drafting.
2.3 Cause Analysis of Dust Collector Blocking
The blocking of the dust collector will cause the resistance of the entire dust removal system to exceed the pressure of the induced draft fan, which will cause the induced draft fan to be unable to extract the combustion exhaust gas and the pressure-relief air from the drying drum mixing building, resulting in the insufficient induced draft. This phenomenon is more common at the operation site of asphalt mixing equipment. Among them, the clogging of the dust collector is divided into the first-grade gravity or inertia duster clogging and the bag duster clogging .
The first-level gravity or inertial dust collector extracts large particles of dust in the exhaust gas from the drying drum and filters them out to the hot aggregate elevator for use as fine aggregate. If the dust filtered by the first-level gravity or inertial dust collector cannot be sent away in time, it will stay and accumulate in the dust collector, eventually blocking the entire dust removal channel.
The clogging of the bag filter is actually the clogging of the filter bag in the bag filter. Poor material permeability of the filter bag decreased permeability of the filter bag viscous oil, and incomplete cleaning of the filter bag will cause the filter bag to be blocked.
(1) The material problem of the dust collector bag. The filter bag used for the bag dust collector of the asphalt mixing equipment is generally recommended to use waterproof and oil-repellent needle felt, such as Nomex needle felt. In addition to good temperature resistance, this needle felt has the advantages of water repellency and oil repellency. If a filter bag with a poor material is used for the bag filter, under the effect of high-temperature exhaust gas, the material of the filter bag will be deformed and degraded, and the air permeability will be reduced, resulting in an increase in the working resistance of the bag filter and poor wind induction.
(2) Insufficient combustion. The fuel oil used in the production of the asphalt mixing equipment has a large viscosity, a poor atomization effect of the burner, or insufficient air distribution of the burner, which will cause insufficient combustion. Once incomplete combustion occurs, the exhaust gas will contain a large number of incompletely combusted oil mists. These oil mists accumulate on the filter bag of the bag filter and mix with the dust to form a sludge to cover and stick to the outer surface of the filter bag. A barrier is formed to reduce the air permeability of the filter bag, resulting in an increase in the working resistance of the bag filter and poor wind induction.
(3) Backflushing and dust removal. There are three types of dust removal methods for bag dust collectors for asphalt mixing equipment: one is high-pressure pulse back-blowing, the other is medium-pressure fan back-blowing, and the third is atmospheric back-blowing. No matter which kind of dust removal method is, the bag filter removes the dust adhered to the outer surface of the filter bag in time while maintaining a certain working resistance; the backflushing power is insufficient, the backflushing interval or backflushing time is inappropriate, and the backflushing The dust that falls after it is re-adsorbed by the filter bag, the so-called secondary dust, will cause poor dust removal effect. A large amount of dust is adsorbed on the outer surface of the filter bag and cannot be removed, which reduces the air permeability of the filter bag, resulting in an increase in the working resistance of the bag filter and poor wind induction.
(4) Mechanical problems. The airbox type pulse backflushing bag dust collector is one of the high-pressure pulse backflushing bag dust collectors. The working characteristic of this type of dust collector is offline backflushing, that is, the ventilation of the backflushing studio is blocked first, and then The studio opened high-pressure blowback air. Due to mechanical failure, some working rooms are not opened after blowing, and the ventilation is always blocked; in this case, the area of the filter bag involved in the work is much smaller than the total working area, and the dust on the filter bag is constantly increasing, resulting in dust removal from the bag. The working resistance of the device increases and the wind is not smooth.
2.4 Cause Analysis of Insufficient Fan Air Volume and Air Pressure
The induced air volume of the induced draft fan configured by the dust removal system is calculated and calculated based on the three factors of the exhaust gas generated by the full combustion of the combustion system, the amount of water vapor after the raw material moisture is evaporated, and the normal coefficient of air leakage. Yes, if this data is incorrectly calculated or the configured induced draft fan's air volume does not reach the calculated air volume, it will lead to insufficient induced air. In addition, the wind pressure is another main parameter of the induced draft fan. The wind pressure is a reflection of the resistance of the induced draft fan to overcome the resistance of the dust removal system. If the selected induced draft fan's wind pressure is not sufficient to overcome the resistance of the dust removal system, it will inevitably cause insufficient induced wind. Blocked in the dust removal pipe or bag filter.
2.5 Cause analysis of poor dust removal effect
Poor dust removal effect is generally due to poor filter bag material, large gaps, damaged filter bags, or problems with the seal between the clean air chamber and the turbid air chamber of the bag filter, which causes some dust to be discharged directly without filtering, resulting in smoke from the chimney and polluting the environment.
3. Troubleshooting plan and measures
The current value of the induced draft fan can be compared with the current value during normal production to determine whether the pipe is leaking air or the system is blocked. Insufficient air pressure and air volume of the induced draft fan, insufficient induced draft and smoke from the drying drum appear at the beginning of the operation of the equipment. The specific judgment basis is: if the induced fan current is less than the current during normal operation and the drying drum smokes, it can be judged that the system is blocked; if the induced fan current is equal to or greater than the current during normal operation, and the drying drum appears Smoke can be judged to be a system leak.
3.1 Pipe leakage
When the system is installed, the connection flange sealing measures are not in place. After the equipment runs for a period of time, the pipe connection flange of the dust removal system is deformed, the pipe is damaged, and the valve of the cold air valve in front of the bag filter is often open. To deal with such problems, first, check whether the cold air valve switch is normal; second, check all dust removal pipes, first-level dust collector housings, and upper and lower boxes of the bag dust collector for damage; and then check the pipeline room and between the pipeline and the dust collector. Whether the connection flange is not tightly sealed.
3.2 System blocking failure
(1) System blocking failure check. First, check whether the mechanical or electrical failure of the damper for the induced draft fan has caused it to be in a normally closed state or a small damper state for a long time; second, check whether there is dust accumulation in the induced air duct or the primary dust removal casing; finally check the dust removal filter Whether the bag is blocked.
(2) The dust filter bag is blocked. There are many reasons for the blocking failure of the dust filter bag, which should be checked and dealt with from the following aspects.
The burner is insufficiently burned or the water vapor content in the exhaust gas is large and condensation is formed on the filter bag. A layer of sludge that is difficult to remove is formed on the outer surface of the filter bag, causing the filter bag to become blocked. In this case, the filter bag needs to be cleaned. The filter bag with poor cleaning effect should be replaced, and the water content of raw materials must be strictly controlled.
The filter bag is of poor quality, and the air permeability decreases under the action of high-temperature exhaust gas, which causes the filter bag to block to a certain extent. This situation can be judged by detecting the pressure difference of the bag filter when the equipment is in idle operation: after a long period of no-load blowing, the surface of the filter bag does not remove the sludge or ash cake layer, and the pressure difference at the inlet and outlet of the bag filter is greater than At 800 Pa, it can be determined that the material of the filter bag is a problem and the filter bag needs to be replaced.
Problems with the blowing system will cause the filter bag to be incompletely dusted, and the surface area of the filter bag will be more and more ash, eventually causing the filter bag to block. This situation is mostly manifested as follows: the equipment runs normally 1 hour before each start-up, and the induced fan current gradually decreases after 1 hour, and the combustion end of the drying drum emits smoke and becomes more and more serious, even if the induced fan door is opened to the maximum. To no avail. This situation is a typical filter bag blockage caused by incomplete cleaning of the filter bag. When encountering this kind of problem, you must first check whether the blowback pressure of the air compressor fan of the injection system can reach the normal working pressure, especially the high-pressure air pressure generated by the air compressor, often due to air compressor problems and pipeline leaks. Insufficient injection pressure caused by problems or leakage of the pulse valve can be effectively solved after the corresponding problems are checked and processed. The second is to check the alignment between the nozzle and the center of the filter bag. If the nozzle and the filter bag are not aligned, the problem of insufficient spray power and poor dust removal effect will be solved. Another is to check the gap between the filter bag and the keel. If the filter bag is closely attached to the keel, the filter bag will not shake when sprayed, which further affects the effect of dust removal. This situation often occurs because the filter bag shrinks after a period of use or the filter bag does not match the keel, which can only be solved by replacing the filter bag or keel. The last is to check the injection control system. If there is a non-operating pulse valve, the injection time or the injection interval is not suitable, it will reduce the dust removal effect. Replace the damaged pulse valve or adjust the injection time and interval according to the requirements. The point of this question.
There are many reasons for the problems in the operation of the dust removal system of the asphalt mixing equipment. As the operation and maintenance personnel, you should gradually analyze and determine the problems according to the methods introduced above to ensure the normal operation of the equipment and maintain the asphalt mixing building and its surrounding environment. In the actual production process, the basic principles of the dust removal equipment must be established, the maintenance and maintenance of the dust removal equipment must be done, and the equipment and pipelines must be maintained in a timely manner. Only by doing this can we ensure the better work of the dust removal device and produce better economic and social benefits for the enterprise. In actual use, in addition to the use and adjustment of the dust removal equipment itself, attention should also be paid to many issues such as the adjustment of the air volume of the combustion system and the change in the negative pressure of the drum. In order to fully and completely burn, so that the exhaust gas contains less dust, and truly realize environmental protection and energy saving.
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