JP5446125B2 - Method for spraying coating agent of air filter and air filtering device - Google Patents

Description

  The present invention relates to a coating agent spraying method for a filter cloth in an air filter for filtering dust and the like in the air, and an air filtering device for realizing the method.

  For example, when air is sent to a blast furnace in an ironworks, high-pressure air is sent via a compressor. At this time, when a compressor that sucks in air and compresses and feeds air into the atmosphere containing dust, the blades are significantly worn by the dust. Therefore, it is necessary to install an air filter on the suction side in order to sufficiently remove dust from the air sent to the compressor.

  An air filter is a device that removes predetermined components from air by passing air such as air or exhaust gas through a filter formed of felt or cloth. That is, normally, air is introduced from the lower portion, and when the air passes through the filter, dust and predetermined components in the air adhere to the filter, thereby purifying the air. The purified clean gas is discharged to the outside from the upper part of the air filter.

  When the air filter is used for a long time, dust gradually adheres to the filter and the differential pressure increases. When the differential pressure increases, the suction force of the compressor decreases, and unnecessary power is required. Therefore, when the differential pressure reaches a predetermined value or periodically, high pressure air is sent into the filter to perform cleaning called backwashing. Thereby, the dust adhering to the filter is shaken down to recover the differential pressure. A hopper is formed in the lower part of the air filter. When a predetermined amount or more of dust is accumulated in the hopper, the dust is discharged from the discharge port at the lower end of the hopper.

  In general, a filter cloth used as a filter does not have a sufficient dust removing ability even when used as it is in a new state. In the initial use, dust in the atmosphere is attached to the filter cloth, so that the attached dust itself has the function of a filter and exhibits the function of the original filter. However, if a new filter cloth is used as it is, dust will penetrate deeply into the filter cloth and will not peel off sufficiently during backwashing, so the differential pressure will not recover even after backwashing, and it is necessary to replace the filter cloth as soon as possible. It may become.

  For this reason, conventionally, a new filter cloth is sprayed with a coating agent made of powder such as diatomaceous earth or calcium carbonate to give a filter function. As a spraying method, a coating agent is sometimes manually applied to an existing filter cloth. For example, it is a heavy labor to manually add several hundred kg of powder. In addition, the same work is required every time backwashing or filter cloth replacement is performed. Further, it is extremely difficult to apply the coating agent uniformly to the filter cloth by human power, and a sufficient coating effect cannot be obtained with non-uniform adhesion. Therefore, in order to attach a sufficient amount of the coating agent to the entire filter cloth, an amount of powder more than necessary is required, which is uneconomical.

  On the other hand, in Patent Document 1, for example, a breathable base material is impregnated with a dispersion liquid containing a powder having a function as a catalyst and polytetrafluoroethylene (PTFE) in advance and heated to a temperature equal to or higher than the melting point of PTFE. Thus, by integrating the powder with a breathable base material, a bag filter is disclosed in which the powder does not easily fall off even if backwashed and the effect of a catalyst or the like can be maintained for a long time.

  Patent Document 2 discloses a filter membrane maintenance method in which an annular release agent injection pipe is installed for each filter cloth and a release agent such as diatomaceous earth or calcium carbonate is sprayed on the filter cloth.

JP 2001-54707 A JP 11-99322 A

  However, the filter disclosed in Patent Document 1 is used for a high-performance bag filter having a catalytic function, and the manufacturing cost required for chemicals and heat treatment is extremely high. In addition, the filter is periodically replaced, and using such an expensive filter increases the running cost.

  Moreover, in the case of the said patent document 2, since a peeling agent injection pipe is installed in the circumference | surroundings for each filter cloth, a structure is complicated. In addition, a large volume of air filter usually has an extremely large number of hundreds of filter cloths arranged at a narrow interval, and if a release agent injection pipe is installed for each filter cloth, there is little space. This hinders the flow of air to be processed and causes an increase in differential pressure. Furthermore, since the gap between the spray hole of the release agent injection tube and the filter cloth is narrow, a large amount of release agent adheres near the injection hole, but only a small amount adheres at a position away from the injection hole. Variations in the amount of release agent attached in the vertical direction. In addition, the adjustment of a large amount of release agent spray pipe provided for each filter cloth is extremely troublesome, and the filter cloth and the release agent spray pipe are installed at a narrow interval. It is difficult to perform maintenance work.

  An object of the present invention is to provide a coating agent spraying method and apparatus for an air filter capable of enhancing a filter effect and allowing a coating agent that easily peels off during backwashing to adhere uniformly to a filter cloth at low cost. is there.

In order to solve the above problems, the present invention is a method of spraying a coating agent on an air filter that removes dust in the air introduced from the atmosphere by attaching it to a filter cloth and supplies clean gas to a compressor for a blast furnace. , spraying a portion of the compressed air emitted from the compressor, flows with powdery coating material into the air filtration vessel, from the upstream side of the process air, wherein the treated filter cloth of the lower or the air filter Then, the coating agent is applied to the surface of the filter cloth by being piggybacked on the flow of the processing air, and a coating agent spraying method for an air filter is provided. The coating agent naturally rides on the filter cloth in the flow of processing air, and the part where the coating agent adheres less has a lower differential pressure than the part where the coating agent adheres much, so the amount adhering naturally is small. The amount of adhesion to the part increases, and it can adhere uniformly to the entire filter cloth.

Further, the air used for spraying the coating agent is through a compressor and is dried at a high temperature, so that the coating agent does not absorb moisture and solidify. Therefore, it is possible to prevent clogging of the pipe that conveys the coating agent. Therefore, it is not necessary to provide a new air dehumidifier or the like for supplying the coating agent, and this can be realized at a low cost.

  It is preferable to stop supplying the coating agent when the differential pressure reaches a predetermined value. By determining the spraying stop of the coating agent based on the differential pressure, the timing of the spraying stop can be grasped quantitatively, so that excessive spraying can be prevented and unnecessary cost is saved.

  Even when the coating agent is not sprayed, it is preferable to always flow a small amount of air into the air filter. By constantly flowing air, it is possible to prevent the sprayed portion of the coating agent from being clogged by dust that has peeled off during backwashing.

Further, according to the present invention, an air filtration device for removing dust in the air introduced from the atmosphere by adhering to the filter cloth and supplying clean gas to the compressor for the blast furnace , the filter cloth is provided inside. An air filter, an air carrier pipe branched from a main pipe through which the compressed air discharged from the compressor passes, a powder carrier pipe that conveys a powdery coating agent and joins the air carrier pipe, and the air Connected to the tip of the transport pipe and disposed in the air filter below the filter cloth or upstream of the processing air to be processed by the air filter, and a spray port for spraying the coating agent was formed. And an air filtering device. Thereby, it can implement with a simple structure using the compressor which is an existing apparatus. In addition, since the spray tube is installed at a position away from the filter cloth, maintenance work such as investigation of spray port clogging and replacement of the filter cloth can be easily performed.

  Further, valves are provided in the air conveyance pipe and the powder conveyance pipe, respectively, and the flow rates of air and the coating agent are adjusted by controlling the opening and closing and the opening degree of the valves. By controlling the valve, the release amount of air and coating agent can be automatically adjusted, and the work burden is greatly reduced.

  According to the present invention, it is possible to disperse the coating agent uniformly and in an appropriate amount on the filter cloth with a simple structure and less work load. Therefore, it is not necessary to spray a useless coating agent, and a filter cloth subjected to a special treatment is unnecessary, so that it can be carried out at a low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an overall configuration of an air filter according to the present invention.

  The air filter 2 has a prismatic housing 3 at the top, and a quadrangular pyramid hopper portion 4 is formed below the housing 3 at the bottom. On the side wall of the housing 3, an air inlet 6 is formed through which air containing dust and the like flows into the air intake chamber 5 of the housing 3. At the upper part of the housing 3, there is provided a discharge port 8 for sending clean gas purified by filtering dust from the discharge chamber 7 to the outside. The discharge port 8 is connected to the discharge duct 9, and the clean gas is sent from the discharge duct 9 to the compressor 10.

  A plurality of filter cloths 11 are disposed inside the housing 3. The filter cloth 11 is formed of a chemical fiber, for example, and has a cylindrical shape in which only the upper part is opened. The air that has flowed into the intake chamber 5 passes through the filter cloth 11 so that dust and the like are filtered. The upper end of the filter cloth 11 is suspended from a beam 12 installed in the housing 2 in the horizontal direction.

  In the housing 3, a mechanism for backwashing is provided for removing dust adhering to the filter cloth 11. As a specific embodiment, for example, an air pipe (not shown) is disposed above the filter cloth 11, and an injection valve directed to the upper opening of each filter cloth 11 is provided on the air pipe. High-pressure air is sprayed from the upper opening of 11 toward the inside of the filter cloth 11. The dust adhering to the outside of the filter cloth 11 is removed by the impact force. The backwashing mechanism is not limited to this method.

  At the lower end of the hopper portion 4, a discharge port 14 having a discharge valve 13 for discharging dust that has been wiped out to the outside is provided.

  Next, the coating agent spraying mechanism will be described.

  In the intake chamber 5 in which a plurality of filter cloths 11 are provided, a spray pipe 22 having a plurality of spray ports 21 is disposed below the filter cloth 11. The spraying port 21 is formed in a size that allows the powdery coating agent to pass smoothly, and is disposed at a position where the coating agent can be uniformly sprayed on all the filter cloths 11 in the intake chamber 5.

  An air conveyance pipe 32 is provided by branching from the middle of the main pipe 31 through which the compressed air sent from the compressor 10 passes. The front end of the air conveyance pipe 32 is branched into a plurality, for example, four, and is connected to the spray pipe 22. An air extraction valve 33 having a pressure adjusting function is provided upstream of the air conveyance pipe 32, that is, near the main pipe 31. Further, one air supply valve 34 having a pressure adjusting function is provided in each branch portion near the inlet of the spray pipe 22 branched from the air transport pipe 32. FIG. 2 is a plan view showing an example of the spray tube 22. A plurality of spray ports 21 are formed over the entire plane of the housing 3. Further, the flow rate of each area obtained by dividing the spray tube 22 into four parts is controlled by the air supply valves 34a, 34b, 34c, and 34d.

  A powder coating agent 42 is accommodated in the powder storage unit 41. As the coating agent 42, for example, calcium carbonate having a particle size of about several tens to several hundreds of μm is used. Other calcium powders and diatomaceous earth may be used. However, a material having high hygroscopicity is not preferable because it hardens due to humidity in the air and causes the spray port 21 to be clogged. The powder storage unit 41 is connected to the air conveyance pipe 32 via the powder conveyance pipe 43, and a powder supply valve 44 having a blocking function is provided in the middle of the powder conveyance pipe 43.

  The opening degree and opening / closing of the air extraction valve 33, the air supply valve 34, and the powder supply valve 44 are determined by a valve opening signal and a valve opening / closing signal from the control unit 45.

  Next, a procedure for spraying the coating agent 42 onto the filter cloth 11 by the air filtration device having the above configuration will be described.

  When the operation of the compressor 10 and the air filter 2 is started or immediately after the initial activation after replacement of the filter cloth 11, when the powder spray switch 46 is pressed, the air extraction valve 33 and the air are automatically turned on by a signal from the control unit 45. The supply valve 34 and the powder supply valve 44 are opened. Thereby, a part of the initial compressed air sent from the compressor 10 flows into the air conveyance pipe 32, and at the same time, the coating agent 42 flows from the powder storage unit 41 to the powder conveyance pipe 43. The coating agent 42 is transported by the air flowing through the air transport pipe 32, and the coating agent 42 is sprayed from the spray port 21 of the spray pipe 22. The opening degree of each of the plurality of air supply valves 34 is set in advance so that the coating agent 42 is uniformly discharged from each spray port 21. Alternatively, an orifice may be installed in the spray tube 22 and the flow rate may be adjusted by the orifice. By adopting such a configuration, the work burden is extremely reduced.

  Based on the pressure signal from the pressure gauge 48 provided in the discharge chamber 7 of the air filter 2 and the pressure signal from the pressure gauge 49 provided in the intake chamber 5, the control unit 45 calculates the differential pressure. When the differential pressure exceeds a specified value, or when the level switch 47 installed in the powder storage unit 41 is activated and the level signal of the coating agent 42 enters the control unit 45, the coating agent 42 is dispersed. It is determined that the powder supply valve 44 is complete and the powder supply valve 44 is closed. Even after the spraying of the coating agent 42 is completed, the air extraction valve 33 and the air supply valve 34 are slightly opened so that a small amount of air is released from the spray port 21. This prevents the dust that has fallen off when the filter cloth 11 is backwashed from being clogged in the spray port 21.

  In the present embodiment, the air that conveys the coating agent 42 is branched from the main pipe 31 and is about 240 ° C. to 250 ° C. processed by the compressor 10. In addition, a dehumidifying device is usually provided between the discharge port 8 and the compressor 10, and the air passing through the main pipe 31 is dry air. Therefore, the coating agent 42 absorbs moisture and hardens, and the spray port 21 is unlikely to be clogged.

In addition, since a part of the air of about 9000 Nm ³ / min flowing through the main pipe 31 is used as the conveying air for the coating agent 42, no equipment for producing new compressed air is required. In the present invention, among the flow rate of, for example, 5 kg / cm ² approximately through the main pipe 31, since the flow to the air transport pipe 32 is small portion and 0.1 kg / cm ² about for the coating material 42 sprayed Does not affect the air flow to the blast furnace.

  Furthermore, according to the present invention, the spray tube 22 is installed at a position away from the filter cloth 11, and no apparatus is installed around the filter cloth 11, so that the flow of the processing air is not hindered. Moreover, it is easy to replace the filter cloth 11 and inspect the spray tube 22.

  Moreover, you may arrange | position the spreading | diffusion pipe | tube 22 in the position of the inlet 6 of the air filter 2 side as shown with a dotted line in FIG. As described above, when the spraying position of the coating agent 42 is set upstream of the processing air by the air filter 2, the sprayed coating agent 42 rides on the flow of the processing air and naturally adheres to the filter cloth 11.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  For example, in the above-described embodiment, the air filter that sucks the atmosphere and sends the processing air to the compressor has been described. However, the bag filter that sucks the exhaust gas and discharges the processing air to the outside is similarly implemented. Is possible. In the case where the main pipe through which the compressed air flows is not provided, a dry air blowing device required for spraying the coating agent may be separately provided.

  The present invention can be applied to an air filtration device used by attaching a coating agent to a filter cloth.

The schematic block diagram which shows the air filtration apparatus concerning this invention. FIG. 2 is a plan view of the spray tube of FIG. 1.

Explanation of symbols

2 Air filter 5 Intake chamber 6 Intake port 7 Discharge chamber 8 Discharge port 10 Compressor 11 Filter cloth 21 Spreading port 22 Dispersion pipe 31 Main pipe 32 Air conveyance pipe 33 Air extraction valve 34 Air supply valve 41 Powder storage part 42 Coating Agent 43 Powder Supply Pipe 44 Powder Transfer Valve 45 Control Unit

Claims (5)

It is a method of spraying a coating agent for an air filter that removes dust in the air introduced from the atmosphere by adhering it to the filter cloth and supplies clean gas to the compressor for the blast furnace ,
The part of the compressed air emitted from said compressor, together with the powdery coating material flowing to the air filter in, sprayed from the upstream side of the process air, wherein the treated filter cloth of the lower or the air filter And
A coating agent spraying method for an air filter, wherein the coating agent is piggybacked on the flow of the processing air and adhered to the surface of the filter cloth.   The method of claim 1, wherein the supply of the coating agent is stopped when the differential pressure reaches a predetermined value.   The method of spraying a coating agent for an air filter according to claim 1 or 2, wherein a small amount of air is always allowed to flow into the air filter even when the coating agent is not sprayed. An air filtration device for removing dust in the air introduced from the atmosphere by attaching it to a filter cloth and supplying clean gas to a compressor for a blast furnace ,
An air filter with a filter cloth inside;
An air conveyance pipe branched from a main pipe through which compressed air discharged from the compressor passes;
A powder conveying pipe that conveys a powdery coating agent and joins the air conveying pipe;
A spray port is formed which is connected to the tip of the air conveyance pipe and is disposed below the filter cloth or upstream of the processing air to be processed by the air filter in the air filter and sprays the coating agent. Sprayed tube,
An air filtration device comprising:   The air transport pipe and the powder transport pipe are each provided with a valve, and the flow rate of air and the coating agent is adjusted by controlling the opening and closing and the opening degree of each valve. 4. The air filtration device according to 4.

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