JP2746785B2 - How to clean bag filters - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of cleaning a bag filter, which removes adhering dust by colliding a high-pressure air pulse at a predetermined pitch with a bag filter for removing dust in a gas to be sent.

[0002]

2. Description of the Related Art A conventional dry filter provided with a bag filter and a filter cleaning device for removing dust adhering to the filter cloth of the bag filter is disclosed, for example, in JP-B-58-24.
No. 168 is disclosed. In this method, the dust-containing gas sent to each cell is sent while being filtered from the lower side of the bag filter to the upper side thereof, and is removed. The bag filter separates the inside of the cell into upper and lower chambers by a horizontal tube sheet, and a sleeve-shaped filter cloth that removes dust in gas is disposed at a plurality of openings concentrically provided on the tube sheet. It is configured.

[0003] Above the tube sheet, an injection pipe of a filter cleaning apparatus of a pulse jet type or the like is arranged.
The injection pipe has a plurality of openings formed in the tube sheet and a plurality of nozzles that can be vertically opposed to each other, is extended in the radial direction of the concentric circle, and rotates around the center of the concentric circle, A high-pressure air pulse is ejected from the nozzle at a predetermined pitch, and the air pulse collides with the filter cloth that was facing at that time, and the dust attached to the filter cloth was wiped off by the vibration. The pressure loss of the bag filter is kept below the set value.

Since the bag filter has a lower filtration rate than other filtration methods, it is necessary to increase the filtration area of the bag filter formed by the filter cloth for filtering blast furnace gas and the like. In view of the maintenance efficiency of the filter cloth, the bag filter is usually divided into a plurality of cells and arranged. For this purpose, the dust-containing gas is transported from an upstream plant such as a blast furnace by a dust-containing duct, and is distributed to each cell via a plurality of auxiliary ducts communicating with the dust-containing gas duct.

[0005]

A comparison between a cell in which dust-containing gas is taken in on the upstream side of the dust-containing gas duct and a cell in which dust-containing gas is taken in on the downstream side of the dust-containing gas duct is shown. Since the particle size of the dust in the gas taken into the latter cell is often smaller than that of the latter, the amount of dust attached to the bag filter attached to the latter cell is usually large.

As described above, the distribution and content of the particle size of the dust in the gas taken into each cell are not always the same. However, in the above-described conventional filter cleaning device, since air cells are sprayed at the same pitch to all cells for cleaning, the degree of clogging in each cell varies, and dust is removed in each bag filter. There is a problem that the performance varies, and it is difficult to maintain a constant dust collection efficiency in the dust collector.

For example, if air pulses are injected into each bag filter at the same pitch, the bag filter of the cell that takes in gas from the downstream side of the dust-containing gas duct has the bug of the cell that takes in gas from the upstream side. The filter is easily clogged as compared with the filter, and the pressure loss is likely to increase. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to maintain a constant dust removal efficiency by a bag filter.

[0008]

In order to achieve the above object, a method of cleaning a bag filter according to the present invention is directed to a dry dust collector in which a bag filter is divided into a plurality of cells and a bag filter is provided for each cell. In the bag filter cleaning method of cleaning the bag filter of each cell by injecting air pulses at a predetermined pitch to the bag filter of each cell, the air pulse for the bag filter having a pressure loss larger than a target value is provided. The injection pitch of each air pulse for the bag filter whose pressure loss is smaller than the target value is shortened in accordance with the increment of the pressure loss relative to the target value, and the injection pitch of each air pulse is set to the increment relative to the target value of the pressure loss. It is characterized in that it is lengthened accordingly.

[0009]

As described in the section "Problems to be Solved by the Invention", the bag filters attached to the cells constituting the dry dust collector are cleaned by using air pulses at the same pitch. However, the amount of dust adhering to each bag filter is different, and the pressure loss of each bag filter is different.

[0010] Then, the dust removal capability of the bag filter having a large pressure loss is reduced, and the dust collection efficiency of the dust collector as a whole is slightly reduced. In the present invention, the pressure loss is detected at any time from the differential pressure between the inlet and outlet sides of the bag filter of each cell to check whether the pressure loss is equal to or higher than the target value, and the cell in which the current pressure loss is larger than the target value Exists, the injection pitch of the air pulse to the cell is shortened in accordance with the increment of the current value with respect to the target value.

If the current value is smaller than the target value, the number of cleanings per unit is too large. Therefore, the injection pitch is lengthened in accordance with the increment of the current value with respect to the target value. The change of the pitch is preferably performed in a predetermined time unit. As a result, the pressure losses of all the bag filters approach the target values, the dust removal efficiency of each bag filter becomes constant, and the dust collection efficiency of the dust collector is kept constant.

[0012]

An embodiment of the present invention will be described with reference to the drawings.
First, the configuration will be described. As shown in FIG. 2, the dry dust collecting apparatus has eight dust collecting cells 1, and the eight dust collecting cells 1 correspond to two filter cleaning devices. Are divided into two sets of dust collecting blocks 2 arranged in a line in groups of four.

The two dust collection blocks 2 are arranged in two rows in parallel, and a duct 3 is arranged between the two dust collection blocks 2. The collected dust-containing gas is distributed to each dust collection cell 1,
The gas removed by each dust collection cell 1 is discharged. As shown in FIG. 1, the dust collection cell 1 includes a bag filter 4.
The upper chamber forms a dust-free gas chamber 1a, and the lower chamber forms a dust-containing gas chamber 1b.
The lower side of the dust-containing gas chamber 1b serves as a hopper to form a dust-collecting chamber 1c for depositing dust removed from the dust-containing gas. A differential pressure gauge 21 for measuring a differential pressure between the upper and lower two chambers 1a and 1b is set for each cell, and each differential pressure gauge 21 is connected to a controller 30. And the outlet pressure is supplied.

The dust accumulated in the dust collection chamber 1c opens the rotary valve 31 at a predetermined timing and discharges the accumulated dust from the dust collection cell 1. The bag filter 4 includes:
It is composed of a tube sheet 4a and a plurality of filter cloths.
As shown in FIG. 3 , a plurality of filter holes 4b are formed concentrically, and a sleeve-shaped or envelope-shaped filter cloth fixed to each filter hole 4b is disposed in the dust-containing gas chamber 1b. .

An injection pipe 5 is provided above the bag filter 4. The injection pipe 5 extends in the radial direction of the tube sheet 4a, and a plurality of nozzles are provided at a predetermined interval on the lower surface thereof.
b can be opposed at a predetermined interval. The injection pipe 5 is provided with a driving device including a motor and a speed reducer at an upper part, and is rotated along the upper surface of the tube sheet at a predetermined speed around the center of the tube sheet by the driving device. .

Each of the dust collection blocks 2 arranged in a line
Each injection pipe 5 installed in each of the four dust collection cells 1 constituting
Are connected by a common compressed air pipe 7 through separate injection pipe solenoid valves 6 for each dust collection block 2, and the common compressed air pipe 7 is connected to one end of a compressed air supply pipe 8 on the dust-free gas discharge side. The other end of each compressed air supply pipe 8 communicates with an individual blower 9 that supplies high pressure air.

As shown in FIG. 4 , the duct 3 is vertically divided by a partition plate 12 which is provided so as to be inclined from an upper portion of the gas inlet 10 to a lower portion of the gas outlet 11. The lower side forms a dust-containing gas duct 13 and the upper side forms a dust-free gas duct 14. Dust-containing gas duct 1
An auxiliary duct 15 is provided on the lower surface of each of the dust collection chambers 1c of each of the dust collection cells 1 so as to face the dust collection chamber 1c from the side. Dust gas chamber 1
a.

The dust-free gas duct 14 is a horizontal flat plate 1.
The gas is circulated through a gas communication port 16a provided in the flat plate 16 by being vertically divided at 6.
The upper chamber is also partitioned at the boundary of the dust collection cell 1, and the partitioned compartment is divided into two by a baffle plate 17 to be divided into a total of eight compartments.
In each of the divided rooms, a hole 18 which is a communication passage provided in one-to-one correspondence with the dust-free gas chamber 1b of the dust-collecting block 1 is provided in a side wall portion of the dust-free gas chamber 1b.

A disk 19 having a larger diameter than the gas communication port 16a is provided above the gas communication port 16a provided in the flat plate 16, and the disk 19 is connected on the upper side. The communication device 16 can be moved up and down by the cylinder device 20 so that the communication port 16a can be closed. As shown in FIG. 1, each of the solenoid valves 6 is connected to a controller 30 and opens and closes at a predetermined cycle according to a command from the controller 30. At normal times, the controller 30 controls each solenoid valve 6 for injection pipes to be opened periodically, for example, at a frequency of two or three times per minute, and controls each cell at predetermined time intervals. The differential pressure of each cell is checked from the differential pressure gauge to check if there is any fluctuation from the target value. Note that the target value has a predetermined width up and down.

In the above-described apparatus, the dust-containing gas sent from the blast furnace or the like is taken into the dust-containing gas duct 13 from the gas inlet 10 of the duct 3, and the dust-containing gas duct 13 passes through the auxiliary duct 15. The dust enters the dust-containing gas chamber 1a of each dust-collecting cell 1 via the filter, and is further sent to a dust-free gas chamber 1b after dust in the gas is removed by a filter cloth. The dust-free gas is sent to the upper chamber 22 of the dust-free gas duct 1b through the hole 18 formed in the wall portion, and further, through the gas communication port 16a opened in the flat plate 10. The gas is sent to the lower chamber 14 and discharged from the gas discharge port 11.

At this time, high-pressure air is sent from each blower 9 to each of the dust collecting blocks 2 through the compressed-air supply pipe 8 to the common-pneumatic pipe 7, that is, the inlet of the injection pipe 6 of each block 2. At this time, the injection pipe solenoid valve 6 controlled by the controller 30 is opened for a predetermined time in a predetermined time unit, for example, twice a minute, and the high-pressure air is in the open state. It is sent into the injection pipe 5 and is jetted downward through a nozzle. The jetted high-pressure air collides with the filter cloth through the filter hole 4b of the tube sheet 4a facing at that time, instantaneously vibrates the filter cloth, and removes dust adhering to the filter cloth. It is deposited in the lower dust collecting chamber 1c.

At this time, for example, if the injection pitch of the high-pressure air from each of the injection pipes 6 is all set to the same pitch, the downstream side of the dust-containing gas chamber 1a of the cell 1 on the upstream side of the duct 3 will be described. Since the dust in the gas taken into the dust-containing gas chamber 1a of the cell 1 has a small particle size, the dust is more easily deposited on the bag filter 4 in the cell 1 on the downstream side, and the bag filter 4 on the downstream side is Becomes larger than the target value.

In this embodiment, when the pressure loss of the bag filter becomes large as described above, the controller 30 inputs the pressure from the differential pressure gauge 21 which measures the differential pressure between the inlet and the outlet of the bag filter 4. Recognizing that the pressure loss has increased from the value fluctuation, the opening / closing pitch of the solenoid valve 6 corresponding to the increment is set earlier than the set value. As a result, the cleaning of the bag filter 4 of the cell 1 on the downstream side per unit time is increased, the clogging of the bag filter 4 is reduced, the pressure loss is reduced, and the dust removal processing capability of the bag filter 4 is reduced to the target value. Is returned to.

If there is a bag filter 4 in which the pressure loss is smaller than the set value, the controller 3
0 recognizes this by the input value from the differential pressure gauge 21 and lengthens the injection pitch to the air pulse from the injection tube 6 in accordance with the increment to the set value of the pressure loss, and thus the unit per unit for the bag filter. Reduce the number of washings. As a result, only the pressure loss of the specific bag filter 4 is increased and the dust removing ability of the specific bag filter 4 is reduced, or only the pressure loss of the specific bag filter 4 is reduced and the gas suction degree of the specific bag filter 4 is increased. As a result, the gas intake of each cell becomes unstable, and the dust removal efficiency of each bag filter 4 is fed back to a predetermined value.
The dust collection efficiency of the dust collector provided with the plurality of bag filters 4 is kept constant.

In the above embodiment, the injection pitch is changed for each bag filter 4. However, the upstream two units in which the particle size of the dust in the taken-in gas is coarse and the particle size of the dust in the gas are small. Control may be performed such that the injection pitch is changed for each group by performing grouping on two groups on the downstream side or the like and grouping the injection pipes 5 facing left and right of two pairs of filter cleaning devices. Absent.

[0026]

As described above, according to the bag filter cleaning method of the present invention, the dust collection efficiency of the dry dust collector is kept constant since the dust removal processing capacity of each cell is always kept constant. There is an effect that it can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a dry dust collector and a filter cleaning device thereof according to an embodiment of the present invention.

FIG. 2 is a top view of the dry dust collector according to the embodiment of the present invention.

FIG. 3 is a view showing a tube sheet according to an embodiment of the present invention.

FIG. 4 is a side sectional view showing a duct of the dry dust collector according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dust collection cell 1a Dust-free gas chamber 1b Dust-containing gas chamber 2 Dust collection block 4 Bag filter 5 Injection pipe 6 Solenoid valve for injection pipe 7 Compressed air common pipe 8 Compressed air supply pipe 9 Blower 21 Differential pressure gauge 30 Controller

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B01D 46/02-46/04 B01D 46/42-42/46

Claims (1)

(57) [Claims] An air pulse is sprayed at a predetermined pitch to each bag filter to remove dust adhering to the bag filter to a dry dust collector in which a plurality of cells are defined and a bag filter is provided for each cell. In the method of cleaning a bag filter to be washed off, an injection pitch of an air pulse for a bag filter having a pressure loss greater than a target value is shortened in accordance with an increment of the pressure loss to a target value, and the pressure loss is reduced to a target value. A method for cleaning a bag filter, characterized in that the injection pitch of an air pulse to a bag filter which is smaller than the above is increased in accordance with an increment with respect to a target value of a pressure loss.