JP2001162123A - Method for preventing dust deposition and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the switching failure problem of a switching damper and duct clogging problem and dioxins resynthesizing problem by preventing dust deposition in a duct of a waste gas treating device. SOLUTION: In the case when the switching damper 18 arranged near the branch part of a main duct and a branch duct for waste gas transportation is closed, a part of the clean gas after waste gas treatment from a recirculation branch duct connected to the immediate upstream part of the switching damper 18 is flowed to prevent the inflow of the waste gas to the immediate upstream part of the switching damper 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment apparatus in which a switching damper is disposed near a branch portion of an exhaust gas conveying duct, and a dust accumulation preventing method for preventing dust from accumulating in the duct and the apparatus. It is about.

[0002]

2. Description of the Related Art In the past 30 years, municipal solid wastes and industrial wastes have been mainly incinerated by incineration. Among the incineration methods, the stair stoker method,
Fluidized bed systems have become widespread and have made significant technological advances. On the other hand, the nature of these wastes has changed drastically with the improvement of lifestyles and economic activity in large urban areas. A large amount of harmful substances such as hydrogen chloride, heavy metals, dioxins, and soot have been included, so that the treatment of exhaust gas has been emphasized.

[0003] On the other hand, incineration ash and dust (dust) discharged from these incinerators also need to be reduced and made harmless, and a technique of melting and solidifying has been developed. In the incinerator ash and soot and dust melting furnaces as well, as in the case of the incinerator, harmful substances are contained in the exhaust gas, so that exhaust gas treatment is required.

[0004] In recent years, as one of a series of exhaust gas treatment methods for exhaust gas from these incinerators and melting furnaces, bag filter type dust collectors have been widely used in place of electric dust collectors which have been conventionally heavily used. It has become to. This is because, in the case of an electrostatic precipitator, there is a problem that dioxins are resynthesized therein.

[0005]

However, even in a bag filter type dust collector, for example, fly ash contained in exhaust gas from a melting furnace has a small particle size, and the fly ash attached to the filter cloth is removed. Even if dropped, the sedimentation speed is low, and in a normal online bag filter, the removed fly ash adheres again to the filter cloth, and the differential pressure of the filter cloth continues to increase. In order to avoid this, a so-called off-line removal method is adopted, in which the bag filter is divided into a plurality of dust removal chambers, and when removing attached fly ash, no gas is passed through the dust removal chamber that removes the fly ash. ing.
In some cases, a spare dust-removing chamber is prepared in case of damage to the filter cloth. However, when this off-line cleaning method is used or when the dust removal chambers are switched and used, it is necessary to provide a switching damper for preventing exhaust gas inflow at the entrance duct of each dust removal chamber. Fly ash in the exhaust gas drifts to the position immediately upstream of the switching damper and settles and accumulates, which hinders the opening / closing operation of the switching damper and, in some cases, may block the duct. is there. Further, although the temperature inside the bag filter is generally 200 ° C. or lower, there is a problem that dioxins may be resynthesized in the accumulated dust even in this temperature range.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and prevents dust from accumulating in a duct of an exhaust gas treatment device, thereby causing a problem of poor opening / closing of a switching damper and a problem of the duct. It is an object of the present invention to provide a method and an apparatus for preventing dust accumulation, which can avoid the problems of clogging and resynthesis of dioxins.

[0007]

In order to achieve the above-mentioned object, a dust accumulation preventing method according to a first invention (an invention according to claim 1) includes a branch duct provided to a main duct for conveying exhaust gas. Is connected, and a switching damper is arranged in the branch duct, and in an exhaust gas treatment device in which the branch duct is connected to a dust removal chamber for removing dust in exhaust gas, the switching damper closes the branch duct. A part of the dust-removed clean gas flows directly upstream of the valve body of the switching damper at the closed position, and flows from the closed valve body toward the main duct. Is formed.

In the first invention, when the switching damper closes the branch duct, in other words, when the gas passing through the dust removal chamber is shut off, dust is removed through the other dust removal chambers. A part of the clean gas that has been switched is caused to flow directly upstream of the damper and returned to the main duct through the non-closed (gas passing) duct, so that the exhaust gas containing dust is closed. Of the branch duct, which is located just upstream of the switching damper.

According to the first aspect of the invention, the exhaust gas containing dust is prevented from flowing into the immediately upstream portion of the closed switching damper by the clean gas, so that dust is deposited on the immediately upstream portion of the switching damper. This has the effect of avoiding problems such as hindering the opening / closing operation of the switching damper and blocking of the duct, and the problem of resynthesis of dioxins.

Next, in the dust accumulation preventing device according to the second invention (the invention according to claim 2), a branch duct is connected to a main duct for conveying exhaust gas, and a switch damper is arranged in the branch duct. In the exhaust gas treatment device having the branch duct connected to a dust removing chamber for removing dust in the exhaust gas, when the switching damper closes the branch duct, the valve body of the switching damper in the closed position is closed. A recirculation duct for flowing a part of the clean gas after passing through the dust removal chamber is connected to the upstream portion.

The second invention relates to an apparatus for embodying the dust accumulation preventing method according to the first invention,
The same operation and effect as those of the first invention are exhibited. Also,
Since a desired configuration can be achieved with a simple configuration of connecting a recirculation duct that switches a part of the clean gas after the exhaust gas treatment to flow immediately upstream of the valve element of the damper,
There is an advantage that it can be easily attached to an existing plant as well as a new plant, and its operation and maintenance are relatively easy.

[0012] In the second invention, the switching damper includes:
A three-way switching damper that opens a recirculation duct when one of the main duct and the branch duct is closed, and closes a recirculation duct when one of the main duct and the branch duct is open (The invention according to claim 3).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the method and apparatus for preventing dust accumulation according to the present invention will be described with reference to the drawings.

FIG. 1 is a front view of a bag filter device according to an embodiment of the present invention, and FIG. 2 is a left side view of the bag filter device.

The bag filter device 1 of the present embodiment is configured by arranging a plurality of (four in this embodiment) dust removal chambers 2, 3, 4, and 5 in parallel. Each of the dust removal chambers 2 to 5 is provided with a clean gas passage 8 at an upper portion by a partition wall 7 for suspending a plurality of filter cloths.
And the lower exhaust gas chamber 9, and the upper end opening of each filter cloth 6 is opened to the clean gas passage 8, so that the exhaust gas chamber 9 and the clean gas passage 8 are communicated via the filter cloth 6. I have.

The exhaust gas chamber 9 is divided into an upper filtration chamber 10 and a lower hopper chamber 11. Below the hopper chamber 11, a discharge mechanism for discharging dust separated and dropped from the filter cloth 6 is provided. A rotary valve 12 is provided.

A main duct 13 connected to, for example, an exhaust gas passage from an incinerator is disposed beside each hopper chamber 11, and a branch duct 14 branched from the main duct 13 and reaching each hopper chamber 11. , 15, 16, and 17, respectively. In addition, each branch duct 14-17
, An inlet damper (switching damper) 18 is inserted slightly downstream of the branch from the main duct 13.

On the other hand, the clean gas passages 8 of the dust removal chambers 2 to 5
Is an outlet side main duct 20 through each chamber outlet damper 19.
, And the clean gas after dust removal is discharged out of the system through the outlet main duct 20 by the action of an induced blower (not shown) provided downstream of the outlet main duct 20. A recirculation main duct 22 is disposed on the upstream side of the induction blower of the outlet side main duct 20 via a flow control damper 21. The recirculation main duct 22 is branched from the recirculation main duct 22 to each of the branch ducts 14 to 17. Recirculation branch ducts 23, 24, 25, and 26 reaching the upstream portion of the switching damper 18 are arranged. Further, a fan 27 is inserted in the recirculation main duct 22.

FIGS. 3 (a) and 3 (b) show the structure of the entrance damper 1 shown in FIG.
8 is a sectional view illustrating the structure of FIG. The inlet damper 18 is provided with branch ducts 14 to 17 installed substantially horizontally.
Shafts (rotary shafts) which are respectively disposed at connecting portions between the first and second recirculation branch ducts 23 to 26 and which are provided at corner portions of the connecting portions.
And a valve element 29 fixed to the support shaft 28 and swinging
This is a swing type switching damper constituted by:
The rotation of the support shaft 28 causes the valve body 29 to move from the branch duct 14 to
17 is closed when the recirculation branch ducts 23-2
6 is opened (FIG. 3 (b)), and the recirculation branch duct 2
When closing 3 to 26, the branch ducts 14 to 17 are used.
In an open state (FIG. 3A). When the branch ducts 14 to 17 are closed as described above, clean gas flows from the recirculating branch ducts 23 to 26 into the branch duct 1.
When the recirculation branch ducts 23 to 26 are closed, the exhaust gas is supplied to the dust removal chambers 2 to 5 through the branch ducts 14 to 17 through the main duct 13 via the upstream portions of the inlet dampers 18 of 4 to 17. You. Further, when the branch ducts 14 to 17 and the circulating branch ducts 23 to 26 are closed by the valve element 29, respectively, the downstream side of the branch ducts 14 to 17 and the inlet of the inlet damper 8 are maintained so that the closed state is maintained. Packings 30, 31 are attached to the connection side of the damper 18 and the recirculation branch ducts 23 to 26, respectively.

In the bag filter device 1 configured as described above, during a normal dust collection operation, the recirculation branch ducts 23 to 26 are closed by the inlet damper 18 and the outlet damper 19 is open. Therefore, exhaust gas flows from the main duct 13 into the dust removal chambers 2 to 5 via the branch ducts 14 to 17, and the dust removal chambers 2 to 5
The dust in the exhaust gas is removed by passing through the filter cloth 6 inside, and the clean gas is discharged out of the system through the clean gas passage 8 and the outlet side main duct 20.

In this case, the filter cloth 6 in each of the dust removal chambers 2 to 5 is used.
Since it is necessary to remove dust adhering to the off-line, usually one of the four dust-removing chambers 2 to 5 is sequentially stopped for a certain period of time, and the other three dust-removing chambers are stopped. The exhaust gas treatment is performed, and at the time of suspension, dust attached to the filter cloth 6 is removed in the suspended dust removal chamber.

For example, when the dust removal chamber 2 is stopped, the recirculation branch duct 23 is switched to the open state by the inlet damper 18 provided in the branch duct 14, and the branch duct 14 is switched to the closed state, and the operation is switched to the dust removal chamber 2. The exhaust damper 2 is stopped, and the outlet damper 19 of the dust removal chamber 2 is switched from an open state to a closed state to maintain the dust removal chamber 2 in a closed state. When the recirculation branch duct 23 is opened, a part of the clean gas passing through the outlet side main duct 20 is drawn into the recirculation main duct 22 through the flow control damper 21 by the action of the fan 27,
It is jetted from the recirculation branch duct 23 to a portion immediately upstream of the entrance damper 18 of the branch duct 14. This clean gas blows off the dust accumulated on the bottom surface immediately upstream of the inlet damper 18 of the branch duct 14, and a mixed gas of the dust and the clean gas is recirculated into the exhaust gas passing through the main duct 13 to remove other dust. It will be sent to rooms 3-5. Further, while the branch duct 14 is closed, the clean gas is continuously jetted to the branch duct 14 immediately upstream of the inlet damper 18 and returned to the main duct 13.
Exhaust gas is prevented from flowing into the branch duct 14 from the main duct 13.

The flow rate of the clean gas injected into the branch duct 14 through the recirculation branch duct 23 is controlled by the fan 2
7, it is set to about 2 m / sec or more.
It is preferable that the amount of exhaust gas flowing into each of the dust removal chambers 3 to 5 is about 1/5 to 1/10. In the case of this embodiment (when four dust chambers are provided), the amount of gas passing through each dust chamber only increases by 3 to 7%.

According to this embodiment, when the branch duct is closed, the dust deposited immediately upstream of the inlet damper is returned to the exhaust gas flowing into the main duct by using a part of the clean gas discharged outside the system. Therefore, problems such as poor opening / closing of the inlet damper and blockage of the branch duct can be solved, and resynthesis of dioxins caused by accumulated dust can be suppressed. In addition, since the equipment has a simple structure, there is no facility cost, and there is an advantage that it can be easily laid not only on a new plant but also on an existing plant, and its operation and maintenance are relatively easy. Simple and easy.

In this embodiment, the inlet damper 18 is used.
Is a swing-type switching damper, but the branch ducts 14 to 17 and the recirculation branch duct 23 are used.
A three-way switching damper having an appropriate structure can be used according to the structures of Nos. To 26.

[Brief description of the drawings]

FIG. 1 is a front view of a bag filter device according to one embodiment of the present invention.

FIG. 2 is a left side view of the bag filter device of the present embodiment.

FIGS. 3A and 3B are cross-sectional views illustrating the detailed structure and operation of an inlet damper (switching damper).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bag filter device 2-5 Dust removal room 6 Filter cloth 8 Clean gas passage 9 Exhaust gas room 10 Filtration room 11 Hopper room 13 Main duct 14-17 Branch duct 18 Inlet damper 19 Outlet damper 20 Outlet side main duct 21 Flow control damper 22 Recirculation main duct 23-26 Recirculation branch duct 27 Fan 28 Support shaft 29 Valve element 30, 31 Packing

Claims (3)

[Claims] An exhaust gas treatment system comprising: a branch duct connected to a main duct for conveying exhaust gas; a switching damper disposed in the branch duct; and the branch duct connected to a dust removal chamber for removing dust in the exhaust gas. In the device,
When the switching damper is closing the branch duct, a part of the dust-removed clean gas flows into the immediately upstream portion of the valve body of the switching damper at the closed position and is closed. A dust accumulation preventing method, comprising forming a gas flow passage extending from a valve body toward a main duct. 2. An exhaust gas treatment system comprising: a branch duct connected to a main duct for conveying exhaust gas; a switching damper disposed in the branch duct; and the branch duct connected to a dust removal chamber for removing dust in the exhaust gas. In the device,
When the switching damper is closing the branch duct, a recirculation duct for flowing a part of the clean gas after passing through the dust removal chamber is connected to a portion immediately upstream of a valve body of the switching damper at the closed position. A dust accumulation preventing device. 3. The switching damper is a three-way switching damper that opens a recirculation duct when the branch duct is closed, and closes the recirculation duct when the branch duct is opened. 3. The dust accumulation preventing device according to 2.