JP3136062B2 - Method for forming precoat layer of bag filter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bag filter device for separating, removing or recovering acidic harmful gas and dust, suspended matter, and the like from a gas stream.

[0002]

2. Description of the Related Art Among the types of bag filter devices currently in practical use, the most widely used type is a filter cloth which is made to carry out a chemical for neutralizing and filtering an acid gas with a combustion gas. A multi-chamber structure applied to a refuse incinerator, in which a dust layer consisting of chemicals and dust, etc., deposited on the filter cloth while flying continuously with the operation and continuation of operation, is removed by a pulse jet method. This type of method will be described as a typical example of the prior art.

FIG. 8 is a view schematically showing a bag filter device conventionally used.

[0004] In FIG. 8, a high-temperature combustion gas including an acidic harmful gas and dust generated in an incinerator (not shown) is cooled by a gas cooling device or the like (not shown) and then enters the pre-absorption reaction section a. Inside the pre-absorption reaction section a, a supply section b for injecting a medicine absorbing the acidic harmful gas is provided.

This medicine is stored in a medicine storage tank c, is cut out by a fixed amount supply device d installed below the medicine storage tank c, and is pneumatically conveyed to the supply section b by a suction blower e. .

[0006] Inside the pre-absorption reaction section a, the medicine continuously supplied from the supply section b reacts to some extent with the acidic harmful gas in the combustion gas, but most of the medicine remains unreacted. Enter f.

That is, the combustion gas entering the bag filter device f contains some reaction products and most unreacted chemicals, together with the acidic harmful gas and dust generated in the incinerator. .

The soot and reaction products and unreacted chemicals in the combustion gas are stored in a filtration chamber f1 of a plurality of unit dust collecting mechanisms (only one chamber is shown in the figure) constituting a multi-chamber bag filter device f. It is filtered by a plurality of suspended filter cloths f2, adheres to the surface of the filter cloth f2, forms a dust layer, and grows gradually.

On the other hand, the acidic harmful gas contained in the combustion gas causes a second-stage absorption reaction with the unreacted drug in the dust layer,
Combined with the above-mentioned filtration work, the combustion gas that has passed through the filter cloth portion becomes a clean gas, and is introduced from the clean gas chamber f3 to the induction ventilator g.
And discharged into the atmosphere from the chimney h.

When the above-described operation is continued, due to the accumulation of the flying chemicals and soot, the airflow resistance of the dust layer gradually increases, and it becomes difficult for the combustion gas to pass.

Therefore, for each row of a plurality of filter cloths f2 constituting a plurality of unit dust collecting mechanisms, a pulse from the sweeping-off apparatus j is supplied during the gas passage according to a command of the control apparatus i according to a predetermined order and interval. Jetting a jet stream to separate the dust layer is a common measure.

The differential pressure between the inside and outside of the filter cloth f2 is detected by a differential pressure detector k.
If the differential pressure exceeds the set value,
There is also a method of initiating intermittent dropping for each row of the plurality of filter cloths f2, and in any case, the dust that has peeled and dropped, that is, the collected ash, is discharged to the outside from the hopper f4 by the discharge device f5. It has been made like that.

Further, there is a case where the concentration of the acidic harmful gas at the outlet of the clean gas chamber f3 is detected by the analyzer m, and the supply amount of the medicine by the quantitative supply device d is adjusted by a command from the control device i.

[0014]

However, according to the above-mentioned conventional method, the main components of acid gas neutralization and dust filtration are the dust layer formed by the continuously flying chemicals and dust, so that the bag filter device f The processing performance will gradually improve over time during operation.

[0015] Therefore, the unit dust collection mechanism immediately after the payment is
Not only the dust layer is not formed, and there is no neutralization / filtration ability, but also low ventilation resistance, so a large amount of combustion gas flows in and a large amount of untreated gas is discharged.

That is, due to the partial shortage of the processing capacity, the processing capacity of the entire bag filter device f is reduced, causing pollution.
It was a general measure to form a dust layer at an early stage by continuously injecting a large amount of a drug as many as five.

As a result, an increase in the dust layer due to unreacted chemicals is promoted, the rise in airflow resistance is accelerated, the interval between wiping offs is shortened, and the life of the filter cloth f2 is shortened.

The filtration speed on the surface of the filter cloth f2 is
In general, since the gas flow rate in the flue is extremely slow, about 1/1000, when the amount of combustion gas is reduced, a large amount of accompanying chemicals becomes stall as soon as it flows into the filtration chamber f1, and the induced draft Even if suction is performed with g, a part of the gas may be separated from the combustion gas and fall into the hopper f4 before reaching the surface of the filter cloth f2.

Due to the oversupply and the drop phenomenon described above,
Not only does the cost of chemicals increase, but it also increases the amount of collected ash (discharged ash) designated as "special waste" because it contains harmful substances such as heavy metals and dioxins. Was causing an increase.

Furthermore, in order to promote the neutralization reaction of the medicine, in the case of FIG. 8 in which the pre-absorption reaction part a is provided, the amount of medicine used and the amount of ash discharged are reduced, but the installation area is increased. There was a problem that the equipment cost was high.

Further, since the wiping operation is performed during the passage of gas, the neutralized flakes are scattered again and re-adhered to the surface of the filter cloth f2 to reduce the processing efficiency and shorten the wiping interval. There was also the problem of bringing.

Therefore, in order to solve these problems, a pre-coat type bag filter device in which a pre-coat layer is formed on the surface of a filter cloth before performing a filtering operation is used. "Control method of bag filter device (Japanese Patent Laid-Open No. 5-123515)" by the present applicant
(Hereinafter referred to as prior application) has been proposed.

FIG. 9 shows an outline of the prior application. The same members as those of the above-described bag filter device are denoted by the same reference numerals, and description thereof will be omitted.

This bag filter device f is also a multi-chamber type and comprises a plurality of unit dust collecting mechanisms (only one room is shown in the figure), and is controlled by a control device i in a manner similar to that described above according to a predetermined method. Perform the payoff and discharge operations.

However, the start of the removal of the first unit dust collecting mechanism is also the time when both the pressure difference between the inside and outside of the filter cloth f2 and the concentration of the acidic harmful gas exceed the set values, that is, when the neutralization reaction is completed. After closing the dampers s provided for each dust mechanism, all the rows of the filter cloth f2 in the mechanism are continuously removed.

After the dropping operation is completed, the control valve v exclusive to the unit dust collecting mechanism is opened, the medicine is transported from the medicine storage tank c by air and blown into the hopper f4, and the surface of the filter cloth f2 in the filtration chamber f1 is removed. After the precoat layer is formed, the damper s is opened to return to a normal filtration operation, the next unit dust collection mechanism is removed, and then the operation proceeds to the precoat layer formation operation.

By the above-mentioned operation, since the precoat layer of the chemical is formed on the surface of the filter cloth f2 of each unit dust collecting mechanism from the beginning, a decrease in the processing capacity immediately after the removal is not caused, and the pre-absorption is performed. Even if the reaction part a is not installed, high efficiency can be always exhibited.

Further, since the precoat layer formed after the neutralization reaction is completed and the attached dust layer are removed, an increase in ash discharged due to unreacted chemicals can be prevented, and there is no need to supply an excessive amount of chemicals. For this reason, the rate of increase of the ventilation resistance is reduced, and the interval between wiping offs is widened, so that the life of the filter cloth f2 can be extended.

However, the chemical transport is not the exhaust gas entrainment method by blowing the flue gas, but the air transport directly into each unit dust collection mechanism. In addition to increasing the amount of air for use and the pressure, it was necessary to add air blowing to the location where the medicine was retained, and the amount of exhaust gas was unnecessarily increased.

Further, the low-temperature air for transporting the chemical is directly blown into the hopper f4 of each unit dust collecting mechanism, and rises to the filtration chamber f1 together with the combustion gas blown into the hopper f4. The air cannot be mixed well, and the air reaches the surface of the filter cloth f2 without increasing the temperature.

Therefore, the part where the low-temperature air is predominant results in the condensation of the moisture in the medium-temperature combustion gas to fix the chemicals on the filter cloth f2, resulting in instability of the processing performance due to insufficient dispensing and an increase in the number of dispensing. , The life of the filter cloth f2 is reduced.

[0032]

A method for forming a precoat layer of a bag filter device according to the present invention has a plurality of unit dust collecting mechanisms, and forms a precoat layer on a filter cloth surface before performing a filtering operation. The method for forming a pre-coat layer of an apparatus, wherein the operation of removing the pre-coat layer is performed in a scheduled order with each unit dust collecting mechanism being in a gas stopped state, and the remaining unit dust collecting mechanism in the gas passing is removed. Supplies the chemicals by the reduced operation, and the growth / formation operation of the pre-coat layer after the removal operation of all the unit dust collection mechanisms is completed, supplies the medicine to all the unit dust collection mechanisms at once and finishes The medicine is not supplied until the next drop-off operation.

[0033]

The removal operation of the pre-coat layer is performed in a predetermined order in a state where the gas is stopped for each unit dust collecting mechanism, and the remaining unit dust collecting mechanism in the gas passing is supplied with the medicine by the reduced operation. While performing, the cleaning operation of all unit dust collecting mechanisms is completed, and the subsequent growth and formation operation of the pre-coat layer is performed by supplying the chemicals to all the unit dust collecting mechanisms at once, and the pre-coat layer is formed in a short time. By forming, without supplying the medicine until the next dispensing operation,
The combustion gas is passed through to neutralize the acidic harmful gas contained and to filter the soot and dust.

[0034]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of a bag filter device in which the method for forming a precoat layer of a bag filter device according to the present invention is performed.

In FIG. 1, reference numeral 1 denotes a gas cooling system for cooling a high-temperature combustion gas including an acidic harmful gas and dust generated in an incinerator (not shown). Then, the air is sucked, passes through the main flue 4 and the branch flue 41, and individually flows into a plurality of unit dust collecting mechanisms constituting the bag filter device 5.

Each of these unit dust collecting mechanisms includes a plurality of filter cloths 6.
, A hopper chamber 52 and a discharge device 53 connected below the filtration chamber 51, and a common dropping device 54 inside and a clean gas damper 55 outside. A clean gas chamber 56 is provided.

The plurality of clean gas dampers 55 are connected to the induction ventilator 3 and a chimney (not shown) via a branch duct 71 and a common clean gas duct 7.

The clean gas duct 7 has an acid harmful gas concentration meter 81, a clean gas flow meter 82, and a bag filter device 5.
A differential pressure gauge 83 for measuring the differential pressure between the entrance and exit of the vehicle is provided. Each of the measuring devices 81, 82, and 83 is connected to the control device 8 including various control devices in addition to the timer device 84.

Reference numeral 9 denotes a harmful gas removing device, which is a chemical storage tank 92 for storing a chemical 91 for neutralizing acidic harmful gas, and a powder pump 93 capable of variable speed operation for discharging and transporting the chemical 91.
And a drug transport pipe 94, and the drug transport pipe 9
4 is communicated in the middle of the flue 4.

Next, the operation control procedure when the precoat layer forming method of the present invention is carried out by the bag filter device configured as described above is changed from the precoat layer forming operation to the ordinary “acid neutralizing harmful gas neutralization and particulate filtration”. Each operation that leads to the precoat layer forming operation after the wiping-out operation through the “operation (hereinafter, simply referred to as a filtration operation)” will be described.

FIG. 2 shows the state of adhesion of the surface of the filter cloth 6 during the filtering operation, FIG. 3 shows the procedure of the precoat layer forming operation, and FIG. 4 shows the procedure of the filtering operation and the removing operation.

First, the precoat layer forming operation is shown in FIG.
This will be described with reference to FIGS.

In step S1, when all of the clean gas dampers 55 attached to the plurality of unit dust collecting mechanisms are opened, the medium-temperature combustion gas 21 including the acidic harmful gas and the dust passes through the flue 4 and passes through each branch. The air flows into each unit dust collecting mechanism of the bag filter device 5 via the flue 41, rises in the hopper chamber 52, and reaches the surface of the plurality of filter cloths 6 suspended in the filtration chamber 51.

At the beginning of the operation, the outer surface of the filter cloth 6 is sprayed with a chemical 91 in advance to form a bridge with the bulky thread portion of the filter cloth main body 61, so that the outer surface of the filter cloth 6 does not peel off even if a later-described wiping operation is performed. It is covered with the initial adhesion layer 62 (see FIG. 2).

Here, the combustion gas 2 reaching the surface of the filter cloth 6
1 passes through the above-mentioned initial adhesion layer 62 and the filter cloth main body 61 (step S2) and is filtered to become the clean gas 22, and the clean gas chamber 56, the clean gas damper 55, and the branch duct 71
Through the clean gas duct 7.

Therefore, the flow rate of the clean gas 22 is measured by the clean gas flow meter 82 provided in the clean gas duct 7 (step S3), and it is determined whether the flow rate is equal to or more than the amount (set value) sufficient to transport the medicine 91. It is determined whether or not it is sufficient (step S4). If it is sufficient, the process proceeds to step S5. If it is within the set value in step S4, a part of the clean gas dampers 55 of the plurality of unit dust collecting mechanisms are removed in step S6. Close and return to step S3.

In step S5, the combustion gas 21 flows into each unit dust collecting mechanism with the clean gas damper 55 opened.

Then, in step S7, the powder pump 93 is activated to cut out the medicine 91 from the medicine storage tank 92 and send the medicine 91 into the flue 4 via the medicine transport pipe 94. Thereby, the medicine 91
Is mixed with the medium-temperature combustion gas 21 to form a mixed gas 23, enters the unit dust collecting mechanism while being stirred and heated in the flue 4, and reaches the surface of the initial adhesion layer 62 of each filter cloth 6. (Step S8).

If this operation is continued, the mixed gas 23
In a dry state that does not condense water, it reaches the surface of the initially adhered layer 62, is filtered, and grows as a drug layer mixed with a small amount of soot to form the precoat layer 63 (step S9).

Next, in step S10, it is determined whether or not a precoat layer has been formed on all unit dust collecting mechanisms. This determination is made based on the amount of the processing gas and the removal rate of the acidic harmful gas, and the like.
The operation time of No. 3 is measured by the timer device 84, and when this time has elapsed, it is considered that the precoat layer has been formed on all the unit dust collecting mechanisms. When a part of the clean gas damper 55 is closed in step S6, the setting is made in consideration of this situation.

When the pre-coat layer 63 is formed by all the unit dust collecting mechanisms in this way, the process proceeds to step S11,
The powder pump 93 is stopped.

Next, the filtering operation and the removing operation performed after the above-described precoat layer forming operation will be described with reference to FIGS. 1, 2 and 4. FIG.

The filter cloth 6 on which the precoat layer has been formed as described above.
The normal filtration operation is performed by passing the combustion gas 21 through (step S12). Here, the combustion gas 21
Dust mixed therein is filtered and deposited on the surface of the precoat layer 63 to form a dust layer 64, and the acidic harmful gas contained therein also causes a neutralization reaction with the chemical 91 forming the precoat layer 63. (Step S13), it becomes a neutral gas. That is, by passing through the filter cloth 6, the combustion gas 21 becomes the clean gas 22 and is discharged to the clean gas chamber 56.

By continuing the passage of the gas, the dust layer 64 gradually grows, increasing the ventilation resistance of the combustion gas 21 and increasing the load on the induction ventilator 3.

Then, the differential pressure gauge 83 detects the differential pressure before and after the bag filter device 5 (step S14), and compares whether the unit time average of the differential pressure is within a set value (step S15). If it exceeds, the process proceeds to step S18, and if it is lower, the process proceeds to step S17 described below.

At the same time, the acid harmful gas concentration meter 81
The unit time average concentration of the clean gas 22 is detected (step S16) and compared with the set value (step S17). If it is low, the process returns to step S14 to continue the operation. If it is high, the process proceeds to the next step S18.

Next, in step S18, it is determined whether or not the withdrawal condition is satisfied, that is, whether or not both the differential pressure and the average value of the concentration per unit time have exceeded the set values.
When the pay-off condition is satisfied, the following pay-off operation is performed in order from the first unit dust collecting mechanism to the last unit dust collecting mechanism according to a command of the control device 8 in accordance with a preset order.

More specifically, first, the clean gas damper 55 of the first unit dust collecting mechanism is closed (step S1).
9) The pre-coat layer 63 and the dust layer 64 are removed from the surface of the initially adhered layer 62 by injecting a pulse jet airflow into the filter cloth 6 by the removing device 54 to cause the clean gas 22 to flow back into the filter cloth 6. Peel off (Step S2
0). At this time, the clean gas damper 55 is closed,
Since the combustion gas 21 has not flowed, the exfoliated ash falls into the hopper chamber 52 without being scattered again.

The falling off ash (collected ash) is discharged by the discharging device 53.
(Step S2) by opening the clean gas damper 55 of the head unit dust collection mechanism
1), the first unit dust collecting mechanism is in the initial gas passing state (step S22).

Subsequently, the supply of the medicine 91 is reduced by operating the variable speed powder pump 93 at a low speed (step S2).
3) In the next unit dust collecting mechanism, a pay-off operation is performed in the same manner as in steps S19 to S23 described above (step S24), and thereafter, a pay-off operation of the unit dust collecting mechanism is performed (step S25). When the removal of all the operating unit dust collection mechanisms is completed (step S26), the process returns to step S3, and proceeds to the operation of growing and forming all the precoat layers.

Here, the above-mentioned medicine amount reducing operation is a means for reducing waste of removing the medicine adhering to the unit dust collecting mechanism.

In the present embodiment, each of the above-mentioned operations is described as issuing a command from the control device 8 in comparison with the detection value from the measuring device. However, when the operation is stable, the operation by the measuring device is performed. Instead of the control, a set cycle control by the timer device 84 may be used, and each measuring device may be used for an alarm.

The supply of the medicine 91 is performed by the powder pump 93.
However, in the case where the effect of raising the temperature of the medicine and the carrier air by the combustion gas 21 is sufficiently obtained, a conventional blowing blower method may be employed instead of the powder pump 93. [Comparison of the conventional method, the prior application method and the method of the present application] FIG. 5 is a diagram comparing the conventional method shown in the upper part with the prior application method shown in the middle part and the present method shown in the lower part. The state of drug supply (shaded area) and the removal operation (black bar area) are shown, and the upper half shows the transition of the neutralization reaction rate average value of the drug layer on all filter cloths during the filtering operation. The numbers with a circle in the upper and middle rows indicate the numbers of the unit dust collection mechanisms in the case of the six-chamber type.

Here, at the time of forming the pre-coat layer, in the conventional method, the medicine is continuously blown into the flue, and in the prior application method, the medicine is sprayed after the drop-off for each unit dust collecting mechanism. In contrast to air transport, in the present application, all the equipment is supplied at once in the flue. In the method of the present application,
When the gas amount is smaller than the specified value, the number of unit dust collecting mechanisms for supplying the drug is reduced and the precoat layer is formed, so that the efficiency of adhering the drug can be improved.

At the time of the removing operation, the conventional method has a disadvantage that the number of times is extremely increased because the removing operation is continuously performed for each row of the filter cloth group. While the payoff is performed every time, in the method of the present invention, there is a difference that all devices are paid off by a series of operations.

Further, in the conventional method, the neutralization reaction rate of the drug as viewed from the entire filter cloth is equivalent to an equivalent ratio of 3 to 5 and is excessively supplied. In order to pay off at, it is inevitably about 30%,
In the prior application method, the neutralization reaction rate is 10 for each unit dust collection mechanism.
Although it rises to almost 0%, it will follow almost 50% as a whole in order to pay off each unit dust collection mechanism. On the other hand, in the method of the present invention, all the devices are removed at the same time,
In order to pre-coat at once, it will rise to almost 100% as it rises to the right. [Experimental Example] FIGS. 6 and 7 show an example of the experimental results of the wiping off, the precoat layer formation and the filtering operation according to the method of the present invention in a bag filter device constituted by six unit dust collecting mechanisms.

When the inlet concentration of HCl is 450 to 600 ppm
Occasionally, under the condition that the outlet concentration is removed to 20 ppm or less, the cleaning is performed in about 6 minutes after the start of the experiment,
Time required to complete the precoat layer formation. Approximately 300 kg of the drug was supplied in about one hour required for forming the precoat layer, of which 6 kg was supplied in the first 6 minutes and 294 kg in the remaining 54 minutes. This drug supply is about 1.5 in terms of blow equivalent ratio.

In this state, the filtration operation was continued without additional supply of the drug, but it could be left for 6 hours until the outlet concentration reached the target concentration of 20 ppm (see FIG. 6).

Further, the differential pressure is steadily increased from 50 mmAq to about 175 mmAq only due to the attachment of soot and dust, which proves that the high-efficiency performance of the present invention is stable and continues for a long time.

[0071]

As described above, according to the present invention, the operation of removing the precoat layer is performed in a predetermined order in each unit dust collecting mechanism while the gas is stopped, and the remaining gas in the gas is removed. The unit dust collection mechanism is supplied with the medicine by the reduced operation, and the growth and formation operation of the pre-coat layer after the cleaning operation of all the unit dust collection mechanisms is completed. Since the gas is supplied after forming the pre-coat layer and passing the gas, there is no reduction in performance immediately after the wiping-off operation, and the above-described conventional method can be performed without additional equipment such as a pre-absorption reactor. A high efficiency is exhibited from the beginning with a drug amount of about 乃至 to の of the system, and the harmful gas removal performance can be properly maintained for a long time.

In the conventional method and the prior application method, the elapsed time after the adhesion of the medicine differs for each unit dust collecting mechanism.
The neutralization reaction rate was also low and unstable.
In the method of the present invention, since the precoat layer is formed substantially simultaneously for all the unit dust collecting mechanisms, the neutralization reaction increases on average in the entire apparatus. Therefore, hunting due to measurement errors and short-term fluctuations does not occur, and at the time the neutralization reaction is completed, the used medicine is effective to remove the injected medicine, and it is only possible to reduce the medicine cost. In addition, since the discharge of unreacted chemicals is reduced, the cost of post-treatment of discharged ash can be reduced. In addition, since the rate of increase of the ventilation resistance is reduced and the absorption of chemicals and soot and dust to the filter cloth due to moisture absorption is avoided, it is easy to remove and the interval can be increased, thereby extending the life of the filter cloth. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a bag filter device in which a method for forming a precoat layer of a bag filter device according to the present invention is performed.

FIG. 2 is a cross-sectional view showing an attached state of a filter cloth surface during a filtering operation.

FIG. 3 is a flowchart illustrating a procedure of a precoat layer forming operation.

FIG. 4 is a flowchart illustrating a procedure of a filtering operation and a removing operation.

FIG. 5 is a diagram comparing the conventional method shown in the upper part, the prior application method shown in the middle part, and the present method shown in the lower part.

FIG. 6 is a view showing an example of an experimental result of a removal operation, a precoat layer formation, and a filtering operation according to the method of the present invention.

FIG. 7 is a diagram showing an example of an experimental result of a removal operation and a precoat layer forming operation according to the method of the present invention.

FIG. 8 is a view schematically showing a conventional precoat-type bag filter device.

FIG. 9 is a diagram schematically showing a conventional bag filter system.

[Explanation of symbols]

 Reference Signs List 5 bag filter device 6 filter cloth 63 precoat layer 8 control device

Claims (1)

(57) [Claims] 1. A method for forming a precoat layer of a bag filter device having a plurality of unit dust collecting mechanisms and forming a precoat layer on the surface of a filter cloth in advance before performing a filtering operation, wherein the operation of removing the precoat layer is performed. Are in the expected order
While the gas flow is stopped for each unit dust collection mechanism,
The residual unit dust collection mechanism in the passing gas has a reduced operation
Supply of chemicals and the removal operation of all unit dust collection mechanisms
Growth and formation operations of the precoat layer after completed, terminates by supplying at once drug for all units precipitator mechanism, until the next払落operated bag filter apparatus characterized by not supplying agent Method for forming a precoat layer.