JPH11192414A - Removal of harmful material by bag filter utilizing active carbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive miniaturizing a bag filter utilizing active carbon by mixing a filter aid of specified bulk density with active carbon. SOLUTION: A bag filter 10 utilizing active carbon is partitioned into two chambers 12, 13 each having plural bags 11. A flue 14 extending from a bag filter is branched into two branch parts 14a, 14b, and the branch parts 14a, 14b are connected to the chambers 12, 13 of the bag filter 10 utilizing active carbon, respectively. By an induced draft fan 15, waste combustion gas is led from the bag filter to the chambers 12, 13 of the bag filter 10 utilizing active carbon, and into this waste combustion gas, a mixture of active carbon and a filter aid of 0.02-0.2 bulk density (for example, perlite and activated clay) is blown by using a feeder 16 on the upstream side from the branching point of the flue 14. In this way, even when the accumulated quantity of active carbon is made large, operation can be performed at high filtration flow velocity with pressure loss between the combustion gas inlet and outlet of the bag filter 1 utilizing active carbon kept at a lot level to enable to make small the required area of the bags 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to dioxins and mercury in combustion exhaust gas generated when municipal solid waste or industrial waste is incinerated by incinerating activated carbon by injecting activated carbon upstream of a bag filter utilizing activated carbon. And related methods for removing harmful substances.

[0002]

2. Description of the Related Art The flue gas of an incinerator for incinerating municipal solid waste and industrial waste contains hydrogen chloride, sulfur oxides, mercury, and dioxins. Conventionally, methods shown in FIGS. 5 to 7 are known as a method for treating exhaust gas. In the following description, the same components and portions will be denoted by the same reference symbols throughout the drawings, without redundant description.

The method shown in FIG. 5 is as follows. That is, using a processing device having a bag filter (1) and a bag filter using activated carbon (2) arranged in series, powder of slaked lime is sprayed on the combustion exhaust gas of the incinerator, and the powder is entrained. Introduce to the upstream bag filter (1). Hydrogen chloride and sulfur oxides in the flue gas are removed to some extent by a neutralization reaction with slaked lime in the flue leading to the bag filter (1). The flue gas introduced into the bag filter (1) comes into contact with dust, slaked lime, etc., which forms a layer on the surface of the filter cloth inside the bag filter (1) when passing through the bag, thereby causing the flue gas to enter the flue gas. The remaining hydrogen chloride and sulfur oxides are removed by a neutralization reaction. Dust and some mercury and dioxins contained in the flue gas are also removed by the bag filter (1). Then, activated carbon is blown into the flue gas that has passed through the bag filter (1), and is introduced into the activated carbon-utilized bag filter (2) along with the activated carbon. In the activated carbon bag filter (2), the activated carbon is deposited on the surface of the filter cloth in the activated carbon bag filter (2), and mercury and dioxins are adsorbed on the activated carbon when the combustion exhaust gas passes through the activated carbon deposition layer. Thus, harmful substances in the combustion exhaust gas are removed.

The method shown in FIG. 6 is as follows. That is, using a processing device equipped with an electrostatic precipitator (3) and an activated carbon bag filter (2) arranged in series,
Slaked lime powder is sprayed on the flue gas of the incinerator, and it is introduced into the electric dust collector (3) along with it. Hydrogen chloride and sulfur oxides in the flue gas are removed to some extent by a neutralization reaction with slaked lime in the flue leading to the electrostatic precipitator (3).
Hydrogen chloride and sulfur oxides in the flue gas introduced into the electrostatic precipitator (3) also come into contact with slaked lime in the electric precipitator (3), whereby hydrogen chloride and sulfur oxides remaining in the flue gas are removed. It is removed by a summation reaction. In addition, the dust contained in the combustion exhaust gas is also removed by the electric dust collector (3). Thereafter, as in the case of the method shown in FIG. 5, activated carbon is blown into the flue gas that has passed through the electrostatic precipitator (3), and the activated exhaust gas is accompanied by the activated carbon to cause a bag filter using activated carbon (2).
Mercury and dioxins are adsorbed on the activated carbon when the flue gas passes through the activated carbon deposition layer formed on the surface of the filter cloth in the activated carbon bag filter (2).
Thus, harmful substances in the combustion exhaust gas are removed.

The method shown in FIG. 7 is as follows. In other words, the electric dust collector (3) and the wet smoke
Using a processing device provided with (4) and a bag filter using activated carbon (2), the flue gas from a refuse incinerator is introduced into an electric dust collector (3) where dust is removed. Then, electric dust collector
The exhaust gas discharged from (3) is introduced into a wet-type smoke washing tower (4), where alkaline water such as caustic soda is sprayed to remove hydrogen chloride and sulfur oxides in the combustion exhaust gas by a neutralization reaction. In addition, part of the mercury contained in the flue gas is also removed in the wet smoke tower (4). Next, activated carbon is blown into the flue gas discharged from the smoke washing tower (4), and is introduced into the bag filter (2) using activated carbon with accompanying the activated carbon. Thereafter, in the same manner as in the method shown in FIG. 5, activated carbon is blown into the flue gas that has passed through the smoke washing tower (4), and is introduced into the activated carbon bag filter (2) together with the flue gas. Mercury and dioxins are adsorbed on the activated carbon when passing through the activated carbon deposition layer formed on the surface of the filter cloth in the activated carbon bag filter (2). Thus, harmful substances in the combustion exhaust gas are removed.

However, any of the methods shown in FIGS. 5 to 7 has the following problems. That is, when an activated carbon deposition layer is formed on the surface of the filter cloth in the activated carbon bag filter (2), the pressure loss when the combustion exhaust gas passes through the activated carbon deposition layer becomes extremely high. Normally, when the pressure loss between the flue gas inlet and the exhaust gas outlet reaches a certain value, for example, 120 mmAq, the activated carbon bag filter (2) removes a part of the activated carbon deposited layer formed on the filter cloth surface. The operation is performed so as to maintain the pressure loss between the flue gas inlet and the exhaust gas outlet, for example, between 100 and 120 mmAq. Since the pressure loss of the activated carbon sedimentary layer on the surface of the filter cloth is very large, if pure carbon is blown in front of the activated carbon bag filter (2), the pressure loss during the above-mentioned operation of the activated carbon bag filter (2) Does not allow a large amount of activated carbon to be deposited on the filter cloth surface. That is, the harmful substance removal performance cannot be improved. In order to increase the performance of removing harmful substances, it is necessary to reduce the filtration flow rate of the activated carbon bag filter (2) to increase the amount of activated carbon deposited, but to reduce the filtration flow rate, the filtration area must be increased. Without
As a result, there is a problem that the volume of the activated carbon bag filter (2) becomes large.

It is an object of the present invention to provide a method for removing harmful substances using an activated carbon bag filter which can solve the above-mentioned problems and can reduce the size of the activated carbon bag filter.

[0008]

Means for Solving the Problems and Effects of the Invention The method for removing harmful substances by using a bag filter utilizing activated carbon according to the present invention comprises:
A method for removing harmful substances in combustion exhaust gas by blowing activated carbon into the upstream side of an activated carbon utilizing bag filter, characterized by mixing a filter aid having a bulk specific gravity of 0.02 to 0.2 with activated carbon. Things.

In the above, as the filter aid, those having a shape like sea urchin, those having a shape like tetrapot,
Balloon-shaped ones are used.

According to the method for removing harmful substances of the present invention, the filter aid having a bulk specific gravity of 0.02 to 0.2 is mixed with the activated carbon blown into the combustion exhaust gas on the upstream side of the activated carbon bag filter. Then, a deposit layer of these mixtures is formed on the surface of the filter cloth in the bag filter using activated carbon. When a mixture of two or more different particulate materials is deposited, the deposited layer is less likely to be in a fine state. Therefore, when the combustion exhaust gas passes through the deposited layer, the pressure loss occurs when only activated carbon is blown. And the pressure loss between the flue gas inlet and the outlet of the activated carbon bag filter is also lower than when only activated carbon is blown. Therefore,
Even if the activated carbon deposition amount is increased, it is possible to operate at a high filtration flow rate while maintaining the pressure loss between the combustion gas inlet and the outlet of the activated carbon utilizing bag filter at a low level,
The required area of the bug is small, and the number of bugs can be reduced when a bug having the same size as the conventional method is used. As a result, the size of the activated carbon bag filter can be reduced, and the cost of the apparatus and the building volume can be reduced.

In the method for removing harmful substances according to the present invention, the mixing ratio of activated carbon and filter aid (activated carbon / filter aid) is preferably 90/10 to 10/90 by weight. When the mixing ratio is larger than 90/10, the effect of reducing the pressure loss is small, and when it is smaller than 10/90, the adsorption performance by activated carbon deteriorates.

In the method for removing harmful substances of the present invention, pearlite may be used as a filter aid. Here, as defined in JIS A5007-1977, pearlite refers to one produced by crushing perlite, obsidian or a lithic rock similar thereto and firing and expanding the pearlite.

Another method for removing harmful substances using a bag filter utilizing activated carbon according to the present invention is a method for removing harmful substances in combustion exhaust gas by blowing activated carbon into the upstream side of a bag filter utilizing activated carbon. Characterized by mixing a filter aid consisting of

In the above, the activated clay is used in the form of a commercial product, that is, in the form of powder or granules.

According to another harmful substance removing method of the present invention,
Since a filter aid made of activated clay is mixed with activated carbon blown into the combustion exhaust gas on the upstream side of the activated carbon bag filter, a deposit layer of these mixtures is formed on the surface of the filter cloth in the activated carbon bag filter. You. When a mixture of two or more different particulate materials is deposited, the deposited layer is less likely to be in a fine state. Therefore, when the combustion exhaust gas passes through the deposited layer, the pressure loss occurs when only activated carbon is blown. And the pressure loss between the flue gas inlet and the outlet of the activated carbon bag filter is also lower than when only activated carbon is blown. Therefore, even if the amount of activated carbon deposited is increased, it is possible to operate at a high filtration flow rate while maintaining the pressure loss between the combustion gas inlet and the outlet of the activated carbon bag filter at a low level. The required area is small, and the number of bugs can be reduced when using bugs of the same size as the conventional method. as a result,
The size of the activated carbon bag filter can be reduced, and the apparatus cost and the building volume can be reduced. In addition, activated clay has the property of adsorbing and removing mercury and dioxins like activated carbon, so that the adsorption performance of mercury and dioxins is improved.

In another method for removing harmful substances according to the present invention,
The mixing ratio of activated carbon and filter aid (activated carbon / filter aid) is
The weight ratio is preferably 90/10 to 10/90. If the mixing ratio is within the above range, a sufficient pressure loss reducing effect can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on specific examples and comparative examples. The activated carbon used in all the following Examples and Comparative Examples is GL-50 manufactured by Norit.

Example 1 This example was performed using the experimental apparatus shown in FIG.

In FIG. 1, a bag filter (1) using activated carbon is used.
Inside (0) are two chambers (12) (1) each having multiple bugs (11).
3), the flue (14) extending from the bag filter (1) in the processing apparatus shown in FIG. 5 is branched into two, and each branch (14a) (14b) is divided into a bag filter (10) using activated carbon. ) Each room (1
2) Connected to (13). Then, the activated carbon bag filter (10) is converted from the bag filter (1) by the induction fan (15).
The flue gas is led to each of the chambers (12) and (13), and a mixture of activated carbon and perlite is mixed with the flue gas on the upstream side of the branch point of the flue (14) at a mixing ratio (activated carbon / pearlite). It was blown into the combustion exhaust gas using a feeder (16) so that the weight ratio became 50/50. In addition. The maximum processing gas capacity of the experimental apparatus shown in FIG. 1 was 150 Nm ³ , and each of the chambers (12) and (13) of the activated carbon bag filter (10) was heated to a predetermined temperature by an electric heater. A filtration flow rate (m / min) at a deposition amount of 200 g / m ² and a pressure loss Δ between the points A and B when the amount of the bug (11) deposited on the filter cloth surface of the mixture was 11.
The relationship with P (mmAq) was determined. The results are shown in the graph of FIG.

Comparative Example 1 Instead of the mixture of activated carbon and perlite, a mixture of activated carbon and diatomaceous earth was mixed at a mixing ratio (activated carbon / diatomaceous earth).
Except that it was blown into the combustion exhaust gas so that the weight ratio became 50/50, in the same manner as in Example 1 above.
The amount of sediment deposited on the filter cloth surface of the bug (11) of the above mixture is 2
A filtration flow rate (m / min) of 00 g / m ² and a point A
And the relationship with the pressure loss ΔP (mmAq) between points B was determined. The results are shown in the graph of FIG.

Comparative Example 2 A filter cloth of bag (11) of activated carbon was prepared in the same manner as in Example 1 except that activated carbon alone was blown into the combustion exhaust gas instead of the mixture of activated carbon and perlite. The filtration flow rate (m / m ² ) was 200 g / m ²
in) and the pressure loss ΔP between points A and B (mmA
q). The results are shown in the graph of FIG.

As is clear from the graph of FIG. 2, the pressure loss is lower at the same filtration flow rate when using a mixture of activated carbon and perlite than when using a mixture of activated carbon alone or a mixture of activated carbon and diatomaceous earth. It can be seen that it is extremely low.

Embodiments 2 to 4 Each chamber (12, 13) of the bag filter (1) of the processing apparatus shown in FIG. 5 to the bag filter (10) using activated carbon of the experimental apparatus shown in FIG.
The mixing ratio of the mixture of activated carbon and perlite (activated carbon / perlite) blown into the flue gas led to the upstream side of the flue (14) from the branch point is 70 / weight ratio.
30 (Example 2), 80/20 (Example 3) and 90
The filtration flow rate when the amount of the bag (11) of the mixture deposited on the filter cloth surface was 200 g / m ^{2 in} the same manner as in Example 1 except that / 10 (Example 4) was used. (M /
min) and the pressure loss ΔP (mmA) between the points A and B.
q). The results are shown in the graph of FIG. FIG. 3 also shows the results of Example 1 and Comparative Example 2.

As is clear from FIG. 3, the effect of reducing the pressure loss becomes more remarkable as the amount of pearlite in the mixture increases.

FIG. 4 shows the effect of the filtration flow rate on the pressure loss in the two cases of Example 1 and Comparative Example 2 in the form of a mathematical expression. The pressure loss in Comparative Example 2 increases in proportion to the filtration flow rate (v) to the power of 1.15, whereas the pressure loss in Example 1 increases in proportion to the filtration flow rate (v) in the 1.0 power. growing. From this result, it can be seen that as the filtration flow rate increases, the effect of reducing the pressure loss becomes more remarkable when a mixture of activated carbon and perlite is used.

The following is further clarified from the results shown in the graphs of FIGS.

Table 1 shows the physical properties of pearlite and diatomaceous earth.

[0028]

[Table 1]

Comparing the physical properties of pearlite and diatomaceous earth, the true specific gravity and the average particle diameter are almost the same, and only the bulk specific gravity of perlite is smaller than activated carbon by about 1 / 2.5. This difference in bulk specific gravity is considered to be effective in reducing pressure loss. Further, the crystal structure of pearlite has a scaly structure with severe irregularities. Even if this structure is mixed with activated carbon, it is considered that pressure loss is reduced because a low bulk specific gravity is maintained. By the way, the bulk specific gravity of activated carbon is 0.4
The bulk specific gravity of the mixture of activated carbon and pearlite at 50/50 was 0.25, which was smaller than the weighted average (0.34).

Embodiment 5 Using the experimental apparatus shown in FIG. 1, the chambers from the bag filter (1) to the activated carbon bag filter (10) of the processing apparatus shown in FIG.
(12) The mixing ratio (activated carbon / pearlite) of the mixture of activated carbon and perlite injected into the flue gas led to (13) on the upstream side of the branch point of the flue (14) is 5 by weight.
It was set to 0/50, and was blown into the flue gas using the feeder (16) to perform a test for removing dioxins in the flue gas. The results are shown in Table 2 together with the test conditions.

Comparative Example 3 A test for removing dioxins in flue gas was conducted in the same manner as in Example 5 except that activated carbon alone was blown into flue gas instead of a mixture of activated carbon and perlite. Was done. The results are shown in Table 2 together with the test conditions.

[0032]

[Table 2]

As is evident from Table 2, when a mixture of activated carbon and perlite is used, even if the same amount of activated carbon is used as in the case of using only activated carbon, the filtration rate is high at a high filtration rate without increasing the pressure loss. In addition, the same dioxin removal performance as in the case of using only activated carbon can be obtained. Therefore, without lowering the dioxin removal performance,
It can be seen that the size of the activated carbon bag filter can be reduced.

Example 6 The relationship between the filtration flow rate and the pressure loss between points A and B was determined in the same manner as in Example 1 except that activated clay was used instead of perlite. As a result, a pressure loss reducing effect similar to that of the first embodiment was achieved.

Example 7 A test for removing dioxins in combustion exhaust gas was conducted in the same manner as in Example 5 except that activated clay was used instead of perlite. as a result. The dioxin removal rate was 97%. From this result, it can be seen that when a mixture of activated carbon and activated clay is used, the dioxin removal rate is higher than when a mixture of activated carbon and perlite is used. This is because activated clay has the property of adsorbing dioxin.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an experimental apparatus used in Examples and Comparative Examples.

FIG. 2 is a graph showing the results of Example 1, Comparative Example 1, and Comparative Example 2, and showing the relationship between the filtration flow rate and the pressure loss.

FIG. 3 is a graph showing the results of Examples 1 to 4 and Comparative Example 2, and showing the relationship between filtration flow rate and pressure loss.

FIG. 4 is a graph showing the effect of the filtration flow rate on the pressure loss in the two cases of Example 1 and Comparative Example 2 in the form of a mathematical expression.

FIG. 5 is a flowchart showing one example of a conventional method for treating exhaust gas generated from an incinerator.

FIG. 6 is a flowchart showing another example of a method for treating exhaust gas generated from a conventional incinerator.

FIG. 7 is a flow chart showing still another example of a method for treating exhaust gas generated from a conventional incinerator.

[Explanation of symbols]

 (10): Bag filter using activated carbon

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI B01J 20/20 (72) Inventor Kiichi Nagaya 1-89, Minami Kohoku, Suminoe-ku, Osaka Nitachi Shipbuilding Co., Ltd. (72) Inventor Kenichi Nagai 1-7-89 Minami Kohoku, Suminoe-ku, Osaka City Inside Nippon Shipbuilding Co., Ltd. (72) Inventor Toshio Hama 1-89-89 Minami Kohoku, Suminoe-ku, Osaka City Inside Nippon Shipbuilding Corporation (72) Inventor Tadao Murakawa 1-7-89 Minami Kohoku, Suminoe-ku, Osaka Nippon Shipbuilding Co., Ltd. (72) Inventor Shinin Morinaga 1-7-89 Minami Kohoku, Suminoe-ku, Osaka Nichichi Shipbuilding Co., Ltd.

Claims (5)

[Claims] 1. A method for removing harmful substances in flue gas by blowing activated carbon into the upstream side of a bag filter utilizing activated carbon, wherein a filter aid having a bulk specific gravity of 0.02 to 0.2 is mixed with the activated carbon. A method for removing harmful substances using a bag filter using activated carbon. 2. Mixing ratio of activated carbon and filter aid (activated carbon /
The method for removing harmful substances by a bag filter using activated carbon according to claim 1, wherein the weight ratio of the filter aid is 90/10 to 10/90. 3. The method according to claim 1, wherein the filter aid is pearlite. 4. A method for removing harmful substances in flue gas by blowing activated carbon into the upstream side of a bag filter utilizing activated carbon, wherein the activated carbon is mixed with a filter aid consisting of activated clay. How to remove harmful substances by using bag filter. 5. Mixing ratio of activated carbon and filter aid (activated carbon /
5. The method for removing harmful substances by using a bag filter utilizing activated carbon according to claim 4, wherein the weight ratio of the filter aid is 90/10 to 10/90.