JPH07328384A - Treatment of exhaust gas in waste refuse incineration equipment - Google Patents

Abstract

PURPOSE:To enhance the wt. loss effect of fly ash generated from waste refuse incineration equipment while enhancing the reactivity of HCl in exhaust gas and slaked lime in collected ash by applying pretreatment to bag filter collected ash again blown into a flue. CONSTITUTION:In waste refuse incineration equipment equipped with a waste refuse incinerator 11, a cyclone 14 extracting coarse particles in the exhaust gas discharged from the waste refuse incinerator, a bag filter 15 extracting fine particles contained in the exhaust gas after passed through the cyclone and a slaked lime supply device 17 blowing slaked lime into the inlet flue of the bag filter, a water spray type cooler 12 cooling the exhaust gas discharged from the waste refuse incinerator is provided to the outlet of the waste refuse incinerator. The whole or a part of the ash collected by the bag filter is blown in the space where the cooling water in the cooler 12 is present in a liquid state or the area on the upstream side of the space to be recycled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating exhaust gas in an incinerator for municipal solid waste, and more particularly to a method for removing hydrogen chloride (HCl) contained in the exhaust gas.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, the removal of HCl from exhaust gas in an incinerator such as municipal waste is performed by blowing slaked lime from a slaked lime feeder 3 into an outlet flue 2 of an incinerator 1. Convert HCl to solid calcium chloride,
A method of removing this calcium chloride together with soot and dust with the electrostatic precipitator 4 has been widely used.

However, it has been clarified that the combustion exhaust gas from municipal waste contains highly toxic organic chlorine compounds such as dioxins, and that these organic chlorine compounds are mainly produced in the electrostatic precipitator, At present, the method of removing HCl with a bag filter is predominant. Further, in order to improve the removal efficiency of HCl in the bag filter, it does not directly act on the purification of the exhaust gas, but it prevents clogging of the bag filter cloth or peels the adhered layer from the bag filter cloth. A method of adding a filter aid having characteristics such as facilitation of slaked lime to slaked lime has been conventionally performed. According to this method, at the outlet of the incinerator 1, several 100 to 1000 p is contained in the exhaust gas.
The HCl gas contained in the concentration of pm can be reduced to about 10 to 20 ppm at the outlet of the bag filter. In addition,
In these cases, due to the low utilization of slaked lime,
About 2 to more molar ratio than theoretical slaked lime amount required to change all HCl gas in exhaust gas to calcium chloride
Four times as much slaked lime is blown into the exhaust gas.

At present, most of the fly ash separated and removed from the exhaust gas by the bag filter is finally landfilled, but recently it is becoming difficult to secure a landfill site, and the refuse incinerator is becoming difficult. There is a strong demand for reduction of fly ash generated from

However, as described above, in the refuse incineration facility in which slaked lime is blown into the flue to treat the exhaust gas, as described above, slaked lime which is several times the amount of slaked lime required to detoxify HCl in the exhaust gas is introduced into the flue. Since it is blown in, a large amount of unreacted slaked lime is contained in the fly ash, making it difficult to reduce the fly ash. Further, in a refuse incineration facility in which a filter aid is added to the flue along with slaked lime, fly ash increases by the amount of the added filter aid.

As a method for improving this, it is effective to blow the slaked lime collected together with the fly ash into the flue again. However, the fly ash concentration in the exhaust gas generated in the refuse incinerator is as high as 10 to ³⁰ g / Nm ³ , so in a system that uses only a bag filter as a dust remover, when the slaked lime collected by the bag filter is reused. In addition, a large amount of fly ash is blown into the flue again, which increases the load on the bag filter and lowers the exhaust gas purification efficiency.

In order to eliminate such inconvenience, the inventors of the present application previously provided a cyclone dust collector 5 at the outlet of the refuse incinerator 1 as shown in FIG. The slaked lime from the slaked lime supplier 3 is blown into the exhaust gas from which the fly ash has been removed, and the remaining ash, reaction products of calcium chloride and unreacted slaked lime are separated from this exhaust gas by a bag filter 6. Proposed a system in which only the collected matter in the bag filter 6 is blown into the inlet side of the cyclone dust collector 5 (Japanese Patent Application No. 6-5871).
issue). According to this system, the amount of fly ash in the gas blown again to the inlet side of the cyclone dust collector 5 can be greatly reduced, so that the unreacted slaked lime is removed without increasing the load of the bag filter 6 so much. It can be effectively used and the amount of fly ash generated from the system can be reduced.

Further, as described in, for example, Japanese Patent Application Laid-Open No. 62-30531, a device for converting slaked lime into slurry or moistening and washing it in order to increase the utilization rate of recycled slaked lime is a waste incineration facility. Conventionally, a technique attached to the has been proposed.

[0009]

However, in the system previously proposed by the present inventors, the system once added to the flue gas reacts with HCl in the exhaust gas, and calcium chloride as a reaction product adheres to the surface. Since the slaked lime is blown into the cyclone dust collector 5 again as it is, the reaction rate cannot be improved as much as theoretically obtained from the amount of slaked lime recycled, and the amount of fly ash can be reduced theoretically. It is much lower than the available value.

Further, if a slaked lime slurryizer or a humidifying / cleaning device is attached to the refuse incineration facility, the facility structure becomes complicated and the facility cost becomes high.

The present invention has been made in order to solve the inconvenience of the prior art, and enhances the utilization rate of recycled slaked lime without complicating the equipment structure,
The purpose is to enhance the effect of reducing fly ash generated from waste incineration equipment.

[0012]

In order to solve the above-mentioned problems, the present invention provides a refuse incinerator, a cyclone for removing coarse particles in the exhaust gas discharged from the refuse incinerator, and an exhaust gas after passing through the cyclone. In a refuse incinerator equipped with a bag filter for removing fine particles contained in, and a slaked lime feeder for blowing slaked lime into the inlet flue of the bag filter, exhaust gas discharged from the refuse incinerator at the outlet of the refuse incinerator. Is provided with a water-injection-type cooler, and all or part of the collected ash collected by the bag filter is supplied in a space in which the cooling water in the cooler exists in a liquid state or an upstream side thereof. It was designed to be blown into and recycled.

[0013]

According to the above means, since the collected ash collected by the bag filter can be mixed with the water in the cooler, calcium chloride which is a reaction product adhering to the surface of slaked lime can be washed away. The slaked lime that has once been blown into the flue and reacted with HCl in the exhaust gas can be restored to the unreacted state again. Therefore, the amount of new slaked lime added to the exhaust gas can be reduced, and as a result, the amount of fly ash generated in the refuse incineration facility can be reduced. According to the experiment, the conventional method has a molar ratio of 2-4 with respect to the amount of HCl in the exhaust gas.
Although the predetermined exhaust gas treatment could not be performed without adding the amount of slaked lime, the amount of slaked lime used could be reduced to 1 to 2 in terms of molar ratio by the above means.

In addition, this type of incinerator requires a cooler for cooling the high-temperature exhaust gas discharged from the refuse incinerator to a temperature suitable for dust removal treatment in the bag filter. If a water-injection type cooler is used as this, and it is also used as a recovery device for the slaked lime that has been used once, the system configuration will be significantly improved compared to the case where a cooler and a slaked lime cleaning device or a slurry device are separately provided. Can be simplified.

[0015]

[Example] Fig. 1 shows a refuse incineration facility according to an example.
In this figure, 11 is a refuse incinerator, 12 is a gas cooler that cools the exhaust gas discharged from the refuse incinerator 11 to a predetermined temperature suitable for dust removal, and 13 is a cooling water source that supplies cooling water to the gas cooler 12. , 14 is a cyclone for removing coarse particles in the exhaust gas, 15 is a bag filter for removing fine particles in the exhaust gas, 16 is a flue connecting the cyclone 14 and the bag filter 15, and 17 is slaked lime supplied to the flue 16. A slaked lime feeder, 18 is a bag ash collecting ash discharge line, and 19 is a ash collecting transport line for carrying the bag filter ash to the gas cooler 12.

The gas cooler 12 is a so-called water spray type cooler for cooling the high temperature exhaust gas passing through the inside by spraying the cooling water supplied from the cooling water source 13.
In the use state, as shown by broken lines in FIGS. 2A, 2B, and 2C, a space 20 in which the cooling water exists in a liquid state is formed in at least a part of the inside.

As shown in FIG. 2 (a), the collected ash transport pipe line 19 can be connected to a space 20 in which the cooling water exists in a liquid state, or as shown in FIG. 2 (b). like,
It can also be connected upstream of the space 20 in the gas cooler 12. Furthermore, as shown in FIG. 2 (c), a flue 11a connecting the refuse incinerator 11 and the gas cooler 12 to each other.
You can also connect to.

The operation of the refuse incineration facility of this embodiment constructed as described above will be described below.

The exhaust gas discharged from the refuse incinerator 11 is
It is introduced into the gas cooler 12 through the flue 11a, the cooling water from the cooling water source 13 is sprayed, and each dust removal device 1 in the wake is introduced.
It is cooled to a predetermined temperature suitable for performing the dust removal process at 4 and 15. In the cyclone 14, coarse particles in the exhaust gas are removed, and the exhaust gas discharged from the refuse incinerator 11 contains 10 to 10 particles.
Fly ash contained at a concentration of 30 g / Nm ³ is 2 to ³ g.
/ Nm ³ or less. The slaked lime from the slaked lime feeder 17 is added to the exhaust gas that has passed through the cyclone 14 in the flue 16, and the harmful HCl gas in the exhaust gas is changed to solid and harmless calcium chloride. Then, fine-grained ash not completely removed by the cyclone 14, chlorides such as dioxins, heavy metals such as mercury or lead, and HC
The bag filter 15 contains calcium chloride chemically changed from l gas and unreacted slaked lime with calcium chloride attached to the surface.
To be collected at. The bag filter collected ash is discharged to the outside through the discharge pipe line 18, and a necessary amount of the bag filter collected ash is conveyed to the gas cooler 12 through the collected ash conveyance pipe line 19.

The bag filter collecting ash introduced into the space 20 in which the cooling water of the gas cooler 12 exists in a liquid state or the upstream side thereof contacts the cooling water in the gas cooler 12. In this process, calcium chloride adhering to the surface of the slaked lime particles is washed away, and the slaked lime is restored to an unreacted state.
Thereafter, the ash collected by the bag filter containing the unreacted slaked lime is blown into the exhaust gas from the refuse incinerator 11, and H
Detoxification of Cl is performed.

Although the gas cooler 12 is installed on the upstream side of the cyclone 14 in the above-mentioned embodiment, the gas cooler 12 is installed downstream of the cyclone 14 by using a cyclone 14 having high temperature resistance. It can also be installed on the side. It is also possible to install the gas coolers 12 on both the upstream side and the downstream side of the cyclone 14 and introduce the bag filter collected ash into either one of the gas coolers.

[0022]

As described above, according to the present invention,
A water injection type gas cooler is installed on the outlet side of the refuse incinerator, and all or part of the bag filter collected ash is blown into the space where the cooling water in the cooler exists in a liquid state or its upstream side. Since it is recycled, calcium chloride, which is a reaction product adhering to the surface of the slaked lime, can be washed away with water in the cooler, and the slaked lime once blown into the flue and reacted with HCl in the exhaust gas is not reused. The reaction state can be restored. Therefore, the amount of new slaked lime added to the exhaust gas can be reduced, and the amount of fly ash generated in the refuse incinerator can be reduced. In addition, in this type of incinerator, a high-temperature exhaust gas discharged from the refuse incinerator requires a cooler for cooling to a temperature suitable for dust removal treatment in a bag filter, and therefore a water jet is used as the cooler. If a combined cooler is used as a recovery device for slaked lime that has been used once, the system configuration is significantly simplified compared to the case where both a cooler and a slaked lime scrubber or slurry maker are provided separately. Can be converted.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a refuse incineration facility according to an embodiment.

FIG. 2 is a schematic cross-sectional view illustrating a method for introducing bag filter collected ash into a gas cooler.

FIG. 3 is a configuration diagram showing a first example of a conventionally known refuse incineration facility.

FIG. 4 is a configuration diagram of a refuse incineration facility previously proposed by the present inventors.

[Explanation of symbols]

 11 Waste Incinerator 12 Gas Cooler 13 Cooling Water Source 14 Cyclone 15 Bag Filter 16 Flue 17 Slaked Lime Supplyer 18 Bag Filter Collected Ash Discharge Pipeline 19 Collected Ash Transport Pipeline 20 Cooling Water Exists space

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Sente 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory

Claims (1)

[Claims] 1. A waste incinerator, a cyclone for removing coarse particles in exhaust gas discharged from the waste incinerator, a bag filter for removing fine particles contained in the exhaust gas after passing through the cyclone, and an inlet of the bag filter. In a refuse incinerator equipped with a slaked lime feeder for blowing slaked lime into a flue, a water-injection type cooler for cooling exhaust gas discharged from the refuse incinerator is provided at the outlet of the refuse incinerator, and the bag filter is used. Exhaust gas treatment in a refuse incineration facility, characterized in that all or part of the collected ash collected is blown into the space in which the cooling water in the cooler exists in a liquid state or its upstream side for recycling. Method.