JP2000042357A - Low temperature recycle type treatment of waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save the cost for waste gas treatment by heating a bag filter collecting material to break an adsorbent particle shell, cooling a collected material containing the broken material of the absorbent and the adsorbent after dioxin decomposition and after that blowing to a waste gas in the upstream of a bag filter. SOLUTION: The particle shell of slaked lime is broken by heating the collected material to about 350 deg.C by a heating device 3 and stirring. The collected material containing the broken material of slaked lime and activated carbon after the decomposition of dioxin are cooled to about 60 deg.C. The absorption efficiency of an acidic component in the waste material, particularly SOx is improved by the cooling. A part of the collected material containing the broken material of slaked lime and the activated carbon after they are cooled is recycled and blown to the waste gas in the upstream from the bag filter 2. As a result, each use quantity of slaked lime and activated carbon is reduced and the removing efficiency of the acidic component and dioxin is improved. Thus the cost for waste gas treatment is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating exhaust gas generated by incineration of municipal waste and industrial waste.

[0002]

2. Description of the Related Art Exhaust gas generated by incineration of waste contains harmful substances such as HCl, SOx and dioxin. In the prior art, as shown in FIG.
The acidic component of x is blown with slaked lime as an absorbent into the exhaust gas, and dioxin is blown with activated carbon as an adsorbent into the exhaust gas, and these are removed from the exhaust gas by collecting them together with fly ash with a bag filter. Fly ash collected by the bag filter heats and decomposes dioxin,
Treated with heavy metal fixatives and then landfilled.

[0003]

In the treatment of exhaust gas, as described above, particles of slaked lime (Ca (OH) ₂ ) are blown into the flue gas of the exhaust gas, whereby H in the exhaust gas is expressed by the following formula.
Generally, exhaust gas is purified by reacting with Cl and SOx.

[0004] 2HCl + Ca (OH) ₂ → CaCl ₂ + 2H ₂ O SOx + Ca (OH) ₂ → CaSO _{x + 1} + H ₂ O

In this method, the HCl and SOx removal rates are about 70% HCl and 30% SOx at an equivalent ratio of 1.
This is because the surface of the slaked lime particles is covered with a shell made of a reaction product (CaCl ₂ , CaSO _{x + 1} ) by the above reaction,
This is because further progress of the reaction is prevented.
That is, even if unreacted slaked lime remains inside the particles, the surface is covered with the reaction product, so that the exhaust gas hardly comes into contact with the unreacted slaked lime portion, and the reaction stops.

An object of the present invention is to reduce the cost of exhaust gas treatment by recycling the unreacted slaked lime.

[0007]

The low-temperature recycling type exhaust gas treatment method according to the present invention is characterized in that acidic component absorbent particles and dioxin adsorbent are blown into exhaust gas, and these are collected together with fly ash by a bag filter, and the collected matter is collected. In an exhaust gas treatment method for thermally decomposing and removing dioxin, the collected matter is heated and the absorbent particle shell generated by the absorption of the acidic component is destroyed. And then blowing the exhaust gas on the upstream side of the bag filter after cooling the collected matter containing the.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, slaked lime is blown into an exhaust gas discharged from an incinerator (1) as an acidic component absorbent and activated carbon is blown as a dioxin adsorbent, and these are blown together with fly ash by a bag filter (2). Collect. The blowing amount of slaked lime and activated carbon is adjusted according to the concentration of dioxin at the inlet, and continuous blowing is performed. One blower is used to share the supply pipe. The surface of the slaked lime particles is covered with a shell made of a reaction product (CaCl ₂ , CaSO _{x + 1} ). Generally, the blowing amount of activated carbon is 50-50.
It is about 0 mg / Nm ³ . The collected matter by the bag filter (2) is heated by the heating device (3) to thermally decompose and remove dioxin.

The heating device (3) performs stirring together with heating. As shown in FIG. 2, an electric heater (7) provided on the inner surface of the casing (4) and a length inside the casing (4) are provided. It mainly comprises a rotating shaft (5) arranged in the direction and a number of stirring blades (6) provided on the rotating shaft (5). The interior of the heating device (3) is in an oxygen-free state or an oxygen-lean state so as not to decompose the activated carbon.

[0010] The collected matter is passed through a heating device (3) for 350 hours.
The particles shell of slaked lime is broken by heating to about ° C and stirring. The collected matter containing the slaked lime debris and the activated carbon after dioxin decomposition is then cooled to about 60 ° C. By this cooling, the absorption efficiency of acidic components, particularly SOx, in the exhaust gas by slaked lime is improved.

A part of the collected matter containing the slaked lime debris after cooling and the activated carbon is recycled and blown into the exhaust gas upstream of the bag filter (2). The amount of collected material can be adjusted. As a result, the usage amounts of slaked lime and activated carbon are reduced by half.

Since the collected matter by the bag filter (2) is designated as specially managed waste, the remaining part of the collected matter is treated with a heavy metal fixing agent and then disposed of in a landfill. As a result, the fly ash amount is reduced to 2/3, and the capacity of the fly ash processing device is reduced to 2/3.

[0013]

According to the low-temperature recycle type exhaust gas treatment method of the present invention, the collected matter containing the broken matter of the absorbent and the adsorbent after dioxin decomposition is destroyed by heating the collected matter of the bag filter and destroying the absorbent particle shell. After cooling, the gas is blown into the exhaust gas upstream of the bag filter, so that the amount of slaked lime and activated carbon blown can be reduced, the efficiency of removing acidic components and dioxins can be improved, and the capacity of the fly ash treatment device can be reduced. Compactness can be achieved. Thus, cost reduction of exhaust gas treatment can be achieved.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of a low-temperature recycling type exhaust gas treatment method according to the present invention.

FIG. 2 is a flow sheet showing an example of a conventional exhaust gas treatment method.

FIG. 3 is a partially cutaway perspective view showing an example of a heating device.

[Explanation of symbols]

 1: incinerator 2: bag filter 3: heating device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/70 B01D 53/34 134A 53/68 (72) Inventor Hirokazu Obata 1 Minami Kohoku, Suminoe-ku, Osaka-shi No. 7-89 Citachi Shipbuilding Co., Ltd. F-term (reference) 4D002 AA02 AA19 AA21 AC04 BA03 BA04 BA12 BA14 DA05 DA12 DA41 EA02 EA08 EA13 EA20 GA01 GA03 GB03 GB06 HA01 4D058 JA04 RA19 SA20 TA02 TA04 UA01 UA03

Claims (1)

[Claims] 1. An exhaust gas treatment method in which an acidic component absorbent particle and a dioxin adsorbent are blown into exhaust gas, and these are collected together with fly ash by a bag filter, and the collected matter is heated to thermally decompose and remove dioxin. After heating the collected matter, breaking the absorbent particle shell generated by the absorption of the acidic component, and cooling the collected matter containing the broken matter of the absorbent and the adsorbent after dioxin decomposition, exhaust gas upstream of the bag filter A low-temperature recycling type exhaust gas treatment method characterized by injecting air into a wastewater.