JP3458181B2 - CFC decomposition method by municipal solid waste incinerator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for combusting and decomposing specific chlorofluorocarbons whose production is regulated as substances that destroy the ozone layer.

Fluorocarbons have been used as a relatively harmless and stable substance to the human body in a very wide range in the past, but in recent years, they have been found to destroy the ozone layer, and production regulations have started from the viewpoint of global environmental protection. It will be completely abolished in 2030. Research on methods for destroying and decomposing CFCs has also progressed, and various methods have recently been proposed. For example, an electric refrigerator contains about 180 g of Freon-12 as a refrigerant, and its heat insulating material contains 700 to 800 g of Freon-11 as a residual foaming agent.
Such existing CFCs must be recovered and destroyed by some method. Of these freons, the refrigerator,
Waste fluorocarbons for refrigerants, such as household air conditioners and car coolers, have their locations determined, so it is possible to extract the fluorocarbons with an appropriate extraction device and disassemble them with a dedicated decomposition device. However, since CFCs used as a foaming agent and remaining in the heat insulating material are dispersed in the heat insulating material in the form of minute bubbles, such CFCs cannot be treated as they are. Therefore, it is necessary to perform a troublesome treatment such as burning and decomposing the residual Freon together with the heat insulating material, or finely crushing the heat insulating material to release the Freon into the air or gas in the crushing environment and treating the reduced concentration of Freon. there were.

There is a demand for a method capable of reliably and safely decomposing such CFCs.

[0004]

2. Description of the Related Art The following method is recommended by the United Nations Environment Program (UNEP) as a technology for burning and decomposing CFCs (Kohei Urano, Chizu Kimura: "Technology for incinerating decomposition of specific CFCs", PPM, 7/1994, pp. 77-83).

Liquid injection method Reactor cracking method Gas / fume oxidation method Rotary kiln method Cement kiln method Municipal solid waste incineration method (for hard urethane foam etc.) Therefore, a method of mixing gas freon into combustion air for combustion decomposition, The above-described method of burning and decomposing the CFCs confined in the heat insulating material together with the heat insulating material in the municipal solid waste incinerator is a known technique.

Since an electric refrigerator or the like brought into a cleaning plant as large-scale waste is usually put into a crushing facility, the refrigerant CFC can be taken out. However, in order to treat CFCs in the heat insulating material, the outer panel of the refrigerator and the heat insulating material are separated before crushing, and only the heat insulating material is incinerated in the combustion furnace, so a new heat insulating material separation step is required. Therefore, at present,
Freon in the heat insulating material of the refrigerator is crushed together with the crushing equipment including the outer plate, and is contained in the exhaust of the crushing equipment and is unavoidably released into the atmosphere.

[0007]

According to the method for decomposing CFCs described in claim 1, when the CFCs are pyrolyzed in a stoker-type refuse incinerator to render them harmless, a secondary gas is supplied near the outlet of the combustion chamber of the incinerator. This is a method characterized by mixing CFCs with air. CFC decomposition method according to claim 2 wherein the strike Freon
Upon harmless thermally decomposed in over-batch waste incinerator, a method characterized by mixing Freon to combustion air supplied to the rearmost portion of the combustion chamber of the <br/> incinerator. The method for decomposing CFCs according to claim 3 is characterized in that, when decomposing CFCs in a stoker-type refuse incinerator to render them harmless, CFCs are mixed with the combustion air supplied to the main combustion stage of the incinerator. Is the way.

[0008]

According to the method for decomposing CFCs described in claim 1, when decomposing CFCs in a incinerator to render them harmless, CFCs are added to secondary air supplied near the outlet of the combustion chamber of the incinerator. The method is characterized by mixing.

In the method for decomposing CFCs according to a second aspect of the present invention, in decomposing CFCs in a incinerator to render them harmless, CFCs are mixed with combustion air supplied to the rearmost portion of the combustion chamber of the incinerator. Is the method.

In the method for decomposing CFCs according to a third aspect of the present invention, when decomposing CFCs by decomposing them in an incinerator to render them harmless, CFCs are mixed with the combustion air supplied to the main combustion stage of the incinerator. Is.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors carried out an experiment using an actual municipal solid waste incinerator to develop such a method. The present invention will be specifically described below using the results obtained by this experiment.

Experimental Example FIG. 1 is a diagram showing a stoker-type municipal solid waste incinerator with an amount of solid waste incineration of 300 t / day. Municipal solid waste is loaded into the furnace from the hopper (1), and in the combustion chamber (2), the drying stage (3), the main combustion stage (4), and the post-combustion stage (5) are placed in this order on the slanted grate. Move
During this period, it is sequentially combusted into ash, and the resulting ash finally falls into the ash treatment chamber (6) from the rear of the furnace. In the case of this furnace, the combustion air required for combustion is located in one location in the drying stage (3) and in the main combustion stage (4).
It is distributed to a total of 6 locations: 2 locations in the post combustion stage (2), 2 locations in the post-combustion stage (5), and 1 location in the final furnace wall (16). Furthermore, the combustion chamber
Secondary air is supplied near the upper outlet of (2). The secondary air is also called furnace temperature control air or overfire air, and is supplied into the furnace from a supply port located adjacent to the rear side of the hopper and above the drying stage (3).
Exhaust gas generated by combustion is the first flue (7), second
After passing through the flue (8), sensible heat is released by the heat recovery device (10) (boiler) provided in the third flue (9), and the electric dust collector (11) and the smoke washing device (12 ), Via the exhaust gas reheater (13),
Emitted from the chimney (14) to the atmosphere.

[0013] In the incinerator having the above structure, the combustion air about 50000~60000Nm ³ / h supplied, or to the secondary air 2000~20000Nm ³ / h, is mixed from a predetermined position Freon at a rate of 15 kg / h An experiment was conducted to measure the decomposition rate. As CFC, CFC-11, which is often contained in the heat insulating material, was used. CFCs were supplied at four points A, B, C, and D in FIG.
That is, point A: wake side combustion air supply line of the two combustion air supply lines arranged in the main combustion stage (4) point B: combustion air from the last wall (16) of the furnace into the furnace Supply line point C: Entire combustion stage (ie drying stage (3), main combustion stage)
(4) The header D point of the combustion air supply line to the post combustion stage (5) and the furnace last wall (16): The secondary air supply line.

FIG. 1 shows an example in which CFC is mixed with combustion air at point A. The liquid chlorofluorocarbon stored in the tank (17) is vaporized through the flow meter (18), the pump (19) and the heater (20), and reaches the point A in the gaseous state through the fluorocarbon supply line (21).

Even when CFCs are mixed in the air at points B, C or D, the supply position is changed by switching the supply line (21), and CFCs are mixed in the air in the vaporized state as described above.

The CFC decomposition rate was measured by analyzing the concentration of CFC-11 remaining in the exhaust gas between the analysis point (15), that is, between the electrostatic precipitator (11) and the smoke washing device (12), and calculating the following formula. It was

Decomposition rate (%) = 100 (1-G × (F1-
F0) / F2)) In the formula, G: dry exhaust gas flow rate (Nm ³ / h) F 1: concentration of Freon-11 in exhaust gas when CFC is supplied (kg / Nm ³ ) F0: in exhaust gas when CFC is not supplied the concentration of CFC ^{-11 (kg / Nm 3) F2} : feed amount of CFC-11 into the air of (kg / h)

The relationship between the decomposition rate at each supply point thus obtained and the average residence time of the first flue in the furnace shown in FIG. 1 was determined. The results of this experiment are shown in the graph of FIG. The following can be said from this result.

When CFCs were supplied from point C to the entire combustion stage, the decomposition rate of CFCs was obviously improved when the first flue residence time was long.

When CFCs were mixed in the main combustion stage air at point A, the decomposition rate was slightly better than that from point C, which was supplied over the whole. This is because a considerable part of the air supplied as the combustion air is supplied as the main combustion stage air, and in the case of point C supply (in this case, the air has a shorter residence time than the main combustion stage). The degradation rate was a little low, and it is to improve.

When CFCs were mixed in the combustion air supplied from the last wall of the furnace into the furnace at the point B, the retention time was the longest and the decomposition rate was good.

Good results were also obtained when supplying CFCs to the secondary air at point D. The decomposition rate in the case of supplying CFCs from this position seems to be inconsistent with the interpretation of the decomposition rate in other places, because the average residence time is the shortest. FIG. 3 shows the temperature distribution and gas flow in the incinerator of this type by simulation calculation. The shaded area in the figure represents the highest temperature part, and the black part represents the lower temperature. As can be seen from FIG. 3, the point D is at the maximum temperature position, and is an optimal position in terms of temperature conditions for supplying CFCs.

From the above experiments, it was found that the preferable supply positions in the case of mixing CFCs in the air for incineration of municipal wastes for combustion decomposition are as follows.

[0024] Position of point D> Position of point B> Position of point A> Position of point C Therefore, not only recovered CFC but also diluted CFC such as exhaust from crushing equipment is stoker-type municipal waste incineration. If supplied from each of the above positions in the furnace, CFCs can be easily decomposed by combustion at a high decomposition rate as shown in the experimental example.

[0025]

As described above, according to the present invention, it is difficult to recover not only the CFCs recovered by using the existing stoker type waste incinerator without installing special equipment, but also the recovery until now. Diluted CFC contained in the exhaust of the existing crushing equipment can be decomposed reliably and with a high decomposition rate,
It can contribute to global environment protection.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of a stoker-type refuse incinerator and a supply position and an analysis point of CFCs in an experiment.

FIG. 2 is a graph showing experimental results.

FIG. 3 is a vertical cross-sectional view of the incinerator showing the temperature distribution and gas flow in the incinerator.

[Explanation of symbols]

1: Hopper 2: Combustion chamber 3: Drying stage 4: Main combustion stage 5: Post combustion stage 16: Furnace last wall 21: Freon supply line

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F23G 7/00 F23G 7/00 ZABZ F23J 15/00 F23L 7/00 Z 15/04 F23J 15/00 D 15/08 J F23L 7 / 00 L (73) Patent holder 000005119 Hitachi Zosen Corporation 1-89 Minami Kohoku 1-89, Suminoe-ku, Osaka-shi, Osaka (74) Above two agents 100060874 Attorney Eisuke Kishimoto (3 outside) (72) Inventor Minoru Sawaji 5-59 Karuizawa-cho, Ikoma-shi, Nara (72) Inventor Takashi Yahagi 2-32-3, Kinrakuji-cho, Amagasaki-shi, Hyogo Takuma Co., Ltd. (72) Ryoji Samejima Kinraku-ji, Amagasaki-shi, Hyogo Town 2-32 Takuma Co., Ltd. (72) Inventor Hiroshi Onishi 5-3-28 Nishikujo, Konohana-ku, Osaka City Nitate Shipbuilding Co., Ltd. (72) Kenji Hota Nishikujo 5 Nishinojo-ku, Osaka Ding No. 3 28 No. 28 Nitto Shipbuilding Co., Ltd. (56) Reference JP-A-9-196349 (JP, A) JP-A-8-224441 (JP, A) JP-A-8-114315 (JP, A) Kaihei 7-88457 (JP, A) JP 8-24364 (JP, A) Japanese Patent Publication 2-15225 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) F23G 7 / 00 F23G 5/00

Claims (3)

(57) [Claims] 1. Municipal solid waste, characterized in that, when pyrolyzing CFCs in a stoker-type refuse incinerator to render them harmless, CFCs are mixed with secondary air supplied near the combustion chamber outlet of the incinerator. Freon decomposition method by incinerator. 2. A city characterized by mixing CFCs with combustion air supplied to the rearmost part of the combustion chamber of the incinerator when the CFCs are pyrolyzed and rendered harmless in a stoker-type refuse incinerator. Freon decomposition method using a garbage incinerator. The 3. Freon Upon harmless thermally decomposed in Stoker incinerator, characterized by mixing Freon to combustion air supplied to the main combustion stage of the incinerator, city
CFC decomposition method using municipal waste incinerator.