JP3230421B2 - Waste treatment method - 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 charging a waste fuel such as industrial waste and municipal solid waste and a solid fuel such as coke to form a deposit layer of the charge in a furnace, and an oxygen-containing gas. The present invention relates to a method of blowing and burning and heating to melt waste.

[0002]

2. Description of the Related Art There are many known techniques for treating waste by a melting method. However, most of these technologies use a vertical furnace, dry-distillate and gasify waste, and discharge ash and incombustibles as a molten material.

FIG. 2 is an explanatory view of a general method of melting waste. 1 is a melting furnace main body, 2 is a loading port for waste and the like provided at the upper part of the furnace, 3 is a tuyere provided at the lower part of the furnace, and 4 is an exhaust gas outlet.

[0004] In this method, waste and coke are charged from the charging port 2, and limestone is further charged as required. As the coke to be charged, for example, in JP-A-56-53314, the diameter of the lump is 40 m.
m to 50 mm are used. These charges are deposited and form a deposit 30 at the bottom of the furnace. As described below, the upper portion of the deposition layer 30 is a carbonization zone,
The lower part is a combustion and melting zone.

[0005] When an oxygen-containing gas is blown from the tuyere 3, carbon such as coke present in the combustion / melting zone below the deposition layer 30 burns. Then, the ash and incombustibles in the waste are melted in the combustion / melting zone by the combustion heat, and the waste is carbonized and gasified in the carbonization zone above the sedimentary layer 30. The residue of the dry distillation of the waste is burned together with the coke at the stage where it falls into the combustion / melting zone below the sedimentary layer 30.

The melt flows down while dropping in the deposition layer 30, accumulates at the furnace bottom, and is extracted from the slag discharge port 5. In addition, although a layer of a molten metal is formed in the molten material, a description relating to its discharge is omitted.

[0007]

However, the viscosity of the molten material (molten slag) generated when the waste is melt-processed is much higher than that of hot metal and the like generated in the blast furnace. During the operation in which the waste is melt-processed, a phenomenon in which the liquid permeability or the gas permeability of the deposition layer 30 decreases often occurs, and the operation becomes abnormal. This problem will be described with reference to FIG.

FIG. 3 is a diagram schematically showing the state of a deposited layer during operation. 1 is a melting furnace main body, 3 is a tuyere provided at the lower part of the furnace corresponding to a combustion / melting zone of a deposition layer, 3
Numeral 0 denotes a deposited layer of the charge, 31 denotes molten slag, and 5 denotes a slag discharge port. A raceway 32 is formed near the tuyere 3, and the high-temperature gas generated in the raceway 32 is sent into the combustion / melting zone of the deposition layer 30. As a result, the combustibles in the combustion / melting zone burn and the ash and the like are melted. The generated melt flows down in the deposition layer 30 as shown by the thick arrow in the figure,
Stored in the furnace bottom.

By the way, in the combustion / melting zone below the deposition layer 30, an unreacted residual portion 33 (a so-called furnace core) is formed in a shape divided into a mountain shape by a dotted line in the figure. You. The residual portion 33 is a portion in which unreacted materials that have been present for a long time in the central region where the combustion / gasification reaction is unlikely to occur are accumulated, and are mainly unburned coke. The coke in the remaining portion 33 gradually burns,
It reacts with the produced CO ₂ to be gasified and consumed, or its bottom moves little by little to the furnace wall side and goes out of the residual portion 33 to replace the one descending from above. However, this update takes a long time. For this reason,
While the coke in the remaining portion 33 stays in the high temperature region for a long time, it is thermally degraded and becomes finer.

When the coke is refined in this way, the porosity of the residual portion 33 is reduced, which greatly affects the liquid permeability and the gas permeability of the residual portion 33.

When the gap in the residual portion 33 becomes narrow, the adhered molten slag becomes difficult to drop, and the flow of the molten slag slows down, so that the molten slag stays in the residual portion 33. For this reason, the amount of the molten slag flowing down to the bottom of the furnace decreases, and it becomes impossible to discharge an amount corresponding to the amount of the generated slag.

When the gap in the remaining portion 33 becomes narrow,
The high-temperature gas sent from the raceway 32 becomes difficult to flow into the inside of the remaining portion 33 and blows upward, so that heat transfer to the inside of the remaining portion 33 becomes poor. For this reason, the temperature of the residual portion 33 decreases, the viscosity of the molten slag existing there increases, and the molten slag stays in the residual portion 33. Then, as in the above case, the slag is in a defective state, and the fluctuation of the blast pressure becomes large, so that it becomes difficult to control the blast and the operation of the melting furnace becomes very unstable.

The present invention solves the above-mentioned problems of the prior art,
It is an object of the present invention to provide a method for melting and processing wastes, which has good liquid permeability and air permeability of a residual portion formed below a sedimentary layer and can perform a stable operation.

[0014]

In order to achieve the above object, in the present invention, coke for iron making and coke for casting are charged as the solid fuel, and charging of coke for casting is performed.
The ratio is in the range of 10% to 30% of the total coke charge.
I do.

It should be noted that, unless otherwise specified, when simply referred to as coke, the coke indicates coke for iron making, and the coke used in the present invention is JIS (K210).
1-1961).

In order to improve the liquid permeability and air permeability of the remaining portion formed below the deposition layer, the present inventors increased the porosity of the remaining portion and kept the porosity from decreasing. I thought about it. Then, in order to satisfy these two items, coke for casting was used for a part of coke to be charged, and coke for casting was present in the above-mentioned remaining portion.

[0017] Coke for casting is dense and robust, has particularly high hot strength, and has low reactivity as compared with that for iron making. Further, as also referred to as large lump coke, the particle size is larger than that of ironmaking coke, and is 80 mm or more, or 120 mm or more.

When the casting coke having such properties is charged and is present in a residual portion formed below the deposition layer,
First, since the particle size is large, the porosity of the remaining portion is increased. Next, since the hot strength is large, the degree of thermal deterioration is small even if the material stays in the high temperature region for a long time, and it is difficult to make the particles fine. In addition, since it has low reactivity and has a large particle size and a small specific surface area, it is difficult to be consumed, and from this aspect, it is difficult to make the particles fine.

However, if the entire amount of coke to be charged is for casting, the coke for casting has a low combustion / gasification reaction rate and may generate heat for melting waste. Since coke cannot be charged, coke for casting and coke for steelmaking are used together.

The ratio of the coke for casting to the total amount of coke charged is preferably about 10% to 30%. If the proportion is less than 10%, the porosity of the residual portion formed below the deposition layer becomes small, and the air permeability and liquid permeability cannot be improved. Also, if more than 30% of the coke for casting is charged, the combustion rate of the coke for casting is low, so that the calorific value is insufficient and the conditions for melting and processing wastes cannot be satisfied.

[0021]

FIG. 1 is a diagram showing operation results when the method of the present invention is carried out. (A) shows the change over time in the amount of slag (the amount of molten slag withdrawn), (b) shows the change over time in the charging amount of coke for casting, and (c) shows the change over time in the ventilation resistance coefficient. . The airflow resistance coefficient is an index indicating the air permeability of the deposited layer, and is expressed by the following equation.

[0022]

(Equation 1)

In this operation, municipal solid waste of 1000 kg / h, iron coke of 100 kg / h, and limestone of 60 kg / h are charged into the melting furnace having the structure shown in FIG. Were continuously extracted. At this time, the target value of the basicity of the generated slag was set to 0.8.

When operating under the above conditions, (a)
As shown in the figure, the fluidity of the molten slag deteriorated from a certain point in time, and the discharge amount (the amount of slag) decreased to about 80% of the expected amount, resulting in an abnormal operation. At this time, the airflow resistance coefficient also increased as shown in FIG. For this reason,
(B) As shown in FIG.
Although charging was performed at a rate of g / hour, the state of insufficient slag was not solved yet, so coke for casting was charged again. As a result, as shown in FIG. 7A, the amount of slag was almost the expected amount (about 250 kg / hour), and the operation could be returned to a normal state.

In the above-mentioned operation, the casting coke is charged intermittently. However, the charging method is not limited to the intermittent charging. It may be charged continuously at a ratio.

[0026]

According to the present invention, waste and solid fuel are charged into a melting furnace, a deposition layer composed of these charges is formed in the lower part of the furnace, and an oxygen-containing gas is blown into this for combustion and heating. This is a method of charging coke for iron making and coke for casting as solid fuel when melting waste.

According to the present invention, by loading a casting coke having characteristics such as high strength, low reactivity, and a large particle size, the residual portion formed under the deposition layer is reduced. Since the porosity is large, and the granulation due to thermal deterioration is unlikely to occur, and the consumption rate is small,
The decrease in the porosity in the remaining portion is suppressed. For this reason, the liquid permeability and air permeability of the residual portion are not impaired, and stable operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of operation results when the method of the present invention is performed.

FIG. 2 is an explanatory diagram of a general method for melting and processing waste.

FIG. 3 is a diagram schematically showing a state of a deposited layer during operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melting furnace main body 2 Charging inlet 3 Tuyere provided at the lower part of furnace 4 Gas outlet 5 Slag outlet 30 Deposited layer of charge 31 Melt 32 Raceway 33 Residual part formed at the lower part of the deposited layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuo Suzuki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Tomohiro Yoshida 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan (56) References JP-A-5-288315 (JP, A) JP-A-7-150264 (JP, A) JP-A-7-146072 (JP, A) JP-A-7-70625 (JP, A) A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F23G 5/24 F23G 5/00

Claims (1)

(57) [Claims] 1. A waste furnace and a solid fuel are charged into a melting furnace, and a deposition layer composed of these charges is formed in a lower part of the furnace. An oxygen-containing gas is supplied from a tuyere provided in a lower part of the furnace to the deposition layer. In the method of blowing and heating to melt the waste, the coke for iron making and the coke for casting are charged as the solid fuel, and the charging ratio of the coke for casting is adjusted to the total coke.
A method for melting and treating wastes, wherein the amount is in the range of 10% to 30% with respect to the amount of mixed waste.