JP3309586B2 - Gasification and melting method of waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste gasification / melting furnace which forms a deposited layer composed of waste and carbon-based combustibles partially flowing in the furnace and generates combustible gas. is there.

[0002]

2. Description of the Related Art Among furnaces which melt incombustible and ash components of waste and generate flammable gas at the same time, the gas temperature in the space above the furnace main body (free board portion) is set to 950 ° C. or higher to reduce dioxin emissions. Japanese Patent Application Laid-Open No. 5-34622 discloses a technique for suppressing generation and using a flammable gas.
There is one disclosed in Japanese Patent Application Laid-Open No. 1 (1994).

[0003] In this technique, the amount of oxygen-containing gas is blown from a tuyere installed at the lower part of the furnace, and the accumulated layer composed of waste and auxiliary fuel introduced from the upper part is caused to partially flow, thereby freeing. At the same time as controlling the temperature of the board to 950 ° C or higher, the combustion heat generated when the combustibles in the waste burn, melts the ash and non-combustibles in the waste, and melts them through the outlet at the bottom of the furnace. Discharge objects.

[0004]

In the above-mentioned technique, both the control of the temperature of the freeboard portion and the control of melting at the furnace bottom are performed by changing the amount of oxygen-containing gas blown from the tuyere. There is a problem as follows.

(1) If the temperature of the freeboard section is controlled by the amount of air blown from the tuyere, it is necessary to maintain the optimum range for melting and the temperature of the freeboard section by the amount of air blown from the tuyere. Because the area that satisfies both the optimal ranges is narrow,
Due to a change in the properties of the waste to be treated or a slight change in the amount of treatment, an appropriate molten state at the furnace bottom cannot often be maintained. (2) Even if the temperature of the free board portion is controlled to 950 ° C. or more, there is a problem that the decomposition of tar cannot be sufficiently performed.

[0006]

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for gasifying and melting waste, comprising the steps of:
Fluidizing gas containing oxygen gas is blown from the tuyere provided at the bottom
See, waste partially flow into the furnace and thereby forming a deposition layer made of carbon-based combustible material, in the gasification method of melting waste to produce a combustible gas, the freeboard section
Measure the temperature of flammable gas and CO gas concentration respectively,
Based on the measurement results, at least one of the air and oxygen gas blown from the air blow port provided above the upper surface of the deposition layer is provided to each supply pipe.
When controlling by the regulating valve, the temperature of the flammable gas
When the measured value is 1000 ° C or less, adjust the opening of the regulating valve.
The amount of air or oxygen gas blown from the air outlet
Increase, before when the temperature measured value is not less than 1200 ° C.
The air blown from the air outlet by adjusting the opening of the regulating valve
The Rukoto reducing the amount or oxygen gas amount, Furibo
The temperature of the flammable gas at the head is 1000 ° C or more and 1200 ° C
Control the following range, the CO gas concentration of the combustible gas
The calorific value of the flammable gas is estimated from the measured value and the following formula,
When the calorific value is 1000 kcal / Nm ³ or less,
Adjust the opening of the air to reduce the amount of air blown from the air outlet
When the estimated calorific value is 1200 kcal / Nm ³ or more
Adjusts the opening of the regulating valve and blows in from the air outlet
By reducing the amount of oxygen gas, the free board
The calorific value of flammable gas is 12 at 1000 kcal / Nm ³ or more.
A gasification and melting method for waste, wherein the method is controlled to a range of 00 kcal / Nm ³ or less . Gas calorific value kcal / Nm ³ = α × (CO gas concentration) × 3.02 where α is a coefficient that changes depending on the properties of the waste.

[0008]

In addition to the tuyere that blows a fluidizing gas containing oxygen gas into the lower part of the furnace main body, a blow port that blows combustion air, oxygen, etc., is provided above the upper surface of the deposition layer, that is, at the free board. The fluidizing gas containing oxygen gas from the furnace is responsible for melting the ash and non-combustible components of the waste, while the flammability of the free board is reduced by the combustion air and oxygen gas blown into the free board from the air outlet . The role of controlling the temperature and the calorific value of the gas, respectively, is shared. That is, the temperature of the flammable gas
Out of the range of 1000 ° C to 1200 ° C
If the air is blown from the
Increase or decrease the amount of gas, the temperature of the flammable gas in the freeboard section
Is controlled within the range of 1000 ° C. to 1200 ° C.
In addition, the measured value of the CO gas concentration of flammable gas and a predetermined formula
And the calorific value of the flammable gas is estimated from
In 1000kcal / Nm ³ or more 1200kcal / Nm ³ following
If it is out of range, the amount of air blown from the air outlet
Or reduce the amount of oxygen gas and generate
The calorific value of flammable gas is 1000 kcal / Nm ³ or more1
Control is performed within the range of 200 kcal / Nm ³ or less.

Thus, the stabilization of melting and flow and the temperature control of the free board can be controlled independently. And, the combustion air blown into the free board part and
By controlling at least one of blowing amount of oxygen gas, the temperature of the combustible gas 1000 ° C. to 1200
℃ or less, and the calorific value of flammable gas is 1000 kca
1 / Nm ³ or more and 1200 kcal / Nm ³ or less .

[0010] Thus, the temperature of the flammable gas is set to 1000 ° C.
At above 1200 ° C , ash is fused to the furnace wall
Without, suppresses the production of dioxin <br/> emissions resulting from the combustion of waste, tar <br/> in combustible gas sufficiently decomposed and removed, fuel gas supplied to the gas turbine
The tar content can be reduced to a level where there is no problem
it can. Further, by suppressing the combustion of the combustible gas in the furnace, the calorific value of the combustible gas generated can be reduced by 1000 k.
It controls cal / Nm ³ or more and 1200 kcal / Nm ³ or less to reduce consumption of expensive blown oxygen gas,
Easy to use for gas turbines.

[0011]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. At the top of the melting furnace 1, there is provided a charging inlet 5 into which waste, auxiliary fuel, slag adjusting material and the like are charged. The melting furnace includes a free board section 1a, a bosh section 1b, and a furnace bottom section 1c in the height direction.

A tuyere 2 is provided around the lower part of the melting furnace 1,
A fluidizing gas containing oxygen is supplied. An air outlet 3 for blowing combustion air, oxygen, or the like is provided around the free board portion 1a.

The amounts of the combustion air and oxygen to be blown are adjusted by an air amount adjusting valve 15 and an oxygen amount adjusting valve 16, respectively. The blown air is heated by steam in the heat exchanger 17 as necessary. Then, the heating temperature is adjusted by a signal from the thermometer 13 to adjust the steam amount by the steam amount adjusting valve 14 so as to maintain the predetermined temperature.

The waste, auxiliary fuel and the like charged in the furnace are deposited in the furnace, and a partial fluidized bed 7 partially flowing by the oxygen-containing gas blown from the tuyere 2 at the lower part of the furnace is formed. . Thereby, the waste and the auxiliary fuel are taken into the sedimentary layer 7 by the flow.

The waste or auxiliary fuel taken into the vicinity of the tuyere 2 is burned by the oxygen-containing gas blown from the tuyere 2. The combustion gas dry-distills and melts the waste by sensible heat while flowing the waste accumulation layer 7. The combustible gas and fine dust generated by the dry distillation and reduction of the waste are discharged from the gas discharge port 6 after staying at the free board section 8 for several seconds.

The concentration of the combustible gas discharged is measured by an analyzer 11.
, The temperature is measured by the thermocouple 12, the temperature of the flammable gas is 1000 ° C. or more, and the calorific value is 1000 kcal / Nm ^3.
As described above, the amount of air blown from the air outlet 3 is controlled.

Here, the calorific value is estimated from the CO concentration in the gas by the analyzer 11. H ₂ and CH are contained in the exhaust gas.
₄ , the calorific value of the gas is smaller than the calorific value calculated only from CO in the exhaust gas, as shown in FIG.
The actual calorific value is higher. Since this ratio changes depending on the property of the waste to be treated, the calorific value is predicted as follows using a coefficient α that changes depending on the property of the waste.

Gas calorific value kcal / Nm ³ = α × (CO gas concentration) × 3.02 Here, the value of coefficient α is 1.3 to 1.8 in the case of shredder dust. In addition, in the range of the control target temperature, as shown in FIG. 3, it is about 1.4 to 1.6. The value of α changes because the ratio of hydrogen or methane to CO changes depending on the temperature.

Also, in the case of municipal solid waste, almost the same method can be applied, and the value is almost the same as that of shredder dust. Specific control will be described below.

In the control, the control of the calorific value is performed while giving priority to the control of the temperature and then the reduction of the oxygen consumption as much as possible. When the temperature of the free board portion is 1000 ° C. or less, the air amount at the air outlet is increased, and when the temperature is 1200 ° C. or more, the air amount is reduced.

When the calorific value is 1200 kcal / Nm ³ or more, the oxygen amount is reduced, and if possible, the air amount is also reduced.
When the calorific value is 1000 kcal / Nm ³ or less, the oxygen amount is increased, and the air amount is reduced as necessary. Table 1 shows the above control contents.

[0022]

[Table 1]

Here, the temperature of the free board is set to 1000 °
The reason why the temperature is controlled to be equal to or higher than C and equal to or lower than 1200 ° C. is that when the temperature is equal to or higher than 1200 ° C., a problem that ash is fused occurs.

The calorific value of the gas is 1000 kcal / Nm
^The reason why the control is made to be ³ or more is that when the generated gas is used for a gas turbine, a calorie gas that can be operated stably can be supplied.

The upper limit of the calorific value of the combustible gas is set to 120
0 kcal / Nm ³ is the expensive oxygen
This is to save gas consumption. In this way, the temperature of the exhaust gas, that is, the temperature of the flammable gas in the free board portion is set to 100
By controlling the temperature between 0 ° C. and 1200 ° C. ,
As shown in (a) and (b) , the concentration of dioxins, that is, the toxic equivalent concentration and the tar concentration can be reduced.

The ash and incombustibles such as wastes and auxiliary fuel that have been introduced are heated from 1300 ° C. to 15 ° C. by the high-temperature combustion gas generated by the oxygen-containing gas blown from the tuyere 2.
The slag is heated to 00 ° C and becomes a molten state.
From the furnace.

On the other hand, the gas discharged from the melting furnace 1 is subjected to a washing treatment in a washing tower 9 and then stored in a gas holder 10 to be used in a power generation device or the like by a gas turbine. Hereinafter, a specific example in which shredder dust is treated as waste will be described with reference to Table 2 in comparison with the conventional method.

[0028]

[Table 2]

Here, No. 1 and No. 2 are conventional cases in which air is not blown from the air outlet, and No. 3 is a case according to the present invention. In No. 1, stable melting was possible, but the temperature of the freeboard portion was as low as 600 ° C. Therefore, in No. 2, the amount of air blown from the tuyere was increased, and the freeboard temperature was increased to 1050 ° C. This is because a decrease in temperature due to reduction of the combustion gas due to flow and blow-through is reduced. However, when the amount of air blow increased, the flow state became too severe and the stability of melting was deteriorated.

On the other hand, as in No. 3, when the temperature of the freeboard portion is controlled by blowing the oxygen-containing gas from the air outlet and burning the combustible gas without changing the air volume from the tuyere. Thus, stable melting was possible while maintaining the temperature of the free board at 1000 ° C. or higher.

[0031]

[0032]

According to the present invention, the temperature of a combustible gas is measured.
The measured value is out of the range between 1000 ° C and 1200 ° C
Air volume or oxygen gas blown from the
Increase or decrease the amount of flammable gas in the freeboard section by 1
It can be controlled within the range of 2,000 ° C to 1200 ° C.
As a result , the concentration of dioxins and the concentration of tar can be reduced. Also, according to the present invention , flammable
From the measured value of the CO gas concentration of the gas and the prescribed formula, it is flammable
The calorific value of gas is estimated, and the estimated calorific value is 1000 kcal
/ Nm ³ or more and out of the range of 1200 kcal / Nm ³ or less
The air or oxygen gas blown from the
And the calorific value of the flammable gas generated in the free board part is increased to 1000 kcal / Nm ³ or more and 1200 kcal /
Nm ³ or less can be controlled.
The combustible gas thus obtained can be used as fuel for gas turbines and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the CO concentration of exhaust gas and the calorific value.

FIG. 3 is an explanatory diagram showing a relationship between a temperature of a free board portion and a coefficient α.

FIG. 4 is an explanatory diagram showing a relationship between the temperature of a free board, a toxic equivalent concentration, and a tar concentration.

[Explanation of symbols]

 2 ... tuyere, 3 ... air outlet, 7 ... sedimentary layer.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsuneo Matsudaira 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Nao Nakamura 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan (72) Inventor Minoru Asanuma 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-5-346218 (JP, A) JP-A-53-32978 (JP) JP-A-4-203802 (JP, A) JP-A-5-272732 (JP, A) JP-A-58-66711 (JP, A) JP-A-1-184314 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) F23G 5/027 F23G 5/00 F27B 1/16

Claims (1)

(57) [Claims] 1. A lower part of a furnace main body provided with a free board part.
Blowing gas containing oxygen gas from the tuyere
To form the waste and the deposited layer made of carbon-based combustible material to partially flow into the furnace, the gasification and melting method for wastes to generate combustible gases, a combustible gas freeboard temperature and CO Gas concentration
Each of them was measured, and based on the measurement results, the blowing amount of at least one of the air and the oxygen gas blown from the air blowing port provided above the upper surface of the deposition layer was respectively measured .
When controlling with a regulating valve provided in a supply pipe, when the measured value of the temperature of the flammable gas is 1000 ° C. or less, the opening degree of the regulating valve is adjusted and the air is blown from the blowing port.
The amount of air or oxygen gas is increased, and the temperature
When the temperature is 200 ° C or more, the opening of the regulating valve is adjusted to
Reduce the amount of air or oxygen gas blown from the
By setting the temperature of the flammable gas in the free board
It was controlled in the range of 000 ° C. or higher 1200 ° C. or less, combustible from the measured values and the following formula of CO gas concentration of the combustible gas
The calorific value of the reactive gas is estimated, and the estimated calorific value is 1000 kcal.
/ Nm ³ or less, adjust the opening of the regulating valve to adjust
The amount of air blown from the air outlet is reduced,
When 1200 kcal / Nm ³ or more, adjust the opening of the regulating valve.
Adjust to reduce the amount of oxygen gas blown from the air outlet
The amount of heat generated by the flammable gas in the freeboard
In 1000kcal / Nm ³ or more 1200kcal / Nm ³ following
A method for gasifying and melting waste, wherein the method is controlled within a range . Gas calorific value kcal / Nm ³ = α × (CO gas concentration) × 3.02 where α is a coefficient that changes depending on the properties of the waste.