JP2001027411A - Gasification melting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily control the combustion heat quantity in a melting furnace to be constant without generating the control delay by unifying the combustion control. SOLUTION: In this melting method, the refuse is directly or partially heated in a gasificatio furnace 1 and termally decomposed, and the generated gas, etc. C obtained in the pyrolysis is burned at high temperature in a rear stage melting furnace 2 to melt the ash into the slag. The auxiliary fuel D and the air B are fed to the melting furnace 2, and the increase/decrease in the feed of the auxiliary fuel D is controlled while maintaining the feed of the aid B at the constant level so that the oxygen concentration of the combustion waste gas from an outlet of the melting furnace is constant, and the combustion heat quantity in the melting furnace 2 is kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasification and melting method for incinerating refuse such as general waste and industrial waste.

[0002]

2. Description of the Related Art In recent years, general waste discharged from households and the like, industrial waste such as sludge, waste plastic, waste oil, and the like, or solid waste such as solid waste fuel (hereinafter simply referred to as "garbage"). As a method for incineration of waste, a gasifier and a melting furnace are used in combination, and the waste is first thermally decomposed in the former gasifier,
Attention has been paid to a gasification and fusion method in which a generated gas or the like containing a combustible gas and a solid combustible material obtained by the thermal decomposition is burned at a high temperature in a subsequent melting furnace to melt ash and turn into slag. In other words, this gasification and melting method has a good combustion efficiency because it is mainly gas combustion, it can perform combustion at a low air ratio and can greatly reduce the amount of exhaust gas, it can make harmful dioxins almost harmless by high temperature combustion, and it can be disposed of. This is because there is an advantage that ash in the material can be converted into harmless slag.

However, in order to efficiently carry out this gasification and melting method, as described above, refuse is thermally decomposed by indirect heating or partial combustion in a gasification furnace, and the generated gas and the like obtained by this thermal decomposition are obtained. Ash is melted at a high temperature in the subsequent melting furnace to melt the ash, and is converted into slag and recovered.Thus, the combustion heat in the latter melting furnace is stabilized to stabilize the combustion, and the furnace temperature is kept constant. It is necessary to keep.

[0004]

However, since the pyrolysis reaction performed in the gasification furnace at the former stage varies depending on various conditions such as the composition and supply amount of refuse, or the heating temperature and the supply amount of air, The amount of heat of the pyrolysis gas sent to the subsequent melting furnace is not constant, and it is difficult to control the amount of combustion heat in the melting furnace as described above. That is, it is difficult to make the heat of combustion in the latter melting furnace constant unless the heat of the pyrolysis gas generated in the former gasifier is adjusted to be constant.

Conventionally, as a countermeasure for keeping the calorific value of the pyrolysis gas in the preceding gasification furnace constant as described above, an auxiliary fuel is supplied to the gasification furnace as described in, for example, JP-A-9-236220. A method of adjusting the supply amount of the auxiliary fuel, or a method of adjusting the supply amount of refuse to the gasifier has been proposed. However, since each method is an adjustment to the former gasifier, it takes several tens of seconds or more for the adjusted result to appear in the latter melting furnace, which causes a control delay (or a response delay). There was a disadvantage.

[0006] In addition, as plastics are separated according to the Containers and Packaging Recycling Law, the calorific value of the waste decreases, and auxiliary fuel is required for melting. However, the method of controlling the amount of auxiliary fuel used has been clarified. Not.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gasification and melting method which does not cause a control delay in controlling the amount of combustion heat in a melting furnace to be constant, and which facilitates management by unifying the combustion control. is there.

[0008]

According to the gasification and melting method of the present invention which achieves the above object, the waste is thermally decomposed by indirect heating or partial combustion in a gasification furnace, and the generated gas or the like obtained by the thermal decomposition is obtained. In a gasification and melting method in which ash is melted and slag is formed by high-temperature combustion in a subsequent melting furnace, an auxiliary fuel and air are supplied to the melting furnace, while maintaining a constant supply amount of the air.
The supply amount of the auxiliary fuel is controlled to increase or decrease so that the oxygen concentration of the combustion exhaust gas from the outlet of the melting furnace becomes constant, and the amount of combustion heat in the melting furnace is made constant.

As described above, the auxiliary fuel and the air are supplied to the subsequent melting furnace, and the supply amount of the air is kept constant, while the supply amount of the auxiliary fuel is reduced by the combustion exhaust gas from the melting furnace. Since the amount of combustion heat in the melting furnace is directly controlled by adjusting the oxygen concentration so as to be constant according to the oxygen concentration, there is no control delay as in the conventional control method. Moreover, since the combustion control is centralized only to the supply amount of the auxiliary fuel, the management can be simplified and the practicality can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a gasification and melting furnace facility for implementing a combustion control method according to the present invention.

In the present invention, "garbage" to be incinerated in the gasification and melting furnace facility includes general waste, sludge, waste plastic, waste oil, and other industrial waste discharged from households, and solid waste fuel. Solid waste.

[0012] As shown in FIG.
The gasification furnace 1 is provided in the first stage, and the melting furnace 2 is provided in the second stage. Further, a heat exchanger 3 for recovering thermal energy in the exhaust gas and an exhaust gas treatment device 4 for detoxifying harmful components in the exhaust gas are connected to the exhaust side of the melting furnace 2.
In the illustrated embodiment, a waste heat boiler 5 is provided in parallel with the heat exchanger 3 so as to effectively use residual heat.

The gasification furnace 1 is provided with a refuse supply path 6 for supplying refuse A and an air supply path 25 for supplying air B. The gasifier 1 indirectly heats or partially burns the refuse B supplied from the refuse supply path 6 at a low air ratio (actual air amount / theoretical air amount) of about 0.3 to reduce the furnace temperature to about 500 ° C.
By maintaining the temperature at 650 ° C., it is thermally decomposed, and generates a combustible gas and a solid combustible (hereinafter referred to as generated gas C) by the thermal decomposition.

In general, a fluidized-bed furnace for performing pyrolysis by partial combustion or a rotary kiln-type furnace for performing pyrolysis by indirect heating is used as the gasifier 1. The generated gas C generated in the gasification furnace 1 is sent to the melting furnace 2 at the subsequent stage, where it is burned at a high temperature by supplying sufficient air. As a result of this high-temperature combustion, the generated gas C melts the ash of the components and flows out to the recovery path 8 to be recovered as slag E. Further, high-temperature combustion exhaust gas F is discharged from the exhaust port 9.

An air supply device 10 and an auxiliary fuel supply device 11 are connected to the melting furnace 2 to supply air B and auxiliary fuel D, respectively. Among them, the air supply device 10 is provided with a blower 12 and a control valve 13 in order in the supply direction, and the control valve 13 is provided with a flow meter 14 on the upstream side.
The opening degree is controlled by the PID controller 15 on the basis of the air amount measured in the step (1), so that the supply amount to the melting furnace 2 is made constant. The amount of air is an amount corresponding to the required combustion amount for maintaining the furnace temperature of the melting furnace 2.

Further, the auxiliary fuel supply device 11 is provided with a pump 16 and a control valve 17 along the supply direction. The control valve 17 is configured to increase or decrease the supply amount of the auxiliary fuel D so that the oxygen concentration of the combustion exhaust gas F on the exhaust port side of the melting furnace 2 is kept constant. That is, the melting furnace 2
The opening degree of the control valve 17 is controlled by the arithmetic and control unit 19 based on the measurement value of the exhaust gas oximeter 18 provided on the exhaust side.

The auxiliary fuel D used here may generally be heavy oil, but may be kerosene, natural gas, propane or the like. In consideration of the time required for combustion in the main combustion part of the melting furnace 2 and the quantitativeness and variability of the supply, the auxiliary fuel used in the present invention is preferably a liquid fuel or a gaseous fuel.

By providing the air supply device 10 and the auxiliary fuel supply device 11 in the melting furnace 2 as described above, air B is supplied from the air supply device 10 at a constant rate, while the air B is generated in the gasification furnace 1. Simultaneously with the supply of the generated gas C, the auxiliary fuel D is supplied from the auxiliary fuel supply device 11 while increasing and decreasing the auxiliary fuel D so as to keep the oxygen concentration of the combustion exhaust gas F coming out of the exhaust port of the melting furnace 2 constant. Internal temperature is about 1
The temperature is kept substantially constant at 250 ° C. to 1450 ° C., and the heat of combustion of the melting furnace 2 is kept constant.

After the combustion as described above, the flue gas F discharged from the melting furnace 2 is sent to the heat exchanger 3 where it is cooled to low-temperature flue gas Fa by heat recovery, and further passes through the flue gas treatment device 4. The harmful components are removed, and the harmful exhaust gas Fb is released into the outside air.

The waste heat boiler 5 provided with the heat exchanger 3 for utilizing the heat of the exhaust gas F is provided with a flow meter 20 and a control valve 22 in a supply path of raw water to be vaporized, and the control valve 22 is a flow meter. The opening degree is adjusted by the PID controller 21 based on the 20 measured values, so that the supply amount of raw water to the waste heat boiler 5 is kept constant. Further, a pressure gauge 23 is provided on the outlet side of the steam generated by the waste heat, and a PID controller 24 controls the output of the PID controller 15 based on the measured value, and controls the supply amount of the air B to the melting furnace 2. The steam pressure is adjusted to be constant.

As described above, in the gasification and melting furnace equipment of the present invention, an air supply device 10 for supplying a constant amount of air to the melting furnace 2 and an oxygen concentration of the combustion exhaust gas F discharged from the melting furnace 2 are provided. Since the auxiliary fuel supply device 11 for variably controlling the supply amount of the auxiliary fuel D so as to keep it constant is mounted, for example, the input amount of the refuse A into the gasifier 1 temporarily increases, and the generated gas When the generation amount of the equal C increases, the amount of air supplied from the air supply device 10 is constant, resulting in insufficient air, and the oxygen concentration of the combustion exhaust gas F decreases. However, the auxiliary fuel supply device 11 operates to reduce the supply amount of the auxiliary fuel D so as to return to the original oxygen concentration according to the decrease.

On the other hand, when the amount of the refuse A into the gasifier 1 is temporarily reduced and the amount of the generated gas C is reduced, the air supply device 10 sends the gas to the melting furnace 2.
Is constant, the air becomes excessive and the oxygen concentration of the combustion exhaust gas F at the outlet of the melting furnace increases. However, the auxiliary fuel supply device 11 operates to increase the supply amount of the auxiliary fuel D so as to return to the original oxygen concentration according to the increase.

Therefore, even if the amount of the refuse A charged into the gasification furnace 1 changes, the amount of combustion heat generated in the melting furnace 2 is kept constant, and the temperature in the furnace of the melting furnace 2 can always be kept constant. . In addition, since the supply amount of the auxiliary fuel is directly adjusted to the melting furnace 2, a control delay (or a response delay) does not occur. In addition, since the combustion heat of the melting furnace can be made constant and the optimum air ratio can be adjusted only by controlling the increase and decrease of the supply amount of the auxiliary fuel, the fuel control can be unified and the management can be simplified.

In the present invention, a fluidized bed type furnace is generally used as a gasification furnace. However, the type of the gasification furnace is not limited to a fluidized bed type as long as it has a function of thermally decomposing waste by indirect heating or partial combustion. Other types may be used.

The oxygen concentration meter for measuring the oxygen concentration of the combustion exhaust gas at the exhaust port of the melting furnace is not particularly limited as long as it can measure the oxygen concentration. It is preferable to use a material which is resistant to corrosive atmosphere and temperature such as dust and chlorine gas in combustion exhaust gas. From such a viewpoint, a zirconia oxygen concentration meter is particularly preferable.

In the combustion control of the present invention, when it is desired to set the temperature inside the melting furnace to be constantly high, it is only necessary to increase the combustion heat of the melting furnace. If you want to increase and lower it, lower it.

When the CO concentration in the exhaust gas is to be reduced steadily, the set value of the oxygen concentration in the combustion exhaust gas at the outlet of the melting furnace may be increased. When it is desired to reduce the amount of exhaust gas constantly, the set value of the oxygen concentration of the exhaust gas at the outlet of the melting furnace may be reduced. Generally, 5.0 to 5.5 vol% (w
et) degree is selected.

[0028]

As described above, according to the present invention, auxiliary fuel and air are supplied to the subsequent melting furnace, and the air supply is maintained at a constant level, while the gas generated in the gasification furnace is maintained. The supply amount of auxiliary fuel at the same time as the supply of product gas, etc.
Since the amount of combustion heat in the melting furnace is directly controlled by increasing or decreasing the oxygen concentration of the combustion exhaust gas from the melting furnace so that the oxygen concentration becomes constant, there is a possibility that a control delay occurs as in the conventional control method. There is no. Moreover, since the combustion control is centralized only to the amount of auxiliary fuel supplied, management is simplified,
Practicality can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a gasification and melting furnace facility used for carrying out the gasification and melting method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasification furnace 2 Melting furnace 10 Air supply device 11 Auxiliary fuel supply device 12 Blower 13 Control valve 16 Pump 17 Control valve 18 Oxygen concentration meter 19 Operation controller A Refuse B Air C Generated gas etc. (combustible gas and solid combustibles ) D auxiliary fuel E slag F flue gas

 ──────────────────────────────────────────────────の Continued on the front page (71) Applicant 000001834 Sanki Kogyo Co., Ltd. 1-4-1, Yurakucho, Chiyoda-ku, Tokyo (72) Inventor Masanori Ikeno 1-1-1, Sonoyama, Otsu, Shiga Prefecture Toray Engineering Inside the Ring Co., Ltd. (72) Inventor Shinichi Tanaka 23 Uji Kozakura, Uji-city, Kyoto Unitika, Central Research Laboratory of Unitika Co., Ltd. (72) Inventor Hiroomi Kamano 1-12-19 Kitahorie, Nishi-ku, Osaka-shi, Osaka Kurimoto Inside the Ironworks (72) Inventor Kazuhiro Manjo 1-4-1 Yurakucho, Chiyoda-ku, Tokyo Sanki Kogyo Co., Ltd.F-term (reference) 3K061 AA24 AB02 AB03 AC01 AC06 AC13 AC19 BA01 BA02 CA01 CA07 FA10 FA21 FA25 NB03 NB30 3K078 AA01 AA02 AA03 BA22 CA02 CA09 CA12 CA21 CA24

Claims (3)

[Claims] 1. A gas that indirectly heats or partially burns garbage in a gasification furnace to thermally decompose, and that generates gas and the like obtained by the pyrolysis at a high temperature in a subsequent melting furnace to melt ash to form slag. In the chemical fusion method, the auxiliary fuel and air are supplied to the melting furnace, and the supply amount of the auxiliary fuel is kept constant while the oxygen concentration of the combustion exhaust gas from the melting furnace outlet is kept constant while the supply amount of the air is kept constant. A gasification and melting method in which the amount of heat of combustion in a melting furnace is controlled by increasing or decreasing as much as possible. 2. The gasification and melting method according to claim 1, wherein an oxygen concentration of the combustion exhaust gas from the melting furnace outlet is detected, and the supply amount of the auxiliary fuel is controlled to increase or decrease based on the detected value. 3. The gasification and melting method according to claim 1, wherein the auxiliary fuel is a liquid fuel or a gaseous fuel.