JP2004132667A - Fluidized bed type gasifying melting furnace system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure stable fluidization and control temperature for solving the problem of temperature increase of a gasifying furnace, especially when treating low quality garbage in a fluidized bed type gasifying melting furnace system. <P>SOLUTION: High oxygen concentration air and high nitrogen concentration air are divided by an air nature separator 16, and stable fluidization characteristics are maintained with restraining combustion of garbage by feeding the high nitrogen concentration air into the gasifying furnace 2. When layer temperature decreases, part of the high oxygen concentration air fed to a melting furnace 3 is fed to the gasifying furnace 2 and the oxygen content is increased for restraining temperature of the gasifying furnace. The high oxygen concentration air is used for combustion inside the melting furnace 3, combustible matter produced in the gasifying furnace 2 and assisting-fuels are burnt at high temperature, and use quantity of the assisting-fuel is decreased for decreasing running costs without changing entire air ratios. The system can be stably operated by securing gas for fluidizing from the high nitrogen concentration air not contributing to combustion and by restraining temperature with the high oxygen concentration air. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fluidized bed gasification / melting furnace system, and more particularly to a fluidized bed gasification / melting furnace system suitable for dealing with a wide range of wastes.
[0002]
[Prior art]
The gasification and melting furnace system pyrolyzes the combustibles in the refuse in the gasification furnace, burns the generated pyrolysis gas in the melting furnace, raises the temperature to above the ash melting point, melts the ash, and reduces the final disposal. It is a system aiming at.
[0003]
When a fluidized-bed gasifier is used as a gasifier in this type of conventional technology, the bed temperature of the fluidized bed is controlled by adding auxiliary fuel for controlling the amount of fluidized air or by adding cooling water. And bed temperature control such as spraying into the gasification furnace. (See Patent Document 1).
[0004]
[Patent Document 1]
JP-A-2001-182925 [0005]
[Problems to be solved by the invention]
However, when combusting waste with relatively low calorific value (hereinafter referred to as low quality waste), especially in waste containing much moisture, most of the calorific value of the waste in the gasification furnace is required to raise the bed temperature. Consumes.
[0006]
Therefore, since it is necessary to remove the amount of heat required for this water evaporation, as a pre-process for putting the refuse into the gas furnace, the water is removed using equipment such as a dryer and a dehydrator to increase the calorific value of the low-quality refuse. The stratum temperature rise is maintained and the amount of auxiliary combustion used in the melting furnace is reduced.
[0007]
In particular, when controlling the amount of air with this system, low-quality garbage with low combustible content in the garbage does not require much combustion air, so the minimum amount of air for maintaining stable fluidization of the fluidized bed is maintained. However, it was difficult to control the bed temperature and the gasification furnace temperature within a certain range.
[0008]
Also, if the temperature rises too high, water will be sprayed into the gasifier even though the water has been removed with a dryer or dehydrator, which is disadvantageous for combustion in the melting furnace. Could be.
[0009]
As described above, it is difficult for the above-described conventional technology to cope with a wide range of fluctuations in the waste quality, and when the waste quality is biased toward low-quality waste, the bed temperature and the gasification furnace temperature are reduced as described above. There was a problem with the control of.
[0010]
An object of the present invention is to provide a fluidized-bed gasification-melting furnace system capable of controlling the temperature while ensuring stable flow, and solving the problem of increasing the temperature of the gasification furnace particularly at low-quality waste.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a fluidized bed gasification and melting furnace system according to the present invention includes a fluidized bed gasification furnace that pyrolyzes refuse to generate a pyrolysis gas, and a melting and combustion method that burns and melts the pyrolysis gas. An air property separating means for separating air into air having a high oxygen concentration and air having a high nitrogen concentration, a first supply means for supplying the air having a high nitrogen concentration to the gasification furnace, Second supply means for supplying air having a high oxygen concentration to the melting furnace.
[0012]
According to the present invention, a gas for fluidization of a gasifier is secured by air having a high nitrogen concentration, which has a small contribution to combustion, and by controlling the temperature with air having a high oxygen concentration, a stable gas is obtained. Can be maintained. In addition, by using air having a high oxygen concentration as combustion air in a melting furnace, it is possible to achieve a higher temperature than burning with normal air, and it becomes easy to maintain the temperature at or above the ash melting point. .
[0013]
In addition, the amount of air can be reduced even when treating low-quality waste such as using auxiliary fuel in a melting furnace without changing the total air ratio from the conventional one, and in recent years there are also guarantees for waste incineration plants. The running cost can be reduced.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be schematically described with reference to FIG. In this example, in a fluidized-bed gasification and melting furnace system for treating refuse, the air is separated into air having a high oxygen concentration and air having a high nitrogen concentration by the air property separation device 16, and the gasification furnace 2 is provided with a nitrogen gas. Stable fluidization is maintained while supplying high-concentration air to suppress refuse combustion. When the gasification furnace inner layer temperature decreases, a part of the high oxygen concentration air to be supplied to the melting furnace 3 is supplied to the gas furnace 2, and the oxygen content is increased to control the gasification furnace temperature. is there.
[0015]
On the other hand, air having a high oxygen concentration is used as combustion air in the melting furnace 3, and combustible substances and auxiliary fuel generated in the gasification furnace 2 are burned at a high temperature, and the amount of auxiliary fuel used is reduced to keep the total air ratio unchanged. The running cost was reduced.
[0016]
As described above, by supplying air with high nitrogen concentration that does not contribute to combustion, stable fluidization of the gasifier is ensured, while air with high oxygen concentration is supplied to the melting furnace as combustion air. Accordingly, it is possible to achieve a higher temperature than burning with normal air, and it is easy to maintain the temperature at or above the ash melting point.
[0017]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a system diagram of a gasification and melting furnace system in the system of the present invention using an air property separation device. The refuse supplied from the refuse supply line 1 is decomposed into combustible gas and char (unburned carbon) in the gasification furnace 2, passes through the gasification furnace outlet connection pipe 20, and is heated to 1300 ° C. or higher in the melting furnace 3. Combustion at high temperature
The slag (molten ash) generated by the high-temperature combustion is discharged from the slag tap 4 to the outside of the system, and the combustion gas passes through the primary combustion chamber 5 and is mixed and burned with the secondary air in the secondary combustion chamber 6 to perform secondary combustion. It is sent to the downstream equipment through the room outlet flue 21.
[0019]
The air supplied to the gasification furnace 2 passes the atmosphere through an air property separation device 16 to be separated into air having a high nitrogen concentration, and is pressurized by a fluidizing air blower 7 and raised by a fluidizing air preheater 9. After warming, it is supplied to the gasifier 2.
[0020]
Air having a high nitrogen concentration supplied to the gasification furnace 2 has a low oxygen concentration involved in the combustion, and is not involved in refuse combustion except for raising the bed temperature in the gasification furnace. This is effective for generating flammable gas.
[0021]
In FIG. 1, reference numeral 8 is a combustion air blower, 11 and 12 are secondary combustion air adjustment dampers and melting furnace air adjustment dampers that operate based on the temperature of the gas at the outlet of the melting furnace, and 14 is a flow having a high nitrogen concentration. Reference numeral 15 denotes a combustion air flow meter having a high oxygen concentration, reference numeral 19 denotes an oxygen concentration meter, reference numeral 22 denotes a control device for controlling the combustion air blower 18, and reference numeral 23 denotes an auxiliary burner.
[0022]
FIG. 2A schematically shows the ratio of the carbon content in the garbage to carbon monoxide. FIG. 2B shows an outline of the ratio of carbon dioxide. As shown in these figures, it can be seen that the CO conversion at which the carbon content in the refuse is transferred to carbon monoxide, which is a heat source in the melting furnace, increases in proportion to the bed temperature.
[0023]
On the other hand, when the oxygen concentration in the air rises, the carbon dioxide is not limited to carbon monoxide but shifts to carbon dioxide, that is, complete combustion and does not work effectively as a heat source of the melting furnace.
[0024]
This also indicates that supplying gas having a low oxygen concentration and a high nitrogen concentration to the gasifier for gasification is effective. In this system, when the bed temperature is lower than the set range by the gasification furnace bed thermometer 17, the oxygen concentration adjusting damper 13 is opened, and the fluidizing blower sucks air having a high oxygen concentration.
[0025]
As a result, the oxygen concentration in the fluidized air, which has been high in nitrogen concentration, rises, and the refuse is burned to increase the bed temperature. This makes it possible to keep the bed temperature constant and supply stable combustible gas and char to the melting furnace.
[0026]
If the bed temperature is on the rise, the air volume of the fluidizing air blower 7 or the temperature rise in the fluidizing air preheater 9 is reduced, and the combustion or decomposition reaction is reduced to keep the bed temperature constant, as in the prior art. To
[0027]
On the other hand, the combustible gas and char generated in the gasification furnace 2 are supplied to the melting furnace 3. The high oxygen concentration air separated by the air property device 16 is pressurized by the combustion air blower 8, heated by the combustion air preheater 10, and then supplied to the melting furnace 3.
[0028]
In the smelting furnace 3, the flammable gas and char generated in the gasification furnace are burned with air having a high oxygen concentration. Because of the high temperature, stable slag formation and discharge are possible.
[0029]
FIG. 3 shows a change in adiabatic combustion temperature due to a change in oxygen concentration in air. From this figure, it can be seen that supplying oxygen-enriched air to the melting furnace is effective because the combustion temperature is maintained at a higher temperature.
[0030]
High-temperature combustion in the melting furnace is effective for stable discharge of slag, but for protection of the equipment, the melting furnace outlet gas thermometer 18 is set to a temperature that does not damage the equipment. Control the amount of combustion air with high oxygen concentration. The remaining air is used for two-stage combustion in the secondary combustion chamber 6.
[0031]
By using the air of different oxygen concentration in the air in the gasification furnace and the melting furnace by using the system of this embodiment, the slag can be easily formed without changing the total air ratio required in the conventional system. Gasification and discharge are possible, and stable operation of the gasification and melting furnace system can be realized.
[0032]
In addition, since the temperature in the melting furnace can be easily increased even during the operation using the auxiliary fuel, the running cost of the gasification and melting furnace system and the plant operation can be reduced.
[0033]
Next, as another embodiment of the present invention, FIG. 4 shows an example in which an oxygen generator 24 is used. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals. In this example, air of about 10 to 30% of the total air ratio required for waste combustion is supplied from the air supply blower 25 to the oxygen generator 24.
[0034]
The amount of oxygen generated by the oxygen generator 24 is adjusted by the oxygen concentration adjusting damper 13 and distributed to the gasification furnace 2 and the combustion air side of the melting furnace 3. On the other hand, the nitrogen from which oxygen has been removed by the oxygen generator 24 is supplied from the oxygen generator 24 to the fluidizing air side of the gasification furnace 2, and is used to maintain stable fluidization in the gasification furnace 2.
[0035]
When the temperature of the gasification furnace layer decreases, the degree of opening of the oxygen concentration adjustment damper 13 is controlled and adjusted by a signal from the gasification furnace temperature meter 17, and oxygen is supplied to the gasification furnace side to reduce waste. Combustion increases bed temperature.
[0036]
When the gasification furnace temperature rises, the temperature of the oxygen concentration adjustment damper 13 and the fluidizing air preheater 9 are controlled by the signal of the gasification furnace temperature clock 17 to lower the bed temperature.
[0037]
Since the air supplied to the melting furnace 3 is supplied with oxygen from the oxygen generator 24, the air has the same effect as the air having a high oxygen concentration, and the high-temperature combustion effect similar to that of the embodiment shown in FIG. 1 is obtained. .
[0038]
【The invention's effect】
As described above, according to the present invention, the operability of the fluidized bed gasification and melting furnace system conventionally operated can be improved, and the running cost can be reduced by reducing the auxiliary fuel at the time of low-quality waste.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention, and is a system diagram of a gasification and melting furnace system using an air property separation device.
FIG. 2 is a graph showing characteristics of transfer of carbon in refuse to carbon monoxide and carbon dioxide.
FIG. 3 is a diagram showing a change in adiabatic combustion temperature due to an increase in oxygen concentration in air.
FIG. 4 shows another embodiment of the present invention, and is a system diagram of a gasification and melting furnace system using an oxygen generator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Garbage supply line 2 Gasification furnace 3 Melting furnace 4 Slag tap 5 Primary combustion chamber 6 Secondary combustion chamber 7 Fluidized air blower 8 Combustion air blower 9 Fluidization air preheater 10 Combustion air preheater 11 Secondary combustion Air adjustment damper 12 Melting furnace air adjustment damper 13 Oxygen concentration adjustment damper 14 Fluidized air flow meter 15 Combustion air flow meter 16 Air property separator 17 Gasifier bed thermometer 18 Melting furnace outlet gas thermometer 19 Oxygen concentration meter 20 Gasification furnace outlet connection pipe 21 Secondary combustion chamber outlet flue 22 Control device 23 Burner burner 24 Oxygen generator 25 Air supply blower

Claims (3)

A fluidized-bed gasifier that pyrolyzes refuse to generate pyrolysis gas and a melting furnace that burns and melts the pyrolysis gas, separating air into air with high oxygen concentration and air with high nitrogen concentration An air property separating means, a first supply means for supplying the air having a high nitrogen concentration to the gasification furnace, and a second supply means for supplying the air having a high oxygen concentration to the melting furnace. A fluidized bed gasification and melting furnace system characterized by the above-mentioned. 2. The fluidized-bed gasification and melting furnace system according to claim 1, wherein the air having the different oxygen concentration is supplied to the gasification furnace and the melting furnace so that combustion can be performed without changing the total air ratio. Fluidized bed gasification and melting furnace system. 3. The fluidized bed gasification and melting furnace system according to claim 1, wherein the gasification furnace fluidized bed and the gasification furnace are adjusted by adjusting a component ratio of combustion air used for fluidizing the gasification furnace. 4. A gasification and melting furnace system characterized by controlling the internal temperature.

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