JP2000320825A - Operation of waste gasifying melting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of converting ash components in waste into melted slags by self combustion heat of the waste without using a combustion promotor such as oil when associated with a low load operation. SOLUTION: In a method wherein solid waste is gasified by a gasifying furnace 1 and then, ash components in the waste are converted to melted slags by high temperature combustion in a melting furnace 3, combustibles such as gas, tar or charcoal are burned using the melting furnace 1 as a combustion chamber during a low load operation, and the combustion ash yet to be converted to slags then generated is trapped and stored. During a high load operation, the combustion ash thus stored is supplied to the gasifying furnace 1 or the melting furnace 3 to be converted to melted slags together with ash components of the burned waste under the high load operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting various kinds of wastes, and more particularly to a method for converting solid wastes into gasified slags by subjecting the ash to waste slag by high-temperature combustion. Here, the various wastes are general municipal waste, industrial waste, solid waste fuel (solidified using waste as a raw material), and the like. In addition, the present invention particularly relates to day and night load (power generation) adjustment in waste power generation.

[0002]

2. Description of the Related Art A method is known in which a gasification process in a gasification furnace and a high-temperature combustion process in a melting furnace are combined, and the waste is gasified and then the ash in the waste is melted and slag-treated by high-temperature combustion. I have. This method makes it difficult to generate harmful organic compounds such as dioxins when incinerating solid waste containing ash, and can reduce and stabilize ash by melting it into slag, This is a gasification melting combustion method combining a gasification step and a high temperature combustion step. In this case, the melting temperature of the ash is 120
Since the temperature is 0 ° C. or higher, it is necessary to burn at a higher temperature in the high-temperature combustion step.

[0003] In general, a melting furnace takes into account the amount of combustion heat generated when combustible gas and combustible particles gasified in a gasification furnace are burned at a high temperature in the melting furnace and the amount of heat released from the surface of the melting furnace. It is planned that the furnace temperature is about 1200 to 1500 °. However, the rated throughput of 75-
Even if the gasification and melting furnace is designed to be capable of high-temperature combustion at a melting furnace temperature of 1250 ° C. or more at a high load of about 100%, at a low load of about 50 to 75% or less of the rated treatment amount, Since the amount of waste supplied is reduced, the amount of combustion heat is reduced only by the combustible gas and combustible fine particles supplied to the melting furnace. In order to perform high-temperature combustion in the melting furnace, an auxiliary material such as oil may be required. is there. On the other hand, when an auxiliary material such as oil is not used, the heat of combustion in the melting furnace is insufficient, so that high-temperature combustion cannot be performed and ash melting processing may not be performed. In other words, when the conventional gasification melting combustion method involves low-load operation, the problem is solved when the ash in the waste is melted only by the self-combustion heat of the waste without using a combustion aid such as oil. There are issues to be addressed.

[0004] In addition, waste combustion power generation is generally performed in which energy is recovered from combustion heat of the waste as electric power which is the most widely used energy during the combustion of the waste.
In waste power generation, heat energy generated by combustion of waste is used for power generation, and a method of recovering steam from waste combustion heat with a waste heat boiler and generating power with a steam turbine / generator is generally used. The power generated by such waste power generation is consumed in the plant and the surplus is sold to a power company.

[0005] Electric power companies use surplus electric power after waste power generation and self-consumption by so-called "daytime" from about 8 o'clock in the morning to about 10 o'clock in the night, so that the electric power company has a high purchase power unit price because of the high power demand. Conversely, in the so-called "nighttime" from about 10 o'clock in the evening to about 8 o'clock in the morning, since there is little power demand, a system is provided for purchasing at a low unit price of purchased power. Depending on the power company,
Daytime power purchase unit price is 4 to 5 of nighttime surplus power purchase unit price
Some have doubled.

Therefore, from the viewpoint of generating waste by using a limited amount of waste, high-load combustion is performed during the daytime when the purchase price of the power company is high, and the amount of generated power is maximized.
There is a demand for an operation method in which low-load combustion operation is performed during the night when the purchase unit price is low to suppress consumption of waste. However, when the low-load operation is performed, there is a problem as described above that the ash melting process cannot be performed only by the self-combustion heat.

Further, as a conventional method of melting waste combustion ash, an electric melting method such as an arc method, an electric resistance method, or a plasma method is often used. In this case, the power generated by the waste combustion power generation is consumed not only in the plant but also as an energy source for the melting treatment of the waste combustion ash. There was a problem that would.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and does not use an auxiliary material such as oil when operating under a low load, and reduces ash content in waste. A method for converting slag into molten slag by the heat of self-combustion of waste. In addition, in the waste gasification and fusion power generation method, from the viewpoint of using only a limited amount of waste to generate waste, it is necessary to use high-load combustion operation during the daytime when the purchase price of the electric power company is high, and to generate power. It is an object of the present invention to provide an operation method of maximizing the amount of waste, and performing low-load combustion operation at night when the purchase unit price is low to suppress consumption of waste. Furthermore, in the waste gasification and fusion power generation method, from the viewpoint of maximizing the amount of power sold, from the viewpoint of maximizing the amount of power sold, without using an electric ash melting method that consumes a large amount of power in the melting process of combustion ash, the amount of power sold is not so large. An object of the present invention is to provide a melting method capable of self-heating melting of waste which does not decrease.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for converting ash in waste into molten slag by high-temperature combustion in a melting furnace after gasifying solid waste in a gasification furnace. The method uses a melting furnace as a combustion chamber at low load to burn gas, tar, char, and other combustible materials, and collects and generates slag-free combustion ash.
The combustion ash is stored and supplied to a gasification furnace or a melting furnace at a high load, and is converted into a molten slag together with the ash of the combustion waste at a high load.

The present invention relates to a method for converting ash in waste into molten slag by high-temperature combustion after gasifying solid waste, wherein the gas is gasified by a gasification furnace using a melting furnace as a combustion chamber at a low load. Combustible gas and combustible fine particles 800 ~
The combustion ash generated by burning at 950 ° C. is collected and stored, and the stored combustion ash is supplied to a gasification furnace or a melting furnace at a high load, and is converted into a molten slag together with the ash of the processing waste at a high load. It is something to do.

The present invention operates a gasification and melting furnace at a low load as a combustion chamber corresponding to a free board of a conventional fluidized bed incinerator, and collects and collects ash that cannot be melted in the form of incineration ash.
It is stored and operated as a conventional gasification and melting furnace at high load, and at this time, ash at low load is also melted.

According to the present invention, it is only required that the waste can be completely burned at low load and the generation of dioxins can be suppressed, and the incinerated ash collected and stored at low load can be self-burned at high load. Utilizes the fact that it can be melted by heat. That is, the amount of heat required to melt the dry ash at room temperature is about 100 to 150 kcal / kg, which is very small compared to the lower calorific value of the waste. The average calorific value utilizes the fact that self-thermal melting can be maintained.

In general, the calorific value of the waste required for self-heating melting depends on the scale of the furnace, but it is about 1500 to 2000 kcal /
kg, the lower calorific value of waste is 2000kcal / kg
In the case of more than about 30%, incineration ash can be additionally melted to about 30 to 40%. At low load, the combustion temperature in a melting furnace (freeboard) used as a combustion chamber corresponding to the freeboard of a fluidized bed incinerator is 850 to 950 ° C.
(About 1120 to 1220K), the combustion temperature under high load is 1
Since the temperature is 300 to 1400 ° C. (about 1570 to 1670 K), the combustion temperature ratio in absolute temperature is about 0.7, and the combustion gas volume is reduced to about 70% due to the temperature decrease. Therefore, as an example, when the load is about 50%, the combustion gas volume is 50% × 0.7, which is about 35%, so that the residence time is about 2.8 times.

That is, when the combustion load is reduced, the amount of combustion exhaust gas is reduced by reducing the amount of combustion itself, and the amount of combustion gas is reduced by using a melting furnace as a combustion chamber and burning at a temperature lower than the melting combustion temperature. That is, since the residence time can be remarkably prolonged due to the double combustion gas amount reduction effect, complete combustion can be sufficiently performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a low-load operation method for waste gasification and melting according to the present invention will be described below with reference to the drawings. It should be noted that the following embodiments are merely examples, and do not limit the technical scope of the present invention. FIG. 1 is a schematic diagram showing a first example of a configuration of an apparatus for performing a low-load operation method for waste gasification and melting according to the present invention, and shows a basic flow of a waste gasification and melting method according to the present invention. Waste a such as general municipal solid waste is supplied to the fluidized bed gasification furnace 1 and then partially oxidized in the fluidized bed, that is, pyrolyzed into gas, and is a solid gas, that is, a product gas accompanied by fine solid carbon. c is discharged from the fluidized bed gasifier 1. The internal swirling type fluidized bed gasification furnace 1 used here actively performs the swirling flow of the fluidized medium such that it descends at the center of the fluidized bed and rises at the periphery thereof, and is preferably at 450 to 850 ° C. Is 450-65
By maintaining the layer temperature at 0 ° C., more preferably at 500 to 600 ° C., the following features can be provided.

1) The waste a can be supplied in a degree of coarse crushing, and the large-sized incombustibles d generated from the waste can be smoothly discharged from the fluidized bed. 2) Since the reaction of pyrolysis gasification becomes relatively slow by keeping the bed temperature low, fluctuations in gas generation can be suppressed. 3) Since the solid carbon content in the layer is well oxidized, the solid carbon content can be finely divided and the heat generated by the oxidation can be effectively used. 4) Good heat diffusion in the layer prevents agglomeration (agglomeration) and allows recovery of valuable metals such as iron, copper and aluminum in an unoxidized state.

As for the bed temperature of the fluidized bed, if the bed temperature is 450 ° C. or lower, the reaction of pyrolysis gasification becomes extremely slow, and there is a concern that undecomposed products may be deposited in the bed. On the other hand, if the bed temperature is 650 ° C. or higher, not only can aluminum not be recovered, but also the reaction of pyrolysis gasification becomes faster, and the gas generation is directly affected by the fluctuation of the amount when the waste a is supplied. A phenomenon that the so-called "rumble" occurs. Above 850 ° C, the risk of agglomeration increases. Therefore, the temperature range of the fluidized bed is 45
The temperature is 0 to 850 ° C, preferably 450 to 650 ° C, and more preferably 500 to 600 ° C.

In the present invention, when the load is low, the waste a
Is supplied to the fluidized bed gasifier 1. The product gas c accompanied by the finely divided solid carbon content from the fluidized-bed gasification furnace 1 is supplied to the melting furnace 3, where the vertical primary combustion chamber 4, the inclined secondary combustion chamber 5, and the vertical tertiary In the combustion chamber 6, the mixture is completely burned at a medium temperature of 800 to 950 ° C while being mixed with the preheated air in a swirling flow.

The ash content in the solid carbon content becomes incinerated ash without being turned into molten slag due to medium temperature combustion. The incineration ash accompanies the combustion exhaust gas, passes through the secondary combustion chamber 5 and the tertiary combustion chamber 6,
It is collected by a dust collector (not shown) downstream. At this time, part of the incinerated ash is discharged from the discharge port 7 between the secondary combustion chamber 5 and the tertiary combustion chamber 6 and collected. The collected ash is stored in an ash hopper 18 for melting at a high load. The combustion ash gas is processed in an exhaust gas treatment facility including a dust collector (not shown) downstream of the tertiary combustion chamber 6.

On the other hand, when the load is high, the incinerated ash e and the waste a that have been collected and stored during the low load operation are supplied to the fluidized bed gasifier 1. The incineration ash e supplied to the fluidized-bed gasification furnace 1 is heated in the fluidized bed and becomes a fine powder, and is supplied to the melting furnace 3 along with the combustible gas c generated in the fluidized-bed gasification furnace 1. The combustible gas c supplied to the melting furnace 3 is mixed with the preheated air in a vertical primary combustion chamber 4 and an inclined secondary combustion chamber 5 in a swirling flow, and while being mixed, 1200 to 1600.
C., preferably at a high temperature of 1300-1400.degree.

At this time, the ash in the solid carbon and the incineration ash e
Becomes a slag mist due to the high temperature, and most of the slag mist is trapped in the molten slag layer on the furnace walls of the primary combustion chamber 4 and the secondary combustion chamber 5 by the action of centrifugal force due to the swirling flow. And the molten slag flowing down the furnace wall is
It is discharged from the discharge port 7 located between the secondary combustion chamber 5 and the tertiary combustion chamber 6, and is directly or indirectly cooled and recovered as slag particles.

Therefore, the ash of the waste at low load can be melted only by the self-combustion heat of the waste without using an auxiliary material such as oil. If the incinerated ash e collected and stored during the low-load operation is dry ash and powdery, the incinerated ash e can be directly supplied to the melting furnace 3.

FIG. 2 is a schematic diagram showing a second example of the configuration of an apparatus for implementing an operation method when the waste gasification / melting system involves low-load operation. In the present embodiment,
Waste power generation is performed by the waste gasification and melting system. In waste power generation, heat energy generated by combustion of waste is used for power generation, and a method of recovering steam from waste combustion heat with a waste heat boiler and generating power with a steam turbine / generator is generally used. FIG. 2 shows an example of the present embodiment using a gasification and melting furnace as a combustion furnace in such a waste power generation system.
Shown in

As explained in the section of the prior art,
The electric power company has to pay surplus power after waste power generation and self-consumption at high so-called “daytime” from around 8:00 am to around 10:00 pm, because of high power demand, In the so-called "nighttime" from about 10 o'clock to about 8 o'clock in the morning, there is a system for purchasing electricity at a low unit price because of low power demand. In some power companies, the unit price for purchasing power in the daytime is four to five times the unit price for purchasing surplus power in the nighttime. Therefore, from the viewpoint of generating waste by using a limited amount of waste, high-load combustion is performed during the daytime when the purchase price of the power company is high, and the amount of generated power is maximized. In addition, there is a demand for an operation method in which low-load combustion operation is performed to suppress waste consumption.

Further, from the viewpoint of maximizing the amount of electric power sold, compared to the electric ash melting method in which a large amount of electric power is consumed in the melting processing of incinerated ash, the self-heating melting of waste which does not decrease the amount of electric power sold much is considered. There is a need for a possible melting method. On the other hand, from the viewpoint of waste treatment, in order to minimize the amount of final disposal, make effective use of ash, and minimize dioxins in exhaust gas and incinerated ash, ash in waste is converted into molten slag. There is a need for a driving method.

Accordingly, the present embodiment is directed to a waste gasification and fusion power generation system that satisfies both the requirements from the viewpoint of maximizing the revenue from selling electricity through waste power generation and the requirements from the viewpoint of waste treatment. This is an operation method involving low-load operation. At a low load, the waste a is supplied to the fluidized-bed gasifier 1. The product gas c accompanied by the fine powdery solid carbon content from the fluidized bed gasification furnace 1 is supplied to the melting furnace 3 and is provided with a vertical primary combustion chamber 4, an inclined secondary combustion chamber 5, and a vertical tertiary combustion chamber. In chamber 6, mixing with preheated air in a swirling flow,
It is completely burned at a medium temperature of 800 to 950 ° C.

Next, the combustion exhaust gas is supplied to the waste heat boiler 13, and the thermal energy possessed by the combustion exhaust gas is recovered to generate superheated steam or saturated steam. The flue gas discharged from the waste heat boiler 13 is supplied to a preheater 1 such as an economizer.
6. The gas passes through a dust collector 17 having an exhaust gas treatment function and is discharged from the chimney to the atmosphere as a low-temperature clean gas.

The ash in the solid carbon is converted into incinerated ash without being turned into molten slag because of the intermediate temperature combustion in the melting furnace 3. The incineration ash accompanies the combustion exhaust gas, and the secondary combustion chambers 5 and 3
A waste heat boiler 13, a preheater 16,
The dust is collected by the dust collector 17. At this time, part of the incineration ash was 2
The waste gas is discharged from the discharge port 7 between the secondary combustion chamber 5 and the tertiary combustion chamber 6, and is also collected and discharged by the waste heat boiler 13 and the preheater 16. The collected ash is stored in an ash hopper 18 for melting at a high load. On the other hand, the superheated steam or the saturated steam is generated by a power generation facility 1 comprising a steam turbine and a generator.
5, and energy recovery is performed as electric power energy. The generated power is consumed on site and sold to power companies.

At a high load, the waste a and the incinerated ash e collected and stored during the low load operation are supplied to the fluidized bed gasifier 1. Since the incineration ash e supplied to the fluidized-bed gasification furnace 1 is heated in the fluidized-bed and becomes a fine powder, the fluidized-bed gasification furnace 1
Is supplied to the melting furnace 3 along with the combustible gas c generated in the above. The combustible gas c supplied to the melting furnace 3 is mixed with the preheated air in a vertical primary combustion chamber 4 and an inclined secondary combustion chamber 5 in a swirling flow, at 1200 to 1600 ° C.
Preferably, it is partially oxidized at a high temperature of 1300 to 1400 ° C.

At this time, the ash in the solid carbon and the incinerated ash e
Becomes a slag mist due to high temperature, and most of the slag mist is captured by the molten slag layer on the furnace walls of the primary combustion chamber 4 and the secondary combustion chamber 5 by the action of centrifugal force due to the swirling flow. The molten slag flowing down the furnace wall is 2
It is discharged from the discharge port 7 between the secondary combustion chamber 5 and the tertiary combustion chamber 6, and is cooled directly or indirectly and then collected as slag particles.

Next, the flue gas is supplied to the waste heat boiler 13, and the thermal energy possessed by the flue gas is recovered to generate superheated steam or saturated steam. The flue gas discharged from the waste heat boiler 13 is supplied to a preheater 1 such as an economizer.
6. The gas passes through a dust collector 17 having an exhaust gas treatment function and is discharged from the chimney to the atmosphere as a low-temperature clean gas. on the other hand,
The superheated steam or the saturated steam is supplied to a power generation facility 15 including a steam turbine and a generator, and energy recovery is performed as power energy. The generated power is consumed on site and sold to power companies.

[0032]

As described above, according to the present invention,
The following effects are obtained. (1) In the waste gasification and melting system, even when low-load operation is involved, the ash of the waste can be made into a self-heating molten slag. (2) In the waste gasification / melting power generation system, low-load operation is performed during a time period when the unit price of electric power is low, and high-load operation is performed during a time period when the unit price of electric power is high, thereby maximizing the income from electric power sales. At the same time, self-melting slag of waste is treated as waste. (3) During low load operation, the combustion gas temperature becomes lower than during high load operation, but the combustion gas residence time becomes about 2.8 times, and dioxin and the like are completely decomposed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first example of a configuration of an apparatus for performing a solid waste melting treatment method of the present invention.

FIG. 2 is a schematic view showing a second example of the configuration of an apparatus for performing the solid waste melting treatment method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluidized bed gasifier 2 Quantitative feeder 3 Melting furnace 4 Primary combustion chamber 5 Secondary combustion chamber 6 Tertiary combustion chamber 7 Outlet 8 Fluidized bed 9 Free board 13 Waste heat boiler 15 Power generation equipment 16 Preheater 17 Dust collection Vessel 18 Ash Hopper

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takahiro Ohshita 11-1 Haneda Asahimachi, Ota-ku, Tokyo F-term in Ebara Corporation 3G081 BA02 BB00 BC11 DA12 3K061 AA23 AB03 AC01 AC03 BA03 BA05 DA14 3K065 AA23 AB03 AC03 BA05 JA03 JA13 3K078 AA05 BA03 CA03 CA21

Claims (3)

[Claims] 1. A method of gasifying solid waste in a gasification furnace and then melting the ash in the waste by high-temperature combustion in a melting furnace, wherein the melting furnace is used as a combustion chamber at a low load. Burns combustibles such as gas, tar and char,
The combustion ash generated at that time is collected and stored, and when the load is high, the combustion ash is supplied to a gasification furnace or a melting furnace, and is converted into a molten slag together with the ash content of the combustion waste at a high load. A method for operating a waste gasification and melting system, comprising: 2. A superheated steam is generated by heat recovery of the combustion exhaust gas discharged from the melting furnace, and the superheated steam is supplied to a power generation facility including a steam turbine and a generator to generate power. A method for operating the waste gasification and melting system according to the above. 3. The method for operating a waste gasification and melting system according to claim 1, wherein the high load operation is performed in the daytime and the low load operation is performed in the nighttime.