JP3859390B2 - Operation method of waste gasification and melting system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to melt processing of various wastes, in particular those concerning the solid waste to how to process and molten slag the ash in the waste by a high-temperature combustion after gasification. Here, various types of waste include general municipal waste, industrial waste, or solid waste fuel (solidified from waste as a raw material).
The present invention particularly relates to daytime and nighttime load (power generation amount) adjustment in waste power generation.
[0002]
[Prior art]
A method is known in which a gasification step in a gasification furnace and a high-temperature combustion step in a melting furnace are combined, and after the waste is gasified, the ash in the waste is melted into slag by high-temperature combustion.
This method makes it difficult to generate harmful organic compounds such as dioxins when incinerating solid waste containing ash, and can reduce and stabilize the ash by melting slag, This is a gasification melt combustion method combining a gasification step and a high temperature combustion step. In this case, since the melting temperature of ash is 1200 ° C. or higher, it is necessary to burn at a higher temperature in the high-temperature combustion process.
[0003]
In general, the melting furnace takes into account the amount of combustion heat generated when the combustible gas and combustible fine particles gasified in the gasifier burn at a high temperature in the melting furnace and the amount of heat released from the surface of the melting furnace. Is planned to be about 1200 to 1500 °.
However, even in a gasification and melting furnace designed so that high-temperature combustion with a melting furnace temperature of 1250 ° C. or higher is possible at a high load of about 75 to 100% of the rated throughput, the rated throughput is 50 to 75%. When the load is less than about%, the amount of waste supplied decreases, so the combustion heat amount decreases only with the combustible gas and the combustible fine particles supplied to the melting furnace. A supplementary flame retardant may be required. On the other hand, when an auxiliary combustor such as oil is not used, the combustion heat in the melting furnace is insufficient, so that high-temperature combustion cannot be performed and the ash content cannot be melted.
In other words, when the conventional gasification melt combustion method is accompanied by low load operation, the problem is solved when the ash content in the waste is melted only by the self-combustion heat of the waste without using an auxiliary combustion material such as oil. There are problems to be solved.
[0004]
In addition, waste combustion power generation is generally performed in which energy is recovered from the combustion heat of waste as electric power that has the highest degree of utilization during waste combustion.
In waste power generation, heat energy generated by combustion of waste is used for power generation. Generally, a waste heat boiler recovers steam with a waste heat boiler and generates power with a steam turbine / generator. The electric power generated by such waste power generation is consumed in the field, and the surplus is sold to an electric power company.
[0005]
Electricity companies use surplus electricity after waste power generation and self-consumption for so-called “daytime” from around 8:00 am to around 10:00 pm, because there is a lot of demand for electricity. In the so-called “nighttime” from about 10 o'clock to about 8 o'clock in the morning, since there is little power demand, a system for purchasing at a low unit price of purchased electricity is provided. Some electric power companies have a unit price for purchasing power in the daytime that is four to five times the unit price for purchasing surplus power at night.
[0006]
Therefore, from the viewpoint of generating waste power using a limited amount of waste, the power company burns at high load during the daytime when the purchase price is high, maximizes the amount of generated power, and the nighttime where the purchase price is cheap. In addition, there is a demand for an operation method that suppresses the consumption of waste by using a low-load combustion operation.
However, in the case of low load operation, there has been the above-mentioned problem that the ash cannot be melted only by the self-combustion heat.
[0007]
Furthermore, as a conventional waste-burning ash melting method, an electric melting method such as an arc method, an electric resistance method, or a plasma method is often used. In this case, the generated power recovered from the waste combustion power generation is not only consumed in the field, but also consumed as an energy source for the melting treatment of the waste combustion ash. There was a problem that it was.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems of the prior art, and in the case of low load operation, no auxiliary combustor such as oil is used, and the ash in the waste is melted by the self-combustion heat of the waste. It is to provide a way to slagging.
In addition, in the waste gasification and fusion power generation method, from the viewpoint of performing waste power generation using a limited amount of waste, the amount of generated power is set to high load combustion operation in the daytime when the purchase price of power companies is high. Is to provide a driving method that suppresses the consumption of waste by performing low-load combustion operation at night when the purchase unit price is low.
Furthermore, in the waste gasification melting power generation method, from the viewpoint of maximizing the amount of electric power sold, the amount of electric power sold is not much, without using an electric ash melting method that consumes a large amount of electric power in the melting treatment of combustion ash. An object of the present invention is to provide a melting method capable of self-thermal melting of waste that does not decrease.
[0009]
[Means for Solving the Problems]
To solve the above problems, a method of operating waste gasification melting system of the present invention, waste in solid waste after gasification in the bed temperature of four hundred and fifty to eight hundred fifty ° C. in a fluidized bed gasification furnace the ash content per the method of combustion or slugging in a melting furnace, rated throughput of 50 to 75% of the low load gas, tar and char at a temperature of 800 to 950 ° C. use as a combustion chamber melting furnace in such of combustibles burning, this time leave the reservoir to discharge combustion ash not slag generated from the discharge port of the melting furnace, the ash is in the high load of 75% to 100% of the rated throughput It is supplied to a fluidized bed gasification furnace or a melting furnace, and melted slag is formed at a temperature of 1200 to 1600 ° C. together with ash content of combustion waste at high load.
According to a preferred aspect of the present invention, the ash collected from the combustion exhaust gas discharged from the melting furnace is added to the combustion ash and supplied to the melting furnace at a high load.
According to a preferred aspect of the present invention, 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.
According to a preferred aspect of the present invention, the daytime is a high load operation and the night is a low load operation .
[0010]
The present invention relates to a method for melting slag of ash in waste by high-temperature combustion after gasification of solid waste, and in a low load, the melting furnace is used as a combustion chamber, and combustible gas gasified in the gasification furnace and Combustible fine particles are burned at 800 to 950 ° C., and the generated combustion ash is collected and stored, and the stored combustion ash is supplied to a gasification furnace or a melting furnace at a high load, and the treatment waste at the high load is It is made to melt into slag with ash.
[0011]
The present invention operates a gasification melting furnace as a combustion chamber corresponding to a free board of a conventional fluidized bed incinerator at low load, collects and stores ash that cannot be melted in the form of incinerated ash, It is sometimes operated as a conventional gasification melting furnace, and at this time, ash content at low load is also melted.
[0012]
The present invention only requires that the waste is completely combusted at low load and that dioxins can be suppressed, and the incinerated ash collected and stored at low load is melted by the self-combustion heat of the waste at high load. Take advantage of what can be processed.
That is, the amount of heat required to melt dry ash at room temperature is about 100 to 150 kcal / kg, which is very small compared to the lower heating value of waste, and even if the treated waste and incinerated ash are mixed and burned The average calorific value is utilized so that self-heat melting can be maintained.
[0013]
Generally, the calorific value of waste necessary for self-heating melting is about 1500 to 2000 kcal / kg depending on the scale of the furnace. Therefore, for a waste having a lower calorific value of about 2000 kcal / kg or more, about 30 The incineration ash can be additionally melted up to about 40%. When the load is low, the combustion temperature in the melting furnace (free board) used as a combustion chamber corresponding to the free board of the fluidized bed incinerator is 850 to 950 ° C. (about 1120 to 1220 K), and the combustion temperature at the high load is 1300 Since it is 1400 degreeC (about 1570-1670K), the combustion temperature ratio in absolute temperature will be about 0.7, and a combustion gas volume will reduce to about 70% by temperature fall.
Therefore, as an example, when the load is about 50%, the combustion gas volume is 50% × 0.7 and is about 35%, so the residence time is about 2.8 times.
[0014]
That is, when the combustion load is reduced, the combustion exhaust gas amount is reduced by the reduction of the combustion amount itself, and further, the combustion gas amount is reduced by burning at a temperature lower than the melting combustion temperature using the melting furnace as a combustion chamber. In other words, since the residence time can be significantly increased by this double combustion gas amount reduction effect, complete combustion is sufficiently possible.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying a low load operation method for waste gasification and melting according to the present invention will be described with reference to the drawings. It should be noted that the following form is merely an example and does not limit the technical scope of the present invention.
FIG. 1 is a schematic diagram showing a first example of the configuration of an apparatus for carrying out the waste gasification melting low load operation method of the present invention, and shows the basic flow of the waste gasification melting method of the present invention.
Waste a such as municipal waste is supplied to the fluidized bed gasification furnace 1 and then partially oxidized, that is, pyrolyzed and gasified in the fluidized bed, and is accompanied by a solid substance, that is, a refined solid carbon content. c is discharged from the fluidized bed gasification furnace 1.
The internal swirl type fluidized bed gasification furnace 1 used here positively causes the swirling flow of the fluid medium to descend at the center of the fluidized bed and to rise at the periphery, and is preferably 450 to 850 ° C., preferably By maintaining the layer temperature at 450 to 650 ° C., more preferably 500 to 600 ° C., the following characteristics can be obtained.
[0016]
1) The waste a can be supplied in a roughly crushed state, and the large-sized incombustible material d generated for this purpose can be smoothly discharged from the fluidized bed.
2) By keeping the bed temperature low, the reaction of pyrolysis gasification becomes relatively slow, so that fluctuations in gas generation can be suppressed.
3) Since the in-layer oxidation of the solid carbon content is good, effective utilization of the heat generated with the pulverization and oxidation of the solid carbon content can be performed efficiently.
4) Since heat diffusion in the layer is good, generation of agglomerates (agglomeration) can be prevented, and valuable metals such as iron, copper, and aluminum can be recovered in an unoxidized state.
[0017]
Describing the layer temperature of the fluidized bed, if the layer temperature is 450 ° C. or lower, the reaction of pyrolysis gasification becomes extremely slow, so there is a concern about the deposition of undecomposed products in the layer.
On the other hand, if the layer temperature is 650 ° C. or higher, not only aluminum cannot be recovered, but the reaction of pyrolysis gasification becomes faster, so gas is generated by the influence of fluctuations in the amount of waste a supplied. The phenomenon of so-called “rage” occurs. Above 850 ° C, the risk of agglomeration increases. For this reason, the temperature range of a fluidized bed is 450-850 degreeC, Preferably it is 450-650 degreeC, More preferably, it is 500-600 degreeC.
[0018]
In the present invention, the waste a is supplied to the fluidized bed gasifier 1 at a low load. 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 gas are supplied. In the combustion chamber 6, complete combustion is performed at a medium temperature of 800 to 950 ° C. while mixing with preheated air in a swirling flow.
[0019]
The ash content in the solid carbon is incinerated ash without melting into slag due to the medium temperature combustion. The incineration ash accompanies the combustion exhaust gas, passes through the secondary combustion chamber 5 and the tertiary combustion chamber 6, and is collected by a dust collector (not shown) downstream. At this time, a part of the incineration ash is discharged and collected from the discharge port 7 between the secondary combustion chamber 5 and the tertiary combustion chamber 6. The collected ash is stored in the ash hopper 18 to be melted 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.
[0020]
On the other hand, when the load is high, the incinerated ash e and the waste a collected and stored during the low load operation are supplied to the fluidized bed gasification furnace 1. The incineration ash e supplied to the fluidized bed gasification furnace 1 is heated in the fluidized bed and becomes fine powder, and is supplied to the melting furnace 3 along with the combustible gas c generated in the fluidized bed gasification furnace 1. While the combustible gas c supplied to the melting furnace 3 is mixed in the swirling flow with preheated air in the vertical primary combustion chamber 4 and the inclined secondary combustion chamber 5, preferably 1200 to 1600 ° C., preferably Partial oxidation is performed at a high temperature of 1300 to 1400 ° C.
[0021]
At this time, the ash in the solid carbon and the incinerated ash e become slag mist due to the high temperature, and most of the slag mist is generated in the primary combustion chamber 4 and the secondary combustion chamber 5 by the action of centrifugal force due to the swirling flow. It is trapped in the molten slag layer on the furnace wall. And the molten slag which flowed down this furnace wall surface is discharged | emitted from the discharge port 7 between the secondary combustion chamber 5 and the tertiary combustion chamber 6, and is collect | recovered as slag grain after being cooled directly or indirectly. .
[0022]
Accordingly, the ash content of the waste at low load can be melted only by the self-combustion heat of the waste without using an auxiliary combustor such as oil. Note that if the incinerated ash e collected and stored during low-load operation is dry ash and powdered, the incinerated ash e can be directly supplied to the melting furnace 3.
[0023]
FIG. 2 is a schematic diagram showing a second example of the configuration of an apparatus for carrying out an operation method in a case where the waste gasification and melting system is accompanied by a low load operation.
In the present embodiment, waste power generation is performed by a waste gasification and melting system. In waste power generation, heat energy generated by combustion of waste is used for power generation. Generally, a waste heat boiler recovers steam with a waste heat boiler and generates power with a steam turbine / generator. An example of this embodiment using a gasification melting furnace as a combustion furnace among such waste power generation systems is shown in FIG.
[0024]
As explained in the section of the prior art, the electric power company uses the surplus power after waste power generation and self-consumption as the power demand in the so-called “daytime” from around 8 am to around 10 am Since there are many, there is a high purchase power unit price, and conversely, a so-called “nighttime” from about 10 o'clock to about 8 o'clock in the morning is a system for purchasing at a low purchase power unit price because there is little power demand. Some electric power companies have a unit price for purchasing power in the daytime that is four to five times the unit price for purchasing surplus power at night.
Therefore, from the viewpoint of generating waste power using a limited amount of waste, the power company burns at high load during the daytime when the purchase price is high, maximizes the amount of generated power, and the nighttime where the purchase price is cheap. In addition, there is a demand for an operation method that suppresses waste consumption by performing low-load combustion operation.
[0025]
Furthermore, from the viewpoint of maximizing the amount of electric power sold, it is possible to achieve self-heating melting of waste that does not significantly reduce the amount of electric power sold, compared to the electric ash melting method that consumes a large amount of electric power for melting incinerated ash. There is a need for a method.
On the other hand, from the viewpoint of waste treatment, in order to minimize the final disposal amount, to effectively use ash, and to minimize dioxins in exhaust gas and incineration ash, the ash in waste is melted into slag. There is a need for driving methods.
[0026]
Therefore, the present embodiment is a low-load operation of the waste gasification melting power generation system that satisfies both the demand from the viewpoint of maximizing the power sales revenue by waste power generation and the demand from the viewpoint of waste treatment. It is a driving method involving.
When the load is low, the waste a is supplied to the fluidized bed gasification furnace 1. The product gas c accompanied by finely divided solid carbon content from the fluidized bed gasification furnace 1 is supplied to the melting furnace 3, and the vertical primary combustion chamber 4, the inclined secondary combustion chamber 5, and the vertical tertiary combustion. In the chamber 6, complete combustion is performed at a medium temperature of 800 to 950 ° C. while mixing with preheated air in a swirling flow.
[0027]
Next, the combustion exhaust gas is supplied to the waste heat boiler 13, and the thermal energy held by the combustion exhaust gas is recovered by heat to generate superheated steam or saturated steam. The combustion exhaust gas exiting the waste heat boiler 13 passes through a preheater 16 such as an economizer and a dust collector 17 having an exhaust gas treatment function, and is released from the chimney to the atmosphere as a low-temperature clean gas.
[0028]
The ash in the solid carbon is incinerated ash without melting into slag due to intermediate temperature combustion in the melting furnace 3. The incinerated ash accompanies the combustion exhaust gas, passes through the secondary combustion chamber 5 and the tertiary combustion chamber 6, and is collected by the downstream waste heat boiler 13, the preheater 16, and the dust collector 17. At this time, a part of the incineration ash 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 the ash hopper 18 to be melted at a high load.
On the other hand, the superheated steam or 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 a power company.
[0029]
At the time of high load, the waste a and the incinerated ash e collected and stored at the time of low load operation are supplied to the fluidized bed gasification furnace 1.
The incinerated ash e supplied to the fluidized bed gasification furnace 1 is heated in the fluidized bed to become fine powder, and is supplied to the melting furnace 3 along with the combustible gas c generated in the fluidized bed gasification furnace 1. While the combustible gas c supplied to the melting furnace 3 is mixed in the swirling flow with preheated air in the vertical primary combustion chamber 4 and the inclined secondary combustion chamber 5, preferably 1200 to 1600 ° C., preferably Partial oxidation is performed at a high temperature of 1300 to 1400 ° C.
[0030]
At this time, the ash content in the solid carbon content and the incineration ash e become slag mist due to high temperature, and most of the slag mist is the furnace of the primary combustion chamber 4 and the secondary combustion chamber 5 by the action of centrifugal force due to the swirling flow. It is trapped in the molten slag layer on the wall. And the molten slag which flowed down this furnace wall surface is discharged | emitted from the discharge port 7 between the secondary combustion chamber 5 and the tertiary combustion chamber 6, and is collect | recovered as slag grain after being cooled directly or indirectly. .
[0031]
Next, the combustion exhaust gas is supplied to the waste heat boiler 13, and the thermal energy held by the combustion exhaust gas is recovered by heat to generate superheated steam or saturated steam. The combustion exhaust gas exiting the waste heat boiler 13 passes through a preheater 16 such as an economizer and 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 saturated steam is supplied to a power generation facility 15 including a steam turbine and a generator, and energy is recovered as electric energy. The generated power is consumed on site and sold to a power company.
[0032]
【The invention's effect】
As described above, according to the present invention, the following effects are obtained.
(1) In a waste gasification and melting system, even when a low load operation is involved, the ash content of the waste can be converted into a self-heated melting slag.
(2) In the waste gasification and fusion power generation system, the power revenue can be maximized by performing low-load operation during the low power selling unit time and high-load operation during the high power unit selling time. At the same time, the waste is converted into self-heated molten slag as waste treatment.
(3) During low-load operation, the combustion gas temperature is lower than during high-load operation, but the combustion gas residence time is about 2.8 times, and dioxins and the like are completely decomposed.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first example of the configuration of an apparatus for carrying out the solid waste melting method according to the present invention.
FIG. 2 is a schematic diagram showing a second example of the configuration of an apparatus for carrying out the solid waste melting method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fluidized bed gasification furnace 2 Fixed supply apparatus 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 18 ash hopper

Claims (4)

Per solid waste to a method of combustion or slugging in a melting furnace to ash in waste after gasification in the bed temperature of four hundred and fifty to eight hundred and fifty ° C. in a fluidized bed gasification furnace, 50 to 75 of the rated processing volume % of low load, such as gas, tar and char at a temperature of 800 to 950 ° C. using a melting furnace as the combustion chamber in combustibles burning, of the melting furnace burning ash not slag generated during the leave reservoir is discharged from the discharge port, at the time of high load 75-100% of the rated processing volume was supplied to the fluidized bed gasification furnace or melting furnace the combustion ash, together with the ash of the combustion waste at the time of high load A method for operating a waste gasification and melting system, wherein the molten slag is formed at a temperature of 1200 to 1600 ° C. The operation of the waste gasification and melting system according to claim 1, wherein ash collected from the combustion exhaust gas discharged from the melting furnace is added to the combustion ash and supplied to the melting furnace at a high load. Method. The generated superheated steam by heat recovery of the discharged flue gas from the melting furnace, according to superheated steam to claim 1 or 2, characterized in that to supply the power plant comprising a steam turbine and generator power Operation method of waste gasification and melting system. The operating method of the waste gasification and melting system according to any one of claims 1 to 3, wherein the daytime is a high load operation and the night is a low load operation.

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