JPH04257609A - Supplying method for air for secondary combustion to refuse incineration furnace in refuse incineration plant - Google Patents

Abstract

PURPOSE:To reduce generation amount of CO and dioxine group by a method wherein refuse is decomposed and gasified in a sand bed and generated unburnt gas is effectively burned in a combustion chamber. CONSTITUTION:Refuse is incinerated in a sand bed and ash is produced. The burned ash undergoes melting treatment in a melting furnace 9. Cooling air is supplied into an exhaust gas duct 9b of the melting furnace 9 to cool down melting exhaust gas, and the heated cooling air is sent through the exhaust gas duct 9b to a combustion air feed nozzle 1a through which secondary air is supplied to a combustion chamber of a furnace body 1. As a result, unburnt combustion gas is prevented from being cooled in the combustion chamber, and the unburnt gas and the secondary combustion air are well mixed together.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to improving a method for supplying air for secondary combustion to a waste incinerator that incinerates materials to be incinerated such as municipal waste, sludge, and industrial waste. For waste incinerators in waste incinerators that make it possible to reduce emissions of harmful substances such as CO gas and dioxins by more effectively burning unburned gas in the combustion chamber of the waste incinerator that makes up the incineration equipment. The present invention relates to a method for supplying air for secondary combustion.

0002

[Prior Art] Garbage incineration equipment is used to treat incinerated materials (hereinafter referred to as garbage) such as municipal waste, sludge, and industrial waste. Some are equipped with furnaces.

[0003] As is well known, such a fluidized bed type waste incinerator is equipped with a sand layer serving as a fluidized bed for fluidizing, decomposing and gasifying the waste thrown into the incinerator, and a sand layer provided above the sand layer. It is equipped with a combustion chamber called a freeboard section in which unburned gas that has been decomposed and gasified is combusted.

[0004] A dispersion plate is provided at the bottom of the fluidized bed type waste incinerator to support the sand layer, and a wind box is provided at the bottom of this dispersion plate. The sand in the sand layer is fluidized by the supplied primary air.

[0005] In addition, in order to pass through the side wall of the furnace body of a fluidized bed type waste incinerator and perform secondary combustion of unburned gas, as shown in FIG. 2, which is a schematic system diagram showing the entire waste incineration equipment, ,
A secondary combustion air blowing nozzle 1a for blowing air for secondary combustion into the freeboard section is provided, and a secondary combustion air heating device 1c is interposed in this secondary combustion air blowing nozzle 1a. The secondary combustion air supply pipe 1b is connected to the secondary combustion air supply pipe 1b.
By blowing secondary combustion air into the freeboard section from the secondary combustion air blowing nozzle 1a, the unburned gas that has risen to the freeboard section is completely combusted.

On the other hand, the combustion exhaust gas generated by the combustion of unburned gas in the freeboard section is transferred from the combustion gas outlet 2 at the upper part of the furnace body 1 to the first combustion exhaust gas duct 3, as shown in the figure. It is discharged into the atmosphere through the recovery equipment 4, the second flue gas duct 5, the flue gas treatment equipment 6, the third flue gas duct 7, and the chimney 8.

[0007] Further, the first combustion exhaust gas duct 3 is connected to an exhaust gas duct 9b of a melting furnace 9 for melting incineration ash discharged from the heat recovery equipment 4 and the exhaust gas treatment equipment 6. In order to cool the molten exhaust gas to 500° C. or lower, a water cooling jacket 9e as a cooling device is fitted onto the outside of the casing 9b.

[0008] Therefore, the unburned gas generated by the decomposition and gasification of waste in the sand layer rises to the freeboard section, where it is blown into the freeboard section by the secondary combustion air blowing nozzle. Secondary combustion is performed using the air, and the combustion exhaust gas generated by the secondary combustion is discharged from the combustion gas outlet 2 in the upper part of the furnace body 1.

The incinerated ash contained in the combustion exhaust gas is recovered by the heat recovery equipment 4 and the exhaust gas treatment equipment 6, respectively, and the recovered incinerated ash is supplied to the melting furnace 9 to be melted. The molten exhaust gas generated during the melting process of the incinerated ash is stabilized and reduced in volume and then disposed of and disposed of in a landfill.The molten exhaust gas generated during the melting process of the incinerated ash is cooled by the water cooling jacket 9e to prevent clogging of the exhaust gas duct.

[0010] In addition, nitrogen oxides (NOX) in the combustion exhaust gas
) For removal, a gas, solution, powder, etc. of an amine nitrogen compound (ammonia, urea, etc.) is supplied as a denitrification reducing agent to the high temperature part of the furnace body 1 to promote the denitrification reaction.

[0011]

[Problems to be Solved by the Invention] By the way, from the secondary combustion air blowing nozzle, the secondary combustion air heated to room temperature or to a temperature of 100 to 250°C by the secondary combustion air heating equipment is heated to the total air Although the air is blown into the freeboard section at a ratio of about 1.6 to 2.0, the viscosity of the secondary combustion air is low at temperatures of about 100 to 250 degrees Celsius, and the high temperature and high viscosity of unburned gas In addition to being difficult to mix with CO2, the low temperature of the secondary combustion air cools the unburned gas, making it unable to fully contribute to the combustion of CO2.
There was a problem that harmful substances such as gas and dioxins were emitted.

Furthermore, in order to stabilize and reduce the volume, the incinerated ash is melted in a melting furnace, but during the melting process of the incinerated ash, unmelted or semi-molten particles and volatile components at a temperature of 1200° C. or higher are removed. Molten exhaust gas is discharged.

As mentioned above, the exhaust gas duct that supplies the molten exhaust gas to the first combustion exhaust gas duct may be clogged, so in order to prevent this, cooling water is supplied to the water cooling jacket, for example. The molten exhaust gas containing unmelted or semi-molten particles and volatile components must be cooled to below 500° C., which is uneconomical in terms of effective use of thermal energy.

In addition, in order to promote the denitrification reaction, the combustion exhaust gas and the denitrification reducing agent must be kept in an appropriate temperature atmosphere (optimally 85%
(about 0 to 950°C).

Therefore, the present invention aims to effectively utilize thermal energy to reliably burn unburned gas, and also to effectively perform thermal decomposition of a reducing agent using the heat of molten exhaust gas.
Secondary air to the waste incinerator in waste incineration equipment that can reduce the amount of reducing agent used and suppress the generation of unreacted ammonia by mixing it with the combustion exhaust gas by entraining it with high-temperature secondary air in the furnace body. The purpose is to provide a method for supplying combustion air.

[0016]

[Means for Solving the Problems] The present invention has been made in view of the above problems, and therefore, a method for supplying air for secondary combustion to a waste incinerator in a waste incineration facility according to claim 1 of the present invention. The gist is that the unburned gas produced by the decomposition and gasification of waste in the sand layer at the bottom of the waste incinerator is subjected to secondary combustion in the combustion chamber installed above the sand layer. In a method for supplying air for secondary combustion to a waste incinerator in a waste incinerator that supplies air, the exhaust gas duct is provided with a cooling device for a melting furnace that melts and processes incinerated ash discharged from the waste incinerator. The molten exhaust gas discharged from the melting furnace is cooled by supplying air for cooling, and the cooling air after cooling the molten exhaust gas is supplied to the combustion chamber as secondary combustion air.

[0017] Furthermore, the gist of the method for supplying air for secondary combustion to the waste incinerator in the waste incineration equipment according to claim 2 of the present invention is that in the method for supplying air for secondary combustion according to claim 1, The method is characterized in that a predetermined amount of an amine nitrogen compound solution or powder is sprayed into the interior of the exhaust gas duct using a cooling device that cools the exhaust gas.

[0018]

[Operation] First, according to the method for supplying secondary combustion air to the waste incinerator in the waste incineration equipment according to claim 1 of the present invention, the molten exhaust gas discharged from the melting furnace is cooled by the cooling air. At the same time, air heated by cooling the molten exhaust gas is supplied to the combustion chamber of the waste incinerator as secondary combustion air.

Next, according to the method for supplying air for secondary combustion to the waste incinerator in the waste incineration equipment according to claim 2 of the present invention, the injected amine-based nitrogen compound solution or powder is thermally decomposed. It becomes reducing substances such as ammonia and is supplied to the combustion chamber of the waste incinerator together with cooling air.

[0020]

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. 1, which is a schematic system diagram showing the entire waste incineration facility, with the same reference numerals representing the same parts and the same functions as the conventional one. Reference numeral 1 shown in the figure is a furnace body of a fluidized bed type waste incinerator, and a combustion exhaust gas outlet 2 at the upper part of the furnace body 1 is connected to a first combustion exhaust gas duct 3, a heat recovery equipment 4, and a second combustion exhaust gas duct 5. , exhaust gas treatment equipment 6, third combustion exhaust gas duct 7, and chimney 8 before being discharged into the atmosphere.

On the other hand, the incinerated ash recovered by the heat recovery equipment 4 and the exhaust gas treatment equipment 6 is supplied with melting air, and is heated by combustion of heavy oil or gas or by electric heat to melt and process the incinerated ash. It is supplied to a melting furnace 9 having a configuration to be described later.

The melting furnace 9 comprises a melting furnace main body 9a and an exhaust gas duct 9b extending outward from the lower part of the melting furnace main body 9a and having an exhaust gas cooling section 9d erected through a constriction section 9c, As shown in FIG. 1, the tip of the exhaust gas duct 9b communicates with a secondary air blowing nozzle 1a provided through the outer wall of the furnace body 1.

[0023] Also, between the connection part of the exhaust gas duct 9b to the melting furnace main body 9a and the constriction part 9b, the cooling air sent from the blower 10 is provided with a damper 11 for cooling. The air is supplied via an air supply pipe 12.

The opening degree of the damper 11 is adjusted according to the detected value of the oxygen concentration meter 3a which detects the oxygen concentration in the combustion exhaust gas passing through the first combustion exhaust gas duct 3. That is, depending on the oxygen concentration in the combustion exhaust gas, the opening degree of the damper 11 is adjusted to adjust the amount of cooling air supplied.

Further, a cooling water injection equipment 9e is attached that sprays cooling water from the middle of the exhaust gas cooling unit 9c in the vertical direction toward the inside downward of the exhaust gas cooling unit 9c. A cooling water supply amount adjustment valve 9f is interposed therein, and the cooling water supply amount adjustment valve 9f is configured to be opened and closed by the output of the exhaust gas temperature detector 13 disposed at the upper part of the exhaust gas duct 9b. There is. The cooling water injection equipment 9e has a particularly useful function when the temperature of the molten exhaust gas is too high, in other words, when the temperature of the molten exhaust gas is too high.

The manner of use of the secondary combustion air supply device having the above configuration will be explained below.
When the amount of air adjusted in step 1 is supplied to the exhaust gas cooling section 9c of the melting furnace 9, this air cools the molten exhaust gas discharged from the melting furnace 9 to 400 to 500°C, and the air state cools the molten exhaust gas. The air is heated to 400 to 500°C and passed through the exhaust gas duct 9b to the secondary combustion air blowing nozzle 1.
a, and the secondary combustion air blowing nozzle 1a.
The air is blown into the freeboard section within the furnace body 1.

In other words, the amount of air supplied from the cooling air supply pipe 12 to the exhaust gas duct 9b depends on the oxygen concentration in the combustion exhaust gas detected by the oxygen concentration meter 3a provided in the first combustion exhaust gas duct 3. At the same time, the temperature of the air is reliably maintained at 400 to 500 DEG C. by the cooling water injection equipment 9e as necessary, and the air is blown into the freeboard section in the furnace body 1.

[0028] Therefore, this secondary combustion air does not have a low viscosity like conventional secondary combustion air at room temperature or 100 to 250°C, so it cannot be effectively mixed with the high temperature and high viscosity unburned gas. In addition, since the degree of cooling of the unburned gas is reduced, the unburned gas can be combusted extremely well at a high temperature.

Furthermore, it has been confirmed that since dust is recovered by installing a dust removal equipment in the exhaust gas duct 9b, it is highly effective in preventing the exhaust gas duct 9b from being clogged by dust.

[0030] In the above, an example was explained in which water is sprayed by the cooling water injection equipment 9e, but a solution of ammonia or urea with a concentration of about 5% aqueous solution as an amine nitrogen compound is sprayed in the water, or urea powder is sprayed in the water. When you inject
It has the effect of reducing NOX in combustion exhaust gas for the following reasons.

This is due to reducing substances such as ammonia (NH3) produced by thermal decomposition of amine nitrogen compounds, resulting in 4NO+4NH3+O2 →4N2
This is because the denitrification reaction represented by +6H2O proceeds in the high temperature section of the furnace body (optimum temperature is 850 to 950°C).

[0032]

Effects of the Invention As detailed above, claim 1 of the present invention
According to the method for supplying air for secondary combustion according to the above, the molten exhaust gas discharged from the melting furnace is cooled by the cooling air, and the air heated by cooling the molten exhaust gas is used as the secondary combustion air for garbage incineration. According to the secondary combustion air supply device according to the third invention, the air is supplied to the combustion chamber of the furnace, and is supplied from the cooling air supply pipe to the exhaust gas duct that discharges the molten exhaust gas of the melting furnace that melts incinerated ash. The cooled air is
While cooling the molten exhaust gas discharged from the melting furnace, the molten exhaust gas itself is heated and flows from the exhaust gas duct into the combustion chamber of the waste incinerator.
Since the air is fed to the secondary combustion air blowing nozzle that blows the air for the next combustion, cooling of the unburned gas is prevented, and the heated air that has become highly viscous is mixed with the unburned gas in the combustion chamber. Since they are mixed, unburned gas is effectively combusted.

Further, according to the method for supplying air for secondary combustion according to claim 2 of the present invention, the injected amine-based nitrogen compound solution or powder is thermally decomposed and delivered to the combustion chamber of the waste incinerator together with the cooling air. Since reducing substances such as ammonia are effectively mixed with the combustion exhaust gas, the denitrification reaction proceeds efficiently and the amount of NOx generated is reduced. Therefore, it is also effective in suppressing white smoke caused by leaked ammonia caused by excessive supply of reducing agent.

Furthermore, as in the prior art, the secondary combustion air blown into the combustion chamber from the secondary combustion air blowing nozzle is
In addition to eliminating the need for a secondary combustion air heating device that heats the air to 0 to 250°C, the amount of cooling water supplied to the cooling device can also be reduced, and the amount of reducing agent supplied for denitrification can be reduced. Therefore, it has a great effect on reducing the initial cost and maintenance cost of waste incineration equipment.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram showing the entirety of a waste incineration facility according to an embodiment of the present invention.

FIG. 2 is a schematic system diagram showing the entirety of a conventional waste incineration facility.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Furnace body of fluidized bed furnace, 1a...Air blowing nozzle for secondary combustion, 2...Combustion exhaust gas outlet, 3...First combustion exhaust gas duct, 3
a...Oxygen concentration meter, 4...Heat recovery equipment, 5...Second combustion exhaust gas duct, 6...Exhaust gas treatment equipment, 7...Third combustion exhaust gas duct, 8...Chimney, 9...Melting furnace, 9a...Melting furnace main body, 9b …
Exhaust gas duct, 9c... Throttle part, 9d... Exhaust gas cooling part, 9
e...Cooling water injection equipment, 9f...Cooling water supply amount adjustment valve, 10
...Blower, 11...Damper, 12...Cooling air supply pipe, 1
3...Exhaust gas temperature detector.

Claims (2)

[Claims] Claim 1: In order to perform secondary combustion of unburned gas generated by the decomposition and gasification of waste in the sand layer at the bottom of the waste incinerator in the combustion chamber provided above the sand layer, two combustion chambers are installed in the combustion chamber.
In a method for supplying air for secondary combustion to a waste incinerator in a waste incinerator that supplies air for secondary combustion, the exhaust gas comprises a cooling device for a melting furnace that melts and processes incinerated ash discharged from the waste incinerator. Waste incineration characterized by supplying cooling air to a duct to cool the molten exhaust gas discharged from the melting furnace, and supplying the cooling air after cooling the molten exhaust gas to the combustion chamber as secondary combustion air. A method of supplying air for secondary combustion to a waste incinerator in equipment. 2. A secondary supply to the waste incinerator in the waste incineration equipment according to claim 1, wherein a predetermined amount of amine-based nitrogen compound solution or powder is sprayed toward the inside of the exhaust gas duct by a cooling device that cools the molten exhaust gas. Combustion air supply method.