JP2979148B2 - Combustion furnace and powder combustion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a powdered fuel obtained by finely pulverizing a fuel obtained by solidifying general waste or industrial waste.
The present invention relates to a technique for performing combustion efficiently and with easy combustion control.

[0002]

2. Description of the Related Art As the problem of garbage is becoming more serious in society, awareness of recycling is increasing, and an increase in the amount of separated paper and plastic is expected to increase. However, since FY1996, the amount of waste paper, mainly magazines, has become surplus and is becoming a social problem. Therefore, increasing demand for used paper is an urgent issue.

[0003] In addition, waste plastic generated as industrial waste together with waste paper is being treated, but at present, most of it depends on landfill or incineration. The problem with landfills is that there is a shortage of landfills, and the generation of toxic gases in incineration.

[0004] In order to solve these problems, RDF (R) is used in which waste paper or waste plastic is solidified into a rod-shaped fuel.
efuse Dust Fuel) or RPF (Refuse Paper and plastic)
Fuel) has been realized. However, the combustion characteristics of these solidified fuels are unstable, and there are limitations in terms of heat recovery efficiency and temperature control. Further, the furnace for combustion has become large, and it has been difficult to install the furnace in a general company.

[0005] On the other hand, there has been proposed an apparatus for burning RDF or RPF which is made into a fine powder fuel by refining it.
Because it is powdered, stable combustion can be performed more than solidified fuel, and high load combustion can be performed.

FIG. 9A shows a conventional powder fuel combustion furnace. Powder fuel is supplied to the furnace 5 by a supply pipe 7. Further, an auxiliary burner 9 is provided adjacent to the supply pipe 7 to burn kerosene and the like. This is because the combustion is assisted by the auxiliary burner 9 because sufficient combustion cannot be performed with the powdered fuel alone and the combustion may not be continued.

FIG. 9B shows a conventional powder fuel combustion furnace according to another type. A fuel supply pipe 4 is connected to the furnace 2 to supply powdered fuel. Since the fuel supply pipe 4 is connected in the tangential direction of the circular cross section of the furnace 2,
It is introduced spirally. Thereby, the residence time of the fuel is lengthened, and the size of the combustion furnace is reduced. Further, kerosene and the like are burned by the auxiliary burner 3 for the same reason as in the furnace of FIG. 9A.

[0008]

However, the above-mentioned conventional apparatus has the following problems.

First, in the conventional apparatus, the powder fuel and the combustion air are supplied only at the same position or adjacent positions, and it is difficult for the powder fuel to ignite due to excessive air or temperature drop. Further, combustion control was not easy, and it was difficult to obtain continuous combustion.

That is, in the conventional method, it is difficult to completely burn the powder fuel, and unburned matter is often generated. Further, there is a problem that the combustion furnace must be enlarged in order to obtain complete combustion.

Second, in order to continue combustion, it is necessary to operate an auxiliary burner, and an auxiliary fuel other than the powder fuel is required. For this reason, there was a problem that running cost increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a combustion furnace which solves the above-mentioned problems, facilitates combustion control, and can reduce both the cost of the apparatus and the running cost.

[0013]

According to a first aspect of the present invention, there is provided a combustion furnace having a combustion main body having a combustion space therein and a gas discharge port at one end side. A powder fuel supply port for supplying body fuel, a primary combustion air supply port provided adjacent to the powder fuel supply port for supplying primary combustion air, and a secondary combustion air supply for supplying secondary combustion air A combustion space from the powder fuel supply port and the primary combustion air supply port so as to burn the primary combustion air and the powder fuel spirally and while moving to the other end side of the furnace body. And the secondary combustion air is introduced into the combustion space from the other end of the furnace body toward the gas discharge port, against the primary combustion air and the powdered fuel, and the spiral shape of the powdered fuel is Through the gas outlet through the central part of the It is characterized in that the the like.

A combustion furnace according to a second aspect of the present invention is characterized in that an auxiliary combustion device for assisting the temperature rise of the combustion furnace and the combustion of the powder fuel in the initial stage of combustion is provided on the other end side of the furnace main body. I have.

A combustion furnace according to a third aspect of the present invention is characterized in that the secondary combustion air is introduced into the combustion space in a spiral shape and proceeds toward an outlet of the furnace body.

A combustion furnace according to a fourth aspect of the present invention is characterized in that a tertiary combustion air supply port for introducing tertiary combustion air is provided near the gas discharge port of the furnace body.

A combustion furnace according to claim 5 is characterized in that the powder fuel supply port and the temporary combustion air supply port are shared.

[0018] The combustion furnace according to claim 6 is characterized in that the gas outlet is installed so as to open downward.

According to a seventh aspect of the present invention, in the powder combustion method, the powder fuel is spirally advanced, and the spirally advanced powder fuel is moved backward at the center of the spiral. It is characterized by burning body fuel.

[0020]

According to the first aspect of the present invention, there is provided a combustion furnace wherein the primary combustion air and the powder fuel are spirally burned while moving to the other end of the furnace body. The secondary combustion air is introduced from the combustion air supply port into the combustion space, and the secondary combustion air is introduced into the combustion space from the other end of the furnace body toward the gas discharge port. The gas is discharged from the gas discharge port through the spiral central portion of the gas.

Therefore, high load combustion can be performed with a long residence time, and the furnace can be downsized. Also, by adjusting the supply of secondary combustion air,
The length of the spiral stroke of the powder fuel can be controlled, and the combustion control can be easily performed. Furthermore, since the introduced powdered fuel spirally progresses around the center of the spiral, which is the combustion promoting portion, it softens, gasifies, and ignites naturally. Therefore, once combustion has occurred, the supply of auxiliary fuel is unnecessary, and running costs can be reduced.

A combustion furnace according to a second aspect of the present invention is characterized in that an auxiliary combustion device for assisting the temperature rise of the combustion furnace and the combustion of the powder fuel in the initial stage of combustion is provided on the other end side of the furnace main body. I have. Therefore, it is possible to easily ignite the powder fuel in the early stage of combustion.

[0023] The combustion furnace according to claim 3 is characterized in that the secondary combustion air is introduced into the combustion space spirally and so as to advance toward the outlet of the furnace body. Thereby, a turbulent flow is generated at the collision point between the powder fuel and the secondary combustion air, and the combustion of the powder fuel is ensured.

A combustion furnace according to a fourth aspect of the present invention is characterized in that a tertiary combustion air supply port for introducing tertiary combustion air is provided near the gas discharge port of the furnace body. Thus, the unburned gas can be completely burned, and the concentration of carbon monoxide can be reduced.

The combustion furnace according to claim 5 is characterized in that the powder fuel supply port and the temporary combustion air supply port are shared. Therefore, the configuration can be simplified.

[0026] A combustion furnace according to claim 6 is characterized in that the gas outlet is installed so as to open downward. Therefore, the ash from the combustion is easily discharged.

According to a seventh aspect of the present invention, in the powder combustion method, the powder fuel is advanced spirally, and the spirally advanced powder fuel is moved backward at the center of the spiral. It is characterized by burning body fuel. Therefore, it is possible to realize a high load combustion by extending the residence time.

[0028]

FIG. 1 shows a combustion apparatus using a combustion furnace according to an embodiment of the present invention. Powdered fuel is supplied to the combustion furnace 10 by a powdered fuel supply pipe 12. In this embodiment, a rod-shaped RDF (Refuse Dust Fuel) or RP
F (Refuse Paper and plastic Fuel) is pulverized into powder and used as powder fuel. In this embodiment, the powder was pulverized to a diameter of 4 mm or less.

The metering device 14 accumulates powdered fuel (crushed RDF or RPF) in the hopper 16 and
A predetermined amount is supplied by rotation of 8. The supplied powdered fuel is sent out to the powdered fuel supply pipe 12 by the blower 20. In this way, the powdered fuel is continuously supplied to the furnace 10 while maintaining a constant amount per unit time. The supply amount of the powder fuel can be adjusted by controlling the rotation speed of the screw 18 by the motor M.

A blower 22 for supplying primary combustion air and a primary combustion air supply pipe 24 are connected to the furnace 10. Similarly, a blower 26 for supplying secondary combustion air, a secondary combustion air supply pipe 28, and a blower 30 for supplying tertiary combustion air, a tertiary combustion air supply pipe 32
Is connected.

One end of the furnace 10 is open, and the other end is provided with an initial combustion support burner 34. Kerosene is supplied to the initial combustion burner 34 from a kerosene tank 36 by a pump 38. The supply of kerosene to the initial combustion burner 34 is controlled by a kerosene metering mechanism CM controlled by the control circuit TIC. In this embodiment, kerosene is used, but heavy oil, gas, or the like may be used.

A secondary combustion furnace 40 is provided at one open end of the furnace 10. A temperature sensor 44 is provided near the entrance of the secondary combustion furnace 40. Secondary combustion furnace 4
Within the zero, a barrier 42 is provided, which causes the combustion ash to fall to the bottom 46. Hot air 48 from which combustion ash has been removed
Is led to a heat exchanger and the like to be recovered.

FIG. 2 is a longitudinal sectional view of the combustion furnace 10. One end of the furnace body 100 is open and the gas outlet 10
It is 4. On the other end side, an initial combustion support burner 34 is provided. The furnace body 100 has a combustion space 102 therein.
And the cross section is a substantially hollow circular shape. A primary combustion air supply port 25 is provided on a side close to the gas discharge port 104. Further, a powder fuel supply port 13 is provided adjacent thereto.

FIG. 3A is a cross-sectional view of the vicinity of the primary combustion air supply port 25. The ring header 108 is connected to the primary combustion air supply pipe 24. Ring header 108
Is connected to the furnace body 1 through a plurality of primary combustion air supply ports 25.
00 combustion space 102. Further, as shown, the primary combustion air supply port 25 is provided along the circular furnace wall of the furnace main body 100 (that is, in the tangential direction of the circle). As a result, the primary combustion air is spirally introduced into the combustion space along the furnace wall. Also,
Powder fuel supplied from the adjacent powder fuel supply port 13 is also spirally introduced into the combustion space along the furnace wall. In addition, a butterfly valve 110 is provided in each primary combustion air supply port 25, and each flow rate can be adjusted.

The introduced powdered fuel proceeds in the direction of the initial combustion burner 34 while drawing a spiral. This is because the slope 112 toward the gas outlet 104 is formed more perpendicularly to the slope 114 toward the initial combustion burner 34.

A swirling air nozzle 106 as a secondary combustion air supply port is provided so as to surround the initial combustion burner 34 provided at the other end of the furnace main body 100. The swirling air nozzle 106 is open on the side facing the furnace main body 100 and closed on the opposite side.

FIG. 3B is a cross-sectional view of the vicinity of the swirling air nozzle 106. The secondary combustion air supply pipe 28 is connected to the swirling air nozzle 106. Secondary combustion air supply pipe 2
The secondary combustion air from 8 is spirally swirled by the swirling air nozzle 106 toward the furnace body 100.

As shown in FIG. 2, a tertiary combustion air supply port 33 connected to a tertiary combustion air supply pipe 32 is provided near the gas discharge port 104 of the furnace body 100. The tertiary combustion air supply port 33 is formed obliquely in a direction toward the gas discharge port 104.

Next, the operation of the combustion furnace will be described. First, the blower 26 is operated to supply secondary combustion air from the swirling air nozzle 106. The secondary combustion air turns around the central axis 120 of the furnace and travels in the direction of the gas outlet 104 as indicated by β in FIG. At the same time, the initial combustion burner 34 is burned. Thereby, the combustion space 1
The temperature of 02 is about 1000 degrees Celsius.

Next, the fixed amount supply device 14 and the blower 22
To supply powdered fuel and primary combustion air.
The primary combustion air and the powder fuel supplied from the powder fuel supply port 13 and the primary combustion air supply port 25 turn around the central axis 120 of the furnace as shown by α in FIG. Proceed in the direction of. In this embodiment, the swirl direction α of the powdered fuel is opposite to the swirl direction β of the secondary combustion air.

The powder fuel absorbs heat in an atmosphere of about 1000 degrees in the process of spirally progressing as indicated by α, ignites while evaporating, softening, and gasifying the contained water and starts burning. In this portion of α, it is preferable to suppress combustion air to a small extent. This is to prevent local high temperature and prevent rapid combustion / high temperature combustion.
That is, the exhaust gas properties are stabilized by moderate combustion, and the temperature is set to a temperature at which no clinker (molten mass) is formed. In addition, in the portion of α, when the amount of combustion air increases, the ambient temperature of the surroundings and the temperature of the furnace wall may decrease, which may hinder ignition and continuous combustion. Therefore, it is preferable that the primary combustion air is supplied with air at an air ratio (= air / fuel) of 2.0, and is adjusted so as to supply about 40% of the air.

The spiral movement allows the residence time (retention distance) to be extended.

The powdered fuel that has spirally moved as indicated by α collides with the secondary combustion air in the γ portion. Some of the particles of the powdered fuel burn in the process α, but there are also unburned matter which has not been burned and has become a molten mass or carbide. Nitrogen and carbon dioxide are present around these unburned substances. Therefore, by the collision with the secondary combustion air and the turbulent flow in the γ portion, these nitrogen and carbon dioxide are eliminated to infiltrate the oxygen, and further, the combustion is promoted in the process of going backward from γ to δ.

In this embodiment, the swirling directions of the primary combustion air and the secondary combustion air are reversed. However, depending on conditions such as the shape of the furnace and the properties of the powdered fuel, the swirling directions are the same. Sometimes it is preferable to do so.

The secondary combustion air supplies about 30% of the whole. Of course, by changing the supply amount (supply pressure) of the secondary combustion air by the butterfly valve 27, the position of the collision point γ can be controlled, and the residence time (residence distance) of the powder fuel can be controlled. . That is, by reducing the supply amount of the secondary combustion air, the collision point γ between the primary air and the secondary air is shifted upward, the spiral stroke α is lengthened, and the residence time (residence distance) of the powder fuel is extended. can do. Conversely, by increasing the supply amount of the secondary combustion air, the spiral stroke α can be shortened, and the residence time (residence distance) of the powder fuel can be shortened.

After the secondary combustion air is given at γ, the powdered fuel is discharged from the gas outlet 104 through the center of the spiral α as shown at δ. At this time, tertiary combustion air is supplied from the tertiary combustion air supply port 33 to further promote combustion. Thereby, the concentration of carbon monoxide in the exhaust gas can be suppressed to 30 ppm or less.

The exhaust gas discharged from the gas outlet 104 is guided to the secondary combustion furnace 40 as shown in FIG. The secondary combustion furnace 40 is provided with a temperature sensor 44.
Once the detected value of the temperature sensor 44 exceeds 1000 degrees, the control circuit TIC closes the kerosene metering mechanism CM1 and stops the initial combustion burner 34. As a result, the combustion by the auxiliary burner 34 is stopped, but since the temperature in the furnace has already exceeded 1000 degrees, the combustion of the powder fuel continues thereafter. In particular, according to this embodiment, the temperature at the position where the powder fuel is supplied becomes 1 by the combustion in the process δ.
Since the temperature is stably maintained at 000 degrees or more, stable combustion can be performed without the auxiliary burner 34.

The control circuit TIC detects the target temperature (1000 degrees) based on the temperature signal from the temperature sensor 44.
If it is lower than this, the supply amount of the powder fixed amount supply device 14 is increased and the air metering mechanism CM2 is opened to increase the supply amount of the primary combustion air. When the detected temperature is higher than the target temperature, the supply amount of the powder fixed amount supply device 14 is reduced, and the air metering mechanism CM2 is closed to reduce the supply amount of the primary combustion air. This allows
The combustion temperature is kept constant.

Although ash is generated in the furnace 10 by the combustion, in this embodiment, the ash does not remain in the furnace 10 because the gas outlet 104 is opened downward.

In this embodiment, the temperature sensor 44
When the detected temperature becomes lower than a predetermined set value, the control circuit TIC activates the auxiliary burner 34 so that an emergency can be dealt with. Further, instead of the monitoring by the temperature sensor 44, a video of a flame or a pressure of combustion air may be monitored.

The combustion mechanism of the combustion furnace according to the above embodiment is schematically shown in FIG. First, at the point A, the powder fuel is supplied. This powder fuel has α
As shown in the figure, it burns while proceeding spirally. Since the spiral travels, the residence distance can be increased. The spirally advanced powdered fuel collides with the secondary combustion air at the point γ, and further burns. Then, as shown by δ, the spiral is discharged so as to flow backward in the central part of the spiral α. Such a backflow makes it possible to further increase the residence time. Further, the temperature of the spiral α portion is maintained at a high temperature by the combustion of the δ portion, thereby enabling stable combustion of the powder.

In this embodiment, 200 × 10 ⁴ kcal / m ³
It is possible to obtain a large combustion load of hr. Therefore, the size of the combustion furnace can be reduced. Therefore, at the level of each company, it becomes possible to use a combustion furnace for boilers, heating devices, and power generation in factories.

As shown in FIG. 6, a turning air supply port 151 for assisting turning may be provided.

Further, as shown in FIG. 7, the combustion furnace 10 may be installed in a horizontal direction according to restrictions on the installation place. Furthermore, as shown in FIG.
The ash may be easily discharged while keeping the height low. Note that, as shown in the embodiment of FIG. 7, a blower 50 may be connected to the secondary combustion furnace 40 to supply combustion air.

In the above embodiment, the hot air from the secondary combustion furnace is used by the heat exchanger, but an aluminum melting furnace may be used as the secondary combustion furnace.

In the above embodiment, the powder fuel supply port 13 and the temporary combustion air supply port 25 are provided adjacent to each other, but they may be shared.

[Brief description of the drawings]

FIG. 1 is a diagram showing a combustion apparatus using a combustion furnace according to one embodiment of the present invention.

FIG. 2 is a diagram showing details of the combustion furnace of FIG. 1;

FIG. 3 is a cross-sectional view of the combustion furnace of FIG.

FIG. 4 is a diagram showing a combustion state of the combustion furnace of FIG. 2;

FIG. 5 is a diagram conceptually showing combustion according to the present invention.

FIG. 6 is a diagram showing an example in which a swirling air supply port 151 is provided in a combustion furnace.

FIG. 7 is a view showing an embodiment in which the combustion furnace 10 is installed horizontally.

FIG. 8 is a diagram showing a case where the combustion furnace 10 is installed obliquely.

FIG. 9 is a view showing a conventional combustion furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Combustion furnace 13 ... Powder fuel supply port 25 ... Temporary combustion air supply port 100 ... Furnace main body 106 ... Swirling air nozzle

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masahiro Nishida 4-12-29 Moridori, Mihara-cho, Minamikawachi-gun, Osaka Nippon Furnace Co., Ltd. (56) References JP-A-8-68520 (JP, A) Actual opening Hei 8-886 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F23C 11/00 305 F23G 5/44 ZAB F23G 5/46 ZAB F23G 5/00-5/00 119 F23G 5/16

Claims (7)

(57) [Claims] 1. A combustion furnace having a furnace body having a combustion space therein and a gas discharge port on one end side, comprising: a powder fuel supply port for supplying powder fuel to a combustion space of the furnace body; A primary combustion air supply port that is provided adjacent to the powder fuel supply port and supplies primary combustion air; and a secondary combustion air supply port that supplies secondary combustion air. Is spirally introduced into the combustion space from the powder fuel supply port and the primary combustion air supply port so as to burn while moving to the other end side of the furnace main body. The fuel is introduced into the combustion space from the other end of the main body toward the gas outlet, and is opposed to the primary combustion air and the powdered fuel, and is discharged from the gas outlet through the spiral central portion of the powdered fuel. Combustion characterized by the fact that . 2. The combustion furnace according to claim 1, wherein an auxiliary device for assisting the temperature rise of the combustion furnace and the combustion of the powder fuel in the initial stage of the combustion is provided at the other end of the furnace main body. Features. 3. The combustion furnace according to claim 1, wherein the secondary combustion air is introduced into the combustion space in a spiral shape and proceeds toward an outlet of the furnace main body. . 4. The combustion furnace according to claim 1, wherein a tertiary combustion air supply port for introducing tertiary combustion air is provided near the gas discharge port of the furnace body. 5. The combustion furnace according to claim 1, wherein the powder fuel supply port and the temporary combustion air supply port are shared. 6. The combustion furnace according to claim 1, wherein the gas outlet is installed so as to open downward. 7. A method of burning a powdered fuel, wherein the powdered fuel is spirally advanced, and the spirally advanced powdered fuel is moved in a direction opposite to a direction in which the spiral advances. A powder combustion method characterized by burning powder fuel in the spiral traveling and the reverse traveling.