JPH1038235A - Combustion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion method which is capable of completely combusting waste plastic and of recovering sufficient heat. SOLUTION: When waste plastic is combusted, vinyl chloride resin is first gasified in an auxiliary gasifying furnace (50) into hydrogen chloride which is in turn removed. Then, it is guided to a gasifying furnace (1) to produce combustion gas. It is combusted in a gas combustion furnace (20). Vapor is produced with heat produced at that time, and power is generated with a steam turbin (40).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a combustion method.
More specifically, the present invention relates to a method for burning solid plastic or fluid fuel.

[0002]

2. Description of the Related Art As is well known, plastics are produced in large quantities as basic materials along with metals and ceramics, and are used in various fields. And the amount of waste is enormous. As a disposal method of plastics, there are a method of collecting and recycling, a method of using as a landfill material, a method of burning and using as heat energy, and the like, and a method of using heat energy is promising. Solid plastic combustion devices include a fixed bed and a fluidized bed, but very few cases are practiced in Japan and overseas. In the fluidized bed furnace combustion apparatus, combustion heat is also recovered. The fluidized bed furnace combustion device is not shown in the figure,
Equipped with a combustion furnace. An air distribution plate is disposed below the combustion furnace, and below the air distribution plate is an air chamber.
A refractory powder composed of a fluidized bed constituent material, such as silica sand, is placed on the air dispersion plate. The space above the refractory powder is a free board portion. Therefore, when air is blown into the refractory powder from the air chamber through the air distribution plate by the pushing fan, the refractory powder that has been in the fixed layer becomes a fluidized bed that resembles a boiling state. Then, when the solid plastic cut into an appropriate size is supplied to the combustion furnace, the solid plastic is heated by the heated refractory powder, and the emission of volatile components is started. The volatiles are burned immediately above the air distribution plate, and the nitrogen oxide concentration increases with the burning. The solid plastic is vaporized and burned in the particulate rich phase. Further, the generated gas reaches the freeboard section and is burned.

On the other hand, there is also known a combustion apparatus in which a heated pipe is disposed inside a gas or liquid fuel combustion apparatus so as to heat or preheat a liquid in the heated pipe. Such a combustion device is known as, for example, a tubular heating furnace for preheating crude oil or the like. As shown in FIG. 4, the tubular heating furnace 90 includes a combustion furnace 92 and a burner 93 disposed therein. An oil pipe 96 is provided in the combustion furnace 92 along the inner wall. Therefore, when gas or oil for fuel is supplied to the burner 93 from the fluid fuel supply pipe 94 and air for combustion is supplied from the air pipe 95, the fluid fuel burns, and the crude oil in the oil pipe 96 is preheated. .

[0004]

The conventional fluidized-bed furnace combustion apparatus can also burn solid plastic as described above. However, there are problems with conventional combustion methods or devices. For example, when solid plastic is burned in a fluidized bed furnace combustion apparatus, a solid phase and a gas phase are mixed in the furnace, that is, a reduction zone and an oxidation zone are mixed in the furnace, resulting in poor combustion efficiency. As a result, the combustion zone cannot be completely burned, and the oxidation zone where a large amount of heat energy exists is mixed in the reduction zone.
Although heat generation of about / kg is expected, sufficient heat cannot be recovered, and the development of new technologies is expected. Further, vinyl chloride resin is also included in the waste plastic, and chlorine-based toxic gas may be generated from the vinyl chloride resin. Further, it is known that when a vinyl chloride resin is burned at about 650 ° C., the piping material in the furnace is greatly corroded.

On the other hand, when a heated pipe is arranged inside a gas or liquid fuel combustion apparatus and the liquid in the heated pipe is heated or preheated by a combustion apparatus,
Since heat spots are generated and nitrogen oxides are generated, there is a disadvantage that initial costs for denitration equipment and the like are increased. In addition, since a heat spot is generated, for example, in the case of a tubular heating furnace 90 for preheating crude oil or the like, the oil pipe 96 may cause caulking, that is, seizure. When seizure occurs, there is also a problem of maintenance such as replacement of piping. In addition, when seizure occurs, the heat transfer resistance increases, and preheating cannot be performed sufficiently. Furthermore, a tubular heating furnace 9 for preheating crude oil, etc.
At 0, the heating efficiency is not always high because the oil pipe 96 is heated by the radiant heat of the flame H as shown in FIG. Further, in order to heat the oil pipe 96 evenly, it is necessary to perform combustion while maintaining the isotherms T, T,... In the tubular heating furnace 90. However, there is also a problem that the furnace wall material is increased to some extent.

The present invention aims to provide a combustion method that solves the above-mentioned problems or disadvantages. Specifically, it is possible to completely burn solid plastic and to recover sufficient heat. It is intended to provide a combustion method. In addition, other inventions have a low generation of nitrogen oxides, have no coking problem when applied to the combustion of a tubular heating furnace for preheating crude oil, etc., and use a combustion method in which the combustion furnace is relatively small and has a large heat transfer amount. It is intended to provide.

[0007]

The above objects of the present invention can be attained by providing a construction in which solid plastic is vaporized in another furnace and then burned in a gas-only furnace. Alternatively, it is configured to recover the chlorine content with hydrochloric acid, and then gasify and burn. Yet another invention is achieved by burning in a lean fluidized bed furnace. That is, in order to achieve the above object, the present invention provides a single-stage process in which solid plastic is introduced into a gasifier when the solid plastic is burned, and the gas vaporized in the single-stage process is introduced into a gas-fired furnace. , And a two-stage process of mixing with combustion air and burning. The invention according to claim 2 uses a fixed bed for the one-stage treatment according to claim 1, and the invention according to claim 3 uses a fluidized-bed furnace for oxidation catalyst for the first and second treatments according to claim 1. In order to use it, the invention according to claim 4 is directed to a relatively low temperature auxiliary gasification furnace to gasify and remove chlorine content before the first-stage treatment according to any one of claims 1 to 3. Thus, the invention of claim 5 dissolves the gasified chlorine gas of claim 4 in water and recovers it as hydrochloric acid, and the invention of claim 6 proposes any of claims 1 to 5 The heat generated during the one- or two-stage process described in any of the above items is configured to be used for the steam turbine. According to a seventh aspect of the present invention, when a fluid fuel is burned, a heated pipe for liquid heating is arranged in a fluidized bed furnace and a porous fluidized bed constituent material such as alumina oxide is burned in a floating state. The invention according to claim 8 is configured such that the heated pipe according to claim 7 is an oil pipe for preheating crude oil or the like.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a combustion apparatus used for carrying out the method of the present invention will be described below. The combustion apparatus according to the first embodiment shown in FIG. 1 includes a gasification furnace 1 for vaporizing waste plastic or solid plastic, a gas combustion furnace 20 for burning gas vaporized in the gasification furnace 1, A gasification furnace 50 for gasifying the resin material of the system, a steam turbine 40 utilizing heat recovered from the gasification furnace 1 and the gas combustion furnace 20, and a silo 60 storing waste plastic. Have been.

The gasification furnace 1 is composed of a fixed-bed or fluidized-bed furnace having a combustion furnace 2, and will be described below by taking a fluidized-bed furnace combustion apparatus as an example. An air distribution plate 3 is provided below the combustion furnace 2 as is well known in the art. Below the air distribution plate 3, an air chamber 4 is connected. An air supply pipe 6 is connected to the air chamber 4, and air for combustion is pushed in by a pushing fan 5. A solid plastic supply pipe 7 is connected to the combustion furnace 2 so that solid plastic from which chlorine has been removed is appropriately supplied.

A cyclone 10 is connected to a product gas discharge pipe 9 connected above the combustion furnace 2. The cyclone 10 separates a product gas and a solid contained in the product gas, and an underflow pipe 11 extends into a fluidized bed 12 described later. The overflow pipe 13 extends toward the gas combustion furnace 20 described below.
1 denotes a cooling pipe arranged in the fluidized bed 12, and the cooling pipe 14 has a pump 15
Thus, turbine water is supplied.

On the air distribution plate 3, a fluidized bed material M is put. Fluidized bed constituent material M is also be practiced in refractory powder, such as conventionally known silica sand, according to the present embodiment, a fluidized bed configuration material M _{is, BaO · 6Al 2 O 3,} SrO ·
6Al ₂ O ₃ , CaO.6Al ₂ O ₃ , MgAl ₂ O _{4 +} α, Z
rO ₂₊ α, K ₂ O · 11Al ₂ O ₃ , La ₂ O ₃ · 11Al ₂ O
_At least one of the _three is selected. The composition, sintering temperature, S / S (Al ₂ O ₃ ) (surface ratio between the additive material and alumina alone) of these fluidized bed constituent materials M and the crystal phases are as shown in Table 1 below. Table 1 Composition Firing temperature ° C S / S Crystal phase (BaO) _0.14 (Al ₂ O ₃ ) _0.86 1450 4.3 BaO.6Al ₂ O ₃ (SrO) _0.14 (Al ₂ O ₃ ) _0.86 1450 3.0 SrO. 6Al ₂ O ₃ (CaO) _0.14 (Al ₂ O ₃ ) _0.86 1450 3.6 CaO.6Al ₂ O ₃ (MgO) _0.10 (Al ₂ O ₃ ) _0.90 1450 0.8 MgAl ₂ O ₄₊ α (ZrO) _0.10 (Al ₂ O ₃ ) _0.90 1450 0.7 ZrO ₂₊ α (K ₂ O) _0.08 (Al ₂ O ₃ ) _0.92 1300 5.0 K ₂ O · 11 Al ₂ O ₃ (La ₂ O ₃ ) _0.08 (Al ₂ O ₃ ) O ₃ ) _0.92 1300 3.0 La ₂ O ₃ .11Al ₂ O ₃ (La ₂ O ₃ ) _0.05 (Al ₂ O ₃ ) _0.95 1200 8.0 La ₂ O ₃ .11Al ₂ O ₃ IA shown in Table 1, The oxide of IIA, IIIB or IVB is calcined and supported on aluminum oxide, and platinum and Similarly, it has an oxidation catalytic action. Such an oxidation catalyst,
Since porous alumina of 0.2 to 10 mmφ is used as a carrier and the additive is calcined, it can be obtained at low cost.

The gas-fired furnace 20 comprises a fluidized-bed furnace combustion apparatus provided with a combustion furnace 22 similarly to the gasification furnace 1. An air distribution plate 23 is provided below the combustion furnace 22. Below the air distribution plate 23 is an air chamber 24 into which air for combustion is supplied by a pushing fan 25 through an air supply pipe 26.

Exhaust pipe 2 continuing above combustion furnace 22
Cyclone 30 is connected to 9. The cyclone 30 separates the combustion exhaust gas from the solid matter contained in the combustion exhaust gas.
Extends into the fluidized bed 32. A heat exchanger 34 is connected to the overflow pipe 33 of the cyclone 30 so that heat in the combustion exhaust gas is recovered. The combustion exhaust gas from which the heat has been recovered is released into the atmosphere by a chimney or the like. The fluidized-bed constituent material M that has an oxidation catalytic action as in the gasification furnace 1 is placed on the air dispersion plate 23.

A steam pipe 41 is arranged in the combustion furnace 22. The steam pipe 41 and the steam drum 42 are connected to the pipe 4
3 and is connected to the steam turbine 40 by a pipe 44. A heating pipe 45 is disposed above the steam pipe 41, and the heating water in the steam drum 42 is supplied to the heating pipe 45 via a pipe 47 by a pump 46, and the heated turbine water is supplied to the heating pipe 45 by a pipe 48. It returns to the steam drum 42. The cooling pipe 14 of the gasification furnace 1 and the steam drum 42 are connected by the pipe 16.

The auxiliary gasification furnace 50 can also be constituted by a fluidized bed furnace combustion apparatus, or other conventional well-known combustion methods can be applied. Furthermore, the chlorine content of the waste plastic, for example, vinyl chloride resin is 250 to 3
Since the gasification is performed at 00 ° C, the gas can be appropriately heated by the heat of 550 to 1000 ° C obtained in the gas combustion furnace 20. Therefore, the structure for heating auxiliary gasifier 50 is not specifically shown. Above the auxiliary gasification furnace 50, a gas dissolving pipe 51 installed horizontally is connected. The gas dissolving pipe 51 is connected to a rising exhaust pipe 52. A large number of watering nozzles 53 are provided on the upper wall of the gas dissolving tube 51. Further, the bottom wall of the gas dissolving pipe 51 is provided with a slope, and a hydrochloric acid discharging pipe 54 is connected to a lowermost position thereof. Reference numeral 55 indicates a container for receiving hydrochloric acid, 60 indicates a silo storing waste plastic, and 61 indicates a solid plastic supply pipe.

Next, the combustion operation of the above embodiment will be described. The solid plastic in the silo 60 is supplied to the auxiliary gasifier 50 through a solid plastic supply pipe 61. Then, the auxiliary gasifier 50 is heated to 250-350 ° C.
Heat to about. When vinyl chloride resin or the like is contained in the solid plastic, chlorine gas is generated. The generated chlorine gas rises toward the gas pipe dissolution 51. In the gas dissolution tube 51, water is sprayed from the watering nozzles 53, 53,. Then, the chlorine gas is dissolved in water and becomes hydrochloric acid, which is received in the container 55. The gas from which the chlorine gas has been removed is discharged from the exhaust pipe 52 to the atmosphere.

The solid plastic from which the resin component generating toxic chlorine gas has been removed is supplied into the combustion furnace 2 of the gasification furnace 1 through the supply pipe 7. The supplied solid plastic is burned as is well known in the art. At this time, the plastic is vaporized at about 400 ° C.
By controlling the amount of air pushed in for combustion by
The combustion temperature is maintained between 400 ° C. and 500 ° C.
Thereby, the solid plastic is gasified and turned into a gas. The vaporized product gas is sent from the overflow pipe 13 of the cyclone 10 to the air chamber 24 of the gas combustion furnace 20.
From the air chamber 24, together with the combustion air, the air distribution plate 23
And is pushed into the fluidized bed 22 and burns. The combustion temperature at this time is controlled to be about 900 ° C. The fluidized bed constituent material M in the combustion exhaust gas is separated by the cyclone 30 and returned into the fluidized bed 32. The combustion exhaust gas from which the fluidized-bed constituent material M has been removed is guided to the heat exchanger 34, where heat is recovered and released into the atmosphere. The recovered heat is used for preheating combustion air.

As described above, the turbine water is pumped by the pump 15 to the cooling pipe 14 of the gasification furnace 1 during combustion in the gasification furnace 1 and the gas combustion furnace 20. The turbine water heated in the fluidized bed 12 is supplied to the steam drum 42.
To be pumped. The turbine water is pumped from the steam drum 42 to the heating pipe 45 by the pump 46, and the heated turbine water returns to the steam drum 42. The steam thus generated is supplied from the steam drum 42 to the gas combustion furnace 20.
The steam is sent to a steam pipe 41 in the inside, is further heated, and drives the steam turbine 40. The steam turbine 40 drives, for example, a generator. The condensate is returned to the steam drum 42 by a condensate pipe 49.

According to the present embodiment, since the solid plastic is once gasified and burned, the solid plastic is completely burned without being mixed with the oxidized region and the reduced region as in the prior art. Therefore, heat energy can be efficiently extracted from the waste plastic. Further, according to the present embodiment, since the fluidized-bed constituent material M acts as an oxidation catalyst, it burns with a small amount of air. Therefore, the amount of incombustible gas in the generated gas generated in the gasifier 1 is reduced. Further, the thermal efficiency of the gas combustion furnace 20 increases. In the above embodiment, the remaining gas from which the chlorine gas generated in the auxiliary gasification furnace 50 has been removed is released into the atmosphere, but together with the generated gas generated in the gasification furnace 1, the gas combustion furnace 20 is used. Can also be supplied. Further, it is clear that the plasticizer can be gasified by maintaining the temperature in the gasification furnace 1 at about 500 ° C. by the heat of the gas combustion furnace 20. Further, when the waste plastic does not include a resin material that generates chlorine gas such as a vinyl chloride resin, the waste plastic can be supplied directly from the silo 60 to the gasification furnace 1.

Next, a combustion apparatus according to a second embodiment will be described with reference to FIG. 2 using a preheating combustion furnace 70 for preheating crude oil and other intermediate refined oil in an oil refinery plant as an example. The preheating combustion furnace 70 is constituted by a fluidized bed furnace combustion device having a combustion furnace 72. An air distribution plate 73 is provided below the inside of the combustion furnace 72 as conventionally known. An air chamber 74 is provided below the air distribution plate 73, and an air supply pipe 76 is connected to the air chamber 74.
5 allows the air for combustion to be pushed in. A fuel supply pipe 77 is provided above the air distribution plate 73 in the combustion furnace 72.

Since the preheating combustion furnace 70 according to the present embodiment is a lean fluidized bed furnace combustion apparatus, the fluidized bed constituent material m is:
During combustion, it is scattered in the combustion exhaust gas. Therefore, a cyclone 80 is connected to a pipe line 78 extending above the combustion furnace 72. This cyclone 80 separates and recovers the fluidized bed constituent material m from the combustion exhaust gas.
The underflow pipe 81 extends near the air distribution plate 73. The overflow pipe 83 of the cyclone 80
Although not shown in the figure, it is connected to the chimney via a heat exchanger, a back filter or the like.

According to the present embodiment, the fluidized bed constituent material m
Means that the diameter of a porous material such as aluminum oxide is 0.2.
It is composed of fine particles of about 10 to 10 mm. Therefore, the fluidized bed constituent material m
Can be fully spread in the combustion furnace 72. Therefore,
The oil pipe 79 is provided so as to meander over the entire inside of the combustion furnace 72.

Next, the combustion operation of the second embodiment will be described. The air for combustion is supplied to the air distribution plate
3 into the fluidized bed component m. At this time,
The superficial velocity is adjusted so that the fluidized bed 82 spreads completely in the combustion furnace 72. Thereby, the diluted fluidized bed 82 in which the fluidized-bed constituent material m is in a floating state is formed. Fluid fuel such as gaseous fuel is supplied from the fuel supply pipe 77. Lean fluidized bed combustion continues. Cyclone 80 with combustion exhaust gas
Fluidized bed constituent material m that has reached
Then, the fluid is returned to the fluidized bed 82 by the underflow pipe 81. The combustion exhaust gas is discharged from the overflow pipe 83 to the atmosphere via a chimney. During the combustion as described above, crude oil and the like are supplied to the oil pipe 79. Crude oil etc.
While exiting 9, it is preheated to a predetermined temperature.

According to the second embodiment, various effects can be obtained. FIG. 3 is a graph showing the combustion temperature according to the present embodiment and the conventional combustion temperature shown in FIG. 4, with the vertical axis representing the height of the combustion furnace and the horizontal axis representing the temperature. As shown in the figure, according to the present embodiment, the combustion temperature A in the combustion furnace 72 does not significantly differ from the average combustion temperature A ′ in the combustion furnace 72, It turns out that it is almost constant regardless of. On the other hand, in the conventional combustion apparatus, the combustion temperature B is low at the average combustion temperature B ′ and is prominently increased by ΔT ° C. at a substantially middle point of the furnace height.
As described above, in the conventional combustion device, a heat spot in which the combustion temperature rises remarkably occurs, and nitrogen oxides are generated. However, according to the present embodiment, since no heat spot is generated, nitrogen oxides are generated. The amount generated is small. Therefore, no denitration equipment is required, and a reduction in initial and running costs is achieved. Further, since no heat spot is generated, there is no possibility of burning of crude oil or the like.
Furthermore, in order to isothermally heat the conventional oil pipe 96, a certain size of the furnace is required. However, according to the present embodiment, since the combustion temperature A is substantially uniform throughout the combustion furnace 72, The combustion furnace 72 can be made small. Furthermore, since the oil pipe 79 is disposed in the lean fluidized bed 82 and is heated in direct contact with the combustion, the fluidized bed constituent material m, etc., higher thermal efficiency can be obtained as compared with conventional radiant heating.

The fluidized bed material constituting m _{is, BaO · 6Al 2 O 3,} SrO · 6Al 2 O 3 exhibit the oxidation catalysis, CaO · 6
Al ₂ O ₃ , MgAl ₂ O ₄₊ α, ZrO ₂₊ α, K ₂ O · 11
At least one of Al ₂ O ₃ and La ₂ O ₃ .11Al ₂ O ₃ can also be used. In this case, porous particles having a small specific gravity, for example, aluminum oxide having a diameter of 0.2 to 10 mm are used as the carrier. This enables oxidation catalyst combustion in a lean fluidized bed furnace.
Then, combustion can be performed with a small amount of combustion air. Since the amount of combustion air is small, the loss of heat energy is small even at a high temperature of 900 ° C. or higher.

[0026]

As described above, according to the present invention, when a solid plastic is burned, the solid plastic is guided to a gasification furnace to vaporize the solid plastic, and the gas vaporized in the one-stage processing is converted to a gas combustion furnace. And a two-stage process of mixing with combustion air and burning, so that a reduction zone and an oxidation zone do not coexist as in the conventional combustion of solid plastic. Therefore, according to the present invention, the effect unique to the present invention that both the combustion efficiency and the heat recovery efficiency are increased is obtained. Further, according to another invention, since the oxidation catalyst fluidized bed furnace is used, combustion can be performed with a small amount of combustion air, and combustion with little loss of heat energy can be performed. According to still another invention, chlorine is gasified and removed, so that environmental pollution by chlorine gas can be prevented. Further, according to another invention, when a fluid fuel is burned, a heated pipe for liquid heating is arranged in a fluidized-bed furnace, and a porous fluidized-bed constituent material such as alumina oxide is burned in a floating state. No heat spot is generated unlike the conventional case. Therefore, the amount of generated nitrogen oxides is small, and no denitration equipment is required, thereby reducing initial and running costs. According to the invention in which the pipe to be heated is an oil pipe for preheating crude oil or the like, the crude oil or the like does not burn.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a fluidized bed furnace combustion apparatus used for carrying out the method of the present invention.

FIG. 2 is a view showing a second embodiment of a fluidized-bed furnace combustion apparatus used for carrying out the method of the present invention, in which (a) is a schematic view and (b) is a second embodiment. 4 is a graph showing a comparison between a combustion temperature according to the present invention and a conventional combustion temperature.

FIG. 3 is a schematic view showing a conventional tubular heating furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasification furnace 2 Combustion furnace 12 Fluidized bed 20 Gas combustion furnace 32 Fluidized bed 40 Steam turbine 50 Auxiliary gasification furnace 70 Preheating combustion furnace 79 Oil pipe 82 Lean fluidized bed M, m Fluid bed constituent material

Claims (8)

[Claims] When a solid plastic is burned, a one-stage process of guiding the solid plastic to a gasification furnace (1) to vaporize the solid plastic, and a gas combustion furnace (20)
And combustion by a two-stage treatment of mixing with combustion air and burning. 2. A combustion method using a fixed bed in the one-stage treatment according to claim 1. 3. A combustion method using an oxidation catalyst fluidized bed furnace for the one- or two-stage treatment according to claim 1. 4. The method according to claim 1, wherein
A combustion method for introducing chlorine into an auxiliary gasification furnace (50) at a relatively low temperature to gasify and remove chlorine components before the step treatment. 5. A combustion method, wherein the gasified chlorine gas according to claim 4 is dissolved in water and recovered as hydrochloric acid. 6. A combustion method for utilizing a heat generated during the one-stage or two-stage treatment according to claim 1 in a steam turbine (40). 7. When burning a fluid fuel, a heated pipe (79) for heating a liquid is placed in a fluidized-bed furnace, and a porous fluidized-bed constituent material (m) such as alumina oxide is put in a floating state. A combustion method characterized by burning. 8. A combustion method according to claim 7, wherein the pipe to be heated is an oil pipe (79) for preheating crude oil or other intermediate refined oil in an oil refinery plant.