JPH10238727A - Waste thermal decomposition treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a chlorine concentration of a thermal decomposition gas which constitutes a thermal decomposition product at a low level, which enhancing a reliability of a heat recovery device and enabling an efficient heat recovery in a waste thermal decomposition treatment device. SOLUTION: A waste thermal decomposition treatment device comprises a waste combustor which burns and thermally decomposes a waste, a waste heat steam generator 5 which generates a steam using a high temperature product generated by the waste combustor as a heat source medium, and an air heater 6 which heats a combustion air for the waste combustor. An exhaust gas discharged from the waste combustor is used as a heat source medium of the air heater 6. The waste combustor includes a dryer 1 which thermally decomposes an organic chloride and removes chlorine and a thermal decomposition device 2 which thermally decomposes the waste dried by the dryer at a low temperature of 450-500 deg.C and produces a thermally decomposed gas of a low chlorine concentration by restricting a formation reaction of hydrogen chloride from alkaline salt. An exhaust discharged from the thermal decomposition device is burnt in a gas combustion gas device and this combustion gas is used as the heat source medium for the air heater 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a thermal decomposition apparatus for wastes, in which the concentration of chlorine in a pyrolysis gas, which is a thermal decomposition product, is reduced, and the reliability and efficiency of the heat recovery apparatus are improved. The present invention relates to a waste pyrolysis apparatus capable of recovering heat.

[0002]

2. Description of the Related Art Waste incineration is widely used as one of the most effective waste disposal methods. In Japan, where land is difficult to landfill, the total amount of waste generated in 1991 is small. About 140,000 tons, more than 70% of the volume, are incinerated daily. The incineration ash generated during the incineration of this large amount of waste has conventionally been landfilled.In recent years, however, due to the tightening of landfill sites in the Tokyo metropolitan area and the strengthening of ash landfill standards, ash has been reduced. There is a need to reduce the weight and make it harmless by using molten slag.

However, in a general waste incineration system, it is difficult to directly convert the ash in the waste into molten slag, so that an incineration ash melting furnace using electricity or kerosene as a fuel separately from the incinerator is required. The fact is being advanced.

[0004] On the other hand, effective use of waste heat generated during incineration of a large amount of waste has been attracting attention for a long time, and 1965.
In 1995, starting with power generation at the Nishiyodo Incineration Plant in Osaka City, 1995
As of the year, power generation using waste heat from more than 150 waste incinerations is being performed.

However, many kinds of wastes are contained in the waste to be incinerated, and especially in organic chlorine compounds such as polyvinyl chloride and in seasonings in kitchen garbage as alkaline salts such as sodium chloride. Chlorine becomes a high concentration of hydrogen chloride, chlorine and alkali salts in the combustion gas during waste incineration. This hydrogen chloride, chlorine and alkali salts cause significant corrosion in waste heat steam generators and air heaters, etc.
For example, in the case of a waste heat steam generator, the steam temperature is set to 300
℃ or less, and the design and operation are performed so as to avoid the corrosion area.

As a thermal decomposition method of this kind of waste, for example, as disclosed in JP-A-64-49816, the waste is heated in an oxygen-free or low-oxygen atmosphere.
Separation of pyrolysis gas and non-volatile residue. The thermal decomposition temperature of the waste may be 300 ° C. or higher, and may be appropriately selected depending on the use of the thermal decomposition product.

[0007]

In this conventional pyrolysis method of waste, two-stage treatment of waste is carried out by focusing on the recovery of metal and the formation of molten slag of residue. The pyrolysis gas and non-volatile residue obtained by the above are burned in a single combustion device. Therefore, the chlorine originally present in the waste will be contained in the combustion gas at a high concentration as in the incineration of the waste, and the waste heat steam generator will reduce the steam temperature to avoid corrosion of the heat transfer tubes. Because of the restrictions, it is not possible to expect a significant improvement in power generation efficiency. Further, in the case of incineration with a single combustion device, when the calorific value of the waste is low, the calorific value of the pyrolysis gas decreases, so that an external fuel supply is required.

As described above, since organic chlorine compounds such as polyvinyl chloride and alkali salts such as sodium chloride contained in seasonings and the like in kitchen garbage are originally present in the waste, when the waste is incinerated, the waste gas becomes exhaust gas. Contains high concentrations of hydrogen chloride, chlorine, and alkali salts.These hydrogen chloride, chlorine, and alkali salts cause significant corrosion in air heaters and waste heat steam generators. in case of,
The steam temperature is kept below 300 ° C and the operation is performed while avoiding the corrosive area. Therefore, the power generation efficiency in the case of waste incineration is about 15%, which is remarkably compared with the efficiency of the latest thermal power plants. It is inefficient.

[0009] From these facts, there is a demand for a waste pyrolysis apparatus which grasps the behavior of chlorine in waste and has high reliability and thermal efficiency in consideration of this behavior.

The present invention has been made in view of the above, and an object of the present invention is to suppress the chlorine concentration of a pyrolysis gas, which is a pyrolysis product, at a low level, to improve the reliability of the heat recovery apparatus and to improve the efficiency of the heat recovery. An object of the present invention is to provide a waste pyrolysis apparatus of this kind that can be recovered.

[0011]

That is, the present invention provides a waste combustion apparatus for burning and pyrolyzing waste, and a waste heat for generating steam using a high-temperature product generated by the waste combustion apparatus as a heat source medium. In a waste pyrolysis treatment device comprising a steam generator and an air heater for heating the combustion air of the waste combustion device, and the exhaust gas of the waste combustion device is used as a heat source medium of the air heater. A drying apparatus for thermally decomposing an organic chlorine compound contained in the waste to remove chlorine, and a pyrolysis of the waste dried by the drying apparatus at a low temperature of 450 to 500 ° C. Along with forming a pyrolysis device that suppresses the production reaction of hydrogen chloride from salt to obtain a pyrolysis gas with low chlorine concentration,
The exhaust gas of the pyrolysis device is burned by a gas combustion device, and the combustion gas is used as a heat source medium of the air heater to achieve an intended purpose.

Further, the present invention provides a waste combustion device for burning and thermally decomposing waste, a waste heat steam generation device for generating steam by using a high-temperature product generated by the waste combustion device as a heat source medium, An air heater for heating the combustion air of the waste combustion device, wherein a waste pyrolysis treatment device in which the waste gas of the waste combustion device is used as a heat source medium of the air heater is provided. A drying apparatus for thermally decomposing an organic chlorine compound contained in the waste to remove chlorine, and removing 450 parts of the waste dried by the drying apparatus.
A pyrolysis apparatus that pyrolyzes at a low temperature of about 500 ° C. and obtains a pyrolysis gas having a low chlorine concentration by suppressing the generation reaction of hydrogen chloride from an alkali salt; A non-volatile residue obtained by pyrolysis in a decomposition device is independently burned at a high temperature, a device for melting ash in the residue into slag, and a gas combustion device for burning exhaust gas of the pyrolysis device are provided. The combustion gas of the gas combustion device is used as a heat source medium of the air heater.

[0013] In this case, the heated air obtained by the air heater is used for indirect heating of the thermal decomposition device, and the exhaust gas is used as a heat source of the drying device. Further, the gas recovered by the air heater and the waste heat steam generator is supplied as a heat source medium of the drying device, and the exhaust gas of the drying device is blown into the high temperature portion at the outlet of the pyrolysis device. Things.

That is, according to the present invention, even when a waste having a low calorific value is targeted, the combustion of the pyrolysis gas, which is a pyrolysis product, and the non-volatile residue is performed in order to minimize the external supply of fuel. Separate the parts and use a facility that performs high-temperature combustion in the non-volatile residue combustion section, where the calorific value is stable at about 3000 kcal / kg or more even if the calorific value of the waste fluctuates. It is possible to make molten slag.

On the other hand, when the waste is dried or thermally decomposed at about 200 to 350 ° C., it is possible that organic chlorine compounds such as polyvinyl chloride contained in the waste are thermally decomposed and chlorine is released to the gas side. It is known, however, that waste contains not only chlorine in organochlorine compounds such as polyvinyl chloride, but also high concentrations of chlorine contained as alkali salts such as sodium chloride in seasonings in kitchen garbage. .

Although chlorine contained as an alkali salt such as sodium chloride does not thermally decompose at about 200 to 350 ° C. at which organic chlorine compounds such as polyvinyl chloride are thermally decomposed, waste is burned in an incinerator at 800 ° C. or more. In some cases, it is generally known to react with sulfurous gas and water to produce hydrogen chloride.

In the present invention, the drying process and the pyrolysis process of the waste are separated, and the waste is first heated to about 300 ° C. in the drying process to convert chlorine contained in an organic chlorine compound such as polyvinyl chloride into a dry gas. Release and remove. Next, in the pyrolysis process, 4
By the low-temperature pyrolysis at 50 to 500 ° C., the reaction of generating hydrogen chloride from an alkali salt such as sodium chloride contained in a seasoning or the like in kitchen garbage is suppressed, and a pyrolysis gas having a low chlorine concentration can be obtained. As a result of using a pyrolysis gas with low chlorine concentration as a heat source and enabling the heating of the pyrolysis unit and the heating of steam while avoiding corrosion of the heat transfer tubes, high-temperature heat recovery becomes possible and the power generation efficiency is reduced to about 25-30%. It is possible to increase.

The following is a more detailed explanation focusing on the behavior of chlorine contained in waste. When city garbage, which is waste from general households, is pyrolyzed at 450 to 500 ° C, the pyrolysis gas contains hydrogen chloride and chlorine generated by the thermal decomposition of organic chlorine compounds such as polyvinyl chloride. Alkaline salts such as sodium chloride derived from seasonings and the like in kitchen garbage are mixed into the sexual residue at a high concentration. The chlorine concentration varies depending on the city where the waste is collected and the season, but the ratio of chlorine contained in organic chlorine compounds such as polyvinyl chloride and chlorine contained as alkali salts in sodium chloride etc.
It is about 1: 1.

Therefore, as a pretreatment of the thermal decomposition apparatus, the waste is dried at about 300 ° C. in a drying apparatus to remove 90% or more of chlorine contained in an organic chlorine compound such as polyvinyl chloride.
Next, the dried waste is subjected to a thermal decomposition apparatus for 450 to 50 hours.
By pyrolyzing at a low temperature of 0 ° C., it is possible to suppress the generation reaction of hydrogen chloride from alkali salts such as sodium chloride contained in seasonings and the like in kitchen garbage, and to obtain a pyrolysis gas having a low chlorine concentration. .

As a result, the heating of the pyrolysis device and the heating of the waste heat steam generator can be carried out without considering the corrosion of the heat transfer tube, using the exhaust gas obtained by burning the pyrolysis gas alone in the gas combustion device. In addition, thermal efficiency can be improved by high-temperature heat recovery. In addition, by heating the pyrolysis unit with heated air indirectly heated by the combustion exhaust gas of the pyrolysis gas, the air induced from the waste pit can be used to further improve the performance of the equipment against material corrosion, and the waste pyrolysis The reliability of the device can be improved.

That is, with the waste pyrolysis treatment apparatus formed as described above, even when the waste has a low calorific value, the supply of fuel from the outside is minimized to minimize the need for the thermal decomposition product. The combustion part of the pyrolysis gas and the non-volatile residue is separated, and even if the calorific value of the waste fluctuates, the calorific value is stable at about 3000 kcal / kg or more. Is carried out, and the ash in the residue can be efficiently converted into molten slag.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments.

[Embodiment 1] FIG. 1 is a schematic configuration diagram of a waste pyrolysis apparatus according to a first embodiment. 1 is a drying device, 2 is a pyrolysis furnace, 6 is an air heater, 7 is a steam heater, and 10 is a power generator. In this embodiment, the waste is supplied to the drying device 1 by the charging device 11, heated by the air heater 6 at the subsequent stage, and directly heated by the heating air at about 300 ° C. through the pyrolysis furnace 2 and the drying furnace air supply pipe 27. Contact drying. In this drying process, an organic chlorine compound such as polyvinyl chloride contained in the waste is thermally decomposed to remove 90% or more of chlorine contained in the organic chlorine compound such as polyvinyl chloride.

Next, the dried waste is supplied to the pyrolyzer 2 by the dry waste input device 12 and is heated at 450 to 500 ° C.
At low temperature to obtain a pyrolysis gas and a non-volatile residue as pyrolysis products. The pyrolysis gas obtained here is sent to the gas combustion device 4 through the pyrolysis gas transfer pipe 17, and a part of the exhaust gas that has heated the pyrolysis furnace 2 is supplied from the combustion furnace air supply pipe 29 as combustion air. And burn.

Since the flue gas has a low chlorine concentration, the flue gas is supplied to the air heater 6 and the steam heater 7 through the gas flue gas transfer pipe 18 and the air heater outlet pipe 19 to perform heat recovery while avoiding corrosion. The exhaust gas at the outlet of the steam heater 7 is connected to a feed water heating area of the waste heat steam generator 5 to further recover heat.

On the other hand, the non-volatile residue is supplied to the combustion device 3 by the non-volatile residue supply device 13, and a part of the exhaust gas heated in the pyrolysis furnace 2 is used as combustion air for the combustion furnace combustion air supply pipe 28. And burns at high temperature to melt the ash in the non-volatile residue and discharge it as molten slag from the slag discharge hole 24. The flue gas is combined with the drying furnace exhaust pipe 30 through the flue gas transfer pipe 14 and transferred to the waste heat steam generator 5 to recover heat.

[0027] All the combustion exhaust gas recovered by the waste heat steam generator 5 is sent to the exhaust gas treatment device 8 by the waste heat steam generator outlet pipe 15 and then processed.
After passing through 6, it is discharged to the exhaust stack 9. Water is supplied to the waste heat steam generator 5 through a water supply pipe 21 to generate steam. This steam is sent to the steam heater 7 through the steam outlet pipe 22 to be heated and supplied to the power generation facility 10 through the heated steam supply pipe 23.

The air is sucked from the waste pit, transferred to the air heater 6 by the air supply pipe 25, heated to 500 to 600 ° C., and supplied to the pyrolysis furnace 2 by the pyrolysis furnace heating air supply pipe 26 for heating. I do. Approximately 300 heated pyrolyzer 2
A part of the exhaust gas of ° C. is supplied from the combustion furnace combustion air supply pipe 28 and the gas combustion furnace combustion air supply pipe 29 as combustion air of the combustion apparatus 3 and the gas combustion apparatus 4. The remaining exhaust gas from the pyrolysis device 2 at about 300 ° C.
7, the waste is supplied to the drying device 1 and the waste is directly contact-dried to thermally decompose and remove chlorine in an organic chlorine compound such as polyvinyl chloride.

Exhaust gas containing chlorine used for drying is blown into a high-temperature portion at the outlet of the combustion device 3 through a drying furnace exhaust pipe 30 to remove odor, and is discharged outside the system through an exhaust gas treatment device 8. In this embodiment, the air used for drying is blown into the outlet of the combustion device 3.
It can also be supplied as secondary combustion air to reduce the amount of exhaust gas.

The chlorine contained in the organic chlorine compound such as polyvinyl chloride in the waste is removed by the drying device 1, but the waste contains an alkali such as sodium chloride derived from seasonings in the kitchen garbage. It also contains significant amounts of salt. However, 450-
In low-temperature pyrolysis at 500 ° C., alkali salts such as sodium chloride do not thermally decompose. Therefore, when pyrolyzing dried waste in this embodiment, the chlorine concentration in the pyrolysis gas is 10% of the chlorine concentration in the waste. % Or less.

Further, by burning this pyrolysis gas alone, a high-temperature combustion gas having a low chlorine concentration can be obtained. Therefore, in the prior art, air heating was designed to avoid high-temperature corrosion and to recover heat at a low temperature of about 300 ° C. or less. Vessel 6, steam heater 7
Thus, heat recovery of 400 to 500 ° C. or more was made possible, and the reliability of the waste pyrolysis apparatus against corrosion of the heat transfer tubes was improved, and the efficiency of the power generation facility 10 by heating steam was improved.

In this embodiment, the case where the drying step is provided is shown. However, even when the drying step is separated,
It is needless to say that the same effect as that of the present embodiment can be obtained by using a waste heated and dried to a temperature at which chlorine in an organic chlorine compound such as polyvinyl chloride is thermally decomposed.

[Embodiment 2] FIG. 2 is a schematic structural view of a waste pyrolysis apparatus according to a second embodiment. In this example, since the flow of the waste treatment from the input of the waste to the combustion of the pyrolysis products is the same as that of the above-described example, the flow of the parts different from the first embodiment will be described below. .

The pyrolysis gas is burned by the combustion air heated by the air heater 6 at the subsequent stage in the gas combustion device 4. This combustion exhaust gas is supplied to the air heater 6 and the steam heater 7 through the gas combustion exhaust gas transfer pipe 18 and the air heater outlet pipe 19, and heat is recovered to about 600 ° C., and then as a heat source for heating the pyrolysis apparatus 2. Supply. Exhaust gas obtained by indirectly heating the pyrolysis device 2 and recovering heat to about 300 ° C. is supplied to the drying device 1 and heat-exchanged directly with waste to dry the waste. The odor is removed by blowing into the high-temperature portion at the outlet, and is discharged outside the system through the exhaust gas treatment device 8.

On the other hand, the non-volatile residue is supplied to the combustion device 3 by the non-volatile residue supply device 13 and is burned at a high temperature by the combustion air heated by the air heater 6 at the subsequent stage, so that the non-volatile residue is contained in the non-volatile residue. The ash is melted and discharged from the slag discharge hole 24 as molten slag. The flue gas is combined with the drying furnace exhaust pipe 30 through the flue gas transfer pipe 14 and transferred to the waste heat steam generator 5 to recover heat.

All the combustion exhaust gas recovered by the waste heat steam generator 5 is sent to the exhaust gas treatment device 8 by the waste heat steam generator outlet pipe 15 and then processed.
The exhaust gas is discharged to the exhaust pipe 9 through the exhaust pipe 9.

Water is supplied to the waste heat steam generator 5 through a water supply pipe 21 to generate steam. The generated steam is sent to the steam heater 7 by the steam outlet pipe 22 and heated, and is supplied to the power generation facility 10 by the heated steam supply pipe 23.

Air is supplied from the waste pit to the air supply pipe 2.
After being transferred to the air heater 6 through the heater 5 and heated to 500 to 600 ° C., it is supplied for heating the pyrolysis furnace 2 by the pyrolysis furnace heating air supply pipe 26. The exhaust gas of about 300 ° C. from the pyrolysis furnace is supplied as combustion air to the gas combustion device 4 and the combustion device 3 through a gas combustion air supply pipe 29 and a combustion furnace combustion air supply pipe 28, respectively.

[0039]

As described above, according to the present invention, the chlorine concentration of a pyrolysis gas, which is a pyrolysis product, is kept low, and the reliability of the heat recovery device is improved and the heat recovery is efficiently performed. This type of waste pyrolysis apparatus can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing an embodiment of a waste pyrolysis apparatus according to the present invention.

FIG. 2 is a schematic system diagram showing another embodiment of the waste pyrolysis apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drying apparatus, 2 ... Thermal decomposition apparatus, 3 ... Combustion apparatus, 4 ... Gas combustion apparatus, 5 ... Waste heat steam generator, 6 ... Air heater,
7: steam heater, 8: exhaust gas treatment device, 9: exhaust stack, 1
0: power generation equipment, 11: input device, 12: dry waste input device, 13: nonvolatile residue supply device, 14: combustion exhaust gas transfer pipe, 15: waste heat steam generator outlet pipe, 16 ...
Exhaust gas treatment equipment outlet pipe, 17 ... pyrolysis gas transfer pipe,
18: gas combustion exhaust gas transfer pipe, 19: air heater outlet pipe, 20: steam heater outlet pipe, 21: water supply pipe, 2
2: Steam outlet pipe, 23: Heated steam supply pipe, 24: Slag discharge hole, 25: Air supply pipe, 26: Pyrolysis furnace heated air supply pipe, 27: Drying furnace air supply pipe, 28: Combustion furnace combustion air Supply pipe, 29 ... air supply pipe for gas combustion furnace combustion,
30 ... drying furnace exhaust pipe.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23G 5/14 ZAB F23G 5/14 ZABD 5/46 ZAB 5/46 ZABZ F23J 1/00 F23J 1/00 B F23L 15/00 F23L 15/00 A (72) Inventor Shogo Sakamoto 3-18-1, Omikacho, Hitachi City, Ibaraki Prefecture Within Ibaraki Hitachi Information Service Co., Ltd. (72) Katsuyuki Ishii 3-18-1, Omikamachi, Hitachi City, Ibaraki Prefecture No. Ibaraki Hitachi Information Service Co., Ltd.

Claims (4)

[Claims] 1. A waste combustion device that burns and pyrolyzes waste, a waste heat steam generator that generates steam using a high-temperature product generated by the waste combustion device as a heat source medium,
An air heater that heats combustion air of the waste combustion device, wherein the waste gas from the waste combustion device is used as a heat source medium of the air heater. A drying apparatus for thermally decomposing an organic chlorine compound contained in the waste to remove chlorine, and thermally decomposing the waste dried by the drying apparatus at a low temperature of 450 to 500 ° C. to produce hydrogen chloride from an alkali salt. And a pyrolysis device that obtains a low-chlorine-concentration pyrolysis gas by suppressing the generation reaction of the gas. The exhaust gas of the pyrolysis device is burned by a gas combustion device, and the combustion gas is used as a heat source medium of the air heater. A waste pyrolysis apparatus characterized in that it is used for: 2. A waste combustion device that burns and thermally decomposes waste, a waste heat steam generator that generates steam using a high-temperature product generated by the waste combustion device as a heat source medium,
An air heater that heats combustion air of the waste combustion device, wherein the waste gas from the waste combustion device is used as a heat source medium of the air heater. A drying apparatus for thermally decomposing an organic chlorine compound contained in the waste to remove chlorine, and thermally decomposing the waste dried by the drying apparatus at a low temperature of 450 to 500 ° C. to produce hydrogen chloride from an alkali salt. And a non-volatile residue obtained by pyrolysis with this pyrolysis apparatus, on the downstream side of the pyrolysis apparatus. A device that performs high-temperature combustion by itself and melts ash in the residue into molten slag,
A gas combustion device for burning exhaust gas from the thermal decomposition device, wherein a combustion gas from the gas combustion device is used as a heat source medium for the air heater. 3. The heating air obtained by the air heater is
The waste pyrolysis apparatus according to claim 1 or 2, wherein the apparatus is used for indirect heating of the pyrolysis apparatus, and the exhaust gas is used as a heat source of the drying apparatus. 4. A gas recovered by the air heater and the waste heat steam generator is supplied as a heat source medium of the drying device, and an exhaust gas from the drying device is blown into a high temperature portion at an outlet of the pyrolysis device. The waste thermal decomposition treatment apparatus according to claim 1 or 2, wherein: