JP2003183677A - Waste treating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste treating system with which reformed gas from a gas reforming apparatus can surely be cooled by a boiler and corrosion in tubes of the boiler is prevented. <P>SOLUTION: This waste treating system is equipped with a thermal decomposition apparatus 4 for heating waste 1 to form pyrolysis gas, a gas reforming apparatus 5 for reforming the pyrolysis gas from the thermal decomposition apparatus 4 and the boiler 10 for cooling the reformed gas from the gas reforming apparatus 5. The boiler 10 comprises a smoke tube boiler hardly to cause corrosion of tubes. Consequently, the corrosion of the tubes in the boiler is prevented and safe operation can be carried out. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste treatment system for reducing the volume of waste, and particularly after reforming pyrolysis gas generated at the time of pyrolysis of waste at a high temperature. , A waste treatment system that can be cooled.

[0002]

2. Description of the Related Art Conventionally, a waste treatment system for reducing the volume of waste by thermal decomposition or the like has been known.

This waste treatment system crushes wastes and other wastes collected from households and business establishments, and thermally decomposes the crushed wastes to reduce their volume and render them harmless. Is intended.

The pyrolysis gas generated when the waste is pyrolyzed is burned at a high temperature by blowing a large amount of air, and a water tube type boiler is used to cool the gas generated at that time. ing.

When the steam generated from the boiler is used to operate the steam turbine to generate electric power, it is necessary to set the steam pressure of the boiler to high temperature and high pressure in order to obtain a large heat drop at the steam turpin. In this case, it is essential to adopt a water tube type boiler having a structure that can withstand high temperature and high pressure. However, when the boiler is operated in a steam setting of high temperature and high pressure, the temperature of the boiler tube enters the high temperature corrosion area, so the boiler tube is significantly corroded, which may lead to a serious boiler disaster such as a hole in the tube. is there.

On the other hand, the pyrolysis gas is not burned in an air-rich state but partially burned in a reducing atmosphere to create a high temperature gas atmosphere, and the pyrolysis gas may be reformed to generate reformed gas. It is considered. The reformed gas is then washed and used as a fuel gas, and the combustion gas is used to operate a gas engine, a gas turbine, a fuel cell and the like to generate electricity.

[0007]

As described above, in the waste thermal decomposition system, the method of changing the amount of heat of the waste into electricity is to completely decompose the thermal decomposition gas generated by thermally decomposing the waste. A method of burning and recovering the generated heat with a steam turbine and converting it to electricity, and a thermal decomposition gas generated by thermally decomposing waste products is partially combusted to perform gas reforming and cleaning, and as a fuel gas. There is a method of taking out and generating electricity.

[0008] In a system for producing a reformed gas by partially burning a pyrolysis gas obtained by thermally decomposing waste, and then taking out a fuel gas, the reformed gas produced is cooled to a temperature at which a bag filter can withstand. There is a need to.
In this case, even if the reformed gas is cooled too much, there is a problem that the filter cloth of the bag filter gets wet because dew condensation of condensed components of the reformed gas occurs in the bag filter.

Further, in the system for taking out the fuel gas after producing the reformed gas by partially burning the pyrolysis gas obtained by thermally decomposing the waste as described above,
A large amount of dust is contained in the reformed gas, and this dust accumulates in the stagnation part of the reformed gas flow path and adheres to the heat transfer tube of the boiler, increasing pressure loss in the gas system and heat transfer performance. Cause a decrease in the.

Further, it is necessary to control the reformed gas temperature so that the temperature of the reformed gas flowing into the bag filter is lower than the temperature at which the filter cloth is not melted and higher than the temperature at which dew condensation occurs on the filter cloth. There is.

The present invention has been made in consideration of the above points, and is a system for extracting a fuel gas after partially combusting a pyrolysis gas obtained by pyrolyzing a waste to generate a reformed gas. In order to improve the corrosion resistance, it is an object of the present invention to provide a waste treatment system in which a large amount of dust contained in the reformed gas does not adhere to the boiler tube.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a thermal decomposition apparatus for heating waste to generate a thermal decomposition gas, and for reforming the thermal decomposition gas from the thermal decomposition apparatus in a high temperature reducing atmosphere. A gas reforming device for generating gas, and a means for cooling the reformed gas from the gas reforming device, the reforming gas cooling means,
This is a waste treatment system characterized by comprising a smoke tube type boiler.

In the present invention, the boiler has a saturated vapor pressure of 0.5.
The waste treatment system is operated at an operating pressure of up to 1.5 MPa.

The present invention is a waste treatment system characterized in that a boiler has a casing and a large number of tubes arranged in the casing, and a soot blow nozzle for blowing the inside of the tubes is provided near the tubes. is there.

The present invention is characterized in that the casing is provided with a water supply pipe for supplying water into the casing and a steam pipe for discharging steam from the casing, and the steam from the steam pipe flows into the soot blow nozzle. Waste treatment system.

The present invention is the waste treatment system, characterized in that a water supply preheater for preheating the water supplied from the water supply source to the boiler is provided on the downstream side of the boiler.

The present invention is provided with a preheating line for sending water from the water supply source to the boiler via the water supply preheater, and a bypass line for sending water from the water supply source directly to the boiler. These preheating line and bypass line are switched. The waste treatment system is characterized by being switchable by a valve.

The present invention is a waste treatment system characterized in that the boiler comprises a rigid smoke tube type boiler.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 are system configuration diagrams showing an embodiment of a waste treatment system according to the present invention.

As shown in FIG. 1, the waste treatment system is provided with a pyrolysis kiln (pyrolysis device) 4 for producing a pyrolysis gas, which is provided as a heat treatment means for pyrolyzing the waste 1, and the pyrolysis. Gas reforming device 5 for reforming the pyrolysis gas from the device 4 in a high-temperature reducing atmosphere to produce reformed gas
And a rigid smoke tube boiler 10 that cools the reformed gas from the gas reforming apparatus 5, and the water supplied from the water supply source 30 to the smoke tube boiler 10 is preheated using the reformed gas from the boiler 10. The water supply preheater 20 is provided.

A bag filter 9 is provided on the downstream side of the feedwater preheater 20, and a gas cleaning device 6 for cleaning the reformed gas is provided on the downstream side of the bag filter 9. The reformed gas cleaned by the gas cleaning device 6 is recovered as fuel gas in the fuel gas recovery device 6a, and then the fuel gas is sent to the power generation facility 7 and burned for power generation.

In this case, the power generation equipment 7 may be a gas engine, a gas turbine, a fuel cell or the like.

Next, referring to FIG. 2, the smoke tube boiler 10 and the feed water preheater 20 will be described in detail. As shown in FIG. 2, the smoke tube boiler 10 includes a casing 10 a and a casing 1 a.
0a, which has a large number of tubes 13 into which the reformed gas sent from the gas reformer 5 flows. A water supply pipe 11 to which water from a steam drum (not shown) is supplied and a steam pipe 12 from which steam generated in the casing 10a is discharged are connected to the casing 10a.

A plurality of soot blow nozzles 15 for blowing the inside of the tube 13 are arranged in the casing 10a, and the steam discharged from the steam pipe 12 flows into these soot blow nozzles 15.
Furthermore, the casing 10 is provided at the bottom of the casing 10a.
A rotary valve 16 that discharges the dust inside a is provided.

The feed water preheater 20 is a casing 20a.
And a soot blow nozzle 25 for blowing the inside of the casing 20a. A circle feeder 27 and a rotary valve 26 for discharging dust inside the casing 20a are provided below the casing 20a. The soot blow nozzle 25 has a boiler 1
The steam discharged from the steam pipe 12 of 0 flows in.

Further, the casing 20 of the feedwater preheater 20
At a, a preheating line 22 is installed to send water from the water supply source 30 into the casing 20a to preheat it and to send it to the brackish water drum on the smoke tube boiler 10 side. Water supply source 30
The water from the can be sent directly to the brackish water drum of the smoke tube boiler 10 via the bypass line 21 without passing through the feed water preheater 20.
2 is connected via a three-way valve (switching valve) 23.

The casing 20a of the feedwater preheater 20
A discharge pipe 24 for sending the reformed gas to the bag filter 9 is connected to the discharge pipe 24, and a thermometer 28 is attached to the discharge pipe 24. The signal from the thermometer 28 is sent to the control unit 23a,
The controller 23a can drive and control the three-way valve 23 to adjust the amount of water supplied to the bypass line 21 and the preheating line 22.

Next, the operation of this embodiment having such a configuration will be described.

First, as shown in FIG. 1, the waste 1 is thermally decomposed in the thermal decomposition apparatus 4 to generate a thermal decomposition gas. The pyrolysis gas flows into the gas reforming apparatus 5 on the downstream side, and in the gas reforming apparatus 5, the pyrolysis gas partially burns in the reducing atmosphere to reach a high temperature of about 1100 ° C. At this time, the pyrolysis gas decomposes tar and dioxin contained in the pyrolysis gas to be reformed into a reformed gas containing hydrogen and carbon monoxide as combustible components.

A large amount of dust is contained in this reformed gas, and about 90% of the dust component consists of carbon. In order to remove the dust in the reformed gas, the reformed gas passes through the bag filter 9 as described later. In this case, the service temperature of the bag filter 9 is generally 250 ° C. or lower, so the temperature of the reformed gas must be lowered to 250 ° C. or lower. Further, the temperature of the reformed gas is 300 to 5
If the temperature is 00 ° C., the decomposed components of dioxin contained in the gas may be resynthesized to generate dioxin again. For this reason, it is necessary to cool the gas to about 200 ° C. at which dioxin resynthesis is unlikely to occur.

Considering these points, the gas reformer 5
The reformed gas from (1) is sent to the smoke tube type boiler 10, and the temperature of the reformed gas is lowered, and the sensible heat amount of the reformed gas is used as steam for heat recovery. At this time, it is necessary to select the steam generation pressure so that the temperature of the tube 13 in the smoke tube boiler 10 is 150 ° C. to 320 ° C. between the low temperature corrosion region and the high temperature corrosion region.

That is, as shown in FIG. 3, when the tube wall temperature is 150 ° C. or lower, an electrochemical corrosion zone is formed and electrochemical corrosion of the tube 13 made of a carbon copper steel tube progresses to 320 ° C. to 480 ° C. In the case of ℃, corrosion proceeds due to the formation of iron chloride or alkali iron sulfate. 480 ° C
In the above cases, corrosion progresses due to decomposition of iron chloride or alkali iron sulfate, and corrosion in the gas layer progresses.

Therefore, the temperature of the tube 13 is 150 ° C.
It is desirable to set the temperature to 320 ° C.

In the present embodiment, a smoke tube type is adopted as the boiler 10, and a rigid type boiler having excellent maintainability such as dust discharge and tube cleaning is used.

The kinetic pressure of the smoke tube boiler 10 is set so that the saturated vapor pressure in the boiler 10 is 0.5 to 1.5 MPa (gauge pressure).

Further, it is preferable that the saturated vapor pressure is set to 0.8 MPa (gauge pressure) and the tube temperature is set to about 180 to 190 ° C. If the evaporation temperature is set higher and the saturated vapor pressure is set to about 2 MPa, it is safer as a corrosion region, but it is difficult to manufacture an inexpensive smoke tube boiler 10. Also, when the saturated vapor pressure is set to about 2 MPa, the boiling temperature becomes about 200 ° C. or higher,
In order to lower the reformed gas temperature to 200 ° C., the feedwater preheater 20 in the latter stage of the boiler 10 becomes large. However, in this case, the feedwater preheater 20 is forced to be used in the low temperature corrosion region, and therefore a problem arises when the shape becomes large.

During this time, in the smoke tube type boiler 10, dust may adhere to the inside of the tube 13. In this case, the flow path of the tube 13 is narrowed, resulting in a decrease in heat transfer performance and an increase in pressure loss of gas flow. In such a case, the steam is jetted from the soot blow nozzle 15 toward the inner wall surface of the tube 13 on which the dust is attached. The soot blow nozzle 15 is provided at the inlet of the casing 10a, the tube 1
No. 3 is provided at the inlet of the first pass, between the first and second passes of the tube 13, and at the inlet of the second pass of the tube 13.

Since dust is attached to the inside of the tube 13 in the smoke tube type boiler 10, the heat transfer performance is reduced and the pressure loss is increased due to the adhesion of dust as compared with the water tube type boiler in which dust is attached to the outside of the tube 13. Although conceivable, the dust in the tube 13 can be reliably removed with a minimum amount of steam injection.

Further, in the water tube type soot blow (dust blow), since a considerable amount of steam is required to remove the dust adhering to the outside of the tube, such as the stationary rotary type, a pyrolysis kiln, a gas reformer, etc. There is a risk that the pressure in the system will swing to the positive pressure side. When the pressure in the system swings to the positive pressure side, not only is bad gas emitted to the human body, but there is the danger that it will burn when it comes in contact with air.

On the other hand, according to the present invention, the dust inside the tube 13 can be removed with a minimum amount of vapor.

As shown in FIG. 2, the steam injected from the soot blow nozzle 15 is the steam generated in the boiler 10 and discharged from the steam pipe 12.

By the way, when the steam is injected from the soot blow nozzle 15, it is conceivable that the gas system kept at a negative pressure swings to the positive pressure side. Therefore, in the present invention, the pressure inside the thermal decomposition apparatus 4, which is normally controlled at -0.05 kPA, is set to -0.
By drafting at a high pressure of 2 kPa, the system can maintain a negative pressure even if the system internal pressure fluctuates toward the positive pressure side due to steam injection.

Next, the reformed gas from the boiler 10 is sent to the feed water preheater 20 and further cooled to 200 ° C. or lower.
In this feed water preheater 20, the reformed gas discharged from the boiler 10 and the water of 50 to 70 ° C. from the feed water source 30 are heat-exchanged, whereby the reformed gas temperature can be further cooled and the amount of generated steam can be increased. can do. However,
During low load operation where the amount of reformed gas becomes small, or when starting up or shutting down the plant, the reformed gas can be sufficiently cooled down to about 200 ° C. without the need for the feed water preheater 20. The presence of the preheater 20 causes a problem that the reformed gas is too cold. If the reformed gas is too cold, the condensed components in the reformed gas may condense on the bag filter 9 to wet the filter cloth.
If the filter cloth gets wet, dust will not fall from the filter cloth, and there is a risk that the reformed gas flow will be blocked.

Therefore, in this embodiment, a preheating line 22 for sending the feed water to the feed water preheater 20 and a bypass line 21 for bypassing the feed water preheater 20 are provided.
And the branching action to the two lines 21 and 22 is the 3-way valve 2
It is performed by 3.

That is, the inlet temperature of the reformed gas to the bag filter 9 is measured by the thermometer 28, and when this measured value becomes higher than the set value, the opening degree of the three-way valve 23 is controlled.
It is controlled by a so that a large amount of feed water flows in the preheating line 22. Similarly, when the reformed gas temperature becomes low,
The opening degree of the three-way valve 23 is controlled so that a large amount of water is guided to the bypass line 21. The reformed gas temperature at the inlet of the bag filter 9 can be controlled by the above method.

Further, in the feed water preheater 20, steam is injected from the soot blow nozzle 25 into the casing 20a as needed.

After that, the reformed gas from the feed water preheater 20 enters the bag filter 9 to remove dust. The reformed gas from which the dust has been removed is then sent to the gas cleaning equipment 6 for cleaning, and is recovered as fuel gas by the fuel gas recovery device 6a and sent to the power generation equipment 7.

As described above, according to the present embodiment, the reformed gas generated by the gas reforming device 5 can be reliably cooled in the smoke tube boiler 10. In this case, by using as the boiler 10 a smoke tube type boiler that does not easily cause tube corrosion by appropriately selecting the temperature, it is possible to reliably prevent corrosion of the tube 13 and adhesion of dust inside the boiler 10.

[0050]

As described above, according to the present invention, the pyrolysis gas produced by pyrolyzing waste in the pyrolysis device can be reformed in the gas reforming device to generate reformed gas. . After that, the reformed gas is cooled by the smoke tube type boiler, so that it can be surely cooled.
At this time, it is possible to reliably prevent corrosion and dust in the tube of the smoke tube boiler.

[Brief description of drawings]

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

FIG. 2 is a view showing a smoke tube type boiler and a feed water preheater.

FIG. 3 is a diagram showing a relationship between a tube temperature and a corrosion temperature of a carbon copper steel tube.

[Explanation of symbols]

4 Pyrolysis device 5 Gas reformer 6 gas cleaning equipment 7 power generation equipment 10 smoke tube type boiler 10a casing 13 tubes 15 soot blow nozzle 20 Water preheater 20a casing 21 Bypass line 22 Preheating line 23 three-way valve 23a Control unit 28 Thermometer 30 water sources

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F23J 3/02 F23J 3/02 Z 15/06 15/00 K (72) Inventor Toru Ono Yokohama, Kanagawa Prefecture 2-4, Suehiro-cho, Tsurumi-ku, Toshiba Inside Keihin Office, Toshiba Corporation (72) Inventor Hiroshi Matsui 2-4, Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa F-Term (Korean) 3K061 AA07 AB02 BA05 BA07 FA10 RA02 3K065 AA07 AB02 BA05 BA07 JA05 JA18 3K070 DA35 4D004 AA01 AC04 BA03 CA04 CA27 CB09

Claims (7)

[Claims] Claim: What is claimed is: 1. A pyrolysis device that heats waste to generate pyrolysis gas, and a gas reforming device that reforms the pyrolysis gas from the pyrolysis device in a high-temperature reducing atmosphere to produce reformed gas. And a means for cooling the reformed gas from the gas reformer, wherein the reformed gas cooling means comprises a smoke tube type boiler. 2. The boiler has a saturated vapor pressure of 0.5 to 1.5M.
The waste treatment system according to claim 1, wherein the waste treatment system is operated at an operating pressure of Pa. 3. The waste according to claim 1, wherein the boiler has a casing and a large number of tubes arranged in the casing, and a soot blow nozzle for blowing the inside of the tube is provided in the vicinity of the tubes. Processing system. 4. The casing is provided with a water supply pipe for supplying water into the casing and a steam pipe for discharging steam from the casing, and the steam from the steam pipe flows into the soot blow nozzle. Item 3. The waste treatment system according to item 3. 5. The waste treatment system according to claim 1, further comprising a water supply preheater provided downstream of the boiler for preheating water supplied from a water supply source to the boiler. 6. A preheating line for sending water from a water supply source to a boiler via a water supply preheater, and a bypass line for sending water from the water supply source directly to the boiler. These preheating line and bypass line are provided by a switching valve. The waste treatment system according to claim 5, wherein the waste treatment system is switchable. 7. The waste treatment system according to claim 1, wherein the boiler comprises a rigid smoke tube type boiler.