JPH11230517A - Combustion treatment apparatus for waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly enhance the generation efficiency of the power generation for waste utilizing a waste heat recovery boiler by allowing a higher temperature and a higher pressure of superheat stream without causing a problem of corrosion attributed to a hydrogen chloride gas in a combustion treatment apparatus for waste. SOLUTION: In a combustion treatment apparatus of waste which is provided with a combustion furnace A of waste, a first heat recovery device 8 to recover heat of a combustion exhaust gas G from the combustion furnace A, a second heat recovery device 10 comprising a waste heat boiler for recovering the heat of the combustion exhaust gas G from the first heat recovery device 8, a third heat recovery device 16 to heat steam S generated in the second heat recovery device 10 by heat recovered with the first heat recovery device 8 and an exhaust gas treatment device for cleaning the combustion exhaust gas G from the second heat recovery device 10, the first heat recovery device 8 is built as a sand heating chamber in which the combustion exhaust gas G is kept in contact with sand C for a heat medium to heat the sand C while the third heat recovery device 16 is built as a steam superheater to heat a superheater pipe 18 of the steam S generated in the second heat recovery device 10 by the heat of the sand C from the first heat recovery device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for the combustion treatment of waste such as municipal solid waste. By improving a heat recovery system for combustion exhaust gas from a combustion device, the present invention relates to a steam superheater tube. The present invention relates to a novel waste combustion treatment apparatus that can increase the temperature and pressure of steam for power generation without causing high-temperature corrosion, and can greatly improve power generation efficiency.

[0002]

2. Description of the Related Art Conventionally, in an apparatus for combusting waste such as municipal solid waste, a combustion exhaust gas G from a combustion furnace A is guided to a boiler K to generate steam S as shown in FIG. The so-called refuse power generation system, in which heat energy is further recovered by an economizer J, the steam S is heated by a superheater L, and the superheated steam S 'is supplied to a steam turbine generator to generate power, is widely used. (JP-A-5-256427, JP-A-5-256428 and the like).

[0003] In the power generation by the steam turbine generator, the higher the temperature and pressure of the superheated steam S 'guided to the steam turbine generator, the higher the power generation efficiency can be obtained. Increasing the temperature and pressure is also an important issue from the viewpoint of effectively utilizing the unused energy of waste. That is, the superheater L that generates the superheated steam S 'for power generation is disposed as close to the exit of the combustion chamber A' of the combustion furnace A as possible, and the steam S is heated by the high-temperature combustion exhaust gas G, and It is desirable to use high temperature and high pressure superheated steam S '.

[0004] However, in the flue gas G from the combustion chamber A 'of the combustion furnace A, hydrogen chloride gas (usually hydrogen chloride gas produced by the combustion of organic chlorine compounds mainly composed of vinyl chloride contained in wastes) is contained. About 600 to 1000 ppm) and sulfur oxides (SOx, usually 60 to 100 ppm, converted to 12% O ₂ ), and exhibit severe corrosiveness at high temperatures.

FIG. 2 shows a corrosion diagram of the flue gas G containing the hydrogen chloride gas. As is clear from FIG. 2, the so-called high-temperature corrosion is corrosion caused by the presence of iron chloride or alkali iron sulfate, and the temperature is 320 ° C.
It is known that it gradually progresses when the temperature exceeds 650 ° C. and peaks at 650 ° C. In other words, between 320 ° C and 480 ° C,
Corrosion occurs due to the formation of iron chloride or alkali iron sulfate, and between 460 ° C and 700 ° C, corrosion occurs due to decomposition of the generated iron chloride or alkali iron sulfate.

That is, when the tube wall temperature exceeds about 300 ° C., the superheater tube of the superheater L and the heat transfer surface of each part of the waste heat boiler K are rapidly corroded due to the progress of the high temperature corrosion. In order to avoid such high-temperature corrosion, the operating pressure and operating temperature of the waste heat boiler, particularly the superheater L,
Each had to be 30 kg / cm ² G and 300 ° C. or less. As a result, it is desirable to increase the steam temperature and pressure in order to improve the efficiency of waste power generation, but in the prior art, it was not possible to increase the temperature and pressure of steam for the reasons described above.

As a measure for preventing the occurrence of the high-temperature corrosion, a method of removing hydrogen chloride gas in the flue gas G in advance and introducing the flue gas G excluding the hydrogen chloride gas into the superheater L is considered. Can be However, the flue gas G discharged from the refuse-burning furnace A, for example, the stoker-type refuse-burning furnace,
Has a high temperature of 850 ° C. to 950 ° C., and is charged with a hydrogen chloride gas absorbing reactant (eg, slaked lime, quicklime, calcium carbonate, sodium carbonate, etc.) and brought into sufficient contact with the hydrogen chloride gas. Even so, calcium chloride or sodium chloride generated from a chemical equilibrium relationship reacts with steam to generate hydrogen chloride again, so that the concentration of hydrogen chloride gas cannot be reduced after all.

[0008]

SUMMARY OF THE INVENTION According to the present invention, the pressure and temperature of the superheated steam for power generation are reduced to about 3 due to the above-mentioned problem in the conventional waste combustion treatment apparatus, that is, the occurrence of so-called high-temperature corrosion.
It is intended to solve the problem that the power generation efficiency cannot be further improved because it is suppressed to 0 kg / cm ² G · 300 ° C. or less, and the superheater is isolated by isolating the superheater tube from the corrosive environment. It is an object of the present invention to provide a waste combustion treatment apparatus capable of preventing pipe corrosion and significantly improving power generation efficiency in waste power generation.

[0009]

In order to further increase the power generation efficiency in waste power generation, it is necessary to increase the pressure and temperature of the superheated steam for power generation to 30 kg / cm ² G · 250 ° C. or more. It is necessary to keep the vessel under less corrosive conditions. On the other hand, in order to maintain the superheater tube under conditions of low corrosion, it is necessary to remove hydrogen chloride gas in the high temperature combustion exhaust gas introduced into the superheater in advance. It is practically impossible to remove hydrogen gas economically with an absorbent. Therefore, the inventors of the present application conceived of indirect heating of the superheater tube by the high-temperature combustion exhaust gas, and repeatedly performed a superheated steam generation test using various heat media and heat recovery devices.

The present invention has been made based on the results of an indirect heating test of the superheater tube with high-temperature combustion exhaust gas. The invention of claim 1 is directed to a waste-burning furnace and a waste-burning furnace. A first heat recovery device that recovers the heat of the combustion exhaust gas of
A second heat recovery device comprising a waste heat boiler for recovering heat of the combustion exhaust gas from the first heat recovery device, and a second heat recovery device for heating the steam generated in the second heat recovery device by the heat recovered in the first heat recovery device. Three heat recovery device, in a waste combustion treatment device provided with an exhaust gas treatment device for purifying the combustion exhaust gas from the second heat recovery device, wherein the first heat recovery device and the combustion exhaust gas and sand for the heat medium And a sand heating chamber for heating the sand by contacting the third heat recovery device with the heat of the sand from the first heat recovery device to heat the superheater tube of the steam generated in the second heat recovery device. A basic configuration of the present invention is to use a steam superheater.

According to a second aspect of the present invention, in the first aspect of the present invention, the waste combustion furnace is a stoker furnace, and the third heat recovery device is operated by the fluidized gas supplied by the circulation blower. The basic configuration of the present invention is a fluidized bed superheater for flowing sand from the apparatus.

According to a third aspect of the present invention, in the first aspect of the present invention, the waste combustion furnace is a stoker furnace and the first heat recovery device is a third heat removal device that removes fly ash and the like by a sieving device. A basic configuration of the present invention is to provide a heat recovery device configured to circulate and supply sand from the recovery device as a heat medium.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the sand for the heat medium has a particle size of 1 to 3.
The use of 2 mm sand is the basic configuration of the present invention.

According to a fifth aspect of the present invention, in the second aspect, the fluidizing gas is air or nitrogen, and the fluidizing gas from the fluidized bed superheater is circulated through the cyclone.
The basic structure of the present invention is to provide an economizer for heating condensate of a steam turbine in a circulation circuit of air or nitrogen.

As shown in FIG. 1, the flue gas G having a high temperature of 850 ° C. to 950 ° C. discharged from the combustion chamber of the waste combustion furnace A passes through the flue gas passage 22 to form the first heat recovery device 8. It is introduced into the lower part of the sand heating chamber 8 of the mold.
Also, sand C for the heat medium is sprayed from above the device,
By bringing the sand C and the flue gas G into direct contact, the sand can be efficiently heated.

The particle size of the sand C is suitably 1 to 2 mm, and the sand C is brought into countercurrent contact with the combustion exhaust gas G from the waste combustion furnace A in the space falling from the top. Heat C. The amount of the sand C to be sprayed is adjusted so that the temperature of the heated sand C becomes 650 ° C. or higher.

Sand is a heat medium excellent in heat resistance and corrosion resistance, and the combustion exhaust gas G from the waste combustion furnace A is 850.
Even at a high temperature of 950 ° C. and a gas in a severe atmosphere containing a high concentration of hydrogen chloride gas of 0.1 to 3%,
There is no need to use special sand.
It can sufficiently withstand use in a state of being in direct contact with the combustion exhaust gas G. The amount of hydrogen chloride adsorbed on the high-temperature sand thus obtained is very small. Therefore, by operating the sand C as a heat transport medium, it is possible to obtain an extremely clean secondary energy source. it can.

The flue gas G discharged from the first heat recovery device 8 is introduced into a waste heat boiler provided as the second heat recovery device 10. Then, the water is heated and evaporated by the heat of the combustion exhaust gas G to generate saturated steam.

The sand heated by the first heat recovery device 8 is supplied to a fluidized bed superheater provided as a third heat recovery device 16 and is heated by a heat through a superheater tube 18 installed in the fluidized bed portion. heating the saturated steam S generated in the second heat recovery unit 10, to produce superheated steam S _1.

As the fluidizing gas E of the third heat recovery unit 16, air or nitrogen is used, which is circulated through the cyclone 19. An economizer 21 can be provided in the circulation circuit of the fluidizing gas E, whereby the condensed water or the drain from the steam turbine is heated to recover heat, and at the same time, the circulated gas can be cooled.

In the third heat recovery device 16, high-temperature sand having a particle diameter of 1 to 2 mm supplied from the first heat recovery device 8 is used as a fluid medium, and the sand C flows slowly. Of fluidized gas E is supplied. At the same time, fly ash H of 0.1 to 0.3 mm is separately supplied and fluidized in order to smoothly transfer heat to the superheater tube 18. Further, fly ash H and sand C of 0.1 to 0.3 mm scattered from the third heat recovery device 16 are collected by the cyclone 19 and circulated and supplied to a lower portion of the third heat recovery device 16. The fly ash H having a diameter of 0.1 to 0.3 mm may be dust collected in a flue gas treatment device, a waste heat boiler 10 or the like, or fly ash H or sand C separated by a sieving device 20 described later.
Is used.

The fluidized sand C from the third heat recovery device 16 is mixed with the fly ash H and discharged from the lower part of the fluidized bed, and then separated by a sieving device 20 such as a wind filter or a vibrating sieve. After removing the fly ash H and the like, only the sand C having a particle size of 1 to 2 mm is returned to the first heat recovery device 8.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flow sheet of a waste combustion treatment apparatus according to an embodiment of the present invention, in which a so-called stoker furnace is used as a waste combustion furnace A. In FIG. 1, 1 is a waste pit, 2 is a waste hopper, 3 is a drying stoker, 4 is a burning stoker, 5 is a post-burning stoker, 6 is a primary combustion chamber of a waste combustion furnace A, and 7 is a secondary combustion. Chamber 8, a sand heating chamber forming a first heat recovery device, 9 a sand hopper, 10 a waste heat boiler forming a second heat recovery device, 11 an air preheater, 12 a rapid cooling tower, 13 a combustion A bag filter which forms the main body of the exhaust gas treatment device, 14 is an induction blower, 15 is a chimney, 16 is a fluidized bed superheater which forms a third heat recovery device, 17 is a circulating air blower, 18 is a superheater tube, and 19 is a cyclone , 20 is a sieving apparatus, 21 is an economizer, A is a waste combustion furnace (stoker furnace), B
Is waste, C is sand, D is combustion residue, G is flue gas, E
The fluidizing gas (air), H is the fly ash particle size 0.1 to 0.3 mm, S is the saturated vapor, S ₁ is superheated steam.

The waste B is stored in the waste pit 1 and is put into the refuse hopper 2 by a crane (not shown) or the like, and is placed on the drying stoker 3 of the waste combustion furnace A via a pusher (not shown). It is sequentially supplied to. Also,
The waste B supplied to the drying stoker 3 is completely burned in the course of being sequentially sent to the combustion stoker 4 and the post-burning stoker 5, and the combustion residue D is discharged into a slag cooling tank (not shown).

Since the waste combustion furnace (stoker furnace) A itself is known, a detailed description thereof is omitted here. Further, in the embodiment of FIG.
Although a stoker furnace is used as a stoker furnace, it is a matter of course that a waste combustion furnace having another configuration, such as a fluidized bed combustion furnace, may be used instead of the stoker furnace.

A sand heating chamber 8 forming the first heat recovery device 8 is disposed adjacent to the secondary combustion chamber 7 of the stoker furnace A, and has a vertical cylindrical shape having a bottom formed in an inverted pyramid shape. The upper space forms a countercurrent contact portion between the sand C and the combustion exhaust gas G as described later.

A sand hopper 9 is provided above the sand heating chamber 8, and sand C having a particle diameter of 1 to 2 mm returned from the third heat recovery unit 16 through the sand disperser 9a flows from the ceiling surface. Spreads downward uniformly. Further, an inflow port 8a of the high-temperature combustion exhaust gas G is provided below the side wall of the sand heating chamber 8 on the side of the secondary combustion chamber 7, and an outflow port of the combustion exhaust gas G is provided above the side wall opposite to the inflow port 8a. 8b are formed respectively.

Approximately 850 ° -9 ° drawn out through the exhaust gas passage 22 from above the secondary combustion chamber 7 of the waste combustion furnace A
The high-temperature combustion exhaust gas G having a temperature of 50 ° C. flows down along the passage 22 and then reverses below it, and flows into the sand heating chamber 8 from the inlet 8 a. The combustion exhaust gas G that has flowed into the sand heating chamber 8 gives heat energy to the sand C by flowing in the sand heating chamber 8 upward while flowing in contact with the falling sand C, This is heated to a temperature above about 650 ° C.

The amount of the sand C to be sprayed from the sand sprayer 9a into the sand heating chamber 8 depends on the temperature of the sand C as described above.
The temperature is adjusted to be 50 ° C. or higher. As mentioned above,
The amount of hydrogen chloride gas and the like in the combustion exhaust gas G adsorbed on the sand C as the heat medium is extremely small and can be almost ignored.

A waste heat boiler 10 forming the second heat recovery unit 10 is provided adjacent to and downstream of the sand heating chamber 8, and the combustion exhaust gas discharged from the first heat recovery unit 8 is provided. The heat retained in G ₁ is recovered to generate saturated steam S. That is, the combustion exhaust gas G ₁ discharged from the first heat recovery unit 8 is still holds the temperature of 350 to 450 ° C., is introduced into the waste heat boiler of the second heat recovery unit 10, the saturation where Generates steam. Further, the combustion exhaust gas G ₂ discharged from the second heat recovery device 10 is supplied to the air preheater 11.
After being recovered by the heat treatment, it is processed by an exhaust gas treatment device including a rapid cooling tower 12 and a bag filter 13, and then discharged to the atmosphere through an induced blower 14 and a chimney 15.

The fluidized bed superheater forming the third heat recovery unit 16 is of a so-called fluidized bed type, and air (or nitrogen) is supplied as a fluidizing gas E from below the fluidized bed by a circulation blower 17. As a result, the third heat recovery device 16
Is formed a fluidized bed portion composed of the sand C and the fluidizing gas E. Further, a superheater tube 18 is provided in the fluidized bed portion of the third heat recovery device 16 to heat the saturated steam S generated in the second heat recovery device 10 so as to generate a superheat for power generation. Steam (temperature 400 ° C, pressure 40kg / cm ²
G) to generate the S _1.

The fluidized bed portion of the third heat recovery device 16 is
Sand C heated in the first heat recovery device 8 is supplied. That is, the high temperature flue gas G in the first heat recovery device 8
The sand C for a heat medium heated to a temperature of 650 ° C. or higher is discharged by gravity from the lower part of the first heat recovery device 8 and flows into the fluidized bed portion of the third heat recovery device 16 through the sand discharge pipe 23. Supplied.

The fluidizing gas E supplied from below the third heat recovery unit 16 has a high temperature of about 450 to 650 ° C. and is discharged from above, and accompanying the cyclone 19. Fly ash and sand having a particle size of 0.1 to 0.3 mm are separated and removed. Thereafter, the fluidized gas E is cooled to about 450 ° C. or less by, for example, heating the condensate of the steam after driving the steam turbine in the economizer 21, and the fluidized gas E is circulated by the circulating air blower 17. Part is returned below. The supply amount of the fluidizing gas E supplied to the third heat recovery device 16 is such that the sand C for the heat medium having a particle size of 1 to 2 mm supplied as the fluidized heat medium slightly moves in the fluidized bed portion. The supply is sufficient.

Further, the fly ash H of 0.1 to 0.3 mm is separately supplied to the fluidized bed portion of the third heat recovery device 16 so that the sand C flowing from the fluid ash H can be supplied from the fly ash H. The heat transfer to the superheater tube 18 is performed smoothly. The fly ash H having a particle size of 0.1 to 0.3 mm is used.
For example, dust ash collected by the waste heat boiler 10 or the combustion exhaust gas treatment device is used. In addition, the third heat recovery device 16
The particle diameter discharged together with the fluidizing gas E from 0.1 to 0.1.
The fly ash H and sand C of 3 mm are collected by the cyclone 19 and returned to the fluidized bed through the pipe 25.

On the other hand, the sand C cooled by applying heat to the saturated steam S via the steam superheater tube 18 in the third heat recovery device 16 is taken out from below the third heat recovery device 16. Sieving device 20 such as a wind screen sorter or a vibrating sieve
Then, the fly ash and the like are sieved and returned to the sand hopper 9 through the sand supply pipe 24.

[0036]

According to the present invention, a high-temperature flue gas generated in a waste incinerator is used as a first heat recovery unit (sand heating chamber).
To make hot sand by contact heat exchange between the combustion exhaust gas and the sand that is the heat medium.
The circulating air is supplied to a third heat recovery device (fluidized bed superheater) using fluidized gas, and the saturated steam is heated through a superheater tube installed in the fluidized bed to obtain superheated steam. For this reason, the superheater tube does not come into direct contact with the combustion exhaust gas containing corrosive gas such as hydrogen chloride gas or sulfur oxide generated in the waste combustion furnace, and the clean atmosphere is completely isolated from the corrosive atmosphere. Since it is operated inside, it is completely free from so-called high-temperature corrosion. As a result, in the conventional so-called waste power generation, the operating condition of the superheated steam is 300 ° C./30 kg / c in order to avoid corrosion of the superheater tube and the like.
Although m ² G was the limit, according to the present invention, 50 m
A superheated steam of 0 ° C. × 100 kg / cm ² G can be obtained, and as a result, the power generation effect in waste power generation can be increased from about 10 to 15% of the conventional to about 30 to 35%. . As described above, the present invention can remarkably increase the heat recovery efficiency due to waste combustion by enhancing the power generation effect of waste power generation, and has excellent practical utility.

[Brief description of the drawings]

FIG. 1 is an overall system diagram of a waste combustion treatment apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a pipe wall temperature and a corrosion rate of a combustion exhaust gas containing hydrogen chloride gas.

FIG. 3 is a schematic explanatory view of a conventional waste combustion treatment apparatus.

[Brief description of reference numerals]

A is a waste combustion furnace (stoker furnace), B is waste, C is sand, D is combustion residue, E is fluidized gas (air), G is combustion exhaust gas, and H is particle size 0.1 to 0.1. 3 mm fly ash, S is saturated steam, S ₁ is superheated steam, 1 is waste pit, 2 is waste hopper, 3 is dry stoker, 4 is combustion stoker, 5 is post-burning stoker, 6 is primary combustion chamber, 7 Is a secondary combustion chamber, 8 is a first heat recovery unit (sand heating chamber), 8a is a flue gas inlet,
8b is a flue gas outlet, 9 is a sand hopper, 9a is a sand disperser, 10 is a second heat recovery unit (waste heat boiler), 11 is an air preheater, 12 is a rapid cooling tower, 13 is a bag filter, 14
Is an induction blower, 15 is a chimney, 16 is a third heat recovery device (fluidized bed superheater), 17 is a circulating air blower, 18 is a heat transfer tube, 19 is a cyclone, 20 is a sieving device, 21 is an economizer, 22 is Flue gas passage, 23 is a sand supply pipe,
24 is a sand supply pipe, 25 is a pipeline.

Claims (5)

[Claims] 1. A combustion furnace for waste, a first heat recovery device for recovering heat of flue gas from the combustion furnace, and a waste heat boiler for recovering heat of flue gas from the first heat recovery device. A second heat recovery device, a third heat recovery device for heating steam generated in the second heat recovery device with heat recovered in the first heat recovery device, and an exhaust gas for purifying combustion exhaust gas from the second heat recovery device In the waste combustion treatment device provided with a treatment device, the first heat recovery device is a sand heating chamber for heating sand by contacting combustion exhaust gas with sand for a heat medium, and the third heat recovery device. A waste combustion treatment device, wherein the recovery device is a steam superheater that heats a superheater tube of steam generated in the second heat recovery device by heat of sand from the first heat recovery device. 2. The waste combustion furnace is a stoker furnace, and the third heat recovery device is a fluidized bed superheater for flowing sand from the first heat recovery device by fluidizing gas supplied by a circulation blower. Item 2. A waste combustion treatment apparatus according to Item 1. 3. The waste combustion furnace is a stoker furnace, and the first heat recovery device is circulated and supplied as sand as a heat medium from the third heat recovery device from which fly ash and the like are removed by a sieving device. The waste combustion treatment device according to claim 1, which is a heat recovery device. 4. The waste combustion treatment apparatus according to claim 1, wherein the heat medium sand is sand having a particle size of 1 to 2 mm. 5. The fluidizing gas is air or nitrogen, the fluidizing gas from the fluidized bed superheater is circulated through a cyclone, and an air or nitrogen circulation circuit is provided with an economizer for heating the condensate of the steam turbine. The waste combustion treatment device according to claim 2, wherein the waste combustion treatment device is configured.