JP2557648Y2 - Heat exchanger - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger which is installed in a combustion device and heats air with high-temperature combustion exhaust gas, for example, a heat exchanger which is installed in an incinerator for incinerating municipal solid waste.

[0002]

2. Description of the Related Art The amount of waste such as municipal waste, various industrial wastes, and sludge has been increasing year by year, and the disposal thereof has become a major social problem in recent years. Most of the waste containing combustibles has been incinerated by incinerators. This is because incineration is the most sanitary, and the volume of waste is reduced, making final disposal easier than other methods.

[0003] In this incinerator, a heat exchanger is installed at the outlet of the combustion furnace to heat the air and cool the combustion exhaust gas in order to effectively use the energy of the high-temperature combustion exhaust gas. . The air is used for combustion and heating of waste, etc., so that air flows through the inside of a heat transfer tube as a heat transfer material provided in a large number in a flow path of a combustion exhaust gas of a heat exchanger so that heat is exchanged. It has become.

[0004] By-products such as municipal waste include various things such as papers, kitchen waste, plastics such as vinyl chloride, rubber leather, and metals. Therefore, the flue gas contains corrosive components such as high concentrations of dust and hydrogen chloride (HCl) and sulfur oxides (SOx) and organic acids which are not so high in concentration. When this high-temperature combustion exhaust gas comes into direct contact with the heat transfer tube, corrosive components in the exhaust gas severely corrode the heat transfer tube,
In addition, the dust that is melted at a high temperature adheres to the heat transfer tube to further promote corrosion.

Therefore, in order to prevent the heat transfer tube from coming into direct contact with the combustion exhaust gas and to suppress rapid progress of corrosion, a ceramic layer having good heat conductivity is applied to the surface of the heat transfer tube on the combustion exhaust gas to a predetermined thickness. Thus, instead of the heat transfer tube, the ceramic layer is in direct contact with the combustion exhaust gas.

[0006]

However, since the ceramic layer is porous, the combustion exhaust gas gradually enters the inside of the ceramic layer from the surface thereof and eventually comes into contact with the heat transfer tube. It was difficult to completely shut off the heat transfer tubes from the flue gas.

Specifically, the combustion exhaust gas containing a corrosive component such as hydrogen chloride contacts the surface of the heat transfer tube through the inside of the ceramic layer, and the temperature of the surface of the heat transfer tube at this time is 300 to 350 ° C. or more. In such a case, it is known that so-called high-temperature gas corrosion occurs and corrosion of the heat transfer tube rapidly progresses.

Therefore, in order to protect the heat transfer tube from high-temperature gas corrosion, the upper limit of the outlet air temperature of the air heated by the heat exchanger is from 250 to 300 ° C. Was previously impossible.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is possible to prevent the heat transfer material from being corroded, and to exchange a larger amount of heat than before to heat the air to a high temperature. It is intended to provide an exchanger.

[0010]

The heat exchanger according to the present invention comprises an exhaust gas passage through which high-temperature and low-pressure combustion exhaust gas containing corrosive components and dust flows, and an air through which relatively low-temperature and high-pressure air flows from the combustion exhaust gas. In the heat exchanger that separates the passage with the heat transfer wall and transfers heat from the combustion exhaust gas to the air, the heat transfer wall has one surface in contact with the air and a plurality of heat transfer walls arranged at predetermined positions. A heat transfer material having a through-hole and a porous material attached to the other surface of the heat transfer material and in contact with the combustion exhaust gas.

[0011]

In the present invention, since the pressure of the air is higher than the pressure of the flue gas, the high-pressure air flows into the through-hole of the heat transfer material in contact with the air, and then flows into the porous material. Penetrate. The air travels in the direction of the exhaust gas while diffusing through the cavity inside the porous material, and finally reaches the surface of the porous material and is mixed with the combustion exhaust gas.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. Fig. 4 shows the installation of the heat exchanger according to the present invention, municipal waste, various industrial wastes, shredder dust,
It is a block diagram which shows the process of the incineration apparatus for incinerating wastes, such as sludge. In this process, waste is incinerated using a combustion melting furnace.

The waste B such as municipal solid waste is subjected to various processes such as receiving, crushing, storing, mixing, etc. by a receiving pre-processing facility (not shown), and then supplied to an input hopper. It is sent to the combustion melting furnace 1 in the process and is burned at a high furnace temperature.

The combustion exhaust gas 3 is discharged from the combustion melting furnace 1, and the molten ash 4 melted in the melting furnace 1 is discharged out of the system from the furnace bottom and collected as reusable molten slag.

A heat exchanger 5 according to the present embodiment is attached to an exhaust gas outlet of the combustion melting furnace 1. This heat exchanger 5
Is an exhaust gas flowing at a high temperature and low pressure (gas inlet temperature T ₁ = about 800 to 1500 ° C., gas inlet pressure P ₁ = about −10 to −490 mmH ₂ O) containing corrosive components such as hydrogen chloride and dust. The passage 6 and the flue gas 3 have a relatively low temperature and high pressure (air inlet temperature T ₃ = about 0 to 300).
° C, air inlet pressure P ₃ = about +100 to +1000 mmH ₂
O) The air passage 8 through which the air 7 flows is partitioned by a heat transfer wall to transfer heat from the combustion exhaust gas 3 to the air 7.

The heat exchanger 5 allows the temperature T ₂ (about 500)
Combustion exhaust gas 3a after cooling to
Is further recovered by the waste heat boiler 9 and then sent to an exhaust gas treatment step 10 equipped with a suction blower. The exhaust gas treatment step 10 collects dust, removes harmful substances, and prevents various treatments such as white smoke prevention. Is discharged from the chimney 11 into the atmosphere.

The temperature T discharged from the combustion air blower 12
_3. The air 7 at a pressure P ₃ is heated by the heat exchanger 5 and the air outlet temperature T ₄ = about 300 to 600 ° C.
The high-temperature air 13 having an air outlet pressure P _{4 of} about +50 to +950 mmH ₂ O flows into the combustion melting furnace 1 and is used as combustion air.

Next, the heat exchanger 5 according to the first embodiment of the present invention will be described in more detail. As shown in FIGS. 5 and 6, an exhaust gas passage 6 having a rectangular cross section is provided at the center of the heat exchanger 5.
An air passage 8 partitioned by a heat transfer wall 17 is provided around the exhaust gas passage 6.

The heat transfer wall 17 has one surface (that is, the outer peripheral surface 2).
5) is in contact with air 7 and has a plurality of through holes 26 (see FIGS. 1 to 3 described later) arranged at predetermined positions, and a heat transfer plate 27 as a heat transfer material having good thermal conductivity. A porous ceramic layer 29 as a porous material that is attached to the entire other surface (that is, the inner peripheral surface 28) of the heat transfer plate 27 and that comes into contact with the combustion exhaust gas 3 is provided. By fixing the ceramic layer 29 to the inner peripheral surface 28 of the heat transfer plate 27,
The heat transfer plate 27 does not directly contact the high-temperature combustion exhaust gas 3 having a corrosive component, thereby preventing rapid progress of corrosion.

The air passage 8 is formed by a heat transfer plate 27 and an outer wall plate 30 provided outside the heat transfer plate 27 at a predetermined interval. The air passage 8
The lower end 31 of the air passage 8 communicates with a lower air chamber 32 for making the pressure of the supplied air 7 uniform and flowing the air uniformly throughout the air passage 8, while the upper end 33 of the air passage 8
Is connected to an upper air chamber 34 for uniformizing the pressure of the high-temperature air 13 obtained by heat exchange and uniformly discharging air from the entire air passage 8.

As the ceramic layer 29, it is preferable to apply a castable material having good thermal conductivity, for example, silicon carbide (SiC) to the entire inner peripheral surface 28 of the heat transfer plate 27 to a thickness of 10 to 50 mm.

FIG. 7 shows the structure of a conventional heat exchanger in which a through hole is not formed in the heat transfer plate 27. In this case, the combustion exhaust gas 3 having a corrosive component such as hydrogen chloride gradually enters the inside of the porous ceramic layer 29 as shown by an arrow C, and comes into contact with the inner peripheral surface 28 of the heat transfer plate 27. The heat transfer plate 27 is corroded. Therefore, in order to prevent the occurrence of the above-mentioned high-temperature gas corrosion, the surface temperature of the heat transfer plate 27 is set to 30 degrees.
It must be between 0 and less than 350 ° C.

Further, in the case of the present process having a combustion melting step, the temperature T ₁ of the combustion exhaust gas 3 sent from the combustion melting furnace 1 instead of the incinerator to the heat exchanger 5 is, for example, 800 Very high temperature, such as ~ 1500 ° C. Since this temperature T ₁ may be higher than the melting temperature (about 1000 ° C.) of the dust contained in the combustion exhaust gas 3, the dust itself is also melted in the exhaust gas, and this dust is deposited on the surface of the ceramic layer 29. And adheres to the surface. When the dust 35 adheres in this manner, potassium (K), calcium (Ca), sodium (Na), etc. contained in the dust 35 become alkali salts or sulfides, so-called precipitation corrosion in which the heat exchanger 5 is corroded. And the heat transfer efficiency is significantly reduced.

On the other hand, in this embodiment,
As shown in FIGS. 1 to 3, the heat transfer plate 27 in contact with the air 7
Are provided with a plurality of through holes 26, and the through holes 26 are arranged at predetermined positions. When the air 7 flowing in the air passage 8 partitioned by the heat transfer wall 17 is compared with the flue gas 3 flowing in the flue gas passage 6, the air 7 has a relatively higher pressure than the flue gas 3. The inside air 7 penetrates into the ceramic layer 29 through the through hole 26 by using the pressure difference as a driving force. Next, the air 7 travels in the direction of the exhaust gas passage 6 while diffusing in a conical shape in the cavity in the ceramic layer 29 as shown by the arrow D, and eventually flows out into the exhaust gas passage 6. As described above, since the air flows in the ceramic layer 29, the flue gas 3 does not enter the ceramic layer 29 and flow in the direction of the heat transfer plate 27 (the direction of arrow C in FIG. 7). The heat transfer plate 27 is not corroded by corrosive components contained in the combustion exhaust gas 3.

In this embodiment, since the dust 35 as shown in FIG. 7 does not adhere to the surface of the ceramic layer 29 and the surface is always kept in a clean state, precipitation corrosion occurs. And there is no fear that the heat transfer efficiency is reduced. Specifically, conventionally, the heat transfer plate 2
The ceramic layer 7 and the ceramic layer 29 are considered consumables and are replaced every two or three years. According to this embodiment, however, the heat exchanger 5 and the ceramic layer 29 can be sufficiently used for ten years or more.
Life can be greatly improved.

The preferred temperature and pressure conditions for the heat exchanger 5 in this embodiment are summarized as follows. Inlet flue gas temperature T ₁ : 800 to 1500 ° C. Inlet flue gas pressure P ₁ : −10 to −490 mmH ₂ O Outlet flue gas temperature T ₂ : 500 to 1300 ° C. Outlet flue gas pressure P ₂ : −20 to -500 mmH ₂ O ・ Inlet air temperature T ₃ : 0 to 300 ° C. ・ Inlet air pressure P ₃ : +100 to +1000 mm H ₂ O ・ Outlet air temperature T ₄ : 300 to 600 ° C. ・ Outlet air pressure P ₄ : +50 to +950 mm H ₂ O As described above, according to the present embodiment, conventionally, 250 to 300
The outlet air temperature T ₄ at which the upper limit was 300 ° C.
The temperature can be significantly increased, such as 0 ° C., and the energy of the combustion exhaust gas can be used effectively.

FIG. 3 is an elevational view showing the arrangement of a plurality of through holes 26 formed in the heat transfer plate 27. Each through hole 26 having a diameter d has a predetermined pitch e in the vertical and horizontal directions. , F. The hole diameter d and the pitches e and f are numerical values determined by various conditions of the ceramic layer 29 and the following conditions, and a preferred embodiment is shown below. Material and porosity of ceramic layer 29: SiC refractory (Ratio of SiC (% by weight; 5 to 80%)) Thickness l of ceramic layer 29: 5 to 100 [mm] Air passage 8 and exhaust gas passage 6 Pressure difference: 10 to 1000 mmH ₂ O. Component and concentration of harmful substances in combustion exhaust gas: One or both gases of SOx and HCl are contained, and the concentration is as follows, for example. SOx; 10 to 1000 ppm HCl; 10 to 5000 ppm System temperature distribution: As shown as the above temperatures T _{1 to} T ₄ . -Hole diameter d: 1 to 50 [mm]-Vertical pitch e: 10 to 500 [mm]-Horizontal pitch f: 10 to 500 [mm]

In FIG. 1, the amount of heat Q ₁ moving from the combustion exhaust gas 3 to the air 7 via the heat transfer wall 17 is expressed by the following equation.

On the other hand, as shown by the arrow D, the heat quantity Q ₂ returned by the air diffusing in the direction of the exhaust gas passage 6 is expressed by the following equation. Here, the air flow rate G diffused through the ceramic layer 29
Since very few, it is easy to suppress the rate of heat Q ₂ to which is returned to the movement quantity of heat Q ₁ to 5% or less.

8 and 9 are views showing a heat exchanger 5a according to a second embodiment of the present invention. FIG. 8 is a transverse sectional view corresponding to FIG. 6, and FIG. 9 is a partially enlarged sectional view of FIG. . The vertical sectional structure of FIG. 8 is the same as that of FIG. As shown, in this embodiment, a tubular heat transfer tube 41 is used as a heat transfer material whose one surface (the inner surface 40) comes into contact with air. Further, a ceramic layer 43 as a porous material is fixed to the other surface (outer surface 42) of the heat transfer tube 41. A large number of the heat transfer tubes 41 are juxtaposed in the vertical direction around the heat exchanger 5 a, and the heat transfer tubes 41 are connected and fixed to each other by a connection plate 44. Each heat transfer tube 4
A plurality of through-holes 45 and 46 are formed at predetermined positions in the first through-hole 1, and air flowing through the inside 8 of the heat transfer tube 41 is
5 and 46, and flows in the direction of the exhaust gas passage 6 in the ceramic layer 43.

In the present embodiment, the anchor 47 is fixed to the heat transfer tube 41 by welding, so that the ceramic layer 43 is firmly fixed to the heat transfer tube 41. Conventionally, the anchor 47 was covered with the castable 48 because the through-holes 45 and 46 were not formed and the anchor 47 was corroded severely by the combustion exhaust gas. Is the ceramic layer 43
The anchor 47 does not corrode because it flows inside, and therefore, the castable 48 may be omitted.

In each of the above embodiments, the heat exchangers 5, 5
Although the case where the combustion air 7 of the combustion melting furnace 1 is heated by a is shown, the air heated by the heat exchanger is not limited to this. For example, the heating air of the pyrolysis drum or other air may be used. Is also good.

Further, the heat transfer material having the through-hole is formed by the first heat transfer material.
Although a plate material as in the embodiment may be used, a mesh-like plate material or the like may be used as long as it has an opening equivalent to a through hole. The same reference numerals in the drawings indicate the same or corresponding parts.

[0034]

[Effects of the Invention] Since the present invention is configured as described above, corrosion of the heat transfer material can be prevented, and the life of the heat transfer material can be greatly extended. Also, since the heat transfer material does not corrode even when heated, the air can be heated to a high temperature by exchanging a larger amount of heat than in the prior art, and the energy efficiency of the entire apparatus can be improved.

[Brief description of the drawings]

FIGS. 1 to 7 are views for explaining a first embodiment of the present invention, and FIG. 1 is a partially enlarged sectional view of a heat exchanger according to the present invention; This shows a case where a hole is drilled.

FIG. 2 is a cross-sectional view taken along line II-II of FIG.

FIG. 3 is an elevation view showing a part of the heat transfer plate of FIG. 1;

FIG. 4 is a block diagram showing a process of the incinerator equipped with the heat exchanger according to the present invention.

FIG. 5 is a longitudinal sectional view of the heat exchanger according to the present invention.

FIG. 6 is a transverse sectional view taken along the line VI-VI in FIG. 5;

7 is a partially enlarged cross-sectional view of the heat exchanger, showing a case of a conventional apparatus in which a through hole is not formed in a heat transfer plate, and is a diagram corresponding to FIG.

8 and 9 are views showing a heat exchanger according to a second embodiment of the present invention, and FIG. 8 is a cross-sectional view corresponding to FIG.

9 is a partially enlarged sectional view of FIG.

[Description of Signs] 3 Combustion exhaust gas 5,5a Heat exchanger 6 Exhaust gas passage 7 Air 8 Air passage 17 Heat transfer wall 25 Outer surface (one surface) 26 Through hole 27 Heat transfer plate (heat transfer material) 28 Inner surface (Other surface) 29, 43 Ceramic layer (porous material) 40 Inner surface (one surface) 41 Heat transfer tube (heat transfer material) 42 Outer surface (other surface)

Claims (1)

(57) [Scope of request for utility model registration] An exhaust gas passage through which a high-temperature and low-pressure combustion exhaust gas containing a corrosive component and dust flows, and an air passage through which a relatively low-temperature and high-pressure air flows relative to the combustion exhaust gas. A heat transfer material having a plurality of through-holes arranged at predetermined positions while having one surface in contact with the air; and And a porous material attached to the other surface of the heat exchanger and contacting the combustion exhaust gas.