JP2786598B2 - Air heater for white smoke prevention - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air heating apparatus for preventing white smoke in a refuse incineration facility for incinerating refuse such as general waste and industrial waste.

[0002]

[Prior Art] With the enforcement of the "Guidelines for Prevention of Dioxin Generation", exhaust gas treatment facilities at refuse incineration facilities
The previous electric dust collector system was changed to the bag filter system, and the temperature of the exhaust gas introduced into the exhaust gas treatment equipment was reduced due to restrictions such as the heat-resistant temperature of the filter cloth.
The temperature dropped significantly from about 00 ° C to 170 to 200 ° C.

[0003] Therefore, in the time zone and season when the outside air temperature decreases, the moisture contained in the exhaust gas turns into white smoke and the surrounding residents are bought. Therefore, in the case of refuse incineration facilities, especially in the case of the water jet cooling type, , White smoke prevention equipment became indispensable.

FIG. 5 shows an example of a schematic flow relating to exhaust gas and air in a water injection cooling type waste incineration plant including a conventional white smoke prevention device.

First, a description will be given along the flow of exhaust gas indicated by a thick line.

In FIG. 5, an exhaust gas b of 800 to 950 ° C. generated by combustion of waste in an incinerator a.
₁ is a water injection nozzle group c ₁ in the gas cooling device c.
It becomes high-humidity exhaust gas b ₂ cooled to around 400 ° C. by water spray from the air, and then, a combustion air preheater d ₁ , a hot water air preheater d ₂ , and white smoke prevention air which constitute the remaining heat utilization equipment It flows into the heater e. The white smoke preventing air heater e is composed of air heater alone e ₁ to e ₄ of the plurality groups (four in the illustrated example).

Here, the exhaust gas b ₂ is subjected to heat exchange in the combustion air preheater d ₁ and the hot water air preheater d ₂ , as will be described later, and the temperature of the exhaust gas b ₃ dropped to 330 to 350 ° C.
Becomes

[0008] Subsequently, the exhaust gas b ₃ is passing through the air heater e for preventing white smoke, further 170 to 200 gas b ₄ becomes that is reduced in temperature to ° C., it is introduced into the bag filter f, 150 to 180 ℃ in clean gas b ₅ next to medium temperature and humidity relative humidity of 40% weak, to reach is sucked into induced draft fan g by mixing flue h.

Next, a description will be given along the flow of air shown by a thin solid line. Combustion air d ₁₁ is sucked at a normal temperature from the top of a garbage pit (not shown) by a push-in blower d ₁₂ , and the combustion air preheater d ₁ in the temperature is raised, conditioned combustion air d ₁₄ next to the required temperature in the bypass regulating damper d _13,
It is sent into the furnace from below the incinerator a.

[0010] The air d ₂₁ which is heated by the hot water air preheater d ₂ is fed by hot water blower d _22, and circulates between the hot air preheater d ₂ and hot water generator d ₂₃ Then, the temperature of the hot water in the hot water storage tank (not shown) is raised.

Further, an air blower e for preventing white smoke (hereinafter, for convenience, some members are referred to as white smoke prevention).
_The cold white air e ₁₂ sucked by ₁₁ and having a very low humidity at room temperature is heated by the white smoke prevention air heater e to 15
0 ℃ sent to white proof temperature air e ₁₃ and becomes a mixed flue h before and after the intermediate temperature Mu wet, mixed with clean gas b ₅ of the above intermediate temperature humid, relative humidity 15 is a state in which white smoke is not generated ~ 17%
And discharged into the atmosphere from a chimney (not shown).

FIG. 6 is a schematic side view showing a structure around a conventional gas cooling device.

[0013] In FIG. 6, the gas cooler c disposed on top of the incinerator a, exhaust gas b ₁ containing from below, is deprived of latent heat by the water spray from the water jet nozzle c _1, cooled exhaust gas b _2, and the is configured to discharge from above.

The structure is such that a heat insulating material c _{3 is provided} inside the outer plate c _2.
After affixed, to construct a desired shape by heat and water material c _4, through the constructs from the outside of the outer plate c ₂ constituted of the above heat insulator c ₃ and the heat-water material c _4, a high pressure (not shown) A plurality of water injection nozzle groups c each having a water source and a water injection amount control valve
₁ is a free-standing structure provided.

[0015] Here, since the properties of the refuse carried into the refuse incineration facility vary widely, the incineration situation changes every moment, and the exhaust gas b ₁ generated even if each control function is activated.
Temperature and amount cannot be constant.

On the basis of the fluctuation of the exhaust gas b _1, the fluctuation of the amount of heat absorbed by the combustion air preheater d ₁ for controlling the combustion state is determined.
To temporally heat load changes in the heated air preheater d ₂ is added to increase or decrease, the temperature and amount of gas exhaust b _2, b ₃ continues the variation is always.

[0017] However, from the relationship of heat resistance and performance of removing bag filter f, since the amount of gas exhaust b ₄ is also varied, the inlet gas temperature of the bag filter f is that needs to be constant, ShiroboAtsushi air the amount of e ₁₃ or is adapted to the adjustment of the water injection amount of the gas cooler c.

The surface temperature of each of the air preheaters d ₁ and d ₂ constituting the residual heat utilization equipment and each of the heat transfer tubes in the white smoke prevention air heater e is determined by the acid temperature contained in the exhaust gas b _{1 to} b _4. In order to prevent low-temperature corrosion due to substances, it is designed to maintain a low-temperature corrosion limit temperature of 150 ° C. or higher.

However, the fluctuations in the exhaust gas temperature and the decrease in the inlet temperature of the exhaust gas treatment equipment described above sometimes cause unfavorable conditions exceeding the assumptions at the time of the initial design, and the low temperature of each equipment after the gas cooling equipment. Damage such as corrosion often occurs.

[0020]

[SUMMARY OF THE INVENTION However, in the inlet portion of the right white Bohiya air e ₁₂ of the air heater alone e ₁ of the first corresponds shown at the bottom of Figure 7, the downstream side of the exhaust gas b ₃ The heat transfer tubes (see the crosses in Fig. 7) tend to be particularly susceptible to corrosion, and especially in the semi-continuous furnace and the mechanized batch furnace where the operation is stopped at night, the winter season is remarkable, and white smoke pollution occurs. However, the repair cost increases.

This is mainly caused by low-temperature corrosion caused by the above-mentioned temperature fluctuation, and it is a general measure to make the entrance of the heat transfer tube where corrosion easily occurs has a double tube structure in advance.

[0022] In the case of the double pipe structure, although higher corrosion rate to extend the overlap of the tube decreases, addition to decreasing the effective heat transfer area, airflow resistance of exhaust gas b ₃ through the double pipe portion In addition to the increased flow, there is a problem that not only a drift occurs but also that the work of removing adhered dust cannot be sufficiently performed, and the heat exchange efficiency is reduced.

The outer plate c of the gas cooling device c shown in FIG.
_TwoIs corroded and the skin c_TwoInsulation material c inscribed in_Three
The phenomenon of collapse has frequently occurred. This is a water injection nozzle
Group c ₁From the exhaust gas b₁Substances contained in
Condensed in a dissolved state, and heat and water resistant material c_FourOccurred in
Leached from cracks and skin c_TwoCorrodes the insulation c_ThreeTo
In order to change the quality, stop operation for repair and repair cost
Is increasing.

[0024]

The air heating apparatus for preventing white smoke according to the first aspect of the present invention is provided in a water jet cooling type incinerator for incinerating refuse such as general waste and industrial waste. A range in which low-temperature corrosion does not occur in an exhaust gas heating type white smoke prevention air heating device that prevents white smoke generated due to moisture contained in exhaust gas discharged from the water injection cooling type waste incinerator. At least one air heater among the air heater group whose exhaust gas temperature has been adjusted is separately disposed at the inlet side of the residual heat utilization equipment, and the remaining air heater is provided between the residual heat utilization equipment and the bag filter. Arranged in between,
A front air heater disposed on the inlet side and a rear air heater disposed between the residual heat utilization equipment and the bag filter are communicated via an air passage.

In the air heating apparatus for preventing white smoke according to the second aspect of the present invention, the air supplied to the air heater provided on the inlet side of the residual heat utilization equipment is supplied to the gas cooling chamber. Air heated by cooling the gas cooling chamber from a cooling space surrounding the heat-resistant and water-resistant material forming the side wall is used.

[0026]

In a group of air heaters whose exhaust gas temperature has been adjusted so as not to cause low-temperature corrosion, at least one air heater is disposed at the inlet side of the facility for utilizing residual heat to allow a relatively high temperature exhaust gas to pass therethrough. The remaining air heater is disposed between the waste heat utilization equipment and the bag filter to allow relatively low temperature exhaust gas to flow.
In addition, the air to be heated is directed to the air heated by cooling the side wall of the gas cooling chamber to the air heater arranged on the high temperature side, and then to the air heater arranged on the low temperature side. After being introduced and heated, it is mixed with exhaust gas containing a large amount of water to prevent white smoke.

[0027]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a schematic flow relating to exhaust gas and air in a water injection cooling type waste incineration plant equipped with a white smoke prevention air heating device according to the present invention.

In FIG. 1, reference numeral 1 denotes a refuse incinerator for incinerating refuse such as general waste and industrial waste, and a gas cooling device 2 similar to the conventional one shown in FIG. Is disposed, and a first air heater 31, which is a front part of the facility for utilizing residual heat and is on the inlet side, is connected by a flue 21.

After the first air heater 31, a combustion air preheater 41 and a hot water air preheater 42, which also constitute the front part of the residual heat utilization equipment, are provided. Certain groups (second, third,
A group of air heaters 32, 33,
34.

Here, the first to fourth air heaters 3
For four units 1 to 34, an air blower 35 for white protection, a connecting air path (air path) 36, and a mixing air path 37 are provided as accessories, and the air heating device 3 for white smoke prevention is configured as a whole. ing.

The push-in blower 411 and the bypass adjusting damper 412 in the combustion air preheater 41, the hot-water blower 421 and the hot-water generator 422 in the hot air preheater 42, and the bag filter 5 and the induction blower 6 are mixed. The configuration of the chimney 7 is the same as the configuration described in the section of the related art, and the details are omitted.

Next, the operation of the white smoke prevention air heating device 3 in the refuse incineration facility configured as described above will be described.

First, a description will be given along the flow of exhaust gas indicated by a thick solid line. Exhaust gas 81 at 800 to 950 ° C. generated by combustion of refuse in refuse incinerator 1 is subjected to a plurality of water injections in gas cooling device 2. The high-humidity exhaust gas 82 is cooled to around 400 ° C. by the high-pressure water sprayed from the nozzle group 22, and reaches the first air heater 31 via the flue 21.

Here, the exhaust gas 82 becomes an exhaust gas 83 whose temperature has been reduced to about 350 ° C. by heat exchange, which will be described later, and then is introduced into the combustion air preheater 41 and the hot water air preheater 42, where it is heated again. After the exchange, the exhaust gas 84 was further cooled to about 300 ° C., and passed through the flue 43 to the second exhaust gas 84.
It enters the third and fourth air heater groups 32, 33, 34.

The exhaust gas 84 is supplied to the second to fourth air heater groups 3
Heat is absorbed by passing through 2, 33 and 34 and 170
Exhaust gas 85 which has been cooled to 200 ° C. is introduced into the bag filter 5 to remove soot and harmful gases, and becomes a moderately humid clean gas 86 having a temperature of 150 to 180 ° C. and a relative humidity of 34 to 40%. The mixture is sucked by the machine 6 and reaches the mixing flue 7.

Next, the flow of air indicated by a thin solid line will be described. The operation of the combustion air 413 and the hot water air 423 is the same as the operation described in the above-described conventional technology, and the description thereof is omitted. Here, the heat exchange of the white smoke prevention air heating device 3 will be described. .

First, the white cool air 91 having a very low humidity at normal temperature, which is sucked by the white blow air blower 35, is heated by the first air heater 31 to become a warm air 92 of about 50 ° C. The road reaches the second to fourth air heater groups 32 to 34 via the path 36, where it becomes a medium-temperature, non-humid, white warm air 93 at about 150 ° C. And this white warm air 93
Is sent to the mixing flue 7 through the mixing air passage 37, and is mixed with the above-mentioned medium-temperature and high-humidity clean gas 86 to produce a clean exhaust gas 87 having a relative humidity of 15 to 17% in which white smoke is not generated.
And is discharged into the atmosphere from a chimney (not shown).

As described above, since the first air heater 31 is separately installed at a relatively high temperature portion on the inlet side of the residual heat utilization equipment, it is possible to maintain the surface temperature of each heat transfer tube at a high temperature, thereby preventing low-temperature corrosion. This can prevent white smoke pollution and increase in repair costs.

Table 1 shows an example of a calculation result of the surface temperature of a portion where there is a risk of low-temperature corrosion among the heat exchanger tubes of the heat exchanger using the white smoke prevention air heating device of the present invention.

[0041]

[Table 1]

As can be seen from Table 1, the first number 2
The downstream side of the inlet of the air heater is 150 to 1 in the conventional example.
What was on the corrosion limit line at 60 ° C was 1 in the case of the present application.
It is 85 ° C or higher, and is in a safe zone in any other part.

FIG. 2 shows, for example, a white smoke prevention curve for exhaust gas at a temperature of 5 ° C. and a humidity of 50%. The range is shown. In the case of the above example,
In FIG. 2, it is located in a white smoke prevention possible range indicated by a circle and no white smoke is generated.

FIG. 3 is a schematic flow diagram showing exhaust gas and air showing another embodiment in a water-injection cooling type waste incineration plant equipped with a white smoke prevention air heating device according to the present invention.
FIG. 4 is a side view showing a schematic structure from the periphery of the gas cooling device to the front part of the residual heat utilization equipment. The same members as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In FIGS. 3 and 4, the gas cooling device 2 disposed at the top of the refuse incinerator 1 forms a cooling space 25 between the gas cooling device 2 and a structural wall 24 surrounded by an outer plate 23 and has a structure. Gas cooling chamber main body 27 constructed of heat and water resistant material 26 inside wall 24 and multiple water injection nozzle groups 2
2 and the flue 21, not only the conventionally used heat insulating material (c ₃ ) is not used, but also the layer thickness of the heat and water resistant material 26 is smaller than that of the conventional method.

As described above, since the heat-resistant and water-resistant material having a smaller thickness than the conventional method is air-cooled without using a heat insulating material, the temperature of the structural wall can be maintained at a high level. Even if coagulated and leached, they evaporate in the cooling space, so that the outer plate and the structural wall do not corrode, and the furnace building cost and repair cost of the gas cooling chamber can be reduced.

Therefore, the white cool air 91 is supplied to the cooling space 25.
Is sent to the lower part of the
While cooling the water resistant material 26, the cooling space 25 is raised to reach the top and reaches the top, and becomes the warm air 192 of 50 ° C. or more, passes through the wind path 136, and enters the first air heater 31. Here, the warm air 192 becomes the warm air 92 heated to 75 ° C. or higher, enters the second to fourth air heater groups 32, 33, and 34, and thereafter, operates as described with reference to FIG.

That is, the surface temperature of the heat transfer tubes of the air heater 31 is further increased by increasing the temperature of the white cool air entering the first air heater 31.

In this embodiment, the gas cooling device 2 is provided at the top of the refuse incinerator 1, but it may be provided on the side of the refuse incinerator 1, Has been described in terms of a four-unit configuration, but any number of division units may be used.

The air preheaters e1 to e4 and the air heater 31 shown in the conventional example and the embodiment are not limited to this type, and the air preheaters e1 to e4 and the air heater 31 are not limited to this type. An in-pipe gas system that allows exhaust gas to pass through may be used.

Further, what constitutes the residual heat utilization equipment is not limited to the combustion air preheater 41 and the hot water air preheater 42. In this embodiment, the combustion air preheater is used as the inlet side of the residual heat utilization equipment. Although the air heater 31 is provided upstream of the air heater 41, the air heater 31 may be provided between the combustion air preheater 41 and the hot water air preheater 42 if the high temperature state can be maintained.

[0052]

As described above, according to the white smoke prevention air heating apparatus according to the first aspect of the present invention, at least one of the air heaters is located at the inlet side of the facility for utilizing residual heat. Separately installed in a relatively high temperature area, it is possible to maintain the surface temperature of each heat transfer tube at a high temperature, prevent white smoke pollution caused by low temperature corrosion and increase repair costs, and make a double pipe structure. This eliminates the necessity and allows the entire heat transfer tube to be used effectively, thereby improving the heat exchange efficiency and facilitating cleaning of attached dust.

Further, according to the white smoke prevention air heating device of the present invention, by cooling the side wall of the gas cooling chamber, the heat and water resistant material can be reduced, and the conventionally used heat insulating material becomes unnecessary. In addition, since the heated air is sent to the air heater, the heat transfer area of the air heater can be reduced due to an increase in the temperature of the incoming air.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a schematic flow relating to exhaust gas and air in a water injection cooling type refuse incineration plant equipped with a white smoke prevention air heating device according to the present invention.

FIG. 2 is a diagram showing a white smoke prevention curve for exhaust gas at a temperature of 5 ° C. and a humidity of 50%.

FIG. 3 is a diagram showing an example of a schematic flow showing another embodiment in a water injection cooling type refuse incineration plant equipped with a white smoke prevention air heating device according to the present invention.

FIG. 4 is a side view showing the schematic structure from the periphery of the gas cooling device to the front part of the residual heat utilization equipment.

FIG. 5 is a diagram showing an example of a schematic flow relating to exhaust gas and air in a water injection cooling type waste incineration facility including a conventional white smoke prevention device.

FIG. 6 is a schematic side view showing a structure around a conventional gas cooling device.

FIG. 7 is a schematic diagram showing a configuration and a corrosion state of a conventional air heater.

[Explanation of symbols]

 2 Gas cooling device 3 Air heater for preventing white smoke 31 First air heater 32 Second air heater 33 Third air heater 34 Fourth air heater 36 Connecting airway (airway)

Claims (2)

(57) [Claims] Claims: 1. A water-jet-cooled refuse incinerator for incinerating refuse such as municipal waste and industrial waste, which is provided by water contained in exhaust gas discharged from the water-jet-cooled refuse incinerator. Air whose exhaust gas temperature has been adjusted so that low-temperature corrosion does not occur.
At least one air heater of the group of heaters is separately disposed at the inlet side of the facility for utilizing residual heat, and the remaining air is disposed.
A heater is provided between the waste heat utilization equipment and the bag filter.
A front air heater arranged on the inlet side,
An air heating device for preventing white smoke, wherein the air heating device disposed between the waste heat utilization equipment and the bag filter is communicated via an air passage. Wherein the air fed into the air heater disposed at the inlet side of the waste heat utilization equipment, structure the side walls of the gas cooling chamber
Gas cooling from the cooling space surrounding the heat and water resistant material to be built
The air heating device for preventing white smoke according to claim 1, wherein air heated by cooling the chamber is used.