JP3016132U - Air heating device with low temperature corrosion protection device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an air heating device equipped with a low temperature corrosion prevention device capable of preventing low temperature corrosion of a heat transfer tube of the air heating device. [Structure] In an air heating device 1 constituted by a plurality of air heaters alone that heats required air by the retained heat of exhaust gas discharged from a refuse incinerator, a part of the air heated by the air heating device 1 is The warm air circulation device 1 returning to the upper air passage 154 located on the exhaust gas downstream side of the air heating device inlet air passage 15
8 is provided, and the warm air circulation device 18 includes a discharge air passage 183 communicated with the upper air passage 154 and an outlet air passage 1 provided in the air heater unit 14 on the exhaust gas upstream side of the air heating device 1.
7, the suction side air passage 181 and the circulation blower 182.
The inlet air passage 15 is divided into at least two upper and lower air passages 154 and 153 by the partition plate 152.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an air heating device for a refuse incineration facility that incinerates waste such as general waste and industrial waste, and particularly to an air heating device equipped with a low temperature corrosion prevention device.

[0002]

[Prior art]

 Exhaust gas boilers and water heaters as well as exhaust gas heating type air heating devices have been used in waste incineration facilities to utilize the residual heat, but all of these are caused by corrosive gas contained in the exhaust gas. Various measures have been taken to prevent high and low temperature corrosion.

Among them, an air heating apparatus for preventing white smoke (hereinafter abbreviated as “white protection”) in a water jet cooling system is most affected by low temperature corrosion as described below. A description will be given as a representative example in the technology and examples.

Due to the enforcement of the “Guideline for prevention of dioxin generation, etc.,” the exhaust gas treatment equipment of the refuse incineration facility was changed from the previous electrostatic precipitator method to the bag filter method, and accordingly, it was introduced into the exhaust gas treatment equipment. Due to restrictions such as the heat resistant temperature of the filter cloth, the temperature of the exhaust gas drastically dropped from about 300 ° C to 170 to 200 ° C, which is close to 150 ° C, which is the low temperature corrosion upper limit temperature of steel materials.

Therefore, during the time period and season when the outside air temperature decreases, the moisture contained in the exhaust gas turns into white smoke, and in order to buy the inhabitants of the surrounding residents, in the case of a waste incineration facility, especially in the case of water injection cooling type The prevention of white smoke became indispensable.

FIG. 4 shows an example of a schematic flow of exhaust gas and air in a water jet cooling type refuse incineration facility 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. 4, the exhaust gas b ₁ of 800 to 950 ° C. generated by the combustion of dust in the incinerator a is about 400 ° C. in the gas cooling device c due to the water spray from the water injection nozzle group c _1. The exhaust gas b ₂ having a high temperature cooled down to, and then flows into the combustion air preheater d ₁ , the hot water air preheater d ₂ and the white air preventive heater e which constitute the residual heat utilization facility. This white air-proof air heater e is composed of a plurality of (4 in the illustrated example) air heater units e _{1 to} e ₄ .

Here, the exhaust gas b ₂ undergoes heat exchange described later in the combustion air preheater d ₁ and the hot water air preheater d ₂ , and becomes exhaust gas b ₃ whose temperature has dropped to 330 to 350 ° C. It

Subsequently, the exhaust gas b ₃ passes through the white air-proof heater e to become the exhaust gas b ₄ whose temperature is further reduced to 170 to 200 ° C., and is introduced into the bag filter f to 150 to 180 ° C. At a relative humidity of less than 40%, it becomes a clean gas b ₅ of moderate temperature and high humidity, which is sucked by the induction ventilator g and reaches the mixed flue h.

[0011] The explanation will be made along the flow of air indicated by the thin solid line, the combustion air d ₁₁ is the press write blower d _12, is sucked at a normal temperature from garbage pit top (not shown), air preheater for combustion After the temperature is raised at d ₁ , the combustion air d ₁₄ adjusted to the required temperature by the bypass adjustment damper d ₁₃ is introduced into the furnace from below the incinerator a.

[0012] 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 The hot water in the hot water storage tank (not shown).

Further, the white cold-proof air e ₁₂ sucked by the white air-proof air blower e ₁₁ and having a very low humidity at room temperature is heated by the white-proof air heater e and has a medium-temperature and low-humidity white heat of about 150 ° C. The warm air e ₁₃ is sent to the mixing flue h and mixed with the above-mentioned medium-temperature and high-humidity clean gas b ₅ to become clean exhaust gas j having a relative humidity of 15 to 17% in a state where white smoke is not generated. Not emitted from the chimney into the atmosphere.

Here, since the properties of the waste that is carried into the waste incineration facility vary widely, the incineration situation changes from moment to moment, and even if each regulation function is activated, the temperature of the exhaust gas b ₁ generated And the amount cannot be constant.

In addition to the fluctuation of the exhaust gas b _1, the fluctuation of the absorbed heat amount of the combustion air preheater d ₁ for adjusting the combustion condition and the change of the heat load of the hot water air preheater d ₂ with time increase and decrease. In order to add, the temperature and gas amount of the exhaust gases b ₂ and b ₃ always keep changing.

However, due to the heat resistance and removal performance of the bag filter f, even if the gas amount of the exhaust gas b ₄ changes, the inlet gas temperature of the bag filter f needs to be constant, so that white warm air cannot be removed. The amount of e ₁₃ or the water injection amount of the gas cooling device c is adjusted.

Further, the surface temperatures of the air preheaters d ₁ and d ₂ constituting the residual heat utilization equipment and the heat transfer tubes in the white air-proof air heater e are the acidic substances contained in the exhaust gases b _{1 to} b _4. In order to prevent the low temperature corrosion due to the above, it is designed to maintain the low temperature corrosion limit temperature of 150 ° C or higher.

However, the fluctuations in the exhaust gas temperature and the decrease in the exhaust gas treatment equipment inlet temperature described above sometimes cause adverse conditions that exceed the assumptions at the time of initial design, and the low temperature is applied to each equipment after the gas cooling equipment. It often causes damage such as corrosion.

[0019]

[Problems to be solved by the device]

However, at the inlet of the white cold-proof air e ₁₂ on the right side of the _first air heater unit e ₁ shown at the bottom of FIG. 5, at the heat transfer tube (marked with x in FIG. 5) downstream of the exhaust gas b ₃ . (See the section) is especially prone to corrosion, especially in the semi-continuous furnaces that stop operation at night, mechanized batch furnaces, etc., which occur remarkably in the winter season, resulting in white smoke pollution and repairs. The cost will increase.

This is mainly due to the low temperature corrosion caused by the above-mentioned temperature fluctuation, and the corrosion-prone corrosion heat transfer tube has a double tube structure in advance, and the double tube is extended as the corrosion progresses. It is common to take measures.

In the case of this double pipe structure, although the corroded portion can be moved by extending the overlapped portion of the pipe, there is a problem that the effective heat transfer area is reduced and the heat exchange efficiency is reduced, which is a fundamental measure. Was not.

[0022]

[Means for Solving the Problems]

 The air heating device equipped with the low-temperature corrosion prevention device of the present invention is installed in a refuse incinerator that incinerates waste such as general waste and industrial waste, and the heat of the exhaust gas discharged from the refuse incinerator is used to retain the heat. In an air heating device composed of a plurality of air heaters alone for heating required air, a part of the air heated by the air heating device is partially exhausted downstream of the inlet air passage of the first stage air heater. A warm air circulation device for returning to a portion located on the side is provided, and the warm air circulation device is connected to a portion located on the exhaust gas downstream side of the inlet air passage of the first stage air heater alone and connected to the discharge side air passage. , A suction side air passage that communicates with the outlet air passage provided at the outlet of the air heating device, and a circulation blower, and the inlet air passage is divided into upper and lower air passages by a partition plate. It is divided into at least two, and the discharge side air passage is connected to the upper air passage. It is those that have been.

[0023]

[Action]

 A part of the air heated by the air heating device is returned to the split air passage located on the exhaust gas downstream side of the inlet air passage of the first stage air heating device by the hot air circulation device, and the air temperature in the air passage is increased. By making the temperature rise, the surface temperature of the heat transfer tube through which the heated air flows is maintained at a temperature higher than the low temperature corrosion limit.

[0024]

【Example】

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

FIG. 1 is a perspective view showing a schematic structure of a first stage and an inlet air passage of a white air protective heating device equipped with a low temperature corrosion prevention device according to the present invention, and FIG. FIG. 3 is a schematic structural diagram of the vicinity of a heating device.

In FIG. 2, reference numeral 1 denotes a white air-proof heating device, which includes a plurality of (four in the illustrated example) air heater single units 11 to 14, a group of inlet air passages 15, and air passages of a plurality of air heaters. It is composed of ducts 161, 162, 163 interconnecting each other, an outlet air passage 17, a warm air circulation device 18, and a white air passage 19.

The individual air heaters 11 to 14 described above are heat exchangers having substantially the same structure for heating the white protective air 2 by the heat retained by the exhaust gas, and are the most commonly used horizontal heat exchangers below. The first-stage air heater unit 11 of the multi-tube type external gas system will be described as a representative.

As shown in FIG. 1, the first-stage air heater unit 11 has a plurality of heat transfer tubes 113 arranged in parallel between the inlet side and outlet side end plates 111-112 of the white air barrier 2. The upper and lower surfaces are open, the front surface is surrounded by a front casing 115 having a plurality of (four in the illustrated example) inspection windows 114, and the back surface is surrounded by a windowless rear casing 116.

The inside of the plurality of heat transfer tubes 113 is a passage for the white air-proof air 2 that flows from right to left in FIG. 1, is surrounded by the end plates 111 and 112 and the casings 115 and 116, and is provided outside the plurality of heat transfer tubes 113. The formed space serves as a passage for the inlet exhaust gas 31 which flows upward from below.

The inlet air passage 15 for feeding the room temperature air 21 sucked by the white-proof air blower 151 into the first-stage air heater unit 11 is arranged horizontally in front of the first-stage air heater unit 11. The divided partition plate 152 divides the lower air passage 153 and the upper air passage 154 into two parts, that is, an upper air passage 154 and a discharge air passage 183 described below.

As shown in FIG. 2, a suction side air passage 181 is connected in the middle of the outlet air passage 17, and a suction side air passage 181 and a circulation blower 182 and a discharge side air passage 183 are provided. The air circulation device 18 circulates a circulation warm air 27 which is a part of the white warm air 26 to be described later.

Next, the flow of the method for preventing low temperature corrosion of the air heating device thus configured will be described with reference to FIG.

In the present invention, the configuration and function of each device from an incinerator (not shown) to the hot water air preheater via the combustion air preheater and the devices and components after the bag filter device will be described in the related art. Since it is the same as that shown in FIG. 4, description thereof will be omitted.

First, explaining along the flow of the exhaust gas 3 indicated by the thick arrow, the inlet exhaust gas 31 whose temperature is lowered to 330 to 350 ° C. by the warm water air preheater 4 must pass through the white air preventive heating device 1. As a result, the temperature of the exhaust gas 32 is further reduced to 170 to 200 ° C., and is introduced into the bag filter device 5. Here, at 150 to 180 ° C., the relative humidity becomes a little less than 40% relative humidity, and the clean gas 33 becomes a medium temperature and high humidity, and is sucked by the induced draft fan 6 and reaches the mixed flue 7.

Next, the flow of the white protective air 2 shown by the thin arrow will be described.

First, the room-temperature air 21 sucked by the white air-proof air blower 151 and having a low relative humidity at room temperature is divided into two by the partition plate 152, and the inside of the lower air passage 153 remains at room temperature. The normal temperature air 21 flowing into the lower half of the heat transfer tube 113 group of 11 is mixed with the circulating hot air 27 described later to become the temperature-raised air 22 of 60 to 70 ° C. It flows into the upper half of the heat pipe group 113.

The warm air 23 heated to about 90 to 100 ° C. by the first-stage air heater single body 11 is heated while passing from the second-stage air heater single body 12 to the fourth-stage air heater single body 14. To become warm air 24 and 25, and finally to warm white air 26 with moderate temperature and low humidity of about 150 ° C.

Here, a part (usually about 20%) of the white warm air 26 is branched from the suction side air passage 181 to form the circulation warm air 27, and the circulation blower 182 passes through the discharge side air passage 183. And the circulating warm air 27 are mixed with each other to form the heated air 22.

On the other hand, the remaining white warm air 28 of the white warm air 26 is sent to the mixed flue 7 through the white wind passage 19 and mixed with the above-mentioned medium-temperature and high-humidity clean gas 33 to generate white smoke. The dehumidified gas 34 with a relative humidity of 15 to 17%, which is a state where it does not occur, is released into the atmosphere from a chimney (not shown).

As described above, by feeding the temperature-raising air 22 by the warm air circulation device 18 above the inlet of the first-stage air heater single body 11, the portion of the heat transfer tube 113 where the tube wall temperature is easily lowered (FIG. It is possible to prevent low-temperature corrosion in the section marked with 5), and to prevent white smoke pollution and increase in repair costs due to low-temperature corrosion.

Table 1 shows the surface of the representative portion of the heat transfer tube 113 on the air inlet side of the single-stage first-stage air heater 11 which has a risk of low temperature corrosion in the white air-proof heating apparatus 1 of the present invention described above. An example of the temperature calculation result is shown, and FIG. 3 shows the portion where the heat transfer tube surface temperature was calculated.

[0042]

[Table 1]

As can be seen from Table 1, the heat transfer tube surface (tube wall) temperature of the exhaust gas most downstream side (P4) at the air inlet portion of the first stage air heater shown by number 4 is 145 to 155 ° C. in the conventional example. However, in the case of the present application, it was found that the room temperature air was raised to 40 ° C. by the circulating hot air, and as a result, it was within the safe range.

Note that, in this example, the white air-proof air heating device of the water injection cooling type is shown as a representative example, but it may be applied to the boiler cooling type, and the combustion air preheater or the hot water air preheating device may be used. It is also applicable to vessels.

Further, although the white multi-tube air heater is exemplified by the horizontal multi-tube type extra-gas type, the vertical multi-tube type or the intra-gas type may be used, and the number of constituents is not limited.

Although the inlet air passage is shown divided into two, it may be divided into three or more depending on the temperature conditions.

[0047]

As described above, according to the present invention, a part of the air heated by the air heating device is supplied to the exhaust gas downstream side of the inlet air passage of the first stage air heating device by the warm air circulation device. By returning to the divided air passages located, the air temperature in the air passages is raised, and from this, the surface temperature of the heat transfer tube through which the heated air flows can be maintained at a temperature higher than the low temperature corrosion limit. It is possible to prevent white smoke pollution and increase in repair costs due to the above, and it is not necessary to use a double tube structure for the heat transfer tube, and the entire heat transfer tube can be effectively used, improving heat exchange efficiency.

[Submission date] March 14, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

[0047]

[Effect of device]

As described above, according to the present invention, a part of the air heated by the air heating device is divided by the warm air circulation device into the split air located on the exhaust gas downstream side of the inlet air passage of the first stage air heating device. by returning to the road, raised the temperature of the air at road該風, can this more該昇temperature air to maintain the surface temperature of the heat transfer tube to flow from the low-temperature corrosion limit to a high temperature, due to the low temperature corrosion It is possible to prevent pollution of white smoke and increase repair costs, and it is not necessary to use a double heat transfer tube structure, and the entire heat transfer tube can be used effectively, improving heat exchange efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a first stage air heater and an inlet air passage of an air heating device equipped with a low temperature corrosion prevention device according to the present invention.

FIG. 2 is a schematic configuration diagram showing the periphery of an air heating device equipped with a low temperature corrosion prevention device according to the present invention.

FIG. 3 is a schematic diagram showing a portion where a heat transfer tube surface temperature is calculated.

FIG. 4 is a diagram showing an example of a schematic flow relating to exhaust gas and air in a water-injection-type refuse incineration facility including a conventional white smoke prevention device.

FIG. 5 is a schematic view showing a configuration and a corrosion state of a conventional air heating device.

[Explanation of symbols]

 1 White-proof air heating device (air heating device) 11 First stage air heater alone 113 Heat transfer tube 15 Inlet air passage 152 Partition plate 153 Lower air passage 154 Upper air passage 17 Outlet air passage 18 Warm air circulation device 181 Intake side wind Road 182 Circulation blower 183 Discharge side air passage 21 Room temperature air 27 Circulating warm air 31 Inlet exhaust gas

Claims (1)

[Scope of utility model registration request] 1. A plurality of air heaters alone, which are provided in a refuse incinerator for incinerating refuse such as general waste and industrial waste, and which heats required air by the heat of exhaust gas discharged from the refuse incinerator. In the air heating device configured as described above, a warm air circulation device is provided that returns a part of the air heated by the air heating device to a portion located on the exhaust gas downstream side of the inlet air passage of the first stage air heater alone. The warm air circulation device includes a discharge side air passage that communicates with a portion of the first stage air heater that is located on the exhaust gas downstream side of the inlet air passage, and an outlet air passage that is provided at the outlet of the air heating device. And a circulation blower, and the inlet air passage is divided into at least two upper and lower air passages by a partition plate.
An air heating device equipped with a low-temperature corrosion prevention device, characterized in that the discharge-side air passage communicates with an upper air passage.