JP2002213735A - Exhaust-gas treatment system and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a stable operation of an exhaust-gas treatment system for a long period of time by precluding the pressure loss in the exhaust gas caused with elapse of time in a heat exchanger and delaying the time of operation shutoff resulting from increase of the pressure loss. SOLUTION: An exhaust gas treatment system is provided with a heat exchanger on an exhaust-gas treatment line for reducing temperature of exhaust gas. A heat transfer element on the heat exchanger 4 is divided plurally, the surface temperature of a part of the divided elements 12A-12C is regulated higher than the surface temperature in the stationary heat transfer state, thereby to dry and peel off a substance adhered to the surface. In this case, order of inflow of heating medium to each element 12A-12C is changed by switching over the valves 14a-14j from order of inflow in the stationary heat temperature state, and the surface temperature of a specific heat-transfer element 12C is made higher than that in the stationary heat-transfer state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment system for removing trace components such as sulfur oxides and soot and dust from exhaust gas discharged from a boiler or the like of a thermal power plant and detoxifying the exhaust gas, and an operating method thereof. It is about.

[0002]

2. Description of the Related Art As one type of an exhaust gas treatment system for detoxifying a large amount of exhaust gas generated from a boiler or the like of a thermal power plant, the exhaust gas is discharged from a boiler 1 as shown in FIG. The exhaust gas that has passed through the air preheater 2 is sent to an electrostatic precipitator 3 to collect dust contained in the exhaust gas, and then the exhaust gas is sent to a heat exchanger 4 for reducing the temperature (for heat recovery). After collecting the heat, the flue gas desulfurization unit 5
Where the exhaust gas is brought into gas-liquid contact with an absorbing solution composed of an aqueous solution in which limestone (CaCO ₃ ) is dissolved or suspended, and the sulfur dioxide gas (SO ₂ ) contained in the exhaust gas is absorbed in the absorbing solution. The exhaust gas is then made harmless, and the exhaust gas is recovered in the heat exchanger 6 for raising the temperature (for reheating). It is widely known that the medium is re-heated by a medium to prevent white smoke and then discharged from the chimney 8 to the atmosphere.

[0003] As another exhaust gas treatment system,
As shown in FIG. 4, a heat exchanger 4 for heat recovery is arranged in front of the electric precipitator 3, discharged from the boiler 1, passed through a denitration device as required, and passed through an air preheater 2. It is also known that the exhaust gas is first recovered by the heat exchanger 4 to lower the temperature and then sent to the electric precipitator 3 to collect the accompanying dust. In the exhaust gas treatment system shown in FIG. 4, the dust removal performance of the electric dust collector 3 depends on the electric resistance of the dust, and the electric resistance of the dust depends on the relative humidity of the exhaust gas. By lowering the temperature of the exhaust gas by the heat exchanger 4 which is disposed before the air preheater 3 and downstream of the air preheater 2, the dust removal performance of the electric precipitator 3 can be improved. The device 3 has an advantage that dust can be collected and removed from the exhaust gas with high efficiency, and SO _{3 in the} exhaust gas can also be removed from the exhaust gas together with the dust while adsorbed on the dust.

[0004]

In the above-mentioned conventional exhaust gas treatment system, the amount of dust in the exhaust gas due to the fuel and operating conditions handled by the combustion equipment such as a boiler, and the temperature condition in the heat exchanger 4 Etc.
In particular, in the heat exchanger 4 for temperature reduction (for heat recovery) in which the flow path of the exhaust gas is narrowed and the exhaust gas temperature is reduced, the dust adheres to the heat transfer element together with the trace components such as moistened SO ₃ and clogs. This is problematic in that the pressure loss of the exhaust gas increases and the load on the desulfurization fan increases. Therefore, in general, these exhaust gas treatment systems are provided with various cleaning devices such as a soot blower and a steel ball spraying device.However, even with these cleaning devices, it is possible to avoid a rise in pressure loss of the exhaust gas that progresses with time. It is not possible, and the operation of the processing system is often stopped due to the increase in the pressure loss, and it becomes necessary to perform cleaning and restoration work in the heat exchanger 4. For this reason, the operation stop of the heat exchanger 4 affects the operation of the subsequent devices, which is one of the causes of lowering the operation rate of the entire processing system, and it is difficult to estimate the stop time in advance. There were also problems in operation management such as difficulty.

[0005] In particular, in the exhaust gas treatment system shown in FIG. 4, although the heat exchanger 4 is installed before the electric precipitator 3, it has the above-mentioned advantages.
Exhaust gas from which soot and the like have not yet been removed will pass through, so that the pressure loss of the exhaust gas due to blockage in the heat exchanger 4 will increase, and inconveniences such as shutting down the processing system due to this will become significant. There was a problem.

[0006] Further, depending on the operating conditions of the boiler 1 side,
Since the pressure loss of the exhaust gas may be further increased, the cleaning device has to be designed to cope with the worst conditions, and there is a problem that the cleaning device is over-equipped.

The present invention has been made to effectively solve the problems of the above-mentioned conventional exhaust gas treatment system, and avoids the pressure loss of the exhaust gas over time in the heat exchanger, thereby reducing the pressure loss. By delaying the resulting operation stop time, stable operation over a long period of time can be realized, and even if a conventional cleaning device is installed, it is not necessary to excessively install the cleaning device excessively. An object of the present invention is to provide an exhaust gas treatment system and an operation method thereof.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, when the pressure loss of the exhaust gas of the heat exchanger rises, the heat transfer element causing the pressure loss rise. The deposits adhere to the heat transfer element via the moisture contained in the exhaust gas, and do not solidify within a few hours. The present inventors have found that it is possible to easily return the powdery substance to the original state by heating, and to peel off the powdery substance, and have accomplished the present invention.

According to a first aspect of the present invention, there is provided an exhaust gas treatment system including a heat exchanger for reducing the temperature of exhaust gas on an exhaust gas treatment line, wherein a heat transfer element of the heat exchanger is divided into a plurality of heat exchangers. A heat transfer element surface temperature control means for adjusting a surface temperature of a part of the plurality of divided heat transfer elements to a temperature higher than a surface temperature in a steady heat transfer state; It is.

In this type of heat exchanger of an exhaust gas treatment system, the heat transfer element having a high temperature surface has less dust (adhering matter) attached to the heat transfer element. Therefore, when the heat transfer element is operated in a steady heat transfer state (normal operation). The inventors have found that dust easily adheres to the surface of the heat transfer element on the low temperature side (downstream in the exhaust gas flow direction). This is because the SO ₃ in the exhaust gas is wetted by the water in the exhaust gas (changes to a mist state) due to the decrease in the temperature, and the wetted SO 3
_{It is considered that when} the trace components (mist form) such as ₃ wet the surface of the heat transfer element, dust easily adheres to the heat transfer element.

Therefore, according to the first aspect of the present invention, when operating in a steady heat transfer state, dust adheres to the surface of some of the heat transfer elements (mainly, the heat transfer element on the low temperature side) and the pressure loss of the exhaust gas is reduced. When the temperature rises, the surface temperature of the heat transfer element is increased in order to remove the attached substance. Then, the substance that has adhered in a wet state to the surface of the heat transfer element in the steady heat transfer state is dried and peeled off by heating. That is, only by changing the surface temperature of the heat transfer element, it is possible to remove the deposits on the heat transfer element of the heat exchanger by the self-cleaning action of the exhaust gas. As a result, it is possible to avoid a rise in pressure loss of the exhaust gas over time in the heat exchanger, and to perform a stable operation for a long time by delaying an operation stop time caused by the rise in the pressure loss. Will be able to In addition, it is preferable to perform the operation | movement which deviated from such normal operation | use (operation | movement for peeling off an adhering matter) at night when operation volume falls. By doing so, the cause of the pressure drop rise can be eliminated by using the surplus capacity at night, and a high level of operation can be performed during normal operation in daytime.

Here, the invention of claim 2 is characterized in that the heat transfer element surface temperature control means comprises means for controlling the temperature of a heat medium (heat absorption medium) flowing into the heat transfer element. It is. The invention of claim 3 is characterized in that the heat transfer element surface temperature control means comprises means for controlling the flow rate of a heat medium (heat absorbing medium) flowing into the heat transfer element.

As a method of increasing the surface temperature of the heat transfer element of the heat exchanger, there are a method of changing the temperature of the heat medium flowing into the heat transfer element and a method of changing the flow rate of the heat medium. . According to the second aspect of the present invention, the surface temperature of the heat transfer element is increased by changing the temperature of the flowing heat medium, that is, by flowing a heat medium having a higher temperature than in the steady operation state. . According to the third aspect of the present invention, the surface of the heat transfer element is changed by changing the flow rate of the inflowing heat medium, that is, by limiting the flow rate of the heat medium (including the inflow stop) as compared with the steady operation state. Try to raise the temperature.

According to a fourth aspect of the present invention, the means for controlling the temperature of the heat medium according to the second aspect includes a pipe for connecting a plurality of divided heat transfer elements in series in an arbitrary order; And a flow path switching means for changing the connection order when connecting in series.

As a method of changing the temperature of the heat medium flowing into the heat transfer element, the invention according to claim 4 changes the order in which the heat transfer elements are connected in series, so that the heat flowing into the corresponding heat transfer element is changed. The medium temperature is changed. That is, when a plurality of heat transfer elements are connected in series, the temperature of the heat medium is low on the upstream side of the flow and high on the downstream side. Therefore, by changing the flow order of the heat medium from the flow order in the steady heat transfer state,
The temperature of the heat carrier flowing into each heat transfer element can be changed. For example, by switching the flow path so that a high-temperature heat medium flows into a heat transfer element into which a low-temperature heat medium has flowed, the surface temperature of a specific heat transfer element can be changed to a steady heat transfer state. The heat transfer element can be dried and peeled off.

According to a fifth aspect of the present invention, in the fourth aspect, the plurality of divided heat transfer elements are arranged in multiple stages in a flow direction of the exhaust gas. The flow passage switching means is controlled so that the heat medium flows from the heat transfer element located on the side to the heat transfer element located on the upstream side, and the heat transfer element is located on the downstream side in the exhaust gas flow direction as the partial heat transfer element. When the surface temperature of the heat transfer element is increased, the heat controlling the flow path switching means so that the heat medium flows from the heat transfer element located on the upstream side in the exhaust gas flow direction toward the heat transfer element located on the downstream side. A medium flow direction switching means is provided.

When the operation is performed with a multi-stage heat transfer element arranged in the flow of the exhaust gas, it is usually set so that the heat medium flows in a direction opposite to the flow direction of the exhaust gas. That is, in the steady heat transfer state, in order to increase the efficiency of heat exchange, the flow path is formed such that the heat medium flows from the heat transfer element located on the downstream side in the exhaust gas flow direction to the heat transfer element located on the upstream side. Control the switching means. As a result, the heat transfer element located on the downstream side in the exhaust gas flow direction has a low temperature, and the heat transfer element located on the upstream side has a high temperature. Here, as described above, it has been found that the adhesion of dust to the heat transfer element is low at a high temperature, but the adhesion of dust to the heat transfer element is high at a low temperature. Therefore, dust will adhere to the downstream heat transfer element having a low temperature. Therefore, when the pressure loss of the heat exchanger increases, the heat medium is set to flow in a direction different from the normal flow direction of the heat medium. That is, the flow path is switched such that the high-temperature heat medium flows through the heat transfer element (the heat transfer element on the downstream side) which is low in the normal operation. By doing so, the substance adhering to the surface of the heat transfer element on the low temperature side (downstream side) in the steady heat transfer state can be dried and separated by heating.

According to a sixth aspect of the present invention, there is provided a method for operating an exhaust gas treatment system, wherein the heat transfer element of the heat exchanger is provided with a heat exchanger for reducing the temperature of exhaust gas on an exhaust gas treatment line. Is divided into a plurality, and by adjusting the surface temperature of some of the divided heat transfer elements to a temperature higher than the surface temperature in the steady heat transfer state, the surface of the heat transfer element It is characterized in that the adhered substance is peeled off. The present invention corresponds to the first aspect of the invention, and produces the same operation as the first aspect of the invention.

According to a seventh aspect of the present invention, in the sixth aspect, the plurality of divided heat transfer elements are arranged in multiple stages in a flow direction of the exhaust gas, and a flow of the heat medium into each heat transfer element is in a steady heat transfer state. In this case, the surface temperature of the specific heat transfer element is higher than the surface temperature in the steady heat transfer state by changing the inflow order. This invention corresponds to the invention of claim 4, and produces the same operation as the invention of claim 4.

According to an eighth aspect of the present invention, in accordance with the sixth aspect, the flow rate of the heat medium into a part of the plurality of divided heat transfer elements is restricted, so that the surface temperature of the heat transfer elements is reduced. Is higher than the surface temperature in the steady heat transfer state. This invention corresponds to the invention of claim 3, and produces the same operation as the invention of claim 3.

[0021]

FIG. 1 shows an essential part of one embodiment of an exhaust gas treatment system according to the present invention. Since the overall configuration of the exhaust gas treatment system is the same as that shown in FIG. 4, only the main parts will be described.

In FIG. 1, reference numeral 4 denotes a heat exchanger for reducing the temperature, and a flue gas desulfurization unit 5 on the exhaust gas treatment line (see FIG. 4).
It is located upstream. The heat exchanger 4 has a plurality of heat transfer elements 12A, 12B, and 12C arranged in multiple stages (three stages in this example) from the upstream side to the downstream side in the exhaust gas flow direction (arrow P direction). ing.

These heat transfer elements 12A, 12B,
A pipe 13 for supplying and discharging the heat medium is connected to 12C. By operating valves (flow path switching means) 14a to 14i, three stages of upper, middle, and lower transmissions are performed via the pipe 13. The heat medium can be passed through the heat elements 12A, 12B, and 12C through a predetermined serial path.

Here, the location of each of the valves 14a to 14i will be briefly described. The first valve 14a is interposed between the heat medium supply port 16 and the inlet of the downstream heat transfer element 12C. Is disposed between the outlet of the downstream heat transfer element 12C and the inlet of the intermediate heat transfer element 12B, and the third valve 14c is connected to the outlet of the intermediate heat transfer element 12B and the inlet of the upstream heat transfer element 12C. The fourth valve 14d is provided between the outlet of the upstream heat transfer element 12A and the heat medium discharge port 17, and the fifth valve 14e is provided between the upstream heat transfer element 1
The sixth valve 14f is interposed between the outlet of 2A and the inlet of the downstream heat transfer element 12C, and the sixth valve 14f is interposed between the heat medium supply port 16 and the inlet of the intermediate heat transfer element 12B. 14g is interposed between the outlet of the upstream heat transfer element 12A and the inlet of the intermediate heat transfer element 12B,
The eighth valve 14h is interposed between the outlet of the intermediate heat transfer element 12B and the heat medium outlet 17, and the ninth valve 1h
4i is interposed between the outlet of the downstream heat transfer element 12C and the heat medium discharge port 17, and the tenth valve 14j is connected between the outlet of the downstream heat transfer element 12C and the inlet of the upstream heat transfer element 12A. It is interposed in.

As a result, at least two routes are provided for the flow of the heat medium from the heat medium supply port 16 to the heat medium discharge port 17 to the heat exchanger 4. That is, one of the two distribution channels is the one shown in FIG.
Is a distribution route in the steady operation mode shown in FIG. In this operation mode, the heat medium is transferred from the downstream heat transfer element 12C to the intermediate heat transfer element 12B by opening the valves 14a to 14d and closing the remaining valves 14f to 14j.
→ It is arranged to flow in series in the order of the upstream heat transfer element 12A.

The other one is a flow path in the peeling operation mode shown in FIG. In this operation mode,
Open the valves 14c, 14f, 14e, 14i and leave the remaining valves 14a, 14b, 14d, 14g, 14h, 14j
Is closed, the heat medium is transferred to the intermediate heat transfer element 12.
B → the upstream heat transfer element 12A → the downstream heat transfer element 12C are circulated in series in this order.

The operation mode is selected by control means (not shown), and the normal operation mode is selected during normal operation.
Execute and select and execute the peeling operation mode only under certain conditions.

Next, an operation method and an operation of the exhaust gas treatment system having the above-described configuration will be described. The overall flow will be described with reference to FIG. First, the exhaust gas discharged from the boiler 1 is guided to an air preheater 2 after passing through a denitration facility (not shown), and is used for preheating the combustion air of the boiler 1, and then is converted into a heat medium by a heat exchanger 4. The heat is recovered, the temperature is lowered to about 90 ° C., and sent to the electric precipitator 3 at the subsequent stage. The dust collected along with the electric dust collector 3 with high efficiency is collected and removed, and S in the exhaust gas is removed.
O _{3 is} also removed from the exhaust gas together with the above-mentioned dust while being adsorbed on the dust. In this way, the exhaust gas having a reduced SO ₃ concentration together with the dust passes through the flue gas desulfurization device 5 by a desulfurization fan (not shown). Then, in this flue gas desulfurization device 5, sulfur dioxide gas (SO ₂ ) contained in exhaust gas is absorbed and oxidized by being brought into gas-liquid contact with an absorbing solution containing an alkali component such as limestone.
A reaction neutralized by the alkali component in the absorbing solution is performed, and the sulfurous acid gas is absorbed and removed. Dust entrained in the exhaust gas is also collected and removed in the absorbent. Next, after the mist content of the exhaust gas passing through the flue gas desulfurization device 5 is removed by a mist eliminator or the like, the exhaust gas is whitened by a heat medium supplied from a supply line 7b of a circulating supply line 7 in a heat exchanger 6 for reheating. After being reheated to 90-100 ° C to prevent smoke,
Released from the chimney 8 to the atmosphere.

In the exhaust gas treatment described above, since the heat exchanger 4 for heat recovery is disposed in front of the electric precipitator 3, dust and the like have not yet been removed from the heat exchanger 4. The exhaust gas will pass through, and as a result, the heat exchanger 4
The pressure loss of the exhaust gas increases due to the blockage in the inside.
Therefore, when the pressure loss increases, the deposits in the heat exchanger, which are the cause, are removed.

That is, during a steady operation, as shown in FIG. 1A, the downstream heat transfer element 12C → the middle heat transfer element 12B → the upstream heat transfer element 12A.
Under such conditions, dust adheres to the heat transfer element 12C located on the downstream side (lower temperature side) as described above. Executes the stripping operation mode. Then, the heat medium flows in series in the order of the intermediate heat transfer element 12B → the upstream heat transfer element 12A → the downstream heat transfer element 12C as shown in FIG. 1B, and is located downstream. The heat transfer element 12C includes an intermediate heat transfer element 12B → an upstream heat transfer element 12A.
After that, the heat medium having a higher temperature than in the steady heat transfer state flows.

As a result, the downstream heat transfer element 12C
Is higher than the surface temperature in the steady heat transfer state, and the high temperature causes the substance adhering to the surface of the heat transfer element 12C to dry and peel off. That is, only by changing the flow order of the heat medium, the deposit on the downstream heat transfer element 12C is naturally removed by the flow of the exhaust gas. Then, the blockage of the heat exchanger 4 due to the deposits over time is eliminated, and an increase in the pressure loss of the exhaust gas can be avoided. As a result, the operation stop time due to the increase in the pressure loss of the exhaust gas is delayed. Can be
It is possible to perform stable operation for a long time.

The surface temperature of the heat transfer element 12C in the steady operation mode and the surface temperature of the heat transfer element 12C in the separation operation mode are shown for reference. Surface temperature is 75 ℃ ～ 8
5 ° C., and the surface temperature in the peeling operation mode is 90 ° C.-1
00 ° C. By raising the temperature to the latter, it is possible to dry and peel off the deposits on the surface of the heat transfer element.

Next, another embodiment of the present invention will be described. FIG. 2 is a schematic configuration diagram of a heat exchanger 24 according to another embodiment. The heat exchanger 24 includes three upper, middle, and lower heat transfer elements 25 from the upstream side to the downstream side in the exhaust gas flow direction,
26 and 27 are arranged, and the heat transfer element 2 of each stage is further arranged.
5, 26, and 27 are divided into a plurality (three in the figure) in a cross-sectional direction (left-right direction in the figure) orthogonal to the flow direction of the exhaust gas. Each of the divided heat transfer elements is denoted by reference numeral 25.
a, 25b, 25c, 26a, 26b, 26c, 27
a, 27b and 27c.

Heat transfer elements 25a, 26a, 27a, 25b, 26 in three stages of upper, middle, and lower rows in each of the left, center, and right rows.
The b, 27b, 25c, 26c, 27c are connected in series for each row, and are connected in parallel between the heat medium supply port 16 and the heat medium discharge port 17. That is, the heat medium supplied from the heat medium supply port 16 flows in the order of the heat transfer element 27 on the downstream side (lower stage) in the exhaust gas flow direction → the heat transfer element 26 in the middle stage → the heat transfer element 25 on the upstream side (upper stage). However, the left side, the center and the right side flow in series independently of each other, and the left side flows in the order of the lower heat transfer element 27a → the middle heat transfer element 26a → the upper heat transfer element 25a. Flows in the order of the lower heat transfer element 27b → the middle heat transfer element 26b → the upper heat transfer element 25b, and the right side flows in the order of the lower heat transfer element 27c → the middle heat transfer element 26c → the upper heat transfer element 25c. It has become.

The lower heat transfer elements 27a, 27
At the inlets of b and 27c, a flow control valve (an open / close valve is also possible) as a means for controlling the flow rate, respectively.
a, 28b, 28c are provided, and open / close valves 29a, 29b, 29c are provided at the outlets of the upper heat transfer elements 27a, 27b, 27c, respectively.

Next, the operation method and operation of the exhaust gas treatment system having the above configuration will be described. Since the entire flow is the same as in the above embodiment, the description is omitted.

In the normal operation mode, all the valves 28
a, 28b, 28c, 29a, 29b, 29c are opened, and all the heat transfer elements 25a, 25b, 25c,
A heat medium is passed through 6a, 26b, 26c, 27a, 27b, 27c to perform heat exchange. As such exhaust gas treatment is performed, a problem of clogging of the heat exchanger 24 arises. Then, when the pressure loss of the heat exchanger 24 rises,
The deposits in the heat exchanger 24, which are the cause, are removed.

That is, in the processing system of this embodiment,
Since the heat medium inflow control can be independently performed for the three rows on the left, center, and right sides, the supply of the heat medium for one row is limited or stopped every certain time. In the figure, the flow of the heat medium in the center row is stopped by closing the on-off valve 28b on the inlet side in the center row. By doing so, the heat transfer elements 27b, 26b, 25 in the center row
b can be made higher than the surface temperature in the steady state heat transfer state, and the high temperature causes the substance adhering to the surfaces of the heat transfer elements 27b, 26b, and 25b to be dried and separated. can do. By performing the same process on the remaining rows, it is possible to remove deposits on all the heat transfer elements. In addition, even if one row of the heat transfer elements does not function due to the execution of the stripping operation mode, the heat exchange capacity itself does not significantly decrease because the other two rows of the heat transfer elements are functioning.

As described above, the adhesion of the heat transfer element to the specific heat transfer element can be easily removed only by stopping the flow of the heat medium to the heat transfer element. Blockage due to the exhaust gas can be eliminated, and an increase in pressure loss of exhaust gas can be avoided. As a result, the stoppage time of the operation due to the increase in the pressure loss of the exhaust gas can be delayed, and stable operation can be performed for a long period of time. This stripping operation mode is desirably performed at night as in the previous embodiment.

In this embodiment, the open / close valve 28
Although the surface temperature of the heat transfer element is raised by completely blocking the flow of the heat medium by a, 28b, and 28c, the flow rate of the heat transfer element can be controlled only by limiting the flow rate without completely blocking the flow. It is also possible to adjust the surface temperature to a high temperature.

Further, in each of the above examples, the case where the present invention is applied to the exhaust gas treatment system shown in FIG. 4 is shown, but the present invention can also be applied to the exhaust gas treatment system shown in FIG. Further, when dust adheres to the heat transfer element of the heat exchanger 6 for reheating, the present invention can be applied to the heat exchanger 6.

Further, in each of the above-described embodiments, the case where the present invention is applied to a heat exchanger in a non-leak type gas gas heater widely used in an exhaust gas treatment system has been described, but the present invention is not limited to this. However, the present invention can be widely applied to a single heat recovery heat exchanger.

[0043]

As described above, according to the first to eighth aspects of the present invention, the heat transfer element of the heat exchanger is divided into a plurality of heat transfer elements and a part of the plurality of divided heat transfer elements. Since the surface temperature of things is adjusted to a higher temperature than the surface temperature in the steady heat transfer state, if dust adheres to the surface of some heat transfer elements and the pressure loss of exhaust gas rises, By increasing the surface temperature of the heat transfer element, a substance that has adhered to the surface of the heat transfer element in a wet state during the steady heat transfer state can be dried and separated by heating. Therefore, while maintaining the function of the heat exchanger, it is possible to avoid an increase in the pressure loss of the exhaust gas over time in the heat exchanger, and by delaying the operation stop time due to the increase in the pressure loss, It is possible to perform stable operation for a long time. Further, compared with the conventional cleaning device, it is possible to suppress an increase in exhaust gas pressure loss with a simple structure and low utility consumption. Therefore, the present invention can be applied irrespective of existing or new construction, and a great effect such as simplification of equipment can be exhibited.

According to the second aspect of the present invention, the flow rate of the heat medium flowing into the heat transfer element is controlled by changing the temperature of the heat medium flowing therein, and according to the third and eighth inventions. Thus, the surface temperature of the heat transfer element is increased, so that the attached structure of the corresponding heat transfer element can be removed by a simple structure in which piping and valves are provided.

In the case of the fourth and seventh aspects, the surface temperature of the corresponding heat transfer element is increased by changing the order in which the heat medium flows through the plurality of divided heat transfer elements. The deposits on the heat transfer element can be easily removed with simple equipment. In particular, in the case of the invention of claim 5, since the attached matter of the heat transfer element located on the downstream side in the flow direction of the exhaust gas can be removed only by changing the flow direction of the heat medium, the most effective is achieved. Can be demonstrated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a main part of an embodiment of an exhaust gas treatment system according to the present invention.

FIG. 2 is a configuration diagram of a main part showing another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a conventional exhaust gas treatment system.

FIG. 4 is a schematic configuration diagram showing another conventional exhaust gas treatment system.

[Explanation of symbols]

4 Heat exchangers 12A, 121B, 12C for temperature reduction 13 Heat transfer elements 13 Pipes 14a-14j Valves (flow path switching means) 24 Heat exchangers 25, 25a-25c Heat transfer elements 26, 26a-26c Heat transfer elements 27, 27a-27c Heat transfer element 28a-28c Open / close valve (means for controlling flow rate of heat medium)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuyuki Takeda, Inventor, 6-15-1, Ginza, Chuo-ku, Tokyo Inside Power Development Co., Ltd. (72) Hiroshi Yoshida, 6-15-1, Ginza, Chuo-ku, Tokyo Power supply (72) Inventor Hiroyuki Nakui 6-15-1, Ginza, Chuo-ku, Tokyo Power Development Co., Ltd. (72) Inventor Tokaibayashi Kaname Yoshi 2-12-1, Tsurumichuo, Tsurumi-ku, Yokohama, Kanagawa Prefecture No. Within Chiyoda Kako Construction Co., Ltd. Chiyoda Chemical Construction Co., Ltd. (72) Inventor Ken Morikami 2--12-1, Tsurumi Chuo, Tsurumi-ku, Yokohama, Kanagawa (72) Inventor Atsushi Watanabe 2-1-1, Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa F-term (reference) in Chiyoda Kako Construction Co., Ltd.3K070 DA03 DA07 DA48 4D002 AA02 AC01 BA03 BA04 BA12 BA13 BA14 BA16 CA01 DA05 DA16 EA02 GA02 GA03 GB03 GB20 HA07

Claims (8)

[Claims] In an exhaust gas treatment system provided with a heat exchanger for reducing the temperature of exhaust gas on an exhaust gas treatment line, a heat transfer element of the heat exchanger is divided into a plurality of heat exchanger elements and the plurality of heat transfer elements are divided. An exhaust gas treatment system comprising a heat transfer element surface temperature control means for adjusting a surface temperature of a part of the heat transfer elements to a temperature higher than a surface temperature in a steady heat transfer state. 2. The exhaust gas treatment system according to claim 1, wherein said heat transfer element surface temperature control means comprises means for controlling a temperature of a heat medium flowing into said heat transfer element. 3. The exhaust gas treatment system according to claim 1, wherein said heat transfer element surface temperature control means comprises means for controlling a flow rate of a heat medium flowing into said heat transfer element. 4. A piping for connecting the plurality of divided heat transfer elements in series in an arbitrary order, and a connection order for connecting the heat transfer elements in series, 3. The exhaust gas treatment system according to claim 2, further comprising a flow path switching means for changing the flow rate. 5. The heat transfer element divided into a plurality of stages is arranged in multiple stages in the exhaust gas flow direction, and is located upstream from the heat transfer element located downstream in the exhaust gas flow direction in a steady heat transfer state. When increasing the surface temperature of the heat transfer element located on the downstream side in the exhaust gas flow direction as part of the heat transfer element, the exhaust gas is controlled by controlling the flow path switching means so that the heat medium flows toward the heat transfer element. A heat medium flow direction switching means for controlling the flow path switching means so that the heat medium flows from the heat transfer element located on the upstream side in the flow direction to the heat transfer element located on the downstream side in the flow direction. Claim 4
An exhaust gas treatment system according to item 1. 6. An exhaust gas treatment system provided with a heat exchanger for reducing the temperature of exhaust gas on an exhaust gas treatment line, wherein a heat transfer element of the heat exchanger is divided into a plurality of heat transfer elements. Exhaust gas characterized in that by adjusting the surface temperature of some of the heat elements to a temperature higher than the surface temperature in the steady state heat transfer state, substances attached to the surface of the heat transfer element are separated. How to operate the processing system. 7. The heat transfer element divided into a plurality of parts is arranged in multiple stages in the flow direction of the exhaust gas, and the flow order of the heat medium into each heat transfer element is changed from the flow order in the steady heat transfer state, so that a specific heat transfer element is provided. The method for operating an exhaust gas treatment system according to claim 6, wherein the surface temperature of the heat transfer element is higher than the surface temperature in a steady heat transfer state. 8. By limiting the amount of heat medium flowing into some of the plurality of divided heat transfer elements,
The method for operating an exhaust gas treatment system according to claim 6, wherein the surface temperature of the heat transfer element is higher than the surface temperature in a steady heat transfer state.