JP2013088094A - Operating method of heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical operating method of a heat exchanger, configured to prevent the scale from depositing on a heat transfer face and/or a flow channel wall surface of a heat exchanger, or to remove the scale deposited on the heat transfer face and/or the flow channel wall surface.SOLUTION: A gas-liquid mixed phase flow is formed by injecting a return gas to a gas cooling water inlet section 61 through a return gas supply pipe 81, with respect to a gas cooling water cooler 51 for cooling the gas cooling water sprayed to the return gas, used in a cooling tower 31 for cooling the return gas circulated in a fuel gas return line 15 of a blast furnace gas firing gas turbine power generation plant 1. The gas-liquid mixed phase flow is supplied to the gas cooling water cooler 51 to remove the scale deposited on the heat transfer face and/or the flow channel wall surface of the gas cooling water cooler 51. The gas-liquid mixed phase flow discharged from the gas cooling water cooler 51 is supplied to the cooling tower 31.

Description

  The present invention relates to a method of operating a heat exchanger that exchanges heat between two fluids across a solid wall, and in particular, prevents the scale from adhering to the heat transfer surface of the heat exchanger or the scale adhering to the heat transfer surface. It is related with the operating method of the heat exchanger to remove.

  FIG. 4 is a process flow diagram showing a schematic configuration of a conventional gas turbine combined power plant 2 that uses as a by-product gas such as blast furnace gas generated along with the operation of an ironworks as a fuel. The gas turbine combined power plant 2 is roughly classified into a gas turbine power generation facility and a steam power generation facility. A gas turbine power generation facility using a low pressure / low calorific value fuel such as blast furnace gas is provided with a fuel compressor 3 for boosting the fuel gas, and the fuel gas whose calorific value is adjusted is boosted by the fuel compressor 3 and burned. In the vessel 5, it is mixed with high-pressure air sent from the air compressor 7 and burned. This combustion gas becomes a drive source of the gas turbine 9, and the gas turbine 9 drives the air compressor 7 and the fuel compressor 3, and also drives the generator 11, thereby generating electric power. On the other hand, the steam power generation facility includes an exhaust heat recovery boiler 101, and the exhaust heat recovery boiler 101 recovers heat from the combustion gas exhausted from the gas turbine 9 to drive the steam turbine 103. The steam exhausted from the steam turbine 103 becomes condensate in the condenser 105, and the condensed water is sent to the exhaust heat recovery boiler 101 by the feed water pump 107.

  The axial flow compressor used in the fuel compressor 3 has a wide surging range, and surging occurs when the flow rate of the fuel gas to be sucked is below a predetermined flow rate. For the purpose of avoiding this, the output decreases and the combustor A part of the discharge gas (fuel gas) is circulated through the fuel gas return line 15 so that the amount of fuel gas sucked does not become a predetermined flow rate or less even if the supply amount to 5 decreases. When the fuel gas is compressed by the fuel compressor 3, the temperature of the fuel gas rises. Therefore, the fuel gas sent to the fuel gas return line 15 is cooled by the gas cooler 23 interposed in the fuel gas return line 15. And returned to the fuel compressor 3.

  The gas cooler 23 is a direct-cooling type cooler that directly brings fuel gas (return gas) and cooling water (gas cooling water) into contact, and the cooling water is cooled by a gas cooling water cooler (not shown). Used cyclically. The gas cooling water cooler is a partition wall type heat exchanger using seawater as a cooling medium, and cools the gas cooling water with seawater. Impurities contained in the return gas are captured by the gas cooling water, and further, the gas cooling water is circulated and used, so that the concentration of the impurities contained in the gas cooling water increases with the progress of operation. Impurities contained in the gas cooling water adhere as scales to the heat transfer surface of the gas cooling water cooler that cools the gas cooling water. For this reason, two gas cooling water coolers are installed, and the switching operation is alternately performed, and the gas cooling water cooler to which the scale is attached is disassembled and cleaned while it is stopped. In such a gas turbine combined power plant 2, the gas coolant cooler may be blocked within a short period, which is a problem.

  The scale adheres to the heat transfer surface of the heat exchanger and also to the wall surface of the flow path, regardless of the gas cooling water cooler of the gas turbine combined power plant 2. This phenomenon is seen, and as a scale removal method, a mechanical removal method such as decomposition and injection of high-pressure water is often used. In addition, a method of passing and dissolving a chemical (for example, refer to Patent Document 1), a method of sending a gas-liquid mixed phase flow into a heat transfer tube, and simultaneously generating ultrasonic waves to mechanically remove scales adhering to the heat transfer tube (See, for example, Patent Document 2).

JP-A-2005-42026 Japanese Patent Publication No. 5-78759

  The method of disassembling and cleaning the heat exchanger is a reliable method but requires a lot of labor. In the method of passing chemicals, it is difficult to dispose of the waste liquid and to clean the heat exchanger after cleaning with chemicals. The method of flowing and cleaning the gas-liquid mixed phase flow through the heat exchanger requires less labor than the above method, but the heat exchanger cleaning method using the gas-liquid mixed phase flow proposed so far is Most of them are for the side, and the cleaning is regarded as a single operation, and the influence of the cleaning operation on the plant or the process is hardly studied. For this reason, the washing | cleaning method of the heat exchanger using the conventional gas-liquid multiphase flow cannot be used depending on a plant and a process.

  For example, the gas forming the gas-liquid mixed phase flow is mostly air or nitrogen gas from the viewpoint of availability and handling. However, when the liquid is a combustible gas or a liquid in which other gas is dissolved, air is used. Or nitrogen gas cannot be used. Further, in the invention described in Patent Document 2, the gas that has passed through the heat transfer tube is collected in a gas reservoir provided in the water outlet side water chamber and discharged by a pump. Some will be discharged. As described above, the heat exchanger cleaning methods that have been proposed so far have problems, and further studies and improvements are required.

  The object of the present invention is to prevent the scale from adhering to the heat transfer surface and / or the channel wall of the heat exchanger, or to remove the scale adhering to the heat transfer surface and / or the channel wall. It is to provide a method for operating a simple heat exchanger.

  The present invention is an operation method of a heat exchanger for exchanging heat between a liquid and another fluid used in a gas-liquid contact device that directly contacts a process gas and a liquid across a solid wall, and the heat exchanger includes: A process gas supply line for injecting a process gas into a liquid inlet of the heat exchanger, injecting a process gas from the process gas supply line, sending a gas-liquid mixed phase flow to the heat exchanger, and a heat transfer surface of the heat exchanger; The operation method of the heat exchanger is characterized in that the scale adhering to the wall surface of the flow path is removed and the gas-liquid mixed phase flow discharged from the heat exchanger is sent to the gas-liquid contact device.

  Further, the present invention is the operation method of the heat exchanger, wherein the gas-liquid mixed phase flow is intermittently sent to the heat exchanger during normal operation of the heat exchanger, and the heat transfer surface and / or the flow path of the heat exchanger Remove the scale adhering to the wall surface, or prevent the scale from adhering to the heat transfer surface of the heat exchanger and / or the channel wall surface, and contact the gas-liquid mixed phase flow heat-exchanged by the heat exchanger with the gas-liquid contact It is characterized by being sent to the device.

  Further, the present invention is the operation method of the heat exchanger, wherein the heat exchanger connects the liquid inlet portion and the liquid outlet portion of the heat exchanger, and sends the liquid from the liquid outlet portion to the heat exchanger to exchange heat. A backwash line for discharging the discharged liquid from the liquid inlet portion and returning the discharged liquid to the liquid outlet portion, and further sending a gas-liquid mixed phase flow from the liquid outlet portion to the heat exchanger via the backwash line, The scale attached to the heat transfer surface and / or the channel wall of the heat exchanger is removed, or the scale adheres to the heat transfer surface and / or the channel wall of the heat exchanger, and the heat exchange is performed by the heat exchanger. A gas-liquid mixed phase flow is sent to the gas-liquid contact device.

  The present invention is also characterized in that, in the operation method of the heat exchanger, the process gas includes a combustible gas and / or a toxic gas.

  Further, the present invention provides the operation method of the heat exchanger, wherein the gas-liquid contact device is a gas cooler that cools a return gas of a blast furnace gas-fired gas turbine power generation facility, and the liquid cools the return gas. It is water, The said heat exchanger is a gas cooling water cooler which cools gas cooling water, It is characterized by the above-mentioned.

  In the operation method of the heat exchanger of the present invention, a process gas is blown into the liquid to be heat exchanged to form a gas-liquid mixed phase flow, the gas-liquid mixed phase flow is sent to the heat exchanger, and the heat transfer surface of the heat exchanger and Since the scale adhering to the flow path wall surface is removed, the heat exchanger can be cleaned without being disassembled. Further, since the process gas is used for forming the gas-liquid mixed phase flow, even if the gas-liquid mixed phase flow discharged from the heat exchanger is sent to the gas-liquid contact device, the process is not adversely affected. Thus, it is not necessary to process the gas contained in the gas-liquid mixed phase flow, and it can be implemented immediately with a simple modification in the actual plant. In particular, when a gas is dissolved in a liquid, it is necessary to remove the dissolved gas if a gas different from the process gas is used. Therefore, the present invention is preferably used for a heat exchanger that performs heat exchange of such a liquid. Can do.

  The operation method of the heat exchanger according to the present invention is such that the gas-liquid mixed phase flow is intermittently sent to the heat exchanger during normal operation of the heat exchanger and adheres to the heat transfer surface and / or the channel wall surface of the heat exchanger. Since the scale is removed and the gas-liquid mixed phase flow heat-exchanged by the heat exchanger is sent to the gas-liquid contact device, the heat exchanger can be washed while operating the heat exchanger. Furthermore, since the gas-liquid mixed phase flow is intermittently sent to the heat exchanger during normal operation of the heat exchanger, it is possible to prevent the scale from adhering to the heat transfer surface and / or the channel wall surface of the heat exchanger. Is preferred. As can be seen, the method of operating the heat exchanger of the present invention is very practical.

  Moreover, since the operation method of the heat exchanger of the present invention can also send a gas-liquid mixed phase flow to the heat exchanger from the so-called backwash direction, the heat transfer surface and / or the channel wall surface of the heat exchanger can be more reliably supplied. Scale adhesion can be prevented, or scale adhered to the heat transfer surface and / or the channel wall surface can be removed. Also in this case, since the gas-liquid mixed phase flow after heat exchange is sent to the gas-liquid contact device that directly contacts the process gas and the liquid, it is not necessary to process the gas contained in the gas-liquid mixed phase flow. It can be implemented immediately with a simple modification.

  In general, when handling flammable gases and / or toxic gases, care should be taken compared to nitrogen gas. In the heat exchanger operating method of the present invention, the heat-exchanged gas-liquid mixed phase flow is sent to the gas-liquid contact device that directly contacts the process gas and the liquid, so that the gas contained in the gas-liquid mixed phase flow is processed. It is unnecessary. For this reason, even if the process gas contains a combustible gas and / or a toxic gas, the operation can be performed safely.

  The gas cooler that cools the return gas of the blast furnace gas-fired gas turbine power generation facility is a cooler that directly contacts the coolant with the return gas. Since this coolant is circulated, the gas that cools this coolant is used. Although the cooling water cooler easily adheres to the scale, application of the operation method of the heat exchanger of the present invention prevents the scale from adhering to the heat transfer surface and / or the channel wall surface of the gas cooling water cooler. Alternatively, the scale attached to the heat transfer surface and / or the channel wall surface can be removed.

1 is a process flow diagram illustrating a schematic configuration of a blast furnace gas-fired gas turbine power plant 1 to which a heat exchanger operating method according to an embodiment of the present invention is applied. FIG. 2 is a detailed view of part A in FIG. 1. It is a figure for demonstrating the operating method of the gas cooling water cooler of FIG. It is a process flow figure showing a schematic structure of conventional gas turbine combined power plant 2 which uses by-product gas, such as blast furnace gas generated with operation of a steelworks, as fuel.

  A case where the operation method of the heat exchanger of the present invention is applied to a gas cooling water cooler of a blast furnace gas-fired gas turbine combined power plant will be described as an example. FIG. 1 is a process flow diagram showing a schematic configuration of a blast furnace gas-fired gas turbine combined power plant 1 to which a heat exchanger operating method according to an embodiment of the present invention is applied.

  First, a schematic configuration of the blast furnace gas-fired gas turbine combined power plant 1 will be described. The blast furnace gas-fired gas turbine combined power plant 1 has the same basic configuration as the conventional gas turbine combined power plant 2 shown in FIG. Portions corresponding to the gas turbine combined power plant 2 of FIG.

  The blast furnace gas-fired gas turbine combined power plant 1 is roughly classified into a gas turbine power generation facility that generates power using blast furnace gas as a fuel, and a steam power generation facility that generates power by recovering heat from the combustion gas exhausted from the gas turbine. Here, mixed gas is used as the heat increasing gas.

  The gas turbine power generation facility includes a fuel compressor 3 that boosts a low-pressure fuel gas to a predetermined pressure, an air compressor 7 that sends out high-pressure air, a fuel gas that is sent from the fuel compressor 3, and a gas that is sent from the air compressor 7. A combustor 5 that mixes and burns the generated air to generate high-temperature and high-pressure combustion gas, a gas turbine 9 that is rotationally driven by the combustion gas delivered from the combustor 5, and a generator 11 that is driven by the gas turbine 9. Is provided. A fuel cutoff valve 13 is provided on the upstream side of the combustor 5. The gas turbine 9 rotates the generator 11 to generate power, and drives the fuel compressor 3 and the air compressor 7.

  The blast furnace gas, which is fuel, is mixed with the mixed gas as necessary via the mixer 27, adjusted to a predetermined calorific value, and then removed by the wet electrostatic precipitator 25, and then the fuel compressor via the fuel line 29. Sent to 3. Since the fuel gas sent to the fuel compressor 3 has a low pressure of about 0.005 MPa (abs), the fuel gas is boosted to a predetermined pressure by the fuel compressor 3 and then sent to the combustor 5. The fuel compressor 3 is an axial compressor, has a wide surging range, and surging occurs when the fuel gas flow rate to be sucked below a predetermined flow rate. For the purpose of avoiding this, the power generation output decreases and combustion occurs. In order to return a part of the discharge gas (fuel gas) to the inlet of the fuel compressor 3 so that the amount of the fuel gas sucked into the vessel 5 does not fall below a predetermined flow rate even if the amount of fuel gas supplied to the vessel 5 decreases. The fuel gas return line 15 is provided.

  A first gas return amount control valve 17 for adjusting a return gas (circulation gas) amount is provided in the middle of the fuel gas return line 15, and a second gas return amount control valve for processing a large amount of return gas. A bypass line 21 provided with 19 is connected. Since the second gas return amount control valve 19 provided in the bypass line 21 can circulate a larger amount of return gas than the first gas return amount control valve 17, the bypass line 21 has a unit trip. Used when flow rate fluctuation is large.

  A gas cooler 23 for cooling the return gas is provided downstream of the first gas return amount control valve 17. The gas cooler 23 is installed for the purpose of increasing the gas density and increasing the compression efficiency of the fuel compressor 3. After the return gas is cooled to a predetermined temperature, the gas cooler 23 enters the fuel line 29 upstream of the wet electrostatic precipitator 25. Will be returned.

  The steam power generation facility includes an exhaust heat recovery boiler 101, and the exhaust heat recovery boiler 101 recovers heat from the combustion gas exhausted from the gas turbine 9 and drives the steam turbine 103. The steam turbine 103 drives the generator 11 disposed on the same axis to generate power. The steam exhausted from the steam turbine 103 becomes condensate in the condenser 105, and is sent to the exhaust heat recovery boiler 101 as boiler feed water by the feed water pump 107. Heat is recovered by the exhaust heat recovery boiler 101, and the combustion gas whose temperature has decreased is discharged from the chimney 109.

  FIG. 2 is a detailed view of part A in FIG. 1 and shows a piping system around the gas cooler 23 and the gas coolant coolers 51 and 52. The gas cooler 23 is a direct contact type cooling tower 31, and the return gas sent from the first gas return amount control valve 17 enters the cooling tower from below the cooling tower 31. A first spray nozzle 33 and a second spray nozzle 35 are provided in the cooling tower, and the return gas comes into contact with the gas cooling water sprayed from the first spray nozzle 33 and the second spray nozzle 35 to reduce the temperature. Get out of the top 37.

  On the other hand, the gas cooling water sprayed from the first spray nozzle 33 and the second spray nozzle 35 and in contact with the return gas is discharged from the lower part of the cooling tower 31 to the gas cooling water pit 41 through the return cooling water pipe 39. The gas cooling water pit 41 communicates with the gas cooling water coolers 51 and 52 and the cooling tower 31 via the cooling water supply line 43. The gas cooling water stored in the gas cooling water pit 41 is sent to the gas cooling water coolers 51 and 52 via the gas cooling water pump 45 provided in the cooling water supply line 43, where heat exchange with seawater is performed. Then, after the temperature is lowered, it is sent to the first spray nozzle 33 and the second spray nozzle 35 through the cooling water supply line 43. Thus, while the gas cooling water cools the return gas, it is circulated and used while being cooled by the gas cooling water coolers 51 and 52. The cooling water supply line 43 includes a bypass line 49 in which a bypass valve 47 that bypasses the gas cooling water coolers 51 and 52 is interposed.

  Two gas-cooled water coolers are installed and operated alternately. The gas cooling water coolers 51 and 52 are plate heat exchangers, and seawater is used as a cooling medium. Seawater is supplied through a gas-cooled seawater pump 58 provided in a seawater supply line 57 connected to a seawater supply line 55 that takes seawater with several intake pumps 53 and feeds seawater to the condenser 101. The seawater whose temperature has been increased by cooling the gas cooling water circulating in the cooling water supply line 43 is returned to the sea through the seawater discharge line 59.

  The two gas cooling water coolers 51 and 52 have gas cooling water inlet valves 65 and 66 at the gas cooling water inlet portions 61 and 62 and gas cooling water outlet valves 67 and 68 at the gas cooling water outlet portions 63 and 64, respectively. And two connecting pipes 69 and 70 and connecting pipes 71 and 72 that connect the gas cooling water inlet portions 61 and 62 and the gas cooling water outlet portions 63 and 64. One communication pipe 70, 72 connects the downstream side of the gas cooling water inlet valves 65, 66 and the downstream side of the gas cooling water outlet valves 67, 68. The other communication pipes 69 and 71 connect the upstream side of the gas cooling water inlet valves 65 and 66 and the upstream side of the gas cooling water outlet valves 67 and 68. The communication pipes 69, 70, 71, 72 are provided with communication valves 73, 74, 75, 76, respectively. The two connecting pipes 69 and 70 and the connecting pipes 71 and 72 function as a backwash line for flowing the gas cooling water in the reverse direction to the gas cooling water coolers 51 and 52.

  A return gas supply pipe 81 for supplying a return gas provided with a gas supply valve 85 is connected in the middle of the pipeline between the gas cooling water inlet 61 and the gas cooling water cooler 51, and a gas cooling water outlet is provided. A return gas supply pipe 82 for supplying a return gas having a gas supply valve 86 is connected in the middle of the pipe line between 63 and the gas cooling water cooler 51. Similarly, between the gas cooling water inlet 62 and the gas cooling water cooler 52, a return gas supply pipe 83 for supplying a return gas provided with a gas supply valve 87 in the middle of the pipe line is connected, and the gas cooling water outlet is connected. A return gas supply pipe 84 for supplying a return gas having a gas supply valve 88 in the middle of the pipe is connected between the section 64 and the gas cooling water cooler 52. The return gas supply pipes 81, 82, 83, and 84 are branched from a return gas supply pipe 89 connected to the fuel gas return line 15 upstream of the first gas return amount control valve 17.

  The return gas cooled by the gas cooler 23 is the fuel gas boosted by the fuel compressor 3, and the fuel gas is removed by the wet electrostatic precipitator 29. Therefore, the return gas contains very little dust, but the return gas Although the gas cooling water for cooling the gas is partially replaced, basically, the gas cooling water is circulated and used, so that the dust concentration in the gas cooling water increases with the operation time. The plate-type heat exchanger, which is the gas cooling water coolers 51 and 52 for cooling the gas cooling water, has a plurality of heat transfer plates, and gas cooling water and seawater are interposed between adjacent heat transfer plates. It is a heat exchanger that exchanges heat alternately, and because the space between the heat transfer plates is narrow, the surface of the heat transfer plate (heat transfer surface) through which the gas cooling water flows and the gas cooling water supply channel (hereinafter simply referred to as the flow channel) ) Dust tends to adhere to and grow on the wall surface.

  In the present embodiment, by operating the gas cooling water coolers 51 and 52 in the following manner, the scale is prevented from adhering to the heat transfer surface and / or the channel wall surface, and the adhering scale is removed. Drawing 3 is a figure for explaining the operating point of a gas cooling water cooler. Here, the gas cooling water cooler 51 is in operation, and the other gas cooling water cooler 52 is stopped.

  FIG. 3A shows a case in which the gas cooling water is sent from the forward direction, and is the same as the flow of the gas cooling water during normal operation. When the gas cooling water is sent from the gas cooling water inlet 61 to the gas cooling water cooler (plate heat exchanger) 51, the return gas is sent from the return gas supply pipe 81 for a short time at the same time. The sent return gas is dispersed in the gas cooling water at the gas cooling water inlet 61 to form a gas-liquid mixed phase flow (gas-liquid two-phase flow), and the gas-liquid mixed phase flow is sent to the plate heat exchanger 51. . Since the gas-liquid mixed phase flow sent to the plate heat exchanger 51 has a larger capacity than the case of only gas cooling water, the flow velocity between the heat transfer plates and through the flow path becomes faster, Since the disturbance also increases, it is possible to prevent the scale from adhering to the heat transfer surface and / or the flow path wall surface, or to remove the adhered scale. The gas-liquid mixed phase flow sent to the plate heat exchanger 51 exchanges heat with seawater to lower the temperature, and is sent to the cooling tower 31 through the gas cooling water outlet 63 and the cooling water supply line 43. Except for returning gas to the gas cooling water inlet 61 and blowing in the gas, there is no difference from the normal operation.

  The timing at which the gas is returned to the gas cooling water and the gas is blown to form a gas-liquid mixed phase flow and sent to the plate heat exchanger 51 can be appropriately selected according to the contamination of the gas cooling water. For example, during normal operation in which only the gas cooling water is sent to the plate heat exchanger 51, for example, a gas-liquid mixed phase flow of about 5 seconds per time is sent about 10 times at intervals of 10 seconds. This method prevents the scale from adhering to the heat transfer surface and / or the channel wall surface rather than removing the scale attached to the heat transfer surface and / or the channel wall surface of the plate heat exchanger 51. Strong meaning. When it is determined that the gas cooling water is very dirty and scale is likely to be generated on the heat transfer surface and / or the channel wall surface of the plate heat exchanger 51, the supply frequency of the gas-liquid mixed phase flow is increased and / or Or what is necessary is just to lengthen supply time.

  Alternatively, the pressure loss of the plate heat exchanger 51 may be detected, and when the pressure loss reaches a predetermined value, a gas-liquid mixed phase flow may be sent. Since the pressure detector 46 is provided at the discharge portion of the gas cooling water pump 45 and the pressure detector 44 is also provided at the cooling water supply line 43 at the inlet of the cooling tower 31, the pressure of the plate heat exchanger 51 is set. The loss can be easily detected from an increase in the discharge pressure of the gas cooling water pump 45 or a decrease in the pressure of the cooling water supply line 43 at the inlet of the cooling tower 31. When it is detected that the pressure loss of the plate heat exchanger 51 has reached a predetermined value, for example, a gas-liquid mixed phase flow of about 5 seconds is sent about 10 times at intervals of 10 seconds, and the pressure loss recovery condition is set as one set. Depending on, this is repeated several sets. Also in this case, the gas-liquid mixed phase flow is sent to the cooling tower 31 after being cooled by the plate heat exchanger 51 as in the normal operation.

  In any case, the gas-liquid mixed phase flow exchanged by the plate heat exchanger 51 is sent to the cooling tower 31 to cool the return gas as gas cooling water. When nitrogen gas is blown into the gas cooling water to form a gas-liquid mixed phase flow, since the nitrogen gas is mixed into the return gas discharged from the cooling tower 31, the calorific value of the fuel gas changes, which is not preferable. Further, the gas used for forming the gas-liquid mixed phase flow needs to have a pressure higher than that of the gas cooling water at the gas cooling water inlet 61, and when nitrogen gas is used, it is necessary to prepare such nitrogen gas. is there.

  In the present embodiment, since the gas-liquid mixed phase flow is formed using the return gas that is the process gas, there is no problem of change in the calorific value of the fuel gas. Furthermore, since the pressure of the fuel gas return line 15 upstream of the first gas return amount control valve 17 is about 1.5 MPa, there is no problem in terms of pressure. Although the temperature is close to 400 ° C., the amount blown into the gas cooling water is small, the heat capacity is overwhelmingly smaller than the gas cooling water, and when the gas is blown back into the gas cooling water, it adiabatically expands and the temperature decreases. Therefore, there is no need to worry about the temperature rise of the gas cooling water. When increasing the amount of gas blown, when the gas-liquid mixed phase flow is frequently sent to the plate heat exchanger 51 and when the return gas is blown into the gas cooling water, there is a concern that the temperature rises. Separately, after cooling with a cooler, it may be blown into the gas cooling water.

  Furthermore, when the heat-exchanged gas-liquid mixed phase flow is returned to the cooling tower 31, processing of scales, dust, etc. contained therein becomes a problem, but since the circulating gas cooling water itself contains dust, It can return to the cooling tower 31 without performing a special process. When a large scale is included in the gas-liquid mixed phase flow discharged from the plate heat exchanger 51, a strainer may be provided in the cooling water supply line 43 at the inlet of the cooling tower 31. The strainer used here may be a known strainer, and two strainers may be provided and switched.

  With reference to FIG. 3B, another operation method of the gas cooling water cooler (plate heat exchanger) 51 will be described. Here, the plate heat exchanger 51 is in operation, and the other plate heat exchanger 52 is stopped. In the operation method of the gas cooling water cooler shown here, the gas cooling water flows from the reverse direction to the normal direction, that is, from the so-called backwash direction. At the same time, the return gas is sent from the return gas supply pipe 82 and the gas-liquid mixed phase flow is sent from the gas cooling water outlet 63 to the plate heat exchanger 51. The gas-liquid mixed phase flow heat-exchanged by the plate heat exchanger 51 is discharged from the gas cooling water inlet 61 and sent to the gas cooling water outlet 67 through the connecting pipe 70, and is the same as the flow of normal gas cooling water. To the cooling tower 31. The timing of this operation is, for example, periodically changing the line from the forward direction to the reverse direction during normal operation, and sending a gas-liquid mixed phase flow of about 5 seconds per time every several hours about 10 times at intervals of 10 seconds. . Further, as in the case of sending the gas-liquid mixed phase flow from the forward direction, such an operation method may be adopted when the pressure loss of the plate heat exchanger 51 increases. Furthermore, when the pressure loss of the plate heat exchanger 51 increases, the gas-liquid mixed phase supply operation from the forward direction and the gas-liquid mixed phase flow supply operation from the reverse direction may be used in combination.

  In the above embodiment, the gas-liquid mixed phase flow is intermittently sent during normal operation of the plate heat exchanger 51 to prevent the scale from adhering to the heat transfer surface and / or the channel wall surface, and the adhering scale is removed. However, the scale adhering to the heat transfer surface and / or the channel wall surface can also be removed by sending a gas-liquid mixed phase flow to the plate-type heat exchanger 52 that is stopped. In this case, one plate-type heat exchanger 51 performs normal operation, and simultaneously sends a gas-liquid mixed phase flow to the stopped plate-type heat exchanger 52 to remove the scale attached to the heat transfer surface and / or the channel wall surface. Just remove it.

  The plate heat exchangers 51 and 52 shown in the present embodiment are configured so that two plate heat exchangers can be operated independently, and the valves provided in each line are also motorized valves. It is easy to change. In addition, automatic operation can be easily performed by using a known controller such as a programmable logic controller. In the present embodiment, the return gas supply pipes 81, 82, 83, 84 are connected to the gas cooling water inlet portions 61, 62 and the gas cooling water outlet portions 63, 64, respectively. By connecting the return gas supply pipes 81 and 83 to the upstream side of 66, the return gas supply pipes 82 and 84 connected to the gas cooling water outlet portions 63 and 64 may be omitted.

  As explained using the above embodiment, the heat exchanger operating method of the present invention is a heat exchanger surface and / or flow path of the heat exchanger while the operation is continued even during the normal operation of the heat exchanger. Since the wall surface can be cleaned and scale can be prevented from adhering to the heat transfer surface and / or the channel wall surface of the heat exchanger, it can be applied to a wide range of heat exchangers. In addition, because process gas is used to form a gas-liquid mixed phase flow, even if the gas-liquid mixed phase flow discharged from the heat exchanger is sent to the gas-liquid contact device, the process and the plant are not adversely affected, and it is easy to apply in an actual plant. This is a practical method. Moreover, since the gas-liquid mixed phase flow discharged from the heat exchanger can be sent as it is to the gas-liquid contact device without processing the contained gas, it contains a lot of carbon monoxide like the blast furnace gas of this embodiment. Even if it is safe.

  As is well known, the gas-liquid mixed phase flow is known to have different flow states depending on the flow velocity and the flow direction, and the separated flow in which the gas phase and the liquid phase are both continuous phases, the liquid plug and the bubble plug, The liquid slag and the bubble slag are categorized into an intermittent flow in which gas slag flows alternately, an annular flow in which gas flows in the center and the liquid flows around the center, and a dispersed flow in which small bubbles are dispersed in the liquid. In the present invention, the gas-liquid mixed phase flow prevents the scale from adhering to the heat transfer surface and / or the channel wall of the heat exchanger, or removes the scale attached to the heat transfer surface and / or the channel wall. Therefore, it is preferable that the gas-liquid mixed phase flow is excellent in the ability to peel off the scale attached to the heat transfer surface or the like. As such a gas-liquid mixed phase flow, a dispersed flow is usually used. However, an intermittent flow may be used according to a target heat exchanger and scale.

  When the gas-liquid mixed phase flow is a dispersed flow, the method is not particularly limited. In the case of the above-described embodiment, for example, the return gas blown into the gas cooling water inlet portion 61 is used in the circumferential multiple directions of the gas cooling water inlet portion 61. Just blow in. Alternatively, a blowing nozzle may be provided at the tip of the return gas supply pipe 81 connected to the gas cooling water inlet 61, and this blowing nozzle may be installed in the piping of the gas cooling water inlet 61.

  In the said embodiment, although the example which uses the plate type heat exchanger 51 as a gas cooling water cooler was shown, a gas cooling water cooler is other partition type heat exchangers, such as a multi-tube heat exchanger, Needless to say. Moreover, although the specific numerical value is shown by the said embodiment, it is naturally anticipated that a numerical value will differ if the equipment to be used differs, and this invention is not limited to the numerical value shown to this embodiment. Further, the heat exchanger to which the operation method of the heat exchanger of the present invention can be applied is not limited to the gas cooling water cooler 51 of the blast furnace gas-fired gas turbine combined power plant 1. The present invention is a partition-type heat exchanger that includes a gas-liquid contact device that directly contacts a liquid and a process gas, and that exchanges heat between the liquid used in the gas-liquid contact device and another fluid via a solid wall. The heat exchanger operating method can be used. The gas-liquid contact device is not limited to the cooling device, and may be a cleaning device that cleans the gas, or a heating device that heats the gas by contacting the gas and the liquid. Also, the liquid is not limited to water, and may be a combustible liquid such as an organic solvent or petroleum.

DESCRIPTION OF SYMBOLS 1 Blast furnace gas-fired gas turbine power plant 2 Gas turbine combined power plant 3 Fuel compressor 15 Fuel gas return line 23 Gas cooler 31 Cooling tower 43 Cooling water supply line 45 Gas cooling water pump 51 Gas cooling water cooler, plate heat Exchanger 52 Gas cooling water cooler, plate heat exchanger 61, 62 Gas cooling water inlet 63, 64 Gas cooling water outlet 65, 66 Gas cooling water inlet valve 67, 68 Gas cooling water outlet valves 69, 70, 71, 72 Connecting pipe 73, 74, 75, 76 Connecting valve 81, 82, 83, 84 Return gas supply pipe 85, 86, 87, 88 Gas supply valve 89 Return gas supply pipe

Claims (5)

A method of operating a heat exchanger for exchanging heat between a liquid and another fluid used in a gas-liquid contact device that directly contacts a process gas and a liquid through a solid wall,
The heat exchanger comprises a process gas supply line for blowing process gas into the liquid inlet of the heat exchanger,
A process gas is blown from the process gas supply line, a gas-liquid mixed phase flow is sent to the heat exchanger, scales adhering to the heat transfer surface and / or the channel wall surface of the heat exchanger are removed, and the gas is discharged from the heat exchanger. A method of operating a heat exchanger, wherein a gas-liquid mixed phase flow is sent to the gas-liquid contact device.   During the normal operation of the heat exchanger, the gas-liquid mixed phase flow is intermittently sent to the heat exchanger, the scale adhering to the heat transfer surface and / or the channel wall surface of the heat exchanger is removed, or the heat exchanger 2. The gas-liquid mixed phase flow, which prevents scale from adhering to the heat transfer surface and / or the flow path wall surface and is heat-exchanged by a heat exchanger, is sent to the gas-liquid contact device. How to operate the heat exchanger. The heat exchanger connects the liquid inlet and the liquid outlet of the heat exchanger, sends the liquid from the liquid outlet to the heat exchanger, discharges the heat exchanged liquid from the liquid inlet, and discharges the discharged liquid to the liquid outlet. With a backwash line that returns to the
Further, a gas-liquid mixed phase flow is sent from the liquid outlet to the heat exchanger via the backwash line, and the scale attached to the heat transfer surface and / or the channel wall surface of the heat exchanger is removed, or the heat exchanger 3. The scale according to claim 1, wherein adhesion of scale to a heat transfer surface and / or a flow path wall surface is prevented, and the gas-liquid mixed phase flow heat-exchanged by a heat exchanger is sent to the gas-liquid contact device. The operation method of the heat exchanger as described.   The method for operating a heat exchanger according to any one of claims 1 to 3, wherein the process gas includes a combustible gas and / or a toxic gas.   The gas-liquid contact device is a gas cooler that cools return gas of a blast furnace gas-fired gas turbine power generation facility, the liquid is gas cooling water that cools the return gas, and the heat exchanger uses gas cooling water. It is a gas cooling water cooler to cool, The operating method of the heat exchanger of any one of Claim 1 to 4 characterized by the above-mentioned.

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