Online cleaning device and method for heat exchanger in coal chemical synthesis gas system

Abstract

The invention relates to the technical field of coal chemical synthesis gas systems, in particular to an online cleaning device and method for a heat exchanger in a coal chemical synthesis gas system.The cleaning device comprises a shell-and-tube heat exchanger, and a tube pass inlet and a tube pass outlet of the shell-and-tube heat exchanger are connected with a crude synthesis gas inlet tube and a crude synthesis gas outlet tube correspondingly; the shell pass inlet and outlet are respectively connected with a water inlet pipe and a water outlet pipe; the inlet and outlet of the shell pass are connected with a circulating cleaning pipe, and the circulating cleaning pipe is connected with a chemical pool, a circulating pump I and a cooling device for cooling liquid in the circulating cleaning pipe; valves are arranged on the water inlet pipe, the water outlet pipe and the circulating cleaning pipe; the medicament tank is connected with a circulating filter pipe, the circulating filter pipe is connected with a filter device and a circulating pump II, and the circulating filter pipe is provided with a valve; online cleaning of the heat exchanger is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal chemical synthesis gas systems, and specifically to an on-line cleaning device and method for heat exchangers in coal chemical synthesis gas systems. Background Art

[0002] In the coal chemical synthesis gas system, coal is first gasified to generate raw synthesis gas. After the raw synthesis gas is heat-exchanged through equipment such as waste heat boilers, it is then cooled through a heat exchanger and an ammonia refrigerating machine, and finally the acidic gases in the raw synthesis gas are removed through the low-temperature methanol washing process. During the long-term operation of the heat exchanger, due to the high temperature of the process medium and the influence of the quality of circulating water, scale is likely to form on the surface of the heat exchanger, thereby reducing the heat transfer efficiency of the heat exchanger, increasing energy consumption, and thus cleaning is necessary. Traditional heat exchanger cleaning methods are mostly off-line cleaning, which requires shutting down the equipment and disassembling the heat exchanger. This not only consumes a large amount of manpower, material resources and time, but also the production system needs to stop during the cleaning process. The shutdown cost of large-scale chemical plants with continuous production is relatively high, and it may also cause safety and environmental protection impacts. Summary of the Invention

[0003] The main purpose of the present invention is to provide an on-line cleaning device and method for heat exchangers in coal chemical synthesis gas systems, so as to solve the problems that the production system needs to stop during the heat exchanger cleaning process in the above-mentioned prior art, and it may cause safety and environmental protection impacts.

[0004] To achieve the above purpose, the present invention provides an on-line cleaning device for heat exchangers in coal chemical synthesis gas systems, including a shell-and-tube heat exchanger. The inlet and outlet of the tube side of the shell-and-tube heat exchanger are respectively connected with a raw synthesis gas inlet pipe and a raw synthesis gas outlet pipe, and the inlet and outlet of the shell side are respectively connected with a water inlet pipe and a water outlet pipe; a circulating cleaning pipe is connected to the inlet and outlet of the shell side, and a chemical agent tank, a first circulating pump and a cooling device for cooling the liquid in the circulating cleaning pipe are connected to the circulating cleaning pipe; valves are provided on the water inlet pipe, the water outlet pipe and the circulating cleaning pipe; the chemical agent tank is connected with a circulating filtration pipe, and a filtration device and a second circulating pump are connected to the circulating filtration pipe, and valves are provided on the circulating filtration pipe.

[0005] Further, the cooling device includes a cooling heat exchanger connected to the circulating cleaning pipe and a chiller connected to the cooling heat exchanger through a pipeline.

[0006] Further, an on-line pH monitor for monitoring the pH value of the liquid in the circulating filtration pipe is connected to the circulating filtration pipe.

[0007] Further, a temperature sensor for monitoring the temperature in the circulating cleaning pipe is connected to the circulating cleaning pipe. The temperature sensor is electrically connected to a PID temperature controller, and the PID temperature controller is electrically connected to the cooling device.

[0008] The present invention also provides an on-line cleaning method for a heat exchanger in a coal chemical synthesis gas system, which is carried out using the above-mentioned on-line cleaning device for a heat exchanger in a coal chemical synthesis gas system, and includes the following steps: S1. The raw synthesis gas of coal chemical industry passes through the tube side of the shell-and-tube heat exchanger, and the cooling water enters the shell side of the shell-and-tube heat exchanger through the water inlet pipe and is discharged through the water outlet pipe; S2. Prepare an aqueous solution of trisodium phosphate and put it into the chemical agent tank; S3. Close the valves on the water inlet pipe and the water outlet pipe, open the valve on the circulating cleaning pipe, and introduce the aqueous solution of trisodium phosphate in the chemical agent tank into the shell side of the shell-and-tube heat exchanger for cleaning, and make the aqueous solution of trisodium phosphate circulate along the circulating cleaning pipe; adjust the temperature of the aqueous solution of trisodium phosphate through the cooling device. After multiple circulations, the temperature of the aqueous solution of trisodium phosphate before entering the shell-and-tube heat exchanger is reduced to 30-35 °C; the temperature of the aqueous solution of trisodium phosphate when it is discharged from the shell-and-tube heat exchanger is 68-72 °C; S4. After the cleaning is completed, close the valve on the circulating cleaning pipe and open the valves on the water inlet pipe and the water outlet pipe.

[0009] Further, in step S2, the pH value of the aqueous solution of trisodium phosphate is 13-14.

[0010] Further, in step S3, the cleaning time of the cleaning liquid lasts for 24-48 hours.

[0011] Further, the temperature of the raw synthesis gas of coal chemical industry before passing through the shell-and-tube heat exchanger is 70-75 °C; the temperature after cooling is 35-40 °C.

[0012] Further, an on-line pH monitor for monitoring the pH value of the liquid in the circulating filter pipe is connected to the circulating filter pipe; In step S3, use the on-line pH monitor to monitor the pH of the liquid in the circulating filter pipe. When the pH value exceeds the set value, add the aqueous solution of trisodium phosphate into the chemical agent tank in time to adjust the pH value to the set value.

[0013] Further, a temperature sensor for monitoring the temperature in the circulating cleaning pipe is connected to the circulating cleaning pipe. The temperature sensor is electrically connected to a PID temperature controller, and the PID temperature controller is electrically connected to the cooling device.

[0014] In step S3, when the temperature sensor monitors that the temperature of the liquid in the circulating cleaning pipe exceeds the set value, it transmits a signal to the PID temperature controller, and the PID temperature controller controls the cooling device to adjust the operating parameters so that the temperature of the liquid in the circulating cleaning pipe is maintained at the set value.

[0015] The present invention can realize the on-line cleaning of the heat exchanger in the coal chemical synthesis gas system. During cleaning, there is no need to stop the vehicle, avoiding adverse effects on safety and environmental protection.

[0016] By providing a circulating filter pipe and a filtering device, the present invention can filter the cleaning agent without affecting the circulating cleaning pipe. As more and more impurities are filtered by the filtering device, the flow rate of the liquid in the circulating filter pipe will be affected, but the flow rate of the liquid in the circulating cleaning pipe will not be affected. After the filtering device has been used for a period of time, the valve on the circulating filter pipe needs to be closed to discharge the impurities in the filtering device, and this will not affect the continuous operation of the circulating cleaning pipe either.

[0017] The cleaning agent of the present invention is selected as an aqueous solution of trisodium phosphate, and the temperature of the aqueous solution of trisodium phosphate is controlled to drop to 30 - 35 °C before entering the shell-and-tube heat exchanger. In this way, the aqueous solution of trisodium phosphate not only serves as a cleaning agent but also replaces the cooling water to exchange heat and cool the raw synthesis gas in coal chemical industry, thus realizing the on-line cleaning of the heat exchanger. Moreover, although the temperature of the aqueous solution of trisodium phosphate is relatively low before entering the shell-and-tube heat exchanger, its temperature rises after heat exchange in the shell-and-tube heat exchanger, and the temperature when it is discharged from the shell-and-tube heat exchanger is 68 - 72 °C. Therefore, the temperature of the aqueous solution of trisodium phosphate in the shell-and-tube heat exchanger is in a better scale removal effect, and the active components of trisodium phosphate can react more effectively with the minerals in the water scale, thus removing the water scale more thoroughly. This avoids the situation where the temperature of the aqueous solution of trisodium phosphate is too high or too low. If the temperature is too high, partial decomposition will occur, reducing the alkalinity and detergency of the solution, and corroding the heat exchanger; if the temperature is too low, the solubility will decrease and the detergency will decline.

[0018] By controlling the pH value of the aqueous solution of trisodium phosphate, the present invention can then control the concentration of the aqueous solution of trisodium phosphate, enabling the concentration and temperature of the aqueous solution of trisodium phosphate to act synergistically to achieve the best detergency effect.

[0019] By controlling the cleaning time of the cleaning liquid to last for 24 - 48 hours, the present invention ensures that the inside of the shell-and-tube heat exchanger can be cleaned thoroughly and can be quickly restored to using cooling water to exchange heat and cool the raw synthesis gas in coal chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The schematic diagrams in the specification, which form a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments and descriptions thereof are used to explain the present invention and do not unduly limit the present invention.

[0021] Figure 1 It is a schematic structural diagram of an on-line cleaning device for a heat exchanger in a coal chemical synthesis gas system in the embodiment; In the figure: 1. Shell-and-tube heat exchanger; 2. Raw syngas inlet pipe; 3. Raw syngas outlet pipe; 4. Water inlet pipe; 5. Water outlet pipe; 6. Circulating cleaning pipe; 7. Chemical agent tank; 8. Circulation pump I; 9. Cooling device; 901. Cooling heat exchanger; 902. Chiller; 10. Circulating filtration pipe; 11. Filtration device; 12. Circulation pump II; 13. Temperature sensor; 14. PH monitor; 15. Automatic chemical dosing device. Detailed implementation manners

[0022] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0023] Embodiment of an on-line cleaning device for a heat exchanger in a coal chemical syngas system As Figure 1 shown, an on-line cleaning device for a heat exchanger in a coal chemical syngas system includes a shell-and-tube heat exchanger 1. The tube-side inlet and outlet of the shell-and-tube heat exchanger 1 are respectively connected with a raw syngas inlet pipe 2 and a raw syngas outlet pipe 3, and the shell-side inlet and outlet are respectively connected with a water inlet pipe 4 and a water outlet pipe 5; the shell-side inlet and outlet are connected with a circulating cleaning pipe 6, and a chemical agent tank 7, a circulation pump I 8 and a cooling device 9 for cooling the liquid in the circulating cleaning pipe 6 are connected to the circulating cleaning pipe 6; valves are provided on the water inlet pipe 4, the water outlet pipe 5 and the circulating cleaning pipe 6; the chemical agent tank 7 is connected with a circulating filtration pipe 10, a filtration device 11 and a circulation pump II 12 are connected to the circulating filtration pipe 10, the filtration device 11 can be a Y-type filter or a basket filter, and a valve is provided on the circulating filtration pipe 10; the chemical agent tank 7 is connected with an automatic chemical dosing device 15 through a pipeline.

[0024] The cooling device 9 includes a cooling heat exchanger 901 connected to the circulating cleaning pipe 6 and a chiller 902 connected to the cooling heat exchanger 901 through a pipeline.

[0025] An on-line PH monitor 14 for monitoring the PH value of the liquid in the circulating filtration pipe 10 is connected to the circulating filtration pipe 10.

[0026] A temperature sensor 13 for monitoring the temperature in the circulating cleaning pipe 6 is connected to the circulating cleaning pipe 6. The temperature sensor 13 is electrically connected to a PID temperature controller, and the PID temperature controller is electrically connected to the chiller 902.

[0027] Embodiment of an on-line cleaning method for a heat exchanger in a coal chemical syngas system An on-line cleaning method for a heat exchanger in a coal chemical syngas system is carried out by using the above-mentioned on-line cleaning device for a heat exchanger in a coal chemical syngas system, and includes the following steps: S1. The raw syngas from coal chemical industry at a temperature of 70 - 75 °C passes through the tube side of the shell-and-tube heat exchanger 1. Cooling water enters the shell side of the shell-and-tube heat exchanger 1 through the water inlet pipe 4 and is discharged through the water outlet pipe 5. S2. Prepare an aqueous solution of trisodium phosphate with a pH value of 13 - 14 and put it into the chemical dosing tank 7. S3. Close the valves on the water inlet pipe 4 and the water outlet pipe 5, open the valve on the circulating cleaning pipe 6, and introduce the aqueous solution of trisodium phosphate in the chemical dosing tank 7 into the shell side of the shell-and-tube heat exchanger 1 for cleaning, and make the aqueous solution of trisodium phosphate circulate along the circulating cleaning pipe 6; adjust the temperature of the aqueous solution of trisodium phosphate through the cooling device 9. After multiple circulations, the temperature of the aqueous solution of trisodium phosphate before entering the shell-and-tube heat exchanger 1 is reduced to 30 - 35 °C; the temperature of the aqueous solution of trisodium phosphate when it is discharged from the shell-and-tube heat exchanger 1 is 68 - 72 °C; the temperature of the raw syngas from coal chemical industry when it is discharged from the shell-and-tube heat exchanger 1 is 35 - 40 °C; the cleaning time of the cleaning liquid lasts for 24 - 48 hours. Use an on-line pH monitor 14 to monitor the pH of the liquid in the circulating filtration pipe 10. When the pH value exceeds the set value, add the aqueous solution of trisodium phosphate into the chemical dosing tank 7 in time to adjust the pH value to the set value. When the temperature sensor 13 detects that the temperature of the liquid in the circulating cleaning pipe 6 exceeds the set value, it transmits a signal to the PID temperature controller. The PID temperature controller controls the chiller 902 to adjust the operating parameters so that the temperature of the liquid in the circulating cleaning pipe 6 is maintained at the set value. S4. After the cleaning is completed, close the valve on the circulating cleaning pipe 6 and open the valves on the water inlet pipe 4 and the water outlet pipe 5.

[0028] The present invention can realize the on-line cleaning of the heat exchanger in the coal chemical syngas system. During cleaning, there is no need to stop the vehicle, avoiding adverse effects on safety and environmental protection.

[0029] By setting the circulating filtration pipe and the filtration device, the present invention can filter the cleaning agent without affecting the circulating cleaning pipe; as more and more impurities are filtered by the filtration device, it will affect the flow rate of the liquid in the circulating filtration pipe, but will not affect the flow rate of the liquid in the circulating cleaning pipe; after the filtration device is used for a period of time, it is necessary to close the valve on the circulating filtration pipe to discharge the impurities in the filtration device, which will not affect the continuous operation of the circulating cleaning pipe either.

[0030] The cleaning agent of the present invention selects an aqueous solution of trisodium phosphate, and controls the temperature of the aqueous solution of trisodium phosphate to be reduced to 30-35 °C before entering the shell-and-tube heat exchanger; the aqueous solution of trisodium phosphate serves both as a cleaning agent and replaces the cooling water to exchange heat and cool the raw synthesis gas in coal chemical industry, thereby realizing the on-line cleaning of the heat exchanger; and the temperature of the aqueous solution of trisodium phosphate is relatively low before entering the shell-and-tube heat exchanger, but the temperature rises after heat exchange in the shell-and-tube heat exchanger, and the temperature when discharged from the shell-and-tube heat exchanger is 68-72 °C; thus, the temperature of the aqueous solution of trisodium phosphate in the shell-and-tube heat exchanger is in a better scale removal effect, and the active components of trisodium phosphate can react more effectively with the minerals in the scale, so as to remove the scale more thoroughly; avoiding the temperature of the aqueous solution of trisodium phosphate being too high or too low. If the temperature is too high, partial decomposition will occur, reducing the alkalinity and detergency of the solution, and corroding the heat exchanger; if the temperature is too low, the solubility will decrease and the detergency will decline.

[0031] The present invention controls the pH value of the aqueous solution of trisodium phosphate, and then can control the concentration of the aqueous solution of trisodium phosphate, so that the concentration of the aqueous solution of trisodium phosphate and the temperature act synergistically to achieve the best detergency effect.

[0032] The present invention controls the cleaning time of the cleaning liquid to last for 24-48 hours, ensuring that the inside of the shell-and-tube heat exchanger can be cleaned thoroughly and can be restored to use the cooling water to exchange heat and cool the raw synthesis gas in coal chemical industry as soon as possible.

[0033] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An online cleaning device for a heat exchanger in a coal chemical synthesis gas system, comprising a shell and tube heat exchanger (1), wherein the tube side inlet and outlet of the shell and tube heat exchanger (1) are respectively connected to a crude synthesis gas inlet pipe (2) and a crude synthesis gas outlet pipe (3), and the shell side inlet and outlet are respectively connected to a water inlet pipe (4) and a water outlet pipe (5); characterized in that: The shell side inlet and outlet are connected to a circulating cleaning pipe (6), and the circulating cleaning pipe (6) is connected to a reagent pool (7), a circulating pump (8), and a cooling device (9) for cooling the liquid in the circulating cleaning pipe (6); valves are provided on the water inlet pipe (4), the water outlet pipe (5), and the circulating cleaning pipe (6); the reagent pool (7) is connected to a circulating filtering pipe (10), and the circulating filtering pipe (10) is connected to a filtering device (11) and a circulating pump (12), and a valve is provided on the circulating filtering pipe (10).

2. The on-line cleaning device for heat exchanger in coal chemical synthesis gas system according to claim 1, characterized in that: The cooling device (9) comprises a cooling heat exchanger (901) connected to the circulating cleaning pipe (6) and a chiller (902) connected to the cooling heat exchanger (901) via a pipeline.

3. The on-line cleaning device for heat exchanger in coal chemical synthesis gas system according to claim 2, characterized in that: The circulation filter tube (10) is connected to an online pH monitor (14) for monitoring the pH value of the liquid in the circulation filter tube (10).

4. The on-line cleaning device for heat exchanger in coal chemical synthesis gas system according to claim 1, characterized in that: The circulating cleaning pipe (6) is connected to a temperature sensor (13) for monitoring the temperature inside the circulating cleaning pipe (6), the temperature sensor (13) is electrically connected to a PID temperature controller, and the PID temperature controller is electrically connected to the temperature reduction device (9).

5. A method for online cleaning of a heat exchanger in a coal chemical synthesis gas system, characterized in that: The method is carried out using the online cleaning device for the heat exchanger in the coal chemical synthesis gas system of claim 1, comprising the following steps: S1, the raw synthesis gas of coal chemical industry passes through the tube side of the shell and tube heat exchanger (1), cooling water enters the shell side of the shell and tube heat exchanger (1) through the water inlet pipe (4), and is discharged through the water outlet pipe (5); S2, prepare a sodium phosphate trihydrate aqueous solution and add it to the reagent pool (7); S3, closing the valves on the water inlet pipe (4) and the water outlet pipe (5), opening the valve on the circulation cleaning pipe (6), passing the trisodium phosphate aqueous solution in the reagent pool (7) into the shell side of the shell and tube heat exchanger (1) for cleaning, and circulating the trisodium phosphate aqueous solution along the circulation cleaning pipe (6); adjusting the temperature of the trisodium phosphate aqueous solution by the cooling device (9), and reducing the temperature of the trisodium phosphate aqueous solution to 30-35° C. before entering the shell and tube heat exchanger (1) after multiple cycles; and the temperature of the trisodium phosphate aqueous solution when discharged from the shell and tube heat exchanger (1) is 68-72° C.; S4. After cleaning is completed, close the valve on the circulating cleaning pipe (6) and open the valves on the water inlet pipe (4) and the water outlet pipe (5).

6. The method for online cleaning of a heat exchanger in a coal chemical synthesis gas system according to claim 5, characterized in that: In step S2, the pH value of the trisodium phosphate aqueous solution is 13-14.

7. The method for online cleaning of a heat exchanger in a coal chemical synthesis gas system according to claim 5, characterized in that: In step S3, the cleaning time of the cleaning solution lasts for 24-48 hours.

8. The method for online cleaning of a heat exchanger in a coal chemical synthesis gas system according to claim 5, characterized in that: The temperature of the crude synthesis gas from the coal chemical industry before passing through the shell heat exchanger (1) is 70-75°C; the temperature after cooling is 35-40°C.

9. The method for online cleaning of a heat exchanger in a coal chemical synthesis gas system according to claim 5, characterized in that: The circulation filter tube (10) is connected to an online pH monitor (14) for monitoring the pH value of the liquid in the circulation filter tube (10); In step S3, an online pH monitor (14) is used to monitor the pH of the liquid in the circulating filter tube (10). When the pH value exceeds a set value, a trisodium phosphate aqueous solution is promptly added to the reagent pool (7) to adjust the pH value to the set value.

10. The method for online cleaning of a heat exchanger in a coal chemical synthesis gas system according to claim 5, characterized in that: The circulating cleaning pipe (6) is connected to a temperature sensor (13) for monitoring the temperature inside the circulating cleaning pipe (6), the temperature sensor (13) is electrically connected to a PID temperature controller, and the PID temperature controller is electrically connected to the temperature reduction device (9). In step S3, when the temperature sensor (13) detects that the temperature of the liquid in the circulating cleaning pipe (6) exceeds the set value, a signal is transmitted to the PID temperature controller, and the PID temperature controller controls the cooling device (9) to adjust the operating parameters so that the temperature of the liquid in the circulating cleaning pipe (6) is maintained at the set value.

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