Equipment and method for recovering nitrogen discharged from liquid nitrogen washing

Abstract

The present application provides an apparatus and method for recovering nitrogen discharged from waste water by washing with liquid nitrogen, comprising: a U-tube circulating water heater, a first pipeline, and a second pipeline. The inlet end of the U-tube circulating water heater is connected to the middle section of the second pipeline through the first pipeline, and the outlet end is used to connect to the fuel gas pipeline network; one end of the second pipeline is connected to the hydrogen separator; a control valve and a shut-off valve are provided on the second pipeline, and the control valve is located between the first pipeline and the hydrogen separator, and the shut-off valve is located between the first pipeline and the end of the second pipeline away from the hydrogen separator. The present invention effectively recovers CO in the discharged nitrogen. Each set of equipment can recover more than 170 NM3 / h of fuel gas and 100 NM3 / h of effective gas, with an annual benefit of more than 640,000 yuan, and a significant energy-saving effect. At the same time, due to the reduction of cold torch discharge, steam consumption is indirectly saved, and the phenomenon of long-term ice accumulation in the buffer tank is completely eliminated, which greatly improves the sanitation around the buffer tank and on the ground.

Description

Technical Field

[0001] The present application belongs to the technical field of chemical equipment, and specifically relates to an apparatus and method for recovering nitrogen discharged from liquid nitrogen washing. Background Art

[0002] The liquid nitrogen scrubbing process operates at low temperatures. Despite cold boxes providing insulation, there are still cooling losses and temperature differential losses in the heat exchanger, necessitating supplemental cooling. The required cooling capacity is provided by the throttling expansion of high-pressure nitrogen (the coke-soak effect). During normal operation, no external cooling is required. However, during startup or during improper operation, supplemental cooling requires low-pressure liquid nitrogen supplied by the air separation unit. During normal operation, the liquid nitrogen scrubbing unit typically has excess cooling capacity. Excess liquid contaminated nitrogen is discharged from the hydrogen separator and flashed in a buffer tank. It then enters the cold flare mains, where it is reheated with steam and then burned in the flare. However, the effective synthetic ammonia content of the liquid contaminated nitrogen is approximately 60%. Existing technical solutions not only waste this effective gas but also consume a considerable amount of steam. Furthermore, the outer wall of the buffer tank is severely iced year-round, requiring regular daily cleaning by staff. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related art, namely, the waste of effective gas and the problem of perennial freezing of the buffer tank.

[0004] In view of this, the first aspect of the present invention provides a device for recovering nitrogen discharged from liquid nitrogen washing. After the liquid nitrogen is discharged from the hydrogen separator, a U-tube circulating water heater is added to effectively recover the CO in the discharged nitrogen; at the same time, the phenomenon of long-term ice accumulation in the buffer tank is completely eliminated.

[0005] The second aspect of the present invention provides a method for recovering waste nitrogen discharged from liquid nitrogen washing, by using the above-mentioned equipment to recover the effective gas in the liquid waste nitrogen.

[0006] The specific technical solutions include the following:

[0007] According to a first aspect of an embodiment of the present application, there is provided an apparatus for recovering nitrogen discharged from liquid nitrogen washing, comprising a U-tube circulating water heater, a first pipeline, and a second pipeline.

[0008] The inlet end of the U-tube circulating water heater is connected to the middle section of the second pipeline through the first pipeline, and the outlet end of the U-tube circulating water heater is used to connect to the fuel gas pipeline network; one end of the second pipeline is connected to the hydrogen separator; a control valve is provided on the second pipeline, and the control valve is located between the first pipeline and the hydrogen separator; a shut-off valve is also provided on the second pipeline, and the shut-off valve is located between the first pipeline and the end of the second pipeline away from the hydrogen separator.

[0009] Furthermore, the device also includes a quick-cut valve; the quick-cut valve is arranged on the first pipeline.

[0010] Furthermore, the device also includes a remote temperature meter for monitoring the circulating water outlet temperature of the U-tube circulating water heater; the remote temperature meter is connected to the quick-cut valve.

[0011] Furthermore, the device also includes an automatic interlocking system for interlocking control of the quick-cut valve and the shut-off valve; the automatic interlocking system is connected to the remote temperature meter.

[0012] Furthermore, a buffer tank is connected to one end of the second pipeline away from the hydrogen separator.

[0013] According to a second aspect of an embodiment of the present application, a method for recovering nitrogen discharged from liquid nitrogen washing is provided. The method uses the apparatus described in any of the above technical solutions to recover nitrogen discharged from liquid nitrogen washing, comprising the following steps:

[0014] Liquid contaminated nitrogen is discharged from the bottom of the hydrogen separator, enters the U-tube circulating water heater through the second pipeline and the first pipeline for reheating, and obtains fuel gas; the fuel gas enters the fuel gas pipeline network and goes to the purge gas resource utilization device to recover effective gas.

[0015] Furthermore, before the liquid contaminated nitrogen is discharged from the bottom of the hydrogen separator, the following steps are also included:

[0016] Close the shut-off valve; open the control valve and the quick-cut valve.

[0017] Furthermore, the method further comprises the following steps:

[0018] When the remote temperature meter detects that the circulating water outlet temperature of the U-tube circulating water heater is lower than 5°C, the automatic interlocking system controls the quick-cut valve to close and opens the shut-off valve at the same time, sending the liquid contaminated nitrogen to the buffer tank for flash evaporation, and then entering the accident flare main pipe to be reheated with steam and then put into the flare for combustion.

[0019] Furthermore, inside the U-tube circulating water heater, the circulating water flows through the shell side, and the liquid contaminated nitrogen flows through the tube side.

[0020] Furthermore, the temperature of the liquid contaminated nitrogen is -190°C to 180°C; the temperature of the fuel gas is 10°C to 30°C.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] This invention incorporates a U-tube circulating water heater after the excess liquid nitrogen is discharged from the hydrogen separator, effectively recovering CO from the discharged nitrogen. Using this method, each unit can recover over 170 Nm³ / h of fuel gas and 100 Nm³ / h of effective gas, resulting in an annual profit exceeding 640,000 yuan and significant energy savings. Furthermore, by reducing the discharge of cold flares, steam consumption is indirectly reduced, and the perennial ice accumulation in the buffer tank is completely eliminated, significantly improving the sanitation of the buffer tank area and the ground. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0024] Figure 1 This is the overall structural diagram of the embodiment of the present application;

[0025] The reference numerals indicate:

[0026] 1-U-tube circulating water heater; 11-inlet end; 12-outlet end;

[0027] 21-first pipeline; 211-quick-cut valve; 22-second pipeline; 221-control valve; 222-shut-off valve;

[0028] 3-Remote temperature gauge;

[0029] 4-Automatic interlocking system;

[0030] 5-Hydrogen separator;

[0031] 6-Fuel gas pipeline network;

[0032] 7- Buffer tank;

[0033] 8-Accident flare master. DETAILED DESCRIPTION

[0034] In order to better understand the above technical solution, the technical solution of the embodiment of the present application is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiment of the present application and the specific features in the embodiment are detailed descriptions of the technical solution of the embodiment of the present application, rather than limitations on the technical solution of the present application. In the absence of conflict, the embodiment of the present application and the technical features in the embodiment can be combined with each other.

[0035] In view of this, according to a first aspect of an embodiment of the present application, there is provided a device for recovering nitrogen from wastewater discharged from liquid nitrogen washing, comprising a U-tube circulating water heater 1 , a first pipeline 21 and a second pipeline 22 .

[0036] like Figure 1 As shown, the inlet end 11 of the U-tube circulating water heater 1 is connected to the middle section of the second pipeline 22 through the first pipeline 21, and the outlet end 12 of the U-tube circulating water heater 1 is used to connect to the fuel gas pipeline network 6; one end of the second pipeline 22 is connected to the hydrogen separator 5; a control valve 221 is provided on the second pipeline 22, and the control valve 221 is located between the first pipeline 21 and the hydrogen separator 5; a shut-off valve 222 is also provided on the second pipeline 22, and the shut-off valve 222 is located between the first pipeline 21 and the end of the second pipeline 22 away from the hydrogen separator 5.

[0037] In actual operation, the control valve 221 is opened and the shut-off valve 222 is closed, and the excess liquid nitrogen is discharged from the bottom of the hydrogen separator 5 and enters the U-tube circulating water heater 1 through the first pipeline and the second pipeline. The U-tube circulating water heater 1 consists of a shell side and a tube side, that is, there is a U-shaped pipe passing through the entire shell inside the shell. In actual operation, the circulating water is in the shell side, and the liquid nitrogen is in the tube side. The liquid nitrogen enters the U-tube circulating water heater 1 from the inlet end 11 in the U-shaped pipe, is heated by the circulating water in the shell side and becomes gaseous fuel gas, and then flows out from the outlet end 12, enters the fuel gas pipeline network 6, and is then sent to the purge gas resource utilization device to recover the effective gas therein.

[0038] Furthermore, in one embodiment, the device further includes a quick-cut valve 211, which is disposed on the first pipeline 21. The quick-cut valve 211 is configured to allow the liquid contaminated nitrogen to enter the U-tube circulating water heater 1 or prevent the liquid contaminated nitrogen from entering the U-tube circulating water heater 1 when the control valve 221 remains open.

[0039] Furthermore, in one embodiment, the device further includes a remote temperature meter 3 for monitoring the circulating water outlet temperature of the U-tube circulating water heater 1 ; the remote temperature meter 3 is connected to the quick-cut valve 211 .

[0040] Furthermore, in one embodiment, the device further includes an automatic interlocking system 4 for interlocking control of the quick-cut valve 211 and the shut-off valve 222 ; the automatic interlocking system 4 is connected to the remote temperature meter 3 .

[0041] In actual operation, the optimal temperature of the circulating water is 35°C. Temperatures too high or too low are detrimental to the process of heating the liquid contaminated nitrogen and converting it into fuel gas. The remote thermometer 3 facilitates monitoring of the circulating water temperature and allows timely adjustments to raise or lower the water temperature. Furthermore, the remote thermometer 3 is connected to the quick-cut valve 211, and the automatic interlocking system 4 is also connected to the remote thermometer 3, enabling automatic control of the valve. When the remote thermometer 3 detects that the circulating water temperature is below 5°C, confirming that the U-tube circulating water heater 1 is not functioning properly, the automatic interlocking system 4 immediately closes the quick-cut valve 211, preventing further entry of the liquid contaminated nitrogen into the U-tube circulating water heater 1, thereby ensuring its safety. Simultaneously, the automatic interlocking system 4 opens the shut-off valve 222, allowing the liquid contaminated nitrogen discharged from the bottom of the hydrogen separator 5 to continue to be discharged through the second pipeline 22, thereby ensuring a stable liquid level within the hydrogen separator 5.

[0042] Furthermore, in one embodiment, a buffer tank 7 is connected to the end of the second pipeline 22 away from the hydrogen separator 5. When the automatic interlocking system 4 closes the quick-cut valve 211 and opens the shut-off valve 222, the liquid contaminated nitrogen enters the buffer tank 7 through the second pipeline 22 for flash evaporation, then enters the emergency flare main 8 for reheating with steam before being put into the flare for combustion. In this way, the liquid contaminated nitrogen that continues to be discharged can be processed in an emergency situation where the U-tube circulating water heater 1 cannot operate, ensuring environmental safety.

[0043] According to a second aspect of an embodiment of the present application, a method for recovering nitrogen discharged from liquid nitrogen washing is provided. The method uses the apparatus described in any of the above technical solutions to recover nitrogen discharged from liquid nitrogen washing, comprising the following steps:

[0044] Liquid contaminated nitrogen is discharged from the bottom of the hydrogen separator 5, enters the U-tube circulating water heater 1 through the second pipeline 22 and the first pipeline 21 for reheating, and obtains fuel gas; the fuel gas enters the fuel gas pipeline network 6, and goes to the purge gas resource utilization device to recover effective gas.

[0045] Furthermore, in one embodiment, before the liquid contaminated nitrogen is discharged from the bottom of the hydrogen separator 5, the following steps are further included:

[0046] Close the shut-off valve 222;

[0047] The control valve 221 and the quick-cut valve 211 are opened.

[0048] Furthermore, in one embodiment, the method further comprises the following steps:

[0049] When the remote temperature meter 3 detects that the circulating water outlet temperature of the U-tube circulating water heater 1 is lower than 5°C, the automatic interlocking system 4 controls the quick-cut valve 211 to close and opens the shut-off valve 222 at the same time, sending the liquid contaminated nitrogen to the buffer tank 7 for flash evaporation, and then entering the accident flare main pipe 8 to be reheated with steam and then put into the flare for combustion.

[0050] Furthermore, in one embodiment, inside the U-tube circulating water heater 1, the circulating water flows through the shell side, and the liquid contaminated nitrogen flows through the tube side.

[0051] Furthermore, in one embodiment, the temperature of the liquid contaminated nitrogen is -190°C to 180°C; and the temperature of the fuel gas is 10°C to 30°C.

[0052] This method has all the beneficial effects of the equipment in the above technical solution, which will not be described in detail here.

[0053] In the present invention, terms such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Terms such as "mounted," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" can refer to a fixed connection, a removable connection, or an integral connection; "connected" can refer to a direct connection or an indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0054] In the description of the present invention, it should be understood that the directions or positional relationships indicated by terms such as "up", "down", "left", "right", "front" and "back" are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0055] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0056] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A liquid nitrogen washing and waste nitrogen recovery device, characterized in that: include: A U-tube circulating water heater (1), a first pipeline (21), a second pipeline (22) and a remote temperature meter (3); The inlet end (11) of the U-tube circulating water heater (1) is connected to the middle section of the second pipeline (22) via the first pipeline (21), and the outlet end (12) of the U-tube circulating water heater (1) is used to connect to the fuel gas pipeline network (6); One end of the second pipeline (22) is connected to the hydrogen separator (5); A control valve (221) is provided on the second pipeline (22), and the control valve (221) is located between the first pipeline (21) and the hydrogen separator (5); A shut-off valve (222) is further provided on the second pipeline (22), and the shut-off valve (222) is located between the first pipeline (21) and an end of the second pipeline (22) away from the hydrogen separator (5); A buffer tank (7) is connected to one end of the second pipeline (22) away from the hydrogen separator (5); A quick-cut valve (211) is provided on the first pipeline (21), and the remote temperature meter (3) is connected to the quick-cut valve (211) for monitoring the circulating water outlet temperature of the U-tube circulating water heater (1); The remote temperature meter (3) is connected to an automatic interlocking system (4) for interlocking control of the quick-cut valve (211) and the shut-off valve (222).

2. A method for recovering nitrogen from wastewater discharged from liquid nitrogen washing, characterized in that: The method of using the device as claimed in claim 1 to recover the nitrogen discharged from liquid nitrogen washing comprises the following steps: Liquid contaminated nitrogen is discharged from the bottom of the hydrogen separator (5), enters the U-tube circulating water heater (1) through the second pipeline (22) and the first pipeline (21) for reheating, and obtains fuel gas; The fuel gas enters the fuel gas pipe network (6) and goes to the exhaust gas resource utilization device to recover the effective gas; When the remote temperature meter (3) detects that the circulating water outlet temperature of the U-tube circulating water heater (1) is lower than 5°C, the quick-cut valve (211) is closed and the cut-off valve (222) is opened to send the liquid contaminated nitrogen to the buffer tank (7).

3. The method according to claim 2, characterized in that Before the liquid contaminated nitrogen is discharged from the bottom of the hydrogen separator (5), the following steps are also included: closing the shut-off valve (222); The control valve (221) and the quick-cut valve (211) are opened.

4. The method according to claim 2, characterized in that The following steps are also included: The automatic interlocking system (4) controls the quick-cut valve (211) to close and simultaneously opens the cut-off valve (222); After the liquid contaminated nitrogen is sent to the buffer tank (7), the liquid contaminated nitrogen flashes through the buffer tank (7) and then enters the emergency flare main pipe (8) to be reheated with steam and then put into the flare for combustion.

5. The method according to claim 2, characterized in that Inside the U-tube circulating water heater (1), circulating water flows through the shell side, and the liquid dirty nitrogen flows through the tube side.

6. The method according to claim 2, characterized in that The temperature of the liquid contaminated nitrogen is -190°C to 180°C; The temperature of the fuel gas is 10°C-30°C.

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