Liquid nitrogen wash molecular sieve advanced cooling system

Abstract

The utility model discloses an advanced cooling system for a liquid nitrogen wash molecular sieve, which is characterized in that a liquid nitrogen spray head is arranged on a pipeline between a regenerated nitrogen inlet pipe and the liquid nitrogen wash molecular sieve, an inlet of the liquid nitrogen spray head is connected with a liquid nitrogen pipe, an adjusting valve is arranged on the liquid nitrogen pipe, and a temperature sensor is arranged on a regenerated nitrogen outlet pipe; and the signal output end of the temperature sensor is electrically connected with the signal input end of the regulating valve. Meanwhile, the methanol washing device is started at the same time, the methanol washing device and the methanol washing device are started synchronously, after the temperature of crude hydrogen at an outlet of the methanol washing device meets the requirement, gas can be guided into the cold box through direct pressurization, the cooling step is omitted, and the starting efficiency is greatly improved; the temperature of nitrogen discharged by the liquid nitrogen wash molecular sieve is detected through the temperature sensor, and the liquid nitrogen flow can be adjusted according to the temperature measured by the temperature sensor, so that the temperature of the liquid nitrogen wash molecular sieve can be adjusted to-60 DEG C.

Description

Technical field:

[0001] The utility model relates to the field of gasification furnace gas purification, in particular to a liquid nitrogen washed molecular sieve advance cooling system. Background technology:

[0002] In the process of synthetic ammonia, the gasifier gas is first processed by the conversion device to convert CO and water into CO2 and H2, and then the generated mixed gas is sent to the methanol washing device of the synthetic ammonia production system to remove CO2 and H2S in the mixed gas. The purified gas is sent to the liquid nitrogen washing device for further purification. The liquid nitrogen washing device mainly consists of two parts, namely molecular sieve and cold box. The purified gas from methanol washing is first sent to the molecular sieve to remove trace CO2, CH3OH and water in the gas, and then sent to the cold box to remove trace CO and CH4 to obtain pure H2 for synthetic ammonia.

[0003] During the start-up phase of the synthetic ammonia production system, since the regenerated molecular sieve is at room temperature, it is necessary to cool the molecular sieve to -60°C, which is close to the temperature of the cold box, before it can be connected to the production system for normal production. Currently, the molecular sieve is cooled using purified gas, i.e., crude hydrogen, sent from the methanol washing device. After start-up, it takes 4-6 hours for the crude hydrogen at the outlet of the methanol washing device to drop to -60°C. During this process, the molecular sieve has no cold source for cooling, and can only start cooling when the crude hydrogen at the outlet of the methanol washing device meets -60°C. In addition, the cooling process of the molecular sieve also takes 3-4 hours, and the system start-up time is relatively long. Before the molecular sieve is cooled to -60°C, all the crude hydrogen sent to the molecular sieve for cooling cannot be sent to the cold box for production, and can only be sent to the flare for combustion, resulting in a large amount of hydrogen. Utility model content:

[0004] The utility model aims to provide a liquid nitrogen-washed molecular sieve advance cooling system.

[0005] The utility model is implemented by the following technical solutions:

[0006] A liquid nitrogen washed molecular sieve precooling system comprises a liquid nitrogen washed molecular sieve, wherein the top inlet of the liquid nitrogen washed molecular sieve is respectively connected to a regeneration nitrogen inlet pipe and a purification gas pipe through pipelines, the bottom inlet of the liquid nitrogen washed molecular sieve is respectively connected to a crude hydrogen pipe and a regeneration nitrogen outlet pipe through pipelines, a liquid nitrogen nozzle is installed on the pipeline between the regeneration nitrogen inlet pipe and the liquid nitrogen washed molecular sieve, the inlet of the liquid nitrogen nozzle is connected to a liquid nitrogen pipe, a regulating valve is installed on the liquid nitrogen pipe, a temperature sensor is installed on the regeneration nitrogen outlet pipe, and a signal output end of the temperature sensor is electrically connected to a signal input end of the regulating valve.

[0007] Preferably, a cut-off valve is installed on the liquid nitrogen pipe.

[0008] Preferably, the bottom inlet of the liquid nitrogen-washed molecular sieve is also connected to a pressure relief pipe, and a pressure relief valve is installed on the pressure relief pipe.

[0009] The utility model has the advantages that the methanol washing device is started at the same time, and the two are carried out synchronously. After the crude hydrogen temperature at the outlet of the methanol washing device reaches the requirement, it can be directly pressurized to guide the gas into the cold box, omitting the cooling step, which greatly improves the start-up efficiency; and the temperature of the nitrogen discharged from the liquid nitrogen washing molecular sieve is detected by the temperature sensor, and the liquid nitrogen flow rate can be adjusted according to the temperature measured by the temperature sensor, so as to ensure that the liquid nitrogen washing molecular sieve can be adjusted to a temperature of -60°C. Description of the drawings:

[0010] Figure 1 It is a structural schematic diagram of the utility model;

[0011] Figure 2 This is a schematic diagram of the use of liquid nitrogen to wash the molecular sieve for early cooling.

[0012] In the figure: liquid nitrogen washed molecular sieve 1, regenerated nitrogen inlet pipe 2, purified gas pipe 3, crude hydrogen pipe 4, regenerated nitrogen outlet pipe 5, liquid nitrogen nozzle 6, liquid nitrogen pipe 7, regulating valve 8, temperature sensor 9, shut-off valve 10, pressure relief pipe 11, pressure relief valve 12. Specific implementation method:

[0013] like Figure 1 As shown, a liquid nitrogen washed molecular sieve pre-cooling system comprises a liquid nitrogen washed molecular sieve 1, the top inlet of the liquid nitrogen washed molecular sieve 1 is respectively connected to the regeneration nitrogen inlet pipe 2 and the purification gas pipe 3 through pipelines, the bottom inlet of the liquid nitrogen washed molecular sieve 1 is respectively connected to the crude hydrogen pipe 4 and the regeneration nitrogen outlet pipe 5 through pipelines, a liquid nitrogen nozzle 6 is installed on the pipeline between the regeneration nitrogen inlet pipe 2 and the liquid nitrogen washed molecular sieve 1, the inlet of the liquid nitrogen nozzle 6 is connected to the liquid nitrogen pipe 7, a regulating valve 8 is installed on the liquid nitrogen pipe 7, a temperature sensor 9 is installed on the regeneration nitrogen outlet pipe 5, and the signal output end of the temperature sensor 9 is electrically connected to the signal input end of the regulating valve 8;

[0014] The liquid nitrogen washed molecular sieve 1 is used in a group of two, one of which is used to purify CO2, CH3OH and water in the crude hydrogen, while the other is used for regeneration; after the synthetic ammonia production system is started up, only one liquid nitrogen washed molecular sieve 1 is put into use, so when pre-cooling is performed, only one liquid nitrogen washed molecular sieve 1 needs to be connected, and the other liquid nitrogen washed molecular sieve 1 is not connected;

[0015] When the liquid nitrogen washed molecular sieve 1 is cooled in advance, the valves connecting the liquid nitrogen washed molecular sieve 1 with the purified gas pipe 3 and the crude hydrogen gas pipe 4 are closed, and the valves connecting the liquid nitrogen pipe 7, the regenerated nitrogen inlet pipe 2 and the regenerated nitrogen outlet pipe 5 are opened. Figure 2As shown, the regenerated nitrogen is injected into the liquid nitrogen washed molecular sieve 1 from the regenerated nitrogen inlet pipe 2, with a flow rate of 3000Nm 3 / h, liquid nitrogen from the air separation unit is sent from the liquid nitrogen pipe 7 to the liquid nitrogen nozzle 6, atomized by the liquid nitrogen nozzle 6 and mixed with the regenerated nitrogen in the pipeline, reducing the temperature of the regenerated nitrogen to form low-temperature nitrogen, and then cooling the liquid nitrogen-washed molecular sieve 1, and the cooled nitrogen is discharged from the regenerated nitrogen outlet pipe 5; at the same time, the methanol washing unit is started at the same time, and the two are carried out synchronously. After the temperature of the crude hydrogen at the outlet of the methanol washing unit reaches the requirement, it can be directly pressurized and guided into the cold box, omitting the cooling step, which greatly improves the start-up efficiency;

[0016] Since the temperature range of the liquid nitrogen-washed molecular sieve 1 during normal production and operation is -40 to -60°C, and the molecular sieve filler is very likely to be damaged or crushed when it is below -70°C for a long time, the purification effect of the liquid nitrogen-washed molecular sieve 1 is reduced; although there is a temperature detection before the low-temperature nitrogen enters the liquid nitrogen-washed molecular sieve 1, after the liquid nitrogen-washed molecular sieve 1 is sent in, the temperature of the liquid nitrogen-washed molecular sieve 1 will increase after the low-temperature nitrogen cools the liquid nitrogen-washed molecular sieve 1. Therefore, the temperature measurement before the liquid nitrogen-washed molecular sieve 1 cannot reflect the actual temperature of the liquid nitrogen-washed molecular sieve 1, and the problem of the liquid nitrogen-washed molecular sieve 1 being too high or too low often occurs; during the liquid nitrogen-washed molecular sieve When the sub-sieve 1 is cooled in advance, the temperature sensor 9 is used to detect the temperature of the nitrogen discharged from the liquid nitrogen-washed molecular sieve 1. After the low-temperature nitrogen passes through the liquid nitrogen-washed molecular sieve 1, its temperature is almost the same as that of the liquid nitrogen-washed molecular sieve 1. The liquid nitrogen flow rate can be adjusted according to the temperature measured by the temperature sensor 9. When the temperature sensor 9 detects that the temperature is lower than -63°C, the opening of the regulating valve 8 is adjusted to 10%. When the temperature sensor 9 detects that the temperature is higher than -43°C, the opening of the regulating valve 8 is adjusted to 100%. In this range, the opening of the regulating valve 8 is adjusted by 10% every 2.5°C to ensure that the temperature of the liquid nitrogen-washed molecular sieve 1 can be adjusted to -60°C.

[0017] A shut-off valve 10 is installed on the liquid nitrogen pipe 7. After the temperature of the crude hydrogen at the outlet of the methanol washing device reaches the requirement, the shut-off valve 10 is closed to block the liquid nitrogen, and the valve connecting the liquid nitrogen washing molecular sieve 1 with the purification gas pipe 3 and the crude hydrogen gas pipe 4 is opened, and the valve connecting the liquid nitrogen pipe 7, the regeneration nitrogen inlet pipe 2 and the regeneration nitrogen outlet pipe 5 is closed, and the liquid nitrogen washing molecular sieve 1 is pressurized. After the pressurization is completed, the gas is guided into the cold box.

[0018] The bottom inlet of the liquid nitrogen washed molecular sieve 1 is also connected to a pressure relief pipe 11 , on which a pressure relief valve 12 is installed. The pressure relief pipe 11 is used for pressure relief when switching between two liquid nitrogen washed molecular sieves 1 , and pressure relief is performed by opening the pressure relief valve 12 .

[0019] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A liquid nitrogen washed molecular sieve precooling system, comprising a liquid nitrogen washed molecular sieve, wherein the top inlet of the liquid nitrogen washed molecular sieve is connected to a regeneration nitrogen inlet pipe and a purification gas pipe through pipelines, and the bottom inlet of the liquid nitrogen washed molecular sieve is connected to a crude hydrogen pipe and a regeneration nitrogen outlet pipe through pipelines, characterized in that: A liquid nitrogen nozzle is installed on the pipeline between the regeneration nitrogen inlet pipe and the liquid nitrogen washed molecular sieve, the inlet of the liquid nitrogen nozzle is connected to the liquid nitrogen pipe, a regulating valve is installed on the liquid nitrogen pipe, a temperature sensor is installed on the regeneration nitrogen outlet pipe, and a signal output end of the temperature sensor is electrically connected to a signal input end of the regulating valve.

2. A liquid nitrogen washed molecular sieve pre-cooling system according to claim 1, characterized in that: A cut-off valve is installed on the liquid nitrogen pipe.

3. A liquid nitrogen washed molecular sieve pre-cooling system according to claim 1 or 2, characterized in that: The bottom inlet of the liquid nitrogen-washed molecular sieve is also connected to a pressure relief pipeline, and a pressure relief valve is installed on the pressure relief pipeline.

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