Molecular sieve regeneration device for liquid nitrogen wash purified gas of synthetic ammonia production device

Abstract

The utility model relates to a molecular sieve regeneration device for liquid nitrogen wash purified gas of a synthetic ammonia production device. In the device, a low-pressure nitrogen pipeline is connected with a molecular sieve adsorber, the bottom of the molecular sieve adsorber is connected with a nitrogen heater through a pipeline, and the nitrogen heater is connected to a phosphoric acid device hot blast stove through a fuel gas pipeline. The top of the molecular sieve adsorber is connected with the liquid nitrogen washing cold box. A track ball valve I is arranged on a connecting pipeline between the bottom of the molecular sieve adsorber and the nitrogen heater; and a regulating valve II is arranged on the nitrogen heater and the fuel gas pipeline. According to the utility model, high-concentration CO adsorbed by the molecular sieve is sent to the hot blast stove of the phosphoric acid device for combustion at the initial stage of the regeneration preheating stage of the liquid nitrogen wash molecular sieve, thereby improving the automatic control level of molecular sieve regeneration programs; the problem of fluctuation of a low first washing device during regeneration of the molecular sieve is effectively solved, the problem that a combustible poisonous gas detector gives an alarm due to direct emptying of high CO during regeneration is thoroughly solved, and part of energy is recycled.

Description

TECHNICAL FIELD

[0001] The utility model relates to synthetic ammonia device liquid nitrogen washing gas purification technology, especially relates to a molecular sieve regeneration method. BACKGROUND

[0002] The purified gas sent by the low temperature methanol washing device enters the nitrogen washing tower in the liquid nitrogen washing cold box after removing CO2, CH3OH by the molecular sieve adsorber, and the qualified fresh synthesis gas is prepared. The molecular sieve adsorber has two, one adsorbs and one regenerates, and is circulated by the molecular sieve automatic control program, and the adsorption and regeneration cycle of each molecular sieve is 48 hours, and a total of forty-two steps. Although the internal pressure of the molecular sieve adsorber is decompressed to a micro positive pressure in the third step and the twenty-fourth step of the automatic control program, a large amount of CO gas still remains in the equipment, and a large amount of CO gas enters the low temperature methanol washing hydrogen sulfide concentration tower together with nitrogen gas in the early stage of using nitrogen gas for preheating, and after being washed in the tail gas washing tower together with the CO2 gas resolved out of the hydrogen sulfide concentration tower, is sent to the flare CO2 emptying cylinder for emptying. The more CO entrained in the emptying gas has no order diffusion due to the similar density and air, triggers the alarm of the combustible and toxic detector in each device area, causes the peculiar smell in the production area, and has a great safety risk. Due to the defects of the automatic control program in the process design, the problem almost becomes a common problem in the liquid nitrogen washing device in the industry. SUMMARY

[0003] The utility model discloses a kind of molecular sieve regeneration devices of synthetic ammonia production device liquid nitrogen washing purified gas. In the device, low-pressure nitrogen gas pipeline is connected with molecular sieve adsorber, molecular sieve adsorber bottom is connected with nitrogen heater by pipeline, and nitrogen heater is connected to phosphoric acid device hot blast furnace by fuel gas pipeline.

[0004] Molecular sieve adsorber is the adsorber of two-stage molecular sieve adsorption device composition, and realizes the effect of one open and one standby in the operation process.

[0005] Molecular sieve adsorber top is connected with liquid nitrogen washing cold box;

[0006] Molecular sieve adsorber bottom is provided with pipeline directly connected to low temperature methanol washing purified gas and fuel gas pipeline.

[0007] Track ball valve one is arranged on the connecting pipeline of molecular sieve adsorber bottom and nitrogen heater.

[0008] Adjusting valve two is arranged on nitrogen heater and fuel gas pipeline.

[0009] Nitrogen heater is connected with adjusting valve one by preheating pipeline one, and adjusting valve one is connected with hydrogen sulfide concentration tower lower part import by preheating pipeline two.

[0010] The liquid nitrogen washing molecular sieve regeneration preheating stage is initially opened to a certain opening degree by adjusting valve two, and then adjusting valve one is closed, high concentration CO in the saturated adsorbed molecular sieve is first discharged to the hot blast furnace of the phosphoric acid device for combustion, adjusting valve two is closed after 30 minutes, adjusting valve one is opened, adjusting valve three is closed, and the displacement regenerated nitrogen is sequentially sent into the hydrogen sulfide concentration tower, the tail gas washing tower and the venting cylinder to avoid the combustible and toxic gas directly discharged through the venting cylinder, to realize the intrinsic safety and effectively purify the site environment.

[0011] The top outlet of the hydrogen sulfide concentration tower is connected with the heat exchanger, the heat exchanger is connected with the lower inlet of the tail gas washing tower through a pipeline, and the top outlet of the tail gas washing tower is connected with the venting cylinder.

[0012] The low-pressure nitrogen pipeline is connected with the preheating pipeline two, and adjusting valve three is arranged on the pipeline.

[0013] In the initial stage of the liquid nitrogen washing molecular sieve regeneration preheating stage, adjusting valve three is adjusted to control the flowmeter two to display about 6000 Nm3 / h, so that the low-pressure nitrogen flow is prevented from being too small to cause the operating condition fluctuation in the hydrogen sulfide concentration tower.

[0014] By increasing the adjusting valve two device step, closing adjusting valve three and opening adjusting valve one in the original regeneration automatic control program preheating stage, the valve linear stroke control parameter is increased, and the production stability of the low methanol washing device during the liquid nitrogen washing regeneration is ensured by orderly and stable switching.

[0015] The connecting pipeline of the low-pressure nitrogen pipeline and the molecular sieve adsorber is provided with flowmeter one and track ball valve two.

[0016] The low-pressure nitrogen passes through flowmeter one through the pipeline, and the flowmeter one is controlled to display 2500-3500 Nm3 / h in the initial stage of the liquid nitrogen washing molecular sieve preheating by adjusting the opening degree of adjusting valve two, so that the low-pressure nitrogen flow is prevented from being too large to affect the normal combustion of the hot blast furnace system. 3 / h, to prevent the low-pressure nitrogen flow from being too large to affect the normal combustion of the hot blast furnace system.

[0017] The connecting pipeline of the preheating pipeline two and the lower inlet of the hydrogen sulfide concentration tower is provided with flowmeter two.

[0018] The utility model discloses the beneficial effect lies in:

[0019] (1) the mixed gas containing high concentration CO in the nitrogen preheating initial stage of the molecular sieve regeneration process is discharged to the hot blast furnace of the phosphoric acid device for combustion, effectively solving the safety risk of the combustible and toxic gas detection instrument alarm caused by the high concentration CO gas in the CO2 gas of the low-temperature methanol washing venting, and affecting the environmental protection emission index.

[0020] (2) In the original 42-step automatic program, one step is added after the fifth step and the twenty-sixth step respectively, that is, opening the regulating valve two, the regulating valve three, and closing the regulating valve one, the step running time is 30 min, which improves the automatic control level of the molecular sieve regeneration program.

[0021] (3) The stroke parameters of the original valve switching are added through the new step and device, and the production stability of the low-methanol washing device during the liquid nitrogen washing regeneration is ensured through orderly and stable switching. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A liquid nitrogen washing purified gas molecular sieve regeneration device of a synthetic ammonia production device.

[0023] In the figure: molecular sieve adsorber 1, nitrogen heater 2, flow meter one 3, regulating valve two 4, phosphoric acid device hot blast furnace 5, track ball valve one 6, regulating valve one 7, low-pressure nitrogen 8, regulating valve three 9, flow meter two 10, hydrogen sulfide concentration tower 11, heat exchanger 12, tail gas washing tower 13, liquid nitrogen washing cold box 14, venting cylinder 15, low-temperature methanol washing purified gas 16, preheating pipeline one 17, preheating pipeline two 18, track ball valve two 19, track ball valve three 20, track ball valve four 21, shut-off valve 22. DETAILED DESCRIPTION

[0024] The technical solutions in the patent will be described clearly and completely in combination with the specific embodiments of the patent. The embodiments are only a part of the embodiments of the patent, not all the embodiments. Based on the embodiments in the patent, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the patent.

[0025] Embodiment 1

[0026] A liquid nitrogen washing purified gas molecular sieve regeneration device of a synthetic ammonia production device, the low-pressure nitrogen pipeline 8 is connected with the molecular sieve adsorber 1, the bottom of the molecular sieve adsorber 1 is connected with the nitrogen heater 2 through a pipeline, and the nitrogen heater 2 is connected to the phosphoric acid device hot blast furnace through a fuel gas pipeline 5.

[0027] The molecular sieve adsorber 1 is an adsorber composed of two-stage molecular sieve adsorption devices, which realizes the effect of one open and one standby during operation.

[0028] The top of the molecular sieve adsorber 1 is connected with the liquid nitrogen washing cold box 14.

[0029] The bottom of the molecular sieve adsorber 1 is provided with a pipeline directly connected to the low-temperature methanol washing purified gas 16 and a fuel gas pipeline 5.

[0030] A track ball valve 6 is installed on the connecting pipe between the bottom of the molecular sieve adsorber 1 and the nitrogen heater 2.

[0031] A regulating valve 4 is installed on the nitrogen heater 2 and the fuel gas pipeline 5.

[0032] Nitrogen heater 2 is connected to regulating valve 7 via preheating pipeline 17, and regulating valve 7 is connected to the lower inlet of hydrogen sulfide concentration tower 11 via preheating pipeline 2 18.

[0033] The top outlet of the hydrogen sulfide concentration tower 11 is connected to the heat exchanger 12, the heat exchanger 12 is connected to the lower inlet of the tail gas scrubbing tower 13 through a pipe, and the top outlet of the tail gas scrubbing tower 13 is connected to the venting cylinder 15.

[0034] The low-pressure nitrogen pipeline 8 is connected to the preheating pipeline 18, and a regulating valve 9 is installed on the pipeline.

[0035] A flow meter 3 and a track ball valve 19 are installed on the connecting pipe between the low-pressure nitrogen pipeline 8 and the molecular sieve adsorber 1.

[0036] A flow meter 210 is installed on the connecting pipe between the preheating pipeline 218 and the lower inlet of the hydrogen sulfide concentration tower 11.

[0037] Example 2

[0038] The following process is performed using the apparatus of Example 1: 5.5MPa low-temperature methanol wash purified gas enters molecular sieve adsorber 1. The molecular sieves in molecular sieve adsorber 1 completely adsorb harmful components such as CO2 and CH3OH in the purified gas. The purified gas then enters liquid nitrogen washing cold box 14 for further treatment. After the molecular sieves in one molecular sieve adsorber 1 become saturated, regeneration begins, while the other molecular sieve adsorber continues adsorption. First, the 5.5MPa purified gas in the regenerated molecular sieve adsorber is depressurized to below 50KPa in the flare main. Then, track ball valves 2-19, 3-20, 4-21, shut-off valve 22, 1-6, and regulating valve 2-4 are opened, while regulating valve 7 is closed. Flow meter 3 displays and controls the flow rate at 2500-3500 Nm. 3 At approximately [per hour], low-pressure nitrogen gas 8 enters the molecular sieve adsorber 1 for preheating and replacement, and then is sent to the hot air furnace 5 of the phosphoric acid unit. Simultaneously with the above operations, regulating valve 3 (9) is opened, and flow meter 2 (10) displays approximately 6000 Nm³ / h, supplying the low-temperature methanol-washed hydrogen sulfide concentration tower 11. After 30 minutes, regulating valve 2 (4) is slowly closed and regulating valve 3 (9) is closed by adjusting the valve stroke. Based on the flow rate, regulating valve 1 (7) is continuously opened to introduce regeneration gas into the low-temperature methanol-washed hydrogen sulfide concentration tower, and the molecular sieve regeneration process continues.

Claims

1. A liquid nitrogen purge gas molecular sieve regeneration apparatus for a synthetic ammonia production plant, characterized by, The low-pressure nitrogen pipeline (8) is connected with the molecular sieve adsorber (1), the bottom of the molecular sieve adsorber (1) is connected with the nitrogen heater (2) through a pipeline, and the nitrogen heater (2) is connected to the hot blast furnace of the phosphoric acid device through the fuel gas pipeline (5).

2. The ammonia production plant LNG purge molecular sieve regeneration unit of claim 1, wherein, The molecular sieve adsorber (1) is an adsorber composed of two-stage molecular sieve adsorption devices, and realizes the effect of one open and one standby during operation.

3. The ammonia production plant LNG purge molecular sieve regeneration unit of claim 2, wherein, The top of the molecular sieve adsorber (1) is connected with the liquid nitrogen washing cold box (14); The bottom of the molecular sieve adsorber (1) is provided with a pipeline directly connected to the low-temperature methanol washing purified gas (16) and a pipeline connected to the fuel gas pipeline (5).

4. The ammonia production plant LNG purge molecular sieve regeneration unit of claim 1, wherein, The connecting pipeline of the bottom of the molecular sieve adsorber (1) and the nitrogen heater (2) is provided with a track ball valve one (6); The nitrogen heater (2) is provided with an adjusting valve two (4) on the fuel gas pipeline (5).

5. The ammonia production plant LNG purge molecular sieve regeneration unit of claim 1, wherein, The nitrogen heater (2) is connected with the adjusting valve one (7) through the preheating pipeline one (17), and the adjusting valve one (7) is connected with the lower inlet of the hydrogen sulfide concentration tower (11) through the preheating pipeline two (18).

6. The ammonia production plant LNG purge molecular sieve regeneration unit of claim 5, wherein, The top outlet of the hydrogen sulfide concentration tower (11) is connected with the heat exchanger (12), the heat exchanger (12) is connected with the lower inlet of the tail gas washing tower (13) through a pipeline, and the top outlet of the tail gas washing tower (13) is connected with the venting cylinder (15).

7. The ammonia production plant LNG purge molecular sieve regeneration unit of claim 6, wherein, The low-pressure nitrogen pipeline (8) is connected with the preheating pipeline two (18), and is provided with an adjusting valve three (9) on the pipeline.

8. The ammonia production plant LNG purge molecular sieve regeneration unit of claim 5, wherein, The connecting pipeline of the low-pressure nitrogen pipeline (8) and the molecular sieve adsorber (1) is provided with a flowmeter one (3) and a track ball valve two (19). The connecting pipeline of the preheating pipeline two (18) and the lower inlet of the hydrogen sulfide concentration tower (11) is provided with a flowmeter two (10).

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