Establishment of the dry gas seal for the syngas compressor

The acceptance criterion for nitrogen purging is the oxygen content

I don’t know what the outlet pressure of the syngas compressor is; I will therefore prepare a description of the dry gas seal system assuming a pressure of 6.85 Mpa (this procedure is for reference only). A. Primary seal procedure: When the compressor is started or stopped, backup high-pressure nitrogen gas (at 6.0 Mpa and at room temperature) is used as the source of gas for the primary seal. This gas enters the compressor’s primary seal system via the G1 flange port, passes through a fine filter, and after flow control by a flow meter, it goes directly into the primary seal chambers on both sides of the compressor. During normal operation, the process gas from the third outlet of the compressor, with a pressure of 6.85 MPa and a temperature of 46°C, is used as the source gas for the primary seal. This gas enters the primary seal circuit via flange connections, is filtered by a fine filter, and then flows directly into the primary seal chambers at both ends of the compressor after passing through a flow meter. The main function of the primary seal gas is to prevent dirty gases inside the compressor from contaminating the primary seal surface. As the compressor rotates at high speed, this gas is pumped through the spiral grooves on the primary seal surface into the primary seal flare chamber, thereby creating a rigid air film between the seal surfaces that serves to lubricate and cool them. The vast majority of this gas enters the machine through the labyrinth at the compressor’s shaft end, with only a very small portion entering the primary seal flare chamber through the sealed end face. B. Secondary sealing process: The secondary sealing gas is high-pressure nitrogen or gas from a post-isolation system. a. (Described using the post-isolation system for the secondary sealing gas) Low-pressure nitrogen at room temperature and around 0.6 MPa.G is used as the source of gas for secondary sealing; this gas enters the sealing system through flange ports, is filtered by filters, and then part of it is regulated to a flow rate of 6 Nm3/h by a flow meter before entering the secondary sealing chambers at both ends of the compressor ； b. (High-pressure nitrogen is used as the secondary sealing gas.) Normal-temperature, 8.1 MPa high-pressure nitrogen is employed as the source of gas for the secondary sealing; this gas enters the secondary sealing circuit after passing through a ball valve, is filtered by a filter, and then its pressure is adjusted to 0.6 MPa using a self-regulating valve. It subsequently flows into the secondary sealing chambers at both ends of the compressor via two flow control orifice plates. The secondary sealing gas serves to prevent a small amount of fluid that leaks from the primary sealing surface from reaching the secondary sealing surface, thereby ensuring the safe and reliable operation of the secondary seal. Most of this gas, along with the small amount of fluid that leaks from the primary sealing surface, enters the flare vent line through the primary sealing discharge chamber, while only a small portion of the gas enters the secondary sealing discharge chamber before being vented at a higher point ； C. Post-isolation gas system: Normal-temperature nitrogen at a low pressure of 0.6 MPa is used as the source for the post-isolation gas. This gas enters the post-isolation gas pipeline after passing through a shut-off valve; its pressure is then adjusted to 0.14 MPa using a self-regulating valve (throttle valve), and it proceeds directly into the compressor’s post-isolation gas sealing chamber via two flow control orifice plates. The main function of the post-isolation gas is to isolate the lubricating oil in the bearings, thereby preventing the secondary sealing surfaces from being contaminated by the oil vapor from the compressor bearings. Part of this gas is vented at a high point along with the small amount of nitrogen that leaks from the secondary sealing surface, while the other part is vented through the rear sealing comb teeth via the bearing lubrication oil vent cap. D. Flare line pipeline process: The majority of the nitrogen, which serves as the sealing gas for the compressor, along with a small amount of gas that leaks from the primary sealing surface, enter the flare line through flow meters and two check valves. Afterwards, (after the pressure is adjusted to 0.19 Mpa using a throttle valve), it is sent to the flare line area

Nitrogen purging of the compressor process gas system (not required for air testing). (1) Open the nitrogen shut-off valve used for purging at the inlet of the first stage of the compressor, and introduce nitrogen into the compressor’s process gas circuit to carry out nitrogen purging； (2) Open the drain valves for the compressor cylinder, the low-point drain valves of the process gas pipelines, as well as the drain valves and vent valves of the intercooler and condenser ； (3) When the oxygen content analyzed at the compressor outlet is below 0.2%, nitrogen displacement is satisfactory ； (4) Shut off the drain lines in each compressor cylinder, the drain lines at the low points of the process gas pipelines, the high-point discharge outlets, and the vent valves of the compressors ；

The standard for successful nitrogen displacement should be the oxygen content

It seems you’re about the same as I was when I first started in this field. Don’t rush; different units and factories have different requirements. Just remember the general steps mentioned above, and once you gain a thorough understanding of your specific unit, you will be in control of it. Don’t ask for any detailed metrics; it’s just for reference. :handshake

I’ll provide you with a plan for putting our unit’s dry gas sealing system into operation: (the tag numbers may vary) 1) Verify that the N2 gas system is functioning properly, with a pressure of 700 KPa. 2) Confirm that the sealing air pressurization device system has passed the trial run and is in standby mode. 3) Open the inlet and outlet isolation valves of 103-JL2L1A/L2A, close the drain valve, and close the inlet and outlet isolation valves of 103-JL2L1B/L2B. 4) Open the isolation gas control valve PCV-4728 and the upstream and downstream shut-off valves, and close the bypass valve. 5) Open the isolation air PIT-4729 pressure guide tube isolation valve, and put PI-4729 into operation. 6) Connect the instruments and put into use the filter pressure difference meters PDI-4710 and PDI-4720 for the low-pressure and high-pressure cylinders. Activate PDV-4711 and PDV-4721, set the pressure difference for PDV-4711/4721 at 90/105 KPa, and close the bypass valve. Close the shut-off valves for the main seal air inlet flow rates FI-4712/4713, FI-4722/4723 of the low and high pressure cylinders. 7) Open the pressure gauges, differential pressure gauges, pressure switches, and root cut-off valves of the 103-J dry gas seal system. Close all vent valves and drain valves. 8) Open the seal pressurization unit outlet to the 103-JHP/LP seal gas system isolation valve. 9) After the buffer nitrogen is put into use, observe the operation of PCV-4728 and verify that the indication value of PI-4729 is between 50 and 70 KPa. 10) When 103-J is in operation, the sealing pressure-raising device activates; PDV-4721 adjusts flexibly, with a pressure difference of 90 KPa. The PDI-4710 reading is less than 35 KPa. PDV-4721 has flexible regulation, with a pressure difference of 105 KPa. The PDI-4720 reading is less than 35 KPa. 11) After the sealing system was put into operation, a comprehensive inspection was carried out on the 103-J sealing system to ensure that the values indicated by FI-4712/4713 were not greater than 254.7 Nm3/h ； The leakage gas FI4714/4715 value for the low-pressure cylinder shall not exceed 4.2 Nm3/h ； The indicated values for FI-4722/4723 should not be greater than 254.0 Nm3/h ； The leakage gas FI-4724/4725 for the high-pressure cylinder should indicate a value not exceeding 12.21 Nm3/h. 12) After the sealing system is put into operation, a leak check should be conducted on the entire system to ensure that there are no leaks. 13) Before starting up 103-J, open the supply isolation valve for the outlet seal air of 103-JHP/LP.

1. Isolation gas, 2. Secondary sealing gas, 3. Main sealing gas applied before startup. (If the nitrogen pressure is lower than the cylinder pressure before driving, pay attention to the operation of the pressure booster.)