Gas treatment unit BPG-50 is designed for gas treatment (fuel, pulse, buffer, etc.) and is an auxiliary unit for operation of the main equipment of booster compressor station (BCS)
Main parts of BPG-50
BPG is located in a block-modular building, which includes:
- process room;
- coolant preparation room;
- Instrumentation, control, and automation equipment;
- ventilation chamber.
The process room contains the following process units:
- gas purification unit (gas inlet No. 1),
- gas flow measurement unit,
- gas heating unit,
- pressure reduction unit,
- gas flow measurement unit (outlet No. 1 and No. 2),
- pressure reduction unit (gas inlet No. 2 and No. 3),
- gas purification unit,
- gas heating unit,
- flow measurement unit,
- flow measurement unit,
- pulse gas treatment unit,
- gas pressure reduction unit of the 1st stage for auxiliaries,
- gas pressure reduction unit of the 2nd stage for auxiliaries,
- gas flow measurement unit.
Operating principle of gas treatment unit BPG-50
Fuel gas treatment
Natural gas from inlet No. 1 enters gas purification unit No. 1. The inlet gas parameters (pressure and temperature) are monitored at the inlet manifold. On the basis of the received data, the valves are controlled before the BPK inlet: when the gas supply to the inlet manifold is lower than the operating pressure (Рop=4.3 ... 5.6 MPa) by 20% within 10 seconds, the inlet valve of the BPG is closed. The gas then enters the gas purification line. After passing through the separator filter, the gas flows through the outlet manifold to the gas flow measurement unit of inlet No. 1. The gas flow is measured on the main measurement line with a flow meter. Then gas is transferred to the pulse gas treatment unit, and the main part goes to the gas heating unit No. 1.
By passing one of the heating lines through the heat exchanger, the gas is heated to the required temperature. After the heating unit, part of the gas is withdrawn to the gas pressure reduction units for auxiliaries (gas to the boiler plant), and the main part of the gas is distributed to the gas pressure reduction unit No.1 and the gas flow measurement unit of outlet No. 2.
When entering the gas pressure reduction unit No. 1, gas passes through one of the pressure reduction lines. By passing through the gas pressure regulator (RD4.1/RD4.2) or control valve (Kl4.1), the gas pressure is reduced from 4.3 ... 5.6 MPa to the required output value of 2.5±0.1 MPa.
After the gas reduction unit No.1, the gas is supplied to the gas flow measurement unit of outlet No. 1.
To prepare gas for the boiler operation, gas is extracted after the gas heating unit No. 1. The gas is fed to the pressure reduction unit SN No. 1 (1st stage of pressure reduction). When passing one of the pressure reduction lines through regulator RD12.1 or RD12.2, the inlet gas pressure of 4.3 ... 5.6 MPa is reduced to 1.0 MPa.
After the pressure reduction unit SN No.1, gas enters pressure reduction unit SN No. 2 (2nd stage of pressure reduction). When passing one of the pressure reduction lines through the regulator, the inlet gas pressure of 1.0 MPa is reduced to 0.03 MPa.
After SN No.2 reduction unit, gas is supplied to the boiler plant and then to the gas flow measurement line based on a vortex flow transducer. The gas then passes through a common manifold to the boilers and distributed among the three gas supply lines to the burners. Two lines of gas supply to the burners work simultaneously; one line is reserved.
Buffer gas preparation
Natural gas from inlets No. 2 and 3 passes to pressure reduction unit No. 2. The instrumentation, control, and automation equipment measures the input parameters of the gas flowing through the inlet manifold.
The gas pressure drops to 4.2 ... 9.9 MPa as it passes through the pressure reduction line. Then the gas enters gas purification unit No. 2, where it is cleaned of large mechanical impurities and droplet moisture. Then the gas enters the separator filter for final purification.
Separated moisture with mechanical impurities is collected in the accumulation parts of the separator and separator filter. When the liquid reaches the maximum level in the accumulation parts, it is discharged into the pressure reduction manifold, where the pressure is reduced to 4.0 MPa, and then enters outlet G1.
After the purification unit, the gas is separated into two streams. One stream is directed to the gas flow measurement unit of outlet No. 4, where the flow of gas intended for the buffer gas of the first start of the gas-compressor unit is measured. The second stream is directed to the gas heating unit No. 2, where the gas passes through one of the heating lines through the heat exchanger and is heated to a temperature of +60 ... +80 °С.
After the heating unit, the gas is directed to the gas flow measuring unit of outlet No. 5. This unit measures the flow rate of gas entering from outlet No. 5 intended for buffer gas during continuous gas-compressor unit operation. A gas filter is installed after the flow meter; outlet flange and outlet manifold are made of stainless steel to prevent the ingress of mechanical impurities in the gas as a result of corrosion of the internal walls of the pipeline. When the unit is operated via the bypass line, the gas is purified without gas flow rate accounting.
Coolant preparation process diagram
Gas heating in the heat exchangers is regulated by changing the flow rate of the coolant using three-way valves from the gas temperature sensors.
The temperature chart of the internal circuit of the coolant preparation unit (for gas heating) is 95/70 °С. The coolant of the internal circuit is water or antifreeze. The inner circuit coolant is heated to 95 °C from the heating supply network through heat exchangers (one operating unit, one reserved unit) or from gas boilers.
The temperature chart of the heating network is 110/70 °C. The heat transfer liquid of the heating network is water.
When operating from heating networks, the flow rate of the coolant is regulated by a two-way valve from the coolant temperature sensor installed on the pipeline. This ensures the required temperature chart of 95/70 °C of the internal circuit. When operating from the heating network, the gas boilers are not working, the gate valves with electric actuators at the boiler outlet are closed, and the gate valve with electric actuator on the pipeline bypass of the coolant past the boilers is open. When the temperature of the coolant at the heat exchanger outlet drops below the accepted temperature chart, the recirculation pumps of the working boilers are activated (two operating boilers, one reserved), and the boilers are started one by one: the first one boiler is started, and if the capacity is not sufficient, the second boiler is started as well. The boilers are started by the same temperature sensor.