Weekly Topic (11.28-12.4): Models Used for the Catalytic Main Fan and Associated Issues
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There are weekly topic discussion sessions in the refining area; everyone is welcome to participate actively. We also hope that people will come up with more valuable topics, and the moderators will award rewards of 5-20 wealth points. Those who post excellently will receive a reward of 10 to 50 Wealth or an equivalent amount of Charm. What are the advantages and disadvantages of centrifugal and axial flow types of fans currently used in the main fans of catalytic cracking units? We hope Haiyou can provide information on the faults that have occurred during operation along with analyses of their causes.
Model AV50—15 (15-stage cascade, fully adjustable static blades). Type: Horizontal split casing, supported at both ends; inlet and outlet. Three units: flue gas turbine, axial flow fan, electric/generator. Incident: Backflow has occurred on occasion.
Model: D800-33. Composition: It consists of a blower, a speed increase gearbox, and a motor. Parameters: Three-stage impeller, rotation speed of 6300 r/min. Issue: Excessive vibration in the speed increase gearbox. Phenomenon: The surface of the pinion is discolored yellow due to overheating
Axial flow air compressor? Model: AV50—12. Control method: All stator vanes are adjustable. Stator vane adjustment range (angle): 22°–78°. Working medium: Air. Molecular weight: 28.84. Adiabatic index: 1.4. Designed flow rate: 1672 Nm3/min. Flow rate adjustment range: +10%–-20%. Designed outlet pressure: 0.4 MPa. Outlet temperature: 160°C (annual average). Shaft power: 6285 KW. Power efficiency: 89%. First-order critical speed: 3220 RPM. Second-order critical speed: 9580 RPM. Maximum continuous speed: 6682 RPM. Tripping speed: 7000 RPM. Speed range: 6270–6682 RPM. Number of stator vanes: 0 guide vanes + 12 stator vanes. Number of rotor vanes: 12. Composition: Exhaust fan – drive shaft – axial flow fan – motor/generator. Catalyst backflow has occurred due to a malfunctioning check valve
Backflow has occurred in centrifugal compressors, axial flow fans, and intermediate extraction condensing steam turbine units; this is a serious operational accident. The check valve became stuck due to lack of maintenance over a long period of time. It operates reliably, with minimal vibration and surge, and is easy to operate.
Generally, centrifugal main fans are used for capacities of less than 1 million tons, while axial flow main fans are used for larger capacities. Models used in this unit: D800-33, D800-31, D1250-36. Accident types: surge, catalyst backflow, unit reversal.
Centrifugal air compressor, model: 6H-4, with four-stage impellers. Components: compressor, speed increase gearbox, motor. Problems encountered: severe oil leakage. Cause: sealing issue. Others: none; operates fairly smoothly
(1) Axial flow compressor: Model AV56–13; operating speed: 5820 r/min; shaft power: 10794 KW; discharge pressure: 0.42 MPa; rotation direction: clockwise (viewed from the air inlet side). (2) Gearbox: Model TA670-SFC; power transmitted: 14000 KW; speed ratio: 5820/1487; rotation direction of the high-speed shaft: clockwise. (3) Motor: Model YCH1000–4; rotation direction: counterclockwise (viewed from the shaft end); rated power: 14000 KW; rated speed: 1487 r/min; rated current: 916 A; cooling method: top-air cooling. (4) Exhaust fan: Model YL12000C; operating speed: 5820 r/min; rotation direction: counterclockwise (viewed from the air inlet side); rated power: 12370 KW. Problem: The angle of the stator blades was installed incorrectly; this caused surging as soon as the machine was started up. The issue was resolved by increasing the angle of the blades.
Same as floor 8! It hasn’t started yet! Axial and centrifugal types are primarily chosen based on economic considerations; axial types are used for large catalytic systems, while centrifugal types are used for smaller devices! Previously, the workshop handled 650,000 tons! It uses an MCL904-20 model; the flow rate is 1250 m3/min and the rotational speed is 6109 r/min!
Catalytic main fan building – What are the main hazardous substances inside the building? and heating and ventilation requirements,