Steps for starting up and shutting down the four-in-one nitric acid plant, along with precautions

Starting steps for the four-in-one unit: When starting a condensing steam turbine, the auxiliary units are started first, while the main unit remains stationary. Below are examples of the startup process of relatively advanced four-in-one units that I have seen, for everyone’s learning and discussion: 1. Starting the seal air system and the cleaning air system ① Supply seal air to each oil seal ； ②Supply seal air to the nitric oxide compressor ； ③Supply cleaning air to the exhaust turbine ； 2. Start the fuel supply system ①Start the main oil pump ； Regulate control oil, lubricating oil, and oil pressure of various bearings ； Put the auxiliary oil pump in automatic mode ； Set the faulty oil pump to automatic mode. Ensure there is oil return in the high-level oil tank ； ②Start the oil demister ； ③Start the electric heater in the oil tank and maintain the oil temperature at 45°C. 3. Start the unit’s barring gear. 4. Start the turbine seal steam system. 5. Start the turbine condensing unit to create a vacuum. 6. Warm up the steam pipes. 7. Reset the unit: the main steam valve opens automatically, the exhaust turbine inlet valve opens automatically, and the exhaust turbine bypass valve closes automatically. (The air compressor vent valve is open, the nitrogen oxide compressor emergency cycle valve is open; the static blades of the air compressor unit are at 0%, and the static blade position of the expander is at 50%. During shutdown, these valves return automatically to their operating positions.) 8. The valve body of the preheating control valve. 9. Driving: By pressing the speed-up button, the turbine automatically increases its speed from 119 to 6500 rpm; at this point, the air compressor’s vent valve and the nitrogen oxide compressor’s emergency cycle valve close automatically ； After 6500, the turbine speed is increased manually ； 10. Monitor the air compressor’s surge curve to ensure it operates along the control curve, gradually increasing its speed. Once the speed required for process ignition is reached, adjust the static vanes of the air compressor and the expander, and regulate the air volume supplied by the air compressor to meet the requirements for process ignition, thereby facilitating the process ignition. As long as the operating procedures are strictly followed and every step is carefully monitored, there generally won’t be any problems.