The adjustment of cold production of air separation unit shall be realized through multi-link cooperative operation, and the core is to balance the supply and demand relationship of cold production of the system.
Dynamic adjustment of expander: rotate the nozzle blade to change the gas flow sectional area. When the opening increases, the expansion air volume increases and the refrigerating capacity increases accordingly; On the contrary. The inlet pressure is controlled by adjusting the opening of the throttle valve in front of the expander. The decrease of the pressure will reduce the gas expansion ratio, thus reducing the refrigerating capacity.
Linkage control of rectification working condition: when the main cooling liquid level is too high, reduce the expansion air volume to avoid deterioration of rectification working condition; On the contrary, the expansion shall be increased in case of insufficient cooling capacity. The reflux liquid amount of the lower column is controlled by the liquid nitrogen throttle valve, which indirectly affects the rectification potential of the upper column, and then regulates the cooling demand.
System pressure and temperature management: appropriately turn down the oxygen and nitrogen supply valves to increase the low and medium pressure and reduce the refrigerating capacity; Conversely, decreasing the pressure increases the cold generation. Regulate the cooling water flow of air compressor to change the inlet temperature of high pressure air. In addition, open the blow off valve at the bottom of the heat exchanger to discharge the subcooled liquefied air and assist in regulating the cooling capacity.
Cooling capacity consumption and balance: when the cooling capacity is excessive, part of the cooling capacity consumed by liquid oxygen can be discharged, but it shall be ensured that the liquid oxygen surface is not lower than the safe value. Regularly check the heat transfer efficiency of the heat exchanger to avoid the loss of cooling capacity caused by the expansion of temperature difference at the hot end; At the same time, the multistage expansion system can be used for cooling in stages to reduce heat loss.
The cooling capacity shall be adjusted slowly and carefully to avoid the violent fluctuation of parameters affecting the rectification working condition. Key parameters such as main cooling liquid level and oxygen purity shall be monitored synchronously during operation to ensure stable operation of the system.
