Regarding the temperature control of the main heat exchanger
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The pressurized expanded air is fed into the upper tower. After the expander is started up during the air separation unit’s commissioning, the temperature in front of the expander is controlled by adjusting the flow rates of the intermediate extraction and bottom extraction streams. To ensure proper operation of the main heat exchanger, and considering the balance of cooling capacity within the heat exchanger, what is an appropriate temperature for the intermediate extraction stream, so that the cooling capacity does not shift either toward the cold side or the hot side? During the startup phase, the temperature behind our expander is usually maintained around -186 degrees. After the accumulation of liquid has ended, the temperature of the intermediate extraction stream in the heat exchanger becomes too low. How can we adjust the flow rates of the intermediate extraction and bottom extraction streams to keep the heat exchanger operating at its optimal condition? Thank you everyone!
Medium extraction is typically used during normal operation; by ensuring sufficient cooling capacity while increasing the temperature before the machine, it allows the expander to achieve a higher refrigeration \"efficiency\". During control, to ensure the minimum load of the expander, it is sufficient to appropriately increase the temperature before the machine. (For reference)
“The supplementary explanation of \"to ensure the minimum load of the expander\" is that, while maintaining the optimal speed of the expander within the allowable range, increasing the temperature before the expander appropriately can improve its cooling efficiency.
It can also be controlled by adjusting the backflow of polluted nitrogen and the forward-flowing air.