The load adjustment range of low pressure small air separation unit is related to the adjustment performance of the raw material compressor, the adjustment performance of the expander, the structural characteristics of the distillation tower and other factors. At present there are imported guide vane of the turbine air compressor flow adjustment range in 75-100%; adjustable nozzle of the turbine expander adjustment range can be in 65-100%. When oxygen is rich and the need to reduce oxygen production, the key is the size of the adjustment margin of the distillation tower. At present, the gauge packing distillation tower load adjustment range of up to 50-100%, while the best adjustment range of the traditional sieve plate tower in 70-100%, load any lower may lead to leakage due to the low speed of the vapour through the sieve holes.
When there is a surplus of oxygen and the oxygen output needs to be reduced, the output of the oxygen product should first be reduced and then the air flow should be reduced accordingly and the expansion air volume should be adjusted according to the main cold liquid level. The liquid air and liquid nitrogen regulating valves sent to the upper tower should also be reduced accordingly to the distillation working conditions. It should be noted that the whole operation should be completed slowly and gradually to maintain a stable distillation condition during the reduction process. If a liquid oxygen storage system is available, then the reduction in oxygen production can increase the production of liquid oxygen. It is more convenient to store the liquid oxygen by reducing the oxygen production and then increasing the amount of expansion air to increase the amount of liquid oxygen removed while keeping the main cooling level constant. To keep the distillation conditions in the upper tower stable, some of the expansion air can be bypassed if necessary.
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