Key points for starting small-scale air separation equipment
Thread Content
For the startup of low-pressure small-scale air separation units, during the early stage of the cooling phase, it is necessary to ensure that the temperature difference on the hot side remains relatively constant. Air enters the expander through the middle valve or the bottom valve of the main heat exchanger – which option is more effective in reducing the startup time? Additionally, is local cooling better or overall cooling better? Our workshop has debated this issue for a long time; alas, it’s because we lack solid evidence to support our arguments. There are not many opportunities to carry out experiments when starting up air separation units. I urge experts to provide compelling evidence – I’m new to this field of air separation technology.
In my opinion, it is better to extract during the initial stage of cooling, as this helps maintain the temperature ahead of the expander, resulting in a larger temperature and enthalpy drop. Later on, adjust the opening degrees of the two valves to reduce the temperature in front of the expander to the set value, thereby increasing the amount of expansion. Also, I think the overall cooling is good. The amount of cooling required by the cooling equipment is fixed; the same amount is needed locally as well as overall. Just trying to spark some discussion.
Our equipment initially used bottom extraction, switched to using both methods toward the end, and finally changed to all middle extraction. The cooling phase should be a full cooling process, so that the temperature of all parts drops evenly and no significant thermal stress is generated. It is beneficial for equipment and pipelines.