Liquid nitrogen cooling tank! Fluctuations!
Thread Content
At the exhaust gas outlet of the cryogenic box, where liquid nitrogen is used for washing, there is a exhaust gas recovery compressor that sends the gas to the second conversion furnace in order to recover some of the CO. However, every time maintenance is carried out on this exhaust gas recovery compressor, the system experiences fluctuations: the pressure difference in the nitrogen washing tower increases, and the gas prevents liquid nitrogen from flowing downward, resulting in a decrease in the liquid level in the nitrogen washing tower. In such situations, it is necessary to reduce the flow rate in order to lower the pressure difference in the tower and restore normal operation. The normal gas flow rate is 93,000 units, but it needs to be reduced to 55,000 units. The temperatures at the cold ends of E05/E06 also decrease by 2°C, while the temperatures at the top and bottom of the washing tower drop by 2°C as well. Could those with more experience help analyze the reasons for this?
The temperature before the nitrogen washing tower decreases for medium-pressure nitrogen; under normal conditions it is -183°C, and it drops slowly to -186°C after the exhaust gas compressor is shut down. The temperature of the feed gas entering the nitrogen washing tower is 1–2°C lower than under normal operating conditions.
The biggest difference between before and after the shutdown is the change in the volume of raw gas entering the cooling box. Before shutdown, 3,600 cubic meters of gas were sent to the second shift converter, and after passing through the low-temperature methanol wash, it returned to the liquid nitrogen cooling box. This 3,600 cubic meters of exhaust gas carried heat, while the raw gas entering the cooling box also contributed heat. After the compressor stops operating, this 3,600 cubic meters of gas is no longer available, resulting in less heat and more cooling capacity – doesn’t this lead to an imbalance in cooling capacity?
It’s probably because there’s an excess of cold capacity in the cryogenic tank; the amount of gas is low, the amount of nitrogen used for washing hasn’t decreased, and when the compressor stops, the fuel gas cannot carry away the cold capacity, resulting in an excess of cold capacity inside the cryogenic tank. I’m a newcomer to methanol washing and nitrogen washing; I’m here to learn*
Has the liquid level in the hydrogen separator risen?
What happens to the exhaust gases after the exhaust compressor stops? Is the traffic normal? Is there a problem with the torch pipeline?
There’s no issue with venting; after the compressor stops, the automatic control valve is set to enable automatic venting
May I ask, what is the CO content in the exhaust gas?