How NHD decarburization improves carbon dioxide purity
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Our company uses NHD decarburization; at low load levels, the purity of carbon dioxide is low. Could anyone among you provide advice on how to increase its purity at such low load levels? Can reducing the solution circulation volume improve purity?
Which sea friend can give some advice? Thank you first.
This post was last edited by ypff on 2009-9-9 at 19:10. Factors affecting the purity of CO2 with low flash point: 1. High pressure in the high-flash tank; 2. Short residence time of NHD liquid in the high-flash tank; 3. High pressure in the low-flash tank; 4. Short residence time of NHD liquid in the low-flash tank; 5. Flashing efficiency: problems with the tower internals and packing; 6. Air leakage into the high-flash tank; 7. Internal leakage in the heat exchanger; 8. Excessively high solution circulation rate. Additionally, an improper setup of the balance tube in the high-flash tank (vortex eliminator) or incorrect settings for the PI parameters of the automatic control valve can lead to air entrainment in the liquid from the high-flash tank, which in turn causes fluctuations in the level (pressure) of the liquid in the low-flash tank as well as fluctuations in the amount of air used for stripping.
When the load is low, there are two main issues to pay attention to: 1. Is the absorption pressure too low?； 2. Is the circulation volume too high? The situation in normal production is complex and requires specific analysis (such as water content, ammonia cooling temperature, etc.). The summary on the third floor covers these aspects quite comprehensively.
At low load, the circulation rate should be reduced, the pressure in the high-flash tank lowered, and the amount of gas lift gas decreased; the temperature can be increased if permitted.
The circulation volume must be too high. But that’s the limit of packed towers; when the liquid volume is low, the absorption efficiency is likely to be poor
What is the reason for raising the temperature here?