Weekly Topic: What are the reasons for high CO2 levels in the purified air?

Low-temperature methanol washing: The circulation volume of methanol is low, the concentration of CO2 in the gas increases, methanol regeneration is poor, the amount of cooling available in the system is limited, the volume of gas entering the system is too high, the gas-liquid ratio is large, the addition rate is fast, and flow deviation occurs in the trays

The last edit to this post was made by 654262293 on 2011-1-10 at 13:23. Reasons for high carbon removal efficiency using propylene carbonate solution: 1. Low circulation rate of the propylene carbonate solution. 2. The temperature of the propylene carbonate liquid is high. 3. The system pressure is low. 4. Poor regeneration, low air lift flow rate. 5. The carbon propyl liquid has a high water content. 6. Blockage of the absorber tower packing, causing flow deviation.

Decarburization is carried out using carbon propylene liquid; the high oxygen content in the purified gas is due to the gas-lift regeneration process used for this liquid, which results in a high oxygen content in the lean liquid. When this lean liquid absorbs CO2 in the absorption tower, the oxygen contained in it is desorbed, thereby increasing the oxygen content in the decarburized and purified gas. When the carbon propylene lean liquid enters the decarburization tower, there is a large pressure difference with the system, resulting in leakage points that allow air to be drawn into the tower, thereby causing high oxygen levels.

Decarburization NHD process: Low circulation volume of the decarburization liquid; high water content in NHD; high temperature of the ammonia cooler; incomplete regeneration of the decarburization liquid. «Blockage at the air intake port»; low system pressure; high hydrogen sulfide content in the transformed gas; excessive gas flow; incorrect instrument readings

This post was last edited by Chemical Gas Purification on 2011-2-9 08:29. Using pressure swing adsorption for carbon removal: 1. As the name implies, it’s pressure swing adsorption; the primary factor here is obviously pressure. Under certain conditions, if the operating adsorption pressure is lower than the designed value, the carbon dioxide content in the gas undergoing carbon removal increases； 2. Adsorption time: If the adsorption time is too long, carbon dioxide in the adsorption tower penetrates through the adsorption layer, resulting in an increase in carbon dioxide levels in the degassed gas ； 3. Vacuum pumping time: If the vacuum pumping time is too short, the amount of carbon dioxide remaining in the adsorption tower increases. Under the same adsorption time conditions, this leads to an increase in the carbon dioxide content in the degassed gas.
4. Increased carbon dioxide content in the feed gas: Under certain conditions, the degassing capacity of pressure swing adsorption remains constant; however, if the carbon dioxide content in the feed gas increases, it results in an increase in the carbon dioxide content in the degassed gas.
5. Valve leakage: When the valves used to switch between towers in pressure swing adsorption experience leakage, the carbon dioxide content in the degassed gas rises. This problem occurs frequently and is difficult to identify.
6. Failure of the adsorption packing: When the adsorption packing fails, the carbon dioxide content in the degassed gas increases (for example, if water or tar in the feed gas is not properly handled, it reduces the service life of the adsorption packing).
7. Reduced vacuum pumping capacity of the vacuum pump: As mentioned earlier, while the vacuum pumping time and the vacuum pumping capacity of the vacuum pump have similar effects, their underlying causes are different. There are many factors that can lead to a decrease in the vacuum pumping capacity of the vacuum pump, which will not be discussed in detail here.
8. Pressure of the air or hydraulic source for the control valves: Whether they are pneumatic or hydraulic valves, low operating pressure can affect the proper opening and closing of these valves, thereby impacting pressure swing adsorption ；

This post was last edited by 654262293 on 2011-1-10 at 13:24. The main reasons for high CO2 levels in the gas purified by the hot-alkali method are: 1. Low decarburization absorption pressure; 2. Inappropriate control of the absorption temperature; 3. Low potassium carbonate content in the total alkali of the absorption solution; 4. Uneven gas-liquid contact within the absorption tower or insufficient contact time; 5. Insufficient circulation volume of the absorption solution, with the system load not matching this circulation volume; 6. Insufficient amount of diethanolamine, which is used to enhance absorption; 7. Mechanical problems with the absorption tower; 8. The absorption solution being dirty

This post was last edited by 654262293 on 2011-1-10 13:24: 1. Gas: high temperature, high carbon dioxide content, low system pressure； 2. Liquid: High temperature, low flow rate, poor desorption, high carbon dioxide content in the lean liquid, and poor liquid quality ； 3. Equipment: tower off-flow, poor gas-liquid distribution, blockages, pump issues, low flow rate, etc

This post was last edited by Chemical Gas Purification on 2011-2-9 08:31. The low-temperature methanol washing process is used: 1. The circulation volume of methanol is low. 2. Low system pressure. 3. The recycling of methanol is not effective. 4. The temperature of lean methanol is high. 5. The system load is too high. 6. Tower packing blockage, flow deviation.

Low-temperature methanol washing: 1. Large fluctuations in the reformate gas load； 2. Significant changes in the components of the transformed gas ； 3. Incomplete regeneration of methanol through washing ； 4. High water content in the methanol wash solution ； 5. Internal leakage in the gas-to-gas heat exchanger ； 6. The data analysis is incorrect ； 7. The adjustment range for the amount of methanol used in washing is too large ； 8. High temperature for methanol washing ； 9. Failure of the wash tower trays or collapse of the tower ； 10. The temperature of methanol being washed in the middle section of the scrubber is high ； 11. High temperature of the transformed gas ； 12. The amount of methanol used for washing is too small or the flow rate is inaccurate ； 13. The space velocity in the transformed gas scrubber is too high ； 14. Deviations of operating pressure, temperature, and load of the scrubber tower from design values ；

The decarburization effect is not good; if low-temperature methanol washing is used, adjust the saturation level of carbon absorption so that it is below 80%, which will result in a greater driving force for mass transfer and thus a better decarburization effect