Composition of NHD decarburization analysis gas
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I would like to ask the experts: What is the CO2 concentration obtained from the NHD decarburization analysis? How much CO and how much H2 is contained in the CO2 gas obtained from NHD decarburization? ? Thank you for the help! ! This post was last edited by Tianya Langji on 2009-2-4 11:35.]
The purity of CO2 obtained through NHD decarburization is greater than 98.5%. The amounts of CO and H2 in the CO2 gas produced by NHD decarburization should not exceed 1%; no specific measurements have been taken! It’s hard to say how much!
It depends on the voltage reduction effect of your factory’s equipment; if it’s good, then a value above 98 should be no problem, but if it’s not good, then it’s hard to say. Our factory has 2 sets of systems. The purity of System A is basically 98-99%, while the highest purity of System B is 96%!
In gas separation, the key factor is the separation pressure; the lower the pressure, the greater the volume of gas that can be separated, but the quality of the gas components may be worse. Conversely, at higher pressures, less gas is separated, but the quality of the gas components may be better. The purity of carbon dioxide depends on the conditions in the preceding processing stages. The transformation yields good results; with low carbon monoxide levels, less of it is produced as a byproduct ； The high-resolution detection of carbon monoxide also increases accordingly. There is also the desulfurization situation in the previous section, which is the same as that of carbon monoxide separation! By controlling the pressure, it is possible to control the purity of the carbon dioxide obtained through separation; therefore, it is recommended that you adjust the pressure in order to regulate the purity of the separated gas!
Our plant’s low-pressure flash pressure is 0.1 MPa, enabling a CO2 purity of over 99%; the remainder is H2, with CO present in the ppm range
It is unknown what proportion of the total CO2 in the shift gas is accounted for by the CO2 vaporized at over 98% The question that remains is whether to use air or steam for stripping?
Of course, air stripping is used; the conditions for NHD decarburization are high pressure and low temperature!
The CO2 concentration derived from NHD decarburization is between 98.5% and 99%； The CO2 gas obtained from NHD decarburization contains approximately 200–450 ppm of CO and about 150–250 ppm of H2.
Our plant’s low-pressure flash pressure is 0.02 MPa, enabling the CO2 purity to reach over 98.5%. CO and H2 were not used as indicators.
Our factory’s product has a purity of 20 kp, slightly less than 99%; the flash point is 0.5 MPa, and the CO2 content is 15 or less
Firstly, the composition, pressure, temperature, etc. of the air entering the absorption tower are not specified. NHD absorption is a physical absorption process; the absorption of gas in NHD liquid follows Henyey’s law. By determining the Henry coefficient, it is possible to calculate the composition of the gas released under different operating conditions (at various flash pressures). The carbon dioxide content in the shift gas produced for synthetic ammonia synthesis using fixed-bed gas generators differs from that in the shift gas obtained from water-coal and pulverized coal gasification; to obtain a gas with a specific carbon dioxide concentration, it is necessary to calculate the composition of each flash based on the high flash point pressure and the low flash point pressure.
I think it is mainly related to the composition of the gas coming from your facility; our plant uses NHD decarburization, and the purity of our carbon dioxide is over 97%, though it can sometimes drop below 96%. We usually adjust this by slightly reducing the high flash pressure !
It’s so nice to see NHD; I haven’t used it in a long time. Two sets of systems have been operated: for the first set, under normal load conditions, the purity of carbon dioxide in the degassed flash gas was between 99.4 and 99.8%, while for the second set it was around 96%. The purity of NHD carbon dioxide is highly dependent on the system load, as well as on the conditions in previous processes and the operations related to high flash points. Additionally, nitrogen is the preferred gas for use in the stripping process thereafter, as water present in air will accumulate within the system; an increase in the water content in the system can affect absorption, and a specialized dehydration device is required to control the water level in the system.
Hello, I have only been in the purification industry for a month and don’t know much about this area. I would like to ask: by reducing the pressure in the high-pressure flash tank, the amount of carbon dioxide emitted from that tank should increase. Would this help to raise the concentration of carbon dioxide in the vapor coming from the low-pressure flash tank? Thank you!
After reducing the high flash point pressure, carbon dioxide will precipitate, and other gases will also be released from the NHD; as a result, the purity of the carbon dioxide emitted when the NHD solution is released at a low flash point increases.
What is the concentration of dioxide absorbed by the rich liquid in the absorption tower?
The carbon dioxide concentration at the inlet of the absorption tower is around 25-30%, although this varies significantly depending on the gas stream.