The problem of liquefying ethane-rich gas
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The post was posted in another forum and got no replies, so it’s being posted again in the crafts forum, hoping more people will see it. . . Hello everyone, I’ve encountered a problem at work: it’s necessary to partially liquefy the ethane-rich gas in order to reduce the C4 content. The gas composition is detailed in the attachment. The initial conditions are a temperature of 40°C and a pressure of 2.5 MPa. I used PROII for the calculations, with the PR equation selected for thermodynamic modeling. As a result, the entire gas was liquefied when the temperature dropped to 25°C. Could the software be giving incorrect results? If not, why? I hope some expert can help resolve this doubt; thank you very much! https://downl.hcbbs.com/forum/202502/24/152628rpcwlxw142n442pk.webp?x-oss-process=style/ossprn https://downl.hcbbs.com/forum/202502/24/152655l0ud0tp0uptuj8x6.webp?x-oss-process=style/ossprn https://downl.hcbbs.com/forum/202502/24/152718v5z35t0cfvnzddvw.webp?x-oss-process=style/ossprn
This post was last edited by sunyanjs on 2025-2-26 at 23:05. Sorry, the uploaded images cannot be displayed. The logistics data entered is as follows: everything liquefies when the temperature drops below 30°C. I have some doubts regarding the calculation results; why can methane/ethane still liquefy at 30°C and 2.5 MPa? That shouldn’t be the case.
TOTAL VAPOR LIQUID DECANT H2O
---------- ---------- ---------- ----------
RATE, KG/HR 143999.8600 23455.7053 120247.6945 296.4601
TEMPERATURE, C 40.10 40.10 40.10 40.10
PRESSURE, KPA 2500.00 2500.00 2500.00 2500.00
MOLECULAR WEIGHT 41.0889 34.6224 42.7827 18.0153
WEIGHT FRACTION 0.1629 0.8351 2.0588E-03
ENTHALPY, KJ/KG 155.5689 382.9301 111.1834 170.1652
CP, KJ/KG-C 3.0591 2.3269 3.1992 4.1727
MASS FLOWRATES, KG/HR
1 - CH4 1331.5800 753.3777 578.2024
2 - C2H6 44657.1800 12672.7742 31984.4058
3 - C2H4 390.8100 141.3282 249.4818
4 - C3H8 42123.8300 5939.4181 36184.4119
5 - C3H6 58.3000 9.2093 49.0907
6 - NC4 30030.5700 1981.7438 28048.8262
7 - IC4 23828.3400 1862.3529 21965.9871
8 - 1BUTENE 68.1300 4.9864 63.1436
9 - IBUTENE 194.6700 14.4293 180.2407
10 - C2BUTENE 56.9100 3.4774 53.4326
11 - T2BUTENE 120.6600 7.7250 112.9350
12 - NC5 0.0400 1.3059E-03 0.0387
13 - IC5 761.1200 27.2418 733.8782
14 - H2O 373.0700 36.2430 40.3669 296.4601
15 - H2S 3.3800 0.9353 2.4447
16 - NH3 0.5100 0.1746 0.3354
17 - CO2 0.6300 0.2721 0.3579
18 - O2 0.0200 0.0135 6.4530E-03
19 - NC6 0.1100 1.3863E-03 0.1086
TOTAL VAPOR LIQUID DECANT H2O
---------- ---------- ---------- ----------
RATE, KG/HR 143999.8600 23455.7053 120247.6945 296.4601
TEMPERATURE, C 40.10 40.10 40.10 40.10
PRESSURE, KPA 2500.00 2500.00 2500.00 2500.00
MOLECULAR WEIGHT 41.0889 34.6224 42.7827 18.0153
WEIGHT FRACTION 0.1629 0.8351 2.0588E-03
ENTHALPY, KJ/KG 155.5689 382.9301 111.1834 170.1652
CP, KJ/KG-C 3.0591 2.3269 3.1992 4.1727
MASS FLOWRATES, KG/HR
1 - CH4 1331.5800 753.3777 578.2024
2 - C2H6 44657.1800 12672.7742 31984.4058
3 - C2H4 390.8100 141.3282 249.4818
4 - C3H8 42123.8300 5939.4181 36184.4119
5 - C3H6 58.3000 9.2093 49.0907
6 - NC4 30030.5700 1981.7438 28048.8262
7 - IC4 23828.3400 1862.3529 21965.9871
8 - 1BUTENE 68.1300 4.9864 63.1436
9 - IBUTENE 194.6700 14.4293 180.2407
10 - C2BUTENE 56.9100 3.4774 53.4326
11 - T2BUTENE 120.6600 7.7250 112.9350
12 - NC5 0.0400 1.3059E-03 0.0387
13 - IC5 761.1200 27.2418 733.8782
14 - H2O 373.0700 36.2430 40.3669 296.4601
15 - H2S 3.3800 0.9353 2.4447
16 - NH3 0.5100 0.1746 0.3354
17 - CO2 0.6300 0.2721 0.3579
18 - O2 0.0200 0.0135 6.4530E-03
19 - NC6 0.1100 1.3863E-03 0.1086