The July 2016 tip of the month (TOTM) considered the presence of methanol in the sour gas stream and determined the quantitative traces of methanol ending up in the sweet gas, flash gas and acid gas streams. To achieve this, the tip simulated a simplified MDEA gas sweetening unit by computer. That tip also studied the effect of feed sour gas temperature, methanol content, and the rate of replacing condensed reflux with fresh water on the sweet gas methanol content. For the two feed sour gas temperatures of 32.2 and 43.3 °C (90 and 110 °F) the tip studied three inlet gas methanol contents of 50, 250, and 500 PPMV. In each case the tip varied rate of freshwater replacement from 0 to 100 % by an increment of 20%. The simulated results are presented graphically.
To improve methanol removal efficiency from the feed sour gas stream, the July 2016 TOTM was revisited, and the following modifications were incorporated.
1. Because the feed gas contains methanol, a known polar compound, we used ProMax simulation software with “Amine Sweetening – Polar PR” instead of “Amine Sweetening – PR” property package to perform all the simulations.
2. In July 2016 TOTM the “Water Draw” stream removed a specified fraction of the condensed reflux, and the “Fresh Water” stream added the same amount of fresh water to the return reflux at the top of regenerator column. A better alternative where the amount of water draw is supplied by the amine makeup tool of ProMax was used.
3. The effect of feed gas pressure on the methanol removal by amine sweetening process for pressures of 600, 800, and 1000 psig (4200, 5600, and 7000 kPag) was investigated and reported.
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