Exergy study of amine regeneration unit using diethanolamine in a refinery plant: A real start-up plant

Abstract

Refinery plants use diethanolamine (DEA) solutions for gas sweetening. The role of DEA is to absorb H 2 S from sour gas. Amine Regeneration Units (ARU) are used to regenerate the rich Amine with H 2 S from refinery units to Lean Amine. An ARU unit of a Middle Eastern refinery that began official production in 2020 was simulated using Aspen HYSYS V.11, and an exergy study was conducted on different equipment. Whereas energy is transformed from one form to another, the exergy is destroyed in an irreversible process. The total exergy was equal to the physical and chemical exergy. The physical exergy was calculated using HYSYS, and the chemical exergy was calculated using a series of equations embedded in Excel. The DEA concentration used was 25 wt%. The exergy destruction rates, destruction efficiency, and percentage share of destruction of each piece of equipment were calculated. The regenerator exhibited the highest destruction rate of 13459.73 kW, and a percentage share of 79.61% of the total destruction. The overall exergy efficiency was 99.7%. The DEA concentration decreased from 25% to 20% as a result of system losses during start-up. Therefore, a case study was conducted to test the effect of this decrease in the H 2 S concentration in the sweet gas, and no effect was observed. An exergy study was conducted using an DEA of 20%. The distribution of the equipment destruction did not change. The total destruction loss increased by 2057.08 kW. From the exergy and operation point of view, the best scenario was to use a 25% concentration, to prevent destruction losses and operation problems.

Exergy Study of Sour Water Stripper Unit of Delayed Coker Unit in a Refinery plant: A Real Start-Up Plant

“…System losses in general for amine may happen due to many purposes explained in section Purposes of amines losses). The study was conducted on two different concentrations (25% and 20%) by weight [25]. A comparison was conducted between the similar equipment of the current study and the previous two studies to conclude the similar relationships between equipment.…”

“…The general equation for the heat transfer across a surface is as follows: (24) where Q, U, A, and ∆Tm are the heat transfer per unit time (W), overall heat transfer coefficient (W/m 2 °C), area of heat transfer (m 2 ), and log mean temperature difference (°C), respectively. The log mean temperature difference was calculated using the following equation: (25) where T1 is the hot-fluid inlet temperature, T2 is the hot-fluid outlet temperature, t1 is the cold fluid inlet temperature, and t2 is the cold fluid outlet temperature.…”

“…The third purpose of the decrease in concentration is the flooding phenomena that happens in high sour gas feed flow rates that also takes a part of the DEA or MDEA to exit with the sweet gas from the top. In the starting-up period, foaming and flooding phenomena were observed in the plant absorbers several times [25,32].…”

“…2 is used especially for regenerating the DEA used in the DCU. Ibrahim et al performed an exergy study for ARU No.1 [25]. Also, they conducted an exergy study for an MDEA scrubber unit of an SRU plant [26].…”

Exergy analysis and performance study for sour water stripper units, amine regenerator units and a Sulphur recovery unit of a refining plant

“…As a result of system losses during start-up, the DEA concentration dropped from 25 to 20%. Exergy studies were carried out on both concentrations to determine the changes that occurred in the various exergy calculations [30,31]. Also, they conducted an exergy study for an MDEA scrubber unit of an SRU plant.…”