Feed gas composition
Amine Acid Gas Amine acid gas
TGTU Recycle TGTU recycle
SWS Acid Gas SWS acid gas
Lean Acid Gas Lean acid gas
Component
Mol% 90.0%
Mol% 30.0%
Mol% 33.0% 33.0%
Mol% 11.0%
H₂S NH₃ CO₂ H₂O
0.0% 5.0% 4.0% 1.0%
0%
0.0%
65.0% 5.0% 0.0% 100%
0.0%
81.0%
33.0%
2.0% 6.0%
Balance
1.0%
Total
100.0%
100.0%
100.0%
Flow rate
kmol/h
kmol/h
kmol/h
kmol/h
Base (design) case
192 107
14 17
67 60
0
Post-revamp
183
Sulphur production
Base (design) case
150 MTPD 110 MTPD
Post-revamp
Table 3
The available fuel gas is a stream of hydrogen-rich gas, with the typical composition shown in Table 4 . A major drawback of using co-firing on a permanent basis is that it increases the potential for coke formation. This can lead to rapid deactivation of the downstream Claus cata- lysts and also increases the process gas and tail gas flow rates beyond the design capacity of the unit, with the tail gas flow exceeding 130% of the base case design value. Thus, implementing co-firing would require a much larger revamp than just adding the co-firing. For these reasons, this option was not implemented. Oxygen enrichment Oxygen enrichment would elevate the furnace operating temperature by removing diluent gases. To achieve the required furnace temperature, the optimal oxygen enrich - ment level was found to be 60%. To create the correct com - bustion and reaction environment with high-level oxygen enrichment, a new high-intensity burner would be needed. Oxygen enrichment became the chosen option for the cli - ent. They also elected to replace the reaction furnace. The replacement of the furnace was not a mandatory change but was included as part of the project only because the existing furnace is old and prone to a number of age-re - lated issues. The acid gas preheater using LP steam is also included in the design, as the LAG is colder than ambient temperature,
and preheating the stream has a positive impact on opti- mising oxygen usage. Table 5 summarises the operating conditions for the unit post-revamp. Since the refinery has oxygen available in situ, not depending on outside suppliers or new installations for the post-revamp high-level oxygen enrichment operations made this the most viable option. A major advantage of the revamp to process the LAG using high-level oxygen enrichment is that the usage of high-level oxygen enrichment reduces the overall flow of process gas and tail gas in the unit, even when the feed gas flow of the unit increased due to the increased flow of the LAG. The unit remained hydraulically capable of processing the feed gas mixture with no major modifications beyond the Claus furnace. The tail gas flow for the revamp opera - tion is less than 70% of the base case. Thus, all equipment downstream of the Claus furnace continued to operate at less than design capacity. The revamp also meant that the unit remained capable of handling the original feed gas composition if needed, along with any variation from mixing the rich AAG and the LAG streams. The oxygen enrichment level can be easily fine-tuned based on the expected feed gas compositions, thus allowing this unit to process a wide range of feed gas compositions.
Unit operating conditions
Parameter
Value
Fuel gas composition
Amine acid gas (kmol/h)
107
SWS gas (kmol/h)
60
Component
Amount in Mol%
Lean acid gas (kmol/h) TGTU recycle (kmol/h)
183
Hydrogen Nitrogen Methane
56 10 22
17 60
Oxygen (kmol/h)
Furnace temperature (ºC) Tail gas flow (% of design)
>1,260
CO₂
5 5 2
<70 <75
Ethane
Sulphur production (% of design)
Propane
Table 4
Table 5
64
PTQ Q1 2025
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