• As fuel gas was not required, this resulted in lower CO₂ release. • Plot space and capital cost were significantly lower. Sulphur savings As a simplified assessment, the potential savings in the SRU are compared when adopting a hybrid or optimised approach versus the conventional design, which operates in air-only mode without AGE and, as such, uses fuel gas co-firing to maintain reaction furnace temperature. This traditional method, favoured for its reliance on read - ily available natural gas, significantly increases the unit’s hydraulic load due to CO₂ in the feed gas, nitrogen from com - bustion air, and additional CO₂ generated during co-firing. Overall, the hydraulic load for the conventional sulphur plant (no enrichment, co-firing only) is approximately 3.2 times higher than that of the hybrid optimised design for the same sulphur load. Key comparison points are summa - rised in Table 4 . It is important to note that the data presented corre- sponds to a single Claus train under both operating sce - narios. In the ‘no enrichment – co-firing only’ case, one train processes 300 MTPD of sulphur, yet the Claus section would need to be approximately 1.6 times larger than that of a plant with maximum enrichment (AGE plus OE), which handles 600 MTPD of sulphur alone. Furthermore, this con - ventional scenario requires three identical Claus units for reliability, compared to only two units in the hybrid design. From a capital cost perspective, a conventional 3 × 300 MTPD SRU (two operating + one standby) with TGT unit is more than twice as expensive as the hybrid configu - ration of 2 × 300 MTPD SRU (air mode) with AGE and a TGT unit. This clearly demonstrates the significant advan - tage of enrichment in optimising sulphur plant design and configuration. Hybrid approach As outlined in the previous section, the hybrid or optimised approach for configuring and designing sulphur plants offers clear advantages over the conventional design. Building on the comparison presented in Table 4, this sec - tion provides a detailed explanation of the key benefits, including: • Improved thermal efficiency. • Less plot space.
Selected plant design parameters
Parameters
Selected hardware
Volume – reaction furnace, ft3 Volume – converter 1 catalyst, ft3 Volume – converter 2 catalyst, ft3 Duty – sulphur condenser 1, MMBtu/hr Duty – sulphur condenser 2, MMBtu/hr Duty – sulphur condenser 3, MMBtu/hr
1,781 1,447 1,447
16.5
9.8 6.1
Table 3
• Enhanced operational flexibility. • Reduced capital expense. • Improved thermal efficiency. • Lower emissions.
Lower CO₂ and almost no nitrogen result in a much higher reaction equilibrium temperature, which leads to a higher furnace temperature. Contaminants are destroyed completely without the requirement of fuel gas co-firing. Eliminating co-firing translates to multiple benefits: u Significantly lower hydraulic loads for the operating unit. v Leading to a much smaller equipment size and hence a smaller sulphur plant. w Lower plot allocations for the sulphur plant. x No usage of fuel gas, thus eliminating issues with hydro - carbon contaminants in downstream equipment. With the sulphur plants designed in the hybrid model, the requirement of a dedicated ‘spare’ train is eliminated. The units are designed with two operating trains, with the potential to ramp up any one of them to cater to the com - plete sulphur load of the facility. Thus, in simple words, the facility can reliably operate without needing a ‘spare’ SRU train. With this hybrid or optimised design, one train can bear the complete sulphur load of the facility. This means that operators get greater uptime without building a spare SRU, and there is no restriction on planning any downtime or maintenance turnarounds an any of the trains. Two trains designed in the hybrid or optimised mode are needed instead of three conventional ones. The additional costs are the capital cost of an oxygen generation unit, most typically a simple vacuum pressure swing adsorption (VPSA) plant. Moreover, in the overall economics, this cost is far below the cost of a full SRU train.
Normal operating fuel gas co-firing vs oxygen enriched mode
Parameters
No enrichment – co-firing only 600 (Two trains combined)
Oxygen-enriched case 600 (One train operating)
Sulphur content in feed, MTPD Claus volume flow, MMSCFD Volume – reaction furnace, ft3 Volume – converter 1 catalyst, ft3 Volume – converter 2 catalyst, ft3 Duty – sulphur condenser 1, MMBtu/hr Duty – sulphur condenser 2, MMBtu/hr Duty – sulphur condenser 3, MMBtu/hr
56.9 (each train) 2,516 (each train) 2,516 (each train) 2,620 (each train) 18.5 (each train) 10.6 (each train) 7.4 (each train)
34.7
1,781 1,447 1,447
16.5
9.8 6.1
Table 4
71
PTQ Q4 2026
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