HP steam
HP steam
H S recycle
Amine-based tail gas treatment unit
Acid gas SWS gas
Acid gas SWS gas
H O scrubber
Incinerator
Claus unit
WSA unit
HP steam
Sulphur
LP steam
Acid
Fuel
Figure 3 Claus SRU (left) and WSA SRU (right) simplified flow schemes
CO₂ emissions: A comparative analysis The WSA process achieves higher energy efficiency than modified Claus processes by producing more steam and consuming less natural gas. This results in lower direct or actual stack CO₂ emissions from flue gas, as the natural gas combustion in the WSA combustor is minimal. The CO₂ content in the acid gas is low and does not significantly affect the stack emissions. And the high H₂S concentration provides a substantial energy input to the WSA combustor, eliminating the requirement for natural gas combustion. For consistency with previous studies by Topsoe and Worley Comprimo comparing Claus and TopClaus SRUs,⁶ this analysis assumes that electricity is supplied by the national grid with a carbon intensity of 330g CO₂eq/kWh. Furthermore, to account for the potential energy value of exported steam, a CO₂ emissions factor of 200g CO₂eq/ kWh is applied, assuming a boiler efficiency of 85% and natural gas as fuel. Table 3 demonstrates the reduced direct and indirect CO₂ emissions associated with the WSA technology. The significant CO₂ emissions savings realised through steam production highlight the strategic importance of maximising its utilisation beyond the SRU facility. By dis - placing fuel consumption in refinery boilers, this energy resource offers a straightforward pathway to reduce Scope 1 GHG emissions. Furthermore, the potential for achieving negative net CO₂ emissions positions refineries to participate in carbon credit programmes. These initiatives incentivise GHG reduction efforts and provide opportunities to offset Scope 2 emis - sions through electricity generation, particularly when direct CO₂ emissions predominantly stem from fired heat - ers rather than boilers. Individual refinery GHG emission profiles will undoubt - edly influence the selection of specific abatement strategies.
require external fuel for combustion. While the incinerator ensures environmental compliance by preventing pollutant emissions, it concurrently contributes to increased CO₂ emissions. • BFW (boiler feed water) and steam: The TGTU regener - ator reboilers demand a considerable amount of LP steam, which exceeds the steam generation from the Claus pro - cess. On the other hand, the WSA process generates a large amount of superheated HP steam without needing any LP steam input. • Cooling water: The WSA process incorporates a cooling step for sulphuric acid, utilising recirculating water. While the direct carbon footprint of water supply and treatment for this process was not quantified, it is likely higher than that of the Claus process due to increased water demand. However, the WSA process eliminates wastewater gener - ation and chemical usage, potentially offsetting the carbon impact associated with water consumption. These preliminary findings indicate that the WSA process offers potential advantages in terms of energy efficiency and reduced carbon emissions compared to the modified Claus process. However, a more comprehensive analysis, including energy and mass balances, is necessary to quan - tify the full extent of these benefits. The subsequent section delves deeper into the case study results, examining energy consumption and emission data. By comparing the two technologies, we can assess the two processes’ overall GHG environmental impact and its potential contribution to the refining industry’s decar - bonisation goals.
Basic utility consumption and production
Claus + amine- based TGTU⁵ Consumption/hr
WSA + H₂O₂- based TGTU
Comparative CO₂ emissions (Claus vs WSA)
Consumption
Claus + amine- WSA + H₂O₂- based TGTU based TGTU
BFW, tons
50
90
Electric power, KWh Natural gas, Nm³
1,850
2,000
Actual stack CO₂ emissions, TPA Equivalent CO₂ emissions from electricity consumption, TPA Equivalent CO₂ emissions reduction from steam production, TPA
12,050
2,300
535
0 0
LP steam, tons
10
5,150
5,600
Cooling water, M³
0
300
Production
Production/hr
–49,800 –32,600
–192,600 –184,70
HP steam, tons LP steam, tons
30 10
88
Total net CO₂ emissions, TPA
0
Table 3
Table 2
38
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