Comparative table for hydrogen blending in fuel gas
Parameters
Units Mol%
Base fuel H₂: 25% CH₄: 35% C₂H₆: 20% C₃H₈: 20%
Medium-level blending
High-level blending
Fuel composition
H₂: 50% CH₄: 24% C₂H₆: 13% C₃H₈: 13%
H₂: 75% CH₄: 11% C₂H₆: 7% C₃H₈: 7%
(hypothetical)
Vol% of base fuel
100
66
34
in mixed fuel gas Vol% of green hydrogen in mixed fuel gas Total mass of mixed fuel gas fired Mass of blended green hydrogen in mixed fuel gas Carbon saving
0
34
66
kg/h
1,840
1,725
1,500
kg/h
0
130
276
kg/h
Base
Base – 600
Base – 1,720
Table 5
Blending green hydrogen Green hydrogen is perceived as the fuel of the future, with ever-new technologies and improvements paving the way for its cost-effective production. Despite regular advance- ments in green hydrogen technologies, hydrogen, per se , remains a costly commodity to burn as fuel in fired heat - ers. In Case Study 3, the 20 Gcal/h fired heater considered in the earlier case study is revisited. For this case study, normal refinery fuel gas is considered the base case, with green hydrogen blended to the base case yielding two more fuel cases termed ‘medium-level H₂ blending’ and ‘high-level H₂ blending’. Compositions of all three fuels and the comparative performance assessment are shown in Table 5. As evident from Table 5, blending fuel gas with green hydrogen saves substantial carbon. However, green hydro- gen economics need a thorough review. For the presented hypothetical scenario, the economics stand as shown in Figure 4 . Thus, blending green hydrogen into refinery fuel gas
is indeed a beneficial proposition due to reduced carbon emissions. However, a massive reduction in green hydro- gen cost is warranted for this strategy to be cost-effective. As of date, overall cost will increase with hydrogen blend- ing, although carbon emission cost will reduce. Electrical vs fossil fuel-fired furnace debate For Case Study 4, the impact of carbon cost on the econom- ics of electrically powered furnaces is evaluated. In recent years, the emergence of green electricity has evinced a lot of interest, especially extending to fired equipment. With large multinational corporations and technology licensors allocating significant research funds into electrical furnaces, a lot of brainstorming is devoted to whether green elec- tricity can be a viable alternative for conventional fossil fuel firing. For this case study, a 15 Gcal/h refinery heater is examined. The case study from Table 6 , represented in Figure 5, opens an interesting observation. If carbon cost is not considered, the operating cost of a fossil fuel-fired furnace will likely win over that of an electrically-fired furnace, and by a large margin. However, if carbon cost is considered in the calculation, the cost of operating a fossil fuel furnace and an electrically powered furnace is comparable. With newer technologies develop - ing in the green genre, the cost of green electricity may decrease further, and the balance beam may even tilt in favour of electrically powered furnaces in the coming decade. The usage of electrical furnaces for high-duty hydrocar- bon heating is still in the development phase, and other associated economics, constraints, maintenance, and relia- bility aspects are being worked out by major industry play - ers before opting for the complete switchover to this new, cleaner technology for process heating. Conclusion Fired heaters are the major sources of carbon emission in an oil refinery. With the vision to achieve net zero and min - imise carbonaceous emissions across all sectors, maximi- sation of operational efficiency of fired equipment is an
140 , 000
120 , 000
100 , 000
80 , 000
60 , 000
40 , 000
20 , 000
0
Base
Medium H blending case
High H blending case
Green h ydrogen cost (Rs/ h ) Total cost (Rs/ h)
Normal fuel gas cost (Rs/ h) Carbon cost (Rs/ h )
Figure 4 Operational cost economics with hydrogen blending
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PTQ Q3 2024
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