Assuming these installations would be mainly solar parks and wind farms, having a combined average capacity factor of 0.23, this would lead to a 22 MW RES capacity in total. And only 512 kg/h of captured CO 2 would be utilised. A snapshot of the mass balance and the energy flows is shown in Table 2 . Summary The RWGS reactor hot effluent and the exotherm of the FT reactor can be used for HP steam generation. In particular, assuming that 50% of the total heat to be removed can be recovered, then starting from ambient temperature and pressure conditions, approximately 600 kg/h of saturated steam at 50 bar can be generated by consuming 1.1 kW for the compression. Also, the retrieved fuel gas is more than enough to cover both the heater duty and the required heat in the RWGS section to keep the reaction temperature constant. Even so, the energy efficiency of the process is calculated at 83%, or 62% if the electrolysis step is included. The co-production of significant amounts of water, as depicted in the mass balance, does not favour the economics of the process. For these to improve, the cost of green hydrogen will have to drop significantly, and there should also be an extra incentive for carbon capture entities to use this route by avoiding additional CO 2 transportation and storage costs. Furthermore, when the CO 2 emissions from an industrial facility are considered, the RES power generation and green hydrogen electrolysis would need to be developed on the GW scale. In particular, the emissions of a 100 kbpd coking/ hydrocracking or a 100 kbpd FCC cracking refinery are in the order of ~200 t/h CO2 . A GtL plant utilising these CO 2 emissions would produce 15 kbpd of synthetic oil, but would require approximately 8.7 GW of RES power installations in a 2.0 GW electrolysis system to generate the required green hydrogen. The above figures are for just one complex refinery. Assuming a target of 25 MW for RES power under the prospective updated version of the National Climate Action Plan and 5 GW for electrolysis under the White Dragon Project proposal respectively, these figures represent nearly 35% and 40% of the total expected capacity of RES and electrolysis to be
Mass flow
512.0 89.0 601.0 kg/h
CO 2
H 2
Total in
Fuel gas (H 2 + methane ~ 93% mol) 58.3 SynOil (H 2 O < 0.15% w/w & CO 2 < 0.02% w/w) 139.4 H 2 O (H 2 O > 99.0% mol) 403.0 Total out 600.7
Energy flow
kW
Type
Compressor
261.1 -19.2 312.0 104.3 -424.9 -504.9 -58.9 -68.0
Electrical power
Expander
Work
Fired heater RWGS reactor
Heating Heating Cooling Cooling Cooling Cooling Heating Cooling Heating Heating Cooling Cooling Heating
H 2 O drum FT reactor
Flash 1 Flash 2 Flash 3 Flash 4 Flash 5 Flash6 Flash 7
19.2 -0.8
9.6 0.8
-3.3 69.7 -4.7
PSA CO 2 /fuel gas
Electrical power
Cooler
Heat exchanger Total cooling Total heating
3.8
-1065.6
449.8
Table 2 Mass balance and energy flows
installed in Greece by 2030. Greece currently has four refineries in operation – two FCC cracking refineries, one coking/hydrocracking refinery and one hydroskimming refinery – with combined verified CO2 emissions in the range of 660-670 t/h. 1 Also, the allocation for the use of RES power is expected to be different. An optimal pathway for Greece to achieve net-zero emissions in all sectors by 2050 (power, industry, transport, buildings, agriculture, waste) would start with eliminating the emissions from the power sector, approximately 27 million tons of CO2 in 2019. For this to happen, it is estimated that installed capacity for wind plus solar would need to reach at least 35 GW by 2050, along with the essential storage and grid investments. Therefore, the level of the annual CO 2 emissions of the refining sector, although comprising only around 27% of the total 21 million tons of the
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