Decarbonisation Technology - November 2021

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Electricity with a CO footprint in the range 0.12-0.15 tCOe / MWh

Figure 3 CO 2 footprint for electricity

available and the required compressor speeds and efficiencies. A key consideration when electrifying crackers is the CO 2 footprint of the electricity available to the plant. The CO 2 reduction benefits of electrification are only fully realised when the electricity available is primarily from renewable sources. Table 2 gives example figures for a 1500 kTA liquid cracker from a paper presented by Technip Energies at the 2021 Ethylene Producer’s Conference. 5 From Table 2 , the reduction in CO 2 emissions based on the EU ETS standard CO 2 footprint for imported electricity is 11% and, based on the CO 2 footprint for imported electricity from wind and hydroelectric sources, is 23%. The above figures are not based on Technip Energies’ Low CO 2 Furnace, which can provide a further reduction in CO 2 emissions. The reduction in fuel firing may result in a reduction in fuel gas import or a surplus of fuel gas for export, depending on the feeds cracked and the plant configuration. Electric furnaces The use of electricity, instead of firing fuel, to provide the heat for the reactions in the cracking furnaces is being investigated by a number of parties, including Technip Energies. The main issues with the use of electric furnace technology do not concern how the heat is applied to the furnace coils (although these techniques need to be developed and proven), but relate to the amount of electricity

required, the CO 2 footprint of the electricity, and the effect on the electricity grid of start-up and shutdown of the cracker. A simple example of an ethane cracking furnace illustrates the importance of the electricity supply on the use of this technology to reduce CO 2 emissions: • Flue gas emissions firing 80 mol% hydrogen, 20 mol% methane fuel (typical fuel for an ethane cracking plant without hydrogen extraction) = 10.3 t/h CO 2 • Electrical power required to provide absorbed radiant duty only = 69-86 MW (range depends on electrical conversion efficiency) • CO 2 emissions required for power supply to give the same CO 2 emissions as firing 80 mol% hydrogen fuel gas = 0.15-0.12 TCO 2 e/MWh The required CO 2 footprint for the electricity supply to the site compared to the current CO 2 footprint for grid electricity for various countries is shown in Figure 3 . 7 Over time, the CO 2 footprint for electricity should decrease, with the phasing out of coal firing and increased use of renewables. Nevertheless, it is clear that to substantially reduce the CO 2 emissions for the complete cracker footprint, it is necessary to source electricity with a very low CO 2 footprint. Taking the above example of an ethane furnace, for a 1500 kTA ethane cracker, the amount of power required to replace the fired absorbed radiant duty is approximately 560 MW. This does not include the additional 30-90 MWh required