Decarbonisation Technology - November 2021

Technip Energies believes a better solution than importing hydrogen generated from electrolysis is to convert the cracker fuel gas to a high hydrogen stream, by steam methane reforming (SMR) or auto thermal reforming (ATR). Technip Energies’ BlueH2 proprietary technology minimises the energy consumed in the reformer, generates no additional steam, and includes capture of the CO 2 . Capture of the CO 2 from the cracker fuel gas is more economical if it is carried out at the outlet of the reformer, rather than from the reforming furnace flue gas, as the pressure at the reformer outlet is higher, and the equipment can be made much smaller, significantly reducing the capital cost. Electrification As noted above, when the fired duty of the furnaces is reduced, one of the main consequences is a reduction in the amount of high-pressure steam generated. Consequently, there is unlikely to be sufficient steam to drive the main compressors in the steam cracker. This leads to the use of electric motor drivers for the compressors, or ‘electrification’ of the cracker. The use of electric motors as drivers for the main steam cracker compressors is not new. Technip Energies has four reference plants (three grassroots, one revamped) where electric motors are used to drive at least two of the three main compressors. These plants were designed this way to take advantage of the low cost electricity then available in certain countries. The main challenges with electrifying steam crackers are: • Experience with electric motors and variable speed drives (VSDs) at the powers required for modern world-scale steam crackers (Technip Energies makes reference to its experience in other industries in which it is a leader, such as LNG) • Avoidance of harmonic resonance between motor drivers and compressors • Influence on the electrical supply grid of stopping and starting large motors • Maintaining compressor efficiencies and speeds when motors are retrofitted • Accommodating VSD equipment and filters (if required) within plot areas which are close to the motors Choices need to be made about how many and which compressors to electrify. These depend mainly on the amount of high-pressure steam

is only reduced if very low CO 2 electricity is available i.e. green hydrogen. As the cracker fuel gas is no longer used in the furnaces, the fuel gas is now surplus • For 376 tCO 2 e/GWh electricity, the CO 2 footprint of the electricity consumed by the electrolyser plus the cracker is greater than the CO 2 emitted by the Source 1 and 2 emissions, when the steam cracker is firing methane fuel (1.72 vs 0.63 tCO 2 e/t HVC) • For 376 tCO 2 e/GWh electricity, the CO 2 footprint of the steam cracker with reformer is 62% less than the steam cracker without reforming the fuel gas (0.24 vs 0.63 tCO 2 e/t HVC) • For 26 tCO 2 e/GWh electricity, the CO 2 footprint of the steam cracker with reformer is 81% less than the steam cracker without reforming the fuel gas (0.12 vs 0.63 tCO 2 e/t HVC) The amount of hydrogen fired should be minimised, by reducing the firing in the furnaces, as described above. This minimises the hydrogen imported to the plant, or makes more hydrogen available from reformed fuel gas. Importing hydrogen leaves a surplus of fuel gas generated in the cracker, which is primarily methane. This fuel gas can be used for power generation, but this generates CO 2 and only improves the overall CO 2 footprint of the cracker if imported electricity has a higher CO 2 footprint than the electricity generated from the cracker fuel gas.

Base Electrified cracker

Furnace firing duty, MW VHP boiler firing duty, MW MP boiler firing duty, MW Fuel gas available, t/h Natural gas import a, t/h Excess fuel gas, t/h

1281

995

- -

44 91 ~ 2 25

91 ~ 2 5.9

t of CO 2 /t of HVC b t of CO 2 /t of HVC c

0.63 0.62

0.55 0.48

Table 2 Comparison of utility and CO 2 figures for a base and electrified 1500 kTA liquid cracker b. Based on ISBL firing and electric import at 376 t of CO 2 /GWh (Standard EU Emissions Trading Scheme [ETS] figure) c. Based on ISBL firing and electric import at 26 t of CO 2 /GWh (wind/hydroelectric power) Notes: a. Natural gas import retained for furnace and flare pilots