Decarbonisation Technology - November 2022

more complicated the refinery complex, the easier the conversion becomes (Rutz, et al. , 2020), (Bacovsky, et al., 2010). Conversion to a biorefinery will likely follow a phased approach. The first step in the conversion is removing carbon from fired sources, while the reduction of fossil feedstocks and replacement with biofeeds and renewable sources will occur over a longer duration. The biorefinery will combine renewable feed sources and fossil sources to manage and reduce Scope 1, 2 and 3 fossil CO₂ emissions (Ohmes, et al., 2022). The power requirements of the refinery will be satisfied from green sources or highly integrated systems. Electricity will increasingly be generated from low-carbon sources such as wind

turbines, solar panels, and nuclear energy. The co-processed steam from gasification or steam methane reforming (SMR) and/or auto thermal reforming (ATR) operations will supplant the steam from on-demand boilers, thereby reducing fired duty, while hydrogen will replace fossil fuel combustion in higher-temperature furnaces. Reducing precombustion emissions entails removal of carbon from the fuel gas system using reforming (SMR and ATR) or gasification technologies (Eide, et al., 2005). The CO₂ from the reforming processes is captured, and the hydrogen is used for the downstream fired sources to produce only water in the flue gas. Oxygen injection is also possible to increase the CO₂ in the stack, thereby improving CO₂ removal (Sharma, et al., 2021). Pre-combustion

Post - combustion carbon capture

Absorption

Adsorption

Cryogenic

Membranes

Pressure or temperature Swing Design

Physical

Chemical

Gas absorption

Gas separation

Alumina

Zeolite

Activated carbon

Dimethyl ethers

Amines

Chilled ammonia

Caustic

Others

Post - combustion removes the carbon after burn ing FG2 FG3 FG4 FG5

Flue gas or vent

FG1

FG5+n

Total FG

Total ue gas + air

5 Pre - combustion removes the carbon prior to burning 2 3 4

Unit No

5+n

Fired heaters

Boilers

Other sources

CO pph

R5+n

Pre - combustion fuel or combustion gas

Oxygen

H production

Cryogenic pure oxygen

Membranes enriched air

SMR with CO capture

Gasication

Figure 2 Pre- and post-combustion carbon removal