Gas 2025 Issue

Maximising value from refinery off-gases

Case studies examine reactor designs shaped by plant needs and gas composition, demonstrating how ROG purification offers compelling economics

Wolf Spaether, Holli Garret, Kristina Morgan and Felix Schulz Clariant

I n the past, refineries viewed off-gases from fluid catalytic cracking (FCC) units, coker units, and similar sources sim- ply as waste streams, burning them as fuel gas or releasing them through flaring. Today, these off-gases are recognised as valuable resources, containing a rich blend of hydrocar- bons, olefins (as much as 30 mol% in off-gas), diolefins, and hydrogen, alongside some undesirable impurities. Refinery integration with ethylene plants aims to max- imise olefin yields. Treating off-gases for removal of critical impurities for the purpose of recovering high-value compo- nents such as ethylene, propylene, paraffins, and hydrogen can be a major part of this strategy to significantly boost the plant’s economics while reducing the CO₂ footprint. However, off-gas compositions vary significantly, espe- cially when factoring in the removal of associated impuri- ties. Both catalytic and adsorptive treatments are essential yet challenging to implement. Currently, across the industry, the proprietary nickel-based

OleMax 100 catalyst series treats more than 1,000 met- ric tons per hour of predominantly refinery-sourced off- gases for nitric oxide, oxygen, acetylene, and heavy metals removal for recovery of hydrocarbon products. This results in more than 300 metric tons per hour of ethylene capac- ity gained and improved process safety within the down- stream cryogenic processing section. In addition to safely removing contaminants, treating and recovering the valu- able components from off-gases with adsorbents and cat- alysts provides added benefits of reducing carbon dioxide and other pollutants emissions that are typically created when used in the refinery fuel gas and flare systems. Against this backdrop, a focus on experience and results in designing new and revamped off-gas catalytic treatment systems is forthcoming. In some cases, these systems are also known as De-Oxo reactors. Through case studies, specialised catalytic reactor designs shaped by plant needs and gas composition are examined. The examples cover

PDH (Catofin)

Mon Pur (PolyMax ActiSorb)

Propylene Ethylene

Polypropylene ( Po l y Max)

ROG / ERU / PRU (OleMax)

O - gas

Polyethylene

C-C-C

Steam cracker light ends

Steam cracker furnaces

Mon Pur (PolyMax ActiSorb)

Naphtha

EO, glycols

recovery (OleMax)

Gasoline Jet fuel Diesel Fuel oil

C-C

Pygas (OleMax)

EDC / PVC (OxyMax)

ODH-E

Methane

Styrene (StyroMax)

Benzene

Aromatic complex

Polystyrene

Ethylbenzene

C-C

Ethane

Xylenes

PTA (H2Max)

PET

NG liquids

Toluene

ROG = Renery o -g as, EPU/PRU = Ethylene/propylene recovery unit, PDH = Propylene dehydrogenation, EO = Ethylene oxide, EDC = Ethylene dichloride, PVC = Poly vinyl chloride, PTA = Pu ri ed terephthalate acid, ODH-E = Oxidative dehydrogenation of ethane

Figure 1 Refinery off-gas treatment is an important link in the crude to chemical value chain where low-value stream contain high-value olefins

Gas 2025