From the choke to the column: where does the potential of LTS in associated petroleum gas processing end?

A unified Aspen HYSYS v 12.1 model was developed to benchmark two competing low temperature routes for associated petroleum gas (APG) valorization: conventional two stage low temperature separation (LTS) and full cryogenic rectification (CR) equipped with a turbo expander. Both schemes were simulated for a “rich” Western Siberian APG (9.0 MPa, 12.6 mol % C₃, Σ C₄+ ≈ 8 mol %). Switching from LTS (–30 °C) to CR (–88 °C) increases C₂+ recovery from 41 % to 64.8 % while raising total refrigeration duty by 24 %. The additional cold demand is partly offset by 93 kW of turbo expander power, improving the net power balance from –248 kW to –155 kW. Relative CAPEX and OPEX indices for CR amount to 1.2 and 1.5, respectively; at spot prices of 140 USD t⁻¹ ethane and 480 USD t⁻¹ propane the incremental investment is repaid in < 2.5 years. A hybrid “LTS→CR” configuration lowers the specific OPEX to 57 kWh t⁻¹, requires only +15 % CAPEX and pays back in ~26 months while preserving 92 % of full scale CR recovery. Deep rectification also cuts the carbon footprint of sales gas by ~18 kg CO₂ eq t⁻¹ – enough to offset ≈ 7 % of annual operating costs under the forthcoming EU CBAM tariff. The study provides a decision matrix linking reservoir pressure and dew point specification to the most cost effective processing route.