Life Cycle Environmental Trade-Offs of Primary BOF Off-Gas Treatment

Upgrading primary basic oxygen furnace (BOF) off-gas treatment changes pollutant removal, utility demand, and energy recovery simultaneously. Its life cycle benefits therefore depend on the energy actually displaced and the additional inputs required to recover it. We compare wet OG cleaning (S0), dry LT cleaning (S1), and sensible-heat recovery coupled with polyphenylene sulfide (PPS) filtration (S2), using treatment of the off-gas associated with 1 t of crude steel as the functional unit (FU). A complete BOF gas (BOFG) carbon balance separates eventual carbon oxidation from energy-substitution credits. The assessment retains an 18-category midpoint framework, while distinguishing the recalculated global warming potential (GWP) from screening-level non-climate estimates. Using the documented background proxies, central GWPs are 118.376, 108.622, and 102.304 kg CO2-eq/FU for S0, S1, and S2 at 50% useful-heat utilization (S2-SS50), respectively. The 8.24% reduction from S0 to S1 is driven by lower utility demand and greater gas recovery. S2-SS50 achieves a further reduction of 5.82% relative to S1. Its heat-utilization break-even ratio is 0.86% under central assumptions, rises to 35.96% under an adverse operating combination with central energy factors, and reaches 82.64% when the energy background is also adverse. These deterministic scenarios show that the additional climate benefit of S2 depends on useful heat demand, operating inputs, and the displaced energy supply. Non-climate screening identifies possible burden shifts but does not establish an overall environmental ranking. Quantitative endpoint comparisons are withheld because they have not been recalculated consistently with the revised carbon inventory.