Experimental Study of High-Pressure Oxy-Fired Direct Contact Steam Generation (HiPrOx-DCSG) with Steam-Assisted Gravity Drainage (SAGD) Produced Water

Direct contact steam generation (DCSG) produces steam-rich gas by directly contacting combustion gases with sprayed water. This water is typically produced water (i.e., recovered condensate) from a process that has already extracted heat from the steam-rich gas. DCSG enables the reuse of produced water for steam generation without the extensive treatment required by conventional boiler systems, making it suitable for applications where a high steam purity is not essential. Key challenges in DCSG include managing impurities during combustion and matching the flue gas pressure with the elevated downstream process pressure, often necessitating pressurized combustion. This requirement becomes advantageous when integrated with carbon capture and storage (CCS), especially with oxy-fired combustion where flue gas, following H₂O condensation, yields a pressurized CO₂-rich stream requiring less energy for downstream capture and compression. This study tested a pilot-scale high-pressure oxy-fired (HiPrOx) DCSG system operating at pressures of 80, 55, and 30 barg and temperatures between 1000 and 1250 °C, using steam-assisted gravity drainage (SAGD) produced water. The system successfully generated a pressurized steam-rich gas containing approximately 90% steam, balanced by CO₂ and trace gases, suitable for CO₂ coinjection into SAGD wells. Oxy-fired combustion effectively removed solids and impurities from the SAGD water; however, burner surface deposition was severe at 80 barg. Deposition was significantly reduced and acceptable at 55 barg and minimal at 30 barg. The results demonstrate the feasibility of HiPrOx-DCSG for utilizing highly contaminated water for steam generation.