Novel external-loop CO₂-lift reactor for desilication of alkaline/surfactant/polymer produced water from oil well

Desilication is one of the most important pretreatment processes that prevent membrane fouling. In addition, it also increases the membrane flux during the filtration of alkaline/surfactant/polymer produced water. We developed a novel external-loop gas-lift reactor to enhance the filtration efficiency. In the modified reactor, CO₂ was pressurized through a porous titanium sintered pipe (mean pore size: 1 μm) to form uniform bubbles. The fine CO₂ bubbles reacted with the highly soluble silicate in water to form polysilicic acid sediments. A two-phase gas-liquid flow was maintained with high mixing. Furthermore, a liquid-falling tube was used to enhance the liquid circulation velocity as the tube separated the gas-liquid phases. A blister type draft tube was introduced in the riser to increase the gas residence time. The well-known Euler model of computational fluid dynamics and the population balance model (PBM) were used to simulate and optimize the reactor. Compared to the original reactor R-1, the novel reactor R-3 had improved the liquid circulation velocity and gas holdup by 369.8% and 25.4%, respectively. The novel reactor R-3 decreased the silica content from 452.3 to 96.7 mg·L⁻¹ in ASP produced water; the removal efficiency of the novel reactor R-3 was 6.3% greater than the conventional external-loop air-lift reactor. The novel reactor should be used in industrial water treatment plants, because it shows better compatibility and efficiency in treating the large amount of oil and silicate in wastewater.