Absorption of SO₂ by single hydrophobic ceramic tubule-based membrane contactor

The emission of SO_x from marine vessels has caused serious environmental problem. Membrane contactor that offers several advantages over conventional tower device such as a compact size, operational flexibility, independent gas and liquid flow, easy scale-up, and modularity is an alternative technology in the application of marine exhaust gas desulfurization. In this work, a single ceramic tubule-based membrane contactor was fabricated from ZrO₂ ceramic membrane with average pore size of 200 nm. A series of experiments of SO₂ absorption were carried out using water as low-cost absorbent. The mass transfer performance of the unmodified and modified membrane was compared and the effects of gas flow rate, absorbent flow rate, feed gas concentration, temperature of absorbent on SO₂ removal efficiency and mass transfer rate were investigated. The long-term stability of ceramic membrane contactor was tested as well. It was found that the overall structures and the surface porosity of ceramic membrane hardly changed by surface modification with hexadecyltrimethoxysilane (HDTMS). The hydrophobic ceramic membrane with contact angle of 132° had higher desulfurization efficiency and overall mass transfer coefficient than those of the unmodified membrane under the same operating conditions. The desulfurization efficiency and mass transfer rate increased as the liquid flow rate increased. The desulfurization efficiency decreased as the gas flow rate and feed gas concentration increased while the mass transfer rate increased. Absorbent with low temperature was more favorable for the absorption of SO₂. CO₂ in the feed gas had little effect on the SO₂ removal efficiency. The ceramic membrane contactor had lower height of transfer unit(HTU)value than conventional packed tower and showed great potential in the application of exhaust gas desulfurization.