Mass Transfer Simulation of Carbon Dioxide Absorption in a Hollow-Fiber Membrane Contactor

Hollow Fiber Membrane Contactors for Post-Combustion Carbon Capture: A Review of Modeling Approaches

Hollow fiber membrane contactors (HFMCs) can effectively separate CO2 from post-combustion flue gas by providing a high contact surface area between the flue gas and a liquid solvent. Accurate models of carbon capture HFMCs are necessary to understand the underlying transport processes and optimize HFMC designs. There are various methods for modeling HFMCs in 1D, 2D, or 3D. These methods include (but are not limited to): resistance-in-series, solution-diffusion, pore flow, Happel’s free surface model, and porous media modeling. This review paper discusses the state-of-the-art methods for modeling carbon capture HFMCs in 1D, 2D, and 3D. State-of-the-art 1D, 2D, and 3D carbon capture HFMC models are then compared in depth, based on their underlying assumptions. Numerical methods are also discussed, along with modeling to scale up HFMCs from the lab scale to the commercial scale.

A Feasibility Study of Ammonia Recovery from Coking Wastewater by Coupled Operation of a Membrane Contactor and Membrane Distillation

More than 80% of ammonia (NH₃) in the steel manufacturing process wastewater is contributed from the coking wastewater, which is usually treated by biological processes. However, the NH₃ in the coking wastewater is typically too high for biological treatment due to its inhibitory concentration. Therefore, a two-stage process including a hollow fiber membrane contactor (HFMC) and a modified membrane distillation (MD) system was developed and applied to reduce and recover NH₃ from coking wastewater. The objectives of this paper are to evaluate different membrane materials, receiving solutions, and operation parameters for the system, remove NH₃ from the coking wastewater to less than 300 mg N/L, which is amenable to the biological process, and recover ammonia solution for reuse. As a result, the polytetrafluoroethylene (PTFE) HFMC using sulfuric acid as a receiving solution can achieve a maximum NH₃-N transmembrane flux of 1.67 g N/m²·h at pH of 11.5 and reduce NH₃ in the coking wastewater to less than 300 mg N/L. The NH₃ in the converted ammonium sulfate ((NH₄)₂SO₄) was then recovered by the modified MD using ice water as the receiving solution to produce ≥3% of ammonia solution for reuse.