The present study continues the development and enhancement of a highly efficient unique hybrid technique—membrane-assisted gas absorption in designing the separation unit, which provides the improvement in mass-transfer of a target component during the ammonia capture process from a process loop of the Haber–Bosch technological route. In order to minimize the absorbent volume to membrane area ratio, the special separation cell was designed based on a combination of two types of hollow fiber membranes, dense gas separation membrane and porous pervaporation membrane. The separation performance tests were implemented under two sets of conditions, sweeping the bore (permeate) side of a cell with helium and hydrogen-nitrogen mix. For both cases, the membrane-assisted gas absorption cell demonstrated high separation efficiency, and the ammonia concentration in the permeate was never lower than 81 mol%; meanwhile, under the hydrogen-nitrogen bore sweep conditions, the ammonia concentration in the permeate reached 97.5 mol% in a single-step process. Nevertheless, there is a product purity–recovery rate trade-off, which is a typical issue for separation processes.

The present paper deals with the complex study of CO₂ capture from combined heat power plant flue gases using the efficient technological design of a membrane cascade type of «Continuous Membrane Column» for binary gas mixture separation. In contrast to well-known multi-step or multi-stage process designs, the cascade type of separation unit provides several advantages. Here, the separation process is implemented in it by creating two counter current flows. In one of them is depleted by the high-permeable component in a continuous mode, meanwhile the other one is enriched. Taking into account that the circulating flows rate overcomes the withdrawn one, there is a multiplicative increase in separation efficiency. A comprehensive study of CO₂ capture using the membrane cascade type of «Continuous Membrane Column» includes the determination of the optimal membrane material characteristics, the sensitivity study of the process, and a feasibility evaluation. It was clearly demonstrated that the proposed process achieves efficient CO₂ capture, which meets the modern requirements in terms of the CO₂ content (≥95 mol.%), recovery rate (≥90%), and residual CO₂ concentration (≤2 mol.%). Moreover, it was observed that it is possible to process CO₂ with a purity of up to 99.8 mol.% at the same recovery rate. This enables the use of this specific process design in CO₂ pretreatment operations for the production of high-purity carbon dioxide.

The present paper deals with the complex study of the CO2 capture from combined heat power plant flue gases using the efficient technological scheme design – membrane cascade type of «Continuous Membrane Column». In contrast to well-known multi-step or multi-stage process designs, the cascade type of separation unit provides several advantages. That apparatus conceptually refers to the distillation columns. Here, the separation process is implemented in it by creating two counter current flows. In one of them is depleted by the high-permeable component in a continuous mode, meanwhile the other one is enriched. Taking into account, that the circulating flows rate overcome the withdrawn ones, there is a multiplicative growth in separation efficiency. A comprehensive study of the CO2 capture using membrane cascade type of «Continuous Membrane Column» includes the determination of optimal membrane material characteristics, the sensitivity study of the process and feasibility evaluation. It was clearly demonstrated that proposed process provides the efficient CO2 capture, which meets the modern requirements in terms of CO2 content (≥ 95 mol.%), recovery rate (≥ 90 %) and residual CO2 concentration (≤ 2 mol.%). Moreover, it was observed, that it is possible to process CO2 with purity up to 99.8 mol.% at the same recovery rate. This allows use of this specific process design in the CO2 pretreatment operations in the production of high-purity carbon dioxide.

A study of the effect of temperature in a wide range (from 258.15 up to 293.15 K) on the gas transport characteristics of asymmetric polymeric gas separation fibers based on polysulfone for the components of a CO₂–N₂ binary gas mixture with various compositions is carried out. Within the framework of the work, the values of the permeability, diffusion, and solubility coefficients of pure gases in the temperature range of interest as well as the values of the permeability coefficient of the components of a CO₂–N₂ binary gas mixture are determined using gas chromatographic analysis of the permeate flow. It is demonstrated in this work that the process of separation the most effectively occurs at room temperature in the case of a low concentration of carbon dioxide (up to 15 mol %) in the binary mixture. It is experimentally shown that the separation process is the most effective at a low temperature (273.15 K) in the rest of the range of concentrations of CO₂. Further decrease in temperature does not make the process of separation of the mixture more effective throughout the entire considered range of concentrations of carbon dioxide.