Hiroshi Mano

Separation and enrichment of carbon dioxide by capillary membrane module with permeation of carrier solution

Abstract A novel facilitated transport membrane for gas separation using a capillary membrane module is proposed in which a carrier solution is forced to permeate the membrane. Both a feed gas and a carrier solution are supplied to the lumen side (high pressure side, feed side) of the capillary ultrafiltration membrane and flow upward. Most of the carrier solution which contains dissolved solute gas, CO 2 in the present case, permeates the membrane to the permeate side (low pressure side, shell side), where the solution liberates dissolved gas to form a lean solution. The lean solution is circulated to the lumen side. This type of capillary membrane module was applied to the separation of CO 2 from model flue gases consisting of CO 2 and N 2 . Monoethanolamine (MEA), diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) were used as carriers or absorbents of CO 2 . The feed side pressure was atmospheric and the permeate side was evacuated at about 10 kPa. CO 2 in the feed gas was successfully concentrated from 5–15% to more than 98%. The CO 2 permeance was as high as 2.7×10 −4 mol m −2 s −1 kPa −1 (8.0×10 −4 cm 3 cm −2 s −1 cmHg −1 ) when the CO 2 mole fraction in the feed was 0.1 and temperature was 333 K. The selectivity of CO 2 over N 2 was in the range from 430 to 1790. The membrane was very stable over a discontinuous one-month testing period.

Cardo polyimide membranes for CO2 capture from flue gases

Publisher Summary This chapter discusses that cardo polyimide hollow fiber membranes were developed as an alternative to existing commercial amine absorption for CO2 capture from flue gases. To investigate the relationship between chemical structures and CO2 separation properties, various cardo polyimides were synthesized to measure CO2 separation properties and some chemical structure was found to give remarkable properties both in CO2 permeation and selectivity. An economic analysis was carried out for CO2 separation using the hollow fiber membrane followed by a liquefaction process. In the cost breakdown of CO2 separation with membrane, the electricity consumption of the vacuum pump, which induce a pressure difference between a feed side and a permeate side of a membrane, contributed 50% or more of the total cost. For further cost reduction, an application of membrane system to pressurized gas streams similar to CO2 removal from natural gas might be a promising way of reducing the cost of CO2 separation.

Development of CO2 Separation Membranes (1) Polymer Membrane

Publisher Summary Exhaust gas from thermal power plants, cement plants, and steel mills consists mostly of N 2 and CO 2 and thus technology to separate these gases is required. This chapter explains how to develop a membrane that provides excellent selectivity for CO 2 and is durable and heat resistant. Furthermore, CO 2 separation membranes need to be modular to cope effectively with the large volumes of exhaust gases from stationary sources. A new cardo type polymer membrane was developed keeping in mind the ongoing problem of global warming. The cardo type polymer has a molecular structure with a bulky loop form. The polymer shows the important characteristics of a high gas permeability and high solubility in organic solvents that provide hollow fiber membrane processability and heat stability derived from an aromatic structure. Since a cardo type polyimide showed the highest CO 2 /N 2 selectivity and CO 2 permeability during the screening of many newly synthesized cardo type polymers, it was selected and a structure function relationship analysis was conducted looking at CO 2 /N 2 selectivity and CO 2 permeability. A new cardo type polyimide structure for CO 2 separation was identified. Then, the wet spinning technology to produce an asymmetric hollow fiber membrane was developed and the membrane in module was incorporated. In addition to using bench-scale testing to obtain basic data for implementing the module, a 1,000MW coal combustion power plant was considered. The information obtained confirmed that in energy terms, the developed membrane separation method is superior to current methods.

CO 2 capture and enrichment by novel hollow fiber facilitated transport membrane module with low energy consumption

Publisher Summary This chapter proposes a novel gas separation method using capillary membrane modules for simultaneous recovery and enrichment of CO2 in simulated flue gases. Several capillary membrane modules were fabricated with different dimensions and experiments were performed at several conditions by using an amine and an amino acid as the carriers of CO2. The energy consumption of the current process is compared to those of conventional gas absorption processes and membrane gas separation processes using polymeric membranes. Both a feed gas and a carrier solution are supplied to the feed side (high pressure side) of the capillary ultrafiltration membrane module and flow upward. Most of the carrier solution that contains dissolved CO2 permeates the membrane to the permeate side (low-pressure side), where the solution liberates CO2 to become a lean solution and the lean solution is returned to the lumen of the capillary module by a pump. Experiments were performed at several operational conditions by using diethanolamine (DEA) and 2, 3-diaminopropionic acid (DAPA) as carriers. The energy required for CO2 capture, enrichment, and liquefaction was about 0.27kWh kgC02-1, which is much lower than those by using polymeric membranes, conventional gas absorption processes consisting of absorption and stripping column. The proposed process is promising for the CO2 recovery with low energy consumption.

Evaluation of Membrane Separation Process of CO2 Recovery

Publisher Summary Various technologies, including CO 2 geological storage and ocean storage, and CO 2 utilization, have been investigated as a countermeasure to the greenhouse effect. Before they are applied to the fields of thermal power plants, cement plants, steel mills, etc., CO 2 must be recovered from the exhaust flue gas from the plants. To recover CO 2 from flue gas, a membrane separation processes is applicable, in which the pressure difference should be applied across the membrane as a permeation driving force. It can be done either by compressing the flue gas with a compressor or connecting a vacuum pump to the permeation side of the membrane module. The energy consumed to operate the equipment is regarded as the CO 2 separation energy. A computer simulation was carried out to estimate the energy and cost for a CO 2 separation process with a membrane applied to the exhaust flue gas from a 1000MW coal combustion power plant. Three types of separation processes, depending on the mode of pressure application were investigated—that is, membrane separation processes driven by decompression, compression, and compression-decompression. It was found that both the energy and cost for CO 2 separation were smallest in the case of the compression-decompression mode. The membrane separation process driven by compression-decompression was the most economical among the three types of processes.