|Separations with chemical reaction:
Carbon dioxide and hydrogennsulfide are the major impurities of natural and refinery gases and synthesis gas for ammonia production. These impurities when present in the gas streams, lead to very serious problems in pipeline transportation and downstream processing of the gases, in liquefaction and in synthesis processes. Removal of these gases to a very low level is also mandatory for environmental reasons. Sweetening of the sour gas streams is very often done by regenerative absorption of the acid gas impurities in chemical solvents such as aqueous alkanolamines. In view of bringing down the processing cost in gas treating the amine processes are undergoing a continuous evolution during the last 10-15 years, since a little improvement in the process is often likely to bring about a large saving due to the large involvement of these processes in natural gas and industrial gas treating. Introduction of innovative amine formulations, concept of sterically hindered amines and the proposal to use blended amine solvents are but a few of the numerous fruits of constant R & D effort on the subject at a few leading R & D house and academic institutions throughout the globe to achieve higher efficiency, better selectivity under relatively lesser energy-intensive conditions. Besides, the mundane reasons of economy of gas treating processes, research on absorption of acid gases in chemical solvents provides a very good academic challenge to a chemical engineer to simultaneously solve problems of heat and mass transfer, chemical reaction kinetics and chemical equilibrium in complex gas-liquid systems.
|CO2 separation using membrane contactors:
The conventional method for CO2 capture is to remove CO2 by absorption into (alkanol)amine solutions using packed or bubble column absorption towers. The high initial investment is a major barrier for widespread utilization of the above technology. Besides, phase dispersion and limited mass transfer areas are the drawbacks of these conventional equipments. Hollow fiber membrane may overcome the disadvantages of the conventional equipment when incorporated into the acid gas treating processes. The compact modular structure of membrane contactors also provides much larger gas-liquid interfaces with known area at the pore mouth of the membrane, as well as the flexibility to scale-up or down. This research aims at synthesis of flat sheet as well as hollow fiber membrane contactors for CO2 separation.
|CO2 separation using facilitated transport polymeric membranes:
Current CO2 separation technology does not applicable for the entire range of separation applications. Amine-based technologies work only at low temperatures and pressure swing adsorption (PSA) as well as cryogenic distillation involves significant energy consumption for separating CO2. In contrast, polymer-based membrane separations are less energy intensive, requiring no phase change in the process, and typically provide low-maintenance operations. However, successful use of a polymer membrane in gas purification requires a membrane that is thermally, chemically, and mechanically stable at high temperature and high pressure. Unfortunately, the commercially available polymeric materials currently employed are not stable in such demanding environments to the degree required. Consequently, there is a compelling need for development of new polymeric membrane that can operate under demanding environmental conditions for extended periods of time while providing a level of performance that is economically sustainable by the end user. CO2-facilitated transport membrane can achieve high selectivity for the gas of interest based on the reversible reaction of the target gas with the active carrier incorporated in the membrane. The current research in this area aims at synthesis of novel polymeric CO2-facilitated transport membrane for acid gas purification.
The Department of Science and Technology (DST), India supported the BOYSCAST fellowship for advanced research in polymeric membrane under the broad area of "Advanced Materials". The research was conducted in collaboration with Professor W. S. Winston Ho (Editor of the Membrane Handbook) in the Department of Chemical & Biomolecular Engineering, the Ohio State University, Columbus, USA.
Industrial effluents containing pollutants like hexavalent chromium and trivalent chromium can cause contamination of water and changes the physical, chemical and biological properties of water. Such water is injurious to the public health and not suitable for domestic and commercial uses. It is also harmful to the animal, plant and aquatic lives. The removal of these pollutants from the industrial effluents, before it passes on to the main water bodies, is essential.