A comparative simulation study of power generation plants involving chemical looping combustion systems
Abstract This work presents a simulation study on both energy and economics of power generation plants with inherent CO 2 capture based on chemical looping combustion technologies. Combustion systems considered include a conventional chemical looping system and two extended three-reactor alternatives (exCLC and CLC3) for simultaneous hydrogen production. The power generation cycles include a combined cycle with steam injected gas turbines, a humid air turbine cycle and a simple steam cycle. Two oxygen carriers are considered in our study, iron and nickel. We further analyze the effect of the pressure reaction and the turbine inlet temperature on the plant efficiency. Results show that plant efficiencies as high as 54% are achieved by the chemical looping based systems with competitive costs. That value is well above the efficiency of 46% obtained by a conventional natural gas combined cycle system under the same conditions and simulation assumptions.
A new type of coal gas fueled chemical-looping combustion
A new type of coal gas fueled chemical-looping combustion is experimentally investigated by means of a fixed-bed reactor operated at elevated pressure. Chemical-looping combustion may be carried out in two successive reactions between two reactors, a reduction reactor (coal gas with metal oxides) and an oxidation reactor (reduced metal with oxygen in the air), which may lead to a breakthrough in clean coal technology by simultaneously allowing efficient use of energy and greenhouse gas control. We have experimentally examined the kinetic behavior between solid looping materials and coal gas in a high-pressure fixed bed reactor. On the basis of the development of suitable material and the good reactivity with the fixed bed reactor, we have identified that the coal gas fueled chemical-looping combustor has much better reactivity than natural gas combustors, and this phenomenon is completely different from direct combustion with natural gas. The promising results obtained here will be valuable for the design of a practical reactor.
Diversity of Electrospinning Approach for Vascular Implants: Multilayered Tubular Scaffolds
Abstract The biomimetics of biological structures found in nature remains one of the most promising approaches to engineer functional tissues from natural or synthetic biocompatible materials for the replacement of damaged or injured parts of the human body. Recently, medical therapeutic regimes have advanced into a new era, overcoming the known mechanical and biological variances that occur when using autologous or synthetic grafts. Basically, the core concept of tissue biofabrication, commonly referred to as tissue engineering, is to find out the favorable cellular microenvironments to grow a living tissue prior to clinical uses. In fact, the ability of stem cells to regenerate is controlled via signaling pathways (growth factors) and supporting materials (scaffolds) that guide the cellular activities. After the first successful experiments to fabricate polymer fibers from their solutions, Cooley proposed the use of an electric field a century ago (Cooley (US 692:631, 1902 ). The electrospinning technique has been continually developed as a fruitful polymer processing technique to draw ultrafine nonwoven fibers. Electrospun polymer fibers have been used for a wide range of technical and biotechnical applications such as filtration, organic solar cells, tissue engineering, and drug releasing implants. In this regard, this review begins with an overview about the various spinning approaches for the fabrication of polymer fibers as well as the basic principles of electrospinning process. In addition, this review will highlight vascular bypass surgery and, in particular, the needs for vascular tissue engineering. Finally, the review includes some of the latest attempts to improve the mechanical and biological properties of electrospun polymeric fibers and summarizes the challenges and prospects for the future. Lay Summary However, vascular defects are treated successfully via bypass surgical bypass grafting using autologous or synthetic vessels. The small-diameter vessels (less than 6) are often associated with high failure rate. This review reports some of the recent features that should be highlighted to fabricate an ideal graft for small-diameter vascular grafts. The review introduces multilayered conduits as an alternative approach to overcome the known mechanical and biological mismatches of single layered vascular grafts of electrospun polymers.