135 research outputs found
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Regenerable Sorbent Development for Sulfur, Chloride and Ammonia Removal from Coal-Derived Synthesis Gas
A large number of components in coal form corrosive and toxic compounds during coal gasification processes. DOE’s NETL aims to reduce contaminants to parts per billion in order to utilize gasification gas streams in fuel cell applications. Even more stringent requirements are expected if the fuel is to be utilized in chemical production applications. Regenerable hydrogen sulfide removal sorbents have been developed at NETL. These sorbents can remove the hydrogen sulfide to ppb range at 316 °C and at 20 atmospheres. The sorbent can be regenerated with oxygen. Reactivity and physical durability of the sorbent did not change during the multi-cycle tests. The sorbent development work has been extended to include the removal of other major impurities, such as HCl and NH3. The sorbents for HCl removal that are available today are not regenerable. Regenerable HCl removal sorbents have been developed at NETL. These sorbents can remove HCl to ppb range at 300 °C to 500 °C. The sorbent can be regenerated with oxygen. Results of TGA and bench-scale flow reactor tests with both regenerable and non-regenerable HCl removal sorbents will be discussed in the paper. Bench-scale reactor tests were also conducted with NH3 removal sorbents. The results indicated that the sorbents have a high removal capacity and good regenerability during the multi-cycle tests. Future emphasis of the NETL coal gasification/cleanup program is to develop multi-functional sorbents to remove multiple impurities in order to minimize the steps involved in the cleanup systems. To accomplish this goal, a regenerable sorbent capable of removing both HCl and H2S was developed. The results of the TGA conducted with the sorbent to evaluate the feasibility of both H2S and HCl sorption will be discussed in this paper
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Hydrogen Separation Membranes Annual Report for FY 2006.
The objective of this work is to develop dense ceramic membranes for separating hydrogen from other gaseous components in a nongalvanic mode, i.e., without using an external power supply or electrical circuitry. This goal of this project is to develop two types of dense ceramic membrane for producing hydrogen nongalvanically, i.e., without electrodes or external power supply, at commercially significant fluxes under industrially relevant operating conditions. The first type of membrane, hydrogen transport membranes (HTMs), will be used to separate hydrogen from gas mixtures such as the product streams from coal gasification, methane partial oxidation, and water-gas shift reactions. Potential ancillary uses of HTMs include dehydrogenation and olefin production, as well as hydrogen recovery in petroleum refineries and ammonia synthesis plants, the largest current users of deliberately produced hydrogen. The second type of membrane, oxygen transport membranes (OTMs), will produce hydrogen by nongalvanically removing oxygen that is generated when water dissociates at elevated temperatures. This report describes progress that was made during FY 2006 on the development of OTM and HTM materials
The Pitfalls of Central Clearing in the Presence of Systematic Risk
Through the lens of market participants' objective to minimize counterparty risk, we provide an explanation for the reluctance to clear derivative trades in the absence of a central clearing obligation. We develop a comprehensive understanding of the benefits and potential pitfalls with respect to a single market participant's counterparty risk exposure when moving from a bilateral to a clearing architecture for derivative markets. Previous studies suggest that central clearing is beneficial for single market participants in the presence of a sufficiently large number of clearing members. We show that three elements can render central clearing harmful for a market participant's counterparty risk exposure regardless of the number of its counterparties: 1) correlation across and within derivative classes (i.e., systematic risk), 2) collateralization of derivative claims, and 3) loss sharing among clearing members. Our results have substantial implications for the design of derivatives markets, and highlight that recent central clearing reforms might not incentivize market participants to clear derivatives
Social Safety Nets for Food and Nutritional Security in India
This paper brings together existing literature on the Mahatma Gandhi National Rural Employment Guarantee Act (MGNRGEA) and the Public Distribution System (PDS) in India, offering a narrative review of the evidence on impacts on food security, health and nutrition of beneficiaries. Both programs operate on a large scale and have the capacity to impact the factors leading to undernutrition. It is evident that despite the deficiencies in implementation, both the MGNREGA and the PDS are inclusive and reach the poor and the marginalized who are likely to also experience greater undernutrition and poor health. Data challenges have however prevented researchers from conducting studies that assess the ultimate impact of these two large-scale programs on health and nutrition. The evidence that exists suggests largely positive impacts indicating a clear potential to make these programs more nutrition sensitive not just by incorporating elements that would
explicitly address nutritional concerns but also by directing specific attention to innovations that strengthen critical complementarities and synergies that exist between the two programs
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