Advances in Ammonia Removal from Hot Coal Gas

Nitrogen occurs in coal in the form of tightly bound organic ring compounds, typically at levels of 1 to 2 wt%. During coal gasification, this fuel bound nitrogen is released principally as ammonia (NH{sub 3}). When hot coal gas is used to generate electricity in integrated gasification combined cycle (IGCC) power plants, NH{sub 3} is converted to nitrogen oxides (NO{sub x}) which are difficult to remove and are highly undesirable as atmospheric pollutants. Similarly, while the efficiency of integrated gasification molten carbonate fuel cell (IGFC) power plants is not affected by NH{sub 3}, NO{sub x} is generated during combustion of the anode exhaust gas. Thus NH{sub 3} must be removed from hot coal gas before it can be burned in a turbine or fuel cell. The objective of this study is to develop a successful combination of an NH{sub 3} decomposition catalyst with a zinc-based mixed-metal oxide sorbent so that the sorbent-catalyst activity remains stable for NH{sub 3} decomposition in addition to H{sub 2}S removal under cycle sulfidation-regeneration conditions in the temperature range of 500 to 750{degrees}C

Scale-Up of Advanced Hot-Gas Desulfurization Sorbents

The overall objective of this project is to develop regenerable sorbents for hot gas desulfurization in IGCC systems. The specific objective of the project is to develop durable advanced sorbents that demonstrate a strong resistance to attrition and chemical deactivation, and high activity at temperatures as low as 343{degrees}C (650{degrees}F). A number of formulations will be prepared and screened in a 1/2-inch fixed bed reactor at high pressure (1 to 20 atm) and high temperatures using simulated coal-derived fuel-gases. Screening criteria will include, chemical reactivity, stability, and regenerability over the temperature range of 343{degrees}C to 650{degrees}C. After initial screening, at least 3 promising formulations will be tested for 25-30 cycles of absorption and regeneration. One of the superior formulations with the best cyclic performance will be selected for investigating scale up parameters. The scaled-up formulation will be tested for long term durability and chemical reactivity

Advanced Hot-Gas Desulfurization Sorbents

The objective of this project is to develop advanced hot-gas desulfurization sorbents for relatively low temperature application that show stable and high sulfidation reactivity at 343 to 538 {degrees}C. A number of zinc-based formulations will be prepared and screened for testing in a fixed-bed reactor at high pressure (1 to 20 atm) and high temperatures using simulated coal-derived fuel gases. One of the superior formulations will be tested for long- term durability and chemical reactivity in the reactor. To prevent sulfation, catalyst additives will be investigated, which would promote a lower regeneration temperature

Advanced Hot-Gas Desulfurization Sorbents

Integrated gasification combined cycle (IGCC) power systems are being advanced worldwide for generating electricity from coal due to their superior environmental performance, economics, and efficiency in comparison to conventional coal-based power plants. Hot gas cleanup offers the potential for higher plant thermal efficiencies and lower cost. A key subsystem of hot-gas cleanup is hot-gas desulfurization using regenerable sorbents. Sorbents based on zinc oxide are currently the leading candidates and are being developed for moving- and fluidized- bed reactor applications. Zinc oxide sorbents can effectively reduce the H{sub 2}S in coal gas to around 10 ppm levels and can be regenerated for multicycle operation. However, all current first-generation leading sorbents undergo significant loss of reactivity with cycling, as much as 50% or greater loss in only 25-50 cycles. Stability of the hot-gas desulfurization sorbent over 100`s of cycles is essential for improved IGCC economics over conventional power plants. This project aims to develop hot-gas cleanup sorbents for relatively lower temperature applications, 343 to 538{degrees}C with emphasis on the temperature range from 400 to 500{degrees}. Recent economic evaluations have indicated that the thermal efficiency of IGCC systems increases rapidly with the temperature of hot-gas cleanup up to 350{degrees}C and then very slowly as the temperature is increased further. This suggests that the temperature severity of the hot-gas cleanup devices can be reduced without significant loss of thermal efficiency. The objective of this study is to develop attrition-resistant advanced hot-gas desulfurization sorbents which show stable and high sulfidation reactivity at 343{degrees}C (650{degrees}F) to 538{degrees}C(1OOO{degrees}F) and regenerability at lower temperatures than leading first generation sorbents

Serine/threonine protein phosphatase PstP of Mycobacterium tuberculosis is necessary for accurate cell division and survival of pathogen

Protein phosphatases play vital roles in phosphorylation-mediated cellular signaling. While there are 11 serine/threonine protein kinases in Mycobacterium tuberculosis, only one serine/threonine phosphatase, PstP, has been identified. Although PstP has been biochemically characterized and multiple in vitro substrates identified, its physiological role has not yet been elucidated. In this study we have investigated the impact of PstP on cell growth and survival of the pathogen in the host. Overexpression of PstP led to elongated cells and partially compromised survival. We find that depletion of PstP is detrimental to cell survival, eventually leading to cell death. PstP depletion results in elongated multiseptate cells, suggesting a role for PstP in regulating cell division events. Complementation experiments performed with PstP deletion mutants revealed marginally compromised survival, suggesting that all the domains including extracellular domain are necessary for complete rescue. On the other hand, the catalytic activity of PstP is absolutely essential for the in vitro growth. Mice infection experiments establish a definitive role for PstP in pathogen survival within the host. Depletion of PstP from established infections causes pathogen clearance, indicating the continued presence of PstP is necessary for pathogen survival. Taken together, our data suggests an important role for PstP in establishing and maintaining infection, possibly via the modulation of cell division events

Attrition Resistant Iron-Based Fischer-Tropsch Catalysts.

The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO and H{sub 2}) to liquid fuels. Since the reaction is highly exothermic, one of the major problems in control of the reaction is heat removal. Recent work has shown that the use of slurry bubble column reactors (SBCRs) can largely solve this problem. Iron-based (Fe) catalysts are preferred catalysts for F-T when using low CO/H{sub 2} ratio synthesis gases derived from modern coal gasifiers. This is because in addition to reasonable F-T activity, the F-T catalysts also possess high water gas shift (WGS) activity. However, a serious problem with the use of Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, making the separation of catalyst from the oil/wax product very difficult if not impossible, and results in a steady loss of catalyst from the reactor. The objectives of this research are to develop a better understanding of the parameters affecting attrition resistance of Fe F-T catalysts suitable for use in SBCRs and to incorporate this understanding into the design of novel Fe catalysts having superior attrition resistance. Catalyst preparations will be based on the use of spray drying and will be scalable using commercially available equipment. The research will employ among other measurements, attrition testing and F-T synthesis, including long duration slurry reactor runs in order to ascertain the degree of success of the various preparations. The goal is to develop an Fe catalyst which can be used in a SBCR having only an internal filter for separation of the catalyst from the liquid product, without sacrificing F-T activity and selectivity

Attrition Resistant Iron-Based Fischer-Tropsch Catalysts

The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+H{sub 2}) to liquid fuels. Since the reaction is highly exothermic, one of the major problems in control of the reaction is heat removal. Recent work has shown that the use of slurry bubble column reactors (SBCRS) can largely solve this problem. Iron-based (Fe) catalysts are preferred catalysts for F-T when using low CO/H{sub 2} ratio synthesis gases derived from modem coal gasifiers. This is because in addition to reasonable F-T activity, the FT catalysts also possess high water gas shift (WGS) activity. However, a serious problem with the use of Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, making the separation of catalyst from the oil/wax product very difficult if not impossible, and results in a steady loss of catalyst from the reactor. The objectives of this research are to develop a better understanding of the parameters affecting attrition resistance of Fe F-T catalysts suitable for use in SBCRs and to incorporate this understanding into the design of novel Fe catalysts having superior attrition resistance. Catalyst preparations will be based on the use of spray drying and will be scalable using commercially available equipment. The research will employ among other measurements, attrition testing and F-T synthesis, including long duration slurry reactor runs in order to ascertain the degree of success of the various preparations. The goal is to develop an Fe catalyst which can be used in a SBCR having only an internal filter for separation of the catalyst from the liquid product, without sacrificing F-T activity and selectivity

Hot-Gas Desulfurization with Sulfur Recovery

The objective of this study is to develop a second generation HGD process that regenerates the sulfided sorbent directly to elemental sulfur using SO{sub 2}, with minimal consumption of coal gas. The goal is to have better overall economics than DSRP when integrated with the overall IGCC system

Death-associated Protein Kinase-1 Expression and Autophagy in Chronic Lymphocytic Leukemia Are Dependent on Activating Transcription Factor-6 and CCAAT/Enhancer-binding Protein-β

Expression of DAPK1, a critical regulator of autophagy and apoptosis, is lost in a wide variety of tumors, although the mechanisms are unclear. A transcription factor complex consisting of ATF6 (an endoplasmic reticulum-resident factor) and C/EBP-β is required for the IFN-γ-induced expression of DAPK1. IFN-γ-induced proteolytic processing of ATF6 and phosphorylation of C/EBP-β are obligatory for the formation of this transcriptional complex. We report that defects in this pathway fail to control growth of chronic lymphocytic leukemia (CLL). Consistent with these observations, IFN-γ and chemotherapeutics failed to activate autophagy in CLL patient samples lacking ATF6 and/or C/EBP-β. Together, these results identify a molecular basis for the loss of DAPK1 expression in CLL

ADVANCED SULFUR CONTROL CONCEPTS

Conventional sulfur removal in integrated gasification combined cycle (IGCC) power plants involves numerous steps: COS (carbonyl sulfide) hydrolysis, amine scrubbing/regeneration, Claus process, and tail-gas treatment. Advanced sulfur removal in IGCC systems involves typically the use of zinc oxide-based sorbents. The sulfides sorbent is regenerated using dilute air to produce a dilute SO{sub 2} (sulfur dioxide) tail gas. Under previous contracts the highly effective first generation Direct Sulfur Recovery Process (DSRP) for catalytic reduction of this SO{sub 2} tail gas to elemental sulfur was developed. This process is currently undergoing field-testing. In this project, advanced concepts were evaluated to reduce the number of unit operations in sulfur removal and recovery. Substantial effort was directed towards developing sorbents that could be directly regenerated to elemental sulfur in an Advanced Hot Gas Process (AHGP). Development of this process has been described in detail in Appendices A-F. RTI began the development of the Single-step Sulfur Recovery Process (SSRP) to eliminate the use of sorbents and multiple reactors in sulfur removal and recovery. This process showed promising preliminary results and thus further process development of AHGP was abandoned in favor of SSRP. The SSRP is a direct Claus process that consists of injecting SO{sub 2} directly into the quenched coal gas from a coal gasifier, and reacting the H{sub 2}S-SO{sub 2} mixture over a selective catalyst to both remove and recover sulfur in a single step. The process is conducted at gasifier pressure and 125 to 160 C. The proposed commercial embodiment of the SSRP involves a liquid phase of molten sulfur with dispersed catalyst in a slurry bubble-column reactor (SBCR)