A Low Cost, High Capacity Regenerable Sorbent for Pre-combustion CO{sub 2} Capture

The overall objective of the proposed research is to develop a low cost, high capacity CO{sub 2} sorbent and demonstrate its technical and economic viability for pre-combustion CO{sub 2} capture. The specific objectives supporting our research plan were to optimize the chemical structure and physical properties of the sorbent, scale-up its production using high throughput manufacturing equipment and bulk raw materials and then evaluate its performance, first in bench-scale experiments and then in slipstream tests using actual coal-derived synthesis gas. One of the objectives of the laboratory-scale evaluations was to demonstrate the life and durability of the sorbent for over 10,000 cycles and to assess the impact of contaminants (such as sulfur) on its performance. In the field tests, our objective was to demonstrate the operation of the sorbent using actual coal-derived synthesis gas streams generated by air-blown and oxygen-blown commercial and pilot-scale coal gasifiers (the CO{sub 2} partial pressure in these gas streams is significantly different, which directly impacts the operating conditions hence the performance of the sorbent). To support the field demonstration work, TDA collaborated with Phillips 66 and Southern Company to carry out two separate field tests using actual coal-derived synthesis gas at the Wabash River IGCC Power Plant in Terre Haute, IN and the National Carbon Capture Center (NCCC) in Wilsonville, AL. In collaboration with the University of California, Irvine (UCI), a detailed engineering and economic analysis for the new CO{sub 2} capture system was also proposed to be carried out using Aspen PlusTM simulation software, and estimate its effect on the plant efficiency

Regenerable Sorbent for CO2 Removal

A durable, high-capacity regenerable sorbent can remove CO2 from the breathing loop under a Martian atmosphere. The system design allows near-ambient temperature operation, needs only a small temperature swing, and sorbent regeneration takes place at or above 8 torr, eliminating the potential for Martian atmosphere to leak into the regeneration bed and into the breathing loop. The physical adsorbent can be used in a metabolic, heat-driven TSA system to remove CO2 from the breathing loop of the astronaut and reject it to the Martian atmosphere. Two (or more) alternating sorbent beds continuously scrub and reject CO2 from the spacesuit ventilation loop. The sorbent beds are cycled, alternately absorbing CO2 from the vent loop and rejecting the adsorbed material into the environment at a high CO2 partial pressure (above 8 torr). The system does not need to run the adsorber at cryogenic temperatures, and uses a much smaller temperature swing. The sorbent removes CO2 via a weak chemical interaction. The interaction is strong enough to enable CO2 adsorption even at 3 to 7.6 torr. However, because the interaction between the surface adsorption sites and the CO2 is relatively weak, the heat input needed to regenerate the sorbent is much lower than that for chemical absorbents. The sorbent developed in this project could potentially find use in a large commercial market in the removal of CO2 emissions from coal-fired power plants, if regulations are put in place to curb carbon emissions from power plants

Novel Sorbent-Based Process for High Temperature Trace Metal Removal

The objective of this project was to demonstrate the efficacy of a novel sorbent can effectively remove trace metal contaminants (Hg, As, Se and Cd) from actual coal-derived synthesis gas streams at high temperature (above the dew point of the gas). The performance of TDA's sorbent has been evaluated in several field demonstrations using synthesis gas generated by laboratory and pilot-scale coal gasifiers in a state-of-the-art test skid that houses the absorbent and all auxiliary equipment for monitoring and data logging of critical operating parameters. The test skid was originally designed to treat 10,000 SCFH gas at 250 psig and 350 C, however, because of the limited gas handling capabilities of the test sites, the capacity was downsized to 500 SCFH gas flow. As part of the test program, we carried out four demonstrations at two different sites using the synthesis gas generated by the gasification of various lignites and a bituminous coal. Two of these tests were conducted at the Power Systems Demonstration Facility (PSDF) in Wilsonville, Alabama; a Falkirk (North Dakota) lignite and a high sodium lignite (the PSDF operator Southern Company did not disclose the source of this lignite) were used as the feedstock. We also carried out two other demonstrations in collaboration with the University of North Dakota Energy Environmental Research Center (UNDEERC) using synthesis gas slipstreams generated by the gasification of Sufco (Utah) bituminous coal and Oak Hills (Texas) lignite. In the PSDF tests, we showed successful operation of the test system at the conditions of interest and showed the efficacy of sorbent in removing the mercury from synthesis gas. In Test Campaign No.1, TDA sorbent reduced Hg concentration of the synthesis gas to less than 5 {micro}g/m{sup 3} and achieved over 99% Hg removal efficiency for the entire test duration. Unfortunately, due to the relatively low concentration of the trace metals in the lignite feed and as a result of the intermittent operation of the PSDF gasifier (due to the difficulties in the handling of the low quality lignite), only a small fraction of the sorbent capacity was utilized (we measured a mercury capacity of 3.27 mg/kg, which is only a fraction of the 680 mg/kg Hg capacity measured for the same sorbent used at our bench-scale evaluations at TDA). Post reaction examination of the sorbent by chemical analysis also indicated some removal As and Se (we did not detect any significant amounts of Cd in the synthesis gas or over the sorbent). The tests at UNDEERC was more successful and showed clearly that the TDA sorbent can effectively remove Hg and other trace metals (As and Se) at high temperature. The on-line gas measurements carried out by TDA and UNDEERC separately showed that TDA sorbent can achieve greater than 95% Hg removal efficiency at 260 C ({approx}200g sorbent treated more than 15,000 SCF synthesis gas). Chemical analysis conducted following the tests also showed modest amounts of As and Se accumulation in the sorbent bed (the test durations were still short to show higher capacities to these contaminants). We also evaluated the stability of the sorbent and the fate of mercury (the most volatile and unstable of the trace metal compounds). The Synthetic Ground Water Leaching Procedure Test carried out by an independent environmental laboratory showed that the mercury will remain on the sorbent once the sorbent is disposed. Based on a preliminary engineering and cost analysis, TDA estimated the cost of mercury removal from coal-derived synthesis gas as $2,995/lb (this analysis assumes that this cost also includes the cost of removal of all other trace metal contaminants). The projected cost will result in a small increase (less than 1%) in the cost of energy

Advanced CO2 Removal and Reduction System

An advanced system for removing CO2 and H2O from cabin air, reducing the CO2, and returning the resulting O2 to the air is less massive than is a prior system that includes two assemblies . one for removal and one for reduction. Also, in this system, unlike in the prior system, there is no need to compress and temporarily store CO2. In this present system, removal and reduction take place within a single assembly, wherein removal is effected by use of an alkali sorbent and reduction is effected using a supply of H2 and Ru catalyst, by means of the Sabatier reaction, which is CO2 + 4H2 CH4 + O2. The assembly contains two fixed-bed reactors operating in alternation: At first, air is blown through the first bed, which absorbs CO2 and H2O. Once the first bed is saturated with CO2 and H2O, the flow of air is diverted through the second bed and the first bed is regenerated by supplying it with H2 for the Sabatier reaction. Initially, the H2 is heated to provide heat for the regeneration reaction, which is endothermic. In the later stages of regeneration, the Sabatier reaction, which is exothermic, supplies the heat for regeneration

Development of a Rapid Cycling CO2 and H2O Removal Sorbent

The National Aeronautics and Space Administration (NASA) planned future missions set stringent demands on the design of the Portable Life Support System (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility on the types of missions. Use of regenerable systems that reduce weight and volume of the Extravehicular Mobility Unit (EMU) is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The carbon dioxide and humidity control unit in the existing PLSS design is relatively large, since it has to remove and store eight hours worth of carbon dioxide (CO2). If the sorbent regeneration can be carried out during the Extravehicular Activity (EVA) with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced. TDA Research, Inc. is developing compact, regenerable sorbent materials to control CO2 and humidity in the space suit ventilation loop. The sorbent can be regenerated using space vacuum during the EVA, eliminating all CO2 and humidity duration-limiting elements in the life support system. The material also has applications in other areas of space exploration including long duration exploration missions requiring regenerable technologies and possibly the Crew Exploration Vehicle (CEV) spacecraft. This paper summarizes the results of the sorbent development, testing, and evaluation efforts to date

Carbon Dioxide Control System for a Mars Space Suit Life Support System

Carbon dioxide (CO2) control during Extravehicular Activities (EVAs) on Mars will be challenging. Lithium hydroxide (LiOH) canisters have impractical logistics penalties, and regenerable metal oxide (MetOx) canisters weigh too much. Cycling bed systems and permeable membranes that are regenerable in space vacuum cannot vent on Mars due to the high partial pressure of CO2 in the atmosphere. Although sweep gas regeneration is under investigation, the feasibility, logistics penalties, and failure modes associated with this technique have not been fully determined. TDA Research, Inc. is developing a durable, high-capacity regenerable adsorbent that can remove CO2 from the space suit ventilation loop. The system design allows sorbent regeneration at or above 6 torr, eliminating the potential for Martian atmosphere to leak into the regeneration bed and into the ventilation loop. Regeneration during EVA eliminates the consumable requirement related to the use of LiOH canisters and the mission duration limitations imposed by MetOx system. The concept minimizes the amount of consumable to be brought from Earth and makes the mission more affordable, while providing great operational flexibility during EVA. The feasibility of the concept has been demonstrated in a series of bench-scale experiments and a preliminary system analysis. Results indicate that sorbent regeneration can be accomplished by applying a 14 C temperature swing, while regenerating at 13 torr (well above the Martian atmospheric pressure), withstanding over 1,000 adsorption/regeneration cycles. This paper presents the latest results from these sorbent and system development efforts

Rapid Cycling CO2 and H2O Removal System for EMU

NASA's planned future missions set stringent demands on the design of the Portable Life Support Systems (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility on the types of missions. Use of regenerable systems that reduce weight and volume of the EMU is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The CO2 and humidity control unit in the existing PLSS design is relatively large, since it has to remove 8 hours worth of CO2. If the sorbent regeneration can be carried out during the extravehicular activity (EVA) with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced. TDA Research, Inc. (TDA) is developing a compact, regenerable sorbent-based system to control CO2 and humidity in the space suit ventilation loop. The sorbent can be regenerated using space vacuum during the EVA, eliminating all duration-limiting elements in the life support system. This paper summarizes the results of the sorbent development and testing, and evaluation efforts. The results of a preliminary system analysis are also included, showing the size and volume reductions provided by the new system

Self-Directed Learning and Intrinsic Motivation Levels in MOOCs

The aim of this study was to determine the relationship between the intrinsic motivation levels and self-directed learning levels of learners within a massive open online course environment. In addition, the relationship between these variables and the technology competences/average daily use times of technology were also studied. This study was conducted with predictive design, one of the relational design types. In this context, a personal information form, self-directed learning scale and intrinsic motivation scale were used as data collection tools. The study had 295 participants who completed at least one full course in “Akadema”, the massive online open course platform of Anadolu University. The results obtained from the study indicate a near-medium level positive statistically significant level of correlation between the self-directed learning and intrinsic motivation levels of learners. Furthermore, the regression analysis conducted in the study resulted in the self-directed learning levels explaining intrinsic motivation levels at a 20.5% ratio. Based on the findings of the study, various recommendations were made regarding developing the technology competences and self-directed learning skills of students