Composition Modification of Zinc Titanate (Zn2TiO4) Based Sorbents for Hot Coal Gas Desulfurization PDF Download
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Author: Kimberly S. Walton
Publisher:
ISBN:
Category :
Languages : en
Pages : 142
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Author: Kimberly S. Walton
Publisher:
ISBN:
Category :
Languages : en
Pages : 142
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
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ISBN:
Category :
Languages : en
Pages : 16
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For new coal gasification systems, zinc titanate sorbents are being developed to remove sulfur from the hot product gas prior to its use in combined cycle turbines and high temperature fuel cells. Although most of the properties of these sorbents are very attractive, there are still concerns about durability over many sulfidation-regeneration cycles and zinc losses due to vaporization. Doping the zinc titanate with other metal ions could alleviate both concerns, which are the objectives of this project. A screening study was completed during the second quarter in which Ni, Cr, Cu, Mg, and Al were evaluated as dopants in zinc titanate. Measurements that were made include solubility, crush strength, and sulfidation-regeneration behavior in a thermogravimetric analyzer. A formulation containing Cr showed the most promise. It and other formulations containing Cr will be emphasized during the remainder of the year. Fixed bed experiments will start during the third quarter.
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Category :
Languages : en
Pages : 18
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For new coal gasification systems, zinc titanate sorbents are being developed to remove sulfur from the hot product gas prior to its use in combined cycle turbines and high temperature fuel cells. Although most of the properties of these sorbents are very attractive, there are still concerns about durability over many sulfidation-regeneration cycles and zinc losses due to vaporization. Doping the zinc titanate with other metal ions could alleviate both concerns, which are the objectives of this project. During the first quarter of effort, several sorbent formulations were prepared and testing begun. The dopants presently under study are Ni, Cr, Cu, and Al. Crush strength results obtained to date show that Ni and Cu dopants have a large positive effect, while Cr gives a small improvement. Measurements were also made of sulfur capacity and sulfidation rates with a thermogravimetric analyzer. Of the three formulations, only the one containing Cr had a high sulfur capacity. X-ray measurements will be relied upon heavily to obtain an understanding of solubility effects and sulfidation mechanisms. Screening experiments will continue on the doped sorbents mentioned above next quarter, and Mg will be studied also.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
For new coal gasification systems, zinc titanate sorbents are being developed to remove sulfur from the hot product gas prior to its use in combined cycle turbines and high temperature fuel cells. Although most of the properties of these sorbents are very attractive, there are still concerns about durability over many sulfidation-regeneration cycles and zinc losses due to vaporization. Doping the zinc titanate with other metal ions could alleviate both concerns, which are the objectives of this project. After a screening study was completed, it was decided that Cr offered more promise as a dopant than Ni, Cu, Mg, and Al. Therefore six new sorbent formulations containing Cr were prepared, and they are now being evaluated with a series of bulk density, X-ray diffraction, crush strength and thermogravimetric analysis (TGA) measurements. Results to date suggest that, while Zn vaporization losses can be reduced with Cr additions, a penalty in chemical reactivity occurs. A fixed bed test was also completed this quarter on a Cr-containing formulation. The H2S breakthrough time was about 11 hours, and utilization of Zn in the sorbent was 60.5%.
Author: Wahab Mojtahedi
Publisher:
ISBN:
Category : Coal
Languages : en
Pages : 16
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Category :
Languages : en
Pages : 14
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The focus of work being performed on Hot Coal Gas Desulfurization is primarily in the use of zinc ferrite and zinc titanate sorbents; however, prior studies at the US Steel Fundamental Research Laboratories in Monroeville, PA, by E.T. Turkdogan indicated that an alternate sorbent, manganese dioxide-containing ore in mixture with alumina (75 wt % ore + 25 wt % Al2/O3) may be a viable alternative to zinc-based sorbents. Manganese, for example, has a lower vapor pressure in the elemental state than zinc hence it is not as likely to undergo depletion from the sorbent surface upon loading and regeneration cycles. Also manganese oxide is less readily reduced to the elemental state than iron hence the range of reduction potentials for oxygen is somewhat greater than for zinc ferrite. In addition, thermodynamic analysis of the manganese-oxygen-sulfur system shows it to be less amenable to sulfation than zinc ferrite. Potential also exists for utilization of manganese higher temperatures than zinc ferrite or zinc titanate. This presentation gives the thermodynamic background for consideration of manganese-based sorbents as an alternative to zinc ferrite. To date the work which has been in progress for nine months is limited at this stage to thermogravimetric testing of four formulations of manganese-alumina sorbents to determine the optimum conditions of pelletization and induration to produce reactive pellets.
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ISBN:
Category :
Languages : en
Pages : 51
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One of the most advantageous configurations of the integrated gasification combined cycle (IGCC) power system is coupling it with a hot gas cleanup for the more efficient production of electric power in an environmentally acceptable manner. In conventional gasification cleanup systems, closely heat exchangers are necessary to cool down the fuel gases for cleaning, sometimes as low as 200--300°F, and to reheat the gases prior to injection into the turbine. The result is significant losses in efficiency for the overall power cycle. High-temperature coal gas cleanup in the IGCC system can be operated near 1000°F or higher, i.e., at conditions compatible with the gasifier and turbine components, resulting is a more efficient overall system. GE is developing a moving-bed, high-temperature desulfurization system for IGCC power systems in which mixed-metal oxides are currently being used as desulfurization sorbents. The objective of this contract is to identify and test fabrication methods and sorbent chemical compositions that enhance the long-term chemical reactivity and mechanical durability of zinc ferrite and other novel sorbents for moving-bed, high-temperature desulfurization of coal-derived gases. Zinc ferrite was studied under the base program of this contract. In the next phase of this program novel sorbents, particularly zinc titanate-based sorbents, are being studied under the remaining optional programs. This topical report summarizes only the work performed under the Option 2 program. In the course of carrying out the program, more than 25 zinc titanate formulations have been prepared and characterized to identify formulations exhibiting enhanced properties over the baseline zinc titanate formulation selected by the US Department of Energy.
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ISBN:
Category :
Languages : en
Pages : 31
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Book Description
In the continuing search for good sorbent materials to remove sulfur for hot, coal-derived gases, zinc titanate sorbents have shown great promise. The objective of this project was to extend the work of prior investigators by developing improvements in the compressive strength and, therefore, the cycle life of these sorbents while maintaining good chemical reactivity. Fifteen formulations were prepared and evaluated. The best properties were obtained by blending relatively course (two micron) ZnO and TiO2 powders to obtain a composition of 50%Zn2TiO4-50%TiO2. When sintered at 1000°C, it had a compressive strength of 28 MPa or 147 N/mm, which is four times higher than values obtained by prior investigators. It also performed well in thermogravimetric analysis measurements of reactivity, both in screening tests and in simulated coal gas.
Author:
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ISBN:
Category :
Languages : en
Pages : 12
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The objectives of this project are to identify and demonstrate methods for enhancing long-term chemical reactivity and attrition resistance of zinc oxide-based mixed metal-oxide sorbents for desulfurization of hot coal-derived gases in a high-temperature, high-pressure (HTHP) fluidized-bed reactor. Specific objectives of this study are the following: {sm_bullet} Investigating various manufacturing methods to produce fluidizable zinc ferrite and zinc titanate sorbents in a particle size range of 50 to 400?m; Characterizating and screening the formulations for chemical reactivity, attrition resistance, and structural properties; Testing selected formulations in an HTHP bench-scale fluidized-bed reactor to obtain an unbiased ranking of the promising sorbents; Investigating the effect of various process variables, such as temperature, nature of coal gas, gas velocity, and chemical composition of the sorbent, on the performance of the sorbent; Life-cycle testing of the superior zinc ferrite and zinc titanate formulations under HTHP conditions to determine their long-term chemical reactivity and mechanical strength; Addressing various reactor design issues; Generating a database on sorbent properties and performance (e.g., rates of reaction, attrition rate) to be used in the design and scaleup of future commercial hot-gas desulfurization systems; Transferring sorbent manufacturing technology to the private sector; Producing large batches (in tonnage quantities) of the sorbent to demonstrate commercial feasibility of the preparation method; and Coordinate testing of superior formulations in pilot plants with real and/or simulated coal gas.
