Simulation and Economic Evaluation of Elemental Sulfur Recovery from Hot Gas Desulfurization Processes PDF Download
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Author: Sen Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 452
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Author: Sen Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 452
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 159
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Engineering evaluations and economic comparisons of two hot-gas desulfurization (HGD) processes with elemental sulfur recovery, being developed by Research Triangle Institute, are presented. In the first process, known as the Direct Sulfur Recovery Process (DSRP), the SO2 tail gas from air regeneration of zinc-based HGD sorbent is catalytically reduced to elemental sulfur with high selectivity using a small slipstream of coal gas. DSRP is a highly efficient first-generation process, promising sulfur recoveries as high as 99% in a single reaction stage. In the second process, known as the Advanced Hot Gas Process (AHGP), the zinc-based HGD sorbent is modified with iron so that the iron portion of the sorbent can be regenerated using SO2 . This is followed by air regeneration to fully regenerate the sorbent and provide the required SO2 for iron regeneration. This second-generation process uses less coal gas than DSRP. Commercial embodiments of both processes were developed. Process simulations with mass and energy balances were conducted using ASPEN Plus. Results show that AHGP is a more complex process to operate and may require more labor cost than the DSRP. Also capital costs for the AHGP are higher than those for the DSRP. However, annual operating costs for the AHGP appear to be considerably less than those for the DSRP with a potential break-even point between the two processes after just 2 years of operation for an integrated gasification combined cycle (IGCC) power plant using 3 to 5 wt% sulfur coal. Thus, despite its complexity, the potential savings with the AHGP encourage further development and scaleup of this advanced process.
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Languages : en
Pages :
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The objective of this project is to develop a hot-gas desulfurization process scheme for control of H2S in HTHP coal gas that can be more simply and economically integrated with known regenerable sorbents in DOE/METC-sponsored work than current leading hot-gas desulfurization technologies. In addition to being more economical, the process scheme to be developed must yield an elemental sulfur byproduct. The Direct Sulfur Recovery Process (DSRP), a leading process for producing an elemental sulfur byproduct in hot-gas desulfurization systems, incurs a coal gas use penalty, because coal gas is required to reduce the SO2 in regeneration off-gas to elemental sulfur. Alternative regeneration schemes, which avoid coal gas use and produce elemental sulfur, will be evaluated. These include (i) regeneration of sulfided sorbent using SO2 ; (ii) partial oxidation of sulfided sorbent in an O2 starved environment; and (iii) regeneration of sulfided sorbent using steam to produce H2S followed by direct oxidation of H2S to elemental sulfur. Known regenerable sorbents will be modified to improve the feasibility of the above alternative regeneration approaches. Performance characteristics of the modified sorbents and processes will be obtained through lab- and bench-scale testing. Technical and economic evaluation of the most promising processes concept(s) will be carried out.
Author: R. H. Lien
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ISBN:
Category : Citric acid
Languages : en
Pages : 36
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Author:
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Category :
Languages : en
Pages : 44
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Favorable results were achieved in the sulfidation of CeO2 by H2S and the regeneration of Ce2O2S by SO2. Successful removal of approximately 99% of the H2S from the sulfidation gas to levels of about 100 ppmv (or lower), and the production of approximately 12% elemental sulfur (as S2) in the regeneration product gas were highlights. Final effort in the preliminary phase included a ten-cycle test at standard sulfidation and regeneration conditions with little or no sorbent deterioration. In the initial test of the detailed experimental phase of the program, the authors investigated the effect of temperature on the regeneration reaction. Results of preliminary tests showed that the Ce2O2S-SO2 reaction did not occur at 350 C, and all subsequent regeneration tests were at 600 C where the reaction was rapid. Significant progress has been made on the process analysis effort during the quarter. Detailed process flow diagrams along with material and energy balance calculations for six design case studies were completed in the previous quarter. Two of the cases involved two-stage desulfurization with steam regeneration, three used two-stage desulfurization with SO2 regeneration, and the sixth was based on single-stage desulfurization with elemental sulfur recovery using the DSRP concept. In the present quarter, major process equipment was sized for each of the six cases. Preliminary annual operating and levelized total cost estimates were then completed for two design cases--one involving two-stage desulfurization with SO2 regeneration and the second based on single-stage desulfurization with DSRP.
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Category :
Languages : en
Pages :
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Advanced integrated gasification combined cycle (IGCC) power plants nearing completion, such as Sierra-Pacific, employ a circulating fluidized-bed (transport) reactor hot-gas desulfurization (HGD) process that uses 70-180[micro]m average particle size (aps) zinc-based mixed-metal oxide sorbent for removing H[sub 2]S from coal gas down to less than 20 ppmv. The sorbent undergoes cycles of absorption (sulfidation) and air regeneration. The key barrier issues associated with a fluidized-bed HGD process are chemical degradation, physical attrition, high regeneration light-off (initiation) temperature, and high cost of the sorbent. Another inherent complication in all air-regeneration-based HGD processes is the disposal of the problematic dilute SO[sub 2] containing regeneration tail-gas. Direct Sulfur Recovery Process (DSRP), a leading first generation technology, efficiently reduces this SO[sub 2] to desirable elemental sulfur, but requires the use of 1-3% of the coal gas, thus resulting in an energy penalty to the plant. Advanced second-generation processes are under development that can reduce this energy penalty by modifying the sorbent so that it could be directly regenerated to elemental sulfur. The objective of this research is to support the near and long term DOE efforts to commercialize the IGCC-HGD process technology. Specifically we aim to develop: optimized low-cost sorbent materials with 70-80[micro]m average aps meeting all Sierra specs; attrition resistant sorbents with 170[micro]m aps that allow greater flexibility in the choice of the type of fluidized-bed reactor e.g. they allow increased throughput in a bubbling-bed reactor; and modified fluidizable sorbent materials that can be regenerated to produce elemental sulfur directly with minimal or no use of coal gas The effort during the reporting period has been devoted to development of an advanced hot-gas process that can eliminate the problematic SO[sub 2] tail gas and yield elemental sulfur directly using a sorbent containing a combination of zinc and iron oxides.
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Category :
Languages : en
Pages :
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Removal of hydrogen sulfide (H2S) from coal gasifier gas and sulfur recovery are key steps in the development of Department of Energy's (DOE's) advanced power plants that produce electric power and clean transportation fuels with coal and natural gas. These plants will require highly clean coal gas with H2S below 1 ppmv and negligible amounts of trace contaminants such as hydrogen chloride, ammonia, alkali, heavy metals, and particulate. The conventional method of sulfur removal and recovery employing amine, Claus, and tail-gas treatment is very expensive. A second generation approach developed under DOE's sponsorship employs hot-gas desulfurization (HGD) using regenerable metal oxide sorbents followed by Direct Sulfur Recovery Process (DSRP). However, this process sequence does not remove trace contaminants and is targeted primarily towards the development of advanced integrated gasification combined cycle (IGCC) plants that produce electricity (not both electricity and transportation fuels). There is an immediate as well as long-term need for the development of cleanup processes that produce highly clean coal gas for next generation power plants. To this end, a novel process is now under development at several research organizations in which the H2S in coal gas is directly oxidized to elemental sulfur over a selective catalyst. Such a process is ideally suited for coal gas from commercial gasifiers with a quench system to remove essentially all the trace contaminants except H2S In the Single-Step Sulfur Recovery Process (SSRP), the direct oxidation of H2S to elemental sulfur in the presence of SO2 is ideally suited for coal gas from commercial gasifiers with a quench system to remove essentially all the trace contaminants except H2S. This direct oxidation process has the potential to produce a super clean coal gas more economically than both conventional amine-based processes and HGD/DSRP. The H2 and CO components of syngas appear to behave as inert with respect to sulfur formed at the SSRP conditions. One problem in the SSRP process that needs to be eliminated or minimized is COS formation that may occur due to reaction of CO with sulfur formed from the Claus reaction. The objectives of this research are to formulate monolithic catalysts for removal of H2S from coal gases and minimum formation of COS with monolithic catalyst supports, [gamma]-alumina wash or carbon coats, and catalytic metals, to develop a catalytic regeneration method for a deactivated monolithic catalyst, to measure kinetics of both direct oxidation of H2S to elemental sulfur with SO2 as an oxidizer and formation of COS in the presence of a simulated coal gas mixture containing H2, CO, CO2, and moisture, using a monolithic catalyst reactor, and to develop kinetic rate equations and model the direct oxidation process to assist in the design of large-scale plants. This heterogeneous catalytic reaction has gaseous reactants such as H2S and SO2. However, this heterogeneous catalytic reaction has heterogeneous products such as liquid elemental sulfur and steam. Experiments on conversion of hydrogen sulfide into elemental sulfur and formation of COS were carried out for the space time range of 130-156 seconds at 120-140 C to formulate catalysts suitable for the removal of H2S and COS from coal gases, evaluate removal capabilities of hydrogen sulfide and COS from coal gases with formulated catalysts, and develop an economic regeneration method of deactivated catalysts. Simulated coal gas mixtures consist of 3,300-3,800-ppmv hydrogen sulfide, 1,600-1,900 ppmv sulfur dioxide, 18-21 v% hydrogen, 29-34 v% CO, 8-10 v% CO2, 5-18 vol % moisture, and nitrogen as remainder. Volumetric feed rates of a simulated coal gas mixture to the reactor are 114-132 SCCM. The temperature of the reactor is controlled in an oven at 120-140 C. The pressure of the reactor is maintained at 116-129 psia. The molar ratio of H2S to SO2 in the monolithic catalyst reactor is maintained approximately at 2 for all the reaction experiment runs.
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Category :
Languages : en
Pages : 47
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The primary objective is to determine the feasibility of an alternate concept for the regeneration of high temperature desulfurization sorbents in which elemental sulfur, instead of SO2 is produced. Iron and cerium-based sorbents were chosen on the basis of thermodynamic analysis to determine the feasibility of elemental sulfur production. Experimental effort on the regeneration of FeS using the partial oxidation concept was completed during the quarter, and attention returned to the sulfidation of CeO2 and regeneration of Ce2O22S. Progress was made in the process simulation effort involving two-step desulfurization using CeO2 to remove the bulk of the H2S followed by a zinc-titanate polishing step. The simulation effort includes regeneration of Ce2O2S using two concepts - reaction with SO2 reaction with H2O. Elemental sulfur is formed directly in the reaction with SO2 while H2S is the product of the regeneration reaction with steam. Steam regeneration is followed by a Claus process to convert the H2S to elemental sulfur. The last test involving partial oxidation regeneration of FeS was completed in early July. Experimental problems were encountered throughout this phase of the program, primarily associated with erratic readings from the total sulfur analyzer. The problems are attributed to variable flow rates through the capillary restrictor, and, in some cases, to steam concentrations which exceeded the capacity of the membrane dryer. Nevertheless, sufficient data was collected to confirm that large fractions of the sulfur in FeS could be liberated in elemental form. Low regeneration temperature ((approximately)600°C), large steam-to-oxygen ratios, and low space velocities were found to favor elemental sulfur production.
Author:
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ISBN:
Category : Power resources
Languages : en
Pages : 438
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Author: United States. Department of Energy
Publisher:
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Category : Coal gasification
Languages : en
Pages : 64
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