Showing papers on "Integrated gasification combined cycle published in 1995"

Direct Observation of Alkali Vapor Release during Biomass Combustion and Gasification. 1. Application of Molecular Beam/Mass Spectrometry to Switchgrass Combustion

Abstract: Electricity from biomass and biomass-derived fuels has become an attractive and viable alternative energy source. Alkali metal release during biomass combustion can cause significant problems in terms of severe fouling and slagging of heat transfer surfaces in boilers thus reducing efficiency, and in the worst case, leading to unscheduled plant shutdown. Future biomass to electricity facilities will benefit from increased efficiencies by incorporating integrated gasification combined cycle systems that use biomass combustion gases to directly drive an aeroderivative turbine. These systems will have even lower tolerances for alkali vapor release because accelerated erosion and corrosion of turbine blades results in shorter turbine lifetimes. One solution to the fouling and slagging problem is to develop methods of hot gas cleanup to reduce the amount of alkali vapor to acceptable levels. A detailed understanding of the mechanisms of alkali metal release during biomass combustion as well as identifying alkali metal containing vapors and how the vapors lead to fouling and slagging could greatly benefit the development of hot gas cleanup technology. This paper demonstrates the application of molecular beam/mass spectrometry to the study of alkali metal speciation and release during switchgrass combustion. We have successfully used this experimental technique to identify alkali metal containing species released during the combustion of switchgrass at four different conditions : 1100 °C in He/O 2 -(20%), 800 °C in He/O 2 (20%), 1100 °C in He/O 2 (5%), and 1100 °C in He/O 2 (10%)/steam(20%). These conditions were chosen to study the effect of temperature, oxygen concentration, and excess steam on alkali metal release and speciation. Initial feedstock composition is the most significant factor which affects the amount and species of alkali metal released during biomass combustion. The switchgrass sample screened in the present study is high in both alkali metal (potassium) and chlorine. As a result, the predominant alkali metal containing species released during switchgrass combustion is potassium chloride. Varying the combustion condition affects the amount of alkali metal released by a factor of 2 or less. Adding excess steam to the combustion environment tends to shift the form of alkali metal release from the alkali chloride to the hydroxide.

Integrated drying of feedstock feed to integrated combined-cycle gasification plant

Abstract: In a combined cycle gasification plant, high-pressure fuel gas from the gasification unit (16) is heated prior to combustion, and is then used to dry the feedstock (12). The moist fuel gas from the drying operation is combusted to drive the turbine in a power plant (22). Alternatively, high-pressure inert gas such as nitrogen is heated in the gasification unit (16) and is then used to dry the coal feed (12). Some of the moist inert gas is recycled, and some of it is passed to the combustion turbine in power plant (22).

H2S Removal from Coal Gas at Elevated Temperature and Pressure in Fluidized Bed with Zinc Titanate Sorbents. 1. Cyclic Tests

Abstract: Simplified integrated gasification combined cycle (IGCC) processes are considered to be among the most efficient and environmentally acceptable technologies for power generation from coal. In such processes the coal is gasified at pressure and the coal gas is cleaned and combusted in a gas turbine. Coal gas cleanup at elevated pressure and temperature in the IGCC processes offers advantages in higher power generation efficiency and simpler plant configuration. Regenerable mixed metal oxide sorbents are the prime candidates for removal of hydrogen sulfide (the main pollutant) from the hot coal gas in the simplified IGCC processes. In this paper, the results of cyclic sulfidation/regeneration tests conducted with two zinc titanate sorbents are presented and discussed. These tests were carried out at high pressure and temperature (20 bar, 550-650°C) in a bench-scale fluidized-bed reactor. The results indicate that the reactivity of both sorbents towards H 2 S gradually decline in cyclic sulfidation/regeneration tests

Hot-gas cleanup−sulfur recovery technical, environmental, and economic issues

Abstract: Advanced high-efficiency integrated gasification combined cycle (IGCC) power systems employing hot-gas cleanup are being developed to produce electric power from coal. Hot-gas cleanup consists of hot particulate removal and hot-gas desulfurization (HGD) technologies that match or nearly match the temperature and pressure of the gasifier and turbine generator. HGD is carried out using solid regenerable metal oxide sorbents that can remove the sulfur down to low parts per million and can be regenerated with air for multicycle operation. Economic studies have shown that HGD results in lower capital and operating costs than conventional cold gas desulfurization. Development of efficient sorbent desulfurization-regeneration reactor and tailgas treatment subsystems properly integrated with the overall IGCC systems is a key requirement for successful commercialization of HGD.

S cycle electric power system

Abstract: The S cycle electric power system embodies a separation condensation unit, a Rankine cycle and the S cycle including coal gasification. Coal, oxygen and steam are converted into high temperature and pressure fuel gas in a coal gasifier. The fuel gas is first utilized to heat recycled carbon dioxide and steam, then to drive a compressor turbine group to produce power. In a main gas turbine group, the fuel gas is burned in the recycled carbon dioxide. Three main turbines are operated at three different pressure levels. The exhaust of the third turbine is employed to heat the recycled carbon dioxide from a 6-stage compressor with intercooling, and to produce steam. Part of the steam goes to coal gasification. The rest of the steam generates power by expansion in a steam turbine. An integrated separation condensation unit produces pure oxygen on site, and captures carbon dioxide formed in fuel combustion. The system has high energy efficiency and zero pollutant emissions including carbon dioxide.

Exergy analysis of hot-gas clean-up in IGCC systems

Abstract: IGCC (integrated coal-gasification combined cycle) has a highly effective gas-cleaning system for purification of coal gas, and it reaches efficiency rates of over 40%. An improvement of efficiency can be effected by cleaning coal gas at higher temperatures. To examine the influence of gas-cleaning at elevated temperatures, an integrated system study was carried out for base systems and systems with hot-gas clean-up at 250, 350 and 600 °C. The results show that the greater part of the improvement in plant efficiency comes from the change from wet-gas purification to dry-gas purification. For three system designs with the Shell gasification process-the base system and two systems with hot-gas clean-up at 250 and 350 °C-an exergy analysis was made, so that the contribution of various units to improved efficiency could be evaluated. From the exergy analysis it became clear that further raising of the gas-cleaning temperature does not significantly improve plant efficiency; this finding supports the earlier exergy analysis.

System Evaluation and LBTU Fuel Combustion Studies for IGCC Power Generation

Abstract: The integration of gas turbines and combined cycle systems with advances in coal gasification and gas stream cleanup systems will result in economically viable IGCC systems. Optimization of IGCC systems for both emission levels and cost of electricity is critical to achieving this goal. A technical issue is the ability to use a wide range of coal and petroleum-based fuel gases in conventional gas turbine combustor hardware. In order to characterize the acceptability of these syngases for gas turbines, combustion studies were conducted with simulated coal gases using full-scale advanced gas turbine (7F) combustor components. It was found that NO{sub x} emissions could be correlated as a simple function of stoichiometric flame temperature for a wide range of heating values while CO emissions were shown to depend primarily on the H{sub 2} content of the fuel below heating values of 130 Btu/scf (5,125 kJ/NM{sup 3}) and for H{sub 2}/CO ratios less than unity. The test program further demonstrated the capability of advanced can-annular combustion systems to burn fuels from air-blown gasifiers with fuel lower heating values as low as 90 Btu/scf (3,548 kJ/NM{sup 3}) at 2,300 F (1,260 C) firing temperature. In support of ongoing economic studies, numerous IGCC systemmore » evaluations have been conducted incorporating a majority of the commercial or near-commercial coal gasification systems coupled with F series gas turbine combined cycles. Both oxygen and air-blown configurations have been studied, in some cases with high and low-temperature gas cleaning systems. It has been shown that system studies must start with the characteristics and limitations of the gas turbine if output and operating economics are to be optimized throughout the range of ambient operating temperature and load variation.« less

H2S Removal From Coal Gas at Elevated Temperature and Pressure in Fluidized Bed with Zinc Titanate Sorbents. 2. Sorbent Durability

Abstract: High-temperature high-pressure sulfur removal is considered as one of the key steps of the hot gas cleanup train of an IGCC process. Coal-derived gasifier gas contains sulfur gases (mainly H 2 S) which are converted to SO 2 when the gas is combusted in the gas turbine. Cyclic sulfidation/regeneration tests were carried out in a pressurized fluidized bed reactor to remove H 2 S from a simulated coal gas to below 100 ppmv, using regenerable zinc titanate sorbents. The results, which were reported in part 1 of this paper, showed that the sorbent reactivity deteriorates in the cyclic process. In part 2, physical, chemical, and structural changes which the sorbents undergo in the cyclic tests are reported and discussed. The results of analyses conducted with fresh and used sorbents indicate that the loss of reactivity and sorbent deterioration is probably due to zinc migration to the surface of the sorbent particle during high-temperature high-pressure cyclic process.

Westinghouse advanced particle filter system

Abstract: Integrated Gasification Combined Cycles (IGCC), Pressurized Fluidized Bed Combustion (PFBC) and Advanced PFBC (APFB) are being developed and demonstrated for commercial power generation application. Hot gas particulate filters are key components for the successful implementation of IGCC, PFBC and APFB in power generation gas turbine cycles. The objective of this work is to develop and qualify through analysis and testing a practical hot gas ceramic barrier filter system that meets the performance and operational requirements of these advanced, solid fuel power generation cycles.

Slipstream testing of hot-gas desulfurization with sulfur recovery

Abstract: The objective of this work is to further the development of zinc titanate fluidized-bed desulfurization (ZTFBD), and the Direct Sulfur Recovery Process (DSRP) for hot gas cleanup of coal gas used in integrated gasification combined-cycle (IGCC) power generation systems. Results are described.

Advanced low-temperature sorbents

Abstract: A number of promising technologies are currently being optimized for coal-based power generation, including the Integrated-Gasification Combined Cycle (IGCC) system. If IGCC is to be used successfully for power generation, an economic and efficient way must be found to remove the contaminants, particularly sulfur species, found in coal gas. Except for the hot gas desulfurization system, all major components of IGCC are commercially available or have been shown to meet system requirements. Over the last two decades, the U.S. Department of Energy/Morgantown Energy Technology Center (DOE/METC) has sponsored development of various configurations of high-temperature desulfurization systems including fixed-bed, moving-bed, transport-bed, and fluidized-bed systems. Because of their mode of operation and requirements for sorbent manufacturing, the fixed-bed systems can generally use the same materials as moving-bed configurations, i.e., pelletized or extruded sorbents, while fluidized-bed (circulating or bubbling configurations) and transport reactor configurations use materials generally described as agglomerated or granulated.The objective of this program is to remove hydrogen sulfides from coal gas using sorbent materials.

Development and commercialization of a biomass gasification/power generation system

Abstract: The US Department of Energy (DOE) has been a leader in the promotion and development of alternative fuel supplies based on renewable energy crops. One promising power generation technology is biomass gasification coupled with either a gas turbine in a combined cycle system or a fuel cell. The gasification of biomass can efficiently and economically produce a renewable source of a clean gaseous fuel suitable for use in these high efficiency power systems or as a substitute fuel in other combustion devices such as boilers, kilns, or other natural gas fired equipment. This paper discusses the development and commercialization of the Battelle high-throughput gasification process for gas turbine based power generation systems. Projected process economics for a gas turbine combined cycle plant are presented along with a description of integrated system operation coupling a 200kW gas turbine power generation system to a 10 ton per day gasifier, and current commercialization activities.

Development of a high temperature moving-bed coal gas desulfurization system

Abstract: GE is developing a moving-bed, high temperature desulfurization system for use in integrated gasification combined cycle (IGCC) power generation systems. Reusable zinc-based mixed-metal oxide sorbents are being developed for this process, now being tested at the pilot plant scale. Recent tests have focused on: (1) evaluation of Z-Sorb{trademark} III sorbent, a proprietary H{sub 2}S sorbent developed by Phillips Petroleum Company, and (2) construction and testing of a circulating fluidized bed (CFB) reactor for HCl removal. Z-Sorb{trademark} III sorbent lost more than 50% of its reactivity and sulfur absorption capacity in less than 200 hours of pilot plant testing. Interactions between the sorbent and steam in the coal gas (and/or regeneration gas) appear to be a likely cause for the loss in reactivity. Development and testing of alternative sorbents is now underway.

Thermal and chemical degradation of inorganic membrane materials. Final report, August 1992--May 1995

Abstract: SRI International conducted a theoretical and experimental program to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate the gaseous products of coal gasification. A variety of developmental efforts are underway, including a number of projects sponsored by the US Department of Energy (DOE), to improve the selectivity and permeability of porous inorganic membranes. DOE is also sponsoring efforts to extend the use of metallic membranes to new applications. Most developmental efforts have focused on hydrogen separation by inorganic membranes, which may be used to maximize hydrogen production from coal gas or to remove H{sub 2}S and NH{sub 3} contaminants via thermal or catalytic decomposition in integrated-gasification combined-cycle (IGCC) systems. Inorganic membranes that have a high separation efficiency and exhibit both thermal and chemical stability would improve the economics of power generation from coal. Membrane materials that have been investigated include glass (silica), alumina, carbon, and metals (Pd and Pt). This report describes inorganic membrane materials, long term membrane exposure tests, membrane permeation tests, coal gasifier exposure tests, conclusions, and recommendations.

Trace metal transformations in gasification

Abstract: The Energy and Environmental Research Center (EERC) is carrying out an investigation that will provide methods to predict the fate of selected trace elements in integrated gasification combined cycle (IGCC) and integrated gasification fuel cell (IGFC) systems to aid in the development of methods to control the emission of trace elements determined to be air toxics. The goal of this project is to identify the effects of critical chemical and physical transformations associated with trace element behavior in IGCC and IGFC systems. The trace elements included in this project are arsenic, chromium, cadmium, mercury, nickel, selenium, and lead. The research seeks to identify and fill, experimentally and/or theoretically, data gaps that currently exist on the fate and composition of trace elements. The specific objectives are to (1) review the existing literature to identify the type and quantity of trace elements from coal gasification systems; (2) perform laboratory-scale experimentation and computer modeling to enable prediction of trace element emissions; and (3) identify methods to control trace element emissions. Results are presented and discussed on the partitioning of trace metals and the model design for predicting trace metals behavior.

Advances in the shell coal gasification process

Abstract: The Shell Coal Gasification Process (SCGP) is a dry-feed, oxygen-blown, entrained flow coal gasification process which has the capability to convert virtually any coal or petroleum coke into a clean medium Btu synthesis gas, or syngas, consisting predominantly of carbon monoxide and hydrogen. In SCGP, high pressure nitrogen or recycled syngas is used to pneumatically convey dried, pulverized coal to the gasifier. The coal enters the gasifier through diametrically opposed burners where it reacts with oxygen at temperatures in excess of 2500{degrees}F. The gasification temperature is maintained to ensure that the mineral matter in the coal is molten and will flow smoothly down the gasifier wall and out the slag tap. Gasification conditions are optimized, depending on coal properties, to achieve the highest coal to gas conversion efficiency, with minimum formation of undesirable byproducts.

Coal utilization technology for reducing carbon dioxide emission

Abstract: Publisher Summary This chapter discusses coal utilization technology for reducing carbon dioxide emission. Developments in coal utilization technology are quite important, particularly considering the mitigation of green house gas (GHG) emissions. Coal can be used not only as combustion fuel but also as a raw material for conversion technologies, such as gasification and liquefaction. Gasification efficiency increases generally with decreasing coal rank. The heating value of the products through the gasification is almost proportionate to the carbon content o f coal, but the heating value of lower rank coals is slightly lower than the proportionate heating value to the carbon content. The gross heating values of the products of coal conversion technologies are calculated for various coals assuming the theoretical reactions. The overall CO2 emissions are estimated, including products combustion and CO2 generated from conversion.

Integrated drying of feedstock feed to IGCC plant

Abstract: In a combined cycle gasification plant, high pressure fuel gas from the gasification unit is heated prior to combustion, and is then used to dry the feedstock. The moist fuel gas from the drying operation is combusted to drive the turbine. Alternatively, high-pressure inert gas such as nitrogen is heated in the gasification unit and is then used to dry the coal feed. Some of the moist inert gas is recycled, and some if it is passed to the combustion turbine.

Prodn of carbon mon:oxide and electric power

Abstract: Prodn. of CO and electric power uses an IGCC (integrated gasification combined cycle) flow sheet incorporating a S-cpds. removal unit. A permeable membrane unit is located between the outlet of the quenched gas from the partial oxidation unit and the fuel inlet to the combined cycle gas turbine. The non-permeable stream from the unit is used as a source of CO, whilst the permeate stream is used as fuel for the gas turbine of the combined cycle unit. The permeate stream is used to strip and recovery CO2 from the S-cpds. removal unit. The side stream of gas is taken and is used for methanol synthesis.

Continuous removal of sulfur oxides at ambient temperature, using activated carbon fibers and particulates

Abstract: The control of sulfur dioxide emissions from fossil fuel combustion and other industry processes has been recognized as one of the major environmental issues, in both developed and developing countries. In the US, energy-intensive and space-consuming sorbent scrubbing processes that are widely used to remove SO{sub 2} from flue gases also produce huge amounts of process wastes. The management and disposal of the by-product wastes by landfill not only represent poor resource utilization, but can cause further environmental and land use problems. This paper describes the use of activated carbon for the control of sulfur dioxide. The effects of heat treatments and particle size are described.

The Puertollano IGCC project, a 335 MW demonstration power plant for the main electricity companies in Europe

Abstract: The paper describes the status of the 335 Mwe gross (ISO conditions) IGCC project of ELCOGAS in Puertrollano/Spain based on the PRENFLO coal gasification process, at the beginning of its third year of engineering and construction. The project is funded within the Thermie programme of the Commission of the European Communities, being its first targeted project. The status of the IGCC project is presented. Coal gasification is based on the PRENFLO entrained-flow principle with dry fuel dust feeding. An almost complete raw gas desulphurization leads to very low SO 2 contents in the flue gas. Sulphur from the coal will be available as elemental sulphur. By saturation of the desulphurized gas and the mixing with the nitrogen from the air separation unit the integrated power plant concept also achieves very low NO x contents in the flue gas. Commissioning tests for the combined cycle plant fed with natural gas will start during mid-1995, and will be followed by one year plant operation, before commissioning of the IGCC power plant.