Pressurized Fluidized Bed Combustion Research Articles

97/02189 Test results from the department of energy's pressurized fluidized bed combustion hot gas cleanup program

Presented here is a summary of operations and conclusions from the last two test campaigns of the Department of Energy`s Pressurized Fluidized Bed Combustion Hot Gas Cleanup Program which was implemented by the American Electric Power Service Corporation. In these tests, the Westinghouse Advanced Particle Filter (APF) operated on a one-seventh flow from the Tidd 70-MWe Pressurized Fluidized Bed Combustor. During these tests, the filter operated as predicted with extremely high particulate removal. During the combined test periods, more than 2,800 hours of operation were accumulated -- two operational periods lasted more than 650 hours. The completion of this program brings the total coal fired operating time of the APF to 5,854 hours.

97/02274 A review of the efficacy of silicon carbide hot-gas filters in coal gasification and pressurized fluidized bed combustion environments

97/02274 A review of the efficacy of silicon carbide hot-gas filters in coal gasification and pressurized fluidized bed combustion environments

97/01969 An assessment of advanced pressurized fluidized-bed combustion power plants

97/01969 An assessment of advanced pressurized fluidized-bed combustion power plants

97/02069 Economics of co-firing waste materials in an advanced pressurized fluidized-bed combustor

97/02069 Economics of co-firing waste materials in an advanced pressurized fluidized-bed combustor

97/01382 Sulfur and sorbent performance in pressurized fluidized-bed combustion of gasification residue

97/01382 Sulfur and sorbent performance in pressurized fluidized-bed combustion of gasification residue

Clean coal technologies

Power generation in Europe and elsewhere relies heavily on coal as the source of energy and this reliance will increase in the future as other fossil fuels become progressively more expensive. The existing stock of coal-fired power stations mainly use pulverized fuel boilers and present designs based on ultrasupercritical steam cycles are as efficient and as low in SOx and NOx emissions as is possible without incurring excessive additional costs. This paper examines the options for coal-based power generation technologies and compares their technical, environmental and economic performance. These options include atmospheric and pressurized fluidized bed combustion and a range of integrated gasification combined cycle systems. Integrated gasification combined cycles give good efficiency and very low emissions, but further optimization is required to make them economically attractive. Conceptual cycles based on pressurized pulverized combustion, dual fuel hybrid cycles, fuel cells and magnetohydrodynamics are also covered in outline.

Performance and stability of porous ceramic candle filters during PFBC operation

Westinghouse's involvement at the American Electric Power (AEP) pressurized fluidized-bed combustion (PFBC) Tidd demonstration plant has recently identified critical issues pertaining to the life of monolithic and fiber reinforced porous ceramic filter elements, as well as process control parameters that impact commercialization of the hot gas filtration technology. Although the nonoxide filter materials primarily undergo oxidation and/or creep, and the oxide-based matrices experience thermal fatigue, both materials exhibit an initial loss of bulk strength, but achieve a conditioned or stabilized strength during operation in the PFBC environment. Continued operation will, however, be required to demonstrate extended viability of the conditioned porous ceramic filter materials in process controlled, advanced coal-fired applications.

Pressurized fluidized bed combustion and gasification of coal using flue gas recirculation and oxygen injection

A combined cycle incorporating pressurized fluidized bed combustion of coal with pure oxygen and recycled flue gas followed by pressurized combustion of the fuel gas using pure oxygen, is a process which produces electricity and heat with a high efficiency and a flue gas with a high CO2 concentration. CO2 recovery from this process can be done more easily than from conventional coal conversion processes. In this way a high efficiency coal conversion process can be realized with low CO2 emissions. The specific aim of the project is to assess the technical feasibility of this process. For this purpose a 1.6 MWth pressurized fluidized bed combustion test rig has been modified to study experimentally the gasification process and the pressurized combustion of the resulting low calorific value fuel gas. The objectives of the project, the modified test rig and the experimental results obtained from combustion experiments with coal, recirculated flue gas and pure oxygen are described. The conversion efficiencies and the emission of harmfull components measured during these experiments are analyzed and compared with values obtained during combustion and gasification using air.

Grimethorpe filter element performance—the final analysis

A demonstration hot gas filter, funded by the Electric Power Research Institute and installed in a pressurised fluidised bed combustor at Grimethorpe, South Yorkshire, UK was operated for a second period in 1991–92 for the Grimethorpe Topping Cycle Project (GTCP). This project was aimed at assessing the feasibility of running a gas turbine on coal-derived gas as part of the development programme for the Air Blown Gasification Cycle (formerly known as the British Coal Topping Cycle).As in previous studies operation of the filter led to progressive changes to the mechanical properties of the tubular clay-bonded silicon carbide filter elements. In order to explain the mechanisms behind these changes and thus determine operating conditions which influence element properties and performance detailed element characterisation and microstructural studies have been carried out. It has been found that slow bond devitrification and the development of a bond-grit interlayer of cristobalite led to changes in the integrity of the interface, with loss of strength and elastic modulus and a decrease in ultrasonic pulse velocity through the material. Microstructural studies suggest that the combination of the upper temperature of operation (≈ 830°C) and the thermal cycling during reverse pulse cleaning to remove the dust cake results in microcracking. While the strength losses experienced did not result in in-plant element failures, the reliability of the elements would be improved if operation can be limited to a temperature at which devitrification of the element's bond material is minimised.

97/00691 An evaluation of disposal and utilization options for advanced coal utilization wastes

If the US is to continue to effectively use its substantial coal reserves, new clean coal technologies must be developed to improve power production efficiency and reduce emissions from power plants. In order to gain information about wastes produced by advanced coal utilization processes, a research project is being conducted to characterize the geotechnical and geochemical properties of advanced coal process wastes. The University of North Dakota Energy and Environmental Research Center (EERC) analyzed 34 of these wastes for their bulk chemical and mineral compositions and for the disposal-related physical properties listed in a table. This paper discusses potentially useful waste management practices for eight bulk waste samples obtained from four different clean coal processes: gas reburning with sorbent injection (GRSI); pressurized fluidized-bed combustion (PFBC); SO{sub x}, NO{sub x}, RO{sub x}, BOX (SNRB); and coal reburning (CR). All four processes have been demonstrated at either full-scale or pilot-scale facilities in the US. Since the properties of advanced process wastes are different from conventional coal combustion wastes, an analysis was performed to identify any potential problems that could occur when standard, off-the-shelf waste management technologies are used for handling and disposal of advanced process wastes. When potential problems were identified, possible alternative technologies were evaluated.

An Assessment of Hybrid Combined Cycle Power Generation Systems Based on a Coal Fired Pressurised Fluidised Bed Combustor

AbstractA hybrid combined cycle electrical power generating scheme burning coal and natural gas is examined using the ECLIPSE chemical process simulator. The technical, environmental and economic performance of this system is presented and comparisons are made with conventional power generation technologies. These comparisons show that the hybrid combined cycle offers improvements in efficiency, CO2 emissions and cost.

Present status of advanced coal-fired power plants

According to IEA data the total installed coal-fired capacity for generation of electricity is about 950 GWe. The units generate annually 5 PWh of electricity, consuming over 2 Gt of coal. The amount of coal used for electricity generation is expected to grow at a compound average rate of 2% per annum in the late 90s. The bulk of growth comes from the OECD countries. Beyond the year 2000 the growth rate of the developing countries will start to surpass the growth rate of the OECD countries. World demand for electricity will increase by a factor of 3–5 over the first half of the next century to about 35–50 PWh in 2050. Should 40% be generated by coal then the 2500 GWe coal-fired capacity must be installed which is the equivalent of 4000 units of 600 MW each. This is a potential market for clean and more efficient coal technologies to penetrate. A new generation of clean coal plants have been developed during the ‘80s and the early ‘90s and various demonstration plants are coming on stream. This report will present a utility view on various competing coal-based technologies for the coming decade: the pulverized coal-fired plant with advanced steam data (PF-USC), the integrated coal gasification/combined cycle plant (IGCC), and the pressurized fluid-bed combustion combined cycle plant (PFBC-CC). Furthermore, the longer-term perspectives of new coal-based technologies for a deregulated market will be addressed.

96/06404 Solids preparation and handling (in pressurized fluidized bed combustion)

96/06404 Solids preparation and handling (in pressurized fluidized bed combustion)

96/05289 Preliminary evaluation of the FIBROSIC candle filter for particulate control in PFBC

The FIBROSIC candle filter element is made by the vacuum-forming of a select blend of alumino-silicate fibres with silica and alumina binders. It is potentially useful as a hot-gas clean-up device for control of particulates in pressurised fluidised-bed combustion (PFBC). Relative to the more widely studied SiC candle filter, it has the advantages of light weight, low cost and reduced tendency to thermal-shock breakage. With Illinois No.6 high-sulphur coal in a laboratory-scale PFBC/alkali sorber facility, filters of both types were tested for particulate-collection efficiency; permeability characteristics; and physical and mechanical strength and integrity. Tests were conducted at 800-825°C with a system pressure of 9.2 bar. Filter-face velocities were 5.1 and 10.2 cm s -1 during test periods of 8 and 9.5 hours for SiC and FIBROSIC candle filters respectively. The filters were periodically cleaned by a reverse jet pulse of nitrogen gas. Both types achieved particulate-collection efficiencies of >99.9% and exhibited comparable permeability characteristics. Although the FIBROSIC candle filter possesses inherently lower bursting strength than the SiC, its physical and mechanical strengths were shown to be sufficient under PFBC conditions.

96/05338 Repowering a steam power plant by means of fluidised-bed combustion and a two-shaft gas turbine

Utilities have been adopting repowering as an option in their plans to meet the growth in loading. In this work, repowering of older and marginally efficient steam plant by conversion to combined-cycle operation is carried out by the addition of a twin-shaft gas-turbine engine and a pressurised fluidised-bed combustor (PFBC). The low-pressure compressor rotates at variable speed to provide the PFBC with the required mass of air to satisfy various load conditions. A computer program was designed for computations of performance. Four arrangements were studied, namely the basic System 1 with a heat-exchanger interposed between the gas turbine and the PFBC, in addition to circulating the condensate of the steam plant through the gas-turbine intercooler; System 2 circulates direct cold water; System 3 cancels the heat-exchanger; System 4 cancels the heat-exchanger and raises the turbine inlet temperature to 1250 °C to anticipate the future performance of advanced systems. Results show that System 2 achieves marginal improvement, whereas System 3 achieves 7.3% higher power and 4% higher efficiency relative to System 1. System 4 achieves figures of 33.4 and 13.2% respectively.

A Review of the Efficacy of Silicon Carbide Hot-Gas Filters in Coal Gasification and Pressurized Fluidized Bed Combustion Environments

Reviews of relevant literature and interviews with individuals cognizant of the state of the art in ceramic filters for hot-gas cleaning were conducted. Thermodynamic calculations of the stability of various ceramic phases were also made. Based on these calculations, reviews, and interviews, conclusions were reached regarding the use of silicon carbide-based ceramics as hot-gas filter media. Arguments are presented that provide the basis for our conclusion that high-purity silicon carbide is a viable material in the integrated coal gasification combined cycle (IGCC) and pressurized fluidized-bed combustion (PFBC) environments we examined. Clay-bonded materials are, we concluded, suspect for these applications, their extensive use not-withstanding. Operations data we reviewed focused primarily on clay-bonded filters, for which a great deal of experience exists. We used the clay-bonded filter experience as a point of reference for our review and analysis.

Development of Ceramic Composite Hot-Gas Filters

A novel type of hot-gas filter based on a ceramic fiber-reinforced ceramic matrix was developed and extended to full-size, 60-mm OD by 1.5-m-long, candle filters. A commercially viable process for producing the filters was developed, and the filters are undergoing testing and demonstration throughout the world for applications in pressurized fluidized-bed combustion (PFBC) and integrated gasification combined cycle (IGCC) plants. Development activities at Oak Ridge National Laboratory (ORNL) and at the 3M Company, and testing at the Westinghouse Science and Technology Center (STC) are presented. Demonstration tests at the Tidd PFBC are in progress. Issues identified during the testing and demonstration phases of the development are discussed. Resolution of the issues identified during testing and the status of commercialization of the filters are described.

96/04170 Pressurized fluidized bed combustion of coals in mixtures of recycled flue gas and oxygen

96/04170 Pressurized fluidized bed combustion of coals in mixtures of recycled flue gas and oxygen

96/04133 Formation of solid deposits in the gas circuit of a pressurized fluidized bed combustion plant

96/04133 Formation of solid deposits in the gas circuit of a pressurized fluidized bed combustion plant

Pressurized fluidized bed gasification of coal using flue gas recirculation and oxygen injection

A combined cycle incorporating pressurized fluidized bed gasification of coal with pure oxygen and recycled flue gas followed by pressurized combustion of the fuel gas using pure oxygen, is a process which produces electricity and heat with a high efficiency and a flue gas with a high CO 2 concentration. CO 2 recovery from this process can be done more easily than from conventional coal conversion processes. In this way a high efficiency coal conversion process can be realized with low CO 2 emissions. The specific aim of the project described in this paper is to to assess the technical feasibility of this process. For this purpose an existing 1.6 MW th pressurized fluidized bed combustion test rig is being modified to study experimentally the gasification process and the pressurized combustion of the resulting low calorific value fuel gas. The paper gives a description of the objectives of the project, the modified test rig and the experimental programme which is planned for the second half of 1995.