Pressurized fluidized bed boiler

Modern technology utilizes fluidized bed boilers, pressurized fluidized bed boilers, and gasification of coal to improve energy extraction and minimize potential pollutants. The lower temperatures of those processes affect the fate of the individual trace elements that are emitted or are associated with the residues from the consumed coal (Table 2 Clarke, 1993). 

An important quantity in the design of bubbling-bed reactors containing internal heat transfer coils is the bed expansion ratio, 8. A model for 8 in terms of a dimensionless drag force, F, was developed by Lofstrand et al. (1995) and compared with experimental work carried out with the pressurized unit at Chalmers University and an atmospheric pressure fluidized bed boiler fitted with bed internals. The bed expansion ratio is defined as... 

Crouse, F. W., Nazemi, A. H., and Lewis, J. P. Performance Analysis of a Pressurized Circulating Fluidized Bed Boiler Combined Cycle Power Plant, Proc. Int. Conf. Fluid. Bed Combust., Volume Data 1982, 7th(l), p. 232 (1983). 

Matthews, F. T. et al. Conceptual Design and Assessment of a Pressurized Circulating Fluidized Bed Boiler. Final Report, Report, ERRI-CS-3206, 124 pp. (1984). 

Alkali vapor transport and deposition is a well-known, though poorly understood, factor in the corrosion or fouling of alloys and ceramics, both in established and developing technologies. Problem areas include oil-fired glass melting operations (21), blast furnaces, boilers, turbines, coal gasification ( ), MHD (23, 24, 25) and coal-fired pressurized fluidized beds (26). 

Finally, the low-sulfur char is used as a clean boiler fuel for electric power generation. The hot char can be used directly, at pressure, with obvious advantages in thermal efficiency by using a pressurized, fluidized-bed combustion system (PFBC). The size consist of the char should ensure good performance when fluidized in the PFBC. Because the char has been partially desulfurized, the flue gas can easily meet a S02 emission specification of less than 0.8 lb per 106 Btu without the need to add limestone. This is in contrast to burning the Wyodak feed coal in a... 

Pressurized fluidized-bed combustion (PFBC) of coal This is probably the most promising application field for inorganic filters, despite the fact that only a few large-scale examples of application have been successfully tested in very recent years [14]. Dust is removed just at the outlet of the boiler, allowing heat recovery from cleaned gases. 

High-pressure fluidized beds are also used in power-station furnaces in a combined cycle in which the products of combustion from the fluidized bed are used to drive a gas turbine, while a steam-tube boiler in the fluid bed raises steam to drive a steam turbine. This system both increases the efii-ciency of the combustion process and reduces pollution. 

Fluidized-bed combustors can be either atmospheric or pressurized (Yeager and Preston, 1986). The atmospheric type operates at normal atmospheric pressure while the pressurized type operates at pressures 6-16 times higher than normal atmospheric pressure. The pressurized fluid-bed boiler offers a higher efficiency and less waste products than the atmospheric fluid-bed boiler. There is also a circulating (entrained) bed combustor which allows for finer coal feed, better fuel mixing, higher efficiency, as weU as an increased sulfur dioxide capture. 

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