Coal Combustion Efficiency Research Articles

Fluidization characteristics of gas-fluidized beds: Air and glass beads system

Good gas-solids contacting and solids mixing are essential features, both for efficient coal combustion and desulfurization of coal in a fluidized-bed combustor. It will therefore be very useful if suitable procedures could be developed to characterize the quality of fluidization in gas-solid systems. Three different procedures are discussed in this article with reference to air and glass beads of four different average sizes: 1. (i) in one scheme, the bed voidage is measured at minimum fluidization and the variation of this quantity with Reynolds number at minimum fluidization is correlated with the powder classification scheme of Saxena and Ganzha and hence with the corresponding fluidization characteristics. A major effort is directed at substantiation and confirmation of this characterization scheme, which relates the fluidization behavior to the Reynolds number at incipient fluidization. 2. (ii) The local heat-transfer coefficient of a probe element immersed in the bed is also measured as a function of the superficial fluidizing velocity and the nature of variation is taken as representing the quality of bed fluidization. 3. (iii) A technique is developed to measure the time-history of the temperature fluctuation of a probe element and to relate this parameter to the bed-fluidization characteristics. Additional experimental data with other solids will be generated in the future to develop these proposed three schemes further for the characterization of bed-fluidization behavior.

ボイラー用炭の新しい評価方法

Although the consumption of coal as a fuel for general industry has been rapidly increased recently in Japan, most, more than a hundred, of coal are imported from foreign countries. A coal firing boiler is usually designed for various coal, but it is important for users to evaluate coal properly to combust it efficiently without any trouble.Conventional evaluation methods were developed for eastern coal in USA and not suitable for Japanese actual situation. Therefore, we, Idemitsu, have developed new evaluation indexes for combustion, handling and so on.We can evaluate the combustibility more precisely than current fuel ratio analysing the combustion procedure of maceral in a experimental furnace and also estimate the NOx emission performance in a commercial boiler with “NOx Index” which was newly developed by Idemitsu. Furthermore, we introduce new indexes for handling property, ash slagging potential, electrostatic precipitability and grindability.The development of clean and high efficient coal combustion technology is also introduced to solve the environmental problem over the world.

Mathematical model of coal combustion in a furnace with a fluidized bed

The authors mathematically simulate the first three levels of the physicochemical processes taking place in a fluidized-bed combustor during the combustion of coal and establish links between these levels. The first of the levels includes the phenomena of heterogeneous and homogeneous kinetics and volatilization occurring at the ionic and molecular level. The second level accounts for the growth and motion of bubbles and for mass and heat transfer between phases in the layer and with the heating surface. The third level includes processes initiated by fields of both external and internal forces such as the hydrodynamics of the bed, circulation of the solid and gas phases, and particle distribution and entrainment. The model makes it possible to calculate coal combustion efficiency and mechanical underfiring. An important difference between this model and existing models is the expanded description of combustion kinetics.

Fluidized-bed combustion: The Australian experience and its application to Asian and Pacific basin countries

Fluidized-bed combustion (FBC) is a promising method for the efficient combustion of coal. It is especially suited to those fuels having properties that present difficulties in conventional combustion systems such as high mineral matter content or low ash fusion temperature. Examples are given of pilot-plant trials to burn coal washery wastes and alkali-salt-bearing low-rank coals.

Smoke Abatement Exhibition at the Science Museum

AN exhibition on the abatement of smoke will be opened at the Science Museum, South Kensington, by the Minister of Health, the Right Hon. Sir Kingsley Wood, M.P., on October 1, and will remain open until October 31. It has been arranged by the National Smoke Abatement Society (by permission of the director of the Museum, Colonel E. E. B. Mackintosh), with the co-operation of interested Government departments and industrial associations. Models and other exhibits demonstrating the efficient combustion of coal in steam-raising and other industrial operations will be shown, and other sections will be devoted to the uses of other natural fuels, namely, anthracite and anthracitic coals, and oil. Another section will exhibit material relating to the generation, distribution, and uses of electricity. The pre-treatment of coal will be demonstrated by exhibits on high-temperature carbonization (gasworks practice) for the preparation of town's gas and gas coke, and on low-temperature carbonization, in which the product of principal interest is the semi-coke. For the scientific investigation of the smoke problem, methods for the measurement of smoke are required, and an exhibit of the Fuel Research Station will be concerned with current researches on this subject, which are being carried out with the view of developing a domestic fire that will burn coal smokelessly. The Department of Scientific and Industrial Research will show exhibits on the nature and causes of smoke, and on the investigation of atmospheric pollution. A section of the exhibition will be devoted to material demonstrating the effects of smoke. The Annual Conference of the National Smoke Abatement Society will be held at the Museum on October 14-17, and will be opened by Captain Harry Crookshank, M.P., Secretary for Mines. Particulars of this Conference may be obtained from the Secretary of the Society, at 36 King Street, Manchester 2.