Pulverised fuel

Fluidised-bed systems produce higher combustion intensities at lower temperatures than combustion of pulverised fuel in conventional fossil-fuel-fired boilers. The mineral matter for corrosion does not form fused salts and is not expected to release corrosive species. Fluidised bed combustors can, therefore, burn lower grade, cheaper fuel in smaller plant with better pollution control than traditional boilers... 

PsychrorneLry sec humidity determination Pugh. F. J, 205,228 PumiM. 1. 209, 228 Pulverised fuel particles 47 ... 

The particles to be removed may range in size from large molecules, measuring a few hundredths of a micrometre, to the coarse dusts arising from the attrition of catalysts or the fly ash from the combustion of pulverised fuels. 

PF, pulverised fuel fgd, flue gas desulphurization IGCC, integrated gasification combined cycle ... 

Nandi Q), in their investigation into the role of inert coal macerals in pulverised fuel... 

Brown, J., Ray, N. J. Ball, M. 1976. The disposal of pulverised fuel ash in water supply catchment areas. Water Resources, 10, 1115-1121. 

Lee, S. Spears, D. A. 1997. Natural weathering of pulverised fuel ash and porewater evolution. Applied Geochemistry, 12, 367-376. 

Lee, S. Spears, D. A. 1998. Potential contamination of groundwater by pulverised fuel ash. In Mather, J., Banks, D., Dumpleton, S. Fermor, M. (eds) Groundwater contaminants and their Migration. Geological Society of London, Special Publications, 128, 51-61,... 

Thompson, D. Argent, B. B. 2002. Thermodynamic equilibrium study of trace element mobilisation under pulverised fuel combustion conditions. Fuel, 81/3, 345-361. 

There is a large class of industrially important heterogeneous reactions in which a gas or a liquid is brought into contact with a solid and reacts with the solid transforming it into a product. Among the most important are the reduction of iron oxide to metallic iron in a blast furnace the combustion of coal particles in a pulverised fuel boiler and the incineration of solid wastes. These examples also happen to be some of the most complex chemically. Further simple examples are the roasting of sulphide ores such as zinc blende ... 

Two typical sets of pressure measurement data for the vertically down and vertically up sections of pipeline are presented in Fig. 2. This shows the location of the pressure tappings and their proximity to the various bends in the pipeline. The data relate to the pneumatic conveying of a fine grade of pulverised fuel ash. Five different bulk particulate materials were investigated in the research programme, the other four being barytes, bentonite, cement and fluorspar. All five materials were capable of being conveyed in dense phase and hence at low velocity. 

Fig. 2. Pressure gradient results for a fine grade of pulverised fuel ash.

Fig. 6. Conveying characteristics for pulverised fuel ash in 81mm bore pipeline.

Fig. 10. Pressure gradient for pulverised fuel ash in 81 mm bore vertically down pipeline.

C-S-H = poorly crystalline or amorphous calcium silicate hydrate of unspecified composition. Ggbfs = ground granulated blast furnace slag. Hep = hardened cement paste. Pfa = pulverised fuel ash (fly ash). 

At the Institute for Process Engineering and Power Plant Technology the pyrolysis and gasification of different biomass has been investigated with special emphasis on the gas, tar and char composition and on the NO reduction efficiency of the produced gas. The gasification experiments have been carried out in an electrically heated lab-scale entrained flow reactor in understoichiometric atmosphere, for the rebum experiments a pulverised fuel combustion reactor was available. The gas, tar and composition as well as the NO, reduction efficiency have been analysed at temperatures of the entrained flow reactor between 400 C and 1300°C and of the flui sed bed reactor between 600°C and 900 C and air ratios of the pyrolysisygasification process between 0 and 0,4. 

The results of pyrolysis of difTerent solid fuels discussed here were performed at the entrained flow reactor. The results of NO reduction eiqieriments have been gained using the pyrolysis gas as rebum fuel in the pulverised fuel combustion reactor. 

Livingston, W.R., Sanyal, A. and Williamson, J., 1983, The role of copper oxychloride in reducing slagging in pulverised fuel fired boilers. Proc. Conf. The Effectiveness of Fuel Additives. Inst. Energy, Leatherhead. 

Three major types of coal combustor are in common use and include chain grate stokers, pulverised fuel burners and fluidised beds. The residence time of the fiiel in the combustion zone of each plant is very different and leads to very different deposition potentials even using coal of similar properties. 

In a pulverised fuel operation the fuel and residues remain in the high temperature region for only 1 to 2 seconds. The majority of the ash (at least 80%) passes through the flue gas system for removal in precipitators. The remainder of the ash goes out of the bottom of the pulverised fuel boiler. Evolution of organic volatile compounds into the gas stream is minimised due to the short residence time of the fuel and incombustibles. 

The method of firing (that is stoker, pulverised fuel, or slagging combustor) will also affect the extent of particular chemical reactions because each of these techniques will have different temperature/time characteristics. 

A number of sophisticated handling systems have been developed for pulverised fuels to ensure that the quantities delivered to the burners/lances are equal and controlled accurately (e.g. [14. 12]). This enables the kilns to be operated at high efficiency, with controlled low levels of CaCOs and high reactivities. 

Artificial hydraulic limes consist mainly of calcium hydroxide, calcium silicates and calcium aluminates. They are produced by blending suitable powdered materials, such as natural hydraulic limes, fully hydrated air limes and dolom-itic limes, pulverised fuel ash, volcanic ash, trass, ordinary Portland cement and blast furnace slag. 

Pozzolanic is used to describe materials, which, like pozzolana, contain reactive silica, and which, when mixed with quicklime and water, set to a hard mass. They include pulverised fuel ash, trass and burnt shale. 

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