Furnace, coal-fired

PPS fiber has excellent chemical resistance. Only strong oxidising agents cause degradation. As expected from inherent resia properties, PPS fiber is flame-resistant and has an autoignition temperature of 590°C as determined ia tests at the Textile Research Institute. PPS fiber is an excellent electrical iasulator it finds application ia hostile environments such as filter bags for filtration of flue gas from coal-fired furnaces, filter media for gas and liquid filtration, electrolysis membranes, protective clothing, and composites. 

Knowledge of the composition of coal ash is usehil for estimating and predicting coal performance in coke making and, to a hmited extent, the folding and corrosion of heat-exchange surfaces in pidverized-coal-fired furnaces. 

The failure took place in a large water-tube boiler used for generating steam in a chemical plant. The layout of the boiler is shown in Fig. 13.1. At the bottom of the boiler is a cylindrical pressure vessel - the mud drum - which contains water and sediments. At the top of the boiler is the steam drum, which contains water and steam. The two drums are connected by 200 tubes through which the water circulates. The tubes are heated from the outside by the flue gases from a coal-fired furnace. The water in the "hot" tubes moves upwards from the mud drum to the steam drum, and the water in the "cool" tubes moves downwards from the steam drum to the mud drum. A convection circuit is therefore set up where water circulates around the boiler and picks up heat in the process. The water tubes are 10 m long, have an outside diameter of 100 mm and are 5 mm thick in the wall. They are made from a steel of composition Fe-0.18% C, 0.45% Mn, 0.20% Si. The boiler operates with a working pressure of 50 bar and a water temperature of 264°C. 

Conventional riffle box, as shown in Fig. 24, used normally for 2-way splitting in coal-fired furnace and boiler applications. 

Fluidized-bed combustion (FBC) is a different technology from conventional pulverized-coal-fired boilers. A mixture of powdered rather than pulverized coal and a sorbent (usually limestone) are injected directly into the furnace and burned while suspended on a bed of high-velocity air. The turbulent mixing of coal and sorbent causes the solids to behave as a pseudo-fluid, enhancing heat generation and transfer at much lower temperatures (800-900 °C) compared to conventional pulverized-coal-fired furnaces (1500 °C) (US Department of Energy 1992). 

Harley, R. A., Mercury Balance on a Large Pulverized Coal-Fired Furnace, J. Air Pollut. Contr. Ass. (September 1973) 23, (9), 773-777. 

Pulverized-Coal-Fired Furnaces Application of the Monte Carlo Method to Anisotropic Scatter. Int. J. Heat Mass Transfer, 26, 1649. 

Coal is burned in many of the world s power plants to generate electricity. Significant air pollution is produced if the stack gases from coal-fired furnaces are not treated before being released to the atmosphere. Untreated gases contain soot (fine unburned carbon particles), nitrogen oxides (NO.x), ash, and sulfur dioxide (SO2). 

Figure 1. Simplified flowsheet of 500 lb/hr pulverized-coal-fired furnace.

R. P. Gupta, T. F. Wall, and J. S. Truelove, Radiative Scatter by Fly Ash in Pulverized-Coal-Fired Furnaces-. Application of the Monte Carlo Method to Anisotropic Scatter, International Journal of Heat and Mass Transfer, 26, pp. 1649-1660,1983. 

M. P. Mengtt and R. Viskanta, An Assessment of Spectral Radiative Heat Transfer Predictions for a Pulverized-Coal Fired Furnace, Heat Transfer—1986, 2, pp. 815-820,1986. 

In principle, Castner s original process was a gradual oxidization of molten sodium in a countercurrent stream of purified and dried air. The equipment. Figure 1, consisted of an iron pipe surrounded by a coal-fired furnace. The ends of the pipe had tight-fitting end plates outside of the furnace. Shallow layers of sodium about 0.5 inch deep were placed in aluminum pans, loaded on tandem carts. The carts were then sealed in the heated iron tube for reaction at about 200° C. Air free of moisture and carbon dioxide was fed to the tube at a con-... 

Coal is a complex and relatively dirty fuel that contains varying amounts of sulfur and a substantial fraction of noncombustible mineral constituents, commonly called ash (Chawla et al. 2011). Table 3.4 shows the common types of corrosion in coal-fired furnaces. High temperatures (above 1000 F) of the superheater/reheater favor the formation of low-melting compounds. 

It is impossible to prevent some degree of interaction between a metallic component and high-temperature gases, so the common term prevention is not strictly applicable. What is meant is a reduction of the interaction to a very low value. The use of cheap low-grade fuels limits the options of improving the corrosion environment. About 30% of annual corrosion costs may be saved with the use of preventive measures. Three common methods are employed to prevent hot ash corrosion for both coal- and oil-fired furnaces. The use of highly resistant surfaces, the ranoval of the undesired contaminants in the fuels, and the use of additives are the most practical methods in this respect. The first two methods are identical for both types of furnaces. The type of preventive additives used in coal-fired furnaces differs from those utilized in oil-fired furnaces. 

The significant amoimts of fluidized bed ashes are generated in 2000 the annual output was 723 thousand tones [ 131 ]. Some part is used in cement industry, as a raw material in Portland cement clinker production. They are also added to concrete on the base of technical approvals. They can be easily distinguished from the ash of pulverized-coal fired furnace, because they do not give the mullite peak on XRD pattern. 

The slag layer ensures that the total amount of heat absorbed by the water-cooled shell of a cyclone furnace will be relatively small and a secondary furnace is necessary to recover thermal energy. This gas-cooling furnace is similar in construction to a pulverized coal-fired furnace with the possible addition of a slag screen to remove droplets of molten slag carried over from the cyclone unit. Several cyclone furnaces are commonly used with a single secondary furnace. 

Of the various methods of conventional combustion techniques, pulverized coal-fired furnaces are preferred for power stations and larger industrial facilities. Combustion processes create very fine effluents of which 70%-90% is carried to the air fly ash and 10%-30% remains as bottom ash (Commission on Energy, 1981). Difficulties in disposing fly ash stem from the enormous quantities collected (Scanlon and Dugan, 1979). 

---