Slurry fuels

The Szego mill has been used for dry as well as wet grinding of coal, in both water and oil, for the preparation of coal-slurry fuels. To grind coal in water to the standard boiler size (80 per cent < 74 im) takes about 7 MJ/Mg (20 kWh/tonne). For micronized grinding, to a 15 xm median size, 2-3 passes through the mill are required and the specific energy... 

Gandolfi, E. A. J., Papachristodoulou, G. and Trass, O. Powder Technology 40 (1984) 269-282. Preparation of coal slurry fuels with the Szego mill. 

The following discussion details some of the recommended procedures used to prepare slurry fuels and to measure their rheological properties. 

Slurry fuels -rheological measurements [RHEOLOGICAL MEASUREMENTS] (Vol 21)... 

Miller. B.G. "Coal-Waier Slurry Fuel Utilization in Utility and Induslrial Boilers," Chem. Eng. Progress, 29 (March 19891. 

Other Solid Briquetted Briquetted Small Particulate Any Slurried Fuel... 

Of the four applications for coal slurries given here, coal slurry fuels have the most stringent requirements. Hence, the following discussion of slurry properties is with reference to coal slurry fuels. 

Coal-water slurry fuels. High-percent-solid slurries that are stable against settling, so they can be pumped, stored, handled, and burned much like heavy fuel oil. Coal-water fuels have about half the heating value of fuel oil, and because of their water content they burn cooler than pulverized coal, leading to lower production of nitrogen oxides. 

Coal slurry fuels are of interest for the following markets ... 

Replacement of Heavy Fuel Oil The original concept for coal-water slurry fuels was as a direct replacement for heavy 5 and 6 fuel oils. The intent was that power plants and industrial heating operations that were using these fuel oils could switch directly to a coal-water slurry with a minimum of modification to their combustors. This requires a very... 

Unlike coal slurry fuels, which are utilized in a fluid form, coal transported by pipeline is used as a solid after dewatering. As a result, it does not need to be stable when stored in tanks, and it is not so critical that its solid loading be maximized. The following variables are important for a pipeline system ... 

Pulido, J.E. Rojas, C.P. Acero, G. Duran, M. Orozco, M. Rheology of Columbian coal-water slurry fuels effect of particle-size distribution. Coal Sci. Technol. 1995, 24, 1585-1588. 

Nodelman, I.G. Pisupati, S.V. Miller, S.F. Scaroni, A.W. Partitioning behavior of trace elements during pilot-scale combustion of pulverized coal and coal-water slurry fuel. J. Hazard. Mater. 2000, 74, 47-59. 

Coal Slurry Combustion and Technology, PETC, 1983 Session VII. Richter, W. Pohl, J. H. Proc. 7th Int. Symp. on Coal Slurry Fuels Preparation and Utilization, PETC, 1985, Paper No. 12, pp. 443-462. 

With the development of coal-water slurry fuels and their successful use in power plants, direct combustion of fines in circulating fluidized beds and the injection of dry coal fines into a number of thermal and metallurgical processes, the interest in tum-ble/growth agglomeration for the size enlargement of coal fines from any source has diminished to almost zero. 

So-called ultrafine metal powders below 1 i in diameter can be made by pyrogenic dissociation of the vapors of the carbonyls of iron, nickel, and cobalt. Aluminum of a particle size below the resolving power of the electron microscope has been formed by evaporation and condensation under vacuum in an inert atmosph e. Similarly, evaporated magnesium has been quenched by JP-4 fuel for directly making a slurry fuel. Also, long ball-milling fine magnesium powder in the presence of a surfactant can lead to particles below I n. Iron or nickel electrolytically deposited on a mercury cathode form very active, often pyrophoric, fine powdm that, however, can be stabilized in order to be handled in air. 

U.S. Department of Energy (1985). Coal Slurry Fuels Preparation and Utilization, U.S. Department of Energy, Pittsburgh. 

The coal-water slurry fuel (CWSF or CWS or CWF) is a fuel that consists of fine coal particles suspended in water. Presence of water in the coal-water slurry reduces harmful emissions into the atmosphere, makes the coal explosion proof, makes use of coal equivalent to use of liquid fuel (e.g., heating oil), and gives other benefits (see the following). A coal-water slurry consists of 55%-70% of fine dispersed coal particles and 30%-45% of water. 

A coal-water fuel (CWF coal-water slurry fuel) is a slurry of coal in water than is typically fed to a combustor for the generation of heat or power. The CWF represents a new type of clean fuel technology that emerged as a way of using coal as a substitute for fuel oil in the petroleum crises of the last century. The basic composition of the fuel is 70% w/w coal, 30% w/w water, and 1% w/w additive to stabilize the slurry. 

Kihm, K. D. and Deignan, P., Dynamic surface tension of coal water slurry fuels. Fuel, 74, 295-300 (1995). 

CWS technology has been under development for well over a century, with the blending of pulverized coal with both water and oil. The first patents for coal-oil mixtures (COM) were issued to Smith and Munsell in 1879, as a means for extending the oil resource and reducing the costs of liquid fuels [11]. Relatively low costs of crude oil over time, however, suppressed interest in this technology. COM interest again arose in the 1970 s due to the oil price shocks, and several types of slurry fuels were developed including COM, with <10 percent water in the fuel slurry, coal-oil-water (COW) suspensions of coal in fuel oil and >10 percent water, coal-methanol fuel (CMS) where fine coal particles are slurried in methanol, and various CWS formulations [11]. 

Table 3.1. Typical Parameters for Coal-Water Slurry Fuels...

Falcone Millra, S., Ji. Morrison, and A.W. Scaroni. 1995. The Utilization of Coal Pond Fines as Feedstock for Coal-Water Slurry Fuels. Proc. 20 Intranational Technical Conference on Coal Utilization Fuel Systems. Coal Slurry Technology Association. Clearwater, FL. March 7-10. 

Trass, O. and E. Gandolfi. 1999. Coal-Slurry Fuels for Environmental Benefit. Proc. 24 International Technical Conference on Coal Utilization and Fuel Systems. Coal Technology Association. Clearwater, FL. March 8-11. pp. 823 - 832. 

Morrison, J.L., B.G. Miller, and A.W. Scaroni. 1997. Coal-Water Slurry Fuel Production Its Evolution and Current Status in the United States. Proc. 14 International Pittsburgh Coal Conference. Taiyuan, Shanxi Province, Peoples Republic of China. Sep 23-27. 

Trass, O. 2001. Coal-Slurry Fuels Where are We and Where Should... 

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