OCR Text |
Show Viscosity. The viscosity of a CWS should certainly be less than 2000 centipoise (Haake viscometer at 100 sec shear rate and 78°F). It is likely that by the time a large-scale utility demonstration of CWS is performed, the optimum, as-fired, CWS viscosity will be well below 500 centipoise. Fuels that can be heated provide an extra degree of freedom in this respect, and this may ultimately give them an advantage over the others. There is no reason, based on the tests performed, to specify a particular rheology (Newtonian, pseudoplastic, dilatant, etc.). Ideally the viscosity should remain below 2000 centipoise at all shear rates above about 50 sec % Material <200 Mesh (74 Microns). For CWS to burn out as well as pulverized coal, there should be at least 70 percent of the particles in the fuel (weight basis) less than 74 microns. Tight oil-designed boilers may require finer particles. Of course, such a change in particle size is only useful if the atomizer can perform well enough to take advantage of it. % Material >50 Mesh (300 Microns). For CWS to burn out as well as normal pulverized coal, there should be no more than one percent (weight basis) of the particles greater than 300 microns. The comments made in the previous paragraph are applicable here as well. Volatile Content. High volatile bituminous coals (as defined by the ASTM) are recommended for use in CWS. Sodium Content of Ash. No sodium-containing additives should be used in the production of CWS. -19- |