Additives for Heat Engine Coal Slurry Fuels

摘要

The objective of this program is to evaluate the use of additives for combustion improvement and control of emissions and ash related difficulties associated with the use of cleaned coal-water slurries in gas turbines and diesel engines. Initial screening of candidate combustion additives is being performed using the thermogravimetric analysis (TGA) method. From experimental results, it appears clear that potassium compounds offer distinct benefits in promoting coal combustion. Sodium hydroxide is somewhat less effective and lithium hydroxide appears to promote soldering. The TGA patterns for all the alkaline compounds show very sharp weight loss rates at ignition, but ignition temperatures and subsequent combustion rates differ significantly. The fouling and corrosion problems associated with the alkali compounds will certainly preclude their use as combustion additives. For the salts tested, generally those additives with organic anions promote ignition over the halides. However, the halide salts seem to be somewhat more effective at sustaining combustion. The work to date has largely stressed soluble metal salts as additives. Insoluble additives would be expected to be present only on the outer surfaces of the coal during combustion. The soluble additives can be reasonably uniformly deposited over the entire wettable surface of the coal, yet in many cases the actual catalyst would be water insoluble. Comparisons with insoluble additives, such as the active catalysts derived from soluble additives (e.g., soluble ferric nitrate generates ferric oxide under combustion conditions, but this is water insoluble) may point to combination improvements due to better catalyst dispersion. 8 references, 5 figures, 7 tables. (ERA citation 09:039487)