OCR Text |
Show Compound Melting Point, C (F) V205 873 (1243) Mg2V20? 927 (1700) MgV206 760 (1400) CaO.V205 778 (1432) Raask (1982), concentrating on boiler fouling and slagging as a result of pulverized coal combustion, observed that volatized potassium appears in the deposits in the form of chlorides or sulfates. He postulated that the deposit build up rate is proportional to the surface tension and inversely proportional to the viscosity and particle size of the deposits. These potassium-rich sulfates form low melting point and extremely corrosive deposits. In burner rig tests, performed by NASA as part of their continuing research into the study of the corrosion of superalloys, doped gases from Jet A fuel combustion were used with dopants of vanadium, molybdeum, tungsten, phosphorous, sodium, and potassium salts (Deadmore, 1978, 1979, 1982-a,b). Addition of vanadium and sodium to the fuel resulted in the formation and deposition of both sodium sulfate and sodium vanadate. In the same study, the addition of phosphorous with sodium resulted in the deposition of sodium phosphate and an undetermined glassy phase deposit. By itself, phosphorous was observed to be less corrosive than sodium, due to the presence of the glassy phase, however, at wall temperatures of 800 C (1472 F), sodium, coupled with phosphorous, was more corrosive than sodium alone due to Na^SO^ solids and a liquid phase of phosphorous-glass. Other studies using the same or similar burner rigs reported increased plugging of air cooling holes due to increased "stickiness" of the deposits when phosphorous was added to the fuel. This was especially true in the presence of iron and 1.5.18 |