| 摘要 |
<p>An additive to a flame reaction is provided which forms noncorrosive deposits on cooler metal surfaces which are more stable than Na2SO4 or K2SO4. The additive preferentially combines with the sodium or potassium, and sulfates of these will not be formed. By adding tungsten to the flame, a complex sodium tungstate is produced on the surface of the cooler metal object in a dense form and corrosion is inhibited. Deposition appears to closely reflect the relative thermodynamic stabilities of these salts and follows the order Na2WO4>Na2SO4>NaCl>Na2CO3. The flame sulfur or chlorine do not remain on the surface in association with the alkali metal. Tungsten can be added in any form desired to the combustion system. The flame processes all chemical tungsten precursors as equivalent sources of tungsten. Suitable salts that are readily available are ammonium metatungstate, paratungstate, or tungstate, tungsten hexacarbonyl, tungsten oxides, tungstic acid or any organo-tungsten compound. The level of tungsten preferably present at an atomic concentration is equal to 1.5 to 2 times that of the sodium in the specific flame environment and possibly a little higher for potassium. The nature of the fuel and possible alkali reduction schemes will control the quantity and mixing method of the additive. The additive may be directly mixed into the fuel or injected into the burned gas regions of the combustor. Ta and Nb also appear as possible substitutes for W in the invention.</p> |
