| 摘要 |
<p>This invention relates to an apparatus, method and product wherein fine particles of fly ash containing carbon are oxidized in a dry, bubbling fluid bed of previously introduced fine particles of the same fly ash so that the subsequently removed particles have reduced carbon content and are useful as pozzolan, suitable for use, without further processing, to replace a portion of cement in concrete. The apparatus comprises a means for introducing said carbon containing fly ash particles into a dry bubbling fluid bed reactor (30). The dry bubbling bed reactor contains fly ash particles (31), means for introducing air into the reactor (34 and 35), means for removing beneficiated fly ash, means for removing heat from the reactor (42), and a means for removing air and combustion products from the reactor (40). The preferred conditions are a temperature of about 1300 °C to 1800 °C, air velocity of between at least about 0.5, but not more than about 3 ft./sec, residence time of at least about 2 minutes but up to 100 minutes, volume ratio of air to fly ash of between about 1,000 and 1,500, and an excess of oxygen between about 5 % and 15 %.</p> |
