Study On The Process Of Coal Gangue Dewatering With The Bypass And The Activity Of The Dewateringcoal Gangue

The pozzolanic activity of dewatering-coal gangue in different calcinated system is tested by the methods of ISO and alkali-corrasion, the optimal thermal condition of coal gangue dewatering is determined; the effect of bypass dust on the activity of dewatering-coal gangue is studied, the performance of cement with activated coal gangue is researched in this dissertation. On the base of these studies, a new technics of coal gangue dewatering with precalcination kiln's by-passing is brought out, the interrelated thermal and technologic calculation is done, the pivotal equipment of this system is studied and designed. At last the hydrating and hardening mechanisms of cement mixed with activated coal gangue is studied by means of determining the rate of heat evolution, DTA, XRD, SEM and liquied composition analysis.The experimental results indicate that the optimal calcinated temperature of coal gangue is 850℃, the quicker the calculated rate and cooled rate, the higher the pozzolanic activity of dewatering-coal gangue is. So the optimal thermal condition of coal gangue-dewatering is that coal gangue is calcinated quickly and cooled suddenly at 850℃. If some appropriate alteration is done on the bases of precalcination kiln's bypass system then the above thermal condition can be fulfilled absolutely. Therefore the technics of coal gangue dewatering with precalcination kiln's by-passing is feasible. Kiln dusts improve the activity of dewatering-coal gangue because the alkali, chlorine, sulfur, etc in the kiln dust accelerate the dissolution of activated SiO2 and Al2O3. But the overmuch amount of kiln dust is unfavorable, and the reasonable amount of kiln dust is 10% by associating with the thermal calculational result of the bypass system.When the activated coal gangue is mixed into Portland Cement, it possesses similar effect as GBFS, such as the setting time of cement is prolonged, the strength is improved. Because of adding activated coal gangue in cement, the amounts of calcium silicate hydrate, hydrogarnet and calcium aluminate hydrate in cement paste are increased and the amount of calcium hydroxide is reduced, which conduce the cement stone structure is more close-grained, so the performance of sulphate resistance is enhanced. After adding activated coal gangue, the amount of alkali in cement is unreduced and a majority of alkali present in the form dissoluble alkali, thus alkali silicate reaction is not restrained...