| Red mud are the waste of aluminum industry. The huge demand of aluminium products immensely stimulates the developments of aluminum industry, making red mud’s emission grow fast. Owning to a large use of Na OH in miner aluminum process, red mud presents strong basicity. Red mud has complex components with different content, which varies with producing areas. There is still no uniform and effectable way to treat red mud. The general treatment for red mud is stacking. After a long time of dumping, a red mud dam comes into being. Red mud dam has great protential safety risk, once the dam were broken, red mud would pour into fields nearby, bringing huge damage to the environment.Water content, p H, and density etc. of red mud were measured in this thesis. Single factor experiment, orthogonal test and repeatly washing were employed to study dealkalization performance of red mud. Apart from that, Sulfur fixation experiments of red mud were also conducted. In this process temperature, time, and air flow were considered to study red mud’s sulfur releasing performance, then sulfur fixation agent and metallic additon were added to explore the impacts on sulfure fixation efficiency. Shale were added in red mud to make sintered bricks, anti-dismantle strength, freeze-thaw and scumming performance were measured to eatimate quality of these bricks. Conclusions were as follows: Dealkalization of red mud(1)The total amount of Na, K was 4.65%, 0.32%, respetively. Ca O was selected as dealkalization agent, and its removal rate for Na+, K+ was 55.35%, 35.44%.(2)Single factor experiment showed that, when particle size was 0.075-0.15 mm, liquid-solid ratio was 5, temperature was 100℃, dealkalization time was 2h, addition of Ca O was 16%, an optimum removal rate was got, which was 73.29% and 52.35% for Na+ and K+.(3)Image contrast of dealkalized red mud and original red mud through SEM showed that, dealkalized red mud presented smoother surface and clearer edge. And XRD anaysis indicated that original red mud contained garnet and calcite and so on. Contrast anaysis showed a diffraction peak weakening of sanidine while an appearing of cancrinite and margarite’s diffractin peak after dealkalization.(4)Orthogonal test indicated the order of primary and secondary for removal rate. Na+ followed the order of temperature > dealkalization agent addition > particle size > dealkalization time > liquid-solid ratio. And the best condition was when temperature was 90℃, dealkalization agent addition was 12%, particle size was beyond 0.6mm, dealkalization time was 3h and liquid-solid ratio was 4. Under this condition, a removal rate of 75.83%,56.54% for Na+, K+ was got.K+ followed the order of dealkalization agent addition > temperature > dealkalization time > particle size > liquid-solid ratio. The best condition for K+ removal was as follows: dealkalization agent addition was 12%, temperature was 90℃, dealkalization time was 3h, liquid-solid ratio was 4 and particle size was 0.075-0.15 mm. Under the best condition, a removal rate of 76.84%, 57.38% for Na+, K+ was got.(5)Repeatly washing experiments showed a promotion on dealkalization rate. After three times washing, removal rate could reach 90.32%, 39.28% for Na+, K+. Desulfurization of red mud(1)The total amount of sulfur in red mud was 0.14%. Titer of KIO3 on red mud was 0.05665 mg/m L.(2)In the condition when temperature was 600℃, sintering time was 60 min and air flow was 0.4 m3/h, sulfur release rate could reach 95.27%.(3)Sulfur fixation efficiency increased with the increase of Ca O addition. Under 600℃ and Ca O addition was 0.1%-0.5%, the best sulfur fixation was 78.31%, 54.38% higher than blank value. Under the same addition of Ca O, sulfur fixation efficiency decreased with increasing temperature.(4)Promotion of metallic addition on Ca O sulfur fixation performance differed, of which Si O2 and Ba(NO3)2 had better performance comprehensively. In 1000℃, sulfur fixation efficiency of adding Si O2, Ba(NO3)2 was 53.22%, 55.73%, respectively, much higher than blank value 38.17%.(5)XRD anaysis of red mud added Ca O showed the appearing of Ca3Al2(Si O4)(OH)8 and Al0.5Si0.75O2.25, which would prevent the degradation of Ca SO4, increasing sulfur fixation efficiency. Sintered bricks made by red mudAnti-dismantle strength of red mud sintered bricks increased with an increase of shale addtion. When shale addition was 20%, anti-dismantle strength was 5.69 Mpa. After freeze-thaw test, the most mess loss was 1.27%, indicated a qualified freeze thawing performance. Lime blowing experiment didn’t bring new cracks to red mud bricks. Red mud treated by dealkalization process had a better scumming performance than original red mud.There were huge available resources in red mud. Researches on minimization, hazard-free treatment, and reutilization of red mud could fundamentally solve problems as field occupying and high protential risk, holding a profound significance. In this thesis, dealkalization and sulfur fixation processes were tried to pretreat red mud, and feasibility of red mud making sintered bricks was preliminarily explored. |
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