The Application of Using Fluidized-Bed Crystallization to Treat Nickel-containing Wastewater
Date Issued
2004
Date
2004
Author(s)
Chan, Feng-Lung
DOI
zh-TW
Abstract
In recent years, fluidized bed pellet reactors have been extensively applied in the removal of anions and cations from wastewater. It improved the disadvantage of producing a large number of sludge easily in traditional unseeded precipitation treatment, and produced reusable pellets as resources. This technology cut down many processors and let the contaminants of heavy metals resource, but no second pollution problems of sludge. On the processor of wastewater, it could fit the emission standard of wastewater easily, and it had even more economical benefit and had no additional treatment equipment. In this research, the crystallization process of a fluidized bed pellet reactor was studied in the treatment of nickel-containing wastewater .The crystallization reactor was connected by three same reactors. Sodium carbonate was added as the reagent solution to form nickel carbonate and nickel hydroxide on the surface of the pellets in fluidized bed reactor. This study investigated the effects of some important factors, including CT/Ni feeding ratio、upflow rate、quantity of pellet、Ni-loading etc. We made experiment by continuous worked for conferring the crystals structure of pellet’s surface in different reactors, and analyzed the coated quantity under optimum operation conditions finally.
The results showed that operated with the different upflow rate and different CT/Ni feeding ratio ,the lower upflow rate increased removal efficiency ,especially on the condition of 23~30 m/h and CT/Ni feeding ratio was 2.5. The processor system would in low supersaturation when CT is not enough .On this condition the first reactor had bad removal efficiency and emission still couldn’t fit to the emission standard of wastewater. In the same way, overdosed of sodium carbonate would lead to high degree of supersaturation, the way would decrease removal efficiency of first reactor, but the filtrated wastewater could fit the emission standard .For the quantity of pellet, the increasing quantity could improve the removal efficiency. But in practical operation, we considered the expand level of pellet when it fluidized, the better amount of pellets should be 1/3~1/4 times of reactor’s height.
For macrocosm treatment ability (under optimum operation conditions), the removal efficiency of the first reactor was about 90% when inflow Ni-loading was 3.61 kg/m2h.The concentration of nickel was less than 1 mg/l and could fit the emission standard as Ni-loading was smaller than 1.87 kg/m2h.On the condition of recirculation, the removal efficiency was more and more terrible with operation time increased as the too low or high CT/Ni feeding ratio. The optimum CT/Ni feeding ratio was 2.
In the continuous process, we used as 35 mg/l of nickel inflowing in the fluidized bed, the results show that the removal efficiency would not decrease as operation time increased. The important factor was that the pellet’s size would more and larger and the interior’s free space of reactor decreased. We must change the pellet in fluidized bed reactors during a series processor. By the way, we observed the variation of pellet’s surface during the processor and discovered that some green crystal coated on pellet’s surface certainty. And then photographed the pellet’s surface by SEM, the images showed that the preceding reactor had the better strict structure. This result also showed that the majority mechanism of crystallization occurred in preceding reactor and sediment occurred in later reactor.
Subjects
流體化床反應槽
結晶
含鎳廢水
擔體
連續操作
crystallization
fluidized bed reactor
nickel-containing wastewater
media
continuous operation
Type
thesis
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