Research Of Water Model On Carbonation Process Of Calcified Residue

In this paper, we aimed at studying the carbonation process-the core process of "Calcification-Carbonation" which was proposed by our group for processing low-grade bauxite and red mud. Pressurized carbonation involved gas-liquid-solid three-phase slurry reactor process. Therefore, the gas-liquid-solid reactor became the core equipment of the new method. Our group innovatively designed and produced a new type of carbonation reactor. We conducted water model experiments based on similarity principle in the air-water-glass beads and CO2-NaOH aqueous systems. At first, we investigated superficial gas velocity, superficial liquid velocity, height-diameter ratio of the reactor and gas-liquid two-phase mixing rule under the conditions of different heights by using high-speed photography and image processing technology. Then we examined the impact of different operating conditions on gas holdup, solid content and CO2absorption rate. It reflected gas agitation effect and bubble miniaturization effect of the carbonation reactor. Through the analysis and summary of the experimental data, we got the following conclusions.Firstly, the image analysis of water model showed that, bubbles in the carbonation reactor were smaller and the mixing effect of gas-liquid was good. With superficial gas velocity, superficial liquid velocity and height-diameter ratio increased, bubble miniaturization effect was better and better. The bubble miniaturization effect was best just in the middle of the reactor.Secondly, the gas holdup went up with the increasing of the superficial gas velocity, went down slightly with the increasing of superficial liquid velocity, increased with the increasing of the liquid-solid ratio, and increased with the increase of the height-diameter ratio. By using the dimensional analysis method, we got the criterion equation relationship of gas holdup under our experimental conditions.Thirdly, solid content was well distributed and had a little change at the central axis of the reactor, while decreased at first and then increased from bottom to top at the other radial position. Superficial gas velocity had little effect to solid content in the middle of the axial direction in the reactor. When the gas velocity was less than7.07m·s-1, solid particles became more and more scarce from bottom to top in the axial direction because of the shortage of suction in the reactor. The effect of the superficial liquid velocity on solid content was only on the top of the reactor near the overflow pipe.Fourthly, volume transfer coefficient increased with the increase of superficial gas velocity. The use ratio of CO2decreased gradually with the increase of superficial gas velocity, but it did not decrease linearly. At low gas flow rates, volume transfer coefficient decreased with the increase of superficial liquid velocity. The use ratio of CO2decreased with the increase of superficial liquid velocity. At high gas flow rates, superficial liquid velocity had little effect on the volume transfer coefficient and use ratio of CO2. The volume transfer coefficient and use ratio of CO2decreased with the increase of the height-diameter ratio. In this experimental condition,Criterion equation on volumetric mass transfer coefficient can be express as follows:Inlet small gas flow rate of the carbon dioxide:The early stage of the reaction:The medium stage of the reaction:The late stage of the reaction:Inlet large gas flow rate of the carbon dioxide:The early stage of the reaction:The medium stage of the reaction:The late stage of the reaction: Fifthly, when superficial gas velocity was21.23m·s-1, superficial liquid velocity was1.769m·s-1, liquid-solid ratio was20and height-diameter ratio was5, the bubble miniaturization effect, the mixing effect of gas-liquid-solid and CO2absorption effect of carbonation reactor were best in the research of water model on carbonation process of calcified residue.