The experiment study of using industrial waste red mud to manufacture foamed blocks
Red mud foamed block is prepared using waste of aluminum oxide production—red mud, soft burning magnesium powder (MgO), bischofite (MgCl<inf>2</inf>·6H<inf>2</inf>O) and various addition agents. The influence of each factor on strength and density of red mud foamed block is analyzed by orthogonal experiment in this paper. The best ratio is obtained as follows: red mud 30%, MgO 40%, F-3 high efficiency composite foaming liquid 3.0 kg, MgCl<inf>2</inf>·6H<inf>2</inf>O 20% and fine sand 5% (all dry ingredients about 700 kg).
Preparation and properties of sintering red mud unburned road brick using orthogonal experiments
Abstract As the major solid waste, Sintering Red Mud (SRM) comes from the process of sintering alumina production. In order to study the application of SRM-URB in road engineering, this paper utilized cement-fly ash-lime to stabilize SRM and adopted normalized orthogonal table of L9 (34) in the orthogonal experiment design, thus acquiring the optimum mix proportion of SRM-URB. It also evaluated the properties of optimal SRM-URB including physical property, shrinkage property, frost resistance property and did research on influences of curing condition, cement content and fly ash content on unconfined compressive strength (UCS) of SRM-URB under 7-day and 28-day curing conditions. Experimental results showed that the prepared SRM-URB with optimal proportion had good road performance and compressive strength under 28-day standard curing condition was greater than 19 MPa, which significantly influenced the UCS. The energy dispersive X-ray spectroscopy (EDS) and the X-ray diffraction (XRD) results showed that SRM contained many hydrated active minerals. The Scanning Electron Microscope(SEM) results showed that C-S-H gel and ettringite came into being, which produced particles and form network structure thus enhancing strength and compactness of SRM-URB. The study shows that SRM is suitable for becoming the raw material of unburned road bricks, whose application in road engineering would be an effective strategy to ease the environmental burden.
Intensification of Bubble Disintegration and Dispersion by Mechanical Stirring in Gas Injection Refining
Water model experiments were performed for establishing highly efficient gas injection refining processes. Mechanical stirring was applied to disintegrate the injected bubbles and to disperse them widely in the bath. The bubble disintegration and dispersion were investigated by changing rotation mode (direction of rotation), rotation speed, blade size of the impeller and gas flow rate. Forward rotation of the impeller induced a stable tangential flow and could not disperse bubbles in the bath due to formation of a vortex around the impeller shaft. The tangential flow could be suppressed by forward–interrupt rotation, which could reduce the vortex formation to some degree. However, forward–interrupt rotation could not disperse the bubbles widely in the bath. Forward–reverse rotation could prevent the vortex formation completely and create a strong shear stress field, which intensified the bubble disintegration and dispersion in the bath. Higher impeller rotation speed and larger blade length in forward–reverse rotation could enhance the bubble disintegration and make the dispersed bubbles smaller. The bubble dispersion zone became wider with larger blade length. The bubble size tended to be larger at higher gas flow rates. However, its dependence on the gas flow rate became smaller at higher impeller rotation speed.