Recycling of Spent Pot Lining First Cut from Aluminum Smelters by Utilizing the Two-Step Decomposition Characteristics of Dolomite

Abstract

Spent Pot Lining First Cut (shortened to SPL-1cut) is a solid waste discharged from a primary aluminum electrolytic production process. SPL-1cut is classified as hazardous waste in China because it contains large amounts of soluble sodium fluoride and a tiny amount of cyanide. Most of SPL-1cut is carbon—about 65%—and its calorific value is 22.587 MJ∙kg−1. There is a high level of sodium fluoride in SPL-1cut—about 15%—and sodium fluoride is randomly distributed in the carbon granule. The recycling of SPL-1cut using dolomite as a reactant, based on the characteristics of the two-step decomposition of dolomite at a high temperature, is discussed. The recycling of SPL-1cut was performed under the following heating conditions: the heating temperature was 850 °C, the holding time was 120 min, and 40% of the dolomite was added to the SPL-1cut. It was found that the cyanides are completely oxidized and decomposed, and dolomite is decomposed into MgO and active CaCO3. At the same time, NaF reacts with active CaCO3 and converts into CaF2. The results provide references for using SPL-1cut as an alternative fuel in the dolomite calcination process of the Pidgeon Process.

Research on the Process, Energy Consumption and Carbon Emissions of Different Magnesium Refining Processes

“…The vacuum carbothermal reduction process consumed 5.656 t of nonrenewable mineral resources, which was 9.689 t less than that of the Pidgeon process. Yifei Wang et al [72] used Spent Pot Lining First Cut (SPL-1cut) as an alternative fuel for dolomite calcination in the Pidgeon process. At 850 • C for 120 min, the cyanide was completely oxidized and decomposed by adding 40% dolomite to the SPL-1cut.…”

Water-to-Cement Ratio of Magnesium Oxychloride Cement Foam Concrete with Caustic Dolomite Powder

“…The water in the solution comes from the crystal water in bischofite and the free water in dissolved bischofite; that is, the total amount of water (m HO ) was the sum of the crystal water (m j ) and free water (m f ), as shown in Equation 11. m j + m f = m HO (11) It can be seen from Equation 11that MgCl 2 -H 2 O of different concentrations was formed after bischofite was dissolved in water, and the proportional relationship between the added m f and the bischofite mass (m Bi ) can be expressed as follows:…”

“…With the continuous growth of the world's requirements for magnesite and the environmental pressure, the price of LMP remains high. MgO a can be produced from the calcination of magnesite or dolomite [10,11]. Dolomite resources are widely distributed [12].…”