PHYSICOCHEMICAL AND TECHNOLOGICAL BASES OF PRODUCTION OF DESULPHURISED CRYOLITE FROM MUSCOVITE-STAVROLITE SHALES OF TAJIKISTAN
Rubrics: 2. CHEMICAL TECHNOLOGY
Authors:
1.
State Institution "Scientific Research Institute of Metallurgy" JSC "Tajik Aluminium Company
(Director)
Dushanbe, Tajikistan
Dushanbe, Tajikistan
3.
Russian Federation
Type:
Article
Pages:
from 84
to 88
Status:
In work
Language:
English
Keywords:
CRYOLITE, ALUMINIUM SULPHATE, POTASSIUM ALUM, SODIUM FLUORIDE, MUSCOVITE-STAVROLTA SHALE, “KURGOVAD” DEPOSIT, SULPHATIZATION, ALUMINIUM PRODUCTION
Abstract (English):
Physicochemical and technological aspects of production of desulfurised cryolite from a mixture of water-dissolved KAl(SO4)2, Al2(SO4)3 and Fe2(SO4)3 obtained by heat treatment of muscovite-stavrolite shale from the deposit “Kurgovad” with sulfuric acid have been investigated. According to the conducted laboratory tests at t - 85-95 °C, τ - 15-20 min. and NaF solution dosage 100% of stoichiometry, with two-fold washing with hot water at ratio S:L=1:4 and filtration with the help of vacuum-filtering unit, the degree of cryolite extraction reaches more than 94%. It was determined that relatively fine cryolite particles were formed at room temperature, which resulted in a prolongation of the filtration process and the absorption of relatively large amounts of sodium sulphate. At the same time the expediency of using a vacuum-filtering unit was established, because at increasing the temperature to 85 ° C sharply increases the removal of sodium sulphate from the composition of cryolite from 10.1 % to almost zero. In this case, the cryolite filtration time is reduced from 30 to 10 minutes. Physico-chemical methods of analysis proved the production of desulphurised cryolite corresponding to the normative requirements of GOST 10561-80 (artificial technical cryolite) and the mineral cryolite (PDF number 25-772). The chemical composition of the obtained cryolite consists mainly of 53.7% F, 12.5% Al and 31.8% Na. After separation of cryolite by filtration, the solid part of the evaporated filtrate was subjected to XRD, which determined the presence of sodium hydrosulphate, tenardite and aphthitalite minerals. The principal technological scheme of cryolite production from muscovite-stavrolite shales of the "Kurgovad" deposit was developed on the basis of the conducted research.
Physicochemical and technological aspects of production of desulfurised cryolite from a mixture of water-dissolved KAl(SO4)2, Al2(SO4)3 and Fe2(SO4)3 obtained by heat treatment of muscovite-stavrolite shale from the deposit “Kurgovad” with sulfuric acid have been investigated. According to the conducted laboratory tests at t - 85-95 °C, τ - 15-20 min. and NaF solution dosage 100% of stoichiometry, with two-fold washing with hot water at ratio S:L=1:4 and filtration with the help of vacuum-filtering unit, the degree of cryolite extraction reaches more than 94%. It was determined that relatively fine cryolite particles were formed at room temperature, which resulted in a prolongation of the filtration process and the absorption of relatively large amounts of sodium sulphate. At the same time the expediency of using a vacuum-filtering unit was established, because at increasing the temperature to 85 ° C sharply increases the removal of sodium sulphate from the composition of cryolite from 10.1 % to almost zero. In this case, the cryolite filtration time is reduced from 30 to 10 minutes. Physico-chemical methods of analysis proved the production of desulphurised cryolite corresponding to the normative requirements of GOST 10561-80 (artificial technical cryolite) and the mineral cryolite (PDF number 25-772). The chemical composition of the obtained cryolite consists mainly of 53.7% F, 12.5% Al and 31.8% Na. After separation of cryolite by filtration, the solid part of the evaporated filtrate was subjected to XRD, which determined the presence of sodium hydrosulphate, tenardite and aphthitalite minerals. The principal technological scheme of cryolite production from muscovite-stavrolite shales of the "Kurgovad" deposit was developed on the basis of the conducted research.
Keywords:
CRYOLITE, ALUMINIUM SULPHATE, POTASSIUM ALUM, SODIUM FLUORIDE, MUSCOVITE-STAVROLTA SHALE, “KURGOVAD” DEPOSIT, SULPHATIZATION, ALUMINIUM PRODUCTION
CRYOLITE, ALUMINIUM SULPHATE, POTASSIUM ALUM, SODIUM FLUORIDE, MUSCOVITE-STAVROLTA SHALE, “KURGOVAD” DEPOSIT, SULPHATIZATION, ALUMINIUM PRODUCTION
