Synthetic cryolite
1 Scope
This stanard specifies the requirements, test methods, conformity with standard, packaging, signing, transporting, storing and order(or contract) content of synthetic cryolite.
This stanard is applicable to cryolite synthesized by hydrofluoric acid, hexafluorosilicic acid or sodium fluorosilicate which is mainly used for the aluminum production.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document(including any amendments) applies.
GB/T 8170, Rules of rounding off for numerical values & expression and judgement of limiting values
YS/T 273(all parts), Chemical analysis methods and physical properties of cryolite
3 Definitions
molecule ratio of synthetic cryolite
molar ratio of NaF to AlF3 in the synthetic cryolite product
4 Requirements
4.1 Grade and class
4.1.1 According to the molecule ratio, synthetic cryolite shall be divided into two classes. One class with molecule ratio between 2.80 and 3.00 shall be defined as high molecule ratio synthetic cryolite, and the other one with molecule ratio between 1.00 and ＜2.80 shall be defined as ordinary synthetic cryolite. Molecule ratio shall be calculated according to formula (1):
………………………(1)
In formula (1):
Na Mass fraction of sodium in synthetic cryolite product, %;
Al Mass fraction of aluminum in synthetic cryolite product, %;
26.9815 Relative atomic mass of aluminum;
22.9897 Relative atomic mass of sodium.
The calculation results shall be kept to the second decimal place.
4.1.2 Synthetic cryolite shall be devided into four grades such as CH-0, CH-1, CM-0 and CM-1. Four grades shall be represented by two English letters and a horizontal line "-" followed by a number,The letter C shall represent the identification code of synthetic cryolite (C is the first letter of cryolite); The letter H and M shall represent the class of synthetic cryolite where H is the high molecule ratio synthetic cryolite, M is the ordinary synthetic cryolite, and the number (0 or 1) is the order number.
4.2 Chemical composition and physical property
The chemical composition and physical property of synthetic cryolite shall meet the regulations in Table 1. Special requirements for chemical composition and physical properties proposed by the purchaser shall be specified in the order (or contract) after being determined by the supplier and the purchaser.
Table 1—Regulations of chemical composition and physical property
class grade chemical composition
% physical property
F Al Na SiO2 Fe2O3 SO42- CaO P2O5 H2O ignition loss
%
Minimum Maximum
high molecule ratio synthetic cryolite CH-0 52.0 12.0 33.0 0.25 0.03 0.50 0.10 0.02 0.20 1.5
CH-1 52.0 12.0 33.0 0.36 0.05 0.80 0.15 0.03 0.40 2.5
ordinary synthetic cryolite CM-0 53.0 13.0 32.0 0.25 0.05 0.50 0.20 0.02 0.20 2.0
CM-1 53.0 13.0 32.0 0.36 0.08 0.80 0.60 0.03 0.40 2.5
4.3 Appearance quality
Cryolite shall be white powder or granule, and agglomerates larger than 10 mm shall be not allowed in the product.
5 Test method
5.1 Chemical analysis methods and physical properties of synthetic cryolite shall be in accordance with YS/T 273(all parts). Rounding comparison method is used to determine the analysis value. The regulation of rounding off for numerical values shall be in accordance with GB/T 8170. The figures of rounded values shall be consistent with the limit values listed in the table.
5.2 Appearance quality shall be checked by visual inspection, and the size of the agglomerates in the product shall be measured with a tool of corresponding accuracy.
6 Conformity with standards
6.1 Inspection and acceptance
6.1.1 Synthetic cryolite shall be inspected by the supplier's technical control department who fills in the product quality certificate to ensure the product quality in accordance with the regulations of this standard.
6.1.2 If the purchaser has any doubt about the product quality, the purchaser shall inform the supplier within 1 month after products are received, and the problem may be solved through consultation by the supplier and the
