High-quality glass sands production
The following technologies are used for glass sands beneficiation:
- glass sands beneficiation in aqueous media (wet technology) using methods of active cleaning, attrition scrubbing, classification and electromagnetic (magnetic) separation;
- chemical extraction of harmful impurities from quartz or glass sand;
- glass sands beneficiation using methods of dry classification and electromagnetic (magnetic) separation.
The majority of mining and beneficiation plants uses wet technology of beneficiation, which allows obtaining treated glass sands with the content of Fe2O3 in the range of 0,020 – 0,050%, while the content of ferric oxide in raw materials is about 0,05 - 0,15%.
The wet technology is quite simple for operation, the equipment for beneficiation is widely produced, but at the same time there are some disadvantages:
- high beneficiation process energy consumption including consumption of natural gas for glass sand drying;
- it is problematic to operate the equipment during winter period;
- short equipment depreciation period due to its abrasive wear and corrosion;
- high cost of building of plant premises due to requirements to operation in high humidity conditions;
- beneficiation process automatic control is complicated;
- return water cleaning systems constructing and operating are required; when the highest quality of sand glass is needed, coagulants for cleaning of return water are required.
Chemical beneficiation methods make it possible to obtain glass sands containing 0,006 – 0,015% of ferric oxide. This method of beneficiation is mainly used for treatment of gangue quartz and sometimes it is used for treatment of glass sands.
To set up a large-scale production of glass sands using this method a number of complicated engineering tasks are to be solved:
- special chemically proof equipment for beneficiation processes;
- development of methods of neutralizing, recovery and storage of waste;
- development of methods and technologies for correction of chemical makeup of working mediums.
In recent times the methods of dry beneficiation are also used for production of treated glass and foundry quartz sands. This is mainly connected with the fact that magnetic separation task has been solved and new modern equipment is manufactured.
There are dry beneficiation lines which perform 2 or 3 stages of magnetic separation at a number of plants. Energy consumption and glass sands production costs are essentially lower in such cases than they are if to use wet technology.
Realignment of mining and processing plants for application of dry technology is restrained by the following factors:
- classification of quartz material using dry high frequency screens does not allow to remove adhesions, films of harmful infusions and foreign particles from grain surface effectively;
- the technology does not allow sufficient averaging of the final products and depends on the quality of the raw sands.
These disadvantages of dry technology can be eliminated by use of abrasive treatment of quartz grain surface (attrition scrubbing) by means of their rubbing friction and removal of products from the final quartz concentrate.