Processing of mercury and rare metals containing coals altering chemical safety issue in Tajikistan
Project Status: 3 Approved without Funding
Duration in months: 36 months
Objective
Since Tajikistan does not have large oil reserves, coals are becoming the main energy source, the study of natural resources of the coals, has been the main objective at the Institute Chemistry of Tajikistan Academy of Sciences (TAS) in the past. These investigations were shown that the coals of all parts of the region have sulfur from 0.41 to 1.21%. Although those sources concern to low-sulfur coals but contain a considerable amount of mercury (1.5- 3 g/t). The average ash content in coals for individual regions ranges from 5.4 to 19.7%. Mercury is one of the most toxic trace impurities in coal. In the process of burning coal at thermal power plants, mercury passes into the environment. It is necessary to have complete information about the content of mercury in coal, smoke gases, fly ash, and other wastes for effective management of processes of cleaning smoke gas and securing chemical safety. By the request of the US Congress, the Environmental Protection Agency (US.SPA) in 1998 prepared 2 reports on mercury in coals: "Study of Hazardous Air Pollutant Emission from Electric Utility Steam Generating Units" and "Mercury Study Report to Congress”. The findings of these reports were: emission of mercury at atmospheric coal burn down is 143. 5 tons is a real threat to the health of the US population.
Emissions of mercury into atmospheric is not suitable for highlands such as Tajikistan. It is known that for separation of mercury from coals is the introduction of sorbent into coal before burning. In this regard, it is important to select adsorbent from local raw materials. The feature of mineralogical composition of Tajik coals has not been studied. US researchers suggested using coals and associated deposits as a raw material for the recovery of rare earth metals (REM), and in China, which is the largest exporter of the REM, most metals are produced as coal processing by-products. Investigations at the Chemistry Institute of TAS showed that Tajik coals to contain rare earth metals from 0.5 to 23 g/t and the extraction REM is the actual problem. Tajik coals contain from 0.007 to 0.009 g/t gold and from 1.5 to 663 g/t silver. The behavior of these metals at burning coals has not been studied. In this regards, very important is the solution of a complex of tasks for effective protection of the environment, securing chemical safety from mercury during the burning of Tajik coals and obtaining pure mercury, REM, and precious metals.
In this context, the purpose of the project is the study of physicochemical bases of technology for processing burning of mercury-containing Tajik coals, investigation of low-temperature vacuum processes on separating mercury, experimental study of extraction of REM and precious metals securing the chemical safety of Tajikistan.
To meet this goal, the following tasks will be undertaken:
1. To develop the methods for mercury adsorption before and after coal burning altering environmental and chemical safety.
2. The ask-slag collection from furnace and ash from the smokestack. Analyses of their composition and forms of location.
3. The development of effective methods for low-temperature vacuum processes for the separation of mercury.
4. Theoretical and experimental study of the production of REM and precious metals from cinder after the distillation of mercury.
