Application of brown coal pyrolytic oils in black coal slurry flotation

This paper deals with the possible use of brown coal pyrolytic oils prepared and applied as described below. First, brown coal samples were drawn from the Most Region (Ceskoslovenska armada Mine) and Sokolov Region (Jiff Mine) and processed to obtain a required grain size. The samples were pyrolyzed in a closed tube reactor at 900 degrees C (5 degrees C/min, holding time of 30 minutes), and the resulting liquid product was collected. As the composition of the pyrolytic oils (content of aliphatic and aromatic hydrocarbons, alcohol, and functional groups) is analogous to that of a conventional flotation agent (in this case Montanol 800), the oils were used in a flotation process to float black coal slurry from the Karvina Region (from Lazy Mine and a settler of Darkov Mine). The pyrolytic oils were applied in a mix with Montanol 800 in a dose of 500 g/t, and the individual proportions of the agents differed from 1:4 to 5:0 (pyrolytic oil:Montanol 800). The final values, i.e. concentrate yields and ash contents, were compared with the reference values obtained when applying pure Montanol 800. The limit of ash content in the flotation concentrate was set at 10%. As coal contains sulphur, the compounds of which transfer into the liquid products during pyrolysis, some brown coal samples underwent bacterial desulphurization using a pure bacterial culture of Acidithiobacillus ferrooxidans, in order to find out whether sulphur content influences the flotation results in any way. The results confirmed that pyrolytic oils may be applied in the black coal slurry flotation process, and concentrates with ash content below 10% may be obtained. However, this can only be achieved through mixing the oils with Montanol 800 as the application of the pyrolytic oil alone did not provide satisfactory results. An indirect output of the experiment was the determination of the net and gross heat of combustion for the pyrolytic gas. The results imply that it may be used as an alternative fuel.