Conversion of coals with various degree of metamorphism in supercritical water with formic acid

Conversion of coals with various degrees of metamorphism in supercritical water (SCW) was studied under the isochoric conditions at the temperatures of 380–800 °C. At conversion, formic acid, increasing the hydrogenating properties of the medium, was added into SCW. The results of conversion are comparable with the results of pyrolysis under the same temperatures. It was found that the degree of conversion in SCW is 10–15 % higher than that at pyrolysis. An addition of formic acid increases the conversion degree. After processing, there are almost no liquid organic substances escaped into SCW. However, some agglomerates, whose strength is comparable with the strength of lump coal, are formed because of dissolution of the organic matter in the mixture of SCW and formic acid.