Purifying filter-clogging coal tar formed from low-temperature coal carbonization

A process for purifying filter-clogging coal tar residues of the type obtained by low-temperature carbonization of coal, and including viscous organic coal tar constituents, particulate solid impurities and liquid water, the process comprising the steps of heating coal at 450.degree.-700.degree. C. and at least substantially in the absence of air to thereby decompose the coal and obtain products including coal tar which contains liquid water, particulate solid impurities, and viscous organic coal tar constituents including light oils which tend to combine with the liquid water to produce a filter-clogging emulsion;

• heating the thus-formed coal tar to a temperature above the boiling point of water and sufficiently high to thereby distill off substantially all of the water and the light oils so as to obtain an intermediate product of increased viscosity and which is substantially free from the presence of liquid water and of the light oil constituents which in combination form the filter-clogging emulsion;
• and subsequently filtering the intermediate product without the use of a diluent to thereby separate the particulate solid impurities from the undistilled viscous constituents of the coal tar, the filtration without the use of a diluent being possible due to the elimination of light oils and water and the consequent absence of filter clogging which would otherwise result from the combination of the light oils with water onto a filter-clogging emulsion.