The Temperatures Required for the Production of Primary Tar
Various statements have been made on the behaviour of coal when gradually heated. Bornstein describes the behaviour of gas flame coal from the Graf Bismarck Colliery as follows:
About 200 degrees Water first split off
200-225 degrees First oily distillate
300 degrees Copious evolution of water
310 degrees First evolution of volatile sulphur compounds
390-400 degrees Main distillation commences
410 degrees First combustible gas
420 degrees Strong evolution of gas.
Fritsche reports on the yield of primary tar at different minimum temperatures. He heated the aluminium retort (Figs. 3 to 5) charged with 20 grams of coal at a constant rate of 10 degrees per minute to the desired temperature,