Method of pyrolyzing brown coal

A two stage method for the rapid pyrolysis of brown coal, said brown coal being rich in ash and saliferous, so as to simultaneously produce high grade coke, a rich pyrolysis exit gas stream of low dust content, and a pyrolysis tar stream of low dust content, which comprises

• (a) providing a feed stream of solid particulate mined brown coal, said brown coal being rich in ash and saliferous;
• (b) fluidizing and drying said brown coal feed stream in a first fluidized bed stage, by passing said brown coal feed stream into said first fluidized bed and above a first foraminous initial flow bottom support disposed below said first fluidized bed, said first fluidized bed and said first support being within a first container comprising a dryer means;
• (c) burning a flammable gas stream with an air stream within a mixing chamber within said first container dryer means and below said first support, and concomitantly passing a recycle drying vapor gas stream and a combustion exhaust gas stream into said mixing chamber, so that hot mixed gas rises from said mixing chamber and through said first support, and fluidizes and heats said brown coal feed stream within said first fluidized bed, whereby said brown coal feed stream is dried in said first fluidized bed and within said first container dryer means by direct heating, with a limited degree of oxidation of the brown coal taking place in said first fluidized bed;
• (d) withdrawing a drying vapor gas mixture stream from said first container dryer means, and from above said first fluidized bed, said drying vapor gas mixture stream containing a first quantity of entrained solid particulate material in the form of fine grains and dust;
• (e) separating said first quantity of entrained solid particulate material from said drying vapor gas mixture stream;
• (f) dividing the drying vapor gas stream derived from step (e) into two portions, a first portion being said recycle drying vapor gas stream of step (c), and a second portion being a discharged-off gas;
• (g) withdrawing a dried coal stream from said first container dryer means, and from said first fluidized bed;
• (h) carbonizing the withdrawn dried coal stream of (g) by rapid pyrolysis, and in a second fluidized bed stage, by passing said dried coal stream into said second fluidized bed and above a second foraminous initial flow bottom support disposed below said second fluidized bed, said second fluidized bed and said second support being within a second container comprising a pyrolysis reactor;
• (i) providing a hot gas stream containing hydrocarbon and alien to carbonization, and comprising a fluidizing medium, said hot hydrocarbon-containing gas stream being at a temperature corresponding to the pyrolysis conditions in said second container pyrolysis reactor of (h);
• (j) passing said hot hydrocarbon-containing gas stream of (i) into said second container pyrolysis reactor below said second support, whereby said hot hydrocarbon-containing gas stream rises through said second support, and fluidizes and carbonizes said dried coal stream in said second fluidized bed, acting as a fluidizing medium and by rapid pyrolysis of said dried coal stream, said second fluidized bed being concomitantly heated by indirect heat exchange with a hot heat exchange fluid stream, the heat exchange fluid stream thereafter being passed into the said mixing chamber as combustion exhaust gas stream of step (c);
• (k) withdrawing a pyrolysis exit gas stream from said second container pyrolysis reactor, and from above said second fluidized bed, said pyrolysis exit gas stream containing a second quantity of entrained solid particulate material in the form of fine grains and dust;
• (l) separating said second quantity of entrained solid particulate material from said pyrolysis exit gas stream;
• (m) cooling the cleaned pyrolysis exit gas stream derived from step (l), so as to condense and separate a product pyrolysis tar stream of low dust content from a product rich pyrolysis exit gas stream of low dust content;
• and
• (n) withdrawing a product coke stream from said second container pyrolysis reactor, and from said second fluidized bed.