GB779901A - Improvements relating to the cracking of coal oil mixtures - Google Patents

Abstract

Pulverized bituminous coal is mixed with heavy mineral oil, the mixture is heated under a pressure of at least 20 atm. to a temperature in the range 280 DEG to 310 DEG C., whereby an extract is formed, and the extract is then cracked at a temperature of about 450 DEG C. under pressure. The cracked product is discharged into a zone of lower pressure where the volatile components are flashed-off, and the pitch-like residue is subjected to coking. Motor fuel <PICT:0779901/III/1> fractions are separated from the vapours. Permanent gases are also obtained, and these may be used to heat the apparatus. If desired, the cracking stage may be carried out in the presence of a catalyst such as aluminium silicate or magnesium silicate. Coal/oil paste is forced by pump 12 against a pressure of more than 20 atm. through heating-coil 13 into cylinder 15 which forms the first of a battery of cylinders in furnace 16. Cylinder 15 contains a rotor 17 which fills it except for a narrow annular space at the wall; and cylinders 15a and 15b are similarly equipped. Cylinders 23, 23a and 23b also have rotors, but of smaller diameter than that in cylinder 15. The top of each cylinder is joined to the bottom of the next by a pipe with a gas-release valve 58. Each rotor is provided with longitudinal scrapers which bear against the wall of the cylinder and force the coal/oil mixture upwardly through the annular space therein. The rotors are driven jointly by motor 20. The coal/oil mixture remains in cylinder 15 for about 7 minutes and is raised to a temperature of about 290 DEG -300 DEG C. therein. The mixture is then passed via gas-separator 22 to cylinder 23, wherein it remains for 30 minutes while being raised to 310 DEG C. From the upper end of cylinder 23, the material is conducted via gas-separator pipe 27 to cylinder 15a, where it is rapidly heated to 390 DEG C. The "extraction process" is then completed in cylinder 23a in which the mixture remains for 30 minutes while it is raised to 410 DEG C. In order to crack the mixture, it is rapidly heated in cylinder 15b to 450 DEG C., and is then passed up cylinder 23b in which it remains for 30 minutes while being heated to 470 DEG C. The cracked product passes through pressure-release valve 32 into one of the coking retorts 34 ... 34c, which is maintained at about 400 DEG -500 DEG C. The flashed vapours enter column 36, and light hydrocarbons and gases are withdrawn from the head of the column. The light hydrocarbons are condensed, and collected in tank 44, while the gases pass on through washer 40 to gasometer 42. Gas from this gasometer is supplied to furnace 16 via line 43. Diesel oil is withdrawn from column 36 through pipe 45 and is collected in tank 47. The heavy oil withdrawn from the column through pipe 48 is cooled in heat-exchanger 14 and collected in tank 50. This heavy oil may be pumped through line 52 to be mixed with powdered coal to form the initial coal/or mixture. When sufficient pitch has accumulated in the retort 34 ... 34c, it is disconnected from furnace 16 and heated to a higher temperature in the range 500 DEG -1000 DEG C. to produce coke. Gas liberated during this stage is admitted to column 36. While coking is being carried out in one retort, another retort is connected to furnace 16 and is being filled with pitch. Specification 465,067 is referred to.