Abstract
ESR of Rapidly Heated Coals Electron spin resonance has been used to examine the free radicals in chars prepared by heating coals to temperatures, in the range 400 C to above 2000 C in the following times: 1 ms, 20 ms, 180 s and several hours. It was concluded that: The stable free radical concentration of chars was critically dependent on the rate and duration of heating. Increases in free radical concentration were concomitant with the release of volatile matter. Free radicals exist in electrically non-conducting chars from which the bulk of their volatile matter has been released by heating in excess of 2000 C for about 1 ms. By heating CRC 301b coal to 660 C in 180 s a char containing approximately 1 unpaired electron per 100 carbon atoms is produced. Oxygen effects were found for all the coals and chars examined regardless of carbon content or heat treatment. The Production of Acetylene from Coal Products by Submerged Arcs A study has been made on the use of a submerged arc for the production of acetylene from coal-based feedstocks. Three laboratory scale apparatuses were constructed and operated; a continuous d. c. arc, and two intermittent a. c. arc systems. Anthracene oil, pitch, and solvent extracts of coal were examined together with phenanthrene and liquid paraffin for comparison. It was concluded that The composition of the gases produced in the a. c. systems depended on the controlled duration of the arcs. Gases containing up to 36% v/v acetylene were produced from anthracene oil, but the concentration of acetylene dropped to 29% when operating at 240 C with a coal solution containing 25% w/w coal substance. The electrical energy consumption was about 7 kW/kg of acetylene, i. e. about two-thirds that of the Carbide process. The overall yield of acetylene could not exceed 25% w/w for aromatic coal-based feedstocks. The large amount of solid carbonaceous material produced could not easily be separated from the feedstook and was an undesirable product.