Improvements in and relating to processes for the production of carbon black and apparatus therefor

摘要

Carbon black is obtained by exploding a hydrocarbon-containing gas, other than acetylene, with considerably more than, preferably at least 1 1/2 times, the minimum amount of oxygen necessary to form an explosive mixture under the reaction conditions, and blowing the black formed out of the reaction chamber by the reaction gases generated. The gases are preferably introduced into the reaction chamber under pressure. In addition to hydrocarbon-containing gases, tars, mineral oils and similar products may also be used as starting materials, if desired with the addition of an oxidizable substance such as hydrogen whereby the lower ignition limit can be modified. Nitrogen oxides can also be employed as a source of oxygen. The reaction is carried out in a suitable pressure vessel which may be provided with cooling or heating means, to facilitate the commencement of the reaction. The products are removed through a suitable valve which may be mechanically operated or operated by the explosion pressure. The explosive mixture is supplied also through a valve which may be positively actuated or operated by the pressure of the gas mixture, preferably only when the vessel is empty. The hydrocarbon-containing gas and the oxygen or gases containing it are preferably compressed separately and fed, after mixing, to the reaction chamber through a large pressureequalizing vessel, which avoids irregularities in the composition of the explosive mixture. The black is separated in a suitable separator, final traces being removed by means of a filter, or an electrostatic precipitator, all of which are preferably kept above the dew point of the exhaust gases to avoid separation of water. Liquid materials may be vaporized or introduced into the reaction chamber as a spray or mist, and the separation apparatus is kept at a temperature sufficiently high to avoid condensation of unburnt oil. Mixtures of hydrocarbon gases with liquid hydrocarbons may also be treated. Any oily material in the carbon black may be removed by solvents or by calcining in a current of gas, e.g. steam at 250-400 DEG C. The mixture is exploded by means of a sparking plug or ignition wire, but after a short time, self-ignition of the mixture occurs. Striking back of the explosion is avoided by keeping the period during which materials are admitted into the pressure vessel, below 0,5 seconds, preferably of the order of 0,01 seconds. Preferably the pressure in the equalizing vessel is at least 1 1/2 times the desired pressure in the reaction chamber before explosion, and the inlet valve is preferably designed to obtain a constant inlet velocity with a sudden closure. Examples describe the decomposition of a gas obtained by splitting coke oven gas; a gas obtained by cracking paraffin; benzene; coal tar creosote oil; naphthalene, and a mixture of a fraction from the decomposition of coke oven gas with coal tar oil. The carbon black produced is suitable for incorporation in rubber and in printing inks. The gas produced is rich in hydrogen, and also may contain carbon monoxide and lower hydrocarbons. It may be used as a heating gas or in explosion machines.