GB795688A - Improvements in the thermal cracking of combustible organic liquids - Google Patents

Abstract

Combustible organic liquids are thermally cracked by burning oxygen or an oxygen-containing gas, in an amount insufficient for complete combustion, below the surface of the liquid. The liquids to which the process may be applied include hydrocarbons, ethers, alcohols and ketones and is particularly suitable for converting mineral oils into acetylene, olefines, lower alkanes, carbon monoxide and hydrogen. Reduced or increased pressures may be used. Ignition may be accomplished by heating the liquid and/or the oxygen so that spontaneous ignition occurs; if the ignition point is above the boiling point of the liquid, pressure may be applied. Heating of the oxygen may be effected by burning a combustible gas such as hydrogen in the oxygen. Alternatively a flame may be introduced in a protective bell, for example a flame of hydrogen burning in an excess of oxygen, the excess oxygen then being used as the oxygen-containing gas. In the case of substances difficult to ignite, a heat-storage material may be arranged in the gas chamber of the combustion zone to store heat and thus ensure ignition. Substances which reduce the ignition point may also be added to the liquid, such as ethers, ethyl nitrite, amyl nitrite and methyl ethyl ketone peroxide in the case of mineral oils. Electrical ignition can be used, either discharge or resistance heaters being used. Strong oxidizing agents may be added to the oxygen such as ozone, nitric acid vapour, nitrogen oxides, chloric acid, perchloric acid, chlorine dioxide, manganese heptoxide, nitrates, chlorates and perchlorates, solids and liquids being added as dust or aerosol respectively. Oxidizing catalysts such as platinized asbestos or other platinum catalyst, magnesium silicates or aluminium silicates such as pumice stone can also be suspended in the liquid. The oxygen may be introduced as bubbles by introduction through a sieve or frit material or slots or a layer of granular material over a grate in the bottom of the vessel, or through a nozzle or bell submerged in the liquid. Alternatively the liquid may be allowed to flow through a tube and oxygen introduced through one or more nozzles so that the oxygen flows as a separate phase or as bubbles; liquid may be recycled after purification and cooling. Where the liquid is stationary in a vessl the depth through which the oxygen passes should be sufficient to ensure that all the oxygen is "burned." Steam or nitrogen may be added to the oxygen to moderate the combustion. In the examples the process is applied to the cracking of diesel oil, octane, crude oil and methyl alcohol to give hydrocarbon mixtures with oxides of carbon and hydrogen.