Abstract: The invention relates to a process and to an apparatus for the conversion of hydrocarbons. According to the invention, at least one first gas containing at least 20% of oxygen by volume and a type of hydrocarbon are first all circulated in separate streams which are parallel to each other, without their being mixed, according to a spatial distribution such that the first gas is surrounded by the hydrocarbon; these substances are introduced into a mixing/reaction chamber at a first given circulation level, and while the substances are then allowed to mix, the oxygen and the hydrocarbon are ignited so as to give rise to the conversion reaction and then, at a second given circulation level situated downstream of the first, a quenching of the resultant mixture is performed in a chamber, the resultant quenched conversion products are recovered. The invention applies particularly to the manufacture of conversion products such as acetylene and ethylene.