A process for preparing acetylene and synthesis gas by partial oxidation of hydrocarbons with oxygen, by first separately preheating the hydrocarbon gas and oxygen gas, and then reacting the gases and cooling the products rapidly. The reactor wall is blanketed with a purge gas stream, introduced through a plurality of feed lines. These feed lines deliver purge gas in a vector direction within a 10° angle of the main flow direction of the reactive gas stream. The purge gas is delivered at multiple stages relative to the main flow direction of the reactive gas stream, and the free cross section of the firing space available to the reactive gas stream, at the height of the feed lines of the purge gas stream, is approximately constant.