Method for producing butadiene by oxidatively dehydrogenating n-butenes

A process for preparing butadiene from n-butenes, which comprises the following steps:

• A) providing a feed gas stream a comprising n-butenes;
• B) introducing the feed gas stream and an oxygen-comprising gas into at least one dehydrogenation zone comprising a dehydrogenation reactor and oxidative dehydrogenation of n-butenes to butadiene, giving a product gas stream b comprising butadiene, unreacted n-butenes, water vapor, oxygen, low-boiling hydrocarbons, optionally carbon oxides and optionally inert gases;
• C) cooling and compressing the product gas stream b in at least one cooling stage comprising at least one quenching column and in at least one compression stage comprising at least one compressor and optionally one or more intermediate cooling units between the compressors, with the product gas stream b being brought into contact with at least one circulated coolant to give at least one condensate stream c1 comprising water and a gas stream c2 comprising butadiene, n-butenes, water vapor, oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases;
• D) separating incondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, possibly carbon oxides and possibly inert gases as gas stream d2 from the gas stream c2 by absorption of the C4-hydrocarbons comprising butadiene medium stream loaded with C4-hydrocarbons and the gas stream d2, and subsequent desorption of the C4-hydrocarbons from the loaded absorption medium stream to give a C4 product gas stream d1;
• E) separating the C4 product stream d1 by extractive distillation using a solvent which is selective for butadiene into a stream e1 comprising butadiene and the selective solvent and a stream e2 comprising n-butenes;
• F) distilling the stream e1 comprising butadiene and the selective solvent to give a stream f1 consisting essentially of the selective solvent and a stream f2 comprising butadiene;
• wherein the steps (i) to (iii) below are carried out:
• (i) avoidance of formation of explosive gas mixtures by monitoring of the oxygen concentration in the oxygen-comprising gas streams fed into 5 the dehydrogenation zone and control of the mass flows of oxygen comprising gas streams and gas streams comprising hydrocarbons in such a way that no explosive gas mixtures can be formed;
• (ii) interruption of the introduction of the oxygen-comprising gas mixture into the dehydrogenation zone when a limit value for the oxygen concentration in the dehydrogenation gas mixture is exceeded;
• (iii) carrying out of the steps A) to F) in apparatuses which are configured so as to be explosion-protected, where liquid-conveying pipes are configured so as to be explosion-protected and gas conduits are configured so as to be detonation-protected.