A reactor with one or more feed lines at one end of the reactor for one or more fluid streams, each having a temperature of 200°C or more, and one or more discharge lines at the other end of the reactor, wherein a main flow direction through the reactor is defined, and the total cross-sectional area of the feed lines ΣA i being smaller than the maximal cross-section A R of the reactor, with internals which supply or remove heat and/or increase the surface on which a reaction takes place, as well as with an equalizing device arranged before the internals in the main flow direction through the reactor, characterized in that - the equalizing device comprises three or more essentially planar components, wherein essentially planar is to be understood that an essentially planar component has a dimension in the main flow direction through the reactor which is of the factor of 2, preferably of the factor of 5, more preferably of the factor of 10 smaller than the dimension perpendicular to the main flow direction through the reactor, which range over the entire cross-section of the reactor, and which are arranged mainly perpendicular to the main flow direction through the reactor, - with openings for one or more fluid streams in such a way that - the hydraulic diameter of any of the three or more essentially planar components being defined by d h = 4 V/O, where V is that part of the volume of the essentially planar component being flown through by the fluid, and where O represents the surface area of the respective essentially planar component being wetted by the fluid is within the range from 0.5 mm to 1/10 of the hydraulic diameter D h of the reactor, and wherein - two in the main flow direction through the reactor directly following and essentially planar components having a distanceless than half of the hydraulic diameter D h of the reactor, and more than the greater value of the two values 10 times hydraulic diameter of the respective upstream positioned essentially planar component and 1/4 of hydraulic diameter of that feed line with the largest cross-sectional area A i. - the equalizing device comprises three or more essentially planar components, wherein essentially planar is to be understood that an essentially planar component has a dimension in the main flow direction through the reactor which is of the factor of 2, preferably of the factor of 5, more preferably of the factor of 10 smaller than the dimension perpendicular to the main flow direction through the reactor, which range over the entire cross-section of the reactor, and which are arranged mainly perpendicular to the main flow direction through the reactor, - with openings for one or more fluid streams in such a way that - the hydraulic diameter of any of the three or more essentially planar components being defined by d h = 4 V/O, where V is that part of the volume of the essentially planar component being flown through by the fluid, and where O represents the surface area of the respective essentially planar component being wetted by the fluid is within the range from 0.5 mm to 1/10 of the hydraulic diameter D h of the reactor, and wherein - two in the main flow direction through the reactor directly following and essentially planar components having a distanceless than half of the hydraulic diameter D h of the reactor, and more than the greater value of the two values 10 times hydraulic diameter of the respective upstream positioned essentially planar component and 1/4 of hydraulic diameter of that feed line with the largest cross-sectional area A i.