Pressure-controlled reactor

A method for the pyrolysis or thermolysis of a fluid or fluidized starting material in a tube bundle reactor including a plurality of heatable reactor tubes, the method comprising:

• feeding the starting material to the tube bundle reactor at one end by at least one supply line, wherein the supply line has several pressure reduction units which enable a positive pressure before the starting material is introduced into individual reactor tubes of the tube bundle reactor and a negative pressure inside the reactor tubes, wherein the pressure reduction units are each associated with one of the reactor tubes and separately supply the reactor tubes, and control a substantially equal inflow of the starting material into individual reactor tubes and the reactor tubes are heated to a decomposition temperature of the starting material in at least a primary section of the reactor tubes, in which the starting material is pyrolyzed or thermolyzed and a pyrolysis or thermolysis product is obtained.