Device for the synthesis of ammonia from an N 2 - and H 2 -containing synthesis gas with at least one first reactor, whereby the device comprises: - a first non-cooled catalyst bed unit; - at least one heat exchanger device; - at least two cooled catalyst bed units (4, 41, 42), whereby each cooled catalyst bed unit (4, 41, 42) is fitted with a plurality of cooling pipes; and - a re-circulating line with at least one feed device and at least one outlet device, whereby the re-circulating line comprises, starting from the feed device, one after the other in downstream arrangement the plurality of cooling pipes the first non-cooled catalyst bed unit, the at least one heat exchanger device (3, 31), and the at least two cooled catalyst bed units (4, 41, 42) up to the outlet device, whereby the plurality of cooling pipes of each cooled catalyst bed unit (4, 41, 42) is connected, on one outlet end of the cooling pipes each, to an exit collecting device, and whereby the re-circulating line comprises at least one bypass line for each cooled catalyst bed unit (4, 41, 42), each of which being arranged between the feed device and the exit collecting device of the plurality of cooling pipes of each cooled catalyst bed unit (4, 41, 42), whereby the re-circulating line comprises at least one control facility that is operatively connected to at least one distributor facility for the at least one bypass line and the plurality of cooling pipes, whereby the control facility is a regulating facility and is operatively coupled to a sensor for detection of a parameter that is an exit temperature of the cooled catalyst bed units (4, 41, 42) for regulation of the distributor facility, whereby the cooling power of the cooled catalyst bed units (4, 41, 42) can be varied via a bypass control and the temperature profile of each cooled catalyst bed unit (4, 41, 42) can be adjusted to the optimal temperature profile for ammonia synthesis. - a first non-cooled catalyst bed unit; - at least one heat exchanger device; - at least two cooled catalyst bed units (4, 41, 42), whereby each cooled catalyst bed unit (4, 41, 42) is fitted with a plurality of cooling pipes; and - a re-circulating line with at least one feed device and at least one outlet device, whereby the re-circulating line comprises, starting from the feed device, one after the other in downstream arrangement the plurality of cooling pipes the first non-cooled catalyst bed unit, the at least one heat exchanger device (3, 31), and the at least two cooled catalyst bed units (4, 41, 42) up to the outlet device, whereby the plurality of cooling pipes of each cooled catalyst bed unit (4, 41, 42) is connected, on one outlet end of the cooling pipes each, to an exit collecting device, and whereby the re-circulating line comprises at least one bypass line for each cooled catalyst bed unit (4, 41, 42), each of which being arranged between the feed device and the exit collecting device of the plurality of cooling pipes of each cooled catalyst bed unit (4, 41, 42), whereby the re-circulating line comprises at least one control facility that is operatively connected to at least one distributor facility for the at least one bypass line and the plurality of cooling pipes, whereby the control facility is a regulating facility and is operatively coupled to a sensor for detection of a parameter that is an exit temperature of the cooled catalyst bed units (4, 41, 42) for regulation of the distributor facility, whereby the cooling power of the cooled catalyst bed units (4, 41, 42) can be varied via a bypass control and the temperature profile of each cooled catalyst bed unit (4, 41, 42) can be adjusted to the optimal temperature profile for ammonia synthesis.