Patent ID: 9695044
Date: 2017-07-04
CPC Classifications: B01J,C01B

Claim:
1. A process for startup and/or shutdown of a plant for preparation of nitric acid from ammonia and oxygenous gas by a single pressure or dual pressure process, in which the ammonia used is oxidized by means of compressed process air over a catalyst, said process air having been compressed in at least one compressor, nitrous gas formed by combustion is cooled in one or more process gas coolers equipped with pipe coils for a cooling medium and in one or more feed water preheaters equipped with pipe coils for a cooling medium, and the cooled nitrous gas is subsequently absorbed at least partly by water, forming nitric acid, and unabsorbed residual gas is expanded in at least one residual gas turbine for a purpose of recovering compressor work, wherein a process gas flowing through the one or more process gas coolers and the one or more feed water preheaters during the startup and/or shutdown of the nitric acid plant is heated in the one or more process gas coolers and/or in the one or more feed water preheaters by charging at least one of the pipe coils in the one or more process gas coolers and/or in the one or more feed water preheaters with a heating medium, and the heated process gas is guided through at least one heat exchanger connected downstream of the one or more process gas coolers and/or the one or more feed water preheaters, thereby transferring thermal energy from the heated process gas to the residual gas that is supplied to the at least one residual gas turbine.