| 摘要 |
A process is described for startup and/or shutdown of a plant for preparation of nitric acid from ammonia and oxygenous gas by the 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 (6), the nitrous gas formed by the combustion is cooled in one or more process gas coolers (3) equipped with pipe coils for a cooling medium and in one or more feed water preheaters (2) 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 the unabsorbed residual gas is expanded in at least one residual gas turbine (11) for the purpose of recovering compressor work. In the process, a process gas flowing through the process gas cooler (3) and the feed water preheater (2) during the startup and/or shutdown of the nitric acid plant is heated in the process gas cooler (3) and/or in the feed water preheater (2) by charging at least one of the pipe coils in the process gas cooler (3) and/or in the feed water preheater (2) with a heating medium, and the heated process gas is guided through at least one heat exchanger (5, 4) connected downstream of the process gas cooler (3) and/or the feed water preheater (2), in order to transfer thermal energy from the heated process gas to the residual gas which is supplied to the at least one residual gas turbine (11).;Also described is an apparatus for performing the process according to the invention, comprising at least one air compressor (6), at least one process gas cooler (3), at least one feed water preheater (2) and at least one residual gas turbine (11), the process gas cooler (3) and the feed water preheater (2) comprising pipe coils (18, 19, 20, 24), at least one of the pipe coils being connected to a source for a heating medium, such that the at least one of the pipe coils in the process gas cooler (3) and/or in the feed water preheater (2) can be charged during the startup and/or shutdown of the apparatus with the heating medium for heating the process gas flowing through the process gas cooler (3) and feed water preheater (2), and at least one heat exchanger (5, 4) being connected downstream of the process gas cooler (3) and/or the feed water preheater (2) in order to transfer thermal energy from the heated process gas to the residual gas which is supplied to the residual gas turbine (11).;These measures and apparatuses can effectively avoid freezing of the residual gas turbine. |
| 主权项 |
1. A process for startup and/or shutdown of a plant for preparation of nitric acid from ammonia and oxygenous gas by the 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 (6), the nitrous gas formed by the combustion is cooled in one or more process gas coolers (3) equipped with pipe coils for a cooling medium and in one or more feed water preheaters (2) 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 the unabsorbed residual gas is expanded in at least one residual gas turbine (11) for the purpose of recovering compressor work, wherein a process gas flowing through the process gas cooler (3) and the feed water preheater (2) during the startup and/or shutdown of the nitric acid plant is heated in the process gas cooler (3) and/or in the feed water preheater (2) by charging at least one of the pipe coils in the process gas cooler (3) and/or in the feed water preheater (2) with a heating medium, and the heated process gas is guided through at least one heat exchanger (5, 4) connected downstream of the process gas cooler (3) and/or the feed water preheater (2), in order to transfer thermal energy from the heated process gas to the residual gas which is supplied to the at least one residual gas turbine (11). |
