UA91614C2 - Process and unit for production of nitric acid (variants) - Google Patents

Abstract

A group of inventions relates to the production of nonconcentrated and concentrated nitric acid and can be used in nitrogen compound making industry, particularly in power technology production schemes of nitric acid, comprising recuperative gas-turbine unit. According to the invention the air through atmosphere passes primary and fine treatment in filter, supplied to the axial flow compressor, where it is compressed to an absolute pressure of 0.73-0.8 MPa in one stage. The compressed air is distributed to several streams, one of which after cooling in the device of air (or water) cooling is supplied to the cooling of recuperative turbine with the temperature of 140-150 °C, another – to the burning in mixture with natural gas in ratio of (11-15):1 and steam in combustion chamber of recuperative turbine, and the main goes to the technology. By the first variant the main stream of air is supplied to the cooling into the plate heat exchanger, and by the second – to the steam generator into "Kompablok" of plate type. After that by the two variants the main stream of cooled air is divided into two streams, the first of which is supplied to gas mixer, where the ammonia evaporated in evaporators and heated in heaters is supplied, and the second – to the cooling into the water cooling device of air. Ammonia-air mixture, obtained in gas mixer, supplied into the contact device, where on platinoid catalyst ammonia is oxidated to nitrogen oxides. Nitrous gas is cooled at first in exhaust-heat boiler, besides the part of hot gases through bypass governing unit is supplied into the main stream for the preparation of mixed gas, and after that in two heaters of residual gases and then supplied for condensation of reaction moisture into the condensation coolers. Besides the second stream of air, cooled in the water cooling device of air to temperature of 140-150 °C, again divided into two streams, directing one to the additional oxidation of nitrous gas to the condensation coolers, after that the cooled and additionally oxidated nitrous gas is supplied into the absorption column for the preparation of production nitric acid, and another – to the blowoff column, where obtained production nitric acid with weight part of 58-60 % is blown from solved in it nitrogen oxides. Residual gases after the absorption column is heated in heaters of residual gases, purified in reactor of catalytic treatment and heated in combustion chamber of the recuperative turbine to the temperature of 650-700 °C by means of mixing with furnace gas – combustion product of natural gas, air and steam. The invention provides the increasing of reliability and operational life of the recuperative turbine, stabilization work of the cooling stage of process air with the use of low-temperature heat of air compression, optimal distribution of air streams, supplied into technology, operating mode optimization of the combustion chamber of the recuperative turbine and improvement of recuperative heating of residual gases and by means of reaction heat the increased efficiency and reliability of the production of nitric acid in general.