Abstract: A process and plant is provided for the production of nitric acid from atmospheric air in which the feed air is passed in succession through a number of stages each comprising a high temperature regenerative nitrogen fixation reactor followed by a catalytic oxidation reactor and a nitric oxide absorber, all operating at superatmospheric pressure. Heat is exchanged between the inlet and outlet gas streams of each stage absorber. The compressors are driven by a turbo-expander powered by the exit gas stream in which fuel has been burned upstream of the turbo-expander. The nitrogen fixation reactors each consist of a pressure vessel enclosing a gas-permeable refractory wall surrounding a furnace chamber in which fuel is burned, the interior of the vessel being divided into two sections by an impermeable wall with a gap for flow through in the furnace zone.