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This new, dual-pressure nitric-acid process is commercially available

By Gerald Ondrey |

Last month, Weatherly Inc., a wholly owned subsidiary of KBR Inc. (Houston; www.kbr.com) introduced its new dual-pressure nitric acid (DPNA) technology, which enables economically viable production of HNO3 in large scale [over 1,000 metric tons per day (m.t./d)], as part of large fertilizer-production complexes. The technology was launched at the 2016 AN-NA (Ammonium Nitrate – Nitric Acid) conference (September 16–23; Eindhoven, the Netherlands).

In the DPNA process (diagram), ammonia is first oxidized with air over a platinum catalyst at high temperature and low pressure (LP). The product of the LP oxidation is passed through a heat exchanger to recover a major portion of the heat. The process gas is cooled and oxidized further in a LP cooler condenser, where NO, NO2, O2 and water combine to form dilute HNO3. Some of the reaction energy is recovered and used to reheat the tail gas. The LP process gas is then compressed in the NOx-gas compressor, and fed to high-pressure (HP) cooler condenser and absorber to form product HNO3 (68%). Tail gas from the absorber is reheated to 1,150°C and used to drive a hot-gas expander to generate power for the air compressor and NOx-gas compressors.

Weatherly’s DPNA process is said to deliver lower operating costs with its more efficient heat-recovery design. Tail gas exits the system at 620°C, compared to the lower (490°C) temperature of alternative DPNA processes. This enables more efficient recovery of heat that is subsequently used to generate energy to power up the system. As a result, the new process offers an operating cost advantage over competing technologies of $4–5/ton of nitric acid produced, says KBR.

The DPNA process also utilizes Weatherly’s vertical reactor — a compact, proven design widely used in mono-pressure HNO3 plants — that requires less steel and piping than traditional plants. That means capital costs for Weatherly plants are 5–10% less than competing designs, says KBR.

nitric-acid process

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