Upstream Catalytic NO Oxidation for Cryogenic Gas Purification

The patent applies preliminary action by installing a catalytic converter upstream of the purification unit to convert NO to NO2 before the gas enters the washing or cryogenic separation stage. This preliminary oxidation step ensures that nitrogen oxides are in a form that can be more effectively removed by downstream purification processes, thereby improving overall NOx removal efficiency without significantly complicating the process.

The catalytic converter acts as an intermediary device between the gas stream and the purification unit. It mediates the chemical transformation of NO to NO2, creating a more favorable condition for subsequent purification. This intermediary step resolves the contradiction by enabling efficient NOx removal while maintaining a relatively simple overall process structure.

The catalytic converter performs preliminary oxidation of NO to NO2 before compression and refrigeration stages. This preliminary action prevents the formation of acid condensates during downstream processing by ensuring nitrogen oxides are in a less reactive form, thereby protecting equipment from corrosion while incurring only moderate additional investment in the catalytic unit.

The patent applies preliminary anti-action by converting NO to NO2 upstream to prevent the harmful effect of acid condensate formation downstream. The catalytic oxidation creates a condition that counteracts the potential corrosion problem before it can occur during compression and refrigeration, thus protecting the system without requiring expensive corrosion-resistant materials throughout.

The patent replaces the thermal-based SNCR process with a catalytic conversion approach. Instead of relying on high-temperature thermal reactions to remove NOx, the system uses a catalytic converter to facilitate NO oxidation at lower temperatures, followed by conventional purification. This substitution eliminates the need for extreme operating temperatures while achieving superior NOx removal efficiency.

The patent changes the operating parameters from high-temperature thermal processing (SNCR at 850-1050°C) to low-temperature catalytic processing (ambient to moderate temperatures). By changing the fundamental parameter of operating temperature and the mechanism of action from thermal to catalytic, the system achieves both lower energy consumption and higher removal efficiency.

The patent segments the NOx removal process into two distinct stages: (1) catalytic oxidation of NO to NO2 in a dedicated converter, and (2) removal of the converted NOx species through conventional washing or cryogenic separation. This segmentation allows each stage to be optimized independently, achieving high overall efficiency while using cost-effective, conventional technologies for the removal stage rather than requiring expensive SCR systems.

The catalytic converter serves as an intermediary that transforms NO into a more removable form (NO2), enabling the use of simpler, lower-cost purification technologies. This intermediary transformation resolves the contradiction by making conventional, cost-effective purification methods sufficient to achieve high NOx removal efficiency, eliminating the need for expensive SCR systems.