Strategizing practical implementation of additional condenser-reboilers (CR) to reduce power consumption of a dual purity cryogenic single column gaseous oxygen plant

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• Single column oxygen plant with near-pure LN2 reflux is reconfigured with 3 CR. • Multi-CR plant generates oxygen with 99.5% and 90% purity with reduced power. • Addition of CR demand appropriate manipulation of the compressor operation. • Operational strategies for compressors and turbine are evolved through analysis. • Proposed plant consumes up to 5.4% less specific power than basic single CR plant. A basic single column cryogenic air separation plant refluxed by nitrogen has a single condenser-reboiler (CR) that produces gaseous oxygen simultaneously at dual purities of 90% and 99.5% at 10 bar and 40 bar, respectively. This basic plant consumes about 42,000 kW in an integrated steel plant of 5 million tons per year. Saving power even by a small percentage holds a great promise to reduce the production cost of steel. In place of pressurizing the entire recycled nitrogen flow to 5.1 bar that feeds the condenser-reboiler of the basic plant, some portions of nitrogen in the modified plant is required at 4.3 bar and 2.8 bar to feed the additional condenser-reboilers. Nitrogen compressor accounts for 20–25% of the net power consumption and putting additional condenser-reboilers reduces it by 15–23% that leads to an overall reduction of the power of 5.4%. As a single column plant can produce pure and impure oxygen simultaneously at different proportions, this paper determines the additional number of reboilers to be installed, their locations in the column and other plant parameters keeping oxygen recovery intact above 99%. The analysis evolves the strategy of operating recycled nitrogen compressors at multiple pressures in modified plant having three condenser-reboilers.