Optimization Strategy for Contradiction Between Intermitting Oxygen Consumption in Converter Steelmaking and Continuous Oxygen Production by Air Separation Unit

Abstract In order to solve the problem of overpressure release of oxygen supply network caused by the contradiction between continuous oxygen production by air separation unit (ASU) and intermitting oxygen consumption in converter steelmaking, a pressure balance strategy for pre-adjusting liquid-vapor ratio of ASU was proposed. Used Aspen Plus software, a full-compression model of an ASU in an iron and steel enterprise was established. Before stopping oxygen consumption in the converter steelmaking, method of pre-adjusting liquid-vapor ratio from the low-pressure distillation column to reduce the oxygen production of the air separation unit was calculated. This strategy consists of two steps. First step is pre-adjusting liquid-vapor ratio from the low-pressure distillation column to reduce the oxygen production of ASU, before stopping oxygen consumption in the converter steelmaking. The second step is the reduction of the supply oxygen production pipe network pressure, when stopping oxygen consumption in the converter steelmaking. The pre-adjusting oxygen production and the starting time are the key of the strategy. The energy consumption analysis of the strategy is carried out. The results show that the strategy reduces the pressure of the oxygen supply pipe network by 1.3% and reduces the large amount of oxygen release, while increase of the energy consumption of ASU is neglected.

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Cutting Oxygen Production-Related Greenhouse Gas Emissions by Improved Compression Heat Management in a Cryogenic Air Separation Unit

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph181910370 ◽

2021 ◽

Vol 18 (19) ◽

pp. 10370

Author(s):

Miroslav Variny ◽

Dominika Jediná ◽

Miroslav Rimár ◽

Ján Kizek ◽

Marianna Kšiňanová

Keyword(s):

Power Consumption ◽

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Ambient Air ◽

Air Separation ◽

Oxygen Production ◽

Gas Emissions ◽

Separation Unit ◽

Air Separation Unit ◽

Air Dryer

Oxygen production in cryogenic air separation units is related to a significant carbon footprint and its supply in the medicinal sphere became critical during the recent COVID-19 crisis. An improved unit design was proposed, utilizing a part of waste heat produced during air pre-cooling and intercooling via absorption coolers, to reduce power consumption. Variable ambient air humidity impact on compressed air dryers’ regeneration was also considered. A steady-state process simulation of a model 500 t h−1 inlet cryogenic air separation unit was performed in Aspen Plus® V11. Comparison of a model without and with absorption coolers yielded an achievable reduction in power consumption for air compression and air dryer regeneration by 6 to 9% (23 to 33 GWh year−1) and a favorable simple payback period of 4 to 10 years, both depending on air pressure loss in additional heat exchangers to be installed. The resulting specific oxygen production decrease amounted to EUR 2–4.2 t−1. Emissions of major gaseous pollutants from power production were both calculated by an in-house developed thermal power plant model and adopted from literature. A power consumption cut was translated into the following annual greenhouse gas emission reduction: CO2 16 to 30 kilotons, CO 0.3 to 2.3 tons, SOx 4.7 to 187 tons and NOx 11 to 56 tons, depending on applied fossil fuel-based emission factors. Considering a more renewable energy sources-containing energy mix, annual greenhouse gas emissions decreased by 50 to over 80%, varying for individual pollutants.

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