Distillation column system and plant for production of oxygen by cryogenic fractionation of air

A plant for production of oxygen by cryogenic fractionation of air, comprising

• a main air compressor for compression of feed air,
• an air precooling unit for precooling of the feed air compressed in the main air compressor,
• an air cleaning unit for cleaning of the precooled feed air,
• a main heat exchanger for cooling of cleaned feed air,
• a first distillation column system for obtaining oxygen by cryogenic fractionation of air, comprising
• a high-pressure column and a low-pressure column,
• a main condenser configured as a condenser-evaporator, the liquefaction space of the main condenser being in flow connection with the top of the high-pressure column,
• and comprising an argon column which
• is in flow connection with an intermediate point in the low-pressure column, and
• has means of drawing off an argon-enriched stream and
• an argon column top condenser which is configured as a condenser-evaporator and is in flow connection with the top of the argon column,
• the low-pressure column has an upper mass transfer region, a lower mass transfer region and a middle mass transfer region,
• the middle mass transfer region has at least one first mass transfer space which is open in the upward direction toward the upper mass transfer region and in the downward direction toward the lower mass transfer region,
• characterized in that
• the upper mass transfer region has a liquid collector at its bottom end,
• the first mass transfer space has a liquid distributor at its top,
• the argon column top condenser is arranged within the low-pressure column between the upper and middle mass transfer regions, and in that
• the argon column top condenser is configured as a forced-flow evaporator, having an evaporation space which has an inlet at its bottom end and an outlet at its top end, and the outlet being connected to the liquid distributor of the first mass transfer space, the system further comprising
• means of introducing liquid from the liquid collector beneath the upper mass transfer region into the inlet of the evaporation space of the argon column top condenser, and
• a vessel, a two-phase conduit which is connected to the outlet of the evaporation space of the argon condenser and to the inlet of the vessel, a gas conduit for drawing off gas from the vessel and containing a control valve, and a liquid conduit for introducing liquid from the vessel into the liquid distributor at the top of the middle mass transfer section;
• a second distillation column system configured according to the first distillation column system,
• a first compressed air substream conduit for introducing cooled feed air from the main heat exchanger into the high-pressure column of the first distillation column system and comprising
• a second compressed air substream conduit for introducing cooled feed air from the main heat exchanger into the high-pressure column of the second distillation column system.

A method of obtaining oxygen by cryogenic fractionation of air with a distillation column system comprising

• a high-pressure column and a low-pressure column,
• a main condenser configured as a condenser-evaporator, the liquefaction space of the main condenser being in flow connection with the top of the high-pressure column,
• and comprising an argon column which
• is in flow connection with an intermediate point in the low-pressure column, and
• has means of drawing off an argon-enriched stream and
• an argon column top condenser which is configured as a condenser-evaporator and is in flow connection with the top of the argon column,
• wherein
• feed air is introduced into the high-pressure column and
• an oxygen product stream is drawn off from the low-pressure column,
• the low-pressure column has an upper mass transfer region, a lower mass transfer region and a middle mass transfer region,
• the middle mass transfer region has at least one first mass transfer space which is open at the top toward the upper mass transfer region and at the bottom toward the lower mass transfer region,
• characterized in that
• the upper mass transfer region has a liquid collector at its bottom end,
• the first mass transfer space has a liquid distributor at its top,
• the argon column top condenser is arranged within the low-pressure column between the upper and middle mass transfer regions,
• the argon column top condenser is configured as a forced-flow evaporator, having an evaporation space which has an inlet at its bottom end and an outlet at its top end, and the outlet being connected to the liquid distributor of the first mass transfer space,
• an argon-enriched fraction is drawn off from the liquefaction space of the argon top condenser,
• liquid from the liquid collector arranged beneath the upper mass transfer region is introduced into the evaporation space of the argon column top condenser), and in that
• the argon column top condenser is controlled by withdrawing a biphasic mixture from the evaporation space of the argon condenser and introducing it into a vessel, drawing off a gas stream from the vessel via a control valve and drawing off a liquid stream from the vessel and introducing it into the liquid distributor at the top of the middle mass transfer section.