The present invention provides an air separation system and an air separation method. The air separation system comprises an air separation apparatus and a nitrogen liquefier. In the air separation apparatus, multiple output pipelines are led out from a rectification column system via a main heat exchanger. In the nitrogen liquefier, a gas delivery pipeline delivers a gas flow expanded by an expander. The air separation system further comprises an intermediary pipeline. An inlet end of the intermediary pipeline is connected to the gas delivery pipeline of the nitrogen liquefier, and an outlet end of the intermediary pipeline is connected to at least one of the multiple output pipelines of the air separation apparatus at a position between the rectification column system and the main heat exchanger, such that the intermediary pipeline delivers a gas flow to the at least one output pipeline. The air separation system and air separation method can be started up smoothly without the use of liquid nitrogen stored externally in reserve.

A request to initiate startup of an air separation plant may be received, and, in response to receiving the request, startup information that identifies a sequence of steps to be automatically executed to start up the air separation plant is retrieved. Each step may be associated with a component of the air separation plant, and may be associated with an action and a set of permissives corresponding to the action. The set of permissives for each action may specify one or more parameters for controlling the execution of the corresponding action. After retrieving the startup information, the system may automatically initiate execution of the sequence of steps, and may monitor the execution of each of the steps. The system may determine, based on the monitoring, whether to modify a parameter specified by one of the permissives corresponding to an executed action.

A distillation column system and a plant are for production of oxygen by cryogenic fractionation of air. The distillation column system has a high-pressure column and a low-pressure column, a main condenser, and an argon column with an argon column top condenser. The low-pressure column comprises an upper mass transfer region, a lower mass transfer region and a middle mass transfer region. The argon column top condenser is arranged within the low-pressure column between the upper and middle mass transfer regions and is configured as a forced-flow evaporator.

A process for separating a gas mixture, a first item of equipment of the process is heated by a first flow of a first heat producer and supplies heat to a first fluid, the first flow of heat producer being heated upstream of the first item of equipment by a heat source, a second item of equipment of the process heats a second fluid while consuming heat, the heat originating from a second flow of the first heat producer heated by the heat source, which heats the second flow of the first heat producer up to an intermediate temperature lower than the second temperature, and by a heater downstream of the source, which heats the second flow of the first heat producer, which has been heated by the heat source, from the intermediate temperature up to a second temperature higher than the first temperature.