Air separation plant and process operating by cryogenic distillation

An air separation process using a first air compressor and a second air compressor that are both supplied by air at atmospheric pressure, a first air purification unit, a second air purification unit, and a cold box,

• wherein, according to a first operating mode, the process includes the steps of:
• sending high-pressure air from the first air compressor to the first air purification unit and from the first air purification unit to the cold box via one or more high-pressure lines;
• and
• sending medium-pressure air from the second air compressor to the second air purification unit and from the second air purification unit to the cold box,
• wherein, according to a second operating mode, the process includes the steps of:
• modifying the second air compressor to produces. high-pressure air instead of producing medium-pressure air, the high pressure being higher than the medium pressure, the high-pressure air of the second compressor being purified in the second purification unit and sent to the cold box via the one or more high-pressure lines.

An air separation process using a first air compressor, a second air compressor, and a third air compressor, a first air purification unit, a second air purification unit, a third air purification unit, a first high pressure valve, a second high pressure valve, a first medium pressure valve, a second medium pressure valve, a third medium pressure valve, a fourth medium pressure valve, a first cold box having a first medium pressure line and a first high pressure line, a second cold box having a second medium pressure line and a second high pressure line,

• wherein, according to a first operating mode, the first high pressure valve, the first medium pressure valve, and the third medium pressure valve are in an open position;
• the second high pressure valve, the second medium pressure valve, and the fourth medium pressure valve are in a closed position;
• and the process includes the steps of:
• compressing a first air stream in the first air compressor to a first pressure P1 to form a high pressure air stream;
• purifying the high pressure air stream in the first air purification unit to form a purified high pressure air stream;
• flowing the purified high pressure air stream through the first high pressure valve;
• introducing a first portion of the purified high pressure air stream into the first cold box using the first high pressure line and;
• introducing a second portion of the purified high pressure air stream into the second cold box using the first high pressure line;
• compressing a second air stream in the second air compressor to a second pressure P2 to form a first medium pressure air stream, wherein P2 is less than P1;
• purifying the first medium pressure air strew the second air purification unit to form a first purified medium pressure air stream;
• flowing the first purified medium pressure air stream through the first medium pressure valve;
• introducing a first portion of the first purified medium pressure air stream into the first cold box using the first medium pressure line and;
• introducing a second portion of the first purified medium pressure air stream into the second cold box using the second medium pressure line;
• compressing a third air stream in the third air compressor to a second pressure P2 to form a second medium pressure air stream;
• purifying the second medium pressure air stream in the third air purification unit to form a second purified medium pressure air stream;
• flowing the second purified medium pressure air stream through the third medium pressure valve;
• introducing a first portion of the second purified medium pressure air stream into the first cold box using the first medium pressure line and;
• introducing a second portion of the second purified medium pressure air stream into the second cold box using the second medium pressure line;
• introducing the purified medium pressure air stream into the medium pressure cold box under conditions effective to separate the purified medium pressure air stream into a second nitrogen rich stream and a second oxygen rich stream;
• wherein, according to a second operating mode, the first high pressure valve and the first medium pressure valve are switched to a closed position, such that first high pressure line and the second high pressure line are riot in fluid communication with the first air purification unit;
• the second medium pressure valve is switched to an open position, and the process includes the steps of:
• modifying the second air compressor such that the second air compressor is configured to produce a gas stream having a third pressure of P3, wherein P3 is greater than P2 and equal to or less than P1;
• compressing the second air stream in the second air compressor to the third pressure P3 to form an alternate high pressure air stream;
• purifying the alternate high pressure air stream in the second air purification unit to form an alternate purified high pressure air stream;
• flowing the alternate purified high pressure air stream through the second medium pressure valve;
• introducing a first portion of the alternate purified high pressure air stream into the first cold box using the first high pressure line;
• introducing a second portion of the alternate purified high pressure air stream into the second cold box using the second high pressure line;
• compressing the third air stream in the third air compressor to the second pressure P2 to form the second medium pressure air stream;
• purifying the second medium pressure air stream in the third air purification unit to form the second purified medium pressure air stream;
• flowing the second purified medium pressure air stream through the third medium pressure valve;
• introducing the first portion of the second purified medium pressure air stream into the first cold box using the first medium pressure line;
• and
• introducing the second portion of the second purified medium pressure air stream into the second cold box using the second medium pressure line.