Cryogenic oxygen production involves first liquefying air, then separating oxygen and nitrogen based on their different boiling points. Air liquefaction requires cooling below -140.6°C. Typically, air separation operates within the temperature range of -172°C to -194°C. Cryogenic oxygen production equipment has the following safety characteristics:
Thermal Insulation: Low-temperature heat exchangers, distillation columns, and other cryogenic vessels and pipelines are housed within insulated cold boxes filled with low thermal conductivity insulation materials to prevent heat ingress from the surroundings and minimize cold loss-otherwise, the equipment cannot operate.
Material Requirements: Materials used for cryogenic equipment must possess sufficient strength and toughness at low temperatures, along with good weldability and machinability. Common materials include aluminum alloys, copper alloys, and stainless steel.
Impurity Removal (High Boiling Point): High boiling point impurities in air, such as moisture and carbon dioxide, must be removed at ambient temperature beforehand. Otherwise, they will block internal channels and render the unit inoperable.
Hydrocarbon Hazard Control: Acetylene and hydrocarbons entering the air separation column can accumulate to dangerous levels, affecting safe operation or even causing explosions. Therefore, purification equipment must be installed to remove them.
Pressure Relief Protection: Sealed containers storing cryogenic liquids will experience automatic pressure rise when external heat causes partial vaporization. Reliable safety devices must be installed to prevent overpressure.
Foundation Protection: Cryogenic liquid leakage into foundations can freeze and crack the base, causing equipment tilting. Therefore, sealing integrity of equipment, pipelines, and valves must be ensured, with consideration for thermal expansion/contraction stresses and deformations.
Organic Material Prohibition: Porous organic materials such as wood or coke soaked in liquid oxygen can undergo violent combustion or explosion when exposed to ignition sources or impact. Thus, no porous organic materials are allowed inside cold boxes. Liquid oxygen discharge must use dedicated pipelines and containers-never floor drains.
Material Compatibility: Long-term impact of cryogenic liquids on carbon steel plates can cause brittle fracture. Therefore, discharge pipelines and collection troughs for cryogenic liquids cannot use carbon steel products.
Asphyxiation Prevention: Nitrogen and argon are asphyxiant gases-their liquid discharge pipes must be routed outdoors. Gas discharge pipes must have adequate discharge height, with outlets not facing platforms or stairways.
Fire Prevention: Oxygen is a strong combustion supporter-its discharge pipes must not vent directly into unventilated buildings.
