The internal structure of the cold box of the air separation equipment is precise and complex, which is the core area of air separation and mainly consists of the following parts:
Heat exchange system
With plate-fin heat exchanger as the core, multi-layer aluminum fins and partition plates are arranged alternately to form an independent flow path. Indirect heat exchange is conducted between feed air and reflux gas (such as pure nitrogen and polluted nitrogen) here to realize the deep cooling of air from normal temperature to - 170 ℃, and recover the cooling capacity to reduce energy consumption. Its compact structure significantly improves the heat transfer efficiency and adapts to the limited space in the cold box.
Rectification system
Including upper and lower double-column structure (HP column and LP column) and argon fractionator (large unit). High-efficiency structured packing or tray is filled in the column, and high-purity separation is realized by the difference of boiling points of oxygen and nitrogen through countercurrent contact of vapor and liquid phases. The condensing evaporators are located at the top of the column and condense gaseous nitrogen into liquid nitrogen, while vaporizing liquid oxygen to provide rising steam to maintain the rectification cycle.
Refrigeration system
Expander is a key equipment, which generates low-temperature cooling capacity through adiabatic expansion of high-pressure gas to provide continuous refrigeration for the rectifying column. Its rotating speed and inlet and outlet pressure are accurately adjusted to ensure the matching of cooling capacity and system load.
Liquid storage and transportation system
Liquid oxygen pump, liquid nitrogen pump and storage tank are used to store and transfer liquid products. The storage tank adopts pearlite cold insulation structure to reduce the loss of cooling capacity.
Piping and Valves
Low-temperature pipes shall be made of stainless steel or aluminum alloy, and connected with equipment to form a closed circulation system. Valves (such as low temperature stop valves and control valves) shall have low temperature resistance and reliable sealing characteristics to ensure stable operation of the process.
