Plate Fin Heat Exchanger | Air Separation Unit (ASU)

The mainstream in the field of air separation is the BAHX aluminum vacuum brazed plate fin heat exchanger, which is the core component of the air separation cold box and serves the cryogenic distillation process. Its working temperature can reach -200 ℃, and it can achieve simultaneous heat exchange of multiple streams.

1、 Basic structure

Stacked by partitions, fins, seals, and flow deflectors, the entire assembly is vacuum brazed into a non removable plate bundle, followed by welding of the current collector box; Fins are commonly serrated, porous, and straight to enhance disturbance and increase heat transfer area.

-Unit volume heat transfer area: 1000-2500 ㎡/m ³ , 5-10 times that of shell and tube heat exchangers, significantly reducing volume and weight.

-Material: Almost all air separators are made of aluminum alloy, which maintains strength at low temperatures, has good thermal conductivity, and is suitable for brazing; High pressure aluminum plate fin structure is used for high-pressure working conditions.

-Media: Compressed air, contaminated nitrogen, oxygen, nitrogen, liquid air, liquid oxygen, liquid nitrogen and other cold and hot fluids.

The main role in the air separation unit

Multiple plate fin heat exchangers are generally installed inside the air separation cold box, with different division of labor:

1. Main Heat Exchanger

The core. Compressed air purified at room temperature (positive flow) exchanges heat with reflux low-temperature oxygen, nitrogen, and polluted nitrogen; Cooling the air to a temperature close to the liquefaction temperature of 170~190 ℃, while recovering the cooling capacity to allow the product gas to reheat and exit the cold box, determines the energy consumption of air separation.

2. Sub cooler

Further supercool the liquid nitrogen and liquid air from the upper tower to reduce throttling gasification rate and improve distillation efficiency.

3. Condenser Evaporator (Main Cooling) Condenser Evaporator

Connect the lower tower and upper tower of the air separation system; The nitrogen at the top of the lower tower condenses and releases heat, while the liquid oxygen at the bottom of the upper tower is heated to evaporate, achieving distillation coupling between the upper and lower towers. It is the heart of air separation distillation.

4. Liquefier

Auxiliary cooling is used in some operating conditions to produce liquid oxygen/nitrogen products.

Application scenarios for supporting air separation

-Large, medium, and small cryogenic air separation units: oxygen production, nitrogen production, and argon production; Gas and liquid product air separation

-Coal chemical air separation, steel smelting air separation, glass industry air separation

-Liquefied air and liquefied nitrogen equipment

-Rare gas (neon helium krypton xenon) extraction device