Cryogenic Air Separation Units

Premium Engineering offers a wide model range of cryogenic ASUs.

Specification of standard cryogenic ASUs
	Oxygen	Nitrogen	Argon
Capacity	up to 70,000 nm³/h	up to 200,000 nm³/h	up to 2,500 nm³/h
Purity	up to 99.9% vol.О₂	up to 0.0001% vol.О₂	up to 0.0001% vol.О₂ up to 0.0001% vol.N₂

The ASUs are designed using the latest innovative technologies which not only provide high energy efficiency but also give the user the option of various operating modes within the framework of one ASU. All our ASUs can be adapted to specific industrial application, according to the customer’s requirements.

Advantages of the cryogenic ASUs
ASUs produce gases with the lowest possible content of impurities (special purity products).	О₂ – 99,5…99,9% N₂ – 99,9995% Ar – 99,9995%
ASUs can produce several gases simultaneously (this is known as complex separation). Cryogenic ASUs offer the customer a choice between gas and liquid output. Implementation of various operating modes within the framework of one ASU with a wide range of product specification.	О₂+N₂ O₂+Ar О₂+N₂+Ar gas liquid gas + liquid
ASUs consume comparatively less power while producing high purity products
Long operation period between two warms-up	up to 2 years
High reliability, long service life	up to 25 years

Cryogenic cycles

ASUs implement highly efficient cryogenic cycles, such as LP cycles with an expander, «two-pressure» cycles, and cycles with an independent circulation loop. Also, they use the boosting of the flow in the booster part of the turboexpander to increase the cooling capacity of the cycle without any additional power consumption. The pressures of the cycle are optimized owing to the thermodynamic efficiency of the process and the availability of the most efficient and reliable equipment, including compressors.

Air drying and purification unit

The unit contains an adsorption type module for the dehydration and purification of air. Each air drying and purification unit has two adsorbent beds, namely zeolite (a molecular sieve) and active aluminum oxide. The regeneration of the adsorbent is performed by the waste gas, at a temperature of up to 180 ⁰С.

High operating reliability and good quality purified air is due to:

The replacement of check valves with remote controlled motor valves.
The use of high quality adsorbents. Monitoring the purification quality of the air assures the reliable and safe operation of the equipment. The air drying and purification unit is equipped with a gas analyzer to monitor the outlet air purity.
Heater types: steam or electric. Power is saved by using a steam heater. In emergencies a back up heater is available (1 operating + 1 standby).

Cold box insulation

The cold box is insulated thermally by filling the void space of the pressure-tight casing with perlite. In addition, a nitrogen blowing method is applied to keep atmospheric moisture away from the cold box («dry insulation»).

This method guarantees the cold box a long service life since it prevents moisture getting into the casing and, consequently, avoids corrosion inside the cold box and possible mechanical damage due to ice accumulation.

With the above insulation, the cold box is protected from moisture attack and maintains its operating capacity throughout its service life.

And, above all, the high quality of this insulation leads to the lowest level of cold loss which, in turn, helps to reduce power consumption.

Materials

All the units in the cold box (columns, heat exchangers etc.), as well as the pipelines are made of high quality aluminum alloys.

Carbon steel is used to fabricate the equipment and the piping in «warm» systems.

Comparable steel alloys are used within each block because this increases the reliability of the equipment and prevents some parts (for example connectors) from becoming weak spots. Using similar steel alloys has other advantages, namely it is then unnecessary to use complicated welding techniques, and there is much less risk of excessive structural loading (which can result from the difference in the thermal deformation of various materials.)

The control system

Air separation units are equipped with a PLC based (SIEMENS products for the base case) control system.

Its functions are:

to control the process of the ASU
to collect and process data about the ASU operation
to form and send signals to the operating desk
to form and send signals to the operating desk
to archive automatically all data during an ASU operation

The system contains a PC based operator desk which displays the operation of the ASU and allows it to be monitored in an interactive mode by an operator.

Packaging

Each ASU is delivered as a complete set, which includes external equipment: for example a group of gas analyzers with a СО₂ analyzer as an obligatory and integral component of the safety circuit.

External filters and silencers are also provided.

In order to meet the requirements of many processes associated with the continuity and reliability of the ASU cycle, the critical components of the ASU (the heater of the purification unit, turboexpander-booster) are backed up. The backup equipment is included in the delivery set. It is installed in parallel to the main machinery.