What is Oxygen
Oxygen is the most important nonmetallic element for sustaining life on Earth. It is represented in the periodic table with symbol O and atomic number 8. The element was discovered in 1774 by Joseph Priestley in Wiltshire, England and independently by Carl Wilhelm Scheele in Uppsala, Sweden. The element has two allotropic forms—O2 & O3. Belonging to the chalcogen group of the periodic table, oxygen is valued for its high reactivity and acts as an oxidizing agent that easily forms oxides with most of the elements and compounds except noble gases. It constitutes 21% of the planet’s atmosphere by volume and 23% by weight.
- Oxygen Purity: 99.7%
Cryogenic distillation process is the only process with which such high purity is attainable. It generates oxygen with purity up to 99.7%, which is considered excellent for industrial and medical applications.
- Oxygen Gas Pressure: 150-200 Bar
Compressed oxygen is moved into high pressure cylinders at a pressure of 150 bar or as required for piping gas systems and captive consumption.
- Flow Rate: 25-1000 Nm3/hour (Customizable)
100-4000 oxygen cylinders can be filled in this flow rate range. Oxygen plants can be customized with the flow required for meeting the requirements of customers.
HOW CRYOGENIC OXYGEN PLANT WORKS
Process technology used in the manufacturing our air separation systems are based on fractional distillation which can recover oxygen and nitrogen from atmospheric simultaneously. Advanced low pressure technology process with Rotary screw compressor (or low oil free piston compressor and turbo expanders is employed. The feed air enters the molecular sieve purification system which removes CO2 and moisture. The air is liquefied by cryogenic cooling using the latest high efficiency heat exchangers and turbo expanders. Liquid air separates into oxygen and nitrogen in the air separation plant.
Oxygen Production Technology Process Layout and Diagram
Technologically cryogenic air separation process is accomplished by integrating the functioning of various components as given in the 3D design layout. Complete working of the technology is described below:
- Fully Automatic Air Compressor
Air is compressed at a low pressure of 5-7 Bar. Such low pressure is attained by using trouble-free rotary compressor (screw/centrifugal) which is manufactured with the advanced technology.
- Pre-Cooling System
After being compressed, the processed air is pre-cooled using low pressure refrigerant to temperature around 12 deg C before it enters the purifier.
- Purification by Purifier
Processed air enters a purifier which is made up of twin molecular sieves and driers working alternatively. The sieves remove impurities such as carbon dioxide, hydrocarbons and moisture before entering the air separation unit.
- Cryogenic Cooling of Air by Turbo Expander
In order to achieve liquefaction the air is cooled to sub-zero temperatures using an efficient turbo expander which provides refrigeration cooling the air to temperature below -165 deg C to -170 deg C.
- Separation of Liquid Air into Oxygen & Nitrogen by Air Separation Column
Cleaned air (free of oil, moisture and carbon dioxide) enters low pressure fin type heat exchanger where it is cooled below sub-zero temperature through air expansion process in the turbo expander. Superb thermal efficiency allows achievement of temperature difference delta T as low as 2 deg C at the warm end of the exchanger. Liquefaction of air is complete before entering the air separation column where the air is separated into oxygen and nitrogen through a process of rectification. Oxygen with purity of 99.7% is available at the outlet of ASU. Nitrogen is also available at the outlet with purity of 99.99% as a second product gas simultaneously without loss of oxygen.
- Compression of Oxygen Filling in the Cylinder
The final product in the form of compressed oxygen is filled into cylinders at a pressure of 150 bar or as required. Oxygen can also be fed into a piped supply system or for captive consumption. In case of liquid plants it is filled into cryogenic liquid tanks.
Configuration and Installations
Universal Boschi has a high level of expertise in erection, commissioning to installation of oxygen gas plants at client’s site. Our engineers and technicians visit the site for installation and maintenance and for providing training to client’s staff. Our engineer will inspect the site conceptualizing the space for installation of various components of an air separation plant. How much space the plant will require depends on the capacity. After finalizing space, the installation of the plant will be configured according to the design layout. After installation, the engineer will demonstrate how the plant starts up and shuts down. However, it must be noted that the plant is capable of being operated continuously for a period of 24 months before it is shut down for a planned defrosting of 12 hours.
Start up and Defrosting Time
Total startup time after defrosting till achieving oxygen product flow: 8 to 10 hours (approx) Defrosting period for the plant is: 12 hours (approx)
The plant can be shut down at any time as per the requirement of the user apart the scheduled maintenance shutdowns which are planned on yearly basis for defrosting
Electricity Specifications for Configuration of the Plant
- Low voltage: 380/400V / 220V, 3-phase, 4-wire system, Earthing for neutral point
- High voltage: 10KV
- Frequency: 50/60Hz
- Field devices and PLC voltage: 24 V. DC
The instrument system of the entire air separation plant will be integrated with the latest PLC system for improving the efficiency of automation.
Important electric signals like current, voltage and power consumption will be displayed on the PLC of the main system for easy and smooth operation.
What are the Uses of Oxygen
Oxygen is used in a wide range of industrial and medical applications. Some of them are given below:
- Steel industry
- Metal fabrication
- Welding, cutting, brazing, heating
- Chemical industry
- Paper & pulp
- Glass blowing
- Waste water treatment
Frequently Asked Questions
Accepted standards for medical oxygen provide guidelines for purity specifications. The standards have been set by bodies like US pharmacopeia, the UK Pharmacopeia, Indian Pharmacopeia and the World Health organizations.
Medical oxygen purity specifications
- Oxygen must not have purity not less than 99%ppm
- Carbon dioxide must not be more than 300ppm
- Water content must remain below 67ppm
- Carbon dioxide must always be less than 7ppm