Nitrogen Plant

Cryogenic Process	Non cryogenic process	Equipment
Types	Buyers Guide

Nitrogen gas plants are nitrogen generating system which can be small, portable size to large tonnage gas plants, like oxygen plants, used for refining, chemical processing and other applications. Infact, in almost all oxygen plants, nitrogen is also produced at the same time.


Nitrogen (N2) constitutes 78.03% of the atmosphere and the gas plants are there to extract nitrogen in its pure form to be used for various industrial purposes. Nitrogen can be produced in liquid and gaseous form simultaneously and both cryogenic and non cryogenic processes are used to produce nitrogen. While the cryogenic process is preferred for large scale gas plants, the non cryogenic process (PSA, VPSA, nitrogen membrane) is preferred for small sized plants. The process of producing oxygen and nitrogen is same in all gas plants.

Five Step Process for the Manufacture of Nitrogen (Cryogenic Process)

• Air Compression: The first step is drawing of air from the atmosphere through suction sir filter and this obstructs dust from getting into the system
  
  
• Air Purification: The next process is the purification of the air. Firstly, the air is cooled in an evaporating cooler. Dry Nitrogen will be bubbled through the water in the cooler to become wet gas. As the water vaporizes, latent heat is absorbed and water gets cooled. Compressed air, cooled in the cooler will pass through a Moisture Separator or Molecular Sieve vessels. Moisture , dust impurities are adsorbed and the gas is passed to the chilling unit for cooling.
  
  
• Air Cooling: The compressed air, which is purified from moisture and impurities, enter the cold box.
  
  
• It initially passes through a Heat Exchanger No.1 and the incoming air will be cooled by the outgoing Oxygen and Nitrogen. The air will be cooled to around -100 degree C and this air is divided into two streams -the main air stream which enters Expansion Engine and the rest of the air will pass through Heat Exchanger No. 2 to be cooled to about -160 degree C. As the air enters the lower column, a part of this air condenses into liquid and falls at the bottom of the column. This liquid is about 60% nitrogen and 40% oxygen and known as the "Rich Liquid". As nitrogen is more volatile it rises to top of the lower column and it becomes liquefied because of the cold it gets from the condenser.
  
  
• Air Separation: Final separation is attained in the upper column. As the rich liquid entering the middle of the upper column flows down, nitrogen evaporates and oxygen continues as liquid. The liquid nitrogen which is also known as the poor liquid enters the top of the column and while flowing down, it comes in contact with any evaporating Oxygen and condenses the same into liquid. Nitrogen being volatile becomes a gas. The entire gaseous nitrogen is piped out through heat exchangers from the top of the column. Generally the purity of Oxygen will be 99.5% and Nitrogen about 96%, when the plant is operated exclusively for oxygen production.
  
  
• Filling of Liquid /Gas Nitrogen: The last step is the filling of purified nitrogen into pumps and cylinders .

Non Cryogenic Manufacturing Process

PSA Process
Using molecular sieves separation technique, the nitrogen generator produces nitrogen gas from atmospheric air. The PSA process for nitrogen generation is similar to that of oxygen but carbon molecular sieve (CMS) is used instead of zeolite molecular sieve (ZMS). Due to the adsorption properties of CMS, it is possible to produce nitrogen by charging two adsorber vessels with compressed air one after the other. While one vessel adsorbs, the other vessel is used in regenerating by pressure reduction. In other words, when compressed air is passed, nitrogen comes out as product gas from one vessel while the other vessel is simultaneously regenerated by de-pressurisation to atmospheric pressure.

Membrane Nitrogen System
By using membrane technology, compressed air is provided from air compressor to separate nitrogen from air. A feed air cleaning system is available in the membrane separator to provide clean air, free from solid particles, oil and water droplets. The clean air will lead to higher efficiency nitrogen production and ensure long life of the membranes.

Equipment required in Nitrogen Plants

Air compressor system Moisture separator N2 Separation Membrane Modules N2 Gas Tanks

Air filter Adsorber Expander Nitrogen pressure and flow regulator

Standard Applications of Nitrogen Gas Plants

• Chemical Manufacturing (Material Transfer, Blanketing)
• Electronics (Storage, Wave Soldering, Furnace Application)
• Food Processing
• Food Packaging
• Laser Cutting
• Tire Filling
• Plastics (Injection Molding)
• Pharmaceuticals (Packaging, Blanketing)
• Heat Treatment (Ferrous & Non-Ferrous Metals)

Types of Nitrogen Plants
Depending on the manufacturing process, nitrogen plants can be classified as follows:

• Membrane Nitrogen Plants: The most automated gas plants designed for production of nitrogen from atmospheric air.
  
  
• Adsorption Nitrogen Plants: Automated systems designed for gaseous nitrogen production from air.
  
  
• Cryogenic Nitrogen Plants: These are cryogenic temperatures based plants designed for production of liquid and gaseous nitrogen from atmospheric air.
  
  
• Mobile Nitrogen Stations: Mobile stations used for air-to-nitrogen production are specially designed for operation in various climatic zones. · Mobile nitrogen compressor stations: These are self-operated and carried nitrogen compressor stations for high-pressure nitrogen recovery.

Buyer's guide
Technical specifications to consider for purchasing nitrogen gas plants are

Size: Large, Medium, Small, Portable Capacity: Pressure Purity Power Consumed Power Supply Power Connected Starting pressure Working Pressure

Air Capacity Starting Time (After Defrost) Starting Time (After Tripping) Areas Required Assembly Height Weight Air Separation Column