A number of vessels sailing the oceans need clean, dry nitrogen (N2) for inerting, purging and blanketing of their cargo tanks. But which role does nitrogen feed air compressors play?
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Helps to prevent unwanted reactions
The main reason for the use of nitrogen on board vessels such as chemical tankers, product tankers and gas carriers is to replace the air atmosphere of the cargo tanks and adjacent space. This helps to prevent unwanted reactions between cargo and air, moisture pick-up and &#; worst case &#; fire explosion hazard.
There are two main types of nitrogen generators. One type uses pressure swing adsorption (PSA) process. The other type is based on hollow fibre membrane technology (see illustration below).
Both the PSA and membrane nitrogen systems utilise clean compressed air from a feed air compressor. The air is fed into the system where primarily the oxygen gas is separated from the air and vented to the atmosphere.
The result is that nitrogen at the required purity (95-99.9%) remains, ready for use or to be stored in a receiver serving as a buffer tank.
Why is clean feed air so important?
Firstly, a nitrogen system uses compressed air as its main source for producing nitrogen, regardless of whether it is based on the PSA or membrane technology. The correct feed air quality is therefore vital for maximising the lifetime of both PSA and membrane systems.
The effect of contaminated feed air into membranes or PSA media (CMS in illustration below), is that they will degrade over time and eventually lead to a costly replacement of either membranes or CMS in order to fulfil the class requirements of the nitrogen system.
We hope this article explains why N2 feed air compressors are vital for any nitrogen system.
Want to learn more?
5 reasons to chose a TMC feed-air (N2) compressor
Download our glossary: Understanding air compressors at sea
General Background
For more information, please visit nitrogen kompressor.
Compressed nitrogen and air are used in many different industries. Although compression methods and equipment are similar, property differences between these gases can impact equipment design.
Nitrogen is a pure gas, while air is a mixture of multiple gases such as nitrogen, oxygen, argon, and other trace gases. Compressing nitrogen is simpler than compressing air since there are no other gases to consider.
Nitrogen is an inert gas, making it less reactive than oxygen or other gases. When compressing nitrogen, it is essential to ensure the gas remains contaminant-free.
Compressing nitrogen and air share many similarities, but their different properties will affect some portions of the equipment design, safety considerations, and compressor packaging.
Nitrogen Applications
As a versatile and essential gas for everyday production, nitrogen covers various applications across many industries. Some include:
Electronics: Nitrogen is used to manufacture electronic components (semiconductors, LCDs, and computer chips) to create a controlled environment free of oxygen and other impurities. Those gases can significantly damage electronic components&#; capabilities. This is a rapidly expanding industry requiring increasing demand for pressurized nitrogen.
Chemical: Nitrogen is also required for many processes, including the production of ammonia and fertilizers. Nitrogen is used to neutralize the potentially harmful effects of oxygen in chemical manufacturing operations through nitrogen blanketing. Nitrogen blanketing introduces nitrogen gas into a storage vessel that will be used to store chemical components or finished chemical products.
Welding: Nitrogen acts as shielding to help improve the welding quality. It protects the weld from surrounding air, which contains moisture and other impurities that can negatively impact weld strength and quality.
Food & Beverage: Nitrogen helps with packaging and preservation. Since nitrogen is an inert gas, it prevents oxidation and spoilage for food products such as potato chips, nuts, fruits, and dairy.
Medical: Nitrogen is used in many intricate surgeries and therapy practices to freeze and destroy abnormal tissue growth. It is also used in medical imaging, like MRIs, to cool the equipment.
For many manufacturing applications, nitrogen is safer as part of the process because it is non-flammable and non-reactive.
However, when compressing nitrogen, there are some additional safety considerations for the compressor to avoid harm to the operator. Since 78% of the air we breathe is nitrogen, nitrogen is assumed to be not hazardous. However, high levels of pure nitrogen can cause you to feel dizzy and lightheaded. Exposure to pure nitrogen without proper ventilation/oxygen present can result in loss of consciousness and even death. To prevent this, nitrogen compressors will typically include the following safety features:
Warning Labels/Instructions: Units will typically be manufactured with additional warning labels that warn of the possibility of nitrogen asphyxiation, particularly for confined spaces.
Solenoid Valves: Additional solenoid valves may be used in the seal gas piping to prevent the flow of nitrogen seal gas to the compressor&#;s seals when the units are not in operation. This will prevent excess nitrogen leakage through buffered seals to the surrounding area and prevent nitrogen from being wasted.
Packaging Nitrogen Compressors
There are a few essential considerations when packaging nitrogen compressors compared to standard air compressors.
Recycle Valve &#; While the design and operation can vary, recycling valves return nitrogen to the process instead of blowing the excess off into atmospheric air. This ensures the customer is not wasting any excess gas and saving money.
Pressure Considerations &#; Nitrogen compressors must withstand higher pressure than normal air compressors. Nitrogen processes will typically have higher nitrogen inlet and discharge pressure resulting in compressor casings and coolers having higher MAWPs (Maximum allowable working pressure).
Combination Machines &#; Packaging dual process machines that compress air and nitrogen not only help support two different processes but can cut capital and operation costs by having one machine instead of two separate machines for their process. It makes the installation and operation simple for end users in the long run.
The main difference between nitrogen and air is the gas properties and the specific applications of these compressors. Nitrogen compressors can handle higher pressures, remove contaminants from gas, and work safely with the unique properties of nitrogen gas.
For additional information on nitrogen compressor and air separation applications, visit our air separation units or download our informational brochure!
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