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Steam Ejectors 

Steam ejectors use steam or gas instead of moving parts to compress a gas.  In a jet or ejector, a relatively high-pressure gas, like steam or air, expands through a nozzle converting that pressure or potential energy to velocity or kinetic energy.  The jet of high-velocity steam or gas entrains the gas to be evacuated or pumped in the suction of the ejector.  The resulting mixture enters the diffuser where velocity energy is converted to pressure at the ejector discharge.

 

Steam jet ejectors use steam as the high-pressure motive fluid to create deep vacuum. Whereas air jet ejectors are utilized when the required capacity is low or steam is not available or desired. The simple construction and lack of moving parts result in a reliable pump with little maintenance, low initial cost that is custom-designed with no limit on size, capacity or materials of construction. These attributes make steam jet and air ejectors the ideal solution for the most demanding applications in oil & gas, chemical and electric power industries. 

Nash is globally recognized for assembling the most cost-effective steam jet and air ejectors. Application engineers ensure maximum performance benefits while optimizing a hybrid system customized to processes, applications and technology requirements. NASH steam jet and air ejectors minimize greenhouse gas emissions and operational efficiency while improving system stability.

Steam Jet And Air Ejector Applications 

  • Sugar – the steam discharged from the steam ejector is reused in the ethanol and sugar production process.
  • Chemical – steam and air jet ejectors maximize output and efficiency while adhering to preventative maintenance and eliminating pollution. 
  • Oil & Gas-liquid ring vacuum pump paired with air ejectors remove oxygen from well injection water. This process prevents corrosion and sub-surface solid build-up.
  • Power – steam and air jet ejectors use direct conversion of thermal power to fluid power without the need of intermediate engines or electrical power generation.  
  • Pulp & Paper – steam and air jet ejectors are engineered systems of paper production and water removal from paper machines. 
  • Other

 

How Steam Ejectors Work

Steam jet ejectors pass steam through an expanding nozzle. The nozzle controls the expansion of steam and converts pressure into velocity; thus, creating a vacuum to transfer gases. 

An ejector operates on a mass basis, not by displacing volume. Ejectors are better suited to handling gases with low molecular weights and when operating at low absolute pressures. These systems are ideally suited to high vacuum applications but are only marginally useful as compressors. 

A jet of motive fluid is supersonic velocity entrains the inlet stream and raises its velocity to the speed of sound as the two flows mix. A stationary sonic shock wave forms in the throat of the diffuser, and absolute pressure rises sharply at this point. More pressure rise occurs along the discharge cone as flow slows down. The most common motive fluid is steam at 80 to 400 psig. Other fluids can be used whenever there is a good reason to avoid mixing steam with the product. A single steam jet ejector can maintain a vacuum of about 27" Hg or about 76mm HgA. By staging steam jet ejectors in series, you can maintain higher vacuum levels. At any level, you can usually save steam by installing on more stages than the practical minimum. System suction pressure can be as low as 0.001 mm HgA with six stages. 


NASH Ejectors

Duties Of Steam Jet Ejectors

  • Paper drying
  • Condenser exhausting
  • Evaporation
  • Reactor vacuum
  • Vacuum distillation
  • Vacuum filtration

 

Advantages Of Steam Ejectors 

  • No moving parts
  • Simple in construction 
  • Easy to maintain 
  • Available in a wide variety of materials 
  • Low investment, high utility cost 
  • Good for low MW gases

 

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