Multi-stage steam-jet-ejector vacuum systems are the solitary devices that can reach the target level of vacuum (300 Pa) and suck large volumes of aggressive vapours and gasses with high temperature and humidity.
Based upon the use of auxiliary equipment, two and three-stage ejectors can be either condensing or noncondensing types. Four, five and six-stage units can also be non-condensing, but usually are condensing types.
Condensing Type Ejectors have an intercondenser between ejectors that reduces steam consumption in later stages by condensing first stage operating steam and condensable vapors; and cooling the air and other non- condensable. The intercondenser may be direct-contact or surface type, arranged barometrically or low-level.
Ejectors are devices used to set in motion a secondary fluid by momentum and energy transfer from a high velocity primary jet. Ejectors can be operated with incompressible fluids (liquids), and with compressible fluids (gases and vapors). The working process in a liquid jet pump or in a gas ejector is the same. A high-pressure fluid with very low velocity at the primary inlet is accelerated to high velocity jet through a converging nozzle for the liquid jet pump or a converging-diverging supersonic nozzle for the gas ejector.
The supersonic or subsonic primary fluid entrains and draws the secondary fluid into the mixing chamber, where the secondary fluid is accelerated. The mixing process of energy and momentum exchange between primary and secondary flow happens through the mixing chamber. The mixing flow structure is complicated in the pump due to the transonic flow and it is difficult to describe by traditional methods.
silencers are used to suppress the noise generated by safety relief valves, process vents, dumping gas to atmosphere during compressor or boiler set-up sequences, de-pressurizing lines for maintenance, ejector discharges and steam exhausts, and the blow down of pipelines for cleaning purposes. silencers consists of an inlet diffuser, an expansion chamber and an absorptive section.
The vented gas enters the inlet diffuser of the silencer and expands across a series of small holes in the diffuser body as it proceeds into the expansion chamber. From there it flows into the absorptive section before being passed into the atmosphere.
The diffuser forces the vented gas to pass through small radial holes normal to the initial gas flow. This breaks the single axial gas jet into a series of smaller radial jets, increasing the frequency of the generated noise so that it can be better attenuated by the absorptive section of the silencer.
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