While the ejector itself can be quite simple, specifying the optimum system to meet specific needs is not simple. Important parameters involved in ejector sizing and staging include pressure of motive gas, required discharge pressure, suction pressure and relative mass flow rates of motive fluid to suction fluid.
For instance, most ejectors use steam as the motive fluid. The quality of the motive steam affects the operation of the unit. The usual requirement is for dry, saturated high-pressure steam. In operation, it is very important to maintain the design quality of steam.
If the quality of the steam is low, suction pressure and capacity will decrease, especially in multistage designs. Excessive steam superheat can also adversely affect the suction capacity of an ejector. It decreases the energy level ratio, and the increase in specific volume tends to choke the diffuser.
Ejectors can generally be applied on a variety of processes as long as the proper conditions exist: the motive fluid pressure drop is large enough to develop high velocities in the nozzles, the difference between suction and discharge pressures is not excessive and the suction fluid flow is small compared with the motive fluid.
Toggle navigation. Contact US Download our Brochure Ejectors are considered an alternative to mechanical vacuum pumps for a number of reasons: No source of power is required other than the motive gas; Because they have no moving parts, they are reliable vacuum producers; They are easy to install, operate and maintain. Ejector Design Very simply, an ejector is a pumping device.
The two major functions of ejectors are as follows: Thermocompressors Thermocompressors are ejectors applied to recompressing spent steam and process fluids. Condensers Condensers may be barometric or surface. Specifying Ejectors While the ejector itself can be quite simple, specifying the optimum system to meet specific needs is not simple.
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VacuMaster Glass. Crane Systems and Jib Cranes. Workshop Equipment. Transport Trolleys. The pressure in the motive nozzle 2 decreases and the velocity rises. At this point the suction flow enters into the ejector head 3 through the suction connection B and is mixed with the motive fluid flowing with high velocity. Part of the kinetic energy is transferred to the suction flow. Motive flow and suction flow pass together - as a mixture - through the diffuser, loosing velocity and gaining pressure.
The increase from suction pressure ps to discharge pressure p d corresponds to the delivery head for the suction flow or to the pressure difference of the jet ejector. This kinetic energy can be released to the suction flow by impulse transfer while both flows mingle. The diffuser converts the kinetic energy of the mixture consisting of motive flow and suction flow back into static pressure energy.
The steam velocity exceeds the sonic velocity accordingly. Motive flow and suction flow are mixed at supersonic velocity and then decelerated to the sonic velocity upon reaching the diffuser throat.
Jet ejectors are used to create vacuum, to compress gases, to convey liquids, to transport granular solids, to mix liquids or gases. The following table summarizes the terms of jet ejectors laid down according to DIN standards When defining certain types of jet ejectors, the standard terms for motive fluid and material delivered gas, steam, liquid, solids can be replaced by specific ones..
The methods described below for insulating jet ejectors, condensers, sound absorbers and pipes are merely suggestions. With this type of insulation, we expect a reduction in noise emissions of about 20 dB A. Insulate both the pipes connected and the jet ejector.
If specifications guarantee particular sound pressure levels, insulation thicknesses have to be calculated individually. If required, we can give you a quote for carrying out the work involved. The materials described below apply to all sound insulation of jet ejectors, condensers, pipes and sound absorbers.
The thickness of the insulation layer must be at least 60 mm. Apply a sound insulation layer 3 mm thick to the inside of the sheet steel jacket. The sound insulation layer must comply with the following physical specifications:.
Ensure that the sound insulation layer and the steel jacket are securely bonded with one another. Figure 4: Illustration gas ejector application to boost production Benefits. Ejectors can be used to recover gas that is vaporized due to working losses from storage tanks which occur when crude level changes and when crude is agitated in tanks and standing losses which occur with daily and seasonal changes in temperature and barometric pressure.
The ejector system must be designed to avoid creating a vacuum in the storage tank vent line. The following technologies can provide similar benefits and may be considered as alternatives to ejector technology:.
Flare gas flow rate variability is common. If this variation is not controlled, the suction pressure created by the gas ejector will also vary. In order to maintain the desired pressure on the low-pressure side of the gas ejector, some standard control techniques are available including the following:. The case study described below provides an overview of the kind of issues that may occur during ejector implementation.
The project consisted of evaluating the benefits of installing an ejector, with Well 5 as motive fluid, and Well 1 and Well 3 as entrained fluid. The justifications for an ejector rather than a booster compressor in this particular case were:. Costs were driven by piping works offshore and associated production losses. One major expectation was the frequent change out of the ejector internals to cope with the decline of the production. The efficiency of an ejector increases with the differential between motive fluid and entrained fluid in terms of flow rate and pressure.
For this reason the project had to be implemented quickly in anticipation of the decline of Well 5. The project was performed within eight months. Additional dynamic information from Well 5 was gained.
A redesign of the ejector was performed with the additional constraint of respecting the initial spacial footprint which was already fixed. The ejector was effective in reducing the wellhead pressures of Well 1 and Well 3 as planned but, unfortunately, the 20 bars reduction was insufficient to restart either of the two wells.
The ejector was a technical success but the candidate wells did not respond as expected.
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