Steam-jet pumps

Fig. 28. A simplified vacuum setup i—vessel being evacuated . 2—cooled traps steam-jet pump 4—vacuum valves 5—fore pump (pum p for preliminary rarefaction)...

A vacuum up to 10 mmHg can be produced by a rotary (or mechanical) pump. Steam-jet pumps operate within the range from 10- ... 

Low vacuum (1 bar-1 mbar) Positive displacement pump Booster diffusion vacuum pump (particularly steam jet pumps) Low vacuum distillation Vacuum circulation evaporator Continuous evaporator with falling or wiped film Rotary evaporator... 

The total waste water volume depends mainly on the vacuum generation (steam-jet pumps consume far more water than water seal pumps with closed seal water loops) and on the spinning and conditioning steps. The options for re-use and treatment of the various waste water streams depend on the given composition [46, TWGComments, 2005]. 

Steam jet pumps are frequently used In the chemical industry for vacuum generation. The main reasons for this are their high operational reliability, their resistance to corrosion, their tolerance of fouling as well as their suitability for very large volume flows. However, when jet pumps are operated with steam as the motive medium, there will inevitably be waste water generated because the motive steam must be condensed. 

Frequently a combination of steam jet pumps and liquid ring pumps is installed. Here, the low suction pressure is achieved by one or several ejector stages, but... 

Liquid jet pump (vacuum technology) A kinetic vacuum pump where the gases are entrained in a stream of fluid or steam. See also Steam jet pump Verneuil tube. 

The injector is a special type of jet pump, operated by steam and used for boiler feed and similar services, in which the fluid being pumped is discharged into a space under the same pressure as that of the steam being used to operate the injector. 

The efficiency of an ejecdor or jet pump is low, being only a few percent. The head developed by the ejector is also low except in special types. The device has the disadvantage of diluting the fluid pumped by mixing it with the pumping fluid. In steam injectors for boiler feed and similar seiwices in which the heat of the steam is recovered, efficiency is close to 100 percent. 

Applications The common Heliflow apphcations are tank-vent condensers, sample coolers, pump-seal coolers, and steam-jet vacuum condensers. Instant water heaters, glycoLwater seivdces, and cryogenic vaporizers use the spiral tube s ability to reduce thermally induced stresses caused in these apphcations. 

The vacuum pump is usually of the steam-jet type if high-pressure steam is available. If nigh-pressure steam is not available, more expensive mechanical pumps may be used. These may be either a water-ring (Hytor) type or a reciprocating pump. 

Vacuum is applied to the chamber and vapor is removed through a large pipe which is connected to the chamber in a manner such that, if the vacuum is broken suddenly, the inrushing air will not greatly disturb the bed of material being dried. This line leads to a condenser where moisture or solvent that has been vaporized is condensed. The noncondensable exhaust gas goes to the vacuum source, which may be a wet or diy vacuum pump or a steam-jet ejector. 

Replacement of the steam-jet ejector with a vacuum pump. The distillation operation will not be affected. The operating cost of the ejector and the vacuum pump are comparable. However, a capital investment of 75,000 is needed to purchase the pump. For a five-year linear depreciation with negligible salvage value, the annualized fixed cost of the pump is I5,000/year. 

BWRs do not operate with dissolved boron like a PWR but use pure, demineralized water with a continuous water quality control system. The reactivity is controlled by the large number of control rods (>100) containing burnable neutron poisons, and by varying the flow rate through the reactor for normal, fine control. Two recirculation loops using variable speed recirculation pumps inject water into the jet pumps inside of the reactor vessel to increase the flow rate by several times over that in the recirculation loops. The steam bubble formation reduces the moderator density and... 

Strahl-antrieb, m. jet propulsion, -apparat, m. jet apparatus (as steam-jet injector, pump, or blower), -asbest, m. plumose asbestos, -baryt, m. radiated barite, Bologna stone, -blende, /. a variety of sphalerite. -dUse, /. jet nozzle. 

Steam Jet syphons Steam Jet exhausters Single-stage vacuum pumps... 

Steam jet syphons Steam jet slurry heater Single-stage vacuum pumps Using air as the motive fluid Air jet exhausters Using liquid as the motive fluid Water jet eductors... 

Figure 6-110. Typical performance curves for steam jet ejectors, liquid ring pumps, and rotary piston oil-sealed pumps. By permission, Ryans, J. L. and Roper, D. L. [24],...

The process designer or mechanical engineer in a process plant is not expected to, nor should he, actually design a mechanical vacuum pump or steam jet, biit rather he should be knowledgeable enough to establish the process requirements for capacity, pressure drops, etc., and understand the operation and details of equipment available. 

Mechanical vacuum pumps are eight to ten times more efficient users of energy than steam jets although, steam Jets are reliable and cost less [23], See Table 6-17. 

Combinations of steam jet ejectors operating in conjunction th mechanical pumps can significandy improve the overall s) stem efficiency, especially in the lower suction pressure torr range of 1 torr to 100 torn They can exist beyond the range cited, but tend to fall off above 200 torr. Each system should be examined indhadually to determine the net result, because the specific manufacturer and the equipment size enter into the overall assessment. Some effective combinations are ... 

Ketterer, S. G. and C. G. Blatchley, Steam Jet Vacuum Pumps, Schutte and Koerting Co. 

---