Water Jet Ejectors

Water ejectors and water jet eductors are also used for mixing liquids, lifting liquids, and pumping and mixing 

Temperature—Pressure—Volume of Saturated Water Vapor Over Ice 

Values obtained from Keenan Keyes— Thermodynamic Properties of Steam . John Wiley Sons, 1936, by permission. 

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Berman LD, Efimochin GI. (1964) Design equations for water jet ejectors. Thermal Eng., 11 (7) 57-62. 

Zinger, fitting Equation 9.35 to their experimental data for a typical water jet ejector... 

FIGURE 9.5 Analogy between water jet ejector and 2-2 type gas-inducing impeller, (a) Water jet ejector, (b) 2-2 type gas-inducing impeller. (Reproduced from Zundelevich, 1979 with permission from John Wiley and Sons. Copyright 1979 American Instimte of Chemical Engineers.)... 

The collection of particles larger than 1—2 p.m in Hquid ejector venturis has been discussed (285). High pressure water induces the flow of gas, but power costs for Hquid pumping can be high because motive efficiency of jet ejectors is usually less than 10%. Improvements (286) to Hquid injectors allow capture of submicrometer particles by using a superheated hot (200°C) water jet at pressures of 6,900—27,600 kPa (1000—4000 psi) which flashes as it issues from the nozzle. For 99% coUection, hot water rate varies from 0.4 kg/1000 m for 1-p.m particles to 0.6 kg/1000 m for 0.3-p.m particles. 

Steam-Jet (Ejector) Systems These systems substitute an ejector for a mechanical compressor in a vapor compression system. Since refigerant is water, maintaining temperatures lower than the environment requires that the pressure of water in the evaporator must be... 

The VPS overhead consists of steam, inerts, condensable and non-condensable hydrocarbons. The condensables result from low boiling material present in the reduced crude feed and from entrainment of liquid from the VPS top tray. The noncondensables result from cracking at the high temperatures employed in the VPS. Inerts result from leakage of air into the evacuated system. Steam and condensable hydrocarbons are condensed using an overhead water-cooled condenser. The distillate drum serves to separate inerts and non-condensables from condensate, as well as liquid hydrocarbons from water. Vacuum is maintained in the VPS using steam jet ejectors. 

Figure 6-7B. Chilled water refrigeration unit using steam jet ejectors. By permission, Croll-Reynolds Co., Inc.

Figure 6-11B. A typical relative comparison of various designs of steam jet ejectors. Based on same steam consumption, 100 psig steam pressure and 85°F water. Curves represent the capacity of ejectors designed for maximum air handling capacity at any one particular suction pressure. By permission, Graham Manufacturing Co.

Figure 6-20B. Air and water vapor mixture data (Dalton s Law)—saturated, (continued). Reprinted by permission. Standards for Sfeam Jet Ejectors, 3rd. Ed., Heat Exchange Institute, 1956 [11].

Although the thermal efficiencies of various mechanical vacuum pumps and even steam jet ejectors vary with each manufacturer s design and even size, the curves of Figure 6-34 present a reasonable relative relationship between the types of equipment. Steam jets shown are used for surf ace intercondensers with 70°F cooling water. For non-condensing ejectors, the efficiency would be lower. 

Instead of rotary pumps, large water jet, steam ejector, or water ring pumps can be used. For batch evacuation, and the production of hydrocarbon-free fore vacuum for sputter-ion pumps, adsorption pumps (see Section 2.1.8.1) are suitable. If the use of oil-sealed rotary vane pumps cannot be avoided, basically two-stage rotary vane pumps should be used. The small amount of oil vapor that backstreams out of the Inlet ports of these pumps can be almost completely removed by a sorption trap (see Section 2.1.4) Inserted In the pumping line. 

Figure 3.5. Vacuum control with steam jet ejectors and with mechanical vacuum pumps, (a) Air bleed on PC. The steam and water rates are hand set. The air bleed can be made as small as desired. This can be used only if air is not harmful to the process. Air bleed also can be used with mechanical vacuum pumps, (b) Both the steam and water supplies are on automatic control. This achieves the minimum cost of utilities, but the valves and controls are relatively expensive, (c) Throttling of process gas flow. The valve is larger and more expensive even than the vapor valve of case (a). Butterfly valves are suitable. This method also is suitable with mechanical vacuum pumps, (d) No direct pressure control. Settings of manual control valves for the utilities with guidance from pressure indicator PI. Commonly used where the greatest vacuum attainable with the existing equipment is desired.

Application ranges of the various kinds of devices for maintenance of subatmospheric pressures in process equipment are shown in Table 7.3. The use of mechanical pumps—compressors in reverse— for such purposes is mentioned earlier in this chapter. Pressures also can be reduced by the action of flowing fluids. For instance, water jets at 40psig will sustain pressures of 0.5-2.0psia. For intermediate pressure ranges, down to O.lTorr or so, steam jet ejectors are widely favored. They have no moving parts, are quiet, easily installed, simple, and moderately economical to operate, and readily adaptable to handling corrosive vapor mixtures. A specification form is in Appendix B. 

Steam jet action in which water is chilled by evaporation in a chamber maintained at low pressure by means of a steam jet ejector. A temperature is 55°F or so is commonly attained, but down to 40°F may be feasible. Brines also can be chilled by evaporation to below 32°F. 

The daily output of a cooler measuring 1650 X 610 X 350 mm and an absorber measuring 1650 X 970 X 350 mm equals 7.5 tons of 30 to 35 per cent hydrochloric acid. As a rule, two graphite absorbers are connected in series and the more diluted acid from the second absorber which contains about 20 per cent HC1 is pumped into the first absorber. The rest of the unabsorbed gas is led through a rubber lined steel absorption tower into the atmosphere. The tower is sprayed with water and the diluted acid obtained is employed as an absorption liquid in the second igurite absorber. The flow of the tail gases is aided by a steam-jet ejector. 

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