Vacuum liquid ring

API Std 681, Liquid Ring Vacuum Pumps and Compressors, 1st Edition, February 1996. 

Vacuum pump (either liquid ring or rotating vanes type)... 

A useful summary of the typical equipment used for developing and maintaining process system vacuum is presented in Table 6-1. Also see Birgenheier [33]. The positive displacement type vacuum pumps can handle an overload in capacity and still maintain essentially the same pressure (vacuum), while the ejectors are much more limited in this performance and cannot maintain the vacuum. The liquid ring unit is more like the positive displacement pump, but it does develop increased suction pressure (higher vacuum) when the inlet load is increased at tlie lower end of the pressure performance curve. The shapes of these performance curves is important in evaluating the system flexibility. See later discussion. 

The most used mechanical vacuum pumps or compressors are reciprocating, liquid-ring, rotary-vane, rotary blower, rotary piston, and diaphragm. 

Rotary blower—liquid ring vacuum pump... 

Figure 6-35. Diagram of liquid ring vacuum pump features. By permission, Nash Engineering Co.

Moisture or even slugs of liquid entering the inlet of a liquid-ring vacuum pump will not harm it. Such liquid becomes an addition to the liquid compressant. Vapor is often condensed in a vacuum pump. The condensate is also added to the liquid compressant. 

Figure 6-37. Typical capacity performance curve for a process liquid ring vacuum pump. Note that the vacuum is expressed here as gauge, referenced to a 30" Hg barometer, when 60°F seal water is used. For higher temperature water, the vacuum will not be as great. By permission, Nash Engineenng Co.

Figure 6-38. Chart for liquid ring vacuum pump to estimate the total volume to be displaced to evacuate a closed vessel to a predetermined vacuum. By permission, Graham Manufacturing Co., Inc.

Vacuum capacities and operating ranges, table, 344, 355 Ejectors, 344, 357 Integrated systems, 344 Liquid ring pumps, 344 Rotary lobe blowers, 344 Rotary piston pumps, 344 Rotary vane pumps, 344 Vacuum equipment, 343 Applications diagram, 352 ASME Code, 344 Pumps, 382 Steam jets, 357 Vacuum flow,... 

Friction losses, air steam, 131 Pressure losses chart, 134 Vacuum pumps, mechanical, 382 Liquid ring pumps, 383-385 Liquid ring volume displaced/ evacuation, 387... 

Fig. 2.3 Liquid ring vacuum pump, schematic (Siemens)...

Acceptance specifications for liquid ring vacuum pumps 1/87... 

Dual-phase extraction cannot remediate heavy chlorinated compounds, pesticides, or heavy hydrocarbons including polychlorinated biphenyls (RGBs), dioxin, fuel oil No. 6, or metals (with the possible exception of mercury). High-velocity pump systems (such as liquid ring vacuum pumps) tend to form emulsions, especially when diesel fuel is part of the recovered fluids. The problem of emulsion can be solved with prepump separation or a de-emulsification unit. 

One option involves the condensation of (or part of) the permeate under atmospheric instead of vacuum conditions. This requires the use of dry-vacuum pumps , able to compress the permeate vapour from vacuum to atmospheric pressure, after which condensation is performed at a higher temperature [23]. In this case, the operating conditions have to be carefully monitored since these pumps may lead to unsuitable heating of the vapour and eventually aroma deterioration, despite the low residence time. Alternatively, the use of liquid ring vacuum pumps where the service liquid can take some of the aromas from the permeate stream has been proposed [24]. 

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