Steam liquid ring

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],...

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... 

Serizawa et al. (2002) studied the flow patterns in steam-water flow. Figure 2.29 shows their observations in a 0.05 mm glass channel. Here a new pattern was identified, namely, liquid ring flow. 

Jets have been partially replaced by liquid ring-seal pumps. These are really positive-displacement compressors. The gas is squeezed between the vanes of the compressor s rotor and a pool of liquid in the compressor s case. Liquid ring-seal pumps are not interesting. They have no character. They are not as complex as steam jets. Anyway, I will discuss positive displacement compressors in later chapters. 

The vacuum system can be equipped with steam ejectors or with liquid ring pumps (vacuum pumps), or a combination. 

One liquid ring vacuum pump is provided to ensure complete evacuation of the steam and quick drying of the chamber and condenser after each sterilization cycle. This pump works under a pressure that is specified in the technical specifications. 

Following the condensing section, and depending on the utility situation at the plant site, either a liquid ring vacuum pump or a two-stage steam jet with an intercondenser is used. A booster ejector is not required to maintain the vacuum level required for evaporation. 

Feng, 2001 7l=0.003-17.52 m/s, 7g=0.0012- 295.3 m/s. Steam water, ranges not given diameters of 50 pm for air-water, and 25 pm for steam-water two-phase flow, steam- water details not given patterns identified over the ranges of flow rates studied patterns identified liquid ring flow and liquid lump flow. 

Noncondensable gas-removal system, to remove and compress the noncondensable gases. A typical system uses two stages of compression. The first stage is a steam jet ejector. The second stage is another steam jet ejector, a liquid ring vacuum pump, or a centrifugal compressor. 

The vacuum at the top of the flash column is often produced by a sequence of three elevated steam-jet eductors with intermediate and final surface condensers to remove the steam. A liquid-ring compressor can be substituted for one or more eductors to conserve steam. Mechanical vacuum pumps are seldom used because of the corrosive nature of the off-gas. The noncondensible sour compressed gas and condensate are led away through a water seal for safety in case of steam system failure. The seal pot is equipped to skim off condensed oil continuously. 

The chemical plant consists of a single-effect vacuum evaporator system for regenerating the solution and liberating the sulfur dioxide. Indirect heat is supplied to the forced-circulation evaporator by using exhaust steam from the refinery. The vacuum is supplied by a liquid ring vacuum pump which also pumps the sulfur dioxide back into the front of the Claus plant. 

For vacuum production reciprocating, rotary positive displacement and liquid ring pumps can be used to pressures from 200 to 10 mmHg. Alternatively steam ejectors can be used when water self is a product, as in evaporation of aqueous solutions. The residual pressures can be lowered under 1 mmHg by using several ejectors in series. 

Install pre-condensers cooled with cooling/chilled water. Use multi-stage steam ejectors arranged in series/series-parallel arrangement. Use liquid ring or dry vacuum pumps... 

Heuristic 46 For pressures down to 10 torr and gas flow rates up to 10,000ft /min at the inlet to the vacuum system, use a liquid-ring vacuum pump. For pressures down to 2 torr and gas flow rates up to 1,000,000 ft /min at the inlet to the vacuum system, use a steam-jet ejector system (one-stage for 100 to 760 torr, two-stage for 15 to 100 torr, and three-stage for 2 to 15 torr). Include a direct-contact condenser between stages. 

For most steam ejector applications, direct contact condensers between stages were frequently used. For vacuum steam stripping, use shell and tube condensers with refrigerant at -8 to -12 °C upstream of the booster ejector with interstage dry condensers plus a liquid ring vacuum pump. 

Section 12.6.3 discusses the various methods of pressure control in vacuum systems. It points out that some situations, more common with liquid-ring pumps than with steam jets, favor allowing atmospheric air to enter the process. This balances capacity and demand. The chlorine recovered here, however, may be combined with the cell gas and processed through liquefaction. In that case, the air added to the system reduces the efficiency of liquefaction (Section 9.1.7.2A). Pressure control by recycling some of the compressed vapor to the vacuum producer then would be a better method. 

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