Motive water

I 3 Liquid Ring Vacuum Pumps in Industrial Process Applications Motive water steam (normally 6-12 barg)... 

Liquid aium can hydrolyze at pH above 3.5. Keep the motive water ratio at about 5 1 to prevent this. 

Motive water (or dilution water) is sometimes used to move the metered chemical to the point of application (Figure 2-3). Water pressure is often supplied from the treatment plant potable water system with proper backflow prevention (sometimes untreated water is also used). Advantages of motive water systems include shortened transport time and improved mixing. Disadvantages include possible changes in the chemical properties (caused by dilution) and added demand on the treatment plant service water system. 

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. 

Ferroelectric Ceramic—Polymer Composites. The motivation for the development of composite ferroelectric materials arose from the need for a combination of desirable properties that often caimot be obtained in single-phase materials. For example, in an electromechanical transducer, the piezoelectric sensitivity might be maximized and the density minimized to obtain a good acoustic matching with water, and the transducer made mechanically flexible to conform to a curved surface (see COMPOSITE MATERIALS, CERAMiC-MATRix). 

Furnaces of this type, such as the steam locomotive furnace—boHet design, had the obvious disadvantage that pressure was limited to ca 1 MPa (150 psi). The development of seamless, thick-waH tubing for stationary power plants (ie, water-tube furnaces) and other engines for motive power, such as diesel—electric, has in many cases ecHpsed the fire-tube boHet. For appHcations calling for moderate amounts of lower pressure steam, however, the modern fire-tube boHet continues to be the indicated choice (5). 

Steam-Jet Systems. Low pressure water vapor can be compressed by high pressure steam in a steam jet. In this way, a vacuum can be created over water with resultant evaporation and cooling water, therefore, serves as a refrigerant. This method frequently is used where moderate cooling (down to 2°C) is needed. The process is inefficient and usually is economically justified only when waste steam is available for the motive fluid in the steam jet. 

Residue Disposal. The major environmental problem in the Bayer process is disposal of bauxite residue which is effected by marine disposal, lagooning, use of underdrain lakes, or semidry disposal. Marine disposal in oceans or rivers, diluting the alkaline residue by large quantities of water, is environmentally unacceptable. Lagooning behind retaining dikes built around clay-sealed ground is commonly used, but there have been isolated leaks into aquifers. This has motivated installation of underdrains between the residue and clay-sealed, plastic-lined, lake bottom. This design removes the hydraulic head from the lake bottom and improves consoHdation of the residue. 

Bubble columns in series have been used to establish the same effective mix of plug-flow and back-mixing behavior required for Hquid-phase oxidation of cyclohexane, as obtained with staged reactors in series. WeU-mixed behavior has been established with both Hquid and air recycle. The choice of one bubble column reactor was motivated by the need to minimize sticky by-products that accumulated on the walls (93). Here, high air rate also increased conversion by eliminating reaction water from the reactor, thus illustrating that the choice of a reactor system need not always be based on compromise, and solutions to production and maintenance problems are complementary. Unlike the Hquid in most bubble columns, Hquid in this reactor was intentionally weU mixed. 

Ideally the historical record of stream water quaUty would extend back to a time when human activities in the drainage basin had no significant effects. This "pristine" condition had probably already passed in most U.S. rivers before any organized water quaUty studies were made, as concern about apparent stream pollution was commonly a motivating factor in starting such studies (see Water, pollution). 

When the range of chemieal types is restricted, regular behavior is often observed. For example, one might choose to study a series of hydroxylic solvents, thus holding approximately constant the H-bonding capabilities within the series. This is a motivation, also, for solvent studies in a series of binary mixed solvents, often an organic-aqueous mixture whose composition may be varied from pure water to pure organic. Mukerjee et al. defined a quantity H for hydroxylic and mixed hydroxyiic-water solvents by Eq. (8-17). 

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... 

In all cases it is important to describe the system, its requirements, control and method of operation in the specifications. The manufacturer needs complete data concerning the motive steam (air or water) and the condensable and non-condensable vapors. 

Although the problems associated with the corrosion and protection of jointed structures have been recognised since the early days of structural fabrication, they have taken on a special significance in the past 15 years. The motivation for the increased impetus is mainly one of concern over possible costly, hazardous or environmentally unfriendly failures particularly those concerned with offshore constructions, nuclear reactors, domestic water systems, food handling, waste disposal and the like. 

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