Deaerators process chemicals

While the ambient-temperature operation of membrane processes reduces scaling, membranes are much more susceptible not only to minute amounts of scaling or even dirt, but also to the presence of certain salts and other compounds that reduce their ability to separate salt from water. To reduce corrosion, scaling, and other problems, the water to be desalted is pretreated. The pretreatment consists of filtration, and may include removal of air (deaeration), removal of CO2 (decarbonation), and selective removal of scale-forming salts (softening). It also includes the addition of chemicals that allow operation without scale deposition, or which retard scale deposition or cause the precipitation of scale which does not adhere to soHd surfaces, and that prevent foam formation during the desalination process. 

The pre-boiler, FW supply should normally be of demineralized quality, such as may be provided by ion exchange, reverse osmosis (RO), or similar process. Extremely efficient mechanical deaeration also is required because the path length from the FW tank to the boiler is usually quite short, and thus the contact time is generally inadequate for the sole use of chemical oxygen scavengers (even catalyzed scavengers). 

The mechanical deaeration oxygen removal process is not 100% efficient, however, and all boiler FW must be further deoxygenated by some form of chemical oxygen scavenger. 

All large industrial WT and power boiler plants utilize deaerators and supplement the DO removal process by means of a suitable chemical oxygen scavenger. Many midsize factories operating FT boilers or FT-WT boiler combinations also employ mechanical deaeration. This is especially common in the United States, Germany, and several other industrialized countries where boiler design custom and practice virtually dictate that a deaerator be included in almost every midsize and larger boiler plant facility. 

Although considerable studies on the use of centrifugal fields in chemical processing have been reported for lab- and pilot-scale operations, little information is public on scale-up criteria for either performance parameters or equipment design. Three examples of commercial use of centrifugal fields are available for review. These include liquid-liquid extraction, water deaeration, and reactive stripping for hypochlorous acid production. 

A more remarkable elongation of the CS lifetime was attained by complex formation of yttrium triflate [Y(OTf)3] with the CS state in photoinduced ET of a ferrocene-anthraquinone (Ec AQ) dyad (53). Photoexcitation of the AQ moiety in Ec AQ in deaerated PhCN with femtosecond (150 fs width) laser light results in appearance of the absorption bands 420 and 600 run at 500 fs, as shown in Eig. 14(a) (53). The absorption bands 420 and 600 nm, which are assigned to AQ by comparison with the absorption spectrum of AQ produced by the chemical reduction of AQ with naphthalene radical anion (53). The decay process obeys first-order kinetics with the lifetime of 12 ps [Eig. um. 

Will not cause defoamer spots Completely volatile at drying temperature Effective deaerater in processing baths Compatible with all chemicals... 

Much has been reported about the HiGee concept in the chemicals and offshore processing sectors, but its use in the food and drink industries has been less evident. Already referred to in Chapters 8 and 9 in the context of oil and gas processing and the chemicals sector, the use of rotating packed beds of the type described in Chapter 6 has been extended to other application areas by GasTran Systems (see Appendix 4) including deaeration of beverages. 

Within the conventional inline process unit, drums and their related items are generally located on either side of a central pipe rack serviced by auxiliary roads for maintenance access. In certain cases (e.g., for flash drums and deaerators), drums can be located above the pipe rack. In chemical plants, drums are generally located at all levels of enclosed or open-sided structures. For eixample, Exhibit 5-4 shows the drum location in a tower reflux system. Exhibit 5-5 shows the typical location of feed surge and compressor suaion drums, and Exhibit 5-6 shows the drum locations in an enclosed chemical plant stnicture. 

RDAs also act in synergy with other chemical additives such as deaerators, which boosts the overall performance of other wet-end chemicals and reduces their consumption. With improved retention as well as with the fixation of colloidal dissolved substances much cleaner white-water is obtained with a COD reduction and over all less deposits are achieved. Consequently a higher degree of process water closure, less volume of waste water and an improved PM runnabihty can be obtained. The waste water is also more easily treated. 

---