Centrifugal skimmers

Vortex or centrifugal skimmers use the difference in density between oil and water to separate them and then selectively remove most of the oil. A water whirlpool or vortex is created that draws the oil into a collection area where it is rotated in a centrifuge, using either the force of the water itself or an external power source. The oil is forced to the centre by the heavier water and pumped from the chamber. These skimmers are not used often, however, because they are susceptible to debris. They... 

Abstrahlung,/. reflection radiation. Abstrebekraft, /. centrifugal force. Abstreicheisen, n. scraper skimmer, abstreichen, jj.i, wipe or scrape off skim strike out deduct. 

The discontinuous or continuous addition of sulfuric acid to sodium chromate solution up to a pH of 3 is technically simple. The resulting solution of sodium dichromate dihydrate is then evaporated to 70% by weight, whereupon almost all the sodium sulfate precipitates out and is separated off. The dichromate solution obtained is in part utilized as such. Further evaporation to ca. 1600 g sodium dichromate/L and cooling to 30 to 40°C leads to crystallization of the dichromate. These processes are either carried out stepwise or continuously. Separation is carried out in a. skimmer or shear centrifuge. 

Imperforate basket centrifuges are vertical baskets that make up a relatively small portion of those sold. They are most often used to collect fine or amorphous solids, especially slimy or sticky ones. The solids are fed into the basket and those that are heavier than the liquid accumulate on the wall, much as they do in the tubular bowl. Because the diameter of the basket is at least an order of magnitude larger than that of the tubular bowl, there is usually space for a discharge mechanism inside the basket. Imperforate bowls often have two instruments a skimmer for liquids and a plow for solids. The clear, less dense liquid supernates... 

The Podbielniak and Alfa Laval centrifugal extractors are essentially continuous differential contactors. The Westfalia and Robatel centrifugal extractors contain discrete mechanical stages, and flow from one to another is effected by spill over discs and skimmers according to usual centrifugal clarifier practice. As the number of discrete stages is increased, the allowable flow rates are proportionately decreased. 

Alternative means for liquid discharge have been developed, largely from other centrifuge types, such as centripetal and skimmer pumps. Decanters have been fitted with discs to improve clarification performance, and sanitary performance has been improved by the development of clean-in-place (CIP) methods. 

There are a number of different discharge methods available that have been specifically developed to overcome certain problems. These include radial discs or plates, deep pond methods, skimmer discs and the use of air pressure. Discharge by nozzles located in the cylindrical part of the centrifuge is another method that has been tried. 

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