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Topics: Gas, Water, Evaporation Pages: 3 (656 words) Published: August 24, 2013
HOLIDAYS HOMEWORK
Chemistry

PRESENTED TO: MISS SAIMA
BY: Fatima JEHANGIR
GRADE: 9(O)

METOHDS OF PURIFICATION & ANYLYSIS
Filtration
Filtration is a mechanical or physical process to separate solid particulates from fluids Filtration is a technique used to separate a solid from a liquid. The solid is separated from the liquid phase by passing the mixture over a filtering media. Filtering media is characterized by being chemically inert to the mixture, and having small pathways for the liquid to pass through, but these pathways should be smaller than the solid particle size. Filtering media can be prepared using paper, fritted-glass, or any porous material. The mixture can be forced through the filter by either gravity or reduced pressure on one side of the filter (by creating a vacuum). It is possible to separate a solid from a liquid by either technique; however there are advantages to each technique.
Crystallization
Crystallization is a significant development, which reduces the energy consumption in the polyester manufacturing process. It allows energy that is retained in the polyester melt to be utilized for the crystallization step. The direct crystallization process starts at the extrusion die, where the melt is formed into several strands of uniform thickness. Depending on the specific pelleting process applied, the strands will be maintained over a short distance and are partially cooled with water before being cut into pellets. The cooling water is maintained at a temperature of 60 to 95 °C. It is preferably separated from the pellets by a centrifugal dryer, with the pellets then being transferred to a crystallizer. In the crystallizer, he pellets are agitated by a fluidizing gas stream in order to prevent agglomeration. For a higher throughput rate, several pelleting systems may converge in a single crystallizer....
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