As part of the process of producing sugar crystals from sugar cane, raw sugar ca
ID: 725743 • Letter: A
Question
As part of the process of producing sugar crystals from sugar cane, raw sugar cane juice is sent to a series of evaporators to remove water. The sugar cane juice, which is 85wt% water, is fed to the first evaporator at 10,000 lb/h. The concentrated juice out of the last evaporator is 40wt% water. First examine a system with two evaporators. Calculate the water evaporated n each evaporator, assuming that the fraction of water in the feed removed in each evaporator is the same. Then, develop a linear model of a flow sheet with N evaporators, assuming that the fractional recovery of water fr,w is each evaporator is the same and that the concentrated juice coming out of the last evaporator still contains 40wt% water.Explanation / Answer
An evaporator is used in an air-conditioning system to allow a compressed cooling chemical, such as Freon or R-410A, to evaporate from liquid to gas while absorbing heat in the process.[1] It can also be used to remove water or other liquids from mixtures. The process of evaporation is widely used to concentrate foods and chemicals as well as salvage solvents. In the concentration process, the goal of evaporation is to vaporize most of the water from a solution which contains the desired product. In the case of desalination of sea water, the reverse purpose applies; evaporation removes the desirable drinking water from the undesired product, salt. One of the most important applications of evaporation is in the food and beverage industry. Foods or beverages that need to last for a considerable amount of time or need to have certain consistency, like coffee, go through an evaporation step during processing. In the pharmaceutical industry, the evaporation process is used to eliminate excess moisture, providing an easily-handled product and improving product stability. Preservation of long-term activity or stabilization of enzymes in laboratories are greatly assisted by the evaporation process. Another example of evaporation is in the recovery of sodium hydroxide in kraft pulping.[2] Cutting down waste-handling cost is another major reason for large companies to use evaporation applications. Legally, all producers of waste must dispose of waste using methods compatible with environmental guidelines; these methods are costly. By removing moisture through vaporization, industry can greatly reduce the amount of waste product that must be processed.
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