Ethanol Is A Widely Used Commodity Chemical With Several Applications

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Ethanol is a widely used commodity chemical chem ical with several applications, including use as a solvent and as a gasoline blendstock in the fuel market. Globally, the major portion of ethanol  production is based on the fermentation of sugars from crop feedstocks, such as sugarcane, corn, cellulosic material and others. World fuel ethanol production is about 85 billion liters annually, with !" resulting from corn ethanol production in the #.$., and another %5" from sugarcane ethanol production in &ra'il. (n view of current environmental issues, including greenhouse gas emissions, fermentation)based ethanol is considered an alternative to fossil fuels since it originates from renewable resources. Technology Description Ethanol from sugarcane is traditionally produced by yeast fermentation of sugarcane molasses. *ommonly, *ommonly, raw sugar is obtained as a co)product, through crystalli'ation of sugarcane raw juice. +he major process steps in sugarcane ethanol production are as follows Milling $ugarcane is delivered from the field to the factory, factory, where it is weighed, cut and shredded before  being conducted to the mills, where the raw cane juice is e-tracted. $ugarcane bagasse is obtained as a residue, and it is burned to generate steam and electricity to supply process demands. Juice Treatment +he raw cane juice is clarified by treatment with phosphate and lime leading to mud formation, which is separated in a clarifier. +he clarifi ed juice is then concentrated under vacuum in a multiple)effect evaporator, forming a sugar syrup. Sugar Crystallization $ugar crystalli'ation is accomplished in two vacuum calandrias, where water is evaporated from the syrup and crystalli'ation is induced by the addition of a seeding solution. +his process forms a massecuite, a mi-ture of liuor and sugar crystals. /e-t, crystalli'ation is completed by cooling in a crystalli'er. +he raw sugar is centrifuged, dried and sent to storage. (n a third calandria) crystalli'er set, a massecuite is formed that will become the seeding solution to b e used at crystalli'ation, and also the molasses for subseuent fermentation. Fermentation +he sugars contained in the molasses are fermented to ethanol by yeast. Gases released from the fermentation are washed with recycle water in a gas)washing column. +he fi nal broth is centrifuged, and the yeast cells are treated with sulfuric acid and recycled to the first fermenter. 0eanwhile, the ethanol)containing wine is sent to a distillation apparatus. Distillation +he ethanol solution is heated and fed to the concentration column. +he overhead of this column is sent to the gas)washing column and the vapor)side product stream, containing about 5!" ethanol, is fed to a rectifying column that generates a 1!" ethanol vapor stream and recycle water, which goes to the gas)washing column. +he ethanol product stream undergoes dehydration in a molecular sieve unit, leading to a product that is 11.5" pure ethanol. Economic Performance 2n economic evaluation of the process was conducted based on data from the fourth uarter of %!3% 4chart. +he following assumptions were taken into consideration  2  million)ton6yr sugarcane processing unit producing %7! million of anhydrous ethanol and %!,!!! ton of raw sugar per year built in &ra'il 4the process euipment is represented in the simplified flowsheet  +he unit operates %3! d6yr   $torage capacity eual to 9! days of operation for sugar and ethanol  $ugarcane cultivation and harvesting costs were not considered  +he electricity surplus generated in the plant is sold to the electric grid +he estimated capital investment 4including total fi-ed investment, working capital and other capital e-penses is about :7! million. +he process reported here allows sugarcane ethanol manufacturers to balance ethanol and sugar  production yields according to demand, rendering the activity fle-ible to market fluctuations. &ra'il is the main sugarcane ethanol producer and e-perienced, in the first semester of %!39, a 7" increase in fuel ethanol consumption when compared to the same period of %!3%.