Recovery ethanol

Fig. 42. Integrated distillation/pervaporation plant for ethanol recovery from fermentors. The distillation columns concentrate the ethanol—water mixture from 5 to 80%. The pervaporation membrane produces a 99.5% ethanol product stream and a 40—50% ethanol stream that is sent back to the distillation...

In this process the addition of water vapor to the sweep stream can be controlled so that the water activity of the gas phase equals that of the beverage. When this occurs, there is no transport of water across the membrane. The water content of both the beverage feed and the sweep stream is kept constant. These conditions must be maintained for optimum alcohol reduction. The pervaporation system controls the feed, membrane, airstream moisture level, and ethanol recovery functions. An operational system has been developed (13). 

The crude product is best purified by sublimation under reduced pressure (100-110°/1 mm.) (recovery 90-95%). Purification can also be effected by recrystallization from acetone (recovery 80-90%), ethyl acetate (recovery 70-80%), or ethanol (recovery 60-70%). The purified 4-methyl-6-hydroxypyrimidine melts at 148-149°. 

Figure 9.10 Integrated distillation-pervaporation plant for ethanol recovery from fermentors...

Anhydrous ethanol recovery from wastewater streams 190 Azeotrope problem ... 

On the basis of the above analysis several alternatives with two or three columns can be imagined. Figure 3.22 depicts only the alternative with two columns, the first for ethanol recovery, while the second is for water removal. This flowsheet accepts relatively concentrated solutions. When diluted solutions are treated the enrichment could be done separately, and hence the flowsheet will contain a maximum of three columns. However, the initial diluted feed may be sent to the water column. In consequence, only two columns are necessary. 

The second distillation column has 30 trays, with the feed on tray 15. It delivers 26 730kg/h distillate where the concentration of ethanol is 92.5% (weight). The reflux ratio is 2. The distillate is free of furfural, the ethanol recovery being 99.5%. The bottoms are mixed with the bottoms of the first column and sent to water purification. 

There are continuing efforts to develop cost-effective processes for fuel alcohol production, although the economics are often dependent on the availability of subsidized feedstocks to compete with traditional fuels derived from oil. The pretreatment and fermentation of such feedstocks, derived from corn, sugar cane, and even municipal waste, yields a dilute aqueous solution of ethanol which must be separated from a complex mixture of waste materials and then concentrated by distillation to remove water. Both batch and continuous production processes have been developed, with the requirement for effective bioseparations during both the pretreatment and ethanol recovery parts of the process. 

ETBE is recovered as the bottoms product of the distillation unit. The ethanol-rich C4 distillate is sent to the ethanol recovery section. Water is used to extract excess ethanol and recycle it back to process. At the top of the ethanol/water separation column, an ethanol/water azeotrope is recycled to the reactor section. The isobutene-depleted C4 stream may be sent to a raffinate stripper or to a molsieve-based unit to remove oxygenates such as DEE, ETBE, ethanol and tert-butanol. 

Reducing ethylene glycol in the water product to a significantly lower value requires only the addition of one or more rectifying trays in the recovery column. An increase in the reflux-feed ratio will do as an alternate method, but to change the ethanol in the water product, the extractive distillation column would have to be operated for higher or lower ethanol recovery than the 99.99% m value. This can be done without difficulty. 

Water 16 ppm (mole basis) Solvent 1.2 ppm (mole basis) Ethanol recovery from feed — 99.99%... 

For the extractive distillation results of Tables V and VI, the reboiler load for the above ethanol rate would be about 20.9 million Btu per hour. The ethanol product contains about 16 ppm of water and about 1.2 ppm of ethylene glycol. For an ethanol recovery of 99.99% ra, 46 total equilibrium trays are required with a reflux-feed ratio of 1.55+ and a solvent-ethanol ratio of 4.09" mole basis. The condenser load is about 13.1 million Btu/hour, and the tower diameter is about 5.3 feet, based on a Glitsch sizing technique. 

Tawfik, W.V., Optimization of Fuel Grade Ethanol Recovery System Using Solvent Extraction, PhD Thesis, Georgia Institute of Technology, Atlanta, GA, 1986. 

Some recent developments in membrane processes for the separation of organic liquids have been previously noted, as has the use of hyperfiltration as applied in ethanol recovery. Filtration per se is of relevance in the processing of nonpasteurized beers, for example in the separation of spent yeasts after fermentation. 

Ethanol recovery from fermentation broth by pervaporation... 

Wu Y, Huang W, Xiao Z, and Zhang Y. Ethanol recovery from fermentation broth by pervaporation using a composite polydimethy-lesiloxane membrane. Chinese J. Chem. Engg. 2004 12(4) 586-589. 

Devrajan, A., Joshi, V. K., Gupta, K., Sheikher, C., and Lai, B. B. (2004). Evaluation of apple pomace based reconstituted feed in rats after solid state fermentation and ethanol recovery. Braz. Arch. Biol. Technol. 47, 93-106. 

An organic chemistry professor performed a flash distillation experiment in a laboratory for his students. A 10-kgmol/h liquid feed mixture consisted of 20 mol % ethanol and 80 mol % water at 1 atm. While the professor was able to determine that 30 mol % of the feed vaporized at 70°F, he lacked the necessary equipment to measure the liquid and vapor compositions of the more volatile component, ethanol. Determine the liquid and vapor compositions, as well as the percent ethanol recovery from the flash. Equilibrium data for the ethanol-water system at 1 atm are provided in MTO.l. 

Processes for the bioproduction of ethanol from cellulosic materials have been studied extensively. Some of the process steps are specialized and beyond the scope of this chapter. However, there are many recent review articles dealing with some specific subjects. Basically, the processes consist of a number of steps. They are availability and collection of raw feedstock [20], size reduction, pretreatment, fractionation of biomass components, enzyme production [21, 22], saccharification, enzyme recycle [23, 24], pentose fermentation, improvement of pentose-fermenting biocatalyst, overcoming of product inhibition, overcoming inhibition by substrate-derived inhibitors, ethanol recovery [25], steam generation and recycling [26], waste treatment, and by-product utilization. 

Black, C., "Distillation Modelling of Ethanol Recovery and Dehydration Processes for Ethanol and Gasohol," Chem. Eng. 

Typical mixtures that can be separated by a process such as this include mixtures of close-boiling aromatics and paraffins using ethanol or methanol as entrainers. The aromatics such as toluene form the higher-boiling azeotrope while the alcohol and the paraffins form the lower-boiling azeotrope. Water is used to remove the alcohol from the azeotropes by extraction. Finally, the alcohol must be separated from the water and recycled. From this standpoint, methanol is preferred over ethanol because the latter forms an azeotrope with water, thus complicating the ethanol recovery. 

If the highest absorbent rate considered is the maximum available but does not meet the required ethanol recovery, what design option(s) would you recommend to meet the specification Support your recommendation with additional calculations. 

T.C. Bowen, L. M. Vane, Ethanol recovery by pervaporation through zeolite, zeolite filled polymeric membranes, US Envir. Protection Agency-National risk Management Research Lab-EPA research bull.. 

---