Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1997-03-24
1998-12-22
Reifsnyder, David A.
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
210774, 210781, 210787, 426 7, 426443, B01D 2126, C02F 166
Patent
active
058514058
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a novel process for clarifying vinasse. More specifically, the invention describes a process where dilute vinasse is clarified by means of a high-efficiency centrifuge. The vinasse is then concentrated and potassium is removed through the controlled crystallization of potassium salts and the separation of these crystals from the liquid.
BACKGROUND
Beet molasses and also beet juice are used as raw material in a wide range of fermentation industries in producing alcohol, yeast, citric acid, glutamic acid, lysine and many other fermentation products. When the primary product has been recovered from the fermentation broth, a dilute by-product broth remains. When this dilute by-product is concentrated, it is generally called "vinasse". The traditional uses of vinasse have been its disposal as waste to the environment (often without concentration), its use as a potassium fertilizer, and its use as an additive in cattle feed. Environmental restrictions have limited the former and consequently increased the use for the latter two purposes. The demand for these two purposes is limited, however, and a serious oversupply situation thus exists on the market. Therefore there is an increased interest in recovering valuable components from vinasse.
For example betaine can be recovered through chromatographic separation method as described in U.S. Pat. Nos. 4,359,430 and 5,127,957 (Heikkila et al.). Betaine can also be recovered by utilizing ion exchangers, which may be either cationic or anionic. Other components which can be recovered are glycerol, monosaccharides, amino acids and succinic acid. The recovery of glycerol and glucose, and the separation of amino acids is described in Burris, B. D., 1986: Recovery of Chemicals such as Glycerol, Dextrose, and Aminoacids from Dilute Broths, International Conference on Fuel Alcohols and Chemicals from Biomass, Miami Beach, Fla. European Patent Application 0,411,780 A2 (Kampen) discloses the recovery of, for example, glycerol, betaine and succinic acid.
The greatest problem with the known methods has been that the column processes such as the chromatographic separation and ion exchange necessitate the use of raw material which contains no substantial amounts of insoluble solids. The clarification of vinasse has been highly expensive and difficult. Vinasse pretreated with known methods is unstable and causes postprecipitation, whereupon the resin used in the column processes rapidly becomes dirty. Due to these problems, it has been in practice highly uneconomical and even impossible to perform the above-described column processes as long-term continuous processes.
For example after alcohol production through yeast fermentation, yeast has in some cases been separated and a part of it has been recirculated back to the fermentation stage, whereas a part has possibly been concentrated to dry yeast. However, the separation of yeast is not then efficient enough, but the fraction transferred to the distillation stage following the separation generally contains over 1% by volume of yeast. After the distillation stage and the concentration of dilute vinasse, the amount of yeast has increased to about 6 vol-%, while the amount of solid salts also increases to about 6 vol-%. Yeast is lighter than concentrated vinasse, whereas solid salts are heavier, whereupon they cannot be separated in a simple manner in one stage.
The process for recovering components from the by-product of fermentation described in European Patent Application 0,411,780 A2 (Kampen) also comprises a clarification step where the by-product obtained after fermentation and distillation is micro-filtered by using inorganic membranes having a pore size in the range of about 0.1 to 10 microns. Example 8 of the reference describes a process for clarifying beet stillage. The beet stillage is a by-product of the fermentation of sugar beet into ethanol, and it is clarified with a process where the stillage is subjected to cross-flow microfiltration utilizing inorganic alpha aluminium o
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Lindroos Mirja
Paananen Hannu
Viljava Tapio
Walliander Pertti
Cultor Oy
Reifsnyder David A.
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