WO2008132281A1

WO2008132281A1 - Method and apparatus for preparing a mixture of ethanol and water by fermentation of fermentable raw material

Info

Publication number: WO2008132281A1
Application number: PCT/FI2008/050226
Authority: WO
Inventors: Antti Pasanen; Mikko Ahokas
Original assignee: St1 Biofuels Oy
Priority date: 2007-04-25
Filing date: 2008-04-25
Publication date: 2008-11-06
Also published as: FI20075288A0

Abstract

The invention relates to a method and an apparatus for preparing a mixture of ethanol and water by fermentation of fermentable raw material. The apparatus comprises a fermentation vessel (3), a separator unit (5) for separating solid matter from a stream of fermentation mixture (4), an evaporator unit (7) for separating an evaporated top stream (8) containing mixture of ethanol and water from said stream of fermentation mixture (4), a chemical extraction unit (12) for mixing a stream of condensed mixture of ethanol and water (10) together with an extractant (13) to form mixture of ethanol and water and extractant, and for allowing said mixture to settle to form a fraction containing extractant and enriched mixture of ethanol and water, and a stripping unit (16) for separating a stream of enriched mixture of ethanol and water (17) from said stream of extractant and enriched mixture of ethanol and water (14).

Description

Method and apparatus for preparing a mixture of ethanol and water by fermentation of fermentable raw material

Field of the invention

The invention relates to a method for preparing a mixture of ethanol and water by fermentation of fermentable raw material as defined in the preamble of independent claim 1.

The invention also relates to an apparatus for preparing a mixture of ethanol and water by fermentation of fermentable raw material as defined in the preamble of independent claim 17.

In modern societies, more and more efficient methods for treating waste and waste water are required of operations that produce waste and waste water. Waste waters and waste produced by industry and communities and containing various fermentable sugars or compounds capable of being converted into fermentable sugars can be treated by using them as ethanol, which reduces the BOD and COD loads contained in the waste waters of industry and communities, and reduces the amount of carbohydrates in waste. Ethanol prepared from waste and waste waters can be refined to suite various uses.

The problem is that the waste and minor flows suited for preparing ethanol often are dispersed, whereby their transportation and costs associated with transportation create an obstacle to economical operations. Furthermore, there is an estimate that it is too expensive to invest in known processes for preparing ethanol from dispersed small flows with an output rate of 200 - 2,000 tons of ethanol/year.

The known industrially applied preparation processes of ethanol that are based on fermentation are relatively big in capacity, about 10,000 - 150,000 tons of ethanol/year. A part of the plants is based on batch fermentation and an ever increasing part in continuous fermentation. Fermented ethanol can be distilled to be e.g. 95 percent by weight or to be a thinner ethanol/water mixture using a distillation apparatus. A distillation apparatus usually comprises stripping which is used to separate the mash from the ethanol/water mixture. Distillation is usually a one or multi-stage batch or continuous distillation. Evaporated distillate can be liquefied using condensers.

WO 2006/125854 discloses a method and an apparatus for preparing a mixture of ethanol and water and an apparatus for preparing a mixture of ethanol and water by fermentation of fermentable raw material. This method and apparatus is suitable for local production of mixture of ethanol and water (containing for example 85% ethanol) by fermentation of fermentable raw materials at the site on which the fermentable raw materials are produced for example as a byproduct or waste at a industrial plant for producing food products.

JP 63094966 A discloses a method for concentration and recovery of fermentation alcohol. In this method is fermentation liquid is transferred from a fermentation tank filled with immobilized microorganisms (e.g. Saccharomyces cerevisiae) through a line to an evaporator and the vapor heated and evaporated in the evaporator is sent through a line to a condenser and condensed to obtain an aqueous solution of alcohol having an alcohol concentration of 15 to 40 wt%. The concentrated solution is pressurized with a pump of a line and supplied to the top of a high-pressure extraction column. An extractant (e.g. carbon dioxide) is introduced into the extraction column through a line to effect the extraction of ethanol. The objective concentrated liquid having an alcohol concentration of preferably 85 to 95wt% is obtained from a line.

JP 59078677 A presents a method for preparing an anhydrous lower alcohol. A dilute aqueous solution of lower alcohol is concentrated into 10-80wt% alcohol concentration by an preconcentation device, the prepared concentrated solution is brought into contact with an organic solvent such as an organic acid, alcohol, ketone, etc. by an extractor, extracted, separated into an extracted solution and the extraction residue by an separator, the extraction residue is returned to the preconcentration device, the extracted solution is optionally introduced to a water reducing device, treated with a dehydrating agent, etc., its water content is reduced, the extracted solution is sent to the an azeotropic separator, separated by an azeotropic constitution consisting of a low-boiling solvent, water, and a lower alcohol with the low- boiling solvent in the extraction solvent, it is returend to the extractor, the azeotropic residue is separated into an anhydrous lower alcohol and the remaining solvent, and the remaining solvent is returned to the extractor. JP 200303047953 A presents a method for recovery of solvent from waste water containing solvent involves separating solvent by steam stripping, condensing resulting steam containing solvent, and extracting solvent followed by dehydrating and recycling. Wastewater containing a solvent is caused to pass through the step of separating the solvent from the wastewater by steam stripping, the step of condensing a vapor containing the separated solvent and subjecting the solvent to a liquid-liquid extraction, and the step of dewatering the extractant used in the former step and then recirculating and reusing the extractant.

Objective of the invention The object of the invention is to provide a new and inventive method and apparatus for preparing a mixture of ethanol and water from suitable fermentable raw material, which method and apparatus is more energy effective than the method and apparatus disclosed in the publication WO 2006/125854.

Short description of the invention

The method of the invention is characterized by the definitions of independent claim 1. Preferred embodiments of the method are defined in the dependent claims 2 to 15. The apparatus of the invention is correspondingly characterized by the definitions of independent claim 17.

Preferred embodiments of the method are defined in the dependent claims 18 to 37. The invention is based partly on the use of a chemical extraction unit in combination with an evaporator unit. A chemical extraction unit uses less energy than an evaporator unit.

In the method is a separator unit used and the apparatus includes a separator unit, which is arranged between the fermentation vessel and the evaporator unit and in which solid matter- containing sludge is separated from the fermentation mixture fed from the fermentation vessel prior to feeding the fermentation mixture into the evaporator unit . In the separator unit is the stream of fermentation mixture coming from the fermentation vessel preferably, but not necessarily, divided into a stream of solid matter containing sludge and into a stream of liquid fermentation mixture i.e. into a stream of fermentation liquid.

Arranging a separator between the fermentation vessel and the evaporator unit makes it possible to feed and process fermentation mixture from the fermentation vessel being in other forms than liquid fermentation mixture or fermentation liquid which is the situation in the method presented in JP 63094966 A. Arranging a separator between the fermentation vessel and the evaporator unit makes it possible to use ordinary micro-organisms such as ordinary yeast in the fermentation vessel and not only immobilized micro -organisms (e.g. Saccharomyces cerevisiae) as is the situation in the method presented in JP 63094966 A, because micro-organisms exiting the fermentation vessel together with the fermentation mixture, which is discharged from the fermentation vessel, can be separated from the fermentation mixture in the separator unit as a part of said solid matter containing sludge and consequently be fed back into the fermentation vessel for further use or reuse.

Arranging a separator between the fermentation vessel and the evaporator unit makes it possible to use a greater variety of fermentable raw materials in the fermentation vessel and to use non-homogenous fermentable raw materials in the fermentation vessel. In the invention the fermentation mixture to be fed out of the fermentation vessel does not have to be in the form of fermentation liquid, because the fermentation mixture can contain particles of solid matter which is after the fermentation vessel removed from the fermentation mixture by means of the separator.

In a preferred embodiment of the invention the solid matter-containing sludge which is removed from the fermentation mixture by means of the separator is recirculated into the fermentation vessel. The solid matter containing sludge contains among others ethanol-producing microbes and sugars, which can be fed back into the fermentation vessel and re-used in the fermentation vessel to raise the level of ethanol-producing microbes and sugars in the fermentation vessel and to give the ethanol-producing microbes and the sugars, which otherwise would be removed from the process, more time to produce ethanol in the fermentation vessel. Due to the lack of a separator in the solution presented in JP 63094966 A, solid matter containing sludge and ethanol-producing microbes and sugars possible exiting the fermentation vessel together with the fermentation liquid cannot be fed back into the fermentation vessel for re-use.

Arranging a separator between the fermentation vessel and the evaporator unit and recirculating solid matter-containing sludge also reduces the volume waste liquids produced by the system in comparison to the solution presented in JP 63094966 A, because waste liquids present in the solid matter-containing sludge separated from the fermentation mixture in the separator can in this preferred embodiment of the invention be re-circulated in the system by feeding said waste liquids together with solid matter-containing sludge back from the separator to the fermentation vessel.

In a preferred embodiment of the invention the stream of fermentation mixture is centrifuged to divide the fermentation mixture into a stream of liquid fermentation mixture and a stream of solid matter containing sludge.

In a preferred embodiment of the invention all the solid matter-containing sludge which is removed from the fermentation mixture by means of the separator is directly as such without further processing recirculated into the fermentation vessel. In a preferred embodiment the evaporator unit comprises a falling film evaporator.

By using a falling film evaporator as an evaporator allows evaporation of the fermentation mixture at a low pressure and at a low temperature. Using of low pressure and temperature does not kill the ethanol producing microbe in the fermentation mixture. In this preferred embodiment, the evaporation of the fermentation mixture is performed in a falling film evaporator at a low pressure and at a low temperature, whereby the ethanol-producing microbe possible present in the fermentation mixture to be fed into the evaporator unit does not die in the conditions of the evaporator and a residual bottom stream produced by the evaporator unit, which residual bottom stream can contain among others ethanol-producing microbes and sugars, can be fed back to the fermentation vessel for re-use of the ethanol-producing microbes and sugars in the process. For example, evaporation using falling film evaporators at a low pressure of about 80 to about 100 mbar , for example 90 mbar enables an evaporation in a temperature of about 38 to 40 ⁰C, for example 39°C. In that case, e.g. yeast does not die in the conditions of the evaporator unit and the yeast can be returned to the fermentation vessel for re -use. If the ethanol producing microbe is separated prior to evaporation or if the ethanol-producing microbe is attached to a carrier in the fermentation vessel, i.e. immobilized, then the evaporation can be performed at atmospheric pressure, which makes the process simpler.

In a preferred embodiment of the invention the residual bottom stream, which is discharged from the evaporator unit, is recirculated in the process and is fed into the fermentation vessel. The residual bottom stream contains among others ethanol-producing microbes and sugars, which can be re-used in the fermentation vessel to raise the level of ethanol-producing microbes and sugars in the fermentation vessel and to give the ethanol-producing microbes and the sugars, which otherwise would be removed from the process, more time to produce ethanol in the fermentation vessel. Recirculating the residual bottom stream from the evaporator unit back to the fermentation vessel also reduces the volume of waste liquid such as waste water produced in comparison to the prior art solutions such as in the solution presented in JP 63094966 A, because instead of simply removing waste liquid from the system, waste liquid in the form of said residual bottom stream can be re-circulated the system in this preferred embodiment of the invention. Prior art solutions such as the solution presented in JP 63094966 A produces large amounts of waste liquids such as waste water, due to the lack of a corresponding possibility for recirculation of waste water such as the residual bottom stream obtained from the evaporator used in the solution presented in JP 63094966 A.

In a preferred embodiment of the invention all the residual bottom stream, which is discharged from the evaporator unit, is directly as such without further processing fed into the fermentation vessel.

In a preferred embodiment the extraction can be performed by liquid-liquid extraction. Usable solvents in the extraction are e.g. tertiary alkylphosphines. In a preferred embodiment the extractant in the extraction unit contains preferably Trioctylphosphine Oxide, Dioctylmonohexylphosphine Oxide, Diliexylmonooctlyphosphine Oxide, Trihexylphosphine Oxide and/or mixtures thereof. In one embodiment of the invention the extractant contains preferably 10 to 20 % Trioctylphosphine Oxide, 30 to 50 % Dioctylmonohexylphosphine Oxide, and 20 to 30 % Dioctylmonohexylphosphine Oxide. The extractant in the extraction unit contains more preferably 12 to 16 % Trioctylphosphine Oxide, 40 to 44 % Dioctylmonohexylphosphine Oxide, and 28 to 32 %. Dioctylmonohexylphosphine Oxide. The extractant in the extraction unit is preferably CYANEX®923 extractant, producer Cytec Industries Inc. In a preferred embodiment the extractant is recirculated from the stripping unit and fed into the extraction unit for re-use in the extraction process in the extraction unit.

The ratio of extractant to mixture of ethanol and water in the extraction unit can be vary between 1 volume unit extractant to 10 volume units of mixture of ethanol and water and 10 volumes unit extractant to 1 volume units of mixture of ethanol and water. It is obvious for a person skilled in the art that the method can be a continuous process or a batch type process and/or that said apparatus can be configured to perform a continuous process or a batch type process.

In the method is fermentation mixture preferably, but not necessarily, continuously from the fermentation vessel into the separator unit. Correspondingly, the apparatus is preferably, but not necessarily, configured to continuously feed fermentation mixture from the fermentation vessel into the separator unit

In the method is fermentation mixture preferably, but not necessarily, continuously from the separator unit into the evaporator unit. Correspondingly, the apparatus is preferably, but not necessarily, configured to continuously feed fermentation mixture from the separator unit into the evaporator unit.

In the method is solid matter containing sludge which contains among others ethanol- producing microbes and sugars and which is separated in the separator unit from the fermentation mixture preferably, but not necessarily, continuously fed from the separator unit into the fermentation vessel. Correspondingly, the apparatus is preferably, but not necessarily, configured to continuously feed solid matter containing sludge, which is separated in the separator unit from the fermentation mixture, from the separator unit into the fermentation vessel.

In the method is said residual bottom stream preferably, but not necessarily, continuously fed from the evaporator unit into the fermentation vessel. Correspondingly, the apparatus is preferably, but not necessarily, configured to continuously feed residual bottom stream from the evaporator unit into the fermentation vessel.

In the method is said evaporated top stream preferably, but not necessarily, continuously fed from the evaporator unit in the form a stream of condensed mixture of ethanol and water into said chemical extraction unit. Correspondingly, the apparatus is preferably, but not necessarily, configured to continuously feed evaporated top stream from the evaporator unit into said chemical extraction unit in the form a stream of condensed mixture of ethanol and water.

List of figures

In the following the invention will described in more detail by referring to the figure, which shows a flow sheet of preferred embodiment of the invention.

Detailed description of the invention The figure shows an example of a method and an apparatus according to the invention for preparing a mixture of ethanol and water by fermentation of fermentable raw materials 1.

Next the method will be described in more detail by referring to the figure. The method comprises a step in which fermentable raw materials 1 and necessarily auxiliary substances 2 are fed into a fermentation vessel 3. The fermentable raw materials 1 are preferably, but not necessarily, selected from sugars and raw materials capable of being hydrolyzed into fermentable sugars. The necessarily auxiliary substances 2 includes preferably, but not necessarily, air, microbes which are able to form ethanol and required nutrients for microbes, like a source of carbon and nitrogen, salts and substances for pH adjusting. The method comprises a step for forming a fermentation mixture 4 in the fermentation vessel 3 using said fermentable raw materials 1 and said necessarily auxiliary substances 2.

The method comprises a step for discharging a stream of fermentation mixture 4 from the fermentation vessel 3. The method comprises preferably, but not necessarily, a step for removing non- fermented matter 40 from the fermentation vessel 3.

The method comprises a step for feeding said fermentation mixture 4 into a separator unit 5 for separating solid matter containing sludge 6 from said stream of fermentation mixture 4. The separation can be performed by centrifugation, filtering or sedimentation in a separator unit 5 to separate solid matter containing sludge 6 from said stream of fermentation mixture 4. Said step for separating solid matter containing sludge 6 from said stream of fermentation mixture 7 is preferably, but not necessarily, in the form of a step for feeding said fermentation mixture 4 into a separator unit 5 for dividing said stream of fermentation mixture 4 into a stream of liquid fermentation mixture 4 i.e. into a stream of fermentation liquid and into a stream of solid matter containing sludge 6.

The fermentation mixture 4 is preferably, but not necessarily, centrifuged in the separator unit 5 to separate solid matter containing sludge 6 from said stream of fermentation mixture 4.

The method comprises a step for discharging said stream of fermentation mixture 4 from the separator unit 5.

The method comprises a step for discharging a stream of solid matter containing sludge 6 from the separator unit 5. Said stream of solid matter containing sludge 6 is preferably, but not necessarily, recirculated in the method from the separator unit 5 and fed into the fermentation vessel 3 . In a preferred embodiment of the invention all the solid matter- containing sludge 6 which is removed from the fermentation mixture 4 by means of the separator unit 5 is directly as such without further processing recirculated into the fermentation vessel 3. Alternatively or in addition said stream of solid matter containing sludge 6 or a part of it can be removed from the process. Removal of solid matter containing sludge is marked with reference numeral 41.

The method comprises a step for feeding said stream of fermentation mixture 4 into an evaporator unit 7. In the figure, said stream of fermentation mixture 4 is directly fed into the evaporator unit 7 from the separator unit 5. The method comprises a step for evaporating said stream of fermentation mixture 4 in the evaporator unit 7 and separating by evaporation said stream of fermentation mixture 4 in the evaporator unit 7 into an evaporated top stream 8 of ethanol and water and a residual bottom stream 9.

In the method is preferably, but not necessary, a falling film evaporator used in the evaporator unit 7 and said fermentation mixture 4 is evaporated in a falling film evaporator.

The method comprises a step for discharging said evaporated top stream 8 of ethanol and water from the evaporator unit 7.

The method comprises a step for condensing said evaporated top stream 8 of ethanol and water to form a stream of condensed mixture of ethanol and water 10. Said evaporated top stream 8 of ethanol and water to form a stream of is preferably, but not necessarily, condensed to a stream of condensed mixture of ethanol and water 10 in a condenser 11. The method comprises a step for discharging said residual bottom stream 9 from the evaporator unit 7. Said residual bottom stream 9 is preferably, but not necessarily, recirculated in the method from the evaporator unit 7 and fed into the fermentation vessel 3 as shown in the figure. In a preferred embodiment of the invention all the residual bottom stream 9, which is discharged from the evaporator unit 7, is directly as such without further processing fed into the fermentation vessel 3.

The method comprises a step for feeding said stream of condensed mixture of ethanol and water 10 into a chemical extraction unit 12. In the figure, said stream of condensed mixture of ethanol and water 10 is directly fed from the evaporator unit 7 to the chemical extraction unit 12. The extraction of said stream of condensed mixture of ethanol and water 10 can be performed in several steps, in other words, it is possible that the chemical extraction unit 12 comprises several sub-units (not shown in the figures) for chemical extraction of said stream of condensed mixture of ethanol and water 10.

The method comprises a step for mixing said stream of condensed mixture of ethanol and water 10 together with an extractant 13 in the chemical extraction unit 12 to form mixture of ethanol and water and extractant.The extraction can be performed by liquid-liquid extraction. Usable solvents or extractants 13 in the extraction are e.g. tertiary alkylphosphines.

In one embodiment of the invention, tertiary alkylphoshines are selected from the group of Trioctylphosphine Oxide, Dioctylmonohexylphosphine Oxide, Dihexylmonooctylphosphine oxide, Trihexylphosphine Oxide and mixtures thereof.

In one embodiment of the invention the mixture of the extractants 13 c an contain preferably 10 to 20 % Trioctylphosphine Oxide, 30 to 50 % Dioctylmonohexylphosphine Oxide, and 20 to 30 % Dioctylmonohexylphosphine Oxide.

The extract in the extraction unit 12 is preferably Cyanex®923 extractant (producer Cytec Industries Inc.) containing 12 to 16 % Trioctylphosphine Oxide, 40 to 44 % Dioctylmonohexylphosphine Oxide, and 28 to 32 % Dioctylmonohexylphosphine Oxide.

The ratio of extractant to mixture of ethanol and water in the extraction unit can be vary between 1 volume unit extractant to 10 volume units of mixture of ethanol and water and 10 volumes unit extractant to 1 volume units of mixture of ethanol and water.

The method comprises a step for allowing said mixture of ethanol and water and extractant to settle in the chemical extraction unit 12 to form two fractions (not shown in the figures) in the chemical extraction unit 12; a first fraction containing extractant and enriched mixture of ethanol and water (not shown in the figure) i.e. a concentrated ethanol mixture and a second fraction containing water 15.

The method comprises a step for discharging a stream mixture of extractant and enriched mixture of ethanol and water 14 from said chemical extraction unit 12, more precisely from said first fraction containing extractant and enriched mixture of ethanol and water 14 in said chemical extraction unit 12.

In the method according to the invention can said a stream of condensed mixture of ethanol and water 10 be continuously fed into the chemical extraction unit 12. Correspondingly can in the method according to the invention a stream of extractant and enriched mixture of ethanol and water 14 be continuously be discharged from said chemical exctraction unit, more precisely, from said first fraction containing extractant and enriched mixture of ethanol and water 14 from the chemical extraction unit 12.

In the method according to the invention it is alternatively possible to feed said condensed mixture of ethanol and water 10 into a chemical extraction unit 12 in batches. Correspondingly it is possible in the method according to the invention to discharge a stream of extractant and enriched mixture of ethanol and water 14 from said chemical exctraction unit, more precisely from said first fraction containing extractant and enriched mixture of ethanol and water from the chemical extraction unit 12 in batches.

In the method shown in the figure is also water 15 removed from the second fraction the extraction unit 12. The method comprises a step for feeding said stream of extractant and enriched mixture of ethanol and water 14 into a stripping unit 16.

The method comprises a step for separating said stream of extractant and enriched mixture of ethanol and water 14 in the stripping unit 16 into a stream of enriched mixture of ethanol and water 17 and a stream containing extractant 18. In the method according to the invention can a second falling film evaporator (not shown in the figure) be used in the stripping unit 16 and said stream of extractant and enriched mixture of ethanol and water 14 is evaporated in said second falling film evaporator to separate said stream of extractant and enriched mixture of ethanol and water 14 in the stripping unit 16 into a stream of enriched mixture of ethanol and water 17 and a stream containing extractant 18.

The method comprises a step for discharging a stream of enriched mixture of ethanol and water 17 from the stripping unit 16.

The method comprises a step for discharging a stream containing extractant 18 from said stripping unit 16.

The method comprises a step for recirculating said stream containing extractant 18 into the extraction unit 12.

It is obvious for a person skilled in the art that the method can be a continuous process or a batch type process. In the method is fermentation mixture 4 preferably, but not necessarily, continuously from the fermentation vessel 3 into the separator unit 5.

In the method is fermentation mixture 4 preferably, but not necessarily, continuously from the separator unit 5 into the evaporator unit 7.

In the method is solid matter containing sludge 6 which contains among others ethanol- producing microbes and sugars and which is separated in the separator unit 5 from the fermentation mixture preferably, but not necessarily, continuously fed from the separator unit 5 into the fermentation vessel 3.

In the method is said residual bottom stream 9 preferably, but not necessarily, continuously fed from the evaporator unit 7 into the fermentation vessel 3.

In the method is said evaporated top stream 8 preferably, but not necessarily, continuously fed from the evaporator unit 7 in the form a stream of condensed mixture of ethanol and water 10 into said chemical extraction unit 12.

The invention also relates to an apparatus according to the invention for preparing a mixture of ethanol and water by fermentation of fermentable raw materials.

The figure shows schematically an apparatus for preparing a mixture of ethanol and water by fermentation of fermentable raw materials 1.

The apparatus comprises a fermentation vessel 3 for forming fermentation mixture 4 of fermentable raw materials 1 and necessarily auxiliary substances 2. The fermentable raw materials 1 are preferably, but not necessarily, selected from sugars and raw materials capable of being hydro lyzed into fermentable sugars. The apparatus comprises first feeding means 19 for feeding said fermentable raw materials 1 and said necessarily auxiliary substances 2 into the fermentation vessel 3.

The apparatus comprises first discharging means 20 for discharging a stream of said fermentation mixture 4 from the fermentation vessel 3. The apparatus also includes an arrangement (not marked with a reference numeral) for removing non- fermented matter 40 from the fermentation vessel 3.

The apparatus comprises a separator unit 5 for separating solid matter containing sludge 6 from said stream of fermentation mixture 4. The separator unit 5 can comprise a centrifuge, filter unit and/or a sedimentation unit to separate solid matter containing sludge 6 from said stream of fermentation mixture 4.

The separator unit 5 comprises preferably, but not necessarily, a centrifuge for separating solid matter containing sludge 6 from said stream of fermentation mixture 4.

The apparatus comprises second feeding means 21 for feeding said stream of said fermentation mixture 4 into the separator unit 5.

In the figure, the second feeding means 21 of the apparatus comprises first conduit 22 means for preferably, but not necessarily, continuously feeding said stream of said fermentation mixture 4 directly from the fermentation vessel 3 to the separator unit 5. In the figure the first conduit means 22 extends between the first discharging means 20 of the fermentation vessel 3 and the second feeding means 21 of the separator unit 5.

The apparatus comprises second discharging means 23 for discharging said stream of fermentation mixture 4 from the separator unit 5.

The apparatus comprises third discharging means 24 for discharging a stream of solid matter containing sludge 6 from the separator unit 5. In the figure, the apparatus comprises second conduit means 25 for preferably, but not necessarily, continuously feeding said stream of solid matter containing sludge 6 directly and preferably, but not necessarily, unprocessed i.e. as removed from the separator unit 5 from the separator unit 5 to the fermentation vessel 3.

In the figure the second conduit means 25 extend between the third discharging means 24 of the separator unit 5 and the fermentation vessel 3.

The apparatus comprises an evaporator unit 7 for evaporating said stream of fermentation mixture 4 in the evaporator unit 7 and for separating said stream of fermentation mixture 4 in the evaporator unit 7 into an evaporated top stream 8 containing mixture of ethanol and water and a residual bottom stream 9. The evaporator unit 7 comprises preferably, but not necessarily, a falling film evaporator for evaporating said stream of fermentation mixture 4 in the evaporator unit 7 and for separating said stream of fermentation mixture 4 in the falling film evaporator into an evaporated top stream 8 containing mixture of ethanol and water and a residual bottom stream 9. The apparatus comprises third feeding means 26 for feeding said stream of fermentation mixture into the evaporator unit 7.

In the figure, the apparatus comprises third conduit means 27 for preferably, but not necessarily, continuously feeding said stream of fermentation mixture 4 directly from the separator unit 5 to the evaporator unit 7, which third conduit means 27 extend between the second discharging means 23 of the separator unit 5 and the third feeding means 26 of the evaporator unit 7.

The apparatus comprises fourth discharging means 28 for discharging said evaporated top stream 8 of ethanol and water from the evaporator unit 7. The apparatus comprises condensing means (not marked with a reference numeral) for condensing said evaporated top stream 8 of ethanol and water to form a stream of condensed mixture of ethanol and water 10.

In the figure, the apparatus comprises fifth conduit means 31 for condensing said evaporated top stream 8 of ethanol and water from the evaporator unit 7 to a stream of condensed mixture of ethanol and water 10 and feeding said stream of condensed mixture of ethanol and water 10 directly to said chemical extraction unit 12. In the figure, the fifth conduit means 31 is provided with a condenser 11.

The apparatus comprises fifth discharging means 30 for discharging said residual bottom stream 9 from the evaporator unit 7. In the figure, the apparatus comprises fourth conduit means 29 for preferably, but not necessarily, continuously feeding said residual bottom stream 9 from the evaporator unit 7 directly and preferably, but not necessarily, unprocessed i.e. as removed from the evaporator unit 7 to the fermentation vessel 3. In the figure, the fourth conduit means 29 extend between the fifth discharging means 30 of the evaporator unit 7 and the fermentation vessel 3. The apparatus comprises a chemical extraction unit 12 for mixing said stream of condensed mixture of ethanol and water 10 together with an extractant 13 in the chemical extraction unit 12 to form mixture of ethanol and water and extractant, and for allowing said mixture of ethanol and water and extractant to settle in the chemical extraction unit 12 to form two fractions; a first fraction containing extractant and enriched mixture of ethanol and water and a second fraction containing water.

It is possible that the chemical extraction unit 12 comprises several sub-units (not shown in the figures) for chemical extraction of said condensed mixture of ethanol and water 10 The extraction can be performed by liquid-liquid extraction. Usable solvents or extractants 13 in the extraction are e.g. tertiary alkylphosphines.

In one embodiment of the invention the mixture of the extractants 13 can contain preferably 10 to 20 % Trioctylphosphine Oxide, 30 to 50 % Dioctylmonohexylphosphine Oxide, and 20 to 30 % Dioctylmonohexylphosphine Oxide.

The extract in the extraction unit 12 is preferably Cyanex®923 extractant (producer Cytec Industries Inc.) containing 12 to 16 % Trioctylphosphine Oxide, 40 to 44 % Dioctylmonohexylphosphine Oxide, and 28 to 32 % Dioctylmonohexylphosphine Oxide

The ratio of extractant to mixture of ethanol and water in the extraction unit can be vary between 1 volume unit extractant to 10 volume units of mixture of ethanol and water and 10 volumes unit extractant to 1 volume units of mixture of ethanol and water. The chemical extraction unit 12 may comprise a separate chemical extraction tank (not shown in the figures) and a settler (not shown in the figures) separate from the chemical extraction tank so that the chemical extraction unit 12 comprises sixth conduit means (not shown in the figures) for feeding mixture of ethanol and water and extractant from the separate chemical extraction tank to the settler. The chemical extraction unit 12 may alternatively comprise a combined chemical extraction tank and a settler (not shown in the figures).

The apparatus comprises fourth feeding means 32 for feeding said condensed mixture of ethanol and water 10 into the chemical extraction unit 12.

The apparatus comprises sixth discharging means 33 for discharging a stream of mixture of extractant and enriched mixture of ethanol and water 14 from said chemical extraction unit from said first fraction containing extractant and enriched mixture of ethanol and water in said chemical extraction unit 12.

In the figure the apparatus comprise seventh discharging means 34 for discharging water from the chemical extraction unit 12. The apparatus comprises a stripping unit 16 for separating said stream of extractant and enriched mixture of ethanol and water 14 in the stripping unit 16 into a stream of enriched mixture of ethanol and water 17 and a stream containing extractant 18.

The stripping unit 16 comprises preferably, but not necessary, a second falling film evaporator. The stripping unit 16 may alternative for example contain a column or a vacuum evaporator.

The apparatus comprises fifth feeding means 35 for feeding said stream of extractant and enriched mixture of ethanol and water 14 into a stripping unit 16. In the figure, the apparatus comprises seventh conduit means 36 for feeding said stream of e xtractant and enriched mixture of ethanol and water directly from the chemical extraction unit 12 to said stripping unit 16. In the figure, the seventh conduit means 36 extend between the sixth discharging means 33 of the chemical extraction unit 12 and the fifth feeding means 35 of the stripping unit 16. The apparatus comprises eight discharging means 37 for discharging a stream containing extractant 18 from said stripping unit 16.

The apparatus comprises ninth discharging means 38 for discharging a stream of enriched mixture of ethanol and water 17 from the stripping unit 16.

The apparatus comprises recirculation means for recirculating said stream containing extractant 18 into the extraction unit 12. In the figure, the recirculation means of the apparatus comprises eight conduit means 39 for feeding said stream containing extractant 18 from the stripping unit 16 directly to the extraction unit 12. In the figure the eight conduit means 39 extend between the eight discharging means 37 of the striping unit and the extraction unit 12.

The apparatus is preferably, but not necessarily, configured to continuously feed fermentation mixture 4 from the fermentation vessel 3 into the separator unit 5.

The apparatus is preferably, but not necessarily, configured to continuously feed fermentation mixture 4 from the separator unit 5 into the evaporator unit 7.

The apparatus is preferably, but not necessarily, configured to continuously feed solid matter containing sludge 6, which is separated in the separator unit 5 from the fermentation mixture, from the separator unit 5 into the fermentation vessel 3.

The apparatus is preferably, but not necessarily, configured to continuously feed residual bottom stream 9 from the evaporator unit 7 into the fermentation vessel 3.

The apparatus is preferably, but not necessarily, configured to continuously feed evaporated top stream 8 from the evaporator unit 7 into said chemical extraction unit 12 in the form a stream of condensed mixture of ethanol and water 10.

It is apparent to a person skilled in the art that as technology advanced, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.

List of reference numerals used:

1. fermentable raw material

2. necessary auxiliary substances

3. fermentation vessel 4. stream of fermentation mixture

5. separator unit

6. stream of solid matter containing sludge

7. evaporator unit

8. evaporated top stream of liquid fermentation mixture 9. residual bottom stream

10. stream of condensed mixture of ethanol and water

11. condenser

12. chemical extraction unit

13. extractant 14. stream of extractant and enriched mixture of ethanol and water

15. water

16. stripping unit

17. stream of enriched mixture of ethanol and water

18. stream containing extractant 19. first feeding means

20. first discharging means

21. second feeding means

22. first conduit means

23. second discharging means 24. third discharging means

25. second conduit means

26. third feeding means

27. third conduit means

28. fourth discharging means 29. fourth conduit means

30. fifth discharging means

31. fifth conduit means

32. fourth feeding means 33. sixth discharging means

34. seventh discharging means

35. fifth feeding means

36. seventh conduit means 37. eight discharging means

38. ninth discharging means

39. eight conduit means

40. non-fermented matter

41. solid matter containing sludge removed from the process

Claims

1. A method for preparing a mixture of ethanol and water by fermentation of fermentable raw material, which method comprises steps for feeding fermentable raw materials (1) and necessarily auxiliary substances (2) into a fermentation vessel (3), forming a fermentation mixture (4) in the fermentation vessel (3) using said fermentable raw materials (1) and said necessarily auxiliary substances (2), discharging a stream of fermentation mixture (4) from the fermentation vessel (3), feeding said stream of fermentation mixture (4) into an evaporator unit (7), evaporating said stream of fermentation mixture (4) in the evaporator unit (7) and separating said stream of fermentation mixture (4) in the evaporator unit ( 7) into a evaporated top stream (8) containing mixture of ethanol and water and a residual bottom stream (9), discharging said evaporated top stream (8) of ethanol and water from the evaporator unit (7), discharging said residual bottom stream (9) from the evaporator unit (7), condensing said evaporated top stream (8) of ethanol and water to form a stream of condensed mixture of ethanol and water (10), feeding said condensed mixture of ethanol and water ( 10) into a chemical extraction unit (12), mixing said stream of condensed mixture of ethanol and water (10) together with an extractant (13) in the chemical extraction unit ( 12) to form mixture of ethanol and water and extractant, allowing said mixture of ethanol and water and extractant to settle in the chemical extraction unit (12) to form two fractions; a first fraction containing extractant and enriched mixture of ethanol and water and a second fraction containing water (15), discharging a stream of extractant and enriched mixture of ethanol and water (14) from said chemical extraction unit (12) from said first fraction containing extractant and enriched mixture of ethanol and water in said chemical extraction unit (12), feeding said stream of extractant and enriched mixture of ethanol and water ( 14) into a stripping unit (16), separating said stream of extractant and enriched mixture of ethanol and water (14) in the stripping unit (16) into a stream of enriched mixture of ethanol and water (17) and a stream containing extractant (18), discharging a stream containing extractant (18) from said stripping unit (16), and discharging a stream of enriched mixture of ethanol and water (17) from the stripping unit (16) characterized by feeding said stream of fermentation mixture (4) from said fermentation vessel (3) into a separator unit (5) for separating solid matter containing sludge (6) from said stream of fermentation mixture (4), discharging said stream of fermentation mixture (4) from said separator unit (5), discharging a stream of solid matter containing sludge (6) from said separator unit (5), and feeding said stream of fermentation mixture (4) from said separator unit (5) into said evaporator unit (7).

2. The method according to claim 1, characterized in that said stream of solid matter containing sludge (6) is recirculated from the separator unit (5) and fed into the fermentation vessel (3), preferably directly and unprocessed from the separator unit (5) into the fermentation vessel (3).

3. The method according to claim 1 or 2, characterized in that the fermentation mixture (4) is centrifuged in the separator unit (5) to separate solid matter containing sludge (6) from said stream of fermentation mixture (4) .

4. The method according to any of the claims 1 to 3, characterized by using a falling film evaporator in the evaporator unit (7), and in that said fermentation mixture (4) is evaporated in said falling film evaporator.

5. The method according to any of the claims 1 to 4, characterized in residual bottom stream (9) is recirculated from the evaporator unit (7) and is fed into the fermentation vessel (3) , preferably directly and unprocessed from the evaporator unit (7) into the fermentation vessel (3).

6. The method according to any of the claims 1 to 5, characterized by condensing said evaporated top stream (8) of ethanol and water to form a stream of condensed mixture of ethanol and water (10) in a condenser (11).

7. The method according to any of the claims 1 to 6, characterized by using an extractant (13) in the extraction unit (12) containing Trioctylphosphine Oxide,

Dioctylmonohexylphosphine Oxide, Dihexylmonooctlyphosphine Oxide, Trihexylphosphine Oxide and mixtures thereof.

8. The method according to any of the claims 1 to 7, characterized by continuous feeding of said condensed mixture of ethanol and water (10) into the chemical extraction unit (12), and by continuous discharging a stream of extractant and enriched mixture of ethanol and water (14) from said chemical extraction unit ( 12) from said first fraction containing extractant and enriched mixture of ethanol and water from the chemical extraction unit (12).

9. The method according to any of the claims 1 to 7, characterized by feeding of said condensed mixture of ethanol and water (10) into a chemical extraction unit (12) in batches, and by discharging a stream of extractant and enriched mixture of ethanol and water (14) from said chemical extraction unit (12) from said first fraction containing extractant and enriched mixture of ethanol and water from the chemical extraction unit (12) in batches.

10. The method according to any of the claims 1 to 9, characterized by using a second falling film evaporator in the stripping unit (16), and in that said stream of extractant and enriched mixture of ethanol and water (14) is evaporated in said second falling film evaporator to separate said stream of extractant and enriched mixture of ethanol and water in the stripping unit (16) into a stream of enriched mixture of ethanol and water (17) and a stream containing extractant (18).

11. The method according to any of the claims 1 to 10, characterized in that recirculating said stream containing extractant (18) from the stripping unit (16) to the extraction unit (12).

12. The method according to any of the claims 1 to 11, characterized by continuously feeding fermentation mixture (4) from the fermentation vessel (3) into the separator unit (5).

13. The method according to any of the claims 1 to 12, characterized by continuously feeding fermentation mixture (4) from the separator unit (5) into the evaporator unit (7).

14. The method according to any of the claims 1 to 13, characterized by continuously feeding solid matter containing sludge (6) from the separator unit (5) into the fermentation vessel

(3).

15. The method according to any of the claims 1 to 14, characterized by continuously feeding residual bottom stream (9) from the evaporator unit (7) into the fermentation vessel (3).

16. The method according to any of the claims 1 to 16, characterized by continuously feeding said evaporated top stream (8) from the evaporator unit (7) in the form a stream of condensed mixture of ethanol and water (10) into said chemical extraction unit (12).

17. An apparatus for preparing a mixture of ethanol and water by fermentation of fermentable raw material, the apparatus comprising a fermentation vessel (3) for forming fermentation mixture (4) of fermentable raw materials (1) and necessarily auxiliary substances (2), first feeding means (19) for feeding said fermentable raw materials (1) and said necessarily auxiliary substances (2) into the fermentation vessel (3), first discharging means (20) for discharging a stream of said fermentation mixture (4) from the fermentation vessel (3), an evaporator unit (7) for evaporating said stream of fermentation mixture (4) in the evaporator unit (7) and for separating said stream of fermentation mixture (4) in the evaporator unit (7) into a evaporated top stream (8) containing mixture of ethanol and water and a residual bottom stream (9), fourth discharging means (28) for discharging said evaporated top stream (8) of ethanol and water from the evaporator unit (7), fifth discharging means (30) discharging said residual bottom stream (9) from the evaporator unit (7), condensing means for condensing said evaporated top stream (8) of ethanol and water to form a stream of condensed mixture of ethanol and water (10), a chemical extraction unit (12) for mixing said stream of condensed mixture of ethanol and water ( 10) together with an extractant (13) in the chemical extraction unit (12) to form mixture of ethanol and water and extractant, and for allowing said mixture of ethanol and water and extractant to settle in the chemical extraction unit (12) to form two fractions; a first fraction containing extractant and enriched mixture of ethanol and water (14) and a second fraction containing water (15), fourth feeding means (32) for feeding said condensed mixture of ethanol and water (10) into the chemical extraction unit (12), sixth discharging means (33) for discharging a stream of extractant and enriched mixture of ethanol and water (14) from said chemical extraction unit (12) from said first fraction containing extractant and enriched mixture of ethanol and water in said chemical extraction unit (12), a stripping unit (16) for separating said stream of extractant and enriched mixture of ethanol and water (14) in the stripping unit (16) into a stream of enriched mixture of ethanol and water (17) and a stream containing extractant (18), fifth feeding means (35) for feeding said stream of extractant and enriched mixture of ethanol and water stream ( 14) of extractant and enriched mixture of ethanol and water into a stripping unit (16), seventh discharging means (34) for discharging a stream containing extractant (18) from said stripping unit (16), and eight discharging means (37) for discharging a stream of enriched mixture of ethanol and water (17) from the stripping unit (16) characterized by comprising a separator unit (5) for separating solid matter containing sludge (6) from said stream of fermentation mixture (4), second feeding means (21) for feeding said stream of said fermentation mixture (4) into said separator unit (5), second discharging means for (23) discharging said stream of fermentation mixture (4) from said separator unit (5), third discharging means (24) for discharging said stream of solid matter containing sludge (6) from said separator unit (5), and third feeding means (26) for feeding said stream of fermentation mixture (4) into the evaporator unit (7).

18. The apparatus according to claim 17, characterized by first conduit means (22) for feeding said stream of said fermentation mixture (4) directly from the fermentation vessel (3) to the separator unit (5).

19. The apparatus according to claim 17 or 18, characterized by second conduit means (25) for feeding said stream of solid matter containing sludge (6) from the separator unit (5) to the fermentation vessel (3), preferably for feeding said stream of solid matter containing sludge (6) directly and unprocessed from the separator unit (5) to the fermentation vessel (3).

20. The apparatus according to any of the claims 17 to 19, characterized in that the separator unit (5) comprises a centrifuge for separating solid matter containing sludge from said stream of fermentation mixture (4).

21. The apparatus according to any of the claims 17 to 20, characterized by third conduit means (27) for feeding said stream of fermentation mixture (4) directly from the separator unit

(5) to the evaporator unit (7).

22. The apparatus according to any of the claims 17 to 21, characterized in that the evaporator unit (7) comprises a falling film evaporator.

23. The apparatus according to any of the claims 17 to 22, characterized by fourth conduit means (29) for feeding said residual bottom stream (9) from the evaporator unit (7) directly to said fermentation vessel (3) , preferably for feeding said residual bottom stream (9) from the evaporator unit (7) directly and unprocessed to said fermentation vessel (3).

24. The apparatus according to any of the claims 17 to 23, characterized by fifth conduit means (31) for condensing said evaporated top stream (8) of ethanol and water from the evaporator unit (7) to said stream of condensed mixture of ethanol and water (10) and for feeding said stream of condensed mixture of ethanol and water (10) directly to said chemical extraction unit (12).

25. The apparatus according to claim 24, characterized in that said fifth conduit means (31) is provided with a condenser (11).

26. The apparatus according to any of the claims 17 to 25, characterized in that the extractant (13) in the chemical extraction unit (12) contains Trioctylphosphine Oxide, Dioctylmonohexylphosphine Oxide, Dihexylmonooctlyphosphine Oxide, Trihexylphosphine Oxide and mixtures thereof.

27. The apparatus according to any of the claims 17 to 26, characterized in that the chemical extraction unit (12) comprises a separate chemical extraction tank and a settler separate from the chemical extraction tank, and that the chemical extraction unit (12) comprises sixth conduit means for feeding mixture of ethanol and water and extractant from the separate chemical extraction tank to the settler.

28. The apparatus according to any of the claims 17 to 27, characterized in that in that the chemical extraction unit (12) comprises a combined chemical extraction tank and a settler.

29. The apparatus according to any of the claims 17 to 28, characterized by seventh conduit means (36) for feeding said stream of extactant and enriched mixture of ethanol and water directly from said chemical extraction unit (12) to said stripping unit (16).

30. The apparatus according to any of the claims 17 to 29, characterized in that the stripping unit (16) comprises a second falling film evaporator.

31. The apparatus according to any of the claims 17 to 30, characterized by recirculation means for recirculating said stream containing extractant (18) into the extraction unit (12).

32. The apparatus according to claim 31 , characterized in that the recirculation means comprises eight conduit means (40) for feeding said stream containing extractant (18) from the stripping unit (16) directly to the extraction unit (12).

33. The apparatus according to any of the claims 17 to 32, characterized by the apparatus being configured to continuously feed fermentation mixture (4) from the fermentation vessel (3) into the separator unit (5).

34. The apparatus according to any of the claims 17 to 33, characterized by the apparatus being configured to continuously feed fermentation mixture (4) from the separator unit (5) into the evaporator unit (7).

35. The apparatus according to any of the claims 17 to 34, characterized by the apparatus being configured to continuously feed solid matter containing sludge (6), which is separated in the separator unit (5) from the fermentation mixture (4), from the separator unit (5) into the fermentation vessel (3).

36. The apparatus according to any of the claims 17 to 35, characterized by the apparatus being configured to continuously feed residual bottom stream (9) from the evaporator unit (7) into the fermentation vessel (3).

37. The apparatus according to any of the claims 17 to 36, characterized by the apparatus being configured to continuously feed evaporated top stream (8) from the evaporator unit (7) into said chemical extraction unit (12).