Process for extracting an alcohol from an initial mixture comprising the alcohol in an aqueous phase

Abstract

The present invention relates to a method for extracting alcohol from an initial mixture (1) containing alcohol in an aqueous phase, wherein: - distillation separation is performed by an isopropanol-butanol distillation column (III) equipped with a condenser (c3) at the top, which aims to separate the mixture into a water-isopropanol azeotropic feed stream (6) at the top and a water-butanol azeotropic feed stream (7) at the bottom; - distillation separation is performed by a heterogeneous azeotropic distillation system, the system comprising at least one water recovery tower (IV) and at least one butanol tower (V) equipped with a reboiler (r5) for recovering butanol (9), so as to allow heat transfer from the top water-isopropanol azeotropic feed stream (6) entering the condenser of the isopropanol-butanol distillation column (III) to the feed stream entering the reboiler of the butanol tower (V).

Description

Technical Field

[0001] This invention relates to a method, particularly for extracting alcohols, from mixtures containing alcohols in an aqueous phase. It can be used to recover alcohols as products from the must obtained at the end of aqueous fermentation of C5 and / or C6 sugars, as known from fermentation processes called IBE (isopropanol / butanol / ethanol) or IBEA (isopropanol / butanol / ethanol / acetone) carried out by “solvent-producing” Clostridium strains. Fermentation must refers to the aqueous medium in which fermentation has taken place. C5 and / or C6 sugars refer to sugars having 5 or 6 carbon atoms. More specifically, this invention relates to the extraction of isopropanol and butanol as key compounds of potential economic value. Existing technology

[0002] In order to address the challenges of the energy transition, a great deal of research is underway to develop “green” methods to provide alternative pathways to obtaining chemical intermediates in petroleum refining and / or petrochemicals.

[0003] Alcohols derived from fermentation processes (such as isopropanol and n-butanol) are among the most promising alternatives to petrochemical derivatives. ABE (acetone-butanol-ethanol) fermentation by microorganisms belonging to the genus *Clostridium* is one of the oldest industrialized fermentations and has been extensively studied. Recently, IBE (isopropanol-butanol-ethanol) fermentation, which produces a mixture of isopropanol, butanol, and ethanol by microorganisms also belonging to the genus *Clostridium*, has become a relatively recent research topic (Dos Santos Vieira et al., *Bioresour Technol*; 2019287:121425 doi:10.1016 / j.biortech2019.121425 Acetone-free biobutanol production: Past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation).

[0004] Regarding the fermentation procedures used in this type of method, production in batch mode for ABE and IBE fermentation has been studied (see, for example, Jones DT, Woods DR, 1986, Acetone-Butanol Fermentation Revisited. Microbiol. Rew., 50(4), 484-524 or Table 16.6 Lopez-contreras A. et al., Chapter 16, Bioalcohol Production: Biochemical Conversion of Lignocellulosic Biomass, 2010).

[0005] Continuous operation methods have also been studied, initially placing cells in suspension within a homogeneous reactor. Improvements to the continuous method have then been proposed by increasing the retention of microbial biomass in the bioreactor, particularly through the use of cells immobilized on a substrate, and / or through the use of recycled and retained cells via a filtration membrane (Vieira et al., 2019 Acetone-free biobutanol production: past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation Biores. Technol., 287; 121425).

[0006] One of the obstacles encountered in the development of fermentation methods is the step of recovering highly diluted products from the fermentation broth. This parameter decisively affects the economic cost of these types of methods. To make such fermentation production methods economically feasible on a large scale, the primary goal is to optimize fermentation performance by maximizing the final titer arc and volumetric productivity in the bioreactor where fermentation takes place. However, once fermentation conditions are optimized, for a given concentration of relevant molecules in the water, it is economically important to improve the energy consumption associated with the stage of extracting relevant molecules from the fermentation broth.

[0007] Many techniques exist for performing this extraction, the most conventional of which utilizes one or more distillation columns in series; however, other techniques involving stripping the mash with a gaseous feed stream have also been developed, for example, in patent WO2018 / 001628.

[0008] This invention focuses on extraction via distillation(s) or distillation(s). Therefore, it aims to improve this extraction process. For a given concentration of fermentation mash, this invention particularly seeks to reduce the energy consumption and / or capital investment required for this extraction in the equipment. Invention Overview

[0010] The first subject of this invention is a method for extracting alcohols from an initial mixture comprising, in an aqueous phase, an alcohol including at least isopropanol and butanol, and optionally ethanol and / or acetone, the method comprising a series of separation operations, including:

[0011] - Distillation separation is performed by at least one distillation column called an isopropanol-butanol column, which aims to separate the initial mixture or a mixture derived from the initial mixture into a water-isopropanol azeotropic feed stream at the top and a water-butanol azeotropic feed stream at the bottom.

[0012] - The purpose is to separate the water-butanol azeotropic feed stream into water and butanol by distillation separation, which is carried out by a heterogeneous azeotropic distillation system, the system comprising at least one water recovery tower, referred to as the water tower, and at least one butanol recovery tower, referred to as the butanol tower.

[0013] According to the present invention, heat transfer occurs from the water-isopropanol azeotropic feed stream entering the condenser of the isopropanol-butanol distillation column to the feed stream entering the reboiler of the butanol column.

[0014] In the context of this invention, "mixture derived from the initial mixture" means a mixture originating from the initial mixture, especially after at least one distillation separation process.

[0015] The condenser of the isopropanol-butanol distillation column and the reboiler of the butanol column can be advantageously combined in the same (and single) unit.

[0016] The extraction according to the invention therefore comprises a series of distillations, each of which requires an energy-consuming heat supply. It is known that columns are typically equipped with a bottom reboiler, which is usually heated by external steam to raise the temperature of the liquid obtained from the bottom of the column to the desired temperature and cause it to partially evaporate, thus generating a gas flow (“vapor traffic”) within the column, and a top condenser to lower the temperature of the top effluent and restore it to the liquid phase, thereby generating a liquid flow within the column. In the case of a series of columns, as in this case, the invention chooses to thermally integrate two distillation columns by selecting columns suitable for thermal integration, i.e.:

[0017] - First, the isopropanol-butanol column, whose top effluent containing isopropanol can have a temperature sufficient to transfer heat, even if its operating conditions must be modified to achieve this temperature.

[0018] - Secondly, the butanol column needs to supply sufficient heat to raise the feedstock to a temperature suitable for distillation, even though it must also be regulated to allow such heat transfer, because heat transfer is only technically feasible when the temperature difference between the “hot” effluent on one side and the “cold” feedstock on the other side is at least 5°C, and preferably at least 10°C.

[0019] Furthermore, this heat transfer has proven highly effective in reducing the overall energy consumption of the process, since the reboiler of the butanol column is heated at least partially, or even entirely, by the heat of condensation from the isopropanol-butanol column: the steam consumption required to heat the reboiler of the butanol column can be reduced, or even eliminated. From an apparatus perspective, the gains are also significant, as the furnace-type heating unit required to generate the steam needed to heat the reboiler can be reduced in size or even eliminated.

[0020] Preferably, the isopropanol-butanol distillation column is equipped with a condenser at the top, and the butanol column is equipped with a reboiler, and heat transfer is carried out through a heat exchanger shared by the two columns, thereby combining the condenser and the reboiler, which is particularly efficient and economical in terms of equipment.

[0021] As previously mentioned above, the thermal integration proposed in this invention may require modification of the operating conditions (temperature, pressure) of the isopropanol-butanol distillation column to ensure that the water-isopropanol effluent has a sufficient temperature at the column outlet to enable this transfer.

[0022] Therefore, the operating pressure of the column can be modified, especially increased. Advantageously, the pressure of the isopropanol-butanol distillation column can be adjusted to at least 3 bar absolute pressure, especially at least 4 bar absolute pressure, preferably up to 10 bar absolute pressure, especially up to 7 bar absolute pressure, especially values ​​of 4.5 to 6.5 bar absolute pressure.

[0023] The isopropanol-butanol distillation column and the butanol column are preferably operated at selected temperatures such that the top water-isopropanol azeotropic feed stream from the isopropanol-butanol distillation column (the “top” feed stream from the column corresponds to the feed stream entering the condenser of the column) is at a temperature T1 that is at least 8°C higher than the temperature T2 of the feed stream leaving the bottom of the butanol column, especially at least 10°C.

[0024] Therefore, preferably, the isopropanol-butanol distillation column and the butanol column are operated at selected temperatures so that the top water-isopropanol azeotropic feed stream from the isopropanol-butanol distillation column is at a temperature T1 of at least 120°C, and especially at most 140°C.

[0025] The operation of the isopropanol-butanol distillation column can be adjusted to maintain a liquid / gas two-phase mixture in the column, especially by applying the aforementioned temperature / pressure conditions, such as a temperature of at least 120°C for the isopropanol-water feed stream leaving the top of the column and / or a pressure of at least 3 bar absolute pressure in the column.

[0026] It has indeed been recognized that modifying the tower's operating conditions (more typically at lower pressures, especially at atmospheric pressure and lower temperatures) allows for the simultaneous acquisition of advantages beyond energy cost reduction: at higher pressures / temperatures, the tower, which tends to operate in a liquid / liquid / gas three-phase medium, is transformed into a liquid / gas two-phase medium only, where the separation zone disappears, thus allowing the tower to operate with typical / conventional internals / packing instead of specific trays adapted to three-phase operation, and thus reducing plant investment and making the tower easier to control.

[0027] It should be emphasized that, where appropriate, the additional energy cost resulting from any increase in pressure / temperature in the isopropanol-butanol column remains far less than the energy gain gained in the butanol column, thus making the present invention highly attractive. It should also be emphasized that such an increase in pressure / temperature in the controlled isopropanol-butanol column has absolutely no adverse effect on the quality, efficiency, or operability of the distillation performed in the isopropanol-butanol column in question.

[0028] The mixture used in the treatment according to the invention may also contain another alcohol, especially ethanol, usually in a minor amount relative to isopropanol and butanol.

[0029] For example, the initial mixture used for treatment may correspond to fermentation mash, which contains two major compounds in the aqueous phase, primarily isopropanol I and butanol B, and minor compounds, especially two minor compounds such as acetone A and ethanol E, characterized as follows:

[0030] -Total concentration of isopropanol I and butanol B: 8 to 30 g / L

[0031] -I / B mass ratio (major product, isopropanol / butanol): 0.25-0.5 / 0.75-0.5

[0032] - If present in the mash, the total concentration of minor products (e.g., acetone A and ethanol E) is 0.1 g / L to 2 g / L.

[0033] In cases where the initial mixture also contains ethanol, distillation separation by at least an isopropanol-butanol distillation column aims to separate the mixture or a mixture derived from the initial mixture into a water-isopropanol-ethanol azeotropic feed stream at the top and a water-butanol azeotropic feed stream at the bottom. The heat transfer according to the invention utilizes the heat of condensation of the water-isopropanol-ethanol mixture in this case.

[0034] According to a preferred embodiment, the heat transfer to the feed stream entering the butanol column reboiler provides all the heat required to operate the column. In this case, a furnace for generating steam to heat the butanol column reboiler can therefore be eliminated.

[0035] According to another embodiment, heat transfer to the feed stream entering the butanol column reboiler provides a portion of the heat required to operate the column, with the remaining heat supplied by another heat source, particularly an external steam source. Therefore, in this case, another heat supply is required, which can be obtained either elsewhere in the facility or via a steam-generating furnace, but is smaller in capacity and consumes less energy compared to the case without heat transfer according to the invention.

[0036] According to another embodiment, the heat provided by the heat transfer to the feed stream entering the butanol column is greater than the heat required for the feed stream entering the butanol column reboiler to operate the column, and in this case a cooler is added to remove the excess heat. A cooler refers to any known technical device, such as one or more condensers.

[0037] An example of a method according to the invention includes a series of operations for separating a mixture in an aqueous phase comprising an alcohol including at least isopropanol and butanol, and optionally ethanol and acetone:

[0038] -(a) The mixture is separated by distillation in a beer column, with the aim of removing at least a portion of the water from the aqueous phase to obtain a concentrated mixture.

[0039] -(b) The concentrated mixture from step (a) is obtained by distillation in a column called the acetone column, and its purpose is to separate acetone from the concentrated mixture to obtain a concentrated mixture leaning towards acetone.

[0040] -(c) Distillation separation by at least one column called an isopropanol-butanol distillation column, and aimed at separating the acetone-poor concentrated mixture obtained in step (b) into a water-isopropanol or water-isopropanol-ethanol azeotropic feed stream at the top and a water-butanol azeotropic feed stream at the bottom.

[0041] -(d) aims to separate the water-butanol azeotropic feed stream obtained in step (c) into a distillation separation of water and butanol, which is carried out by a heterogeneous azeotropic distillation system comprising at least one water recovery tower, referred to as a water tower, and at least one butanol recovery tower, referred to as a butanol tower.

[0042] The initial mixture comprising alcohols including at least isopropanol and butanol, and optionally ethanol and / or acetone in the aqueous phase, is advantageously a mash obtained by fermentation of a sugar-containing liquid, particularly a sugar-containing liquid derived from lignocellulosic biomass, under the action of microorganisms, especially solvent-producing strains, preferably selected from at least one of the following: bacteria, especially Clostridium (such as Clostridium butyricum or Clostridium fibrinolyticum), Escherichia coli, yeasts, especially Saccharomyces cerevisiae. These microorganisms can naturally be native microorganisms or can be derived from native microorganisms through genetic modification according to known techniques.

[0043] Indeed, a particular characteristic of this mash is its high water dilution, thus requiring various separations, and especially concentration steps, such as step (a) mentioned earlier above.

[0044] The initial mixture processed according to the invention can therefore have an organic compound concentration of 2 to 40 g / L, particularly 5 to 35 g / L or 8 to 30 g / L, which are typical concentrations encountered in fermentation mash. Organic compounds refer to the relevant molecules that the invention seeks to isolate and economically utilize, particularly those derived from alcohols and / or solvents.

[0045] According to one embodiment of the invention, the initial mixture (1) comes from only one source, from only one production process starting from a single raw material; for example, it is a fermentation mash obtained from a single fermentation using a single type of microorganism, which, due to the selected method, directly contains a mixture of organic compounds, i.e., a mixture of alcohols, that the invention seeks to separate.

[0046] According to another embodiment, the initial mixture according to the invention can combine two or more mixtures with different compositions, each mixture containing one or more alcohols in the aqueous phase. Such combination may involve mixing, particularly mixing two or more mashes obtained by fermentation of sugar-containing solutions with different microorganisms, each mash subsequently having its own composition. The mixing of these different streams, such as the mixing of these different mashes, can optionally be carried out prior to any separation treatment using the invention, or in a dedicated premixing section, or during the separation step in the process according to the invention: for example, the different streams / mashes can be injected together into a separation device, such as into the first distillation column (e.g., a mash column, as described later below) of the facility according to the invention, and then mixed directly in the device without premixing.

[0047] Therefore, the following can be conceived: - on the one hand, producing a first mash in the form of a first mixture containing isopropanol by fermentation; and - on the other hand, producing a second mash in the form of a second mixture containing butanol by another fermentation, and combining the two mashes to process them together according to the invention (by mixing them upstream of or within the facility where the invention is implemented, the mixing actually taking place during their treatment by the isopropanol-butanol tower). Each of the two mashes may contain different impurities or other related molecules (ethanol, etc.).

[0048] Therefore, the separation of two or more different mashes is ultimately achieved through a single facility and a single method.

[0049] Therefore, for the production of a first mash specifically containing isopropanol, please refer to the article "Employing Escherichia coli for C2-C6 Bioalcohol Production", L. Liang et al., Front. Bioeng. Biotechnol., 03.07.2020.

[0050] Furthermore, for the production of a second mash specifically containing butanol, please refer to the article "Genetic engineering of non-native hosts for 1-butanol production and its challenges: a review", S. Nawab et al., Microb Cell Fact, 27.03.2020.

[0051] Another subject of the present invention is any facility for extracting alcohols by implementing the above-described method.

[0052] Another subject of the invention is an apparatus for extracting alcohols from an initial mixture comprising, in an aqueous phase, an alcohol including at least isopropanol and butanol, and optionally ethanol and / or acetone, the apparatus comprising a series of separation sections, including:

[0053] - A distillation separation section consisting of at least one distillation column, referred to as an isopropanol-butanol column and equipped with a condenser, wherein the distillation separation is intended to separate the initial mixture or a mixture derived from the initial mixture into a water-isopropanol or water-isopropanol-ethanol azeotropic feed stream at the top and a water-butanol azeotropic feed stream at the bottom.

[0054] - A distillation separation section designed to separate the water-butanol azeotropic feed stream into water and butanol, wherein the distillation separation is carried out by a heterogeneous azeotropic distillation system, the system comprising at least one water recovery tower, referred to as a water tower, and at least one butanol recovery tower, referred to as a butanol tower, equipped with a reboiler.

[0055] This allows it to provide heat transfer from the top water-isopropanol or water-isopropanol-ethanol azeotropic feed from the isopropanol-butanol distillation column entering the condenser to the reboiler feed entering the butanol column.

[0056] The facility preferably includes a heat exchanger shared by the isopropanol-butanol distillation column and the butanol column, and it ensures heat transfer from the water-isopropanol or water-isopropanol-ethanol azeotropic feed flow entering the condenser of the isopropanol-butanol distillation column to the feed flow entering the reboiler of the butanol column, the shared heat exchanger combining the condenser and the reboiler.

[0057] The facility may include a series of stages for separating an initial mixture, which in an aqueous phase contains alcohols including at least isopropanol and butanol, and optionally ethanol and acetone:

[0058] -(a) A section for separating the mixture by distillation, comprising at least one mashing tower and designed to remove at least a portion of the water from the aqueous phase to obtain a concentrated mixture.

[0059] -(b) A section for separating the concentrated mixture from step (a) by distillation, comprising at least one column called an acetone column and designed to separate acetone from the concentrated mixture to obtain a concentrated mixture lean in acetone.

[0060] -(c) Distillation separation section, comprising at least one distillation column called an isopropanol-butanol column and designed to separate the acetone-poor concentrated mixture obtained in step (b) into a water-isopropanol or water-isopropanol-ethanol azeotropic feed stream at the top and a water-butanol azeotropic feed stream at the bottom.

[0061] -(d) aims to separate the water-butanol azeotropic feed stream obtained in step (c) into a distillation separation section for water and butanol, which includes at least one heterogeneous azeotropic distillation system, the system including at least one water recovery tower referred to as the water tower and at least one butanol recovery tower referred to as the butanol tower.

[0062] The apparatus according to the invention may also include an additional condenser at the top of the isopropanol-butanol column to remove excess heat from the azeotropic feed stream if the heat available in the top water-isopropanol or water-isopropanol-ethanol azeotropic feed stream exceeds the heat required for the feed stream entering the butanol column reboiler.

[0063] The invention is described in more detail below with the aid of non-limiting examples and the accompanying drawings:

[0064] List of Attachments

[0065] Figure 1

[0066] Figure 1 An example of a facility representing existing technology for separating relevant molecules in aqueous solutions.

[0067] Figure 2

[0068] Figure 2 This represents a modification according to a non-limiting embodiment of the invention. Figure 1 Facilities.

[0069] The same reference numerals in one figure and another figure represent the same material flow, device and heat exchange.

[0070] These two diagrams are highly schematic: they are flowcharts not drawn to scale. The facilities are presented in a simplified form for easier reading, especially for understanding the apparatus / flow used in this invention, rather than showing all the apparatuses in the form of furnaces, exchangers, coolers / compressors, tower reboilers, tower condensers, etc., which are effectively provided in this type of industrial facility and are known to those skilled in the art.

[0071] In all the attached figures:

[0072] - Numerical markings indicate fluid flow; Roman numeral markings indicate distillation columns, and markings with letters indicate apparatus;

[0073] For clarity, "separation section" is referred to as a single column in the form of a distillation column. However, it is clear that a separation section may contain / actually contain multiple columns installed in series and / or in parallel, and they may contain other separation devices to function as at least one distillation column, such as liquid / gas separators in the form of one or more tanks.

[0074] Description of the implementation plan

[0075] In the following non-limiting examples, the object of the present invention is to recover the main products from an aqueous solution, namely isopropanol on the one hand and n-butanol on the other hand, which also contains two other minor components, namely acetone (considered herein as an impurity to be removed) and ethanol (chosen herein to be retained together with isopropanol).

[0076] As shown above, the initial mash (entering the mash tower) consists of the following:

[0077] -Total concentration of isopropanol I and butanol B: 8 to 30 g / L

[0078] -I / B mass ratio (major product, isopropanol / butanol): 0.25-0.5 / 0.75-0.5

[0079] - Total concentration of minor products acetone a and ethanol e: 0.1 g / L to 2 g / L.

[0080] As a non-limiting example, the fermentation mash used in the present invention has the following composition and the following characteristics:

[0081] - Concentrations of isopropanol I, butanol B, ethanol e, and acetone a in water: 19.6 g / L

[0082] - Weight ratio I / B / e+a = 40.8 / 56.1 / 3.1

[0083] - The concentration of acetone a is approximately twice that of ethanol e.

[0084] This aqueous solution is a fermentation mash obtained from a liquid composed of C5 and / or C6 sugars and fermented in a known manner, for example, according to the intermittent or continuous methods mentioned in the preface, under the action of microorganisms derived from Clostridium strains. Further details regarding the fermentation methods themselves can be found in the scientific publications cited for the intermittent method.

[0085] The composition of the feed stream entering the isopropanol-butanol column is as follows:

[0086] -Water: 35 to 45% by weight

[0087] - The rest consists of IBea

[0088] -I / B mass ratio r (major product, isopropanol / butanol): 0.25-0.5 / 0.75-0.5

[0089] - Concentration of acetone a: 0.1 to 1 g / L

[0090] - Ethanol concentration: 2 to 10 g / L

[0091] The obtained isopropanol has two viable uses:

[0092] - It can be converted into propylene. In fact, the hydrated isopropanol product (with ethanol as a minor product) obtained by the method and facility according to the invention is a suitable raw material for conversion into propylene because it results in the production of a hydrated isopropanol fraction (containing a small amount of ethanol), since isopropanol and water exhibit an azeotrope that cannot be completely separated by distillation alone.

[0093] - After water removal, it can also be used as a solvent. In this case, an additional dehydration process must be considered to remove water from the isopropanol / water azeotrope. Such processes include distillation with a third substance (benzene, cyclohexane, etc.), pressure swing distillation (PSD) (a term indicating distillation at two different pressures), temperature swing adsorption (TSA) (a term indicating adsorption regulated by temperature) or pressure swing adsorption (PSA) (a term indicating adsorption regulated by pressure), or pervaporation.

[0094] The resulting butanol (in this case, n-butanol) is produced in a quasi-pure form in the method and apparatus according to the invention. “Quasi-pure” means a butanol content of at least 98% by weight, especially at least 98.5% by weight or 99% by weight (or at most 2% by weight, especially at most 1.5% by weight or 2% by weight of impurities) in the liquid phase involved.

[0095] For the sake of brevity, the term "IBea" may be used to refer to a mixture of isopropanol, butanol, ethanol, and acetone in water. Example

[0096] Example 1 (Comparative)

[0097] This embodiment corresponds to the following: Figure 1 The implementation of facilities.

[0098] Figure 1 The separation facilities shown will be described from “upstream” to “downstream”, and these terms will be understood based on the overall flow direction of the fermentation mash and the extracted products through the facility.

[0099] Mash 1 arrives from the fermentation section (not shown) at a concentration of approximately 8 to 30 g / L of IBea mixture and a temperature of 34 to 37°C.

[0100] The first column, I, commonly referred to as the mash column, pre-concentrates the mash 1 to approximately 60% by weight of IBea, which appears at the top of the column as a concentrated IBea mixture stream 2, and removes approximately 97% to 99% of the feed water at the bottom of the column. This water 3 at the bottom of column I contains 50 to 1000 ppm by weight of IBea and is referred to as "Vinasse". Typically, this column I operates at essentially atmospheric pressure, but can also be operated at up to 3 bar absolute pressure. It has 10 to 20 theoretical plates. It represents the entire separation method (this term refers to...) Figure 1 The steam consumption of the method implemented in the facility shown is approximately 70% to 90%. Depending on its pressure, column I operates in a temperature range of approximately 100 to 140°C (excluding the condenser). A feed / effluent exchanger can be installed on column I to preheat the feed (malt 1). This feed, initially at 34-37°C, returns to column I at a temperature of 70 to 85°C after passing through the feed / effluent exchanger e1.

[0101] The second column, known as the acetone column, serves to remove acetone, which is considered an impurity in this process. Typically, this column operates at approximately atmospheric pressure, but can also be operated at up to 3 bar absolute pressure. It comprises 30 to 50 theoretical plates. It represents approximately 2% to 6% of the steam consumption of the entire separation process. Stream 2 enters column II. Acetone stream 4 exits the column at the top, and lean acetone stream 5 exits at the bottom.

[0102] The third column, known as the isopropanol-butanol column III, produces an isopropanol / water azeotrope at the top, i.e., feed stream 6, which also contains a small amount of ethanol as a minor compound introduced with the mash. The composition of this azeotrope is 11 to 15% by weight of water. At the bottom of the column, a feed stream with a composition close to that of the water / n-butanol azeotrope, approximately 50% / 50% (by weight), is obtained; this is feed stream 7. Here, this column III operates at atmospheric pressure, and the column has a pressure of 1.5 bar absolute at the top. It comprises 30 to 70 theoretical plates; in this embodiment, 50 theoretical plates are present. Under these pressure conditions, plate numbering begins at condenser c3, and a gas / liquid / liquid three-phase region is observed between plates 27 and 50 below the plates specific to the three-phase operating mode of this column. This column III represents approximately 7% to 15% of the steam consumption of the entire separation process.

[0103] The last two columns, IV and V, are coupled: they constitute a heterogeneous azeotropic distillation system suitable for a water / n-butanol binary system, the principle of which is known. At the bottom of water column IV, water contained in the heterogeneous azeotrope is obtained (feed stream 8), and at the bottom of butanol column V, n-butanol with a purity of 98 to 99.5% by weight is obtained (feed stream 9). Both columns operate essentially at atmospheric pressure and can withstand pressures up to 2 bar absolute. Both columns IV and V have 7 to 15 theoretical plates. Water column IV represents 1% to 3% of the steam consumption of the entire separation process, and butanol column V represents 4% to 8% of the entire separation process.

[0104] All columns I through V are equipped in the known manner of distillation columns:

[0105] -The condensers at the top of the column are c1, c2, c3, and c4. The last condenser, c4, is shared by columns IV and V.

[0106] - And reboilers r1, r2, r3, r4, r5 at the bottom of the column, used to heat the bottom stream of the column. These reboilers can be selected from the following reboilers in a known manner: vertical thermosiphon reboiler, kettle reboiler, furnace reboiler, or "once-through" reboiler.

[0107] - and optionally, reflux tanks b1, b2, b3, b4 downstream of condensers c1 to c4.

[0108] The steam consumption of the entire separation method described herein varies from 12 to 50 MJ steam / kg IBea. This depends on the IBea concentration of the initial feedstock 1 (i.e., the mash recovered after fermentation) and various design choices for the facility (the operating conditions of the tower, the tower design in terms of the number of trays, feed location, etc.).

[0109] Regarding energy consumption in isopropanol column III and butanol column V:

[0110] - The condenser C3 of the isopropanol tower III needs to discharge 1.43 MJ / kg IBea of ​​usable heat at a temperature of approximately 80°C.

[0111] - The reboiler r3 of the same column III consumes 1.48 MJ / kg IBea of ​​heat in the form of reboiling steam.

[0112] - Butanol column V consumes 0.9 MJ / kg IBea of ​​heat in the form of reboiler steam (reboiler r5). This heat is required at a heat level of approximately 120°C under the considered operating pressure.

[0113] Example 2 (according to the present invention)

[0114] This embodiment corresponds to the following: Figure 2 The implementation, modification and improvement of the facilities. Figure 1 The facilities. Only the features described in detail / specified are related to... Figure 1 The facility schemes differ in those features, but are otherwise the same.

[0115] According to this Example 2, heat transfer is added from isopropanol-butanol column III to butanol column V. To achieve this, the pressure of column III is increased: it is selected to be operated at a pressure between 4 and 7 bar absolute pressure, and more specifically, at approximately 5.5 bar absolute pressure (measured at the top of the column), instead of at atmospheric pressure. This pressure increase results in an increase in the operating temperature of column III. Thus, the top temperature of the column increases to at least 120°C, especially as high as 125°C to 130°C, while the same temperature is only about 80°C under standard operation at near atmospheric pressure according to Example 1. At the top of the column, heat energy must be discharged, and with this temperature increase, the amount of heat energy to be discharged from the top effluent in the condenser c3 of column III is close to or even slightly higher than the amount of heat energy to be supplied at the reboiler r5 of butanol column V operating at approximately 120°C at atmospheric pressure.

[0116] By increasing the temperature at the top of column III, the heat discharged from the condenser c3 of column III can be transferred via a new heat connection T to the reboiler r5 of the butanol column, which operates at approximately 120°C under near-atmospheric pressure. Therefore, only one heat exchanger is needed, shared by both columns, constituting both the condenser c3 of column III and the reboiler r5 of column V; they can be assembled into a single unit c3+r5. Thus, two units (the condenser of the isopropanol-butanol column III and the reboiler of the butanol column V) are replaced by a single heat exchanger, and the steam generation unit associated with the reboiler r5 of column 5 can be eliminated.

[0117] If the heat to be discharged at tower III is not exactly equal to the heat to be supplied to tower V, there are many options:

[0118] - If the amount is higher, add an additional condenser c3' (e.g., a type of cooler called a "trim cooler") to the top of tower III. This additional condenser will be smaller than the initial condenser c3 at the top of the tower because less heat needs to be dissipated compared to the condenser c3 in Example 1. Example 2 and Figure 2 This represents the situation. All the top feed stream 6 from column III enters a common exchanger c3+r5, which combines the condenser c3 of column III and the reboiler r5 of column V. The hot effluent leaving this common exchanger enters an additional condenser c3'. At the outlet of this condenser c3', the feed stream is split in two: one portion returns to column III as reflux; the remaining portion, the distillate, leaves the method as a product.

[0119] - If the amount is lower, steam supplementation must be provided at the reboiler r5 of column V, and therefore a heating device (not shown in the figure) must be used to generate steam; however, this supplementation is still significantly less than the amount of steam required when there is no such heat transfer between the two columns; therefore, a much smaller heating device (furnace type) can be used, with a much lower heating capacity than in the case of Example 1.

[0120] Surprisingly, it has been found that increasing the pressure of column III offers another advantage: at atmospheric pressure, a liquid / liquid separation zone exists in the column due to the presence of the isopropanol / n-butanol / water ternary system. This type of liquid / liquid / gas three-phase zone typically requires the installation of specific column internals, which are more expensive and more complex to implement than conventional distillation trays. By increasing the pressure according to the invention, the three-phase separation zone disappears from the column, and therefore the column can be operated with conventional internals, such as valve trays or perforated trays, bulk or structured packing, thereby further reducing facility investment.

[0121] Regarding energy consumption in isopropanol-butanol column III and butanol column V:

[0122] - The condenser c3 of this third tower III needs to discharge 1.44 MJ / kg IBea of ​​heat, which can be obtained at a temperature of 129.5°C; this temperature increase relative to Example 1 is a result of the increased operating pressure of the tower.

[0123] The fifth column, V, namely the butanol column V, requires a reboiling heat in the form of 0.9 MJ / kg IBea at a heat level of 119.5 °C. Heat transfer between the condenser of column III and the boiling station of column V is thus made possible. Here, 1.44 – 0.9 = 0.54 MJ / kg IBea (instead of 1.43 MJ / kg IBea according to Example 1) must be discharged at the level of condenser c3 of the isopropanol-butanol column III: the heat to be discharged is less than in Example 1, and the apparatus will be smaller. Finally, the heat to be supplied to the reboiler r3 of the isopropanol column III is 1.71 MJ / kg instead of 1.48 MJ / kg, corresponding to an increase of 0.23 MJ / kg (due to the increase in pressure).

[0124] Table 1 below summarizes the energy data for towers III and V according to Examples 1 and 2, and provides a detailed calculation of the resulting energy gain:

[0125] Table 1

[0126]

[0127] By comparing these data regarding the energy operation of towers III and V, it is confirmed that the following gains are simultaneously achieved through this invention:

[0128] - In terms of the energy of removing heat from tower III, the gain G2 of heat removal is 0.89 MJ / kg IBea, which corresponds to a 62% reduction in cooling energy consumption (0.89 / 1.43 x 100 = ).

[0129] - Furthermore, in terms of the energy supplied to tower V, the gain G1 in the supplied heat is 0.67 MJ / kg IBea, which corresponds to a 28% reduction in heating energy consumption (0.67 / 2.38 x 100 = ).

[0130] Therefore, it can be seen that, overall, relative to the conventional use of these two columns, the heat transfer between the two distillation columns according to the present invention ultimately results in significant energy gains in both cooling (consumption is significantly reduced by more than half) and heating (significantly reduced by at least 20%), without requiring any significant additional costs in terms of equipment. By combining the condenser c3 and reboiler r5 into a single unit and reducing the heat to be discharged at the additional condenser c3' (“trimcooler”) by 62%, this additional condenser c3' according to Embodiment 2 of the present invention is / can be significantly smaller than the condenser c3 of Embodiment 1. It should be noted that, as mentioned earlier above, the addition of such an additional condenser remains optional, depending on the specific circumstances encountered.

Claims

1. A method for extracting alcohols from an initial mixture (1), said initial mixture (1) comprising an alcohol including at least isopropanol and butanol, and optionally ethanol and / or acetone in an aqueous phase, said method comprising a series of separation operations, including: - Distillation separation is carried out by at least one distillation column, referred to as isopropanol-butanol column (III) and equipped with a condenser (c3) at the top, and is intended to separate the initial mixture or mixture derived from the initial mixture into a water-isopropanol azeotropic feed stream (6) at the top and a water-butanol azeotropic feed stream (7) at the bottom. -The purpose of the distillation separation of the water-butanol azeotropic feed stream into water and butanol is to be carried out by a heterogeneous azeotropic distillation system, the system comprising at least one water recovery tower referred to as the water tower (IV) and at least one butanol recovery tower referred to as the butanol tower (V) and equipped with a reboiler (r5). The feature is that heat transfer occurs from the top water-isopropanol azeotropic material flow (6) entering the condenser of the isopropanol-butanol distillation column (III) to the material flow entering the reboiler of the butanol column (V).

2. The method as claimed in the preceding claim, characterized in that, Heat transfer is carried out through a heat exchanger (c3+r5) shared by the isopropanol-butanol distillation column (III) and the butanol column (V), which combines the condenser (c3) and the reboiler (r5).

3. The method of claim 1 or 2, wherein, The operation of the isopropanol-butanol distillation column (III) is adjusted to maintain a liquid / gas two-phase mixture in the column.

4. The method of claim 1 or 2, wherein, The operation of the isopropanol-butanol distillation column (III) is regulated by applying a temperature of at least 120°C and / or an absolute pressure of at least 3 bar to maintain a liquid / gas two-phase mixture in the column.

5. The method of claim 1 or 2, wherein, The pressure of the isopropanol-butanol distillation column (III) is adjusted to a value of at least 3 bar absolute pressure.

6. The method of claim 1 or 2, wherein, The pressure of the isopropanol-butanol distillation column (III) is adjusted to a value of at least 4 bar absolute pressure.

7. The method of claim 1 or 2, wherein, The pressure of the isopropanol-butanol distillation column (III) is adjusted to a maximum absolute pressure of 10 bar.

8. The method as described in claim 1 or 2, characterized in that, The pressure of the isopropanol-butanol distillation column (III) is adjusted to a maximum absolute pressure of 7 bar.

9. The method as described in claim 1 or 2, characterized in that, The pressure of the isopropanol-butanol distillation column (III) is adjusted to an absolute pressure of 4.5 to 6.5 bar.

10. The method as described in claim 1 or 2, characterized in that, The isopropanol-butanol distillation column (III) and the butanol column (IV) are operated at selected temperatures such that the top water-isopropanol azeotropic feed stream (6) from the isopropanol-butanol distillation column (III) is at a temperature T1 that is at least 8°C higher than the temperature T2 of the feed stream leaving the bottom of the butanol column (V).

11. The method as described in claim 1 or 2, characterized in that, The isopropanol-butanol distillation column (III) and the butanol column (IV) are operated at selected temperatures such that the top water-isopropanol azeotropic feed stream (6) from the isopropanol-butanol distillation column (III) is at a temperature T1 that is at least 10°C higher than the temperature T2 of the feed stream leaving the bottom of the butanol column (V).

12. The method as described in claim 1 or 2, characterized in that, The isopropanol-butanol distillation column (III) and the butanol column (V) are operated at selected temperatures such that the top water-isopropanol azeotropic feed stream (6) from the isopropanol-butanol distillation column (III) is at a temperature T1 of at least 120°C.

13. The method as described in claim 1 or 2, characterized in that, The isopropanol-butanol distillation column (III) and the butanol column (V) are operated at selected temperatures so that the top water-isopropanol azeotropic feed stream (6) from the isopropanol-butanol distillation column (III) is at a temperature T1 of up to 140°C.

14. The method as described in claim 1 or 2, characterized in that, The initial mixture (1) also contains ethanol, and the distillation separation performed by at least the isopropanol-butanol distillation column (III) is intended to separate the mixture or a mixture derived from the initial mixture into a water-isopropanol-ethanol azeotropic stream (6) at the top and a water-butanol azeotropic stream (7) at the bottom.

15. The method as described in claim 1 or 2, characterized in that, The heat transfer to the feed stream entering the butanol column (V) provides all the heat required to operate the column to the feed stream entering the reboiler (r5) of the butanol column (V).

16. The method as described in claim 1 or 2, characterized in that, The heat transfer to the feed stream entering the butanol column (V) provides a portion of the heat required to operate the column, while the remaining heat is supplied by another heat source.

17. The method as described in claim 1 or 2, characterized in that, The heat transfer to the feed stream entering the butanol column (V) provides a portion of the heat required to operate the column, with the remaining heat supplied by an external steam source.

18. The method as described in claim 1 or 2, characterized in that, The heat provided by the heat transfer to the feed stream entering the butanol column (V) is greater than the heat required for the feed stream entering the reboiler (r5) of the butanol column (V) to operate the column, and a cooler (c3') is added to remove the excess heat.

19. The method as described in claim 1 or 2, characterized in that, It includes the following series of operations for separating an initial mixture (1), which contains in an aqueous phase an alcohol comprising at least isopropanol and butanol, and optionally ethanol and acetone: -(a) The mixture is separated by distillation in a mash tower (I), which aims to remove at least a portion of the water from the aqueous phase to obtain a concentrated mixture (2). -(b) The concentrated mixture from step (a) is obtained by distillation separation in a column called the acetone column (II), and is intended to at least partially separate acetone from the concentrated mixture (2) to obtain an acetone-poor concentrated mixture (5). -(c) Distillation separation by at least one column called isopropanol-butanol distillation column (III), which is designed to separate the acetone-poor concentrated mixture obtained in step (b) into a water-isopropanol or water-isopropanol-ethanol azeotropic feed stream (6) at the top and a water-butanol azeotropic feed stream (7) at the bottom. -(d) aims to separate the water-butanol azeotropic feed stream obtained in step (c) into a distillation separation of water and butanol, which is carried out by a heterogeneous azeotropic distillation system comprising at least one water recovery tower referred to as the water tower (IV) and at least one butanol recovery tower referred to as the butanol tower (V).

20. The method as described in claim 1 or 2, characterized in that, The initial mixture (1) comprising an alcohol including at least isopropanol and butanol, and optionally ethanol and / or acetone in the aqueous phase is a mash obtained by fermentation of a sugar-containing liquid under microbial action.

21. The method as described in claim 1 or 2, characterized in that, The initial mixture (1) comprising alcohols including at least isopropanol and butanol, and optionally ethanol and / or acetone in the aqueous phase is a mash obtained by fermentation of a sugary liquid derived from lignocellulosic biomass under the action of microorganisms of a solvent-producing strain.

22. The method as described in claim 21, characterized in that, The microorganism is selected from at least one of the following: bacteria, yeast.

23. The method as described in claim 22, characterized in that, The bacteria are Clostridium species, Escherichia coli, and / or the yeast is a yeast of the Saccharomyces cerevisiae type.

24. The method as described in claim 1 or 2, characterized in that, The initial mixture (1) combines two or more mixtures with different compositions, each of which contains one or more alcohols in the aqueous phase.

25. The method as described in claim 1 or 2, characterized in that, The initial mixture (1) combines two or more different mashes obtained by fermentation with sugar solutions.

26. An apparatus for extracting alcohols from an initial mixture (1), said initial mixture (1) comprising, in an aqueous phase, an alcohol including at least isopropanol and butanol, and optionally ethanol and / or acetone, said apparatus comprising a series of separation sections, including: - A distillation separation section performed by at least one distillation column, referred to as isopropanol-butanol column (III) and equipped with a condenser (c3) at the top, and said distillation separation is intended to separate the initial mixture or a mixture derived from said initial mixture into water-isopropanol or water at the top. -Isopropanol-ethanol azeotropic material stream (6) and water-butanol azeotropic material stream at the bottom (7), -A section designed to separate the water-butanol azeotropic feed stream (7) into water and butanol by a heterogeneous azeotropic distillation system, the system comprising at least one water (8) recovery tower, referred to as the water tower, and at least one butanol (9) recovery tower, referred to as the butanol tower and equipped with a reboiler (r5). The device is characterized by comprising a heat exchanger shared by the isopropanol-butanol distillation column (III) and the butanol column (V) and an optional additional condenser (c3'), wherein the heat exchanger ensures heat transfer from the top water-isopropanol or water-isopropanol-ethanol azeotropic feed stream (6) entering the condenser (c3) to the feed stream entering the reboiler (r5) of the butanol column (V), wherein the heat exchanger shared by the isopropanol-butanol distillation column (III) and the butanol column (V) combines the condenser (c3) and the reboiler (r5), and the additional condenser (c3') is located at the top of the isopropanol-butanol column (III) for discharging excess heat from the top water-isopropanol or water-isopropanol-ethanol azeotropic feed stream (6).

27. The apparatus as claimed in claim 26, characterized in that, It includes the following series of sections for separating an initial mixture, which in the aqueous phase contains alcohols including at least isopropanol and butanol, and optionally ethanol and acetone: -(a) A section for separating the mixture by distillation, comprising at least one mashing tower (I) and designed to remove at least a portion of the water from the aqueous phase to obtain a concentrated mixture. -(b) A section for separating the concentrated mixture from step (a) by distillation, comprising at least one column called an acetone column (II) and designed to separate acetone from the concentrated mixture to obtain a concentrated mixture lean in acetone. -(c) The distillation separation section, comprising at least one distillation column referred to as the isopropanol-butanol column (III), is designed to separate the acetone-poor concentrated mixture obtained in step (b) into a water-isopropanol or water-isopropanol-ethanol azeotropic feed stream at the top and a water-butanol azeotropic feed stream at the bottom. -(d) The distillation separation section, which aims to separate the water-butanol azeotropic feed stream obtained in step (c) into water and butanol, includes at least one heterogeneous azeotropic distillation system, the system including at least one water recovery tower referred to as the water tower (IV) and at least one butanol recovery tower referred to as the butanol tower (V).

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