Systems and methods for integrated CO2 reuse using vapor compression

Systems and methods are disclosed for optimizing the process energy required for the conversion of carbon dioxide (CO2) to biochemicals through vapor compression. Mechanical or thermal vapor compression are used to minimize both the process energy and the cooling in condensers, integrating the heat required by those processes and reusing heat that is typically lost. Some variations provide a process for producing biochemicals from biomass, comprising: cooking biomass to release saccharides; fermenting the saccharides to generate a biochemical in aqueous solution, and carbon dioxide; hydrogenating the carbon dioxide with a hydrogen source to generate an additional quantity of biochemical; feeding the fermentation-derived biochemical, as well as the CO2-derived biochemical, to a distillation column for purification; and compressing vapors from the distillation column, using mechanical vapor recompression and/or thermal vapor recompression, to recover heat of distillation that is utilized elsewhere in the biorefinery to reduce overall process energy usage.

FIELD OF THE INVENTION

The present invention generally relates to the conversion of carbon dioxide into chemical products and integration of vapor compression into the conversion process.

BACKGROUND OF THE INVENTION

Bio-fermentation plants typically generate carbon dioxide (CO2) as a metabolic by-product of fermentation, in addition to the primary bioproduct. In some cases, this CO2is captured and used, but as often it is vented to the atmosphere as a waste product. Processes are being developed to convert this carbon dioxide to a variety of chemical products, many of which require recovery and refinement of the final products through distillation. The process energy consumed in the distillation of bioproducts often constitutes the largest process energy demand as well as the largest source of carbon dioxide emissions resulting from combustion-supplied heat.

Historically, many processes generating carbon dioxide have emitted the CO2gas without further processing for conversion, reuse, or sequestration. Concerns regarding the impact of CO2emissions accelerating anthropogenic climate change have spurred efforts to capture and use or sequester those emissions. Currently, CO2is used in enhanced oil recovery, dry ice manufacturing, firefighting, manufacturing, refrigeration, food processing, and many other applications.

It is technically known that CO2may function as a chemical precursor, for its carbon and/or its oxygen content. Natural photosynthesis converts CO2into sugars in plant matter. Commercial synthesis of chemical products from CO2is an active area of research, typically utilizing catalytic reactions at high temperatures to produce valuable products. Often, significant energy is required to meet the required conditions for processing CO2to chemicals. The high energy barrier reduces the commercial feasibility of these options, despite the advantages of a readily available, high-quality source of CO2from bio-fermentation plants.

Improved processes and systems are desired commercially for converting carbon dioxide into useful chemicals and materials. Such processes and systems may be implemented within biorefineries designed for conversion of biomass into high-value biofuels and biochemicals.

SUMMARY OF THE INVENTION

Some variations of the invention provide a process for producing biochemicals from a biomass feedstock, the process comprising:

(a) cooking a biomass feedstock in a heated cooking solution, to release saccharides from the biomass feedstock;

(b) fermenting the saccharides to generate a first biochemical in aqueous solution, and carbon dioxide;

(c) hydrogenating the carbon dioxide with a hydrogen source to generate a second biochemical;

(d) feeding the first biochemical in the aqueous solution to a first distillation column, to generate a purified first biochemical;

(e) feeding the second biochemical to the first distillation column, or to a second distillation column, to generate a purified second biochemical; and

(f) compressing vapors from the first distillation column, using mechanical vapor recompression and/or thermal vapor recompression, to recover heat of distillation of the first biochemical.

In some embodiments, the process further comprises mechanically treating the biomass feedstock prior to step (b).

In some embodiments, the first biochemical in aqueous solution is preheated via heat exchange with the heated cooking solution, prior to feeding the first biochemical in the aqueous solution to the first distillation column.

In some embodiments, the heat of distillation from step (f) is utilized, at least in part, for the heating the heated cooking solution in step (a).

In these or other embodiments, the process further comprises dehydration of the purified first biochemical, to generate a highly purified first biochemical. The heat of distillation from step (f) may be utilized, at least in part, for the dehydration of the purified first biochemical.

In these or other embodiments, the process further comprises evaporation and/or drying of a bottoms stream from the first distillation column, to generate a stillage product. The heat of distillation from step (f) may be utilized, at least in part, for the evaporation and/or drying of the bottoms stream from the first distillation column.

In certain embodiments, the heat of distillation from step (f) may be utilized, at least in part, for directly or indirectly providing heat in step (c), for the hydrogenation reaction.

In some embodiments, in step (f), the vapors are compressed using mechanical vapor recompression. Optionally, the mechanical vapor recompression may be driven by a combined heat and power system.

In some processes, in step (c), the hydrogen source is water. The water may be derived from the aqueous solution. In certain embodiments, the water is, or includes, recycled steam condensate.

In some processes, the carbon dioxide from fermentation passes directly to step (c). In some embodiments, all CO2hydrogenated in step (c) is from the carbon dioxide generated in step (b).

The first biochemical may be the same as the second biochemical, or different than the second biochemical. In either embodiment, and preferably when the first biochemical is the same as the second biochemical, the second biochemical is fed to the first distillation column.

When the first biochemical is different than the second biochemical, the second biochemical may be fed to the second distillation column, wherein vapors from the second column are compressed, using mechanical vapor recompression and/or thermal vapor recompression, to recover heat of distillation of the second biochemical.

Other variations of the invention provide a system for producing biochemicals from a biomass feedstock, the system comprising:

a cooking stage configured for cooking a biomass feedstock in a heated cooking solution, to release saccharides from the biomass feedstock;

a fermentation stage configured for fermenting the saccharides to generate a first biochemical in aqueous solution, and carbon dioxide;

a catalytic or reactor vessel configured for hydrogenating the carbon dioxide with a hydrogen source to generate a second biochemical;

a first distillation column configured for separating a purified first biochemical from the aqueous solution;

optionally, a second distillation column configured for purifying the second biochemical;

a vapor recompression unit configured for mechanical vapor recompression and/or a thermal vapor recompression, wherein the vapor recompression unit is disposed in vapor-flow communication with the first distillation column, and wherein the vapor recompression unit is configured to recover heat of distillation from the first distillation column.

In some embodiments, the system further comprises a dehydration unit configured for removing additional water from the purified first biochemical. The system may be configured to utilize at least some of the heat of distillation in the dehydration unit.

In some embodiments, the system further comprises a stillage-processing unit configured for evaporation and/or drying of a bottoms stream from the first distillation column, to generate a stillage product. The system may be configured to utilize at least some of the heat of distillation in the stillage-processing unit.

The vapor recompression unit may be a mechanical vapor recompression unit. Optionally, the mechanical vapor recompression unit is driven by a combined heat and power system.

In some systems, a second distillation column is present in the system. Additional distillation columns may be present in some configurations.

Some systems are designed such that the first biochemical is different than the second biochemical. Other systems are designed such that the first biochemical is the same as the second biochemical.

In various systems, the first biochemical and the second biochemical may be independently selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, n-butanol, isobutanol, 2-butanol, tert-butanol, acetone, acetic acid, lactic acid, perylene, phenol thiazine, dihydrophenazine, 5,10-di(4-methoxyphenyl)-5,10-dihydrophenazine, 5,10-dihydrophenazine, 5,10-di(4-trifluoromethylphenyl)-5,10-dihydrophenazine, and combinations thereof.

These and other embodiments, features, and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following detailed description.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Certain embodiments of the present invention will now be described in more detail, in a manner that will allow a person of ordinary skill in this art to make and use the present invention. All references herein to the “invention” shall be construed to refer to non-limiting embodiments disclosed in this patent application.

Unless otherwise indicated, all numbers expressing conditions, concentrations, yields, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending at least upon the specific analytical technique. Any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in its respective testing measurements.

As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention belongs. If a definition set forth in this section is contrary to or otherwise inconsistent with a definition set forth in patents, published patent applications, and other publications that are incorporated by reference, the definition set forth in this specification prevails over the definition that is incorporated herein by reference.

With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of” or, alternatively, by “consisting essentially of.”

The use of vapor compression provides a means of increasing the temperature and pressure of vapors so that their heat of condensation is usable in upstream and downstream processing. Standard practice uses cooling water to condense vapors at low temperatures when forming final products or inter-process sub-products, losing the heat of condensation to cooling water, thereby preventing reintroduction and reuse of that heat. Vapor compression allows for the reuse of the heat of condensation when increased pressure raises the condensing temperature to a point above the temperature required for use in the process. Vapor compression is well-established in single-process applications such as water desalination and evaporation.

The present invention is predicated, at least in part, on integrated designs that optimize vapor compression between multiple processes. A process that converts generated CO2into a product is integrated into the overall plant vapor-compression system, providing opportunities to optimize energy efficiency and carbon intensity through options unavailable for single-process designs.

Integrating mechanical compression with multiple plant processes can minimize heat losses by providing advantages not available for typical cascaded heat integration. In cascaded heat integration, where energy can only be cascaded from higher to lower temperatures and pressures, the staged reduction in temperature and pressure eventually drops below the requirements for plant processes, at which point steam or process vapors are condensed, losing their latent heat. Vapor compression provides a means to raise these temperatures and pressures to a level that can be condensed and reintroduced, meeting process requirements, while minimizing energy lost to the environment. The complexity of balancing process energy needs across multiple processes has historically discouraged attempts at designing systems utilizing mechanical vapor compression in favor of simply cascading heat and discarding the heat of compression once vapors become “low-grade”, i.e. too low for reuse. When vapor compression was used, process designers have historically applied vapor compression to isolated processes with the advantage of lowering the energy to that isolated process, but not realizing the greater benefit available through the integration of multiple processes.

The present inventors have discovered several advantages of integrating multiple processes in commercial system designs and, according to the present disclosure, incorporating carbon dioxide processing into these integrated designs. Means of reintroducing the latent heat of upgraded vapors and/or steam may include condensing in various heat exchangers such as reboilers or evaporators, or may include direct injection, depending on the quality and composition of the process vapors or steam.

Various methods have been proposed for utilizing the carbon dioxide produced in fermentation processes. These methods typically require significant energy to achieve the pressures and temperatures necessary to optimize product conversion and purification. Even transportation, storage, and sequestration of CO2require that the low-pressure carbon dioxide from fermentation is compressed prior to handling.

The reaction products from the catalytic conversion of carbon dioxide to biochemicals is typically a mixture of biochemicals and water, and potentially by-products, depending on the specific chemistry. The final biochemical products must normally be refined or purified to reach commercial quality. A typical titer for ethanol in the beer of a dry mill ethanol plant is about 15% by weight, with the balance being water together with non-fermentable residue. Many fermentation processes producing butanol or other products have titers of less than 5 wt % with water. Biochemicals produced from CO2conversion (rather than sugar fermentation) will also usually have at least as much water content as biochemical product streams from fermentation. Many biochemicals form azeotropes with water and require distillation with final dehydration to attain a required quality. The distillation and dehydration of biochemicals—from both fermentation and CO2conversion—represent process areas in which vapor compression can be applied for reductions in process energy.

The thermal process energy required to drive the production and refinement of biochemical end products from the conversion of carbon dioxide is large and represents a major portion of the process energy required to produce the final biochemical product. Therefore, process energy reductions and more-efficient processing enhance the economic advantages of catalytic, electrochemical, or thermal conversion of CO2to biochemicals. The separation of the CO2-derived biochemical products by vapor compression improves the efficiency of the overall process through recapture of the heat of condensation.

As an example of a potential application, a biorefinery may be designed for the conversion of biomass into high-value biofuels and biochemicals. The distillery process in the biorefinery typically has fermentation as the initial process for the conversion of the biomass (sugar) substrate, where carbon dioxide is a major stoichiometric co-product of fermentation by yeast or bacteria. The carbon dioxide co-product of fermentation provides a relatively inexpensive and high-quality source of CO2, often requiring minimal processing to meet requirements as a feed for conversion. In the case of ethanol from grain, approximately one-third of the mass of fermented biomass is converted to carbon dioxide of relatively high purity, minimizing the production of greenhouse gases often entailed in the separation and clean-up processes required by competing sources of CO2. Reducing CO2processing energy requirements improves the economic incentives for installing and operating systems for CO2capture and reuse. Although a wide range of process options exist for use of fermenter carbon dioxide, and many new technologies are being developed, the approach and principles described herein may be flexibly applied to any proposed process design. Several examples are listed, below.

One example is catalytic hydrogenation of CO2into methanol (CH3OH) using copper-zinc oxide catalysts at a temperature of about 260° C.:
CO2+3H2→CH30H+H2O

Another example is catalytic conversion of CO2into ethanol using ruthenium-halide and phosphonium-halide catalysts:
xCO+yCO2+(2x+3y)H2→(x/2+y/2)C2H5OH+(x/2+3y/2)H2O
wherein x and y are adjustable in the feed composition to the reactor. For a feed with CO2and no CO (x=0), producing one mole of ethanol (C2H5OH) requires two moles of CO2, and co-produces three moles of water, so that the ethanol is dilute.

In the above examples for producing methanol and ethanol, hydrogen is a reactant. Hydrogen may be obtained from an on-site hydrogen plant (e.g., via steam-methane reforming, following by separation of H2from syngas), for example. When both CO and H2are reactants to the CO2-conversion reactor, the CO and H2may be provided as syngas that may be obtained through various means, such as an on-site steam-methane reformer or a gasifier that converts a process stream into syngas, for example.

In some embodiments, CO or H2are not necessary as reactants. For example, CO2may be electrochemically converted into a product, such as ethanol or ethylene. In such embodiments, CO and/or H2may be intermediate species generated during conversion, but may not need to be separately fed to the reactor.

Also, H2O is typically, but not necessarily, a reactant in the conversion of CO2to products. Even when H2O is not a reactant, it may be generated as a reaction intermediate. Typically, H2O will be present as a solvent, or gas-entraining liquid, for reactants and products.

An example of a relevant electrochemical reaction is the conversion of carbon dioxide to ethanol. A generalized electrochemical catalysis reaction describing the conversion of carbon dioxide to ethanol is:
2CO2+9H2O+12e−→C2H5OH+12OH−
which utilizes electrons, in the form of electrochemical reduction, to selectively reduce carbon dioxide to ethanol in the presence of electrochemical catalysts (e.g., copper-silver composite catalysts). The OH−ions may be neutralized to salts that may be removed from the product. Generally, in an electrochemical system, there will be an excess of water present.

Other possible products of CO2conversion include, but are not limited to, alkanes, olefins, aromatics, heterocyclics, and other complex organic compounds. Photochemical reactions may be utilized to provide the necessary energy to split the CO2molecule for conversion to products. Photochemical reactions may generate electrons for direct reduction such as in the reaction shown above, may generate heat that thermally converts CO2, or may utilize photons from sunlight or from other sources (e.g., lasers) to convert CO2. All of these reactions almost invariably lead to a watery biochemical product requiring distillation and possible dehydration to meet commercial product specifications.

Some variations of the invention provide a method for the modification and augmentation of a distillery or biorefinery with the addition of advanced distillation methods for heat management by mechanical (or thermal) vapor recompression of vapors recovers the heat of distillation providing a reduction in process thermal energy, wherein the separation and refinement of the produced fermented biochemicals have additional organic products resulting from carbon dioxide reformation or conversion. Some variations provide a system in which the mechanical (or thermal) vapor recompression is sized or operated in concert with existing heat-integrated processes to reduce the thermal energy required in processes of distillation and evaporation with or without dehydration. A standard steam generator may be operated at a reduced rate as a result of the reduction in steam energy demand due to energy recovered by the mechanical (or thermal) vapor recompression of distillation vapors.

The concept of mechanical vapor compression in distillation has been deployed in reducing process requirements in refining for many decades. It has also been widely deployed in water desalination and process evaporation. Mechanical vapor compression, when used in distillation, recycles the heat of distillation by a closed heat pump, as disclosed, for example, in U.S. Pat. Nos. 4,340,446, 4,422,903, 4,539,076, 4,645,569, 4,692,218, 4,746,610, 5,294,304, 7,257,945, 8,101,217, 8,101,808, 8,114,255, 8,128,787, 8,283,505, 8,304,588, 8,535,413, and 8,614,077, which are hereby incorporated by reference herein. Thermal vapor compression, when used in distillation, evaporation, dehydration, and drying, recycles latent heat by a closed heat pump, as disclosed for example in U.S. Pat. Nos. 5,772,850, 4,536,258, and 4,585,523, which are hereby incorporated by reference herein. These methods of energy recovery have been rarely utilized, however, in the distillation processes of bio-fermentation producers.

In this disclosure, mechanical vapor recompression (MVR) and/or thermal vapor recompression (TVR) are preferably used to produce vapor that meets conditions to best integrate and optimize energy recovery between processes, and to reduce overall process thermal energy usage in the biorefinery. The heat of condensation of the compressed vapors provides energy that may be used elsewhere, i.e. beyond the distillation process. Heat exchangers utilizing multiple effects, thermal vapor recompression, and/or mechanical vapor recompression are used to balance process conditions by increasing or decreasing vapor energy to serve process design requirements.

All instances of “vapor compression,” “vapor recompression,” MVR, TVR, and the like mean mechanical vapor recompression, thermal vapor recompression, or a combination thereof. Thermal vapor recompression may also be referred to as thermocompression or steam compression.

A more detailed description of certain embodiments of the present invention such that a person of ordinary skill in this art can make and use the present invention follows. Note that all references herein to the “invention” shall be construed as references to embodiments of the invention.

In various embodiments, a starting biomass feedstock may be selected from agricultural crops and/or agricultural residues. In some embodiments, agricultural crops are selected from starch-containing feedstocks, such as corn, wheat, cassava, rice, potato, millet, sorghum, or combinations thereof. In some embodiments, agricultural crops are selected from sucrose-containing feedstocks, such as sugarcane, sugar beets, or combinations thereof.

The flow diagrams ofFIGS. 1 and 2display a biorefinery in which biochemical is produced from biomass by grinding, cooking, and fermenting the biomass, then distilling and/or dehydrating the resulting product. The biorefinery has support for steam-driven processing and mechanical vapor recompression in distillation, with or without dehydration. The fermentation produces a beer solution of non-fermented biomass with a water-diluted biochemical, and carbon dioxide. The carbon dioxide is reacted (e.g., catalytically) to form watery biochemicals that also require distillation and, potentially, dehydration.

FIG. 1depicts a biorefinery in which the produced biochemical requires dehydration to complete the water removal for the production of commercial-quality biochemical.FIG. 2depicts a biorefinery in which the biochemical can reach commercial quality without dehydration and therefore this embodiment does not include a dehydration stage in the process. The biorefinery includes an additional process stage in which the carbon dioxide from fermentation is converted to a biochemical, which may be the same as the biochemical produced in the bio-fermentation (as shown inFIGS. 1and2), or different than that biochemical. The biochemical produced from carbon dioxide is then processed through the biorefinery's distillation process, in the same distillation columns as those utilized for the fermentation-derived biochemical (as shown inFIGS. 1 and 2), or in different distillation column(s). The finished product of the distillation may require dehydration if it forms an azeotrope.

Each ofFIGS. 1 and 2contains a mechanical vapor recompression system in evaporation, distillation, and, forFIG. 1, dehydration. Each ofFIGS. 1 and 2displays steam generation used to balance process thermal energy requirements. Mechanical vapor compression provides a variable means of offsetting the thermal energy required by varying the portion of the vapors that are compressed. In each ofFIGS. 1 and 2, there is mechanical vapor recompression within distillation. InFIG. 1only, there is mechanical vapor recompression within dehydration.

The bio-fermentation process for the production of fermentation-based biochemicals, along with carbon dioxide conversion to a biochemical, is described inFIG. 1andFIG. 2and may include the following general stages:

an optional milling stage or device(s) which process biomass by physically dividing the feedstock materials, such as with a grinding or extrusion process which exposes the internal parts of the feedstock;

a cooking stage which uses various combinations of controlled temperatures, pressures, stirring, and special chemical conditioning, optionally with enzymes or acid catalysts, for breaking polysaccharides into saccharides (e.g., glucose and/or xylose);

a heat-exchanger stage which cools the cook solution to fermentation temperatures and, conversely, heats post-fermentation products to distillation temperatures;

a fermentation stage in which the fermentation liquid has biological agents introduced to ferment to carbon dioxide plus desired watery biochemical products, wherein the biochemical products pass directly to the distillation, and wherein the carbon dioxide passes directly to the catalytic or reactor vessel;

a catalytic or reactor vessel configured to convert the carbon dioxide gas (from fermentation), optionally with water vapors (optional stream shown inFIGS. 1and2) and optionally with other reactants such as H2or CO, reacting with CO2to form additional watery biochemical products;

a distillation stage after the fermented products have been pre-heated in the heat exchanger of the heat-exchanger stage, wherein the biochemical top products are separated from the fermentation waters;

a condensation stage in which the vapors from the distillation stage are passed on to a cooling system where the heat of distillation is discarded or where the vapors are mechanically compressed to recover the heat of distillation;

a stillage handling stage for the bottom product of the distillation stage, for recovering wet co-products of the fermentation for further processing and possible drying and, potentially, evaporation to concentrate thin stillage;

a dehydration stage for the biochemical products from the distillation stage, if it has not sufficiently separated the biochemicals from the fermentation water; and

a storage stage in which the high-grade biochemical goes to storage.

Some embodiments are shown inFIG. 1andFIG. 2having a common process path with the process flow beginning with raw biomass being stored in bin1, which delivers the biomass substrate via delivery duct2to a milling/extrusion process3. The milling/extrusion process3is a mechanical pretreatment that reduces the biomass substrate to a suitable size such that the internal portions of the raw biomass are exposed for chemical conversion and processing. The milled biomass flour passes via duct4where additional chemicals, which may include enzymatic agents, are added to the cooking process in cooking vessel6(also referred to as a cook tank).

The biomass flour passing from duct4is mixed with process water from process line5where the mixed flour and process water enter cooking vessel6. Within cooking vessel6, required temperatures and pressures are attained through the addition of process steam from line7, completing chemical conversion to fermentable saccharides with the assistance of stirring system8.

The product of chemically converted slurry from cooking vessel6passes via process line9to heat exchanger10where the heat invested into the cook process is removed prior to fermentation, which typically occurs at lower temperatures than cooking. The cook slurry, after being cooled in heat exchanger10, is transported by process line11, which is controlled via valve system12, to a battery of fermenters. The fermenters may be configured as a batch or continuous fermentation system, with stirring system13. A fermentation-derived first biochemical is produced within the fermenters. Carbon dioxide co-product of the fermentation process passes via dotted line14to reactor vessel16(labeled Catalytic or Reactor Vessel).

The fermentation-derived CO2may be referred to as biocarbon dioxide or renewable carbon dioxide, since the CO2is derived from biomass, rather than, for example, fossil-fuel combustion. This may be shown from a measurement of the14C/12C isotopic ratio of the carbon dioxide, using, for example, ASTM D6866.

The catalytic or reactor vessel16is configured to reduce the carbon dioxide by hydrogenation to form organic alcohols, alkanes, olefins, aromatics, and/or other chemicals, which collectively may be referred to as CO2-derived biochemicals or a second biochemical, which is preferably (but not necessarily) the same molecule as the first biochemical. The catalytic or reactor vessel16may utilize catalysis, electrolysis, thermolysis (thermal reformation), or a combination thereof, to convert the carbon dioxide to more complex organics. The temperature of the catalytic or reactor vessel16may be operated from about 300° C. to about 2000° C., for example, and the pressure of the catalytic or reactor vessel16may be from about 1 bar to about 100 bar, for example. Various catalysts may be present within the catalytic or reactor vessel16, such as metal-oxide catalysts, e.g. CuO, ZnO, or ZrO2. In some embodiments (e.g., employing electrolysis or other electrochemical reactions), the catalytic or reactor vessel16is configured, such as with electrodes within the reactor, to receive electrical power via source103.

In certain embodiments, the catalytic or reactor vessel16utilizes a biocatalyst for hydrogenating CO2. Bioconversion of H2/CO2to acetic acid, ethanol, or other products is well-known. Any suitable microorganisms may be utilized that have the ability to convert CO2, co-fed with CO and/or H2. Anaerobic bacteria, such as those from the genusClostridium, have been demonstrated to produce ethanol from CO, H2, or CO2via the acetyl CoA biochemical pathway. For example, various strains ofClostridium ljungdahliithat produce ethanol from gases are described in U.S. Pat. Nos. 5,173,429, 5,593,886, and 6,368,819.

Because organic molecules typically contain hydrogen, a source of H atoms is necessary in the catalytic or reactor vessel16. The hydrogen source may be water, hydrogen gas, syngas, or methane, for example. In the embodiments ofFIGS. 1 and 2, water enters the catalytic or reactor vessel16via line77. The watery reaction products from the catalytic or reactor vessel16pass via line78to the distillation process18for refinement.

In some embodiments, the hydrogen source is relatively pure hydrogen that may be obtained from separation of syngas. The syngas may be produced in a steam-methane reforming reactor, or in a biomass gasifier, for example.

The fermentation slurry that contains the desired biochemical product (i.e., the first biochemical) as a watery solution with other soluble and insoluble side products passes via valve-controlled line15to the distillation system18(labeled Distillation) via process line17. The biochemical product of the fermentation is heated via heat exchanger10that passes heat, recovered from the high-temperature cook slurry feeding into the fermentation system, to the fermentation product.

The distillation system18further processes the watery fermented solution to separate desired biochemical products from the water, thereby yielding a top product which has a biochemical product composition that may approach an azeotrope with water. An azeotropic composition will require dehydration (as shown forFIG. 1), whereas a composition which may be near-purity with respect to the desired biochemical (as shown forFIG. 2) will not require dehydration. The azeotrope or nearly pure biochemical product passes out of the distillation system as vapors via vapor line19that leads to one of two different process paths.

In the case where the vapors pass to a standard distillation condenser20, the condensed distillation top product passes via liquid line21to holding reflux tank22(labeled Reflux Tank1).

In the case where the vapors pass away from the condenser, the top product of the distillation system18passes via vapor line19, which is potentially split with the condenser system20to an optional vapor line41that passes to compressor42. The compressor42receives mechanical energy from an electrical source102.

The distillation condenser system20is cooled by cooling system23(labeled Cooling Tower). The cooling water from cooling system20passes via pipe24to circulation pump25. This pump transfers the cooling water by valve-controlled pipe26to condenser20, after which the cooling water is returned via pipe27to cooling system23.

The distillation top product leaving the condenser passes via liquid line29to the reflux tank/buffer and then to distillation system18as reflux. The remainder of the condensed distillation top product from distillation system18that does not pass to reflux is either the final biochemical product, pure or sufficiently pure, or an azeotrope with water that passes via liquid line30to dehydration system (54a).

The bottom product of the distillation system18which contains the heavy components as stillage, passes via liquid line31to pump32. The bottom product then passes via line33to one of two potential paths where it passes to final bottom products via liquid line33or cycles through reboiler-condenser(s)43via liquid line(s)48. The final bottom product passes away from the distillation system18via liquid line34where the stillage is further processed to recover co-products having commercial value. Additionally, bottom products may be centrifugally separated and the centrate, thin stillage, may be returned to the reboiler-condenser(s)43prior to passing to line48.

The distillation system18may in part be driven thermally by a steam generator35, where the production steam passes via steam line36with a control valve37, potentially serving other thermal demands in the system such as steam line7to the cook process. The steam generator35is fueled via fuel line200. The bidirectional steam line38forms a means of transporting potential waste heat from a compressor52optionally driven by a combined heat and power system via steam line53as well as steam from the steam generator35. The steam line39is controlled by a valve40to control delivery of steam to potentially drive the distillation system18.

The reboiler-condenser(s)43produces condensate that is nearly pure biochemically inFIG. 2, or an azeotrope inFIG. 1, passing via liquid line44to compression side reflux tank45(labeled Reflux Tank2). The condensed pure or azeotrope biochemical product passes via liquid line46to the distillation system18.

The compression side reflux tank45passes the residual condensate as distillation top product via liquid line47, inFIG. 1, to the dehydration system (54b); or, inFIG. 2, to the Anhydrous Product Tank74.

The electricity driving the mechanical power for compressor42is provided via electrical source102, in bothFIG. 1andFIG. 2. InFIG. 1, electricity driving the compressor52is provided via electrical source104.

Steam line38connects to steam line7that heats the cook tank6and, inFIG. 1, connects to steam line56that drives the azeotrope dehydration vaporizer55. The steam generator35provides the balance of steam required to operate the process beyond the thermal heat recovered by the mechanical vapor recompression.

When an azeotrope requires further removal of water to reach the desired biochemical product quality, the distillation top product passes via liquid lines30and47to a vapor-phase, molecular-sieve, pressure-swing dehydration system or other final dehydration system. This system receives the azeotropic product via line54c. The liquid or vapor azeotropic product moving to the dehydration system from the distillation is preferably vaporized, such as superheated vapors at an increased pressure, which occurs in heat exchanger55(labeled Azeotrope Vaporizer Heat Exchanger).FIG. 1includes a compressor52, wherein a portion of the biochemical vapors are further compressed, passing via line53directly to the dehydration via line61, thereby removing the need for additional external heat from generated steam. The steam, via line56, condenses as the azeotrope vaporizes or superheats vapors via line54c, with the azeotropic vapors passing via vapor line61to the dehydration system. The process steam which drives the vaporizer heat exchanger55condenses and the liquid condensate is recycled to steam generator35via condensate line57. The liquid condensate then passes to recycle pump58where the recycle condensate is returned to steam generator35.

FIG. 1shows the pressurized, vapor-phase dehydration system depicted as a three-bottle system, though the number of bottles may be two or greater. The dehydration system passes the pressurized vapors via a three-valve configuration, wherein one of the bottles is in dehydration mode while the two alternative bottles are being regenerated under low pressure. The three bottles are cycled in a round-robin style with each bottle being used for a period based on the capacity of the dehydration medium while the alternative bottles are regenerating through application of a vacuum to recover the captured water. A portion of the dehydrated product is used to backflush the regenerated bottles, so the regenerated bottle can be placed back in service when the captured water is removed.

The dehydration system passes the pressurized vapors via vapor line61to a system of control valves62a/62b/62c, where an open valve passes the pressurized vapors to the appropriate vapor line63a/63b/63c, which passes the product to the dehydrating bottle64a/64b/64c, that is in service during that period of operation. The dehydrated product passes through the dehydrating bottle via the exiting control valves65a/65b/65c, to vapor line66as anhydrous biochemical product.

The dehydration bottles being regenerated pass a fraction of the dehydrated vapors from the one active bottle to backflush the regenerating bottles. The low-pressure bottle is controlled by control valves67a/67b/67c, with the regeneration vapors containing a mixture of the regenerated water vapors and the backflush anhydrous product passing via vapor line68. The regeneration is driven by a vacuum pump system69, where the vapors are pumped via line70. The dehydration regeneration product is returned to the distillation system18via line71for re-distillation of the regeneration product containing the backflush product.

The final anhydrous biochemical product from the dehydration process passes as a vapor to an anhydrous condenser reboiler72, where the final product is condensed and passed via liquid line73to storage tank74(labeled Anhydrous Biochemical Tank). The anhydrous condenser is cooled by the condenser water via condensate water line75, wherein the heated water is vaporized to steam in reboiler72, with the steam passed via steam line75for use in driving the thermal demands of the biorefinery.

A portion of the cooling water, including the makeup water from lines300and301, provides water for condenser72, where the excess water passes to a catalytic or reactor vessel16via line77, providing water as a hydrogen source for the hydrogenation or other reactions of CO2within the catalytic or reactor vessel16.

In the process depicted inFIGS. 1-2, there are various stream splits. One skilled in the arts of biorefinery design/operation or chemical engineering will be able to determine the split fractions in order to achieve the desired process outcome, while maintaining mass balance. The process may be simulated to determine split ratios that best achieve the desired energy integration.

FIG. 1andFIG. 2provide a flow diagram demonstrating a method and system in some embodiments. One skilled in the art, in view of the present disclosure, will be able to design a vapor-compression system for use within the distillation process of the biorefinery. Such a biorefinery may produce a wide variety of products including, but not limited to, methanol, ethanol, 1-propanol, 2-propanol, n-butanol, isobutanol, 2-butanol, tert-butanol, acetone, acetic acid, lactic acid, perylene, phenol thiazine, dihydrophenazine, 5,10-di(4-methoxyphenyl)-5,10-dihydrophenazine, 5,10-dihydrophenazine, 5,10-di(4-trifluoromethylphenyl)-5,10-dihydrophenazine, and other heterocyclic compounds. Co-products include, but are not limited to, dried distillers grains (DDG), dried distillers grains with solubles (DDGS), still bottoms, sugars, lignin, and exported energy.

As an example of the general principles taught herein, a biorefinery may be configured to produce ethanol, by fermenting saccharides using yeast as well as by catalytically hydrogenating CO2(from fermentation) to an additional quantity of ethanol. It will be understood by a skilled artisan that the present invention is by no means limited to the biorefinery being an ethanol plant.

In addition, as will be appreciated by a person of ordinary skill in the art, the principles of this disclosure may be applied to many biorefinery configurations beyond those explicitly disclosed or described in the drawings hereto. Various combinations are possible and selected embodiments from some variations may be utilized or adapted to arrive at additional variations that do not necessarily include all features disclosed herein. In particular, while some embodiments are directed to ethanol as the primary biofuel/biochemical, the present invention is by no means limited to ethanol. One or more additional distillation or other separation units may be included to separate components of a fermentation mixture. Also, in some embodiments, the primary product is less volatile than water (at atmospheric pressure), rather than more volatile, as is the case with ethanol. An example of a biofuel/biochemical less volatile than water is isobutanol.

Most distillation processes heat beer fed to a distillation column with steam to raise its temperature to the beer's boiling point and then continue to add energy with steam as needed to overcome the beer's heat of evaporation or latent heat, converting the ethanol in the beer into vapors. Ethanol's lower boiling point (versus water) causes the ethanol to vaporize and exit the top of the distillation column. The solids in the beer, along with water and other liquids with boiling points higher than that of ethanol, are collected in the bottom of the distillation column and then transferred to a centrifuge where a wet cake containing solids and a significant proportion of liquids is separated from a liquid centrate. This wet cake is typically transferred to a dryer where the solids are dried to a moisture level appropriate for storage and shipping. Meanwhile, the alcohol vapors exiting the top of the distillation column are typically directed to a water-cooled condenser where they condense, transferring their heat of condensation to condenser cooling water prior to transfer of the condensate to a dehydration process for final upgrading to a marketable ethanol product (as required by azeotropic limitations in making high-purity ethanol).

In should be noted that regardingFIGS. 1 and 2, specific unit operations may be omitted in some embodiments and in these or other embodiments, other unit operations not explicitly shown may be included. Various valves, pumps, meters, sensors, sample ports, etc. are not shown in these block-flow diagrams. Additionally, multiple pieces of equipment, either in series or in parallel, may be utilized for any unit operations. Also, solid, liquid, and gas streams produced or existing within the process may be independently recycled, passed to subsequent steps, or removed/purged from the process at any point.

In certain embodiments, a combined heat and power (CHP) sub-system is included in the overall system. An optional CHP sub-system has a CHP engine and is configured to provide mechanical, electrical, and/or thermal energy for driving vapor compression, wherein the CHP sub-system and vapor compression may be integrated and configured so that residual waste heat of the CHP engine offsets process thermal energy usage in the biorefinery.

For example, an MVR unit may be configured with a standard steam generator to reduce thermal energy required in the distillation. The optional CHP engine may be sized in concert with (i) mechanical demand of the MVR unit and (ii) thermal energy demand of the biorefinery. The waste heat recovered by a CHP system optionally provides at least some of the thermal energy demand of the biorefinery, and may drive an optional TVR unit.

As another example using CHP, a TVR unit may be configured with a standard steam generator to reduce thermal energy required in distillation. The optional CHP engine may be sized in concert with (i) thermal demand of the TVR unit and (ii) thermal energy demand of the biorefinery. The waste heat recovered by a CHP system optionally provides at least some of the motive vapor to drive a TVR vapor jet and/or provide for the thermal energy demand of the biorefinery.

The biorefinery may be a retrofit to an existing plant. In other embodiments, the biorefinery is a greenfield plant.

All publications, patents, and patent applications cited in this specification are incorporated herein by reference in their entirety as if each publication, patent, or patent application was specifically and individually put forth herein. This specification hereby incorporates by reference commonly owned U.S. Pat. No. 9,925,476, issued Mar. 27, 2018, and U.S. Pat. No. 9,925,477, issued Mar. 27, 2018, and U.S. patent application Ser. No. 15/711,699 filed Sep. 21, 2017 (published on Feb. 1, 2018 as U.S. Patent App. Pub. No. 2018/0028934 A1).

In this detailed description, reference has been made to multiple embodiments of the invention and non-limiting examples and drawings relating to how the invention can be understood and practiced. Other embodiments that do not provide all of the features and advantages set forth herein may be utilized, without departing from the spirit and scope of the present invention. This invention incorporates routine experimentation and optimization of the methods and systems described herein. Such modifications and variations are considered to be within the scope of the invention defined by the claims.

Therefore, to the extent that there are variations of the invention which are within the spirit of the disclosure or equivalent to the inventions found in the appended claims, it is the intent that this patent will cover those variations as well. The present invention shall only be limited by what is claimed.