RU2800360C1 - Advanced carbon capture in fermentation - Google Patents

Abstract

FIELD: biotechnology.

SUBSTANCE: group of inventions is described, including a method for obtaining at least one product using microbiological fermentation (embodiments). In one embodiment, the method includes the steps of directing carbonaceous material to a gasification zone to produce a substrate, directing the substrate to a bioreactor containing a culture of at least one carboxydotrophic microorganism selected from the genus Clostridium, and anaerobically fermenting the substrate to at least one product selected from group consisting of alcohols, acids and their mixtures.

EFFECT: invention expands the range of means for making alcohols and acids using microbiological fermentation of a gas stream.

18 cl, 18 dwg, 5 tbl, 2 ex

Description

The field of technology to which the invention belongs

The present invention relates to devices and methods aimed at improving the overall carbon capture and/or increase the overall efficiency of the methods, including microbiological fermentation. In particular, the present invention relates to improving carbon capture and/or improving the efficiency of processes involving the microbiological fermentation of a CO-containing substrate obtained from an industrial source.

State of the art

Around the world, ethanol is rapidly taking over as the main hydrogen-enriched liquid motor fuel. World consumption of ethanol in 2005 is estimated at 12.2 billion gallons. The global market for fuel ethanol production is also predicted to grow rapidly in the future due to increased interest in ethanol in Europe, Japan, the US and some developing countries.

For example, in the US, ethanol is used to produce E10, a 10% mixture of ethanol and gasoline. In the E10 mixture, ethanol acts as an oxygen enriching component, increasing combustion efficiency and reducing the formation of air pollutants. In Brazil, ethanol accounts for approximately 30% of motor fuel demand, both blended with gasoline as an oxygen enrichment component and as a clean fuel on its own. In addition, in Europe, the environmental anxiety that accompanies the effects of greenhouse gas emissions has prompted the European Union to challenge its members to switch to sustainable motor fuels such as biomass-derived ethanol.

Most fuel ethanol is produced by the traditional yeast fermentation process, in which the main source of carbon is crop-derived carbohydrates, such as sucrose extracted from sugar cane or starch extracted from cereals. However, the cost of these carbohydrate feedstocks depends on their value as human food or animal feed, while growing starch or sucrose source crops for ethanol production is not economically viable in any geographic setting. Therefore, there is interest in developing technologies for converting cheaper and/or more abundant carbon feedstocks into fuel ethanol.

CO is the main, uncombined, energy intensive by-product of the incomplete combustion of organic materials such as coal or petroleum and petroleum-derived products. For example, the Australian steel industry is reported to produce and emit more than 500,000 tons of CO2 annually.

Catalytic processes can be used to convert gases predominantly composed of CO and/or CO and hydrogen (H ₂ ) into a variety of fuels and chemicals. Microorganisms can also be used to convert these gases into fuels and chemicals. Such biological processes, although generally slower than chemical reactions, have several advantages over catalytic processes, including greater selectivity, higher yield, lower energy consumption, and greater resistance to poisoning.

The ability of microorganisms to grow on CO as the sole source of carbon was first discovered in 1903. This was subsequently found to be a property of organisms that use the acetyl coenzyme A (acetyl-CoA) metabolic pathway of autotrophic growth (also known as the Woods-Ljungdahl metabolic pathway and the carbon monoxide dehydrogenase/acetyl CoA synthase (CODH/ACS) metabolic pathway )). A variety of anaerobic organisms, including carboxydotrophic, photosynthetic, methanogenic, and acetogenic organisms, have been shown to metabolize CO into various end products, namely _CO2 , _H2 , methane, n-butanol, acetates, and ethanol. All such organisms, although using CO as their sole carbon source, produce at least two of these end products.

It has been shown that anaerobic bacteria, for example from the genus Clostridium, produce ethanol from CO, CO ₂ and H ₂ via the acetyl CoA metabolic pathway. For example, various strains of Clostridium ljungdahlii that produce ethanol from gases are described in WO 00/68407, EP 117309, US Pat. The bacteria Clostridium autoethanogenum sp is also known to produce ethanol from gases (Arbini et al., Archives of Microbiology 161, pp 345-351 (1994)).

However, the production of ethanol by microorganisms during the fermentation of gases is always associated with the formation of acetate and/or acetic acid. Because some of the available carbon is converted to acetate/acetic acid rather than ethanol, the efficiency of ethanol production using such fermentation processes may be less than desired. In addition, if the acetate/acetic acid bypass product is not used for some other purpose, it can cause disposal problems. Microorganisms convert acetate/acetic acid to methane and hence the potential for increased greenhouse gas emissions.

Microbiological fermentation of CO in the presence of H ₂ can result in essentially complete conversion of carbon to alcohol. However, in the absence of a sufficient amount of H ₂ , some of the CO is converted to alcohol, while a significant part is converted to CO ₂ , as shown by the following reaction equations:

6CO + 3H ₂ O → C ₂ H ₅ OH + 4CO ₂

12H ₂ + 4CO ₂ → 2C ₂ H ₅ OH + 6H ₂ O

The formation of CO ₂ makes carbon capture generally inefficient and, if released to the atmosphere, contributes to the amount of greenhouse gases emitted.

In the application WO 2007/117157, the description of which is incorporated herein by reference, describes a process in which alcohols, in particular ethanol, are formed during the anaerobic fermentation of gases containing carbon monoxide. The acetate produced as a by-product of the fermentation process is converted to hydrogen gas and carbon dioxide gas, either of which can be used in the anaerobic fermentation process. WO 2008/115080, the description of which is incorporated herein by reference, describes a process for the production of alcohol(s) in several fermentation steps. By-products resulting from the anaerobic fermentation of the gas(s) in the first bioreactor can be used to produce products in the second bioreactor. In addition, the by-products of the second fermentation step can be recycled to the first bioreactor to be converted into products.

Documents US 7078201 and WO 02/08438 also describe an improved method for the production of ethanol by changing the conditions (eg, pH and redox potential) of the liquid nutrient medium in which the fermentation is carried out. As stated in these publications, similar processes can be used to produce other alcohols such as butanol.

Even small improvements in the fermentation process aimed at producing one or more acids and/or one or more alcohols can make a significant difference in terms of the efficiency and, more specifically, the cost-effectiveness of such a process.

For example, regardless of the source of the feedstock for the fermentation reaction, problems can arise in the event of interruptions in the supply of feedstock. More specifically, such interruptions can be detrimental to the production efficiency of the microorganisms used to carry out a given reaction and, in some cases, in addition to this, can be detrimental to them. For example, where CO gas from an industrial off-gas stream can be used to produce acids/alcohols in fermentation reactions, there may be times when this stream is not produced. At this time, the microorganisms used to carry out the reaction may go into an inactive, unproductive state or hibernation. When the flow is resumed, it may take some time before the full restoration of the productivity of microorganisms for the implementation of the desired reaction. Therefore, a significant advantage can come from finding a means to reduce or eliminate such a delay.

Another example; Many industrial processes use scrubbing systems or separate scrubbers to reduce the concentration of particulate matter (such as dust) and other off-gas pollutants. Known systems of dry and wet gas cleaning. In a wet scrubbing system, water or other liquids are used to “flush” contaminants from the gas stream. A typical wet scrubbing system can be seen in steel mills where water is used to treat off-gases from various stages of steel production, such as gases from coke ovens, blast furnaces, BOFs or electric arc furnaces. Although gas cleaning has the advantage of reducing the amount of contaminants in the exhaust gases, the contaminants are not destroyed in any way. Unwanted substances simply pass from the gas to solid or powder form, or to the irrigation water or liquid. Thus, the water or liquid used in the gas cleaning system becomes a waste stream generated in this industry. The disposal of such waste poses a threat to the environment. The need to clean and dispose of such waste is also a significant material burden on production.

Although conventional industrial gas scrubbers (as found in steel mills) remove some of the contaminants from industrial off-gas streams, it is recognized in the art that these gases need further purification and/or other treatment before they can be fed into a fermentation reaction due to the perceived detrimental effect of such gases on the microorganisms used to carry out the reaction. See, for example, Datar et al., Fermentation of biomass-generated producer gas to ethanol, 2004, Biotechnology and Bioengineering Vol. 86, pp. 587-594. To carry out additional stages of gas cleaning and/or processing in an industrial plant, free space is needed, which is especially problematic if the fermentation process is organized in an existing plant. Therefore, there is a need for improved processes in which additional gas cleaning or other processing steps are not required, or at least minimized.

It is an object of the present invention to provide device(s) and/or method(s) that eliminate or improve at least one of the disadvantages known in the art and to provide new methods for improved and/or expanded production of various useful products.

The essence of the invention

In a first aspect, a microbiological fermentation carbon capture method is provided, which method includes:

i. receiving from the production process flow(s) of flue or off-gas containing CO;

ii. directing this stream(s) to a bioreactor in which one or more types of microorganisms are cultured;

iii. the enzymatic activity of this culture in a bioreactor to produce one or more products.

In some embodiments of the invention, this method includes capturing at least part of the CO ₂ contained in the gas using a device for removing CO ₂ from one or both streams:

i. flow before entering the bioreactor;

ii. stream after it exits the bioreactor.

In certain embodiments, the method includes a first gas separation step, which first gas separation step comprises (i) receiving a gas stream; (ii) essentially separating at least one portion of this gas stream, which portion contains one or more components of this gas stream; and (iii) directing at least a portion of the separated portion(s) to the bioreactor. In one of the embodiments of the invention, this at least part of the separated portion(s) sent to the bioreactor contains CO.

In certain embodiments, the method includes a second gas separation step, which second gas separation step comprises (i) receiving a gas stream; (ii) essentially separating at least one portion of this gas stream, which portion contains one or more components of this gas stream; and (iii) directing at least a portion of the separated portion(s) to a CO ₂ removal device. In one embodiment of the invention, this gas separation step essentially separates CO ₂ from the gas stream and directs the separated CO ₂ to a CO ₂ removal device.

In certain embodiments of the invention, this method includes intermediate storage of the gas stream and the direction of at least a portion of this stream in the bioreactor, essentially in a continuous mode. In one embodiment of the invention, this intermediate storage step includes (i) receiving an intermittent or non-constant gas flow into a storage device; (ii) directing from the storage device a substantially continuous flow of gas into the bioreactor.

In certain embodiments of the invention, this method includes mixing one or more gas streams with at least one other stream.

In certain embodiments of the invention, this method includes adding irrigation water from the production process to the bioreactor.

In a second aspect, a system is provided for capturing carbon by microbiological fermentation, which system has an inlet for receiving flue or off-gas from a manufacturing process, and which system in operation provides for directing at least a portion of this gas to a bioreactor to produce products by microbiological fermentation.

In some embodiments of the invention, this system includes a CO ₂ removal device configured, in operation, to capture at least a portion of the CO ₂ contained in one or both streams:

i. flow before entering the bioreactor;

ii. stream after it exits the bioreactor.

In certain embodiments of the invention, the system includes a first gas separator configured, in operation: (i) receiving a gas stream; (ii) essentially separating at least one portion of this gas stream, which portion contains one or more components of this gas stream; and (iii) directing at least a portion of the separated portion(s) to the bioreactor. In one embodiment of the invention, this gas separator is adapted to, in operation, essentially separate CO from the gas stream and direct the separated CO to the bioreactor.

In certain embodiments of the invention, the system includes a second gas separator configured, in operation: (i) receiving a gas stream; (ii) essentially separating at least a portion of this gas stream, which portion contains one or more components of this gas stream; (iii) directing at least a portion of the separated portion to a CO ₂ removal device. In one embodiment of the invention, the second gas separator is adapted to separate CO ₂ from the gas stream and direct the separated CO ₂ to a CO ₂ removal device.

In some embodiments of the invention, this system includes a storage device configured, in operation, to provide a substantially continuous flow of substrate into the reactor. In certain embodiments of the invention, this storage device includes a storage tank designed to:

i. receiving intermittent or intermittent gas/substrate flow;

ii. directing a substantially continuous flow of gas/substrate to the bioreactor.

In certain embodiments of the invention, this system includes a mixer configured, in operation, to connect the gas stream with at least one other stream before directing the combined stream to the bioreactor.

In certain embodiments of the invention, this system includes at least one measuring device for monitoring the composition of at least one gas stream supplied to the bioreactor and/or leaving the bioreactor. In certain embodiments of the invention, this system includes a control device for directing at least a portion of one or more gas stream/outlet stream(s) to one or more of the following devices:

i. bioreactor;

ii. a device for removing CO ₂ ;

iii. first gas separator

iv. second gas separator

v. storage device;

vi. mixer;

vii. outlet device,

wherein the specific target device from (i)-(vii) is selected, at least in part, based on data received by the measuring device.

In a third aspect, a system is provided for improving overall carbon capture in a process for producing products in a bioreactor by microbiological fermentation of a substrate, which system has a CO ₂ removal device for capturing at least a portion of the CO ₂ contained in one or both of the streams:

i. flow before entering the bioreactor;

ii. stream after it exits the bioreactor.

In the fourth aspect, a system is provided for improving the efficiency of methods for producing products using microbiological fermentation of gas (gases), when the supply of said gas (gases) is intermittent, which system includes a storage device designed to receive and store at least a portion of the gas, and the bioreactor is adapted to receive at least a portion of the gas from this storage device.

In a fifth aspect, a system is provided for improving the efficiency of processes for producing products by microbial fermentation of gas(s), which system includes a gas separator for receiving a gas stream and directing at least a portion of said stream to a bioreactor.

In a sixth aspect, a steel plant is provided that provides for the production of alcohols by microbiological fermentation of exhaust gas(s).

In accordance with certain aspects, the devices and methods of the present invention provide for their use in processes for the production of alcohols, more specifically ethanol and/or butanol, by anaerobic fermentation of gases containing carbon monoxide. Additionally or alternatively, acids such as acetic acid or acetate can be produced. However, the present invention is not limited to this and is intended to cover other fermentation reactions, including aerobic fermentation, which form various products, such as isopropanol or H ₂ , and reactions that do not include the fermentation of carbonaceous gases.

Embodiments of the present invention find particular application in the fermentation of a CO containing gaseous substrate to produce acids and/or alcohols, although certain aspects of the present invention are not limited to CO containing substrates. The gaseous substrate may contain gas obtained as a by-product of the manufacturing process. In certain embodiments of the invention, the manufacturing process is selected from the group that includes the production of ferrous metal products, the production of non-ferrous metal products, oil refining processes, biomass gasification, coal gasification, power generation, carbon black production, ammonia production, methanol production, and coke production. Most preferably, the gaseous substrate contains a gas obtained from a steel plant.

In certain preferred embodiments of the invention, the gaseous substrate contains from 20% vol. CO up to 100% vol. CO, for example, from 50% vol. CO up to 95% vol. CO, for example, from 50% vol. CO up to 70% vol. CO. A gaseous substrate with a lower concentration of CO, for example 6%, can also be used, especially when H ₂ and CO ₂ are also present.

In preferred embodiments of the invention, the fermentation reaction is carried out using one or more strains of carboxydotrophic bacteria.

Carboxydotrophic bacteria are preferably selected from Clostridium, Moorella and Carboxydothermus. Most preferably, the carboxydotrophic bacteria are Clostridium autoethanogenum.

Brief description of the drawings

Hereinafter, the present invention is described in detail with reference to the accompanying figures, which show:

Fig. 1 is a diagram of a system including a downstream CO ₂ removal device in accordance with certain embodiments of the present invention.

Fig. 2 is a diagram of a system including a downstream CO ₂ removal device in accordance with certain embodiments of the present invention.

Fig. 3: diagram of a system including a device for removing CO ₂ downstream of the bioreactor along the process stream and a device for returning the substrate stream to the bioreactor.

Fig. 4 is a diagram of a system including a gas separator located upstream of the bioreactor in accordance with certain embodiments of the present invention.

Fig. 5 is a diagram of a system including a gas separator downstream of the bioreactor, in accordance with certain embodiments of the present invention.

Fig. 6 is a diagram of a system including two gas separators, one gas separator located upstream of the bioreactor, and one gas separator located downstream of the bioreactor, in accordance with certain embodiments of the present invention.

Fig. 7 is a diagram of a system including a storage tank in accordance with certain embodiments of the present invention.

Fig. 8 is a diagram of a system including an optional storage tank in accordance with certain embodiments of the present invention.

Fig. 9 is a diagram of a system including a compressor in accordance with certain embodiments of the present invention.

Fig. 10a is a diagram of a system including a plurality of substrate flow sources and a storage reservoir, in accordance with certain embodiments of the present invention.

Fig. 10b is a diagram of a system including a plurality of substrate flow sources and a storage reservoir, in accordance with certain embodiments of the present invention.

Fig. 11 is a diagram of a system including a storage tank and a CO ₂ removal device in accordance with certain embodiments of the present invention.

Fig. 12 is a diagram of a system for capturing carbon from an off-gas stream, in accordance with certain embodiments of the present invention.

Fig. 13 is a diagram of a system including a mixer in accordance with certain embodiments of the present invention.

Fig. 14: An illustration of the growth of microorganisms over time in the case where the gases come from a steel plant.

Fig. 15: An illustration of the synthesis of a product, namely the production of acetate, over time in the case where the gases come from a steel plant.

Fig. 16: illustration of microbial growth and product synthesis over time in laboratory environments.

Fig. 17: illustration of microbial growth and product synthesis over time using laboratory media mixed 1:1 with steel mill spray water.

Detailed description of the invention

In accordance with certain methods of the present invention, the off-gases of industrial processes can be used as an additive and/or the main raw material of fermentation reactions with minimized stages of additional processing of these gases before they are sent to the bioreactor in which the fermentation process is carried out. This is particularly surprising since it is generally accepted that off-gases contain contaminants that adversely affect the growth and/or survival of the microorganisms used for fermentation. The present invention is particularly useful when off-gases are generated during steel production, in particular when these gases contain CO and are used to produce alcohols (e.g. ethanol, butanol, isopropanol) and/or acids (e.g. butyric acid, acetic acid and/or acetate) and/or hydrogen. Although there are many different microorganisms capable of carrying out such processes, the present invention is particularly useful for fermentation processes that use Clostridium autoethanogenum.

A particular value of this aspect of the present invention lies in the fact that it makes it possible to reduce the number of stages of pre-treatment of off-gases prior to their use in the fermentation reaction or to eliminate such stages. Thus, the invention provides a wider suitability and/or applicability of such fermentation processes, especially in existing industrial plants where there is a limited, given area for the system of equipment intended to carry out the fermentation. In addition, since these off-gases do not undergo any or limited purification and/or pre-treatment, the use of embodiments of the present invention can also improve the quality or reduce the amount of waste from these production processes due to the fact that it is no longer necessary to treat waste or pollutants generated in the gas cleaning and/or pre-treatment processes.

Off-gases from industrial processes other than steel production can be used in the processes of the present invention in a similar manner. The present invention is readily applicable to fermentation reactions that use gaseous substrates other than carbon monoxide as a source of carbon and energy, produce alcohols other than ethanol, produce hydrogen, and/or that use microorganisms other than Clostridium autoethanogenum.

Substrates suitable for use in fermentation processes often also contain CO ₂ . In addition, many fermentation reactions, such as those where CO is converted to products containing acids and/or alcohols, can produce significant amounts of CO ₂ . The present invention relates to methods, systems and processes aimed at improving the capture of total carbon in such fermentation reactions.

In accordance with the methods of the present invention, by removing CO ₂ (or other gases) from the substrate stream, the concentration of CO (or the partial pressure of CO in the gaseous substrate) is increased, and thus the efficiency of fermentation reactions in which CO is the substrate is increased. By increasing the partial pressure of CO in the gaseous substrate, the mass transfer of CO in the fermentation media increases. In addition, the composition of the gas streams used as feedstock for the fermentation reaction can have a significant impact on the efficiency and/or costs of carrying out this reaction. For example, the presence of O ₂ can reduce the efficiency of an anaerobic fermentation process. In addition, the treatment of unwanted or unnecessary gases in the stages of the fermentation process before or after fermentation can increase the costs of such stages (for example, where the pressure of the gas stream before entering the bioreactor is increased, energy is expended on compressing the gas that is not required for fermentation). Additionally or alternatively, the CO ₂ component of a particular substrate stream may be of value when used in another reaction, including another fermentation reaction.

In addition, in accordance with the methods of the present invention, increasing the concentration of CO ₂ in the stream, for example, increasing the partial pressure of CO ₂ in the gaseous stream, improves the efficiency of the process that uses CO ₂ such as fermentation. Examples of processes that use CO ₂ , such as fermentation, are well known in the art. Examples of some such processes are detailed in WO 2006/108532 and incorporated herein by reference.

Certain aspects of the present invention generally relate to systems and methods for increasing overall carbon sequestration in processes involving microbiological fermentation. In specific embodiments of its implementation, the present invention relates to the capture of CO ₂ from the streams of the substrate supplied to the fermentation reaction. Alternatively or additionally, the present invention relates to capturing CO ₂ from off-gas streams after the stream has left the bioreactor. In specific embodiments of the present invention, the substrate supplied to the fermentation reaction contains CO.

In addition, it may be desirable to remove and/or capture carbonaceous components such as CO ₂ and/or CH ₄ in order to increase overall carbon capture in the processes described above. In addition, or alternatively, the components of a particular gas may be more valuable when used elsewhere than in the fermentation reaction (eg, H ₂ is of great importance as a fuel).

Certain aspects of the present invention generally relate to systems and methods for improving the efficiency of product manufacturing processes by microbial gas fermentation, in particular by using at least one process for separating gas from a gas stream used as a fermentation feedstock and/or a gas stream resulting from the fermentation. In one of the embodiments of the invention, the gas separator is designed to essentially separate at least one portion from the gas stream, which portion contains one or more components. For example, a gas separator can separate CO ₂ from a gas stream containing the following components: CO, CO ₂ , H ₂ , where CO ₂ can be sent to a CO ₂ removal device, and the remaining gas stream (containing CO and H ₂ ) can be sent to a bioreactor.

The gas streams produced during manufacturing processes, such as the batch production of steel from iron in a steel mill, can be discontinuous in nature, which may be undesirable if these gases are used for bioconversion. In addition, the nature of these streams may be such that the composition of the gas changes cyclically in different phases of a particular industrial process. For example, in the steelmaking process, during those periods when mainly oxygen-free gases are formed, the concentration of CO is the highest. On the contrary, when these gases are mostly free of CO, significant amounts of O ₂ may be present. Many fermentation reactions, such as those carried out by anaerobic bacteria, in particular carboxydotrophic bacteria, require a high concentration of CO, which is substantially free of O ₂ .

Certain aspects of the present invention generally relate to systems and methods for improving the efficiency of product manufacturing processes by microbial gas fermentation, where the gas streams (or other sources such as dissolved gases and/or carbohydrates) used as fermentation reaction feedstock are inherently variable. Specific embodiments of the invention are described in the context of the steel industry using carboxydotrophic bacteria to produce acids and/or alcohols, in particular ethanol or butanol. Upon review of the present description, it will become clear to those skilled in the art that this invention can be applied to various industries, as well as at various stages of the steelmaking process. In addition, upon consideration of the present description, it will become clear to those skilled in the art that the present invention may be applied to other fermentation reactions, including reactions that use the same or different microorganisms. Therefore, it is understood that the scope of the present invention is not limited to the specific embodiments and/or applications described, on the contrary, it should be understood that the invention relates to any fermentation process in which at least one element used as a raw material of this process is supplied in an intermittent mode, for example, in which off-gases of an industrial process are used, which gases are produced in an intermittent mode.

Certain aspects of the present invention generally relate to systems and methods for improving the efficiency of product manufacturing and/or carbon capture processes by microbiological fermentation of substrate streams, where substrate streams are mixed with additional streams to optimize composition according to microbiological fermentation conditions.

Surprisingly, it has been found that when BOF main process reflux water or BOF off-gas stream from a steel mill is mixed with standard microorganism growth media in a carbon monoxide gas fermentation reaction to produce ethanol according to the methods of the present invention, the growth of Clostridium autoethanogenum as well as their ability to produce ethanol is improved. This is particularly surprising since the water was expected to contain contaminants that could be detrimental to the growth and/or survival of microorganisms.

This fact is very valuable in terms of improving the quality or reducing the amount of waste in production processes, increasing the efficiency of fermentation reactions, reducing the amount of media needed to support fermentation reactions, and therefore reducing operating costs. Thus, the present invention can help reduce the amount of acetate by-products generated during such fermentation reactions. This can be beneficial in cases where acetate is not used and would otherwise be discarded, increasing production costs and exacerbating environmental problems.

Based on the results obtained, the present invention makes it possible to use irrigation water as the main raw material for fermentation reactions. Irrigation water from production processes other than steel production can be used in a similar way. In addition, the present invention is readily applicable to fermentation reactions that use gaseous substrates other than carbon monoxide as a source of carbon and energy, produce alcohols other than ethanol, generate hydrogen, and/or that use microorganisms other than Clostridium autoethanogenum.

One or more features of any two or more of the above aspects of the invention may be combined and used in the same system to obtain their respective benefits.

Definitions

Unless otherwise indicated, the following terms used in this specification have the following meanings:

The term "carbon capture" in the context of the present invention means the removal of carbon compounds, including CO ₂ and/or CO, from a stream containing CO ₂ and/or CO, and:

- either converting CO ₂ and/or CO into products,

- either the conversion of CO ₂ and / or CO into substances suitable for long-term storage,

- either the capture of CO ₂ and / or CO substances suitable for long-term storage;

or a combination of these processes.

The term "substrate containing carbon monoxide" and terms like it should be understood as covering any substrate in which carbon monoxide is available to one or more strains of bacteria that use it, for example, for growth and/or fermentation.

The term "gaseous substrates containing carbon monoxide" means any gas containing carbon monoxide. This gaseous substrate usually contains a significant proportion of CO, preferably at least from about 5% vol. up to about 100% vol. CO.

The term "bioreactor" means a fermentation device consisting of one or more tanks and/or a column or piping, including a stirred tank reactor (CSTR), an immobilized cell bioreactor (ICR), a trickle bed reactor (TBR), a bubble column reactor, a gas lift fermenter, a membrane reactor such as a hollow fiber membrane fermenter (HFMBR), a static mixer, or other tanks or other devices suitable for gas-liquid contact.

The term "co-substrate" means a substrate which, although not necessarily the main source of energy and material for the synthesis of a product, can be used to synthesize a product if it is added to another substrate, such as the main substrate.

The term "acid" in the context of this document includes both carboxylic acids and the corresponding carboxylate anions, for example, a mixture of free acetic acid and acetate, present in the contents of the fermenter, as described herein. The ratio of the amount of free acid to the amount of carboxylate in the contents of the fermenter depends on the pH of this system. In addition, the term "acetate" encompasses both acetate as a salt per se and a mixture of free acetic acid and acetate, such as a mixture of this salt and free acetic acid, present in the contents of the fermenter, as described herein.

The term "limited concentration" means a concentration of a given component in the microbiological fermentation medium that is low enough to be certain to be depleted at some stage of the fermentation.

The term "discontinuous stream" means not only streams that are not available in continuous mode, but also streams that do not always have a given composition.

The term “irrigation water” refers to water or other liquids resulting from the purification of gas streams generated during industrial processes such as the production of ferrous metal products, the production of non-ferrous metal products, oil refining processes, coal gasification, biomass gasification, power generation, carbon black production and coke production.

The term "directly" used in relation to directing industrial flue or off-gas to the bioreactor means that there is no or minimal treatment of these gases, such as cooling and removal of solid particles, before they are fed into the bioreactor (note: an oxygen removal step may be needed in the case of anaerobic fermentation).

The term "target composition" is used herein to refer to the desired amount and type of components in a material, such as a gas stream. More specifically, a gas is considered to have a "specified composition" if it contains a specific component (e.g., CO and/or CO ₂ ) and/or contains a specific component in a specific amount and/or does not contain a specific component (e.g., a contaminant harmful to microorganisms) and/or does not contain a specific component in a specific amount. In determining whether a gas stream has a given composition, more than one component may be considered.

The term "flow" is used to refer to the movement of material entering, flowing through, and exiting one or more process steps, such as material fed into a bioreactor and/or optional CO ₂ removal device. The composition of the stream may change as it passes through certain stages. For example, as a stream passes through a bioreactor, the CO content of the stream may decrease while the CO ₂ content may increase. Similarly, as the stream passes through the CO ₂ removal step, its CO ₂ content decreases.

Unless the context dictates otherwise, the phrases "fermentation", "fermentation process" or "fermentation reaction" and the like, as used herein, cover both the growth phase and the biosynthetic phase of the product of this process.

The terms “increased efficiency”, “improved efficiency”, and the like, as used in relation to a fermentation process, include, but are not limited to, an increase in one of the following: the growth rate of microorganisms during fermentation, the volume or mass of the target product (such as alcohols) produced per unit volume or mass of the substrate (such as carbon monoxide) consumed, the productivity or level of production of the target product, and the relative proportion of the target product compared to other fermentation by-products; and, in addition, may reflect the value (which may be positive or negative) of any by-product formed during this process.

In one aspect, the present invention relates to systems and methods for increasing overall carbon capture in microbial fermentation product manufacturing processes, which systems and methods include at least one CO ₂ removal step performed on substrates and/or streams prior to (i.e., upstream) or after (i.e., downstream) the fermentation reaction. In certain embodiments of the present invention, the substrate contains CO. Typically, the substrate is gaseous; however, the present invention is not limited to this.

In one aspect, the present invention relates to systems and methods for improving the efficiency of product manufacturing processes by microbial fermentation of gases, which systems and methods include at least one gas separation step performed on these gases before (i.e., upstream) or after (i.e., downstream) the fermentation reaction. As noted above, in certain embodiments of the invention, the gaseous substrate used for microbiological fermentation contains CO; however, the present invention is not limited to this.

In another specific aspect, the present invention relates to systems and methods for improving the efficiency of food production processes by microbial fermentation of gases, especially in cases where the supply of these gases is inherently intermittent. In certain embodiments of the invention, the gaseous substrate used for microbiological fermentation contains CO; however, the present invention is not limited to this.

In addition, the present invention provides methods and systems for the production of alcohol using microbiological fermentation. These methods and systems involve the use of off-gases from manufacturing processes, such as steel production, for the fermentation reaction, where prior to such use, these gases undergo little or no further processing. In certain embodiments of the invention, off-gases from one or more production processes and/or from alternative sources are combined or mixed in order to obtain a stream with a given or optimized composition corresponding to the conditions of the fermentation reaction.

The present invention also provides methods and systems for optimizing the composition of a CO-containing substrate stream coming, at least in part, from any manufacturing process, such as steelmaking.

The present invention also provides methods for producing alcohol using microbiological fermentation and methods for improving the efficiency of alcohol production using microbiological fermentation. In one of the embodiments of the invention, these methods involve the use of any production process in the fermentation reaction of the reflux water.

Although certain embodiments of the present invention, namely those involving the production of ethanol by anaerobic fermentation using CO as the main substrate, are clearly valuable improvements in technology of great interest today, it should be understood that this invention is applicable to the production of alternative products, such as other alcohols, and the use of alternative substrates, in particular, gaseous substrates, as will become clear to specialists in this field, to which the present invention relates, upon consideration of this description. For example, gaseous substrates containing carbon dioxide and hydrogen can be used in specific embodiments of the invention. In addition, this invention is applicable to fermentation processes aimed at the production of acetate, butyrate, propionate, caproate, ethanol, propanol and butanol, as well as hydrogen. For example, these products can be produced by fermentation, which uses microorganisms of the genus Moorella, Clostridia, Ruminococcus, Acetobacterium, Eubacterium, Butyribacterium, Oxobacter, Methanosarcina and Desulfotomaculum.

Certain embodiments of the present invention involve the use of gas streams coming from one or more production processes. Such processes include steelmaking processes, in particular processes that produce a gas stream with a high CO content or a CO content in excess of a predetermined level (ie, 5%). In accordance with such embodiments of the invention, carboxydotrophic bacteria are used in one or more bioreactors to produce acids and/or alcohols, in particular ethanol or butanol. Those skilled in the art upon review of this description will appreciate that the present invention may be applied to various industries or to various gas streams, including exhaust gases from internal combustion engines. In addition, those skilled in the art upon review of this disclosure will recognize that the present invention is applicable to other fermentation reactions, including those using the same or different microorganisms. Therefore, it is understood that the scope of the present invention is not limited to the specific described variants of its implementation and/or application, on the contrary, it should be interpreted in a broader sense; for example, the source of the gas stream is not limited except that at least one of its components is suitable as a raw material for the fermentation reaction. The present invention is particularly applicable to improving overall carbon capture and/or production of ethanol and other alcohols from gaseous substrates such as automotive exhaust and industrial waste gases with a high CO volume content.

Fermentation

Methods for the production of ethanol and other alcohols from gaseous substrates (such as those described in the prior art section above) are known. Such methods are described, for example, in documents WO 2007/117157 and WO 2008/115080, as well as US patent No. 6340581, 6136577, 5593886, 5807722 and 5821111, each of which is incorporated herein by reference.

A number of anaerobic bacteria are known that are capable of fermenting CO to form alcohols, including n-butanol and ethanol, acetic acid, and suitable for use in the method of the present invention. Examples of such bacteria suitable for use in the context of the present invention include bacteria of the genus Clostridium, such as the strain Clostridium ljungdahlii, including those described in WO 00/68407, EP 117309, US Pat. stridium carboxydivorans (Liou et al., International Journal of Systematic and Evolutionary Microbiology 33: pp 2085-2091) and Clostridium autoethanogenum sp (Arbini et al., Archives of Microbiology 161, pp 345-351 (1994)). Other suitable bacteria are those of the genus Moorella, including Moorella sp HUC22-1 (Salai et al., Biotechnology Letters 29: pp 1607-1612) and the genus Carboxydothermus (Svetlichny, V.A. et al., (1991) Systematic and Applied Microbiology 14: 254-260). The description of each of these publications is incorporated herein by reference. In addition, other carboxydotrophic anaerobic bacteria can be used by those skilled in the art in the processes to which the present invention relates. When considering the present description, it will also become clear that in the processes to which the present invention relates, a mixed culture of two or more varieties of bacteria can be used.

The cultivation of the bacteria used in the method of the present invention may be carried out using any number of processes known in the art for growing anaerobic bacteria and fermenting substrates using them. Examples of techniques are given in the Examples section below. Additionally, the following processes using gaseous fermentation substrates can be used, as outlined in the following articles: (i) K.T.Klasson et al., (1991). Bioreactors for synthesis gas fermentations resources. Conservation and Recycling (Bioreactors for synthesis gas fermentation reactions. Conservation and recycling), 5; 145-165; (ii) K.T.Klasson et al., (1991). Bioreactor design for synthesis gas fermentations. fuel. (Design of a bioreactor for the fermentation of synthesis gas. Fuel.) 70. 605-614; (iii) K.T.Klasson et al., (1992). Bioconversion of synthesis gas into liquid or gaseous fuels. Enzyme and Microbial Technology. (Bioconversion of synthesis gas into liquid and gaseous fuels. Enzymatic and microbiological technology) 14; 602-608; (iv) J. L. Vega et al. (1989). Study of Gaseous Substrate Fermentation: Carbon Monoxide Conversion to Acetate. 2. Continuous culture. (Substrate gas fermentation study: conversion of carbon monoxide to acetate. 2. Continuous culture) Biotech. Bioeng. 34.6.785-793; (vi) J. L. Vega et al. (1989). Study of Gaseous Substrate Fermentation: Carbon Monoxide Conversion to Acetate. 1. Batch culture. (Study of gaseous substrate fermentation: conversion of carbon monoxide to acetate. 1. Batch culture) Biotechnology and Bioengineering. 34.774-784; (vii) J. L. Vega et al. (1990). Design of Bioreactors for Coal Synthesis Gas Fermentations. Resources, Conservation and Recycling. (Design of bioreactors for the fermentation of synthesis gas obtained by coal gasification. Resources, conservation and recycling) 3. 149-160; all articles are incorporated herein by reference.

One example of a microorganism suitable for use in the context of the present invention is Clostridium autoethanogenum. In one embodiment, the Clostridium autoethanogenum is a Clostridium autoethanogenum with distinct strain characteristics that has been entered into the German Resource Center for Biological Material (DSMZ) under attachment identification number 19630. In another embodiment, Clostridium autoethanogenum is a Clostridium autoethanogenum with distinct strain characteristics with attachment number DSMZ 10061.

Fermentation can be carried out in any suitable reactor. In some embodiments, the bioreactor may include a first reactor, a growth reactor, in which microorganisms are grown, and a second reactor, a fermentation reactor, into which the contents of the growth reactor are fed and in which most of the fermentation product (e.g., ethanol and acetate) is produced.

In accordance with various embodiments of the invention, the carbon source for the fermentation reaction is a gaseous substrate containing CO. The gaseous substrate may be a CO-containing off-gas produced as a by-product in an industrial process, or may come from another source such as automobile exhaust. In certain embodiments of the invention, the production process is selected from the group that includes the production of ferrous metal products, for example, carried out in a steel mill, the production of non-ferrous metal products, oil refining processes, biomass gasification, coal gasification, power generation, carbon black production, ammonia production, methanol production, and coke production. In these embodiments, the CO-containing gas can be removed from the manufacturing process before it is released to the atmosphere using a conventional method. Depending on the composition of the gaseous CO-containing substrate, it may also be desirable to treat it to remove any undesirable impurities, such as dust particles, prior to feeding the substrate to fermentation. For example, the gaseous substrate may be filtered or scrubbed using known methods.

Containing CO gaseous substrate, ideally, contains a significant proportion of CO, for example, from about 5% vol. up to about 100% vol. CO or from 20% vol. up to 95% vol. CO or from 40% vol. up to 95% vol. CO or from 60% vol. up to 90% vol. CO or from 70% vol. up to 90% vol. CO. Gaseous substrates with lower concentrations of CO, eg 6%, may also be acceptable, especially if H ₂ and CO ₂ are still present.

While it is not necessary for the gaseous substrate to contain any amount of hydrogen, the presence of hydrogen is generally not detrimental to product formation in accordance with the methods of the present invention. However, in certain embodiments of the invention, the gaseous substrate is substantially free of hydrogen (less than 1%). The gaseous substrate may also contain some CO ₂ , for example, from about 1% vol. up to about 30% vol. or, for example, from about 5% vol. up to about 10% vol. _CO2 .

As noted previously, the presence of hydrogen in the substrate stream can result in increased overall carbon capture efficiency and/or ethanol productivity. For example, WO 0208438 describes the production of ethanol using gas streams of various compositions. In a preferred embodiment of the invention, a substrate stream containing 63% H ₂ , 32% CO and 5% CH ₄ was fed into the C. ljungdahlii bioreactor in order to promote microbial growth and increase ethanol production. When the culture reached a steady state and microbial growth was no longer the main goal, the substrate flow was changed to 15.8% H ₂ , 36.5% CO, 38.4% N ₂ and 9.3% CO ₂ to provide a slight excess of CO and increase ethanol production. This document also describes gas streams with higher and lower concentrations of CO and H ₂ .

Therefore, to increase alcohol production and/or overall carbon capture, it may be necessary to change the composition of the substrate stream. In addition, or alternatively, the formulation may be modified (i.e., adjusted CO, CO ₂ and/or H ₂ concentrations) to optimize the efficiency of the fermentation reaction and ultimately increase alcohol production and/or overall carbon capture.

In some embodiments, the source of the CO-containing gaseous substrate may be the gasification process of organic material such as methane, ethane, propane, coal, natural gas, crude oil, low-value refinery residues (including petroleum coke), municipal solid waste, or biomass. Biomass contains by-products from extraction and food processing, such as sugar from sugar cane or starch from maize or cereals; or non-food biomass waste from the forestry industry. Any of these carbonaceous materials can be subjected to gasification, that is, partial combustion in the presence of oxygen to produce synthesis gas (a gas containing significant amounts of H ₂ and CO). The gasification process typically produces synthesis gas with an H ₂ /CO molar ratio of about 0.4:1 to 1.2:1, along with smaller amounts of CO ₂ , H ₂ S, methane and other inert compounds. This ratio in the produced gas can be changed by methods known to those skilled in the art and are detailed in WO 200701616. However, to adjust the CO:H ₂ ratio in the product, for example, the following conditions in the gasification system can be changed: feed composition (especially the C:H ratio), operating pressure, temperature profile (affecting rapid cooling of the product mixture) and the oxidizer used (air, oxygen-enriched air, pure O ₂ or steam; however, the use of steam gives a higher ratio of CO: H ₂ ). Therefore, the operating conditions of the gasification system can be adjusted to produce a substrate stream of a given composition to match fermentation conditions, or to be mixed with one or more other streams to provide an optimized or targeted composition to produce increased alcohol yield and/or increase overall carbon capture in the fermentation process.

In other embodiments, the CO-containing substrate may be obtained from a hydrocarbon steam reforming process. Hydrocarbons, such as those constituting natural gas, can be reformed at high temperature to produce CO and H ₂ according to the following equation:

C _n H _m + nH ₂ O → nCO + (m / 2 + n) H ₂

For example, steam reforming of methane involves reacting steam with methane to produce CO and H ₂ at elevated temperature (700-1100°C) in the presence of a nickel catalyst. The resulting stream (containing 1 mole of CO and 3 moles of H ₂ for each mole of CH ₄ converted) can be sent directly to the fermenter or mixed with a substrate stream from another source to increase ethanol productivity and/or overall carbon capture during the fermentation. Alcohols such as methanol can also be reformed to produce CO ₂ and H ₂ which can be used in a similar manner.

In another embodiment of the invention, the CO-containing substrate is obtained from a steelmaking process. In the steel industry, iron ore is crushed, pulverized and subjected to pre-treatment such as sintering and granulation, and then sent to a blast furnace where it is smelted. In the smelting process, coke acts as a source of carbon, which is a reducing agent that reduces iron ore. Coke is also a heat source for heating and melting materials. The hot metal is decarburized in an oxygen converter by injecting a high-velocity jet of pure oxygen directed at the surface of the hot metal. The oxygen reacts directly with the carbon inside the hot metal to form carbon monoxide (CO). Consequently, a CO rich gas stream exits the BOF. In accordance with certain embodiments of the present invention, this stream is used as feedstock for one or more fermentation reactions. However, as those skilled in the art will appreciate, CO can be produced at other stages of the steel making process and, in accordance with various embodiments of the invention, these alternative sources can be used in place of or in combination with BOF off-gases. Depending on the specific source (i.e., specific stage of the steelmaking process), the CO content in the exhaust gases may vary. In addition, there may be periods during which one or more such flow is interrupted, especially on batch systems.

Typically, the effluents from the steelmaking decarburization stage contain a large amount of CO and a small amount of H ₂ . Although such streams can be sent directly to the bioreactor with little or no additional processing, it may be desirable to optimize the composition of the substrate stream in order to achieve higher efficiency in alcohol production and/or overall carbon capture. For example, the concentration of H ₂ in the substrate can be increased before this stream is fed to the bioreactor.

In accordance with specific embodiments of the present invention, streams from two or more sources can be combined and/or mixed in order to obtain a given and/or optimized substrate stream. For example, a high CO stream, such as an off-gas from a steel converter, may be combined with a high H ₂ stream, such as off-gas from a steel mill coke oven.

The initial stage of steel production usually involves the reduction of iron ore using coke. Coke is a source of hard carbon fuel used to smelt and reduce iron ore and is typically produced in a steel mill. In the coke making process, bituminous coal is fed into a series of pressurized furnaces where it is heated at high temperature in the absence of oxygen, typically in cycles of 14 to 36 hours. The solid carbon remaining in the kiln is coke. It is transferred to a cooling tower, where it is cooled by spraying water or circulating an inert gas (nitrogen), then screened and sent to a blast furnace.

The volatile compounds generated during this process are typically treated to remove tar, ammonia, naphthalene, phenol, light ends and sulfur before the gas is used as fuel to heat furnaces. The gas resulting from the production of coke is usually characterized by a high content of H ₂ (typical composition: 55% H ₂ , 25% CH ₄ , 6% CO, 3% N ₂ , 2% other hydrocarbons). As such, at least a portion of the coke oven gas may be sent to the fermentation process for mixing with the CO containing stream to improve alcohol production and/or overall carbon capture. It may be necessary to process the off-gas from the coke oven before it is sent to the fermenter to remove by-products that may be toxic to the crop.

Alternatively or additionally, an intermittent CO-containing stream, such as a converter off-gas stream, may be combined and/or mixed with a substantially continuous CO-containing and optionally H ₂ -containing stream, such as synthesis gas generated from the gasification process, as previously described. In certain embodiments of the invention, a substantially continuous flow of substrate into the bioreactor is thus maintained. In a specific embodiment of the invention, the flow generated in the gasification system can be increased and/or decreased in accordance with the intermittent supply of CO from an industrial source in order to maintain a substantially continuous flow of substrate with the desired or optimized composition. In another embodiment of the invention, the conditions in the gasification system can be changed, as described above, to increase or decrease the CO:H ₂ ratio in accordance with the intermittent supply of CO from an industrial source in order to maintain a substantially continuous flow of substrate with a given or optimized content of CO and H ₂ .

Typically, the substrate streams used in the context of the present invention are gaseous; however, the invention is not limited to this. For example, carbon monoxide can be fed into the bioreactor in a liquid. For example, the liquid may be saturated with a gas containing carbon monoxide and then fed into the bioreactor. This can be done according to standard techniques. For example, a microbubble dispersion generator can be used for this purpose (Hensirisak et al., Scale-up of microbubble dispersion generator for aerobic fermentation; Applied Biochemistry and Biotechnology Volume 101, number 3, October 2002).

It will be appreciated that for bacterial growth and CO to ethanol fermentation, in addition to the gaseous substrate containing CO, the bioreactor must be supplied with a proper liquid nutrient medium. The nutrient medium must contain enough vitamins and minerals for the growth of the microorganisms used. Anaerobic media suitable for ethanol fermentation using CO as the sole carbon source are known in the art. For example, suitable media are described in US Pat. See the Examples section of this document for more examples of environments.

Desirably, the fermentation is carried out under appropriate conditions for the desired fermentation reaction (eg CO in ethanol). Reaction conditions that should be considered include pressure, temperature, gas flow, liquid flow, pH of the medium, redox potential of the medium, intensity of agitation (if a stirred tank reactor is used), inoculum concentration, the maximum gaseous substrate concentration to ensure that the amount of CO in the liquid phase is unlimited, the maximum product concentration that excludes inhibition of its formation.

Optimum reaction conditions depend in part on the particular microorganism used. However, in general, it may be preferable to carry out the fermentation at a pressure above atmospheric pressure. Operation at elevated pressure allows one to significantly increase the intensity of CO transition from the gas phase to the liquid phase, where it can be used by microorganisms as a carbon source for the production of ethanol. This, in turn, means that the residence time (defined as the volume of liquid in the bioreactor divided by the flow rate of the feed gas) can be reduced when the bioreactors are maintained at elevated rather than atmospheric pressure.

In addition, since the degree of conversion of CO to ethanol is partly a function of the residence time of the substrate, achieving a given retention time, in turn, determines the required volume of the bioreactor, in the case of a pressurized reactor, the required volume of the bioreactor is much less, and, therefore, the capital cost of the fermentation equipment is lower. In accordance with the examples given in US patent No. 5593886, the volume of the reactor can be reduced in a linear relationship with the increase in the working pressure in the reactor, that is, bioreactors operating at a pressure of 10 atmospheres should have a volume that is one tenth of the volume of reactors operating at a pressure of 1 atmosphere.

The advantages of carrying out the fermentation of gas to ethanol at elevated pressure are also already described in other publications. For example, WO 02/08438 describes processes for fermenting gas to ethanol at 30 psi. inch (206.8 kPa) and 75 psi. inch (517.1 kPa), which provides an ethanol performance of 150 g/l/day and 369 g/l/day, respectively. However, there are examples of fermentation processes carried out using similar media and feed gas compositions at atmospheric pressure, producing 10 to 20 times less ethanol per liter per day.

It is also desirable that the supply rate of the CO-containing gaseous substrate be such that the concentration of CO in the liquid phase is guaranteed to be unlimited. The reason is that due to the limited amount of available CO, the crop can consume ethanol, which is the product.

Product extraction

The fermentation reaction products can be recovered using known methods. Examples of such methods include those described in WO 2007/11757, WO 2008/115080 and US Pat. and extractive fermentation.

Stripping the ethanol from the contents of the fermenter gives an azeotropic mixture of ethanol and water (i.e., 95% ethanol and 5% water). Subsequently, anhydrous ethanol can be produced using molecular sieve ethanol dehydration technology, which is also known in the art.

The extractive fermentation technique involves the use of a water-miscible solvent, which poses a low risk of toxic effects on the fermenting microorganisms, in order to recover ethanol from the dilute contents of the fermenter. For example, a solvent that can be used in this type of extraction process is oleyl alcohol. In this case, oleyl alcohol is continuously fed into the fermenter, where this solvent rises to form a layer on the surface, which is continuously separated and passed through a centrifuge. The water and cells are readily separated from the oleyl alcohol and returned to the fermenter, while the ethanol-rich solvent is fed to the flasher. Most of the ethanol evaporates and condenses, while the non-volatile oleyl alcohol is reused in the fermentation process.

Acetate can also be recovered from the contents of the fermenter by methods known in the art. For example, an adsorption device may be used which has an activated charcoal filter. In this case, microorganism cells are first removed from the contents of the fermenter using a suitable separation method. Numerous filtration-based methods are known in the art for obtaining cell-free fermenter contents from which the product is to be recovered. Then, the cell-free filtrate containing ethanol and acetate is passed through a column containing activated charcoal to adsorb the acetate. Acetate in the form of an acid (acetic acid) rather than a salt (acetate) is more readily adsorbed by activated charcoal. Therefore, it is preferable to reduce the pH of the contents of the fermenter before it is fed into the activated carbon column to less than about 3 so that most of the acetate is converted to the form of acetic acid.

Acetic acid adsorbed on activated charcoal can be recovered by elution using methods known in the art. For example, ethanol can be used to elute the bound acetate. In certain embodiments of the invention, the ethanol that is produced in the fermentation process can be used to elute the acetate. Since the boiling point of ethanol is 78.8°C and the boiling point of acetic acid is 107°C, ethanol can be easily separated from acetate by a method based on the difference in volatility, such as distillation.

Other methods for recovering acetate from the contents of the fermenter are known in the art and can also be used in the methods of the present invention. For example, US Pat. Nos. 6,368,819 and 6,753,170 describe a solvent and co-solvent system that can be used to extract acetic acid from the contents of a fermenter. As with the oleyl alcohol based system described above for extractive ethanol fermentation, the systems described in US Pat. The solvent/co-solvent system containing acetic acid is then separated from the contents of the fermenter by distillation. Thereafter, a second distillation step can be applied to purify the acetic acid from the solvent/co-solvent system.

The fermentation reaction products (e.g., ethanol and acetate) can be recovered from the contents of the fermenter by continuously withdrawing a portion of the contents from the fermenter, separating the microbial cells from the fermenter (conveniently by filtration), and recovering, simultaneously or sequentially, one or more products. The ethanol is conveniently recovered by distillation, the acetate can be recovered by adsorption on activated charcoal using the methods described above. The separated microorganism cells can be returned to the fermenter. The cell-free filtrate remaining after the extraction of ethanol and acetate can also be returned to the fermenter. Nutrients (such as B vitamins) can be added to this cell-free filtrate to restore the nutrient medium before it is returned to the fermenter. In addition, if the pH of the fermenter contents was changed as described above in order to enhance the adsorption of acetic acid on the activated charcoal, the pH must be changed back to the original pH of the fermenter contents before the filtrate is returned to the bioreactor.

CO removal ₂

According to certain embodiments of the invention, the CO ₂ removal system includes devices for selectively separating CO ₂ from the mixed stream and a device for converting CO ₂ into products and/or preparing CO ₂ for storage or further use. Alternatively, this system includes a device for converting CO ₂ in the stream directly into products and/or compounds suitable for storage or further use.

In one embodiment of the invention, CO ₂ is selectively separated from the mixed gas stream using any separation device known in the art, such as in the example methods below. Other methods of separating CO ₂ that can be used in embodiments of the invention include extraction with a metal oxide, such as CaO, and the use of porous carbon, or extraction with a selective solvent, for example, extraction with an amine.

Amines such as aqueous monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA), diisopropanolamine (DIPA), and methyldiethanolamine (MDEA) are widely used in industry to remove CO ₂ and hydrogen sulfide from natural gas streams and refinery process streams.

CO ₂ separated in such processes can be temporarily stored. Many examples of interim storage of CO ₂ are known in the art, such as underground storage (geosequestration), oceanic storage, and mineral storage (eg, conversion to metal carbonates).

In underground storage, hydrogen dioxide is injected, typically in a supercritical state, directly into underground geological formations. Oil fields, gas fields, saline formations, unusable coal seams and saline-filled basalt formations have been proposed as storage sites. Various physical (eg, largely impermeable shield rock) and geochemical trapping mechanisms are used to prevent CO ₂ from reaching the surface. The Intergovernmental Panel on Climate Change has estimated that well-selected, adapted and properly operated underground storage facilities can hold CO ₂ for millions of years, and these storage facilities are capable of holding more than 99% of injected CO ₂ for more than 1000 years.

Several options have been proposed for ocean storage: (i) "dissolution" injection, where CO ₂ is injected by ship or pipeline into the water to a depth of 1000 m or more and the CO ₂ is substantially dissolved; (ii) "lake" storage of CO ₂ directly on the sea floor at depths greater than 3000 m, where CO ₂ is denser than water and is believed to form a "lake" that retards the dissolution of CO ₂ in the environment; (iii) conversion of CO ₂ to biocarbonates (using limestone); (iv) storage of CO ₂ in solid clathrate hydrates already present on the ocean floor or use in growing new solid clathrates.

For mineral storage, an exothermic reaction of CO ₂ with metal oxides present in excess is carried out to form stable carbonates. This process takes place in nature for many years, resulting in the formation of most of the terrestrial limestone. The reaction rate can be increased, for example, by carrying out the reaction at a higher temperature and/or pressure or by pre-treating the minerals, although this method is associated with additional energy costs.

Alternatively, the separated CO ₂ can be used to make products, as in the case of direct or indirect conversion to hydrocarbons. A well known hydrocarbon production process is the production of methanol from CO ₂ and H ₂ . Also known in the art is the catalytic or electrochemical dissociation of water to form oxygen and hydrogen ions, where the hydrogen ions can be used to convert CO ₂ to hydrocarbons. If CO ₂ is heated to 2400°C, it splits into carbon monoxide and oxygen. The Fischer-Tropsch process can be used to convert CO to hydrocarbons. In such processes, CO can be returned to the fermentation process. For example, the desired temperature can be achieved by using a camera with a mirror that focuses sunlight on a gas. Alternatively, the separated CO ₂ can be used in the subsequent fermentation reaction(s) to produce products. Those skilled in the art will recognize that there are many examples of microbial fermentation reactions in which CO ₂ is converted to products. For example, CO ₂ can be converted to methane by anaerobic fermentation using methanogenic microorganisms. Examples of this and other related fermentation processes are described in WO 2006/108532, cited above. Additional examples of fermentation reactions using CO ₂ to produce products are given in the documents WO 2007/117157 and WO 2008/115080 mentioned above.

CO ₂ is also a good raw material for syngas production. CO ₂ may be fed into the reformer (coal gasification system) to reduce methane consumption and improve/increase the H ₂ :CO ratio. Therefore, in one embodiment of the invention, at least a portion of the separated CO ₂ can be sent to a coal gasification system integrated into the fermentation process.

In another embodiment of the present invention, the separated CO ₂ can be converted into products such as concrete and cement. To mimic the marine cement produced by corals during the formation of their shells and reefs, magnesium and/or calcium can be combined with CO ₂ to form carbonates.

CO ₂ is also readily taken up by algae during photosynthesis, which can be used to remove carbon from waste streams. Algae grow rapidly in the presence of CO ₂ and sunlight and can be harvested and converted into products such as biodiesel and/or alcohol.

Alternatively, CO ₂ can be directly captured from the stream without additional separation steps. For example, in a particular embodiment of the invention, a stream, preferably a gaseous stream containing CO ₂ , may be fed to a second fermentation system in order to convert CO ₂ into products.

Gas separation

In accordance with certain embodiments of the present invention, the method used to separate the gas includes one or more stages of cryogenic fractionation, molecular filtration, adsorption, pressure swing adsorption or absorption. Whichever process is used, gas separation can be carried out to isolate at least a portion of one or more of the following components: H ₂ , O ₂ , CO ₂ and CO from the gas stream. In addition or alternatively, in accordance with embodiments of the present invention, gas separation can be applied to remove one or more portions from the gas stream (for example, N ₂ , O ₂ ) so that the remaining stream can be used more efficiently, for example, in a bioreactor.

Adsorption is the accumulation of gases, liquids or solutions on the surface of a solid or liquid. Absorption is a process in which one substance, such as a solid or liquid, absorbs another substance, such as a liquid or gas, incorporated into the smallest pores or spaces between its molecules.

Pressure Swing Adsorption (PSA) is an adiabatic process that can be used to scrub gases to remove associated impurities by adsorption onto the appropriate fixed bed adsorbents present in high pressure pressure vessels. The regeneration of adsorbents is carried out by countercurrent depressurization and, at low pressure, blowing with previously extracted gas close in quality to the product. To obtain a continuous product flow, it is preferable to have at least two adsorbers so that at least one adsorber is available to receive a gas stream (such as an off-gas/exhaust/biogas stream) and actually produce a product of the desired purity. Simultaneously, successive steps of depressurization, purge and repressurization to adsorption pressure are performed on another adsorber(s). Conventional adsorbents can be easily selected by those skilled in the art depending on the type of impurities to be adsorbed and removed. Suitable adsorbents include zeolite molecular sieves, activated carbon, silica gel or activated alumina. Combinations of layers of adsorbents can be used, one on top of the other, thereby separating the contents of the adsorber into a number of separate zones. Pressure fluctuation adsorption involves fluctuations in parameters such as pressure, temperature, flow rate, and composition of the gaseous and adsorbed phases.

Purification or separation of gases using normal mode pressure swing adsorption takes place at feed gas temperatures close to room temperature, whereby the components to be removed are selectively adsorbed. Ideally, adsorption should be sufficiently reversible to allow regeneration of adsorbents at close ambient temperatures. Pressure swing adsorption can be used to treat and/or purify the most common gases, including CO, CO ₂ and H ₂ . Examples of pressure swing adsorption methods are detailed in Ruthven, Douglas M. et al., 1993 Pressure Swing Adsorption, John Wiley and Sons.

Molecular sieve is a material containing tiny pores of precise and uniform size, which is used as an adsorbent for gases and liquids. Molecules that are small enough to pass through these pores are adsorbed, while larger molecules are not. A molecular sieve is similar to a regular filter, but it functions at the molecular level. Molecular sieves are often formed from aluminosilicate minerals, clays, porous glasses, microporous charcoal, zeolites, activated carbon, or synthetic compounds with an open structure through which small molecules such as nitrogen and water molecules can diffuse. Methods for regenerating molecular sieves include pressure changes (eg in oxygen concentrators) and heating and purging with a carrier gas.

The membranes can be used, for example, to separate hydrogen from gases such as nitrogen and methane, to recover hydrogen, to separate methane from biogas, or to remove water vapour, CO ₂ , H ₂ S or volatile organic liquids. Various membranes, including porous and non-porous, can be selected in accordance with the existing purpose, as will become clear to experts in this field when considering the present description. For example, a palladium membrane only transfers H ₂ . In a certain embodiment of the invention, CO ₂ can be separated from the gas stream using a CO ₂ permeable membrane. The CO ₂ separated from the stream may be sent to a CO ₂ removal device, such as the previously described gasification device.

Cryogenic fractionation involves compressing a gas stream and cooling it to a temperature low enough to permit separation by distillation. It can be used, for example, to remove CO ₂ . Certain components (eg water) are usually removed from the stream prior to cryogenic fractionation.

In some methods, the removal of oxygen from a gaseous stream may be used to produce anaerobic streams enriched in CO and/or CO ₂ . In addition, oxygen can be removed biologically, for example, by passing the combustion gases through a sealed fermenter that contains optional aerobic microorganisms, a reduced carbon substrate, and nutrients required by the microorganisms. These optional aerobic microorganisms can consume oxygen and produce anaerobic streams enriched in CO and/or CO ₂ .

Alternative methods for separating or removing O ₂ from gaseous streams are also known in the art. However, for example, oxygen can simply be reduced and/or removed using hot copper or a catalytic converter.

Designing a gas separation process to suit a particular gas source can make a bioconversion process economically viable that would otherwise be uneconomical. For example, by properly separating CO from an automotive exhaust stream, a usable energy source can be obtained from that stream and unwanted gas emissions can be reduced. In accordance with one embodiment of the present invention, the gaseous substrate comprises synthesis gas containing CO and H ₂ , and gas separation is carried out to remove hydrogen from this stream so that it can be separated and used as a fuel outside the fermentation process. CO can be used as a raw material for the fermentation reaction.

Intermittent gas flows

In accordance with various aspects of the present invention, the fermentation substrate is obtained from an industrial source. Typically, substrates obtained from industrial sources are gaseous, such gases may have variable composition and/or pressure and, in some cases, may be discontinuous in nature. In certain embodiments, the present invention provides a means of correcting or "smoothing" the supply of gaseous substrate to the fermentation bioreactor to produce products, especially during periods when the substrate supply is inherently intermittent or intermittent. Any known means of achieving continuity or "smoothing" of the gaseous substrate flow may be used; however, specific embodiments of the invention include processes or devices that include at least one accumulator device suitable for receiving an intermittent flow of substrate and supplying a substantially continuous flow of substrate to the bioreactor.

In particular embodiments of the invention, this storage device includes a storage tank suitable for receiving discontinuous gas flows. Prior to being fed into this storage tank, the intermittent flow may be compressed; alternatively, the storage tank may be expandable as the substrate flow is received. For example, a storage tank may include a "floating roof" that rises and falls according to the amount of gaseous substrate. Floating roof storage tanks are known in the art, for example they are used to match fluctuations in gas supply and demand. The storage tank may be adapted to supply a substantially continuous flow of substrate to the fermentation bioreactor and, as such, may include a flow control device for the flow therefrom.

In such embodiments, the storage tank functions as a reservoir for the substrate. However, in accordance with an alternative embodiment of the invention, the storage tank can be replaced by another form of storage with a similar function. For example, alternative forms include one or more absorption, adsorption, and pressure and/or temperature fluctuations. Additionally or alternatively, the substrate may be dissolved in a liquid present in a reservoir or held in a matrix, such as a porous solid material, until needed. In a specific embodiment of the present invention, the substrate can be dissolved in the liquid present in the storage tank and, if necessary, fed into the bioreactor directly in solution.

Alternatively, the bioreactor itself may be designed such that the head space above the liquid fermentation broth acts as a reservoir for intermittent flow. For example, the system may include a device for compressing the gaseous substrate stream (when present) and feeding it into the bioreactor. The headspace pressure at the top of the bioreactor increases as more substrate is added. Thus, the substrate is constantly available for conversion into products by microbiological fermentation.

In another embodiment of the invention, the system may be adapted to receive gaseous substrate streams from a plurality of discontinuous sources. Such a system may include devices for connecting streams and/or switching between streams in order to provide a substantially continuous flow of the substrate into the bioreactor.

Microorganisms used for fermentation generally have an acceptable temperature range, above or below which the reaction rate is significantly reduced. As such, the system may include a cooling device so that when the substrate is in limited supply, the bioreactor medium can be cooled and thereby slow down the fermentation reaction and reduce substrate consumption. Conversely, when the flow of the substrate is increased, the temperature inside the bioreactor can be raised to the upper end of the temperature range to increase the reaction rate.

Alternatively or additionally, the cooling device may be designed to equalize the load on the cooling system so as to reduce the maximum load on the cooling system of the fermentation system. For example, suppose that the load on the cooling system, corresponding to the need to remove heat from the feed gas stream and/or fermentation exothermic heat at a certain period (during gas treatment), is 2 MW. In order to keep the temperature of the contents of the fermentation reactor constant at this time, heat must be removed at precisely this rate so that the temperature in the reactor remains constant. Therefore, during those periods when there is no gas to be treated and exothermic heat production essentially stops, the load on the cooling system is zero. Thus, especially when used in large-scale industrial production, there are periods when the load on the cooling system is very high, which imposes significant restrictions on this system. When leveling the load on the cooling system, its required maximum is reduced. That is, it becomes possible to work with a less powerful cooling system, although in a continuous (or more continuous) mode.

Using the parameters of the previous example, but suppose that the periods when the gas is available for processing and when the gas is not processed are the same in duration; then 1 MW of thermal energy can be continuously removed from the fermentation reactor. Under these conditions, when gas treatment occurs, the rate of heat removal lags behind the input/generation of heat, and the temperature in the fermenter will rise. When there is no gas flow, but cooling continues, the temperature in the fermenter will drop. Thus, a cooling system rated for a continuous load of 1 MW is needed, not a system rated for 2 MW that only runs half the time. However, the rise and subsequent drop in temperature must be limited so that the temperature in the tank does not go beyond the acceptable range for microorganisms. Thus, in accordance with particular embodiments of the invention, the load on the cooling system, when it is not constant, can be "smoothed" so that its changes are more gradual and / or limited, with a smaller difference between the maximum and minimum load on the cooling system.

Industrial waste gas as a raw material for fermentation

In accordance with other aspects of the present invention, industrial off-gases are used for the fermentation reaction with no or only minimal additional gas purification or pre-treatment applied to make the gas suitable for fermentation.

Off-gases can be generated from any number of industrial processes. The present invention is particularly well suited to support the production of ethanol from gaseous substrates such as industrial off-gases with a high CO volume content. Examples include gases from the production of ferrous metal products, the production of non-ferrous metal products, oil refining, coal gasification, biomass gasification, power generation, carbon black production, ammonia production, methanol production, and coke production. In a specific embodiment of the invention, off-gases are generated during the production of steel. For example, those skilled in the art will appreciate that off-gases generated at various stages of the steelmaking process have a high concentration of CO and/or CO ₂ . In particular, the off-gas generated during the decarburization of steel according to various steelmaking methods, for example, in an oxygen converter (for example, a BOF or BOF), contains a lot of CO and a little CO ₂ , which makes it suitable for use as a substrate for anaerobic carboxydotrophic fermentation.

Off-gases resulting from the carburization of steel are, if necessary, passed through water to remove particulate matter before being fed into a chimney or flue, through which the off-gas is vented to the atmosphere. Typically, the gases are forced into the chimney by one or more fans.

In certain embodiments of the invention, at least a portion of the off-gas generated during the decarburization of steel is diverted to the fermentation system by means of a suitable piping. For example, a conduit or other transfer device may be connected to a steel mill chimney to divert at least a portion of the off-gas to the fermentation system. Likewise, one or more fans may be used to divert at least a portion of the exhaust gas to the fermentation system. In particular embodiments of the present invention, the conduit is designed to transfer at least a portion of the off-gas from steel decarburization to the fermentation system. Devices for regulating and supplying gases to a bioreactor are well known to those skilled in the art, for which the present invention is intended.

Although a steel plant may be designed for substantially continuous production of steel and hence off-gases, in certain respects the process may be discontinuous. Typically, the decarburization of steel is a batch process that takes from several minutes to several hours. As such, the conduit may be designed to divert at least a portion of the off-gas, such as the gas generated from the decarburization of steel, to the fermentation system if the off-gas is found to have a predetermined composition.

The pH of the contents of the bioreactor during fermentation can be adjusted according to requirements. The proper pH value depends on the conditions necessary for the implementation of a particular fermentation reaction, taking into account the culture media and microorganisms used, which should be understood by specialists in this field, for which the present invention is intended. In one preferred embodiment of the invention, when fermenting a CO-containing gaseous substrate using Clostridium autoethanogenum, the pH can be adjusted in the range of about 5.5-6.5, most preferably about 5.5. Other examples include pH 5.5 to 6.5 using Moorella thermoacetica to produce acetic acid, pH 4.5 to 6.5 using Clostridium acetobutylicum to produce butanol, and pH 7 using Carboxydothermus hydrogenaformans to produce hydrogen. Those skilled in the art are aware of the proper means of maintaining the desired pH in the bioreactor. However, for example, aqueous bases such as NaOH and aqueous acids such as H ₂ SO ₄ can be used to increase or decrease the pH of the fermentation medium and maintain the desired pH.

A further advantage of the present invention is that, due to the absence or minimal cleaning and/or other gas treatment carried out on the off-gases prior to their use in the fermentation reaction, these gases contain additional material generated during the production processes, which additional material can be used, at least in part, as a feedstock for the fermentation reaction.

Stream Mixing

As previously noted, it may be desirable to mix an industrial off-gas stream with one or more additional streams to improve efficiency, alcohol production, and/or overall carbon capture in the fermentation reaction. Without wishing to be bound by any particular theory, in some embodiments of the present invention, carboxydotrophic bacteria convert CO to ethanol according to the following equation:

6CO + 12H ₂ + 3H ₂ O → C ₂ H ₅ OH + 4CO ₂

However, in the presence of H ₂ the transformation is, in general, the following:

6CO + 12H ₂ + 3H ₂ O → 3C ₂ H ₅ OH

Therefore, when industrial streams contain high CO but little or no H ₂ , it may be desirable to mix one or more H ₂ containing streams with CO containing off-gas prior to feeding the mixed substrate stream to the fermenter. The overall efficiency, alcohol productivity and/or overall carbon capture of the fermentation depends on the stoichiometric ratio of CO and H ₂ in the mixed stream. However, in specific embodiments of the invention, the mixed stream may essentially contain CO and H ₂ in the following molar ratios: 20:1, 10:1, 5:1, 3:1, 2:1, 1:1 or 1:2.

In addition, it may be desirable to supply CO and H ₂ at different stages of fermentation in a specific molar ratio. For example, substrate streams with a relatively high content of H ₂ (such as 1:2 CO:H ₂ ) can be fed to the fermentation during the start-up and/or rapid microbial growth stages. However, when growth slows down so that the culture maintains a substantially constant cell density, the CO content may be increased (eg, to at least 1:1 or 2:1 or higher, where the H ₂ concentration may be greater than or equal to zero).

Mixing of the streams can also have additional advantages, especially in cases where the CO-containing effluent stream is inherently discontinuous. For example, an intermittent effluent stream containing CO may be mixed with a substantially continuous stream containing CO and optionally H ₂ and fed to the fermenter. In particular embodiments of the invention, the composition and flow rate of the substantially continuous flow can be changed in accordance with the change in discontinuous flow in order to maintain the supply of the substrate flow to the fermenter with a substantially constant composition and flow rate.

Mixing two or more streams to obtain a given composition may involve changing the flow rates of all streams, or one or more streams may be kept constant while the other stream(s) is changed to "tune" or optimize the substrate stream to obtain the desired composition. Streams that are produced continuously, require little or no additional processing (such as accumulation), such a stream can be fed directly to the fermenter. However, it may be necessary to provide an intermediate store of streams when one or more of them arrive intermittently and/or when streams arrive continuously but are used and/or produced at different rates.

Those skilled in the art will appreciate the need to monitor the composition and flow rates of such streams prior to mixing them. The composition of the mixed stream can be controlled by changing the proportions of the constituent streams in order to achieve a given or desired composition. For example, the main gas stream may be predominantly CO and a secondary gas stream with a high concentration of H ₂ may be mixed with it so as to obtain a given H ₂ :CO ratio. The composition and flow rate of the mixed stream can be controlled by any method known in the art. The mixed flow rate can be adjusted independently of the mixing operation; however, the costs with which the individual constituent flows are diverted must be regulated within certain limits. For example, when intermittently produced flow is continuously withdrawn from the intermediate storage, its flow rate must be such that the intermediate storage is neither empty nor completely filled.

At the mixing point, the individual constituent gases are fed into a mixing chamber, which is usually a small tank or pipe section. In such cases, this tank or pipe may be provided with static mixers, such as baffles, positioned to enhance turbulent movement and rapid homogenization of the individual components.

If desired, an intermediate mixed flow accumulator may also be provided to maintain a substantially constant flow of substrate to the bioreactor.

The system may optionally include a processor to monitor the composition and flow rates of the constituent streams and to regulate the mixing of these streams in the proper proportions to obtain the desired or desired mixture. For example, certain components may be supplied on an as needed or on a first come first served basis to optimize alcohol production efficiency and/or overall carbon capture.

It may not be possible or cost effective to supply CO and H ₂ in a certain ratio all the time. As such, a system adapted to mix two or more streams, as described above, can be tuned to optimize said ratio given the available sources. For example, in cases where there is an inadequate supply of H ₂ , the system may include a device to divert excess CO from the system to provide an optimized flow and obtain improved alcohol production efficiency and/or overall carbon capture. In certain embodiments of the invention, the system provides for continuous monitoring of the flow and composition of at least two streams and their connection in order to obtain a single mixed substrate stream of optimal composition and the presence of a device for directing the optimized substrate stream to the fermenter. In specific embodiments of the invention using carboxydotrophic microorganisms for alcohol production, the substrate stream of optimal composition contains at least 0% H ₂ and up to about 1:2 CO:H ₂ .

By way of non-limiting example, specific embodiments of the invention include the use of a steel decarburization converter gas as a source of CO. Typically, such streams contain little or no H ₂ , therefore, it may be desirable to combine a stream containing CO with a stream containing H ₂ to obtain a more appropriate CO:H ₂ ratio. H ₂ is often formed in large quantities in a steel mill in a coke oven. Therefore, a coke oven off-gas stream containing H ₂ can be mixed with a converter off-gas stream containing CO to obtain a desired composition.

Additionally or alternatively, a gasification facility may be provided to produce CO and H ₂ from a variety of sources. The stream generated in the gasifier may be mixed with the stream containing CO to obtain a desired composition. Those skilled in the art will appreciate that the conditions in the gasification apparatus can be controlled so as to obtain a specific CO:H ₂ ratio. In addition, the capacity of the gasification apparatus can be increased and decreased to increase and decrease the flow rate of the CO and H ₂ containing stream produced by the gasification apparatus. Therefore, the stream from the gasifier can be mixed with a substrate stream containing CO in order to optimize the CO:H ₂ ratio to improve alcohol productivity and/or overall carbon capture. In addition, the capacity of the gasifier can be increased and decreased to produce a stream of varying flow rates and/or compositions that can be mixed with an intermittent CO containing stream to obtain a substantially continuous stream of a given composition.

Other sources of CO and/or H ₂ containing streams that can be mixed with a CO containing substrate stream include hydrocarbon reforming processes such as natural gas and/or methane and methanol reforming.

Adding irrigation water

In accordance with the present invention, the irrigation water is used for the fermentation reaction in order to increase the growth efficiency of microorganisms and increase the production of the product.

Irrigation water may come from any suitable industrial source, as described herein above. In a particular embodiment of the present invention, the spray water is obtained from a process for cleaning one or more off-gases generated during steelmaking. For example, irrigate water is obtained from the treatment of off-gases from coke ovens, blast furnaces, BOFs, and/or electric arc furnaces.

In certain embodiments of the invention, the source of irrigation water is the same production process from which the (gaseous) substrate for fermentation comes; for example, both the spray water and the substrate (off-gases containing CO) come from the same steel plant.

Irrigation water can be used in untreated form directly after the gas cleaning system or device of the production process. However, the irrigation water may be treated to remove or at least reduce its residual solids content. Irrigation water treatment methods are known to those skilled in the art for which the present invention is intended. However, before being fed into the fermenter, the irrigation water, for example, may be filtered, centrifuged or settled.

As described above, the pH of the irrigation water can be adjusted before use. The proper pH depends on the conditions required for the particular fermentation reaction, taking into account the culture media and microorganisms used, as is known to those skilled in the art for which the present invention is intended. In one preferred embodiment of the invention, when fermenting a CO-containing gaseous substrate using Clostridium autoethanogenum, the pH can be adjusted in the range of about 5.5-6.5, most preferably about 5.5. Other examples include pH 5.5 to 6.5 using Moorella thermoacetica to produce acetic acid, pH 4.5 to 6.5 using Clostridium acetobutylicum to produce butanol, and pH 7 using Carboxydothermus hydrogenaformans to produce hydrogen.

Irrigation water can be supplied to the fermentation reaction with a suitable device. For example, it can be fed directly from the scrubber to the bioreactor in which the fermentation takes place or is to be carried out. Alternatively, it can be taken from the scrubber for storage into a suitable chamber equipped with a device for feeding it to the bioreactor; or it can be withdrawn from the scrubber, stored and manually fed into the bioreactor. The supply of irrigation water to the bioreactor may be continuous; or irrigation water can be supplied at certain times during the fermentation reaction or as needed, depending on the circumstances.

In one of the embodiments of the invention, the irrigation water is mixed with nutrient media intended for use in the fermentation reaction, and then fed into the bioreactor using any of the devices mentioned above. Therefore, the present invention also provides a composition containing a mixture of appropriate nutrient media and irrigation water. Those skilled in the art for whom the present invention is intended will be aware of the proper nutrient media used in microbiological fermentation. However, for example, we point out that such an environment may contain sources of nitrogen, phosphates, potassium, sodium, sulfur, ions of a number of metals, B vitamins, etc. Examples of environments are provided in this document in the Examples section.

The amount of irrigation water used can be such that the nutrient media/irrigation water ratio is up to about 1:9. In one preferred embodiment of the invention, irrigation water is used in a ratio of approximately 1:1 to nutrient media.

As will become clear, irrigation water from specific processes may contain components that are toxic or harmful to certain micro-organisms. That is, the present invention does not exclude any of the pretreatment processes, however, provides for the elimination of such additional processes, if possible. Alternatively or additionally, the proportion of irrigate water in the contents of the bioreactor can be adjusted so that potentially toxic or harmful components are present at less than acceptable concentrations.

Irrigation water as the main feedstock

In another embodiment of the present invention, the fermentation reaction is carried out using only reflux water as a feedstock. In other words, irrigation water is the main source of carbon for the fermentation reaction. In this embodiment, the fermentation reaction can be carried out essentially as previously described, however, it is not necessary to supply or capture CO-containing gases or supply an alternative carbon source.

Irrigation water can be fed into the bioreactor in which the fermentation is carried out, as described above. In one of the embodiments of the invention, water is fed into the bioreactor continuously and directly from the gas cleaning system or device in an amount corresponding to maintaining optimal conditions for the fermentation reaction.

In a related embodiment of the invention, the irrigation water is sent to storage and then fed to the bioreactor at times when no alternative feedstock or substrate is available. For example, the off-gas flows generated in some steelmaking processes are not constant, but intermittent. When these gases cannot be supplied to the fermentation reaction, reflux water is supplied to the bioreactor to maintain alcohol production and improve the overall reaction efficiency. Such processes, in which fermentation media are added to the reflux water and fed into the bioreactor, can be carried out using cell retention techniques (eg, cross-flow membrane filtration, continuous centrifugation, or cell-immobilized apparatus). In this embodiment, a mixture of reflux water and fermentation media may flow through the reactor to provide nutrition to the bacteria. The advantage of this option is that the irrigation water contains a large amount of dissolved carbon monoxide. Since most of the production costs associated with the use of gaseous substrates for fermentation is the acquisition and operation of equipment that provides mass transfer of gaseous CO from the gas phase to the liquid phase, the use of liquid streams that already contain CO significantly reduces these costs.

General provisions

Embodiments of the present invention are described by way of example. However, it should be understood that specific steps or steps needed in one embodiment may not be needed in another. Conversely, the steps or steps included in the description of any particular embodiment may, if necessary, be successfully used in those embodiments of the invention where they are not specifically noted.

While the present invention has been described generally with reference to any type of stream that can be moved back and forth in a given system(s) by any known transfer device, in certain embodiments, the substrate and/or effluent streams are gaseous. It will be appreciated by those skilled in the art that certain stages may be connected to each other by appropriate conduits or similar devices configured to receive or move flows throughout the system. A pump or compressor may be used to facilitate the transfer of these streams to a particular stage. In addition, a compressor may be used to increase the pressure of the gas supplied to one or more stages, such as a bioreactor. As described herein above, the pressure of the gases in the bioreactor can affect the efficiency of the fermentation reaction carried out therein. Thus, the pressure can be adjusted to improve the fermentation efficiency. Pressure values applicable to common reactions are known in the art.

In addition, the systems or methods of the present invention may optionally include devices for regulating and/or controlling other parameters in order to improve the overall efficiency of the process. The system may include one or more processors for adjusting and/or controlling certain parameters of a given process. For example, specific embodiments of the invention may include a measuring device for monitoring the composition of the substrate and/or effluent stream(s). In addition, specific embodiments of the invention may include a device for controlling the supply of substrate stream(s) to a particular stage or element in a particular system, if the measuring device determines that this stream has a composition corresponding to a particular stage. For example, in cases where the gaseous substrate stream contains little CO or a lot of O ₂ , which can have a negative effect on the fermentation reaction, this substrate stream can be directed without passing through the bioreactor. In particular embodiments of the invention, the system includes a device for monitoring and controlling the destination of the substrate stream and/or flow rate so that a stream with the desired or suitable composition can be supplied to a particular stage.

In addition, it may be necessary to heat or cool certain component or substrate stream(s) prior to or during one or more of the steps in the process. In such cases, known means of heating or cooling may be used. For example, heat exchangers can be used to heat or cool the substrate streams.

In addition, this system may include one or more stages of pre/post processing, aimed at improving the performance or increase the efficiency of a particular stage. For example, the pretreatment step may include a device for removing solids and/or long chain hydrocarbons or tars from the gaseous substrate stream. Other possible preliminary or subsequent operations include the separation of the desired product(s) at certain stages, such as, for example, the production stage carried out in a bioreactor (eg, separation of ethanol by distillation).

Various embodiments of the installations of the present invention are illustrated in the accompanying figures. Alternative embodiments shown in FIG. 1-13 have elements in common, and the same reference numerals are used to refer to the same or similar elements throughout the various figures. Only new elements are described (compared to FIG. 1) of FIG. 2-13, so these figures should be read in conjunction with the description of FIGS. 1.

Fig. 1 is a diagram of a system 101 according to one embodiment of the present invention. The incoming stream 1 of the substrate enters the system 101 through the appropriate pipeline. Substrate inlet stream 1 contains CO and optionally CO ₂ and, in certain embodiments of the invention, this substrate stream is an off-gas stream from a manufacturing process, such as liberated during carburization of steel in an oxygen converter. The content of the components in the gas stream 1 may fluctuate. An optional valve 2 can be used to divert stream 1 elsewhere (shown as stream 3) if it is determined that stream 1 does not have a predetermined composition. For example, if CO is to be produced from stream 1, a minimum CO content can be set for stream 1, then this stream is directed, bypassing further processing in system 101, if the minimum CO content requirement is not met. Such a threshold may be set to exclude unprofitable or inappropriate processing of any flow. Any device known in the art can be used to determine if a gas has a given composition. In addition, the term "target composition" refers not only to substances that should be present in stream 1, but also to undesirable components. For example, stream 1 may be rejected if there is a certain contaminant in that stream 1.

As will become clear to those skilled in the art, the valve 2 may be located anywhere in the system 101. For example, it may be placed after the processing step in the bioreactor 5.

If it is determined that stream 1 has a desired composition, it is sent to an optional pre-treatment 4. Pre-treatment 4 may be aimed at controlling various parameters of this stream, including temperature and the content of contaminants or other undesirable components or constituents. It can also be used to add components to a given stream. This depends on the particular source of gas stream 1 and/or the particular fermentation reaction and/or the microorganisms selected for its implementation.

The pre-treatment 4 may be performed at any location in the system 101 or may be omitted, or multiple pre-treatment steps 4 may be performed at different locations in the system 101. This will depend on the particular source of gas stream 1 and/or the particular fermentation reaction and/or the microorganisms chosen to carry it out. For example, additional pre-treatment (multiple pre-treatment steps) may be carried out upstream of the CO ₂ removal device 8 to control the parameters of the flow entering the CO ₂ removal device 8 .

After optional pre-treatment, the stream can be sent to the bioreactor 5 using any known transfer device. For example, one or more fans and/or a pump may be used to move flow in the system. Bioreactor 5 is designed to carry out the desired fermentation reaction in order to produce products. In accordance with certain embodiments of the invention, the bioreactor 5 is designed to treat a CO-containing substrate to produce one or more acids and/or one or more alcohols. In one specific embodiment of the invention, the bioreactor 5 is used to produce ethanol and/or butanol. The bioreactor 5 may include more than one tank, each tank being designed to carry out the same reaction and/or different steps within a particular fermentation process and/or different reactions, including different reactions of different fermentation processes, which may include one or more common steps.

The bioreactor 5 can be provided with a cooling means in order to regulate the temperature in it within the limits acceptable for use in the particular fermentation reaction of the microorganisms to be carried out.

The products produced in the bioreactor 5 may be recovered using any recovery process known in the art. However, in some embodiments of the present invention, at least part of the product may exit the bioreactor 5 in stream 7 containing components such as CO ₂ and, optionally, unconverted CO. Such streams may optionally be processed in the product recovery device 6 to recover any product before the substantially product-free stream 7 is sent to the CO ₂ removal device 8 .

The CO ₂ removal device 8 is designed to receive a stream 7 from which at least a portion of the CO ₂ present therein is removed and an effluent stream 9 remains. In certain embodiments, the CO 2 removal device 8 is designed to separate at least a portion of the CO ₂ component of _the stream 7 and is capable of capturing the separated CO ₂ and/or converting it into products suitable for further use or storage. Alternatively, the CO ₂ removal device 8 may be designed to directly capture the CO ₂ from the stream 7 and/or convert it to products.

If the bioreactor 5 includes a plurality of stages or individual tanks, the effluents after at least a subset of such stages may enter the device 8 to remove CO ₂ . In addition, more than one CO ₂ removal device 8 may be provided downstream of the process stream so that the same stream undergoes multiple CO ₂ removal steps, or the same or different removal operations may be performed on streams from different stages or from different fermentation tanks.

In accordance with an alternative embodiment of the invention shown in FIG. 2, the CO ₂ removal device 8 is located upstream of (upstream of) the bioreactor 5 (rather than downstream as in FIG. 1). Thus, according to the embodiment shown in FIG. 2, the CO ₂ removal device 8 may be used to capture CO ₂ from the substrate stream before it is fed to the bioreactor 5. Optional valve 2 may be designed such that if it is determined that the CO ₂ content is too low to rationally and/or efficiently capture CO ₂ , this stream may be directed directly to the bioreactor 5. Alternatively, stream 3 may be removed from the system altogether, for example, in cases where such the stream is unsuitable for CO ₂ removal or fermentation.

In accordance with the embodiment of the invention shown in FIG. 3, a _CO2 removal device 8 is located downstream of the bioreactor 5, and a valve 10 is provided to direct stream 9 back to bioreactor 5 if it is determined that enough CO2 is left in stream 9 for further fermentation to produce products. However, if it is determined that the content of CO in this stream is less than the required level, this stream can be directed elsewhere (shown as stream 11). The embodiment of the invention shown in FIG. 3 also includes the co-benefits of both embodiments shown and in FIG. 1 and in FIG. 2.

In FIG. 4 is a diagram of a system 104 in accordance with yet another embodiment of the present invention. The incoming gas stream 1 enters the system 104 through a suitable conduit. The incoming gas stream 1 may be an off-gas stream from a manufacturing process, such as liberated during the carburization of steel in an oxygen converter. The incoming gas stream 1 preferably contains at least one carbon-based gas. In specific embodiments, the gas stream 1 contains CO and/or CO ₂ . The content of the components in the gas stream 1 may fluctuate. An optional valve 2 can be used to divert stream 1 elsewhere (shown as stream 3) if it is determined that stream 1 does not have a desired composition. For example, if CO is to be produced from stream 1, a minimum CO content can be set for stream 1, then this stream is directed, bypassing further processing in system 104, if the minimum CO content requirement is not met. Such a threshold may be set to exclude unprofitable or inappropriate processing of any flow. Any device known in the art can be used to determine if a gas has a given composition. As indicated above, the term "target composition" refers not only to substances that should be present in stream 1, but also to undesirable components. For example, stream 1 may be rejected if there is a certain contaminant in that stream 1.

As will become clear to those skilled in the art upon review of the present disclosure, valve 2 may be located anywhere in system 104. For example, it may be placed after a processing step in gas separator 13.

If it is determined that the stream 1 has a given composition, it is sent to the gas separator 13. In it, at least the first component of this stream is separated from the gas stream 1, leaving the other component. Either this at least first component or the remaining component can be diverted as stream 12, with the other component sent to optional pre-treatment 4 and bioreactor 5. Thus, if the gas stream fed to the fermentation reaction is to be CO, CO can be separated from the rest of the stream, then only this CO (or CO rich stream) is sent to bioreactor 5. Alternatively, one or more components (for example, O ₂ and/or H ₂ ), which are at least partially removed, and the remaining stream is sent to the bioreactor 5.

As will become clear to those skilled in the art upon review of the present description, the gas separator 13 may include one or more stages or separate devices, where at each stage one or more gases are separated.

Additional description of processes and devices for gas separation is given in this document below.

As indicated above, pre-treatment 4 may be performed at any location in system 104 or may be omitted, or multiple pre-treatment steps 4 may be performed at different locations in system 104. The use of pre-treatment 4 may depend on the particular source of gas stream 1 and/or the particular fermentation reaction and/or the microorganisms chosen to carry it out.

The bioreactor 5 is designed to carry out a given fermentation reaction. In accordance with certain embodiments of the invention, the bioreactor 5 is designed to treat a CO-containing substrate to produce one or more acids and/or one or more alcohols. In specific embodiments of the invention, the bioreactor 5 is used to produce ethanol and/or butanol. The bioreactor 5 may include more than one tank, with each tank designed to carry out the same reaction and/or different stages within a particular fermentation process and/or different reactions, including different reactions, including different reactions of different fermentation processes, which may have one or more common stage.

The bioreactor 5 can be provided with a cooling means in order to regulate the temperature in it within the limits acceptable for use in the particular fermentation reaction of the microorganisms to be carried out.

In accordance with an alternative embodiment of the invention shown in FIG. 5, the gas separator 13 is located after (downstream) the bioreactor 5 (and not before it, as in Fig. 4). Thus, in accordance with the embodiment of the invention shown in FIG. 5, a gas separator 13 may be used to separate one or more components from the gases generated during the fermentation reaction in the bioreactor 5 and/or to separate gases that have been fed into the bioreactor 5 but not used therein. If the bioreactor 5 includes a plurality of stages or separate vessels, the gases leaving after at least a subset of such stages may enter a gas separator 13. In addition, more than one gas separator may be provided downstream of the process stream (downstream) so that the same stream passes through several stages of separation, or the same or different separation operations can be carried out in relation to gas streams of different stages or from different fermentation tanks.

In accordance with the embodiment of the invention shown in FIG. 6, gas separators 13 are located before and after the bioreactor 5 with the attendant advantages of both embodiments shown and in FIG. 4 and in FIG. 5.

A pump or compressor (not shown) may be provided upstream of the bioreactor 5 to increase the gas pressure in the bioreactor 5. As described herein above, the pressure of the gases in the bioreactor may affect the efficiency of the fermentation reaction carried out therein. Thus, the pressure can be adjusted to improve the fermentation efficiency. Pressure values applicable to common reactions are known in the art.

Gas stream 1 may contain many different streams. Different processing elements may be assigned to different threads, and only a subset of the elements is common. For example, the first stream may enter the first gas separator, the second stream may enter the second gas separator. The effluents from the first and second gas separators can then be sent to a common bioreactor. Other levels of commonality or differences are within the scope of the present invention.

In FIG. 7 is a diagram of a system 107 in accordance with one embodiment of the present invention. The off-gas stream 14 enters the system 107 through an appropriate piping from a manufacturing process (eg, carburizing steel in an oxygen converter). Flow 14 is discontinuous in nature, as indicated by the dotted line. Stream 14 may be a constant stream in the sense that it is supplied continuously, but the content of particular gases in this stream may change over time. For example, the CO content in stream 14 may change from high to low over time. Regardless of whether stream 14 is actually produced continuously or intermittently, during those periods when its content of a given gas is too low to support the fermentation reaction (or the content of undesirable gas (for example, O ₂ ) is too high), using valve 2, stream 14 can be redirected somewhere else, including to the atmosphere (shown as stream 3). During those periods when stream 14 contains a given gas at a given concentration, valve 2 directs the resulting stream 15 to storage tank 16. Stream 15 is also shown in dashed line due to its possibly intermittent nature.

The accumulative storage tank 16 functions as a reservoir supplying gas to the bioreactor 5 after any pre-treatment of this gas at the pre-treatment stage 4. Pre-treatment 4 can be carried out anywhere in the system 1 or even not be carried out depending on the specific source of the gas stream 14 and / or the specific fermentation reaction and / or the microorganisms selected for its implementation.

Preferably, a stable gas stream 17 exits the storage tank 16 and is sent to pre-treatment 4 and then to the bioreactor 5 as a stable stream 18. Streams 17 and 18 are shown with a solid line, reflecting their essentially continuous nature. In the storage tank 16, the gas can be compressed in order to reduce the volume required for it. A valve (not shown) or other devices may be used for the gas flow system from the storage tank 16. The flow rate of the gas is preferably constant and is adjusted so that there is always some gas in the storage tank 16 and the tank is never emptied. In accordance with one embodiment of the invention, the operation of the valve may be controlled by a control device (not shown) in order to change the flow rate of gas 15 depending on the amount of gas present in the reservoir. More specifically, when the amount of gas in the storage tank 16 becomes less than a predetermined level, the flow of gas from the storage tank 16 can be reduced so that, although the optimal amount of gas is not supplied to the bioreactor 5, a reduced amount is supplied, which can at least reduce the impact on the productivity of the bioreactor 5 by providing improved conditions for the microorganisms residing in the bioreactor 5.

Thus, in the embodiment of the invention shown in FIG. 7, the intermittent nature of the flow 14 is mitigated by the intermediate accumulation of gas in the storage tank 16.

As will be appreciated by those skilled in the art for whom the present invention is intended, the storage tank 16 preferably includes an outlet for removing off-gases from the fermentation process. The bioreactor 5 can also be provided with a cooling means in order to control its temperature within acceptable limits for microorganisms.

In accordance with an alternate embodiment of the system 107, the storage tank 16 is replaced with an alternative form of storage capable of performing the same or a similar function. Such forms may include one or more of absorption, adsorption, and pressure and/or temperature fluctuations. In accordance with one embodiment of the invention, the gas is stored in solution, which is then fed into the bioreactor 5. This arrangement can reduce the processing time in the bioreactor 5, since the required gases are dissolved before they enter the bioreactor 5.

In the configuration shown in FIG. 8, a storage tank 16 is optional, as indicated by the dotted line. In those embodiments where storage tank 16 is omitted, stream 14 is sent to bioreactor 5 as and when it is available and of acceptable composition, as streams 19 and 20 are intermittent in nature. As stated above, this option is not ideal for certain microorganisms or processes. If a storage tank 16 is provided, a part of the stream 15 can be diverted into it so that when the stream 15 enters, the gas is sent to both the bioreactor 5 and the storage tank 16. The gas directed to the storage tank 16 can be stored there until the time when the stream 15 stops flowing. Then at least a small gas flow can be directed from the storage tank 16 to the bioreactor 5.

As will be appreciated by those skilled in the art, the off-gas stream 14 from any manufacturing process may be at a high temperature. The acceptable temperature ranges for microorganisms vary, however, for anaerobic bacteria commonly used to produce alcohols such as ethanol, they are in the order of 30°C-50°C. The gas stream 14 can cause the temperature in the bioreactor 5 to rise, exacerbated by the exothermic nature of the fermentation process, resulting in the need for a cooling agent to be included in the system. In accordance with one of the embodiments of the invention, the discontinuous nature of the stream 14 is taken into account when developing a means of cooling the bioreactor 5. More specifically, during those periods of time when the stream 14 does not enter or does not have a given composition, the temperature in the bioreactor 5 can be reduced to a value at the lower limit of the temperature range acceptable for the microorganisms used (for example, up to 30 ° C). Then, when the flow 14 of gas of a given composition is resumed, it is possible to increase the temperature inside the bioreactor 5, thus reducing the requirements for the cooling means provided when the gas is supplied to the bioreactor 5. Thus, for anaerobic bacteria commonly used to produce alcohols such as ethanol, it is acceptable that the temperature in the bioreactor 5 approaches 50°C. In accordance with one embodiment of the invention, in the event that the temperature in the bioreactor 5 approaches the maximum allowable value, the supply of gas stream 14 to the bioreactor 5 can be stopped, even if it comes with the desired composition, in order to facilitate temperature control within the bioreactor 5. In such cases, the gas can be sent to storage for later use or diverted somewhere else where it can be subjected to further processing, as will be obvious to specialists in this field of technology from consideration of this description. In particular embodiments of the present invention, load balancing is provided for the cooling system.

In FIG. 9 is a diagram of a system 109 according to another embodiment of the present invention. The compressor 22 serves to compress the intermittent stream 21 as it enters, directing the compressed stream 23 to the bioreactor 5. Thus, in accordance with the embodiment of the invention shown in FIG. 9, the bioreactor 5 effectively functions as both a fermentation tank and a storage tank, holding pressurized gas inside when stream 14 arrives and has a predetermined composition. When the flow 14 is interrupted, or when the composition of the flow does not correspond to the desired, the off-gases can be slowly released from the bioreactor 5 so that the gas pressure in the bioreactor 5 drops, but so that the amount of any of the necessary gases is continuously maintained or sufficiently well maintained, sufficient to avoid significant periods of time during which the microorganisms are deprived of these gases.

In FIG. 10a and 10b are diagrams of plants 110a and 110b according to another embodiment of the present invention in which a plurality of discontinuous gas streams 14a and 14b are used to feed the fermentation reaction in the bioreactor 5. So, when stream 14a is not supplied or does not have a given composition, stream 14b can be fed into the bioreactor 5 as an alternative. As will be appreciated by those skilled in the art, there may be more than two sources of gas flow. In addition, the degree of commonality between the processing steps of these streams may vary depending on the particular composition of each of the streams. The configuration shown in Fig. 10a and 10b can be implemented in a steel mill using various streams generated at different stages of the steelmaking process. Additionally or alternatively, other sources of gas may be used. For example, in the case of fermentation using anaerobic bacteria to produce alcohols such as ethanol, traditional sources (eg, biomass) can be used to provide this stream.

In FIG. 11 is a diagram of a system 111 in accordance with another embodiment of the present invention, including several of the steps previously described herein. Discontinuous flow 14 is converted to a substantially continuous flow 17 as previously described with reference to FIG. 7. A substantially continuous stream 17 is sent to a gas separator 13 for separating CO ₂ from other components of the substrate stream, such as CO. The separated stream 12 containing CO ₂ is sent to a CO ₂ remover 8 where it can be converted into products suitable for later use or storage. The remainder of the CO containing stream is sent to an optional pre-treatment 4 and then to the bioreactor 5. An optional conduit 24 may be provided by which the CO ₂ containing stream exiting the bioreactor 5 is sent back to the CO ₂ removal device 8 where it can be converted into products suitable for later use or storage.

In FIG. 12 is a diagram of a system 112 in accordance with yet another embodiment of the present invention. BOF 25 may be part of a manufacturing process, such as steel decarburization, and is the source of effluent 1. In particular embodiments, effluent 1 contains CO and/or CO ₂ . The effluent 1 is sent to an optional pre-treatment 4a. Typically, the pre-treatment is carried out in a scrubber or water bath adapted to remove particulate matter from stream 1. The valve 2a is designed to divert at least part of the stream 1 into the chimney 26, if it is determined that the composition of this stream does not correspond to the specified one. The discharged flow is shown by arrow 3a. Typically, the effluent to stack 26 is vented to the atmosphere as indicated by arrow 27. Typically, this stream is gaseous and can be moved to stack and optionally within system 113 by one or more fans and/or pumps.

If stream 1 is determined to have the desired composition, it may be sent to optional heat exchanger 28a as stream 14. Typically, stream 14 is intermittent and may require cooling. The heat exchanger 28a may be any heat exchanger known in the art. However, for example, it may be a shell and tube heat exchanger. An optional pre-treatment 4b can be applied to remove any remaining solids from this stream, if desired. For example, a membrane filter can be used to remove remaining solids from this stream. The pre-treatment 4b may also include the removal of condensed water from the optionally cooled stream, for example in a baffle separator or other suitable condensate collection device known in the art.

This stream may be pressurized by any suitable device, such as a gas compressor 22, before it is fed to the oxygen removal stage 29. Any suitable means of removing oxygen may be used, however, for example, stage 29 of removing oxygen may include the use of a hot copper catalyst or catalytic converter. This stream may be cooled by an optional heat exchanger 28b before it is fed into the retention tube 30. The retention tube 30 is long enough that before the stream reaches valve 2b its composition can be determined by any suitable measuring device (not shown). If it is determined that the composition of this stream corresponds to the desired one, by means of valve 2b it can be directed to the storage tank 16. If the composition is not suitable for fermentation, for example, the oxygen content is too high, valve 2b can divert this flow into the chimney 26 (as shown by arrow 3b). From storage device 16, bioreactor 5 receives a substantially continuous stream of substrate 17, which optionally undergoes a 4c pretreatment. An optional pretreatment 4c may be used to remove unwanted contaminants such as microbes from stream 17. For example, a sterilizing filter or membrane may be used to remove unwanted bacteria from the stream. The effluent 3c leaving the bioreactor 5 can also be directed to the chimney 26.

A measuring device for determining the composition of the stream may optionally be provided at any point in the system. For example, a device for determining the composition of O ₂ , CO and/or CO ₂ can be installed upstream of the valve 2a downstream of the process stream, upstream of the holding tube or valve 2b downstream of the process stream and/or upstream of the bioreactor 5 downstream of the process stream. In addition, because these streams are potentially flammable in nature, safety equipment, such as a flame arrester, may also be provided anywhere in the system.

In FIG. 13 is a diagram of a system 113 according to another embodiment of the present invention. Stream 1 and off-gas stream 31, one or both of which may be discontinuous in nature, are sent to mixer 32. Mixer 32 is designed to control the flow rate of at least two streams (such as streams 1 and 31) and mix these streams to obtain a stream of a given composition (stream 33). Undesired streams, such as streams with improper composition, can be removed from the system 113, as indicated by arrow 3, while streams with a given composition 33 can be directed to an optional accumulator 16, to an optional pre-treatment 4 and then to a bioreactor 5 for conversion into products. The composition and flow rates of streams 1, 3, 31 and 33 may be monitored continuously or otherwise by any method known in the art.

Stream 1 and/or stream 31 may additionally or alternatively bypass mixer 32 based on its individual composition. This order allows one of the streams 1, 31 to be used when only one of them has an improper composition.

In particular embodiments, the mixer 32 includes a mixing chamber, which is typically a small tank or piece of pipe. In such cases, this tank or pipe can be provided with a mixing device, such as baffles, positioned so as to intensify turbulent movement and rapid homogenization of the individual components.

In certain embodiments of the invention, the mixer 32 includes a device for controlling the mixing of two or more streams in order to obtain a given optimized flow of the substrate 33. For example, the mixer 32 may include a device for controlling the flow rate of each of the streams 1 and 31 entering the mixer 32, so that a given composition of the stream 33 (for example, a given CO:H ₂ ratio) is obtained. The mixer also preferably includes a control device (operating in continuous or otherwise) after the mixing chamber downstream of the process stream. In particular embodiments of the invention, the mixer includes a processor for adjusting the flow rates and/or composition of the various streams based on data from the monitor.

EXAMPLES

Hereinafter, the present invention is further and more specifically described with reference to the following non-limiting examples.

Unless otherwise noted, the media and solutions used in the fermentation processes described in these examples contain the following components.

Wednesdays:

Table 1
Composition of LM23 and LM33 media Environments component Concentration per 1.0 l of media (LM23) Concentration per 1.0 l of media (LM33) MgCl ₂ 6H ₂ O 0.5 g 0.5 g NaCl 0.2 g 0.2 g _CaCl2 0.2 g 0.2 g 100 mmol buffer - sodium phosphate (pH 6.0) * 160 ml - _{NaH2PO4 _} - 2.04 g _NH4Cl 0.6 g 2.5 g 85 _{% H3PO4} 0.05 ml - KCl 0.15 g 0.15 g Combined solution of metallic trace elements (LS06) 10 ml 10 ml Combined solution of B vitamins (LS03) 10 ml 10 ml Resazurin (stock solution 1000 mg/l) 1 ml 2 ml _FeCl3 0.0025 g 0.01 g Cysteine HCl monohydrate 0.75 g 0.5 g agarose (optional) 15 g 15 g Distilled water up to 1 l up to 1 l * combination of NaH ₂ PO ₄ (13.2 g) and Na ₂ HPO ₂ ⋅7H ₂ O (1.1 g) in H ₂ O (1 l)

table 2
Composition of a solution of B vitamins (LS03) and a solution of metal trace elements (LS06) Combined solution of B vitamins (LS03) per 1 liter ref. solution Combined solution of metallic trace elements (LS06) per 1 liter ref. solution Biotin 20.0 mg Nitrilotriacetic acid 1.5 g Folic acid 20.0 mg MgSO ₄ ⋅7H ₂ O 3.0 g Pyridoxine hydrochloride 10.0 mg MnSO ₄ ⋅H ₂ O 0.5 g Thiamine⋅HCl 50.0 mg NaCl 1.0 g Riboflavin 50.0 mg FeSO ₄ ⋅7H ₂ O 0.1 g A nicotinic acid 50.0 mg Fe(SO ₄ ) ₂ (NH ₄ ) ₂ ⋅6H ₂ O 0.8 g Calcium D-(*)-pantothenate 50.0 mg CoCl ₂ ⋅6H ₂ O 0.2 g Vitamin B12 50.0 mg ZnSO ₄ ⋅7H ₂ O 0.2 g p-Aminobenzoic acid 50.0 mg CuCl ₂ ⋅2H ₂ O 0.02 g Lipoic acid 50.0 mg AlK(SO ₄ ) ₂ ⋅12H ₂ O 0.02 g Distilled water up to 1 l _{H3BO3 _} 0.30 g NaMoO ₄ ⋅2H ₂ O 0.03 g Na ₂ SeO ₃ 0.02 g NiCl ₂ ⋅6H ₂ O 0.02 g Na ₂ WO ₄ ⋅6H ₂ O 0.02 g Distilled water up to 1 l

Methodology

environments

Solutions of LM23 and LM33 media were prepared at pH 5.5 as follows. All ingredients except for cysteine HCl were mixed in 400 ml of distilled water. The solution was deoxygenated by heating to boiling and random cooling to room temperature while constantly blowing a gas containing 95% CO and 5% CO ₂ . After cooling, cysteine HCl was added and the pH of the solution was adjusted to 5.5 before making up the volume of the solution to 1000 ml (for example 1) or 500 ml (for example 2). Anaerobicity was maintained during all experiments.

Waste gas from a steel mill

Steel mill off-gas was received from New Zealand Steel Glenbrook, located in Glenbrook, New Zealand. More specifically, the gas was collected and stored in gas-tight bags or steel gas cylinders at a pressure of 100-130 bar. Steel mill off-gas stored in bags was removed from them through a gas-tight butyl rubber diaphragm. The composition of the off-gas from a steel mill varies over time depending on the stage of steel production. However, in this case the gas was collected during the decarburization process, and such gases typically contain 43-50% CO; 17-20% CO ₂ ; 2-3% H ₂ ; 27-34% N ₂ .

Irrigation water of a steel mill

The water used to wash (clean) the oxygen converter off-gas stream at New Zealand Steel Glenbrook, located in Glenbrook, New Zealand, was filtered once with a Buchner funnel and a vacuum line through S95 filter paper. The pH of the filtered water was adjusted to 5.5 and a gas containing 95% CO and 5% CO ₂ was bubbled through it for 45 minutes before further use.

bacteria

Clostridium autoethanogenum obtained from the biological material bank in Germany (DSMZ). The identification number assigned to these bacteria in DSMZ 10061. Alternatively, Clostridium autoethanogenum was used under the insertion identification number in DSMZ 19630.

Sampling and Analytical Procedures

Media samples were taken at certain intervals for 5 days. Every time samples were taken, precautions were taken to prevent gas from entering or exiting the whey reactors/flasks.

All samples were used to measure the optical density at 600 nm (spectrophotometer) to determine the density of cells in culture, the concentration of substrates and products were determined using high performance liquid chromatography (HPLC) and gas chromatography (GC). HPLC was routinely used to quantify acetate and ethanol. GC was used to determine the amount (in percent by volume) of carbon monoxide, carbon dioxide, hydrogen and nitrogen gases.

HPLC

Agilent 1100 HPLC instrument. Mobile phase: 0.0025 N sulfuric acid. Flow rate and pressure: 0.800 ml/min. Column: Alltech IOA; catalog number 9648, 150x6.5 mm, particle size 5 µm. Column temperature: 60°C. Detector: refractive index. Detector temperature: 45°C.

Sample preparation method: 400 µl of sample + 50 µl of 0.15 M ZnSO ₄ +50 µl of 0.15 M Ba(OH) ₂ in an Eppendorf tube. Centrifugation 10 min at 12,000 rpm, 4°C. Transfer 200 µl of the conditioned medium to an HPLC vial and inject 5 µl into the HPLC instrument.

Gas chromatography

A two-channel gas chromatograph CP-4900 Micro-GC was used: channel CP-4900 molecular sieve 5A PLOT, 10 m, inner diameter 0.25 mm, 4.2 sec backwash, injector and column temperature 70°C, carrier gas argon 200 kPa, injection 40 milliseconds; channel CP-4900 PoraPLOT Q, 10 m, inner diameter 0.25 mm, injector temperature 70°C, column temperature 90°C, carrier gas helium 150 kPa, injection 40 milliseconds. Measurement duration 20 sec. The duration of the working cycle of the method is 2 minutes. The sampling line was heated to 70° C. and connected to a Nafion dryer.

Example 1 . Fermentation using steel mill off-gas

Example 1a (serum flask)

Incubation was carried out in sealed 250 ml serum flasks, each containing 50 ml of media. The headspace in each serum flask was first purged with CO ₂ three times before evacuation, then filled with steel mill off-gas to a final pressure of 25 psig (172.3 kPa). 1 ml of Clostridium autoethanogenum inoculum was added to each flask. Next, a shaking incubator was used and the reaction temperature was maintained at 37°C.

Media samples were taken at equal intervals for 15 days. Every time samples were taken, precautions were taken to prevent gas from entering or escaping from the serum flasks.

All samples were used to measure cell density in culture and the amount of acetate.

As seen in FIG. 14 and 15, cell growth and acetate production increased during the initial 10 days, after which it slowly decreased. Thus, cell growth and acetate production could be easily maintained with the off-gas from the steel mill, even though no further treatment had been carried out on the gas before it was used for the fermentation reaction.

Example 1b (serum flask)

Incubation was carried out in sealed 234 ml serum flasks, each containing LM33 medium. The 184 ml headspace in each serum flask was first purged with steel mill off-gas three times before evacuation, then filled to 30 psig (206.8 kPa). 2 ml of Clostridium autoethanogenum inoculum was added to each flask. Next, a shaking incubator was used and the reaction temperature was maintained at 37°C. The results of these experiments are shown in Table 3.

Table 3
Serum flask (30 psig);
50% CO; 18% CO ₂ ; 3% H ₂ ; 29% N ₂ ) Day 0 1 2 Biomass, g/l 0.08 0.22 0.19 Acetate, g/l 0.4 1.4 3.2 Ethanol, g/l 0 0 0.3 Overpressure, psig thirty 28 18

Example 1c (10 L Stirred Flow Reactor)

A Bioflo 3000 bioreactor was filled with 5 L of LM33 without cysteine and vitamin solution (LS03) and autoclaved for 30 min at 121°C. After cooling, the medium was purged with N ₂ and a solution of LS03 was added, as well as cysteine. Then, before applying 150 ml of Clostridium autoethanogenum culture inoculum, the gas was changed to steel mill off-gas. The temperature in the bioreactor was maintained at 37°C and agitation was carried out at 200 rpm at the beginning of the culture development with a gas flow rate of 60 ml/min. During the growth phase, stirring was increased to 400 rpm, the gas flow was set to 100 ml/min. The pH was adjusted to 5.5 and maintained by automatic addition of 5M NaOH. The results of the experiment, including gas consumption, are shown in Table 4.

Table 4
Fermentation in a flow reactor with a stirrer in the supply of off-gas from a steel mill Day 1 2 3 4 5 Biomass, g/l 0.05 0.08 0.30 0.28 0.20 Acetate, g/l 0.40 0.78 2.76 3.10 4.03 Ethanol, g/l 0.00 0.00 0.00 0.48 0.71 Gas supply, ml/min 60 60 100 100 100 CO, %, in the supplied gas 49.5 49.5 49.5 49.5 49.5 CO ₂ , %, in the supplied gas 17.5 17.5 17.5 17.5 17.5 H ₂ , %, in the supplied gas 2.9 2.9 2.9 2.9 2.9 N ₂ , %, in the supplied gas 27.7 27.7 27.7 27.7 27.7 Gas output, ml/min 55 55 73 94 92 CO, %, in outgoing gas 49.2 35.8 16.4 46.1 45.5 CO ₂ , %, in outgoing gas 16.9 30.6 44.6 21.1 21.1 H ₂ ,%, in the outgoing gas 3.2 3.2 1.1 3.2 3.2 N ₂ , %, in outgoing gas 30.4 30.4 37.8 29.5 30.2

Example 1d (50 L gas-life reactor)

A 50 L gas-lief reactor (2900 mm high x 150 mm diameter, with 200 mm high x 95 mm diameter guide tube) was filled with 37 L of LM33 media sterilized on a 0.2 micrometer filter (Pall KA2 DFL P2 filter). Nitrogen was bubbled through this medium for 18 hours, then switched to steel mill off-gas and 5 L of Clostridium autoethanogenum culture seed was added. The temperature in the gas lift reactor was maintained at 37°C, mixing was carried out by recirculation in the space above the gas medium with a flow rate of 15 l/min. Initially, the flow rate of the gas supplied to the reactor was 500 ml/min. The overpressure in the space above the medium was maintained at 8 psig (55.1 kPa). During the growth phase of microorganisms, the gas supply to the reactor was increased to 1000 ml/min. The pH was adjusted to 5.5 and maintained by automatic addition of 5M NaOH. The results of the experiment, including gas consumption, are shown in Table 5.

Table 5
Fermentation in a gas-lift reactor with the supply of off-gas from a steel mill Day 1 2 3 4 5 Biomass, g/l 0.15 - - 0.36 0.36 Acetate, g/l 0.87 3.93 7.90 9.44 10.86 Ethanol, g/l 0.00 0.00 0.21 0.38 0.48 Gas supply, ml/min 500 500 1000 1000 1000 CO, %, in the supplied gas 43.6 43.6 43.6 44.3 44.3 CO ₂ , %, in the supplied gas 19.7 19.7 19.7 20.0 20.0 H ₂ , %, in the supplied gas 2.8 2.8 2.8 2.8 2.8 N ₂ , %, in the supplied gas 33.9 33.9 33.9 32.8 32.8 Gas output, ml/min 341 - - 690 716 CO, %, in outgoing gas 29.1 - - 33.1 41.3 CO ₂ , %, in outgoing gas 29.5 - - 28.5 22.7 H ₂ ,%, in the outgoing gas 2.9 - - 3.0 2.6 N ₂ , %, in outgoing gas 38.4 - - 34.8 33.5

Specific embodiments of the present invention extend the applicability of microbiological fermentation reactions using industrial off-gases, especially for the production of ethanol by the bacteria Clostridium autoethanogenum. Off-gases containing CO, obtained directly from industrial processes, can be used as a substrate in fermentation reactions to produce products such as acetate and/or ethanol. This is the result of capturing the carbon contained in the off-gases, and thus improves the quality or reduces the amount of waste generated in production processes, in particular steel production, and reduces the costs associated with the practical use of fermentation reactions.

Example 2 . Fermentation with irrigation water

In a continuous stream of gas containing 95% CO and 5% CO ₂ , 25 ml of LM23 media were dispensed into 250 ml serum flasks and mixed with either 25 ml of distilled water (control flasks) or 25 ml of deoxygenated pH-adjusted reflux water (experimental flasks). All flasks were sealed with a gas-tight butyl rubber septum and sealed by crimping the lid prior to autoclaving at 121°C for 20 minutes.

After cooling, all serum flasks were filled with 1 ml of inoculum of a Clostridium autoethanogenum culture that was actively growing in an atmosphere of 95% CO and 5% CO ₂ . The space above the culture was filled with 95% CO and 5% CO ₂ to a pressure of 35 psig (241.3 kPa). The first sample of the medium was taken from each flask under aseptic conditions. The flasks were placed in a shaking incubator at 37°C.

Media samples were taken at the same interval for 15 days. Each time samples were taken, the headspace in each flask was purged three times with 95% CO and 5% CO ₂ before pressurizing to 35 psig (241.3 kPa).

All samples were used to measure cell concentration and the amount of ethanol and acetate in each culture.

results

As can be seen in FIG. 16 and 17, the effects of adding 50% irrigation water to the medium include:

1. Reduced production of acetate;

2. 45% increase in the final density of bacteria;

3. 45% increase in ethanol production.

As such, specific embodiments of the present invention provide an increase in the efficiency of bacterial growth and alcohol production during fermentation reactions, in particular the production of ethanol by the bacteria Clostridium autoethanogenum. As an additive to the nutrient media used in fermentation reactions, waste from production processes can be used. In particular, irrigation water can be used as an alternative base feedstock or substrate for microbiological fermentation reactions. The result of this is an increase in the quality or a decrease in the amount of waste generated during industrial processes, in particular steel production, a decrease in the amount of media needed to support fermentation reactions, and a decrease in the formation of acetate, which is a by-product in the production of ethanol by fermentation, thus increasing the overall efficiency of fermentation reactions and reducing the costs associated with the implementation of such reactions in practice.

The present invention has been described with reference to certain preferred embodiments to enable the reader to practice the invention without undue experimentation. Those skilled in the art will appreciate that the present invention may be embodied in a large number of variations and modifications other than those specifically described herein. It is to be understood that the invention includes all such variations and modifications. In addition, headings, headings, etc. are given to facilitate the reader's understanding of this document and should not be construed as limiting the scope of the present invention. The contents of all patent applications, patents and publications cited in this document, in their entirety, are incorporated into the description by reference.

More specifically, as will be appreciated by those skilled in the art, implementation of the embodiments of the present invention may include one or more additional elements. In a specific example or in the present description, only the elements necessary for understanding the present invention in its various aspects could be shown. However, the scope of the present invention is not limited to the described embodiments and includes systems and/or methods in which there is one or more additional steps and/or one or more replaced steps and/or systems and/or methods that do not include one or more steps.

Any reference to prior art in this specification is not and should not be construed as an admission or any form of indication that this prior art forms part of the public knowledge in the art in any country.

In the present description and any claim of the following claims, unless the context indicates otherwise, the words "comprise", "comprising", etc. should be considered as inclusive and not exclusive, that is, in the sense of "including but not limited to".

Claims (22)

1. A method for obtaining at least one product using microbiological fermentation, including stages in which a) sending the carbonaceous material to a gasification zone operating under gasification conditions, whereby at least a portion of the carbonaceous material is converted to a substrate containing CO and H ₂ ; And b) sending said substrate to a bioreactor containing a culture of at least one carboxydotrophic microorganism selected from the genus Clostridium and anaerobically fermenting said substrate to at least one product selected from the group consisting of alcohols, acids and mixtures thereof. 2. The method of claim 1, wherein the carbonaceous material is selected from the group consisting of crude oil, petroleum coke, municipal solid waste, biomass, and mixtures thereof. 3. The method of claim 2, wherein the carbonaceous material is municipal solid waste. 4. The method of claim 1 wherein CO and H ₂ are present in a ratio of about 0.4:1 to about 1.2:1. 5. The method according to p. 1, where the substrate additionally contains CO ₂ . 6. The method of claim 1 wherein the alcohol is selected from the group consisting of ethanol, butanol and mixtures thereof. 7. The method of claim 1, wherein the acid is selected from the group consisting of acetate, lactic acid, and mixtures thereof. 8. The method of claim 1 wherein the microorganism is selected from the group consisting of Clostridium autoethanogenum, Clostridium ljungdahli, Clostridium ragsdalei, Clostridium carboxydivorans and mixtures thereof. 9. The method of claim 8 wherein the microorganism is Clostridium autoethanogenum . 10. The method according to claim 9, wherein the microorganism is a strain of Clostridium autoethanogenum , which is listed in the German biological material bank (DSMZ) under the attachment identification number DSM 19630. 11. The method of claim 4, wherein the ratio of CO and H ₂ present in the substrate is changed by adjusting at least one parameter selected from the group consisting of feedstock composition, operating pressure, operating temperature, and oxidizer used. 12. The method according to claim 1, wherein the substrate containing CO and H ₂ is mixed with an intermittent off-gas stream containing CO. 13. The method of obtaining at least one product using microbiological fermentation, including stages in which a) sending a carbonaceous material selected from municipal solid waste, biomass, or mixtures thereof, to a gasification zone operating under gasification conditions, whereby at least a portion of the carbonaceous material is converted into a substrate containing CO and H ₂ ; And b) sending said substrate to a bioreactor containing a culture of at least one carboxydotrophic microorganism selected from the genus Clostridium, and anaerobically fermenting said substrate to at least one product selected from the group consisting of ethanol, butanol, acids and mixtures thereof. 14. The method of claim 13 wherein CO and H ₂ are present in a ratio of about 0.4:1 to about 1.2:1. 15. The method of claim 13, wherein the substrate containing CO and H ₂ is mixed with an intermittent off-gas stream containing CO. 16. The method of claim 13 wherein the microorganism is selected from the group consisting of Clostridium autoethanogenum, Clostridium ljungdahli, Clostridium ragsdalei, Clostridium carboxydivorans and mixtures thereof. 17. The method of claim 16 wherein the microorganism is Clostridium autoethanogenum . 18. The method of claim 13 wherein the carbonaceous material is municipal solid waste.

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