Synthesis gas fermentation process and apparatus with high co mass transfer coefficient

Abstract

The present application relates to a syngas fermentation process and apparatus having a high CO mass transfer coefficient. The process includes directing syngas into a reactor vessel through a gas sparger located below a liquid level in the reactor vessel. The syngas is directed at a flow rate effective to maintain a pressure inside the reactor vessel to at least about 1 psig. About 0.01 to about 12 kilowatts / m 3 stirring energy of the culture medium. The process is effective to provide a volumetric CO mass transfer coefficient of about 100 to about 1500 / hr.

Description

[0001] This application is a divisional application of the international application date of May 31, 2012, international application number PCT / US2012 / 040319, which entered the Chinese national phase on December 30, 2013, application number 201280032688.0, and invention title "Syngas Fermentation Method and Apparatus with High CO Mass Transfer Coefficient".

[0002] This application claims priority to U.S. Provisional Applications Nos. 61 / 571,564 and 61 / 571,565, filed June 30, 2011, and 61 / 573,845, filed September 13, 2011, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application provides a method and apparatus for effectively improving carbon monoxide (CO) mass transfer. More specifically, it balances factors including syngas mass, syngas injection, reactor pressure, and mixing to provide an improved volumetric CO mass transfer coefficient during syngas fermentation. Background Technology

[0004] Anaerobic microorganisms can produce ethanol from carbon monoxide (CO) through the fermentation of gaseous substrates. Fermentation using anaerobic microorganisms from the genus *Clostridium* produces ethanol and other useful products. For example, U.S. Patent No. 5,173,429 describes *Clostridium ljungdahlii* ATCC No. 49587, an anaerobic microorganism that produces ethanol and acetate from synthesis gas. U.S. Patent No. 5,807,722 describes a method and apparatus for converting waste gas into organic acids and alcohols using *Clostridium ljungdahlii* ATCC No. 55380. U.S. Patent No. 6,136,577 describes a method and apparatus for converting waste gas into ethanol using *Clostridium ljungdahlii* ATCC Nos. 55988 and 55989.

[0005] CO is typically supplied to fermentation as part of a gaseous substrate in the form of syngas. Gasification of carbonaceous materials to produce a generator gas or syngas comprising carbon monoxide and hydrogen is well known in the art. Such gasification processes typically involve partial oxidation or air-lean oxidation of the carbonaceous material, wherein less than a stoichiometric amount of oxygen is supplied to the gasification process to promote carbon monoxide production, as described in WO 2009 / 154788.

[0006] Fermentation of gaseous substrates can be challenging because at least a portion of the gaseous substrate must be dissolved in an aqueous fermentation broth before it can be metabolized by the microbial culture. Fermentation that utilizes gaseous substrates to provide carbon and energy sources for fermentation is particularly challenging because a significant amount of substrate needs to be dissolved in the fermentation broth before metabolism can occur. Since CO2 provides the carbon source for anaerobic fermentation, substrates with low solubility in aqueous fermentation broths, such as CO2, require highly efficient mass transfer into the broth. Attempts to improve CO2 mass transfer are described in U.S. Patent Nos. 5,972,661 and 7,201,884 and WO 2011 / 028137. Summary of the Invention

[0007] This invention provides a method and apparatus for effectively increasing the volumetric CO mass transfer coefficient during syngas fermentation. In one embodiment, a method for syngas fermentation is provided, the method comprising introducing the syngas into a reactor vessel via a gas injector or gas distributor. The gas injector is located below the liquid level in the reactor vessel, and the syngas is introduced at a flow rate that effectively maintains the pressure inside the reactor vessel at at least about 1 psig and, in another embodiment, at least about 10 psig. The syngas has a CO / CO2 molar ratio of at least about 0.75. The flow rate is from about 0.01 to about 12 kW / m³. 3 The amount of culture medium provides stirring energy to the reactor vessel. The method effectively provides at least about 10 g ethanol / (L·day) STY and a volumetric CO mass transfer coefficient of about 100 to about 1500 / hour.

[0008] In another embodiment, a method for syngas fermentation is provided, the method comprising introducing syngas into a reactor vessel via a gas injector. The gas injector is located below the liquid level in the reactor vessel, and the syngas is introduced at a flow rate that effectively maintains the pressure inside the reactor vessel at at least about 1 psig and, in another embodiment, at least about 10 psig. The syngas has a CO / CO2 molar ratio of at least about 0.75, and, in another embodiment, has a CO content of at least about 20 mol%. The syngas is contacted with at least one gas dispersing impeller located above the gas injector, and the syngas is mixed with acetic acid-producing bacteria using at least one mixing impeller located above the gas dispersing impeller. The gas dispersing impeller and the mixing impeller are operatively connected to a mixer via a drive shaft. The mixer provides a power output of about 0.3 to about 12 kW / m³. 3 In another case, it is approximately 0.7 to approximately 12 kW / m 3 And in another case, it is approximately 0.9 to approximately 12 kW / m 3Energy input for stirring the culture medium. The method effectively provides a volumetric CO2 mass transfer coefficient of approximately 100 to approximately 1500 / hour.

[0009] In one case, the gas sprayer includes an orifice with a diameter of 10 mm or less, and in another case, the orifice has a diameter of 2.5 mm or less. Syngas can also be effectively introduced at a flow rate of 25 m / sec or higher at the orifice outlet and / or a pressure drop of approximately 0.5 to approximately 2.5 psi across the sprayer orifice.

[0010] In another embodiment, a method for improving the volumetric CO mass transfer coefficient is provided. The method includes introducing the syngas into a reactor vessel via a gas injector. The gas injector is located below the liquid level in the reactor vessel, and the syngas is introduced at a flow rate that effectively maintains the pressure inside the reactor vessel at at least about 1 psig and, in another embodiment, at least about 10 psig. The syngas has a CO / CO2 molar ratio of at least about 0.75, and, in another embodiment, has a CO content of at least about 20 mol%. The syngas is contacted with at least one gas dispersion impeller and one mixing impeller. The gas dispersion impeller and the mixing impeller are typically operatively connected to a mixer via a drive shaft. The mixer provides a power output of about 0.3 to about 12 kW / m³. 3 In another case, it is approximately 0.7 to approximately 12 kW / m 3 And in another case, it is approximately 0.9 to approximately 12 kW / m 3 Energy input for stirring the culture medium. The method effectively provides a volumetric CO2 mass transfer coefficient of approximately 100 to approximately 1500 / hour.

[0011] A bioreactor is provided, comprising a shell defining a reactor vessel that effectively maintains a pressure of at least about 1 psig and, in another case, at least about 10 psig. A stirrer is at least partially disposed within the reactor vessel and at least partially below the liquid level within the reactor vessel. The stirrer is operatively connected to a drive shaft and effectively provides a pressure of about 0.3 to about 12 kW / m³. 3 In another case, it is approximately 0.7 to approximately 12 kW / m 3 And in another case, it is approximately 0.9 to approximately 12 kW / m 3Energy input for stirring the culture medium. At least one mixing impeller is operatively connected to the drive shaft and positioned below the liquid level of the culture medium, and at least one gas dispersing impeller is operatively connected to the drive shaft and positioned below the mixing impeller. A gas sprayer is positioned below the gas dispersing impeller, the gas sprayer comprising orifices with a diameter of approximately 10 mm or less, which effectively provides a gas velocity of approximately 25 m / sec or higher at the outlet of the orifices. The bioreactor may also include a feed chamber positioned at the lower end of the reactor vessel.

[0012] In another embodiment, a bioreactor is provided, comprising a shell defining a reactor vessel that effectively maintains a pressure of at least about 1 psig and, in another embodiment, at least about 10 psig. A stirrer is at least partially disposed within the reactor vessel and at least partially below the liquid level within the reactor vessel. The stirrer is operatively connected to a drive shaft and effectively provides a pressure of about 0.3 to about 12 kW / m³. 3 In another case, it is approximately 0.7 to approximately 12 kW / m 3 And in another case, it is approximately 0.9 to approximately 12 kW / m 3 Energy input for stirring the culture medium. At least one mixing impeller is operatively connected to the drive shaft and positioned below the liquid level of the culture medium, and at least one gas dispersing impeller is operatively connected to the drive shaft and positioned below the mixing impeller. A gas sprayer is positioned below the gas dispersing impeller, the gas sprayer comprising orifices with a diameter of approximately 10 mm or less, which effectively provides a gas velocity of approximately 25 m / sec or higher at the outlet of the orifices. The bioreactor also includes a feed chamber positioned at the lower end of the reactor vessel, the feed chamber comprising a feed chamber sprayer and a feed chamber mixer.

[0013] In another embodiment, a method for syngas fermentation is provided, the method comprising inoculating acetic acid-producing bacteria into a culture medium contained in a feed chamber portion of a reactor vessel, the culture medium filling at least about 75% of the total volume of the feed chamber. The acetic acid-producing bacteria are contacted with syngas for a time effectively providing a cell density of at least about 5 g / L. The culture medium is added to the reactor vessel to provide a liquid level within the reactor vessel. Syngas is introduced into the reactor vessel via a gas injector located below the liquid level within the reactor vessel. The syngas is introduced at a flow rate that effectively maintains the pressure inside the reactor vessel at at least about 1 psig and, in another embodiment, about 10 psig. The syngas has a CO / CO2 molar ratio of at least about 0.75 and is contacted with at least one gas dispersing impeller located above the gas injector. The syngas and acetic acid-producing bacteria are mixed using at least one mixing impeller located above the gas dispersing impeller. The gas dispersing impeller and the mixing impeller are typically operatively connected to a stirrer via a drive shaft. The stirring energy input is from about 0.3 to about 12 kW / m³. 3 Culture medium. The method effectively provides a volumetric CO2 mass transfer coefficient of approximately 100 to approximately 1500 / hour.

[0014] In another embodiment, a method for syngas fermentation is provided, the method comprising: inoculating acetic acid-producing bacteria into a culture medium contained in a feed chamber portion of a reactor vessel, the culture medium effectively filling at least about 75% of the total volume of the feed chamber; contacting the acetic acid-producing bacteria with syngas for a time effectively providing a cell density of at least about 3 g / L; adding culture medium to the reactor vessel and maintaining the cell density at about 3 g / L; adding culture medium until a liquid level is achieved in the reactor vessel; introducing syngas into the reactor vessel via a gas injector located below the liquid level in the reactor vessel; introducing the syngas at a flow rate that effectively maintains the pressure inside the reactor vessel at at least about 1 psig and, in another embodiment, about 10 psig; the syngas having a CO / CO2 molar ratio of at least about 0.75 and contacting it with at least one gas dispersing impeller located above the gas injector; and mixing the syngas and acetic acid-producing bacteria using at least one mixing impeller located above the gas dispersing impeller. The gas dispersion impeller and the mixing impeller are operably connected to a mixer via a drive shaft, the mixer providing approximately 0.3 to approximately 12 kW / m³. 3 Energy input to the culture medium. The method effectively provides a volumetric CO2 mass transfer coefficient of approximately 100 to approximately 1500 / hour. Attached Figure Description

[0015] The above and other aspects, features and advantages of the method will become more apparent from the figures below.

[0016] Figure 1 This is a perspective view of a bioreactor.

[0017] Figure 2A and 2B A bottom view of the gas inlet / sprayer is shown.

[0018] Figure 3 This is a cross-sectional view of the gas sprayer.

[0019] Figure 4A and 4B This is a top cross-sectional view of the reactor vessel, showing the different impeller assemblies.

[0020] Figure 5 An alternative construction for the feed chamber of a bioreactor is shown.

[0021] Throughout the several views of the accompanying drawings, corresponding reference numerals indicate the respective components. Those skilled in the art will recognize that the elements in the figures are illustrated simply and clearly, and are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to others to aid in understanding the various aspects of the methods and apparatus of the invention. Furthermore, common but well-known elements that are useful or necessary where commercially feasible are not shown, in order to illustrate these various aspects with less obstruction. Detailed Implementation

[0022] The following description should not be viewed in a limiting sense, but is made merely for the purpose of describing the general principles of exemplary embodiments. The scope of the invention should be determined with reference to the claims.

[0023] Syngas fermentation efficiency is improved by modifying conditions to increase the volumetric CO mass transfer coefficient. The provided methods and apparatus effectively provide volumetric CO mass transfer coefficients of approximately 100 to approximately 1500 / hour, in another case approximately 200 to approximately 1100 / hour, in another case approximately 200 to approximately 900 / hour, in another case approximately 300 to approximately 800 / hour, in another case approximately 400 to approximately 700 / hour, and in another case approximately 500 to approximately 600 / hour. Variables affecting the CO mass transfer coefficient include syngas injection, reactor vessel pressure, syngas mass, and gas dispersion and mixing.

[0024] The method presented in this paper effectively provides a high level of productivity. In this regard, the method effectively provides a STY (space-time yield) of at least about 10 g ethanol / (L·day). Possible STY values ​​include about 10 g ethanol / (L·day) to about 200 g ethanol / (L·day), in another case about 10 g ethanol / (L·day) to about 160 g ethanol / (L·day), in another case about 10 g ethanol / (L·day) to about 120 g ethanol / (L·day), in another case about 10 g ethanol / (L·day) to about 80 g ethanol / (L·day), in another case about 20 g ethanol / (L·day) to about 140 g ethanol / (L·day), in another case about 20 g ethanol / (L·day) to about 100 g ethanol / (L·day), in another case about 40 g ethanol / (L·day) to about 140 g ethanol / (L·day), and in yet another case about 40 g ethanol / (L·day) to about 100 g ethanol / (L·day).

[0025] definition

[0026] Unless otherwise defined, the following terms, as used throughout this disclosure, are defined as follows and may include the singular or plural forms of the definitions determined below:

[0027] The term "about" used to modify any quantity refers to the variation in quantity encountered under real-world conditions, such as in a laboratory, pilot plant, or production plant. For example, the quantity of an ingredient or measurement used in a mixture or quantity, when modified by "about," includes the variation and degree of care typically used in the measurement under experimental conditions in a production plant or laboratory. For example, the quantity of a product component, when modified by "about," includes the variation between different batches in multiple batches of experiments in a plant or laboratory, as well as the variation inherent in the analytical method. Whether or not modified by "about," a quantity includes equivalents of said quantity. Any quantity stated herein and modified by "about" may also be used in this disclosure as a quantity not modified by "about."

[0028] When used herein, "carbon-containing material" refers to carbon-rich materials such as coal and petrochemical products. However, in this specification, carbon-containing material includes any carbon material, whether in a solid, liquid, gaseous, or plasma state. Among a large number of items that can be considered as carbon-containing materials, this disclosure envisions: carbon-containing materials, carbon-containing liquid products, carbon-containing industrial liquid recyclables, carbon-containing municipal solid waste (MSW or MSW), carbon-containing urban waste, carbon-containing agricultural materials, carbon-containing forestry materials, carbon-containing wood waste, carbon-containing building materials, carbon-containing plant materials, carbon-containing industrial waste, carbon-containing fermentation waste, carbon-containing petrochemical co-products, carbon-containing alcohol production co-products, semi-anthracite (carbonaceous coal), tires, plastics, waste plastics, coke oven tar, soft fibers, lignin, black liquor, polymers, waste polymers, polyethylene terephthalate (PETA), polystyrene (PS), sewage sludge, animal waste, crop residues, energy crops, forestry processing residues, wood processing residues, livestock manure, poultry manure, food processing residues, fermentation process waste, ethanol co-products, distiller's grains, waste microorganisms, or combinations thereof.

[0029] The term "fibersoft" (or "fibrosoft" or "fibrousoft") refers to a type of carbonaceous material resulting from the softening and concentration of various substances; in one instance, carbonaceous materials are produced through vapor pressure heat treatment of various substances. In another instance, soft fibers can include fibrous paste-like materials produced from the vapor pressure heat treatment of municipal, industrial, commercial, and medical waste.

[0030] The terms “municipal solid waste” or “MSW” or “msw” refer to waste that may include household, commercial, industrial and / or residual waste.

[0031] The term "syngas" or "synthetic gas" refers to a gaseous mixture containing varying amounts of carbon monoxide and hydrogen. Examples of production methods include steam reforming of natural gas or hydrocarbons to produce hydrogen, coal gasification, and in certain types of waste-to-gasification facilities. The name derives from their use as an intermediate in the production of synthetic natural gas (SNG) and in the production of ammonia or methanol. Uses of syngas include as an intermediate in the production of synthetic petroleum for use as fuel or lubricant via Fischer-Tropsch synthesis and in the previously used Mobil methanol-to-gasoline process. Syngas consists primarily of hydrogen, carbon monoxide, and some carbon dioxide, and has less than half the energy density (i.e., BTU content) of natural gas. Syngas is combustible and is commonly used as a fuel source or as an intermediate in the production of other chemicals.

[0032] The terms “fermentation,” “fermentation process,” or “fermentation reaction” are intended to encompass both the growth phase and the product biosynthesis phase of the process. In one context, fermentation refers to the conversion of CO into alcohols.

[0033] When used herein, “mass transfer” refers to the transfer of atoms or molecules, particularly substrate atoms or molecules, from the gas phase to an aqueous solution. Mass transfer coefficients can be calculated according to the equations described by Younesi et al. (Iranian Journal of Biotechnology, Vol. 4, No. 1, January 2006), which is incorporated herein by reference. The following equation represents CO2 bioconversion (X... CO and volumetric mass transfer coefficient:

[0034]

[0035] k L a: Volumetric mass transfer coefficient

[0036] X CO CO2 bioconversion %

[0037] R: constant

[0038] T: Temperature

[0039] V L Liquid volume

[0040] H: Henry's constant (CO = 1.226 L·atm·mmol) -1 )

[0041] v g Gas volume

[0042] When the terms “increased efficiency” or “high efficiency” are used in connection with a fermentation process, they include increasing one or more of the following parameters: the growth rate of the microorganisms in the fermentation, the volume or mass of the desired product (e.g., alcohols) produced per unit volume or mass of substrate (e.g., carbon monoxide) consumed, the production rate or level of the desired product, and the relative proportion of the desired product produced to other fermentation byproducts.

[0043] Bioreactor Design

[0044] Figure 1This is a perspective view of a bioreactor apparatus. The bioreactor apparatus includes a shell 105 defining a reactor vessel 100. The reactor vessel 100 may be substantially cylindrical, and the cross-section of the reactor vessel may be shaped as circular, substantially circular, or other shapes that effectively improve mixing and mass transfer. The shell 105 may be formed of any material known to withstand operating pressures of at least about 1 psig and up to at least about 250 psig and to be compatible with the culture medium. The following pressures can be used under various conditions: approximately 5 to approximately 200 psig, approximately 5 to approximately 100 psig, approximately 5 to approximately 50 psig, approximately 5 to approximately 25 psig, approximately 10 to approximately 200 psig, approximately 10 to approximately 100 psig, approximately 10 to approximately 50 psig, approximately 10 to approximately 25 psig, approximately 15 to approximately 200 psig, approximately 15 to approximately 100 psig, approximately 15 to approximately 50 psig, approximately 15 to approximately 25 psig, approximately 20 to approximately 200 psig, approximately 20 to approximately 100 psig, approximately 20 to approximately 50 psig, and approximately 20 to approximately 25 psig. Some examples of suitable materials include stainless steel, steel with appropriate lining, and glass.

[0045] As in Figure 1 As further shown, syngas enters reactor vessel 100 through gas inlet / distributor / sprayer 120. Dispersion and further mixing of the syngas are achieved using at least one gas dispersion impeller 225 and at least one mixing impeller 220 coupled to drive shaft 200. Drive shaft 200 is supported by a mixer support plate 210. Gas is discharged from reactor vessel 100 through exhaust valve 170. Reactor vessel 100 may also include baffles 300 to further enhance mixing. In this case, baffles 300 may extend approximately 25% above the unventilated liquid level 115 to allow for the use of higher operating liquid levels if low-foaming is detected in the system.

[0046] In another embodiment, reactor vessel 100 may include addition ports 230. Addition ports 230 may include, for example, one or more acid addition ports, one or more base addition ports, and one or more nutrient addition ports. In this case, the addition ports may be equally spaced around the perimeter of the reactor vessel. The ports may be on the same or different horizontal planes. In one embodiment, reactor vessel 100 includes at least four equally spaced culture medium addition ports adjacent to mixing impeller 220. The ports may be spaced at a 45° angle around the perimeter of reactor vessel 100.

[0047] An aerated liquid level 110 and a non-aerated liquid level 115 are maintained in reactor vessel 100. Maintaining a non-aerated liquid level 115 in reactor vessel 100 allows for more efficient mass transfer and helps maintain control over foaming. In this case, maintaining a non-aerated liquid level 115 in reactor vessel 100 effectively provides at least about 1% of the total volume of reactor vessel 100 as headspace. In another case, the non-aerated liquid level 115 provides about 1% to about 75% of the total volume of reactor vessel 100 as headspace. In various different cases, the headspace may include the following percentages of the total reactor volume: about 5% to about 50%, about 10% to about 50%, about 15% to about 50%, about 20% to about 50%, about 25% to about 50%, about 30% to about 50%, about 30% to about 40%, and about 30% to about 35%. Reactor vessel 100 may also include at least one liquid inlet 130, which assists in controlling foaming and allows for adjustment of the reactor liquid volume. The liquid inlet 130 may be in the form of a nozzle. The reactor vessel 100 may also include other ports 190.

[0048] As in Figure 1 As further shown, reactor vessel 100 may also include a feed chamber 400 and a vortex eliminator 410 disposed within the feed chamber and above the culture medium outlet 420. The feed chamber 400 and vortex eliminator 410 effectively prevent gas from being extracted through the culture medium outlet 420. Culture medium extracted through the culture medium outlet 420 can be sent to a culture medium recirculation loop 450 or a culture medium filtration loop 460. Culture medium from the culture medium recirculation loop 450 can be sent to a cooler / heat exchanger 500, and the cooled culture medium 510 can be recycled back to reactor vessel 100.

[0049] The feed chamber 400 effectively allows bubbles to rise back into the reactor vessel 100. In this configuration, the liquid in the feed chamber 400 should be as undisturbed as possible, and the bubbles must rise out of the feed chamber 400 at a faster rate than the liquid is drawn downwards into the chamber. In this configuration, less than approximately 2% of the gas is drawn to the pump through the culture medium outlet 420.

[0050] The culture medium from the culture medium filtration loop 460 can be sent to the recirculation filter 600. The concentrated cells 610 are returned to the reactor vessel 100, and the permeate 620 is sent for further processing. Further processing may include the separation of desired products such as ethanol, acetic acid, and butanol.

[0051] In another scenario, the bioreactor can be constructed without an impeller. For example, the bioreactor can be constructed as an airlift reactor or a bubble cap reactor. In these reactor configurations, a power output of approximately 0.01 to approximately 12 kW / m² is provided.3 Energy required for stirring the culture medium.

[0052] Syngas and Syngas Injection

[0053] Syngas is introduced into bioreactor 100 through gas inlet / sprayer 120. Syngas can be supplied from any known source. In one case, the syngas can be derived from the gasification of carbonaceous material. Gasification involves the partial combustion of biomass in a limited oxygen supply. The resulting gas consists primarily of CO and H2. In this case, the syngas contains at least about 20 mol% CO, in one case about 20 to about 100 mol% CO, in another about 30 to about 90 mol% CO, in another about 40 to about 80 mol% CO, and in yet another about 50 to about 70 mol% CO. The syngas has a CO / CO2 molar ratio of at least about 0.75. Examples of suitable gasification methods and apparatus are provided in U.S. Serial Nos. 61 / 516,667, 61 / 516,704, and 61 / 516,646, all of which were filed on April 6, 2011, and are all incorporated herein by reference.

[0054] The bioreactor may include a CO concentration gradient, wherein the CO concentration near the sprayer is higher than the CO concentration at higher planes of the bioreactor. In this case, the bioreactor includes a ratio of approximately 100:1 to approximately 10:1 between the CO concentration at the bottom level (sprayer level) and the CO concentration at the top level of the bioreactor.

[0055] One factor that can affect the mass transfer rate of CO in aqueous media is the partial pressure of the gaseous substrate containing CO. In this case, the mass transfer rate can be increased by enriching or removing unwanted components to increase the proportion of CO in the gaseous stream. In this case, the gaseous stream has less than about 10 ppm of oxidized or non-oxidized aromatic compounds.

[0056] Figure 2A and 2B A bottom view of the gas inlet / sprayer 120 is shown. In this case, the gas inlet / sprayer 120 may include an inlet conduit 530 communicating with the sprayer assembly 540. The sprayer assembly 540 may be substantially annular or circular as shown, or may be any other shape, such as straight, rectangular, or freeform. When the sprayer assembly 540 is annular, its diameter is approximately 30 to approximately 100% of the diameter formed by the gas dispersing impeller 225, and in various different cases approximately 40 to approximately 90%, approximately 40 to approximately 80%, and approximately 50 to approximately 70%.

[0057] The bottom portion of the gas sprayer assembly 540 may include a plurality of orifices 550. The diameter of the orifices 550 is capable of effectively providing a gas velocity of approximately 25 m / sec or greater at the orifice outlet, or in another case, a gas velocity of approximately 25 m / sec to approximately 75 m / sec at the orifice outlet. In various different cases, the gas velocity may include the following ranges: approximately 25 to approximately 75 m / sec, approximately 25 to approximately 50 m / sec, approximately 25 to approximately 40 m / sec, approximately 25 to approximately 30 m / sec, approximately 30 to approximately 75 m / sec, approximately 30 to approximately 50 m / sec, approximately 30 to approximately 40 m / sec, approximately 35 to approximately 75 m / sec, approximately 35 to approximately 50 m / sec, approximately 35 to approximately 40 m / sec, approximately 40 to approximately 75 m / sec, approximately 40 to approximately 50 m / sec, and approximately 50 to approximately 75 m / sec. In this case, the orifices have a diameter of approximately 10 mm or less, and in another case, a diameter of approximately 2.5 mm to approximately 1.0 mm.

[0058] Figure 3 A cross-sectional view of the sprayer assembly 540 is shown. In this case, the dashed arrow lines indicate the gas flow through the orifices 550. A line drawn towards the midpoint of the sprayer assembly indicates an angle of 120° (shown as α). The orifices can be located at any angle along the sprayer assembly. In one case, the sprayer assembly 540 includes approximately one to approximately five rows of parallel orifices 550. The orifices 550 are spaced apart and point downwards. Figure 3 As shown, the sprayer assembly 540 includes five rows of parallel holes 550 spaced 30° apart, for a total of 790 holes. The downward-pointing direction of the holes effectively prevents scaling or clogging and helps minimize backflow into the sprayer assembly 540.

[0059] Gas dispersion and mixing

[0060] Refer again Figure 1 The reactor vessel 100 also includes a mixing assembly comprising a drive shaft 200, at least one mixing impeller 220, and at least one gas dispersing impeller 225. The mixing impeller 220 is generally located below the liquid level 110. In one embodiment, the reactor vessel 100 includes two or more mixing impellers 220. The gas dispersing impeller 225 is located below the mixing impeller 220. The reactor vessel 100 may include one or two or more gas dispersing impellers 225.

[0061] Now for reference Figure 4AEach mixing and gas dispersion impeller assembly includes a hub 500 and a set of impellers arranged around a drive shaft 200. Each impeller includes an arm 510 attached to the hub 500 and having one or more blades 520. The blades can be mixing impellers or gas dispersion impellers. The mixing impeller assembly includes at least two blades and may include up to six blades. Examples of mixing impellers include low-energy impellers such as marine impellers or marine propulsion systems. In another case, the gas dispersion impeller assembly includes at least two blades and may include up to six blades. Examples of gas dispersion impellers include high-energy impellers such as Rushton impellers or concave impellers. Figure 4B and Figure 4A Similarly, the difference is that blade 520 is directly attached to hub 500.

[0062] After the drive shaft 200 rotates, the syngas introduced through the gas inlet / sprayer is entrained in small bubbles in the culture medium and moves around the generally circular cross-section of the reactor vessel 100. The drive shaft is operatively connected to and can be used to rotate any suitable agitator, such as an electric motor, engine and gearbox, or hydraulic motor. In this case, the agitator provides approximately 0.3 to approximately 12 kW / m³. 3 In another case, approximately 0.7 kW / m 3 Approximately 12 kW / m 3 And in critical situations, 0.9 kW / m 3 Approximately 12 kW / m 3 Energy input to the culture medium.

[0063] Bioreactor Operation

[0064] In one scenario, the fermentation process is initiated by adding a suitable culture medium to the reactor vessel. The liquid contained in the reactor vessel can include any type of suitable nutrient medium or fermentation broth. The nutrient medium contains vitamins and minerals that effectively allow the growth of the microorganisms used. Anaerobic media suitable for ethanol fermentation using CO2 as a carbon source are known. Examples of suitable fermentation media are described in U.S. Patent No. 7,285,402, which is incorporated herein by reference.

[0065] The culture medium is sterilized to remove unwanted microorganisms, and the reactor is inoculated with the desired microorganisms. In one case, the microorganisms used include acetic acid-producing bacteria. Examples of useful acetic acid-producing bacteria include bacteria of the genus *Clostridium*, such as *Clostridium ljungdahlii* strains, including those described in WO 2000 / 68407, EP 117309, U.S. Patents 5,173,429, 5,593,886 and 6,368,819, WO 1998 / 00558 and WO2002 / 08438; *Clostridium autoethanogenum* strains (German DSMZ accession numbers DSM 10061 and DSM 19630), including those described in WO 2007 / 117157 and WO 2009 / 151342; and *Clostridium ragsdalei* (P11, ATCC BAA-622) and *Alkalibaculum bacchi* (CP11, ATCC). BAA-1772, including those described in U.S. Patent Nos. 7,704,723 and “Biofuels and Bioproducts from Biomass-Generated Synthesis Gas” (Hasan Atiyeh, presented in Oklahoma EPSCoR Annual State Conference, April 29, 2010), and Clostridium carboxidivorans (ATCC PTA-7827) described in U.S. Patent Application No. 2007 / 0276447. Other suitable microorganisms include those of the genus Moorella, including Moorella sp. HUC22-1, and those of the genus Carboxydothermus. Each of these references is incorporated herein by reference. Mixed cultures of two or more microorganisms may be used.

[0066] Some examples of useful bacteria include *Acetogenium kivui*, *Acetoanaerobium noterae*, *Acetobacterium woodii*, *Alkalibaculumbacchi* CP11 (ATCC BAA-1772), *Blautia producta*, *Butyribacterium methylotrophicum*, *Caldanaerobacter subterraneous*, *Caldanaerobacter subterraneous pacificus*, *Carboxydothermus hydrogenoformans*, *Clostridium aceticum*, *Clostridium acetobutylicum*, *Clostridium acetobutylicum* P262 (DSM-19630), and *Clostridium autoethanogenum* (DSM-19630). *Clostridium autoethanogenum* (DSM 10061), *Clostridium autoethanogenum* (DSM 23693), *Clostridium autoethanogenum* (DSM 24138), *Clostridium carboxidivorans* P7 (ATCC PTA-7827), *Clostridium coskatii* (ATCC PTA-10522), *Clostridium drakei*, *Clostridium ljungdahlii* PETC (ATCC 49587), *Clostridium ljungdahlii* ERI2 (ATCC 55380), *Clostridium ljungdahlii* C-01 (ATCC 55988), *Clostridium ljungdahlii* O-52 (ATCC 55988). Clostridium magnum (55889), Clostridium pasteurianum (German DSMZ accession number DSM 525), Clostridium ragsdaliP11 (ATCC BAA-622), Clostridium scatologenes, Clostridium thermoaceticum, Clostridium ultunense, Desulfotomaculum kuznetsovii, Eubacterium limosum, Geobacter sulfurreducens, Methanosarcina acetivorans, Methanosarcina barkeri, Morrella thermoacetica, Morrella thermoautotrophica, Oxobacter pfennigii, Peptostreptococcus productus, Ruminococcus productus, Thermoanaerobacter kivui and mixtures thereof.

[0067] After inoculation, an initial feed gas supply rate is established to effectively supply the initial microbial population. The effluent gas is analyzed to determine its contents. The results of the gas analysis are used to control the feed gas rate. Once the desired liquid level is reached, the liquid phase and cell material are withdrawn from the reactor and replenished with culture medium. In this case, the bioreactor is operated to maintain a cell density of at least about 2 g / L, and in another case about 2 to about 50 g / L, and in various other cases about 5 to about 40 g / L, about 5 to about 30 g / L, about 5 to about 20 g / L, about 5 to about 15 g / L, about 10 to about 40 g / L, about 10 to about 30 g / L, about 10 to about 20 g / L, and about 10 to about 15 g / L. Cell density can be controlled via a recirculation filter 600. Under relevant conditions, the bioreactor is operated to provide liquid residence times of approximately 10 to 400 hours, and in various cases approximately 10 to 300 hours, approximately 10 to 200 hours, approximately 10 to 100 hours, approximately 10 to 75 hours, approximately 10 to 60 hours, approximately 10 to 50 hours, approximately 10 to 40 hours, approximately 10 to 30 hours, and approximately 10 to 20 hours. In these cases, the liquid residence time (LRT) can be calculated as follows.

[0068]

[0069] Syngas is introduced into the bioreactor at a rate that effectively maintains the pressure within the bioreactor at at least about 1 psig, and in another case, about 10 to about 250 psig. In various other cases, the pressure may be about 10 to about 200 psig, about 10 to about 100 psig, about 10 to about 75 psig, about 10 to about 50 psig, about 10 to about 25 psig, about 20 to about 250 psig, about 20 to about 200 psig, about 20 to about 100 psig, about 20 to about 75 psig, about 20 to about 50 psig, about 20 to about 25 psig, or about 30 to about 250 psig. Approximately 30 to approximately 200 psig, approximately 30 to approximately 100 psig, approximately 30 to approximately 75 psig, approximately 30 to approximately 50 psig, approximately 40 to approximately 250 psig, approximately 40 to approximately 200 psig, approximately 40 to approximately 100 psig, approximately 40 to approximately 75 psig, approximately 40 to approximately 50 psig, approximately 50 to approximately 250 psig, approximately 50 to approximately 200 psig, approximately 50 to approximately 100 psig, and approximately 50 to approximately 75 psig.

[0070] In one scenario, in fermenters of certain sizes, syngas is introduced at a rate of approximately 10 to approximately 50 ft. 3 A rate of / sec and in another case approximately 25 to 35ft 3 Syngas is introduced into the gas inlet / sprayer 120 at a rate of / sec. Pressure is controlled by adjusting the rate of syngas introduction in conjunction with the rate of gas discharge from the reaction vessel. Pressure can be measured in the reactor headspace or at the bottom of the reactor vessel.

[0071] In one scenario, the sprayer orifice 550 and the pressure drop across it are important for improving the volumetric mass transfer rate of CO. The pressure drop across the sprayer orifice 550 needs to be high enough to ensure the distribution of bubbles around the sprayer assembly 540. In this case, the spray effectively provides a pressure drop of about 0.5 psi to about 2.5 psi, and in another scenario, about 1 psi to about 2 psi across the sprayer orifice 550. The sprayer orifice 550 offers advantages compared to other spray forms. For example, the sprayer orifice 550 effectively avoids fouling, as can occur when using sintered metal sprayers. Furthermore, the sprayer orifice 550 effectively provides a consistent bubble size that contributes to improved mass transfer.

[0072] Another factor that may affect the mass transfer rate is the gas residence time. In this case, the bioreactor effectively provides a gas residence time of at least about 2 minutes, in another case about 2 minutes to about 15 minutes, and in yet another case about 5 to about 10 minutes. The gas residence time (GRT) can be determined according to the following formula:

[0073]

[0074] Temperature and ionic strength can also affect the mass transfer rate. In this case, the temperature of the bioreactor is approximately 30 to approximately 50 °C.

[0075] Alternative configurations of the feed chamber 400 are shown in Figure 5 In this case, the feed chamber 400 is used as a growth reactor during startup. The feed chamber is configured to include a feed chamber sprayer 600. The feed chamber also includes a feed chamber mixer. The feed chamber mixer can be configured with any known mixing device. For example, gas mixing can be performed using an impeller (not shown) or an airlift fermenter equipped with a baffle 620. As in Figure 5 As shown, the airlift fermenter effectively allows bubbles 610 and cells to circulate around the feed chamber 400. Other reactor designs can be used, including bubble reactors and external gas loop or jet reactors.

[0076] An alternative feed chamber configuration is utilized by inoculating acetic acid-producing bacteria into a culture medium contained in the feed chamber portion of the reactor vessel. The culture medium in the feed chamber fills at least about 75% of the total volume of the feed chamber, in another case at least about 80%, in another case at least about 85%, in another case at least about 90%, and in yet another case at least about 95%. The feed chamber is injected with syngas and mixed to effectively deliver the target cell density for a period of time. In this case, the target cell density is about 5 to about 40 g / L, and in various other cases about 5 to about 30 g / L, about 5 to about 20 g / L, about 5 to about 15 g / L, about 10 to about 40 g / L, about 10 to about 30 g / L, about 10 to about 20 g / L, and about 10 to about 15 g / L. After the target cell density is reached, the culture medium level is allowed to rise outside the feed chamber and into the reactor vessel up to the previously indicated level. Injection and mixing in the feed chamber are stopped, and fermentation proceeds as previously described.

[0077] In another case, the cell density in the feed chamber is brought to a level of at least about 3 g / L or any cell density described herein. Once a cell density of at least about 3 g / L is reached, culture medium is added at a rate that effectively allows the cell density level to be maintained at at least about 3 g / L. After the desired culture medium level is reached, spraying and mixing in the feed chamber are stopped, and fermentation proceeds as previously described.

[0078] Example

[0079] Pilot-scale fermentation was conducted to determine k. L a. The measured k LThe yield (a) is approximately 60 g ethanol / (L·day) STY (space-time yield). K is obtained by forced reaction under mass transfer-limited conditions or zero dissolved CO concentration. L The estimation of 'a'. This is achieved by instantaneously reducing the gas flow rate or stirring rate to make the cells excessive relative to the available gas. Under these conditions, CO is reacted as soon as it dissolves, making the reaction mass-limited. The difference between the CO dissolved in the solution and the CO in the feed gas and the CO in the products is the same. In a mass-limited system, this difference is the mass transfer rate under given conditions.

[0080] The basic equation used is k L a = C kla (P g / V l ) a v b sg

[0081] in

[0082] k L a = volumetric mass transfer coefficient (m 3 gas / s / m 3 liquid)

[0083] C kla =Constants of a given system

[0084] P g = Power consumption of the aeration mixer (W)

[0085] V l =Liquid volume (m³) 3 )

[0086] v sg = Surface gas velocity (m / s)

[0087] a = scale-up constant

[0088] b = scale-up constant

[0089] The test was conducted at 6 psig (top pressure) and measured at 60 g ethanol / (L·day) STY. The results are as follows:

[0090]

[0091] Although the invention disclosed herein has been described with reference to specific embodiments, examples and applications, those skilled in the art can make numerous modifications and alterations thereto without departing from the scope of the invention as set forth in the claims.

Claims

1. A method for anaerobic fermentation of syngas, the method comprising: The syngas is introduced into the stirred tank reactor vessel via a gas injector located below the liquid level in the reactor vessel. The gas injector includes orifices with a diameter of 10 mm to 1.0 mm, and the syngas is introduced at a rate of 10 to 50 ft. 3 The synthesis gas is introduced into the gas injector at a rate of / sec, through a downward-pointing orifice in the gas injector, the flow rate effectively providing a pressure drop across the injector of 0.5 to 2.5 psi, a gas velocity of 25 m / sec or higher at the outlet of the orifice, and effectively maintaining the pressure inside the reactor vessel at at least 1 psig, wherein the synthesis gas has a CO / CO2 molar ratio of at least 0.75, and the method provides a gas residence time of 5 to 10 minutes, a liquid residence time of 10 to 400 hours, and a cell density of 5 to 40 g / L; The synthesis gas is brought into contact with at least one gas dispersion impeller located above the gas sprayer; as well as The syngas is mixed with at least one acetic acid-producing bacterium using at least one mixing impeller located above the gas dispersing impeller. The gas dispersion impeller and mixing impeller are operatively connected to a mixer via a drive shaft, the mixer providing 0.9 to 12 kW / m³. 3 Energy input for stirring the culture medium. The method described therein effectively provides a volumetric CO mass transfer coefficient of 200 to 1100 / hour and a space-time yield of 20 g to 140 g ethanol / (L·day).

2. The method of claim 1, wherein the gas sprayer comprises an orifice with a diameter of 2.5 mm to 1.0 mm.

3. The method of claim 1, wherein the synthesis gas is introduced at a flow rate that effectively maintains the pressure within the reactor vessel at at least 10 psig.

4. The method of claim 1, wherein the method effectively provides a cell density of 10 to 40 g / L.

5. The method of claim 1, wherein the synthesis gas has a CO content of at least 20 mol%.

6. The method of claim 1, wherein the synthesis gas comprises less than 10 ppm of oxidized or non-oxidized aromatic compounds.

7. The method of claim 1, wherein the acetic acid-producing bacteria is selected from Kavulacillus acetogenes (Kavulacillus acetogenes). Acetogenium kivui ), moist anaerobic acetic acid bacteria ( Acetoanaerobium noterae Acetobacter wuerii ( Acetobacterium woodii ), with accession number ATCC BAA-1772 Alkalibaculum bacchi CP11 Blautia producta Methyltrophic butyric acid bacteria ( Butyribacterium methylotrophicum ), Caldanaerobacter subterraneous , Caldanaerobacter subterraneous pacificus, Carboxydothermus hydrogenoformans, Clostridium acetic acid ( Clostridium aceticum Clostridium acetonebutanol ( Clostridium acetobutylicum Clostridium acetone-butanol, with German DSMZ accession number DSM 19630 ( Clostridium acetobutylicum P262, German DSMZ accession number DSM 10061 Clostridium autoethanogenum The German DSMZ accession number is DSM 23693. Clostridium autoethanogenum The German DSMZ accession number is DSM 24138. Clostridium autoethanogenum Clostridium carbon oxidizingus with accession number ATCC PTA-7827 Clostridium carboxidivorans P7, with accession number ATCC PTA-10522 Clostridium coskatii , Clostridium drakei Clostridium listeriforme with accession number ATCC 49587 Clostridium ljungdahlii ) PETC Clostridium listeriforme with accession number ATCC55380 Clostridium ljungdahlii ) ERI2 Clostridium listeriforme with accession number ATCC 55988 Clostridium ljungdahlii ) C-01 Clostridium listeriforme with accession number ATCC 55889 Clostridium ljungdahlii ) O-52 , Clostridium magnum Clostridium pasteurellum with German DSMZ accession number DSM 525 Clostridium pasteurianum The collection number is ATCC BAA-622. Clostridium ragsdali P11 , Clostridium scatologenes Clostridium thermophilum ( Clostridium thermoaceticum ), Clostridium ultunense Kuhl's desulfurized enterobacteria ( Desulfotomaculum kuznetsovii ), Eubacterium mucosus ( Eubacterium limosum ), Geobacter sulfurreducens , Methanosarcina acetivorans Pasteurella multocida ( Methanosarcina barkeri ), thermospermia ( Morrella thermoacetica ), Morrella thermoautotrophica , Oxobacter pfennigii Produces Peptostreptococcus ( Peptostreptococcus productus ), producing rumen cocci ( Ruminococcus productus ), Thermoanaerobacter kivui and its mixtures.

8. The method of claim 1, wherein the reactor vessel includes at least four equally spaced culture medium addition ports adjacent to the mixing impeller.

9. The method of claim 8, wherein the addition port is spaced at a 45° angle around the periphery of the reactor vessel.

10. The method of claim 1, wherein the reactor vessel includes a baffle extending 25% above the unventilated liquid level.

11. The method of claim 1, wherein an unventilated liquid level is maintained in the reactor vessel to provide a top space of 1% of the total volume of the reactor vessel.

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