WO2013135917A1

WO2013135917A1 - Method for storing solar energy in the form of environmentally friendly fuels

Info

Publication number: WO2013135917A1
Application number: PCT/ES2012/070167
Authority: WO
Inventors: Daniel GONZÁLEZ GONZÁLEZ; Daniel GONZÁLEZ URANGA
Original assignee: Guradoor, S.L.
Priority date: 2012-03-14
Filing date: 2012-03-14
Publication date: 2013-09-19
Also published as: UY34241A; ES2425694B1; ES2425694A1

Abstract

The invention relates to a method for storing solar energy captured by a parabolic concentrating solar collector having a tank coupled thereto which contains a saline solution and which both supports possible forces to which the solar collector my be subjected, as well as heating and supplying one or more tanks for anaerobic fermentation of biomass containing a bacterium of the species Clostridium acetobutylicum, in order to obtain ethanol, butanol and acetone by fermentation of said biomass (ABE fermentation), these fermentation by-products being continuously extracted from the fermentation tanks and conveyed to storage tanks where they are mixed with other fuels in order to obtain high-octane industrial fuel mixtures with a high energy capacity. The method, which can be carried out on an industrial scale, is clean and environmentally friendly and provides high production yields.

Description

PROCEDURE FOR THE STORAGE OF SOLAR ENERGY IN THE FORM OF ECOLOGICAL FUELS

The present invention relates to a process for storing energy from the sun in the form of ecological fuels, it being understood in this sense to obtain fuels from solar energy and biomass, the result of which is a biofuel product.

More specifically, the present invention relates to a process for the storage of solar energy captured by a parabolic concentration solar collector to which a tank containing a saline solution is attached at its base and that acts both supporting the possible efforts to which The parabolic solar concentration collector is subjected to facilitate temperature and feed one or more anaerobic biomass fermentation tanks containing a bacterium of the species Clostridium acetobutylicum, to obtain ethanol, butanol and acetone by fermentation of said biomass according an ABE fermentation, these fermentation by-products being continuously extracted from the fermentation tanks to storage tanks where they are mixed with other fuels, for example petroleum derivatives already known, to obtain industrial fuel mixtures of high octane and energy capacity .

Clostridium acetobutylicum (from the Latin acetum, vinegar and butylicum of butyrum, butter, from the Greek boutyron), also called the Weizmann organism (1874-1952), breaks down sugars and starches and uses them as a source of energy according to a fermentation process, giving as main products acetone, butanol and ethanol and a certain amount of hydrogen gas recoverable, in addition to acetic acid, lactic acid, icos propionic acids and isopropanol. These bacteria mainly use molasses as a substrate (Ni Y. and Sun Z. (2009), Recent progress on industrial fermentative production of acetone-butanol-ethanol by Clostridium acetobutylicum in China, App. Microbiol. Bitechnol. 83: 415-423) and It is a forced anaerobic species with a cane shape that has a chromosome of 3.94 Mpb and a plasmid of 192 Kpb. In strains wild, this plasmid is indispensable for solventogenesis (Lee SY, Park JH, Jang SH, Nielsen LK, Ki m J. and Jung KS (2008), Fermentative butanol, production by Clostridia. Biotechnol. Bioeng., 101: 209-228 ). C. acetobutylicum has the advantage of being very diverse in the substrates it metabolizes, using glucose, galactose, cellobiose, mannose, xylose and arabinose. In addition, the battery of enzymes that releases the medium, including a- and β-amylases, a- and β-glucosidases, pululanases, amylopululanases, among others, is also diverse. During the production process of butanol with Clostridium the bacterium undergoes an important physiological change: acetic and butyric acids are released into the environment during the exponential growth phase, being reabsorbed into the cell to be metabolized to butanol, acetone and, although to a much lesser extent, in ethanol.

This is because C. acetobutylicum lacks homeostasis at the pH level, so it depends intimately on the extracellular pH. The presence of acids in the medium can cause a loss of the protonic potential of the cell, inactivating it. The pH is very important during the acetone-butanol fermentation, since the solvent is started at a low pH. However, if it is below 4.5 (before a sufficient amount of organic acids is formed), the solvent will be diminished and unproductive. A simple way to increase growth, the use of carbohydrates as well as the production of butanol is to increase the buffer capacity of the medium. Depending on the culture conditions and the type of substrate used, batch fermentations take from 2 to 6 days to complete, reaching the final total concentration of solvents produced from 12 to 20 g / l, being able to separate these by distillation of the fermentation medium (Lee et al., 2008).

Butanol formation marks the beginning of a sporulation phase in the Clostridium, causing crop inactivation. It has been observed that continuous cultures with integrated separation systems in s / íu give the highest butanol titers. Thus, the group of Ezeji et al. (Ezeji TC, Qureshi N. and Blaschek HP (2004) Acetone Butanol Ethanol (ABE) production from concentrated substrate: Reduction in substrate inhibition by fedbatch technique and product inhibition by gas stripping, Appl. Microbiol Biotechnol., 63: 653-658) obtained productivity of 0.91 g / l / h of butanol by removing it from the active culture medium by means of a carrier gas. In 1983 Lin and Blaschek characterized a strain of C. acetobutylicum that reached butanol production titres of 7.9 g / l in a medium containing 6% corn extract. In that work, the authors reported the development of butanol tolerant mutants that they obtained through consecutive transfers to media with gradually larger amounts of butanol. In fact, one of its tolerant strains reported the highest percentage of consumption of cabobo id id time, the highest yield of consumption and nabutanolyla with the highest concentration achieved (1 8.6 g / l of butanol). However, since C. acetobutylicum has mixed fermentation, significant amounts of acetone and ethanol were also produced, even in the adapted strain (Lin YL and Blaschek HP, Butanol production by a butanol-tolerant strain of Clostridium acetobutylicum in extruded corn broth, Appl. Environ. Microbiol. 45: 966-973). Using batch cultures with 6% glucose and strains of C. beijerinckii, titers of up to 1 8.6 g / l of butanol were achieved (Formanek J., Mackie R., Blaschek HP (1997), Enhanced butanol production by Clostridium beijerinckii BA101 grown in semidefined P2 medium containing 6 percent maltodextrin or glucose, Appl. Environ. Microbiol., 63: 2306-2310), although 8.6 g / l acetone was also produced.

Thus, the industrial application of ABE fermentation is still very limited, both due to the high cost of recovery-separation of the products and their low concentration, in particular due to the low yields of butanol, as well as due to the inactivation of the microorganism during the production of acetone-butanol-ethanol. The recent interest in the production of butanol from biomass has allowed reexamination of ABE fermentation to include strategies that reduce or eliminate the toxicity of butanol in the culture medium or genetically modify the organism to obtain a better product specificity and yield ( Chukwuemeka et al., 2007, BioTechnology, Year 2009, Vol. 13 No. 3).

For its part, it is known that butanol can be used per se as fuel in internal combustion engines, although it is usually used in the form of a mixture with conventional fuels. Because it is a non-polar compound, its similarity with gasoline is greater compared to ethanol. Currently, the industrial production of butanol from natural sources is based on the developments of Du Pont, BP and Butalco, which is studying the production of genetically modified yeasts to obtain bioethanol from cellulosic materials. The advantages of the use of butanol compared with that of ethanol are essentially that the former better tolerates possible contamination with water and that it is less corrosive than ethanol, which facilitates its use in gasoline distribution facilities, also The mixtures obtained from butanol and fuel are conventional and have a lower tendency to phase separation than ethanol, which is favored by the synergy in the vapor pressure of the butanol mixtures and Gasol inas with ethanol content, which facilitates storage and distribution.

In this sense, the octane rating of n-butanol is similar to that of gasoline, presenting a RON (Research Octane Number) of 96 and a MON (Motor Octane Number) of 78, resulting in a number (R + M) / 2 of 87, while t-butanol reaches an RON of 105 and a MON of 89. Similarly, when a higher viscosity is desired for the final fuel, blends with butanol allow a viscosity similar to that of diesel fuel to be obtained. The following table shows different characteristics of gasoline fuels and alcohols currently used.

In WO 2010/024715, "Strain of Clostridium acetobutylicum and a method of producing organic solvents", a method for producing organic solvents comprising the anaerobic culture of the strain of Clostridium acetobutylicum 3108 in a medium supplemented with carbon sources, preferably milk whey (Example 3), by fermentation of sucrose and molasses at 36.5 ° C.

WO 2010/000649 A1, "Method for the combined production of butanol and hydrogen", refers to a process for the combined production of butanol and hydrogen from biomass comprising the steps of fermenting the biomass to obtain butanol in a first reaction mixture, removing the butanol and hydrogen from this first mixture to obtain an effluent and subsequently using the effluent as a substrate in a second reaction mixture, in particular in a process for obtaining hydrogen.

The object of the invention is to provide a method for the storage of the solar energy captured by a solar collector of parabolic concentration, hereinafter solar collector, to which a tank containing, for example at its base, is coupled saline solution and that acts both supporting the possible efforts to which the solar collector is subjected and to facilitate the temperature and feed one or more anaerobic biomass fermentation tanks that contain a bacterium of the species Clostridium acetobutylicum, to obtain ethanol, butanol and acetone by fermentation of said biomass according to an ABE fermentation, these fermentation by-products being continuously extracted from the fermentation tanks to storage tanks where they are mixed with other fuels, for example petroleum derivatives already known, for obtain industrial fuel mixtures of high octane and energy capacity, being the p Procedure applicable to industrial scale, clean and environmentally friendly and high productivity.

For this, the process of the invention is essentially based on using the energy of the sun concentrated in the said solar collector to heat a tank containing a solution of various salts whose effect is, on the one hand, to avoid the possible mechanical stresses to which the solar collector due to environmental conditions such as high winds, terrain elevations, etc., and, on the other hand, supplement with fermentation-promoting components one or more anaerobic biomass fermentation tanks, where biomass fermentation is carried carried out according to an ABE type process using the bacterium Clostridium acetobutylicum. The result of this fermentation is the obtaining of ethanol, butanol and acetone, and hydrogen in a smaller proportion, these by-products being continuously extracted from the fermentation tanks to storage tanks where they are mixed with other fuels to obtain industrial fuel mixtures.

ABE fermentation is influenced by the presence of certain inorganic salts, as well as by the amount of glucose present in the fermentation medium. In this regard, Frederic Monot et al. (in "Acetone and Butanol Production by Clostridium acetobutylicum in a Synthetic Medium", Applied and Environmental Microbiology, 1982, p. 1318-1324 Vol. 44, No. 6) have shown that the presence in the culture medium of Fe ²⁺ and K ⁺ favors bacterial growth and the conversion of sugars in the solvents sought.

Thus, the process of the invention includes the steps of: i) using the solar energy collected in a solar collector to heat a tank located at the base thereof containing a solution of inorganic salts that include Fe ²⁺ and K ⁺ ions; ii) supplement with this solution that includes Fe ²⁺ and K ⁺ ions anaerobic fermentation tanks containing Clostridium acetobutylicum as well as a source of carbohydrates, carrying out the fermentation process of this type of carbon under conditions of supplementation to the medium of said ions and their conversion to acetone, ethanol and butanol; iii) continuous extraction of solvents and H ₂ resulting from the fermentation process to corresponding storage tanks; Y iv) mixing of the solvents obtained with other alcohols or conventional fuels and application of the hydrogen gas obtained for other industrial processes or for storage.

In an exemplary embodiment of the process of the invention, the solar collector used in step i) is of the type described in Spanish patent application No. 201031 287, of the same applicant, since it has great advantages in terms of stability and self-orientation Thus, starting for example from the parabolic collector mentioned, at the base of this one, a tank is arranged to accommodate a solution of inorganic salts containing Fe ²⁺ and K ⁺ ions, for example a solution of ferrous sulfate and KCI buffered with NaH ₂ PO ₄ -2H ₂ O and Na ₂ HPO3-12H ₂ O (see Frederic Monot et al., Supra). This tank can be arranged in the base of the solar collector as part of the base of the same, thereby reducing the absorption of the mechanical stresses supported by the solar collector itself or it constitutes an element attached to the base of the solar collector itself.

Preferably, the heating temperature of stage i) reached in the tank containing the Fe ²⁺ and K ⁺ ion solution ranges between 35 and 50 ° C, with a temperature of 46 ° C being especially preferred.

In process step ii), part of this heated solution is fed to at least one fermentation tank containing the Clostridium acetobutylicum bacteria together with a source of carbohydrates, where fermentation is preferably carried out at 46 ° C. In a preferred embodiment of the invention, said carbohydrate source is cassava, potato or sweet potato pulp, which is fed directly to the tanks after a previous treatment to facilitate fermentation.

In step iii), the solvents resulting from the fermentation are continuously extracted, for example by distillation, providing the appropriate temperature from the solar collector itself, so that the deterioration of the bacteria is not produced by its transformation to spore. For its part, the hydrogen gas by-product of the fermentation can be reused in multiple industrial processes, for example for use in the formation of alcohols based on synthesis gas, or for storage.

Claims

1. Procedure for the storage of solar energy captured by a parabolic concentration solar collector characterized in that it includes the steps of: i) using the solar energy collected in the solar collector to heat a tank containing a solution of inorganic salts that include ions Fe ²⁺ and K ⁺ ; ii) supplement with this solution that includes Fe ²⁺ and K ⁺ ions anaerobic fermentation tanks containing Clostridium acetobutylicum as well as a source of carbohydrates, carrying out the process of fermentation of such carbohydrates under supplementation conditions at medium of said ions, and their conversion to acetone, ethanol and butanol; iii) continuous extraction of solvents and H ₂ resulting from the fermentation process to corresponding storage tanks; and iv) mixing of the solvents obtained with other alcohols or conventional fuels and reuse of the hydrogen gas obtained as a by-product.

2. Method according to claim 1, characterized in that the solution used in step ii) as a source of Fe ²⁺ and K ⁺ ions is a solution of ferrous sulfate and KCI buffered with NaH ₂ PO ₄ -2H ₂ O and Na ₂ HPO ₃ -12H ₂ O

3. Method according to claim 1 or 2, characterized in that the heating temperature of stage i) reached in the tank containing the Fe ²⁺ and K ⁺ ion solution ranges between 35 and 50 ° C.

4. Method according to claim 3, characterized in that the temperature is 46 ° C. Method according to claim 1, characterized in that the carbohydrate source of stage ii) is cassava, potato or sweet potato pulp.

Procedure according to claim 1, characterized in that the continuous extraction of the solvents of step iii) is carried out by fractional distillation and because the by-product of hydrogen gas is recycled industrially.