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Title:
ENERGY EFFICIENT FERMENTATION PROCESS INTEGRATED WITH AN EXTRACTION PROCESS USING A SUPERCRITICAL FLUID
Document Type and Number:
WIPO Patent Application WO/2013/044081
Kind Code:
A1
Abstract:
There is disclosed herein an integrated manufacturing process, wherein a fermentation process is integrated with an extraction process that uses a supercritical fluid. The process ferments a carbohydrate to produce a fermentation product and gaseous CO2, then compresses the gaseous CO2 to form a supercritical CO2 using the supercritical CO2 as an extractant to separate one component from a mixture.

Inventors:
CALABRESE RAFAEL JANUARIO (BR)
Application Number:
PCT/US2012/056644
Publication Date:
March 28, 2013
Filing Date:
September 21, 2012
Export Citation:
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Assignee:
DU PONT (US)
International Classes:
C12P7/06; B01J13/00; C12F3/02
Domestic Patent References:
WO2011021856A22011-02-24
WO2001028675A12001-04-26
Foreign References:
EP2361741A12011-08-31
US20100139154A12010-06-10
Other References:
KHOSRAVI-DARANI K; VASHEGHANI-FARAHANI E: "Application of supercritical fluid extraction in biotechnology", CRITICAL REVIEWS IN BIOTECHNOLOGY, vol. 25, 2005, pages 231 - 242, XP008158772
SOLEIMANI DORCHEH ET AL: "Silica aerogel; synthesis, properties and characterization", JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ELSEVIER, NL, vol. 199, no. 1-3, 1 November 2007 (2007-11-01), pages 10 - 26, XP022409626, ISSN: 0924-0136
TOMASKO; GUO: "Kirk-Othmer Encyclopedia of Chemical Technology", 14 April 2006, JOHN WILEY & SONS, INC., article "Supercritical Fluids"
OLIVERIO, PROCEEDINGS OF THE INTERNATIONAL SOCIETY OF SUGAR CANE TECHNOLOGY, vol. 27, 2010
OLIVERIO ET AL., PROC. INT. SOC. SUGAR CANE TECHNOL., vol. 27, 2010
LEVENTIS AND KOEBEL,: "Aerogel Handbook", 2011, SPRINGER
HUSING; SCHUBERT: "Ullman's Encyclopedia of Industrial Chemistry", 15 December 2006, article "Aerogels"
Attorney, Agent or Firm:
SANTOPIETRO, Lois A. (Legal Patent Records Center4417 Lancaster Pik, Wilmington Delaware, US)
Download PDF:
Claims:
Claims

What is claimed is:

1 . An integrated manufacturing process comprising a fermentation process integrated with an extraction process that uses a supercritical fluid.

2. A integrated manufacturing process comprising:

a) fermenting a carbohydrate to produce a fermentation product and gaseous CO2;

b) compressing the gaseous CO2 to form a supercritical CO2; and c) using the supercritical CO2 as an extractant to separate a component from a mixture.

3. The process of Claim 2 wherein the mixture is a gel.

4. The process of Claim 2 wherein the component is a continuous phase.

5. The process of Claim 2 wherein separating the component from the mixture forms an aerogel.

6. The process of Claim 2 wherein the fermentation product and the component is ethanol.

7. The process of Claim 6 further comprising after step b:

contacting a hydrogel with the ethanol to remove water from the hydrogel to form the gel.

8. An integrated manufacturing process comprising: a) fermenting a carbohydrate to produce a fermentation product, gaseous CO2 and thermal energy;

b) forming a supercritical CO2 from the gaseous CO2 and the thermal energy;

c) using the supercritical CO2 as an extractant to separate a component from a mixture; and

d) separating the component from the supercritical CO2 by

reducing the pressure to form a liquid phase CO2.

9. The process of claim 8 further comprising:

e) recycling the liquid phase CO2 by mixing the liquid phase CO2 with the gaseous CO2 in step b).

10. An integrated manufacturing process comprising:

a) fermenting a carbohydrate to produce a fermentation product, gaseous CO2, and thermal energy wherein the thermal energy is transferred to a cooled water stream forming a heated water stream;

b) compressing the gaseous CO2 to form a liquid CO2;

c) forming a supercritical CO2 from the liquid CO2 and the thermal energy from the heated water stream to form a cooled water stream;

d) using the supercritical CO2 as an extractant to separate a

component from a mixture;

e) separating the component from the supercritical CO2 by reducing the pressure to form a liquid phase CO2.

1 1 . The process of claim 10 further comprising recycling the cooled water stream from step c) to step a).

12. The process of claim 10 further comprising recycling the liquid phase CO2 from step e) to step b).

13. The process of Clainn 8 wherein separating the component from the mixture forms an aerogel. 14. The process of Claim 10 wherein separating the component from the mixture forms an aerogel.

Description:
TITLE

ENERGY EFFICIENT FERMENTATION PROCESS INTEGRATED WITH AN EXTRACTION PROCESS USING A SUPERCRITICAL FLUID

Field of the Invention

This invention relates to an energy efficient fermentation process integrated with an extraction process that uses a supercritical fluid. Background

Conventional fermenters frequently run at a carbohydrate

concentration that is no more than about 10 wt%. Higher feed

concentrations are often not possible because the bacteria cells used for fermentation exhibit reduced activity at carbohydrate concentrations higher than about 10 wt%. In addition, undesirable bacteria cells become more active at higher carbohydrate concentrations, catalyze undesirable reactions in the fermenter, and thereby compromise selectivity of the reaction to the product of interest.

One approach to controlling the concentration of carbohydrates in a fermentation reaction is to dilute the reaction mixture with water. This not only uses large volumes of water, but makes recovery of the fermentation product more difficult in view of the need to separate the product from the water. Use of large volumes of water also increases the amount of stillage and other waste material left behind after completion of the fermentation reaction, and disposal of such waste material in a cost-effective, environmentally benign manner is difficult. In addition, when the source of water to be added to the fermentation reaction is a fresh water source such as a river, the water must typically be treated with a biocide to limit the growth of undesirable bacteria in the fermenter.

Problems such as described above can be mitigated if a fermenter can be cooled to operate at a temperature less than about 30°C. When the reaction is run at cooler temperatures, there is less need for dilution of the reaction mixture, and less water will in such case be added to the reaction mixture. This ameliorates the recovery and disposal problems caused by the use of large volumes of water. In addition, the growth of undesirable bacteria is inherently reduced at a lower reaction temperature.

Despite the benefits of running a fermentation reaction at lower temperatures, many fermenters in hot, humid climates currently operate above about 32° C. The cooling of a fermenter would require chillers with very large energy loads. For most fermentation processes, the capital and operating costs of adding such cooling capacity would make the

fermentation process uneconomical. A need thus remains for a

fermentation process that can be run on a more energy efficient basis, particularly a process where the fermentation reaction can be cooled at a reasonable cost.

One by-product of fermentation reactions is CO2. One use to which the CO 2 can be utilized is in the manufacture of aerogels. Aerogels are nanoporous materials that have the lowest known thermal conductivity and the highest insulation value. Even though aerogel insulation could significantly reduce energy losses in buildings, appliances, vehicles and other parts of the cold chain, the high cost of manufacturing aerogels has previously reduced their attractiveness because the payback time for investment in their use is quite long. The high cost of the aerogel is due primarily to the high cost of raw materials needed to make the sol (the precursor to the gel), and the high cost associated with the supercritical drying of the alcogel, which relies on the presence of CO 2 to displace the solvent contained in the alcogel. Supercritical drying with CO2 is usually required to prevent the pore structure of an aerogel from collapsing due to capillary forces.

Similar materials could indeed be cheaper to manufacture than aerogels that require supercritical drying, but the thermal performance is not as good as aerogels obtained from supercritical drying. Manufacturing aerogels by the use of supercritical drying with CO2 will thus continue to be the process of choice for the foreseeable future. Aerogels have been known for over 70 years but they have not made a significant commercial impact primarily because of the high cost of manufacturing. Thus, even though aerogel insulation could significantly reduce energy losses in buildings, appliances, transportation and the cold chain, aerogels are not prevalently used because the payback time for investment is too long.

Therefore, if the two processes - fermentation and aerogel manufacturing - can be synergistically combined, there is the potential for producing cost effective aerogel product.

Summary

There is disclosed herein an integrated manufacturing process, comprising a fermentation process integrated with an extraction process that uses a supercritical fluid.

In another embodiment, the process further comprises the steps: a) fermenting a carbohydrate to produce a fermentation product and gaseous CO2;

b) compressing the gaseous CO2 to form a supercritical CO2; and c) using the supercritical CO2 as an extractant to separate a

component from a mixture.

Brief Description of the Drawings

Figure 1 illustrates an aerogel process.

Figures 2, 4A and 4B illustrate a conceptual schematic of certain embodiments of the methods hereof.

Figure 3 illustrates a schematic of the integration fermentation process in concert with the manufacturing of aerogels.

Figure 5 illustrates a flow sheet of a fermentation process that converts sugar must to ethanol.

Figure 6 illustrates the entering and leaving streams to and from the heat exchanger employed in a typical sugar mill to control the temperature of the fermenter. Figure 7 illustrates the flow diagram for a chiller and the heat exchanger used to cool the fermenter.

Figure 8 illustrates the energy, raw materials and equipment requirements in an organic aerogel manufacturing process that is set up as a standalone unit without the advantage of energy and material integration with a fermentation based manufacturing process.

Figure 9 illustrates a flow sheet for the gelation process used for this example.

Figure 10 illustrates a distillation column used to separate the water and concentrate the ethanol stream.

Figures 1 1 A, 1 1 B, and 12 illustrate a process flow sheet for heating and compressing the liquid CO2.

Figure 13 illustrates a simplified process diagram highlighting the pertinent process streams involved in cooling the fermentation vessel in the ethanol plant.

Detailed Description

Disclosed herein are methods related to the operation of a fermentation process on a more energy efficient basis. In certain particular embodiments, the methods hereof take advantage of the fact that, although CO2 is a byproduct of the fermentation process, it is nevertheless a chemical compound that itself has several valuable uses. Therefore, the fermentation process combined with an extraction process utilizes the CO2 to produce a low cost aerogel.

As seen in Figure 1 , a typical aerogel process requires large amounts of a solvent such as ethanol in the washing step, and large amounts of CO 2 and energy in the supercritical drying step. The

supercritical drying step in an aerogel process requires the use of a large compressor to compress the CO2 to be used to obtain effective drying of the alcogel. One embodiment of the methods hereof, thus, involves the operation of a fermentation process in concert with the manufacturing process of aerogels. A schematic of the integration can be seen in Figures 2 and 3. A solvent such as ethanol, CO2 and excess energy (steam and electricity) can be obtained from a fermenter such as a sugar mill/bio-fuel plant.

Fermentation processes suitable for such purpose can use switch grass, corn products such as corn stover or corn cobs, or other cellulosic materials as the carbohydrate feedstock. Such carbohydrates can be fermented by the action of bacteria such as Saccharomyces or

Lactobacillus. Other aspects of such a fermentation process are described in USP 2010/0139154, which is by this reference incorporated in its entirety as a part hereof for all purposes.

A compressor as used for the compression of CO2 to form a supercritical CO2 stream for use in the supercritical drying of the alcogel can be used to treat some or all of the outflow stream coming from the fermenter. The compression process will be able to separate a

fermentation product such as ethanol and water from the CO2 stream, cycle the original stream less CO2 back to the fermenter, and route the clean CO2 stream for use in the supercritical cycle of the aerogel plant. The CO2 that is not used in the aerogel plant can also be used or sold for other applications. The decompression step in the supercritical CO2 cycle is similar to a refrigeration cycle with sufficient energy load to cool the fermenter to a preferred temperature.

A schematic of a manufacturing plant where a solvent such as bio- ethanol and aerogels are produced by methods that achieve energy integration is shown in Figures 2, 4A and 4B.

The benefits to the aerogel plant include

Existing Infrastructure

Process integration

Excess electricity and steam

Access to on-site CO 2 Connect into ethanol stream

The benefits to the biorefinery include:

Higher efficiency of fermenters

Savings in energy

Reduced stillage and disposal cost

Lower water & biocide usage

Opportunity to sell CO 2 Various embodiments of the methods hereof are as set forth below.

Any of these embodiments can be combined with any one or more of the other embodiments, viz:

A method of preparing supercritical CO 2 , comprising (a) fermenting a carbohydrate to prepare a fermentation product, CO 2 and a waste material, (b) separating the waste material from the fermentation product, (c) burning the waste material to yield thermal energy, and (d) applying the thermal energy to compress the CO 2 . Step (d) can comprise burning the waste material to generate electricity, and powering a compressor with the electricity.

A method of separating a fermentation product from water, comprising (a) fermenting a carbohydrate to prepare a fermentation product in a mixture with water, (b) providing a supercritical CO 2 , (c) cooling the supercritical CO 2 to reduce the temperature thereof and extract thermal energy therefrom, and (d) applying the extracted thermal energy to heat the mixture of the fermentation product and water to separate the components of the mixture. The method can also comprise preparing CO 2 in the fermentation process and compressing the CO 2 produced in the

fermentation process to provide the supercritical CO 2 .

A method of cooling a fermentation process, comprising (a) fermenting a carbohydrate to prepare a fermentation product, (b) providing a supercritical CO 2 , (c) cooling the supercritical CO 2 to reduce the temperature thereof and extract thermal energy therefrom, and (d) applying the extracted thermal energy to cool the fermentation process. Step (d) can also comprise heating, with the extracted thermal energy, a mixture of a refrigerant and an absorbent in an absorption chiller to separate refrigerant, in vapor form, from the absorbent, and increase the pressure of the refrigerant vapor. The method can also comprise preparing gaseous CO 2 in the fermentation process and compressing the CO 2 produced in the fermentation process to provide the supercritical CO 2 .

A method of cooling a fermentation process that liberates thermal energy, comprising (a) providing a supercritical CO 2 , and (b) releasing the pressure on the supercritical CO 2 to absorb the thermal energy as liberated by the fermentation process. The fermentation process can be conducted in a fermenter, and step (b) can comprise releasing pressure on the supercritical CO 2 proximate to a thermal energy transfer medium that is proximate also to the fermenter or a feed thereto.

A method of preparing an alcogel, comprising (a) fermenting a carbohydrate to prepare a fermentation product, and (b) contacting a hydrogel with the fermentation product to expel water from the hydrogel and give an alcogel. The fermentation product can comprise an alcohol.

A method of displacing a volatile chemical from a substrate, comprising (a) fermenting a carbohydrate to produce a fermentation product and gaseous CO 2 , (b) separating the gaseous CO 2 from the fermentation product, and (c) contacting the substrate with the gaseous CO 2 as produced from fermentation to expel the volatile chemical from the substrate. The method can further comprise compressing the gaseous CO 2 before contact with the substrate. The substrate can comprise an alcogel, and a solvent can be expelled from an alcogel to give an aerogel.

A method of displacing a volatile chemical from a substrate, comprising (a) compressing CO 2 to form a supercritical CO 2 ,(b) exposing the supercritical CO 2 to a thermal energy transfer medium to provide a cooled CO 2 , (c) further compressing the cooled CO 2 , (d) contacting the substrate with the further compressed CO 2 to expel the volatile chemical from the substrate, and (e) releasing the pressure on the CO2 in proximity to the thermal energy transfer medium to absorb thermal energy therefrom.

A method of providing a purified CO 2 , comprising (a) fermenting a carbohydrate to produce a fermentation product in a mixture with water and gaseous CO2, and (b) compressing the mixture to separate water and/or the fermentation product from the CO2.

A method of providing a supercritical CO 2 , comprising (a) fermenting a carbohydrate to produce a fermentation product in a mixture with water and CO2, (b) separating the CO2 from the mixture, and (c) compressing the CO2 forming supercritical CO2.

An integrated manufacturing process, comprising a fermentation process integrated with an extraction process that uses a supercritical fluid.

For purposes of this application, a supercritical fluid is defined as a fluid that is near or above both its critical pressure and critical temperature. The preparation and properties of supercritical fluids are well known in the art; see for example "Supercritical Fluids", Kirk-Othmer Encyclopedia of Chemical Technology, Tomasko and Guo, 14 APR 2006, John Wiley & Sons, Inc. A particularly suitable fluid is CO2. For purposes of this application, supercritical CO2 is defined as being above about 800° C and 20 PSI (0.59 MPa).

Examples of extraction processes include but are not limited to the separation of azeotropic mixtures, such as ethanol and water, extracting materials such as flavors and fragrances from food and natural plant materials, removal of caffeine from products such as coffee and tea, purification of pharmaceuticals, polymers, or environmental materials, and removal of long chain alcohols from sugar cane crude wax (a byproduct of sugar cane production).

Also described is an integrated manufacturing process comprising: a) fermenting a carbohydrate to produce a fermentation product and gaseous CO2,

b) compressing the gaseous CO 2 to form a supercritical CO 2 ; c) using the supercritical CO 2 as an extractant to separate one component from a mixture.

The mixture can be a gel, and the component can be a continuous phase. In one embodiment, an aerogel is formed after the separation of the component from the mixture. In another embodiment the fermentation product and the component is ethanol. In yet another embodiment the process further comprises after step b: contacting a hydrogel with the ethanol to remove water from the hydrogel to form the gel.

A gel is typically an interconnected colloidal state in which a dispersed phase has combined with a continuous phase to produce a viscous product. The gel can be an alcogel (in which the continuous phase is an alcohol) or a hydrogel (in which the continuous phase is water).

Also described is an integrated manufacturing process comprising: a) fermenting a carbohydrate to produce a fermentation product gaseous CO 2 and thermal energy;

b) forming a supercritical CO 2 from the gaseous CO 2 and the thermal energy;

c) using the supercritical CO 2 as an extractant to separate a

component from a mixture; and

d) separating the component from the supercritical CO 2 by

reducing the pressure to form a liquid phase CO 2.

In one embodiment the process further comprises:

e) recycling the liquid phase CO2 by mixing the liquid phase CO2 with the gaseous CO2 in step b).

In one embodiment, an aerogel is formed after the separation of the component from the mixture. Also described is an integrated manufacturing process comprising: a) fermenting a carbohydrate to produce a fermentation product, gaseous CO 2 , and thermal energy wherein the thermal energy is transferred to a cooled water stream forming a heated water stream;

b) compressing the gaseous CO 2 to form a liquid CO 2 ;

c) forming a supercritical CO 2 from the liquid CO 2 and the thermal energy from the heated water stream to form a cooled water stream;

d) using the supercritical CO 2 as an extractant to separate a

component from a mixture;

e) separating the component from the supercritical CO 2 by

reducing the pressure, to form a liquid phase CO 2 .

In one embodiment the process further comprises recycling the cooled water stream in step c) to step a).

In one embodiment the process further comprises recycling the liquid phase CO 2 formed in step e to step b).

In one embodiment, an aerogel is formed after the separation of the component from the mixture.

Although various embodiments of the methods hereof have been described and illustrated with specific reference to the production of ethanol as a fermentation product, the methods hereof are not limited to ethanol as a fermentation product, or to the production of an alcohol as the

fermentation reaction.

Where a range of numerical values is recited or established herein, the range includes the endpoints thereof and all the individual integers and fractions within the range, and also includes each of the narrower ranges therein formed by all the various possible combinations of those endpoints and internal integers and fractions to form subgroups of the larger group of values within the stated range to the same extent as if each of those narrower ranges was explicitly recited. Where a range of numerical values is stated herein as being greater than a stated value, the range is

nevertheless finite and is bounded on its upper end by a value that is operable within the context of the invention as described herein. Where a range of numerical values is stated herein as being less than a stated value, the range is nevertheless bounded on its lower end by a non-zero value.

In this specification, unless explicitly stated otherwise or indicated to the contrary by the context of usage, where an embodiment of the subject matter hereof is stated or described as comprising, including, containing, having, being composed of or being constituted by or of certain features or elements, one or more features or elements in addition to those explicitly stated or described may be present in the embodiment. An alternative embodiment of the subject matter hereof, however, may be stated or described as consisting essentially of certain features or elements, in which embodiment features or elements that would materially alter the principle of operation or the distinguishing characteristics of the embodiment are not present therein. A further alternative embodiment of the subject matter hereof may be stated or described as consisting of certain features or elements, in which embodiment, or in insubstantial variations thereof, only the features or elements specifically stated or described are present.

In this specification, unless explicitly stated otherwise or indicated to the contrary by the context of usage, amounts, sizes, ranges, formulations, parameters, and other quantities and characteristics recited herein, particularly when modified by the term "about", may but need not be exact, and may also be approximate and/or larger or smaller (as desired) than stated, reflecting tolerances, conversion factors, rounding off, measurement error and the like, as well as the inclusion within a stated value of those values outside it that have, within the context of this invention, functional and/or operable equivalence to the stated value. EXAMPLES

Example 1

This example shows the performance of a typical fermenter in a sugar mill ethanol plant and the cooling loop employed to control the temperature in the fermenter.

Figure 5 shows a flow sheet of a fermentation process that converts sugar must to ethanol. The size of fermentation plant can vary over a wide range but all calculations presented to demonstrate the present invention are based on a fermentation plant that produces 90,000 m 3 of ethanol per year. Those skilled in the art of producing ethanol from sugar will know that the chosen plant size is typical in the ethanol industry.

Table 1 shows the size, composition and temperature of the major process streams in the sugar to ethanol fermentation plant. Sugar must, water and yeast are added to the fermentation vessel. Since aerobic fermentation process is exothermic, the temperature in the fermenter can rise to undesirable levels. In order to control the temperature in the fermenter, part of the wine from the fermenter is sent to a plate heat exchanger where it is cooled with help of process water from the cooling towers. The rest of the wine exiting the fermenter is sent to a centrifuge where the yeast is separated from the wine and is recycled back to the fermenter. The ethanol water solution is sent to the beer well and then to the distillation column where ethanol is separated from water. The ethanol rich stream from the distillation condenser is sent to a molecular sieve column, where it is further purified to yield almost anhydrous ethanol. The waste or stillage from the distillation column is collected and disposed. Table 1

Sugar cane is predominantly produced in temperate and tropical regions of the world where, during the sugar cane season, the ambient wet bulb temperatures can be high. For example, typical wet bulb temperature in Brazil during the sugar and ethanol production season may be around 30° C. As a result, the cooling water from the cooling towers can be 30° C or higher.

Figure 6 shows the entering and leaving streams to and from the heat exchanger employed in a typical sugar mill to control the temperature of the fermenter. Table 2 shows the size, temperature and enthalpy of the streams entering and leaving the heat exchanger. The net energy exchanged in the heat exchanger for this example is 10,640 MM Btu/hr. It can also be seen that the temperature of the fermenter can be no lower than 32° C.

Table 2

Example 2

This example shows the energy used in separating ethanol from water in the distillation train of a typical sugar mill ethanol plant.

According to Table 1 the energy and water needed to separate the water from ethanol at the distillation column are:

Energy: 151 .2 MMBtu/hr;

Water: 1500000 kg/h. Example 3

This example shows the improvement in ethanol yield possible if the fermenter can be cooled to 30° C.

Dedini S/A, Sao Paulo, Brazil evaluated the advantages of cooling the ethanol fermentation process to temperatures below 32° C. The study was carried out on a semi industrial scale fermentation process comprising a 100 m 3 fed batch fermenter, a lithium bromide absorption chiller and 315 m 3 /hr evaporative cooling tower. Results from the study were published by Oliverio et. al., in the Proceedings of the International Society of Sugar Cane Technology (Vol. 27, 2010). In this study the fermentation unit was run at different temperatures at and below 32° C and its effect was evaluated by measuring a number of dependent variables including the concentration of ethanol in the fermentation broth and the total yield of ethanol from the plant.

Table 3 shows that ethanol yields in the plant were improved from 85.05% to 86.79% when the temperature of the fermenter was reduced from 32° C to 30° C.

Table 3

Example 4

This example shows the size of a chiller and the additional heat exchange needed to cool the fermenters in order to improve ethanol yield of the plant that produces 90,000 m 3 of ethanol per year.

As was previously presented in this invention, reducing the temperature in the fermenter to 30° C or lower can have a significant impact on the ethanol yields, quantity of stillage generated and the energy used for ethanol water separation. In Example 1 , it was shown that by using water from cooling towers, the temperature of the sugar must being recycled back to the fermenter can only be cooled to 32° C.

In order for the same stream to be cooled to 30° C, a chiller will need to be installed at the ethanol plant. Figure 7 shows the flow diagram for a chiller and the heat exchanger used to cool the fermenter. Table 4 shows the size, temperature and enthalpy of the streams when a chiller is installed and the heat load required for the chiller.

Table 4

Example 5.

Example 3 showed the increase in ethanol yield if the fermentation process could be run at 30° C. This example shows additional savings in energy and reduction in waste stillage if the fermentation process can be cooled to 30° C.

It has been shown (Oliverio et al, Proc. Int. Soc. Sugar Cane Technol.,Vol. 27, 2010) that if a chiller can be installed in a sugar mill ethanol plant so as to allow the fermentation process to run at temperature at or below 30° C, the sugar concentration in the fermenter can be increased allowing for a) higher ethanol concentration in the fermenter , b) lower water usage in the ethanol plant, c) lower energy usage in the ethanol water distillation process and d) lower energy usage for the distillation process. Table 5 shows the effect of increasing the ethanol concentration in the fermenter from 8% to 15%. If the fermenter can be run at ethanol concentration of 1 1 .98 % (12%), Table 5.1 shows that stillage production can be reduced by 34% by volume and stream required for the distillation step can be reduced by 23% by weight.

Table 5

Examples 6 and Figure 8 are presented to demonstrate the energy, raw materials and equipment requirements in an organic aerogel manufacturing process that is set up as a standalone unit without the advantage of energy and material integration with a fermentation based manufacturing process. Aerogels of both inorganic and organic

compositions are well known. See, for example, the Aerogel Handbook (Editors Leventis and Koebel, 201 1 , Springer) and Aerogels (Husing and Schubert, Ullman's Encyclopedia of Industrial Chemistry, 15 Dec 2006 DOI: 10.1002/14356007.c01_c01 .pub2). All aerogel processes requiring supercritical extraction will benefit from integration with a fermentation process. But in order to demonstrate the advantages of an integrated process all of the examples presented hereafter assume an aerogel manufacturing plant that produces an organic aerogel formed by the reaction between phenol and formaldehyde. The size of the aerogel manufacturing plant is assumed to be such that it produces 90,000 m 3 of aerogel/year.

A flow sheet for a typical phenol formaldehyde aerogel process is shown Figure 8. Phenol and formaldehyde are reacted in an aqueous solution, in the presence of a base catalyst to form a low molecular weight phenol formaldehyde resin precursor. The precursor in dilute form is further reacted in the presence of an acid catalyst to form a hydrogel. The water in the hydrogel is removed by washing with the help of another solvent such as ethanol. The resulting phenol formaldehyde gel rich in ethanol is transferred to a super critical extraction unit where the ethanol is removed from the gel thus producing a phenol formaldehyde aerogel.

Example 6

This example shows the energy used to convert an organic phenol formaldehyde solution to a hydrogel in a phenol formaldehyde aerogel manufacturing process.

As has been discussed previously, the formation of a gel is an important precursor in the manufacture of aerogel. Figure 8 and Figure 9 show a flow sheet for the gelation process used for this example. Phenol and dilute formaldehyde solution are reacted in the presence of acid catalyst to form a crosslinked hydrogel. A particle formation process may be integrated with the gelation process in order to convert the hydrogel being formed into discrete gel beads. In order to facilitate the gelation process, energy needs to be supplied to the gelation process. Depending on the chemistry used and the rate of the gelation reactions, gelation may be carried out over a wide range of temperature. However, for this example gelation is assumed to be carried out at 65° C. Thus 4550 kg/hr of condensate steam at 85° C is supplied to heat the gelation vessel .

Example 7

This example demonstrates the distillation process and the energy needed to concentrate and recycle the ethanol stream back to the washing unit.

After the water washing step, the water ethanol stream exiting the washing unit needs to be separated so that concentrated ethanol can be recycled back to the water washing step. Figure 10 shows a distillation column used to separate the water and concentrate the ethanol stream. Table 6 shows the composition and enthalpy of the different streams entering and leaving the distillation column. Aspen model based

calculations show that distillation column comprising 12 plates and running at a reflux ratio of 2.5 is required to achieve the desired separation of ethanol from water. In order to accomplish this separation 32.3 MMBtu/hr of energy is required to cool the condenser and 32.4 MMBtu/hr of energy is needed in for the reboiler. The net result of the separation is 1230 kg/hr of stillage from distillation column bottom. Table 6

Example 8

This example shows the energy required to prepare the liquid CO 2 needed for supercritical extraction in the aerogel manufacturing process.

For a 90,000 m 3 aerogel plant about 10,267 Kg/hr of supercritical carbon dioxide would be needed for the supercritical extraction of ethanol.

In a standalone aerogel plant, liquid CO 2 will need to be shipped from an external source. Liquid CO2 is usually stored and shipped at 24 atm and -

13° C in special high pressure vessels.

At the aerogel plant liquid CO2 will be compressed and heated to 85 atm and 30° C to reach supercritical conditions for CO 2 . The process flow sheet for heating and compressing the liquid CO2 is shown in Figures 1 1A, 1 1 B, and 12, and the enthalpy associated with each stream is presented in

Table 7 (with the assumption of entropy across the compressor).

Based on thermodynamic calculations, the total energy required to heat up the liquid carbon dioxide from -13 °C to 30 °C would be around 3

MMBtu/hr. In the process of purchasing liquid CO2 a cooling system is needed to keep the temperature at -13° C during transportation and storage. Liquid transportation and storage in the integrated process is not required.

During the supercritical liquid extraction a 1200 kg/hr of

decompression to atmosphere is required but in the integrated process this decompression can be routed for the first stage of the compressor and only a small amount of CO 2 is required to compensate the process losses.

Table 7

Example 9

As of 201 1 , without the deployment of new merchant CO 2 plants, there are about 36 standing CO2 plants which are only fed by ethanol by- product raw gas. This represents about 32% of the total number of fermentation plants serving the merchant sector. The total number of merchant CO 2 plants is around 1 1 1 in the United States. Further, numerous additional CO2 plants are under consideration, or slated to be built alongside future of existing ethanol ventures, (see reference at site:

http://www.biofuelsdigest.com/bdigest/201 1 /1 1 /23/carbon-dioxide- applications-%E2%80%93-a-key-to-ethanol-project-developments / )

A 90,000 m 3 ethanol plant will generate about 85,000 ton of CO 2 that can be liquefied and sold in the market with minor investments and operational costs.

The examples that follow show the advantages of lower energy and material usage and reduced investment in process equipment when an ethanol fermentation process is integrated with an aerogel manufacturing process. For the examples that follow, an integrated ethanol aerogel process is assumed to produce 90,000 m 3 of ethanol per year and 90,000 m 3 of aerogel per year. Thus the integrated process is assumed to produce the same amount of ethanol and aerogel as was assumed above for ethanol and aerogel plants running separately without the advantage of energy, material and process equipment integration.

Example 10

In Example 3 the advantage of cooling the fermentation process in a standalone sugar mill ethanol plant was presented. In order to accomplish the desired cooling of the fermentation process, Example 4 showed the size of a separate refrigeration unit required and the energy used to operate the refrigeration unit. This example shows that the same desired cooling of the fermentation process can be achieved by energy and material integration of process streams in the ethanol and aerogel process without the operation of a separate refrigeration unit with considerable savings in energy cost.

Figure 13 shows a simplified process diagram highlighting the pertinent process streams involved in cooling the fermentation vessel in the ethanol plant. In this example the use part of the water from the cooling tower (streams 17 and 18) exchanging heat (through the heat exchanger HEX3) with the liquid carbon dioxide (streams 9, 16 and 19) that is pumped to be used in the supercritical extraction is shown. The temperature for pumping the liquid carbon dioxide is 5 °C and the temperature required for the supercritical extraction is 30 °C so this temperature difference can be used to cool down the cooling water. This water will be used to complement the fermentation cooling.

Table 8

According to Oliverio et al (op cit.) with this integration the following savings can be obtained:

Ethanol mill savings:

34% of dilution water (for 90,000 m 3 of ethanol 324,000 m 3 of water); 34% of stillage (for 90,000 m 3 of ethanol 324,000 m 3 of stillage);

23% of steam (for 90,000 m 3 of ethanol 54,000 ton of steam).

Aerogel process savings:

Cost and logistics for liquid carbon dioxide (carbon dioxide is available at ethanol plant)

450 kg/h of saturated steam (heating can be done using condensate instead of steam)

Ethanol supply (ethanol will be used as a catalyst and can be all recovered) 3 MMBtu/h Energy required to heat CO 2 .