WO2012069063A1 - Continuous production of high purity carbon dioxide - Google Patents

Continuous production of high purity carbon dioxide Download PDF

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Publication number
WO2012069063A1
WO2012069063A1 PCT/DK2011/050453 DK2011050453W WO2012069063A1 WO 2012069063 A1 WO2012069063 A1 WO 2012069063A1 DK 2011050453 W DK2011050453 W DK 2011050453W WO 2012069063 A1 WO2012069063 A1 WO 2012069063A1
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carbon dioxide
step
fermentation
organic matter
gas
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PCT/DK2011/050453
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French (fr)
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Michael Gregers Mortensen
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Union Engineering A/S
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/50Carbon dioxide

Abstract

The present invention relates to a process for continuous production of high purity carbon dioxide from organic matter by a method selected from: fermentation, combustion or a combination of both where the purification of carbon dioxide is adjustable to the source of the carbon dioxide.

Description

Continuous production of high purity carbon dioxide

Introduction

The present invention relates to a process for the continuous production of high-purity carbon dioxide from organic matter, such as from biomass fermentation and combustion. Moreover, the invention relates to the product obtained and a plant for the said process.

Background of the invention

Carbon dioxide is produced by a vast variety of processes, such as from oil fields, combustion of coal, natural gasses etc. as well as a side product from fermentation of organic matter.

Bioethanol is an alcohol produced by fermentation of sugar components of plant materials and is produced primarily from sugar and starch crops. With advanced technology being developed, cellulosic biomass, such as trees and grasses, are also used as feedstocks for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive. Bioethanol is widely used in the USA and in Brazil.

Biologically produced alcohols, i.e. bioethanol, most commonly ethanol, and less commonly propanol and butanol, are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches, or cellulose.

Several hundred plants in Brazil produce bioethanol of the waste product (molasses) from the production of sugar from sugarcanes. The production of bioethanol is limited to the harvest season from April to November in the central and southeast region of Brazil and from September to March for the north-northeast region. More than 2/3 of the plants in Brazil are producing both sugar and ethanol.

In the modern plants the main object of the milling process is to extract the la rgest possi ble amount of sucrose from the cane, and a secondary but important objective is the production of bagasse (the residual cane-waste) with low moisture content. Bagasse is used as boiler fuel and burned for electricity generation allowing the plant to be self- sufficient in energy and to generate electricity for the local power grid as well as carbon dioxide as a waste product. In 2009 Brazil produced 24.9 billion liters of bioethanol which represents 37.7% of the world's total ethanol for use as fuel.

Fermentation of biomass is one of the sources of carbon dioxide production, such as during the production of bioethanol. This carbon dioxide formed from the fermentation process is often released to the atmosphere either directly or the gas has been slightly purified through a filter before release.

It is now realized that it has become a desire to be able to recover the high purity carbon dioxide produced; however, there is presently no incentive to do so because the production is seasonal and providing carbon dioxide recovery means therefore is too expensive.

Summary of the Invention

In one aspect, the present invention relates to a process for the continuous production of high purity carbon dioxide from organic matter comprising the steps of:

a) providing the organic matter;

b) producing carbon dioxide from the organic matter by a method selected from : fermentation, combustion of said organic matter and a combination of both;

c) providing a control means receiving input from the selection of step b);

d) purifying the gaseous carbon dioxide produced under step b) by a process comprising the consecutive steps of:

i. absorbing the gaseous carbon dioxide i n a n a bsorber by means of an absorbing agent providing at least a liquid carbon dioxide rich stream;

ii. stripping the liquid carbon dioxide rich stream to provide at least a gaseous carbon dioxide rich stream;

iii. compressing the gaseous carbon dioxide rich stream in order to provide at least a compressed carbon dioxide rich stream

iv. optionally, dehydrating the compressed carbon dioxide rich stream, and

v. scrubbing the compressed, optionally dehydrated, gaseous carbon dioxide rich stream and/or filtrating the compressed, optionally dehydrated, carbon dioxide rich stream through activated carbon.

wherein, when the production method under step b) is fermentation, the purification of step d) is diverted in directing means A4 by in- put received by the control means to avoid the steps i. and ii.

Thus, in a first aspect, the present invention provides a method in which there is provided means for continuous production and recovery of carbon dioxide when produced from various sources of organic matter.

The problem recognized is solved by providing a continuous production of carbon dioxide combined with a flexible recovery process. A control means communicates with the selected carbon dioxide production method and ensures that the carbon dioxide produced under step b) is directed in step d) for optimal purification.

This is based on the recognition that the desire is partly due to environmental demands but also the opportunity to profit from the carbon dioxide produced when recovered at high purity. However, it is necessary that there is a continuous production of carbon dioxide in order for the investment in a carbon dioxide recovery plant to be profitable. But if the process for producing carbon dioxide is seasonal the necessary production of carbon d ioxid e i s not provid ed for, a nd consequently the cost of providing a carbon dioxide recovery plant is too high having the consequence that the high purity carbon dioxide is not recovered.

The purification step d) comprises mea ns for purifying gas originating from both fermentation and combustion and the route differs depending on whether the gas is a fermentation gas or a combustion gas/flue gas. The gaseous carbon dioxide produced by either one of the production methods or both can be combined in the compression step d) iii. and the subsequent steps and be finally purified by the same method using the same equipment thus reducing the cost of installation and optimising the operating costs.

Therefore, the initial expenses are minimized because two purification processes are merged at a point where the downstream purifica- tion is independent on the source of the gas. The process is designed so that a minimum of different steps are required upstream of the merging point while the high purity is still achieved.

In a presently preferred embodiment the production method is combustion and the organic matter is a fossil fuel or a fermentation product such as bioethanol. Thereby the fuel used may be available at the same site as the site where fermentation gas is also produced, i.e. a bioethanol plant. Description of the drawings

Figure 1 is a schematic diagram of the process according to the invention.

Figure 2 is schematic flow diagram embodying particular embodiments of purification step d) of the invention.

Detailed description of the invention

In the context of the present invention it is contemplated that organic matter comprises matter originating from a once-living organism, is capable of decay, or is the product of decay, or is composed of organic compounds, and may be organic residues from crops, sugar- canes, and maize. Organic matter also contemplates fermentation products of the organic matter, such as ethanol and other alcohols. Organic matter also contemplates fossil fuels and natural gases. Functionally defined, organic matter contemplates any organic material that produces carbon dioxide when combusted or fermented.

The terms organic matter and organic material may be used interchangeably.

Streams

Feed stream from combustion (fc); feed stream from fermenta- tion (ff); carbon dioxide rich liquid (ll);carbon dioxide rich gas (gl); compressed carbon dioxide (g2); recovered or filtrated carbon dioxide gas (g3); recovered and filtrated carbon dioxide gas (g3'); carbon dioxide-depleted liquid (12); flash gas (g4); flashed carbon dioxide rich liquid II'. Units

Fermentation tank (Al); Combustion unit (A2); control means (A3); directing means (A4); absorbing unit (A5); stripping unit (A6); compressing means (A7); high pressure scrubbing unit (A8); activated carbon filter (A9); flash column (A10).

The terms gas and gaseous stream may be used interchangeably.

Traditionally, bioethanol plants are supplied with organic matter throughout the year thereby providing the continuous production of carbon dioxide. Therefore, there are only provisions for recovering fermentation gas. However, in regions where such supply is not an option there will be periods of the year where the production stands still and there will be no production of carbon dioxide.

When carbon dioxide can be produced from either fermentation, combustion, or a combination of both, a stable production of carbon dioxide is provided for the regions where fermentation of for example organic matter into bioethanol production stands still for either shorter or longer periods.

The organic matter is provided and carbon dioxide is produced either as a product of fermentation or as a product of combustion of the organic matter or combustion of the fermentation product.

In figure 1 the overall process is illustrated schematically. In the first step organic matter is provided for fermentation, combustion or a combination of both in a fermentation tank Al and combustion unit A2, respectively. From each of these units carbon dioxide is produced. The produced carbon dioxide used as the feed stream in the purification step d) is denoted ff when produced during fermentation and fc when produced during combustion.

Depending on the source of production of the feed stream, con- trol means A3 connected to directing means A4, such as a valve, located in each carbon dioxide feed line, directs the feed stream to either step d) i. or d) iii. as required by the invention in its broadest sense.

It is contemplated that at least one fermentation unit Al and at least one combustion unit A2 is present. Lines for feeding produced car- bon dioxide are present and connected to each unit, and each of these lines comprise directing means A4 for the carbon dioxide to be directed to the appropriate point of the purification in step d).

When carbon dioxide originates from a combustion process the produced carbon dioxide fc is directed to the first mandatory purification step, absorption, in an absorbing unit A5, providing at least a carbon dioxide rich liquid II. The carbon dioxide rich liquid II is stripped in a subsequent stripping step in stripping unit A6 providing at least a carbon dioxide rich gas gl.

The carbon dioxide rich gas gl may at this point be merged with a feed stream ff from a fermentation process if any such is operating at the same time.

The optionally merged gases are compressed in a compressing means A7, to provide compressed carbon dioxide g2. The compressed carbon dioxide g2 is then subjected to high pressure scrubbing in a high pressure scrubbing unit A8 or filtrated through an activated carbon filter A9 to provide recovered carbon dioxide g3 or recovered filtrated carbon dioxide g3'.

Referring now to figure 2 various embodiments of step d) of the invention will be explained in more details. Figure 2 illustrates 5 different embodiments for recovery of carbon dioxide produced according to the invention. All elements may be interchanged if appropriate. It is contemplated that the recovery process comprises at least the mandatory elements from the route 1, 2, or 3, that is compression and high pressure scrubbing or filtration when produced by fermentation, and the routes 4 or 5 that is, absorption, stripping, compression and high pressure scrubbing or filtration, when produced by combustion.

Further purification steps may be included as illustrated but the invention should not be limited to these embodiments. The steps for pu- rifying the gaseous carbon dioxide produced under step b) are consecutive steps, i.e. are performed successively in the listed order this, however, should not exclude that further steps may be included prior to, in between and/or after the mandatory steps. The important thing is the consecutive order of these mandatory steps. When the carbon dioxide is produced by combustion of the organic matter the gaseous stream may follow either route 4 or 5. Fossil fuels, fermentation products or a combination of both may be combusted. Providing the opportunity for both combustion types makes the process more flexible and cost efficient, as a product from a fermentation process can be used as the source for producing carbon dioxide through combustion also.

In addition to producing carbon dioxide, combustion of the fermentation products may provide heat and electricity and therefore the fermentation process can be utilized optimally when for example there is a higher demand for heat/electricity than for the fermentation product, such as bioethanol. Regardless of the use of the fermentation product there is provided means for recovering carbon dioxide produced. Thus, an additional valuable product, high purity carbon dioxide, is produced continuously regardless of the source.

Organic matter is combusted in the combustion unit A2. Depending on the purity of the organic matter the combustion unit may be of a special type for facilitating complete combustions. The choice of combustion unit is within the skill of the art.

The produced carbon dioxide fc directed by directing means A4 operated by the control means A3 is initially purified in a low pressure water scrubber before being absorbed in an absorbing unit A5 using an absorbing agent, physical or chemical.

In the absorption step d) i. any absorbing agent capable of ab- sorbing carbon dioxide from a feeding gas either chemically or physically, may be applied. As examples of physical absorbing agents selexol, methanol, purisol, genosorb or morphysorb can be mentioned. As examples of chemical absorbing agents any amine-based absorbing agent can be mentioned. By the term "amine-based" absorbing agent is meant any agent, in which an amine group is incorporated as for example alka- nolamines, such as monoethanolamine, diethanolamine, diisopropa- nolamine, methyldiethanolamine and triethanolamine, amino-alcohols, such as amino-diethylene-glycol, and amino acids and amino acids salts and derivatives thereof. Preferably, an amine-based absorbing agent is used. Other suitable absorbing agents are those mentioned in WO 2005/087349 and WO 2005/087350.

When performing the absorption and stripping under low pressure, i.e. at pressures below 2 bara, the absorbing agent is most often an aqueous solution of one of the above-mentioned amine-based agents. However, mixtures comprising two or more of the listed agents in any mixing ratio may also be used in the method according to the present invention. It is within the skills of a practitioner to determine the optimal amount and composition of the absorbing agent in order to achieve a suitable absorption procedure.

In the absorption unit a carbon dioxide rich liquid II and a carbon dioxide depleted gas is generated. The carbon dioxide depleted gas is most often disposed. If comprising high amounts of carbon dioxide the gas may be recycled and subjected to another absorption cycle.

The carbon dioxide rich liquid II leaving the absorption unit is then subjected to a stripping step d) ii. in a stripping unit A6. In the stripping unit A6, the carbon dioxide rich liquid II is separated into a carbon dioxide-rich gas gl and a carbon dioxide-depleted liquid 12 in the stripping unit.

In a particular embodiment the method further comprises a flashing step between the absorption step and the stripping step as illustrated in route 4. The flashing step facilitates the removal of all nitrogen containing contaminants present in the feed gas. The carbon dioxide rich liquid II leaving the absorption column is in this embodiment heated and pressurised to a pressure higher than or equal to the pressure of the liquid leaving the absorber. It is within the knowledge of a skilled person to perform such processes.

The introduction of the flashing step in the method of the present invention makes it possible to produce a stripper gas, gl, which is substantially free of oxygen, and only contains traces of nitrogen oxides. However, in order to achieve this beneficial effect the flash column, A10, must operate at a higher temperature and a pressure, which is higher than or close to the equilibrium conditions of the carbon dioxide rich liquid stream, II, leaving the absorption unit A5. Under such conditions, the thus heated and pressurised liquid entering the flash column will be unsaturated and the release of non-saturated components is possible. Hence, due to the new equilibrium conditions substantially all 02 and the main part of NOx will be removed in the flash column in the flash gas g4, and therefore never reach the stripping unit A6.

In a preferred embodiment the temperature of the liquid obtained after pressurising and heating before entering the flash column is in the range of 70°C to 140°C, more preferred in the range of 90°C to 120°C, and most preferred in the range of 95°C to 110°C, and the pres- sure of said liquid is in the range of 0.1 bar to 3 bar, more preferred in the range of 0.2 to 2 bar, and most preferred in the range of 1 bar to 2 bar. Operating outside these ranges is normally not economically feasible. A person skilled in the art will know how to perform such pressurising and heating procedures.

The flashing step provides a ca rbon d ioxide lea n gas a nd a flashed carbon dioxide rich liquid II'. The gas formed in the flashing step, the flash gas g4, which may comprise a significant amount of carbon dioxide in addition to oxygen, N2, nitrogen oxides and optionally water, sulphurous compounds and volatile organic compounds, may be recycled to the absorption unit A5 in order for a further recovery procedure of the carbon dioxide. Alternatively, the said gas may be disposed of.

The flashed carbon dioxide rich liquid I I' leaving the flash column A10 is pressurised to a pressure that is higher than or equal to the pressure of the flashed carbon dioxide rich liquid II' leaving the flash column A10 before entering the stripping unit A6. A person skilled in the art will know how to perform such a pressurisation.

If the flashing step is omitted the carbon dioxide rich liquid II leaving the absorbing unit A5 is treated as described immediately above, i.e. the liquid is pressurised to a pressure that is higher than or equal to the pressure of the liquid leaving the absorption unit A5 before entering the stripping unit.

In the stripping unit A6 the pressurised carbon dioxide rich liquid (I I or I I') from the flashing or absorption column is separated into a carbon dioxide rich gas gl and a carbon dioxide-depleted liquid 12. Due to the removal of oxygen and nitrogen oxides in the flash column, when applied, the 02 and NOx content will be reduced dramatically in the stripper off gas, i.e. the carbon dioxide rich gas gl. Because of the reduced amount of NOx and the very limited amount of 02 in the stripper off gas, the equilibrium reaction : NO + V2O2 <-> N02, will shift to the left to form mainly NO.

The carbon dioxide-depleted liquid I2 obtained in the stripping step, which mainly comprises the absorbing agent, optionally an aqueous solution of the absorbing agent, may be recycled and mixed with the fresh absorbing agent used for absorbing the feed gas fc in step d) i. However, before entering the absorption unit A5, an adjustment of the temperature and/or the pressure of said liquid may be required.

The stripping unit A6 to be used may be any packed column known in the art. Examples of suitable stripping units are columns, which contain internals or mass transfer elements such as trays or random or structured packing. It is within the state of the art to determine the optimal parameters for the striping unit.

The carbon dioxide rich gas gl may further be purified in a scrubber such as a low pressure water scrubber (illustrated in route 4) or a potassium permanganate (PPM) scrubber (illustrated in route 5), the latter being less preferred due to the environmental impact of the chemicals used.

However, the content of contaminants in the carbon dioxide rich gas gl is often so low, particularly when including a flashing step, that a subsequent oxidation is no longer required. Hence, the consumption of chemicals is reduced and no subsequent disposal of these used chemicals is necessary.

The further purification now substantially follows the steps of routes 1, 2 or 3 of figure 2. Thus, the carbon dioxide rich gas gl ob- tained after the stripping step is compressed in the compressing means A7 to provide the compressed carbon dioxide stream g2.

The compressed carbon dioxide stream g2 may contain water. If the compressed carbon dioxide g2 contains water, the stream may be subjected to a dehydration step as illustrated in route 3. The compressed carbon dioxide gas g2 is then, in addition to being compressed, cooled before entering the optional dehydrator. Hereby the water content is reduced. The compression itself may also cause the water to be separated off.

The pressurisation in the compression step d) iii. may be performed in one or more compression steps e.g. 1, 2 or 3 or even more. The number of compression steps is chosen so as to save energy and cost of equipment.

If the compressed carbon dioxide g2 is water-free the dehydra- tion step may be omitted and the compressed carbon dioxide is subjected to a further purification step d) v. in a high pressure scrubbing unit A8 and/or is filtrated using activated carbon A9 as illustrated in routes 1 and 2.

The high pressure scrubbing unit A8 may be a high pressure water scrubber (route 1) or a carbon dioxide scrubber using high purity carbon dioxide as scrubbing liquid (route 3). If the scrubbing unit is a water scrubber any dehydration is performed after the water scrubbing.

If the scrubbing step is performed using carbon dioxide as the scrubbing liquid, the dehydration step may be integrated in the scrub- bing step using an alcohol such as ethanol, preferably bioethanol and may thus be omitted before the carbon dioxide scrubbing unit A8 illustrated in route 3 .

In the final steps illustrated, the recovered carbon dioxide g3 or recovered and filtrated carbon dioxide g3' is finally purified by means of distillation followed by liquefaction. An optional final filter may be provided. Hereby high purity carbon dioxide is produced. In the context of the present invention high purity carbon dioxide contemplates a stream having a content of carbon dioxide that is higher than 95% (w/w), more preferred higher than 97% (w/w) and even more preferred more than 99% (w/w).

In a particular embodiment the produced carbon dioxide of step b) is a fermentation gas ff.

If the carbon dioxide produced in step b) originates from a fermentation process the control means A3 receives input that the gas is a fermentation gas and signals that the obtained gaseous carbon dioxide ff is directed so that the absorption and stripping steps i. and ii., before compression, are omitted. Then the recovery process will for example follow the routes 1, 2 and 3 of figure 2, and the carbon dioxide produced in step b) is thus in step c) redirected or diverted so that the absorption step d) i., the optional flashing step and the stripping step d) ii. i.e. the steps of route 4 and 5, are circumvented or bypassed.

The diversion facilitated by the input received by the control means control means of step c) may be controlled and performed auto- matically or manually whereby the directing means A4 diverts the gaseous streams to the respective purification steps. Such means are well known in the art and thus, the diversion may for instance be performed by directing the gaseous carbon dioxide from the production step to the compression step d) iii. in the directing means by opening and closing one or more valves. If the production is switched to combustion the diversion can easily be omitted by closing the one or more valves.

The carbon dioxide produced by fermentation ff is optionally de- foamed and subjected to one or more scrubbing steps. Defoaming is optional and the necessity depends on the nature of the incoming gas, which again is affected by the operation of the fermentation tanks. De- foaming may be necessary in order to avoid damaging compressors or clogging of i.a. valves downstream in the process line.

The one or more scrubbing steps may use water (i.e. a low pressure water scrubber) and/or potassium permanganate (PPM). Scrubbing may be performed before compression, such as once or twice, or after compression.

Because carbon dioxide production from fermentation is not always constant, a buffer tank, a so-called balloon, may be present after the initial defoaming and scrubbing which acts as a reservoir allowing more steady operation of the plant as it allows for a more constant flow of carbon dioxide to the further purification steps.

It is within the knowledge of the person skilled in the art to determine the optimal size of the balloon. Depending on the process parameters set for the downstream process the purpose of the balloon is to provide a more stable flow of gas to be further purified.

The first mandatory step in the purification step d) when the gaseous stream originates from a fermentation process is the compression step d) iii. It is also contemplated that gaseous streams originating from both combustion and fermentation may be merged by means of a mixer and compressed simultaneously at this stage. Thus, it is possible that carbon dioxide from both fermentation and combustion may be produced and recovered at substantially the same time, if necessary.

The compressed carbon dioxide g2 originating from a fermenta- tion process or a combustion process or a combination of both is in embodiment 1 further purified in a scrubbing unit A8, such as a high pressure water scrubber or a carbon dioxide scrubber using high purity liquid carbon dioxide as the scrubbing solution.

When a water scrubber as illustrated in route 1 of figure 2 is used, the recovered carbon dioxide gas g3 may be filtered, preferably in an activated carbon filter prior to subjecting the gas stream to a dehydration step to provide the recovered and filtered carbon dioxide gas g3'.

The water scrubbing step may be inserted before or after compression depending on the origin of the stream. When originating from a flue gas the scrubbing process is often performed prior to compression.

The water scrubber washes out water-soluble components of the gas stream.

When using a high pressure water scrubber after compression, as illustrated in route 1 of figure 2, the amount of water to be used is substantially reduced compared to water scrubbing under lower pressures, normally used in the industry, i.e. close to ambient pressure. When doubling the pressure water consumption can typically be halved.

The recovered carbon dioxide gas g3 leaving the high pressure water scrubber may still contain impurities such as traces of H2S which are undesirable for high purity carbon dioxide. Thus, the recovered carbon dioxide gas g3 from the high pressure water scrubber is in the embodiment of route 1 subjected to the filtration step in an activated carbon filter A9.

In another embodiment illustrated in route 2, the scrubber step is omitted and the compressed carbon dioxide g2 is subjected to the filtration step d) v. using activated carbon. The purpose is to purify and deodorize the stream before the final distillation and liquefaction.

Other kinds of mechanical filters may be used. However, the ac- tivated carbon filter is preferred as odours or other organic material can be removed from the gas stream by this activated carbon filter.

The odourless gas stream may in both routes 1 and 2 be subjected to a dehydration step prior to being purified in a distillation column for final purification. The distilled high purity carbon dioxide is also in all embodiments shown liquefied in a liquefaction step. The liquefaction step may however be omitted if the distilled high purity carbon dioxide is not for storage.

In the embodiment shown as route 3, a carbon dioxide scrubber is used in step d) v. as the high pressure scrubbing unit A8. In this em- bodiment a sulphur filter may also be present, as illustrated, in order to remove sulphurous components which are highly undesired in the final product. The gas leaving the sulphur filter may be subjected to a dehydration step if necessary.

When using a carbon dioxide scrubber, the yield of carbon diox- ide will increase, as compared to the other routes, because carbon dioxide is not transferred to the waste stream as is the case with the high pressure water scrubbing step wherein carbon dioxide will be absorbed in water, resulting in a loss of carbon dioxide.

In addition, when the carbon dioxide scrubber comprises inte- grated dehydration means, such as bioethanol from the fermentation process, water will be removed during the carbon dioxide scrubbing step. Thus, a drying filter or other dehydrating step may be omitted, as any water present will be removed in the carbon dioxide scrubber. Consequently, the regeneration of for example the drying filter, normally consuming approximately 3 percent of the carbon dioxide stream, is avoided also resulting in a higher yield.

The carbon dioxide scrubbing is performed for example as disclosed in PCT/DK2009/050159 where a high purity liquid carbon dioxide stream from a down stream purification step or so obtained is used as the scrubber solution entering the scrubbing unit at the top section of the scrubbing unit. Thereby trace impurities are absorbed in the liquid carbon dioxide scrubber solution resulting in a very clean recovered carbon dioxide gas stream g3 leaving the scrubber. The liquid carbon diox- ide solution used as the scrubbing liquid may be reboiled and fed to the scrubber column for further recovery of carbon dioxide in order to further increase the yield.

The outlet gas stream from the carbon dioxide scrubber, i.e. the recovered carbon dioxide gas g3, may be further filtered, preferably in an activated carbon filter as described above.

The recovered carbon dioxide gas g3 from the carbon dioxide or water scrubbers may be subjected to a final purification step such as distillation and liquefaction.

In summary, it is contemplated that the purification step d) of the invention contemplates at least absorption and stripping followed by compression and absorption and/or adsorption when the gaseous carbon dioxide is a flue gas and that the purification step d) at least comprises compression and absorption and/or adsorption when the gaseous carbon dioxide is a fermentation gas. The remaining steps and operations serve to further improve the quality and nature of the resulting carbon dioxide. Elements of the embodiments explicitly mentioned may be omitted or added and combined with elements from the five routes of figure 2 in order to provide carbon dioxide at the desired purity. Therefore, such further embodiments not explicitly mentioned are also within the scope of the present invention.

Claims

C L A I M S
1. A process for the continuous production of carbon dioxide from organic matter comprising the steps of:
a) providing organic matter;
b) prod uci ng ca rbon d ioxide from the orga nic matter by a method selected from : fermentation, combustion of said organic matter and a combination of both,;
c) providing a control means receiving input from the selection of step b);
d) purifying the carbon dioxide prod uced under step b) by a process comprising the consecutive steps of:
i. absorbing by means of a carbon dioxide absorbing agent ii. stripping
iii. compressing
iv. optional dehydrating, and
v. high pressure scrubbing and/or activated carbon filtration wherein, when the production method under step b) is fermentation, the purification of step d) is diverted by means of the control means to avoid the steps i. and ii.
2. The process according to claim 1, wherein the production in step b) is combustion and the organic matter is fossil fuel or a fermentation product of the organic matter.
3. The process according to any of the preceding claims, wherein the purification further comprises a final liquefaction step.
4. The process accord i ng to a ny of the preced i ng cla i ms, wherein the production method in step b) is combustion, and wherein the purification of step d) further comprises the steps of flashing prior the stripping in step d) ii.
5. The process according to the claims 1, 3 or 4, wherein the production method of step b) is fermentation, and the gaseous carbon dioxide is defoamed before the compression of step d) iii.
6. The process according to any of the previous claims wherein the scrubbing of step d) v. is carbon dioxide scrubbing, optionally with an integrated dehydration step.
7. The process according to any of the previous claims wherein the carbon dioxide obtained is used for enhanced oil recovery, sequestration or in the food and beverage industry.
PCT/DK2011/050453 2010-11-26 2011-11-25 Continuous production of high purity carbon dioxide WO2012069063A1 (en)

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WO2007009461A2 (en) * 2005-07-18 2007-01-25 Union Engineering A/S A method for recovery of high purity carbon dioxide from a gaseous source comprising nitrogen compounds
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WO2009127217A1 (en) * 2008-07-16 2009-10-22 Union Engineering A/S Method for purification of carbon dioxide using liquid carbon dioxide

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