degarson's invention

8/14/2019 DeGarson's Invention

1/11

LITERATURE REVIEW:

Combustion exhaust gas is a gaseous mixture just as air is a gaseous mixture, though with a different compositionfrom that of air; Air is a mixture of nitrogen, oxygen, trace amounts of carbon dioxide and a few other distinct noble

gases, in different percentages: while, combustion exhaust gas from various sources mostly contain these pollutants;nitrogen oxides, un-burnt hydrocarbons, carbon monoxide, carbon dioxide and sulfur dioxide, in varying percentages.

In the search and research for solutions to pollution, with the advent and application of catalytic converters tocombustion exhaust gas, carbon monoxide is converted to carbon dioxide, while nitrogen oxides are converted to

nitrogen and oxygen, and un-burnt hydrocarbons are converted to carbon dioxide and water.However, global warming and acid rainfall still occur because of the carbon dioxide and sulfur dioxide still

contained in combustion exhaust gas treated with catalytic converters.As avoiding such global environmental pollution presently proves to be better than possible, being actually already

proven as practical, economical and profitable; one would like the biblical Mary, definitely, have to ask, the bigquestion- How can this thing be? And here is the simple answer : By using gas compression, cryogenic fractional

distillation, and liquefaction to produce or separate and store carbon dioxide and sulfur dioxide from combustionexhaust gas treated with catalytic converters: the carbon dioxide separated and stored (from combustion exhaust gas)can be used for producing, fire extinguishers, carbonic acid etc; and the sulfur dioxide separated and stored (fromcombustion exhaust gas) can be used for producing, fertilizers, food preservatives, bleach, sulfuric acid etc.

The realization or conclusion was reached upon the well known and long proven fact that: Gas compression,cryogenic fractional distillation and liquefaction are well known practical methods for separating liquid as well asgaseous mixtures into the individual liquids or gases that make up the mixtures.

Presently these methods are used in separating or producing and storing nitrogen, as well as oxygen, from air: and

they are also used in separating or producing and storing carbon dioxide, nitrogen and argon, from combustion exhaust

gas (containing 10% of oxygen by volume, preferably, for economical reasons).It can further be concluded that immediate or later application(s) of the present realization or invention would

greatly benefit the environment and everyone [especially members of OPEC whose crude oil have high sulfur content,

because the present invention makes desulfurization of their crude oil unnecessary, as combustion of their (high sulfurcontent) crude oil fractions would mean, more sulfur dioxide is separated and stored, from combustion exhaust gas,

using the present invention]: To be categorical, everyone who would benefit from the application of the presentinvention are; crude oil fractions producers, marketers, and consumers, as well as industries that produce carbondioxide and sulfur dioxide, and industries that use carbon dioxide and sulfur dioxide as raw materials.

As carbon dioxide and sulfur dioxide are major useful industrial chemicals/raw materials, when both are produced

using the present invention, they may be sold by crude oil fractions consumers to crude oil fractions marketers, who inturn sell off to industries that produce carbon dioxide and sulfur dioxide, and industries that use either of bothchemicals; these industries would of course spend less than they usually did to buy the chemicals produced this way: soeveryone profits.

These industries and crude oil fractions producers would also be principal and profiting partners in producing, andmarketing the present invention; they would also be responsible for integrating the present invention with presently

used -past, present day and future technology, so again everyone profits.

Note:For the smooth integration of the present invention with various sources of combustion exhaust gas, the appropriate

apparatus recommended herein may be customized (size and shape wise), and set up (arrangement wise-by expertfabricators and technicians) as it is convenient to manufacture, assemble, and use; being that, of course, the present

invention is by no means limited to the forms of embodiment described and illustrated, which have been given by wayof example: On the contrary, the present invention includes all technical equivalents to the means described, as well as

their combinations, if the latter are carried out according to the gist.-The present invention is certainly practical and economical being a modified and simplified version of the already

known and proven practical and economical invention patent number 5100635. [As with Invention patent number5100635, the present method provides an opportunity for reducing the cost for manufacturing liquid carbon dioxide,

same goes for sulfur dioxide, and it makes combustion exhaust gas a viable and attractive carbon dioxide (and sulfurdioxide) source.] The present invention is also simpler and, cheaper to manufacture, and use, as its task is easier and, a

bit different from the task performed by invention patent number 5100635; being the task of the present invention iseasier and, different from that of invention patent number 5100635, the present invention therefore only employs some

parts of the process and apparatus employed in invention patent number 5100635, that is only the parts vital forcarrying out the task/agenda of the present invention-

-In other words, - the proof that the present invention is capable or viable, obviously derives from proof of previousand numerous applications of the methods for separation of gaseous mixtures, mentioned above; the proof also derives

from numerous scientific reports prescribing that trace or no emissions of carbon dioxide and sulfur dioxide incombustion exhaust gas- would help much in solving the global warming and acid rainfall problems.


2/11

AIM:

Carbon dioxide and Sulfur dioxide separation or -production/extraction- from combustion exhaust gas, by gascompression, cryogenic fractional distillation and the liquefaction, and storage of both gaseous compounds for later

use: Thereby making Crude Oil Fractions use Eco-Friendly, Economical and Profitable.

DIAGRAM(S):Schematic of the present invention [on last page of this document], tagged FIGURE 1.

FIGURE 1 -is a schematic process flow diagram, illustrating a method for the co-production of carbon dioxide andsulfur dioxide according to the method of the present invention.

INVENTOR:

DeGarson Oghenekevwe, et al.

REFERENCE(S):U.S. Patent number 5,100,635, issued to Krishnamurthy, et al.http://www.patentgenius.com.

U.S. Patent number 4,690,702, issued to Paradowski et al.Other References:

Quoted within the document; Page 5.

ABSTRACT:The present invention is directed to a method for extracting carbon dioxide and sulfur dioxide from combustion

exhaust gas pre-treated with catalytic converters to handle nitrogen oxides, un-burnt hydrocarbons and carbonmonoxide; the method comprises the steps of (a) treating the exhaust gas to remove particulate matter, (b) compressingthe exhaust gas to a pressure in the range from about 25 psia to about 200 psia, (c) purifying the exhaust gas to removetrace contaminants, (d) separating the exhaust gas to produce a carbon dioxide rich fraction and a sulfur dioxide rich

fraction, (e) liquefying the carbon dioxide rich fraction and distilling off volatile contaminants to produce pure carbondioxide, (f) purifying the sulfur dioxide rich fraction to remove contaminants, and (g) cryogenically fractionallydistilling the sulfur dioxide rich fraction to produce pure sulfur dioxide.

As carbon dioxide and sulfur dioxide are major useful industrial chemicals/raw materials, the ones produced using

the present invention may be sold by crude oil fractions consumers to crude oil marketers, who in turn sell off toindustries where carbon dioxide and sulfur dioxide are useful; these industries would of course spend less than theyusually did to buy the chemicals produced this way: so everyone profits: These industries and crude oil fractions

producers would also be principal and profiting partners in producing, and selling the present invention; this includes

integrating the present invention with past, present day and future technology, so again everyone profits.The present invention may apply to combustion exhaust from internal combustion engines, and gas flare points, and

for the smooth integration of the present invention with various sources of combustion exhaust gas, the appropriateapparatus recommended herein may be customized and set up as is convenient.

- The present invention is certainly practical and economical being a modified and simplified version of the alreadyknown and proven practical and economical invention patent number 5100635. The present invention is also simpler

and cheaper to manufacture and use as its task is easier and a bit different from the task performed by invention patentnumber 5100635; as the task of the present invention is easier and different from that of invention patent number5100635, the present invention therefore only employs some parts of the process and apparatus employed in invention

patent number 5100635, that is only the parts vital to the task/agenda of the present invention.

- In other words, - the proof that the present invention is capable or viable, obviously derives from proof of previousand numerous applications of the methods for separation of gaseous mixtures, mentioned above; the proof also derivesfrom numerous scientific reports prescribing that trace or no emissions of carbon dioxide and sulfur dioxide incombustion exhaust gas- would greatly help solve the global warming and acid rainfall problems.
http://www.patentgenius.com/http://www.patentgenius.com/http://www.patentgenius.com/http://www.patentgenius.com/


3/11

Claim:

We claim:

1. A method for extracting carbon dioxide and sulfur dioxide from combustion exhaust gas which comprises the steps

of:

(a) Treating the exhaust gas to remove particulate matter;

(b) Compressing the exhaust gas to a pressure in the range from about 25 psia to about 200 psia;

(c) Purifying the exhaust gas to remove trace contaminants;

(d) Separating the exhaust gas to produce a carbon dioxide rich fraction and a sulfur dioxide rich fraction;

(e) Liquefying the carbon dioxide rich fraction and distilling off components that are more volatile than carbon dioxide;

(f) Purifying the sulfur dioxide rich fraction to remove the little- left over carbon dioxide that escaped extraction;and

(g) Cryogenically fractionally distilling the sulfur dioxide rich fraction to remove oxygen and argon there-from.

2. The method according to claim 1, wherein the exhaust gas in step (a) is treated with a water absorption shower toremove particulate matter.

3. The method according to claim 1, wherein the exhaust gas in step (b) is compressed to a pressure in the range fromabout 25 psia to about 120 psia.

4. The method according to claim 1, wherein the exhaust gas in step (c) is purified to remove little- left overnitrogen oxide contaminants by treating the exhaust gas with ammonia in the presence of a selective catalyst to producenitrogen and water.

5. The method according to claim 1, wherein the exhaust gas in step (c) is purified to remove little- left over carbonmonoxide contaminants by treating the exhaust gas with an oxidation catalyst.

6. The method according to claim 1, wherein the exhaust gas in step (c) is purified to remove tracecontaminants bytreating the exhaust gas with a potassium permanganate scrubber.

7. The method according to claim 1, wherein the exhaust gas in step (c) is purified to remove water vapor by treating

the exhaust gas with a desiccant.8. The method according to claim 1, wherein the exhaust gas in step (d) is separated by pressure swing adsorption to

produce a carbon dioxide rich fraction and a sulfur dioxide rich fraction.

9. The method according to claim 1, wherein the sulfur dioxide rich fraction in step (f) is purified to removecontaminants by passing the sulfur dioxide fraction through a bed of zeolite molecular sieves.

Note: Molecular weight, Critical Temperature and Critical Pressure of CO2/carbon dioxide, 56g/mol, 31 degree

Centigrade and 73 Atm respectively. Molecular weight, Critical Temperature and Critical Pressure of SO2/sulfurdioxide, 64.06g/mol, 157.6 degree Centigrade and 78.84 bar respectively. [1 Atm = 1.01325 bar]

O2 = 32, C = 24, S = 32.


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Description: BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a method for producing carbon dioxide, and (perhaps optionally) sulfur dioxide,

from a combustion exhaust gas. - More particularly, the present invention is directed to a method for separating carbondioxide and sulfur dioxide from combustion exhaust gas treated with catalysts or catalytic converters to handle nitrogen

oxides, un-burnt hydrocarbons and carbon monoxide

2. Description of the Prior Art

The commercial preparation of carbon dioxide and sulfur dioxide is well known in the art. Carbon dioxide is normallyproduced as a by-product from chemical processes for producing ammonia, hydrogen, ethanol, ethylene oxide, and

gasoline, as well as in fermentation reactions and carbonate decompositions.

The preparation of carbon dioxide generally involves the steps of crude gas generation, purification and separation,compression and liquefaction, drying, and rectification distillation.

Generation of crude carbon dioxide involves the combustion of liquid fuels such as fuel oil, or solid fuels such asanthracites, coke, charcoal, and the like, with excess air to promote complete oxidation of the fuel and to provide acarbon dioxide rich combustion exhaust gas.

Purification of the combustion exhaust gas generally involves several separate treatments to provide a gas having highpurity. These purification treatments include -washing, -absorption, -adsorption, -desorption, and the -removal ofreducing substances. Washing generally involves a water absorption shower (water wash) to remove solids (soot,

carried off ashes, etc.) and at the same time to cool the combustion gases. Various scrubbing solutions are generallyemployed to remove contaminants and to reduce the components in the combustion gas mixture to carbon dioxide,

nitrogen, and oxygen. The combustion exhaust gas may also be passed through a tower containing a re-circulatingoxidizing solution such as potassium permanganate to remove traces of organic impurities carried with the gas.

The washed and scrubbed combustion gas is then separated to obtain a carbon dioxide rich fraction. In one separation

method, the combustion gas mixture is circulated through a counter-current shower of an absorbing solution such aspotassium carbonate, mono-ethanol-amine, and the like. Carbon dioxide can be desorbed by heating the carbon dioxidesaturated solution to a temperature above 100.degree. C. In another separation method, the combustion mixture isseparated by selectively adsorbing the carbon dioxide on a zeolite bed in a pressure swing adsorption system.

The purified and separated carbon dioxide is then compressed to a pressure in the range from about 230 psia to about

400 psia, dried by contacting the gas with a desiccant that can be regenerated, and then the gas is liquefied by loweringthe temperature of the gas. Finally, a rectification distillation step eliminates the small amount of nitrogen, oxygen, and

argon to provide carbon dioxide having a purity of about 99.9% by volume.

The commercial preparation of sulfur dioxide is well known in the art. Sulfur dioxide is used to make sulfuric acid,being converted to sulfur trioxide, and then to oleum, which is made into sulfuric acid. Sulfur dioxide for this purpose

is made when sulfur combines with oxygen.

Sulfur dioxide can be prepared by burning sulfur: S8 + 8 O2 8 SO2

The combustion of hydrogen sulfide and organosulfur compounds proceeds similarly.

2 H2S(g) + 3 O2(g) 2 H2O(g) + 2 SO2(g)

Roasting sulfide ores such as iron pyrites, sphalerite (zinc blende) and cinnabar (mercury sulfide) also releases SO2:4 FeS2(s) + 11 O2(g) 2 Fe2O3(s) + 8 SO2(g)

2 ZnS(s) + 3 O2(g) 2 ZnO(s) + 2 SO2(g)HgS(s) + O2(g) Hg(g) + SO2(g)

Sulfur dioxide is a by-product in the manufacture of calcium silicate cement: CaSO4 is heated with coke and sand in

this process: 2 CaSO4(s) + 2SiO2(s) + C(s) 2 CaSiO3(s) + 2 SO2(g) + CO2(g)

Action of hot sulfuric acid on copper turnings produces sulfur dioxide.

Cu(s) + 2H2SO4(aq) CuSO4(aq) + SO2(g) + 2H2O(l)


5/11

REFERENCES:

U.S. Pat. No. 3,493,339, issued to Weir et al., discloses a method for producing carbon dioxide and separating argon

which comprises combusting a carbonaceous material in a mixture of argon and oxygen and separating the combustionproducts to obtain carbon dioxide and argon.

U.S. Pat. No. 4,414,191, issued to Fuderer, discloses a pressure swing adsorption method for purifying hydrogen for

ammonia synthesis. Nitrogen at elevated pressure is used as the purge gas in the pressure swing adsorption separationand the nitrogen in the purified gas is employed in the ammonia synthesis stream.

U.S. Pat. No. 4,797,141, issued to Mercader et al., discloses a method for obtaining carbon dioxide and nitrogen fromthe oxygen rich exhaust gas of an internal combustion engine or turbine. The method comprises the steps of cooling theexhaust gas, separating carbon dioxide from the cooled gas by absorbing the carbon dioxide in an alkaline solution,

recovering the carbon dioxide by liberating the gas from the carbonated solution, compressing and liquefying thecarbon dioxide, recovering the nitrogen by purifying the gas to remove contaminants, and compressing and liquefyingthe nitrogen.

U.S. Pat No. 4,690,702, issued to Paradowski et al. , discloses a method and an apparatus for cryogenic fractionaldistillation of a gaseous feed comprising a contact purifying refrigeration column into the bottom of which is injecteda partially condensed gaseous feed, the said column producing in its head portion a residue gas and in its bottom

portion a liquid which is injected into a fractionating column producing in its head portion a distillate which is at least

partially condensed and injected into the head portion of the column to recover in the bottom liquid of this column the

heavy compounds contained in the vaporized fraction of the gaseous feed.

U.S. Pat. No. 5,100, 635, issued to Krishnamurthy, et al., discloses a method for carbon dioxide production from

combustion exhaust gases with nitrogen and argon by-product recovery; basically, preferably working with combustionexhaust gas containing less than about 10% oxygen by weight which comprises the steps of (a) treating the exhaust gas

to remove particulate matter, (b) compressing the exhaust gas to a pressure in the range from about 25 psia to about 200psia, (c) purifying the exhaust gas to remove trace contaminants, (d) separating the exhaust gas to produce a carbondioxide rich fraction and a nitrogen rich fraction, (e) liquefying the carbon dioxide rich fraction and distilling offvolatile contaminants to produce pure carbon dioxide, (f) purifying the nitrogen rich fraction to remove contaminants,

and (g) cryogenically fractionally distilling the nitrogen rich fraction to produce pure nitrogen.

While the above methods provide improvements in the production of carbon dioxide, none but one of these methodsare entirely satisfactory.

Conventional sources for producing carbon dioxide are carbon dioxide rich gases such as waste gases from ammonia,

hydrogen, ethanol, and ethylene oxide plants. These carbon dioxide sources are not always available or are not alwaysreliable especially at locations of high carbon dioxide demand. Other common problems with the production of carbon

dioxide are low product yield and energy inefficient separation methods. Conventional gas generation methods do notteach the preparation of food grade carbon dioxide as well as pure nitrogen and argon from combustion exhaust gases.Hence there was a need for an improved method for producing carbon dioxide.

U.S. Pat. No. 5,100, 635, issued to Krishnamurthy, et al., is the needed improved method for producing food gradecarbon dioxide from combustion exhaust gas, as well as pure nitrogen and argon as by-products.

However the present invention [being the modified and, simplified version of the invention U.S. Pat. No. 5,100, 635,

issued to Krishnamurthy, et al.], would well perform the task of carbon dioxide and sulfur dioxide extraction fromcombustion exhaust gas and the liquefaction and storage of both gaseous compounds for later use.

With the present invention therefore:1. The ecological system is better protected from global warming caused significantly by the release of greenhouse gas-carbon dioxide in combustion exhaust gas; and

2. The ecological system is better protected from acid rains caused by reactions between atmospheric water andthe carbon dioxide and sulfur dioxide in combustion exhaust gas.

This is so also, because the present invention is aimed at economical, eco-friendly and profitable energy crude

fraction(s) use; and the modified -methods or -technologies disclosed here show this to be practical and viable for theenergy industry and its end users.The techniques used in the Invention here disclosed- are simple and age old as well as common place to those in the

energy industry.


6/11

SUMMARY OF THE INVENTION

The present invention is directed to a method for extracting carbon dioxide and sulfur dioxide from combustion exhaust

gas pre-treated with catalytic converters to handle nitrogen oxides, un-burnt hydrocarbons and carbon monoxide; themethod comprises the steps of (a) treating the exhaust gas to remove particulate matter, (b) compressing the exhaust gas

to a pressure in the range from about 25 psia to about 200 psia, (c) purifying the exhaust gas to remove tracecontaminants, (d) separating the exhaust gas to produce a carbon dioxide rich fraction and a sulfur dioxide rich fraction,

(e) liquefying the carbon dioxide rich fraction and distilling off volatile contaminants to produce pure carbon dioxide,(f) purifying the sulfur dioxide rich fraction to remove contaminants, and (g) cryogenically fractionally distilling the

sulfur dioxide rich fraction to produce pure sulfur dioxide.As carbon dioxide and sulfur dioxide are major useful industrial chemicals/raw materials, the ones produced using

the present invention may be sold by crude oil fractions consumers to crude oil marketers, who in turn sell off toindustries where carbon dioxide and sulfur dioxide are useful; these industries would of course spend less than they

usually did to buy the chemicals produced this way: so everyone profits: These industries and crude oil fractionsproducers would also be principal and profiting partners in producing, and selling the present invention; this includesintegrating the present invention with past, present day and future technology, so again everyone profits.

The present invention may apply to combustion exhaust from internal combustion engines, and gas flare points, and


The present invention is clearly practical and economical being a modification of the already known practical andeconomical invention patent number 5100635. The present invention is also simpler and cheaper to manufacture and

use as its task is easier and a bit different from the task performed by invention patent number 5100635; as the task of

the present invention is easier and different from that of invention patent number 5100635, the present inventiontherefore only employs some parts of the process and apparatus employed in invention patent number 5100635, that isonly the parts vital to the task/agenda of the present invention.


7/11

DETAILED DESCRIPTION OF THE INVENTION

Applicants will find that the production and application of the present invention is, economical, eco-friendly, efficient

and profitable for manufacturers of the present invention, crude oil fractions producers, marketers, and consumers, aswell as industries where carbon dioxide and sulfur dioxide are useful raw materials.

The Conversion of contaminants in the combustion exhaust gas to an easily disposable form and separation and

recovery of the useful components (CO2 and SO2) also provides an efficient and attractive option to meet clean airregulations and environmental control.

The present invention is directed to a method for extracting carbon dioxide and sulfur dioxide from combustion exhaustgas pre-treated with catalytic converters to handle nitrogen oxides, un-burnt hydrocarbons and carbon monoxide; themethod comprises the steps of (a) treating the exhaust gas to remove particulate matter, (b) compressing the exhaust gas

to a pressure in the range from about 25 psia to about 200 psia, (c) purifying the exhaust gas to remove tracecontaminants, (d) separating the exhaust gas to produce a carbon dioxide rich fraction and a sulfur dioxide rich fraction,(e) liquefying the carbon dioxide rich fraction and distilling off volatile contaminants to produce pure carbon dioxide,(f) purifying the sulfur dioxide rich fraction to remove contaminants, and (g) cryogenically fractionally distilling the

sulfur dioxide rich fraction to produce pure sulfur dioxide.As carbon dioxide and sulfur dioxide are major useful industrial chemicals/raw materials, the ones produced using

the present invention may be sold by crude oil fractions consumers to crude oil marketers, who in turn sell off toindustries where carbon dioxide and sulfur dioxide are useful; these industries would of course spend less than they

usually did to buy the chemicals produced this way: so everyone profits: These industries and crude oil fractions

producers would also be principal and profiting partners in producing, and selling the present invention; this includesintegrating the present invention with past, present day and future technology, so again everyone profits.

The present invention may apply to combustion exhaust from internal combustion engines, and gas flare points, and


The present invention is clearly practical and economical being a modification of the already known practical andeconomical invention patent number 5100635. The present invention is also simpler and cheaper to manufacture anduse as its task is easier and a bit different from the task performed by invention patent number 5100635; as the task ofthe present invention is easier and different from that of invention patent number 5100635, the present invention

therefore only employs some parts of the process and apparatus employed in invention patent number 5100635, that isonly the parts vital to the task/agenda of the present invention.

Fuel such as natural gas, methane, coke, coal, fuel oil, or similar carbon-containing compounds may be combusted with

air. The fuel supply may also be waste or exhaust gases from other sources. For example, in a combined cycle powerplant, a gas engine or turbine may be initially used and the exhaust gas from the engine is further combusted in a fired

heater with supplementary fuel to generate steam. The combustion exhaust gas may be obtained from a number ofsources such as a power plant, cement and lime plants, and chemical plants such as ammonia plants and hydrogen

plants. Chemical plant waste gases from refinery fluid catalytic cracking unit regeneration gases and combustionexhaust gas from incinerators may also be used. Combustion exhaust gas from automobiles and crude fraction fuelled

power generators may also be used.

Now for the task intended to be performed by Invention-patent no 5100635, it is practical but not economical toproduce CO2, N2, and argon from combustion exhaust gases from internal combustion engines or turbines: because as

such combustion exhaust gases contain high amounts of oxygen, the gas separation is uneconomical. This is so becausetypically an internal combustion engine uses 70% to 300% excess air to ensure complete combustion of the fuel and to

prevent the engine or turbine from overheating during the combustion process. This level of excess air means that theoxygen concentration in the exhaust gas will be very high, typically about 17%. Because there is no substantial

reduction in the oxygen concentration in the exhaust gas of an engine compared to the oxygen concentration in air(about 20%), there is no appreciable energy or capital cost savings advantage for producing nitrogen from the carbondioxide depleted exhaust gas from an engine compared to the conventional production of nitrogen from air.

However with the slightly different aim/agenda of the present invention [being producing carbon dioxide and sulfurdioxide from combustion exhaust gases from internal combustion engines], regardless of the amount of oxygen presentin the combustion exhaust gas, the task of the present invention is both practical and economical. This is because the

present invention is just invention patent number 5100635 -modified, and simplified.

The method for extracting carbon dioxide and sulfur dioxide from a combustion exhaust gas can be better understoodby reference to FIGURE 1 [contained on the last page of the document] in which like numerals refer to like parts of theinvention drawn as FIGURE 1 (FIG. 1).


8/11

Although the present invention is described and illustrated in connection with preferred embodiments, applicants intend

that modifications and variations may be used without departing from the spirit of the present invention.

Referring to FIG. 1, combustion exhaust gas (stack gas, combustion gas, exhaust gas, feed gas, waste gas) is fedthrough gas feed conduit 1 to pre-purification unit 2 to remove particulate matter from the combustion exhaust gas.

This is combustion exhaust gas pretreated with catalysts or catalytic converters to handle nitrogen oxides, un-burnt

hydrocarbons and carbon monoxide.

Pre-purification unit 2 may be a washing column wherein combustion gas is admitted from the bottom of the unit and awater absorption shower is administered to the gas from the top of the unit to remove solids (soot, carried off ashes,etc.).

The washing column may at the same time cool the gas.

The pre-purified combustion exhaust gas is then fed through gas feed conduit 3 to compressor 4. Compressor 4compresses the combustion gas to the separation pressure. In general, the combustion exhaust gas is compressed to a

separation pressure in the range from about 25 psia to about 200 psia, preferably from about 25 psia to about 120 psia,and more preferably from about 40 psia to about 100 psia.

The compressed combustion exhaust gas is then fed through gas feed conduit 5 to the purification unit -6 where trace

contaminants such as nitrogen oxides, and water are removed. For example, nitrogen oxides (NO.sub.x, NO, NO.sub.2)

maybe removed by treating the feed gas with ammonia and a selective catalyst (commercially available, for example,from Norton Company, Ohio) to convert the nitrogen oxides to nitrogen and water. Other methods to remove nitrogenoxides include moving bed adsorption on activated carbon (Bergbau-Forschung process) and potassium permanganate

scrubbing may also be included in the purification to reduce trace contaminants such as NO.sub.x to the desired level.The presence of nitrogen oxides and sulfur oxides in the combustion exhaust gas should be reduced to less than about 1

ppm to meet food grade specifications for liquid carbon dioxide products. Levels of carbon monoxide in the exhaustgas at concentrations higher than ambient can be removed by catalytic oxidative conversion to carbon dioxide. Watervapor can be removed, for example, by passing the feed gas through a tower containing a desiccant that can beregenerated, such as silica gel, alumina, or zeolite. Silica gel may be periodically regenerated by passing dry nitrogen

heated to a temperature above 100.degree- Centigrade, through the tower.

The purified combustion exhaust gas is then passed through gas feed conduit 7 to separation unit 8 to separate the gasto produce a carbon dioxide rich fraction and a sulfur dioxide rich fraction. The separation of the feed gas can be

carried out by any conventional method.

In one embodiment, the combustion exhaust gas may be circulated through carbon dioxide absorption columns(alkaline solutions such as mono-ethanolamine, potash, etc.) wherein carbon dioxide is absorbed to form a carbonated

solution and sulfur dioxide and the remaining gases pass though the column. The carbonate solution can be regeneratedby passing steam or fluid at a temperature of about 125.degree- Centigrade, -through the carbonated solution; this willat the same time release the absorbed carbon dioxide where there is little or no other gas to mix with, meaning high

purity carbon dioxide is all that is left for compression/liquefaction.

In another embodiment the combustion exhaust gas is separated into a carbon dioxide rich fraction and a sulfur dioxide

rich fraction using the Invention U.S. Pat No. 4,690,702, issued to Paradowski et al. as unit 8: In this case unit 8 is anapparatus set up according to the process disclosed in sheet 1 of 3 of the schematic process flow diagrams of the

Invention U.S. patent 4,690,702, issued to Paradowski et al.

In another preferred embodiment, the combustion exhaust gas is separated through carbon dioxide absorption columnshaving lime water/calcium hydroxide [Ca (OH) 2]. On absorption of CO2 (carbon dioxide), when saturated with CO2,Ca (OH) 2 becomes Ca (HCO3) which is then heated/decomposed to produce steam/water (H2O), Calcium oxide(CaO) residue, and CO2 which is then collected over water then later dried with a desiccant that can be regenerated.

Lime water is recovered for reuse when the CaO residue is made to react with water (H2O), preferably recovered fromwater formed when Ca (HCO3) was heated/decomposed.


9/11

In a preferred embodiment, the combustion exhaust gas is separated in a pressure swing apparatus into a carbon dioxide

rich stream and a sulfur dioxide rich stream. The carbon dioxide rich fraction from separation unit 8 is then fed throughgas feed conduit 9 to liquefaction unit 10 wherein the carbon dioxide is liquefied and the volatile contaminants are

removed by distillation to produce pure carbon dioxide. Liquid carbon dioxide is produced by conventional processingsteps that include compressing the gas to a pressure between about 230 psia and about 400 psia and cooling the gas to a

temperature between about -8.degree- Fahrenheit, and about -50.degree- Fahrenheit. The more volatile impurities areremoved from the liquid carbon dioxide by distillation. Pure carbon dioxide is then vented from liquefaction unit 10

through feed conduit 11 to carbon dioxide product reservoir 12.

The sulfur dioxide rich fraction from separation unit 8 is then fed through gas feed conduit 13 to purification unit 14where the sulfur dioxide (and nitrogen) rich fraction is purified to remove trace contaminants. Preferably, the sulfurdioxide (and nitrogen) rich fraction is purified by passing the gas through a bed of zeolite molecular sieves to removetrace contaminants such as carbon dioxide.

Pure sulfur dioxide gas is then generated by cryogenic fractional distillation. The sulfur dioxide (and nitrogen) richfraction from nitrogen purification unit 14 is fed through gas feed conduit 15 to heat exchanger 16 where the feed gas iscooled to close to the liquefaction point of sulfur dioxide (with cooling energy derived from the outgoing product gas

stream). Cooled sulfur dioxide gas from heat exchanger 16 is fed through gas feed conduit 17 to feed expander 18where the sulfur dioxide gas is further cooled and partially liquefied. Cooled sulfur dioxide gas from feed expander 18is fed through gas feed conduit 19 to sulfur dioxide generator 20 where pure sulfur dioxide is cryogenically fractionallydistilled from oxygen, nitrogen and argon. Pure sulfur dioxide product gas passes from sulfur dioxide generator 20

through gas feed conduit 21 to sulfur dioxide product reservoir 22.

The carbon dioxide and sulfur dioxide depleted combustion exhaust gas is then released to the environment through gasfeed conduit 23.

As set out above, carbon dioxide and sulfur dioxide can preferably be separated by pressure swing adsorption. In apressure swing adsorption system (PSA), a gaseous mixture is passed at an elevated pressure through a bed of anadsorbent material which selectively adsorbs one or more of the components of the gaseous mixture. Product gas,enriched in the un-adsorbed gaseous component(s), is then withdrawn from the bed. The adsorption bed may be

regenerated by reducing the pressure of the bed.

The term "gaseous mixture", as used herein, refers to a gaseous mixture, such as air, primarily comprised of two ormore components having different molecular size. The term "enriched gas" refers to a gas comprised of the

component(s) of the gaseous mixture relatively un-adsorbed after passage of the gaseous mixture through the adsorbentbed.

The enriched gas generally must meet a predetermined purity level, for example, from about 90% to about 99%, in the

un-adsorbed component(s). The term "lean gas" refers to a gas exiting from the adsorption bed that fails to meet thepredetermined purity level set for the enriched gas. When the strongly adsorbed component is a desired product, a co-current depressurization step (co-current with respect to direction of the feed gas) and a co-current purge step of thestrongly adsorbed component are added.

The selectivity of the adsorbent material in the bed for a gaseous component is generally governed by the volume of the

pore size and the distribution of that pore size in the adsorbent. Gaseous molecules with a kinetic diameter less than, orequal to, the pore size of the adsorbent are adsorbed and retained in the adsorbent while gaseous molecules with a

diameter larger than the pore size of the adsorbent pass through the adsorbent. The adsorbent thus sieves the gaseousmolecules according to their molecular size, The adsorbent may also separate molecules according to their different

rates of diffusion in the pores of the adsorbent.

Zeolite molecular adsorbents adsorb gaseous molecules with some dependence upon crystalline size. In general,adsorption into zeolite is fast and equilibrium is reached typically in a few seconds. The sieving action of zeolite is

generally dependent upon the difference in the equilibrium adsorption of the different components of the gaseousmixture.

When air is separated by a zeolite adsorbent, nitrogen is preferentially adsorbed over oxygen and the pressure swing

adsorption method may be employed to produce an oxygen enriched product. When carbon dioxide, nitrogen, andargon are separated by a zeolite adsorbent, carbon dioxide is the adsorbed component and nitrogen and argon are theun-adsorbed components.


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The sieving action of carbon molecular sieves is generally not dependent upon differences in equilibrium adsorption

but rather by differences in the rate of adsorption of the different components of the gaseous mixture. When air isseparated by carbon molecular sieves, oxygen is preferentially adsorbed over nitrogen and the pressure swing

adsorption method may be employed to produce a nitrogen enriched product. When argon and oxygen are separated bycarbon molecular sieves, argon is the un-adsorbed component and oxygen is the adsorbed component.

As a gaseous mixture travels through a bed of adsorbent, the adsorb-able gaseous components of the mixture enter and

fill the pores of the adsorbent. After a period of time, the composition of the gas exiting the bed of adsorbent isessentially the same as the composition entering the bed.

This period of time is known as the break-through point. At some time prior to this breakthrough point, the adsorbentbed must be regenerated. Regeneration involves stopping the flow of gaseous mixture through the bed and purging thebed of the adsorbed components generally by venting the bed to atmospheric or sub-atmospheric pressure.

A pressure swing adsorption system generally employs two adsorbent beds operated on cycles which are sequenced tobe out of phase with one another by 180.degree. so that when one bed is in the adsorption step, the other bed is in theregeneration step. The two adsorption beds may be connected in series or in parallel. In a serial arrangement, the gas

exiting the outlet end of the first bed enters the inlet end of the second bed. In a parallel arrangement, the gaseousmixture enters the inlet end of all beds comprising the system. Generally, a serial arrangement of beds is preferred forobtaining a high purity gas product and a parallel arrangement of beds is preferred for purifying a large quantity of agaseous mixture in a short time cycle.

As used herein, the term "adsorption bed" refers either to a single bed or a serial arrangement of two beds. The inlet endof a single bed system is the inlet end of the single bed while the inlet end of the two bed system (arranged in series)isthe inlet end of the first bed in the system. The outlet end of a single bed system is the outlet end of the single bed and

the outlet end of the two bed system (arranged in series) is the outlet end of the second bed in the system. By using twoadsorption beds in parallel in a system and by cycling (alternating) between the adsorption beds, product gas can be

obtained continuously.

Between the adsorption step and the regeneration step, the pressure in the two adsorption beds is generally equalized byconnecting the inlet ends of the two beds together and the outlet ends of the two beds together. During pressure

equalization, the gas within the pores of the adsorption bed which has just completed its adsorption step (under highpressure) flows into the adsorption bed which has just completed its regeneration step (under low pressure) because ofthe pressure differential which exists between the two beds. This pressure equalization step improves the yield of the

product gas because the gas within the pores of the bed which has just completed its adsorption step has already been

enriched. It is also common to employ more than one pressure equalization step. When a number of pressureequalizations steps are employed, it is common to have more than two beds in the adsorption system.

Gas separation by the pressure swing adsorption method is more fully described in "Gas Separation by Adsorption

Processes", Ralph T. Yang, Ed., Chapter 7, "Pressure Swing Adsorption: Principles and Processes" Buttersworth 1987,which reference is incorporate herein by reference.

Throughout this application, various publications have been referenced. The disclosures in these publications are

incorporated herein by reference in order to more fully describe the state of the art.

It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the artmay make many variations and modifications without departing from the spirit and scope of the invention, so for the

smooth integration of the present invention with various sources of combustion exhaust gas, the appropriate apparatusrecommended herein may be customized and set up as is convenient.

All such modifications and variations are intended to be included within the scope of the invention as defined in theappended claims.


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degarson's invention

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