Method and apparatus for improving the efficiency of an SMR process for producing syngas while reducing the CO2 in a gaseous stream

Abstract

A system and method for increasing the production of Syngas from an SMR (Steam Methane Reforming) processing plant by providing CO2 as an additional feedstock, such as from an exhaust stream of a Corn-to-Ethanol plant, or from a power plant or industrial plant, like a cement plant. The CO2 steam and methane are introduced into the SMR reactor heated to about 870° C. and at about one atmosphere such that a reaction takes place that produces Syngas comprising CO, Hydrogen (H2) and carbon dioxide (CO2). The Syngas is then cleaned and provided to a Fischer-Tropsch synthesis reactor or other Bio-catalytic synthesis reactor to produce Ethanol or other high value liquid fuel.

Description

TECHNICAL FIELD

The present invention relates generally to GTL (Gas To Liquid) feedstock preparation and more specifically to improving the efficiency of the SMR (Steam Methane Reforming) process while at the same time reducing the presence of carbon dioxide (CO₂). In a specific embodiment, the carbon dioxide such as from a biomass fermenter (such as an Ethanol fermenter) or a gaseous exhaust stream from power plants and other types of industrial plants is reduced while increasing the efficiency of the SMR (Steam Methane Reforming) process for forming a Syngas (CO+H₂). The syngas, in turn, can be used in the production of liquid fuels, such as for examples only, Ethanol, Diesel, Methanol, Butanol, Jet Fuel, Gasoline and other.

BACKGROUND

Concern about global warming eventually leads to discussions about the need to reduce the amount of carbon dioxide that pours into the earth's atmosphere on a daily basis from power plants and other industrial factories. At the same time, concerns about dwindling supplies of fossil fuels have encouraged the development of liquid fuels such as Ethanol as future replacement fossil fuels. The cost of preparation of feedstock, such as syngas generation is typically the most expensive part of GTF (Gas to Liquid) methods of producing a liquid fuel such as Ethanol. In the SMR process this cost typically represents about 50% of the total CAPEX (Capital Expense). Further the present SMR process is not particularly efficient and, unfortunately, results in as much or more carbon dioxide being introduced into the atmosphere as does burning fossil fuels.

The SMR process is a mature “catalytic” process that operates at about 870 degrees C. (1,600 degrees F.) and at pressures of between about 35 psig and 550 psig. As will be appreciated by those skilled in the art, the SMR process has been optimized for productivity and efficiency over many years of industrial applications. However, the process is limited to the use of gaseous and/or liquid feed-stocks only, and primarily operates on Methane gas as a Carbonaceous feedstock to produce Syngas (CO and H₂). An F-T [Fischer-Tropsch] converter) is typically used with the SMR process to convert the resulting Syngas to Ethanol. Some existing SMR plants feedback the exhaust or tail gas from the F-T converter to the SMR reaction chamber to control, balance or selectively adjust the ratio of the H₂ and CO in the resulting Syngas. Adjusting or balancing the H₂/CO ratio of the Syngas is often desired or necessary because the Syngas leaving the SMR reactor typically contains an excess of H₂ for efficient conversion by the F-T reactor. However, until this invention a separate stream of CO₂ has never been used as an additional feed-stock.

The SMR reaction is:CH₄+H₂OCO+3H₂, and the Water-Gas Shift reaction is:CO+H₂OCO₂+H₂.

Therefore, a method for more efficiently producing a Syngas, (easily convertible to Ethanol and other liquid fuels) by the SMR process while at the same time removing CO₂ from gaseous streams exhausted by industrial plants would offer many advantages in cost, as well as, an overall reduction in the carbon dioxide dumped into the atmosphere.

SUMMARY OF THE INVENTION

The present invention discloses methods and apparatus for reducing the carbon dioxide that is often present in an industrial gaseous streams exhausted or emitted from a biomass fermenter and other various power plants and types of industrial plants, such as (for example only) a cement plant. For example, the typical gaseous exhaust stream of about 400,000 lbs/hr total from an industrial cement plant will contain about 30%-40% (about 160,000 lbs/hr) of carbon dioxide (CO₂). However, instead of being exhausted to the atmosphere, according to this invention, the gaseous stream from a biomass fermenter, or any other source of CO₂ is provided to the reaction chamber of an SMR processing plant where at least a portion is converted to Syngas and thereby significantly increases the efficiency of an SMR (Steam Methane Reforming) plant. In addition to the normal chemical reactions that take place in a standard SMR process (i.e. CH₄+H₂OCO+3H₂ and CO+H₂OCO₂+H₂), the CO2 added as a feed-stock results in another reaction (CO₂+H₂CO+H₂O) taking place in the chamber such that the CO₂ from the gaseous stream is also converted to CO in the Syngas. The Syngas can then be used as a feedstock for the production of Ethanol.

For example, a bio-catalytic process, or a catalytic process such as a Fischer-Tropsch process could be used to produce the Ethanol.

Simply put, this inventive process reduces the carbon dioxide in the atmosphere and increases the formation of Syngas in an SMR plant by introducing CO₂ into the SMR reaction chamber as an original feedstock along with the normal SMR feeds of methane, steam and oxygen.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a simplified block diagram illustrating the standard SMR process;

FIG. 2 is the same simplified block diagram of an SMR process as FIG. 1 except that it includes the addition of CO₂ as a reactant introduced into the SMR chamber to increase the efficiency of the process while consuming CO₂; and

FIG. 3 is a more detailed illustration of the process of FIG. 2 for the production of Ethanol.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the various embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

Referring now to FIG. 1 there is shown a simplified block diagram of a standard well known SMR processing plant that includes the reaction chamber 10 that receives its carbonaceous input from a methane source at input 12. The reaction chamber 10 further receives steam (H₂O) at input 14 and oxygen O₂ (if necessary) at input 16. As is well known in the art, SMR plants produce syngas primarily comprised of carbon monoxide (CO), hydrogen (H₂) and Carbon Dioxide (CO₂) at output 18. The syngas output is then typically provided to a Fischer-Tropsch reactor 20 to produce Ethanol at output 22. In addition, the Fischer-Tropsch process may produce a tail gas, indicated at 24, that contains CO₂ along with CO, H₂ and CH₄. This tail gas may be used as a purge gas, burned as a heat source, vented to the atmosphere or collected and sequestered or otherwise disposed of as indicated at 26. Alternately, about one third of the tail gas may be recycled back to the SMR reactor as shown at 28.

In some existing SMR plants about one third of the exhaust or tail gas 24 from the F-T converter is provided to the SMR reaction chamber 10 to control, balance or selectively adjust the ratio of the H₂ and CO in the resulting Syngas. Adjusting or balancing the H₂/CO ratio of the Syngas is often desired or necessary because the Syngas leaving the SMR reactor typically contains an excess of H₂ that prevents the most efficient conversion by the F-T reactor which prefers a higher level of CO.

The Ethanol from the F-T reactor, or Methanol, may then be provided to a product upgrading step as shown at block 30 to convert the Ethanol or Methanol to other liquid products such as LPG, Diesel, Naptha, etc.

As shown in FIG. 2, and according to the present invention, there is illustrated a simplified block diagram of the same SMR plant discussed with respect to FIG. 1, except that it further incorporates the improvement of the present invention such that CO is formed by both the feed-stock of CO₂ combining with methane and the normal SMR reaction of Steam and Methane. The improved SMR processing operates at between about 700 degrees centigrade and 1,000 degrees centigrade, and between about 35 psig and 450 psig.

The process of this invention increases the H₂/CO ratio and consequently the amount of Ethanol production, while consuming and removing CO₂ from the atmosphere. More specifically, as shown, the addition of a CO₂ stream to the SMR chamber 10 at input 32 may be from biomass reactor or other industrial plant or source, such as for example only, a cement plant. That is, instead of being exhausted to the atmosphere, sequestered or otherwise disposed of, according to this invention, the gaseous CO₂ stream 32 is provided to the reaction chamber 10 of an SMR processing plant. In addition to the normal reactions of a standard SMR process (i.e. CH₄+H₂OCO+3H₂ and CO+H₂OCO₂+H₂), the CO₂ added as a feed-stock results in another, reaction (CO₂+H₂CO+H₂O) taking place in the chamber such that the CO₂ from the gaseous stream is also converted to Syngas (CO+H₂). That is, the carbon (C) provided by the methane (CH₄) source 12 combines with one of the oxygen (O) atoms of the carbon dioxide (CO₂) molecules to form two molecules of carbon monoxide (2 CO) which, of course also reduces the amount of carbon dioxide (CO₂) in the reaction chamber. In the case of methane, in addition to the normal carbon monoxide, more hydrogen is produced (i.e. 3H₂). It will also be appreciated that it is not likely that all of the added or reformed carbon dioxide (CO₂) will be converted to 2CO (i.e. carbon monoxide). However, the steam (H₂O) may also react with some of the carbon monoxide (CO) to reform some carbon dioxide (CO₂) and some hydrogen (H₂). Consequently, the reaction chamber discharges Syngas as indicated on line 18 comprised of carbon monoxide (CO), hydrogen (H₂) and a reduced amount of carbon dioxide (CO₂) to a reactor 20, such as a Fischer-Tropsch reactor.

Thus, it is seen that at this stage of the process the carbon dioxide (CO₂) has been reduced and the carbon monoxide (CO) in the Syngas increased. This provides a significant economic advantage, since as has been discussed; some bio-catalytic processes are more effective using Syngas with a higher percentage of carbon monoxide (CO) as feed stock.

Referring now to FIG. 3, there is shown a more detailed version of the process of FIG. 2. Components, processes and conduits that are the same as in FIG. 2 are identified by the same reference numbers. As shown, the Syngas from the SMR reactor 10 is provided by line 18A to a Syngas Cleanup and Heat Recovery process 34 and then provided on Line 18B to a Methanol Synthesis or Ethanol Process, such as a Fischer-Tropsch synthesis reactor shown as block 36. As known by those skilled in the art, the Fischer-Tropsch reactor may be used to convert the Syngas to Ethanol 56. Alternately, a bio-chemical reactor could be used.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A process for increasing the amount of syngas production in a SMR (Steam Methane Reforming) process by converting carbon dioxide (CO2) to carbon monoxide, the process comprising: providing an SMR reaction chamber having inputs and an output;maintaining said SMR reaction chamber at a temperature of between 700° C. and 1000° C.;providing methane (CH4) to said reaction chamber as a feed-stock;providing H2O to said reaction chamber as a feed-stock;providing a gaseous stream comprising carbon dioxide (CO2) from a source external to an input of said reaction chamber as a feed-stock;reacting materials in said reaction chamber, the reacting materials consisting essentially of said methane (CH4), said H2O and said carbon dioxide (CO2) to form syngas comprising carbon monoxide (CO) and hydrogen (H2), said syngas being formed by combing said methane (CH4) with said H2O, and by combining said methane (CH4) with said carbon dioxide (CO2), and wherein the amount of any carbon dioxide (CO2) that does not combine with said methane (CH4) being less than the amount of carbon dioxide CO2 provided in said gaseous stream to said reactor; anddischarging said formed syngas at said output.

2. The process of claim 1, wherein said H2O provided as a reactant into said reaction chamber is steam.

3. The process of claim 1, wherein said reaction chamber is maintained at a temperature of about 870° C.

4. The process of claim 1, wherein said discharged carbon monoxide and hydrogen of said syngas are provided to a bio-catalytic reactor to produce Ethanol or Methanol.

5. The process of claim 4, wherein said bio-catalytic reactor is a Fischer-Tropsch synthesis reactor.

6. The process of claim 4, wherein an output of said bio-catalytic reactor is provided to another bio-catalytic reactor to provide additional Ethanol or Methanol.

7. A process for increasing the amount of syngas production in an SMR process and for consuming carbon dioxide (CO2), the process comprising: providing an SMR reaction chamber having inputs and an output;maintaining said SMR reaction chamber at a temperature of between 700° C. and 1000° C.;providing methane (CH4) to an input of said reaction chamber as a feed-stock;providing H2O to an input of said reaction chamber as a feed-stock;introducing a gaseous stream containing carbon dioxide (CO2) from a source external to an input of said reaction chamber as a feed-stock;reacting materials in said SMR reaction chamber, wherein the reacting materials consisting essentially of said methane (CH4), said H2O and said carbon dioxide (CO2) CO2 to form a syngas output comprising carbon monoxide (CO), hydrogen (H2) and unreacted carbon dioxide (CO2), said syngas being formed by combing said methane (CH4) with said H2O and by combining said methane (CH4) with said (CO2), such that the amount of unreacted carbon dioxide (CO2) in said syngas is less than the amount of carbon dioxide introduced in said reaction chamber by said gaseous stream;discharging said formed syngas at an output.

8. The process of claim 7, wherein said formed syngas comprising carbon monoxide and hydrogen is provided to a bio-catalytic reactor to produce Ethanol or Methanol.

9. The process of claim 7, wherein an output of said bio-catalytic reactor is provided to another bio-catalytic reactor to produce additional Ethanol or Methanol.

10. The process of claim 7, wherein said H2O provided as a reactant into said reaction chamber is steam.

11. The process of claim 7, wherein said reaction chamber is maintained at a temperature of about 870° C.

12. The process of claim 8, wherein said bio-catalytic reactor is a Fischer-Tropsch synthesis reactor.

13. The process of claim 4, wherein said bio-catalytic reactor produces a tail gas containing carbon dioxide (CO2) and further comprising recycling said carbon dioxide (CO2) to said SMR reaction chamber.

14. The process of claim 5, wherein said Fischer-Tropsch synthesis reactor produces a tail gas containing carbon dioxide (CO2) and further comprising recycling said carbon dioxide (CO2) to said SMR reaction chamber.

15. The process of claim 7 wherein said unreacted carbon dioxide (CO2) is recycled to said SMR reaction chamber.

16. The process of claim 1 wherein said carbon dioxide (CO2) that does not combine with said methane (CH4) is recycled to said SMR reaction chamber.

17. The process of claim 8, wherein said bio-catalytic reactor produces a tail gas containing carbon dioxide (CO2) and further comprising recycling said carbon dioxide (CO2) to said SMR reaction chamber.

18. The process of claim 12, wherein said Fischer-Tropsch synthesis reactor produces a tail gas containing carbon dioxide (CO2) and further comprising recycling said carbon dioxide (CO2) to said SMR reaction chamber.