Sulphur-assisted carbon capture and storage (CCS) processes and systems

Abstract

A system for carbon capture includes an oxy-fuel combustor for combusting a hydrocarbon with pure oxygen to produce heat energy and carbon dioxide, a COS converter for converting the carbon dioxide to COS, a transport means for transporting the COS, a sulphur recovery unit for recovering sulphur from the COS and an adjunct sulphur-burning power plant for combusting the sulphur to generate energy for powering one or more carbon capture and storage processes.

Claims

1. A system for carbon capture and storage, the system comprising: an oxy-fuel combustor for combusting a hydrocarbon with pure oxygen to produce heat energy and carbon dioxide; a COS converter for converting the carbon dioxide to COS; a transport means for transporting the COS; a sulphur recovery unit for recovering sulphur from the COS; a sulphur-burning power plant for combusting the sulphur to generate energy for powering one or more carbon capture and storage processes.

2. The system as claimed in claim 1 wherein the sulphur recovery unit also recovers carbon dioxide from the COS for sequestering the carbon dioxide in a sequestration site.

3. The system as claimed in claim 2 wherein the sulphur-burning power plant supplies power to a carbon dioxide compressor for pressurizing carbon dioxide for injection into the sequestration site.

4. The system as claimed in claim 2 wherein the sulphur-burning power plant supplies power to an air separation unit that supplies the pure oxygen to the oxy-fuel combustor.

5. A system for carbon capture and storage, the system comprising: a combustor for combusting a hydrocarbon with oxygen to produce heat energy and carbon dioxide; a COS converter for converting the carbon dioxide to COS; a sulphur recovery unit for recovering sulphur from the COS; a sulphur-burning power plant for combusting the sulphur to generate energy for powering one or more carbon capture and storage processes.

6. The system as claimed in claim 5 wherein the sulphur recovery unit also recovers carbon dioxide from the COS for sequestering the carbon dioxide in a sequestration site.

7. The system as claimed in claim 6 wherein the sulphur-burning power plant supplies power to a carbon dioxide compressor for pressurizing carbon dioxide for injection into the sequestration site.

8. The system as claimed in claim 6 wherein the sulphur-burning power plant supplies power to an air separation unit that supplies the pure oxygen to the combustor.

9. The system as claimed in claim 5 wherein the sulphur recovery unit is connected via pipeline to the COS converter.

10. A system for carbon capture and storage, the system comprising: a combustor for combusting a hydrocarbon to produce heat energy and carbon dioxide; a COS converter for converting the carbon dioxide to COS by reacting the carbon dioxide with CS.sub.2 supplied from a CS.sub.2 generator; a sulphur recovery unit for recovering sulphur from the COS using a SO.sub.2 reduction unit disposed at the CO.sub.2 sequestration site wherein the sulphur recovery unit also recovers carbon dioxide from the COS for sequestering the carbon dioxide in the CO.sub.2 sequestration site; a sulphur-burning power plant for combusting the sulphur at the CO.sub.2 sequestration site to generate energy for powering one or more carbon capture and storage processes.

11. The system as claimed in claim 10 wherein the sulphur-burning power plant combusts a portion of the sulphur recovered from the COS while supplying a remainder of the sulphur to the CS.sub.2 generator.

12. The system as claimed in claim 11 wherein the sulphur-burning power plant combusts sulphur to generate energy, wherein said energy is supplied to power a carbon dioxide compressor for pressurizing carbon dioxide for injection into the sequestration site.

13. The system as claimed in claim 11 wherein the sulphur-burning power plant combusts sulphur to generate energy, wherein said energy is supplied to power an air separation unit that supplies the pure oxygen to the oxy-fuel combustor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0044] FIG. 1 schematically depict the three prior-art methods of carbon capture;

[0045] FIG. 2 schematically depicts a carbon capture oxy-fueled system integrated with an adjunct sulphur-fueled power generation plant in accordance with one embodiment of the present invention;

[0046] FIG. 3 schematically depicts a carbon capture oxy-fueled system integrated with a “methane-sulphur” CS.sub.2 generation plant and an adjunct sulphur-fueled power generation plant in accordance with another embodiment of the present invention;

[0047] FIG. 4 schematically depicts a standalone sulphur-fueled power generation plant adapted to accept CO.sub.2 from a limestone calcination-cement production plant in accordance with another embodiment of the present invention;

[0048] FIG. 5 schematically depicts a process of transporting CO.sub.2 and sulphur from an oil sands exploration site; and

[0049] FIG. 6 schematically depicts a COS transportation vessel having a sulphur-burning engine.

[0050] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.

DETAILED DESCRIPTION OF THE DRAWINGS

[0051] As illustrated in the embodiment represented by FIG. 3, the concentrated stream of CO.sub.2 14 produced by the combustion of a hydrocarbon such as coal by the oxy-fuel system 100 is converted to carbonyl sulphide (COS) 30 by reaction with carbon disulphide 24 in a reactor 300 as reaction (1), and is used in a reactor 500 as a reducing agent of sulphur dioxide (SO.sub.2) 40, the product of sulphur fueled “adjunct” power generation plant 400, reaction (2) to sulphur 50, and carbon dioxide 56, reaction (3). The oxygen required for this system is provided by a water electrolysis unit 800.

CO.sub.2 Conversion: CO.sub.2+CS.sub.2.fwdarw.2COS   (1)

Adjunct Power Plant: 1/2S.sub.2+O.sub.2.fwdarw.SO.sub.2+heat   (2)

CO.sub.2, S.sub.2 Recovery: SO.sub.2+2COS.fwdarw.2CO.sub.2+3/2S.sub.2   (3)

[0052] There are patents and scientific literature describing COS synthesis by a catalytic reaction between CO.sub.2 and CS.sub.2. For example, Rosen et. al. in Canadian Patent No. 780780 which is hereby entirely incorporated by reference, disclosed a process for producing carbonyl sulphide in a yield of about 90% or more by the reaction of carbon dioxide and carbon disulfide (2) if the reaction is conducted at moderately elevated temperatures in the range of 100 to 600° C. and in the presence of high surface area catalysts such as activated silica gel, activated zeolites, activated alumina and activated charcoal.

[0053] Furthermore, 100% CS.sub.2 conversion to COS at 300° C. in the reaction of carbon dioxide and carbon disulfide over various metal oxide catalysts such Al.sub.2O.sub.3, ZrO.sub.2, ThO.sub.2 is reported by Masatoshi Sugioka, Atsushi Ikeda and Kazuo Aomura, A Study for Effective Utilization of Carbon Dioxide—The Synthesis of Carbonyl Sulfide and Carbon Monoxide by the Reaction of Carbon Dioxide and Carbon Disulfide, Bulletin of the Faculty of Engineering, Hokkaido University, 93:35-42, 1979-01-31.

[0054] Nemeth et. al., in Hungarian Patent No. 185 221 discloses a process for producing carbonyl sulphide of high purity by reaction (1) in continuous running.

[0055] Furthermore, Nemeth et. al., in Hungarian Patent No. 202 452 discloses a process for the production of carbonyl sulphide from carbon dioxide and carbon disulphide in the presence of a catalyst. In this process, carbon dioxide and carbon disulphide react in the presence of a 98% pure gamma-aluminium oxide catalyst. The catalyst contains 1% silicon dioxide and traces of sodium oxide, sulphate ions, iron and other metals.

[0056] Carbon disulphide is a common industrial solvent in a wide variety of applications. It is used for dissolving residues from oil well casings and pipelines, for unplugging sour gas wells obstructed by elemental sulphur, as a solvent in emulsion polymerization and the production of nitrocellulose and polyvinyl, as well as many other uses. Some rayon manufacturers produce their own carbon disulfide. Modern plants generally produce carbon disulfide of about 99.99% purity although never before in the context of CO.sub.2 capture.

[0057] The formation of carbon disulfide 24 in reactor 200 in this embodiment uses methane from natural gas as the source of carbon 20 and sulphur 54. The process can be represented by equation (4):

CH.sub.4+2 S.sub.2.fwdarw.CS.sub.2+2 H.sub.2S   (4)

[0058] Thermodynamically, the reaction is very favorable for carbon disulphide formation, and with the methane-sulphur system, carbon disulphide of over 90-mole percent per pass can be realized. For equation (4), starting with methane and solid sulphur at 25° C., and ending with gaseous products at 600° C., the reaction is endothermic. However, the reaction of methane and sulphur vapour in the diatomic form is actually exothermic and superheating of the sulphur offers a means of reducing process temperatures at which the sulphur dissociates.

[0059] Guennadi in German Patent DE102004013283

[0060] provides a method for producing carbon disulphide without fuel use. This German patent discloses the combined production of carbon disulphide and sulphuric acid. In the proposed technology, instead of the natural gas fuel, sulphur combustion products are the main heat transfer medium. The thermal energy is formed by the oxidation of sulphur to sulphur dioxide. In the embodiment depicted in FIG. 3, the required heat 92 for the superheating of the sulphur is provided by the Claus Plant 900 where the sulphur is recovered from hydrogen sulphide 22 formed from the methane-sulphur process.

[0061] The sulphur recovery plant 900 includes the Claus Plant with a sulphur dioxide generator that employs the sulphur submerged combustion method (also referred to herein as a “bubbling chamber”, “sulphur vaporizer”, or “sulphur evaporator”), whose function was described in greater detail in CA 2,700,746, US 2009235669 and U.S. Pat. No. 7,543,438,

[0062] which are hereby incorporated by reference.

[0063] The submerged sulphur combustion method has been commercially used for sulphur dioxide production since 1989 by Calabrian Corporation. This method has been modified and applied to fit the unique requirements of an oxygen-fired Claus plant by Brown & Root Braun (“NoTICE” process) (U.S. Pat. No. 5,204,082).

[0064] In the process of sulphur combustion in oxygen at the sulphur-fuelled power plant 400, it is important to ensure complete combustion of sulphur and to control the temperature. In the stoichiometric combustion of sulphur with oxygen, the calculated temperature when the reactants (SO.sub.2, SO, S.sub.2, S and O.sub.2) are in equilibrium, taking into account the dissociation process, is about 3000° C. The temperature exceeding 5000° C. occurs in the stoichiometric combustion of diatomic sulphur (S.sub.2) in oxygen. The temperature can be reduced to a permissible level, which depends on the nature of the materials used, by adopting one or more of the following measures or techniques disclosed by the following patents:

[0065] U.S. Pat. No. 7,052,670 discloses a method in which the temperature of the combustion of sulphur and oxygen is controlled by means of pre-defined S, O.sub.2, and SO.sub.2 ratios.

[0066] Canadian Patents No. 930930 and 978721, and U.S. Pat. No. 3,803,298 provide a method of combustion of sulphur with oxygen in interstages.

[0067] Furthermore, Applicant's Canadian Patent No. 2,700,746, and US Patent Application Publication No. 2010/0242478 as well as U.S. Provisional Patent Applications 61/704,834 and 61/715,425 disclose various sulphur combusting technologies, systems and methods. The methods generally entail steps of evaporating liquid sulphur to generate sulphur dioxide gas and sulphur vapour, combusting the sulphur vapour with oxygen to generate heat, and reducing the sulphur dioxide (either at high temperature or catalytically) to carbon dioxide and sulphur vapour by reacting the sulphur dioxide with carbonyl sulphide.

[0068] In U.S. Pat. No. 7,631,499 the combustion system is a multiple-stage combustion system comprising a series of successive (sequentially arranged) combustors that burn sulphur vapour at a desired temperature such that, at each successive stage, the combustion of the sulphur is burnt with a stoichiometric deficiency of oxygen. In one embodiment, the multiple-stage combustion system may be an axially staged combustion system for a gas turbine engine. The multi-stage combustion system can be used to burn sulphur in stages.

[0069] U.S. Pat. No. 4,107,557 discloses an MHD generator system that comprises a burning chamber in which sulfur is burned with oxygen at a temperature upwards of 8000 F with an additive of a readily ionizable seed material to form a partially ionized stream of SO.sub.2 and seed material.

[0070] Stanley et al., in U.S. Pat. No. 4,354,354, disclosed a method in which the seed, in form of potassium sulphate (K.sub.2SO.sub.4) is fed into an MHD combustor, mechanically recovered and recycled without need for regeneration.

[0071] A method and apparatus for combine-closed-cycle magneto-hydrodynamic generation is disclosed by Shiota et. al., in U.S. Pat. No. 5,086,234.

[0072] FIG. 4 depicts a system that comprises a CaCO.sub.3 calciner 1 that receives carbon and oxygen and produces CaO and CO.sub.2. The calciner 1 may be part of a cement production plant for manufacturing cement clinker from limestone (CaCO.sub.3). In most embodiments, the cement production plant includes a preheater for preheating the limestone, a calciner for calcination, and a rotary kiln for high-temperature burning at about 1450° C. to make the clinker that is then ground or milled into powder form with a small quantity of gypsum to make ‘Ordinary Portland Cement’ (OPC). In this calcination process of heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450° C. in a kiln, carbon dioxide is produced. The carbon dioxide from the cement plant may be captured using the CCS technologies described herein, namely by converting the carbon dioxide to COS, transporting the COS to a sulphur-recovery site where sulphur is recovered from the COS and then combusted. Carbon dioxide that reforms when the sulphur is recovered may then be sequestered at a suitable sequestration site. Energy harnessed from the combustion of sulphur may then be used to power one or more of the CCS processes such as injection of carbon dioxide into underground formations or saline aquifers. The energy harnessed from the combustion of sulphur may also be used to supply power to the cement manufacturing plant.

[0073] As further illustrated in FIG. 4, the carbon dioxide from the calciner is supplied to a COS converter 300 (labelled “CO.sub.2 converter” in the figure). The converter 300 receives the carbon dioxide from the calciner 1 and receives the CS.sub.2 from a CS.sub.2 generator 200 and converts the carbon dioxide into COS for transport via pipeline (or other transport means) 30 to a sulphur dioxide reducer (“SO.sub.2 reduction unit” or “S & CO.sub.2 recovery unit”) 500 that receives sulphur dioxide from a sulphur-fuelled power plant 400 (sulphur-burning plant). The SO.sub.2 reduction unit 500 provides sulphur to a CS.sub.2 generator 200 (that, in turn, supplies the CS.sub.2 to the COS converter (“CO.sub.2 converter” 300). As illustrated in this embodiment, the SO.sub.2 reduction unit (S & CO.sub.2 recovery unit) 500 provides sulphur to the sulphur-burning plant 400. The sulphur-burning plant 400 (sulphur combustor) generates power (e.g. electric power) which is delivered to the air-separation unit (ASU) 700 for separating the oxygen from the air. The oxygen is fed into the calciner 1 and also into the sulphur combustor of the sulphur-fuelled plant 400 as shown in FIG. 4. The waste sulphur dioxide from the sulphur combustion at the sulphur-burning plant 400 is fed into, and reduced by, the reduction unit 500 so this process does not emit any sulphur dioxide. The carbon dioxide from the reduction unit 500 may be sequestered in a suitable sequestration site.

[0074] The present invention may thus be utilized for carbon capture in a variety of different applications including any hydrocarbon or fossil fuel combustion process (e.g. burning coal, natural gas or petroleum) that produces carbon dioxide. This invention may also be used to capture carbon in a cement cement production process that produces carbon dioxide as a byproduct. This invention may thus be understood more broadly as a carbon capture technology for capturing anthropogenic carbon dioxide (i.e. carbon dioxide that is produced by power-generating stations, industrial processes or other manmade sources).

[0075] FIG. 5 depicts a system that comprises a CS.sub.2 generator that receives coke or methane as well as sulphur to generate CS.sub.2 which is then supplied to a COS generator. The COS generator receives carbon dioxide from a combustor (hydrocarbon combustion process such as the combustion of coke). The COS in liquid form is then shipped via pipeline (or other transport means) to a sulphur recovery and power generation plant where elemental sulphur is recovered and burned to generate power and where carbon dioxide is sequestered. As shown in this figure, other COS may be sent to a port for export abroad (transhipment via a seaport). The system of FIG. 5 may be particularly useful, for example, in Western Canada. The COS generator may be disposed at an oil sands exploitation site such as the oil sands at Fort McMurray, Canada. COS may then be sent via pipeline and shipped abroad via Port Rupert on the Canadian Pacific coast while carbon dioxide may be sequestered in the Western Canadian Sedimentary Basin. This figure shows how the system may be applied to a real-world scenario. Clearly, this is merely an illustrative example and the system may of course be applied to any other comparable scenario.

[0076] FIG. 6 depicts a sulphur-powered vehicle, in this case a seagoing vessel or ship that is fully or partially powered by the combustion of sulphur. The ship in this case is a tanker or freighter capable of carrying COS. One or more COS liquid container(s) is provided as shown. Some of the COS may be drawn from the container(s) and converted into sulphur and carbon dioxide. The carbon dioxide is stored on the ship in a carbon dioxide containment vessel. The sulphur may be combusted to provide heat energy which can be harnessed to drive a ship turbine as part of the ship's engine. The ship of FIG. 6 thus has a sulphur-combustion engine that draws on the onboard COS supply for its fuel. Although a ship is illustrated in FIG. 6, it should be understood that this concept may be applied to other vehicles, including trains (in which the locomotive has a sulphur-combusting engine) or to other land vehicles having a sulphur-combusting engine.

[0077] This invention has been described in terms of specific embodiments, implementations and configurations which are intended to be exemplary only. Persons of ordinary skill in the art will appreciate, having read this disclosure, which many obvious variations, modifications and refinements may be made without departing from the inventive concept(s) presented herein. The scope of the exclusive right sought by the Applicant(s) is therefore intended to be limited solely by the appended claims.