GB2615109A

GB2615109A - Extraction device

Info

Publication number: GB2615109A
Application number: GB2201121.7A
Authority: GB
Inventors: Pearce Matthew; Middleton Ray
Original assignee: Purifire Labs Ltd
Current assignee: Purifire Labs Ltd
Priority date: 2022-01-28
Filing date: 2022-01-28
Publication date: 2023-08-02
Also published as: GB202201121D0

Abstract

The invention relates to an apparatus for the extraction of solid and/or liquid carbon dioxide from exhaust flue gas, comprising a primary heat exchanger 10, which connects to a first heat exchanger 20, which cools the flue gas, and a storage tank 36, comprising a throttle valve 32 and a storage capacity. In some embodiments, there may be multiple heat exchangers, or gaseous nitrogen may be transferred from the storage tank for use in the heat exchanger.

Description

EXTRACTION DEVICE

FIELD OF THE INVENTION

The invention relates to an apparatus for the extraction of solid and/or liquid carbon dioxide from exhaust flue gas. The invention also relates to methods for extracting solid or liquid carbon dioxide from exhaust flue gas.

BACKGROUND OF THE INVENTION

Global carbon dioxide emissions amount to over 10 giga tonnes per year. Simultaneously, there is a considerable requirement for carbon dioxide in a multitude of applications, such as urea fertiliser production, enhanced oil recovery processes, production of food and beverages, and other industrial processes. Approximately 250 million tonnes of carbon dioxide, corresponding to approximately 2.5% of all global emissions, are used each year for these purposes. Presently, almost all such carbon dioxide is derived from fossil fuel based sources.

In line with multiple unilateral governmental policies to reduce atmospheric global emissions of carbon dioxide, many nations are either decommissioning, scrapping or modifying existing coal-fired power stations or considering other abatement alternative scenarios. Coal-fired power stations emit approximately 80 tonnes of carbon dioxide gas per hour for every 100 MWh of electricity power generation capacity, depending on their construction and the coal fuel type being burned. This gross carbon dioxide emissions capacity exceeds comparative tonnages remediated for bioenergy with carbon capture and storage (BECCS). Moreover, BECCS is prohibitively expensive at a cost of between $80-200/tonne of carbon dioxide gas removal, and biomass co-fired with coal reduces the efficiency of electricity generation. Post combustion carbon capture and storage with amine scrubbing technologies in coal-fired power plants is a recent technology application, but even with subsidies it is expensive, typically costing between $80/tonne of carbon dioxide for first of a kind technologies and $60/tonne of carbon dioxide for next of a kind technology.

Retro-conversion of older coal-fired electricity power generation plants for carbon dioxide remediation was not considered as a future possibility when these plants were built, resulting in low availability of physical space and high costs. With many coal-fired power plants not able to be converted into environmentally benign non-polluting retro-fitted alternatives, some are now being shut down as a result of new legislation policies. This, in turn, drives an increased demand for electricity generation from alternative sources.

There exists an urgent and unmet need for carbon capture processes that are efficient, scalable and inexpensive. To avoid expensive and wasteful decommissioning of existing coal-fired electricity power generation plants, there exists an urgent and unmet need for carbon capture processes that reduce the carbon dioxide emissions from these plants to the environment. There is also an unmet industrial demand for carbon dioxide that is not derived directly from virgin fossil fuels e.g. for use in the ammonia fertiliser, enhanced oil recovery, medical, food and beverage industries.

SUMMARY OF THE INVENTION

The present invention solves the above-mentioned problems by providing an apparatus for extracting solid and/or liquid carbon dioxide from exhaust flue gas. Advantageously, the apparatus of the invention can be used to extract and capture carbon dioxide that would otherwise be released into the atmosphere, thereby reducing contributions to global carbon dioxide emissions. Carbon dioxide extracted by the invention may be stored to prevent its entry into the atmosphere. Carbon dioxide extracted by the invention may also be used in industry, e.g. to reduce the reliance on carbon dioxide produced from virgin fossil fuels, thereby further reducing carbon dioxide emissions. The present invention is not limited to any particular type of exhaust flue gas. Likewise, the present invention is not limited to any particular type of flue. As such, the apparatus of the invention can advantageously be used to extract carbon dioxide from a range of sources, such as exhaust flue gases, such as from boilers, engines, and fossil fuel-fired power stations.

The invention provides an apparatus for extracting solid and/or liquid carbon dioxide from exhaust flue gas, the apparatus comprising: a) a primary heat exchanger for receiving and cooling the exhaust flue gas; b) a primary compressor in fluid communication with the primary heat exchanger for receiving and compressing cooled exhaust flue gas from the primary heat exchanger; and c) a carbon dioxide collection vessel in fluid communication with the primary compressor, wherein the carbon dioxide collection vessel comprises: (i) a throttling valve for receiving compressed cooled exhaust flue gas from the primary compressor; and (ii) a holding tank for containing solid and/or liquid carbon dioxide.

In some embodiments, the apparatus further comprises one or more secondary heat exchangers for receiving and cooling compressed cooled exhaust flue gas from the primary compressor prior to passage of the compressed cooled exhaust flue gas to the carbon dioxide collection vessel.

In some embodiments, the carbon dioxide collection vessel further comprises an outlet for gaseous nitrogen, wherein the outlet is in fluid communication with the primary heat exchanger and/or the outlet is in fluid communication with one or more of the secondary heat exchangers.

In some embodiments, the apparatus further comprises means for connecting in fluid communication the primary heat exchanger and the exhaust flue.

In some embodiments, the apparatus further comprises a gas bypass system for venting excess exhaust flue gas, wherein the gas bypass system is situated between the primary heat exchanger and the exhaust flue.

In some embodiments, the primary heat exchanger comprises an array of conduits for receiving gaseous nitrogen from the carbon dioxide collection vessel. In some embodiments, the array of conduits forms a labyrinth chamber for receiving the exhaust flue gas.

In some embodiments, the secondary heat exchanger comprises an array of conduits for receiving gaseous nitrogen from the carbon dioxide collection vessel. In some embodiments, the array of conduits forms a labyrinth chamber for receiving the compressed cooled exhaust flue gas.

In some embodiments, the apparatus further comprises an impeller for propelling the exhaust flue gas into the primary heat exchanger.

In some embodiments, the apparatus further comprises one or more impellers for propelling the compressed cooled exhaust flue gas into one or more of the one or more secondary heat exchangers.

In some embodiments, the apparatus further comprises a secondary compressor for receiving and compressing compressed cooled exhaust flue gas from the primary compressor.

In some embodiments, one or more of the one or more secondary heat exchangers is situated between the primary compressor and the secondary compressor.

In some embodiments, one or more of the one or more secondary heat exchangers is situated between the secondary compressor and the carbon dioxide collection vessel.

In some embodiments, one or more of the secondary heat exchangers is situated between the primary compressor and the secondary compressor; and one or more of the secondary heat exchangers is situated between the secondary compressor and the carbon dioxide collection vessel.

In some embodiments, the apparatus further comprises one or more valves for maintaining unidirectional flow of exhaust flue gas.

The invention also provides a method for producing solid and/or liquid carbon dioxide from exhaust flue gas, the method comprising: a) delivering exhaust flue gas to a primary heat exchanger to provide cooled exhaust flue gas; b) compressing the cooled exhaust flue gas to provide compressed cooled exhaust flue gas, and optionally delivering the compressed cooled exhaust flue gas to a secondary heat exchanger; and c) throttling the compressed cooled exhaust flue gas through a throttling valve to provide solid and/or liquid carbon dioxide.

In some embodiments, the method further comprises separating gaseous nitrogen from the solid and/or liquid carbon dioxide and supplying the separated gaseous nitrogen to the primary and/or secondary heat exchanger.

In some embodiments, the cooling comprises reducing the temperature of the gas to less than -10°C. In some embodiments, the compressing comprises compressing the gas to at least 1 MPa.

In some embodiments, the method further comprises converting solid carbon dioxide to carbon dioxide ice. In some embodiments, conversion of solid carbon dioxide to carbon dioxide ice is by hydraulic pressing.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based on the surprising discovery that solid and/or liquid carbon dioxide can be efficiently extracted from exhaust flue gas by varying the pressure and temperature of the exhaust flue gas. The apparatus and method of the invention advantageously provide a means for reducing the carbon dioxide emissions of energy generating devices. Moreover, carbon dioxide extracted by the apparatus and method of the invention has a number of applications in industry. Carbon dioxide extracted by the apparatus and methods of the invention may also be stored, to prevent its entry to the atmosphere, thereby reducing contributions to greenhouse gases.

Advantageously, the apparatus of the invention can be used to reduce the carbon dioxide emissions from existing electricity generating power stations by extracting carbon dioxide from the exhaust flue gases generated by said power stations. Reducing the negative environmental impact of these power stations, by reducing their carbon dioxide emissions without sacrificing the efficiency of energy generation, may help avoid these power stations being decommissioned.

Liquid carbon dioxide extracted using the apparatus and methods of the invention can be stored in subterraneous storage systems. Liquid carbon dioxide at high subterraneous pressures may be maintained for a long time in liquid state due to increased pressure from burial in subterranean lakes of liquid carbon dioxide, resulting in limited surface leakage over an extended period of time. This is a desirable alternative to the current practise of allowing carbon dioxide to be released into the atmosphere. Liquid carbon dioxide extracted using the apparatus of the invention may also be used to produce pressure changes within underground water and oil reservoirs, for applications such as instigating enhanced oil recovery and/or additional extraction of oil from otherwise depleted oil reservoirs.

Exhaust flue gas is typically generated by the combustion of a fuel, such as a fossil fuel (e.g. coal), biofuel or sustainable fuel. Exhaust flue gas may be generated by various energy generating devices, e.g. boilers, engines, generators, and power stations (e.g. fossil fuel-fired power stations).

In some embodiments, exhaust flue gas is treated by flue gas desulphurisation (FGD) methods to remove sulphur dioxide prior to delivery of the exhaust flue gas to the apparatus of the invention. In 10 some embodiments, exhaust flue gas is post-desulphurisation exhaust flue gas. Typical post-desulphurisation exhaust flue gas comprises mainly gaseous carbon dioxide and nitrogen.

The apparatus of the invention comprises a primary heat exchanger for receiving and cooling exhaust flue gas. The primary heat exchanger may be any heat exchanger capable of reducing the temperature of the exhaust flue gas.

In some embodiments, the primary heat exchanger comprises one or more conduits for receiving coolant. The conduit(s) act as a conductor of heat from the exhaust flue gases to the coolant thereby simultaneously cooling the exhaust flue gas and increasing the temperature of the coolant. In some embodiments, the primary heat exchanger comprises a plurality of conduits for receiving coolant. In some embodiments, the primary heat exchanger comprises an array of conduits for receiving coolant.

In some embodiments, the array of conduits forms a labyrinth chamber for receiving the exhaust flue gas. Advantageously, an array of conduits provides a large surface area for contacting the exhaust flue gas in the labyrinth chamber thereby allowing even faster cooling of the exhaust flue gas.

In some embodiments, the conduits comprise a heat tolerant, conducting material. In some embodiments, the conduits comprise a metal or metal alloy. In some embodiments, the metal or metal alloy comprises steel (e.g. stainless steel, austenitic steel or austenitic stainless steel), copper, aluminium and/or titanium.

In some embodiments, the coolant is gaseous nitrogen. In some embodiments, the coolant is gaseous nitrogen extracted from the exhaust flue gas. As used herein, extracted gaseous nitrogen refers to gaseous nitrogen that has been extracted from the exhaust flue gas.

In some embodiments, the coolant is an exogenous coolant. An exogenous coolant may be employed to cool the exhaust flue gas in one or more heat exchangers during initiation of the carbon dioxide extraction process. In some embodiments, the exogenous coolant is used to cool exhaust flue gas until sufficient gaseous nitrogen is extracted from the exhaust flue gas to sufficiently cool the primary and/or secondary heat exchangers e.g. to achieve the desired level of cooling. In some embodiments, the exogenous coolant is used in addition to extracted gaseous nitrogen to cool exhaust flue gas in the primary heat exchanger and/or one or more secondary heat exchangers.

In some embodiments, the primary heat exchanger and/or secondary heat exchangers comprise one or more conduits for receiving exogenous coolant which are separate from the one or more conduits configured to receive extracted gaseous nitrogen. In some embodiments, the apparatus comprises a compressor and an evaporator in fluid communication with the one or more exogenous coolant conduits. In some embodiments, exogenous coolant is circulated through the primary and/or secondary heat exchangers, the compressor and evaporator, Circulation may be automatic or may be manually controlled. In some embodiments, exogenous coolant is circulated through the primary and/or secondary heat exchangers during initiation of the carbon dioxide extraction process. In some embodiments, exogenous coolant is circulated through the primary and/or secondary heat exchangers to increase the rate of cooling of exhaust flue gas by the primary and/or secondary heat exchangers.

The exogenous coolant may be any coolant suitable to cool exhaust flue gas in the primary and/or secondary heat exchangers. In some embodiments, the exogenous coolant is exogenous gaseous nitrogen. In some embodiments, the exogenous coolant is a gas or liquid refrigerant. In some embodiments, the exogenous coolant comprises one or more of fluorocarbon, chlorofluorocarbon (R12), hydrochlorofluorocarbon (R22), hydrofluorocarbon (R410A, R134) freon, ammonia, sulphur dioxide, non-halogenated hydrocarbon, R404A, R407A, R407C, R407F, and R507.

After cooling exhaust flue gas in the primary heat exchanger, coolant comprising extracted gaseous nitrogen is typically vented into the atmosphere.

In some embodiments, the primary heat exchanger comprises a control means for regulating the flow of coolant through the conduit(s). The rate of flow of the coolant determines the rate of cooling of the exhaust flue gas. Increasing the flow of coolant typically increases the rate of cooling of the exhaust flue gas. Reducing the flow of coolant typically reduces the rate of cooling of the exhaust flue gas. The control means may comprise flow sensors. The control means may reduce the flow of coolant in response to reduced flow of exhaust flue gas into the primary heat exchanger. The control means may increase the flow of coolant in response to increased flow of exhaust flue gas into the primary heat exchanger. In some embodiments, the control means is configured to control the flow of extracted gaseous nitrogen through the conduit(s). In some embodiments, the control means is configured to control the flow of exogenous coolant through the one or more exogenous coolant conduits. In some embodiments, the control means comprises a coolant valve configured to control the flow of coolant through the conduit(s). In some embodiments, the coolant valve is a flow control valve.

In some embodiments, the apparatus further comprises an impeller for propelling exhaust flue gas into the primary heat exchanger. The impeller may be any rotatable component capable of propelling exhaust flue gas into the primary heat exchanger. In some embodiments, the apparatus comprises a manifold for housing the impeller.

In some embodiments, the apparatus further comprises means for connecting in fluid communication the primary heat exchanger to the exhaust flue. Typically, the connection means is configured to connect to the exit point of an exhaust flue, i.e. the region of an exhaust flue that releases exhaust flue gas into the environment. In some embodiments, the connecting means is configured to direct exhaust flue gases to ground level, or a subterranean level. In some embodiments, the impeller is situated between the connection means and the primary heat exchanger.

The primary heat exchanger is typically configured to allow a gas flow rate that is the same or higher than the maximum gas flow rate of the exhaust flue during normal operation of the energy generating device to which the exhaust flue is connected, e.g. engine, boiler or power station.

In some embodiments, the apparatus further comprises a gas bypass system for venting excess exhaust flue gas. Typically, the gas bypass system is situated between the primary heat exchanger and the exhaust flue. The gas bypass system provides a regulatory control mechanism to avoid unwanted back pressure on the exhaust flue, e.g. when the flow of exhaust flue gas in the exhaust flue exceeds the maximum flow rate of the apparatus e.g. the maximum flow rate of the primary heat exchanger.

In some embodiments, the gas bypass system comprises a partitioned parallel exhaust chamber with a gaseous flow control mechanism. In some embodiments, the gas bypass system comprises a partitioned parallel exhaust chamber having a modified heat and pressure take-off. Advantageously, a modified heat and pressure take-off ensures that exhaust flue modifications do not compromise the designed operations and efficiency of the energy generating device. In some embodiments, the gas bypass system comprises a unidirectional gas flow valve flap.

In some embodiments, the primary heat exchanger is configured to cool the exhaust flue gas to a temperature of less than -10°C, less than -15T, less than -20T, less than -25T, less than -30°C, less than -35T, less than -40T, less than -45°C, less than -50T, less than -55T, or less than -60T. As used herein, cooled exhaust flue gas refers to exhaust flue gas that has been cooled by the primary heat exchanger.

The apparatus also comprises a primary compressor in fluid communication with the primary heat exchanger for receiving and compressing cooled exhaust flue gas from the primary heat exchanger.

The primary compressor compresses cooled exhaust flue gas from the primary heat exchanger to provide compressed cooled exhaust flue gas.

In some embodiments, the apparatus further comprises one or more secondary heat exchangers for cooling compressed cooled exhaust flue gas from the primary compressor prior to passage of the compressed cooled exhaust flue gas to the carbon dioxide collection vessel.

In some embodiments, the apparatus further comprises one or more secondary compressors for compressing compressed cooled exhaust flue gas from the primary compressor prior to passage of the compressed cooled exhaust flue gas to the carbon dioxide collection vessel.

In some embodiments, the apparatus further comprises: (i) a secondary compressor for receiving and compressing compressed cooled exhaust flue gas from the primary compressor; and (ii) a secondary heat exchanger for receiving and cooling compressed cooled exhaust flue gas from the secondary compressor.

In some embodiments, the apparatus further comprises: (i) a secondary heat exchanger for receiving and cooling compressed cooled exhaust flue gas from the primary compressor; and (ii) a secondary compressor for receiving and compressing compressed cooled exhaust flue gas from the secondary heat exchanger.

In some embodiments, the apparatus further comprises: (i) a secondary heat exchanger for receiving and cooling compressed cooled exhaust flue gas from the primary compressor; (ii) a secondary compressor for receiving and compressing compressed cooled exhaust flue gas from the secondary heat exchanger; and (iii) a tertiary heat exchanger for receiving and cooling compressed cooled exhaust flue gas from the secondary compressor. In this embodiment, during operation the cooled exhaust flue gas from the primary heat exchanger is: (i) compressed by the primary compressor; (ii) cooled by the secondary heat exchanger; (Hi) compressed by the secondary compressor; and then (iv) cooled by the tertiary heat exchanger, prior to passage of the compressed cooled exhaust flue gas to the carbon dioxide collection vessel.

In some embodiments, the secondary heat exchanger is configured to receive and cool compressed cooled exhaust flue gas from both the primary compressor and the secondary compressor. In this embodiment, during operation the cooled exhaust flue gas from the primary heat exchanger is: (i) compressed by the primary compressor; (ii) cooled by the secondary heat exchanger; (iii) compressed by the secondary compressor; and then (iv) cooled by the secondary heat exchanger prior to passage of the compressed cooled exhaust flue gas to the carbon dioxide collection vessel.

The compressor may be any compressor capable of increasing the pressure of a gas. In some embodiments, the primary compressor and/or secondary compressor is a high volume reciprocating compressor or a rotational gas compressor.

As used herein, cooled compressed exhaust flue gas refers to exhaust flue gas that has been cooled in the primary heat exchanger and compressed by the primary compressor. In embodiments comprising a secondary compressor, the term cooled compressed exhaust flue gas also refers to exhaust flue gas that has been cooled in the primary heat exchanger and compressed by both the primary and secondary compressors. The term cooled compressed exhaust flue gas also refers to exhaust flue gas that has been cooled in the primary heat exchanger, compressed by at least the primary compressor, and cooled by one or more secondary heat exchangers.

Heat exchangers for receiving and cooling compressed cooled exhaust flue gas from a compressor may be any heat exchanger capable of reducing the temperature of a gas. In some embodiments, the one or more secondary heat exchangers comprise one or more conduits for receiving coolant. In some embodiments, the one or more secondary heat exchangers comprise an array of conduits for receiving coolant. In some embodiments, the array of conduits forms a labyrinth chamber for receiving the compressed cooled exhaust flue gas from the primary compressor and/or the secondary compressor. In some embodiments, the conduits comprise a heat tolerant, conducting material. In some embodiments, the conduits comprise a metal or metal alloy. In some embodiments, the metal or metal alloy comprises steel (e.g. stainless steel, austenitic steel or austenitic stainless steel), copper, aluminium and/or titanium.

In some embodiments, the coolant is gaseous nitrogen. In some embodiments, the coolant is gaseous nitrogen extracted from the exhaust flue gas. In some embodiments, the coolant is an exogenous coolant. In some embodiments, the exogenous coolant is exogenous gaseous nitrogen.

In some embodiments, the one or more secondary heat exchangers comprise control means for regulating the flow of coolant through the conduit(s). In some embodiments, the control means for regulating the flow of coolant through the conduit(s) of the primary heat exchanger also controls the flow of coolant through the conduit(s) of the one or more secondary heat exchangers.

In some embodiments, the conduit(s) of the primary heat exchanger are in fluid communication with the conduit(s) of the one or more secondary heat exchangers.

In some embodiments, the one or more secondary heat exchanger comprise an impeller for propelling compressed cooled exhaust flue gas into the one or more secondary heat exchangers.

In some embodiments, the primary compressor is configured to compress the exhaust flue gas to at least 1 MPa, at least 2 MPa, at least 3 MPa, at least 4 MPa, at least S MPa, at least 6 MPa, at least 7 MPa, at least 8 MPa, at least 9 MPa, or at least 10 MPa. In some embodiments, the secondary compressor is configured to compress the exhaust flue gas to at least 1 MPa, at least 2 MPa, at least 3 MPa, at least 4 MPa, at least S MPa, at least 6 MPa, at least 7 MPa, at least 8 MPa, at least 9 MPa, or at least 10 MPa. In embodiments wherein the apparatus comprises a primary compressor and a secondary compressor, in some embodiments, the primary compressor is configured to compress the exhaust flue gas to at least 1 MPa, and the secondary compressor is configured to compress the exhaust flue gas to at least 10 MPa.

In some embodiments, the one or more secondary heat exchangers are configured to cool the exhaust flue gas to a temperature of less than 0°C, less than -5°C, or less than -10°C.

The apparatus also comprises a carbon dioxide collection vessel. The carbon dioxide collection vessel comprises: (i) a throttling valve for receiving compressed cooled exhaust flue gas; and (ii) a holding tank for containing solid and/or liquid carbon dioxide.

In some embodiments, the throttling valve is configured to receive compressed cooled exhaust flue gas from the primary compressor. In some embodiments, the throttling valve is configured to receive compressed cooled exhaust flue gas from the secondary compressor. In some embodiments, the throttling valve is configured to receive compressed cooled exhaust flue gas from the one or more secondary heat exchangers.

The throttling valve may be any valve that is capable of changing unilateral flow into turbulent flow. A throttling valve typically comprises an inlet and an outlet. In some embodiments, the cross-sectional area of the throttling valve outlet is at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold, at least 50-fold, at least 60-fold, at least 70-fold, at least 80-fold, at least 90-fold, or at least 100-fold greater than the cross-sectional area of the throttling valve inlet. In some embodiments, the cross-sectional area of the throttling valve outlet is at least 50-fold greater than the cross-sectional area of the throttling valve inlet.

In some embodiments, the carbon dioxide collection vessel comprises a tubular cone extending from the throttling valve outlet wherein the tubular diameter of the cone increases as it extends outwards from the throttling valve.

In some embodiments, the carbon dioxide collection vessel further comprises an outlet for gaseous nitrogen. In some embodiments, the outlet for gaseous nitrogen is in fluid communication with the primary heat exchanger and/or the outlet is in fluid communication with one or more of the secondary heat exchangers. In some embodiments, the outlet is in fluid communication with a gaseous nitrogen storage vessel which is in fluid communication with the primary heat exchanger and/or the one or more secondary heat exchangers. As described in more detail above, the apparatus may comprise a control means for regulating the flow of extracted gaseous nitrogen through the primary heat exchanger and/or through the one or more secondary heat exchangers.

The holding tank is typically configured to accommodate the volumetric space required for the collection of solid and/or liquid carbon dioxide.

In some embodiments, the apparatus is insulated to reduce heat influx from the external environment.

In some embodiments, the apparatus comprises transfer conduits for delivering exhaust flue gas through the apparatus from one component of the apparatus to a subsequent component of the apparatus. In some embodiments, the transfer conduits are insulated. Components of the apparatus include the primary heat exchanger, the primary compressor, and the carbon dioxide collection vessel. Components of the apparatus may also comprise one or more secondary heat exchanger and one or more secondary compressors.

In some embodiments, the apparatus further comprises one or more valves for maintaining unidirectional flow of exhaust flue gas. In some embodiments, the valves are cryogenic non-return check valves. Advantageously, valves prevent thermal bridging and maintain states of matter.

In some embodiments, the apparatus further comprises additional heat exchangers and/or compressors for maintaining the temperature and pressure of the exhaust flue gas within the apparatus.

The invention provides a method for producing solid and/or liquid carbon dioxide from exhaust flue gas, the method comprising: a) delivering exhaust flue gas to a primary heat exchanger to provide cooled exhaust flue gas; b) compressing the cooled exhaust flue gas to provide compressed cooled exhaust flue gas, and optionally delivering the compressed cooled exhaust flue gas to: (i) a secondary heat exchanger and/or (ii) a secondary compressor; and c) throttling the compressed cooled exhaust flue gas through a throttling valve to provide solid and/or liquid carbon dioxide.

In some embodiments, the method of the invention comprises delivering exhaust flue gas to the apparatus of the invention as described above.

In some embodiments, the method further comprises separating gaseous nitrogen from the solid and/or liquid carbon dioxide to provide extracted gaseous nitrogen. The extracted gaseous nitrogen may be collected and stored. In some embodiments, the method comprises supplying the extracted gaseous nitrogen to the primary heat exchanger and/or secondary heat exchanger.

In some embodiments, the method comprises employing an exogenous coolant to cool the exhaust flue gas in the primary heat exchanger during initiation of the carbon dioxide extraction process. In embodiments wherein the apparatus comprises one or more secondary heat exchangers, in some embodiments, the method comprises employing an exogenous coolant to cool the exhaust flue gas in one or more of the secondary heat exchangers during initiation of the carbon dioxide extraction process.

In some embodiments, the exogenous coolant is used to cool exhaust flue gas until sufficient gaseous nitrogen is extracted from the exhaust flue gas to sufficiently cool the primary and/or secondary heat exchangers e.g. to achieve the desired level of cooling. In some embodiments, the exogenous coolant is used in addition to extracted gaseous nitrogen to cool exhaust flue gas in the primary heat exchanger and/or one or more secondary heat exchangers. In some embodiments, the exogenous coolant is exogenous gaseous nitrogen.

In some embodiments, the method comprises regulating the flow of coolant through the primary heat exchanger and/or the secondary heat exchanger. The rate of flow of the coolant determines the rate of cooling of the exhaust flue gas. Increasing the flow of coolant typically increases the rate of cooling of the exhaust flue gas. Reducing the flow of coolant typically reduces the rate of cooling of the exhaust flue gas.

In some embodiments, the primary heat exchanger cools exhaust flue gas to a temperature of less than -10°C, less than -15°C, less than -20°C, less than -25°C, less than -30°C, less than -35°C, less than -40°C, less than -45°C, less than -50°C, less than -55°C, or less than -60°C. In some embodiments, the primary heat exchanger cools exhaust flue gas to a temperature of less than -30°C, optionally less than -40°C.

In some embodiments, the compressing comprises compressing the exhaust flue gas to least 1 MPa, at least 2 MPa, at least 3 MPa, at least 4 MPa, at least 5 MPa, at least 6 MPa, at least 7 MPa, at least 8 MPa, at least 9 MPa, or at least 10 MPa. In some embodiments, compressing comprises compressing the exhaust flue gas to at least 10 MPa. In some embodiments, the compressing comprises compressing the cooled exhaust flue gas more than once. In some embodiments, the method comprises initially compressing the exhaust flue gas to at least 1 MPa and then subsequently compressing the exhaust flue gas to at least 10 MPa.

In some embodiments, the method further comprises delivering compressed cooled exhaust flue gas to a secondary heat exchanger. In some embodiments, the secondary heat exchanger cools the compressed cooled exhaust flue gas to a temperature of less than 0°C, less than -5°C, or less than -10°C.

In some embodiments, the method comprises: (i) compressing the cooled exhaust flue gas; (ii) cooling the compressed cooled exhaust flue gas; (iii) compressing the cooled exhaust flue gas; and then (iv) cooling the compressed cooled exhaust flue gas. In some embodiments, the method comprises: (i) compressing the cooled exhaust flue gas to less than 1 MPa; (ii) cooling the compressed cooled exhaust flue gas to a temperature of less than -10°C; (iii) compressing the cooled exhaust flue gas to less than 10 MPa; and then (iv) cooling the compressed cooled exhaust flue gas to a temperature of less than -10°C.

In some embodiments, the method comprises collecting solid carbon dioxide and allowing it to melt to form liquid carbon dioxide. In some embodiments, carbon dioxide is maintained at a pressure of at least 1 MPa, at least 2 MPa, at least 3 MPa, at least 4 MPa, or at least 5 MPa in the holding tank. In some embodiments, carbon dioxide is maintained at a pressure of 3 MPa in the holding tank. In some embodiments, liquid carbon dioxide is stored in cryogenic pressure vessel equipment.

In some embodiments, the method further comprises converting solid carbon dioxide to carbon dioxide ice. In some embodiments, solid carbon dioxide is converted to carbon dioxide ice by hydraulic pressing.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures which are not drawn to scale.

Figure 1 provides a schematic representation of an exemplary apparatus according to the invention comprising primary heat exchanger, primary compressor, and carbon dioxide collection vessel.

Figure 2 provides a schematic representation of another exemplary apparatus according to the invention comprising primary heat exchanger, primary compressor, secondary heat exchanger, and carbon dioxide collection vessel.

Figure 3 provides a schematic representation of another exemplary apparatus according to the invention comprising primary heat exchanger, primary compressor, secondary compressor, and carbon dioxide collection vessel.

Figure 4 provides a schematic representation of another exemplary apparatus according to the invention comprising primary heat exchanger, primary compressor, secondary heat exchanger, secondary compressor, tertiary heat exchanger, and carbon dioxide collection vessel.

An exemplary apparatus according to the invention is shown in Figure 1. The apparatus of the invention comprises a primary heat exchanger 10, a primary compressor 20, and a carbon dioxide collection vessel 30 comprising a throttling valve 32 and a holding tank 36. The apparatus may comprise means 12 for connecting to an exhaust flue. The apparatus may further comprise an impeller 14 for propelling exhaust flue gas into the primary heat exchanger 10. The carbon dioxide collection vessel 30 may comprise an outlet 34 for extracting gaseous nitrogen, and a gaseous nitrogen transfer conduit 40 in fluid communication with the primary heat exchanger 10.

The apparatus of Figure 2 comprises all features of the apparatus of Figure 1 and additionally comprises a secondary heat exchanger 60 for receiving and cooling compressed cooled exhaust flue gas from the primary compressor 20 prior to transfer of the compressed cooled exhaust flue gas to the throttling valve 32. In this embodiment, the gaseous nitrogen transfer conduit 40 may also be in fluid communication with the secondary heat exchanger 60.

The apparatus of Figure 3 comprises all features of the apparatus of Figure 1 and additionally comprises a secondary compressor 25 for receiving and compressing compressed cooled exhaust flue gas from the primary compressor 20 prior to transfer of the compressed cooled exhaust flue gas to the throttling valve 32.

The apparatus of Figure 4 comprises the features of the apparatus of Figure 1 and additionally comprises: a secondary heat exchanger 60 for receiving and cooling compressed cooled exhaust flue gas from the primary compressor 20; a secondary compressor 25 for receiving and compressing compressed cooled exhaust flue gas from the secondary heat exchanger 60; and a tertiary heat exchanger 65 for receiving and cooling compressed cooled exhaust flue gas from the secondary compressor 25. In this embodiment, the gaseous nitrogen transfer conduit 40 may also be in fluid communication with the secondary heat exchanger 60 and/or tertiary heat exchanger 65.

Transfer conduits 50-58 are for transferring exhaust flue gas through the apparatus as depicted in Figures 1-4.

Specific example

The invention will now be described with reference to the following non-limiting example.

Exhaust flue gases may be redirected from the exhaust flue exit point that connects with the open-air environment, such as the above ground open air exit of a chimney into the lower atmosphere between 20 and 100 metres above ground level. The exhaust flue exit may be adapted to connect to a connection means, e.g. tubing comprising a 180° bend, to redirect exhaust flue gases towards the primary heat exchanger which may be at ground level. This downward directional tubing may connect to a manifold housing an internal impeller for propelling exhaust flue gases into the primary heat exchanger, optionally into a labyrinth chamber of the primary heat exchanger. This downward directional tubing may connect directly to the primary heat exchanger. The primary heat exchanger may comprise a labyrinth chamber comprising a network array matrix of interconnecting channels and tubing that inter-collectively contain a series of pressure vessel conduits acting as a large heat exchanger for the transport of a coolant, e.g. cold and vented gaseous nitrogen. This cold, gaseous nitrogen does not typically come into direct contact with the exhaust flue gases. The pressure vessel tubing of the conduits acts as a conductor of heat from the exhaust flue gases into the coolant, e.g. the gaseous nitrogen, thereby heating the coolant and simultaneously cooling the exhaust flue gases in the heat exchange chiller labyrinth. The exhaust flue gases may be cooled to a temperature of at least -40°C. Gaseous nitrogen may be allowed to cool and vented to the atmosphere after flowing through the conduits of the primary heat exchanger.

Control over the temperature of the exhaust flue gases in the primary heat exchanger may be performed by control means configured to control the rate of flow of the cold gaseous nitrogen in the heat exchange chiller labyrinth. Increasing the rate of flow of cold gaseous nitrogen cools the exhaust flue gases quicker and slowing the rate of flow of cold gaseous nitrogen helps prevent the exhaust flue gases cooling down below the desired temperature, e.g. -40°C. Flow rate may be controlled by flow sensors in the cold gaseous nitrogen pumping system. The size of the heat exchange chiller labyrinth is typically designed to match the known maximum gas flow rate obtained from the exhaust flue during functional operation of the engine, boiler or coal-fired power station, so that the thermodynamic heat fluxes of the two temperature regimes are synchronised to accommodate from the known temperature of the gases upon leaving the original chimney design until exiting the heat exchange chiller labyrinth system. Typically, this may result in a temperature drop from between 50°C and 90°C to between -10°C and -40°C, ideally at least -30°C, or preferably at least -40°C.

The main function of chilling the exhaust flue gases is to prepare the gases for phase change. The heat exchange chiller labyrinth itself does not initiate the phase change -it changes the temperature of the gases but not the pressure. As such, the exhaust flue gases are typically cooled to a temperature of -40°C and remain in gaseous state at the point of leaving the primary heat exchanger. As the cooled exhaust flue gases leave the primary heat exchanger, the external surface of the transfer conduits that deliver cooled exhaust flue gases through the apparatus are typically insulated to ensure that the gases remain at their cooled temperature throughout their transitionary passage to formation of primarily solid carbon dioxide and secondarily liquid carbon dioxide.

Upon leaving the heat exchange chiller labyrinth, the cooled exhaust flue gas is typically delivered via transfer conduit(s) to a primary compressor. The primary compressor may compress the exhaust flue gases from approximately 10 KPa to approximately 1 M Pa. After primary stage compression, exhaust flue gases may be partially warmed as a result of a reduction in their volume during the compression process. Exhaust flue gases may then be chilled back to about -10°C in a secondary heat exchanger. The compressed cooled exhaust flue gas may then be compressed by a secondary compressor to compress the compressed cooled exhaust flue gas from approximately 1 M Pa to 10 MPa. Compressed cooled exhaust flue gases may then be chilled back to -10°C via exposure to the same secondary heat exchanger or a tertiary heat exchanger.

Compressed cooled exhaust flue gases typically contain multiphase flow of gaseous nitrogen, as well as chilled gaseous carbon dioxide. Other majority contaminants from coal-fired power station may have previously been removed using a flue gas desulphurisation cleaning process for removal of 50x, prior to delivery of the exhaust flue gas to the primary heat exchanger, thus ensuring that most of the gases in the apparatus comprise gaseous nitrogen and carbon dioxide. This cold gas mixture may be maintained within the system by means of placement of cryogenic non-return check valves in unidirectional flow. Check valves may help to prevent thermal bridging and maintain states of matter. Optionally, adjacent and strategically placed heat exchangers and/or maintenance compressors may be present to ensure that during transit of the exhaust flue gases through the apparatus, the temperature and pressure of the gas is maintained.

The compressed cooled exhaust flue gas is delivered to a throttling valve. The throttling valve acts to change unilateral liquid flow into turbulent flow. In the throttling valve there is typically an adiabatic drop due to the pressure drop with increased gas velocity. Simultaneously, upon ejection of the compressed cooled exhaust flue gas from the throttling valve, the tubular aperture may be significantly increased, e.g. at least 50-fold, so that the cross-sectional area of the compressed cooled exhaust flue gas before the throttling valve is significantly smaller than the cross-sectional area, e.g. 1/50 of the cross-sectional area, of the venting tube after the throttling valve. Simultaneously, the exit from the throttling valve may extend in a tubular cone orientation as the output end of the contents of throttling valve of the compressed cooled exhaust flue gas extend into the larger aperture holding chamber. The tubular cone extension on the output side of the throttling valve may act to create cyclonic turbulent flow and a sudden drop in pressure, with a simultaneous drop in temperature. This typically creates the phase change formation from gaseous cold carbon dioxide into a deposition phase transition, or reverse sublimation process into solid carbon dioxide 'snow' at a temperature below -78°C and mixed with cold gaseous nitrogen. The cold gaseous nitrogen may be vented, collected and pumped for reverse passage through the primary and/or secondary heat exchangers. The holding tank is typically designed to accommodate the volumetric space required for the input of solid carbon dioxide 'snow', so that its accumulation can readily be melted from solid carbon dioxide 'snow' into liquid carbon dioxide. The entire cooled zone from the primary heat exchanger through to the carbon dioxide collection vessel may be insulated to prevent heat influx from the external environment. The liquid carbon dioxide product may be stored using conventional cryogenic pressure vessel equipment of either tank or bulk storage systems, and transported to pertinent markets worldwide. Alternatively, hydraulic pressing may be used as a functional methodology to change the form of solid crystalline carbon dioxide snow into compressed carbon dioxide ice, or dry ice.

The apparatus may comprise a gas bypass system for venting excess exhaust flue gas, wherein the gas bypass system is situated between the primary heat exchanger and the exhaust flue. The purpose of the gas bypass system is to act as a regulatory control mechanism, coupling to the exhaust flue and preceding placement of the primary heat exchanger described herein. The gas bypass system simultaneously avoids unwanted back pressure on the engine or boiler, allowing smooth, continuous and uninterrupted flow of exhaust flue gases from the engine or boiler, thereby ensuring that the regulatory control feedback mechanism for the temperature and pressure of the engine or boiler is functional. The exhaust flue gas bypass system may be constructed as a partitioned parallel exhaust chamber with a warmer than ambient temperature internal gaseous flow control mechanism. The secondary partitioned parallel exhaust chamber may have a modified heat and pressure take-off ensuring that exhaust flue modifications do not compromise or have any effects on the designed operations and efficiency of the engine or boiler by means of a unidirectional gas flow valve flap.

Claims

Claims 1. An apparatus for extracting solid and/or liquid carbon dioxide from exhaust flue gas, the apparatus comprising: a) a primary heat exchanger for receiving and cooling the exhaust flue gas; b) a primary compressor in fluid communication with the primary heat exchanger for receiving and compressing cooled exhaust flue gas from the primary heat exchanger; and c) a carbon dioxide collection vessel in fluid communication with the primary compressor, wherein the carbon dioxide collection vessel comprises: (i) a throttling valve for receiving compressed cooled exhaust flue gas from the primary compressor; and (ii) a holding tank for containing solid and/or liquid carbon dioxide.
2. The apparatus of claim 1 further comprising one or more secondary heat exchangers for receiving and cooling compressed cooled exhaust flue gas from the primary compressor prior to passage of the compressed cooled exhaust flue gas to the carbon dioxide collection vessel.
3. The apparatus of claim 1 or claim 2, wherein the carbon dioxide collection vessel further comprises an outlet for gaseous nitrogen, wherein the outlet is in fluid communication with the primary heat exchanger and/or the outlet is in fluid communication with one or more of the secondary heat exchangers.
4. The apparatus of any preceding claim further comprising means for connecting in fluid communication the primary heat exchanger and the exhaust flue.
5. The apparatus of any preceding claim further comprising a gas bypass system for venting excess exhaust flue gas, wherein the gas bypass system is situated between the primary heat exchanger and the exhaust flue.
6. The apparatus of any preceding claim, wherein the primary heat exchanger comprises an array of conduits for receiving gaseous nitrogen from the carbon dioxide collection vessel.
7. The apparatus of claim 6, wherein the array of conduits forms a labyrinth chamber for receiving the exhaust flue gas.
8. The apparatus of any of claims 2-7, wherein the secondary heat exchanger comprises an array of conduits for receiving gaseous nitrogen from the carbon dioxide collection vessel.
9. The apparatus of claim 8, wherein the array of conduits forms a labyrinth chamber for receiving the compressed cooled exhaust flue gas.
10. The apparatus of any preceding claim further comprising an impeller for propelling the exhaust flue gas into the primary heat exchanger.
11. The apparatus of any preceding claim further comprising one or more impellers for propelling the compressed cooled exhaust flue gas into one or more of the one or more secondary heat exchangers.
12. The apparatus of any preceding claim further comprising a secondary compressor for receiving and compressing compressed cooled exhaust flue gas from the primary compressor.
13. The apparatus of any preceding claim, wherein one or more of the one or more secondary heat exchangers is situated between the primary compressor and the secondary compressor.
14. The apparatus of any preceding claim, wherein one or more of the one or more secondary heat exchangers is situated between the secondary compressor and the carbon dioxide collection vessel.
15. The apparatus of any preceding claim, wherein: (a) one or more of the secondary heat exchangers is situated between the primary compressor and the secondary compressor; and (b) one or more of the secondary heat exchangers is situated between the secondary compressor and the carbon dioxide collection vessel.
16. The apparatus of any preceding claim, wherein the apparatus comprises one or more valves for maintaining unidirectional flow of exhaust flue gas.
17. A method for producing solid or liquid carbon dioxide from exhaust flue gas, the method comprising: a) delivering exhaust flue gas to a primary heat exchanger to provide cooled exhaust flue gas; b) compressing the cooled exhaust flue gas to provide compressed cooled exhaust flue gas, and optionally delivering the compressed cooled exhaust flue gas to a secondary heat exchanger; and c) throttling the compressed cooled exhaust flue gas through a throttling valve to provide solid and/or liquid carbon dioxide.
18. The method of claim 17, wherein the method further comprises separating gaseous nitrogen from the solid and/or liquid carbon dioxide and supplying the separated gaseous nitrogen to the primary and/or secondary heat exchanger.
19. The method of claim 17 or claim 18, wherein the cooling comprises reducing the temperature of the gas to less than -10°C.
20. The method of any of claims 17-19, wherein the compressing comprises compressing the gas to at least 1 MPa.
21. The method of any of claims 17-20, wherein the method further comprises converting solid carbon dioxide to carbon dioxide ice by hydraulic pressing.