Technical field

The invention relates to methods and systems for upgrading burning facilities. More accurately, the invention relates to a method for upgrading an existing burning facility for oxygen combustion.

Background

Conventional burning facilities, such as heat and/or power plant boilers, are designed for combustion of fuel using air as an oxidant, releasing carbon dioxide (CO2) and nitrogen oxides (NO _X ) into the atmosphere. These gases are known for their greenhouse effect, and thus it is of crucial importance to eliminate their emissions.

The conventional methods for carbon capture from flue gases typically rely on amine scrubbing, adsorption processes or membrane filtering, all of which are complicated, expensive, and energy-consuming processes. The conventional methods lower the net power produced e.g., by a power plant.

Oxygen combustion is presented as a solution against nitrogen oxide emissions. However, using conventional technologies, oxygen combustion facilities are expensive to build, to run and to maintain. One challenge lies in the composition of the oxidant itself. Air comprises ca. 21 vol-% of oxygen and ca. 78 vol-% nitrogen of the total air volume. Thus, replacing air with pure oxygen would lead to an increase in oxygen concentration inside the burning facility from 21 vol-% to 100 vol-%, leading to uncontrollable combustion and possibly to an explosion, or at least to melting of the structures of the burning facility.

There is a large number of existing burning facilities that may be upgraded for oxygen combustion. Thus, simple, cost-effective methods for upgrading without a need for major modifications to the burning facility itself are needed. Summary

An object of the present invention is to provide a simple way to upgrade an existing burning facility for oxygen combustion that does not require major modifications to the burning facility.

The object is attained with the invention having the characteristics presented below in the independent claims. Some preferable embodiments are disclosed in the dependent claims.

The features recited in the dependent claims and the embodiments in the description are mutually freely combinable unless otherwise explicitly stated. The exemplary embodiments presented in this text and their advantages relate by applicable parts to all aspects of the invention, both the system and the method, even though this is not always separately mentioned.

An aspect of the present invention is a method for upgrading a burning facility. The method comprises the following steps: connecting a gas mixer to an exhaust line of the burning facility at a first position located upstream from a second position in a direction of flow of a flue gas of the burning facility for forming an output gas based on a mixture of the flue gas received by the gas mixer at the first position and the second position; connecting a wet scrubber between the first position and the second position; connecting an oxygen dilution equipment to the burning facility; and connecting an output of the gas mixer to the oxygen dilution equipment connected to the burning facility.

In a second aspect, the invention provides a system comprising a burning facility, an oxygen dilution equipment, a wet scrubber connected to an exhaust line of the burning facility, and a gas mixer. The oxygen dilution equipment is configured to feed diluted oxygen to the burning facility. The wet scrubber is configured to obtain dry flue gas from wet flue gas received from the exhaust line. The gas mixer is configured to form an output gas based on a mixture of the dry flue gas and the wet flue gas. The gas mixer is connected to the wet scrubber for receiving dry flue gas and to the exhaust line for receiving wet flue gas. The gas mixer is further connected to the oxygen dilution equipment for feeding the output gas to the oxygen dilution equipment for diluting oxygen received by the oxygen dilution equipment.

In a third aspect, the invention provides a method comprising: treating, by a wet scrubber, wet flue gas from a burning facility, into dry flue gas; forming, by a gas mixer, an output gas based on a mixture of the dry flue gas and the wet flue gas; feeding, by the gas mixer, the output gas to an oxygen dilution equipment connected to the burning facility; feeding, by the oxygen dilution equipment, oxygen diluted by the output gas from the gas mixer to the burning facility.

The present invention provides a simple method and system for upgrading an existing burning facility for oxygen combustion. An advantage of the invention is that existing burning facilities can be converted for oxygen combustion with simple and cost-efficient instrumentation. No major changes in the internal structure of the burning facility are necessary, and even the combustion profile of the burning facility can be maintained.

A further advantage of the present invention is that NO _X emissions resulting from conventional combustion using air may be eliminated.

Another advantage of the oxygen combustion over conventional air combustion is an improved energy efficiency of the combustion process. Temperature of nitrogen increases in the burning facility, resulting in a heat loss. Using oxygen instead of air as an oxidant, the heat loss associated with flow-through nitrogen in the burning facility is eliminated, resulting in an improved efficiency.

A yet another advantage of the present invention is that carbon dioxide emissions from burning facilities may be drastically reduced or even completely eliminated without complicated and expensive external carbon capture equipment. Brief description of the drawings

Figure 1 presents a system according to an embodiment of the invention,

Figure 2 presents a method for oxygen combustion according to the invention, and

Figure 3 presents a method for upgrading a burning facility according to the invention.

Detailed description

In this application, the following reference numerals will be used:

100 system

101 burning facility

102 synthetic fuel production facility

103 hydrogen production facility

104 oxygen dilution equipment

105 carbon dioxide refining equipment

106 wet scrubber

107 first control device

108 exhaust line

109 second control device

110 gas mixer

112 heat exchanger

114 oxygen production facility

202-208 steps of Fig. 2

302-306 steps of Fig. 3

According to the invention, the system comprises a burning facility 101. The burning facility 101 is configured to produce a CO2-rich flue gas based on the combustion of fuel at the burning facility 101 using oxygen.

In the present examples, combustion of fuel at the burning facility is performed using combustion gas formed based on oxygen that is diluted with recirculated flue gas. The combustion process produces CO2, whereby total amount of CO2 in the combustion gas is lower than that in flue gas of the burning facility, i.e., wet flue gas. Therefore, the total amount of CO2 in the flue gas of the burning facility is higher than the CO2 content in the combustion gas. Moreover, the flue gas of the burning facility may have also a high CO2 content with respect to burning facilities, where fuel is combusted using air, where CO2 content in the dry flue gas is typically in the range of 10-20 vol-%. Therefore, the flue gas of the burning facility in the present examples may be referred to CO2-rich flue gas.

The present invention can be utilized in various different burning facilities. Suitable burning facilities may be power plant furnaces or boilers, as well as industrial plant furnaces. In certain embodiments, the burning facility may be a heat plant boiler, a power plant boiler, a combined heat and power plant (CHP) boiler, a fluidized bed boiler, a recovery boiler, a rotary kiln, a cement kiln or a lime kiln.

In certain embodiments, the fuel is a fossil fuel, such as a crude oil distillate, coal or lignite, natural gas or shale gas. In other, preferred embodiments, the fuel is a renewable fuel, preferably a biofuel, more preferably a solid fuel or biomass fuel, such as sugar-producing crops, starch-producing crops, oil- producing crops, wood-based fuel. Suitable solid fuels or biomass fuels may originate from, e.g., grass, bagasse, sugarcane, corn, rapeseed, palm, straw, hardwood, softwood, bark, or any combination thereof. In an embodiment, the fuel is a solid wood-based biomass fuel, such as bark. In other embodiments, the fuel is a waste-based fuel, preferably solid or gaseous industrial or municipal waste, such as gas from animal waste, landfill gas, gas from coal mines, sewage gas, or combustible industrial waste gas. In other embodiments, the fuel may comprise fossil fuel, renewable fuel, waste-based fuel, or any combination thereof. An advantage of the present invention is that the burning facility may be operated on full capacity irrespective of fuel characteristics. Especially with biofuels, water content of the fuel varies depending on source and season. The design of burning facilities is typically based on a certain water content of the fuel. When using fuel with a high water content, capacity of the burning facility has to be reduced due to the limited allowed pressure drop in the exhaust line of the burning facility. With the oxygen combustion combined with circulation of flue gas as the oxygen diluent, composition of the flue gas can be optimized to compensate for this limitation, thus maintaining full capacity of the plant even with wet fuel. In certain embodiments, the oxygen used for combustion at the burning facility 101 is produced at an oxygen production facility 114. The oxygen production facility is configured to feed the produced oxygen to the burning facility. The oxygen production facility can be any facility, equipment, or reaction vessel capable of producing oxygen as a product of a chemical reaction using suitable reactants. The oxygen may be produced e.g., by air separation, such as cryogenic distillation, pressure swing adsorption, membrane separation; or oxygen evolution, such as electrolysis or chemical oxygen generation. In a preferred embodiment, the oxygen production facility is a water electrolysis equipment.

According to the invention, the burning facility comprises an oxygen dilution equipment 104. The oxygen dilution equipment 104 is used to feed diluted oxygen to the burning facility 101. Especially in burning facilities designed for air combustion, dilution of the oxygen is of essential importance. Too high oxygen content in the burning facility 101 may increase the temperature inside the burning facility to such an extent that may destroy the burning facility. In a fluidized bed boiler, for example, feeding pure oxygen would probably melt the bed. With the use of oxygen dilution equipment 104, oxygen may be diluted with the output gas generated at the gas mixer 110.

The burning facility 101 may simultaneously be used to generate electric power and/or heat; and/or to host a chemical reaction. The flue gas is generated as a by-product at the burning facility 101 . The advantage of oxygen combustion compared to air combustion is that no nitrogen is present in the burning facility. With no nitrogen passing through the combustion process, the generated flue gas has a considerably higher concentration of carbon dioxide compared to flue gas generated at air combustion. Another advantage of oxygen combustion compared to conventional air combustion is that no nitrogen oxides are generated. According to the invention, oxygen is used for combustion of fuel at the burning facility 101. Typically, oxygen is used in a stoichiometric excess compared to the fuel to ensure a complete combustion. Characteristics of the used fuel may invoke a need for the stoichiometric excess. For example, a higher oxygen excess is needed for wood fuel with a high moisture content (“wet wood”) compared to fuel with a low moisture content. If the oxygen excess is too low, or if oxygen is present in less than stoichiometric ratio to the fuel, the combustion will be incomplete, producing harmful carbon monoxide and/or elemental carbon. An oxygen excess too high, on the other hand, may affect the combustion balance in the burning facility. In a typical combustion process, the oxygen excess may be e.g., 1- 10 % by volume, preferably 2-5 % by volume, calculated from the total volume of the dry flue gas produced upon combustion.

In certain embodiments, the system comprises a first control device 107 operatively connected to the oxygen dilution equipment 104 and the burning facility 101 . The first control device 107 is configured to measure one or more operational characteristics of the burning facility 101 and/or the exhaust line 108. The one or more operational characteristics, such as pressure, temperature, flow rate of combustion gas, carbon monoxide concentration, oxygen concentration, or any combination thereof, may be measured at one or more points within burning facility 101 and/or at the exhaust line 108. Preferably, the one or more operational characteristics are measured at multiple points within the burning facility 101 and/or at the exhaust line 108 to create a combustion profile for the burning facility 101. The measurements provide controlling operation of the system, e.g., the combustion.

According to the invention, the system 100 comprises a wet scrubber 106 connected to an exhaust line 108 of the burning facility 101 for obtaining dry flue gas from wet flue gas received from the exhaust line. Typical scrubbing liquids in wet scrubbers may be selected from water, aqueous solutions of sodium hydroxide, calcium hydroxide, sodium carbonate, or any combination thereof. In an embodiment, the wet scrubber 106 is a water scrubber, and the scrubbing liquid is water.

In an example, the wet scrubber 106 may be structurally integrated into the burning facility 101 , or it can be a stand-alone equipment. In an example, the wet scrubber is integrated into the burning facility for example, when the exhaust line is fixed to the wet scrubber for conducting at least a part of the flue gas through the wet scrubber. On the other hand, the wet scrubber may be a stand-alone equipment, when the wet scrubber can be detached from the exhaust line without a service break of the burning facility.

The wet scrubber 106 functions as a carbon capture equipment in the system. Thus, the need of an external carbon capture equipment is completely eliminated. The wet C02-rich flue gas received from the exhaust line 108 of the burning facility 101 may be lead through the wet scrubber 106 to obtain dry CO2-rich flue gas. The dry CC>2-rich flue gas comprises at least 70 % by volume, preferably at least90 % by volume carbon dioxide (CO2), of the total volume of the dry CO2-rich flue gas. The dry CO2-rich flue gas may comprise 70-100% by volume, preferably 80-99% by volume, more preferably 90-99% by volume, such as 95-98% by volume carbon dioxide (CO2), of the total volume of the dry CO2-rich flue gas. The dry CO2-rich flue gas may also comprise less than 10% by volume, preferably less than 5% by volume, such as 1-10% or 2-5% by volume oxygen, of the total volume of the dry CCh-rich flue gas, due to the oxygen excess at the combustion. The dry CO2-rich flue gas also comprises a minor water vapour content according to a dew point at the gas temperature. The dry CO2-rich flue gas may also comprise trace amounts of other elements or compounds originating from the fuel, such as nitrogen, sulphur and/or their oxides.

In certain embodiments, the system 100 further comprises a carbon dioxide refining equipment 105 configured to remove traces of nitrogen, sulphur and/or their oxides, and/or oxygen from the dry CO2-rich flue gas. The carbon dioxide refining equipment is typically located downstream of the wet scrubber 106. When the dry CO2-rich flue gas is treated with the refining equipment 106 to remove traces of nitrogen, sulphur and/or their oxides, and/or oxygen, essentially pure carbon dioxide is obtained. After refining, the dry CO2-rich flue gas comprises at least 99% by volume, such as 99-100% by volume CO2, of the total volume of the dry CO2-rich flue gas.

According to the invention, the system 100 comprises a gas mixer 110. The gas mixer 110 forms an output gas based on a mixture of the dry CO2-rich flue gas and the wet CO2-rich flue gas. The gas mixer 110 is connected to the wet scrubber 106 for receiving the dry CO2-rich flue gas and to the exhaust line 108 for receiving the wet CO2-rich flue gas. With the use of the gas mixer 110, output gas comprising CO2, water, and possibly trace amounts of nitrogen, sulphur and/or their oxides, and oxygen, with a highly controllable water content may be generated. In certain embodiments, the gas mixer 110 may be placed downstream of the carbon dioxide refining equipment 105. In this example, trace amounts of nitrogen, sulphur and/or their oxides, and oxygen are removed from the gas stream before entering the gas mixer 110. Thus, the gas mixer 110 generates output gas consisting essentially of CO2 and water, with a highly controllable water content.

According to the invention, the gas mixer 110 is connected to the oxygen dilution equipment 104. Thus, the output gas from the gas mixer 110 may be fed to the oxygen dilution equipment 110. The oxygen dilution equipment 104 then dilutes the oxygen received from the oxygen production facility 114 using the output gas generated at the gas mixer. The advantage of the connection between the gas mixer 110 and oxygen dilution equipment 104 lies in the circulation of the flue gas back to the burning facility 101 as the oxygen diluent. The output gas, originating from the flue gas of the burning facility 101 , consists entirely of combustion products. Therefore, the output gas is an inert oxygen diluent that does not react at the combustion. Compared to conventional air oxidant, the oxygen diluted with the output gas does not produce any nitrogen oxides at the combustion. The oxygen content in a combustion chamber of the burning facility 101 can be precisely determined by determining the ratio of the output gas to the oxygen at the oxygen dilution equipment 104.

In certain embodiments, the system comprises a second control device 109 operatively connected to the gas mixer 110. The second control device controls a volume ratio of wet flue gas to dry flue gas for forming the output gas at the gas mixer. The volume ratio of wet flue gas to dry flue gas at the gas mixer 110 may be varied according to different needs. The volume ratio of wet flue gas to dry flue gas may vary from 100:0 to 0:100 [vol-%:vol-%], such as 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, or 0:100 [vol-%:vol-%]. In an example, the volume ratio of wet flue gas to dry flue gas may be controlled based on a combustion temperature of the burning facility. The combustion temperature may be increased or decreased based on adjusting the ratio.

In certain embodiments, the second control device 109 is configured to control the volume ratio of wet flue gas to dry flue gas at the gas mixer 110 for forming the output gas based on determining a need to control a combustion temperature of the burning facility 101 . The wet scrubbing process decreases the temperature of the flue gas. Thus, in case the temperature of the burning facility 101 needs to be decreased, a larger amount of dry flue gas may be used to form the output gas, and the volume ratio of wet flue gas to dry flue gas may be 50:50, 40:60, 30:70, 20:80, 10:90 or 0:100 [vol-%:vol-%]. On the other hand, leading the hot, wet flue gas back to the burning facility 101 keeps the temperature decrease at the burning facility 101 to a minimum. Thus, if needed, the volume ratio of wet flue gas to dry flue gas may be 100:0, 90:10, 80:20, 70:30, 60:40, or 50:50 [vol-%:vol-%]. In an example, the volume ratio of wet flue gas to dry flue gas may be controlled based on temperature measurements of combustion temperature of the burning facility. If the combustion temperature is determined to be too low, a proportion of the wet flue gas may be increased. If the combustion temperature is determined to be too high, a proportion of the dry flue gas may be increased.

In certain embodiments, the second control device 109 is configured to control the volume ratio of wet flue gas and dry flue gas at the gas mixer for forming the output gas based on determining a need to feed dry flue gas to a synthetic fuel production facility 102. It may be beneficial to keep the volume ratio of wet flue gas to dry flue gas towards a majority of dry flue gas, e.g., 50:50, 40:60, 30:70, 20:80, 10:90, or even 0:100 [vol-%:vol-%]. In an example, the need to feed dry flue gas to a synthetic fuel production facility 102 may be determined based on an amount of dry flue gas. A part of the dry flue gas is used by the gas mixer to form excess output gas. If it is determined that there is excess dry flue gas that is not fed to the gas mixer, the excess dry flue gas may be fed to the synthetic fuel production facility 102.

The invention provides a method for oxygen combustion in an upgraded burning facility. The method comprises a step of treating wet flue gas from the burning facility 101 by a wet scrubber 106 into dry flue gas. The wet scrubber treatment effectively removes moisture from the flue gas, functioning therefore as a carbon capture step in the process. Thus, an external carbon capture step is completely avoided in the method.

In certain embodiments, the method comprises a step wherein at least a part of the dry flue gas is fed to a synthetic fuel production facility 102 by the wet scrubber 106. The synthetic fuel production facility 102 may convert carbon dioxide contained in the flue gas into a synthetic fuel in a chemical reaction. The synthetic fuel may be selected from low-molecular weight aliphatic hydrocarbons or alcohols, such as methane, methanol, ethane, ethanol, propane, propanol, butane, butanol, or biodiesel. Synthetic fuels may be used, e.g., as a traffic fuel, for transportation or shipping purposes.

The method for oxygen combustion in the upgraded burning facility according to the invention further comprises steps of

- treating 202, by a wet scrubber 106, wet flue gas from a burning facility 101 , into dry flue gas;

- forming 204, by a gas mixer, an output gas based on a mixture of the dry flue gas and the wet flue gas;

- feeding 206, by the gas mixer, the output gas to an oxygen dilution equipment 104 connected to the burning facility 101 ;

- feeding 208, by the oxygen dilution equipment 104, oxygen diluted by the output gas form the gas mixer, to the burning facility 101 .

The output gas, being a mixture of the dry flue gas and wet flue gas, comprises CO2, water, and possibly trace amounts of nitrogen, sulphur and/or their oxides, and oxygen. The water content may be determined to a high accuracy using the gas mixer. The output gas is fed to the oxygen dilution equipment to dilute the oxygen used for combustion, and further back to the burning facility. The output gas originates entirely from the combustion process, making it an inert oxygen diluent. Thus, the output gas does not interfere with the combustion process, resulting in clean combustion and well-known flue gas composition. For example, nitrogen oxides (NO _X ) are drastically decreased or even completely eliminated using the method of the invention.

In an embodiment, the method comprises feeding, by the wet scrubber 106, at last a part of the dry flue gas to a synthetic fuel production facility 102. In an example, a part of the dry flue gas may be fed to the gas mixer 110 and a part of the dry flue gas may be fed to the synthetic fuel production facility 102. In this way efficient utilization of the dry flue gas may be supported.

In certain embodiments, the method further comprises the steps of

- measuring one or more operational characteristics of the burning facility 101 and/or the exhaust line 108; and controlling dilution of oxygen received by the oxygen dilution equipment 104 based on the measured one or more operational characteristics of the burning facility 101 and/or the exhaust line 108.

Controlling the oxygen dilution enables a precise regulation of the combustion process at the burning facility 101. In an optimal situation, the combustion profile of the burning facility may be maintained identical to conventional combustion with air. Thus, no technical modifications to the burning facility 101 itself are necessary. In an example, the measured one or more operational characteristics of the burning facility 101 and/or the exhaust line 108 may be obtained by temperature measurements, pressure measurements and/or measurements of content of flue gas.

In certain embodiments, the method further comprises a step of controlling a volume ratio of wet flue gas to dry flue gas at the gas mixer 110 for forming the output gas. The volume ratio of wet flue gas to dry flue gas may vary from 100:0 to 0:100 [vol-%:vol-%], such as 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, or 0:100 [vol-%:vol-%]. In an example, the ratio may be controlled by a control device. In an example, the volume ratio of wet flue gas to dry flue gas may be controlled based on a combustion temperature of the burning facility. The combustion temperature may be increased or decreased based on adjusting the ratio.

In certain embodiments, the volume ratio of wet flue gas to dry flue gas at the gas mixer 110 for forming the output gas is determined based on determining a need to control a combustion temperature of the burning facility 101 . The wet scrubbing process decreases the temperature of the flue gas. Thus, in case the temperature of the burning facility 101 needs to be decreased, a larger amount of dry flue gas may be used to form the output gas, and the volume ratio of wet flue gas to dry flue gas may be 50:50, 40:60, 30:70, 20:80, 10:90 or 0:100 [vol-%:vol-%]. On the other hand, leading the hot, wet flue gas back to the burning facility 101 keeps the temperature decrease at the burning facility 101 to a minimum. Thus, if needed, the volume ratio of wet flue gas to dry flue gas may be 100:0, 90:10, 80:20, 70:30, 60:40, or 50:50 [vol-%:vol-%]. In an example, the volume ratio of wet flue gas to dry flue gas may be controlled based on temperature measurements of combustion temperature of the burning facility. If the combustion temperature is determined to be too low, a proportion of the wet flue gas may be increased. If the combustion temperature is determined to be too high, a proportion of the dry flue gas may be increased.

In certain embodiments, the volume ratio of wet flue gas to dry flue gas at the gas mixer 110 for forming the output gas is determined based on a need to feed dry flue gas to the synthetic fuel production facility 102. The synthetic fuel production facility 102 may require dry CO2 for an efficient reaction. Thus, it may be beneficial to keep the volume ratio of wet flue gas to dry flue gas towards a majority of dry flue gas, e.g., 50:50, 40:60, 30:70, 20:80, 10:90, or even 0:100 (vol-%:vol-%). In an example, the need to feed dry flue gas to a synthetic fuel production facility 102 may be determined based on an amount of dry flue gas. A part of the dry flue gas is used by the gas mixer to form excess output gas. If it is determined that there is excess dry flue gas that is not fed to the gas mixer, the excess dry flue gas may be fed to the synthetic fuel production facility 102.

In an example in accordance with at least some embodiments, a control device may be operatively connected to one or more equipment of a system 100, for example one or more of an oxygen dilution equipment 104, a burning facility

101 , a gas mixer 110, a synthetic fuel production facility 102, an oxygen production facility 114, a carbon dioxide refining equipment, a wet scrubber 106, and other device(s) for receiving and sending information for example messages comprising measurements and/or control commands. Accordingly, the control device may send control commands to one or more of the oxygen dilution equipment 104, the burning facility 101 , the gas mixer 110, the synthetic fuel production facility 102, the oxygen production facility 114, the carbon dioxide refining equipment, the wet scrubber 106, and the other device(s). On the other hand, the control device may receive information such as measurements from one or more of the oxygen dilution equipment 104, the burning facility 101 , the gas mixer 110, the synthetic fuel production facility

102, the oxygen production facility 114, the carbon dioxide refining equipment, the wet scrubber 106, and the other device(s). Examples of the measurements comprise temperature measurements, pressure measurements and content of flue gas. Content of the flue gas may be measured for example regarding content of carbon monoxide, content of oxygen and/or content of CO2, whereby burning at the burning facility may be monitored. Examples of other device(s) of the system comprise may be sensors for example one or more of temperature sensors, pressure sensors, oxygen sensors, carbon monoxide sensors and CO2 sensors. The other device(s) may be deployed to the system for measuring operation of the oxygen dilution equipment 104, the burning facility 101 , the gas mixer 110, the synthetic fuel production facility 102, the oxygen production facility 114, the carbon dioxide refining equipment and/or the wet scrubber 106. It should be noted that instead of having a single control device connected to the one or more of the oxygen dilution equipment 104, the burning facility 101 , the gas mixer 110, the synthetic fuel production facility 102, the oxygen production facility 114, the carbon dioxide refining equipment and the wet scrubber 106, one or more further control devices may be provided. For example, one control device may be connected to the gas mixer 110 and optionally to other device(s) such as a sensor configured to measure operation of the gas mixer. Another control device may be connected to the oxygen dilution equipment 104 and the burning facility and optionally to other device(s) such as a sensor configured to measure operation of the oxygen dilution equipment 104 and/or the burning facility. In an example, communications between a control device and the oxygen dilution equipment 104, the burning facility 101 , the gas mixer 110, the synthetic fuel production facility 102, the oxygen production facility 114, the carbon dioxide refining equipment, the wet scrubber 106 and/or the other device(s) may be digital communications for example over a wired or wireless connection. Examples of the connections comprise field bus technologies such as Profibus, Scanbus, Internet Protocol and Ethernet connections. In an example, the control device may comprise memory that stores instructions that when executed by the control device cause one or more functionalities described with an example and/or embodiment described herein.

Referring to Fig. 3, there is provided a method for upgrading a burning facility. The method comprises a step 302 of connecting a gas mixer 110 to an exhaust line 108 of a burning facility 101. The gas mixer 110 is positioned at a first position located upstream from a second position in a direction of flow of a flue gas of the burning facility 101 . The gas mixer 110 forms an output gas based on a mixture of the flue gas received by the gas mixer at the first position and the second position. The method further comprises a step 304 of connecting a wet scrubber 106 between the first position and the second position. The method comprises a step 305 of connecting an oxygen dilution equipment 104 to the burning facility 101. The method further comprises a step 306 of connecting an output of the gas mixer 110 to the oxygen dilution equipment 104 connected to the burning facility 101 . At the gas mixer 110, an output gas comprising carbon dioxide (CO2), water, and possibly trace amounts of nitrogen, sulphur and/or their oxides, and oxygen, with a highly controllable water content may be generated.

In certain embodiments, the method further comprises, e.g., at step 306, a step of connecting the oxygen dilution equipment 104 and the burning facility 101 to a first control device 107 for controlling dilution of oxygen received by the oxygen dilution equipment 104. One or more operational characteristics of the burning facility 101 and/or the exhaust line 108 are measured by the first control device 107. The one or more operational characteristics, such as pressure, temperature, flow rate of combustion gas, carbon monoxide concentration, oxygen concentration, or any combination thereof, may be measured at one or more points within burning facility 101 and/or at the exhaust line 108. Preferably, the one or more operational characteristics are measured at multiple points within the burning facility 101 and/or at the exhaust line 108 to create a combustion profile for the burning facility 101. Based on the combustion profile, the dilution of oxygen is controlled at the oxygen dilution equipment 104 to maintain an optimal combustion at the burning facility 101.

In certain embodiments, the method further comprises, e.g., at step 306, a step of connecting the gas mixer 110 to the first control device 107, or to a second control device 109, for controlling a ratio of the wet flue gas and the dry flue gas for forming the output gas. The output gas generated at the gas mixer comprises CO2, water, and possibly trace amounts of nitrogen, sulphur and/or their oxides, and oxygen. By controlling the ratio of wet flue gas to dry flue gas, water content of the output gas can be determined to a high accuracy.

In an embodiment an apparatus, or a control device, comprises at least one processor and a communications unit, for example a transceiver. The processor is operatively connected to the communications unit for controlling the communications unit. The apparatus may comprise a memory. The memory may be operatively connected to the processor. It should be appreciated that the memory may be a separate memory or included to the processor and/or the transceiver. The memory may store instructions that, when executed by the at least one processor causes execution of one or more functionalities in accordance with a method described herein. In an example, the transceiver is configured to perform digital communications for example over a wired or wireless connection. Examples of the connections comprise field bus technologies such as Profibus, Scanbus, Internet Protocol and Ethernet connections.

Embodiments may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and/or hardware may reside on memory, or any computer media. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer- readable media. In the context of this document, a “memory” or “computer- readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

Reference to, where relevant, “computer-readable storage medium”, “computer program product”, “tangibly embodied computer program” etc., or a “processor” or “processing circuitry” etc. should be understood to encompass not only computers having differing architectures such as single/multi- processor architectures and sequencers/parallel architectures, but also specialized circuits such as field programmable gate arrays FPGA, application specify circuits ASIC, signal processing devices and other devices. References to computer readable program code means, computer program, computer instructions, program instructions, instructions, computer code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device as instructions for a processor or configured or configuration settings for a fixed function device, gate array, programmable logic device, etc.