Technical field

The present invention relates to recovering heat from combustion of fuel to district heating. More precisely, the invention relates to a carbon-neutral method for efficient heat recovery to district heating from oxygen combustion of fuel.

Background

District heating is a system for distributing heat generated in a centralized location, i.e., a district heating plant, through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. Heat for district heating systems may be produced in heat plants or in combined heat and power plants (CHP). Conventionally, the heat or CHP plants are fueled by fossil fuels, although the focus is turning to renewable fuels. District heating is a major source of carbon dioxide emissions in many countries and municipalities. Therefore, carbon-neutral ways of producing heat for district heating are needed.

Summary

An object of the present invention is to provide efficient heat recovery of energy from combustion of fuel to be efficiently utilized in district heating systems.

A further object of the present invention is to provide a simple and cost-efficient system for carbon capture in burning facilities.

These objects are 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.

A typical method according to the present invention comprises the following steps: receiving, by a wet scrubber connected to an exhaust line of a burning facility, wet flue gas from oxygen combustion at the burning facility; capturing, by the wet scrubber, combustion pollutants from the wet flue gas received from the burning facility; and circulating, by the wet scrubber, scrubbing liquid, e.g., water from the wet scrubber to a heat exchanger for district heating.

A typical system according to the invention comprises a wet scrubber connected to an exhaust line of a burning facility configured to receive wet flue gas from oxygen combustion at the burning facility, wherein the system is configured to: circulate scrubbing liquid, e.g., water from the wet scrubber to a heat exchanger for district heating.

An advantage of the present invention is that capturing carbon from the flue gas is significantly simplified compared to conventional combustion and carbon capture systems. With no nitrogen (N2) or its oxides (NO _X ) in the flue gas, the need for external amine scrubbing equipment, often being complicated and energy-consuming devices, is 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.

An advantage of the present invention is an improved efficiency of district heating. The present invention allows for accurate control of a district heating facility and process together with efficient heat recovery. A further advantage of the present invention is that NO _X emissions resulting from conventional combustion using air may be eliminated.

Brief description of the drawings

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

Figure 2 presents a method 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

202-206 steps of Fig. 2

A method according to the invention comprises the steps of: receiving 202, by a wet scrubber 106 connected to an exhaust line of a burning facility 101 , wet flue gas from oxygen combustion at the burning facility 101 ; capturing 204, by the wet scrubber 106, combustion pollutants from the wet flue gas received from the burning facility 101 ; and circulating 206, by the wet scrubber 106, scrubbing liquid, e.g., water from the wet scrubber 106 to a heat exchanger 112 for district heating.

A system 100 of the present invention comprises: a wet scrubber 106 connected to an exhaust line of a burning facility configured to receive wet flue gas from oxygen combustion at the burning facility 101 , wherein the system is configured to: circulate 206 scrubbing liquid, e.g., water, from the wet scrubber 106 to a heat exchanger 112 for district heating.

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 removes pollutants from a flue gas from a burning facility using a scrubbing liquid, e.g., water. The flue gas may comprise pollutants in particle form, gaseous form, or both. Typical examples of pollutants include dust, particulates, water, sulphur, chlorine and fluorine. The wet scrubber receives wet flue gas originating from oxygen combustion at the burning facility 101 from the exhaust line. In the wet scrubber, the flue gas is brought into contact with a scrubbing liquid, e.g., water, by spraying it with the scrubbing liquid, by forcing it through a pool of scrubbing liquid, or by some other contact method with the scrubbing liquid, so as to remove the pollutants. Water constitutes a majority of the pollutants in the flue gas in terms of volume of the pollutants. Therefore, the flue gas that is received from combustion may be referred to as a wet flue gas, and the flue gas at the output of the wet scrubber, after removal of the pollutants, especially water, may be referred to as a dry flue gas. At least a part of the wet flue gas is fed to the wet scrubber. The wet scrubber has a mist eliminator for separating droplets of scrubbing liquid from the output flue gas. The wet scrubber 106 condenses steam, or water vapour, contained in the flue gas into the liquid phase. The water condenses when the temperature decreases below the dew point, or, in other words, when the relative humidity reaches 100%. Condensation occurs typically at a range of temperatures, the higher end of which is determined by the dew point. Lower end of the condensing range is typically dictated by capacity of a heat reservoir, e.g., the heat exchanger 112. Typically, in systems where the wet scrubber is operatively connected to the heat exchanger 112 for district heating, the lower end of the condensing range is in the range of 40-50°C. The condensing temperature increases with an increasing partial pressure of water vapour in the flue gas. After the wet scrubbing treatment, the dry flue gas comprises a minor water vapour content according to the dew point at the actual gas temperature.

In the system according to the present invention, the partial pressure of water vapour in the flue gas in considerably higher than compared to a flue gas from conventional air combustion, leading to higher condensing temperatures. In this context, the term “condensing temperature” should be understood as the higher end of the condensing range, i.e., the dew point of water in the wet scrubber. In conventional systems, the condensing temperature is typically in the range of 60-65°C. With the present invention, however, the condensing temperature may be increased to be in the range of 70-100 or 90-100°C, preferably 80-90 or 92-98°C, more preferably 85-90°C. With an increased condensing temperature compared to conventional systems, more heat energy may be transferred to the district heating via the heat exchanger 112. Thus, the water for the district heating system requires less external heating, e.g., by a primary steam from a heat plant or a combined heat and power (CHP) plant, to reach a desired temperature upon entering the district heating system.

The wet scrubber 106 functions as a carbon capture equipment in the system. Thus, the need of an external carbon capture equipment is eliminated. The wet flue gas received from the exhaust line 108 of the burning facility 101 may be lead through the wet scrubber 106 to obtain dry flue gas.

In the method according to the present invention, the wet flue gas is received from a burning facility 101 from oxygen combustion at the burning facility 101 . The corresponding system comprises a burning facility 101 configured to produce a flue gas based on oxygen combustion of fuel at the burning facility 101 . 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.

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 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 burning facility may comprise a carbon dioxide refining equipment 105 configured to remove traces of nitrogen, sulphur and/or their oxides, and/or oxygen from the dry flue gas. The carbon dioxide refining equipment is typically located downstream of the wet scrubber 106. When the dry 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 flue gas comprises at least 99 % by volume, such as 99-100 % by volume CO2, of the total volume of the dry flue gas.

According to the invention, scrubbing liquid, e.g. water, is circulated from the wet scrubber to a heat exchanger 112 for district heating. District heating is a system for distributing heat generated in a centralized location, i.e., a district heating plant, through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is typically transformed through hot water as the heat carrier. The hot water is transferred into a heat distribution center of a building. The heat energy is delivered to the heating network of the building directly from the hot water, or preferably via a heat exchanger. The heat may be used to heat indoor spaces and domestic water in the building. The heat may also be utilized in ventilation. The heat carrier water is recirculated back to the district heating plant for reheating, and may be termed returning water. Temperature of the water entering the system of insulated pipes is typically higher than 50°C, preferably higher than 90°C or higher than 100°C. In certain examples, the water entering the system of insulated pipes is pressurized, and the temperature of the water is 110-130°C. Temperature of the returning water is typically 40-60°C lower than temperature of the water entering the system of insulated pipes. Typical temperature of the returning water may be in the range of 15-50°C, preferably 25-45°C.

Using the present invention, the condensing temperature of the water at the wet scrubber may be increased to e.g. 95 70-90°C, preferably to 85-90°C, i.e., 5-30°C higher, such as 10-15°C higher, preferably 25-30°C higher than when using a conventional air combustion. Thus, the temperature difference of the water compared to the entrance temperature of the district heating system is also increased by ca. 5-30°C, such as 10-15°C, or even 25-30°C. Heating the water entering the district heating system consumes a considerably smaller amount of energy with the higher condensing temperature, compared to a conventional system. The decrease in energy consumption may be in the range of 10-50%, such as 10, 20, 30, 40 or even 50% compared to a conventional system. Thus, less external heating, e.g. by a primary steam from a heat plant or a combined heat and power (CHP) plant, is needed to reach the same entrance temperature for the water entering the district heating system.

In certain embodiments, the system comprises a gas mixer 110. The gas mixer 110 forms an output gas comprising a mixture of wet flue gas originating from combustion received from the exhaust line prior to the wet scrubber and the dry flue gas received from the wet scrubber. The gas mixer 110 is connected to output of the wet scrubber 106 for receiving the dry flue gas and to the exhaust line 108 for receiving the wet 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. The gas mixer 110 may also be placed downstream of the optional 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. The desired volume ratio of the wet flue gas originating from combustion, received from the exhaust line prior to the wet scrubber, to the dry flue gas received from the wet scrubber may be defined at the gas mixer. The volume ratio of wet flue gas to dry flue gas at the gas mixer may be determined based on a need of heat energy at the heat exchanger 112 for district heating.

In cold circumstances, e.g. during winter, the need for heat energy at the district heating may be high, and as much of the heat contained in the flue gas is directed to district heating as possible. The ratio of the wet flue gas to the dry flue gas at the gas mixer may therefore be 50:50, 40:60, 30:70, 20:80, 10:90, or even 0:100 [vol-%:vol-%]. In certain situations, the wet flue gas is fed to the wet scrubber in its entirety, and the ratio of the wet flue gas to the dry flue gas at the gas mixer may be 0:100 [vol-%:vol-%]. When all flue gas is directed to the wet scrubber, the amount of heat energy withdrawn from the flue gas with the use of the heat exchanger 112 is at its maximum.

Conversely, in warm circumstances, e.g. during summer, the need for heat energy at the district heating is low. In this situation, it is beneficial to recirculate as much of the heat energy back to the combustion process as possible. Therefore, the ratio of the wet flue gas to the dry flue gas at the gas mixer may be 50:50, 60:40, 70:30, 80:20, 90:10, or even 100:0 [vol-%:vol-%]. In other words, the minority or even none of the flue gas is circulated to the wet scrubber 106. During summertime, the combustion process produces a surplus of waste heat. Together with the low energy need at the district heating, the quality of recovered heat and not the amount is of importance. Circulating a majority of the hot, wet flue gas back to the combustion process increases the partial pressure of water vapor in the flue gas leading to a higher condensing temperature in the scrubber, and thus a higher temperature of the scrubbing water. This reduces the need for the expensive external primary steam to increase the temperature to desired district heating temperature.

In certain embodiments, the system comprises a control system comprising at least one control device configured to control the ratio of wet flue gas to dry flue gas at the gas mixer 110. The ratio of wet flue gas to dry flue gas at the gas mixer is controlled based on at least one of - determining a need to control a combustion temperature of the burning facility 101 ,

- determining a need to feed the dry flue gas to a synthetic fuel production facility 102, and

- determining a need of heat energy at the heat exchanger 112 for district heating.

The control system may utilize a dedicated optimization algorithm. The control system and the optimization algorithm may continuously control and optimize the combustion process online using measured parameters, such as the combustion temperature, the need of carbon dioxide at the synthetic fuel production, and the need of heat at the district heating.

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 ratio of the wet flue gas to the dry flue gas at the gas mixer 110 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 ratio of the wet flue gas to the dry flue gas at the gas mixer 110 may be 100:0, 90:10, 80:20, 70:30, 60:40, or 50:50 [vol-%:vol-%],

A yet another advantage of the present invention is that it provides corrosion protection in the burning facility. For example in burning facilities utilizing solid biomass fuel, such as wood, water in the fuel may cause severe corrosion due to partial condensing of water vapor at the cold end of the flue gas draft of the burning facility. The corrosion effect is pronounced when the fuel is very wet during rainy seasons, or contains even snow during winter days. Using the present invention, the combustion process in the burning facility may be continuously controlled. In case of wet fuel, the ratio of wet flue gas to dry flue gas at the gas mixer can be directed to a majority of dry flue gas, even to 100 vol-% dry flue gas. The dry flue gas may be recirculated to the back to the combustion process to compensate for the additional water intake originating from the wet fuel.

In an embodiment, at least a part of the treated, dry flue gas from the output of the wet scrubber 106 is fed by the wet scrubber to a synthetic fuel production facility 102. The wet scrubber may be operatively connected to the synthetic fuel production facility 102 and configured to feed dry flue gas from the wet scrubber 106 to the synthetic fuel production facility 102.

In certain embodiments, the control device is configured to control the volume ratio of wet flue gas to dry flue gas at the gas mixer based on determining a need to feed the dry flue gas to a 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 ratio of the wet flue gas to the dry flue gas at the gas mixer 110 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 embodiment, the CO2 generated at the combustion is captured in a fuel synthesis at the synthetic fuel production facility 102. The synthetic fuel may be selected from low-molecular weight aliphatic hydrocarbons or alcohols, such as methane, methanol, ethane, ethanol, propane, propanol, butane, butanol; and biodiesel. Synthetic fuels may be used e.g. as a traffic fuel, for transportation or shipping purposes.

In certain embodiments, the synthetic fuel is methanol (CH3OH), synthesized in a direct CO2 hydrogenation process according to the following reactions:

CO2 + H ₂ -> CO + H ₂ O CO + 2 H ₂ -> CH3OH

Compared to hydrogen, methanol is easier and safer to transport, to handle and to store. The need for pressurized containers is eliminated.

In an embodiment, temperature of the scrubbing liquid, e.g. water is measured by the first control device. The ratio of the wet flue gas fed to the wet scrubber to the dry flue gas output by the wet scrubber is controlled by the first control device based on the measured temperature.

In certain embodiments, the wet flue gas and the dry flue gas are CO2-rich gases. 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 output gas of the burning facility, i.e., wet flue gas. Therefore, the total amount of CO2 in the output gas of the burning facility is higher than the total amount of CO2 in the combustion gas. Moreover, the output 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 output gas of the burning facility in the present examples may be referred to CO2-rich flue gas. The CO2-rich flue gas obtained from the output of the burning facility may be treated with the wet scrubber 106, as described above. The treated dry flue gas obtained from the output of the wet scrubber 106 may thus be termed dry CO2-rich flue gas. The dry CO2-rich flue gas comprises at least 70% by volume, preferably at least 90% by volume, 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 2-4% by volume oxygen, of the total volume of the dry CO2-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 burning facility further 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. 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 needed.

In certain embodiments, 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 104. The oxygen dilution equipment 104 then dilutes the oxygen received from an 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 an embodiment, the oxygen dilution equipment dilutes oxygen received from an oxygen production facility 114. The oxygen production facility 114 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. In an embodiment, the water electrolysis is powered by renewable electricity, preferably wind power.

Figure 1 presents a schematic diagram of a system 100 according to an embodiment of the present invention. The system comprises a hydrogen production facility 103, an oxygen production facility 114, a synthetic fuel production facility 102, a burning facility 101 , an oxygen dilution equipment 104, a first control device 107 operatively connected to the oxygen dilution equipment 104 and the burning facility 101 , an exhaust line 108, a wet scrubber 106, a carbon dioxide refining equipment 105, a gas mixer 110, a second control device 109 operatively connected to the gas mixer 110, and a heat exchanger 112 for district heating.

Figure 2 presents a schematic diagram of the method according to the present invention. The method comprises receiving 202, by a wet scrubber 106 connected to an exhaust line of a burning facility 101 , wet flue gas from oxygen combustion at the burning facility 101 ; capturing 204, by the wet scrubber 106, combustion pollutants from the wet flue gas received from the burning facility 101 ; and circulating 206, by the wet scrubber 106, scrubbing liquid, e.g., water from the wet scrubber to a heat exchanger 112 for district heating.

In an example in accordance with at least some embodiments, a control system comprising at least one 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 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 wet scrubber 106, and the other device(s). Examples of the measurements comprise, for example, 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.

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.