A multifuel capable network and method for operating a heating system

Abstract

The invention relates to a multifuel capable network for at least one heating system comprising: a mixing station (50) for blending at least two inlet gases to a fuel mixture, a pressure regulator (41), at least two inlet gas sources (10) connecting to the mixing station (50), a flow regulator (21) for each inlet gas sources (10), a flow rate measuring unit (22) for each inlet gas sources (10), at least one of heating system (60) each comprising at least one burner (80), a gas flow regulating system (81) and an air flow regulating system (82) for each burner (80), a gas supply grid (90) between the mixing station (50) and the heating system / s (60)), a mixing station controller (100), and a heating system controller / s (200).

Description

[0001] A MULTIFUEL CAPABLE NETWORK OF HEATING SYSTEMS

[0002] BACKGROUND

[0003] Many industries use furnaces to heat materials that they produce. One typical example is the steelmaking industry where furnaces are used for many applications.

[0004] Most typically the heat in furnaces is generated by combustion. This makes furnaces a major source of carbon dioxide emissions. A lot of effort has been put to reduce the carbon footprint of industrial furnaces during recent years. One action has been to replace combustion-driven furnaces with electrical ones. If the electricity is renewable (e.g. solar or wind), the carbon footprint of furnaces is decreased dramatically when compared, for example, with coal or natural gas driven furnaces. For several energy-intensive manufacturing processes, a combination of energy gases and electrification is essential. In the steel industry, for instance, electrification is often feasible, where heat is supplied through resistive heating elements for heat treatment. However, certain processes demand high temperatures, up to 1340°C. These extreme temperatures, coupled with limited space for installing electric elements, present distinct advantages for combustion systems. It remains, and will continue to be, important to supply energy in the form of energy gases. This is particularly relevant considering that electrification is progressing in other, more suitable parts of the process, which may also result in constraints regarding available power capacity from the electricity grid. A combination of different energy sources provides the best foundation for safe and reliable production. Enabling fossil-free energy from energy gases is therefore of utmost importance. Hence, combustion will play an important role in the future as well.

[0005] As industry must continue to use combustion-based furnaces, there is now a growing interest in using non-fossil fuels. Renewable hydrogen, biogas, renewable dimethyl ether (rDME) and bio propane are examples of low-carbon alternatives for natural gas (NG), liquefied natural gas (LNG) and for liquified petroleum gas (LPG). However, to achieve the ambitious goal of fossil- free production, further measures are required. It is essential that this transition is carried out in a way that provides the industry with the conditions to maintain strong competitiveness in the global market. A gas mixing system with variable blending of different energy gases creates the conditions for transitioning production without the need to implement an entirely new system all at once. This approach allows for modular introduction of fossil-free energy gases, which can be expanded gradually in line with availability and investment capacity. Unlike other systems, this solution provides flexibility and the possibility of a phased transition without requiring significant investments in storage and large-scale infrastructure expansion.

[0006] SUMMARY OF THE INVENTION

[0007] The invention relates to a multifuel capable network for at least one heating system comprising: a mixing station (50) for blending at least two inlet gases to a fuel mixture; a pressure regulator (41) for controlling the pressure of the mixing station (50); at least two inlet gas sources (10) connecting to the mixing station (50) of which at least one being an energy gas; a flow regulator (21) for each inlet gas sources (10) that is configured to regulate the flow from the gas source (10) to the mixing station (50); a flow rate measuring unit (22) for each inlet gas sources (10) for measuring the flow rate to the mixing station (50) from each inlet gas source (10); at least one heating system (60) each comprising at least one burner (80); a gas flow regulating system (81) and an air flow regulating system (82) for each burner (80); a gas supply grid (90) between the mixing station (50) and the heating system / s (60) for delivering the fuel mixture to the heating system / s (60); a mixing station controller (100) controlling the flow regulators (21), thereby controlling the relative flow from each inlet gas source (10) to the mixing station (50) and dynamically regulating the relative proportions of each inlet gas in the fuel mixture to obtain a desired blend of the fuel mixture, a heating system controller / s (200) controlling the gas flow regulating system (81) and the air flow regulating system (82).

[0008] Preferably, the mixing station controller (100) is configured to o receiving output signals from the pressure regulator (41) and the flow rate measuring units (22), o controlling the total flow through from all inlet gas sources (10) to the mixing station (50) based on the output signal of the pressure regulator (41) to keep the pressure of the mixing station (50) around a target value. o determining at least one real time fuel mixture parameter of the fuel mixture at the mixing station (50), o determining a flow rate of the fuel mixture through the grid (90), o estimating the time delay / s for the fuel mixture to reach at least one heating system (60) based on the determined flow rate in the grid (90) and a grid distance and volume from the mixing station (50) to the heating system / s (60), o estimating real time fuel mixture parameter / s at the heating system / s (60) based on the estimated time delay / s, and o transmitting time delayed real time fuel mixture parameter / s to the heating system controller (200) of the heating system / s (60).

[0009] Preferably, the heating system controller (200) is configured to o receiving the time delayed estimated real time fuel mixture parameter / s from the mixing station controller (100), and o controlling the gas flow regulating system (81) and the air flow regulating system (82) of the least one burner (80) based on the time delayed estimated real time fuel mixture parameter / s. o monitoring the flow rate of the fuel and flow rate of the oxygen source to each burner (80) to calculate an actual lambda value for the lambda control, adjusting the fuel flow and / or the oxygen source flow to keep lambda within a lower and upper threshold.

[0010] Preferably, real time fuel mixture parameter / s is the energy density of the fuel mixture. The energy density, such as a calorific value and / or a wobbe index, of the fuel mixture can be derived using known gas data for each inlet gas sources (10), the relative share of each inlet gas sources (10) from flow rate measuring units (22), the pressure from pressure regulator (41), and a temperature of the fuel mixture in the mixing station (50).

[0011] Preferably, the heating system controller (200) is configured to modulating power by real-time adjustments of firing times of the burner / s (80), in frequency and / or duration, based on the energy density of the fuel mixture.

[0012] Preferably, the heating system controller (200) is configured to modulating power by controlling the flow rate to the burner / s (80) such that the flow rate is increased when the energy density is lower and decreased when the energy density is higher.

[0013] Preferably, the composition of fuel mixture is real time adjusted based on at least one timevariable factor such as supply availability at the premises and / or cost of the gas source and / or cost of producing the gas source.

[0014] Preferably the network has the following restrictions: o the gas supply grid (90) having a grid length of at least 50m o the number of heating systems (60) > 2 o the number of burners (80) in each heating system (60) > 4

[0015] The invention also relates to a method for operating at least one heating system connected to gas supply grid comprising of the steps: a) Mixing of at least two gaseous fuels in a mixing station (50) to a fuel mixture; b) supplying the fuel mixture to at least one heating system (60) connecting to the mixing station (50) through a gas supply grid (90); c) controlling the total flow of the inlet gases (10) to the mixing station (50) based on an output signal from a pressure regulator (41) of the mixing station (50), such that the total flow rate to the mixing station (50) is increased when the pressure drops below a target value and decreased when the pressure comes above a target value. d) estimating a time delay for the fuel mixture to reach the heating system / s (60); e) estimating real time fuel mixture parameter / s at the heating system / s (60) based on the time delay / s of the fuel mixture to reach the heating system / s (60); and f) controlling at least one burner of the heating system / s (60) based on the estimated real time fuel mixture parameter.

[0016] Preferably, further comprising one or more of the steps: g) pulsing the burners (80) to compensate for a varying energy density of the fuel mixture. h) controlling the flow rate to at least one of the bumer / s (80) to compensate for a varying energy density of the fuel mixture, i) adjusting the composition of fuel mixture in real time based on at least one timevariable factor such as supply availability at the premises and / or cost of the gas source and / or cost of producing the gas source.

[0017] Features of the system include:

[0018] A Multifuel Mixing and Supply System for Industrial Furnaces

[0019] A mixing station designed to blend at least two energy gases to create a fuel mixture, adaptable to fossil-free or renewable fuel sources, enabling a modular transition without requiring extensive system overhauls.

[0020] Dynamic Fuel Control Mechanism

[0021] A control system that autonomously regulates the blend of incoming gases, optimizing fuel composition in real-time based on supply availability, price, and operational demand, enhancing cost-efficiency and reducing emissions.

[0022] Precise Flow Regulation for Distributed Combustion

[0023] A gas supply grid connecting the mixing station to multiple furnaces, with flow regulation based on individual furnace energy requirements, supporting continuous or pulsed burner operation while minimizing energy losses. Adaptive Real-Time Adjustment of Air-to-Fuel Ratio (A / F Ratio)

[0024] An automatic system that adjusts the air and fuel flows to each burner in real-time, alternatively immediately in connection with the next burner cycle, based on dynamic fuel mixture properties and lambda (X) values, to maintain safe and efficient combustion and reduce NOx emissions by controlling the oxygen content in the furnace chamber. The lambda value (X) is defined by dividing the observed A / F ratio with the stochiometric A / F ratio of the fuel mixture.

[0025] Safety and Monitoring Protocols

[0026] A several-sensor system for safety and operational control, with continuous X monitoring and response capabilities that trigger safety shutdowns if deviations from safe oxygen levels are detected, with manual reset for enhanced security.

[0027] Time-Delay Estimation for Fuel Parameter Accuracy

[0028] A predictive model within the control system that estimates the delay in fuel mixture delivery to burner positions, allowing for real-time adjustment of combustion parameters at each burner, ensuring uniform energy output and correct air supply.

[0029] Individual Burner Control for Zoned Temperature Regulation

[0030] A furnace control system capable of independently modulating burner states (open / closed) across different furnace zones, allowing precise temperature control throughout the furnace length and width for optimal material processing. The system can, but does not need to, control opening / closing if installed on an existing furnace with existing control system to manage burner control.

[0031] System-Wide and Burner-Specific Locking Mechanisms

[0032] A layered locking system providing both common for all burners and individual burner control, ensuring individual control, and fast shutdown for emergency events, enhancing overall operational safety and flexibility.

[0033] Calorific Value Compensation and Firing Adjustment

[0034] Real-time adjustments to firing times based on the calorific value of the fuel mixture, optimizing combustion duration for lower or higher energy densities to maintain consistent heating performance. Comprehensive Pre-Ignition Safety Sequence

[0035] A built-in safety sequence that pre-purges the system, checks for integrity and pressure, and calibrates starting positions of control flaps before burner ignition, ensuring safe operational conditions from startup.

[0036] BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Fig. 1 is a schematic overview of a multifuel capable network of heating systems,

[0038] Fig. 2 is a schematic overview of a heating system,

[0039] Fig. 3 is an overview of the flow regulation to the mixing station.

[0040] DETAILED DECRIPTION OF THE INVENTION

[0041] Figure l is a schematic overview of a multifuel capable network for at least one heating system, such as industrial furnaces and / or boilers.

[0042] The network of heating systems comprises a mixing station 50. The mixing station 50 is capable of blending inlet gases from at least two inlet gas sources 10 to form a fuel mixture. At least one of the inlet gas sources 10 is an energy gas. Preferably at least two of the inlet gas sources 10 are energy gases. Optionally one or more of the inlet gases sources 10 can be a low or non-energy gas, for instance nitrogen and / or air. These could be used to dilute the energy concentration of the fuel mixture.

[0043] The energy gases can e.g. be any one of hydrogen (preferably renewable hydrogen), any methane (CH4) based gas such as biogas, natural gas (NG), Liquified natural gas (LNG), and further any one of renewable dimethyl ether (rDME), propane (preferably bio propane), liquefied petroleum gas (LPG), and syngas. Preferably at least one of the energy gas sources is produced from renewable energy sources. These energy gases should be understood only as examples. The invention enables using other gases as well.

[0044] The purpose of the heating system network is to be able to run on any variation of fuel blends, so that the system in real time can autonomously regulate the blend of incoming gases, optimizing fuel composition in real-time based on supply availability, price, and operational demand, enhancing cost-efficiency and reducing emissions. Since the factors can vary in real time, the system needs to be able to quickly adapt the composition of the fuel mixture, and handling the varying fuel mixture at the consumption end.

[0045] In one example, green hydrogen is produced in situ when the electrical net has capacity and / or when the price is favorable. Therefore, the hydrogen content could vary by the hours depending on price and / or availability of electricity for hydrogen production. Hence, it is possible to regulate the fuel mixture to minimize gas and CO2 costs in real time.

[0046] The mixing station 50 does not set any limits on the mass fractions, energy fractions or volume fractions of the individual inlet gases. For instance, the hydrogen fraction can be 0. . . 100%.

[0047] The mixing station 50 includes a mixer 30 that blends incoming inlet gases to a fuel mixture. The mixer 30 is preferably a static mixer using turbulence to form a uniform or close to uniform blend. The mixer 30 is preferably followed by a mixing tank 40 that functions as a buffer for the fuel mixture. The mixing tank 40 also acts as a damper providing a stable pressure to the gas supply grid 90. The mixer 30 could be integrated with the inlet to the mixing tank 40. Optionally a further mixer could be provided at the outlet of the mixing tank 40.

[0048] In a minimum configuration the mixing station 50 is configured without a mixing tank 40. The he mixer 30 could be implemented as direct pipe mixing or as a separate unit in which the mixing take place However, in a preferred embodiment the mixing station 50 includes the mixer 30 and the mixing tank 40.

[0049] Each inlet gas source 10 is connected to the mixer 30 via a flow control system 20. The flow control system 20 controls the mass flow rate of each inlet gas to the mixing station 50. The flow control system 20 includes one or more fluid control valve per gas source 10 that functions as a flow regulator 21 and a flow rate measuring unit 22 per gas source 10. Thereby each gas source 10 can be supplied accurately to the mixing station 50 by a feedback control loop. The flow control system 20 is monitored and controlled by a mixing station controller 100, e.g. a programmable logic controller (PLC). The mixing station controller 100 controls the blend of the fuel mixture 100 by controlling the mass flow from each gas source 10 to the mixing station 50, through control signals to respective flow control system 20. The proportion of each gas in the blend is set in the controller 100 either by manually input or input calculated by the mixing station controller 100 based on e.g. current fuel gas prices. A pressure regulator 41 controls the pressure of the mixing tank 40. The inlet gas sources 10 has pressures larger than the that of the mixing tank 40. For instance, hydrogen source can have an over pressure of 30-800 bar, which would need to be downregulated by the flow control system 20 before entering the mixer 30. Other gas sources 10 could have an overpressure close to the that of the mixing tank 40.

[0050] The mixing station 50 is connected via the gas supply grid 90 to plurality of heating systems 60. The gas supply grid 90 connects to a gas train 65 of each heating system 60. The mixing tank 40 and the gas grid 90 forms a shared volume up to the gas trains 65. This volume preferably has an over pressure in the range of 1 - 10 bar. The gas trains 65 down regulates the pressure to a suitable operating pressure for the burners 80 of the heating system 60, e.g. an over pressure of 50-150 mbar.

[0051] The gas supply grid 90 typically has a grid length of more than 50 m. The grid length can be e.g. larger than 100 or 200 m.

[0052] The heating systems 60 are preferably industrial furnaces but could be any kind of heating systems 60 powered by gas fired burners 80, e.g. gas-powered boilers for industrial use or in residential or commercial buildings. The number of grid-connected heating systems 60 is in the figure shown as three but could be from one and upward. The minimum connected heating systems could e.g. be 1, 2, 3, 4, or 5. Preferably there are at least two heating system 60.

[0053] Each heating system 60 is powered by one or more burners 80, and each burner 80 has access to an oxygen source 70. The oxygen source 70 is typically ambient air from combustion air fan but could also be pure oxygen depending on what type of burners 80 that are used. The number of burners 80 in a heating system 60 can be from one and upward. The minimum can e.g. be 1, 2, 3, 4, 5, 6, 8, 10, or 12. Preferably there are at least two burners 80 in each heating system 60. A typical range is 4 - 30, preferably 6 - 24, more preferably 8- 22.

[0054] The heating systems 60 can have one or more heating zones, typically 2 - 5 heating zones. Each heating zone can be heated with one or more burners. 80, such as 2- 10, or 4 - 8 burners 80 in each heating zone.

[0055] The burner operation can be pulsed or continuous. By pulsing the burner operation, the heat produced from a fuel mixture having varying energy density can be averaged out. The flow rate of the fuel mixture to each burner 80 is preferably controlled so that the flow rate is increased when the energy density of the fuel mixture is lower and vice versa.

[0056] A gas supply grid 90 connecting the mixing station 50 to multiple heating system 60, with flow regulation based on individual heating system 60 energy requirements, supporting continuous or pulsed burner operation while minimizing energy losses.

[0057] Each heating system 60 is controlled by heating system controller 200, e.g. a programmable logic controller (PLC). A heating system controller 200 can control one or more heating system 60, typically one.

[0058] The mixing station 50 and the grid 90 forms one gas volume. The distance to a particular heating system 60 can e.g. by hundreds of meters, which means it can be a substantial time delay for a new fuel mixture to reach a particular burner. By monitoring and controlling the pressure of this volume the energy demand can be estimated. For each burner 80 that is active, the flow in the grid 90 increases.

[0059] A pressure regulator 41 is provided at the mixing station 50, preferably to the mixing tank 40, which output signal is sent to the mixing station controller 100. The output signal of the pressure regulator 41 in combination with a set gas composition input is used to control the total gas supply through the flow control system / s 20 and thereby adjust the mass flow rates to the mixing tank 40 of each inlet gas.

[0060] The output signal of the pressure regulator 41 is treated as an estimate of the energy demand, or mixed gas mass flow demand. This signal is multiplied by the desired mass fraction of each inlet gas in order to produce the desired mass flow of each inlet gas. The flow control system 20 preferably includes flow controllers and gas source supply valves. The flow controllers can translate the desired mass flows to signals which act on the gas source supply valves. This creates a decoupling control system which enables gas pressure and flow to be controlled by a robust, optionally fail-safe, control system. The desired mass or energy fraction of each individual inlet gas can thereby be determined by the mixing station controller 100. The temperature and pressure of each inlet gas is also measured and sent to the mixing station controller 100. The pressure regulator 41 ensure that the pressure variation in the gas supply grid is kept stable in spite of large changes in mixed gas demand, while at the same time the mixing station controller 100 can change the fuel mixture composition in real time during operation.

[0061] Due to the decoupling control, there are no significant limits on how fast the composition of the mixed gas can change as a function of time. This has particular value when one of the inlet gases is hydrogen, produced with electrolysis, which often calls for fast changes due to interaction with the electrical power market.

[0062] By providing known physical properties for each inlet gas source to the mixing station controller 100, it can determine the properties of the mixture, since it knows the relative proportion of each gas component. The properties can be parametrized and the calculations can be done in real time by the mixing station controller 100. This gives the gas properties at a given time at the mixing station 50. One such property is the stochiometric A / F ratio of the fuel mixture which can be used for lambda control of the burners 80. Another property is the calorific value of the fuel mixture so that real-time adjustments to firing times based on the calorific value of the fuel mixture can be done. By optimizing combustion duration for lower or higher energy densities it is possible to maintain consistent heating performance.

[0063] The inlet gas properties can be defined by one or more of the following parameters: density (kg / Nm3) of each gas component calorific value (MJ / kg) of each gas component relative mass of each gas component relative molar ratio of each gas component relative molar volume of each gas component stochiometric A / F ratio of each gas component Temperature of each gas component

[0064] - Energy share of each gas component

[0065] The fuel mixture can be defined by one or more of the following parameters at the mixing station: density (kg / Nm3) calorific value (MJ / kg) stochiometric A / F ratio

[0066] Temperature

[0067] - Pressure adiabatic flame temperature (°C)

[0068] - Flame velocity (m / s)

[0069] - Reynolds number

[0070] - Wobbe index (MJ / kg)

[0071] All the parameters of the mixture can be derived using known gas data for each gas component, and the relative share of each gas component through the mass flow meter / s, and the total pressure and the temperature of the mixture in the mixing tank.

[0072] However, the time delay for the particular mixture to reach respective burner position (within a heating system the burner positions can be con considered to be the heating system position in the gas supply grid 90) must be taken into consideration. Depending on the demand, i.e. how many burners 80 of each heating system 60 that are operating, the flow rate in the gas grid 90 can vary considerably. For instance, if only a single burner 80 in one of the heating systems 60 is active, the flow rate in the grid 90 will be at a minimum, whereas if all burners 80 in all heating systems 60 are active the flow rate will be at maximum. Hence, the time delay for a particular fuel mixture to reach the position of a particular heating system 60 in the grid 90 can vary considerably.

[0073] The flow rate can be modulated to account for the by the particular mix of the fuel mixture. If the fuel mixture has a lower energy density, the flow rate is preferably higher to compensate for the lower energy density. For instance, in a fuel mixture with 100% hydrogen the flow rate can be around three times higher than that of 100 % natural gas to reach similar power output. Energy density cam be derived from the calorific value and / or the Wobbe index.

[0074] The flow rate can be an average for the entire grid 90, but in more complex grids 90, the flow rate is determined for each branch. The flow rate can either be measured or estimated.

[0075] The mixing station controller 100 determines in real time the time delay for the fuel mixture to reach different positions in the grid 90. For this estimation, the flow in the grid 90 can be estimated as a plug flow. The length of the pipes of the grid 90 and their diameter are used to determine the volume of the grid. The mass flow through each flow control system 20 of the inlet gases, gives the total flow rate (Nm3 / h) of the grid 90, when the pressure of the mixing tank 40 and grid volume is stable.

[0076] If flow rates are measured in the grid 90, for instance at each heating system 60, the estimates of the gas mixture flow rates in the grid 90 can be improved by balancing mass flow rates of the incoming gases to the mixing station 50, outgoing flow rate of the mixing station 50, and measured flow rates in the grid 90 by data reconciliation.

[0077] Hence, the time delay estimation for the fuel parameter accuracy can be expressed as a dynamic gas grid model within the mixing station controller 100 that estimates the delay in fuel mixture delivery to burner positions, allowing for real-time adjustment of combustion parameters at each burner, ensuring a uniform energy output.

[0078] Fig. 2 shows one example of a heating system 60 in more detail. The heating system 60 connects to the gas grid 90 via a gas train 65. The gas train 65 down regulates the grid pressure to a pressure suitable for the burners 80. This pressure can vary from system to system. The gas train may optionally comprise flow rate sensors. The heating system 60 is controlled by a heating system controller 200 which is in data connection with the mixing station controller 100. The heating system controller 200 is connected to a gas flow regulating system 81, an air flow regulating system 82, and an igniter of each burner 80. Furthermore, it is connected to one or more temperature sensors 61 of the heating system for receiving temperature data. It can also be connected to one or more oxygen sensors 62 measuring the oxygen content of the flue gases. It goes without saying that it could receive input from many more sensors that can be used to optimize the control of the heating system 60.

[0079] The heating system controller 200 is configured to receiving the time delayed estimated real time fuel mixture parameter / s from the mixing station controller 100, and controlling the gas flow regulating system 81 and the air flow regulating system 82 of the least one burner 80 based on the time delayed estimated real time fuel mixture parameter / s. Based on the time delayed estimated real time fuel mixture parameter / s, the heating system controller 200 can adjust the fuel and air flows to achieve a desired lambda value adapted to the fuel mixture. The power output may be modulated by turning on and off the firing of the burners. The heating system controller 200 may be configured to modulating power by controlling each burner 80 to be turned off and on in pulsating manner, where the frequency of on / off and the duration of on / off can be used to adjust to desired heat output. Thus, the heating system controller 200 is capable of independently modulating burner states (open / closed) across different furnace zones, allowing precise temperature control throughout the furnace length and width for optimal material processing. For instance, the frequency and / or duration of the firing times can be used to compensate for different calorific value of the fuel mixture, i.e., real-time adjustments to firing times based on the calorific value of the fuel mixture, optimizing combustion duration for lower or higher energy densities to maintain consistent heating performance.

[0080] The heating system controller 200 may be configured to modulating power by controlling the flow rate, via the gas flow regulating system 81, to the bumer / s 80 such that the flow rate is increased when the energy density is lower and decreased when the energy density is higher. Preferably, such that the power output varies less than 30 % between a fuel mixture of 100 % of the highest power output gas (e.g. 100 % natural gas) and that of a 100 % of the lowest power output gas (e.g. 100 % H2). The time delayed estimated real time fuel mixture parameter / s preferably a stochiometric A / F ratio of the fuel mixture and using said timed delayed stochiometric A / F ratio as a base for a lambda control of each burner 80 at the corresponding heating system 60.

[0081] The lambda value of the burner / s 80 can therefore be automatically adjusted based on the estimated real time fuel mixture parameter / s at its position in the gas supply grid. Theis precise control can be used to reduce the scale formation and NOx emissions in the furnace due to controlling the oxygen content in the furnace atmosphere.

[0082] Preferably, the furnace control system can also adapt for calorific value of the fuel mixture. For instance, if the calorific value is low, the firing time (open state) can be set to be longer than when the fuel mixture has a high calorific value.

[0083] The heating system controller 200 may also modulate power at continuous combustion, where the power modulating is achieved through flow control of the fuel mixture. I.e. as an alternative or complement to pulse controlled power modulation. The system is designed to optimize the retrofit or new installation of various types of burners 80.

[0084] A general description of these systems is as follows:

[0085] Option 1 : Cold air burners, central recuperators, or recuperative burners, operated either continuously or in pulses. This setup is suitable for burners 80 where the pressure drop across the gas and air can be considered relatively constant. Active adjustment enables variable ratio control to accommodate changes in the relationship between gas and air due to the varying properties and air requirements of the mixed gas. Ratio control also accounts for and compensates any necessary adjustments that may impact combustion air.

[0086] Option 2: Regenerative, recuperative, or central recuperator burners where, for various reasons, pressure drops in the system cannot be considered constant. These burners require individual active regulation to maintain optimal combustion. This system’s active control can be advantageous considering operational conditions, location, or specific process requirements for each burner 80.

[0087] Each burner 80 in this system is equipped with a remotely controlled flow control flap in both the air and gas supply lines, along with dedicated flow measurement devices to ensure safety and operational accuracy. Safety regulations require separate sensors for control and safety functions, meaning that while the burner is in operation, these sensors continuously monitor flow rates, allowing real-time calculation of the actual lambda (X) value. The heating system controller 200 can maintain an average X value within a specified acceptable range, with the target ideally close to 1.0 for optimal combustion.

[0088] Lambda Control and Safety Measures

[0089] To maintain safe operation, the system actively responds to any significant deviation in X. If drops below the safe threshold (indicating insufficient oxygen) for a specified duration, the system will shut down the burner and close the gas valve. If remains within the acceptable range, the system proceeds to the next bum cycle without interruption. Dynamic adjustments to gas and air flows are performed to maintain optimal X values, enhancing burner efficiency.

[0090] In cases of repeated X deviations outside the acceptable range, the burner will enter a locked state and require manual intervention to reset. Thresholds for warnings and automatic shutdowns are predefined during commissioning, along with the degree of gas flow reduction following a fault to ensure safe, controlled shutdowns.

[0091] Burner Operation and Flow Adjustments

[0092] The burners are designed to operate with synchronized gas and air flows, with the gas valve opening slightly after the air valve to ensure smooth ignition. The air supply can be controlled by a motorized flap, ensuring sufficient airflow before X monitoring begins.

[0093] The heating system controller continuously monitors and averages air and gas flow values. If adjustments are needed to maintain the target X, these corrections take priority. When is within the desired range, power adjustments are made by fine-tuning the air flap position to match the current airflow and gas requirements.

[0094] System Response and Safety Monitoring

[0095] To safeguard against deviations, control valve positions are actively monitored, with any discrepancies triggering system alerts. The furnace is also equipped with a safety sequence that initiates before burner ignition, including system integrity checks and pre-purging. This prepurging sequence ensures the air flap is correctly positioned for reliable startup.

[0096] General and Individual Burner Locking System

[0097] The furnace operates with both a general interlocking system and individual burner interlocks. During startup, a “Ready to Run” signal is sent to the gas mixing station, awaiting authorization. This enables coordinated shutdown of all burners if necessary. Once authorized, the furnace enters ready mode, and each burner receives an individual enable signal from the mixing station, allowing for gas valve activation and flame ignition.

[0098] In the event of an emergency or shutdown, the system removes the furnace enable signal, automatically closing the gas valves. The air and gas flaps remain in their last known positions, ensuring a controlled and safe response until the system is reset. This comprehensive control approach enhances operational flexibility while maintaining stringent safety standards. Figure 3 describes a decoupling control of mixing of “N” inlet gases. Gas flows are controlled with flow controllers FC1,FC2, FCN, which obtain setpoints from “x” -blocks which multiply pressure regulator PCI output signal, interpreted as total required mixed gas flow, with the mass fractions rl, r2, ..., rN. Mass fractions can be entered by the user or calculated by a higher-level optimization system which, for instance, minimizes the total cost of mixed gas production.

Claims

CLAIMS1. A multifuel capable network for at least one heating system comprising: a mixing station (50) for blending at least two inlet gases to a fuel mixture; a pressure regulator (41) for controlling the pressure of the mixing station (50); at least two inlet gas sources (10) connecting to the mixing station (50) of which at least one being an energy gas; a flow regulator (21) for each inlet gas sources (10) that is configured to regulate the flow from the gas source (10) to the mixing station (50); a flow rate measuring unit (22) for each inlet gas sources (10) for measuring the flow rate to the mixing station (50) from each inlet gas source (10); at least one heating system (60) each comprising at least one burner (80); a gas flow regulating system (81) and an air flow regulating system (82) for each burner (80); a gas supply grid (90) between the mixing station (50) and the heating system / s (60) for delivering the fuel mixture to the heating system / s (60) a mixing station controller (100) controlling the flow regulators (21), thereby controlling the relative flow from each inlet gas source (10) to the mixing station (50) and dynamically regulating the relative proportions of each inlet gas in the fuel mixture to obtain a desired blend of the fuel mixture, a heating system controller / s (200) controlling the gas flow regulating system (81) and the air flow regulating system (82).

2. The multifuel capable network according to claim 1, wherein the a mixing station controller (100) is configured to receiving output signals from the pressure regulator (41) and the flow rate measuring units (22), and controlling the total flow through from all inlet gas sources (10) to the mixing station (50) based on the output signal of the pressure regulator (41) to keep the pressure of the mixing station (50) around a target value.

3. The multifuel capable network according to claim 1 or 2, wherein- the mixing station controller (100) is configured to: o determining at least one real time fuel mixture parameter of the fuel mixture at the mixing station (50), o determining a flow rate of the fuel mixture through the grid (90), o estimating the time delay / s for the fuel mixture to reach at least one heating system (60) based on the determined flow rate in the grid (90) and a grid distance and volume from the mixing station (50) to the heating system / s (60), o estimating real time fuel mixture parameter / s at the heating system / s (60) based on the estimated time delay / s, and o transmitting time delayed real time fuel mixture parameter / s to heating system controller (200) of the heating system / s (60); and the heating system controller (200) is configured to o receiving the time delayed estimated real time fuel mixture parameter / s from the mixing station controller (100), and o controlling the gas flow regulating system (81) and the air flow regulating system (82) of the least one burner (80) based on the time delayed estimated real time fuel mixture parameter / s.

4. The multifuel capable network according to claim 3, wherein the time delayed estimated real time fuel mixture parameter / s include a stochiometric A / F ratio of the fuel mixture, and using said timed delayed stochiometric A / F ratio as a base for a lambda control of each burner (80) at the corresponding heating system (60).

5. The multifuel capable network according to claim 4, wherein the heating system controller (200) monitors the flow rate of the fuel and flow rate of the oxygen source to each burner (80) to calculate an actual lambda value for the lambda control, adjusting the fuel flow and / or the oxygen source flow to keep lambda within a lower and upper threshold.

6. The multifuel capable network according to any one of the preceding claims, wherein a real time fuel mixture parameter / s is the energy density of the fuel mixture.

7. The multifuel capable network according to claim 6 wherein the heating system controller (200) is configured to modulating power by real-time adjustments of firing times of the burner / s (80), in frequency and / or duration, based on the energy density of the fuel mixture.

8. The multifuel capable network according to claim 6 or 7, wherein the heating system controller (200) is configured to modulating power by controlling the flow rate to the burner / s (80) such that the flow rate is increased when the energy density is lower and decreased when the energy density is higher.

9. The multifuel capable network according to any one of the preceding claims, wherein the composition of fuel mixture is real time adjusted based on at least one time-variable factor such as supply availability at the premises and / or cost of the gas source and / or cost of producing the gas source.

10. The multifuel capable network according to any one of the preceding claims, wherein the network has the following restrictions: o the gas supply grid (90) has a grid length of at least 50m o the number of heating system / s (60) > 2 o the number of burners (80) in each heating systems > 411. A method for operating at least one heating system connected to gas supply grid comprising of the steps: a) mixing of at least two gaseous fuels in a mixing station (50) to a fuel mixture, b) supplying the fuel mixture to at least one heating system (60) connecting to the mixing station (50) through a gas supply grid (90), c) controlling the total flow of the inlet gases (10) to the mixing station (50) based on an output signal from a pressure regulator (41) of the mixing station (50), suchthat the total flow rate to the mixing station (50) is increased when the pressure drops below a target value and decreased when the pressure comes above the target value d) estimating a time delay for the fuel mixture to reach the heating system / s (60), e) estimating real time fuel mixture parameter / s at the heating system / s (60) based on the time delay / s of the fuel mixture to reach the heating system / s (60), and f) controlling at least one burner of the heating system / s (60) based on the estimated real time fuel mixture parameter.

12. The method according to claim 11, further comprising the steps of: g) pulsing the burners (80) to compensate for a varying energy density of the fuel mixture.

13. The method according to claim 11 or 12, further comprising the steps of: h) controlling the flow rate to at least one of the bumer / s (80) to compensate for a varying energy density of the fuel mixture.

14. The method according to any one of claims 11 - 13, further comprising the steps of: i) adjusting the composition of fuel mixture in real time based on at least one timevariable factor such as supply availability at the premises and / or cost of the gas source and / or cost of producing the gas source.

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