Patent Description:
The present disclosure relates to heat generators, and more specifically to biomass-based heat generator control.

Solid fuels, such as biomass, wastes, or coal, have long been used as a source of fuel for energy generation. Traditionally, solid fuel is combusted in an enclosed or semi-enclosed space, and the combustion of the solid fuel generates energy in the form of heat. In more recent history, efforts toward green energy, energy efficiency, and waste reduction have led to a resurgence of solid-fuel-based energy generation. A modern solid-fuel heat generator combusts solid fuel in a furnace or other enclosure, and the heat produced by the combustion and pyrolysis is used to generate steam. The steam is used to deliver heat to heat sinks, or fed through a turbine to generate power, or used to produce other useful work.

Due to characteristics inherent to solid fuels, the combustion process of solid fuels is somewhat irregular and unpredictable. Indeed, unlike gaseous fuels where the combustion reactions are rapid because of intimate gas-to-air mixing, solid fuel burning is slower and less predictable due to varying degrees of moisture content, density, surface-area-to-volume ratio, exposed fuel-to-air surface area, chemical composition, and the like. In addition, the feeding process of solid fuel into the heat generator is often irregular, and may lead to spikes or dips in heat production. These characteristics vary over time, cannot typically be measured accurately with sensors, and will change throughout the combustion process, making it very difficult to maintain the heat release at its desired target. Because of these difficult combustion dynamics, traditional solid-fuel heat generator control strategies are designed to respond to variations in heat release by modulating the fuel input of solid fuel to the heat generator. Modulation of fuel input will result in a slow correction in heat release, making it very difficult to maintain the generator heat release at its target and forcing the system to rely on other faster actuators for total process heat balance, such as steam condensing, steam venting, and supplementary gas firing. For example, document <CIT> discloses a method for modulating a solid-based combustion process determining a current instantaneous heat release for a solid-fuel-based heat generator, comparing the current instantaneous heat release to a current firing rate demand and when the current instantaneous heat release does not correspond to the current firing rate demand, adjusting operational characteristics of the heat generator such as air flows or the feeding of solid fuel.

It remains there is a need for improved solid-fuel heat generator controls.

The present invention is drawn to a system and a method according to independent claims <NUM> and <NUM>. Preferred embodiments thereof are presented in the dependent claims.

The system comprises a solid-fuel-based combustion heat generator system producing steam equipped with: a set of sensors; a setpoint adjustor within the heat generator system; a steam distribution system; and a boiler comprising a steam outlet through which the produced steam exits a boiler drum, the boiler being coupled to the steam distribution system so that steam produced within the boiler is routed toward the steam distribution system via the steam outlet; the system comprising a slow-speed controller; an Instant Heat Release, IHR, virtual sensor configured to estimate an IHR of the heat generator system based on first values measured by one or more of the sensors, of at least the rate of steam flow in the steam outlet and the steam pressure in the boiler drum; and a high-speed controller configured to receive from the slow-speed controller a current firing rate demand based on second values measured by one or more of the sensors, of an energy level of the steam in the steam distribution system, to receive the estimated IHR from the IHR virtual sensor, to make a comparison of the received current firing rate demand and the received estimated IHR. and to instruct the setpoint adjustor to adjust an underfire air flow within the heat generator system based on the comparison.

The method for regulating a solid-fuel-based combustion process for a heat generator system producing steam equipped with a set of sensors; a setpoint adjustor within the heat generator system; a steam distribution system; a boiler comprising a steam outlet through which the produced steam exits a boiler drum, the boiler being coupled to the steam distribution system so that steam produced within the boiler is routed toward the steam distribution system via the steam outlet; and a slow-speed controller; comprises the steps of: estimating by an IHR virtual sensor an IHR of the heat generator system based on first values measured by one or more of the sensors, of at least the rate of steam flow in the steam outlet and of the steam pressure in the boiler drum; - receiving by the high-speed controller the estimated IHR from the IHR virtual sensor; making a comparison of the received current firing rate demand and the received estimated IHR; and instructing the setpoint adjustor to adjust an underfire air flow within the heat generator system based on the comparison.

Further features and advantages of embodiments described herein may become apparent from the following detailed description, taken in combination with the appended drawings, in which:.

With reference to <FIG>, a solid-fuel heat generator system <NUM> is shown. The solid-fuel heat generator system <NUM> serves to perform combustion of solid fuel <NUM>, thereby producing heat <NUM>. The solid-fuel heat generator system <NUM> includes a furnace <NUM>, a boiler <NUM>, and a steam distribution system <NUM>. The furnace <NUM> and the boiler <NUM> are coupled such that heat produced within the furnace <NUM>, via the combustion of solid fuel <NUM>, heats water in the boiler <NUM>, producing steam.

The boiler <NUM> includes a boiler drum <NUM>, which is provided with water for the production of steam via the heating action of the furnace <NUM>. The boiler <NUM> also includes a steam outlet <NUM>, through which steam produced within the boiler drum <NUM> exits the boiler drum <NUM>. The boiler <NUM> and the steam distribution system <NUM> are coupled so that steam produced within the boiler <NUM> is routed toward the steam distribution system <NUM> via the steam outlet <NUM>. The steam distribution system <NUM> then routes the steam produced by the solid-fuel heat generator system <NUM> to turbines or other steam-based energy consumers. It should be noted that although the foregoing discussion focuses primarily on steam boilers, in embodiments not covered by the present invention the systems and methods described herein may also be applied to hot water boilers, or any other suitable kind of boiler.

The furnace <NUM> is a substantially-enclosed structure which may be cylindrical, oblong, rectangular, or any other suitable shape. The furnace <NUM> may be made of any suitable heat-resistant material, for example carbon steel. The furnace <NUM> has defined therein an opening through which solid fuel <NUM> is fed to the furnace <NUM>, for example via a conveyor belt <NUM>. The conveyor belt <NUM> is configured for ferrying solid fuel <NUM> toward the furnace <NUM> for combustion. The conveyor belt <NUM> may be any suitable mechanism for transporting the solid fuel and for depositing it within the furnace <NUM>, for example via the opening in the furnace <NUM>. The conveyor belt <NUM> may acquire the solid fuel <NUM> via any suitable mechanism, and may interact with a reserve of solid fuel in any suitable fashion. It should be noted that other approaches for providing fuel to the furnace <NUM> are also considered.

The furnace <NUM> has disposed therein a surface grate <NUM>, for example a grate, on which the solid fuel <NUM> rests for combustion. The surface grate <NUM> may span the entire width of the furnace <NUM>, and may be angled with respect to a floor of the furnace <NUM> at any suitable inclination. The surface grate <NUM> may be made of any suitably heat-resistant material, for example steel, and may be provided with a cooling system using air or water for cooling purposes. In some embodiments, the surface grate <NUM> has defined therein one or more apertures or holes through which air or other oxidant elements may be directed underneath the solid fuel <NUM>. In some embodiments, the surface <NUM> is coupled to one or more motors or similar element which causes motion in the surface <NUM>. For example, the motors may adjust the speed of the surface grate <NUM> and/or imparts a vibratory movement to the surface grate <NUM> which causes the solid fuel <NUM> to move along the surface grate <NUM>. In some other embodiments, the surface grate <NUM> is stationary.

The furnace <NUM> also has typically two or more air inlets, including at least an underfire air inlet <NUM> and optionally an overfire air inlet <NUM> The air inlets <NUM>, <NUM> are configured for providing air or other oxidant elements to the furnace <NUM>, thereby aiding the combustion of the solid fuel <NUM>. The underfire air inlet <NUM> may be located at any suitable location under or within the surface grate <NUM>, and thus below or approximately level with the combustion process of the solid fuel <NUM>. In some embodiments, the underfire air inlet <NUM> impinges substantially directly on the surface grate <NUM>. The overfire air inlet <NUM> may be located at any suitable location above the combustion process of the solid fuel <NUM>. In some embodiments, each of the air inlets <NUM>, <NUM> is a series of air inlets. For example, the overfire air inlet <NUM> may include a plurality of air inlets located at different positions within the furnace <NUM>. In some embodiments, the air inlets <NUM>, <NUM> are provided with dampers, which may be manual or automatic, for adjusting the air flow into the furnace <NUM>. In some embodiments, the overfire air inlet <NUM> is eschewed.

The furnace <NUM> also has one or more air outlets, including at least a flue gas outlet <NUM>. The flue gas outlet <NUM> provides a venting path for fumes and other gases produced by the combustion of the solid fuel <NUM>, collectively called "flue gas", to vent from the furnace <NUM>. In some embodiments, the flue gas outlet <NUM> vents the flue gas to an outside environment. In some other embodiments, the flue gas outlet <NUM> vents the flue gas to a subsequent processing stage or system. For example, part or all of the flue gas is used as part of further heat recovery processes. In another example, the flue gas is processed to remove certain chemicals or particulates found therein before being vented to the outside environment. In some embodiments, the flue gas outlet <NUM> is a plurality of flue gas outlets located at various positions about the furnace <NUM>.

Located within and proximate to the solid-fuel heat generator system <NUM> are a plurality of sensors <NUM>. The sensors <NUM> are used to track, measure, and control various data points regarding characteristics of the components of the solid-fuel heat generator system <NUM>, including the furnace <NUM>, the boiler <NUM>, and the steam distribution system <NUM>. Some of the sensors <NUM> may be used to infer fuel input characteristics, measure changes heat input-to-output balance, track characteristics of the surface grate <NUM>, for example the relative height of the solid fuel <NUM> on the surface grate <NUM> by measuring the differential pressure between the base of the grate <NUM> and the furnace <NUM>, a temperature of the surface grate <NUM> or in the vicinity of the surface grate <NUM>, and the like. In addition, some of the sensors <NUM> may be used to measure a pressure level in the boiler drum <NUM>, a rate of steam flow through steam outlet <NUM>, and the like. Still other types of sensors are considered.

The solid-fuel heat generator system <NUM> is also provided with a control system <NUM> which regulates the operation of the solid-fuel heat generator system <NUM> based on information collected by the sensors <NUM> and other inputs, for instance from a control interface used by one or more operators of the solid-fuel heat generator system <NUM>. In some embodiments, the control system <NUM> is communicatively coupled to the sensors <NUM> to obtain data from the sensors about the characteristics of the solid-fuel heat generator system <NUM>. In other embodiments, the sensors <NUM> are communicatively coupled to the control interface or another high-level central controller, which then provides the control system <NUM> with the necessary information.

The control system <NUM> regulates the operation of the solid-fuel heat generator system <NUM> with the aim of causing the boiler <NUM> to produce steam at a substantially stable and constant rate based on a desired level of demand for steam. Stable and controllable steam generation by the boiler <NUM> means reliable steam delivery to the steam distribution system <NUM>. This, in turn, means that the amount of steam available to the steam distribution system <NUM> is not constrained by the ability of the solid fuel steam generator <NUM> to follow the total steam demand set by the different turbines and heat sinks. To do this, the control system <NUM> is configured to alter the combustion process within the furnace <NUM> to maintain an instantaneous heat release (IHR) at target and to attenuate any uncontrolled heat release variations.

With reference to <FIG>, there is shown a diagram of a control system <NUM> for modulating a solid-fuel based combustion process. The control system <NUM> may, for example, be an implementation of the control system <NUM>. The control system <NUM> includes a slow-speed controller <NUM>, an IHR virtual sensor <NUM>, a high-speed controller <NUM>, and a setpoint adjustor <NUM>.

The slow-speed controller <NUM> is configured for obtaining a first set of sensor values from one or more of the sensors <NUM>, and may include steam flow, steam drum pressure, and the like. The slow-speed controller <NUM> measures an energy level of the steam header system <NUM>, for example based on the steam pressure.

The IHR virtual sensor <NUM>, receives a current firing rate demand for the furnace <NUM> from the slow-speed controller <NUM> based on the first set of sensor values. In some embodiments, the current firing rate demand is established as a requisite value for the IHR for the furnace <NUM>. The IHR demand of the furnace <NUM> is the total required amount of instantaneous heat to be produced by the combustion of the solid fuel <NUM> in the furnace <NUM>.

The IHR virtual sensor <NUM> is configured for obtaining a second set of sensor values from one or more of the sensors <NUM>, and may include furnace temperature, furnace pressure, flue gas composition, drum temperature, drum pressure, and the like. In some embodiments, the IHR virtual sensor <NUM> calculates an estimation of the process IHR for the furnace <NUM> based on the second set of sensor values.

In order to measure or estimate the IHR, the IHR virtual sensor <NUM> is used to produce a value for the current IHR based on a variety of information, including that received from the sensors <NUM>. In some embodiments, the IHR virtual sensor <NUM> determines the IHR based on a rate of steam flow from the boiler <NUM> and a pressure in the boiler drum <NUM>. For example, the IHR can be expressed via the following equation: <MAT> where Fsteam is a steaming rate of the boiler <NUM> (e.g. in units of mass over time), K is a predetermined constant, and <MAT> is a pressure differential for the boiler drum <NUM> (e.g. in units of pressure over time). In some embodiments, K is selected so that any variation in the steaming rate caused by pressure changes downstream of the boiler <NUM>, for example in the steam distribution system <NUM>, are discarded as false indications of heat release change. For example, a more complex formula for IHR, with one or more non-linear parameters and where variables and rates-of-change of variables are combined dynamically, may be used. In another example, a neural network or other machine-learning system is used within the virtual sensor to compute and estimate a process value for IHR that can be used as one or more control variables based on the target IHR received by the slow-speed controller <NUM>.

In some embodiments, the IHR virtual sensor <NUM> uses additional information to determine the IHR. For example, the chemical composition of the flue gas expelled at the flue gas outlet <NUM>, for instance a concentration of O<NUM> therein, is used as an additional factor for the IHR virtual sensor <NUM>. In another example, a temperature of the surface <NUM> and/or a mass distribution of solid fuel <NUM> on the surface <NUM> is used as an additional factor for the IHR virtual sensor <NUM>. Still other factors may be used to supplement or augment the IHR virtual sensor <NUM>, including any of the factors listed hereinabove.

The high-speed controller <NUM>, is configured for receiving the current firing rate demand from the slow-speed controller <NUM> and the IHR from IHR virtual sensor <NUM>. In some embodiments, the high-speed controller is configured for operating in substantially real-time for instance at least at an execution rate faster than <NUM> seconds. In some embodiments, the firing rate demand is representative of a requisite value for the IHR of the furnace <NUM>. The firing rate demand and the IHR may be provided in any suitable format, and may be received by the second controller via any suitable wired or wireless means. In some embodiments, the second controller is provided with a default firing rate demand which remains substantially unchanged, for example because of long response times for steam pressure and steam flow to changes in air flow and fuel input, and thus steps <NUM> and <NUM> may be skipped.

The high-speed controller <NUM> is also configured to compare the IHR, obtained from the IHR virtual sensor <NUM>, to the current firing rate demand obtained from the slow-speed controller <NUM>. Changes in the IHR vis-à-vis the firing rate demand occur as the combustion process takes place within the furnace <NUM>, and may be attributable to a variety of factors that are either difficult or impractical to measure directly. However, measurable effects throughout the solid-fuel heat generator system <NUM> can serve as a proxy for determining or estimating the IHR and/or changes in the IHR, via the virtual sensor. In some embodiments, the high-speed controller <NUM> is also configured for projecting changes in the IHR and/or to establish trends in the IHR based on one or more past values of the IHR.

For example, changes in the IHR results in changes in the flue gas composition (H<NUM>O, concentration of excess O<NUM>, CO, NOX, and the like) and a furnace temperature profile, for instance from the combustion site at the surface <NUM> up to the flue gases at the flue gas outlet <NUM>. Additionally, heat transfer differences may be observed, for instance through energy balance calculations, at later elements like steam superheaters, economizers, air heaters, or other heat exchangers using flue gases.

In addition, changes in the IHR result in several measurable effects within the boiler <NUM>, for instance changes in the pressure and/or temperature in the boiler drum <NUM>, steaming production rate of the boiler <NUM>, and a water level in the boiler drum <NUM>. For example, an increase in the IHR will vaporize some water contained in the boiler drum <NUM>, causing a measurable increase in a level of steam in the boiler drum <NUM>, a change in the pressurization of the boiler drum <NUM>, as well as an increased steaming rate by the boiler <NUM>. Conversely, a reduction in heat release depressurizes the boiler drum <NUM>, causes a shrink of the level of water in the boiler drum <NUM> due to the sudden reduction of steam volume within the bank, and decreases the steaming rate of the boiler <NUM>.

In some embodiments, the high-speed controller <NUM> also compares the current IHR to at least one previously-determined IHR. In some embodiments, the comparison is measured in terms of a relative variation of the current IHR with respect to the previously-measured IHR. In other embodiments, the comparison is measured in terms of an absolute variation of the current IHR vis-à-vis the previously-measured IHR. Still other comparisons are considered.

The setpoint adjustor <NUM> is configured for receiving instructions from the high-speed controller <NUM> for adjusting the underfire air flow, provided by the underfire air inlet <NUM>, based on the comparison between the IHR and the current firing rate demand, or any other suitable factors, as performed by the second controller. By adjusting the underfire air flow, the combustion process of the solid fuel <NUM> is altered, thereby adjusting the IHR to compensate for deviations in the IHR.

For example, if the high-speed controller <NUM> determines that the IHR is lower than the current firing rate demand, for instance as set by the first controller, the underfire air flow is rapidly increased, forcing more air into the solid fuel <NUM>, that will lead to an increased combustion reaction and heat release. Conversely, if the IHR is over the firing rate demand, for instance as set by the first controller, the underfire air flow is rapidly decreased to reduce the amount of oxygen flowing to the solid fuel <NUM> thereby reducing the combustion inside the furnace.

In some embodiments, a certain tolerance for the IHR is allowed to the high-speed controller <NUM>. For example, the IHR is only considered to require adjustment of the underfire air flow when current IHR strays from the current firing rate demand by more than a predetermined tolerance. The predetermined tolerance may be a percent deviation, a number of standard deviations, or any other suitable value.

Optionally, the setpoint adjustor <NUM> is configured for adjusting one or more other operating characteristics of the solid-fuel heat generator system <NUM> based on the current IHR. This may include adjusting the overfire air flow rate provided by the overfire air inlet <NUM>, adjusting the rate of flow of solid fuel <NUM> to the furnace <NUM>, and/or a rate of movement of the surface <NUM> when the level of fluctuation does not correspond to the current firing rate demand. For example, when the surface <NUM> is a grate, a rate of vibration of the grate is adjusted by the setpoint adjustor <NUM>. In another example, when the overfire air inlet <NUM> includes a recycled flue gas inlet, the rate of flow of recycled flue gas is adjusted by the setpoint adjustor <NUM>. Still other embodiments are considered.

In some embodiments, the underfire air flow <NUM> and optionally other operating characteristics of the solid-fuel heat generator system <NUM> are substantially continuously adjusted in response to the IHR and/or changes in the current firing rate demand. The control system <NUM> is configured for iteratively adjusting the various setpoints of the furnace <NUM> in response to further changes to the IHR and/or the current firing rate demand. For example, a subsequent firing rate demand can be obtained, and the control system <NUM> further adjust the underfire air flow and optionally the other operating characteristics of the solid-fuel heat generator system <NUM> based on further changes to the IHR. Changes to the IHR occur following changes to the fuel burning process, and due to some adjustments performed by the setpoint adjustor <NUM>.

In some embodiments, the control system <NUM> operates periodically at any suitable interval. For example, the operation of the control system <NUM> is repeated several times per second, every second, every few seconds, several times per minute, every minute, every few minutes, several times per hour, every hour, every few hours, several times per day, or at any other suitable interval. In some other embodiments, the control system <NUM> is operated in response to the control system <NUM> receiving a request to perform various operations, or any other suitable trigger.

In some embodiments, a minimum time delay between the previously-determined IHRs and the current IHR is set. The time delay may be used to ignore or filter process variables <NUM> to validate them and eliminate outliers for their use as input variables when determining the current level of fluctuation.

The control system <NUM> provides a rapid feedback loop which may be used to stabilize the heat release of the biomass combustion system <NUM> by adjusting the underfire air flow provided by the underfire air inlet <NUM>, and optionally other operational parameters, based on the fluctuation of the IHR. The method <NUM> may reduce the short-term variability of steam production. In some embodiments, the method <NUM> is used to adjust the operation of the solid-fuel heat generator system <NUM> on a scale of minutes, for instance having a closed-loop time constant of less than two minutes.

With reference to <FIG>, the control systems <NUM> and <NUM> may be implemented by a computing device <NUM>, comprising a processing unit <NUM> and a memory <NUM> which has stored therein computer-executable instructions <NUM>. The processing unit <NUM> may comprise any suitable devices configured to cause a series of steps to be performed so as to implement the functionality of the control systems <NUM> and <NUM>, such that instructions <NUM>, when executed by the computing device <NUM> or other programmable apparatus, may cause the functions/acts/steps specified in the methods described herein to be executed.

The memory <NUM> may comprise non-transitory computer readable storage medium such as, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. The memory <NUM> may include a suitable combination of any type of computer memory that is located either internally or externally to device such as, for example, random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. The memory <NUM> may comprise any storage means (e.g., devices) suitable for retrievably storing the computer-executable instructions <NUM> executable by processing unit <NUM>.

It should be noted that various types of computer systems and logic approaches may be employed, as appropriate. This includes fuzzy logic, deviation, model predictive controllers, adaptive PID control, and the like. Additionally, any suitable type of machine learning or artificial intelligence system may be used, including both supervised and unsupervised neural networks, and the like.

With reference to <FIG>, an embodiment of the control system <NUM> is configured to interface with the sensors <NUM>, a control interface <NUM>, and a database or other storage medium <NUM>. The sensors <NUM> are configured for obtaining information about the operating characteristics of the solid-fuel heat generator system <NUM> and for providing the information to the control system <NUM>, and optionally to the control interface <NUM>. The control interface <NUM> is configured for providing the control system <NUM> with the firing rate demand, and optionally with the information from the sensors <NUM>. The database <NUM> is configured for storing an array of previously-determined IHR, past control actions, for receiving and storing the current IHR, and for providing the previously-determined IHR to the control system <NUM>.

The control system <NUM> includes an IHR module <NUM> and an adjustment module <NUM>. The adjustment module <NUM> may be provided with a plurality of units which are each configured for adjusting the operation of a particular element of the solid-fuel heat generator system. For example, the adjustment module <NUM> includes an underfire flow unit <NUM>, which controls the rate of underfire air flow via the underfire air inlet <NUM>, an overfire flow unit <NUM>, which controls the rate of overfire air flow via the overfire air inlet <NUM>, a fuel flow unit <NUM>, which controls the rate of flow of solid fuel <NUM> to the furnace <NUM>, and a surface control unit <NUM>, which controls the movement of the surface <NUM>. In other examples, the adjustment module <NUM> may include fewer units, or additional units, as appropriate.

The IHR module <NUM> is configured for optionally receiving the current firing rate demand, for example from the control interface <NUM>,. The fluctuation module <NUM> may receive the current firing rate demand over any suitable wired or wireless communication path, and in any suitable format.

The IHR module <NUM> is also configured for determining the current IHR and the previously-determined IHR. The IHR module <NUM> uses the information received from the sensors <NUM> and/or the control interface <NUM> to determine the current IHR and, optionally obtains the previously-determined IHR from the database <NUM>. The IHR module <NUM> then compares the current IHR with the current firing rate demand, and any other values, as appropriate.

When the current IHR does not correspond to the current firing rate demand, the IHR module <NUM> sends an indication to the adjustment module <NUM> and instructs the adjustment module <NUM> to adjust the underfire air flow. The adjustment module <NUM>, via the underfire air unit <NUM>, adjusts the underfire air flow in response to the indication received from the fluctuation module <NUM>, as per step <NUM>.

Optionally, the indication from the IHR module <NUM> to the adjustment module <NUM> also instructs the adjustment module <NUM> to adjust other operational parameters of the solid-fuel heat generator system <NUM>. The adjustment module <NUM> then effects the changes to the operational parameters of the solid-fuel heat generator system <NUM> via the appropriate units <NUM>, <NUM>, <NUM>. For example, the adjustment module <NUM> effects a change to the overfire air flow via the overfire flow unit <NUM>. In another example, the adjustment module <NUM> effects a change in the rate of vibration of the grate in the furnace <NUM> via the surface control unit <NUM>.

With reference to <FIG>, in some embodiments the IHR virtual sensor <NUM> and the high-speed controller <NUM> collaborate to implement a method <NUM>. It should be noted that in other embodiments, the method <NUM> is implemented by more or fewer components.

At step <NUM>, optionally a current firing rate demand is received. At step <NUM>, an IHR is determined via a virtual sensor. At step <NUM>, the IHR is compared to the current firing rate demand. At step <NUM>, an underfire air flow is adjusted when the instantaneous heat release does not correspond to the current firing rate demand. At step <NUM>, at least one of overfire air flow, a rate of fuel flow, and a rate of movement of a surface is adjusted when the instantaneous heat release does not correspond to the current firing rate demand.

The methods and systems for modulating a solid-fuel-based combustion process described herein may be implemented in a high-level procedural or object-oriented programming or scripting language, or function block logic, or ladder logic, or state-based algorithms, or a combination thereof, to communicate with or assist in the operation of a computer system, for example the computing device <NUM>. Alternatively, the methods and systems for modulating a solid-fuel-based combustion process described herein may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems for generating solid-fuel-based energy described herein may be stored on a storage media or a device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the methods and systems for modulating a solid-fuel-based combustion process described herein may also be considered to be implemented by way of a non-transitory computer-readable storage medium having a computer program stored thereon. The computer program may comprise computer-readable instructions which cause a computer, or more specifically the at least one processing unit of the computer, to operate in a specific and predefined manner to perform the functions described herein.

Claim 1:
A system comprising a solid-fuel-based combustion heat generator system (<NUM>) producing steam equipped with:
- a set of sensors (<NUM>);
- a setpoint adjustor (<NUM>) within the heat generator system;
- a steam distribution system (<NUM>); and
- a boiler (<NUM>) comprising a steam outlet (<NUM>) through which the produced steam exits a boiler drum (<NUM>), the boiler being coupled to the steam distribution system so that steam produced within the boiler (<NUM>) is routed toward the steam distribution system (<NUM>) via the steam outlet (<NUM>);
the system comprising:
- a slow-speed controller (<NUM>);
- an Instant Heat Release, IHR, virtual sensor (<NUM>) configured to estimate an IHR of the heat generator system based on first values measured by one or more of the sensors (<NUM>), of at least the rate of steam flow in the steam outlet (<NUM>) and the steam pressure in the boiler drum (<NUM>); and
- a high-speed controller (<NUM>) configured to receive from the slow-speed controller (<NUM>) a current firing rate demand based on second values measured by one or more of the sensors (<NUM>), of an energy level of the steam in the steam distribution system (<NUM>), to receive the estimated IHR from the IHR virtual sensor, to make a comparison of the received current firing rate demand and the received estimated IHR, and to instruct the setpoint adjustor (<NUM>) to adjust an underfire air flow within the heat generator system based on the comparison.