Abstract: A method for obtaining information on quality of combustion of a liquor in a chemical recovery boiler. The method comprises entering a value of a first input parameter to a computational model configured to determine, based on the value of the first input parameter, a value of the quality of combustion of the liquor in the chemical recovery boiler, and at a first time, running the computational model to obtain a first modelling result. The method comprises measuring, from the chemical recovery boiler a value indicative of carryover to obtain a measurement result; comparing the first modelling result with [a] the measurement result or [b] a result derived from the measurement result, to obtain a primary comparison result; and adjusting the value of the first input parameter based on the primary comparison result to obtain an adjusted value of the first input parameter.

Abstract: A heated water recirculation system includes a water heater having a water inlet and a water outlet. The heated water recirculation system further includes a flow detector positioned to detect inflow water flowing into the water heater through the water inlet. The heated water recirculation system also includes a controller configured to control operations of a recirculation pump based on a detection of the inflow water flowing into the water heater through the water inlet. The water heater is configured to provide heated water through the water outlet, and the recirculation pump is configured to circulate the heated water through the heated water recirculation system.

Abstract: A method for providing a warning of the risk of Legionella in a fluid conductor, the method including determining the percentage of a duration a fluid is disposed in the fluid conductor at a temperature in which Legionella can thrive during a period, wherein if the percentage of the duration is greater than about 50% of the period, a first indication of a risk of Legionella is raised.

Abstract: A flue gas analyser for determining the efficiency of a burner burning a supply gas and producing a flue gas by: calculating an efficiency of the burner based on a detected amount of a first target gas in the flue gas and an expected amount of the first target gas in the flue gas; predicting an amount of a second target gas in the flue gas based on the efficiency of the burner; estimating a composition of the supply gas based on a detected amount of the second target gas in the flue gas and the predicted amount of the second target gas in the flue gas; and correcting the calculated efficiency of the burner based on the estimated composition of the supply gas.

Abstract: A carbon monoxide shutoff system for an engine of a portable electrical generator has a carbon monoxide gas sensor, a microcontroller, and an output indicator. The carbon monoxide gas sensor generates an output electrical current proportional to a detected concentration of ambient carbon monoxide. The microcontroller has an input connected to the carbon monoxide gas sensor, and an output connected to an operational control of the engine. A deactivation signal generated by the microcontroller in response to detection of a deactivation condition is based upon the output electrical current from the carbon monoxide gas sensor matching predefined value and duration thresholds. The deactivation signal is operative to stop the engine.

Abstract: Provided is a boiler configured to perform heating by a heat generation section provided with heat generation bodies in a container and capable of properly charging a circulation path including, as part thereof, the inside of the container with required gas. A boiler includes: heat generation bodies; a container configured such that the heat generation bodies are provided inside and configured chargeable with gas with higher specific heat than that of air; and a circulation path including, as part thereof, the inside of the container, the circulation path being a path in which gas circulates. When the charging process of charging the circulation path with the gas is performed, a circulation amount and a gas concentration in the circulation path are monitored.

Abstract: The present disclosure relates to a network-based centralized security monitoring (CSM) system. An example CSM includes one or more memory devices configured to store instructions thereon that, when executed by one or more processors, cause the one or more processors to receive a plurality of parameter data elements comprising one or more characters for a plurality of parameter types from a monitored site, determine for each of the plurality of parameter types a number of occurrences of a plurality of different character groups in the plurality of parameter data elements, generate a count structure indicating the number of occurrences of the plurality of different character groups in the plurality of parameter data elements for each of the plurality of parameter types, and generate a security signature for the monitored site, the security signature comprising the count structure for each of the plurality of parameter types.

Abstract: Power conversion efficiency using variable switching frequency. At least some of the example embodiments are power circuit controllers including a voltage sense input and a control signal output. The power circuit controller varies an output frequency of the control signal output between a first frequency and a second frequency based on a source voltage supplied to the power controller. Both the first frequency and the second frequency are non-zero.

Abstract: Arrangements for controlling a climate control system are provided. A hazard detector of a group of smart devices may detect a carbon monoxide (CO) alarm condition at the hazard detector. The hazard detector may transmit, via a relatively low-power mesh communication network, an indication of the CO alarm condition to one or more other smart devices. A spokesman node of the relatively low-power wireless communication network may translate the indication of the CO alarm condition from a first wireless communication protocol to a second wireless communication protocol. The spokesman node may transmit the indication of the CO alarm condition to a system controller via a relatively high-power wireless communication network and the second wireless communication protocol. A system controller of the climate control system may transmit a signal to turn off at least part of the climate control system.

Abstract: A water feeding system provided with: a first feed water line through which first feed water flows; a second feed water line through which second feed water having a lower pressure than the first feed water flows; a first heater that heats the first feed water; a first feed water introducing line that guides first heated feed water, which is the first feed water that has been heated by the first heater, to the second feed water line; a medium heat exchanger that causes the first heated feed water to exchange heat with a medium, thereby cooling the first heated feed water and heating the medium; and a cooling water injecting line that injects cooling water having a lower temperature than the first heated feed water into the first feed water introducing line, at a position located further to the second feed water line side than the medium heat exchanger.

Abstract: A system for controlling activity in a combustion chamber. The system does not necessarily need to be mechanically adjusted and yet may provide precise control of a fuel air mixture ratio. A sensing module of the system may have a mass flow sensor that relates to air flow and another sensor that relates to fuel flow. Neither sensor may need contact with fuel. Fuel and air to the system may be controlled. Pressure of the fuel and/or air may be regulated. The sensors may provide signals to a processor to indicate a state of the fuel and air in the system. The processor, with reliance on a programmed curve, table or the like, often based on data, in a storage memory, may regulate the flow or pressure of the fuel and air in a parallel fashion to provide an appropriate fuel-air mixture to the combustion chamber.

Abstract: The current disclosure relates to a method of steam generation. Particularly, the current disclosure relates to steam generation supply apparati and associated control systems that are used for enhanced oil recovery. Certain embodiments are provided including methods and associated control systems related to the startup as well as main steam pressure header control or maintenance of a desired steam quality for such steam generation systems during normal operation.

Abstract: Methods and systems for providing appliances with gas quality information are described herein. One system includes a single calorimeter or a single gas chromatograph configured to determine a calorific value of a gas being supplied to an area having a plurality of appliances and communicate the calorific value of the gas to the plurality of appliances.

Abstract: A system includes a waste heat recovery heat exchanger configured to heat a heating fluid stream by exchange with a heat source in a crude oil associated gas processing plant; and an Organic Rankine cycle energy conversion system. The Organic Rankine cycle energy conversion system includes a heat exchanger configured to heat a first portion of a working fluid by exchange with the heated heating fluid stream; and a cooling subsystem including one or more cooling elements each configured to cool one or more of a process stream from the crude oil associated gas processing plant and a cooling water stream for ambient air cooling by exchange with a second portion of the working fluid.

Abstract: Disclosed herein is an apparatus for reactor power control of a steam turbine power generation system including a reactor, a high-pressure turbine to which steam is supplied from the reactor through a main steam pipe, a low-pressure turbine to which the steam discharged from the high-pressure turbine is supplied via a moisture separator reheater, a branch pipe branched from the main steam pipe to be connected to the moisture separator reheater, a generator connected to the low-pressure turbine, a condenser for condensing the steam discharged from the low-pressure turbine, a condensate pump for feeding condensate condensed by the condenser, and feed water heaters for heating the condensate, the apparatus including a branch pipe control valve provided on the branch pipe and a control unit for controlling an opening degree of the branch pipe control valve.

Abstract: A boiler system equipped with a boiler group mixedly provided with a step value control boiler and a proportional control boiler. A boiler number control device is configured to control the number of boilers in the boiler group, and includes an output controller configured to control a combustion state of the boiler group so as to cause the proportional control boiler to output steam equivalent to a required steam flow according to a required load, and an output switcher configured to switch, under a condition that a steam flow outputted from the proportional control boiler reaches a predetermined steam flow exceeding a steam flow at a possible combustion point of the step value control boiler, output of the steam flow at the combustion point from the proportional control boiler to the step value control boiler.

Abstract: A method for controlling a temperature of steam for a steam power plant is provided. A state regulator controls the temperature of the steam at an outlet of a superheater using a feedback of multiple medium states of the steam in the superheater. An aim herein is to achieve a stable and precise control of the steam temperature. This is achieved in that the state regulator is a linear regulator, the feedback matrix of which is ascertained such that the regulator has the control quality of a linear-quadratic regulator.

Abstract: There is described herein a method and system for dispatching a single steam flow command to multiple control elements by prioritizing control elements and measuring responsiveness and availability of the control elements using feedbacks. The dispatched single steam flow command may then be adjusted as a function of the responsiveness of each control element.

Abstract: Systems and methods for controlling a climate control system of a smart-home environment that includes a plurality of smart devices are provided. One method includes detecting, with a hazard detector of the smart devices, a level of carbon monoxide (CO) at the hazard detector that exceeds a threshold CO level at a location of the hazard detector, determining, by one of the smart devices, that the climate control system includes a combustion based heat source, and in response to the detecting and the determination, transmitting, by a system controller of the climate control system, a first signal to turn off at least one aspect of the climate control system.

Abstract: A method for starting a continuous steam generator is provided. The steam generator includes a combustion chamber provided with a plurality of burners, a water-steam separation device that is mounted downstream of evaporator tubes of the water-steam separation device on a flow-medium side. The amount of water flowing into the water-steam separation device during a starting process is kept to a minimum. The firing power of at least one of the burners is adjusted in accordance with a filling level characteristic value of the water-steam separation device.

Abstract: A method for operating a recirculating waste heat steam generator is provided, in which in a pressure stage of the recirculating waste heat steam generator, the feed water mass flow is guided on the basis of a specified desired value in order to control the water level in a drum. The method should give a recirculating waste heat steam generator a particularly high degree of efficiency and simultaneously a particularly high level of operational flexibility. For this purpose the thermal input introduced into an evaporator of the pressure stage is used as input variable in the determination of the desired value.

Abstract: A boiler group includes a plurality of boilers. Each of the boilers has a unit amount of steam and a maximum variable amount of steam. A controller includes a deviation calculator for calculating a deviation amount between a necessary amount of steam and an output amount of steam, a boiler selector for selecting the plurality of boilers in order of load factors, and an output controller for varying an amount of steam of a boiler selected first by the boiler selector by the maximum variable amount of steam—when the deviation amount is at least the—maximum variable amount of steam, and varying the amount of steam of the first selected boiler by the unit amount of steam for the deviation amount when the deviation amount is less than the maximum variable amount of steam.

Abstract: The current disclosure relates to steam generation and supply apparati and associated control systems. Particularly, the current disclosure relates to such steam generation supply apparati and associated control systems that are used for enhanced oil recovery. Certain embodiments are provided including methods and associated control systems related to the startup as well as main steam pressure header control or maintenance of a desired steam quality for such steam generation systems during normal operation.

Abstract: A flow state controlling device controls, to a specified flow state, fluid of a gas/liquid two-phase flow that flows through a flow path. The flow state controlling device includes a pressure acquiring portion that acquires pressure information relating to pressure of the fluid, a mass velocity acquiring portion that acquires mass velocity information relating to a mass velocity of the fluid, a dryness fraction acquiring portion that acquires dryness fraction information relating to the dryness fraction of the fluid, and a controlling portion that controls, based on the pressure information, the mass velocity information and the dryness fraction information, a pressure controlling device that is able to change a pressure of the fluid, a mass velocity controlling device that is able to change a mass velocity of the fluid, and a heat controlling device that is able to change the latent heat of the fluid.

Abstract: The current disclosure relates to steam generation and supply apparati and associated control systems. Particularly, the current disclosure relates to such steam generation supply apparati and associated control systems that are used for enhanced oil recovery. Certain embodiments are provided including methods and associated control systems related to the startup as well as main steam pressure header control or maintenance of a desired steam quality for such steam generation systems during normal operation.

Abstract: The current disclosure relates to steam generation and supply apparati and associated control systems. Particularly, the current disclosure relates to such steam generation supply apparati and associated control systems that are used for enhanced oil recovery. Certain embodiments are provided including methods and associated control systems related to the startup as well as main steam pressure header control or maintenance of a desired steam quality for such steam generation systems during normal operation.

Abstract: The current disclosure relates to steam generation and supply apparati and associated control systems. Particularly, the current disclosure relates to such steam generation supply apparati and associated control systems that are used for enhanced oil recovery. Certain embodiments are provided including methods and associated control systems related to the startup as well as main steam pressure header control or maintenance of a desired steam quality for such steam generation systems during normal operation.

Abstract: A ventilation system includes a connection determinator configured to determine that N-th, second, and sixth humidity controlling ventilation devices are connected to an identical second duct bank in a situation where when fans of the second and sixth humidity controlling ventilation devices are driven, and the rotational speed of a fan of the N-th humidity controlling ventilation device is changed, a power detector detects fluctuations in the power consumed by the fan of each of the second and sixth humidity controlling ventilation devices.

Abstract: Disclosed is a hot water supply system provided with a tank which holds a high-temperature liquid, and a heating means for generating the high-temperature liquid which is stored in the aforementioned tank. In the lower portion of the aforementioned tank is provided a water-heating heat exchanger which heats the water to be supplied to a hot water terminal by means of the liquid present in the lower portion of the aforementioned tank. Further, a hot water supply circuit is provided which conducts water to the aforementioned hot water supply terminal. The aforementioned hot water supply circuit splits into a water-heating path passing through the aforementioned water-heating heat exchanger, and a bypass path bypassing the aforementioned water-heating heat exchanger, and is provided with a hot water supply circuit control mechanism which controls the circulation state of the water in the aforementioned water-heating path and the aforementioned bypass path.

Abstract: When a detection temperature by a hot-water tank thermister (42) has been equal to or lower than a re-heating determination temperature over at least a re-heating determination time, a tank controller (50) performs a sterilization process by heating hot water within a hot-water tank (30) by means of a heat pump unit (60); and when the detection temperature by the hot-water tank thermister (42) has been equal to or lower than a determination temperature for prohibiting the use of hot water in the hot-water tank over at least a determination time for prohibiting the use of hot water in the hot-water tank, the tank controller (50) performs only a temperature regulation control via heating while keeping a hot-water flow regulation valve (34) in a closed state.

Abstract: A novel 3-Input-3-Output (3×3) Fuel-Air Ratio Model-Free Adaptive (MFA) controller is introduced, which can effectively control key process variables including Bed Temperature, Excess O2, and Furnace Negative Pressure of combustion processes of advanced boilers. A novel 7-input-7-output (7×7) MFA control system is also described for controlling a combined 3-Input-3-Output (3×3) process of Boiler-Turbine-Generator (BTG) units and a 5×5 CFB combustion process of advanced boilers. Those boilers include Circulating Fluidized-Bed (CFB) Boilers and Once-Through Supercritical Circulating Fluidized-Bed (OTSC CFB) Boilers.

Abstract: A level control system is provided. The system includes multiple sensors configured to measure multiple parameters related to a drum, wherein the multiple parameters include a drum liquid level, a vapor flow rate leaving the drum, a downstream pressure of the drum, and a feed-liquid flow rate entering the drum. The system also includes a level controller configured to adjust a level control valve in accordance with a signal representative of the drum liquid level, a signal representative of the downstream pressure and a signal representative of a given drum liquid level set point. The level controller is further configured to receive a feedback signal representative of a combination of a fraction of the signal representative of the drum liquid level and a fraction of the signal representative of the downstream pressure.

Abstract: The invention provides a method and a system for controlling floor heating or climate regulating systems with long time constants. According to the invention, a flow of a fluid is provided through the floor or through a similar medium with large thermal inertia. An induced heat is determined by adding up a plurality of differences between an inlet temperature of the fluid when it enters the medium and an outlet temperature of the fluid when it leaves the medium. The temperatures are sampled with a fixed sampling time and within a fixed period of time, and a corresponding change in temperature of the medium over the fixed period of time is determined. In the future, the temperature of that medium is controlled by use of a ratio between the induced heat and the change in temperature.

Abstract: The invention provides a method and a system for controlling floor heating or climate regulating systems with long time constants. According to the invention, a flow of a fluid is provided through the floor or through a similar medium with large thermal inertia. An induced heat is determined by adding up a plurality of differences between an inlet temperature of the fluid when it enters the medium and an outlet temperature of the fluid when it leaves the medium. The temperatures are sampled with a fixed sampling time and within a fixed period of time, and a corresponding change in temperature of the medium over the fixed period of time is determined. In the future, the temperature of that medium is controlled by use of a ratio between the induced heat and the change in temperature.

Abstract: A system including a reductant tank, a receiver, a first valve, a reductant supply line, a plurality of sensors, and a controller is provided. The reductant tank is configured to store a reductant. The receiver is configured to receive a supply of the reductant from an off-board reservoir. The first valve is in communication with the reductant tank and is configured to control a reductant flow into the reductant tank. The reductant supply line is in fluid communication with the receiver and is configured to provide the reductant flow to the first valve. The plurality of sensors is configured to generate a signal. The controller is in communication with the plurality of sensors. The controller is configured to issue a command to a heating element to modulate a temperature of the reductant supply line based, at least in part, on the signal generated by the plurality of sensors.

Abstract: A method for controlling a water level of a drum of a heat recovery steam generation system for a combined cycle power plant is provided. The method includes determining an optimum drum water level during start up operation of the heat recovery steam generation system based on a characteristic chart model. The characteristic chart model is generated based on a plurality of vapor pressures of the drum and a plurality of temperatures of drum metal at the time of the start up operation of the heat recovery steam generation system.

Abstract: A hydronic heating system comprises a water line, one or more boilers, and a control. In operation, the water line facilitates a circulation of water through a building and the boiler(s) heat the water as the water flows through the water line. The control calculates a system energy load for operating boilers. The calculation of the system energy load is a function of a set-point water temperature for the hydronic heating system, a supply water temperature of water flowing relative to a supply point of the water line, a return water temperature of water flowing relative to return point of the water line and a flow rate of water flowing relative to a flow sense point of the water line.

Abstract: A steam generation system delivers heats water and carbon dioxide at high temperatures in the presence of one or more plasma arc torches and converts the materials into hydrogen and carbon monoxide. The converted gas is delivered to a heat recovery steam generator (“HRSG”) to produce steam, which may be used to power a steam turbine. Depending on the amount of steam and/or power desired, the system may use a control system to vary the flow, temperature and pressure of the gas delivered to the HRSG. The control system may do this by bringing additional torches on-line or off-line in the processing chamber, by adding unheated gas directly from a supply source, shunting the gas from the HRSG, and varying the flow of water delivered to the HRSG.

Abstract: Methods and Systems for controlling boiler systems are disclosed. In one illustrative embodiment, a derivative action control is used reduce the likelihood of overshoot from a newly activated boiler. When a newly activated boiler becomes active, the boiler is held at a low firing rate for a predetermined period of time. The predetermined period of time may be cut short or even entirely eliminated under certain conditions. The methods and devices are further adapted for use in multi-stage boiler systems. In one embodiment, only the first stage of a multi-stage boiler system that becomes active is held at the low firing rate.

Abstract: A boiler control system for efficiently controlling the operation of a packaged boiler is provided. The system includes a combustion air control system, a fuel control system, a flue gas sensing system, and a boiler controller. The boiler controller is in operative communication with the combustion air control system, fuel control system, and the flue gas sensing system. Based upon a system demand, the boiler controller controls coarse-level operation of the combustion air control system and the fuel control system. The flue gas sensing system includes an oxygen sensor and a flue gas differential sensor that senses a change in a characteristic of the flue gas. When the flue gas differential sensor senses a change in the flue gas characteristic that meets a flue gas differential setpoint, the boiler controller controls fine-level operation of the combustion air control system to efficiently control the amount of oxygen in the flue gas.

Abstract: When a detection temperature by a hot-water tank thermister (42) has been equal to or lower than a re-heating determination temperature over at least a re-heating determination time, a tank controller (50) performs a sterilization process by heating hot water within a hot-water tank (30) by means of a heat pump unit (60); and when the detection temperature by the hot-water tank thermister (42) has been equal to or lower than a determination temperature for prohibiting the use of hot water in the hot-water tank over at least a determination time for prohibiting the use of hot water in the hot-water tank, the tank controller (50) performs only a temperature regulation control via heating while keeping a hot-water flow regulation valve (34) in a closed state.

Abstract: A steam generating device comprising: a housing (2) having a cavity therein; a water supply port (3) open in the housing (2); a water supply device (21) for supplying water into the housing (2) from the water supply port (3); a steam generating heater (4) embedded in the housing (2) and evaporating the water supplied from the water supply port (3); a discharge port (8) open in the housing (2) and discharging the steam generated by the steam generating heater (4); and a temperature sensor (5) for detecting the temperature of the housing (2). The water supply device (21) is driven when the temperature of the housing (2) becomes higher than a predetermined driving temperature (T1), and the water supply device (21) is stopped when the temperature of the housing (2) becomes lower than a predetermined stop temperature (T2) that is lower than the predetermined driving temperature (T1).

Abstract: The present invention relates to a control program, a controller, and a boiler system that are related to a boiler group including a plurality of boilers controlled in combustion at stepwise combustion positions.

Abstract: A high-strength heat resisting cast steel which has high creep rupture strength at temperatures of 620° C. or above, high toughness, and good weldability. A method of producing the steel, a steam turbine casing, a main steam valve casing, and a steam control valve casing, each casing being made of that steel, as well as a steam turbine power plant using those components are also provided. The high-strength heat resisting cast steel contains 0.06-0.16% by mass of C, 0.1-1% of Si, 0.1-1% of Mn, 8-12% of Cr, 0.1-1.0% of Ni, 0.7% or less of Mo, 1.9-3.0% of W, 0.05-0.3% of V, 0.01-0.15% of one or more of Nb, Ta and Zr in total, 0.1-2% of Co, 0.01-0.08% of N, and 0.0005-0.01% of B, the balance being Fe and unavoidable impurities.

Abstract: A method and an apparatus of controlling combustion in an oxyfuel combustion boiler are provided which ensure a sufficient furnace heat absorption through prevention of lowering of flame temperature, enabling oxyfuel combustion operations to be performed in a stable manner. A boiler-brought-in oxygen density which is an oxygen density for a total amount of gases introduced into a coal burning boiler is calculated and a flow rate of total recirculating gases is controlled such that the boiler-brought-in oxygen density falls within a predetermined range.

Abstract: Methods and devices for controlling multi-stage boiler systems. In one illustrative embodiment, the number of stages to be used is determined in a staging control sequence in response to a heating load, and in some cases, the individual stages are modulated to meet a heating load. In some embodiments, the staging control sequence may include observation of both heating load and the rate of change of the heating load. In another illustrative embodiment, the staging control compares a measured temperature to a setpoint and monitors changes in the measured temperature to make staging decisions. Various control methods are also provided to help achieve improved stability and efficiency, as desired.

Abstract: A boiler control method and system. A BFI (bed fuel inventory) value associated with a boiler can be estimated by detecting data from the boiler utilizing an inferential sensor. The bed fuel inventory value can then be stabilized at a particular value utilizing a feedback controller electrically connected to the inferential sensor, in order to optimize the bed fuel inventory value for varying operating conditions of the boiler, thereby permitting a thermal power associated with the boiler to be increased or decreased faster by respectively increasing or decreasing a primary air supply rate associated with the boiler.

Abstract: Provided is a method for operating a non-condensing boiler at maximum non-condensation efficiency, and more particularly a method for operating a non-condensing boiler, capable of supplying an appropriate amount of excess air for combustion of a burner, avoiding damaging a heat exchanger due to the condensed water generated at the heat exchanger, and effectively improving the heat efficiency.

Abstract: The invention relates to a process for operating a continuous steam generator. The aim of the invention is to provide, with little technical complexity and for any operating state, a synchronous variation of the feed-water mass flow passing through the evaporator heating surface and of the heat input into the evaporator heating surface. To this end, a regulating device for the discharge of feed-water is allocated to a device for adjusting the feed-water mass flow. The control variable of said regulating device is the feed-water mass flow, while its set-point value in relation to the feed-water mass flow depends on the set-point value associated to the power of the steam generator. The actual value of the feed-water density at the entry of the pre-heater is fed to the regulating device for the discharge of feed-water as one of the input values.

Abstract: A boiler control system for efficiently controlling the operation of a packaged boiler is provided. The system includes a combustion air control system, a fuel control system, a flue gas sensing system, and a boiler controller. The boiler controller is in operative communication with the combustion air control system, fuel control system, and the flue gas sensing system. Based upon a system demand, the boiler controller controls coarse-level operation of the combustion air control system and the fuel control system. The flue gas sensing system includes an oxygen sensor and a flue gas differential sensor that senses a change in a characteristic of the flue gas. When the flue gas differential sensor senses a change in the flue gas characteristic that meets a flue gas differential setpoint, the boiler controller controls fine-level operation of the combustion air control system to efficiently control the amount of oxygen in the flue gas.