Abstract: A method for controlling two-stage combustion furnaces having a first stage operated with sub-stoichiometric airflow and a second stage operated with excess air, whereby the first stage airflow is controlled such that the ratio of first stage airflow to total airflow is maintained less than ##EQU1## where N lies between zero and unity.

Abstract: Methods and apparatus for regulating furnace combustion air flow are provided which measure a gaseous combustion product in furnace gas after combustion, generate a present signal responsive to the measurement and change flow rate of combustion air in response to the generated signal in a manner the same as flow rate was changed in response to a previously generated signal if the present signal relates to the previous signal in the manner the previous signal related to a signal ancestor thereto but change the flow rate of combustion air in response to the generated signal in a manner opposite the manner the flow rate was changed in response to the previously generated signal if the present signal relates to the previous signal in a manner opposite the manner the previous signal related to a signal immediately ancestor thereto.

Abstract: A gas combustion apparatus is disclosed wherein an oxygen sensor having electrodes on both surfaces of a base body is fixed in advance at a position such that the oxygen sensor is within the exhaust gas a combustion flame under normal conditions and a combustion flame under oxygen deficiency conditions is brought into contact with only the measuring side electrode. The oxygen sensor is preferably mounted to a heat-resistance holder having an opening such that the measuring side electrode corresponds with the opening.

Abstract: A draft control system for furnaces comprises an auxiliary channel in communication both with ambient air and the flue of the furnace, a main draft control means for regulating the entrance of ambient, auxiliary draft air into the flue, and auxiliary draft control means mounted in the auxiliary channel for dampening the effect of extreme changes in external conditions on the main draft control means. Thus, uniform draft and efficient combustion is maintained in the furnace under a wide variety of conditions. The main draft control means comprises counter-balanced draft control plates which are initially set in an open position so that they can either open or close in order to efficiently regulate the draft in the flue. The auxiliary draft control means comprises, in one embodiment, an isolation damper plate rotationally mounted in the auxiliary channel, or, in a second embodiment, a set of louvred panels.

Abstract: A combustion device includes a fuel-air ratio controller. A control is coupled to receive a first signal functionally related to the status of the fuel-air controller and a second signal from an oxygen sensor which is functionally related to the oxygen in the discharge gases from the combustion zone. The control is operative to provide an output signal to a fuel regulator for adjusting the fuel delivered to the combustion zone in relation to the oxygen in the discharge gases.

Abstract: In a control system for a gas heated water or air heater, the use of the supplied fuel gas is to be improved by automatically determining and supplying the amount of air which is required for obtaining complete combustion. A gas control valve feeds a burner with the required amount of gas dependent on the demand of heat. A sensor responding to the content of oxygen or carbon dioxide within the flue gases is located in the stack and the output signal of this sensor is compared with a set point within an electric controller. In case of a control deviation, the output signal of the controller controls an adjustable source of air under pressure formed by a fan with subsequent air control valve in such a manner that the required amount of air for reaching optimum combustion is supplied.

Abstract: A system for marginally adjusting the fuel flow to a burner to maintain the proper oxygen content in the exhaust from the burner is disclosed. The burner is of the type where both the fuel and air flow rates are adjusted in a substantially fixed ratio in response to load changes on the system with the fuel being adjusted by a fuel control valve mounted in a fuel supply line. A self-operating pressure regulating valve having an actuator responsive to the differential pressure across the fuel control valve is mounted in the fuel line upstream of the fuel control valve. A set point adjustment mechanism is mounted on the regulating valve actuator to adjust the set point of the regulating valve in response to an oxygen controller which senses the oxygen content in the stack gases. The set point adjustment mechanism has a cam assembly which continously adjusts the set point of the regulator actuator by varying the compression on a spring loaded diaphragm therein.

Abstract: A method of firing a pulverized fuel-fired steam generator furnace wherein a mixture of recirculated cleaned flue gas and air is supplied to the mill for drying the pulverized fuel in the mill and transporting the pulverized fuel to the furnace. The volume flow rate of the gaseous mixture of recirculated flue gas and air is controlled in response to the feed rate of fuel to the mill to maintain a mixture to fuel ratio in the transport stream of about but not less than 1.5. The volume flow rate of recirculated flue gas with respect to the volume flow rate of air is controlled to maintain the oxygen content of the gaseous mixture at a level of at least 12% by volume and preferably in the range of 12 to 15% by volume.

Abstract: The efficiency of a furnace is substantially maximized by manipulating the amount of oxygen supplied to the combustion process in the furnace so as to provide a desired oxygen concentration in the flue gas which will result in substantially maximum furnace efficiency. Feed forward control based on the fuel flow rate may also be utilized to enable the control based on oxygen concentration in the flue gas to respond more quickly to a change in the fuel flow rate.

Abstract: A furnace air volume control apparatus for controlling the volume of furnace air to achieve efficient burning is disclosed. The apparatus includes regulating valves positioned within supply air inlets and exhaust gas outlets of the furnace. A measured data receiver positioned on the exhaust gas side transmits a measuring signal to a control unit connected to the regulating valves. The control unit includes a storage unit for storing valve positions assigned to respective burner loads. By monitoring various exhaust gas parameters with the measured data receiver and control unit valve position, adjustment in response to changes in the burner load is possible by comparing a previously stored valve position recalled from the storage unit with a characteristic curve. The valve adjusting value stored in the storage unit is essentially congruent with the change in burner load. After exhaust gas stabilization has occurred in response to different burner loads precise correction of the valve position value occurs.

Abstract: A combustion safety apparatus wherein combustion exhaust gas of a burner is arranged to be introduced into a detecting tube having a tubular oxygen concentration cell element, and a safety valve is arranged to be controlled in operation by the output of the cell element. The detecting tube is in communication at its outlet opening with a mixing tube of the foregoing burner or another burner.

Abstract: A method and system for controlling the combustion of, for example, coal or bark in a stoker boiler or black, liquor in a recovery boiler to provide operation at maximum efficiency. Control loops are provided for primary or undergrate air and secondary or overfire air. The undergrate air control loop is adjusted as a function of carbon dioxide or steam/fuel ratio, and the overfire air control loop is adjusted as a function of carbon monoxide. In addition to carbon monoxide, combustibles and opacity may be used. Air redistribution is also used to minimize combustibles or CO or opacity.

Abstract: A combustion control system for a furnace monitors the oxygen content, carbon monoxide content and temperature in the flue gas exhausting from the combustion chamber. These parameters are used to calculate total heat loss due to unreacted oxygen and the other excessive air components associated therewith, and carbon monoxide. Such heat loss calculations are continuously made and compared to determine whether total heat loss, oxygen related heat loss and carbon monoxide heat loss are increasing or decreasing. Depending upon the combination of increase and decrease associated with the various heat losses, the combustion air supply is increased or decreased. In this manner it is possible to minimize heat loss and maximize furnace efficiency even though the combustion characteristics of the combustion unit may change with time.

Abstract: A combustion control system which utilizes non-linear parameters for controlling a combustion process with greater efficiency than has heretofore been available is disclosed. According to the method, the quantity of carbon monoxide, unburned hydrocarbons, and/or opacity is measured and compared with a predetermined value for that parameter. Error signals for each parameter are generated and supplied to an error selector which chooses the error signal of the largest magnitude. The error signal is then compensated for the non-linear relationship between the parameter and the amount of excess air supplied to the combustion process. Other operations, including checking the proposed control signal output against one or more constraints are performed, and if satisfactory, an output signal is supplied to a servo-mechanism for controlling the air flow to the combustion process.

Abstract: In a recovery boiler having a plurality of air inputs, with the primary air input closest to the bed of the boiler, a fuel input, a smelt output, and an exhaust output, a method of controlling the combustion of fuel in the boiler to operate at the maximum reduction efficiency. The method includes the steps of measuring the amount of sulphur dioxide at the exhaust output; and varying the amount of air entering into the boiler through the primary air input until the minimum amount of sulphur dioxide is measured at the exhaust output.

Abstract: There is provided a combustion appliance with a safety device. An oxygen partial pressure sensor made up of a transition metal oxide or rare earth metal oxide is normally disposed in a position in which the excess air ratio downstream of a flame formed by a burner can be detected and, at times of abnormality, within the flame. The resistance change of said oxygen partial pressure is detected and the combustion is stopped when incomplete combustion occurs due to oxygen depression, clogging of the primary air orifice of the burner or clogging of the combustion chamber with the products of combustion.

Abstract: An afterburner for use as a secondary combustion chamber in a starved-air combustor system to further combust any combustible material in the combustion gas and entrained solid particle material discharge from the combustion chamber of the starved-air combustor system. The afterburner is lined with refractory and includes a diverter plate positioned transversely to the incoming flow of combustion gases. The afterburner is divided into a plurality of reaction zones, each of which has an associated reaction air supply. The diverter plate imparts a cyclonic flow to the combustion gas which is enhanced by air injected in the combustion zones. The temperature of the gas discharged from the afterburner is monitored and the flow of reaction air controlled responsive to changes in discharge gas temperature from a predetermined temperature.

Abstract: A microprocessor based controller for regulating the position of a stack damper in a combustion furnace by feedback control adjusting damper position in view of an operator input target value of excess oxygen and an actual monitored excess oxygen value. A feedforward control overrides the feedback control for a time period initiated by the feedforward control responding to process variables indicating increase in combustion demand.

Abstract: Furnace performance is controlled during start-up or very low load operation at a time when the minimum air flow required to be supplied to the furnace is significantly greater than that required to burn the fuel being supplied to the furnace. Decreased furnace heat absorption is accomplished by supplying a larger quantity of the air immediately adjacent the fuel input location for the purpose of diluting the combustion gases and immediately decreasing their temperature level. Increased furnace heat absorption is obtained by introducing a greater portion of the air flow into the furnace at a location remote from the fuel being burned so that the gases at the fuel location remain at a high temperature, and transfer heat to the walls, before being diluted by the incoming air.

Abstract: The fuel supply to a boiler (11) is controlled by a fuel valve (17) driven by a motor (18) in response to measured steam pressure at (12) in relation to a demanded pressure. The motor (18) adjusts at the same time a damper (36) for supplying combustion air at (13). Air supply at (13) can also be controlled in response to the pressure drop across a register (38) as measured by airlines (51). The invention provides an over-riding control in response to too much or too little oxygen in the exhaust gases in the stack (15). The oxygen level is measured by a detector (26), and if it is outside limits set at (29) a motor (41) operates a valve (42) connected between the airlines (51). A timer with a contact T1 ensures that the control in response to oxygen level is only operative for a small part of each of a number of repeated 10 second cycles.

Abstract: A method of controlling the opacity of the exhaust of the combustion of solid fuel and air in a furnace comprises measuring the opacity of the exhaust. The amount of air and the direction (i.e., increase or decrease) entering into the furnace is changed. The opacity of the exhaust is measured again. The later measured value of opacity is compared to the earlier measured value. The amount of air entering into the furnace is controlled based upon the comparison.

Abstract: This invention relates to an improvement in control apparatus which prevents formation of smoke in a combustion process. The conventional control includes apparatus for first providing the proper flow of either air or fuel to the process to satisfy the required demand for heat. A ratio device is then used to determine the flow of the remaining component necessary for obtaining proper combustion conditions. Where the BTU content of the fuel is likely to vary, a device for analyzing stack gases, typically an oxygen probe is then used to provide a signal to adjust the ratio device based on conditions indicated by the stack gases. The improvement of this invention includes a device for determining when the proportion of the exhaust gas component is outside limitations indicating smoking may occur and an emergency control device actuated when such conditions exist for rapidly adjusting the proportions of fuel and air supplied to the process in order to prevent smoking.

Abstract: A method and apparatus for the heat treatment of industrial wastes wherein at least some of the constituent materials of the wastes are subjected to combustion and/or to pyrolysis to produce flue gases and, in some applications, a residue. The supply of an oxygenated combustion-supporting gas to the wastes is regulated as a function of at least one sensed predetermined characteristic of the flue gases. The oxygenated gas may be a mixture of air and substantially pure oxygen, the feed rate of one or both of these being regulated in response to the sensed temperature and/or oxygen content of the flue gases. Such regulation maintains the oxygen content of the flue gases within the range of from 0 to 7%; and the temperature of the flue gases may be maintained from 400.degree. to 1200.degree. C. and, preferably within a range of 50.degree. C. in this region.

Abstract: The preferred embodiment of the invention disclosed herein includes apparatus for and steps of separating glass, metal and other generally non-combustible material from refuse to provide a volume of generally combustible refuse, shredding this volume of combustible refuse into relatively small particles, mixing these particles with primary combustion air and conveying the resultant mixture of air and particles into a combustion chamber. The combustion chamber is preheated by auxiliary heating means to a temperature sufficient to cause the mixture to be self-igniting in the combustion chamber. Secondary combustion air is fed to the combustion chamber at spaced-apart points within the chamber for assuring a complete combustion process.

Abstract: Apparatus and method for changing the calibrated linkage relationship between two flow control devices of combustion apparatus without impeding the normal operation of the associated process. Means are provided, responsive to remote, manual or automatic control, to calibrate a jackshaft linkage type of control apparatus in order to provide for range changes and zero adjustment.

Abstract: A method of and apparatus for controlling the feed amount of air for combustion in a natural draft type heating furnace is disclosed, in which the draft pressure, the oxygen concentration in a combustion gas, the opening degree of a damper for controlling the flow rate of the combustion exhaust gas, the flow rate of a fluid to be heated and the temperatures of the fluid to be heated at inlet and outlet portions of the heating furnace are measured, and the feed amount of air for combustion is controlled based on measured values obtained at predetermined time intervals or corrected values thereof.

Abstract: Control method and apparatus for optimizing the operation of a natural draft combustion zone through which a conduit containing a process fluid to be heated passes, by decreasing the supply of combustion air until one or more of the following predetermined limiting conditions is reached: maximum CO in the flue gas, minimum O.sub.2 in flue gas, minimum draft in the combustion zone, maximum temperature of the outer surface of said conduit, and increase in the rate of fuel addition above a minimum amount. When a limiting condition is reached, the supply of combustion air is increased until the limiting condition is no longer present, and the cycle then repeated.

Abstract: The well-known "Jack-shaft" or "Single-point" positioning or a two-point parallel combustion control system has been modified by a trim link member articulated on the master arm to introduce a phase angle between the master arm associated with fuel supply adjustment and the slave arm associated with the combustive agent supply adjustment in a combustion engine, boiler, heater, or the like, thereby to permit oxygen or air-to-fuel ratio adjustment at all times.

Abstract: This invention is a control for a burner enabling it to operate efficiently with very little excess air but providing a main control for the fuel and for the combustion air in response to demand, and an auxiliary control in response to the amount of free oxygen in the products of combustion. The latter quantity can be measured by a zirconia cell, and there are means for controlling its temperature accurately so that the reading is reliable. The controls in response to demand and excess air respectively are applied alternately in a cycle with a period of no control to enable the effect of an adjustment to be established before further control is applied.

Abstract: Control method and apparatus for optimizing the operation of a natural draft combustion zone through which a conduit containing a process fluid to be heated passes, by decreasing the supply of combustion air until one or more of the following predetermined limiting conditions is reached: maximum CO in the flue gas, minimum O.sub.2 in flue gas, minimum draft in the combustion zone, maximum temperature of the outer surface of said conduit, and increase in the rate of fuel addition above a minimum amount. When a limiting condition is reached, the supply of combustion air is increased until the limiting condition is no longer present, and the cycle then repeated.

Abstract: A method and apparatus is provided for controlling the operation of a reforming furnace used to decompose at least a portion of a feed stream. A byproduct fuel from subsequent process steps, which is a result of decomposition of the feed in the reforming furnace, is used as one fuel source to fire the reforming furnace. A supplemental fuel such as natural gas is used as a supplemental fuel source to fire the furnace. The control system provides a prediction of the heat required to decompose the feed in the furnace. The amount of heat which can be supplied by the byproduct fuel stream is then determined. This amount of heat is subtracted from the total predicted heat required and sufficient supplemental fuel is supplied to make up the difference between the predicted required heat and the heat which can be supplied by the byproduct fuel stream.The control system also monitors the temperature of the effluent flowing from the reforming furnace.

Abstract: A differential controller for a jackshaft or a positioning combustion system having an input shaft coupled to a fuel valve and an output shaft coupled to an air damper. The controller includes means for sensing a transmitted signal indicative of the level of oxygen in the products of combustion and in response thereto differentially adjusts the vernier position of the output shaft relative to the input shaft to provide optimum fuel use under all operating conditions. The controller includes means for precluding differential travel between the shafts at low fire (load) positions. As load demand increases the controller enables differential travel to occur with increasing demand, with the amount of differential travel permitted being a function of increasing load. The maximum range of differential travel is adjustably predetermined.

Abstract: A system for the continuous analysis of furnace gasses for carbon dioxide and oxygen levels is disclosed. Materials which would be detrimental to the measuring instruments are removed before the gasses reach the measuring instruments. In particular, moisture content is removed by condensation at temperatures near freezing whereafter the gas is permitted to continuously warm up as it goes through the measuring instruments so that no condensation takes place in the measuring instruments.

Abstract: A gas monitor system to monitor combustable or flammable gases present in the exhaust flue of the monitored equipment and to adjust the damper on a real time basis as the system is operated to continuously adjust the concentration of combustible or flammable gases in the monitored equipment. The system also includes self-check calibration circuitry to regularly check that the system is in calibration and that the sensor element in the exhaust has not suffered from a sensitivity decrease. Calibration gas is fed to the sensor on a regular basis. If the calibration circuitry does not complete a proper timing cycle, the system is disabled indicating that the instrument is out of calibration or the sensor is defective.

Abstract: A method and apparatus is provided for controlling the operation of a reforming furnace used to decompose at least a portion of a feed stream. A by-product fuel from subsequent process steps, which is a result of decomposition of the feed in the furnace, is used as one fuel source to fire the furnace. The control system monitors the byproduct fuel stream and the feed stream to a decomposition side of the furnace and determines the feed rate of additional fuel required to fire the furnace, which feed rate is correspondingly controlled. The control system includes means for determining various selected variables as sensed by suitable analyzers and flow rate meters and comparing certain variables to determine the flow rate of the additional fuel required to fire the furnace.

Abstract: A regulation system for adjusting the influx of air to a combustion zone in which an off-gas and one or more auxiliary fuels are burned. Manifestations of the composition and mass flow rates of the various fuels flowing to the combustion zone are applied to the control system. The system accommodates the signals and determines the molar proportions of the fuel components. It further determines the molar flow rate of oxygen which is theoretically necessary for complete combustion. A representation of a desired amount of excess air is then factored in and a representation of the proportion of molecular oxygen which will appear in the combustion products for the desired excess air percentage. The latter factor is used to determine the setpoint in a control loop whereby the fuel/air ratio is maintained in accordance with an output from an oxygen-sensing transducer in the flue which receives the combustion products.

Abstract: Fuel is burned in a primary combustion chamber with less than the air required for stoichiometric combustion so that the combustion gases have a high carbon monoxide (CO) and hydrocarbon content and the temperature of the gases is held below that at which significant nitrogen oxides (NO.sub.2) would be produced. The combustion gases are then passed through a secondary combustion zone in which more air is injected into the gas stream to oxidize the CO and hydrocarbons to carbon dioxide (CO.sub.2). The secondary burner comprises a plurality of foraminous tubes through which secondary air is emitted. Combustion in the secondary zone is maintained at a temperature below that at which nitrogen oxides (NO.sub.x) will be produced in significant quantities.

Abstract: In the operation of a conventional coke oven battery, a target flue temperature for each oven group is set on the basis of details of coal charge consisting of the weight, the particle size, the moisture content, the volatile matter content and the timing of charging of the coal charge, so as to achieve a target net coking time and a target soaking time given by a coke production schedule. Then, the temperature is measured for individual flues at certain intervals of time and deviations of thus measured flue temperatures from said target flue temperature are calculated by computer, to set a flow rate and a calorific value of the fuel gas for each oven group. A stack draft is set and controlled by computer so that an optimum combustion may take place in response to changes in the flow rate and the calorific value of the fuel gas.

Abstract: A combustion control system is operated based on the detection of smoke density. A photoelectric device measures the intensity of light directed through the smoke by a lamp in order to measure the smoke density. This measurement is employed to control fuel and/or air supply or the like. To provide a standard reference, light is directed from the lamp through an alternate path not affected by the smoke to the photoelectric device. A shutter mechanism alternately exposes the photoelectric device to light passing through or circumventing the smoke. The photoelectric measurement is compared with a standard and the comparison is used to adjust circuitry connected to the photoelectric device to stabilize the effects of the latter. A continuous monitoring of the adjustment is carried out to determine when an acceptable range of adjustment has been exceeded. A smoke density amplifier is employed to increase effectiveness.

Abstract: In a carbon black production system having a reactor with a combustion zone and a reaction zone, substantial uniformity of the carbon black produced by the reactor is maintained by regulating the flow of fuel to the combustion zone in response to a signal representative of the temperature within the combustion zone. As an alternative to, or in conjunction with, control in response to a signal representative of the combustion zone temperature, the flow of fuel to the combustion zone can be regulated in response to a signal representative of the rate of combustion heat released by the fuel entering the combustion zone.

Abstract: Combustion control is effected by the use of a smoke detector and by solid state devices for the detection and amplification of electrical signals produced by a photoelectric cell for the purpose of controlling a motor which in turn adjusts fuel and air supplies. The electrical circuits include triac switches effective for running a servo-mechanism or motor in one direction or the other according to the density of the smoke in a flue venting combustion products from a combustion chamber. Light emitting diodes may be connected to op-amps for purposes of indicating the type of control being effected. A smoke accumulating means is employed for amplifying the products of combustion to facilitate the detecting and measuring of the same.