GB1565310A - Method and apparatus for controlling fuel to oxidant ratioof a burner - Google Patents
Method and apparatus for controlling fuel to oxidant ratioof a burner Download PDFInfo
- Publication number
- GB1565310A GB1565310A GB50138/77A GB5013877A GB1565310A GB 1565310 A GB1565310 A GB 1565310A GB 50138/77 A GB50138/77 A GB 50138/77A GB 5013877 A GB5013877 A GB 5013877A GB 1565310 A GB1565310 A GB 1565310A
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- Prior art keywords
- fuel
- oxidant
- burner
- control
- ratio
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- 239000000446 fuel Substances 0.000 title claims description 136
- 230000001590 oxidative effect Effects 0.000 title claims description 84
- 239000007800 oxidant agent Substances 0.000 title claims description 81
- 238000000034 method Methods 0.000 title claims description 28
- 238000002485 combustion reaction Methods 0.000 claims description 41
- 239000007789 gas Substances 0.000 claims description 33
- 238000010586 diagram Methods 0.000 claims description 23
- 239000000203 mixture Substances 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 14
- 230000001939 inductive effect Effects 0.000 claims description 7
- 238000012544 monitoring process Methods 0.000 claims description 7
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 6
- 238000012937 correction Methods 0.000 claims description 6
- 230000004907 flux Effects 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 4
- 239000008246 gaseous mixture Substances 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 3
- 238000005259 measurement Methods 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 206010016754 Flashback Diseases 0.000 claims description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 2
- 229910021529 ammonia Inorganic materials 0.000 claims description 2
- 238000009529 body temperature measurement Methods 0.000 claims description 2
- 239000001569 carbon dioxide Substances 0.000 claims description 2
- 230000003197 catalytic effect Effects 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- 238000012423 maintenance Methods 0.000 claims description 2
- 231100000572 poisoning Toxicity 0.000 claims description 2
- 230000000607 poisoning effect Effects 0.000 claims description 2
- 238000010791 quenching Methods 0.000 claims description 2
- 230000000171 quenching effect Effects 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 7
- 238000005070 sampling Methods 0.000 description 5
- 239000000376 reactant Substances 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000007812 deficiency Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000004320 controlled atmosphere Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000000246 remedial effect Effects 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N1/00—Regulating fuel supply
- F23N1/02—Regulating fuel supply conjointly with air supply
- F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2221/00—Pretreatment or prehandling
- F23N2221/10—Analysing fuel properties, e.g. density, calorific
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2227/00—Ignition or checking
- F23N2227/20—Calibrating devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2233/00—Ventilators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
- F23N5/10—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Regulation And Control Of Combustion (AREA)
Description
(54) METHOD AND APPARATUS FOR CONTROLLING
FUEL TO OXIDANT RATIO OF A BURNER
(71) We, BATTELLE DEVELOPMENT
CORPORATION, of 505 King Avenue,
Columbus, Ohio 43201, United States of
America, a Body Corporate organized under the laws of the State of Delaware, one of the United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described and by the following statement:- Maintaining constant temperatures and atmospheres in furnaces, boilers, and other combustion chambers using gaseous hydrocarbons as the source of heat requires the employment of a fuel with a fairly constant composition and heating value and an oxidant (usually air) in definite eroportions to the fuel.Worldwide, the user of producer gas, town gas, and other low, variable heating value gases has been superseded by the use of natural gas which has had an acceptably uniform heating value for most uses. However, present changes in natural gas distribution toward large pipeline networks and regasification of liquified natural gas may result in gas with some variation in composition. For most thermal processes the magnitude of the variation may be acceptable; however, in others it may not.
Furthermore, the trend toward coal gasification will once again introduce wider variations and low heating value gas into industrial processes. A number of solutions exist for utilizing these variable heating value gases in thermal processes requiring constant heat. For example, one method involves constantly measuring the changes in temperature produced by the burning fuel of variable calorific value and then varying the mass flow of gaseous fuel to compensate for these changes. This is shown by U.S. Patent 2,780,414 to De Heer wherein the temperature is also observed in an auxiliary burner. Other U.S. Patents to
Kappel (2,818,246), Andrews (3,407,022),
Dailey (2,866,602), and Schmidt (1,849,335: 1,933,641: 2,349,521) disclose various ways of controlling air to fuel ratios in burning zones.However, they are directed mainly to controlling the amount of heat produced and not to controlling the fuel to oxidant ratio of the gas and oxidant as is the present invention.
In ordinary burners wherein the ratio of air to fuel gas is mechanically fixed or wherein the air is admitted by inspiration, the changing of the mass flow of fuel gas to compensate for calorific variations can result in changed burning conditions and atmospheres inside the combustion zones.
For example, rich fuel/air mixtures can result in pollutants in the form of unburned hydrocarbons and carbon monoxide and in a
reducing atmospheres in the combustion
zone. Lean mixtures can result in an oxidiz
ing atmosphere in the combustion zone, excessive nitrogen oxides and in heat losses as a result of having to heat excess air which is then lost in the exhaust.
One present method of controlling the fuel to air ratio consists of measuring the gas composition (particularly the oxygen level) of the exhaust gas with an analyzer and feeding the information back to the feed gas and air lines to compensate for variations.
In some processes, however, this remedial type of compensation can be slow, and damage to the products being thermally treated may occur before the change is made. In addition, some analyzers work only on the one side of the stoichiometric ratio.
It is, therefore, an object of the present invention to provide a solution to the problem of controlling the amount of excess or deficiency of oxidant with respect to the stoichiometric ratio of fuel and oxidant to burners in a combustion zone. The solution is in the way of prevention rather than an attempted remedy of damaging variations in burning conditions caused by variation in fuel composition and heating value (per standard volume of fuel).
It is another object of the invention to provide a method for burning variable calorific value fuel in an efficient manner in installations such as boilers, and in also using the fuel for "non-efficient" combustion, such as in controlled atmosphere furnaces.
In accordance with the objectives, the invention is a method and apparatus for continuously and automatically determining the stoichiometric ratio of oxidant to variable composition fuel in a control burner and continuously supplying the main burners of a combustion zone with pre-set multiples of the fuel and oxidant flow to the control burner, the pre-set multiples being related to the deviation from the stoichiometric ratio desired in the combustion zone.
The method for controlling the gaseous fuel to oxidant ratio to a main burner employing variable composition fuel comprises burning quantities of the fuel and oxidant in a control burner, monitoring the change in some property of the burning or burned gases which has an extreme (maximum or minimum) value near the stoichiometric fuel to oxidant ratio, adjusting the quantities of fuel or oxidant to the control burner to bring the monitored property to its extreme value thereby finding the stoichiometric ratio for the oxidant and the instantaneous fuel composition, and supplying the main burner with pre-set multiples of the fuel and oxidant flow in the control burner. The relative multiples of fuel and oxidant to the main burner are determined from the desired variation from the stoichiometric ratio established in the control burner.
The stoichiometric ratio of fuel to oxidant is found in the control burner by an automatic searching technique for a property of the burned or burning gases which has an extreme value as a function of the fuel to oxidant ratio at or near the stoichiometric ratio. One way of automatic searching comprises periodically inducing a variation (or pulse) in the fuel to oxidant ratio of the gases burned in the control burner and comparing the direction of change in the monitored property with the direction of the change in the fuel to oxidant ratio. The deviation from the stoichiometric ratio may be determined from the relative changes of the two variables and a permanent compensating change may be made to the fuel to oxidant ratio before inducing another pulse.Since the monitored property has an extreme value near the stoichiometric ratio, it only remains to continue pulsing to find the extreme value of the property, which is the point where a small pulse results in little or no change in the monitored property.
The above method for controlling burner fuel to oxidant ratio may be combined with temperature or heat responsive means which can be used to determine the calorific value of the variable fuel and adjust the flow of fuel to the combustion zone to maintain the necessary heat for the thermal conditioning. The above inventive method would then adjust the oxidant flow in response to the change in fuel flow to maintain the predetermined combustion conditions (lean or rich) in the combustion zone. Several rapid iterations of the sequence may be required to keep the combustion zone at both proper temperature and atmosphere.
Apparatus according to the invention comprises elements for practising the method including a control burner, means for supplying fuel and oxidant to the control burner, means for measuring the burning property in the control burner, means for adjusting the supply of fuel and oxidant to the control burner to achieve the stoichiometric ratio in response to information from the property measuring means and means for supplying the main burner with preset multiples of the fuel and air flow in the control burner.
The present invention will be further described with reference to the accompanying drawings, wherein;
Figure 1 is a schematic diagram of the fuel to oxidant ratio control system of the invention combined with a heat control system.
Figure 2 is a curve of one property (temperature) which has a maximum value near the stoichiometric ratio and which may be monitored in the invention to find the stoichiometric ratio in the control burner.
Figures 3 and 4 are representations showing the cause (pulse) and effect (temperature change) in the control burner as the control method is practiced using temperature as the monitored property. The diagrams also show the outputs of other electronic control elements in the system.
The invention pertains to controlling the ratio of fuel to oxidant to a main burner in a combustion zone. The term "stoichiometric ratio" is used herein to mean the definite ratio of reactants (fuel to oxidant) which yields complete reaction without excess of any reactant in the products. For example, the stoichiometric ratio (molar) of CH4 to
O2 is 1:2 according to the balanced reaction CH4+202eC02+2H20 - The term quantity (of reactants) is also used in a broad sense to include quantity over a period of time or flow rate of reactants.
Heating or calorific value implies a standard set of conditions for a specific volume of fuel.
Figure 1 shows a schematic diagram of apparatus embodying the invention when utilized with a combustion chamber or zone
1 and a source of variable composition fuel 6. The apparatus of Figure 1 includes a system for keeping constant the heat supplied to the combustion zone by varying fuel flow and the fuel/oxidant ratio control system of the invention for adjusting the air supply in response to changing fuel flow.
The combustion zone has a main burner 2 and supply lines 3 and 4, respectively connected to an oxidant supply fan 5 and the variable fuel source 6. Valves 7 and 8 control the flow of gases in the supply lines to the main burner. These valves are connected to drive servo-motors 9 and 10 which may actuate the valves by means of electromagnets ot pneumatics, for example.
The drive servo-motors 9 and 10 are in turn activated by control loops incorporating the rest of the system. The first loop is the fuel/oxidant ratio control system of the invention and includes drive member 9 and the valve 7 on the air supply line along with the control system hardware to be described hereinafter. The second loop is the heat control system for maintaining constant heat to the combustion chamber. It includes the drive member 10, the valve 8 on the fuel supply line, a calorimeter device 32 for measuring the calorific value of the fuel and therefore the instantaneous power to the combustion chamber, and known data recognition hardware to be hereinafter described for implementing a fuel supply adjustment through the second loop in response to information from the calorimeter. The calorimeter is shown as part of a control burner 15.The control burner includes burner head 14 for admitting fuel and oxidant to the control burner. The output of the control burner 15 is preferably connected to the combustion chamber 1.
Since the general concept of a calorimeter system of fuel control is known in itself, as earlier disclosed, it will not be described in great detail. In general, however, quantities (a fraction of the flow) of air and fuel from the main burner supply lines are directed to the control burner through sampling pipe lines 11 and 13, respectively. The fractional flow of fuel may be fixed by the sampling technique but the air pipe line 11 has appropriate valving 12, 33 for varying the flow of air. Valve 34 and valve 35 are pre-set to create the necessary pressure drops to insure the flow of air and gas samples through the sampling pipe lines 11 and 13. The larger the impedance of valves 34 and 35, the larger the mass flow rates through the control burner.
The fuel and air are burned in the control burner 15 and the temperature of a fluid (usually water), within hollow sleeve 17 and flowing from an input 18 to an output 19, is recorded by thermocouples 20 and 21. The thermocouple outputs are fed to regulator
22 which compares the temperature difference with a programmed reference value and then activates drive motor 10 to adjust the fuel flow to the main burner, and fractionally to the control burner; through valve
8. The temperature difference is a function of the instantaneous heat flux or power to the combustion chamber from the main burner and, therefore when calibrated, may be used to determine what adjustment in fuel flow is necessary to achieve the desired heat flux.
The objective of the first loop (the fuel/oxidant ratio control system of the invention) is to adapt the air rate to the combustion chamber to the variations in flow and heating value of the fuel so as to maintain constant combustion and thermal processing conditions in the combustion zone.
This control over the fuel/oxidant ratio is accomplished by measuring and monitoring, in a control burner, a property of the burning or burned gases which has a maximum or minimum value as a function of the fuel to oxidant ratio near the stoichiometric ratio, adjusting the rate of flow to the control burner to maximize (or minimize) the monitored property and supplying the main burner with pre-set multiples of the flow being fed to the control burner. Excess fuel or oxidant relative to the stoichiometric ratio is provided to the combustion chamber by changing the relative pre-set multiples of fuel and oxidant.
In the system of Figure 1, temperature of the burning gases is chosen as the monitored property and the control burner 15 is utilized as the location of monitoring the property. As seen in Figure 2, temperature of burning gases has a peak value as a function of oxidant to fuel ratio (A) at or near the stoichiometric ratio (X)- The fuel/oxidant ratio control system of
Figure 1 includes a thermocouple 23 placed at the extreme end of a refractory sleeve 16 and a short distance from the tip of the flame. The temperature is monitored at a location upstream of the calorimeter portion which extracts heat from the burned gases. The thermocouple 23 is connected to a control circuit including a filter 24, a comparator 25, an algebraic multiplier 26, and a control element 31 of the drive member 9, which ultimately controls valve 7 on the air supply line.This type of electronic control circuit and these control devices are well known in the art and by themselves form no part of the inventive process. Their use will be described hereinafter.
The above electronic circuit is designed for inducing a variation in the fuel to air and it acts in cooperation with the circuit for inducing a variation in the fuzl to air ratio, for together searching the property function to find the maximum value as a function of fuel to air ratio. The circuit for inducing a variation also comprises wellknown elements such as a wave generator 28, an electromagnet 29, which controls valve 30 for pulsing the air flow in pipe l la to the control burner, and delay member 27 which connects with the algebraic multiplier 26. Valve 33 cooperates with valve 30 to determine the amplitude of the air flow rate fluctuations. The impedance of valve 33 is much smaller than the impedance of valve 30, so that the amplitude of the fluctuations is much smaller than the average flow rate through valve 33.Valve 33 is then pre-set before calibration of the sampling system.
The system of Figure 1 operates in the following manner. Initially, since the flows of fuel and air to the main burner are proportional to the flows in the control burner, it is necessary to "pre-set the multiples" of the stoichiometric flow to the control burner which are desired in the combustion chamber. For example, if excess air is desired in the main burner, then the multiple of the air flow will be pre-set greater than the multiple of the fuel flow.
The exact multiples may be arrived at by calibrating the system using a reference fuel (a fuel with constant known properties) and an oxygen analyzer (for lean conditions) in the exhaust from the combustion zone. The main burner 2 is thus fed with the reference fuel, the quantity of oxygen in the exhaust is measured and the valve 7 is adjusted to provide the desired excess air (or excess gas). Once this rate of air is fixed, the flame temperature in the control burner is maximized by varying the air flow in sampling pipe line 11 using control valve 12, and taking care that the fuel flow stays constant until the flame temperature has reached a maximum. During this calibration the valve 30 is half open to simulate the average rate of air flow to the control burner during the searching operation of the invention.A closer approximation can be made by determining what percentage of time the valve is open during operation and then opening the valve this percentage during calibration. At this stage, the system is calibrated to provide the desired atmosphere in the combustion zone relative to the combustion conditions in the control burner, and valve 12 should, therefore, be locked in position.
This calibration operation may be carried out during the initial operation of the apparatus and may be checked intermittently thereafter. It is important to note that during the calibration, the regulator 22 and the thermocouple 23 must be disconnected from the control loops.
After calibration, the whole system is
made operational and the main burner and
control burner are provided with gas flow.
The gases are burned in both burners and
the control of heat input to the combustion
chamber is provided by control of the fuel
flow with the previously described
calorimeter system wherein the regulator 22
causes the servo-motor 10 to actuate valve 8
in response to the difference in the
temperature drop across the calorimeter
and the reference temperature drop
programmed in the regulator.
The fuel/oxidant ratio control system of
the invention operates concurrently with
the heat control loop. In operation, the
thermocouple 23 measures the flame
temperature in the control burner.
However, since the fuel heating value is
varying (though slowly relative to the pulses
in the flow), the temperature at the
stoichiometric ratio is also varying so that
the important measurement is the relative
maximum temperature as a function of fuel
to air ratio rather than the absolute
temperature itself. To find this maximum,
the system searches the temperature versus
fuel to air curve for the peak value. The
wave generator 28 feeds the electromagnet
29 by signals of a certain frequency, for
example as illustrated by the diagrams 3a and 4a shown in Figures 3 and 4. The valve
30 is normally closed so that the signals
actuate the electromagnet to open valve 30,
the letters 0 and F of diagram 3a signifying,
respectively, the open and closed state of
the valve.The result of this operation is that
the flow of air in the pipe 11 fluctuates at the
signal frequency shown in diagram 3a and
induces a periodic variation at a constant
amplitude AS of the air to fuel ratio
introduced into the control burner. The
diagram shown in Figure 2 illustrates the
effect of these variations AR on the
temperature variation AT. It is seen that the
closer the air to fuel ratio is to ,i. e. to the
stoichiometric ratio, the lower the
magnitude of AT, both when there is a
deficiency and an excess of air, the curve
being symmetrical with respect to the
stoichiometric ratio.
However, the slope of the tangents to the
curve of Figure 2 change sign according to
whether the gas mixture is rich or lean. In
practice, this change of slope has the
following significance; if A < X then T, < T2
when the air to fuel ratio increases by AA.
On the other hand, when A > x, T, > T2 for
the same increase in A.
The functional diagram of Figure 3
illustrates the case in which A < x. When the
valve 30 opens, T 2 becomes greater than T,
(see diagram 3c). The time lag between the
opening of valve 30 and the increase in
temperature is due to the reaction time of the control burner-thermocouple assembly.
Consequently, the signal of the generator 28 may be transmitted by element 27 to the algebraic multiplier 26 with a certain time delay "r", as illustrated by diagram 3b.
The principal function of the multiplier 26 is to generate positive signals if AT increases when valve 30 opens, and negative signals if aT decrease when the valve opens. In the example given in Figure 3, the multiplier signals, illustrated by diagram 3e are positive and are transmitted to one of the two terminals of the control element 31. The second terminal of this element receives the signal shown in diagram 3dwhich is given by the comparator 25 and which is proportional to the difference between the average of the fluctuations in temperature (established by filter 24), and the actual instantaneous level of the fluctuation. The signal shown in diagram 3d indicates to the control element 31 the size of the correction to be made, while the signal shown in diagram 3e indicates the direction of that correction.AT=0 would signify that the flame temperature was equal to Tmax, i.e.
that A=x- The control element 31 acts through the drive member 9 on the valve 7 which controls the air flow in supply line 3. This adiustment of the rate of air to the control burner 15 also causes an adjustment in rate of air to the combustion chamber burner 2 in accordance with the initially calibrated pre-set multiple.
Figure 4 illustrates a correction when A > x. The symmetry with respect to Figure 3 is seen, T decreasing instead of increasing when valve 30 is opened by the signal shown in diagram 4a, and the algebraic multiplier 26 producing a negative signal shown in diagram 4e.
Once again, it is emphasized that individual elements of the apparatus utilized in the invention are generally known. The invention is the combination of these elements and steps which allows the maintenance of constant combustion conditions when using variable-composition fuels without the time and expense of measuring the mass flow of the fuel or the fuel composition.
As alternatives in the above described example of the invention it is possible and sometimes desirable to monitor a property other than temperature in the fueVoxidant ratio control loop. For example, other properties which have peak values, as a function of the fuel to oxidant ratio, near the stoichiometric ratio include: the amount of water vapor or carbon dioxide in the burned gases, the degree of ionization in the burned gases, flash-back velocity gradient, blow-off velocity gradient, heat flux and quenching distance. The latter property has a minimum value near the stoichiometric ratio, and the search technique can be used to find the minimum value of the property or the maximum of the inverse property.
Instruments for measuring these properties and others are all well-known in the art. Such measurements might be more desirable than temperature because of the lag in the response time and the poisoning of the thermocouple during the temperature measurement.
In the searching operation it is equally possible to pulse the fuel flow rather than the air flow. The temperature variation should then vary in the opposite direction to the variation caused by an air pulse.
Additionally, the shape of the signal from the wave generator need not be a square wave as shown in Figures 3 and 4. Any output which is sufficient to periodically pulse the flow of fuel or oxidant to the control burner according to the invention is sufficient to function in the system.
The heat control loop with the calorimeter was described as functioning by adjusting the fuel in response to variable heating value gas. Actually, this loop might also adjust the air to a first approximation and then allow the fuel/oxidant ratio control loop to fine tune the air flow. This would be useful for programmed changes in the heat flux demand to the combustion chamber.
The above described control system is useful in combustion systems wherein thermal processing requires critical atmospheric conditions. It is also useful in thermal processes requiring reducing or non-oxidizing atmospheres, and it is useful in any systems where conservation of fuels through efficient combustion is desired.
These uses suggest several possible systems, for example, large-scale atmosphere gas generators, catalytic reformers for hydrogen production, gaseous feedstock control systems in chemical and petrochemical industries such as ammonia production, refinery heater combustion systems using refinery off-gases as fuel and industrial boilers fired by large single burners or separately piped multiple burners.
WHAT WE CLAIM IS:
1. A method for continuously controlling a gaseous mixture comprising an oxidant and a fuel of variable composition or variable heating value to maintain a predetermined fuel to oxidant ratio in a main burner, comprising,
(a) burning a quantity of the fuel and the oxidant in a control burner,
(b) monitoring the change in magnitude of a property of the burning or the burned fuel and oxidant in the control burner, said property having an extreme value as a
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (8)
1. A method for continuously controlling a gaseous mixture comprising an oxidant and a fuel of variable composition or variable heating value to maintain a predetermined fuel to oxidant ratio in a main burner, comprising,
(a) burning a quantity of the fuel and the oxidant in a control burner,
(b) monitoring the change in magnitude of a property of the burning or the burned fuel and oxidant in the control burner, said property having an extreme value as a
function of the fuel to oxidant ratio at about the stoichiometric ratio,
(c) adjusting the fuel to oxidant ratio to the control burner such that the magnitude of the monitored property is substantially at its extreme value, and
(d) supplying said main burner with independent, pre-set multiples of the quantity of fuel and the quantity of oxidant in the control burner such that said predetermined fuel to oxidant ratio to the main burner is maintained.
2. The control method of Claim 1 wherein the monitored property in the control burner is selected from the group consisting of temperature, the amount of H2O, the amount of CO2 and the amount of ionization.
3. The control method of Claim 1 or 2 wherein the adjustment of the fuel to oxidant ratio necessary to bring the monitored property to its extreme value is determined by a search of the magnitudes of the monitored property as a function of various fuel to oxidant ratios.
4. The control method of Claim 1, 2 or 3 wherein the fuel to oxidant ratio is adjusted to bring the magnitude of the monitored property to its extreme value by the steps comprising
(a) periodically inducing a variation in the fuel to oxidant ratio in the control burner,
(b) measuring the direction of the change in the magnitude of the monitored property,
(c) comparing the direction of the change in the magnitude of the monitored property with the variation in fuel to oxidant ratio to the control burner whereby to determine whether the change in magnitude of the monitored property is characteristic of an excess of fuel or oxidant with respect to the stoichiometric ratio,
(d) varying the quantity of fuel or oxidant in the control burner to substantially eliminate the excess of fuel or oxidant with respect to the stoichiometric ratio,
5.Apparatus for continuously controlling a gaseous mixture comprising an oxidant and a variable composition or variable heating value fuel to a predetermined fuel to oxidant ratio in a main burner comprising,
(a) a control burner separate from the main burner,
(b) means for supplying metered quantities of fuel and oxidant to the control burner,
(c) means for monitoring the change in magnitude of a property of burning or burned quantities of fuel and oxidant in the control burner, said property having an extreme value as a function of the fuel to oxidant ratio at about the stoichiometric ratio,
(d) means for adjusting the fuel to oxidant ratio to about the stoichiometric ratio in the control burner in response to information from the means for monitoring said property in the control burner, and
(e) means for supplying the main burner with independent, pre-set multiples of the quantity of fuel and the quantity of oxidant in the control burner such that said predetermined fuel to oxidant ratio to the main burner is maintained.
6. The apparatus of Claim 5 wherein the means for adjusting the fuel to oxidant ratio comprises
(a) means for periodically inducing a variation of the fuel to oxidant ratio in the control burner,
(b) means for comparing the direction of the change in the magnitude of the monitored property with the variation in the fuel to oxidant ratio in the control burner whereby to determine whether the change in magnitude of the monitored property is characteristic of an excess of fuel or oxidant with respect to the stoichiometric ratio, and
(c) means for varying the fuel to oxidant ratio in the control burner for reducing the excess of fuel or oxidant with respect to the stoichiometric ratio in response to information from the means for comparing.
7. A method of continuously controlling fuel/oxidant ratio, substantially as herein described with reference to the accompanying drawings.
8. Apparatus for continuously controlling a gaseous mixture, substantially as herein described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB50138/77A GB1565310A (en) | 1977-12-01 | 1977-12-01 | Method and apparatus for controlling fuel to oxidant ratioof a burner |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB50138/77A GB1565310A (en) | 1977-12-01 | 1977-12-01 | Method and apparatus for controlling fuel to oxidant ratioof a burner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1565310A true GB1565310A (en) | 1980-04-16 |
Family
ID=10454812
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB50138/77A Expired GB1565310A (en) | 1977-12-01 | 1977-12-01 | Method and apparatus for controlling fuel to oxidant ratioof a burner |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1565310A (en) |
Cited By (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2486204A1 (en) * | 1980-07-04 | 1982-01-08 | Snam Spa | METHOD FOR ADJUSTING THE THERMAL POWER OF A SYSTEM SUPPLIED WITH NATURAL GAS HAVING A VARIABLE HEAT POWER, AND APPARATUS SUITABLE FOR THIS APPLICATION |
| EP0055852A1 (en) * | 1980-12-27 | 1982-07-14 | Hitachi, Ltd. | Method and apparatus for controlling combustion of gasified fuel |
| EP0075369A1 (en) * | 1981-09-18 | 1983-03-30 | N.V. Nederlandse Gasunie | Method and device for keeping the heat load on gas-fired equipment constant |
| GB2140587A (en) * | 1983-05-23 | 1984-11-28 | Kelsall Spurr John Kenneth Fra | Improvements in and relating to combustion processes |
| GB2155205A (en) * | 1984-03-01 | 1985-09-18 | Bodenseewerk Perkin Elmer Co | Gas control device for a burner for an atomic absorption spectrometer |
| FR2588061A1 (en) * | 1985-10-02 | 1987-04-03 | Brunel Gerald | Process and installation for regulating the combustion of a gas burner of a heat or force generator such as a boiler or the like, to obtain a specific combustion |
| EP0221799A1 (en) * | 1985-10-02 | 1987-05-13 | Societe D'etude Et De Construction De Chaudieres En Acier Seccacier | Gas burner combustion regulation method and apparatus for a heat or force generator, especially a boiler or the like, to obtain a specific combustion |
| GB2185810A (en) * | 1986-01-28 | 1987-07-29 | Landis & Gyr Ag | Methods of and apparatus for regulating the amounts of gas and air for gas blower burners |
| GB2186962A (en) * | 1986-02-26 | 1987-08-26 | Mor Flo Ind Inc | Forced draft controlled mixture heating system using a closed combustion chamber |
| US4766883A (en) * | 1986-02-26 | 1988-08-30 | Mor-Flo Industries, Inc. | Forced draft controlled mixture heating system using a closed combustion chamber |
| FR2613040A1 (en) * | 1987-03-25 | 1988-09-30 | Pramata | METHOD AND INSTALLATION FOR CONTROLLING A COMBUSTIBLE GAS CONSUMPTION SITE POWERING DIFFERENT POINTS OF USE |
| US5022352A (en) * | 1990-05-31 | 1991-06-11 | Mor-Flo Industries, Inc. | Burner for forced draft controlled mixture heating system using a closed combustion chamber |
| US5085579A (en) * | 1991-03-25 | 1992-02-04 | Mor-Flo Industries, Inc. | Powered chamber combustion system and burner therefor |
| EP0560454A3 (en) * | 1992-03-12 | 1994-01-19 | Flameco Eclipse Bv | |
| FR2712961A1 (en) * | 1993-11-26 | 1995-06-02 | Lorraine Laminage | Real-time adjustment of a fuel burner with variable characteristics, in particular for metallurgical heating furnaces. |
| EP0829683A3 (en) * | 1996-09-12 | 1999-03-10 | Mitsubishi Denki Kabushiki Kaisha | Combustion system and operation control method thereof |
| FR2811411A1 (en) * | 2000-07-05 | 2002-01-11 | Rational Ag | Gas burner for cooking appliance includes detector sensing properties of gas fuel and adjusting fuel mixture accordingly to achieve power output |
| WO2012167914A3 (en) * | 2011-06-10 | 2014-05-08 | Vdeh-Betriebsforschungsinstitut Gmbh | Device for oxidizing the oxidizable fractions of a fuel gas sample for quality determination of the fuel gas |
-
1977
- 1977-12-01 GB GB50138/77A patent/GB1565310A/en not_active Expired
Cited By (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2486204A1 (en) * | 1980-07-04 | 1982-01-08 | Snam Spa | METHOD FOR ADJUSTING THE THERMAL POWER OF A SYSTEM SUPPLIED WITH NATURAL GAS HAVING A VARIABLE HEAT POWER, AND APPARATUS SUITABLE FOR THIS APPLICATION |
| EP0055852A1 (en) * | 1980-12-27 | 1982-07-14 | Hitachi, Ltd. | Method and apparatus for controlling combustion of gasified fuel |
| EP0075369A1 (en) * | 1981-09-18 | 1983-03-30 | N.V. Nederlandse Gasunie | Method and device for keeping the heat load on gas-fired equipment constant |
| GB2140587A (en) * | 1983-05-23 | 1984-11-28 | Kelsall Spurr John Kenneth Fra | Improvements in and relating to combustion processes |
| GB2155205A (en) * | 1984-03-01 | 1985-09-18 | Bodenseewerk Perkin Elmer Co | Gas control device for a burner for an atomic absorption spectrometer |
| FR2588061A1 (en) * | 1985-10-02 | 1987-04-03 | Brunel Gerald | Process and installation for regulating the combustion of a gas burner of a heat or force generator such as a boiler or the like, to obtain a specific combustion |
| EP0221799A1 (en) * | 1985-10-02 | 1987-05-13 | Societe D'etude Et De Construction De Chaudieres En Acier Seccacier | Gas burner combustion regulation method and apparatus for a heat or force generator, especially a boiler or the like, to obtain a specific combustion |
| GB2185810B (en) * | 1986-01-28 | 1989-11-01 | Landis & Gyr Ag | Methods of and apparatus for regulating the amounts of gas and air for gas blower burners |
| GB2185810A (en) * | 1986-01-28 | 1987-07-29 | Landis & Gyr Ag | Methods of and apparatus for regulating the amounts of gas and air for gas blower burners |
| GB2186962A (en) * | 1986-02-26 | 1987-08-26 | Mor Flo Ind Inc | Forced draft controlled mixture heating system using a closed combustion chamber |
| US4766883A (en) * | 1986-02-26 | 1988-08-30 | Mor-Flo Industries, Inc. | Forced draft controlled mixture heating system using a closed combustion chamber |
| GB2186962B (en) * | 1986-02-26 | 1990-03-21 | Mor Flo Ind Inc | Forced draft controlled mixture heating system using a closed combustion chamber |
| FR2613040A1 (en) * | 1987-03-25 | 1988-09-30 | Pramata | METHOD AND INSTALLATION FOR CONTROLLING A COMBUSTIBLE GAS CONSUMPTION SITE POWERING DIFFERENT POINTS OF USE |
| EP0284517A3 (en) * | 1987-03-25 | 1989-02-15 | Societe D'etude Et De Construction De Chaudieres Automatiques En Acier Seccacier | Regulation method and apparatus of a combustible gas consumption site supplying several consumption points |
| US5022352A (en) * | 1990-05-31 | 1991-06-11 | Mor-Flo Industries, Inc. | Burner for forced draft controlled mixture heating system using a closed combustion chamber |
| US5085579A (en) * | 1991-03-25 | 1992-02-04 | Mor-Flo Industries, Inc. | Powered chamber combustion system and burner therefor |
| EP0560454A3 (en) * | 1992-03-12 | 1994-01-19 | Flameco Eclipse Bv | |
| US5622491A (en) * | 1992-03-12 | 1997-04-22 | Flameco-Eclipse, B.V. | Gas burner having a pack of stacked metal plates at the combustion chamber inlet |
| FR2712961A1 (en) * | 1993-11-26 | 1995-06-02 | Lorraine Laminage | Real-time adjustment of a fuel burner with variable characteristics, in particular for metallurgical heating furnaces. |
| EP0661499A1 (en) * | 1993-11-26 | 1995-07-05 | Sollac S.A. | Real time control of a burner for gases with differing characteristices, especially for a metallurgical furnace for reheating |
| TR28665A (en) * | 1993-11-26 | 1996-12-25 | Lorraine Laminage | Especially for a metallurgical heating furnace, a gas burner with variable properties is set in real time. |
| EP0829683A3 (en) * | 1996-09-12 | 1999-03-10 | Mitsubishi Denki Kabushiki Kaisha | Combustion system and operation control method thereof |
| US5957063A (en) * | 1996-09-12 | 1999-09-28 | Mitsubishi Denki Kabushiki Kaisha | Combustion system and operation control method thereof |
| FR2811411A1 (en) * | 2000-07-05 | 2002-01-11 | Rational Ag | Gas burner for cooking appliance includes detector sensing properties of gas fuel and adjusting fuel mixture accordingly to achieve power output |
| WO2012167914A3 (en) * | 2011-06-10 | 2014-05-08 | Vdeh-Betriebsforschungsinstitut Gmbh | Device for oxidizing the oxidizable fractions of a fuel gas sample for quality determination of the fuel gas |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |