JPH06509158A - Combustion device and method in porous matrix element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] matrix element invention p kono FIELD OF THE INVENTION This invention relates generally to combustion devices and technology, and more particularly to flame control and stability. Improved combustion equipment and effective to increase and reduce NOx emissions Regarding the method.

My main friend is small Environmental pollution caused by NOx emissions from combustion is an industrial fuel user. It is of great interest not only to the public, but also to the public. In the early 1960s, the fruit of public concern that levels of smog and air pollutants are increasing Prompted by government agencies to issue no. imposed a reduction requirement. These restrictions expanded in the 1970s and 1980s. It has come to include virtually all industries that have combustion equipment. accept these challenges The industries involved have already developed a variety of technologies to meet new needs. combustion process The most widely used modification is to reduce the N-mountain generated in combustion. It is a technology that has been developed. Furthermore, as a major control method for certain applications, multiple stack gas treatment Although several technologies have been developed and are emerging, natural gas is the fuel of choice. seems to have limited use.

Nitrogen oxides (NOX) are produced by the conversion of chemically bound nitrogen in fuels or As a result of thermal fixation of nitrogen in the combustion air through rapid N OX J formation ( Thermal NOx4) is produced during the combustion process. “A hot N0XJ, that is, a guy like this The fuel (e.g. coal gas) used by the ``Thermal NO,J generation'' due to high-temperature combination of free nitrogen and oxygen In addition to the If.

It is advantageous for the production of compounds. ``Rapid Now J'' is the force formed early in the flame. ・All of these mean nitrogen oxides that are not produced by the Zeldvinci mechanism. Quick N Ox is caused by (1) interaction between certain hydrocarbon components and nitrogen components and/or (2 ) caused by an excess amount of oxygen atoms leading to premature NOx formation. Regarding ignition of natural gas Virtually all NO emissions are from thermal fixation or "thermal N08" or arises from rapid NOx. The production rate has a strong temperature dependence, usually around 1800°K. (2800”F) and is usually made more favorable by the presence of excess oxygen. Ru. At these temperatures, generally stable nitrogen molecules dissociate to form nitrogen atoms, which then The nitrogen atoms react with oxygen atoms and hydroxyl radicals to mainly form NO. to be accomplished.

Generally no, formation can reduce nitrogen and oxygen atomic concentrations at peak combustion temperatures. or by reducing the peak combustion temperature and residence time in the combustion zone. It can be delayed further. This is due to changes in operating conditions, modifications to burner design or by using combustion modification techniques such as combustion system modifications. I can do it.

Of the combustion modification methods listed above, burner design modification is the most widely used.

Low NOx burners generally reduce flame turbulence and slow the mixing of fuel and air. is designed to establish a fuel-enriched zone where combustion begins. The manufacturer is 4 It calls for a nominal reduction of 0 to 50%, but the predicted NOx emissions and the actual reductions are Significant differences have been observed between the emissions produced. The basis for these differences is The reason for this is the reaction dynamics of diffusive combustion and the simultaneous efforts to control heat and mass transfer. due to the complexity of the

Examples of the aforementioned and related NOx reduction techniques are the disclosures of the following US patents:

Decorso's U.S. Pat. No. 4,787,208 describes an enriched primary combustion zone and A low NOx combustor is disclosed having a depleted second combustion zone. deprived of oxygen This suppresses NOx formation in the enriched combustion zone and reduces NOx formation in the depleted combustion zone. This is suppressed by low combustion reaction temperature. Ceramic cylinder is part of the combustion chamber used as minutes.

Furuya et al., U.S. Pat. No. 4,731,989, discloses catalytic combustion followed by non-catalytic thermal combustion. A combustion method for reducing NOx emissions in which combustion occurs is disclosed.

U.S. Pat. No. 4,534,165 to Davis Jr. et al. For operation fitted with a single downstream “pilot” zone that is supplied with fuel and N08 by supplying fuel in stages and controlling the flow of fuel i1. We are seeking to minimize emissions.

Decorso's U.S. Pat. No. 4,112.676 generally describes It shows an expanded 11kF sintering type combustor.

Billebry's U.S. Pat. No. 4,726.181 provides a method for reducing NOx levels. It provides a two-stage catalytic combustion intended for

U.S. Pat. No. 4,730.599 to Kendall et al. uses heterogeneous catalytic combustion and A gas-ignited radiant tube heating system that requires low No. 8 catalytic combustion is disclosed.

U.S. Pat. No. 4,285,193 to Shanaka et al. Minimizing NOx formation through the use of a combination of non-catalytic and catalytic combustion A gas turbine combustor intended for use is disclosed.

Penofel's US Pat. No. 3,846,979 states that combustion occurs at approximately 3300@F. , in a two-stage combustion process in which the effluent is quenched and the effluent undergoes catalytic oxidation. Low No., release is described.

U.S. Pat. No. 4,087,962 to Beremant et al. A combustor that utilizes a non-adiabatic flame is disclosed. fuel-air mixture It flows in the direction through the porous wall, the opposite side of which acts as the fuel surface. radiant heat sink a second surface of the burner is located adjacent to the second surface of the burner to cause combustion of the fuel-air mixture; removes the radiant energy produced by the do.

The inventors believe that although the combustor operates near the stoichiometric mixture ratio, its temperature is No. It says it's low enough to prevent emissions. In one embodiment, the radiant heat shield The tank further includes a porous plate.

U.S. Patent of which Ronald D. Herr, one of the applicants of this application, is the patentee No. 4,811,555, a combination of reduced pressure and catalytic oxidation combustion A co-generation system is described in which NOx is controlled by processing bottle waste.

U.S. Patent No. 4.405 to Manokgil et al., co-owned by Ronald D. Hel. ．． No. 587, the N08 content of the spent stream is reduced by treating it and reducing and reducing it. It is controlled by subjecting it to high temperature combustion in the combined oxidation zone.

Recent work by some of our co-inventors or other inventors has shown that high porosity and high melting Porous matrix (PM) comprising fibers, beads or other materials with temperature Utilizes a highly porous inert media matrix that provides a contained combustion reaction within This creates a combustor that produces Preference is given to using ceramic foam.

This ceramic sponge-like material is designed to provide a flow path for combustible mixtures. porosity (typically about 90%). Energy release due to gas phase reactions is Increase the temperature of the gas flowing through the porous matrix in the post-flame zone .

This then conveniently heats the porous matrix in the post-flame zone. to gas Evacuation from the hot post-flame zone is a porous material due to the relatively high release of solids. This serves to heat the pre-flame zone of the quality, which then heats the incoming reactants. Heat. This thermal feedback mechanism has some implications for free combustion flames. Produces deep flavor characteristics. These have higher burning rates, higher capacitive energy Including increased ghee release rate and flame stability, extending both depleted and enriched flammability limits .

In addition to the ability to achieve very high radiation from a very compact combustor, the flame The increase in temperature can be ignored. Is this NOXII? Regarding the purpose of I weight This is a point to consider.

Construct a one-dimensional mathematical model including radiation and accurate multi-stage chemical mechanics did. This model consists of a premixed flame in an inert highly porous medium. used to predict structure and burning rate. The various predictions of this model are It has been discussed by et al. ASME Publication HT D 1987 Volume 81 Y, By Jarria, V., P., Calais, W., A., Fiveland and W. Yuen. Edited by Y. K. Cheno, R. D., Matthews and J. System. , R. Howell, “On the structure of premixed flames in highly porous inert media.” Effects of Radiation; Processing of the Join Meaning of ・The Japanese Anne's Suit Section of the... Compassion Insu Ni, 1987, pp. 266-268, Y, K.

Cheno, R.D., Matthews, J.R., Howell, Z., H., Lu and P.L., Ha. ``Premixed combustion in porous inert media''; and ``Premixed Combustion in Porous Inert Media''; Yaki-related 1st Moxibustion 2nd Mbosium International Magazine PS-201 Y , K., Cheno, R.D., Matthews, ■, G., Lim, Z., Lu, J., and R., Howe. L and S.

See "Experimental and Theoretical Studies of Combustion in Porous Inert Media" by P. Nichols.

These publications indicate that porous matrix (PM) combustors are This shows that it is possible to provide the benefits of However, these publications However, it is not related to the problem of NOx emissions, but is focused on the effective reduction of NOx emissions. This is even less relevant.

However, the latter publications do not mix a fuel, such as natural gas, and an oxygen source, such as air, and the The composite is filled with a porous matrix whose voids occupy virtually all of the areas where combustion occurs. By the method of being burned in at least two consecutive combustion zones providing a site No. 554.748, where combustion takes place. It is reaching. Preferably the method utilizes three such combustion zones. 1st That is, the most second-stream zone is filled with the porous matrix and the mixed The compound is supplied here in a fuel-starved condition. In the second consecutive zone the said The mixture becomes fuel enriched and in the third stage the mixture becomes fuel starved.

U.S. Patent Application No. 670.286, of which this application is a continuation-in-part, is An important issue to be investigated is the Franche bag from post-flame to pre-flame zone. It refers to The latter zone contains ceramic foam and/or flow mixing and and ceramic honeycombs, glass beads or other media, or simply a mixture without media. Including joint space. From the post-flame zone where combustion, by definition, is desirable to occur. Aside from creating a serious or actual danger, No, it is sought to be avoided in order to eliminate or reduce generation. System that is accurate? ■This is impossible combustion. Fuel/air through PM combustion zone By providing a sufficient amount of airflow, it is possible to overcome the amount of flame back migration that may occur. It is believed that the problem can be eliminated by using a higher flow rate. death However, this is not true in the true system that exists in PM burners, e.g. A porous medium having a general shape passes through such a cylinder fuel-air flow through a plane across said cylinder acting on the normal axial flow of the mixture This results in non-uniform speed. In particular, the cylinder - Flow stagnation is likely to occur on the surrounding wall. Therefore, simply the flow rate of the fuel-air mixture Simply increasing the unwanted flame flashback to the pre-flame zone is generally not sufficient to ensure that this does not occur.

The issues raised above are addressed by Fleming, U.S. Pat. No. 4,643,667. It is recognized in Among these, Fleming identified a substance with an inherent low thermal conductivity. a first preheating layer comprising a first preheating layer having an inherent high thermal conductivity and also providing a discharge surface; at least two separate and adjacent layers of the first fuel layer comprising a material comprising: A catalystless porous phase fuel device comprising porous plates is disclosed.

The presence of low conductivity materials tends to limit heating in the initial zone, thereby Rudge Yuba eliminates the occurrence of ri, but the structure recommended by Fleming Construction is extremely complex and difficult to achieve. Adjacent while still offering the above-mentioned benefits. The presence of a lower conductivity material in contact with the Creates a pressure drop in the flow.

The device of the invention of U.S. Pat. No. 11,670.286 uses fuel such as natural gas and oxygen. source, for example, a mixture for receiving and mixing air and further forming a stream of flammable mixture. fitting and flow forming means are fitted. The combustible mixture has voids substantially confined by a porous high temperature resistant matrix that provides the sites where all combustion occurs. flow toward a downstream combustion zone, which zone is connected to said mixing and flow forming means. and an inlet end for receiving the combustible flow. The temperature of the combustible mixture at the inlet end cooling means for maintaining the temperature below the ignition temperature are proximate to the inlet end of said combustion zone. installed in the porous matrix downstream of the cooling means or on the post-flame side. limit the flame produced by combustion. The cooling means typically includes one or more consisting of a generally toroidal metal body having internal cooling channels of . This metal body surrounds and is in thermal contact with the inlet end of the combustion zone. the metal body Means is fitted for circulating a refrigerant through the refrigerant, typically water but other means. The cooling body may be a liquid medium or a gas containing air. It is installed in such a way that it does not intrude on the matrix, so that the flowing fuel and No impedance is introduced into the oxygen source mixture.

The invention of U.S. Pat. No. 11,670,286 is based on U.S. Pat. 4.748 as well as a single stage porous matrix bar. It can also be applied to In any of these cases, the cooling means located at the inlet end of the first (or single) stage (i.e. before the cough stage) ing. The cooling stages in each case act in such a way that sharp discontinuities in temperature occur (porous post-fire even in the presence of the aforementioned flow stagnation (which tends to occur at the periphery of the matrix). There is a substantial risk of flashbanking from combustion flames present in the flame PM zone. I try not to let it happen. By removing the furanotsuyu hack potential, Eyes explored in porous media burners for the special purpose of reducing NO8 emissions A highly stable and well-formed material that provides highly controlled combustion conditions, which is one of the goals of It can be seen that a cold flame is generated.

The combustion process is thus provided, allowing control of low NO9 combustion. fuel and Oxygen sources such as gas and air are mixed to form a combustible stream. This flow is porous and high temperature. It is fed to the inlet end of the combustion zone defined by the resistance matrix. said mixture the matrix that provides the voids or sites for substantially all of the combustion to occur; The combustion products flow out the outlet end of the matrix. Combustion zone inlet the end is cooled to maintain the temperature of the combustible mixture at the inlet end below the ignition temperature; This confines the flame generated by combustion in the porous matrix to the downstream side of the cooling means. Set.

Destination Ω overview In our aforementioned prior application, the advantage of a two-stage PM burner is that the first or upstream zone maintains one zone in a combustion-rich state and a second or downstream zone in a fuel-starved state. It was thought that this could be best achieved by doing so. Unexpectedly, N08 and A significant reduction in CO and CO was achieved by using a fuel-deficient first stage and a fuel-enriched second stage. It has been found that this can be achieved. Although not required for NOx reduction, this Such an arrangement is preferably in conjunction with the first stage cooling means as described above, i.e. the first combustion It is installed and used close to the inlet end of the baking zone. Incorporating cooling means The foregoing, including best achieving a wide range of equivalence in the operation of the present invention. preferred to achieve its advantages.

In this way, the low N08 combustion device according to the present invention each uses the porous matrix. comprising first and second combustion zones filled with said combustion zone, said second zone being filled with said downstream of the first zone. Mix fuel and oxygen and transfer it to the first combustion zone means for supplying the first zone to the first zone to establish a fuel starvation condition therein; Supplying the combustion products to the second zone and augmenting it with sufficient fuel and additional oxygen to form fuel-enriched combustion conditions therein to complete the oxidation of the products from the first zone. There is a means to do so.

Heat transfer by convection and radiation within the porous matrix element of the first zone is Preheat the incoming fuel/air mixture above the theoretical adiabatic flame temperature of the mixture. This causes a wide range of fuel/air mixtures to become fuel starved. heat transfer by radiation from the non-porous wall of the second stage. The temperature of the second stage operated at enriched fuel/air ratio conditions is an overall lower flame temperature. , thereby minimizing thermal and rapid NO1 production.

In such cases, porous matrices have limited voids due to the porosity of the foam. porous ceramics such as reticulated liquid alumina or zirconia foam. It can comprise a couform. Similarly, the matrix may be made of, for example, ceramic. materials that can withstand the high temperatures of combustion processes such as carbon fibers, ronds, fibers or other media. It may also include a packed bed. In these cases the void is the mutual space between the media limited by. Unlike some prior art techniques, the present invention allows virtually all of the The combustion of the process occurs on the surface of the ceramic or porous tube etc. rather than on the matrix. It is important to point out here that what happens within the void of Even more noteworthy The thing is that we can use different matrices in successive zones, so that given The matrix of zones may be one of e.g. porous ceramic foam and the other a packed bed. It may comprise one or more consecutive sections, such as.

Easy guide to the ward plate Φ The invention is further illustrated in the following detailed description, which should be read in conjunction with the accompanying drawings. will be readily apparent.

FIG. 1 is a schematic vertical cross-section of a preferred embodiment of a two-stage combustion device according to the present invention, and FIG. 2 of the equivalence ratio of the draftsman's device when it is operated in a single stage configuration. Figure 3 is a graph of No,'fA degrees as a function, at various temperatures and equivalence ratios. 3 is a graph showing equilibrium NO8 formation for a mixture of methane and air in Figure 4 shows a diagram of the type shown in Figure 1 for a fixed flow rate and a specified equivalence ratio in the second stage. It is a graph showing the temperature distribution in the axial direction in the combustion device.

The new day is here Referring to the drawings, and in particular to FIG. 1, a combustor or burner arrangement incorporating features of the present invention is shown. The location is indicated generally by the reference numeral 50. The combustor or burner 50 is located along its longitudinal axis so that the gas flow flows upwards along the longitudinal axis .

Burner 50 has a base 12 conveniently formed of metal such as steel. There is.

A hollow vertical column 14 is connected to the base 12, and a conduit 1 is provided inside the column 14. 5 is formed. Column 14 extends upwardly to flange 17 . Ne A threaded rod 19 is inserted between the flange 17 and the outside of the toroid member body or ring 36. It extends in the vertical direction and holds therein a capsule sleeve 42 that can be made of quartz. ing. The premixed reactants (i.e., fuel and air) enter the first stage inlet 16 and The mains into which fuel and air are introduced before being fed through the second stage inlet 18. burner 5 through a two-stage mixing system (not shown) consisting of the following mixing sections: Enter 0. Premixed air and fuel are effectively confined in conduit 15 from inlet 16. The premixed second stage air and fuel proceed into a defined second mixing chamber. The reactant is passed from the inlet 18 through the conduit 20 through multiple channels to uniformize the flow of the C1 reactant. Can be made of porous ceramic cylinder containing flow channels or other heat resistant Proceed to the distributor 22 consisting of the substance. In any case, there are two purposes to provide a fuel or other oxidizing combustible mixture that is well mixed with air in similar equivalence ratios. Thus, one is provided to the first stage and the other to the second stage.

A void 28 (at conduit 154) is located above this mixing section in the burner core. The burner cores of FIG. 1 located below the preheating section 30 are each From partially stabilized zirconia (PSZ), which generally has a spongy appearance The preheating or pre-flame section 30 is a porous ceramic cylinder consisting of 7 cylinders and It comprises a combustion or post-flame section 32. Reticulated silica alumina fluoride Other ceramic forms such as the flooring of saddles, balls, rondos, etc. Packed beds are preferred as are typically found in combustion equipment where the pressure drop is low. Other formulations that can withstand the temperatures present can also be used. Forms that can be used in this invention silica alumina, partially stabilized zirconia, etc. High-tech ceramic nitrogen characterized by having about 5 to 65 pores (ppi) Includes silicone and silicone carbide foams. Section 30 ceramic form is standard Typically it has about 65 ppi and that of section 32 has about 10 ppi. Se The average porosity of the ramic media varies from 84 to 87%, while for example 10 ppi The thermal conductivity of the ceramic is approximately IW/m-K.

Cooling means 34 comprising an impenetrable flame holder are made of porous ceramic sections. utilized to stabilize the first reaction or combustion zone 44 confined within the chamber 32; be done. The cooling means 34 comprises a channel extending inside the periphery of the entire toroidal member. The above-mentioned usually toroid-shaped member 36 made of brass, for example, is water-cooled by a I can see that there is. The cooling water flows from the channel 38 to the outer toroid member 3. 6 is fed through channel 38 by an inlet and an outlet (not shown) projecting into Ru. Other cooling media can also be supplied to the internal channels 38, including air. This can also be achieved with gas. However, water is easily available and is used for cooling purposes. is the preferred medium.

A member 36, typically toroidal in shape, reaches the inner diameter end of the flow capsule sleeve 42. It is noted that it extends inwardly and includes a bulge 40. Therefore, the innermost part of member 36 The limp 40 is connected to the outer periphery or sections 3o and 32 of the ceramic core. It can be seen that there is qualitative contact. Typically, different materials are used to construct a ceramic core. It has a porosity that is actually in the pre-flame area as mentioned in Figure 1. The core section 3° has a porosity of 65 ppi while there is actual flame combustion. 30 and 32 in which the main core section 32 has a porosity of 10 ppi. Utilize a few adjacent ceramic cefsilanes. Separated sections as shown If a comb is used, the cooling means or flame holder 34 may be a porous cell. It is thus inserted between two sections of lamic. But it's worth noting The cooling means is thus in close proximity to the inlet end of the combustible stream of the core section 32. located and in thermal contact with the flow inlet end 43 of the first combustion zone 44. That is.

Ignition of the fuel-air mixture flowing through burner 10 occurs at final outlet 35 or by any conventional means including igniting the flow at a convenient intermediate flow point. It can be implemented more easily.

The use of flame holder 34 allows the flame holder to react in zone 44 while maintaining a stable reaction zone. It is believed to allow for a wide range of adjustment of the combinations of equivalence ratios and flow rates utilized. It will be done.

For the apparatus shown in Figure 1, the flame stability limits for different equivalence ratios are similar to Figure 1. but compared to that achieved when the device without the flame holder 34 is operated. increase substantially. In the absence of a flame holder, an effective flame stabilization mechanism is The only heat loss is from the inlet and outlet areas of the heater. Flame holder 34 exists This allows lower flow rates to be used while keeping the reaction zone in a relatively constant position. Ru.

Such use also allows for rapid transitions between such stable operating conditions. 2:1 These are practical due to the general need to have a turndown ratio between This is an important characteristic when applied to

The flow of combustion products from the first combustion zone 44 is fed to the second combustion zone 52. It is thought that Zone 52 may also be the same or different from matrix 32 in zone 44. It can be constructed from a porous ceramic matrix 54 that has a

In the two-stage mode of operation of FIG. 1, the fuel and oxygen-containing gas to be supplied are 150 to 250% typically 200% chemical to fuel. The mixture is fed into the chamber 15 with oxygen present in the stoichiometric mixing, thereby The mixture becomes a fuel "starved" mixture. 3. Mixing without air preheating The object has a temperature of 4 degrees to 80 degrees Fahrenheit. Fuel and oxygen in the first combustion zone 44 The mixture of containing gases is ignited and combustion occurs at temperatures between 2000 and 80oO°F, typical occurs at 2400″F.

After the combustion-depleted mixture is combusted in zone 44, additional combustion and oxygen-containing gas is added to the product gas from zone 44 through inlet 18 into conduit 2o, and 6o is produces a fuel "enriched" mixture in which 95% and typically 80% stoichiometric oxygen is present. The enriched mixture is heated between 1800 and 2600 degrees Fahrenheit, typically about 220 degrees Fahrenheit. Combustion occurs in a second combustion zone 52 at a temperature of 0''F.

This temperature range is low enough that nitrogen can be removed by either "thermal" or "rapid" reaction mechanisms. Prevents oxide formation. Control of this temperature range is important for fuel-air storage and porous media. This is achieved by the combined effect of radiant heat transfer from the surface of the

In this operation, a portion of the combustion air and/or fuel is inside the PM first combustion zone 44. Bypassing the combustion and initial premixture of air. Ignition and combustion of the initial mixture Occurs in fuel-starved conditions as a result of preheating generated by radiative feedback .

Peak ignition temperatures are reduced as a result of radiative and convective preheating with minimal NOx production. occurs in the zone of The bypassing air and/or fuel then enters the first combustion zone 4 The excess is mixed with the product formed at 4 and before the outlet of the PM burner at 35. Oxidizes flammable materials. The cooling effect of radiant heat transfer from the PM burner is reduced overall. The theoretical flame of the total combined fuel/air mixture in the second zone is a little Generate a temperature lower than the temperature. This combined effect can be achieved by using a single stage or using diffusion combustion. makes it possible to achieve the lowest NOx levels possible with any multi-stage burner.

As a result, all fuel and all oxygen passing through a single combustion zone such as zone 44 Significant improvements in No. 1 and Fi 2 distribution are achieved. typically combustion Standard diffusion flame burners or single-stage preheaters where the A reduction of, for example, 50 to 80% compared to a premix burner is achieved.

Therefore, in the method and apparatus shown in FIG. It is mixed with air in the stage to raise the combustion temperature in zone 44 to 1500°K (2500″’ F) to minimize thermal NO. In this stage, the fuel is is converted to CO, but not completely converted up to COt. In the second stage or zone 52, The remaining fuel is added to provide additional heat release, but the temperature is again 1500°K. (2500°F). The radicals from the first stage attack the fresh fuel and Rapid NO0 production is slowed down as energy is rapidly released by oxidation of CO. . At the same time the presence of the cooling means 34 eliminates the return of the flame to the pre-flame section and Combustion downstream of combustion engine 44 is fully stabilized and controlled to minimize NO8 as described above. It is ensured that

Example In operation of apparatus 50, burner start-up is from the first stage inlet section. This was done by feeding a low flow stoichiometric mixture. Then turn the burner on to the second stage. It was ignited at mouth 35. A stoichiometric mixture with a low flow rate allows the reaction zone to reach the second stage burner control. It was allowed to be transmitted upstream through A. This process uses a burner made of quartz Tracked visually through wall 42. As the flame moves to the first stage flame core, The fuel and air flow rates were gradually increased to achieve the desired first stage equivalence ratio and flow rate. . When performing single-stage experiments, the start-up order is complete. In the second stage experiment , the burner is stationary in the first stage before the second stage reactants are introduced through inlet 18. It is permissible to arrive at state operations.

Burner operating conditions have comparable energy release and overall equivalence ratios of mono-membrane vs. 2. selected to allow comparison of emissions from one stage bar to another. Single stage burner discharge , using a two-stage burner system without adding additional fuel or air to the second stage. can be obtained. In the two-stage experiment, both depletion/enrichment and enrichment/deficiency configurations were used. I looked into the tion. The flow rate of fuel and air in the first stage is ■l′″”=v+”’ / [+ (ρ1.r/ρfuel) (φ+ / A F -t)) (1 )V, funI=VIair (ρ1.r/ρfunO(φ+/AF, t )) is subtracted from (2) by 1, where the stoichiometric value for the mixture of methane and air is The fuel-air ratio is 17.2, and the density ratio of air to methane is 1.805. Ru. In Equations 1 to 4, the equivalence ratio (φ) is determined by the stoichiometric empty ratio depending on the actual air/fuel ratio. It is defined as the air/fuel ratio divided by the air/fuel ratio. Therefore, an equivalence ratio of less than 1 is while an equivalence ratio greater than 1 represents an enrichment operating condition. The second stage air flow rate is The relationship between the equivalence ratio of the body, the equivalence ratio of the first and second stages (φ1 and φ2), and the first stage air flow rate derived as a number.

V tair = y, air (φ1-φ.,)/(φ.,-φ!) (3 ) where φ. , represents the combined overall equivalence ratio of the first and second stages. 2nd stage Fuel flow rate was derived as a function of second stage air flow rate and equivalence ratio.

V! fweL=y, sir (ρ1../ρfa*L) (φ!/A F @L) (4) The overall equivalence ratio is based on the desired enrichment operating conditions for the first stage (equivalence ratio and total flow rate of reactants), set the deficient equivalence ratio for the second stage and enrichment/air by calculating the required fuel and air flows to obtain the desired total equivalence ratio. Maintained in a deficient two-stage configuration. used to make comparisons Depletion/enrichment configurations reverse the operating conditions obtained by the above analysis. This was achieved by

Porous media burner 50 operates at 50 slpm in a single stage configuration Baseline NO at various equivalence ratios showed stable combustion within the matrix. 8 production was determined. As shown in Figure 2, from 0.6 (67% excess air) to 1. Stable combustion was achieved at equivalence ratios up to 5 (50% excess fuel). 0.6 to 0 ．． Range from 5 to 15 ppmv which is 3% O2 when dry corrected at equivalent ratios up to 8. The NOe level within the circle was quite low.

Higher NOL under operating conditions with excess fuel compared to conditions with excess oxygen The reason for the formation of bells is not easily understood, but there are two possible reaction routes. This seems to be the result of. Under oxidizing conditions, most NO8 is produced by the following formula: Formed by Dovinoch reaction.

0 + N8 → No + N N + 0! → No + 0 The first step is rate-limiting and occurs at high temperatures (>2799°F) (5), at equilibrium Very high levels of NOx are formed under oxidizing conditions. Figure 3 shows various temperatures. and the equilibrium No. of the mixture of methane and air in the equivalence ratio, indicating the formation, 0.87 (approximately 3% 0.) equivalent ratio, N in the range of 1000 to 4000 p p m v Oyo levels are possible at temperatures above 2400°F. But Zeldovich reaction Due to the high activation energy and long residence time required to complete the Figure 2 shows that only a small equilibrium level of N08 is achieved at an equivalence ratio of 0.87. 3 due to the small residence time in the matrix and the cooling effect of radiative heat transfer. 0 to asppmv indicating that only NO8 was formed in the PM burner. Ru.

In a fuel-rich flame, the excess hydrocarbon radicals and NOl is formed from HCN produced by reactions between nitrogen elements. many conditions Below, the likely route from HCN to No is initiated by the reaction of HCN with oxygen atoms. This is the order in which

ctb + N! → HCN + NHHCN + Q → No + HC (5) Equilibrium NOx formation under fuel-rich conditions dries out at temperatures above 2800°F. The level ranges from 10 to 200 ppm. Single stage data presented in Figure 2 Under actual ignition conditions, PM burners produce equilibrium NOx levels of 25 to 50%. This indicates that it will occur. The conclusion drawn from these data is that oxidative conditions No, under the condition that the rate of formation is limited. On the other hand, under excessive fuel conditions, NOx Formation approaches equilibrium conversion and this is the limiting factor for the level of NO8 formed.

At temperatures below 2400°F, equilibrium NOx formation at fuel-rich combustion conditions approaches zero. It turns out that This means that the PM bar can be operated not only under oxidizing conditions but also under reducing conditions. points out the need to maintain a low temperature in the tank.

In Figure 4, the equivalence ratio of the first stage is 1.2, the equivalence ratio of the second stage is 0.4, and the total is 0.8. 7 (3% excess OX). Ru. The average temperature under the multistage condition was 1324°C (2416°F), same condition The average axial temperature of single stage combustion at 1420°C (2588°F) It was (4).

The low temperature profile of combustion under multi-stage conditions is second stage heat due to the combined effect of distributing fuel and air and radiative heat conduction. Due to loss.

Table 1 summarizes the results of emission measurements obtained at various burner operating conditions.

Case 1 is a single-stage combustion, Case 2 is a two-stage combustion consisting of a first enrichment stage and a second depletion stage; Base 3 is a two-stage combustion consisting of a first depletion stage and a second enrichment stage. The heat release rate (Q) of the fuel is the mass flow rate of fuel multiplied by the lower heating value. These results are shown in the first and second stages. No formation in the two-stage burner (case 3) where are fuel starved and fuel enriched, respectively. It shows that the amount decreases. A similar trend regarding NO emissions is observed when the overall equivalence ratio is 1. ．． observed when it is 0.

Table I PM burner two-stage versus single-stage combustion *CO not detected As expected, the highly depleted mixture φ = 0.6 in the first stage and the second stage The best results were obtained under multi-stage conditions of fuel-enriched mixture φ-1,4 (Case 3 and and 6). The relative flow velocity in each stage varies between cases 3 and 6 to achieve the desired total equivalence ratio. was gotten.

Cases 1 and 4 are single-stage combustion conditions operated at φ = 0.87 and 1.0, respectively. It is. compared to 10 and 20 ppmv, respectively, of multistage combustion at the same total equivalence ratio. It should be noted that NO8 levels of 23 and 36 ppmv were obtained in the dry state. It is possible.

Cases 2 and 5 are two-stage combustion conditions where the first stage is fuel-rich combustion and the second stage is fuel-starved. , giving a total equivalent ratio of 0.87 and 1.0, respectively. N08 generation is Even in the case of excess C01), it is within the dry range of 35 to 38 ppmv (1.6 from>2.5%).

Cases 3 and 6 not only have the lowest N08 emissions but also the lowest CO levels. It should be noted that

These results demonstrate that the first stage is a fuel-deficient equivalence ratio and the second stage is a fuel-enriched equivalence ratio. Combustion offers significant advantages over single stage combustion at equivalent total equivalence ratios. It shows. The reason for these results is the thermal N formation is inhibited in the first stage due to the low flame temperature achieved at high excess air conditions. This is because In the second stage, the combustion-enriched mixture is added; The combined effect of unreacted oxygen (at a small concentration) and ceramic porous Due to the effect of radiant heat conduction, which reduces the flame temperature at the outlet end of the trix tube, cyano NOx formation from mechanisms is suppressed. Undetectable level of C in cases 3 and 6 O shows good combustion characteristics even at a theoretical fuel-air ratio (φ = 1.0). Ru.

The following conclusion is drawn.

1. Two-stage combustion in porous media burners has lower average axial direction compared to single-stage combustion Produces a positive temperature.

2. Two-stage combustion, where the first stage is deficient and the second stage is combustion enrichment, is a single stage combustion with the same total equivalence ratio. NO8 and CO are lower than combustion.

3. Two-stage combustion, in which the first stage is combustion enrichment and the second stage is deficient, is a single stage combustion with the same total equivalence ratio. Does not present any significant advantage over combustion.

4. Two-stage combustion, in which the first stage is deficient and the second stage is combustion enrichment, is a total stoichiometric fuel-empty Very low NO and CO emissions, providing maximum fuel efficiency with minimum emissions. do.

Various changes and modifications may be made without departing from the invention as defined in the appended claims. , as described in the described and illustrated embodiments. Therefore, the above It is understood that all matters contained in the description and drawings are illustrative only and are not intended to be limiting. should be interpreted.

FIG.1 0 0 0 0 (id O() ψ　　　　　　　　　 No, concentration (ppm) Temperature (°C) International search report. ,,T/IK 057M. . □１□＾−P、〜PCT/υS Continuation of 92102084 front page (81) Designated countries EP (AT, BE, CH, DE.

DK, ES, FR, GB, GR, IT, LU, MC, NL, SE) , CA, J.P., K.R. (72) Inventor: Gardiner, William See.

United States 78703 Texas, Austin, Marie Ante Ro 2612 (72) Inventor Howell, John Earl.

United States 78703 Texas, Austin, Carpay Lane 3 200 (72) Inventor Matthews, Ronald Dee.

United States 78756 Texas, Austin, Sinclair 4508 (72) Inventor Nichols, Steven P.

United States 78704 Texas, Austin, Glensor Play Su 2116

Claims (7)

[Claims] 1. A second zone is downstream of the first zone, and its air gap allows substantially all combustion to occur. each filled with a porous high temperature resistant matrix that provides sites for first and second combustion zones; mixing fuel and a gaseous oxygen source and having a fuel deficiency therein; supplying a combustible mixture to the inlet end of said first combustion zone to establish conditions; means for supplying combustion products from said first zone to said second zone and Increase that fuel ratio with enough additional fuel to form a fuel-rich combustion state therein. means for thereby completing the oxidation of the product from said first zone; and said entry. the first to maintain the temperature of the combustible mixture at the mouth end below the ignition temperature; located close to the inlet end of the combustion zone of the porous matrix, thereby the cooling means for restricting the flame generated by combustion within the cooling means to the downstream side of the cooling means; A burner device for controlled low NOx combustion. 2. Generally, the cooling means surrounds and is in thermal contact with the inlet end of the combustion zone. comprising a toroidal hollow metal member and means for circulating a refrigerant through said tube. The burner device according to claim 1. 3. The burner device according to claim 2, wherein the refrigerant is water. 4. The burner device according to claim 2, wherein the refrigerant is air. 5. The member is installed so as not to invade the inside of the porous matrix. , so as not to impede the flow of the fuel-air mixture through the matrix. 3. The burner device according to claim 2, wherein 6. The first matrix is the initial combustion zone of the gaseous mixture arranged in series. combustible mixture of fuel and oxidizer through two porous ceramic matrices and cool the mixture as it flows into the surface of the matrix. from the first matrix while maintaining the mixture temperature of the surface below its ignition temperature. Eliminating backflow of flame to the upstream side, combustion of the first matrix is caused by fuel starved oxidation the combustion products from the first matrix and additional fuel and oxidizer may be added to the flow of said second matrix to cause combustion in said second matrix to occur in a fuel-enriched state. A combustion method for controlled low NOx combustion comprising: 7. A second zone is downstream of the first zone and its air gap is where substantially all combustion occurs. said first part each filled with a porous high temperature resistant matrix that provides a 1 and 2 combustion zones; in which the fuel and gaseous oxygen source are mixed and a fuel starvation condition is present therein; a hand supplying a combustible mixture to the inlet end of said first combustion zone to establish a condition; stage; supplying combustion products from said first zone to said second zone and supplying oxygen and increase the fuel ratio with enough additional fuel to form a fuel-rich combustion state therein. said control comprising means for completing the oxidation of the product from said first zone. Controlled low NOx combustion burner device.