FLAMELESS OXY-FGR: AN ENERGY EFFICIENT COMBUSTION CONCEPT THAT COMPLIES WITH ENVIRONMENTAL REGULATION AND OFFERS

DIRECT CO2 CAPTURE SOLUTION FOR EXISTING AND NEW GAS FURNACES

Clotilde Villermaux1, Stephane Maurel

1, Thierry Hortaned

1, Thierry Bellin-Croyat

1, Thierry Ferlin

1

1. GDF SUEZ, Research and Innovation Division

361, Avenue du Président Wilson – BP 33 - 93211, Saint-Denis La Plaine - France

Keywords: 1.Flameless oxy-FGR combustion; 2. Flameless combustion with synthetic air; 3: Energy efficiency; 4. Direct CO2 capture; 5. Ultra-low NOx emissions.

1 Introduction/Background

Today, energy efficiency is becoming one of the most important issues for industrial plants. In a

context of high prices and volatility of energy, GDF SUEZ’s challenge is to meet the issues of industrials users. That means finding a compromise between flexibility and global efficiency of industrial tools, suppressing plant bottlenecks while adapting industrial plants to environment constraints in order to match regulation and face opportunities and risks from CO2 markets.

GDF SUEZ’s commitment to sustainable development reflects the values and principles to which the

Group adheres and which underpin its policy of customer service. In line with this commitment, GDF SUEZ has launched R&D projects to develop energy-efficient solutions that comply with the problem of global warming, directly linked to the energy consumption [1].

Considering CO2 issues, the first step to CO2 capture is the use of a chemical sorbent such an amine

to scrub the CO2 from the flue gas. The main asset of this technology is not to modify the industrial furnace, so not to jeopardize the production. However, this post-treatment is still expensive and as there is no effect on furnace, there is no improvement on efficiency either. Thus, today, as industrial end users don’t see direct benefits to their production, they cannot justify the additional costs that would imply the CO2 post-treatment investment needed to prepare CO2 capture.

However, in industrial furnaces, improvement of the CO2 capture process and further treatments can become interesting if we take into account the potential benefit on radiative heat transfer of H2O and CO2 high concentration in flue gases and in furnace space.

Standard oxyfuel is a promising technique for CO2 capture but it has several major drawbacks: the oxygen cost, the need to deeply redesign the furnace, the occurrence of hot spots that could harm the furnace or the heated product and the NOx emissions dependency on air leaks. By combining oxyfuel with Flue Gas Recirculation (FGR), it is possible to treat most of these drawbacks.

GDF SUEZ is the coordinator of the national French project TACoMA (Advanced Combustion

Techniques to Control Atmospheric emissions). The other partners are IFP, TOTAL, Divergent and ICARE (CNRS), and it is funded by ANR (National Research Agency). In this project, the flameless oxy-FGR combustion regime will be aimed in order to make the furnace work in a configuration range that will strongly limit NOx production, while improving energy efficiency and simplifying CO2 post treatment and handling.

Its objective is to evaluate, test and develop flameless oxyfuel combustion techniques with Flue Gas

Recirculation (flameless oxy-FGR) for easiest CO2 capture. Its industrial target is to develop innovative combustion systems for the revamping of existing industrial furnaces as well as the building of new ones adapted to CO2 capture.

The project began in December 2006 and is composed of three main steps:

� Fundamental works on kinetics, test and validation of numerical tools on academic configuration from literature,

� Experimental understanding of this combustion concept, through test rigs, specifically built in the frame of this project, and validation of the previous numerical tools (CFD, global tools), with the experimental measurements,

� Economical evaluation of the technical solution. This paper presents the experimental part of GDF SUEZ activity in that project, particularly the semi-

industrial test facility that have been set up and the first results of the test of flameless combustion with synthetic air, obtained by an external flue gas recirculation of oxyfuel combustion.

.

2 Oxy-FGR combustion or synthetic air combustion Oxyfuel combustion with FGR can be obtained by:

� Internal recirculation following the principle of a oxyfuel flameless regime, � External recirculation of the fumes and mixing with O2 at the burner nozzle in order to create a

synthetic air, replacing the classical air combustion. These to ways can be combined to achieve flameless oxy-FGR combustion so called flameless

combustion with synthetic air.

a. Flameless oxyfuel combustion regime

The flameless oxyfuel regime has been studied by the Swedish Royal Institute of Technology and Linde AG [2]. This company sells gas burners that run in such oxycombustion flameless regime. Already implemented in furnaces in metallurgy industry in Swede and France, Linde and the Swedish Royal Institute of Technology communicated some results in comparison to classical aero-combustion [3-4]:

� A 25 to 40 % decrease of specific consumption, and so CO2 emission and/or 30 to 50% increase of heating capability,

� A decrease of NOx emission, � A smaller influence of air leaks to NOx emission, � A better temperature homogeneity than in classical oxyfuel combustion.

However, these retrofits needed a full re-design of the furnace, particularly because of the reduction

of the fumes volume compared to aero-combustion. Specific studies had also to be done in order to adapt this implementation to the different cases.

b. Synthetic air combustion

The second way to dilute the flame with the fumes is to recirculate the products of combustion by an external recirculation, and mix them with oxygen before or within the burner: it is called combustion with synthetic air O2/CO2/H2O. The volume of the fumes is then not as reduced as for oxycombustion. Thus existing furnaces can be retrofitted with a reduced re-design.

Frasier [5] get the patent of the concept of synthetic air in 2000. This patent proposes an assembly

for oxyfuel furnaces equipped with regenerative or recuperative systems to the retrofit with synthetic air. This patent is not maintained any longer.

Mattocks [6], one of the authors of the patent, published a survey applied to a regenerative glass furnace. One of the expected results is an improved radiative heat transfer to the glass while a reduction to NOx emissions. This theoretical approach showed that:

� 60% of the fumes recirculated should lead to save 14% of energy. � Even with an air leakage up to 10% of the fumes, the NOx emissions are reduced up to 88%

compared to classical air combustion. The influence of this particular atmosphere to the chemical reactions of the wall materials was also

presented, including the presence of the pollutants. This analytic analysis shows good perspectives in term of heating and environmental performances,

with limited retrofit of an existing furnace. However, this specific application study has not been experimentally tested. This step is essential to confirm the first results and plan an industrial application.

In term of experiments, a couple of years later, the R&D center CANMET [7] compared a natural gas

burner in a 300kW semi-industrial furnace operating with classical air, with a dry synthetic air with (28% O2 - 72% CO2) obtained by external recirculation of the fumes, and with O2 enriched air (28% O2 - 72 % N2). The main results are

� Heat transfers obtained with combustion with the dry synthetic air are similar to those obtained with classical air combustion while reducing NOx emissions

� Heat transfers and temperatures levels are much higher with O2 enriched air, leading to a drastic increase of NOx emissions These important tests demonstrated the potential performances of the synthetic air, and the

possibility to use synthetic air with conventional burners in a perspective of CO2 capture and sequestration. The concept of synthetic air combustion has also been studied for a boiler dedicated to electricity

production in the frame of the European project Encap [8]. At the University of Chamlers, in a 100 kW pilot

furnace, a 80 kW propane burner was tested with a synthetic (dry) air (composed with 27% O2 – 73 % CO2) obtained by external fumes recirculation. The flame temperature is similar to the aero combustion one, and the burner behaviour is the same. However, with the same level of temperature, the radiation intensity is increased (from 20 to 30%), due to the increase of CO2 concentration [9]. The authors also presented a theoretical study on the radiative properties of this synthetic air compared to the classical air. This project shows then the possible industrialisation of the combustion concept. It confirmed the interest in term of heat transfer and NOx reduction, associated to a CO2 capture solution.

All this R&D activities show a great potential to the use of synthetic air in several configurations.

However there is no result on the use of synthetic air in flameless regime. Nevertheless, this combination could be interesting by maximising the benefits such as homogeneity of heat transfer, lower NOx emission, increase of efficiency, and direct CO2 capture possibility for existing and new furnaces. GDF SUEZ contribution in the project is then the study of this particular concept of combustion: synthetic air in flameless regime for gas combustion, or flameless oxy-FGR gas combustion. To achieve this study, one of GDF SUEZ activity has been to set up a specific facility. It is presented just below.

3 Semi-industrial scale facility to test and optimize flameless oxy-FGR combustion concept

The aim of theses tests is to gauge the efficiency on heat transfer and on air emissions of external recirculating flue gases on the burner nozzle. Starting with a classic flameless aerocombustion layout, the aim is to create synthetic air with cryogenic oxygen and a flue gas recirculation using the same burner equipment as for aerocombustion.

a. Flameless burner tested

The HRS-DL [10-11] burner (figure 1) is a nozzle-mixing burner. It was developed by NFK with a nominal thermal input of 200 kW. This regenerative burner with standard honeycomb structure works by pair. The operation limiting temperature for this burner was fixed at 1350°C.The burner head is very similar to the Twinbed II model of North American Manufacturing Company. It implements the fuel staging and strong impulses on the reactants to support the fume internal recirculation.

The burner lays out of a regenerative heat capacity made up of interchangeable refractory blocks

with standard honeycomb structure. Below 800°C, the fuel is directed entirely in the central air flow thanks to the side injectors. Beyond, the fuel is divided between the side injectors and two lances laid out on the diagonal of the burner.

Figure 1: Assembly of the HRS-DL burner from NFK [9-10]

The burner used is in the frame of this project has been extrapolated from the NFK burner. It consists of two off-axis natural gas injectors set symmetrically around a central air duct (figure 2). GDF SUEZ performed several previous R&D projects testing this burner in the same furnace, in flameless combustion regime with classical air, and characterising its performances in term of heat transfer and NOx emissions [12-16]. .

Figure 2: flameless burner nozzle connected to the combustion chamber

This 200 kW burner has been installed on a 500 kW furnace that is instrumented to allow the measurements of global characterisation of the combustion regime, and detailed measurements in the flame.

b. GDF SUEZ semi-industrial scale furnace

The 500 kW furnace was designed and set up at GDF SUEZ to allow easy change of the air combustion components while keeping same other operating conditions (figure 3). The aim of this study is to contribute to this understanding in order to be able to give some keys to extend the combustion concept to other combustion applications.

Every relevant parameter such as combustive temperature, input power, air ratio can be separately

controlled: � The chamber dimensions are about 1m width, 0,95m height and 4,00 m length, � The maximum temperature is about 1350°C, � A motor driven water tube thermal load of 300 kW on the crown for temperature adjusting in the

furnace.

Figure 3: GDF SUEZ 500 kW furnace

This furnace is designed to recreate industrial conditions and is fully monitored. The front part of this furnace is designed for in-flame measurements (figure 4).

2 natural gas injectors 1 oxidant injector air / synthetic air

In flame measurements

Thermal load

Electric preheater

Mobile waterproof wall

Measurement probe

Chimney

BurnerMain chamber

Measurement space

Optical access

Burner preheater

connection

In flame measurements

Thermal load

Electric preheater

Mobile waterproof wall

Measurement probe

Chimney

BurnerMain chamber

Measurement space

Optical access

Burner preheater

connection

Figure 4: Top view of the test furnace

For every firing case, the following parameters are monitored At the burner nozzle

� Combustive temperature in °C, � Combustive volumic flow in m3(n)/h, � Combustive pressure in mbar, � Natural gas volumetric rate in m3(n)/h, � Combustive composition (volume fraction dry basis).

At the exhaust chimney:

� Flue gases composition on volumic dry basis (CO2, O2, NOx), � Flue gases temperature in °C,

In the furnace:

� Crown temperatures in °C, � Pressure in mmCE,

On the crow, there are several temperature measurement probes:

� Measurement at 85mm, 285mm, 485mm, 685mm , 885mm, � Security temperature probe located at 1500mm of burner door, � Various probe in the furnace chamber located at: 3170mm, 3470mm, 3770mm, 4070mm, and

4370mm. For energy balance calculations:

� Water temperature (input, out put) of the thermal load in °C, � Water flow rate in m3/h, � Wall outside temperature in °C, � Outside air temperature in °C.

Detailed in-flame measurements in stationary mode were carried out for some firing cases:

� Temperature field mapping by fine-wire thermocouple, � Stable species concentration fields mapping (CH4, O2, CO, CO2 and NOx) by sampling with a sonic

nozzle probe These experimental data will be used for a better knowledge of the physicochemical characteristics of

these flames but also for validation of the numerical simulation of the burner.

c. Recirculation loop

The recirculation loop (figure 5) is designed to bring the flue gases from the exhaust area of the furnace to the burner nozzle.

In that study, in order to keep the same gas power input, the amount of oxygen has been kept

identical for all the trials. The only way to change the relative composition of oxygen in the synthetic air is to modify the flow rate of the recirculating fumes.

This recirculation loop includes:

� A two stages water/flue gas heat exchanger, � A recirculation fan operating between 50 m3(n)/h and 200 m3(n)/h and with flue gases below

temperature 250°C, � A control diaphragm with pressure probe upstream and downstream for flow rate measures, � An indirect electric flue gases preheater to avoid water vapour contact on electric resistor.

Beside this recirculation loop we made the cryogenic oxygen feeding. This feeding includes:

� A specific oxygen preheater, � A flow rate measurement system.

The aim of this loop was to create synthetic air at the burner nozzle by recirculating the desired

amount of flue gas. Both H2O and CO2 are recirculated. So the recirculating loop had to be designed in order to fulfil both

constraints: � The recirculating fan works only with flue gases at a temperature below 250°C, � Flue gases have a high content of water vapour. In order to keep the ratio of CO2 versus H2O, the

temperature in the recirculation loop had to be higher water condensation one.

Figure 5: GDF SUEZ semi-industrial scale facility equipped with a 200 kW flameless gas burner to test and optimize flameless oxy-FGR (extern Flue Gas Recirculation) combustion concept

4 Experiments and results

a. Firing conditions

Several case-tests were studied around the reference following operating conditions: � Thermal input = 200 kW, � Air fuel ratio = 1.1, � Preheated air temperature ~ 200°C (electric powered air preheaters were used), � Furnace temperature ~ 1200°C.

Flameless burner Flue Gas Recirculation (FGR)

The water tube thermal load position on the crown has not been moved for all the firing conditions. This simulates constant load of a furnace, absorbing an amount of the total power input in the furnace.

Some tests have been carried out with classical air:

� Tests with cold air and preheated air (~220°C), � Air fuel ratio equal to 1,1 means 2% O2 in the dry fumes.

Several tests have been carried out with synthetic air

� O2 component in synthetic air (%vol.): 25%, 35% et 45%, � Preheating temperature: ~220°C, � Air fuel ratio equal to 1,1 means around 8% O2 in the dry fumes.

b. Flameless oxidation regime

Flameless combustion has been developed when applying fuel or air staging to regenerative burners to the maximum level of a total staging, i.e. to a configuration where air and fuel injections are distant. Because of the large jet velocities of fuel and air associated to this staging, strong recirculation of flue gas occurs in the combustion chamber. Mixing of recirculating combustion products with air and fuel induces this specific diluted combustion regime named HiTAC combustion, flameless combustion or mild combustion [17-19].

Its main characteristics are the global homogeneity of heat release, the non-visibility of the reaction zones, and the very low NOx emissions that can be divided by ten compared to a conventional regenerative burner [20].

One important challenge of this study is to use a flameless burner that have been designed for air

combustion (so for a particular range of air impulse to achieve enough recirculation to dilute the reactants), and to test if the flameless regime can be reached with synthetic air.

In that study, in order to keep the same gas power input, the amount of oxygen has been kept identical for all the trials. The only way to change the relative composition of oxygen in the synthetic air is to modify the flow rate of the recirculating fumes.

Figure 6: Relative air impulse of the tested burner (compared to the classical air impulse at the same level of preheating temperature: 200°C)

In the range 25% O2 to 45% O2, the synthetic air flow, and so its impulse, is drastically reduced in comparison to classical air combustion. As a consequence, the air impulse, that is necessary to create the recirculation in the furnace, can be notably perturbed. For example, looking at the figure 6, the synthetic air that could provide an air impulse similar to classical air would be a synthetic air composed with less than 24% of O2. For a synthetic air with 45% O2, the air impulse is less than a quarter to the classical air impulse.

The question is then whether the air impulse will be strong enough to reach the reactant dilution

leading to flameless regime. One important result is, as shown figure 7, that we noted that flameless regime is reached and

stabilised for all the synthetic air tested, even for a synthetic air with 45% O2.

air 25% O2 35% O2 45%O2

Figure 7: Flameless regime for air and synthetic air combustion obtained with classical NFK flameless burner – preheating temperature: 200°C

NOx emissions: The characteristics of oxy-fuel combustion are fast chemical reaction ratio, high flame peak

temperature and a visible flame. The potential problems of traditional oxy-fuel technologies are refractory damages, non-uniform heating and a particularly large influence of air leakage on NOx emission.

Figure 8: NOx emissions (kg/h) measured with the NFK burner operating with air and with synthetic air preheated at 200°C

One of the most important characteristics of the flameless regime is the possibility to decrease the NOx emissions even with high preheating air combustion, or for high furnace temperature: the temperature in the reaction zone stays very close to the furnace temperature, limiting the thermal NOx formation.

In that study, the flameless regime is obtained while using a no-nitrogen oxidant, leading to very

reduced peaks of temperature in the furnace. NOx emissions should be then very low, even in case of air leakage.

Figure 8 presents the NOx emissions that have been measured at the exhaust furnace for different air

feedings: classical air with different levels of preheating temperature, and with 200°C preheated synthetic air with different O2 rate.

As expected, the level of NOx is very low, even very close to zero in the case of synthetic air and

whatever the rate of O2. Indeed, even if we can notice a slight trend to increase NOx emissions with the O2 rate in synthetic air, the general level stays more ten times lower than in the case of flameless preheated air combustion.

Experimental in-flame investigation: Under operation, following detailed measurements were carried out in stationary mode:

� Temperature field mapping (see example figure 9) by sampling with a suction pyrometer, � Stable species concentration fields mapping (CH4, O2, CO, CO2 and NOx) by sampling with a sonic

nozzle probe. Figure 9 presents temperature fields that have been extrapolated from in-flame temperature

measurements for flameless preheated air and flameless preheated synthetic air (35% O2) combustion.

Figure 9: Average flame temperature measurements- Air preheated at 200°C Up: flameless aero combustion. Resulting furnace temperature 1090°C

Down: flameless synthetic air (35% O2) combustion. Resulting furnace temperature 1180°C

We can observe weak temperature gradients: due to the recirculation, the temperature is

homogeneous and about the furnace temperature. This uniform distribution of temperature in the furnace and the absence of high peak of temperature avoid the NOx formation.

We notice a much more homogeneous temperature field, and a higher furnace temperature in the case of flameless synthetic air combustion: using an air flameless burner, with the same amount of gas power as for air combustion, we can achieve a more uniform and higher average heat transfer with synthetic air, while drastically decreasing NOx emissions.

These measurements analysis allows the study of the mechanisms governing the combustion mode

as well on the flame stabilisation conditions and the combustion products recirculation rate quantification that is responsible of the species dilution, and of the identification of the NOx formation mechanism.

As a result of the employed resources, this study constitutes an original work that allowed providing

the data still rare in the literature. In the long term, this work should lead to a better understanding of the phenomena governing flameless oxidation like helping us in its application to other industrial application types.

These measurements also fed the discussion on the methods used to simplify the burner

representation for CFD simulation, satisfactorily and at an acceptable CPU time cost (low mesh number). This is the object of the next step of the project.

Combustion efficiency:

100%

110%

120%

130%

140%

150%

20% 25% 30% 35% 40% 45% 50%

O2 in synthetic air (% vol.)

Co

mb

usti

on

eff

icie

ncy :

syn

theti

c a

ir / a

ir (

%)

synthetic air (~200°C)

air

Air 200 °C

Air 20 °C

Figure 10: Relative combustion efficiency of the NFK flameless burner running with 200°C preheated synthetic air

Figure 10 shows the relative combustion efficiency of the flameless burner running with 200°C preheated air (air and synthetic air compared to flameless combustion with cold air).

We notice that

� The O2 rate has to be higher than 26% to obtain higher combustion efficiency than air combustion for the same level of preheating temperature.

� Small influence of the O2 rate on the NOx emissions in spite of a greater impact on the combustion efficiency with the same gas power input: up to 40% in comparison to cold air, and up to 30% in comparison to air combustion at the same level of preheating temperature and with the same gas power. The combustion efficiency increases with the O2 rate even if, in the same time, the volume of the oxidant decreases and so the enthalpy of the oxidant entering the burner decreases.

5 Summary/Conclusions/Perspectives

GDF SUEZ Research and Innovation Division is very much involved in flameless combustion since a long time. The better understanding of the combustion phenomena of the “flameless-oxidation” mode developed within the different activities presented in this paper but also the design tools as other coming results of this project, will enable to implement this technology and give guarantees on the performances of future installations like on the products heating quality or productivity.

The main conclusion of these tests is that a flameless burner designed for classical air is also

available for stable flameless synthetic (O2/CO2/H2O) air combustion, or flameless oxy-FGR combustion. In comparison to flameless aero-combustion, the noticed improvements are:

� Using a classical air flameless burner, with the same amount of gas power as for air combustion, we can achieve a more uniform and higher average heat transfer with synthetic air, while drastically decreasing NOx emissions

� The NOx emissions stay drastically low whatever the rate of O2 in the synthetic air � The combustion efficiency is increased up to 30 % without increasing the preheating temperature and

for the same the gas power input (even if, in the same time, the volume of the oxidant decreases and so the enthalpy of the oxidant entering the burner decreases). Synthetic air combustion can then be considered as a smart combustion solution that can both give a

solution to direct capture and afford opportunities to improve the furnace efficiency while complying environmental regulation. In addition to that, this combustion concept that uses an air feeding burner, needs oxygen but can turn back to air feeding whenever necessary, leading to a flexible drive of the industrial installation.

The results of this work indicate that such synthetic air combustion in a flameless regime (flameless

oxy-FGR) offers excellent potential for retrofit to existing furnaces for easy CO2 emission abatement. Other benefit of this combustion concept includes considerable reduction of NOx emissions, and improved furnace efficiency due to a much better heat transfer homogeneity than pure oxy-combustion and a higher temperature profile and a lower gas volume to the chimney than classical air combustion.

The next steps are also the development of the knowledge and design tools to better understand and

optimize the performances and the advantages of this technology. The objective is to be a partner to analyse the opportunity and work to the adaptation of this combustion concept to industrial processes in regards to their specific issues. Acknowledgements

Financial support by ANR (French National Research Agency) is gratefully acknowledged.

References

[1] M. Florette, J. Rückheim, G. Voigtlander, H. Wendel, “Gaz de France’s current and future involvement in CCS projects - A commitment to sustainable development”, First French German Symposium on Geological Storage of CO2, Postdam, June 21-22, 2007

[2] Krishnamurthy N, Woldzimierz B, Lugnet A (2004), “Development of High Temperature Air and OxyFuel Combustion Technologies for minimized CO2 and NOx emissions in Industrial Heating”, The Join International Conference on “Sustainable Energy and Environment (SEE)

[3] Schéele J., Gartz M., Rainhard P., Lantz M., Riegert J.P., Soederlund S, (2008) “Flamless oxyfuel combustion for increased production and reduced CO2 and NOx emissions”, Stahl und Eisen, Vol 128 n°7, pp. 35-40, 2008

[4] Blasiak, K. Narayanan, W. Yang, T.Ekman, A. Lugnet, “Flameless oxyfuel combustion - Technology, modelling and benefits in use”, International Steelmaking Conference 2005, ATS, 2005

[5] Argent R.D., Hoyle C.J., Dickinson G., Ward T, Mattocks G.R., “Synthetic air assembly for oxyfuel fired furnaces”, Patent n° US6126440A

[6] Mattocks G.R., “Use of synthetic air for combustion in regenerative furnaces”, Glass Technol., 1998, Vol. 35 n° 5, pp. 148-156

[7] Tan Y., Douglas, M.A., Thambimuthu K.V, “CO2 capture using oxygen enhanced combustion strategies for natural gas power plants”, Fuel, 2002, Vol. 81, pp 1007-1016

[8] Anderson K., “Fundamental oxy-fuel combustion research carried out within the ENCAP project”, IAE GHG oxy-fuel Inaugural Workshop 2005

[9] Andersson K., Johnson F., “Flame and radiation characteritics of gas-fired O2/CO2 combustion”, Fuel, 2007, Vol 86, pp. 656-668

[10] Hasegawa, High temperature air combustion as a core technology in developing advanced industrial furnaces, Proceedings of the Forum on High Performance Industrial Furnace and Boiler, 09-09/03/1999

[11] T. Hasegawa, R. Tanaka, T. Niioka, in Proc. ASPACC97, May-June, Osaka, Japan, pp. 290, 1997 [12] Kara Y., Aguilé F., Qinqueneau A., Touzet A., Porcheron L., « Characterization of burners operating in

flameless oxidation mode – experimental results », Totem 25 FRIF, October 2003. [13] Masson E., Honoré D., Boukhalfa A., Porcheron L., Maurel S., Aguilé F., Meunier P., Quinqueneau

A.,“An experimental characterization of flameless combustion at semi-industrial scale”, Proceedings of the European Combustion Meeting 2003, Orléans.

[14] E. Masson, D. Honoré, A. Boukhalfa, L. Porcheron, S. Maurel, F. Aguilé, P. Meunier, A. Quinqueneau, Proceedings of the 14th IFRF Member’s conference, the International Flame Research Foundation, IFRF, Noordwijkerhout, Netherlands, 2001

[15] Quinqueneau A., Touzet A., Oger M., « Experimental studies on regenerative industrial burners operating in flameless oxidation mode », IGRC, 2001.

[16] Quinqueneau A., Aguilé F., Porcheron L., Touzet A., « Flameless oxidation applied to high temperature process- overview of Gaz de France R&D activities on the subject”, Word Gas Congress (Tokyo, June 2003).

[17] M. Katsuki, T. Hasegawa, Proc. Comb. Inst. 27:3135 (1998). [18] J.A. Wünning, J.G. Wünning, Prog. Energy Combust. Sci., 23:81-94 (1997). [19] A. Cavaliere, M. de Joannon, Prog. Energy Combust. Sci. 30:329-366 (2004). [20] M. Flamme, Energy Conversion and Management, 42: 1919-1935 (2001).