Injection of Pulverized Coal and Natural Gas into Blast Furnaces for Iron-making: Lance Positioning and Design

Abstract

Injecting pulverized coal and natural gas into blast furnaces for ironmaking decreases metallurgical coke requirements, providing a net decrease in the CO₂ emissions and in many cases, operating costs associated with iron production. Ideally, the fuel would enter the raceway partially reacted and the injection would not have negative impacts on the equipment or process. Success in achieving this outcome is sensitive to the details of how the injection is implemented. Given this sensitivity and that it is difficult to make accurate, detailed observations in blast furnaces or devise representative pilot-scale experiments, computational fluid dynamics (CFD) has become a useful and complementary tool for the analysis and design of fuel injection methodologies. This study uses CFD to examine the interaction of the blast air and fuel flows in the blowpipe and tuyere nozzle for different fuel injection strategies. Important operating issues such as initiation of partial combustion and heat loads on the tuyere nozzle are examined. It was found that two key fuel injection strategies developed separately for coal and natural gas can be combined effectively in a single combined fuel lance that leverages a bluff body effect to help coal dispersion and has radial nozzles to improve natural gas combustion. The bluff body effect is a simple process whereby the interaction between the blast air flow and a thick-walled lance creates a wake that can impart coal dispersion without the complexity or costs of adding an auxiliary dispersive fluid, such as an annular swirling flow of air. The performance of this combined fuel lance is compared against two configurations for separate fuel lances.

1. Introduction

In the basic operation of a blast furnace for ironmaking, metallurgical coke, iron ore, and limestone flux are supplied through the top of the furnace while hot air is blown through tuyeres (nozzles) into the lower section. The hot blast air partially combusts the coke to generate the heat and reducing gas required for iron ore reduction and smelting. Frequently the blast air is enriched with oxygen and hydrocarbon fuel injected into the tuyeres, enabling a reduction in metallurgical coke requirements and improved productivity of the furnace, which results in energy, emissions, and, in many cases, cost savings. One limit to the injection of hydrocarbon fuel is its global cooling effect on the furnace relative to the corresponding use of metallurgical coke alone. Hydrocarbon injection does, however, provide advantages by introducing hydrogen into the furnace. The presence of hydrogen reduces the pressure drop of gas flow through the coke/ore burden or, alternatively, the upward force opposing the burden descent, because hydrogen is a lighter and less viscous gas. Hydrogen as a reducing agent and water vapour as the reaction product also diffuse more rapidly in and out of the iron ore pellets as compared to the primary reducing agent carbon monoxide and its reaction product carbon dioxide because of their higher diffusivities.

Designing an effective hydrocarbon fuel injection lance is challenging in terms of achieving partial combustion and controlling heat loads on the tuyeres. The hot blast air, travelling at approximately 150 m/s, provides only 5–10 milliseconds for combustion reactions to initiate in the tuyere. However, partially combusting the hydrocarbon fuel results in local heat release, which can damage the tuyeres. The high-speed blast air, typically having a temperature of 1100°C, presents a harsh environment for observation and measurement. Furthermore, it is not practical and it is expensive to carry out a trial-and-error approach in real furnaces. On the other hand, using laboratory measurements to obtain commercial-scale predictions presents significant uncertainty. Consequently, computational fluid dynamics (CFD) modeling has been increasingly used, along with observational data—at both pilot and commercial scales—and traditional methods of analysis to help understand and design injection strategies.

CFD studies have been carried out for blast furnace injection but detailed studies on the co-injection of pulverized coal (PC) and natural gas (NG) are sparse in the open literature. Shen et al.¹⁾ and Shen et al.²⁾ studied PC injection in the blowpipe, tuyere, and simplified raceway and validated the combustion model against measurements in a test rig. They found that coal burnout strongly depends on the availability of oxygen and that representation of the actual geometry is important. The lance had an annular design, with coal and nitrogen conveyed through the center and a coolant—oxygen, air, or methane—conveyed through the outer ring, all without swirl. Shen et al.³⁾ then extended the model to include the raceway geometry and the coke bed, using the same injection lance geometry. Andahazy et al.⁴⁾ performed a CFD analysis to examine the differences between injection of oil and coke oven gas through a simple pipe lance for a commercial furnace. Yeh et al.⁵⁾ performed CFD studies of pulverized coal and blast furnace top gas (BFG) injection and found that coal burnout decreased with increasing BFG injection because the BFG consumed oxygen, reducing the amount of oxygen available to react with the coal. They also noted swirling of the blast air caused by the presence of the injection lances and its effect on mixing. Chui et al.⁶⁾ developed a CFD model and compared its predictions to measurements from a pilot-scale reactor, supporting their modeling approach.

A few experimental studies have been carried out in laboratories and commercial furnaces, some accompanied by corresponding models. Mathieson et al.⁷⁾ reviewed successive generations of combustion test rigs, each attempting to provide a closer approximation to the actual blast furnace. Test rig configuration was demonstrated to have a significant effect on coal burnout. An earlier laboratory study by Jamaluddin et al.⁸⁾ found that coal grind, devolatilization characteristics, and dispersion of the injected coal had significant effects on coal burnout. The difficulty of obtaining measurements in the lower part of a commercial blast furnace is apparent in the paper by Nogami et al.⁹⁾ They reported measured temperatures in the coke bed but only to a maximum of 1200°C, at which point the thermocouples, which descended with the burden materials, melted.

Different types of injection strategies have been described for both PC and NG injection. Uchiyama et al.¹⁰⁾ presented modeling results for four different PC injection strategies, including a simple straight lance, a lance with swirling flow, a lance tip designed to impart radial velocity to the flows, and a thick-walled high turbulence lance. Their model predicted better coal burnout for the high turbulence lance, compared with the other designs. This was substantiated by an experimental comparison between the high turbulence and simple lances. Canadian and U.S. patents by Harrison and Drebert^11,12) described a fluid hydrocarbon (ostensibly NG) lance design where the end was substantially blocked off and much of the NG flow was directed through a series of radial nozzles. This was expected to improve mixing between the NG and blast air, and consequently improve combustion compared to a simple open pipe NG lance.

Recently, Holmes et al.¹³⁾ described the implementation and performance of PC and NG co-injection (via separate, simple straight lances) on an existing blast furnace. Majeski et al.¹⁴⁾ reported on CFD modeling studies of PC and NG co-injection via the use of separate lances. The natural gas entered through a simple pipe and the coal entered downstream via the central part of an annular pipe with a swirling annular flow of cooling air which could be either enabled or disabled. Mixing, combustion, and heat loads to the tuyere were examined. It was found that disabling the swirling annular flow effectively increased the thickness of the lance, creating a bluff body effect that behaved similar to the high turbulence lance described by Uchiyama et al.¹⁰⁾ This bluff body effect increased coal dispersion and consequently devolatilization compared to the case where the annular swirl was enabled, implying that PC injection performance can be improved by simple lance design without the added complexity and costs of an auxiliary fluid injection (e.g., swirl).

Based on past work reported in the literature and some non-reported internal studies, a concept for a combined PC and NG fuel lance was developed and is presented here. The combined fuel lance integrates the coal dispersing bluff body effect reported by Uchiyama et al.¹⁰⁾ with the radial NG nozzles described by Harrison and Drebert.^11,12) The design objectives for this combined fuel lance were to simplify lance configuration, reducing the need for two lances to one, and to control NG mixing and combustion to minimize impingement on the tuyere wall. This paper presents the combined-lance design and its predicted performance and compares it against two configurations using separate PC and NG lances.

2. Model Description

2.1. Model Overview

The calculations were performed using the software platform ANSYS-CFX^®. The gas flow field is described by a set of 3-D, steady state, Reynolds averaged, Navier-Stokes equations, closed by the standard κ-ε turbulence model. Mass fractions for several gas species are solved. Particles of pulverized coal are modeled by Lagrangian tracking in which turbulent dispersion is included and full coupling of mass, momentum, and energy of particles with the gas phase is implemented. The Discrete Transfer radiation model is used with sixteen rays and a gas composition-dependent absorption coefficient. Radiant exchange is included in the coal particle energy balance.

The model accounts for two heterogeneous coal reactions. Devolatilization is modelled according to an Arrhenius reaction rate with rate constant given by:   

$$k_{Devol}=(20\mathrm{\hspace{0.17em} }000\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$s$}\right.)e^{-\hspace{0.17em}\hspace{0.17em}\frac{5\mathrm{\hspace{0.17em} }000\hspace{0.17em}K}{T_{Particle}}}$$(1)

where the pre-exponential and the activation energy are derived from the paper by Badzioch and Hawksley¹⁵⁾ and the rate is zero below an onset temperature of 773 K. The char oxidation rate, in which C+½O₂→CO, is determined by a combination of O₂ diffusion to the particle surface and a chemical Arrhenius rate with rate constant given by:   

$$k_{Char}=\left(0.09962\raisebox{1ex}{$kg$}\!\left/ \!\raisebox{-1ex}{$m^{2}s\cdot Pa$}\right.\right)\hspace{0.17em}{e}^{-\hspace{0.17em}\hspace{0.17em}\frac{6\mathrm{\hspace{0.17em} }831\hspace{0.17em}K}{T_{Particle}}}$$(2)

where the pre-exponential and the activation energy are derived from the paper by Lockwood et al.¹⁶⁾ and the rate is zero below an onset temperature of 773 K. The devolatilization and char oxidation parameters are the same as those used in the validation study that is described in Section 3 of this paper.

Gas-phase chemical reactions are accounted for using the slower of the mixing-limited and chemical kinetics-limited rates. For mixing-limited reactions, the Eddy Dissipation Model (EDM) is used, with the rate given by:   

$$R_{EDM}=A_{EDM}\left(\frac{\epsilon }{\kappa }\right)min\left([\text{fuel}],\frac{[\text{oxidant}]}{C_{Stoich}}\right)$$(3)

For chemical kinetics-limited reactions, the finite rate chemistry (FRC) model is used, with the rate given by:   

$$R_{FRC}=A_{FRC}{T}^b{e}^{\left(\frac{-E_a}{\Re T}\right)}{\left[\text{fuel}\right]}^c{\left[\text{oxidant}\right]}^d$$(4)

In the gas phase, there is one reaction accounting for the partial oxidation of coal volatiles, where volatiles + 0.36O₂ → 0.4CO + 0.56H₂O. This reaction is assumed to be controlled by the rate of turbulent mixing and the EDM model is used with A_EDM = 1.5. Methane oxidation is assumed to occur via the four reactions:   

$$C{H}_4+½O_2\to CO+2H_2,$$

  

$$C{H}_4+H_{2}O\to CO+3H_2,$$

  

$$H_2+½O_2\to H_{2}O,\mathrm{a}\mathrm{n}\mathrm{d}$$

  

$$CO+H_{2}O\leftrightarrow C{O}_2+H_2.$$

The rate is controlled by the slower of the EDM and FRC rates, where A_EDM = 4.0 while A_FRC, E_a, b, c, and d are from the paper by Jones and Lindstedt.¹⁷⁾

2.2. Coal Properties

As reported by Chui et al.,⁶⁾ it is expected that volatile yield under blast furnace tuyere and raceway conditions will be higher than in standardised proximate analysis tests due to the much higher heating rate. To account for this in the present study, a yield-adjusted coal composition of 55.6% volatile matter, 39.2% char, and 5.2% ash by mass was used as input to the model. The devolatilization and char reactions described by the rates in Eqs. (1) and (2) can proceed in parallel (i.e., they are not constrained to proceed sequentially), but the evaporation process is not modeled. In practice, the moisture content is about 2% for PC injected into the blast furnace. The volatile matter is assumed to have the physical properties of CH₄ for modeling purposes. The coal particle size distribution is based on measured data and is provided in Fig. 1. This distribution was implemented by tracking twenty-eight distinct particle sizes, aggregated into nine groups for statistics. A total of 28000 particles were tracked.

Fig. 1.

Coal particle size distribution used for the model.

2.3. Blowpipe and Tuyere

The blowpipe and tuyere geometries are as described in Harrison and Drebert.^11,12) The inner surface of the tuyere is lined so it was assigned a surface temperature of 900°C and an emissivity of 0.95. The blowpipe inner surface is treated as adiabatic and was also assigned an emissivity of 0.95. The blast air has a temperature of 1100°C and flow rate of 2.99 kg/s. Enriched with oxygen, it consists of 28.5% O₂ and 3% H₂O by volume, with the balance being N₂. The outlet at the end of the tuyere nozzle was assigned an absolute pressure of 350 kPa and a radiation temperature (i.e., a hot black surface representing radiation from the raceway) of 1843°C.

2.4. Lance Configuration

The separate and combined-lance configurations are shown in Fig. 2. The three cases referred to in this paper are: Case 1, a separate-lance configuration in which the annular swirling cooling flow is disabled; Case 2, a separate-lance configuration in which a low swirl is applied to the coal lance via the annular cooling air; and Case 3, a combined lance configuration where both coal and natural gas are injected via a single lance. The natural gas lance geometry for Cases 1 and 2 and the natural gas injection geometry for Case 3 are as described in Harrison and Drebert.^11,12)

Fig. 2.

Cut-away view of the model domain: blowpipe, tuyere, and lances. Red represents the blast air inlet with flow direction indicated by the vectors on the left images. Orange represents the cooling/swirl flow inlet. Blue is the pulverized coal inlet and green is the natural gas inlet. (a) Cases 1 and 2 use the separate-lance design with simple pipe natural gas lance and a larger, downstream pulverized coal lance with annular cooling air flow. (b) Case 3 uses the combined-lance design with coal injection in the center and an annular flow of natural gas that exits through radial holes near the end of the lance.

2.4.1. Separate Lances

The PC flow is modeled through part of the PC lance before it enters the tuyere as shown in Fig. 2(a). Lance surfaces that are exposed to the coal/air flow were assigned temperatures of 38°C, while lance surfaces that are exposed to the blast air were assigned temperatures of 1038°C. Both internal and external lance surfaces were assigned an emissivity of 0.90. The natural gas lance is modeled as a solid which participates in heat transfer between the blast air and natural gas flows. It was assigned an emissivity of 0.90 and a temperature-dependent conductivity was used, with a nominal value of 14.2 W/(m·K) at 100°C.

The natural gas has a simplified composition of 97.7% CH₄ and 0.685% CO₂ by volume (balance N₂) and enters the model domain at a temperature of 38°C with a flow rate of 0.164 kg/s. The pulverized coal carrier is air with a temperature of 38°C and flow rate of 0.0689 kg/s. The coal has a temperature of 38°C and a flow rate of 0.296 kg/s.

The annular cooling (swirl) air flow in the coal lance was varied. In Case 1, it was disabled to emulate the thick-walled, bluff body lance described by Uchiyama et al.¹⁰⁾ and to assess its effect on the flow dynamics. In Case 2, a low amount of swirl was applied with a flow rate of 0.0528 kg/s and a temperature of 371°C and it is introduced to the model at the face of the lance. The velocity profile of the swirl was determined from CFD simulations of the annular flow inside the lance in a previous study. The swirl vane angle is 9 degrees.

2.4.2. Combined-Lance

The material properties of the combined PC/NG injection lance are the same as those of the NG lance in the separate-lance configuration. The lance participates in heat transfer between the flows of blast air, natural gas, and coal/air. The coal/air flow rates and properties are the same as those of the PC lance in the separate-lance configuration. The temperature, composition, and flow rate of the natural gas are the same as those of the NG lance in the separate-lance configuration. In this configuration, the annular natural gas flow provides cooling for the lance. By moving to a single, combined-lance, there is more flexibility in lance positioning so the lance has been relocated inwards and upwards. This places the lance tip center on the tuyere centerline, and it enters the blowpipe at the same angles as the PC lance in the separate-lance cases.

3. Model Validation

The modeling strategies described here have been used in the past on similar studies of commercial blast furnaces, so confidence has been developed over time in the overall approach. Validation work was carried out and documented in the paper by Chui et al.⁶⁾ That validation work is briefly described here.

Natural Resources Canada/CanmetENERGY developed a pilot plant facility that simulates blast furnace blowpipe-tuyere conditions. Its main component is a cylindrical reactor (1 m in length, 0.03 m internal diameter) consisting of an insulated, refractory-lined inner core and a steel shell. Natural gas and coal were injected into this cylindrical reactor, and sampling ports, positioned 0.65 m downstream of the coal injection point, sampled O₂, CO₂, and CO.

The CFD model used by Chui et al.⁶⁾ was similar to the model used in this work, except for the treatment of radiation and the gaseous combustion model, which used a combination of the flamelet formulations for premixed and non-premixed combustion. According to the CO₂ and CO gas measurements, the CFD model predicted combustion reasonably well, only under-predicting the level of CO₂ and CO by 10–15%. The gaseous combustion model in the present work predicts a more rapid onset of combustion compared to the model used by Chui et al.,⁶⁾ so it would be expected to provide earlier heating of the coal, thereby producing CO₂ and CO predictions that are closer to the measurements.

In addition to the pilot plant validation, the natural gas injection concept involving radial holes has been successfully implemented in a commercial steel plant operating in Canada. The combined natural gas and coal injection lance has not been tested in a commercial plant.

4. Results and Discussion

This work is the most recent in a progression of blast furnace injection modeling studies that have been carried out over the past 12 years at CanmetENERGY. Figure 3 shows the evolution of NG and coal conversion and how they relate to the predicted tuyere outlet temperature. Although NG injection rate, other operating conditions, and lance configuration have all varied over the course of this work, there does appear to be a general positive correlation between tuyere outlet temperature and coal conversion.

Fig. 3.

Key indicators predicted by the CFD model versus the year of the study. Green: CH₄ conversion is the percentage of injected methane that undergoes reaction. Blue: Coal conversion is the percentage of coal combustibles that undergo reaction, either devolatilization or char combustion. Red: mass-flow averaged tuyere outlet temperature.

It was discussed by Uchiyama et al.¹⁰⁾ and Majeski et al.¹⁴⁾ that a bluff body effect by the coal lance on the blast air is a simple and effective method for dispersing pulverized coal, especially for the smaller particles. This effect is illustrated in Fig. 4, in which the smaller particles are increasingly affected by the wake region downstream of the lance. The superiority of the bluff body effect (Case 1) was established based on comparison to a low-swirl case (Case 2), so it is possible that a higher-swirl case, which is not considered here, would have provided comparable benefit. However, the bluff-body approach simplifies lance design and does not require additional gas injection for swirling, which incurs additional operational costs and can cause undesired cooling. Based on this, the bluff body concept was chosen as the starting point for an integrated combined-fuel lance concept.

Fig. 4.

Particle trajectories for different particle sizes in Cases 1 and 2. Fifty trajectories for each size are shown. Yellow: 3.0, 3.6 μm. Blue: 58, 68 μm. Red: 275, 325 μm.

As discussed in Section 2.4, the results for three designs are presented. Case 1 is a separate-lance configuration that employs a bluff-body effect by the PC lance on the blast air, Case 2 is a separate-lance configuration that applies a low swirl to the annular cooling air in the coal lance, and Case 3 is the combined-lance configuration that employs the bluff body effect and radial nozzles for the NG.

Figure 5 shows the results for the partial combustion of coal. In the few milliseconds available in the tuyere, the coal partially devolatilizes but little char combustion occurs. As reported by Majeski et al.,¹⁴⁾ the separate-lance configuration without swirl (Case 1), which employs the bluff body effect, has a higher level of coal reaction than the separate-lance with swirl (Case 2). The combined-lance concept that uses the bluff-body effect and radial lancing of the NG (Case 3) is superior to both separate-lance designs in devolatilization of larger coal particles. The amount of char combustion in the combined-lance design (Case 3) is less than that of the dual-lance design without swirl (Case 1) and may be limited by oxygen availability. However, the significant increase in devolatilization is of sufficient value that the combined-lance design is considered to have overall better predicted performance in terms of coal reaction.

Fig. 5.

Coal flow rate versus particle diameter, showing the amount of devolatilization and char oxidation, for Case 1: left bar; Case 2: middle bar; and Case 3: right bar.

Figure 6 shows methane (Fig. 6(a)) and coal volatile (Fig. 6(b)) concentrations on vertical planes across the tuyere nozzle, as well as the extent of PC dispersion at each plane. There is more methane reaction in the combined-lance design because of the improved mixing with the blast air, as it is injected through multiple radial holes rather than through the straight pipe found in the separate-lance configurations. The level of methane reaction and the enveloping of the PC by hot combustion products lead to the increased coal devolatilization. For the separate-lance configurations, the devolatilization of coal is higher in the bluff-body approach (Case 1) compared to the low-swirl approach (Case 2), as noted above. It can also be observed in Fig. 6 that the PC stream no longer interacts with the tuyere wall in the combined-lance case (Case 3), whereas it does interact towards the tuyere bottom and outlet in the separate-lance cases (Cases 1 and 2). This is likely due to the new lance position and is a more desirable operating condition as it would reduce the possibility of slag build-up or erosion of the tuyere liner and nose.

Fig. 6.

The volume fractions (wet) of (a) natural gas methane, and (b) coal volatiles, on vertical cross-sections along the tuyere for the three cases. The white outline on each plane represents a PC concentration of 1 g/m³, indicating the extent of coal particle dispersion.

Figure 7 shows the availability of oxygen on vertical planes along the tuyere nozzle (Fig. 7(a)) and temperature on a vertical plane on the axis of the blowpipe (Fig. 7(b)). The natural gas rapidly consumes available oxygen where the two are mixed. Where PC and oxygen overlap, oxygen levels tend to stay higher longer indicating slower reaction with the coal and its volatiles, consistent with the heating required to start coal-related reactions. As noted earlier, in the combined-lance configuration (Case 3), the methane that surrounds the coal consumes the available oxygen, leaving little oxygen for volatiles and char combustion. For the separate-lance configurations, the superiority of the bluff-body approach for coal dispersion is reflected in lower oxygen concentration and higher temperature in the region where the coal particles are located for Case 1 compared to Case 2. In the separate-lance configurations, high temperatures are found at the top of the tuyere where NG is burning and at the bottom where hot combustion products have been advected by a swirl in the blast air flow induced by the lances. In the combined-lance configuration, high temperatures tend to be more evenly distributed radially in the tuyere, but are found to interact with the tuyere wall at the bottom near the outlet. This result suggests that the location of the flame with respect to the tuyere could be improved by further design iterations.

Fig. 7.

(a) The volume fraction (wet) of oxygen on vertical cross-sections along the tuyere for the three cases and (b) the temperature on a vertical plane on the axis of the blowpipe. The white outline on each plane represents a PC concentration of 1 g/m³, indicating the extent of coal particle dispersion.

The concentrations of carbon monoxide and hydrogen, gases associated with partial (i.e., incomplete) combustion, are shown in Fig. 8. Partial combustion of natural gas occurs rapidly after mixing with the blast air, producing both carbon monoxide and hydrogen. Partial combustion of the coal volatiles also occurs, producing noticeable quantities of carbon monoxide within the area of PC dispersion.

Fig. 8.

The volume fractions (wet) of (a) carbon monoxide and (b) hydrogen on vertical cross-sections along the tuyere for the three cases. The white outline on each plane represents a PC concentration of 1 g/m³, indicating the extent of coal particle dispersion.

The total heat transfer to the inside surface of the tuyere is predicted to be: 58.0 kW for Case 1, 52.9 kW for Case 2, and 59.1 kW for Case 3. It is predicted that the combined-lance configuration does not significantly increase the total heat load on the tuyere. The heat flux to the inside surface of the tuyere is shown in Fig. 9. There is a baseline heat flux at the tuyere exit of approximately 600 kW/m² (green in colour) caused by radiation from the raceway. In the separate-lance configurations, the highest heat fluxes are located at the top of the tuyere because of the proximity of natural gas combustion, although there are also locally high heat fluxes at the bottom where hot combustion products have been transported close to the wall, as was shown in Fig. 7(b) (Cases 1 and 2). The highest heat flux for the combined-lance configuration is at the bottom of the tuyere where high temperatures were observed near the wall in Fig. 7(b) (Case 3).

Fig. 9.

Heat flux on the tuyere nozzle inside surface. Positive is for heat leaving the fluid phase and going into the tuyere wall.

5. Conclusions

A combined-fuel lance configuration for injecting both pulverized coal and natural gas into blast furnace tuyeres was presented, along with its expected performance. This combined-lance design was compared to two separate-lance alternatives, one using a bluff-body effect to disperse PC and the other using an auxiliary swirling flow. The combined-lance was shown to provide effective heating of the coal particles by natural gas combustion, which resulted in increased coal devolatilization compared to the separate-lance configurations. One drawback relative to the separate-lance, bluff-body configuration was reduced char combustion. However, the combined lance is still considered an improvement because of its enhanced coal devolatilization. Although the details of PC and/or NG injection will vary from furnace to furnace, two key design concepts should be generally applicable. The first is the effectiveness of the bluff body effect by the coal lance on the blast air for dispersing coal particles to initiate reaction. The second is the use of an annular flow of natural gas for lance cooling, with the natural gas exiting the lance radially into the blast air to enhance natural gas combustion.

Acknowledgements

This work was supported by the Government of Canada’s Program of Energy Research and Development. The authors would like to thank Robert Wargo from U. S. Steel Research and Technology Center for reviewing this manuscript. The authors would like to thank United States Steel Corporation for permission to publish this manuscript.

U. S. Steel Disclaimer

The material in this paper is intended for general information only. Any use of this material in relation to any specific application should be based on independent examination and verification of its unrestricted availability for such use and a determination of suitability for the application by professionally qualified personnel. No license under any patents or other proprietary interests is implied by the publication of this paper. Those making use of or relying upon the material assume all risks and liability arising from such use or reliance.

Nomenclature

A reaction rate parameter

C_stoich stoichiometric coefficient

E_a activation energy

k reaction rate constant

R reaction rate

T temperature

ε turbulence kinetic energy dissipation rate

κ turbulence kinetic energy

ℛ universal gas constant

[fuel] concentration (e.g., of fuel)

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