A BURNER PIPE ASSEMBLY FOR A MULTIFUEL BURNER OF A ROTARY KILN SYSTEM

Abstract

 The present application describes a burner pipe assembly having a particular design adapted to implement pulsed combustion in an efficient way and allowing to improve the efficiency of burning fluid fuels in rotary kiln systems. In fact, by implementing pulsed combustion, the burner pipe assembly of the present application allows for more precise control over fuel flow and flame profile, resulting in greater energy efficiency and more complete combustion. The assembly comprises an air intake chamber (1) formed by at least one radial jet nozzle (4), a diffuser (6), a combustion chamber (2) having at least one fluid fuel jet nozzle (5), an exhaustion duct (3) and a valve module, adapted to control de admission of air into the air intake chamber (1) and the admission of fluid fuel into the combustion chamber (2) according to a specific admission frequency.

Description

FIELD OF THE APPLICATION

[0001] The present application is enclosed in the field of combustion equipment, and more particularly relates to burner assemblies optimized for burning hydrogen or natural gas in combustion chambers of rotary kiln systems adapted for the production of clinker.

PRIOR ART

[0002] In recent years, there has been a growing interest in using hydrogen or natural gas as a fuel in cement kilns to reduce the sector's carbon emissions. However, the properties of such fluids and the respective heat transfer mechanisms in combustion systems are different from traditional fuels, resulting in different flame characteristics and generated heat.

[0003] In this context, pulsed combustion emerges as an alternative that, in theoretical terms, would allow achieving several advantages, including high combustion efficiency combined with a reduction in pollutant emissions such as nitrogen oxide and carbon monoxide.

[0004] However, the modelling of such type of process is quite complex because it involves multiple dynamic interactions, related to transient turbulent flows, acoustic resonance waves, transient heat transfers, and various chemical reactions. This complexity has hindered the design of pulsed combustion systems, resulting in technical configurations that prove to be insufficient to allow state-of-the-art systems to achieve the theoretical advantages underlying the concept of pulsed combustion.

[0005] The present solution intended to innovatively overcome such issues.

SUMMARY OF THE APPLICATION

[0006] The present application describes a burner pipe assembly having a particular design adapted to implement pulsed combustion in an efficient way and allowing to improve the efficiency of burning fluid fuels, such as hydrogen or natural gas, in rotary kiln systems. In fact, by implementing pulsed combustion, the burner pipe assembly of the present application allows for more precise control over fuel flow and flame profile, resulting in greater energy efficiency and more complete combustion.

[0007] Additionally, the burner pipe assembly of the present application also aims to reduce harmful emissions, such as nitrogen oxide and carbon monoxide.

[0008] In order for these objectives to be achieved, the burner pipe assembly comprises a particular design, formed by the following elements:

• an air intake chamber comprising at least one radial air jet nozzle, arranged perpendicularly to the axis of the burner pipe and operable to control de admission of air into the chamber;
• a diffusor, interconnecting the air intake chamber and a combustion chamber; the diffuser comprising a diffuser wall disposed in a transversal plane in relation to the axis of the burner pipe and being provided with a plurality of bores adapted to diffuse the air in the air intake chamber to the combustion chamber;
• a combustion chamber comprising at least one fluid fuel jet nozzle arranged to inject fluid fuel into the combustion chamber in an angle between 30° to 90° in relation to the axis of the burner pipe;
• an exhaustion duct adapted to exhaust combustion gases from the combustion chamber.

[0009] In addition, a valve module is used, being adapted to control the operation of the air jet and of the fluid fuel jet nozzles, in such a way as to allow the entry of air into the air intake chamber and the entry of fluid fuel through the fluid fuel jet nozzles (5) to the combustion chamber (2), according to a specific admission frequency.

[0010] It is also an object of the present application a multifuel burner assembly for a rotary kiln system, comprising the burner pipe assembly also described in the present application.

[0011] Finally, as another object of the present application, a rotary kiln system is described, being comprised by the multifuel burner assembly and the burner pipe assembly also described in the present application.

DESCRIPTION OF FIGURES

[0012] 

Figure 1 - representation of the burner pipe assembly according to one embodiment described in the present application. The numerical references represent:

1 - air intake chamber;

2 - combustion chamber;

3 - exhaustion duct;

4 - radial air jet nozzles;

5 - fluid fuel jet nozzles;

6 - diffuser;

Figure 2 - representation of an embodiment of the rotary kiln system described in the present application, wherein the numerical references represent:

7 - burner pipe assembly;

8 - multifuel burner assembly;

9 - rotary kiln system.

DETAILED DESCRIPTION

[0013] The more general and advantageous configurations of the present application are described in the Summary of the application. Such configurations are detailed below in accordance with other advantageous and/or preferred embodiments of implementation.

[0014] In a preferred object of the present application, it is described a burner pipe assembly (7) for a multifuel burner assembly (8) of a rotary kiln system (9).

[0015] The burner pipe assembly (7) according to the present application uses pulsed combustion technology, in which the fluid fuel may be injected into the combustion chamber (2) in pulses. This allows for more precise control over the flame characteristics and therefore an optimization of the sintering process.

[0016] The burner pipe assembly (7) is also designed to achieve an adequate mixture between the secondary air, which comes from cooling, the primary air, and the existing combustion in the multifuel burner (8).

[0017] As a consequence of its design, the burner pipe assembly (7) of the present application provides a reduction in the consumption of fossil fuels, facilitating the use of alternative or lower quality fuels. It also contributes to cleaner emissions by reducing levels of nitrogen oxide and carbon monoxide. In addition, adaptability to different energy sources and increased operational safety are other benefits of the proposed burner assembly (7).

[0018] The burner pipe assembly (7) is designed to be capable of reaching temperatures up to 2008° Celsius, making it suitable for use in clinker production processes that require high temperatures.

[0019] The burner pipe assembly (7), as well as its embodiments, will be described below with the help of Figure 1.

[0020] The burner pipe assembly (7) is comprised by an air intake chamber (1) comprising at least one radial air jet nozzle (4), arranged perpendicularly to the axis of the burner pipe (7) and operable to control de admission of air into the chamber (1).

[0021] In one embodiment of the burner pipe assembly (7), the air intake chamber (1) may comprise between 2 to 5 radial air jet nozzles (4). Preferably, the air intake chamber (1) has 3 radial air jet nozzles (4). This number allows obtaining an adequate arrangement of nozzles (4), which guarantees a well-distributed air flow through the diffuser (6), in order to maximize combustion efficiency.

[0022] In another embodiment of the burner pipe assembly (7), the radial air jet nozzles (4) are structurally adapted to provide an airflow in the air intake chamber (1) between 10 to 120 Nm³/h at a pressure between 50 to 300 mbar, preferably an airflow in the air intake chamber (1) of 21,9 Nm³/h at a pressure of 240 mbar.

[0023] The burner pipe assembly (7) is further comprised by a diffusor (6), for interconnecting the air intake chamber (1) and a combustion chamber (2). The diffuser (6) comprises a diffuser wall disposed in a transversal plane in relation to the axis of the burner pipe (7) and being provided with a plurality of bores adapted to diffuse the air in the air intake chamber (1) to the combustion chamber (2).

[0024] In one embodiment of the burner pipe assembly (7), the diffuser's wall comprises between 10 to 20 bores, through which the air injected into the air intake chamber (1) is diffused to the combustion chamber (2). Each bore of the diffuser's wall may have a diameter between 6 to 15mm. Such configuration for the diffuser's wall may be explained in the following way: the number of bores allows to create a structural element that forces the air to pass along the entire diffuser (6), distributing the air flow in an efficient manner. In turn, the diameter of each bore, which also depends on their number, is determined in order to force the air to pass through the diffuser (6) at a specific velocity determined to improve combustion. Consequently, by having a diffuser's wall comprising between 10 to 20 bores and each bore having a diameter ranging from 6 to 15 mm, it is achieved a proper structural configuration that allows for a better distribution of the air through the diffuser (6), which improves the combustion.

[0025] The burner pipe assembly (7) further comprises a combustion chamber (2). Said combustion chamber (2) comprises at least one fluid fuel jet nozzle (5) arranged to inject fluid fuel into the combustion chamber (2) in an angle between 30° to 90° in relation to the axis of the burner pipe (7).

[0026] In one embodiment of the burner pipe assembly (7), the combustion chamber (2) comprises between 2 to 4 fluid fuel jet nozzles (5). Preferably, the combustion chamber (2) comprises 2 fluid fuel jet nozzles (5), which guarantees a good distribution of the fluid fuel, such as hydrogen or natural gas, inside the combustion chamber (2). In fact, the use of 2 nozzles (5) therefore makes it possible to optimize the mixture between air and fuel, without greatly increasing the manufacturing costs that would be associated with the introduction of more nozzles (5).

[0027] Additionally, each fluid fuel jet nozzle (5) is arranged to inject fluid fuel into the combustion chamber (2) in an angle of 45° in relation to the axial direction of the pipe (7). The configuration of this angle improves combustion performance, as the fuel enters the combustion chamber (2) in line with the flow direction, preventing reverse flow (for example, air entering the nozzle (5)).

[0028] In another embodiment of the burner pipe assembly (7), the fluid fuel jet nozzles (5) are structurally adapted to provide a fluid fuel flow in the combustion chamber (2) between 5 to 100 Nm3/h at a pressure between 200 to 600 mbar, preferably a fluid fuel flow in the combustion chamber (2) of 10 Nm3/h at a pressure of 450 mbar.

[0029] In one embodiment of the burner pipe assembly (7), the fluid fuel is hydrogen gas and the fluid fuel jet nozzles (5) are further adapted to connect to a hydrogen gas source. Alternatively, the fluid fuel is natural gas and the fluid fuel jet nozzles (5) are further adapted to connect to a natural gas source.

[0030] The burner pipe assembly (7) further comprises an exhaustion duct (3) adapted to exhaust combustion gases from the combustion chamber (2).

[0031] The burner pipe assembly (7) further comprises a valve module adapted to control the operation of the air and fluid fuel jet nozzles (4, 5), in such a way as to allow the entry of air into the air intake chamber (1) and the entry of fluid fuel through the fluid fuel jet nozzles (5) to the combustion chamber (2), according to a specific admission frequency.

[0032] In one embodiment, the air and fluid fuel admission frequency is between 50 to 200 Hz, preferably 100Hz. This admission frequency allows to achieve an optimized flame profile.

[0033] In another object of the present application, it is described a multifuel burner assembly (8) for rotary kiln systems, that is comprised by a burner pipe assembly (7) as previously described.

[0034] More particularly, and with the aid of Figure 2, the burner pipe assembly (7) is located inside the multifuel burner assembly (8) and it is arranged below a horizontal centre plane of said multifuel burner assembly (8). Even more particularly, the burner pipe assembly (7) is arranged so as to make an angle between +1° and +10° with respect to the axis of the multifuel burner assembly (8), preferably an angle of +4° with respect to the axis of the multifuel burner assembly (8). The lateral view of the rotary kiln system (9) highlights the placement of the dedicated burner pipe assembly (7).

[0035] The position of the burner pipe assembly in relation with the multifuel burner assembly (8) and its angled-up arrangement allows the jet pulses of fluid fuel to capture unburnt particles falling from the flame jet of the multifuel burner assembly (8) and reignite them, thus improving the overall efficiency of the rotary kiln system (9) and reducing contamination of the clinker product with unburnt solid fuels.

[0036] It is also an object of the present application a rotary kiln system (9) comprising the multifuel burner assembly (8).

[0037] As a result of the integration between the burner pipe assembly (7) and the multifuel burner assembly (8) described in the present application, the efficiency of combustion of solid fuels of the rotary kiln system is improved.

EMBODIMENTS

[0038] In a preferred embodiment of the burner pipe assembly (7), it is comprised by:

• an air intake chamber (1) comprised by 3 radial air jet nozzles (4), each one being structurally adapted to provide an airflow in the air intake chamber (1) of 21,9 Nm³/h at a pressure of 240 mbar.
• the diffuser's wall comprising between 10 to 20 bores, each bore having a diameter between 6 to 15mm.
• a combustion chamber (2) comprised by 2 fluid fuel jet nozzle (5), each nozzle (5) being arranged to inject fluid fuel into the combustion chamber (2) in an angle of 45° in relation to the axial direction of the pipe, and being structurally adapted to provide a fluid fuel flow in the combustion chamber (2) of 10 Nm³/h at a pressure of 450 mbar.
• the admission frequency of the valve module is 100 Hz.

Experimental results of this design:

[0039] It is compared the operation of the rotary kiln system (9) with and without the burner pipe assembly (7).

[0040] The example assumes the rotary kiln system (9) operates with an energy mix of 33% fossil fuel (Petroleum coke) and 67% alternative fuel (Fuel Derived from Waste), which translates into feed flows of 3.1 t/h and 7.2 t/h, respectively. Additionally, ventilation of 8300 Nm³/h of primary air in the burner pipe assembly (7), and 68000 Nm³/h of secondary air, coming from the clinker cooler and at a temperature of 870 °C, is considered. The burner pipe assembly (7) is also placed below the main furnace of the multifuel burner assembly (8) at an angle of 10° upwards.

Example 1:

[0041] Example 1 considers that the burner pipe assembly (7) operates with 10 Nm³/h of hydrogen at 450 mbar pressure and 22 Nm³/h of air at 240 mbar pressure, whose combustion generates a jet of hot gases at a temperature of approximately 2100 °C.

[0042] By comparing the phenomenon of combustion of solid fuels with and without the operation of the burner pipe assembly (7), it was possible to observe through simulations an increase of 7% in the efficiency of the combustion of the overall process, as well as a slight increase in the levels of NOx emitted, from approximately 4300 ppm to 4600 ppm with the addition of hydrogen.

Example 2:

[0043] Example 2 considers that the burner pipe assembly (7) operates with 60 Nm³/h of hydrogen at 450 mbar pressure and 148 Nm³/h of air at 240 mbar pressure, whose combustion generates a jet of hot gases at a temperature of approximately 2100 °C.

[0044] By comparing the phenomenon of combustion of solid fuels with and without the operation of the burner pipe assembly (7), it was possible to observe, through simulations, an increase of 21% in the efficiency of the combustion of the overall process, as well as an increase in the levels of NOx emitted, from approximately 4300 ppm to 5400 ppm with the addition of hydrogen.

[0045] As a conclusion, the burner pipe assembly (7) with pulsed combustion technology, as described, offers an efficient and environmentally friendly alternative to clinker production in rotary kiln systems (9), which is very significant for the cement industry, helping to achieve more sustainable production practices.

[0046] As will be clear to one skilled in the art, the present invention should not be limited to the embodiments described herein, and a number of changes are possible which remain within the scope of the present invention.

[0047] Of course, the preferred embodiments shown above are combinable, in the different possible forms, being herein avoided the repetition all such combinations.

Claims

1. A burner pipe assembly (7) for a multi-fuel burner assembly (8) of a rotary kiln system (9), comprising:

- an air intake chamber (1) comprising at least one radial air jet nozzle (4), arranged perpendicularly to the axis of the burner pipe assembly (7) and operable to control de admission of air into the chamber (1);

- a diffusor (6), interconnecting the air intake chamber (1) and a combustion chamber (2); the diffuser comprising a diffuser wall disposed in a transversal plane in relation to the axis of the burner pipe assembly (7) and being provided with a plurality of bores adapted to diffuse the air in the air intake chamber (1) to the combustion chamber (2); and

- a combustion chamber (2) comprising at least one fluid fuel jet nozzle (5) arranged to inject fluid fuel into the combustion chamber (2) in an angle between 30° to 90° in relation to the axis of the burner pipe assembly (7);

- an exhaustion duct (3) adapted to exhaust combustion gases from the combustion chamber (2);

the assembly further comprises:
a valve module adapted to control the operation of the air and fluid fuel jet nozzles (4, 5), in such a way as to allow the entry of air into the air intake chamber (1) and fuel through the fluid fuel jet nozzles (5) to the combustion chamber (2), according to a specific admission frequency.

2. Assembly (7) according to claim 1, wherein the admission frequency is between 50 to 200 Hz.

3. Assembly (7) according to claim 2, wherein the admission frequency is 100 Hz.

4. Assembly (7) according to any of the previous claims, wherein the air intake chamber (1) comprises between 2 to 5 radial air jet nozzles (4); preferably, the air intake chamber (1) comprises 3 radial air jet nozzles (4).

5. Assembly (7) according to claim 4, wherein the radial air jet nozzles (4) are structurally adapted to provide an airflow in the air intake chamber (1) between 10 to 120 Nm3/h at a pressure between 50 to 300 mbar; preferably an airflow in the air intake chamber (1) of 21,9 Nm3/h at a pressure of 240 mbar.

6. Assembly (7) according to any of the previous claims, wherein the diffuser's wall comprises between 10 to 20 bores, through which the air injected into the air intake chamber (1) is diffused to the combustion chamber (2); each bore having a diameter between 6 to 15mm.

7. Assembly (7) according to any of the previous claims, wherein the combustion chamber (2) comprises between 2 to 4 fluid fuel jet nozzles (5); preferably, the combustion chamber (2) comprises 2 fluid fuel jet nozzles (5).

8. Assembly (7) according to claim 7, wherein each fluid fuel jet nozzle (5) is arranged to inject fluid fuel into the combustion chamber (2) in an angle of 45° in relation to the axial direction of the burner pipe assembly (7).

9. Assembly (7) according to claims 7 or 8, wherein the fluid fuel jet nozzles (5) are structurally adapted to provide a fluid fuel flow in the combustion chamber (2) between 5 to 100 Nm3/h at a pressure between 200 to 600 mbar; preferably a fluid fuel flow in the combustion chamber (2) of 10 Nm3/h at a pressure of 450 mbar.

10. Assembly (7) according to any of the previous claims, wherein the fluid fuel is hydrogen gas; the fluid fuel jet nozzles (5) being further adapted to connect to a hydrogen gas source.

11. Assembly (7) according to any of the previous claims 1 to 9, wherein the fluid fuel is natural gas; the fluid fuel jet nozzles (5) being further adapted to connect to a natural gas source.

12. A multifuel burner assembly (8) for a rotary kiln system (9), comprising a burner pipe assembly (7) according to any of the previous claims.

13. Multifuel burner assembly (8) according to claim 12, wherein the burner pipe assembly (7) is located inside the multifuel burner assembly (8) and it is arranged below a horizontal centre plane of said multifuel burner assembly (8).

14. Multifuel burner assembly (8) according to claim 13, wherein the burner pipe assembly (7) is arranged so as to make an angle between +1° and +10° with respect to the axis of the multifuel burner assembly (8); preferably an angle of +4° with respect to the axis of the multifuel burner assembly (8).

15. A rotary kiln system (9) comprising a multi-fuel burner (8) according to claims 12 to 14.

Drawing