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KR-20260066502-A - MILD COMBUSTION SYSTEM AND MILD COMBUSTION METHOD

KR20260066502AKR 20260066502 AKR20260066502 AKR 20260066502AKR-20260066502-A

Abstract

The present application relates to a mild combustion system and a mild combustion method. According to the present application, a mild combustion system and a mild combustion method can be provided that improve combustion operation performance by reducing the generation of moisture in the exhaust gas during mild combustion.

Inventors

  • 정용호
  • 박준영
  • 김희진

Assignees

  • 현대제철 주식회사

Dates

Publication Date
20260512
Application Date
20241104

Claims (14)

  1. Oxidizing agent supply device for supplying an oxidizing agent; A separation membrane that selectively captures carbon dioxide gas from external flue gas; An oxidizing agent dilution device that produces a diluted oxidizing agent by mixing the oxidizing agent supplied from the above oxidizing agent supply device and the residual gas not captured by the above separation membrane; Fuel supply device for supplying fuel; A main combustor in which fuel supplied from the above fuel supply device is combusted by a diluted oxidizer produced in the above oxidizer dilution device; and A mild combustion system comprising a heat exchanger that exchanges heat with the main exhaust gas discharged after combustion of a diluted oxidizer supplied to the main combustion unit.
  2. In Article 1, A mild combustion system further comprising a control unit that controls the oxygen concentration of the diluted oxidizer produced in the above-mentioned oxidizer dilution device to be greater than 0 vol% and less than or equal to 10 vol%.
  3. In Article 1, A mild combustion system in which the residual gas comprises nitrogen gas with a higher concentration than the oxidizer.
  4. In Article 1, The above oxidizer is air in a mild combustion system.
  5. In Article 1, The above fuel is hydrogen fuel, and The above hydrogen fuel is a mild combustion system with a self-ignition temperature of 500°C or higher and 640°C or lower.
  6. In Article 5, The above hydrogen fuel is combusted in a mild combustion system under the conditions of the following general formula 1: [General Formula 1] T in > T ig In the above general formula 1, T in is the atmosphere temperature (°C) inside the main combustor formed by the diluted oxidizer supplied to the main combustor, and T ig is the spontaneous ignition temperature (°C) of the hydrogen fuel.
  7. In Article 6, A mild combustion system in which the above hydrogen fuel further satisfies the conditions of the following general formula 2 during combustion: [General Formula 2] T F -T in < T ig In the above general formula 2, T F is the flame temperature (°C) generated by the combustion reaction of hydrogen fuel, T in is the atmosphere temperature (°C) inside the main combustor formed by the diluent oxidizer supplied to the main combustor, and T ig is the spontaneous ignition temperature (°C) of the hydrogen fuel.
  8. Oxidizing agent supply step of supplying an oxidizing agent through an oxidizing agent supply device; A separation step for selectively capturing carbon dioxide gas from external flue gas through a separation membrane; An oxidizing agent dilution step of preparing a diluted oxidizing agent by mixing the oxidizing agent supplied from the oxidizing agent supply device and the residual gas not captured by the separation membrane in an oxidizing agent dilution device; Fuel supply step of supplying fuel through a fuel supply device; A main combustion step in which fuel supplied from the above fuel supply device is combusted in a main combustor by a diluted oxidizer produced in the above oxidizer dilution device; and A mild combustion method comprising a heat exchange step of exchanging heat through a heat exchanger with the main flue gas discharged after combustion in the main combustion chamber, wherein the diluted oxidizing agent supplied to the main combustion chamber is heat-exchanged with the main flue gas discharged after combustion in the main combustion chamber.
  9. In Article 8, A mild combustion method further comprising a control step for controlling the oxygen concentration of a diluted oxidizer produced in the above-mentioned oxidizer dilution device to be greater than 0 vol% and less than or equal to 10 vol%.
  10. In Article 8, A mild combustion method in which the residual gas comprises nitrogen gas with a higher concentration than the oxidizer.
  11. In Article 8, The above oxidizer is air in a mild combustion method.
  12. In Article 8, The above fuel is hydrogen fuel, and The above hydrogen fuel is a mild combustion method having a self-ignition temperature of 500°C or higher and 640°C or lower.
  13. In Article 12, The above hydrogen fuel is combusted under the conditions of the following general formula 1 in a mild combustion method: [General Formula 1] T in > T ig In the above general formula 1, T in is the atmosphere temperature (°C) inside the main combustor formed by the diluted oxidizer supplied to the main combustor, and T ig is the spontaneous ignition temperature (°C) of the hydrogen fuel.
  14. In Article 13, A mild combustion method in which the above hydrogen fuel further satisfies the conditions of the following general formula 2 during combustion: [General Formula 2] T F -T in < T ig In the above general formula 2, T F is the flame temperature (°C) generated by the combustion reaction of hydrogen fuel, T in is the atmosphere temperature (°C) inside the main combustor formed by the diluent oxidizer supplied to the main combustor, and T ig is the spontaneous ignition temperature (°C) of the hydrogen fuel.

Description

Mild Combustion System and Mild Combustion Method This application relates to a mild combustion system and a mild combustion method. Radiant tube thermal systems are devices that heat the tube by allowing high-temperature combustion gases to flow through it via combustion, and indirectly heat the surrounding atmosphere through the radiant heat energy emitted from the high-temperature tube; they are widely utilized in many industrial sites. When combustion proceeds through a burner installed inside a radiator tube, localized overheating of the radiator tube is unavoidable due to the flame shape or the uneven flow of high-temperature combustion gases inside the tube. This leads to localized thermal stress concentration, which can cause cracks in the radiator tube or, in severe cases, perforations, which can increase the maintenance costs of the radiator tube thermal equipment. Mild (moderate or intense low-oxygen dilution) combustion is characterized by the combustion reaction occurring throughout the entire combustion chamber without localized high-temperature regions. Consequently, applying mild combustion allows for the avoidance of localized thermal stress concentration and enables stable combustion operation at low flame temperatures, thereby suppressing the generation of nitrogen oxides (NOx) caused by heat. Generally, the oxidizer (air) can be mixed with combustion flue gas to lower the oxygen concentration within the oxidizer before injection, in order to reduce the flame temperature generated during combustion. Meanwhile, hydrogen fuel is one of the carbon-free fuels that does not emit carbon dioxide, and since it can replace existing fossil fuels for carbon neutrality, its development is actively underway. The hydrogen mild combustion method is attracting attention because operating radiant tube thermal systems using this method not only avoids localized thermal stress concentration but also improves system efficiency through uniform temperature distribution within the tubes and reduces nitrogen oxide (NOx) and carbon dioxide emissions. FIG. 1 is a schematic block diagram illustrating a mild combustion system according to one embodiment of the present application. Figure 2 is a graph showing the flame temperature generated by the combustion reaction of hydrogen fuel according to the oxygen concentration of the diluted oxidizer at different temperatures of the diluted oxidizer. FIG. 3 is a flowchart illustrated exemplarily to explain a mild combustion method according to one embodiment of the present application. In the description of numerical ranges in this specification, the notation “X~Y” indicates X or greater and Y or less, unless otherwise specifically stated. Additionally, “greater than or equal to” may be replaced with “greater than,” and “less than or equal to” may be replaced with “less than.” In addition, regarding the numerical ranges described stepwise in this specification, any upper or lower limit value described in any numerical range may be substituted with an upper or lower limit value of another numerical range described stepwise, or may be substituted with a value shown in the examples. Hereinafter, the mild combustion system of the present application will be described with reference to the attached drawings. The attached drawings are exemplary and the mild combustion system of the present application is not limited to the attached drawings. FIG. 1 is a schematic block diagram illustrating a mild combustion system according to one embodiment of the present application. As shown in FIG. 1, the mild combustion system of the present application includes an oxidizer supply device (1), a separator (2), an oxidizer dilution device (3), a fuel supply device (4), a main combustor (5), and a heat exchanger (6). According to the mild combustion system of the present application, the generation of moisture in the flue gas during mild combustion can be reduced, thereby improving combustion operation performance. The above oxidizing agent supply device (1) is a device that supplies an oxidizing agent to the above oxidizing agent dilution device (3). For example, air commonly used in the industry can be used as the oxidizing agent mentioned above. The above-mentioned separator (2) is a membrane that selectively captures carbon dioxide gas from the external exhaust gas. In this specification, "external" refers to the outside of the mild combustion system. For example, the external exhaust gas may be exhaust gas known in the art, and in one embodiment, it may be exhaust gas discharged from an auxiliary combustor provided separately from the main combustor (5). Furthermore, the auxiliary combustor may be a combustor that uses the same fuel as the main combustor (5), as well as any combustor known in the art that uses a different fuel than the main combustor (5). In one example, the separator (2) may be of the hollow fiber type. The hollow fiber separator (2) may be configured such that when gas