Search

JP-2026076037-A - heating furnace

JP2026076037AJP 2026076037 AJP2026076037 AJP 2026076037AJP-2026076037-A

Abstract

[Problem] To provide a heating furnace that uses ammonia as a fuel gas and can ensure good heating and flame stability. [Solution] A heating furnace having a burner that heats an object to be heated by burning a fuel gas with an oxidizing gas, wherein the fuel gas contains ammonia and the oxidizing gas has an oxygen concentration of 90% or more. [Selection Diagram] Figure 1

Inventors

  • 手操 周平
  • 村上 真二
  • 萩原 義之
  • 山口 雅志

Assignees

  • 日本酸素株式会社

Dates

Publication Date
20260511
Application Date
20241023

Claims (7)

  1. It has a burner that heats an object to be heated by burning a fuel gas with an oxidizing gas, The aforementioned fuel gas contains ammonia. The oxidizing gas is a heating furnace with an oxygen concentration of 90% or more.
  2. The furnace side wall has a burner on which the burner is installed, The heating furnace according to claim 1, wherein the burner has a fuel injection port, a first oxidizer injection port surrounding the fuel injection port, and a second oxidizer injection port located radially outward of the first oxidizer injection port without surrounding it.
  3. The heating furnace according to claim 2, wherein the ejection direction of the second oxidizing agent ejection port is inclined radially outward from the first oxidizing agent ejection port toward the ejection direction of the first oxidizing agent ejection port.
  4. The heating furnace according to claim 3, wherein the inclination angle θα [°] at which the ejection direction of the second oxidizing agent ejection hole is inclined radially outward from the first oxidizing agent ejection hole toward the ejection direction of the first oxidizing agent ejection hole is 0 ≤ θα ≤ 15.
  5. The heating furnace according to claim 2, wherein, when the surface of the object to be heated that is melted by the burner is referred to as the upper surface, the second oxidizing agent ejection port is located below the first oxidizing agent ejection port.
  6. The furnace side wall has a burner on which the burner is installed, The heating furnace according to claim 2, wherein when the surface of the object to be heated that is melted by the burner is called the top surface, the height H [m] from the top surface of the object to be heated to the center of the fuel injection hole, the distance L [m] between the furnace side wall and the opposite furnace side wall facing the furnace side wall in the left-right direction when viewed in the front-rear direction perpendicular to the plane containing the injection axis of the fuel injection hole along the vertical direction, and the inclination angle θβ [°] in which the injection axis of the fuel injection hole is tilted downward in the injection direction with respect to the top surface of the object to be heated when viewed in the front-rear direction, are 0.1 ≤ H ≤ 2 and H/L ≤ tanθβ ≤ 2H/L.
  7. The heating furnace according to claim 1, wherein the burner is embedded in the side wall of the furnace.

Description

This invention relates to a heating furnace. A burner is known that heats an object by burning a fuel gas with an oxidizing gas (see, for example, Patent Document 1). Patent No. 4261753 This is a cross-sectional view showing a heating furnace according to one embodiment of the present invention.Figure 1 is a cross-sectional view of the burner.This is an external view as seen in the direction of arrow A in Figure 2.Figure 3 is an external view showing a modified example of the burner.This graph shows the relationship between the oxygen concentration of the oxidizing gas and the adiabatic theoretical flame temperature.This graph shows the relationship between the oxygen concentration of the oxidizing gas and the combustion rate.This graph shows the relationship between the oxygen concentration of the oxidizing gas and the heat transfer coefficient ratio. The following describes embodiments of the present invention with reference to the drawings. As shown in Figure 1, in one embodiment of the present invention, the heating furnace 1 has a burner 3 that heats the object to be heated 2 by burning a fuel gas with an oxidizing gas. The fuel gas contains ammonia, and the oxidizing gas has an oxygen concentration of 90% or more. The fuel gas is not particularly limited as long as it contains ammonia, but it is preferable that it contains ammonia as its main component (i.e., the ammonia component is greater than 50% but less than or equal to 100%). The oxidizer gas is not particularly limited as long as its oxygen concentration is 90% or higher, but it is preferable to use oxygen-enriched air and configure the oxidizer gas to have an oxygen concentration of 90% or higher. The heating furnace 1 heats the object to be heated 2 by radiant heat transfer from the flame produced by burning fuel gas in the burner 3, and by convective heat transfer from the flow of combustion gases generated by the combustion, melting it as needed. The object to be heated 2 is not particularly limited and may be, for example, a metal such as aluminum, or glass. The radiant intensity and flame stability of burner 3 are related to the flame temperature and combustion rate, which in turn are related to the oxygen concentration of the oxidizer gas. Figure 5 shows the relationship between the oxygen concentration of the oxidizer gas and the adiabatic theoretical flame temperature of ammonia, and Figure 6 shows the relationship between the oxygen concentration of the oxidizer gas and the combustion rate of ammonia. As can be seen from Figures 5 and 6, increasing the oxygen concentration to over 90% can nearly maximize the flame temperature (radiant intensity) and combustion rate (flame stability). Increasing the oxygen concentration of the oxidizer gas also leads to a higher combustion gas temperature, which is advantageous for convective heat transfer. Figures 5 and 6 show a comparison of the relationship not only with ammonia but also with methane ( CH₄ ), a representative fossil fuel. It can be seen that ammonia has a lower flame temperature and combustion rate compared to fossil fuels ( CH₄ ), which puts it at a disadvantage. The following is a comparison of the chemical formulas for the combustion of CH₄ (methane) and NH₃ (ammonia). CH₄ + 2O₂ + 8N₂ → CO₂ + 2H₂O + 8N₂ ... Equation (1) CH₄ + 2O₂ →CO 2 + 2H 2 O ...Formula (2) NH 3 +0.75O 2 +3N 2 → 1.5H₂O + 3.5N₂ ...Equation (3) NH3 + 0.75O2 → 1.5H₂O + 0.5N₂ ...Equation (4) Equation (1) shows the case when CH4 is burned in air. Equation (2) shows the case when CH4 is burned in oxygen. Equation (3) shows the case when NH3 is burned in air. Equation (4) shows the case when NH3 is burned in oxygen. CO₂ and H₂O , which are included on the right-hand side of each equation, are known as radiant gases, and these gases contribute to the radiant performance of the flame. Comparing the equations, the concentrations of each radiant gas are as shown in the table below, and it can be seen that changing the oxidizer from air to oxygen improves the radiant performance of the flame. However, in equation (2), the CO₂ concentration in the exhaust gas increases. Also, in equation (3), the CO₂ concentration is zero, and the concentration of radiant gases is greater than in equation (1). In equation (4), where the oxidizer is changed from air to oxygen, the concentration of radiant gases increases even further. Figure 7 shows the relationship between the overall heat transfer coefficient (heat transfer coefficient) due to the flame and combustion gases and the oxygen concentration of the oxidizer gas (considering convective and radiant heat transfer). Figure 7 compares the case where CH4 is used as the fuel gas and the case where ammonia is used. In Figure 7, the heat transfer coefficient is shown as an indexed heat transfer coefficient ratio so that the value when CH4 is used as the fuel gas and air is used as the oxidizer gas (i.e., the oxygen concentration is approximately 20%) is the baseline value of 1. Sin