A method for controlling hydrogen-doped combustion in a float glass furnace

Abstract

The application provides a hydrogen-doped combustion control method for a float glass melting furnace, relates to the technical field of float glass, and adopts a mixed gas of natural gas and hydrogen as fuel for combustion and heating in a material melting area, adopts pure natural gas for combustion and heating in a refining area, and adopts a defoaming device to perform defoaming treatment at the head end of the refining area to weaken the negative influence caused by hydrogen combustion.

Description

Technical Field

[0001] This invention relates to the field of float glass technology, and in particular to a method for controlling hydrogen-infused combustion in float glass melting furnaces. Background Technology

[0002] The promotion and application of hydrogen energy is facing a series of complex and critical issues. These issues not only involve the maturity and improvement of the technology itself, but also relate to multiple aspects such as energy security, environmental protection, economic benefits, and social development. Green hydrogen is an essential path for the diversification of electricity and a key to achieving carbon neutrality. The development of hydrogen energy needs to overcome the limitations of production, storage, transportation, and use, and its future lies in its application. Methanol is an important hydrogen storage medium. Based on the carbon emissions of raw materials and production processes, it can be divided into non-renewable methanol based on fossil fuels and renewable methanol based on renewable energy sources. Methanol produced by decomposing water using renewable energy sources such as solar and wind power to produce green hydrogen, coupled with carbon dioxide hydrogenation technology, is called "green methanol" (also known as electro-methanol).

[0003] With increasing surplus electricity from clean energy sources such as hydropower, nuclear power, wind power, and solar power, the use of these clean energy sources for hydrogen production via water electrolysis and methanol production via carbon dioxide hydrogenation, along with chemical energy storage, solves the problem of surplus electricity. Methanol is then used in natural gas blending with hydrogen, employing methanol-water reforming to obtain a stable and inexpensive hydrogen source, while also utilizing the methanol produced from surplus electricity. Simultaneously, carbon dioxide capture technology is used to purify the carbon dioxide generated during the hydrogen production process and return it to the green methanol production plant, addressing the carbon source issue for methanol plants. Through these pathways, a closed-loop carbon cycle is constructed, using carbon dioxide and methanol as the carriers of electricity. This energy path involves neither the generation nor the introduction of new carbon, perfectly combining clean electricity with hydrogen energy.

[0004] Introducing hydrogen into large float glass melting furnaces involves considerations beyond just achieving carbon neutrality and calculating economic benefits. It also requires maintaining consistent glass quality. Natural gas has been used as fuel for decades, and its combustion atmosphere, production processes, and furnace structure are mature and well-established. Changing the combustion method will inevitably affect the existing glass quality. This is why hydrogen-blended combustion has not been widely adopted in large float glass melting furnaces under the current circumstances.

[0005] Existing technical problems: The combustion reaction of natural gas is: CH4 + 2O2 → CO2 + 2H2O; the combustion reaction of hydrogen is: 2H2 + O2 → 2H2O. Meanwhile, the lower heating value of natural gas is 8000–8500 kcal / Nm³, and that of hydrogen is 2600 kcal / Nm³. According to the law of conservation of energy, the theoretical replacement rate for converting into equivalent heat energy is 0.36 per cubic meter of water. 3 Natural gas or 1m 3The complete combustion of hydrogen produces 1.6 kg of water. Replacing natural gas with hydrogen increases the amount of water produced by about three times.

[0006] As can be seen from the above, the application of hydrogen-infused combustion technology in glass melting furnaces can lead to an increase in the foam layer on the surface of the molten glass due to the generation of water vapor, which in turn increases the number of bubbles and affects the quality.

[0007] Float glass production has strict control over the combustion atmosphere. Due to the characteristics of hydrogen combustion, the atmosphere is unstable and can easily cause Fe in the molten glass to become unstable. 3+ To Fe 2+ The transformation affects the color of the glass.

[0008] Natural gas combustion is characterized by slow combustion, stable atmosphere, high air requirement, and oxidation-prone combustion; while hydrogen combustion is characterized by extremely fast combustion, intense atmosphere, low air requirement, and easy oxygen deficiency, especially on the side near the material, where oxygen deficiency is obvious. Incomplete combustion flue gas has a significant impact on glass quality and furnace atmosphere. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention proposes a combustion control method that can reduce the negative impact of hydrogen-infused combustion on melting furnaces.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: a method for controlling hydrogen-added combustion in a float glass melting furnace, wherein the material processing zone uses a mixture of natural gas and hydrogen as fuel for combustion heating, and the clarification zone uses pure natural gas for combustion heating.

[0011] Defoaming equipment is used to perform defoaming treatment at the beginning of the clarification zone.

[0012] Multi-stage flame heating is used to heat the hydrogen-infused combustion feedstock zone.

[0013] The formation of a multi-stage flame includes, but is not limited to, a burner nozzle comprising several jet pipes, with the diameter of each jet pipe gradually decreasing from the center of the nozzle outwards.

[0014] Of course, premixed combustion gas can also be introduced into different jet pipes separately, so that the flame length of the central jet pipe is longer than that of the outer jet pipes.

[0015] In the hydrogen-blended combustion mixture, hydrogen accounts for 15% of the fuel volume, and the air-fuel ratio is 7.91 to 11.25.

[0016] Compared with the prior art, the present invention has the following advantages: 1. Change the way hydrogen-blended fuel is used, from the whole kiln to the chemical zone. At the same time, combine it with the use of defoaming equipment in the foam zone, which can effectively reduce and eliminate the problem of foam layer increase.

[0017] The blended fuel with 15% hydrogen has an air-fuel ratio that is 1.13-1.25 times that of pure natural gas, and the residual oxygen content in the flue gas increases by 0.2-0.5%.

[0018] The oxygen deficiency in natural gas caused by hydrogen depleting oxygen allows for partial re-combustion of the incompletely burned flue gas, optimizing the kiln atmosphere, reducing tail gas treatment pressure, and improving heat utilization. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the gas path in a float glass furnace.

[0020] Figure 2 This is a partial cross-sectional view of a hydrogen-doped burner.

[0021] Figure 3 This is a schematic diagram showing the distribution of each jet pipe in a hydrogen-blended burner.

[0022] Illustration: 1. Defoaming equipment; 2. Air jet pipe. Detailed Implementation

[0023] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0024] like Figure 1 As shown, furnaces 1-3 are the material processing zone, and furnaces 4-6 are the clarification zone. Of course, the gradual change in the glass raw material morphology does not clearly distinguish between the material processing zone and the clarification zone; this is just a rough division. Natural gas is fed into the furnace in two ways. Furnaces 1-3 are fed a hydrogen-mixed gas, which needs to be premixed with oxygen, natural gas, and hydrogen before combustion. The combustion gas entering furnaces 4-6 is a premixed gas of oxygen and natural gas. Defoaming equipment is installed at furnace 4. In the figure, the thin solid line is the path of the mixed gas of natural gas and oxygen, the thick dashed line is the path of the mixed gas of natural gas, hydrogen, and oxygen, and the thin dashed line is the path of pure hydrogen.

[0025] like Figure 2 and Figure 3 As shown, hydrogen-infused combustion employs a multi-stage flame method. This can be achieved by simply replacing the burner end with multiple jet pipes 2. Under the same gas pressure, the larger the diameter of the jet pipe 2, the shorter the flame, and the smaller the diameter, the longer the flame. Therefore, the diameter of each jet pipe 2 can be gradually reduced from the inside to the outside. In this way, the outer flame is longer and the inner flame is smaller. As is well known, incomplete combustion often occurs in the inner flame. That is to say, the shorter flame ejected by the larger jet pipe 2 is prone to producing incompletely burned flue gas, while the longer outer flame can perform secondary heating and combustion during the outward diffusion of this flue gas.

[0026] Taking a 700T / D float kiln as an example, the foam zone is between furnace #3 and furnace #5, with the foam layer being the thickest in furnace #4. This invention mainly adopts two technical methods to reduce the foam layer.

[0027] The hydrogen-blended combustion method was changed from hydrogen-blended combustion throughout the entire kiln to hydrogen-blended combustion in the front 1#, 2#, and 3# small furnaces. Defoaming equipment 1 was introduced into furnace #4 to reduce the foam layer through defoaming technology.

[0028] Principle: In the float glass production process, the first three pairs of small furnaces belong to the material melting zone. The melting and combustion of glass raw materials will generate a large amount of water vapor and foam. Using it in the front zone has a smaller impact on quality compared to the last three pairs of small furnaces. At the same time, combined with the defoaming equipment installed in the No. 4 small furnace, the foam layer can be effectively reduced and eliminated.

[0029] Solving the problem of unstable hydrogen combustion atmosphere Theoretically, when natural gas is completely combusted, the air-fuel ratio is 9.5 times, while that of hydrogen is 2.4 times. Based on a 15% hydrogen blending ratio and a hydrogen replacement rate of 0.36, the air-fuel ratio of the mixture is 7.08 times. When this ratio is applied to the actual air volume for production experiments, the temperature and atmosphere changes inside the furnace are significantly different from the predicted situation.

[0030]

[0031] Experimental principle: Because hydrogen undergoes explosive combustion, when the mixture is ejected, the hydrogen rapidly combusts by drawing air, causing incomplete combustion of the natural gas and producing black smoke. Furthermore, the overall flame shortens, reducing the thermal efficiency of the fuel mixture and resulting in a temperature drop, thus failing to achieve energy-saving effects. Further increasing the air-fuel ratio improves the black smoke situation, raises the temperature inside the furnace, and shifts the combustion atmosphere towards an oxidizing state.

[0032] Experimental results: When using a 15% hydrogen-blended fuel mixture, the air-fuel ratio needs to be multiplied by 1.13-1.25 to ensure complete combustion of natural gas, and the corresponding flue gas residual oxygen content process index needs to be increased by 0.2-0.5%. By increasing the combustion air pressure and using a large-diameter burner, the problem of shorter flames can be solved to some extent.

[0033] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for controlling hydrogen-added combustion in a float glass melting furnace, characterized in that, The chemical processing zone uses a mixture of natural gas and hydrogen as fuel for combustion and heating, while the clarification zone uses pure natural gas for combustion and heating.

2. The method for controlling hydrogen-added combustion in a float glass melting furnace according to claim 1, characterized in that, Defoaming equipment (1) is used to defoam at the beginning of the clarification zone.

3. The method for controlling hydrogen-added combustion in a float glass melting furnace according to claim 1, characterized in that, Multi-stage flame heating is used to heat the hydrogen-infused combustion feedstock zone.

4. The method for controlling hydrogen-added combustion in a float glass melting furnace according to claim 3, characterized in that, The formation of a multi-stage flame includes, but is not limited to, the nozzle of the burner including several jet pipes (2), and the diameter of each jet pipe (2) gradually decreases from the center of the nozzle outward.

5. A method for controlling hydrogen-added combustion in a float glass melting furnace according to claim 1, 2, 3, or 4, characterized in that, In the hydrogen-blended combustion mixture, hydrogen accounts for 15% of the fuel volume, and the air-fuel ratio is 7.91 to 11.25.

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