Modified red mud preparation and ammonia fluidized bed catalysis-heat storage combustion method

Abstract

The invention discloses a modified red mud preparation and ammonia fluidized bed catalysis-heat storage combustion method, and belongs to the technical field of new energy and solid waste recycling. Aiming at the problems of high ignition energy, unstable combustion, NOx emission and the like in ammonia combustion, the method comprises the following steps: adding a hydrochloric acid solution with a sodium-acid ratio of (1: 0.26)-(1: 0.28) into red mud, and stirring to fully dissolve the red mud; and cooling to room temperature, filtering and washing until the pH value is neutral to obtain the modified red mud. Not only can NOx emission of NH3 combustion be reduced and NH3 combustion efficiency be improved, but also stockpiling pressure of red mud is relieved, utilization of carbon-containing energy is reduced, metal resources are saved, huge economic benefits are formed, and solid waste resource utilization is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy and solid waste resource utilization, and specifically relates to a method for preparing modified red mud and an ammonia fluidized bed catalytic-thermal storage combustion method. Background Art

[0002] Fossil fuel combustion and its CO2 emissions have become important energy and environmental issues today, and the development of new efficient and clean combustion technologies is urgent. Ammonia, as a new carbon-free hydrogen-rich fuel that can replace fossil fuels, has the characteristics of low liquefaction cost, convenient storage and transportation, superior energy density per unit volume, and strong safety. However, ammonia combustion has the problems of high ignition energy, unstable combustion, and NOx emissions. Therefore, the development of ammonia-fueled combustion systems is of great significance to the green and low-carbon transformation of the power industry.

[0003] The co-combustion of ammonia and coal is one of the important combustion technologies with ammonia as the main fuel, which is of great significance to reducing carbon emissions during coal combustion. In the field of ammonia-coal co-combustion, many studies are devoted to updating the combustion system method and transforming the ammonia burner. In terms of updating the gas-solid mixing method of the combustion system, patent CN114877315A invented an ammonia-coal multi-stage preheating combustion method, which changes the one-stage preheating method to a three-stage preheating method; patent CN115597062A invented an ammonia-coal co-combustion system, which realizes the cascade utilization of ammonia by designing multiple branches through the conveying component; patent CN117571913A discloses an experimental-level ammonia-coal turbulent combustion test system for industrial boilers, which changes the air intake and mixing methods. In terms of updating the mixed ammonia fuel form, patent CN117167737A invented a low-nitrogen combustion system of micronized coal and ammonia and its working method; patent CN117146268A invented a multi-fuel clean combustion system and method of coal powder after low-temperature pyrolysis by catalyst and then mixed with ammonia for combustion; patent CN115854339A invented a combustion device and method for coupling coal with ammonia / methane; patent CN115930220A invented a method for plasma-assisted coal-fired boilers to mix with ammonia for combustion. These methods aim to optimize the combustion process, improve combustion efficiency, and reduce NOx emissions through the design and improvement of the combustion system mixing method or fuel form. In terms of ammonia burner modification, patent CN116183811A invented a flat flame combustion experimental device for ammonia-coal co-combustion; patent CN116518365A invented a W-shaped flame boiler for ammonia / anthracite combustion; patent CN114738755A invented an ammonia-coal co-combustion burner for a four-corner cut-circle coal-fired boiler; patent CN117927949A invented a new type of burner with four layers of cylinder walls set on a cylindrical body; patent CN114484438A invented a coal and ammonia dual-purpose burner device. These burner modifications not only enhance fuel adaptability, but also improve the ignition stability of coal powder. Although the above patents have significantly improved the combustion performance of ammonia-coal co-combustion through improvements in the combustion system or device, there are still problems of a certain amount of CO2 emissions and high NOx emission risks. Pure ammonia combustion can achieve zero CO2 emissions. Patent CN116105130A invented a circulating fluidized bed boiler system that achieves pure ammonia combustion, which is characterized by zero carbon emissions. Patent CN111322610A invented an ammonia fluidized bed combustion device and power generation system and its combustion method, but there are problems such as difficult to control oxygen content, unstable combustion, and high NOx emissions. Summary of the invention

[0004] In view of the problems of high ignition energy, unstable combustion, and NOx emission in ammonia combustion, the present invention provides an ammonia fluidized bed catalytic-thermal storage combustion method, which improves the shortcomings of high ignition energy, unstable combustion, and high NOx emission of ammonia combustion through catalysis and thermal storage of special materials, and provides a material modification method using solid waste red mud as raw material, which realizes pure ammonia low-nitrogen efficient combustion while efficiently utilizing the beneficial components in red mud. In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing modified red mud and ammonia fluidized bed catalysis-thermal storage combustion, comprising adding a hydrochloric acid solution with a sodium-acid ratio of 1:0.26-1:0.28 to the red mud, stirring to fully dissolve the red mud; cooling to room temperature, filtering and washing to a neutral pH value to obtain modified red mud.

[0005] Furthermore, the sodium oxide content in the red mud is less than 5wt%.

[0006] Furthermore, the stirring to fully dissolve the red mud is specifically carried out at 50-60° C., at a stirring speed of 400-450 r / min, and for 45-55 minutes.

[0007] Furthermore, the filtration is specifically carried out under a 0.45 micron microporous filter membrane.

[0008] Furthermore, the washing is specifically performed using distilled water for 5 to 8 times until the pH value is neutral.

[0009] The specific method of modified red mud catalytic-thermal combustion in ammonia fluidized bed is: Furthermore, the modified red mud is placed in a fluidized bed boiler as bed material for catalytic-thermal storage combustion.

[0010] Furthermore, the modified red mud is placed in the furnace bed layer, and ammonia is fed in from the wind chamber at the bottom of the furnace to fully contact with the modified red mud. A secondary air inlet is set on the left side of the upper part of the bed layer to let air in. The feeding amount can be adjusted according to the red mud composition, but the overall ammonia state is maintained in a slight excess; air is intermittently passed through the primary air to adjust the redox cycle state of the red mud.

[0011] Choice of acid: Use hydrochloric acid, which has strong acidity and weak oxidizing property. It is not enough to react with Fe at low concentration. 3+ When sulfuric acid is used, it will react with calcium oxide to form a precipitate, blocking the pore structure; when nitric acid is used, the nitrogen element in it will interfere with the ammonia catalysis-heat storage combustion process.

[0012] Determination of acid amount: According to the formula: M n+ + A b- = n / bMA (where M n+ Represents metal ions, A b- Represents the selected acid ion, such as Fe3+ + 3Cl - = FeCl3) to obtain the amount of acid consumed for all components of red mud to react completely with acid / theoretical amount of acid; Compared with the prior art, the present invention has the following advantages: Red mud storage occupies a large amount of land resources and causes environmental pollution. The present invention uses hydrochloric acid to carry out pickling treatment on the red mud, which is simple to operate and low in cost. This not only brings economic benefits, but also promotes the resource utilization of solid waste by effectively utilizing various metal components in the red mud, reduces dependence on carbon-containing energy, and thus solves the carbon emission problem.

[0013] The proposed ammonia fluidized bed catalytic-thermal storage combustion operation method can not only reduce the NOx emissions generated during the NH3 combustion process, but also further improve the NH3 combustion efficiency by adjusting the feed air volume according to the red mud composition.

[0014] From the above, it can be seen that the present invention is a method for preparing modified red mud and a system for ammonia fluidized bed combustion, which can not only reduce NOx emissions from NH3 combustion and improve NH3 combustion efficiency, but also alleviate the storage pressure of red mud, reduce the use of carbon-containing energy, save metal resources, form huge economic benefits, and realize the resource utilization of solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the flow chart of modified red mud of the present invention.

[0016] Figure 2 It is a schematic diagram of the ammonia fluidized bed combustion system of the present invention.

[0017] Figure 3 This is a schematic diagram of the adsorption effect of modified red mud on ammonia.

[0018] Figure 4 This is a diagram of the combustion effect of ammonia. DETAILED DESCRIPTION

[0019] In order to gain a deeper understanding of the present invention, we will provide a comprehensive and detailed description of the present invention. However, the present invention has multiple implementations and is not limited to the specific examples listed herein. The presentation of these examples is intended to deepen the comprehensive understanding of the disclosure of the present invention.

[0020] The red mud described in the present invention is Bayer process red mud produced in the alumina industry, and its main components include iron oxide content of more than 53wt% and sodium oxide content of less than 5wt%.

[0021] Example 1

[0022] like Figure 1As shown, red mud with an iron oxide content of 55.45wt% and a sodium oxide content of 4.6wt% was selected, and a hydrochloric acid solution with a sodium-acid ratio of 1:0.26 was added, and stirred at a stirring speed of 400r / min for 50 minutes to fully dissolve the red mud; after cooling to room temperature, it was filtered and washed until the pH value of the red mud dropped to a neutral state, thereby obtaining modified red mud; After the modified red mud is dried, put it into Figure 2 The ammonia combustion experiment was carried out in the fluidized bed shown in the figure, and the results of the ammonia adsorption effect of the modified red mud were obtained, as shown in Figure 3 As shown, ammonia adsorption increased by 31.5% and nitrogen oxide emissions decreased by 10%.

[0023] Example 2

[0024] like Figure 1 As shown, red mud with an iron oxide content of 55.45wt% and a sodium oxide content of 4.6wt% was selected, and a hydrochloric acid solution with a sodium-acid ratio of 1:0.28 was added, and stirred at a stirring speed of 400r / min for 50 minutes to fully dissolve the red mud; after cooling to room temperature, it was filtered and washed until the pH value of the red mud dropped to a neutral state, thereby obtaining modified red mud (MRM); After the modified red mud is dried, put it into Figure 2 Ammonia combustion experiments were carried out in the fluidized bed shown in FIG. Figure 4 It can be seen that the NH3 conversion rate with modified red mud is always higher than that without modified red mud. The NH3 conversion rate without modified red mud increases with the increase of equivalent ratio; the NH3 conversion rate with modified red mud decreases with the increase of equivalent ratio. When the equivalent ratio is 1, the NH3 conversion rate is the largest. (NH3 conversion rate refers to the percentage of the amount of ammonia reacted to the amount of ammonia input) The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. Although the illustrative specific embodiments of the present invention are described above to facilitate the understanding of the present invention by the technical personnel in the field, it should be clear that the present invention is not limited to the scope of the specific embodiments. For the ordinary technical personnel in the field, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A method for preparing modified red mud and ammonia fluidized bed catalysis-thermal storage combustion, characterized in that: A hydrochloric acid solution with a sodium-acid ratio of 1:0.26 to 1:0.28 is added to the red mud, and the red mud is stirred to fully dissolve. After cooling to room temperature, the red mud is filtered and washed until the pH value is neutral to obtain modified red mud.

2. The method for preparing modified red mud and ammonia fluidized bed catalysis-thermal storage combustion according to claim 1, characterized in that: The red mud sodium oxide content is less than 5wt%.

3. The method for preparing modified red mud and ammonia fluidized bed catalysis-thermal storage combustion according to claim 1, characterized in that: The stirring is performed to fully dissolve the red mud, specifically at 50-60° C., at a stirring speed of 400-450 r / min, for 45-55 minutes.

4. The method for preparing modified red mud and ammonia fluidized bed catalysis-thermal storage combustion according to claim 1, characterized in that: The washing is specifically performed 5 to 8 times using distilled water.

5. Application of the modified red mud obtained by the preparation method according to claim 1 in ammonia fluidized bed catalysis-thermal storage combustion.

6. The use of the modified red mud obtained by the preparation method according to claim 5 in ammonia fluidized bed catalysis-regenerative combustion, characterized in that: The modified red mud is placed in a fluidized bed boiler as bed material for mixed combustion with ammonia.

7. The use of the modified red mud obtained by the preparation method according to claim 6 in ammonia fluidized bed catalysis-regenerative combustion, characterized in that: Place the modified red mud in the furnace bed layer, feed ammonia from the wind chamber at the bottom of the furnace to fully contact with the modified red mud, set a secondary air port on the left side of the upper part of the bed layer to let in air, the feed amount can be adjusted according to the red mud composition, but the overall ammonia is maintained in a slightly excessive state; Air is passed intermittently in the primary wind to adjust the redox cycle state of the red mud.

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