Central electrode structure dielectric barrier discharge synergistic enhanced combustion device for coal and ammonia

Abstract

The present invention is a dielectric barrier discharge assisted enhanced combustion device for coal and ammonia with a central electrode structure. The structure of the auxiliary combustion device includes: a high-voltage electrode, a grounded electrode, an ammonia storage tank, a first porous ceramic, a second porous ceramic, a gas flow controller, etc. The central electrode is the high-voltage electrode, and the outside is the grounded electrode. The high-voltage electrode is cylindrical and has threads on the surface of the electrode discharge area; the grounded electrode is placed by wrapping the high-voltage electrode with a hollow cylinder, and an ammonia injection channel is reserved on the side of the grounded electrode; the ammonia storage tank is connected to the combustion device through a gas flow controller. The present invention uses dielectric barrier discharge to generate dispersed low-temperature plasma, which is coupled with the flame plasma of coal and ammonia combustion to further promote the dispersion of discharge, helping to form a larger area of discharge plasma in the reaction cavity. The intervention of dielectric barrier discharge plasma can improve the combustion efficiency, and the use of ammonia can reduce pollutant emissions.

Description

Technical Field

[0001] The present invention belongs to the field of combustion assisted by dielectric barrier discharge plasma, and uses the low-temperature plasma generated by dielectric barrier discharge to synergistically enhance the combustion of coal and ammonia. Background Art

[0002] The present invention uses DBD plasma to assist combustion. During the discharge process, electrons collide with neutral particles, causing the neutral particles to ionize, excite, and dissociate. The high-energy active groups generated during this period affect the chemical reactions during the combustion process.

[0003] Plasma-assisted combustion technology has been widely used, and the benefits it brings are considerable. As an excitation, discharge plasma affects the chemical effect, temperature rise effect, and aerodynamic effect during the combustion process, and can effectively shorten the ignition time, improve the combustion efficiency, and reduce pollutant emissions. Summary of the Invention

[0004] In the present invention, ammonia is introduced into the discharge combustion cavity and the combustion device is optimized. The present invention uses a central electrode to synergistically enhance the combustion of coal and ammonia. The discharge generating device designed with the central electrode has a lower breakdown voltage compared to the flat electrode, and the discharge channel and discharge intensity are enhanced; the heat released by the plasma and coal combustion is used to ignite ammonia. The ignition of ammonia in the discharge combustion cavity can replace part of the calorific value of coal combustion and reduce the emission of polluting gases. In addition, the ammonia burned by the plasma will generate high-concentration active groups, keeping it within a relatively stable range. The discharge plasma and combustion plasma promote each other and jointly improve the combustion efficiency and reduce the pollution emissions.

[0005] The present invention is a device for synergistically enhancing the combustion of coal and ammonia based on a central electrode. The device consists of a high-voltage electrode, a ground electrode, an ammonia storage tank, a gas flow controller, a first porous ceramic, and a second porous ceramic; the high-voltage and ground electrodes are fixed to the second porous ceramic, coal is placed on the first porous ceramic, the ammonia is regulated by the gas flow controller, and there are corresponding devices for feeding coal blocks and transporting out the burned residues outside the discharge combustion cavity.

[0006] Preferably, the high-voltage electrode is fixed at the central position of the second porous ceramic, and the ground electrode is fixed around the high-voltage electrode.

[0007] Preferably, the surface of the discharge area of the high-voltage electrode is surrounded by threads, and the ground electrode is a hollow cylinder with reserved holes on its side.

[0008] Preferably, the distance between the high-voltage electrode and the low-voltage electrode is about 40 mm, and they are fixed on the second porous ceramic. The diameter of the second porous ceramic is about 74 mm and the thickness is about 12 mm.

[0009] Preferably, the diameter of the first porous ceramic is slightly smaller than that of the grounding electrode and is suspended in the second porous ceramic, and is fixed on the high-voltage electrode through a fixing bracket.

[0010] Preferably, the ammonia storage tank is connected to the reserved small hole of the grounding electrode through a gas flow controller.

[0011] Preferably, the plasma generation power supply is a kHz AC power supply, with a power of 0.8 kW - 2 kW, a peak-to-peak voltage of 0 - 40 kV, an AC frequency of 5 - 30 kHz, a modulation pulse frequency of 100 - 1000 Hz, and a controllable duty cycle range of 1 - 100%.

[0012] Preferably, the gap between the high-voltage electrode and the grounding electrode serves as the discharge combustion chamber.

[0013] Preferably, coal is placed on the first porous ceramic and ammonia is introduced, and the discharge plasma is used to synergistically enhance the combustion of coal and ammonia.

[0014] Preferably, ammonia is introduced into the discharge combustion chamber through a gas flow controller. Ammonia can replace part of the calorific value generated by coal, facilitate the ignition of ammonia by absorbing the energy released by coal combustion, reduce the amount of coal used, and thus reduce pollutant emissions, and can provide more active groups.

[0015] Preferably, ammonia is evenly distributed in the discharge combustion chamber through the first porous ceramic and is in full contact with coal.

[0016] Preferably, the ammonia for combustion under the action of the plasma can improve the plasma dispersion and the concentration of active groups in the chamber, so as to enhance the uniformity of the discharge plasma and improve the combustion efficiency.

[0017] Preferably, the plasma generated by the discharge and the plasma of coal combustion promote each other and act together. The discharge plasma improves the flame stability, and the flame plasma further reduces the discharge voltage and the power output of the power supply.

[0018] The present invention will bring the following benefits:

[0019] (1) The present invention uses the discharge plasma to synergistically enhance the combustion of coal and ammonia, which helps to improve the combustion efficiency. The use of ammonia reduces the amount of coal used and the emission of pollutants.

[0020] (2) The present invention adopts a DBD plasma generating device, using coal as the dielectric and combustion raw material. The DBD plasma generating device has a low cost and can form a relatively stable low-temperature plasma under atmospheric pressure. The central electrode creates a highly non-uniform electric field, and the non-uniform electric field is more conducive to the formation of a diffuse discharge plasma. Compared with a flat electrode, its discharge channel is stable, the discharge starting time is shorter, and the temperature of the discharge combustion chamber is stable.

[0021] (3) The bottom of the present invention uses porous ceramics, which is beneficial for the dropping of combustion residues and the flow of air. In addition, the presence of pores helps to fix the high-voltage electrode.

[0022] (4) The present invention uses the first porous ceramic to place coal and suspends the bottom porous ceramic on the high-voltage electrode. The diameter of the first porous ceramic is smaller than that of the low-voltage electrode to prevent coal from directly contacting the bottom and causing surface discharge during the discharge process. Moreover, the presence of pores makes the ammonia gas evenly distributed in the discharge combustion cavity.

[0023] (5) Introducing ammonia gas into the discharge combustion cavity can shorten the ignition time. Ammonia can replace part of the coal to burn, reducing heat value and pollutant emissions. The concentration of groups required in the combustion chain reaction will also increase correspondingly under the action of plasma and ammonia, improving the combustion efficiency.

[0024] (6) The present invention controls and adjusts the parameters of the applied voltage amplitude and frequency, ammonia gas flow rate, and central electrode spacing. The most suitable combustion control parameters are determined by measuring the lift height of stable flame combustion, the change in coal quality, and the change in temperature. Description of the Drawings

[0025] For a more intuitive description of the invention, the entire discharge combustion device is described with reference to the drawings. The drawings do not represent the final device style.

[0026] Att Figure 1 It is a schematic diagram of a DBD plasma synergistic enhanced coal and ammonia combustion device based on a central electrode.

[0027] Reference numerals in the drawings: 1 - gas flow controller, 2 - coal block transporter, 3 - ammonia storage tank, 4 - combustion residue transporter, 5 - grounding electrode, 6 - high-voltage electrode, 7 - kHz high-voltage AC power supply, 8 - the first porous ceramic, 9 - fixing bracket, 10 - the second porous ceramic. Detailed Embodiments

[0028] The following will describe the specific operation method of the device of the present invention in conjunction with the patent drawings. The drawing device is a simplification of the actual object and does not represent the final actual drawing.

[0029] In this specification, for related terms such as "installation", "fixation", and "connection", if there is no special explanation, they can be understood in a broad sense. For example, the connection between devices can be fixed, detachable, or directly integrated in future actual applications. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Att Figure 1It is a schematic diagram of the device for plasma-assisted enhanced combustion of coal and ammonia. The high-voltage electrode is fixed at the center of the second porous ceramic. The high-voltage electrode can be selected from titanium wire, tungsten wire, etc., and there are threads wound around the surface of its discharge area to increase the discharge contact area. The grounding electrode is used as the outer electrode, and small holes for introducing ammonia are reserved on its side. The grounding electrode can be made of 304 stainless steel, iron, etc. as the material. Coal is placed on the first porous ceramic. The ammonia storage tank 3 is connected to the small holes reserved on the grounding electrode through a flow controller. The frequency, amplitude, and duty cycle of the kHz high-voltage AC power supply can all be adjusted. The selection of the porous ceramic is based on: insulation, high temperature resistance, difficulty of electrode fixation, air flow rate of the device, and convenience of handling combustion residues.

[0031] The discharge combustion chamber is formed by the gap between the high-voltage electrode and the grounding electrode. Under kHz high-voltage excitation, non-equilibrium discharge occurs at atmospheric pressure to generate low-temperature plasma, and the electron temperature is as high as 100 eV. Using coal as the DBD dielectric, the plasma acts on the flame plasma of coal combustion to accelerate the flame propagation speed, and the energy released by combustion is transferred to ammonia to achieve ammonia ignition.

[0032] Compared with the patent with the application number CN113365404A of this team, in this invention, ammonia is introduced into the discharge combustion chamber, and the plasma generating device uses a central electrode. The structures of the electrodes are different, the electric field distributions are different, the functions achieved are also quite different, and the applicable coal qualities are also different.

[0033] This invention uses a central electrode to replace the flat electrode. In the subsequent experiments of this team, it is found that when using the central electrode, the applied voltage is reduced, the formation time of the discharge channel in the discharge combustion chamber is short, stable, and the discharge effect is strong. The use of the central electrode structure in this invention can save power consumption, improve combustion efficiency, and shorten the ignition time.

[0034] The working principle of introducing ammonia into the discharge combustion chamber in this invention: The entry of ammonia with different flow rates will change the flow field distribution in the discharge combustion chamber, affect the heat transfer and plasma transport processes, and at the same time affect the discharge intensity and plasma diffusivity. Ammonia absorbs the energy released by coal combustion for ignition, and the concentration of active groups formed inside the discharge combustion chamber by plasma excitation increases. Since the combustion of coal is a complex chain reaction, the addition of active groups can reduce the bond energy required for the chain reaction and promote the progress of the chain reaction. In the discharge combustion chamber, the discharge plasma and the combustion plasma are coupled with each other to synergistically enhance the combustion of coal and ammonia.

[0035] With the pending patent CN113898964A, an integrated system and method for reducing CO2 emissions from coal-fired power generation units by co-firing ammonia, the plasma is used to act on ammonia to crack it into a hydrogen-ammonia mixed gas, which is then mixed into the pulverized coal combustion to reduce the emission of polluting gases. The action mechanism of the present invention is different from this. The plasma is used to assist the combustion of lump coal instead of cracking ammonia. The energy released by coal combustion is used to ignite ammonia. Through the action of the plasma on the ignited ammonia, the concentration of active groups such as H and OH in the combustion reaction cavity is increased, reducing the bond energy required for the coal chain reaction, and realizing the interaction between the plasma discharge and the flame plasma to jointly promote the combustion process, achieving the purpose of improving the combustion efficiency and reducing pollutant emissions.

[0036] The standard parts used in the present invention can all be purchased from the market. The special-shaped parts can be customized according to the description in the specification and the drawings. The specific connection methods of each part all adopt conventional means such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts, and equipment all adopt conventional models in the prior art. Coupled with the circuit connection adopting the conventional connection method in the prior art, it will not be elaborated here. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0037] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A central electrode structure dielectric barrier discharge synergistic enhancement coal and ammonia combustion device, characterized in that: It includes a gas flow controller, a coal block transporter, an ammonia storage tank, an ash residue transporter, a ground electrode, a high-voltage electrode, a kHz high-voltage AC power supply, a first porous ceramic, a fixing bracket and a second porous ceramic. The high-voltage electrode, the ground electrode and the second porous ceramic form a central electrode. The gap between the high-voltage electrode and the ground electrode serves as a discharge combustion chamber. The high-voltage electrode and the ground electrode are fixed by the second porous ceramic at the bottom. The ground electrode serves as an outer electrode and has a reserved small hole for ammonia to pass through on its side. The ammonia storage tank is connected to the reserved small hole on the ground electrode through the gas flow controller. Coal is placed on the surface of the first porous ceramic. The coal serves as a dielectric and a combustion raw material. There is the coal block transporter above the central electrode and the ash residue transporter below the central electrode.

2. The dielectric barrier discharge synergistic enhancement coal and ammonia combustion device according to the central electrode structure described in claim 1, characterized in that: The high-voltage electrode is about 40 mm away from the low-voltage electrode and is fixed on the second porous ceramic. The diameter of the second porous ceramic is about 74 mm and the thickness is about 12 mm.

3. The dielectric barrier discharge synergistic enhanced coal and ammonia combustion device according to the central electrode structure described in claim 1, characterized in that: The diameter of the first porous ceramic is smaller than that of the external low-voltage electrode and it floats on the second porous ceramic and is fixed on the high-voltage electrode through the fixing bracket.

4. The dielectric barrier discharge synergistic enhanced combustion device for coal and ammonia according to the central electrode structure described in claim 1, characterized in that: The ammonia is introduced into the discharge combustion chamber through the gas flow controller. The ammonia can replace part of the calorific value generated by the coal, facilitate the ignition of ammonia by absorbing the energy released by coal combustion, reduce the coal consumption, and thus reduce the pollutant emissions, and can provide more active groups.

5. The dielectric barrier discharge synergistic enhancement coal and ammonia combustion device according to the central electrode structure described in claim 1, characterized in that: The ammonia makes the ammonia evenly distributed in the discharge combustion chamber through the first porous ceramic and fully contact with the coal.

6. The dielectric barrier discharge assisted enhanced combustion device for coal and ammonia with the central electrode structure according to claim 1, wherein: The ammonia burned by the action of plasma can enhance the plasma dispersion and the concentration of active groups in the chamber to strengthen the uniformity of the discharge plasma and improve the combustion efficiency.

7. The dielectric barrier discharge synergistic enhanced coal and ammonia combustion device according to the central electrode structure described in claim 1, characterized in that: The plasma generated by the discharge and the plasma of coal combustion promote each other and act together. The discharge plasma improves the flame stability, and the flame plasma further reduces the discharge voltage and reduces the power output of the power supply.

Images