Ammonia, hydrogen and natural gas mixed combustion system

Abstract

The invention discloses an ammonia, hydrogen and natural gas mixed combustion system which comprises a hearth, a combustor, a heat exchanger, a mixer and a storage tank, the combustor and a conical combustion cavity are installed in the hearth, the storage tank is provided with a first branch pipeline through a conveying pipe and connected with the heat exchanger, and the heat exchanger is connected with an inlet of the mixer; an outlet of the mixer is connected with a fuel input port of the combustor; the conveying pipe is provided with a second branch pipeline to be connected with an ejection opening of a first ejector, the first ejector is installed on a smoke recirculation pipe connected with a hearth smoke exhaust pipeline bypass, and the other end of the smoke recirculation pipe is connected with an auxiliary fuel inlet of the combustor. The method has the beneficial effects that the problem of transportation danger of hydrogen is solved, and the ignition performance is improved; the stable ignition and combustion of the ammonia gas are ensured, and the carbon deposition phenomenon is avoided; and the temperature of a combustion area is gentle, and a local high-temperature area is avoided, so that the generation of nitrogen oxides can be reduced.

Description

Technical Field

[0001] The invention belongs to the field of combustion technology, and in particular relates to an ammonia, hydrogen and natural gas mixed combustion system. Background Art

[0002] Comprehensive use of various technologies, such as carbon capture technology and the application of zero-carbon emission hydrogen energy, ammonia energy, etc., and the fundamental means is to reform the energy system and introduce carbon-free energy.

[0003] Hydrogen (H 2 ) and ammonia (NH 3 ) is a common carbon-free energy source that has attracted more and more attention in recent years, but it is expensive. 2 ) and ammonia (NH 3 ) to replace part of the natural gas fuel can not only reduce carbon emissions, but also avoid the fuel price being too expensive, killing two birds with one stone. However, at this stage, traditional combustion equipment mainly targets natural gas (CH 4 ) design, the addition of hydrogen and ammonia will significantly affect the combustion characteristics, and the structure of traditional combustion equipment must be improved.

[0004] Hydrogen (H 2 ) It is flammable and explosive, dangerous to transport, and needs to be re-laid as a direct fuel supply. 2 Supplying dedicated pipelines is currently difficult to achieve. 3 The calorific value is low, the ignition stability is not as good as natural gas, and the nitrogen content is high. It is also necessary to prevent the possible excessive nitrogen oxide emissions. This determines that the ammonia, hydrogen and natural gas mixed combustion system must be redesigned.

[0005] The Chinese invention patent application with application publication number CN115419892A discloses a boiler system for combustion of ammonia mixed with hydrogen, which includes a mixer 1, an inlet of the mixer 1 is connected to hydrogen and a first-path ammonia, and the mixed gas 1 exiting the mixer 1 is heated by a heat exchanger 1 and then sent to a burner in the boiler. The system is characterized in that the tail gas exiting the boiler is heated by a secondary heat exchanger to heat the second-path ammonia, and the heated second-path ammonia enters an ammonia decomposition tower for cracking to obtain hydrogen and is recycled to the mixer 1, and the third-path ammonia and the tail gas exiting the secondary heat exchanger are connected to a mixer 2, and the mixed gas 2 exiting the mixer 2 is cooled by a secondary air preheater and then sent to a denitrification tower for flue gas denitrification, and the tail gas exiting the denitrification tower is heated by a heat exchanger 1, and the air exiting the secondary air preheater is sent to the boiler. Although the invention produces hydrogen by cracking ammonia and then mixes it with ammonia for combustion, thus achieving energy utilization and stable combustion of ammonia, and reducing the emission of nitrogen oxide pollutants through denitrification and flue gas recycling, it cannot solve the problems of the danger of transporting ammonia and hydrogen and the difficulty in burning ammonia, and the combustion efficiency of the system is relatively low.

[0006] The Chinese invention patent application with application publication number CN115614778A discloses an ammonia-hydrogen co-combustion combustion chamber and a combustion method of ammonia-hydrogen co-combustion, an ammonia-hydrogen co-combustion combustion chamber, comprising a combustion chamber body, an ammonia pyrolysis chamber arranged inside or outside the combustion chamber body, the ammonia pyrolysis chamber existing in the combustion chamber body or constructed outside the combustion chamber body by using the combustion chamber body wall, utilizing the high temperature wall of the combustion chamber body or the high temperature environment in the combustion chamber body to pyrolyze the ammonia in the ammonia pyrolysis chamber to produce hydrogen, the hydrogen enters the combustion chamber body from the hydrogen hole of the ammonia pyrolysis chamber, and is mixed and burned with the ammonia sprayed into the combustion chamber body fuel nozzle, and the high-pressure air entering the combustion chamber body, to realize ammonia-hydrogen co-combustion. The technical solution of the invention directly integrates the ammonia decomposition hydrogen production device into the combustion chamber, fully utilizes the high temperature pyrolysis ammonia of the combustion chamber wall, eliminates the complex ammonia cracking device arranged separately, and simplifies the structure of the overall ammonia-hydrogen co-combustion device. However, the structure is too complicated and difficult to maintain. In addition, due to the non-flammability of ammonia, the fuel combustion efficiency is not high, and the issue of how to mix it with natural gas is not addressed. Summary of the invention

[0007] In order to solve the problems raised by the above background technology, the present invention provides a safe and environmentally friendly ammonia, hydrogen and natural gas mixed combustion system.

[0008] The technical solution adopted by the present invention to solve its technical problems is: an ammonia, hydrogen and natural gas mixed combustion system, which includes a furnace, a burner, a conical combustion chamber, a heat exchanger, a mixer and a storage tank, the burner is installed on the front end side wall of the furnace, the conical combustion chamber is installed in the furnace, and the heat exchanger is installed in the furnace and is located between the burner and the flue gas emission outlet; a pressure reducing valve is provided at the outlet of the storage tank, and is connected to the heat exchanger through a delivery pipe provided with a first branch pipeline, the outlet of the heat exchanger is connected to the inlet of the mixer, and the outlet of the mixer is connected to the fuel input port of the burner; the delivery pipe is provided with a second branch pipeline connected to the ejection port of the first ejector, the first ejector is installed on a flue gas recirculation pipe connected to a bypass of the furnace exhaust pipe, and the other end of the flue gas recirculation pipe is connected to the auxiliary fuel inlet of the burner.

[0009] The mixer is connected to the Roots blower through an air duct, and air is input into the mixer to adjust the ammonia decomposition mixture after preheating and decomposition.

[0010] The air duct is provided with a branch air duct connected to the ejection port of the second ejector. The second ejector is installed on the outlet flue gas recirculation pipe of the first ejector and is used to introduce air, adjust the ejected ammonia, and then input it into the burner for combustion.

[0011] The center of the burner includes a first porous ceramic plate, a second porous ceramic plate and a plurality of ceramic balls, and the ceramic balls are filled between the first porous ceramic plate and the second porous ceramic plate.

[0012] The diameter of the ceramic balls is 10-20 mm, and the number of rows between the first porous ceramic plate and the second porous ceramic plate is 5-8. The ceramic balls can effectively prevent combustion backfire and play the role of flame arrester.

[0013] The through-hole diameters of the first porous ceramic plate and the second porous ceramic plate are 1-3 mm, which can effectively prevent combustion backfire and play a role in stabilizing the flame.

[0014] The outer side of the center of the burner is wrapped by a shell to form an annular cavity. The annular cavity is provided with two auxiliary fuel inlets at the inlet and a multi-hole injection plate with an inclined angle at the outlet. The multi-hole injection plate is provided with a plurality of fuel injection holes, and the aperture of the fuel injection holes is 1-3mm.

[0015] The multi-hole injection plate is at an angle of 45 degrees to the center line of the burner outlet to prevent backfire and stabilize the flame.

[0016] The conical combustion chamber is arranged at the burner outlet.

[0017] A porous plate is arranged on the wall surface of the conical combustion chamber facing the burner side, and a plurality of fuel injection holes are arranged on the porous plate. The aperture of the fuel injection holes is 1-3mm, which is used to prevent backfire and play a role in stabilizing the flame.

[0018] Preferably, the two porous plates on the side of the conical combustion chamber facing the burner have an inclination angle, and the inclination angle is 45 degrees with the center line of the burner outlet.

[0019] Preferably, the distance between the conical combustion chamber and the center line of the burner outlet is 1 / 2-5 / 6 of the outer diameter of the burner, and the length of the porous plate of the conical combustion chamber is 1 / 8-1 / 10 of the outer diameter of the burner.

[0020] Compared with the prior art, the beneficial effects of the present invention are: it solves the problem of dangerous transportation of hydrogen, effectively utilizes the residual pressure of ammonia and the residual heat of furnace flue gas to decompose ammonia into hydrogen and nitrogen, and at the same time the temperature is increased, which improves the ignition performance; it can prevent flashback during hydrogen combustion to ensure stable ignition and combustion of hydrogen; it can ensure that ammonia and natural gas can be burned out smoothly without carbon deposition; the temperature in the combustion area is relatively gentle, and no local high temperature area will appear, so the generation of nitrogen oxides can be reduced, solving the problem of increased nitrogen oxide emissions due to ammonia combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is a structural block diagram of an ammonia, hydrogen and natural gas mixed combustion system of the present invention;

[0022] Figure 2 The three-dimensional structure diagram of the hood;

[0023] Figure 3 This is a cross-sectional view of the hood axis. DETAILED DESCRIPTION

[0024] The present invention is further described below with reference to the accompanying drawings. It is worth noting that these specific embodiments are only representative specific embodiments of the present invention, and the specific methods, devices, conditions, materials, etc. exemplified therein are not intended to limit the present invention or the corresponding specific embodiments. In addition, the devices in the figures are only used to express their relative positions and are not drawn according to their actual proportions, so please make this clear in advance. In addition, the description of the front, rear, etc. in the text is based on the Figure 1 As a reference standard, the arrows in the figure indicate the direction of fluid flow.

[0025] A gas-hydrogen-natural gas mixed combustion system, such as Figure 1 As shown, it includes a furnace 5, a burner 7, a conical combustion chamber 14, a heat exchanger 1, a mixer 10, a storage tank 8 and a Roots blower 12. The burner 7 is installed on the front side wall of the furnace 5, the conical combustion chamber 14 is installed in the furnace 5, and the heat exchanger 1 is installed in the furnace 5, located between the burner 7 and the flue gas discharge outlet. A pressure reducing valve 9 is provided at the outlet of the storage tank 8, and a first branch pipeline is provided through a delivery pipe to connect with the inlet of the heat exchanger 1, the outlet of the heat exchanger 1 is connected with the inlet of the mixer 10, and the outlet of the mixer 10 is connected with the fuel input port of the burner 7; the delivery pipe is provided with a second branch pipeline to connect with the ejection port of the first ejector 13, the first ejector 13 is installed on the flue gas recirculation pipe connected to the furnace exhaust pipe bypass, and the other end of the flue gas recirculation pipe is connected with the auxiliary fuel inlet 6 of the burner 7. The Roots blower 12 is connected to the mixer 10 through an air duct, and inputs air into the mixer 10 to provide oxygen for the premixed combustion of the preheated and decomposed ammonia decomposition mixture.

[0026] The air duct is provided with a branch air duct connected to the injection port of the second ejector 11. The second ejector 11 is installed on the outlet flue gas recirculation pipe of the first ejector 13, and is used to introduce air to adjust the injected ammonia and flue gas mixture, and then input it into the annular cavity 3 of the burner 7 through the auxiliary fuel inlet 6 and then injected into the furnace 5 for combustion.

[0027] A hood is provided in the mixer 10, and the hood is connected to the outlet pipe of the heat exchanger 1. The hood is evenly provided with air outlets, and is used to evenly fill the preheated and decomposed mixed gases such as hydrogen and nitrogen into the mixer 10. The air inlet of the mixer 10 is a tangential air inlet setting, and the air enters the mixer 10 tangentially, and the mixed gases such as hydrogen and nitrogen are stirred by the airflow, so that the mixing is more uniform.

[0028] Preferably, the mixer 10 is provided with a plurality of hoods, preferably four hoods, which are respectively connected to the outlet pipes of the heat exchanger 1. Figure 2 and Figure 3 As shown, the hood includes an air duct 101, a hood body 102 and an air outlet duct 103. The hood body 102 is installed on the top of the air duct 101. The side wall of the hood body 102 is provided with an air duct cavity 104 which is connected with the air duct 101 through a through hole 106. The air outlet duct 103 is fixed on the side wall of the hood body 102, and the air outlet in the air outlet duct 103 is connected with the air duct cavity.

[0029] Preferably, the through holes are staggered in two rows, the number of which is 20. The width of the air induction cavity is 90 mm. The outlet of the air outlet pipe 103 is tilted downward, and the tilt angle is 40 degrees. Preferably, there are four air outlet pipes 103, which are evenly distributed on the side wall of the cap body 102. The ammonia, hydrogen and nitrogen mixed gas input by the above-mentioned hood structure is more evenly mixed under the stirring of the tangentially input air.

[0030] Liquid ammonia is convenient and safe to transport. Therefore, the present application first delivers the liquid ammonia to the user in a storage tank 8, and then forms 0.8MPa ammonia after decompression through a pressure reducing valve 9. At the same time, the decompressed ammonia is passed through a heat exchanger 1 to absorb the waste heat of the high-temperature flue gas in the furnace 5, and directly decomposes the ammonia into a mixed gas containing hydrogen and nitrogen, thus solving the problem of the dangerous transportation of hydrogen. In other words, the transportation of hydrogen and ammonia is transformed into the transportation of liquid ammonia, and the safety factor is greatly improved. The decompressed ammonia is divided into two paths, one of which enters the bypass flue gas recirculation pipe of the furnace exhaust. The high-pressure ejection suction effect of the first ejector 13 is used to inhale a part of the high-temperature flue gas and mix it with the decompressed ammonia for heating, which not only recovers the waste heat of the flue gas, but also realizes the self-circulation of carbon dioxide, which not only improves the ignition performance of ammonia but also reduces carbon dioxide emissions, killing two birds with one stone. The other path enters the heat exchanger 1 in the furnace. The decompressed ammonia absorbs the waste heat of the high-temperature flue gas in the furnace through the heat exchanger 1, and directly decomposes the ammonia into hydrogen and nitrogen. At the same time, the temperature is increased, which improves the ignition performance.

[0031] The channel center of the burner 7 includes a first porous ceramic plate 31, a second porous ceramic plate 32 and a plurality of ceramic balls 4, and the ceramic balls 4 are filled between the first porous ceramic plate 31 and the second porous ceramic plate 32. Preferably, the diameter of the ceramic balls is 15 mm, and the number of rows between the first porous ceramic plate 31 and the second porous ceramic plate 32 is 6 rows, which can effectively prevent combustion flashback. Through holes are set on the first porous ceramic plate 31 and the second porous ceramic plate 32, and the aperture is 2 mm, which can effectively prevent combustion flashback and stabilize the flame. After part of the ammonia is decomposed into hydrogen and nitrogen, it is mixed with air and undecomposed ammonia in the mixer 10 and enters the center of the burner 7, and then passes through the first porous ceramic plate 31, the ceramic balls 4 and the second porous ceramic plate 32 in turn, and then sprays out of the furnace for combustion, which can prevent flashback during hydrogen combustion. At the same time, since the combustion is carried out on the surface of the second porous ceramic plate 32, the second porous ceramic plate 32 has good heat resistance and can burn red without being damaged, thus playing the role of a flame stabilizing disk and ensuring the stable ignition and combustion of ammonia.

[0032] The outer side of the center of the burner 7 is wrapped by the shell to form an annular cavity 3, and the annular cavity 3 is connected with two auxiliary fuel inlets 6. A porous injection plate 2 with an inclined angle is provided at the fuel injection part at the outlet, and the conical combustion chamber 14 is installed in the furnace 5 at the outlet of the burner 7. Preferably, the angle between the porous injection plate 2 and the center line of the burner 7 outlet is 45 degrees. The aperture of the fuel injection hole on the porous injection plate 2 is 2mm, which is used to prevent backfire and stabilize the flame. The side wall of the conical combustion chamber 14 facing the burner is provided with a porous plate, and the aperture of the fuel injection hole on the porous plate is 2mm, which is used to prevent backfire and stabilize the flame. Preferably, the two porous plates on the side of the conical combustion chamber 14 facing the burner have an inclined angle, and the inclined angle is an angle with the center line of the burner outlet, which is 45 degrees. The distance between the conical combustion chamber 14 and the center line of the burner outlet is 2 / 3 of the outer diameter of the burner, and the length of the porous plate of the conical combustion chamber is 1 / 9 of the outer diameter of the burner 7.

[0033] A mixed gas composed of ammonia, carbon dioxide, oxygen, hydrogen and water vapor in the air at a temperature of about 200 degrees Celsius enters the annular cavity 3 and is ejected and burned through a porous injection plate 2 of a metal material inclined at a 45-degree angle. Although ammonia has poor ignition performance, it is very easy to ignite because the gas fuel has been preheated to 200 degrees. At the same time, ammonia is not easy to burn, and the use of a porous injection plate 2 can play a role in stabilizing combustion. After natural gas and air are mixed, they enter the conical combustion chamber 14 and are ejected and burned through the porous plate on the rear side. The ammonia fuel ejected from the porous injection plate 2 inclined at a 45-degree angle forms a counter-flame to ensure that both ammonia and natural gas can be burned smoothly without carbon deposition. At the same time, since the combustion zone of natural gas is far away from the central porous medium combustion zone, the temperature of the combustion zone is relatively gentle, and there will be no local high-temperature zone, so the generation of nitrogen oxides can be reduced. The combustion air is sent to the fuel gas by the Roots blower before combustion to be fully mixed with it, and the porous medium and porous plate are used to prevent backfire. The combustion speed is fast and the efficiency is high, which is much stronger than the ordinary diffusion type natural gas burner. It can ensure the smooth ignition and burnout of ammonia.

[0034] The above is only a preferred embodiment of the present invention, and should not be used to limit the scope of the present invention. That is, all simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the invention description are still within the scope of the patent of the present invention.

Claims

1. An ammonia, hydrogen and natural gas mixed combustion system, characterized in that: It includes a furnace, a burner, a conical combustion chamber, a heat exchanger, a mixer and a storage tank, the burner is installed on the front end side wall of the furnace, the conical combustion chamber is installed in the furnace, and the heat exchanger is installed in the furnace and is located between the burner and the flue gas emission outlet; a pressure reducing valve is provided at the outlet of the storage tank, and is connected to the heat exchanger through a delivery pipe provided with a first branch pipeline, the outlet of the heat exchanger is connected to the inlet of the mixer, and the outlet of the mixer is connected to the fuel input port of the burner; the delivery pipe is provided with a second branch pipeline connected to the ejection port of the first ejector, the first ejector is installed on a flue gas recirculation pipe connected to a bypass of the furnace exhaust pipe, and the other end of the flue gas recirculation pipe is connected to the auxiliary fuel inlet of the burner.

2. The ammonia, hydrogen and natural gas mixed combustion system according to claim 1, characterized in that: The inlet of the mixer is connected to the Roots blower through an air duct, and air is input into the mixer.

3. The ammonia, hydrogen and natural gas mixed combustion system according to claim 2, characterized in that: The air duct is provided with a branch air duct connected to the ejection port of the second ejector, and the second ejector is installed on the outlet flue gas recirculation pipe of the first ejector.

4. The ammonia, hydrogen and natural gas mixed combustion system according to claim 3, characterized in that: The burner includes a first porous ceramic plate, a second porous ceramic plate and ceramic balls, and the ceramic balls are filled between the first porous ceramic plate and the second porous ceramic plate.

5. The ammonia, hydrogen and natural gas mixed combustion system according to claim 4, characterized in that: The diameter of the ceramic balls is 10-20 mm, and the number of rows between the first porous ceramic plate and the second porous ceramic plate is 5-8.

6. The ammonia, hydrogen and natural gas mixed combustion system according to claim 4, characterized in that: The pore sizes of the first porous ceramic plate and the second porous ceramic plate are 1-3 mm.

7. The ammonia, hydrogen and natural gas mixed combustion system according to claim 6, characterized in that: The outer side of the center of the burner is wrapped by a shell to form an annular cavity. The annular cavity is provided with two auxiliary fuel inlets at the inlet and a multi-hole injection plate with an inclined angle at the outlet. The multi-hole injection plate is provided with fuel injection holes.

8. The ammonia, hydrogen and natural gas mixed combustion system according to claim 7, characterized in that: The multi-hole injection plate is at an angle of 45 degrees to the center line of the burner outlet, and the aperture of the fuel injection hole is 1-3 mm.

9. The ammonia, hydrogen and natural gas mixed combustion system according to claim 7, characterized in that: The conical combustion chamber is arranged at the burner outlet, and the two porous plates of the conical combustion chamber facing the burner have an inclination angle, and the porous plates are provided with fuel injection holes. The inclination angle is 45 degrees with the center line of the burner outlet, and the aperture of the fuel injection hole is 1-3mm.

10. The ammonia, hydrogen and natural gas mixed combustion system according to claim 9, characterized in that: The distance between the conical combustion chamber and the center line of the burner outlet is 1 / 2-5 / 6 of the outer diameter of the burner, and the length of the porous plate of the conical combustion chamber is 1 / 8-1 / 10 of the outer diameter of the burner.

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