Combustor for N2O reduction using plasma
The plasma-based N2O reduction combustor thermally decomposes N2O and reduces NOx emissions in ammonia-fueled ships by using a novel combustor design with plasma treatment and a scrubber, achieving significant emission reductions without additional costly equipment.
Patent Information
- Authority / Receiving Office
- KR · KR
- Patent Type
- Patents
- Current Assignee / Owner
- NATIONAL KOREA OCEAN UNIVERSITY IND -UNIVERSITY COOP GROUP
- Filing Date
- 2024-02-28
- Publication Date
- 2026-07-29
AI Technical Summary
Existing technologies struggle to efficiently reduce nitrous oxide (N2O) emissions from ammonia-fueled engines in ships without expensive SCR equipment, while also addressing the increase in nitrogen oxides (NOx) emissions.
A plasma-based N2O reduction combustor utilizing an inner and outer nozzle, a quartz tube as a dielectric barrier, and a metal mesh electrode, where methane and nitrous oxide are supplied through separate nozzles, mixed by a swirler, and treated with plasma to thermally decompose N2O, followed by a scrubber to clean NOx and SOx emissions.
The combustor effectively reduces N2O emissions by over 90% and simultaneously decreases NOx emissions by up to 15%, without the need for expensive SCR equipment, enhancing the environmental performance of ammonia-fueled ships.
Smart Images
Figure 112024023048333-PAT00001_ABST
Abstract
Description
Technology Field
[0001] The present invention relates to a combustion device for reducing N2O. More specifically, it relates to a combustion device for reducing N2O (nitrous oxide), one of the greenhouse gases, utilizing plasma to reduce it by a pyrolysis method. Background Technology
[0002] Recently, significant efforts to reduce greenhouse gas emissions are required not only domestically but also globally across various fields, including manufacturing and shipping.
[0003] The Kyoto Protocol designated six major greenhouse gases as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC), and sulfur hexafluoride (SF6), and since 2020, the Paris Climate Agreement has imposed greenhouse gas reduction obligations on 195 parties to prevent climate change.
[0004] In addition, efforts are underway to reduce greenhouse gas emissions in the shipping sector, with the goal of reducing emissions by 70% under the International Maritime Organization (IMO)’s MARPOL Annex VI (Prevention of Air Pollution from Gas) and by 100% by 2050.
[0005] Among the six major greenhouse gases, N2O has a lower emission rate compared to CO2, but its global warming potential (GWP) is 310 times that of CO2. It is stable due to its triple bond structure, so it does not decompose in the Earth's atmosphere for 150 years, and it decomposes in the stratosphere due to ultraviolet rays, destroying the ozone layer, so it can be considered one of the major causes of global warming.
[0006] The sources of N2O emissions include human and natural factors. Among human factors, thermochemical N2O emissions resulting from fuel combustion account for 1 million tons of CO2eq, representing a very large proportion of total N2O emissions. Small diesel engines used on land are being developed with the goal of reducing NOx emissions, as NOx emissions are dominant over N2O emissions; meanwhile, marine diesel engines used at sea emit a significant amount of N2O, so research and development to reduce this is continuing.
[0007] Meanwhile, unlike conventional hydrocarbon-based fuels, ammonia (NH3) fuel has the advantage of not containing carbon, so it does not generate carbon dioxide, a greenhouse gas.
[0008] In addition, significant cost reductions are expected with the emergence of small-scale green ammonia production plants using renewable energy starting in 2025 and large-scale plants by 2030. However, as ammonia has a calorific value of 0.44 times that of gasoline and a significantly slower flame propagation speed, the development of a method to burn ammonia fuel by co-firing it with existing fuels is underway.
[0009] At this time, the amount of nitrogen oxides emitted into the atmosphere increases, so the development of efficient exhaust gas reduction devices to address this is also very important.
[0010] Prior Art: KR Registered Patent Publication No. 10-2274348 (Published July 6, 2021) The problem to be solved
[0011] The present invention was devised to solve the aforementioned problems, and aims to provide a plasma-based N2O reduction combustor that reduces N2O emitted from ships equipped with ammonia engines and effectively cleans additionally generated NO2, thereby enabling the simultaneous reduction of N2O and NOx in eco-friendly ships without expensive SCR equipment. means of solving the problem
[0012] A combustor for N2O reduction utilizing plasma according to the present invention, devised to achieve the above objective, comprises: an inner nozzle connected to a high-voltage power supply unit to apply high voltage; an outer nozzle positioned coaxially with the inner nozzle and located in the outer direction of the inner nozzle; and a metal mesh comprising a stainless steel material that is wound around the outer surface of a quartz tube and serves as another electrode. It includes a quartz tube that surrounds an inner nozzle and an outer nozzle and acts as a dielectric barrier between the two electrodes, wherein methane is supplied to the inner nozzle and oxygen and nitrous oxide are supplied to the outer nozzle, wherein a swirler is mounted on the outer surface of the inner nozzle to mix the oxidizer introduced from the outer nozzle, wherein methane (CH4), which is the fuel supplied to the inner nozzle, is partially guided through a hole perforated in front of the swirler mounted on the outer surface of the inner nozzle, mixed with the oxidizer supplied from the outer nozzle, and then flows into the swirler, wherein the fuel remaining in the inner nozzle is entirely guided through a hole perforated in rear of the swirler relative to the swirler and enters the flame face together with the gas mixture introduced into the outer nozzle. Effects of the invention
[0013] According to the present invention, N2O is reduced by applying plasma in combustion, and NO2 additionally generated after pyrolysis is washed with a scrubber, thereby having the effect of simultaneously reducing N2O and NOx. Brief explanation of the drawing
[0014] FIG. 1 is a configuration diagram of a combustion device for reducing N2O using plasma according to a preferred embodiment of the present invention, FIG. 2 is a drawing showing a photograph of a prototype of a plasma-based N2O reduction combustor according to a preferred embodiment of the present invention. FIG. 3 is a drawing showing a swirler of a combustion device for reducing N2O using plasma according to a preferred embodiment of the present invention. Figure 4 is a graph showing the experimental results of the decomposition rates of N2O, NO, and NO2 in a basic flame without applied plasma. Figure 5 is a graph showing the experimental results of the decomposition rates of NO2, N2O, and NO using a plasma-based combustor for reducing N2O according to a preferred embodiment of the present invention. Specific details for implementing the invention
[0015] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, it should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the present invention, such detailed description is omitted. Additionally, while preferred embodiments of the present invention will be described below, the technical concept of the present invention is not limited or restricted thereto and can be modified and implemented in various ways by those skilled in the art.
[0016] In this invention, a small combustor simulating a ship's smokestack is fabricated, optimal conditions for thermally decomposing N2O through a methane flame are derived, and plasma is applied to the methane flame to investigate the effects of the plasma applied to the methane flame on N2O thermal decomposition and nitrogen oxide emissions. Through this, the effects of gas flow rate and the voltage and frequency to which the plasma is applied on the N2O reduction rate are investigated to suggest a direction that can contribute to the advancement of optimal N2O reduction technology.
[0017] FIG. 1 is a configuration diagram of a combustion device for reducing N2O using plasma according to a preferred embodiment of the present invention, FIG. 2 is a photograph of a prototype of a combustion device for reducing N2O using plasma according to a preferred embodiment of the present invention, FIG. 3 is a diagram showing a swirler of a combustion device for reducing N2O using plasma according to a preferred embodiment of the present invention, FIG. 4 is a graph showing experimental results of the decomposition rate of N2O, NO, and NO2 in a basic flame without applying plasma, and FIG. 5 is a graph showing experimental results of the decomposition rate of NO2, N2O, and NO using a combustion device for reducing N2O using plasma according to a preferred embodiment of the present invention.
[0018] A combustion device (1) for reducing N2O using plasma according to a preferred embodiment of the present invention relates to a technology for reducing N2O (nitrous oxide), which is one of the greenhouse gases, by a pyrolysis method.
[0019] Specifically, a combustion device (1) for reducing N2O using plasma according to a preferred embodiment of the present invention is configured to include an inner nozzle (10), an outer nozzle (20), a mixing chamber (30), a quartz tube (40), a metal mesh (50), a swirler (60), and a scrubber (70), as shown in FIGS. 1 to 3.
[0020] The inner nozzle (10) is made of stainless steel, one end is formed as a protrusion, and the other end is supplied with methane (CH4) corresponding to fuel.
[0021] The inner nozzle (10) is connected to a high-voltage power supply and acts as an electrode.
[0022] The outer nozzle (20) is positioned coaxially with the inner nozzle (10) and is located on the outer side of the inner nozzle (10).
[0023] Air and nitrous oxide (N2O), which are oxidizing agents, are supplied to the outer nozzle (20).
[0024] The mixing chamber (30) delivers the fuel, methane (CH4), to the end of the inner nozzle and causes the fuel to be injected from the end of the inner nozzle.
[0025] A quartz tube (40) is provided to surround the inner nozzle (10) and the outer nozzle (20) and acts as a dielectric barrier between the two electrodes.
[0026] The metal mesh (50) is wound around the outer surface of the quartz tube (40) and serves as another electrode. This serves as a ground.
[0027] The metal mesh (50) is made of a metal material including stainless steel.
[0028] A swirler (60) is mounted on the outer surface of the inner nozzle (10) and mixes the oxidizing agent (Air) introduced from the outer nozzle (20).
[0029] The outer surface of the inner nozzle (10) is perforated with a predetermined diameter, and a plurality of holes (80) are perforated at the front and rear ends of the swirler (60) based on the swirler (50).
[0030] Methane (CH4), which is fuel supplied to the inner nozzle (10), is partially guided into a hole (80) perforated in front of the swirler (60) mounted on the outer surface of the inner nozzle (10), mixed with an oxidizer supplied from the outer nozzle (20), and then flows into the swirler (50).
[0031] The fuel remaining in the inner nozzle (10) is all guided to the hole (80) perforated at the rear end of the swirler (60) relative to the swirler (60) and enters the flame surface together with the gas mixture flowing into the outer nozzle (20).
[0032] More preferably, four holes (80) are perforated at the front end of the swirler (50) so that some of the fuel supplied to the inner nozzle (10) is guided and mixed with the oxidizer supplied from the outer nozzle, and then flows into the swirler (50). The fuel remaining in the inner nozzle is all guided to six holes (80) perforated at the rear end of the swirler relative to the swirler (50) and enters the flame surface together with the gas mixture flowing into the outer nozzle (20).
[0033] The reason the number of holes drilled in the internal nozzles drilled in the front and rear ends of the swirler are maintained in a ratio of 4:6 based on the swirler is to prevent flashback to the inside of the front end of the swirler (50).
[0034] Based on a methane premixed flame, the lean flammability limit corresponds to an equivalent ratio of 0.46, and the rich flammability limit corresponds to an equivalent ratio of 1.64.
[0035] Generally, since lean combustion with excess air is adopted in industrial sites to prevent the generation of Thermal NOx, flashback can be prevented if the fuel ratio is maintained lower than an equivalence ratio of 0.46.
[0036] Accordingly, the combustion device according to the present invention introduces and applies a design standard of injecting 40% of the fuel flow rate at the upstream end of the swirler and 60% at the downstream end of the swirler.
[0037] A scrubber (70) is provided to clean nitrogen oxides and sulfur oxides, including NO2 and SO2, that are additionally generated after plasma treatment.
[0038] A scrubber (70) is provided on one side of a plasma combustor to remove nitrogen oxides and sulfur oxides that are additionally generated after thermal decomposition by plasma treatment.
[0039] [Experimental Example 1]
[0040] Applying plasma within the combustion can affect flame stabilization, flame propagation speed improvement, and reduction of exhaust gases due to thermal decomposition.
[0041] When hydrocarbon fuels burn, ions, electrons, and neutrons are generated through chemical ionization. Neutrons account for the majority of these, while electrons account for the majority of negative charges. When an electric field is applied, a short circuit occurs between the ground and the high-voltage electrode, resulting in locally high temperatures and the occurrence of streamer phenomena. Through this, we intend to induce the thermal decomposition of nitrous oxide, a greenhouse gas, to investigate changes in combustion products.
[0042] CASE Φ Ujet(cm / s) N2O (L / min) Air (L / min) CH4 (L / min) Voltage (kV) Hz 1 0.7 307 0.3 12.64 0.929 0 x 2 7 3K 3 5K 4 10 3K 5 5K 6 407 16.86 1.239 0 x 7 7 3K 8 5K 9 10 3K 10 5K
[0043] In this experiment, methane, oxygen, and nitrogen were mixed and combusted at an equivalence ratio of 0.7, and nozzle exit velocities of 307 cm / s and 407 cm / s, respectively, were adopted. N2O was supplied at a fixed flow rate of 0.3 L / min. In addition, the experiment was conducted in a total of 10 cases as shown in Table 1, with the reference flow rate, applied voltage, and applied frequency as variables.
[0044] A swirler combustor with an inner diameter of 11 phi was used for uniform flow, and a quartz tube with an inner diameter of 33 phi was installed to observe the characteristics during combustion.
[0045] A high-voltage generator (Trek, 10 / 10B-HS) was installed in the swirler combustor, and a ground mesh was installed on the outside of the quartz tube to form DBD (Dielectric Barrier Discharge) conditions.
[0046] An exhaust gas analyzer (Testo, testo-350 MARITIME) and FTIR equipment were used to measure the composition and concentration of exhaust gas. Voltages of +7kV and +10kV were applied relative to the VRMS, and frequencies were set to 3000Hz and 5000Hz.
[0048] [Experimental Results]
[0049] Figure 4 shows the amount of N2O decomposed in the Default state, assuming that the basic flame without plasma application is the Default state, analyzed via FTIR. It can be confirmed that more than 90% of N2O is reduced using only the combustor of the present invention without plasma supply.
[0050] Meanwhile, when plasma was supplied, it was found that the N2O reduction rate of Default actually decreased at a nozzle exit velocity of 307 cm / s, and at a nozzle exit velocity of 407 cm / s, the N2O reduction rate improved regardless of the applied frequency and applied voltage when plasma was supplied.
[0051] Generally, when plasma is applied, the flame velocity increases, and while the local flame temperature increases, the flame area decreases. Also, since N2O reduction requires only high temperatures around 1400K, and considering that it is above 2000K, the N2O reduction rate must depend on the heat transfer area rather than the reaction temperature.
[0052] Therefore, it is determined that at a nozzle exit velocity of 307 cm / s, the flame area decreases when plasma is applied, resulting in a decrease in the N2O reduction rate. On the other hand, at a nozzle exit velocity of 407 cm / s, the flow rate is relatively large, and the flame has a relatively large flame area sufficient to completely cover the inner wall of the combustor chamber composed of a quartz tube.
[0053] Therefore, since the flame area was judged to be close to saturation, no significant change in the flame area was observed regardless of whether plasma was applied.
[0054] In addition, it is believed that the N2O reduction rate is improved because the electric field strength of the plasma increases due to the relatively large flame area, which increases the amount of charge composed of cations and anions generated by chemical diphosphorization.
[0055] Figure 4 shows the amount of NO generated when experiments were conducted at each nozzle exit velocity, measured using the exhaust gas analyzer TESTO. It can be seen that approximately 4.5–5% is generated in the default case as N2O decomposes. When plasma is applied, it was found that low NO is generated regardless of the nozzle exit velocity, applied frequency, and applied voltage.
[0056] Figure 4 shows the amount of NO2 generated at each flow rate as measured by TESTO. It can be seen that approximately 0.23–0.26% is generated in the default case as N2O decomposes. When plasma is applied, it was found that relatively high NO2 is generated regardless of the nozzle exit velocity, applied frequency, and applied voltage.
[0057] Figure 5 is a graph showing the N2O decomposition rate, NO decomposition rate, and NO2 decomposition rate in a plasma-applied combustor according to the present invention. Referring to Figure 5, the values represent the decomposition of N2O when plasma is applied. Unlike the default, it can be seen that up to 2% more decomposition occurs at a nozzle exit velocity of 407 cm / s, and the highest reduction rate can be observed at 7 KV and 3 KHz.
[0058] Referring to Figure 5, which shows the amount of NO generated when plasma is applied, it can be seen that the generation rate decreased by 10% and 13% respectively compared to the default value at each flow rate.
[0059] Figure 5 is a graph showing the amount of NO2 generated at each flow rate when plasma is applied, and the amount of NO2 generated increased by 10% and 15%, respectively. It is believed that this is because oxygen atoms generated during the N2O decomposition process combined with NO by the plasma.
[0060] In this experiment, the N2O decomposition rate and NOx production amount were experimentally observed according to changes in nozzle exit velocity, applied voltage, and applied frequency when plasma was applied to a methane flame.
[0061] It was confirmed that when plasma was applied to the flame by applying an electric field, the N2O decomposition rate was reduced by 2% more than the default at a nozzle exit velocity of 407 cm / s.
[0062] In addition, it was confirmed that when plasma was applied, the amount of NO produced decreased by 10–15% and the amount of NO2 produced increased by 10–15%, which confirmed that an oxidation reaction converting NO to NO2 occurred due to the plasma.
[0063] Therefore, the combustor according to the present invention allows for the expectation of a plasma combustor capable of simultaneously reducing N2O and NOx in eco-friendly ships without expensive SCR equipment.
[0064] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications, changes, and substitutions within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiments and accompanying drawings. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention. Explanation of the symbols
[0065] 10 : Internal nozzle 20 : External nozzle 30 : Mixing chamber 40 : Quartz tube 50 : Metal Mesh 60 : Swirler 70 : Scrubber 1 : Plasma-based combustor for N2O reduction
Claims
Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 An inner nozzle connected to a high-voltage power supply and performing the function of an electrode by applying high voltage; an outer nozzle positioned coaxially with the inner nozzle and located outwardly from the inner nozzle; a metal mesh made of a metal material wound around the outer surface of a quartz tube and serving as another electrode; a quartz tube provided surrounding the inner nozzle and the outer nozzle and serving as a dielectric barrier between the two electrodes; A mixing chamber that delivers methane (CH4), a fuel, to the end portion of an inner nozzle and causes the fuel to be injected at the end portion of the inner nozzle; wherein methane is supplied to the inner nozzle and oxygen and nitrous oxide are supplied to the outer nozzle; wherein a swirler is mounted on the outer surface of the inner nozzle to mix the oxidizer flowing in from the outer nozzle; wherein the inner nozzle has an outer surface perforated to a predetermined diameter and the swirler has multiple holes perforated at the front and rear ends relative to the swirler, and wherein the number of holes perforated in the inner nozzle at the front and rear ends relative to the swirler is machined in a ratio of 4:6; wherein the methane (CH4), a fuel supplied to the inner nozzle, is partially guided to the hole perforated at the front end of the swirler mounted on the outer surface of the inner nozzle, mixed with the oxidizer supplied from the outer nozzle, and then flows into the swirler; and wherein the fuel remaining partially in the inner nozzle is at the rear end of the swirler relative to the swirler A plasma-based N2O reduction combustor comprising a scrubber for cleaning nitrogen oxides and sulfur oxides, including NO2 and SO2, additionally generated after plasma treatment, which are all guided through perforated holes and enter the flame face together with the gas mixture flowing into the external nozzle.