Fuel gas through-flow steam boiler

Abstract

The invention discloses a fuel gas through-flow steam boiler which comprises an upper collecting box, a lower collecting box and a water pipe set communicating the upper collecting box and the lower collecting box, and is characterized in that the water pipe set comprises a flame root cooling pipe, the flame root cooling pipe is located on the outer side of the water pipe set, and the inner side of the flame root cooling pipe is a combustion area used for flame combustion; a gap exists between every two adjacent flame root cooling pipes, a flow guide plate connected with the flame root cooling pipes is arranged on the outer side of each gap, and a plurality of air holes are formed in each flow guide plate and used for allowing combustible gas to penetrate through. Gas channels for combustible gas to flow are formed between the flow guide plates and the pipe walls of the adjacent flame root cooling pipes; flames can be effectively controlled after combustible gas is introduced into the gas channel and ignited, so that the generation of nitrogen oxides is reduced, the heat of the flames is reasonably utilized, the steam generation amount is increased, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of steam boilers, and specifically relates to a gas-fired once-through steam boiler. Background Technology

[0002] Once-through steam boilers are a type of steam boiler. Due to their advantages such as small furnace size, fast gas production, high fuel combustion efficiency, and relatively compact equipment footprint, they have become one of the development directions of steam boilers in recent years. Traditional gas-fired once-through steam boilers typically consist of an upper header, a lower header, and a water pipe assembly connecting the two. The flame enters unidirectionally and burns directly in the water pipe assembly area to heat the water inside the pipes. The resulting steam-water mixture is separated by a gas-liquid separator connected to the upper header to obtain qualified steam for subsequent use.

[0003] Traditional gas-fired once-flow steam boilers directly ignite the heating water pipes or boiler jacket water, allowing the flame to burn freely. This results in several problems: firstly, poor flame stability; low air-fuel ratios lead to incomplete combustion due to oxygen deficiency, increasing carbon monoxide levels in the flue gas and exceeding emission standards; secondly, it wastes fuel and increases fuel consumption. Thirdly, the flame is easily affected by the incoming airflow velocity, causing disordered flame distribution, higher temperatures in the flame center, and increased nitrogen oxide production. Temperature control in concentrated flame areas is difficult. Conventional solutions involve adding excess air to participate in combustion, cooling the flame and controlling nitrogen oxide formation; however, this compromises the problem of incomplete combustion and increased carbon monoxide due to lower flame temperatures. Traditional steam boilers not only have excessively high air-fuel ratios and low heat utilization rates, but also negatively impact boiler steam generation efficiency. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a gas-fired once-through steam boiler, which features two sets of flames in either relative combustion or "L"-shaped combustion, allowing the flames to converge and burn in a specific area. This addresses the problem of incomplete carbon monoxide combustion at the tail of the flame under low air-fuel ratio conditions in single-sided combustion, which leads to increased carbon monoxide emissions in the exhaust gas. Meanwhile, by setting up cooling pipes and guide plates at the flame root to form a special gas channel, the combustible gas is first compressed through section P1 after being introduced, which can effectively reduce the influence of the gas flow rate on the gas in the gas channel. Then, it is expanded through section P2, which can control the flame root after ignition to be fixed in section P2. This can effectively determine the position of the flame intersection area, and furnace water pipes are arranged at the intersection combustion position to absorb the heat in this area and avoid the continuous high temperature from increasing the amount of nitrogen oxides generated.

[0005] The specific solution is as follows: a gas-fired once-through steam boiler, including an upper header, a lower header and a water pipe assembly connecting the two, the water pipe assembly including a flame root cooling pipe, the flame root cooling pipe being located outside the water pipe assembly, and the inner side of the flame root cooling pipe being a combustion zone for flame combustion. There is a gap between adjacent flame root cooling pipes. Outside the gap is a guide plate connected to the flame root cooling pipe. The guide plate is provided with several air holes for combustible gas to pass through. A gas channel for the flow of combustible gas is formed between the guide plate and the pipe wall of the adjacent flame root cooling pipe; On the horizontal cross-section of the gas passage, the line connecting the nearest ends of adjacent flame root cooling pipes is designated as the dividing line. The part of the gas passage from the guide plate to the dividing line is segment P1. Within segment P1, the length of the line connecting the walls of adjacent flame root cooling pipes gradually decreases from the outside to the inside. The part from the dividing line to the edge of the combustion zone is segment P2. Within segment P2, the length of the line connecting the walls of adjacent flame root cooling pipes gradually increases from the outside to the inside.

[0006] The combustible gas is first evenly divided by the air holes on the guide plate, which in turn separates the pressure inside and outside the guide plate, reducing the pressure entering the gas channel. This allows the combustible gas to enter the gas channel in an orderly manner from the outside to the inside through the air holes. The pressure difference can effectively reduce the risk of deflagration and make combustion safer. After entering the gas channel, the combustible gas first accumulates in section P1, which effectively reduces the impact of the incoming airflow on the gas velocity in the gas channel.

[0007] After the gas in section P1 overflows, it gradually flows to section P2. During the flow, the combustible gas is gradually compressed and accelerated. After flowing into section P2, the combustible gas gradually expands and slows down, making the gas flow velocity in section P1 greater than that in section P2. When the igniter ignites the combustible gas, the gas flow velocity characteristics of sections P1 and P2 will have a fixed anchoring effect on the flame root, which can effectively control the flame root in section P2, keeping the flame in a controllable state, avoiding free combustion of the flame, and thus avoiding free convergence of the flame during combustion, solving the problem of temperature disorder in different areas of the flame. Traditional single-sided combustion boilers, under low air-fuel ratio (the ratio of air to combustible gas), suffer from reduced combustion efficiency at the flame tail due to excessively low oxygen content. This leads to incomplete combustion, with some residual carbon monoxide being emitted unburned, resulting in carbon monoxide escape and excessive carbon monoxide emissions in the exhaust gas. Simultaneously, the low air-fuel ratio prevents the combustion zone temperature from being diluted by the cold air, resulting in a high overall combustion temperature. When the flame temperature exceeds 1500℃, nitrogen and oxygen in the air undergo a violent thermal reaction at high temperatures, generating large amounts of nitrogen oxides. This leads to high nitrogen oxide content in the exhaust gas, with nitrogen oxide generation increasing by 2-3% for every 100℃ increase in temperature. To reduce the content of carbon monoxide and nitrogen oxides in exhaust gas, traditional boilers can only increase the air-fuel ratio to allow more air to participate in the combustion reaction, thereby making combustion more complete and reducing carbon monoxide emissions. However, a large amount of air will dilute the temperature of the combustion zone, leading to a decrease in the combustion temperature and thus a decrease in the nitrogen oxide content in the exhaust gas. Also, because some heat is consumed by the air due to the high air-fuel ratio, the temperature of the combustion zone decreases, resulting in an increase in the amount of flue gas. This reduces the heat supplied to water to generate steam, thereby reducing the steam generation efficiency and increasing energy consumption for the same amount of steam production.

[0008] Preferably, the two rows of flame root cooling pipes are respectively arranged opposite each other along the outer edge of the water pipe group, and the combustible gas enters along the gas channel and is ignited to form two sets of flames that burn opposite each other.

[0009] By setting up two opposing flames to converge and burn in a specific area under control, unlike the disorderly convergence of free flames on one side, the flames can be controlled at the root while the tails of the two flames converge and burn in a targeted manner. This focuses more on the locations where carbon monoxide cannot be fully burned or escapes. The residual carbon monoxide is burned by the converging flames, reducing gas escape. Therefore, the carbon monoxide content in the exhaust gas can still be reduced without increasing the air-fuel ratio.

[0010] Because the convergence causes changes in the pressure and velocity of the flames, when the two flames come into contact, the two flames with momentum collide head-on, causing the axial velocity at the central convergence area to decrease sharply. The momentum forms static pressure in the vertical direction, and the axial velocity is converted into radial velocity due to the increase in pressure, so that the flame spreads in the radial direction to form a flame surface, thereby increasing the combustion area and increasing the reaction area between the flame and the combustible gas. This intensifies the flame and makes the combustion more complete.

[0011] At the same time, the two sets of combustible gases are ignited after passing through two rows of gas channels that are set opposite to each other, forming two sets of flames that burn opposite to each other and generate heat at the same time. The heating effect is faster and the steam generation efficiency is higher. Preferably, the water pipe assembly also includes furnace water pipes, with at least one row of furnace water pipes located in the intersection area of ​​the two sets of flames to block the direct convergence of the two sets of flames and absorb the temperature of the flame intersection area so that the flame temperature is below 1500°C, effectively suppressing the generation of nitrogen oxides during combustion. The convergence of two flames intensifies the combustion reaction and generates a large amount of heat. If this heat is not consumed in time, the temperature in the convergence area will rise, which in turn will lead to an increase in the amount of nitrogen oxides generated, exceeding emission standards. However, by installing furnace water pipes in the flame convergence area, the furnace water pipes, which are filled with cold water, absorb the heat and use it to generate steam, thus solving this problem, reducing the temperature at the convergence point, preventing the flame temperature in the convergence area from rising above 1500°C, and inhibiting the generation of nitrogen oxides. Meanwhile, since the flame root is controlled between the two flame root cooling pipes, the flame root cooling pipes will absorb the heat of the flame root to cool the flame root temperature and prevent the temperature from exceeding 1500℃. For the flame of the injection premixed combustion mode that is ignited after the combustible gas is continuously introduced into the gas channel, the combustible gas and the combustion air have been premixed before combustion. Therefore, the flame root reaction is the most intense and the flame root temperature is the highest. If the flame root temperature is lower than 1500℃, the overall flame temperature will be lower than 1500℃ in the absence of flame convergence.

[0012] At the point where the flames meet, the flame temperature is controlled by the furnace water pipes, while at the point where the flames do not meet, the flame temperature is controlled by the cooling pipes at the flame root, in order to control the flame temperature during the overall combustion process and suppress the generation of nitrogen oxides as a whole.

[0013] Compared with traditional boilers, the lower air-fuel ratio results in lower energy consumption. At the same time, the method of controlling the temperature of the combustion zone to suppress the generation of nitrogen oxides is not to absorb the combustion heat by the low temperature air as in traditional boilers, but to absorb it by the cold water in the furnace water pipes. This suppresses the generation of nitrogen oxides and further improves the steam production efficiency. Therefore, the boiler of this application not only reduces energy consumption and improves steam production efficiency, but also maintains the emission of carbon monoxide and nitrogen oxides in the exhaust gas to meet the standards even with a low air-fuel ratio.

[0014] Alternatively, the cooling pipes at the base of the two rows of flames are vertically arranged along the two adjacent outer edges of the water pipe group, and the combustible gas enters along the gas channel and is ignited to form two sets of flames in an "L" shape.

[0015] When the two sets of flames burn in an "L" shape, the axial momentum of the two high-momentum flames no longer directly opposes each other compared to relative combustion, but interacts at a certain angle as soon as they are ejected. Due to the entrainment effect between the two flames, the high-temperature combustion products will be continuously entrained and mixed with fresh reactants to provide a stable ignition source. Therefore, the flame has high stability and strong anti-interference ability. At the same time, this process will burn and consume the residual carbon monoxide, which will also greatly reduce the carbon monoxide content in the exhaust gas. Since the two flames initially intersect, in order to avoid the temperature rising due to the flames intersecting, the furnace water pipes need to be evenly distributed at the point where the two flames mix, so as to enhance the effect of heat absorption by the flames.

[0016] Preferably, the water pipe assembly also includes membrane wall pipes, which are distributed on the outside of the water pipe assembly. A convection zone connected to the combustion zone is formed on the inside of the membrane wall pipes, and a convection pipe is provided in the convection zone.

[0017] The flame burns in the combustion zone, directly heating the cooling pipes at the flame root. At the same time, the high-temperature gas flow from the flame combustion flows to the connected convection zone, where the high-temperature gas flow convection pipes and membrane wall tubes provide indirect heating. Since the heat in the convection zone is generated in the combustion zone, the areas of the combustion zone and the convection zone need to be set in a suitable ratio to ensure sufficient heat to heat the water in the convection pipes and membrane wall tubes to boiling, while avoiding excess heat that would waste resources.

[0018] The diameter of the flame root cooling pipe can be the same as or smaller than that of the membrane wall pipe. The specific size can be adjusted according to the size of the furnace.

[0019] Preferably, the distance d from the guide vane to the dividing line is in the range of 0 < d ≤ r; When d equals r, the guide vane is at its longest; the closer d is to 0, the shorter the guide vane length.

[0020] Preferably, the projected area of ​​segment P1 on the horizontal cross-section of the gas channel is S1, and the projected area of ​​segment P2 on the horizontal cross-section of the gas channel is S2. When the cooling pipes at the root of the adjacent flame are relatively fixed, both S1 and S2 increase with the increase of d.

[0021] The guide vane can be connected at any position between the dividing line and the outermost line connecting the adjacent flame root cooling pipe. As the distance d gradually increases, the length of the guide vane gradually increases, and the initial flow channel of the combustible gas gradually widens. When the initial flow rate Q remains constant, the longer the guide vane, the smaller the ratio of the dividing line length to the guide vane length, and the better the acceleration effect of the P1 section. Consequently, when released in the P2 section, the gas velocity decreases to a greater distance from the flame propagation speed, and the larger the area of ​​S2 becomes. After the combustible gas is ignited, its thermal expansion will cause some of the flame to return. The larger the area of ​​S2, the more flames return. The returned flames re-ignite the combustible gas in the P2 section, forming a stable ignition source, thus resulting in higher flame stability. The larger the area of ​​S2, the farther the flame root is from the flame root cooling pipe, and therefore the cooling effect will decrease accordingly. The distance d from the guide vane to the dividing line is within the range of 0 < d ≤ r, which can meet the flame control requirements. The size of d can be selected independently according to different preset effect preferences.

[0022] Preferably, the vent is positioned near the junction of the guide plate and the cooling pipe at the root of the flame.

[0023] Because the diameter of the flame root cooling pipe is much larger than the width of the gas channel, combustible gas entering the gas channel at any angle will be blocked by the flame root cooling pipe on one side. The flame root cooling pipe blocks the combustible gas, thereby changing the flow direction and speed of the combustible gas, which in turn generates turbulence in the gas channel, making the gas mix more fully and promoting more complete combustion.

[0024] Alternatively, the vents can be positioned in the middle of the baffle plate, allowing combustible gas to pass through the middle of the cooling pipes at the roots of two adjacent flames.

[0025] The vent is located in the middle of the guide plate. The direction of the combustible gas ejected from the vent is between the two flame root cooling pipes. Therefore, it will not be blocked by the flame root cooling pipes when it is ejected. After the gas enters the flame channel, the flow rate slows down and then disperses to both sides. The flow process is uniform. When it flows out of the P1 section, it accelerates more stably, and thus the flame stability is higher.

[0026] Preferably, the deflector is arranged in any one of the following forms: flat plate, arc, or V-shaped bend.

[0027] Preferably, when the guide plate is arranged in an arc or V-shape, the middle part of the guide plate bends and protrudes outward toward the outside of the cooling pipe at the root of the flame.

[0028] When the air hole is set in the middle of the baffle, the arc or V-shaped bend setting relative to the flat baffle will cause the combustible gas to actively separate. This setting further reduces the influence of the initial flow velocity at the air hole on the combustible gas in section P1, so the flow of combustible gas is more stable, and thus the flame stability is high. When the vents are positioned close to the flame root cooling pipes, they can be arranged in a row near one of the flame root cooling pipes, or in two rows near the two flame root cooling pipes respectively. This arrangement will not have the effect of actively separating combustible gases. The guide plates, which are arranged in an arc or V-shape, will cause the vents to face in different directions depending on the connection angle. When the angle between the guide plate and the flame root cooling pipe is less than 90°, the combustible gas will be blocked by the flame root cooling pipe when it enters. When the angle between the guide plate and the inner side of the connection point of the flame root cooling pipe is greater than or equal to 90°, the gas will enter without obstruction. After the gas is injected, it will be blocked by the flame root cooling pipes in the opposite direction, forming gas turbulence, which makes the gas mix more fully and is conducive to more complete combustion. Alternatively, when the guide vane is set in an arc or V-shape, the middle part of the guide vane bends and protrudes towards the inside of the cooling pipe at the root of the flame.

[0029] When the vent is bent inward, the combustible gas will flow inward after flowing out of the vent, and at the same time, it will flow against the bulge on both sides under the action of pressure. Compared with the vent bending in the direction of combustible gas access, the combustible gas will not separate actively. Therefore, the combustible gas in section P1 is greatly affected by the original flow velocity of the vent. Since the combustible gas will also flow against the vent on both sides, the stability is slightly lower than when it is bent outward. Therefore, the flow velocity of the airflow from the outside should not be too high when this is set up.

[0030] Preferably, the pores are configured as circular holes.

[0031] Preferably, the vent is rectangular, and the length direction of the vent is perpendicular to the axis of the cooling pipe at the root of the flame.

[0032] Alternatively, the shape of the pores is not limited to rectangles or circles; any shape such as triangles or polygons can also be selected.

[0033] The guide plate should not be too thin or too thick, as both will increase the difficulty of welding and make it difficult to connect the guide plate to the cooling pipe at the root of the flame.

[0034] The beneficial effects of this invention are as follows: (1) The present invention sets up flames for relative combustion or “L” type combustion, so that the flames can react with each other, avoiding the gas escape phenomenon caused by incomplete combustion of carbon monoxide under low air-fuel ratio, reducing energy consumption while effectively controlling carbon monoxide emissions.

[0035] (2) The present invention utilizes the special layout of the structure to control the flame, thereby fixing the flame combustion position and adjusting the combustion temperature. The flame temperature in the combustion zone is limited by the cooling pipe at the flame root and the furnace water pipe, especially solving the problem of temperature rise when the flames meet, so that the flame temperature does not exceed 1500℃, thereby suppressing the generation of nitrogen oxides, reducing the content of nitrogen oxides in the exhaust gas, and reducing the cost of exhaust gas treatment.

[0036] (3) The present invention enhances the stability of the flame by special combination of the air hole and the flame root cooling pipe, while increasing the controllability of the flame, accurately controlling the position of the flame root, making the temperature distribution clearer, which is conducive to the control and utilization of the temperature of each area of ​​the flame, and indirectly affects the complete combustion.

[0037] (4) The present invention achieves the rational utilization of flame heat through the reasonable layout and special setting of pipelines. The heat of each area is fully absorbed by the water in each pipeline, which improves the steam generation efficiency. Attached Figure Description

[0038] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0039] Figure 1 This is a schematic front view of Embodiment 1 of the present invention; Figure 2 This is a right-side view of Embodiment 1 of the present invention; Figure 3 This is a top half-sectional view of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the distribution of the guide plate and pipes in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the guide plate structure in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the horizontal cross-section of the gas channel in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the distribution of the guide plate and pipes in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the horizontal cross-section of the gas channel in Embodiment 3 of the present invention; Figure 9 This is a schematic diagram of the horizontal cross-section of the gas channel in Embodiment 4 of the present invention; Figure 10 This is a schematic diagram of the guide plate structure in Embodiment 5 of the present invention; Figure 11 This is a schematic diagram of the horizontal cross-section of the gas channel in Embodiment 5 of the present invention; Figure 12 This is a schematic diagram of the horizontal cross-section of the gas channel in Embodiment 6 of the present invention; Figure 13 This is a schematic diagram of the guide plate structure in Embodiment 7 of the present invention; Figure 14 This is a schematic diagram of the guide plate structure in Embodiment 8 of the present invention; Figure 15 This is a schematic diagram of the horizontal cross-section of the gas channel in Embodiment 9 of the present invention; Figure 16 This is a schematic diagram of the horizontal cross-section of the gas channel in Embodiment 10 of the present invention; Figure 17 This is a schematic diagram of the guide plate structure in Embodiment 10 of the present invention; Figure 18 This is a schematic diagram of the guide plate structure in Embodiment 11 of the present invention; In the attached diagram: 1-lower header, 2-water pipe assembly, 21-flame root cooling pipe, 22-membrane wall pipe, 23-convection pipe, 24-furnace water pipe, 3-upper header, 4-guide plate, 41-vent, 5-gas passage, 51-P1 section, 52-P2 section. Detailed Implementation

[0040] To more clearly illustrate the overall concept of this application, a detailed explanation is provided below with reference to the accompanying drawings.

[0041] In the description of this application, it should be understood that the terms indicating connection relationships should be interpreted broadly. In this application, the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0042] Example 1 A gas-fired once-through steam boiler includes an upper header 3, a lower header 1, and a water pipe assembly 2 connecting the two. The water pipe assembly 2 is characterized in that the water pipe assembly 2 includes a flame root cooling pipe 21, the flame root cooling pipe 21 is located outside the water pipe assembly 2, and the inner side of the flame root cooling pipe 21 is a combustion zone for flame combustion. There is a gap between adjacent flame root cooling pipes 21. There is a guide plate 4 connected to the flame root cooling pipe 21 on the outside of the gap. The guide plate 4 is provided with several air holes 41 for combustible gas to pass through. A gas passage 5 for the flow of combustible gas is formed between the walls of the guide plate 4 and the adjacent flame root cooling pipe 21. On the horizontal cross-section of the gas passage 5, the line connecting the nearest ends of adjacent flame root cooling pipes 21 is designated as the dividing line. The portion of the gas passage 5 from the guide plate 4 to the dividing line is segment P1 51. Within segment P1 51, the length of the line connecting the walls of adjacent flame root cooling pipes 21 gradually decreases from the outside to the inside. The portion from the dividing line to the edge of the combustion zone is segment P2 52. Within segment P2 52, the length of the line connecting the walls of adjacent flame root cooling pipes 21 gradually increases from the outside to the inside.

[0043] The water pipe assembly 2 also includes a membrane wall pipe 22, which is distributed on the outside of the water pipe assembly 2. A convection zone connected to the combustion zone is formed on the inside of the membrane wall pipe 22, and a convection pipe 23 is provided in the convection zone.

[0044] The two rows of flame root cooling pipes are respectively set opposite to each other along the outer edge of the water pipe group 2. The combustible gas enters along the gas channel 5 and is ignited to form two sets of flames that burn opposite to each other.

[0045] The water pipe assembly 2 also includes a furnace water pipe 24, which is located in the intersection area of ​​the two sets of flames to block the direct intersection of the two sets of flames and can absorb the temperature of the flame intersection area so that the flame temperature is below 1500℃.

[0046] The distance from the guide vane 4 to the dividing line is d=r; The guide plate 4 is set in a V-shape. The middle part of the guide plate 4 bends and protrudes outward towards the outside of the combustible gas access direction of the flame root cooling pipe 21. The air hole 41 is set in the middle position of the guide plate 4, so that the combustible gas passes through the middle of the two adjacent flame root cooling pipes 21. The air hole 41 is set as a round hole structure.

[0047] The thickness of the guide plate 4 is 1 / 10 of the pipe wall thickness.

[0048] Cold water is introduced into the lower header 1, and gradually rises along the water pipe group 2 until the upper header 3 is full. Combustible gas is introduced through several vents 41 and enters the gas channel 5. Initially, the gas is compressed. As the gas gradually fills P1 and flows out of P1 section 51, it accelerates. Upon entering P2 section 52, the flow rate decreases, and the igniter ignites the gas, forming a flame in P2 section 52 that flows into the combustion zone. At this time, the cooling pipe 21 at the flame root absorbs heat from the flame root to cool it. Simultaneously, the water inside the pipe is heated and boils, generating steam. The two sets of flames interact... The furnace water pipe 24 at the junction absorbs the heat of the flame at the junction to cool the flame. At the same time, the water in the pipe is heated and boiled to produce steam. The high-temperature airflow generated by combustion will flow to the convection zone due to thermal motion. The heat in the airflow will heat the convection pipe 23 and membrane wall pipe 22 in the convection zone, causing the water in the convection pipe 23 and membrane wall pipe 22 to boil rapidly and generate a large amount of steam. The steam is separated into gas and liquid by a gas-liquid separator. The separated water returns to the lower header 1 or upper header 3 through the pipe for evaporation. The upper header 3 or lower header 1 is equipped with a water inlet for water replenishment at any time.

[0049] This invention creates a special gas channel by setting up cooling pipes and guide plates at the flame root, effectively controlling the position of the flame root after the combustible gas is ignited. This allows for a relative combustion scheme, enabling the flames to converge and burn. This convergence effectively solves the problem of incomplete carbon monoxide combustion at the flame tip due to low combustion temperature and low air-fuel ratio. The location of the convergence area can be determined from the flame root position, and furnace water pipes are arranged in this area to absorb the flame temperature at the convergence point, keeping it below 1500℃ and effectively suppressing the formation of nitrogen oxides during combustion. By combining the above solutions, this invention enables combustible gases to still meet emission standards even with a low air-fuel ratio of 1.1, which not only reduces energy consumption but also reduces emissions of nitrogen oxides and carbon monoxide while maintaining low energy consumption.

[0050] The following are the data on the content of each gas in the exhaust gas after the device in this embodiment detects the exhaust gas parameters:

[0051] The emission standard for CO concentration in exhaust gas is 80 ppm, while the emission standard for NOx concentration is 30 ppm. Within the emission standards, the lower the air-fuel ratio, the less energy is consumed. Even with an air-fuel ratio of 1.1, the equipment in this application can still control the NOx concentration within the emission standards, greatly reducing energy consumption and lowering operating costs.

[0052] Example 2 The difference from Embodiment 1 is that in this embodiment, the two rows of flame root cooling pipes 21 are vertically arranged along the two adjacent outer edges of the water pipe group 2. The combustible gas enters along the gas channel 5 and is ignited to form two sets of flames that burn vertically. The rest of the structure is the same.

[0053] Compared to relative combustion, vertical combustion involves the two flames merging to form a large convergence zone. The furnace cooling pipes absorb heat in this convergence zone, and due to the increased number of furnace cooling pipes, the amount of steam generated is greater than in relative combustion.

[0054] Example 3 The difference from Embodiment 1 is that in this embodiment, the middle part of the guide plate 4 bends and protrudes towards the inside of the flame root cooling pipe 21, while the rest of the structure is the same.

[0055] Example 4 The difference from Example 1 is that in this example, d=0.5r, while the rest of the structure is the same.

[0056] At this time, the length of the guide plate 4 decreases, and the area S1 of the P1 region also decreases accordingly, shortening the acceleration process. Compared with Example 1, the flow rate change will decrease, the flame stability will decrease, and the cooling effect will increase.

[0057] Example 5 The difference from Embodiment 1 is that in this embodiment, the air hole 41 is located at the junction of the guide plate 4 and the flame root cooling pipe 21, and the angle between the surface where the air hole 41 is located and the tangent of the weld on the side of the combustion zone is 45°. The rest of the structure is the same.

[0058] Example 6 The difference from Embodiment 1 is that in this embodiment, the air hole 41 is located at the junction of the guide plate 4 and the flame root cooling pipe 21, and the angle between the surface where the air hole 41 is located and the tangent of the weld on the side of the combustion zone is 90°. The rest of the structure is the same.

[0059] When the included angle is 90°, the flame root cooling pipe 21 does not obstruct the combustible gas at all, but the combustible gas will collide with the opposite flame root cooling pipe 21 to form turbulence, resulting in low flame stability.

[0060] Example 7 The difference from Embodiment 1 is that in this embodiment, the air hole 41 is located at the junction of the guide plate 4 and the flame root cooling pipe 21; the air hole 41 is rectangular, and the length direction of the air hole 41 is perpendicular to the axial direction of the flame root cooling pipe 21. The rest of the structure is the same.

[0061] Example 8 The difference from Embodiment 7 is that in this embodiment, the length direction of the air hole 41 is parallel to the axial direction of the flame root cooling pipe 21, while the rest of the structure is the same.

[0062] Example 9 The difference from Embodiment 1 is that the guide plate 4 in this embodiment is arranged in an arc shape, while the rest of the structure is the same.

[0063] Example 10 The difference from Embodiment 1 is that the guide plate 4 in this embodiment is a flat plate, while the rest of the structure is the same.

[0064] Example 11 The difference from Embodiment 1 is that in this embodiment, the guide plate 4 is a flat plate, and the air hole 41 is located at the junction of the guide plate 4 and the flame root cooling pipe 21. The rest of the structure is the same.

[0065] For any parts not mentioned in this application, existing technologies may be used or referenced.

[0066] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0067] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A gas-fired once-through steam boiler, comprising an upper header, a lower header, and a water pipe assembly connecting the two, characterized in that, The water pipe assembly includes a flame root cooling pipe, which is located outside the water pipe assembly, and the inner side of the flame root cooling pipe is the combustion zone. There is a gap between adjacent flame root cooling pipes, and a guide plate connected to the flame root cooling pipe is located outside the gap. The guide plate is provided with a number of air holes for combustible gas to pass through. A gas channel for the flow of combustible gas is formed between the guide plate and the pipe wall of the adjacent flame root cooling pipe. On the horizontal cross-section of the gas channel, the line connecting the nearest ends of adjacent flame root cooling pipes is designated as the dividing line. The portion of the gas channel from the guide plate to the dividing line is segment P1. Within segment P1, the length of the line connecting the walls of adjacent flame root cooling pipes gradually decreases from the outside to the inside. The portion from the dividing line to the edge of the combustion zone is segment P2. Within segment P2, the length of the line connecting the walls of adjacent flame root cooling pipes gradually increases from the outside to the inside.

2. A gas-fired once-through steam boiler according to claim 1, characterized in that, The two rows of flame root cooling pipes are respectively arranged opposite each other along the outer edge of the water pipe group. Combustible gas enters along the gas channel and is ignited to form two sets of flames that burn opposite each other.

3. A gas-fired once-through steam boiler according to claim 1, characterized in that, The two rows of flame root cooling pipes are vertically arranged along the two adjacent outer edges of the water pipe group. Combustible gas enters along the gas channel and is ignited to form two sets of flames in an "L" shape.

4. A gas-fired once-through steam boiler according to claim 2 or 3, characterized in that, The water pipe assembly also includes a furnace water pipe, which is located in the intersection area of ​​the two sets of flames to absorb the temperature of the flame intersection area and keep the flame temperature below 1500℃.

5. A gas-fired once-through steam boiler according to claim 1, characterized in that, The water pipe assembly also includes membrane wall pipes, which are distributed on the outside of the water pipe assembly. A convection zone is formed on the inside of the membrane wall pipes and is connected to the combustion zone. A convection pipe is provided in the convection zone.

6. A gas-fired once-through steam boiler according to claim 1, characterized in that, The distance d from the guide plate to the dividing line is in the range of 0 < d ≤ r.

7. A gas-fired once-through steam boiler according to claim 6, characterized in that, The projected area of ​​segment P2 on the horizontal cross-section of the gas channel is S2, and the projected area of ​​segment P1 on the horizontal cross-section of the gas channel is S1. When the adjacent flame root cooling pipes are relatively fixed, both S1 and S2 increase with the increase of d.

8. A gas-fired once-through steam boiler according to claim 1, characterized in that, The guide plate is configured in any of the following ways: flat, arc, or V-shaped bend.

9. A gas-fired once-through steam boiler according to claim 8, characterized in that, The air vent is located near the junction of the guide plate and the flame root cooling pipe.

10. A gas-fired once-through steam boiler according to claim 8, characterized in that, The air vent is located in the middle of the guide plate.

11. A gas-fired once-through steam boiler according to claim 9 or 10, characterized in that, The vent is rectangular, and the length direction of the vent is perpendicular to the axis of the cooling pipe at the root of the flame.

12. A gas-fired once-through steam boiler according to claim 9 or 10, characterized in that, The pores are configured as circular holes.

13. A gas-fired once-through steam boiler according to claim 8, characterized in that, When the guide plate is arranged in an arc or V-shape, the middle part of the guide plate bends and protrudes outward toward the outside of the flame root cooling pipe.

14. A gas-fired once-through steam boiler according to claim 8, characterized in that, When the guide plate is arranged in an arc or V-shape, the middle part of the guide plate bends and protrudes towards the inside of the flame root cooling pipe.

Images