Heat insulation spray gun in urea direct injection technology
By employing a double heat insulation structure and reinforcing rib design in the urea direct injection gun, the problem of premature vaporization or decomposition of urea solution at high temperatures is solved, ensuring injection stability and mixing uniformity, improving denitrification effect, and enhancing the thermal stability and deformation resistance of the spray gun.
Patent Information
- Application Number
- CN202522195032.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-17
- Publication Date
- 2025-12-09
- Estimated Expiration
- 2035-10-17
Smart Images
Figure CN223642030U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to urea direct injection technical field especially relates to a heat insulation spray gun in urea direct injection technology. BACKGROUND
[0002] Urea direct injection pyrolysis technology is a high-efficiency and energy-saving technology in the field of flue gas denitrification, which realizes the reduction of nitrogen oxides by directly using high-temperature flue gas to decompose urea solution to produce ammonia. A urea solution with a certain concentration is atomized by a urea direct injection pyrolysis device and then sprayed into the flue duct of the transition section of the gas turbine outlet, and the exhaust gas of the gas turbine is used to pyrolyze the urea solution into a reducing agent required for the SCR denitrification reaction.
[0003] In the existing urea direct injection pyrolysis technology, if the urea solution is in contact with high temperature during spraying, it may vaporize or decompose in advance, forming solid crystalline substances. These crystals will gradually accumulate and block the nozzles or pipelines, affecting the normal spraying of the urea solution. The urea crystals will hinder the full mixing of the solution and the high-temperature flue gas, leading to a decrease in pyrolysis efficiency and insufficient ammonia production, which in turn affects the denitrification effect. Moreover, the vaporization of the urea solution in the nozzle reduces the effective penetration distance of the liquid droplets and decreases the mixing uniformity.
[0004] To solve the problem of urea solution vaporizing or decomposing in advance to form solid crystalline substances during spraying, a heat insulation layer pipeline is arranged outside the cooling air inlet pipe, and a heat preservation layer is arranged inside the heat insulation layer pipeline. The cooling air inlet pipe directly introduces cooling gas, which carries away part of the heat transferred to the urea solution pipeline, forming a first dynamic heat insulation barrier. The heat preservation layer is added inside the heat insulation layer pipeline, forming a second static heat insulation barrier. The heat preservation layer further reduces the heat transfer from the high-temperature flue gas to the urea solution pipeline by inhibiting heat conduction and convection, prolongs the heat transfer path, and reduces the heat flux density. The double heat insulation structure significantly reduces the outer wall temperature of the urea solution pipeline, keeping it below the urea crystallization temperature, thereby avoiding the vaporization or decomposition of the urea solution before spraying.
[0005] However, in the existing urea direct injection pyrolysis technology, high temperature can cause the heat expansion of the sleeve, and the sleeve is prone to radial / axial deformation due to thermal stress concentration. Moreover, during the operation of the double-fluid atomizing spray gun, the spraying impact of compressed air and urea solution causes high-frequency vibration, which can lead to the initiation of fatigue cracks at the root of the spray gun. UTILITY MODEL CONTENT
[0006] The utility model aims at solving the defects in the prior art and provides a heat insulation spray gun in urea direct injection technology, which solves the problem of urea solution vaporizing or decomposing in advance to form solid crystalline substances before spraying.
[0007] To achieve the above-mentioned purpose, the utility model adopts the following technical solutions:
[0008] A heat-insulated spray gun for urea direct injection technology includes a urea direct injection gun body. A heat-insulating layer pipe is disposed on the outside of the urea direct injection gun body. A sealed air inlet is provided at the bottom end of the heat-insulating layer pipe. Two spray gun sealed air interfaces are provided on the outer surface of the heat-insulating layer pipe, allowing the heat-insulating layer pipe to be connected to the outside of the urea direct injection gun body. Four reinforcing ribs are uniformly fixedly connected to the outer surface of the heat-insulating layer pipe. These reinforcing ribs are streamlined and used to modify the flow field distribution. The reinforcing ribs form a rigid support network through a spiral distribution, effectively limiting the radial / axial deformation of the heat-insulating layer pipe caused by thermal expansion. By fitting the heat-insulating layer pipe onto the outside of the urea direct injection gun body, the atomized urea solution flowing inside the urea direct injection gun body will not vaporize or decompose before injection.
[0009] As a further improvement of this utility model, a urea solution pipe is fixedly connected to one end of the urea direct injection gun body. An atomizing air inlet pipe is fixedly connected to the bottom end of the urea solution pipe near the urea direct injection gun body. A cooling air inlet pipe is also fixedly connected to the bottom end of the urea solution pipe near the atomizing air inlet pipe. Urea solution, atomizing air, and cooling air are sequentially introduced through the urea solution pipe, atomizing air inlet pipe, and cooling air inlet pipe, thereby producing a cooled atomized urea solution.
[0010] As a further improvement of this utility model, a nozzle is provided at the bottom of the end of the urea direct injection gun body away from the urea solution pipeline, and the nozzle is used to spray out the generated urea solution.
[0011] As a further improvement of this utility model, the inlets of the urea solution pipeline, the atomizing air inlet pipe, and the cooling air inlet pipe are horizontal and in the same direction. The atomizing air injected into the atomizing air inlet pipe atomizes the urea solution injected into the urea solution pipeline, and the cooling air injected into the cooling air inlet pipe cools the atomized urea solution.
[0012] As a further improvement of this utility model, the inclination angle of the reinforcing rib is set to 30~60°, and an insulation layer is provided inside the insulation layer pipe. The insulation layer material is air gel, and the insulation layer pipe is located outside the cooling air inlet pipe. The inclination angle of 30~60° makes the reinforcing rib and the pipe form an "oblique support", which transforms the concentrated stress into a dispersed oblique tensile stress, avoids local stress concentration, and reduces the risk of crack initiation.
[0013] Compared with the prior art, the advantages of this utility model are as follows:
[0014] 1. The cooling air inlet pipe and the insulation layer pipe provide double insulation, which significantly reduces the temperature of the outer wall of the urea solution pipe to a temperature far below the urea crystallization temperature. This fundamentally prevents the urea solution from prematurely vaporizing or decomposing to form solid crystals before injection.
[0015] 2. By using reinforcing ribs, which are spirally distributed to form a three-dimensional support network, the bending and torsional stiffness of the pipeline is significantly improved. In high-temperature environments, the radial / axial deformation of the pipeline caused by thermal expansion is effectively limited by the rigid network. Attached Figure Description
[0016] Figure 1 This is a three-dimensional structural diagram of the present invention.
[0017] Figure 2 This is a three-dimensional structural diagram of the present invention from another angle.
[0018] In the diagram: 1. Urea solution pipeline; 2. Atomizing air inlet pipe; 3. Cooling air inlet pipe; 4. Urea direct injection gun body; 5. Insulation layer pipeline; 6. Sealed air inlet; 7. Spray gun sealed air interface; 8. Reinforcing rib; 9. Nozzle. Detailed Implementation
[0019] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.
[0020] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.
[0021] See attached document Figure 1 -Appendix Figure 2 A heat-insulated spray gun for urea direct injection technology includes a urea solution pipe 1, an atomizing air inlet pipe 2, a cooling air inlet pipe 3, a urea direct injection gun body 4, a heat insulation layer pipe 5, a sealing air inlet 6, a spray gun sealing air interface 7, a reinforcing rib 8, and a nozzle 9.
[0022] An example is given of using direct injection pyrolysis of urea solution to produce ammonia. In this invention, the reducing agent used in the SCR flue gas denitrification device is urea. The technology employs direct injection pyrolysis of urea to produce ammonia, whereby the urea solution is atomized and injected into the gas turbine exhaust transition flue. The heat from the gas turbine exhaust is used to pyrolyze the urea solution into the reducing agent required for SCR denitrification. The above technical solution is common knowledge in the prior art and will not be elaborated further below.
[0023] The specific process is as follows: First, a 50% urea solution is diluted with demineralized water and then transported through urea solution pipeline 1. Next, atomizing air is introduced into the pipeline 2 to atomize the urea solution. Then, cooling air is introduced into the pipeline 1 through the cooling air inlet pipe 3 to deliver condensing air, thereby generating cooled atomized urea solution. After dilution with demineralized water, the viscosity of the 50% urea solution is significantly reduced, decreasing pipeline transport resistance and avoiding increased pumping energy consumption or pipeline blockage risks caused by high viscosity. The atomizing air breaks the urea solution into micron-sized droplets, increasing the droplet surface area. - It has twice the capacity, allowing for more thorough contact with high-temperature flue gas, increasing the pyrolysis rate, and shortening the ammonia generation time to 0.1-1 seconds, thus meeting the requirements for rapid response.
[0024] Because the heat insulation layer pipe 5 installed on the outside of the urea direct injection gun body 4 is connected through the spray gun sealing air interface 7, after the cooling air enters the pipe 3 to cool the urea solution, it is further insulated by the heat insulation layer inside the heat insulation layer pipe 5. At the same time, heat is dissipated inside the heat insulation layer pipe 5 through the sealing air inlet 6. Finally, the atomized urea solution is sprayed out through the nozzle 9. The cooling air enters the pipe 3 and carries away the local heat of the urea solution pipe through flow, forming the first dynamic heat insulation barrier; while the air gel insulation layer inside the heat insulation layer pipe 5 inhibits heat conduction through low thermal conductivity, forming the second static heat insulation barrier. The combination of the two significantly reduces the temperature of the outer wall of the urea solution pipe, far below the urea crystallization temperature, fundamentally preventing the urea solution from prematurely vaporizing or decomposing to form solid crystals before injection. Moreover, the spray gun sealing air interface 7 ensures a tight connection between the heat insulation layer pipe 5 and the urea direct injection gun body 4, preventing cooling air leakage or intrusion of external high-temperature flue gas, and maintaining the sealing and stability of the heat insulation system. The sealing air inlet 6 injects air to resist the positive pressure of the boiler. The injected air creates a slight positive pressure in the sealed area, forming a "dynamic air curtain" that prevents high-temperature flue gas from flowing back into the urea injection pipe and also prevents external cold air from seeping in. Together with the insulation layer pipe 5 and the cooling air inlet pipe 3, this forms a "dynamic-static" dual insulation system. The cooling air carries away heat through internal flow, while the air injected into the sealed area forms an air film on the outside, further reducing heat transfer from the high-temperature flue gas to the urea solution pipe.
[0025] Four reinforcing ribs 8 are evenly arranged on the outside of the insulation layer pipe 5, with the ribs 8 having an inclination angle of 30~60°. This spiral distribution forms a rigid support network, effectively limiting the radial / axial deformation of the insulation layer pipe caused by thermal expansion. The reinforcing ribs 8, through their spiral distribution, form a three-dimensional support network, significantly improving the pipe's bending and torsional stiffness. In high-temperature environments (300~700℃), the radial / axial deformation of the pipe caused by thermal expansion is effectively limited by the rigid network. The 30~60° inclination angle design creates an "oblique support" between the reinforcing ribs 8 and the pipe, transforming concentrated stress into dispersed oblique tensile stress, avoiding localized stress concentration, and reducing the risk of crack initiation.
[0026] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.
Claims
1. A heat-insulating spray gun for urea direct injection technology, comprising a urea direct injection gun body (4), characterized in that, The urea direct injection gun body (4) is provided with a heat insulation layer pipe (5) on the outside. The bottom end of the heat insulation layer pipe (5) is provided with a sealed air inlet (6). The outer surface of the heat insulation layer pipe (5) is provided with two spray gun sealed air interfaces (7). The spray gun sealed air interfaces (7) can connect the heat insulation layer pipe (5) to the outside of the urea direct injection gun body (4). The outer surface of the heat insulation layer pipe (5) is uniformly fixed with four reinforcing ribs (8). The reinforcing ribs (8) are all streamlined and are used to change the flow field distribution.
2. The heat-insulating spray gun in the urea direct injection technology according to claim 1, characterized in that, One end of the urea direct injection gun body (4) is fixedly connected to a urea solution pipe (1), and the bottom end of the urea solution pipe (1) is fixedly connected to an atomizing air inlet pipe (2) on the side of the urea direct injection gun body (4). The bottom end of the urea solution pipe (1) is located on the side of the atomizing air inlet pipe (2) near the urea direct injection gun body (4) and is fixedly connected to a cooling air inlet pipe (3).
3. The heat-insulating spray gun in the urea direct injection technology according to claim 2, characterized in that, The urea direct injection gun body (4) has a nozzle (9) at the bottom of one end away from the urea solution pipeline (1), and the nozzle (9) is used to spray the atomized urea solution.
4. The heat-insulating spray gun in the urea direct injection technology according to claim 2, characterized in that, The inlets of the urea solution pipeline (1), the atomizing air inlet pipe (2), and the cooling air inlet pipe (3) are horizontal and in the same direction. The atomizing air injected into the atomizing air inlet pipe (2) atomizes the urea solution injected into the urea solution pipeline (1), and the cooling air injected into the cooling air inlet pipe (3) cools the atomized urea solution.
5. The heat-insulating spray gun in the urea direct injection technology according to claim 1, characterized in that, The inclination angle of the reinforcing rib (8) is set to 30~60°. The insulation layer pipe (5) is provided with an insulation layer inside. The insulation layer is made of air gel. The insulation layer pipe (5) is located outside the cooling air inlet pipe (3).