A urea pyrolysis system with urea solution concentration device

Abstract

This utility model discloses a urea pyrolysis system with a urea solution concentration device, belonging to the technical field of urea pyrolysis equipment. The urea solution concentration device includes an evaporator; a heating device is provided inside the evaporator; the heating device is used to heat the urea solution in the evaporator; a steam regulating valve is provided on the evaporator; the steam regulating valve is used to control the temperature of the evaporator. This utility model's urea pyrolysis system, by adding a urea solution concentration device, increases the concentration of the urea solution before it enters the pyrolysis furnace, thereby reducing the overall energy consumption of the urea pyrolysis system and significantly reducing the heat demand of the pyrolysis furnace. This allows for smaller requirements on the selection of the pyrolysis furnace, high-temperature gas pipelines, valves, spray guns, etc. Furthermore, by adding a urea solution concentration device to a traditional urea pyrolysis system, a capacity expansion project can be carried out, thereby achieving the expansion of the denitrification pyrolysis system.

Description

Technical Field

[0001] This utility model belongs to the technical field of urea pyrolysis equipment, specifically relating to a urea pyrolysis system with a urea solution concentration device. Background Technology

[0002] Selective Catalytic Reduction (SCR) technology, based on urea pyrolysis, is widely used in current flue gas denitrification projects as an important means to effectively reduce the content of nitrogen oxides (NOx) in flue gas. This technology relies on an electric heater or an in-furnace gas-to-gas heat exchanger as a heat source to heat and decompose the urea solution, producing ammonia (NH3). Subsequently, the NH3 generated by pyrolysis is injected into the denitrification flue through a specially designed ammonia injection pipe. Under the action of a catalyst, the NH3 reacts with NOx in the flue gas. X A chemical reaction occurs, reducing it to harmless nitrogen (N2) and water (H2O), thereby achieving the goal of flue gas purification and meeting increasingly stringent environmental emission standards.

[0003] In traditional urea pyrolysis systems, such as Figure 1 As shown, urea solution is transported from the plant's urea station to the pyrolysis furnace, where it is atomized and injected into the furnace by spray guns and compressed air. The high-temperature flue gas at the furnace inlet provides the necessary heat for the pyrolysis of the urea solution, causing it to decompose into pyrolysis product gases containing NH3, carbon dioxide (CO2), and water vapor (H2O). These gases are then introduced into the flue gas denitrification system, where they react with NO... X Catalytic reduction reaction is carried out. However, in the denitrification design of thermal power plants, due to differences in coal quality and actual power plant operating conditions, the denitrification inlet parameters often have significant uncertainties. To ensure compliance with mandatory national environmental emission standards, denitrification design usually needs to consider a certain margin. However, setting this margin involves a trade-off between investment costs and actual adaptability: too large a margin may lead to increased investment costs, while too small a margin may bring the risk of downtime for modification. Currently, the modification scheme of urea pyrolysis SCR system often involves the dismantling and redesign of the entire system, which undoubtedly further increases the modification cost.

[0004] To address the aforementioned issues, the concentration of the urea solution is a crucial factor in the design of a urea pyrolysis system. Higher urea solution concentrations require lower solution flow rates and less total heat for pyrolysis, thus reducing the size of the system. However, high-concentration urea solutions also imply higher crystallization temperatures, placing greater demands on the heat tracing of pipelines within the plant area; otherwise, crystallization and blockage in the pipelines can easily occur. Therefore, this invention proposes adding a urea solution concentration device before the pyrolysis furnace to concentrate the urea solution and prevent potential crystallization and blockage problems during the transport of high-concentration urea solutions through the plant's pipelines. Utility Model Content

[0005] The purpose of this invention is to address the aforementioned shortcomings by providing a urea pyrolysis system with a urea solution concentration device. By adding a urea solution concentration device to the traditional urea pyrolysis system, the concentration of the urea solution is increased, while simultaneously preventing crystallization and pipeline blockage caused by high-concentration urea solution entering the urea pyrolysis furnace, ultimately reducing the total heat required for urea pyrolysis. To achieve the above objective, this invention provides the following technical solution:

[0006] A urea solution concentration device includes an evaporator; the evaporator is equipped with a heating device for heating the urea solution in the evaporator; the evaporator is equipped with a steam regulating valve for controlling the temperature of the evaporator.

[0007] Furthermore, the heating device is a heating coil or an electric heating rod.

[0008] Furthermore, the steam regulating valve is an electric regulating valve or a pneumatic regulating valve.

[0009] Furthermore, the evaporator is equipped with a stirrer.

[0010] Furthermore, the evaporator is equipped with a steam trap.

[0011] Furthermore, the evaporator is equipped with a level gauge, a thermometer, and an exhaust pipe; the exhaust pipe is equipped with an exhaust pipe switch valve.

[0012] A urea pyrolysis system includes the aforementioned urea solution concentration device and pyrolysis furnace; the pyrolysis furnace is equipped with a spray gun; the spray gun is connected to the urea solution concentration device via a first pipe; the spray gun is connected to the evaporator of the urea solution concentration device via the first pipe.

[0013] Furthermore, a booster pump is installed on the first pipeline; the booster pump is located on the first pipeline at a position lower than the bottom of the evaporator.

[0014] Furthermore, a spray gun regulating valve is provided on the first pipe near the spray gun.

[0015] Furthermore, the evaporator is provided with a urea solution inlet and a urea solution outlet; the urea solution outlet is connected to an external urea storage tank through a second pipe; the second pipe is provided with a reflux switch valve.

[0016] The beneficial effects of this utility model are:

[0017] 1. This utility model increases the concentration of urea solution before it enters the pyrolysis furnace by adding a urea solution concentration device to the traditional urea pyrolysis system, thereby reducing the overall energy consumption of the urea pyrolysis system.

[0018] 2. The urea pyrolysis system of this utility model significantly reduces the heat demand of the pyrolysis furnace by increasing the concentration of the urea solution. This allows for a reduction in the selection of pyrolysis furnace, high-temperature gas pipelines, valves, spray guns, etc., while the cost of the newly added urea concentration device and supporting accessories is relatively small, which can save investment costs to a great extent.

[0019] 3. The urea pyrolysis system of this utility model can be used for the expansion and renovation of traditional urea pyrolysis systems. It only requires the addition of a urea concentration device and supporting accessories to the traditional urea pyrolysis system to achieve the expansion of the denitrification pyrolysis system without dismantling the original pyrolysis system, thereby saving costs and improving work efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a traditional urea pyrolysis system;

[0021] Figure 2 This is a schematic diagram of the urea pyrolysis system of this utility model;

[0022] In the attached diagram: 1-solution regulating valve, 2-evaporator, 3-booster pump, 4-steam regulating valve, 5-heating device, 6-steam trap, 7-spray gun regulating valve, 8-reflux switch valve, 9-exhaust pipe, 10-stirrer, 11-level gauge, 12-thermometer, 13-spray gun, 14-pyrolysis furnace. Detailed Implementation

[0023] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0024] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also mean including the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0025] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0026] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. The meaning of such spatial relative terms includes different orientations of the device in use or operation, in addition to the orientation depicted in the figure. For example, if the device in the figure is flipped, then an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0027] Example 1

[0028] See attached Figure 2This utility model discloses a urea solution concentration device, comprising an evaporator 2. The evaporator 2 is used to store the urea solution to be concentrated, and its design and selection can be based on the actual urea solution consumption of the project. A heating device 5, which can be a heating coil or an electric heating rod, is installed inside the evaporator 2 to heat the urea solution and increase its concentration. A steam regulating valve 4 is installed on the evaporator 2 to control the temperature inside. The steam regulating valve 4 uses compressed air as a power source and a cylinder as an actuator. It is driven by accessories such as an electric valve positioner, converter, solenoid valve, and position holding valve to achieve on / off or proportional regulation. It receives control signals from the industrial automation control system to regulate various process parameters such as the flow rate, pressure, and temperature of the pipeline medium. Since there is a one-to-one correspondence between the temperature and concentration of a saturated urea solution (see Appendix B of the Technical Specification for Flue Gas Denitrification Design of Thermal Power Plants DL / T5480-2013, the relationship curve of urea solution density, temperature, solubility and boiling point), the concentration of the heated urea solution in the evaporator 2 can be controlled by controlling the temperature in the evaporator 2 through the steam regulating valve 4. When the urea solution reaches the required concentration, the heating device 5 stops heating.

[0029] Specifically, the steam regulating valve 4 can be an electric regulating valve or a pneumatic regulating valve. Electric regulating valves are driven by electrical energy, while pneumatic regulating valves are controlled by an air source. Pneumatic regulating valves offer fast response, safety, reliability, and strong adaptability, but their accuracy is limited, they require a stable air source, and they generate noise. Electric regulating valves offer high control accuracy, convenient remote control, and energy efficiency, but their response is slow, they require a stable power supply, and they are susceptible to electromagnetic interference.

[0030] Specifically, the evaporator 2 is equipped with a stirrer 10. The stirrer 10 is used to stir the urea solution in the evaporator 2, so that the temperature and concentration of the urea solution in the evaporator 2 are more uniform when heated.

[0031] Specifically, the evaporator 2 is equipped with a steam trap 6. The steam trap 6 can automatically remove condensate and non-condensable gases such as air from the evaporator 2 without leaking steam. The steam trap has the function of preventing steam from escaping and draining water, which can ensure uniform heat distribution to the heating equipment. The steam trap 6 can be a disc type or a float type steam trap.

[0032] Specifically, the evaporator 2 is equipped with a level gauge 11, a thermometer 12, and an exhaust pipe 9, with an exhaust pipe switch valve on the exhaust pipe 9. The level gauge 11 is used to monitor the level of the urea solution in the evaporator 2; the thermometer 12 is used to monitor the temperature inside the evaporator 2; the exhaust pipe 9 is located at the top of the evaporator 2 and is used to discharge the gas in the evaporator 2. The gas mainly consists of water vapor, and also contains a small amount of NH3 and CO gas produced by the hydrolysis of the urea solution. This gas can be directly discharged into the flue gas of the SCR inlet flue through the exhaust pipe 9 to participate in the denitrification reaction. In addition, when the heating device 5 uses an electric heating rod, it can be omitted, and the steam trap 6 and thermometer 12 can be omitted.

[0033] Example 2

[0034] See attached Figure 2 A urea pyrolysis system includes a urea solution concentration device and a pyrolysis furnace 14 as described in Example 1. A spray gun 13 is provided on the pyrolysis furnace 14. The spray gun 13 is connected to an evaporator 2 via a first pipe. The concentrated urea solution in the evaporator 2 reaches the spray gun 13 through the first pipe. The spray gun 13 atomizes the urea solution and sprays it into the pyrolysis furnace 14 to generate a pyrolysis product gas composed of NH3, CO2, and H2O. The atomized urea solution is more easily pyrolyzed. A spray gun 13 regulating valve 7 is also provided on a second pipe near the inlet of the spray gun 13 to control the flow rate of the urea solution entering the pyrolysis furnace 14, thereby controlling the NOx concentration at the denitrification outlet. One spray gun 13 regulating valve 7 controls one spray gun 13. The number of regulating valves and spray guns 13 can be determined according to the urea solution flow rate.

[0035] Specifically, a booster pump 3 is installed on the first pipeline. The booster pump 3 is used to pressurize the concentrated urea solution and send it into the spray gun 13. The booster pump 3 is located below the bottom of the evaporator 2 on the first pipeline. After the booster pump 3 pressurizes the urea solution and sends it into the spray gun 13, since the concentrated urea solution is close to saturation, the installation position of the booster pump 3 must be lower than the evaporator 2, with sufficient net positive suction head (NPSH) to prevent cavitation of the pump.

[0036] Specifically, a spray gun 13 regulating valve 7 is installed on the first pipe near the spray gun 13. A spray gun 13 regulating valve 7 is also installed on the second pipe at the inlet of the spray gun 13 to control the flow rate of urea solution entering the pyrolysis furnace 14, thereby controlling the NOx concentration at the denitrification outlet. One spray gun 13 regulating valve 7 controls one spray gun 13, and the number of regulating valves and spray guns 13 can be determined according to the urea solution flow rate.

[0037] Specifically, the evaporator 2 is equipped with a urea solution inlet and a urea solution outlet. The urea solution enters the evaporator 2 through the urea solution inlet, and a solution regulating valve 1 is installed at the urea solution inlet to control the liquid level of the urea solution entering the evaporator 2. The solution regulating valve 1 can be an electric or pneumatic regulating valve. The urea solution outlet is connected to an external urea storage tank through a second pipeline. A reflux switch valve 8 is installed on the second pipeline. When the entire system stops operating, the reflux switch valve 8 is opened, and the remaining urea solution in the evaporator 2 is transported back to the urea storage tank through the second pipeline.

[0038] Example 3:

[0039] A 600MW coal-fired power generating unit, with a denitrification inlet NOx concentration of 200mg / m³ 3 When a denitrification efficiency of 90% is achieved using a traditional urea pyrolysis system, the pyrolysis furnace 14 is designed to produce 142 kg / h of ammonia, requiring approximately 500 kg / h of 50% urea solution. It is equipped with five urea solution spray guns 13, each with a designed flow rate of 100 kg / h. The total heat required for urea solution pyrolysis is approximately 350 kW (at an outlet temperature of 400°C for the pyrolysis furnace 14), and the required high-temperature air flow rate at 600°C is approximately 6600 Nm³. 3 / h (including 10% margin), the high-temperature pyrolysis pipeline diameter is selected as DN650, the diameter of pyrolysis furnace 14 is 2m, and the diameter of the outlet pipeline of pyrolysis furnace 14 is DN600.

[0040] The urea pyrolysis system of this invention is used to pyrolyze urea solution. The evaporator 2 is Φ800X1200. The level gauge 11 and thermometer 12 are both remote measuring points. The solution regulating valve 1 is a DN20 electric regulating valve. The booster pump 3 is a fixed frequency vertical centrifugal pump. A total of 4 spray guns 13 and 4 spray gun regulating valves 7 are provided. The steam regulating valve 4 is an electric regulating valve. The drain valve is a disc-type drain valve. The exhaust pipe 9 switch valve is a DN65 electric switch valve. The reflux switch valve 8 is a DN20 electric switch valve. During operation, the position of the urea solution entering the evaporator 2 is controlled to be within the normal operating level by controlling the opening of the solution regulating valve 1 and observing the display value of the level gauge 11; then, the temperature inside the evaporator 2 is controlled by controlling the opening of the steam regulating valve 4 and observing the display value of the thermometer 12, thereby controlling the final concentration of the urea solution in the evaporator 2 after heating and concentration; finally, the ammonia production of the urea pyrolysis system is controlled by controlling the opening of the spray gun 13 regulating valve 7, ultimately controlling the NOx emission value of the boiler.

[0041] Calculations show that, using the urea pyrolysis system of this invention to pyrolyze urea solution, when the temperature of evaporator 2 is controlled at 122℃, the urea solution concentration at the outlet of evaporator 2 is approximately 75%, the flow rate is 333 kg / h, the total heat required for urea solution pyrolysis is approximately 205 kW, and the required high-temperature air flow rate at 600℃ is approximately 4000 Nm³. 3 / h, the high-temperature pyrolysis pipeline diameter is selected as DN500, the diameter of pyrolysis furnace 14 is 1.6m, the outlet pipeline diameter of pyrolysis furnace 14 is DN450, and the heat required for evaporator 2 is 110KW.

[0042] In summary, this project adopts the urea pyrolysis system of this utility model. The urea pyrolysis system reduces heat by 35KW, achieves an energy saving rate of 10%, reduces the weight of the inlet pipe of the pyrolysis furnace 14 by 23%, the weight of the pyrolysis furnace 14 by 20%, and the weight of the outlet pipe of the pyrolysis furnace 14 by 25%. The valves, insulation and other accessories related to the pipes will also be reduced accordingly.

[0043] Example 4:

[0044] A 600MW coal-fired power generating unit originally had a designed NOx concentration of 200mg / m³ at the denitrification inlet. 3 The NOx concentration at the outlet was 20 mg / m³. 3 Using a traditional urea pyrolysis system, with design data as shown in Example 3, the actual highest NOx concentration at the denitrification inlet was 300 mg / Nm³ due to changes in coal quality during operation. 3 Under the designed ammonia production capacity, the highest NOx concentration at the denitrification outlet is 120 mg / Nm³. 3 It does not meet the national standard of 50mg / Nm 3 The mandatory emission standards necessitate denitrification and capacity expansion retrofitting. Conventional retrofitting involves dismantling the original urea pyrolysis system and redesigning it in the same location. However, by adopting the urea pyrolysis system of this invention, the urea solution concentration can be increased to 75%. Without altering the original system, the output of the original urea pyrolysis system can be increased to 213 kg / h, ammonia production increased by 50%, and the inlet NOx concentration reduced from 320 mg / Nm³. 3 Boiler flue gas concentration reduced to 50 mg / Nm³ 3 This greatly reduces the cost of denitrification retrofitting.

[0045] All technical features in this embodiment can be freely combined according to actual needs. The above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications and substitutions should be covered within the scope of the claims of this utility model. Technologies, shapes, and structural parts not described in detail in this utility model are all known technologies.

[0046] The above embodiments are preferred implementations of this utility model. In addition, other implementations are also included. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this utility model.

Claims

1. A urea pyrolysis system with a urea solution concentration device, characterized in that: The device includes a urea solution concentration unit and a pyrolysis furnace (14); the pyrolysis furnace (14) is equipped with a spray gun (13); the spray gun (13) is connected to the evaporator (2) of the urea solution concentration unit through a first pipe; the urea solution concentration unit includes an evaporator (2); the evaporator (2) is equipped with a heating device (5); the heating device (5) is used to heat the urea solution in the evaporator (2); the evaporator (2) is equipped with a steam regulating valve (4); the steam regulating valve (4) is used to control the temperature of the evaporator (2).

2. The urea pyrolysis system with a urea solution concentration device according to claim 1, characterized in that: The heating device (5) is a heating coil or an electric heating rod.

3. The urea pyrolysis system with a urea solution concentration device according to claim 2, characterized in that: The steam regulating valve (4) is an electric regulating valve or a pneumatic regulating valve.

4. A urea pyrolysis system with a urea solution concentration device according to claim 3, characterized in that: The evaporator (2) is equipped with a stirrer (10).

5. A urea pyrolysis system with a urea solution concentration device according to claim 4, characterized in that: The evaporator (2) is equipped with a steam trap (6).

6. A urea pyrolysis system with a urea solution concentration device according to claim 5, characterized in that: The evaporator (2) is equipped with a level gauge (11), a thermometer (12) and an exhaust pipe (9); the exhaust pipe (9) is equipped with an exhaust pipe switch valve.

7. A urea pyrolysis system with a urea solution concentration device according to claim 1, characterized in that: A booster pump (3) is provided on the first pipeline; the booster pump (3) is located on the first pipeline at a position lower than the bottom of the evaporator (2).

8. A urea pyrolysis system with a urea solution concentration device according to claim 1, characterized in that: A spray gun regulating valve (7) is provided on the first pipe near the spray gun (13).

9. A urea pyrolysis system with a urea solution concentration device according to claim 1, characterized in that: The evaporator (2) is provided with a urea solution inlet and a urea solution outlet; The urea solution inlet is equipped with a solution regulating valve (1); the urea solution outlet is connected to an external urea storage tank through a second pipe; the second pipe is equipped with a reflux switch valve (8).

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