Low-load scr denitration inlet flue gas temperature adjusting system and method

Abstract

The application provides a low-load SCR denitration inlet flue gas temperature adjusting system and method, relates to the technical field of boiler flue gas denitration temperature control, and solves the problems of insufficient heat supplement, complex modification and the incapability of realizing cross-period heat distribution caused by the simple dependence on the internal heat redistribution of a boiler under a low-load working condition, realizes stable improvement of the inlet flue gas temperature of the SCR denitration system under a deep peak regulation condition, guarantees the denitration efficiency, reduces the real-time heat supplement cost of electric heating, and improves the operation flexibility and economic efficiency of the power plant.

Description

Technical Field

[0001] This invention relates to the field of boiler flue gas denitrification temperature control technology, specifically to a low-load SCR denitrification inlet flue gas temperature regulation system and method. Background Technology

[0002] Selective catalytic reduction (SCR) denitrification technology is an important technical route for ultra-low NOx emission control in circulating fluidized bed boilers. Typically, the SCR reactor is located between the economizer and air preheater in the boiler's tail flue area. After the flue gas mixes with the reducing agent, it flows through the SCR catalyst bed, where the NOx is reduced to nitrogen and water under the action of the catalyst. The denitrification efficiency of the SCR catalyst is closely related to the inlet flue gas temperature. Commonly used catalysts need to operate within a relatively stable temperature window. In engineering, the commonly suitable temperature window is approximately 300℃ to 400℃, with the specific temperature range determined by the catalyst type, flue gas composition, and operating conditions.

[0003] Under high-load conditions, the boiler furnace heat release intensity and tail flue gas temperature are relatively high, and the SCR inlet flue gas temperature can generally meet the catalyst activity requirements. However, with the large-scale integration of new energy sources and the grid's requirement for deep peak shaving of coal-fired units, the low-load operating time of coal-fired units has increased significantly. When the boiler is operating at low load, the furnace outlet flue gas temperature, tail flue gas temperature, and economizer outlet flue gas temperature may all decrease, causing the SCR inlet flue gas temperature to fall below the catalyst's efficient reaction range. At this time, even if the ammonia injection rate is increased, it is difficult to achieve the ideal denitrification efficiency, and it may lead to problems such as ammonia escape and downstream equipment deposition and corrosion.

[0004] Existing SCR inlet flue gas temperature regulation technologies mainly achieve this through flue gas bypass, hot air injection, feedwater bypass, hot water recirculation, economizer grading, and water-cooled temperature control or flow path switching. These solutions can improve the problem of insufficient SCR inlet flue gas temperature under low load to some extent, but they still have the following shortcomings: First, some solutions rely on the existing high-temperature flue gas, hot air, or water-side heat exchange conditions during the current boiler operation, which is essentially a redistribution of heat within the boiler. The ability of a single solution to increase flue gas temperature may be limited under extremely deep peak-shaving conditions. Second, some solutions require modification of high-temperature flue gas pipelines, high-temperature and high-pressure feedwater systems, or economizer systems, which is difficult to implement and requires high investment. Third, there is a lack of existing technologies that combine electric heating energy storage during periods of surplus power with heat storage and release during periods of low load, and directly supplement the upstream of the SCR catalyst layer with high-temperature air or heated circulating flue gas.

[0005] Therefore, there is still a need for an SCR denitrification inlet flue gas temperature regulation system suitable for low-load and deep peak-shaving conditions. This system should be able to provide a controllable, stable, and flexible heat source upstream of the SCR catalyst layer through electric heating, high-temperature air injection, flue gas reinjection, and heat storage and release, without significantly altering the boiler's main heating surface and high-temperature, high-pressure water system. This would increase the SCR inlet flue gas temperature and ensure the stable and efficient operation of the SCR denitrification system under low-load conditions. Summary of the Invention

[0006] This disclosure provides a low-load SCR denitrification inlet flue gas temperature regulation system and method. Its main purpose is to solve the problem that under low-load operating conditions, the SCR denitrification inlet flue gas temperature is lower than the catalyst's suitable reaction temperature window, which leads to a decrease in denitrification efficiency and an increased risk of ammonia slip.

[0007] To achieve the above objectives, a first aspect of the present invention provides a low-load SCR denitrification inlet flue gas temperature regulation system, comprising: The temperature monitoring module is configured to detect the flue gas temperature in the upstream flue of the SCR reactor and generate a temperature signal. An air supply module, configured to deliver air; The flue gas extraction module is configured to extract flue gas from the upstream flue of the economizer. The heat storage module is fluidly connected to the air supply module and the flue gas extraction module, respectively, and is configured to use the heat stored therein to perform primary heating of the air and / or flue gas entering the heat storage module. An electric heating module is connected to the outlet of the heat storage module and is configured to perform secondary heating on the gas after the primary heating. A hot gas injection module is connected to the outlet of the electric heating module and is configured to inject the gas heated in the secondary stage into the upstream flue of the SCR reactor. The control module is communicatively connected to the temperature monitoring module, air supply module, flue gas extraction module, heat storage module, and electric heating module, respectively. It is configured to receive the temperature signal and, based on a comparison of the temperature signal with a preset lower temperature limit, control the air supply module and / or the flue gas extraction module to provide air and / or flue gas to the heat storage module, and control the heat release of the heat storage module and the heating power of the electric heating module, so that the temperature of the gas injected through the hot gas injection module reaches the set temperature.

[0008] In one embodiment of the present invention, the hot gas injection module includes an injection main pipe and a plurality of injection branch pipes connected to the injection main pipe. The plurality of injection branch pipes are arranged along the cross-sectional direction of the upstream flue of the SCR reactor. Each injection branch pipe is provided with at least one nozzle to uniformly inject the gas after secondary heating into the flue gas.

[0009] In one embodiment of the present invention, the temperature monitoring module includes a first temperature sensor disposed in the upstream flue of the SCR reactor and a second temperature sensor disposed in the upstream flue of the economizer. The control module is further configured to receive a second temperature signal generated by the second temperature sensor and utilize the second temperature signal when determining the heat replenishment method.

[0010] In one embodiment of the present invention, the control module is further configured to: acquire a boiler load signal; and determine that the system enters a low-load supplementary heating mode when the boiler load is lower than a preset load threshold or the temperature signal is lower than the preset lower temperature limit.

[0011] In one embodiment of the present invention, the control module is further configured to: select one mode to operate from the following based on the deviation between the temperature signal and the preset lower limit of temperature, the remaining heat storage of the heat storage module, the temperature of the flue gas upstream of the economizer, and electricity price information: an air heating supplementary heating mode that only activates the air supply module, a combined supplementary heating mode that simultaneously activates the air supply module and the flue gas extraction module, and a high-temperature flue gas auxiliary supplementary heating mode that prioritizes activating the flue gas extraction module when limiting the power consumption of the electric heating module.

[0012] In one embodiment of the present invention, the control module is further configured to: when the boiler load is higher than a preset high load threshold or during a period of surplus power, control the thermal storage module to enter a charging mode, and use an electric heating module or an external power source to heat and store the thermal storage medium in the thermal storage module.

[0013] In one embodiment of the present invention, the control module is further configured to: when starting supplementary heating, start the air supply module and / or flue gas extraction module after the temperature signal is lower than the preset lower limit for a first preset time; when exiting supplementary heating, stop supplementary heating or reduce the supplementary heating intensity after the temperature signal is higher than the preset exit temperature for a second preset time.

[0014] In one embodiment of the present invention, the heat storage medium in the heat storage module includes at least one of magnesia bricks, refractory bricks, cast iron, ceramic heat storage body or molten salt.

[0015] In one embodiment of the present invention, the inlet of the flue gas extraction module is located on the flue after the superheater outlet and before the economizer inlet, so as to extract the flue gas that has not yet been cooled by the economizer.

[0016] To achieve the above objectives, a second aspect of the present invention provides a method for adjusting the inlet flue gas temperature of a low-load SCR denitrification system, comprising: Detect the flue gas temperature in the upstream flue of the SCR reactor; When the flue gas temperature is lower than the preset lower limit, based on the deviation between the flue gas temperature and the preset lower limit and the remaining heat storage capacity of the heat storage module, one of the following heat replenishment modes is selected for execution: air heating heat replenishment mode, combined heat replenishment mode, or high-temperature flue gas auxiliary heat replenishment mode. In the selected heat replenishment mode, air and / or flue gas drawn from the upstream flue of the economizer are supplied to the heat storage module. The heat stored in the heat storage module is used to perform primary heating of the air and / or flue gas. Then, the gas after primary heating is subjected to secondary electric heating, and the gas after secondary heating is injected into the upstream flue of the SCR reactor. Based on the flue gas temperature, the supply of air and / or flue gas, the heat release of the heat storage module, and the heating power of the electric heater are adjusted to maintain the flue gas temperature within a preset temperature range.

[0017] When the charging conditions are met, the heat storage module stores heat.

[0018] The low-load SCR denitrification inlet flue gas temperature regulation system and method of this invention have the following beneficial effects: First, the present invention can rapidly increase the inlet flue gas temperature of the SCR catalyst bed under low boiler load or deep peak shaving conditions, so as to keep the SCR catalyst within a suitable reaction temperature window and improve the denitrification efficiency under low load.

[0019] Secondly, by injecting the supplementary heating medium into the flue gas mixing section upstream of the SCR catalyst layer, the supplementary heating system is relatively decoupled from the boiler combustion system, reducing the impact on the main combustion organization and heating surface arrangement of the boiler, making it suitable for retrofitting existing units.

[0020] Third, this invention utilizes the sensible heat of flue gas upstream of the economizer or other high-temperature areas through high-temperature flue gas bypass reinjection, reducing the energy required to directly heat cold air and improving the economic efficiency of heat replenishment.

[0021] Fourth, the present invention enables the storage of heat during periods of high load or surplus power and the release of heat during periods of low load through a heat storage device, which is beneficial for absorbing surplus power and reducing the power demand for real-time heat replenishment during low load.

[0022] Fifth, this invention achieves closed-loop regulation through temperature sensors and a control system, which can dynamically adjust the flow rate of the supplementary heating medium, the electric heating power, the circulating flue gas volume, and the valve opening according to the SCR inlet flue gas temperature, avoiding excessively low or high flue gas temperatures or uneven local mixing, thereby improving the safety and stability of the system.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of a low-load SCR denitrification inlet flue gas temperature regulation system according to an embodiment of the present invention; Figure 2 This is a flowchart of a low-load SCR denitrification inlet flue gas temperature regulation and control method according to an embodiment of the present invention.

[0025] Among them, 1-tail flue; 2-high temperature flue gas extraction fan; 3-air fan; 4-heat storage device; 5-electric heating device; 6-control center; 7-hot gas injection device; 8-air preheater; 9-SCR reactor; 10-SCR inlet thermometer; 11-economizer; 12-superheater post-thermometer; 13-superheater. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] The following description, with reference to the accompanying drawings, describes a low-load SCR denitrification inlet flue gas temperature regulation system and method according to an embodiment of the present invention.

[0029] Example 1 Figure 1 This is a schematic diagram of a low-load SCR denitrification inlet flue gas temperature regulation system according to an embodiment of the present invention, as shown below. Figure 1 As shown, it includes: The temperature monitoring module is configured to detect the flue gas temperature in the upstream flue of the SCR reactor and generate a temperature signal. The air supply module is configured to supply air; the flue gas extraction module is configured to extract flue gas from the upstream flue of the economizer. The heat storage module is fluidly connected to the air supply module and the flue gas extraction module, respectively, and is configured to use the heat stored therein to perform primary heating of the air and / or flue gas entering the heat storage module. An electric heating module is connected to the outlet of the heat storage module and is configured to perform secondary heating on the gas after the primary heating. A hot gas injection module is connected to the outlet of the electric heating module and is configured to inject the gas heated in the secondary stage into the upstream flue of the SCR reactor. The control module is communicatively connected to the temperature monitoring module, air supply module, flue gas extraction module, heat storage module, and electric heating module, respectively. It is configured to receive the temperature signal and, based on a comparison of the temperature signal with a preset lower temperature limit, control the air supply module and / or the flue gas extraction module to provide air and / or flue gas to the heat storage module, and control the heat release of the heat storage module and the heating power of the electric heating module, so that the temperature of the gas injected through the hot gas injection module reaches the set temperature.

[0030] An embodiment of the present invention provides a low-load SCR denitrification inlet flue gas temperature regulation system that can stably increase the SCR inlet flue gas temperature under low-load and deep peak-shaving conditions, keeping the SCR catalyst layer inlet flue gas temperature within a suitable reaction temperature window, thereby improving the low-load denitrification efficiency and reducing the risk of SCR denitrification system shutdown, increased NOx emissions, and increased ammonia slip caused by insufficient flue gas temperature.

[0031] Example 2 The following description, in conjunction with the accompanying drawings, details an embodiment of the present invention: a low-load SCR denitrification inlet flue gas temperature regulation system.

[0032] like Figure 1 As shown, this invention provides an SCR denitrification inlet flue gas temperature regulation system for low-load operation. The system includes a tail flue 1, a high-temperature flue gas extraction fan 2, an air fan 3, a heat storage device 4, an electric heating device 5, a control center 6, a hot gas injection device 7, an air preheater 8, an SCR reactor 9, an SCR inlet thermometer 10, an economizer 11, a superheater post-thermometer 12, and a superheater 13.

[0033] The boiler tail flue connects sequentially to the superheater, economizer, SCR reactor, and air preheater along the main flue gas flow direction. An SCR catalyst layer is installed inside the SCR reactor. The outlet of the hot gas injection device is located upstream of the SCR reactor. The hot gas injection device includes multiple injection branches arranged along the flue gas cross-section to improve the mixing uniformity of the supplementary heating medium and the main flue gas.

[0034] The air supply pipeline is connected to the air fan, heat storage device, electric heating device, and hot gas injection device. After being heated by the electric heating device and the heat storage device, the air becomes high-temperature air, enters the hot gas injection device, and is injected into the flue upstream of the SCR catalyst layer.

[0035] The flue gas extraction pipeline inlet is located in the upstream flue of the economizer. The pipeline connects to a heat storage device via a high-temperature flue gas extraction fan. Within the heat storage device, the flue gas mixes with and is heated by the air. Subsequently, it passes through an electric heating device, and once the set temperature is reached, it is injected into the upstream section of the SCR catalyst layer via a hot gas injection device, where it mixes with the flue gas in the flue. Thus, some of the high-temperature flue gas can bypass the economizer cooling process and be directly or after heating back into the flue before the SCR inlet.

[0036] The thermal storage device can store heat through electric heating when the boiler is under high load, during periods of surplus electricity, or during periods of low electricity price, and release heat under low load conditions to heat the air entering the thermal storage device and / or extract flue gas.

[0037] The control system is connected to temperature sensors, electric heating devices, heat storage devices, high-temperature flue gas extraction fans, and air fans. Two temperature sensors are installed inside the flue: an SCR inlet thermometer 10 and a superheater post-thermal thermometer 12, to form a closed-loop control.

[0038] When the boiler is under low load and the flue gas temperature at the SCR inlet measured by the SCR inlet thermometer 10 is lower than the preset lower limit, the control center 6 prioritizes activating the air heating supplementary heating mode. In this mode, the high-temperature flue gas extraction fan 2 stops operating, the air fan 3 starts, and air enters the heat storage device 4 through the air supply pipeline, where it exchanges heat with the heat storage medium and undergoes primary heating. The air preheated by the heat storage device 4 enters the electric heating device 5, where it undergoes secondary heating or temperature fine-tuning to form high-temperature air that meets the set temperature requirements.

[0039] High-temperature air enters the upstream flue gas mixing section of the SCR reactor 9 through the hot gas injection device 7, and is fully mixed with the main flue gas through multiple injection branches or nozzles arranged along the cross-section of the tail flue 1, thereby increasing the inlet flue gas temperature of the SCR reactor 9.

[0040] Based on the feedback signal from the SCR inlet thermometer 10, the control center 6 adjusts the airflow of the air fan 3, the heat release of the heat storage device 4, and the heating power of the electric heating device 5. When the heat released by the heat storage device 4 is sufficient to meet the heat replenishment requirements, the electric heating device 5 may not be started or may operate at low power; when the air temperature is still lower than the set value after the heat storage device 4 releases heat, the electric heating device 5 replenishes the required heat and performs fine-tuning of the outlet temperature.

[0041] When the SCR inlet flue gas temperature deviation is large, or when the air heating supplementary heating mode alone cannot meet the target flue gas temperature requirement, the control center 6 activates the combined supplementary heating mode. In this mode, the air fan 3 and the high-temperature flue gas extraction fan 2 operate simultaneously, and the air and the high-temperature flue gas extracted from the outlet of the superheater 13 and the inlet of the economizer 11 enter the heat storage device 4 together.

[0042] Air and high-temperature flue gas are mixed in the heat storage device 4, and primary heating is performed using the sensible heat of the high-temperature flue gas itself and the heat released by the heat storage medium. The mixed supplementary heating gas after primary heating enters the electric heating device 5, where secondary heating or temperature fine-tuning is performed. After reaching the set temperature, it is injected into the upstream flue of the SCR reactor 9 through the hot gas injection device 7.

[0043] In the combined heating mode, the control center 6 adjusts the airflow, high-temperature flue gas extraction rate, heat release from the heat storage device 4, and power of the electric heating device 5 based on parameters such as the SCR inlet flue gas temperature deviation, the flue gas temperature after the superheater, the temperature of the heat storage device 4, and the electricity price. This mode is suitable for operating conditions with a large flue gas temperature gap, insufficient single air heating capacity, or the need to rapidly increase the SCR inlet flue gas temperature.

[0044] When the residual heat of the thermal storage device 4 is insufficient, and the current electricity price is high or the power consumption of the electric heating device 5 needs to be limited, the control center 6 determines whether the flue gas upstream of the economizer 11 has usable sensible heat based on the flue gas temperature measured by the thermometer 12 after the superheater. When the conditions for high-temperature flue gas extraction are met, the control center 6 activates the high-temperature flue gas auxiliary heating mode.

[0045] In this mode, air fan 3 continues to operate, and high-temperature flue gas extraction fan 2 extracts a portion of the high-temperature flue gas from the outlet of superheater 13 and before the inlet of economizer 11, and sends it to the heat storage device 4. The high-temperature flue gas is mixed with air as an auxiliary heat source. The mixed gas is heated in the heat storage device 4 using the sensible heat of the high-temperature flue gas and the residual heat of the heat storage device 4, and then enters the electric heating device 5 for secondary heating or temperature fine-tuning.

[0046] When the mixed gas after primary heating has reached the set temperature, the electric heating device 5 can stop operating; when the temperature of the mixed gas is still lower than the set value, the electric heating device 5 only supplements the remaining heat. By introducing high-temperature flue gas, the operating power and electricity consumption of the electric heating device 5 can be reduced, thereby lowering the supplementary heating cost during periods of high electricity prices.

[0047] Corresponding to the aforementioned low-load SCR denitrification inlet flue gas temperature regulation system, such as Figure 2 As shown, a control method is also proposed, which includes the following steps: Step 1: Collect boiler operating parameters. Control center 6 collects operating parameters such as boiler load, flue gas temperature before SCR inlet measured by SCR inlet thermometer 10, flue gas temperature upstream of economizer measured by superheater post thermometer 12, temperature of thermal storage device 4, outlet temperature of electric heating device 5, flow rate of air fan 3, and flow rate of high-temperature flue gas extraction fan 2.

[0048] Step 2: Determine whether to enter low-load supplementary heating mode. When the boiler load is lower than the preset load threshold, or the flue gas temperature before the SCR inlet measured by the SCR inlet thermometer 10 is lower than the preset lower limit, the control center 6 determines that the system has entered low-load supplementary heating mode.

[0049] Step 3: Select the supplementary heating method. The control center 6 selects from the following supplementary heating modes based on the SCR inlet flue gas temperature measured by the SCR inlet thermometer 10, the temperature and remaining heat storage of the heat storage device 4, the high-temperature flue gas temperature measured by the superheater post-thermometer 12, the current electricity price or power surplus, and the SCR inlet flue gas temperature deviation: air heating supplementary heating mode, combined supplementary heating mode, or high-temperature flue gas auxiliary supplementary heating mode. All three modes use the heat storage device 4 for primary heating and the electric heating device 5 for secondary supplementary heating or temperature fine-tuning. When the SCR inlet flue gas temperature deviation is small, and air supplementary heating alone can meet the flue gas temperature requirements, the air heating supplementary heating mode is prioritized. The air fan 3 is started, allowing air to pass sequentially through the heat storage device 4 and the electric heating device 5 for heating before being injected into the upstream flue of the SCR reactor 9. When the SCR inlet flue gas temperature deviation is large, or when the air heating supplementary heating mode alone cannot meet the target flue gas temperature requirement, a combined supplementary heating mode is adopted. Air fan 3 and high-temperature flue gas extraction fan 2 are simultaneously activated, allowing the air and extracted high-temperature flue gas to mix within the heat storage device 4 and undergo primary heating, followed by secondary supplementary heating via electric heating device 5. When the remaining heat in the heat storage device 4 is insufficient and the current electricity price is high, or when it is necessary to limit the electric heating power, the high-temperature flue gas auxiliary supplementary heating mode is prioritized. When the flue gas temperature after the superheater meets the extraction conditions, the high-temperature flue gas extraction fan 2 is activated, utilizing the sensible heat of the high-temperature flue gas to increase the temperature of the mixed gas entering the heat storage device 4, thereby reducing the power consumption of the electric heating device 5. When the heat release of the heat storage device 4 or the sensible heat of the high-temperature flue gas is insufficient, the control center 6 increases the output power of the electric heating device 5 to bring the supplementary heating gas to the set temperature. Based on the feedback signal from the SCR inlet thermometer 10, the control center 6 adjusts the airflow, high-temperature flue gas extraction rate, heat release of the heat storage device 4, and power of the electric heating device 5 in real time to maintain the SCR inlet flue gas temperature within the preset temperature range.

[0050] When switching between different supplementary heating modes, the control center 6 sets the temperature hysteresis and the minimum running time. Supplementary heating is started when the SCR inlet flue gas temperature is lower than the preset lower limit and remains below the preset lower limit for a preset time; supplementary heating is stopped or the supplementary heating intensity is reduced when the SCR inlet flue gas temperature is higher than the exit temperature and remains above the preset exit temperature for a preset time, thereby avoiding frequent start-stop of the fan and electric heating device due to short-term fluctuations in flue gas temperature.

[0051] Step four, perform supplementary heating adjustment. The control center 6 adjusts the operating status of the air fan 3, the high-temperature flue gas extraction fan 2, the heat storage device 4, and the electric heating device 5, so that the air and / or the extracted high-temperature flue gas are mixed and heated in the heat storage device 4, and then precisely heated by the electric heating device 5, and then injected into the flue gas mixing section upstream of the SCR reactor 9 through the hot gas injection device 7, where it is fully mixed with the main flue gas.

[0052] Step 5: Maintain stable SCR inlet flue gas temperature. Control center 6 uses the SCR inlet flue gas temperature measured by SCR inlet thermometer 10 as the primary control target, maintaining the SCR reactor 9 inlet flue gas temperature within a preset suitable temperature window. This preset suitable temperature window can be determined based on the SCR catalyst type. For vanadium-titanium SCR catalysts commonly used in coal-fired units, it is preferably controlled within the range of 300℃ to 400℃, but can also be adjusted according to the catalyst model and actual flue gas conditions.

[0053] Step Six: Exit supplementary heating or switch to thermal storage. When the boiler load increases and the flue gas temperature before the SCR inlet measured by the SCR inlet thermometer 10 meets the denitrification requirements, the control center 6 gradually reduces the supplementary heating intensity until it exits the low-load supplementary heating mode. When the boiler is operating at high load, the SCR inlet flue gas temperature meets the requirements, or there is a surplus of electricity, the control center 6 controls the thermal storage device 4 to enter the charging mode to reserve heat for subsequent low-load supplementary heating.

[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A low-load SCR denitrification inlet flue gas temperature regulation system, characterized in that, include: The temperature monitoring module is configured to detect the flue gas temperature in the upstream flue of the SCR reactor and generate a temperature signal. An air supply module, configured to deliver air; The flue gas extraction module is configured to extract flue gas from the upstream flue of the economizer. The heat storage module is fluidly connected to the air supply module and the flue gas extraction module, respectively, and is configured to use the heat stored therein to perform primary heating of the air and / or flue gas entering the heat storage module. An electric heating module is connected to the outlet of the heat storage module and is configured to perform secondary heating on the gas after the primary heating. A hot gas injection module is connected to the outlet of the electric heating module and is configured to inject the gas heated in the secondary stage into the upstream flue of the SCR reactor. The control module is communicatively connected to the temperature monitoring module, air supply module, flue gas extraction module, heat storage module, and electric heating module, respectively. It is configured to receive the temperature signal and, based on a comparison of the temperature signal with a preset lower temperature limit, control the air supply module and / or the flue gas extraction module to provide air and / or flue gas to the heat storage module, and control the heat release of the heat storage module and the heating power of the electric heating module, so that the temperature of the gas injected through the hot gas injection module reaches the preset temperature value.

2. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 1, characterized in that, The hot gas injection module includes an injection main pipe and multiple injection branch pipes connected to the injection main pipe. The multiple injection branch pipes are arranged along the cross-sectional direction of the upstream flue of the SCR reactor. Each injection branch pipe is provided with at least one nozzle to uniformly inject the gas after secondary heating into the flue gas.

3. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 1, characterized in that, The temperature monitoring module includes a first temperature sensor installed in the upstream flue of the SCR reactor and a second temperature sensor installed in the upstream flue of the economizer. The control module is further configured to receive a second temperature signal generated by the second temperature sensor and to utilize the second temperature signal when determining the heat replenishment method.

4. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 1, characterized in that, The control module is further configured to: acquire the boiler load signal; and determine that the system enters a low-load supplementary heating mode when the boiler load is lower than a preset load threshold or the temperature signal is lower than the preset lower temperature limit.

5. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 4, characterized in that, The control module is further configured to select one of the following modes for operation based on the deviation between the temperature signal and the preset lower limit of the temperature, the remaining heat storage capacity of the heat storage module, the temperature of the flue gas upstream of the economizer, and the electricity price information: an air heating supplementary heating mode that only activates the air supply module, a combined supplementary heating mode that simultaneously activates the air supply module and the flue gas extraction module, and a high-temperature flue gas auxiliary supplementary heating mode that prioritizes activating the flue gas extraction module when limiting the power consumption of the electric heating module.

6. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 1, characterized in that, The control module is further configured to: when the boiler load is higher than the preset high load threshold or during a period of surplus power, control the thermal storage module to enter the charging mode, and use an electric heating module or an external power source to heat and store the thermal storage medium in the thermal storage module.

7. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 1, characterized in that, The control module is further configured to: when starting supplemental heating, start the air supply module and / or flue gas extraction module after the temperature signal is lower than the preset lower limit for a first preset time; when exiting supplemental heating, stop supplemental heating or reduce the supplemental heating intensity after the temperature signal is higher than the preset exit temperature for a second preset time.

8. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 1, characterized in that, The heat storage medium in the heat storage module includes at least one of magnesia bricks, refractory bricks, cast iron, ceramic regenerators, or molten salt.

9. The low-load SCR denitrification inlet flue gas temperature regulation system according to claim 1, characterized in that, The inlet of the flue gas extraction module is located on the flue after the superheater outlet and before the economizer inlet, in order to extract the flue gas that has not yet been cooled by the economizer.

10. A method for regulating the inlet flue gas temperature in a low-load SCR denitrification system, characterized in that, include: Detect the flue gas temperature in the upstream flue of the SCR reactor; When the flue gas temperature is lower than the preset lower limit, based on the deviation between the flue gas temperature and the preset lower limit and the remaining heat storage capacity of the heat storage module, one of the following heat replenishment modes is selected for execution: air heating heat replenishment mode, combined heat replenishment mode, or high-temperature flue gas auxiliary heat replenishment mode. In the selected heat replenishment mode, air and / or flue gas drawn from the upstream flue of the economizer are supplied to the heat storage module. The heat stored in the heat storage module is used to perform primary heating of the air and / or flue gas. Then, the gas after primary heating is subjected to secondary electric heating, and the gas after secondary heating is injected into the upstream flue of the SCR reactor. Based on the flue gas temperature, the supply of air and / or flue gas, the heat release of the heat storage module, and the heating power of the electric heater are adjusted to maintain the flue gas temperature within a preset temperature range. When the charging conditions are met, the heat storage module stores heat.

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