Air leakage control method and system for boiler dry slag removal system based on heat balance

Abstract

The invention belongs to the technical field of energy conservation and emission reduction of coal-fired boilers, and particularly relates to a boiler dry slag removal system air leakage control method and system based on heat balance. Measuring or calculating the following key parameters in real time: scanning a slag layer at the upper part of the fire grate in real time by using a laser scanning system, and measuring the slag discharge amount; the infrared temperature measuring assembly is used for measuring the surface temperature of the slag in real time; based on the slag discharge amount and the surface temperature, combined with physical parameters such as the specific heat capacity of the slag, heat carried by the slag is calculated; total cooling air quantity and cooling air temperature are measured in real time through an air quantity measuring device, and input refrigerant heat is calculated according to the total cooling air quantity and cooling air temperature; s2, establishing a heat balance model and performing joint optimization; and S3, performing intelligent control execution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal-fired boiler energy saving and emission reduction technology, in particular to a boiler dry slag removal system air leakage control method and system based on heat balance. BACKGROUND

[0002] At present, dry slag removal technology is widely used in coal-fired units, but it has exposed a significant coal-saving bottleneck in operation. The core problem is that the system air leakage rate is much higher than the design value (design value is 0.5-1.0%, actual value is as high as 4-5% or even higher). The existing control system usually only controls the outlet slag temperature as a single parameter, and lacks effective monitoring and regulation of the total cold air entering the furnace bottom, which has a large blind area.

[0003] Excessive cold air leakage into the furnace will cause a series of negative effects:

[0004] 1. Negative impact on combustion: reduces the furnace temperature, causes the flame center to move upward, worsens the air dynamic field, increases the carbon content of fly ash and the generation of nitrogen oxides (NOx), and threatens the safety of the heating surface.

[0005] 2. Negative impact on heat transfer: causes the organized air volume at the air preheater to decrease relatively, the heat transfer efficiency to decrease, and the exhaust gas temperature to rise. This problem is particularly prominent when the boiler is running at low load, because the relative air leakage is larger and the exhaust gas temperature rises more.

[0006] The existing technology lacks accurate measurement and comprehensive optimization control of key parameters such as total cold air entering the furnace bottom and slag carrying heat, and cannot maximize the reduction of invalid cold air while ensuring the safe operation of the dry slag machine. Therefore, there is an urgent need for a new method and system that can systematically solve the air leakage problem of the dry slag removal system. SUMMARY

[0007] The present application aims to overcome the above-mentioned defects of the prior art, and provides a boiler dry slag removal system air leakage control method and system based on heat balance. The present application aims to accurately measure key parameters and achieve dynamic balance of cooling air volume and slag heat through intelligent optimization algorithm, so as to significantly reduce the air leakage rate at the furnace bottom under the premise of ensuring the safety of the equipment, and ultimately achieve the purpose of reducing the exhaust gas temperature, reducing the combustible content of fly ash, and improving the overall operation efficiency of the boiler.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solution: a boiler dry slag removal system air leakage control method based on heat balance, comprising the following steps:

[0009] S1: Key parameter soft measurement: through the deployed sensor system, the following key parameters are measured or calculated in real time:

[0010] Real-time scanning of the slag layer on the upper part of the grate by a laser scanning system to measure the slag discharge amount;

[0011] Real-time measurement of the surface temperature of the slag by an infrared temperature measurement component;

[0012] Based on the slag discharge amount and the surface temperature, combined with physical parameters such as the specific heat capacity of the slag, the heat carried by the slag is calculated;

[0013] Real-time measurement of the total cooling air volume and the cooling air temperature by an air volume measurement device, and calculation of the input refrigerant heat based on the same;

[0014] S2: Establishing a heat balance model and joint optimization:

[0015] Establishing a heat balance model with the heat carried by the slag and the input refrigerant heat as the core;

[0016] Taking the boiler load, the furnace negative pressure, the outlet slag temperature, the furnace bottom air temperature, the main / side air door opening degree, the slag discharge amount, the dry slag cooler current and the like as input variables for joint optimization;

[0017] Adopting a leakage air-cooling balance control strategy to optimize the above multiple variables to solve the optimal cooling air volume set value under the current working condition, with the optimization target of "maximizing the boiler efficiency"; the strategy changes the traditional single control mode of the outlet slag temperature;

[0018] S3: Intelligent control execution:

[0019] According to the optimal cooling air volume set value obtained in S2, the total air volume entering the dry slag cooler is accurately controlled by adjusting the opening degree of the main and side air doors;

[0020] When the boiler is running at a low load, the cooling air volume bypass optimization control is started to further intelligently reduce the "unorganized cooling air volume" that must be excessively introduced to maintain the slag temperature and finally leaks into the furnace.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The present application realizes accurate perception of key parameters, realizes real-time and non-contact accurate measurement of the slag discharge amount and the heat carried by the slag for the first time through the combination of laser scanning and infrared temperature measurement, and breaks through the original measurement blind area. Through accurate measurement of the total cooling air volume, a true basis is provided for control. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application is a structural schematic diagram; DETAILED DESCRIPTION

[0024] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0025] With reference to Figure 1 As shown in the figure, a boiler dry deslagging system air leakage control method based on heat balance comprises the following steps:

[0026] S1: Key parameter soft measurement: through the deployed sensor system, the following key parameters are measured or calculated in real time:

[0027] The slag layer on the upper part of the grate is scanned in real time by using a laser scanning system to measure the deslagging amount; the surface temperature of the slag is measured in real time by using an infrared temperature measurement component; based on the deslagging amount and the surface temperature, combined with the physical property parameters such as the specific heat capacity of the slag, the heat carried by the slag is calculated; the total cooling air volume and the cooling air temperature are measured in real time by using an air volume measuring device, and the input refrigerant heat is calculated accordingly;

[0028] S2: Establishing a heat balance model and joint optimization:

[0029] A heat balance model with the heat carried by the slag and the input refrigerant heat as the core is established; the boiler load, the furnace negative pressure, the outlet slag temperature, the furnace bottom air temperature, the main / side air door opening degree, the deslagging amount, the dry cooler current and other parameters are taken as input variables for joint optimization; a leakage- cooling balance control strategy is adopted, and the "maximization of boiler efficiency" is taken as the optimization target to perform joint optimization calculation on the above multiple variables to solve the optimal cooling air volume set value under the current working condition; the strategy changes the traditional single control mode of the outlet slag temperature;

[0030] S3: Intelligent control execution:

[0031] According to the optimal cooling air volume set value obtained in S2, the total air volume entering the dry deslagging machine is accurately controlled by adjusting the opening degree of the main and side air doors; when the boiler is running at a low load, the cooling air volume bypass optimization control is started to further intelligently reduce the "unorganized cooling air volume" that must be excessively introduced to maintain the slag temperature and finally leaks into the furnace.

[0032] A boiler dry deslagging system air leakage control system for implementing the above method comprises:

[0033] A dry deslagging soft measurement system: used for intelligently calculating the key parameters that cannot be directly measured; the system comprises:

[0034] Slag Measurement Unit: A laser scanner and infrared thermometer installed on the upper part of the grate are used to acquire the slag discharge volume and slag temperature in real time, and to calculate the heat carried by the slag.

[0035] Air volume and temperature measurement unit: includes an air volume measuring device for measuring the total cooling air volume entering the dry slag removal system and a temperature sensor for measuring the air temperature;

[0036] The intelligent air leakage control system is based on a central processing controller, which incorporates the heat balance model and joint optimization algorithm. This controller receives various signals from the soft measurement system and the boiler DCS, performs the joint optimization calculation, and outputs damper control commands.

[0037] Actuators: including main damper actuators and side damper actuators controlled by the central processing controller, used to adjust the opening and control the cooling air volume;

[0038] Cooling airflow bypass optimization system: As a functional module of the aforementioned intelligent air leakage control system, it is specifically designed to implement a more aggressive airflow reduction strategy under low load conditions to further suppress unorganized air leakage.

[0039] Achieving precise sensing of key parameters: By combining laser scanning and infrared thermometry, real-time, non-contact, and precise measurement of slag discharge volume and its carried heat is achieved for the first time, breaking through the previous measurement blind spots. Accurate measurement of total cooling air volume provides a solid basis for control. Adopting a multi-variable collaborative intelligent control strategy: Upgrading from single "slag temperature control" to multi-variable joint optimization control aimed at "optimal boiler efficiency," achieving system-level optimization and more precise and scientific control. Reducing air leakage rate and flue gas temperature: By fundamentally reducing cooling air volume, the system air leakage rate is effectively reduced from the actual 4-5% or higher to near the design level, thereby significantly reducing the flue gas temperature, especially under low-load conditions. Comprehensively improving boiler efficiency: While reducing flue gas temperature, the improved combustion conditions in the furnace reduce the carbon content of fly ash, further improving boiler combustion efficiency and achieving comprehensive energy savings. For every 3% reduction in furnace air leakage rate, the flue gas temperature can be reduced by 5-8℃, the combustible content in fly ash can be reduced by approximately 0.3 (smoke) to 1.0 (lean) percentage points, and the boiler efficiency can be increased by approximately 0.12-0.35 percentage points. Ensuring system safety: All controls are implemented under the premise of ensuring the dry ash machine is not damaged by overheating, achieving a balance between safety and energy efficiency.

[0040] In a preferred embodiment, the hardware is first deployed: a dustproof, high-temperature resistant laser scanner and infrared thermometer are installed at a suitable location above the grate of the boiler slag cooler. High-precision airflow meters and temperature sensors are installed on the air inlet header or key air ducts of the dry slag removal system. The central processing controller can be implemented by adding a new functional module to the plant-level DCS system or by adding an advanced optimized controller.

[0041] During system operation, the soft measurement system continuously sends data such as slag discharge volume, slag temperature, total air volume, and air temperature to the central processing controller. The controller's built-in optimization algorithm runs every 30 seconds to 1 minute, comprehensively considering constraints such as the current boiler load and furnace negative pressure, to calculate a set of optimal damper opening commands that maximize boiler efficiency while ensuring that the outlet slag temperature does not exceed the safety threshold, and then sends them to the actuators.

[0042] When the boiler load is less than 50% of the rated load, the bypass optimization system is activated. Based on the original optimization, a stricter upper limit for cooling air volume is applied to actively and safely further reduce the intake of cold air.

[0043] The introduction of the "soft measurement" concept: This involves real-time calculation of the "heat carried by slag," which is difficult to measure directly, using measurable parameters. The "air leakage-cooling balance" control strategy: Its core is to establish a balance between heat input (cold air) and heat output (slag), with overall boiler efficiency as the optimization objective.

[0044] "Multi-variable joint optimization": It is no longer a single-loop PID control, but a MIMO (multiple input multiple output) optimization control that comprehensively considers the parameters of multiple subsystems such as combustion, heat transfer, and slag discharge.

[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling air leakage in a boiler dry ash removal system based on heat balance, characterized in that: Includes the following steps: S1: Soft measurement of key parameters: The following key parameters are measured or calculated in real time through a deployed sensor system: A laser scanning system is used to scan the slag layer above the grate in real time and measure the amount of slag discharged; an infrared temperature measuring component is used to measure the surface temperature of the slag in real time; based on the amount of slag discharged and the surface temperature, combined with physical properties such as the specific heat capacity of the slag, the heat carried by the slag is calculated; the total cooling air volume and cooling air temperature are measured in real time through an air volume measuring device, and the heat input of the refrigerant is calculated accordingly. S2: Establishing a heat balance model and joint optimization: A heat balance model is established with the heat carried by the slag and the heat of the input refrigerant as the core. Multiple parameters, such as boiler load, furnace negative pressure, outlet slag temperature, furnace bottom air temperature, main / side damper opening, slag discharge rate, and dry cooler current, are used as input variables for joint optimization. A leakage-cooling balance control strategy is adopted, with "maximizing boiler efficiency" as the optimization objective. The above multiple variables are jointly optimized to solve for the optimal cooling air volume setpoint under the current operating conditions. This strategy changes the traditional mode of single control of outlet slag temperature. S3: Intelligent Control Execution: Based on the optimal cooling air volume setting value obtained from S2, the total air volume entering the dry slag machine is precisely controlled by adjusting the opening of the main and side air dampers. When the boiler is running at low load, the cooling air volume bypass optimization control is activated to further intelligently reduce the "unorganized cold air volume" that must be excessively introduced to maintain the slag temperature and ultimately leaks into the furnace.

2. A boiler dry ash removal system leakage control system for implementing the above method, characterized in that: include: Dry slag removal soft measurement system: used for intelligent calculation of key parameters that cannot be directly measured; The system includes: Slag Measurement Unit: A laser scanner and infrared thermometer installed on the upper part of the grate are used to acquire the slag discharge volume and slag temperature in real time, and to calculate the heat carried by the slag. Air volume and temperature measurement unit: includes an air volume measuring device for measuring the total cooling air volume entering the dry slag removal system and a temperature sensor for measuring the air temperature; The intelligent air leakage control system is based on a central processing controller, which incorporates the heat balance model and joint optimization algorithm. This controller receives various signals from the soft measurement system and the boiler DCS, performs the joint optimization calculation, and outputs damper control commands. Actuators: including main damper actuators and side damper actuators controlled by the central processing controller, used to adjust the opening and control the cooling air volume; Cooling airflow bypass optimization system: As a functional module of the aforementioned intelligent air leakage control system, it is specifically designed to implement a more aggressive airflow reduction strategy under low load conditions to further suppress unorganized air leakage.

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