Automatic control method and system for desulfurization oxidation air

Abstract

The application discloses a kind of desulfurization oxidation wind automatic control method and system, comprising the following steps: the original flue gas flow is divided into multiple load intervals, the SO2 concentration of absorption tower entrance is divided into multiple sulfur fraction intervals, with original flue gas flow and entrance SO2 concentration as control variable, the reasonable demand range of oxidation air volume is determined by theoretical calculation and operation data, and the corresponding ladder corresponding relationship table is generated;Real-time acquisition of the original flue gas flow and absorption tower entrance SO2 concentration of desulfurization system;According to the current acquisition parameter matching to corresponding ladder interval.The application, maximization uses existing coal-fired power plant desulfurization system condition, in not additional increase system or equipment case, by design control logic, realize the automatic control of variable frequency desulfurization oxidation wind, simultaneously by establishing unit load and flue gas sulfur fraction joint control model, realize the ladder type automatic regulation of oxidation fan air volume, to reach the purpose of energy saving, stable operation.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization technology, and in particular to an automatic control method and system for desulfurization oxidation air. Background Technology

[0002] Limestone-gypsum wet desulfurization is currently the most widely used flue gas desulfurization technology in coal-fired power plants. Sulfur-containing flue gas reacts with limestone slurry in the absorption tower to produce calcium sulfite. Simultaneously, oxidizing air is blown into the tower to oxidize the calcium sulfite into calcium sulfate, which ultimately crystallizes to form the byproduct gypsum. The oxidizing air in the tower is supplied by an oxidation blower, which is a key piece of equipment in the wet desulfurization system.

[0003] Traditional oxidation blowers typically use Roots-type blowers, but the biggest problems with Roots-type oxidation blowers are low efficiency, high energy consumption, and a lack of active adjustment capabilities. Subsequently, variable frequency centrifugal oxidation blowers emerged. These blowers significantly improve conversion efficiency and can adjust the oxidation airflow, effectively reducing energy consumption. Moreover, besides high efficiency, the most important advantage of variable frequency centrifugal blowers is their ability to adjust the oxidation airflow according to the unit's operating conditions, preventing excessive or insufficient oxidation airflow.

[0004] However, in actual adjustment, operators cannot determine the most reasonable adjustment amount for the oxidation air volume. Therefore, there is an urgent need to find a method to automatically adjust the oxidation air volume to maximize the utilization of the variable frequency centrifugal fan's function, ensuring the normal operation of the desulfurization system while reducing fan energy consumption. Currently, the common automatic control of oxidation fans uses monitoring the calcium sulfite content in the absorption tower to control the oxidation air volume, but this method has high investment costs, is prone to meter failure, and requires significant maintenance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings mentioned above by providing an automatic control method and system for desulfurization oxidation air, achieving stable and reliable automatic control of oxidation air under all operating conditions.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an automatic control method for desulfurization oxidation air, comprising the following steps: The original flue gas flow rate is divided into multiple load ranges. Within each load range, the sulfur content range is further divided according to the SO2 concentration at the inlet of the absorption tower. Based on the maximum operating condition of the range, the maximum oxidation air volume of the range is calculated using the desulfurization oxidation air design theory. This value is then used as the set value for the range, thereby generating a corresponding desulfurization oxidation air step relationship table. Real-time data collection of raw flue gas flow rate and SO2 concentration at the inlet of the absorption tower in the desulfurization system; Based on the currently collected parameters, match the corresponding step interval and query the oxidation air volume setting value corresponding to that interval; The oxidation air volume setpoint is processed by delay and then output to the frequency converter of the oxidation fan to control the speed of the oxidation fan and adjust the oxidation air volume. In automatic control mode, an airflow offset function is provided, allowing operators to manually fine-tune the airflow based on the oxidation airflow setpoint.

[0007] Furthermore, the load range is a series of independent ranges divided according to the high, medium and low operating loads of the unit, and the sulfur range is a series of independent ranges divided according to the high and low SO2 concentration at the inlet of the absorption tower.

[0008] Furthermore, the load range and sulfur range intersect to form multiple independent stepped matching ranges, each of which corresponds to an independent oxidation air volume setting value, thereby achieving stepped matching between air volume and unit operating conditions.

[0009] Furthermore, the delay processing specifically includes: When a change in the current parameter across ranges is detected, triggering a new airflow setting, a 60-second timer is started. If the parameter remains within the new range during the timer period, the new airflow setting is output; if the parameter returns to the original range during the timer period, the adjustment is canceled.

[0010] Furthermore, the airflow offset function is only effective in automatic control mode, and the offset adjustment range is limited to ±5m³ / min. After the operator adjusts the offset, the current airflow setting value is synchronously updated to the superposition value of the step setting value and the offset value. When the parameter switches to a new step setting value across intervals, the offset value is automatically reset.

[0011] An automatic control system for desulfurization oxidation air, employing any one of the automatic control methods for desulfurization oxidation air, includes: The data acquisition module is used to obtain the raw flue gas flow rate and SO2 concentration at the inlet of the absorption tower in the desulfurization system; The logic processing module has a built-in ladder correspondence table, which is used to match the ladder interval according to the collected parameters and output the corresponding oxidation air volume setting value. The delay processing module is used to perform delay stabilization processing on the oxidation air volume setpoint and to filter instantaneous fluctuations in parameters. The frequency converter module is used to receive the processed set value and control the frequency converter of the oxidation blower to adjust the blower speed; The human-computer interaction module provides an "automatic / manual" switch button and an airflow offset setting function. Furthermore, the data acquisition module reuses existing measuring instruments in the power plant.

[0012] Furthermore, the human-machine interface is integrated into the power plant's DCS system.

[0013] Furthermore, the logic processing module supports parallel processing of multiple units, and the control logic of each unit is independent and can be configured individually.

[0014] The beneficial effects of this invention are reflected in: This invention maximizes the use of existing coal-fired power plant desulfurization system conditions. Without adding additional systems or equipment, it achieves automatic control of variable frequency desulfurization oxidation air by designing control logic. At the same time, by establishing a joint control model of unit load and flue gas sulfur content, it achieves step-by-step automatic adjustment of oxidation fan air volume and avoids frequent adjustments of oxidation fan, thereby achieving the purpose of energy saving and stable operation. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This invention discloses an automatic control method for desulfurization oxidation air, comprising the following steps: The original flue gas flow rate is divided into multiple load ranges. Within each load range, the sulfur content range is further divided according to the SO2 concentration at the inlet of the absorption tower. Based on the maximum operating condition of the range, the maximum oxidation air volume of the range is calculated using the desulfurization oxidation air design theory. This value is then used as the set value for the range, thereby generating a corresponding desulfurization oxidation air step relationship table. Real-time data collection of raw flue gas flow rate and SO2 concentration at the inlet of the absorption tower in the desulfurization system; Based on the currently collected parameters, match the corresponding step interval and query the oxidation air volume setting value corresponding to that interval; The oxidation air volume setpoint is processed by delay and then output to the frequency converter of the oxidation fan to control the speed of the oxidation fan and adjust the oxidation air volume. In automatic control mode, an airflow offset function is provided, allowing operators to manually fine-tune the airflow based on the oxidation airflow setpoint.

[0017] This invention achieves automatic adjustment of oxidation air under all operating conditions by relying on existing conventional monitoring parameters on the inlet side of the desulfurization system, without the need for additional monitoring instruments or outlet side parameters. This solves the problems of poor reliability and high cost caused by relying on additional sulfite meters or outlet SO2 meters in existing technologies. At the same time, through dual-parameter stepped control, combined with delayed filtration and bias fine-tuning, it achieves automatic matching of air volume and operating conditions, while avoiding frequent adjustments of the fan. It balances the convenience of automatic control and the flexibility of manual fine-tuning, effectively reducing fan energy consumption and protecting the fan equipment.

[0018] It should be noted that the monitoring and control principle of this invention is as follows: In the absorption tower system, SO2 in the flue gas is absorbed by the slurry and reacts to form calcium sulfite. By consuming sufficient oxygen, the calcium sulfite will be further oxidized to calcium sulfate. Calcium sulfate combines with water to finally form calcium sulfate dihydrate, which is gypsum. In this reaction process, based on the flue gas volume and the measured SO2 concentration, the approximate required oxidation air volume can be calculated according to the desulfurization oxidation air design principle. This oxidation air volume is controlled by the oxidation blower. In all coal-fired power plants, flue gas flow rate and SO2 concentration in the flue gas are equipped with measuring instruments to control flue gas pollutant emissions. Therefore, the real-time oxidation air demand can be calculated using existing real-time measurement data, thereby adjusting the oxidation blower frequency.

[0019] In one embodiment, the load range is a series of independent ranges divided according to the high, medium and low operating loads of the unit, and the sulfur range is a series of independent ranges divided according to the high and low SO2 concentration at the inlet of the absorption tower.

[0020] This design uses the two most critical factors affecting oxidation air volume demand—unit operating load and coal sulfur content—as the basis for dividing the range. This allows for precise matching of the unit's actual operating conditions and provides a reasonable basis for subsequent stepped air volume adjustment.

[0021] In one embodiment, the load range and the sulfur range intersect to form multiple independent stepped matching ranges. Each stepped matching range corresponds to an independent oxidation air volume setting value, thereby achieving a stepped matching between the air volume and the unit's operating conditions.

[0022] This design, through the intersection of two-dimensional intervals, forms a multi-dimensional stepped matching interval. Each interval corresponds to an independent airflow setting value, achieving a stepped matching of airflow and operating conditions, rather than the real-time dynamic adjustment in existing technologies. Under this logic, as long as the parameters do not cross intervals, the airflow remains stable, effectively reducing the number of fan adjustments, making it more fan-friendly, and solving the problem of frequent fan operation in existing real-time adjustment schemes. At the same time, the oxidation airflow setting value of each step is based on the oxidation airflow calculated with the maximum parameter of that step as a reference, giving the oxidation airflow of that step a certain redundancy, ensuring that the oxidation airflow can meet the actual airflow requirement of that step, and reducing the risk caused by the inconsistency between theoretical calculations and actual operating airflow requirements.

[0023] In one embodiment, the delay processing specifically includes: When a change in the current parameter across ranges is detected, triggering a new airflow setting, a 60-second timer is started. If the parameter remains within the new range during the timer period, the new airflow setting is output; if the parameter returns to the original range during the timer period, the adjustment is canceled.

[0024] This design incorporates a 60-second stabilization judgment mechanism to address the issue of instantaneous fluctuations in flue gas parameters. A new airflow setting value is only output when the parameters truly stabilize within the new range. If the fluctuation is only instantaneous, the adjustment is canceled. This mechanism effectively filters out instantaneous parameter fluctuations, completely avoids frequent adjustments to the fan, further protects the fan equipment, extends its service life, and ensures the stability of the system operation.

[0025] In one embodiment, the air volume offset function is only effective in automatic control mode, and the offset adjustment range is limited to ±5m³ / min. After the operator adjusts the offset, the current air volume setting value is synchronously updated to the superposition value of the step setting value and the offset value. When the parameter switches to a new step setting value across the interval, the offset value is automatically reset.

[0026] This design, based on stepped automatic control, provides a small range of manual fine-tuning functions, which can adapt to special working conditions and solve the problem that fixed steps cannot fully cover all special scenarios. At the same time, an automatic offset reset mechanism is designed. When the working condition switches to a new step range, the offset is automatically reset, which avoids the manually adjusted offset value being carried over to the new working condition, resulting in air volume deviation under the new working condition. This balances flexibility and control accuracy.

[0027] An automatic control system for desulfurization oxidation air, employing any one of the automatic control methods for desulfurization oxidation air, includes: The data acquisition module is used to obtain the raw flue gas flow rate and SO2 concentration at the inlet of the absorption tower in the desulfurization system; The logic processing module has a built-in step correspondence table, which is used to match the step interval according to the collected parameters and output the corresponding oxidation air volume set value. The delay processing module is used to perform delay stabilization processing on the oxidation air volume setpoint and to filter instantaneous fluctuations in parameters. The frequency converter module is used to receive the processed set value and control the frequency converter of the oxidation blower to adjust the blower speed; The human-computer interaction module provides an "automatic / manual" switch button and an airflow offset setting function.

[0028] This design allows all modules to work together to complete the entire process of automatic control, from parameter acquisition, interval matching, delay processing to air volume adjustment. It also provides a human-machine interface to support mode switching and bias adjustment by operators, achieving fully automatic and stable control of oxidation air, which can automatically adapt to changes in operating conditions without manual intervention.

[0029] In one embodiment, the human-machine interface is integrated into the power plant's DCS system.

[0030] With this design, all control logic and interactive interfaces are integrated into the power plant's existing DCS system. No new independent hardware equipment is required. Functional upgrades can be completed simply through logic configuration, resulting in extremely low implementation costs. As long as the power plant has adjustable oxidation fans, functional upgrades can be achieved quickly, making it highly adaptable.

[0031] In one embodiment, the logic processing module supports parallel processing of multiple units, and the control logic of each unit is independent and can be configured individually.

[0032] With this design, the logic processing module can support the parallel control of multiple units simultaneously, and the control logic of each unit is independent of each other. Parameters such as zone division and air volume setting can be configured separately according to the actual situation of different units, which can adapt to units with different capacities and configurations, further improving the adaptability of the solution and facilitating the unified deployment of multiple units in power plants.

[0033] The present invention will be further described below with reference to embodiments: Taking the desulfurization oxidation fan B of Unit #1 in a power plant as an example, its air volume is adjustable from 60 to 110 m³ / min. "Automatic" and "Manual" control buttons are set in the DCS system, and the two are interlocked.

[0034] When in "Automatic" mode, the system executes the following control logic: It collects the following real-time data: raw flue gas flow rate Q (km³ / h); SO2 concentration C at the absorber inlet (mg / m³); it divides the flue gas into three levels based on Q, and within each level, it further divides it into three grades based on C. Based on the maximum values ​​of Q and C within each range, the maximum required oxidation air volume for that range can be calculated using desulfurization principles, and this value is used as the setpoint for that range. (The maximum required oxidation air volume under maximum operating conditions can be referenced based on the unit's rated design oxidation air volume):

[0035] The system determines the current range based on the table above, and after a 60-second delay, outputs the corresponding oxidation air volume command to the frequency converter to adjust the fan speed.

[0036] In addition, the system also adds an oxidation air volume "offset" button with an offset range of ±5m³ / min. This means that under the same conditions, the oxidation air volume will be increased or decreased by the offset setting value. The "offset" button is only effective in automatic mode. By setting the "offset", the oxidation air volume can be adjusted more flexibly, thereby better matching the required air volume under actual working conditions.

[0037] When the "manual" mode is activated, the system's oxidation airflow will be manually adjusted.

[0038] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0039] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0040] Additionally, "multiple" refers to two or more.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automatic control method for desulfurization oxidation air, characterized in that, Includes the following steps: The original flue gas flow rate is divided into multiple load ranges. Within each load range, the sulfur content range is further divided according to the SO2 concentration at the inlet of the absorption tower. Based on the maximum operating condition of the range, the maximum oxidation air volume of the range is calculated using the desulfurization oxidation air design theory. This value is then used as the set value for the range, thereby generating a corresponding desulfurization oxidation air step relationship table. Based on the currently collected parameters, match the corresponding step interval and query the oxidation air volume setting value corresponding to that interval; The oxidation air volume setpoint is processed by delay and then output to the frequency converter of the oxidation fan to control the speed of the oxidation fan and adjust the oxidation air volume. In automatic control mode, an airflow offset function is provided, allowing operators to manually fine-tune the airflow based on the oxidation airflow setpoint.

2. The automatic control method for desulfurization oxidation air according to claim 1, characterized in that: The load range is a series of independent ranges divided according to the high, medium and low operating loads of the unit, and the sulfur range is a series of independent ranges divided according to the high and low SO2 concentration at the inlet of the absorption tower.

3. The automatic control method for desulfurization oxidation air according to claim 2, characterized in that: The load range and sulfur range intersect to form multiple independent stepped matching ranges. Each stepped matching range corresponds to an independent oxidation air volume setting value, realizing a stepped matching between air volume and unit operating conditions.

4. The automatic control method for desulfurization oxidation air according to claim 1, characterized in that: The delay processing specifically involves: When a change in the current parameter across ranges is detected, triggering a new airflow setting, a 60-second timer is started. If the parameter remains within the new range during the timer period, the new airflow setting is output; if the parameter returns to the original range during the timer period, the adjustment is canceled.

5. The automatic control method for desulfurization oxidation air according to claim 1, characterized in that: The airflow offset function is only effective in automatic control mode, and the offset adjustment range is limited to ±5m³ / min. After the operator adjusts the offset, the current airflow setting value is synchronously updated to the superposition value of the step setting value and the offset value. When the parameter switches to a new step setting value across the range, the offset value is automatically reset.

6. An automatic control system for desulfurization oxidation air, employing the automatic control method for desulfurization oxidation air according to any one of claims 1-5, characterized in that, include: The data acquisition module is used to obtain the raw flue gas flow rate and SO2 concentration at the inlet of the absorption tower in the desulfurization system; The logic processing module has a built-in ladder correspondence table, which is used to match the ladder interval according to the collected parameters and output the corresponding oxidation air volume setting value. The delay processing module is used to perform delay stabilization processing on the oxidation air volume setpoint and to filter instantaneous fluctuations in parameters. The frequency converter module is used to receive the processed set value and control the frequency converter of the oxidation blower to adjust the blower speed; The human-computer interaction module provides an "automatic / manual" switch button and an airflow offset setting function.

7. The automatic control system for desulfurization oxidation air according to claim 6, characterized in that: The data acquisition module reuses existing measuring instruments in the power plant.

8. The automatic control system for desulfurization oxidation air according to claim 6, characterized in that: The human-machine interface is integrated into the power plant's DCS system.

9. The automatic control system for desulfurization oxidation air according to claim 6, characterized in that: The logic processing module supports parallel processing of multiple units, and the control logic of each unit is independent and can be configured individually.

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