Semi-dry type deacidification tower control system for waste incineration flue gas

Abstract

The invention discloses a control system of a semi-dry deacidification tower for waste incineration flue gas, which realizes accurate cleaning through real-time three-dimensional material level detection and dynamic anti-blocking control, or controls the flow of flue gas cooling water through a regulating valve of a cooling water system, and also controls the concentration of slurry through a semi-dry absorbent slurry preparation system according to needs. According to the anti-blocking device, combustion adjustment of the incinerator is conducted according to needs, so that ash deposition in the semi-dry type deacidification tower is relieved, the safety, stability and economical efficiency of a flue gas purification system and a control system are improved, and a mixed control mode that the anti-blocking device of the semi-dry type deacidification tower gives priority to the time sequence and the material level is formed.

Description

Technical Field

[0001] This invention belongs to the field of waste incineration flue gas treatment technology, specifically relating to a semi-dry deacidification tower control system for waste incineration flue gas. Background Technology

[0002] Waste incineration is an important method for treating municipal solid waste, but it generates a large amount of acidic gaseous pollutants (such as SO2, HCl, and HF) during the process. To meet flue gas emission standards, waste incineration plants generally use semi-dry desulfurization towers to remove acidic gases from the flue gas. The semi-dry desulfurization tower reacts with absorbents such as lime slurry in the flue gas, generating dry substances (such as CaSO3 and CaCl2). Some of these dry substances flow downstream with the flue gas, while others adhere to the inner wall of the desulfurization tower and the ash hopper. After a period of reaction, these retained dry substances, along with unreacted absorbents, often cause ash accumulation inside the semi-dry desulfurization tower. Furthermore, due to the high humidity and condensation properties of waste incineration flue gas, the risk of dust absorbing moisture and caking is high, necessitating timely cleaning.

[0003] After a period of explosive growth, the waste incineration industry has seen waste incineration plants begin co-firing unscreened aged waste due to insufficient raw waste. Furthermore, leachate concentrate, used to achieve zero wastewater discharge, is often entirely used to prepare absorbent slurry for flue gas desulfurization. These developments impact flue gas purification systems: on the one hand, the introduction of large amounts of inorganic salts and other impurities significantly reduces the efficiency of the flue gas desulfurization reaction, leading to a substantial increase in absorbent consumption and fly ash production; on the other hand, the large fluctuations in combustion conditions after co-firing aged waste result in high and volatile concentrations of acidic gases, making online matching of flue gas desulfurization process parameters more difficult. Consequently, the risk of ash blockage in the desulfurization tower increases sharply.

[0004] Furthermore, existing desulfurization tower anti-clogging systems generally lack ash accumulation trend sensing technology, fail to fully follow the principle of quantitative change leading to qualitative change, and frequently miss the optimal window for ash accumulation prevention. As a result, ash clogging in desulfurization towers is becoming increasingly frequent, and subsequent treatment is often costly, time-consuming, and risky. Therefore, frequent and severe clogging in semi-dry desulfurization towers has become a major pain point restricting the continuous, safe, stable, and economical operation of incineration plants.

[0005] Therefore, it is necessary to propose a new semi-dry deacidification tower control system to solve the above problems.

[0006] Patent CN108211763B provides a control system for a semi-dry deacidification tower. The main control module controls and prevents clogging based on the tower's weight data. The weight data from the weighing module in CN108211763B typically originates from four support points at the bottom of the tower. For equipment with a tower diameter typically on the order of 10 meters, this data is insufficient to accurately reflect the ash accumulation within the tower, and its precision needs improvement.

[0007] Semi-dry deacidification towers suffer from the following problems to varying degrees during actual operation, which not only affect the operating efficiency of the equipment but may also lead to serious safety hazards and economic losses:

[0008] I. Current Status and Challenges of Dust Accumulation Problem:

[0009] 1) Lack of ash accumulation monitoring. Currently, most semi-dry desulfurization towers lack effective level detection systems, resulting in the inability to perceive the ash accumulation status in the tower in real time. Specifically, this manifests as: (1) Unknown ash accumulation trend: It is impossible to grasp the distribution and thickness changes of ash accumulation in the tower in real time, making it difficult to trigger preventive cleaning in a timely manner; (2) Delayed passive operation and maintenance: Manual intervention is only carried out after ash has hardened, missing the best treatment window (the difficulty of cleaning increases significantly after hardening); (3) Inefficient system coordination: It is difficult for operators to combine the ash accumulation status with flue gas parameters to optimize the operation of the incinerator and purification system. These problems not only increase the workload and cost of manual cleaning, but may also cause large pieces of ash to fall unexpectedly after hardening, leading to shutdown or even safety accidents.

[0010] 2) The control strategy of the anti-clogging device is crude. Most of the existing anti-clogging devices adopt a fixed time sequence start-stop mode, which does not fully consider the non-uniform distribution characteristics of ash accumulation in the tower (affected by factors such as the non-strict axisymmetry of the tower body and flue gas deviation). Specifically, it is manifested in the following ways: (1) Insufficient accuracy of the time sequence control mode: areas with different ash accumulation levels cannot be cleaned in a differentiated manner, and there is a risk of local dust accumulation; (2) Accumulation of local caking risk: areas that are not thoroughly cleaned for a long time are prone to forming caking blocks, and the accidental fall of large ash bodies may cause the furnace to shut down or even cause a safety accident; (3) Limitations of manual intervention: it relies on operators to indirectly judge the degree of ash accumulation based on the changes in the inlet and outlet pressure difference, which is highly subjective and has a delayed response. This crude anti-clogging strategy is difficult to meet the actual operation requirements, resulting in poor anti-clogging effect.

[0011] 3) Existing detection technologies lack reliability. Existing detection technologies have the following problems in practical applications: (1) Limited accuracy of weighing modules: Some towers collect weight data through four support points at the bottom, but due to the large size of the towers (both the diameter and height reach 10 meters), it is difficult to accurately reflect the details and trends of ash distribution; (2) Failure of level detection devices: Conventional level switches or continuous level gauges are easily affected by false level interference (such as non-axisymmetric structure and uneven ash accumulation in the tower), resulting in distorted detection data. Therefore, they are not used in existing semi-dry deacidification towers. These problems seriously affect the reliability of detection data, making the formulation and implementation of anti-blocking strategies lack a scientific basis.

[0012] 4) New challenges in the industry exacerbate the ash accumulation problem. In recent years, the waste incineration industry has generally adopted two measures: using leachate membrane concentrate to prepare absorbent slurry to achieve the goal of zero wastewater discharge; and co-firing aged waste to make up for insufficient waste volume. Both of these measures have led to an increase in flue gas dust content and absorbent consumption, which further exacerbates fly ash production and ash accumulation rate: (1) When using leachate membrane concentrate (Cl- plasma concentration of 10000mg / L-28000mg / L) to prepare absorbent slurry, not only is the activity of the slurry reduced, but the adhesion of fly ash is also increased; (2) After co-firing aged waste: the dust, unburned carbon particles and heavy metal enriched ash in the flue gas increase significantly, which further exacerbates the ash accumulation rate and caking tendency; the combustion conditions fluctuate greatly, and the concentration of acidic gas is high and fluctuates greatly, which increases the difficulty of tracking the flue gas purification system, increases absorbent consumption and fly ash production, and increases the probability of fly ash absorbing moisture and caking in the tower. These new challenges make the ash accumulation problem more complicated and serious. Summary of the Invention

[0013] Purpose of the invention: To address the above problems and better follow the principle of quantitative change leading to qualitative change, this invention proposes a semi-dry desulfurization tower control system for waste incineration flue gas. This system achieves ash accumulation trend perception through visualized dynamic detection of ash accumulation without blind spots in the desulfurization tower. It adopts a "time-sequence-based, level-priority" mode to control the anti-clogging device, enabling timely and precise interlocking control of the anti-clogging devices in different zones to start and stop as needed to clean the ash accumulation. This improves the initiative, response speed, and automation level of the desulfurization tower anti-clogging system control. Furthermore, it can interlock control the cooling water flow rate, absorbent slurry concentration, or combustion control system.

[0014] Technical solution: To achieve the purpose of this invention, the technical solution adopted by this invention is: a control system for a semi-dry desulfurization tower for waste incineration flue gas, comprising: a three-dimensional level detection module and a dynamic anti-clogging control module;

[0015] The three-dimensional level detection module is used to detect the level thickness of each zone of the deacidification tower in real time and determine whether the actual thickness deviation at a certain position in the ash hopper area or side wall area of ​​the deacidification tower is greater than the set value.

[0016] The dynamic anti-blocking control module is used to perform the following operations:

[0017] When the system accumulates dust to a certain extent, and the actual thickness deviation at a certain location in the dust hopper area or side wall area exceeds the set value, and this continues for a set time, the anti-blocking device corresponding to that location will be automatically activated once.

[0018] Then, it is determined again whether the actual thickness at that location is greater than the set value. If it is, the system will automatically activate the corresponding anti-blocking device several times according to the minimum set cycle.

[0019] Next, it checks again whether the actual thickness at that location is greater than the set value. If it is still greater, an alarm is displayed.

[0020] Furthermore, the three-dimensional level detection module includes a three-dimensional level detection device installed at the top of the deacidification tower;

[0021] The deacidification tower is divided into an ash hopper area and a side wall area, and a level thickness model is established for each area. Radar scanning is used to obtain the three-dimensional distribution data of ash accumulation in the tower in real time, and the location and thickness deviation of the ash accumulation area are identified.

[0022] Furthermore, the dynamic anti-clogging control module includes an anti-clogging device for the ash hopper area of ​​the deacidification tower and an anti-clogging device for the sidewall area of ​​the deacidification tower;

[0023] The dynamic anti-blocking control sequence is activated first, followed by the sidewall, and then the accumulated ash is removed continuously.

[0024] Furthermore, the sidewall anti-blocking device consists of four silo wall vibrators evenly distributed circumferentially at 90° intervals.

[0025] Furthermore, the ash hopper anti-blocking device consists of three air hammers spaced 120° apart and installed on the ash hopper;

[0026] The air hammers start automatically according to the set cycle interval. The three air hammers start automatically according to the set action sequence, action interval, and action time.

[0027] Furthermore, if the accumulated ash cannot be effectively removed, the cooling water flow rate, absorbent slurry concentration, or incinerator combustion adjustment system should be interlocked; or interlocked control should be implemented with other flue gas purification equipment or incinerator auxiliary systems.

[0028] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0029] 1) The system's safety and stability are better guaranteed. Through the full-space coverage, high-precision modeling, and real-time response of the three-dimensional level detection system, timely and accurate preventive cleaning of ash accumulation can be carried out proactively, preventing the accumulation and spread of risks and the occurrence of accidents. This completely changes the passive, blind, and lagging nature of existing technologies for cleaning ash accumulation in deacidification towers, improves the safety and stability of the entire plant, and significantly improves operation and maintenance efficiency and economy.

[0030] 2) Eliminating the influence of subjective factors, it provides guidance for optimizing the operation of the flue gas purification system and adjusting the combustion of the incinerator. Operation and maintenance personnel can intuitively understand the ash accumulation in the tower based on the level detection. This is not only important for anti-clogging operations, but also for online adjustments of absorbent slurry concentration and flow rate, cooling water flow rate, flue gas temperature at the reaction tower outlet, boiler load, and the proportion of aged waste co-firing.

[0031] 3) It can interlock with the cooling water flow rate, absorbent slurry concentration, or combustion control system to promote the continuous, stable, and efficient operation of the control system.

[0032] 4) Higher ash removal efficiency. Adopting a hybrid control mode of "time-based, level-priority" ensures routine maintenance while prioritizing level control to handle stubborn ash buildup or sudden increases in ash accumulation, resulting in improved overall ash removal efficiency. The probability of ash caking and passive cleaning is significantly reduced, correspondingly decreasing the workload, cycle, and expenses of boiler shutdown maintenance. Through hybrid control, the anti-clogging system can shift from "reactive handling" to "proactive prevention," leading to safer and more stable operation, and more time-saving, labor-saving, and cost-effective maintenance.

[0033] 5) Less ineffective energy consumption and more efficient energy management. Ineffective energy consumption is reduced by dynamically adjusting anti-blocking parameters (such as the number of impacts and the duration of action). Attached Figure Description

[0034] Figure 1 This is a structural block diagram of a semi-dry deacidification tower control system according to the present invention.

[0035] Figure 2 This is a schematic diagram of a semi-dry deacidification tower.

[0036] Among them, 1-semi-dry deacidification tower, 2-air distributor, 3-atomizer, 4-three-dimensional level detection device. Detailed Implementation

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] This invention discloses a semi-dry desiccant tower control system for waste incineration flue gas. It achieves precise cleaning through real-time three-dimensional level detection and dynamic anti-clogging control, or by controlling the flue gas cooling water flow rate through regulating valves in the cooling water system. Alternatively, it can control the slurry concentration through the semi-dry absorbent slurry system as needed, adjusting the incinerator combustion as required. This alleviates ash accumulation inside the semi-dry desiccant tower, improves the safety, stability, and economy of the flue gas purification and control systems, and forms a hybrid control mode of "time-based, level-priority" for the semi-dry desiccant tower anti-clogging device. The structural block diagram of the semi-dry desiccant tower control system and the schematic diagram of the semi-dry desiccant tower are shown below. Figure 1 , Figure 2 .

[0039] The anti-clogging device typically consists of three air hammers (spaced 120° apart) mounted on the ash hopper. The air hammers usually activate automatically at set intervals (5-60 minutes). The three air hammers activate automatically according to a set sequence (forward, reverse, random), interval (10-60 seconds), and duration (1-3 seconds).

[0040] Traditional anti-clogging devices are usually only on the ash hopper, not on the straight cylindrical sidewall. Ash hopper areas typically have them, but they are added to the sidewall. The timing of their activation follows the principle of "ash hopper first, then sidewall" and continuous operation to avoid exacerbating the risk of ash hopper clogging.

[0041] This invention adds an anti-clogging device to the side wall of the deacidification tower, consisting of four circumferentially distributed (90° apart) bin wall vibrators; at the same time, it adds a three-dimensional level detection device deployed at the top of the deacidification tower, and divides the deacidification tower into ash hopper area and side wall area to establish level thickness models respectively. It applies radar scanning technology to obtain three-dimensional distribution data of ash accumulation in the tower in real time, and accurately identifies the location and thickness deviation of the ash accumulation area.

[0042] After passing through the flue gas inlet, the flue gas needs to be evenly distributed into a circulating flow and directed towards the droplet outlet of the centrifugal atomizer located on the central axis of the reaction tower to facilitate the deacidification reaction. The three-dimensional level detection device is installed in a convenient location between the central cylinder and the side wall on the top cover for easy installation and monitoring.

[0043] After the waste incineration and flue gas purification system underwent trial operation, a reasonable threshold for the material level thickness in each zone was obtained (±5% of the design value). After the system has been running for a period of time, internal ash accumulation will inevitably occur. With the sequential activation of the ash hopper anti-clogging device, some of the accumulated ash will be cleared. When the system accumulates ash to a certain extent, and the actual thickness deviation at a certain location in the ash hopper area or side wall area exceeds the set value, the anti-clogging device at that location (the specific location where the detected actual ash thickness deviation exceeds the set value) will be automatically activated once after a 30-second delay (to prevent signal fluctuations and misjudgments).

[0044] Then, the system checks again whether the actual thickness at that location exceeds the set value. If it does, the system automatically activates the corresponding anti-blocking device three times according to the minimum set cycle. Then, it checks again; if the thickness still exceeds the set value, an alarm is displayed, prompting production personnel to pay attention, strengthen inspections and observations, and manually clear the blockage online if necessary.

[0045] The control system for a semi-dry desulfurization tower for waste incineration flue gas described in this invention operates as follows:

[0046] Process flow: The flue gas from the waste incineration flows in through the flue gas inlet and enters the deacidification tower through the air distributor. It reacts with the absorbent slurry droplets sprayed by the atomizer to carry out the deacidification reaction. The reaction products (including unreacted absorbent, i.e., impurities) and part of the fly ash in the original flue gas will inevitably be deposited in the ash hopper and side walls.

[0047] 1) System initialization:

[0048] During system trial operation, initial data on ash accumulation inside the tower are acquired using a three-dimensional level detection device. Level thickness models for each zone are then established, and reasonable level thickness thresholds (±5% of design value) and time-series baseline parameters are set. The time-series baseline parameters refer to the baseline or initial values ​​of the various time-series parameters mentioned above.

[0049] Three-dimensional level detection is a technology used to determine the three-dimensional distribution and volume of materials in a container or cavity. It can provide detailed contour information of the material surface, such as the location of the highest and lowest points and slope changes, providing rich data support for process control and material management. It has advantages such as non-contact measurement, high accuracy and visualization.

[0050] 2) Real-time monitoring:

[0051] The three-dimensional level real-time detection device continuously scans the ash accumulation inside the tower and transmits the data to the control module. The control module refers to the three-dimensional level detection device.

[0052] 3) Judgment and Response:

[0053] Based on the received data, the control module performs a comprehensive scan of the ash hopper area and sidewall area to determine if there are any locations where the ash accumulation thickness exceeds the set value. If a location is found where the ash accumulation thickness exceeds the set value, the anti-blocking device at that location will automatically activate once after a 30-second delay (to prevent false judgments caused by signal fluctuations).

[0054] 4) Repeat judgment and interlock control:

[0055] If the ash accumulation thickness still exceeds the set value, the system will automatically activate the corresponding anti-clogging device three times according to the minimum set cycle. If the ash accumulation still cannot be effectively removed, the system will display an alarm to alert the operating personnel, and can interlock and control the cooling water flow, absorbent slurry concentration, or incinerator combustion adjustment system as needed.

[0056] In addition to real-time three-dimensional level detection devices using radar scanning technology, other high-precision level detection technologies, such as laser ranging and ultrasonic ranging, can also be considered. These technologies can also achieve three-dimensional distribution detection of ash accumulation inside the tower, but they may differ in terms of cost, accuracy, and applicability.

[0057] Regarding anti-clogging devices, in addition to air hammers and bin vibrators, other types of vibrators or impact devices, such as air cannons and pneumatic impactors, can also be considered. These devices can also clean up accumulated dust, but they may differ in terms of vibration effect, energy consumption, and maintenance costs.

[0058] Regarding interlocking control systems, in addition to controlling cooling water flow, absorbent slurry concentration, or incinerator combustion adjustment systems, interlocking control with other flue gas purification equipment or incinerator auxiliary systems can be considered. For example, interlocking control of flue gas recirculation systems and dust removal systems can further improve flue gas purification efficiency and overall plant operating efficiency.

[0059] In terms of zone weight control, based on operational experience and flue gas flow distribution (through CFD simulation), higher ash removal priority is assigned to areas prone to ash accumulation (such as the flue gas deflection side), and the time series baseline is dynamically adjusted.

Claims

1. A control system for a semi-dry desulfurization tower for waste incineration flue gas, characterized in that, The system includes a three-dimensional level detection module and a dynamic anti-blocking control module; The three-dimensional level detection module is used to detect the level thickness of each zone of the deacidification tower in real time and determine whether the actual thickness deviation at a certain position in the ash hopper area or side wall area of ​​the deacidification tower is greater than the set value. The dynamic anti-blocking control module is used to perform the following operations: When the system accumulates dust to a certain extent, and the actual thickness deviation at a certain location in the dust hopper area or side wall area exceeds the set value, and this continues for a set time, the anti-blocking device corresponding to that location will be automatically activated once. Then, it is determined again whether the actual thickness at that location is greater than the set value. If it is, the system will automatically activate the corresponding anti-blocking device several times according to the minimum set cycle. Next, it checks again whether the actual thickness at that location is greater than the set value. If it is still greater, an alarm is displayed.

2. The control system according to claim 1, characterized in that, The three-dimensional level detection module includes a three-dimensional level detection device installed at the top of the deacidification tower; The deacidification tower is divided into an ash hopper area and a side wall area, and a level thickness model is established for each area. Radar scanning is used to obtain the three-dimensional distribution data of ash accumulation in the tower in real time, and the location and thickness deviation of the ash accumulation area are identified.

3. The control system according to claim 1, characterized in that, The dynamic anti-clogging control module includes an anti-clogging device for the ash hopper area of ​​the deacidification tower and an anti-clogging device for the sidewall area of ​​the deacidification tower. The dynamic anti-blocking control sequence is activated first, followed by the sidewall, and then the accumulated ash is removed continuously.

4. The control system according to claim 3, characterized in that, The sidewall anti-blocking device consists of four silo wall vibrators evenly distributed circumferentially at 90° intervals.

5. The control system according to claim 3 or 4, characterized in that, The ash hopper anti-blocking device consists of three air hammers spaced 120° apart and set on the ash hopper; The air hammers start automatically according to the set cycle interval. The three air hammers start automatically according to the set action sequence, action interval, and action time.

6. The control system according to claim 1, characterized in that, If ash accumulation cannot be effectively removed, interlock control the cooling water flow, absorbent slurry concentration, or incinerator combustion adjustment system; or interlock control with other flue gas purification equipment or incinerator auxiliary systems.

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