Method and system for regulating desulfurization wastewater discharge by online monitoring of chloride ions

Abstract

The application discloses a kind of by chloride ion online monitoring regulation and control desulfurization wastewater discharge method, comprising: based on the experience value of power plant DCS system monitoring online data and desulfurization system limestone consumption, gypsum production, gypsum chlorine content, evaporation water quantity, the corresponding relationship curve of desulfurization slurry chloride ion concentration and desulfurization wastewater water quantity is calculated;According to the relationship curve and chloride ion concentration preset value, the wastewater discharge of power plant desulfurization wastewater treatment is judged;Chloride ion online monitoring instrument is equipped in power plant DCS system, and the application also discloses a kind of by chloride ion online monitoring regulation and control desulfurization wastewater discharge system, based on the desulfurization system chloride ion concentration control desulfurization wastewater discharge reduction optimization method can realize desulfurization system slurry quality improvement, absorption tower chloride ion control stability, equipment corrosion is greatly reduced, gypsum chlorine content is stable and meets standard, desulfurization wastewater discharge reduction and can be adjusted with power plant wastewater assimilation capacity change.

Description

Technical Field

[0001] This invention relates to a method and system for regulating the discharge of desulfurization wastewater through online monitoring of chloride ions, belonging to the field of wet desulfurization technology. Background Technology

[0002] Desulfurization in coal-fired power plants employs limestone-gypsum wet desulfurization. In achieving desulfurization, wet desulfurization also requires consideration of chloride ion control and absorber water balance. A portion of the chloride in coal is released into the flue gas during coal combustion in coal-fired power plants (99%), and almost all of this chloride then enters the desulfurization slurry as it flows through the desulfurization system. In addition, the desulfurization system also receives chloride from limestone and process makeup water. The slurry circulates continuously within the absorber tower under the action of a circulating pump, undergoing a continuous absorption process, during which the slurry density increases. When the slurry density increases to a certain level, the slurry discharge pump starts operating, delivering a certain amount of slurry to the gypsum hydrocyclone. After separation by the gypsum hydrocyclone, the slurry with lower solids content becomes the top flow and then enters the recycled water tank. The underflow from the hydrocyclone enters the vacuum belt conveyor to separate desulfurization gypsum with a certain water content. A portion of the filtrate with higher solids content returns to the tower, while the remaining filtrate enters the recycled water tank for storage. As needed, it is mixed with limestone powder to form limestone slurry. A portion of the water in the recycled water tank enters the wastewater hydrocyclone. After separation, the underflow returns to the absorption tower, and the top flow is the desulfurization wastewater.

[0003] When the slurry density decreases to a certain level, the slurry discharge pump stops operating, and the desulfurization system stops producing desulfurization wastewater and gypsum. At this time, demister flushing water and water carried by the raw flue gas are continuously fed into the absorption tower, while a large amount of evaporated water is discharged from the absorption tower. Due to the limited storage capacity of the recycled water tank, when the water storage in the recycled water tank is insufficient, process water is needed to prepare limestone slurry. During the operation of the slurry discharge pump, although the slurry in the absorption tower undergoes complex circulation in equipment such as the gypsum hydrocyclone, wastewater hydrocyclone, and vacuum belt conveyor, the chloride ions output from the desulfurization system outside the absorption tower only have two paths: desulfurization gypsum and wastewater; the remaining chloride ions return to the absorption tower. However, during the shutdown phase of the slurry discharge pump, chloride ions continuously accumulate in the absorption tower.

[0004] Analysis of the chloride balance in the absorber of a wet desulfurization process reveals that it is inseparable from the water balance. Chloride ion migration occurs not only during the addition / discharge of process water, limestone slurry, and gypsum slurry from the absorber, but also during processes such as washing the filter cake to reduce the chloride ion content in the gypsum. Due to the recycling of water in the desulfurization system and the continuous absorption of chloride ions from the flue gas by the desulfurization slurry, chloride ions gradually accumulate in the absorber slurry. When the chloride ion concentration in the absorber slurry reaches a certain level, desulfurization wastewater needs to be discharged to reduce the chloride ion concentration in the desulfurization system.

[0005] The desulfurization system requires slurry discharge and replenishment, resulting in water evaporation and a significant amount of replenishment water. To maintain a stable slurry level in the absorber tower, a certain amount of water must also be discharged. Furthermore, chloride ions accumulate in the absorber tower slurry. Considering the performance of the wet desulfurization process and the availability of corrosion-resistant materials, a certain amount of wastewater also needs to be discharged outside the system to limit the Cl- concentration in the process slurry. The wastewater discharge rate is determined by calculating the wastewater discharge volume based on the impurity concentration to be controlled in the FGD system. Alternatively, without considering the impurity concentration, the wastewater discharge volume can be determined based on the system's water balance and the amount of excess water that needs to be discharged. Finally, the larger of the two methods is taken as the wastewater discharge volume.

[0006] Factors such as different control measures for chloride concentration, the sensitivity of the absorption tower performance to chloride concentration, and whether strict design requirements are imposed on water consumption (or wastewater discharge) can lead to significant differences in wastewater discharge. For example, the FGD system (2 boilers, 1 tower, and spray tower) of Units 3 and 4 of a thermal power plant is designed with coal containing 1.04% sulfur and 0.035% chloride, a flue gas volume of 90,000 m³ / h (W), and a slurry Cl- concentration controlled at <20,000 × 10⁻⁶ (20 g / L). The designed wastewater discharge to the wastewater treatment system is only 1.9 m³ / h. The FGD system (one boiler, one tower) of Units 3 and 4 of a certain power plant was designed with coal containing 4.02% sulfur and 0.035% chloride, and a single tower processing capacity of 915,000 m² / h. Because the Cl- concentration was controlled at a low level (<1000×10⁻⁶ (1 g / L)), no requirements were specified for wastewater discharge. Therefore, the designed wastewater discharge was as high as 71.6 m³ / h (this FGD system did not have a wastewater treatment device). This shows that the volume of desulfurization wastewater is related to the mass concentration of chloride ions in the desulfurization slurry.

[0007] If the chloride ion concentration in the desulfurization slurry is too high, it will cause pore corrosion, crevice corrosion, and stress corrosion of equipment and pipelines. If the concentration exceeds the limit, it will even hinder the effective operation of the absorption tower and reduce its service life. It will also inhibit the physical and chemical reaction processes in the absorption tower, affect SO2 absorption, and reduce desulfurization efficiency. Since the presence of chloride ions will inhibit the dissolution of limestone, the amount of limestone consumed will increase with the increase of chloride concentration. At the same time, the amount of limestone remaining in the gypsum slurry will increase, which will reduce the desulfurization efficiency and make it difficult for subsequent gypsum dewatering. This will lead to an increase in the water content in the finished gypsum, affecting the quality of gypsum and seriously affecting the safe, stable and economical operation of the desulfurization system.

[0008] If the chloride ion concentration in the desulfurization slurry is too low, the amount of wastewater discharged will increase in order to reduce the chloride ion content in the absorption tower. This may lead to a larger desulfurization wastewater treatment system, increased reagent consumption, and higher operating costs. The investment and operating costs of zero-discharge systems are highly sensitive to the amount of water treated. Taking the currently common desalination technology as an example, the investment cost is 1.5 million yuan per ton of water, and the operating cost is 100 yuan per ton of water, resulting in high desulfurization wastewater treatment costs. The treatment capacity of desulfurization wastewater treatment systems is limited, and there is no solution when the wastewater discharge exceeds the treatment capacity. There are also a series of problems such as increased water consumption in the desulfurization system.

[0009] Therefore, it is necessary to monitor the degree of chloride ion enrichment in the desulfurization slurry in real time, and then control the chloride ion concentration within a reasonable range.

[0010] However, the operation of the desulfurization system is complex. The entire wet desulfurization process involves multiple stages. The types of water entering and leaving the absorption tower vary, and the water volume (liquid level) changes. The chloride ion concentration in the slurry inside the absorption tower also fluctuates within a large range. Furthermore, the large volume of the slurry in the absorption tower makes it difficult to manually control the chloride concentration. The power plant's method of adjusting the chloride ion concentration by adding water or draining slurry based on the slurry chloride concentration obtained from offline sampling chemical analysis is lagging and further increases the inaccuracy of chloride ion control. Summary of the Invention

[0011] The purpose of this invention is to provide a method and system for regulating the discharge of desulfurization wastewater through online monitoring of chloride ions, so as to overcome the defects of the prior art.

[0012] A method for regulating desulfurization wastewater discharge through online chloride ion monitoring includes:

[0013] Based on the online monitoring data of the power plant's DCS system and the relevant empirical values ​​of limestone consumption, gypsum production, gypsum chloride content, and evaporation water volume of the desulfurization system, the corresponding relationship curve between the chloride ion concentration of the desulfurization slurry and the volume of desulfurization wastewater was calculated.

[0014] The wastewater discharge from the power plant's desulfurization wastewater treatment is determined based on the relationship curve and the preset chloride ion concentration value; the power plant's DCS system is equipped with an online chloride ion monitoring instrument.

[0015] Furthermore, the criteria for determining wastewater discharge volume include:

[0016] The upper limit of the desulfurization wastewater discharge volume that meets the zero wastewater discharge requirement corresponds to the lower limit of the chloride ion concentration control value of the desulfurization slurry. This lower limit corresponds to the lower limit of the chloride ion concentration control value when the desulfurization slurry is discharged, and the discharge of slurry begins.

[0017] Furthermore, the criteria for judging wastewater discharge volume also include situations where the slurry density does not meet the discharge requirements:

[0018] If the chloride ion concentration of the desulfurization slurry is below the lower limit of chloride ion concentration control or reaches the lower limit of chloride ion concentration control, then no slurry will be discharged.

[0019] If the chloride ion concentration in the desulfurization slurry reaches the upper limit of chloride ion concentration control, the slurry will be discharged, and the reuse of high-chlorine water from the absorption tower will be reduced.

[0020] Furthermore, the slurry discharge also includes situations where the slurry density meets the discharge requirements:

[0021] If the chloride ion concentration in the slurry does not reach the lower limit of chloride ion concentration control, start the slurry discharge pump and increase the reuse of high-chlorine water from the absorption tower;

[0022] If the chloride ion concentration of the desulfurization slurry reaches the lower limit of chloride ion concentration control but does not reach the upper limit of chloride ion concentration control, the slurry discharge pump will be started normally.

[0023] If the chloride ion concentration in the desulfurization slurry reaches the upper limit of the chloride ion concentration control, the slurry discharge pump should be started, and the reuse of high-chlorine water from the absorption tower should be reduced during slurry discharge.

[0024] Furthermore, the chloride ion online monitoring instrument uses an ion-selective electrode, which is installed in the desulfurization slurry sampling pipeline to obtain the chloride ion concentration of the absorption tower slurry in real time.

[0025] A system for regulating desulfurization wastewater discharge through online chloride ion monitoring, the system comprising:

[0026] The DCS system is equipped with an online chloride ion monitoring instrument. The CS system is used to determine the wastewater discharge from the power plant's desulfurization wastewater treatment based on the monitoring data and the preset range of chloride ion concentration.

[0027] Furthermore, the DCS system is also used to: control the lower limit of chloride ion concentration in desulfurization slurry according to the upper limit of desulfurization wastewater discharge volume with zero wastewater discharge, which corresponds to the lower limit of chloride ion concentration control when desulfurization slurry is discharged, and start discharging slurry.

[0028] Furthermore, the DCS system is also used to determine,

[0029] When the slurry density does not meet the slurry discharge requirements:

[0030] If the chloride ion concentration of the desulfurization slurry is below the lower limit of chloride ion concentration control or reaches the lower limit of chloride ion concentration control, then no slurry will be discharged.

[0031] If the chloride ion concentration of the desulfurization slurry reaches the upper limit of chloride ion concentration control, the slurry will be discharged and the reuse of high-chlorine water in the absorption tower will be reduced.

[0032] When the slurry density reaches the discharge requirement:

[0033] If the chloride ion concentration in the slurry does not reach the lower limit of chloride ion concentration control, start the slurry discharge pump and increase the reuse of high-chlorine water from the absorption tower;

[0034] If the chloride ion concentration of the desulfurization slurry reaches the lower limit of chloride ion concentration control but does not reach the upper limit of chloride ion concentration control, the slurry discharge pump will be started normally.

[0035] If the chloride ion concentration in the desulfurization slurry reaches the upper limit of the chloride ion concentration control, the slurry discharge pump should be started, and the reuse of high-chlorine water from the absorption tower should be reduced during slurry discharge.

[0036] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the desulfurization wastewater discharge reduction optimization method based on the control of chloride ion concentration in the desulfurization system can achieve desulfurization wastewater reduction and absorption tower chloride ion control optimization, thereby improving the slurry quality of the desulfurization system, stabilizing the chloride ion control in the absorption tower, greatly reducing equipment corrosion, ensuring that the chlorine content of gypsum is stable and meets the standards, and reducing desulfurization wastewater discharge, which can be adjusted according to changes in the power plant's wastewater absorption capacity. Attached Figure Description

[0037] Fig. 1 This is a schematic diagram of the chlorine balance in the desulfurization system of this invention;

[0038] Fig. 2 This is a conceptual curve showing the relationship between the discharge of desulfurization wastewater and chloride ions in the desulfurization slurry according to the present invention;

[0039] Fig. 3 This invention describes a control process for regulating wastewater discharge based on chloride ion monitoring data. Detailed Implementation

[0040] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0041] like Figs. 1-3 As shown, a method for regulating desulfurization wastewater discharge through online chloride ion monitoring is disclosed. The method includes: optimizing desulfurization wastewater discharge by regulating the chloride ion concentration of the desulfurization slurry based on online monitoring of key indicators such as chloride ion inflow and outflow in the desulfurization system and chloride ion concentration in the absorption tower. The method includes the following steps:

[0042] A. Using online data such as flue gas volume and absorber level monitored by the power plant's DCS system, as well as relevant empirical values ​​such as limestone consumption, gypsum production, gypsum chloride content, and evaporation water volume of the desulfurization system, calculate the corresponding relationship curve between the chloride ion concentration of the desulfurization slurry and the volume of desulfurization wastewater.

[0043] B. Based on the relationship curve and the preset chloride ion concentration value, determine the wastewater discharge volume of the power plant's desulfurization wastewater treatment, which corresponds to the upper limit of the desulfurization wastewater discharge volume to meet zero wastewater discharge. Given this lower limit, the chloride ion concentration of the desulfurization slurry is controlled at the lower limit of chloride ion concentration during slurry discharge; that is, slurry discharge is only permitted when the chloride ion concentration reaches or exceeds this value. The power plant's DCS system is equipped with an online chloride ion monitoring instrument. Considering the limitations of the online chloride ion monitoring instrument in actual control, slurry discharge can be considered when the online chloride ion monitoring data reaches the lower limit of chloride ion concentration control of 3000 ppm.

[0044] C. To prevent excessively high chloride ion concentrations in the desulfurization slurry of the absorption tower from causing harm, an upper limit for chloride ion concentration control is set. This means that when the chloride ion concentration reaches this value, slurry discharge must be accelerated. To ensure the utilization rate of limestone in the slurry and that the gypsum quality meets standards, slurry density is still used as a reference indicator for slurry discharge. Furthermore, a series of actions are taken by the control equipment based on the chloride ion concentration monitoring value of the absorption tower. Considering the need to reduce absorption tower corrosion, ensure desulfurization process efficiency, and guarantee that the chloride content of the gypsum meets standards, the upper limit for chloride ion concentration is set at 30,000 ppm. However, considering the limitations of the online chloride ion monitoring instrument in actual control, where online ion monitoring typically has a large absolute error at high ion concentrations, and since the desulfurization system's chloride ion control index is based on online monitoring data, to prevent the actual chloride ion concentration in the absorption tower from exceeding 30,000 ppm, the actual control upper limit is set at 27,000 ppm.

[0045] D. If the chloride ion concentration of the desulfurization slurry in the absorption tower is lower than the lower limit of chloride ion concentration control, the slurry continues to circulate, i.e., no slurry is discharged. If the slurry density does not meet the discharge requirements, but the chloride ion concentration of the desulfurization slurry in the absorption tower reaches the lower limit of chloride ion concentration control, no slurry is discharged. If the slurry density does not meet the discharge requirements, but the chloride ion concentration of the desulfurization slurry in the absorption tower reaches the upper limit of chloride ion concentration control, then slurry discharge must be carried out, and the reuse of high-chlorine water in the absorption tower should be reduced, i.e., the amount of wastewater underflow from the hydrocyclone should be reduced.

[0046] E. If the slurry density meets the discharge requirements, but the chloride ion concentration of the desulfurization slurry in the absorption tower does not reach the lower limit of chloride ion concentration control, then start the discharge pump and increase the reuse of high-chlorine water in the absorption tower, that is, increase the amount of wastewater hydrocyclone bottom flow water reused.

[0047] F. If the slurry density meets the discharge requirements and the chloride ion concentration of the desulfurization slurry in the absorption tower reaches the lower limit of chloride ion concentration control but does not reach the upper limit of chloride ion concentration control, then the discharge pump will be started normally.

[0048] G. If the slurry density meets the discharge requirements and the chloride ion concentration of the desulfurization slurry in the absorption tower reaches the upper limit of the chloride ion concentration control, the discharge pump should be started. During discharge, the reuse of high-chlorine water in the absorption tower should be reduced, that is, the amount of wastewater hydrocyclone bottom flow water reused should be reduced.

[0049] Further explanation of the above methods:

[0050] During the desulfurization slurry discharge process, although the slurry in the absorption tower undergoes complex circulation in equipment such as gypsum hydrocyclones, wastewater hydrocyclones, and vacuum belt conveyors, the chloride ions output from the desulfurization system outside the absorption tower only have two paths: desulfurization gypsum and wastewater. All other chloride ions return to the absorption tower. During the slurry circulation process, chloride ions are enriched in the absorption tower. Fig. 2 The entry and exit of chloride ions in the desulfurization system is described.

[0051] According to the law of conservation of mass, the change in chlorine content within the desulfurization system of the absorption tower is equal to the difference in chlorine content between the inlet and outlet of the system: In the formula, Δq represents the change in chloride ion content in the desulfurization system, and q in q represents the mass flow rate of chlorine in the inlet flue gas. CaCO3 Let q be the mass flow rate of chlorine in quicklime. H2O The mass flow rate of chlorine in the desulfurization process water, q out The mass flow rate of chlorine in the outlet flue gas is generally taken as 0, q CaSO4 Let q be the mass flow rate of chlorine in gypsum. f This represents the mass flow rate of chlorine in the desulfurization wastewater.

[0052] Furthermore, q f =C*V; △q=C2*V2-C1*V1; where C is the chloride ion concentration of the desulfurization wastewater, C1 is the chloride ion concentration of the slurry before the absorption tower discharges, and C2 is the chloride ion concentration of the slurry after the absorption tower discharges; substituting into (1) yields

[0053]

[0054] Under normal circumstances, the chloride ion concentration in the slurry does not fluctuate significantly, meaning that C, C1, and C2 are relatively close. Dividing both sides of the equation by C easily yields the result. The model shows that when the chloride ion concentration in the absorption tower is stable, the discharge of desulfurization wastewater is approximately inversely proportional to the chloride ion concentration in the desulfurization slurry. Fig. 3 This is a conceptual curve showing the relationship between desulfurization wastewater discharge and the controlled chloride ion concentration in the desulfurization slurry. With a constant chloride content in the inlet and outlet systems and a constant chloride ion content within the desulfurization system, the higher the chloride ion concentration in the desulfurization slurry during discharge, the lower the amount of desulfurization wastewater discharged.

[0055] To mitigate corrosion of the absorption tower and ensure desulfurization efficiency, the upper limit of chloride ion concentration is set at 30,000 ppm. However, considering the limitations of online chloride ion monitoring instruments in actual control, which typically have large absolute errors at high ion concentrations, and since the chloride ion control index of the desulfurization system is based on online monitoring data, the actual control upper limit is set at 27,000 ppm to prevent the actual chloride ion concentration in the absorption tower from exceeding 30,000 ppm.

[0056] The lower limit of chloride ion concentration control is estimated based on the water-chlorine balance model of the desulfurization system. After calculating the relationship curve between the desulfurization wastewater discharge and the chloride ion control concentration of the desulfurization slurry based on power plant-specific data, the chloride ion concentration of the slurry is controlled when the absorber discharges slurry to ensure that the power plant's desulfurization wastewater generation does not exceed the desulfurization wastewater disposal capacity, taking into account the power plant's desulfurization wastewater disposal capacity.

[0057] The slurry discharge operation should be initiated when the chloride concentration of the slurry is higher than the preset lower limit of chloride ion concentration control. If the slurry chloride ion concentration in the absorption tower is lower than this value, the discharged slurry will have a low chloride ion concentration. To discharge a certain amount of chloride ions accumulated in the absorption tower, the discharge volume will be high, resulting in excessive desulfurization wastewater discharge. When the online chloride ion monitoring data is lower than the lower limit of chloride ion concentration control, the slurry should be circulated as much as possible. When the online chloride ion monitoring data is higher than the lower limit of chloride ion concentration control, slurry discharge can be considered.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for regulating desulfurization wastewater discharge through online monitoring of chloride ions, characterized in that, include: Based on the online monitoring data of the power plant's DCS system and the relevant empirical values ​​of limestone consumption, gypsum production, gypsum chloride content, and evaporation water volume of the desulfurization system, the corresponding relationship curve between the chloride ion concentration of the desulfurization slurry and the volume of desulfurization wastewater was calculated. The wastewater discharge from the power plant's desulfurization wastewater treatment was determined based on the relationship curve and the preset chloride ion concentration value. The power plant's DCS system is equipped with an online chloride ion monitoring instrument. The criteria for determining wastewater discharge volume include: The upper limit of the desulfurization wastewater discharge volume that meets the zero wastewater discharge requirement corresponds to the lower limit of the chloride ion concentration control value of the desulfurization slurry. This lower limit corresponds to the lower limit of the chloride ion concentration control value when the desulfurization slurry is discharged, and the discharge of slurry begins. The criteria for judging wastewater discharge also include situations where the slurry density does not meet the discharge requirements: If the chloride ion concentration of the desulfurization slurry is below the lower limit of chloride ion concentration control or reaches the lower limit of chloride ion concentration control, then no slurry will be discharged. If the chloride ion concentration of the desulfurization slurry reaches the upper limit of chloride ion concentration control, the slurry will be discharged and the reuse of high-chlorine water in the absorption tower will be reduced. The slurry discharge also includes when the slurry density meets the slurry discharge requirements: If the chloride ion concentration in the slurry does not reach the lower limit of chloride ion concentration control, start the slurry discharge pump and increase the reuse of high-chlorine water from the absorption tower; If the chloride ion concentration of the desulfurization slurry reaches the lower limit of chloride ion concentration control but does not reach the upper limit of chloride ion concentration control, the slurry discharge pump will be started normally. If the chloride ion concentration in the desulfurization slurry reaches the upper limit of the chloride ion concentration control, the slurry discharge pump should be started, and the reuse of high-chlorine water from the absorption tower should be reduced during slurry discharge.

2. The method for regulating desulfurization wastewater discharge by online monitoring of chloride ions according to claim 1, characterized in that, The online chloride ion monitoring instrument uses an ion-selective electrode and is installed in the desulfurization slurry sampling pipeline to obtain the chloride ion concentration of the absorption tower slurry in real time.

3. A system for regulating desulfurization wastewater discharge through online chloride ion monitoring, characterized in that, The system includes: The DCS system is equipped with an online chloride ion monitoring instrument. The CS system is used to determine the wastewater discharge from the power plant's desulfurization wastewater treatment based on the monitoring data and the preset range of chloride ion concentration. The DCS system is also used to: control the lower limit of chloride ion concentration in desulfurization slurry according to the upper limit of desulfurization wastewater discharge volume with zero wastewater discharge, which corresponds to the lower limit of chloride ion concentration control when desulfurization slurry is discharged, and start slurry discharge; The DCS system is also used to determine... When the slurry density does not meet the slurry discharge requirements: If the chloride ion concentration of the desulfurization slurry is below the lower limit of chloride ion concentration control or reaches the lower limit of chloride ion concentration control, then no slurry will be discharged. If the chloride ion concentration of the desulfurization slurry reaches the upper limit of chloride ion concentration control, the slurry will be discharged and the reuse of high-chlorine water in the absorption tower will be reduced. When the slurry density reaches the discharge requirement: If the chloride ion concentration in the slurry does not reach the lower limit of chloride ion concentration control, start the slurry discharge pump and increase the reuse of high-chlorine water from the absorption tower; If the chloride ion concentration of the desulfurization slurry reaches the lower limit of chloride ion concentration control but does not reach the upper limit of chloride ion concentration control, the slurry discharge pump will be started normally. If the chloride ion concentration in the desulfurization slurry reaches the upper limit of the chloride ion concentration control, the slurry discharge pump should be started, and the reuse of high-chlorine water from the absorption tower should be reduced during slurry discharge.

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