Online control of the oxidation state of desulfurization slurry by Ca2+ concentration and pH in the slurry

Abstract

Ca in desulfurization slurry 2+ A method for controlling the oxidation state of a slurry online by concentration and pH, comprising: 2+ The step of acquiring the concentration and pH value, and calculating the oxidation air excess coefficient (α) and the pH value of the slurry by the oxidation air excess coefficient (α)-pH-SO3 under the oxidation air amount. 2- Enter the concentration model and calculate the SO3 in the desulfurization slurry. 2- Then, the real-time concentration of SO3 in the desulfurization slurry is obtained. 2- and the real-time concentration of SO3 when CaSO3 precipitates. 2- Calculating a CaSO3 precipitation index pi based on the critical concentration of CaSO3; and controlling the amount of oxidation air based on the CaSO3 precipitation index pi to remove Ca from the desulfurization slurry. 2+ and controlling the oxidation state of the slurry online by concentration and pH.

Description

[Technical field]

[0001] The present disclosure belongs to the technical field of chemistry, and relates to a method for the detection of Ca in a desulfurization slurry. 2+ The present invention relates to a method for controlling the oxidation state of a slurry online by concentration and pH.

[0002] This application is filed based on a Chinese patent application bearing application number 202210827492.6 and filing date July 14, 2022, and claims priority to the Chinese patent application, the entire contents of which are hereby incorporated by reference into this application. [Background technology]

[0003] Currently, coal-fired power generation units mainly use a wet desulfurization process using limestone-gypsum to remove SO2 from flue gas. The SO2 in the flue gas is captured in a slurry and then decomposed into reduced +4 sulfur species (H2SO3, HSO3 - , SO3 2- ) and is oxidized by the oxidizing fan to Ca 2+ When the slurry is under-oxidized, H2SO3, HSO3 - , SO3 2- Tetravalent sulfur substances such as these are produced, and the pH of the desulfurization slurry is usually controlled at 4-6, at which point the H2SO3 content can be ignored. The degree of oxidation of the desulfurization slurry in the absorption tower can be evaluated based on the sulfite content in the slurry, and by controlling the oxidation state of the slurry in real time and precisely adjusting the amount of oxidation air, this contributes to the realization of safe, energy-saving operation and automatic control of the desulfurization system.

[0004] The analysis of sulfite content in desulfurization slurry mainly adopts manual sampling and laboratory detection methods. Because sulfite itself is easily oxidized, the oxidation state of the slurry tested by this method is significantly delayed compared with the actual situation, so the laboratory detection results are significantly deviated from the actual slurry situation, and the quality of the gypsum cannot be ensured. Summary of the Invention [Problem to be solved by the invention]

[0005] The purpose of this disclosure is to 2+ The aim is to provide a method for online control of the oxidation state of the slurry through concentration and pH. [Means for solving the problem]

[0006] In order to achieve the above object, the Ca in the desulfurization slurry described in the present disclosure 2+ The method of controlling the oxidation state of the slurry online by concentration and pH is as follows: Ca in the slurry 2+ obtaining concentration and pH values; The oxidation air excess coefficient (α) and the pH value of the slurry are calculated by the oxidation air excess coefficient (α)-pH-SO3 under the oxidation air amount. 2- Enter the concentration model and calculate the SO3 in the desulfurization slurry. 2- Then, the real-time concentration of SO3 in the desulfurization slurry is obtained. 2- and the real-time concentration of SO3 when CaSO3 precipitates. 2- calculating a CaSO3 precipitation index pi based on the critical concentration of The amount of oxidation air is controlled based on the CaSO3 precipitation index pi, and the Ca in the desulfurization slurry is 2+ and controlling the oxidation state of the slurry online by concentration and pH.

[0007] In some embodiments, the Ca in the slurry 2+ The concentration was measured in real time by a calcium ion meter, and the pH value of the slurry was measured in real time by a pH meter.

[0008] In some embodiments, the method further comprises: Oxidation air excess coefficient (α)-pH-SO3 under various oxidation air amounts 2- establishing a concentration model; SO3 when CaSO3 precipitates 2- and determining a critical concentration of

[0009] In some embodiments, the oxidation air excess coefficient α is the ratio of the amount of oxidation air actually supplied by the absorber to the theoretical amount of oxidation air required to completely oxidize the SO2 captured by the absorber under conditions where the flue gas is considered to be capable of naturally oxidizing 10% of the SO2, i.e., JPEG2025503316000002.jpg2154, where Q is the amount of oxidation air actually supplied by the absorption tower, and S is the amount of SO2 captured by the absorption tower. The values ​​of Q and S are both obtained as real-time data by the DCS system.

[0010] In some examples, the SO3 2- The critical concentration of Ca 2+ and SO3 2- The solubility product constant K sp From the formula Determined by JPEG2025503316000003.jpg1730.

[0011] In some examples, the oxidation air excess coefficient (α)-pH-SO3 under various oxidation air amounts is 2- In the process of establishing the concentration model, specifically, 1) While keeping the amount of oxidation air constant, the SO2 processing amount of the absorption tower is adjusted by changing the load of the unit or adjusting the opening of the bypass valve. When the SO2 processing amount of the absorption tower changes, the oxidation air excess coefficient α also changes accordingly. Chemical analysis by iodometric titration method shows that the +4 valence sulfur substances H2SO3, HSO3 - and SO3 2- The total concentration of H2SO3, HSO3, and the excess oxidation air coefficient α and the sulfur species H2SO3, HSO3 - and SO3 2- The relationship between the total concentration of 2) Adjust the amount of oxidation air and repeat step 1) so that the range of oxidation air amounts includes low, medium, and high SO2 throughput of the absorption tower. The oxidation air excess coefficient α and the +4 sulfur species H2SO3, HSO3 under various oxidation air amounts are calculated. - and SO3 2- The relationship between the total concentration of 3) The oxidation air excess coefficient α and the +4 sulfur species H2SO3, HSO3 under various oxidation air amounts obtained in step 2) - and SO3 2- The relationship between the total concentration of and the fitting equation was obtained: 4) H2SO3, HSO3 - and SO3 2- The effect of pH on the concentration distribution relationship was introduced into the fitting equation, and the oxidation air excess coefficient (α)-pH-SO3 under various oxidation air amounts was calculated. 2- Establish a concentration model.

[0012] In some embodiments, the oxidation air excess factor (α)-pH-SO 2- SO3 in slurry in the process of establishing concentration model 2- In the process of determining the concentration, First, the +4 valence sulfur substances H2SO3, HSO3 - and SO3 2- The total concentration of H2SO3, HSO3 at various pH levels was then obtained. - and SO3 2- According to the dissociation equilibrium relationship of SO3 in the slurry 2- The concentration of H2SO3 is calculated, and when the pH value of the slurry is controlled between 4 and 6, the H2SO3 content can be neglected.

[0013] In some embodiments, the CaSO3 precipitation index pi is the amount of SO3 in the slurry. 2- Real-time concentration of and SO3 2- is the ratio of the critical concentration of

[0014] In some embodiments, when 0.8≦pi≦1, the system is in good oxidation and the amount of oxidation air is maintained the same; when pi<0.8, the system is in an over-oxidation state and the amount of oxidation air is decreased; when pi>1, the system is in an under-oxidation state and the amount of oxidation air is increased. [Brief description of the drawings]

[0015] [Figure 1] This is a schematic diagram of the relationship between the oxidation air excess coefficient α and the total concentration of the +4 sulfur species H2SO3, HSO3 -, and SO3 2-, as well as the proportion of sulfite radicals at various pH values. [Diagram 2] Figure 3-D diagram of the oxidation air excess coefficient (α)-pH-SO3 2-concentration model under various oxidation air amounts. [Diagram 3] FIG. 1 is a logic diagram of an online control designed based on the CaSO3 precipitation index (pi). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In order to allow those skilled in the art to better understand the aspects of the present disclosure, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings in the embodiments of the present disclosure. However, it is clear that the described embodiments are only some embodiments of the present disclosure, not all embodiments, and do not limit the scope of the present disclosure. In addition, in the following description, in order to avoid unnecessary confusion of the concepts disclosed in the present disclosure, the description of known configurations and technologies will be omitted. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present disclosure.

[0017] The drawings show schematic diagrams of the structures of the embodiments disclosed in the present disclosure. These drawings are not drawn to scale, and some details may be enlarged or omitted for clarity. The shapes of various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are illustrative, and may vary in practice due to manufacturing tolerances or technical constraints. Those skilled in the art may separately design regions / layers having different shapes, sizes, and relative positions according to actual needs.

[0018] As shown in FIG. 1, FIG. 2 and FIG. 3, the Ca in the desulfurization slurry described in the present disclosure 2+ The method of controlling the oxidation state of the slurry online by concentration and pH is to determine the Ca 2+ Including concentration and pH value monitoring, determination of CaSO3 precipitation index pi, and online oxidation control.

[0019] Ca in the desulfurization slurry according to the present disclosure 2+ The method of controlling the oxidation state of the slurry online by concentration and pH is to determine the Ca 2+ The step of acquiring the concentration and pH value, and calculating the oxidation air excess coefficient (α) and the pH value of the slurry by the oxidation air excess coefficient (α)-pH-SO3 under the oxidation air amount. 2- Enter the concentration model and calculate the SO3 in the desulfurization slurry. 2- Then, the real-time concentration of SO3 in the desulfurization slurry is obtained. 2- and the real-time concentration of SO3 when CaSO3 precipitates. 2- Calculating a CaSO3 precipitation index pi based on the critical concentration of CaSO3; and controlling the amount of oxidation air based on the CaSO3 precipitation index pi to remove Ca from the desulfurization slurry. 2+ and controlling the oxidation state of the slurry online by concentration and pH.

[0020] In some embodiments, the Ca in the slurry 2+ The concentration was measured in real time by a calcium ion meter, and the pH value of the slurry was measured in real time by a pH meter.

[0021] In the process of determining the CaSO3 precipitation index pi, 1) the oxidation air excess coefficient (α)-pH-SO3 under various oxidation air amounts 2- Establish a concentration model, and 2) the concentration of SO3 when CaSO3 precipitates. 2- Determine the critical concentration and 3) calculate the CaSO3 precipitation index pi.

[0022] The oxidation air excess coefficient α is the ratio between the amount of oxidation air actually supplied by the absorption tower and the theoretical amount of oxidation air required to completely oxidize the SO2 captured by the absorption tower under conditions where it is considered that 10% of the SO2 in the flue gas can be naturally oxidized, i.e., JPEG2025503316000004.jpg2154 where Q is the amount of oxidation air actually supplied by the absorption tower, and S is the amount of SO2 captured by the absorption tower. The values ​​of Q and S are both obtained in real time by the DCS system.

[0023] The SO3 2- In the process of determining the concentration, first, the +4 valence sulfur substances H2SO3, HSO3 in the slurry are determined by chemical analysis using iodometric titration. - and SO3 2- The total concentration of H2SO3, HSO3 at various pH levels was then obtained. - and SO3 2- According to the dissociation equilibrium relationship of SO3 2- The concentration of H2SO3 is calculated, and when the pH value of the desulfurization slurry is controlled between 4 and 6, the H2SO3 content can be neglected.

[0024] The oxidation air excess coefficient (α)-pH-SO3 under various oxidation air amounts 2- The concentration model is obtained through testing, specifically: 1) While keeping the amount of oxidation air constant, the SO2 processing amount in the absorption tower is adjusted by changing the load of the unit or adjusting the opening of the bypass valve. When the SO2 processing amount in the absorption tower changes, the oxidation air excess coefficient α also changes accordingly. Chemical analysis by iodometric titration method shows that the +4 valence sulfur substances H2SO3, HSO3 - and SO3 2- The total concentration of H2SO3, HSO3, and the excess oxidation air coefficient α and the sulfur species H2SO3, HSO3 - and SO3 2- The relationship between the total concentration of 2) Adjust the amount of oxidation air and repeat step 1) so that the range of oxidation air amounts includes low, medium, and high SO2 throughput of the absorption tower. The oxidation air excess coefficient α and the +4 sulfur species H2SO3, HSO3 under various oxidation air amounts are calculated. - and SO3 2- The relationship between the total concentration of 3) The oxidation air excess coefficient α and the +4 sulfur species H2SO3, HSO3 under various oxidation air amounts obtained in step 2) - and SO3 2- The relationship between the total concentration of and the fitting equation was obtained: 4) H2SO3, HSO3 - and SO3 2- The effect of pH on the concentration distribution relationship was introduced, and the oxidation air excess coefficient (α)-pH-SO3 under various oxidation air amounts was calculated. 2- Establish a concentration model.

[0025] SO3 when CaSO3 precipitates 2- In the process of determining the critical concentration, specifically, SO3 2- The critical concentration is Ca 2+ and SO3 2- The solubility product constant K sp From the formula

[0026] Determined by JPEG2025503316000005.jpg1730, Ca 2+ The concentration is obtained in real time by a calcium ion meter.

[0027] The CaSO3 precipitation index pi is the amount of SO3 in the slurry. 2- Real-time concentration of and SO3 2- The ratio of the critical concentration to the SO3 in the desulfurization slurry. 2- The real-time concentration of is calculated by the oxidation air excess factor (α)-pH-SO3 2- Obtained by the model.

[0028] In the online oxidation control, the control logic is designed based on the CaSO3 precipitation index pi: when 0.8≦pi≦1, the system is in good oxidation and the amount of oxidation air is maintained; when pi<0.8, the system is in over-oxidation and the amount of oxidation air is reduced; when pi>1, the system is in under-oxidation and the amount of oxidation air is increased.

[0029] The adjustment of the amount of oxidation air can be realized by changing the number of oxidation fans and their combination form or the frequency of the oxidation fans.

[0030] Ca in the desulfurization slurry according to the present invention 2+ When specifically implementing the method of controlling the oxidation state of the slurry online by concentration and pH, the Ca 2+ Concentration, pH value and oxidation air excess coefficient (α)-pH-SO3 2- Using a concentration model, the SO3 in the desulfurization slurry 2- The real-time concentration of CaSO3 is determined, the CaSO3 precipitation index pi is calculated from the concentration, and finally, the oxidation air amount is controlled by the index, thereby controlling the oxidation state of the wet desulfurization slurry in real time, thereby ensuring the quality of gypsum, the process is simple, the monitoring result is accurate, and the practicality is very high. In the description of this disclosure, the terms "first", "second", etc. are merely for the purpose of explanation and should not be understood as indicating or implying relative importance. In the description of this disclosure, "plurality" means two or more unless otherwise specified.

[0031] Descriptions of processes or methods depicted as flowcharts or otherwise may be understood to represent modules, fragments or portions of code that comprise one or more executable instructions for implementing particular logical functions or process steps. Also, the scope of the preferred embodiments of the present disclosure includes other implementations, in which functions may be performed out of the order shown or discussed, such as substantially simultaneously or in reverse order, depending on the functionality involved, as should be understood by those skilled in the art.

[0032] In the description herein, a statement referring to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described with reference to the embodiment or example are included in at least one embodiment or example of the present disclosure. In the present specification, general expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0033] Although the present disclosure has been described in detail above using general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made based on the present disclosure. Therefore, any of these modifications or improvements made without departing from the spirit of the present disclosure belong to the scope of the claims of the present disclosure.

Claims

【Request 1】 Ca in desulfurization slurry ２＋ 1. A method for online control of the oxidation state of a slurry by concentration and pH, comprising: Ca in the slurry ２＋ obtaining concentration and pH values; The oxidation air excess coefficient (α) and the pH value of the slurry are calculated by the oxidation air excess coefficient (α)-pH-SO ３ ２－ The concentration model is input to the SO ３ ２－ and then obtain the real-time concentration of SO in the desulfurization slurry. ３ ２－ Real-time concentration of CaSO ３ When precipitated, SO ３ ２－ Based on the critical concentration of CaSO ３ Calculating the precipitation index p; CaSO ３ The amount of oxidation air is controlled based on the precipitation index pi, and the Ca in the desulfurization slurry is ２＋ and controlling the oxidation state of the slurry online by the concentration and pH of the Ca in the desulfurization slurry. ２＋ A method for controlling the oxidation state of the slurry online through concentration and pH. 【Request 2】 Ca in the slurry ２＋ The Ca concentration in the desulfurization slurry according to claim 1 is measured in real time by a calcium ion meter, and the pH value of the slurry is measured in real time by a pH meter. ２＋ A method for controlling the oxidation state of the slurry online through concentration and pH. 【Request 3】 Oxidation air excess coefficient (α) under various oxidation air amounts - pH - SO ３ ２－ establishing a concentration model; CaSO ３ When precipitated, SO ３ ２－ and determining a critical concentration of Ca in the desulfurization slurry according to claim 1. ２＋ A method for controlling the oxidation state of the slurry online through concentration and pH. 【Request 4】 The oxidation air excess coefficient α is the ratio of the exhaust gas to the total SO ２ The amount of oxidation air actually supplied by the absorption tower and the amount of SO captured by the absorption tower under conditions that are considered to be capable of natural oxidation. ２ is the ratio of the amount of oxidation air required to completely oxidize the [0010] where Q is the amount of oxidation air actually supplied by the absorption tower, and S is the amount of SO trapped by the absorption tower. ２ The amount of Ca in the desulfurization slurry according to claim 3, wherein the values ​​of Q and S are obtained in real time by a DCS system. ２＋ A method for controlling the oxidation state of the slurry online through concentration and pH. 【Request 5】 CaSO ３ When precipitated, SO ３ ２－ The critical concentration of Ca ２＋ and S.O. ３ ２－ Solubility product constant K ｓｐ From the formula [0025] The Ca in the desulfurization slurry according to claim 3 is determined by ２＋ A method for controlling the oxidation state of the slurry online through concentration and pH. [Request 6] Oxidation air excess coefficient (α) under various oxidation air amounts - pH - SO ３ ２－ In the process of establishing the concentration model, specifically, 1) By changing the load of the unit or adjusting the opening of the bypass valve while keeping the amount of oxidation air constant, the SO ２ Adjust the processing volume to reduce the SO ２ When the treatment amount changes, the oxidation air excess coefficient α also changes accordingly, and various SO ２ +4 sulphur substance H under treatment conditions ２ SO ３ , H.S.O. ３ － and S.O. ３ ２－ The total concentration of the oxidation air excess coefficient α and the +4-valent sulfur substance H ２ SO ３ , H.S.O. ３ － and S.O. ３ ２－ The relationship between the total concentration of 2) Adjust the amount of oxidation air and repeat step 1) to adjust the low, medium, and high SO ２ The oxidation air excess coefficient α and the +4 sulfur substance H under various oxidation air amounts are calculated by including the treatment amount. ２ SO ３ , H.S.O. ３ － and S.O. ３ ２－ The relationship between the total concentration of 3) The oxidation air excess coefficient α and the +4-valent sulfur substance H under various oxidation air amounts obtained in step 2) ２ SO ３ , H.S.O. ３ － and S.O. ３ ２－ The relationship between the total concentration of and the fitting equation was obtained: 4) H ２ SO ３ , H.S.O. ３ － and S.O. ３ ２－ The effect of pH on the concentration distribution relationship was introduced into the fitting equation, and the oxidation air excess coefficient (α)-pH-SO ３ ２－ Establish a concentration model for Ca in the desulfurization slurry according to claim 5. ２＋ A method for controlling the oxidation state of a slurry online through concentration and pH. 【Request 7】 SO in the slurry ３ ２－ In the process of determining the concentration, First, the +4 valence sulfur substance H in the slurry was determined by chemical analysis using iodometric titration. ２ SO ３ , H.S.O. ３ － and S.O. ３ ２－ The total concentration of H was then calculated at various pH values. ２ SO ３ , H.S.O. ３ － and S.O. ３ ２－ According to the dissociation equilibrium relationship of SO in the slurry, ３ ２－ The concentration of H is calculated, and when the pH value of the slurry is controlled between 4 and 6, ２ SO ３ The Ca content in the desulfurization slurry according to claim 6 is negligible. ２＋ A method for controlling the oxidation state of a slurry online through concentration and pH. 【Request 8】 CaSO ３ The precipitation index pi is the amount of SO in the slurry. ３ ２－ Real-time concentrations of and SO ３ ２－ The ratio of Ca in the desulfurization slurry according to claim 1 to the critical concentration of ２＋ A method for controlling the oxidation state of a slurry online through concentration and pH. 【Request 9】 The Ca in the desulfurization slurry according to claim 1, wherein when 0.8≦pi≦1, the system is in a good oxidation state and the amount of oxidation air is maintained as it is; when pi<0.8, the system is in an over-oxidation state and the amount of oxidation air is decreased; when pi>1, the system is in an under-oxidation state and the amount of oxidation air is increased. ２＋ A method for controlling the oxidation state of a slurry online through concentration and pH.

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