Online analysis system for content of sulfur trioxide in wet-process phosphoric acid process

Abstract

The utility model provides a sulfur trioxide content on-line analysis system in a wet-process phosphoric acid process, and relates to the technical field of industrial on-line pretreatment and detection. Clear liquid is extracted by the circulating sampling device through a stoste sampling pump capable of rotating forwards and reversely so as to obtain a backwashing pipeline, the quantitative pre-sampling device is connected with the titration reaction device through a pipeline, the other end of the quantitative pre-sampling device is connected with a sample switching valve, and a sample is quantitatively extracted to the titration reaction device through a clear liquid taking pump; the quantitative reagent adding device quantitatively extracts a selected reagent through a reagent pump and pushes the reagent into the titration reaction device, a sample and the reagent are subjected to a titration reaction, the change in the reaction process is measured, and the content of sulfur trioxide is obtained; the whole process is automatically controlled, manual subjective judgment is eliminated, manual operation is reduced, the analysis efficiency is improved, and the accuracy of a measurement result is improved; and the backflushing valve and the cleaning device are arranged to prevent impurities from being separated out, so that the smoothness of the pipeline is guaranteed, and the stability of the system is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to industrial on -line pretreatment and detection technical field especially, it is a kind of sulfur trioxide content on -line analysis system in wet-process phosphoric acid process. BACKGROUND

[0002] Wet-process phosphoric acid production usually uses sulfuric acid as one of reactants, and sulfuric acid reacts with phosphate rock (main component is calcium fluorophosphate Ca5F (PO4) 3) to generate phosphoric acid and byproduct phosphogypsum calcium sulfate (main component is calcium sulfate). In this process, sulfuric acid will ionize hydrogen ion (H + ) and sulfate ion, (SO4 2- ) will further combine with hydrogen ion (H + ) to form sulfur trioxide. By controlling the concentration of sulfur trioxide, the reaction process can be made to obtain suitable phosphogypsum crystallization. The crystallization form and size of phosphogypsum have important influence on subsequent filtration operation. Suitable crystallization form and size can improve filtration efficiency and reduce production cost. Controlling the concentration of sulfur trioxide can also guide the control of the amount of concentrated sulfuric acid added in the reaction. Too much sulfuric acid will cause the content of sulfate in the product to increase, affecting product quality; while too little sulfuric acid may not completely replace P2O5 in the ore powder, reducing production efficiency. Therefore, by regularly testing these indicators, the amount of sulfuric acid added can be accurately controlled to optimize production cost and product quality.

[0003] In the prior art, it is not easy to control the amount of sulfuric acid added to optimize the concentration of sulfur trioxide (or sulfuric acid). Too much sulfuric acid will cause the content of sulfate in the product to exceed the standard, damaging product quality; while too little sulfuric acid may not fully replace P2O5 in phosphate rock, thereby reducing production efficiency. Therefore, the current industry often uses the method of regularly testing related indicators to accurately regulate the amount of sulfuric acid added, in order to achieve the best balance of production cost and product quality.

[0004] During the test, manual titration is a common analysis method, which involves using a pipette to accurately measure a certain volume of barium chloride (BaCl2) solution and injecting it into a beaker, and then adding sodium rose bengal indicator, which is: 1. The toxicity (safety level S24 / 25) of sodium rose bengal increases the safety risk during operation, and the operator must strictly follow the safety procedures. 2. Manual titration also requires high precision and skill from the operator, as the judgment of the titration endpoint (i.e. the color of the solution changes to white) largely depends on the subjective visual judgment and experience accumulation of the operator, which not only may lead to systematic bias in measurement results, but also may reduce the stability of the experiment due to the fatigue and distraction of the operator. 3. When the high-temperature reaction slurry discharged from the wet-process phosphoric acid reaction tank enters the automated analysis system, its temperature gradually decreases. During this process, impurities such as potassium, sodium and magnesium salts in the slurry may crystallize and precipitate as the temperature decreases. The precipitated crystals gradually accumulate in the automated equipment, forming scale, which not only affects the accuracy of the analysis data, but also threatens the stable operation of the system. Practical new type content

[0005] The main purpose of the present application is to provide an online analysis system for sulfur trioxide content in wet-process phosphoric acid process, which solves the technical problems of high safety risk, subjective judgment error leading to systematic bias and impurity precipitation in the prior art.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is: an online analysis system for sulfur trioxide content in wet-process phosphoric acid process, comprising:

[0007] The circulating sampling device comprises a reversible stock solution sampling pump, one end of the stock solution sampling pump is connected to the tank liquid pool through a pipeline, and the other end of the stock solution sampling pump is connected to a liquid inlet valve and a backflush valve for continuously extracting sample clear liquid and backwashing the pipeline to prevent scaling;

[0008] The quantitative pre-sampling device is connected to the titration reaction device, and the quantitative pre-sampling device comprises a clear liquid sampling pump connected to the titration reaction device through a pipeline, the other end of the clear liquid sampling pump is connected to a multi-channel sample switching valve, the sample switching valve is connected to the circulating sampling device through a clear liquid circulating pump, and the sample switching valve is used to quantitatively extract the sample into the titration reaction device;

[0009] The quantitative reagent adding device is symmetrically arranged with the quantitative pre-sampling device, the quantitative reagent adding device is connected to the titration reaction device, and comprises a reagent adding pump connected to the titration reaction device through a pipeline, the other end of the reagent adding pump is connected to a multi-channel reagent switching valve, the reagent switching valve is used to realize switching of different reagents, and the reagent adding pump is used to extract and push the selected reagent into the titration reaction device; the reagent comprises barium chloride, sodium rose bengal and pure water;

[0010] The titration reaction device comprises a reaction cup and a reaction cup cover arranged on the reaction cup, and a quantitative pre-sampling device and a quantitative reagent adding device are respectively connected to the reaction cup cover through pipelines and extend into the reaction cup, so that the titration reaction is carried out and the measurement result is obtained.

[0011] In the preferred solution, the titration reaction device further comprises: an overflow port arranged above the reaction cup, a magnetic stirring rod arranged inside the bottom surface of the reaction cup, and a groove arranged on one side of the bottom of the reaction cup and connected to an external waste discharge pump.

[0012] In the preferred solution, the titration reaction device further comprises: the reaction cup is made of transparent material, and an absorbance sensor is further arranged inside the reaction cup and used for detecting the absorbance value change in the discoloration reaction process of the solution.

[0013] In the preferred solution, a filtering device is further arranged and used for filtering the calcium sulfate crystals in the tank liquid to obtain the clear liquid, the clear liquid is extracted into a filtering container through a clear liquid circulating pump, and a backflush valve is arranged between the filtering container and the circulating sampling device.

[0014] A plurality of filter membranes are arranged inside the filtering container, and a groove is arranged directly below the bottom of the filtering container and connected to an external waste discharge pump through a pipeline.

[0015] In the preferred solution, the circulating sampling device further comprises: a liquid inlet valve and a liquid inlet backflow valve arranged between the liquid inlet valve and the tank liquid pool.

[0016] A clear liquid backflow valve is arranged between the upper portion of one side of the filtering container and the tank liquid pool.

[0017] In the preferred solution, the circulating sampling device, the quantitative pre-sampling device, the quantitative reagent adding device and the titration reaction device are electrically connected to an external PLC control system.

[0018] The present application provides a sulfur trioxide content online analysis system in a wet-process phosphoric acid process, and the embodiment extracts the clear liquid through the circulating sampling device through the reversible stock solution sampling pump 1 to perform the extraction and backwashing pipeline, the quantitative pre-sampling device is connected to the titration reaction device through the clear liquid pump through the pipeline, and the other end is connected to the sample switching valve; the sample switching valve can receive the sample from the circulating sampling device, and the sample is quantitatively extracted into the titration reaction device through the clear liquid pump; similarly, the quantitative reagent adding device adds the selected reagent quantitatively and pushes it into the titration reaction device through the reagent pump, the sample and the reagent perform the titration reaction, and the content of sulfur trioxide is obtained by measuring the change in the reaction process; the embodiment is automatically controlled throughout the process, eliminates the subjective judgment of manual operation, improves the analysis efficiency, improves the accuracy of the measurement result, the circulating sampling device continuously extracts the sample, ensures the real-time monitoring of the sulfur trioxide content, and sets the backflush valve and the cleaning device to avoid the precipitation of impurities, ensures the smoothness of the pipeline, and improves the stability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0020] Figure 1 This is a schematic diagram of the structure of the online analysis system of this utility model;

[0021] Figure 2 This is a flowchart of the operation of the sulfur trioxide concentration detection system of this utility model;

[0022] Figure 3 This is a graph showing the change in absorbance values ​​during the sulfur oxidation reaction process of this utility model.

[0023] In the diagram: 1. Original liquid sampling pump; 2. Inlet valve; 3. Inlet reflux valve; 4. Clear liquid reflux valve; 5. Sludge discharge valve; 6. Backflush valve; 7. Filter membrane; 8. Filter container; 9. Clear liquid circulation pump; 10. Sample switching valve; 11. Clear liquid collection pump; 12. Reagent switching valve; 13. Reagent addition pump; 14. Reaction cup; 15. Reaction cup lid; 16. Magnetic stir bar; 17. Overflow port; 18. Waste discharge pump. Detailed Implementation

[0024] Example 1

[0025] like Figures 1-3 As shown, an online analysis system for sulfur trioxide content in a wet-process phosphoric acid production process includes:

[0026] The filtration device is used to filter the calcium sulfate crystals in the tank solution to obtain a clear liquid. The clear liquid is then pumped into the filtration container 8 by the clear liquid circulation pump 9. The backwash valve 6 is located between the filtration container 8 and the circulation sampling device.

[0027] The circulating sampling device includes a raw liquid sampling pump 1 that can be rotated forward and backward. One end of the raw liquid sampling pump 1 is connected to the tank liquid via a pipeline, and the other end of the raw liquid sampling pump 1 is connected to an inlet valve 2 and a backwash valve 6 via a pipeline, which are used to continuously extract sample clear liquid and backwash the pipeline to prevent scaling.

[0028] The quantitative pre-sampling device is connected to the titration reaction device. The quantitative pre-sampling device includes a clear liquid pump 11 connected to the titration reaction device through a pipeline. The other end of the clear liquid pump 11 is connected to a multi-channel sample switching valve 10. The sample switching valve 10 is connected to a circulating sampling device through a clear liquid circulation pump 9, which is used to quantitatively extract the sample into the titration reaction device.

[0029] The quantitative reagent addition device and the quantitative pre-sampling device are symmetrically arranged. The quantitative reagent addition device is connected to the titration reaction device and includes a reagent addition pump 13 connected to the titration reaction device through a pipeline. The other end of the reagent addition pump 13 is connected to a multi-channel reagent switching valve 12, which is used to switch between different reagents. The reagent addition pump 13 draws and pushes the selected reagent into the titration reaction device. The reagents include barium chloride, sodium rosemate, and pure water.

[0030] The titration reaction device includes a reaction cup 14 and a reaction cup cover 15 arranged on the reaction cup 14, and the quantitative pre-sampling device and the quantitative reagent adding device are respectively connected to the reaction cup 14 through the reaction cup cover 15 and extend into the reaction cup 14, so as to perform the titration reaction and obtain the measurement result.

[0031] In the embodiment, the calcium sulfate crystals in the tank liquid are filtered by the filtering device to obtain the clear liquid without impurities, the clear liquid is extracted by the positive and negative reversible raw liquid sampling pump 1 of the circulating sampling device to perform the extraction and backwashing pipeline, the clear liquid pump 11 of the quantitative pre-sampling device is connected to the titration reaction device through the pipeline, and the other end is connected to the sample switching valve 10; the sample switching valve 10 can receive the sample from the circulating sampling device, and the sample is quantitatively extracted to the titration reaction device through the clear liquid pump 11; similarly, the quantitative reagent adding device adds the selected reagent quantitatively extracted and pushed into the titration reaction device through the reagent pump 13, the sample and the reagent perform the titration reaction, and the content of sulfur trioxide is obtained by measuring the change in the reaction process; the embodiment is automatically controlled throughout, eliminates the subjective judgment of manual operation, reduces the manual operation, improves the analysis efficiency, improves the accuracy of the measurement result, the circulating sampling device continuously extracts the sample, ensures the real-time monitoring of the content of sulfur trioxide, and sets the backflush valve and the cleaning device to avoid the precipitation of impurities, ensure the smoothness of the pipeline, and improve the stability of the system.

[0032] The filtering process of the embodiment specifically includes five parts of "liquid inlet, filtration, backflush, sedimentation, and residue discharge".

[0033] Specifically, the following steps are included:

[0034] S1, the liquid inlet process, the liquid inlet backflow valve 3 is closed, the liquid inlet valve 2 and the clear liquid backflow valve 4 are opened, the raw liquid sampling pump 1 extracts the industrial raw liquid to be filtered from the tank liquid and pumps it into the filtering container 8 to start the filtration.

[0035] S2, the filtration process, when filtering, the clear liquid passes through the filter membrane 7 into the upper cylinder of the filtering container 8, and the suspended particles in the liquid are intercepted on the filter membrane surface to form a filter cake. After the clear liquid extraction process is completed, step S3 is performed.

[0036] S3, the backflush process, the liquid inlet backflow valve 3 is opened, the liquid inlet valve 2 is closed, and the backflush valve 6 is opened, and the filtered clear liquid is used to backflush downward, and the filter cake is quickly separated from the filter membrane surface.

[0037] S4, the sedimentation process, after backflush, the filter cake is settled to the bottom cone of the filtering container 8, and then is gathered to the residue discharge valve 5.

[0038] S5, the residue discharge process, when the filter cake reaches a certain amount, the residue discharge valve 5 is opened, the filter cake is quickly discharged, and the residual filter cake remaining on the filter membrane surface is quickly separated from the filter membrane surface through secondary backflush.

[0039] After filtration, sampling is performed, which improves the accuracy of the test.

[0040] As shown in Figure 1 The quantitative pre-sampling device includes a sample switching valve 10 and a supernatant pump 11. After the sample is extracted, it is stored in the supernatant pump 11, which is then added to the reaction cup as a titrant for the sulfur trioxide reaction. The specific steps are as follows: the forward rotation of the supernatant circulating pump 9 for 60 seconds makes the supernatant fill the circulating pipeline, the sample switching valve 10 is switched to the 10-1 port, the supernatant pump 11 extracts the sample rinse, it is switched to the 10-5 port to discharge to the waste liquid, and then the valve is switched to the 10-1 port, and 10 mL of pre-sampling is stored in the supernatant pump 11.

[0041] In this embodiment, the liquid inlet pipeline of the stock solution sampling pump 1 is below the supernatant liquid level, and the liquid outlet pipeline is suspended. Forward rotation is used for circulating sampling, and reverse rotation is used for dilute sulfuric acid backwashing to prevent pipeline scaling.

[0042] The reagent pump 13 extracts and pushes different reagents into the reaction cup. When different reagents are switched, the syringe and pipeline are rinsed and cleaned to ensure the accuracy of the measurement.

[0043] In the preferred embodiment, the circulating sampling device, the quantitative pre-sampling device, the quantitative reagent adding device, and the titration reaction device are electrically connected to the external PLC control system.

[0044] In this embodiment, the PLC control system is used to realize the automatic control of the entire test system. The functions of the entire online analysis system are as follows:

[0045] 1) Automatic sampling: automatically extract the sample from the tank liquid according to the preset sampling period and sampling amount.

[0046] 2) Reagent addition: automatically select and add an appropriate amount of reagent according to the needs of the titration reaction.

[0047] 3) Titration and measurement: perform titration reaction in the titration reaction device and automatically measure and record the changes during the reaction process.

[0048] 4) Data processing and reporting: process and analyze the measurement data, generate reports, and store or transmit them to other systems.

[0049] In this embodiment, the PLC control system is used to improve the analysis efficiency and reduce the errors and interference of manual operation, ensuring the accuracy and reliability of the measurement results. Other control systems can be used to achieve similar functions according to actual needs.

[0050] The quantitative reagent adding device comprises a reagent switching valve 12 and a reagent adding pump 13, and the switching of barium chloride 12-1, sodium rose bengal 12-2, pure water 12-5 and waste liquid 12-6 is realized through the switching of the selected valve.

[0051] S1, water adding process, switching valve port to 12-5, reagent injection pump 13 extracts 50 milliliters of water through 13-3 and adds the water into the reaction cup 14.

[0052] S2, barium chloride adding process, switching valve port to 12-1, reagent injection pump 13 extracts 2 milliliters of barium chloride for rinsing, the rinsing liquid is pushed out to the waste liquid port 12-6 through the reagent injection pump 13, and the reagent injection pump 13 extracts 2 milliliters of barium chloride again and adds the barium chloride into the reaction cup 14 through 13-3.

[0053] S3, reagent injection pump 13 cleaning process, switching valve port to 12-5, reagent injection pump 13 extracts 5 milliliters of pure water, and the cleaning liquid is pushed out to the waste liquid port 12-6 through the reagent injection pump 13.

[0054] S4, sodium rose bengal adding process, switching valve port to 12-2, reagent injection pump 13 extracts 0.3 milliliters of sodium rose bengal for rinsing, the rinsing liquid is pushed out to the waste liquid port 12-6 through the reagent injection pump 13, and the reagent injection pump 13 extracts 0.3 milliliters of sodium rose bengal again and adds the sodium rose bengal into the reaction cup 14 through 13-3.

[0055] In the preferred solution, the titration reaction device further comprises: the reaction cup 14 is provided with an overflow port 17 at the top, the bottom surface of the reaction cup 14 is internally provided with a magnetic stirring rod 16, and a groove is formed on one side of the bottom of the reaction cup 14 to connect an external waste liquid pump 18.

[0056] The overflow port 17 in the embodiment is used to discharge the excess liquid when the liquid in the reaction cup 14 exceeds the preset liquid level.

[0057] The magnetic stirring rod 16 and the external magnetic stirrer (such as a motor) uniformly stir the liquid in the reaction cup, accelerate the mixing and reaction rate of the substances in the titration reaction, and improve the efficiency and accuracy of the titration reaction.

[0058] The waste liquid pump 18 is used to extract the waste liquid generated after the titration reaction from the reaction cup, thereby improving the cleanliness of the reaction cup and improving the accuracy of the test.

[0059] In the preferred solution, the filtering device further comprises:

[0060] The filtering container 8 is internally provided with a plurality of filter membranes 7, and a groove is formed at the bottom of the filtering container 8 to connect an external waste liquid pump 18 through a pipeline.

[0061] The filtering container 8 in the embodiment is made of corrosion-resistant and high-pressure-resistant materials and is the main part of the filtering device, which is used to accommodate the solution to be filtered and the filter membranes 7.

[0062] Further, the filter membrane 7 used in this embodiment can be made of reinforced polypropylene material, with a 2-micron pore size, a diameter of 70 mm, and a length of 400 mm.

[0063] The waste pump 18 is used to remove the impurities and waste accumulated at the bottom of the filter container 8 after filtration, ensuring the cleanliness of the filter container and prolonging its service life and improving its economic efficiency.

[0064] The cleaning and waste removal process of this embodiment uses the waste pump 18 to remove the solution after the reaction in the reaction cup 14. After the solution is removed, the cleaning of the reaction cup 14 and the backwashing process of the sampling pipeline can be performed simultaneously. The specific steps are as follows:

[0065] S1 Cleaning process, reagent switching valve 12 is put into valve port switching 12-5, 50 ml of purified water is pumped, reagent pump 13 is switched to 13-3 to add to reaction cup 14, and waste pump 18 is started to remove the liquid in reaction cup 14.

[0066] S2, backwashing process, sample switching valve 10 valve port switching 10-2, 5 ml of 6-8% dilute sulfuric acid is pumped by sample pump 11, the reverse rotation of sample circulating pump 9 is started, valve port switching 10-1 is switched to push the dilute sulfuric acid to the sampling pipeline, and the backwashing of the sampling pipeline is realized to prevent the crystallization of the sample from blocking the pipeline.

[0067] In the preferred embodiment, the circulating sampling device further comprises an inlet liquid reflux valve 3 between the inlet liquid valve 2 and the tank liquid pool;

[0068] The clear liquid reflux valve 4 is arranged between the upper part of one side of the filter container 8 and the tank liquid pool.

[0069] In this embodiment, the inlet liquid reflux valve 3 and the clear liquid reflux valve 4 further improve the functionality and flexibility of the system.

[0070] In the preferred embodiment, the titration reaction device further comprises: the reaction cup 14 is made of transparent material, and an absorbance sensor 19 is further arranged inside the reaction cup 14, which is used to detect the change of absorbance value during the discoloration reaction of the solution.

[0071] In this embodiment, the reaction cup 14 is made of transparent material, such as glass or high-transparency plastic.

[0072] The absorbance sensor is used to detect the change of absorbance value during the discoloration reaction of the solution, and the reaction endpoint is automatically recognized by algorithm. The algorithm includes steps such as noise reduction processing, sliding window maximum value finding, and compensation for human eye endpoint error. The algorithm can be adjusted and optimized according to the actual situation to adapt to changes in different concentration ranges and reaction conditions.

[0073] In this embodiment, the absorbance sensor of the titration reaction apparatus uses a 590nm wavelength light source, the magnetic stir bar 16 is used to mix the reaction liquid, the absorbance acquisition plate is placed through the reaction cup 14 and faces the light source to collect the voltage value, and the reaction cup 14 is surrounded by a light shield to isolate the interference of external light.

[0074] In the chemical reaction process, the sample pre-sampled and stored in the supernatant injection pump 11 is added uniformly to the reaction vessel 14 at a rate of 0.025 ml per drop, controlled by a motor via valve switching 11-1 of the supernatant pump 11, at a rate of 1 drop per second. After the stoichiometric point of the reaction is completed, the reaction endpoint is automatically identified by an algorithm. The algorithm steps are as follows:

[0075] S1. First, noise reduction processing is performed on the absorbance curve A.

[0076] S2, perform Gaussian smoothing on A n times. When the relative error between the smoothed curve and the unsmoothed curve is reduced to a certain threshold b=0.1, the smoothing is complete.

[0077] S3 uses a sliding window approach to find the maximum value. A window of length c=15 is used to traverse the curve. When the maximum value appears at the beginning of the window, the endpoint is considered to have been initially found.

[0078] S4, set the endpoint calibration number d=7 to simulate the process of human eye recognizing the white endpoint of chemical reaction.

[0079] Example 2

[0080] Further explanation in conjunction with Example 1, such as Figure 2 As shown, an online operation procedure for detecting sulfur trioxide concentration in wet-process phosphoric acid is provided, including the following steps:

[0081] S1. Automatic filtration process for obtaining supernatant: Start the raw liquid sampling pump 1, close the inlet reflux valve 3 and backflush valve 6, open the inlet valve 2 and supernatant reflux valve 4 to filter and obtain supernatant.

[0082] S2. Circulating Sampling Process: Start the supernatant circulation pump 9 to begin circulating sampling. The supernatant pump 11 draws 10 mL of sample and stores it in a syringe. After sampling is completed by the supernatant pump 11, the filtration device stops filtering and begins backflushing to remove slag.

[0083] S3. Reagent addition process: Add 50 mL of water to reaction cup 14 using reagent pump 13, switch reagent switching valve 12 to the barium chloride reagent port, and draw 2.0 mL of barium chloride solution into reaction cup 14; then switch valve to the sodium roserin reagent port and draw 0.2 mL of sodium roserin solution into reaction cup.

[0084] S4, titration reaction and concentration calculation process: the supernatant stored in the internal syringe of the supernatant pump 11 is added to the reaction cup 14 according to the process control of the program at a volume of 0.025 mL per second. The absorbance sensor reads the absorbance value in real time, generates a titration curve, and the algorithm automatically identifies the mutation inflection point of the stoichiometric point. Then, the concentration of the supernatant is calculated according to the stoichiometric point reaction formula.

[0085] S5, pipeline backwashing process: the sample switching valve 10 is switched to dilute sulfuric acid, the supernatant pump 11 extracts dilute sulfuric acid, the sample switching valve 10 is switched to 10-1, and the supernatant circulating pump 9 is reversed to realize dilute sulfuric acid backwashing. The supernatant pump 11 is reversed to realize dilute sulfuric acid backwashing to prevent pipeline scaling.

[0086] After the titration reaction is completed, the titration reaction curve generated in step S4 is as shown in Figure 3 The mutation inflection point in this embodiment is (volume 4.400, absorbance 1.415).

[0087] The beneficial effects of this embodiment include:

[0088] 1) In the titration reaction, the process of adding the sample to the titrant is developed to the process of adding the sample to the reagent: the photometric titration method is used in the titration process, combined with the algorithm for recognizing the white end point by simulating the human eye, to realize high-precision concentration detection. The repeatability of multiple measurements is within 1.5%, and the extreme difference is within 0.4 mg / mL, which significantly improves the accuracy and reliability of the detection.

[0089] 2) Through the PLC control system, the whole process automation from filtration, sampling, reagent addition, chemical reaction to waste discharge is realized, and the shortest cycle is 30 minutes. The whole process does not require manual intervention, and the automatic control also enables the system to run continuously, and the measurement results can be uploaded to the MES system and compared with the production process requirement index to provide timely data support for production adjustment, and provide strong technical support for the production optimization and quality control of the wet-process phosphoric acid process.

[0090] 3) In view of the characteristics of the sample prone to scaling, the system is designed with an automatic sulfuric acid backwashing function, which effectively prolongs the service life of the equipment, and the maintenance cycle of the equipment can be maintained for more than one month, reducing the maintenance cost and workload.

[0091] The above embodiment is only a preferred technical solution of the present application, and should not be regarded as a limitation of the present application. The protection scope of the present application should be based on the technical solution claimed in the claims, including equivalent replacement schemes of the technical features claimed in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present application.

Claims

1. An online analysis system for sulfur trioxide content in a wet-process phosphoric acid production process, characterized in that, include: The circulating sampling device includes a forward and reverse reversible raw liquid sampling pump (1). One end of the raw liquid sampling pump (1) is connected to the tank liquid pool through a pipeline, and the other end of the raw liquid sampling pump (1) is connected to an inlet valve (2) and a backwash valve (6) for continuously extracting sample clear liquid and backwashing the pipeline to prevent scaling. The quantitative pre-sampling device is connected to the titration reaction device. The quantitative pre-sampling device includes a clear liquid pump (11) connected to the titration reaction device through a pipeline. The other end of the clear liquid pump (11) is connected to a multi-channel sample switching valve (10). The sample switching valve (10) is connected to a circulating sampling device through a clear liquid circulation pump (9) for quantitatively extracting the sample into the titration reaction device. The quantitative reagent addition device and the quantitative pre-sampling device are symmetrically arranged. The quantitative reagent addition device is connected to the titration reaction device and includes a reagent addition pump (13) connected to the titration reaction device through a pipeline. The other end of the reagent addition pump (13) is connected to a multi-channel reagent switching valve (12) for switching between different reagents through the reagent switching valve (12). The reagent addition pump (13) draws and pushes the selected reagent into the titration reaction device. The reagents include barium chloride, sodium rosehipate and pure water. The titration reaction apparatus includes a reaction cup (14) and a reaction cup lid (15) set on the reaction cup (14). The quantitative pre-sampling device and the quantitative reagent addition device pass through the reaction cup lid (15) and extend into the reaction cup (14) through pipes, respectively, for performing titration reactions and obtaining measurement results.

2. The online analysis system for sulfur trioxide content in the wet-process phosphoric acid production according to claim 1, characterized in that, The titration reaction apparatus also includes: an overflow port (17) above the reaction cup (14), a magnetic stir bar (16) inside the bottom surface of the reaction cup (14), and a slot on one side of the bottom of the reaction cup (14) to connect to an external waste pump (18).

3. The online analysis system for sulfur trioxide content in the wet-process phosphoric acid production according to claim 2, characterized in that, The titration reaction apparatus also includes: a reaction cup (14) made of transparent material, and an absorbance sensor (19) inside, used to detect the change in absorbance value during the color change reaction of the solution.

4. The online analysis system for sulfur trioxide content in the wet-process phosphoric acid production according to claim 1, characterized in that, It also includes a filtration device for filtering calcium sulfate crystals in the tank solution to obtain a clear liquid. The clear liquid is then pumped into the filter container (8) by the clear liquid circulation pump (9). A backflushing valve (6) is installed between the filter container (8) and the circulation sampling device. The filter container (8) has several filter membranes (7) inside. The filter container (8) has a slot at the bottom right below the bottom, which is connected to an external waste pump (18) through a pipe.

5. The online analysis system for sulfur trioxide content in the wet-process phosphoric acid production according to claim 1, characterized in that, The circulating sampling device also includes: a liquid inlet valve (2) and a liquid tank liquid pool are provided with a liquid inlet return valve (3); A clear liquid return valve (4) is provided between the upper part of one side of the filter container (8) and the tank liquid pool.

6. The online analysis system for sulfur trioxide content in the wet-process phosphoric acid production according to claim 1, characterized in that, The circulating sampling device, quantitative pre-sampling device, quantitative reagent addition device, and titration reaction device are all electrically connected to an external PLC control system.

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