On-line detection device and method for fluorine ions in phosphoric acid refining

Abstract

The invention relates to phosphoric acid production, and particularly provides an on-line detection device and method for fluorine ions in phosphoric acid refining, and the detection device comprises a reaction cup, a detection electrode and an analysis unit; the conveying unit is used for extracting, quantifying and conveying liquid; the detection unit is used for detecting the absorbance of a solution in the reaction cup; the judging unit is used for judging whether the absorbance reaches a threshold value or not and sending an instruction for stopping conveying the alkaline solution and the non-phosphoric acid solution to the conveying unit when the absorbance reaches the threshold value; the calculation unit is used for obtaining the volume value V of the buffer solution according to the absorbance and the amount of the liquid, and the conveying unit conveys the buffer solution into the reaction cup according to the volume value V; the control unit is used for controlling the conveying unit to quantify and convey any liquid. The method has the advantages of accurate detection and the like, and is applied to phosphoric acid refining.

Description

TECHNICAL FIELD

[0001] The present application relates to phosphoric acid refining process, particularly to the fluorine ion on-line detection device and method in phosphoric acid refining. BACKGROUND

[0002] In the engineering process of wet-process phosphoric acid refining technology, the produced phosphoric acid contains impurity fluorine, fluorine and other ions and compounds react to form substances which have different degrees of harm to products, equipment and environment, etc. Therefore, real-time identification of fluorine content is crucial for timely adjustment of process feeding and other controls.

[0003] Phosphoric acid has the characteristics of high viscosity and smoothness, which increases the complexity and difficulty of fluorine ion content detection in phosphoric acid, resulting in that only laboratory manual analysis measurement is available at present, and no automatic on-line detection is available. SUMMARY

[0004] To solve the above problems in the prior art, the present application provides a fluorine ion on-line detection device in phosphoric acid refining.

[0005] The purpose of the present application is achieved by the following technical solutions: A fluorine ion on-line detection device in phosphoric acid refining, comprising a reaction cup, a detection electrode and an analysis unit; the on-line detection device further comprises: a conveying unit, the input end of the conveying unit is connected to a sampling pool, an indicator, a buffer solution, an alkali solution, a non-phosphoric acid solution and water, and the output end is connected to the reaction cup, the conveying unit is used for extracting, quantifying and conveying liquid; a detection unit, the detection unit is used for detecting the absorbance of the solution in the reaction cup and sending the judgment unit; a judgment unit, the judgment unit is used for judging whether the received absorbance reaches a threshold value, and issuing an instruction to the conveying unit to stop conveying the alkali solution and the non-phosphoric acid solution when the threshold value is reached; a calculation unit, the calculation unit is used for obtaining a volume value V of the buffer solution according to the absorbance and the amount of liquid, and the conveying unit conveys the buffer solution into the reaction cup according to the volume value V; a control unit, the control unit is used for controlling the conveying unit to quantify and convey any liquid.

[0006] The present application also provides a fluorine ion on-line detection method in phosphoric acid refining, and the purpose of the present application is achieved by the following technical solutions.

[0007] A fluorine ion on-line detection method in phosphoric acid refining, comprising the following steps: (A1) the conveying unit extracts and quantifies the phosphoric acid sample, the buffer, the indicator and water at different times, and conveys the liquid to the reaction cup, so that the solution level in the reaction cup reaches the detection position of the detection unit; (A2) the conveying unit gradually sends the alkali solution into the reaction cup, and the detection unit outputs the absorbance; (A3) the judging unit judges whether the received absorbance reaches a first threshold value, and issues an instruction to the conveying unit to stop conveying the alkali solution when the first threshold value is reached; (A4) the conveying unit gradually sends the non-phosphoric acid solution into the reaction cup, and the detection unit outputs the absorbance; (A5) the judging unit judges whether the received absorbance reaches a second threshold value, and issues an instruction to the conveying unit to stop conveying the non-phosphoric acid solution when the second threshold value is reached; (A6) the calculating unit obtains the volume value V of the buffer solution according to the absorbance and the amount of liquid; (A7) the conveying unit re-conveys the buffer solution into the reaction cup according to the volume value V, and the electrode in the reaction cup outputs a potential value; (A8) the calculating unit obtains the content of the fluorine ion in the phosphoric acid sample by using the potential value and a mapping relationship.

[0008] Compared with the prior art, the present application has the beneficial effects that: 1. The combination of the conveying unit, the detection unit, the judging unit, the calculating unit and the control unit realizes real-time and online detection of the fluorine content in wet-process phosphoric acid, which is of great significance for timely adjusting the process feeding and other controls; 2. The automatic detection is realized, and the efficiency is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0009] The disclosure of the present application will become more apparent with reference to the drawings. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. In the drawings: Figure 1 is a structural schematic view of the online detection device for fluorine ion in phosphoric acid refining according to the present application; Figure 2 is a flow schematic view of the online detection method for fluorine ion in phosphoric acid refining according to the present application. DETAILED DESCRIPTION

[0010] Figures 1-2The following description illustrates optional embodiments of the invention to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to teach the technical solutions of the invention. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the optional embodiments described below, but is defined only by the claims and their equivalents.

[0011] Example 1.

[0012] The online fluoride ion detection device in phosphoric acid purification according to embodiments of the present invention, such as... Figure 1 As shown, it includes: This invention comprises 41, a detection electrode 42, and an analysis unit.

[0013] The input end of the delivery unit is connected to the sampling cell 11, indicator, buffer solution, alkaline solution, non-phosphoric acid solution and water respectively, and the output end is connected to the reaction cup 41. The delivery unit is used to extract, quantify and deliver liquids.

[0014] The detection unit is used to detect the absorbance of the solution in the reaction vessel 41 and send it to the judgment unit.

[0015] The judgment unit is used to determine whether the received absorbance has reached the threshold, and when the threshold is reached, it sends an instruction to the delivery unit to stop delivering the alkaline solution and non-phosphoric acid solution.

[0016] The calculation unit is used to obtain the volume value V of the buffer solution based on the absorbance and the amount of liquid, and the delivery unit delivers the buffer solution into the reaction vessel according to the volume value V.

[0017] The control unit is used to control the delivery unit to deliver any liquid in a quantitative manner.

[0018] To obtain an accurate volume value V, the volume value V is further defined as follows:

[0019] C1 and V1 are the molar concentration and volume of the added alkaline solution (such as sodium hydroxide solution), respectively; C2 and V2 are the molar concentration and volume of the added non-phosphoric acid solution (such as nitric acid solution), respectively; ΣB i A1 is the total volume of water, indicator, and buffer solution applied to reaction vessel 41. A2 is the absorbance before and after applying alkaline solution to reaction vessel 41. A3 is the absorbance after applying non-phosphoric acid solution to reaction vessel 41. w is the mass fraction of phosphoric acid.

[0020] To accurately quantify and deliver the liquid, the delivery unit further includes: The first multi-channel directional valve 31 has its input terminals connected to the sampling cell 11, the indicator, and water, respectively. The first injection pump 22 is connected to the common port of the first multi-channel directional valve 31 and the reaction cup 41 respectively; The second multi-channel directional valve 32 has its input terminals connected to fluoride ion standard solution, buffer solution, and water, respectively. The second injection pump 23 is connected to the common port of the second multi-channel directional valve 32 and the reaction cup 41.

[0021] To accurately control the application of alkaline and non-phosphoric acid solutions, the detection unit further includes: The first detection module 51 includes a first light source and a detector. The output wavelength of the first light source includes 590nm, and the first detector outputs the absorbance before and after the addition of the alkaline solution. The second detection module 52 includes a second light source and a second detector. The output wavelength of the second light source is 450 nm, and the second detector outputs the absorbance after the addition of a non-phosphoric acid solution.

[0022] An online detection method for fluoride ions in phosphoric acid purification according to an embodiment of the present invention, namely, the working method of the detection device of this embodiment, is as follows: Figure 2 As shown, it includes the following steps: (A1) The delivery unit extracts and quantifies the phosphate sample, buffer solution, indicator and water in a timed manner, and delivers the liquid to the reaction cup 41 so that the liquid level in the reaction cup 41 reaches the detection position of the detection unit; (A2) The delivery unit gradually delivers the alkaline solution into the reaction vessel 41, and the detection unit outputs the absorbance. (A3) The judgment unit determines whether the received absorbance reaches the first threshold, and sends an instruction to the delivery unit to stop delivering the alkaline solution when the first threshold is reached; (A4) The delivery unit gradually delivers the non-phosphoric acid solution into the reaction vessel 41, and the detection unit outputs the absorbance. (A5) The judgment unit determines whether the received absorbance reaches the second threshold, and when the second threshold is reached, it sends an instruction to the delivery unit to stop delivering the non-phosphoric acid solution; (A6) The calculation unit obtains the volume value V of the buffer solution based on the absorbance and the amount of liquid; (A7) The delivery unit delivers the buffer solution into the reaction cup 41 again according to the volume value V, and the electrode in the reaction cup outputs a potential value; (A8) The calculation unit uses the potential value and mapping relationship to obtain the fluoride ion content in the phosphoric acid sample.

[0023] To obtain an accurate mapping relationship, the mapping relationship is further obtained as follows: Standard solutions of the same volume but different fluoride ion contents are respectively delivered to reaction vessel 41. The electrode outputs a potential value, establishes a mapping relationship between fluoride ion content and potential value, and saves the value.

[0024] To accurately calculate the volume value V, the volume value V is further defined as:

[0025] C1 and V1 are the molar concentration and volume of the added alkaline solution, respectively; C2 and V2 are the molar concentration and volume of the added non-phosphoric acid solution, respectively; ΣB i A1 is the total volume of water, indicator, and buffer solution applied to reaction vessel 41. A2 is the absorbance before and after applying alkaline solution to reaction vessel 41. A3 is the absorbance after applying non-phosphoric acid solution to reaction vessel 41. w is the mass fraction of phosphoric acid.

[0026] Example 2: An application example of the online detection device and method for fluoride ions in phosphoric acid purification according to Embodiment 1 of the present invention.

[0027] In this application example, such as Figure 1 As shown, in the delivery unit, the input of the first multi-channel directional valve 31 is connected to the sampling cell 11, the indicator (bromocresol green in this example), and pure water, respectively. The peristaltic pump 21 is connected to the sampling cell 11 at both ends, and the port of the first multi-channel directional valve 31 is connected to the outlet of the peristaltic pump 21. The first syringe pump 22 is connected to the common port of the first multi-channel directional valve 31 and the reaction cup 41, respectively. The input of the second multi-channel directional valve 32 is connected to the fluoride standard solution, the buffer solution (citric acid-sodium citrate buffer in this example), and pure water, respectively. The second syringe pump 23 is connected to the common port of the second multi-channel directional valve 32 and the reaction cup 41, respectively.

[0028] In the detection unit, the first light source of the first detection module 51 has an output wavelength of 590 nm, and the first detector outputs the absorbance before and after the addition of the alkaline solution. The second light source of the second detection module 52 has an output wavelength of 450 nm, and the second detector outputs the absorbance after the addition of the non-phosphoric acid solution.

[0029] An electrode 42 and a liquid level sensor 43 are installed inside the reaction vessel 41. The electrode 42 is connected to the analysis unit and outputs a potential value.

[0030] The online detection method for fluoride ions in phosphoric acid purification in this embodiment, i.e., the working method of the detection device in this embodiment, is as follows: Figure 2 As shown, the detection method includes the following steps: (A0) Through the operation of the second multi-channel directional valve 32 and the second injection pump 23, standard solutions with different fluoride ion contents are quantitatively delivered to the reaction cup 41, and then pure water is delivered to the reaction cup 41. The solution volume in the reaction cup is V0, thus obtaining standard solutions with the same volume (100mL) but different fluoride ion contents.

[0031] Electrode 42 outputs a potential value x corresponding to each standard solution, thereby establishing a mapping relationship between fluoride ion content Y and potential value Y=k(-lgx)+b, where k and b are constants, and this relationship is saved.

[0032] (A1) Through the operation of the peristaltic pump 21, the first multi-channel directional valve 31 and the first injection pump 22, and the operation of the second multi-channel directional valve 32, the phosphoric acid sample (volume of 5 mL), buffer (0.5 mL citrate-sodium citrate buffer), indicator (0.1 mL bromocresol green) and pure water are extracted and quantified (in the sampling cell 11) in time intervals, and the four liquids are delivered to the reaction cup 41 so that the solution level in the reaction cup 41 reaches the detection position of the detection unit (automatically detected by the liquid level sensor 43).

[0033] (A2) Through the operation of the second multi-channel directional valve 32 and the second injection pump 23, sodium hydroxide solution is gradually dripped into the reaction cup 41, the first light source emits 590nm light, the first detector receives the transmitted light and outputs the absorbance.

[0034] As sodium hydroxide solution is continuously added, the absorbance increases.

[0035] (A3) The judgment unit determines whether the received absorbance reaches the first threshold (at this time, the color of the solution in the reaction cup 41 changes from yellow to blue), and sends a command to the delivery unit to stop delivering the alkaline solution when the first threshold is reached, and obtains the volume V1 of the added sodium hydroxide solution, the absorbance A2 when the addition of the alkaline solution is stopped, and the absorbance A1 before the addition of the alkaline solution.

[0036] (A4) Through the operation of the second multi-channel directional valve 32 and the second injection pump 23, the nitric acid solution is gradually dripped into the reaction cup 41, the second light source emits 450nm light, the second detector receives the transmitted light and outputs the absorbance.

[0037] As nitric acid solution is continuously added, the absorbance decreases.

[0038] (A5) The judgment unit determines whether the received absorbance has reached the second threshold (at this time, the color of the solution in the reaction cup 41 changes from blue to yellow), and sends a command to the delivery unit to stop delivering the nitric acid solution when the second threshold is reached, and obtains the volume V2 of the dropped nitric acid solution and the absorbance A3 at this time.

[0039] (A6) The calculation unit obtains the volume value of the buffer solution V = 15.68 mL according to the following formula.

[0040]

[0041] C1 is the molar concentration of the added substance, such as sodium hydroxide solution, and C2 is the molar concentration of the added nitric acid solution. ΣB i is the total volume of water, indicator, and the first applied buffer solution added to reaction vessel 41, and w is the mass fraction of phosphate.

[0042] (A7) Through the operation of the second multi-channel directional valve 32 and the second injection pump 23, the delivery unit delivers buffer solution and pure water to the reaction cup 41 again according to the volume value V, so that the volume of the mixed liquid in the reaction cup 41 is 100mL (consistent with the volume of 100mL when the mapping relationship is established), and the electrode outputs the potential value in the reaction cup 41.

[0043] (A8) The analysis unit uses the potential value and mapping relationship to obtain the fluoride ion content in the phosphoric acid sample.

[0044] The results of multiple tests are as follows.

[0045]

[0046] It is evident that the analytical precision is significantly improved after adopting the scheme proposed in this application.

[0047] Example 3: The application example of the online detection device and method for fluoride ions in phosphoric acid purification according to Embodiment 1 of the present invention differs from that in Embodiment 2.

[0048] 1. The multi-channel directional valve is replaced by a combination of multiple solenoid valves, each of which controls whether a certain type of liquid passes through.

[0049] 2. Use potassium hydroxide instead of alkaline solutions, and use sulfuric acid solution instead of non-phosphoric acid solutions.

Claims

1. An online detection device for fluoride ions in phosphoric acid purification, comprising a reaction vessel, a detection electrode, and an analysis unit; characterized in that, The online detection device also includes: The delivery unit has its input end connected to the sampling cell, indicator, buffer solution, alkaline solution, non-phosphoric acid solution and water respectively, and its output end connected to the reaction cup. The delivery unit is used to extract, quantify and deliver liquids. A detection unit is used to detect the absorbance of the solution in the reaction vessel and send it to a judgment unit. The judgment unit is used to determine whether the received absorbance reaches a threshold, and when the threshold is reached, it sends an instruction to the delivery unit to stop delivering the alkaline solution and non-phosphoric acid solution. The calculation unit is used to obtain the volume value V of the buffer solution based on the absorbance and the amount of liquid, and the delivery unit delivers the buffer solution into the reaction vessel according to the volume value V; A control unit is used to control the delivery unit to quantitatively deliver any liquid.

2. The detection device according to claim 1, characterized in that, The volume value V is: C1 and V1 are the molar concentration and volume of the added alkaline solution, respectively; C2 and V2 are the molar concentration and volume of the added non-phosphoric acid solution, respectively; ΣB i A1 is the total volume of water, indicator, and buffer solution applied to the reaction vessel. A2 is the absorbance before and after applying the alkaline solution to the reaction vessel. A3 is the absorbance after applying the non-phosphoric acid solution to the reaction vessel. w is the mass fraction of phosphoric acid.

3. The detection device according to claim 2, characterized in that, The alkaline solution is a sodium hydroxide solution, and the non-phosphoric acid solution is a nitric acid solution.

4. The detection device according to claim 1, characterized in that, The conveying unit includes: The first multi-channel directional valve has its input terminals connected to the sampling cell, indicator, and water, respectively. A first injection pump is connected to the common port of the first multi-channel directional valve and the reaction cup, respectively. The second multi-channel directional valve has its input terminals connected to fluoride ion standard solution, buffer solution, and water, respectively. The second injection pump is connected to the common port of the second multi-channel directional valve and the reaction cup, respectively.

5. The detection device according to claim 1, characterized in that, The detection unit includes: The first detection module includes a first light source and a detector. The output wavelength of the first light source includes 590 nm, and the first detector outputs the absorbance before and after the addition of the alkaline solution. The second detection module includes a second light source and a second detector. The output wavelength of the second light source is 450 nm, and the second detector outputs the absorbance after the addition of a non-phosphoric acid solution.

6. An online detection method for fluoride ions in phosphoric acid purification, comprising the following steps: (A1) The delivery unit extracts and quantifies phosphate sample, buffer, indicator and water in time intervals, and delivers the liquid to the reaction cup so that the liquid level in the reaction cup reaches the detection position of the detection unit; (A2) The delivery unit gradually delivers the alkaline solution into the reaction vessel, and the detection unit outputs the absorbance. (A3) The judgment unit determines whether the received absorbance reaches the first threshold, and sends an instruction to the delivery unit to stop delivering the alkaline solution when the first threshold is reached; (A4) The delivery unit gradually delivers the non-phosphoric acid solution into the reaction vessel, and the detection unit outputs the absorbance. (A5) The judgment unit determines whether the received absorbance reaches the second threshold, and when the second threshold is reached, it sends an instruction to the delivery unit to stop delivering the non-phosphoric acid solution; (A6) The calculation unit obtains the volume value V of the buffer solution based on the absorbance and the amount of liquid; (A7) The delivery unit delivers the buffer solution into the reaction vessel again according to the volume value V, and the electrode in the reaction vessel outputs a potential value; (A8) The analysis unit uses the potential value and mapping relationship to obtain the fluoride ion content in the phosphoric acid sample.

7. The detection method according to claim 1, characterized in that, The mapping relationship is obtained as follows: Standard solutions of the same volume but different fluoride ion contents are respectively delivered to the reaction vessel. The electrode outputs a potential value, and a mapping relationship between fluoride ion content and potential value is established and saved.

8. The detection method according to claim 6, characterized in that, The volume value V is: C1 and V1 are the molar concentration and volume of the added alkaline solution, respectively; C2 and V2 are the molar concentration and volume of the added non-phosphoric acid solution, respectively; ΣB i A1 is the total volume of water, indicator, and buffer solution applied to the reaction vessel. A2 is the absorbance before and after applying the alkaline solution to the reaction vessel. A3 is the absorbance after applying the non-phosphoric acid solution to the reaction vessel. w is the mass fraction of phosphoric acid.

9. The detection method according to claim 8, characterized in that, The alkaline solution is a sodium hydroxide solution, and the non-phosphoric acid solution is a nitric acid solution.

10. The detection method according to claim 6, characterized in that, The buffer solution is a citrate-sodium citrate buffer solution, and the indicator is bromocresol green.

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