A system for inhibiting vapor condensation industrial purification phosphoric acid stripping defluorination concentration stability

Abstract

The application discloses a system for inhibiting steam condensation and stabilizing the concentration of phosphoric acid in fluorine stripping in industrial purification, comprising a membrane filter, a clear liquid aeration tank, a heat exchanger, a stripping fluorine removal tower, a premixer and a decoloring tower; the discharge port of the membrane filter is in pipeline communication with the feed port of the clear liquid aeration tank; the discharge port of the clear liquid aeration tank is in pipeline communication with the feed port of the heat exchanger; the discharge port of the heat exchanger is in pipeline communication with the feed ports of the stripping fluorine removal tower and the premixer; and the discharge port of the premixer is in pipeline communication with the feed port of the decoloring tower. The system can directly obtain phosphoric acid with a mass concentration of 75% to 77% and a colority of 10 to 20 black cent units without increasing the concentration of phosphoric acid in the concentration equipment.

Description

Technical Field

[0001] This application relates to the field of phosphoric acid production technology, and in particular to a system for suppressing the decrease in acid concentration in the stripping defluorination tower during a wet phosphoric acid purification process. Background Technology

[0002] In my country, most refined phosphoric acid production equipment is small to medium-scale, and a major problem is excessively high acid concentration reduction in the stripping defluorination tower. In current phosphoric acid production, to obtain phosphoric acid with an acid concentration above 75%, the filtered phosphoric acid needs to be concentrated. The existing process has the following problems: 1. After defluorination in the stripping defluorination tower, the phosphoric acid concentration decreases by 4-6% relative to the feed concentration, sometimes reaching as high as 8%. Current treatment involves re-feeding the phosphoric acid to the concentration unit for further stripping to increase the acid concentration. However, this increases production costs and reduces efficiency, especially in large-scale industrial production where energy waste is severe. To reduce energy waste and ensure the final acid concentration, the phosphoric acid concentration at the second-effect concentration entering the stripping process needs to be increased to 83% to offset the acid concentration drop. However, this feed concentration exceeds the design capacity of the concentration equipment, causing a 40% increase in equipment corrosion rate, shortening the equipment's lifespan from 5 years to 3 years, and increasing annual maintenance costs by 800,000 yuan.

[0003] 2. In the existing production method, concentrated phosphoric acid needs to be reacted with hydrogen peroxide to remove organic impurities. The existing decolorization process has low hydrogen peroxide oxidation removal efficiency, and the TOC (total organic carbon content in phosphoric acid) after decolorization is 65 ppm. To ensure the TOC removal rate, the amount of hydrogen peroxide used needs to be increased, which increases the production cost by 12%. With the increasing market demand for electronic-grade and food-grade refined phosphoric acid, the existing process is not able to directly obtain phosphoric acid with a color of 20 black units and a mass concentration of over 75%.

[0004] The information disclosed in the background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This application addresses the aforementioned technical problems by providing a system for suppressing the decrease in acid concentration in the stripping defluorination tower during the wet phosphoric acid purification process. After operation, this system can effectively control the decrease in phosphoric acid concentration after defluorination, achieving an acid concentration decrease of less than 2%. The TOC value of phosphoric acid after decolorization is reduced to 40-45 ppm. Under the same production capacity, the amount of hydrogen peroxide used is reduced by 30%, effectively reducing production costs. After decolorization, phosphoric acid with a mass concentration of 75%-77% and a color of 10-20 black units can be obtained.

[0006] This application provides a system for suppressing the decrease in acid concentration in the stripping defluorination tower during a wet phosphoric acid purification process, comprising: a membrane filter, a clear liquid aeration tank, a heat exchanger, a stripping defluorination tower, a premixer, and a decolorization tower; The outlet of the membrane filter is connected to the inlet of the clear liquid aeration tank; the outlet of the clear liquid aeration tank is connected to the inlet of the heat exchanger. The heat exchanger outlet is connected to the inlet pipelines of the stripping defluorination tower and the premixer, respectively. The outlet of the premixer is connected to the inlet of the decolorization tower via a pipeline.

[0007] Preferably, the steam inlet of the heat exchanger is connected to the steam main through a steam pipe, and a steam flow meter, a steam thermometer, a pressure gauge, and a temperature control valve are installed on the steam pipe; A discharge pipe is installed at the phosphoric acid outlet of the heat exchanger, and a phosphoric acid temperature sensor is installed on the discharge pipe.

[0008] Preferably, it includes: a branch pipe, a protective valve, and a preheating valve; protective valves are respectively installed on the steam pipes on both sides of the temperature control valve; Both ends of the branch pipe are connected to the steam pipe outside the protection valve; A preheating valve is installed on the branch pipe.

[0009] Preferably, it includes: a flow regulating valve and a flow display; the flow regulating valve is disposed on the discharge pipe and electrically connected to the flow display.

[0010] Preferably, it includes: an acid pickling condensate tank, a cleaning condensate tank, a conductivity detector, and a pneumatic two-position valve; A drain pipe is installed on the outlet of the circulating hot water of the heat exchanger. The drain pipe is connected to the pickling condensate tank via a pickling branch pipe. The drain pipe is connected to the cleaning condensate drain tank via a cleaning branch pipe; Pneumatic two-position valves are installed on the cleaning branch pipe and the pickling branch pipe respectively.

[0011] Preferably, it includes: a hydrogen peroxide storage tank; the hydrogen peroxide storage tank is connected to the hydrogen peroxide inlet pipeline of the premixer.

[0012] Preferably, the decolorization tower includes: a first decolorization tower and a second decolorization tower; the first decolorization tower and the second decolorization tower are connected in series, and a premixer is installed on the pipeline connecting the first decolorization tower and the second decolorization tower.

[0013] Preferably, it includes: a delivery pump and a control valve; the delivery pump and the control valve are spaced apart on the pipeline connecting the membrane filter and the clear liquid aeration tank.

[0014] Preferably, it includes: a control valve; the control valve is installed on the pipeline connecting the stripping defluorination tower and the premixer.

[0015] Preferably, it includes: a control valve; the control valve is disposed on the pipeline connecting the heat exchanger and the premixer.

[0016] The beneficial effects that this application can produce include: 1) The system provided in this application for suppressing the decrease in acid concentration in the stripping defluorination tower during the wet phosphoric acid purification process can control the acid drop to within 2% after operation. At the same time, the TOC content is reduced to 40~50ppm after decolorization treatment, and the amount of hydrogen peroxide used is reduced by 30% compared with the existing process. This effectively controls the production cost and can directly obtain phosphoric acid with a color of 20 black units and a mass concentration of over 75% without multiple concentrations.

[0017] 2) The system provided in this application for suppressing the decrease in acid concentration in the stripping defluorination tower during the wet-process phosphoric acid purification process has been applied in the Yunnan Sanhuan Zhonghua ammonium dihydrogen phosphate production unit, reducing the concentration of stripped defluorinated acid from 6.2% to 2.5%, saving 664,100 yuan in annual costs, and extending the equipment lifespan to 8 years. Industrial verification has been completed, and it is suitable for promotion in 50,000-100,000-ton-level refined acid plants in the same industry. Attached Figure Description

[0018] Figure 1 A schematic diagram of the apparatus used in a system for suppressing the decrease in acid concentration in the stripping defluorination tower during a wet phosphoric acid purification process in at least one embodiment provided in this application; Legend: Membrane filter 13, clear liquid aeration tank 116, heat exchanger 2, steam flow meter 1, steam thermometer 11, pressure gauge 111, phosphoric acid temperature sensor 112, temperature control valve 115, protection valve 114, preheating valve 113, stripping defluorination tower 3, flow regulating valve 312, conductivity detector 121, manual control valve 122, pneumatic two-position valve 123, steam reflux port 126, pickling condensate tank 124, cleaning condensate tank 125, first decolorization tower 4, second decolorization tower 41, premixer 5, hydrogen peroxide storage tank 51, transfer pump 14, control valve 141. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] Technical means not detailed in this application and not used to solve the technical problems of this application are all set according to common general knowledge in the field, and multiple common general knowledge setting methods can be implemented.

[0022] See Figure 1 The system provided in this application for suppressing the decrease in acid concentration in the stripping defluorination tower during the wet phosphoric acid purification process includes: a membrane filter 13, a clear liquid aeration tank 116, a heat exchanger 2, a steam flow meter 1, a steam thermometer 11, a pressure gauge 111, a phosphoric acid temperature sensor 112, a temperature control valve 115, a protection valve 114, a preheating valve 113, a stripping defluorination tower 3, a flow regulating valve 312, a flow display, a conductivity detector 121, a manual control valve 122, a pneumatic two-position valve 123, a steam reflux interface 126, an acid washing condensate tank 124, a cleaning condensate tank 125, a first decolorization tower 4, a second decolorization tower 41, a premixer 5, a hydrogen peroxide storage tank 51, a transfer pump 14, and a control valve 141. Phosphoric acid, concentrated to 79% by the concentration equipment, is then de-weighed, crudely decolorized, and processed through membrane filter 13 to effectively reduce arsenic and lead impurities. It is then buffered in a clean acid aeration tank 116, which is connected to membrane filter 13 via piping. The outlet of the clean acid aeration tank 116 is connected to the inlet of heat exchanger 2 via piping, and a transfer pump 14 and a control valve 141 are installed on this connected pipe. After preheating in heat exchanger 2, the phosphoric acid temperature at the outlet of heat exchanger 2 is 100~120℃. The outlet of heat exchanger 2 is connected to the inlet of stripping defluorination tower 3 via piping, and a flow regulating valve 312 is installed on this connected pipe. The flow regulating valve 312 has a flow monitoring function, and the obtained phosphoric acid feed flow rate is displayed on a flow indicator electrically connected to the flow regulating valve 312, allowing operators to obtain the flow rate and adjust the opening of the flow regulating valve 312 according to the flow conditions. Monitor in real time whether the temperature of phosphoric acid entering the stripping defluorination tower (3) reaches 100~120℃. If the temperature of phosphoric acid is lower than 100℃, increase the steam flow rate entering the heat exchanger (2) to 1.5~2.2 m. 3 / h, if the phosphoric acid temperature is higher than 120℃, reduce the steam flow rate entering the heat exchanger (2) to 1.2~1.5m. 3 / h.

[0023] The outlet of the stripping defluorination tower 3 is connected to the inlet of the premixer 5 via a pipeline, and a control valve 141 is installed on the connecting pipeline. The hydrogen peroxide inlet of the premixer 5 is connected to the hydrogen peroxide storage tank 51 via a pipeline. Phosphoric acid and hydrogen peroxide are premixed in the premixer 5 and then decolorized. The outlet of the premixer 5 is connected to the pipeline of the first decolorization tower 4; the outlet of the first decolorization tower 4 is connected to the inlet of the second decolorization tower 41 via a pipeline. This allows the phosphoric acid to undergo further decolorization after defluorination treatment. The premixer 5 is installed on the pipeline connecting the second decolorization tower 41 and the first decolorization tower 4, and this premixer 5 is connected to the hydrogen peroxide storage tank 51 via a pipeline.

[0024] The inlet of heat exchanger 2 is connected to the main steam pipe for introducing steam into the heat exchange layer of heat exchanger 2. The condensate outlet of heat exchanger 2 is connected to the pickling condensate tank 124 and the cleaning condensate tank 125 respectively. This is used to recover the water formed after steam condensation. A steam flow meter 1, a steam thermometer 11, a pressure gauge 111, and a temperature control valve 115 are installed on the pipe connecting the inlet of heat exchanger 2 to the main steam pipe. A discharge pipe is installed on the phosphoric acid outlet of heat exchanger 2, and a phosphoric acid temperature sensor 112 is installed on the discharge pipe. The phosphoric acid temperature sensor 112 is electrically connected to the temperature control valve 115 and is used to control the steam flow entering heat exchanger 2 according to the phosphoric acid temperature at the phosphoric acid outlet of heat exchanger 2. When the phosphoric acid outlet temperature is lower than 100℃, the opening of the temperature control valve 115 is increased to effectively increase the temperature of phosphoric acid. When the phosphoric acid outlet temperature is higher than 120℃, the opening of the temperature control valve 115 is decreased to effectively decrease the temperature of phosphoric acid.

[0025] In one specific embodiment, a steam return port 126 is also provided on the drain pipe; the steam at the top of the drain pipe is returned to the steam main pipe through the steam return port 126 to prevent the steam from directly hitting each tank.

[0026] A drain pipe is installed at the condensate outlet of heat exchanger 2. A conductivity detector 121 and a manual valve 122 are installed on the drain pipe. The ends of the drain pipe are connected to an acid water branch pipe and a cleaning water branch pipe, respectively. The other end of the acid water branch pipe is connected to an acid pickling condensate tank 124, and the other end of the cleaning water branch pipe is connected to a cleaning condensate tank 125. Pneumatic two-position valves 123 are installed on both the acid water and cleaning water branch pipes. These valves are electrically connected to the conductivity detector 121, thereby controlling the opening of the pneumatic two-position valves 123 on the acid water and cleaning water branch pipes according to the pH value of the condensate discharged from the drain pipe. This allows for the classified storage of condensate based on changes in the pH value of the condensate, facilitating subsequent use.

[0027] In one specific embodiment, the outlet of heat exchanger 2 is connected to the inlet of premixer 5, thereby enabling the process to be controlled according to the needs of the material being processed. For phosphate materials that do not require defluorination, they can be directly decolorized. At this time, the amount of hydrogen peroxide required during the decolorization process is effectively controlled, and the TOC content is reduced to 40~50ppm after decolorization.

[0028] In one specific embodiment, the outlet of the stripping defluorination tower 3 is connected to the inlet pipeline of the next process equipment, so as to adjust the phosphoric acid treatment process as required and realize that some phosphoric acid does not need to be defluorinated.

[0029] In one specific embodiment, the system includes: a protection valve 114, a preheating valve 113, and a branch pipe; the inlet of the heat exchanger 2 is connected to the main steam pipe via a steam pipe, and a temperature control valve 115 is installed on the steam pipe, with protection valves 114 installed at both ends of the temperature control valve 115; both ends of the branch pipe are connected to the steam pipe outside the protection valves 114; and a preheating valve 113 is installed on the steam pipe. When the heat exchanger 2 needs to be activated, the preheating valve 113 can be opened first and the protection valve 114 closed, steam can be introduced to preheat the heat exchanger 2 to the preset temperature, and then phosphoric acid can be introduced to ensure stable continuous production.

[0030] In one specific embodiment, the heat exchanger 2 is a 91㎡ vertical shell-and-tube graphite heat exchanger. The heat exchanger 2 can withstand phosphoric acid corrosion at 120℃ and has a heat transfer coefficient of 300W / (m²・℃), which meets the temperature rise requirement of 40℃ at a flow rate of 15m³ / h.

[0031] In one specific embodiment, the control between the temperature self-control valve 115 and the phosphoric acid temperature sensor 112 adopts a Siemens S7-1200 PLC + fuzzy PID algorithm to achieve dynamic adjustment of steam flow, temperature control accuracy of ±1℃, and response time <10s. The Siemens S7-1200 PLC + fuzzy PID algorithm is a commonly used algorithm and module in this field, and its specific structure and algorithm operation method will not be described in detail here.

[0032] Comparison of running examples: Example 1: 1. Feeding conditions: In the continuous industrial production operation of Sanhuan Chemical, phosphoric acid with a concentration of 79% and a temperature of 76~84℃ is processed using the system provided in this application and the unit before modification. The phosphoric acid entering the membrane filter 13 is obtained from the concentration obtained by the concentration equipment. The material of the concentration equipment is 904 stainless steel. The corrosion rate of the concentration equipment is calculated based on the concentration of phosphoric acid of 79%, the concentration temperature of 86~90℃, and the concentration vacuum degree of 11~12KPa.

[0033] 2. The main process flow of the equipment used in the system provided in this application is as follows: phosphoric acid flows through heat exchanger 2, stripping defluorination tower 3, premixer 5, first decolorization tower 4, and second decolorization tower 41. The original structure of the device was: membrane filter 13 and stripping defluorination tower 3 were connected by pipelines; stripping defluorination tower 3 and premixer 5 were connected by pipelines; premixer 5 and first decolorization tower 4.

[0034] The results are shown in the table below: Table 1 The data in Table 1 (except for chromaticity) are the average values ​​after multiple samplings, and the chromaticity values ​​are the range values ​​obtained from multiple measurements. The steam consumption before the modification is the steam consumption at the defluorination tower.

[0035] As shown in Table 1, the system provided in this application can effectively control the decrease in phosphoric acid concentration after defluorination and decolorization, while obtaining a large amount of condensate for use in other production processes. After adopting the system provided in this application, steam consumption is effectively controlled, the TOC value is significantly improved after decolorization, and the amount of hydrogen peroxide used is effectively reduced when the TOC value is significantly improved. The color of the obtained phosphoric acid is stable within the required range, and the concentration of the obtained phosphoric acid meets the requirements, thus eliminating the problem of acid degradation leading to product non-compliance.

[0036] Example 2: The difference from Example 1 is that, in order to obtain phosphoric acid with a concentration of over 75% that meets the target using the original equipment, the concentration of phosphoric acid in the concentrate after processing is 84%. The concentration of phosphoric acid discharged from the concentration equipment of the apparatus provided in this application is 79%. The corrosion rate of the concentration equipment was calculated based on common knowledge in the art, combined with the concentration of the phosphoric acid being processed, the temperature, and the material of the concentration equipment. The results are shown in the table below: Table 2 As shown in the table above, before the modification, in order to obtain phosphoric acid meeting the 75% concentration requirement, the acidity of the phosphoric acid in the concentration equipment was increased, leading to an increased corrosion rate in the concentration equipment and thus shortening its service life. However, acid degradation could not be avoided, and the various indicators after decolorization failed to meet the requirements. Therefore, changing the phosphoric acid concentration entering the equipment could not solve the problems existing in the production equipment. The system provided in this application, however, can control the phosphoric acid concentration processed by the concentration equipment, thereby extending the equipment life to 8 years.

[0037] The system has been operating stably at the 62,500 tons / year refined acid plant of Yunnan Sanhuan Zhonghua, with all indicators meeting the standards. It has achieved a balance of social, environmental, and economic benefits, and has strong demonstration and promotion value. (1) Capacity increase: Annual capacity increased from 62,500 tons to 67,500 tons, with an additional output of 5,000 tons. Based on a selling price of RMB 6,400 / ton and a production cost of RMB 5,800 / ton, the annual revenue increased by RMB 3 million. (2) Cost savings: The amount of hydrogen peroxide used is reduced by 0.5 kg / t, resulting in annual savings of 59,700 yuan; Equipment maintenance costs were reduced from 800,000 yuan to 300,000 yuan, resulting in annual savings of 500,000 yuan. Condensate is recycled at a rate of 18,000 tons / year, valued at 104,400 yuan. (3) Total economic benefits: 300 + 66.41 = 366.41 million yuan / year, with an investment payback period of 96 days.

[0038] (4) Safety assurance: The corrosion rate of equipment is reduced by 64%, reducing safety hazards such as acid leakage and improving production safety.

[0039] (5) Resource utilization: The condensate recovery rate has been increased to 90%, saving 18,000 tons of water per year.

[0040] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification processes using steam condensation, characterized in that, include: Membrane filter (13), clear liquid aeration tank (116), heat exchanger (2), stripping defluorination tower (3), premixer (5), decolorization tower; The outlet of the membrane filter (13) is connected to the inlet of the clear liquid aeration tank (116); the outlet of the clear liquid aeration tank (116) is connected to the inlet of the heat exchanger (2). The outlet of the heat exchanger (2) is connected to the inlet pipeline of the stripping defluorination tower (3) and the premixer (5), respectively; The outlet of the premixer (5) is connected to the inlet pipe of the decolorization tower.

2. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 1, characterized in that, The steam inlet of the heat exchanger (2) is connected to the steam main pipe through a steam pipe. A steam flow meter (1), a steam thermometer (11), a pressure gauge (111), and a temperature control valve (115) are installed on the steam pipe. A discharge pipe is installed on the phosphoric acid outlet of the heat exchanger (2), and a phosphoric acid temperature sensor (112) is installed on the discharge pipe.

3. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 2, characterized in that, include: Branch pipe, protection valve (114), preheating valve (113); protection valve (114) is installed on the steam pipes on both sides of the temperature control valve (115); Both ends of the branch pipe are connected to the steam pipe outside the protection valve (114); A preheating valve (113) is installed on the branch pipe.

4. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 2, characterized in that, include: Flow regulating valve (312) and flow display; the flow regulating valve (312) is installed on the discharge pipe and electrically connected to the flow display.

5. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 1, characterized in that, include: Pickling condensate tank (124), cleaning condensate tank (125), conductivity detector (121), pneumatic two-position valve (123); A drain pipe is installed on the outlet of the circulating hot water of the heat exchanger (2); The drain pipe is connected to the pickling condensate tank (124) via a pickling branch pipe; The drain pipe is connected to the cleaning condensate tank (125) via a cleaning branch pipe; Pneumatic two-position valves (123) are installed on the cleaning branch pipe and the pickling branch pipe respectively.

6. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 1, characterized in that, include: Hydrogen peroxide storage tank (51); the hydrogen peroxide storage tank (51) is connected to the hydrogen peroxide inlet pipeline of the premixer (5).

7. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 1, characterized in that, The decolorization tower includes: a first decolorization tower (4) and a second decolorization tower (41); the first decolorization tower (4) and the second decolorization tower (41) are connected in series, and a premixer (5) is installed on the pipeline connecting the first decolorization tower (4) and the second decolorization tower (41).

8. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 1, characterized in that, include: The pump (14) and control valve (141) are spaced apart on the pipeline connecting the membrane filter (13) and the clear liquid aeration tank (116).

9. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 1, characterized in that, include: Control valve (141); The control valve (141) is installed on the pipeline connecting the stripping defluorination tower (3) and the premixer (5).

10. The system for suppressing the concentration stability of phosphoric acid stripping defluorination in industrial purification according to claim 1, characterized in that, include: Control valve (141); The control valve (141) is installed on the pipeline connecting the heat exchanger (2) and the premixer (5).

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