TWI675007B - Secondary crystallization system for the formation of sodium fluoride and sodium fluoroaluminate crytals from hydrofluoric acid solution and its crystallization control method - Google Patents

Abstract

The invention provides a secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution and a crystallization operation control method thereof. The crystallization process mainly includes a crystallization agent of sodium hydroxide and sodium carbonate in the first stage. , Through the quality control dosing, add to the high-concentration hydrofluoric acid waste stock solution with a fluoride ion concentration of 40g / L or more to perform the crystallization reaction to obtain sodium fluoride crystals and medium-low concentration hydrofluoric acid with a fluoride ion concentration of 25g / L or more The reaction solution; and in the second stage crystallization procedure, a crystallization agent including sodium aluminate is added to the medium-low concentration hydrofluoric acid reaction solution through quality control to perform a crystallization reaction to obtain sodium fluoroaluminate crystals and fluoride ion concentration The hydrofluoric acid waste liquid below 60mg / L can achieve the purpose of systematic and stable production of sodium fluoride crystals and sodium fluoroaluminate crystals with high crystal purity and high economic benefits.

Description

Secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from hydrofluoric acid solution and crystallization operation control method thereof

The present invention relates to a crystallization system, in particular to a secondary crystallization system using hydrofluoric acid solution for secondary crystallization to generate sodium fluoride and sodium fluoroaluminate crystals with high economic benefits, and a crystallization operation control method thereof.

According to the fact, high-concentration hydrofluoric acid (HF, 49%) or hydrofluoric acid mixed acid is widely used in etching technology for semiconductors (IC), liquid crystal display panels (TFT-LCD), solar cells and other technology industries. Various concentrations of as high as 49% or as low as 0.5% of bulk hydrofluoric acid waste acid require waste liquid treatment.

Current hydrofluoric acid waste liquid treatment methods include adding calcium-containing compounds such as CaO, Ca (OH) 2, and CaCl2 to react with fluoride ions in the waste liquid to form calcium fluoride (CaF2) sludge cake, or, for example, Taiwan Invention Patent No. No. I233428, the fluorine ions in the hydrofluoric acid waste liquid are chemically coagulated with specific agents to remove the fluoride ions in the waste liquid. However, the former two methods have the problems of difficulty in operation and high cost. In addition, the calcium fluoride sludge cake has a large volume and the purity of the calcium fluoride which reaches the recovery standard is quite limited, which fails to produce economic benefits. Can form sodium fluoroaluminate crystals (Na3AlF6, commonly known as cryolite) for recycling. However, in the coagulation process, PAC (Polyalumi-num Chloride) can be used as a coagulant to affect cryolite. The purity of the crystals, especially the cryolite in the pre-patent of the patent, was not made with suitable crystallization degree and environment, and the purity is more difficult to reach the standard for recycling.

It is worth noting that many literatures have suggested that hydrofluoric acid and sodium aluminate can generate sodium fluoroaluminate crystals via the following reaction formula: 12HF + 3NaAlO ₂ → Na ₃ AlF ₆ + 2AlF ₃ + H ₂ O (see TW 102144345 (Prior art); Therefore, the inventor of this case has filed an application for Taiwan Invention Patent No. 101125989 based on this technology, "Crystalization system and method for crystallization of sodium fluoroaluminate crystals from hydrofluoric acid waste liquid," as shown in Figure 1. As shown, the crystallization system includes a sodium aluminate medicament tank V2 and a high-concentration hydrofluoric acid waste liquid tank V1 through its batch quantitative control sections F1 and F2, respectively, and flows into a constant flow and uniformly dispersed addition located at the upper part of the system reaction tank. The drug section A and the batch-type crystallization reaction section R at the lower part of the reaction tank control the sodium aluminate medicament to be added in a batch quantitatively and uniformly by using a constant flow rate and the through-hole distribution of the dispersion plate in the uniformly added dosing section A. The reaction is carried out in the acid waste liquid. After standing for crystallization, it enters the microfiltration section S to separate the cryolite crystals and transport the filtered liquid to the low-concentration hydrofluoric acid waste liquid treatment section W for processing.

Although the technical solution previously proposed by the inventor of the present case has been able to obtain cryolite crystals with a purity of up to 96%, the factors affecting the purity of the crystals include not only the method of contacting the hydrofluoric acid with sodium aluminate in a liquid stream, but also the content of impurities in the solvent. And the pH value of the solution, the inventor of this case further proposed the Taiwan invention patent No. 102144345, "Crystal system equipment for generating sodium fluoroaluminate crystals from hydrofluoric acid solution and crystallization operation control method", which is mainly Through the dispersing disk and control disk provided in the system reaction tank, the liquid flow form and flow rate of the contact reaction of the sodium aluminate agent and the hydrofluoric acid waste liquid are controlled, and the pH value / fluoride ion detection connected to the system reaction tank through a loop shape In addition, it monitors the pH value and fluoride ion concentration of the reaction solution of the hydrofluoric acid waste solution and sodium aluminate agent to effectively control the factors affecting the purity of the crystal during the operation of the system and ensure that the system can stably produce the crystal purity for recycling and reuse. Cryolite achieves the purpose of effectively recovering fluoride ions and generating cryolite crystals with high economic benefits.

It is also worth noting that sodium fluoride is an ionic compound with a molecular formula of NaF. At room temperature, it is a colorless crystal or white solid with no odor. It is an important fluoride product and is widely used in the fields of wood preservatives, wine fungicides, electrolytic aluminum regulators, dental fluoride agents, and other fields. At present, the hydrofluoric acid neutralization method is a commonly used and mature sodium fluoride production process. Hydrofluoric acid neutralization method uses sodium hydroxide to neutralize hydrofluoric acid to obtain sodium fluoride, and the reaction formula is as follows: HF + NaOH → NaF + H2O. The conventional production process of sodium fluoride includes: adding hydrofluoric acid with a concentration of 40% by weight to a lead reaction kettle, and then slowly adding sodium hydroxide to neutralize the reaction solution until it becomes neutral; finally, crystallization, centrifugal dehydration, Dry to obtain sodium fluoride product. This process has the advantages of simple process and stable product quality. However, this process has the problem of serious equipment corrosion, so the material requirements of the equipment are very high, and the neutralization method uses commercially available hydrofluoric acid as a raw material. The production cost of sodium fluoride is relatively high, and it lacks market competitiveness at this stage and needs further improvement.

The purpose of the present invention is to provide a secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution. The first-stage crystallization process will include a first-stage crystallization agent including sodium hydroxide and sodium carbonate. , Through the quality control dosing, add a high-concentration hydrofluoric acid waste stock solution with a fluoride ion concentration of more than 40g / L to perform a crystallization reaction to obtain sodium fluoride crystals and medium-low concentration hydrofluoric acid with a fluoride ion concentration of 25g / L A reaction solution; and in a second-stage crystallization procedure, a second-stage crystallization agent including sodium aluminate is added to the medium-low concentration hydrofluoric acid reaction solution through quality control to perform a crystallization reaction to obtain sodium fluoroaluminate crystals and The hydrofluoric acid waste liquid with a fluoride ion concentration below 60mg / L can achieve the purpose of systematically and stably producing sodium fluoride crystals and sodium fluoroaluminate crystals with high crystal purity and high economic benefits.

The reason is that in order to achieve the above object, the present invention provides a secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution, including: a control processor; a first crystallization reaction section, which is The control processor is electrically controlled; the first crystallization reaction section controls the batch input of a high-concentration hydrofluoric acid waste stock solution through the control processor, and adds the first crystallization agent to the hydrofluoric acid waste solution in a quality-controlled manner through the control processor. A crystallization reaction is performed in the first crystallization agent is a sodium hydroxide solution containing sodium carbonate to generate a reaction solution of sodium fluoride crystals and a medium-low concentration hydrofluoric acid; a second crystallization reaction section is for controlling the electrical properties of the processor. It is controlled and connected with the output end of the first crystallization reaction section; the second crystallization reaction section inputs the medium-low concentration hydrofluoric acid reaction solution through the control processor in batches, and is added to the second through the control processor under quality control A crystallization agent is crystallized into the medium-low concentration hydrofluoric acid reaction solution, and the second crystallization agent is a sodium aluminate solution to generate sodium fluoroaluminate crystals and a low-concentration hydrofluoric acid waste solution. Thereby, the purpose of systematically and stably producing sodium fluoride crystals and sodium fluoroaluminate crystals with high crystal purity and high economic benefits is achieved.

The present invention further provides a secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution, including: a control processor; a first crystallization reaction section for electrically controlling the control processor; The first crystallization reaction section controls the batch input of the high-concentration hydrofluoric acid waste stock solution through the control processor, and adds the first crystallization agent to the hydrofluoric acid waste liquid through the control processor to control the quality of the crystallization reaction. The crystallization agent is a sodium hydroxide solution containing sodium carbonate to generate a reaction solution of sodium fluoride crystals and low-concentration hydrofluoric acid. A second crystallization reaction section is electrically controlled by the control processor and reacts with the first crystal. The output end of the section is connected; the second crystallization reaction section inputs the medium-low concentration hydrofluoric acid reaction solution through the control processor in batches, and adds a second crystallization agent to the medium-low concentration hydrogen through the control processor in a quality control manner. A crystallization reaction is performed in a hydrofluoric acid reaction solution, and the second crystallization agent is a sodium aluminate solution to generate sodium fluoroaluminate crystals and a low-concentration hydrofluoric acid waste liquid; The medicine space and the reaction space, the medicine injection space and the reaction space are communicated through a reflux pump provided outside the second crystallization reaction section, and the reflux pump sucks the reaction solution containing crystal nuclei in the reaction space to the medicine injection space to form Seed nuclei. Therefore, in addition to achieving the purpose of systematically and stably producing sodium fluoride crystals and sodium fluoroaluminate crystals with high crystal purity and high economic benefits, the reaction solution containing crystal nuclei is further refluxed by a reflux pump to increase the crystallization rate.

Further, the secondary crystallization system of the present invention further includes a first pH detection section for determining a pH reaction end point of the crystallization process in the first stage, and a second pH detection for determining a pH reaction end point of the crystallization process in the second stage. segment.

Further, the secondary crystallization system of the present invention further includes a fluoride ion concentration detection section FD for determining the second-stage crystallization procedure to determine the end point of the initial crystallization reaction of the second-stage crystallization procedure, which is convenient to cooperate with the second pH detection section D2. Fine-adjust the pH value to reach the precise end of the crystallization reaction, and ensure that the concentration of the low-concentration hydrofluoric acid waste liquid output at the end of the second-stage crystallization process is lower than the discharge concentration.

Further, in the secondary crystallization system of the present invention, the first crystallization agent outputs a uniformly dispersed drip-shaped liquid through a first quality control dosing section to the first crystallization reaction section and the high-concentration hydrofluoric acid waste stock solution is discharged. A crystallization reaction is performed; the sodium aluminate solution flows through a second quality control dosing section to output uniformly dispersed droplets into the second crystallization reaction section to perform a crystallization reaction with the medium-low concentration hydrofluoric acid reaction solution. Thereby, by reacting the first crystalline agent and the second crystalline agent to form a drip-like liquid stream with the hydrofluoric acid waste liquid, the crystallization rate of the crystallization reaction is increased, and the sodium fluoride crystals and sodium fluoroaluminate are recovered from the waste liquid. Crystal efficiency.

Further, the secondary crystallization system of the present invention further includes a first solid-liquid separation section and a second solid-liquid separation section, which are used to quickly separate crystals and liquids in the reaction solution that reaches the end of the reaction. In addition, the first solid-liquid separation section and the second solid-liquid separation section may be further connected to the first cleaning treatment section and the second cleaning treatment section, respectively, to discharge the separated liquid, or input clean water or other appropriate The cleaning liquid is cleaned in the first solid-liquid separation section and the second solid-liquid separation section to avoid impurities remaining and ensure the purity of the crystals.

Further, the high-concentration hydrofluoric acid waste stock solution of the secondary crystallization system of the present invention is stored in a high-concentration hydrofluoric acid waste liquid tank, and is connected to the first crystallization reaction section through a metering inflow control section to output high-concentration hydrogen in batches. The hydrofluoric acid discards the stock solution to the first crystallization reaction section. The first crystalline agent is stored in a sodium carbonate solution storage tank containing sodium carbonate, and the second crystalline agent is stored in a sodium aluminate solution storage tank.

In addition, in order that the secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to the present invention can surely produce sodium fluoride and sodium fluoroaluminate crystals with high economic benefits, the present invention provides the same System crystallization operation control method. The method includes a preliminary setting procedure, a first-stage crystallization procedure, and a second-stage crystallization procedure. The preliminary setting procedure includes a parameter setting step. The first-stage crystallization procedure includes input of a high-concentration hydrofluoric acid waste stock solution. Step, the first-stage crystallization agent adding step and the sodium fluoride crystal processing step, the second-stage crystallization procedure includes a medium-low concentration hydrofluoric acid reaction solution input step, the second-stage crystallization agent adding step, and the sodium fluoroaluminate crystal processing step :among them:

The parameter setting step: set the parameter item and its value range through the control processor;

The high-concentration hydrofluoric acid waste stock solution input step: inputting the high-concentration hydrofluoric acid waste stock solution in batches into the reaction space of the first crystallization reaction section according to the set value of the parameter setting step;

The first-stage crystallization agent adding step: according to the setting value of the parameter setting step, output the sodium carbonate-containing sodium hydroxide solution to the first quality control dosing section to form a drip-like liquid flow and fall into the first crystallization reaction In the reaction space of the section, the sodium carbonate solution containing sodium carbonate and the high-concentration hydrofluoric acid waste stock solution are subjected to crystallization reaction, and a sodium fluoride crystal and a medium-low concentration hydrofluoric acid reaction solution are generated;

The sodium fluoride crystal processing step: collecting and cleaning the sodium fluoride crystal;

The medium-low-concentration hydrofluoric acid reaction solution input step: inputting the medium-low-concentration hydrofluoric acid reaction solution in batches into the reaction space of the second crystallization reaction section according to the set value of the parameter setting step;

The second-stage crystallization agent adding step: according to the set value of the parameter setting step, output the sodium aluminate solution to the second quality control dosing section to form a drip-like liquid flow and fall into the reaction space of the second crystallization reaction section Inside, the sodium aluminate solution is subjected to a crystallization reaction with the medium-low concentration hydrofluoric acid reaction solution to generate sodium fluoroaluminate crystals and a low-concentration hydrofluoric acid waste liquid;

Sodium fluoroaluminate crystal processing step: Collect and wash the sodium fluoroaluminate crystal.

Further, the crystallization operation control method further includes performing a first-stage pH detection step, a standing reaction step, and a first-stage solid-liquid separation step between the first-stage crystallization agent adding step and the sodium fluoride crystal processing step. After the end point of the crystallization reaction is determined by using the measured pH value, solid-liquid separation is performed on the sodium fluoride crystal.

Further, the crystallization operation control method further includes performing a second-stage fluoride ion detection step, a second-stage pH value detection step, and a standing reaction between the second-stage crystallization agent adding step and the sodium fluoroaluminate crystal processing step. Step and the second-stage solid-liquid separation step, in order to determine the initial crystallization reaction end point by using the measured fluoride ion concentration, and then use the measured pH value to fine-tune the reaction solution to the pH value set in the parameter setting step, Sodium crystals were subjected to solid-liquid separation.

Further, the second-stage crystallization agent adding step further includes extracting the reaction solution containing crystal nuclei from the reaction space of the second crystallization reaction section and returning the reaction solution to the dosing space, so as to improve the second-stage crystallization procedure of sodium fluoroaluminate crystals. rate.

Regarding the technology, means, and other effects adopted by the present invention to achieve the above-mentioned objectives, a preferred and feasible embodiment is described in detail below with reference to the drawings.

In order to facilitate understanding of the present invention, the following is described with reference to the accompanying drawings and embodiments.

Some embodiments of the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different aspects, but they do not depart from the scope of the present invention, and the descriptions and drawings therein are essentially for the purpose of illustration, not for limitation. this invention.

As shown in FIG. 1, the secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to the present invention mainly includes a first-stage crystallization procedure and a second-stage crystallization procedure. The first-stage crystallization procedure is based on Reaction formula: HF + NaOH → NaF + H ₂ O, 2 HF + Na ₂ CO ₃ → 2 NaF + CO ₂ + H ₂ O, using sodium carbonate solution containing sodium carbonate as the first crystallization agent CR1 and high concentration hydrogen The first crystallization reaction of HHF waste raw liquid HHF is performed to generate recyclable sodium fluoride crystal C1 and medium-low concentration hydrofluoric acid reaction liquid LHF. The second-stage crystallization procedure is based on the reaction formula: 3Na ⁺ + Al ^{3 +} + 6F- → Na ₃ AlF ₆ , using the sodium aluminate solution as the second crystallization agent CR2 to react with the low- and medium-concentration hydrofluoric acid reaction solution LHF formed after the first-stage crystallization procedure, and perform a second crystallization reaction to generate a recoverable Used sodium fluoroaluminate crystal C2 and low concentration hydrofluoric acid waste liquid that meets the discharge standards.

In the embodiment of the present invention, the fluoride ion concentration of the high-concentration hydrofluoric acid waste stock solution HHF is 40 g / L or more, and preferably 40 to 55 g / L; the fluoride ion concentration of the low-concentration hydrofluoric acid reaction solution LHF It is 25 g / L or more, and preferably 25 to 30 g / L. The fluoride ion concentration of the low-concentration hydrofluoric acid waste liquid is 60 mg / L or more.

Specifically, as shown in FIG. 1, the equipment in the first-stage crystallization process includes a high-concentration hydrofluoric acid waste liquid tank V1 and its metering inflow control section F, a sodium carbonate-containing sodium hydroxide solution storage tank V2, a first A quality control dosing section A1, a first crystallization reaction section R1, a first pH detection section D1, a first solid-liquid separation section SE1, and a first cleaning treatment section W1. The equipment in the second-stage crystallization program includes a sodium aluminate solution storage tank V3, a second quality control dosing section A2, a second crystallization reaction section R2, a fluoride ion concentration detection section FD, a second pH value detection section D2, The second solid-liquid separation section SE2 and the second cleaning treatment section W2. The above devices are all electrically connected to the control processor P and work according to a set value inside the control processor P.

The high-concentration hydrofluoric acid waste liquid tank V1 is connected to the first crystallization reaction section R1 through the metering inflow control section F. The metering inflow control section F is electrically controlled by the control processor P to output the high-concentration hydrogen in batches. The hydrofluoric acid waste stock solution HHF is passed to the first crystallization reaction section R1. The sodium carbonate-containing sodium hydroxide solution storage tank V2 is electrically controlled by the control processor P to output the first crystalline agent CR1 to the first quality control dosing section A1.

The first crystallization reaction section R1 is electrically controlled by the control processor P. The first crystallization reaction section R1 inputs the high-concentration hydrofluoric acid waste stock solution HHF through the control processor P in batch control, and passes through the control processor P quality. The first crystallization agent CR1 is controlledly added to the hydrofluoric acid waste liquid for crystallization reaction. The first crystallization agent CR1 is a sodium hydroxide solution containing sodium carbonate to generate sodium fluoride crystal C1 and medium-low concentration hydrofluoric acid. Reaction liquid LHF. Specifically, the first crystallization agent CR1 outputs a uniformly dispersed drip-shaped liquid through a first quality control dosing section A1 to flow into the first crystallization reaction section R1 to perform a crystallization reaction with the high-concentration hydrofluoric acid waste stock solution HHF.

In the first stage of the crystallization process, the end point of the crystallization reaction is determined by starting the second pH detection section D2 and the first quality control dosing section A1 to adjust the dosing amount of the sodium aluminate solution until the pH measurement value reaches the control processor P Dosing stops after the set value of. The first pH detection section D1 is electrically controlled by the control processor P and is connected to the first crystallization reaction section R1. The first pH detection section D1 controls and measures the first crystallization reaction section through the control processor P. The pH value of the reaction solution inside R1, and the control processor P determines the reaction end point of the first crystallization reaction section R1 according to the measured pH value. Specifically, the first pH detection section D1 includes a pH meter and a loop pipe connected between the pH meter and the first crystallization reaction section R1, so that the control processor P controls the work extraction of the first pH detection section D1. After the pH of the reaction solution of the first crystallization reaction section R1 is measured, it is transported back to the first crystallization reaction section R1 to continue the reaction.

The first solid-liquid separation section SE1 is electrically controlled by the control processor P and is connected to the output of the first crystallization reaction section R1. The first solid-liquid separation section SE1 controls and separates the first through the control processor P. The sodium fluoride crystal C1 output from the crystallization reaction section R1 and the medium-low concentration hydrofluoric acid reaction solution LHF. Preferably, in order to ensure the cleaning of the first solid-liquid separation section SE1, the liquid output end of the first solid-liquid separation section SE1 is connected to the first cleaning processing section W1, and the first cleaning processing section W1 is the control processor. P is electrically controlled for forming a path for outputting the medium-low concentration hydrofluoric acid reaction solution LHF or inputting clean water to clean the sodium fluoride crystal C1 in the first solid-liquid separation section SE1.

The sodium aluminate solution storage tank V3 is electrically controlled by the control processor P to output the second crystalline agent CR2 to the second quality control dosing section A2. The second crystallization reaction section R2 is electrically controlled by the control processor P and is connected to the output terminal of the first crystallization reaction section R1. The second crystallization reaction section R2 is input to the low-medium concentration through the control processor P in batch control. Hydrofluoric acid reaction liquid LHF, and through the control processor P, a second crystallization agent CR2 is added to the medium-low concentration hydrofluoric acid reaction liquid LHF for crystallization reaction. The second crystallization agent CR2 is a sodium aluminate solution. To generate sodium fluoroaluminate crystal C2 and low concentration hydrofluoric acid waste liquid. Specifically, the sodium aluminate solution flows through a second quality control dosing section A2 to output uniformly dispersed droplets into the second crystallization reaction section R2 to perform a crystallization reaction with the medium-low concentration hydrofluoric acid reaction solution LHF.

In the second-stage crystallization procedure, the end point of the crystallization reaction is determined through the preliminary determination of the fluoride ion value through the fluoride ion concentration detection section FD to reach the set value of the control processor P, and then the second pH detection section D2 is started to cooperate with the second The quality control dosing section A2 finely adjusts the dosing amount of the sodium aluminate solution, and stops the dosing until the measured value of the pH reaches the set value of the control processor P.

The fluoride ion concentration detection section FD is electrically controlled by the control processor P and is connected to the second crystallization reaction section R2; the fluoride ion concentration detection section FD controls and measures the inside of the second crystallization reaction section R2 through the control processor P The concentration of fluoride ion in the reaction solution; the control processor P determines the initial reaction end point of the second crystallization reaction section R2 based on the measured fluoride ion, and the control processor P measures the second crystal reaction section R2 according to the measured value. The final pH of the second crystallization reaction section R2 determines the end point of the reaction. Specifically, the fluoride ion concentration detection section FD includes a fluorine meter and a loop pipe connected between the fluorine meter and the second crystallization reaction section R2, so that the control processor P controls the fluorine ion concentration detection section FD to extract a second After measuring the fluoride ion concentration in the reaction solution of the crystallization reaction section R2, it is transported back to the second crystallization reaction section R21 to continue the reaction.

The second pH detection section D2 is electrically controlled by the control processor P and is connected to the second crystallization reaction section R2. The second pH detection section D2 controls and measures the second crystallization reaction section through the control processor P. The pH value of the reaction solution in R2, and the control processor P determines the reaction end point of the second crystallization reaction section R2 according to the measured pH value. Specifically, the second pH detection section D2 includes a pH meter and a loop pipeline connected between the pH meter and the second crystallization reaction section R2, so that the control processor P controls the work extraction of the second pH detection section D2. After the pH value of the reaction solution in the second crystallization reaction section R2 is measured, it is transported back to the second crystallization reaction section R21 to continue the reaction.

The second solid-liquid separation section SE2 is electrically controlled by the control processor P and is connected to the output of the second crystallization reaction section R2; the second solid-liquid separation section SE2 controls and separates the second through the control processor P The sodium fluoroaluminate crystal C2 output from the crystallization reaction section R2 and the medium-low concentration hydrofluoric acid reaction solution LHF. Preferably, in order to ensure the cleaning of the second solid-liquid separation section SE2, the liquid output end of the second solid-liquid separation section SE2 is connected to the second cleaning processing section W2, and the second cleaning processing section W2 is the control processor. P is electrically controlled for forming a path for outputting the low-concentration hydrofluoric acid waste liquid or inputting clean water to clean the sodium fluoroaluminate crystal C2 in the second solid-liquid separation section SE2.

In the embodiment of the present invention, as shown in FIG. 4, the bodies of the first crystallization reaction section R1 and the second crystallization reaction section R2 are both crystallization reaction tanks; the first quality control dosing section A1 and the second quality. The control dosing section A2 includes a dispersion plate with a plurality of liquid holes and a control plate on the dispersion plate with a plurality of through holes. Among them, the dispersion plate and control of the first quality control dosing section A1. The plate is set in the crystallization reaction tank of the first crystallization reaction section R1, and the dispersion plate and the control plate of the second quality control dosing section A2 are set in the crystallization reaction tank of the second crystallization reaction section R2; The inside of the crystallization reaction tank is separated from the dispersion plate and the control plate to form an upper injection space (corresponding to the internal space of the quality control dosing unit A21 in FIG. 4) and a lower reaction space (corresponding to the crystal deposition portion in FIG. 4). Internal space of A22), the first quality control dosing section A1 controls the control disc to rotate through the control processor P to adjust the number of through holes of the control disc and the liquid holes of the dispersion disc and adjust the number of Drops from the dosing space to the reaction space The flow of the sap flow. The control panel and dispersing disc number of holes in the first quality control dosing section A1 and the adjusting mechanism and adjusting method thereof have been disclosed in the Taiwan invention patent No. 101125989 previously filed by the inventor of the present application "Self-generating hydrofluoric acid waste liquid" The crystallization system of sodium fluoroaluminate crystals and its crystallization method "will not be repeated here.

Further, as shown in FIG. 4, the second crystallization reaction section R2 includes a second crystallization reaction tank A20, and the upper part of the second crystallization reaction tank A20 forms a quality control dosing section A21 (ie, a dosing space), and the lower part forms a crystal. Deposition part A22 (that is, reaction space), so that the sodium aluminate solution drips from the quality control dosing part A21 into the reaction space, and then performs a crystallization reaction with the low-concentration hydrofluoric acid reaction solution LHF, and forms particles in the crystal deposition part A22 The larger crystal C21 and the smaller crystal nucleus C22. In order to increase the crystallization rate of the sodium fluoroaluminate crystal C2, a reflux pump A23 can be further provided outside the second crystallization reaction tank A20 between the quality control dosing section A21 and the crystal deposition section A22, thereby utilizing the The reflux pump A23 sucks the reaction solution containing the crystal nucleus C22 in the reaction space to form a seed crystal nucleus in the injection space, so that the crystal nucleus C22 and the sodium aluminate solution are dropped into the low- and medium-concentration hydrofluoric acid reaction solution LHF. In this way, the crystallinity of sodium fluoroaluminate in the second-stage crystallization procedure of the present invention is improved.

In the secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to the present invention, pipes, pumps, and valve connections are connected between each section of equipment to control the liquid transportation state and quantity. . The pump is electrically connected to the control processor P and controlled by the control processor P. The valve includes an electric valve and / or a manual control valve to cooperate with the overall liquid conveyance of the control system. In addition, the high-concentration hydrofluoric acid waste liquid tank V1, the sodium carbonate-containing sodium hydroxide solution storage tank V2, the sodium aluminate solution storage tank V3, and the first crystallization reaction section R1 and the second crystallization reaction section R2 are preferably provided inside. There is a liquid level gauge, so that the control processor P can detect the liquid level status in each section of equipment through the liquid level gauge.

The above explained the connection relationship and function between the devices of the secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from the hydrofluoric acid solution of the present invention. Below, please refer to FIG. 2 with reference to FIG. 3 to describe the crystallization operation control method of the secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to the present invention.

The crystallization operation control method of the present invention includes a preliminary setting procedure, a first-stage crystallization procedure, and a second-stage crystallization procedure. The preliminary setting procedure includes a parameter setting step S1. The first-stage crystallization procedure includes a high-concentration hydrofluoric acid waste stock solution input step S2. 1. The first-stage crystallization agent adding step S3, the first-stage pH detection step S4, the standing reaction step S5, the first-stage solid-liquid separation step S6, and the sodium fluoride crystal processing step S7. The second-stage crystallization process includes the following steps: Low-concentration hydrofluoric acid reaction solution input step S8, second-stage crystallization agent addition step S9, second-stage fluoride ion detection step S10, second-stage pH detection step S11, standing reaction step S12, and second-stage solid-liquid separation Step S13 and the sodium fluoroaluminate crystal processing step S14.

The parameter setting step S1: Set parameter items and their numerical ranges through the control processor P. Wherein, the parameter setting step S1 further includes, after completing the parameter setting, setting a dispersion plate and a control plate of the first quality control dosing section A1 according to the flow demand of the first-stage crystalline agent to regulate the sodium hydroxide solution containing sodium carbonate The flow velocity falling into the reaction space in the first crystallization reaction section R1; and, according to the crystallization agent flow demand in the second stage, a dispersion plate and a control plate of the second quality control dosing section A2 are set to regulate the sodium aluminate solution falling into the first The flow rate of the reaction space in the second crystallization reaction section R2.

The high-concentration hydrofluoric acid waste stock solution input step S2: According to the setting value of the parameter setting step S1, the high-concentration hydrofluoric acid waste stock solution HHF is input into the reaction space of the first crystallization reaction section R1 in batches.

The first-stage crystallization agent adding step S3: according to the setting value of the parameter setting step S1, the sodium carbonate solution containing sodium carbonate is output to the first quality control dosing section A1 to form a drip-like liquid flow and fall to the first In a reaction space of a crystallization reaction section R1, the sodium carbonate-containing sodium hydroxide solution is caused to crystallize with the high-concentration hydrofluoric acid waste stock solution HHF, and a sodium fluoride crystal C1 and a medium-low concentration hydrofluoric acid reaction solution are generated. LHF. Specifically, in this step, after the completion of the high-concentration hydrofluoric acid waste stock solution HHF inflow, the slow infusion method is started, and the second quality control dosing section A2 is added to add sodium carbonate-containing sodium hydroxide solution. (The first crystallizing agent CR1). At this stage, a medicament is added for the stationary reaction, and the pH is controlled as the endpoint of the reaction.

The first stage pH detection step S4: introducing the reaction solution in the first crystallization reaction section R1 into the first pH detection section D1 to measure the pH of the reaction solution; wherein, in the first stage pH detection step S4, The reaction end point determination step S41 is a set value of the reaction end point according to the pH value of the parameter setting step S1. When the pH value of the reaction solution does not reach the set value, the first-stage crystallization agent adding step S3 and the first-stage pH are repeatedly performed. The value detection step S4 is performed until the pH value of the reaction solution reaches a set value, and the process proceeds to the standing reaction step S5.

The standing reaction step S5: Stop outputting the sodium carbonate-containing sodium hydroxide solution to the first quality control dosing section A1, and leave the reaction solution in the first crystallization reaction section R1 to stand according to the value set in the parameter setting step S1. To perform a crystallization reaction to generate sodium fluoride crystal C1.

In the first solid-liquid separation step S6, the generated sodium fluoride crystal C1 is solid-liquid separated from the reaction solution.

The sodium fluoride crystal processing step S7: collecting and washing the sodium fluoride crystal.

Specifically, in the standing reaction step S5, the first-stage solid-liquid separation step S6, and the sodium fluoride crystal processing step S7, when it is determined that the first-stage reaction end point is reached and the dosing is stopped, the standing reaction is maintained for 30-60 minutes. Start the solid-liquid separation with the first solid-liquid separation section SE1. The liquid part will enter the crystallization reaction tank of the second crystallization reaction section R2, and the solid (sodium fluoride crystal C1) will remain in the first solid-liquid separation section SE1. After all the liquid part enters the second crystallization reaction section R2, the first cleaning treatment section W1 is started to clean the sodium fluoride crystal C1 in the first solid-liquid separation section SE1. After the cleaning is completed, the crystal is taken out. The water content of the sodium fluoride crystal C1 obtained in this step is about 50% by weight, and the water content can be further reduced by entering a drying process.

The medium-low-concentration hydrofluoric acid reaction solution input step S8: according to the parameter setting step S1, the medium-low-concentration hydrofluoric acid reaction solution LHF is input into the reaction space of the second crystallization reaction section R2 in batches. In this step, the medium-low concentration hydrofluoric acid reaction liquid LHF is a hydrofluoric acid waste liquid having a fluoride ion concentration of about 25 g / L or more.

The second-stage crystallization agent adding step S9: according to the parameter setting step S1, the sodium aluminate solution is output to the second quality control dosing section A2 to form a drip-like liquid stream and fall into the second crystallization reaction section. In the reaction space of R2, the sodium aluminate solution is subjected to a crystallization reaction with the medium-low concentration hydrofluoric acid reaction solution LHF, and sodium fluoroaluminate crystal C2 and a low-concentration hydrofluoric acid waste liquid are generated. Wherein, the second-stage crystallization agent adding step S9 further includes extracting the reaction solution containing the crystal nucleus C22 from the reaction space of the second crystallization reaction section R2 and returning it to the dosing space, thereby forming a dynamic crystallization reaction to improve the second-stage crystallization. C2 crystallization rate of sodium fluoroaluminate crystals in the program.

In the second stage fluoride ion detection step S10, the reaction solution in the second crystallization reaction section R2 is introduced into the fluoride ion concentration detection section FD to determine the fluoride ion solubility of the reaction solution; wherein the second stage fluoride ion detection step S10 is The reaction end point determination step S101 is the set value of the fluoride ion concentration reaction end point according to the parameter setting step S1. When the fluoride ion concentration of the reaction solution does not reach the set value, the second-stage crystallization agent adding step S9 and the second step are repeatedly performed. In step S10 of the fluoride ion detection step, until the fluoride ion concentration of the reaction solution reaches a set value, the process proceeds to the second step of pH value detection step S11. Specifically, in this step, the set value of the reaction endpoint of the fluoride ion concentration is lower than 3 g / L.

The second stage pH detection step S11: introducing the reaction solution in the second crystallization reaction section R2 into the second pH detection section D2 to measure the pH value of the reaction solution; wherein, in the second stage pH detection step S11, The reaction end point judgment step S111 is based on the pH value of the parameter setting step S1. The reaction end point setting value is repeatedly executed when the pH value of the reaction solution does not reach the set value, and the water sample pH adjustment step S112 and the second stage pH value are repeatedly performed. Step S11 is detected, and when the pH value of the reaction solution reaches a set value, the process proceeds to the standing reaction step S12. Specifically, in this step, the set value of the reaction endpoint of the pH value is 7; thereby, when the pH measurement value of the reaction solution reaches 7, the fluoride ion concentration in the reaction solution can be reduced to about 60 mg / L or less, Emission standard concentration.

The standing reaction step S12: Stop outputting the sodium aluminate solution to the second quality control dosing section A2, and leave the reaction solution in the second crystallization reaction section R2 to stand for crystallization according to the value set in the parameter setting step S1. The reaction produces sodium fluoroaluminate crystal C2.

In the second solid-liquid separation step S13, the generated sodium fluoroaluminate crystal C2 is solid-liquid separated from the reaction solution.

The sodium fluoroaluminate crystal processing step S14: Collect and clean the sodium fluoroaluminate crystal C2.

Specifically, in the standing reaction step S12, the second-stage solid-liquid separation step S13, and the sodium fluoroaluminate crystal processing step S14, when it is determined that the second reaction stage reaches the end of the reaction and the dosing is stopped, the dynamic reaction time is maintained for 10 minutes. After that, the reflux pump A23 was stopped to conduct circulation up and down, and the reaction solution was left to stand for 30 minutes, and then the second solid-liquid separation section SE2 was started for solid-liquid separation. The liquid portion of the second solid-liquid separation section SE2 enters the subsequent discharge procedure, and the solid portion (sodium fluoroaluminate crystal C2, cryolite) will remain in the second solid-liquid separation section SE2. After the liquid has entered the subsequent discharge procedure, Start to clean the sodium fluoroaluminate crystal C2 in the second solid-liquid separation section SE2 with clean water. After cleaning, remove the crystal. The moisture content of the sodium fluoroaluminate crystal C2 obtained in this step is about 50% by weight, and the moisture content can be further reduced by entering a drying process.

In the embodiment of the present invention, as shown in FIG. 3, the method of the present invention further includes an automatic mode determination step S15. The automatic mode determination step S15 is preset by the control processor P as an automatic mode or a manual mode. In the automatic mode, the control processor P automatically controls the high-concentration hydrofluoric acid waste stock solution input step S2 to repeatedly execute the foregoing steps. When in the manual mode, the control processor P stops automatic control and returns to the parameter setting step. After S1 finishes parameter setting, it starts automatic control.

In addition, the overall system of the present invention may be a batch operation or a continuous batch operation. If continuous batch operation is used, when the reaction solution enters the second crystallization reaction section R2, the next batch of high-concentration hydrofluoric acid waste stock solution HHF can flow to the first crystallization reaction section R1.

The following provides specific embodiments of the secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to the present invention, and a method for controlling the crystallization operation thereof, which includes laboratory-level embodiments: Example 1, Example Second, and mold factory-level embodiments: Embodiment three, embodiment four.

In Example 1 and Example 2, both the first-stage crystallization process and the second-stage crystallization process used a 10-liter crystallization reaction tank (first crystallization reaction section R1, second crystallization reaction section R2); batch reaction The high concentration of hydrofluoric acid waste stock solution is 5 liters. More specifically, the crystallization reaction tank is a round plastic barrel made of PP, and the volume of the reaction tank is 10 liters; the high-concentration hydrofluoric acid waste stock solution is an actual hydrofluoric acid waste solution taken from a semiconductor factory.

The laboratory-level test steps of the first embodiment and the second embodiment are described as follows:

(1) Manually measure, pour 5 liters of concentrated hydrofluoric acid waste stock solution into the first crystallization reaction tank.

(2) Carry out the first-stage crystallization procedure: After the completion of the hydrofluoric acid inflow, begin to add a liquid reagent containing sodium hydroxide / sodium carbonate (a sodium carbonate-containing hydroxide in a slow inflow manner) by using a 1-liter burette. Sodium solution), the composition ratio of the liquid medicament is: 1 liter of sodium hydroxide solution with a mass concentration of 22.5 wt% is added with 50 g of sodium carbonate powder with a purity of 99%. In the first-stage crystallization program, a static reaction is used to add a medicament, and the change in the pH value is monitored during the reaction. The reaction in the first-stage crystallization program uses pH = 3 as the control endpoint.

(3) After confirming that the end point of the first-stage reaction is reached, stop the dosing, wait for 30-60 minutes to stand for the reaction, and then start the solid-liquid separation with a filter with a vacuum suction device. The solid (sodium fluoride crystal) will remain on the membrane filter paper of the filter, and the liquid part will be poured into the original reaction barrel. The crystals on the membrane filter paper are washed with water. After cleaning, the crystals are taken out and dried in an oven. After the drying process is completed, the samples are bottled and analyzed for purity.

(4) Perform the second-stage crystallization procedure: sample the hydrofluoric acid solution entering the second crystallization reaction tank, and analyze the fluoride ion concentration. Then, a 1-liter burette was used to add the liquid medicament sodium aluminate in a slow instillation manner. This sodium aluminate solution was self-configured and the component mass ratio was Na / Al = 1.6.

(5) In the second-stage crystallization procedure, the dosage of sodium aluminate is controlled by the fluoride ion concentration. When the fluoride ion concentration is lower than 3g / L, the pH value is used to fine-tune the dosage of aluminate. Sodium, and pH = 7 was used as the control endpoint. The fluoride ion concentration in the reaction solution after the reaction in this step can be reduced to below 60 mg / L.

(6) Make sure that the second-stage crystallization program reaches the end of the reaction. After stopping the dosing, maintain the reaction time for 10 minutes, and then start the solid-liquid separation with a filter with a vacuum suction device.

(7) The solid (sodium fluoroaluminate, cryolite) will remain on the membrane filter paper of the filter, and the liquid part can be discharged into the water tank. The crystals on the membrane filter paper are washed with water. After cleaning, the crystals are taken out and dried in an oven. After the drying process is completed, the samples are bottled and analyzed for purity.

The specific experimental conditions and measurement results of the above Example 1 and Example 2 are shown in Table 1 below.

The third embodiment and the fourth embodiment of the mold factory-level test steps are described as follows: In the third and fourth embodiments, the automatic mode of the mold factory system is used, and the specific system equipment can use the application previously filed by the inventor of the present case 102144345 The crystallization system equipment in the "Taiwan invention patent" Crystal system equipment for generating sodium fluoroaluminate crystals from hydrofluoric acid solution and crystallization operation control method "will not be repeated here. The following steps are the operation steps in the automatic mode.

A. First stage crystallization procedure (sodium fluoride crystal)

(1) After confirming the following operating parameters, start the automatic mode and start operation. Parameter items Value range Put in high-HF volume 30-60 liters First volume of sodium hydroxide 30-60 liters Fine-tune the volume of sodium hydroxide 100-500 ml End of reaction pH setting 3 -7 Dehydrator running time 30 seconds-5 minutes Reaction time 10-60 minutes Fine-tune the reaction standing time 5-10 minutes Monitoring system measurement time 5- 20 minutes Water rinse monitoring system time 15 minutes

(2) Start the output pump of the high-concentration hydrofluoric acid waste stock solution (High-HF, HHF) (metering inflow control section F) and inject it into the first crystallization reaction tank (the first crystallization reaction section) according to the setting of the processing capacity. R1) within.

(3) After the high-concentration hydrofluoric acid waste stock solution is completely injected into the first crystallization reaction tank, the output pump of the sodium carbonate-containing sodium hydroxide solution storage tank is started, and the medicine is added into the reaction tank according to quality control.

(4) According to the setting of the reaction standing time, the system is standing still.

(5) After the reaction standing time is reached, the pumps of the pneumatic valves (pneumatic valves introduced and discharged into the reaction tank) and the monitoring system are started, and the water sample (reaction solution) is introduced into the monitoring system (the first pH detection section D1) ), Set the measurement time of the system to be monitored, and read the data to determine whether it is the end point of the reaction. In the third and fourth embodiments of the present invention, the system further includes a storage device for sodium fluoride crystals provided outside the first crystallization reaction tank, and the storage device communicates with the first crystallization reaction tank to form a closed internal circulation loop; Therefore, when the pump of the monitoring system is started, the water current will bring the crystals in the storage device storing the sodium fluoride crystals into the reaction tank through the closed internal circulation loop, and the seeding process is performed.

(6) If the pH value of the end point of the reaction is not reached, close the pump of the monitoring system and each pneumatic valve, and enter the procedure for fine adjustment and input of the first crystallization agent (sodium hydroxide solution containing sodium carbonate); that is, start the first crystallization agent storage tank The output pump is injected into the upper dispersion disk tank body of the first crystallization reaction tank according to the setting of the fine adjustment of the mass of the sodium oxyoxide solution containing sodium carbonate.

(7) After the fine-tuning reaction standing time is reached, start the pneumatic valves (pneumatic valves introduced and discharged into the reaction tank) and the pump of the monitoring system, and the water sample (reaction solution) will be introduced into the monitoring system (the first pH detection section D1) ), The measurement time of the system to be monitored is set, and the data is read to determine whether it is the end point of the reaction. If the pH value of the end point of the reaction is not reached, continue to repeat step (6) until the end value of the pH value of the reaction is reached.

(8) After reaching the set pH value at the end of the reaction, start the first separator to separate and clean the crystals. The crystals and low-HF hydrofluoric acid reaction solution (Low-HF, LHF) will be discharged into the dehydration by gravity flow. In the machine, after the first solid-liquid separation, the low- and medium-concentration hydrofluoric acid reaction liquid LHF is first discharged to the second-stage crystallization reaction tank for storage, and then the clean water pneumatic valve is started for cleaning operations. When the clean water level reaches the setting, After the value is closed, the clean water pneumatic valve is closed, and then solid-liquid separation is performed, and the separated washing wastewater is discharged to the washing wastewater tank for storage. This cleaning action will be repeated three times.

(9) The cleaning waste water tank is provided with high and low liquid levels to control the cleaning waste water pump and discharge the cleaning waste liquid out of the system.

(10) When the cleaning operation reaches the set value, the system enters the second-stage crystallization procedure, and the sodium fluoride crystals stored in the first separator are manually taken out.

B. Second-stage crystallization procedure (sodium fluoroaluminate crystals)

(1) When the second crystallization reaction tank reaches the set liquid level, the system turns on the second crystallization reaction tank reflux pump (reflow pump A23).

(2) Start the output pump of the sodium aluminate solution storage tank, and add the sodium aluminate agent into the second crystallization reaction tank according to the quality control.

(3) When the set reaction time is reached, each pneumatic valve (pneumatic valve introduced and discharged into the reaction tank) and the pump of the monitoring system are started, and the water sample (reaction solution) is introduced into the monitoring system (fluoride ion concentration detection section FD, second In the pH detection section D2), the measurement time of the system to be monitored is set, and the data is read to determine whether it is the end point of the reaction.

(4) If the pH value or fluoride ion concentration set point is not reached, close the pump of the monitoring system and each pneumatic valve, and enter the procedure for fine adjustment and input of the second crystallization agent (sodium aluminate solution); that is, start the second crystallization agent storage tank The output pump is injected into the second crystallization reaction tank according to the setting of the fine-tuning input sodium aluminate quality.

(5) After reaching the fine-tuning reaction stand-by time, start each pneumatic valve (pneumatic valve introduced and discharged into the reaction tank) and the pump of the monitoring system, and the water sample (reaction solution) will be introduced into the monitoring system (fluoride ion concentration detection section FD, In the second pH detection section D2), the measurement time of the system to be monitored is set, and the data is read to determine whether it is the end of the reaction. If the pH and the set value of fluoride ion are not reached, continue to repeat step (4) until Reached the end of the reaction pH value and fluoride ion set value.

(6) After reaching the end of the reaction pH value and fluoride ion set value, start the second separator to separate and clean the crystals. The crystals and low-concentration hydrofluoric acid waste liquid will be discharged into the dehydrator by gravity flow, and then pass through For the first solid-liquid separation, discharge the low-concentration hydrofluoric acid waste liquid to the cleaning wastewater tank, and then start the clean water pneumatic valve for cleaning operations. When the injected clean water level reaches the set value, close the clean water pneumatic valve, and then perform solid-liquid separation. The separated washing wastewater is discharged to the washing wastewater tank for storage. This cleaning action will be repeated three times.

(7) The cleaning waste water tank is provided with high and low liquid levels to control the cleaning waste water pump and discharge the cleaning waste liquid out of the system.

(8) After the cleaning operation reaches the set value, the system can restart the first-stage crystallization operation, and the crystal stored in the second separator needs to be manually taken out.

The specific experimental conditions and measurement results of the above Examples 3 and 4 are shown in Table 1 below.

 Table I  First stage crystallization process  Item  Unit  Example one  Example two  Example three  Embodiment 4  Reaction volume  L  5  5  60  60  Fluoride ion concentration  mg / L  250,000  250,000  250,000  250,000  Volume of sodium hydroxide solution containing sodium carbonate  L  2.8  3.1  44  36  Operating time  min  45  45  120  120  Endpoint pH  pH  2.5  2.84  2.75  2.94  Outflow fluoride ion  mg / L  64,800  53,500  24,080  23,900  Second stage crystallization process  Item  Unit  Example one  Example two  Example three  Embodiment 4  Reaction volume  L  5  5  60  60  Fluoride ion concentration  mg / L  64,800  53,500  24,080  23,900  Sodium aluminate  L  2  1.8  twenty three  twenty two  Operating time  min  60  60  120  120  Endpoint pH  pH  6.9  6.6  6.4  7  Outflow fluoride ion  mg / L  47  33  twenty three  25

Therefore, the secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to the present invention and a method for controlling the crystallization operation thereof, through the combination of the first-stage crystallization procedure and the second-stage crystallization procedure, can achieve a high Concentrated hydrofluoric acid waste stock solution fully reacts to produce economical sodium fluoride crystals and sodium fluoroaluminate crystals. At the same time, it effectively reduces the concentration of fluoride ions in the waste stock solution to meet the emission standards. It can be concentratedly discharged without additional treatment, reducing high concentrations. Disposal cost of hydrofluoric acid waste stock solution. At the same time, the present invention effectively controls the factors affecting the purity of the crystal during the operation of the system through the pH value detection and / or fluoride ion concentration detection in each crystallization program, and the solid-liquid separation section and the cleaning treatment section to ensure that the system can stably produce crystal purity Sodium fluoride crystals and sodium fluoroaluminate crystals (cryolite) that can be recovered and reused can achieve the purpose of improving the recovery rate of fluoride ions and the purity of the resulting crystals with high economic benefits.

P‧‧‧Control Processor

V1‧‧‧High-concentration hydrofluoric acid waste tank

F‧‧‧Measurement inflow control section

V2‧‧‧Sodium hydroxide solution storage tank containing sodium carbonate

V3‧‧‧Sodium Aluminate Solution Storage Tank

A1‧‧‧The first quality control dosing section

A2‧‧‧Second Quality Control Dosing Section

R1‧‧‧First crystallization reaction section

R2‧‧‧Second crystallization reaction section

D1‧‧‧The first pH detection section

D2‧‧‧Second pH detection section

FD‧‧‧Fluoride ion concentration detection section

W1‧‧‧The first cleaning treatment section

W2‧‧‧Second cleaning treatment section

SE1‧‧‧The first solid-liquid separation section

SE2‧‧‧Second solid-liquid separation section

C1‧‧‧Sodium fluoride crystal

C2‧‧‧Sodium Fluoroaluminate Crystal

HHF‧‧‧High concentration hydrofluoric acid waste stock solution

LHF‧‧‧ Medium-low concentration hydrofluoric acid reaction solution

CR1‧‧‧First Crystallizer

CR2‧‧‧Second Crystallizer

A20‧‧‧Second crystallization reaction tank

A21‧‧‧Quality Control Dosing Department

A22‧‧‧ Crystal Deposit Department

A23‧‧‧Return pump

C21‧‧‧ Crystal

C22‧‧‧ crystal core

S1‧‧‧Parameter setting procedure

S2‧‧‧High concentration hydrofluoric acid waste stock solution

S3‧‧‧The first step of crystallizing agent adding step

S4‧‧‧The first stage pH detection step

S41‧‧‧Reaction end judgment steps

S5‧‧‧Still reaction step

S6‧‧‧The first solid-liquid separation step

S7‧‧‧Sodium fluoride crystal processing steps

S8‧‧‧Medium and low concentration hydrofluoric acid reaction solution input steps

S9‧‧‧Second-stage crystallizing agent adding step

S10‧‧‧Second stage fluoride ion detection step

S101‧‧‧Reaction end judgment steps

S11‧‧‧Second stage pH detection step

S111‧‧‧Reaction end judgment steps

S112‧‧‧ Fine adjustment step of pH value of reaction solution

S12‧‧‧Still reaction step

S13‧‧‧Second stage solid-liquid separation step

S14‧‧‧Sodium fluoroaluminate crystal processing steps

S15‧‧‧Automatic mode judgment steps

FIG. 1 is a schematic diagram of a conventional crystallization system for generating sodium fluoroaluminate crystals from a hydrofluoric acid solution. FIG. 2 is a schematic diagram of the overall structure of a secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to the present invention. FIG. 3 is a schematic flowchart of a crystallization operation control method of the system of the present invention. FIG. 4 is a schematic diagram of an operation of performing a dynamic crystallization reaction in a crystallization reaction tank of a first crystallization reaction stage in a second-stage crystallization procedure of the present invention.

Claims (24)

A secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution, including: a control processor; a first crystallization reaction section, which is electrically controlled by the control processor; the first crystallization reaction A batch of high-concentration hydrofluoric acid waste stock solution is input through the control processor in batches, and a first crystallization agent is added to the hydrofluoric acid waste solution through the control processor for quality control. The first crystallization agent contains A solution of sodium carbonate and sodium hydroxide to generate a reaction solution of sodium fluoride crystals and low-concentration hydrofluoric acid; a second crystallization reaction section, which is electrically controlled by the control processor and is the output terminal of the first crystallization reaction section Connection; the second crystallization reaction section inputs the medium-low concentration hydrofluoric acid reaction solution through the control processor in batches, and adds a second crystallization agent to the medium-low concentration hydrofluoric acid reaction solution through the control processor in a quality control manner A crystallization reaction is carried out in the second crystallization agent is a sodium aluminate solution to generate sodium fluoroaluminate crystals and a low-concentration hydrofluoric acid waste solution. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 1 of the scope of the patent application, wherein the secondary crystallization system further includes: a first pH detection section, The control processor is electrically controlled and connected to the first crystallization reaction section; the first pH detection section controls and measures the pH value of the reaction solution inside the first crystallization reaction section through the control processor, and the control processor Determine the reaction end point of the first crystallization reaction section according to the measured pH value; a second pH detection section, which is electrically controlled by the control processor and is connected to the second crystallization reaction section; the second pH detection section The pH value of the reaction solution inside the second crystallization reaction section is controlled and measured by the control processor, and the control processor determines the reaction end point of the second crystallization reaction section according to the measured pH value. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 2 of the scope of the patent application, wherein the secondary crystallization system further includes: a fluoride ion concentration detection section for the The control processor is electrically controlled and connected to the second crystallization reaction section; the fluoride ion concentration detection section controls and measures the fluoride ion concentration of the reaction solution inside the second crystallization reaction section through the control processor; The measured fluoride ion determines the initial reaction end point of the second crystallization reaction section, and the control processor determines the final reaction end point of the second crystallization reaction section according to the pH value measured in the second pH detection section. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to any of claims 1 to 3, wherein the first crystallization agent is subjected to a first quality control process. The uniformly dispersed droplets output from the medicine section flow into the first crystallization reaction section for crystallization reaction with the high-concentration hydrofluoric acid waste stock solution; the sodium aluminate solution outputs uniformly dispersed droplets through a second quality control dosing section The liquid phase flows into the second crystallization reaction section to perform a crystallization reaction with the medium-low concentration hydrofluoric acid reaction solution. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 4 of the scope of patent application, wherein the first crystallization reaction section and the second crystallization reaction section are both crystallization reactions. The first quality control dosing section and the second quality control dosing section each include a dispersion plate with a plurality of liquid holes and a control plate with a plurality of through holes on the dispersion plate; The dispersion plate and the control plate of the first quality control dosing section are provided in a crystallization reaction tank of the first crystallization reaction section, and the dispersion plate and the control plate of the second quality control dosing section are provided in the second crystallization reaction section. A crystallization reaction tank; the inside of the crystallization reaction tank is separated from the dispersion plate and the control plate to form a dosing space and a reaction space, the first quality control dosing section and the second quality control dosing section pass through the The control processor controls the control disk to rotate, so as to adjust the number of matching holes between the through holes of the control disk and the liquid holes of the dispersion disk, and adjust the flow rate of the drip-shaped liquid flow falling from the medicine injection space to the reaction space. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 5 of the scope of the patent application, wherein the secondary crystallization system further includes: a first solid-liquid separation section, The control processor is electrically controlled and connected to the output end of the first crystallization reaction section; the first solid-liquid separation section controls the control processor to separate the sodium fluoride crystals output from the first crystallization reaction section and the low-medium concentration Hydrofluoric acid reaction liquid; a second solid-liquid separation section, which is electrically controlled by the control processor and connected to the output end of the second crystallization reaction section; the second solid-liquid separation section controls and separates the control through the control processor The sodium fluoroaluminate crystals output from the second crystallization reaction section and a medium-low concentration hydrofluoric acid reaction solution. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 6 of the scope of patent application, wherein the secondary crystallization system further includes: a first cleaning treatment section for the The control processor is electrically controlled and connected to the liquid output end of the first solid-liquid separation section. The first cleaning treatment section is used to form a path for outputting the medium-low concentration hydrofluoric acid reaction solution or to input clean water to clean the first solid-liquid. A sodium fluoride crystal in the separation section; a second cleaning processing section, which is electrically controlled by the control processor and is connected to the liquid output end of the second solid-liquid separation section; The path of the concentrated hydrofluoric acid waste liquid or the input of clean water to clean the sodium fluoroaluminate crystals in the second solid-liquid separation section. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 1 of the scope of the patent application, wherein the fluoride ion concentration of the high-concentration hydrofluoric acid waste stock solution is 40 g / L or more The fluoride ion concentration of the low-concentration hydrofluoric acid reaction solution is 10 g / L or more; the fluoride ion concentration of the low-concentration hydrofluoric acid waste solution is 60 mg / L or more. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to any of claims 1 to 3, wherein the crystallization system further includes: a high-concentration hydrofluoric acid The waste liquid tank is connected to the first crystallization reaction section through a metering inflow control section. The metering inflow control section is electrically controlled by the control processor to batch output the high-concentration hydrofluoric acid waste stock solution to the first crystallization reaction. Section; a sodium carbonate solution storage tank containing sodium carbonate, which is electrically controlled by the control processor to output the first crystalline agent to the first quality control dosing section; and a sodium aluminate solution storage tank, which is The control processor is electrically controlled to output the second crystalline medicament to the second quality control dosing section. A secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution, including: a control processor; a first crystallization reaction section, which is electrically controlled by the control processor; the first crystallization reaction A batch of high-concentration hydrofluoric acid waste stock solution is input through the control processor in batches, and a first crystallization agent is added to the hydrofluoric acid waste solution through the control processor for quality control. The first crystallization agent contains A solution of sodium carbonate and sodium hydroxide to generate a reaction solution of sodium fluoride crystals and low-concentration hydrofluoric acid; a second crystallization reaction section, which is electrically controlled by the control processor and is the output terminal of the first crystallization reaction section Connection; the second crystallization reaction section inputs the medium-low concentration hydrofluoric acid reaction solution through the control processor in batches, and adds a second crystallization agent to the medium-low concentration hydrofluoric acid reaction solution through the control processor in a quality control manner A crystallization reaction is performed in the second crystallization agent, which is a sodium aluminate solution to generate sodium fluoroaluminate crystals and a low-concentration hydrofluoric acid waste liquid; a medicine injection space and The application space and the reaction space communicate with each other through a reflux pump provided outside the second crystallization reaction section. The reflux pump draws the reaction solution containing crystal nuclei in the reaction space to the seed space to form a seed crystal. nuclear. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 10 of the scope of patent application, wherein the secondary crystallization system further includes: a first pH detection section, The control processor is electrically controlled and connected to the first crystallization reaction section; the first pH detection section controls and measures the pH value of the reaction solution inside the first crystallization reaction section through the control processor, and the control processor Determine the reaction end point of the first crystallization reaction section according to the measured pH value; a second pH detection section, which is electrically controlled by the control processor and is connected to the second crystallization reaction section; the second pH detection section The pH value of the reaction solution inside the second crystallization reaction section is controlled and measured by the control processor, and the control processor determines the reaction end point of the second crystallization reaction section according to the measured pH value. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 11 of the scope of the patent application, wherein the secondary crystallization system further includes: a fluoride ion concentration detection section for the The control processor is electrically controlled and connected to the second crystallization reaction section; the fluoride ion concentration detection section controls and measures the fluoride ion concentration of the reaction solution inside the second crystallization reaction section through the control processor; The measured fluoride ion determines the initial reaction end point of the second crystallization reaction section, and the control processor determines the final reaction end point of the second crystallization reaction section according to the pH value measured in the second pH detection section. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution according to any one of claims 10 to 12, wherein the first crystallization agent is subjected to a first quality control process. The uniformly dispersed droplets output from the medicine section flow into the first crystallization reaction section for crystallization reaction with the high-concentration hydrofluoric acid waste stock solution; the sodium aluminate solution outputs uniformly dispersed droplets through a second quality control dosing section The liquid phase flows into the second crystallization reaction section to perform a crystallization reaction with the medium-low concentration hydrofluoric acid reaction solution. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 13 of the scope of the patent application, wherein the first crystallization reaction section and the second crystallization reaction section are both crystallization reactions. The first quality control dosing section and the second quality control dosing section each include a dispersion plate with a plurality of liquid holes and a control plate with a plurality of through holes on the dispersion plate; The dispersion plate and the control plate of the first quality control dosing section are provided in a crystallization reaction tank of the first crystallization reaction section, and the dispersion plate and the control plate of the second quality control dosing section are provided in the second crystallization reaction section. A crystallization reaction tank; the inside of the crystallization reaction tank is separated from the dispersion plate and the control plate to form a dosing space and a reaction space, the first quality control dosing section and the second quality control dosing section pass through the The control processor controls the control disk to rotate, so as to adjust the number of matching holes between the through holes of the control disk and the liquid holes of the dispersion disk, and adjust the flow rate of the drip-shaped liquid flow falling from the medicine injection space to the reaction space. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 14 of the scope of patent application, wherein the secondary crystallization system further includes: a first solid-liquid separation section, The control processor is electrically controlled and connected to the output end of the first crystallization reaction section; the first solid-liquid separation section controls the control processor to separate the sodium fluoride crystals output from the first crystallization reaction section and the low-medium concentration Hydrofluoric acid reaction liquid; a second solid-liquid separation section, which is electrically controlled by the control processor and connected to the output end of the second crystallization reaction section; the second solid-liquid separation section controls and separates the control through the control processor The sodium fluoroaluminate crystals output from the second crystallization reaction section and a medium-low concentration hydrofluoric acid reaction solution. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 15 of the scope of patent application, wherein the secondary crystallization system further includes: a first cleaning treatment section for the The control processor is electrically controlled and connected to the liquid output end of the first solid-liquid separation section. The first cleaning treatment section is used to form a path for outputting the medium-low concentration hydrofluoric acid reaction solution or to input clean water to clean the first solid-liquid. A sodium fluoride crystal in the separation section; a second cleaning processing section, which is electrically controlled by the control processor and is connected to the liquid output end of the second solid-liquid separation section; The path of the concentrated hydrofluoric acid waste liquid or the input of clean water to clean the sodium fluoroaluminate crystals in the second solid-liquid separation section. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 10 of the scope of the patent application, wherein the fluoride ion concentration of the high-concentration hydrofluoric acid waste stock solution is 40 g / L or more The fluoride ion concentration of the low-concentration hydrofluoric acid reaction solution is 10 g / L or more; the fluoride ion concentration of the low-concentration hydrofluoric acid waste solution is 60 mg / L or more. The secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution as described in item 10 of the scope of the patent application, wherein the crystallization system further includes: a high-concentration hydrofluoric acid waste liquid tank through A metering inflow control section is connected to the first crystallization reaction section. The metering inflow control section is electrically controlled by the control processor to output the high-concentration hydrofluoric acid waste stock solution to the first crystallization reaction section in batches. A sodium hydroxide solution storage tank is electrically controlled by the control processor to output the first crystalline agent to the first quality control dosing section; and a sodium aluminate solution storage tank is electrically controlled by the control processor. Control to output the second crystalline medicament to the second quality control dosing section. A crystallization operation control method of a secondary crystallization system for generating sodium fluoride and sodium fluoroaluminate crystals from a hydrofluoric acid solution. The method includes a preliminary setting program, a first-stage crystallization program, and a second-stage crystallization program. Including the parameter setting step, the first-stage crystallization program includes a high-concentration hydrofluoric acid waste stock solution input step, the first-stage crystallization agent adding step, and the sodium fluoride crystal processing step. The second-stage crystallization program includes a medium-low concentration hydrofluoric acid. Step of inputting reaction solution, step of adding crystallizing agent in the second stage, and step of processing sodium fluoroaluminate crystal; among which: the parameter setting step: setting the parameter item and its value range through the control processor; the input step of the high-concentration hydrofluoric acid waste stock solution : According to the setting value of this parameter setting step, the high-concentration hydrofluoric acid waste stock solution is batch input into the reaction space of the first crystallization reaction stage; The first stage crystallization reagent adding step: According to the setting value of this parameter setting step, The sodium carbonate solution of sodium carbonate is output to the first quality control dosing section to form a drip solution And fall into the reaction space of the first crystallization reaction section, so that the sodium carbonate-containing sodium hydroxide solution and the high-concentration hydrofluoric acid waste stock solution undergo crystallization reaction, and generate sodium fluoride crystals and low-concentration hydrofluoric acid Reaction solution; the sodium fluoride crystal processing step: collecting and cleaning the sodium fluoride crystal; the medium-low concentration hydrofluoric acid reaction liquid input step: reacting the medium-low concentration hydrofluoric acid according to the set value of the parameter setting step The liquid batch is input into the reaction space of the second crystallization reaction section; the second-stage crystallization agent adding step: according to the set value of the parameter setting step, the sodium aluminate solution is output to the second quality control dosing section to form a drip-shaped liquid Flow and fall into the reaction space of the second crystallization reaction section, so that the sodium aluminate solution and the medium-low concentration hydrofluoric acid reaction solution perform a crystallization reaction, and generate sodium fluoroaluminate crystals and low-concentration hydrofluoric acid waste liquid ; Sodium fluoroaluminate crystal processing step: Collect and clean the sodium fluoroaluminate crystal. The method for controlling crystallization operation according to item 19 in the scope of the patent application, wherein the first-stage crystallization procedure further includes performing a first-stage pH value between the first-stage crystallization agent adding step and the sodium fluoride crystal processing step. A detection step, a standing reaction step, and a first-stage solid-liquid separation step; wherein: the first-stage pH detection step: introducing the reaction solution in the first crystallization reaction section into the first pH detection section to measure the reaction solution; pH value; wherein, the reaction end point judgment step of the first stage pH detection step is based on the set value of the pH reaction end point of the parameter setting step. When the pH value of the reaction solution does not reach the set value, the first step is repeatedly performed. The first-stage crystallization agent adding step and the first-stage pH value detecting step, until the pH value of the reaction solution reaches a set value, enter the standing reaction step; the standing reaction step: stopping the sodium carbonate-containing sodium hydroxide solution Output to the first quality control dosing section, and leave the reaction solution in the first crystallization reaction section to stand still according to the set value of the parameter setting step to perform crystallization reaction to generate fluorine Sodium chloride crystals; the first solid-liquid separation step: solid-liquid separation of the generated sodium fluoride crystals from the reaction solution. The crystallization operation control method according to item 20 of the patent application scope, wherein the first-stage crystallization procedure further includes performing a second-stage fluorine between the second-stage crystallization agent adding step and the sodium fluoroaluminate crystal processing step. Ion detection step, second stage pH detection step, standing reaction step and second stage solid-liquid separation step; wherein: the second stage fluoride ion detection step introduces the reaction solution in the second crystallization reaction section into the fluoride ion concentration The fluoride ion solubility of the reaction solution is measured in the detection section; wherein the reaction end point judgment step of the second stage fluoride ion detection step is based on the fluoride ion concentration reaction end point setting value of the parameter setting step, and the fluoride ion concentration in the reaction solution When the set value is not reached, the second-stage crystallization agent adding step and the second-stage fluoride ion detection step are repeatedly performed until the fluoride ion concentration of the reaction solution reaches the set value, and the second-stage pH value detection step is entered; Second stage pH detection step: introducing the reaction solution in the second crystallization reaction section into the second pH detection section to measure the reaction The pH value of the reaction step in the second stage pH detection step is based on the set value of the pH reaction end point of the parameter setting step. When the pH value of the reaction solution does not reach the set value, it is repeatedly executed. The pH adjustment step of the reaction solution and the pH detection step of the second stage, until the pH value of the reaction solution reaches a set value, enter the standing reaction step; the standing reaction step: stop outputting the sodium aluminate solution to the second The quality control dosing section, and the reaction solution in the second crystallization reaction section is allowed to stand still according to the set value of the parameter setting step, so as to carry out the crystallization reaction to generate sodium fluoroaluminate crystals; this second stage solid-liquid separation step: The sodium fluoroaluminate crystals were separated from the solid solution in the reaction solution. The crystallization operation control method according to any one of claims 19 to 21, wherein the parameter setting step further includes, after completing the parameter setting, setting a first quality control dosing according to the first-stage crystallization agent flow demand. Dispersion plate and control plate in the stage to regulate the flow rate of the sodium carbonate-containing sodium hydroxide solution falling into the reaction space in the first crystallization reaction stage; and a second quality control dosing stage is set according to the flow demand of the crystallization agent in the second stage A dispersion plate and a control plate to regulate the flow rate of the sodium aluminate solution falling into the reaction space in the second crystallization reaction section. The crystallization operation control method according to any one of claims 19 to 21, wherein the second-stage crystallization agent adding step further includes extracting the reaction solution containing crystal nuclei from the reaction space of the second crystallization reaction section to reflux. Into the dosing space. The crystallization operation control method according to any one of claims 19 to 21, wherein the method further includes an automatic mode judgment step, where the control processor presets the current operation as the automatic mode or Manual mode; when in the automatic mode, the control processor automatically controls the high-concentration hydrofluoric acid waste stock solution input step to repeat the previous steps; when in the manual mode, the control processor stops automatic control and returns to the parameter After the setting procedure is completed, the automatic control is started.