A method and system for concentrating and purifying triethylamine hydrochloride

Abstract

The application discloses a method and system for concentrating and purifying triethylamine hydrochloride, and relates to the technical field of chemical separation and purification, and aims to solve the problems of non-continuous production, poor product quality and high energy consumption caused by the inability to effectively remove phosphorus in the solid NaOH dehydration method in the prior art. The method is used for treating triethylamine hydrochloride solution containing phosphorus and having an organic phosphorus proportion of not less than 80% in terms of total phosphorus content, and comprises the following steps: S1, concentrating to a water content of 30% to 45% to form a mixture of crystals and mother liquor; S2, performing solid-liquid separation to obtain wet powder and phosphorus-containing mother liquor; and S3, dissolving the wet powder in water, then concentrating to a water content of 30% to 45% again, and performing solid-liquid separation to obtain a product with a total phosphorus content of less than 0.03%. The system comprises a primary dissolving kettle, a primary concentrating device, a primary solid-liquid separation device, a secondary dissolving kettle, a secondary concentrating device and a secondary solid-liquid separation device connected in sequence, and the primary concentrating device is provided with a water content detection control unit. The application can be used for the recovery and purification of triethylamine hydrochloride in the production process of glyphosate by the glycine method.

Description

Technical Field

[0001] This invention relates to the field of chemical separation and purification technology, specifically to a concentration and purification method and system for recovering triethylamine hydrochloride from glyphosate production mother liquor. Background Technology

[0002] Glyphosate is the most widely used non-selective herbicide globally, and its production mainly employs two processes: the glycine process and the iminodiacetic acid process. Among these, the glycine process has become the mainstream technology for glyphosate production in my country due to its mature technology, readily available raw materials, and suitability for large-scale industrial production, accounting for over 70% of the total production capacity.

[0003] In the glycine-based glyphosate production reaction system, triethylamine acts as a key acid-binding agent and catalyst, combining with the hydrogen chloride generated in the reaction to drive the reaction forward. After the reaction, triethylamine exists in the material system as triethylamine hydrochloride. To reduce production costs and achieve resource recycling, industrially, triethylamine hydrochloride needs to be separated and recovered from the mother liquor and regenerated into free triethylamine for reuse in the synthesis process.

[0004] Currently, domestic glyphosate producers generally use the solid NaOH dehydration method to recover triethylamine. A typical process flow is as follows: first, the glyphosate mother liquor is neutralized with liquid alkali to convert triethylamine hydrochloride into free triethylamine; then, after settling and separation, crude triethylamine containing water is obtained; finally, solid sodium hydroxide is manually added to the crude triethylamine for deep dehydration, yielding the finished triethylamine for recycling.

[0005] However, as the glyphosate industry continues to increase its requirements for production cost control and product quality, the aforementioned traditional solid NaOH dehydration method has gradually revealed the following technical defects:

[0006] I. Poor production continuity and low automation. The solid NaOH dehydration method employs an intermittent batch reactor operation mode, requiring manual weighing and addition of solid sodium hydroxide for each batch. This operation is cumbersome and labor-intensive. Solid sodium hydroxide is highly corrosive, posing safety hazards such as skin burns and dust inhalation during manual addition. Furthermore, intermittent operation leads to significant fluctuations in product quality between batches, which is detrimental to the stable operation of downstream processes.

[0007] Second, the inability to effectively remove phosphorus impurities limits product purity. The composition of glyphosate production mother liquor is extremely complex, containing not only triethylamine hydrochloride but also a considerable amount of phosphorus-containing compounds. Testing shows that the total phosphorus content in the triethylamine hydrochloride separated from the mother liquor is typically around 0.9%. Further phosphorus speciation analysis indicates that, based on the total phosphorus content, approximately 20% is orthophosphate, and approximately 80% is organophosphorus compounds (mainly including methylphosphonic acid, iminodiacetic acid derivatives, etc.). If these phosphorus impurities are not effectively separated, they will enter the subsequent regeneration process along with the triethylamine hydrochloride, not only affecting the quality of the regenerated triethylamine but also potentially accumulating during recycling, adversely impacting the glyphosate synthesis reaction. The core function of the solid NaOH dehydration method is only physical dehydration, and it has virtually no ability to separate and remove phosphorus impurities from the system.

[0008] Third, phosphorus resource waste and increased environmental burden. Phosphorus compounds in the mother liquor are not recovered and are discharged into environmental treatment systems as wastewater, not only wasting phosphorus resources but also increasing the enterprise's wastewater treatment burden and environmental costs. Given the increasingly precious nature of phosphorus resources, achieving phosphorus separation and recovery has significant economic and environmental value.

[0009] Fourth, high energy consumption and insufficient economic efficiency. The dehydration step in the solid NaOH dehydration method relies on the chemical water absorption of solid sodium hydroxide. The consumed sodium hydroxide cannot be regenerated and is a disposable consumable, resulting in high operating costs. At the same time, the heat generated in the process is not effectively recovered and utilized, resulting in low overall thermal efficiency.

[0010] To address the shortcomings of traditional processes, the industry has explored alternative treatment routes. For example, some methods involve high-temperature incineration of the lower layer of the mother liquor after separation to decompose organic matter and remove phosphorus impurities. However, this incineration process is extremely energy-intensive, requires a complex exhaust gas treatment system, resulting in high overall operating costs, and fails to yield triethylamine hydrochloride. Other methods employ nanofiltration membrane separation technology to purify the triethylamine hydrochloride solution, but nanofiltration membranes have high investment costs, are prone to clogging due to organic matter, require frequent chemical cleaning, incur high maintenance costs, and have a limited lifespan. Ion exchange resin adsorption is used to remove phosphorus impurities, but the resin has limited adsorption capacity, requires periodic regeneration, occupies a large area, and is difficult to treat as regeneration wastewater, with complex operating procedures. Still others use organic solvent extraction to recover triethylamine hydrochloride, but organic solvents are expensive, flammable, and explosive, posing safety hazards, and the phosphorus removal effect is not considered.

[0011] In summary, existing technologies, whether traditional solid NaOH dehydration methods or subsequent methods such as incineration, nanofiltration membranes, ion exchange resins, and organic solvent extraction, all suffer from drawbacks such as complex processes, high costs, and inconvenient operation. More importantly, none of these methods recognize the phase distribution patterns of phosphorus impurities (especially organic phosphorus, which accounts for up to 80% of the total phosphorus content) in the triethylamine hydrochloride system under specific physical conditions, and fail to utilize simple, low-cost physical methods to achieve efficient and selective separation of phosphorus impurities. Therefore, developing a simple, highly efficient, continuously operable, and energy-efficient triethylamine hydrochloride purification method and system remains a critical technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0012] The technical problem to be solved by this invention is: in view of the shortcomings of the existing technology, the purification of triethylamine hydrochloride requires complex means such as chemical reagents, high-temperature incineration or membrane separation, and cannot effectively remove organophosphorus compounds. How to provide a concentration and purification method and system that can efficiently remove phosphorus through physical means, achieve continuous production and obtain high-quality products with total phosphorus content of less than 0.03%?

[0013] This invention provides the following technical solution:

[0014] A method for concentrating and purifying triethylamine hydrochloride, used to treat a phosphorus-containing triethylamine hydrochloride solution, wherein the mass percentage of organic phosphorus in the solution is not less than 80% based on the total phosphorus mass, includes the following steps:

[0015] S1: The triethylamine hydrochloride solution is concentrated, and the concentration endpoint is controlled so that the water content of the resulting concentrated solution is 30% to 45%, forming a mixture of triethylamine hydrochloride crystals and mother liquor;

[0016] S2: Perform solid-liquid separation on the mixture to obtain triethylamine hydrochloride wet powder and phosphorus-containing mother liquor;

[0017] S3: After dissolving the triethylamine hydrochloride wet powder in water, concentrate it again to a water content of 30% to 45%, and then perform solid-liquid separation to obtain a triethylamine hydrochloride product with a total phosphorus content of less than 0.03%.

[0018] Furthermore, the total phosphorus content in the solution is 0.5% to 1.5%.

[0019] Furthermore, based on the total phosphorus mass in the solution, the mass percentage of organic phosphorus is not less than 85%, and the organic phosphorus includes methylphosphonic acid and / or iminodiacetic acid derivatives.

[0020] Furthermore, the solid-liquid separation in step S2 and / or step S3 is performed by centrifugation at a speed of 2000–3000 r / min.

[0021] Furthermore, the concentration employs multi-effect evaporation, and the secondary steam generated by evaporation is compressed and reused for heating through a thermal integration unit, and / or the condensate generated by evaporation is exchanged with the feed liquid for heat.

[0022] Furthermore, at least a portion of the phosphorus-containing mother liquor obtained in step S2 is returned and combined with the triethylamine hydrochloride solution described in step S1 for further concentration; and / or, a secondary mother liquor is obtained after solid-liquid separation in step S3, at least a portion of which is returned and combined with the solution obtained after dissolving the triethylamine hydrochloride wet powder in the next batch of step S3 for further concentration.

[0023] The present invention also provides a triethylamine hydrochloride concentration and purification system, comprising:

[0024] A primary dissolving vessel is used to dissolve phosphorus-containing triethylamine hydrochloride raw materials;

[0025] A primary concentration device is connected to the outlet of the primary dissolving vessel and is used to concentrate the dissolved triethylamine hydrochloride solution. The primary concentration device is equipped with a moisture detection and control unit to control the concentration endpoint so that the water content of the resulting concentrated solution is 30% to 45%, so as to form a mixture of triethylamine hydrochloride crystals and mother liquor.

[0026] A primary solid-liquid separation device is connected to the outlet of the primary concentration device and is used for solid-liquid separation of the mixture to obtain primary wet powder and phosphorus-containing mother liquor;

[0027] A secondary dissolving vessel is connected to the solid phase outlet of the primary solid-liquid separation device and is used to receive and dissolve the primary wet powder.

[0028] A secondary concentration device is connected to the outlet of the secondary dissolving kettle and is used to further concentrate the dissolved primary wet powder.

[0029] A secondary solid-liquid separation device is connected to the outlet of the secondary concentration device and is used to perform solid-liquid separation on the material after secondary concentration to obtain a triethylamine hydrochloride product with a total phosphorus content of less than 0.03%.

[0030] Furthermore, a stratification tank and an intermediate tank are provided before the primary dissolution vessel. The stratification tank is used to automatically overflow and stratify the dissolved material into an upper layer of solvent and a lower layer of triethylamine hydrochloride solution. The intermediate tank is used to receive the lower layer of triethylamine hydrochloride solution and transport it to the primary concentration device. The upper outlet of the stratification tank is connected to a solvent receiving tank for recovering the upper layer of solvent and reusing it in the front-end process.

[0031] Furthermore, the primary concentration device and / or secondary concentration device are multi-effect evaporation devices and are equipped with a thermal integration unit. The thermal integration unit includes a steam compressor and a heat exchanger, which are used to compress the secondary steam generated by evaporation and supply it back to the heating chamber, and / or to exchange heat between the condensate generated by evaporation and the feed liquid. The moisture detection and control unit is selected from at least one of an online refractometer, an online densitometer, or a near-infrared moisture analyzer.

[0032] Furthermore, the primary solid-liquid separation device and / or the secondary solid-liquid separation device is a centrifuge with an adjustable speed range of 2000–3000 r / min; the liquid phase outlet of the primary solid-liquid separation device is connected to the feed pipeline of the primary concentration device via a pipeline, for combining the phosphorus-containing mother liquor with the triethylamine hydrochloride solution to be concentrated and then entering the primary concentration device together; and / or, the liquid phase outlet of the secondary solid-liquid separation device is connected to the feed pipeline of the secondary concentration device via a pipeline, for combining the secondary mother liquor with the solution after secondary dissolution and then entering the secondary concentration device together.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] I. Achieving Efficient Physical Phosphorus Removal through Specific Moisture Content Control. Through extensive experimentation, the inventors unexpectedly discovered that when a triethylamine hydrochloride solution is concentrated to a specific water content range of 30%–45%, phosphorus impurities in the system (especially organic phosphorus, accounting for no less than 80% of the total phosphorus content) significantly accumulate in the mother liquor phase rather than entering the triethylamine hydrochloride crystalline phase due to their much higher solubility in the high-ionic-strength aqueous phase. Based on this non-obvious physicochemical principle, selective phosphorus separation can be achieved simply by controlling the water content at the concentration endpoint and subsequent solid-liquid separation, without the introduction of any chemical reagents or the need for high-temperature incineration or membrane separation equipment.

[0035] II. Two-stage purification achieves total phosphorus <0.03%. Single concentration and solid-liquid separation can only reduce the total phosphorus in wet powder to about 0.1% to 0.2%, which cannot meet the high purity requirements. This invention redissolves the wet powder in step S3, then concentrates it again to a water content of 30% to 45% and performs solid-liquid separation. The secondary recrystallization effect further reduces the residual phosphorus content in the crystals, and the total phosphorus of the final product can be stably below 0.03%. This two-stage setup is not a simple repetition, but a synergistic phosphorus removal mechanism based on the requirement that both concentrations be controlled within a specific water content range. The first crystallization destroys the original phosphorus-triethylamine hydrochloride blend structure, discharging most of the phosphorus into the mother liquor; the second recrystallization further distributes and deeply removes the trace amounts of phosphorus remaining in the first wet powder, which is a necessary technical means to achieve the target purity.

[0036] Third, it achieves continuous production and significantly reduces energy consumption. The entire process involves continuous material flow, eliminating the need for intermittent feeding and overcoming the intermittent operation defects of traditional solid NaOH dehydration methods. Furthermore, by configuring a thermal integration unit on the concentration unit, the secondary steam from evaporation is compressed and reused, and the condensate is preheated for feeding. Taking a single triple-effect evaporator with a processing capacity of 5t / h as an example, without thermal integration, the steam consumption per unit product is approximately 0.45t steam / t of evaporated water. After configuring a steam compressor (compression ratio 1.8) and a condensate preheater, the steam consumption per unit product can be reduced to 0.32t steam / t of evaporated water, a reduction of approximately 29%. If an MVR evaporator is further used to replace the multi-effect evaporator, the steam consumption per unit product can be reduced to below 0.15t steam / t of evaporated water, a reduction of over 60%.

[0037] IV. Full Resource Recovery and Environmentally Friendly. By combining the phosphorus-containing mother liquor with the triethylamine hydrochloride solution to be treated for concentration, and optionally by setting up a stratified tank at the front end of the system to recover the solvent, a closed-loop material circulation is achieved. Under steady-state operating conditions, phosphorus discharge from the system is mainly achieved through partial discharge of the secondary mother liquor, with the daily phosphorus discharge amounting to more than 95% of the phosphorus brought in by the raw materials. There is no unlimited accumulation of phosphorus within the system, which improves the overall recovery rate of triethylamine hydrochloride and reduces waste emissions. Attached Figure Description

[0038] Figure 1 A process flow diagram of the triethylamine hydrochloride concentration and purification method provided by the present invention; Detailed Implementation

[0039] Figure 1 The complete process flow of the triethylamine hydrochloride concentration and purification method provided by the present invention is shown below. Figure 1 The present invention will be described in further detail below.

[0040] This method treats a phosphorus-containing triethylamine hydrochloride solution derived from the upstream process of glyphosate production using the glycine method. The total phosphorus content in this solution typically ranges from 0.5% to 1.5%, with a typical value of around 0.9%. Phosphorus speciation analysis reveals that, based on the total phosphorus content in the solution, organic phosphorus constitutes no less than 80% (mainly including methylphosphonic acid, iminodiacetic acid derivatives, etc.), with the remainder being orthophosphate.

[0041] Through systematic research, the inventors discovered that when the proportion of organic phosphorus in the solution is not less than 80% based on the total phosphorus content, by concentrating the solution to a water content of 30%–45%, the solubility of organic phosphorus compounds (mainly including methylphosphonic acid, iminodiacetic acid derivatives, etc.) in the high-ionic-strength aqueous phase is much higher than that of triethylamine hydrochloride. This results in their selective retention in the mother liquor phase rather than entering the triethylamine hydrochloride crystalline phase, achieving a phosphorus removal rate of over 80%. If the proportion of organic phosphorus is less than 80%, the proportion of orthophosphate is too high. During concentration, orthophosphate is more likely to co-precipitate with triethylamine hydrochloride due to the common ion effect, leading to a significant decrease in the physical phosphorus removal effect. This discovery forms the technical basis of the method of this invention.

[0042] Before concentration, the phosphorus-containing triethylamine hydrochloride raw material can be added to a dissolving vessel, and soft water is added. Under stirring, the material is fully dissolved to form a triethylamine hydrochloride solution. The purpose of using soft water is to avoid introducing impurity ions such as calcium and magnesium. If hard water is used, the calcium and magnesium ions in the water will react with the orthophosphate in the system to form insoluble calcium phosphate or magnesium phosphate precipitates. These precipitates may be trapped by triethylamine hydrochloride crystals during subsequent concentration, forming intercrystalline inclusions that severely affect the phosphorus removal efficiency and product purity. Therefore, the use of soft water is an important auxiliary condition for achieving efficient physical phosphorus removal. If the raw material is already in solution, it can proceed directly to the next process.

[0043] After dissolution, the material is pumped to a separatory tank, where it automatically separates into an upper solvent phase and a lower triethylamine hydrochloride solution phase. The separatory tank is equipped with an overflow weir or outlet; the upper solvent phase overflows into a solvent receiving tank, where it is collected and reused in the upstream glyphosate production process, achieving solvent recycling. The lower triethylamine hydrochloride solution enters an intermediate tank for temporary storage. The intermediate tank buffers flow fluctuations between upstream and downstream processes, ensuring a continuous and stable feed for subsequent concentration processes. It should be noted that the separatory tank, solvent receiving tank, and intermediate tank are suitable for applications where the triethylamine hydrochloride feedstock contains organic solvents that need to be recovered. If the feedstock does not contain solvents requiring separation, this separation step can be omitted, and the material directly enters the primary concentration unit.

[0044] The triethylamine hydrochloride solution in the intermediate tank is continuously pumped to a primary concentration unit for concentration (i.e., step S1). The primary concentration unit can be a multi-effect evaporator, such as a double-effect, triple-effect, or quadruple-effect evaporator, or an MVR evaporator. The primary concentration unit is equipped with a moisture detection and control unit to monitor the water content of the concentrate in real time and precisely control the concentration endpoint at a water content of 30%–45%, forming a mixture of triethylamine hydrochloride crystals and the mother liquor, which is in the form of a slurry suspension. The moisture detection and control unit can be selected from at least one of an online refractometer, an online densitometer, or a near-infrared moisture analyzer.

[0045] The inventors conducted a systematic experimental study on the water content at the concentration endpoint. Using a triethylamine hydrochloride solution with a total phosphorus content of 0.92% as raw material (82% organic phosphorus based on total phosphorus content), the solution was concentrated at different water content endpoints, and then solid-liquid separation was performed under the same conditions (centrifugation at 2500 r / min). The results are shown in the table below:

[0046] 55% 0.52% 43% 48% 23% 55% Large volume of mother liquor, easy to separate 50% 0.38% 59% 65% 30% 65% Separation went smoothly 45% 0.18% 80% 86% 52% 78% Separation went smoothly 40% 0.12% 87% 92% 61% 85% Separation went smoothly 35% 0.10% 89% 94% 65% 88% Separation went smoothly 30% 0.09% 90% 95% 68% 90% Separation is acceptable, but viscosity has increased slightly. 25% 0.08% 91% 96% 70% 92% Excessive viscosity makes separation difficult, and crystals severely encapsulate the mother liquor.

[0047] The data in the table above shows that the removal rate of organophosphorus compounds is significantly higher than that of orthophosphate under all moisture content conditions. This is because organophosphorus compounds (such as methylphosphonic acid and iminodiacetic acid derivatives) have a much higher solubility than triethylamine hydrochloride in concentrated solutions with high ionic strength. As concentration proceeds, water evaporates continuously, and the ionic strength of the solution continues to increase. Triethylamine hydrochloride preferentially crystallizes out due to solubility supersaturation, while organophosphorus compounds remain in the mother liquor and rarely enter the crystalline phase. Although orthophosphate has relatively low solubility, its solubility is also inhibited to some extent in a high ionic strength environment. Most of it also remains in the mother liquor, but a small amount remains in the crystals through entrainment in the mother liquor or surface adsorption, hence its relatively low removal rate. This data fully demonstrates that an organophosphorus content of no less than 80% of the total phosphorus content is a key prerequisite for achieving efficient physical phosphorus removal.

[0048] Experimental results show that when the water content is higher than 45%, although the separation operation is easy, phosphorus impurities are not fully enriched in the mother liquor, resulting in a high residual phosphorus content (>0.18%) in the crystalline product after solid-liquid separation, a phosphorus removal rate of less than 80%, incomplete crystal precipitation, and a low wet powder yield. When the water content is lower than 30%, the viscosity of the concentrate is too high, making solid-liquid separation difficult. The phenomenon of crystals carrying phosphorus-containing mother liquor is aggravated, resulting in a large amount of residual mother liquor in the wet powder after solid-liquid separation. Although the absolute value of phosphorus removal rate is slightly higher, the separation efficiency drops sharply, making it unsuitable for continuous industrial production. When the water content is controlled within the range of 30% to 45%, it can ensure sufficient enrichment of phosphorus impurities in the mother liquor phase (phosphorus removal rate ≥80%), maintain good solid-liquid separation performance, and keep the wet powder yield at a reasonable level (78% to 90%). In particular, when the moisture content is in the range of 35% to 40%, the phosphorus removal rate can reach over 87%, the wet powder yield is over 85%, and the separation operation is smoothest, making it a particularly preferred concentration endpoint range. The target moisture content of the primary concentrate can be selected from 30%, 32%, 35%, 38%, 40%, 42%, or 45% depending on the specific material characteristics.

[0049] To further verify the effect of the proportion of organic phosphorus on phosphorus removal efficiency, the inventors also conducted a comparative experiment: using four groups of triethylamine hydrochloride solutions with the same total phosphorus content (0.92%) but with organic phosphorus proportions of 60%, 70%, 80%, and 90% respectively based on the total phosphorus content as raw materials, the solutions were concentrated to a water content of 40% under the same conditions and then subjected to solid-liquid separation. The results are shown in the table below:

[0050] 60% 0.35% 62% 58% 70% 0.23% 75% 74% 80% 0.12% 87% 92% 90% 0.08% 91% 95%

[0051] Comparative experimental results show that when the proportion of organic phosphorus in the total phosphorus content is less than 80%, the total phosphorus removal rate decreases significantly. This is because as the proportion of orthophosphate increases, the co-precipitation ratio of orthophosphate increases during the concentration process, and more orthophosphate crystallizes out with triethylamine hydrochloride, resulting in a significant reduction in the physical phosphorus removal effect. Therefore, an organic phosphorus content of not less than 80% in the total phosphorus content is an important boundary condition for the effective application of the method of this invention.

[0052] The concentrated liquid is pumped to a primary solid-liquid separation unit for solid-liquid separation (i.e., step S2), producing primary wet powder and phosphorus-containing mother liquor. The primary solid-liquid separation unit can be a centrifuge, specifically a horizontal spiral sedimentation centrifuge, a horizontal scraper discharge centrifuge, or a vertical centrifuge. The adjustable range of the centrifuge speed is preferably 2000–3000 r / min, for example, 2000 r / min, 2200 r / min, 2500 r / min, 2800 r / min, or 3000 r / min. The selection of the speed is based on the following: below 2000 r / min, the centrifugal force is insufficient, solid-liquid separation is incomplete, the moisture content of the wet powder is too high, and residual phosphorus in the mother liquor will contaminate the product; above 3000 r / min, equipment investment and operating energy consumption increase significantly, while the improvement in separation efficiency tends to plateau, resulting in decreased economic efficiency. The range of 2000–3000 r / min achieves the optimal balance between separation efficiency and equipment economy. After one concentration and one solid-liquid separation, the total phosphorus content in the wet powder can be reduced to 0.1% to 0.2%, and the total phosphorus removal rate reaches 80% to 90%.

[0053] The phosphorus-containing mother liquor separated by the primary solid-liquid separation equipment is enriched with a large amount of phosphorus impurities discharged from the crystals, while still containing a certain amount of triethylamine hydrochloride. To achieve closed-loop material circulation, the phosphorus-containing mother liquor is returned in whole or in part through pipelines and combined with the phosphorus-containing triethylamine hydrochloride solution to be treated before entering the primary concentration unit for concentration, thereby improving the total recovery rate of triethylamine hydrochloride.

[0054] Regarding the material balance of phosphorus during long-term total reflux operation of the mother liquor, taking a daily processing capacity of 10 tons of triethylamine hydrochloride feedstock (total phosphorus content 0.9%, with organic phosphorus accounting for 82% of the total phosphorus content) as an example, the primary mother liquor is completely refluxed to the primary concentration process, and the secondary mother liquor is refluxed to the secondary concentration process. Under steady-state operating conditions, the total phosphorus concentration in the solution entering the primary concentration unit remains stable between 1.5% and 2.0%. Phosphorus discharge from the system is mainly achieved through partial discharge of the secondary mother liquor, with the daily phosphorus discharge amounting to over 95% of the phosphorus brought in by the feedstock. The phosphorus entering the final product accounts for only about 2% to 3% of the phosphorus brought in by the feedstock. The phosphorus concentration in each storage tank within the system reaches steady-state equilibrium after 72 hours of continuous operation, and there is no issue of unlimited phosphorus accumulation.

[0055] The primary wet powder produced by the primary solid-liquid separation equipment is conveyed to the secondary dissolving tank via a screw conveyor. Alternatively, a belt conveyor, tubular chain conveyor, or pneumatic conveying device can be used to achieve closed continuous conveying. Soft water is added to the secondary dissolving tank, and the primary wet powder is completely dissolved under stirring to form a homogeneous triethylamine hydrochloride solution, preparing for further concentration. Soft water is also used here to avoid introducing new impurities such as calcium and magnesium ions that could affect the purity of the secondary crystallization.

[0056] The solution after secondary dissolution is pumped to a secondary concentration unit for further concentration (i.e., the re-concentration in step S3). The secondary concentration unit can be the same as or different from the primary concentration unit, and can also be a multi-effect evaporator or an MVR evaporator. Similar to primary concentration, secondary concentration also requires precise control of the water content at the concentration endpoint within the range of 30%–45% to ensure that residual phosphorus impurities are again enriched in the liquid phase. The secondary concentrate is pumped to a secondary solid-liquid separation device for a second solid-liquid separation (i.e., the re-solid-liquid separation in step S3), ultimately yielding a triethylamine hydrochloride product with a total phosphorus content of less than 0.03%. The secondary solid-liquid separation device can also be a horizontal spiral sedimentation centrifuge, a horizontal scraper discharge centrifuge, or a vertical centrifuge, with the speed adjustable range preferably between 2000 and 3000 r / min.

[0057] It is important to note that with only one concentration and one solid-liquid separation, the total phosphorus content in the wet powder product is typically still between 0.1% and 0.2%, which cannot meet the high purity requirements. This is because, during the first crystallization process, although most phosphorus impurities are enriched in the mother liquor phase and removed, trace amounts of phosphorus-containing mother liquor remain in the wet powder in the form of surface adsorption or intercrystalline encapsulation. By redissolving the wet powder in soft water and then performing a second concentration and a second solid-liquid separation, the original crystal structure is completely destroyed, and the phosphorus impurities remaining in the first crystallization are released and redistributed. In the new concentration and crystallization process, these residual phosphorus impurities again follow the rule of preferential retention in the mother liquor phase in high ionic strength solutions and are further discharged into the secondary mother liquor, thus achieving deep phosphorus removal. Experimental data shows that after two-stage purification, the total phosphorus content of the product can be stably reduced to below 0.03%, and the total phosphorus removal rate reaches over 97%. This purity cannot be achieved with a single purification; the two-stage setup is a necessary technical means based on the deep purification mechanism of secondary recrystallization, rather than simple repetition.

[0058] The secondary mother liquor separated by the secondary solid-liquid separation equipment has a high concentration of triethylamine hydrochloride and a low phosphorus content, making it highly valuable for recovery. This secondary mother liquor is returned through pipeline and combined with the next batch of solutions after secondary dissolution before entering the secondary concentration unit for further concentration, thereby increasing the overall recovery rate of triethylamine hydrochloride.

[0059] To further reduce system energy consumption, a thermal integration unit can be configured for the primary and / or secondary concentration units. The thermal integration unit includes a steam compressor and a heat exchanger. The steam compressor is connected to the secondary steam outlet and heating chamber inlet of the concentration unit, respectively, to mechanically compress the secondary steam generated by the concentration unit, raise its temperature and pressure, and then resupply it as a heat source to the heating chamber of the concentration unit, thereby recovering the latent heat of the secondary steam and significantly reducing live steam consumption. The heat exchanger is located between the feed line and the condensate discharge line of the concentration unit, and is used to exchange heat between the high-temperature condensate discharged from the concentration unit and the low-temperature feed liquid entering the concentration unit. The sensible heat of the condensate is used to preheat the feed liquid, further reducing energy consumption. Plate heat exchangers, shell-and-tube heat exchangers, or spiral plate heat exchangers can be selected. Taking a triple-effect evaporator with a single unit capacity of 5t / h as an example, without thermal integration, the steam consumption per unit product is approximately 0.45t steam / t evaporated water. After configuring a steam compressor (compression ratio 1.8) and a condensate preheater, the steam consumption per unit product drops to 0.32t steam / t evaporated water, a reduction of approximately 29%. If an MVR evaporator is further used to replace the multi-effect evaporator, the steam consumption per unit product can be reduced to below 0.15t steam / t evaporated water, a reduction of over 60%. Through the cascade energy recovery of the thermal integration unit, the process economy is significantly improved.

[0060] The triethylamine hydrochloride concentration and purification system provided by this invention includes a primary dissolving vessel, a layering tank, an intermediate tank, a primary concentration device, a primary solid-liquid separation device, a secondary dissolving vessel, a secondary concentration device, and a secondary solid-liquid separation device connected in series. The outlet of the primary dissolving vessel is connected to the inlet of the layering tank; the lower outlet of the layering tank is connected to the inlet of the intermediate tank; the outlet of the intermediate tank is connected to the inlet of the primary concentration device; the outlet of the primary concentration device is connected to the inlet of the primary solid-liquid separation device; the solid phase outlet of the primary solid-liquid separation device is connected to the inlet of the secondary dissolving vessel; the outlet of the secondary dissolving vessel is connected to the inlet of the secondary concentration device; and the outlet of the secondary concentration device is connected to the inlet of the secondary solid-liquid separation device. The upper outlet of the layering tank is connected to a solvent receiving tank. The liquid phase outlet of the primary solid-liquid separation device is connected to the inlet pipeline of the primary concentration device via a pipeline for returning the phosphorus-containing mother liquor; the liquid phase outlet of the secondary solid-liquid separation device is connected to the inlet pipeline of the secondary concentration device via a pipeline for returning the secondary mother liquor. The primary and secondary concentration units are each equipped with a thermal integration unit, which includes a steam compressor and a heat exchanger. The steam compressor is connected to the secondary steam outlet and the heating chamber inlet of the corresponding concentration unit, respectively, and the heat exchanger is located between the feed pipeline and the condensate discharge pipeline of the corresponding concentration unit.

[0061] To more intuitively demonstrate the technical solution of the present invention, the following provides a complete embodiment that integrates various preferred conditions.

[0062] Example 1

[0063] 1000 kg of triethylamine hydrochloride raw material, separated from the mother liquor of glyphosate production via the glycine method, was collected. The total phosphorus content was 0.92%, with organic phosphorus accounting for 82% of the total phosphorus (mainly including approximately 55% methylphosphonic acid and approximately 27% iminodiacetic acid derivatives), and orthophosphate accounting for 18%. The raw material was added to a primary dissolving vessel along with 1500 kg of soft water. After stirring and dissolving, the solution was transferred to a separation tank and allowed to settle and separate. Approximately 80 kg of the upper solvent layer overflowed into a solvent receiving tank and was recycled to the upstream process. Approximately 2420 kg of the lower triethylamine hydrochloride solution was sent to an intermediate tank.

[0064] The solution was fed into a triple-effect evaporator for primary concentration (step S1). The water content at the concentration endpoint was monitored and controlled in real time using an online density meter to be 38%, yielding approximately 1580 kg of concentrated liquid in a slurry suspension. The concentrated liquid was then fed into a horizontal scraper centrifuge for solid-liquid separation at 2500 r / min (step S2), yielding approximately 760 kg of primary wet powder (water content 15%, total phosphorus content measured to be 0.13%). The primary mother liquor, approximately 820 kg, was returned in its entirety and combined with the triethylamine hydrochloride solution to be processed subsequently for further concentration.

[0065] The primary wet powder is conveyed in a closed system via a screw conveyor to a secondary dissolving vessel. After being fully dissolved in 850 kg of soft water, it is sent to an MVR evaporator for secondary concentration (the second concentration in step S3), controlling the final water content to 35%. The secondary concentrate is then sent to a horizontal screw centrifuge for solid-liquid separation at 2500 r / min (the second solid-liquid separation in step S3), yielding approximately 510 kg of wet powder. Testing shows that the total phosphorus content of this product is 0.021%, meeting the quality standard requirement of less than 0.03%. Approximately 440 kg of the secondary mother liquor is returned and combined with the solution from the subsequent secondary dissolution for further concentration.

[0066] In this embodiment, the total phosphorus removal rate of the product (relative to the total phosphorus in the raw material) is (0.92%×1000-0.021%×510) / (0.92%×1000)×100%≈98.8%, and the total recovery rate of triethylamine hydrochloride (based on the wet powder of the product) is approximately 51%. If the triethylamine hydrochloride in the reflux mother liquor is included, the total recovery rate of triethylamine hydrochloride in the system exceeds 95%.

[0067] Example 2

[0068] 2000 kg of triethylamine hydrochloride raw material, separated from the mother liquor of glyphosate production via the glycine method, was collected. The total phosphorus content was 0.85%, with organic phosphorus comprising 85% (mainly 60% methylphosphonic acid and 25% iminodiacetic acid derivatives) and orthophosphate comprising 15%. The raw material was added to a primary dissolving vessel along with 3000 kg of soft water. After stirring and dissolving, the solution was transferred to a separation tank and allowed to settle and separate. Approximately 150 kg of the upper solvent layer overflowed into a solvent receiving tank; approximately 4850 kg of the lower triethylamine hydrochloride solution entered an intermediate tank.

[0069] The solution was fed into a double-effect evaporator for initial concentration (step S1). The water content at the end of the concentration was controlled to be 40% using an online refractometer, yielding approximately 2980 kg of concentrated liquid. The concentrated liquid was then fed into a horizontal spiral sedimentation centrifuge for solid-liquid separation at 2200 r / min (step S2), yielding approximately 1520 kg of primary wet powder (water content 16%, total phosphorus content measured to be 0.11%). The primary mother liquor, approximately 1460 kg, was returned in its entirety and combined with the triethylamine hydrochloride solution to be processed subsequently for further concentration.

[0070] The primary wet powder is conveyed to the secondary dissolving kettle via a tubular chain conveyor. After being fully dissolved in 1700 kg of soft water, it is sent to a triple-effect evaporator for secondary concentration (the second concentration in step S3), controlling the final water content to 35%. The secondary concentrate is sent to a horizontal scraper discharge centrifuge for solid-liquid separation at 2200 r / min (the second solid-liquid separation in step S3), yielding approximately 1020 kg of wet powder. Testing shows that the total phosphorus content of this product is 0.018%, meeting the quality standard requirement of less than 0.03%. Approximately 870 kg of the secondary mother liquor is returned and combined with the solution from the subsequent secondary dissolution for further concentration.

[0071] In this embodiment, the total phosphorus removal rate of the product is approximately 98.9%, and the total recovery rate of triethylamine hydrochloride in the system exceeds 95%.

[0072] In summary, the core inventive point of this invention lies in the discovery of a physicochemical law that, when triethylamine hydrochloride solution is concentrated to a water content of 30%–45%, phosphorus impurities, mainly organophosphorus compounds, selectively accumulate in the mother liquor phase due to their high solubility in a high-ionic-strength aqueous phase. Based on this law, a two-stage physical purification process was designed, consisting of "controlled water content concentration—solid-liquid separation—redissolution—re-controlled water content concentration—re-solid-liquid separation" (e.g., Figure 1 (As shown). This method uses a specific raw material with an organic phosphorus content of not less than 80% in terms of total phosphorus content as the treatment target. Through two concentrations, the water content is precisely controlled within a window of 30% to 45%, achieving efficient transfer and separation of phosphorus impurities from the crystalline phase to the mother liquor phase. The final product has a stable total phosphorus content of less than 0.03%. The entire process requires no chemical additives, no high-temperature incineration, and no membrane separation equipment, making it a green, low-cost, continuous production method.

[0073] During system operation, the main material flow is as follows: primary dissolving vessel → stratification tank → intermediate tank → primary concentration unit → primary solid-liquid separation unit → secondary dissolving vessel → secondary concentration unit → secondary solid-liquid separation unit, ultimately yielding the product. The recycled material flow includes: primary mother liquor returned from the primary solid-liquid separation unit, combined with the triethylamine hydrochloride solution to be treated, and then entering the primary concentration unit together; secondary mother liquor returned from the secondary solid-liquid separation unit, combined with the solution after secondary dissolution, and then entering the secondary concentration unit together; solvent returned from the stratification tank to the upstream process via the solvent receiving tank; and the thermal integration unit recovers and utilizes the heat from secondary steam and condensate. The entire process achieves continuous operation and closed-loop material circulation.

[0074] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the inventive concept and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for concentrating and purifying triethylamine hydrochloride, used to treat a phosphorus-containing triethylamine hydrochloride solution, wherein the mass percentage of organic phosphorus in the solution is not less than 80% based on the total phosphorus mass, characterized in that... Includes the following steps: S1: The triethylamine hydrochloride solution is concentrated, and the concentration endpoint is controlled so that the water content of the resulting concentrated solution is 30% to 45%, forming a mixture of triethylamine hydrochloride crystals and mother liquor; S2: Perform solid-liquid separation on the mixture to obtain triethylamine hydrochloride wet powder and phosphorus-containing mother liquor; S3: After dissolving the triethylamine hydrochloride wet powder in water, concentrate it again to a water content of 30% to 45%, and then perform solid-liquid separation to obtain a triethylamine hydrochloride product with a total phosphorus content of less than 0.03%.

2. The method according to claim 1, characterized in that, The total phosphorus content in the solution is 0.5% to 1.5%.

3. The method according to claim 1, characterized in that, Based on the total phosphorus mass in the solution, the organic phosphorus content is not less than 85%, and the organic phosphorus includes methylphosphonic acid and / or iminodiacetic acid derivatives.

4. The method according to claim 1, characterized in that, The solid-liquid separation in step S2 and / or step S3 is performed by centrifugation at a speed of 2000–3000 r / min.

5. The method according to claim 1, characterized in that, The concentration process employs multi-effect evaporation, and the secondary steam generated by evaporation is compressed and reused for heating through a thermal integration unit, and / or the condensate generated by evaporation is exchanged with the feed liquid for heat.

6. The method according to claim 1, characterized in that, At least a portion of the phosphorus-containing mother liquor obtained in step S2 is returned and combined with the triethylamine hydrochloride solution described in step S1 for further concentration; and / or, a secondary mother liquor is obtained after solid-liquid separation in step S3, at least a portion of which is returned and combined with the solution obtained after dissolving the triethylamine hydrochloride wet powder in the next batch of step S3 for further concentration.

7. A triethylamine hydrochloride concentration and purification system, characterized in that, include: A primary dissolving vessel is used to dissolve phosphorus-containing triethylamine hydrochloride raw materials; A primary concentration device is connected to the outlet of the primary dissolving vessel and is used to concentrate the dissolved triethylamine hydrochloride solution. The primary concentration device is equipped with a moisture detection and control unit to control the concentration endpoint so that the water content of the resulting concentrated solution is 30% to 45%, so as to form a mixture of triethylamine hydrochloride crystals and mother liquor. A primary solid-liquid separation device is connected to the outlet of the primary concentration device and is used for solid-liquid separation of the mixture to obtain primary wet powder and phosphorus-containing mother liquor; A secondary dissolving vessel is connected to the solid phase outlet of the primary solid-liquid separation device and is used to receive and dissolve the primary wet powder. A secondary concentration device is connected to the outlet of the secondary dissolving kettle and is used to further concentrate the dissolved primary wet powder. A secondary solid-liquid separation device is connected to the outlet of the secondary concentration device and is used to perform solid-liquid separation on the material after secondary concentration to obtain a triethylamine hydrochloride product with a total phosphorus content of less than 0.03%.

8. The system according to claim 7, characterized in that, A stratification tank and an intermediate tank are provided before the primary dissolving vessel. The stratification tank is used to automatically overflow and stratify the dissolved material into an upper layer of solvent and a lower layer of triethylamine hydrochloride solution. The intermediate tank is used to receive the lower layer of triethylamine hydrochloride solution and transport it to the primary concentration device. The upper outlet of the stratification tank is connected to a solvent receiving tank for recovering the upper layer of solvent and reusing it in the front-end process.

9. The system according to claim 7, characterized in that, The primary concentration unit and / or secondary concentration unit are multi-effect evaporation units and are equipped with a thermal integration unit. The thermal integration unit includes a steam compressor and a heat exchanger, which are used to compress the secondary steam generated by evaporation and supply it back to the heating chamber, and / or to exchange heat between the condensate generated by evaporation and the feed liquid. The moisture detection and control unit is selected from at least one of an online refractometer, an online densitometer, or a near-infrared moisture analyzer.

10. The system according to claim 7, characterized in that, The primary solid-liquid separation equipment and / or secondary solid-liquid separation equipment is a centrifuge with an adjustable speed range of 2000-3000 r / min; the liquid phase outlet of the primary solid-liquid separation equipment is connected to the feed pipeline of the primary concentration device through a pipeline, which is used to combine the phosphorus-containing mother liquor with the triethylamine hydrochloride solution to be concentrated and then enter the primary concentration device together. And / or, the liquid phase outlet of the secondary solid-liquid separation equipment is connected to the feed pipeline of the secondary concentration device through a pipeline, so as to combine the secondary mother liquor and the solution after secondary dissolution and then enter the secondary concentration device together.

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