System for recovering phosphoric acid solvent by hydrochloric acid method
By combining a distillation column, heat exchanger, and condenser, the solvent recovery problem in the hydrochloric acid-based phosphoric acid system was solved, achieving efficient solvent recovery and reuse of calcium chloride, reducing production costs and environmental pollution.
Patent Information
- Application Number
- CN202422928176.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-12-16
- Estimated Expiration
- 2034-11-29
AI Technical Summary
Existing technologies cannot efficiently recover the solvent in the raffinate of the hydrochloric acid-based phosphoric acid system, resulting in high solvent consumption, increased production costs, and difficulty in effectively utilizing calcium chloride, leading to the accumulation of phosphogypsum and environmental pollution.
A system combining a distillation column with a heat exchanger and a condenser is used to recover the solvent in the raffinate through heat exchange, distillation and phase separation processes, forming a calcium chloride solution which is then returned to the hydrochloric acid-based phosphoric acid system for recycling.
It achieves efficient solvent recovery, reduces production costs, improves the quality of calcium chloride solution, reduces steam consumption, reduces phosphogypsum emissions, and protects the environment.
Smart Images
Figure CN223668676U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present patent relates to the technical field of chemical production, in particular to a system for recovering solvents in hydrochloric acid method phosphoric acid, specifically a new process for recovering solvents in raffinate by rectification column, removing the raffinate of solvents to become calcium chloride solution, and returning the obtained solvents to the hydrochloric acid method phosphoric acid system after condensation and phase separation for continuous use. BACKGROUND
[0002] The domestic wet-process phosphoric acid generally uses the process technology of decomposing phosphate rock with sulfuric acid, and the main by-product of this process technology is phosphogypsum, the main component of which is CaSO42H2O. About 4-5 tons of phosphogypsum can be produced per ton of phosphoric acid (calculated as 100% P2O5) produced. The annual discharge of phosphogypsum in China is close to 68 million tons, and the utilization rate of phosphogypsum is only about 5%. Long-term accumulation of phosphogypsum will cause pollution of surface water and groundwater, and setting up a storage yard requires a lot of land, high cost, and large investment. At present, phosphogypsum has become one of the largest solid waste discharged in the chemical industry. Wet-process phosphoric acid produced by decomposing phosphate rock with sulfuric acid is mainly used for fertilizer production due to its high impurity content, and it is difficult to be widely used in other industrial fields besides fertilizer production. At present, the annual production of sulfur-based compound fertilizer in China exceeds 10 million tons, and the by-product hydrochloric acid (containing HCl with a mass concentration of ≥31%) exceeds 3.2 million tons. These hydrochloric acids are given to other industries at a low price or with a subsidy. If these hydrochloric acids are used to produce phosphoric acid, more than 500,000 tons of high-quality phosphoric acid (calculated as 100% P2O5) can be produced, which can be used to produce sulfur-based compound fertilizer or other industries, while the consumption of sulfuric acid (containing H2SO4 with a mass concentration of 98%) is reduced by more than 1.5 million tons, and the discharge of phosphogypsum is reduced by more than 2.5 million tons.
[0003] The reaction of decomposing phosphate rock with hydrochloric acid proceeds very quickly, so it is not necessary to grind the phosphate rock too finely, and it can be ground to a particle size of ≤1 mm. The material formed by decomposing phosphate rock with hydrochloric acid basically does not contain components that are easy to scale, and the material is easy to transport and process. The produced phosphoric acid can be concentrated to a very high concentration or made into superphosphoric acid, and the utilization rate of steam can easily reach the index of consuming 0.4-0.5 tons of steam per ton of effluent. The purity of the finished phosphoric acid is higher than that of sulfuric acid method phosphoric acid, and it can be directly used in places with higher purity requirements, such as the production of industrial phosphate or feed-grade phosphate. When the phosphoric acid is concentrated to a P2O5 content of ≥64.8%, the chlorine ions in the phosphoric acid can be completely removed.
[0004] The hydrolysate obtained after hydrochloric acid decomposition of phosphate rock mainly contains phosphoric acid and calcium chloride. Calcium chloride is a highly water-soluble salt, difficult to separate using conventional methods. A liquid-liquid extraction method using organic solvents to separate calcium chloride is feasible. The "salting-out effect" caused by the presence of calcium chloride makes this process quite successful, and the resulting phosphoric acid has high purity. Although the solvent is essentially in a closed-loop liquid-liquid extraction cycle, some solvent always dissolves in the raffinate. Due to the large amount of calcium chloride present, the amount of solvent dissolved in the raffinate is lower than the amount dissolved in water; for example, about 1% of n-butanol dissolves in the raffinate. Since solvent consumption directly affects the production cost of the target product—for example, using n-butanol as a solvent, for every ton of phosphoric acid produced (based on 100% P₂O₅), more than 130 kg of n-butanol dissolves in the raffinate—the solvent in the raffinate must be recovered.
[0005] Therefore, there is an urgent need to provide a system and method for recovering phosphoric acid solvent using the hydrochloric acid method, which has a short process, requires few equipment, has low manufacturing costs, large production capacity, and good recovery effect. Utility Model Content
[0006] The purpose of this invention is to provide a system and method for solvent recovery in hydrochloric acid-based phosphoric acid production. The raffinate from the hydrochloric acid-based phosphoric acid system is first heated in a heat exchanger. After heat exchange, the raffinate is sent to a distillation column, where the solvent is removed to obtain a calcium chloride solution for reuse. The resulting solvent is then condensed, separated, and returned to the hydrochloric acid-based phosphoric acid system for continued use. This patent aims to solve problems related to solvent recovery, reducing the production cost of hydrochloric acid-based phosphoric acid, purifying calcium chloride, facilitating calcium chloride reuse, saving energy, reducing consumption, and protecting the environment.
[0007] The objective of this utility model can be achieved through the following technical solutions:
[0008] A system for recovering phosphoric acid solvent using a hydrochloric acid process includes a distillation column. The output of the raffinate from the hydrochloric acid phosphoric acid system is connected to the middle section of the distillation column via a heat exchanger. The output of the top of the distillation column is connected to a condenser and a phase separator. The output of the bottom of the phase separator is connected to the upper section of the distillation column.
[0009] In the above system, the steam output pipe from the boundary area is connected to the bottom of the distillation column.
[0010] In the above system, the output end at the bottom of the distillation column is connected to the heat exchanger.
[0011] The method realized by the system is that the raffinate from the hydrochloric acid method phosphoric acid system is heated to a temperature of greater than or equal to 85 DEG C by a heat exchanger and then enters a rectifying tower, low-pressure steam from a boundary area is used to heat calcium chloride solution at the bottom of the tower, the descending calcium chloride solution containing solvent in the rectifying tower exchanges heat and mass with the ascending steam containing solvent, the steam containing solvent at the top of the tower is removed from the top outlet A to a solvent recovery section, and the calcium chloride solution at the bottom of the tower is removed to a raffinate heat exchange section.
[0012] In the method, the calcium chloride solution at the bottom of the tower exchanges heat with the raffinate by a heat exchanger.
[0013] In the method, the steam containing solvent from the raffinate rectifying section enters a condenser, is indirectly cooled by cooling water from the boundary area in the condenser, and then enters a phase separator, the condensed liquid containing solvent is separated into a light phase and a heavy phase in the phase separator, the heavy phase is returned to the rectifying tower as reflux liquid, and the light phase is removed from the light phase outlet B of the phase separator to the hydrochloric acid method phosphoric acid system as a target product, i.e., solvent.
[0014] In the method, the solvent mass concentration of the raffinate from the hydrochloric acid method phosphoric acid system is less than or equal to 10%, and the calcium chloride mass concentration is greater than or equal to 10%.
[0015] In the method, the calcium chloride solution at the bottom of the tower has a concentration greater than or equal to 10% and a temperature greater than or equal to 90 DEG C.
[0016] In the method, the weight ratio of the heavy phase to the light phase is less than or equal to 5:1.
[0017] In some specific technical solutions, the content of the solutions is as follows:
[0018] A system for recovering solvent of phosphoric acid produced by a hydrochloric acid method, which comprises a heat exchanger, a rectifying tower, a condenser, a phase separator, and a calcium chloride solution delivery pump. A raffinate pipeline from the hydrochloric acid method phosphoric acid system is connected to the pipe inlet A of the heat exchanger, the pipe outlet C of the heat exchanger is connected to the feed inlet C of the rectifying tower, the top outlet A of the rectifying tower is connected to the pipe inlet A of the condenser, the pipe outlet C of the condenser is connected to the feed inlet A of the phase separator, and the light phase outlet B of the phase separator is connected to a solvent pipeline to the hydrochloric acid method phosphoric acid system.
[0019] In the system, the heavy phase outlet C of the phase separator is connected to the reflux liquid inlet B of the rectifying tower, the calcium chloride solution outlet D of the rectifying tower is connected to the shell inlet D of the heat exchanger through the calcium chloride solution delivery pump, and the shell outlet B of the heat exchanger is connected to a calcium chloride solution delivery pipeline to the boundary area.
[0020] In the system, the steam inlet E of the rectifying tower is connected to a steam pipeline from the boundary area, the shell inlet D of the condenser is connected to a circulating cooling water pipeline from the boundary area, and the shell outlet B of the condenser is connected to a circulating cooling water return pipeline to the boundary area.
[0021] In the system, the rectifying tower can be a packed tower or a plate tower.
[0022] A method for recovering solvent in hydrochloric acid method phosphoric acid system by using the above system, the method comprises the following sections, and the recoverable solvents are not only one kind:
[0023] (1) raffinate heat exchange section: the raffinate (solvent mass concentration ≤10%, calcium chloride mass concentration ≥10%) from the hydrochloric acid method phosphoric acid system enters the heat exchanger pipe from the heat exchanger pipe inlet A, the calcium chloride solution (calcium chloride mass concentration ≥10%, temperature ≥90°C) from the calcium chloride solution outlet D of the rectifying tower enters the heat exchanger shell from the heat exchanger shell inlet D through the calcium chloride solution conveying pump. In the heat exchanger, the calcium chloride solution and the raffinate are indirectly heat-exchanged, the calcium chloride solution is cooled and goes to the boundary zone from the heat exchanger shell outlet B for reuse, and the raffinate is heated (temperature ≥85°C) and goes to the raffinate rectification section from the heat exchanger pipe outlet C.
[0024] (2) raffinate rectification section: the heated raffinate (solvent mass concentration ≤10%, calcium chloride mass concentration ≥10%, temperature ≥85°C) from the raffinate heat exchange section enters the rectifying tower from the rectifying tower feed port C, and the low-pressure steam from the boundary zone enters the rectifying tower from the rectifying tower steam inlet E to directly heat the calcium chloride solution at the bottom of the tower. In the rectifying tower, the descending calcium chloride solution containing solvent and the ascending steam containing solvent are heat-exchanged and mass-exchanged, the temperature of the calcium chloride solution continuously increases, the content of the solvent continuously decreases, the temperature of the steam continuously decreases, and the content of the solvent continuously increases. The steam containing solvent (temperature ≥80°C) at the top of the tower goes to the solvent recovery section from the top outlet A, and the calcium chloride solution (calcium chloride mass concentration ≥10%, temperature ≥90°C) at the bottom of the tower goes to the raffinate heat exchange section from the calcium chloride solution outlet D.
[0025] (3) solvent recovery section: the steam containing solvent (temperature ≥80°C) from the raffinate rectification section enters the condenser from the condenser pipe inlet A, is indirectly cooled in the condenser by using the cooling water from the boundary zone, and the cooled steam containing solvent goes to the phase separator from the condenser pipe outlet C through the phase separator feed port A. In the phase separator, the steam containing solvent is divided into a light phase and a heavy phase, the heavy phase is returned to the rectifying tower as a reflux liquid from the phase separator heavy phase outlet C through the rectifying tower reflux liquid inlet B, and the light phase is taken as a target product, the solvent, from the phase separator light phase outlet B and is reused in the hydrochloric acid method phosphoric acid system; the weight ratio of the heavy phase to the light phase is ≤5:1.
[0026] The beneficial effects of the present application are as follows:
[0027] The patent provides a system and method for recovering solvent of hydrochloric acid method phosphoric acid, which can basically remove the solvent contained in the raffinate, recover the target product-solvent, and improve the quality of calcium chloride solution. The solvent used in hydrochloric acid method phosphoric acid production is often expensive, and recycling the solvent in the raffinate can greatly reduce the production cost of hydrochloric acid method phosphoric acid. Taking n-butanol as an example, 127.6 kg of n-butanol can be recovered per ton of phosphoric acid (100% P2O5) produced, and the recovery rate of n-butanol is more than 97%; the n-butanol content of the calcium chloride solution recovered from n-butanol decreases from 1% to 0.029%. About 90% of the heat required in the distillation process is used to heat the feed to the boiling point, and the waste heat of the calcium chloride solution leaving the bottom of the distillation column is used to preheat the feed. The heat recovery is 60%, and the steam consumption is reduced to 800 kg per ton of phosphoric acid (100% P2O5) produced. The system and method of the patent have the advantages of short process, less equipment, low cost, large production capacity, and good recovery effect. BRIEF DESCRIPTION OF DRAWINGS
[0028] Figure 1 The process flow diagram in the patent
[0029] Among them, heat exchanger 1, rectification tower 2, condenser 3, phase separator 4, calcium chloride solution delivery pump 5. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the patent will be described clearly and completely below with reference to the drawings in the embodiments of the patent. Obviously, the described embodiments are part of the embodiments of the patent, not all. The components of the embodiments of the patent described and shown in the drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the patent provided in the drawings is not intended to limit the scope of the claimed patent, but only represents selected embodiments of the patent. Based on the embodiments in the patent, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the patent. The embodiments of the patent will be described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are intended to explain the patent, and cannot be understood as limiting the patent.
[0031] The patent will be further described below with reference to the drawings and specific embodiments.
[0032] As Figure 1A system for recovering solvent of hydrochloric acid process phosphoric acid, characterized in that the system comprises a heat exchanger 1, a rectifying tower 2, a condenser 3, a phase separator 4, and a calcium chloride solution delivery pump 5. A raffinate pipeline from the hydrochloric acid process phosphoric acid system is connected to the pipe inlet A of the heat exchanger 1, the pipe outlet C of the heat exchanger 1 is connected to the feed inlet C of the rectifying tower 2, the top outlet A of the rectifying tower 2 is connected to the pipe inlet A of the condenser 3, the pipe outlet C of the condenser 3 is connected to the feed inlet A of the phase separator 4, and the light phase outlet B of the phase separator 4 is connected to a solvent pipeline of the hydrochloric acid process phosphoric acid system.
[0033] The heavy phase outlet C of the phase separator 4 is connected to the reflux liquid inlet B of the rectifying tower 2, the calcium chloride solution outlet D of the rectifying tower 2 is connected to the shell inlet D of the heat exchanger 1 through the calcium chloride solution delivery pump 5, and the shell outlet B of the heat exchanger 1 is connected to a calcium chloride solution delivery pipeline of the boundary area.
[0034] The steam inlet E of the rectifying tower 2 is connected to a steam pipeline from the boundary area, the shell inlet D of the condenser 3 is connected to a circulating cooling water pipeline from the boundary area, and the shell outlet B of the condenser 3 is connected to a circulating cooling backwater pipeline of the boundary area.
[0035] The rectifying tower 2 can be a packed tower or a plate tower.
[0036] A method for recovering solvent of hydrochloric acid process phosphoric acid by using the above system comprises the following sections, and more than one kind of recoverable solvent is taken as an example of n-butanol, the rectifying tower is a plate tower and contains 24 tower plates.
[0037] (1) Raffinate heat exchange section: the raffinate (solvent mass concentration 1%, calcium chloride mass concentration 22.91%) from the hydrochloric acid process phosphoric acid system enters the pipe of the heat exchanger 1 from the pipe inlet A, the calcium chloride solution (calcium chloride mass concentration 21.74%, temperature 102°C) from the calcium chloride solution outlet D of the rectifying tower 2 enters the shell of the heat exchanger 1 from the shell inlet D through the calcium chloride solution delivery pump 5. In the heat exchanger 1, the calcium chloride solution and the raffinate are indirectly heat-exchanged, the calcium chloride solution is cooled and then sent to the boundary area from the shell outlet B of the heat exchanger 1 for reuse, and the raffinate is heated (temperature 92°C) and then sent to the raffinate rectification section from the pipe outlet C of the heat exchanger 1.
[0038] (2) Raffinate rectification section: the raffinate (solvent mass concentration 1%, calcium chloride mass concentration 22.91%, temperature 92°C) from the raffinate heat exchange section is fed into rectification column 2 from feed port C of rectification column 2, feed port C is located above the 14th column plate, low-pressure steam (temperature 133°C, pressure 0.3 MPa) from the boundary zone is fed into rectification column 2 from steam inlet E of rectification column 2 to directly heat the calcium chloride solution at the bottom of rectification column 2. The descending calcium chloride solution containing solvent in rectification column 2 exchanges heat and mass with the ascending steam containing solvent, the temperature of the calcium chloride solution continuously increases, the solvent content continuously decreases, the temperature of the steam continuously decreases, and the solvent content continuously increases. The a-butanol and H2O azeotrope (solvent mass concentration 63%, temperature 90°C) at the top of the column is removed from the top outlet A to the solvent recovery section, and the calcium chloride solution (calcium chloride mass concentration 21.74%, temperature 102°C) at the bottom of the column is removed from the calcium chloride solution outlet D to the raffinate heat exchange section.
[0039] (3) Solvent recovery section: the a-butanol and H2O azeotrope (solvent mass concentration 63%, temperature 90°C) from the raffinate rectification section is fed into condenser 3 from the pipe passage inlet A of condenser 3, is indirectly cooled in condenser 3 using cooling water (upper water temperature 25°C, return water temperature 33°C) from the boundary zone, and the cooled condensate containing a-butanol is fed into phase separator 4 from the pipe passage outlet C of condenser 3 through feed port A of phase separator 4. The condensate containing a-butanol is separated into a light phase (solvent mass concentration 80%) and a heavy phase (solvent mass concentration 6%) in phase separator 4, the heavy phase is returned to the 24th column plate of rectification column 2 as reflux liquid from heavy phase outlet C of phase separator 4 through reflux liquid inlet B of rectification column 2, the light phase is removed as the target product, solvent, from light phase outlet B of phase separator 4 to the hydrochloric acid method phosphoric acid system for reuse, and the weight ratio of the heavy phase to the light phase is 4:1.
[0040] The results of using the patent to run examples such as shown in Table 1
[0041] Table 1 Performance evaluation results of a 100 tons / day hydrochloric acid method phosphoric acid (calculated as 100% P2O5) solvent recovery device
[0042]
[0043]
Claims
1. A system for solvent recovery of phosphoric acid by hydrochloric acid process, characterized by, The system comprises a rectifying tower (2), an output end of raffinate from a hydrochloric acid method phosphoric acid system is connected with a middle part of the rectifying tower (2) through a heat exchanger, an output end of a top of the rectifying tower (2) is connected with a condenser (3) and a phase separator (4), an output end of a bottom of the phase separator (4) is connected with an upper part of the rectifying tower (2).
2. The system for solvent recovery of phosphoric acid as per claim 1, wherein, A steam output pipeline from the boundary area is connected with a bottom of the rectifying tower (2).
3. The system for solvent recovery of phosphoric acid as per claim 1, wherein, An output end of the bottom of the rectifying tower (2) is connected with the heat exchanger (1).