A production system for preparing high-purity hydrochloric acid by a gas phase purification absorption method

Abstract

The utility model discloses a production system of high purity hydrochloric acid is prepared to gas phase purification and absorption method. The system includes primary purification unit, secondary purification unit, absorption unit and finished product refining unit through pipeline and communicates in proper order, the primary purification unit includes primary purification tower, primary circulating tank, primary circulating pump and primary acid cooler, the secondary purification unit includes secondary purification tower, secondary circulating tank, secondary circulating pump and secondary acid cooler, the absorption unit includes absorption tower, absorption circulating tank, absorption circulating pump, reagent hydrochloric acid cooler and ultrapure water cooler, the finished product refining unit includes ion exchange column and precision filter. The utility model discloses tower tank integrated structure design and the high corrosion -resistant material of pertinence, integrated DCS automatic control system, can directly handle hydrogen chloride in industrial waste gas, realizes continuously, stably producing reagent grade or electronic grade high purity hydrochloric acid, has the advantages such as low energy consumption, no waste acid residue generation, product purity is high.

Description

Technical Field

[0001] This utility model relates to the field of manufacturing processes and equipment for high-purity chemical reagents, specifically to a production equipment technology and process for manufacturing reagent-grade hydrochloric acid and electronic-grade hydrochloric acid using a gas-phase purification-absorption method. Background Technology

[0002] The traditional production processes for high-purity reagent hydrochloric acid (referring to hydrochloric acid with extremely low impurity content, hereinafter the same) in China are mainly divided into two categories: multi-stage distillation purification technology for industrial hydrochloric acid and desorption-reabsorption technology for industrial hydrochloric acid. Both of these processes rely on production systems (equipment) with many inherent defects.

[0003] 1. Production system based on distillation purification technology This type of system uses 31% industrial hydrochloric acid as raw material, and its core equipment is a distillation unit. This unit is typically made of quartz glass or polytetrafluoroethylene (PTFE), which has significant drawbacks: First, quartz and PTFE have poor thermal conductivity, resulting in low heat exchange efficiency. The distillation process requires a large amount of electricity (typically 1000-1500 kWh per ton of product), leading to extremely high system energy consumption. Second, these materials have limited mechanical strength, making it difficult to scale up a single unit. Large-scale production necessitates multiple units connected in parallel, increasing equipment investment and floor space requirements, and significantly raising leakage and safety risks due to the increased number of connection points. Furthermore, the system requires a pretreatment unit to remove physical impurities from the raw acid, which generates waste acid and residue, increasing the burden of subsequent environmental treatment.

[0004] 2. Production systems based on analysis-reabsorption technology The core of this type of system is the analytical apparatus, which typically uses graphite analytical towers / reactors. While graphite offers high heat exchange efficiency, allowing for larger-scale systems, its design also presents serious problems: graphite equipment has poor mechanical strength, is easily damaged, and poses significant safety risks during production; more importantly, graphite itself contains many impurities that can easily detach and enter the product during operation, contaminating the hydrochloric acid reagent and affecting product quality. From the perspective of system operation, during the analytical process, when the hydrochloric acid concentration drops to approximately 20%, hydrogen chloride forms an azeotrope with water. To control impurity precipitation, the system must be designed with a dedicated discharge process to treat the large quantities of low-concentration (~20%) waste dilute hydrochloric acid generated. This complicates the system process and introduces significant environmental burdens and economic costs.

[0005] In summary, existing high-purity hydrochloric acid production systems generally suffer from structural and fundamental defects, including insufficient equipment material performance (leading to high energy consumption, low strength, and product contamination), unreasonable system structural design (resulting in waste liquid discharge and high safety risks), and inability to adapt to industrial waste gas raw materials. These systems all start with commercial industrial hydrochloric acid, and their structure and materials determine that they cannot efficiently and cleanly treat industrial waste gas rich in hydrogen chloride generated during chemical processes.

[0006] Therefore, there is an urgent need for innovation in system structure and equipment materials to develop a specialized production system that is compact, highly corrosion-resistant, produces no waste liquid, and can directly treat industrial waste gas, in order to achieve continuous, stable, and green production of high-purity hydrochloric acid. This utility model is proposed based on this equipment-level requirement. Utility Model Content The purpose of this invention is to provide a high-efficiency, low-energy-consumption reagent hydrochloric acid production system.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A production system for preparing high-purity hydrochloric acid by gas-phase purification and absorption method includes a primary purification unit, a secondary purification unit, an absorption unit, and a finished product refining unit connected in sequence by pipelines. The primary purification unit includes a primary purification tower, a primary circulation pump, and a primary acid cooler. The primary purification tower includes a primary circulation tank, a packed tower disposed on the primary circulation tank, and a demister disposed on the upper part of the packed tower. The secondary purification unit includes a secondary purification tower, a secondary circulation pump, and a secondary acid cooler; the secondary purification tower includes a secondary circulation tank, a packed tower disposed on the secondary circulation tank, and a demister disposed on the upper part of the packed tower; The absorption unit includes a reagent hydrochloric acid absorption tower, an absorption tower circulation pump, an absorption tower hydrochloric acid cooler, and an ultrapure water cooler; the reagent hydrochloric acid absorption tower includes a reagent hydrochloric acid circulation tank, a packed absorption tower, an ultrapure water spray section, and a demister connected sequentially from bottom to top. The finished product refining unit includes an ion exchange column and a finished product acid precision filter; Furthermore, both the primary and secondary purification towers are equipped with PTFE hydrophobic membrane filter cartridges at their top, with the secondary tower having a higher precision than the primary tower.

[0008] Furthermore, the primary purification tower, the secondary purification tower, and the absorption tower all adopt an integrated tower-trough structure, and the primary circulation tank, the secondary circulation tank, and the absorption circulation tank at the bottom are all independent cavities.

[0009] Furthermore, the tube side material of the primary acid cooler and the secondary acid cooler is silicon carbide (SIC), and industrial hydrochloric acid flows through the tube side; the shell side material is steel lined with PE, and circulating cooling water flows through the shell side; the tube side material of the absorption tower hydrochloric acid cooler is high-purity silicon carbide (SIC), and high-purity hydrochloric acid flows through the tube side; the shell side material is steel lined with PE, and chilled water flows through the shell side.

[0010] Furthermore, the primary circulation pump, the secondary circulation pump, and the absorption tower circulation pump are all fluoroplastic-lined magnetic pumps, and their flow-through components are made of steel lined with fluoroplastic F46 or high-purity PFA.

[0011] The hydrochloric acid ion exchange column is filled with polishing resin for adsorbing residual chlorine; the finished acid precision filter uses a high-purity PTFE membrane filter element with a filtration accuracy of 0.03μm to 0.1μm.

[0012] Furthermore, the system also includes an intermediate analysis tank for storing semi-finished hydrochloric acid and a finished product storage tank for storing finished hydrochloric acid, wherein both the intermediate analysis tank and the finished product storage tank are made of high-purity PTFE lined material.

[0013] Furthermore, the system also includes an exhaust gas fan, the inlet of which is connected to the top outlet of the reagent hydrochloric acid absorption tower, and its impeller and other flow-through components are made of Hastelloy C-276 or fiberglass (FRP).

[0014] Furthermore, the inner lining material of the primary and secondary purification towers is PO or PTFE; the inner lining material of the reagent hydrochloric acid absorption tower, hydrochloric acid ion exchange column and finished acid precision filter is high-purity PTFE.

[0015] Furthermore, the system is also equipped with a distributed control system (DCS), which is electrically connected to flow meters, temperature sensors, level gauges, regulating valves, acid concentration meters, and other instruments installed on each circulation pipeline.

[0016] The ultrapure water cooler is a plate heat exchanger, and its plates are made of 316L stainless steel.

[0017] The gas-phase purification and absorption method for preparing high-purity hydrochloric acid provided by this invention has the following significant advantages compared with the prior art: Raw material innovation and comprehensive resource utilization: This utility model system can directly treat industrial waste gas containing hydrogen chloride of any concentration range generated during the production of potassium sulfate or chlor-alkali chemicals, realizing the resource utilization of industrial waste gas, reducing raw material costs, and avoiding the limitations of traditional processes that use commercial industrial hydrochloric acid as raw material. Simultaneously, its utilities, such as power supply and distribution, circulating water, chilled water, ultrapure water, and tail gas treatment, can rely on the upstream potassium sulfate or chlor-alkali chemical plant's utility systems, reducing redundant investment and secondary pollution.

[0018] System structure optimization and space saving: The tower and absorption tower are integrated into one unit, which is compact and reduces the number of equipment connection points and floor space. At the same time, it reduces the risk of system leakage and installation investment costs.

[0019] Material innovation and product purity assurance: High corrosion-resistant materials are selected specifically for different corrosive environments and purity requirements in different processes: Q235 lined with PO / PTFE is used for primary and secondary purification towers; Q235 lined with high-purity PTFE is used for absorption towers, ion exchange columns, filters and storage tanks; silicon carbide (SIC) is used for heat exchangers; and F46 or high-purity PFA is used for pump flow parts.

[0020] These material choices effectively prevent contamination of the product by the equipment materials, ensuring that the final product meets reagent-grade or electronic-grade purity requirements.

[0021] Significantly reduced energy consumption: This utility model system mainly relies on the power consumption of circulating pumps, fans and other moving equipment, without the need for heat sources such as steam and gas required by traditional distillation or desorption processes. The energy consumption is far lower than that of existing technologies. The examples show that the power consumption per ton of product is only 17-18 kWh.

[0022] Environmentally friendly and clean production: The system achieves zero waste acid and zero residue generation throughout the entire process through two-stage purification, absorption, and high-efficiency demisting (PTFE hydrophobic membrane filtration), combined with ion exchange and precision filtration. The by-product industrial hydrochloric acid can be reused, completely solving the environmental problem of traditional processes generating 20% ​​waste dilute hydrochloric acid or pre-treated waste acid.

[0023] High degree of automation and stable operation: The system integrates a DCS distributed control system, which can automatically adjust key parameters such as temperature, flow rate, liquid level and concentration to achieve continuous and stable operation, reduce human intervention and improve the consistency and stability of product quality.

[0024] High adaptability and convenient expansion: The system design can flexibly adapt to the treatment of hydrogen chloride waste gas with different concentration ranges, and the equipment specifications can be expanded according to the capacity requirements. The implementation examples provide implementation schemes from 20kt / a to 100kt / a, demonstrating its good potential for large-scale application.

[0025] In summary, this utility model system, through innovative equipment structure, material selection, and control system integration, successfully provides a specialized equipment capable of efficient, clean, and continuous production of high-purity hydrochloric acid. It solves the technical problems of high energy consumption, significant pollution, and limited product purity in existing high-purity hydrochloric acid production systems, demonstrating significant technological advancement and application value. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the production system for preparing high-purity hydrochloric acid using the gas-phase purification and absorption method of this invention. Figure 2 This is a schematic diagram of the structure of the primary purification tower of this utility model; Figure 3 This is a schematic diagram of the hydrochloric acid absorption tower of this utility model; The attached diagram is labeled as follows: 1. Process water from the ultrapure water station; 2. Frozen water to the refrigeration water station; 3. Frozen water from the refrigeration water station; 4. Circulating water to the circulating water station; 5. Circulating water from the circulating water station; 6. 31% hydrochloric acid to the industrial hydrochloric acid storage tank; 7. HCl gas from the potassium sulfate Brønsted acid outlet; 8. Tail gas to the potassium sulfate tail gas treatment unit; 9. Finished product storage tank; 10. Industrial hydrochloric acid storage tank; 11. Acid discharge to the underground hydrochloric acid tank; 20. Primary purification tower; 21. Primary circulating pump; 22. Primary acid cooler; 23. 24. Primary circulation tank; 25. Packed tower; 30. Demister; 31. Secondary purification tower; 32. Secondary purification tower circulation pump; 43. Secondary purification tower cooler; 44. Reagent hydrochloric acid absorption tower; 45. Absorption tower circulation pump; 46. Absorption tower hydrochloric acid cooler; 50. Reagent hydrochloric acid circulation tank; 61. Packed absorption tower; 72. Ultrapure water spray section; 83. Demister; 94. Hydrochloric acid ion exchange column; 10. Finished acid precision filter; 11. Tail gas fan; 12. Intermediate analysis tank; 13. Finished acid transfer pump. Detailed Implementation

[0027] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model, but this does not constitute a limitation on the protection scope of the present utility model.

[0028] Hydrochloric acid is an aqueous solution of hydrogen chloride, possessing a strong, pungent odor and high corrosiveness. Hydrogen chloride is readily soluble in water, exhibiting very high solubility, reaching up to 80% under standard conditions. At normal pressure, its solubility is primarily affected by temperature and concentration. By controlling the temperature of the absorbent, hydrochloric acid of varying concentrations can be obtained. Furthermore, by removing and suppressing hydrogen chloride or hydrogen chloride-containing gases, as well as the amount of impurities in the absorbent, high-purity hydrochloric acid with low impurities can be produced.

[0029] This invention utilizes the high solubility of hydrogen chloride gas, and the characteristic that its solubility varies with temperature. By controlling the acid temperature to suppress its absorption rate, the concentration of hydrochloric acid washing solution and the hydrogen chloride-containing gas being washed is stabilized. This ensures that the hydrogen chloride-containing gas is purified while maintaining a high concentration. Furthermore, the hydrophobic properties of a hydrophobic membrane demister remove impurity-containing acid mist from the gas, achieving further purification and impurity removal. Simultaneously, by controlling the absorbent temperature to increase the solubility of hydrogen chloride, the product achieves the designed high concentration. For trace amounts of residual chlorine that may not be completely removed by the washing and purification process, an ion exchange column is used for adsorption and removal. Finally, a precision filter is used to remove micro-solid physical impurities from the hydrochloric acid, ensuring that the product's impurity content fully meets standards, resulting in a reagent-grade / electronic-grade high-purity hydrochloric acid product.

[0030] See Figure 1-3 This production system is used to treat industrial waste gas containing hydrogen chloride from potassium sulfate or chlor-alkali chemical processes. Through multi-stage purification, absorption, and refining, it continuously produces reagent-grade or electronic-grade high-purity hydrochloric acid. The system adopts a modular design and integrates DCS automatic control to achieve efficient, low-consumption, and waste-free clean production.

[0031] The system mainly consists of the following units connected in sequence via pipes: Primary purification unit Includes: a primary purification tower 20, a primary circulation pump 21, and a primary acid cooler 22, wherein the primary purification tower 20 includes a primary circulation tank 23, a packed tower 24, and a demister 25. Raw gas 7 enters packed tower 24 from the bottom of the primary purification tower; After circulating acid is pumped from the circulating tank to the acid cooler for cooling, part of it flows back into the upper part of the tower for spraying, and part of it is discharged as by-product industrial hydrochloric acid. After purification, the gas passes through the demister 25 at the top of the tower and then enters the secondary purification tower 30.

[0032] Secondary purification unit Includes: a secondary purification tower 30, a secondary purification tower circulation pump 31, and a secondary purification tower cooler 32; wherein the secondary purification tower 30 includes a secondary circulation tank, a packed tower, and a demister; The gas exiting the primary purification tower enters the lower part of the secondary purification tower. In this embodiment, the primary purification unit includes a primary circulation tank, a packed tower disposed on the primary circulation tank, and a demister disposed on the upper part of the packed tower. The primary purification unit and the secondary purification unit have the same structure. After cooling, part of the circulating acid flows back into the tower spray and part flows into the primary circulation tank. After purification, the gas passes through the demister at the top of the tower and then enters the reagent hydrochloric acid absorption tower 40.

[0033] Absorption unit Includes: a reagent hydrochloric acid absorption tower 40, an absorption tower circulation pump 41, an absorption tower hydrochloric acid cooler 42, and an ultrapure water cooler; the reagent hydrochloric acid absorption tower 40 includes a reagent hydrochloric acid circulation tank 43, a packed absorption tower 44, an ultrapure water spray section 45, and a demister 46 connected sequentially from bottom to top. The gas exiting the secondary purification tower enters the lower part of the absorption tower; After cooling, part of the absorbed acid is recycled back to the middle of the tower for spraying, and part is produced as semi-finished hydrochloric acid. After cooling, ultrapure water is sprayed from the top of the tower for secondary absorption. After passing through the demister 46, the exhaust gas is drawn by the exhaust gas fan 70 to the exhaust gas treatment unit (8) for potassium sulfate.

[0034] Finished product refining unit Includes: 50 ion exchange columns, 60 precision filters for finished acid. The semi-finished hydrochloric acid produced by the absorption tower is successively dechlorinated by an ion exchange column and impurities removed by a precision filter before entering the intermediate analysis tank 80. Qualified products are sent to reagent hydrochloric acid finished product storage tank 9 via finished product acid transfer pump 90, while unqualified products are sent to industrial hydrochloric acid storage tank 10.

[0035] auxiliary systems Includes: intermediate analysis tank 80, finished product storage tank, exhaust gas fan 70, DCS control system, refrigeration unit, circulating water station, etc. The DCS system connects with the electrical and instrumentation components of each unit, such as flow meters, temperature sensors, level gauges, regulating valves, and acid concentration meters, to achieve automatic control. The process flow for preparing high-purity hydrochloric acid using the gas-phase purification and absorption method of this invention is as follows: Level 1 purification: Mixed tail gas with a hydrogen chloride content of 16% to 35% (or higher) and a temperature of about 45°C, which comes from the potassium sulfate unit after acid washing pretreatment in the B acid section, or mixed gas with hydrogen chloride at a higher HCl concentration and a certain temperature from chlor-alkali chemical plant, enters the lower part of the primary purification tower.

[0036] Industrial hydrochloric acid with a concentration of 31% and a temperature of approximately 45°C in the primary circulation tank at the bottom of the primary purification tower is pumped to the primary acid cooler and cooled to 35-40°C. A portion of this acid enters the primary purification tower from the top and is evenly sprayed downwards by the acid separator, coming into countercurrent contact with the upward-flowing hydrogen chloride-containing gas. This process absorbs a small amount of hydrogen chloride gas and simultaneously washes and purifies the gas. The washing acid is then returned to the primary circulation tank at the bottom of the tower for further circulation and washing. The remaining hydrochloric acid, accounting for approximately 5% of the total acid produced by the system, is bypassed to the industrial hydrochloric acid storage tank. To maintain a stable liquid level in the primary circulation tank, a higher concentration of 31% hydrochloric acid is introduced from the outlet of the secondary purification tower's circulation pump into the primary circulation tank of the primary purification tower via a bypass.

[0037] The acid concentration in the primary purification tower is controlled by adjusting the cooling water flow rate of the primary acid cooler, which in turn controls the inlet acid temperature of the primary purification tower. The primary acid cooler uses circulating water to indirectly cool the hydrochloric acid, and the inlet / outlet water temperature is generally controlled at approximately 32℃ / 40℃, but this is adjusted according to the actual acid temperature control requirements.

[0038] After being purified by spraying hydrochloric acid in the primary purification tower, the hydrogen chloride-containing gas is further de-acidified by the demister at the top of the tower to remove impurities before being sent to the lower part of the secondary purification tower.

[0039] Secondary purification: Gas containing hydrogen chloride from the primary purification tower enters the lower part of the secondary purification tower.

[0040] Low-impurity hydrochloric acid with a concentration of 31% and a temperature of 40-45℃ is pumped into the secondary circulation tank at the bottom of the secondary purification tower and cooled to 33-38℃ by the secondary purification tower circulation pump. A portion of this acid then enters the upper acid collector inside the secondary purification tower and is sprayed downwards evenly, coming into counter-current contact with the hydrogen chloride-containing gas from the primary purification tower flowing upwards. This process absorbs a small amount of hydrogen chloride gas and simultaneously performs secondary washing and purification of the gas. The washing acid is then returned to the secondary circulation tank at the bottom of the tower for further circulation and washing. The remaining portion of hydrochloric acid, accounting for approximately 5% of the total acid produced by the system, is bypassed and sent to the primary circulation tank of the primary purification tower to maintain a stable liquid level in the secondary circulation tank of the secondary purification tower. To maintain the acid concentration and a certain level of cleanliness in the secondary purification tower, a certain amount of pure water is added to the secondary circulation tank, and the inlet temperature of the secondary purification tower is controlled to achieve stability.

[0041] The secondary purification tower cooler uses circulating water to indirectly cool hydrochloric acid. The inlet / outlet water temperature is generally controlled at about 32℃ / 40℃, but the specific temperature can be adjusted according to the actual acid temperature control requirements.

[0042] The hydrogen chloride-containing gas, after being washed and purified by low-impurity hydrochloric acid spraying in the secondary purification tower, is further sent to the lower part of the absorption tower after the acid mist containing trace impurities is removed by the demister at the top of the tower.

[0043] absorb: Clean gas containing hydrogen chloride from the secondary purification tower enters the lower part of the absorption tower.

[0044] The reagent hydrochloric acid at the bottom of the reagent hydrochloric acid absorption tower, with a concentration of 37% and a temperature of approximately 25°C, is pumped to the absorption tower's hydrochloric acid cooler and cooled to about 15°C. A portion of this cooler then enters the upper part of the absorption tower and is sprayed downwards evenly by the acid separator, where it comes into countercurrent contact with the clean hydrogen chloride-containing gas from the secondary purification tower, absorbing most of the hydrogen chloride gas. The absorbent acid, having completed the first-stage absorption, is returned to the bottom of the tower's reagent hydrochloric acid circulation tank for continued absorption. Another portion of the reagent hydrochloric acid exiting the absorption tower's reagent hydrochloric acid cooler is bypassed, its output controlled by the given circulation tank level. After residual chlorine is removed by an ion exchange column and impurities are removed by a precision filter, the semi-finished reagent hydrochloric acid is sent to intermediate analysis tanks to maintain a stable level in the absorption tower's circulation tank. The semi-finished reagent hydrochloric acid in intermediate analysis tanks A and B is awaiting testing.

[0045] After primary absorption by circulating hydrochloric acid, the remaining hydrogen chloride gas continues upward through the upper part of the absorption tower, where it is mixed countercurrently with ultrapure water at around 15°C that enters the spray from the upper part to complete secondary absorption. At the same time, the acid concentration in the reagent hydrochloric acid absorption tower and the reagent hydrochloric acid circulation tank is stabilized by controlling and adjusting the spray volume of ultrapure water through a hydrochloric acid concentration meter.

[0046] The hydrochloric acid cooler in the absorption tower and the ultrapure water cooler for the process spray both use chilled water for indirect cooling. The inlet / outlet water temperature of the chilled water is controlled at approximately 7℃ / 15℃, which can be adjusted according to the actual acid temperature and the process spray water temperature control requirements.

[0047] The hydrogen chloride-containing gas, after being absorbed by the secondary ultrapure water, can achieve an absorption rate of 99.99%. After the tail gas is de-misted by the demister at the top of the tower, it is then drawn by the tail gas fan to the tail gas treatment section of the potassium sulfate unit or the chlor-alkali chemical unit for further treatment.

[0048] Quality control and storage / transportation: Semi-finished reagent hydrochloric acid, with a concentration of 36%–38% and a temperature of approximately 15°C, is produced from the bypass of the reagent hydrochloric acid absorption tower after dechlorination and impurity removal and is then sent to intermediate analysis tanks A / B. After sampling and testing, the qualified reagent hydrochloric acid is pumped from the finished product reagent hydrochloric acid storage tank to the finished product reagent hydrochloric acid storage tank. Unqualified products are sent to the industrial hydrochloric acid storage tank. The two intermediate analysis tanks A / B are switched every 6 hours. The reagent hydrochloric acid from the finished product hydrochloric acid storage tank is pumped out by the reagent hydrochloric acid loading pump and then loaded onto trucks for sale via a quantitative filling system.

[0049] The main process equipment involved in this utility model uses materials with low impurities, high purity, and high corrosion resistance, all selected to meet the corresponding product purity requirements, in order to ensure that the equipment used in the production process of high-purity hydrochloric acid does not contaminate the final product.

[0050] The main process equipment, key manufacturing materials, and quantities of this utility model are listed in the table below:

[0051] Automation control This invention utilizes a DCS distributed control system to achieve highly automated control, reduce human intervention, and ensure continuous, stable, and safe production.

[0052] Unit load: Within the designed capacity range, the unit output value is given and input. The speed of the unit's tail gas fan frequency converter is controlled by the hydrogen chloride gas concentration analyzer in the first-stage purification tower of the unit, so as to control the amount of raw material gas (i.e., the amount of hydrogen chloride) entering the unit system and realize the unit load control.

[0053] Primary purification tower: Given the inlet acid temperature of the primary purification tower, the circulating acid concentration and the cooling water flow rate to the primary acid cooler are controlled by the inlet acid temperature signal; given the inlet hydrochloric acid flow rate of the primary purification tower, the speed of the variable frequency primary circulation pump is controlled by the flow signal to stabilize the inlet acid flow rate; given the liquid level of the primary purification tower circulation tank, the bypass regulating valve at the outlet of the primary circulation pump is controlled by the level gauge to control the output of by-product industrial hydrochloric acid.

[0054] Secondary purification tower: Given the inlet acid temperature of the secondary purification tower, the circulating acid concentration and the cooling water flow rate into the secondary purification tower cooler are controlled by the inlet acid temperature signal. At the same time, the acid concentration signal controls the secondary purification water supply regulating valve to control the process water supply to the secondary circulation tank. Given the inlet hydrochloric acid flow rate of the secondary purification tower, the variable frequency secondary purification tower circulation pump speed is controlled by the flow rate signal to stabilize the inlet acid flow rate. Given the liquid level of the secondary purification tower circulation tank, the liquid level gauge controls the secondary purification tower circulation pump outlet bypass regulating valve to control the amount of hydrochloric acid supplied to the primary purification tower circulating acid tank by the liquid level signal.

[0055] Absorption Tower: Given the inlet hydrochloric acid flow rate of the absorption tower, the speed of the variable frequency absorption tower circulating pump is controlled by the flow signal to stabilize the acid flow rate into the tower; given the liquid level in the absorption tower circulating tank, the liquid level gauge controls the bypass regulating valve at the outlet of the absorption tower circulating pump to control the hydrochloric acid flow rate to the intermediate reagent hydrochloric acid tank; given the inlet acid concentration of the absorption tower, the flow rate of the absorption process water is controlled by the regulating valve of the secondary absorption spray water in the absorption tower; given the inlet hydrochloric acid temperature of the absorption tower, the flow rate of the chilled water in the absorption tower acid cooler is controlled by the inlet acid temperature signal; given the temperature of the secondary absorption spray water in the absorption tower, the flow rate of the chilled water in the ultrapure water cooler is controlled by the inlet process water temperature signal.

[0056] In summary, this application has the following innovations: Raw materials: Hydrogen chloride waste gas with a full concentration range can be used.

[0057] Process: (1) Utilizing the high solubility of hydrogen chloride gas and the fact that different temperatures correspond to different solubilities, the raw material gas is washed and purified while ensuring the product concentration and purity. (2) In view of the fact that trace residual chlorine impurities are difficult to remove by acid washing, an ion exchange column is designed for adsorption and removal to ensure that the product indicators meet the standards.

[0058] Equipment: (1) Select materials according to the different purity and working conditions of each process. For example, select corrosion-resistant materials of general purity before the secondary purification tower and corrosion-resistant high-purity materials after the absorption tower. (2) Select PTFE hydrophobic membrane filter cartridge type low resistance high efficiency demister to achieve gas and liquid separation and impurity removal, and ensure the purity of raw material gas. (3) The key tower is optimized on the basis of ordinary packed tower. Through clever design, the tower, tank and gas / liquid separation and impurity removal are integrated into one structure, so that the tower achieves the effect of low pressure drop and multi-functionality, making the process flow simpler and more efficient, the equipment occupies less space and investment, and the operating energy consumption is lower. It is more effective in controlling the intake of external impurities that affect product quality. In particular, the absorption tower adopts a single tower two-stage absorption design on the basis of the above, so that the single tower absorption rate can reach 99.99%, increasing the yield and significantly reducing the tail gas concentration, reducing the tail gas treatment pressure of downstream units.

[0059] Automatic control: Utilizing the DCS distributed control system, the main production process of the unit can run automatically after the design parameters are input, and no manual intervention or adjustment is required under normal operating conditions.

[0060] Example 1: Take a 20kt / a gas phase absorption method high-purity reagent hydrochloric acid production unit as an example.

[0061] Process Flow Description The HCl-containing waste gas from the Mannheim process potassium sulfate production unit is cooled by the carbon crystal cooler of the potassium sulfate production unit, and then pretreated by acid washing in the B acid section. The resulting HCl-containing mixed gas has a mass concentration of about 25% and a temperature of about 45°C, and is used as the main raw material for this unit.

[0062] The above-mentioned raw material gas has the following volumetric composition: approximately 81% air, approximately 17% hydrogen chloride, and 1.5%–2% moisture, and contains a certain amount of metallic, non-metallic, and other compound impurities, with a flow rate of approximately 3500 m³ / h. 3 The exhaust gas, drawn by the exhaust fan at the outlet of the absorption tower of the production unit, first enters the lower part of the primary purification tower. From bottom to top, it is pumped from the bottom circulation tank of the tower to the primary acid cooler and cooled to about 35°C. Then, it is washed and purified by the acid separator at the top of the tower, which sprays about 31% hydrochloric acid in a countercurrent flow. Finally, it undergoes gas-liquid separation by the hydrophobic membrane filter cartridge demister at the top of the tower, completing the primary purification of the raw gas.

[0063] The 31% concentration primary scrubbing hydrochloric acid, contaminated by the raw gas, is used as a byproduct of the unit. Its level is controlled by the primary circulation tank level signal, which regulates the bypass valve at the outlet of the circulation pump at a rate of 0.1–0.2 m. 3 The amount produced per hour is continuously bypassed and temporarily stored in the industrial hydrochloric acid (A acid) storage tank of the potassium sulfate plant.

[0064] The raw gas from the top outlet of the primary purification tower enters from the bottom of the secondary purification tower. It is cooled to approximately 33°C by a circulating pump from the bottom circulation tank of the secondary purification tower. Then, it undergoes secondary washing and purification by countercurrent spraying of approximately 31% hydrochloric acid from the acid separator at the top of the tower. Simultaneously, approximately 5% HCl from the total raw gas content is absorbed. The raw gas then passes through a hydrophobic membrane filter cartridge demister at the top of the tower for gas-liquid separation, completing the secondary purification process.

[0065] The 31% concentration secondary scrubbing hydrochloric acid contaminated by the raw material gas is controlled by the secondary circulation tank level signal, which controls the bypass regulating valve at the outlet of the circulation pump at a rate of 0.1–0.2 m. 3 The flow rate is continuously bypassed and fed into the primary purification tower circulation tank at a rate of / h to balance the liquid level and carry away impurities. To ensure the relative cleanliness of the secondary washing hydrochloric acid, 0.1–0.2 m³ of the solution is added to the secondary circulation tank. 3 / h of pure water.

[0066] The clean raw gas, after being washed and purified by two-stage packed towers and membrane filtration, enters the lower part of the absorption tower from the top outlet of the secondary purification tower. It rises from bottom to top and is cooled to approximately 15°C by the hydrochloric acid cooler pumped from the bottom circulation tank of the absorption tower. Then, it comes into countercurrent contact with approximately 37% high-purity hydrochloric acid sprayed from top to bottom by the acid separator in the middle of the tower. Approximately 90% of the total raw gas content, including HCl, is absorbed in the primary stage. The gas continues to rise and is sprayed downwards to approximately 2 meters by the water separator at the top of the absorption tower. 3 The gas is subjected to countercurrent contact with pure water at approximately 15°C per hour, and the remaining HCl is absorbed in a secondary stage, with a total absorption rate of 99.99%. After the tail gas passes through the demister at the top of the absorption tower to remove acid foam, it is drawn by the tail gas fan at the tower outlet to the tail gas treatment system of the potassium sulfate unit for further processing.

[0067] The 37% high-purity hydrochloric acid semi-finished product is continuously produced via the bypass regulating valve at the outlet of the circulating pump, controlled by the liquid level signal of the absorption tower circulation tank. It is produced at a rate of about 2.5t / h. The acid is further degraded by an ion exchange column to remove free chlorine, and then enters the high-purity hydrochloric acid intermediate tank after passing through a precision filter. After sampling and testing, the qualified product is pumped to the high-purity hydrochloric acid storage tank, while the unqualified product is pumped to the industrial hydrochloric acid finished product storage tank.

[0068] Main process technical parameters

[0069] Main equipment

[0070] Example 2: Take a 100kt / a gas phase absorption high-purity reagent hydrochloric acid production unit as an example.

[0071] Process Flow Description The HCl-containing waste gas with a mass concentration of approximately 35% from the Mannheim process potassium sulfate production unit is cooled by the carbon crystal cooler of the potassium sulfate production unit, and then pretreated by acid washing in the B acid section. The resulting HCl-containing mixed gas has a mass concentration of approximately 25% and a temperature of approximately 45°C, and is used as the main raw material for this unit.

[0072] The above-mentioned raw material gas has the following volumetric composition: approximately 81% air, approximately 17% hydrogen chloride, and 1.5%–2% moisture, and contains a certain amount of metallic, non-metallic, and other compound impurities. The flow rate is approximately 17,500 m³ / s. 3 The exhaust gas, drawn by the exhaust fan at the outlet of the absorption tower of the production unit, first enters the lower part of the primary purification tower. From bottom to top, it is pumped from the bottom circulation tank of the tower to the primary acid cooler and cooled to about 35°C. Then, it is washed and purified by the acid separator at the top of the tower, which sprays about 31% hydrochloric acid in a countercurrent flow. Finally, it undergoes gas-liquid separation by the hydrophobic membrane filter cartridge demister at the top of the tower, completing the primary purification of the raw gas.

[0073] The 31% concentration primary scrubbing hydrochloric acid contaminated by the raw gas is used as a byproduct of the unit. The bypass regulating valve at the outlet of the circulating pump is controlled by the level signal from the primary circulating tank, maintaining a flow rate of 0.5–1 m. 3 The amount produced per hour is continuously bypassed and temporarily stored in the industrial hydrochloric acid (A acid) storage tank of the potassium sulfate plant.

[0074] The raw gas from the top outlet of the primary purification tower enters from the bottom of the secondary purification tower. It is cooled to approximately 33°C by a circulating pump from the bottom circulation tank of the secondary purification tower. Then, it undergoes secondary washing and purification by countercurrent spraying of approximately 31% hydrochloric acid from the acid separator at the top of the tower. Simultaneously, approximately 5% HCl from the total raw gas content is absorbed. The raw gas then passes through a hydrophobic membrane filter cartridge demister at the top of the tower for gas-liquid separation, completing the secondary purification process.

[0075] The 31% concentration secondary scrubbing hydrochloric acid contaminated by the raw material gas is controlled by the secondary circulation tank level signal, which controls the bypass regulating valve at the outlet of the circulation pump at a rate of 0.5–1 m. 3 The flow rate is continuously bypassed and fed into the primary purification tower circulation tank at a rate of / h to balance the liquid level and carry away impurities. To ensure the relative cleanliness of the secondary washing hydrochloric acid, 0.5–1 m³ of the solution is added to the secondary circulation tank. 3 / h of pure water.

[0076] The clean raw gas, after being washed and purified by two-stage packed towers and membrane filtration, enters the lower part of the absorption tower from the top outlet of the secondary purification tower. It rises from bottom to top and is cooled to approximately 15°C by the hydrochloric acid cooler pumped from the bottom circulation tank of the absorption tower. Then, it comes into countercurrent contact with approximately 37% high-purity hydrochloric acid sprayed from top to bottom by the acid separator in the middle of the tower. Approximately 90% of the total raw gas content, including HCl, is absorbed in the primary stage. The gas continues to rise and is sprayed downwards to a depth of approximately 10m by the water separator at the top of the absorption tower. 3 The gas is subjected to countercurrent contact with pure water at approximately 15°C per hour, and the remaining HCl is absorbed in a secondary stage, with a total absorption rate of 99.99%. After the tail gas passes through the demister at the top of the absorption tower to remove acid foam, it is drawn by the tail gas fan at the tower outlet to the tail gas treatment system of the potassium sulfate unit for further processing.

[0077] The 37% high-purity hydrochloric acid semi-finished product is continuously produced via the bypass regulating valve at the outlet of the circulating pump, controlled by the liquid level signal of the absorption tower circulation tank. It is produced at a rate of about 12.5 t / h. The acid is further degraded by an ion exchange column to remove free chlorine, and then enters the high-purity hydrochloric acid intermediate tank after passing through a precision filter. After sampling and testing, the qualified product is pumped to the high-purity hydrochloric acid storage tank, while the unqualified product is pumped to the industrial hydrochloric acid finished product storage tank.

[0078] Main process technical parameters

[0079] Main equipment

[0080] Consumption quota

[0081] The above description is the preferred embodiment of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and these improvements and modifications are also considered to be within the protection scope of this utility model.

Claims

1. A production system for preparing high-purity hydrochloric acid using a gas-phase purification and absorption method, characterized in that, It includes a primary purification unit, a secondary purification unit, an absorption unit, and a finished product refining unit, which are connected sequentially by pipelines; The primary purification unit includes a primary purification tower, a primary circulation pump, and a primary acid cooler. The primary purification tower includes a primary circulation tank, a primary circulation tank, a packed tower disposed on the primary circulation tank, and a demister disposed on the upper part of the packed tower. The secondary purification unit includes a secondary purification tower, a secondary circulation pump, and a secondary acid cooler; the secondary purification tower includes a secondary circulation tank, a packed tower disposed on the secondary circulation tank, and a demister disposed on the upper part of the packed tower; The absorption unit includes a reagent hydrochloric acid absorption tower, an absorption tower circulation pump, an absorption tower hydrochloric acid cooler, and an ultrapure water cooler; the reagent hydrochloric acid absorption tower includes a reagent hydrochloric acid circulation tank, a packed absorption tower, an ultrapure water spray section, and a demister connected sequentially from top to bottom. The finished product refining unit includes an ion exchange column and a finished product acid precision filter; Both the primary and secondary purification towers are equipped with PTFE hydrophobic membrane filter cartridges at the top, with the secondary tower having a higher precision than the primary tower.

2. The production system according to claim 1, characterized in that, The primary purification tower, secondary purification tower, and absorption tower all adopt an integrated tower-trough structure, and the primary circulation tank, secondary circulation tank, and absorption circulation tank at the bottom are all independent cavities.

3. The production system according to claim 1, characterized in that, The tube side of the primary acid cooler and the secondary acid cooler is made of silicon carbide (SIC), and the shell side is circulated with cooling water; the tube side of the absorber hydrochloric acid cooler is made of high-purity silicon carbide (SIC), and the shell side is circulated with chilled water.

4. The production system according to claim 1, characterized in that, The primary circulation pump, secondary circulation pump, and absorption tower circulation pump are all fluoroplastic-lined magnetic pumps, and their flow-through components are made of steel lined with fluoroplastic F46 or steel lined with high-purity PFA.

5. The production system according to claim 1, characterized in that, The hydrochloric acid ion exchange column is filled with polishing resin for adsorbing residual chlorine; the finished acid precision filter uses a high-purity PTFE membrane filter element with a filtration accuracy of 0.03μm to 0.1μm.

6. The production system according to claim 1, characterized in that, The system also includes an intermediate analysis tank for storing semi-finished hydrochloric acid and a finished product storage tank for storing finished hydrochloric acid. Both the intermediate analysis tank and the finished product storage tank are made of high-purity PTFE lined material.

7. The production system according to claim 1, characterized in that, The system also includes an exhaust gas fan, the inlet of which is connected to the top outlet of the reagent hydrochloric acid absorption tower, and its impeller is made of Hastelloy C-276 or fiberglass (FRP).

8. The production system according to claim 1, characterized in that, The lining material of the primary and secondary purification towers is PO or PTFE; the lining material of the reagent hydrochloric acid absorption tower, ion exchange column and finished acid precision filter is high-purity PTFE.

9. The production system according to claim 1, characterized in that, The system is also equipped with a distributed control system (DCS), which is electrically connected to flow meters, temperature sensors, level gauges and regulating valves, acid concentration meters and instruments installed on each circulation pipeline.

10. The production system according to claim 1, characterized in that, The ultrapure water cooler is a plate heat exchanger, and its plates are made of 316L stainless steel.

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