Device for preparing calcium chloride dihydrate by using industrial hydrochloric acid or waste hydrochloric acid

Abstract

The utility model provides a device for preparing calcium chloride dihydrate by using industrial hydrochloric acid or waste hydrochloric acid, which comprises a hydrochloric acid reactor, a tail gas treatment unit, a neutralization reactor, a plate-and-frame filter press and a filtering and refining unit, comprising a precision filter, an ultrafiltration device, a countercurrent multi-effect evaporation system, a crystallization slicing machine and a drying and packaging system, the system treats waste with waste, environmental protection, high efficiency and economical efficiency are considered, and a sustainable waste acid treatment solution is provided for chemical enterprises.

Description

Technical Field

[0001] This utility model relates to the field of calcium chloride dihydrate preparation technology, and in particular to an apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid. Background Technology

[0002] In chemical production processes, especially in industries involving chlor-alkali, pesticides, pharmaceuticals, and dyes, large quantities of hydrochloric acid are often generated as a byproduct. This byproduct hydrochloric acid is complex in composition (potentially containing impurities such as organic matter and heavy metal ions) and fluctuates greatly in concentration, making it difficult to directly reuse in production. It is typically classified as industrial waste acid. Since hydrochloric acid is a strictly controlled hazardous chemical, its storage, transportation, and disposal must comply with stringent environmental regulations, resulting in high waste acid treatment costs and environmental pressures for enterprises.

[0003] Limitations of traditional processing methods:

[0004] Neutralization method: using lime or sodium hydroxide to neutralize waste hydrochloric acid to produce calcium chloride or sodium chloride solution, but the added value of the product is low and a large amount of salt-containing waste residue is generated, which still needs further treatment, resulting in high overall cost.

[0005] Incineration: High-temperature decomposition of hydrochloric acid to recover hydrogen chloride gas, but it requires large equipment investment, high energy consumption, and is uneconomical for low-concentration waste acid.

[0006] Direct emissions or outsourced treatment: Direct emissions have been prohibited due to environmental policies, while outsourced treatment costs have been rising year by year, increasing the burden on enterprises.

[0007] Furthermore, traditional treatment methods also present resource waste and environmental protection conflicts: waste hydrochloric acid is rich in chloride ions and potentially usable components (such as calcium and magnesium ions), but traditional methods fail to achieve resource utilization, resulting in the waste of chlorine. At the same time, secondary pollution may be generated during the treatment process (such as soil salinization caused by the landfilling of neutralization residue).

[0008] There are also bottlenecks in the process technology: Equipment corrosion: Hydrochloric acid and high-concentration calcium chloride solutions are highly corrosive to equipment made of common materials such as carbon steel, resulting in short equipment life and high maintenance costs. A contradiction between energy consumption and purity: When evaporating and concentrating calcium chloride solutions, single-effect evaporation has high energy consumption, while multi-effect evaporation is prone to scaling, affecting heat transfer efficiency; in addition, incomplete removal of impurities may lead to insufficient product purity, making it difficult to meet the requirements of food-grade or high-value-added applications.

[0009] To address the aforementioned issues, a green process is urgently needed that can efficiently treat industrial waste hydrochloric acid and transform it into a high-value product. Based on this, this application proposes an integrated device and process for preparing calcium chloride dihydrate from industrial waste hydrochloric acid. The process involves the neutralization reaction of waste hydrochloric acid with limestone to generate a calcium chloride solution. Combined with multi-stage filtration, countercurrent multi-effect evaporation, and crystallization drying technologies, the waste acid is converted into calcium chloride dihydrate (CaCl2·2H2O) with a purity of over 99%. Utility Model Content

[0010] This invention proposes a device for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid, solving the problem of difficult disposal of large quantities of hydrochloric acid, a byproduct of chemical production processes. The technical solution of this invention is implemented as follows:

[0011] An apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid, comprising the following equipment units connected in sequence:

[0012] The hydrochloric acid reactor is used for the neutralization reaction of industrial waste hydrochloric acid with limestone, and its outlet is connected to the tail gas treatment unit.

[0013] The exhaust gas treatment unit includes an exhaust gas induced draft fan and an exhaust gas cleaning and absorption tower, which are used to treat the reaction exhaust gas and generate exhaust gas that meets emission standards.

[0014] The neutralization reactor is connected to the outlet of the hydrochloric acid reactor and is used for secondary neutralization with quicklime.

[0015] Plate and frame filter press, connected to the outlet of the neutralization reactor, is used to separate solid residues from the neutralized wastewater;

[0016] The filtration and purification unit includes a precision filter and an ultrafiltration device for multi-stage filtration of the pressure filtrate;

[0017] A countercurrent multi-effect evaporation system, connected to the outlet of an ultrafiltration unit, is used to concentrate calcium chloride solution;

[0018] A crystallizer and slicer are connected to the concentrate outlet of a countercurrent multi-effect evaporation system to form flaky calcium chloride dihydrate.

[0019] A drying and packaging system for drying and packaging flake calcium chloride dihydrate.

[0020] Furthermore, the hydrochloric acid reactor includes a pH monitoring device to control the reaction pH value between 3 and 8, and its feed end is equipped with a limestone conveying system.

[0021] Furthermore, an alkaline spraying device is installed inside the exhaust gas cleaning absorption tower, wherein the alkaline solution is a sodium hydroxide solution.

[0022] Furthermore, the countercurrent multi-effect evaporation system uses a titanium alloy evaporator with a steam pressure of 1.0–1.8 MPa.

[0023] Furthermore, the turbidity of the water produced by the ultrafiltration device is ≤100 NTU, and its membrane module is made of polyvinylidene fluoride.

[0024] Furthermore, the drying and packaging system includes a fluidized bed dryer and a vibrating screen, with a drying temperature >90℃ and <120℃.

[0025] Furthermore, a first filtrate buffer tank is provided between the precision filter and the plate and frame filter press for temporarily storing the filtrate.

[0026] Furthermore, the filtration accuracy of the precision filter is 50–100 μm.

[0027] Furthermore, a first filtrate buffer tank is provided between the filtration and refining unit and the plate and frame filter press for temporarily storing the filtrate.

[0028] Furthermore, a second filtrate buffer tank is provided between the ultrafiltration unit and the countercurrent multi-effect evaporation system for temporarily storing the ultrafiltration filtrate.

[0029] Compared with existing technologies, this solution has the following advantages:

[0030] (1) Balancing environmental protection and resource recycling, industrial waste hydrochloric acid is converted into high-value calcium chloride dihydrate, reducing waste acid emissions and pollution, and avoiding the waste residue generated by traditional neutralization methods. The exhaust gas treatment unit (alkaline spray) ensures that acidic gases (such as HCl and CO2) are emitted in compliance with standards, reducing environmental risks.

[0031] (2) High-efficiency production and high-quality products: The multi-effect evaporation system (made of titanium alloy) combined with waste heat recovery significantly reduces energy consumption and achieves high concentration efficiency. The ultrafiltration device (PVDF membrane) and precision filter are used in combination to effectively remove impurities.

[0032] (3) Durable and low-cost equipment: Key equipment (evaporator, reactor) is made of corrosion-resistant titanium alloy, which extends service life and reduces maintenance costs. Modular design (such as filtrate buffer tank and tail gas treatment) is adaptable to different waste hydrochloric acid compositions, reducing the difficulty of raw material processing.

[0033] (4) Automation and stability: real-time monitoring of pH, temperature and pressure parameters, precise control of reaction conditions, and ensuring process stability and product quality consistency.

[0034] (5) Significant economic benefits: the resource utilization of waste hydrochloric acid reduces outsourced treatment costs, has high added value, and broadens the revenue channels for enterprises. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of an apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid according to the present invention;

[0037] Figure 2 This is a flowchart of a method for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid according to the present invention.

[0038] Explanation of reference numerals in the attached drawings: 1. Hydrochloric acid reactor; 2. Neutralization reactor; 3. Plate and frame filter press; 4. First filtrate buffer tank; 5. Precision filter; 6. Precision filtrate buffer tank; 7. Ultrafiltration device; 8. Second filtrate buffer tank; 9. Countercurrent multi-effect evaporation system; 10. Crystallizer slicer; 11. Drying and packaging system; 12. Tail gas scrubbing absorption tower; 13. Tail gas exhaust fan. Detailed Implementation

[0039] The technical solution of this utility model will be clearly and completely described below with reference to its embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0040] Reference Figure 1 This utility model provides an apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid, comprising the following equipment units connected in sequence:

[0041] Hydrochloric acid reactor 1 is used for the neutralization reaction of industrial waste hydrochloric acid and limestone, and its outlet is connected to the tail gas treatment unit. The tail gas treatment unit includes a tail gas induced draft fan 13 and a tail gas cleaning absorption tower, which is used to treat the reaction tail gas and generate tail gas that meets emission standards. Neutralization reactor 2 is connected to the liquid outlet of hydrochloric acid reactor 1 and is used for secondary neutralization with quicklime. Plate and frame filter press 3 is connected to the liquid outlet of neutralization reactor 2 and is used to separate solid residues in the neutralized wastewater. Filtration and purification unit includes a precision filter 5 and an ultrafiltration device 7, which is used for multi-stage filtration of the filter press filtrate. Countercurrent multi-effect evaporation system 9 is connected to the liquid outlet of ultrafiltration device 7 and is used to concentrate calcium chloride solution. Crystallization slicer 10 is connected to the concentrated liquid outlet of countercurrent multi-effect evaporation system 9 and is used to form flaky calcium chloride dihydrate. Drying and packaging system is used to dry and package the flaky calcium chloride dihydrate.

[0042] Furthermore, an alkaline spraying device is installed inside the tail gas cleaning absorption tower, wherein the alkaline solution is sodium hydroxide solution. The countercurrent multi-effect evaporation system 9 uses a titanium alloy evaporator with a steam pressure of 1.0–1.8 MPa. The ultrafiltration unit 7 produces water with a turbidity ≤100 NTU, and its membrane module is made of polyvinylidene fluoride. The drying and packaging system includes a fluidized bed dryer and a vibrating screen, with a drying temperature >150℃. A filtrate buffer tank 84 is provided between the filtration and purification unit and the plate and frame filter press 3 for temporarily storing the filtrate. The precision filter 5 has a filtration accuracy of 50–100 μm.

[0043] Among them, A-industrial (waste) hydrochloric acid, B-limestone, C-quicklime, D-reaction calcium solution, E-neutralized calcium solution, F-pressure filter calcium solution, G-pressure filter residue, H-fine filtration calcium solution, I-ultrafiltration calcium solution, J-saturated steam, L-concentrated calcium solution, R-reaction tail gas, O-flaky calcium chloride dihydrate, P-product calcium chloride dihydrate, and Q-compliant exhaust gas.

[0044] Reference Figure 2 As shown, the main process for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid is as follows:

[0045] Industrial hydrochloric acid or waste hydrochloric acid is temporarily stored in the hydrochloric acid tank area and then pumped into hydrochloric acid reactor 1. Limestone (CaCO3) solid particles are then transported into hydrochloric acid reactor 1 through a conveying system for reaction. The amount of hydrochloric acid and limestone added is controlled by monitoring the pH value in hydrochloric acid reactor 1.

[0046] The exhaust gas generated by the reaction is drawn by the exhaust gas fan to the exhaust gas scrubbing treatment unit (including exhaust gas induced draft fan 13 and exhaust gas scrubbing absorption tower 12) for treatment and then discharged in compliance with standards. The calcium chloride solution (hereinafter referred to as reaction calcium solution) generated by the reaction overflows into the neutralization reactor 2.

[0047] The calcium solution reacts with quicklime (CaO) in neutralization reactor 2, and the solution is purified by adjusting the pH value.

[0048] The neutralized calcium solution is then passed through a plate and frame filter press 3 to remove reaction residues and precipitates, and the resulting filtrate is buffered in a first filtrate buffer tank 4. After passing through a precision filter (precision filter 5 and precision filtrate buffer tank 6), it enters an ultrafiltration unit 7 to remove suspended impurities and further refine the solution to obtain a refined calcium solution.

[0049] After passing through the second filtrate buffer tank 8, the refined calcium solution is transported to the calcium chloride countercurrent multi-effect evaporation system 9. After evaporation and concentration, a calcium chloride solution of 68-74% is obtained, which is then transported to the calcium chloride dihydrate crystallizer 10 for slicing to form flaky calcium chloride dihydrate.

[0050] The flaky calcium chloride dihydrate obtained by crystallization is then dried, screened and packaged by a calcium chloride drying and packaging system 11 (including a fluidized bed dryer and a vibrating screen, with a drying temperature >90℃ and <120℃) to obtain the product calcium chloride dihydrate.

[0051] The control parameters for this process are as follows:

[0052] pH control range for hydrochloric acid reactor 1: 3–8

[0053] pH control range for neutralization reactor 2: 8–14

[0054] Ultrafiltration permeate turbidity: ≤100 NTU

[0055] Calcium chloride evaporation saturated vapor pressure: 1.0 MPa~1.8 MPa

[0056] The main materials used in calcium chloride evaporation equipment are: TA2, TA10, and TA9.

[0057] Calcium chloride evaporation feed concentration: 10%–35%

[0058] Concentration of calcium chloride evaporation product: 68%–74%

[0059] Drying temperature of calcium chloride dihydrate: >150℃

[0060] Calcium chloride dihydrate product content: 99%–107%.

[0061] Furthermore, an alkaline spraying device is installed inside the exhaust gas cleaning absorption tower, wherein the alkaline solution is a sodium hydroxide solution.

[0062] Furthermore, the countercurrent multi-effect evaporation system 9 uses a titanium alloy evaporator with a steam pressure of 1.0 to 1.8 MPa.

[0063] Furthermore, the turbidity of the water produced by the ultrafiltration device 7 is ≤100 NTU, and its membrane module is made of polyvinylidene fluoride.

[0064] Furthermore, the drying and packaging system includes a fluidized bed dryer and a vibrating screen, with a drying temperature >150°C.

[0065] Furthermore, a filtrate buffer tank 84 is provided between the filtration and refining unit and the plate and frame filter press 3 for temporarily storing the filtrate.

[0066] Furthermore, the precision filter 5 has a filtration accuracy of 50–100 μm.

[0067] This system treats waste with waste, taking into account environmental protection, high efficiency and economy, and provides chemical companies with a sustainable waste acid treatment solution.

[0068] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid, characterized in that, This includes the following device units connected in sequence: Hydrochloric acid reactor (1) is used for the neutralization reaction of industrial waste hydrochloric acid and limestone, and its outlet is connected to the tail gas treatment unit. The exhaust gas treatment unit includes an exhaust gas induced draft fan (13) and an exhaust gas cleaning absorption tower (12) for treating the reaction exhaust gas and generating exhaust gas that meets emission standards. Neutralization reactor (2) is connected to the outlet of hydrochloric acid reactor (1) and is used for secondary neutralization with quicklime; Plate and frame filter press (3) is connected to the outlet of neutralization reactor (2) and is used to separate solid residues in neutralized sewage. The filtration and purification unit includes a precision filter (5) and an ultrafiltration device (7) for multi-stage filtration of the pressure filtrate; The countercurrent multi-effect evaporation system (9) is connected to the outlet of the ultrafiltration device (7) and is used to concentrate calcium chloride solution; A crystallizer (10) is connected to the concentrate outlet of a countercurrent multi-effect evaporation system (9) to form flaky calcium chloride dihydrate. A drying and packaging system (11) is used for drying and packaging flake calcium chloride dihydrate.

2. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, The hydrochloric acid reactor (1) includes a pH monitoring device for controlling the reaction pH value between 3 and 8, and its feed end is equipped with a limestone conveying system.

3. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, The tail gas cleaning and absorption tower (12) is equipped with an alkaline spraying device, and the alkaline solution is a sodium hydroxide solution.

4. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, The countercurrent multi-effect evaporation system (9) uses a titanium alloy evaporator with a steam pressure of 1.0 to 1.8 MPa.

5. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, The ultrafiltration device (13) produces water with a turbidity of ≤100 NTU, and its membrane module is made of polyvinylidene fluoride.

6. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, The drying and packaging system (8) includes a fluidized bed dryer and a vibrating screen, with a drying temperature >90℃ and <120℃.

7. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, A first filtrate buffer tank (4) is provided between the precision filter (5) and the plate and frame filter press (3) for temporarily storing the filtrate.

8. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, The precision filter (9) has a filtration accuracy of 50-100 μm.

9. The apparatus for preparing calcium chloride dihydrate using industrial hydrochloric acid or waste hydrochloric acid as described in claim 1, characterized in that, A second filtrate buffer tank (8) is provided between the ultrafiltration device (7) and the countercurrent multi-effect evaporation system (9) for temporarily storing the ultrafiltration filtrate.

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