Lithium hydroxide granulation process of carbon dioxide absorbent

Abstract

The invention discloses a lithium hydroxide granulation process of a carbon dioxide absorbent, and relates to the technical field of lithium hydroxide granulation, uniform particle size distribution is beneficial to dispersion and reaction uniformity in the subsequent processing process, the problem of inconsistent product performance caused by particle size difference is avoided, and the test of a universal material testing machine shows that the lithium hydroxide granulation process can be used for preparing lithium hydroxide granules. The average compressive strength of the prepared lithium hydroxide particles is 5N / particle, and the lithium hydroxide particles have better mechanical strength, are not easy to break in the storage, transportation and industrial processing processes, can effectively reduce the generation of dust, reduce the risk of environmental pollution, ensure the quality stability of the product and meet the basic requirements on the particle strength in actual production. After the product is placed in an environment with the humidity of 70% for 24 hours, the weight gain rate of the particles is increased by 50-70%, and compared with ungranulated powdery lithium hydroxide, the hygroscopicity is remarkably improved, which is benefited from the micropore loose structure of the particles and the protective effect of the binder, the storage stability of the product in a humid environment is effectively improved, and the absorption function of the product on carbon dioxide in air is increased.

Description

Technical Field

[0001] This invention relates to the field of lithium hydroxide granulation technology, specifically to a lithium hydroxide granulation process for a carbon dioxide absorbent. Background Technology

[0002] Lithium hydroxide plays a vital role in modern industry. In confined spaces, underground engineering, and underwater mobile spaces, carbon dioxide absorbents prepared from lithium hydroxide can effectively purify the environment. However, in practical applications, powdered lithium hydroxide suffers from problems such as hygroscopicity, dust generation, and poor flowability, severely impacting production efficiency and product quality. Granulating lithium hydroxide can effectively solve these problems, improving the product's storage, transportation, and processing performance. Currently, the application of granulation technology in lithium hydroxide production is still immature. Different granulation processes and parameters significantly affect product performance; therefore, developing efficient and stable granulation processes has significant practical and economic value. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a lithium hydroxide granulation process for carbon dioxide absorbents.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a lithium hydroxide granulation process for a carbon dioxide absorbent, comprising lithium hydroxide powder, wherein the lithium hydroxide granulation process steps are as follows:

[0005] Granulation: Weigh lithium hydroxide powder, add binder, and place in a high-speed mixer granulator to evenly disperse the binder in the lithium hydroxide powder. Then, turn on the agitator and granulation blade, and slowly add deionized water. Continue granulation for 10 minutes.

[0006] Molding: The granulated material is transferred to a twin-screw extruder and extruded to obtain cylindrical wet granules;

[0007] Drying: Place the wet granules into a fluidized bed dryer for drying;

[0008] Screening: The dried particles are screened using a vibrating screen.

[0009] Testing: The particle size distribution was measured using a laser particle size analyzer, the compressive strength of the particles was determined using a universal testing machine, and the hygroscopicity of the particles in an environment with 70% humidity was tested using the weight loss method.

[0010] Preferably, the lithium hydroxide powder is battery-grade lithium hydroxide powder with a purity of 99.9%, and its impurity content (sodium, potassium, calcium, magnesium, etc.) is less than 0.01%.

[0011] Preferably, the binder in the granulation step is polyvinylpyrrolidone with a mass fraction of 5%.

[0012] Preferably, in the granulation step, the binder is first premixed at a speed of 300-400 r / min for 5 min to uniformly disperse the binder in the lithium hydroxide powder.

[0013] Preferably, in the granulation step, the stirring paddle speed is adjusted to 800-900 r / min, and the granulation blade speed is 1500-1700 r / min.

[0014] Preferably, the amount of deionized water added in the granulation step is 10% of the raw material mass.

[0015] Preferably, the twin-screw extruder used in the forming step employs a die with a bore diameter of 3mm.

[0016] Preferably, in the drying step, the wet particles are placed in a fluidized bed dryer and dried at 80°C for 30 minutes to reduce the moisture content to below 0.5%.

[0017] Preferably, in the screening step, particles with a diameter range of 2.5-3.5 mm are collected as the target product.

[0018] Beneficial effects

[0019] This invention provides a lithium hydroxide granulation process for carbon dioxide absorbent. The process achieves 85% particle size distribution within the 2.5mm range, with a relatively concentrated particle size distribution and a D50 (volume average particle size) of 2.5-3.5mm, meeting the particle size requirements for industrial applications. This uniform particle size distribution facilitates dispersion and reaction uniformity during subsequent processing, avoiding inconsistencies in product performance due to particle size differences. Universal testing shows that the prepared lithium hydroxide particles have an average compressive strength of 5N / particle, exhibiting good mechanical strength. The particles are not easily broken during storage, transportation, and industrial processing, effectively reducing dust generation and environmental pollution risks while ensuring product quality stability and meeting the basic particle strength requirements in actual production. Hygroscopicity tests show that after 24 hours in a 70% humidity environment, the weight gain rate of the particles is 50-70%, significantly improving hygroscopicity compared to ungranulated powdered lithium hydroxide. This is attributed to the microporous and loose structure of the particles and the protective effect of the binder, effectively improving the product's storage stability in humid environments and enhancing its carbon dioxide absorption capacity. Detailed Implementation

[0020] The present invention will now be described in detail;

[0021] Example 1:

[0022] Granulation process: Weigh a certain amount of lithium hydroxide powder, add 5% (mass fraction) of binder polyvinylpyrrolidone (PVP), and place it in a high-speed mixer granulator. First, premix at 300 r / min for 5 min to ensure the binder is evenly dispersed in the lithium hydroxide powder. Then, turn on the agitator and granulator blade, adjusting the agitator speed to 800 r / min and the granulator blade speed to 1500 r / min, while slowly adding an appropriate amount of deionized water (10% of the raw material mass), and continue granulation for 10 min.

[0023] Forming and Drying: The granulated material is transferred to a twin-screw extruder and extruded through a 3mm orifice die to obtain cylindrical wet granules. The wet granules are then placed in a fluidized bed dryer and dried at 80℃ for 30 minutes to reduce the moisture content to below 0.5%.

[0024] Screening and Testing: The dried granules were screened using a vibrating sieve, and granules with a diameter range of 2.5 mm were collected as the target product. The particle size distribution was measured using a laser particle size analyzer, the compressive strength of the granules was determined using a universal testing machine, and the hygroscopicity of the granules in an environment with 70% humidity was tested using the weight loss method.

[0025] Example 2:

[0026] Granulation process: Weigh a certain amount of lithium hydroxide powder, add 5% (mass fraction) of binder polyvinylpyrrolidone (PVP), and place it in a high-speed mixer granulator. First, premix at 400 r / min for 5 min to ensure the binder is evenly dispersed in the lithium hydroxide powder. Then, turn on the agitator and granulator blade, adjusting the agitator speed to 900 r / min and the granulator blade speed to 1700 r / min, while slowly adding an appropriate amount of deionized water (10% of the raw material mass), and continue granulation for 10 min.

[0027] Forming and Drying: The granulated material is transferred to a twin-screw extruder and extruded through a 3mm orifice die to obtain cylindrical wet granules. The wet granules are then placed in a fluidized bed dryer and dried at 80℃ for 30 minutes to reduce the moisture content to below 0.5%.

[0028] Screening and Testing: The dried granules were screened using a vibrating sieve, and granules with a diameter range of 3.5 mm were collected as the target product. The particle size distribution was measured using a laser particle size analyzer, the compressive strength of the granules was determined using a universal testing machine, and the hygroscopicity of the granules in an environment with 70% humidity was tested using the weight loss method.

[0029] Detection methods

[0030] In experiments, the adsorption effect of lithium hydroxide particles on carbon dioxide can be detected by the following common methods:

[0031] 1. Quality Method

[0032] Experimental principle: Lithium hydroxide reacts with carbon dioxide to produce lithium carbonate and water. The amount of carbon dioxide adsorbed is calculated by measuring the increase in sample mass before and after adsorption.

[0033] Experimental Procedure: Accurately weigh a certain amount of lithium hydroxide particles using a high-precision balance, place them in an adsorption device, and introduce carbon dioxide gas at a specific flow rate and concentration. The adsorption reaction is carried out under specific temperature and humidity conditions. After the reaction is complete, weigh the sample again, calculate the mass difference, and then calculate the amount of carbon dioxide adsorbed based on the chemical reaction equation.

[0034] 2. Capacity method

[0035] Experimental principle: The adsorption effect is determined by measuring the relationship between the pressure or volume change of carbon dioxide gas in the system and the amount of adsorption after lithium hydroxide adsorbs carbon dioxide.

[0036] Experimental Procedure: Lithium hydroxide particles were placed in a sealed adsorption container equipped with a pressure sensor or volume measuring device. A certain amount of carbon dioxide gas with known pressure and volume was introduced. Pressure or volume changes were monitored in real time during the adsorption reaction. The amount of carbon dioxide adsorbed was calculated using the ideal gas law and other relevant formulas.

[0037] 3. Thermogravimetric analysis

[0038] Experimental principle: Under a programmed temperature control environment, the change in mass of lithium hydroxide particles during the adsorption of carbon dioxide is measured with temperature to analyze the adsorption effect.

[0039] Experimental Procedure: A suitable amount of lithium hydroxide particles was placed in the sample cell of a thermogravimetric analyzer. The experiment was conducted under a specific atmosphere (such as a mixture containing carbon dioxide) and heating rate. The instrument recorded the mass change curve with temperature. Based on the curve's characteristics and mass loss, information such as the adsorption capacity of lithium hydroxide for carbon dioxide and the adsorption temperature range were analyzed.

[0040] 3. Spectroscopic analysis method

[0041] Experimental principle: Using techniques such as infrared spectroscopy or Raman spectroscopy, the characteristic spectral changes of samples before and after lithium hydroxide adsorbs carbon dioxide are detected to determine whether an adsorption reaction has occurred and the types and contents of adsorption products, thereby indirectly evaluating the adsorption effect.

[0042] Experimental procedure: Before and after adsorption, the lithium hydroxide particles were subjected to spectral analysis. The changes in the position and intensity of characteristic peaks in the spectra before and after adsorption were compared. For example, the appearance and increased intensity of the characteristic absorption peak of carbonate ions in the infrared spectrum indicated that a carbon dioxide adsorption reaction had occurred. The change in adsorption amount can be further analyzed semi-quantitatively by observing the changes in peak intensity.

[0043] Experimental results

[0044] Particle size distribution: Laser particle size analysis results show that particles within the 2.5mm range account for 85%, indicating a relatively concentrated particle size distribution. The D50 (volume average particle size) is 2.5mm, meeting the particle size requirements of most industrial applications. A uniform particle size distribution is beneficial for dispersion and reaction uniformity in subsequent processing, avoiding inconsistencies in product performance caused by particle size differences.

[0045] Compressive strength: Universal testing machine tests show that the average compressive strength of the prepared lithium hydroxide particles is 5 N / particle, exhibiting good mechanical strength. They are not easily broken during storage, transportation, and industrial processing, effectively reducing dust generation and environmental pollution risks, while ensuring product quality stability and meeting the basic requirements for particle strength in actual production.

[0046] Hygroscopicity: Hygroscopicity test results show that after being placed in a 70% humidity environment for 24 hours, the weight gain rate of the granules is 50-70%, which is significantly higher than that of ungranulated powdered lithium hydroxide. This is due to the microporous structure of the granules and the protective effect of the binder, which effectively improves the storage stability of the product in humid environments and increases its carbon dioxide absorption capacity.

[0047] Process optimization discussion: Comparative experiments were conducted by changing the type and dosage of binder, the amount of water added during granulation, and the drying temperature and time. The results showed that when the binder PVP dosage was below 3%, the particle strength was insufficient, making them prone to breakage during subsequent processing; above 7% affected product purity and subsequent application performance. When the water content was below 8%, the granulation effect was poor, and particle formation was difficult; above 12% led to excessively long drying times and may even cause particle agglomeration. Excessively high drying temperatures (>100℃) caused partial decomposition of lithium hydroxide, affecting product quality; excessively short drying times (<20min) resulted in excessive residual moisture. Considering all factors, the currently determined process parameters represent the optimal granulation conditions. The addition of a foaming agent can improve the microporous structure inside the particles, increasing their porosity.

[0048] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

Claims

1. A lithium hydroxide granulation process for a carbon dioxide absorbent, comprising lithium hydroxide powder, characterized in that, The lithium hydroxide granulation process steps are as follows: Granulation: Weigh lithium hydroxide powder, add binder, and place in a high-speed mixer granulator to evenly disperse the binder in the lithium hydroxide powder. Then, turn on the agitator and granulation blade, and slowly add deionized water. Continue granulation for 10 minutes. Molding: The granulated material is transferred to a twin-screw extruder and extruded to obtain cylindrical wet granules; Drying: Place the wet granules into a fluidized bed dryer for drying; Screening: The dried particles are screened using a vibrating screen. Testing: The particle size distribution was measured using a laser particle size analyzer, the compressive strength of the particles was determined using a universal testing machine, and the hygroscopicity of the particles in an environment with 70% humidity was tested using the weight loss method.

2. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... The lithium hydroxide powder used is battery-grade lithium hydroxide powder with a purity of 99.9%, and its impurity content (sodium, potassium, calcium, magnesium, etc.) is less than 0.01%.

3. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... The binder in the granulation step is polyvinylpyrrolidone with a mass fraction of 5%.

4. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... In the granulation step, the binder is first premixed at a speed of 300-400 r / min for 5 min to ensure uniform dispersion of the binder in the lithium hydroxide powder.

5. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... In the granulation step, the stirring paddle speed is adjusted to 800-900 r / min, and the granulation blade speed is 1500-1700 r / min.

6. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... In the granulation step, the amount of deionized water added is 10% of the raw material mass.

7. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... In the forming step, the twin-screw extruder uses a die head with a bore diameter of 3mm.

8. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... In the drying step, the wet particles are placed in a fluidized bed dryer and dried at 80°C for 30 minutes to reduce the moisture content to below 0.5%.

9. The lithium hydroxide granulation process for a carbon dioxide absorbent according to claim 1, characterized in that... In the screening step, particles with a diameter range of 2.5-3.5 mm are used as the target product.