A method for in-situ regeneration of waste alumina desiccant by low-temperature impregnation

Abstract

The present invention discloses a method for in-situ regeneration of waste alumina desiccant by low-temperature impregnation, including surface pretreatment, low-temperature impregnation with cleaning solution, low-temperature impregnation with repairing solution and calcination treatment. The pretreatment adopts mechanical scrubbing, ultrasonic cleaning or a combination of the two; the cleaning solution is selected from at least one of an acid solution or an alkaline solution, the repairing solution is selected from an aluminum salt solution, and the cleaning solution and the repairing solution are both impregnated at 0 to 10°C; the calcination treatment is carried out in an air atmosphere. The present invention provides a method for regenerating waste alumina desiccant by low-temperature impregnation, which reduces the reaction rate by low-temperature impregnation, thereby unblocking the original pore structure channel without destroying the strength of the alumina particles, and regenerating a new pore structure on the basis of the existing pore structure, thereby obtaining activated alumina with high specific surface area and high pore volume.

Description

Technical Field

[0001] The invention relates to a low-temperature impregnation in-situ regeneration method for a waste alumina desiccant, belonging to the technical field of solid waste regeneration. Background Art

[0002] Activated alumina is widely used in chemical, environmental protection, petrochemical, oil refining, natural gas, oxygen production and other industries because of its good thermal stability, wear resistance, high strength and large specific surface area. After a certain period of use, the pore structure of alumina used to dry compressed air is blocked by adsorbents, and part of the pore structure is damaged, thus losing its original activity. The abandonment of deactivated alumina desiccant not only causes serious waste of resources, but also causes environmental pollution. Therefore, it is necessary to regenerate the discarded alumina desiccant.

[0003] The methods of waste alumina regeneration are mainly divided into crushing and reorganization regeneration and in-situ activation regeneration. Since the crushing and reorganization regeneration method is relatively complex, has high energy consumption and large discharge of three wastes, the in-situ activation regeneration method is mainly used. In-situ activation regeneration has direct calcination method and acid-base impregnation method. The direct calcination method is mainly used to regenerate desiccants that only absorb water, while the substances adsorbed by industrial waste alumina are relatively complex, and a large amount of sediment is also attached to the surface of alumina particles during the stacking process, so acid-base impregnation method is often used for regeneration.

[0004] Waste alumina is regenerated by acid-base impregnation. It is difficult to remove impurities in the pores of alumina with low concentrations of acid and alkali. Although high concentrations of acid and alkali can remove impurities in the pores, expand the pore volume and increase the specific surface area, high concentrations of acid and alkali react violently with alumina during the impregnation process, causing significant damage to the internal pores and external morphology of the alumina particles, resulting in a significant decrease in the mechanical strength of the alumina particles, which is not conducive to reuse after regeneration.

[0005] Zheng Yunhong et al. used 6-20% nitric acid to impregnate the waste regeneration agent alumina (alumina used in the production of hydrogen peroxide by the anthraquinone method) and found that a better specific surface area can be obtained by impregnation with 8% nitric acid solution (Zheng Yunhong et al., Microstructure Study of Waste Activated Alumina Regenerated by Nitric Acid Impregnation Method, Bulletin of Silicate, 2007, 26(4): 821-825). Compared with the regeneration agent alumina, the desiccant alumina has a larger specific surface area and a relatively fragile pore structure. The higher acidity will seriously damage the strength of the alumina particles. Guan Baohong et al. proposed a regeneration method for waste industrial activated alumina by impregnation activation with acid or alkali solution combined with surfactant and repair with aluminum sulfate (Guan Baohong et al., ZL201611146633.9). However, there are also problems of pore structure destruction and low particle integrity, and the surfactant cleaning solution needs to consume additional air. The present invention intends to provide a method for in-situ regeneration of waste alumina desiccant by low-temperature immersion. Through the low-temperature immersion repair method, the reaction rate of acid or alkali solution with alumina is reduced, thereby removing impurities in the pores without destroying the internal pore structure of alumina and the integrity of the particles, thereby expanding the pore volume and increasing the specific surface area. Summary of the invention

[0006] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a method for in-situ regeneration of waste alumina desiccant by low-temperature impregnation.

[0007] The present invention adopts the following technical solutions:

[0008] A method for in-situ regeneration of waste alumina desiccant by low-temperature impregnation, characterized by comprising the following steps:

[0009] (1) Pretreatment: removing impurities on the surface of waste alumina desiccant;

[0010] (2) Low-temperature immersion in acid or alkali solution: remove impurities in the internal pores of the waste alumina without destroying the internal pores and surface morphology of the alumina;

[0011] The cleaning liquid is selected from at least one of an acid solution and an alkaline solution;

[0012] (3) Low-temperature immersion treatment with repair solution: repairing the damaged pores and surface morphology inside the alumina after treatment in step (2);

[0013] The repair solution is selected from aluminum-containing solutions;

[0014] (4) Calcination treatment: drying and calcining the alumina treated in step (3) to obtain activated alumina;

[0015] The calcination treatment is carried out in an air atmosphere.

[0016] Preferably, in step (1), the pretreatment process adopts water bath mechanical scrubbing, ultrasonic cleaning or a combination of the two to remove impurities such as mud and grease adsorbed on the surface;

[0017] Further preferably, the rotation speed of the water bath mechanical scrubbing is 200-600 rpm, and the solid-liquid ratio is 1:3-10;

[0018] More preferably, the frequency of ultrasonic cleaning is 15-60 kHz, and the solid-liquid ratio is 1:1-10.

[0019] Preferably, in step (2), the acid solution comprises at least one of hydrochloric acid solution, nitric acid solution, sulfuric acid solution, and phosphoric acid solution;

[0020] The alkali solution includes at least one of a sodium hydroxide solution, a sodium carbonate solution, and a sodium bicarbonate solution;

[0021] The cleaning liquid can expand the pore cross-section and pore volume, increase the specific surface area, increase the number of pores, and improve the surface properties. Low concentration of cleaning liquid or short immersion time has poor activation effect on waste alumina, and high concentration of cleaning liquid or too long immersion time will have adverse effects on pore structure and particle strength. By reducing the immersion temperature of the cleaning liquid and reducing the reaction rate between the cleaning liquid and alumina, the purpose of removing impurities in the pores, expanding the pore volume and increasing the specific surface area can be achieved with less or no damage to the internal pores and external morphology of alumina. Low temperature can appropriately increase the concentration of the cleaning liquid, reduce the immersion time, and increase the integrity of the particles. The immersion cleaning effect is also related to the solid-liquid ratio and the ultrasonic frequency.

[0022] Preferably, the concentration of the cleaning solution is 5.0-20.0 wt%, the immersion time is 3-60 min, the immersion temperature is 0-10° C., the solid-liquid ratio is 1:1-10, and the ultrasonic frequency is 40-80 kHz;

[0023] More preferably, the solid-liquid ratio in the cleaning solution is 1:1-3, and the cleaning solution is immersed in the solution with the aid of ultrasonic treatment, and the ultrasonic frequency is 15-60 kHz.

[0024] The repair liquid is mainly used to repair the damage to the original pore structure caused by the immersion of the cleaning liquid. The aluminum oxide treated in step (2) is filtered, dried, and the repair liquid is added. It is found that the dry aluminum oxide will preferentially absorb water, causing the components of the repair liquid to precipitate on the surface of the aluminum oxide, and the purpose of repairing the internal pores of the aluminum oxide cannot be achieved. By lowering the immersion temperature of the repair liquid, the rate at which the dry aluminum oxide absorbs water in the repair liquid is reduced, so that the components in the repair liquid enter the internal pores of the aluminum oxide, and a new pore structure is grafted on the basis of the existing pore structure, thereby increasing the specific surface area of ​​the aluminum oxide.

[0025] Preferably, in step (3), the aluminum-containing solution is selected from aluminum nitrate solution, aluminum sulfate solution, aluminum chloride solution, and sodium aluminate solution, and the concentration of the aluminum-containing solution is 5.0-12.0 wt % calculated as Al2O3; the immersion time of the repair liquid is 15-60 min, and the immersion temperature is 0-10°C.

[0026] More preferably, the repair solution is an aluminum sulfate solution.

[0027] Preferably, in step (3), the calcination process conditions are:

[0028] The heating rate is 5-20K / min;

[0029] Air intake is 150~400m 3 / (h·t), low temperature impregnation can reduce the use of surfactants, so the amount of air intake can also be appropriately reduced;

[0030] The calcination temperature is 300-600°C and the time is 30-120 minutes.

[0031] Preferably, in steps (1) to (3), after treatment, solid-liquid separation and drying are required before entering the next treatment process, wherein the drying temperature is independently selected from 80 to 120° C., and the drying time is independently selected from 1.0 to 5.0 h. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Attached Figure 1 The process flow chart of the low-temperature impregnation regeneration of waste alumina in the present invention; DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 4.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 0°C, and it was maintained for 30 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 5°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, maintained for 2 hours, and calcined at 300m 3 / (h·t) rate of air flow, the specific surface area is 271m2 / g, white alumina product with a strength of 170N / grain.

[0036] Comparative Example 1

[0037] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 4.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 15°C, and the temperature was maintained for 30 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 5°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, maintained for 2 hours, and calcined at 300m 3 / (h·t) air volume is introduced at a rate of 264m 2 / g, white alumina product with a strength of 112N / grain.

[0038] Comparative Example 2

[0039] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 4.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 20°C, and the temperature was maintained for 30 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 5°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, maintained for 2 hours, and calcined at 300m 3 / (h·t) air volume is introduced at a rate of 256m 2 / g, white alumina product with a strength of 107N / grain.

[0040] Example 2

[0041] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 4.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 0°C, and it was maintained for 45 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 5°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, maintained for 2 hours, and calcined at 300m 3 / (h·t) air volume is introduced at a rate of 285m 2 / g, white alumina product with a strength of 184N / grain.

[0042] Example 3

[0043] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 4.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 0°C, and it was maintained for 120 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 5°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, maintained for 2 hours, and calcined at 300m 3 / (h·t) air volume is introduced at a rate of 312m 2 / g, white alumina product with a strength of 161N / grain.

[0044] Example 4

[0045] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 20.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 0°C, and it was kept for 10 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 5°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, and kept for 2 hours. During the calcination process, the temperature was adjusted at 300m 3 / (h·t) rate of air flow, the specific surface area is 300m 2 / g, white alumina product with a strength of 172N / grain.

[0046] Comparative Example 3

[0047] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 20.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 20°C, and it was maintained for 10 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 10°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, maintained for 2 hours, and calcined at 300m 3 / (h·t) air volume is introduced at a rate of 208m 2 / g, white alumina product with a strength of 96N / grain.

[0048] Comparative Example 4

[0049] The waste alumina was impregnated with water at a ratio of 1:5, and the alumina balls were suspended and rubbed by mechanical stirring. After 20 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the pretreated alumina was immersed in a 4.0wt% nitric acid solution at a volume ratio of 1:1, the immersion temperature was 0°C, and it was maintained for 10 minutes. The solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 105°C forced air drying oven for 2 hours; the cleaned alumina was immersed in a 20°C saturated aluminum sulfate solution at a volume ratio of 1:1 for 120 minutes, the solid and liquid were separated, the liquid was reused, and the solid phase was placed in a 150°C forced air drying oven for 2 hours, and then placed in a calcining furnace and heated to 500°C at a rate of 17K / min, maintained for 2 hours, and calcined at 300m 3 / (h·t) air volume is introduced at a rate of 182m 2 / g, white alumina product with a strength of 90N / grain.

Claims

1. A method for in-situ regeneration of waste alumina desiccant by low-temperature immersion. It is characterized in that The steps include: (1) Pretreatment: Use water bath mechanical scrubbing and / or ultrasonic cleaning to remove impurities on the surface of the waste alumina desiccant; (2) Low-temperature immersion in cleaning solution: Under the premise of maintaining the original pore structure and integrity, low-temperature cleaning solution immersion treatment is used to remove impurities in the internal pores of alumina; The cleaning solution is selected from nitric acid solution; The low-temperature immersion temperature of the cleaning solution is 0-10°C; (3) Low-temperature immersion in repair solution: repairing the internal pores and surface morphology of alumina after solid-liquid separation and drying treatment in step (2); The repair solution is selected from aluminum-containing solutions; The low-temperature immersion temperature of the repair liquid is 0-10°C; (4) Calcination treatment: The alumina treated in step (3) is dried and calcined in an air atmosphere to obtain activated alumina.

2. The method for in-situ regeneration of waste alumina desiccant by low-temperature impregnation according to claim 1, It is characterized in that In step (1), the pretreatment process includes water bath mechanical scrubbing, ultrasonic cleaning or a combination of the two, and the washing water is recycled.

3. The method for in-situ regeneration of waste alumina desiccant by low-temperature immersion according to claim 1, It is characterized in that In step (2), the concentration of the nitric acid solution is 5.0-20.0 wt %, the immersion time is 3-60 min, and the solid-liquid ratio is 1:(1-10); The nitric acid solution is immersed in an ultrasonic treatment, and the ultrasonic frequency is 40 to 80 kHz.

4. The method for in-situ regeneration of waste alumina desiccant by low-temperature immersion according to claim 1, It is characterized in that In step (3), the aluminum-containing solution is selected from aluminum nitrate solution, aluminum sulfate solution, aluminum chloride solution, sodium aluminate solution, and Al 2 O 3 The concentration of the aluminum-containing solution is 5.0-12.0wt%; The immersion time of the repair liquid is 15 to 60 minutes.

5. The method for in-situ regeneration of waste alumina desiccant by low-temperature immersion according to claim 1, It is characterized in that In step (4), the calcination process conditions are: The heating rate is 5-20K / min; Air intake is 150~400m 3 / (h·t); The calcination temperature is 300-600°C and the time is 30-120 minutes.

6. The method for in-situ regeneration of waste alumina desiccant by low-temperature immersion according to claim 1, It is characterized in that In steps (1) to (3), after treatment, solid-liquid separation and drying treatment are required before entering the next treatment process, wherein the drying treatment temperature is independently selected from 80 to 120° C., and the drying treatment time is independently selected from 1.0 to 5.0 h.

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