Method for preparing modified granular activated carbon from fibrous plant raw materials and activated carbon

Abstract

The invention discloses a method for preparing modified granular activated carbon from fibrous plant raw materials and activated carbon, which comprises the following steps: soaking light fibrous plant raw materials difficult to process in citric acid, shredding, adding a certain amount of sodium humate, and fully mixing with diammonium hydrogen phosphate or ammonium dihydrogen phosphate; the preparation method comprises the following steps: preparing heavy particles with the particle size of 8mm-10mm through a hot press molding process at the temperature of 130-190 DEG C by using a granulator, carbonizing at a certain heating speed and temperature, introducing a certain amount of CO2 / N2 or air / water vapor mixed gas, and finally carrying out gradient activation at 850-950 DEG C-1000 DEG C to prepare the high-performance heavy particle active carbon. The defect that a traditional fibrous plant raw material is easily entrained by airflow to enter a tail gas system in the rotary furnace carbonization and activation process due to low density is overcome, and the light fibrous raw material can stably produce activated carbon. Meanwhile, the heavy granular activated carbon is subjected to modification treatment to prepare the modified granular activated carbon.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection materials, and particularly relates to a method for preparing modified granular activated carbon from fibrous plant raw materials and the activated carbon. BACKGROUND

[0002] Fibrous plant raw materials such as hemp fibers, palm fibers, corn hairs, cottonseed hulls, coconut husks, etc. have a fine filament structure and are light in density. In the process of industrialized production of activated carbon, the volume of the same weight of the fibrous plant raw materials is large, and the fibrous plant raw materials are difficult to transport. In the carbonization and activation process in a rotary furnace, the fibrous plant raw materials are easily carried into the tail gas system by activation gas, combustion gas and gas generated in the process, and normal production cannot be achieved. The fibrous plant raw materials only appear in the activated carbon experiments in university laboratories and cannot be used in activated carbon factories.

[0003] Irregular or regular granular activated carbon and modified activated carbon are usually prepared from expensive raw materials such as coconut shells, walnut shells and apricot shells, and the cost of the raw materials is high, and the price of the activated carbon is high. SUMMARY

[0004] In view of this, the present application aims to provide a method for preparing modified granular activated carbon from fibrous plant raw materials and the activated carbon.

[0005] In order to achieve the above technical purposes, the technical scheme adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a method for preparing modified granular activated carbon from fibrous plant raw materials, comprising:

[0007] The fibrous plant raw materials are cut into filaments with a length of 1 mm to 5 mm, the moisture content is adjusted to 10% to 20%, 5% to 15% of humic acid sodium and 1% to 3% of diammonium hydrogen phosphate or ammonium dihydrogen phosphate based on the dry weight of the fibrous plant raw materials are added and fully mixed, and then the mixture is hot-pressed into heavy granules with a size of 8 mm to 10 mm by a granulator at a temperature of 130 DEG C to 190 DEG C.

[0008] The heavy granules are placed in a rotary furnace, carbonized at a temperature of 400 DEG C to 700 DEG C for 1 h to 3 h under a nitrogen atmosphere at a temperature increasing rate of 5 DEG C / min to 10 DEG C / min, and then switched to a mixed gas with a volume ratio of CO2 / N2 or air / water vapor of 1:1 to 5, and activated at a temperature gradient of 5 DEG C / min to 10 DEG C / min to 850 DEG C, 950 DEG C and 1000 DEG C in stages, and each stage is kept for 15 min to 30 min, to obtain heavy granular activated carbon with an iodine value of 1000 mg / g or more.

[0009] After the heavy granular activated carbon is crushed and sieved, the heavy granular activated carbon is immersed in an ethanol solution of 5 wt% to 10 wt% of aminopropyl triethoxysilane (KH-550), and then dried and solidified at a temperature of 120 DEG C to 180 DEG C to obtain irregular granular activated carbon with a hydrophobic surface.

[0010] Or, the heavy granular activated carbon and 5%~30% soluble metal salt solution are impregnated according to 1:3~10 mass ratio, and are baked at 300℃~500℃ under nitrogen protection for 1h~3h to prepare the modified granular activated carbon loaded with metal.

[0011] In some embodiments, the soluble metal salt is at least one of copper nitrate, iron nitrate, silver nitrate, magnesium nitrate, manganese nitrate, and potassium permanganate.

[0012] In some embodiments, the fibrous plant raw material is soaked in a 5%~30% mass concentration of citric acid solution for 1h~3h before being cut into shreds.

[0013] In some embodiments, the hot-pressing pressure of the granulator is controlled at 10MPa~50MPa.

[0014] In some embodiments, the ethanol solution of aminopropyltriethoxysilane (KH-550) is impregnated for 30min~60min.

[0015] In some embodiments, the fibrous plant raw material is at least one of hemp fiber, palm fiber, corn hair, cotton seed hull, and coconut palm.

[0016] In some embodiments, the crushing and screening is performed by using a pair of roller crushers, the roller spacing is adjusted to 0.25mm~3.35mm, and the screen mesh size is 6mesh~60mesh.

[0017] In some embodiments, the heavy granules are pre-dried at 100℃~120℃ for 1h~3h before carbonization, and the moisture is controlled below 10%.

[0018] In the second aspect, the present application provides an activated carbon, which is prepared by the preparation method of the first aspect.

[0019] Compared with the prior art, the present application has the beneficial effects that:

[0020] The technical scheme is characterized in that: the light and difficult-to-process fibrous plant raw material is cut into 1mm-5mm, then 5%-15% of humic acid sodium and 1%-3% of diammonium hydrogen phosphate or ammonium dihydrogen phosphate by dry weight of the fibrous plant raw material are added and fully mixed, and then the mixture is hot-pressed by a granulator at 130°C-190°C to form heavy particles with a diameter of 8mm-10mm, so that the problem that the fibrous raw material is easily taken away by airflow in industrial production due to low density is solved. After the heavy particles are carbonized at 400°C-700°C for 1h-3h at a temperature rising rate of 5°C / min-10°C / min in a rotary furnace, mixed gas with a volume ratio of CO2 / N2 or air / water vapor of 1:1-5 is introduced, and the heavy particles are activated at 850°C→950°C→1000°C at a temperature rising rate of 5°C / min-10°C / min, and each segment is kept for 15min-30min, so that high-performance heavy particle activated carbon with an iodine value of ≥1000mg / g is prepared. The defect that the fibrous plant raw material is easily taken into the tail gas system by airflow in the carbonization and activation process in the rotary furnace is overcome, and the light fibrous raw material can be stably used in industrial production. DETAILED DESCRIPTION

[0021] The application will be further described below in conjunction with examples. It is particularly pointed out that the following examples are only used to illustrate the application, but do not limit the scope of the application. Similarly, the following examples are only part of the examples of the application, not all examples, and all other examples obtained by those skilled in the art without creative labor are within the scope of the application.

[0022] In the first aspect, the embodiment provides a method for preparing modified granular activated carbon from fibrous plant raw material, comprising:

[0023] The fibrous plant raw material is cut into 1mm-5mm, the moisture content is adjusted to 10%-20%, 5%-15% of humic acid sodium and 1%-3% of diammonium hydrogen phosphate or ammonium dihydrogen phosphate by dry weight of the fibrous plant raw material are added and fully mixed, and then the mixture is hot-pressed by a granulator at 130°C-190°C to form heavy particles with a diameter of 8mm-10mm;

[0024] The heavy particles are placed in a rotary furnace, heated to 400°C-700°C at a temperature rising rate of 5°C / min-10°C / min in a nitrogen atmosphere for carbonization for 1h-3h, then switched to mixed gas with a volume ratio of CO2 / N2 or air / water vapor of 1:1-5, heated to 850°C→950°C→1000°C at a temperature rising rate of 5°C / min-10°C / min for segmented activation, and each segment is kept for 15min-30min, so that heavy particle activated carbon with an iodine value of ≥1000mg / g is prepared;

[0025] The heavy granular activated carbon is crushed and sieved, then immersed in a 5wt%-10wt% ammonia propyl triethoxysilane (KH-550) ethanol solution, dried and cured at 120°C-180°C to obtain irregular granular activated carbon with a hydrophobic surface modification;

[0026] Alternatively, the heavy granular activated carbon is immersed in a 5%-30% soluble metal salt solution at a 1:3-10 mass ratio, then calcined at 300°C-500°C for 1h-3h under nitrogen protection to obtain modified granular activated carbon loaded with metal. The soluble metal salt is at least one of copper nitrate, iron nitrate, silver nitrate, magnesium nitrate, manganese nitrate, and potassium permanganate.

[0027] The method for preparing modified granular activated carbon from fibrous plant raw materials provided in this embodiment fully considers the characteristics of fibrous plant raw materials and the actual needs of industrial production. The fibrous plant raw materials are cut to a length of 1mm-5mm, which can ensure uniformity and material flowability in the subsequent granulation process, and also avoids the problem of insufficient mechanical strength caused by too short fibers.

[0028] Adjusting the water content to 10%-20% ensures that the material has suitable plastic deformation capacity in the granulator, and also avoids the difficulty of hot pressing caused by too high moisture. The addition of 5%-15% of the dry weight of the fibrous plant raw material of sodium humate and 1%-3% diammonium hydrogen phosphate or ammonium dihydrogen phosphate for sufficient mixing ensures that sodium humate can effectively play a binding role without excessive cost increase; the addition amount of diammonium hydrogen phosphate or ammonium dihydrogen phosphate takes into account the pore-forming effect and economy, and also provides a necessary nitrogen source for the subsequent activation process. Hot pressing at 130°C-190°C by the granulator to make 8mm-10mm heavy granules can ensure the softening and binding effect of lignin and sodium humate in the plant raw materials, prevent premature decomposition of diammonium hydrogen phosphate or ammonium dihydrogen phosphate, and ensure the stability of the obtained granules in the rotary furnace, ensuring the sufficiency of the activation reaction.

[0029] In the carbonization and activation stage, the process of carbonization at 5℃ / min~10℃ / min to 400℃~700℃ for 1h~3h can effectively avoid the severe decomposition of fibrous raw materials, ensuring the structural stability of the carbonized product. Subsequently, switch to a mixed gas of CO2 / N2 or air / water vapor with a volume ratio of 1:1~5 for activation. This ratio can ensure the activation effect of CO2 or water vapor, and avoid excessive ablation through the protective effect of N2 or water vapor. The segmented activation design of 5℃ / min~10℃ / min gradient to 850℃→950℃→1000℃, with each segment holding for 15min~30min, can precisely control the development of pore structure, ensuring the production of high-quality heavy granular activated carbon with an iodine value of ≥1000mg / g, while avoiding the risk of pore structure collapse caused by single high temperature.

[0030] In some optional embodiments, the resulting heavy granular activated carbon can be subsequently modified according to needs:

[0031] Hydrophobic modification: impregnated with 5wt%~10wt% of amino propyl triethoxysilane (KH-550) ethanol solution, dried and cured at 120℃~180℃, to obtain irregular granular activated carbon with hydrophobic surface modification, suitable for VOCs adsorption and other fields requiring hydrophobic performance;

[0032] Catalytic modification: impregnated with 5%~30% soluble metal salt solution at a mass ratio of 1:3~10, and calcined at 300℃~500℃ for 1h~3h under nitrogen protection, to obtain modified granular activated carbon loaded with metal, suitable for catalytic oxidation desulfurization and denitrification reactions.

[0033] Optionally, in the subsequent modification process, the heavy granular activated carbon is crushed and sieved, and then impregnated in 5wt%~10wt% of amino propyl triethoxysilane (KH-550) ethanol solution. This concentration range can ensure sufficient surface modification effect, avoiding the problems of waste and pore blockage caused by excessive concentration. The temperature selection of 120℃~180℃ for drying and curing ensures the sufficient crosslinking and curing of amino propyl triethoxysilane (KH-550), preventing the destruction of the activated carbon structure caused by excessive temperature.

[0034] Another modification method is to impregnate the heavy granular activated carbon with 5%~30% soluble metal salt solution at a mass ratio of 1:3~10. This concentration range can ensure the sufficient loading of metal salt, and calcination at 300℃~500℃ for 1h~3h under nitrogen protection can achieve the decomposition and stabilization of metal salt, avoiding the sintering and deactivation of metal salt caused by excessive temperature. This embodiment can flexibly prepare activated carbon products with specific functions according to different application needs.

[0035] In some embodiments, the fibrous plant material is soaked in a 5-30% mass concentration citric acid solution for 1-3 hours before being cut into shreds.

[0036] In this embodiment, the citric acid solution pretreatment can effectively remove metal ions from the surface of the fibers to improve the purity of the activated carbon product, and partially hydrolyze the cellulose to improve the plasticity during subsequent hot pressing. The 5-30% mass concentration range ensures sufficient acidolysis effect while avoiding excessive damage to the fiber structure. The 1-3 hour soaking time ensures sufficient reaction while avoiding a decrease in fiber strength due to long-term treatment.

[0037] In some embodiments, the hot pressing pressure of the granulator is controlled at 10-50 MPa.

[0038] The 10-50 MPa pressure range ensures that the fibers and sodium humate are sufficiently bonded and formed into dense heavy particles, while ensuring smooth discharge of the granulated particles.

[0039] In some embodiments, the ethanol solution of aminopropyl triethoxysilane (KH-550) is immersed for 30-60 minutes, and then solid-liquid separation is performed using a filtration device.

[0040] The 30-60 minute immersion time ensures that the silane is sufficiently grafted to the surface of the activated carbon to form a stable hydrophobic layer. The use of a filtration device for solid-liquid separation can remove excess solution, preventing solvent residue from affecting the modification effect during drying, while maintaining an appropriate degree of moisture to facilitate subsequent solidification.

[0041] An inlet temperature of 180-200°C can quickly remove moisture, prevent metal salt migration and aggregation, and improve the uniformity of subsequent calcination.

[0042] In some embodiments, the fibrous plant material is at least one of hemp fiber, palm fiber, corn hair, cotton seed hulls, and coconut palm. These raw materials have abundant cellulose and natural pore structures, making them suitable for preparing high specific surface area activated carbon. Different combinations of raw materials can adjust the pore size distribution and surface chemical properties to meet different application requirements.

[0043] In some embodiments, the crushing and screening is performed using a pair of roller crushers with a roller spacing of 0.25-3.35 mm and a screen mesh size of 6-60 mesh. The pair of roller crushers can reduce excessive pulverization and avoid the impact of excessively fine powder on subsequent modification or application. The roller spacing of 0.25-3.35 mm and the 6-60 mesh screen can separate out activated carbon particles suitable for adsorption or catalysis.

[0044] In some embodiments, the heavy particles are pre-dried at 100-120°C for 1-3 hours before carbonization, with the moisture controlled below 10%. The pre-drying removes free water and prevents the particles from breaking due to rapid evaporation of water during carbonization. The temperature of 100-120°C avoids decomposition of heat-sensitive components, and the drying time of 1-3 hours ensures uniform reduction of moisture to below 10%, improving the stability of the carbonization process.

[0045] In a second aspect, the present embodiments provide an activated carbon made by the manufacturing method of the first aspect.

[0046] For ease of understanding, the following examples are provided:

[0047] A method for making modified granular activated carbon from fibrous plant raw materials, comprising the following steps:

[0048] (1) After the fibrous plant raw materials are cut into strands, the moisture is adjusted to 10-20%, and a small amount of sodium humate is added. The heated rolling of the granulator softens the lignin and sodium humate in the plant raw materials, and heavy granular materials with a diameter of 8-10 mm are produced.

[0049] (2) The obtained granular materials are carbonized in a rotary furnace and activated at high temperature in a water vapor and oxygen atmosphere to produce heavy granular activated carbon.

[0050] (3) The heavy granular activated carbon is sieved to a certain mesh size and can be used as irregular or regular granular activated carbon; after being crushed, it can be used as powdered activated carbon.

[0051] The fibrous plant raw materials in step (1) can be hemp fibers, palm fibers, corn hairs, cotton seed hulls, coconut husks, etc. The amount of sodium humate added is 5-15% of the dry weight of the plant raw materials.

[0052] In step (2), the carbonization temperature is 400-700°C, and the carbonization temperature is 400-700°C, with a holding time of 10-60 minutes. The activation temperature is 850-1000°C, and the activated carbon is activated to an iodine value ≥950 mg / g.

[0053] The present application has the following advantages:

[0054] (1) After the fibrous plant raw materials are cut into strands, a small amount of sodium humate is added, and the heated rolling during the granulation process reduces the frictional resistance, making the materials more easily extruded and formed in the granulator, producing heavy granules with high compressive strength, facilitating transportation of the production process conveying equipment, and meeting the anti-crushing requirements in carbonization and activation conditions. At the same time, sodium humate contains inorganic salt components (such as Ca 2+ , Mg 2 + Metal ion compounds) that can act as a skeleton to improve strength.

[0055] (2) The raw material is added with sodium humate and hot-pressed, the prepared granules are compact, and can be used as irregular or regular granular activated carbon or can be crushed and used as powder activated carbon.

[0056] (3) The added diammonium hydrogen phosphate or ammonium dihydrogen phosphate acts as a catalyst to promote the dehydrogenation and dehydration of cellulose / hemicellulose, inhibit the generation of tar, and reduce carbon loss; promote the formation of a cross-linked structure of the fibrous plant raw material, and enhance the mechanical strength; at the same time, the decomposition plays a role in etching the carbon layer, and after elution, a developed mesopore is left; and plays a role in increasing the ignition point of the activated carbon product. The added sodium humate acts as a binder and at the same time introduces oxygen-containing surface functional groups, produces basic groups (such as pyrones) to enhance the chemical adsorption of acidic gases (such as H2S, SO2, etc.). The two additives play a synergistic role to increase the strength and adsorption performance of the finished activated carbon.

[0057] The above technical solution cuts the fibrous plant raw material with low weight and difficult to process to 1mm-5mm, then fully mixes 5%-15% of sodium humate and 1%-3% of diammonium hydrogen phosphate or ammonium dihydrogen phosphate based on the dry weight of the fibrous plant raw material, and then hot-presses the mixture into 8mm-10mm heavy granules by a granulator at 130℃-190℃ to solve the problem that the fibrous raw material is easily carried away by air flow due to low density in industrial production. After the heavy granules are carbonized at 400℃-700℃ for 1h-3h at a temperature rising rate of 5℃ / min-10℃ / min in a rotary furnace, a mixed gas with a volume ratio of CO2 / N2 or air / water vapor of 1:1-5 is introduced, and the mixed gas is activated at 850℃→950℃→1000℃ with a holding time of 15min-30min in each section, to obtain high-performance heavy granular activated carbon with an iodine value of ≥1000mg / g. The defects that the fibrous plant raw material is easily carried into the tail gas system by air flow during the carbonization and activation of the traditional fibrous plant raw material in the rotary furnace are overcome, so that the light fibrous raw material can stably participate in industrial production.

[0058] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0059] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application, essentially or in other words, the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute all or part of the steps of the method of each embodiment of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0060] The above only describes some embodiments of the present application, and does not limit the protection scope of the present application. Any equivalent device or equivalent process transformation, or direct or indirect application in other related technical fields using the content of the present application specification.

Claims

1. A method for preparing modified granular activated carbon from fibrous plant materials, characterized in that: include: The fibrous plant material is cut into shreds to a length of 1 mm to 5 mm, the moisture content is adjusted to 10% to 20%, 5% to 15% of the dry weight of the fibrous plant material sodium humate and 1% to 3% of diammonium hydrogen phosphate or ammonium dihydrogen phosphate are added and mixed thoroughly, and then hot-pressed at 130° C. to 190° C. in a granulator to form heavy-weight granules of 8 mm to 10 mm. The heavy particles are placed in a rotary kiln, heated to 400°C to 700°C at a rate of 5°C / min to 10°C / min under a nitrogen atmosphere for carbonization for 1 hour to 3 hours, and then switched to a mixed gas of CO2 / N2 or air / water vapor with a volume ratio of 1:1 to 5, and heated to 850°C → 950°C → 1000°C at a gradient rate of 5°C / min to 10°C / min for staged activation, with each stage being kept for 15 minutes to 30 minutes, to obtain heavy granular activated carbon with an iodine value ≥1000 mg / g; The heavy granular activated carbon is crushed and sieved, and then immersed in an ethanol solution of 5 wt% to 10 wt% aminopropyltriethoxysilane, and dried and solidified at 120° C. to obtain irregular granular activated carbon with hydrophobic surface modification; Alternatively, heavy granular activated carbon is impregnated with 5% to 30% soluble metal salt solution at a mass ratio of 1:3 to 10, and after impregnation, solid-liquid separation is performed using a filtration device, and then calcined at 300° C. to 500° C. for 1 hour to 3 hours under nitrogen protection to obtain metal-loaded modified granular activated carbon.

2. The method for preparing modified granular activated carbon from fibrous plant materials according to claim 1, characterized in that: The soluble metal salt is at least one of copper nitrate, iron nitrate, silver nitrate, magnesium nitrate, manganese nitrate and potassium permanganate.

3. The method for preparing modified granular activated carbon from fibrous plant materials according to claim 1, characterized in that: The fibrous plant raw material is pretreated by soaking in a citric acid solution with a mass concentration of 5% to 30% for 1 hour to 3 hours before being shredded.

4. The method for preparing modified granular activated carbon from fibrous plant materials according to claim 1, characterized in that: The hot pressing pressure of the granulator is controlled at 10 MPa to 50 MPa.

5. The method for preparing modified granular activated carbon from fibrous plant materials according to claim 1, characterized in that: The immersion time of the aminopropyltriethoxysilane ethanol solution is 30 minutes to 60 minutes.

6. The method for preparing modified granular activated carbon from fibrous plant materials according to claim 1, characterized in that: The fibrous plant raw material is at least one of hemp fiber, palm fiber, corn hair, cottonseed hull, and coconut palm.

7. The method for preparing modified granular activated carbon from fibrous plant materials according to claim 1, characterized in that: The crushing and screening adopts a double-roll crusher, the roller spacing is adjusted to 0.25mm-3.35mm, and the mesh number of the screen is 6-60 meshes.

8. The method for preparing modified granular activated carbon from fibrous plant materials according to claim 1, characterized in that: The heavy particles are pre-dried at 100° C. to 120° C. for 1 to 3 hours before carbonization, and the moisture content is controlled below 10%.

9. An activated carbon, characterized in that The activated carbon is prepared by the preparation method according to any one of claims 1 to 9.