Physical method for preparing walnut shell activated carbon

Abstract

The invention relates to the field of adsorption material preparation, in particular to a physical method for preparing walnut shell activated carbon. Comprising the following steps: (1) carbonizing a walnut shell sample in a rotary furnace, and starting to charge for carbonizing when the temperature of the rotary furnace is increased to a set temperature; (2) sieving the walnut shell carbonized material through a 4-8-mesh sieve; (3) adding the screened walnut shell carbonized material into a microwave activation furnace for activation to obtain an activated material; (4) crushing the obtained activated material, and screening activated carbon with specified granularity to obtain walnut shell activated carbon; the preparation method is beneficial to formation of an activated carbon pore structure, pores in the activated carbon are richer, the technical index of the activated carbon is improved, and the prepared activated carbon is high in specific surface area and has a developed pore structure; the microwave activation can enable the carbonized material to reach a high-temperature activation condition in a short time, and is low in energy consumption, simple to operate, small in environmental pollution and uniform in heating.

Description

Technical Field

[0001] This invention relates to the field of adsorption material preparation, specifically to a physical method for preparing walnut shell activated carbon. Background Technology

[0002] Activated carbon is an excellent adsorbent. It is manufactured from raw materials such as charcoal, bamboo charcoal, various fruit shells, and high-quality coal through a series of physical and chemical processes including crushing, sieving, catalyst activation, rinsing, drying, and screening. It possesses both physical and chemical adsorption properties, selectively adsorbing various substances in the gas and liquid phases to achieve purposes such as decolorization, purification, disinfection, deodorization, and decontamination. Activated carbon is widely used in various aspects of industrial and agricultural production, such as alkali-free deodorization (refining and desulfurization) in the petrochemical industry, ethylene desalination (refining filler), catalyst carriers (palladium, platinum, rhodium, etc.), water purification, and wastewater treatment; power plant water treatment and protection in the power industry; chemical catalysts and carriers, gas purification, solvent recovery, and decolorization and refining of oils and fats in the chemical industry; treatment and gas purification of beverages, wines, monosodium glutamate mother liquor, and harmful gases in the food industry; and related industries such as cigarette filters, wood flooring moisture-proofing and odor absorption, automotive gasoline evaporation pollution control, and the preparation of various impregnating agents. Walnut shell activated carbon offers good hygiene and safety, making it a better solution for applications where hygiene and safety are concerns regarding the use of coal-based activated carbon. As a type of fruit shell activated carbon with a high specific surface area, walnut shell activated carbon features excellent adsorption performance, a large specific surface area, and well-developed pores. Besides the food and beverage industry, walnut shell activated carbon is also widely used in drinking water and water purification.

[0003] Walnut shell activated carbon contains no metal ions and can replace coal and other raw materials in the food and pharmaceutical industries. Coal is a non-renewable resource, and the raw coal needed for activated carbon production is limited to a portion of high-quality refined coal. Walnut shells, on the other hand, are a renewable resource, and my country, as a major walnut producer, has abundant walnut shell resources. Using walnut shells as raw material, through carbonization, screening, activation, crushing, and screening processes, the prepared walnut shell activated carbon not only has a relatively simple preparation process but also features a large specific surface area and a well-developed pore structure. Furthermore, the raw materials used in this technology are abundant in nature.

[0004] Publication number CN106904611B, "A method for preparing walnut shell activated carbon," describes a process where walnut shells are cleaned, sieved, and graded before being stored in a raw material storage tank. After carbonization and activation, a second impurity removal process is performed, followed by crushing and packaging to obtain walnut shell activated carbon. However, this method requires the removal of the heartwood (a type of wood embedded in the walnut shell) only after the final sieve, increasing energy consumption in intermediate processes. Furthermore, the high carbonization temperature in this method damages the porous structure formed within the walnut shell, affecting its strength and other technical properties.

[0005] The publication number CN106348295A, "Preparation Method of Walnut Shell Activated Carbon," describes a method for preparing activated carbon from walnut shells. The method involves washing, drying, and crushing walnut shells, followed by carbonization to obtain carbonized material. KOH is then mixed with the carbonized material, deionized water is added, and the mixture is impregnated at room temperature. The mixture is then activated under an inert gas atmosphere, and after cooling, an activated material is obtained. This activated material is then soaked in hydrochloric acid, filtered, washed with deionized water, and dried to obtain walnut shell activated carbon. However, this method requires the use of strong acids and bases such as KOH and hydrochloric acid, which is not environmentally friendly or safe for human use, and is also costly.

[0006] It is evident that existing methods for activating walnut shells with activated carbon suffer from problems such as high energy consumption, complex operation, and environmental pollution. Summary of the Invention

[0007] This invention addresses the problems of high energy consumption, complex operation, and environmental pollution associated with existing walnut shell activated carbon activation methods by providing a physical method for preparing walnut shell activated carbon. This invention employs microwave activation, which can rapidly bring the carbonized material to high-temperature activation conditions, resulting in the decomposition of organic matter and activation reactions between high-temperature water molecules, thus endowing it with adsorption properties. Microwave activation, with its high efficiency and environmental friendliness, and its unique heating method and rapid response, solves the problems of high energy consumption, complex operation, and environmental pollution associated with traditional activated carbon activation methods.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing walnut shell activated carbon by physical method, comprising the following steps: (1) Carbonize the walnut shell sample in a rotary kiln. Set the feed temperature of the rotary kiln to 200℃-300℃, the middle temperature to 400℃-500℃, and the discharge temperature to 500℃-600℃. When the rotary kiln temperature reaches the set temperature, start feeding for carbonization. (2) Pass the walnut shell carbonized material through a 4-8 mesh sieve. The purpose is to remove impurities and walnut heartwood carbonization from the walnut shell carbonized material, thereby reducing the impact on the performance of the walnut shell activated carbon. (3) The sieved walnut shell carbonized material is added to a microwave activation furnace for activation to obtain activated material. The microwave activation method has low energy consumption, simple operation, low environmental pollution and uniform heating.

[0009] (4) The obtained activated material is crushed and activated carbon of a specified particle size is sieved to obtain walnut shell activated carbon.

[0010] As a further limitation of the technical solution of the present invention, in step (3), after the walnut shell carbonized material enters the microwave activation furnace, it is heated to 850℃-900℃ at a heating rate of 20℃ / min-30℃ / min, and water vapor is introduced at a rate of 10ml / min-15ml / min. After activation for 40min-70min, the water vapor is turned off and the temperature is lowered to room temperature to obtain the activated material.

[0011] As a further limitation of the technical solution of the present invention, the motor frequency in step (1) is 15-30HZ.

[0012] As a further limitation of the technical solution of the present invention, the particle size of the walnut shell activated carbon in step (4) is 4-50 mesh.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention can save costs by introducing water and air during activation. At high temperature, water vaporizes into water vapor in activated carbon. The water vapor and air slowly overflow as activating agents, which is conducive to the formation of the pore structure of activated carbon, making the internal pores of activated carbon more abundant, improving the technical indicators of activated carbon, and the prepared activated carbon has a high specific surface area and a well-developed pore structure.

[0014] 2. The walnut shell raw material used is extremely abundant in nature and can partially replace the current activated carbon material mainly based on raw coal. Renewable resources replace non-renewable resources like raw coal. The carbon dioxide emitted during the walnut shell conversion process is equal to the amount absorbed during growth, and the amount of carbon dioxide released into the atmosphere is almost zero. This invention allows for independent control of raw materials and can alleviate the environmental pollution caused by the large-scale burning of waste walnut shells, achieving high-value utilization of biomass.

[0015] 3. Screening to remove impurities such as peach wood during the intermediate preparation process can reduce the impact during activation and reduce energy consumption.

[0016] 4. Microwave activation can solve problems such as high energy consumption, complex operation, and environmental pollution, and enables the organic matter inside activated carbon to react evenly, resulting in a more uniform distribution of pore structure. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments. Example 1

[0018] Walnut shells were placed in a rotary kiln with an inlet temperature of 240℃, a middle section temperature of 400℃, and an outlet temperature of 520℃. The motor frequency was 18Hz. The carbonized material was quickly passed through a 5-mesh sieve. The sieved walnut shell carbonized material was then placed in a microwave activation furnace and heated to 850℃ at a heating rate of 25℃ / min. Steam was introduced at a rate of 12ml / min and activated for 50 minutes. After activation, the steam was turned off, and the material was cooled to room temperature to obtain activated material. The activated material was crushed and sieved to a particle size of 4-50 mesh to obtain walnut shell activated carbon sample 1. Example 2

[0019] Walnut shells were placed in a rotary kiln with an inlet temperature of 270℃, a middle section temperature of 460℃, and an outlet temperature of 580℃. The motor frequency was 22Hz. The carbonized material was quickly passed through a 7-mesh sieve. The sieved walnut shell carbonized material was then placed in a microwave activation furnace and heated to 900℃ at a heating rate of 28℃ / min. Steam was introduced at a rate of 14ml / min and activated for 65 minutes. After activation, the steam was turned off, and the material was cooled to room temperature to obtain activated material. The activated material was crushed and sieved to a particle size of 4-50 mesh to obtain walnut shell activated carbon sample 2.

[0020] The technical specifications of the activated carbon obtained in Examples 1-2 are shown in Table 1.

[0021] Table 1 Technical Specifications of Activated Carbon

[0022] The activated carbon prepared by the method of this invention has good technical indicators and can be used in water treatment, gas adsorption and other fields.

Claims

1. A method for preparing walnut shell activated carbon using physical methods, characterized in that, Includes the following steps: (1) Carbonize the walnut shell sample in a rotary kiln. Set the feed temperature of the rotary kiln to 200℃-300℃, the middle temperature to 400℃-500℃, and the discharge temperature to 500℃-600℃. When the rotary kiln temperature reaches the set temperature, start feeding for carbonization. (2) Pass the carbonized walnut shell material through a 4-8 mesh sieve; (3) Add the sieved walnut shell carbonized material to a microwave activation furnace for activation to obtain activated material; (4) The obtained activated material is crushed and activated carbon of a specified particle size is sieved to obtain walnut shell activated carbon.

2. The method for preparing walnut shell activated carbon by physical method according to claim 1, characterized in that, In step (3), the walnut shell carbonized material is heated to 850℃-900℃ at a heating rate of 20℃ / min-30℃ / min after entering the microwave activation furnace. Water vapor is introduced at a rate of 10ml / min-15ml / min. After activation for 40min-70min, the water vapor is turned off and the temperature is lowered to room temperature to obtain the activated material.

3. The method for preparing walnut shell activated carbon by physical method according to claim 1, characterized in that, In step (1), the motor frequency is 15-30 Hz.

4. The method for preparing physical activated carbon from walnut shells according to claim 1, characterized in that, In step (4), the particle size of the walnut shell activated carbon is 4-50 mesh.

Images