Method for preparing activated carbon from traditional Chinese medicine residues

Abstract

The invention discloses a method for preparing activated carbon from traditional Chinese medicine residues, which comprises the following steps: (1) pretreatment: carrying out crushing, screening and ash content treatment on the traditional Chinese medicine residues, and carrying out pre-drying and dehydration, (2) electromagnetic cracking and carbonization, and (3) activation. And (4) post-treatment: carrying out acid pickling, water washing and vacuum drying. Electromagnetic cracking carbonization is used for replacing traditional carbonization, waste heat of electromagnetic cracking is adopted for pre-drying, the overall energy consumption is greatly reduced, and the carbonization time is shortened; the KOH low-pressure activation can be used for obviously reducing the metal residue risk while keeping the high adsorption performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of activated carbon preparation, in particular to a method for preparing activated carbon by using traditional Chinese medicine residues. BACKGROUND

[0002] Activated carbon is a kind of porous adsorbent, which is widely used in petroleum, chemical industry, food, medicine, light industry, environmental protection and other fields. The raw materials for manufacturing activated carbon are various, including wood, coal, fruit shells, etc. Traditional Chinese medicine residues are solid wastes generated in the production and processing process of traditional Chinese medicine resources, which are generally wet materials and can easily rot if not treated for a long time, causing great pollution to the environment. The current treatment method of traditional Chinese medicine residues is rough, which generally adopts the methods of stacking, landfilling and incineration, polluting the environment and occupying land. However, traditional Chinese medicine residues are rich in nutrients and contain cellulose, protein and other organic matter and some inorganic matter, which are a kind of biological resources that have not been fully utilized and have broad development prospects.

[0003] The method for preparing activated carbon by using traditional Chinese medicine residues can not only solve the problem of traditional Chinese medicine residue treatment, but also solve the problem of high cost of raw material source of activated carbon. However, the traditional method for preparing activated carbon by using traditional Chinese medicine residues usually needs pre-drying treatment, and the high-temperature carbonization time is long, which needs to be impregnated by zinc chloride, phosphoric acid and the like, resulting in high energy consumption, easy generation of waste gas pollution, low thermal efficiency, easy residual of chemical activator in activated carbon, high risk of heavy metal precipitation, and therefore it is necessary to improve. SUMMARY

[0004] The present application aims to provide a method for preparing activated carbon by using traditional Chinese medicine residues to solve the problems in the background art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a method for preparing activated carbon by using traditional Chinese medicine residues, comprising the following steps:

[0006] (1) The traditional Chinese medicine residues are crushed, sieved and treated with ash, the particle size of the crushed and sieved traditional Chinese medicine residues is 3-5 mm, and the ash content is <4%; (2) the traditional Chinese medicine residues are pre-dried and dehydrated by using electromagnetic field heating, so that the water content of the traditional Chinese medicine residues is ≦15%;

[0007] (2) The pre-treated traditional Chinese medicine residues are put into an electromagnetic cracking reactor for carbonization, nitrogen is filled into the electromagnetic cracking reactor, the carbonization temperature is 390-410℃, the heating rate is 10-15℃ / min, and the holding time is 40-50min;

[0008] (Three) activation: after carbonization, the traditional Chinese medicine residue is put into the KOH solution for immersion, the immersion time is 2-4h, the concentration of KOH solution is 8-10%, then the low-pressure reactor is activated, the low-pressure reactor is filled with nitrogen, the activation pressure is 0.8-1.5MPa, the activation temperature is 380-420℃, and the holding time is 60-90min;

[0009] (Four) post-processing: using 5-6% dilute nitric acid at 80-85℃ temperature washing, making ash content <2%, and washing to neutral, then vacuum drying at 100-105℃ for 4-5h, making moisture content <3%.

[0010] As a preferred embodiment of the present application, the ash treatment in step (one) is soaked in 5-6% dilute hydrochloric acid for 30-40min.

[0011] As a preferred embodiment of the present application, the temperature of electromagnetic field heating in step (one) is 50-80℃, and the frequency is 1-3kHz.

[0012] As a preferred embodiment of the present application, the pre-drying dehydration in step (one) uses the waste heat of electromagnetic cracking in step (two).

[0013] As a preferred embodiment of the present application, the frequency of electromagnetic field in step (two) is 15-25kHz.

[0014] As a preferred embodiment of the present application, the nitrogen flow rate in step (two) and step (three) is 1-2L / min, and the oxygen content is maintained <0.5%.

[0015] Compared with the prior art, the present application has the following advantages: the present application uses electromagnetic cracking carbonization instead of traditional carbonization, and the pre-drying uses the waste heat of electromagnetic cracking, so that the overall energy consumption is greatly reduced, and the carbonization time is shortened; the KOH low-pressure activation retains high adsorption performance while significantly reducing the risk of metal residue. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0017] Embodiment 1: a method for preparing activated carbon from traditional Chinese medicine residue, comprising the following steps:

[0018] (I) Pretreatment: (1) The traditional Chinese medicine residues are crushed, screened and ash treated, the particle size of the crushed and screened traditional Chinese medicine residues is 5 mm, the ash treatment is soaking in 6% dilute hydrochloric acid for 30 min, and the ash content is controlled to be 3%; (2) The traditional Chinese medicine residues are pre-dried and dehydrated by electromagnetic field heating, the water content of the traditional Chinese medicine residues is 15%, the temperature of the electromagnetic field heating is 80°C, the frequency is 3 kHz, and the pre-drying and dehydration uses the waste heat of the electromagnetic cracking in step (II).

[0019] (II) Electromagnetic cracking and carbonization: The pretreated traditional Chinese medicine residues are put into an electromagnetic cracking reactor for carbonization, the frequency of the electromagnetic field in the electromagnetic cracking reactor is 15 kHz, nitrogen is filled into the electromagnetic cracking reactor, the flow rate of the nitrogen is 2 L / min, the oxygen content in the electromagnetic cracking reactor is maintained to be 0.4%, the carbonization temperature is 390°C, the temperature rising speed is 15°C / min, and the temperature is kept for 50 min.

[0020] (III) Activation: The carbonized traditional Chinese medicine residues are immersed in a KOH solution for 4 h, the concentration of the KOH solution is 8%, and then the traditional Chinese medicine residues are activated in a low-pressure reactor, nitrogen is filled into the low-pressure reactor, the flow rate of the nitrogen is 2 L / min, the activation pressure is 1.5 MPa, the activation temperature is 420°C, and the temperature is kept for 60 min.

[0021] (IV) Post-treatment: The traditional Chinese medicine residues are washed with 6% dilute nitric acid at a temperature of 85°C to make the ash content to be 1%, and then washed with water until neutral, and then vacuum dried at 105°C for 5 h to make the water content to be 2%.

[0022] Example 2: A method for preparing activated carbon from traditional Chinese medicine residues, comprising the following steps:

[0023] (I) Pretreatment: (1) The traditional Chinese medicine residues are crushed, screened and ash treated, the particle size of the crushed and screened traditional Chinese medicine residues is 3 mm, the ash treatment is soaking in 5% dilute hydrochloric acid for 40 min, and the ash content is controlled to be 2%; (2) The traditional Chinese medicine residues are pre-dried and dehydrated by electromagnetic field heating, the water content of the traditional Chinese medicine residues is 13%, the temperature of the electromagnetic field heating is 50°C, the frequency is 1 kHz, and the pre-drying and dehydration uses the waste heat of the electromagnetic cracking in step (II).

[0024] (II) Electromagnetic cracking and carbonization: The pretreated traditional Chinese medicine residues are put into an electromagnetic cracking reactor for carbonization, the frequency of the electromagnetic field in the electromagnetic cracking reactor is 25 kHz, nitrogen is filled into the electromagnetic cracking reactor, the flow rate of the nitrogen is 1 L / min, the oxygen content in the electromagnetic cracking reactor is maintained to be 0.3%, the carbonization temperature is 410°C, the temperature rising speed is 10°C / min, and the temperature is kept for 40 min.

[0025] (Three) Activation: After carbonization, the traditional Chinese medicine residue is immersed in KOH solution, the immersion time is 4h, the concentration of KOH solution is 10%, and then activated in a low-pressure reactor, the low-pressure reactor is filled with nitrogen, the nitrogen flow rate is 1L / min, the activation pressure is 0.8MPa, the activation temperature is 380℃, and the holding time is 90min;

[0026] (Four) Post-processing: Wash with 5% dilute nitric acid at 80℃ to make the ash content 1.5%, and then wash with water to neutral, and then dry at 100℃ under vacuum for 4h to make the moisture content 1%.

[0027] Example 3: A method for preparing activated carbon from traditional Chinese medicine residue, comprising the following steps:

[0028] (One) Pretreatment: (1) The traditional Chinese medicine residue is crushed, sieved and ash treated, the particle size of the crushed and sieved traditional Chinese medicine residue is 4mm, the ash treatment is to soak in 5.5% dilute hydrochloric acid for 35min to control the ash content to 3.5%; (2) Pre-drying and dewatering using electromagnetic field heating to make the moisture content of the traditional Chinese medicine residue 14%, the electromagnetic field heating temperature is 70℃, the frequency is 2kHz, and the pre-drying and dewatering uses the waste heat of the electromagnetic cracking in step (two).

[0029] (Two) Electromagnetic cracking carbonization: The pretreated traditional Chinese medicine residue is put into an electromagnetic cracking reactor for carbonization, the electromagnetic field frequency in the electromagnetic cracking reactor is 20kHz, the electromagnetic cracking reactor is filled with nitrogen, the nitrogen flow rate is 1.5L / min, the oxygen content in the electromagnetic cracking reactor is maintained at 0.2%, the carbonization temperature is 400℃, the heating rate is 13℃ / min, and the holding time is 45min;

[0030] (Three) Activation: After carbonization, the traditional Chinese medicine residue is immersed in KOH solution, the immersion time is 3h, the concentration of KOH solution is 9%, and then activated in a low-pressure reactor, the low-pressure reactor is filled with nitrogen, the nitrogen flow rate is 1.5L / min, the activation pressure is 1MPa, the activation temperature is 400℃, and the holding time is 80min;

[0031] (Four) Post-processing: Wash with 5.5% dilute nitric acid at 83℃ to make the ash content 1.8%, and then wash with water to neutral, and then dry at 103℃ under vacuum for 4.5h to make the moisture content 2.5%.

[0032] In the above embodiments, the residual heat of electromagnetic cracking is usually 80-90℃, which is more than 40% energy saving than traditional electric heating. The energy consumption of traditional hot air drying for pre-drying is usually 1.5-1.8kwh / kg, the energy consumption of electromagnetic field pre-drying of the present application is 0.8-1kwh / kg, the energy consumption of low-pressure activation of the present application is 1.1kwh / kg, and the energy consumption of traditional activation is 1.8-2.1kwh / kg. The total energy consumption of the present application is about 34% lower than that of the traditional method. The activated carbon prepared in the above embodiments is detected for the following parameters, and the data are as follows.

[0033] Index This application Conventional method Specific surface area 1100-1300 m 2 / g]] 800-1000 m 2 / g]] Proportion of mesopores 40-45% 25-35% Iodine adsorption value 900-1000 mg / g 800-840 mg / g Chemical residue K + <60ppm]]> Zn 2+ >300 ppm

[0034] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present application, which are used to illustrate the technical solutions of the present application, but not to limit them. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some technical features thereof, within the technical scope disclosed by the present application. Such modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing activated carbon using Chinese medicinal herb residue, characterized in that, Includes the following steps: (a) Preprocessing (1) The Chinese medicine residue is crushed, screened, and ash-treated. The particle size of the crushed and screened residue is 3-5 mm, and the ash content is <4%. (2) The residue is pre-dried and dehydrated using electromagnetic field heating so that the moisture content of the Chinese medicine residue is ≤15%. (ii) Electromagnetic pyrolysis carbonization The pretreated Chinese medicine residue is fed into an electromagnetic pyrolysis reactor for carbonization. Nitrogen gas is introduced into the electromagnetic pyrolysis reactor. The carbonization temperature is 390-410℃, the heating rate is 10-15℃ / min, and the holding time is 40-50min. (III) Activation The carbonized Chinese herbal medicine residue is immersed in KOH solution for 2-4 hours with a KOH solution concentration of 8-10%. Then it is activated in a low-pressure reactor, which is filled with nitrogen gas at an activation pressure of 0.8-1.5 MPa and an activation temperature of 380-420℃ for 60-90 minutes. (iv) Post-processing Wash with 5-6% dilute nitric acid at 80-85℃ to reduce ash content to <2%, then wash with water until neutral, and finally vacuum dry at 100-105℃ for 4-5 hours to reduce moisture content to <3%.

2. The method according to claim 1, characterized in that: The ash treatment in step (a) involves soaking the food in 5-6% dilute hydrochloric acid for 30-40 minutes.

3. The method according to claim 1, characterized in that: The electromagnetic field heating in step (i) is at a temperature of 50-80℃ and a frequency of 1-3kHz.

4. The method according to claim 1, characterized in that: The pre-drying and dehydration in step (i) utilizes the residual heat from the electromagnetic pyrolysis in step (ii).

5. The method according to claim 1, characterized in that: The electromagnetic field frequency in step (ii) is 15-25kHz.

6. The method according to claim 1, characterized in that: In steps (ii) and (iii), the nitrogen flow rate is 1-2 L / min to maintain an oxygen content of <0.5%.