CN102701200A - Method for preparing active carbon from municipal sludge by two-step thermal decomposition - Google Patents

Abstract

The invention discloses a method for preparing activated carbon by two-step pyrolysis of urban sludge, which belongs to the technical field of activated carbon. The dried municipal sludge is pyrolyzed and carbonized at 400-550°C for 30-90 minutes, and then 2-4mol/l active agent is added to the carbonized sample for impregnation and activation treatment, and then pyrolyzed at 450-600°C Activated sludge activated carbon can be obtained. The present invention adopts a two-step pyrolysis method to carbonize and activate the sludge, and activates the activator on the carbonized sludge, which greatly reduces the demand for the activator, and at the same time provides a way for the sludge to be used as a resource, and realizes the goal of waste treatment. Harmless, reduced, resourceful.

Description

A method for preparing activated carbon by two-step pyrolysis of municipal sludge

technical field

The invention relates to a method for preparing sludge activated carbon using residual sludge from urban sewage treatment plants as the main raw material, which is suitable for the removal of various toxic gases and COD and colored substances in sewage, and belongs to the technical field of activated carbon.

Background technique

In recent years, with the development of urban sewage treatment industry, the output of urban sludge has increased sharply. The sludge output is large and its composition is complex. If it is not properly treated, it will cause serious environmental pollution. The treatment and disposal of sludge is an urgent problem to be solved, and the utilization of sludge as a resource has attracted more and more attention. Researchers at home and abroad have used the characteristics of a large amount of organic matter in sludge to prepare sludge into carbon-containing adsorbents. At present, the methods of preparing activated carbon from sludge mainly include physical activation method, chemical activation method and microwave activation method. Among them, the chemical activation method is widely used because of the relatively high quality of activated carbon produced. The chemical activation method mainly uses a one-stage pyrolysis activation method to prepare activated carbon, directly impregnates the dried sludge with an activator, and performs pyrolysis activation to prepare activated carbon. Therefore, the research and development of a method for preparing sludge activated carbon with low activator demand and high adsorption capacity has guiding significance for the large-scale industrial utilization of activated carbon prepared from sludge.

Contents of the invention

The purpose of the present invention is to provide a two-step pyrolysis sludge activated carbon preparation process using residual sludge from urban sewage treatment plants as the main raw material. The obtained sludge activated carbon is suitable for removing various toxic gases and COD and colored substances in sewage.

A method for preparing sludge-based activated carbon by urban two-step pyrolysis provided by the present invention is characterized in that it comprises the following steps:

1) Dry the sludge from the urban sewage treatment plant to a water content below 10%, grind and sieve, and retain the sludge particles with a particle size range of 20 mesh to 100 mesh;

2) Heating the sludge particles at a heating rate of 10-20°C/min to 400-550°C for carbonization for 30-90min, using nitrogen as the protective gas during the carbonization process;

3) Mix the carbide obtained in step 2) with 2-4mol/l activator solution at a mass ratio of 1:1-1:4, soak at room temperature for 12-24h, and then dry to constant weight to obtain an activated sample;

4) Heat the activated sample to 450-600°C at a heating rate of 10-20°C/min, after pyrolysis and activation for 30-90min, cool in nitrogen, and then wash with hydrochloric acid and distilled water at 70-80°C to neutral , dried to obtain sludge activated carbon.

The activator is preferably one of ZnCl ₂ , H ₃ PO ₄ , and KOH.

The advantage of the present invention is that the excess sludge of the sewage treatment plant is recycled, and the carbonized sample is activated by an activator, which saves the use of an activator ^. In terms of its adsorption performance, the yield of activated carbon prepared by two-stage pyrolysis is not much different from that of one-stage pyrolysis. Activated carbon is generated from excess sludge, which makes waste sludge a resource and greatly solves the problem of the outlet of excess sludge. Therefore, the adsorbent has the characteristics of simple preparation and low cost.

The present invention will be further described below in combination with specific embodiments.

Detailed ways

The sludge used in the following examples is the residual sludge from the secondary settling tank of the sewage treatment plant.

Example 1

1) Dry the sludge until the moisture content is below 10%, grind and sieve, and retain the sludge particles with a particle size range of 20-100 mesh;

2) The sludge particles are heated up to 400°C for 60 minutes at a heating rate of 10°C/min and carbonized for 60 minutes. Nitrogen is used as the protective gas during the carbonization process;

3) Mix the carbonized sample with 4mol/l zinc chloride solution at a mass ratio of 1:2, soak at room temperature for 12 hours, and then dry to constant weight to obtain an activated sample;

4) The activated sample was heated to 450°C at a heating rate of 10°C/min, and after pyrolysis and activation for 90 minutes, it was cooled in nitrogen, then washed with hydrochloric acid and distilled water at 70°C, and dried to obtain sludge activated carbon;

The specific surface area of sludge activated carbon is 425m ² /g, and the yield is 37.02%.

Example 2

1) Dry the sludge until the moisture content is below 10%, grind and sieve, and retain the sludge particles with a particle size range of 20-100 mesh or less;

2) The sludge particles were heated to 450°C for 90 minutes at a heating rate of 15°C/min and carbonized for 90 minutes. Nitrogen was used as the protective gas during the carbonization process;

3) Mix the carbonized sample with 3mol/l zinc chloride solution at a mass ratio of 1:3, soak at room temperature for 24 hours, and then dry to constant weight to obtain activated sludge particles;

3) The activated sludge particles are heated up to 500°C at a heating rate of 15°C/min, and after pyrolysis and activation for 30 minutes, they are cooled in nitrogen, then washed with hydrochloric acid and distilled water at 80°C, and dried to obtain sludge activated carbon. ;

The specific surface area of sludge activated carbon is 485m ² /g, and the yield is 40.12%.

Example 3

1) Dry the sludge until the moisture content is below 10%, grind and sieve, and retain the sludge particles with a particle size range of 20-100 mesh or less;

2) The sludge particles are heated up to 500°C for 30 minutes at a heating rate of 20°C/min and carbonized for 30 minutes. Nitrogen is used as the protective gas during the carbonization process;

3) Mix the carbonized sample with 2mol/l zinc chloride solution at a mass ratio of 1:1, soak at room temperature for 24 hours, and then dry to constant weight to obtain an activated sample;

4) The activated sample was heated to 550°C at a heating rate of 20°C/min, and after pyrolysis and activation for 60 minutes, it was cooled in nitrogen, then washed with hydrochloric acid and distilled water at 75°C, and dried to obtain sludge activated carbon;

The specific surface area of sludge activated carbon is 470.64m ² /g, and the yield is 37.26%.

Example 4

1) Dry the sludge until the moisture content is below 10%, grind and sieve, and retain the sludge particles with a particle size range of 20-100 mesh or less;

2) The sludge particles are heated up to 550°C for 30 minutes at a heating rate of 10°C/min and carbonized for 30 minutes. Nitrogen is used as the protective gas during the carbonization process;

3) Mix the carbonized sample with 4mol/l zinc chloride solution at a mass ratio of 1:4, soak at room temperature for 24 hours, and then dry to constant weight to obtain an activated sample;

4) The activated sample was heated up to 600°C at a heating rate of 10°C/min. After pyrolysis and activation for 60 minutes, it was cooled in nitrogen, then washed with hydrochloric acid and distilled water at 70°C, and dried to obtain sludge activated carbon;

The specific surface area of sludge activated carbon is 470.64m ² /g, and the yield is 37.26%.

Comparative example 1

1) Dry the sludge until the moisture content is below 10%, grind and sieve, and retain the sludge particles with a particle size range of 20-100 mesh or less;

2) Mix the sludge granule sample with 4mol/l zinc chloride solution at a mass ratio of 1:4, soak at room temperature for 24 hours, and then dry to constant weight to obtain activated sludge granules;

3) The activated sludge particles are heated up to 600°C at a heating rate of 10°C/min, and after pyrolysis and activation for 60 minutes, they are cooled in nitrogen, then washed with hydrochloric acid and distilled water at 70°C, and dried to obtain sludge activated carbon. ;

The specific surface area of sludge activated carbon is 251m ² /g, and the yield is 39.10%.

It can be seen from the above comparative examples and examples that the present invention saves the use of activators, and the specific surface area of the obtained activated carbon is much larger than that of the one-step method.

Claims (2)

1. A method for preparing gac by municipal sludge two-step pyrolysis, is characterized in that, comprises the following steps: 1) Dry the sludge from the urban sewage treatment plant to a water content below 10%, grind and sieve, and retain the sludge particles with a particle size range of 20 mesh to 100 mesh; 2) Heat the sludge particles at a heating rate of 10-20°C/min to 400-550°C for carbonization for 30-90min, and use nitrogen as the protective gas during the carbonization process; 3) Mix the carbide obtained in step 2) with 2-4mol/l activator solution at a mass ratio of 1:1-1:4, soak at room temperature for 12-24h, and then dry to constant weight to obtain an activated sample; 4) Heat the activated sample to 450-600°C at a heating rate of 10-20°C/min, after pyrolysis and activation for 30-90min, cool in nitrogen, and then wash with hydrochloric acid and distilled water at 70-80°C to neutral , dried to obtain sludge activated carbon. 2. The method according to claim 1, characterized in that the activator is one of _ZnCl2 , _H3PO4 , KOH _.