Method for regenerating activated carbon from waste tire carbon black

Abstract

The present invention relates to the field of waste tire treatment, and mainly relates to a method for regenerating activated carbon from waste tire carbon black, comprising the following steps: (1) pyrolysis and pretreatment; (2) granulation; and (3) activation. The inventor has found through research that the ash content and volatile content of carbon black obtained by tire pyrolysis are between 15% and 20% and 5% and 9%, respectively. The present invention firstly performs acid washing and alkali washing on the pyrolysis carbon black to remove the ash content and volatile content in the carbon black, and then granulates and activates, which greatly improves the iodine value of the regenerated activated carbon, that is, improves the adsorption performance of the regenerated activated carbon; granulating the coarse carbon black can reduce the carbon loss in the high-temperature activation process, and greatly improves the utilization rate of waste tires.

Description

Technical Field

[0001] The invention relates to the field of waste tire treatment, and mainly relates to a method for regenerating activated carbon from waste tire carbon black. Background Art

[0002] With the rapid development of the economy, the popularity of automobiles has been promoted, resulting in an increasing amount of tires, resulting in a large accumulation of waste tires and serious environmental pollution. The recycling of waste tires has become a major issue in the world today. In the future, the recycling of waste tires in my country will be a sunrise industry. Common ways to recycle waste tires mainly include: incineration, thermal cracking, production of rubber powder and particles, etc. For example, it can be used to produce dock fish reefs, rubber products and runways, and can also be used to make waterproof materials, or can be added to asphalt to make asphalt more stable. Usually, waste tires are used to prepare carbon black products by thermal cracking the waste tires, and the residues from the thermal cracking are used as carbon black products; however, such carbon black products have a high degree of environmental pollution, high ash content, poor dispersibility, poor compatibility with rubber, low selling price, poor economic benefits, and weak market competitiveness.

[0003] How to make pyrolysis carbon black be applied in more aspects and increase its added value is an urgent problem that needs to be solved at present. Carbon black is relatively cheap, but the fixed carbon on a dry basis can reach more than 75%, and the carbon content is high. It can be considered to be made into other high-value-added products. As we all know, the activated carbon market is good. Consider granulation to make granular activated carbon, and obtain finished activated carbon after activation to increase tire recycling profits. Most researchers consider studying the preparation of activated carbon. Due to its special porous structure, large specific surface area, strong adsorption capacity, it has a wide range of uses. It is mainly used for air purification, urban sewage treatment, deep treatment of drinking water, impurity removal of printing inks, product decolorization, etc. Activated carbon is now in short supply and the market price is very high.

[0004] However, in the prior art, the treatment of tire pyrolysis carbon black is mostly to directly activate it, and the iodine value of the obtained regenerated activated carbon can never meet the activity requirements of activated carbon, thus restricting the progress of waste tire treatment. Summary of the invention

[0005] The purpose of the present invention is to provide a method for regenerating activated carbon from waste tire carbon black. The tire pyrolysis carbon black is first subjected to a series of pretreatments to remove components that affect its activity, and then granulated and activated, which can greatly improve the performance of the regenerated activated carbon.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for regenerating activated carbon from waste tire carbon black, comprising the following steps:

[0007] (1) Pyrolysis and pretreatment: After the waste tires are pyrolyzed and carbonized, they are subjected to magnetic separation to remove iron and then ground to obtain coarse carbon black powder, which is then acid washed, then alkaline washed and then washed with water to obtain coarse carbon black;

[0008] (2) Granulation: Adding a granulating agent to the crude carbon black and granulating the carbon black to obtain granulated crude carbon black;

[0009] (3) Activation: Place the granulated crude carbon black in a rotary kiln regeneration furnace, introduce air and water vapor, and activate it at 850-950°C to obtain regenerated activated carbon.

[0010] The inventors have found through research that the ash and volatile matter of carbon black obtained by tire pyrolysis are between 15% and 20% and 5% and 9% respectively. The present invention first performs acid washing and alkali washing on the pyrolysis carbon black to remove the ash and volatile matter in the carbon black, and then granulates and activates it, which greatly improves the iodine value of the regenerated activated carbon, that is, improves the adsorption performance of the regenerated activated carbon; granulating the coarse carbon black can reduce the carbon loss in the high-temperature activation process, greatly improving the utilization rate of waste tires.

[0011] Specifically, in the step (1), the particle size of the coarse carbon black powder obtained after grinding is 200-400 meshes; the acid used in the pickling process is at least one of sulfuric acid, nitric acid and perchloric acid, and the mass concentration of the acid is 10-15%; the alkali used in the alkali washing process is at least one of sodium hydroxide and potassium hydroxide, and the mass concentration of the alkali is 5-10%; after alkali washing, the coarse carbon black powder is washed with distilled water to neutrality. After the waste tire is treated by the cracking and carbonization process, the carbon slag discharged from the thermal cracking reactor is magnetically removed by the magnetic separation iron removal machine of the pretreatment unit to remove the impurities of steel wire and iron filings, forming coarse carbon black and recovering it through the silo; the coarse carbon black is ultra-finely ground by a carbon black powder pulverizer to a particle size similar to that of industrial carbon black, which is about 200-400 meshes.

[0012] In the step (2), the amount of granulating agent added is 1-3% of the total weight of the mixed material in the granulator; waste activated carbon is added to the crude carbon black powder during granulation, and the amount added is 10-30% of the mass of the crude carbon black powder. Since the ground carbon black has a smooth surface, light density, good dispersibility, and is not easy to bond, a certain amount of granulating agent needs to be added to bond with the granulator to enhance mechanical properties and increase service life. The granulating agent is at least one of sodium silicate, molasses, stearic acid, polysaccharides, lignin, and coal tar.

[0013] When granulating, it is necessary to select a suitable granulating agent to granulate the treated carbon black. The granulating agent can be organic or inorganic. If the granulating agent is too little, the granulation bonding performance is poor and the bonding effect is not strong; if the granulating agent is too much, the weight loss rate is high under the high temperature conditions of the activation stage, leaving a large number of gaps, and the columnar blocks are connected and fused with each other. At the same time, it is necessary to consider adding some inorganic binders to improve the mechanical strength of carbon black. Therefore, the granulating agent can enhance the mechanical strength of carbon black on the one hand, and improve the antioxidant capacity and adsorption of carbon black on the other hand, so that the activation effect is better.

[0014] The activation process is to use a rotary kiln regeneration furnace to dry and activate the granulated coarse carbon black, and introduce a small amount of air and water vapor. At this time, some waste activated carbon can be added, and the waste activated carbon is formed by adsorbing VOCs organic matter, such as waste activated carbon produced by pharmaceutical companies, or waste activated carbon produced by adsorbing chemical tail gas. It should be noted here that it must not be waste activated carbon after adsorbing heavy metals. This is because the scheme of the present invention utilizes the VOCs, i.e., volatile organic matter, adsorbed in the waste activated carbon. During the activation process, the organic waste gas adsorbed by the waste activated carbon is analyzed at high temperature and reacts with oxygen to generate water vapor, carbon dioxide and other gases, thereby further improving the activation effect. Therefore, on the other hand, the technical scheme of the present invention also provides a direction for the treatment of waste activated carbon that adsorbs VOCs.

[0015] The regenerated activated carbon is precipitated at the bottom of the rotary kiln and is cooled, packaged and recycled to obtain the finished activated carbon. The rotary kiln uses a flake seal with better sealing effect, which can effectively reduce energy consumption. The continuous rotation of the rotary kiln allows the granulated activated carbon to be fully turned over, so that the water vapor contacts the activated carbon more evenly and the activation effect is better.

[0016] Activation is carried out at a temperature of 850-950°C. Within a certain temperature range, the higher the carbonization temperature, the longer the carbonization time, the greater the amount of water vapor, the more carbon skeletons are formed, the more narrow voids are formed, and the stronger the adsorption is. However, too high a temperature and too much water vapor will cause over-activation, forming large pores with poor strength, while too low a temperature will result in fewer carbon pores, which is not conducive to improving the iodine value of adsorption.

[0017] Compared with the prior art, the beneficial effects of the present invention are: first, pyrolysis carbon black contains ash, which will cover the active points of carbon black. Ash removal is the key, and acid washing is needed to effectively remove the ash and open the original pores on the surface of carbon black; second, by adding a granulating agent, the mechanical strength and bonding properties of carbon black are changed, the degree of agglomeration between carbon black particles is improved, and granulation is carried out by a granulator at the same time to improve the regeneration rate of activated carbon black; third, the carbon black is regenerated by heating and gasification with a rotary kiln regeneration furnace equipment, with low energy consumption, stable equipment operation, continuous turning to make the carbon black and water vapor effectively and evenly contact and activate, the regeneration effect is good, and the iodine value is significantly restored; fourth, in order to further improve the adsorption performance of carbon black, a part of waste activated carbon is added to the carbon black as a further improvement to improve the regenerated iodine value. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0019] After the waste tires are treated by the cracking and carbonization process, the carbon slag discharged from the thermal cracking reactor is magnetically removed by the magnetic separation iron remover in the pre-treatment unit to remove steel wire iron impurities, forming coarse carbon black and recovering it through the silo; the coarse carbon black is ultra-finely ground by the carbon black powder crusher to obtain coarse carbon black powder with a particle size of about 350 mesh.

[0020] Example 1

[0021] (1) Take 100g of the above crude carbon black powder in a beaker, slowly add 500mL of 10% nitric acid solution (solid-liquid ratio is 1:10) in a fume hood, filter the obtained crude carbon black powder into a beaker, add 500mL of water to rinse, stir for 10min, and use the filtrate for later use; stir and react for 20min and then filter, put the filtered carbon black into a beaker, add 500mL of 1mol / L sodium hydroxide solution, stir for 10min and then filter.

[0022] (2) The carbon black is washed twice with the filtrate after the first water washing, stirred for 5 minutes and then filtered. The filtered carbon black is placed in a beaker, stirred with water, and repeatedly filtered and washed. When the pH of the filtrate reaches 7, it is placed in a drying oven and dried at 105°C for 3 hours to obtain crude carbon black.

[0023] (3) Weigh 50 g of the above crude carbon black, add 2% of the binder sodium stearate and stir evenly for 10 minutes, then add 20 ml of 60°C hot water in a constant temperature water bath at about 60°C and put it into a granulator for granulation. The granulated crude carbon black has a length of 3 cm and a diameter of 7 mm. Put it in a drying oven and dry it at 105°C for 2 hours.

[0024] (4) Take 20g of the above-mentioned granulated crude carbon black and put it into the rotary kiln regeneration equipment for regeneration, turn on the temperature controller, and set the temperature rise curve: after raising the temperature to 300°C at a rate of 4°C / min, keep the temperature constant for 20min; then raise the temperature to 600°C at a rate of 4°C / min, keep the temperature constant for 20min; then raise the temperature to 900°C at a rate of 4°C / min, open the water vapor valve to introduce water vapor at a flux of 0.3ml / min, keep the temperature constant for 40min, close the equipment temperature controller and steam valve, keep the furnace body rotating and nitrogen being introduced, and when the temperature drops to room temperature, turn off the equipment to obtain regenerated activated carbon.

[0025] Example 2

[0026] (1) Take 100g of the above crude carbon black powder in a beaker, slowly add 500mL of 10% nitric acid solution (solid-liquid ratio is 1:10) in a fume hood, filter the obtained crude carbon black powder into a beaker, add 500mL of water to rinse, stir for 10min, and use the filtrate for later use; stir and react for 20min and then filter, put the filtered carbon black into a beaker, add 500mL of 1mol / L sodium hydroxide solution, stir for 10min and then filter.

[0027] (2) The carbon black is washed twice with the filtrate after the first water washing, stirred for 5 minutes and then filtered. The filtered carbon black is placed in a beaker, stirred with water, and repeatedly filtered and washed. When the pH of the filtrate reaches 7, it is placed in a drying oven and dried at 105°C for 3 hours to obtain crude carbon black.

[0028] (3) Weigh 50 g of the above crude carbon black, add 2% of the binder sodium stearate and stir evenly for 10 minutes, then add 20 ml of 60°C hot water in a constant temperature water bath at about 60°C and put it into a granulator for granulation. The granulated crude carbon black has a length of 3 cm and a diameter of 7 mm. Put it in a drying oven and dry it at 105°C for 2 hours.

[0029] (4) Take 20g of the above-mentioned granulated crude carbon black and put it into the rotary kiln regeneration equipment for regeneration, turn on the temperature controller, and set the temperature rise curve: after raising the temperature to 300°C at a rate of 4°C / min, keep the temperature constant for 20min; then raise the temperature to 600°C at a rate of 4°C / min, keep the temperature constant for 30min; then raise the temperature to 900°C at a rate of 4°C / min, open the water vapor valve to introduce water vapor at a flux of 0.3ml / min, keep the temperature constant for 50min, close the equipment temperature controller and steam valve, keep the furnace body rotating and nitrogen being introduced, and when the temperature drops to room temperature, turn off the equipment to obtain regenerated activated carbon.

[0030] Example 3

[0031] The regenerated activated carbon was prepared by the same method as in Example 1, wherein 10% nitric acid was replaced with 15% nitric acid, and other conditions were the same as in Example 1.

[0032] Example 4

[0033] The regenerated activated carbon was prepared by the same method as in Example 2, wherein 10% nitric acid was replaced with 15% nitric acid, and other conditions were the same as in Example 2.

[0034] Example 5

[0035] Regenerated activated carbon was prepared by the same method as in Example 1, wherein the granulating agent 2% sodium stearate was changed to 1% sodium stearate + 1% instant powdered sodium silicate, and other conditions were the same as in Example 1.

[0036] Example 6

[0037] Regenerated activated carbon was prepared by the same method as in Example 2, wherein the granulating agent 2% sodium stearate was changed to 1% sodium stearate + 1% instant powdered sodium silicate, and other conditions were the same as in Example 2.

[0038] Example 7

[0039] Regenerated activated carbon was prepared by the same method as in Example 1, wherein the water vapor was introduced by opening the water vapor valve when the temperature was raised to 900°C, and the water vapor was introduced by opening the water vapor valve when the temperature was raised to 950°C, and the other conditions were the same as in Example 1.

[0040] Example 8

[0041] Regenerated activated carbon was prepared by the same method as in Example 2, wherein the water vapor was introduced by opening the water vapor valve when the temperature was raised to 900°C, and the water vapor was introduced by opening the water vapor valve when the temperature was raised to 950°C, and the other conditions were the same as in Example 2.

[0042] Example 9

[0043] Regenerated activated carbon was prepared by the same method as in Example 1, wherein powdered waste activated carbon produced by a certain manufacturer's pesticide production was added during granulation, the mass of which was 20% of the mass of the crude carbon black, and the other conditions were the same as in Example 1.

[0044] Example 10

[0045] Regenerated activated carbon was prepared by the same method as in Example 2, wherein powdered waste activated carbon produced by a certain manufacturer's pesticide production was added during granulation, the mass of which was 20% of the mass of the crude carbon black, and the other conditions were the same as in Example 2.

[0046] Table 1 is the test results of the above examples. It can be seen from the data in the table that the idea of ​​using the method of the present invention to prepare activated carbon using carbon black produced by catalytic cracking in tires is feasible and has good effects. The iodine value of the original carbon black is increased from 213g / kg to more than 800g / kg, and the regeneration rate is high. The iodine value of carbon black can be increased by appropriately increasing the acidity. The granulating agent can be added by adding organic and inorganic granulating agents. If only organic granulating agents are added, the mechanical strength of carbon black is poor. If only inorganic granulating agents are added, carbon black cannot be effectively granulated. If too little granulating agent is added, the granulation bonding performance is poor and the bonding effect is not strong. If too much granulating agent is added, the weight loss rate is high, and the activated carbon will leave a large number of gaps. On the one hand, adding part of the waste activated carbon is to improve the adsorption of carbon black and increase the iodine value of the overall system; on the other hand, it can be considered to synergistically activate and regenerate part of the waste activated carbon. The activation temperature is 900-950℃, the activation time is 50min, and the iodine value can reach above 850g / kg, which can meet the requirements of normal exhaust gas adsorption and wastewater treatment activated carbon, and achieve the goal of making activated carbon from waste tire pyrolysis carbon black, which can reduce carbon emissions and carbon pollution, increase the added value of products, and further achieve the purpose of comprehensive recycling of carbon.

[0047] Table 1 Performance test of regenerated activated carbon prepared in each embodiment

[0048]

Claims

1. A method for regenerating activated carbon from waste tire carbon black, comprising the following steps: (1) Cracking and pretreatment: After the waste tires are cracked and carbonized, they are subjected to magnetic separation to remove iron and grinding to obtain a crude carbon black powder. The crude carbon black powder is firstly acid-washed, then alkaline-washed and washed with water to obtain a crude carbon black. The alkali used in the alkaline washing process is sodium hydroxide, and the concentration of the alkali is 1 mol / L. (2) Granulation: adding a granulating agent to the crude carbon black and then granulating to obtain granulated crude carbon black, wherein the granulating agent is at least one of sodium silicate, molasses, stearic acid, polysaccharides, lignin, and coal tar, and the amount of the granulating agent added is 1 to 3% of the total weight of the mixed material in the granulator; during granulation, waste activated carbon is added to the crude carbon black powder, wherein the waste activated carbon is formed by adsorbing VOCs-type organic matter; (3) Activation: Place the granulated crude carbon black in a rotary kiln regeneration furnace, introduce air and water vapor, and activate it at 850-950°C to obtain regenerated activated carbon.

2. The method for regenerating activated carbon from waste tire carbon black according to claim 1, characterized in that: In the step (1), the particle size of the coarse carbon black powder obtained after grinding is 200 to 400 meshes.

3. The method for regenerating activated carbon from waste tire carbon black according to claim 1, characterized in that: In the step (1), the acid used in the pickling process is at least one of sulfuric acid, nitric acid and perchloric acid, and the mass concentration of the acid is 10-15%.

4. The method for regenerating activated carbon from waste tire carbon black according to claim 1, characterized in that: In the step (1), after alkali washing, the crude carbon black powder is washed with distilled water until it becomes neutral.

5. The method for regenerating activated carbon from waste tire carbon black according to claim 1, characterized in that: In the step (2), the amount of waste activated carbon added is 10 to 30% of the mass of the crude carbon black powder.

Images