Biological Regeneration Method Carbon Regeneration Kilns For Water Treatment

Biological Regeneration Method Carbon regeneration

The biological regeneration method is to use domesticated bacteria to resolve the organic matter adsorbed on the activated carbon and further digest and decompose it into H2O and CO2. The biological regeneration method is similar to the biological method in wastewater treatment, and there are also aerobic and anaerobic methods. Since the pore size of activated carbon itself is very small, some only a few nanometers, microorganisms cannot enter such pores, and it is usually believed that cell autolysis occurs during the regeneration process, i.e. cell enzymes flow to the extracellular, and activated carbon has adsorption effect on enzymes, thus forming an enzymatic center on the surface of carbon, and promoting the decomposition of pollutants and achieving the purpose of regeneration. The biological method is simple and easy to implement, with low investment and operating costs, but it takes a long time and is greatly influenced by water quality and temperature.

Regeneration process

After the preliminary pretreatment, the waste powdered activated carbon is dried by a paddle dryer to remove most of the water, and then enters the static carbonization furnace for high-temperature carbonization to further volatilize the organic matter in the waste carbon, and then is activated and regenerated by the fluid activation furnace. The generated high-temperature flue gas is cooled and heat exchanged in a high-temperature heat exchange box, and the finished product is collected by a cyclone separator and a bag dust collector. Waste granular activated carbon directly enters the rotary kiln for activation and regeneration. The production process is adjusted according to the characteristics of the waste carbon. The finished product is packaged directly after cooling. The exhaust gas generated by the two sets of devices enters the secondary combustion chamber to continue incineration. The incineration temperature in the secondary combustion chamber is above 1100°C. The flue gas generated by the incineration recovers heat through the waste heat boiler. The flue gas undergoes rapid cooling, dry acid removal, bag dust collector, and spraying. After washing in the shower tower and heating the flue gas, the smoke is discharged into the atmosphere in compliance with safety standards. The ignition and combustion-supporting fuel of this device uses natural gas, and SNCR is used for denitration.

Activation and Principles

Activation is to use process measures to make the carbonized material have a good pore structure and a large specific surface area while maintaining the strength of the carbon, so as to achieve the technical properties required by activated carbon, such as (Alan, iodine value, ash, volatile matter, moisture, etc.)
(1) The basic principle of the gas activation method: The gas activation method is to put the carbonized material into the activation furnace and heat it to 800-950°C to perform an oxidation reaction with the gas activator, making it have a developed pore structure and a large ratio. There are many types of activated carbon with surface area, such as water vapor, carbon dioxide, oxygen, chlorine, etc. Currently, water vapor activation is the most common method in China.
Water vapor activation is a series of complex chemical reactions between water vapor and carbonized materials under high temperature conditions, which makes the pore structure of the carbonized materials more developed and the specific surface area increased. How do these chemical reactions change the properties of the carbonized materials? It is generally believed that the activation reaction ultimately achieves the purpose of activation through the following stages.
The thermal decomposition of carbonization continues at high temperatures, because the temperature has risen to 800-950°C. During the heating process, further pyrolysis removes the disordered carbon and tar products that exist in the pores of the carbonized material during carbonization, making the The blocked pores are opened, and at the same time, the high-temperature activated gas-water vapor can react chemically with the pyrolysis products that have opened the pores but are still firmly adsorbed on the pore surface at a considerable reaction rate to generate simple compounds. The surface of the graphite crystal of carbon becomes clean, so that the water vapor reacts with the exposed part of the carbon, causing this part of the carbon to be burned, forming new fine pores, and at the same time increasing the specific surface area inside the carbon. The gas generated by the activation reaction leaves the carbon surface and new unsaturated carbon atoms appear, that is, new active points are exposed to the surface of the microcrystals, and a new activation reaction occurs. The reaction rate between water vapor and carbon is higher than that at high temperatures. The pyrolysis reaction is much slower, so that a new pore structure can be formed through the reaction of part of the carbon. Therefore, the oxygen content (air) must be strictly controlled during the activation process to avoid serious damage to the carbon surface. The activation reaction continues, the carbon surface is continuously burned, and the pores continue to expand, and finally meet the process requirements. Due to different properties of raw materials, different activation media and process conditions, the pore structures of the final carbon particles are different. Different pore structures Suitable for use requirements in different industries.

Technical advantages of the process

It turns out that the activated carbon regeneration process is a one-step method, that is, after the waste carbon is dried, it directly enters the fluidized activation furnace for carbonization and activation. During the activation process, a large amount of steam needs to be added for surface oxidation reaction. The generated flue gas and the high-temperature desorbed organic flue gas are mixed and then enter the tail gas treatment system to be heated to 1100°C for denitrification treatment. The total amount of flue gas at this time is about 8000-10000N.M3/h, and the required fuel is converted into 350N.M3/h natural gas, which consumes a lot of energy.
The latest process features are: after drying the waste carbon, it is carbonized at high temperature in an advanced static furnace to desorb and analyze more than 95% of the organic matter in the waste carbon. During this process, the static furnace is completely anaerobic, and the organic matter produced is The amount of flue gas is very small. After spray washing, most of the organic matter and ash are dissolved in the water. When the circulating washing water COD reaches a certain concentration, it enters the waste liquid disposal workshop. At this time, the amount of harmful flue gas entering the tail gas treatment is very large. Small, the air volume is about 1000N.M/h, plus the amount of flue gas generated during drying, the air volume is about 5000M3/h, which is about 50% of the original process, which greatly reduces the energy consumption of exhaust gas treatment. The carbonized carbon, Then it enters the fluid activation furnace for activation. At this time, the tail gas of the fluid activation furnace can be completely emptied directly.
The optimized process has low requirements for ash content, organic matter content, etc. in the waste carbon market (even waste carbon from sewage plants can be carbonized). It can also provide different qualities of recycled carbon according to the requirements of recycled carbon dealers. Make the operation of the entire project flexible. At the same time, reducing treatment costs can also face the impact of future disposal prices due to the rise of the incineration industry.