Chemical activation

The chemical activation method is to prepare activated carbon by uniformly mixing various carbon-containing raw materials with chemicals and undergoing processes such as carbonization, activation, recycling of chemicals, rinsing, and drying at a certain temperature. Phosphoric acid, zinc chloride, potassium hydroxide, sodium hydroxide, sulfuric acid, potassium carbonate, polyphosphoric acid and phosphate esters, etc. can all be used as activating reagents. Although the chemical reactions that occur are different, some have corrosion, hydrolysis or dehydration effects on the raw materials. Some have an oxidizing effect, but these chemicals can all have a certain promoting effect on the activation of raw materials. Among them, the most commonly used activators are phosphoric acid, zinc chloride and potassium hydroxide. The activation principle of the chemical activation method is not very clear. It is generally believed that the chemical activator has the effect of corroding and dissolving cellulose, and can decompose and separate the hydrogen and oxygen contained in the hydrocarbons in the raw material, in the form of small molecules such as H2O, CH4, etc. Escape, creating a lot of pores. In addition, the chemical activator can inhibit the formation of tar by-products and prevent the tar from blocking the pores generated during the pyrolysis process, thereby increasing the yield of activated carbon. To

Physical activation method

The physical method is usually called the gas activation method, which is to combine the carbonized raw materials with water vapor, flue gas (mixed gas of water vapor, CO2, N2, etc.), CO or air at a high temperature of 800 ~ 1000 ℃. Contact, thereby proceeding the process of activation reaction. The basic process of the physical activation method mainly includes carbonization, activation, impurity removal, crushing (ball milling), refining and other processes. The preparation process is clean and there is little liquid phase pollution. To

During the preparation process, the oxidizing high-temperature activated gas disordered carbon atoms and heteroatoms first react to open the originally closed pores, and then the surface of the basic crystallites are exposed, and then the activated gas continues with the carbon atoms on the surface of the basic crystallites. An oxidation reaction occurs, causing the pores to expand continuously. Some unstable carbon is gasified to generate CO, CO2, H2 and other carbon compound gases, thereby creating new pores, and at the same time tar and uncarbonized materials are also removed, and finally activated carbon products are obtained. The developed specific surface area of activated carbon comes from the increase in the pore volume of mesopores and macropores, and the formation of macropores, mesopores and micropores are interconnected and connected. Because the physical process is relatively simple, the exhaust gas produced is mainly CO2 and water vapor, which has little environmental pollution, and the final activated carbon product has a high specific surface area, a developed pore structure, and a wide range of applications. Therefore, the production of activated carbon worldwide More than 70% of manufacturers use physical methods to produce activated carbon. A large amount of waste heat is generated during the carbon activation process, which can meet the heat energy required for raw material drying, waste heat boiler production of high-temperature steam, product washing and drying, etc.

Physical-chemical activation method

The physical-chemical activation method, as the name implies, is a combination of physical activation and chemical activation, that is, the carbon is first treated with a chemical method, and then further activated with a physical method (steam or CO2). Foreign researchers have prepared super activated carbon with a specific surface area of up to 3700m2/g through the combined activation method of H3PO4 and CO2. The specific steps are to soak wood raw materials with H3PO4 at 85°C, carbonize at 450°C for 4 hours, and then activate it with CO2. The physical method and chemical method are combined, and the carbonization tail gas of the physical method is used to supply heat for chemical production, so as to achieve no coal consumption during the production process, and obtain physical activated carbon and chemical activated carbon at the same time