Patent of lignite dehydration

1. chemical activation method chemical activation method is a method of adding chemicals to raw materials, then heating in inert gas medium, and carbonizing and activating at the same time. Plant raw materials such as sawdust are usually used. Drug activation method has three disadvantages: ① it is very corrosive to equipment; (2) polluting the environment; (3) Chemical activator remains in activated carbon, so its application is limited. 1. 1. The manufacturing process of zinc chloride method is that concentrated zinc chloride solution with specific gravity of about 1.8 is added to raw materials, mixed, soaked in zinc chloride, and then heated in an air-free rotary furnace at 600-700℃. Due to the dehydration of zinc chloride, the activation of phosphoric acid by 1.2 phosphoric acid method is in principle to mix finely divided raw materials with phosphoric acid solution, then dry the mixture and heat it to 400 ~ 600℃ in the converter. The well-known technological process is carried out at a relatively high temperature (1 100℃). Recently, the chemical activation method with alkali as activator, that is, the chemical activation method with alkaline activator such as potassium hydroxide, has attracted people's attention. The activated carbon with specific surface area of 29 1.8m 2/g was obtained by mixing coal char with potassium hydroxide and then performing secondary heat treatment at low temperature and high temperature in argon flow. Add 1 ~ 5 times of potassium hydroxide to the carbonized walnut shell or petroleum coke, fully mix, introduce nitrogen into the system for protection, dehydrate at low temperature and activate at high temperature to obtain advanced activated carbon. During the four years from 197 1 to 1974, American Standard Oil Company applied for five patents for making activated carbon from petroleum coke. The key points are as follows: petroleum coke is oxidized into petroleum coke acid by nitric acid, and then activated by excessive potassium hydroxide under different technological conditions. Activated carbon with specific surface area of1000 ~ 2600 m/g was prepared. This activation method has low yield, complex process and difficult raw material treatment, so it has not been applied in industry. So in 1978, the company disclosed the patent of activating petroleum coke at 850℃ with triple potassium hydroxide. Kansal Coke and Chemical Company of Japan reduced the pressure to 800℃. 3,000m2/g activated carbon. 1.2 gas activation method gas activation method is a method of activating raw materials at 600 ~ 1 200℃ after carbonization. Its main working procedures are carbonization and activation. Carbonization refers to heating raw materials to remove volatile components in advance, so that the carbonized materials are suitable for the next activation. The carbonization process is divided into below 400℃. The reaction is divided into three stages: the oxygen bond cleavage reaction at 400 ~ 700℃ and the deoxidation reaction at 700 ~1000℃. Raw materials, whether chain molecular substances or aromatic molecular substances, are condensed into plane molecules of benzene rings through the above three reaction stages, forming carbonized products with three-dimensional network structure. The low adsorption capacity of carbonized materials is due to the fact that carbon contains some hydrocarbons, and the pore volume is small and the pores are blocked. The activation phase usually involves exposing carbon to an oxidizing gas medium at about 900℃ and treating it. In the first stage of activation, the adsorbed substances are removed and the blocked pores are opened. Further activation, so that the original pores and channels expand; Subsequently, due to the selective oxidation of the highly reactive part of the carbonaceous structure, a microporous structure is formed. 1.2. 1 Carbon-containing raw materials for preparing activated carbon by microwave heating are preheated above 600℃, then contacted with steam, carbon dioxide, oxygen-containing gas or gas generated by activation, and then directly heated by microwave, so that activation can be completed. However, raw materials such as coal, oil and wood. It can be prepared by ordinary activation method, and it is impossible to heat coal, asphalt, wood and other raw materials to the full activation temperature by microwave. If the raw material is irradiated by microwave, the temperature can reach about 100℃ at first because of the moisture, and then when the moisture evaporates, the heat is extremely small, so the temperature should be raised to above 100℃. It may not be possible, or it may take a long time. 1.2.2 The microwave heating steam activation method of activated carbon can significantly expand the internal surface area of activated carbon. The specific process is as follows: firstly, the raw materials are made into a certain particle size and specific gravity, and steam is introduced to fully stir them to make them evenly wet. According to the capillary phenomenon, there is free water in the micropores between the fibers of plant cellulose raw materials, which makes the raw materials wet and expand. Then, using these free water as electrolyte, microwave radiation makes the free water evaporate quickly, producing vapor pressure, which is exploded from the inside of the raw material. This rapid action expands the space between fibers, and at the same time, it dries quickly, resulting in countless cracks, which makes the porous structure of raw materials more obvious and further increases the internal surface area. Then continuous dry distillation and carbonization are carried out, and steam is introduced at the same time, and the steam continuously flows to the porous and cracked parts of raw materials, so that the fixation of hydrogen carbide is inhibited and eliminated until carbonization. 1.3 combination of drug activation and gas activation gas activation and drug activation are sometimes used together. Further steam activation can produce products with special pore distribution and increase the number of pores in a wide range. When using activated carbon to treat gas containing substances that can block carbon pores, for example, when using granular activated carbon to remove benzene from urban gas, the pores of activated carbon are blocked by diolefins in urban gas and rapidly age. In order to produce activated carbon that can be used in this situation, this combined activation method is applied. Benzorbang brand activated carbon of Ji Le Company is the representative of this kind of activated carbon. 1.4 continuous carbonization and activation method adopts simple flow furnace to continuously carbonize and limit oxidation and activation of activated carbon, which is labor-saving in operation and good in product quality. This method is characterized in that activated carbon raw materials with water content adjusted to 15% ~ 30% are continuously fed into a flowing furnace, and at the same time, a proper amount of air is blown from the bottom of the furnace to carbonize the furnace and limit oxidation activation. Before and when the raw materials are put into the furnace, only a small amount of kindling is sent into the furnace, and a proper amount of air is blown from the lower part of the furnace to promote the partial combustion of the raw materials, thus heating the raw materials themselves. The temperature and carbonization speed in the furnace are adjusted by the amount of air blown in and the amount of feed. Blasting is not only used for partial combustion and heating of raw materials, but also for fluidized particles and continuous activation reaction during carbonization. 1.5 fluidized bed one-step production of activated carbon The fluidized bed one-step production of activated carbon is a new process developed in recent years. After screening, the raw materials are directly sent to the fluidized bed at the initial fluidization speed for carbonization and activation, and the activation temperature and gas distribution are uniform, which can effectively activate the reaction raw materials. It can treat both powdery raw materials and granular raw materials, and the production process is simple. Has aroused great concern. Anthracite activated carbon produced by British National Coal Bureau has been put into commercial operation. However, single-stage fluidized bed is generally suitable for intermittent operation, and the activation of continuous operation is uneven. Misi Tazaki's research shows that with the increase of the number of fluidized beds, the same activation products can be obtained by continuous operation and intermittent operation. However, the process wear is serious when manufacturing shaped activated carbon. If fine coal powder particles are mixed with molding materials for activation, the wear can be greatly reduced. Powder activated carbon and granular activated carbon can be prepared at the same time. The process is simpler than adding inert fine particles, and the production capacity of the equipment is also large. 1.6 rapid carbonization activation method The researchers believe that the rapid pyrolysis process can be used to produce cheap activated carbon, which has good adsorption performance and can be directly used as gasification raw materials without regeneration after use. The existing experimental results show that rapid pyrolysis can significantly improve the specific surface area of activated carbon. The introduction of high temperature steam medium has a significant effect on the surface structure of activated carbon during rapid pyrolysis. Qiu Jieshan and others used a falling bed radiation furnace with potassium carbonate as catalyst. The possibility of producing activated carbon by catalytic rapid carbonization of Huangxian lignite in steam medium was discussed. The results show that the pore structure index and adsorption performance of the experimental activated carbon have reached or approached the level of some commercially available activated carbons. 1.7 lignite semi-coke forming activation process is widely used to prepare activated carbon from lignite. First, lignite is carbonized. Then the semi-coke is crushed to less than 0.65438 0 mm, and asphalt binder is added to make briquette. After being crushed, the briquettes are activated in an activation furnace. Granular or powdered activated carbon can be made by screening or grinding. This process is used in Australia and Europe. Other production methods: 1.8 Zhang Shuangquan and others discussed the new process of preparing coal-based activated carbon with nitrate as the main oxidation composite catalyst, and used this catalyst to unify catalysis and oxidation. The results show that barium nitrate is the best catalyst. Potassium compound is a good catalyst for making activated carbon; Co-catalyst phosphorus plays an important role in the development of pore structure of activated carbon; The ash in the raw materials hindered the performance of the catalyst; The composite catalyst used in the experiment can increase the activation reaction speed by more than l times, obtain higher adsorption performance at the same loss of ignition rate, or increase the activation yield at the same loss of ignition rate, thus reducing the production cost of activated carbon. Robert of Australia mixed 70 ~ 75 ml of 20% potassium hydroxide solution with 20 g of dried raw coal or acid-washed coal to form a gelatinous paste, and pressed it into a coal section with a diameter of 6 mm with a die press. After drying, the diameter becomes 3 mm, which is relatively hard. Then distilled 16 h under the protection of nitrogen at 900℃, and the potassium salt was recovered from the dry distillation carbon by leaching with dilute acid to prepare the product. The specific surface area of raw coal activated carbon is L 340 m/g, and the specific surface area of acid-washed coal activated carbon is L 500 m2/g. There are similar processes in the United States, but the amount of potassium hydroxide is larger. The surface area of that prepare powdered activate carbon is as high as 3,000 square meters/gram. However, in the United States, raw lignite and sub-bituminous coal are treated with dilute acid (such as phosphoric acid). The main purpose of treatment is not to leach minerals, but to cross-link some components in coal, and then directly briquette and activate them to produce activated carbon. Both yield and activity have been greatly improved. 2.2. 1 Development trend of activated carbon preparation. Traditional preparation of activated carbon mostly takes wood, charcoal, sawdust, coconut shell and stone as raw materials. With the enhancement of social environmental awareness, especially the 1998 catastrophic floods in the Yangtze River, Songhua River and Nenjiang River basins, people have personally realized the enormous negative impact of ecological deterioration on national survival and sustainable development. The country soon banned the felling of natural forests, which led to the shrinking of the sources of wood and charcoal, that is, the raw materials for preparing activated carbon were greatly limited, and the price was also on the rise. In this case, it is of great prospect and significance to adopt a feasible new process to prepare activated carbon with mineral raw materials instead of biomass raw materials. Sometimes the composition is very different. If the same preparation method is adopted, the quality of activated carbon and the maximum utilization rate of materials are greatly limited. Therefore, the preparation of activated carbon in the future will be diversified, novel and targeted on the basis of traditional preparation. With the emergence of new application fields of activated carbon and the demand for new products with better performance, it is an important task for the activated carbon industry to develop energy-saving and efficient new processes and equipment, improve product quality and reduce production costs.