1 several methods 1.1 Chemical method for drug elution For high-concentration, low-boiling organic matter adsorbates, chemical regeneration should be considered first. (1) Regeneration of inorganic agents. It refers to the removal of adsorbate by a chemical such as inorganic acid (sulfuric acid, hydrochloric acid) or alkali (sodium hydroxide), also known as acid-base regeneration. For example, carbon adsorbing a high concentration of phenol is washed with a sodium hydroxide solution, and the desorbed phenol is recovered as a sodium phenolate salt. The carbon which adsorbs heavy metals in the wastewater can also be regenerated by this method, and the regenerating agent uses HCl or the like. (2) Organic solvent regeneration. The organic matter is dissolved by benzene, acetone and methanol to extract the adsorbate adsorbed on the activated carbon. . For example, carbon adsorbing high concentrations of phenol can also be regenerated with an organic solvent. The saturated charcoal treated with activated carbon in the coking plant gas washing wastewater can also be regenerated with an organic solvent. Chemical regeneration method using chemical elution sometimes recovers useful substances from the regeneration liquid. The regeneration operation can be carried out in the adsorption tower. The loss of activated carbon is small, but the regeneration is not complete, the micropores are easily blocked, and the recovery of adsorption performance is affected. Rate, the adsorption performance is significantly reduced after repeated regeneration. 1.2 Biological regeneration method The domesticated activated carbon is used to treat the spent activated carbon, and the organic matter adsorbed on the activated carbon is degraded and oxidatively decomposed into CO 2 and H 20 to restore its adsorption performance. The method for regenerating saturated carbon by using microorganisms is only suitable for adsorbing susceptible microorganisms. The carbon of the decomposed organic matter is saturated, and the decomposition reaction must be thorough, that is, the organic matter is finally decomposed into CO 2 and H 20 , otherwise there is a possibility of being adsorbed by the activated carbon. If the treated water contains organic matter that is difficult to degrade or hard to desorb, the biological regeneration effect will be affected. In recent years, the strong adsorption characteristics of activated carbon to organic matter and dissolved oxygen in water, and the surface of activated carbon as a good carrier for microbial aggregation and growth, under the appropriate conditions, simultaneously exert the adsorption of activated carbon and the biodegradation of microorganisms. The water treatment technology is called Biological Activated Carbon (BAC). This method can make the use cycle of activated carbon many times longer than the usual adsorption cycle, but after using for a certain period of time, the part that is adsorbed by activated carbon and difficult to biodegrade will still affect the effluent quality. Therefore, in the deep treatment of drinking water, too long an adsorption cycle of activated carbon will be difficult to ensure the quality of the effluent, and regular replacement of activated carbon is necessary. 1.3 Wet oxidation method This regeneration process is commonly used to regenerate powdered activated carbon, such as powdered charcoal added to enhance aeration tank processing capabilities. The adsorbed saturated carbon slurry is heated to 200-250 ° C, and pressurized with air to (300-700) X104P, and the organic matter adsorbed by the activated carbon in the reaction tower is oxidatively decomposed under high temperature and high pressure to regenerate the activated carbon. The regenerated carbon is cooled by a heat exchanger and sent to a carbon storage tank for reuse. The ash after carbonization of the organic matter is periodically discharged after being accumulated at the bottom of the reactor. The wet oxidation method is suitable for treating adsorbent substances with high toxicity and biodegradability. The temperature and pressure must be determined according to the characteristics of the adsorbate, as this directly affects the recovery rate of carbon adsorption performance and the loss of carbon. The regeneration system of this regeneration method has many auxiliary facilities, so the operation is troublesome. 1.4 Electrolytic oxidation The organic matter adsorbed by the activated carbon is oxidatively decomposed by using a strong oxidant such as [O], [C1], which is generated during electrolysis. However, in actual operation, there are problems such as corrosion, passivation, and clogging of metal electrodes. Insoluble electrode--Graphite has the disadvantages of large volume, high electrical resistance, high power consumption, etc., so it has not been applied in practice. 1.5 Heating regeneration method According to the temperature at which the organic matter decomposes and desorbs during heating, the heating regeneration is classified into low-temperature heating regeneration and high-temperature heating regeneration. (1) Low temperature heating regeneration method. For the saturated carbon which adsorbs a low molecular weight hydrocarbon having a low boiling point and an aromatic organic substance, the carbon is generally regenerated by steam blowing at 100 to 200 ° C, and regeneration can be carried out in the adsorption tower. The desorbed organic vapor can be recycled after being condensed. Activated carbon regeneration commonly used for gas adsorption. The steam stripping method is also used for the regeneration of saturated activated carbon for the pre-treatment of process water in the beer and beverage industries. (2) High temperature heating regeneration method. In the water treatment, the activated carbon adsorbs mostly thermal decomposition type and hardly desorbed organic matter, and the adsorption cycle is long. The high-temperature heating regeneration method is usually heated at a high temperature of 850 ° C, so that the organic matter adsorbed on the activated carbon is carbonized and activated to achieve the purpose of regeneration, the adsorption recovery rate is high, and the regeneration effect is stable. Therefore, high temperature heating is generally employed for the regeneration of activated carbon for water treatment. After dehydration of activated carbon, the whole process of heating and regeneration generally goes through the following three stages. (1) Drying stage. The wet carbon having a water content of 50% to 86% is heated at a temperature of 100-150 ° C to evaporate the adsorbed water in the carbon particles, and at the same time, some of the low-boiling organic substances are also volatilized. The heat consumed in this stage accounts for 50% to 70% of the total energy consumption during the whole process of regeneration. (2) The roasting stage, or carbonization stage. The pelletized carbon is heated to a temperature of 150 to 700 °C. Different organic substances are eliminated from the matrix of activated carbon in the form of volatilization, decomposition, carbonization and oxidation as the temperature increases. Usually, at this stage, the recovery rate of recycled carbon has reached 60% to 85%. (3) Activation phase. After the organic matter is carbonized at a high temperature, a considerable portion of the carbide remains in the activated carbon micropores. At this time, the carbide needs to be gasified by an oxidizing gas such as steam or carbon dioxide, and the residual carbide is vaporized to a gas such as CO 2 or CO at about 850 ° C. The surface of the micropore is cleaned to restore its adsorption performance. The reaction formula of residual carbides and oxidizing gases is as follows: C + O2 → CO2↑ C + H2O → CO↑+H2↑ C + CO2 → 2CO↑ During high temperature regeneration, oxygen has a great influence on the matrix of activated carbon, so it must be operated under micro-positive pressure conditions. Excessive oxygen will cause the activated carbon to burn and ash, while too low an amount of oxygen will affect the furnace temperature and regeneration effect. Therefore, the oxygen in the general high-temperature heating regenerator must be strictly controlled, the residual oxygen content is less than 1%, the CO content is about 2.5%, and the steam injection amount is 0.2-1 kg/kg activated carbon (determined according to the furnace type). The advantages and disadvantages of activated carbon regeneration equipment are mainly reflected in: adsorption recovery rate, carbon loss rate, strength, energy consumption, auxiliary material consumption, regeneration temperature, regeneration time, impact on human body and environment, equipment and basic investment, operation management and maintenance degree. In addition, any activated carbon high-temperature heating regeneration device needs to be properly solved to prevent carbon particles from sticking to each other, sintering into blocks and causing local fire or blockage of passages, and even causing running defects. 2 Several devices for high temperature heating regeneration The high-temperature heating activated carbon regeneration system is composed of a dehydration device, an activated carbon conveying, a high-temperature heating regeneration device, activated carbon cooling, an exhaust gas treatment, and an activated carbon storage tank. There are also heat sources for heating, such as fuel, natural gas, gas or coke, as well as electric and steam boilers. Among them, the regeneration device is the main one. Heating regeneration devices come in many forms. At present, there are many types of multi-layer, rotary, fluidized bed, and moving bed type used at home and abroad. 2.1 multi-layer Also known as vertical multi-stage regenerative furnace, or multi-layer furnace. It is mainly used for the regeneration of granular carbon. It is widely used in the United States and has been introduced in China. Suitable for large-scale activated carbon regeneration, the general regeneration amount is greater than 2t / d. Its characteristics are: using natural gas or oil as fuel, steam activation, from the top of the furnace to supply saturated carbon, using a rotating arm to push the carbon to the next layer, from top to bottom 6 layers. (1) Drying section. The first to third layers have a residence time of 15 minutes and a furnace temperature of 100 to 700 °C. (2) Roasting section. 4th layer, residence time 5 mln, furnace temperature 700 ~ 800 ° C (3) Activation zone. The 5th to 6th floors have a residence time of 10 minutes and a furnace temperature of 800 to 900 °C. The water vapor is activated in this section. The regenerated charcoal is drained after being quenched with a water tank. The recovery rate of iodine value of recycled carbon is 86%-95%, and the carbon regeneration loss rate is 7%~15% (because there are both burning and turning wear). The steam consumption is 1 kg/kg activated carbon, and the total energy consumption is 4 925 kcal/kg activated carbon (equivalent to 5.72 kW·h/kg activated carbon). 2.2 Rotary Also known as the converter, there is a one-stage or two-stage type, with internal combustion type direct heating or external combustion type indirect heating. The internal combustion type carbon regeneration loss is large, the external combustion type efficiency is low, and the activation section must be slightly positive pressure and activated by water vapor. Fig. 5 shows a two-stage rotary type regenerative device, an internal combustion type converter for the drying section, and an external combustion type converter for the roasting and activation sections. combustion The rotary regenerative device is relatively simple to operate. The length of the one-stage converter body is up to 15m, so the furnace body is often deformed. After the temperature of the activation section rises to 750°C, it is not easy to rise again. The regeneration recovery rate is related to the highest temperature reached. The residence time is 3~4 h, the carbon regeneration loss rate is 5% to 7%, and the total energy consumption is 7 899 kcal/kg activated carbon (equivalent to electricity consumption 9.18 kW·h/kg activated carbon). 2.3 Fluidized bed type Also known as fluidized bed regenerative furnace, there are two types of internal combustion and external combustion, one or more sections. Used abroad to regenerate powdered carbon and spherical carbon. Burn heavy oil or gas, and pass water vapor from the bottom of the furnace to make the carbon fluidized. The activated carbon flows from top to bottom, and is dried, calcined, and activated (800 to 900 ° C). Fig. 6 is a two-stage external combustion fluidized bed regeneration device. The furnace temperature, water vapor dosage and fluidization state are difficult to adjust, and the regeneration loss rate is 7% to 10%, and the regeneration time is 7 to 10 hours. Energy consumption 3 326 ~ 11 341 kcal / kg activated carbon) (equivalent to electricity consumption 3.87 ~ 13.18 kW, h / kg activated carbon). 2.4 moving bed Also known as vertical moving bed regenerator. The regeneration part is composed of two layers of stainless steel tubes, and the carbon moves from top to bottom in the two tube compartments. The water vapor in the inner tube is discharged from the pores into the partition layer in the activation section, and is oxidized with activated carbon. The outer tube is in contact with the combustion chamber to conduct heat to the activated carbon, and the regeneration gas is discharged from the upper vent to the combustion chamber for disposal, and the exhaust gas is removed by the side chimney. The bottom of the furnace has a disc discharge device for discharging the regenerated charcoal. The furnace type is simple in structure and convenient in operation and management. Because the regeneration time is up to 6h, the furnace body height is 12m, the water vapor volume is 0.2kz/kg activated carbon), the gas temperature inlet is 1000 °C, the outlet is 70-80 °C, and the regeneration loss is 3% to 4%, total energy consumption is about 6 950 kcal/kg activated carbon (equivalent to 8.07 kW·h/kg activated carbon), heat recovery type total energy consumption is 3 360 kcal/kg activated carbon (equivalent power consumption 3.9kW·h/ Kg activated carbon). The disc furnace developed in China is also a moving bed type. The activated carbon moves from top to bottom in a tubular passage formed by a hollow tray, and the regeneration gas is discharged from the gap of the tray. Heavy diesel oil is used as fuel. The temperature of the furnace combustion chamber reaches 1 110~1 300 °C. The heat is transferred from the gap of the tray and the tray to the activated carbon, and the water vapor is passed from the bottom of the furnace. The activated carbon is regenerated in the furnace. 2.5 Electric heating regeneration device The high-temperature heating regeneration device with electric energy is a microwave oven, a far-infrared furnace and a direct-energized regenerative furnace. (1) Microwave heating. The microwave is generated by the periodic variation of the voltage of the magnetron (or the klystron), and the internal polar molecules of the microwave absorber are repeatedly moved at high speed to generate thermal energy. The regenerative furnace body is a microwave resonance crucible. The microwave frequencies used for the drying or heating process are 970 MHz and 2450 MHz. The advantage of microwave regeneration is that the microwave causes the carbon itself to heat up, the heating speed is fast, the high temperature required for regeneration can be quickly reached, and the device volume is small. The disadvantage is that the heating in the furnace is not uniform (the microwave energy is not uniformly absorbed), and sometimes the phenomenon of carbon sintering occurs. In addition, microwave radiation needs better shielding. When the leakage energy is greater than 0.01 w/cm 2 and the contact time is above 6 min, the health of the human body is damaged. In the process of microwave generation and transportation, the magnetron itself consumes 30% to 40% of the power, and the regeneration energy consumption is generally 1.46 kW, h/kR activated carbon. (2) Far infrared ray regeneration device. Far-infrared heating, generally used for drying activated carbon, is also used for regeneration, and its effect depends on the ability of the object to be heated to absorb infrared rays of specific wavelengths. The radiator is generally coated with a silicon carbide plate, and the matching of the radiation wavelengths directly affects the heating efficiency. When the coating is a combination of ferric oxide and zirconia, the energy consumption for regeneration is about 1.45 kW, h/kg activated carbon. (3) Directly energizing the heating regeneration device. The carbon has a Joule heat generated by the electric resistance of the carbon itself and the contact resistance between the carbon particles, and gradually reaches the regeneration temperature, and then is activated by the steam. Japan's regenerative furnaces are batch and continuous. Japanese continuous direct current regeneration device. The charcoal stayed in the furnace for 6h, the recovery rate of regenerated iodine value was 94%-96%, the regeneration loss rate was 1%-3%, and steam activation was used. The steam consumption was reduced to 0.5kW·h/ks activated carbon. Deodorization power consumption 0.05 kW·h/kg activated carbon. Regenerated electricity consumption is 1 kW·h/kg activated carbon, and the total energy consumption is 1.59 kW·h/kg activated carbon. The direct electric heating regeneration device developed in China is a two-stage continuous regeneration device that regenerates saturated carbon after deep treatment of drinking water. The drying section heats the air to 200 °C by the electric heating chamber, and then the hot air enters the bottom of the fluidized bed dryer, and the wet carbon is dried for 1 h, so that the moisture content (dry basis) of the wet carbon is reduced from 76% to 6%, and the electricity consumption is reduced. 1.55 kW·Vkg activated carbon, dry carbon enters the effective section 0.1mX0.1m, the effective height is 3.0 m direct electric heating regenerator, the residence time is 14 min, complete roasting and activation. The power consumption is 0.22 kW·h/kg of activated carbon, and the total power consumption is 1.77 kW·h/kg of activated carbon. The iodine adsorption recovery rate can reach 96% to 98%, and the total regeneration loss rate is 3%. 3 discharge high temperature heating regeneration method 3.1 Introduction to the method This is a completely different regeneration method than the conventional high temperature heating regeneration method. The traditional method is to directly heat the activated carbon through the furnace body indirectly or in the furnace space under closed conditions, so that the carbon gradually warms up from the surface and the inside, and finally reaches a high temperature of 850 ° C and is introduced with water vapor. Foreign scholars believe that the normal heating regeneration temperature can not exceed 10 °C / mid, in order to prevent carbon matrix burning, so the whole process of regeneration for up to 6h. In this method, the carbon itself is rapidly heated, and the three stages of drying, roasting and activation are rapidly completed within 5 to 10 minutes. It does not need to be operated under closed conditions and does not require steam activation. It can be in contact with air at a high temperature of 850 ° C, and it can be naturally cooled without being completely ashed. Its strength is also unaffected, the carbon loss rate is <2%, and the iodine adsorption recovery rate is 95% to 100%. The discharge regeneration method is not only efficient but also consumes less energy. The dry carbon (dry basis moisture content is about 6%) regenerative power consumption is only 0.18 ~ 0.20 kW · h / kg activated carbon. The wet carbon (dry base moisture content is about 86%) is about 0.8kW·h/kg activated carbon in the whole process of regeneration. The power consumption is 1/7 of the energy consumption of the multi-layer furnace. It is the heat recovery moving bed regeneration furnace. It consumes 1/5; it is 1/10 of the energy consumption of the heat-recycling moving bed regenerator; it is 1/2 of the energy consumption of the direct-energized second-stage furnace. The discharge high-temperature heating regeneration method is similar to the direct current regeneration method in that it utilizes the conductivity of carbon itself and has electrical resistance. However, the high-temperature heating regeneration of the discharge is to control the energy, forcibly forming a pulsed electric orphan, and discharging the carbon to be regenerated. The discharge frequency is about 3,000 times/min, so that the whole process of regeneration is completed in 5 to 10 minutes, and the regeneration temperature reaches 800. -900 ° C. The activated carbon forced discharge regeneration method and device successfully developed in China (invention patent No. 85100619.A) has been applied to the regeneration of activated carbon in gold mines, thermal power plants, beer, beverage, chemical and other industries for many years. The principle is shown in Figure 11. The forced discharge regenerator with a regeneration capacity of 100 ks/h has a plane size of only 1.6 mX 2.0 m and a height of 2.5 m. In recent years, there has been a new innovation in the high-temperature discharge regeneration method--activated carbon frequency-frequency discharge pulsation regeneration device (patent number ZL01210957.6), which makes the discharge high-temperature regeneration device more efficient, smaller in volume, and has a regeneration capacity of 100kg/h. The size is only 1.3 mXl.2 m and the height is only 2.0 m. It is a kind of activated carbon regeneration device worth promoting. 3.2 Function of the discharge process The discharge regeneration has excellent effects in that it has the following functions during discharge: (1) The high temperature causes the adsorbed organic matter to rapidly vaporize and carbonize. (2) The gas heat release and electric hammer effect in the discharge latitude, so that the activated carbon adsorbate is decomposed by instantaneous ionization. (3) The ultraviolet rays formed by the discharge cause ozone in the air between the carbon particles to partially generate ozone, and discharge and oxidize the adsorbate. (4) The adsorbed water becomes superheated steam in an instant and undergoes an aqueous oxidation reaction with the carbide. 3.3 Comparison of regeneration effects The following comparisons were made between the effects of high-temperature heating regeneration and multi-layer, moving bed type regeneration devices: (1) Comparison with the effect of a multi-layer regenerator (8 layers). For the representative phenol of aromatic compounds, there are many carbonized residues. It is generally considered that it must be activated by steam activation to remove it. It is repeatedly regenerated 15 times by discharge regeneration method (adsorption amount 100-120 mg/z activated carbon, regeneration time 7 min), each time The measured value of post-regeneration intensity was the same as that of new carbon. The recovery rate of iodine value was 97.1%, and the recovery rate of phenol value was 97.2%. Pomono is regenerated in the multi-layer regenerative furnace (8 layers) for 30 min, activated by superheated steam, and regenerated at 850-950 °C. The activated carbon used in the advanced treatment of domestic sewage is regenerated 9 times. The iodine adsorption rate was 95%, and the strength decreased from 78% to 63.7%. (2) Comparison with the effect of the moving bed type regenerator. The effect of activated carbon for tertiary treatment of refinery industrial wastewater after regeneration in a moving bed regenerator is compared with that of the discharge regeneration method. The regeneration time of the discharge regeneration method is only 9.5 min, and the recovery of the iodine value, phenol value and methylene blue value of the regenerated carbon is better than that of the regeneration for 6 h, and the moving bed type regenerative furnace activated by superheated steam (two kinds of regeneration) The test charcoal of the device is the same kind of saturated carbon). (3) Effect after carbon regeneration for deep purification of drinking water. The column is used for the recovery of adsorption performance of carbon after deep regeneration of drinking water after discharge regeneration. 4 Conclusion (1) For the regeneration of saturated activated carbon used for water treatment, the regeneration effect of the high-temperature heating regeneration method is the best. (2) In the high-temperature heating regeneration device, the regeneration effect is better with a moving bed type or multi-layer type regeneration device. Rotary operation is more convenient, but the regeneration effect is related to the highest temperature that can be achieved. (3) In the heating and regenerating device using electric energy, the direct-energized regenerative device has more application value. (4) Discharge high-temperature heating regeneration method has the advantages of simple equipment, convenient operation, small volume, small footprint, low power consumption, high efficiency, no need for water vapor activation, low carbon consumption, and high adsorption recovery rate. It is a kind of activated carbon regeneration device worth promoting. PVC Electrical Tape,Wonder PVC Electrical Insulation Tape,Liquid Electrical Tape Fenghua Jade Motor Co., Ltd. , http://www.flagtapes.com
Several methods of regeneration of activated carbon