Basic introduction
Activated carbon regeneration (i.e. activation) technology refers to the use of physical or chemical methods to remove adsorbed impurities adsorbed on activated carbon without destroying the original structure of activated carbon, restoring its original adsorption performance, so as to achieve the purpose of reuse. value. The application range of activated carbon is becoming more and more extensive. However, because activated carbon is easily saturated and loses its adsorption capacity during use, it must be replaced frequently to achieve the best results. Each time the new carbon is replaced or the waste carbon is disposed of, the operating costs of the enterprise will increase, so the regeneration of saturated activated carbon must be considered to achieve the purpose of circular economy. Activated carbon regeneration and expanded utilization of secondary activated carbon resources are the most effective ways to recycle waste carbon. Therefore, the recycling and reuse of activated carbon has strong economic and social benefits. At the same time, the recycling and regeneration of activated carbon is also supported and encouraged by national policies.
Mainly adopts external heat regeneration method. The equipment structure and material selection are relatively special. The principle is that part of the volatile organic matter adsorbed during the drying process is desorbed at high temperature and converted into waste gas, which is evaporated together with water vapor; during the carbonization process, most of the organic matter is carbonized and adsorbed in the pores of the activated carbon; during the activation process In the process, the remaining organic compounds are pyrolyzed at a higher temperature, and the waste activated carbon is activated in the presence of a quantitative oxidant (water vapor or a small amount of oxygen). The activated carbon restores the original pores and creates new pores, achieving the purpose of regenerating the waste activated carbon. External thermal heating regeneration has the advantages of high regeneration rate and short regeneration time, and is a mainstream process for activated carbon regeneration.
process flow
1.1. Raw materials
Testing: Waste powdered activated carbon enters the site for sampling and testing. The qualified ones are temporarily stored in the qualified warehouse, and the unqualified ones are temporarily
stored in the unqualified warehouse and then returned.
1.2. Furnace compatibility
Before entering the rotary kiln, according to the detection results of waste activated carbon, the waste activated carbon containing relatively high chlorine and fluorine content is matched with
the waste activated carbon containing relatively low chlorine and fluorine content or without chlorine and fluorine. The materials are mixed evenly before entering the furnace. , to ensure that
the chlorine and fluorine content in the waste activated carbon entering the furnace is relatively stable.
1.3 Feeding
In the waste activated carbon storage warehouse, the waste activated carbon packed in tons of bags and tons of barrels is placed in the feed hopper using a crane, forklift, etc., and the waste
powdered activated carbon is sent to the external heating system through a sealed lifting and discharging device and a feeding mechanism. Inside the rotary kiln.
1.4 Regeneration
In the external heating rotary regeneration furnace, the waste powdered activated carbon slowly moves forward under the influence of the inclination and gravity of the external heating rotary
regeneration furnace. During the movement, the material contacts the inner tube wall of the external heating rotary regeneration furnace; the heat source is Provided by furnace tail heat source
room (diesel and liquefied gas).
When entering the front section of the external heat rotary regeneration furnace (that is, the temperature is lower than 600°C), the material exchanges heat with the heat in the external heat
rotary regeneration furnace. The water in the waste powdered activated carbon evaporates, and at the same time, some low-boiling point organic liquids Then evaporate.
After the drying treatment in the front section of the external heating rotary kiln, it enters the rear section of the external heating rotary regeneration furnace (that is, the temperature
is higher than 800°C), and a small amount of air and water vapor are introduced, and the waste gas adsorbed by the waste powdered activated carbon is regenerated. It is desorbed at high
temperature and reacts with oxygen to produce water vapor, carbon dioxide and other gases. The regenerated activated carbon is deposited at the bottom of the rotary kiln, collected by
negative pressure quenching, packaged and recycled to obtain the finished powdered activated carbon; the regenerated flue gas is first burned in the secondary combustion chamber. Then it
enters the exhaust gas treatment system and is discharged from the 35-meter-high exhaust pipe.
The external heating rotary kiln is divided into waste powder activated carbon feeding section, carbonization section, activation section and activated carbon discharging section. The waste
powdered activated carbon maintains a certain amount in the feeder above the feed inlet of the rotary kiln, forming a natural seal to isolate the gas in the furnace from the outside world.
In the carbonization section, the temperature control facilities automatically control the temperature of each section to around 800°C; in the activation section, the average spacing between
temperature control facilities is 3 to 4 meters, and the temperature of each section is automatically controlled to around 900°C. In the activated carbon discharging section, the powdered
activated carbon is directly collected through the negative pressure quenching collection system for rapid collection.
In the external heating rotary regeneration kiln, the waste heat boiler transports part of the generated water vapor through the steam delivery pipe to mix with the materials. After
high-pressure injection, the materials and steam are fully contacted, providing the necessary oxygen, gas and water vapor, and in the subsequent Under the pull of the fan, the activated carbon
flows from the furnace head to the furnace tail. The first stage is the carbonization section, which carbonizes the adsorbed volatile substances and high-boiling point organic matter remaining
in the pores of the activated carbon. High-boiling organic matter is decomposed and carbonized in the adsorbed state, and remains in the form of fixed carbon. The remaining char generated
during the carbonization process is decomposed at 900°C using gases such as carbon dioxide and oxygen. Oxygen has strong oxidizing properties and can easily cause excessive consumption
of activated carbon. It is generally not used, and oxygen should be strictly controlled in the heating regeneration furnace. This project chooses to use water vapor to decompose oxidative gases
in an anaerobic environment. The material is gradually opened through steam activation pores under the action of high temperature. The regeneration process is a high-temperature anaerobic
process, in which organic elements and halogens mainly undergo oxidation reactions to form stable oxides. Heavy metals mainly exist in the form of ash in activated carbon end products.
Among them, some heavy metals such as Ag are loaded in dust and emitted in the form of oxides.
The following reactions occur on the surface of activated carbon:
C+O2=CO2 2C+O2=2CO
2CO+O2=2CO2 N+O2=NO2 C+O2=CO2
C+ 2H2O=2H2+ CO2 C+ H2O= H2+ CO C+ CO2=2CO
Azo compound=N2+free radical 2H2+O2=2H2O S+O2=SO2
Cl -+H+=HCl
F -+H+=HF
The occurrence of these chemical reactions not only vaporizes the carbon atoms on the capillary surface of the activated carbon, expands the capillary pores, and forms a new active surface,
but also releases a large amount of flammable gases in the process. The oxygen reaction can release a large amount of heat energy, which can be used as a heat source to maintain the furnace
temperature. The adsorbed substances are carbonized, activated or burned at high temperature to complete the regeneration process. If the heat energy is insufficient during the regeneration
process, the heat energy will be replenished through the heat source chamber at the end of the regeneration furnace.
Regeneration exhaust gas is generated during this process, which is introduced into the secondary combustion chamber for combustion, processed by exhaust gas treatment facilities, and
then discharged through the 35m1# exhaust pipe.
The powdered activated carbon in this project adopts countercurrent external heat regeneration method.
1.5 cooling
Due to the negative pressure, the regenerated powdered activated carbon passes through the closed conveying pipe and enters the coil collector for cooling. The cooled material is then
collected by the cyclone collector and bag collector, and then transferred and packed into the warehouse. The coil collector uses recycled water as cooling water to flow in the inner tube of the
cooler to take away the heat of the activated carbon and reduce the temperature of the activated carbon. The cooling water is recycled and regularly discharged to wastewater treatment facilities
to remove impurities for reuse.
1.6 Screening and packaging
The regenerated powdered activated carbon is cooled, sealed under negative pressure, packed into bags, and then screened again for impurity removal before being packaged and stored for
sale.
1.7 Finished product storage
The packaged powdered activated carbon is sold directly as finished product.
Flue gas treatment process
The main pollutants in regeneration flue gas are smoke dust, acidic components (SO2, NO2, HCl, HF), CO, dioxins, etc. The flue gas purification treatment system completes the cooling,
deacidification and dust removal of combustion flue gas, and needs to control harmful substances such as dioxins.
The flue gas purification process is as follows: the regenerated flue gas after combustion in the secondary combustion chamber undergoes SNCR at a temperature of 1100°C. After denitration,
the heat is recovered through the waste heat boiler to reduce the flue gas temperature to 550°C, and then enters the quenching tower and is atomized with recycled water. Rapid cooling ensures
rapid cooling within 1 second in the temperature range of 550℃~200℃, which can effectively prevent the regeneration of dioxins. Then the flue gas enters the dry deacidification tower, and
absorbers such as quicklime and powdered activated carbon are sprayed into the absorbent. It is deposited on the bag wall of the bag dust collector to form a filter cake, so that the deposited
absorbent can continue to absorb gaseous pollutants and dioxins in the flue gas to achieve the purpose of deacidification and removal of pollutant dioxins. The absorbent is deposited on the
bag wall of the bag dust collector to form a filter cake, allowing the deposited absorbent to continue to absorb gaseous pollutants in the flue gas. The flue gas after being dusted by the bag
dust collector is drawn by the induced draft fan into the wet deacidification tower, and is further deacidified by spraying alkali liquid. After the deacidification is completed, it enters the
demister for water and gas separation, and then the flue gas is adsorbed by activated carbon. The box further absorbs and removes the remaining trace harmful components in the flue gas.
The exhaust gas is finally heated to 120 degrees by the flue gas heating device and dewhitened before entering the exhaust pipe and discharged into the atmosphere. The entire flue gas process
is under negative pressure. The flue gas collection method is hard-connected, and the collection efficiency is 100%.
The flue gas purification system of this project has emergency treatment measures. First, a spark trap is set up on the main road to prevent sparks from burning subsequent equipment
when the flue gas purification system cannot operate normally (such as water outage, equipment damage, etc.) Destruction; when the main equipment or auxiliary equipment fails, the rotary
kiln immediately stops and alarms, opens the bag bypass valve, and the remaining flue gas in the flue enters the alkali spray tower for spraying and defogging, then enters the activated carbon
adsorption tower for treatment, and then Then it is discharged outside through the induced draft fan.
The regenerated flue gas after combustion in the secondary combustion chamber undergoes "SNCR denitrification + quenching + dry deacidification + dry dioxin removal + bag dust removal
+ wet deacidification + water separation + activated carbon adsorption treatment + flue gas reheating" Finally, it is discharged through a 35m high exhaust pipe.
Product Parameter
