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What are the reasons for the high-pressure drop of activated carbon adsorption box?
What are the reasons for the high-pressure drop of activated carbon adsorption box?The high-pressure drop of the activated carbon adsorption box is usually caused by design defects, improper operation, or insufficient maintenance. The following are the specific reasons and analysis:1. Activated carbon performance problems Adsorption saturation After the adsorption of pollutants by activated carbon reaches saturation, the pores are blocked, resulting in increased airflow resistance. For example, when dealing with VOC waste gas, if the activated carbon is not replaced in time, the pressure drop after adsorption saturation may soar from the initial 300Pa to more than 800Pa. Particles are crushed and pulverized. Activated carbon is broken by friction during transportation, loading, or operation, resulting in fine powder clogging the bed. For example, frequent starting and stopping of equipment leads to particle collisions, and the pressure drop can increase by more than 50% when the pulverization rate exceeds 10%. 2. Equipment design and structure problems Uneven airflow distribution The air inlet is not equipped with a diversion device, which causes the gas to wash the local activated carbon layer and accelerate the blockage. For example, in one factory, the pressure drop increased from 200Pa to 600Pa in 3 months because there was no air distribution plate. Insufficient cross-sectional area The flow rate of the empty tower is too high (for example, more than 0.5m/s), resulting in a sharp increase in the resistance of the gas through the activated carbon layer. For example, in the design air volume of 10000m³/h adsorption box, if the cross-sectional area is only 10 square meters, the empty tower flow rate of 0.28m/s (close to the critical value), easily causes abnormal pressure drop. 3. Poor intake condition Preconditioning deficiency The dust, oil mist, or viscous material in the exhaust gas/wastewater enters the adsorption tank directly and adheres to the surface of the activated carbon. For example, a spray paint exhaust gas treatment system without a dust collector may increase the pressure drop by 100-200Pa per week. Uncontrolled temperature and humidity High temperature (> 60℃) or high humidity (> 90% RH) caused the decrease of water condensation or chemisorption efficiency in activated carbon pores. For example, the exhaust gas from the printing and dyeing plant goes directly into the adsorption tank without cooling, and the pressure drop doubles in 2 weeks. 4. Improper operation The adsorption time is too long. The adsorption bed is not switched in time or the regeneration period is too long, resulting in excessive adsorption of activated carbon. For example, in a catalytic combustion system, the regeneration interval was extended from 4 to 8 hours, and the pressure drop increased from 250Pa to 500Pa. Excessive regeneration temperature During the regeneration process, the temperature exceeds the activated carbon tolerance limit (such as > 800℃), resulting in the destruction of the pore structure and the increase of resistance. For example, if the regeneration temperature is too high for sinter-activated carbon, the pressure drop increases by 300%. 5. Inadequate maintenance and management Not regularly blowback or clean Dust or impurities accumulate on the surface of the activated carbon and are not removed by the blowback system. For example, an electronics factory stopped working for 1 month due to a blowback system failure, and the pressure drop increased from 150Pa to 450Pa. The activated carbon layer is laminated. The activated carbon layer is not loosened for a long time, resulting in particle compaction and decreased permeability. For example, in an adsorption chamber that has not replaced activated carbon for 3 years, the bed density increased from 450kg/m³ to 600kg/m³, and the pressure drop increased by 200%. Typical case Exhaust gas treatment of a petrochemical plant: Because no pretreatment equipment was installed, catalyst dust entered the adsorption tank, the pressure drop rose from 180Pa to 800Pa within 3 months, and the activated carbon layer was completely blocked. Urban sewage treatment plant: the activated carbon adsorption tank has not been backwashed for a long time, and the suspended matter is trapped, resulting in the pressure drop from 120kPa to 400kPa, and the treatment flow rate is reduced by 50%. Solution proposal: Monitor the pressure difference regularly (it is recommended to record it every 2 hours) and set the alarm threshold (such as the initial value + 50%). Strengthen pretreatment (such as adding cyclone dust removal + filter cotton), and control the intake dust concentration < 10mg/m³. Check the activated carbon layer every quarter, and find powder or hardening in time to replenish or replace. Optimize operation parameters (such as empty tower flow rate ≤0.3m/s, regeneration temperature control at 700-750℃). The above measures can effectively prevent the problem of high-pressure drop and ensure the stable operation of the adsorption system. |
