Investigation On The NO Removal Process Of Ultra-Low Temperature Adsorption-Rapid Regeneration

Nitrogen oxide(NOx)is one of the common air pollutants,and the most mature flue gas control method currently used is the selective catalytic reduction technology(NH3-SCR)with NH3 as the reducing agent.The vanadium-titanium-based catalysts commonly used in NH3-SCR are biologically toxic,and the corrosiveness of NH3 also makes potential ammonia leakage and ammonia escape have certain safety hazards.As an alternative technology to NH3-SCR,the reducing agent for NO reduction by CO is easily available,the catalyst cost is low,so it has broad application prospects.Aiming at the dual role of oxygen in the NO removal by CO,a set of decoupling process was proposed in our group,which was realized by rotating the reactor.Based on this,we improved the NO removal efficiency by setting different zone temperatures and extending the residence time of the catalyst,and proposed a set of ultra-low temperature adsorption-rapid regeneration reactors for use in low-temperature flue gas after deSO2 and dehydration.The interior of the ultra-low temperature adsorption-rapid regeneration reactor is divided into three areas,and the catalyst unit is divided into two parts to complete the adsorption-regeneration cycle at different temperatures.The key to the operation of the reactor is that the breakthrough time of the catalyst is greater than the sum of the regeneration time and the cooling time.For this,we prepared a variety of materials and determined that coconut shell activated carbon(abbreviated as AC)with excellent adsorption performance was used as the research subject for modification testing After activation by nitric acid or potassium hydroxide,the NO adsorption performance of AC is enhanced.Loading active metals on this basis,the NO adsorption performance is weakened,but the NO reduction ability is given,thereby shortening the temperature difference in cooling.AC-based materials were characterized by BET,XPS,XRD,and elemental analysis.Relying on the characterization data and learning from the virtual porous carbon method,the corresponding molecular structure model was established.The adsorption form,adsorption site and adsorption type of NO AC-based materials were studied.The unevenness of the graphite crystallite layer is the main adsorption site of NO,and the adsorption of NO here is physical adsorption of multiple layers.The metal atoms that form bonds with the graphite crystallite layer affect the physical adsorption of NO around it to varying degrees.Very few NO atoms may chemically react with Co atoms within a distance of 2A.The amount of physical adsorption obtained by calculation accounts for the majority,and the desorption or dissociation of physical adsorption form of NO is easy to chemically adsorb,which provides a theoretical basis for rapid regeneration.Only activated AC-based materials were characterized by TPD to obtain the optimal regeneration temperature of 300℃,and metal-loaded carbon-based materials were tested for NO removal efficiency by CO to obtain the optimal regeneration temperature of 200℃.Three consecutive adsorption-regeneration cycles were tested in a mobile reactor.The time relationship of the three regeneration methods is feasible.The penetration time of the material with high temperature thermal regeneration method attenuates significantly.the regeneration effect of low-concentration CO continuous regeneration is the best,but the exhaust gas contains CO and NOx at the same time,which is more difficult to deal with.The effect of closed regeneration of high-purity CO is slightly worse,but it is simple to operate and has more application value.FTIR characterization of carbon-based materials in different states also verified the existence of chemical adsorption,and most of the formed NOx species could be desorbed at high temperatures.CO could compete with NO in adsorption and oxidation-reduction reactions,thus showing a better regeneration effect.In order to speed up the cooling rate,the carbon consumption rate of the carbon carrier in the air was further tested.Before 250℃,the carbon consumption rate is small and grows slowly,but at 300℃,it increases several times,which cannot be ignored.When the temperature is below 200℃,using external air cooling+air blowing AC-based materials is a faster way to cool down.Although the time relationship of carbon-based materials at 300℃ is feasible,the carbon consumption rate is too high and it cannot be used for a long time.In summary,the combination of high-purity CO closed reduction regeneration+air blowing and cooling is an ideal regeneration method,and Fe4Co/ACH is a more suitable NO removal material for this reactor.