Study On Oxidative Stabilization Of Pitch Spheres In Fluidized Bed Reactor

Pitch based spherical activated carbons (PSACs) can be prepared from pitch through crushing, spheroidizing, oxidative stabilization, carbonization, and activation processes. Among these processes, oxidative stabilization of pitch spheres is the most energy-and time-consuming step. At present, the oxidation reactor used is fixed bed oxidation furnace, which has many disadvantages, such as low oxidation efficiency, huge energy consumption, and easily burning pitch spheres, and so on. Therefore, it is urgent to develop a new type of oxidation reactor with high efficiency. In this work, the fluidized bed was successfully developed as the oxidation reactor for pitch spheres. By enhancing the heat and mass transfer, the oxidation efficiency of pitch spheres in the fluidized bed was 5 times higher than that in fixed bed oxidation reactor. In addition, PSACs were prepared from the oxidized pitch spheres through carbonization and activation. The adsorption behavior of CO2 over the PSACs was also investigated.The oxidation behavior of pitch spheres was studied in the self-designed fluidized bed reactor. The fluidization characteristics of pitch spheres were investigated. When the inlet velocity of the air reached to 0.21m/s, pitch spheres started to be fluidized, and subsequently the bed was in the bubbling phase. Under this condition, the bed was heated to 300℃for 2h with a rate of 0.5℃/min to oxidize pitch spheres. After the oxidation in the fluidized bed, oxidized pitch spheres with smooth surface morphology were obtained. Carbonized pitch spheres with smooth surface morphology were prepared through carbonization of the oxidized pitch spheres. In the fluidized bed, the gas-solid contact is more sufficient and the resistance of mass transfer in the gas film is lower than those in the fixed bed oxidation reactor, which promotes the diffusion of O2 molecule into the internal part of pitch spheres, and thus enhances the oxidation efficiency of pitch spheres.PSACs were prepared through steam activation of the carbonized pitch spheres. The pore structures of PASCs were controlled by changing the activation time. Moreover, the adsorption behavior of CO2 over PSACs was studied. Results indicated that the adsorption capacity of PSACs with specific Surface area of 1020m2/g was 0.66 mmol CO2/g PSAC at 25℃. PSACs exhibited high CO2 adsorption capacity at the conditions of high CO2 concentration, low temperature and humidity, and small space velocity.