Study Of Characteristics Of Oxidation Stabilization Process Of Coal Pitch Spheres

Oxidation stabilization is a key process in the preparation of coal pitch-based spherical activated carbon.Because of its long-time consumption and heavy energy consumption,it becomes an important factor restricting the industrialization and large-scale development of the industry.In order to further develop the coal pitch deep processing industry and meet the domestic demand for high quality activated carbon,this paper carried out the related research on the oxidation stabilization process of coal pitch spheres in rotary kiln,aiming at grasping the characteristics of oxidation stabilization process and providing theoretical and data support for the optimization control of operating parameters of the rotary kiln.The characteristics and kinetics of the oxidation stabilization process of coal pitch spheres were investigated by thermogravimetric analysis.The effects of particle size range,heating rate and oxidative temperature were researched.Components characteristics and the surface topography before and after the reaction of coal pitch spheres were analyzed by EI and SEM.The results show that the oxidation stabilization process can consist of four stages:light component pyrolysis,preliminary oxidation,oxidative weight increment and constant temperature oxidative weightlessness.Reducing particle size,selecting moderate heating rate and increasing the oxidative temperature is beneficial to the oxidation stabilization.A tubu furnace test research system for the oxidation stabilization of coal pitch spheres was established.The effects of heating rate,bulk thickness,oxidative temperature and oxygen concentration on the gas desorption characteristics and solid morphology of coal pitch spheres were researched.The results show that the C-H of fatty side chain and some aromatic rings of the coal pitch spheres are broken during the oxidation stabilization process,and the broken bonds are cross-linked and condensed to form the stable fused ring structure or absorb oxygen to form the heat-resistant oxygen-containing functional groups such as C-O or C=O.At the same time,low molecular gases such as CO₂,CO,CH₄ and H₂O and high molecular aromatic hydrocarbons such as naphthalene,benzothiophene and fluoranthene was desorbed.Furthermore,decreasing heating rate,choosing moderate bulk thickness,increasing oxidation temperature or the oxygen concentration lead to an increase of CO₂ and CO production quantity.The C content is decreased and the O content is increased obviously and more stable oxygen-containing functional groups are formed,which help to increase the degree of oxidation reaction and improve oxidation stabilization effect.Built on the thermogravimetric analysis and gas detection results,the kinetic model of oxidation reaction of coal pitch spheres was proposed.The industrial rotary kiln was regarded as the research object to establish the three-dimensional flowing model coupling heat transfer,mass transfer and chemical reactions of the oxidation weight increment process of coal pitch spheres as the basis of the Euler-Euler method.Numerical simulations were carried out and the effects of air flow rate and rotational speed on the gas-solid flow,heat transfer and reaction characteristics of the rotary kiln were investigated,which provided guidance for the optimal control of operating parameters.The results demonstrate that the particles in the kiln are in rolling motion,and the accumulation area can be clearly divided into the active layer with high velocity and active reaction,and the passive layer with small speed and almost no mixing.The conversion rate of coal pitch spheres increases slightly with air flow rate raising,but increases significantly as the rotational speed increases.Finally,combined with the test and numerical simulation results,the optimal test operation scheme for the temperature range control was determined,which air flow rate is 3m³/h and rotational speed is 0.035rad/s.The pilot test of the oxidation stabilization of coal pitch spheres on the rotary kiln was carried out well.Consequently,the coal pitch oxidized spheres with good appearance and high quality was obtained.