Study On Hydrodynamics Of P-Xylene (PX) Oxidation Reactor

This research investigated the key technologies for designing large-scale industrial PX oxidation reactor and the development of a new style PX oxidation reactor. A serious of technical suggestions have been proposed for the structure intensification of existed reactor and the design of a new reactor after the investigation on the relationships between hydrodynamics and geometrical structures of two existed representative PX oxidation reactors. Some proposals have already been applied for the modification of a PTA process in a company and created economic value.This research consisted of three parts which were shown as follows:1) Structure Optimization of Existed PX Oxidation ReactorBased on the systematical investigation on the hydrodynamics of two existed industrial-scale PX oxidation reactors, the gas sparger design and impeller flooding etc. were optimized.The design of shallow bubble column PX oxidation reactor is usually controlled by gas dispersion, liquid mixing and solid suspension. This research investigated the influences of aspect ratio, gas sparger, bottom shape and short size draft tube on the reactor performance. The optimized structure design was accordingly proposed.The maximum capability of hydrofoil/turbine mixed impellers stirred vessel PX oxidation reactor is generally controlled by the impeller flooding. This research investigated the hydrofoil impeller flooding characters of the reactor with high gas velocity and high solid concentration. The relationship between the position of gas inlet and flooding impeller was also investigated and the optimized position of gas inlet was found.2) Foundamental ResearchAn electrical capacitance tomography (ECT) method corresponding to the high gas flow rate in the industrial PX oxidation reactor has been developed to identify bubbling/jetting regimes transition from large submerged orifices. The influences of the nozzle diameter on the flow regime transition were investigated during the gas bubbling process. The critical nozzle diameter for distinguishing small nozzles from large nozzles was proposed.With the particle image velocimetry technique (PIV) and the large eddy simulation (LES), the flow pattern and the trailing vortex structure of a hydrofoil impeller stirred reactor were investigated. The difference between flow patterns induced by axial flow impeller and those induced by radial flow impeller was understood and the occurrence of the impeller flooding was accordingly explained.3) Industrial ApplicationBased on the structure optimization and basic research results, a new PX oxidation reactor has been designed. And the reasonable combination of mixed flow and plug flow in the new reactor was carried out to match with the PX oxidation character. The new reactor has apparent advantages in structure and performance compared with the two existed PX oxidation reactors. With further optimized structure, bright industrial prospects can be foreseen...