전산유체 기법을 이용한 용존공기부상법에서의 접촉조 조건변화에 따른 충돌효율평가

Abstract

Dissolved air flotation (DAF) is a solid-liquid separation process that uses fine rising bubbles to removeparticles in water. Most of particle-bubble collision occurs in the DAF contact zone. This initial contactconsidered by the researchers to play a important role for DAF performance. It is hard to make upconceptual model through simple mass balance for estimating collision efficiency in the contact zonebecause coupled behavior o the fsolid-liquid-gas phase in DAF system is so complicate. In this study, 2-phase(gas-liquid) flow equations for the conservation of mass, momentum and turbulencequantities were solved using an Eulerian-Eulerian approach based on the assumption that very smallparticle is applied in the DAF system. For the modeling of turbulent 2-phase flow in the reactor, thestandard k-εmode l(liquid phase) and zero-equation(gas phase) were used in CFD code because it is widelyaccepted and the coefficients for the model are well established. Particle-bubble collision efficiency wascalculated using predicted turbulent energy dissipation rate and gas volume fraction.As the result of this study, the authors concluded that bubble size and recycle ratio are play importantrole for flow pattern change in the reactor. Predicted collision efficiency using CFD showed good agreementwith measured removal efficiency in the contact zone. Also, simulation results indicated that collisionefficiency at 15% recycle ratio is higher than that of 10% and showed increasing tendency of the collisionefficiency according to the decrease of the bubble size.