Flow Field Numerical Simulation And Structural Optimization Of Internal Circulation Anaerobic Reactor

As one of the most efficient anaerobic reactors Internal Circulation(IC) anaerobic reactor has been widely used to treat the wastewater from beer brewing, potato processing, papermaking and other industrial production, according to the previous researches of the IC anaerobic reactor, the vast majority of research priorities was focus on the reactor startup, operation characteristics and removal rate of organic matter, and seldom studied the efficient mass transfer effect of the internal flow field characteristics.The determination of anaerobic reactor hydrodynamics characteristics is the core technology of optimization design, amplification and operation of these reactors, the uniformity of velocity distribution affects the effective volume of the reactor, and local flow field of shearing action leads to the formation and keep process of anaerobic granular sludge.Therefore in this paper the water distribution uniformity of the pipe network water distributor, the flow field characteristics of the first reaction chamber, and the circulation of the structure of the circulation were simulated by means of fluent software. The main conclusions of simulation and engineering structural optimization recommendations as follows.(1) For pipe network, the max water flow of the orifices on the outermost layer of pipes, and the variation of different water flow curve exhibited a marked serration. The slower of feed water flow rate and the smaller of orifices diameter, the better water distribution uniformity, and the much number of orifices, the better water distribution uniformity. Inlet flow velocity and orifices diameter had the greatest impact on water distribution uniformity by orthogonal test analysis. The water distribution uniformity increased with increasing wall roughness within limits. The same performance on the water flow of the orifices of every layer distribution pipe was shown wherever the orifices jam occurred, but it had a great influence on water distribution uniformity.(2) For different water feed and return line back, fluid shaped the strong vortex flow at the bottom of the first reaction chamber, the fluid flow was gradually transition from mixed flow to push flow, and the flow properties of chamber of inflow of30holes were showed the most beneficial to mass transfer between the fluids mixing. Compared with flat bottom reaction chamber, the reactor wall and center location to join conical diversion structures could weaken the eddy current energy consumption which occurring in the bottom of the chamber, the rising rate of fluid where the reactor center and near wall have increased, and the fluid flow alternation of up and down have intensify.(3) The internal circulation flow increases with decreasing guide plate gap, air seal clearance as well as the vertical Angle of under gas sealing plate, the results of structural optimization design for the guide plate showed that the larger internal circulation flow with the single guide plate structure of three-phase separator. Internal circulation flow appeared increases then decreased the riser pipe diameter, and the optimal riser pipe diameter is32mm resulted from this paper. The internal circulation flow increases with decreasing fluid rise velocity and outlet pressure. In the reactor startup phase, it could reduce the gas pressure in the gas and liquid separator to speed the reactor startup, and the best rising liquid flow rate was the result of fluidization of sludge, loss of granular sludge and the flow of internal circulation.