Research On Numerical Simulation For The Flow Characteristics Of Internal Circulation Anaerobic Reactor

As an important representative process of the third generation of anaerobic reactors, the internal circulation anaerobic reactor (IC reactor) has been widely used in industrial wastewater treatment for its high handling performance, stable operation, high volumetric loading and the produce of available methane energy. At present the most researches of the IC reactor are for the wastewater treatment technology research of reactor, and only a few people study the flow characteristics within the reactor. However, flow characteristics have a great impact on the wastewater treatment effect of IC reactor, so using computational fluid dynamics numerical simulation method to study the flow characteristics of the IC reactor has great reference value and theoretical significance.Firstly, this paper briefly introduces the basic structure of the IC reactor, process principles, advantages and basic theories require by computational model. By summarizing of the application of IC reactors at home and abroad and the use of computational fluid dynamics methods in the anaerobic reactor, significance and the main content of this research project is presented. This paper studied the flow characteristics within the first anaerobic reaction chamber and the internal circulation system in the reactor, and the results show that:(1) When the baffle angle of three-phase separator and the height of installation is fixed, the liquid velocity and turbulent kinetic energy in the first anaerobic reaction chamber at the bottom of the area have no obvious change. However, with the increase of the iteration time, the pressure is reduced while the gas holdup is increased. And in the three-phase separator area, both the pressure and gas holdup is reduced with the increase of the iteration time, but the liquid velocity is opposite,and turbulent dynamic phenomenon in the area is also obvious..(2) When the height of installation for the three-phase separator is fixed and the baffle angle of three-phase separator changed, the study found the following phenomenon:In the bottom area of the first anaerobic reaction chamber, pressure, turbulent kinetic energy, liquid velocity and the gas holdup were all increased with the increase of the baffle angle of three-phase separator. In the three-phase separator region, turbulent kinetic energy and liquid velocity increased with the increase of the baffle angle of three-phase separator, while the gas holdup decreased and the pressure presented a nonlinear characteristics, besides the higher of baffle angle of the three-phase separator, the more prone to the phenomenon of turbulence in the reaction chamber, the more obvious the reflux.(3) When the baffle angle of three-phase separator is fixed and the height of installation for three-phase separator changed, we found that the pressure and gas holdup in the bottom area of the first anaerobic reaction chamber is increased firstly,then decreased, while the turbulent kinetic energy and the liquid velocity had few changes. In the three-phase separator area, with increasing the height of installation, the pressure is increased, while the turbulent kinetic energy and the liquid velocity decreased, and the gas holdup is still increased first, and then decreased.(4) Through the numerical simulation on the internal circulation system within IC reactor, the study found that the method of computational Fluid mechanics which is used to simulate the flow characteristics of IC reactor is feasibility, the simulation flow properties and the actual flow characteristics are the same, and it is successful to realize the inner circle of liquid in the reactor.(5) Through changing the gas inlet velocity, the study on the characteristics within the reactor found that the turbulent kinetic energy, axial velocity distribution and radial velocity distribution in IC reactor is less influenced by the gas inlet velocity. However the pressure in the bottom area of the IC reactor is decreased with increasing the gas inlet velocity, while the situation in the other areas is opposite. And besides, the gas holdup in the IC reactor is increased with the increase of the gas inlet velocity.It is the first time to simulate the flow characteristics within the IC reactor in this paper, and the simulation results are the similar with the actual results. It will provide the certain reference value for the structure optimization design of the IC reactor.