Experimental Study And CFD Simulation Of Mixing Process In Biogas Fermentation System

The development of new energy has become the inevitable trend of development according to the requirement of sustainable development strategy, especially with the development potential of methane in the renewable energy. Biogas is a technology which can will waste into clean energy, biogas production process and technical research’s importance has attracted more and more attention. The stir in the fermentation process plays a very important role, because biogas yield will be guaranteed when the fermentation strain fermentation raw material with full contact in biogas production process. But the marsh gas stirring device always references to other industry standards, and there have not the device for the characteristics of methane gas producing, based on the needs of the long development of biogas industry, biogas stirring device of exploratory will be researched in this paper.With the rapid development of computing technology, CFD numerical simulation technology in the agitating device is applied more and more widely. Biogas fermentation raw material composition is complex, but the influence of mixing process of physical properties are mainly rheological properties and density, the research show the manure of livestock is the pseudo plastic fluid, low concentrations of raw materials also can be approximated in a Newtonian fluid. In this paper, biogas fermentation mixing content as solid-liquid mixing system for study, research object is arranged as two-phase system of solid particles—water, solids concentration of8%, average particle diameter is0.63mm, viscosity is set to165.99mPa s, density p=1.2g/cm3.This article from two angles the test and numerical simulation to the marsh gas stirring device for research, the biogas fermentation effect of no mixing, two layer, three layer stirring paddle are studied in test, the result show the role of stirring in biogas fermentation process; through CFD numerical simulation technology to simulate the mixing process of fluid flow field’s distribution, this paper uses the Fluent software, In this paper, use Eulerian—Eulerian two-fluid theory to describe the two-phase flow in the mixing tank. Use standard κ—ε two-phase turbulence model to describe the characteristics of turbulent system, Act on the use of multiple references mixing tank fluid dynamic characteristics of two-phase flow, use CFD to simulate three dimensional flow field. Then compare results with experimental data.the marsh gas stirring device internal structure optimized on the basis of determination of numerical simulation technology in the study of the feasibility of biogas stirring device. This article from two aspects of the different mixing layer stirring paddle and different from the height of the base to the stirring device analysis. The main research results include: (1) This study based on the comparative of without stirring, two and three-layer impellers, the results showed that two or three layer stirring paddle stirring device gas production than no mixing should be higher than20%, three layer paddle stirring device gas effect is the best.(2) Based on the test research and simulation analysis, experiment results and numerical simulation of gas flow distribution effect has consistency, the application of CFD simulation technology in biogas fermentation raw material mixing process is feasible.(3) The study of the stirring paddle layer and the blades away from the bottom height of the stirring effect, based on mixing process fluid velocity field analysis of a layer of paddle, paddle two layer and three layer stirring paddle reach. three kinds of stirring paddle on the mixing device of fluid flow velocity distribution has different degree of influence, to mixed the purpose of the uniform, three kinds of stirring paddle in the three layer stirring paddle agitator stirring effect is good, the stirring device and the liquid height diameter H=D=200mm cases, from the bottom height value O=40mm mixing effect is the best.