ENHANCEMENT OF BIOGAS PLANTS EFFICIENCY BY THE IMPROVEMENT OF HYDRAULIC MIXING
Mixing appears to be necessary for effective operation of biogas plants and consistency of feedstock fermentation inside the reactor. Mixing plays an important role as it leads to more close connection between microorganism and a substrate, even distribution of рН and temperature, and furthermore, prevents stratification of the sediment and crust formation and helps to release biogas bubbles.
Within the scope of this work the study of hydraulic mixing for a tank with two input pipes was carried out (pic.1). The substrate stream from the side input pipe ensures sediment mixing at the bottom of the tank. The substrate stream from the upper input pipe prevents crust build up on the surface of the liquid. At a certain distance from the input pipe there is a reflecting partition to reduce the opportunity for crust formation.
Assessment of mixing quality was carried out taking into account the intensity of biogas formation. Dependencies of mixing quality change on time and substrate input were received. Numerical investigations of organic substrate circulation in tanks with different location of input and output pipes show that the given location of the pipes provides better mixing (mixing rate increases by 3 times). Reflecting partition prevents from crust formation and influences mixing quality. In this case mixing improves with the increase of distance from upper input and of reflecting partition radius.
Efficiency of anaerobic digestion process improves at the expense of homogeneous fermentable organic matter maintenance that is achieved by modification of the reactor components.
Enhancement of biogas plants efficiency by the improvement of hydraulic mixing
1. The Branch of Research Center of Power Engineering Problems of Institution the Russian Academy of Sciences the Kazan Scientific Centre RAS ENHANCEMENT OF BIOGAS PLANTS EFFICIENCY BY THE IMPROVEMENT OF HYDRAULIC MIXING I.A. Trakhunova
10. 2 , 3 – the most popular types of load 1 – type of load suggested in this research Numerical investigations of organic substrate circulation in tanks with different location of input and output pipes Type of load 1 Type of load 2 Type of load 3
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12. To estimate the quality of mixing the following criterion is suggested :
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14. Reflecting partition prevents from crust formation Values of h and r 0 used in the calculation 1- h =0.96, r 0 = 0.1; 2 - h =0.9, r 0 = 0.1; 3 - h =0. 85 , r 0 = 0.1 4 - h =0.96, r 0 = 0.2; 5 - h =0.96, r 0 = 0.05; 6 – without reflecting partition.
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16. Dependencies of mixing quality change on time t [s] and substrate input Q [m 3 /s] 1- h =0.96, r 0 = 0.1 Q =0.0002; 2 - h =0.9, r 0 = 0.1, Q =0.0002; 3 - h =0.85, r 0 = 0.1, Q =0.0002; 4 - h =0.96, r 0 = 0.05, Q =0.0002; 5 - h =0.96, r 0 = 0.2, Q = 0.0002; 6 - h =0.96, r 0 = 0.1, Q =0.0001; 7 - h =0.96, r 0 = 0.1, Q =0.0003.
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