Performance Analysis of One Stage Anaerobic Digester Before and After Restating to Production Biogas/Biomethane

Abstract

In this work, biogas and biomethane production in a one-stage anaerobic digester (AD) are investigated. Four batch digesters were rotated at different speeds: 180 rpm for the first anaerobic digester (d1), 120 rpm for the second (d2), 60 rpm for the third (d3), and no speed at fourth digester (d4). Anaerobic digestion (AD) process of these digesters was thermophilic at 55℃ and 1 bar. The substrates were three liters of water, 1.5 kg of potatoes (PT), and 1.5 kg of moist cow dung (CD). Rotating speed, pressure, temperature, residence time (RT), and restarting time were investigated in theoretical and experimental energies of an anaerobic digester (AD). The simulation of one-stage anaerobic digestion (AD) is studied using Aspen Plus software. The simulations showed that increasing AD pressure by one to three bars in one stage increased biomethane production by 32%. Increasing the temperature from 35 to 70 degrees increased biomethane output by 38%. Increasing AD residence duration to 384 days increased biomethane concentration by 52.23%. The move increased AD's gross heating value by 1.73%. The experiment's findings were obtained by holding the system at 1 bar, 55℃, and varying the restarting time between 6 and 24 hours. The average biogas volume increase between the 1st-AD and the 4th-AD before rest, after restarting, and after/before restating AD operations is 118%, 124.5%, and 10.96%, respectively. The average biogas concentration increases between the 1st-AD and the 4th-AD before restating, after beginning, and after/before restating AD processes is 17.31%, 20.65%, and 6.4%, respectively. For the first and fourth digestors, the absolute average deviation (AAD) of biomethane content was 3.78% and 3.21%, respectively. Experimental and simulation data agreed. Finally, digestor performance was directly proportional to AD restarting time for one stage, with the optimal interval after 6 hours.