Effect of continuous micro-aeration on hydrogen production by coal bio-fermentation

In order to study the effect of micro-aeration on hydrogen production from coal, bituminous coal D from the Yima mining area was selected. An experiment to simulate hydrogen production by bio-fermentation was carried out with mine water as the source of bacteria. The results show that with an increasing aeration rate, the hydrogen production continuously decreased. At the end of gas production, the total hydrogen production under aeration rates of 0.0015 L/h, 0.015 L/h and 0.15 L/h was 3.60 mL/g, 1.50 mL/g and 0.58 mL/g, respectively. The molar concentrations of volatile fatty acids (VFAs) in the reaction liquid increased continuously, and the pH decreased overall. The COD content of the liquid phase first increased and then decreased. The COD degradation rates of three different aeration rates at the end of hydrogen production were 43.67%, 16.26% and 5.87%, respectively. With the increasing aeration rate, the dominant hydrogen producing bacteria during bio-fermentation gradually changed from Clostridium to Propionibacterium, and the type of fermentation also changed from butyric acid-type fermentation to propionic acid-type fermentation. In conclusion, the experimental results provide a theoretical basis for exploring hydrogen production via coal bio-fermentation under continuous micro-aeration.