抄録
A comprehensive study was carried out to examine the possibilities of separating phases by rapid recycle of the leachate from the solid state acidification reactor to the methanation reactor at 55°C with dried sorghum feed.
As a control reactor of phase separation system, a plug flow reactor in which solids pass through the reactor and are wasted in the same sequence in which they enter, begin to fail at organic loading rates of greater than 4.0 TVS/l-d. The maximum methane production rate inthis single stage plug flow reactor, approached 1.45 v/v-d and 83.1% TVS removal effciency at a solid retention time of 68 days.
The production of 20% of the total system methane in the acidification reactor at organic rates of 30g TVS/l-d indicates that separation of phase was unsuccessfully by a rapid leachate removal. Even though the solids retention time was only 4.6 days, the methanogenes were percent in the acidification reactor to produce a singificant quantity of methane. As organic loading rates increased (5g TVS/l-d to 30g TVS/l-d) the methane production rates of acidification reactor were suppressed from 0.82 v/v-d to 0.72 v/v-d, while the methane production rates of methanation reactor were increased from 0.88 v/v-d to 2.87 v/v-d. The TVS removal efficiencies decreased substantially from 82.1% to 28.8%, as the organic loading rates increased.
The average volatile fatty acids concentration of acidification reactor varied from 245 to 175mg/l as acetic acid concentration. The half saturation velocity constant of Monod equation, Ks, for methanogenesis is likely much lower than the substrate concentrations achieved in these studies, approximately 200 mg/las acetic acid.
