Abstract. This paper performs a batch experiment for pre-acidification treatment and methane production from chicken manure by the two-stage anaerobic fermentation process. Results shows that the acetate was the main component in volatile fatty acids produced at the end of pre-acidification stage, accounting for 68% of the total amount. The daily biogas production experienced three peak period in methane production stage, and the methane content reached 60% in the second period and then slowly reduced to 44.5% in the third period. The cumulative methane production was fitted by modified Gompertz equation, and the kinetic parameters of the methane production potential, the maximum methane production rate and lag phase time were 345.2 ml, 0.948 ml/h and 343.5 h, respectively. The methane yield of 183 ml-CH4/g-VSremoved during the methane production stage and VS removal efficiency of 52.7% for the whole fermentation process were achieved.
This paper designed a range of 0.1 ~ 250 kHz sine wave sweeping constant current source, which sine wave generator based on FPGA chip and DDS technology, the desired sine wave frequency was obtained by controlling the frequency control words. Low-pass filter circuit was realized by using the LTC1560-1, conversion circuit from the voltage to the current was consisted of a Howland current pump. The constant current source shows a good spectral impedance purity and amplitude.
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