Biomedical Engineering Reference
In-Depth Information
VSS/day and maximum hydrogen yield of 1.37-2.14 mol/mol hexose were obtained
at a COD concentration of 34 g/L. Zhao et al. [ 46 ] optimized the hydrogen
production from sucrose in a UASB reactor using response surface methodology,
finding that the maximum hydrogen yield of 1.62 mol/mol hexose was achieved
when the wastewater contained 14.5 g/L sucrose and the bioreactor was operated
at an HRT of 16.4 h.
The suitability of any process lies in its capacity to be scaled up to the industrial
level. In 1999, a pilot-scale study for biohydrogen production was performed in a
continuous fermentor with a working volume of 1.48 m 3 for over 200 days. The
system was fed with molasses-containing wastewater and was operated at an OLR
from 3.1 to 85.6 kg COD/m 3 /day. The hydrogen yield first increased with the
increase of the OLR, but decreased when the OLR exceeded 68.2 kg COD/m 3 /day.
The maximum hydrogen production rate was 5.57 m 3 H 2 /m 3 /day, with a specific
production rate of 0.75 m 3 H 2 /kg VSS/day. At an OLR of 35-55 kg COD/m 3
reactor/day, the hydrogen yield reached 26.13 mol/kg COD removed [ 47 ]. This
achievement was selected as one of the ten top science and technology break-
throughs in China in 2000.
In 2005, the first full-scale demonstration project of fermentative hydrogen
production was conducted for 1 year, with a capital investment of CNY 21
million. The system consisted of seed sludge acclimation and enrichment,
fermentative hydrogen production, hydrogen purification, fermentative methane
production from residues of hydrogen production, and wastewater treatment.
A 100-m 3 CSTR (working volume of 64.5 m 3 ) was designed for the fermentative
hydrogen production from molasses-containing wastewater. Under the operation
parameters of an OLR of 14-45 kg COD/m 3 /day, pH 4.4-5.0, and alkalinity over
500 mg/L (CaCO 3 ), the reactor performed the ethanol-type fermentation with an
average hydrogen productivity of 285 m 3 /day and a maximum productivity of
588 m 3 /day. Through bioaugmentation by supplying efficient hydrogen-producing
microorganisms, the average hydrogen productivity was enhanced to 334 m 3 /day,
corresponding to a volumetric hydrogen production rate of 5.26 m 3 /m 3 /day and a
specific rate of 0.83 m 3 H 2 /kg VSS/day. Over 95% of the total sugars in the
feedstock were degraded. The hydrogen purification system, which consisted of a
desulfurization tower and a pressure swing adsorption tower for CO 2 removal,
improved the hydrogen content in the biogas from 40-54% to 99.99%. The esti-
mated cost of producing 99.9% H 2 was CNY 1.37 per cubic meter. The hydrogen
produced was used to generate electricity via fuel cells. The effluent from the
process was used for fermentative methane production followed by a wastewater
treatment process. The final effluent met the national discharge standards.
3 Biohydrogen Production from Lignocellulosic Biomass
China is a large agriculture country, with 80% of its population living in rural
areas. About 700 million tons of lignocellulosic wastes such as corn stover and
wheat straw are produced annually. These kinds of biomass usually contain
Search WWH ::




Custom Search