C.-C. Lien et al.
fr om t he conver s i on of natural biomass. The major portion of biogas is carbon dioxide (CO2), a mmonia ( NH3),
hydrogen sulfide (H2S) and methane (CH4), of which hydrogen sulfide apparently is the most toxic to both hu-
mans and animals. Agricultural by-products are often the problem of environmental pollution and affect human
health. T he major source of methane contained in the atmospheric is agricultural activities, including straw and
cattle, pigs and other livestock. Theoretically, the methane productivity can be measured in terms of volatile
solid s (VS) . The theo retic al metha ne p roduc tivity i s hi gher i n pig ( 516 l·kg−1 VS) and sow (530 l·kg−1 VS) ma-
nure than in da ir y ca ttle manure (468 l·kg−1 VS) [1 ] .
Biogas production has the potential to be an efficient means of emphatically decreasing greenhouse gas emis-
sions in a number of areas of the animal production life cycle [2]-[4]. If the amount of manure produced by a
fattening pig is 0.13 ton organic material (volatile solids, VS) per fattening pig place and year, this could pro-
duce around 0.29 MWh biogas per year [5]. One of the biggest factors limiting for the use of bio gas is re lated to
the hydrogen sulfide content, which is very corrosive to internal combustion engines [6] [7]. Most of the co m-
mercial technologies for the removal of H2S content are chemically based and expensive to operate [8]-[10]
thereby reducing the economic value of use of the biogas. The easiest method of biogas purification is water
scrubbing which uses of the characteristics of hydr ogen sulfid e so lub le in water [11].
This study intends to design a simple desulfurization equipment of water scrubbing to reduce the hydrogen
sulphide content of the biogas. Pressurized biogas through the aeration plate to produce many small biogas bub-
bles and the bubb les will full contact with water in order to achieve adsorption effect of desul furization. A sim-
ple water scrubbing column to reduce the H2S content was desi gned in this study. Different water levels and
biogas flow rate were conducted to detect hydrogen sulphide content in biogas after water scrubbing, and then
investigate t he desulfurization efficienc y o f biogas purific a tion.
2. Materials and Metho ds
The test of desulfurization in b iogas was cond ucted in a ho g farm with feeding 700 pigs. Bioga s produced from
anaerobic digestion processes of the three-stage waste-water of pig’s manure. The energy source of lamp using
biogas-combustion was used to keep warm of weaned pigs. A desulfurization equipment of water scrubbing
with a transparent acrylic cylinder column (diameter as 0.248 m and height as 1.2 m) was designed to observe
the situation o f desulfurization in bio gas. The water were transported into transparent acrylic cylinder column at
the upper inlet, the water level could be measured. The water drained away at the bottom outlet and accom-
plished circulating water system. The aera tion plate was p laced in the bottom of the co lumn and the bioga s will
be pressurized into the column as small b ubbles to sufficient contact with water to remove the hydrogen sulfide
in biogas by positive way with pressure mac hine. The biogas flow rate could be measured by flow meter before
biogas into t he aeratio n pla te .
The concentrations of hydrogen sulfide will be measured at the up per outlet of biogas by the detection device
(range 500 ppm - 12000 ppm) which is composed of gas ta king implement and dete ction tubes at the measured
area of upper outlet. The schematic of de sulfurization in biogas using water scrubbing showed in Figure 1 Then,
the circulat ing water s ystem was set on the basis of the or igina l de sulf uriz atio n equ ip ment of water scrubbing to
avoid the water of the column saturated that maintain a stable removal efficiency of the hydrogen sulfide. The
aeration plate and the small biogas bubbles in the water column are shown in Figur e 2.
The test of water scrubbing would be conducted with the different water level (50, 60 and 70 cm) of the col-
umn and the flow rate (50, 100 and 140 l/min) of the biogas. The concentrations of hydro gen sulfide will be de-
tected at the upper outlet of biogas after the water scrubbing time as 90 sec and 30 sec, and whether the circulat-
ing water system was induce to investigate the removal efficiency of desulfurization of water scrubbing. The
removal efficiency was calculated as follow equation.
( )( )
Removal efficiency %/100
AB A=−∗
(1)
where A: the concentration of H2S (before water scrubbing) (ppm), B: the concentration of H2S ( after water
scrubbing ) (ppm).
3. Results and Discussion
The re sults of removal efficiency of H2S content for biogas in different water level with biogas flow rate 140
l/min after water scrubbing 30 sec and 90 sec were shown as Table 1a nd Table 2 which was clearly indicated
