Environmental Engineering Reference
In-Depth Information
15.7
Water scrubber plant (Copyright: Fraunhofer IWES).
[35]. The gas desorbed at this expansion step leaves the top of the flash
column and is returned to the untreated gas flow between the first and
second raw gas compression step [35, 36]. This is done to reduce methane
slip of the upgrading plant. The water, which at that stage contains mainly
dissolved CO
2
and H
2
S, enters the desorption column top and is expanded
to ambient pressure. Air is blown in at the bottom of the desorption column
to assist the degassing of the water [13]. At the end of this process,
regenerated water is obtained, which can be re-stored for absorption in the
scrubber. The dissolved off-gas leaves the column at the top end of the
desorption column. The off-gas still contains some CH
4
and is thus usually
treated further [8, 9, 13].
According to manufacturer information [23], controllability in the range
40-100% (compared to nominal load) is possible. One plant operator has
reported [30] that controllability in the range 25-110% is possible.
The electricity demand of the process varies from 0.20 to 0.30 kWh
el
/m
n
3
raw gas [11, 13, 23, 34]. Current warranty values of one technology provider
are 0.22 kWh
el
/m
n
3
(for larger plant capacities) and 0.25 kWh
el
/m
n
3
(for
small plant capacities) referring to product gas pressures of 5 bar (absolute
pressure) [15]. A plant operator reported an average specific electricity
demand of 0.26 kWh
el
/m
n
3
[30].
Specific water demands are stated by one manufacturer to be 1-3m
3
/day
depending on plant size [15]. These values correspond to specific water
demands of 2.1 to 3.3 litres per day per cubic metre of raw gas upgrading
Search WWH ::
Custom Search