Environmental Engineering Reference
In-Depth Information
for technical equipment and the plant itself. The plant layout must allow
easy access for vehicles to the storage facilities for substrate and
digestate. Plant components that require controls must be able to be
reached easily. In the case of eventual feedstock increase, the layout
should also allow expansions such as additional digesters and storage
areas.
.
Basic infrastructure should be present on a project site, including close
access to roads, water and electricity. Existing facilities on the site (e.g.
tanks, storage places, buildings and vehicles) should be integrated as far
as possible into the planning in order to keep costs low. Legal
limitations may exist and should be checked for conformity.
.
The plant site should offer possibilities for energy use or transport. The
presence of a natural gas pipeline in proximity gives the option of biogas
upgrading to biomethane and injection into the grid. In the case of
transformation by co-generation, utilisation of the produced heat
should be considered: district heating schemes or nearby industrial
processes are frequent purchasers. The transformation unit should be
placed near the injection possibility to the electricity, heat or gas grid.
.
Transport distances for feedstock and digestate on the site must be kept
as short as possible in order to ease operation of the plant.
8.6
Process control technology
Process control technology helps to manage and track plant operations.
Parameter registration and plant control can be automated, which simplifies
the work of the operator and allows independent running of the plant
during weekends and holidays.
Most plants use a programmable logic controller (PLC) for process
control. This consists of a central processing unit (CPU) and different
modular units, which must be chosen depending on the individual needs for
the plant. When programming the processor, the desired degree of
automation is chosen. The processor allows converting inputs into reactions
of the controlling unit. The inputs can be measurements or time-controlled
signals, leading to a specific action on the plant such as closing valves,
starting mixing, giving alerts, etc. Visualisation of processes is also part of
the control system; individual and connected processes can be displayed.
Selected measurements and activities are saved onto a database, which
allows long-term monitoring. Further options for control systems are e-mail
and sms alarm functions or the possibility of remote controlling where the
internet is used for data transfer.
Despite all technological progress, every plant must keep the option of
manual control for the case of unexpected events or breakdown within the
controlling technology.
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