|
Dry anaerobic digestion in amBiogas®
reactors and
aerobic stabilisation of the digestate in amBiocell®
bio-cells.
Ambientalia has always been committed to
development of technical solutions at the service of the
Environment. In the sector of the biological treatment of
waste it has fine-tuned a system for the biostabilisation of
residual waste destined for the dump (ambiSystem) and,
subsequently, technology for management of the intensive phase
of the composting process in aerated bio-cells (amBiocell).
Both solutions achieve high qualitative standards of the
products obtained, respectively the biostabilised waste to be
dumped and the compost for soil correction.
Ambientalia aimed to take a further step, anticipating the
direction that would be taken by the sector: in fact the
conversion of waste into fertilizers through biological
processes remains an operation of great environmental value,
but the high energy consumption involved in the treatment is
increasingly less sustainable. Efforts must therefore be
concentrated on the possibility of exploiting the energy of
biomasses and waste, an operation that becomes preparatory and
not alternative to the subsequent conversion into compost.
Only in this way is the virtuous circle closed: organic waste
becomes an energy and agronomic resource, with a healthy
balance sheet.
The result of these considerations was amBiogas, the
Ambientalia technology for anaerobic digestion of biomasses
and organic waste and for cogeneration of electricity and
heat, applied in synergy with amBiocell, the aerobic
composting technique employed for conversion into compost of
the digestate residual from anaerobic processes.
AMBIOGAS®
AMBIENTALIA®, THE STRENGTH OF
AN INNOVATIVE IDEA.
AmBiogas is a technology devised, developed and patented by
Ambientalia S.r.l. for the anaerobic dry digestion of waste and
biomasses.
The technique of dry digestion, based on processes of fermentation of
solid matrices with a dry matter content of up to 50%, has indubitable
advantages of a technical nature in comparison with traditional wet
digestion (DM max 10%) inasmuch as it avoids dilution of the process
materials with large quantities of water; consequently there is a
considerable reduction in the volumes of digestate for disposal.
Moreover, management of a solid digestate is far less problematical
and burdensome than that of a liquid product.
It should be pointed out that dry digestion takes place in batteries
of reactors rather than in one large size digester, which means
greater operational flexibility and no risk of total blocking of
energy production in the case of interruptions in the biological
process.
The amBiogas anaerobic dry digester fine-tuned by Ambientalia is
distinguished by important features that differentiate it from other
similar solutions (front loading parallelepiped module reactors).
Reactors of this type are loaded by mechanical shovels through a front
opening, so the height has to be increased by about 1.5–2 metres
beyond working height so that the material can be dumped from the
shovel. This creates a gap between material and ceiling of about one
third of total module volume. As is well known, the heat and damp
emanated by the mass rise up into the empty space, and to obviate this
dispersion greater energy is required to keep the mass at mesophilic
temperatures (around 36°C).
In the amBiogas digester this is avoided by means of a mobile false
ceiling: during filling and emptying it is raised to the height
necessary for the operator to enter with the mechanical vehicle;
during the process it is lowered, creating a cavity of about 300-500
mm between the ceiling itself and the material deposited in the
reactor.
Using horizontal module reactor technology the most critical phases
for the operators, due to the intense production of aqueous vapour and
odorigenous emissions by the mass under transformation, are the
loading and unloading of materials, carried out with mechanical
shovels. The amBiogas digesters are equipped with a process-air
suction system that creates and maintains suitable environmental
conditions so that the operators can enter.
These and other solutions make the amBiogas digester a unique and
highly innovative system.
Description of the reactor
The amBiogas dry digester consists of a parallelepiped module of the
following dimensions: working width max 9 metres, max length 35
metres, height of internal structure in reinforced concrete 5.5
metres, height at false ceiling 5.3 metres. The structure is in
reinforced concrete treated with resins to ensure airtightness and is
integrated with panels in insulating materials for high heat
retention.
The heaters, consisting of pipes in PE with antioxidising barrier,
sunk in the floor, are fed with hot water to heat the mass. The front
hatch, of the tip-up type, opening upwards by means of pneumatic
pistons, is in sandwich panels of AISI 304 STAINLESS steel. Insulated
internally, airtightness is ensured by an inflatable gasket. The
closure system is by means of pneumatic bolts with safety lock which
can be unlocked only with the ambiControl management software.
The digester has (on demand) a false ceiling which is mobile by means of pneumatic
cylinders in airtight plastic material. Along the whole perimeter of
the module, in correspondence to the “bed” of the false ceiling (if
provided) in the
lowered position, there are special closures in synthetic material
which ensure the maintaining of temperature and humidity.
During loading and unloading operations the false ceiling is raised to
facilitate the work of the mechanical shovel. In the course of the
anaerobic process it is lowered, leaving a cavity between itself and
the biomass.
To maximise working volume while at the same time protecting the hatch
from the thrust of loaded material, a retaining partition is
provided which is closed in the final loading phases.
The system for collecting the percolate emitted by the masses under
processing consists of drainage grilles with discharge pipes where,
due to the slope of the reactor floor, the refluxes converge, and of
an underground storage tank for the first collection.
To ensure airtightness the “hydraulic seal” system is used, in which
the discharge piping is immersed in a water trap for the first
collection and send through pumps to the main storage tank. The percolate in the storage tanks is maintained at a
constant, software-controlled temperature.
The digester is equipped with a sprinkler system with anti-blocking
nozzles, pump-fed with percolate from the storage tanks, preheated by
means of an exchanger powered by the cogenerator. Distribution of
percolate on the biomass has a twofold function: microbic inoculation
and the maintaining of mesophilic temperature.
As mentioned previously, the digester is moreover equipped with a
forced aeration system which permits suction of the air inside the
reactor to remove the foul-smelling gaseous emissions in the filling
and emptying phases.
A motorised airtight valve is set between the main suction manifold
and the recovery conduit from the reactor. The aspirated air is
conveyed to the bio-filter for purification.
Each reactor is equipped with an autonomous suction system in order to
be completely independent.
amBiogas consists of variable-width modules which, since they
are easy to paint,
can be integrated into the surrounding environment.
Front hatch. |
Inflatable gasket for airtightness. |
ambiControl software display |
> Biogas Management
> Aerobic
stabilisation of amBiocell digestate
>
Presentation and data sheet (PDF)
|
