Converting Waste Agricultural Biomass into a Resource - UNEP

oil production period in the mills. The stored product is processed in some six
months.
The alperujo is then put through a physical process using decanters, or
horizontal centrifuges, to extract pomace oil and further alperujo. An annual
production of some 2000 tonnes of pomace oil is expected, which will be sent
to the refineries before being used for human consumption.
The alperujo has good heating value but also contains a high level of
moisture, rendering it unviable for combustion. Therefore this residue must be
dried before being used as fuel.
Phase II: drying the alperujo
About 240,000 tonnes/year of olive oil residue (orujo) is available. This
residue has a moisture level of 65% - 70% and must be dried before it can be
recycled. The drying system consists of a horizontal drier (trommel-type)
which uses hot gases from a combustion chamber for drying.
In the past, the dried pulp residue (orujillo), normally with the stones removed,
was combusted in a chamber to generate hot gases of 500°C. The drying
process consisted of two phases. In the first phase, approximately 48% of the
moisture was driven out. Then the material went into a second dryer where its
moisture was reduced to 10% - 12%. Some of the dried orujillo obtained was
used as fuel for the drying process itself and the remainder sold to industrial
facilities such as brick factories. However, the introduction of natural gas in
Spain has considerably decreased the demand for orujillo.
In view of the special characteristics of the dryer, the heat required appeared
very well in line to the latent heat in a gas turbine generator package, which
produces gases at a temperature of around 500°C. This led to the
development of a drying phase along with the use of the TBM-T-130 gas
turbine generator, which is able to supply heat for the dryers while producing
electrical energy. The special combustion characteristics of the gas turbine
generator package ensure that the exhaust gases are clean, without any
traces of lubrication oil or pollutants.
At the end of the process, two different products with a high specific value are
obtained. Of these, orujillo with a moisture content of 10% - 12% is suitable
for direct combustion. It is also recyclable,
either for sale to third parties or for use in the new cogeneration plant, which
is connected to the Endesa grid. The dried orujillo, the other product, is stored
in a silo in an area near the cogeneration plant.
Job Potential
1
The plant is being operated in three shifts with two operators and a
supervisor. Furthermore there are two maintenance engineers and two plant
managers. The project provides 19 jobs in total.
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