Process Description

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Energy Recovery Plant
How it works 


The energy recovery from municipal waste consists in recovering calorific energy through a controlled thermal treatment process and transforming it into electrical energy.

The Energy Recovery Plant's main goal is the controlled thermal treatment of municipal waste that cannot be recovered through organic and multi-material recycling processes, thus recovering its internal energy in order to produce electrical energy.

But in order to obtain energy, a dynamic process has to take place. Waste from the several collection circuits in the Municipalities that are part of LIPOR is transported into the Plant and stored in a reception pit that has a six days capacity, by current production standards. The waste disposal occurs within a closed building, kept under low pressure in order to avoid odour from spreading. Waste is later transferred by a claw into the two treatment lines, where it is burned at high temperatures (1,000 ºC to 1,200 ºC) in the presence of an excessive amount of oxygen.

The combustion process produces high temperature gases that go through an energy recovery boiler, which uses the heat to produce steam. This will later be transformed into electrical energy in a turbo group. The Plant is self-sufficient and provides 90% of its production to the National Electrical Grid through a transformation station integrated in the complex.

The gases and inert materials that result from the combustion process are controlled by a rigorous control and environmental monitoring system. The gases are neutralised and filtered through high efficiency equipments before being released into the atmosphere, while slag and inert ashes are disposed of in a Landfill.

The Plant's operation is directly controlled by a Commission appointed by the Ministry of Environment and chaired by the Portuguese Waste Institute. It is supported by an External Monitoring Programme (PMExt) that assesses the environmental and social reality in the surrounding area.

Slag Recovery Project

From the Municipal Waste (MW) treatment at the Energy Recovery Plant we obtain two by-products: inert ashes and slag. The properties of this material are a consequence not only of the combustion process itself, but also of the raw material, the MW. As in most areas, the MW produced in LIPOR's associated Municipalities includes combustible material - paper, cardboard, plastics and, in small percentages, textiles and wooden packages - and inorganic materials - glass, metal and other materials. The main component of slag is non-combustible material that can be used as granular material to replace soil or natural aggregates obtained by the extraction industry.

Its most common uses are as:

 Granular material for landfills;
 Aggregates for paving, as granular bases or mixed with bituminous and hydraulic binders;
 Aggregates for concrete products, such as concrete blocks and prefabricated elements or in situ concrete;
 Aggregates in maritime works, such as artificial reefs or coast protection;
 Daily landfill cover.

Waste Disposal Sites
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