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Large scale, high capacity, linked MPE Systems for Vacuum Enhanced Remediation  

foto3 newsletter6  Large scale, high capacity, linked MPE Systems for Vacuum Enhanced Remediation  
In 2014 Geostream has designed and built a multi-phase extraction system (MPE) consisting of 72 skids including the mechanical and electrical equipment and tools connecting them together for a site of national interest.

One of the first projects launched by the Petrolchimico di Porto Torres (SS) plant is concerned with groundwater and soil sanitation using Multi Phase Extraction technology (MPE). In environmental terms, Porto Torres is one of 39 sites of national interest and the approved characterization plan covers more than 1,500 hectares.

However, the selected technology provided a feature particularly needed for the application of an MPE system, whose suction depths are greater than those traditionally expected for this type of system. In fact, extraction is carried out via shafts equipped with three pipes: a high depression one for multiphase intake (air/water/product); a low depression one for the air/VOC intake phase; and the final one connected to a compressed air production central intended to pressurize the shaft and allow the intake of the multiphase mixture from depths of more than 9 m below ground level.

The implemented system is connected to 180 intake shafts and produces a continuously extracted air flow rate of more than 7,000 m3/ h; the expected concentrations of pollutants are about 10 g/m3. This means that about 70 kg/h of contaminant mass will be extracted during the initial stage: about 1.7 tonnes per day. More than 45,000 screws and over 80 km of electric cables have been used to produce the 72 planned skids.

Among the particular features of the plant design, it is worth mentioning the use of 12 internal and external ATEX-certified dry screw vacuum units where the suction box is flushed with nitrogen. There are also 4 batteries with heat exchangers for reducing the temperature of the gases in order to optimize and maximize the subsequent active carbon treatment process. Finally, the 4 tanks for the recovery of the multiphase mixture extracted from the shafts are equipped with the same number of pre-vacuum nitrogen treatment systems, as well as the related equipment to ensure the complete absence of oxygen inside the tank, in order to eliminate the combustible agent and minimize the danger of explosion.

The areas affected by the installation of the MPE modules are generally not in factory areas classified in accordance with the ATEX Directive. However, due to the presence of organic vapours in air flows and of supernatant hydrocarbon products, the new installations were made to include all equipment and instruments in ATEX Zone 2.

expertEx Large scale, high capacity, linked MPE Systems for Vacuum Enhanced Remediation  

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