Three Hexact dynamic disc screens for the treatment of compost and solid waste in the Hera Group’s Bologna facility

Ecostar dynamic disc screens combine exceptional performance with compact size, a small footprint and low power consumption

The Hera Group is one of the largest national multi-utility companies in Italy. It mainly operates in the environmental (waste management), water and energy sectors, but it also provides services such as lighting and telecommunications. The group has developed several cutting-edge environmental projects that all revolve around a key concept for the company: the circular economy. Among them is a waste sorting initiative that stands out not only due to its hi-tech, sustainable nature but also because of the commendable behaviour by the general public. The project in question is run by the Hera Group company Herambiente, which is a leading Italian name in urban and industrial waste processing and recovery. In 2018, it opened a facility in the Sant’Agata Bolognese area of Bologna that uses complex technological procedures to produce compost and biomethane from domestic organic waste and green waste. In the same year, Ecoimpianti installed three Ecostar Hexact dynamic disc screens for the treatment of compost and solid waste in Herambiente’s anaerobic digestion plant.

How the partnership between Hera, Ecoimpianti and Ecostar began

Herambiente started building work on the anaerobic digestion plant in April 2017 and began supplying biomethane to the network in October 2018. The pre- and post-mechanical processing sections were constructed by Ecoimpianti Srl, a company that specializes in designing and making turnkey industrial waste processing plants in Italy and worldwide. With 20 years of experience in the field to its name, Ecostar was the perfect choice as a supplier to Ecoimpianti, which purchased and installed three new Hexact disc screens and two loading hoppers for the Sant’Agata Bolognese plant.

Ecostar machines in operation

  • Two Hexact disc screens pre-select the solid urban waste entering the plant, separating the organic fraction from the non-compostable fraction (overfill).
  • Another Hexact disc screen is used downstream from the anaerobic digestion process to refine the compost before it is put on the market as a natural soil amendment.
  • The two loading hoppers are used to feed the refining line from two different sections of the plant.

Hexact’s strengths for the treatment of compost and solid waste

Following a meticulous joint planning process with Ecoimpianti that took into account all of the client’s needs and objectives, Ecostar designed two Hexact 6000 screening machines to separate the organic fraction of urban solid waste. Using just two 7.5 kW motors, they have a screening capacity of 30 t/h and screening sections of 0-70mm and > 70mm. The highly efficient machines in the Bologna plant are based on Dynamic Disc Screening technology and feature innovative technological solutions. Among their many benefits are: superb separation of bags and organic waste, excellent bag cleaning thanks to the up-and-down movement produced by the hexagonal discs, high productivity, unbeatable reliability and very low maintenance requirements.

The cornerstone of the Hexact system is Ecostar DDS (Dynamic Disc Screening) technology, which is based on three concepts:

  • SCREENING DISCS. Ecostar discs are made of Hardox and have a flat profile. Thanks to their special shape, the material flows over the screening discs and is subjected to up-and-down movement that separates the waste components.
  • FREE MANIFOLDS. Each drive shaft is coated with free manifolds which are independent of the rotation of the shaft itself. The free manifolds prevent the material that is being screened from twisting around the shaft and clogging it, thus giving superior separation results and considerably reducing downtime.
  • REAL-TIME ADJUSTMENTS TO SCREENING SIZE. Real-time changes to the predetermined screening section (± 30%) can be made by varying the speed of the shafts with the inverter. The choice of screening sections ranges from 10 mm to 350 mm.

The third machine is a Hexact 6000 screen for the treatment of compost, with a screening capacity of 30 t/h and sections of 0-40mm and > 40mm. It offers great screening precision with both dry and wet material.

The reasons for choosing Ecostar were discussed by Alessio Silvestri, the Technical Director of both Ecoimpianti and this project: “For this plant, we needed innovative technology that combined exceptional performance with low power consumption and high levels of productivity. In addition, we needed to take up as little space as possible in the premises and we wanted stationary, modular machines so that they could be easily integrated into the Hera Group’s system. Consequently, Ecostar sprang to mind. The Hexact stationary screen met all of our requirements and enabled us to achieve our client’s goal.”

Hexact at work: the results

The new Hexact machines and the two hoppers were installed in the first half of 2018, after a 6-month planning process. The Ecostar team worked alongside Ecoimpianti’s technical department every step of the way.

“The Ecostar screens are proving very capable of doing the job for which they were selected, which is sending the clean organic material to the biodigesters. The latter are constantly fed thanks to the regular quantity and quality of the selected organic fraction,” stated Ecoimpianti’s Technical Director Alessio Silvestri, who was responsible for the start-up and testing phase.

Herambiente’s Hexact 6000 disc screens in numbers:

Working length: 6000 mm

Weight: 7 t

Production capacity: 30 t/h

Installed power: 2 x 7.5 kW

Solid waste screening fraction: 0-70mm and > 70mm

Compost screening fraction: 0-40mm and > 40mm

Works with wet material

Anti-clogging system

Anti-wrapping system

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About Herambiente and the Hera Group

Herambiente is part of the Hera Group and a leading Italian name in urban and industrial waste processing and recovery. In 2018, it opened a facility in the Sant’Agata Bolognese area of Bologna that uses complex technological procedures to produce compost and biomethane from domestic organic waste and green waste. Not content with just producing biogas, the Group has decided to reward the commendable behaviour of people who dispose of their waste responsibly. Through partnerships with public transport companies and filling stations, it is making the green fuel available in their local areas.

Herambiente has invested €37 million and brought about a real paradigm shift. With an outlook that revolves around sustainability and cutting-edge technology, it has transformed a traditional linear economy process into a circular economy one.

The Hera Group is one of Italy’s biggest players in urban waste management. It provides an integrated service in seven provinces in Emilia-Romagna and the province of Padua, covering 198 municipalities in total. In addition, it serves 57 municipalities in the province of Pesaro and Urbino and 94 municipalities in Friuli-Venezia Giulia.

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