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La Chaux-de-Fonds, CHE

Service, Overhauls & Retrofits


350'000 t/a

Energy recovered

district heat, electricity

Thermal energy

2 x 75.5 MWth

Ringjet Stage Installed for Better Dust Separation and Catalyser Protection

The catalyser at the WtE plant in La Chaux-de-Fonds had been causing the operators various difficulties ever since it was installed in 2001. The catalyser had been fitted to the plant (1 line, 56,000 t/a), which at the time had already been running for seven years, to augment the existing flue gas treatment system, which incorporated a wet scrubber. Shortly after installation, however, the scrubber started having problems with dust and aerosol separation, leading to deposits of particulate in the catalyser.

These problems were discussed at a routine meeting between VADEC and HZI. HZI’s process engineers came up with the idea of building an additional cleaning stage into the flue gas treatment process, and submitted a proposal to VADEC for this solution. VADEC was convinced, and in May 2017 commissioned HZI to supply a ringjet stage to replace the existing wet electrostatic precipitator. This ringjet stage is designed to allow smooth, uninterrupted operation, protecting the catalyser from dust deposits by reducing the amount of dust and aerosols in the flue gas.

Results / Solution

Scrubber installed, 4 metres in diameter and 8 metres in height, equipped with 44 HZI RingJets, to replace the old electrostatic precipitator

  • Scrubber dimensioned for nominal flue gas throughput of 75,000 Nm3/h (max. 92,000 Nm3/h)
  • In light of the flue gas routing in the plant, the scrubber works on a downflow basis (flow from top to bottom)
  • HZI RingJet stage reduces the amount of dust from 10 to < 1mg/Nm3
  • Turnkey solution, with client involved in preparation works and on-site organisation


  • VADEC Réseau de valorisation des déchets – Arc Jurassien

Time Frame

  • April 2017 to September 2017


  • On-site analysis and study
  • Dismantling wet electrostatic precipitator
  • Installing new scrubber section, including connecting ducts and complete water-cycle equipment

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