Scientific blog · Technology and flue gas treatment
Soot scrubber for wood-fired ovens, biomass boilers and pellet stoves: NEWSCRUB AH — BIOMASS
Artur Cokaj ·
Four water-based scrubbers from 250 to 650 m³/h for pizzerias, bread ovens, biomass boilers and pellet stoves, with model data and the numbers of IMQ certificate 297 and the test reports.
For wood-fired ovens, bread ovens, biomass boilers and pellet stoves ETC Group builds the NEWSCRUB AH — BIOMASS family: four water-based scrubbers with nominal airflows from 250 to 650 m³/h and flue connections from Ø 200 to Ø 300 mm. These are the machines ETC supplies for a pizzeria with one oven, for a bakery or for a domestic or small commercial boiler.
AH 250, AH 300 and Clinear 250L are covered by type-examination certificate no. IMQ 297 Rev. 0 of 16/07/2018 (file 50AR00040), issued to ETC Group by IMQ, a notified body, under Machinery Directive 2006/42/EC. Dust reduction was measured by the laboratory MADE HSE S.r.l., ACCREDIA LAB no. 0656, in test reports 14LA11644 and 14LA11645 of 09/12/2014.
The BIOMASS models
| Model | Nominal airflow | Flue connection | W × D × H | Water in tank | Nozzles | Empty / operating weight |
|---|---|---|---|---|---|---|
| NEWSCRUB AH200 — BIOMASS | 250 m³/h | Ø 200 mm | 745 × 560 × 670 mm | 42 l | 5 | 49 / 91 kg |
| NEWSCRUB AH250 — BIOMASS | 250 m³/h | Ø 250 mm | 940 × 610 × 670 mm | 63 l | 7 | 57 / 120 kg |
| Clinear 250L BIOMASS | 320 m³/h | Ø 250 mm | 990 × 740 × 660 mm | 81 l | 8 | 62 / 143 kg |
| NEWSCRUB AH300 — BIOMASS | 650 m³/h | Ø 300 mm | 1,100 × 850 × 670 mm | 110 l | 9 | 80 / 190 kg |
The NEWSCRUB AH200 — BIOMASS works up to 250 m³/h with natural draught alone. With an extractor fan the airflow increases, but ETC recommends not exceeding 800 m³/h.
Which model for which installation?
For a pellet stove, small oven or domestic boiler: NEWSCRUB AH200 — BIOMASS. For a pizzeria with a single wood-fired oven: NEWSCRUB AH250 — BIOMASS or Clinear 250L BIOMASS, depending on airflow and space. For large ovens, bakeries, more powerful biomass boilers or two ovens on the same scrubber: NEWSCRUB AH300 — BIOMASS, if the design and airflows allow it.
The connection diameter alone is not enough to choose. The type of appliance and fuel, flue gas airflow and temperature, duct route and length, and any extractor fan already present are all needed. If there is a grill under the hood, the right model is in the ROASTER family.
How it connects to the oven
The scrubber goes on the flue duct, close to the oven, halfway along or at the end; the closer it is to the oven, the less flue remains to be cleaned. It can sit lower than the oven only with correctly sized forced extraction. The extractor fan, when needed, is mounted after the machine, on its own brackets and not resting on the scrubber. The downstream duct is airtight, made of AISI 316L stainless steel, rising at a slope of at least 5°.
Temperatures and result
With inlet flue gas at 120-150 °C, on a correctly sized wood-fired oven the flue gas leaves at 45-50 °C, saturated with vapour. Occasional sparks and embers are wetted and extinguished along the path. In a UNI EN 13284-1 test (ACCREDIA LAB no. 0656, reports 14LA11644 and 14LA11645) an ETC AH series scrubber reduced dust by 95.2%, from 516.5 to 24.8 mg/Nm³. The water retains soot and large particles; vapour, gases and odours decrease but do not disappear.
Daily use
- At start-up the pump starts when the float signals water at the first level.
- During service, pressure (about 2 bar), atomisation and level are checked.
- At the end of service the oven is closed, the scrubber is switched off, then the water is drained, manually or with the automatic valve.
- If there is a risk of frost the machine must be emptied.
The flue section between oven and scrubber is untreated and must be cleaned at least every three months. It is also the first point to check when draught drops.