Valmet’s net sales in 2018 were approximately EUR 3.3 billion. ACS’s system was installed to pre-separate particulate matter from BFB boiler’s emissions in the new 109MWth / 34.5MWe Thermoelectric Biomass Power Plant at CELBI (Celulose Beira Industrial S.A.) in Figueira da Foz, Portugal. CELBI was formed in 1965 and is one of the most efficient global producers of eucalyptus pulp, having an installed production capacity superior to 700 thousand tons. With over 50 years of existence, Celbi is a reference producer in the European scene.
Identifying the problem and solution
ACS was challenged by Valmet to design a solution to be integrated in the flue gas treatment of the Thermoelectric Biomass Plant. The raw flue gas coming from the 109MWth BFB boiler (bubbling fluidized bed combustion technology) carries high load of fly ashes and sand particulates. These elements are particularly abrasive and could not be directly treated by the final filter due to high wear and clogging problems. Furthermore, other gaseous effluents as acid gas (HCl, HF and SO2), needed to be cleaned by feeding hydrated lime. Therefore, the global dry flue gas treatment solution consisted in a sequence of: ACS cyclones to pre-separate the high load of abrasive dust, then a hydrated lime feeding system for acid gas reduction, followed by final bag house filter, to remove residual dust.
Taking that the dust was very abrasive, ACS designed a special cyclone system, optimized for this process, with a geometry that provides low pressure drop and low gas velocities, while minimizing re-entrainment effect. Furthermore, a wear protection lining consisting of 30mm of cement bonded hard compound was installed in the inner surfaces of the cyclones and hoppers.
The general solution was a Hurricane 2 SD 4000 cyclone system: a battery of two SD cyclones with diameter 4000mm, installed in parallel, each one with a hopper and air-lock dust discharge system by means of a heavy-duty rotary valve and, as referred above, the wear protection inner lining. Besides the operational features, this system was compliant with Valmet’s performance requirement of 50% minimum dust separation, while providing expected separation efficiency of 66.3.
About hurricane cyclones
Hurricane cyclones are patented numerically optimized cyclones. Hurricane geometries maximize powder collection for each different application, while minimizing reentrainment and keeping pressure drop at reasonable levels. Hurricane cyclones demonstrate impressive efficiencies in capturing very fine powders with a Volume Median Diameter (VMD) of less than 5μm. These cyclones are the output of nonconvex nonlinear problems formulated and solved after years of work in partnership with the Faculty of Engineering of Porto and incorporate the most recent findings of the impact of agglomeration in the cyclone collection efficiency (Chemical Engineering Journal 162 (2010) 861–876). A single Hurricane is more efficient than any other known cyclone available in the market for the same pressure drop
System specifications |Emissions
- Expected separation efficiency (%) [66.3 – 67.2]
- Expected emissions (mg/Nm3 dry at 6% O2 ) [7 016]
- Guaranteed maximum emissions (mg/Nm3dry at 6% O2) [7 500]
- Guaranteed pressure drop at design point (kPa) [0.8 +/- 0.1]
- Solids [Eucaliptus wood waste and bark, forest residues]
- Particle size distribution
- Temperature (ºC) 
- Actual flow rate (m3/h) [422 121]
- Normalized flow rate (Nm3/hdry) [182 295]
- Max. dust concentration at inlet (mg/Nm3dry at 6% O2) [2 100]
- Max. SiO2 content in the particulate (%wt) 
- Site location [Outdoors]
ACS’ solution was installed on the first quarter of 2019 and is running perfectly ever since. After six-month operation, during a programmed stop, inspection to the interior of the cyclones was carried out, to observe the wear protection lining, which was concluded to be in perfect conditions. The large-scale hurricane SD cyclones is confirmed to be an excellent solution. By pre-separating the heavy wear and abrasive dust, it enables a complete flue gas treatment for BFB boilers, when integrated with the neutralizer for acid gas reduction and a final bag house for residual dust, while saving the latters from wear and blocking problems.Click here for more information about Advanced Blending Solutions