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- Ciclones de recirculação: aplicação à lavagemPublication . Fonseca, Ana; Salcedo, Romualdo; Orfão, José; Chibante, Vânia; yesThe main purpose of this research project is to study at a laboratory-scale the application of recirculating cyclones to the dry scrubbing of acid gases using solid particles of Ca(OH)2. A new system will be used, based on the combination of very high efficiency reverse-flow cyclones with a straight-through cyclone concentrator, which will simultaneously remove the injected solid particles and promote their partial recirculation. The possibility of dryscrubbing of acid gases in recirculating cyclones seems very promising: if the expectations are confirmed, this is a low cost technology, highly efficient both for the dry-scrubbing of acid gases and for the removal of particulate pollutants. O projecto de investigação aqui apresentado tem como principal objectivo o estudo, à escala laboratorial, da aplicação de ciclones de recirculação à lavagem de gases ácidos com partículas sólidas de Ca(OH)2. O equipamento utilizado é um sistema inovador, baseado na combinação de um ciclone de fluxo invertido de muito elevada eficiência com um ciclone concentrador de passo simples, que simultaneamente remove as partículas sólidas e promove a sua recirculação parcial. A possibilidade de efectuar a lavagem de gases ácidos neste tipo de equipamento parece deveras promissora: a confirmarem-se as expectativas, estamos perante uma tecnologia de baixo custo e altamente eficiente quer para a lavagem a seco de gases ácidos como para o despoeiramento do gás.
- Dry-Scrubbing of Acid Gases in Recirculating CyclonesPublication . Chibante, Vania; Fonseca, Ana; Salcedo, RomualdoThis paper describes a laboratory-scale study on the use of recirculating cyclones as reaction chambers for dry scrubbing of gaseous HCl with solid slaked lime particles. This gas cleaning system combines a numerically optimized reverse flow gas cyclone (RS_VHE geometry) with a straight-through cyclone concentrator, which simultaneously increases the capture of the solid particles and promotes their partial recirculation. A laboratory-scale study was undertaken to test this technology and to compare its performance to a modified Stairmand HE reverse flow cyclone without recirculation. The experimental conditions were: reaction temperature ≈326K, gas flow rate ≈2.9x10-4Nm3.s-1 and relative humidity of the gas ≈8.5%. The experimental variables tested were the solids load (1.0-9.2 x10-7kg.s-1) and HCl concentration (0.4-2.8 x10-2mol.m-3) in the inlet gas. The experimentally obtained particulate removal efficiencies with the recirculating cyclones (≈98%) were higher than those obtained with the Stairmand HE cyclone (≈93%), with the additional advantage of having significantly lower pressure drop. As for the acid removal efficiencies (≈10 to 96%), no significant differences were found between the two systems tested under the same experimental conditions. The possibility of using optimized recirculating cyclones for gas cleaning in a dry scrubbing process is very promising, since this is a low cost technology, highly efficient both for the removal of acid gases and for the capture of solid particles, which has the advantage of not requiring a post-reaction de-duster.