Experimental research on purifying ultrafine nanoparticle by SBA-15 and its filtration mechanism

Getting insight into the influence of coexisting airborne nanoparticles on gas adsorption performance over porous materials

Adsorption as one of the most important air cleaning methods has been extensively applied during which the coexisting airborne nanoparticles (NPs) with sizes close to adsorbent pore sizes could inevitably influence gas adsorption processes. In this work, the influence of sub-20 nm NPs on toluene adsorption on ZSM-5 zeolites exchanged with different cations (Li⁺, Na⁺ and K⁺) were studied based on gas-and-particle coexisting adsorption/filtration tests. Affinities for both toluene and NPs on adsorbents follow Li-ZSM-5 > Na-ZSM-5 > K-ZSM-5 regarding the orders of charge density, pore size, and internal and external specific surface areas. The toluene adsorption was shown to be impaired by coexisting NPs from perspectives of thermodynamics and kinetics. For Li-ZSM-5, Na-ZSM-5 and K-ZSM-5, significant relative reductions of 10.4 %, 10.5 % and 16.0 % in toluene adsorption capacity at the lower feed concentration, and of 20.3 %, 15.2 % and 2.3 % in mass transfer coefficient at the higher feed concentration were observed, respectively. The influential mechanisms regarding competitiveness between toluene and NPs in interaction with cationic and porous surfaces were accordingly proposed, which are of practical significance for selecting robust adsorbents under realistic harsh air conditions.

A novel gas-solids separator scheme of coupling cyclone with circulating granular bed filter (C-CGBF)

A novel gas-solids separator scheme of coupling cyclone with circulating granular bed filter (C-CGBF) was proposed. The influences of the operating regimes, the inlet dust concentrations and the inlet gas flow rates on the scheme were investigated in a pilot-scale cold-model experimental apparatus. The pressure drop and the collection efficiency were measured and analyzed. It was shown that, differing from that under the fixed bed (FB) operating regime, the pressure drop tended to assume a steady state after an increasing period under the moving bed (MB). Experiments under the MB revealed that stable/high collection efficiency, typically exceeding 95%, was achieved with considerably low pressure drop. The dust hold-up in the built-in granular bed and the filter cake formed on the outer screen wall contributed to high collection efficiency, as well as increased the pressure drop. Furthermore, the individual contribution of the cyclone shell and the built-in granular bed to the total collection efficiency under the MB were investigated. The size distributions of the captured particles were also analyzed. The contribution ratios of the cyclone shell were around 80%, while the majority of the particles captured by it were larger than 10 μm.