Pale Lager Clarification Using Novel Ceramic Hollow-Fiber Membranes and CO<inf>2</inf> Backflush Program

Abstract

In this work, the cross-flow microfiltration (CFMF) performance of a rough pale lager, produced in the industrial brewery Birra Peroni Srl (Rome, Italy), was assessed in a bench-top rig, equipped with a 0.8-μm ceramic hollow-fiber membrane module, to overcome the recognized inefficacy of back-flushing cleaning techniques in ceramic multi-channel monolithic modules. In total recycle CFMF trials, as the transmembrane pressure difference (TMP) was increased from 0.59 to 3.56 bar, the quasi-steady-state permeation flux (J*) tended to a limiting value increasing with the cross-flow velocity (vS). To minimize the overall membrane surface to be installed for a prefixed permeate recovery, it was found to be expedient to operate at the aforementioned high cross-flow velocity and TMP of 3.56 bar, thus obtaining quite a high quasi-steady-state permeation flux (mean, μ = 173 L m−2 h−1; standard deviation, sd = 7 L m−2 h−1; number of observations, N = 12). The energy consumption per liter of permeate collected was found to be practically independent of the operating variables vS and TMP selected (μ = 55 W h L−1; sd = 2 W h L−1; N = 21). Yet, a permeate flux greater than 100 L m−2 h−1 was achieved on condition that TMP was greater than 2 bar and vS varied from 4 to 6 m s−1. A few validation batch CFMF tests, carried out using pre-centrifuged, PVPP-stabilized, and cartridge-filtered rough pale lager at TMP = 3.56 bar, vS = 6 m s−1, and 10 °C under a predefined CO2 backwashing program, resulted in an average permeation flux (μ = 239 L m−2 h−1; sd = 24 L m−2 h−1; N = 2) by far greater than that (50–100 L m−2 h−1) claimed at 0–2 °C by the three CFMF processes commercially available. Finally, it was proved the easy transferability of the lager beer clarification and stabilization process, previously developed in a single-tube membrane module, to a ceramic hollow-fiber membrane module industrially upscalable.