In situ investigation of soft cake fouling layers using fluid dynamic gauging

Abstract

Cake fouling is a phenomenon contributing to flux decline during cross-flow filtration. Its behaviour is also difficult to predict, especially for challenging separations where organic materials often form compressible cakes with a high resistance. In this study Kraft lignin was used as a model material for organic foulants in cross-flow microfiltration experiments, and a non-contact fluid dynamic gauging (FDG) technique in pressure-mode configuration was used to study the cake fouling layers in situ. A new and enhanced FDG equipment was used; enabling an increased accuracy of the fouling layer thickness measurements and capable of producing higher fluid shear stresses on the surface of the cake layer for strength measurements. Using FDG, very thin fouling layers were observed; in addition, FDG was used to investigate their cohesive and adhesive strengths, showing that over a 10-fold increase in fluid shear stress was required to remove foulant closer to the membrane compared with that on the surface of the cake.

Shear stress in a pressure-driven membrane system and its impact on membrane fouling from a hydrodynamic condition perspective: a review

“…The shear stress induced by this mechanism is similar to that induced by cross‐flow. However, the shear stress value (0–50 Pa) induced by FDG was found to be larger than that induced by common cross‐flow due to the special FDG geometry. Thus, the shear stress induced by FDG was sufficient to deform the cake layer on the membrane surface formed by some particles, including modified lignin, yeast, and tap water with solids (Table ).…”

“…Various methods can be employed to induce shear stress in the membrane system, including rotation, spacer, varied gas bubble, fluid dynamic gauging, turbulence promoter, and vibration . The estimated magnitude of shear stress on a membrane surface, summarised in Table , is in the range of 0–100 Pa under different conditions (i.e.…”

“…In addition, many investigations have confirmed that increased aeration rates or cross‐flow velocity (which thereby increases shear stress) may reduce membrane fouling by controlling the deposition of particles on the membrane . In general, it is assumed that the stronger the shear stress, the weaker the fouling .…”

Lignin recovery from spent alkaline pulping liquors using acidification, membrane separation, and related processing steps: A review

“…Second, the flux of permeate passing through a membrane tends to fall during continued usage due to such fouling phenomena as pore plugging and cake formation (Fane and Fell 1987;Hubbe et al 2009;Shi et al 2014). Indeed, membrane fouling has been reported in studies related to black liquor (Jin et al 2013;Mattsson et al 2015;Haddad et al 2017a-c). Mattsson et al (2015) used an innovative dynamic gauging test to study softcake fouling by precipitated softwood kraft lignin.…”

Investigation of cake fouling and pore blocking phenomena using fluid dynamic gauging and critical flux models

“…An automated fluid dynamic gauging (FDG) technique [5] was used to track the thickness and strength of cake layers. This is applied to the cross-flow MF of lignin, a substance which has earlier been found to be relatively self-adhesive [6]. Using this data it is possible to infer how fouling phenomena at the surface of the membrane and in a growing cake fouling layer on top influence flux decline individually.…”