Foam breaking — key process in detoxification of kraft mill effluents by foam separation

Abstract

A study was undertaken to demonstrate on pilot plant scale the performance of a turbine foam breaking system and to develop the design parameters for large scale application. Among various configurations a 3‐blade vaned‐disc turbine was found to be optimal for foam breaking. Major process variables controlling foam breaking were system design, tip velocity, rotation speed, and foam load. A foam breaking system with only restricted liquid draw‐off performed 3 ‐ 16 times better than a conventional flow through system. A 38 cm diameter turbine operating at 1800 τ/min (3600 cm/s tip velocity) collapsed up to 1.2 m3/min (42 ft3/min) of foam. Design equations developed for sizing of foam breakers suggest that a 61 cm (2‐ft) diameter 21 kW turbine will collapse 4.7 m3/min of foam. For a 95 × 103m3/d foam separation plant, approximately 12 foam breakers are required. Capital costs are estimated at $108,000.

The effect of organic loading rate on foam initiation during mesophilic anaerobic digestion of municipal wastewater sludge

“…Sludge -centrate samples were obtained by centrifuging either the feed (feed-centrate) or digested sludge (digested-centrate) samples at 2000 g for 15 minutes and subsequently collecting the supernatant. The foaming potential was determined by measuring the foam height after aeration at 0.5 L minute -1 for 10 minutes (NG et al 1977, Morey et al 1999, Desphande and Barigou 2000, Desphande and Barigou 2001, Dedhia et al 2004, Nakajima and Mishima 2005. The apparatus comprised of a column (length: 1 m, diameter: 5.2 cm) with a plastic, fine-bubble diffuser placed at the bottom.…”

C2Hn fragments on metal surfaces

“…This is much higher than that of the coefficients in the double-f expansion. 6 Molecular calculations. c Surface calculations.…”

Foam Rupture by Mechanical and Vibrational Methods

“…A number of studies have emerged over the last thirty years and have been reviewed by Deshpande and Barigou [3]. Some early investigations [4,5] looked at arrangements suitable for foams generated in wastewater and pulp mill effluents in which the unwanted foam was channeled to a different vessel where it was then destroyed. With the recent advances in reactor technology, most of the later studies employed in-situ installations of foam breakers [3].…”

“…Mechanical foam destruction takes place mainly through the action of shear forces, although other forces such as suction and centrifugal can play a significant role [5]. One way to increase the shear forces acting to break a foam is to force the foam through narrow passages at high velocities.…”