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Continuous production of dissloved oxygen free water using nitrogen micro-bubbles generated by a new motionless mixer

100%

Seekkuarachchi I. N. , Kumazawa H.

2006

tom Nr 6s

208-209

The process of continuous production of dissolved oxygen free water was investigated by means of desorption of dissolved oxygen into nitrogen micro-bubbles, which were generated in a new motionless mixer named Ramond Supermixer. The pressure drop across the mixer and the volumetric mass transfer coefficient during the desorption of oxygen from water were measured for various combinations of process variables, liquid and gas velocities and a number of mixing units with the aim to derive the respective correlations.

Homo- i kopolimeryzacja styrenu, inicjowana nadsiarczanem potasu bez użycia emulgatora, przebiegająca w warunkach statycznych. Cz. I. Homopolimeryzacja styrenu

84%

Wilson-Polit D. , Orzechowski A. , Grzywa-Niksińska I. , Grzywa E. , Izmailova V. , Oganesyan A. , Gritskova I.

2000

tom T. 45, nr 5

399-404

A mechanism in suggested for homopolymerization of styrene, which is based on interfacial tension (σ1,2), ζ-potential, and product particle size distribution measurements. The homopolymerization was carried out in the water phase at 60oC or 80oC under static conditions (no stirring) with no emulsifier used; it was initiated with K2S2O8. At the first stage, initiation of polymerization in the water phase yields surface active oligomeric radicals part of which, soluble in monomer, are transferred from the water to the monomer phase, according with their solubility. Polymerization continues at the interfacial layer. As a result of this transformation and initiation of polymerization the s1,2 tension becomes very low and the monomer gets crushed. Polymer—monomer particles are formed from the monomer drops. In the process of obtaining polymers in the polymer—monomer particles, the density of which is lower than that of monomer and the particles are detached from the interfacial boundary and are passing into the water phase which becomes turbid. At the initial stage of polymerization, the polymer—monomer particles formed from monomer microdrops vary in size (Figs. 7, 8) because the stability factors (ζ-potential-controlled electrostatic factor and structural-mechanical factors) are forming in time at the interfacial adsorption layer of polymer—monomer particles. This mechanism is inconsistent with the Fitch et al. theory of homogeneous nucleation of particles. Presumably the low σ1,2-value conditioned by processes occurring at the interfacial boundary in the systems investigated is the reason for particulation of the monomer phase and formation of microdrops which are the major source for the formation of polymer—monomer particles.