High pressure flocculation

Another technique—pres sure-shift freezing—also shows promise. In this technique the material is subjected to high pressure (200 MPa) and cooled to -15 C. Under these conditions the water does not freeze. However, when the pressure is released suddenly, many small ice crystals form. This has two results the small ice crystals do not rupture any structures present, but by dehydrating the unfrozen material the remaining stmcture is aggregated and stiffened by the introduction of secondary cross-links. At low concentration of solids there are too few interconnecting chains for there to be a load-bearing continuum, and the material tends to flocculate and settle out. 

Dickinson, E. and Pawlowsky, K. 1996. Effect of high-pressure treatment of protein on the rheology of flocculated emulsions containing protein arxl polysaccharide. J. Agric. Food Chem. 44 2992-3000. 

Abstract A united mathematical model for the rheological and transport properties of saturated clays is proposed. The foundation of the model is the unification of filtration s consolidation theory and the theory of the stability of lyophobic colloids, which is based on the conception of disjoining pressure as a surplus in relation to hydraulic pressure. This pressure is caused by surface capacities and exists in water films between clay particles. In this work it is shown that the problem of the shrinkage of a clay layer can be reduced to the well known problem. We obtained the approximate solution for pressing the water out of a clay layer. The solution that we obtained requires introduction of a concept for the limit shear stress for clays. We investigated the model, and explained some characteristic features of transfer processes in clays (the existence of anomalous high pressures in clays, the flocculation at diffusion in clays, etc.). It is shown that solutions which we received are in harmony with results of experiments. 

Consider the use of flocculants or deep cone. Flocculant dosage should be related to feed inlet concentration, see also Section 9.3. Include high pressure water purge lines for both forward and reverse flow at > 1 m/s. Raise and lower the rake once per shift. For startup, pump feed into the empty tank and recycle underflow until the design underflow densities are achieved. 

Browarzik et al calculated asphaltenes flocculation at high pressures for methane + crude oil - - 2,2,4-trimethylpentane [i-octane] using continuous thermodynamics where 2,2,4-trimethylpentane acts as a precipitant. The asphaltene flocculation was considered to be a liquid -b liquid equilibrium. Browarzik et al applied the van der Waals equation of state. The polydispersity of the crude oil was considered to be described by the solubility parameter of the Scatchard-Hildebrand theory. Within this distribution the asphaltenes represent the species with the highest solubility parameters. The calculated results were compared to experimental data. For oils with a very low content of asphaltenes the model describes the experimental flocculation data reasonably well. However, on contrary to the experimental results, the model predicts the asphaltenes to show a higher flocculation tendency with increasing asphaltenes content of the crude oil. Based on these comparisons further work was undertaken by Browarzik et al and the associates formed... 

This process, often called conventional calibration, has several limitations. Separation is based on size, not molar mass, so results are relative to the calibration standards. The chemical types of standards are limited and may not be available for copolymers. The range of molar masses is also limited and calculation of higher molar mass samples may rely upon extrapolated parts of the calibration curve. High molar mass polymers such as flocculants may block column frits and pores of the packing, and the relatively high pressure may degrade the polymer by shearing. 

Applications cabinets, chipboard, construction materials (high pressure laminates), fiber glass sizing agent, furniture, insulation, kitchen utensils, paper laminates, water flocculation ... 

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