Slurry Rheology Studies

FIGURE 2.10 Effect of conditioning time on glass transition temperature, Eg, assigned as a temperature at the peak of the DMA loss modulus. Eg, measured at three different oscillating frequencies of 1, 10, and 100 Hz, is shown for the specimens with longitudinal and transverse groove orientations. 

Detecting and characterizing subtle differences in slurry properties due to the above effects are an ongoing challenge. 

An example of the steady-state rheometric test at room temperature for various slurries of similar chemical compositions is shown in Fig. 2.11. Slurry viscosity decreases as shear rate increases hence, the tested slurry is a non-Newtonian liquid and cannot be characterized by measuring viscosity at a single shear rate. Decrease in the slurry viscosity can also be ascribed to the deagglomeration of the slurry particles caused by shearing. A steady-state rheometric test distinguishes the slurries with only minor differences in their compositions, as shown in Fig. 2.11. One area of further opportunity in terms of 

FIGURE 2.11 Rheometric steady-state test dependence of slurry viscosity rj on shear rate. The test was conducted for seven slurry samples with only subtle differences in slurry compositions and/or manufacturing processes. 

FIGURE 2.12 Rheometric frequency sweep test of slurries conducted at 5-30 °C. G, G , and complex = rj + if] reduce as temperature increases. 

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A study of the packing behaviour of glass fibres, its dependence on fibre dimensions and its influence on slurry rheology. 

A study, relevant to recirculation behaviour in a RRIM machine, of polyol and polyol slurry rheology at shear rates in the range 0-103 s 1. This study is based on viscometry with modified cone and plate geometry. 

Shaheen, E.I. (1971) Rheological study of viscosities and pipeline flow of concentrated slurries. Powder Tech., 5, 245. 

The flow of compressible and non-compressible liquids, gases, vapors, suspensions, slurries and many other fluid systems has received sufficient study to allow definite evaluation of conditions for a variety of process situations for Newtonian fluids. For the non-Newtonian fluids, considerable data is available. However, its correlation is not as broad in application, due to the significant influence of physical and rheological properties. This presentation is limited to Newtonian systems, except where noted. 

In this section we give a description of the colloidal interactions which govern the state of dispersion and rheology of calcium carbonate slurries. The description is based on a series of fundamental experimental studies that have been described in more detail in previous publications. ... 

The aim of the present study was to determine rheologic characteristics of wet grain slurries using a helical impeller viscometer. The collected data were analyzed to develop a model describing the rheologic behavior of wet grain slurries. 

Stickel JJ, Knutsen JS, Liberatore MW, Luu W, Bousfield DW, KUngenberg DJ, Scott CT, Root TW, Ehrhardt MR, Monz TO. (2009). Rheology measurements of a biomass slurry an inter-laboratory study. RheolActa, 48(9), 1005-1015. 

Studies of process characteristics such as fouling and flux decline, cake properties, concentration polarization and performance with non-Newtonian slurries represent another area of fast development. The non-Newtonian slurries, which exhibit complex rheological behaviour, arise in various industrial apphcations such as paints, coatings, and joint treatment compounds. 

During the feasibility study, samples of the ore are sent to a rheology lab. Samples should be taken from different boreholes. Some boreholes may yield coarser material at the higher levels but finer materials at deeper depth. This information is used to predict the performance of the pumps throughout the lifetime of the project. For example, in the earlier years of the project, the slurry may be coarser and of heterogeneous flow. As the life of the project progresses, finer material may be pumped at higher concentrations as non-Newtonian flows. 

The different phases of the engineering of a slurry pipeline are presented in this chapter. It is not always a straightforward process and may involve trade-off studies based on the rheology of the slurry, the budget restrictions, the size and capabilities of the equipment, and mining plans. 

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