Effect of particle size, blend ratio and some selective bio‑additives on rheological behaviour of high‑concentration iron ore slurry

Abstract

The influence of particle size, blend ratio and some selective bio-additives on the rheological behaviour of an Indian iron ore sample in a slurry concentration range of 60-75% by mass was evaluated. The rheological parameters were measured using a high-precision ThermoFisher Scientific HAAKE TM RheoStress TM 1 Rheometer. The iron ore slurry samples indicated non-Newtonian flow behaviour and fitted quite well with the Bingham plastic model in the studied range of concentrations. The specific multimodal iron ore samples with a broad size distribution indicated a substantial reduction in slurry viscosity, yield stress and improved solids loading compared to monomodal ones. The reduction in apparent viscosity at a given shear rate for the specific iron ore slurry sample was correlated to a distribution modulus () derived from the Farris theory. The application of small dosages (0.8-1% w/w of total solids) of two selective bio-additives extracted from Indian spinach (Basella alba) and Bellyache bush (Jatropha gossypifolia Linn) further reduced the Bingham viscosity and yield stress values through surface modification at higher solids loading. The increase in yield stress values with an increase in solids concentration was attributed to the formation of loosely packed flocs and immobilisation of water within them, thus increasing particle-particle and particle-fluid friction. The bio-additives may be able to improve the fluid mobility among the particles, thus reducing the internal friction constituting the flocs and facilitating the slurry flow with the application of a reasonably lesser shearing force. The study reveals that the blending of fines with coarse iron ore at a controlled particle size distribution supplemented by small dosages of low-cost additives may be employed for preparation and transportation of high-concentration iron ore slurry with improved pipe economics.

Rheology of Slurry: A Review

“…With gradual increase in concentration, it advances to acquire non-Newtonian properties with a steeply increasing viscosity as the shear rate decreases (Fig. 2) [8,34,37].…”

“…Senapati et al [34] conducted a series of experiments blending fine particles in coarser slurry suspensions of iron ore in fixed blend ratio of 4:1 thereby attaining a bidisperse suspension. The size ratio (λ) that is the ratio of larger diameter to smaller particles given by, λ = highly affects the the viscosity of the slurry.…”

“…A high solid concentration with small inter-particle distance generates a high attractive force and a specific shear force is required to break apart incoherent flocs and overcome internal friction between fine particles to intiate flow [35,36]. It is hence observed that the bimodal and multimodal particle distribution of iron ore influence the apparent viscosity than the unimodal distribution from the Figure 4(b) [34,37,50].…”

“…Figure 7 -(a) Effect of size ratio (λ) on the apparent viscosity for the three iron ore particle distributions, and (b) Effect of particle size distribution on apparent viscosity of iron ore slurry at high solid concentration [34].…”

“…At an experiment conducted by Senapati et al [34] it is observed that some selective additives can influence the flow behaviour and acts as a stabilising agent of iron ore slurry. The fundamental role of chemical dispersants is to decrease or completely terminate the yield stress of slurry.…”