Determining Optimum Water Content for Iron Ore Granulation using Agitation Torque of Wet Ore Powder

Abstract

Wet granulation of iron ore powders is a key process in ironmaking. In wet granulation, it is important to determine the optimum content of water added to the original ore powders. To determine the optimum water content, it is important to understand the saturation state in wet ore powder, which can be done by measuring the agitation torque of the wet powder. This study proposes a methodology for determining the optimum water content of various iron ore powders using the agitation torque of wet ore powders. First, measurement of the agitation torque and wet granulation of various iron ore powders were conducted. By comparing the results, it was found that the optimum water content, which was defined as the minimum water content required to diminish fine particles in the original powder, corresponded to the water content exhibiting the maximum agitation torque, regardless of the original powder. Using the agitation torque at different water contents, the saturation degree S, which is the volume ratio of water to the interparticle voids, was calculated, resulting in a range of 0.999 ≤ S ≤ 1.173 at the optimum water content. This suggests that the state between the funicular and capillary states is a suitable saturation state for the wet granulation of ore powders. Consequently, it was demonstrated that it is possible to determine the optimum water content for wet granulation of various iron ore powders based on the water content exhibiting the maximum agitation torque of wet ore powders.

Optimum Water Content Estimation for Wet Granulation of Iron Ore Powders with Quicklime Binder

“…In this study, mixtures of fine ore, coarse ore, and CaO were used for wet granulation and torque measurement. Mass fractions of fine and coarse ores were set to fine:coarse = 80:20 wt% or 50:50 wt% 23) . The mass fraction of CaO powder was set to 0-5 wt% relative to the whole ore powder 8,26) .…”

“…Figure 2 shows a schematic of the mixer torque rheometer (MTR, Caleva Process Solutions Ltd.) used to measure the agitation torque of the wet ore powder 23) . The MTR comprises a bowl, a Table 1 Fig.…”

“…For wet granulation of iron ore powders, for the first time, the use of agitation torque has been proposed in our previous study 23) . Our previous study demonstrated that the optimum water content for ore powders can be estimated based on the water content at which the agitation torque showed the maximum value when the water content is increased 23) . However, the scope of the previous study 23) was limited.…”

“…Our previous study demonstrated that the optimum water content for ore powders can be estimated based on the water content at which the agitation torque showed the maximum value when the water content is increased 23) . However, the scope of the previous study 23) was limited. In particular, iron ore powders with CaO-an important binder material for successful granulation-were beyond the scope of the study, and thus were not investigated.…”

Iron Ore Granulation for Sinter Production: Developments, Progress, and Challenges

“…In addition to the moiture capacity-based calculation of the optimum moisture content shown in Equation 8, Otsu et al proposed a method to determine the optimum moisture content of iron ore using the agitation torque of wet ore fines. The optimum moisture content corresponds to the moisture content that exhibits the maximum agitation torque 98) . Since the surface tension of water decreases with the increase of temperature 99) , according to Equation 1, the addition of hot water in the iron ore granulation process is beneficial to increase the capillary binding force and improve the granulation performance.…”