Prediction of suitable water content in granulation of sintering mixture based on Litster’s model

Abstract

Suitable water content plays a decisive role in the granulation of sintering mixtures. Herein, a method was proposed to predict the suitable water content for effective granulation on the basis of Litster’s granulation model. The granulation effectiveness of a sintering mixture was predicted by the model, with the allowance error of ± 10%. The effects of the water absorption properties, particle size composition and content of adhesive particles on the suitable water content were studied. The results showed that the allowable error of prediction was within ± 0.5% compared to the experimentally determined suitable water content. With an increase in adhesive powder content of mixtures with higher water absorption, the suitable water content increased to achieve similar granulation effectiveness. Moreover, as the amount of concentrates increased, the suitable water content first increased and then remained steady. The influence of the water absorption characteristics of the adhesive particles on the suitable water content was less than that of their particle size composition in the mixture.

Appendix

1.1 Calculation flow of average particle size of granules

For a given ore blending condition, ${x}_{0.5}$ can be obtained according to Eq. (6). Then, α($x$) can be calculated by ${x}_{0.5}$ in Eq. (2). Based on the Litster’s granulation model, the calculation flow is as follows.

The ratio of layer mass to nuclei mass of granules in ith size, ${R}_{i}$, is shown in following formula:

$$R_{i} = \frac{{\sum\limits_{i = 1}^{n} {\sum\limits_{k = 1}^{m} {\left[ {\left( {1 - \alpha_{i} } \right)\delta_{k} \omega_{ik} } \right]} } }}{{\sum\limits_{i = 1}^{n} {\sum\limits_{k = 1}^{m} {\alpha_{i} \delta_{k} \omega_{ik} } } }}$$

(7)

where n is the total particle size number; α_i is the partition coefficient of the particles with ith size; and ω_ik is the mass fraction of component k in ith size.

The mass fraction of granules in ith size, ${\omega }_{\mathrm{g}i}$ (%) is depicted in Eq. (8):

$$\omega_{ {\text g} {i}} = \alpha_{i} (1 + R_{i} )\sum\limits_{k = 1}^{m} {(\delta_{k} \omega_{ik} )}$$

(8)

The adhering layer thickness of granules in ith size (d–dl grain size), ${\varDelta }_{i}$, in mm, is described in Eq. (9):

$$2\varDelta_{i} = \frac{{R_{i} dl}}{4}$$

(9)

The top size of granule in ith size, ${x}_{i}$, in mm, can be calculated as follows:

$$x_{{{\text{g}}i}} = dl + 2\varDelta_{i}$$

(10)

Finally, the average particle size of granules, $\overline{d}$, in mm, can be obtained from Eq. (11):

$$\overline{d} = \sum\limits_{i = 1}^{n} {x_{{\text g}{i}} \cdot \omega_{{\text g}{i}} } /100$$

(11)