Page 30 - Mines and Minerals Reporter eMagazine - Volume October 2021

TECHNOLOGY

mixed with pure iron ores have mentioned the SMR process. 650–900 C, 2.5–15.0 min, and 10%–35%, respectively. The
The aim of this work is to assess the possibility of using bio- composition of gaseous products was displayed in an infra-
mass as a reductant for SMR, and the experimental indexes of red gas composition analyzer (Gasboard-3100 Wuhan China),
hematite mixed with straw-type biomass are calculated under which monitors the SMR process in real-time. The furnace
different conditions after magnetic separation. According to tube was removed from the suspension roasting system and
the results of the phase transformation and microstructure cooled to room temperature under a nitrogen atmosphere
evolution of hematite, hematite changes to magnetite in a until the completion of the roasting process. Afterward, the
stepwise manner, indicating the feasibility of straw-type bio- roasted products were investigated by XRD analysis (X pert-
mass as a reductant under suitable experiments. A vibrating pro, PANalytical B.V., Netherlands), scanning electron micros-
sample magnetometer is used to detect the magnetic prop- copy (ULTRA PLUS, Zeiss, Germany & SSX-550, Hitachi, Japan),
erties of the roasted samples. Furthermore, in addition to gas as well as vibrating sample magnetometry (JDAW-2000D,
product analysis, the regulations of main reducing gases are YingPu, China).
revealed during the SMR process.
The roasted products were separated by using a Davis Tube
Materials and methods Tester (RX/CXG50, Tangshan China) in at a magnetic field in-
tensity of 104 kAm 1. Prior to the separation experiment, 8 g of
the nitrogen-cooled samples was milled by a handheld milling
Materials
machine (Tree) to ensure that the particles were less than 0.1
mm. Both magnetic concentrates and nonmagnetic tailings
Straw collected from Liaoning Province, China, was prepared were filtered, dried and weighed after separation. The drying
as a reductant in the SMR process. Prior to all experiments, the process was conducted in an oven at a temperature of 80 C.
strawtype biomass was cut into 2–3 cm pieces and crushed The recovery of iron was used to evaluate the efficiency of the
by a pulverizer to be a powder-like particle size of 0.9 cm. All
magnetization roasting process, which was calculated based
on the following equation:
Table 2 Phase compositions of iron in the hematite ore sample (%).
Compositions Fe in carbonate Fe in magnetite Fe in hematite Fe in sulfide Fe in silicate TFe
Mass fraction 0.07 2.13 64.81 0.18 0.85 67.70
Distribution 0.10 3.15 95.73 0.27 1.26 100.00

straw-type biomass samples were dried for 10 h at 80 C. The
results of preliminary, elemental and constituent analysis are
shown in Table 1. The hematite obtained from Liaoning Prov-
ince, China contained TFe 67.70%, FeO 0.53%, SiO2 1.16%, where a, b, h are the iron grades of the feedstock, magnetic
Al2O3 0.47%, CaO < 0.05%, MgO 0.11%, P 0.035%, S 0.013%, concentrates and tailings, respectively; and e the recovery of
and LOI 1.94%. It was required that the particle size distribu- the iron concentrate.
tion of the pure ore sample be such that 70% of the material
passed 200 mesh (0.074 mm). The sample of iron ore charac-
terized by X-ray diffraction (XRD) analysis was hematite. The
result of phase analysis is shown in Table 2.

Methods
The experimental system is illustrated in Fig. 1. The roasting
system included a gas supply device, a gas flow controller, a
temperature controller, and an online gas composition analyz-
er. For the magnetization experiment, the hematite and straw-
type biomass were mixed naturally in a certain mass ratio, and
the mixed sample was subsequently placed into a furnace
tube. N2 was utilized as carrier gases to exhaust air, at a flow
rate of 300 mL/min. The electronic furnace was turned on,
and a heating rate of 15 C was set. When the roasting furnace
reached a specific temperature under the heating of roasting
device, the furnace tube was quickly put into it. The ranges of Fig. 2.a. Effects of roasting time on gaseous products. (Gas Flow Curves)
roasting temperature, roasting time and biomass dose were

28 MINES & MINERALS REPORTER / OCTOBER 2021