Effect of temperature on suspension magnetization roasting of hematite using biomass waste as reductant:A perspective of gas evolution

The magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon neutrality.The effects of temperatures on suspension magnetization roasting of hematite using biomass waste for evolved gases have been investigated using TG-FTIR,Py-GC/MS and gas composition analyzer.The mixture reduction process is divided into four stages.In the temperature range of 200-450℃ for mixture,the release of CO_(2),acids,and ketones is dominated in gases products.The yield and concentration of small molecules reducing gases increase when the temperature increases from 450 to 900℃.At 700℃,the volume concentrations of CO,H_(2) and CH_(4) peak at 8.91%,8.90% and 4.91%,respectively.During the suspension magnetization roasting process,an optimal iron concentrate with an iron grade of 70.86%,a recovery of 98.66% and a magnetic conversion of 45.70% is obtained at 700℃.Therefore,the magnetization reduction could react greatly in the temperature range of 600 to 700℃ owing to the suitable reducing gases.This study shows a detail gaseous evolution of roasting temperature and provides a new insight for studying the reduction process of hematite using biomass waste.

Reaction behavior and non-isothermal kinetics of suspension magnetization roasting of limonite and siderite

In order to develop limonite and decrease CO_(2) emissions,siderite is proposed as a clean reductant for suspension magnetization roasting(SMR) of limonite.An iron concentrate(iron grade:65.92wt%,iron recovery:98.54wt%) was obtained by magnetic separation under the optimum SMR conditions:siderite dosage 40wt%,roasting temperature 700℃,roasting time 10 min.According to the magnetic analysis,SMR achieved the conversion of weak magnetic minerals to strong magnetic minerals,thus enabling the recovery of iron via magnetic separation.Based on the phase transformation analysis,during the SMR process,limonite was first dehydrated and converted to hematite,and then siderite decomposed to generate magnetite and CO,where CO reduced the freshly formed hematite to magnetite.The microstructure evolution analysis indicated that the magnetite particles were loose and porous with a destroyed structure,making them easier to be ground.The non-isothermal kinetic results show that the main reaction between limonite and siderite conformed to the two-dimension diffusion mechanism,suggesting that the diffusion of CO controlled the reaction.These results encourage the application of siderite as a reductant in SMR.

Fluidized magnetization roasting of refractory siderite-containing iron ore via preoxidation-low-temperature reduction

Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ore.However,the reduction roasting of siderite(FeCO3)generates weakly magnetic wüstite,thus reducing iron recovery via weak magnetic separation.We systematically studied and proposed the fluidized preoxidation-low-temperature reduction magnetization roasting process for siderite.We found that the maghemite generated during the air oxidation roasting of siderite would be further reduced into wüstite at 500 and 550℃due to the unstable intermediate product magnetite(Fe_(3)O_(4)).Stable magnetite can be obtained through maghemite reduction only at low temperature.The optimal fluidized magnetization roasting parameters included preoxidation at 610℃for 2.5 min,followed by reduction at 450℃for 5 min.For roasted ore,weak magnetic separation yielded an iron ore concentrate grade of 62.0wt%and an iron recovery rate of 88.36%.Compared with that of conventional direct reduction magnetization roasting,the iron recovery rate of weak magnetic separation had greatly improved by 34.33%.The proposed fluidized preoxidation-low-temperature reduction magnetization roasting process can realize the efficient magnetization roasting utilization of low-grade refractory siderite-containing iron ore without wüstite generation and is unlimited by the proportion of siderite and hematite in iron ore.

Mechanism for suspension magnetization roasting of iron ore using straw-type biomass reductant

As an alternative reductant for fossil fuel in the future,straw-type biomass contributes to emission reduction and green utilization in the suspension roasting process.In this study,the influences of the roasting time,roasting temperature and dose of straw-type biomass after suspension magnetization roasting(SMR) and separation were investigated.The optimal conditions were determined to be a roasting time of 7.5 min with a straw-type biomass dose of 20 wt% and a roasting temperature of 800℃ in which an iron grade of 71.07% and recovery of 94.17% were obtained for the iron concentrate.The maximum saturation magnetization under optimal conditions was 35.05 A·m^(2)·g^(-1),and the gaseous regulation of the biomass revealed that cumulative reducing gas volume was 293.93 mL at the optimal roasting time of450 s.The transformation of hematite to magnetite was detected by X-ray diffraction(XRD).During microstructure evolution,the outer layer consisting of fissures and tiny holes continuously deepened toward the core.

Magnetizing Roasting Mechanism and Effective Ore Dressing Process for Oolitic Hematite Ore

Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.

Application of multi-stage dynamic magnetizing roasting technology on the utilization of cryptocrystalline oolitic hematite:A review

A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To recover iron from oolitic hematite, we developed a novel multistage dynamic magnetizing roasting technology. Compared with traditional magnetizing roasting technologies, this novel technology has the following advantages: firstly, the oolitic hematite is dynamically reduced in a multi-stage roasting furnace, which shortens the reduction time and avoids ringing and over-reduction;secondly, the novel dynamic magnetizing roasting technology has strong raw material adaptability, and the size range of raw materials can be as wide as 0–15 mm;thirdly, the roasting furnace adopts a preheating-heating process, and the low-calorific value blast furnace gas can be used as the fuel and reductant, which greatly reduces the cost. The actual industrial production data showed that the energy consumption in the roasting process can be less than 35 kg of standard coal per ton of raw ore. The iron grade of the concentrate and iron recovery reached 65% and 90%, respectively.

Recovery of Ferric Oxide from Bayer Red Mud by Reduction Roasting-Magnetic Separation Process

A great amount of red mud generated from alumina production by Bayer process was considered as a low-grade iron ore with a grade of 5wt% to 30wt% iron.We adopted the reduction roastingmagnetic separation process to recover ferric oxide from red mud.The red mud samples were processed by reduction roasting,grinding and magnetic separating respectively.The effects of different parameters on the recovery rate of iron were studied in detail.The optimum techqicalparameters were proposed with 700 ℃roasting for 20 min,as 50wt% carbon and 4wt% additive were added.The experimentalresults indicated that the iron recovery and the grade of totaliron were 91% and 60%,respectively.A novelprocess is applicable to recover ferric oxide from the red mud waste fines.

Recovery of iron from Baotou rare earth tailings by magnetizing roast

The difference of physicochemical properties among minerals in Baotou rare earth tailings is not significant,which leads to a great difficulty in separation of minerals.In this article,the process of magnetizing roast and low-intensity magnetic separation was used to recover iron.Effect of calcination temperature,holding time and carbon/oxygen ratio on roasting efficiency was investigated.The parameters evaluating magnetizing roast efficiency and theoretical value were determined.X-ray diffraction(XRD)analysis was used to investigate the conversion of Fe phase after roasting.The results show that the best magnetizing roast conditions are calcination temperature of 650℃,holding time of 2.5 h,and carbon/oxygen molar ratio of 3.85.The best magnetization rate is 2.36,which is close to the theoretical value of 2.33.Based on experiments of low-intensity magnetic separation under different intensities,the best current intensity is 2.0 A to obtain the best separation results.Under the best condition,the concentrate grade of iron is 45.45% and the recovery of iron is 68.36%.Most of rare earth,fluorine,and phosphorus are enriched in the magnetic separation tailings.The XRD analysis shows that Fe exists in Fe2O3 before roasting and exists in Fe3O4after roasting.

Effect of Biochar as Reductant on Magnetizing-roasting Behavior of Pyrite Cinder

The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was in- vestigated. The key of magnetizing-roasting is the gasification reaction between reductants and CO2. Since biochar could react with CO2 more rapidly at lower temperature, the reactivity of biochar is better than that of anthracite. The gasification of biochar could produce reducing condition of φco/（φco--φco2 ） about 10 %- 20 % between 700-- 800 ℃, which is in accord with the atmosphere and temperature of Fe2 O3 reduction. So it is beneficial to the reduc- tion of iron mineral of pyrite cinder. Compared with anthracite, bioehar could decrease the roasting temperature from 825 to 750 ℃ and roasting time from 20 to 15 min, which shows that a better effect of magnetization could be ob- tained in the condition of lower temperature and shorter time. Using biochar as reductant, iron concentrate extracted from pyrite cinder as about 64% iron grade could be produced, and the recovery is over 90% under the condition of above 90% grinding particle less than 0. 045 mm and magnetic intensity of 0. 124--0. 194 T.

Iron recovery and rare earths enrichment from Bayan Obo tailings using Coal-Ca(OH)2-NaOH roasting followed by magnetic separation

The recovery of iron and enrichment of rare earths from Bayan Obo railings were investigated using Coal Ca（OH） 2 NaOH roasting followed by magnetic separation. The influences of roasting temperature, roasting time, coal content, milling time, Ca（OH）2 dosage and NaOH dosage on the iron and rare earths recovery were explored. The results showed that the magnetic concentrate containing 70.01 wt. % Fe with the iron recovery of 94.34G and the tailings of magnetic separation containing 11.46 wt. % rare earth oxides （REO） with the REO recovery of 98. 19% were obtained under the optimum conditions （i. e. , roasting temperature of 650℃, roasting time of 60 min, coal content of 2.0%, milling time of 5 min, and NaOH dosage of 2.0%）. The Ca（OH）2 dosage had no effect on the separation of iron and rare earths. According to the mineralogical and morphologic analysis, the iron and rare earths of Bayan Obo tailings could be utilized in subsequent ironmaking process and hydrometallurgy process.

Preparation of Chromium-iron Metal Powder from Chromium Slag by Reduction Roasting and Magnetic Separation

Chromium slag（CS）has become one of the most hazardous solid waste containing chromium and iron.Based on its characteristics,the technology of reduction roasting and magnetic separation was employed to treat CS.The major impurity element of CS is magnesium and it exists in magnesium ferrite phase,which is hard to recover iron in the absence of additives.During reduction roasting,additives（Al2O3and CaF2）could destroy the structure of magnesium ferrite and improve the iron grade and recovery.The final product,i.e.chromium-iron powder,contains 72.54% Fe and 13.56% Cr,with the iron recovery of 80.34% and chromium recovery of 80.70%.