Measurement of thermal properties of iron oxide pellets

Takegoshi, Eisyun; Hirasawa, Yoshio; Imura, Sadahisa; Shimazaki, Toshiharu

doi:10.1007/bf00505502

Cited by 16 publications

(9 citation statements)

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“…Due to the slower heat up process in Ar and N2 gases, the corresponding reduction rates are lower. Similarly, in our work, the reduction degree of hematite particles in pure CO 2 at 1710 K can reach the same value of the ore in N 2 gas and in 69.5 vol pct CO 2 + 30.5 vol pct N 2 gas ) 1000 [34] Conductivity of Ore k P (W m À1 K À1 ) 1 [34,35] [33] Surface Emissivity of Ore/Wall e P 0.5 at 1785 K. Moreover, Figure 10 also indicates that, although pure CO 2 can effectively accelerate the heat transfer process, even as high as 69.5 vol pct of CO 2 cannot significantly raise the reduction degree of ore in thermal decomposition. As shown in Figure 8(c), it can be noted that the reaction rate constants of hematite particles in PCR4¢ gas are higher than those in PCR2¢ gas for the 110 lm particles.…”

Section: ½15supporting

confidence: 85%

Reduction Kinetics of Fine Hematite Ore Particles in Suspension

Chen

Zeilstra

Stel

et al. 2021

Metall Mater Trans B

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Suspension reduction kinetics of hematite ore particles at 1710 K to 1785 K was described by the Johnson-Mehl-Avrami-Kolmogorov model with Avrami exponent of 1.405. The apparent activation energy is 105.5 kJ mol−1 with the rate determining step of nucleation and growth. The reduction degree of the hematite at the endpoint is a linear function of temperature and the logarithmic oxygen potential of the reacting gas. A peak function of reaction rate constant with particle size has been verified in this work, and the maximum value of the reaction rate is located at around 85 µm particle size. The influence of heat transfer on the reaction process has been evaluated. The results suggest that the heating-up process for large particles, 244 µm particles, for instance, cannot be ignored. It can retard the reaction rate compared to small particles. Normally, the reaction rate constant decreases linearly with the increase of ln[p(O2)] of the reacting gas mixture. However, 95 vol pct CO2 in the reacting gas can accelerate the reaction rate of thermal decomposition of hematite due to the emissivity of CO2 gas. It results in a higher reaction rate of 110 µm particles in 95 vol pct CO2-containing gas than that in other less CO2-containing gases.

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Section: ½15supporting

confidence: 85%

Reduction Kinetics of Fine Hematite Ore Particles in Suspension

Chen

Zeilstra

Stel

et al. 2021

Metall Mater Trans B

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“…The total oxide deposit thickness was 288 nm, consisting of layers of chromium oxide (204 nm thickness) and iron oxide (84 nm thickness). Using oxide thermal conductivities from the literature [27,28] and a thickness weighted average, it was found that k = 8.5 W/m K and R oxide = 3.4 × 10 -8 m 2 K/W. The oxide thermal resistance (R oxide ) is several orders of magnitude lesser than the R c values measured in Fig.…”

Section: Resultsmentioning

confidence: 88%

Effect of substrate oxidation on spreading of plasma-sprayed nickel on stainless steel

McDonald¹,

Moreau²,

Chandra³

2007

Surface and Coatings Technology

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Plasma-sprayed, molten nickel particles (∼ 60 μm diameter) were photographed during impact on oxidized 304L stainless steel surfaces that were maintained at either room temperature or at 350°C. Steel coupons were oxidized by heating them at different temperatures. A fast chargecoupled device (CCD) camera captured time-integrated images of the spreading splat. A two-color pyrometer collected thermal radiation from particles and recorded the evolution of their temperature after impact. Molten nickel particles impacting on oxidized steel at room temperature fragmented significantly, while heating the surfaces produced splats with disk-like morphologies. Impact on steel that was highly oxidized induced the formation of finger-like splash projections at the splat periphery. Thermal contact resistance between splats and non-heated oxidized steel was calculated from splat cooling rates and found to decrease as the degree of oxidation increased. On heated, oxidized steel thermal contact resistance was much lower and did not change significantly with the degree of oxidation. It was concluded that thermal contact resistance was largely influenced by adsorbates on the steel surface that evaporated when the surface was heated or oxidized.

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“…While the coefficient of determination between the dual porosity model and the experimental data, 0.90, is relatively high, the model overestimates the bed thermal conductivity at high temperatures. Takegoshi et al [38] observes that the thermal conductivity of iron oxide pellets is influenced by the extent of reduction of the pellets, with reduced particles exhibiting a much lower thermal conductivity than their oxidized counterparts at the same temperature. This may explain the difference between the experimental results and the model at high temperatures.…”

Section: Discussionmentioning

confidence: 99%

Ultra-High Temperature Thermal Conductivity Measurements of a Reactive Magnesium Manganese Oxide Porous Bed Using a Transient Hot Wire Method

Hayes

Masoomi

Schimmels

et al. 2021

Journal of Heat Transfer

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The effective thermal conductivity of packed beds of magnesium-manganese oxide pellets is a crucial parameter for engineering Magnesium Manganese Oxide (Mg-Mn-O) thermochemical energy storage devices. We have measured the effective thermal conductivity of a packed bed of 3.66 ±0.516 mm sized magnesium manganese oxide (Mn to Mg molar ratio of 1:1) pellets in the temperature range of 300 to 1400°C. Since the material is electrically conductive at temperatures above 600°C, the sheathed transient hot wire method is used for measurements. Raw data is analyzed using the Blackwell solution to extract the bed thermal conductivity. The effective thermal conductivity standard deviation is less than 10% for a minimum of three repeat measurements at each temperature. Experimental results show an increase in the effective thermal conductivity with temperature from 0.50 W/m °C around 300°C to 1.81 W/m °C close to 1400°C. We propose a dual porosity model to express the effective thermal conductivity as a function of temperature. This model also considers the effect of radiation within the bed, as this is the dominant heat transfer mode at high temperatures. The proposed model accounts for micro-scale pellet porosity, macro-scale bed porosity, pellet size, solid thermal conductivity (phonon transport), and radiation (photon transport). The coefficient of determination between the proposed model and the experimental results is greater than 0.90.

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Measurement of thermal properties of iron oxide pellets

Cited by 16 publications

References 0 publications

Reduction Kinetics of Fine Hematite Ore Particles in Suspension

Reduction Kinetics of Fine Hematite Ore Particles in Suspension

Effect of substrate oxidation on spreading of plasma-sprayed nickel on stainless steel

Ultra-High Temperature Thermal Conductivity Measurements of a Reactive Magnesium Manganese Oxide Porous Bed Using a Transient Hot Wire Method

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