Particulate matter filtration of the flue gas from iron-ore sintering operations using a magnetically stabilized fluidized bed

CFD simulation of gas–solid fluidized bed hydrodynamics; prediction accuracy study

The present study aims at increasing the prediction accuracy of simulating gas–solid fluidized bed hydrodynamics. Two simulation packages, Fluent and MFIX, were used to predict the pressure drop, voidage, and solid-phase velocities by solving mass, momentum, and energy balance equations. A 2D multi-fluid Eulerian model with the kinetic theory of granular flow (KTGF) was applied to simulate the process by considering two different drag models. The same comparative criterion of average absolute relative deviation (AARD%) was considered to compare the present simulation with the previous works. Compared to the prior works, the minimum decrease in error (AARD% of 5.91%) was 3.17% related to the estimation of the time-averaged voidage by applying the Gidaspow model, while the maximum reduction in error (ARRD% of 5.88%) was 17.35% attributed to the prediction of pressure drop by employing the Syamlal-O’Brien model, both in Fluent software. However, MFIX software was the best CFD tool in predicting time-averaged voidage by AARD% values less than 9% under all conditions. Furthermore, similar patterns in contours were observed for solid-phase volume fraction and gas/solid phase velocities in both simulation tools, which are compatible with results from the literature without any significant difference.

Immobilization of cellulase on magnetic nanoparticles for rice bran oil extraction in a magnetic fluidized bed

This paper presents a method for extracting rice bran oil using magnetic immobilized cellulase (MIC) in a magnetic fluidized bed (MFB). Cellulase was immobilized on Fe3O4/SiO x -g-P (glycydylmethacrylate) with an average grain size of 120 nm. The rice bran was hydrolyzed using MIC combined with magnetic immobilized alkaline protease to extract rice bran oil. Under intermittent conditions, the MIC concentration was 1.6 mg/g, the liquid to material ratio was 4:1, the enzymatic hydrolysis time was 150 min, and the oil yield was as high as 85.6 ± 1.20% at 55 °C. The fluid in the MFB had a magnetic field strength of 0.022 T, a flow velocity of 0.005 m/s, and an oil extraction rate of 90.3%. This provides a theoretical basis for the extraction of rice bran oil using the subsequent MFB hydroenzyme method.

Life cycle assessment of ultra-low treatment for steel industry sintering flue gas emissions

The largest contributor to pollutant emissions is the sintering process in steel industry. Ultra-low emission policy for the Chinese steel industry states that emission concentrations of particulate matter, SO₂ and NO_x should not exceed 10, 35 and 50 mg/m³ respectively. The emission concentrations of the steel industry are the same as the ultra-low emission policy for the coal-fired power industry, but the pollutant control technologies of the two industries are different. Life cycle assessment method is applied to analyze the latest ultra-low treatment process for sintering flue gas emissions which includes electrostatic precipitation, ozone oxidation, wet desulfurization, wet denitration, condensation dehumidification and wet electrostatic precipitation. Following this novel ultra-low emission treatment, the concentrations of particulate matter, SO₂, NO_x, and PCDDs in the sintering flue gas decreased very significantly, attaining the new emission standard. With 1 ton of sinter as the functional unit and "cradle to gate" as the system boundary, the environmental impact of the process is 0.1811 and the total economic cost is 172.79 RMB, of which internal cost is 34.64 RMB and external cost is 138.15 RMB. The main environmental impacts result from applying the wet denitration and ozone oxidation processes. Sodium sulfite in the wet denitration process, and electricity and liquid oxygen in the ozone oxidation process are the key inputs that cause environmental impact. These findings are useful for a further optimization of the ultra-low emissions process from both the environmental and economic perspective, which is applicable in other regions of the world.

Magnetized fluidized bed with binary admixture of magnetizable and nonmagnetizable particles

Magnetic fields were used to successfully improve the fluidization quality of magnetizable particles, forming the magnetized fluidized bed (MFB). Moreover, researchers found that the binary admixture of magnetizable and nonmagnetizable particles could also be used in the MFB, creating the admixture MFB. Consequently, the MFB technique is no longer restricted to the few magnetizable particles in nature and can be extended to numerous nonmagnetizable particles. Nevertheless, research on the admixture of MFB is far from sufficient, severely hindering its commercial application in the chemical and biochemical industries. To deepen our understanding in this area, this review summarizes the relevant findings, which mainly include (1) transport phenomena in the gas-solid admixture MFB with Geldart B particles; (2) elimination of the abnormal fluidization phenomena in the gas-solid admixture MFB with Geldart C particles; (3) flow regime transition of the liquid-solid admixture MFB under both the magnetization-FIRST and magnetization-LAST operation modes; and (4) application of the pure MFB in the fields of gas filtration and coal dry separation. Finally, critical comments are made on the shortcomings of the reported research with the hope that more efforts could be devoted to these aspects in the future.