The fluidized bed ironmaking technology has attracted the attention of many researchers for decades as a direct reduction ironmaking method with many advantages. This process has been applied as a pretreatment method in many non-blast furnace ironmaking processes. However, the sticking problem hindered its development greatly. Defining the essential cause of sticking, and fundamentally solving this problem are the key steps encountered by this process. The research works related to the prevention of sticking problem during fluidized bed reduction of fine iron ore are comprehensively summarized in this article. The causes of sticking, the influencing factors of sticking and the solution of sticking are firstly discussed, followed by the analysis on the possible development direction of future fluidized bed ironmaking technology.

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The thermal decomposition mechanism of K-feldspar with industrial waste of FGD gypsum to produce soluble potassium (K) salt was investigated. Effects of the reaction temperature and the amount of reagents used on the recovery of K were studied. The results showed that increasing the reaction temperature and mass ratio of CaCO3/KAlSi3O8 and CaSO4/KAlSi3O8 was beneficial to the decomposition of K-feldspar. The recovery ratio of K was higher than 90% with the mass ratio of KAlSi3O8:CaSO4:CaCO3 = 1:1:3 at 1373 K for 40 min, and the product K2SO4 with a purity of 91.3% was obtained. A crystal structure disintegration mechanism for KAlSi3O8 was proposed on the basis of the characterization of phase transformation sequences by XRD, FTIR, and SEM/EDS. It was found that two product layers formed successively during the KAlSi3O8 decomposition process. K was enriched in the outer product layer, and the decomposition rate was controlled by Ca diffusion through the inner one. Based on the experimental results, a kinetics model of K-feldspar decomposition was established using the Crank-Ginstling-Brounshtein equation, and the apparent activation energy was determined.

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As an environmentally hazardous waste, blast furnace (BF) flue dust had a potential to reduce CO2 emission if recycled as fuels or reducing agents due to the high carbon content. The structure of carbon was a principal factor to the reactivity of carbon conversion and therefore was highly relevant to efficient utilization. In this work, the characteristics and chemical structures of carbonaceous materials in BF flue dust were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, and Raman analysis. The results showed that the aromatic structure of crystalline carbon was dominant in carbonaceous materials. Polymeric aromatic carbon and oxygen-containing groups (epoxide and esters carbon) existed on the surface. The stacking height (L c ), the in-plane crystallite sizes (L a ), and the interlayer spacing (d 002) of the aromatic structure layer were 2.45, 3.31, and 0.347 nm, respectively. The mass ratios of chars and cokes to carbonaceous matter were estimated to be 90.56% and 9.44%, respectively, by Raman spectroscopy. Then, the combustion reactivity was studied by thermogravimetric analysis using the Kissinger–Akahira–Sunose kinetics method. The activation energy as a function of conversion degree was determined. The results thus provided fundamental information for the utilization of BF flue dust for thermochemical conversion.