Gasification of iron coke and cogasification behavior of iron coke and coke under simulated hydrogen-rich blast furnace condition

To explore the iron coke application in hydrogen-rich blast furnace,which is an effective method to achieve the purpose of low carbon emissions,the initial gasification temperature of iron coke in CO_(2) and H_(2)O atmosphere and its cogasification reaction mechanism with coke were systematically studied.Iron coke was prepared under laboratory conditions,with a 0-7wt%iron ore powder addition.The properties of iron cokes were tested by coke reactivity index(CRI)and coke strength after reaction(CSR),and their phases and morphology were evolution discussed by scanning electron microscopy and X-ray diffraction analysis.The results indicated that the initial gasification temperature of iron coke decreased with the increase in the iron ore powder content under the CO_(2) and H_(2)O_((g))atmosphere.In the 40vol%H_(2)O+60vol%CO_(2) atmosphere,CRI of iron coke with the addition of 3wt%iron ore powder reached 58.7%,and its CSR reached 56.5%.Because of the catalytic action of iron,the reaction capacity of iron coke was greater than that of coke.As iron coke was preferentially gasified,the CRI and CSR of coke were reduced and increased,respectively,when iron coke and coke were cogasified.The results showed that the skeleton function of the coke can be protected by iron coke.

Inhibition mechanism between sodium(Na3AlF6)and sulfur on coke reactivity

Inhibition mechanism between sodium （NaaAlF6） and sulfur on coke reactivity was investigated by simulating petroleum coke with low-impurity pitch coke and by impurity doping. The mechanism was discussed by scanning electron microscopy, energy-dispersive spectrometry, and X-ray powder diffraction. Results show that Na effectively inhibited S catalysis during carbon-air/CO2 reactions, and S inhibited the catalysis of Na during carbon- air reaction to a certain extent. A stable structure with a Na-to-S atomic ratio of 1.4 and a cyclic reaction system of ＂Na2SO3→ Na2S→Na2CO3→ Na2SO3＂ were likely the keys to producing this mutual inhibition.

CO_2 Gasification Characteristics of High and Low Reactivity Cokes

In order to effectively utilize the high reactivity coke, the gasification characteristics of high and low reactivity cokes were investigated at 1100 ℃. Low reactivity coke A and high reactivity coke B were chosen and charged into the reaction tube in two methods. The results indicated that the mass loss ratio of high reactivity coke in mixed cokes was more significant than that of single high reactivity coke in the middle stage of reaction. Nevertheless, the mass loss ratio of low reactivity coke in mixed cokes was less than that of single low reactivity coke. It was mainly attributed to gas diffusion and internal reaction of coke. When high and low reactivity cokes were mixed, the practical average mass loss ratio was nearly the same as the weighted average. The microscopic structures of coke indicated that with the increase of reaction time, the external and internal layers of low reactivity coke reacted more uniformly with CO2, whereas the reaction degree of external layer of high reactivity coke was obviously higher.

Effects of Additives on Sulfur Transformation,Crystallite Structure and Properties of Coke during Coking of High-sulfur Coal

High-sulfur coal, as an alternative coal source, has a relatively high proportion in coal reserves. However, the feature of high sulfur content, which can cause environmental pollution and poor quality of molten iron, restrains its utilization in coking industry. Coking experiments of high-sulfur coal with Fe2O3, La2O3 and CaO as additives were carried out in order to fix the sulfur in coke. The effects of additives on sulfur distribution, crystallite structure, surface morphology and properties of coke were investigated. The results indicate that CaO can be used as sulfur-fixing agent in coking process, and CaS is the main mineralogical phase of the sulfur-contained mineral constituents in coke. Fe2O3 and La2O3 facilitate the conversion of CaO to CaS. The additives mainly influence the crystallite height and the average interlayer spacing doo2 of coke. The addition of La2O3 increases the value of the crystallite height while the addition of CaO and Fe2O3 decreases it. CaO leads the pores of coke to increase with its physical action and agglomerating characteristic. Fe2O3 and C can form （Fe,C）, resulting in the pulverization and erosion of the pore wall. La2O3 makes the coke surface become more compact and thinner. The reactivity of coke increases with the decrease of crystallite height and crystallite layer number.

A comparison study of existence forms of Fe species in coke for solution loss reaction of carbon

Fe species were loaded by two different loading ways （absorption method and addition method） to investigate their effect on thermal properties of coke. The particulate coke reactivity of coke samples indicated that the added sample showed higher catalytic activity than the adsorbed sample at first, owing to the decreased structure and properties of coke and more catalytic active sites caused by the strong interaction between Fe species and coke. The presence of Fe species in the added sample weakened the microstructure of coke, and the Fe species were easier to be reduced than those in the absorbed sample due to its different existence form in coke. With further increased loading of Fe species, the different existence positions of Fe species caused more decrease in surface active sites in the added sample than in the adsorbed sample, leading to lower catalytic activity of added sample when the total iron content exceeded 1%. The catalytic mechanism implied that there may be a catalytic dominant factor change in the reaction between the catalytic effect of iron species and carbon surface active sites in coke; the catalytic effect of iron species is dominant in the reaction at first, but the catalytic effect of carbon surface active sites is dominant in the reaction with the further increased loading amount of Fe species.