High-sulfur Coke Research Articles

Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack

Circulating Fluidized Bed (CFB) combustion is a clean technology for burning, with advantages of adapting to a large variety of fuel, high combustion efficiency, lower NOx emissions, and stable operation. The residue collected from the ash-hoppers of the electrostatic precipitator of the CFB boiler is called CFB fly ash. This paper presents the hydration development on the application of CFB fly ash to activating blast furnace slag (BFS) as a supplementary binder material (SBM) for replacement of Portland cement in making concrete. Investigation of the hydration products of cement pastes prepared with combinations of BFS and CFB fly ash were conducted by means of X-ray diffraction, thermal gravimetric analysis, and scanning electronic microscope. Test results show that the main hydration products of the CFB fly ash-BFS blended pastes were found to be hydrated calcium silicate (C-S-H), ettringite, gypsum, and some portlandite. Considering that CFB fly ash produced from the combustion of high-sulfur coke has high SO3 contents, the volume stability of mortar made from CFB fly ash-activated BFS was subjected to tests in accordance with ASTM C1012 and ASTM C1038 for evaluating the internal and external sulfate attack, respectively. The results indicate that, due to the high sulfur (SO3) content of CFB fly ash, the expansion caused by internal sulfate attack (ISA) increased with increasing proportion of CFB fly ash in the mixture. In contrast, no significant expansion was observed in the external sulfate attack (ESA) test, regardless of the proportion of CFB fly ash in the mixture. In order for the CFB fly ash to serve as a supplementary binder material and to maintain adequate volume stability, the amount of CFB fly ash used for the activation of BFS is recommended to be no more than 20% of the SBM.

Reduction and Desulfurization of Petroleum Coke in Ammonia and Their Thermodynamics

NH3-reducing desulfurization was demonstrated using a high-sulfur coke calcining desulfurization experiment at 1000 °C, and the sulfur chemical reactions of the three aromaticities of thiophene were studied during desulfurization. Results showed that NH3-reducing desulfurization could significantly remove sulfur in the coke, and the best operation temperature was approximately 800 °C, at which more than 80% of organic sulfur could be removed. The physical and chemical indicators of petroleum coke after desulfurization were not affected. Thermodynamic calculation results showed that the desulfurization reaction was more favorable at higher temperatures. However, the reaction was also affected by other factors; thus, the desulfurization efficiency decreased when the desulfurization temperature exceeded 800 °C. This paper presents a specific explanation of this phenomenon.

Batch analysis of H2-rich gas production by coal gasification using CaO as sorbent

ABSTRACTIn this study, a clean coal gasification technology was developed for production of H2-rich gas from coal with CaO as sorbent. The conditions including [CaO]:[C] ratios, reaction temperature, and reaction time for the coal gasification process were optimized. The products were H2, CH4, CO, and CO2. The highest H2 percentage (82.66%) for bituminous coal was obtained at [CaO]:[C] = 2:1 and T = 1203 K. Meanwhile, the highest H2 percentages for high-sulfur coal and high-sulfur coke were 77.41 and 81.57% at [CaO]:[C] = 1:4 and T = 1203 K, respectively. Moreover, the residual H2S were 0.28 and 2.19%, correspondingly.

Understanding of Halogen Impacts in Fluidized Bed Combustion

There is growing interest in cofiring coal with industrial wastes, some of which have an elevated halogen content. This study looks at the effects of adding halogens in a CFBC system. Experimental work was carried out on a pilot plant miniscale circulating FBC unit to which NaCl and I2 were added during the combustion of a high-sulfur coke and a low-sulfur bituminous coal at typical FBC temperatures. Further, the effects of limestone addition and cofiring with natural gas in conjunction with halogen addition were also investigated. Results showed that the halogen species inhibited CO and suppressed NO reduction and N2O formation. The distribution of halogen-containing products was predicted by the FACT thermodynamic database package for a wide range of combustion temperatures and other operating parameters. Results indicated that fuel type and combustion conditions have a pronounced effect on the amount of halogen or halide released. Dramatic changes in halogen products and their distribution were produced by changing the fuel from coal to petroleum coke, by adding limestone, and by cofiring with natural gas. A CFBC NO/N2O model has been employed which is based on the general kinetic model and a single particle NO/N2O formation model. The model uses the semi-theoretical approach with some measured parameters as inputs. It is capable of describing the NO, N2O, and HCN concentration histories satisfactorily even in the case of iodine addition.

Influence of High-Sulfur Cokes on Anode Performance in Alumina Reduction

The characteristics of a variety of fluid and delayed cokes have been examined both in the laboratory and as fillers in statistically significant numbers of full-size reduction cell anodes. Sulfur content ranged 1–5%; sulfur emission and anode performance indicated unique coke properties independent of sulfur level. Performance of high-sulfur filler anodes ranged from excellent to poor, and depends much more on the amount of oxidant-accessible surface than on sulfur level. The significance of coke blend compatibility was investigated to improve anode performance with available fillers as coke quality changes.