Ash Fusion Characteristics of a High Aluminum Coal and Its Modification

Abstract

High aluminum coal (HAC, Al 2 O 3 in its ash content ranges 38−51%) is abundant and plays an important role in energy and chemical product in China. The ash fusion characteristics of HAC and its modification behaviors by coal blending or flux were investigated by ash fusion temperature (AFT) analyzer, X-ray fluorescence spectrometry, X-ray diffractometry combined with normalized reference intensity ratio method, and scanning electron microscopy. The AFT variation is manly dependent on mineral composition and its transformation. A large amount of high melting point (MP) mullite formation results in HAC (Sunjiahao coal, SJH) AFT high. Compare with the coal blending of Shenmu (SM) and Xiangyuan (XY), CaO addition provides a better way to adjust ash fusion characteristics of SJH. For coal blending, that calcium and iron element in low AFT coal react with high MP mineral and then evolve into eutectic and amorphous matter makes the AFT of SJH mixtures decrease. The formations of low MP anorthite, and gehlenite, and their eutectic resulting from the reaction of CaO and mullite lead to a decrease in the AFT.

Regulation of ash fusion behaviors for high aluminum coal by high calcium coal addition

“…3 Blending coal not only improves ash viscosity-temperature characteristics but also is more economical and efficient for raw material complementary and product structure optimization. 17 To make high-AFT coal meet the requirements of liquid slag discharge in the EFG, the coal preparation method is generally carried out by mixing the high-AFT coal with the low AFT coal. However, the regulation of AFTs was mainly focused on the control of HSAC, and little attention has been paid to other high melting point (MP) coals (e.g., HAC and HCC).…”

“…The FTs of HAC and HCC are usually high (HAC: >1600 C; HCC: >1400 C). It was found that even if the blending coal mass ratio reached 60%, the FTs of mixed ashes did not decrease to meet the requirement of the EFG; however, when CaO reached 20%, the FTs of mixed ashes have been decreased to <1380 C. 17 Therefore, it is necessary to improve the coal preparation principle. For example, coal-blending experiments of Pingsuo coal and Shenhua coal and Tianci coal and Xiaotun coal indicated that the variation in the contents of mullite and anorthite were the main reason leading to the AFTs change.…”

“…,17 Thus, failed to react with a quartz crystal with the increase in Al 2 O 3 (MP: 2050 C) that belongs to inert oxides and has a high MP, resulting in higher AFT of A HAC . It was clear that the content of CaO, Fe 2 O 3 , and MgO in A H and A X was significantly higher than A HAC especially that the content of their CaO was 50.07% and 37.75%; they were typicalT A B L E 3 Ash chemical compositions and their fusion temperatures of raw coalsAbbreviations: B/A, basic/acidic; DT, deformation temperature; FT, flow temperature; HT, hemisphere temperature; ST, softening temperature.…”

“…The FTs of HAC and HCC are usually high (HAC: >1600 C; HCC: >1400 C). 17 To make high-AFT coal meet the requirements of liquid slag discharge in the EFG, the coal preparation method is generally carried out by mixing the high-AFT coal with the low AFT coal. For example, coal-blending experiments of Pingsuo coal and Shenhua coal and Tianci coal and Xiaotun coal indicated that the variation in the contents of mullite and anorthite were the main reason leading to the AFTs change.…”

“…For example, the ash fusion characteristics of HAC and its modification behaviors by adding low AFT coal (Shenmu and Xiangyang) and calcium oxide (CaO) were investigated. It was found that even if the blending coal mass ratio reached 60%, the FTs of mixed ashes did not decrease to meet the requirement of the EFG; however, when CaO reached 20%, the FTs of mixed ashes have been decreased to <1380 C. 17 Therefore, it is necessary to improve the coal preparation principle. In this manuscript, the coal gasification principle of coal blending is not determined by the AFT level of coal but by its ash composition.…”