Title: A deep insight on the coal ash-to-slag transformation behavior during the entrained flow gasification process

Abstract

Recent research provided deep insight on the coal ash-to-slag transformation characterization during the entrained flow gasification process, with experimentation on a 40 kg/hr (dry basis) coal-fed opposed multi-burner (OMB) entrained flow gasifier and simulation via FactSage™ software. A general mechanism is presented to relate the gasifier design temperature, ash fluid temperature, and operating temperature with the degree of the slag polymerization. The change of the high temperature zone, the corresponding particle residence time in the high temperature zone, and syngas composition have obvious effects on the slag mineral transformation behavior. Mineral types formed on the wall of the gasifier chamber were mainly anorthite (CaAl₂Si₂O₈), aluminum oxide (Al₂O₃), and calcium sulfide (CaS). These minerals transformed to anorthite and diopside (CaMgSi₂O₆) at the slag hole zone, while the minerals at the lock hopper were anorthite, orthoclase (KAlSi₃O₈), quartz (SiO₂), gypsum (CaSO₄), calcite (CaCO₃), and halite (NaCl). FactSage™ predicted minerals as anorthite, diopside, orthoclase, and albite (NaAlSi₃O₈), etc., where the slag temperature was below the ash fluid temperature and when the ratios of CO/CO₂ and (CO + H₂)/CO₂ were lower than 1.0 and 2.0, respectively. By simulation, residual carbon was found to be the dominant factor over syngas composition to cause mineral transformation,more » and this was verified experimentally. The Ca-based crystals, typically anorthite, was shifted to diopside, near the slag hole zone, and a linear relationship was found between the content ratios of diopside/(anorthite + diopside), CaO/SiO₂, and (CaO + MgO)/SiO₂. A dimensionless number, θ, was defined to characterize the changing chemical composition and the degree of slag polymerization, with temperature deviation from the design condition. Three zones of θ were identified and related to the deviation between the actual gasification condition from the design condition. Finally, a low slag polymerization degree corresponded with a higher temperature deviation between the actual condition and design condition, and this proved that increased residual carbon content and changing iron valence state increased the mineral types when the slag temperature was below the ash fluid temperature.« less

Authors:

Shen, Zhongjie ^[1]; Nikolic, Heather ^[1]; Caudill, Landon S. ^[1]; Liu, Kunlei ^[2]

---

+ Show Author Affiliations

1. Univ. of Kentucky, Lexington, KY (United States). Center for Applied Energy Research
2. Univ. of Kentucky, Lexington, KY (United States). Center for Applied Energy Research; Univ. of Kentucky, Lexington, KY (United States). Dept. of Mechanical Engineering

Publication Date:

Wed Dec 16 00:00:00 EST 2020

Research Org.:

Univ. of Kentucky, Lexington, KY (United States)

Sponsoring Org.:

USDOE Office of Fossil Energy (FE)

OSTI Identifier:

1849250

Alternate Identifier(s):

OSTI ID: 1775777

Grant/Contract Number:  

FE0031506

Resource Type:

Accepted Manuscript

Journal Name:

Fuel

Additional Journal Information:

Journal Volume: 289; Journal Issue: C; Journal ID: ISSN 0016-2361

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

01 COAL, LIGNITE, AND PEAT; 42 ENGINEERING; Energy & fuels; Engineering; Entrained flow gasification; Coal ash-to-slag transformation; Temperature; Syngas composition; Residual carbon