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Title: Viscosity Determination of Molten Ash from Low-Grade US Coals

In entrained slagging gasifiers, the fluidity of the molten ash is a critical factor for process control since it affects slag formation, the capture of inorganic constituents, refractory wear, and slag drainage along the gasification chamber walls. The use of western coal, or mixtures of eastern and western coals as gasifier feedstock, is likely to occur as western coals become available and technological issues that hinder their use are being resolved. In the present work, the viscosity of synthetic slags with ash chemistries simulating the western U.S. coals, was experimentally measured at a Po2 = 10- 8 atm in the temperature range of 1773–1573 K (1500–1300 °C) using a rotating-bob viscometer. Alumina spindles and containment crucibles of both alumina and zirconia were used. Crystallization studies of this slag using a confocal scanning laser microscope found that a (Mg,Fe)Al2O4-based spinel precipitated at temperatures below 1723 K (1450 °C), and this agreed with FactSage equilibrium phase prediction. The same spinels were observed in the post-viscometry experiment slags when ZrO2 crucibles were used and assumed to be in equilibrium with the slag at the higher temperatures. Zirconia dissolution resulted in a slight increase in the solid fraction present in slags at lower temperatures,more » compared to spinel fraction. Crystal precipitation changed the apparent activation energy and required a longer stabilization times for viscosity measurements. The viscosity results were used in predictive equations based on Veytsman and Einstein's models, with critical nucleation temperatures and the solid fraction calculated with FactSage. In the simulated eastern/western coal feedstock blends based on ash compositions, the fractions of the solid precipitates were also calculated using the thermodynamic program FactSage for each blend composition, and the plastic viscosity of each eastern/western coal slag blend was predicted using Veytsman's model and compared to available experimental data.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [2]
  1. National Energy Technology Laboratory (NETL), Pittsburgh, PA, and Morgantown, WV (United States); URS Corp., Albany, OR (United States)
  2. National Energy Technology Laboratory (NETL), Pittsburgh, PA, and Morgantown, WV (United States); Carnegie Mellon Univ., Pittsburgh, PA (United States)
  3. Carnegie Mellon Univ., Pittsburgh, PA (United States)
  4. National Energy Technology Laboratory (NETL), Pittsburgh, PA, and Morgantown, WV (United States)
  5. US Dept. of Energy, Washington, DC (United States). Office of Clean Energy Systems
Publication Date:
OSTI Identifier:
1114763
Report Number(s):
TPR--3861
Journal ID: ISSN 0334-6455
Grant/Contract Number:
FE0004000
Type:
Accepted Manuscript
Journal Name:
High Temperature Materials and Processes
Additional Journal Information:
Journal Volume: 31; Journal Issue: 4-5; Journal ID: ISSN 0334-6455
Publisher:
de Gruyter
Research Org:
National Energy Technology Laboratory - In-house Research, Pittsburgh, PA, and Morgantown, WV (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE)
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; SLAGS; VISCOSITY; CRYSTALLIZATION; COAL coal gasifier; plastic viscosity