Deep insight into the ash fusibility and viscosity fluctuation behavior during co-gasification of coal and indirect coal liquefaction residue
Abstract
Co-gasification of coal and indirect coal liquefaction residue (ICLR) is an effective approach to large-scale utilization of ICLR. In this work, the effect of ICLR addition on ash fusion characteristics and viscosity-temperature characteristics of YCW coal were studied by means of ash fusion temperature analyzer (AFTA), XRD, high-temperature-rotary-viscometer, high-temperature heating stage coupled with optical microscope (HTSOM) and FactSage thermodynamics software. The results showed that with the increase of ICLR mass fraction, the low-temperature eutectic anorthite melted into a liquid phase, resulting in a linear decrease of AFTs. Moreover, the causes of viscosity fluctuation were revealed according to the in-situ crystallization morphology variation and viscosity-temperature characteristic curves. It was found that the formation of a large number of "barbed-shape" needle-like crystals during the cooling process was the main reason for the significant viscosity fluctuation. With the addition of ICLR, the length-diameter ratio and volume fraction of the "barbed-shape" needle-like crystals decreased significantly, resulting in the decrease of viscosity fluctuation. When the addition amount of ICLR was 3%, the "barbed-shape" needle-like crystals were not precipitated during the entire crystallization process, and the viscosity no longer fluctuated. As the mass fraction of ICLR increased to 5%, no crystals precipitation was observed in the cooling process. At this time, the slag sample showed the glass slag characteristics. Therefore, for entrained-flow gasification, the addition of ICLR could improve the gasification efficiency by reducing the gasifier operating temperature, and avoid slag-tapping problems by alleviating the viscosity fluctuation. More importantly, it could realize the resource treatment of hazardous waste and transform hazardous waste into solid waste.
- Publication:
-
Fuel
- Pub Date:
- December 2021
- DOI:
- 10.1016/j.fuel.2021.121620
- Bibcode:
- 2021Fuel..30521620Z
- Keywords:
-
- Co-gasification;
- Indirect coal liquefaction residue;
- Viscosity fluctuation;
- Ash fusion characteristics;
- Crystallization behavior