Abstract
We conducted molecular dynamics (MD) simulations to investigate the structural evolution of molten slag composed of wheat straw (WS) and Shenhua (SH) coal. The content of wheat straw in the slag was varied from 0 to 100 wt%. The MD results indicated a slight reduction in the sharpness of the radial-distribution-function curve of each ion–oxygen pair and a decrease in bonding strength with increasing WS content. WS introduced many metal ions to the ash system, increasing its overall activity. The number of bridging and non-bridging oxygen atoms changed upon straw addition, which affected the stability of the system. There were relatively few highly coordinated Si ions. The number of low-coordination Si was highest for a WS content of 30%, at which the density reached a minimum value. The degree of ash polymerization was analyzed by counting the number (Q) of tetrahedra with the number (n) of the bridging oxygen atoms. With increasing WS content, Q4 (tetrahedral Si) decreased, whereas Q3, Q2, Q1, and Q0 increased. Q4 reached a minimum value for a WS content of 30%, at which point the degree of ion aggregation was the weakest and the degree of disorder was the strongest.
Highlights
Coal gasification is important for the high-efficiency utilization of coal, production of liquid fuel and hydrogen, reduction of iron, and other processes
The melting temperature of SH coal ash is lower than other coal, which is suitable for a flow bed gasifier with liquid slag discharge
SH coal ash and wheat straw (WS) ash were prepared under the ASTM D3174-12 standard in which the final ashing temperature was set at 575 ◦C to minimize the loss of volatile elements such as Na [19]
Summary
Coal gasification is important for the high-efficiency utilization of coal, production of liquid fuel and hydrogen, reduction of iron, and other processes. Understanding the network structure for the cogasification ash of biomass and coal is important when designing the gasifier and selecting the operating temperature and fuel ratio [1,2]. Because of the high SiO2 content in coal ash, the structure of silicates is of particular importance for understanding the structure and behavior of slags.
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