Co‐combustion and ash characteristics of Zhundong coal with rice husk hydrochar prepared by the hydrothermal carbonization technology for co‐combustion

Abstract

The high content of the AAEMs in Zhundong (ZD) coal causes easily slagging on the heating surface of boilers, and the addition of rice husk hydrochar (RHC) is expected to alleviate slagging by introducing SiO2 content. ZD coal is co‐fired with RHC according to different blend ratios, co‐combustion ashes are prepared subsequently at different temperatures. The co‐combustion characteristics of blends are studied firstly by using TGA, considering the combustion process can bring impacts on ash characteristics. Then the effects of the blend ratio and ashing temperature on the ash characteristics are discussed. The ash samples are characterized by XRF, ICP‐AES, XRD and SEM. The results show that an increase in the blend ratio of the RHC reduces the ignition temperature and lengthens the burnout time, which transforms the ash characteristics. The contents of quartz, gehlenite and andalusite greatly increase. The number of fine particles in the ash decreases, while the particle size increases. The ash fusion temperatures (AFTs) are at the lowest value at 8:2 and exceed totally that of ZD coal at 7:3. Considering to increase the AFTs of ZD coal, at least the blend ratio of 7:3 of ZD coal and RHC is recommended for co‐combustion.

Modeling ash deposition and shedding during oxy-combustion of coal/rice husk blends at 70% inlet O2

“…with the results reported inYang et al (2022) andWang et al (2020a) for coal-RH blends at similar ratios. However, a slightly earlier onset of burnout prediction (closer to the burner) is noted in the OXY70 scenarios as a result of higher oxidizer O 2 concentrations.…”

“…Despite these advantages, operating at an optimum blend ratio (Coal: RH) is also important. RH-Coal co-combustion characteristics such as ignition time and temperature, burnout time, ash transformation characteristics and ash fusion temperature at different blending ratios have been investigated by Yang et al (2022) and Wang et al (2020a). Yang et al (2022) recommended a blend ratio (Zhungdong coal: RH hydrochar) of at least 7:3 to avail the benefits of co-combustion.…”

“…RH-Coal co-combustion characteristics such as ignition time and temperature, burnout time, ash transformation characteristics and ash fusion temperature at different blending ratios have been investigated by Yang et al (2022) and Wang et al (2020a). Yang et al (2022) recommended a blend ratio (Zhungdong coal: RH hydrochar) of at least 7:3 to avail the benefits of co-combustion. Similarly, Chao et al (2008) and Kwong et al (2007) identified 10 wt%-30 wt% of RH in the fuel feed as an optimum range for minimizing pollutant emissions per unit energy output.…”

Occurrence Mode of Sodium in Zhundong Coal, China: Relationship to Maceral Groups

“…To solve the slagging problem, it is crucial to explore the occurrence characteristics of different Na species, particularly watersoluble Na. Techniques including hydrothermal treatment [17,18], dynamic leaching [5], and ion-exchange methods [19,20] have been adopted to remove Na from Zhundong coal at the laboratory scale, but actual production is limited by poor efficiency and high costs. Meanwhile, the utilization of Zhundong coal has also been under pressure from emerging coal-staged utilization industries such as liquefaction [21] and gasification [22], which creates an increased demand for the maceral separation and individual processing of coal.…”