碩士生: 蕭楷潾
畢業年分: 2018年8月
論文名稱: 最佳焙燒條件生質炭與煤炭之混燒特性 (中文) / Co-Firing Characteristics of Coal Blended with Biochar with Optimal Torrefaction Condition
英文摘要:
In this study, the main purpose is to investigate the combustion behavior of biomass and coal cofiring by optimizing biomass torrefaction condition. It provides an optimal approach and guideline for selecting the optimal torrefaction condition for biomass cofiring. The Taguchi method was used for the parameter optimization of biomass torrefaction in terms of torrefied temperature, N2 flow rate, and residence time. Regarding the S/N ratio evaluation, three indicators based on distinct combustion-relevant features were proposed to be the optimization goal of the Taguchi method. The biochar, made by three optimal torrefaction conditions, partially mixed with pulverized coal at different blending ratios (25%, 50%, and 75%) for carrying out biomass cofiring experiment. In addition, the single pellet combustion and the pulverized coal/biochar combustion were performed to observe the combustion behavior of various fuels. According to those results, the biochar with low torrefied degree has higher overall combustion efficiency but worst combustion stabilization in the pulverized coal boiler. As the torrefaction degree of biomass increased, the fuel characteristics of biochar are similar to coal, and the combustion stabilization is further improved. In the period of single pellet burning, the addition of the biochar in coal can enhance the ignition ability effectively. The flame temperature distribution, elapsed time for various combustion stages, pollutant emission, overall combustion efficiency and flame height were measured and discussed. In addition, a spray combustion system was established to examine the combustion characteristics of torrefied biochar compared with coal in terms of flame temperature and gas emission. The results of the pulverized coal combustion presented that the biochar with S index case and PB index case have similar combustion behaviors. Once the BBR is above 50%, the volatile burning time increases. In addition, all cases of BBR above 50% are better in the overall combustion efficiency, but worst in combustion stabilization for the pulverized coal boiler.
