生質燃料於氣化爐混燒及熱電系統之研析

近年來，由於核能議題甚囂塵上，再生能源再度成為重要之議題，然而再生能源之發展雖已日益成熟，但如何提高其轉換效率則為重要之課題。其中以氣化技術作為再生能源科技的一部分，透過在高溫及缺氧條件下將生質燃料做分解以產生較高熱值之合成氣，可用於發電之用途，並由於氣化之溫度相當高，若能將過程中產生的廢熱加以回收，便可提升整體系統之效率。本研究目的在於探討銻化鉍(Bi2Te3)低溫熱電材料於下抽式氣化爐做廢熱回收的情形，首先量測熱電模組之特性參數與性質，其次研究稻殼和柳杉在不同比例的混合情形下於下抽式氣化爐氣化產氣的情形，最後將熱電模組貼附於氣化爐的觸媒管壁上做廢熱回收的探討。實驗結果發現，在氣化方面H2的最大含量分別在100%柳杉和100%稻殼為17.82 vol.%、15.89 vol.%；而在純柳杉之氣化條件下，在當量比0.4的時候可得最佳冷煤氣效率63.59%。然而，最佳之產氣熱值則是在稻殼與柳杉各半混燒時可得到最佳值5.75 MJ/m3。在廢熱回收方面熱電模組產生之最大功率及能量密度分別為5.8W及180.6W/m2，而在整體熱電氣化爐系統之可用功效率，最佳效率在100%柳杉和75%柳杉分別為55.46%和54.49%，在當混燒稻殼含量增加時，其可用功效率則會降至44.2% ~ 46.7%。

關鍵字

氣化反應；熱電模組；生質燃料；廢熱回收；效率

並列摘要

The aim of this study is to investigate the use of waste heat that is recovered from a multifuel biomass (Japanese cedar and rice husk) gasifier. In the gasification process, the low heating value of the biomass can be transferred to a high heating value for combustible gaseous fuel, which is a form that is widely used in industry and power plants. Conventionally, some cleaning processes must be conducted under higher operating temperatures than the low temperatures typically used to burn biomass. Thus, a catalytic reactor was designed before installing the scrubber in the downdraft gasifier system to effectively utilize the waste heat. The experimental results show that the temperature of the gasifier outlet is approximately 250-400℃; dolomite is used for tar removal in the catalytic reactor. To further improve the use of waste heat, a thermoelectric generator is added to recover waste heat. The thermoelectric generator system is manufactured using a Bi2Te3-based material and is composed of eight thermoelectric modules on the surface of the catalytic reactor. The measured surface temperature of the catalytic reactor is 100-250℃, which is the correct temperature for using Bi2Te3 as a thermoelectric generator. The results of this study show that the maximum hydrogen concentration is approximately 17.82vol% from pure Japanese cedar gasification and approximately 15.89vol% from pure rice husk gasification. The optimal operation of the gasification performance was found when the fuel is pure Japanese cedar at Φ = 0.4, and the obtained cold gas efficiency (CGE) at these conditions is approximately 63.59%. However, the optimal available biogas condition was found when 50% Japanese cedar and rice husk are mixed at Φ = 0.2, with a biogas high heating value (HHV) of approximately 5.75 MJ/m3. The performance of the thermoelectric generation system (TEG) that is used for waste heat recovery shows that the maximum power output of the thermoelectric generator system is 5.8 W and that the thermoelectric generator power density is approximately 180.6 W/m2. In this study, the total efficiency of a multifuel gasifier with a waste heat recovery system from thermoelectric generation modules was also investigated. The maximum exergetic efficiencies for 100% and 75% Japanese cedar are 55.46% and 54.49%, respectively. As the rice husk ratio increased, the maximum exergetic efficiency decreased to 44.2%~46.7%.

並列關鍵字

Gasification ； Thermoelectric, Biomass ； Heat recovery ； Efficiency

參考文獻

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生質燃料於氣化爐混燒及熱電系統之研析

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