新型被動式進料甲醇蒸氣重組器之設計與研究

A novel passively-fed methanol steam reformer

羅凱帆(Kai-Fan Lo)

指導教授 ： 王訓忠

國立清華大學/工學院/動力機械工程學系/博士(2012年)

https://doi.org/10.6843/NTHU.2012.00145

摘要

在本實驗中對甲醇水蒸氣重組器(MSR)提出一個簡單創新的燃料供給方法，利用單一熱源以被動的方式將固定比例之水和甲醇注入重組器中進行反應，控制熱源至蒸發塊之間熱通量即可控制燃料的蒸發量，以達到所需之固定燃料比例，其中調整熱源至蒸發塊之熱阻是主要控制熱通量的方式，在傳統進料方式需要兩個液體幫浦來達到此一目的，利用此方法可減少幫浦數量，因此系統可以更簡化，並減少使用幫浦能量的消耗，本實驗即對此方法的可行性進行驗證。
在第一階段以電加熱來驗證此方法的可行性，第二階段以一U型腔體之觸媒燃燒，以甲醇燃燒加熱取代電加熱，在不同反應溫度下水和甲醇進料比率為 0.8 ~ 1.47，並驗證了燃燒器在重組器中溫度高度均勻分佈，第三階段為燃燒器針對氣態氫氣和液態甲醇兩種燃料進行反應，主要目標是重組器啟動時以甲醇為升溫燃料，當反應開始進行後以燃料電池尾氣殘餘氫氣作為燃燒用之燃料來源，本實驗中以稀釋的燃燒觸媒來達到目標，無論甲醇或是模擬燃料電池尾氣之氫氣和二氧化碳的混合氣燃燒後都有高度的溫度均勻性。
在兩段式的升溫過程中，重組器須先燃燒甲醇，經過25分鐘達到270度C，之後轉為氫氣和二氧化碳混合氣，再經過20分鐘使重組器達到278度C穩定，此時重組甲醇反應率可達到95%，一氧化碳濃度為1.04%，氫氣濃度75.1%，二氧化碳濃度23.6%，最後以CO移除器將CO濃度降低，使燃料可由抗CO燃料電池堆使用。

關鍵字

甲醇蒸氣重組器 ； 被動式 ； 觸媒燃燒 ； 氫氣 ； 兩階段

並列摘要

This work presents a simple novel feeding method for a methanol steam reformer (MSR). Using a single heat source, a fixed ratio of water and methanol vapor can be fed into the reformer in a passive way. By adjusting the thermal resistances of the two separate heat paths, different amounts of heat, related to the stoichiometric ratio and heats of evaporation, are conducted to two separate evaporators to vaporize the liquid fuels. Compared with the conventional practice that the feeding ratios are actively controlled with two pumps, no pump is needed in this novel feeding system. Thus, the controlling system can be simplified and the auxiliary power consumption can be minimized. Experiments are conducted to verify the feasibility of this novel fuel-feeding method. In the first stage, an electric heater is used as the heat source. In the second stage, a methanol-burning catalytic combustor in a u-turn-channel is integrally machined under a two-turn serpentine channel reformer to replace the electric heater. Water/methanol feed ratios of 0.8~1.47 are managed under different reaction temperatures. Highly uniform temperature distributions throughout the reformer are demonstrated. The third stage is to make the catalytic combustor workable with both hydrogen and methanol fuels. The aim is to reutilize the exhaust hydrogen from a fuel cell under stable operation but burn methanol during the start-up. To resolve the highly different fuel reactivities, a suitably diluted catalyst formula demonstrates uniform temperature distributions burning with either liquid methanol or an H2/CO2 mixture simulating the exhaust gas from a fuel cell. In a two-stage process, it first takes 25 min to reach 270 ℃ by burning methanol. After the fuel is switched to the H2/CO2 mixture, another 20 min is needed to attain an optimal steady state which yields a high methanol conversion of 95% and acceptably low CO fraction of 1.04% at a reaction temperature of 278 ℃. The H2 and CO2 concentrations are 75.1% and 23.6%. Finally, the CO product in the reformate is successfully removed using the preferential oxidation (PROX) method. Thus, the reformate of the present novel MSR is readily applicable to anti-CO fuel cells.

並列關鍵字

methanol reformer ； passtively ； catalyst combustor ； hydrogen ； two-stage

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