Analysis of Proton Conducting Solid Oxide Fuel Cell Hybrid Systems with Anode and Cathode Recycling

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Title:	Analysis of Proton Conducting Solid Oxide Fuel Cell Hybrid Systems with Anode and Cathode Recycling
Authors:	柯莫;Sasmoko
Contributors:	機械工程學系
Keywords:	空氣當量比;熱電共生效率;乙醇;燃料當量比;燃料利用率;微渦輪機;質子傳輸型固態氧化物燃料電池;回收;水氣燃料比率;air stoichiometry;CHP;ethanol;fuel stoichiometry;fuel utilization;MGT;p‒SOFC;Recycling;steam to fuel
Date:	2016-06-24
Issue Date:	2016-10-13 14:49:22 (UTC+8)
Publisher:	國立中央大學
Abstract:	p‒SOFC(質子傳輸型固態氧化物燃料電池)是一個適當應用於發電系統之燃料電池，本研究為p‒SOFC搭配MGT(微型渦輪機)以及藉由未反應氫氣和氧氣的CHP(熱電效率)。利用Matlab / Simulink 模擬，控制變因為50顆電池、0.1 m2反應面積。此外，分析了3個系統，包含系統1、系統2和系統3，其中系統2在增加陰極和陽極回收後，擁有最佳的性能表現，操作變因為燃料利用率、水氣燃料比率、空氣當量比、燃料當量比。在系統比較部分，系統2由於將空氣熱交會氣置於重組器前能增加產氫地反應速率。不同系統間的元件操作溫度也不同。由於較多的熱量被利用到系統1的重組器，故系統1比系統2和3擁有較高的氫氣產率，然而，系統1燃料電池輸出功比系統2還要低，是因為重組器出口溫度是三個系統最低，因此，可用能的分析結果顯示系統2的可用能損失最低 (5.193 kW) ，比起系統1(6.170 kW) 和系統3(6.635 kW) ，熱交換器能減少損失大約0.977 kW。系統參數分析結果如下: 首先，增加燃料利用率從60 %到90 %，雖然燃料利用率增加，電堆消耗更多氫氣，能夠提高p‒SOFC輸出功率從3 kW到3.9 kW，但同時也減少進入燃燒室的燃料，MGT輸出功率從1.9 kW下降到1.4 kW，電堆效率、系統效率、CHP效率分別增加從45 %到58 %、66 %到73 %、72 %到79 %。接下來，增加水氣燃料比率從3到3.5，p‒SOFC輸出功率增加從3.7 kW到3.8 kW，造成此結果主因為氫氣生成量從28.7 mmol/s到29.1 mmol/s，然而，增加水氣燃料比率從3.5到5時，燃料此時在重組器內被稀釋，氫氣生成量從29 mmol/s到26.9 mmol/s，減少p‒SOFC輸出功率從3.8 kW到3.4 kW，電堆效率、系統效率和CHP效率分別從57 %到52 %、72 %到68 %、79 %到74 %。第三，空氣當量比從2到4時，會降低電堆輸出功率從3.9 kW到3.1 kW，主要是由於氫氣流量從27.6 mmol/s到27.2 mmol/s，同樣地，p‒SOFC電流輸出從95.92 A到94.54 A，相反地，MGT輸出功率從1.4 kW增加到2.1 kW，質量流率從100 mmol/s提高到150 mmol/s為其增加之原因，然而，壓縮機消耗功由0.5 kW增加到1 kW，電堆效率、系統效率、CHP效率分別為58 %到47 %、73 %到65 %、79 %到71 %。第四，由於氫氣生成量從22 mmol/s到33 mmol/s，燃料當量比從1到1.3， p‒SOFC輸出功率從3 kW到4 kW，當燃料當量比從1到1.2時，電堆效率很明顯地從53 %提升到58 %，當燃料當量比從1.2到1.3時，電堆效率從58 %下降到54 %，其原因是重組器內燃料與水不平衡比例，氫氣生產量只有稍微地增加。簡單來說，最佳化參數包含燃料利用率為83 %、水氣燃料比率為3、空氣當量比無2、燃料當量比為1.2。最後，整合陰極與陽極回收系統為最具前瞻性，系統效率可增加6.81 %，是由於增加氫氣產量、增加各元件操作溫度與減少壓縮機做功。 ;p‒SOFC is an appropriate fuel cell type to be applied in the power generating system. p‒SOFC is combined with MGT and CHP to utilize the hydrogen and oxygen unreacted from the stack. Some parameters are fixed by using Matlab / Simulink such as 50 cells, membrane area of 0.1 m2. Furthermore, three cases, cases 1, 2, and 3, are analyzed, and the best case, case 2, is installed with anode and cathode recycling, to increase system performance. Some parameters are varied to be analyzed such as fuel utilization, steam to fuel, air stoichiometry, and fuel stoichiometry. In case comparison, case 2 shows the better performance than case 1 and case 3, where installation of a fuel heat exchanger before reformer is highly recommended in order to increase the reaction rate in reformer. Operating temperature in each component in every case is difference. Case 1 produces higher hydrogen production than case 2 and case 3 due to heat used to heat the reformer in case 1 is higher than other cases, however, the power in case 1 is lower than case 2 due to heat output of reformer in case 1 is lower than other cases. Furthermore, the result of exergy analysis shows that case 2 has lower exergy destruction (5.193 kW) than case 1 (6.170 kW) and case 3 (6.635 kW), where installation of heat exchanger can decrease exergy destruction around 0.977 kW. For parameters analysis results: First, the result of fuel utilization shows that increasing fuel utilization from 60 % to 90 % can increase p‒SOFC power output from 3 kW to 3.9 kW due to stack consumes more fuel, however, MGT power output decreases from 1.9 kW to 1.4 kW due to decreasing fuel unreacted in the combustor. The efficiency of p‒SOFC, power system, and CHP increases from 45 % to 58 %, 66 % to 73 %, and 72 % to 79 %, respectively. Second, increasing steam to fuel from 3 to 3.5 can increase p‒SOFC power output from 3.7 kW to 3.8 kW due to increasing hydrogen production from 28.7 mmol/s to 29.1 mmol/s. However, increasing steam to fuel ratio from 3.5 to 5 can decrease p‒SOFC power output from 3.8 kW to 3.4 kW due to fuel dilution in the reformer, and decreasing hydrogen production from 29 mmol/s to 26.9 mmol/s. The efficiency of p‒SOFC, power system, and CHP decreases from 57 % to 52 %, from 72 % to 68 %, and 79 % to 74 %, respectively. Third, increasing air stoichiometry from 2 to 4 can decrease p‒SOFC power output from 3.9 kW to 3.1 kW due to decreasing hydrogen production from 27.6 mmol/s to 27.2 mmol/s. Consequently, p‒SOFC electrical current decreases from 95.92 A to 94.54 A. In another hand, MGT power output increases from 1.4 kW to 2.1 kW due to increasing mass flow rate from 100 mmol/s to 150 mmol/s, however, compressor power also increases from 0.5 kW to 1 kW. The efficiency of p‒SOFC, power system, and CHP decreases from 58 % to 47 %, from 73 % to 65 %, and from 79 % to 71 %, respectively. Fourth, increasing fuel stoichiometry from 1 to 1.3 can increase p‒SOFC power out from 3 kW to 4 kW due to increasing hydrogen production from 22 mmol/s to 33 mmol/s, where there is an increase significantly of p‒SOFC power output when fuel stoichiometry is set from 1.0 to 1.2, and p‒SOFC efficiency increases from 53 % to 58 %. However, fuel stoichiometry from 1.2 to 1.3 can decrease p‒SOFC efficiency from 58 % to 54 % due to fuel is not balance with water in the reformer. Consequently, hydrogen production only increases slightly. Briefly, the optimum parameters are fuel utilization of 83 %, steam to fuel ratio of 3, air stoichiometry of 2, and fuel stoichiometry of 1.2. The last, Combination between cathode recycling and anode recycling shows promising performance, where power system efficiency increases up to 6.81 % due to increasing hydrogen production, increasing operating temperature in each component, and decreasing compressor work. Keywords: air stoichiometry, CHP, ethanol, fuel stoichiometry, fuel utilization, MGT, p‒SOFC, Recycling, and steam to fuel
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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