成果報告書詳細
管理番号20110000000888
タイトル*平成22年度中間年報 固体酸化物形燃料電池システム要素技術開発 基礎的・共通的課題のための研究開発 石炭ガス化ガス中の微量成分に関する調査研究
公開日2011/9/28
報告書年度2010 - 2010
委託先名国立大学法人名古屋大学
プロジェクト番号P08004
部署名新エネルギー部
和文要約和文要約等以下本編抜粋:1.1 はじめに
石炭は,他の化石資源(石油,天然ガスなど)に比べ埋蔵量が多く,また世界中に幅広く存在している.しかも他の資源に比べ安価であることから,今後も重要なエネルギーの一つであると言える.しかし石炭は単位発熱量あたりの二酸化炭素,窒素酸化物(NOX)および硫黄酸化物(SOX)の排出が大きいことが問題点として挙げられる.特に石炭に含まれる微量金属成分は,ガス化過程において揮発しガス中で塩化物や硫化物の形態をとる可能性がある.これらの化合物は高い腐食性を有する物があり,次世代型石炭利用高効率発電の筆頭であるIGFC において,燃料電池の電極材料の劣化要因となることが懸念されている.米国などで模擬ガス燃料に幾つかの不純成分をドープするアプローチにより,いくつかの単独成分が有する被毒機構が紐解かれてきている.しかし,石炭ガス化ガスに含まれる不純物は多種多様な上,プロセス(ガス化、精製)の仕様や石炭種に大きく左右される.個々の成分の被毒(化学的、物理的、電気化学的)機構と同時に,極めて複雑な複合的被毒・劣化現象の観察と機構解明も重要な課題であり,ガス化およびガス精製のプロセス構成と燃料ガス化ガス中の微量成分の濃度や形態の関連付けが必要である.そこで本研究では石炭ガス化ガス中の微量成分によるSOFC の劣化特性を解明するための基礎データ収集を目的とし以下の点について実験および解析を行っている.
・ボタン型SOFC における発電実験(微量成分添加を含む)
・熱力学平衡論による微量成分の化合物形態計算
・素反応速度解析による反応挙動予測
英文要約Title: Effects of trace elements in syngas from coal gasification on SOFC degradation (FY2008-FY2011)FY 2010 Annual Report
Ichiro NARUSE, Ryo YOSHIIE (Nagoya University)
Trace elements in syngas from coal gasification process, such as alkali, sulfide and heavy metals are known
to have poisoning effects to electrode materials in SOFC. There are several reports from USA, those have
shown a gradual degradation of SOFC performances due to heavy metal doped fuel gas. However, compositions of
actual syngas from coal gasification process are much complicated, and poisoning effects are simultaneously
caused by various impurities included in coal. Then, objective of this study is to clarify the quantitative
relationship between emissions of trace elements and the degradation of SOFC performance, and their mechanisms.
Degradation behaviors of the power generation performance were experimentally examined in poisoning
tests of SOFC button cell (Ni-YSZ/YSZ/Pt button type cell, anode diameter 10mm) with simulated coal
gasification gas (H2 22% + CO2 20% + CO 15% + CH4 3% + N2 40%) doped with vapor Se and As hydrides.
Temperature of the reaction part was kept constant at 900degC. Fuel gas feeding rate was set to
be 100cc/min, while air feeding rate was 150cc/min. Humidity in fuel gas was controlled as saturation pressure at
65degC. And Se hydride resulted in reversible degradation for the SOFC performance, while As hydride resulted
in irreversible degradation.
As a result of SEM/EDX analyses of a SOFC button cell after its Se and As poisoning test, solid As compounds
was observed on the surface of anode, while Se compounds was not at all.
To understand poisoning effects in SOFC performance, reactions between Se and As compounds and Ni dispersed in
anode electrode materials covered with syngas atmosphere have been investigated by thermal equilibrium
calculations, Factsage Ver 6.1. As a result, As was found to be easy to react with Ni, causing the degradation
of SOFC performance. In contrast, Se was found to be free from chemical reactions with Ni.
This fact implies that reversible degradation caused by Se could be due to physical absorption of Se hydride
on the surface of anode.
From additional thermal equilibrium calculations, P was also confirmed to react with Ni on the surface of anode,
resulting in irreversible degradation as well as As. Na was found to condense on the surface of anode as sodium
silicates if a small amount of SiO2 vapor existed in syngas.
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