成果報告書詳細
管理番号20130000000971
タイトル*平成24年度中間年報 ゼロエミッション石炭火力技術開発プロジェクト 革新的CO2回収型石炭ガス化技術開発 物理吸収法におけるサワーシフト反応最適化研究
公開日2013/10/1
報告書年度2012 - 2012
委託先名株式会社日立製作所
プロジェクト番号P10016
部署名環境部
和文要約1. 共同研究の内容及び成果等
(1) 研究内容
石炭火力発電からのCO2削減を目的として、平成22 年度から「革新的CO2 回収型石炭ガス化技術開発」において、高効率かつ高炭素回収率を実現するためのCO2 分離回収技術の開発を実施している。CO2分離回収技術としては、「物理吸収法」を取り上げ、酸素吹噴流床ガス化設備(EAGLE)を用いてガス化設備および発電システムへの適用性の確認や技術確立を行うこととしている。物理吸収設備はサワーシフト反応設備とCO2分離回収設備から構成されている。サワーシフト反応設備では、H2S を含む石炭ガス化ガス(生成ガス)中に水蒸気を添加して、サワーシフト触媒上で(1)式に示したCO シフト反応によりH2 とCO2 を生成させる。一般に、CO2への転換率を上げるためには化学平衡上、水蒸気を過剰に供給する必要があり、その結果として発電効率の大幅な低下を招く。一方、水蒸気供給量を削減すると式(2)、(3)に示すような、CO シフト反応以外の副反応が発生し、炭素析出等により触媒の健全性が低下する可能性がある。
CO + H2O → H2 + CO2(1)
nCO + (2n+1)H2 → CnH2n+2 + nH2O(2)
2CO → C + CO2(3)
(2)式はFischer-Tropsh反応(以下,FT反応)と呼ばれるもので、COとH2から炭化水素を合成する反応である。COがCO2ではなくCH4や炭化水素に変換されると、CO2回収型IGCCにおいては炭素回収率の低下という影響も現れる。また、生成ガスのように高濃度のCOを含む場合、(3)式に示すCOの不均化反応(Boudouard反応)により炭素が生成することも知られている。これらの反応により触媒上へ炭素が析出すると触媒は劣化する。
本研究では、サワーシフト触媒のCO シフト性能および触媒の健全性を踏まえ、蒸気添加量の下限値を把握するために、反応温度や蒸気添加量等の各種運転パラメータと、シフト反応率、副生成物および触媒への炭素析出等の関係を定量的に評価し、CO シフト性能、触媒の健全性、炭素回収率等の観点からサワーシフト反応の最適運用条件を決定することを目的とした。
英文要約“Development of Innovative Coal Gasification Technology with CO2 Capture” is aiming at reduction CO2 emission of coal power generation. We are developing especially a high efficiency CO2 capture system which is appropriate to next generation IGCC from 2010. “Physical absorption system” is selected as a CO2 capture technology to coal gasification and power generation system. Feasibility demonstration and technology development is conducted by the oxygen blown entrained coal gasifier (EAGLE).CO in syngas from coal gasification has to be converted into CO2 by water gas shift reaction process. This process uses steam and this steam usage is one of the reason for decreasing the efficiency of power generation with CO2 capture.
Thus steam usage should be minimized however reduction of steam usage causes sub reaction, typically Boudouard reaction, which produces carbon. The carbon deposit on the catalyst might deteriorate performance of the catalyst.
The aim of this study is to obtain a minimize steam quantity without performance deterioration of the sour shift catalyst. Experiments were planed to acquire a relationship between operation conditions such as steam quantity, reaction temperature and a performance of the catalyst such as CO conversion ratio and carbon deposition.

In 2012, the commercialized catalyst for sour water gas shift reaction were tested to acquire the relation between selectivity of the reaction and H2/CO ratio by the lab scale equipment under pressurized conditions. The result shows that the amount of hydoro carbon and alcohol production becomes higher as the H2/CO ratio arises. However, the ammout of carbon depositon has no relation with the H2/CO ratio. In addition, the carbon deposition doesn't occur by the gas without CO in the additional experiments.
The result that the reaction of carbon deposition needs CO as a source of C and it doesn't need H2 suggests that the carbon deposition is caused by the Boudouard reaction. According to the equilibrium theory, the Boudouard reaction proceeds faster as the temperature become lower. This fact was also confirmed by the results of the last year. We considered that under low temperature condition, the activity of the commercialized catalyst is low, and this leads to the high velocity of Boudouard reaction. So we estimated whether the amount of carbon deposition will be decreased by the catalyst which has high activity under low temperature condition.
The amount of carbon deposition of the catalyst which has high activity under 200 - 250C is 1/6 of the commercialized catalyst. This result suggests that the catalyst with high activity under low temperature can reduce the steam usage.
So we conducted 120 hours of bench scale experiment using the syngas of the coal gasification. We confirmed that the amount of the carbon deposition of the catalyst with high activity under low temperature is 1/2 - 1/3 of the commercialized catalyst.
In 2013, the lab scale experiments to acquire the relation between activity of the reaction and the carbon deposition onto the catalyst and the bench scale experiments to estimate the the reliability of the catalyst by the long hour operation are planed. By the results of these experiments, the plant operation conditions to embody both high reliablity and high efficiency will be decided.
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