成果報告書詳細
管理番号20130000000478
タイトル*平成24年度中間年報 省エネルギー革新技術開発事業 先導研究 高温酸素燃焼技術の研究開発
公開日2013/6/21
報告書年度2012 - 2012
委託先名国立大学法人東北大学流体科学研究所 日本ファーネス株式会社
プロジェクト番号P09015
部署名省エネルギー部
和文要約「和文要約等本編抜粋」
1. 研究開発の内容及び成果等
開発課題
酸素燃焼(oxyfuel combustion)リジェネバーナに関する研究開発は世界的にも未だ実施されていない未着手の研究課題である。世界初の当該技術開発はエネルギー消費の大幅低減とCO2 回収の両面でのメリットがあり、それを実現するには基礎段階の現象理解に基づいた高温酸素燃焼炉の研究開発およびそれによる技術評価を有機的に組み合わせる必要がある。また、実験の安全を考慮した研究計画、つまり燃焼の基礎特性の把握、酸素富化条件(酸化剤がO2/N2/CO2 混合気)、純酸素条件(酸化剤がO2/CO2 混合気)と段階を踏んで研究を進める必要がある。これらにより、高温酸素燃焼技術の省エネルギー特性と排気特性を定量評価することが最終目標である。本年度の中間目標は、高温酸素富化条件を対象に、燃え切り時間や火炎長等の燃焼基礎データの取得し、これらの試験結果をもとに小型燃焼試験炉を製作し、その基礎特性(燃焼安定性、炉内温度分布の均一性、排気特性)を把握することである。
英文要約 High-temperature oxy-fuel combustion technology can further improve energy efficiency by reducing exergy loss and this leads to reduction of CO2 and NOx emissions compared with high-temperature air combustion technology. The objective of this project is to confirm and evaluate the energy and emission performance of high-temperature oxy-fuel combustion technology through obtaining fundamental knowledge on combustion characteristics and developing a lab-scale furnace. The first half of this project focused on the high-temperature oxygen-enriched condition (O2/N2/CO2 mixture for oxidizer) and the latter half will focus on the high-temperature oxy-fuel condition (O2/CO2 mixture for oxidizer) to conduct experiments step by step.
Two experimental methods were employed in the fundamental part of this project: counterflow flame experiment and co-axial jet flame experiment. Extinction limits were identified by the counterflow flame experiment for various temperatures and CO2 concentrations of the oxidizer stream in the high-temperature oxygen-enriched condition. Numerical computation with a detailed chemical kinetics was also conducted and computational results were in good agreement with experimental results. The measured data were utilized for designing the lab-scale furnace.
By co-axial jet flame experiment, the effects of temperature and CO2 concentration of the oxidizer stream on combustion regime, flame length and NOx concentration of the exhaust gas were investigated. With an increase of the CO2 concentration, the stable combustion region became narrow, the flame length became short and the NOx concentration decreased. With a decrease of the oxidizer temperature, the NOx concentration decreased. These measured data were also utilized for designing the lab-scale furnace.
In order to conduct the high-temperature oxy-fuel combustion tests by using the lab-scale furnace, the furnace on which a test burner is installed was designed and developed. The designed test burner is similar to a single-type regenerative burner for high-temperature air combustion. However, the regenerative media is smaller than that for high-temperature air combustion because of the smaller volume of oxidizer for high-temperature oxy-fuel combustion. The firing rate of 43kW is decided by referring the fundamental research as described above. The essential point of the burner design was that it has functions of flue gas recirculating and it is mixed with oxygen before preheating. The test furnace size is 0.5 m of width, 0.5 m of height, and 0.5 m of length, and then the furnace load per unit volume is 172 kW/m3. The furnace has a water cooling system for keeping constant furnace temperature in order to measure accurate data of gas emission and heat transfer. The periodic switching of flue gas and oxidizer flowing into the regenerative media is automatically controlled by PLC installed in the control panel.
By the developed lab-scale furnace, combustion characteristics in the high-temperature oxygen-enriched condition were investigated. The developed lab-scale furnace attained stable combustion. For reference, those in the high-temperature air condition were also investigated and compared with those in the high-temperature oxygen-enriched condition. Flow rate of exhaust gas in the high-temperature oxygen-enriched condition was 30 % lower than that in the high-temperature air condition. This means the high-temperature oxygen-enriched combustion reduced enthalpy loss in the exhaust gas. CO and NOx emissions in the high-temperature oxygen-enriched condition were the same order as those in the high-temperature air condition. The temperature profile in the furnace was measured and the maximum temperature difference was 58 K in the high-temperature oxygen-enriched condition. The uniform temperature profile was attained in the high temperature oxygen-enriched condition by the present lab-scale furnace.
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