TED-AJ03-KN4 RECENT ADVANCES IN COMBUSTION TECHNOLOGY FOR HEATING PROCESSES
スポンサーリンク
概要
- 論文の詳細を見る
High thermal efficiency of heating processes and low pollutant emissions into environment have been final goals of combustion engineers in the last quarter century, and the reduction of nitric oxide emission, particularly, has been one of the toughest struggles. However, an innovative technology for heating furnaces has been developed as the result of collaboration among industries and academia organized under the national project of Japan. The technology is called here "highly preheated air combustion", though the same concept is sometimes called Flameless combustion or invisible flame in other situations. It is a sort of regenerative combustion run with highly preheated air being paid much attention recently for its accomplishment in not only energy saving but also low nitric oxides emission. In the project characteristics of combustion with highly preheated air were studied fundamentally to understand the change of combustion regime and the reason for the compatibility between high performance and low nitric oxides emission. It was found that combustion was sustained even in an extremely low concentration of oxygen if the combustion air was preheated higher than the auto-ignition temperature of the fuel. As an application of the principle, we can reduce nitric oxides emission by dilution of combustion air with plenty of recirculated burned gas in the furnace, that is practically realized by the high momentum ejection of preheated combustion air into the furnace. Dilution with burned gas makes the oxygen content of the oxidizer low before combustion, which decreases temperature fluctuations in flames as well as the mean temperature, hence low nitric oxides emission. The highly preheated air is generated by use of ceramic honeycomb regenerators installed on both sides of the furnace. A large amount of waste heat can be recovered by these alternating flow type regenerators, and the temperature level of preheated air usually reaches within 100K of the furnace operating temperature by well-designed regenerators, which results in higher thermal efficiency of furnaces, hence the reduction of carbon dioxide emission. Adding to this fact, it is noted that combustion in low oxygen circumstances, produced by dilution of preheated air with plenty of burned gas in the furnace, generates lower flame temperatures even with the use of highly preheated air, which contributes to reduce nitric oxide emission. As a result, energy saving and reduction of nitric oxide emission are compatible in this new technology using highly preheated air. This is the most important and attractive character of highly preheated air combustion. Further, a high quality heating of materials, higher heat transfer rate, and better controllability of operation are expected. Optimum design procedure should be taken into account in the application of the technology to new fields. Finally, the applicability of highly preheated air combustion to other fields than industrial furnaces has been discussed.[figure]
- 一般社団法人日本機械学会の論文