Development of Advanced Industrial Furnace Using Highly Preheated Combustion Air

Abstract

Results are presented on the thermal and chemical characteristics of flames using high-temperature combustion air and liquified petroleum gas (LPG) as the fuel. The stability limits of these flames are extremely wide as compared to any other method of flame stabilization. This study is part of the Japan national project directed to develop advanced industrial furnace designs that provide approximately 30% energy savings and hence CO 2 reduction, 30% reduction in the furnace size, and 25% reduction of pollutants including NO x as compared to current designs. The objective here is to establish conditions that permit significant reduction in energy consumption, high efficiency, and low pollution from a range of furnaces. Data have been obtained on mean flame temperature and temperature fluctuations, flame emission spectra, emission intensity of C 2 and CH species from within the flames, and overall pollutant emission from the flames. The uniformity of temperature in the furnace was found to be far greater with low oxygen concentration combustion air preheated to 1000°C as compared to that obtained with roomtemperature air or that found in conventional flames. Emission of NO x and CO was much lower with combustion air preheated to high temperatures with low oxygen concentration. The chemiluminescence intensity of CH and C 2 radicals is significantly affected by the preheat temperature of the combustion air and oxygen concentration in the oxidant. The flame signatures revealed important flame characteristics under high-temperature air combustion conditions. The advantages of utilizing highly preheated combustion air (in excess of 1000°C) in various types of furnaces are given. The new and advanced furnace design utilizes high-efficiency regenerators and behaves essentially as a well-stirred reactor with uniform thermal and chemical characteristics. Because each furnace design requires unique features, it is imperative that each furnace must be optimized to satisfy the functional requirements of the furnace. In this paper a relatively simple diagnostic methodology is presented, which assists in a rational furnace design and optimization process.