A High-Temperature Sr0.8La0.2MnAl11O19-α Catalytic Heat-Recirculating Burner and Its Application

• Main Authors: Yi-Hsin Chao, 趙依心
• Other Authors: Shenq-Yang Shy
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/96207579692831421170

碩士 === 國立中央大學 === 機械工程研究所 === 94 === This study aims to construct a high-temperature catalytic heat-recirculating combustor using a Swiss-roll burner (SRB) and a high temperature Sr0.8La0.2MnAl11O19-α catalyst, which features high-efficiency and near-zero [NOx] emissions. Fuels are premixed methane/air mixtures at different equivalence ratios (φ), which are used in a 1.5-turn SRB for the performance test, including measurements of temperature distributions inside the SRB, heat-recirculation rate (HR), concentrations of emissions (NOx and CO), etc. Then, a new reaction platform is designed to quantitatively investigate various characteristics of such high-temperature Sr0.8La0.2MnAl11O19-α catalyst, from its preparation and production to the effect of φ, from temperature variations before and after the honeycomb catalytic sector to the effect of space velocity (SV), and from the degradation of the surface area of such catalyst after long time operation to measurements of emissions. The goal is to combine the above two technologies to design a high-temperature, high-efficient, very-low-NOx burner. The time evolution of temperature distributions inside the SRB are measured using as many as eleven K- and R-type thermocouples for which these data are recorded by a PCLD-818 data acquisition card an a GeniDAQ software at a sampling rate of 1 Hz. Emissions are measured by the standard flue-gas analyzer. The photographs and surface area of the high-temperature catalyst are obtained from the Scanning Electron Microscopy (SEM) and the Accelerated Surface Area and Porosimetry System (ASAP). Results for φ=0.5 reveal that all measured temperature data at various positions of the SRB increase with increasing Ref (Ref=VfDin/ν) increases from 370 to 980, where Vf, Din, and ν are the supply reactant velocity, the SRB channel width, and the kinematic viscosity of reactants, respectively. The highest temperature at various Ref and all occurs near a previously-designed flame holder in the central combustion chamber, confirming the flame holding feature for stable combustion in the center of the SRB. Furthermore, the HR of the SRB is found to be increased with Ref as well. Concerning the high-temperature catalyst, the initial temperature (To) condition to start up the high-temperature catalyst at φ=1.3 is To=500oC. Temperature measurements show that the temperature after the high-temperature catalyst (Tc-out) increases from 1,050oC to 1,300oC when values of SV increase from 76,000 1/h to 465,000 1/h. However, when values of SV are larger or equal to 310,000 1/h, Tc-out not only ceases its increase but also decreases slightly. Values of [NOx] and [CO] are only 1.9 and 2.1 ppm when SV=76,000 1/h. Even for SV=465,000 1/h, values of [NOx] and [CO] are all below 12 ppm. The longevity test of the high-temperature catalyst at φ=0.5, To=500oC, and SV=76,000 1/h show that the surface area of the catalyst would decrease from its initial value 25 m2/g to 5~8 m2/g when about 52 operation hours are applied. Finally, we use the SRB as a pre-heater to burn first rich CH4/air mixtures (φ=1.3), so that its high temperature off-gas (To>500oC) with remaining CH4/air fuels can be further reacted in the high-temperature honeycomb catalytic sector. This new device is believed to be of useful in gas turbine applications and in dealing with many industrial off-gas fuels. Thus, the goals of saving energy and reducing pollutants can be achieved.