GREENHOUSE GAS CATALYTIC REFORMING FOR LANDFILL GAS TO ENERGY TECHNOLOGIES
Municipal Solid Waste decomposition in landfills produces a gas mixture (LFG) of approximately 50％ carbon dioxide and 50％ methane that has an average energy value of 500 btu ft-3. Methane emissions from waste management constituted 27％ of the total anthropogenic methane emissions in 2007 according to the Energy Information Administration’s Emissions of Greenhouse Gases Report. Currently LFG is vented, collected and flared or collected and converted to energy. Since land filling will continue to be used in the foreseeable future, it makes sense to design landfills that capture the maximum possible amount of methane for use in generating power. However, because of the low heating value of LFG, most engines need to be modified considerably and require a consistent composition of the fuel. LFG variation leads to higher pollutant emissions, such as NOX, CO and unburned hydrocarbons (UHC) and emissions waiver are often required before LFG thermal energy projects are permitted. One solution is to catalytically reform the LFG to syngas to produce more robust combustion or a more consistent feedstock for liquid fuel production. This research investigates the viability of a Rh/γ-Al2O3 catalyst to reform LFG, and explores auto-thermal reforming (ATR) as a way to eliminate the need for external heat transfer by generating it internally in a monolithic reactor. ATR is the process of combusting some fuel with air or O2 to provide heat for concurrent endothermic reforming reactions. The results to be presented demonstrate that ATR does indeed provide heat from the combustion of CH4, and also allows for tuning of the H2/CO ratio. Immediately following the combustion, higher temperatures and the presence of water generated from the reaction allow for steam reforming, producing H2/CO ratios of approximately 3. As the flow continues through the reactor CO2 and CH4 are consumed at approximately 1:1 ratios, and the H2/CO ratio decreases to 1.2, more characteristic of dry reforming. Finally, toward the exit of the reactor the reverse water gas shift reaction engages and consumes H2 and CO2, decreasing the H2/CO ratio further to 1.1. The output of the catalytic reactor was simulated to investigate the suitability of landfill gas (LFG) as an alternative fuel for a spark ignition (SI) internal combustion (IC) engine, and experimentally determine the effects of carbon dioxide on the engine performance and exhaust emissions: carbon monoxide (CO), unburned hydrocarbon (UHC), and oxides of nitrogen (NOX). For this purpose, a 160cc 5 hp four-stroke Honda GC160E-QHA type engine was modified for using gas fuel. The engine was connected with a small generator which functioned as different electrical loads: 0 watt to 2400 watts. Simulated landfill gas mixtures that ranged in CH4/CO2 ratios (about 50％ CH4/50％ CO2) were compared with pure CH4. Equivalence ratio was increased according to electrical loads: about 0.6 to 0.9. Exhaust emissions -CO, UHC and NOX -were analyzed by ENERAC 700. During the use of pure CH4, the CO and UHC decreased from 527.3ppm to 241.8ppm and from 74.8ppm to 35.6ppm respectively while the NOX increased from 24.8ppm to 126.7ppm. In case of a simulated landfill gas consisting of 50％ CH4 and 50％ CO2, whereas the CO and UHC were changed from 943.2ppm to 766.9ppm and from 153.1ppm to 111.3ppm respectively, the NOX became higher from 12.4ppm to 99.8ppm according to electrical loads. This research presents a viable catalyst and process for utilizing LFG cleanly and more efficiently using a precious metal monolith supported catalyst, for a variety of different applications such as synthesis gas for fuel cells, direct heating, or Fischer Tropsch gas to liquids technology without coke formation. The ATR process requires O2 or air, and results in lower energy input by the user, a cleaner burning fuel, and full conversion of CH4 and CO2 known green house gases.
Land fill gas to energy waste-to-energy autothermal reforming catalytic reforming
Marco J. Castaldi McKenzie Kohn Jechan Lee
Earth & Environmental Engineering Department (HKSM) Columbia University, 500 West 120th street New Y Earth & Environmental Engineering Department (HKSM) Columbia University, 500 West 120th streetNew Yo
国际会议
北京
英文
69-80
2010-05-17（万方平台首次上网日期，不代表论文的发表时间）