Modeling of Waste-to-energy (WTE) Combustion With Continuous Variation of the Solid Waste Fuel Masato NakamuraEarth Engineering Center, Columbia University, New York, NY “Computational Modeling of Industrial Combustion Systems”, Fuels and Combustion Technology Session2003 ASME International Mechanical Engineering Congress and RD&D Expo, Washington D.C. Nov. 15, 200311/15/2003 Masato NakamuraOverview Background Current problems Objectives Calculation methods Results ConclusionsMass-burn WTE11/15/2003 Masato NakamuraSchematic Diagram of the Reverse Acting Grate (Combustion Chamber)RB1FB1Outlet of AshFBn: fixed bar (step)RBn: reciprocating bar (step)26oInlet of Solid Waste11/15/2003 Masato Nakamura Complexity of combustion process. Æ Non-homogeneous municipal solid waste (MSW). Æ Transient phenomena (channeling/break-up). Unstable combustion caused by the inlet flow of highly non-homogeneous MSW. Æ Unstable burnout point. The lack of flow (& mixing) control. Æ Incomplete combustion of solid waste.Background11/15/2003 Masato NakamuraCurrent Problems Channeling of air flow through the grate results in Æ A high excess air requirement (energy loss) Æ Lowering temperature in the chamber The relationship between fuel flow at inlet and transient phenomena Æ Not fully understood Æ Not included in existing WTE combustion models11/15/2003 Masato NakamuraObjectives Developing a mathematical model to characterize and quantify solid flow and mixing processes of the highly non-homogeneous MSW. Simulating the behavior of solid waste particles that affects formation of channels and break-up.Understanding the effects of solid flow on transient phenomena and mixing mechanism during combustion processes on mass burn grates by:11/15/2003 Masato NakamuraP=0P=0.2 P=0.4 P=0.6P=0.8P=1.0Square Lattice Site Percolation Model  Occupation of burning particles for different values of P Particles Æ Clusters Æ PathsMSW at inlet (20% voids)Ash at outlet Combustion Processon the traveling grate11/15/2003 Masato Nakamura(a) Channeling (b) Break-up (Subsidence) Channeling and Break-up of MSW in the Percolation Model on the GrateParticles -> Clusters -> Paths11/15/2003 Masato NakamuraCalculation Methods Monte Carlo simulation for continuous variation of MSW with percolation theory for transient phenomena (break-up and channeling of solid materials). Component of MSW in NYC. Paper 26.6 %, Cardboard 4.7%, Textiles 4.7%, Rubber&Leather 0.2%, Wood 2.2 %, Glass 5%, Metals 4.8% Other 4.6% and Plastic 8.9% ..etc. Matlab programming. FLIC (Fluid Dynamic Incinerator Code)  Linux computer (CPU: 1.8MHz, memory: 256MB) with VMware for Windows 98 environment.11/15/2003 Masato Nakamura00.10.20.30.40 5 10 15 20Sample NumberComponent probablilty papercardboardplastictextilesrubber & leatherwoodglassmetalsotherTime Series of Continuous Variation of MSW ComponentsComposition of 20 Random SamplesObtained by Monte Carlo Simulation11/15/2003 Masato NakamuraResult of percolation model for transient phenomenaCalculation Results of the MSW Combustion on the Reverse Acting Grate11/15/2003 Masato NakamuraTransient phenomena during the combustion processesCalculation Results of the MSW Combustion on the Reverse Acting GrateVoids•Pv: Void Probability•Pc: Critical Probability•Pch: Channeling Probability•Pa: Ash Probability011/15/2003 Masato NakamuraCombustion probability in the each zoneZone 1Zone 2Zone 3Zone 4Zone 5Zone 6Zone 7Zone 800.10.20.30.40.50.60.70.80.9112345678Zone NumberCombustion Probability (Volume %)Calculation Results of the MSW Combustion on the Reverse Acting GrateInletOutletPch = 0.75Pa = 0.89Pv = 0.2Pc = 0.59Pv: Void ProbabilityPc: Critical ProbabilityPch: Channeling ProbabilityPa: Ash Probability11/15/2003 Masato NakamuraConclusions The results obtained are promising and it is hoped to gain a better understanding of the governing combustion and flow/mixing mechanism using the Monte Carlo method.  The percolation model has identified the importance of transient phenomena such as channeling and break-up of solid waste on the combustion process on the grate. The governing parameters such as void probability (Pv), channeling probability (Pch), critical probability (pc),and ash probability (pa) were established by this model.11/15/2003 Masato NakamuraAcknowledgements Prof. N. J. Themelis, Dr. H. Zhang and Dr. K. Millrath at Earth Engineering Center, Columbia University  The Earth Institute, Columbia University (funded as 2003 Spring Research Assistantship) Waste-to-energy Research and Technology (WTERT)