Modeling of Waste-to-energy (WTE) Combustion With Continuous - - PowerPoint PPT Presentation

Modeling of Waste-to-energy (WTE) Combustion With Continuous Variation of the Solid Waste Fuel

Masato Nakamura

Earth Engineering Center, Columbia University, New York, NY

“Computational Modeling of Industrial Combustion Systems”, Fuels and Combustion Technology Session 2003 ASME International Mechanical Engineering Congress and RD&D Expo, Washington D.C. Nov. 15, 2003

11/15/2003 Masato Nakamura

Overview

Background Current problems Objectives Calculation methods Results Conclusions

Mass-burn WTE

11/15/2003 Masato Nakamura

Schematic Diagram of the Reverse Acting Grate (Combustion Chamber)

RB1 FB1

Outlet of Ash FBn: fixed bar (step) RBn: reciprocating bar (step)

26o

Inlet of Solid Waste

11/15/2003 Masato Nakamura

• Complexity of combustion process.
• Non-homogeneous municipal solid waste (MSW).
• Transient phenomena (channeling/break-up).
• Unstable combustion caused by the inlet flow of

highly non-homogeneous MSW.

• Unstable burnout point.
• The lack of flow (& mixing) control.
• Incomplete combustion of solid waste.

Background

11/15/2003 Masato Nakamura

Current Problems

• Channeling of air flow through the grate results in
• A high excess air requirement (energy loss)
• Lowering temperature in the chamber
• The relationship between fuel flow at inlet and

transient phenomena

• Not fully understood
• Not included in existing WTE combustion models

11/15/2003 Masato Nakamura

Objectives

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 Nakamura

P=0 P=0.2 P=0.4 P=0.6 P=0.8 P=1.0

Square Lattice Site Percolation Model

• Occupation of burning particles

for different values of P

• Particles Clusters Paths

MSW at inlet (20% voids) Ash at outlet

Combustion Process

• n the traveling grate

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(a) Channeling (b) Break-up (Subsidence)

Channeling and Break-up of MSW in the Percolation Model on the Grate

Particles -> Clusters -> Paths

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Calculation 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 Nakamura

0.1 0.2 0.3 0.4 5 10 15 20

Sample Number Component probablilty

paper

cardboard

plastic

textiles rubber & leather wood glass metals

• ther

Time Series of Continuous Variation of MSW Components

Composition of 20 Random Samples Obtained by Monte Carlo Simulation

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Result of percolation model for transient phenomena

Calculation Results of the MSW Combustion on the Reverse Acting Grate

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Transient phenomena during the combustion processes

Calculation Results of the MSW Combustion on the Reverse Acting Grate

Voids

• Pv: Void Probability
• Pc: Critical Probability
• Pch: Channeling Probability
• Pa: Ash Probability

11/15/2003 Masato Nakamura

Combustion probability in the each zone

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 2 3 4 5 6 7 8

Zone Number Combustion Probability (Volume %)

Calculation Results of the MSW Combustion on the Reverse Acting Grate

Inlet Outlet

Pch = 0.75 Pa = 0.89 Pv = 0.2 Pc = 0.59 Pv: Void Probability Pc: Critical Probability Pch: Channeling Probability Pa: Ash Probability

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Conclusions

• 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
• f 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 Nakamura

Acknowledgements

• 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) Council