Biomass and Coal Characteristics: Implications for Cofiring David A. Tillman Foster Wheeler Power Group, Inc. Clinton, NJ

Abstract

Basis of the Analysis Fuel Characterization Research at The Energy Institute of Pennsylvania State University –Proximate and Ultimate Analysis –Drop Tube Reactor Testing (400 – 1700 o C) »Determine maximum volatile release »Determine fuel reactivity »Determine nitrogen and carbon volatile release – 13 C NMR Testing Develop Relationships to Full Scale Cofiring Testing

Focus of the PSU Research Nitrogen Evolution from Solid Fuels Governs NO x Formation from Fuel Nitrogen –NO x Control is Favored by Volatile Nitrogen –NO x Control is Favored by Nitrogen Rapidly Evolving from the Fuel Mass Understanding Nitrogen Evolution Patterns can Assist in Explaining NOx Reduction with Biomass and Low Rank Coals Understanding Nitrogen Evolution Patterns for a Given Suite of Fuels can Influence Fuel Selection

Support for this Research USDOE – NETL and USDOE – EERE in Sponsoring Biomass Cofiring Technology Assessment USDOE – NETL, USDOE – EERE, and EPRI in Sponsoring Cofiring Research and Demonstration Projects with a Variety of Coals in Cyclone and PC Boilers –Albright Station, Willow Island Station –Bailly Station, Michigan City Station –Seward Station, Shawville Station –Allen Fossil Plant, Colbert Fossil Plant

Background: Previous Studies Baxter et. al., Seminal Paper on Nitrogen Evolution from Coals as a Function of Residence Time Research for USDOE and EPRI, Sponsored by USDOE and Performed by The Energy Institute of Pennsylvania State University and by Foster Wheeler Power Group, Inc.

Methodology - 1 Select Representative Biomass Fuels –Sawdust –Urban Wood Waste –Fresh Switchgrass –Weathered Switchgrass Basis of Selection –Commonly used in cofiring applications –Represent woody and herbaceous biomass Select Reference Coals –Black Thunder [PRB] –Pittsburgh #8

Methodology - 2 Sawdust source: West Virginia [Willow Island Cofiring Project] Urban Wood Waste source: produced from a blend of plywood, particleboard, and paneling to be highly similar to the urban wood waste at Bailly Generating Station, with particular attention to nitrogen content Weathered Switchgrass source: Gadsden, Alabama [Southern Co. and Southern Research Institute Cofiring Project] Fresh Switchgrass source: Southern Co. and Auburn University

Methodology - 3 Characterize the Incoming Fuel –Proximate and Ultimate Analysis –Heating Value Air Dry and Grind Fuel Pyrolyze Fuel in Drop Tube Reactor (DTR) –400 o C – 1700 o C –Argon Environment Determine Distribution of Nitrogen in Incoming Fuel (volatile N vs char N) Determine Nitrogen, Carbon, and Total Volatile Evolution as a Function of Temperature

Methodology - 4 Basic Premise: If nitrogen is in volatile form, and if nitrogen volatiles evolve more rapidly than carbon volatiles or total volatile matter, then NO x formation is more easily controlled by combustion mechanisms If nitrogen is in char form, or if nitrogen volatile evolution lags behind carbon volatile evolution or total volatile evolution, then NO x formation control by combustion mechanisms is more difficult and less effective

Analysis of Biomass Fuels

Distribution of Fuel Nitrogen

Maximum Volatile Nitrogen Yield

Sawdust Nitrogen and Carbon Volatile Yields

Sawdust Nitrogen and Carbon Evolution Normalized to Total Volatile Matter Evolution

Nitrogen and Carbon Volatile Evolution from Urban Wood Waste

Nitrogen and Carbon Volatile Evolution from Fresh Switchgrass

Nitrogen and Carbon Volatile Evolution from Weathered Switchgrass

Nitrogen and Carbon Volatile Evolution from Weathered Switchgrass Normalized to Total Volatile Evolution

Nitrogen and Carbon Evolution from Black Thunder PRB Coal

Nitrogen and Carbon Volatile Evolution from Pittsburgh #8 Coal

Nitrogen and Carbon Volatile Evolution from Pittsburgh #8 Coal Normalized to Total Volatile Yield

Nitrogen/Carbon Atomic Ratios in Char Normalized to N/C Ratio in Initial Fuel

NO x Reductions at Albright

NO x Reductions at Albright (2) NO x = – (C m ) (EO 2 ) – (SOFA) Definitions: –C m is cofiring percentage, mass basis [0 – 10] –EO 2 is excess O 2 at furnace exit (wet basis) [1 – 4] –SOFA is separated overfire air damper positions for all 3 levels [0 – 240] r 2 = 0.87, 68 observations Probabilities of random occurrence: equation, 4.2x ; intercept, 2.3x ; C m, 1.2x10 -5 ; EO 2, 5.9x10 -4 ; SOFA, 5.0x10 -22

NO x Reduction at Seward Station

NO x Reduction at all EPRI Demos

Conclusions Fuel reactivity is a key to NOx control using staged combustion Biomass fuels, in general, are highly reactive although weathering reduces nitrogen reactivity in switchgrass The relative reactivity of biomass, and various coals, can be used as a technique to evaluate potential in NO x management The DTR technique for analyzing fuels has significant benefits in evaluating initial combustion processes applied to NO x management