Pilot-scale Testing and Predictive Model Development for Use in Minimizing NO
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Pilot-scale Testing and Predictive Model Development for Use in Minimizing NO X Emissions and Unburned Carbon when Cofiring Biomass with Coal. DOE Cooperative Agreement No. DE-FC26-00NT40895 Project Officer: Sean Plasynski.

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Pilot-scale Testing and Predictive Model Development for Use in Minimizing NOX Emissions and Unburned Carbon when Cofiring Biomass with Coal

DOE Cooperative Agreement No. DE-FC26-00NT40895

Project Officer: Sean Plasynski

Larry Felix* Steve Niksa Kevin Davis Douglas Boylan

P. Vann Bush* Hong-Shig Shim


Emissions Benefits of Biomass Cofiring in Minimizing NO

  • CO2 Reduction from Unburned Fossil Carbon

  • SO2 Reduction from Displaced Sulfur

  • Lower NOX Emissions (from Reducing Fuel Nitrogen, at a minimum)

  • Higher Fuel Volatility from Biomass

  • LOI Reduction (from Displaced Coal, at a minimum)


Cofiring Research in Minimizing NO

  • In 2000, The U.S. DOE National Energy Technology Laboratory, through the Office of Energy Efficiency and Renewable Energy’s Biomass Power Program has Funded 11 New Research Grants to Study Biomass Cofiring

  • This presentation presents selected results from one of these grants: “Development of a Validated Model for Use in Minimizing NOX Emissions and Maximizing Carbon Utilization When Cofiring Biomass with Coal”


Specific Program Objectives in Minimizing NO

  • Develop a consistent, extensive biomass cofiring database

    • relationships between NOx and biomass cofiring parameters

    • effects on flame stability, carbon burnout, slagging and fouling, and particulate and gaseous emissions

  • Develop and validate a biomass cofiring model

    • forecast NOx and LOI for given fuel combination with specified cofiring configuration

    • optimize cofiring configuration to minimize NOx and unburned carbonfor specified fuels


PROJECT TEAM in Minimizing NO

Southern Research Institute

Southern Company

(Combustion Research Facility)

Niksa Energy Associates

(Cofiring Process Model)

Reaction Engineering International

(CFD Simulations)

Mesa Reduction, Inc

(Biomass Preparation)


Project Flow Chart in Minimizing NO

CFD Model of Combustor

Biomass NOx-LOI Model

Combustion+Gas Chemistry Models

Controlled Pilot-Scale Cofiring Tests

Database

NOx-LOI

Other Combustion &

Emission Properties


EXPERIMENTAL PROGRAM in Minimizing NO


Combustion Research Facility in Minimizing NO

  • All testing conducted at the SRI/SCS 6.0 MMBtu/hr Combustion Research Facility (at 3.5 MMBtu/hr)

  • Continuous measurement and logging of ~ 200 pertinent process parameters

  • In-situ testing for mass emissions, particle size, char, pyrometry, ash resistivity, gases (O2 at furnace exit and at CEM location, CO, CO2, SO2, NOX, NH3, H2O, HCl).

  • On-site wet chemical flue gas and ash analyses, CHN (for carbon in ash), fuel heat value measurement

  • Instrumented CE-Raymond Model 352 Deep Bowl mill


Pilot-Scale Test Facility in Minimizing NO

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Typical Coals in Minimizing NO


Biomass Fuel Analyses in Minimizing NO


Test Cases in Data Base in Minimizing NO


SELECTED TEST RESULTS in Minimizing NO

  • NOX Reductions from Cofiring Biomass

  • High, Medium, and Low Volatile / FC Ratios

  • Single (Mainly) and Dual-Register Burner

  • Sawdust and Switchgrass

  • 15% Overfire Air

  • 0% to 20% Biomass


What Do These Data Reveal? in Minimizing NO

  • There is No Guarantee that NOX Emissions will be Reduced when Coal is Cofired with Biomass

  • Complex Relationships Exist Among Furnace Operating Parameters, Burner Design, Cofiring Geometry, Biomass Choice, and Coal

  • NOX Reductions from Adding Biomass can be Much Greater than, Equal to, or Much Less than than the Amount of Fuel Nitrogen Replaced when Biomass is Cofired with Coal


General Conclusion in Minimizing NO

In Order to Understand the Nature of the Interactions that have been Observed, Fundamental Questions of Fuel Chemistry and Combustion Must be Addressed


MODEL DEVELOPMENT in Minimizing NO


Model Requirements in Minimizing NO

  • Model results must agree with results in the experimental database - no adjustable parameters in the submodel for gas phase chemistry.

  • The model must incorporate a formalism that is generally applicable to any biomass cofiring configuration - from pilot-scale to full-scale.


Model Assumptions in Minimizing NO

  • It is not currently possible to incorporate detailed chemical reaction mechanisms into conventional CFD simulations of pulverized coal and biomass flames - The reaction mechanism for chemistry in the gas phase contains 444 elementary reactions among 66 species, including all relevant radicals and N-species (Glarborg et al. 1998).

  • To predict NOX and LOI, incorporate detailed gas-phase chemistry through advanced CFD post-processing methodology developed by NEA.


Model Implementation in Minimizing NO

  • Perform CFD simulation of the SRI/SCS pilot-scale furnace for as many test conditions as feasible using REI and REI’s Configurable Fireside Simulator to predict residence time distributions, temperature fields, and mixing intensities within the furnace.


Furnace Exit in Minimizing NO

Furnace

Zones

Burnout Zone

OFA Zone

Mixing Layer

Core

Core

ERZ

ERZ


Model Implementation in Minimizing NO

  • Define an equivalent network of idealized reactor elements for the pilot-scale furnace from the conventional CFD simulations.

  • The network is “equivalent” to the CFD flowfield in so far as it represents the bulk flow patterns in the flow. To the extent that the residence time distribution, thermal history, and entrainment rates are similar in the CFD flowfield and reactor network, the chemical kinetics evaluated in the network represent the chemistry in the CFD flowfield.


DEVOLATILIZATION ZONE in Minimizing NO

8 CSTRs, 65 ms

NO REDUCTION ZONE

8 CSTRs, 73 ms

Char

Primary Air

Volatiles

Char

DEVOLATILIZATION ZONE, 65 ms

NO REDUCTION ZONE, 128 ms

Primary Air

MIXING LAYER

19 CSTRs, 508 ms

Secondary Air

Tertiary Air (OFA)

OFA ZONE

6 CSTRs, 156 ms

LOI + Fly ash

BURNOUT ZONE

1460 ms

Exhaust Gases

Reactor Network


Model Implementation in Minimizing NO

3. The reactor network is a computational environment that accommodates realistic chemical reaction mechanisms. Mechanisms with a few thousand elementary chemical reactions can now be simulated on ordinary personal computers, provided that the flow structures are restricted to the limiting cases of plug flow or perfectly stirred tanks.


MODEL VALIDATION in Minimizing NO

  • Pick Representative Cases

  • Predict NOX and LOI

  • Compare with Measurement


Predicted vs. Measured NO in Minimizing NOX


Questions in Minimizing NO


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