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Formation and reduction of NOx in pressurised fluidised bed combustion of coals and chars

Objective

PFBC has the potential of reducing NOx emissions. It is the aim of this joint project to elucidate the most relevant factors of PFBC NOx formation and reduction so that a mathematical model can be developed for the rational description and effective exploitation of low NOx combustion.

Six main areas have been identified for investigation:

1) De-volatilisation tests in a pressurised drop tube furnace: De-volatilisation tests of coal of different particle size at various pressures and evaluation of the fuel-N release ratio. Evaluation of kinetic data of char combustion at various pressures and oxygen partial pressures. Comparison of these kinetic data with results from PFBC.

2) Effects of coal rank on the nitrogen release mechanism: De-volatilisation tests of several coals of different rank and evaluation of the fuel-N release ratio. Study of the effect of particle heating rate and size on the fuel-N release ratio.

3) Char nitrogen conversion to NOx in PFBC: Preparation of chars from selected coals and procurement of residual chars from gasification plants (combined cycle schemes) for PFB combustion tests. Combustion tests on coals and chars in a small scale PFBC. Evaluation of optimum conditions for reducing NOx emissions. Evaluation of freeboard effects.

4) Reduction of NOx by char: Preparation of char samples for NOx reduction studies. Measurement of NOx reduction kinetics and evaluation of effects of excess air level, temperature, ammonia injection, and of catalytic activity of cyclone fines.

5) Mathematical model of NOx emissions from PFBC: Selection of most important parameters and most appropriate relationships between selected parameters and NOx emission. Validation of model predictions with combustion results from PFBCs.

6) Tests on staged combustion and additive injection in a PFBC test rig: Experiments on staged PFB combustion and on additive injection planned in consideration of the results obtained in tasks 1-4.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Deutsche Montan Technologie - Gesellschaft für Forschung und Prüfung mbH (DMT)
Address
Franz-fischer-weg 61
45307 Essen
Germany

Participants (3)

British Coal plc
United Kingdom
Address
Hobart House Grosvenor Place
SW1X 7AE London
Danmarks Tekniske Universitet
Denmark
Address

2800 Build Lyngby
TECHNISCHE UNIVERSITEIT DELFT
Netherlands
Address
Julianalaan 134
2628 BL Delft