Towards the modelling and control of NOx emission in a fluidized bed sludge combustor

Sludge incineration is a widely used technology because of its large volume reduction and complete organic destruction. However, incineration does encounter a number of drawbacks, among which are notably carbon monoxide (CO) and nitrogen oxides (NOx) emissions. Carbon monoxide emissions are efficiently avoided by oxygen regulation in the furnace. Nitrogen oxide (NOx) formation, however, is very complex and not well known. This paper proposes a dynamic model of sludge combustion in an industrial fluidized bed combustor mainly focused on NOx formation. The model is tuned with industrial data. A control strategy is proposed to improve on the current industrial regulation, simultaneously ensuring CO and NOx control, yet without decreasing the combustion efficiency. The results are sufficiently acceptable for this process to be carried out in a real incinerator plant.

[1]  Prabir Basu,et al.  Circulating Fluidized Bed Boilers: Design and Operations , 1991 .

[2]  D. Tree,et al.  Reactivity of NH3 and HCN during low-grade fuel combustion in a swirling flow burner , 2007 .

[3]  Gemma Grasa,et al.  Circulating fluidized bed combustion in the turbulent regime: modelling of carbon combustion efficiency and sulphur retention , 2001 .

[4]  Peter McKendry,et al.  Energy production from biomass (Part 2): Conversion technologies. , 2002, Bioresource technology.

[5]  Gilles Flamant,et al.  Modeling for simulation of fluidized‐bed incineration process , 2001 .

[6]  Herbert Baumann,et al.  Formation and reduction of NO x in pressurized fluidized bed combustion of coal , 1995 .

[7]  J. S. Dennis,et al.  The devolatilisation of particles of a complex fuel (dried sewage sludge) in a fluidised bed , 2007 .

[8]  P. Gayán,et al.  Circulating fluidised bed co-combustion of coal and biomass , 2004 .

[9]  Qinhui Wang,et al.  A mathematical model for a circulating fluidized bed (CFB) boiler , 1999 .

[10]  A. Jensen,et al.  NH3 oxidation catalysed by calcined limestone—a kinetic study☆ , 2002 .

[11]  Jouni P. Hämäläinen,et al.  Importance of solid fuel properties to nitrogen oxide formation through HCN and NH3 in small particle combustion , 1993 .

[12]  A. Jensen,et al.  NH3 oxidation catalyzed by partially sulphated limestone—modelling and experimental work , 2004 .

[13]  Robert Scharler,et al.  Experimental investigation of nitrogen species release from different solid biomass fuels as a basis for release models , 2008 .

[14]  Rafael Font,et al.  Kinetic models for the pyrolysis and combustion of two types of sewage sludge , 2005 .

[15]  Anastasia Zabaniotou,et al.  Utilization of sewage sludge in EU application of old and new methods--A review , 2008 .

[16]  A. Jensen,et al.  Fuel nitrogen conversion in solid fuel fired systems , 2003 .

[17]  Jan Erik Johnsson,et al.  Formation and reduction of nitrogen oxides in fluidized-bed combustion☆ , 1994 .

[18]  J. Werther,et al.  Sewage sludge combustion , 1999 .

[19]  Kang Li,et al.  Modelling and Prediction of NOx Emission in a Coal-Fired Power Generation Plant , 2004 .

[20]  Gilles Flamant,et al.  DEM-LES simulation of coal combustion in a bubbling fluidized bed Part II: coal combustion at the particle level , 2004 .

[21]  Gilles Flamant,et al.  DEM-LES of coal combustion in a bubbling fluidized bed. Part I: gas-particle turbulent flow structure , 2004 .

[22]  J. Vaxelaire,et al.  Use of a transient model to simulate fluidized bed incineration of sewage sludge. , 2006, Journal of hazardous materials.

[23]  Pia Kilpinen,et al.  Char-nitrogen oxidation under fluidised bed combustion conditions: single particle studies ☆ , 2002 .

[24]  John R. Grace,et al.  Dynamic modeling for simulation and control of a circulating fluidized‐bed combustor , 1997 .

[25]  J. S. Dennis,et al.  Thermogravimetric measurements of the kinetics of pyrolysis of dried sewage sludge , 2006 .

[26]  P. Agarwal,et al.  Mathematical modeling of fluidized bed combustion. 4: N2O and NOX emissions from the combustion of char , 2001 .

[27]  Peter McKendry,et al.  Energy production from biomass (Part 1): Overview of biomass. , 2002, Bioresource technology.

[28]  Jean Vaxelaire,et al.  Analytical study of the pyrolysis process in a wastewater treatment pilot station , 2004 .

[29]  U. Kortela,et al.  Dynamic model for a bubbling fluidized bed coal combustor , 1994 .

[30]  J. R. Howard.  Fluidized Bed Technology: Principles and Applications, , 1989 .

[31]  Bie Rushan,et al.  A coal combustion model for circulating fluidized bed boilers , 2000 .

[32]  K. Tran,et al.  In-situ catalytic abatement of NOx during fluidized bed combustion—A literature study , 2008 .

[33]  Enrico Biagini,et al.  Devolatilization rate of biomasses and coal–biomass blends: an experimental investigation , 2002 .

[34]  B. M. Gibbs,et al.  Modelling of NO and N2O emissions from biomass-fired circulating fluidized bed combustors , 2002 .

[35]  Paolo Bolzern,et al.  A model of a bubbling fluidized bed combustor oriented to char mass estimation , 2000, IEEE Transactions on Control Systems Technology.

[36]  Modelling of NOx emissions from pressurized fluidized bed combustion : a parameter study , 1997 .