Dodds D.,Swinburne University of Technology |
Naser J.,Swinburne University of Technology |
Staples J.,HRL Technology |
Black C.,HRL Technology |
And 2 more authors.
Powder Technology | Year: 2011
The boiler efficiency of a Lignite fuelled power station can be significantly affected by the distribution of the coal within the boiler furnace. The mill-duct systems are designed to allow sufficient resident time for the raw Lignite to dry. The raw Lignite, which contains approximately 66% water, is conveyed by post combustion hot off-take gases and delivered to the furnace with an appropriate distribution to ensure when mixed with sufficient oxygen, complete combustion occurs. The mill-duct systems for a lignite fuelled boiler are generally very complex and as such, are not yet fully understood. The distributions of the coal and gas mixture within these complicated mill ducts have been investigated experimentally and numerically to better understand the flow patterns. Isokinetic sampling of the gas and coal was undertaken within the lower, intermediate and upper legs of a mill-duct system downstream of the grinding mill under standard operating load at the Loy Yang B power station in the Latrobe Valley, Australia. CFD modelling using an Eulerian/Lagrangian approach, due to the low solids-to-gas ratio, was used to achieve good agreement with the experimental data. The gas-coal mixture must travel through a series of bends before entering the furnace and a bias of coal flow toward the outer wall of the upper and lower legs was noted downstream of the bend at the trifurcation for the mill-duct legs. The slightly different geometry configuration of the intermediate resulted in a more homogenous coal and gas flow but a significantly lower coal loading than the upper and lower legs. © 2010 Elsevier B.V.
Antony M.,Monash University |
Hoadley A.F.A.,Monash University |
Campisi A.,HRL Technology
Proceedings of the 23rd International Conference on Efficiency, Cost, Optimization, Simulation, and Environmental Impact of Energy Systems, ECOS 2010 | Year: 2010
Oxyfuel combustion is one of the CO2 capture technologies for the capture and storage of CO2 from power stations. A techno-economic analysis has been completed for the retrofit of oxy-fuel combustion to a 200 MW brown coal (lignite) boiler. The existing unit was simulated using Thermoflex software and validated against plant performance data. Oxyfuel components, including the ASU, flue gas recirculation, CO2 compression and lignite partial drying were then retrofitted to the validated model. It was then optimised to improve the thermal efficiency and reduce the energy penalty. The overall net efficiency of the boiler decreased from 23.1% in the reference plant to 16.4% in the oxyfuel retrofit, even though there was an increase in gross efficiency from 24.6% to 28.8% which was due in particular to the partial drying of the lignite. The cost of CO2 avoidance was calculated to be A$45.04/tCO2, based on an IRR of 7% (zero inflation) and a project life of 25 years.
Vuthaluru H.B.,Curtin University Australia |
Doshi V.,Curtin University Australia |
Korbee R.,HRL Technology |
Kiel J.H.A.,Energy Research Center of the Netherlands |
And 2 more authors.
Fuel | Year: 2014
The co-firing technology of biomass with coal has been implemented to enhance the usage of biomass in power generation, thus reducing the release of greenhouse gas emissions. This study deals with the fireside issues, namely ash-related issues that arise during co-firing of coal and biomass. Ash release from biomass can lead to ash deposition problems such as fouling and slagging on surfaces of power generation boilers. The scope of this paper includes the development of a conceptual model that predicts the chemical composition of inorganics in coal and biomass and its release behaviour when combusted. An advanced analytical method was developed and introduced in this work to determine the speciation of biomass. The method known as pH-controlled extraction analysis was used to determine the inorganic speciation in three biomass samples, namely wood chips, wood bark and straw. The speciation of biomass and coal was used as an input to the model to predict the behaviour and release of ash. It was found that the main minerals species released as gas phases during the combustion of biomass are KCl, NaCl, K2SO4 and Na2SO4. Gas-to-particle formation calculations for such minerals were carried out to determine the chemical composition of coal and biomass when cooling takes place in the boiler. It was found that the possibility of heterogeneous condensation occurring on the heat exchange surface of boilers is much higher than homogeneous condensation. Preliminary study of interaction between coal and biomass during ash formation showed that Al, Si and S elements in coal may have a 'buffering' effect on biomass alkali metals, thus reducing the release of alkali-gases that can cause deposition and corrosion issues during co-firing. The results obtained in this work can be used in future work to determine the ash deposition of coal and biomass in boilers. © 2014 Elsevier Ltd. All rights reserved.