scholarly journals Flexibility of CFB Combustion: An Investigation of Co-Combustion with Biomass and RDF at Part Load in Pilot Scale

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4665
Author(s):  
Jens Peters ◽  
Jan May ◽  
Jochen Ströhle ◽  
Bernd Epple
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Power Plants ◽  
Circulating Fluidized Bed ◽  
Low Cost ◽  
Low Rank ◽  
Hydrodynamic Conditions ◽  
Fluidized Bed Combustion ◽  
Water Steam ◽  
The Impact

Co-combustion of biomass and solid fuels from wastes in existing highly efficient power plants is a low-cost solution that can be applied quickly and with low effort to mitigate climate change. Circulating fluidized bed combustion has several advantages when it comes to co-combustion, such as high fuel flexibility. The operational flexibility of circulating fluidized bed (CFB) co-combustion is investigated in a 1 MWth pilot plant. Straw pellets and refuse-derived fuel (RDF) are co-combusted with lignite at full load and part loads. This study focusses on the impact on the hydrodynamic conditions in the fluidized bed, on the heat transfer to the water/steam side of the boiler, and on the flue gas composition. The study demonstrates the flexibility of CFB combustion for three low-rank fuels that differ greatly in their properties. The co-combustion of RDF and straw does not have a negative effect on hydrodynamic stability. How the hydrodynamic conditions determine the temperature and pressure development along the furnace height is shown. The heat transfer in the furnace linearly depends on the thermal load. It increases slightly with an increasing share of straw and the influence of the hydrodynamic conditions on the heat transfer was low.

Modelling Fuel and Sorbent Attrition During Circulating Fluidized Bed Combustion of Coal

2003 ◽  
Author(s):  
D. Barletta ◽  
A. Marzocchella ◽  
P. Salatino ◽  
S. G. Kang ◽  
P. T. Stromberg
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Surface Wear ◽  
Fluidized Bed Combustion ◽  
Coal Fuel ◽  
Primary Fragmentation ◽  
The Impact ◽  
Constitutive Parameters ◽  
Fluidized Bed Combustor ◽  
Circulating Fluidized Bed Combustion

A simulation model of a circulating fluidized bed combustor, based on a one-dimensional description of bed hydrodynamics and a simplified formulation of the population balance equation on fuel and bed solids, has been set up. The model specifically aims at assessing the extent of fuel and sorbent attrition during circulating fluidized bed combustion of coal. Fuel attrition is modelled as a function of carbon loading and of the relevant operating variables while taking into account primary fragmentation of coal and secondary fragmentation and attrition by surface wear of its char. Modelling of sorbent attrition accounts for primary fragmentation of limestone upon calcination as well as attrition by surface wear of lime. To this end time- and conversion-dependent attrition rate is averaged over the sorbent particle lifetime in the reactor. Attrition submodels and their constitutive parameters are based on previous work by the research group in Naples. Coal char combustion and lime sulphation are modelled considering intrinsic reaction kinetics as well as boundary layer and intraparticle diffusion of reactants. The impact of attrition phenomena on the performance of the fluidized bed combustor is characterized by looking at carbon combustion efficiency, at sulphur capture efficiency, at the balance between bottom and fly ashes. The influence of operating parameters like fuel particle size, Ca/S ratio, gas superficial velocity, extent of air staging is investigated. The sensitivity of results of model computations to the parameters expressing fuel and sorbent attrition is presented and discussed.

scholarly journals Fluidized bed combustion with the use of Greek solid fuels

2003 ◽  
Vol 7 (2) ◽  
pp. 33-42
Author(s):  
Emmanuel Kakaras ◽  
Panagiotis Grammelis ◽  
George Skodras ◽  
Panagiotis Vourliotis
Keyword(s):  
Fluidized Bed ◽  
Brown Coal ◽  
Circulating Fluidized Bed ◽  
Pilot Scale ◽  
Thermal Capacity ◽  
Low Rank ◽  
Fluidized Bed Combustion ◽  
Bubbling Fluidized Bed ◽  
Combustion Technology ◽  
Combustion Tests

The paper is an overview of the results obtained up to date from the combustion and co-combustion activities with Greek brown coal in different installations, both in semi-industrial and laboratory scale. Combustion tests with Greek lignite were realized in three different Circulating Fluidized Bed Combustion (CFBC) facilities. Low rank lignite was burned in a pilot scale facility of approx. 100kW thermal capacity, located in Athens (NTUA) and a semi-industrial scale of 1.2 MW thermal capacity, located at RWE's power station Niederaussem in Germany. Co-combustion tests with Greek xylitic lignite and waste wood were carried out in the 1 MWth CFBC installation of AE&E, in Austria. Lab-scale co-combustion tests of Greek pre-dried lignite with biomass were accomplished in a bubbling fluidized bed in order to investigate ash melting problems. The obtained results of all aforementioned activities showed that fluidized bed is the appropriate combustion technology to efficiently exploit the low quality Greek brown coal either alone or in conjunction with biomass species.

Design Considerations of Oxy-Fuel Fired Supercritical Pressure Circulating Fluidized Bed Boilers

2006 ◽  
Author(s):  
Prabir K. Halder
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Flue Gas ◽  
Circulating Fluidized Bed ◽  
Fuel Combustion ◽  
Cfb Boiler ◽  
Design Considerations ◽  
Effective Manner ◽  
The Impact ◽  
Fluidized Bed Boilers

Researchers around the globe are focussing on the capture and storage of carbon dioxide generated from the combustion of coal in boilers for power generation. Oxygen fired boilers have the advantage of creating CO2 rich flue gas which enables the CO2 to be captured in a more cost effective manner compared to post combustion capture of CO2 from an air fired boiler. This paper discusses design considerations for oxy-fuel fired supercritical circulating fluidized bed boilers. A 420 MWe supercritical CFB boiler firing coal with oxygen has been considered for the study. An analytical/semi-empirical model has been developed to model fuel combustion and heat transfer in the furnace and convection pass. The fuel burns with oxygen supplied at the bottom of the bed and the fluidization velocity and bed temperature is controlled by flue gas recirculation. The model is used to design the boiler and determine its performance characteristics. The heating surfaces, recirculation ratios and other parameters have been designed to achieve the required boiler capacity. The impact of the CO2 rich flue gas on CFB boiler design is compared with conventional air blown CFB boilers. The study reveals that oxy-fuel combustion in a CFB combustor does not alter the heat transfer characteristics when compared with combustion with air. In the convection bank, oxyfuel combustion increases both convective and radiative components of heat transfer, thereby reducing the size of the heat transfer banks required.

High Velocity Arc-Sprayed Coating by CrB Powder Wire for Elevated Temperature Erosion Protection in Circulating Fluidized Bed Boilers

2008 ◽  
Vol 373-374 ◽  
pp. 85-88
Author(s):  
Yun Jing Song ◽  
Hua Ling Deng ◽  
Shi Rong Xiao ◽  
Wen Hua Shi
Keyword(s):  
Elevated Temperature ◽  
Fluidized Bed ◽  
Amorphous Phase ◽  
High Velocity ◽  
Power Plants ◽  
Circulating Fluidized Bed ◽  
Low Cost ◽  
Arc Spraying ◽  
Powder Wire ◽  
Sprayed Coating

The coatings for elevated temperature erosion resistance in circulating fluidized bed (CFB) boilers were fabricated by high velocity arc spraying process and CrB powder wire. The microstructure and phase component of the coating were examined by optical microscopy(OM) and Transmission electron microscopy (TEM). The properties including microhardness, adhesion strength and in-situ erosion rate of the coating were measured. The failure mechanism was also discussed based on the experimental data. The OM results showed that the coating consisted of individual flat lamella, thin oxide layer, porosity and very small amount of particle which characterized as different shape and color respectively. TEM results indicated that the phases within the lamella were mainly composed of α phase, amorphous phase and other nanosized particle phase of Fe23(C,B)6, Cr23C6 etc.. The amount of amorphous phase near the substrate was more than that in the other area indicating that the appearance of amorphous phase was related to the high cooling rate of the coating. The microhardness was about 860~1100HV0.2. The coating exhibited high erosion-corrosion resistance, which was about six times as 20G steel. The advantage of the coating with excellent performance, simple process and low cost made it possible to find potential application in power plants.

scholarly journals The Influence of Fluidized Bed Combustion Fly Ash on the Phase Composition and Microstructure of Cement Paste

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2838
Author(s):  
Michał A. Glinicki ◽  
Daria Jóźwiak-Niedźwiedzka ◽  
Mariusz Dąbrowski
Keyword(s):  
Phase Composition ◽  
Fly Ash ◽  
Fluidized Bed ◽  
Cement Paste ◽  
Power Plants ◽  
Circulating Fluidized Bed ◽  
Thermal Analyses ◽  
Hardened Cement ◽  
Fluidized Bed Combustion ◽  
Cement Pastes

Fly ashes from coal combustion in circulating fluidized bed boilers in three power plants were tested as a potential additive to cement binder in concrete. The phase composition and microstructure of cement pastes containing fluidized bed fly ash was studied. The fractions of cement substitution with fluidized bed fly ash were 20% and 30% by weight. X-ray diffraction (XRD) tests and thermal analyses (derivative thermogravimetry (DTG), differential thermal analysis (DTA) and thermogravimetry (TG)) were performed on ash specimens and on hardened cement paste specimens matured in water for up to 400 days. Quantitative evaluation of the phase composition as a function of fluidized bed fly ash content revealed significant changes in portlandite content and only moderate changes in the content of ettringite.

scholarly journals Research on the Expansion Characteristics and Compressive Strength of Mortars Containing Circulating Fluidized Bed Combustion Desulfurization Slag

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Zhi Cheng ◽  
Zhijun Cheng ◽  
Hua Hou ◽  
Tao Han ◽  
Lan Liu
Keyword(s):  
Compressive Strength ◽  
Fluidized Bed ◽  
Power Plants ◽  
Circulating Fluidized Bed ◽  
Linear Expansion ◽  
Chemical Activation ◽  
Expansion Rate ◽  
Fluidized Bed Combustion ◽  
Mechanical Grinding ◽  
Circulating Fluidized Bed Combustion

Circulating fluidized bed combustion (CFBC) desulfurization slag is a waste residue discharged from coal power plants. In this article, expansion characteristics and compressive strength of mortars containing CFBC desulfurization slag were evaluated, subjected to mechanical grinding time, the amount of additive, and chemical activation. Correlations between the linear expansion rate and compressive strength were investigated. The hydration products of cement-slag cementitious system were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that mechanical grinding can increase both the expansion and compressive strength of mortars containing CFBC desulfurization slag, and the compressive strength and linear expansion can develop in coordination. While increasing the amount of the fine desulfurization slag, the linear expansion rate increases, and the compressive strength reaches to the maximum when the amount is 30%. Moderate sodium sulfate as an activator can both promote the compressive strength and increase the expansion of mortars.

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