Author index

Modelling and experimental validation of a fluidized-bed reactor freeboard region: Application to natural gas combustion

Limiting NO x and SO 2 emissions from an industrial-size fluidised-bed combustor

A technique for determining devolatilization rates of large coal particles in a fluidized bed combustor

Experiment and grey relational analysis of seaweed particle combustion in a fluidized bed

This work investigated the energy output from the fluidized bed combustion of Lafia-Obi coal using five range of fuel equivalent diameters (FED) of 125 µm, 250 µm, 355 µm, 2.5 mm and 5.0 mm. Energy output in response to variation in bed temperature, FED, bed pressure, and fluidizing velocity was examined in the fluidized bed heat exchanger. Results indicated an increase in heat transfer rate by 80, 11 and 25% when 5 mm coal was reduced to 355, 250 and 150 µm respectively. Bed temperature increased by 8% for 355 µm and decreased by 6% when 5.0 mm coal was fired. Higher bed pressure was observed when larger particle sizes (5.0 and 2.5 mm) were fired. This resulted in poor bed temperature and increasing fluidization velocity and thus, reduced steam discharge temperature at the heat exchanger outlet. http://dx.doi.org/10.4314/njt.v37i4.16

The objective of this study is to fully utilize the local sand retrieved from Pahang river as a bed material in FBC. The proposed work will study through experiments to deduce a new classification of local river sand in a fluidized bed based on the minimum fluidization velocity of inert particles according Geldart’s classification operated at five different temperatures: 55, 82, 108, 124 and 148 °C respectively. River sand was chosen as a fluidizing medium due to its characteristics that can withstand high operating temperature of more than 1000 °C. Apart from that, its cheap cost and availability make it preferred choice for the operation. The results show that the minimum fluidizing velocity of the sand, \( U_{\text{mf}} \) was found increasing as the temperature increased for the sands operated at low temperature, but maintaining almost at the same value, for the sands operated higher operating temperature respectively. The findings agree well with the reported trend by previous authors, in which their results based on the bed operated at combustion temperature which is above 800 °C. Thus, it can be conclude that the local sands, will exhibits the same trend for the application of fluidized bed combustor.

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Release of volatiles from large coal particles in a hot fluidized bed

Chapter 5 - Fluidized Bed Combustion and Coal Gasification

Fluidized bed combustion and fragmentation of wet sewage sludge

Testing of cold scaled bed modeling for fluidized-bed combustors

The overall objectives of this project are to develop experimental techniques for measuring the forces of fluidized particles, and to predict the solid-gas performance in fluidized beds by using data analysis system, and by elucidating the intrinsic mechanism of erosion and attrition phenomena in fluidized beds. The reduction of erosion and attrition rates is one of the critical engineering problems for the design and operation of fluidized bed combustors. Specifically, the objectives are to: (1) develop the experimental techniques to measure the forces of solid particles prevailing in fluidized beds: (2) measure and characterize the forces of solid particles in various types of fluidized beds with various configurations (conventional and spouted fluidized beds) and with different scales (10, 20, and 30cm) under various fluidization conditions (particle size, bed aspect ratio and gas velocity); (3) find and verify the mechanism of erosion rates of in-bed tubes and attrition rates of fluidized particles by forces of solid particles in fluidized beds. We developed three different kinds of measurement methods, i.e., fracture sensitive sensor, piezoelectric sensor and gas pressure fluctuation method. By using these methods the exact forces of solid particles, including the transient corporate in fluidized beds, were systematically measured. Simultaneously, the erosion rates of in-bed tubes and attrition rates of fluidized particles were measured. 69 figs., 9 tabs.

The 165 MWe circulating fluidized bed boiler at the Nova Scotia Power Inc. (NSPI) Point Aconi Generating Station, located in eastern Cape Breton Island, Nova Scotia, is Canada’s largest fluidized bed unit. Fluidized bed combustion (FBC) allows the burning of high sulphur (S) fuels with in situ capture of S (removal of SO2). The lower operating temperature of the FBC system (870 C versus 2000 C for pulverized coal boilers) permits the combustion of a wide range of ‘opportunity’ fuels (e.g., petroleum coke , low grade coals, tires, and wood waste sludge) in an environmentally acceptable manner. The use of large amounts of a limestone sorbent in FBC results in a high rate of sulphur capture (90%), however, the rate of residue production is approximately two-times higher than that from conventional pulverized coal-fired boilers. While the residue is currently disposed in a fully engineered residue management site, there are environmental, financial, and other incentives for NSPI to fmd beneficial uses for the residue to minimize placement of the by-product in the landfill.

The rapid depletion of oil and the environmental impact of combustion has motivated the search for clean combustion technologies. Fluidised bed combustion (FBC) technology works by suspending a fuel over a fast air inlet whilst sustaining the required temperatures. Using biomass or a mixture of coal/biomass as the fuel, FBC provides a low-carbon combustion technology whilst operating at low temperatures. Understanding the hydrodynamic processes in fluidised beds is essential as the flow behaviours causing heat distributions and mixing determine the combustion processes. The inlet velocities and different particle sizes influence the flow behaviour significantly, particularly on the transition from bubbling to fast fluidising regimes. Computational modelling has shown great advancement in its predictive capability and reliability over recent years. Whilst 3D modelling is preferred over 2D modelling, the majority of studies use 2D models for multiphase models due to computational cost consideration. In this paper, two-fluid modelling (TFM) is used to model a 3D circulating fluidised bed (CFB) initially focussing on fluid catalytic cracker (FCC) particles. The transition from bubbling to fast fluidisation over a range of velocities is explored, whilst the effects on the bubble diameter, particle distributions and bed expansion for different particle properties including particle sizes are compared. Drag models are also compared to study the effects of particle clustering at the meso-scale.

The relationship between the tendency of lignites to agglomerate and their fusion characteristics in a fluidized bed combustor