Fluidised calcining

Formation of emissions from fluidised-bed combustion is considerably different from that associated with grate-fired systems. Flyash generation is a design parameter, and typically >90% of all soHds are removed from the system as flyash. SO2 and HCl are controlled by reactions with calcium in the bed, where the lime-stone fed to the bed first calcines to CaO and CO2, and then the lime reacts with sulfur dioxide and oxygen, or with hydrogen chloride, to form calcium sulfate and calcium chloride, respectively. SO2 and HCl capture rates of 70—90% are readily achieved with fluidi2ed beds. The limestone in the bed plus the very low combustion temperatures inhibit conversion of fuel N to NO. ... 

Calcium looping consists of two fluidised bed reactors, namely carbonator and calciner. In the... 

Otero, A.R. and Garcia, V.G., Cake formation in a fluidised bed calciner, Chem. 

J. Bayens et al., The development, design and operation of a fluidised bed calciner , Zement Kalk Gips 12,1989,620. 

One of the driving forces for developing new designs of kiln is that substantial quantities of calcium carbonate are available in a finely divided form. The sugar and paper/wood pulp industries, for example, produce a calcium carbonate sludge (see sections 30.4 and 32.16), which can be calcined and recycled. Many plants use rotary kilns for this purpose, while some use fluidised bed kilns [16.6,16.48,16.49]. 

In dry generators, the carbide is reacted with a controlled excess of water to produce acetylene, steam and hydrated lime with 1 to 2 % of excess water. Part of the hydrated lime may be calcined to quicklime and recycled to the carbide furnace. The remainder, which acts as a purge for impurities, can be used in many of the applications described for hydrated lime (see also section 20.10). Few details of kilns used for the dehydration of carbide lime appear to have been published. Kampmann [31.4] mentions granulation and briquetting of the hydrate, presumably for feeding into a rotary kiln. Other techniques, such as fluidised bed calcining would also appear to be appropriate (see section 16.4.11). 

B-MFI was prepared as described elsewhere [21]. The catalyst was extruded, crushed and sieved in fractions of 0.5-1.0 mm for fixed bed experiments and 63-250 pm for the fluidised bed. The jdelded material was calcined in air with two steps. The B-MFI was first dried 4 h by 120°C to remove the physisorbed water from the surface and after this calcined by 550°C for 8 h. The catalyst was characterised with XRD (Siemens D5000), ICP AES (Spectroflame D) and FT-IR (Protege 460). 

Before 1996, roaster operation was spasmodically interrupted by occurrences of low bed pressure, highly coarse bed calcine, bed de-fluidisation preceded by bed temperature breaks, high levels of particle elutriation and gas train blockages. 

Rotating fluidised-bed Suspended particles in a fluid bed are given a tangential velocity Combustion, calcining, catalyst reactivation, gasification/pyrolysis, pasteurisation (clinical waste, herbs and spices), and desorption 5... 

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