Desulfurization particle size distribution

Particle size distribution relating to gas cleaning is well understood in the industry. This section deals with general rules of thumb. Certain important issues not included in this section are flue gas desulfurization, flue gas denitrification, hazardous waste gas cleaning, waste incineration gas cleaning, and removal of CO2 from flue gas. All these topics have special requirements, which must be considered separately in the design process. 

A novel Double Draw-Off (DDO) ciystallizer has been designed in order to improve the particle size distribution in the precipitation of CaS03 V 20 simulated Flue Gas Desulfurization (FGD) liquor. The effects of DDO ratio and residence time on the mean particle size were studied. Industrial conditions were maintained in all experiments as far as practical. Significant improvement in mean particle size was achieved. The performance of an actual industrial DDO ciystallizer (DuPont) for gypsum ciystallization was reported. 

Setekleiv and Svendsen [180] used the same laser difliraction particle sizer to characterize the ability of mesh pads to separate droplets from the gas stream in a scrubber. Droplets in the size range 30-1000 p,m with a bi-modal distribution was obtained at low pressure. A rough sketch of the mounting of the laser diffraction instrument used in this work is shown in Fig. 13.17. Numerous applications of the LD particle sizer for solid particle size distribution measurements characterizing aerosols and suspensions can be found in the literature. Only a few examples of laser diffraction solid particle size distribution measurements relevant for fluidized bed system characterization are mentioned in this report. Garea et al. [71] measured the solid sorbent particle size distribution in a fluidized bed in-duct desulfurization reactor under in-duct conditions by laser diffraction. Ferrer et al. [66] studied fluidized bed combustion of refuse-derived fuel in presence of protective coal ash and measured the fly ash particle size distribution with a laser diffraction method. Tanneur et al. [192] measured the solid particle size distribution in a fluidized bed by use of a diffraction particle size analyzer. 

Improved control devices now frequently installed on conventional coal-utility boilers drastically affect the quantity, chemical composition, and physical characteristics of fine-particles emitted to the atmosphere from these sources. We recently sampled fly-ash aerosols upstream and downstream from a modern lime-slurry, spray-tower system installed on a 430-Mw(e) coal utility boiler. Particulate samples were collected in situ on membrane filters and in University of Washington MKIII and MKV cascade impactors. The MKV impactor, operated at reduced pressure and with a cyclone preseparator, provided 13 discrete particle-size fractions with median diameters ranging from 0,07 to 20 pm with up to 6 of the fractions in the highly respirable submicron particle range. The concentrations of up to 35 elements and estimates of the size distributions of particles in each of the fly-ash fractions were determined by instrumental neutron activation analysis and by electron microscopy, respectively. Mechanisms of fine-particle formation and chemical enrichment in the flue-gas desulfurization system are discussed. 

In previous studies, Sooter (2) and Satchell (3) observed that reducing the particle size of the Nalcomo 474 catalyst from 8-10 mesh to 40-48 mesh did not have any significant effect on the desulfurization and denitrogenation of Raw Anthracene Oil under similar experimental conditions as employed in this study. This suggests that the fluid distribution and hence the fluid dynamic effects, were not important in the trickle bed reactors as operated for this work. If these effects were important then the reduction in particle size should increase conversion of the HDS and HDN by improving fluid distribution and reducing the intraparticle diffusion resistances. 

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