Coal particle size distribution

COAL PARTICLE SIZE DISTRIBUTION Particle Size (Microns) Weight Percent... 

The dynamic and steady-state characteristics of a shallow fluidized bed combustor have been simulated by using a dynamic model in which the lateral solids and gas dispersion are taken into account. The model is based on the two phase theory of fluidization and takes into consideration the effects of the coal particle size distribution, resistance due to diffusion, and reaction. The results of the simulation indicate that concentration gradients exist in the bed on the other hand, the temperature in the bed is quite uniform at any instant in all the cases studied. The results of the simulation also indicate that there exist a critical bubble size and carbon feed rate above which "concentration runaway" occurs, and the bed can never reach the steady state. 

Figure 6. The effects of three chemical additives on product coal particle size distribution while milling at constant conditions, (O) No Additives (A) 2 Ibs/ton Calcium Hydroxide (D)...

Experimental determination of pulverized coal particle size distribution... 

Keyser, M., Conradie, M., Coertzen, M., and Dyk, J.V. (2006) Effect of coal particle size distribution on packed bed pressure drop and gas flow distribution. Fuel, 85 (10-11), 1439-1445. 

Mechanical Properties. Mechanical properties (4,6,55) are important for a number of steps in coal preparation from mining through handling, cmshing, and grinding. The properties include elasticity and strength as measured by standard laboratory tests and empirical tests for grindabiUty and friabihty, and indirect measurements based on particle size distributions. 

The carbon raw material in the form of coke, coal or natural or synthetic graphite is ground and sieved (following calcination at 700-1300°C to control volatiles, if necessary) to give a desired particle size distribution. The distribution depends upon the size of the artifact to be formed and the method of forming. 

A small sample of a coal slurry containing particles with equivalent spherical diameters from 1 to 500 pm is introduced into the top of a water column 30 cm high. The particles that fall to the bottom are continuously collected and weighed to determine the particle size distribution in the slurry. If the solid SG is 1.4 and the water viscosity is 1 cP, over what time range must the data be obtained in order to collect and weigh all the particles in the sample ... 

The relatively wide particle size distributions of the pulverized coal and fly ash (e.g., 1 pm to 200 pm) seem to be the major contributing factor to the effects described above (i.e., the materials tested by Geldart [1973] had fairly narrow size distributions),... 

In practice, we have a number of solid fuels, for example biofuels (forest or agricultural derived biofuels), coal, municipal solid waste (MSW) and many others [23]. A fuel bed is composed of varying sizes of solid-fuel particles, also called polydispersed solid-.fuels [15]. The fuel chemistry is different depending on whether it is coal, biofuel or MSW. The fuel bed can be dry or consist of moisture. The fuel physics are for example, particle size distribution, particle shape, particle density and bed permeability. 

Toxicology. Epidemiological evidence suggests that workers intimately exposed to the products of combustion or distillation of bituminous coal are at increased risk of cancer at many sites, including lungs, kidney, and skin. The chemical composition and particle size distribution of coal tar pitch volatiles (CTPV) from different sources are significant variables in determining toxicity. ... 

Hitde DC, Stukel JJ Particle size distribution and chemical composition of coal tar fumes. Am Ind Hyg Assoc J 37 199-204, 1976... 

A number of environmental applications [3] have been performed in order to size characterize colloids collected in rivers (riverbome particles, SPM, and sediments), clay samples and ground limestone (from soils), coal particles, diesel soot particles (from combustion processes), or airborne particles in urban areas (from waste incinerators, vehicles, household-heating systems, and manufacturing). In many of these cases, not only the size but also the particle size distribution was important and thus, in conjunction with the traditional UV detector, specific detectors such as ETAAS, ICP-MS, ICP-AES were used [40] in order to obtain more detailed, more specific compositional information. 

Particle size distributions of smaller particles have been made using electrical mobility analyzers and diffusion batteries, (9-11) instruments which are not suited to chemical characterization of the aerosol. Nonetheless, these data have made major contributions to our understanding of particle formation mechanisms (1, 1 ). At least two distinct mechanisms make major contributions to the aerosols produced by pulverized coal combustors. The vast majority of the aerosol mass consists of the ash residue which is left after the coal is burned. At the high temperatures in these furnaces, the ash melts and coalesces to form large spherical particles. Their mean diameter is typically in the range 10-20 pm. The smallest particles produced by this process are expected to be the size of the mineral inclusions in the parent coal. Thus, we expect few residual ash particles smaller than a few tenths of a micrometer in diameter (12). 

Previous work has shown that the 3.3-5.5 /xm coal fraction has a particle size distribution similar to that of respirable mine dust collected on personal samplers during mining operations (13). This fraction was used for the spark-source analyses. The coals used in this investigation are identified in Table I. The respirable dusts were obtained from personal sampler filters submitted to the Dust Group, Pittsburgh Technical Support Center, Federal Bureau of Mines. The samples were collected during actual mining operations. 

Suspension Polymerization. The suspension or pearl polymerization process has been used to prepare polymers for adhesive and coaling applications and for conversion to poly(vinyl alcohol). Suspension polymerization are carried out with monomer-soiubie initiators predominantly, with low levels of stabilizers Continuous tubular polymerization of vinyl acetate in suspension yields stable dispersions of beads with narrow particle size distributions at high yields. 

Size consist particle size distribution of coal (ASTM D-2013 ASTM D-2234 ASTM D-4915 ASTM D-4916). 

In addition, the TRW samples were analyzed by the SEM-AIA technique described previously (13). The SEM-AIA data on the mineral phase identification and distribution between the size fractions are presented in Table VI for all three samples of raw and treated coal. The SEM-AIA data show the nearly complete removal of many minerals and a reduction of more than 90X in the overall content of the coal as a result of treatment by the TRW Gravimelt Process. No major changes in particle size distribution were observed, although the pyrite distribution shifted somewhat towards the coarse fraction after processing. 

Particulate emissions from the synthetic fuels were very low, on the order of 0.01 lb per million BTU, and approximately one order of magnitude less than particulate emissions from No. 6 fuel oil. Data on particulate morphology and submicron particle size distributions Indicate a unlmodal size distribution for the No. 6 fuel oil and the SRC-II fuels while Indicating a blmodal size distribution for the H-Coals. Burners out of service and low excess air (LEA) operation did not significantly contribute added particulate emissions although 1t did tend to shift the unlmodal distributions toward a larger number of smaller particles. 

In an earlier study (15) we addressed some of the problems in obtaining accurate concentration-vs-particle-size distributions for elements in stack aerosols collected downstream of an electrostatic precipitator and a Venturi wet scrubber at a coal-fired power plant. The problems investigated were error associated with the use of the... 

The Model. The physical system considered is an entrained bed reactor. Pulverized coal, carried by a gas stream, mixes with hot gas at the reactor entrance. As coal particles are carried their temperatures increase and devolatilization takes place. For practical purposes the particle size distribution was approximated by 10 discrete cuts. Since the devolatilization kinetics are highly temperature dependent and the temperature transient of a particle is affected by its size and mass separate account must be taken of each of the 15 reactions in each of the 10 different size particles. Without any detail on the derivation of the model, the equations can be summarized as ... 

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