Fineness and particle size distribution

The pellets are then delivered in bulk by lorry, train or boat and also in large or small sacks to consumers. Pellets are burned in pellet furnaces to produce heat in small-, medium- and large-scale facilities. Since the quality of pellets may vary during production there are some parameters that can be used to evaluate this. The most important physical parameters are bulk density, pellet density, durability, which can be measured by determining the amount of fines, and particle size distribution of the raw material. Chemical parameters include pellet moisture content, calorific heat value as a determinant of energy content, element content (such as K, Mg, Ca, N, S, Cl), ash content and ash melting behaviour in order to prevent the agglomeration of the ash in the furnace. The net calorific heat value of pellets is about 19 MJ kg-1, which is less than 50% of the oil equivalent. Pellets consist... 

There are four fundamental properties of carbon blacks which determine how these materials can be used with optimization. One Fineness and particle size distribution (Figure 2.39) influence blackness and tint. Two Structure within the carbon black particle and the aggregation of the particles (also called structure. Figure 2.39) influence dispersibility and electrical conductivity. Three Porosity and pore-size distributions influence viscosity and coverage requirements. Four The presence of surface functionality influences wettability, viscosity and electrical conductivity. In carbon black usage, it is their external surfaces, with oxygen functionality in some cases, which dominate their sorption properties, as distinct from the internal microporosity as found in activated carbon. Carbon blacks are supplied by manufacturers both as powders and as pellets. 

Fluidized-bed reaction systems are not normally shut down for changing catalyst. Fresh catalyst is periodically added to manage catalyst activity and particle size distribution. The ALMA process includes faciUties for adding back both catalyst fines and fresh catalyst to the reactor. 

Some concerns directly related to a tomizer operation include inadequate mixing of Hquid and gas, incomplete droplet evaporation, hydrodynamic instabiHty, formation of nonuniform sprays, uneven deposition of Hquid particles on soHd surfaces, and drifting of small droplets. Other possible problems include difficulty in achieving ignition, poor combustion efficiency, and incorrect rates of evaporation, chemical reaction, solidification, or deposition. Atomizers must also provide the desired spray angle and pattern, penetration, concentration, and particle size distribution. In certain appHcations, they must handle high viscosity or non-Newtonian fluids, or provide extremely fine sprays for rapid cooling. 

This review has shown that most studies on barley starches have been focused on understanding the fine structures, particle size distribution, chemical composition, gelatinization properties and susceptibility towards enzyme hydrolysis. However, there is a dearth of information on the rheological and retrogradation characteristics of barley starches from different cultivars. Furthermore, the response of small and large barley starch granules towards physical and chemical modification needs investigation. Research in the above areas is underway in our laboratories. It is hoped that this study may improve the utilization of different types of barley starches for specific products within the food and paper industry. 

During these temperature and gas treatments, processes like reduction, oxidation and sintering take place. In Chapter 2 it is clarified what processes are responsible for the final metal particle size and particle size distribution. This is done using a combination time resolved extended X-ray absorption fine structure spectroscopy (quick EXAFS) and mass spectrometry. 

Particle size large pellets ( 8-20 mm), as uniform as possible no fines medium size ( 2-6mm) and uniform no fines broad particle-size distribution (w0.02-6 mm) high fines content acceptable fine (0.02-0.5 mm), with narrow particle size distribution... 

Due to their simplicity side-wall samplers are superficially attractive (Figure 1.37) but serious errors in concentration and particle size distribution can arise unless the particles are fine, the concentration is high and a very high sampling velocity is used. A projection extending from the pipe wall only marginally improves sampling efficiency [29]. 

Figures 12a and 12b summarize the solids and particle size distributions in both the Suncor and Syncrude tailings ponds. Although there is a sharp change in density at the interface between the recycle water and the fine tails, the gradual densification or settling of the mineral sus-...

A crystallizer equipped with the devices for product classification and fines destruction can efficiently improve the particle size and particle size distribution. With the fines destruction, a portion of the small particles can be eliminated in such a way that the number of crystals in the crystallizer can be controlled within the required range. When this method is complemented with classified product removal, the size of the crystals in the product is controlled on the other hand, an undesired increase in the amount of small crystals is prevented. With this method, it is possible to obtain crystals of a uniform and large size. 

In fine-chemicals production, plants are often multipurpose for reasons of flexibility. ISPR is difficult to achieve in non-dedicated equipment, particularly when it is operated batchwise. For instance, reactive distillations can virtually only be achieved in a dedicated, steady state system. Control over the crystal quality (composition and particle size distribution) in a reactive crys-talliser is practically impossible when the concentrations of product, substrates and contaminants vary widely. 

Particle size and particle size distribution strongly affect initial viscosity of plastisol but less likely the gelation rate. The viscosity of plastisol between 90 and 160°C is also influenced by these variables. In this range of temperatures, plastisols containing PVC having lower particle sizes develop higher viscosities. The higher the number of fine... 

In addition to the overall fineness, the particle size distribution also has a significant effect on cement properties, and these may be controlled— to a degree— by classification. In general, the fluidity of the cement paste is rednced both when there are too many fine particles and when there are too few. An optimnm particle size distribution exists at which the fluidity of the produced mix is optimal (Uchida et al, 1992). The optimum particle size distribution depends on many factors, among which a crucial role is played by the quantity of very fine particles that is, those with diameters of about 10 //m or less. For more detail on the subject the reader should turn to the original literature (Frigione and Mara, 1976 Sumner eta/., 1986). 

Prominent markets today for fine CaCOs are as fillers in paper, paint, PVC, rubber, putty, cosmetics, and toothpaste and as an antacid and a calcium supplement in foods. Surface-coated grades are also produced and are more easily dispersed in organic materials. CaCOs is also used to coat paper, and its use as a filler has increased rapidly with the increase in alkaline papermaking. Many small precipitation plants now operate at papermill sites. Controlled precipitation of calcium carbonate allows control of crystal geometry and particle size distribution. This allows custom production with attractive properties for various markets. With the recent expansion in precipitated calcium carbonate capacity, there are fewer possibilities for disposal of the relatively low-quality material from a brine plant. 

The rate of feed and the particle size distribution of the material supplied to the classifier affect the classification result. Therefore these two parameters should be kept constant during the period of the trials, and the grinding plant should be operating under steady conditions (equilibrium). In order to compensate for any variations in the feed, the samples of the material flow rates A, F and G are taken over periods of 5 —10 minutes at close intervals of 1 —2 minutes. Gross samples of the three flows — classifier feed, fines, tailings — are respectively prepared and the specific surface values and particle size distributions are determined. 

PCC (Precipitated Calcium Carbonate) is by definition a very fine, high purity processed calcium carbonate with controlled morphology, particle size and particle size distribution. PCC is often used in the production of paper [1], but can also be used in different fields of applications, mainly as fillers (in paints, polymers...). There is therefore a need for Lhoist to further improve its expertise in the field of synthetic carbonates and to develop innovative synthetic carbonates with new properties and especially new morphologies. For this purpose, an area in which Lhoist does not have much experience has been explored, that is the production of synthetic carbonates starting from a natural dolomite (CaC03.MgC03) instead of limestone (CaCOs). 

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