![]() ![]() A simple treatment assumes the particles are spheres that will just pass through a square hole in a "sieve". The way in which "size" is expressed is open to a wide range of interpretations. Range analysis is suitable when a particular ideal mid-range particle size is being sought, while cumulative analysis is used where the amount of "under-size" or "over-size" must be controlled. ![]() ![]() It may also be presented in "cumulative" form, in which the total of all sizes "retained" or "passed" by a single notional "sieve" is given for a range of sizes. The PSD may be expressed as a "range" analysis, in which the amount in each size range is listed in order. However, the idea of the notional "sieve", that "retains" particles above a certain size, and "passes" particles below that size, is universally used in presenting PSD data of all kinds. Some methods of determination allow much narrower size ranges to be defined than can be obtained by use of sieves, and are applicable to particle sizes outside the range available in sieves. The PSD is usually determined over a list of size ranges that covers nearly all the sizes present in the sample. "% of sample between 45 μm and 53 μm", when sieves of these sizes are used. Thus, the PSD is defined in terms of discrete size ranges: e.g. The most easily understood method of determination is sieve analysis, where powder is separated on sieves of different sizes. PSD is usually defined by the method by which it is determined. In contrast to the large numerical values noted for flow Reynolds number, particle Reynolds number for fine particles in gaseous mediums is typically less than 0.1. For values less than 0.1, the particulate sample can be considered to be monodisperse. This value is also determined mathematically. Α: Relative standard deviation or degree of polydispersity. The value of σ g determines the slope of the least-squares regression curve. This value is determined mathematically by the equation: The MMD is considered to be the average particle diameter by mass. The log-normal distribution mass median diameter. A value equal to 1.0 indicates all data fit perfectly within the hyperplane.ĭ 50: Mass-median-diameter (MMD). The closer this value is to 1.0, the better the data fit to a hyperplane representing the relationship between the response variable and a set of covariate variables. R 2: Least-squares coefficient of determination. Ρ g: Gas or sample matrix density (g/cm 3) The filterability of the liquid is determined largely by the size of the particles. The PSD plays an important part in the cake formation, cake resistance, and cake characteristics. They can be very efficient at the collection of very fine particles.įilter Press used for filtering liquids by cake filtration mechanism. The greater the contact of the gas and liquid streams, the higher the dust removal efficiency.Įlectrostatic precipitators use electrostatic forces to separate dust particles from exhaust gases. In these systems, the scrubbing liquid (usually water) comes into contact with a gas stream containing dust particles. Wet scrubbers that use liquid are commonly known as wet scrubbers. Higher efficiency models can collect particles down to 10 μm.įabric filters are one of the most efficient and cost effective types of dust collectors available and can achieve a collection efficiency of more than 99% for very fine particles. Settling chambers will normally only collect very large particles, those that can be separated using sieve trays.Ĭentrifugal collectors will normally collect particles down to about 20 μm. Particle size distribution can greatly affect the efficiency of any collection device. Significance in the collection of particulate matter It affects the reactivity of solids participating in chemical reactions, and needs to be tightly controlled in many industrial products such as the manufacture of printer toner, cosmetics, and pharmaceutical products. It affects the strength and load-bearing properties of rocks and soils. The PSD of a material can be important in understanding its physical and chemical properties. A log-normal distribution of coal-fired fly ash. particles into the PSD that is then called a grain size distribution. Significant energy is usually required to disintegrate soil, etc. In granulometry, the particle-size distribution ( PSD) of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amount, typically by mass, of particles present according to size. ![]()
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