White Paper Sieve Analysis - Different methods for a variety of applications
The determination and knowledge of the particle size distribution is an essential part of the quality control process for industrial products. From incoming and production control to research and development sieve analyses are used to determine a number of parameters or simply the particle size. Easy handling, low investment cost and high accuracy make sieve analysis one of the most frequently used procedures for measuring the particle size. This white paper gives an overview of the different sieving techniques and describes the necessary steps to ensure reliable results.
White Paper: Ultrafine Grinding with Laboratory Ball Mills
How are nano particles produced? The “Bottom-Up” method synthesizes particles from atoms or molecules. The “Top-Down” method involves reducing the size of larger particles to nanoscale, for example with laboratory mills. Due to their significantly enlarged surface in relation to the volume, small particles are drawn to each other by their electrostatic charges. Nano particles are produced by colloidal grinding which involves dispersion of the particles in liquid to neutralize the surface charges. Both water and alcohol can be used as dispersion medium, depending on the sample material. Factors such as energy input and size reduction principle make ball mills the best choice for the production of nanoparticles.
Anche se la macinazione viene svolta in condizioni ideali, gli stress meccanici che il campione esercita sulla superficie degli strumenti di macinazione può causare abrasione. Tuttavia, selezionando un mulino e degli accessori adatti è possibile minimizzare questo effetto. Se il campione deve essere macinato a pezzature inferiori ai 100 microns, le forti forze meccaniche richieste aumentano l’abrasione.
I mulini a taglienti vengono utilizzati in diverse aree della preparazione dl campione alle analisi successive. Tipiche applicazioni includono la riduzione di combustibili da rifiuto, la macinazione di campioni di biomasse per ricerche nell’ambito delle energie rinnovabili, il controllo dei prodotti nell’abito delle normative RoHS and WEEE, o nel recupero dei materiali preziosi – la varietà di campione è notevole.
Por lo general se asocia a la noción "fragmentación", el machacamiento, de sustancias sólidas mediante fuerza mecánica. Pero también la división de líquidos en gotas o de gases en bollas representa un proceso de fragmentación.
Los más precisos resultados de trituración en el más breve tiempo se consiguen con los nuevos molinos planetarios de bolas, de Retsch. Con el PM100 y el PM200, Retsch presenta una nueva generación de molinos planetarios de bolas con uno o dos unidades de trituración, que establecen nuevos estándares de rendimiento en este segmento de la producción.
El nuevo molino ultracentrífugo ZM 200 de RETSCH es un molino de rotor no sólo extremadamente rápido y cuidadoso con el material molido, sino también de uso universal gracias a su amplia gama de accesorios.
Nanoteilchen, d.h. Partikel mit einem Durchmesser von weniger als 100 Nanometer, werden seit vielen Jahren von Wissenschaftlern erforscht. Zum einen lassen sie sich im „Bottom-up“ Verfahren aus Atomen oder Molekülen synthetisieren. Im “Top-Down“ Verfahren hingegen werden größere Partikel, z.B. mit Hilfe von Labormühlen, zerkleinert. Kleine Partikel weisen durch das extrem vergrößerte Verhältnis von Oberfläche zu Volumen erhöhte Oberflächenladungen auf, so dass die Partikel elektrostatisch zueinander gezogen werden. Daher können Nanopartikel nur durch Nassvermahlung (Kolloidvermahlung) erzeugt werden.
Representative sampling of large sample volumes is an integral part of the physical and chemical analysis of bulk goods and has a decisive influence on the quality of the results. Extraction of a sample from the bulk is not always carried out in a way to ensure representativeness. This is a widespread flaw in the quality control process with a negative impact on the subsequent analysis results. Therefore, more attention should be paid to the correct sampling procedure. Sample division is often considered as a labor-intensive process which not always leads to representative results. RETSCH provides some convenient solutions which help to improve working conditions and thereby the quality of the sampling process.
A typical laboratory sample of coal often consists of 10 kg or more. Depending on the type of coal, each sample piece may have dimensions of 150 mm x 70 mm x 70 mm or even more. When dealing with rather inhomogeneous materials like lignite it is not sufficient to take one of the big lumps and crush it to obtain a few grams which can then be used for analytical processes such as the determination of the calorific value or sulfur content. One piece of coal taken randomly from the laboratory sample will never entirely represent the original sample; using such a sample for analysis will therefore lead to unreliable results which cannot be reproduced.
The XRD-Mill McCrone preserves the crystal lattice structure of the sample -
With resources becoming increasingly scarce, innovative technologies allowing for sustainable use of raw materials are much sought after. The mineralogist Dr. Robert Moeckel is researching mineral and metallic raw materials at the Helmholtz-Institute for Technology of Resources in Freiburg, Germany. Dr. Moeckel´s research projects involve pulverization and homogenization of mineral samples prior to x-ray diffraction (XRD) analysis.
The biggest challenge when developing a high energy ball mill is controlling the temperature. The very high energy produced by ball milling leads to an extreme heat increase inside the grinding jars. RETSCH solved this problem by creating an innovative integrated water-cooling system. Grinding breaks for cooling, which are unavoidable in conventional ball mills even after only 30 minutes grinding at moderate speed, are usually not necessary when using the High Energy Ball Mill Emax.
Re-using raw materials is an important factor in powder metallurgical
processes. RETSCH offers a range of instruments which are suitable for
sieving powders and pulverizing metal parts both of which are
re-introduced into the production process.
The most common types of coal (lignite, bituminous and anthracite) are distinguished by their different chemical and physical properties. The calorific value of coal can be determined by analyzing its carbon content, for example with combustion analyzers. In addition, efficient management of the desulfurization plant requires control of the sulfur content. Compared to the large amount of coal a typical laboratory sample consists of - a 10 liter bucket or even more - the sample volume required for analysis is fairly low, only approx. 1 g. The standard DIN 51701 defines the sample amount to be tested as this relates to the particle size: The bigger the particles are, the more sample material is required.
The Emax is an entirely new type of ball mill which was specifically designed by RETSCH for high energy milling. The impressive speed of 2,000 min-1, so far unrivaled in a ball mill, in combination with the special grinding jar design generates a vast amount of size reduction energy. The unique combination of impact, friction and circulating grinding jar movement results in ultrafine particle sizes in the shortest amount of time. Thanks to the new liquid cooling system, excess thermal energy is quickly discharged preventing both sample and mill from overheating, even after long grinding times.
A faultless and comparable analysis is closely linked to an accurate sample handling. Only a sample representative of the initial material can provide meaningful analysis results. Rotating dividers and rotary tube dividers are an important means to ensure the representativeness of a sample and thus the reproducibility of the analysis. Correct sample handling consequently minimizes the probability of a production stop due to incorrect analysis results. Thus correct sample handling is the key to effective quality control.
The SM 300 excels especially in the tough jobs where other cutting mills fail. It has a freely selectable speed range from 700 to 3,000 rpm with high torque. The mill is convenient to operate and easy to clean. Reliable and extremely efficient sample preparation in the laboratory is now guaranteed with the SM 300.
The following situation is typical for many production plants: After a routine quality check, the production process is stopped or an already produced batch is suspended, because the analysis results were not within the relevant critical values. But does the tested product really deviate from the specifications? The quality control managers are convinced of this because modern analysis instruments provide results with very low tolerances. The sample in question was tested several times and the result was confirmed. The question is why the product does not match the specifications although the production parameters have not been changed in any way. The possibility that the tested product is indeed deficient cannot be excluded. However, it is often not the product itself which causes irregular analysis results but a lack of understanding of the steps which come before the analysis.
Particle analysis of large quantities of bulk goods is usually done by vibratory sieving. In most vibratory sieve shakers in the market the sieve stack is mounted on springs which oscillate vertically. However, to evenly distribute the material over the entire sieve surface, the so called 3D vibratory sieving as it is used in the AS 450 control is the most suitable method. This is characterized by a circular motion superimposing the vertical throwing motion so that the sample material is moved over the whole sieve.
Particle size analysis and particle size distribution are important criteria for the quality control of bulk materials. In a running production process, the results of a quality check must be available quickly to allow for immediate adjustment of the production parameters. Depending on the expected particle size and sample volume, different sieving methods and sieving machines are suitable for analysis. The method used for particle size analysis is primarily determined by the fineness of the material to be sieved. For dry sieving of samples with particle sizes below 40 microns, air jet sieving is the method of choice.
Efficient separation - Regional Office for Geology & Mining, Germany