CEMTEC - continuous research and development.
Pycnometer and test vessels for determining density

Density

As always mixtures of different components are treated in the area of raw material processing, determination of the apparent density or bulk density is an important parameter for the entire process design and calculation of the material flows. It is used for scientific empirical modelling as well as for analytical calculations. Furthermore, the raw density of an unknown mineral composition can be characterized to a limited degree.

In our laboratory we can determine the
• apparent density and
• bulk density loose and shaken according to various industrial standards and specifications.

The different densities are determined with conventional test instruments and apparatus such as
• liquid pycnometers
• standardized measuring vessels or
• helium pycnometers

Blaine analyser


Surface

Besides particle size analysis, measurement of the specific surface of a sample is the most important dispersion characteristic and is often incorporated for quality testing or quality comparison in production. It is an important parameter in the characterization of porous and powdery solids as well as a clear indicator for the newly created surface when determining the optimum comminution step. That makes measurement of the surface an indispensable part of the product analysis.

We can determine the surface in our laboratory as follows:
• as per Blaine and
• using the BET method

The Blaine measurement is based on the principle of time measurement, which requires a certain volume of air to flow through a definite test amount. The specific surface can be calculated based on the density, device constants, a standardized reference sample and the viscosity of the air. Using the instrument specially developed at CEMTEC, specific surfaces of several 100 to 50,000 Blaine (cm²/g) can be measured.

The surface determination according to the BET method, named after its inventors Brunauer, Emmett and Teller, is based on the property of solids to adsorb gas molecules on their surface. Knowledge of the adsorption therms of the gas (usually nitrogen) enables the number of adsorbent gas molecules to be calculated. Multiplying the number by the space requirement of the molecule, in the case of nitrogen 16,2x10-20 m², yields the sample surface.

Vibrating screens

Grain size analysis

Particle size analysis is necessary for extensive characterization of a product. The result of a particle size analysis is the particle size distribution, from which various characteristic parameters can be calculated. The particle size distribution of a product has a significant effect on the material properties. Depending on the respective particle size, various methods are used at CEMTEC:
• Screening by manual screening, screen tower and air jet screen
• Sedimentation process
• Laser diffraction

The relevant particle size distribution also depends on the measuring principle here. Our experts therefore work out the best analysis method for determining the particle size of the desired product jointly with the customer, so as to ensure an optimum characterization.

Our laboratory allows us to cover the above spectrum for particle size determination. The following equipment is available for this:
• Large number of hand screens (measuring range 45 µm - 72,000 µm)
• Vibrating screen type Retsch / type Fritsch (measuring range 45 µm - 72,000 µm)
• Air jet screen type Hosokawa Alpine (measuring range 20 µm - 250 µm)
• Sedigraph II, type Micrometrics (measuring range 0.10 - 300 µm)
• Mastersizer 2000, type Malvern (measuring range 0.02 - 2,000 µm)

Air jet screen, type Hosokawa Alpine
Mastersizer 2000, type Malvern

Moisture determination

Various methods such as the drying method, Karl Fischer method, infrared absorption (surface moisture) etc. can be used to determine the moisture content. Besides the Karl Fischer method, the drying method is primarily used for determining the moisture of bulk materials in laboratories. This very accurate gravimetric method of drying is also used in our laboratory. Besides the product fineness, the moisture content of the material to be processed is in many cases definitive for selection of the optimum milling plant as well as the design of the various material handling components such as chutes and hoppers.

The moisture content of the supplied samples is determined using the above method with the following instruments:

• Drying cabinet Tmax = 300 °C for sample quantity Mmax = approx. 50 kg
• AND MX 50 moisture analyzer for powdery nonflammable materials Tmax = 200 °C, Mmax = 10 g

To determine the moisture content, we alternatively have the option of determining the percent by weight of volatile components or the ignition loss in the kiln at a maximum temperature of Tmax = 1300 °C.