Separation Processes

Laboratory of Separation Processes was established under the Heat Transfer and Fluid Flow Laboratory within the framework of the NETME Center project in 2012. The research of this lab focuses on environmental chemical engineering processes including membrane separations (air/liquid filtration, membrane contactors, hollow-fiber membranes and filtration materials testing), absorption processes (separation of gaseous pollutants using wet scrubber), adsorption and water treatment. This also includes numerical simulations (CFD) and computational analysis based on theoretical models (e.g. predicting the filtration efficiency and pressure drop of air filtration materials). The research further includes preparation and characterization of filtration membranes based on geopolymers and alkali-activated secondary materials (fly ash and blast-furnace slag), preparation and characterization of ultrafine powder materials. Last it is health risk assessment of air, water and soil pollution. This includes risk analysis of airborne particulate matter and bounded harmful substances such as heavy metals, polycyclic aromatic hydrocarbons etc. For further information, refer to our publications.

Gas-liquid absorption processes to remove gaseous contaminants from air are crucial in many industrial facilities and are basic means for air pollution mitigation associated with large-scale industrial operations. To ensure a reduction of gaseous (also solid particles) pollutants released from such processes, a lot of industrial operations have adopted a gas scrubbing system as a post-treatment of produced polluted gases. However, such a system is very difficult to optimize to ensure adequate use of absorption liquids, their regeneration and energy requirements to operate such an equipment. Therefore, it is necessary to know the relationships between gas and liquid phase in the gas scrubber sprinkler head which mostly occurs in highly turbulent conditions. This determines the gas/liquid interface area necessary for absorption of the pollutant into the absorption liquid.

Numerical simulation is a powerful tool for optimization and behavior prediction of the gas scrubbing units. An example below shows possibilities of simulations on a smaller scale unit developed within the framework of a Czech Technology Agency project.

The Quantachrome 3Gzh porometer represents a state-of-the-art device in with exceptional performance in a compact bench-top unit controlled by PC-based software. This model allows the best match between material properties and instrument performance (sensitivity, accuracy and reproducibility) for a wide variety of filtration materials, including non-wovens, textiles, papers, ceramic, sintered metals, hollow fibers etc. The 3Gzh model allows for measuring pore size from 500 µm to 13 nm quickly and reproducibly. It can also perform gas permeability measurement with selectable single pressures and averaged or over a range of pressures.

Determination of particle size distribution has been extensively used to control, monitor and investigate properties of different powder materials including pigments (Al, TiO2), coal, food and beverage powders, pharmaceuticals, fly ash, blast-furnace slag, cement, grinded ion-exchange resins etc. The Malvern Mastersizer 2000 laser diffraction analyzer is used to evaluate particle size distribution of powder materials in the size range of 0.02 µm to 2000 µm. It can be used for both dry and wet samples (suspensions) from milligram quantities (e.g. precious pharmaceuticals) to measurement of bulk materials. The system for sample dispersion, instrument control and measurement is fully automated, thus dramatically reducing the user intervention. The major source of possible inaccuracies and measurement variability is thus removed, obtaining reliable, comparable and high-quality results.

The Olympus BX 41 is a special type of microscope which measures the light passed through the sample. It is suitable for characterization of morphology/size of translucent incompact samples such as granular materials, powders and fibers. Continuous observation over the wide objective magnification from 1.25x to 100x is possible without condenser change.

Spiral jet mill is a device for ultrafine comminution of soft materials (Mohs hardness up to 3) with brittle-crystalline fracture behavior in the size range of 10 to 150 µm. The grinding process is very clean and possibly sterile because the mill has no rotating components. There are consequently no bearings and shaft seals, and thus no lubricants are used.

The feed product is conveyed to the mill using an integrated injector charged with compressed air as well as the tangentially ordered Laval nozzle ring in the milling chamber. Comminution is the result of interparticle collisions caused by the particles flowing at different speeds in the nozzle jet. The spiral flow and a special discharge-area geometry subjects the particles to a classification – only fine particles are discharged, coarse particles remain in the mill. The most common requirements at a maximum feed size of approx. 1.5 mm are end-product fineness values with a d97 ranging between approx. 5 and 30 µm. Dosing capacity is in the range of 150 – 2800 ml/h.

This device (in accordance with the DIN EN 9001 standard) is suitable for analysis of any dry particulate material with a sample weight of 0.3 to 100 g. Material is moved only by air so the powder quality is not affected. The particles are blown upward by an air blade rotating arm (18 rpm) where the agglomerates should be broken when hitting the cover, particles are then sucked using a negative pressure (1500-5500 Pa according to settings) through the loosen sieve openings.

Various sieves are available fulfilling DIN ISO 3310-1 with a mesh size of 20, 45, 63, 90, 125, 200, 500, 1000, 1500 and 2000 µm. Part of the air jet sieve assembly are an L-type industrial vacuum cleaner, Sartorius TE 802 laboratory scales and a GAZ 120 high performance cyclone for almost complete under-sieve fraction collection without any contamination.

The Alpine ATP Turboplex air classifier is ideal for ultra-fine classification of superfine powders. It can produce fines in the range of d97 = 4 µm or finer. The material’s fineness can be controlled by altering the speed of the classifier wheel. Rejected material is discharged at the bottom of the classifier. The mono-bloc design is ideal for processing abrasive materials such as feldspar and quartz.

Thinky ARV-310 mixer is used for mixing of water-like liquids, pastes, powders, mixtures of high and low viscosities. It can also mix adhesives, inks, cosmetics, pharmaceuticals, nano-particles, precious metal fillers etc. Combining vacuum pressure reduction function with rotation and revolution mixing enables efficient elimination of submicron air bubbles. With rotation and revolution movement under vacuum pressure reduction, deaeration of high-viscosity materials, which was considered difficult, can now be performed with excellent quality. The processing time can be further reduced compared to the atmospheric mixer. The maximum weight of the mixed material is 310 g, standard containers are of 300 ml.

Filtration panel was developed for testing the properties of filter media in the form of plane and cylindrical filters and hollow-fiber membranes. It is a device with 4 inter-switchable circuits with flow meter/controller, pressure meter/controller upstream and downstream of the filter (pressure drop) and turbidimeter to measure turbidity of the filtered liquid. All is connected to an Endress+Hauser M RSG40 Memograph data logger. Maximum pressure of the installed air-operated diaphragm pump is 5 bars with a flow rate of 24 l/s. It is possible to simulate filtration of different type of liquid media including wastewaters, oil/water emulsions, beverages etc., using different types of filter media including ceramics, non-wovens, paper filters, polymeric membranes, with different geometries (planar, tubular, hollow fibers).

Gas chromatography (GC) is a basic qualitative and quantitative analytical separation method. The method is based on the separation and analysis of chemical compounds that can be vaporized without decomposition. Typical uses of the GC method include testing of purity of various substances or separating the different compounds from a mixture. Separation of the different compounds from the mixture is carried out between a stationary and mobile phase. Chromatography column is the stationary phase (capillary column) and the mobile phase is a carrier gas. The common carrier gases are hydrogen, nitrogen, helium and argon. There are different types of the stationary phases (capillary columns), e.g. WCOT (wall coated open tubular), SCOT (support coated open tubular) or PLOT (porous layer open tubular). The main difference is in different anchor of the thin layer of the stationary phase on the inner side of the column wall. Type of the column defines the range of the analytes.

The GC8000 Series is equipped with a HS 500 headspace sampler, a split/splitless injector, a flame ionization detector (FID) and a VOCOL capillary column (diphenyl dimethyl polysiloxane with crosslinking moieties). The column is as long as 105 m, with an inner diameter of 0.53 mm and a film thickness of 3 µm). Nitrogen is used as a carrier gas.

The FID detector is suitable for detection of organic carbon compounds due to the ability of the organic carbons to form cations and electrons upon pyrolysis which generates a current between the electrodes. VOCOL capillary column is suitable for analysis of volatile organic compounds. Halogenated hydrocarbons can also be analyzed using this column (chlorethanes). Detection limits of the chromatograph are in µg/l.