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2017

December 2017 - Flooding in DN15 stirred-pulsed extraction column
 

In extraction columns, breakdown of the counter-current flow resulting from too high flow rates or an excessive energy input is called flooding. In the DN15 extraction column, flooding is visually detected. During normal operation, the stirred cells in the column are filled with many small droplets (yellow dyed organic phase), which are surrounded by the continuous phase. However, when the flooding point is reached, intense coalescence of the droplets at the column wall and column internals occurs. Consequently, the droplets form a second continuous phase, which leads to plugging of the column.

Contact: Sebastian Soboll

Corresponding publication: S. Soboll, I. Hagemann, N. Kockmann. Performance of Laboratory-Scale Stirred-Pulsed Extraction Columns with Different Diameters. Chem. Ing. Tech., 2017, 89, 1611-1618.

bdm_12_2017_fluten

November 2017 - Gas-liquid mass transfer and selectivity in coiled capillaries

Gas-liquid mass transfer can be enhanced by employing helically coiled capillaries, which induce Dean vortices and improve radial mixing. A colorimetric method based on the consecutive oxidation of leuco-indigo carmine was utilized to investigate mass transfer and chemical selectivity in straight and coiled capillaries with high temporal and spatial resolution. Significant differences in concentration distributions were observed as a result of different flow characteristics. Coiled capillaries provided higher conversion, but lower selectivity towards the intermediate product compared to straight capillaries.

Contact: Waldemar Krieger

Corresponding publication: W. Krieger, J. Lamsfuß, W. Zhang, N. Kockmann. Local Mass Transfer Phenomena and Chemical Selectivity of Gas-Liquid Reactions in Capillaries. Chem. Eng. Technol.  2017, vol. 40 (11), p. 2134-2143

bdm_11_2017_cfi_selectivity2

October 2017 - Size dispersion effects in plug flow crystallization

Continuous processing of fine chemicals is in recent discussion. Suitable equipment concepts are required to transfer common unit operations, such as crystallization, from batch to continuous mode. A tubular cooling crystallizer was developed by our group based on the coiled flow inverter (CFI) design with a horizontal configuration of the coils. Depending on the tube geometry, the flow rate, the particle size and physical properties, a homogeneous suspension flow and a moving sediment flow regime can be observed.

The seeded cooling crystallization of l-alanine/water was carried out in the stirred batch vessel, and in both flow regimes in the tubular crystallizer. While the product crystal size distribution (CSD) is mainly determined by growth and growth rate dispersion (GRD), further size dispersion due to a significant particle residence time distribution (RTDS) of can be observed in the moving sediment flow regime. The CSD resulting from the homogeneous flow regime indicates a RTDS close to ideal plug flow.

The study comprises experimental work and population balance equation modeling, whereas growth and growth rate dispersion kinetics were estimated from the batch data and were transferred to the flow scenarios to avoid an over-fitting of the model.

Contact: Norbert Kockmann

Corresponding publication: L. Hohmann, T. Greinert, M. Matuschek, K. Wohlgemuth, N. Kockmann, Suspension Flow Characteristics, Solid Phase Axial Dispersion, and Product Size Distribution in a Continuous Tubular Crystallizer, ProcessNet Jahrestreffen Mechanische Flüssigkeitsabtrennung und Kristallisation, Cologne, 2017

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September 2017 - Turbulent gas-liquid dispersion behind micronozzles

Micronozzles can be employed for the refinement of gas-liquid flow. Increased interfacial area is generated in turbulent conditions, hence, mass transport limitations are reduced. Various bubble breakup mechanisms have been identified in this study. From top to bottom: Laminar bubble breakup results into two daughter bubbles (top) or satellite bubble are sheared off at the tail of the mother bubble. Often daughter bubble size distribution are of bimodal shape and rather large daughter bubble diameters are obtained. In turbulent breakup mean daughter bubble diameter is shifted to smaller values, thus, phase boundary area is increased. Daughter bubble size distribution feature a unimodal shape. For high void fractions φ bubble coalescence is observed within the micronozzle and annular flow is observed downstream. Further increase in volumetric flow rate, results into disturbed annular flow with turbulent eddies being clearly visible (bottom).

Contact: Felix Reichmann

Corresponding publication: F. Reichmann, M. Koch, N. Kockmann, Investigation of Bubble Breakup in Laminar, Transient, and Turbulent Regime Behind Micronozzles, Proc. 15th ICNMM 2017, Cambridge MA, USA.

bdm_09_2017_turbulent-dispersion

August 2017 - Modular CFI

The lower left image represents the required elements of the modular CFI. Assembling steps of the elements in order to fabricate a complete modular CFI setup in a frame-wise configuration are shown in top position. In step 1 all the elements of a single frame-wise CFI are represented. In step 2 the screws are inserted to the 90° connectors. Afterward, until step 6 the coil tube diameters are fixed to the 90° connectors to assemble a frame-wise CFI configuration by screwing. Please note that the zigzag CFI configuration can also be assembled by using the same 90° connectors. A plate (PVC, 200 × 200 × 20 mm) is used to insert the frames of the modular CFI by using stainless steel threaded rods (Lrod = 250 mm; drod = 8 mm) maintaining a stable structure.

Contact: Norbert Kockmann

Corresponding publication: S. K. Kurt, M. Akhtar, K. D. P. Nigam, N. Kockmann. Gas-Liquid-Solid Flow Profile and Reactive Particle Precipitation in a Modular Coiled Flow Inverter. Ind. Eng. Chem. & Res., early view, 2017, DOI: 10.1021/acs.iecr.7b02240.

bdm_08_2017_modular-cfi

July 2017 - CFI with Taylor-Dean flow

For straight tube, Taylor vortices are symmetrically represented with respect to the tube centerline at the longitudinal view. By coiling the straight tube on an axis forming a helically coiled tube (HCT), enhanced mixing can be achieved inside the liquid slug due to the centrifugal force (FC) acting perpendicular to the flow direction. The black points indicate the stagnant points inside the Dean vortices at the first coil of the CFI. At the second coil, the green points indicate the centers of the perturbed Taylor vortices (cf. at the first coil with the red points). After the 90° bend (at the second coil) the black points are perturbed by the centrifugal force, which has changed its direction by bending. New Dean vortices (solid line) are generated perpendicular to the previous vortices (dashed line). The perturbation of these points is also achieved by changing the flow direction with another 90° bend along the CFI. Therefore, CFI can provide an enhanced radial mixing, that is, narrow residence time distribution in comparison to a HCT and straight tube with a G−L slug flow pattern.

Contact: Norbert Kockmann

Corresponding publication: S. K. Kurt, M. Akhtar, K. D. P. Nigam, N. Kockmann. Gas-Liquid-Solid Flow Profile and Reactive Particle Precipitation in a Modular Coiled Flow Inverter. Ind. Eng. Chem. & Res., early view, 2017, DOI: 10.1021/acs.iecr.7b02240.

bdm_07_2017_cfi-two-phase

June 2017 - Particle precipitation in Coiled Flow Inverter

Continuous precipitation of calcium carbonate (CaCO3) was investigated for modular CFI made of polyvinyl chloride (PVC) tubes (di = 3.2 mm) with slug flow patterns. CaCO3 was continuously precipitated along CFI with a conversion of ca. 90%. CFI provided a narrower particle size distribution with median particle diameters around 28 μm and more uniform morphology in comparison to a batch reactor.

Contact: Norbert Kockmann

Corresponding publication: S. K. Kurt, M. Akhtar, K. D. P. Nigam, N. Kockmann. Gas-Liquid-Solid Flow Profile and Reactive Particle Precipitation in a Modular Coiled Flow Inverter. Ind. Eng. Chem. & Res., early view, 2017, DOI: 10.1021/acs.iecr.7b02240.

bdm_06_2017_cfi-particle

May 2017 - Residence time distribution measurement in DN15 stirred-pulsed extraction column

Axial backmixing is an important issue in extraction columns, since it significantly reduces the extraction performance. To investigate axial backmixing in the DN15 stirred-pulsed column, residence time distributions of the continuous (aqueous) phase were measured with potassium chloride as tracer, whose concentration was detected via electrical conductivity. Suitable conductivity electrodes were manufactured in the TU Dortmund workshops.

Contact: Sebastian Soboll

Corresponding publication: S. Soboll, N. Kockmann. Effect of the pulsation pattern in pulsed-stirred extraction columns. ProcessNet Jahrestreffen Extraktion, Weimar, Germany, 2016.

bdm_05_2017_rtd

April 2017 - Optical method for local mass transfer studies

Gas-liquid mass transfer plays an important role in chemical industry and still demands comprehensive research. This picture depicts a non-invasive measurement technique to study local concentration profiles and selectivity in capillaries. It is based on the consecutive air oxidation of leuco-indigo carmine which exhibits two color changes during the reaction (yellow-red-blue). After processing the original image, information from the different color channels is utilized to determine the concentration distributions of each indigo carmine species.

Contact: Waldemar Krieger

Corresponding publication: W. Krieger, S.K. Kurt, F. Warnebold, E. Bayraktar, O. Mierka, S. Turek, N. Kockmann. Gas-Liquid Mass Transfer and Chemical Reactions in Helical Capillary Flow Reactors with Alternating Bends. ProcessNet Jahrestreffen Mikroverfahrenstechnik, Frankfurt, Germany, 2017. 

bdm_04_local-concentration

March 2017 - DN32 stirred-pulsed extraction column

This figure illustrates the operational window (left) of the DN32 stirred-pulsed extraction column (right), which is currently investigated in our lab. By varying stirrer speed and pulsation intensity, high extraction performance is achieved over a broad loading range. Compared to a conventional Kühni column of the same size [1], the stirred-pulsed column shows a significantly higher extraction performance at equal loadings.

[1] P. Kolb, PhD thesis, TU Kaiserslautern, 2004

Contact: Sebastian Soboll

Corresponding publication: S. Soboll, N. Kockmann. Scale-up of miniaturized stirred-pulsed extraction columns. ProcessNet Jahrestreffen Extraktion, Cologne, Germany, 2017.

bdm_03_2017

February 2017 - Modularization in the process industry

Modularization in the process industry is widely discussed when focusing on an accelerated time-to-market and reduced engineering effort. Information handling throughout the whole process and plant life cycle paves this way. Starting from the block flow diagram (BD) of a process, a ‘block representation frame’ can successively be filled with all related information. ‘Selection and configuration tools’ lead to a systematic selection/configuration of suitable designs while accessing ‘module databases’ of existing designs. This information handling approach can be applied regardless of the scope of modularization, e.g. on unit operations, plant sections, or plants and independent from the application levels from laboratory to production/operation. This research results from a collaboration with Laboratory of Plant and Process Design.

Contact: Norbert Kockmann

Corresponding publication: L. Hohmann, K. Kössl, N. Kockmann, G. Schembecker, C. Bramsiepe. Modules in process industry - A life cycle definition. Chem. Eng. Proc., 2017, vol. 111, p. 115-126.

bdm_02_2017_modul

January 2017 - Continuous reaction calorimetry in microreactors

The reaction calorimeter based on 6 Seebeck elements (TEG) allows for space and time resolved heat flux measurement within a microreactor. Kinetic and thermodynamic data such as the heat of reaction can be obtained. Additionally, reactor surface temperature is obtained with an IR-camera. The diagram shows the local heat flux profile and temperature profile across the reactor for the highly exothermic oxidation of sodium thiosulfate with hydrogen peroxide (ΔhR= -556.7 kJ/mol).

Contact: Felix Reichmann

Corresponding publication: F. Reichmann, S. Millhoff, N. Kockmann. Continuous Reaction Calorimetry in Microreactors for Highly Exothermic Reactions Using Seebeck Elements. ProcessNet Jahrestreffen Reaktionstechnik, Würzburg, Germany, 2017.

bdm_01_2017_calori



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Photo of Prof. Dr.-Ing. Norbert Kockmann

Prof. Dr.-Ing. Norbert Kockmann

Telephone: 0231 755-8077
Fax: 0231 755-8084

Address:

Technische Universit├Ąt Dortmund
Fakult├Ąt Bio- und Chemieingenieurwesen
Arbeitsgruppe ApparateDesign
Geschossbau 3

Room 511