Technologies of Heat and Mass Transfer

Funded by: DFG/AiF–Cluster (CV) 6
Project Management: Research Association of the German Food Industry
Project ID: DFG 40 806 2554
Time: 2018 – 2021

Undesired foam formation is a serious matter in today’s industrial production of food and beverages as well as in the field of CO2 post-combustion capture technologies due to the direct consequences of impairment in production or even production down-times.

In distillation columns, for example, foam formation results in increased pressure drops and a reduction in the operational and separating capacity. Until now, high safety loadings, complex trial-and-error processes and the usage of antifoaming agents are the only measures to control these negative impacts.

The DFG/AiF research cluster aims at the development of an interdisciplinary approach to prevent, inhibit and destroy foams in industrial processes using exclusively physical methods. Within this framework, the following subprojects are carried out at our institute.

Subproject 4“Design of processes and apparatuses for the evaporation of foaming fluid-systems”
Subproject 4 focusses on the foam formation under boiling conditions. A mini plant thermosiphon reboiler is taken into operation to evaluate different foam management strategies such as the introduction of ultrasound or the incorporation of hiTRAN elements. Furthermore, the variation of operational parameters such as heat flux and liquid levels are examined.

Contact: Laura Strodtmann M. Sc.

Subproject 7“Development of a strategy to control the formation of undesirable foam in the chemical and food processing industry”
Subproject 7 aims at the evaluation of foam formation in distillation columns, for instance, thermal desorption units. In comparison to subproject 4, the operation of a pilot plant enables the additional examination of foam characteristics in a glass column used for thermal separation. Furthermore, the findings of subproject 4 are used to compare the Scale-Up from the mini plant (subproject 4) to the pilot plant in subproject 7.

Contact: Rolf Staud M. Sc.

Rising film evaporators are characterized by the flow direction of the feed. In this case the feed is pumped from the bottom towards the top of an evaporation pipe. During this process a part of the feed changes its state from liquid to vapour and an annulus flow is formed. In the center of the pipe the exhaust vapour flows at high velocity towards the upper part of the pipe. On the wall the annulus thin film is driven by the power of the upwards stream against gravity. In rising film evaporators due to the high vapour velocities the danger of droplet entrainments is increased. Therefor suitable entrainment protections must be installed. At the same time high vapour rates are required to let the film rise. Advantageous single pass of the fluid, the simple design and short resident times.

At the institute a stainless steel rising film evaporator in pilot-plant scale is installed. The evaporation pipe has the dimensions of 2500 mm x 30 mm x 2 mm. The Feed and the concentrate glass vessels possess a double shell. Further the connection pipes are electric heatable. This result in the possibility of evaporate liquids near its solid state. On the heating side different fluids can be used to hit the preferable heating parameters. On the one hand a thermodynamic analysis due to the evaluation of the measurement points is possible. On the other hand a high velocity camera allow to observe the droplet entrainment at the inlet of the liquid/vapour separator.

Funded by: AIF/ZIM
Project ID: KF2614405ST4
Time: 01.03.2015 - 28.02.2017

Within this project, diverse image analysis methods are combined with a new measurement technique to investigate the properties of falling films. It focuses on the evaporation of highly viscous and particle loaded liquids. The use of the new method of film analysis in combination with a thorough investigation of heat transfer enables optimizing of the design of falling film evaporators for problematic liquids. Thus, heat transfer can be improved with optimized internal flows. Hence, equipment costs are reduced. Moreover, electrical energy is saved through a decreased pump duty.

Chemical reactions do not yield the desired product alone, but also a variety of byproducts and unreacted educts. Hence, separation processes are of great importance in the process industry. Particularly the distillation is of importance and the most frequently used technique for the separation of mixtures.
The separation performance of distillation columns and the fluid dynamics within the apparatus are strongly influenced by the physical properties of the substances, which are processed. However, for high viscous liquids no data is available in open literature and up to now no standardized test systems existed to investigate the influence of viscosity. Therefore, such a mixture was chosen and characterized. Using this mixture, experiments were carried out at a wide range of operating conditions. Then, the determined effects are quantified and modelled.
To achieve an understanding of the effects inside the apparatus and their interdependencies, not only distillation experiments in the miniplant scale are carried out, but also optical methods are used to investigate the fluid dynamics of liquid on structured surfaces.
The aim is to improve models and thereby allow a design of columns even for high viscosities and unusual operational conditions.

Thermosiphon reboilers (TSR) are widely used as reboilers in the chemical and petrochemical industry. The main reasons are the low investment and operating costs. Heat transfer and fluid dynamics are strongly linked in thermosiphon reboilers. Therefore, the operation range of these evaporators is limited. To expand the operation range a TSR with pillow plates is investigated at the ICTV. Furthermore, the research objective is the development of short-cut design equations.

Funded by: Federal Ministry for Economic Affairs and Energy (BMWi)
Project Management: PTJ Jülich
Project ID: 03ET1395I
Time: 01.11.2016 - 31.10.2019

The BMWi-Joint-Project aims at the improvement of energy and resource efficiency of fluidic separation processes due to the reduction of droplet entrainment in vapour/liquid counter current processes.
An insufficient phase separation and droplet entrainment significantly influences the efficiency of thermal and fluidic separation processes. Within TERESA all relevant intersection points of a separation column, a) the feed pipe up to column entrance, b) entrance zone within the column, c) column head and d) the column sump or the vapour separator after a flash evaporator will be considered.

Workpackage 4.3 “Experimental investigation of column sump/flash evaporator“
Part of the ICTV is to investigate the influence of different materials, instruments and varied operating conditions on droplet formation and entrainment. The results will be expressed by dimensionless numbers which will help to develop new flow maps depending on droplet diameter and/or droplet distribution beside default parameters like flow velocity and phase fraction. These advanced flow maps will be used to estimate optimal operating conditions, without droplet entrainment, for given separators.

Workpackage 1 „Communication and dissemination“
The ICTV is responsible for the technical and scientific communication in the cooperative project.

Contact: Dr.-Ing. Katharina Jasch

Thin-film evaporators are very important for the evaporation and distillation of problematic substances and systems. On the one hand these are thermally sensitive media like they occur in the food production or pharmaceutical industry. On the other hand it is about the handling of recycling streams, which are often highly viscous, solids-containing, fouling or foaming. Especially if falling film evaporators can no longer be operated with the product, thin-film evaporators are indispensable. Due to the number of variable operating and equipment parameters thin-film evaporators can be optimized to the application and properties of the respective product. However, this flexibility has the disadvantage that the influencing parameters currently cannot be described completely. There is no generally accepted and safe calculation basis for designing or scale-up of thin-film evaporators.

Therefore this investigations at the ICTV aim for the thermal and fluid dynamic characterization of thin-film evaporators to give a calculation basis for designing and scale-up. Experiments are carried out at a steam-heated thin-film evaporator with stainless steel. By means of constructive measures it is possible to operate the apparatus as short-path evaporator or even as reactor.

Contact: Stefan Jahnke M. Sc.

Thermosiphon reboilers have been established themselves for evaporation aqueous solution and as bottom heating units for rectification columns in chemical industry. They are characterized by a high heat transfer rate, low investment and operation costs as well as simple cleaning and maintenance. Their circulation is induced by themselves due to the density difference between the single-phase inlet and the vapor-liquid-mixture at the outlet. Because of the coupling of heat transfer and fluid dynamics, the operating range of this reboiler type is limited. A description of operating behaviors of this apparatus is difficult, especially at its operating limits. The operating range of thermosiphon reboilers can be enlarged by the use of insert, so that they can be stably operated at low absolute pressures and small driving temperature differences between heat side and product side. The actual research activity is focused on the stable operating range of thermosiphon reboilers with inserts and its thermal and fluid dynamical operating behavior under low operating pressure, small driving temperature difference as well as for viscous working liquids.

Contact: Yan Lu M. Sc.