Efficient thermal separation processes
Thermal separation processes such as rectification, distillation, absorption, desorption and extraction are central unit operations in chemical process industries. The vapor-liquid separation processes are very energy-intensive, since they involve multiple sequences of evaporation and condensation. Approximately 3 % of the world’s energy is consumed by thermal separation processes, while 40 % of the energy in process industries itself is used by distillation and rectification processes. Since the energy consumption scales linearly with the column capacity, it can reach up to 10 to 100 MW for industrial separation processes.
The energy- and resource-intensive thermal separation processes demand innovative optimization approaches to intensify the contact between involved fluidic phases, such as enhancement of turbulence in each phase as well as increase in interfacial area, to favor mass and heat transfer processes. Besides, effective vapor-liquid separation is crucial for reduction of auxiliary equipments needed to compensate for process design uncertainties. Any carry-over of droplets in the vapor phase (called entrainment) should be eliminated, as far as possible, to achieve the desired product specifications.
Experimental and theoretical investigations concerning fundamental transport phenomena on separation internals are essential for better understanding of thermal fluid separation. For example, column trays are subjected to fluid dynamics analyses for improved design and operation.
The ongoing research on separation processes comprises of following investigations:
Fluid dynamics and mass transfer in sandwich packings
Within the scope of the DFG-funded project, the fluid dynamic behavior of sandwich packings is comprehensively studied at HZDR. For this purpose, experimental studies are carried out in a 100 mm diameter column operated with water and air in the counter-current mode. The ultrafast X-ray tomography permits noninvasive imaging of the complex and highly dynamic flow patterns inside the packing.
Droplet formation and reduction in thermal separation devices
Droplet formation at specific positions in separation columns and the entrained by the vapor phase drastically reduce the separation capacity of columns. Core of the investigations at HZDR within the joint project ‘TERESA’ is the characterization of flow regimes and evolving droplet spectra in feed pipes with flash evaporation.
Fluid dynamics and separation efficiency of column trays
Flow and mixing patterns are studied at high spatial and temporal resolution via advanced measurement and imaging techniques in tray columns. A column fitted with sieve trays and a wire-mesh sensor is installed and hydraulic data are utilized to develop new modeling methodologies to quantify the tray separation efficiency.
Tools and Methods for Designing High Performance Trays
Within the framework of a collaborative iGF-project with TU Munich and Ruhr-Universität Bochum extensive experimentation and theoretical modelling of the two-phase flow on high performance trays is carried out. The HZDR is in charge of developing advanced measurement techniques as well as new approaches for large-scale CFD simulations.