TERESA

Thermal separation processes contribute significantly to energy and resource consumption in the process industry. This applies, for example, to rectification columns in which the thermal separation of substances takes place in countercurrent flow. In this process, mainly mixtures are separated which, due to their material properties, differ strongly from the extensively investigated water/air systems. The lack of design data for organic material systems is challenging for the design of separation processes and the operation of separation columns and often results in large safety margins and oversized apparatus and plants. There is a need for research regarding

• Separation of droplets to avoid critical operating conditions, product contamination and damage to downstream process units,
• Flash evaporation in the feed line to realize optimal thermal fluid dynamic feed conditions into the column,
• Contacting of vapor and liquid phases by means of separation-effective internals such as structural packings and random packing.

A refrigerant (3M™Novec649™) cycle is operated in the TERESA test plant. The pressurized and heated refrigerant is flash evaporated through a valve (forced circulation flash evaporation, CUEV). The generated two-phase flow enters a column (test separator, 300 mm and 500 mm diameter at 2.25 m and 1.15 m height) via a feed line (4 m length, 200 mm diameter). The vapor drawn off at the head of the test separator is liquefied in a condenser, then combined with the liquid phase from the sump of the test separator and subsequently subcooled. By means of an electric heater (240 kW) and circulation pump (throughputs up to 9500 kg/h), the refrigerant is conditioned for flash evaporation and circulated in the circuit.

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The two-phase flow can thereby be adjusted by varying the mass flow rate and vapor fraction at variable operating conditions upstream (up to 25 bar and 180°C) and downstream (up to 11.5 bar and 143°C) of the flash valve. As a result, the material properties of the 3M™Novec649™ refrigerant (IUPAC: 1,1,1,2,2,4,5,5-nonafluoro-4-(trifluoromethyl)pentan-3-one, CAS number: 756-13-8) can be adjusted in ranges that are particularly relevant to thermal separation processes and have been little studied. These include low surface tensions (< 10 mN/m), low viscosities and variable vapor-liquid density differences.

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The automated TERESA facility is extensively instrumented and equipped with special measurement technology (imaging Wire-mesh sensors, Process microscope) to investigate fluid dynamic processes.

Acknowledgement

The experimental facility was designed as part of the BMWi joint project „TERESA“ and was commissioned in 2019. Responsibility for the content lies with the author.