Industry operators typically perform energy-intensive distillation, such as in crude oil refineries so as to separate chemical mixtures into their individual components. Scientists at the Technische Universität Kaiserslautern (TUK) are designing a camera system that tracks this process.
It measures whether a high degree of droplet formation is present, which can negatively impact the separation of components. In the days to come, this technology could take countermeasures every time the applicable measurement data vary—and can also save energy. At the 2018 ACHEMA, the exhibition on process technology in Frankfurt, they will be showcasing the technology at the research stall of the state of Rhineland-Palatinate (Hall 9.2, Stand A86a) from 11 to 15 June.
During distillation, liquids are vaporized and then divided into their constituents following the ensuing condensation of the vapor. A typical example can be taken from the refining of crude oil, where the crude oil is divided into high-boiling heavy oil, petroleum, and diesel, as well as into lower-boiling gasoline or kerosene.
“This common procedure involves a high amount of energy consumption,” says Jonas Schulz, who analyzes this procedure as part of his doctoral studies at the chair of separation science and technology under Professor Dr. Hans-Jörg Bart.
In the US alone, distillation is accountable for half of the energy costs connected with thermal separation processes in the chemical sector. This incurs costs exceeding USD 100 billion annually. The TUK engineers are creating a technology that will enhance energy efficiency in the future. Their method is based on a camera system that screens the process.
“Distillation in the chemical industry takes place in what are known as ‘fractionating columns’,” explains Markus Lichti, who also contributed to the project.
These columns are cylindrical installations that have a series of distillation plates. These can be arranged in several ways, based on the application, including plates with a sieve-like surface.
Separation takes place as part of an on-going process in which vapor is formed at the very beginning by incorporating the corresponding mixture into the middle of the column. It flows downwards through the separate plates and is heated in the lower section of the column. It then rises to the top as vapor. The mixture is repeatedly fed into the system to prevent the reaction from ending.
“In turn, the vapour heats the liquid, which then begins to boil and rise as vapour,” adds Schultz, while illustrating the principle. “It then cools again and collects in liquid form on the next highest plate.”
Consequently, the constituents of the liquid that have a lower boiling point vaporize again and move up to the following distillation plate in the column. This process carries on over several levels, until the liquid with the lowest boiling point has collected on the highest plate.
“Contamination occasionally occurs during distillation, since the liquid does not separate properly into the individual components,” Lichti continues.
This can be caused by a variety of different factors, such as a clearly increased vapor flow, undue pressure, or inadequate liquid in the system. For instance, it is possible for the vapor and liquid to mix on the plate to such an extent that the vapor takes away some of the droplets from the liquid phase. Experts allude to this as entrainment. The droplets move up to the following plate where they stay; in the refining of crude oil, for instance, a little of the heavy oil can accumulate with the diesel, thus altering its chemical properties.
The camera system created by the scientists at Kaiserslautern may offer a solution to this in the coming days. The camera is combined into a probe - a stainless-steel tube - which protects it from the hot vapor. The probe is inserted into the fractionating column via an access slot. This access slot looks like the principle of a drawer in which the probe is secured in place. A glass plate allows the camera to peer into the interior of the column. High-contrast images are facilitated by means of lighting technology kept in another access slot directly opposite.
“Our system is designed in such a manner that these access slots can be positioned at different points of the fractionating column,” Schulz expounds. This enables the process to be inspected from the edge or in the middle, for instance. “Using the images, we can see how large the droplets are and how quickly they form,” the engineer continues. “Our technology allows us to measure parameters that could not be observed before.”
The camera is regulated by a software program that also examines the images and thus spots entrainment. So far, there have not been any studies into how this process takes place precisely. The data acquired offer the researchers understanding, for example, into whether the parameters have to be organized differently for the distillation process.
In the future, the industry could utilize the software as part of an automatic control system that starts countermeasures every time the measurements digress, as well as to save heating energy and lower operating costs. Furthermore, the technology can save material—for instance, if it displays that certain distillation plates are not required or their surface is not adequately fine.
The Kaiserslautern scientists from the Faculty of Mechanical Engineering and Process Technology will showcase their system at the exhibition (Hall 9.2 Stand A86a). Their research forms part of the TERESA project (droplet formation and reduction in material exchange apparatus), sponsored by the Federal Ministry for Economic Affairs and Energy (BMWi). In addition to the scientists of the TUK, the Ruhr-University Bochum, Braunschweig University of Technology and Helmholtz-Zentrum Dresden-Rossendorf are also taking part in the project. The following partners from industry are involved: HZDR Innovation GmbH and industrial companies Envimac Engineering GmbH, Falk & Thomas Engineering GmbH, Linde AG, Munters-Euroform GmbH, DencoHappel GmbH, Raschig GmbH, RVT Process Equipment GmbH as well as Horst Weyer und Partner GmbH.