»
»
»
»
Energy Transition
Figure 2: Kelvion tubular heat recovery unit. Figure 3: Kelvion’ s Rekuluvo / Rekugavo heat recovery solution. is a perfect solution for exchanging heat between two‘ close-to-atmospheric’ gases. The construction provides a countercurrent flow which enables close temperature approaches and high thermal efficiencies. Compared with other technologies, such as the tubular type described above, it is much more compact and lighter weight. However, both types are sufficiently accessible for cleaning.
Air-cooled heat exchangers using Groovy and Diesta In both the regenerator column condenser and in the lean amine cooler, large amounts of heat must be dissipated. An often selected heat exchanger type in these positions is the air cooled heat exchanger( ACHE). The outside of the tube is provided with thin aluminum fins to enlarge the area which is in contact with the ambient air as much as possible. Although the air is moved through the tube bundle by the use of big electrical motor drive fans, the heat transfer coefficient on the air-side remains low. To improve the heat transfer coefficient on the air-side, Kelvion introduced the Groovy fin( see picture 4), almost two decades ago. Instead of normal flat fins, the fin is provided with three waves, or‘ grooves’. When the air passes the tube, the groove causes the air to bend a bit behind the tube as well, which significantly improves the heat transfer. Of course, at the same air velocity, this groove gives a slightly higher pressure drop. Therefore, it is fair to make a comparison at equal fan power. And
it turns out that at equal fan power, the Groovy Fin provides up to 20 % higher heat transfer coefficient. More than 5,000 bundles with Groovy fins have been installed worldwide in various processes. There can also be a significant heat transfer resistance on the inside of the tube, which happens with fluids that have an elevated viscosity. This is exactly the case in the lean amine cooler, where the viscosity gets even higher because of the cooling. To overcome this, Kelvion introduced the DIESTA tube which an acronym that stands for Double Internally and Externally Structured Tube for Air fin coolers. For both Groovy Fins and DIESTA, a special HTRI plug-in( dll file) has been developed which can be obtained on request from Kelvion. It is obvious that when the heat transfer coefficients in the air-cooled heat exchangers get higher, the required heat transfer area will be lower. Hence, a smaller heat exchanger can be used. In fact, selecting Groovy or DIESTA will lead to a 10-20 % smaller installation which reduces costs in the foundation, steel structure and installation plot.
Regeneration reboiler When licensors are marketing their amine technology, they often mention the energy per tonne of captured CO 2
. Most of this heat is used inside the regenerator reboiler. As an average number, 2.3 GJ per tonne CO 2 is used as heat in the reboiler [ 2 ]. Using this number, a project that aims to capture 8 MTPA of CO 2 requires a reboiler of 580 MW.
Figure 4: Kelvion’ s Groovy finned tube for air cooled heat exchanger.
Figure 5: Kelvion’ s DIESTA tube for air cooled heat exchanger. www. heat-exchanger-world. com Heat Exchanger World April 2025
25