Lightweight Offshore Condenser Skid

The goal of the project lightweight offshore condenser skid is to reduce the weight of such a skid by up to 50 percent so that it can be light weight enough to install broadly offshore. This project builds upon results from development of new lighter-weight systems for compact offshore steam cycles in KPN COMPACTS. Eight out of ten kilos of CO2 emitted from the platforms come from the gas turbines that provide the platform with power. However, the exhaust contains large amounts of useful heat that is not currently utilized. By hooking up a steam turbine that can produce power from the excess heat, the "combi plant" can produce power from the combustion heat twice. This way the platform's power demand is covered by a lower gas consumption- and with a CO2 release that is 17 to 21 % lower. Bottoming cycles with steam turbines that can be used in this way already exist, but they are too heavy and large to be used on many of the platforms. Only 3 of the platforms on the Norwegian continental shelf have bottoming cycles installed. IPN Condenser Skid has therefore aimed to reduce the weight of the skid (module) that contains the steam turbine and condenser. This skid is part of a bottoming cycle that produces power from the exhaust of offshore gas turbines. The overall design of the bottoming cycle, considering results from IPN Condenser Skid, is managed in the COMPACTS project (#233947). IPN Lightweight Condenser Skid had two sub-objectives, the first of which was to reduce the weight of the seawater-cooled steam condenser by 50%. The weight of the condenser was reduced by investigating novel condenser designs as an alternative to the standard plain shell-and-tube condensers. They were compared in terms of weight, size reduction and performance. By detailed optimization of the internal heat exchanger geometry the size of the condenser was reduced by 21 % for the 16 MW system and by 53% for the 12 MW system. The second sub-objective was to reduce the weight of the condenser skid framework (containing condenser and steam turbine) by 50%. The housing for the skid was previously in steel in the reference system and was designed in Aluminium in this project. IPN Lightweight Condenser Skid has achieved 49% and 4% weight reduction of the condenser skid for a 12 MW system and a 16 MW system, respectively when comparing to a reference system. However for the 16MW system the turbine and generator were not optimized so further weight reductions are likely to be possible. IPN Lightweight Condenser Skid is a collaboration between Marine Aluminium (project owner), SINTEF and several major oil companies and actors in the supplier industry.

Marine Aluminium's main motivation for the proposed R&D project is to produce a lightweight offshore condenser skid. This goes hand in hand with currently ongoing commercial developments of new lighter-weight systems for compact offshore steam cycles. Weight reduction is crucial in order to be able to implement them to existing platforms. The concept is that key components such as condensers will be optimised for weight reduction, making also a lighter weight installation framework possible. A novel condenser design will be evaluated as an alternative to the standard plain shell-and-tube condensers. It will be compared in terms of weight and size reduction and increased performance. The condensation rate will be investigated experimentally. It has the potential of reducing the weight and footprint of the offshore condenser by up to 50%. This will result in a secondary weight reduction in the framework for the condenser and the other components on the crate that contains the condenser, steam cycle and expander. An ultralight-weight framework will be designed in Aluminium for this novel low-footprint condenser skid. The aim is to reduce the the nearly 200 tonnes current condenser skids by 50 %. Our challenge is that this kind of structure has not been produced in Aluminium before, so the need for a good design basis and concept specification is highly needed. The condenser skid can be part of a compact offshore steam cycle to be tested in a subsequent DEMO project. The reduction of weight of offshore equipment is crucial to obtaining an energy efficient oil and gas business. Steam cycles have not been implemented offshore due to large weight and volume. There are potential projects on the NCS right now that would benefit from a successful outcome by reduced weight allowing installation.This will enable more efficient use of energy from oil and gas production on the Norwegian Continental Shelf with a potential 25% reduction in fuel use and CO2 emissions.