CO₂ compressors

Alongside gas and steam turbines as main components, special turbomachinery will also play an important role in air separation and the compression of carbon dioxide in CO₂ capture and storage systems in the low-emission power plant of the future.

The reason for this is that turbomachinery of this type consists of compressors and, in certain cases, turbine drives for these compressors. Two main aspects stand out here:

• New, larger types of compressors and drive steam turbines have to be developed for the large physical quantities of gas that have to be compressed in power plants with CO₂ capture.
• The high energy consumption of CO₂ capture must be reduced in order for this technology to be introduced. Process considerations dictate that turbomachinery will consume the majority of this energy. For this reason, improvement of this equipment to reduce its energy consumption is necessary. 

New axial compressors will have to be developed for initial compression of large amounts of CO₂ at the power plant. Radial compressor units could then be used to transport the CO₂ from the power plant to the storage site. However, even larger systems will be required in the future to deal with the amounts of CO₂ involved. In addition, the efficiency of these systems will have to be increased significantly. Compressors of this type require very high pressures. These pressures can be achieved by a number of radial stages that are fitted around a gearwheel. In this manner, each compressor can be operated in its optimum operating range.

A current project involves the piping of CO₂ from a power plant in North Dakota in the USA to Weyburn, Saskatchewan, Canada, where it is used to increase the extraction pressure in oil fields. Even systems of this scale will not be large enough for the power plants of the future. Instead, they will have to become even bigger and more powerful. This results in new challenges for the development of stages and the rotor dynamics of the overall system.

Systems of this type that are operated on the power plant site and carry out initial compression of CO₂ are driven by steam turbines. Compressors in special pumping stations for CO₂ along the transport pipeline are driven by industrial gas turbines, on the other hand. It must be possible to control both turbine types over a wide performance range depending on the flow situation. This equipment must also be very reliable, as compressor pumping stations can be at very remote locations. For this reason, on-site work by technicians would be expensive. The compressors should therefore have long maintenance intervals.

MAN Diesel & Turbo SE manufactures gas and steam turbines as drive equipment for compressors, for example, and is a member of AG Turbo. Since AG Turbo's joint research work started to concentrate increasingly on CO₂ issues under the COORETEC banner, MAN has been contributing its expertise in the areas of compressors and smaller turbines as drive machinery. These products are suitable for use in compressing and transporting gases of all types, including CO₂.

If the combustion product CO₂ is to be captured using methods such as gas scrubbing in power plants in future, it must be reused – in the plastics industry, for example – or else stored separately from the atmosphere. Possible means of storing CO₂ in Germany are presented by exhausted gas fields in northern Germany or deep layers that carry saltwater, i.e. aquifiers.

Compressing CO₂, transporting it over hundreds of kilometres and then injecting it at a considerable depth – these are the elements of a North American project that MAN is involved in. CO₂ captured in what is currently the only industrial coal-gasification plant in the world, in North Dakota, USA, is pumped through pipelines to oil fields in Weyburn in the Canadian province of Saskatchewan. It is forced into storage here and, in so doing, used to increase the oil extraction pressure, thus improving yields and extending the life of the oil fields. The CO₂ pipeline is 370 kilometres long and has a diameter of 356 millimetres. MAN is supplying the geared compressors for this project.

Organisation carrying out research: MAN Diesel & Turbo SE

Highly efficient compressors for CO₂-free power plants: Radial stages with high suction capacity
Project number: 0327715J

 

Compressors for CO₂-free power plants: Highly efficiency spiral geometry
Project number: 0327716E

 

Highly efficient compressors for CO₂-free power plants: 3-D return blading
Project number: 0327715O

 

CO₂ reduction by increasing efficiency; Expansion; Project: Optimised steam removal/addition modules for compressor drives
Project number: 0327717A

Development of multi-shaft compressors and screw compressors for energy-optimised compression of CO₂ in power plants with CO₂ capture
Project number: 0327717F

Development of a product range of transonic process compressors for CO₂-free power-generation processes and future fuel-production processes
Project number: 0327752B

 

Entwicklung innovativer Verdichtungs-Technologien für hoch kompressible, korrosive Gase (CO₂) mit hohen spezifischen Massenströmen und geringen spezifischen Volumenströmen
Project number: 0327752D

 

Anlagentechnik und Automatisierung von CCS-Strängen
Project number: 0327718J

 

Teillastverhalten von Regelventilen in Einströmgehäusen von Kompressorantriebsturbinen
Project number: 0327718U

 

Kontur- und Spieloptimierung der Hochdruck-Beschaufelung von Kompressor-Antriebsturbinen
Project number: 0327719K

 

Optimierung großer Mehrwellenkompressoren für CCS-Anwendungen
Project number: 0327718V