Successful test using liquid nitrogen in place of LNG
By Jack Burke28 February 2023
Seeing higher reliability, space savings compared to conventional turbine structure
Mitsubishi Heavy Industries and Mitsubishi Heavy Industries Marine Machinery and Equipment (MHI-MME) said they have successfully tested using liquid nitrogen as a substitute for liquefied natural gas (LNG) as cryogenic energy and verified stable operation under cryogenic environment successfully.
The companies hope the innovation will lead to more stability and higher reliability of LNG cryogenic power generation systems and application in future hydrogen cryogenic power generation.
The companies said they tested a 100 kW class cryogenic Organic Rankine Cycle (ORC) power generation using the world’s first “next-generation oilless cryogenic turbine generator.” The innovative generator adapts the turbine generator featuring a hermetically sealed oilless structure, of the kind used in ORC generation, to cryogenic power generation(Note1). The testing demonstrated that with the use of liquid nitrogen as the cryogenic energy source, it is possible to secure a stable refrigerant cycle and the specified regeneration output without freezing-induced clogging, etc. even under conditions more severe than the low temperatures of conventional LNG (cryogenic generation.
The new ORC turbine generator, developed in-house applying MHI Group’s comprehensive turbine and cryo-temperature technologies, adopts oilless magnetic bearings and a hermetically sealed structure that prevents refrigerant leakage outside the system. Improvements for refrigerant power generation were made based on the Company’s operating track record in ORC power generation, enabling higher reliability, space savings and maintenance-free operation compared to the turbine structure used in earlier LNG-cooled power generation (steam turbines with open-end type, featuring forced-lubricated sleeve bearings).
In the demonstration testing, which was conducted in January 2023 at MHI’s Research & Innovation Center in the Nagasaki District, cryogenic power generation was performed by an intermediate fluid using a Rankine Cycle using cryogenic energy. Besides using liquid nitrogen (boiling point: approx.-196℃) in place of the conventionally adopted LNG (boiling point: -160℃), the test simulated actual LNG vaporization equipment such as a marine FGSS (fuel gas supply system) and offshore/onshore LNG vaporization equipment. The testing provided useful results in terms of understanding the refrigerant cycle properties and the phase changes of cryo-temperature media such as LNG or liquid nitrogen, and also confirmed the system’s controllability. These results suggest the potential for further stabilization and reliability in LNG refrigerant generation systems, and also support expectations of the use of hydrogen (boiling point: approx. -253℃), seen as a promising decarbonized fuel, for cryogenic power generation.
MHI Group is currently strengthening its position in the Energy Transition, and the development of a next-generation turbine generator by MHI and MHI-MME will contribute to the creation of new power generation business making effective use of unused refrigeration heat and waste heat. MHI Group said it will pursue further development of solutions that will contribute to the reduction of greenhouse gas emissions and the protection of the environment.