Conference Program

Eriks Arajs

In 2022, Linde received the order to deliver two large helium refrigeration systems operating at 4.5 K and 1.9 K for the European Organization for Nuclear Research (CERN) in Geneva, Switzerland. The two identical plants will be installed at opposing points along the circumference of the Large Hadron Collider (LHC). They will facilitate the peak luminosity by a factor of five beyond the LHC’s design value.

Due to the operation of the superconducting magnets at 1.9 K, parts of the cryoplant operate at a very low pressure, down to 15 mbar a. While operating in a steady state, each of the cryoplants delivers up to 14 kW of equivalent power at 4.5 K, including 3.25 kW at 1.9 K (isothermal and non-isothermal),13.5 kW at 60 K to 90 K as well as various loads having 4.5 K supply.

The very low pressure at which the liquid helium is evaporated inside the LHC’s magnets to achieve 1.9 K leads to a high-volume flow of gaseous helium returning from the LHC experiment to the cryoplant. Cold compressors lower the volume flow, which pre-compresses the helium returning from the experiment before it is conveyed to the refrigeration cold box. Due to smaller volume flow, heat exchangers can be designed to be more compact, and the warm screw compressor requires lower capacity.

Since the LHC is located underground, each cryoplant is split into two separate cold boxes. The larger main cold box (refrigerator) is located at the surface, and a second, smaller cold box, which contains mainly the cold compressors, is in the underground cavern close to the experiment.

The combination of floating pressure in all four pressure stages with an integrated 3,500 L LHe phase separator enables rapid adaptation to load changes without using a variable frequency drive for the main compressors. A floating pressure cycle maintains high efficiency even during turndown operation.

The paper covers the process design according to CERN's specification and the control strategies for load adaption.

Lutz Decker (Linde Kryotechnik AG) & Alexander Alekseev (Linde GmbH)

Liquid hydrogen is currently attracting a lot of attention for two applications: as a replacement for fossil fuels in heavy-duty trucks or planes and as a potential hydrogen carrier for energy transport over long distances. This is mainly due to the high energy density of LH2 in terms of mass. Other advantageous characteristics of LH2 are a) high purity, b) reduced risk potential due to low pressure, and c) extensive experience in handling LH2, as this fluid has been used commercially for decades for applications in space and electronics. Today, the relatively high specific cost is considered to be the main drawback of LH2. In the future, the cost of LH2 for mass production of LH2 can be significantly reduced through economies of scale, which in turn requires a concerted ramp-up of the supply chain from well to wheel. This presentation will discuss the LH2 supply chain mentioned above, including the interfaces to green/blue hydrogen production at the beginning of this chain and to LH2 applications at the end of this chain. An overview of available key hardware components and process plants will be given, and requirements for key hardware components for future large-scale infrastructure will be considered.

Lutz Decker

The global hydrogen liquefaction capacity has increased dramatically in recent years. The consequences of climate change and current political upheavals continue to push for an accelerated expansion of even greater capacities. At the same time, there is a growing need to improve the efficiency of energy-intensive liquefaction. Data on the efficiency of modern liquefiers is scarce, and various academic studies propagate 6.4 kWh/kg hydrogen as a target for the specific energy consumption of liquefaction and outline extremely complex and investment-intensive processes. However, the market for hydrogen mobility requires above all a significant reduction in the overall costs (investment and operation) of these plants. For today's rather small plants (up to about 5 tons of liquid hydrogen per day [tpd]), the investment determines the total cost. Efficiency plays a minor role. Future, larger liquefaction plants will allow the focus to be on efficiency. This is countered by the requirement to install only technically proven solutions, as the plant must be economically viable. The next generation of medium-sized plants (>15 tpd) will soon be in operation and will demonstrate progress. The target value propagated above is technically achievable, but only with the repeated construction of large plants (200 tpd and more) and great technical effort. This will require a simultaneous increase in consumption volumes and an appropriate economic policy framework.

Thanks to continuous improvements and innovations, the efficiency of Linde's latest 5 tpd hydrogen liquefier in Leuna, Germany, has been significantly increased, even under economic conditions. For example, the specific power consumption for the actual refrigeration circuit (< 80 K) was reduced by up to 30%.

Marco Mühlegger

Linde Kryotechnik AG is known as a supplier of high quality products in the field of cryogenics. This results in the fact, that still many users are operating helium liquefaction and refrigeration systems that are 30 years and older. Technology has developed and the efficiencies of todays cryogenic plants have increased. Instead of replacing the entire cryogenic plant an upgrade of only dedicated components might be already a benefit and does not involve too high cost.

The most effective method to increase efficiency and consequently improve performance by considering the restrictions of space and accessibility is the use of state-of-the-art turbines.

The new approach presented here combines existing infrastructure with state-of-the-art turbine technology by means of a special adapter. The adapter allows a modification of the turbines without the need to change the inner design of the cold box.

The turbine adapter technology can be used for liquefiers and refrigerators as well as different process mediums like helium or hydrogen.