- Research conducted for storing hydrogen in a heat transfer oil that acts as a liquid organic hydrogen carrier (LOHC)
- Coriolis flow controllers were used to dose LOHC into reactor vessel
- The loaded LOHC can be stored at ambient conditions, one of many advantages over gaseous hydrogen storage
Wagner Mess- und Regeltechnik, assisted German R&D companies to find a new technique of hydrogen storage: in synthetic aromatic-based heat transfer oils that are normally used in bakery systems and other high temperature applications. Here the heat transfer oil acts as a liquid organic hydrogen carrier, LOHC. In this setup, high temperature Coriolis flow meters combined with WADose HPLC pump play an important role.
Hydrogen Storage Requirements
The companies investigate at which pressure the reaction performs best for loading and unloading. To this end, accurate flows of LOHC and hydrogen must be supplied to the reactor. Tricky part here is the change of viscosity of the LOHC before and after the catalytic reaction. The mass flow meters need to be able to cope with these viscosity changes.
Flow Control for Hydrogen Streams
- Ability to dose and pump viscous liquids
- Accuracy & high temperature
- Flow meters need to be able to cope with viscosity changes
Using Flow Controller with Dosing Pump
In one setup, the LOHC is heated up to reach the right viscosity range and is brought to a higher-pressure level by a Wadose HPLC pump with heating element. A high temperature Coriolis flow meter with suitable electronics and a control valve is used here to dose the LOHC to the reactor vessel.
In a different setup, the dosing of the LOHC at higher viscosities also works very well with HNP pumps in combination with the Coriolis mass flow meters. Here the medium does not have to be heated up very much because the pump copes very well with high viscosities.
Integrated Dosing System for Reactor Vessel
Of the hydrogen that is fed to the LOHC process, the flow is only measured. This hydrogen (that leaves the electrolyzer in a previous stage prior to entering the reactor vessel) is pressure-controlled.
For this application, several Bronkhorst instruments are being used for several aspects of the process:
- to apply a pressure
- for pumping
- for measuring and controlling media
- to reveal the media density
- to measure relevant temperatures
The combination of these devices makes it a highly functional solution.
Information about Hydrogen Storage Research
The hydrogen is stored inside the liquid hydrogen carriers via a catalytic reaction. The liquid now has a low viscosity and looks like water. After hydrogenation, the viscosity is increased and the liquid looks like honey. When loaded with hydrogen, this LOHC is flame-retardant, which makes it a safe transport medium for hydrogen to the location of use where the hydrogen can be unloaded from this carrier liquid.
Loading and Unloading Hydrogen in Heat Transfer Oil
The loaded LOHC can be stored at ambient conditions, which is (another) advantage over gaseous hydrogen. This loading and unloading is a reversible process; hydrogenation (loading) requires higher pressures, is exothermic and therefore releases energy, whereas dehydrogenation (unloading) is an endothermic process which requires energy and therefore higher temperatures, both catalyst driven.