Thermophysical Properties of Hydrogen-Natural Gas Blends

Hydrogen is an ideal fuel because it can be burned with oxygen, releasing only water or in the case of hydrogen fuel cells it reacts with oxygen without burning. Hydrogen can be produced in a number of different ways, such as using spare capacity from renewables to power electrolysers splitting water into hydrogen and oxygen. Ideally the produced hydrogen is transported via pipelines to the point of use or to storage sites where it can be easily accessed. To achieve this requires a purpose built distribution network along with metering stations which will cost many billions of pounds.

There have been a number of feasibility studies looking at the possibility of making use of the existing natural gas distribution network. Most of the studies have considered the idea of blending hydrogen with natural gas at various hydrogen concentrations between 5 and 50%. The hydrogen could then be separated out before being used or the hydrogen-natural mixture can be burned directly in domestic appliances or vehicles. Overall the strategy can deliver significant reductions in greenhouse gas emissions helping the UK to meet its commitments to the Paris Climate Agreement.

The feasibility studies conducted so far have focussed on the safety of transporting the hydrogen-natural gas blends in the existing pipelines from the point of view of potential problems of pipeline integrity as a result of hydrogen cracking and risks associated with leakage of such gas mixtures. In addition there have been a number of studies on required modifications to existing domestic appliances and vehicles so that they can safely burn the gas mixture. To date there have been limited published studies on the thermophysical properties of hydrogen-natural gas blends. This is of particular importance from a number of practical aspects such as setting drying requirements to avoid water condensation, density for gas metering.

This PhD project will utilise state-of the art experimental equipment, for measurements of density, speed of sound, viscosity, thermal conductivity, water content and hydrate stability. These measurements will be carried out over the range of pressures and temperatures relevant to the current network of natural gas pipelines. The experiments will fall into three main categories as follows:

1. Thermodynamic properties of gases: density will be measured with vibrating-tube densitometers and speed of sound with ultrasonic cells.

2. Transport properties of gases: viscosity will be measured with either vibrating-wire or capillary viscometers, while thermal conductivity will be measured by means of the transient-hot-wire method.

3. Water content measurements will be made using TDLAS and chilled mirror and hydrate equilibrium measurements will be made using mixed autoclave cells.

Existing models, in particular the ISO 20765-2 model will be modified to match the new experimental data, either by readjusting binary interaction parameters or modifying mixing rules. The two expected main results from this project proposal would be: new experimental data in mixed NG-H2 and the development and validation of original models. The models will be tested in a transient flow simulator such as OLGA. The results of this project will be published in high impact journals.

The successful candidate should have a degree in Petroleum Engineering and preferably both the ability, gained through relevant experience, to work in a PVT laboratory and also to conduct thermodynamic modelling work.

To make an application please visit the website.