CCS
Deployment of carbon capture and storage (CCS) will be a central part of the green transition. Design and flow assurance in the entire CCS chain relies on predictions from thermophysical models. Accuracy is a must to achieve safe and cost efficient deployment.
The figure depicts the phase behavior of a CO2 rich mixture with argon. The boundaries of phase change represented by the state-of-the-art for natural gas, GERG-2008 (dashed curves), has significant errors at high pressures compared to the most accurate equation of state for CCS called EoS-CG (solid curves).
Formation of Hydrates
Hydrates are solid water structures, stabilized by guest molecules. Formation of hydrates is a real risk in CCS, even with water concentrations as low as a few hundred parts per million. Formation of hydrates must be avoided, since they can block pipelines, obstruct valves and be a safety risk.
Equations of state that account for the polar interactions between water and CO2 and give accurate representations of the water solubility are needed to provide reliable predictions of hydrate formation boundaries. Much data has been published the last 15 years, which should be taken advantage of to thoroughly validate a methodology.
Dry ice and pure solids
When the temperature decreases or the pressure increases in CCS, there is a risk of forming solid CO2, also called dry ice.
The temperature and pressure at which dry ice forms is different in mixtures than in pure CO2, and depends on the nature and concentration of the impurities that are present, as shown in the figure.
Similar to hydrates, dry ice can obstruct flow and should be avoided. It is important to know the limits when solids can precipitate from the mixture.
Salt precipitation in reservoirs
Precipitation of salts can lead to clogging of pores, and thus hamper injection of CO2. Calcium and Magnesium carbonates, sulfates, potentially chlorides and silicates may precipitate depending on concentration, PH, temperature and pressure.
The solubility limits of salts can be estimated using equations of state for electrolytes or activity coefficient models. Under certain conditions, it may also be necessary to consider chemical reactions, in particular when several electrolytes are present simultaneously.
Transport properties
Examples of transport properties are viscosities, thermal conductivities, diffusion coefficients and thermal diffusion coefficients. The viscosity is a key property for flow of fluids in pipes or reservoirs. The thermal conductivity determines the rate of heat transfer. Diffusion and thermal diffusion are slower ways to transport components, e.g. in a reservoir due to concentration or temperature gradients.
- GAS MIXTURES: The most accurate methodology to calculate transport properties of gases is kinetic gas theory, which allows the viscosities, thermal conductivities, diffusion coefficients and thermal diffusion coefficients of most components to be calculated within a few percent of experimental data.
- LIQUID MIXTURES: Extended corresponding state theory is arguably the most accurate methodology to calculate the transport properties of liquid-phase mixtures. The theory can predict transport properties nearly within the experimental accuracy.
Energy efficiency and exergy
Improving the energy efficiency of industrial processes is a central part of the green transition. Exergy analysis is the most important tool to analyze and identify ways to improve energy efficiency. A challenge in this regard is that environmental variables such as temperature and relative humidity may vary considerably from location to location, which will influence the outcome from the exergy analysis.
Hydrogen
In the future, hydrogen will play an important role as a clean energy carrier, as an environmentally friendly reduction agent for metals and as a chemical. This makes it important to describe the properties of hydrogen in various mixtures. The hydrogen-methane mixture is particularity important as it is a main mixture in hydrogen production by use of steam reforming, and in various transport scenarios in pipelines. The thermophysical properties of hydrogen are also important in hydrogen production and utilization.
Liquid hydrogen
Liquid hydrogen is a promising way to transport large amounts of hydrogen across long distances. Liquefaction of hydrogen is energy intensive, and requires conversion of ortho-hydrogen to para-hydrogen prior to storage and transport.
We provide the most accurate thermophysical models available for both spin isomers of hydrogen as well as "normal hydrogen", and we will incorporate a thermodynamic model for non-equilibrium hydrogen, where the spin-isomer composition can deviate from the equilibrium composition.
Ammonia
We believe that ammonia will play an important role as an energy carrier in the future, in addition to its use in agriculture. Accurate knowledge of ammonia’s thermophysical properties is needed to design efficient, safe, and cost-effective systems for the transport and use of ammonia. Accurate thermophysical properties will be needed in the following applications:
- Production/cracking: Production of ammonia is is energy intensive. Cracking of ammonia can be used to produce hydrogen, which can further be exploted in conventional fuel cells.
- Utilization: Improving the performance of fuel cells or combustion chambers using ammonia as fuel requires precise knowledge of the thermophysical properties of many types of mixtures with ammonia.
- Transport: Safety assessments and studies of events where large amounts of ammonia is released into the ambient, requires reliable estimates of the thermophysical properties of ammonia-water-air mixtures.