Internship | The behaviour of CO2 in control valves for carbon sequestration

To reduce carbon emissions to the atmosphere there are many plans to capture and store CO2 in the subsurface within the next few years. The transport from capture plant to the subsurface occurs through a system of pipelines and wells. To control this system, valves are of crucial importance. The goal of this project is to determine the flow behaviour of CO2 in a valve, both to better predict the phase distribution and temperatures downstream of the valve and to predict where inside the valve wear and tear may occur.

To reduce carbon emissions to the atmosphere there are many plans to capture and store CO2 in the subsurface within the next few years. The transport from capture plant to the subsurface occurs through a system of pipelines and wells. In the Netherlands, storage occurs in depleted natural gas reservoirs at a depth of about 3 kilometers, which are currently at low pressure. The transport lines are operated at pressures above 80 bar to keep the CO2 in the higher density liquid phase. As a result, control valves are required to make sure the CO2 flows into the reservoirs at the required flow rates while keeping the pipeline at pressure.

CO2 differs from other fluids that are often transported in pipelines, such as water and oil and natural gas in two important ways: (1) the phase boundary between liquid and gas is located at pressures and temperatures encountered in injection wells and (2) the surface tension between liquid and gaseous CO2 is very low. When the pressure and temperature change over a control valve, this causes fast evaporation of CO2 inside the valve. This is known as flashing. Flashing is required in many CO2 injection systems, as the presence of gas in the injection well reduces the hydrostatic pressure in the well allowing controlled injection into the low pressure reservoirs. Accurately predicting the phase distribution downstream of the valve is therefore important to predict flow control. Furthermore, the flashing behaviour inside the valve often leads to wear and tear. Understanding where flashing occurs can therefore help in valve design.

The goal of this project is to determine the flow behaviour of CO2 in a valve, both to better predict the phase distribution and temperatures downstream of the valve and to predict where inside the valve wear and tear may occur. This end CFD simulations of CO2 flow through a valve are performed, taking into account the phase transition in the valve. In a previous MSc internship a start was made with these simulations and 1D simulations were successfully executed. In these simulations it was possible to determine the temperature inside and downstream of the valve. In this project these simulations should be extended to 2D and 3D, such that the exact geometry of the valve can be taken into account. The results of the simulations should be compared to existing valve models. Furthermore, the simulation results can later be compared to the results of CO2 experiments.

We are looking for a student who is enthusiastic, critical and a team-player. We expect you to work hard and independently on your own project, but ask for help if needed. Knowledge on fluid mechanics and experience with experimentation is highly preferred.

Duration: 8/9 months, graduation.

You want to work on the precursor of your career; a work placement gives you an opportunity to take a good look at your prospective future employer. TNO goes a step further. It’s not just looking that interests us; you and your knowledge are essential to our innovation. That’s why we attach a great deal of value to your personal and professional development. You will, of course, be properly supervised during your work placement and be given the scope for you to get the best out of yourself. Furthermore, we provide:

• A highly professional, innovative working environment, with top experts as colleagues.
• A suitable internship allowance (615 euro for wo- and hbo-students, 390 euro for mbo-students, for a full-time internship).
• Eight hours of leave per internship month (for a full-time internship).
• A free membership of Jong TNO, where you can meet TNO-colleagues and join several activities, such as sports activities, (work-related) courses or the yearly ski-trip.
• Use of a laptop.
• An allowance for travel expenses in case you don’t receive an OV-card.

At TNO, we innovate for a healthier, safer and more sustainable life. And for a strong economy. Since 1932, we have been making knowledge and technology available for the common good. We find each other in wonder and ingenuity. We are driven to push boundaries. There is all the space and support for your talent and ambition. You work with people who will challenge you: who inspire you and want to learn from you. Our state-of-the-art facilities are there to realize your vision. What you do at TNO matters: impact makes the difference. Because with every innovation you contribute to tomorrow’s world. Read more about TNO as an employer.

At TNO we encourage an inclusive work environment, where you can be yourself. Whatever your story and whatever unique qualities you bring to the table. It is by combining our unique strengths and perspectives that we are able to develop innovations that make a real difference in society. Want to know more? Read what steps we are taking in the area of diversity and inclusion.

After the first CV selection, the application process will be conducted by the concerning department. TNO will provide a suitable internship agreement. If you have any questions about this vacancy, you can contact the contact person mentioned below.

Important to be aware of before applying:

• Before the start of the internship, the internship agreement from TNO needs to be signed, by the intern, TNO and the educational institution. This agreement is established in cooperation with Universiteiten van Nederland according to the UNL-template. If you are not a student at a Dutch college or university, or if you are a mbo-student, the TNO internship agreement will apply. In that case, a ‘proof of educational institution’ and a ‘proof of internship as part of course’ is needed. TNO doesn’t sign other contracts.
• Furthermore, you have to be registered at an educational institution to be eligible to do a paid internship at TNO. If you are not studying at a university you are only eligible for a work experience internship (unpaid, maximum of 8 weeks).
• Interns at TNO must be in possession of a Dutch residential address at the start of the internship. It is not possible to work from abroad.