CCUS property lab (DK4.3)

CCUS property lab

In the CCUS property lab we able to analyse a variety of properties, which are crucial for developing new innovative solvents for CO2 capture. These include phase equilibria (solid-liquid (SLE), vapour-liquid (VLE)), reaction kinetics, density, viscosity, degradation, corrosion, speed of sound, surface tension, and heat of absorption.

The facilities are supported by skilled technical and scientific staff. The units have been for various Danish and EU funded projects.

Many of the equipment are specially designed by skilled researchers from the group and cannot be purchased anywhere else.

Wetted wall column (WWC):

The Wetted Wall cell is used to measure intrinsic parameters relating to absorption processes such as reaction kinetics, mass transfer coefficients and so on. It has been used to study solvents for CO2 capture, such as MEA, MDEA, CESAR1, MDEA with enzymes, potassium carbonate and ammonia.

Detailed description: The gas comes from N2 and CO2 bottles. The flow and the pressure of the gases sent to the chamber are controlled by the mass flow controllers. The gas is then saturated with water and reaches the reaction chamber that consists of a glass tube that can resist a pressure of up to 10 bars. The gas outlet, on the top of the chamber, comprises a needle valve to reduce the pressure to atmospheric. The gas passes through an acid wash section to remove the ammonia present in the gas phase and through a condenser to remove the water.

The concentration of carbon dioxide is then measured with a gas analyzer and sent to the fume hood. An alternative would be to measure the gas before it is condensed and washed and by correcting the actual value of the CO2 pressure by evaluating the pressure of ammonia and water using the thermodynamic model.

When MEA is used, it can be assumed that the amount of MEA in the gas phase is negligible. The liquid is pumped from a stainless-steel tank to the chamber, after it passes through the oil tank to control its temperature.

It flows through the stainless-steel tube and on its surface as a homogeneous film where it can react with the gas. The liquid leaves the chamber by its bottom and is transferred back to the liquid tank. Therefore, the liquid is used in a closed loop.

It is assumed that the CO2 loading of the solvent does not significantly change during an experiment.

A cooling bath is used to control the temperature. The water is circulated around the chamber to maintain a constant temperature. The experiments will be conducted in the temperature range of 0-80 °C. The liquid reactor is about 2 liters and the main chamber about 0.25 liters.

Rotating cylinder electrode (RCE):

The equipment is an electrochemical test cell designed for corrosion experiments. It consists of a glass cell, which is filled with an aqueous test solution. The test metal sample (working electrode) is submerged in the solution as well as a reference electrode and a counter electrode. All electrodes are connected to a potentiostat, which monitors and controls the potential and current of the electrochemical cell. The working electrode is a so-called rotating cylinder electrode (RCE) that can be rotated in the solution to create specific hydrodynamic/diffusion conditions around the electrode.

The set-up has been extended to include a multiple gas supply system, consisting of four flow controllers, a gas mixing vessel as well as a various safety measures, valves and alarms for SO2 experiments. For SO2 experiments, refer to the relevant safety approval document.

Solid-liquid equilibria (SLE) and Vapour-liquid equilibria (VLE):

The SLE are measured using a modified Beckmann apparatus. The experimental setup is shown in the figure above.

The VLE setup (see the PID diagram above) illustrates the experimental apparatus. At its core is a 280 cm³ stainless steel reactor (HiP GC-5), housed within a tank connected to an external circulating bath (Julabo FP50-ME) to maintain precise temperature control. This reactor was specifically selected to minimize leakage during experiments, as in-house experience with CO2 solubility measurements has consistently shown that polymer-based seals tend to fail after short use. To address this issue, the HiP GC-5 reactor employs metal gaskets exclusively, ensuring a reliable seal.

To maintain a constant temperature inside the reactor (Figure 5.1), the surrounding tank was insulated with EPDM foam (HT/Armaflex), capable of withstanding temperatures up to 423 K. However, due to operational constraints, the setup was limited to a working range of 310 K to 410 K. Stainless steel tubing connecting the reactor to the pressure transmitter (Yokogawa EJX310A) was also insulated with the same material to minimize heat loss and prevent cold spots in the system.

Temperature inside the reactor was continuously monitored using a high-precision platinum resistance thermometer (Pt100 DIN 1/10) fitted into the reactor’s thermowell. For effective mixing, a magnetic stirrer (2mag MIX Eco HT) operating at 1200 rpm was installed beneath the reactor, ensuring homogeneity within the system.