The first step in the Carbon Capture and Sequestration (CCS) process is capturing or separating the CO2 from the fuel source used at power generation plants, refineries or industrial manufacturing facilities (steel and cement industries for example). Capture is the most costly and energy-intensive step of the CCS step.
The use of chemical sorbents is today one of the most popular absorption technique for the CO2 capture in post combustion processes. In such an industrial process, the amine solution is introduced at the top of an absorption tower while the exhausted fume containing carbon dioxide is introduced at the bottom. As an intimate contact is reached in the absorption tower, the amine solution chemically absorbs the carbon dioxide from the gaseous stream. Such a process especially requires two types of thermodynamic parameters: gas solubility and enthalpy of absorption. The enthalpy of absorption, according to the amount of absorbed gas and the corresponding heat capacities of solutions, define the temperatures of the fluids when they exit the adsorption columns.
Flow mixing calorimetry is the ideal technique for measuring such enthalpies of adsorption. In order to work under pressure, a dedicated high pressure mixing vessel is adapted to be used on the Setaram C80 calorimeter.
DESCRIPTION OF THE HIGH PRESSURE FLOW MIXING VESSEL
The mixing vessel is made of a stainless steel tube in a helicoidal shape into a cylindrical container. The length of the tube in closed thermal contact with the cylinder is about 240 cm. The fluids (CO2 and amine solution) are introduced at the upper part of the vessel in two vertical and concentrical tubes. The fluids are preheated at the temperature of the calorimetric vessel before entering the calorimetric zone, in order to avoid thermal perturbation due to the variation of heat capacity of the fluids. The mixing (dissolution, reaction) starts when the thinner part of the tube is reached at the bottom part of the vessel. The resulting mixture is extracted from the vessel through the oulet tube. The heat that is associated with the reaction, is exchanged between the rolled tube and the calorimetric block through the wall of the vessel in a isothermal mode.
The flow mixing vessel operates from room temperature to 200 °C and for a range of fluid pressure from 0.1 to 20 MPa. The fluid flowrates vary from 50 to 1500 μ.min-1, that allow to cover a wide range of mixture composition.
The High Pressure Flow Mixing calorimetric vessel is mainly dedicated to the investigation of CO2 absorption in liquid sorbents (especially amines). But the calorimetric vessel can also apply to any liquid-liquid and liquid-gas flow mixing under normal or high pressure.
An example is given for the enthalpy of solution of CO2 in a primary amine AMP (2-amino-2-mrthyl-1-propanol).