Carbonatación de residuos de la construcción como alternativa para la reducción de co2. Posible aplicación al almacenamiento de CO2 en canteras restauradas con residuos

Laburpena

The constant emissions of greenhouse gases (GHG) have made it necessary to develop technologies and measures to reduce emissions of these gases into the atmosphere. International organizations have established constant objectives for the reduction of their emissions due to the inevitable harmful effect of these gases in the earth’s climate system, especially the increase of the global average temperature and its dramatic consequences, the well-known climate change. It is for this reason that a series of measures have been taken, mainly related to the change or improvement of the efficiency of energy production, usually coming from the burning of fossil fuels. Although, in 2005, the Intergovernmental Panel on Climate Change (IPCC) established CO2 capture and storage (CCS) systems as a technology for reducing emissions of these gases as a development strategy. Following this philosophy, the research project of this PhD thesis combines two of the bases of CCS, mineral carbonation and geological storage at lower depths and surface pressure and temperature conditions. For this purpose, the construction and demolition waste will be used as a starting material for carbonation, specifically bricks as they are one of the main components of this waste. Since these wastes are highly available and provide them with a second useful life, in other words, giving them an added value that they did not have. Together with the fact that they are cheap and have an appropriate particle size in storage make the process economically and environmentally sustainable. In the first part of this thesis project, the feasibility of the proposed method will be studied on three different types of bricks commonly used in the construction of buildings and dwellings. Establishing the mineralogical transformations involved in the process of mineral carbonation in presence of water, as well as the mechanisms that are given to achieve the fixation of CO2 in conditions of medium-low pressure (10 bars) and ambient temperature for different sizes of representative particles and at different reaction times at laboratory scale. In order to do this, it was necessary to characterize the starting raw material and monitor the carbonation tests, quantifying the retained CO2 value. For the second part, a reaction chamber was designed, a pilot plant scale, such as to imitate the recovery of a depleted or disused clay quarry, using as filled these construction wastes and directly injecting a flow of CO2, at low pressures and ambient temperature. These experiments combine mineral carbonation and the principles of geological storage. The brick considered to have performed best in the smaller scale tests (laboratory scale) was used as a filler (host material) and blue marls (common clay) as sealing rock. Again, the carbonation reaction and its evolution over time were monitored, as well as the mechanisms involved the briks reactivity and the interaction of CO2 with the clay layer.