Ultramafic Rock-Based Filters Enable CO2 Capture in Simulated Emission Streams

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 228354, “Ultramafic Rock-Based Filters for CO2 Capture in Simulated Emission Streams: An Experimental Approach With Combustion Cells,” by Elif Akiska and Sinan Akiska, Texas A&M University and Ankara University, and Berna Hascakir, SPE, Texas A&M University. The paper has not been peer-reviewed. _ Because of their high magnesium content, ultramafic rocks are considered excellent candidates for CO2 sequestration through mineral carbonation. Despite extensive studies on mineral carbonation and the reactivity of ultramafic rocks in subsurface conditions, few works have explored their direct application as reactive filtration media for carbon capture under simulated industrial flue-gas environments. This study explores the carbon capture and mineralization potential of ultramafic rock powders when exposed to flue gases generated from combustion of a crude oil and mesquite-derived charcoal. Materials and Methods In almost all experimental studies conducted thus far, the focus has been on the physicochemical conditions of mafic-ultramafic rocks and their constituent reactive minerals. However, very few of these studies have integrated mineralogical-petrographical investigations with X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA/DSC), and Fourier transform infrared (FTIR) spectroscopy. In this study, various ultramafic rocks with differing olivine and serpentine contents were analyzed to determine CO2-uptake specifications. Fig. 1 presents hand specimens of three ultramafic rock samples collected from the Edige magnesite deposits located in Ankara, Turkey. During fieldwork, the specimens were manually fractured using a hammer and examined onsite, with preference given to those containing little or no visible carbonate minerals. The mineralogical composition of each sample was initially analyzed using XRD. Analyses were performed with a diffractometer equipped with a copper X-ray tube, Xe-T detector, and a 90-sample automatic loader. The resulting diffractograms were processed to identify mineral phases. Based on combined XRD and petrographic analysis, Sample 20 was identified as comprising serpentine, olivine, orthopyroxene, and minor magnesite; Sample 22 included serpentine, olivine, talc, and minor dolomite; and Sample 26 consisted of olivine, serpentine, and orthopyroxene. All three samples are classified mineralogically as harzburgite. To evaluate the carbon capture and storage (CCS) potential of these rock samples, combustion experiments were conducted using a laboratory-scale combustion setup. Two separate combustion experiments were conducted to simulate CO2 and flue-gas emissions from hydrocarbon-rich sources. The first experiment employed 46.6 °API crude oil, reservoir rock, and formation brine with a total-dissolved-solids content exceeding 120,000 ppm. The second experiment utilized charcoal derived from mesquite trees. Both experiments were conducted using an identical combustion setup designed to mimic industrial-scale emitters such as power plants or refineries. Throughout both experiments, continuous flue-gas-composition monitoring was conducted using a gas analyzer system, enabling real-time quantification of CO2, carbon monoxide, and other gas-phase products. Before and after each experiment, the ultramafic rock filters were weighed to assess mass changes associated with gas capture and mineral transformation. Their FTIR spectra also were recorded to identify chemical bonding changes and carbonate or hydrocarbon-related absorption bands.