Carbon dioxide capture using excavated landfill materials

Abstract

Greenhouse gases, which contribute to the warming of the earth’s climate, are rising at alarming rates which results in excessive global warming. The biggest contributor to this climate change is CO2. This project intends to test the viability of using excavated landfill material (ELM) to produce sorbents for calcium looping to capture CO2. The thermogravimetric analysis (TGA) conducted on the raw ELM showed that it had certain ability to capture CO2, but the carbon capture rate was modest at 18.4-246.4 mg/g. Thus, there is a potential for the ELM to be turned into sorbents for calcium looping. The ELM was washed with distilled water (DI) to produce the washed ELM ashes and the ELM wash-water. From an ICP-OES test conducted on the resulting wash-water, the mean calcium content of all the ELM samples was found to be 3204 mg/kg. The ELM sorbents were generated through modification using calcium hydroxide binding and limestone doping with the ELM washed ashes and the ELM wash water, respectively to assess if it will improve the carbon capture capacity and cyclic stability of the sorbents. TGA was conducted on the enhanced sorbents. The TGA results of the individual calcium hydroxide binded sorbents compared to the pure calcium hydroxide showed that the cyclic stability had improved, although the carbon capture rate of ELM sorbents 304.4-322.7 mg/g are not as high as pure calcium hydroxide, 561.0 mg/g. The TGA results for the individual limestone doped sorbents show that the ELM wash-water had improved the carbon capture rate of the limestone. All the ELM were then mixed to create a sample that was more homogeneous and representative of the content in the landfill, and the enhanced sorbents are produced from this mixture as well. The mixed enhanced sorbents were prepared for cold model testing for preliminary testing in a fluidised bed reactor (FBR) by sieving it to the proper particle sizes. From the cold model, the Geldart group classification, minimum fluidisation velocity (Umf) and attrition rates were experimentally determined. Subsequently, the sorbents were put through a hot model FBR to determine their suitability in being utilised for carbon capture at high temperatures, which demonstrate its potential for further upscaling and application. Further studies could be conducted in the future to improve the carbon capture rate of the sorbents produced from ELM and to test the ELM using Fourier Transform Infrared (FTIR) spectrometer to study the changes in chemical structure of the material during carbonation.