CO2 sequestration by steelmaking slags for the production of precipitated calcium carbonate - From laboratory to demonstration stage

Abstract

Humanity faces many challenges that we have to overcome in a very short time. The two most alarming challenges that we have to address immediately and collectively are 1) climate change, due to the increase of the greenhouse gases (primarily CO2) produced by human activities, and 2) resource depletion, partially due to the intensive demand for manufacturing goods. Therefore a business-as-usual scenario is not responsible. Industrial solid waste, such as steelmaking slags, is considered to be a suitable raw material for carbon dioxide sequestration due to its high content of calcium oxides. In addition, the utilization of steelmaking slags for carbon dioxide sequestration is beneficial for the iron and steel industries, where both slag and a large quantity of carbon dioxide are produced. Slag is a non-metallic by-product from iron and steel production that consists of various combinations of calcium, magnesium, and aluminum silicates. Not all steel slag is utilized innovatively to ensure zero waste and added value in the steel production chain. Very large amounts of this material are being dumped in slag disposal areas that could result in negative impacts on both human health and the environment in the long term. The objective of this dissertation is to illustrate the feasibility of utilizing both steelmaking slags and the CO2 in the flue gas from steelmaking processes in an alternative method for the production of precipitated calcium carbonate. The feasibility study was originally conducted at laboratory scale where the basic chemistry was investigated and different process parameters (e.g., temperature, pressure, solvent concentration, etc.) were optimized. After that, we designed and constructed a 200 L reactor pilot-plant test facility for proof-of-concept of the technology. After we received very valuable and interesting results from both the laboratory-scale and pilot-scale tests, the project entered the pre-commercialization phase, where the design of 2500- L reactors for a demonstration plant is ongoing.