Carbon dioxide sequestration by mineral carbonation

Autor: Huijgen, W.J.J.
Přispěvatelé: Wageningen University, Rob Comans, G.J. Witkamp
Jazyk: angličtina
Rok vydání: 2007
Předmět:
Popis: The increasing atmospheric carbon dioxide (CO2) concentration, mainly caused by fossil fuel combustion, has lead to concerns about global warming. A possible technology that can contribute to the reduction of carbon dioxide emissions is CO2 sequestration by mineral carbonation. The basic concept behind mineral CO2 sequestration is the mimicking of natural weathering processes in which calcium or magnesium containing minerals react with gaseous CO2 and form solid calcium or magnesium carbonates: (Ca,Mg)SiO3 (s} + CO2 (g) ->(Ca,Mg)CO3 (s) + SiO2 (s)Potential advantages of mineral CO2 sequestration compared to, e.g., geological CO2 storage include (1) the permanent and inherently safe sequestration of CO2, due to the thermodynamic stability of the carbonate product formed and (2) the vast potential sequestration capacity, because of the widespread and abundant occurrence of suitable feedstock. In addition, carbonation is an exothermic process, which potentially limits the overall energy consumption and costs of CO2 emission reduction. However, weathering processes are slow, with timescales at natural conditions of thousands to millions of years. For industrial implementation, a reduction of the reaction time to the order of minutes has to be achieved by developing alternative process routes.The aim of this thesis is an investigation of the technical, energetic, and economic feasibility of CO2 sequestration by mineral carbonation.In Chapter 1 the literature published on CO2 sequestration by mineral carbonation is reviewed. Among the potentially suitable mineral feedstock for mineral CO2 sequestration, Ca-silicates, more particularly wollastonite (CaSiO3), a mineral ore, and steel slag, an industrial alkaline solid residue, are selected for further research. Alkaline Ca-rich residues seem particularly promising, since these materials are inexpensive and available near large industrial point sources of CO2. In addition, residues tend to react relatively rapidly with CO2 due to their (geo)chemical instability.Various process routes have been proposed for mineral carbonation, which often include a pre-treatment of the solid feedstock (e.g., size reduction and/or thermal activation). The only available pre-treatment option that has proven to be energetically and potentially economically feasible is conventional grinding.Two main types of process routes can be distinguished; (1) direct routes in which carbonation takes place in a single step process, either in a gas-solid or a gas-liquid-solid process, and (2) indirect routes in which the Ca is first extracted from the silicate matrix and subsequently carbonated in a separate process step. The aqueous route in which Ca-silicates are directly carbonated in an aqueous suspension at elevated temperature and CO2 pressure is selected as the most promising process route for further investigation. The following key issues for further research are identified: the reaction rates and mechanisms of mineral carbonation as well as its energy consumption and sequestration costs. Another important aspect of mineral carbonation is the destination of the carbonated products.In Chapter 2 the mechanisms of aqueous steel s!ag carbonation are studied experimentally. Process variables, such as particle size, temperature, and carbon dioxide pressure are systematically varied and their influence on the carbonation rate is investigated. The maximum carbonation degree reached is 74% of the Ca content in 30 minutes at 19 bar CO2 pressure, 100 0C, and a particle size of
Databáze: OpenAIRE
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