Kinetikexperiment på Ilmenit, LD-slagg och järnsand som syrebärare.

Abstract

In Paris 2015 the decision was made that the global temperature would not exceed a 2°C increase since the industrial revolution. To reach this goal more environmentally friendly methods have to be developed. One such method is Carbon Capture Storage(CCS), this method captures carbon dioxide before or after the combustion stage to then store it underground. The big challenge is to find an economical and energy sustainable method to extract the carbon dioxide from air. Chemical looping Combustion(CLC) is one such method that is being researched. The CLC method splits the reaction in two parts, an air reactor and a fuel reactor. Where in the air reactor the bed material oxidizes and is transported to the fuel reactor where the bed material is reduced. With this method air and fuel never mix, which results in a flue gas without nitrogen. As this flue gas is not diluted with nitrogen the gas can be used for CCS. There are similar methods to CLC, Chemical Looping Reforming(CLR) and Chemical Looping Gasification(CLG), where the flue gas instead of carbon dioxide contains carbon monoxide and hydrogen also known as Syngas. Syngas can be used for fuel or chemical production. In this report the kinetics of three iron-based oxygen carriers; Ilmenite, LD-slag and Järnsand were tested in the mass conversion interval of 1>ω>0.98. In these experiments the method; pulsing was used, which means that the fuel gas was introduced in short time periods, this was used mainly to avoid back-maxing in the analyser. The oxygen carriers were tested at different temperatures and ω to determine how these two factors influenced the reaction. The experiments showed that ω did not have any effect on the conversion rate for Ilmenite, but for LD-slag and Järnsand the conversion rate drastically dropped when they were not fully oxidized. Järnsand gave multiple indications of reforming methane to carbon monoxide and hydrogen to a higher degree instead of conversion to carbon dioxide and water, but still had a lower conversion rate of methane than both LD-slag and Ilmenite. Ilmenite was the most promising oxygen carrier for both CLC and CLR/CLG as it had the highest conversion rate to both carbon dioxide and carbon monoxide. The formation of carbon monoxide for Ilmenite and LD-slag was less than the carbon dioxide formation for every experiment, therefore these should be tested in an environment with lower oxygen concentration to get a deeper understanding of its application in CLR/CLG.