Chemical looping combustion of hard coal and torrefied biomass in a 1 MWth pilot plant. (October 2017)

• Record Type: Journal Article
• Authors: Ohlemüller, Peter; Ströhle, Jochen; Epple, Bernd
• Is Part Of: International journal of greenhouse gas control. Volume 65(2017)
• Page Start: 149
• Page End: 159
• Publication Date: 2017-10
• Subjects: Chemical looping combustion -- Pilot plant -- CO2 capture -- Hard coal -- Torrefied biomass; Greenhouse gases -- Environmental aspects -- Periodicals; Air -- Purification -- Technological innovations -- Periodicals; Gaz à effet de serre -- Périodiques; Gaz à effet de serre -- Réduction -- Périodiques; Air -- Purification -- Technological innovations; Greenhouse gases -- Environmental aspects; Periodicals; 363.73874605
• DOI: 10.1016/j.ijggc.2017.08.013
• Languages: English
• ISSNs: 1750-5836

Abstract

Highlights: More than 100 h stable CLC operation in 1 MWth scale with autothermal and partial autothermal conditions was achieved. The use of ilmenite as oxygen carrier showed better conversion of gases than iron ore leading to lower oxygen demand in the case of ilmenite. Beside pure hard coal, a fuel blend with torrefied biomass was used as fuel resulting in high CO2 reduction compared to conventional combustion systems. Abstract: Chemical looping combustion (CLC) is an emerging CO2 capture technology utilizing two interconnected circulating fluidized beds (CFB). An oxygen carrier is oxidized in the air reactor and reduced in the fuel reactor. In comparison to a classic oxyfuel process, no air separation unit is required to provide the oxygen needed to burn the fuel. The solid fuel, such as coal or biomass, is gasified in the fuel reactor, and the products from gasification are oxidized by the oxygen carrier. This work presents results of 110 h autothermal and partial autothermal CLC operation with ilmenite and iron ore as oxygen carriers. Hard coal and a fuel blend of hard coal and torrefied biomass were used as fuels. The results show that the oxygen demand of the fuel reactor required for a complete conversion of unconverted gases was in the range of 27%. At the same time, the carbon capture efficiency was low in the present configuration of the 1 MWth pilot. This means that unconverted char left the fuel reactor and burned in the air reactor. The reason for this is that no carbon stripper unit was used during these investigations. Some possible modifications like an oxygen carrier with oxygen uncoupling, a lower fuel feeding point or a secondary fluidization of the fuel reactor could significantly enhance the carbon capture efficiency.