(739a) Clc Coal Combustion in a 10 Kw Pilot Plant

Chemical looping combustion (CLC) is a technology in which the oxygen required for the fuel combustion reaction is supplied by a metal oxide (oxygen carriers, OC). The principle is based on the continuous circulation of OC particles between two interconnected reactors. In a first reactor, called "Air reactor", the oxygen carrier is oxidized by air . Then the OC particles are conveyed to a second reactor, called "Fuel reactor", where they are reduced by a fuel stream. Finally, the oxygen carrier particles are recycled to the Air reactor to start a new cycle. Therefore, direct contact between air and fuel is prevented, leading to the formation of a rich CO₂-H₂O flue gas, which can be easily condensed and captured.

Contrariwise to post-combustion or oxycombustion technologies, in chemical looping combustion the CO₂ separation is inherent to the process and therefore no energy is expended for the capture [1]. Thanks to this, chemical looping combustion is considered as one of the most promising CO₂ capture technology.

As part of a partnership between IFPEN and TOTAL, a 10kWth pilot plant has been built in 2010 at IFPEN facilities. This CLC prototype unit is composed of three interconnected bubbling fluidized bed reactors, which are separated by loop seals that prevent gas leakage between reaction zones. The pilot solid circulation rate is controlled by non mechanical L-valves adapted to high temperature operation.

After a first period of tests where the pilot was validated on gaseous feeds [2], the prototype was modified for solid fuels testing in the beginning of 2011. An additional capacity was added to separate the unburned carbon from the oxygen carrier, and a solid fuel dosing injection system was implemented on the fuel reactor. The paper will present some important results obtained from the continuous 10kWth pilot operation with South African coal. Among the results, impact of different important parameters affecting coal conversion will be exposed, such as : -          Temperature effect between 850°C and 940°C, -          Residence time between 5 and 30min, -          Steam partial pressure.

References:

[1] Figueroa et al., "Advances in CO₂ capture technology – The US DOE carbon sequestration program", Int. J. of greenhouse gas control, 2008, vol. 2 9-20

[2] Hoteit et al. ECCRIA 2010