Sulfur oxides, abbreviated to SOx, refer to both sulfur dioxide (SO2) and sulfur trioxide (SO3) that are gaseous pollutants emitted by the combustion of low-grade fuels, including heavy oils, sour gases and coal.
Current Flue Gas Desulfurization (FGD) technologies mainly use limestone or CaO (quicklime) as sulfur scavenger. They consume water and produce significant stocks of calcium sulfate, a non-regenerable solid that has limited market outlets and is sometimes considered as waste.
To tackle this problem, a multi-partner team has launched a two-phase program in order to develop a new, regenerative FGD concept. This partnership includes a GE Power team (Belfort, France), three research laboratories (IS2M-MPC, LGRE from University of Haute Alsace, Mulhouse and ICB-UTBM-LERMPS, Belfort), a ceramic material testing center (ICAR, Moncel les Luneville, France) and a consultancy organization skilled in materials (Zephir Alsace, Mulhouse). The main objective was to design a regenerable adsorbent that would not release any solid waste but would allow instead the recovery of sulfur in the form of H2SO4 (sulfuric acid) which is a valuable chemical commodity.
A first subprogram, executed from September 2012 through March 2015 and called “DeSOx New Gen”, enabled the different partners to identify and test at lab scale a regenerable and durable adsorbent. This adsorbent, used initially in powder form, involved an organized mesoporous silica (SiO2), which was used as a support and was impregnated with copper oxide (CuO) likely to undergo reversible sulfation. Such binary system proved capable of achieving large numbers of successive adsorption/regeneration cycles (more than fifteen attained in the lab) without undergoing substantial activity loss.
A second subprogram, initiated in September 2017 and called “AdSOx”, aimed to obtain and test a bead-shaped form of the previously developed adsorbent in view of industrial applications. This product in bead-shaped adsorbent was then evaluated in 2019 in a pilot combustion rig, the flue gases of which were representative of a real industrial combustion installation in terms of SOx, NOx, CO, CO2, H2O and PM (particulate matter). In these rig tests, the performances of the adsorbent for the capture of SOx, including its capability to be regenerated for multi-cyclic use, have been assessed in fluidized bed and most recently in fixed bed conditions.
This paper outlines the most significant steps and outcomes of this collaborative two-phase development program. It also illustrates the interesting capabilities of mesoporous materials for the design of highly active sorption and catalytic systems.