Selective oxidation processes for ultra-efficient fuel and waste conversion, materials recycling, gas synthesis and processing.
Paper in proceedings, 2017
This paper presents and discusses a concept of a two-step selective oxidation technology. A new concept that provides for efficient conversion of fuels, wastes and chemicals combined with recycling of materials with the potential to enable negative emissions of carbon dioxide and zero emissions of other pollutants. The aim of the concept is to turn - what is today considered as waste or side streams - into useful products. The proposed process enable controlled oxidation atmospheres, while avoiding dilution of ambient nitrogen. The first step is based on oxidation of organic material by means of metal-based particles (oxygen carriers, OC), which transfer oxygen and catalytic surfaces in between three reactors; this part of the process will be referred to as oxygen looping (OXL). Most of the previous experience on this OC technology stems from lab-scale research and so called Chemical-Looping systems and the reactor system is based on fluidized beds (FB). These experiences indicate two promising features of the OXL process; the possibility to reach complete conversion under near stoichiometric air to fuel conditions and that the content of the outlet stream from the process, in addition to water and oxides of other pollutants, mainly NOx and SOx, consists of concentrated carbon dioxide. Recent findings from experiments with OC as bed material in industrially relevant conditions (75 MWth) indicate promising features for scale-up of OC techniques and that common FB combustion issues can be abated by the use of OC as bed material. The second oxidation step concerns gas cleaning which uses pressure as a driving force for selective oxidation (referred to as PGC, Pressurized Gas Cleaning). When the flue gas is cleaned at elevated pressure, the oxidation of NO to NO2 is strongly enhanced. NO2 is dissolved into the water which promotes fast absorption of SO2 via H2SO3 into the condensate. According to recent theoretic findings, the final result is complete conversion of NOx and SOx into pure acids. Combined, these two oxidation processes (OXL-PGC) could therefore potentially enable conversion of fuels with complete separation of all major gas components at a minimum cost. These gases may be turned into new products and the CO2 may also be captured and stored (CCS).