E. Kawecka-Cebula

Co-combustion of biomass and bituminous coal in a fluidized two-bed reactor

ABSTRACT The combustion of hazelnut shells and bituminous coal was studied in a novel reactor with two disks, supporting two fluidized beds located one above the other. The reactor allows for the study of the impact of the fuels’ vertical arrangement in the combustion zone on SO2 emission. The biomass and coal were combusted in separate beds or as a mixture. The gas species concentrations were measured. A major drop in the SO2 coal emission was observed when the coal was combusted underneath the biomass bed, and a minor one, when above.

Investigations of the Dephosphorization of Liquid Iron Solution Containing Chromium and Nickel

The most up-to-date trends in stainless steel production—aiming at the reduction of production costs—consist of the substitution of steel scrap by hot metal, coming from the reduction of iron-chromium ores. This process requires a more extensive dephosphorization. The dephosphorization process, when applied to chromium steels, requires slag with high dephosphorization properties, as either chromium or chromium oxide entering the slag decreases distinctly the efficiency of the process. The results of laboratory investigations on the dephosphorization of liquid iron solutions containing chromium and nickel are presented. In particular, the study was focused on the selection of the optimal slag composition and the way the slag should be added. The slags based on calcium and fluorite with cryolite additions were considered. It was shown that the variables with the greatest impact on the dephosphorization process include chromium and nickel levels, temperature, and slag basicity. A statistical analysis was performed and regression equations were set. The results may be of use for the design of new methods of production of high-chromium steels.

Retention of S with Lignite Using Cedarnut Shell in the Co-combustion Process Performed in a Fluidized Bed Combustor

ABSTRACT The mix of high-sulfur lignite with cedarnut shell of high K2O content in ash was combusted in a fluidized bed reactor. When grain size distribution was identical, SO2 emission was the same as in the case of lignite alone. Under the same conditions, co-combustion of bituminous coal with cedarnut shells showed a significant drop of the SO2 emission. Reduction of SO2 emission was obtained by increasing the lignite grain size in order to extend the process of its combustion. When the lignite grain size was three times larger than the biomass grain size, the SO2 emission was 50% of the previous value, when six times larger it was 30%. This means that S retention takes place when SO2 released during lignite combustion is in direct contact with the biomass mineral residues. The most significant SO2 emission reduction occurred when lignite was combusted with biomass ash, not with raw biomass.

Comparison of hazelnut and peanut shells combustion in bubbling fluidized-bed combustor

ABSTRACT The combustion of peanut and hazelnut shells was studied in an atmospheric bubbling fluidized bed. The impact of the enrichment of air with oxygen and the flow rate of fluidizing gas on CO2 and CO concentrations was analyzed. It was stated that in air enriched with oxygen up to 25% the mole ratios of CO2 to CO were improved by 15–30%, depending on the flow rate used. For the peanut shell the combustion of volatiles with a hematite as an oxygen carrier was also studied. The effects were observed above ~ 450°C.

The Chemical-Looping Combustion of Propane with Iron (III) Oxide as an Oxygen Carrier

ABSTRACT The chemical-looping combustion of propane with the use of hematite and alumina-supported hematite carriers was studied in a fixed-bed reactor at 960°C, 910°C, and 870°C. In multiple cycles of the reduction/oxidation process, the concentrations of CO2 and CO in outlet gases were measured. The reactivity of the carriers was lowest in the first cycle. The conversion of propane was getting worse when the flow rate of propane was too high. The samples of the hematite carrier in the reduction stage were examined by X-ray diffraction (XRD) and thermogravimetric analysis (TGA) methods. Wustite and magnetite were detected as reduced forms of hematite. The theoretical analysis of the reduction paths of hematite by the propane decomposition products to Fe3O4, FeO, and Fe were conducted to investigate the pattern of the CO2 curve.