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The reduction of NO by potassium-containing activated carbons and briquettes prepared from a bituminous coal was investigated. Partial washing of KOH activated carbons produced samples with different potassium contents. Briquetting with a binder containing potassium, at different binder/coal ratios, also allowed carbons with different potassium contents to be obtained. The NO-carbon reaction was...
The effect of low-concentration SO 2 on the adsorption of NO over activated carbon was studied using adsorption--desorption profiles obtained during thermal analysis-mass spectrometry. Using three different gas mixtures and adsorption temperatures between 293 and 413 K with NO and SO 2 as the reactants, it was determined that NO 2 and SO 2 were the primary adsorbed...
Activated coke (AC) acts both as an adsorbent for SO x and air toxic materials and as a catalyst for NO x reduction in flue gas treatment at temperatures of 100-200°C. AC has a surface area of 150-250 m 2 g -1 , which is less than that of conventional activated carbons, and an SO 2 adsorption capacity of 60-120 mg g -1 which is less influenced...
The role of O- and N-containing surface species in the course of NO reduction over phenol-formaldehyde resin char and amorphous 13 C was investigated. The presence of O-containing complexes on the char surface was shown to increase the reactivity towards NO by providing free reactive sites. The presence of O 2 also enhanced the NO reduction reaction greatly. A mass balance...
The literature on the kinetics of the NO-carbon reaction is reviewed. Data are examined both from studies in which catalysis played no role and from studies in which catalysts were present as a result of addition or as natural inclusions (i.e. in coals). It is concluded that there generally exist three distinct reaction regimes, defined in terms of reaction temperatures. There is a near-ambient-temperature...
Calcium-containing carbons were tested as low-temperature sorbents for SO 2 . CaO particles dispersed on carbon were prepared by thermal decomposition of calcium acetate. Samples with calcium contents ranging from 1.5 to 8.0 wt% were analysed. CO 2 chemisorption was used to characterize the area of the CaO particles available to interact with and retain SO 2 . CaO surface...
The reduction of NO by CO over silica was studied in the temperature range from 873 to 1273 K under an initial gas (NO, CO) pressure of 395 Pa. Reduction was carried out by a volumetric technique with a mass spectrometer for the analysis of the gaseous phase. The catalytic activity of silica is enhanced by its pretreatment in air or in vacuum in the temperature interval 873-1273 K and as a result...
The release of nitrogen oxides during coal combustion has a major environmental impact. In low-NO x burners and fluidized bed combustors the char nitrogen is the major contributor to nitrogen oxide emissions. In this review the release of nitrogen oxides during the combustion of chars is considered in relation to coal and char structural characteristics. The changes in the nitrogen functionality...
The three-way catalysts currently used for controlling NO x gaseous pollutants from IC engines cannot be used under lean conditions such as diesel engine exhausts. Approaches to NO x reduction have therefore focused on direct decomposition of NO to its elements or selective catalytic reduction with hydrocarbons to N 2 . Metal-doped ZSM-5 catalysts are active in these reactions,...
The combined DeSOx-DeNOx-air toxics removal process using activated coke (AC) has been applied to flue gas cleanup: the DeSOx-DeNOx process for SO x -NO x -containing flue gas from coal boilers and the RFCC process; the DeNOx process for FBC boiler flue gas; and the DeNOx and toxics reduction process for refuse incinerator flue gas. Schematic process flow diagrams and AC performance...
Catalytic oxidation of NO (380 ppmv) to NO 2 over activated carbon fibres of moderate surface area (∼800 m 2 g -1 ) at room temperature was carried out, to develop oxidative removal of NO from flue gas. The heat treatment of pitch-based activated carbon fibres of moderate surface area markedly increased the conversion of NO to 87% in dry air, 62% in air of 80% relative...
Continuous removal of SO 2 as aqueous H 2 SO 4 over polyacrylonitrile-based activated carbon fibres (PAN-ACF) was studied kinetically at room temperature to determine the effects of SO 2 (20-1000 ppmv), O 2 (0-10 vol.%) and H 2 O (0-10 vol.%) concentrations and W/Q ratio (mass of ACF/volumetric flow rate of gas). An oxygen level > 3 vol.% was sufficient...
Sulfur dioxide was continuously converted to aqueous sulfuric acid using a polyacrylonitrile-based activated carbon fibre catalyst (PAN-ACF) in a packed-bed reactor system. The qualitative effects of residence time and oxygen, nitrous oxide, sulfur dioxide, and water concentrations were reported in Part 1. The conversion conditions were chosen to be typical of those expected in flue gas streams:...
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