Wyniki wyszukiwania - BazTech

1

Transformations of mercury in processes of solid fuel combustion : review

Czaplicka M., Pyta H.

Archives of Environmental Protection

|

2017

|

Vol. 43, no. 4

82--93

EN

The paper presents current reports on kinetics and mechanisms of reactions with mercury which take place in the exhaust gases, discharged from the processes of combustion of solid fuels (coals). The three main stages were considered. The first one, when thermal decomposition of Hg components takes place together with formation of elemental mercury (Hg0). The second one with homogeneous oxidation of Hg0 to Hg2+ by other active components of exhaust gases (e.g. HCl). The third one with heterogeneous reactions of gaseous mercury (the both - elemental and oxidised Hg) and solid particles of fly ash, leading to generation of particulate-bound mercury (Hgp). Influence of exhaust components and their concentrations, temperature and retention time on the efficiency of mercury oxidation was determined. The issues concerning physical (gas-solid) and chemical speciation of mercury (fractionation Hg0-Hg2+) as well as factors which have influence on the mercury speciation in exhaust gases are discussed in detail.

PL

Artykuł stanowi podsumowanie aktualnego stanu wiedzy nt. kinetyki i mechanizmów reakcji z udziałem rtęci, w tym reakcji homogenicznych i heterogenicznych, zachodzących w spalinach z procesów spalania paliw stałych. Opisano wpływ składników spalin i temperatury na efektywność utleniania rtęci. Omówiono również zagadnienia fizycznej i chemicznej specjacji rtęci w gazach spalinowych, jak również wpływ różnych czynników na specjację rtęci.

2

Sorpcja cynku na dolomicie ze złóż rudnych

Girczys J.

Inżynieria Mineralna

|

2005

|

R. 6, nr 1

45-54

PL

Oznaczano wielkość sorpcji cynku z roztworów wodnych na drobnoziarnistym dolomicie ze złoża rud Zn-Pb rejonu bytomskiego. Wykazano, że sorpcja ma charakter reakcji heterogenicznej, w której decydującym o wydajności czynnikiem jest dyfuzja substratów i produktów w warstwie przy powierzchni ziarna. Wskazano na warunki zmieniające wartość sorpcji i ich znaczenie dla możliwości wykorzystania drobnoziarnistego dolomitu jako podłoża składowisk, chroniącego przed migracją jonów metali ciężkich do środowiska.

EN

The value of sorption of zinc from water solutions on fine-grained dolomite coming from a Zn-Pb ore deposit of the Bytom area (Poland). It has been demonstrated that sorption has a nature of a heterogeneous reaction, in which the factor that decides on the efficiency is the diffusion of substrates and products in the layer close to grain surface. It has been pointed at the conditions changing the value of sorption and their importance for the possibility of using the fine- grained dolomite as a base of landfills, protecting against the migration heavy metal ions into the environment

3

Modelowanie heterogenicznych reakcji związków organicznych w atmosferze

Isidorov V., Jaroszyńska J.

Wiadomości Chemiczne

|

1998

|

[Z] 52, 7-8

569-586

EN

Any organic substances emitted from various sources into the oxygen-containing atmosphere are subjected to oxidation in sunlight-initiated reactions. The role of various processes in the sinks is different and inconstant because it depends not only on the physico-chemical properties of specific compounds but also on varying environmental conditions, solar radiation level, the content of anthropogenic pollutants and dust in the atmosphere, aerosol particles composition, etc. [1-3]. A fundamental property of the Earth's atmosphere is its heterogeneity. Billions of tons of continuosly renewed, finely dispersed material of tremendous surface and excess free energy are annually emitted into it. Aerosol particles formed during weathering of the Earth's crust mainly consist of minerals based on silica (pyroxene, epidote, mica, quartz, etc.) as well as apatite, magnetite, ilmenite, etc. [13-15]. The particles of NaCl and KCl in the sea aerosol contain as inclusion in the crystalline lattice the atoms of many metals (Fe, Mn, Cr, Cu, Ti, Zn, etc.) [9]. This composition of the main components of natural aerosol ensures the appearance of impurity conductivity upon irradiation with light in the near UV or even in the visible spectral regions (Tab.3). As a results of irradiation, various active centres (free radicals and ions) are formed on the particles, thus ensuring the possibility of photochemosorption of volatile components [16-21]. Therefore, there is no doubt that the surface of solid particles of atmospheric aerosol should serve as an arena on which various chemical transformations with the participation of sorbed components take place (Tab. 5). The results of laboratory investigations of the oxidation of isoprene, monoterpenes [43-45, 47], aromatic hydrocarbons [36, 44-46, 48, 50-52] and halocarbons [27, 28, 30] on particles of metal oxides, desert sand, volcanic ash, sea salt, and calcium carbonate are reported. The only gaseous oxidation product was CO2, however, a broad spectrum of intermediates is detected on the particle surface. The values of rate constants for heterogeneous oxidation of different organic compounds indicate that these reactions can compete with gas-phase oxidation and, hence, deserve attention as a possible sink of Corg in the atmosphere [48, 58-60].