Универзитет у Београду, Технолошко-металуршки факултет
Abstract
Analiza kvaliteta ĉvrstih materijala, u zavisnosti od namene, obuhvata: tehniĉku analizu,
elementarnu analizu, analizu makrokomponenata i mikrokomponenata. Poseban analitiĉki
zadatak predstavlja analiza anjona u sloţenoj matrici ĉvrstog uzorka. U literaturi i
analitiĉkoj praksi postoji veliki broj metoda za odreĊivanje halogenih elemenata, od
klasiĉnih do savremenih (instrumentalnih), koje se razlikuju kako po principima rada, tako i
po kriterijumima koji karakterišu analitiĉke tehnike, od kojih treba izdvojiti taĉnost i
reproduktivnost.
Predmet rada ove doktorske disertacije su halogeni elementi u uglju. Halogeni elementi u
uglju su prisutni u niskim koncentracijama, ali je uticaj ovih elemenata na ţivotnu sredinu i
zdravlje ljudi od posebnog znaĉaja. Istraţivanja u okviru ove disertacije obuhvataju analizu
halogenih elemenata u uglju, rezultate istraţivanja pirohidrolitiĉke metode za odreĊivanje
halogenih elemenata, kao i primenu eksperimentalnog dizajna za razvoj analitiĉkih
metodologija.
Cilj ove doktorske disertacije bio je da se utvrdi metodologija i odrede uslovi za
istovremeno odreĊivanje fluora, hlora i broma u uglju. U okviru ove disertacije primenjene
su statistiĉke metode za organizaciju i izvoĊenje eksperimenata, i tehnike za obradu i
analizu dobijenih rezultata. Primenom frakcionisanog faktorijskog dizajna ispitan je uticaj
šest promenljivih na sagorevanje uglja u kiseoniĉnoj bombi i apsorpciju gasovitih
jedinjenja koja se tokom sagorevanja izdvajaju iz uglja. Ispitan je uticaj poĉetnog pritiska
kiseonika, dodatak katalizatora i pomoćnog goriva na sagorevanje uglja, kao i tip
apsorpcionog rastvora, dodatak redukcionog agensa i vreme hlaĊenja bombe nakon
sagorevanja na apsorpciju gasovitih jedinjenja. Koncentracija jona u apsorpcionom rastvoru
merena je potenciometrijski jon-selektivnom elektrodom (za fluorid-jon) i jonskom
hromatografijom. Rezultati frakcionisanog faktorijskog dizajna su analizirani pomoću
Pareto-grafika, grafika glavnih efekata i dijagrama interakcije parametara. UtvrĊeno je da
se dodatkom katalizatora i povećanjem pH vrednosti apsorpcionog rastvora smanjuje
koncentracija halogenid-jona u apsorpcionom rastvoru. S druge strane, povećanjem
poĉetnog pritiska kiseonika i dodatkom pomoćnog goriva, povećava se izdvajanje
halogenih elemenata iz uglja tokom sagorevanja u atmosferi kiseonika.
Na osnovu rezultata preliminarnih istraţivanja, pritisak kiseonika i zapremina pomoćnog
goriva su detaljnije ispitani primenom metodologije odgovora površine. Rezultati
optimizacionih eksperimenata razmatrani su analizom grafika odgovora površine, procene
regresionih koeficijenata i analize varijansi. Pošto su se optimalni uslovi za odreĊivanje
fluora i hlora razlikovali, definisan je grupni parametar - ukupni halogeni u uglju (engl.-
total halogen in coal, TCX). Ukupni halogeni u uglju su izraţeni preko hlora, a hlor je
izabran iz razloga što predstavlja dominantan halogeni element u uglju. Optimalni uslovi
metode odreĊivanja ukupnih halogena u uglju sagorevanjem u kiseoniĉnoj bombi su:
pritisak kiseonika od 2,5 MPa, zapremina pomoćnog goriva od 150 µL, apsorpcioni rastvor
je voda uz dodatak 0,5 % rastvora vodonik-peroksida i hlaĊenje kiseoniĉne bombe u
ledenom kupatilu 15 minuta nakon sagorevanja uglja. Masa uzorka je bila 0,5 g.
Validacija predloţene metode za odreĊivanje fluora i hlora sagorevanjem u kiseoniĉnoj
bombi uraĊena je analizom internih referentnih uzoraka uglja i sertifikovanih referentnih
ugljeva (BCR 460 i NIST 1632c). Relativna standardna devijacija odreĊivanja fluora bila je
manja od 5,0 %, a procenat izdvojenog fluora u odnosu na referentnu vrednost veći od 95
%. Relativna standardna devijacija odreĊivanja hlora bila je manja od 6,0 %, a procenat
izdvojenog hlora veći od 85 %, što znaĉi da je odreĊivanje fluora i hlora predloţenom
metodom precizno i reproduktivno. Predloţenom metodom je odreĊen i sadrţaj sumpora u
uglju. Validacija metode za odreĊivanje sumpora je pokazala da je standardna devijacija
merenja manja od 6 %, uz dobru ponovljivost.Comprehensive analysis of the quality of solids, depending on the application, includes:
technical analysis, elemental analysis, analysis of the macrocomponents and
microcomponents. A special analytical task is the analysis of anions in a complex matrix of
solid samples. In literature and in analytical practice there are a number of methods for the
determination of halogens, from classic to contemporary (instrumental), which differ
according to the principles of work, and according to criteria that characterize the analytical
techniques of which accuracy and reproducibility should be allocated.
The subject of the work of this doctoral thesis are halogen elements in coal. Halogen
elements in coal are present in low concentrations, but the impact of these elements on the
environment and human health is of particular importance. Research in this thesis are
designed in the field of analysis of the halogen elements in coal, the results of
pyrohydrolityc methods for the determination of halogens, as well as on the application of
experimental design for the development of analytical methodologies.
The aim of this doctoral thesis was to establish methodology and determine the conditions
for simultaneous determination of fluorine, chlorine and bromine in coal. Within this
dissertation statistical methods were applied for the plan and for conducting experiments,
and techniques for processing and analysis of results. Applying fractional factorial design,
the influence of six variables on coal combustion in oxygen bomb and absorption of
gaseous compounds during combustion was investigated. The analyzed variables were
oxygen pressure, catalysts, combustion aid, type of absorbent solution, reducing agent and
bomb cooling time. The concentration of ions in the absorption solution was measured by
ion-selective electrode (the fluoride-ion) and by ion chromatography. The results of
fractional factorial design were analyzed using Pareto-graphics, graphics of main effects
and interaction plots. It was found that with the addition of the catalyst and with the
increase of pH value of the absorption solution the concentration of halide ions in the
absorption solution decreases. On the other hand, increase of oxygen pressure and the
addition of combustion aid, increases the separation of halogens from the coal during
combustion in an oxygen atmosphere.
On the basis of preliminary studies, oxygen pressure and combustion aid were examined in
more detail by using response surface methodology. Results of the optimization
experiments were discussed using response surface plots, estimateted regression
coefficients and analysis of variance. Since the optimum conditions for the determination of
fluorine and chlorine differed, the group parameter - total halogens in coal (TCX) was
defined. Total halogen in coal are expressed in terms of chlorine and it was chosen because
it is the dominant halogen element in coal. The optimal parameters for the determination of
halogens in coal were 0.5 g of coal samples, oxygen pressure of 2.5 MPa, 5 cm3
of H2O as
the absorption solution, 5 cm3
of H2O2 as reducing reagent, 150 µL of mineral oil as the
combustion aid, and a cooling interval of 15 minutes after combustion.
Validation of proposed method was performed by determination of fluorine and chlorine in
in-house prepared reference coal samples and in certified reference materials (BCR 460 and
NIST 1632c). The relative standard deviation of determination of fluorine was less than
5.0%, and recovery was greater than 95%. The relative standard deviation of determination
of chlorine was less than 6.0%, and recovery greater than 85%.The method was sensitive,
with good reproducibility and accuracy. The proposed method was applied for
determination of sulfur in coal. Validation of a method for determining the sulfur content is
shown that the standard deviation of measurements was less than 6%, with a good
reproducibility.
The limit of detection (LOD) and limit of quantification (LOQ) is estimated for ion
chromatography measurements and standard deviation of determining ions in the mixed
standard solution of the lowest concentration. It has been found that the LOD and LOQ for
fluorine were 0.4 mg / kg and 1.26 mg / kg; chlorine 0.84 mg / kg and 2.79 mg / kg; sulfur
2.2·10-5 % and 7.2·10-5 %. The proposed method was applied for the determination of
fluorine, chlorine and sulfur in Kolubara and Kostolac coal samples