Authors:Tiit Kaljuvee, Merli Keelmann, Andres Trikkel, and Rein Kuusik
biggest of them are concentrated in USA, Russian Federation, Congo, Brazil, China, etc. Active exploitation of OS takes place in Estonia (for electricity generation and for shale oil production), Brazil (shale oil), China (shale oil), modestly in Israel
The results obtained by studying decarbonization of different samples of Estonian limestone and dolomite and the following
sulphation or carbonation of calcined products to estimate their SO2 and CO2 binding ability were presented. Experiments were
carried out with thermogravimetric equipment(Q-Derivatograph, MOM and Labsys™, SETARAM) – calcination of the samples in the
atmosphere of air with the heating rate 10 K per minute using multiplate crucibles, the following sulphation or carbonation
of the calcined products after cooling to the fixed temperature (temperature range 400–900C) under isothermal conditions
in the flow of air-SO2 or air-CO2 mixture. Chemical, X-ray, BET nitrogen dynamic desorption, etc. methods for the characterization of the initial samples,
intermediate and final products were used.
In addition, the possibilities of recurrent use of oil shale ashes taken from different technological points at operating
thermal power plants (Estonian and Baltic TTPs, Estonia) as sorbents for SO2 binding from gaseous phase were studied, as well as the possibilities of activation of these ashes towards SO2 binding.
The results of these studies confirmed the high reactivity of Estonian limestone and dolomite towards SO2 and CO2. Dependence of SO2 binding mechanism on the SO2 concentration has been established. Modelling of SO2 capture of dolomite and limestone was carried out to establish the kinetic parameters of these processes. The possibilities
of activation of oil shale ashes and their effective recurrent use for binding SO2 and CO2 from gaseous phase were confirmed.
The dynamics of SO2 emission during thermooxidation of Estonian oil shale, its semicoke, different samples of coal and their mixtures, as well
as the influence of Estonian oil shale ash addition (for modelling the CFBC process) on the dynamics were studied. The experiments
were carried out with thermogravimetric equipment under dynamic heating conditions (5 K min-1) in the atmosphere of dried air, with simultaneous gastitrimetric EGA.
It was established that SO2 emission from the fuels started at 200-320C. Depending on the form of sulphur (organic, pyritic, sulphate), the emission
took place in two or three steps, and continued up to 580-650C, during which 35-75% of the total sulphur was emitted into
the gaseous phase. Regulating the mole ratio of free CaO/S in the mixtures of fuels with oil shale ash addition the emission
of SO2 ceased abruptly at 460-540C and it was limited to the level of 7-30%.
The combined thermogravimetric (TG) Fourier transform infrared (FTIR) techniques were used for studying the gaseous compounds
evolved at thermooxidation of oil shale samples from different deposits (Estonia, Jordan, Israel). In addition to H2O and CO2as the major species, the formation and emission of CO, SO2, HCl and a number of organic species as methane, ethane, ethylene, methanol, formic acid, formaldehyde, chlorobenzene, etc.
was determined. Differences in the absorbance of respective bands in FTIR spectra depending on the origin of oil shale and
on the heating rate used were established.
Authors:Kadri Siimer, Tiit Kaljuvee, Tõnis Pehk, and Ilmar Lasn
Thermal behaviour of industrial UF resins modified by low level of melamine was followed by TG-DTA technique on the labsysTM instrument Setaram together with the 13C NMR analysis of resin structure and testing boards in current production at Estonian particleboard factory Pärnu Plaaditehas
AS. DTA curve of UF resin which has been cocondensed during synthesis with even low level of melamine shows the shift of condensation
exotherm and water evaporation endotherm to considerable higher temperatures. The effect of melamine monomer introduced to
UF resin just before curing was compared. The effect of addition of urea as formaldehyde scavenger was studied.
Authors:T. Kaljuvee, I. Rudjak, E. Edro, and A. Trikkel
The effect of heating rate on the thermal behavior of ammonium nitrate (AN) and on the kinetic parameters of decomposition
of AN and its blends with limestone and dolomite was studied on the basis of commercial fertilizer-grade AN and several Estonian
limestone and dolomite samples. Experiments were carried out under dynamic heating conditions up to 900 °C at heating rates
of 2, 5, 10 and 20 °C min−1 in a stream of dry air using Setaram Labsys 2000 equipment. For calculation of kinetic parameters, the TG data were processed
by differential isoconversional method of Friedman. The variation of the value of activation energy E along the reaction progress α showed a complex character of decomposition of AN—interaction of AN with limestone and dolomite
additives with the formation of nitrates as well as decomposition of these nitrates at higher temperatures.
Authors:K. Siimer, P. Christjanson, T. Kaljuvee, T. Pehk, I. Lasn, and I. Saks
The thermal behaviour of MUF resins from different suppliers with different content of melamine was studied, along with the
13C NMR spectroscopic analysis of resin structure and the testing of particleboards in current production at Estonian PB factory
Pärnu Plaaditehas AS. The chemical structure of resins from DMSO-d6 solutions was analysed by 13C NMR spectroscopy on a Bruker AMX500 NMR spectrometer. The melamine level in different MUF resins is compared by the ratios
of carbonyl carbon of urea and triazine carbon of melamine in 13C NMR spectra. Curing behaviour of MUF resins was studied by stimultaneous TG-DTA techniques on the Labsys™ instrument Setaram.
The shape of DTA curves characterisises the resin synthesis procedure by the extent of polymerisation of UF and MF components
and is in accordance with structural data.
Authors:T. Kaljuvee, M. Toom, A. Trikkel, and R. Kuusik
The extensive use of fossil fuels in energy production causes serious
pollution of atmosphere with SO2, CO2,
NOx, etc. In Estonia the electricity production is
based mainly on the pulverized firing (PF) of low-grade local fuel –
Estonian oil shale (EOS) which is characterized by a low calorific value (~9
MJ kg–1) and a high content of mineral matter
(65–70%) from which approximately 50% are carbonates. Since 2004, also
two boilers based on circulating fluidized bed combustion (CFBC) of EOS are
The present study is focused on the comparative
investigation of the efficiency of different ashes collected from different
technological points of CFB and PF boilers as sorbents for SO2.
The influence of experimental temperature on the SO2-binding
characteristics of ashes as well as the possibilities of activation of ashes
(grinding, hydration) were investigated. It was shown that the SO2-binding
capacity of initial ashes at 700C and p(SO2)=190
mm Hg was for CFBC ashes 24–30 mg and for PF ashes 10–23 mg SO2
per 100 mg sample, the best binding capacities belonging to economizer ash
(ECOA) and electrostatic precipitator ash from the 1st field (PESPA1f), respectively.
However, during initial stage of binding the best results were obtained with
air pre-heater ash (PHAA) and ESPA1f (both CFBC ashes). Grinding improved
the SO2-binding ability, being the most effective in
the case of bottom ash (BA) from CFBC and cyclone ash (PCA) from PF –
increase in binding capacity 2 and 2.3 times, respectively. As compared to
initial CFBC ashes, the binding characteristics of PF ashes remained lower
even after grinding. Hydration and previous calcination improved the binding
characteristics only of PF ashes. Hereby, the SO2-binding
ability of CFBC ashes is better than of PF ashes and they are more promising
sorbents for acidic gases, for example, for sulphur dioxide.
Ammonium nitrate (AN) is one of the main nitrogen fertilizers used in fertilization programs. However, AN has some serious
disadvantages — being well soluble in water hardly 50% of the N-species contained are assimilated by plants. The second disadvantage
of AN is associated with its explosive properties. The aim of this paper was to clarify the influence of different lime-containing
substances — mainly Estonian limestone and dolomite — as internal additives on thermal behaviour of AN.
Commercial fertilizer grade AN was under investigation. The amount of additives used was 5, 10 or 20 mass%, or calculated
on the mole ratio of AN/(CaO, MgO)=2:1 in the blends. Experiments were carried out under dynamic heating condition up to 900°C
(10°C min−1) in a stream of dry air or N2 by using Setaram Labsys 2000 equipment coupled to Fourier transform infrared spectrometer (FTIR).
The results of analyses of the gaseous compounds evolved at thermal treatment of neat AN indicated some differences in the
decomposition of AN in air or in N2. At the thermal treatment of AN’s blends with CaCO3, MgCO3, limestone and dolomite samples the decomposition of AN proceeds through a completely different mechanism — depending on
the origin and the content of additives, partially or completely, through the formation of Mg(NO3)2 and Ca(NO3)2.
Authors:I. Rudjak, T. Kaljuvee, A. Trikkel, and V. Mikli
The thermal behaviour of ammonium nitrate (AN) and its prills coated with limestone and dolomite powder was studied on the
basis of commercial fertilizer-grade AN and six Estonian limestone and dolomite samples. Coating of AN prills was carried
out on a plate granulator and a saturated solution of AN was used as a binding agent. The mass of AN prills and coating material
was calculated based on the mole ratio of AN/(CaO + MgO) = 2:1. Thermal behaviour of AN and its coated prills was studied
using combined TG-DTA-FTIR equipment. The experiments were carried out under dynamic heating conditions up to 900 °C at the
heating rate of 10 °C min−1 and for calculation of kinetic parameters, additionally, at 2, 5 and 20 °C min−1 in a stream of dry air. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman
was used to calculate the kinetic parameters. The results of TG-DTA-FTIR analyses and the variation of the value of activation
energy E along the reaction progress α indicate the complex character of the decomposition of neat AN as well as of the interactions
occurring at thermal treatment of AN prills coated with limestone and dolomite powder.