Sedimentological and Surface Characteristics of the Northern and Central Adriatic Sediments

The results of this investigation reveal mutual relationship between some sedimentological and surface chemical characteristics, such as granulometric and mineral composition, specific surface area (SSA) and organic matter content, of northern and central Adriatic surface sediments. Grain size distribution and mineral composition enabled the reconstruction of the sedimentation pattern in the northern and central Adriatic Sea. It was shown that sands are spread in the east, along the Croatian coast. Toward the west, the share of finer sediments increases, so that the western region (parallel to the Italian coast) is covered with pelites. Such a pattern is typical for the northern Adriatic and the 401-407 profile of the central Adriatic. Most of the central region is covered with pelites. Granulometric and mineral composition are interrelated, indicating that sediments having more clay minerals (aluminosilicates) are always fine-grained, while coarser sediments contain more quartz and carbonates. The SSA and organic matter content are dependent on the grain size and mineral composition - fine-grained clay minerals have larger SSA’s and contain more organic matter attached to their surface. These organic substances influence considerably the SSA of sediments. It was noted that, after removing the organics, the SSA of sediments changed. This indicates that, effecting the SSA of sediments, organic matter effects their adsorptive ability

Low Temperature Selective Catalytic Reduction of Nitrogen Oxides in Production of Nitric Acid by the Use of Liquid Ammonia

U radu je prikazana primjena niskotemperaturne selektivne katalitičke redukcije dušikovih oksida u otpadnom plinu od proizvodnje dušične kiseline. Selektivna katalitička redukcija provodi se heterogenim katalizatorom TiO2/WO3 nanesenim na nosač od Al2O3 velike aktivne površine po obujmu, oblika pčelinjeg saća. Prikazana je učinkovitost selektivne katalitičke redukcije u temperaturnom području otpadnog plina od 180 do 230 °C uz izravnu primjenu tekućeg amonijaka, bez prethodnog isparavanja u plinovito stanje. Posebnom izvedbom sustava za izravno doziranje tekućeg amonijaka te omogućavanjem učinkovite homogenizacije s otpadnim plinom postignute su emisije dušikovih oksida od 100,0 do 185,0 mg m-3 izrađenih kao NO2 u otpadnom plinu. Pokazano je da niskotemperaturna selektivna katalitička redukcija uz izravnu primjenu tekućeg amonijaka otvara novu mogućnost za smanjenje emisije dušikovih oksida u proizvodnji dušične kiseline. Istodobno se izbjegava svaka mogućnost pojave dušikovih oksida nakon heterogenog katalizatora u procesu naknadnog iskorištenja energije otpadnog plina u plinskoj turbini. Izravnom primjenom tekućeg amonijaka omogućen je jednostavniji sustav selektivne katalitičke redukcije dušikovih oksida u otpadnom plinu, bez dodatne operacije isparavanja i predgrijavanja te se ostvaruje ekonomski i energetski učinkovitije smanjenje emisije dušikovih oksida uz poštovanje zakonskih odredbi o graničnim emisijama.This paper presents the application of low-temperature selective catalytic reduction of nitrous oxides in the tail gas of the dual-pressure process of nitric acid production. The process of selective catalytic reduction is carried out using the TiO2/WO3 heterogeneous catalyst applied on a ceramic honeycomb structure with a high geometric surface area per volume. The process design parameters for nitric acid production by the dual-pressure procedure in a capacity range from 75 to 100 % in comparison with designed capacity for one production line is shown in the Table 1. Shown is the effectiveness of selective catalytic reduction in the temperature range of the tail gas from 180 to 230 °C with direct application of liquid ammonia, without prior evaporation to gaseous state. The results of inlet and outlet concentrations of nitrous oxides in the tail gas of the nitric acid production process are shown in Figures 1 and 2. Figure 3 shows the temperature dependence of the selective catalytic reduction of nitrous oxides expressed as NO2in the tail gas of nitric acid production with the application of a constant mass flow of liquid ammonia of 13,0 kg h-1 and average inlet mass concentration of the nitrous oxides expressed as NO2 of 800,0 mgm-3 during 100 % production capacity. The specially designed liquid-ammonia direct-dosing system along with the effective homogenization of the tail gas resulted in emission levels of nitrous oxides expressed as NO2 in tail gas ranging from 100,0 to 185,0 mg m-3. The applied low-temperature selective catalytic reduction of the nitrous oxides in the tail gases by direct use of liquid ammonia is shown in Figure 4. It is shown that low-temperature selective catalytic reduction with direct application of liquid ammonia opens a new opportunity in the reduction of nitrous oxide emissions during nitric acid production without the risk of dangerous ammonium nitrate occurring in the process of subsequent energy utilization of tail gas through a gas turbine. With the direct application of liquid ammonia it is possible to create the simpler system of selective catalytic reduction of tail-gas nitrous oxides, thus avoiding the additional processes of vaporization and preheating, and thereby achieving an economic and energetic-efficient procedure for their reduction down to legally prescribed limits

Femtosecond laser pulse train effect on Doppler profile of cesium resonance lines

We present direct observation of the velocity-selective optical pumping of the Cs ground state hyperfine levels induced by the femtosecond (fs) laser oscillator centered at either D2 (6 2S1/2↦6 2P3/2, 852 nm) or D1 (6 2S1/2↦6 2P1/2, 894 nm) cesium line. We utilized previously developed modified direct frequency comb spectroscopy (DFCS) which uses a fixed frequency comb for the excitation and a weak cw scanning probe laser centered at the 133Cs 6 2S1/2↦6 2P3/2 transition (D2 line) for ground levels population monitoring. The frequency comb excitation changes the usual Doppler absorption profile into a specific periodic, comblike structure. The mechanism of the velocity selective population transfer between the Cs ground state hyperfine levels induced by fs pulse train excitation is verified in a theoretical treatment of the multilevel atomic system subjected to a pulse train resonant field interaction

Low Temperature Selective Catalytic Reduction of Nitrogen Oxides in Production of Nitric Acid by the Use of Liquid

This paper presents the application of low-temperature selective catalytic reduction of nitrous oxides in the tail gas of the dual-pressure process of nitric acid production. The process of selective catalytic reduction is carried out using the TiO₂/WO₃ heterogeneous catalyst applied on a ceramic honeycomb structure with a high geometric surface area per volume. The process design parameters for nitric acid production by the dual-pressure procedure in a capacity range from 75 to 100 % in comparison with designed capacity for one production line is shown in the Table 1. Shown is the effectiveness of selective catalytic reduction in the temperature range of the tail gas from 180 to 230 °C with direct application of liquid ammonia, without prior evaporation to gaseous state. The results of inlet and outlet concentrations of nitrous oxides in the tail gas of the nitric acid production process are shown in Figures 1 and 2. Figure 3 shows the temperature dependence of the selective catalytic reduction of nitrous oxides expressed as NO2in the tail gas of nitric acid production with the application of a constant mass flow of liquid ammonia of 13,0 kg h^-1 and average inlet mass concentration of the nitrous oxides expressed as NO₂of 800,0 mgm^-3 during 100 % production capacity. The specially designed liquid-ammonia direct-dosing system along with the effective homogenization of the tail gas resulted in emission levels of nitrous oxides expressed as NO₂ in tail gas ranging from 100,0 to 185,0 mg m^-3. The applied low-temperature selective catalytic reduction of the nitrous oxides in the tail gases by direct use of liquid ammonia is shown in Figure 4. It is shown that low-temperature selective catalytic reduction with direct application of liquid ammonia opens a new opportunity in the reduction of nitrous oxide emissions during nitric acid production without the risk of dangerous ammonium nitrate occurring in the process of subsequent energy utilization of tail gas through a gas turbine. With the direct application of liquid ammonia it is possible to create the simpler system of selective catalytic reduction of tail-gas nitrous oxides, thus avoiding the additional processes of vaporization and preheating, and thereby achieving an economic and energetic-efficient procedure for their reduction down to legally prescribed limits

High performance illitic clay-based geopolymer : Influence of the mechanochemical activation duration on the strength development

Proceedings of the 3rd International Conference on Calcined Clays for Sustainable Concrete, New Delhi, INDE, 15-/10/2019 - 17/10/2019Demonstrate the feasibility of an illitic clay-based geopolymer is the purpose of this study. If the thermal activation of standard precursors such as kaolin is a well-known process, the reactivity of illitic precursors required the combination of thermal and mechanochemical activation. The structural changes of the precursor material submitted to various grinding durations were followed by X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) and the amorphous phase rate calculated from XRD analyses was correlated with this parameter as well as the compressive strength (Rc) of the manufactured geopolymers. Mechanical properties increased with the grinding time and the decrease of L/S ratio of the geopolymer paste. Illitic clay-based geopolymers may reach high performance as demonstrated with a Rc at 28 days reaching 102 MPa. Finally, the relations between the amorphisation rate and the compressive strength of the geopolymers have been highlighte