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

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

Extraction and evaluation of natural occurring bioactive compounds and change in antioxidant activity during red winemaking

Phenolic composition of red wines from Stanušina, a grape variety indigenous of the Republic of Macedonia, was compared with the regional Vranec and the international Cabernet Sauvignon. The extent of skin contact (i.e. maceration time) on levels of phenolic compounds and antioxidant activity of wines was evaluated. A total of 19 phenolic compounds were identified and quantified. Among these malvidin-3-glucoside and its derivatives were the major compounds, while caftaric acid was the predominant cinnamic acid derivative, followed by catechin, the main flavan-3-ol. The concentration of hydroxycinnamic acids, anthocyanins and (+)-catechin ranged from 224 to 511 mg/L, 22 to 360 mg/L and 26 20 to 375 mg/L, respectively and peaked at 3rd, 6th and 9th day of maceration, respectively. However, prolong maceration slightly decreased their concentration. Stanušina wines presented high levels of hydroxycinnamic acids and antioxidant activity