Reduction and Analysis of Low Temperature Shift Heterogeneous Catalyst for Water Gas Reaction in Ammonia Production

Radi dobivanja dodatnih količina vodika nakon reakcija parnog reformiranja prirodnog plina te zaštite rada heterogenog katalizatora za sintezu amonijaka bitno je postići i održavati maksimalnu aktivnost, selektivnost i stabilnost heterogenog katalizatora niskotemperaturne pretvorbe (konverzije) vodenog plina. Budući da se heterogeni katalizator isporučuje u oksidiranom obliku, presudno je provođenje pravilnog postupka redukcije. Pravilnim postupkom redukcije i kontinuiranom analizom njegova rada osigurava se nužno potrebna aktivnost, selektivnost i stabilnost tijekom primjene. Da bi se uspješno provela redukcija heterogenog katalizatora za niskotemperaturnu pretvorbu vodenog plina, potrebno je osim procesne opreme za provođenje postupka redukcije primjenjivati pouzdan i realan sustav za mjerenje temperature radi učinkovitog uvida u temperaturne profile unutar reaktora pri provedbi egzotermne reakcije kroz sve slojeve heterogenog katalizatora. Kako bi se provjerila učinkovitost redukcije te omogućila analiza njegova rada, potrebno je u pravilnim razdobljima određivati odnos odgovarajućih temperaturnih profila i konstante ravnoteže reakcije. To se postiže analizom temperaturnih profila u pojedinim slojevima heterogenog katalizatora putem "S" i padajućih temperaturnih krivulja. Na temelju dobivenih podataka može se na zadovoljavajući način određivati optimalna temperatura na ulazu u reaktor kako bi se osigurao maksimalni vijek katalizatora. U radu je opisana redukcija heterogenog katalizatora in situ te dan prikaz sustava za praćenje temperature unutar pojedinih slojeva, kako bi se postigao minimalan sadržaj ugljikova (II) oksida na izlazu iz reaktora. Opisani sustav za praćenje temperature kroz slojeve heterogenog katalizatora osigurao je uspješnu redukciju koja se zasnivala na optimalnom povećanju temperature na ulazu u reaktor. Primijenjenim sustavom postignute su zadovoljavajuće katalitičke značajke (aktivnost, selektivnost i stabilnost). Također je omogućeno predviđanje rada katalizatora te donošenje odluke o potrebi njegove zamjene, što izravno utječe na smanjenje troškova proizvodnje.In order to obtain additional quantities of hydrogen after the reforming reactions of natural gas and protect the ammonia synthesis catalyst, it is crucial to achieve and maintain maximum possible activity, selectivity and stability of the low temperature shift catalyst for conversion of water gas reaction during its lifetime. Whereas the heterogeneous catalyst comes in oxidized form, it is of the utmost importance to conduct the reduction procedure properly. The proper reduction procedure and continuous analysis of its performance would ensure the required activity, selectivity and stability throughout the catalyst’s service time. For the proper reduction procedure of the low temperature shift catalyst, in addition to process equipment, also necessary is a reliable and realistic system for temperature measurements, which will be effective for monitoring the exothermal temperature curves through all catalyst bed layers. For efficiency evaluation of low shift temperature catalyst reduction and its optimization, it is necessary to determine at regular time intervals the temperature approach to equilibrium and temperature profiles of individual layers by means of “S” and “die off” temperature exothermal curves. Based on the obtained data, the optimum inlet temperature could be determined, in order to maximally extend the service life of the heterogeneous catalyst as much as possible, and achieve the optimum equilibrium for conversion of the water gas. This paper presents the methodology for in situ reduction of the low temperature shift heterogeneous catalyst and the developed system for monitoring its individual layers to achieve the minimum possible content of carbon monoxide at the exit of the reactor. The developed system for temperature monitoring through heterogeneous catalyst layers provides the proper procedure for reduction and adjustment of optimum process working conditions for the catalyst by the continuous increase of reactor inlet temperature. The applied system provides maximum catalytic activity, selectivity and stability, as well as enables prediction of the catalyst\u27s performance, which can be the basis for a proper decision on its timely replacement, and significant reduction of production costs

Architecture and Design of the McMaster NEUDOSE Communication Radio Subsystem

The communication subsystem is responsible for ensuring robust communication between the McMaster NEUDOSE CubeSat and the Ground Station located at McMaster University. This subsystem sends the collected scientific data, system telemetry (health), and telecommand from the onboard instruments using two different communication radio frequencies

Risk Factors for Intraoperative Hypertension during Surgery for Primary Hyperparathyroidism

Objective: To investigate the incidence and identify risk factors for the occurrence of intraoperative hypertension (IOH) during surgery for primary hyperparathyroidism (pHPT). Subjects and Methods: The study included 269 patients surgically treated between January 2008 and January 2012 for pHPT. IOH was defined as an increase in systolic blood pressure >= 20% compared to baseline values which lasted for 15min. The investigated influence were demographic characteristics, surgical risk score related to physical status (based on the American Society of Anesthesiologists [ASA] classification), comorbidities, type and duration of surgery, and duration of anesthesia on IOH occurrence. The investigated factors were obtained from the patients' medical history, anesthesia charts, and the daily practice database. Logistic regression analysis was done to determine the predictors of IOH. Results: Of the 269 patients, 153 (56.9%) had IOH. Based on the univariate analysis, age, body mass index, ASA status, duration of anesthesia, and preoperative hypertension were risk factors for the occurrence of IOH. Multivariate analysis showed that independent predictors of IOH were a history of hypertension (OR = 2.080, 95% CI: 1.102-3.925, p = 0.024) and age (OR = 0.569, 95% CI: 0.360-0.901, p = 0.016). Conclusion: In this study, a high percentage (56%) of the patients developed IOH during surgery for pHPT, which indicates that special attention should be paid to these patients, especially to the high-risk groups: older patients and those with a history of hypertension. Further, this study showed that advanced age and hypertension as a coexisting disease prior to parathyroid surgery were independent risk factors for the occurrence of IOH

Aim: To review the 8-year experience of the Department of Esophagogastric Surgery, First Surgical University Hospital in Belgrade in the surgical

Surgical experience of the national institution in th

/STRU^NI RAD UDK 616.33-005.1-02:615.212.06

Terapija manifestnog krvavljenja iz gornjeg dela digestivnog trakta uzrokovanog uzimanjem nesteroidnih antiinflamatornih lekova (NSAIL

Risk factors for intraoperative hypotension during thyroid surgery

Background: Hypotension is a common adverse effect of IV anaesthetics, especially during the induction of anaesthesia. The aim of our study was to determine the incidence and risk factors for intraoperative hypotension (IOH) in thyroid surgery, as well as to determine whether and to what extent IOH affects the occurrence of postoperative hypotension. Material/Methods: The study included 1252 euthyroid patients, ASA 2 and ASA 3 status (American Society of Anesthesiologists physical status classification), who had thyroid surgery between 2007 and 2011. IOH was defined as a decrease in systolic blood pressure of >20% of baseline values. We studied the influence of demographic characteristics (sex, age, body mass index-BMI), comorbidity, type and duration of surgery, and anaesthesia on the occurrence of IOH. Univariate and multivariate logistic regression were used to determine predictors of occurrence of IOH. Results: IOH was registered in 6.5% of patients. The most common operation was thyroidectomy. Patients with IOH were younger, had lower BMI, and significantly less often had hypertension as a coexisting disease. The multivariate regression model identified BMI and the absence of hypertension as a coexisting disease, and as independent predictors of occurrence of IOH. Significantly more patients with IOH had postoperative hypotension (9.9% vs. 2.4%, p=0.000). Conclusions: IOH is common, even during operations of short duration and with minimal bleeding. It is necessary to pay special attention to these patients, given that many of these patients remained hypotensive during the postoperative period. © Med Sci Monit

Looking at Zagreb: The Italian State as a Popularizer of Contemporary Art

In 1965, at the 12th International Conference of Critics, Artists and Art Scholars, held in Rimini, Verucchio and San Marino and devoted to the theme Art and Technology, Italian art critic Giulio Carlo Argan declared that Yugoslavia had overcome the problem of the relationship between art and technology. His statement concerned to the cultural milieu of Zagreb that Argan had known from the early Sixties. In the same year, Palma Bucarelli, the chief curator of the Rome National Gallery, attended the Brezovica conference held for Nova tendencija 3, to present a project in which the museum had a significant role as a state institution that had to encourage contemporary art in order to free artists from the pressures of the art market and private art galleries. In 1963, another art scholar, Umbro Apollonio, the curator of the Venice Biennale Archive for Contemporary Arts who had directly participated in the Venice exhibition Nuova tendenza 2, claimed that Italian Public Art School needed a new relationship between teaching and industries. My presentation aims to highlight how Argan, Bucarelli, Apollonio and other Italian scholars hoped for the state to intervene in the Italian art system and also how their ideas were inspired by the Croatian political and cultural situation of the 1960s