Computational fluid dynamic modelling of stirred reactors : power, baffle stresses, mixing times and semi-batch precipitation

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Occupational position and alcohol use disorders in Poland

ObjectivesThe following analysis covers the role of the occupational structure in the prevalence of alcohol use disorders (AUDs). The authors investigated whether the occupational position affected the prevalence of AUDs among men and women, and how this relationship varied in lifetime and past year periods.Material and MethodsData were taken from the General Population Survey on Mental Health in Poland (EZOP) utilizing the Composite International Diagnostic Interview questionnaire (N = 2806). Binary and multiple regression models were employed to assess the risk of AUDs adjusted for the occupational structure and socio-demographic variables.ResultsThe occupational position affects the prevalence of AUDs in men, while it has no impact on AUDs in women. Skilled and non-skilled workers suffer from AUDs to a greater extent than those in higher occupational positions. However, the risk of alcohol harm in women seems to be equally distributed across the occupational structure.ConclusionsThe uneven pattern of alcohol harm in men and women can be possibly explained by shifting working conditions and work environments, as well as traditional gender roles affecting alcohol behaviors. The findings of the study support further development of the occupational position concept in alcohol research. The problem of harmful alcohol drinking in women across the occupational structure warrants a more in-depth inquiry

Computational Fluid Dynamics of Ammonia Synthesis in Axial-Radial Bed Reactor

Ammonia synthesis by the Haber–Bosch method is a typical and effective implementation of the chemical process in the large-scale fertiliser industry. Due to the growing demand for fertilisers and food, it is desirable to study this process thoroughly using modern numerical methods to improve the operation of existing devices and facilitate the design of new devices in industrial installations. This manuscript focuses on the influence of the catalyst bed parameters on the ammonia synthesis process. Variants with different sizes of catalyst particles and modifications of the geometry of catalytic beds were considered. The axial-radial Topsoe converter with magnetite as a catalyst, commonly used in modern fertiliser industry beds, was investigated using Computational Fluid Dynamics. As a result, contours of velocity, pressure, concentration, and rate of ammonia formation were obtained. The analysis of the obtained results made it possible to determine the gradient of ammonia production rate in the catalyst bed and designate zones with negligible reaction rates. The authors also proposed possible bed geometry modifications to reduce bed volumes without affecting the converter’s performance

Computational Fluid Dynamics of Influence of Process Parameters and the Geometry of Catalyst Wires on the Ammonia Oxidation Process and Degradation of the Catalyst Gauze

The ammonia oxidation reaction on solid platinum–rhodium gauze is a critical step in nitric acid production. As the global demand for food and fertilisers keeps steadily growing, this remains an essential reaction in the chemical industry. However, harsh conditions inside ammonia burners lead to the degradation of catalytic meshes, severely hindering this process. This manuscript is focused on two issues. The first is the influence of catalyst gauze geometry and process parameters on the efficiency of ammonia oxidation on platinum–rhodium gauze. The second investigated problem is the influence of geometry on catalyst fibre degradation and the movement and deposition of entrained platinum particles. Computational Fluid Dynamics was utilised in this work for calculations. Different catalyst gauze geometries were chosen to examine the relationship between wire geometry and heat and mass transfer by analysing temperature and flow fields. Significantly, the analysis of the temperature gradient on the catalyst surface allowed us to estimate the spots of highest wire degradation and to track lifted platinum particles. The Discrete Phase Model was used to calculate entrained platinum particle trajectories and their deposition’s localisation and efficiency