Angolan Industry and Chemical Engineering Journal

The Proposal for Monolithic Coefficients for Reinforced Concrete Columns Strengthened by Partial Reinforced Concrete Jacketing

2023-12-20T05:06:09-03:00

Reinforced concrete (RC) jacketing is one of the most widely adopted methods for strengthening RC structures. Full jacketing is adopted in the case of interior columns and monolithic behaviour is easily ensured. However, in the case of corner and edge columns, partial reinforced concrete jacketing should be considered. Partial jacketing also leads to a significant increase in stiffness and resistance, but monolithic behaviour is not achieved. For this reason, and in order to provide guidance for design, it is necessary to consider monolithic coefficients. The monolithic coefficient (K) is the relationship between the behaviour of the jacketed reinforced concrete element and the behaviour of an equivalent monolithic element, i.e. with the same geometry and materials. The value of K is unity for monolithic behaviour and less than 1 otherwise. To obtain a K value close to 1, it is necessary to ensure good adhesion between the jacketing and the original column. The main aim of the PhD thesis presented here is to propose K values for different design cases. The proposals will be based on numerical studies, validated with experimental tests and sensitivity analyses. The proposals will be compared with the K values proposed by EC 2 & 8-3, fib MC 2010 & 103, and ACI 318. Numerical models and experimental tests on columns strengthened by partial jacketing will analyse multiple parameters such as cracking, deformation and resistance.

The Study of Gas Mixture Non-Ideality

2023-12-20T05:16:11-03:00

In the realm of chemical thermodynamics, the investigation primarily centers on the dynamics of pure substances, sidelining the molecular interplay forces that are pivotal among disparate molecular entities in a mixture. This approach is instrumental in elucidating the principles governing the non-ideal behavior of gases. The divergence from ideal gas behavior in both singular gases and their mixtures is quantifiable by the disparity between their actual conduct and the theoretical predictions founded on ideal gas laws. This study endeavors to evaluate the thermodynamic characteristics of a CH4-CO2 mixture through the application of the Van Der Waals and Soave-Redlich-Kwong cubic state equations, utilizing a computational program designed as a thermodynamic computational tool. The outcomes of this study facilitate the characterization of non-ideal gas mixture behaviors, discerning the compressibility factor's variation in response to pressure alterations across diverse temperatures and compositions within a specified pressure ambit. Concurrently, the availability of empirical data in scientific literature enables the corroboration of the more precise state equation, which can be subsequently employed for examining the authentic behavior of gas mixtures. Additionally, the multitude of thermodynamic models delineated in scholarly articles permits the computation of associated thermodynamic energies for each case study, along with the determination of activity and fugacity coefficients, which are integral in phase equilibrium analyses of gas mixtures. The findings underscore the dominance of attractive forces at diminished pressures and repulsive forces at escalated pressures. The analytical comparison with empirical data demonstrates that the Soave-Redlich-Kwong equation, especially when considering the acentric factor—a parameter that accounts for the molecular dimensions in the mixture—exhibits superior precision in depicting the real behavior of the gas mixtures.

The Thermodynamic Analysis of a Gas Mixture Utilizing Peng-Robinson and Soave-Redlich-Kwong Cubic Equations of State

2023-12-20T05:28:18-03:00

Cubic equations of state are mathematical models used to describe the thermodynamic behavior of pure substances or mixtures of substances by calculating physical and chemical properties under different pressure and temperature conditions. These equations are widely employed in various scientific fields, particularly in chemical engineering, for the thermodynamic study of physical and chemical processes involving phase equilibrium. Thus, the knowledge derived from these studies enables the development of industrial processes, the synthesis of new processes and materials, the study of chemical reaction kinetics, analysis of experimental data, and more. Therefore, this study aims to describe deviations from ideality in real gases, evaluated based on the behavior of the compressibility factor (Z) as a function of pressure (P) for a binary mixture involving hydrogen (H2) and carbon dioxide (CO2). In ideal gases, the system has a compressibility factor equal to one at any pressure, unlike real gases, where the compressibility factor can assume values smaller or larger than unity. To achieve this, a logical algorithm was developed for evaluating the compressibility factor using the Peng-Robinson (P-R) and Soave-Redlich-Kwong cubic equations of state, with mathematical resolution carried out using the Microsoft EXCEL SOLVER. The calculation procedure involved transforming the initial equations into cubic equations through linearization, followed by the calculation of compressibility factors that determine the phenomena associated with molecular attraction and repulsion within the referenced gas mixtures for different compositions, temperatures, and within a specific pressure range. The results of this analysis revealed the predominance of attractive and repulsive forces within the studied pressure range, with the transition occurring in the pressure range of 400 to 450 atm for both mathematical equations under evaluation. Furthermore, these attraction and repulsion phenomena are strongly influenced by the proportion of each gas in the mixture and the operating temperature. Therefore, understanding these phenomena enhances the scientific understanding of industrial processes involving phase equilibrium, especially when implemented in separation operations.

The Characterization of Borututu (Cochlospermum angolense welw) Flower Extracts Obtained by Pressurized Liquid

2023-12-20T05:51:11-03:00

medicinal plants are known as natural sources and can explore the various parts (fruit, seed, flower, leaf, stem, root) as nutrients (vitamins, minerals, proteins and fibers) necessary for the correct maintenance of health, which can be used for therapeutic purposes; and/or ingredients in food production, medicines as promising alternatives. The Borututu plant (Cochlospermum angolense welw) is an indigenous tree from Angola, and has great potential as a source of bioactive extracts. Only the root has been used as an infusion by populations in the treatment of malaria due to its hepatoprotective effects. In recent decades, other extraction techniques have been studied with the aim of developing processes to obtain functional extracts from plant matrices. Among the alternatives linked to new technologies, the application of the Pressurized Liquid Extraction Technique (PLE), as an efficient and ecological technique compared to conventional solid-liquid extraction processes, was applied in this study to obtain bioactive extracts from flowers of the borututu plant.
Different green/ecological solvents (water, ethanol and ethyl acetate) were evaluated at different extraction temperatures (50-200ºC), in short extraction times (10 minutes). The extracts produced were chemically characterized by colorimetric techniques. The PLE technique allowed high extraction yields to be obtained with less solvent consumption in short periods and with extracts with a high content of phenolic compounds and high antioxidant capacity, surpassing extracts obtained by the traditional method (infusion). This technique allowed ethanol extracts to be obtained at 200°C, generating a high concentration of total phenolic compounds (TPC) and a high yield of 16.27% and 34.26mg/g, respectively. The highest antioxidant capacity was 2029 µmol/g, obtained with water at 150°C. It is concluded that flower extracts demonstrated potential for the production of functional ingredients on an industrial scale.

The Challenge for Angolan Professionals to Participate in International and Scientific Activities

2023-12-23T12:10:49-03:00

There is evidence of an increase in the number of professionals regularly participating in academic and scientific activities at an international level over the last 9 years. But Angola is excluded from this increase through the challenges that we will demonstrate in this study. This study aims to identify the challenges that Angolan professionals face in participating in international academic and scientific activities. Participating in international activities is an opportunity to get to know new academic and scientific cultures, new people, technologies, and languages. Among the most requested countries we have: England, USA and Canada. The author carried out a qualitative study using semi-structured interviews with 24 participants from different sectors in Luanda-Angola. Data were analysed thematically using codes. The investigator used the following data bases search as Science Direct, Science Online, and Sage Premier, Sage research Online, Social Theory, PubMed, Medline and Google School. 24 professionals participated in the study, men predominated with 13 (54.2%) and women with 11 (45.8%). Sixteen (66.7%) were health professionals, 3 (12.5%) police offices, 2 (8.3%) Forensic psychologist, 2 (8.3%) Pastors and 1 (4.2%) Mechanical Engineer. The challenges identified in the study are: Lack of command of international languages such as English and French, lack of financial conditions, lack of interest, and lack of knowledge of the importance of participating in academic and scientific activities. Participating in international activities is an opportunity to get to know new academic and scientific cultures, new people, technologies, and languages that will influence your professional path.

The Development of Biotechnological Techniques for the Processing and Use of Bovine Chymosin on an Industrial Scale

2024-02-13T06:52:35-03:00

Chymosin is an enzyme, traditionally obtained from the fourth stomach of young ruminants, used in the coagulation of milk to make cheese. In the present work we will address other aspects that are difficult to resolve during the processing of this protein, its activation, purification process and alternatively, its immobilization in various chromatographic matrices that allow its manipulation under more technically industrial and economically beneficial industrial conditions. The process consisted of cloning the coding gene for this enzyme, using optimized codons for its overexpression in Escherichia coli, with the pBAD/HIS vector under the control of the pBAD promoter inducible by L-arabinose, as it is a more economically profitable process. The process consisted of cloning the coding gene for this enzyme, using optimized codons for its overexpression in Escherichia coli, with the pBAD/HIS vector under the control of the pBAD promoter inducible by L-arabinose, as it is a more economically profitable process. Overexpression of the gene generates inclusion bodies that can be denaturalized by washing with NaOH, for subsequent opening of the protein by dilution and adjustment of the pH with glycine, in a more easily manipulated way. Once unfolded, prochymosin is activated by a drastic change in pH, first at pH 2 and then rising to pH5 to increase its activation process. After this process, a highly active protein was obtained, tested under its natural substrate, milk. Due to the complexity of the activation-reactivation- purification process that takes place at very acidic pHs, its control becomes difficult, which is why new alternatives are being sought to overcome this inconvenience. The more conservative alternative found was the use of immobilization techniques on different polymeric supports (agarose based) and on magnetic particles (magnetic nanoparticles), previously functionalized, so that in a single step we could carry out the purification process and protein activation. When using polymeric supports, the immobilization results were very poor (below 20%), mainly due to pore clogging problems in this type of resin; whilst, the use of magnetic nanoparticles completely changed the scenario, obtaining yields of almost 100% and retention of enzymatic activity at values close to 85%.

The Mooring Floating Offshore Oil Platforms with Polyester Cables

2024-02-13T08:47:08-03:00

The offshore oil industry plays a crucial role in the exploration and production of energy resources, requiring constant innovation and technological advances to ensure safe and efficient operations. The mooring of floating platforms is one of the critical areas in this context, directly influencing the stability and safety of structures in challenging marine environments. This article sets out to explore the use of polyester ropes in mooring offshore platforms, highlighting the benefits, challenges and technological advances associated with this application.

The Proposes For the Use of The Cleaner Production Tool (P+L) in the Hope Plastic Solid Waste Recycling Process

2023-12-20T05:23:46-03:00

Companies, as transformers of raw materials into finished products, have great responsibility in the protection, handling and use of available natural resources. Therefore, all efforts to promote sustainable development must be prioritized. In this context, the objective of this research is to present a proposal for the use of the environmental management tool Cleaner Production (P+L), in the HDPE plastic solid waste recycling process, in the recycling unit at the Glopol factory. Through semi-structured interviews and questionnaires, submitted to the Operators and the Production Supervisor of the aforementioned unit, it was possible to characterize the Glopol factory's recycling unit, and thus, find the main gaps inherent to the process, particularly in the separation operations. , washing and extrusion, which culminate in high water consumption and excessive waste generation (sludge and liquid effluent derived from the washing operation, and plastic sludge from the extrusion operation). After diagnosing the situation present at the Glopol factory, the proposal for adopting the P+L environmental management tool was presented, starting from planning and organization, to the implementation method, where it was possible to estimate that with the implementation of this tool, in recycling unit at the Glopol factory, it would be possible to reduce the water consumption of that unit by up to 25%, ensuring greater preservation of the natural resource. It was also possible to estimate that this adoption would bring a reduction of up to 40% in the waste generated, since through the adoption of the P+L tool, plastic waste would undergo sorting, and with this, the sludge generated in the washing, would be less and less. Such sludge would have a more environmentally correct destination, that is, it would be seen as a by-product of the process, and not as waste. As a result of the new reprocessing route for plastic sludge generated in the extrusion operation, operational gains were observed for Glopol, as the adoption of the P+L tool would bring a reduction in the plastic sludge reprocessing steps, and consequently in the time for this effect.