Selection of numerical method for solving ordinary differential equation systems for a high-speed model of hydrocarbons steam cracking

Relevance. Caused by the need to increase production of light olefins. The use of advanced process control systems and Real–Time Optimization makes it possible to increase the efficiency of steam cracking plants, but requires a high-speed mathematical model of the process. Aim. To select a method for numerical solution of systems of ordinary differential equations, which provides the highest speed when calculating the reaction coil of a steam cracking furnace. Reducing the time spent on calculating each scenario will allow the proposed model to be used for real-time process optimization tasks. Object. Mathematical model of ethane steam cracking, numerical methods for ordinary differential equations systems solution. Methods. System analysis, mathematical modeling. To solve the ordinary differential equations systems, various explicit numerical methods were used, differing in approach to integration step determination. Results. The authors have developed and tested a steady-state model of ethane steam cracking. The developed model was used to compare the calculation time required for solving ordinary differential equations systems using different numerical methods. It was demonstrated, that the use of an adaptive integration step reduces calculation time by more than 20 times (from more than 11 hours to 34 minutes) while maintaining the accuracy of calculations. This is due to different reaction rates through the length of the reaction coil – in areas of high temperatures and high concentrations of reagents, a reduction in the integration step is required to obtain the desired accuracy. And in low reaction rates areas an increase in the step and reduction in the total calculated iterations are acceptable

Mathematical model for investigation of alkylbenzenes sulfonation

The relevance. Lack of experimental data that allow developing a scientifically based method for calculating and designing film-type reactors, which are also used to produce alkylbenzenesulfonic acids. These acids, in their turn, are currently the main components of synthetic detergents. The issue of increasing reactor equipment efficiency can be most effectively solved using mathematical models built on a physical and chemical basis. The aim. Development of a mathematical model of alkylbenzenes sulfonation, taking into account a substance mass transfer from a gas phase to a liquid phase. Software implementation of the developed model, as well as the use of the developed mathematical model for studying the influence of the process parameters on its efficiency. Object. Alkylbenzenes sulfonation with sulfuric anhydride in a multitube film reactor. Methods. Mathematical modeling is used to perform all computational operations, a modern high-level general-purpose programming language with automatic memory management is used. The quantum-chemical methods for determining thermodynamic parameters of chemical reactions were used. Results. The paper considers the principles of constructing a mathematical model of sulfonation. The authors have developed the calculation program in the Python programming language and assessed the accuracy of description of a real process and the influence of the system technological parameters on a product yield and quality, taking into account a substance interfacial transfer. The system of practical recommendations for improving the alkylbenzenes sulfonation resource efficiency was developed. The mathematical model adequately describes the process. The calculated data are compared with the real data from the operating unit for alkylbenzenes sulfonation with sulfuric anhydride

UNSTEADY-STATE SIMULATION OF GASOLINE FRACTION PYROLYSIS

The relevance of the research is caused by the need of alkenes production increase as well as deepening understanding of the coke formation. The direction of petrochemical complex development and increase of pyrolysis efficiency is resources-saving, minimizing the volume of operations cost and the probability of occurrence of accidents. The main aim of the research is to develop a mathematical model for gasoline fraction pyrolysis, which will consider coke formation and its effect on the kinetic, hydrodynamic and thermodynamic components of the process. Object of the research is gasoline fraction pyrolysis process; dynamic of hydrocarbon stream composition during the process and coke formation side process. Methods. The methodological basis of the research is the system analysis and the method of mathematical modeling. In addition, quantum-chemical methods are used to calculate the thermodynamic and kinetic parameters of target and side chemical reactions occurring during the processing of hydrocarbon raw materials, and electron-structural methods based on the density functional theory; methods of computational fluid dynamics for the study of flow regimes and the deposition of coke particles on the walls of the coil; developed experimental methods for determining the optimal consumption of hydrocarbon raw materials and steam, predicting the duration of the inter-regeneration cycle of the pyrolysis furnace. Results. A non-stationary model of gasoline fraction pyrolysis was created to describe the coking side process along the length of the pyrolysis tube and over time. With the model, the rate of coke layer formation was calculated considering the technological parameters and the composition of feedstock. The calculated rate is 3,12∙10–7 mm per second. The results also made it possible to obtain the thickness distribution of the coke layer in the radiant coil, which indicates the acceleration of side processes towards the end of the process. This is due to formation of a significant amount of unsaturated compounds. It was found that changing the main parameters has two opposite effects. Thus, with an increase in temperature and pressure, both the yields of target products and the growth rate of the coke layer increased. An increase in the consumption of raw materials leads to a decrease in both of these parameters

New Genome-Wide Algorithm Identifies Novel In-Vivo Expressed Mycobacterium Tuberculosis Antigens Inducing Human T-Cell Responses with Classical and Unconventional Cytokine Profiles

16 páginas, 8 figuras. Disponoble información suplementaria en: http://www.nature.com/srepNew strategies are needed to develop better tools to control TB, including identification of novel antigens for vaccination. Such Mtb antigens must be expressed during Mtb infection in the major target organ, the lung, and must be capable of eliciting human immune responses. Using genome-wide transcriptomics of Mtb infected lungs we developed data sets and methods to identify IVE-TB (in-vivo expressed Mtb) antigens expressed in the lung. Quantitative expression analysis of 2,068 Mtb genes from the predicted first operons identified the most upregulated IVE-TB genes during in-vivo pulmonary infection. By further analysing high-level conservation among whole-genome sequenced Mtb-complex strains (n = 219) and algorithms predicting HLA-class-Ia and II presented epitopes, we selected the most promising IVE-TB candidate antigens. Several of these were recognized by T-cells from in-vitro Mtb-PPD and ESAT6/CFP10-positive donors by proliferation and multi-cytokine production. This was validated in an independent cohort of latently Mtb-infected individuals. Significant T-cell responses were observed in the absence of IFN-γ-production. Collectively, the results underscore the power of our novel antigen discovery approach in identifying Mtb antigens, including those that induce unconventional T-cell responses, which may provide important novel tools for TB vaccination and biomarker profiling. Our generic approach is applicable to other infectious diseases.We acknowledge funding by EC HORIZON2020 TBVAC2020 (Grant Agreement No. 643381); EC ITN FP7 VACTRAIN project (the text represents the authors’ views and does not necessarily represent a position of the Commission who will not be liable for the use made of such information), The Netherlands Organization for Scientific Research (NWO-TOP Grant Agreement No. 91214038); European Research Council (ERC TB-ACCELERATE Grant Agreement No. 638553). Funding was also supplied by the Ministerio de Economía y Competitividad (Spanish Government) research grant SAF2013-43521-R, and the European Research Council (ERC) (638553-TB-ACCELERATE) (to IC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe