Optimiranje smjesa u proizvodnji dizelskih i benzinskih goriva

Nafta se ujedno naziva i crno zlato zbog svoje uloge u zadovoljavanju potreba čovječanstva za energijom. Većina svjetskih energetskih potreba još uvijek se zadovoljava iz fosilnih izvora, čije se količine rapidno smanjuju. Unazad posljednjih tridesetak godina rastom svijesti o negativnom utjecaju izgaranja goriva na okoliš, te činjenicom da je sirove nafte sve manje, razvijene su norme koje propisuju minimalne zahtjeve kvalitete goriva kako bi se smanjio utjecaj njihovog izgaranja na okoliš. Tehnološka konfiguracija rafinerija, u kombinaciji sa strategijom poslovanja snažno je povezani sa normama kvalitete goriva, jer se samo efikasnim i preglednim proizvodnim procesom može postići maksimalno iskorištenje raspoloživih sirovina kako bi se dobilo gorivo zadovoljavajuće kvalitete. Proizvodnja visokokvalitetnih komponenti minimalnih odstupanja ostvariva je vođenjem procesa putem računala, koje će osim vođenja procesa omogućiti stvaranje baze podataka koja će omogućiti detaljnu analizu procesa i pronalaženja potencijalnih poboljšanja. Budući da motorno gorivo mora zadovoljiti istovremeno deset do petnaest specifikacija, namješavanje se pokazalo kao jedno od krucijalnih područje pri kreiranju konačnog proizvoda. Optimizacija namješavanje u proizvodnji benzinskih i dizelskih goriva omogućuje praćenje tehničko tehnoloških mogućnosti u odnosu na ekonomski aspekt proizvodnje, efikasnost uporabe dostupnih komponenti, te minimiziranje uporabe komponenti goriva sa visokom cijenom. Ukratko možemo reći da se uporabom matematičkog programiranja u optimizaciji namješavanja motornih goriva, kroz povećani broj alternativa i brzim odgovorom na novonastale situacije, stvara prostor za uštede u poslovanju. Bitna je i činjenica da se postiže smanjenje vremena potrebno za cijeli proizvodni ciklus goriva, jer se smanjuje potreba za naknadnim namješavanjem. Razlikujemo dva temeljna pristupa namješavanju: eksperimentalni temeljen na metodologiji pokusa sa smjesama, te proizvodni korišten u praksi gdje su važećim normama točno definirana svojstva komercijalnih motornih goriva. Ovim diplomskim radom obuhvaćena su oba pristupa, te je dan pregled dostupnih programskih rješenja za optimiranje značajki goriva. Simulacijom optimiranja omogućuje se proizvodnja važećim normama sukladnih goriva uz minimalne moguće štetne emisije

Upravljanje radnim nalozima u održavanju

Cilj ovog završnog rada je detaljan opis procesa formiranja i lansiranja radnih naloga u održavanju tvrtke Ina Rafinerija Nafte Sisak. Konkurentno poslovanje nezamislivo je bez odgovarajućeg informacijskog sustava koji pruža potporu upravljanju radnim nalozima, te je u svrhu toga dan pregled ERP (Enterprise resource planning) sustava SAP koji se koristi u Ina kompaniji. Dana je analiza procesa upravljanja radnim nalozima te su definirana moguća poboljšanja

A Two-Phase VIKOR Model for Track Layout Evaluation of Passenger Rail Stations

Passenger stations are transit hubs where several railway lines interchange. They have important roles in providing train operations and passenger services. Interrelations between track layouts and technological performances are important for reducing bottleneck effects and raising the operational effectiveness of rail networks. To the best of our knowledge, in previous research the assessment of track layouts has not been considered with respect to various technological aspects including railway operations, safety, and passenger services but rather as a single criterion for analysis of different individual performance indicators. We propose a new two-phase decision making approach for the complex evaluation of track layout alternatives. The first phase model is a VIKOR method for ranking track layouts by criteria related to: railway capacity, safety issue, and passenger-pedestrian fluctuations. Next, in the second phase, we use marginal analysis to find Pareto front and compare the alternatives ratings by calculating performance-benefit coefficients. To show the applicability of the proposed model, we employ an illustrative example of a passenger rail station and evaluate six different track layout alternatives. The effectiveness of the proposed model is demonstrated comparing the proposed two-phase model with traditional VIKOR

Modeling of the reactions of a calcium-based sorbent with sulfur dioxide

A mathematical model of calcium sorbent reactions for the simulation of sulfur dioxide reduction from pulverized coal combustion flue gasses was developed, implemented within a numerical code and validated against available measurements under controlled conditions. The model attempts to resemble closely the reactions of calcination, sintering and sulfation occurring during the motion of the sorbent particles in the furnace. The sulfation was based on the partially sintered spheres model (PSSM), coupled with simulated particle calcination and sintering. The complex geometry of the particle was taken into account, with the assumption that it consists of spherical grains in contact with each other. Numerical simulations of drop down tube reactors were performed for both CaCO3 and Ca(OH)(2) sorbent particles and results were compared with experimental data available from the literature. The model of the sorbent reactions will be further used for simulations of desulfurization reactions in turbulent gas-particle flow under coal combustion conditions

Heat Transfer to a Boiling Liquid – Numerical Study

Due to extensive research efforts within the past thirty years, the mechanisms by which bubbles transfer energy during pool boiling are relatively well understood and have various applications in reactors, rockets, distillation, air separation, refrigeration and power cycles. In this paper, CFD analysis of heat transfer characteristics in nucleate pool boiling of saturated water in atmospheric conditions is performed in order to find out the influence of heat flux intensity on pool boiling dynamics. The investigation is carried out for four cases of different heat flux intensities and obtained results for velocity fields of liquid and void fractions are discussed. Grid independent test is also performed to improve the accuracy of calculation. In this way, complete picture of two-phase mixture behaviour on heated wall is represented

Calcium based sorbent calcination and sintering reaction models overview

Several models considering the pulverized sorbent reactions with pollutant gases were developed over the past years. In this paper, we present a detailed overview of available models for direct furnace injection of pulverized calcium sorbent suitable for potential application in CFD codes, with respect to implementation difficulty and computational resources demand. Depending on the model, variations in result accuracy, data output, and computational power required may occur. Some authors separate the model of calcination reaction, combined with the sintering model, and afterwards model the sulfation. Other authors assume the calcination to be instantaneous, and focus the modelling efforts toward the sulfation reaction, adding the sintering effects as a parameter in the efficiency coefficient. Simple models quantify the reaction effects, while more complex models attempt to describe and explain internal particle reactions through different approaches to modelling of the particle internal structure

Multicriteria decision-making in railway route planning and design

U radu je prikazana metodologija izbora trase u procesu planiranja i projektiranja željezničke pruge koja se temelji na metodama višekriterijskog odlučivanja. Predložena metodologija omogućava cjelovito i sustavno rješavanje ovog problema, čiji krajnji rezultat je prijedlog najpovoljnije trase u skladu s usvojenim kriterijima i realnim ograničenjima. Razvijena metodologija je bazirana na metodi kompromisnog rangiranja (VIKOR), a njena verifikacija provedena je na primjeru izbora jedne od četiri varijante trase željezničke pruge na dionici Koridora X, između stanica Inđija i Novi Sad.The route selection methodology, based on multicriteria decision-making and applied in railway route planning and design, is presented in the paper. The proposed methodology enables an integrated and systematic resolution of this problem, and it results in the most favourable route proposal based on predefined criteria and real-life constraints. The technology is based on the compromise ranking method (VIKOR), and it has been checked during selection of one out of four railway route alternatives on the Corridor X, between Inđija and Novi Sad train stations

Modeling of the reactions of a calcium-based sorbent with sulfur dioxide

A mathematical model of calcium sorbent reactions for the simulation of sulfur dioxide reduction from pulverized coal combustion flue gasses was developed, implemented within a numerical code and validated against available measurements under controlled conditions. The model attempts to resemble closely the reactions of calcination, sintering and sulfation occurring during the motion of the sorbent particles in the furnace. The sulfation was based on the partially sintered spheres model (PSSM), coupled with simulated particle calcination and sintering. The complex geometry of the particle was taken into account, with the assumption that it consists of spherical grains in contact with each other. Numerical simulations of drop down tube reactors were performed for both CaCO3 and Ca(OH)(2) sorbent particles and results were compared with experimental data available from the literature. The model of the sorbent reactions will be further used for simulations of desulfurization reactions in turbulent gas-particle flow under coal combustion conditions

Fuzzy multicriteria decision-making in railway infrastructure planning and design

U radu je prikazan pristup neizrazitog višekriterijskog odlučivanja u procesu planiranja i projektiranja željezničke infrastrukture koji omogućava cjelovito i sustavno rješavanje problema postojanja faktora neizvjesnosti i neodređenosti prilikom procjene vrijednosti kriterijskih funkcija. Predloženi pristup višekriterijskog odlučivanja je predstavljen u okviru metodologije za izbor najpovoljnije trase dvokolosiječne željezničke pruge. Za vrednovanje varijantnih rješenja trase u radu su upotrebljeni trouglasti neizraziti brojevi, a za rangiranje je primijenjena neizrazita VIKOR metoda.A fuzzy multicriteria approach in the railway infrastructure planning and design, enabling an integrated and systematic solving of uncertainty and indeterminacy problems in the evaluation of criteria functions, is presented in paper. The proposed multicriteria decision making approach is presented in the scope of the methodology for selecting the most favourable route of a double track railway. Triangular fuzzy numbers are used to evaluate variant solutions, while the VIKOR fuzzy method is used for route ranking

Modeling of Pulverized Coal Combustion for In-Furnace Nox Reduction and Flame Control

A cost-effective reduction of NO, emission from utility boilers firing pulverized coal can be achieved by means of combustion modifications in the furnace. It is also essential to provide the pulverized coal dfffitsion flame control. Mathematical modeling is regularly used for analysis and optimization of complex turbulent reactive flows and mutually dependent processes in coal combustion furnaces. In the numerical study, predictions were performed by an in-house developed comprehensive three-dimensional differential model of flow, combustion and heat/mass transfer with submodel of the fuel- and thermal-NO formation/destruction reactions. Influence of various operating conditions in the case-study utility boiler tangentially fired furnace, such as distribution of both the fuel and the combustion air over the burners and tiers, fuel-bound nitrogen content and grinding fineness of coal were investigated individually and in combination. Mechanisms of NO formation and depletion were found to be strongly affected by flow, temperature and gas mixture components concentration fields. Proper modifications of combustion process can provide more than 30% of the NO, emission abatement, approaching the corresponding emission limits, with simultaneous control of the flame geometry and position within the furnace. This kind of complex numerical experiments provides conditions for improvements of the power plant furnaces exploitation, with respect to high efficiency, operation flexibility and low emission.Turbulence Workshop, Aug 31-Sep 02, 2015, Univ Belgrade, Fac Mech Engn, Belgrade, Serbi