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The objective of this project is to optimize the SAPREF oil refinery steam distribution in which imbalances between the various levels presently require the venting of steam from the lowest level. The overall steam balance shows that the problem originates from an excess of high·pressure (HP) steam production for too few medium pressure steam users and turbines. We proposed to solve this problem by considering the replacement of selected steam turbines with electrical drives. Given a set of demands of electricity, mechanical power and steam at various pressure levels, the objective is to recommend configuration changes to minimize overall cost. This is not a trivial problem, as steam not passed down through turbines to lower levels can create a shortage there, so a combination of replacements is required. The variables of the problem are both decision variables on every steam turbine and continuous variables, such as flows and enthalpies. These decision variables are integer variables, 0 or 1 for every steam turbine. Depending on whether it is kept on steam use or replaced with an electrical drive, these variables are as follows: E = 0: keep the existing steam turbine E - 1: switch it to an electrical drive. A complete and realistic model of this utility section must be constructed in order to represent the actual distribution accurately. This model will include an objective function to minimize, some equality and inequality constraints, and some cost functions. If we want this model to be accurate, we shall have to deal with nonlinearities to avoid simplifications, and these non-linearities could lead to infeasabilities or sub-optimal solutions. So we are facing a typical MTNLP (Mixed Integer Non-Linear Programming) problem to find optimal configuration changes which will maximize the return on investment, meeting the electrical, mechanical and steam demands of the refinery. In order to solve this difficult optimization problem we shall use the user-friendly package GAMS (General Algebraic Modeling System). / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2001.

Recent experimental and simulation studies -conducted at the Department of Petroleum Engineering at Texas A&M University - confirm oil production is accelerated when propane is used as an additive during steam injection. To better understand this phenomenon, distillation experiments were performed using seven-component synthetic oil consisting of equal weights of the following alkanes: n-C5, n-C6, n-C7, n-C8, n-C9, nC10, and n-C15. For comparison purposes, three distillation processes were investigated: dry-, steam-, and steam-propane-distillation, the latter at a propane:steam mass ratio of 0.05. The injection rate of nitrogen during dry-and steam-distillation was the same as that of propane during steam-propane distillation, 0.025 g/min, with steam injection rate kept at 0.5 g/min. The distillation temperatures ranged from 115°C to 300°C and were increased in steps of 10°C. The cell was kept at each temperature plateau (cut) for 30 minutes. Distillation pressures ranged from 0 psig for dry distillation to 998 psig for steam-and steam-propane distillation. The temperature-pressure combination used represented 15°C superheated steam conditions. Distillate samples were collected at each cut, and the volume and weight of water and hydrocarbon measured. In addition, the composition of the hydrocarbon distillate was measured using a gas chromatograph. Main results of the study may be summarized as follows. First, the hydrocarbon yield at 125°C is highest with steam-propane distillation (74 wt%) compared to steam distillation (58 wt%), and lowest with dry distillation (36 wt%). This explains in part the oil production acceleration observed in steam-propane displacement experiments. Second, the final hydrocarbon yield at 300°C however is the same for the three distillation processes. This observation is in line with the fact that oil recoveries were very similar in steam- and steam-propane displacement experiments. Third, based on the yields of individual hydrocarbon components, steam-propane distillation lowers the apparent boiling points of the hydrocarbons significantly. This phenomenon may be the most fundamental effect of propane on hydrocarbon distillation, which results in a higher yield during steam-propane distillation and oil production acceleration during steam-propane displacement. Fourth, experimental K-values are higher in distillations with steam-propane for the components n-hexane, n-heptane, n-octane, and n-nonane. Fifth, vapor fugacity coefficients for each component are higher in distillations with steam-propane than with steam. Finally, Gibbs excess energy is overall lower in distillations with steam-propane than with steam. The experimental results clearly indicate the importance of distillation on oil recovery during steam-or steam-propane injection. The experimental procedure and method of analysis developed in this study (for synthetic oil) will be beneficial to future researchers in understanding the effect of propane as steam additive on actual crude oils.

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Steam is a commonplace utility in chemical processing plants across the globe. The many benefits of steam ensure its continued use, but concerns about the cost of energy and of the equipment associated with steam systems has led to the development of a number of techniques to reduce energy and capital costs. One such topic is the reduction of boiler purchase cost, brought about by a reduction in steam flowrate. Recent publications have shown that the flowrate of steam required for heating purposes can be minimised by employing hot liquid reuse, with systematic methods developed for targeting the minimum flowrate, and synthesising the heat exchanger network. In this work, a mathematical analysis has been performed to gain insight on how choosing different steam levels affects the minimum total steam flowrate. The analysis covered both the traditional practice of only utilising latent heat, as well as the new practice of hot liquid reuse. It was found that the lowest flowrate obtainable occurs in the case of hot liquid reuse, when only a single high pressure steam level is considered. Since the need to provide shaft work or generate electricity necessitates the presence of steam turbines on plants, the inclusion of additional steam levels is unavoidable. For this reason, a novel MINLP formulation was developed to provide a holistic coverage of the heat exchanger network and the power block. The purpose of the new formulation is to target the minimum total steam flowrate, whilst simultaneously selecting the optimum saturation temperatures for the additional steam levels, designing the turbines to meet shaft work requirements and synthesizing the heat exchanger network. Application of this new method to a case study yielded a 28.6% reduction in total steam flowrate, compared to common design practice. i I, Sheldon Grant Beangstrom, with student number 27069771, declare that:  I understand what plagiarism entails and am aware of the University of Pretoria‟s policy in this regard.  This dissertation is my own, original work. Where the work of another has been used (whether from a printed source, the internet or otherwise) due acknowledgement has been given and reference made in accordance with the departmental guidelines.  I have not made use of another student‟s previous work in an attempt to submit it as my own.  I have not allowed, nor will I allow another person to copy this work with the intention of presenting it as his or her own work.  The material presented in this dissertation has not been submitted to another institution in partial or whole fulfilment of another degree. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Chemical Engineering / unrestricted

M.Phil. / The aim of this study is to achieve a greater output by scrutinizing the present way of coordinating the efforts Qf Steam Industries in South Africa to achieve a sustainable industrial development by using energy source efficiently and effectively. Furthermore into the study we look at obstacles that prevents and those that leads to maximum utilization of energy management measures, and also highlights the effects of implementing cheap available energy source in South Africa...

A combined cycle is one of the thermal cycles used in thermal power plants. It consists of a combination of a gas and a steam turbine, where the waste heat from the gas turbine is used for steam generation in the heat recovery steam generator. The aim of the diploma thesis was the conceptual design of a combined cycle electricity source and the balance calculation of the cycle. The calculation is based on the thermodynamic properties of the substances and the basic knowledge of the Brayton and Rankin-Clausius cycle. The result is the amount and parameters of air, flue gases, and steam/water in individual places and the technological scheme of the source, in which these parameters are listed.