Browsing by Subject "process integration"
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Item Design and Analysis of Flexible Biodiesel Processes with Multiple Feedstocks(2011-10-21) Pokoo-Aikins, Grace AmarachukwuWith the growing interest in converting a wide variety of biomass-based feedstocks to biofuels, there is a need to develop effective procedures for the design and optimization of multi-feedstock biorefineries. The unifying goal of this work is the development of systematic methodologies and procedures for designing flexible multifeedstock biorefineries. This work addresses four problems that constitute building blocks towards achieving the unifying goal of the dissertation. The first problem addresses the design and techno-economic analysis of an integrated system for the production of biodiesel from algal oil. With the sequestration of carbon dioxide from power plant flue gases, algae growth and processing has the potential to reduce greenhouse gas emissions. Algae are a non-food oil feedstock source and various pathways and technologies for obtaining algal oil were investigated. Detailed economic and sensitivity analysis reveal specific scenarios that lead to profitability of algal oil as an alternative feedstock. In the second problem, a new safety metric is introduced and utilized in process design and selection. A case study was solved to assess the potential of producing biodiesel from sewage sludge. The entire process was evaluated based on multiple criteria including cost, technology and safety. The third problem is concerned with incorporating flexibility in the design phase of the development of multi-feedstock biofuel production processes. A mathematical formulation is developed for determining the optimal flexible design for a biorefinery that is to accommodate the use of multiple feedstocks. Various objective functions may be utilized for the flexible plant depending on the purpose of the flexibility analysis and a case study is presented to demonstrate one such objective function. Finally, the development of a systematic procedure for incorporating flexibility and heat integration in the design phase of a flexible feedstock production process is introduced for the fourth problem. A mathematical formulation is developed for use in determining the heat exchange network design. By incorporating the feedstock scenarios under investigation, a mixed integer linear program is generated and a flexible heat exchange network scheme can be developed. The solution provides for a network that can accommodate the heating and cooling demands of the various scenarios while meeting minimum utility targets.Item Integrated approaches to the optimization of process-utility systems(2009-05-15) Al-Azri, Nasser AhmedThe goal of this work is to develop a conceptual framework and computational tools for the optimization of utility systems in the process industries. The emphasis is devoted to the development of systematic design techniques aimed at identifying modifications to the process and the associated utility-systems to jointly optimize the process and the utility system. The following contributions describe the specific results of this work: ? Development of shortcut methods for modeling and optimizing steam systems and basic thermodynamic cycles with the objective of using these methods in the optimization of combined heat and power. To enable efficient mathematical programming formulations, simple yet accurate correlations have been developed for the thermodynamic properties of steam in the utility system. ? Optimization of multi-level steam system for combined process requirements and power cogeneration. A general procedure is developed to determine rigorous cogeneration targets and the optimal configuration of the system with the associated design and operating variables. ? Graph theory methods are also used to optimize the pipeline layout in the plant for the distributing the utilities. ? Finally, because of the nonconvex nature of much of the developed optimization formulations, a global optimization method has also been suggested by using interval analysis and simulated annealing. The techniques proposed in this work are compared to previous works and their applicabilities are presented in case studies. These techniques outperform previously suggested ones in terms of the accuracy, computational efficiency and/or optimality.Item Process simulation, integration and optimization of blending of petrodiesel with biodiesel(2009-05-15) Wang, TingWith the increasing stringency on sulfur content in petrodiesel, there is a growing tendency of broader usage of ultra low sulfur diesel (ULSD) with sulfur content of 15 ppm. Refineries around the world should develop cost-effective and sustainable strategies to meet these requirements. The primary objective of this work is to analyze alternatives for producing ULSD. In addition to the conventional approach of revamping existing hydrotreating facilities, the option of blending petrodiesel with biodiesel is investigated. Blending petrodiesel with biodiesel is a potentially attractive option because it is naturally low in sulfur, enhances the lubricity of petrodiesel, and is a sustainable energy resource. In order to investigate alternatives for producing ULSD, several research tasks were undertaken in this work. Firstly, base-case designs of petrodiesel and biodiesel production processes were developed using computer-aided tools ASPEN Plus. The simulations were adjusted until the technical criteria and specifications of petrodiesel and biodiesel production were met. Next, process integration techniques were employed to optimize the synthesized processes. Heat integration for petrodiesel and biodiesel was carried out using algebraic, graphical and optimization methods to maximize the integrated heat exchange and minimize the heating and cooling utilities. Additionally, mass integration was applied to conserve material resources. Cost estimation was carried out for both processes. The capital investments were obtained from ASPEN ICARUS Process Evaluator, while operating costs were calculated based on the updated chemical market prices. The total operating costs before and after process integration were calculated and compared. Next, blending optimization was performed for three blending options with the optimum blend for each option identified. Economic comparison (total annualized cost, breakeven analysis, return on investment, and payback period) of the three options indicated that the blending of ULSD with chemical additives was the most profitable. However, the subsequent life-cycle greenhouse gas (GHG) emission and safety comparisons demonstrated that the blending of ULSD with biodiesel was superior.Item Productivity enhancement through process integration(Texas A&M University, 2006-10-30) Alotaibi, Meteab AujianA hierarchical procedure is developed to determine maximum overall yield of a process and optimize process changes to achieve such a yield. First, a targeting procedure is developed to identify an upper bound of the overall yield ahead of detailed design. Several mass integration strategies are proposed to attain maximum yield. These strategies include rerouting of raw materials, optimization of reaction yield, rerouting of product from undesirable outlets to desirable outlets, and recycling of unreacted raw materials. Path equations are tailored to provide the appropriate level of detail for modeling process performance as a function of the optimization variables pertaining to design and operating variables. Interval analysis is used as an inclusion technique that provides rigorous bounds regardless of the process nonlinearities and without enumeration. Then, a new approach for identification of cost-effective implementation of maximum attainable targets for yield is presented. In this approach, a mathematical program was developed to identify the maximum feasible yield using a combination of iterative additions of constraints and problem reformulation. Next, cost objectives were employed to identify a cost-effective solution with the details of design and operating variables. Constraint convexification was used to improve the quality of the solution towards globability. A trade-off procedure between the saving and expenses for yield maximization problem is presented. The proposed procedure is systematic, rigorous, and computationally efficient. A case study was solved to demonstrate the applicability and usefulness of the developed procedure.Item Resource conservation and optimization via process integration(Texas A&M University, 2006-04-12) Gabriel, Frederico BurjackThe process industries are characterized by the enormous use of natural resources such as raw materials, solvents, water, and utilities. Additionally, significant amounts of wastes are discharged from industrial facilities. As the world moves toward sustainable progress, that is, meeting the demand of the current generation without affecting or compromising the new generation, future process facilities must focus on resource conservation and pollution prevention. The purpose of this work is to introduce a new process integration methodology for the conservation and optimization of resources in the process industries. The work is also geared towards reducing waste discharge from the processing facilities. The optimal management of fresh resources and waste disposal requires the appropriate allocation, generation, and separation of streams and species. Material recycle/reuse/substitution, reaction alteration, and process modification are some of the main strategies employed to conserve resources in the process industries. The overall problem addressed in this dissertation can be stated as follows: Given is a process with a number of streams (sources) that are characterized by certain criteria (e.g., compositions of certain compounds, targeted properties) where these streams can be utilized in a number of process units (sinks) if they satisfy given constraints on flow rate, compositions, and/or properties. Additionally, interception devices may be used to adjust stream criteria. The objective is to develop targeting procedures and synthesis tools for the identification of minimum usage of fresh resources, minimum discharge of waste, and maximum integration of process resources. The devised methodology addresses four classes of problems: ?? Targeting techniques using direct recycle strategies ?? Recycle and interception procedures for single-component systems ?? Recycle and interception procedures for multi-component systems ?? Property integration for direct recycle strategies The framework provided by this dissertation couples traditional mass integration with groundbreaking property integration techniques to target, synthesize and optimize a plant for maximal conservation of resources. In particular, this work introduces new techniques such as material recycle pinch analysis, simultaneous recycle and interception networks, and property-based allocation. Additionally, graphical, algebraic, and optimization approaches are developed and validated with case studies in order to illustrate the applicability of the devised procedures.