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Synthesis and screening of technology alternatives is a key process-development activity in the process industries. Recently, this has become particularly important for the conceptual design of biorefineries. A structural representation (referred to as the chemical species/conversion operator) is introduced. It is used to track individual chemicals while allowing for the processing of multiple chemicals in processing technologies. The representation is used to embed potential configurations of interest. An optimization approach is developed to screen and determine optimum network configurations for various technology pathways using simple data. The design of separation systems is an essential component in the design of biorefineries and hydrocarbon processing facilities. This work introduces methodical techniques for the synthesis and selection of separation networks. A shortcut method is developed for the separation of intermediates and products in biorefineries. The optimal allocation of conversion technologies and recycle design is determined in conjunction with the selection of the separation systems. The work also investigates the selection of separation systems for gas-to-liquid (GTL) technologies using supercritical Fischer-Tropsch synthesis. The task of the separation network is to exploit the pressure profile of the process, the availability of the solvent as a process product, and the techno-economic advantages of recovering and recycling the solvent. Case studies are solved to illustrate the effectiveness of the various techniques developed in this work. The result shows 1, the optimal pathway based on minimum payback period for cost efficiency is pathway through alcohol fermentation and oligomerized to gasoline as 11.7 years with 1620 tonne/day of feedstock. When the capacity is increased to 120,000 BPD of gasoline production, the payback period will be reduced to 3.4 years. 2, from the proposed separation configuration, the solvent is recovered 99% from the FT products, while not affecting the heavier components recovery and light gas recovery, and 99% of waster is recycled. The SCF-FT case is competitive with the traditional FT case with similar ROI 0.2. 3, The proposed process has comparable major parts cost with typical GTL process and the capital investment per BPD is within the range of existing GTL plant.

Student Number : 9611112G - PhD thesis - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment / Attainable Region analysis is a chemical process synthesis technique that enables a design engineer to find process unit configurations that can be used to identify all possible outputs, by considering only the given feed specifications and permitted fundamental processes. The mathematical complexity of the attainable regions theory has so far been a major drawback in the implementation of this powerful technique into standard process design tools. In the past five years researchers focused on developing systematic methods to automate the procedure of identifying the set of all possible outputs termed the Attainable Regions. This work contributes to the development of systematic numerical formulations for attainable region analysis. By considering combinations of fundamental processes of chemical reaction, bulk mixing and heat transfer, two numerical formulations are proposed as systematic techniques for automation of identifying optimal process units networks using the attainable region analysis. The first formulation named the recursive convex control policy (RCC) algorithm uses the necessary requirement for convexity to approximate optimal combinations of fundamental processes that outline the shape of the boundary of the attainable regions. The recursive convex control policy forms the major content of this work and several case studies including those of industrial significance are used to demonstrate the efficiency of this technique. The ease of application and fast computational run-time are shown by assembling the RCC into a user interfaced computer application contained in a compact disk accompanying this thesis. The RCC algorithm enables identifying solutions for higher dimensional and complex industrial case studies that were previously perceived impractical to solve. The second numerical formulation uses singular optimal control techniques to identify optimal combinations of fundamental processes. This formulation also serves as a guarantee that the attainable region analysis conforms to Pontryagin’s maximum principle. This was shown by the solutions obtained using the RCC algorithm being consistent with those obtained by singular optimal control techniques.

Most of the available tools and methods applied in the design of chemical processes are not effective at the critical early stages of design when the process data is very limited. Businesses are often under pressure to deliver products in shorter times and this in turn prevents the evaluation of options. Early identification of options will allow for the development of an experimental program that will support the design process. The main objective of this work is to apply the Process Synthesis approach to develop a structured method of designing a process using mostly qualitative information based on limited experimental data, prior experience, literature and assumptions. Fischer-Tropsch (FT) synthesis of hydrocarbons from syngas generated by reforming natural gas and/or coal has been used as a case study to illustrate this method. Simple calculations based on experimental data and basic thermodynamics have been used to generate some FT Synthesis flowsheet models. The evaluation of different flowsheet models was done using carbon efficiency as a measure of process efficiency. It was established that when choosing the optimal region for the operation and design of an FT Synthesis process, the influence of the system parameters must be well understood. This is only possible if the kinetics, reactor, and process design are done iteratively. It was recommend not to optimize the reactor independent of the process in which it is going to be used without understanding the impact of its operating conditions on the entire process. Operating an FT Synthesis process at low CO per-pass conversions was found to be more beneficial as this will avoid the generation of high amounts of methane which normally results in large recycles and compression costs. Whether the process is run as a once-through or recycle process, the trend should be to minimize the formation of lighter gases by obtaining high Alpha values because carbon efficiency increases with the increase in value. Experiments should be performed to obtain process operating conditions that will yield high values. However, if the aim is to maximize diesel production by hydrocracking long chain hydrocarbons (waxes), then an optimal value should be targeted to avoid the cost of hydrocracking these very heavy waxes. The choice of the syngas generation technology has a direct impact on the carbon efficiency of an FT synthesis plant. This study has established that running an FT synthesis process with syngas obtained by steam reforming of natural gas with CO2 addition can yield high carbon efficiencies especially in situations were CO2 is readily available. In FT synthesis, CO2 is normally produced during energy generation and its emission into the environment can be minimized by using it as feed during the steam reforming of natural gas to produce syngas.

Catalysts are involved in a very large number of processes leading to the production of industrial chemicals, fuels, pharmaceutical, and to the avoidance, as well as the clean-up of environmental pollutants. In respect to the latter aspect, efforts are being made by different stake-holders (governments, researchers, industrials, etc) in order to prevent or to minimize pollution of our cities. A notably way to reduce pollution for a friendly environment is to make use of clean fuels. After years of research work, it is only recently that dimethyl ether alone or when combined with methanol has been identified as a potential alternative clean fuel. Nonetheless, the technology used for the methanol synthesis from syngas requires high pressure (>120 atm) to reach an acceptable CO conversion. The dimethyl ether production from methanol in a separate unit makes DME more expensive than methanol. However, the transformation of syngas directly into dimethyl ether can be used to relieve the thermodynamic constraints requiring operation at high pressure. If the synthesis of methanol and dimethyl ether takes place in the same reactor, the process should, in principle, be able to operate at a much lower pressure, making it a potentially cheaper process to produce methanol and dimethyl ether. The catalysts that need to be used for this coproduction have to be catalytically stable, selective and able to catalyze the main reactions (methanol and dimethyl ether synthesis) involved in this process at the same temperature. Unfortunately, existing commercial methanol/DME catalysts are not able to function efficiently in the presence of large concentrations of water or at high temperature. Thus, it is relevant to have a catalyst satisfying the above criteria. Recently, it has been reported that a supported gold catalyst could be used for methanol synthesis; accordingly this study has developed bifunctional gold-based catalysts for the methanol and DME synthesis. This study utilized process synthesis approach to determine the optimal operating conditions for methanol/dimethyl ether production that yielded results used to drive an experimental programme to get the most useful information for designing a process route. In a comparative way and by using the feed compressor work load per unit of valuable material generated as objective function, this study showed that the system where methanol is co-produced with DME is more efficient than the one involving the production of methanol alone and this is applicable for the operating reactor temperatures of 500-700K and the loop pressure ranging from 10 to 100 atm. The catalysts systems chosen in this study were consisted in the physical mixture of gold-based catalysts incorporating respectively gamma-alumina and zeolite-Y. The gold-based catalysts were prepared by a co-precipitation method, then characterized by XRD, Raman Spectrometry and Transmission Electron Microscopy and, afterwards tested using a 1/4 inch tubular fixed bed reactor between 573 and 673K at 25 atm. Amongst the catalysts tested at 673K, and 25 atm, 5%Au/ZnO/γ-Al2O3 produced both methanol and dimethyl ether with moderate yield, whereas 5%Au/ZnO/LZ Y-52 gave high dimethyl ether selectivity (75.7%) with a production rate of 252.3 μmol.h-1.g -1 cat . The presence of hydrocarbons detected by the GC-FID in the gas products requires that further investigations be done to determine the eventual source and optimize this new catalyst system based on gold for a large scale coproduction of methanol and dimethyl ether from syngas.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17164号 / 工博第3654号 / 新制||工||1555(附属図書館) / 29903 / 京都大学大学院工学研究科化学工学専攻 / (主査）教授 長谷部 伸治, 教授 田門 肇, 教授 宮原 稔 / 学位規則第4条第1項該当

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21130号 / 工博第4494号 / 新制||工||1698(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 長谷部 伸治, 教授 大嶋 正裕, 教授 佐野 紀彰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In the last decade Process Synthesis has been an emerging active area of research. Since 1999 at COMPS, we have continuously applied this technique to many studies and recently have carefully started to consider the integration of this technique with others to simplify multilevel process design. In this regard the need for new tools that do not require very accurate data or experimental technique has become an imperative for the initial analysis of systems. This thesis presents some of these results.Process synthesis requires new rapid tools for the assessment and comparison of new technologies (possibilities) in the process development stage.This thesis examines and formulates process synthesis problems in the case of separation processes (separation with mixing , separation with reaction).Using simple generic vectorial tools, the thesis addresses the folowing issue: How the topology and mapping of the process vector field defines patterns that may be used for alternative process synthesis solution and design (structure selection ,stability analysis or controllability etc...) . The tools presented are intended for preliminary process design and feasibility studies and will allow for simple comparisons of various options.The key principle used in the study is the exploitation of the generic vectorial representation of fundamental physical phenomena (separation, mixing , reaction) in the process models as used for process synthesis and analysis.The demonstrated power of this approach is that it allows one to exploit the formal mathematical similarities between the different processing modes. Extensive topological Reactive Column Profile has been generated and analysed, offering new insights for manipulation of process behaviour in process synthesis and design. The significance of the contribution of this research is in offering extended fundamental insigths in creating process synthesis options for reactive-separations systems, creating the essential structural basis for subsequent mathematical optimisation of the performanceof process designs.