Thermal Stability Analysis of Hydroprocessing Unit

Thermal stability is one of the most critical safety issues in the hydroprocessing units. Runaway reactions in the units can lead to catastrophic consequences as the reactors are being operated at high temperature and pressure, and the reactor effluent is a highly explosive mixture which contains hydrogen and hydrocarbons. For example, a fire and explosion due to a runaway reaction in a hydrocracking unit caused one death and forty-six injuries in 1997, in California. While the temperature runaway is the topic which has been studied extensively, most of the studies worked on simple reactions and little focused on the complex reactions such as hydroprocessing reactions. Also, in the studies on the hydroprocessing reactions, a lumping kinetic model was used which is less accurate and requires experiments for each application. In this research, the thermal stability of a naphtha hydrotreater will be analyzed by using a commercial process simulator ProMax where a novel mechanistic kinetic model, Single Event Kinetics has been integrated. Also, a simplified model will be established by using the data provided by ProMax for further analysis. The continuity and energy equations and parametric sensitivity equations will be solved by Matlab based on the methodology presented by Morbidelli and Varma

Fuel production by hydrocracking of non-olefinic plastics and vacuum gasoil blends

306 p.The catalytic hydrocracking of different blends of non-olefinic polymers (polystyrene, polymethylmethacrylate and polyethylene terephthalate) with vacuum gasoil has been studied to produce fuel streams suitable for inclusion in refinery pools. For this purpose, a catalyst synthesized in the laboratory composed of Pt and Pd supported on a zeolite Y has been used. For all the mixtures, the influence of the operating conditions (time, temperature, pressure) and the effect they have on the yields of the fractions of interest (naphtha and light cycle oil), as well as on their composition, have been tested. In addition, special attention has been paid to the physicochemical phenomena that take place during the reactions in order to analyze the catalyst behaviour and the different causes of its deactivation with a view to its implementation in industrial units. The use of advanced analytical techniques has allowed to establish the compositional framework of all samples regardless of their heavy nature, which has allowed to determine the mechanisms of hydrocracking of plastics, as well as the routes of elimination of different families of compounds. Finally, kinetic modelling of these systems has been carried out for the optimization of the operating conditions by performing simulations aiming at the maximum conversion of the plastics and maximum yield of the target fractions, while minimizing the products of less interest

Superstructure Optimization of Naphtha Processing System with Environmental Considerations

The objective of this research project is to develop an optimization-based mathematical model in the form of a mixed-integer linear program (MILP) for determining the optimal configuration of a petroleum refmery. The scope for this project is to formulate the superstructure representation model for a refinery focusing on the subsystem of naphtha hydroprocessing in order to select the most economical and cost efficient process route. The alternatives for all streams are evaluated and the optimal configuration is proposed based on market demand by incorporating logical constraints and mass balance using the GAMS modeling language platform. Based on the information and knowledge about the physics of the problem of naphtha processing unit, we represent all these possible processing alternatives on a superstructure. Carbon dioxide emission factors bave also been considered in which relevant data is obtained using the carbon weighting tonne (CWT) method. Computational studies are conducted on a representative numerical example to illustrate the proposed modeling approach

Refinery hydrogen network optimisation with improved hydroprocessor modelling

Heavier crude oil, tighter environmental regulations and increased heavy-end upgrading in the petroleum industry are leading to the increased demand for hydrogen in oil refineries. Hence, hydrotreating and hydrocracking processes now play increasingly important roles in modern refineries. Refinery hydrogen networks are becoming more and more complicated as well. Therefore, optimisation of overall hydrogen networks is required to improve the hydrogen utilisation in oil refineries. In previous work for hydrogen management many methodologies have been developed for H2 network optimisation, all with fixed H2/Oil ratio and H2 partial pressure for H2 consumers, which may be too restrictive for H2 network optimisation. In this work, a variable H2/Oil and H2 partial pressure strategy is proposed to enhance the H2 network optimisation, which is verified and integrated into the optimisation methodology. An industrial case study is carried out to demonstrate the necessity and effectiveness of the approach. Another important issue is that existing binary component H2 network optimisation has a very simplistic assumption that all H2 rich streams consist of H2 and CH4 only, which leads to serious doubts about the solution's validity. To overcome the drawbacks in previous work, an improved modelling and optimisation approach has been developed. Light-hydrocarbon production and integrated flash calculation are incorporated into a hydrogen consumer model. An optimisation framework is developed to solve the resulting NLP problem. Both the CONOPT solver in GAMS and a simulated annealing (SA) algorithm are tested to identify a suitable optimisation engine. In a case study, the CONOPT solver out-performs the SA solver. The pros and cons of both methods are discussed, and in general the choice largely depends on the type of problems to solve.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Techno-Economic Studies of Coal-Biomass to Liquids (CBTL) Plants with CO2 Capture and Storage (CCS)

Due to insecurity in the crude oil supply and global warming, various alternative technologies for fuel production are being investigated. In this project, indirect, direct, and hybrid liquefaction routes are investigated for production of transportation fuels from coal and biomass. Indirect coal liquefaction (ICL) and direct coal liquefaction (DCL) technologies are commercially available, but both processes are plagued with high carbon footprint. Furthermore, significant amount of hydrogen is required in the DCL process leading not only to higher cost but resulting in considerable amount of CO2 production. Addition of biomass and application of carbon capture and storage (CCS) technologies are studied for reducing the carbon footprint. However, these two options can lead to higher capital and operating costs. Due to easy availability and low cost of the shale gas in the U.S., utilization of shale gas in the direct and hybrid routes was investigated for producing hydrogen at a lower cost with reduced CO2 emission in comparison to the traditional coal gasification route. Because the quality of the syncrude produced from ICL and DCL technologies vary widely, the hybrid coal liquefaction technology, a synergistic combination of ICL and DCL technologies, is investigated for reducing the penalty of downstream syncrude upgrading unit through optimal blending.;In the indirect CBTL plant, coal and biomass are first gasified to syngas. Then the syngas is converted to syncrude via Fischer-Tropsch (FT) synthesis. CO2 is captured from both raw syngas and FT vapor product. In the direct CBTL plant, coal and biomass are directly converted into syncrude in the catalytic two-stage liquefaction (CTSL) unit by adding hydrogen produced from gasification of coal/biomass/liquefaction residue or reforming of shale gas. Significant amount of CO2 that is generated in the hydrogen production unit(s) is captured to satisfy the target extent of CO2 capture. In the hybrid CBTL plant, pre-processed coal and biomass are sent to either syngas production unit or the CTSL unit. Produced syngas is sent either to FT unit or hydrogen production unit. Naphtha and diesel products from the FT unit and the CTSL unit are blended to reduce the syncrude upgrading penalty. Different CCS technologies are considered and optimized for the indirect, direct and hybrid CBTL plant depending on the sources of CO2 containing stream and corresponding CO2 partial pressure.;While several studies have been conducted for indirect CBTL processes, studies on direct and hybrid CBTL processes at the systems level and investigation of CCS technologies for these processes are scarce. With this motivation, high fidelity process models are developed for indirect, direct, and hybrid CBTL plants with CCS. These models are leveraged to perform comprehensive techno-economic studies. Contributions of this project are as follows: (1) development of the systems-level and equipment-level process models and rigorous economic models in Aspen Plus, Aspen Custom Modeler, Aspen Exchanger Design and Rating, and Aspen Process Economic Analyzer platforms, (2) sensitivity studies to analyze the impact of key design parameters (i.e. biomass/coal ratio, operating conditions of key equipment, extent of CCS, CCS technologies, blending ratio of the syncrude and products in the hybrid route) and investment parameters (i.e. price of coal and biomass, project life, plant contingency and plant capacity) on key efficiency measures, such as thermal and carbon efficiency, as well as economic measures, such as the net present value, internal rate of return and break-even oil price, (3) comparisons and analyses of trade-offs of indirect, direct, and hybrid CBTL technologies

Techno-economic, uncertainty, and optimization analysis of commodity product production from biomass fast pyrolysis and bio-oil upgrading

Advanced biofuel is a promising replacement to fossil fuels for the purpose of protecting the environment and securing national energy supply, but the high cost of producing advanced biofuels makes it not as competitive as petroleum-based fuels. Recent technology developments in biomass fast pyrolysis and bio-oil upgrading introduced several innovative pathways to convert bio-oil into other commodity products, such as bio-asphalt, bio-cement, dextrose and benzene, toluene, xylene (BTX). Before commercializing these products, a comprehensive techno-economic analysis should be employed to examine the economic feasibility of producing them. This thesis compared the economic performance of biofuels, biochemicals, and hydrocarbon chemicals portfolios and optimized the product selection of an integrated bio-refinery. Based on a fast pyrolysis and bio-oil fractionation system, three product portfolios were proposed: biofuels (gasoline and diesel), biochemicals (bio-asphalt, cement and dextrose) and hydrocarbon chemicals (BTX and olefins). The production process, operating costs and capital costs were simulated based on the model data, experimental data, and literature data. Minimum product selling price (MPSP), maximum investment cost (MIC) and net present value (NPV) were used to evaluate and compare the economic performance of three portfolios with a 10% internal rate of return (IRR). A bio-refinery concept integrating all products was proposed to improve the flexibility to respond to changes in the market prices of the proposed products. The ratio of bio-oil upgrading to different product groups was manipulated to maximize the NPV under different price situations. Several major conclusions were drawn from this study. Due to high capital costs and operating costs associated with biofuels production, hydrocarbon chemical and biochemical products can be attractive bio-refinery products. However, there has been limited development of the hydrocarbon chemical and biochemical product technologies. This study attempts to address this risk by evaluating the uncertainty in the NPV and MIC. In particular, the biochemicals scenario has the highest MIC, which indicates that it has the greatest potential for remaining profitable with increased capital investment. The hydrocarbon chemicals production yields relatively high revenues and is more robust to fluctuations in market prices based on historical data. Biofuels production is economically attractive only when the price of transportation fuels is at historically high values

Doctor of Philosophy

dissertationA Uinta Basin bitumen was hydrotreated over a sulfided Ni-Mo on alumina commercial hydrodemetallation catalyst. The catalyst was on-stream continuously for more than 1,000 hours. The data were obtained with the reactor operating as a fixed bed reactor in the upflow mode to ensure complete wetting of the catalyst and nearly isothermal operation. The deactivation of the catalyst was monitored by the decline in the API gravity of the total liquid product with time-on-stream at a standard set of conditions. The primary process variables studied were reactor temperature (620-685 K; 656-775 °F), liquid weight hourly space velocity (0.24-1.38 h'1) and total reactor pressure (11.3-16.7 MPa; 1634-2423 psia). The hydrogen/oil ratio was fixed in all experiments at 890 m3/m3 (5000 scf H/bbl). The extent of heteroatom and metals removal, residuum (>1000 °F) conversion and molecular weight reduction were determined as a function of process operating variables. Simulated distillation of the hydrotreated total liquid products was used to compute residuum conversion and product distributions. Conradson carbon residue conversion and pour point reduction were also determined as functions of process operating conditions. Hydrodenitrogenation, hydrodesulfurization, hydrodemetallation and residuum conversion data were analyzed using a modified power rate law model. regression and ordinary differential equation solver techniques for the analysis of laboratory data. Simple first-order power rate law expressions for The apparent kinetic parameters were obtained by combined hydrodenitrogenation and hydrodesulfurization were obtained for bitumen hydrotreating over the hydrodemetallation catalyst. Higher than first-order kinetic data for residuum conversion and nickel removal were organized by invoking two parallel first-order reactions for the facile and refractory fractions. A molecular weight reduction model was proposed to examine the extent of residuum conversion to gas-oil, middle distillate and gases. The first-order rate constants were also determined. The hydrodemetallation catalyst was less active for nitrogen, sulfur and residuum conversion than the hydrodenitrogenation catalyst. Nitrogen, sulfur, and metals removal; residuum conversion; and product distributions are discussed for bitumen hydrotreating over the hydrodemetallation and hydrodenitrogenation catalysts