Optimize design for heavy crude
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Abstract:
Addition of atmospheric residuum hydrotreating with fluid catalytic cracking or delayed coking appear to be most attractive for converting a typical light crude refinery to heavy crude operation. Examination of seven alternative approaches for accomplishing this conversion shows a range in economic results that illustrate the general conclusions but require specific examination for each refinery to determine its optimum choice. During 1978-1982, many refiners initiated projects to permit processing lower quality heavier crudes with the capability for converting residuum to transportation fuel products. A substantial price differential between light and heavy crude and a low residual fuel oil value provided a twofold incentive for these projects. Recently, crude price differentials have shrunk, and high-sulfur residual fuel oil values have risen almost to crude prices. Some analysts believe that this is a temporary market situation and that incentives will be restored within five years as heavy crudes become more available and outlets for high-sulfur fuel oil become more limited. Various processing schemes are possible for use in converting a typical light crude refinery. Several of these are considered in a screening evaluation.Keywords:
Refinery
Residuum
Refining (metallurgy)
Synthetic crude
Fuel oil
Residual oil
Petroleum product
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This paper describes the heavy oil upgrading projects which had been designed for residuum hydrotreating followed by delayed coking. It is demonstrated that combining residuum hydrotreating with delayed coking gives a refinery the flexibility to meet its light product demand while processing heavier crudes. Based on this processing scheme, the Chevron U.S.A. Pascagoula residuum conversion project will start up in late 1983. The improved catalyst systems developed should allow operation at high residuum conversion levels while maintaining reasonable catalyst life. 9 refs.
Residuum
Refinery
Refining (metallurgy)
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Certain design and operating steps can improve the efficiency of delayed cokers. This fact is important because during the last decade of the petroleum business, a significant change has taken place in the refining industry. Heavy, cheaper crudes are making up a greater part of our imports and refinery runs, while demand for residual fuel has declined. Of the 1982 refinery runs, 31% were heavy as compared to 21% of runs in 1979. (By definition, a heavy crude yields 15% or greater residuum at 1,050/sup 0/F.) Refiners are adding resid conversion to upgrade the heavier feedstocks to meet demands for economically competitive light products. A majority of refiners are turning to delayed coking to upgrade the low value fuel oil to more valuable lighter liquids.
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Upgrade
Refining (metallurgy)
Residuum
Synthetic crude
Fuel oil
Petroleum product
Delayed coker
Liquid fuel
Residual oil
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Trends in quality of crude feedstocks to US refineries and the problems in processing and utilization caused by the changing feed quality were reviewed. The quality of feedstocks declined in the period 1978 to 1985. This is shown, for example, by declining in API gravity from 34.3 to 32.4 and an increase in sulfur content from 0.78 to 0.91%. The lower quality was due primarily to a decline in quality of imported rather than domestic crudes. The shift in crude quality was not caused by a shortage of conventional crude, but resulted from economic factors which encouraged the utilization of cheaper heavier crudes. While domestic throughput decreased significantly during this period, the fraction of the residual material being upgraded increased. The increased conversion was driven by heavier feedstocks, a sustained demand for distillate products, a decreased demand for residual fuels, and an increased conversion capacity by industry. The majority of the upgrading relied largely on carbon rejection techniques. A variety of problems are associated with the utilization of lower quality feedstocks and increased resid processing. These include both problems in the refinery and problems with product quality. The understanding of fundamental petroleum chemistry of heavy crudes and resids is inadequatemore » to predict their processing behavior. Processing flexibility for resids from heavy crudes is limited due largely to their metals content and propensity for coke formation. Other problems discussed include those with desalting, naphthenic acids, hydrotreating, cat cracking, and thermal operations. The change in feedstock quality and increased resid upgrading did not negatively affect overall gasoline quality, but have negatively affected quality of heavier fuels. Heavier feedstocks and increased resid processing result in more aromatic diesel cuts with poorer diesel ignition quality. 24 refs., 11 figs., 2 tabs.« less
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Residual oil
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Flexibility in residuum hydroprocessing becomes a requirement as fuel oil demand weakens, crude slates tend to be heavier, and variability in crude oil cost and supply become the norm. One means of providing flexibility is to incorporate residuum hydrotreating ahead of a heavy oil catalytic cracking unit which converts heavier components into lighter, more valuable products. Alternatively, significant conversion of the residuum to lighter products can be achieved by the operation of the residuum hydrotreater at a higher severity to facilitate hydrocracking reactions. This paper focuses on the design and selection of catalytic systems in the framework of a unified reactor modeling scheme for such residuum hydroprocessing applications.
Residuum
Delayed coker
Fluid catalytic cracking
Fuel oil
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Operation of atmospheric residual desulfurization units for catalytic cracker feed treatment at two Phillips Petroleum Co. refineries has resulted in benefits to both refinery operations. At Phillips' Sweeny and Borger, Tex., facilities, the new operations have resulted in greater flexibility in the choice of crude charge to refineries. Additionally, these facilities have provided a significant increase gasoline and distillate yields, decrease in the yield of residual fuel oil despite an increase in the amount of heavy crude charged. This article presents operating data from each of these refineries in the form of operation comparisons before and after installation of the new facilities to show the benefits from the hydrotreating-catalytic cracking scheme.
Refinery
Fluid catalytic cracking
Refining (metallurgy)
Residual oil
Fuel oil
Jet fuel
Petroleum product
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The energy used to refine crude oil into a spectrum of products is a small fraction of the energy contained in the products and varies considerably from refinery to refinery depending on refinery configuration, crude oil composition, and amounts of gasoline and distillate produced. The manufacture of some products such as lube oils and petrochemicals increases energy usage. The refinery energy change associated with small changes in gasoline volumes cannot be assigned in an absolute way. However, an approximation is possible by exploring how the energy is allocated over the refinery product slate. This paper gives some details about this approximation. 18 refs.
Refinery
Petrochemical
Petroleum product
Fraction (chemistry)
Refining (metallurgy)
Fuel oil
Energy source
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The world increase in heavy crudes has forced refiners to develop different processes that upgrade the yields and product properties recovered from these crudes. However, some of the optimized and new processes are not able to handle whole heavy crude oils, due to the high viscosity and corrosion of their long and short residues. The different processes for heavy crudes can be classified in two areas: physical (vg. Liquid Extraction) and chemical processes. The catalytic hydrotreating process, which belongs to this last classification, has demonstrated to be an economical upgrading process for heavy crude oil. This paper describes the development by the Mexican Petroleum Institute of the process to hydrotreat maya heavy crude. The effect of the operating conditions, the catalyst ---- development and the technical - economical analysis are presented. The product properties and yields are compared with the results obtained with light crude oil like isthmus.
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Synthetic crude
Fuel oil
Refining (metallurgy)
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Deteriorating crude quality plus lower heavy fuel demand have encouraged refiners such as Chevron USA to consider conversion of residuum to more valuable light products. Chevron residuum hydrotreating unit will substantially improve conversion. Specifically tailored, noncylindrical systems of crude mixtures 10% Maya/ 90% Arab heavy for example, were designed to improve catalyst life. CCH system can perform better than standard RDS catalyst systems. The conversion of the vacuum bottoms fraction of the residuum feedstock is also discussed, few tailored catalysts giving better results.
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Chevron (anatomy)
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The demand for residual fuel oil has been declining, while the demand for distillates, such as kerosene, jet fuel and diesel oil, has been growing steadily. In Japan, the share of heavy crude oils in the total crude oils imported is gradually increasing, while the residual fuel oil consumed is decreasing it's share in the Product-mix. This situation increases the need for the heavy oil upgrading. In the United States, it is said that crude oil input to refineries will have a lower quality and will require additional bottoms upgrading investment in the early 1990s. On the other hand, there has only been a few processes to date which can upgrade vacuum residue efficiently and economically. Asahi Chemical Industry Co., Ltd. has been laying the groundwork for a superior residual hydro-thermal-cracking technology which would be useful for producing light oils appropriate not only for the intermediate feed in the petroleum refinery but also as the feedstock for olefins production, and developed a new highly active catalyst which exhibited the capability of cracking vacuum residue with around 90% conversion at the bench scale unit. Based on the achievement of this development, Asahi, Nippon Mining Co., Ltd. and Chiyoda Chemical Engineering andmore » Construction Co., Ltd. decided to collaborate on the development of this process named SOC (Super Oil Cracking) with the demonstration plant under the sponsorship of the governmental research organization, RAROP (Research Association for Residual Oil Processing).« less
Residual oil
Kerosene
Fuel oil
Refinery
Jet fuel
Co-processing
Synthetic crude
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The current refining trend is to run heavier crudes with a growing emphasis on bottom of the barrel resid upgrading. In general, a reduction in light crude availability and a corresponding increase in the price differential between light and heavy crudes makes the processing of heavier crudes highly attractive. US Department of Energy data indicate that between 1985 and 1989 the average API gravity of crude being processed in the US dropped from 32.46 to 32.14 degrees while the average sulfur content increased 0.15 wt%. As crudes get heavier and the demand for light, clean fuels increases, expanded resid upgrading capacity is rapidly becoming a necessity for most refiners. The coking process has existed since the early 1900's, and delayed coking is still favored as a relatively low cost resid upgrading option. Consistent with the objective of maximizing resid conversion, recent trends in delayed coking include maximizing liquid yields and reducing the production of petroleum coke by operating coke drums at lower pressures. Typically, the incremental liquid gained at lower pressures is worth significantly more than coke and can be further upgraded to lighter products. In addition, the driving force to minimize coke make has been accelerated by the worseningmore » quality of crude oils. As vacuum resid feedstocks become heavier, contaminants in coke such as sulfur and metals are increased, making the coke less marketable. In the case of an existing coker which is capacity limited by coke make, a reduction in coke yield can be quite valuable. This paper discusses the design features and presents the economics associated with building a low pressure delayed coker with a 15 psig coke drum operating pressure versus a more conventional 25 psig design.« less
Delayed coker
Coker unit
Refining (metallurgy)
Synthetic crude
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