A description of the yield changes that occur during hydrocracking is complicated by the large number of different molecules involved. Here a kinetic model is discussed that represents this wide spectrum of compounds as a series of 50°F boiling range cuts. Each of the heavier cuts cracks via a first-order reaction to form a series of lighter cuts. One parameter describes the effect of boiling point on the rate constant. Two other parameters determine what products will be generated as each cut cracks. With a feed distillation and values for these three parameters, the model predicts product distillation curves as a function of conversion level for both once-through and recycle liquid operation with a standard error of about 1%. Values for these parameters are given for a variety of feeds and catalysts. They depend on catalyst type and feed paraffin content.
Disturbances in a fixed-bed reactor are controlled by exploiting the interaction between the traveling waves of temperature and concentration within the bed. A secondary reactant stream, injected at an intermediate point along the bed and modulated in accordance with temperature measurements only, provides a localized and traveling corrective action that annihilates a disturbance by the time it reaches the reactor effluent. Calculations for a first-order, homogeneous, exothermic reaction show that a temperature upset is the most difficult disturbance to control. Further, because of the dominance of the slower thermal wave in these reactors, the task of composition control is similar to that of temperature control. An approximation technique, developed to match both the short-and long-time behavior of the reactor and its controllers, simplified the study of the dynamics of the reactor under control.
Paraho shale oil is too high in nitrogen (2.2%) and other contaminants to be used directly as a fuel in most current applications. The key to successful shale oil refining is a hydrotreating process to remove these contaminants. In this study, nitrogen was reduced to concentrations as low as 1 ppm in the hydrotreated whole oil in a single catalytic stage using a catalyst containing nickel, tungsten, silica, and alumina. However, it is economically preferable to hydrotreat at less severe conditions to convert the shale oil to a premium synthetic crude containing about 500 ppm of nitrogen. This synthetic crude resembles a typical hydrorefined petroleum gas oil and is suitable for downstream processing to specification transportation fuels in conventional modern refineries.fois chapter presents results of a Chevron Research Company study sponsored by the U.S. Department of Energy (DOE) to demonstrate the feasibility of converting whole shale oil to a synthetic crude resembling a typical petroleum distillate. The synthetic crude thus produced then can be processed, in conventional petroleum-refining facilities, to transportation fuels such as high-octane gasoline and diesel and jet fuels. The raw shale oil feed used in this study is a typical Colorado shale oil produced in a surface retort in the so-called indirectly heated mode.Crude shale oil is an important potential source of transportation fuels when properly refined. However, although it is low in sulfur compared with mid-East crudes, it is much higher in nitrogen than typical petroleum crudes. The shale oil used in this study contains 2.2 wt % nitrogen; typical petroleum crudes contain less than 0.3% nitrogen. 0-8412-0456-X/79/33-179-025$06.75/l
Chevron Research Company, under a contract sponsored by the U.S. Department of Energy (DOE), is conducting a program to determine the feasibility and estimate the costs of using modern petroleum processing technology to produce distillate fuels, such as high octane gasoline, jet fuel, and diesel, from a number of synthetic crude feedstocks. Pilot plant tests for the key processing steps are being conducted to the extent needed to make reasonable estimates of commercial plant performance.The first feedstock studied under this contract was Paraho shale oil. In a series of recent papers (1-4) and a DOE report (5), three basic shale oil processing routes for the production of transportation fuels were studied: hydrotreating followed by hydrocracking, hydrotreating followed by fluid catalytic cracking (FCC), and severe coking followed by hydrotreating. It was concluded that shale oil can be refined to high quality transportation fuels via modern state-of-the-art refining technology and that it can serve as a substitute for crude oil in a refinery equipped with modern hydrotreating facilities. The key to successful shale oil refining is the initial hydrotreating step which removes contaminants (nitrogen, sulfur, oxygen, olefins, and metallic contaminants) and permits the use of conventional conversion and refining processes to make finished products.This chapter reports results of a similar study to determine the feasibility of converting solvent refined coal (SRC) to transportation fuels. The next chapter discusses upgrading of H-Coal process products.The SRC process, in its two forms, is one of the major processes under current study in programs sponsored by the DOE for conversion of coal to either (1) a solid deashed low sulfur product or (2) a low boiling liquid.In the original SRC process (6), now designated as SRC-I, coal is dissolved under moderate hydrogen pressure in an
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