Refinery, scheme

Other Studies - The complete DOE report (9) includes a sixth case not discussed in this paper. This case is a refinery scheme for production of gasoline by catalytic cracking of a lower hydrogen content feed than in Case 3A. In this case, No. 2 heating oil was a second major product. 

From an FCC viewpoint, there is not a clear definition of resid cracking. If we consider the overall refinery scheme, all materials not qualifying for gas oil type specifications are resid, which in fact means that the traditional FCC feed, Vacuum Gasoil (VGO), is nearly 100% resid, or to be more specific a fuel oil. 

The catalytic reforming process is, together with catalytic cracking, one of the most important processes in modem refinery schemes. It is used to convert low octane n-alkanes and cycloalkanes with 5 to 10 carbon atoms contained in the petroleum naphtha into high-octane isoalkanes and aromatics gasoline components and hydrogen. Typically, reformer reactors operate at temperatures of 425-525 °C and hydrogen pressures of 0.5-3.0 MPa. 

Since most of the petrochemicals from the petrochemical refinery scheme have values in the U.S. which are so intimately involved with premium fuel values and have price trends which are buffered by fuel refinery requirements and economics, the petrochemical refinery must be considered in an oil industry context. 

Cracking processes to convert heavy liquids to lighter liquids also make gases. Another way to make more liquid products is to combine gaseous hydrocarbons. A few small molecules of a gas can be combined to make one bigger molecular with fairly specific properties. Here, a gas separation unit is added to the refinery scheme to isolate the individual types of gases. When catalytic... 

Low temperature characteristics of a diesei fuei affect more its fuel feed system than its behavior when burning. However, we will examine them here because of their strong impact on refinery flow schemes. 

This type of study, applied over all the cuts, enables the refinery flow scheme to be defined in order to satisfy a given set of market conditions starting from one or more crude oil feedstocks. 

Hybrid Crystallization/Adsorption Process. In 1994, IFP and Chevron announced the development of a hybrid process that reportedly combines the best features of adsorption and crystallization (59,99). In this option of the Eluxyl process, the adsorbent bed is used to initially produce PX of 90—95% purity. The PX product from the adsorption section is then further purified in a small single-stage crystallizer and the filtrate is recycled back to the adsorption section. It is reported that ultrahigh (99.9+%) purity PX can be produced easily and economically with this scheme for both retrofits of existing crystallization units as well as grass-roots units. A demonstration plant was built at Chevron s Pascagoula refinery in 1994. 

The butane-containing streams in petroleum refineries come from a variety of different process units consequently, varying amounts of butanes in mixtures containing other light alkanes and alkenes are obtained. The most common recovery techniques for these streams are lean oil absorption and fractionation. A typical scheme involves feeding the light hydrocarbon stream to an absorber-stripper where methane is separated from the other hydrocarbons. The heavier fraction is then debutanized, depropanized, and de-ethanized by distillation to produce C, C, and C2 streams, respectively. Most often the stream contains butylenes and other unsaturates which must be removed by additional separation techniques if pure butanes are desired. 

Conventional Refining Process. The conventional refining process is based on complex selective dissolution and precipitation techniques. The exact process at each refinery differs in detail (12—14), but a typical scheme is outlined in Figure 2. 

The actual solvent extraction processes used, including the specific extractants and the order in which the components are separated, vary from refinery to refinery. However, a typical scheme is shown in Figure 3 (12). 

An old variation of the conversion type is a catalytic combination unit. Development of this scheme was necessitated by the rising cost of refinery construction after World War II and by the great demand for capital for postwar expansion. The scheme reduced the investment and operating costs for refining equipment. The basic feature of the combination unit lies in the integration of the fractionation facilities of the reduced crude distillation and catalytic cracking sections. 

The arrangement of light ends separation facilities is an important factor in overall refinery economics. The development of the optimum scheme for a particular application often involves postulation of a number of alternatives and comparison of the economics for each. 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

A modern refinery is a complicated collection of conversion processes, each tailored to the properties of the feed it has to convert. The scheme shown in Fig. 9.1 summarizes the most important operations some reasons for these processes are given in Tab. 9.2, along with relevant catalysts. First the crude oil is distilled to separate it into fractions, varying from gases, liquids (naphtha, kerosene and gas oil), to the heavy residue (the so-called bottom of the barrel ) that remains after vacuum distillation. 

Figure 9.1. Simplified processing scheme of an oil refinery. [Adapted from J.W. Gosselink, CatTech, 4 (1998) 127.]...

Hydrogenolysis of butane was used to study the catalysis of the RhPt particles in mesoporous silica. This is a test reaction of reforming of alkanes in oil refinery, and methane, ethane, and propane are formed by the cleavage of terminal or central C-C bond (Scheme 1). 

Pyrrolidones fit well into the bio-refinery concept since they may be produced in a scheme beginning with the fermentation of a portion of the bio-refineiy s sugar product into succinate. Pyrrolidones are a class of industrially important chemicals with a variety of uses including polymer intermediates, cleaners, and green solvents which can replace hazardous chlorinated compounds. 

In this section, we will begin by discussing overall process designs and process alternatives. Most of the designs come from processes patented by EBC, although other players have contributed recently as well. The alterations to processes come from variations in the raw material to be desulfurized, (diesel vs. crude oil), or from point of application perspective (before or after HDS, in oil field vs. in refinery, etc.) or from changes to reaction schemes (complete desulfurization vs. stopping at an intermediate... 

In terms of the process, very little has been achieved. The mass transfer limitations still exist although emulsification has solved the problem partially, but not without creating another problem downstream in separation of the product from the rest of the stream and the issue still needs further work. The IP portfolio contains very few real process concepts. The patented material refers to a BDS process several times, but the process referred to, is no more than a simple description of the pH, temperature, etc., and the particular use of a given biocatalyst in an application. Some protected subject matter concerns the integration of a bioprocess into the flow sheet of the refinery, but again those are no more than theoretical scheme proposed for implementation, with no actual evidence with real feedstocks. 

The alkylation unit in a petroleum refinery is situated downstream of the fluid catalytic cracking (FCC) units. The C4 cut from the FCC unit contains linear butenes, isobutylene, n-butane, and isobutane. In some refineries, isobutylene is converted with methanol into MTBE. A typical modern refinery flow scheme showing the position of the alkylation together with an acid regeneration unit is displayed in Fig. 1. 

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