Refinery, fractionator

Gas Oil A refinery fraction boiling within a typical temperature range between 330°F and 750°F (165.6°C and 398.9°C). Diesel fuel, kerosene, and heating oil fall into this fraction. 

The SR method is suitable for modeling absorbers and strippers. For some extremely wide boiling systems, especially those with noncondensables, it is the best method. It has been found to work very well for the side strippers of a refinery fractionator. Absorbers typically have a rich gas bottom stage feed and a lean oil top stage feed. The equations of the SR method do not allow its direct use for reboiled absorbers, absorbers with condensers, or distillation columns. For these columns, other methods like that of Tomich (Sec. 4.2.8) or Russell Sec. 4.2.10) can be used. 

The best-known presentations are by Tomich (32), Holland (8), and Orbach et al. (33). These vary in their choice of Newton-Raphson equations and independent variables and each may solve a different range of columns, These methods have been shown to work well for wide-boiling mixtures including refinery fractionators, absorber-stripper columns, and reboiled absorbers. 

Iations should be better for columns with few stages and many components, and has been shown to work well for refinery fractionators. 

Russell s method is one of the methods used in the MULTIFRAC option for multiple columns in ASPENPlus and is the column method in HYS1M of Hyprotech of Calgary, Alberta. Russell s method as written by Richard Russell is in the PD+Plus system available from Deer-haven Technical Software in Deer haven, Massachusetts. The HYSIM and PD+Plus versions of Russell s method have been found to work well for refinery fractionators with sidestrippers and other similar columns including columns for which a version of Boston s method failed. 

Process temperature, as well as waste polyolefin composition and type of catalyst used are then the most important process parameters. It is evident that a process temperature below 500°C is the most suitable range for refinery fractions while 600°C and higher are appropriate for olefins production. 

The design of refinery fractionation columns can be complex. The pump-around streams function as intermediate condensers and remove surplus heat from the column. This heat is usually recovered by heat exchange with the cold crude oil feed. Oil refineries are often designed to handle many different crude oils with... 

Eor optimum use of the various refinery fractions in gasoline, they must be blended to obtain the correct volatility and rate of combustion for the engines in which they are to be employed. Winter conditions require more volatile... 

Purification of Individual Molecular Species. The chemical process industries use large amounts of hydrocarbons, which can be individually recovered and purified from petroleum refinery fractions. Examples would include ethane, propene, butadiene, isoprene, benzene, toluene, and xylenes. Sometimes distillation must be supplemented with liquid-liquid extraction, as well as extractive and azeotropic distillation, to purify these materials. The technology of recovering individual chemical species will be dealt with in other parts of this encyclopedia. 

The most abundant heteroatom is invariably sulfur, appearing in concentrations from below 0.1 wt. % in North African or Indonesian light crudes to over 5 wt. % in Venezuelan heavy crudes (Boscan) or Canadian tar sands. A wide variety of sulfur containing compounds are present in petroleum and refinery fractions, ranging from thiols to thiophenes the most important classes of organosulfur compounds of interest for our purposes are represented in Fig. 1.1. 

The complex nature of the HDS and HDN problems requires a broad, transdisciplinary approach in order to try to answer the most varied questions related to these important classes of reactions. The key issues include the practical aspects related to process and product engineering, a precise knowledge of the nature and the composition of petroleum and of refinery fractions, and the thermodynamics and detailed kinetics of the different processes involved. Also, a number of more fundamental solid-state and surface chemistry considerations regarding the preparation, the characterization, and the resulting properties of HDS and HDN catalysts, as well as the complicated reaction mechanisms involved for the various important families of substrates, need to be understood in depth. Even though some very impressive achievements have been disclosed over the last 30-40 years, it seems that some of the major new discoveries desired today may have been held back by the lack of a better understanding of some key issues. Of particular importance are the nature and the structure of HDS-HDN active sites on metal sulfide catalysts, and the intimate details of the elementary reactions implicated in the commonly accepted catalytic schemes. 

In some services (e.g., refinery fractionators), vapor approaching the chimney tray is hotter than the chimney tray liquid. Heat will be transferred from the vapor to the liquid. If the vapor is condensable, some will condense on the bottom face of the chimney tray. The net result is analogous to leakage. The author is familiar with situations where refractory was installed on the bottom face of the chimney tray. In all these cases, steps were also taken to minimize leakage, making it difficult to independently assess the effectiveness of the refractory. For multicomponent, partially condensable vapor condensing on an uninsulated bottom face of a chimney tray (e.g., in a refinery fractionator), a typical heat transfer coefficient is 15 Btu/(h ft °F) (237). 

When the column feed passes through a heater (e.g., a refinery fractionator or vacuum tower), any water lying at low points in the coils must be blown out prior to startup. In multipass coils, water must be separately blown out of each pass block valves are sometimes installed on each pass to permit this (7). If blowing into the tower, it must be performed when the tower can still tolerate water. The coils must be kept hot and/or purged from then on to prevent condensation. One pressure surge incident (7) occurred when water accumulated in one heater pass entered a refinery vacuum tower which was under full vacuum and circulating 280°F oil. 

Direct-contact condensers (Fig. 15.14f). These are used for minimizing pressure drop in vacuum condensation. To accomplish this, the direct-contact zone contains low-pressure-drop internals such as packings, or is a spray chamber. Another common application is intermediate heat removal ("pumparounds ) in refinery fractionators. Here the main purpose is to maximize heat recovery at the highest possible temperature levels. A third common application is intermediate heat removal from absorbers or reactive distillation columns in which an exothermic reaction takes places. In all these applications, condensation... 

The composition control loops can be interactive. Crude oil distillation and other refinery fractionators are examples where these loops are very interactive (362). In such services, undecoupled composition (or temperature) controls are usually unsatisfactory, and product streams are drawn on flow control. 

Side-stream strippers are common in refinery fractionators. The control system depends on whether the stripper feed is withdrawn from... 

It was pointed out earlier that a compression screw pump was used to provide catalyst circulation in the initial 100 /D plant and that it caused serious operating problems. Fortunately the concept of the standpipe to build up pressure was conceived at this opportune moment and was soon put to use. It may seem surprising, but the standpipe concept was only accepted after considerable persuasion and discussion. Confirmation was needed, so a standpipe 100 feet high was set up on one of the refinery fractionation columns at Baton Rouge, filled with catalyst, and aerated. Pressure gauges confirmed the calculated buildup in pressure, and when a valve at the bottom was opened the catalyst ran out as though it were a liquid. 

The inside-out algorithm has become one of the most popular methods because of its robustness and its ability to solve a wide variety of columns. The inside-out ncept was developed by Boston and Sullivan (69) and Boston (70). Russell (72) present an inside-out method that works well for many refinery fractionators. Jelinek (73) presented a simplified Russell method. 

Prime G+ process uses two reactors. In the first reactor, selective hydrogenation of diolefins and conversion of mercaptans occurs, as shown in Fig. FRCN means full range catalytic naphtha. The bottom stream from the splitter, which separates Light Catalytic Naphtha (LCN) and Heavy Catalytic Naphtha (HCN) after the first reactor, is desulfurized by a novel catalyst. The Prime G+ process is reported to be operating at more than 50 refineries. Fractionation is a practical approach to separate competing components to be treated separately over the best catalysts. 

Each procedure will be presented as a narrative explaining in detail the required steps. These, together with the others presented in this work, describe design methods for all types of refinery fractionation processes. This work does not consider the absorber since this is very rarely found in the refinery. In addition, the literature is well stocked with absorber design procedures only new or, at least, previously unpublished work is presented here. 

Although a pyrolysis gas quench lower physically appears to be very similar to other types of refinery fractionators considered previously, there is very little process similarity. Strictly speaking, a quench tower is a direct-contact gas cooler and scrubber, and any separation that occurs is limited to a single stage flash. However, this type of tower is included for discussion because the general calculation procedure is similar to those used elsewhere and because the analysis of the pyrolysis oil separation is handled most easily by using petroleum oil techniques. 

Many solvents have been proposed or used for extracting oilseeds, but later have been found ineffective in extracting oil or have been disallowed because of health concerns about residues in food and feed products and exposure of employees. Essentially all commercial oil extraction now is done with hexane, a petroleum refinery fraction with a boiling point of 65 to 68°C (149-155°F) that consists of 48 to 98 percent n-hexane with the balance being short-chain homologs and branched compounds. Currently, ethyl and isopropyl alcohol are attracting the most attention as alternative extraction solvents. 

XI.1.2 The relationship is based on regression of data on 315 fuels having luminometer numbers falling within the range from -2 to 100. There were 160 Jet A, A-1, JP-4, and JP-S fuels in this group. The remaining fuels were diesel fuels, kerosines, blends of refinery fractions, and other miscellaneous petroleum fractions. 

This chapter discusses several key modeling steps regarding thermophysical properties of crude oil and petroleum fractions. The basic process for developing a set of pseudocomponents for modeling refinery fractionation systems is as follows ... 

---