Atmospheric residue

Crude oil topped at 260°C or atmospheric residue or vacuum residue... 

Beyond 340°C in the reboiler, the residue begins to crack thermally. If the distillation is stopped at this point, the residue is called the atmospheric residue. In order to continue, the distillation is conducted under a low pressure, vacuum", so as to reduce the temperature in the reboiler. 

SARA (Saturates, Aromatics, Resins, Asphaltenes) analysis is widely practiced on heavy fractions such as vacuum and atmospheric residues and vacuum distillates for two purposes ... 

Feedstock Paraffinic crude Naphthenic crude Vacuum distillate Vacuum residue Deasphalted atmospheric residue... 

Characteristics Atmospheric residue (Arabian light) Vacuum residue (VR) Visbroken residue (on VR) LCO (low sulfur) HCO (low sulfur)... 

Vacuum distillation of the atmospheric residue complements primary distillation, enabli r.ecoyery of heavy distillate cuts from atmospheric residue that will un r o further conversion or will serve as lube oil bases. The vacuum residue containing most of the crude contaminants (metals, salts, sediments, sulfur, nitrogen, asphaltenes, Conradson carbon, etc.) is used in asphalt manufacture, for heavy fuel-oil, or for feed for others conversion processes. 

Applied to atmospheric residue, its purpose is to produce maximum diesel oil and gasoline cuts while meeting viscosity and thermal stability specifications for industrial fuels. 

Figure 10.7 presents the case of an FCC feedstock comprising a mixture of vacuum distillate and light atmospheric residue, and the case of an FCC feedstock composed of vacuum distillate and DAO, as well as the constraints of such configurations. 

Figure 10.8 presents a variant of the FCC process, the RCC (Residue Catalytic Cracking) capable of processing heavier feedstocks (atmospheric residue or a mixture of atmospheric residue and vacuum distillate) provided that certain restrictions be taken into account (Heinrich et al., 1993). 

The conversion products, other than gas and hydrogen sulfide (H2S), are essentially a gasoline fraction that, after pretreatment, will be converted by catalytic reforming an average quality distillate fraction to be sent to the gas oil pool and an atmospheric residue or vacuum distillate and vacuum residue whose properties and impurity levels (S, N, Conr. 

Conversions of atmospheric residues are 20 to 35 weight % and 50 to 65% on vacuum residue. 

American Petroleum Institute atmospheric residue atmospheric residue hydroconversion American Society for Testing and Materials Association pour la Valorisation des Huiles Lourdes Anstalt fur Verbrennungskraftmaschinen List Bureau of Mines Correlation Index bromine number... 

Processing residue or purchased feedstocks. Sometimes, the option of processing supplemental feed or other components, such as atmospheric residue, vacuum residue, and lube oil extract, is a means of increasing the yields of higher-value products and reducing the costs of raw material by purchasing less expensive feedstocks. 

The distillation of crude oil under conditions slightly above atmospheric pressure is limited by the maximum temperature that can be tolerated by the materials being distilled, otherwise there would be decomposition. Further separation of the bottoms of the column (the atmospheric residue) would require higher temperature, and therefore... 

FAU 5.5 NiO(1.7) M0O3 (6.7) Arabian heavy atmospheric residue Autoclave 410°G 9.8MPa 74.9% liquid product, 52% HDS activity, 26.8% HDN activity Contains mesopores [123]... 

FIGURE 2.10 Comparing MAB catalyst with a standard residual catalyst at extreme metal contaminant levels with atmospheric residue in the ACE unit. (O) LZM resid catalyst, ( ) MAB. 

Catalyst Evaluation Using an ARCO Pilot Unit on North Sea Atmospheric Residue... 

At the end of the 1970s Statoil cracked a North Sea atmospheric residue for the first time in M. W. Kellogg s circulating pilot nnit in Texas [1]. This pilot unit was qnite large, with a capacity of one barrel a day. The test in this pilot nnit was very snccess-ful and showed that North Sea atmospheric residnes were very suitable feedstocks for a residue fluid catalytic cracker, and that North Sea atmospheric residnes gave very promising prodnct yields. 

Some years later Statoil decided to start a project within catalytic cracking in order to learn more abont residue fluid catalytic cracking in general, and particnlarly abont catalysts suitable for this process. The project started as a prestudy for the residue fluid catalytic cracker unit (FCCU) that Statoil was planning to bnild at the Mongstad refinery in Norway. The intention was to crack North Sea atmospheric residue directly, without first using a vacuum gas distillation tower followed by cracking... 

The ARCO pilot unit is a well-established pilot unit originally designed for vacuum gas oil as feed. This small circulating pilot unit is working at atmospheric pressure [2]. The common way to investigate residue feedstocks at that time, in the mid-1980s, was to mix them into vacuum gas oil and calculate their yields by comparison with the clean vacuum gas oil [3]. Statoil, however, wanted to study the atmospheric residue directly and this was not possible without some modifications of the ARCO pilot unit. The successful result of this was published some years later [4]. 

The feeds used in all experiments presented in this paper are North Sea atmospheric residues originating from the atmospheric distillation tower at the Statoil Mongstad refinery in Norway. After the start-up of the residue fluid catalytic cracker at this refinery in 1989, the same feed has been used both in the commercial FCCU and in the ARCO pilot unit at Chalmers. Typical data for some North Sea atmospheric residue feeds used in the ARCO pilot unit are shown in Table 3.1. 

Typical North Sea Atmospheric Residues Used in the ARCO Pilot Unit at Chalmers... 

Already during the hrst years a lot of important new information was gained. It was demonstrated that the decision to use the same feed for testing as was used in the commercial unit was correct [4,5] because the ranking of the catalysts was found to be dependent on the feed used in the tests. Despite the fact that it is much more troublesome and much more time-consuming to perform the tests with an atmospheric residue than with a vacuum gas oil, the tests should be performed with the same North Sea atmospheric residue as used in the commercial FCCU. The importance of this is always under discussion, but we are very firm at this point. 

One important question we have asked ourselves many times since we managed to crack the North Sea atmospheric residue in the ARCO pilot unit for the first time was if the results are reliable. Does the pilot unit show the same trend and ranking as expected for the commercial FCCU, and can the yields from the pilot unit be used for modeling Initially there was no answer to these qnestions since no commercial data were available for comparison. The only possibility was to compare the tests done in the ARCO pilot unit with the tests done in the pilot nnit at M. W. Kellogg s some years earlier. 

The test at M. W. Kellogg s and the test in the ARCO pilot nnit were done with different feeds, with different catalysts and in different pilot nnits, so it was not expected that the yields should be identical. The feed to the M. W. Kellogg s pilot unit was a synthetic Statfjord atmospheric residne and the catalyst used was a Filtrol 900 catalyst containing nickel and vanadinm contaminants [1]. This pilot unit was also pressurized. In the ARCO pilot unit at Chalmers the feed was a laboratory distilled Statfjord atmospheric residue and the catalyst was an almost metal-free EKZ eqnilibrinm catalyst from Katalistiks. The ARCO nnit is working at atmospheric pressnre. 

Another important question that had to be answered was if the results in the ARCO pilot unit were repeatable when North Sea atmospheric residue is used as feed. The repeatability is well demonstrated in ARCO pilot units with vacuum gas oils, but this had to be confirmed for atmospheric residue feedstocks. To be able to achieve repeatability in the ARCO unit, independent of the feed used, the catalyst circulation has to be calibrated for each single catalyst the first time it is used in the pilot unit. If the same catalyst is used more than once, it is not necessary to calibrate the catalyst circulation again according to ARCO [7]. We have experienced the same, but nevertheless the calibration of the catalyst circulation is always checked by a single point measurement if a catalyst is used more than once. 

Figures 3.1 through 3.6 show the repeatability of results in our ARCO unit when North Sea atmospheric residue is used as feed. The time between the first test and the repeatability check is about 2 years. As can be seen in Figures 3.1 through 3.6, the two tests give almost the same results in the ARCO pilot unit even with a North Sea atmospheric residue feed. This shows that the ARCO unit is just as suitable for a residue feed as for a vacuum gas oil feed.

When discussing the suitability of the ARCO pilot unit for cracking atmospheric residues, this cannot be done without touching on the question about how to prepare the catalysts for testing. An equilibrium catalyst used in a commercial residue FCCU contains significant amounts of metal contaminants, especially nickel and vanadium. Fresh catalysts must therefore be impregnated with these metals and deactivated before the catalysts can be nsed in the pilot unit. We have shown that this... 

We have proved that the ARCO pilot unit is repetitive when it is used with an atmospheric residue feed. But it is necessary to impregnate and deactivate the catalysts in a repetitive way if this should be the case. 

One of the objectives when our project started was to use North Sea atmospheric residues as feeds in the ARCO pilot unit. It was comprehensively shown during the very hrst years of the project that the ranking of the catalysts were dependant on the feed used [4,5]. The results of the tests done at this time showed that all the catalysts tested could be divided into three groups, all with their own characteristics, depending on the matrix surface area. 

It has been observed that catalysts aimed for cracking of North Sea atmospheric residues need a high RE content. A fully RE exchanged catalyst was able to crack... 

All the observed yield responses to changes in the RE content of the catalysts were in the same direction as those observed for vacnnm gas oil reported in the literature. This indicated that these changes are trne also for North Sea atmospheric residue. 

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