Residue feed

Influence of the feed coke produced from distillation residue is less structured, less crystalline than that from a cracking residue. If the residue feeding the unit is highly contaminated with sulfur and metals, it is still coke, but is disqualified for certain applications. 

Feed residue coke is the small portion of the (non-residue) feed that is directly deposited on the catalyst. This coke comes from the very heavy fraction of the feed and its yield is predicted by the Conradson or Ramsbottom carbon tests. 

Steam is used to disperse and atomize the oil/residue feed... 

An RFCC is distinguished from a conventional vacuum gas oil FCC in the quality of the feedstock. The residue feed has a high coking tendency and an elevated concentration of contaminants. 

Greater levels of nitrogen and sulfur in the residue feed increase emissions of NO. and SOj from the regenerator. 

Minimizing Detrimental Effects of Processing Residual Feeds... 

Like gas absorption, liquid-liquid extraction separates a homogeneous mixture by the addition of another phase - in this case, an immiscible liquid. Liquid-liquid extraction carries out separation by contacting a liquid feed with another immiscible liquid. The equipment used for liquid-liquid extraction is the same as that used for the liquid-liquid reactions illustrated in Figure 7.4. The separation occurs as a result of components in the feed distributing themselves differently between the two liquid phases. The liquid with which the feed is contacted is known as the solvent. The solvent extracts solute from the feed. The solvent-rich stream obtained from the separation is known as the extract and the residual feed from which the solute has been extracted is known as the raffinate. 

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. 

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.

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. 

The ARCO pilot unit is also used for evaluation of different atmospheric residue feeds. Reference catalysts are used in these investigations. The results from one such test is presented here, where two residue feeds B and C (see Table 3.1) are compared with each other. The catalyst used in this study was an equilibrium catalyst, see Table 3.11. 

The two residue feeds B and C have almost identical boiling point distribution, but the density and the Conradson carbon content value are somewhat higher for feed C than for feed B. This indicates that feed C should be a little bit more difficult to crack than the B feed and this was also notified when the two feeds were to be tested in the pilot unit. 

The zeolite and matrix surface areas of the catalyst can be optimized using the ARCO pilot unit with North Sea atmospheric residue feeds. 

The total surface area of a FCC catalyst is the sum of the zeolite and matrix surface areas and is therefore not useful for optimizing of the catalysts. However, the ratio between the zeolite and the matrix surface areas (ZSA/MSA) is a valuable parameter, and has been used for optimization of vacuum gas oil catalysts [4] as well as catalysts for North Sea long residue feeds [9,13]. Additional information about the catalyst is also gained by studying the yields as a function of the zeolite surface area and as a function of the matrix surface area [9]. The regression analysis in this paper is performed at a constant conversion of 75 wt%. 

Additional support for our observations was found when catalysts A-1 to A-3 were stndied. Catalyst A-1 was developed according to the old recommendations for a residue catalyst with a moderate zeolite surface area and a large active matrix snrface area. The catalyst did not give as good naphtha selectivity as expected when the North Sea long residue feed was cracked. An attempt to improve this was made with catalyst A-2 where the matrix surface was lowered, while the zeolite surface area was kept the same. The naphtha selectivity was however not improved, and it was concluded that the zeolite surface area was too low. So in catalyst A-3 the zeolite snrface area instead was increased compared with the base catalyst A-1. Now the naphtha selectivity increased, but the gas yields also increased dramatically. This catalyst did indicate that a possible way to go could be to increase the zeolite surface... 

The zeolite to matrix surface area ratio can be used for optimization of catalysts for catalytic cracking of atmospheric residues. For North Sea long residues this ratio should be as large as possible, but the ratio should not exceed an upper limit. For the main catalyst type (A) used in this investigation the upper limit of the ZSA/ MSA ratio was around 3.5. There is also a lower limit for the matrix surface area. If the matrix surface area is lower than this limit, the catalyst will not be able to crack all the heavy components in the residue feed, and the coke on the matrix will increase dramatically. This will prevent the catalyst from working properly. Different type of catalysts must be optimized individually, as well as different type of long residues. 

Another commercial trail of MIP-CGP for processing intermediate-based sour residual feed has been put on stream in SINOPEC Cangzhon Company in 2005. Table 5.6 shows the commercial comparison of CGP-2 and CGP-1. After shifting to CGP-2 the propylene yield increased by 1.15%, and the light ends yield increased by 0.57%. The snlfnr content of gasoline was decreased from 840 to 580 J,g/g. The olehn content, RON and MON of gasoline remained essentially constant. 

In the process (Figure 9-37), the residue feed is slurried with a small amount of finely powdered additive and mixed with hydrogen and recycle gas prior to preheating. The feed mixture is routed to the liquid phase reactors. The reactors are operated in an up-flow mode and arranged in series. In a once through operation conversion rates of >95% are achieved. Typically the reaction takes place at temperatures between 440 and 480°C and pressures between 150 and 250 bar. Substantial conversion of asphaltenes, desulfurization and denitrogenation takes place at high levels of residue conversion. Temperature is controlled by a recycle gas quench system. 

Vanadium contamination has higher effect on conversion of residue feed... 

Comparing the 750°F+ and 850°F+ residual feed conversion above indicates sizable conversion for the 850°F+ SRC (26-47%) and considerably smaller conversion for 750°F-(- SRC feed (4-35%). This leads to the conclusion that the major product from SRC conversion was material boiling between 750° and 850°F. For samples taken at 76 and 83 hr on-stream, approximately 20% of the feed SRC went to 750°-850°F distillate. Only about 5% went to 750° F distillate since further conversion to 750° F material was much slower. For the sample taken at 101 hr on-stream, the residual SRC conversion for 850°F and 750°F cut points,... 

Excessive heat generation in the regenerator is a particular problem when using residual feed when coke formation is higher. Residual fuel FCC operations generally have additional heat removal mechanisms in the regenerator. This can be steam raising coils or external catalyst coolers. 

A practical application of this process could be in setting up a counter-current flow of acidified water treatment residual feed against an acid sweep solution through a stack of cation-exchange membranes. The process schematic is shown in Figure 34.4 [35]. 

Al recovery prohle led to idenhhcahon of three zones of mass transport, namely a kinetically driven linear zone, an equihbrium-driven saturahon zone, and an osmosis-driven diluhon zone. All three zones were observed in Nahon 117 during a 24 h experimental mn. For lonac MC 3470, only the linear zone was observed during the period of experimentation. Apphcahon of diffusion dialysis had a desired effect in transfer of acid molecules from the residual WTR feed to fresh WTR sweep solution. It helped in raising the pH of residual feed from 1-1.5 to approximately 3.0. The simultaneous reduchon of pH on the fresh WTR sweep soluhon helped in dissolving aluminum ions from the solid phase into the aqueous phase up to 40%. 

Heavy Arabian and Kuwait atmospheric residue feeds were used for evaluating kinetic parameters, temperature response, and metal deposition profiles for RM-430 catalyst. The data from these experiments indicated a one and one-half order dependence for metal removal at the process conditions tested. The temperature response of RM-430 catalyst is shown in Figure 1. The activation energy for vanadium and nickel were Vanadium -36.1 kcal/mol. Nickel -27.3 kcal/mol. 

Hydrodemetallation tests were conducted with Kuwait atmospheric residue feed at operating conditions selected to simulate the guard reactor in a typical residue processing service. In one such test, the temperature was initially held constant at a typical residue start-of-run (SOR) temperature condition for nearly three and one half months and then raised to a typical middle-of-run (MOR) temperature condition and maintained at that level for an additional equivalent length of time. In an another similar experimental run, SOR temperature was maintained for nearly two months and then the temperature was raised to a typical end-of-... 

The performance of the catalysts was studied in a fixed bed reactor testing unit. A 50 ml sample of the catalyst diluted with an equal volume of carborundum was used in the test. In a typical test run in which the catalyst is presulfided, the diluted catalyst is loaded in the reactor and the unit is pressurized with H2 to a pressure of 30 bar. The reactor is heated to 200°C and the presulfiding feed, which consists of gas oil spiked with 5% DMDS, is introduced at a rate of 100 ml/h. The reactor temperature is then raised to 250°C gradually in 2 hours. These conditions are maintained for 8 hours, then the temperature is raised again to 350°C gradually in 8 hours, and maintained under these conditions for an additional 8 hours. The residue feed is then introduced and the unit is brought to the operating conditions of the test, namely, P = 120 bar LHSV = 2.0 T = 425°C Hj/Oil = 1000 VN. 

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