In residue hydroprocessing

Generally, an amount of coke on the catalyst increases from the entrance to the exit of the fixed bed reactors in residue hydroprocessing (1, 6, 7). Tamm et al. showed the highest remained catalyst activity at the outlet of the bench-scale fixed-bed reactor after a constant desulfurization operation (1), while Myers et al. found the highest catalyst deactivation rate in the last stage of three-stage pilot-scale expanded-bed reactors after a 60 - 70% vacuum residue conversion operation (7). These results from two typical reactor operations support that the catalyst deactivation in a lower... 

Effect of Process Conditions and Catalyst Properties on Catalyst Deactivation in Residue Hydroprocessing... 

COMPARISON OF OPERATIONAL MODES IN RESIDUE HYDROPROCESSING M. de Wind , Y. Miyauchi and K. Fujita ... 

In this paper we discuss the effect of the mode of operation on catalyst deactivation and product properties in residue hydroprocessing. Other mentioned issues have been addressed in other publications [1-2]. 

Table 1 gives a comparison of two operational modes practiced in residue hydroprocessing MHC and HDS. In the MHC mode of operation, usually heavy feedstock is processed at a relatively high liquid space velocity and temperature to produce maximum middle distiUate. The desulfurized bottoms are fed to a vacuum tower to produce FCC feedstock, are used as a blending stock for... 

In residue hydroprocessing units, heat release is high, but some licensors avoid using intra-reactor quench because residue feeds often form lumps of coked-bonded catalyst in fixed-bed units. In reactors with complex internals, such lumps are very hard to remove during a catalyst change-out. Therefore, fixed-bed residue units often comprise three or more 1-bed reactors in series with quench in between. In many cases, the first reactor is guard bed filled with one or catalysts designed to remove metals. 

Matsnshita, K., Marafi, A., Hauser, A., Stanislaus, A. 2004. Relation between relative solubU-ity of asphaltenes in the prodnct oU and coke deposition in residue hydroprocessing. Fuel 83(11-12) 1669-1674. 

Ideally one would therefore choose a model, similar to that of described in Ref. (65), in which the reactor is split into a number of sectors, and in which for each the activity of the catalyst is calculated as a function of time. This is essentially what the RESIDS model (14,50) does for residue hydroprocessing it correlates local catalyst activity/deactivation with local reaction rates for HDM, HDS, etc. Thus, at any time and location in the reactor, the actual state and activity of the catalyst are defined, allowing predictions of complex multi-catalyst/multi-bed systems over a range of feedstocks and conditions. For this the catalyst activity and... 

In order to minimize these problems, the refiners are often forced to operate at low conversion levels (ca. 50%). Despite its importance as a critical factor limiting the maximum conversion attainable in commercial residue hydroprocessing units, the problem of sediment... 

A pretreated (1) residue Maya has been hydrogenated in a hydroprocessing unit provided with a continuous stirred tank reactor (CSTR). 

Alvarez A, Ancheyta J. Modeling residue hydroprocessing in a multi-fixed-bed reactor system. Appl. Catal. A Gen. 2008 351 148-158. 

In addition to scale-up difficulties, there are a number of problems related to the stable operation of a bubble column associated with hydrodynamics. For example, consider the important commercial application of bubble columns in hydroprocessing of petroleum resids, heavy oils and synthetic crudes. Hydrodynamic cold flow and hot flow studies on the Exxon Donor Solvent coal liquefaction process (Tarmy et al., 1984) showed that much of the literature correlations for the hydrodynamic parameters (holdup, interfacial area and dispersion coefficients) obtained with cold flow units, at ambient conditions, are not applicable for commercial units operating at relatively higher pressures. In addition, the flow pattern in commercial units was considerably different. In the hydroprocessing of petroleum residues by the H-Oil and LC-Fining processes, refinery operations have experienced problems with nonuniform distribution of gas and liquid reactants across the distributor, maintaining stable fluidization and preventing temperature excursions (Beaton et al., 1986, Fan, 1989 and Embaby, 1990). Catalyst addition, withdrawal and elutriation have also been identified as problems in these hydrotreaters. 

Alvarez, A., Ancheyta, J. 2008. Modehng residue hydroprocessing in amulti-fixed-bed reactor system. Appf. Catal.A 351(2) 148-158. 

Eccles (1993) modeled the kinetics of residue hydroprocessing in an EBR by using the power-law model. The reactor was assumed to behave as a liquid phase back-mixed tank. The model consists of a single equation for estimation of frequency factor and includes residue conversion and all the reactor-independent variables. 

Al-Dalama, K., Stanislaus, A. 2006. Comparison between deactivation pattern of catalyst in fixed-bed and ebullating-bed residue hydroprocessing units. Chem. Eng. J. 120 33-42. 

Colyar, 3.3., Wisdom, L.1.1997. The H-OIL process A worldwide leader in vacuum residue hydroprocessing. In NPRA Annual Meeting, March 16-18, Convention Center, San Antonio, TX. 

Hydroprocessing reduces the Conradson carbon residue of heavy oils. Conradson carbon residue becomes coke in the FCC reactor. This excess coke must be burned in the regenerator, increasing regenerator air requirements. 

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