Simulator hydrocracker

To facilitate the maintenance and updating of plant performance inputs, we have developed and implemented an LP preprocessor. This preprocessor automatically generates and stores in the LP database the usage of equipment and utilities, the product yields, and the product properties for six process units at Sun Petroleum Products Company s Toledo Refinery. Linked to the preprocessor are three already existing process simulators a fluid catalytic cracker or FCC simulator, a hydrocracker simulator, and a catalytic reformer simulator. 

The hydrocracker simulator was also converted to subroutine form for inclusion in the nonlinear programming model of the Toledo process complex. The subroutine was considerably simplified, however, to save computer time and memory. The major differences are (1) the fractionation section is represented by correlations instead of by a multi-stage separation model, (2) high pressure flash calculations use fixed equilibrium K-values instead of re-evaluating them as a function of composition, and (3) the beds in each reactor are treated as one isothermal bed, eliminating the need for heat balance equations. 

The feed to the hydrocracker consists of the heavy naphtha cut from the base crude mix and light cycle oil from the base FCC operation. The hydrocracker simulator requires a description of each of these feeds in terms of the hydrocarbon components shown in Table I. Since these components are not directly measured in the crude assay nor are they predicted by the FCC simulator, special techniques were developed to estimate them from available data. 

The hydrocracker simulator also requires a description of the unit and its operation in terms of equipment dimensions and constraints, operating variables, and unit parameters. Standard or default values are stored in the preprocessor. The user can change the values of any of the following in specifying the base... 

No convergence problems were found in linking the hydrocracker simulator to the preprocessor and running on a wide range of alternate operations and feed property changes. 

The reformer simulator also requires a description of the feed in terms of hydrocarbon components. These are shown in Table II. Fortunately, most of these components are measured in the crude assay and are predicted by the hydrocracker simulator. 

For the heavy and light hydrocrackates, the hydrocracker simulator includes a product fractionation subroutine which distributes components between adjacent fractionator cuts using a Fenske-type formulation. 

The present paper presents batch autoclave data on the direct hydrocracking of a single sub-bituminous coal from the Powder River basin of southeastern Montana. Comparative data were also obtained with the Pittsburgh Seam bituminous coal that was used in the previous work (I). Data on the regeneration of simulated spent melts from such an operation are also given in a continuous bench-scale, fluidized-bed combustion unit. 

The melt used in this work was prepared from the residue of hydrogen-donor extraction of Colstrip coal with tetralin solvent in such a way as to simulate the composition of an actual spent melt. The extraction was conducted in the continuous bench-scale unit previously described (17) at 412°C and 50 min residence time. The residue used was the solvent-free underflow from continuous settling (17) of the extractor effluent. The residue was then precarbonized to 675°C in a muffle furnace. The melts were blended to simulate the composition of a spent melt from the direct hydrocracking of the Colstrip coal by blending together in a melt pot zinc chloride, zinc sulfide, and ammonium chloride, ammonia, and the carbonized residue in appropriate proportions. Analysis of the feed melt used in this work is given in Table I. 

Feeds. Properties of two hydrofined test feeds are given in Table I. The California gas oil blend was used in tests simulating a hydrocracking unit producing both naphthas and jet fuel, the Mid-Continent blend in tests representing a unit producing naphtha as the major product. 

Figure 6.5 a Product distribution for hydrocracking catalyzed by an ERI-type zeolite, showing the window effect observed by Chen et ai. b simulation of n-C- in an ERI cage (window size = 0.36 nm xO.51 nm). Thanks to Dr. David Dubbeldam for the zeolite simulation snapshot. 

In the fourth step, the preprocessor generates plant performance data for the FCC, gas oil hydrocracker, motor reformer and BTX reformer. For each of these process units, the preprocessor calls the appropriate process simulator which computes the usage of equipment and utilities, product yields, and product properties for all base and alternate operations specified by the user. For all of the FCC operations, the feed properties are those of the atmospheric plus vacuum gas oil from the base crude mix blended with a specified fraction of deasphalter overhead. 

For all of the hydrocracker operations, the feed properties are those of the heavy naphtha from the base crude mix blended with a specified fraction of light cycle oil from the base FCC operation. For all of the motor reformer operations, the feed properties are those of the motor naphtha from the base crude mix blended with heavy hydrocrackate from the base hydrocracker operation. For all of the BTX reformer operations, the feed properties are those of the BTX naphtha from the base crude mix blended with light hydrocrackate from the base hydrocracker operation. Finally, for each process unit, the process simulator computes the change in plant performance associated with a fixed perturbation of each feed property about the base operation. 

Activities in the FCC, hydrocracker, motor and BTX reformer submatrices represent (1) feed streams from each of the crude operations and from other process units, (2) material transfers between process units simulating... 

For some widely practiced processes, especially in the petroleum industry, reliable and convenient computerized models are available from a number of vendors or, by license, from proprietary sources. Included are reactor-regenerator of fluid catalytic cracking, hydro-treating, hydrocracking, alkylation with HF or H2SO4, reforming with Pt or Pt-Re catalysts, tubular steam cracking of hydrocarbon fractions, noncatalytic pyrolysis to ethylene, ammonia synthesis, and other processes by suppliers of catalysts. Vendors of some process simulations are listed in the CEP Software Directory (AIChE, 1994). 

Limited naphtha in the crude (5 wt %) plus that obtainable from single-pass hydrocracking appear insufficient for economical derivation of chemical feedstocks. Therefore, simulated recycle was attempted. After... 

Several of the commercial simulation programs offer preconfigured complex column rigorous models for petroleum fractionation. These models include charge heaters, several side strippers, and one or two pump-around loops. These fractionation column models can be used to model refinery distillation operations such as crude oil distillation, vacuum distillation of atmospheric residue oil, fluidized catalytic cracking (FCC) process main columns, and hydrocracker or coker main columns. Aspen Plus also has a shortcut fractionation model, SCFrac, which can be used to configure fractionation columns in the same way that shortcut distillation models are used to initialize multicomponent rigorous distillation models. 

Bhutan), N., Ray, A. K. and Rangaiah, G. P. (2006). Modeling, simulation and multiobjective optimization of an industrial hydrocracking unit. Industrial and Engineering Chemistry Research 1354-1372. 

Martens, G. G. Hydrocracking on Pt/US-Y zeolites Fundamental kinetic modeling and industrial reactor simulation , PhD Thesis, Ghent University (2000). 

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