Representation of the Atmospheric Residue

To represent the feed properly for modeling the VDU, we need to pay attention to two requirements (1) using a sufficient number of pseudocomponents to represent the atmospheric residue, and (2) having good-quality assay data for the atmospheric residue. 

High-quality assay data for the atmospheric residue are always desirable in modeling a VDU. For VDU simulation, there are three ways to obtain assay data of the atmospheric residue (1) stream results of ADU simulation ifwe build the ADU and VDU models together (2) analysis of the atmospheric residue and (3) back-blending the assay data of VDU product streams if product analyses are available. 

We need to consider a number of issues when applying each approach to represent the feed for modeling purposes. Specifically, when we build the ADU and VDU models together, the representation of the atmospheric residue is reliable if a detailed feed representation of crude oil is available (by either crude assay or back-blending product analysis) and the ADU model performs correctly. 

However, we must pay more attention to correctly representing the atmospheric residue while using VDU operation and production data to build a VDU model. This follows because the atmospheric residue is an intermediate stream rather than a final product, and a detailed stream analysis is usually not available. Most likely, we can only have the analysis results of the distillation curve below 540 °C and the bulk density of the atmospheric residue. While using commercial simulators to construct the atmospheric residue based on an incomplete feed analysis, the resulting pseudocomponent distribution may not represent atmospheric residue well. 

Boiling-Point Range Boiling-Point Width of Each Pseudocomponent Number of Pseudocomponents per 100 °F 

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