2023p4

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University of British Columbia *

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476

Subject

Chemistry

Date

Dec 6, 2023

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pdf

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4

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1 Assignment 4 Due: Thursday, 30 November 2023, 23:59 pm Use Hysys to simulate a vacuum crude column in oil refinery. Stream Vacuum Feed is the bottom stream from an Atmospheric Crude Column (not part of this simulation). It is pumped by the pump P-101 and heated in a fired furnace FH-100. To account for the formation of the cracking gas and liquid in the furnace, as well as air leaks to the column, calculations of the flow rates of cracking gas, liquids, and leaks is performed in the block Feed Cracking. Stream S-4 is fed to the vacuum column (Figure 1). This column has the following products: VC-Ovhd, LVGO (Light Vacuum Gas Oil), HVGO (Heavy Vacuum Gas Oil), and VC Resid. Figure 1. Part of the oil refinery with vacuum furnace and vacuum crude column. Specifications Vacuum Feed Assay (adjusted to 1atm) TBP Distillation Assay Liq Vol % T ( ° F) 1 540.4 2 580.8 5 642.8 10 697.0 30 831.8 50 935.7 70 1097.8 90 1298.0 98 1485.4 Cut the assay into individual components using AutoCut. Define a blend and install the stream Vacuum Feed. Vacuum Feed: F = 41,560 bbld (std id liq vol flow), T = 630 F, P = 31 psia. P-101: Centrifugal Pump. Outlet pressure 140 psia, Adiabatic efficiency 75%. CHBE 476 Modeling and Optimization in Chemical Engineering Department of Chemical and Biological Engineering The University of British Columbia Tutorial 1 Monday, 9 September 2019, 4–5:45 pm Bulk Properties Bulk density 18 API_60 Molecular Weight 460
2 Furnace FH-100: Use fired heater. Radiant Zone Inlet: S-1. Radiant Zone Outlet: S-3. Fuel Streams: Natural Gas. Air Feed in SS Mode: Air. Combustion Product: S-2. Model Selection. Steady State Model: Simple Fired Heater. Efficiency = 70%. Natural Gas: T = 100 F, P = 70 psia, initial flow rate = 3,000 lb/hr. Composition: methane 90 mol%, ethane 10 mol%. Once the simulation converges, adjust the flow rate of this stream such that the temperature of the stream S-3 = 745 F. Report the flow rate of Natural Gas required to achieve this temperature. Air: T = 100 F, P = 70 psia, initial flow rate = 70,000 lb/hr. Composition: nitrogen 79 mol%, oxygen 21 mol%. Once the simulation converges, adjust the flow rate of this stream so that the mole fraction of O2 in S-2 = 0.04. Report the air flow rate needed to achieve this. The preheated feed composition (stream S-3) is adjusted for cracking in the furnace. Cracking Corrections and Leaks flow rate: These calculations are performed in the calculation block Feed Cracking using the following heuristics: Cracking gas flow rate: ࠵? !"#$%&’( *#+ (lb/hr) = ࠵? ,#$--. /001 (barrel/hr) 24 (hr/day) ∙ 0.6 Cracking gas composition (mol/mol): C2 = 0.75, C3 = 0.25 Cracking liquid flow rate: ࠵? !"#$%&’( 2&3-&1 (lb/hr) = ࠵? ,#$--. /001 (barrel/hr) 1000 ∙ 30 Cracking liquid composition (mol/mol): assume n-C11 = 0.5, n-C12 = 0.5 for simplicity. Leaks flow rate – to account for air leaks to the vacuum column the following formula is used: ࠵? 20#%+ (lb/hr) = 6 7 ࠵? ,#$--. /001 (barrel/hr) 1000 For simplicity, use the Leaks composition (mol/mol) as N2 = 1. Perform the calculation of the leaks flow rate in the block Feed Cracking, which is also used for the cracking corrections. Note : The mass balance must be preserved—the mass flow rates of streams S-3 and S-4 should be the same (as well as their temperatures). To account for the pressure drop in the furnace, specify the pressure of the stream S-4 = 4 psia. Vacuum Column Absorber (no condenser, no reboiler). Number of stages = 8. Pressures: P top = 0.155 psia, P bottom = 0.425 psia.
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