naphtha characterization and hydrodesulfurization
DESCRIPTION
Refinery Operations Naphtha Characterization Syn Gas Production needs Characterization methodology GBHE VULCAN software Impurities in crude HDS Report HDS Design method HDS Design guideTRANSCRIPT
By Gerard B. Hawkins Managing Director, CEO
Refinery Operations Naphtha Characterization Syn Gas Production needs Characterization methodology GBHE VULCAN software Impurities in crude HDS Report HDS Design method HDS Design guide
Crude Oil and Petroleum Products can characterized two ways
Physical Chemical
Don’t need to know exact chemical composition Products largely go into fuel industry Need to know how easily it can be handled ◦ Viscosity, density
How much heating or energy value it has ◦ Calorific Value
Cut points are approximate
Distillation defines quality of crude ◦ Hence quality of
fractions
Quality = Octane # = Profit
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Kerosene
Heavy Naphtha
Light Naphtha Light Ends
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Boiling Range Density (Specific Gravity) Viscosity Refractive Index Calorific Value
Only Physical characteristics
Summary Report is approximate
Target is octane value of feedstock as inferred by Gasoline, Naphtha and Gas Oil content
Crude Oil and Petroleum Products contain multitude of chemical species
Typically categorised as hydrocarbons i.e. compounds solely comprised of carbon & hydrogen atoms Can be ◦ simple e.g. Propane C3H8 ◦ complex e.g. ‘chicken wire’ compounds .. multiple ring stuctures
Chemical composition ◦ PONA Paraffins Olefins Naphthenes Aromatics
Average Molecular Weight Carbon: Hydrogen ratio
Sulfur species Chloride species Nitrogenous species Arsenic Heavy Metals ◦ Mercury, Nickel, Vanadium, Copper
Salt
Its in the feed, where does it end up?
Depends on boiling point
B Pt depends on species
Need to understand speciation!
So looking at sulfur compounds…………
Boiling Point at atm Pressure
Thermal decomposition temperature
degC degC Methyl mercaptan CH3SH 6 150 Ethyl mercaptan C2H5SH 35 150 Propyl mercaptan C3H7SH 67 150 n-butyl mercaptan C4H9SH 99 150 i-butyl mercaptan C4H9SH 89 225-250 phenyl mercaptan C6H5SH 169 200 cyclohexyl mercaptan C6H11SH 159 200 phenyl benzyl sulphide C6H5SC6H4CH3 197 300 diethyl sulphide C2H5SC2H5 92 400 diphenyl sulphide C6H5SC6H5 296 450 dimethyl disulfide CH3SSCH3 110 ~150 2,5-dimethylthiophene (CH3)2C4H2S 137 475 benzothiophene C6H5C4H2S 221 800 dibenzothiophene C6H5C4SC6H5 332 800 thiophene C4H4S 84 900 tetrahydrothiophene C4H8S 121
Boiling Point at atm Pressure
Thermal decomposition temperature
degC degC thiophene C4H4S 84 900 diethyl sulphide C2H5SC2H5 92 400 dimethyl disulphide CH3SSCH3 110 ~150 tetrahydrothiophene C4H8S 121 640 phenyl mercaptan C6H5SH 169 200
Straight run Naphtha
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Boiling CurveThiopheneDiethyl SulfideDimethyl DisulfideTetrahydrothiophenePhenyl Mercaptan
PONA Analysis (w/w)Paraffins = 84.3%Olefins = 2.3%Naphthenes = 11.4%Aromatics = 2.0%
Space Velocity ◦ SV is defined as Liquid Hourly Space Velocity, LHSV
◦ LHSV because
Naphtha is a liquid as supplied to plant battery limits
Naphtha pumped into plant
Flow measurement easier as liquid rather than vapor
Naphtha Flow (1) ◦ Vapor flow calculated from mass flow and Naphtha
average M Wt ◦ Vapor flow = 22.414 * Naphtha mass flow / M Wt
Nm3/hr kg/hr Naphtha Flow (2) ◦ Volumetric liquid flow calculated from liquid density ◦ Liquid flow = Naphtha mass flow / Liquid density m3/hr kg/hr kg/m3
LHSV = Liquid flow / Catalyst Volume
GBHE Mediterranean Client - Naphtha/LPG feed VULCAN DSMAKE Ver 2.0 NAPHTHA RATE 342.8 kgmol/hr NAPHTHA MOLECULAR WEIGHT 56.8 NAPHTHA DENSITY 600.0 kg/m3 HYDROGEN RECYCLE MOLAR RATIO 0.270 TEMPERATURE 360.0 C PRESSURE 33.3 atma = 33.4 kg/cm2g INLET H2S 1.0 ppm w/w = 1 ppm w/w S INLET disulphides(DMDS) 0.0 ppm w/w INLET mercaptans (Phenyl mercaptan) 151.3 ppm w/w = 44 ppm w/w S INLET sulphides (DES) 0.0 ppm w/w INLET tetrahydrothiophene 14.2 ppm w/w = 5 ppm w/w S INLET thiophene 0.0 ppm w/w EXIT NON-REACTED SULPHUR 0.2 ppm w/w S CATALYST DENSITY 710.0 kg/m3 Reduced thiophene rates used, see CFR 127662 NUMBER OF BEDS OF ZNO 2.0 LIFE REQUIRED PER BED 200.0 days CATALYST VHT-S101/VHT-N101 VOLUME 4.85 m3 LIQUID HOURLY SPACE VELOCITY 6.695 /hr – should be max 2.0 /hr Therefore increase volume to 4.85 * 6.695 / 2 = 16.25 m3
How does it work? Calculates catalyst volume for each species based
on kinetics Allows for equilibrium effects of H2S Has inbuilt catalyst activity factor based on VHT-S101 and VHT-N101 Adds volumes together to give answer.