NOVEM-NLAHX (HTRI Technology-November 2002)b
21
HTRI Process Heat Transfer Technology - Fouling and PHE - HTRI Process Heat Transfer Technology - Fouling and PHE - Hans U. Zettler Heat Transfer Research, Inc. NOVEM/NLAHX Meeting The Hague, The Netherlands November 29 th , 2002 Hans U. Zettler Heat Transfer Research, Inc. NOVEM/NLAHX Meeting The Hague, The Netherlands November 29 th , 2002 Outline Outline l Benefits of using HTRI Technology l Crude Oil Fouling Research l HTRI Xchanger Suite - Xphe
-
Upload
vsraochemical1979 -
Category
Documents
-
view
258 -
download
6
Transcript of NOVEM-NLAHX (HTRI Technology-November 2002)b
HTRI Process Heat Transfer Technology
- Fouling and PHE -
HTRI Process Heat Transfer Technology
- Fouling and PHE -
Hans U. ZettlerHeat Transfer Research, Inc.
NOVEM/NLAHX MeetingThe Hague, The Netherlands
November 29th, 2002
Hans U. ZettlerHeat Transfer Research, Inc.
NOVEM/NLAHX MeetingThe Hague, The Netherlands
November 29th, 2002
OutlineOutline
lBenefits of using HTRI TechnologylCrude Oil Fouling ResearchlHTRI Xchanger Suite - Xphe
Using HTRI TechnologyFouling Research
Using HTRI TechnologyFouling Research
l Important to effectively benefit from progress in heat transfer researchlNeed to distinguish between true fouling
and safety factorslShould consider effect of operating
conditions and fluid characteristics
Cooling Water Fouling Rate Correlation
Cooling Water Fouling Rate Correlation
lOriginal Formulation of “Deposit – Removal Concept”
−
−ΩΡ==
basg
nd
ff
f
RC
TRE
Cdt
dR
dt
kx
dτ
21 exp
Cooling Tower WaterCooling Tower Water
lSeven year study: 40 water compositionslExhibited asymptotic rate behaviorlAsymptotic fouling factor solved from rate
equation with deposit term = removal term
( )
−=
sag
bs
aCf TR
ETCCCR expexp 6
543* ττ
Behavior of a Selected Cooling Water
Behavior of a Selected Cooling Water
0.0001
0.001
0.01
0.1
1.0
2 4 6 8 10 12
Velocity, ft/sec
Fo
ulin
g F
acto
r, h
r ft
2°F
/Btu
Surface Temperature, °C
65.5
54.4
76.7
TEMA fouling factor
Water Fouling ModelWater Fouling Model
Cooling water fouling model
SummarySummary
lCooling water fouling example confirms advantage of research incorporated in HTRI Xchanger Suite
Crude Oil Fouling Research Overview
Crude Oil Fouling Research Overview
l Background
l Summary of Results
l Plots of All Data
l Prediction Model
l Recent Surface Studies
l Conclusions
Studies to DateStudies to Date
l Conditions– Temperatures– Flow velocities
l Surfaces– Stainless, carbon steel, polished, finned
l Properties/Components – Physical properties (density, viscosity)– Inorganics: sulfur, metals (except salt)– Component types (CII)
Results: Ranking ofImportant Parameters
Twelve Crudes
Results: Ranking ofImportant Parameters
Twelve Crudes
l Surface temperature
l Velocity
l Component types
l Surface
l Inorganics (except salt)
l Other physical properties
Surface TemperatureEffect > 260 °C (500 °F)Surface Temperature
Effect > 260 °C (500 °F)
l Fouling rate is exponentially related to surface temperature
l Arrhenius function is applicable
– Activation energy, function of reaction typel cracking straight chain molecules
l asphaltene decomposition
Component TypesTypical Concentrations
Component TypesTypical Concentrations
l Asphaltenes (<5 – 10%)– Cause fouling as function of surface
temperature and residence time on surface
l Aromatics and Resins (40 – 60%)
– Have stable cyclic molecules that stabilize asphaltenes in solution
l Saturates (30 – 60%)
– Have straight or branched-chain single-bond molecules
– Cause fouling by
l destabilizing asphaltenes, which causes them to clump in large groups (micelles) that decompose at the surface
l cracking to coke at high surface temperature
Component TypesTypical Concentrations
Component TypesTypical Concentrations
Colloidal Instability Index (CII)Colloidal Instability Index (CII)
l Definition
)()(
AromaticsResinssAsphalteneSaturatesCII
++=
l Apparent effects, based on current research– Low range < 0.5: Stable crude, low fouling– High range >1.2: Unstable crude, high fouling– Mid-range: No effect correlated between CII and
fouling
VelocityVelocity
l Low velocity– Diffusion limited
– Fouling increases with velocity
l High velocity
– Deposit shearing
– Fouling decreases with velocity
VelocityVelocity
l Mid-range– Direct velocity effects difficult to correlate
Fo
ulin
g R
ate
Velocity
– Indirect effects on wall temperature are significant
Recent Surface StudiesRecent Surface Studies
l Fins: Increase on-stream time by providing more surface for deposition
l Surface roughness: fouling rates
– Highest to lowestl carbon steel
l stainless steel
l electropolished stainless steel
Inorganics/PropertiesInorganics/Properties
l Reactive sulfur– Some indication it increases fouling
l Other inorganics (except salt) – No conclusive evidence of effects
l Properties (density, viscosity)– No conclusive evidence of effects
ConclusionsConclusions
l At given velocity and within certain ranges, crudes foul according to the Arrhenius reaction rate equation
l Crudes that have very low or very high values of CII, however, do not fit the pattern and require special evaluation
l Bulk temperature may be more important than once thought
l Surface enhancements have some potential but more research is needed
BenefitsBenefits
l Current: On-stream time can be increased by using higher velocities
l Future: Deposit-removal model, in combination with component effects, is potentially a valuable tool to quantify effects of higher velocity in designing lower fouling crude exchangers
HTRI Xchanger Suite ®Concept
HTRI Xchanger Suite ®®Concept
l Consistent Microsoft® Windows® interface (GUI)
l Design/rating of multiple unit types– Air coolers– Economizers– Shell-and-tube exchangers– Plate heat exchangers– Interactive shell-and-tube tubesheet layout– HTRI Property Generator
l Platform for future units
Xphe 2.0Xphe 2.0
l New HTRI Xchanger Suite component
– Calculation engine/interface combination
– Heat transfer and pressure drop for plate and frame exchangers
l Look and feel of Xchanger Suite
– Xace, Xist, Xtlo
Xphe InterfaceXphe Interface
Calculation OptionsCalculation Options
l Rating
l Simulation
l Design
– Grid design
– Classic design
– Grid of classic designs
l Single-phase liquid
GeometryGeometry
l One to six hot/cold passes
l Mixed passes, e.g., 1 hot/2 cold
l One or two plate types
– Up to three effective chevron angles
l Multiple sub-streams (plate groups)
– Maximum 12 total
GeometryGeometry
l Cocurrent or countercurrent flow
– Within and between passes
l Internal plate databank
l User-defined plate type databank
IncrementationIncrementation
1
10
1 2 3 4 5 6
IncrementationIncrementation
1
10
1 2 3 4 5 6
Internal Plate DatabankInternal Plate Databank
User-defined Plate DatabankUser-defined Plate Databank
User-defined Plate DatabankUser-defined Plate Databank
New plate in user databank
Plate ConfigurationPlate Configuration
l Passes– Four hot/three cold– Channel specification automatically
calculated
Port ArrangementPort Arrangement
Reports ViewReports View
Graphs View – 3DGraphs View – 3D
Graphs View – 2DGraphs View – 2D
