Upload
hakhue
View
215
Download
0
Embed Size (px)
Citation preview
Richard L. Chapman
23rd National Tanks Conference
St. Louis, MO
March 21, 2012
ULSD Corrosion Issue-- Preventable, Treatable?
Agenda
ULSD Corrosion Assessment
Likely Causes
Recent Observations
Biological Testing
Low MW Species Results
Water Bottoms Testing
Housekeeping!
Summary
Assessment -- ULSD Corrosion Issue
Innospec involved in and studying problem for several years:
Member of CDFA Task Force
Internal company testing of key fuel/water properties:
Working with several refining and/or marketer customers;
Mostly affects retail/commercial UST & dispensing systems
Sporadic, inconsistent occurrence geographically;
Most OEM’s say not an issue.
ULSD Corrosion – Assessment
Samples from Innospec customers
across the US:
Majority of samples non-passing
for NACE corrosion
Mixture of tank and dispenser
samples
“Good housekeeping” customers
seem to have less problems?
Submersible Pump & Riser(L/H side is Al; R/H side is steel)
Submersible Pump Head(in vapor space -- never contacts fuel)
Recent photos from fiberglass UST
– Newer site tested positive for microbial activity
ULSD Corrosion – Assessment
Inside of steel tank caps (spare openings, highest point in UST, no fuel contact)
Bulbous globules thought to be of a microbial nature
ULSD Corrosion – Assessment
After 3 monthsNew steel corrosion coupon
ULSD Corrosion – UST Detail
No one cause, but rather a mixture……….
Microbial influence getting a lot of attention:
Low MW acids as microbial by-products valid;
Explains both fuel and vapor space corrosion;
Not uncommon to be positive for microbial activity
and/or higher low MW acids, yet have passing NACE;
Salt and other contaminants also a contributing factor?
ULSD Corrosion Update – Likely Causes
Corrosion inhibitor depletion (aka “soap”) theory – acidic additives
form soaps if contacted with excessive tank water cations from
salts or caustic:
Tank water from manufacturing processes (caustic/salt
upsets, biodiesel) provides Na, Ca, source etc.;
Corrosion protection lessened;
Effect similar to soaps formed from acidic lubricity improvers
(mono acids, etc.) and sodium/calcium – lubricity lessened
Poor housekeeping, no biological monitoring, improper application
of biocides exacerbates problem;
ULSD Corrosion Update – Likely Causes
Innospec Fuel Specialties testing ULSD terminal and retail tank
samples:
Bug testing, low MW acids, pH since early 2011
NACE corrosion testing (TM-0172) – ongoing, many years.
Majority of more recent samples positive for biological activity:
HY-LiTE (ASTM D 7463) and/or aerobic/anaerobic cultures;
Majority of samples (tank and dispenser) from nationwide survey
of varied suppliers show non-passing NACE results
ULSD Corrosion Problem – Recent Observations
Low MW acids present in most samples – acetic acid (as
acetate) predominates:
Acid/acetate determination by Ion Chromatography (IC);
pH results very variable, but usually low (4-6):
Addition of a specific biocide produces:
Excellent kill -- no culture growth, reduction in ATP
counts over time;
Raises pH to > 7.00
ULSD Corrosion Problem – Recent Observations
Biological activity established using ATP analyzer and culture tests:
Merck-Millipore HY-LiTE® ATP Analyzer (ASTM D7463) – 5 minute
result, reported as RLUs (relative light units):
<1000 RLU – negative;
1000-5000 RLU – positive – action level, possibly treat
>5000 RLU – positive, heavy – definitely treat with biocide
Culture Tests:
Anaerobic Organisms -- Easicult® S;
Aerobic Organisms (bacteria, fungi, molds)
– Easicult®
– Microbe Monitor 2 ( MM2)
Microbial testing in general agreement – positive HY-LiTE® results
typically showed positive bacteria, fungi, molds presence and vice-versa
ULSD Corrosion– Biological Testing
No single method appears to give accurate representation of what’s happening in the storage tank:
Example -- Detection of Viable Microbes:
HY-LiTE® detects ATP for a short period after using biocide and achieving a kill:
Cultures of the same samples show no growth*;
Trend can continue until ATP level is negligible;
Example -- Low MW Acid Species:
Anions still detected after neutralization (pH change from 4.61 to 8.04 still had significant levels of acetate, etc.)
Some culture media may need a neutralizer prior to using certain types of media.
ULSD Corrosion – Biological Testing
*MICROBIOLOGICAL MONITORING ON-SITE, E.C.Hill, D.J.Collins and
G.C.Hill, ECHA Microbiology Ltd
Biological Testing -- ULSD Retail Tank Example
0
2000
4000
6000
8000
10000
12000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Posi ve Culture - pH 4.61 Nega ve Culture - 8.04 RLU
mg/L
anio
n
Acetate
Formate
Lactate
HyLite RLU
Before Biocide After Biocide
Low MW acid species still
present after biocide - pH
4.61 => 8.04
Samples tested for low MW acids also revealed very high sodium levels:
Average of set was 4401 ppm Na (high = 7626 ppm);
Average of much larger data set from across the US was lower at 2492 ppm Na – still considered high…
Highest level observed ~23,138 ppm or roughly 2.3%!
Na levels roughly 20X average Ca levels (next highest cation concentration);
Suggests that some ULSD corrosion problems might be due to salt (in addition to bugs/low MW acid)?
ULSD Corrosion – Water Bottoms Testing
ULSD Corrosion – Water Bottoms Testing
0
5000
10000
15000
20000
25000
CO
9
CT
1
DE
1
FL
2
IA 5
LA
1
MA
1
ME
3
MI 3
MN
2
MO
2
MT
2
NE
1
NJ 1
NY
7
OH
2
OR
18
PA
40
SD
1
TN
1
TX
1
UT
2
VA
3
WA
1
WI 4
WY
3
pp
m
State
Sodium Levels by State in Water Phase
Housekeeping & Potential Fuel Quality Issues
– What’s Not in the Specs
Fuel specs don’t address water/contaminants that can lead to fuel
storage, dispensing, and vehicle engine problems:
No real water spec – BS&W spec (500 ppm) meaningless;
NACE corrosion – typically measured at refinery – tends to
degrade as fuel moves downstream – usually unknown at end
user;
Particulate/sediment – no gravimetric or particle size distribution
requirement (other than BS&W). OEM’s prefer PSD;
Manufacturing/blending contaminants – caustic, sulfates, salts,
surfactants -- usually well controlled but upsets do occur and can
lead to end user problems.
Housekeeping Concerns – Water!
Change from LSD to ULSD altered diesel fuel composition:
Holds half as much water �more tank water bottoms;
Increased environmental concerns/cost-cutting efforts
� harder to dispose of water bottoms;
End result � more water staying in tanks longer
Housekeeping – Changes in ULSD,-- Impact on biological problems
Changes in ULSD Impact on Microbial Growth
↓ Sulfur reduction 500 to <15 ppm ↑Sulfur antagonistic to microbial
growth
↓Aromatic and/or Olefin Content (includes phenolic compounds)
↑Aromatic and Phenolic
compounds are good growth inhibitors
↑ Saturates ↑Saturates preferred food source
compared to aromatics
↑ Water (free, non-dissolved) ↑ Free water availability increases
More Water Means…..
More potential bug problems – need water to grow;
Contaminates collect in water bottoms – salts, soaps, are
usually water soluble -- carried through distribution system;
Increased storage tank corrosion – more water leads to
premature corrosion -- especially if the water is caustic or
salt-laden.
Housekeeping Concerns – What Can Be Done?
Minimize upstream contaminants to fuel distribution system;
Manage water -- drain tank bottoms routinely;
Routine Testing:
Bug testing – prevents biological growth, helps control
downstream problems;
Proper biocide addition kills bugs and prevents corrosive
acids from forming;
Fuel corrosion -- protection diminishes as fuel travels downstream;
Cation testing -- high metals level can lead to problematic fuel.
Role of Fuel Additives
Quality fuel additives essential to good fuel quality:
Stability additives -- prolongs fuel life, limits oxidation and metal reactions;
Corrosion inhibitors -- protects metal in fuel systems;
Conductivity improvers – lessens static electricity, prevents fires/explosions;
Lubricity improvers – provides needed lubrication in diesel injection systems;
Biocides – preventive use minimizes bugs which may lead to corrosion;
Anti-foulant additives – counteracts fuel degradation & contaminant inter-
actions that lead to filter/injector plugging;
Refinery process streams and finished blends should be routinely tested/optimized
with proper additives & treat rates. Most refiners/suppliers already do this.
Summary-Conclusions
Fuel specs may not identify contaminants that can lead to poor fuel quality
and vehicle problems – corrosion just one of these;
Storage tanks susceptible to water build-up and related problems;
Water is fuel’s enemy – carries contaminants, leads to bugs, causes
corrosion;
Routine bug testing essential in preventing problems – fuel-soluble biocide;
Corrosion more problematic w ULSD & biofuels – end use NACE testing?
Quality fuel additives essential to good fuel storage, handling and
performance:
Fuel must be regularly tested -- correct additive type, optimum treat
rate;
Corrosion protection ensured all the way to final customer;
NACE spec within ASTM D975? - CDFA results may dictate this;
Terminal addition of corrosion inhibitor needed?
Good Housekeeping ensures fuel cleanliness - every fuel handler does their
part;
No water – no bug growth, no solvent to carry weak acids, Na
salts/contaminants;
Water/sediments routinely drawn off storage tanks;
Biological and cation monitoring of tank bottoms important – gives early
warning;
Additives important part in controlling bug growth, corrosion, fuel stabilization
ULSD Corrosion – Future Needs?
Contact Information
Rick Chapman
Industry Liaison Manager
Innospec Fuel Specialties
(630) 386-3406