Mercaptan oxidation in aqueous waste
Fig. 1. Mercaptan
Tert butyl mercaptan (TBM) and dimethyl sulfide (DMS) are
oxidized to destruction in an aqueous-waste solution containing
methanol (MeOH), monoethylene glycol
(MEG), ammonia and hydrocarbon sources using advanced
oxidation process (ozone, hydrogen peroxide and uV). The
aqueous solution in the trial mimics the expected waste stream
from a gas-transport pipeline.
Background to the problem.
PSE Kinsale Energy required a process to dispose of an
aqueous waste stream in a gas-storage project. Injection gas constitutes
odorized natural gas containing 4.7 ppmv and 1.3 ppmv of TBM
and DMS respectively. This is injected into an offshore
reservoir during summer for winter withdrawal. Withdrawn gas is
expected to be water saturated, and hydrate inhibitors, MEG and
MeOH, are injected. The aqueous waste generated from the
onshore separator contains MEG/MeOH, TBM/DMS and trace amounts
of native petroleum species (alkanes, cyclics, phenol,
Initial treatment options.
Due to the uncertainty of produced water flowrates (from 10
m3/d to 100 m3/d) and the relatively low
absolute value of flows, disposal is best achieved by
third-party offsite disposal. Third-party water-treatment
plants cannot accept a waste with mercaptan (thiol).
Pilot-trial results. Phase 1 of trials by PSE Kinsale Energy
was to establish background rates of MEG/MeOH destruction. If
the process achieved significant MEG/MeOH destruction, disposal
could be implemented within the site and transport
infrastructure could be avoided. Batches ran up to two hours.
Achieved destruction for samples of different chemical oxygen
demand (COD) concentrations, respectively 98 mg/l and 35 mg/l,
were 45% and 12%. This did not yield a viable disposal process
and was unexpected.
Phase 2 dosed mercaptan and petroleum species into MEG/MeOH
solutions. The trials were located in a remote area due to odor
potency. Vials were opened under a liquid surface to prevent
gas escape, and equipment was rinsed with hypochlorite to
destroy mercaptan odor. The trial equipment was placed under a
fume-hood with an extract fan fitted with a KOH/KI-impregnated
In tests, mercaptan odor was not evident after 30 minutes.
Subsequent trials with varying solution strengths confirmed
this. Increasing the background COD from 700 mg/l to 2,400 mg/l
equivalent did not significantly affect the mercaptan
destruction rate as detected by the trial operators, as shown
in Fig 1.
Attempts to identify a rate of reaction were not possible;
the reaction was quicker than one simple residence time (50
liters circulated at 1m3/h).
In Phase 3, two batches of a fully simulated waste with
petroleum species were processed for 120 minutes. The analysis
to confirm odor destruction was three-fold:
Liquid samples were taken at time intervals and
analyzed for mercaptan.
After 120 minutes, the batch was transferred to a
barrel for headspace analysis using graphite adsorption
Liquid samples were taken at time intervals and
subsequently sampled by an odor panel. Mercaptan destruction
was confirmed within 60 minutes.
The advanced oxidation process using ozone/uV rapidly and
selectively destroyed mercaptan in an aqueous waste containing
MeOH, MEG and petroleum species. Competitive behavior was
negligible despite the higher concentrations of the potentially
competing species. Despite the inference in published research,
the oxidation process was not capable of destroying MeOH or MEG
in a time suitable for process implementation.
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Wastewater treatment exceeds standards
The result of a four-year development effort, GEs
next-generation membrane bioreactor (MBR) wastewater-treatment
technology, LEAPmbr, is claimed to
offer the lowest life-cycle costs available from any MBR
technology, while also being cost-competitive with conventional
treatment. These cost savings, along with operational
simplicity and a compact footprint, derive from innovations to
the popular GE ZeeWeed 500 MBR product line. Cost and
efficiency savings include:
A minimum 30% reduction in energy costs
A 15% improvement in productivity (greater
A 50% reduction in membrane aeration equipment and
controls, leading to a simpler design with lower construction, installation and maintenance costs
A 20% reduction in physical footprint, leading to
further reduced construction and installation costs,
as well as lower ongoing consumption of cleaning chemicals.
MBR technology consists of a
suspended-growth biological reactor integrated with GEs
high-performance, rugged ZeeWeed hollow-fiber ultra-filtration
membranes. ZeeWeed membranes are immersed in a membrane tank,
in direct contact with the water to be treated, which is known
as mixed liquor. Through a permeate pump, a vacuum is applied
to a header connected to the membranes. The vacuum draws the
water through the ZeeWeed membranes, filtering out solids,
along with bacteria and viruses. The filtered water, or
permeate, can then be further treated, reused or discharged as
Select 2 at www.HydrocarbonProcessing.com/RS
Alliance brings together production technology
UOP LLC, a Honeywell company, has formed a licensing
alliance with ExxonMobil Research & Engineering Co. (EMRE)
to offer integrated solutions for producing lubricant oils and
high-quality fuels. The agreement between Honeywell UOP and
EMRE will reportedly provide a one-stop solution for refiners
to maximize lubricant oil and diesel fuel production levels.
The alliance harmonizes EMRE technology, used to produce lube
base oils for use in motor oil, with UOP hydroprocessing
solutions that produce the high-quality feedstocks needed for lubricant
Users will also have access to integrated process design
solutions for EMRE fuel-dewaxing technologies and UOP
hydroprocessing solutions to produce high-cetane, ultra-clean
diesel for cold climates in a single engineering package.
By bringing together these two well-established
portfolios, we are maximizing solutions for our customers to
produce more and better products from each barrel of
crude, said Pete Piotrowski, vice president and general
manager of Process Technology and Equipment for
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Redesigned analyzer for H2S in crude oil
Fig. 2. Applied
Analytics headspace system.
The OMA-300 hydrogen sulfide (H2S) analyzer
crude oil edition from Applied Analytics, Inc. (AAI) is a
specialized configuration of the OMA-300 H2S system.
Equipped with a headspace sample-conditioning system, it
monitors an opaque liquid process. When a sample is too dark or
dirty to transmit a light signal, the headspace system is said
to produce a representative vapor-phase sample that can be
easily monitored via ultraviolet-visible absorbance
spectroscopy and correlated to the chemical composition of the
AAI has always offered a highly effective solution for
measuring H2S in opaque liquids, but the current
demand for crude analysis has given us cause to rethink our
offering, said Dan Murphy, senior mechanical engineer.
The process resulted in modifications to the crude oil
edition of the OMA-300 H2S. The refined design puts
everything in one enclosure and adds the capability to monitor
multiple crude streams at once using multiple headspace columns
running in parallel.
Select 4 at www.HydrocarbonProcessing.com/RS
Renewable fuel options for condensing hydronic boiler
Fig. 3. Fultons
Fultons Vantage boiler, which has been available since
2003 as an ultra-high-efficiency condensing hydronic boiler, is
said to be drawing attention for its ability to use B100
biodiesel and ultra-low-sulfur (under 15 ppm) heating oils for
full condensing operation. As a result of comprehensive
testing at the independent Brookhaven National Laboratory, it
has been proven that the Vantage can meet or exceed the thermal
efficiencies attainable with natural gas, said Erin
Sperry, Fultons commercial heating product manager.
The biodiesels used in the Brookhaven testing facility
included biodiesels produced from both soybeans and recycled
tallow. According to findings, ignition on B100 biodiesel, even
from a cold start, was identical to traditional No. 2 heating
oil. Testing also discovered that carbon-monoxide emissions and smoke-number readings
were essentially maintained at zero during steady-state
operation and at a normal excess-air level of 25%. Following
test runs, burner head inspections found no significant coke
deposits and measurable reductions for NOx,
SO2 and soot were observed. Predicted corrosion
rates were in the acceptable range for the application.
Boiler-jacket lossmonitored using the standards of the
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE) Standard 103was found to be 0.2% of
steady-state input, a very low value.
At Brookhaven, boiler efficiency was measured using both an
indirect flue-loss method and a direct input/output method. As
typically observed with hydronic boilers, efficiency and
condensate collection rate are impacted by the return-water
temperature. At high fire with a return-water temperature of
122°F, efficiency was found to be 88%. At low fire with a
return-water temperature of 90°F, efficiency was 93%. Under
BTS-2000 test conditions of 80°F, return-water temperature
and 180°F supply-water temperature, the rated efficiency
was 98% at high fire.
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