EMULSIFICATION OF HYDROCARBON GAS OILS TO INCREASE
EFFICACY OF WATER BASED HYDROGEN SULFIDE SCAVENGERS
BACKGROUND OF THE INVENTION
Field of the Invention
|000 11This invention relates generally to processing heavy oil, and more
particularly, to methods for removing hydrogen sulfide in heavy oil with an aqueousbased
scavenger/oil emulsion.
Description of Related Art
[0002] Fossil products, and notably heavy oil, often contain significant
quantities of hydrogen sulphide, H S, which is a toxic, highly corrosive, inflammable
and explosive gas. The risk of exposure to hydrogen sulfide from handling heavy oil is a
health and safety concern during storage, transportation (shipping, truck or pipeline)
and processing.
[00031 Hydrogen sulfide scavengers can be used to remove hydrogen sulfide
from heavy oil. It is known to be possible to reduce the hydrogen sulphide content
present in aqueous mediums by using aqueous solutions of aldehydes such as
formaldehyde, glyoxal, and glutaraldehyde (see for example the U.S. Pat. Nos.
4,680,127 and 5,284,635). However, simple addition of water-based hydrogen sulfide
scavengers to heavy oil provides poor results. Additionally, when dispersed in a heavy
oil, water-based scavengers such as glyoxal will eventually settle out of the heavy oil
into an acidic aqueous phase and settle to the bottom of processing equipment. This
aqueous phase may run along the bottom of the processing or refinery equipment as
small tributaries in pipelines or stagnate at the bottom of holding tanks. This acidic
aqueous phase is highly corrosive and can cause troughing in the processing or refinery
equipment.
[0004| What is needed is an improved method for removing hydrogen sulfide
from hydrocarbon media without causing corrosion to processing equipment.
I
SUMMARY OF THE INVENTION
0005 In one aspect, the invention is directed to a method for reducing the
amount of hydrogen sulfide present in heavy oil and reducing the amount of corrosion
in processing equipment contacting the heavy oil. The method includes the steps of
adding an aqueous-based scavenger containing one or more aldehydes to the heavy oil
using a static mixer injection system and creating an aqueous-based scavenger/heavy oil
emulsion using a high shear/high velocity pump. In one embodiment, the method
further includes diverting a portion of the heavy oil into a scavenger addition branch,
adding the aqueous-based scavenger to the portion of the heavy oil and forming the
emulsion in the addition branch, and adding the aqueous-based scavenger/oil emulsion
to the heavy oil in the processing equipment. In one desirable embodiment, the
aqueous-based scavenger is glyoxal. The various embodiments provide an improved
hydrogen sulfide scavenging process for heavy oil that reduces hydrogen sulfide while
minimizing corrosion to processing equipment.
[0006] The present invention and its advantages over the prior art will become
apparent upon reading the following detailed description and the appended claims with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[00071 The above mentioned and other features of this invention will become
more apparent and the invention itself will be better understood by reference to the
following description of embodiments of the invention taken in conjunction with the
accompanying drawings, wherein:
[0008] FIG. 1 is a schematic diagram of an aqueous-based scavenger addition
system for use with hydrocarbon media processing equipment.
DETAILED DESCRIPTION OF THE INVENTION
|0009] The invention will now be described in the following detailed description
with reference to the drawings, wherein preferred embodiments are described in detail
to enable practice of the invention. Although the invention is described with reference
to these specific preferred embodiments, it will be understood that the invention is not
limited to these preferred embodiments. But to the contrary, the invention includes
numerous alternatives, modifications and equivalents as will become apparent from
consideration of the following detailed description.
|00 10 | The singular forms "a," "an" and "the" include plural referents unless
the context clearly dictates otherwise. The endpoints of all ranges reciting the same
characteristic are independently combinable and inclusive of the recited endpoint. All
references are incorporated herein by reference.
|00 11] The modifier "about" used in connection with a quantity is inclusive of
the stated value and has the meaning dictated by the context (e.g., includes the tolerance
ranges associated with measurement of the particular quantity).
[00 12 1 "Optional" or "optionally" means that the subsequently described event
or circumstance may or may not occur, or that the subsequently identified material may
or may not be present, and that the description includes instances where the event or
circumstance occurs or where the material is present, and instances where the event or
circumstance does not occur or the material is not present.
|00 13 ] Turning now to Figure 1, a hydrogen sulfide scavenger addition system
10 is fluidically connected to processing equipment 1 for hydrocarbon media. The
scavenger system 10 reduces the amount of hydrogen sulfide present in the hydrocarbon
media, such as heavy oils, by adding an aqueous-based scavenger in a manner so as to
desirably avoid causing significant corrosion to processing equipment 12. Aqueousbased
scavengers are useful for the elimination of hydrogen sulphide present in various
fluids and notably are particularly effective at eliminating the hydrogen sulphide present
in heavy oils which can exist in the form of water in oil or oil in water emulsions. The
processing equipment 12 in contact with the heavy oil may be any type of equipment
that can be used for processing the hydrocarbon media, such as pipelines and holding
tanks. Processing equipment 1 subject to corrosion is general ly processing equipment
made of carbon steel, but any type of processing equipment may be protected. The
heavy oil may be any type of heavy o il containing hydrogen sulfide. In one
embodiment, the heavy oil includes, but is not limited to, gas oil, naphtha, FCC slurry,
diesel fuel, fuel oil, jet fuel, gasoline, kerosene or vacuum residua. In one embodiment,
the heavy oil may be at an elevated temperature to aid in transport in the processing
equipment 12. For example, the heavy oil may be at a temperature of from about
ambient to about 150 °C. Typically, the temperatures required to move the heavy oil in
the processing equipment 12 is about 80 °C.
|0014| In the illustrated embodiment, a portion of the heavy oil flowing through
the processing equipment 12 is diverted from the processing equipment 12 into the
scavenger addition system 10 via a scavenger addition branch 14. A static mixer 6 is
used to initially mix the scavenger with the portion of heavy oil flowing through the
system 10. In one embodiment, the static mixer 16 comprises an injection quill
dispersion system 18. The scavenger is added to the diverted heavy oil flow in a
continuous manner with the injection quill 18 located generally at the center of the
addition branch 14 in the direction of the heavy oil flow. The injection quill 18
desirably has an open-ended tube (not shown) cut at about a 45° angle with a slot. It
utilizes the turbulence created to achieve distribution of the injected scavenger into the
heavy oil flow in the addition branch 14. The scavenger injection rate is controlled with
an injection pump 20 or shut-off valve 22 in addition line 24. A suitable injection quill
18 is available from Metal Samples Corrosion Monitoring Systems of Munford, AL.
Alternately, the scavenger may be injected into the heavy oil by any conventional in¬
line injection system and may be injected at any point in-line suitable to allow the
scavenger to mix with the heavy oil.
[0015] After addition of the scavenger to the heavy oil, an aqueous-based
scavenger/oil micro-emulsion is formed using a high shear/high velocity mixer or pump
30. In one embodiment, an inline high shear pump 30 such as one available from
Silverson Machines, Inc. of East Longmeadow, MA. The diverted portion of the heavy
oil flow in the scavenger addition system 10, now containing the micro-emulsion, is
then returned to the heavy oil flow in the processing equipment 12. Alternately, the
scavenger may be added to the heavy oil flowing through the processing equipment
without diverting a portion of the flow such that the entire heavy oi flow flows through
the scavenger addition system 10.
|0016| According to the invention, the scavenger is a dispersed aqueous phase
containing about 20 to 70% of one or more aldehydes chosen from the group constituted
by formaldehyde, glyoxal, glutaraldehyde, glycolaldehyde or glyoxylic acid. In one
desirable embodiment, the water-based scavenger added to the heavy oil to reduce the
hydrogen sulfide is Glyoxal. Glyoxal is a water-soluble aldehyde and may include
oligomers of glyoxal. Glyoxal is commercially available as a 40 weight percent
aqueous solution. The scavenger may also contain an enhancing additive to catalyze the
reaction of actives with the hydrogen sulfide. In one embodiment, the enhancing
catalyst is a quaternary ammonium salt. The quaternary ammonium salt desirably is
added in an amount of about 2.5 wt %.
[0017] The glyoxal is added to the heavy oil in an amount sufficient to reduce
the levels of hydrogen sulfide in the heavy oil. In one embodiment, glyoxal may be
added in an amount of from about I ppm to about 2000 ppm, and desirably between
about I ppm and about 500 ppm by volume, based on the velocity of the heavy oil
through the processing equipment and the concentration of hydrogen sulfide. In another
embodiment, glyoxal may be added in an amount of from about 10 ppm to about 200
ppm by volume. Any amount of hydrogen sulfide in the heavy oil may be reduced and
the actual amount of residual hydrogen sulfide will vary depending on the starting
amount. In one embodiment, the hydrogen sulfide levels are reduced to 150 ppm by
volume or less, as measured in the vapor phase, based on the volume of the heavy oil.
In another embodiment, the hydrogen sulfide levels are reduced to 100 ppm by volume
or less, as measured in the vapor phase, based on the volume of the heavy oil. In
another embodiment, the hydrogen sulfide levels are reduced to 50 ppm by volume or
less, as measured in the vapor phase, based on the volume of the heavy oil. In another
embodiment, the hydrogen sulfide levels are reduced to 20 ppm by volume or less, as
measured in the vapor phase, based on the volume of the heavy oil. It is believed that
emulsification of the water-based scavenger in the hydrocarbon media greatly increases
the surface area of the aqueous phase. This increased surface area in combination with
the temperature required to move the hydrocarbon media in the pipeline allows for
efficient transfer of actives into the hydrocarbon phase. This effective application of the
scavenger reduces the amount of chemical that is needed to be added to the hydrocarbon
media. Additionally, aided by turbulent flow in the pipeline, the water-based
scavenger/oil micro-emulsion takes several hours to separate. Typically, this allows
sufficient time for the heavy oil to flow through the processing equipment 12 and into a
suitable storage facility, thus, reducing any corrosion effects on the processing
equipment 12.
[0018] While the disclosure has been illustrated and described in typical
embodiments, it is not intended to be limited to the details shown, since various
modifications and substitutions can be made without departing in any way from the
spirit of the present disclosure. As such, further modifications and equivalents of the
disclosure herein disclosed may occur to persons skilled in the art using no more than
routine experimentation, and all such modifications and equivalents are believed to be
within the scope of the disclosure as defined by the following claims.

What is claimed is:
CLAIMS
1. A method for removal of hydrogen sulphide present in heavy oil in