U.S. patent application number 15/078850 was filed with the patent office on 2016-07-14 for functional fluid and a process for the preparation of the functional fluid.
The applicant listed for this patent is Specialist Process Technologies Limited. Invention is credited to Kevin E. Collier, Theodore E. Dickinson, David John Parkinson.
Application Number | 20160199775 15/078850 |
Document ID | / |
Family ID | 37654515 |
Filed Date | 2016-07-14 |
United States Patent
Application |
20160199775 |
Kind Code |
A1 |
Dickinson; Theodore E. ; et
al. |
July 14, 2016 |
Functional Fluid and a Process for the Preparation of the
Functional Fluid
Abstract
A functional fluid for the removal of contaminates such as but
not limited to, acid causing components in gas, sulfur components
and carbon oxides from fluid streams, and removal and treatment of
NO.sub.X & SO.sub.X from post combustion emissions. Also
described is the manufacturing process to produce the functional
fluid both in a batch atmospheric process system as well as a
closed system capable of operating at above or below atmospheric
conditions.
Inventors: |
Dickinson; Theodore E.;
(Huffman, TX) ; Parkinson; David John; (Clevedon,
GB) ; Collier; Kevin E.; (Kaysville, UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Specialist Process Technologies Limited |
Tortola |
|
VG |
|
|
Family ID: |
37654515 |
Appl. No.: |
15/078850 |
Filed: |
March 23, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14054403 |
Oct 15, 2013 |
|
|
|
15078850 |
|
|
|
|
13309361 |
Dec 1, 2011 |
8591767 |
|
|
14054403 |
|
|
|
|
12092887 |
Oct 10, 2008 |
8080225 |
|
|
PCT/GB2006/004164 |
Nov 7, 2006 |
|
|
|
13309361 |
|
|
|
|
Current U.S.
Class: |
252/192 |
Current CPC
Class: |
C09K 15/02 20130101;
B01D 2252/10 20130101; B01D 2252/103 20130101; Y02C 20/40 20200801;
B01D 53/1493 20130101; Y02C 10/06 20130101 |
International
Class: |
B01D 53/14 20060101
B01D053/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2005 |
GB |
0522694.9 |
Mar 9, 2006 |
EP |
06251247.0 |
Claims
1-58. (canceled)
59. A product, comprising: a functional fluid having a specific
gravity of about 1.25 to 5, and a pH of from about 9 to about 13,
obtained by reacting silicon, alkali metal hydroxide and a solution
comprising water and a chlorine source in a reactor vessel at a
temperature of no greater than about 200.degree. F. (93.degree.
C.), wherein the chlorine source is chlorine gas or liquid
chlorine.
60. The product according to claim 59, wherein the silicon and
alkali metal hydroxide are added to the reaction vessel prior to
the addition of the solution comprising water and chlorine.
61. The product according to claim 59, wherein the chlorine source
is liquid chlorine.
62. The product according to claim 61, wherein the water and liquid
chlorine are in a ratio of from about 10:1 to about 30:1 by
volume.
63. The product according to claim 59, wherein the water and liquid
chlorine are in a ratio of about 20:1 by volume.
64. The product according to claim 59, wherein the amount of
silicon to alkali metal hydroxide is in a ratio of from about 1:5
to about 5:1 by volume.
65. The product according to claim 64, wherein the amount of
silicon to alkali metal hydroxide is about 1:1 by volume.
66. The product according to claim 59, wherein additional solution
comprising water and liquid chlorine is added at a rate sufficient
to maintain the reaction until one or more of the metal silicon or
alkali metal hydroxide is spent.
67. The product according to claim 59, where the reaction
temperature is no greater than about 175.degree. F. (80.degree.
C.).
68. The product according to claim 59, wherein the metal of the
alkali metal hydroxide is lithium, sodium or potassium.
69. The product according to claim 68, wherein the metal is
sodium.
70. The product according to claim 69, wherein the sodium hydroxide
is in solid form.
71. The product according to claim 69, wherein the sodium hydroxide
is in the form of an aqueous solution.
72. The product according to claim 59, wherein the silicon is
silicon metal grade 441.
73. The product according to claim 59, wherein the silicon
comprises particles having a mean particle diameter ranging from
about 1 mm to about 150 mm.
74. The product according to claim 73, wherein the silicon
comprises particles having a mean particle diameter ranging from
about 24 mm to about 150 mm.
75. The product according to claim 59, wherein the water is
distilled water.
76. The product according to claim 59, wherein the reactor vessel
is open to the atmosphere.
77. The product according to claim 59, wherein the reactor vessel
is closed to the atmosphere.
78. The product according to claim 59, wherein the silicon and
sodium hydroxide in solid form are loaded to a height equivalent of
about 30% of the reactor vessel's volume, prior to addition of the
solution comprising water and liquid chlorine.
Description
[0001] The present invention generally relates to a functional
fluid and particularly to a functional fluid for use in, for
example, the treatment and removal of acids, sour components (e.g.
H2S), and CO2, CO, NOX and SOX gases from fluid streams (e.g. a
hydrocarbon based fluid stream) or post combusted fuels or gases.
The invention also relates to a process for the preparation of the
functional fluid.
BACKGROUND OF THE INVENTION
[0002] In the extraction, processing and refining, storage and
combustion of hydrocarbon and carbon based compositions (e.g. crude
oil, synthetic crudes, natural gas, coal and coke) significant
quantities of toxic substances are encountered and/or produced.
These substances include, for example, hydrogen sulfide gas,
mercaptans, SO.sub.X gases (e.g SO.sub.2 and SO.sub.3) and NO.sub.X
gases (e.g NO, NO.sub.2 and N.sub.2O). Hydrogen sulfide and
mercaptans are often extracted with crude oil. Carbon dioxide,
carbon monoxide and SO.sub.X gases can be produced during crude oil
processing and refining. NO.sub.X gases can be produced upon
combustion of hydrocarbon based fuels. Furthermore, post combustion
fumes from coal fired power stations, coking plants and steel
production plants generally contain one or more of these gases.
There is therefore a continuing need for the development of
compositions and processes which permit the removal of these gases
from hydrocarbon based streams, chimneys and exhausts.
[0003] H.sub.2S scavenging compounds typically comprise amine
adducts and the preparatory methods thereof often require the use
of complex reaction protocols and environmentally toxic reaction
materials. For example, GB 2409859 describes an oil-soluble sulfur
scavenger including substantially monomeric aldehyde-amine adducts
from the reaction of at least one sterically hindered primary or
secondary amine and a molar excess of at least one aldehyde, or a
donor thereof.
[0004] US Patent Application No. 2005/0214199 describes a large
surface area manganese oxide compound used for removing pollutants
such as NO.sub.X, SO.sub.X, and CO by adsorption and oxidation. The
manganese oxide is prepared by the reaction of a bivalent manganese
salt with alkali metal permanganate and hydroxide solutions in the
presence of ion-exchanged water under specific reaction conditions.
Removal rates of up to 35% are reported with respect to carbon
monoxide.
[0005] Thus, there is a need for further compositions for use in
the removal of toxic substances. There is also a need for
compositions which can be prepared by way of relatively straight
forward and economical reaction protocols. There is also a need for
the preparation and isolation of compositions which have
multifunctional use in a number of applications, such as those
described above.
SUMMARY OF THE INVENTION
[0006] According to a first aspect of the present invention there
is provided a process for the preparation of a functional fluid
comprising reacting silicon, alkali metal hydroxide and a solution
comprising water and chlorine in a reaction vessel at a temperature
no greater than about 200.degree. F. (93.degree. C.).
[0007] Optional features of the first aspect of the invention are
the subject of the dependent claims.
[0008] Thus, the process provides for the preparation and isolation
of a new functional fluid by way of an economical and relatively
straightforward process. The functional fluid has been found to
have utility in a number of applications as an electron donor,
reducing agent or antioxidant. Advantageously, the process provides
a scavenging functional fluid without the need to include expensive
organic chemicals which can result in the formation of reaction
by-products. Such by-products can be problematic and expensive to
dispose of, due to environmental concerns. A further advantage is
that the functional fluid can be prepared under atmospheric or
pressured conditions.
[0009] According to a second aspect of the invention there is
provided a functional fluid having a specific gravity of about 1.25
to 5, and a pH of from about 9 to about 13, obtainable by the
process of the first aspect of the invention.
[0010] Another advantage of the invention lies in the preparation
and isolation of a functional fluid, which has multifunctional use.
For example, in the oil and gas production industry the functional
fluid can be used as an H.sub.2S scavenger in crude oil pumping
pipes and as a corrosion inhibitor in the pipes. The fluid can
further be used in the treatment of CO.sub.2 and NO.sub.2 which is
produced during refining of the crude oil, and/or upon combustion
of the crude product.
[0011] The functional fluid of the second aspect of the invention
may be used as a CO, CO.sub.2 or H.sub.2S scavenger.
[0012] The functional fluid may be used as a H.sub.2S scavenger in
wet oil and gas production systems.
[0013] The functional fluid may be used in the treatment of
NO.sub.X (e.g. NO and NO.sub.2) and SO.sub.X (e.g. SO.sub.2 and
SO.sub.3) gases.
[0014] The functional fluid may be used in sour gas treatment
systems.
[0015] The functional fluid may be used as a corrosion
inhibitor.
[0016] The functional fluid may be used as a pacifier of carbon
steel in order to reduce corrosion rates associated with acid
gases.
[0017] The functional fluid may be used as an antifoaming
agent.
[0018] The functional fluid may be used in the removal of
contaminants from waste water or boiler feed water.
[0019] The functional fluid may be used as a store for hydrogen
gas.
[0020] In accordance with a third aspect of the invention, there is
provided a process for the desulfurization of a gaseous hydrocarbon
feedstock comprising: [0021] (i) contacting the gaseous hydrocarbon
feedstock with a functional fluid as specified in the first and
second embodiments under conditions suitable to form a
sulfur-enriched functional fluid; and [0022] (ii) recovering a
desulfurized gaseous hydrocarbon feedstock from the sulfur-enriched
functional fluid.
[0023] The process of the third aspect of the invention may
optionally further comprise, the steps of: [0024] (iii) contacting
the sulfur-enriched functional fluid with a flocculating agent
under conditions sufficient to allow precipitation of sulfur from
the sulfur-enriched functional fluid; and [0025] (iv) separating
the precipitated sulfur from the fluid to recover a functional
fluid as specified in the first or second aspect of the
invention.
[0026] In accordance with a fourth aspect of the invention, there
is provided a process for the removal of CO.sub.2 from a gaseous
hydrocarbon feedstock, having a CO.sub.2 component, comprising the
steps of: [0027] (i) contacting the functional fluid and the
gaseous hydrocarbon feedstock under conditions sufficient to
dissolve the CO.sub.2 in the functional fluid; [0028] (ii)
separating the gaseous hydrocarbon feedstock from the functional
fluid; and [0029] (iii) depressurizing the functional fluid to
cause the evolution of CO.sub.2 gas from the functional fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will
now be made, by way of example, to the following drawings, in
which:
[0031] FIG. 1 is a schematic representation of an atmospheric
process for the manufacture of the functional fluid of the
invention;
[0032] FIG. 2 is a schematic representation of an above or below
atmospheric pressure closed system for the manufacture of
functional fluid of the invention;
[0033] FIG. 3 is a schematic representation of a process for the
removal of H.sub.2S from a methane gas feed;
[0034] FIG. 4 is a schematic representation of an example of a
desulfurization process applied to an existing desulfurization
process as a retrofit; and
[0035] FIG. 5 is a schematic representation of a process for the
removal of CO.sub.2 from a methane gas feed.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The functional fluid is formed by the reaction of an alkali
metal or derivative thereof and silicon. The reactants used in the
reaction process will first be described.
Silicon
[0037] Silicon used in the process of the invention can be
elemental silicon, or silicon metal. Silicon metal exists in a
number of purity grades. Examples of silicon metal which can be
used in the process are silicon metal grade 551 (98.5% Si, 0.5% Fe
maximum content, 0.10% Ca maximum content), silicon metal grade 553
(98.5% Si, 0.5% Fe maximum content, 0.30% Ca maximum content),
silicon metal grade 441 (99% Si, 0.5% Fe maximum content, 0.10% Ca
maximum content), silicon metal grade 442 (99% Si, 0.4% Fe maximum
content, 0.20% Ca maximum content), silicon metal grade 4406 (99.3%
Si, 0.4% Fe maximum content, 0.06% Ca maximum content), silicon
metal grade 4403 (98.5% Si, 0.4% Fe maximum content, 0.03% Ca
maximum content), silicon metal grade 331 (99.3% Si, 0.3% Fe
maximum content, 0.10% Ca maximum content), silicon metal grade
3305 (99.4% Si, 0.3% Fe maximum content, 0.05% Ca maximum content),
silicon metal grade 3303 (99.4% Si, 0.3% Fe maximum content, 0.03%
Ca maximum content), silicon metal grade 2204 (99.5% Si, 0.2% Fe
maximum content, 0.04% Ca maximum content), silicon metal grade
2202 (99.5% Si, 0.2% Fe maximum content, 0.02% Ca maximum content)
or silicon metal grade 1501 (99.5% Si, 0.15% Fe maximum content,
0.01% Ca maximum content).
[0038] Silicon metal grade 441 is the preferred grade of silicon
metal used in the process for preparing the functional fluid of the
invention.
[0039] The silicon or silicon metal can comprise a range of
particle sizes. These particles can be in the form of large chunks
or ingots (e.g. having a mean diameter up to about 150 mm), or in
powder form. In one embodiment, the silicon or silicon metal
comprises particles with a mean particle diameter of between about
1 mm and about 150 mm. In another embodiment, the silicon or
silicon metal comprises particles with a mean particle diameter of
between about 24 mm and 150 mm. In a further embodiment, the mean
particle diameter is greater than about 10 .mu.m, such as greater
than 100 .mu.m, for example greater than 500 .mu.m. The mean
particle diameter may also be less than 10 mm, for example less
than 5 mm, such as less than 2 mm or less than 1 mm. Where the
particles are non-spherical, the term "diameter" refers to the
largest dimension of the particle.
[0040] Some individual particles may have a diameter outside the
specified values. However, preferably at least 50%, for example at
least 95%, such as 99% of the particles have a diameter within the
specified values. In an embodiment, substantially all of the
particles have a diameter within the specified range.
Alkali Metal Hydroxide
[0041] The alkali metal hydroxide used in the process can comprise
lithium hydroxide, sodium hydroxide or potassium hydroxide. In one
embodiment sodium hydroxide is used. Combinations of lithium
hydroxide, sodium hydroxide and potassium hydroxide can also be
used in the process.
[0042] The alkali metal hydroxide (e.g. sodium hydroxide) can be
used in solid form or in the form of a prepared aqueous solution of
the alkali metal hydroxide. In solid form the alkali metal
hydroxide can be in the form of flakes, pellets or powder.
[0043] Alternatively, the alkali metal hydroxide can be replaced by
other alkali and alkaline earth metal hydroxide such as rubidium
hydroxide, beryllium hydroxide, magnesium hydroxide, calcium
hydroxide, strontium hydroxide or barium hydroxide.
Water and Chlorine Solution
[0044] The water and chlorine solution used in the process
comprises water, preferably distilled water, and a source of
chlorine. The chlorine source may be chlorine gas which is then
dissolved in water.
[0045] In a preferred embodiment, the chlorine source is liquid
chlorine, also known as sodium hypochlorite (NaOCl).
[0046] The water (preferably distilled) and liquid chlorine are
combined in a ratio of between about 10:1 to about 30:1 by volume
(water:liquid chlorine), for example between about 15:1 and about
25:1. In one embodiment, the ratio of water to chlorine is about
20:1.
[0047] The water and liquid chlorine can be combined prior to
addition to the reaction vessel comprising the silicon and alkali
metal hydroxide, or the water and chlorine can be added separately,
in situ.
The Process and Resultant Functional Fluid
[0048] As discussed below, the duration of the process of the first
aspect of the invention will depend on factors such as reaction
temperature and reactant particle size (due to the effect of
particle size on the surface area considerations). The duration of
the reaction will be shorter when smaller particles are used and
longer when larger particles are used. In most embodiments, the
reaction duration will be longer than about an hour, for example
longer than about 3 hours such as longer than about 6 hours. The
reaction duration may also be less than about 3 days for example
less than about 2 days such as less than about 1 day or less than
about 12 hours. Since the reaction is exothermic, control of the
reactant particle size provides a means of controlling to some
extent the rate of reaction and hence the degree to which the
reaction vessel requires cooling during the process of the first
aspect.
[0049] The reaction vessel is maintained at a temperature below
about 93.degree. C. Subject to this constraint, in some
embodiments, the reaction temperature may be maintained at a
temperature of greater than about 60.degree. C., for example
greater than about 70.degree. C. In an embodiment, the reaction
temperature is maintained at a value of about 80.degree. C.
[0050] The following discussion is limited to a process comprising
silicon metal grade 441 and sodium hydroxide, by way of example.
References to FIGS. 1 and 2 of the drawings are also included to
assist in the understanding of the process of the invention.
However, these are non-limiting, and the skilled person will be
aware that the following discussion will be typical for a number of
alternative systems as described above.
[0051] Typically, silicon metal grade 441 and alkali metal
hydroxide are combined in a reactor vessel. FIG. 1 shows an
atmospheric batch process for the manufacture of the functional
fluid of the invention. An open reactor 1, preferably manufactured
from stainless steel, is loaded with silicon (silicon metal grade
441) 2 of a size distribution in the range of 24 mm to 150 mm mean
diameter. The silicon 2 is loaded to a height equivalent to 30% of
the reactor's volume including the voidage of the silicon particles
2. Sodium hydroxide 3 (in flake form) is added to the silicon 2 in
reactor 1, to a level approximately equivalent to the voidage
available in the silicon 2, such that the level of solids in the
reactor is substantially unchanged. This is achieved by thoroughly
mixing the silicon 2 and the sodium hydroxide 3. The amount of
silicon to sodium hydroxide is typically about 1:1 by volume. It
will be clear to the skilled person that the size of the silicon
particles used will affect the rate of reaction (i.e. upon addition
of the water-chlorine solution) depending on the surface area of
the silicon particles.
[0052] Distilled water 4 is dosed with liquid chlorine 5, for
example in a ratio of water to liquid chlorine of about 20:1 by
volume, prior to introducing the same into reactor 1, and the
reaction between the components begins. The water-chlorine solution
is added to a level (level 6 in FIG. 1) at least equal to or
greater than the level of the silicon/sodium hydroxide mix, such
that the silicon/sodium hydroxide is completely immersed in
water-chlorine solution.
[0053] Typically, there will be a time lag before any noticeable
reaction occurs. This time lag will depend on the amount of
reactants used (i.e. the volume ratio of the silicon to sodium
hydroxide), and the particle size of the silicon 2 and sodium
hydroxide 3. The resulting exothermic reaction begins to effervesce
with the release of hydrogen gas 7 and steam 8. Therefore, suitable
safety measures are to be employed. The reaction temperature is
maintained such that it does not exceed about 200.degree. F.
(93.degree. C.), and is preferably maintained below about
175.degree. F. (80.degree. C.). The temperature of the reaction is
maintained using an external heating/cooling means 10, for example,
by the use of a heating/cooling jacket. Additional water and/or
water-chlorine solution is added as the reaction proceeds to
maintain the level of the solution above the silicon/sodium
hydroxide (i.e. to match the losses attributable to the hydrogen
gas and steam losses).
[0054] Under the conditions described above, the reaction typically
takes up to six hours, after which the degree of effervescence
starts to diminish, and the resultant functional fluid is ready for
decanting through outlet 9 by way of a suitable filtration medium
to remove any unwanted particulate, which may continue to react.
The finished chemical is then stored in sealed drums ready for
utilization.
[0055] FIG. 2 shows an example of a closed or pressurized system
apparatus, which can be operated at above or below atmospheric
pressure. A hopper 33 is loaded with the same quantities and
qualities as described for FIG. 1, of silicon 21 and sodium
hydroxide 20, for a given batch size. However it has been found in
practice that in a closed system, such as that shown in FIG. 2,
silicon of a considerably smaller particle size distribution as low
as 1 mm can be used, thus enabling the surface area of silicon
available for contact to be increased substantially. This, together
with the ability to control the pressure within the vessel by a
pressure control means 29 allows the reaction to be more
controlled, and hence reduces the time required for reaction of the
silicon to produce the required chemical. The silicon 21 and the
sodium hydroxide 20, are fed from the hopper 33, controlled by a
valve means 28, into the reaction pressure vessel 27. The valve
means 28 then closes, and a pump 24 starts, which is fed by a water
23 and chlorine 22 mixture. This mixture reports by way of valve
means 25 to a vortex generator 31, situated within the pressure
vessel 27. The reaction then begins and is further accelerated by
the constant inter-mixing of the particles 20 and 21 and liquid 22
and 23, by the centrifugal forces within the vortex.
[0056] The hydrogen gas and steam generated by this reaction are
collected in the upper portion of pressure vessel 27, and the
pressure inside the pressure vessel 27, is controlled to the
required set point by a pressure sensor, controller and a pressure
control valve 29. The gases removed from the pressure vessel 27 can
be routed to a flame arrestor 30, and or a scrubber/condenser 37,
which in turn, if required, can re-route the hydrogen back into the
pressure reactor 27 without the associated water vapor caused by
the reaction. Thus the hydrogen can be reabsorbed to further enrich
the chemical, or if not required can be stored or led to a disposal
flare. It is a further requirement of the process, that the liquid
level in the pressure reactor 27 stays within required level
limits. Therefore the level indicator 26 has the ability to run the
pump 24 and to actuate valve means 25 to add makeup water as
required. When pump 24 is not in operation and it is required to
maintain the vortex within pressure reactor 27, then a pump 40
starts and re-circulates the chemical product through the vortex
generator 31 as required to keep the solids 20 and 21 in
suspension.
[0057] A cooling jacket 41 can be fed with a cooling medium in
order to regulate the process temperature to within the required
limits by interaction with the temperature controller 32. If
required, a vacuum may be employed on the vapor outlet 29, which in
some conditions will enhance the production of chemical. When the
chemical reaction is complete, the pump 40 stops and valve means 39
closes. The valve means 34 opens and the product chemical reports
to the filter 35, and on to storage vessel 36.
[0058] The role of the liquid chlorine in the reaction is not fully
understood, but without wishing to be bound by theory it is
believed that the chlorine acts as an electron sink to the
reaction. If liquid chlorine is not used, then sodium silicate
salts will form instead of the functional fluid. If an aqueous
sodium hydroxide solution is used, then the time lag will be much
shorter due to the presence of liquid water prior to the addition
of the water-chlorine solution. In these circumstances, the liquid
chlorine should be added prior to effervescence to minimize
silicate formation.
[0059] The functional fluid prepared by the reaction described
above is a typically clear and transparent, viscous liquid having a
specific gravity of about 1.25 to 5, for example about 5, and a pH
in the range of from about 9 to about 13, for example from about 9
to about 12. The functional fluid, however, can sometimes appear
translucent. The functional fluid may be used as prepared, or can
be used in a diluted form; for example, the functional fluid may be
diluted to a specific gravity of about 1.25 prior to use.
Characterization of Functional Fluid of the Invention
[0060] The precise composition and form of the functional fluid is
not fully understood, but it is believed that silicon and alkali
metal ions form a water soluble monomeric inorganic complex upon
reaction with the water chloride solution. It is not clear if the
chlorine, probably present as chloride ions, forms part of the
inorganic complex. The resulting functional fluid comprising the
silicon-alkali metal complex is found to be electron rich (possibly
comprising free electrons), and readily acts as a reducing agent in
the presence of other chemicals with the conversion of these
chemicals to water soluble salts, or even elemental compounds. For
example, upon reaction between the functional fluid and H.sub.2S,
elemental sulfur can be formed.
[0061] Thus, the functional fluid of the present invention has the
ability to selectively remove targeted contaminates from any carbon
based fluid stream.
Utility of the Functional Fluids of the Present Invention
[0062] The functional fluid of the invention has utility in a
number of applications, for example: [0063] as a CO.sub.2 Scavenger
[0064] as a H.sub.2S Scavenger [0065] in the treatment of NO.sub.X
(e.g. NO and NO.sub.2) & SO.sub.X (e.g. SO.sub.2 and SO.sub.3)
gases [0066] as a Corrosion inhibitor [0067] in the enhancement of
existing sour gas treatment systems such as Amine plants [0068] in
the removal of contaminates from water e.g. pre-treatment of boiler
feed water and waste water treatment for Volatile Organic Compounds
(VOC) and Methyl Tertiary Butyl Ether (MTBE) and destruction of
many forms of bacteria such as feta coli forms, cryptosporidium and
legionnaires [0069] rejection of Hydrocarbons from oil wetted
solids, for example, in tight rock formations through which oil is
flowing, the functional fluid wets the production zone and is
attracted to the rock formation, thus forcing the oil off the rock,
reducing drag and improving oil flow [0070] in the removal of all
types of sulfur containing substances, in particular carbonyl
sulfide (COS) which is know to hydrolyze with water to form
H.sub.2S, S, and CO.sub.2 [0071] as an anti foaming agent [0072] as
a flame retardant [0073] as an anti-oxidant corrosion inhibitor,
for example, when the chemical is injected into a pipeline or
vessel made from carbon steel, it has the ability to protect the
pipeline or vessel from corrosion [0074] as a medicament or in the
manufacture of a medicament, for example, for the treatment of an
insect bite, a virus and/or blood condition.
Process for Desulfurization of Gaseous Hydrocarbon Feedstocks
[0075] In the third aspect of the invention, the gaseous
hydrocarbon feedstock (which may be, for example, natural methane
gas) may be contacted with the functional fluid of the invention
using any suitable apparatus known in the art for that purpose. For
example, an inline mixer/contactor or a counter current flow
stripping tower may be used.
[0076] By contrast with prior art desulfurization units such as
amine systems, the process of the third aspect does not require
boilers, heaters, acid stripping or re-injection process units. The
process of the third aspect may therefore be carried out at ambient
temperature, for example greater than about 5.degree. C., such as
greater than 10.degree. C. or greater than about 15.degree. C. The
process temperature may be less than about 60.degree. C., for
example less than about 40.degree. C., such as less than 30.degree.
C. This process is therefore particularly useful in e.g.
pretreating natural methane gas prior to processing in Liquified
Natural Gas (LNG) plants offshore, where close proximity of heat
sources to the cryogenic units and cool boxes would present a
hazardous operation.
[0077] The process of the third aspect of the invention may
optionally further comprise, the steps of: [0078] (iii) contacting
the sulfur-enriched functional fluid with a flocculating agent
under conditions sufficient to allow precipitation of sulfur from
the sulfur-enriched functional fluid; and [0079] (iv) separating
the precipitated sulfur from the fluid to recover the functional
fluid of the first or second aspect of the invention.
[0080] The flocculating agent may be any known flocculating agent
capable of inducing sulfur precipitation in the alkaline
environment of the functional fluid. For example, the flocculating
agent may be an alkali metal halide, preferable sodium
chloride.
[0081] The precipitated sulfur may be separated by any suitable
separation process. For example a plate filter press may be used.
Use of a plate filter press has been found to give a reasonably dry
solid suitable for skip disposal from site. Tests to date have
shown that the solids generated by this process are suitable for
land farming and result in minimal environmental impact.
[0082] The process in accordance with the third aspect of the
invention has been found to be capable of reducing the level of
hydrogen sulfide in natural methane gas from a level in the region
of 10,000 ppm to a level of less than 1 ppm.
[0083] The process may further comprise the step of recycling the
recovered functional fluid for use in step (i) of the third aspect
of the invention.
[0084] Prior to recycling, the pH of the recovered functional fluid
may be modified to be greater than about 12, for example to a pH of
about 13. This may be achieved by adding an alkali metal hydroxide,
for example sodium hydroxide.
[0085] The gaseous hydrocarbon feedstock may be any gaseous
hydrocarbon feedstock but would most typically be a feedstock
comprising predominantly methane such as natural gas.
[0086] The third aspect of the invention will now be illustrated by
reference to a process for the removal of H.sub.2S from a methane
feedstock. References to FIGS. 3 and 4 of the drawings are also
included to assist in the understanding of the process of the
invention. However, these are non-limiting, and the skilled person
will be aware that the following discussion will be typical for a
number of alternative systems as described above.
[0087] FIG. 3 shows a three stage process exemplifying the third
aspect of the invention.
[0088] The gas to be treated is fed to the stage one contactor in
which the functional fluid (designated MonoChem) and the sour gas
are caused to contact each other. The functional fluid strips out
the H.sub.2S and rejects the methane gas. The on spec sweetened gas
then exits the stage one contactor and is directed towards either a
tertiary polishing system or, if the gas condition is acceptable,
to an export gas pipeline for use.
[0089] The functional fluid enriched with H.sub.2S from the stage
one contactor is then directed, under level control in the case of
a contacting tower, to stage two, to a secondary smaller
mixer/contactor, with enough residence time to act as a development
tank. Flocculent is added to the MonoChem stream on the inlet to
this tank to allow the sulfur to flocculate and develop as a
solid.
[0090] The liquid and solids mixture from stage two, is then
directed towards stage three, which can be any form of
liquids/solids filtration or clarification. In practice, a plate
filter press has proven to be adequate for this purpose, giving a
reasonably dry solid suitable for skip disposal from site. Tests to
date have shown that the solids generated by this process are
suitable for land farming with minimal environmental concerns.
[0091] The liquid filtrate from stage three is recycled to stage
one, for reuse in the process. Depending on the pH of the recycled
functional fluid and its specific gravity, a pH correction chemical
may be added to maintain the pH of the functional fluid at about
13.
[0092] In FIG. 3 the functional fluid of the invention is
re-circulated in the system at a flowrate determined by the amount
of H.sub.2S to be removed from the gas stream. In one example 10 US
gallons per minute (37.85 liters per minute) (was sufficient to
remove up to 10,000 ppm of H.sub.2S from 700,000 standard cubic
feet per day (SCFD) (19,822 cubic meters per day) of natural
gas.
[0093] The above mentioned process has also proved to be of use in
removing CO.sub.2. The CO.sub.2 can be witnessed flashing off to a
gas phase again once the MonoChem pressure is dropped. To date,
CO.sub.2 levels of up to 10,000 ppm together with 10,000 ppm of
H.sub.2S in a methane gas stream have been removed
simultaneously.
The Retrofit Application of the Process of the Third Aspect
[0094] In practice, existing gas treatment process plants, such as
Amine and Claus units can be a bottleneck in systems where the
inlet conditions have changed for whatever reason, for example:
[0095] Volume of gas increases [0096] Pressure drops [0097] Volume
of H.sub.2S increases [0098] Variations in Inlet Temperature
[0099] Changes of this type, to the inlet of Amine systems can
upset the operation and require system changes, which in most cases
set up and cause chain reactions in plant operation leading to
major upsets.
[0100] Due to the simplicity of the MonoChem functional fluid
system it is now possible to offer a process stage to be applied
upstream of existing gas sweetening plants to effectively
debottleneck the process, or to substantially reduce maintenance
cost where the existing system is of the absorption type, which
requires spent material to be removed and replaced.
[0101] FIG. 4 shows such a system.
[0102] In FIG. 4, a functional fluid compact contactor system is
positioned in front of an existing gas treatment plant. The
functional fluid compact contactor can optionally be bypassed or
can be used to treat a proportion of the total flow of gas to be
treated. The proportion of gas treated can be sufficiently large
such that when re-combined with the untreated gas, the resultant
ppm of H.sub.2S left in the system is manageable by the existing
gas treatment plant.
[0103] In FIG. 4, several inline mixer/contactors are used in
series with each unit having MonoChem injected into it. Each unit
is capable of removing up to 50% of the bulk H.sub.2S in the gas
inlet as described in Table 1 below. This is an example
illustrating the process. The removal efficiency of each stage is
dependant on factors such as the condition of the functional fluid
at each stage and the levels of contaminate present in the feed at
that stage:
TABLE-US-00001 TABLE 1 H.sub.2S in ppm H.sub.2S out ppm Contactor
Mixer 1 6000 3000 Contactor Mixer 2 3000 1500 Contactor Mixer 3 750
375 Contactor Mixer 4 375 188 Contactor Mixer 5 188 94
[0104] Generally, it can be said that the more units that are
employed, then the better the H.sub.2S removal will be, although
there will be a point at which the benefit gained from extra units
is minimal.
[0105] The retrofit system is normally designed to achieve an
overall removal level of up to 95% leaving the final H.sub.2S to be
removed in the existing equipment. Such a retrofit system offers
several advantages to the process plant operators, such as: [0106]
By use of hot tapping into the existing plants inlet piping, the
modifications need not necessarily cause a plant shut down. [0107]
If required the existing Amine tower can be converted quickly to a
system using MonoChem with the MonoChem reporting to the
development tank and filter units used to recover the MonoChem from
the pipeline contactors. In this way, the Amine plants downstream
units are rendered redundant, thus substantially reducing emissions
from the site. [0108] No liquid acid is formed thus there is no
need to remove a liquid acid from site. [0109] The possibility of
conversion of sulfur solids into fertilizer, for commercial use.
Selective Removal of CO.sub.2 from a Gaseous Hydrocarbon Feedstock
Comprising CO.sub.2 and Sulfur Components
[0110] In accordance with a fourth aspect of the invention, there
is provided a process for the removal of CO.sub.2 from a gaseous
hydrocarbon feedstock, having a CO.sub.2 component, comprising the
steps of: [0111] (i) contacting the functional fluid and the
gaseous hydrocarbon feedstock under conditions sufficient to
dissolve the CO.sub.2 in the functional fluid; [0112] (ii)
separating the gaseous hydrocarbon feedstock from the functional
fluid; and [0113] (iii) depressurizing the functional fluid to
cause the evolution of CO.sub.2 gas from the functional fluid.
[0114] In this aspect of the invention, the gaseous hydrocarbon
feedstock (which may be, for example, natural methane gas) may be
contacted with the functional fluid of the invention using any
suitable apparatus known in the art for that purpose. For example,
an inline mixer/contactor or a counter current flow stripping tower
may be used.
[0115] The pressure at which the functional fluid and gaseous
hydrocarbon feedstock are contacted will depend on the degree of
CO.sub.2 removal from the feedstock required. Under conditions of
higher pressure, more CO.sub.2 will dissolve in the functional
fluid. Typically, the pressure of the system will be greater than 1
atm, for example greater than 5 atm such as greater than 10 atm.
The pressure may also typically be less than 30 atm, for example
less than 20 atm.
[0116] In an alternative embodiment, the functional fluid and
gaseous hydrocarbon feedstock may be contacted under conditions of
ambient or even below ambient pressure, provided that, following
step (ii) above (the separation of the gaseous hydrocarbon
feedstock from the functional fluid), the pressure is further
lowered to cause evolution of CO.sub.2 from the functional
fluid.
[0117] The solubility of CO.sub.2 in the functional fluid is
believed to be inversely proportional to the fluid temperature.
Therefore, in order to increase the solubility of CO.sub.2 in the
functional fluid, the functional fluid may be provided at a reduced
temperature. The fluid may in principle be provided at any
temperature above its freezing point, with the highest CO.sub.2
solubility being exhibited at the lowest temperatures. However,
there is an economic consideration associated with cooling the
functional fluid and so in some embodiments, the fluid will be
provided at higher temperatures. In some embodiments, the fluid is
provided at a temperature of below about 50.degree. C., for example
below about 40.degree. C. or below about 30.degree. C. The fluid
may also be provided at a temperature below about 20.degree. C. for
example below about 10.degree. C. In a preferred embodiment, the
fluid is provided at a temperature below about 5.degree. C., such
as in the range from about 1-3.degree. C., for example about
2.degree. C.
[0118] The process may further comprise the step of liquefying the
separated CO.sub.2 gas obtained in step (iii) of the process. This
process is therefore advantageous in that it allows the collection
of CO.sub.2 for commercial applications, not least to prevent it
escaping to the environment. Liquidized CO.sub.2 has a well
advanced market in the following areas: [0119] (a) Downhole
fractionation (CO.sub.2 fracs). [0120] (b) Secondary or Enhanced
Oil Recovery (EOR) formation flooding. [0121] (c) PLM and NGL
treatment for stranded gas. [0122] (d) Many other Commercial and
Industrial uses of CO.sub.2.
[0123] In an alternative embodiment, which is presently less
preferred, following dissolution of the CO.sub.2 in the functional
fluid it is possible to break the bond between the CO.sub.2 and the
functional fluid and filter out the carbon content as a solid,
typically bicarbonate of soda, with O.sub.2 being released into the
system. In this embodiment, the functional fluid is sacrificed as a
scavenger and so results in depletion of the functional fluid.
[0124] In an embodiment of the fourth aspect of the invention, the
hydrocarbon feed comprises sulfur-containing compounds (such as
H.sub.2S) in addition to the CO.sub.2 component specified. It has
surprisingly been found that by providing the functional fluid at a
reduced temperature, it is possible to selectively separate
CO.sub.2 from the hydrocarbon feedstock, without removal of the
H.sub.2S component. In this embodiment of the invention, the
functional fluid may be provided at a temperature below about
5.degree. C., preferably in the range from about 1-3.degree. C.,
for example at a temperature of about 2.degree. C.
[0125] The process may also further comprise the removal of the
sulfur compounds of the separated gaseous feedstock using the
process of the third aspect of the invention.
[0126] The fourth aspect of the invention will now be illustrated
by reference to a process for the removal of CO.sub.2 from a
methane feedstock containing CO.sub.2 and H.sub.2S. Reference to
FIG. 5 of the drawings is included to assist in the understanding
of the process of the invention. However, reference to this figure
is non-limiting, and the skilled person will be aware that the
following discussion will be typical for a number of alternative
systems as described above.
[0127] FIG. 5 below shows a typical system for use when CO.sub.2
and H.sub.2S coexist in a methane gas stream and it is required
that CO.sub.2 be selectively removed for the gas stream.
[0128] For the removal of CO.sub.2 from a natural methane gas
stream, pressurized methane gas and associated CO.sub.2 is directed
into contactor T101 where a stream of the functional fluid of the
invention (M), at a temperature around 1 to 2.degree. C., is
distributed above typically a random packing inside a
counter-current stripping tower. The gas contacts the functional
fluid, where the CO.sub.2 associated with the gas preferentially
dissolves in the functional fluid. The functional fluid rejects the
methane gas which then exits the contactor. A level control valve
(L) allows the functional fluid with the CO.sub.2 in solution to
exit the contactor where it is directed to the CO.sub.2 extraction
vessel T102, by way of an array of spray nozzles. A drop in
pressure in vessel T102 together with the agitation caused by the
spray nozzles drives the CO.sub.2 out of the solution. The CO.sub.2
exits the top of T102 by way of a mist eliminator. Depending on the
process and local environmental regulations, the CO.sub.2 can then
be flared or liquidized for use in flooding or used in other
applications.
[0129] The functional fluid free of CO.sub.2 exits the bottom of
T102 and is pumped through a refrigerated heat exchanger to cool it
back to the required 1 to 2.degree. C. The functional fluid leaves
the heat exchanger and is directed to contactor T101 through the
spray nozzle which soaks the contactor packing and the process is
repeated. Little or no MonoChem is consumed in the process; any
losses are replenished by a MonoChem make up system.
EXAMPLES OF USE
[0130] A functional fluid was prepared and tested as follows:
[0131] The functional fluid was tested on exhaust gases from a gas
turbine fueled with natural gas, running at about 720 rpm.
NO.sub.R, CO, O.sub.2 and CO.sub.2 levels were monitored over a
period of 1 hour. The results are shown in Table 1A and 1B. In
experiments C-1A, C-2A and C-3A, the levels of gases in the exhaust
were measured over 1 hour. In experiments C-1B, C-2B and C-3B the
exhaust gases were passed through the functional fluid in a
contacting vessel, and the levels of gases in the exhaust after
passing through the functional fluid were measured for 1 hour.
TABLE-US-00002 TABLE 1A Destruction Destruction Test run C-1A C-1B
(%) C-2A C-2B (%) Ambient conditions (inches of Hg) 29.86 29.86
29.79 29.79 Temp (.degree. F. dry) 51 52 52 52 Temp (.degree. F.
wet) 46 48 48 48 Humidity (lb x/lb air 0.0054 0.0061 0.0061 0.0061
Engine speed 720 722 721 722 (rpm) Emissions NO.sub.X (ppmvd) 2217
130 94.1 2224 134 94.0 CO (ppmvd) 6025 446 92.6 5736 528 90.8
O.sub.2 (%) 0.2 19.4 0.14 19.2 CO.sub.2 (%) 11.9 0.42 11.9 0.5
TABLE-US-00003 TABLE 1B Test run C-3A C-3B Destruction (%) Ambient
conditions (inches of Hg) 29.82 29.82 Temp (.degree. F. dry) 51 51
Temp (.degree. F. wet) 47 47 Humidity (lb .times. /lb air 0.0059
0.0059 Engine speed (rpm) 721 720 Emissions NOx (ppmvd) 2101 91
95.7 CO (ppmvd) 6316 548 91.3 O.sub.2 (%) 0.14 19.1 CO.sub.2 (%)
11.7 0.57
* * * * *