Title: APPARATUS AND METHOD FOR REMOVAL OF SULFURCONTAINING
IMPURITIES
FIELD OF INVENTION
The present invention relates to an apparatus for removal 5 of sulfur-containing
impurities. The invention employs trough distributor and fiber bundle arrangement
for an efficient and economical mass transfer.
BACKGROUND
10 Impurities in the crude oil are a perennial problem in petroleum industry since the
very beginning of crude oil extraction. The type and amount of the impurities keep
on changing as various types of crude oil are processed to obtain various petroleum
products. The impurities include various sulfur compounds, nitrogen compounds,
organometallic compounds, inorganic salts, etc.
15
Of the above mentioned, impurities like naphthenic acid in diesel, hydrogen
sulphide, mercaptans and COS in gasoline, LPG, naphtha and kerosene are
presumed to be the most detrimental. These impurities, if not removed from the
product, may cause unsuccessful working of any subsequent unit operation and may
20 lead to degradation of storage tanks, thereby causing substantial monetary loss.
Moreover, if these impurities, especially sulfur compounds, remain in the final
product (such as gasoline, diesel, kerosene, etc.) even at low concentrations, it can
deteriorate the environment. Consequently, due to the stringent norms of the
environmental agencies such as Environmental Protection Agency (EPA), United
25 Nations Environment Programme (UNEP), Central Pollution Control Board
(CPCB) etc., it has become very important to control the emission of these toxic
components and bring them down to the lowest possible values. The tolerable limit
of these impurities may vary for different countries. Nevertheless, the common
motive of these agencies is to minimize the emission caused thereof to almost ‘zero’
30 value or closer to it.
3
Thus, it is desirable to develop apparatus and methods which can efficiently and
economically remove these impurities, especially the sulfur-containing impurities.
Amine absorption is one such method of removing H2S. MEROX (developed by
UOP) is another well-known method of mercaptan removal. In a usual
desulphurization unit, amine absorption is followed 5 by MEROX. This is an
economic means of desulphurization, however, it generates waste in the form of
spent caustic and may suffer from operational problems like caustic carryover with
LPG. Other non-H2S desulphurization methods include conventional hydrotreater,
installation of scrubbers to remove SOx at the emission point, etc. These methods
10 require a large expensive reactor, catalysts and result in a lesser recovery 46 and
separation of sulfur compounds.
Therefore, in order to overcome the above difficulties and limitations, the present
disclosure relates to non-dispersive techniques to enhance the sulphur removal
15 process. The non-dispersive techniques, as the name suggests, do not require any
external means to disperse the fluid. Dispersion occurs solely by means of the
gravitational force acting on the weight of the fluid to be dispersed. Continuous film
contactor (CFC) is one such example of the non-dispersive technique available in
the market. The contactor of a CFC contains fibers 32 to provide large interfacial
20 area.
Such contactors are disclosed in reference such as US5904849, US7207445 and
US3992156. These references disclose a two stage reactor comprising a plurality of
packed fiber bundle contactor. The bundle is packed with metallic fibers 32. The
25 fluid mixture forms after the second distributor, trickles down over the packed fiber
bundle for remaining reactor length. The packed fiber bundle extends downward to
the separator, where the fluids are separated. Although, these documents describe
an advantageous mass transfer means, yet they have certain limitations. One such
limitation is the choking of the entrance for first liquid due to high amount of
30 external impurities (such as rust particles, muck etc.) in the feed which is made to
enter a confined area. Inefficient mass transfer is another limitation associated with
4
above inventions. Since the fiber bundle is packed inside a tube, the effective area
for mass transfer gets reduced due to overlapping of several fibers 32 and hence the
above described apparatuses provide lesser mass transfer for a given volume of
reactor.
5
Moreover, the conventional methods use caustic as one of the fluid for removal of
sulfur-containing impurities in the apparatuses discussed above. Caustic has a
congealing property which poses operational problems like clogging of reaction
space, especially at the inlet of caustic. Clogging reduces the mass transfer and
10 results in an inefficient separation of sulfur-containing impurities.
The present disclosure overcomes the above limitations and provides an apparatus
for removal of sulfur containing impurities and a method for the same.
15 SUMMARY
The apparatus of the present disclosure broadly comprises two distribution plates
for efficient distribution of fluids with specially treated metallic fibers 32 loosely
hung. The apparatus employs trough distributor and fiber bundle arrangement for
an efficient and economical mass transfer between two fluids. Compartmentalized
20 channels and guiding vanes 54 are provided to avoid choking and ensure intimate
contact between the two fluids, thereby resulting in an efficient removal of sulfur
impurities by the apparatus.
The main objective of the present invention is to provide an efficient and low energy
25 consumption apparatus for removal of sulfur-containing impurities.
Another objective of the present invention is to provide a method for removal of
sulfur-containing impurities.
5
Yet another objective of the present invention is to enhance the reaction space for
removal of sulfur containing impurities thereby increasing the mass transfer
between the two fluids.
Yet another objective of the present invention is to provide 5 efficient reactant
distribution to avoid congealment of the fluids.
An apparatus for non-dispersive contacting of two fluids, the apparatus includes a
pipe configured to be placed vertically, a first distributor plate placed in the pipe
10 and positioned horizontally along a first plane perpendicular to the longitudinal axis
and defining a top section between the top end of the pipe and the first distributor
plate, the top section configured to receive a first fluid. A second distributor plate
is positioned below the first distributor plate horizontally along a second plane
perpendicular to the longitudinal axis and the second distributor plate defines a
15 middle section of the pipe between the first distributor plate and the second
distributor plate and a bottom section of the pipe below the second distributor plate.
At least one distributor box is placed vertically in the pipe and extending from the
top section to the bottom section, the distributor box having a hollow cross-section
with a first end configured to receive a first fluid and the distributor box defining a
20 gap between distributor box and the second distributor plate to allow a second fluid
flow from the middle section towards the bottom section through the gap. A
plurality of fibers are placed in the distributor box, the fibers are positioned along
the length of the distributor box and a portion of fibers positioned below the first
distributor plate are crimped.
25
In an aspect, the apparatus has at least one distributor box with a plurality of legs at
a second end.
In an aspect, the second distributor plate is configured to partially support the
30 distributor box.
6
In an aspect the apparatus has the second distributor plate has a plurality of
holes/openings.
In an aspect entire length of the fibers below the first distributor plate are crimped.
5
In an aspect the guiding vanes are provided on the second end of the distributor box,
the guiding vanes are configured to direct flow of the second fluid towards the
fibers.
10 In an aspect the top section is configured to receive the first fluid and the middle
section is configured to receive the second fluid.
In an aspect the fibers above the first distributor plate are linear.
15 In an aspect the apparatus is configured to be attached to a separator vessel.
In an aspect, the distributor box is rectangular in cross-section.
In an aspect the bunch of crimped fibers is configured to self-support weight of
fibers partially.
20
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 schematically illustrates a cross-sectional front view of the apparatus for
removal of sulfur containing impurities in accordance with an embodiment.
FIG. 2 schematically represents a top view of the first distributor plate of the
25 apparatus in accordance with an embodiment.
FIG. 3 schematically illustrates a top view of the second distributor plate of the
apparatus in accordance with an embodiment.
FIG. 4 schematically illustrates a perspective view of a distributor box in
accordance with an embodiment.
30 FIG. 5 schematically illustrates a perspective view of the guiding vanes on the
second end of the distributor box.
7
DETAILED DESCRIPTION OF THE INVENTION
An apparatus 10 for removal of sulfur containing impurities is provided. The
apparatus 10 as disclosed may be used for non-dispersive contacting/mixing of two
fluids. The apparatus 10 of the present invention is a co-current 5 type two-stage
distribution reactor with separate entry for each fluid. The apparatus 10 has a pipe
12 forming a body of the apparatus 10. The pipe 12 is configured to be positioned
vertically along a longitudinal axis 14. The apparatus 10 further has a first
distributor plate 16 and a second distributor plate 18. The first distributor plate 16
10 is positioned vertically above the second distributor plate 18 along the length of the
pipe 12 such that the first distributor plate 16 divides the pipe 12 into a top section
20 and a middle section 22 and the second distributor plate 18 divides the pipe 12
between the middle section 22 and a bottom section 24. The first distributor plate
16 is configured to hydraulically seal the top section 20 from the middle section 22.
15 Apart from dividing the pipe 12 into the top, middle and bottom section 24, the first
distributor plate 16 and the second distributor plate 18 are configured to support a
distributor box 26 in the apparatus 10.
The apparatus 10 has at least one distributor box 26 positioned along the
longitudinal axis 14 of the pipe 12 such that a first end 28 of the distributor box 26
20 is positioned in the top section 20 and a second end 30 is positioned in the bottom
section 24. In the embodiment as illustrated in FIG.s 1-3, three trough distributor
boxes 26 are shown. A first distributor box 26 is placed in the middle portion along
the longitudinal axis 14 and the other two distributors boxes are positioned on either
side of the first distributor box 26 along the longitudinal axis 14. In an embodiment
25 any number of distributor box 26es may be provided as required. The dimensions
of the distributor boxes 26 may be designed based on the dimensions of the other
components of the apparatus or other requirements as needed.
The distributor box 26 is of hollow cross section and has plurality of elongated
30 fibers 32 placed in the distributor box 26. The distributor box 26 may be open at the
first end or may have a cover 28 and is open at the second end 30. The fibers 32 at
8
one end are hung from the first end 28 of the distributor box 26 such that a length
of the fibers 32 are positioned within the hollow portion of the distributor box 26
and the fibers 32 run along the length of the distributor box 26. The fibers 32 may
be hung from the first end 28 using any suitable means, for e.g. tie rods. The other
end of the fibers 32 hang out from the second end 30 of the distributor 5 box 26 in the
bottom section 24 as shown in FIG. 1. The length of the fibers 32 hanging out from
the second end 30 may vary depending on the configuration of the apparatus 10
along with other components. As the first distributor plate 16 seals the top section
20 from the middle section 22 only passage the liquid has to flow from the top
10 section 20 towards the middle section 22 is through the hollow portion of the
distributor box 26 along with the fibers 32. In the embodiment as illustrated, the
distributor box 26 is shown to be of substantially rectangular cross-section. It may
be understood that in an alternate embodiment, the distributor box 26 may be of any
other suitable shape and size.
15
Further, it is to be noted that the fibers 32 have a linear section 34 and a crimped
section 36. The fibers 32 positioned in the top section 20 are straight/linear, whereas
the fibers 32 hanging below the top section 20 or the first distributor plate 16, i.e.
in the middle section 22, bottom section 24 and below, are crimped. The plurality
20 of fibers 32 in the top section 20 are linearly designed for immediate distribution of
first fluid and complete wetting of the fiber surface. Also, the linearly placed fibers
32 ensure more free space and hence prevent clogging of the distributor box 26 due
in the top section 20 due to congealing properties, if any, in the first fluid.
25 Once the plurality of fibers 32 pass across the first distributor plate 16, the said
fibers 32 are no longer linear in shape and are crimped for the remaining length.
The fibers 32 are crimped in order to provide an increased effective area for mass
transfer. Crimping the fibers 32 increases non-dispersive mixing/contacting of the
first liquid and the second liquid. Also, crimping of the fibers 32 may aid in effective
30 weight distribution of the fibers 32 by self-supporting of fibers 32 along the length
of fibers 32. The bunch of crimped fibers 32 may engage and contact each other
9
such that the overall weight of the fibers 32 is partially supported by the fibers 32
themselves. This way excess load of the fibers 32 may be prevented on the first end
28 of the distributor box 26. It may be understood that any type of fibers 32 suitable
for the purpose may be used, such as metallic fiber, glass fiber, hollow fibers 32 or
5 polymeric fibers 32.
The apparatus 10 further has a first inlet 38 for feeding a first fluid into the
distributor box 26. The first inlet 38 is configured to supply a fluid, such as naphtha,
LPG, ATF, crude, oil etc. into the top section 20. A second inlet 40 is provided in
10 the middle section 22 to introduce a second fluid, such as a basic medium, in the
middle section 22.
To allow flow of liquid from the middle section 22 towards the bottom section 24,
the distributor box 26 is arranged such that a gap 42 is provided between the outer
15 surface of the distributor box 26 and the second distributor plate 18. The dimensions
of the gap 42 may be designed such that desired amount of second liquid is allowed
to flow down trickling on the surface of the distributor box and contact the fibers
32 of the distributor box 26. It may be understood that positioning and dimension
of the gap 42 may be designed as per the requirement keeping the function of the
20 gap 42 to allow contacting of the second fluid with the first fluid and the fibers 32
in the distributor box 26.
A top end 44 of the pipe 12 may be covered 46 using a cover 46 and the bottom end
may have an open end 48 which is fluidly connected to another component such as
25 a separator vessel (not shown). In the embodiment as illustrated in FIG. 1 the length
of the fibers 32 is shown ending in the bottom section 24. However, it may be
understood that in an embodiment the length of the fibers 32 may be provided such
that the fibers 32 extend beyond the bottom end of the apparatus 10 entering a
separator vessel as desired. In an embodiment, the fibers 32 may be sufficiently
30 long enough and extend further into the separator disposed below the reactor
column forming a heap of fibers 32 in the separator vessel.
10
As shown in FIG. 4, the distributor box 26 may have plurality of legs 50 towards
the bottom end such that the passage in the hollow cross section of the distributor
box 26 is divided into plurality of separate passages by the hollow cross section of
each leg. The portion of the distributor box 26 where division of 5 the distributor box
26 into separate legs 50 takes place may be placed in the middle section 22. In the
embodiment as illustrated in FIG.s 1-4, there is first distributor box 26 with three
legs 50 and two distributor boxes 26 with two legs 50 each. Only the first distributor
box 26 is shown in FIG. 4 for simplicity. The division of the distributor box 26 in
10 plurality of legs 50 also provides for additional point of entry for the second fluid
through the gap 42. Moreover, this way the fibers 32 are divided into separate
smaller bundles for better exposure of the fibers 32 to the second fluid. It may be
understood that the number of legs 50 and dimensions of the legs 50 in a distributor
box 26 may be designed according to requirement, e.g. depending on the overall
15 dimension or size of the apparatus 10.
The operation of the apparatus 10 is described as follows. The first fluid is
introduced in the top section 20 via the first inlet 38 at desired rate of flow. With
20 the supply of first fluid, the level of first fluid may rise up to the first end 28 of the
distributor box 26. As the first end 28 is an open end 48, upon the level of the first
fluid reaching the height of first end 28, the first fluid may enter the hollow portion
of the distributor box 26 and contact the surface of the fibers 32 and wet the fibers
32. The first fluid flows in an axial direction due to the action of gravity and reaches
25 the second distribution plate of the reactor column. Further, due to gravity, the first
fluid will travel down towards the bottom end of the apparatus 10 along with the
length of the fibers 32. A second fluid is supplied in the middle section 22 of the
apparatus 10. The second fluid introduced in the middle section 22 may contact the
first fluid and the fibers 32 via the gap 42 provided between the distributor box 26
30 and the second distributor plate 18 along the thickness of the second distributor
plate 18. After escaping from the gap 42, the second fluid may trickle down on the
11
surface of the distributor box 26 and contact with the fibers and the first fluid at the
second end 30 of the distributor box 26. After the first fluid contacts the second
fluid, both the fluids may trickle down together along the remaining length of the
fibers 32 towards and below the bottom end of the apparatus 10.
5
The fluids trickling down the fibers 32 are separated in a separator vessel disposed
below the reactor column. The separator vessel separates the two fluids on the basis
of physical properties of fluids. Preferably the first fluid may be a caustic solution
while the second fluid may be a hydrocarbon liquid such as light naphtha, kerosene,
10 liquefied petroleum gas (LPG), etc.
In an embodiment of the present disclosure, the second distributor plate 18 may be
provided with plurality of holes 52 as shown in FIG. 3. The holes 52 may be
configured such that they prevent any major flow of the second fluid through the
15 holes 52 and avoid any pressure build up in the middle section 22 due to continuous
supply of second fluid in the middle section 22. In an embodiment the holes 52 may
also allow the second fluid to drip/flow on a heap of fibers 32 present beneath the
second distributor plate 18 to provide for additional contacting of the fluids. The
holes 52 may be provided in any number as required.
20
Further, in an embodiment, the second distributor may be provided with guiding
vanes 54 positioned on the second end 30 of the distributor box 26. FIG. 5 illustrates
an enlarged view of the second end 30 of the distributor box 26 showing the guiding
vanes on the second end 30. The guiding vanes 54 may be configured to direct the
25 flow of the second fluid trickling on the distributor box 26 towards the fibers 32.
The guiding vanes 54 may be of any shape as required.
It is pertinent to note here that the height of the apparatus 10 is one of the essential
factors for determining the extent of mass transfer desired. This means that for
30 fluids where a limited mass transfer is required, a shorter height of the apparatus 10
column will suffice. While, in case of an equilibrium mass transfer a sufficiently
12
larger height will be required. Additionally, instead of increasing the height of the
apparatus 10, several other parameters of the apparatus 10 can be varied to get the
desired mass transfer. Such parameters can be the pipe 12 diameter, density of fibers
32, extent of crimping in fiber, etc.
5
The apparatus 10 of the present disclosure has various advantages. Some of these
advantages are low energy consumption due to use of non-dispersive techniques
hence no caustic carryover with the product, efficient contacting, avoids any water
wash, lesser caustic circulation, less settling time, very easy to retrofit on the
10 existing caustic wash facilities. Further, for given height of the apparatus 10 it
allows more caustic flow with desired distribution due to crimped fibers 32. Further,
the invention provides a compartmentalized approach and guiding vanes 54 for
efficient interaction.
15 The foregoing description describes only a few of the many possible
implementations of the present invention. It may be understood that various
modifications can be made, and that many changes can be made in the preferred
embodiments without departing from the principles of the invention. These and
other modifications in the nature of the invention or the preferred embodiments will
20 be apparent to those skilled in the art from the disclosure herein, whereby it is to be
distinctly understood that the foregoing descriptive matter is to be interpreted
merely as illustrative of the invention and not as a limitation.
2
List of Reference Numerals
Apparatus 10
Pipe 12
Longitudinal axis 14
First distributor plate 16
Second distributor plate 18
Top section 20
Middle section 22
Bottom section 24
Distributor box 26
First end 28
Second end 30
Fibers 32
Linear section 34
Crimped section 36
First inlet 38
Second inlet 40
Gap 42
Top end 44
Cover 46
Open end 48
Legs 50
Holes 52
Guiding vanes 54

We claim:
1. An apparatus 10 for non-dispersive contacting of two fluids, the apparatus 10
comprising:
a pipe 12 configured to be placed vertically;
a first distributor plate 16 placed in the pipe 12 and positioned horizontally
along a first plane perpendicular to the longitudinal axis 14 and defining a top
section 20 between the top end 44 of the pipe 12 and the first distributor plate 16,
the top section 20 configured to receive a first fluid;
a second distributor plate 18 positioned below the first distributor plate 16
horizontally along a second plane perpendicular to the longitudinal axis 14, the
second distributor plate 18 defining a middle section 22 of the pipe 12 between the
first distributor plate 16 and the second distributor plate 18, and a bottom section
24 of the pipe 12 below the second distributor plate 18;
at least one distributor box 26 placed vertically in the pipe and extending
from the top section 20 to the bottom section 24, the distributor box 26 having a
hollow cross-section with a first end 28 configured to receive a first fluid and the
distributor box 26 defining a gap between distributor box 26 and the second
distributor plate to allow a second fluid flow from the middle section 22 towards
the bottom section 24 through the gap;
a plurality of fibers 32 placed in the distributor box 26, the fibers 32
positioned along the length of the distributor box 26;
characterized in that, a portion of fibers 32 positioned below the first
distributor plate 16 are crimped.
2. The apparatus 10 as claimed in claim 1, wherein the at least one distributor box 26
has a plurality of legs 50 at a second end 30.
3. The apparatus 10 as claimed in claim 2, wherein the second distributor plate 18 is
configured to partially support the distributor box 26.
4
3. The apparatus 10 as claimed in claim 1, wherein the second distributor plate 18 has
a plurality of holes 52.
4. The apparatus 10 as claimed in claim 1, wherein entire length of the fibers 32 below
the first distributor plate 16 are crimpled.
5. The apparatus 10 as claimed in claim 1 wherein guiding vanes 54 are provided on
the second end 30 of the distributor box 26, the guiding vanes 54 configured to
direct flow of fluid towards the fibers 32.
6. The apparatus 10 as claimed in claim 1, wherein the top section 20 is configured
to receive the first fluid and the middle section 22 is configured to receive the
second fluid.
7. The apparatus 10 as clamed in claim 1, wherein the fibers 32 above the first
distributor plate 16 are linear.
8. The apparatus 10 as claimed in claim 1, wherein the apparatus 10 is configured to
be attached to a separator vessel.
9. The apparatus 10 as claimed in claim 1, wherein the distributor box 26 is
rectangular in cross-section.
10. The apparatus 10 as claimed in claim 1, wherein the bunch of crimped fibers 32 is
configured to self-support weight of fibers 32 partially.