Title of Invention

A NOVEL ROTATING PACKED BED (RPB) DEVICE FOR DISTILLATION PROCESS

Abstract The present invention relates to a rotating packed bed (RPB) device provided for distillation of fluids, and a process of distillation of fluids or effective mass transfer between fluids, wherein said process comprising a distillation apparatus comprising a reboiler and / or condenser integrated with rotating packed bed (RPB) device, with or without casing, wherein said RPB device consisting annular split packing.
Full Text FIELD OF INVENTION
The present invention relates to a novel process of distillation for fluids or effective mass
transfer between fluids. The present invention also relates to a distillation apparatus which comprises of a re-boiler and / or condenser, integrated with a novel rotating packed bed (RPB) device which is optionally provided with a casing for carrying out the process of distillation of fluids or effective mass transfer between fluids. BACKGROUND AND PRIOR ART
A Gas-Liquid contacting device in a chemical process industry involves transfer of chemical component / components from one phase to the other. The mass transfer between fluids will be either "liquid -film controlled" or "gas film controlled", depends on the resistance offered at interface formed between liquid and gaseous phase, while said phases diffuses across the interface. Enhancement of mass transfer rate is achieved by reduction of Controlling Mass Transfer Resistances, or by increasing the Interfacial Area between the two phases, or by both. Effectuating the said enhancement by technologies/strategies enables the physical sizes of conventional process engineering units to be significantly reduced. This is the gist of Process Intensification that has become a mantra among process industries.
The performance intensity of any equipment built with an objective to provide interface mass transfer or phase separation is partly dictated by the relative velocities at the interface. Large velocities imply high mass transfer coefficients. Large specific surface areas (small droplets, thin films, etc) ensures good mass transfer rate. The imposed centrifugal force on a multiphase system has been observed to be crucial in determining the fluid dynamic and hence the separation behavior. A large imposed force allows the use of packing with large specific surface area. If gas velocity increases, the system hydraulic capacity as well as the mass transfer coefficients get enhanced. Also, immersed bodies or channels which have a small characteristic dimension are intrinsically superior when performing a heat, mass or momentum operation. With above observations, Colin Ramshaw has concluded that the application of high imposed centrifugal force to multiphase mass transfer and separation system can intensify-the performance of an

equipment significantly ("Opportunities for exploring centriftigal fields". The Chemical Engineer, June 1987). The Rotating Packed Beds (RPB's) exploits this strategy of operating under centrifugal fields to intensify the operation into a compact mode, which is not in the reachof units that rely on terrestrial gravitation.
Ramshaw et al. (U.S. Patent 4,283,255) has claimed a process and apparatus for effecting mass transfer between two fluid phases, one of which is a liquid. The process comprises charging the fluids to a single packing rotating element which has a large interfacial area and which is permeable to the fluids and rotating the single packing element such that the fluids are subjected to an acceleration of at least 300 m.s-1 they flow through the same. The said patent also discusses distillation apparatus that deploys a plurality of permeable rotating elements in series, wherein the plurality of permeable element are rotatable about a common axis, each with its associated fluid collecting means, vaporizing means to vaporize a liquid (reboiler) and the vapor of which may be charged to the series of rotating elements and liquefying means to liquefy a vapor (condenser) discharged from the said series of permeable rotating elements. In conventional distillation and absorption columns, the gravitational field inherently governs the flow of Hquid and gas and the mass transfer rates. If this field is replaced by a centrifligal field of about 500 g to 1000 g high process intensification can be achieved. This leads to miniaturization of equipments and attendant benefits. The RPB, also known as HIGEE, has been proposed for carrying out distillation absorption and similar operations. It has been claimed that a volume reduction by a factor of 100 or more is possible by using such apparatus thus. In 1999 Dow Chemicals (D. Trent and D. Tirtowidjojo, "Commercial operation of a rotating packed bed (RPB) and other applications of RPB technology". BMR Group, London, 2002, p 11) has put a RPB into use in commercial absorption operation for production of hypochlorous acid similar to the HIGEE proposed by Ramshaw et al in their U.S. Patent No.4,283,255. The use of conventional RPB for distillation has not gained commercial acceptance.
Zheng et al. ""Pressure Drop of Centripetal gas Flow through Rotating Beds", Ind. Eng. Chem. Res., 39 (3), 829-834, 2000 and Sandilya et al. "Gas-phase mass* transfer in a centrifugal contactor", Ind. Eng. ("Chem. Res., 40, 384-392, 2001 indicate that the gas

rotates along with the packing without slip. Therefore, the gas flow is similar to its flow in a stationary rotor. As the slip velocity between the wet packing and the vapor in the radial direction is less than 3 m/s, no enhancement in kg is to be expected due to rotation of the bed. For distillation the controlling resistance is on the gas side. The conventional RPB's (single packing element) are not expected to lead to enhancement in kg. Hence, the intensification is only due to increased interfacial area and throughputs, which results in modest volume reducdon of about 10 times. Therefore, the design needs modification. The packing element in the conventional RPB system is essentially in the form of a single undivided unit. Hence, angular velocity throughout the packing elements is constant. The Applicants would like to highlight that due to the construction of the packing element in the form of a single undivided unit, the mass transfer coefficient decreases with increase in radius, hence RPB system of larger diameter cannot be constructed and operated efficiently. Thus, the prior art teaches use of a series of smaller diameter RPB unit for effective mass transfer. It should be noticed that for accomplishing distillation, it is essential to use two or more conventional RPB systems. As each of the conventional RPB system essentially has casing and fluid collecting means, for carrying the process of distillation, two or more conventional RPB systems having two or more casing, and two or more fluid collecting means are required.
The process for distillation is conventionally carried using distillation apparatus which comprises a reboiler, a condenser, two conventional RPB system acting as stripping section and two conventional RPB system acting as enriching section. Thus, it can be noticed that such a distillation apparatus of components, occupies larger volume of space and is costly to construct.
From the above descriptions of prior art, it is clear that there is a need for a more economical and simple process for distillation of fluids or effective mass transfer between fluids and apparatus /device thereof which overcomes drawbacks of higher volume of the equipment /device / plant, less value of liquid-film transfer coefficient and gas-film transfer coefficient, limitation of fluids or chemical mixture etc.
OBJECTIVES OF INVENTION
The main object of the present invention is to increase mass transfer rate between two fluid
phase, wherein one of the fluid phase is a liquid phase.

Another objective of the present invention is to provide a novel rotating packed bed
device useful for process intensification in a distillation process.
Yet another objective of the present invention is to provide a novel miniature reboiler /
condenser unit integrated with a RPB device for use in distillation process.
Still another objective of the present invention is to provide system for distillation of
chemicals having less volatile difference and having lesser no. of components.
SUMMARY OF THE INVENTION
The present invention relates to a rotating packed bed device provided with or without
casing which can be integrated centrally inside to a Reboiler / Condenser for enhancing mass transfer rate between fluids in a distillation process.
STATEMENT OF INVENTION
The present invention relates to a rotating packed bed (RPB) device for distillation of
fluids, said device characterized such that
a top (1) and a bottom plate (2) located parallel to each other, plurality of annular permeable packing elements (3, 4) attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap (5), and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means (6) for feeding a liquid component outwardly onto the packing and one or more outlet means (7) for collecting a vapor component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.
The present invention relates to a reboiler / condenser for use in distillation process, said
reboiler /condenser comprising;
a reboiler (8) / condenser (9) vessel integrated centrally inside with a rotating packed bed
(RPB) device, wherein said RPB device comprising:

a top (1) and a bottom plate (2) located parallel to each other, plurality of annular permeable packing elements attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap (5), and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same
and said device being provided with one or more feeding means for feeding a
liquid component outwardly onto the packing and one or more outlet means
for collecting a vapor component which flows inwardly through the packing
elements thereby coming in contact with the outwardly flowing liquid
component.
The present invention relates to a distillation apparatus comprising one or more a reboiler
(8) integrated with a rotating packed bed (RPB) device as claimed in claim 1 and one or
more condenser (9) optionally integrated with RPB device for carrying out a distillation
process, wherein said rotating packed bed device comprising:
a reboiler / condenser vessel integrated centrally inside with a rotating packed bed (RPB) device, wherein said RPB device comprising: a top and a bottom plate located parallel to each other, plurality of annular permeable packing elements attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap, and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means for feeding a liquid component outwardly onto the packings and one or more outlet means for collecting a vapour component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.

The present invention further relates a process for effective mass transfer between two fluid phases, the first of which is liquid and the other being a gas, said process comprises the steps of:
a) charging the said first fluid to a rotational packed bed (RPB) device, having a top and a bottom plate located parallel to each other, plurality of annular permeable packing elements being attached to an inner surface of the top and the bottom plate such that the packing elements are separated from each other by a small gap, and thereof form concentric annular circles with gaps among them,
b) rotating the top and bottom plates of the RPB device in co-direction / counter direction about an axis such that the liquid fluid flows radially outwards away form the said axis and said gaseous fluid flows radially inwards towards the said axis, and
c) collecting at least a proportion of one of the fluids discharged from the said RPB unit.
BRIEF DESCRIPTION OF FIGURES
Figure 1 shows the comparison of the present RPB device with conventional RPB rotor.
Figure 2 (a) & 2 (b) shows sectional front view and top view of a rotating packed bed
device.
Figure 3 represents a RPB device showing a gas withdrawal system.
Figure 4 shows the RPB device having stripping and enriching section and also depicts
the entry places of the feed for this particular set up.
Figure 5 represent a Reboiler integrated centrally inside with RPB device.
Figure 6 represent a system having separate RPB device integrated inside to reboiler and
in condenser for enriching and stripping sections.
Figure 7 shows a comparison of the total pressure drop (KPa) across the RPB
device for co- and counter rotation in dry bed.
Figure 8 shows a comparison of the total pressure drop for co- and counter
rotation in (KPa) across the RPB device for co -and counter roatation in
irrigated bed.

Figure 9 compares the effect of increasing radius of the packing on volumetric gas-side mass transfer coefficient between conventional RPB unit & the present RPB unit (a) With all packing elements, (b) Without the last packing (where slip velocity would not exist)
DETAIL DESCRIPTION OF INVENTION
The present invention relates to a rotating packed bed device provided with or without
casing for distillation process of fluids, said device comprising
a top and a bottom plate located parallel to each other, plurality of annular permeable packing elements attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap, and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements are being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means for feeding a liquid component outwardly onto the packings and one or more outlet means for collecting a vapour component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.
In an embodiment of the present invention wherein packing elements form stripping and /
or enriching sections.
In one embodiment of the present invention wherein the packing elements are made of
metal foam or wound wire mesh.
In one another embodiment of the present invention wherein packing elements are made of
aluminum foam.
Yet another embodiment of the present invention wherein the feeding means consist one or
more hollow shaft provided at an outer surface of the top plate & extended between the top
and bottom plates.

Yet another embodiment of the present invention wherein the hollow shaft is provided with
pores radially.
Still another embodiment of the present invention wherein the vapour collecting outlet
means is located on the top surface of the top plate and encompasses the feeding means.
Yet another embodiment of the present invention wherein the vapour collecting outlet
means is located at central location or a few centimeters away from the central location of
the RPB device.
Yet another embodiment of the present invention wherein rotating means are electric
motors.
Yet another embodiment of the present invention wherein a single electric motor is used to
rotate the top and bottom plates in co-directions.
Yet another embodiment of the present invention wherein two electric motors are used to
rotate the top and bottom plates in counter directions.
Still another embodiment of the present invention wherein the top plates and the bottom
plates are rotated at a angular speed in counter directions.
Still another embodiment of the present invention wherein said plates are rotated at a
angular speed in the range of 1000 to 3000 rpm in counter directions.
Yet another embodiment of the present invention wherein the packing elements have outer
surface in circular or in sinusoidal curvature.
Yet another embodiment of the present invention wherein the annular permeable packing
elements have width is in the range of 0.25 to 1.0 cm.
Yet another embodiment of the present invention wherein the gap between two successive
annular permeable packing elements is constant or in increasing /decreasing order.
Yet another embodiment of the present invention wherein gap between packing elements is
constant among annular packings.
Still another embodiment of the present invention wherein gap between packing elements
is in the range 0.5 to 0.75 cm.
Yet another embodiment of the present invention wherein said device enhances 10 to 50
times the mass transfer value per unit volume.

Yet another embodiment of the present invention wherein said device enhances the
throughputs of fluids by 5 to 10 times.
Yet another embodiment of the present invention wherein said device enhances gas side
mass transfer coefficient KG by a value in the range of 4 to 110.
A further embodiment of the present invention relates to a reboiler / condenser for use in
distillation process, said reboiler /condenser comprising;
a reboiler / condenser vessel integrated centrally inside with a rotating packed bed (RPB)
device, wherein said RPB device comprising
a top and a bottom plate located parallel to each other, plurality of annular permeable packing elements attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap, and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements are being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means for feeding a liquid component outwardly onto the packings and one or more outlet means for collecting a vapour component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.
In an embodiment of the present invention wherein packing elements form stripping and /
or enriching sections.
In one embodiment of the present invention wherein the packing elements are made of
metal foam or wound wire mesh.
In one another embodiment of the present invention wherein packing elements are made of
aluminum foam.
Yet another embodiment of the present invention wherein the feeding means consist one or
more hollow shaft provided at an outer surface of the top plate & extended between the top
and bottom plates.

Yet another embodiment of the present invention wherein the hollow shaft is provided with
pores radially.
Still another embodiment of the present invention wherein the vapour collecting outlet
means is located on the top surface of the top plate and encompasses the feeding means.
Yet another embodiment of the present invention wherein the vapour collecting outlet
means is located at central location or a few centimeters away from the central location of
the RPB device.
Yet another embodiment of the present invention wherein rotating means are electric
motors.
Yet another embodiment of the present invention wherein a single electric motor is used to
rotate the top and bottom plates in co-directions.
Yet another embodiment of the present invention wherein two electric motors are used to
rotate the top and bottom plates in counter directions.
Still another embodiment of the present invention wherein the top plates and the bottom
plates are rotated at a angular speed in counter directions.
Still another embodiment of the present invention wherein said plates are rotated at a
angular speed in the range of 1000 to 3000 rpm in counter directions.
Yet another embodiment of the present invention wherein the packing elements have outer
surface in circular or in sinusoidal curvature.
Yet another embodiment of the present invention wherein the annular permeable packing
elements have width is in the range of 0.25 to 1.0 cm.
Yet another embodiment of the present invention wherein the gap between two successive
annular permeable packing elements is constant or in increasing /decreasing order.
Yet another embodiment of the present invention wherein gap between packing elements is
constant among annular packings.
Still another embodiment of the present invention wherein gap between packing elements
is in the range 0.5 to 0.75 cm.
Yet another embodiment of the present invention wherein said device enhances 10 to 50
times the mass transfer value per unit volume.

Yet another embodiment of the present invention wherein said device enhances the
throughputs of fluids by 5 to 10 times.
Yet another embodiment of the present invention wherein said device enhances gas side
mass transfer coefficient KG by a value in the range of 4 to 110.
A still further embodiment of the present invention relates to a distillation apparatus
comprising one or more reboiler integrated with a rotating packed bed (RPB) device and
one or more condenser optionally integrated with RPB device for distillation process,
wherein said rotating packed bed device comprising:
a top and a bottom plate located parallel to each other, plurality of annular permeable packing elements attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap, and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements are being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means for feeding a liquid component outwardly onto the packings and one or more outlet means for collecting a vapour component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.
In an embodiment of the present invention wherein packing elements form stripping and /
or enriching sections.
In one embodiment of the present invention wherein the packing elements are made of
metal foam or wound wire mesh.
In one another embodiment of the present invention wherein packing elements are made of
aluminum foam.
Yet another embodiment of the present invention wherein the feeding means consist one or
more hollow shaft provided at an outer surface of the top plate & extended between the top
and bottom plates.

Yet another embodiment of the present invention wherein the hollow shaft is provided with
pores radially.
Still another embodiment of the present invention wherein the vapour collecting outlet
means is located on the top surface of the top plate and encompasses the feeding means.
Yet another embodiment of the present invention wherein the vapour collecting outlet
means is located at central location or a few centimeters away from the central location of
the RPB device.
Yet another embodiment of the present invention wherein rotating means are electric
motors.
Yet another embodiment of the present invention wherein a single electric motor is used to
rotate the top and bottom plates in co-directions.
Yet another embodiment of the present invention wherein two electric motors are used to
rotate the top and bottom plates in counter directions.
Still another embodiment of the present invention wherein the top plates and the bottom
plates are rotated at a angular speed in counter directions.
Still another embodiment of the present invention wherein said plates are rotated at a
angular speed in the range of 1000 to 3000 rpm in counter directions.
Yet another embodiment of the present invention wherein the packing elements have outer
surface in circular or in sinusoidal curvature.
Yet another embodiment of the present invention wherein the annular permeable packing
elements have width is in the range of 0.25 to 1.0 cm.
Yet another embodiment of the present invention wherein the gap between two successive
annular permeable packing elements is constant or in increasing /decreasing order.
Yet another embodiment of the present invention wherein gap between packing elements is
constant among annular packings.
Still another embodiment of the present invention wherein gap between packing elements
is in the range 0.5 to 0.75 cm.
Yet another embodiment of the present invention wherein said device enhances 10 to 50
times the mass transfer value per unit volume.

Yet another embodiment of the present invention wherein said device enhances the
throughputs of fluids by 5 to 10 times.
Yet another embodiment of the present invention wherein said device enhances gas side
mass transfer coefficient KG by a value in the range of 4 to 110.
A still further another embodiment of the present invention relates to a process for
effective mass transfer between two fluid phases, the first of which is liquid, and the other
being a gas, said process comprises the steps of:
a) charging the said first fluid to a rotational packed bed device having a top and a bottom plate located parallel to each other, plurality of annular permeable packing elements being attached to an inner surface of the top and the bottom plate such that the packing elements are separated from each other by a small gap, and thereof form concentric annular circles with gaps among them,
b) rotating the top and bottom plates of the RPB device in co-direction / counter direction about an axis such that the liquid fluid flows radially outwards away form the said axis and said gaseous fluid flowing radially inwards towards the said axis, and
c) collecting at least a proportion of one of the fluids discharged from the said RPB unit.
In an embodiment of the present invention wherein in step (a), liquid fluid enters at a temperature 300 ^ K and at a pressure 1 atm.
In another embodiment of the present invention wherein in step (b), said plates are rotated at a angular speed in co direction or in counter direction.
In another embodiment of the present invention wherein in step (b), said plates are rotated at a angular speed in the range of 1000 to 3000 rpm.
Yet another embodiment of the present invention wherein in step (b), said plates are rotated at a angular speed 3000 rpm in the counter direction.
The RPB device have been provided with or without casing comprises permeable annular packing located concentrically to a top plate and a bottom plate and rotate in counter or co-direction. The perforation of packing elements offers large interfacial area for effectuating mass transfer. The gap between the packings is of the order 0.5-0.75 cm. The gap may be

in order of increasing/ decreasing or constant between all the packing elements. The radial width of the split packing ring is of order 0.75-1.0 cm. If the width increases beyond this range the performance may deteriorate. The said device is rotated at a angular speed in the range of 1000 to 3000 rpm in co direction or in counter direction about an axis such that the liquid fluid flows radially outwards away from the said axis and said gaseous fluid flows radially inward to the said axis. The angular slip velocity increases with radius as the angular velocity between the consecutive elements increases with radius. Therefore the transfer coefficient increases with radius. The packing materials are metallic foams, etc. which has positive influence on the limits for the spectrum of chemicals that can be used in RPB. The annular packings form enriching and stripping sections which are functionally identical to the conventional distillation columns, but the flow rates of gas and liquid streams differs in each section. The enriching/stripping operations can be staged in a reboiler vessel by housing a novel RPB device with it, or separately by housing a novel RPB device in a reboiler and in a condenser vessel. In the latter case, the stripping section and the reboiler, and the enriching section and the condenser are coupled as shown in figures 6. This leads to high intensification of gas-side mass transfer coefficient which is controlling resistance in distillation and other processes including reactive separations. The RPB device of the present invention is not coupled with reboiler and condenser unlike in the conventional RPB; rather it is inserted in either or both reboiler and condenser. This arrangement eliminates the need for additional casing and the associated piping required in the conventional RPB.
The integration of RPB device with one of the units to stage distillation eliminates the column and thereby reduces heat gain/loss across the column. Roughly half the heat that is lost/gain in a conventional column is saved by staging distillation using novel RPB. The integration of RPB device with reboiler or condenser or both or of similar units eliminates the casing is a unique feature.
The gas flow into the eye of rotor has been prevented by withdrawing through one or two sides of the rotor. Thus, the countercurrent flow of liquid and gas at the inner radius is avoided in present RPB device. This permits the liquid to grip the packing by the time gas

flow is encountered. This minimizes entrainment of liquid with outgoing gas and enhances
the permissible throughputs and leads to intensification of the process.
The proposed RPB device is capable for carrying out the distillation /absorption process
for all types of fluids like benzene-toluene, toluene-xylene, ammonia-water, ethanol-water,
processing of natural gas, propane-propylene, ethane-ethylene, etc.
The present configuration for staging distillation can be operated for all the range of
pressures and temperatures at which industrial distillation columns are being operated and
capable to achieve relative velocity of 10-20 times for enhancing mass transfer rates per
unit volume compared to conventional columns.
The proposed design allows the introduction of feed in between the annular rings. Hence a
single packing element can be used. Nevertheless it doesn't preclude use of two packing
elements.
In the present invention, distillation can be staged in a single RPB accommodated either in
the reboiler or the condenser thus eliminating the need of a casing for the RPB and reduces
the volume of the equipment by a few times than the HI GEE proposed by Ramshaw et al.
The working of present invention described more in details with reference to the
accompanying figures.
The novel RPB unit designed with the split packing has higher flooding velocities as
shown in figure 1 than the conventional RPB. A single RPB unit can be used for both
stripping and enriching unlike the conventional RPB, which requires a minimum of two
units. In conventional RPB the gas-side mass transfer coefficient decreases with increase in
radius and hence we are limited to have small rotors and therefore many rotors in series
whereas in present RPB device, mass transfer coefficient increases with increase in radius
and hence effectuate more process intensification than the conventional RPB and gas-side
mass transfer coefficient doesn't have limitations like that of a conventional RPB. The
novel RPB unit designed with the split packing can subdue all shortcomings by its unique
design and mode of operation.
The sectional front view and top view of a rotating packed bed device as shown in figure 2
(a) and (b) illustrates the design of a rotating packed bed device which is useful to enhance
the gas-side mass transfer coefficient. As shown in figure 1, that the top and bottom plates

are fitted with fin like annular packing rings. The packing material are metal foam, wound wire mesh etc. for the top and bottom plates, and are rotate in opposite directions Sufficient gaps are provided to avoid brushing against each other. The centrifugal field has the same direction, though the packing elements are rotating in counter direction. The angular direction of vapor gets reversed as it flows through the successive packing elements. Slip velocity of 20 m/s or more can be achieved in contrast to the angular slip velocity of few cm/s in the conventional rotor. In between the packing elements, liquid flows as fine drops throughout the periphery of packing element. However, the packing rings width has to be adjusted to get the desired enhancement in mass transfer. The RPB device with a gas withdrawal system to enhance throughputs is shown in figure 3, The upper limits of RPB's throughput are limited by its flooding characteristics. In a conventional rotor, the liquid is sprayed onto the packing or introduced as jets in the inner radius of packing at which the gas velocity is highest in the rotor. At the onset of conditions prior to flooding, liquid drops get entrained and contaminate the vapor product; and leads to entrainment 'flooding'. At this condition, a significant fraction of liquid gets thrown back into the eye. The said liquid fraction flows as a thick film on the bottom plate by passing the contact with the vapor. The said thick film leads to reduction of mass transfer rate and contamination of the liquid product. In the present invention to enhance throughputs, the gas is prevented from entering the eye of rotor by withdrawing it about a few centimeters from the eye as shown in figure 2. This permits the liquid to grip the packing before it comes into contact with the vapor stream. The entrainment can occur only due to shearing of the liquid film that is held to the packing. Therefore, the entrainment is less even if throughputs are higher by 3 -5 times compared to a conventional rotor.
The RPB device having show feed entry of fluid between stripping and enriching sections is shown in figure 4. The novel RPB that has been proposed is capable to accomplish both stripping and enriching operations with a present rotor design having feed entry as shown in figure 4. The RPB rotor made of fin-like packing elements permits the introduction of feed in the desired radial location by the design given show in figure 4. The feed is introduced through hollow shaft into a jacket fixed to the bottom plate. A few

(2-6) perforated tubes are provided to the jacket through the bottom plate. The liquid or vapor flows onto the packing as jets. Unlike in the conventional RPB's, vapor can also be fed in the novel RPB.
A system in which RPB device is integrated inside to a reboiler is shown in figure 5 and an operational system for stage distillation with a reboiler and condenser. The said system shall foresee the conventional still columns as redundant. The stripping and enriching sections are integrated along with the reboiler/condenser by housing a present RPB within the reboiler/condenser. Unlike the conventional schemes proposed for staging distillation with RPB's having a casing, the proposed scheme for distillation/absorption operations do not require the RPB to be housed within a casing. The sketch of the present distillation unit with the stripping and enriching sections integrated with the reboiler is shown in Figure 5. This makes the unit compact. The heat gain/loss is reduced, which is of significance for cryogenic distillation. Moreover, the holdup and transients are reduced. Distillation can be accomplished at high pressure. The present system is capable to achieve high mass transfer rate by operating at high pressure, more than compensates the negative effect due to reduction in the relative volatility (for majority of systems). This reduces the size of the unit further.
The distillation apparatus comprising a reboiler and a condenser integrated both with RPB device is shown in figure 6 whereas the relative volatility is small between fluids. To combat the situation of large rotor and unacceptable mechanical stresses, the distillation could be staged in a reboiler and condenser having two RPB rotors, i.e. one rotor to integrate stripping with reboiler and other to integrate enriching with the condenser as shown in Figure 6. In the present system the rotor integrated with the condenser has to be within a casing.
The effect of increasing radius of the packing on volumetric gas-side mass transfer coefficient between conventional RPB unit & the present RPB unit (a) With all packing elements, (b) Without the last packing (where slip velocity would not exist) is shown in figure 9. In fact in the conventional rotor the slip velocity and hence mass transfer coefficient decreases with increase in radius. On the other hand, the slip velocity and

hence mass transfer coefficient increases with radius in the novel RPB unit as shown in
figure 9.
BRIEF DESCRIPTION OF TABLE
Table 1 shows the estimated gas-side mass transfer coefficients for packed column
conventional RPB and split RPB.
Table 2 depicts the operating conditions for distillation with RPB device for three systems
like Toluene- Benzene, Toluene-p Xylene and Ammonia- water
DETAIL DESCRIPTION OF TABLE
Table 1 shows the estimated gas-side mass transfer coefficients for the air-water system at latm and 300 K, for a rotor with a metal foam packing having surface area of2500m2/m3 and porosity of 0.9; and with the inner and outer radius of 0.01m and 0.4 m respectively for the single packing element; and split packing rings of 1cm radial width and a gap of 0.5 cm are given in the table. Also given are the estimated values for the packed column filled with the Raschig ring of 1½ inch nominal size. The gas-side mass transfer coefficients estimated for varying gas velocities (VG) as well as liquid velocities (VL) has been reported in Table 1. The trends that the packed bed, conventional RPB and the split ring RPB take with increasing gas and liquid velocities can be observed from the table.

(Table Removed)
Table 2 shows the estimated gas mass transfer coefficient wherein a rotating packed bed dimensions with split packing having thickness of one packing is 1 cm and width is I m and a gap of 5mm between two successive packing. The fluid flow rate of 10 kg/s. the table shows the operating conditions for three systems like Toluene- Benzene, Toluene-p

Xylene and Ammonia- water wherein RD stand for reflux ratio which is 1.5 times of minimum reflux ratio. In case of Toluene and Benzene system overall volumetric mass transfer coefficient, KOGa, is 186.85s"' and total no. of packing is 20. In case of Toluene-p-Xylene KOGa is 127.11s-1 and total no. of packing is 22 and in case of Ammonia water system KOGa is 52.06 s-1 and total no of packing is 4.Velocity of Gas and Liquid at inner radius is given which are free from flooding.
(Table Removed)
Wherein : Nomenclature:
P = Pressure, atm
F = Feed, kg/s
xF = Feed composition
RD = Reflux ratio
Ri = Inner Radius, m
RF = Radius at which feed will introduce, m
Roi = For feed, some space is required. So after Rp a space
of 65 mm is kept. And then again packing start from Roi, m
Ro = Outer radius, m
h = Height of Packing, m
NpR = No. of Packing for rectifying section
NPS = No. of Packing for stripping section
NpT = Total no of Packing
VG = Superficial velocity of gas at inner radius, m/s
VL = Superficial velocity of liquid at inner radius, m/s
ΔPc = Pressure drop due to centrifugal, atm
ΔPD = Pressure drop due to centrifugal, atm
ΔPT = Total Pressure drop, atm
KOGα =Overall volumetric mass transfer coefficient, s-1

ADVANTAGES
1. In the present invention, integration of RPB device with reboiler or condenser or both or of similar units eliminates the casing is a unique feature. This results in further intensification or results in compact units and leads to lower capital costs.
2. The countercurrent flow of liquid and gas at the inner radius is avoided which is unique feature of RPB. The gas flow into the eye of rotor has been prevented by withdrawing through one or two sides of the rotor. This permits the liquid to grip the packing by the time gas flow is encountered. This minimizes entrainment of liquid with outgoing gas and enhances the permissible throughputs. The proposed RPB has higher flooding velocities, which leads to further intensification of the process.
3. The integration of RPB with one of the units to stage distillation eliminates the column and thereby the heat gain/loss across the column. Roughly half the heat that is lost/gain in a conventional column is saved by staging distillation using novel RPB.
4. The proposed RPB device is capable for carrying out the distillation /absorption process for all types of fluids like benzene-toluene, toluene-xylene, ammonia-water, ethanol-water, processing of natural gas, propane-propylene, ethane-ethylene, etc.
5. The present configuration for staging distillation can be operated for all the range of pressures and temperatures at which industrial distillation columns are being operated and capable to achieve relative velocity of 10-20 times for enhancing mass transfer rates per unit volume compared to conventional columns.
6. In the present RPB device, the angular slip velocity increases with radius as the angular velocity between the consecutive elements increases with radius. Therefore the transfer coefficient increases with radius.
7. The present design of RPB allows the introduction of feed in between the annular rings. Hence a single packing element is sufficient to achieve effective mass transfer between fluids in a distillation process.

8. A single RPB unit can be used for both stripping and enriching unlike the conventional RPB, which requires a minimum of two units.
9. In present RPB device, mass transfer coefficient increases with increase in radius and hence effectuates more process intensification than the conventional RPB and gas-side mass transfer coefficient. It doesn't have limitations like that of a conventional RPB, wherein gas-side mass transfer coefficient decreases with increase in radius and hence the present RPB device is not limited to have small rotors and therefore many rotors in series.
10. The novel RPB definitely has a vital role to play in restructuring the sizes of chemical industries in the 21st century as the size of the unit goes down, the inventory of chemicals decreases and enhances the safety of the process.




WE CLAIM
1) A rotating packed bed (RPB) device for distillation of fluids, said device
characterized such that
a top (1) and a bottom plate (2) located parallel to each other, plurality of annular permeable packing elements (3, 4) attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap (5), and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means (6) for feeding a liquid component outwardly onto the packing and one or more outlet means (7) for collecting a vapor component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.
2) A rotating packed bed device as claimed in claim 1, wherein the packing elements (3, 4) form forming stripping and / or enriching sections.
3) A rotating packed bed device as claimed in claim 1, wherein the packing elements are made of metal foam or wound wire mesh.
4) A rotating packed bed device as claimed in claim 3, wherein the packing elements are made of aluminum foam.
5) A rotating packed bed device as claimed in claim 1, wherein the feeding means (6) consist one or more hollow shaft provided at an outer surface of the plate & extended between the top and bottom plates.
6) A rotating packed bed device as claimed in claim 5, wherein the hollow shaft is providing with pores radially, in the length between the top plate and the bottom plate for spraying fluid outwardly onto the packings.
7) A rotating packed bed device as claimed in claim 1, wherein the vapor collecting outlet means is located on the outer surface of the top plate encompasses the feeding means.

8) A rotating packed bed device as claimed in claim 1, wherein the vapor collecting outlet means is located at a central location or a few centimeters away from the central location of the top plate.
9) A rotating packed bed device as claimed in claim 1, wherein rotating means are electric motors.
10) A rotating packed bed device as claimed in claim 9, wherein a single electric motor is used to rotate the top and bottom plates in co-direction.
11) A rotating packed bed device as claimed in claim 9, wherein two electric motors are used to rotate the top and bottom plates in counter directions.
12) A rotating packed bed device as claimed in claim 1, wherein the top plates and the bottom plates are rotated at a angular speed in counter directions.
13) A rotating packed bed device as claimed in claim 1, wherein said plates are rotated at a angular speed in the range of 1000 to 3000 rpm in counter directions.
14) A rotating packed bed device as claimed in claim 1, wherein the packing elements have outer surface in circular or in sinusoidal curvature.
15) A rotating packed bed device as claimed in claim 1, wherein the annular permeable packing elements has width is in the range of 0.25 to 1.0 cm.
16) A rotating packed bed device as claimed in claim 1, wherein the gap between packing elements is constant or in increasing /decreasing order.
17) A rotating packed bed device as claimed in claim 17, wherein the gap between
two successive annular permeable packing elements is constant among annular
packings.
18) A rotating packed bed device as claimed in claim 1, wherein the gap between two successive annular permeable packing elements is in the range 0.5 to 0.75 cm.
19) A rotating packed bed device as claimed in claim 1, wherein the said device enhances 10 to 50 times the mass transfer value per unit volume.
20) A rotating packed bed device as claimed in claim 1, wherein the said device enhances the throughputs of fluids by 5 to 10 times.
21) A rotating packed bed device as claimed in claim 1, wherein the said device enhances gas side mass transfer coefficient KG by a value in the range of 4 to 110.

22) A reboiler / condenser for use in distillation process, said reboiler /condenser
comprising;
a reboiler (8) / condenser (9) vessel integrated centrally inside with a rotating packed bed (RPB) device as claimed in claim 1, wherein said RPB device comprising:
a top (1) and a bottom plate (2) located parallel to each other, plurality of annular permeable packing elements attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap (5), and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means for feeding a liquid component outwardly onto the packing and one or more outlet means for collecting a vapor component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.
23) A reboiler / condenser as claimed in claim 22, wherein the packing elements form stripping and / or enriching sections.
24) A reboiler / condenser as claimed in claim 22, wherein the packing elements are made of metal foam or wound wire mesh.
25) A reboiler / condenser as claimed in claim 24, wherein the packing elements are made of aluminum foam.
26) A reboiler / condenser as claimed in claim 22, wherein feeding means consist one or more hollow shaft provided at an outer surface of the top plate & extending between the top and bottom plates.
27) A reboiler / condenser as claimed in claim 27, wherein hollow shaft having pores radially.

28) A reboiler / condenser as claimed in claim 22, wherein the vapor collecting outlet means is located on the top surface of the top plate encompasses the feeding means.
29) A reboiler / condenser as claimed in claim 22, wherein the vapor collecting outlet means is located at central location or a few centimeters away from the central location of the top plate.
30) A reboiler / condenser as claimed in claim 22, wherein rotating means are electric motors.
31) A reboiler / condenser as claimed in claim 30, wherein a single electric motor is used to rotate the top and bottom plates in co-directions.
32) A reboiler / condenser as claimed in claim 30, wherein two electric motors are used to rotate the top and bottom plates in counter directions.
33) A reboiler / condenser as claimed in claim 22, wherein the top plates and the bottom plates are rotated at a angular speed in counter directions.
34) A reboiler / condenser as claimed in claim 22, wherein the said plates are rotated at a angular speed in the range of 1000 to 3000 rpm.
35) A reboiler / condenser as claimed in claim 22, wherein the packing elements have outer surface in circular or in sinusoidal curvature.
36) A reboiler / condenser as claimed in claim 22, wherein the annular permeable packing elements have width is in the range of 0.25 to 1.0 cm.
37) A reboiler / condenser as claimed in claim 22, wherein the gap between annular permeable packing is constant or increasing /decreasing order.
38) A reboiler / condenser as claimed in claim 37, wherein the gap between two successive annular permeable packing elements is constant among annular packings.
39) A reboiler / condenser as claimed in claim 38, wherein gap between two successive annular permeable packing elements is in the range 0.5 to 0.75 cm.
40) A reboiler / condenser as claimed in claim 22, wherein said device enhances 10 to 50 times the mass transfer value per unit volume.
41) A reboiler / condenser as claimed in claim 22, wherein said device enhances the throughputs of fluids by 5 to 10 times.

42) A reboiler / condenser as claimed in claim 22, wherein said device enhances gas side mass transfer coefficient KG by a value in the range of 4 to 110.
43) A reboiler / condenser as claimed in claim 1, wherein said RPB is located in upper zone of reboiler.
44) A distillation apparatus comprising one or more a reboiler (8) integrated with a rotating packed bed (RPB) device as claimed in claim 1 and one or more condenser (9) optionally integrated with RPB device as claimed in claim 1 for carrying out a distillation process, wherein said rotating packed bed device comprising:
a reboiler / condenser vessel integrated centrally inside with a rotating packed bed (RPB) device, wherein said RPB device comprising: a top and a bottom plate located parallel to each other, plurality of annular permeable packing elements attached to an inner surface of the top plate and the bottom plate such that the packing elements are separated from each other by a small gap, and thereof forming concentric annular circles with gaps among them, a said concentric annular packing elements being rotatable along a common axis in counter or co-direction for communicating fluid flow from one to another,
said plates are coupled to one or more rotating means for rotating the same and said device being provided with one or more feeding means for feeding a liquid component outwardly onto the packings and one or more outlet means for collecting a vapour component which flows inwardly through the packing elements thereby coming in contact with the outwardly flowing liquid component.
45) A distillation apparatus as claimed in claim 44, wherein the packing elements form stripping and / or enriching sections.
46) A distillation apparatus as claimed in claim 44, wherein the packing elements are made of metal foam or wound wire mesh.
47) A distillation apparatus as claimed in claim 44, wherein the packing elements are made of aluminum foam.

48) A distillation apparatus as claimed in claim 44, wherein the feeding means consist one or more hollow shaft provided at an outer surface of the top plate & extending between the top and bottom plates.
49) A distillation apparatus as claimed in claim 50, wherein the hollow shaft having pores radially.
50) A distillation apparatus as claimed in claim 44, wherein the vapour collecting outlet means is located on the top surface of the top plate encompasses the hollow shaft.
51) A distillation apparatus as claimed in claim 44, wherein the vapour collecting outlet means is located at central location or a few centimeters away from the central location of the top plate.
52) A distillation apparatus as claimed in claim 44, wherein rotating means are electric motors.
53) A distillation apparatus as claimed in claim 52, wherein a single electric motor is used to rotate the top and bottom plates in co-directions.
54) A distillation apparatus as claimed in claim 54, wherein two electric motors are used to rotate the top and bottom plates in counter directions.
55) A distillation apparatus as claimed in claim 44, wherein the top plates and the bottom plates are rotated at a angular speed in counter directions.
56) A distillation apparatus as claimed in claim 44, wherein said plates are rotated at a angular speed in the range of 1000 to 3000 rpm.
57) A distillation apparatus as claimed in claim 44, wherein the packing elements have outer surface in circular or in sinusoidal curvature.
58) A distillation apparatus as claimed in claim 44, wherein the packing elements have width is in the range of 0.25 to 1.0 cm.
59) A distillation apparatus as claimed in claim 44, wherein the gap between packing elements is constant or increasing /decreasing order.
60) A distillation apparatus as claimed in claim 44, wherein the gap between two successive permeable packing elements is constant among annular packing.
61) A distillation apparatus as claimed in claim 44, wherein the gap between two successive permeable packing elements varying in the range 0.5 to 0.75 cm.

62) A distillation apparatus as claimed in claim 44, wherein said device enhances 10 to 50 times the mass transfer value per unit volume.
63) A distillation apparatus as claimed in claim 44, wherein said device enhances the throughputs of fluids by 5 to 10 times.
64) A distillation apparatus as claimed in claim 44, wherein said device enhances gas side mass transfer coefficient KG by a value in the range of 4 to 110.
65) A distillation apparatus as claimed in claim 44, wherein the said RPB device is located centrally in upper zone of reboiler and condenser.
66) A process for effective mass transfer between two fluid phases, the first of which is liquid and the other being a gas, said process comprises the steps of:
a) charging the said first fluid to a rotational packed bed (RPB) device as
claimed in claim 1, having a top and a bottom plate located parallel to
each other, plurality of annular permeable packing elements being
attached to an irmer surface of the top and the bottom plate such that the
packing elements are separated from each other by a small gap, and
thereof form concentric armular circles with gaps among them,
b) rotating the top and bottom plates of the RPB device in co-direction / counter direction about an axis such that the liquid fluid flows radially outwards away form the said axis and said gaseous fluid flows radially inwards towards the said axis, and
c) collecting at least a proportion of one of the fluids discharged from the said RPB unit.

67) A process as claimed in claim 66, wherein in step (a), liquid fluid is enters at a temperature 300 º K and at a pressure 1 atm.
68) A process as claimed in claim 66, wherein in step (b), said plates are rotated in at a angular speed in the co direction or in counter direction.
69) A process as claimed in claim 66, wherein in step (b), said plates are rotated at a angular speed in the range of 1000 to 3000 rpm.
70) A process as claimed in claim 66, wherein in step (b), said plates are rotated at a angular speed 3000 rpm in counter direction.

71) A rotating packed bed device, a reboiler /condenser for use in distillation process, a distillation apparatus and a process for effective mass transfer between fluids substantially as herein described with reference to the accompanying drawings.



Documents:

358-DEL-2004-Abstract-(05-03-2008).pdf

358-DEL-2004-Abstract-(13-10-2008).pdf

358-del-2004-abstract.pdf

358-DEL-2004-Cancelled-(05-03-2008).pdf

358-DEL-2004-Claims-(13-10-2008).pdf

358-del-2004-claims-(cancelled).pdf

358-del-2004-claims.pdf

358-DEL-2004-Correspondence-Others-(13-10-2008).pdf

358-del-2004-correspondence-others.pdf

358-del-2004-correspondence-po.pdf

358-DEL-2004-Description (Complete)-(13-10-2008).pdf

358-del-2004-description (complete).pdf

358-DEL-2004-Drawings-(13-10-2008).pdf

358-del-2004-drawings.pdf

358-DEL-2004-Form-1-(13-10-2008).pdf

358-del-2004-form-1.pdf

358-del-2004-form-18.pdf

358-DEL-2004-Form-2-(13-10-2008).pdf

358-del-2004-form-2.pdf

358-DEL-2004-Form-26-(13-10-2008).pdf

358-del-2004-form-26.pdf

358-del-2004-form-3.pdf

358-del-2004-form-5.pdf

358-del-2004-petition-138.pdf

abstract.jpg


Patent Number 226874
Indian Patent Application Number 358/DEL/2004
PG Journal Number 07/2009
Publication Date 13-Feb-2009
Grant Date 29-Dec-2008
Date of Filing 04-Mar-2004
Name of Patentee INDIAN INSTITUTE OF TECHNOLOGY, KANPUR
Applicant Address DEPARTMENT OF CHEMICAL ENGINEERING, KANPUR 208016, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 DAVULURI PRAHALADA RAO DEPARTMENT OF CHEMICAL ENGINEERING,INDIAN INSTITUTE OF TECHNOLOGY KANPUR 208016, INDIA
PCT International Classification Number B 01 D 1/30
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA