CLIAMS:1. A system for separating aromatics from an effluent stream comprising aromatics and water, said system comprising a distillation column comprising:
• a plurality of plates, removably disposed in a spaced vertical configuration in said system, each of said plates separated from each other by a first pre-determined distance, and having a plurality of upwardly extending primary conduits configured on an operative upper surface thereof, to facilitate a passageway for a gaseous mixture comprising aromatics and water therethrough,
wherein, each of said primary conduits are spaced from each other by a second pre-determined distance;
• a bubble-cap, removably disposed on each of said primary conduits, said bubble-cap having an operative top surface and a skirt downwardly extending therefrom, said skirt having a plurality of notches configured thereon, said notches upwardly extending from the edge of said skirt with decreasing cross-section,
wherein, said notches are adapted to attenuate intermixing of the aromatics and the water;
• a slotted ring, having a plurality of slots configured along an operative lower periphery of said slotted ring, said slotted ring disposed around said skirt, to retain the aromatics and facilitate through-path for the water;
• a secondary conduit, downwardly extending from a free end of each of said plates, to facilitate through-path for the water between consecutive plates; and
• a weir, of a pre-determined height configured on each of said plates to enable retention of said gaseous mixture in a condensed form thereon, said weir having at least one opening configured on an operative lower portion, to facilitate through-path for the water to said secondary conduit.
2. The system as claimed in claim 1, wherein the shape of said plurality of notches is convexo-concave-convexo with smooth edges.
3. The system as claimed in claim 1, wherein said first pre-determined distance ranges from 350mm to 500mm.
4. The system as claimed in claim 1, wherein said second pre-determined distance ranges from 1.5 times to 2.0 times the diameter of the bubble cap.
5. The system as claimed in claim 1, wherein the diameter of the bubble-cap ranges from 25mm to 200mm.
6. A process for separating aromatics from an effluent stream comprising aromatics and water in a system comprising a distillation column, said process comprising the following steps:
• introducing said effluent stream in said distillation column;
• heating said effluent stream at a first pre-determined temperature and at a pre-determined pressure to obtain a gaseous mixture comprising aromatics and water;
• allowing said gaseous mixture to rise upwards at a pre-determined flow-rate through a plurality of upwardly extending primary conduits configured on each plate of a plurality of plates removably disposed in a spaced vertical configuration in said distillation column;
• cooling said gaseous mixture at a second pre-determined temperature to form a condensate comprising water and aromatics;
• returning said condensate in said distillation column;
• allowing stripping of said condensate with said gaseous mixture coming out of said bubble-cap removably disposed on each of said primary conduits, to form an upper layer comprising aromatics and a lower layer comprising water;
• retaining the aromatics on each of said plates by a weir of a pre-determined height configured on each of said plates, and a slotted ring disposed around a skirt of a bubble-cap; and
• collecting said upper layer from an operative top portion of said system and said lower layer from an operative lower portion of said system.
7. The process as claimed in claim 6, wherein said pre-determined pressure ranges from 0.5 to 2 kg/cm2g.
8. The process as claimed in claim 6, wherein said first pre-determined temperature ranges from 100 to 150ºC.
9. The process as claimed in claim 6, wherein said second pre-determined temperature ranges from 80 to 90 ºC.
10. The process as claimed in claim 6, wherein loading of the distillation column diameter is 25 to 30 percent of the flooding capacity. ,TagSPECI:FIELD
The present disclosure relates to a system and a process for separating aromatics from an effluent stream containing aromatics.
DEFINITION
Azeotrope is a mixture of different fluids, wherein the fluids cannot be separated from each other.
BACKGROUND
Aromatics such as benzene, toluene, xylene, and the like are obtained from various chemical processes. A significant percentage or amount of the aromatics is obtained from petroleum refining, particularly by catalytic reforming of naphtha. Effluent streams produced as a result of the chemical processes, comprise aromatics approximately in the range of 250 to 50000 ppm. The aromatics are detrimental and non-biodegradable, and therefore the stream cannot be discharged directly into the surrounding water bodies without prior treatment. Hence, the “Environmental Protection Agency (EPA)” has mandated a near complete removal of aromatics from effluent streams, before discharging such streams into the surrounding water bodies. In accordance with EPA, the amount of the aromatics in a pre-treated effluent stream should not exceed approximately 20 ppm, and also the amount of benzene in a pre-treated effluent stream should not exceed approximately 10 ppm.
Various conventional processes such as,
• contacting the effluent stream with a series of activated carbon beds;
• air stripping;
• steam stripping;
• direct incineration of the effluent streams, and the like,
are used for separating aromatics from effluent streams, before discharging the effluent streams into surrounding water bodies.
However, conventional systems and conventional processes have the following drawbacks:
• ineffective removal of aromatic compounds;
• air pollution;
• generation of secondary effluent;
• generation of carcinogenic dioxane in the effluent stream, and the like.
Hence, there is a need for a system and a process to overcome the drawbacks associated with conventional systems and conventional processes for separating aromatics from effluent streams.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a system for separating aromatics from an effluent stream.
Another object of the present disclosure is to provide a process for separating aromatics from an effluent stream.
Yet another object of the present disclosure is to provide a system and a process for separating aromatics from an effluent stream that is efficient.
Still another object of the present disclosure is to provide a system and a process for separating aromatics from an effluent stream that is economical.
Yet another object of the present disclosure is to ameliorate one or more drawbacks associated with conventional systems and conventional processes for separating aromatics from an effluent stream.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a system for separating aromatics from an effluent stream comprising aromatics and water. The system comprises a distillation column that includes a plurality of plates, a plurality of upwardly extending primary conduits, a bubble-cap, a plurality of notches that are configured on a skirt of the bubble-cap, a slotted ring that is disposed around the skirt of the bubble-cap, a secondary conduit, and a weir of a pre-determined height.
The present disclosure also provides a process for separating aromatics from an effluent stream comprising aromatics and water in the system that comprises the distillation column. In the first step, the effluent stream is introduced in the distillation column. The effluent stream is then heated in the distillation column at a first pre-determined temperature and at a pre-determined pressure to obtain a gaseous mixture of aromatics and water. The gaseous mixture, then rises upwards at a pre-determined flow-rate and passes through the primary conduits. A condensate comprising aromatics and water is formed by cooling the gaseous mixture at a second pre-determined temperature. The condensate is returned to the distillation column and stripped with the gaseous mixture coming out of the bubble-cap to form an upper layer comprising the aromatics and a lower layer comprising water. The aromatics are retained on the plates by the weir and the slotted ring. The upper layer and the lower layer are then collected from an operative top portion and an operative bottom portion of the distillation column, respectively.
The notches of the present disclosure attenuate dispersion and intermixing of the aromatics and the water.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The disclosure will now be described with reference to the accompanying non-limiting drawings:
Figure 1 illustrates a schematic view of a system for separating aromatics from an effluent stream comprising aromatics and water in accordance with an embodiment of the present disclosure, wherein the system comprises a distillation column;
Figure 2 illustrates a schematic view of the distillation column of Figure 1;
Figure 3 illustrates a schematic view of a bubble-cap of Figure 2;
Figure 4 illustrates a top view of a slotted ring and a weir plate of Figure 2;
Figure 5 illustrates a schematic view of the slotted ring of Figure 2, wherein the slotted ring is disposed around a skirt of the bubble cap of Figure 2;and
Figure 6 illustrates a schematic view of the weir plate of Figure 2.
DETAILED DESCRIPTION
The disclosure will now be described with reference to the accompanying embodiments, which do not limit the scope and ambit of the disclosure. The description provided is purely by the way of embodiments and illustrations.
The embodiments herein, the various features, and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The embodiments described herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice these embodiments herein. Accordingly, the embodiments should not be construed as limiting the scope of the present disclosure.
The description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The drawbacks allied with the conventional systems and the conventional processes for separating aromatics from an effluent stream are:
• ineffective removal of the aromatics from the effluent stream;
• air pollution;
• generation of secondary effluent;
• generation of carcinogenic dioxane in the effluent stream, and the like.
The present disclosure, therefore, envisages a system and a process to separate aromatics from effluent stream, that obviates the drawbacks of conventional systems and conventional processes.
The aromatics present in an effluent stream form an azeotrope with water present in the effluent stream. The azeotrope cannot be separated by conventional systems and conventional processes. The present disclosure envisages a system and a process for separating the azeotrope of aromatics and water. Specifically, the present disclosure envisages a system and a process for separating the azeotrope of benzene and water.
Figure 1 illustrates a schematic view of a system for separating aromatics from an effluent stream comprising aromatics and water in accordance with an embodiment of the present disclosure, wherein the system S comprises a distillation column Di. In accordance with the present disclosure, the system S includes at least one heat recovery unit R, at least one pre-heater P, and a dosage unit Du.
In accordance with the present disclosure, the distillation column Di includes,
o a plurality of plates 10, that are removably disposed in a spaced vertical configuration in the distillation column Di;
o a plurality of upwardly extending primary conduits 12, configured on an operative upper surface U of each of the plates 10;
o a bubble-cap 14, that is removably disposed on each of the primary conduits 12;
o a weir 16 of a pre-determined height, that is configured on each of the plates 10; and
o a secondary conduit 18, that extends downwardly from a free end E of each of the plates 10 (as shown in Figure 2).
In accordance with the present disclosure, each of the plates 10 in the distillation column Di is separated from each other by a first pre-determined distance ranging from 350 mm to 500 mm.
In accordance with the present disclosure, each of the primary conduits 12 is spaced from each other by a second pre-determined distance of 2.0 times the diameter of each bubble cap when the bubble cap is upto 100 mm size, and thereafter 1.5 times the diameter of each bubble cap size.
In accordance with the present disclosure, the distillation column Di includes a re-boiler (not shown in Figure 1 and Figure 2), a condenser C’ (as shown in Figure 1), and a liquid phase settler L (as shown in Figure 1).
In accordance with the present disclosure, the bubble-cap 14 has an operative top surface 14a and a skirt 14b. The skirt 14b of the bubble-cap 14 extends downwardly from the operative top surface 14a of the bubble-cap 14. A plurality of notches 14c is configured on the skirt 14b (as shown in Figure 3). Specifically, the notches 14c extend upwardly from the edge OL of the skirt 14b towards the operative upper surface 14a of the bubble-cap 14 with a decreasing cross-section (as shown in Figure 3)
In accordance with the present disclosure, the diameter of the bubble-cap 14 ranges from 25mm to 200mm.
In accordance with the present disclosure, the distance between each of the plates 10 can change by changing the diameter of the bubble-cap 14.
In accordance with the present disclosure, the shape of the notches 14c is convexo-concave-convexo with smooth edges 14d (as shown in Figure 3). In accordance with one embodiment of the present disclosure, the smooth edges 14d of the notches 14c are polished to 400 grit finish.
In accordance with the present disclosure, the width of the notches 14c ranges from 10mm to 25mm.
In accordance with the present disclosure, the length of the notches 14c ranges from a minimum of 10 mm to eighty percent of the height of bubble cap, depending on the size of bubble cap.
In accordance with the present disclosure, a slotted ring 20 (not shown in Figure 2) is disposed around the skirt 14b of the bubble cap 14 (as shown in Figures 4 and 5). A plurality of slots 20’ is configured along an operative lower periphery (not shown in Figure 5) of the slotted ring 20 (as shown in Figures 4and 5).
In accordance with the present disclosure, the weir 16 (as shown in Figures 2, 4, and 6) has at least one opening 16a that is configured on an operative lower portion 16b of the weir 16 (as shown in Figure 6).
In accordance with one embodiment of the present disclosure, the distillation column Di is a bubble-cap distillation column that is capable of separating the azeotrope of aromatics and water.
In accordance with another embodiment of the present disclosure, the distillation column Di is a bubble-cap distillation column that is capable of separating the azeotrope of benzene and water.
In accordance with another aspect of the present disclosure, there is provided a process for separating aromatics from an effluent stream comprising aromatics and water in the system S that comprises the distillation column Di. During the process, the effluent stream (ES) comprising aromatics and water is introduced in the distillation column Di from point A (as shown in Figure 2). In accordance with the present disclosure, the effluent stream ES contains aromatics in the range of 250 ppm to 50000 ppm. In one embodiment, benzene is present in the effluent stream in the range of 250 ppm to 5000 ppm.
The effluent stream (ES) is heated at a first pre-determined temperature and at a pre-determined pressure to obtain a gaseous mixture of aromatics and water. The gaseous mixture V rises upwardly in the distillation column Di at a pre-determined flow-rate through the plurality of upwardly extending primary conduits 12 (as shown in Figure 2). The gaseous mixture V is then introduced into the condenser C’ (as shown in Figure 1). In the condenser C’, the gaseous mixture V is cooled at a second pre-determined temperature to form a condensate C comprising aromatics and water. The condensate C is returned to the distillation column (as shown in Figure2).The condensate C is stripped with the gaseous mixture V that is coming out of the bubble-cap 14, to form an upper layer comprising the aromatics and a lower layer comprising water. The aromatics are retained on each of the plates 10 and the slotted ring 20. The upper layer comprising aromatics is collected from an operative top portion of the distillation column Di, and the lower layer (LL) comprising water is collected from an operative bottom portion of the distillation column Di.
In accordance with the present disclosure, the condensate C is introduced into the liquid phase settler L that is disposed in between the distillation column Di and the condenser C’, to separate the water (WR) from the aromatics (AR) (as shown in Figure 1). In accordance with one embodiment of the present disclosure, the water (WR) is substantially free of aromatics, and has a residual total aromatics of less than 20 ppm and benzene less than 10 ppm. The aromatics (AR) that is separated from the water (WR) can be further used for varied applications. The water (WR) (comprising a small amount of the aromatics (AR)) is returned into the distillation column Di.
In accordance with one embodiment of the present disclosure, at least one heat recovery unit R can be used for pre-heating the effluent stream (ES) by utilizing the heat content from the lower layer (LL) that is collected from the operative lower section of the distillation column Di, thereby making the process energy efficient (as shown in Figure 1). The lower layer (LL) is then discharged into the surrounding water bodies and/or used for varied applications.
In accordance with the present disclosure, at least one pre-heater P is used for pre-heating the effluent stream (ES), thereby making the process energy efficient (as shown in Figure 1).
In accordance with the present disclosure, the smooth edges 14d of the notches 14c of the bubble-cap 14 minimizes the turbulence of the gaseous mixture V coming out of the bubble-cap 14, thereby attenuating the dispersion and the intermixing of the upper layer (aromatics) and the lower layer (water).
In accordance with the present disclosure, at least one additive from the dosage unit Du is added in the distillation column to prevent re-dispersion and intermixing of the upper layer and the lower layer (as shown in Figure 1).
In accordance with one embodiment of the present disclosure, the concentration of the additive in the effluent stream is in the range of 1 ppm to 10 ppm.
In accordance with the present disclosure, the slotted ring 20 that is disposed around the skirt 14b of the bubble cap 14 (as shown in Figures 4 and 5), retains the upper layer and at the same time provides a passageway for the lower layer.
In accordance with one embodiment of the present disclosure, the slotted ring 20 facilitates in increasing the retention time of the upper layer on each of the plates 10. Due to this, the concentration of the aromatics in the upper layer increases.
In accordance with the present disclosure, the upper layer being lighter than the lower layer floats on the top of the lower layer, thereby increasing the retention time of the upper layer on each of the plates 10. This results in re-evaporation of the upper layer by prolonged contact of the upper layer with the gaseous mixture V coming out of the bubble-cap 14, thereby increasing the concentration of the aromatics in the upper layer.
In accordance with the present disclosure, at least one opening 16a,which is configured on the operative lower portion 16b of the weir 16, facilitates through-path of the lower layer (water) to the secondary conduit 18.
In accordance with the present disclosure, the secondary conduit 18 facilitates through-path for the lower layer between the consecutive plates. As the lower layer travels towards the operative lower portion of the distillation column Di, the purity of water increases (this signifies the separation of the aromatics from water).
In accordance with the present disclosure, the effluent stream (ES) is heated at a first pre-determined temperature ranging from 100 to 150ºC.
In accordance with the present disclosure, the effluent stream (ES) is heated at a pre-determined pressure ranging from 0.5 to 2 kg/cm2g.
In accordance with the present disclosure, the pre-determined flow-rate, at which the gaseous mixture V rises upwardly in the distillation column, is in such a manner that the “loading” of the distillation column diameter is 25 to 30 percent of the “flooding capacity”. The normal industry practice is 50 to 70 percent of flooding range. The velocity is dependent on temperature and pressure whereas “loading” is always at particular temperature and pressure.
In accordance with the present disclosure, the gaseous mixture V is cooled at the second pre-determined temperatureranging from 80 to 90 ºC.
The system and the process of the present disclosure,
o provides better contact of the condensate C and the vapours V;
o attenuates the dispersion and the intermixing of the upper layer (aromatics) and the lower layer (water);
o provides efficient separation of the upper layer and the lower layer;
o reduces the amount of benzene present in the effluent stream (in the range of 250 ppm to 25000 ppm) to approximately less than 10 ppm; and
o reduces the amount of the aromatics present in the effluent stream (in the range of 250 ppm to 50000 ppm) to approximately less than 20 ppm.
TECHNICAL ADVANCEMENT
The system and process for separating the aromatics from the effluent stream of the present disclosure, has several technical advantages including, but not limited to, the realization of a system and a process:
• that separates aromatics from an effluent stream effectively;
• that is reliable; and
• that is economical.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary.
In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principle of the invention. These and other modifications in the nature of the invention or the preferred embodiments will 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.