DESC:FIELD
The present disclosure relates to a process for reducing odor from odorous off-gas streams, particularly refinery off-gas streams.
DEFINITION
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which it is used indicates otherwise.
Off-gases refer to gases that are produced as a byproduct of an industrial process. The off-gases formed at refineries often contain components such as mercaptans, diolefins, olefins, CO2, CO, hydrocarbons, H2S, CS2 and various organic sulfur species etc, all of which are harmful to the environment and subject to increasingly stricter regulations.
Odorous compounds refer to the compounds such as hydrogen sulphide, mercaptans, ammonia, amines, aromatic hydrocarbons and the like causing bad odor.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
The refinery processes in petroleum industry lead to the generation of off-gases having an unpleasant odor. The odor is mainly caused by the presence of sulphur compounds, nitrogen compounds and hydrocarbons.
Conventionally, scrubbing or incineration techniques are implemented to control or reduce the odor. Another conventional approach is to chemically neutralize the odor-causing compounds present in such off-gases. Further, photo-catalytic decomposition of the odor causing components present in the diary, poultry and pig farms is disclosed.
However, these techniques are not only practically ineffective, tedious and costly but also environmentally unfavorable.
There is, therefore, felt a need for a simple and environmental-friendly process for effective reduction of odor from petroleum refinery off-gases.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide an economical and environment-friendly process for reducing odor from odorous off-gas stream.
Still another object of the present disclosure is to provide a simple apparatus for reducing odor from odorous off-gas 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 relates to a process for reducing odor from odorous off-gas stream.
The process comprises contacting said refinery off-gas stream at a predetermined flow rate with an adsorbent, in the presence of steam and UV radiations having wavelength in the range of 100 to 280 nm, at a predetermined temperature and at a predetermined pressure to obtain an odorless off-gas stream. The process involves passing the refinery off-gas stream through the reaction chamber containing the adsorbent at a flow rate is in the range of 200 to 300 mL/m, at temperature in the range of 30°C to 60°C, under pressure in the range of 1-2 bar. The adsorbent comprises a fibrous polymeric substrate uniformly dispersed with a photo-catalyst. The photo-catalyst is titanium oxide.
The concentration of odorous compounds in the odorless off-gas stream is less than 10 ppm.
The present disclosure further provides an apparatus for reducing odor from odorous off-gas stream. The apparatus comprises a reaction chamber equipped with a UV light source, inlet for off gas stream, inlet for steam, adsorbent trays and outlet for treated off gas stream.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a schematic representation of the process for reducing odor from odorous off-gas stream;
Figure 2 illustrates a gas chromatogram of Wet Air Oxidation (WAO) off gas stream before treatment; and
Figure 3 illustrates a gas chromatogram of Wet Air Oxidation (WAO) off gas stream after treatment.

DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and process, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the process and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The odorous off-gas stream generated by the petroleum refineries usually have a bad odor owing to the presence of odor-causing compounds such as hydrogen sulphide, mercaptans, ammonia, amines, aromatic hydrocarbons and the like. The conventional processes are associated with drawbacks such as they do not lead to complete decomposition of odorous compounds, use a large quantity of chemical reagents thereby generating a large amount of chemical waste and generation of air pollutants.
The present disclosure provides a simple, inexpensive and environment-friendly approach for reducing odor from odorous off-gas stream originating from petroleum refinery having the concentration of the odorous compounds more than 30 ppm.
The process comprises contacting said refinery off-gas stream at a predetermined flow rate with an adsorbent, in the presence of steam and UV radiations having wavelength in the range of 100 to 280 nm, at a predetermined temperature and at a predetermined pressure to obtain an odorless off-gas stream. The concentration of odorous compounds in the odorless off-gas stream is less than 10 ppm.
In an exemplary embodiment of the present disclosure, the concentration of odorous compounds in the odorless off-gas stream is less than 5 ppm.
In accordance with the embodiments of the present disclosure, the adsorbent is provided in a reaction chamber. The odorous off-gas stream is passed through the reaction chamber.
In accordance with the embodiments of the present disclosure, the predetermined flow rate is in the range of 200 to 300 mL/m; the predetermined temperature is in the range of 30°C to 60°C and the predetermined pressure is in the range of 1 bar to 3 bar.
In an exemplary embodiment of the present disclosure, the odorous off-gas stream is passed through the reaction chamber at a flow rate of 250 mL/m; at a temperature of 30°C and under pressure of 1 bar.
The adsorbent comprises a photo-catalyst uniformly dispersed in a spongy polymeric substrate. The photo-catalyst is titanium oxide and the polymeric substrate is raffia grade polymer fiber.
The present disclosure further provides an apparatus for reducing odor from odorous off-gas stream. The apparatus comprises a reaction chamber equipped with a UV light source, inlet for off gas stream, inlet for steam, adsorbent trays and outlet for treated off gas stream.
In accordance with the embodiments of the present disclosure, the UV light source is adapted to emit UV radiations having wavelength in the range of 100 to 280 nm.
In accordance with the embodiments of the present disclosure, the walls of the reaction chamber are coated with the photo-catalyst powder.
Typically, the ultraviolet light source is a UV lamp emitting radiations in the wavelength range of 100 nm to 280 nm.
The UV radiations initiates photo-catalytic process that causes decomposition of the odor causing compounds present in the odorous off-gas stream, thereby reducing the odor of the odorous off-gas stream.
In accordance with the present disclosure, the odorous off- gas streams such as Crude Distillation Unit (CDU) hotwell off gas stream; Wet Air Oxidation (WAO) off gas stream; Delayed Coker Unit (DCU) off gas stream; Sulfur Recovery Unit (SRU) off gas stream; and Slop Oil tank stream can be effectively treated by the process of the present disclosure to substantially reduce odor.
The process of the present disclosure is further described in detail with the help of Figure 1.
The odorous off-gas stream is passed through the reaction chamber (1) equipped with adsorbent plates (4) and UV lamp (5). The odorous off-gas stream is introduced at a constant flow rate in the range of 200 to 300 mL/m through an inlet (3). The temperature of the reaction chamber is maintained at 30 to 60°C. The reaction chamber (1) equipped with an inlet (2) for feeding steam to the reaction chamber (1) to maintain moist atmosphere in the chamber.
In the reaction chamber (1), UV radiations initiates photo-catalytic process that causes decomposition of the odor causing compounds present in the odorous off-gas stream. The treated stream with reduced odor is collected at outlet (6).
The process of the present disclosure is simple and economical. Moreover, the process does not require large quantities of chemical reagents and is more environmental friendly than the conventional techniques.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Experiment 1: Reducing odor from odorous off-gas stream
Wet air oxidation (WAO) off-gas stream comprising plurality of odorous compounds (given in table 1) was passed through reaction chamber (1) comprising adsorbent disks (4) and UV lamp (5). The odorous off-gas stream was introduced through inlet (3) at constant flow rate of 250 mL/m. The temperature of the reaction chamber was maintained at 30-60°C. Steam was introduced in to the reaction chamber (1) through inlet (2) in order to maintain moist atmosphere in the reaction chamber (1).
The treated off gas stream was collected at outlet (6) and further analysed for odorous compounds using Sulphur Chemiluminescence Detector (SCD) gas chromatography.
The results are tabulated in Table 1.
Odorous compounds Retention Time Before treatment After treatment
Area
(SCD gas chromatogram) Concentration ppm Area
(SCD gas chromatogram) Concentration, ppm
Hydrogen Sulphide 1.846 0 NIL 0 NIL
Carbonyl sulphide 2.02 10934 10.71 2870 2.81
Carbon disulphide 4.74 443 0.46 0 NIL
Methyl Mercaptan 2.86 64497 65 1669 1.68
Ethyl Mercaptan 4.03 5908 6.16 198 0.2
Experiment 2: Reducing odor from odorous off-gas stream
Similar procedure as disclosed in the experiment 1 was followed to reduce odor from the odorous crude distillation unit (CDU) off-gas stream.
The results are tabulated in Table 2.
Odorous compounds Retention Time Before treatment After treatment
Area Concentration, ppm Area Concentration, ppm
Hydrogen Sulphide 1.86 4737040 476 127395 128
Carbonyl sulphide 2.02 1041 1.02 305 0.32
Carbon disulphide 4.74 6300 6.55 4061 4.22
Methyl Mercaptan 2.85 903 0.91 401 0.40
Ethyl Mercaptan 4.05 614 0.64 323 0.34

From table 1 and table 2, it is evident that the process of the present disclosure effectively decomposes odorous compounds present in the odorous off-gas stream, thereby reducing odor from the off-gas stream.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for reducing odor from odorous off-gas stream produced in petroleum refinery processes, wherein the process:
- effectively reduces odor from odorous off-gas stream;
- is simple and economical; and
- is environment-friendly.
The embodiments herein and 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 examples used 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 the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments 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 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 disclosure 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 disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure 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 disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure 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 disclosure and not as a limitation.

,CLAIMS:WE CLAIM
1. A process for reducing odor from a refinery off-gas stream having the concentration of the odorous compounds greater than 30 ppm, said process comprising:
contacting said refinery off-gas stream at a predetermined flow rate with an adsorbent, in the presence of steam and UV radiations having wavelength in the range of 100 to 280 nm, at a predetermined temperature and at a predetermined pressure to obtain an odorless off-gas stream,
where in the concentration of odorous compounds in the odorless off-gas stream is less than 10 ppm.
2. The process as claimed in claim 1, wherein the concentration of odorous compounds in the odorless off-gas stream is less than 5 ppm.
3. The process as claimed in claim 1, wherein said predetermined flow rate is in the range of 200 to 300 mL/m.
4. The process as claimed in claim 1, wherein said predetermined temperature is in the range of 30 °C to 60 °C.
5. The process as claimed in claim 1, wherein said predetermined pressure is in the range of 1 bar to 3 bar.
6. The process as claimed in claim 1, wherein said adsorbent is provided in a reaction chamber and said refinery off-gas stream is passed through said reaction chamber.
7. The process as claimed in claim 1, wherein said adsorbent comprises a photo-catalyst dispersed in a spongy polymeric substrate.
8. The process as claimed in claim 7, wherein said photo-catalyst is titanium oxide.
9. The process as claimed in claim 7, wherein said polymeric substrate is raffia grade polymer fibers.
10. An apparatus for reducing odor from refinery off-gas stream, said apparatus comprising:
a reaction chamber equipped with a UV light source, an inlet for the off gas stream, an inlet for steam, adsorbent trays and an outlet for the treated off gas stream.
11. The apparatus as claimed in claim 10, wherein said UV light source is adapted to emit UV radiations having wavelength in the range of 100 to 280 nm.
12. The apparatus as claimed in claim 10, wherein walls of said reaction chamber are coated with a photo-catalyst powder.