Claims:1. A method for recovering liquid petroleum vapors contained in the air leaving a storage tank during transfer of liquid petroleum from a delivery tank to said storage tank, said method comprising the following steps:
• directing the air from said storage tank to a vapor recovery unit comprising a heat exchanger and a chiller with a coolant circulating therein;
• circulating said coolant through said heat exchanger and allowing the air to cool to a pre-determined temperature in said heat exchanger, thereby facilitating condensation of the petroleum vapors to obtain condensed liquid petroleum and the air with reduced content of liquid petroleum vapors; and
• collecting said condensed liquid petroleum in an auxiliary tank and optionally returning said condensed liquid petroleum from said auxiliary tank to said storage tank.

2. The method as claimed in claim 1, wherein the air with reduced content of liquid petroleum vapors is vented to the atmosphere from the vapor recovery unit.

3. The method as claimed in claim 1, wherein said coolant comprises a mixture of ethylene glycol and water.

4. The method as claimed in claim 2, wherein ethylene glycol in said mixture is present in an amount ranging from 25% to 35% of the total mixture.

5. The method as claimed in claim 1, wherein the temperature of the air entering said vapor recovery unit is in the range of 35ºC to 45ºC.
6. The method as claimed in claim 1, wherein said pre-determined temperature is in the range of 1ºC to 5ºC.

7. A system for recovering liquid petroleum vapors contained in the air leaving a storage tank during transfer of liquid petroleum from a delivery tank to said storage tank, said system comprising:
• a delivery conduit adapted for directing the liquid petroleum to said storage tank;
• a vapor recovery unit comprising said heat exchanger and a chiller, wherein said vapor recovery unit is adapted to cool the air from said storage tank to a pre-determined temperature in a heat exchanger, thereby facilitating condensation of the petroleum vapors to obtain condensed liquid petroleum and the air with reduced content of liquid petroleum vapors; and
• an auxiliary tank adapted for:
o receiving said condensed liquid petroleum from said vapor recovery unit; and
o optionally returning said condensed liquid petroleum to said storage tank.

8. The system as claimed in claim 7, includes:
• a first conduit adapted for venting the air from said storage tank to the atmosphere; and
• a second conduit adapted for venting the air with reduced content of liquid petroleum vapors from said vapor recovery unit to the atmosphere.

9. The system as claimed in claim 7, includes at least one valve adapted for controlling the flow rate of:
• the air from said storage tank to the atmosphere via said first conduit; and
• the air from said storage tank to said vapor recovery unit. , Description:FIELD
The present disclosure relates to a method and a system for recovering liquid petroleum vapors displaced during decantion.
DEFINITIONS
As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
Liquid petroleum – refers to petroleum distillates that are volatile in nature, for example, motor spirit.
Floating roof tank – refers to a storage tank having a roof that floats on the surface of the stored liquid.
Heat Exchanger – refers to an equipment built for efficient heat transfer from one medium to another.
Chiller – refers to an equipment that removes heat from a liquid via a vapor-compression or an absorption refrigeration cycle.
BACKGROUND
Liquid petroleum is volatile in nature and it is used as a fuel to drive internal combustion engines. The liquid petroleum being volatile in nature is stored in floating roof tanks that are constructed above the ground. However, at liquid petroleum filling stations, popularly known as “Petrol Pumps”, the liquid petroleum is stored in storage tanks that are underground.
The liquid petroleum is stored and transported in delivery tanks. The delivery tanks may be disposed on trucks. Conventionally, the liquid petroleum contained in the delivery tanks is transferred/decanted to the storage tanks via delivery pipes at the liquid petroleum filling stations. Transfer of the liquid petroleum from the delivery tanks is performed under gravity.
During the transfer of the liquid petroleum to the storage tanks, a portion of the air equivalent to the liquid petroleum to be decanted is displaced from the storage tanks and vented to the atmosphere through vent pipe installed at the liquid petroleum filling stations. Venting of the liquid petroleum vapors to the atmosphere, results in loss of the liquid petroleum from the storage tanks.
Research has shown that the air vented to the atmosphere from the storage tanks contains the liquid petroleum approximately in an amount in the range of 0.1% to 0.15% of the total liquid petroleum decanted in the storage tanks.
Further, the portion of the air vented to the atmosphere can cause damage to the environment, since the portion of the air contains the liquid petroleum vapors including hydrocarbons.
Thus, there is felt a need for a method and a system for obviating loss of liquid petroleum from storage tanks to the atmosphere.
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.
An object of the present disclosure is to provide a method and a system that obviates the loss of liquid petroleum from storage tanks to the atmosphere.
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 envisages a method for recovering liquid petroleum vapors contained in the air leaving a storage tank during transfer of liquid petroleum from a delivery tank to the storage tank. In order to recover the liquid petroleum vapors, an equivalent amount of air from the storage tank is directed to a vapor recovery unit. The vapor recovery unit comprises a heat exchanger and a chiller with a coolant circulating therein. The coolant is circulated through the heat exchanger, to cool the air to a pre-determined temperature in the heat exchanger, thereby facilitating condensation of the liquid petroleum vapors to obtain condensed liquid petroleum and the air with reduced content of liquid petroleum vapors. The condensed liquid petroleum is then collected in an auxiliary tank and the collected condensed liquid petroleum is optionally returned to the storage tank. The air with reduced content of liquid petroleum vapors is vented to the atmosphere from the vapor recovery unit.
The system for recovering petroleum vapors contained in the air leaving a storage tank during transfer of liquid petroleum from a delivery tank to the storage tank is also provided.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
A method and a system for recovering liquid petroleum vapors contained in the air leaving a storage tank during transfer of liquid petroleum from a delivery tank to the storage tank in accordance with the present disclosure will now be described with the help of the accompanying drawing, in which:
FIG 1 illustrates a system for recovering liquid petroleum vapors in accordance with the present disclosure.
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 way of example and illustration.
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 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.
Mostly, when liquid petroleum is transferred from delivery tanks to storage tanks, a portion of the air contained in the storage tanks is displaced and vented to the atmosphere. This results in loss of the liquid petroleum from the storage tanks. Further, the liquid petroleum vapors vented to the atmosphere can cause damage to the environment.
In order to obviate the loss of the liquid petroleum from the storage tanks to the atmosphere, there is a need to recover the liquid petroleum vapors from the air leaving the storage tanks.
The present disclosure, therefore, provides a method and a system for recovering the liquid petroleum vapors contained in the air leaving the storage tanks during the transfer of the liquid petroleum from the delivery tank trucks to the storage tanks.
The system 100 of the present disclosure is depicted in FIG.1. In accordance with the present disclosure, the system 100 comprises:
• a delivery tank 2 adapted for storing and transporting the liquid petroleum;
• a delivery conduit 4 adapted for directing the liquid petroleum from the delivery tank 2 to a storage tank 6;
• the storage tank 6 adapted for storing the liquid petroleum;
• a vapor recovery unit 8, that includes a heat exchanger 8a and a chiller 8b, wherein the vapor recovery unit 8 facilitates cooling of the air to a pre-determined temperature, thereby facilitating condensation of the liquid petroleum vapors to obtain condensed liquid petroleum and the air with reduced content of liquid petroleum vapors; and
• an auxiliary tank 10 adapted for:
o receiving the condensed liquid petroleum from the vapor recovery unit 8; and
o returning the condensed liquid petroleum to the storage tank 6.
The system 100 of the present disclosure also comprises:
• a first conduit 12a adapted for venting the air from the storage tank 6 to the atmosphere at the time of decanting;
• a second conduit 12b adapted for venting the air with reduced content of liquid petroleum vapors from the vapor recovery unit 8 to the atmosphere;
• a plurality of valves 14a, 14b and 14c, that is adapted for controlling the flow rate of:
o the air from the storage tank 6 to the atmosphere via the first vent conduit 12a;
o the air from the storage tank 6 to the vapor recovery unit 8 via a closed conduit 7; and
o the condensed liquid petroleum from the auxiliary tank 10 to the storage tank 6.
Additionally, the chiller 8b comprises a pump (not shown in FIG.1) adapted for circulating the coolant through the heat exchanger 8a.
In accordance with the present disclosure, the heat exchanger 8a does not have any moving parts and electrical connections.
Typically, the heat exchanger 8a is a plate heat exchanger.
The method of the present disclosure is carried out in the following steps:
• in the first step, the air leaving the storage tank 6 is directed via the closed conduit 7 to the vapor recovery unit 8 that comprises the heat exchanger 8a and the chiller 8b with the coolant circulating therein;
• in the second step, the coolant from the chiller 8b is circulated in the heat exchanger 8a, to cool the air to a pre-determined temperature in the heat exchanger 8a, thereby facilitating condensation of the liquid petroleum vapors to obtain condensed liquid petroleum and the air with reduced content of liquid petroleum vapors; and
• in the third step, the condensed liquid petroleum from the heat exchanger 8a is collected in the auxiliary tank 10. From the auxiliary tank 10, the condensed liquid petroleum is optionally returned to the storage tank 6.
In accordance with the present disclosure, the temperature of the air entering the vapor recovery unit 8 is in the range of 35ºC to 45ºC.
In accordance with the present disclosure, the chiller 8b includes a coolant comprising a mixture of ethylene glycol and water.
Typically, the coolant facilitates cooling to subzero temperatures.
In accordance with the present disclosure, the temperature of the coolant circulated through the heat exchanger 8a is in the range of -4ºC to -8ºC.
In accordance with the present disclosure, 25 % ethylene glycol mixed with water is used to circulate through the heat exchanger 8a.
In accordance with the present disclosure, the pre-determined temperature, to which the air is cooled in the heat exchanger 8a, is in the range of 1ºC to 5ºC.
The method and the system of the present disclosure can be used during the transfer of the liquid petroleum from the delivery tank 2 to the storage tank 6.
The method and the system of the present disclosure are capable of:
o recovering approximately 0.1% liquid petroleum (of the total liquid petroleum decanted in the storage tank 6) in the air leaving the storage tank 6; and
o obviating the release of the liquid petroleum into the environment, thereby preventing harm to the environment.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a method and a system that:
o obviates the loss of the liquid petroleum from the storage tank;
o recovers approximately 0.1% liquid petroleum; and
o obviates the release of the liquid petroleum into the environment, thereby preventing harm to the environment.
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 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.