MXPA00003663A - Vapor recovery system employing oxygen detection - Google Patents

Abstract

A vapor recovery system (18) is provided to direct measurements of the oxygen concentration within vapor emissions displaced from a fuel tank (10) during refueling to adjust the operating speed of a vapor pump (26).

Description

VAPOR RECOVERY SYSTEM USING DETECTION OF OXYGEN BACKGROUND OF THE INVENTION 1. Field of the invention. The present invention deals with vapor recovery systems used in connection with fuel dispensing devices, and, more particularly, with a method and system for monitoring the recovered vapor emissions and adjusting the flow velocity of the pumped vapors to eliminate the uptake excessive air 2. Description of the related art. The evaporative properties of the liquid fuel create a vapor condition inside the fuel tanks of the vehicles where a volume of volatilized fuel lies on the volume of liquid fuel. During the course of refueling the vehicle, the gasoline flowing into the fuel tank displaces the existing fuel vapor and causes vapors that are harmful to the environment to be forced out of the tank and into the atmosphere unless measures are followed. of precaution to capture and eliminate vapors released. The increase in public awareness of the adverse consequences to the environment and health has encouraged government authorities to request the design of fuel distribution systems to eliminate the release of vapors into the atmosphere by collecting vapors for storage and possible recycling. These concerns have led to the development of various systems designed to capture and return the emissions of vapors given off to a storage tank, which typically corresponds to the underground installation located in the service station where the fuel supply is maintained. The vapors recovered can then be transported to a processing site where the vapors are returned to the liquid form in a recycling operation or otherwise disposed of by appropriate means. A class of conventional vapor recovery systems uses a vacuum pump to assist in the capture of fuel vapors and their subsequent transfer to a storage tank. The vacuum pump sucks the volatile vapors in an intake line that transports the captured vapors back to the storage tank. The suction action generated by the vacuum pump is normally sufficient to capture the vapor emissions, thus making obvious the need for any sealing element such as a bellows element that is otherwise used to surround the nozzle and seal the vapor recovery duct to the fuel intake neck of the tank. The intake port of the vapor intake line only needs to be located near the intake neck of the fuel tank from which the vapors emanate. It is very important in all these vacuum assisted vapor recovery systems that the volume of the gas mixtures drawn through the vapor recovery vacuum intake pipe is very close to the volume of steam that is displaced by the flowing gasoline. to the fuel tank. If the volume of vapor that is being captured is less than that which is being displaced, the unrecovered portion will dissipate in the atmosphere. On the contrary, if the volume of steam that is being captured is greater than that which is being removed from the tank, the excess volume will consist of atmospheric air that is recovered together with the vapors. Both conditions must be avoided. Several configurations have been proposed that focus on making adjustments calculated for the flow velocity generated by the vacuum pump in the measurements produced by detector devices that monitor the fuel supply and vapor recovery operations. U.S. Patent No. 5,355,915 for Payne reveals a fuel distributor with vapor recovery that includes a steam pump driven by an electric motor. The sensors are provided to generate pulse train signals representative of the flow rate of the liquid fuel pump and the steam pump. A controller is provided to control the speed of the steam pump based on the comparison of the flow rates of the liquid fuel pump and steam pump, as indicated by their respective pulse train signals. The controller also monitors whether the liquid pump is operating, whether the steam pump motor is running and the electric current for the steam pump motor. The appropriate action is taken by the controller to deactivate the steam pump when the parameters being monitored indicate a deactivation or error condition. U.S. Patent No. 5,417,256 for Hartsell et al. discloses a fuel distribution system that includes a steam pump that provides vacuum suction along a main vapor recovery route. The system also includes a bifurcated tube coupled with the main vapor path to provide a bifurcated vapor recovery path, and an adjustable vapor flow valve integrated into the bifurcated tube and having an adjustable opening, which varies the impedance of the route of vapor recovery. A fuel sensor is provided to generate a signal representative of the flow velocity of the fuel being dispensed, while a vapor flow sensor supplies a signal indicative of the actual vapor flow rate. A controller responds to the flow rate signal for the distributed fuel and generates a control signal to adjust the vapor flow valve so as to balance the actual vapor flow rate at a required or desired vapor flow rate. calculated on the basis of the flow velocity of the liquid fuel and a comparison based on a relationship between the temperatures of the liquid fuel and the atmosphere. U.S. Patent No. No. 5,040,577 to Pope discloses a fuel delivery system comprising a set of vapor recovery elements that includes a recovery pump that aspirates the vapor emissions issued through a recovery tube in accordance with a controllable volumetric flow rate. A microprocessor is provided to control the recovery pump so that it sucks the steam at a flow rate equal to the volumetric flow rate of the fuel delivery pump that regulates fuel distribution. Other adjustments can be made to the vapor flow rate in response to the data provided by the pressure sensors indicating the hydraulic pressure on the intake side of the pump. U.S. Patent No. 5,269,353 to Nanaji et al. discloses an apparatus for pumping vapor recovered in a liquid fuel distributor with vapor recovery having a vapor passage that is used to recover the vapors from the fuel. The apparatus includes a steam pump whose operation induces the vapors to enter and traverse the vapor passage and through a steam pump inlet to a steam pump outlet. The vapor pump is characterized by a flow velocity correlated with a specified operating speed that is inversely proportional to the differential pressure that exists between the inlet and outlet of the steam pump. The sensors are provided to generate signals representative of these vapor pump pressures. A transducer generates a liquid fuel flow signal indicative of the flow velocity for the fuel being distributed. The electronic circuits are provided to derive the flow rate of the steam pump from the differential pressure and then implement the appropriate settings to the operating speed of the steam pump so that the steam pump flow rate equals to the speed of liquid fuel flow. The above systems are almost exclusively related to the adjustment of the flow velocity of the vapors based on measurements that are not directly probative nor indicative specifically of the concentration of hydrocarbons of the recovered vapors. Any necessary adjustments are made in response to direct measurements of the volumetric flow rates of the fuel being distributed and the vapors drawn, measures that are then used to determine the specific change that is required in the speed of operation of the steam pump in order to equalize the flow velocity of vapors with the speed of liquid fuel. The general purpose of tracking the vapor flow rate for the liquid fuel velocity is to ensure that the volumetric volume of vapor recovered is the same as the volumetric quantity of the vapor that is being displaced by the distributed fuel. However, the only true measure of performance is based on whether and to what extent it is preventing excess air from being pumped into the vapor recovery line along with vapor emissions. Measured against this performance standard, the accuracy of the above systems is not possible to verify, and is potentially inaccurate, since measurements of the recovered vapor have not been obtained to determine its hydrocarbon or air content. U.S. Patent No. 5,507,325 for Finlayson reveals a vapor recovery system for fuel distributors that incorporates a measurement of a vapor-to-air ratio in its control device that regulates the process of vapors recovery. The vapors that move from the tank are collected through a vapor intake orifice and are pumped by a variable speed vacuum pump to a vapor storage tank. A flow meter produces a signal representative of the liquid fuel flow velocity. A series of vapor-to-air ratio sensors are provided to produce signals representative of the vapor-to-air ratio as measured in a variety of locations that are close to the tank orifice. The sensors used by the Finlayson reference operate specifically to detect the physical presence of fuel vapors in the detection environment. A controller is provided to determine a base pickup speed (based on the liquid fuel flow rate) in which to operate a steam pump, whose base pump speed is then adjusted according to the signals generated by the sensors of Vapor-air ratio in order to minimize the amount of fuel vapor escaping into the atmosphere and minimize the amount of air contained in the gas mixture that is sucked along the vapor intake line. The Finlayson vapor recovery system is an advance over the systems described above as it provides an element by means of which the content of the composition of the recovered emissions (ie vapor against air) can be directly measured. This allows a more accurate assessment of whether the steam pump is inducing the correct volumetric flow of the volatile emissions in the recovery line. However, there are problems in the Finlayson system that stem from the fact that the sensors are specifically designed to detect the presence of fuel components. The condensation of vapors within the intake line is a recurring problem that arises when temperature and pressure differentials within the vapor recovery system reach the threshold conditions. Accumulation or even transient deposition of condensed fuel vapors in the sensing sensors will produce false readings of the fuel content in the monitored environment and lead to incorrect adjustment of the steam pump speed. In addition, any determination of air content, which provides only the most accurate measure of the efficiency of the vapor recovery process, is based on a calculation and not a real physical reading. Therefore what is needed in the art is a system that monitors the ephemeral vapor emissions that move from a tank during the fuel supply and that adjusts to the speed of vapor recovery based on the direct measurements of the concentration of air in the monitored environment, from which a concentration of hydrocarbons can be derived and used to properly vary the speed of operation of the steam pump. SUMMARY OF THE INVENTION The present invention provides a vapor recovery system that monitors the recovered vapor emissions and generates detection data that indicate the concentration of oxygen in the vapor stream. This measure is then used as the basis for deriving the concentration of hydrocarbons. The speed of operation of the steam pump is adjusted according to the concentration derived from hydrocarbons. The invention comprises, in a form thereof, a vapor recovery system, operatively associated with a fuel distribution element having a nozzle for delivering the fuel in a receiving tank through the nozzle, comprising an element of vapor collection, a detection element and a controlling element. The vapor collection element, which is positioned near the nozzle of the fuel distributing element, variably collects the vapors from the receiving tank. The sensing element, located near the nozzle of the fuel distributing element, detects an oxygen concentration in the vapors of the receiving tank. The controlling element, which is operatively connected to the vapor capture means and responds to the concentration of oxygen detected by the sensor element, controls the speed of the steam collection by means of the vapor collection element as a function of the concentration of the vapor. oxygen detected. The controlling element includes a fuel concentration element, sensitive to the concentration of oxygen detected by the sensor element, to determine a concentration of hydrocarbons in the vapors of the receiving tank, as it is derived from the concentration of oxygen detected. The controlling element also includes a vapor velocity determining element, sensitive to the concentration of hydrocarbons determined by the fuel concentration element, to generate a control signal applied to the vapor capture element and representative of a rate of capture of the vapor. vapors that is effective to minimize the presence of oxygen in the vapors collected by the vapor collection element.

The vapor collection element comprises a vapor admission element, integrally associated with the fuel distributing element and having a vapor inlet orifice positioned near a terminal portion of the nozzle and also having a vapor outlet orifice. , to provide a passage of vapors between the vapor inlet orifice and the vapor outlet orifice. The vapor collecting element further comprises a controllable steam pump element, coupled to the vapor intake element, to controlly generate a variable vacuum action within the vapor intake element which is effective for sucking the vapors in the duct of vapors through the vapor inlet hole. The invention comprises in another form thereof, a system for supplying fuel to a receiving tank, comprising a fuel distributing element, a vapor collecting element, a sensor element and a control element. The fuel distributor element, which operates to draw fuel from a supply tank and has a nozzle, distributes fuel through the nozzle into an intake of the receiving tank. The vapor collection element, which is positioned near the nozzle of the fuel distributing element, collects the vapors from the receiving tank at an adjustable flow rate. The sensing element, which is positioned near the nozzle of the fuel distributing element, detects an oxygen concentration in the vapors of the receiving tank. The control element, operatively linked to the vapor capture element and sensitive to the concentration of oxygen detected by the sensor element, adjusts the flow velocity of the vapor collection element according to the oxygen concentration detected. The control element includes a fuel bypass element for deriving a concentration of hydrocarbons in the vapors collected by the vapor collection element based on the detected oxygen concentration and a vapor velocity adjustment element for adjusting the speed of the vapor. flow of the vapor collection element according to the concentration derived from hydrocarbons. The flow rate adjustment provided by the vapor velocity adjustment element is operative to reduce the presence of oxygen in the collected vapors. The vapor collection element includes a steam pump to controllably generate a variable vacuum action that is effective to suck the vapors into the passage. The invention comprises, in yet another form thereof, a method for recovering vapors from a fuel storage tank, comprising the steps for collecting the vapors under the influence of a controllable pumping action that generates a vapor flow rate adjustable; detect an oxygen concentration in the vapors; and controlling the pumping action to adjust the flow velocity of the vapors according to the oxygen concentration detected. The step to control the pumping action includes the steps to derive a concentration of hydrocarbons in the vapors based on the concentration of oxygen detected; and adjusting the steam flow rate as a function of the concentration derived from hydrocarbons to minimize the presence of oxygen in the vapors collected. The vapor capture step includes the step of providing an operating steam pump for sucking vapors in accordance with a controllable operating speed. The invention, in yet another form thereof, comprises a method for supplying a tank with fuel, comprising the steps for distributing fuel in the tank; Vacuum the vapors from the tank according to an adjustable flow rate; detect an oxygen concentration in the vapors from the tank; and adjust the flow velocity to aspirate the vapors from the tank as a function of the oxygen concentration detected. The flow rate adjustment step includes the steps for deriving a concentration of hydrocarbons in the vapors based on the concentration of oxygen detected; and adjust the flow velocity as a function of the concentration of hydrocarbons derived to minimize the presence of oxygen in the vapors inhaled. The step for sucking the vapors from the tank includes the step to provide a working steam pump for the suction vapors according to a controllable operating speed. An advantage of the present invention is that by measuring the hydrocarbon indirectly through the measurement of available oxygen, instead of measuring the hydrocarbon directly within the vapor recovery line, a more stable and improved measurement is provided. Another advantage of the present invention is that the developed system reduces the interactions between the assisted vapor recovery systems and the on-board fuel recovery systems (ORVR). BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned characteristics and other characteristics and advantages of this invention, and the way to obtain them, will be more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention. taken in conjunction with the corresponding drawings in which: Figure 1 is a block diagram of the illustration of a vapor recovery system according to the present invention; and Figure 2 is a graph illustrating a representative temporal response profile indicating an oxygen concentration with time ratio that is measured by the oxygen detection unit employed in the vapor recovery system of Fig. 1. The corresponding reference characters indicate the corresponding parts along several views. The exemplification set forth herein illustrates a preferred embodiment of the invention, in one form, and such exemplification should not be construed as limiting the scope of the invention in any way. DETAILED DESCRIPTION OF THE INVENTION Fig. 1 illustrates, a block diagram form, a system for fueling a tank 10 with liquid fuel from a supply tank 12 using a fuel delivery system 14 and for collecting and transferring the fuel. ephemeral vapor emissions from tank 10 to a storage facility 16 using a vapor recovery system 18 according to the present invention. The illustrated system applies particularly to consumer-activated fuel supply operations. Accordingly, in these applications, the tank 10 corresponds to the fuel tank of a vehicle and the supply tank 12 corresponds to the fuel storage chamber typically located in an underground area on the property of a service station.

This is standard in the industry for recovered vapors that are to be directed back to the supply tank 12, avoiding the need for any separately constructed vapor storage facility 16. The fuel delivery system 14 includes a delivery apparatus of fuel 20 attached to a supply tank 12 and operative for pumping the liquid fuel from the supply tank 12 along the fuel line 22. The system 14 further includes a set of fuel distributing elements 24 attached with an apparatus of fuel delivery 20 and adapted with coupling capability with an opening of the tank 10 for distributing the liquid fuel pumped into the tank 10. In automotive applications, the fuel distributor assembly 24 will be preferably configured in the form of a nozzle having a distribution portion that can be inserted, at least in part, into a filling mouth which defines the fuel recharge inlet passage of the tank 10. The fuel delivery system 14 is well known in the art by the experts and is generally representative of any arrangement capable of delivering fuel to the tank 10. The interior of the tank 10 will usually consist of a quantity of liquid fuel, with the remainder of the volume occupied by volatile fuel vapors. The process for distributing liquid fuel that will be displaced and forced out of the tank 10 by the same through its fuel refill orifice. The vapor recovery system 18 of the present invention is designed to capture these displaced ephemeral vapor emissions while minimizing the collection of atmospheric air. The illustrated vapor recovery system 18 includes a steam pump 26, a controller 28 and an oxygen detection unit 30. In brief, the system 18 operates so that the vapor emissions displaced from the tank 10 are captured under the influence of a vacuum action generated by the steam pump 26, producing a flow of volumetric steam whose speed is regulated by the controller 28 in response to the level of oxygen concentration present in the vapor emissions detected by the oxygen detection unit. The steam pump 26 is coupled to a vapor passage represented by the vapor intake line 32, which is positioned in a sufficiently close relationship relative to the tank opening 10 so that substantially all of the displaced vapors can be recovered at through a vapor intake line 32. The vapor passage can be formed as an annular conduit concentrically placed around the of the liquid fuel line transporting fuel to the tank 10, and preferably extending from the supply tank 12 to a termination point at or near the nozzle orifice where the fuel emerges. It should be obvious to those skilled in the art that any type of steam admission arrangement can be adapted for use in conjunction with the present invention, including, for example, a vapor pipe that traverses the interior of the fuel supply hose. The vapor pump 26 creates a vacuum or suction action that induces vapor emissions to approach the intake port of the steam intake line 32 to be sucked into line 32 and transported to the vapor storage facility 16. The suction action induced by the vapor pump 26 generates a volumetric flow within the line 32 which is regulated by the speed of operation of the vapor pump 26. This operating speed is controlled in an adjustable manner by a signal of control generated by the controller 28. Accordingly, the vapor pump 26 produces a volumetric vapor stream within the vapor intake line 32 which is characterized by a variable flow rate that can be controlled. The oxygen detection unit 30 monitors the environment of the emissions close to the opening of the tank 10 and general the signals 34 indicating the level of oxygen concentration in the monitored environment. Depending on the number of monitoring sites desired, the oxygen detection unit 30 may comprise one or a plurality of oxygen sensing elements. Each oxygen sensor provides a direct measure of the oxygen concentration in the monitored environment. Any suitable type of oxygen sensor known to those skilled in the art can be used. For example, one type of detection unit is the Figaro GS oxygen sensor, which generates an electric current flowing between terminal electrodes that is proportional to the concentration of oxygen in the mixture of gases to be measured. The change in the output voltage through a resistor through which the current flows is representative of the oxygen concentration. A characteristic of the vapor environment is that the presence of hydrocarbons in the fuel reduces the amount of oxygen available in a given sample of air, thus suggesting a mechanism by means of which the concentration of hydrocarbons can be determined from the measurements to oxygen. In particular, the direct measurement of the oxygen concentration according to the oxygen sensor is a sufficient basis from which the concentration of hydrocarbons can be derived. This indirect measure is a reliable indicator of the concentration of hydrocarbons since, as is known, variations in the concentration of hydrocarbons will directly influence the concentration of oxygen. Determine and then evaluate these levels of concentration is an important aspect of the entire methodology to optimally regulate the flow rate generated by the vapor pump 26. As discussed below, the interpretation of the oxygen concentration data is carried out by the controller 28, which initiates the necessary action indicated to adjust the operating speed of the vapor pump 26. The controller 28 receives as input signals the detection data 34 from the oxygen detection unit 30, whose data represents the oxygen concentration level measured in the analyzed environment, and controls the speed of operation of the vapor pump 26 according to a concentration derived from hydrocarbons of the oxygen concentration. More specifically, the controller 28 is provided with a processing unit that derives the concentration of hydrocarbons from the oxygen concentration data and then determines the flow velocity that the vapor pump 26 must generate, using the concentration level derived from hydrocarbons as the basis for determining the flow velocity. This determination of the flow velocity is affirmed on a performance objective aimed at minimizing the presence of oxygen in the vapor stream collected. The vapor flow rate in general must have a direct relationship with the level of hydrocarbon concentration. For example, at low levels of hydrocarbon concentration, a reduced flow velocity is indicated in order to eliminate or at least minimize the recovery of excess oxygen. It may even be desirable to completely deactivate the steam pump 26 (ie, suspend its pumping action) if the hydrocarbon concentration level falls below a non-zero threshold value that appears to represent an operational baseline. In sum, the controller 28 determines what adjustment must be made to the operating speed of the steam pump 26 to effect the required change in the induced flow rate. The controller 28 provides a signal generator for converting the pump speed adjustment data to a pump control signal 36 representative of the required flow rate and suitable for varying the operating speed of the vapor pump 26. The vapor pump 26 is sensitive to the pump control signal 36 provided by the controller 28 and adjusts its operating speed, and therefore the induced vapors flow rate, according to the pump control signal 36. The flow rate of the steam pump in general will be subjected to reduction or termination with increasing levels of detected oxygen concentration, which indicates a reduction in the concentration of the hydrocarbons. Conversely, at low concentration levels that indicate a hydrocarbon-rich environment, it may be desirable to increase the flow velocity to ensure that hydrocarbon emissions are not escaping into the environment. The vapor recovery system 18 has the ability to provide protection against excessive increases in flow velocity since any increase in excess of the operating speed of the particular pump at which the entire volume of displaced vapors is being recovered will be detected. by the oxygen sensors as an increase in the measured oxygen concentration, which will automatically indicate the controller 28 to reduce the operating speed of the vapor pump 26. This process continues until the optimum flow rate corresponding to a presence is reached minimum oxygen in the monitored vapors. The individual oxygen sensors of the oxygen detection unit 30 can be placed at several detection sites. For example, in order to obtain a measurement of oxygen concentration inside the tank, the oxygen sensors can be installed in any portion of the nozzle that is placed inside the tank 10 when the nozzle is coupled to the opening of the tank to distribute the fuel. In addition, the oxygen sensors can be placed within the vapor intake line 32 in order to detect the oxygen concentration of the recovered vapors. A series of oxygen sensors located at several detection sites has the ability to generate an oxygen concentration profile based on the position that can be used by the controller 28 to provide highly accurate regulation of the vapor pump 26. The sensors of Oxygen can be protected with demisting pads or other suitable protective material to immunize the sensors for the presence of condensed vapor in the recovery line. The oxygen sensors are adapted to transmit their detection measurements in a communication link for the controller 28, which together with the vapor pump 26 is preferably located inside the kiosk of the station serving the customer. It is preferable for the entire series of oxygen sensors that will be integrated into the fuel delivery system 14, contrary to the impractical approach of upgrading fuel tanks with oxygen sensors. The controller 28 can be any suitable device or component to implement the indicated control functions. For example, the controller 28 may be an analog control circuit or a programmable digital microprocessor as is known to those skilled in the art.

The necessary interconnections and interfaces between the subsystems of the vapor recovery system 18 are conventional series known to those skilled in the art. The steam recovery system 18 operates preferably on a continuous basis for the duration of any fuel refilling activity. This operating mode will present a continuous supply of oxygen concentration signals to the controller 28 from the series of oxygen sensors and the automatic adjustment of the operating speed of the steam pump 26 based on the concentration derived from hydrocarbons. The flow velocity generated by the vapor pump 26 is therefore continuously regulated to minimize the presence of atmospheric air in the vapors collected. Figure 2 is a graph showing the output voltage of oxygen sensors against time to illustrate the chain oxygen concentration detected in response to variations in hydrocarbon concentration. While this invention has been described as a preferred design, the present invention may have other modifications within the spirit and scope of this disclosure. This application therefore covers any variation, use or adaptation of the invention using its general principles. Furthermore, this application covers said modifications of the present disclosure as they come within the practice known or accustomed in the art to which this invention pertains and which falls within the limits of the appended claims.

Claims (19)

CLAIMS: 1. A steam recovery system, operatively associated with a fuel distributor element having a nozzle for delivering fuel to a receiving tank through the nozzle, comprising: vapor collection element, placed near the nozzle of the fuel distributor element, to alternately capture the vapors of the receiving tank; detector element, placed near the nozzle of the fuel distributing element, to detect an oxygen concentration in the vapors of the receiving tank; and controlling element, operatively connected to the vapor collecting element and responsive to the oxygen concentration detected by the detector element, to control the speed of the vapor uptake by the vapor collecting element as a function of the oxygen concentration detected. 2. The vapor recovery system according to the
1. Claim 1, wherein the controlling element includes: fuel concentration element, with response to the concentration of oxygen detected by the detector element, to determine a concentration of hydrocarbons in the vapors of the receiving tank, as deduced from the concentration of oxygen detected; and vapor velocity determining element, with response to the concentration of hydrocarbons by the fuel concentration element, to generate a control signal applied to the vapor capture element and representative of an effective vapor capture rate to minimize the presence of oxygen in the vapors collected by the vapor collection element. 3. The vapor recovery system according to claim 1, wherein the vapor collection element comprises: vapor intake element, integrally associated with the fuel distributing element and having a vapor inlet orifice placed close to the vapor. a terminal portion of the nozzle and further having a vapor exit orifice, to provide a passage for vapors between the vapor inlet orifice and the vapor exit orifice; and controllable steam pump element, attached to the vapor admission element, to generate with control capacity a variable vacuum action within the vapor intake element that is effective for the aspiration of the vapors in the passage of vapors through from the inlet of the vapors. 4. The vapor recovery system according to claim 3, wherein the controlling element includes: vapor flow rate control element, attached to the controllable steam pump element and responsive to the oxygen concentration detected by the element sensor, now vary the vacuum action of the steam pump element according to the concentration of oxygen detected. The vapor recovery system according to Claim 3, wherein the sensing element includes: an oxygen sensor for detecting the concentration of oxygen within the vapor passage of the vapor intake element. 6. The vapor recovery system according to claim 3, wherein the detector element includes: an oxygen sensor for detecting oxygen concentration within an interior space of the receiving tank. The vapor recovery system according to Claim 3, wherein the oxygen sensor is integrally secured to the nozzle of the fuel distributing element and properly positioned so that it is placed inside the receiving tank when the nozzle is attached to an opening of the receiving tank during fuel supply operations. 8. The vapor recovery system according to claim 3, wherein the sensing element includes: an oxygen sensor that senses the concentration of oxygen outside an opening of the receiving tank where the fuel is emptied by means of the distributing element. gas. 9. The vapor recovery system according to Claim 8, wherein the oxygen sensor is integrally secured to the nozzle of the fuel distributing element. 10. A system for supplying fuel to a receiving tank, comprising: fuel dispensing element, operative to take fuel out of the supply tank and having a nozzle to distribute the fuel through the nozzle in an inlet of the receiving tank; - Vapor capture element, placed near the nozzle of the fuel distributor element, to collect the vapors of the receiving tank at an adjustable flow rate; detector element, placed near the nozzle of the fuel distribution element, to detect an oxygen concentration in the vapors of the receiving tank; and control element, operatively coupled to the vapor capture element and responsive to the concentration of oxygen detected by the detector element, to adjust the flow rate of the collection element according to the oxygen concentration detected. The fuel supply system according to Claim 10, wherein the control element includes: fuel bypass element for deriving a concentration of hydrocarbons in the vapors collected by the vapor collection element based on the oxygen concentration perceived and vapor velocity adjustment element for adjusting the flow velocity of the vapor collection element according to the concentration of hydrocarbons derived therefrom. The fuel supply system according to Claim 11, wherein the flow rate adjustment provided by the vapor velocity adjustment element is operative to reduce the presence of oxygen in the collected vapors. 13. The fuel supply system according to claim 12, wherein the vapor collection element includes: vapor-pumping element to generate with control capability a variable vacuum action that is effective for sucking vapors in a vapor passage . 14. A method for recovering vapors from a fuel storage tank, comprising the steps of: collecting the vapors under the influence of a controllable pumping action that generates a vapor flow rate; detect an oxygen concentration of the vapors; and controlling the pumping action to adjust the flow velocity of the vapors according to the oxygen concentration detected. The method for recovering vapors according to Claim 14, wherein the step for controlling the pumping action includes the steps for: deriving a concentration of hydrocarbons in the vapors based on the concentration of the oxygen detected; and adjust to vapor flow rate as a function of the concentration of hydrocarbons derived to minimize the presence of oxygen in the vapors collected. 16. The vapor recovery method according to Claim 15, wherein the step of capturing the vapors includes the step to: provide an operating steam pump for sucking vapors in accordance with a controllable operating speed. 17. A method of refueling a tank, comprising the steps to: distribute the fuel in the tank; suction the tank vapors according to an adjustable flow rate; detect an oxygen concentration in the vapors from the tank; and adjust the flow rate to suck the vapors from the tank as a function of the oxygen concentration detected. 18. The fuel supply method according to Claim 17, wherein the step of adjusting the flow rate includes the steps for: deriving a concentration of hydrocarbons in the vapors based on the concentration of oxygen detected; and adjusting the flow velocity as a function of the concentration of hydrocarbons derived to minimize the presence of oxygen in the sucked vapors. 19. The fuel supply method according to Claim 18, wherein the step for sucking the vapors from the tank includes the step to: provide an operating steam pump for sucking vapors in accordance with a controllable operating speed.