Method of recovering vapors emitted when a liquid is dispensed

(10) Number:

AT 409 486 B (19)

REPUBLIC

AUSTRIA

Patent office ₍₁₂₎ PATENT WRITING (21) Application number: A713 / 99 (51) IntCl.⁷: B67D 5/378 (22) Filing date: 04/22/1999 B67D 5/08 (42) Start of patent term: 01/15/2002 (45) Date of issue: 08/26/2002 (30) (56)

Priority:

04/24/1998 FR 9805196 claimed. Citations:

DE4431547C1 EP315738A2 US3826291A US 4306594A (73) Patent owner:

TOKHEIM SERVICES FRANCE F-92350 LE PLESSIS ROBINSON (FR).

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PROCESS FOR RECOVERING LEAKED VAPORS DURING LIQUID DISTRIBUTION

The method is used to recover vapors emitted during the distribution of a liquid, for example during the distribution of fuel, in a device comprising:

Means for distributing the liquid,

Means for measuring the liquid throughput Ql,

Means for recovering the vapors with a steam flow rate Q_v, controlled by a specific size g of these recovery agents,

Means for measuring the steam flow rate Q_v.

The process includes steps that consist of:

carry out an initial calibration of the recovery means by air suction, for each value g ° of g the air flow rate Q_v, is measured to create a table To:

T "= [g⁰,, Qd for every distribution n:

. gradually the liquid throughput Q_L. measured and a value g '¹, of g with the help of the table T „.i = [gⁿ'' i, Qvi]: T_n.i = [g '¹j, Ql] is determined,. the steam flow rate Q_v is measured per step,. a coefficient K_n depending on the deviations between the values ​​of Q_L. and Q_v is calculated,. a new table T_n to be used for the distribution n + 1: T_n = [g, Qvi] = K_n.T₀ is created.

DVR 0078018

I.

AT 409 486 B

The invention relates to a method for recovering emitted vapors during the distribution of liquid inside a container.

A particularly advantageous application of the invention is, for example, in the field of fuel distribution for motor vehicles, for the recovery of the hydrocarbon vapors that escape from the fuel tank of these vehicles to the extent that it is filled with liquid fuel.

Devices for distributing fuel for motor vehicles are known in different embodiments. For example, EP 315 738 A2 describes a device for distributing fuel for motor vehicles, which is equipped with a flow meter for fuel, the output signal of which is forwarded to a pulse generator which delivers a sequence of pulses that a computer converts into volume and price, which then appear on a display device. Each pulse of the pulse generator represents a certain volume of fuel. The aim of this European prior publication is to compensate for the wear and tear of the fuel flow meter by means of a self-calibration method based on comparison so that the "weight of each pulse supplied by the pulse generator is modified by a correction factor. Means for recovering fuel vapors that escape when the tank is filled with fuel are not provided in this device.

DE 44 31 547 C1 also describes a device for dispensing fuel for motor vehicles which is equipped with a nozzle that contains the ends of a nozzle and a vapor recovery hose that is mounted coaxially to the central part of the same. The interior of the nozzle consists of a system of valves on which the fuel flow acts in such a way that the vapor recovery hose is opened and the passage opening of the hose is regulated. This is obviously an open-loop system with an initial setting and without any possibility of postponed recalibration of the hydraulic parameters of the steam recovery line.

No. 4,306,594 A further discloses a device for distributing fuel for motor vehicles, which comprises a fuel distribution line which is equipped with a hydraulic motor, which apparently includes a flow meter for fuel, and with a vapor recovery line to which a recovery pump is connected which allows the recovered steam to flow with a steam flow rate Qv. The recovery pump is driven by the output shaft of the unit formed by the hydraulic motor and flow meter, namely via a drive belt. An adjustable valve, which is mounted parallel to the recovery pump, also enables the steam flow rate Qv to be adjusted. However, this setting is done once and for all and there is no continuous recalibration to compensate for the development of the hydraulic parameters of the vapor recovery line over time.

US 3 826 291 A further shows a device for distributing fuel for automobiles which is similar to that published in US 4 306 594 A, the vapor recovery pump being driven directly by the output shaft of the fuel flow meter. However, the pump is not provided with an adjustable valve that allows the steam flow to be regulated. Here, too, it is an open-loop system that is also set so that the pressure loss in the vapor recovery line is zero.

A device for distributing liquid, such as fuel for motor vehicles, for example, comprises, very generally, means for distributing this liquid, consisting essentially of distributors equipped with pumps capable of delivering the fuel at a liquid flow rate Q._L. from a storage tank to the fuel tank of the vehicles. The distributors also include a liquid measuring device connected to a pulse generator, which enables a computer to determine the amount and the price of the fuel dispensed, which appear in plain text on a display device with which the distributors are equipped.

Furthermore, this device, if it is intended for the recovery of the emitted hydrocarbon vapors, includes recovery means which are able to recover these vapors with a steam flow rate Q._v through a line from the fuel tank of the vehicles to a recovery tank, for example the storage tank, the steam flow rate Q_v is determined by a quantity g which is specific for this recovery agent, in such a way that between the steam flow rate Q_v and the liquid flow rate Q_L.

AT 409 486 B has a ratio Q_v = k Q_L. where k is equal to or close to 1. Finally, the measuring devices allow the steam flow rate Q_v to determine.

Most commonly, these recovery means consist of a pump that draws the vapors from the fuel tank for delivery to the hydrocarbon storage tank. The specific variable g is therefore the speed of rotation of this pump, which is actuated by the pulse generator of the distribution means.

In most cases, however, it is not possible in a simple manner to specify a pump speed that is proportional to the liquid throughput Q_L. is.

In fact, the operating conditions of the individual systems can be very different 10 due to:

- the pressure losses in the recovery line, both in the supply line and in the discharge line of the pump,

- the possible presence of calibrated flap valves on the recovery tank, which can generate a pressure in it that differs from atmospheric pressure and accordingly means an additional pressure loss at the pump in the recovery line,

- the internal leakage of the recovery pump depending on the pressure difference in the inflow and outflow lines, which affects their efficiency.

In short, in order to achieve a given steam flow rate Qv, the recovery pump must be given a device-dependent rotational speed.

In order to take the above-mentioned parameters into account, it is customary to calibrate the entire device when setting up the system on site. During this calibration, a speed of the recovery pump and the corresponding steam flow rate Q are determined_v is measured by means of a flow meter or a gas meter. Thus, with a sufficient number of measurements, the relationship between the speed and the steam flow rate Q_v determined to define the characteristics of the pump under operating conditions. This ratio is stored in a microprocessor.

In normal operation, the flow meter is removed and, in the case of a distribution of hydrocarbons, with a liquid flow rate Q_L. the microprocessor searches in memory for the speed that must be given to the recovery pump so that Q_v = QlThis known recovery process, however, has the following disadvantages:

- the pressure drops in the recovery line can increase over time due to:

. partial and increasing clogging by dust,. a change in the cross-section of the elastomer hoses due to prolonged contact with hydrocarbons. This is particularly the case in the feed line to the pump, which generally consists of an elastomer hose surrounded by a pressurized liquid, this part representing the core of a coaxial hose,

- the internal leakage of the pump, which can increase with wear, for example in radial vane pumps,

- The vapor density of the hydrocarbons changes with the temperature of the fuel tanks of the vehicles as a function of the increase in the ambient temperature, which changes the influence of the pressure losses in the inlet and outlet.

- The vapor pressure in the recovery tank can also change with the hydrocarbons and the temperature.

To solve the technical problem, the aim of this invention is to provide a method for

To propose recovery of emitted vapors during the distribution of liquid inside a container by means of a device comprising:

- Means for distributing the liquid, which are able to disperse this liquid with a liquid throughput Q_l to transport from a tank to this container, measuring devices for the liquid flow rate Q_l,

- means for recovering the vapors capable of removing these vapors with a steam flow rate Q_v from the fuel tank to a recovery tank, the vapor flow rate Q_v is determined by a quantity g specific for this recovery agent,

AT 409 486 B

- Measuring devices for the steam flow Q_v, whereby the method, in view of the slow course of the specific parameters of the steam circulation in the recovery line, would allow a re-calibration deviating from the specific variable g as a function of the measured steam throughput Q_vperform.

The solution to the technical problem posed is, according to the invention, that this method comprises steps which consist in:

- to carry out an initial calibration of the means of recovery by air suction, varying the quantity g by step i and by taking, for each value g ° of g, the corresponding steam flow rate Q_Vi the air is measured so that an initial calibration table T_O is created:

To = [g °, Qvd

- for every distribution n of the liquid:

. the liquid throughput Q at regular intervals_L. to measure and one

To determine the value g ^ j of the quantity g, which is determined with the help of the calibration table T_n.i = [gⁿ'¹i.Qvi] the recovery agent must be specified

Tn-1 = [gⁿ'¹j-Qi-] with Q_Vi = Ql,. the steam flow rate Q_v to measure at each time interval,. a similarity coefficient K_n depending on the deviations between the measured values ​​of Q_L. and Q_v to calculate, . a new calibration table T_n for the following distribution n + 1 according to T._n = [g, Q_Vl] = K_n.To use is

As can be seen in detail below, the method according to the invention uses a value for the specific variable g in a distribution of liquid which results from the calibration table which was created in the course of the previous distribution, whereas a new, updated calibration table with regard to this on the following distribution is created.

In order to take into account any pressure losses in the line, the invention provides that the steam throughput Q_v is measured by a value Q of the flow rate of the vapors supplied by a flow meter placed in series with the recovery means, Q being corrected by a factor of the pressure P / Pa, where P is the pressure measured on the flow meter and Pa the Is atmospheric pressure.

According to a perfection of the method according to the invention:

an initial correspondence table H_O created in which the steam flow rate Q_v associated with the flow rate Q of the vapors indicated by the flow meter (123):

Ho = [Q ° h Qv,]

- with the distribution n of the liquid:

. the throughput Qⁿ the vapors indicated by the flow meter with the flow rate Qⁿ'¹j, which is determined by the correspondence table H_n-i is defined, compared

Hm = [Qⁿ¹j, Ql] with Q_Vi = Ql,. the value gⁿ‘¹j changed per step 5g in the course of the distribution in such a way that the

Value of Qⁿ that of Qⁿ‘¹j approximates,. After the distribution, a second coefficient of similarity K becomes_n depending on the

Deviations between the measured values ​​of Qⁿ and Q_v, calculated,. a new correspondence table H_n for use for the following distribution n + 1 prepared by:

H_n = [Qⁿh Q_Vi] = k_n.Ho

This perfection makes it possible to use gⁿ'¹i to change the quantity g supplied by the calibration table in such a way that the steam throughput Q_v as far as possible to the throughput Q defined by the table Hm_Vi and thus the liquid flow rate Q_L.approaches, but without fully reaching it.

Two, but non-limiting, specific embodiments of the method according to the invention are proposed.

In a first embodiment, these recovery means consist of a recovery 4

AT 409 486 B tion pump with a fixed speed and a valve with a variable opening, the specific size g being the effective cross-section of the passage of this valve.

In a second embodiment, the recovery means consist of a recovery pump with variable speed, the specific quantity g being the speed of this recovery pump.

What the invention consists of and how it can be implemented is explained in more detail on the basis of the following description with reference to the accompanying drawings, without thereby restricting the invention.

Fig. 1 is a diagram of a first embodiment of the method according to the invention.

2 is a diagram of a second embodiment of the method according to the invention.

Figure 3 is a diagram illustrating the initial calibration table of the method of the present invention.

Figure 4 is a diagram illustrating the initial correspondence table of the method of the invention.

The diagram in FIG. 1 shows a device for distributing liquid, for example fuel, inside a fuel tank of a vehicle, which is not shown.

This device comprises means for distributing fuel, consisting essentially of a pump P_L. exist, which is able to deliver the fuel L with a liquid flow rate Q_L. from a storage tank 100 through a line 110 in the direction of the fuel tank to a tap 111.

As already mentioned above, a distributor 112, possibly including the liquid pump P, comprises_L., a meter 113 in series with the pump P_L. is arranged on the line 110 in such a way that a pulse generator 114 connected to the measuring device 113 sends a pulse signal corresponding to the liquid throughput Q_L. which a computing device 115 then converts into the quantity and the price displayed on a display device 116.

The device in FIG. 1 further comprises means for recovering the vapors V which escape during the distribution of the liquid in the fuel tank of the vehicle. In the example in FIG. 1, the means for recovery essentially comprise a recovery pump P_vwith a variable speed w, which is able to disperse the vapors with a steam flow rate Q_v from the fuel tank through the nozzle 111 and through the line 120 to a recovery tank 100, which in the case of FIG. 1 is simply the liquid fuel storage tank.

For practical reasons, the steam flow rate Q_v measured by means of a value Q of the steam flow rate obtained from a in series with the pump P_v arranged flow meter 123, where Q is corrected by a pressure factor P / Pa, where P is the pressure measured by a sensor 122 at the level of the flow meter 123 and Pa is the atmospheric pressure:

Qv = Q x P / Pa

For example, the flow meter 123 can advantageously consist of a liquid oscillator.

In Fig. 2 the recovery means consist of a pump P._v fixed speed Wo and a variable orifice valve 126.

Regardless of the embodiment selected, the method according to the invention in its entirety consists in providing a specific variable g of the recovery agent with a value, such as the resulting steam throughput Q_v, to be specified, which corresponds to that of the liquid throughput Q_l comes as close as possible. In the examples in FIGS. 1 and 2, the variable g is the variable speed W of the recovery pump P_v, or the effective cross section Rx of the passage of the valve 126.

For this purpose, control electronics 121, 121 ′ receive information about the liquid throughput Q coming from a pulse generator 114_L. and on the other hand the information about the steam flow rate Q coming from the measuring devices 123, 122_v. This information is then processed by the control electronics in a manner which will now be described in detail, so that the motor M_v the recovery pump P_v or a control signal is applied to the solenoid valve 126 which is capable of the specific variable g, the speed W of the pump P_v, or the effective cross section Rx of the solenoid valve 126 to a through

AT 409 486 B to bring the control electronics specified value that the best match between the flow rates Q_v and Q_L. results.

The method according to the invention comprises a first e initial calibration phase of the recovery means by air suction.

During this first phase the liquid flow is not active. In contrast, the pump P_v for the recovery of the vapors and enables air to be drawn in through the opening of the tap 111. The control electronics 121 or 121 'supply the motor M_v the pump P_v or a fixed excitation signal to the solenoid valve 126 during a period of time At which corresponds to a value g ° of the respective specific variable g, the index 0 indicating that this is the initial calibration phase. The excitation signal is then increased step by step, which leads to a step-by-step increase in the value g °. Each step i thus corresponds to a known value g ° i and a value Qvi of the steam throughput, which results from the value Qi of the throughput, which is read on the flow meter 123 and corrected by the factor of the pressure Pi / Pa.

The totality of the relationships g ° i and Q_Vi result in an initial calibration table T._O:

T₀ = [gi, Q_Vi]

This table T_O, which is illustrated by the curve in Fig. 3, is stored in the control electronics.

After the initial calibration, the recovery device is ready for the first distribution of liquid. The user removes the nozzle 111 and fills the fuel tank of his vehicle with a liquid throughput Q_L., the value of which is transmitted from the measuring device 113 to the control electronics, which are listed in table T_O is looking for the value g ° j, which is to be given to the quantity g, the Q_Vj = Ql corresponds to:

To = [g ° j, Ql]

Now, however, the steam throughput, which corresponds to g ”, Q_L. because the device was calibrated with air. Since the density of liquid vapors, when it comes to fuels, is higher than that of air, the pressure loss increases, which tends to increase the absolute pressure P when the pump P is drawn in_v is reduced and consequently the steam throughput Qv is reduced. To really Q_L. to achieve, one would have to increase g, as shown in FIG. 3, to a value g, in order to reduce the efficiency of the recovery pump P._v to compensate. This is precisely the aim of the method according to the invention. It is in fact during the distribution of the liquid flow rate Q_L. measured at regular intervals, for example every 500ms, and stored in the control electronics. Of each value Q measured in this way_l is guided by means of table T._O the value g ° to get the quantity g. Furthermore, every 500 ms the values ​​Q read from the flow meter 123 and the values ​​P read from the measuring sensor 122 are measured and stored.

After this first distribution, the value Q of each pair of stored values ​​of Q and P becomes_v derived from the steam flow rate:

Qv = Q x P / Pa

Finally, a similarity coefficient is determined according to the deviations between the different values ​​Q._L. and Q_v calculated in such a way that a new calibration table T is created for use in the following distribution:

T, = [g¹,, Qv ^ KvTo

For example, the similarity coefficient K] can be calculated as follows. For each measurement carried out every 500 ms, a ratio K \ defined by:

K¹i = Qli / Qvi where the coefficient Ki is obtained as the average of all ratios of K \.

Accordingly:

Ti = [K_ig° i, Q_Vi]

The second distribution enables the liquid flow rate Q to be measured_L. the corresponding value g¹j, which gives the quantity g by:

T₁ = [g¹j, Ql]

If this has not resulted in a significant change in terms of the pressure losses in line 120 and the density of the vapors, then corresponds to that indicated by g¹, specified steam flow rate Q_valmost exactly the liquid flow rate Q_L.. In general, there will be fluctuations in the case

AT 409 486 B determine of temperature rises in the recovery pump Pv, especially if, for example, the customers of a gas station refuel at very short time intervals at peak times. During the day, the vehicles, like the fuel in the fuel tanks, get warmer and the density of the vapors increases.

In the same way as in the first distribution, the values ​​Q and P are stored at regular intervals so that after the distribution a series of values ​​of Qv can be calculated which correspond to the corresponding values ​​of Q._L. are compared in order to obtain a new similarity coefficient K₂ derive and a new calibration table T₂ to specify:

T₂ = [g²j, Qvil⁼ K₂.To which is used for the third distribution, so the same process is repeated from distribution to distribution.

It should be noted that the use of a flow meter 123 and a pressure sensor 122 make it possible to detect anomalies in the operation of the device for the recovery of vapors, such as:

- an abnormal change in pressure drop. If the pressure loss is too great, the line may be clogged or there may be a leak, if the pressure is too low,

if it is not possible to achieve the desired steam flow, although the speed w of the pump Pv or the effective cross-section Rx of the valve 126 have the respective maximum value. From this it can be deduced that either the pump Pv is worn out or that the pressure loss in the recovery line is too great,

- if the steam flow rate Q_v Zero, the liquid flow rate Q_L. but is not zero. It can be concluded from this that the pump P_v is no longer operational.

In all cases it is possible to trigger an alarm.

The method of vapor recovery described above can be perfected as follows.

During the initial calibration phase by sucking in air, in addition to the calibration table T_O, another table H_O, a so-called initial correspondence table, in which the steam flow rate Q_v is related to the flow rate Q of the vapors indicated by the flow meter 123:

Ho = [Q ° ,, Qvi]

This table H_Owhich is shown in the graph in Fig. 4 illustrates the relationship between the flow rate of the vapors read on the flow meter and the effective flow rate of the vapors. This curve is dependent on the density of the vapors and the pressure loss in the line.

When the liquid, for example fuel, is distributed for the first time, the control electronics look for T in the initial calibration table_O the value g ° j, which is to be specified for the duration of the time interval of 500 ms of size g, corresponding to Q_Vj = Ql, as explained above. During the same period, the values ​​Q¹, P¹ and Q_L. stored. Here, too, it is again true that vapors from fuel are involved, whereas Table T_O with air was established that the effective throughput Q_v the vapors will be too low (Q_v &lt;Ql)

The control electronics therefore compare the throughput Q indicated by the flow meter at each time interval¹ with the value Q °:

_{ή 0} H₀ = [Q °, Ql]

In general, one will have Q &lt;Q ° (see FIG. 4). In order to compensate for this deviation, one changes the value of the quantity g step by step, starting from g “, in the course of the distribution, in such a way that the value Q¹ approaches the value Q ° until it possibly reaches it.

After the first distribution of the liquid, the control electronics define a series of steam throughput values ​​Q based on the values ​​Q \ and Ρ \, which were stored at regular intervals of 500 ms_Vi = Q \ x P \ / Pa, which allow a second similarity coefficient k¹·, Depending on the deviations between Q ·, and Q_Vi, and a similarity coefficient k · ,, which results from the mean value of the coefficients k \. The coefficient k-ι is used for the correspondence table H_O update for the following distribution of the liquid:

H ^ .Ho ^ QVQvi]

AT 409 486 B

For example, k \ / Q_V1 and

H, = [k-iQ®, Q_Vi]

This process is identical for the second distribution of the liquid as well as for the following.