MXPA96004302A - Procedure and device for the reduction of emissions in bottling ducts of storage deposits of almacenamie - Google Patents

Abstract

The present invention relates to a process for the separation of a vapor mixture of liquid and gas formed on a liquid that is in a container, and which is passed from the container through at least one membrane device with at least one a separation membrane on the intake side of which a negative pressure is generated by means of at least one pumping device, and the permeate enriched with the vapor of the liquid is recycled inside the container, characterized in that in order to balance the positive pressure, the The vapor mixture of the liquid and gas is removed from the container through a duct in such a way that the spent fractions retained in the vapor of the liquid are withdrawn through an external duct, which, depending on the positive pressure prevailing in the container, the pumping device is turned on when the predetermined positive pressure is exceeded

Description

PROCEDURE AND DEVICE FOR THE REDUCTION OF EMISSIONS IN BREATHING DUCTS OF STORAGE DEPOSITS Field of the Invention The invention relates to a method and a device for the separation of a liquid / gas vapor mixture formed on a liquid found in a reservoir, the mixture being discharged out of the reservoir through a discharge conduit for compensation of excess pressure. Especially, the invention relates to a method and a device for the separation of a mixture of hydrocarbon vapor and gas, which is expelled from the breathing conduit of a reservoir for example underground for liquid hydrocarbons, especially fuel for combustion engines, for the compensation of the excess pressure that reigns in the tank. Background of the Invention In service stations, the fuel reserve is generally found in underground storage tanks, which are in communication with the atmosphere for pressure compensation through at least one ventilation installation, the so-called conduit of breathing, so that no inadmissible excess pressure or negative pressure can be produced. Especially in the case of the extraction of fuel from the storage tank or filling of the storage tank with fuel, the free volume is modified above the liquid level, so that air pressure circulates from the environment to the pressure compensation. through the breathing duct to the reservoir or the fuel-gas vapor mixture that is in the free space above the liquid is expelled into the ambient air from the breathing duct. However, oscillations of the pressure in the storage tank can also occur due to oscillations of the temperature in the tank, evaporation of liquid or oscillations of the air pressure. The compensation of a negative pressure prevailing in the storage tank through the inflow of air can be designated as non-problematic for example with respect to the charging of the environment. On the other hand, in the compensation of excess pressure in the storage tank, a vapor-air mixture charged with fuel vapor is expelled into the environment, so that the environment is charged to an undesired extent or people who work in this area experience a detriment to their health. Description of the State of the Art For the reduction of the emission of a vapor-gas mixture when transferring fuel from the storage tank to the tank of a car, so-called active return systems are known, which are sucked in by means of a pumping installation. corresponding vapor-gas mixtures that are produced when a car is refueled and driven back to the storage tank of the service station. In general, systems of this type are used so that the volume of the vapor-gas mixture returned is equal to the volume of the extracted fuel. To increase the effectiveness of such return systems, it is desirable that the volume of the vapor-gas mixture returned be at least equal, but advantageously greater than the volume of the extracted fuel. This has the consequence that even in the case of a fuel extraction, a rise in the pressure in the storage tank, which would be compensated through the discharge, can occur through the return of a larger volume to the storage tank. of the vapor-gas mixture that is above the liquid through the breathing duct into the environment. Since the breathing ducts are not equipped in general or only with insufficient filter elements, the forced compensation of pressure would greatly reduce the effectiveness of the return system used when refueling a car, since, in effect, in the area of the spout column the emission of harmful substances can be reduced, but in another area of the service station a certain amount of a vapor-air mixture charged with fuel vapor is expelled.

SUMMARY OF THE INVENTION The invention has the task of creating a device, with which the emission of harmful substances in the area of the breathing duct of a reservoir for the storage of liquids, especially of automobile fuels, can be reduced. Description of the invention The task is solved by means of a method according to the invention characterized in that the vapor-liquid-gas mixture is conducted from the tank through at least one membrane installation with at least one separation membrane, in which side of the permeate a negative pressure is generated at least at intervals by means of at least one pumping installation for the generation of a negative pressure and the permeate enriched with the vapor of the liquid is conducted back to the tank, and because the depleted fraction retained With the liquid vapor is discharged through the discharge conduit. This method according to the invention for reducing the emission of harmful substances in the area of the discharge conduit of a storage tank can be carried out using simple means. Especially in the case of using semi-permeable gas separation membranes, which can preferentially filter vapors, it can be ensured that through the negative pressure, the liquid-gas vapor mixture circulating through the membrane installation is released to a large extent of liquid vapor. Therefore, the mixture exiting from the discharge conduit does not represent any damage to the environment or only non-essential damage. According to an advantageous configuration of the invention, it is provided that the pumping device is connected as a function of the excess pressure in the tank when a predetermined excess pressure is exceeded. This has the advantage that the pumping installation is only in operation when a steam-gas mixture is discharged, so that the energy consumption can be kept low. Furthermore, in this embodiment of the method there is the possibility that the ventilation of the tank for the compensation of a negative pressure in the tank can be carried out by means of the discharge conduit, since when the pumping installation is disconnected and when air flows in There is no danger from the environment that the separation membrane will be obstructed by particles that eventually exist in the environment. In another convenient configuration of the invention, the discharge conduit can be closed by means of at least one overpressure valve and the pumping installation is switched on depending on the position of the valve when the valve is open and disconnected when the valve is closed. This procedure has the advantage that the reservoir for the fuel is completely closed in the case of pressure equilibrium, so that the diffusion processes which also take place without pressure between the vapor-gas mixture can not take place. above the liquid, on the one hand, and the outer atmosphere, on the other hand. Furthermore, this procedure can be carried out with very simple means, since, for example, only a mechanical switch must be present, which can be activated by the valve body, for example the ball of the valve, and immediately connects the valve. Pumping installation. In a convenient configuration of the invention, it is provided that the pumping device for generating the negative pressure on the permeate side of the separation membrane is connected as a function of the position of an extraction valve and / or a valve filling the reservoir fluid when the valve is open. This has the advantage that especially in the case of active influence of the state of filling of the tank, a vapor-gas mixture optionally produced in this case is released from the liquid vapor charge. This is especially convenient when the extraction system containing the extraction valve is provided with a so-called active return system, described at the beginning for vapor-gas mixtures, which are produced when liquid is transferred, for example when refueling a car. In fact, in this case a determined volume, usually greater than the vapor-gas mixture aspirated in the assortment gun, is returned as that of the liquid extracted from the tank, being carried out by virtue of the reduced extraction speed and the reduced return velocity of the vapor-gas mixture which results in a compensation of the pressure through the breathing duct in general without any considerable elevation of the pressure beforehand. Especially in the case of use of an overpressure switch for the activation of the pumping installation, there is a danger that it will not react due to the slow extraction of the steam-gas mixture, which is carried out without raising the pressure, so that the vapor-gas mixture reaches the environment without the separation of a permeate enriched with the liquid vapor. The device according to the invention for separating a vapor-liquid-gas mixture that is produced above a liquid found in a tank, the mixture of which can be discharged out of the tank through a discharge conduit for compensation of the excess pressure, especially for carrying out the method according to any of the preceding claims, has at least one membrane installation with at least one separation membrane, whose intake side for the liquid-gas vapor mixture is connected with the reservoir and whose side of the retained fraction is connected to the discharge conduit, the permeate side being connected for the return of the enriched permeate with the liquid vapor to the reservoir through a pumping installation for the generation of a negative pressure on the permeate side of the separation membrane. In this case, it can be envisaged that an excess pressure switch is present, whose manometer recorder is connected to the interior of the tank and which cooperates with the pump for the generation of a negative pressure, in such a way that in case If a predetermined pressure is exceeded, the pump is switched on. In a convenient configuration of the invention, it is provided in this case that the discharge line has at least one throttling element. This has the advantage that an excess vapor-gas mixture possibly present in the reservoir can not simply escape through the discharge conduit, but first an excess pressure is formed, so that the commutator can react. overpressure. In this case it may be convenient that the throttle element is configured as a perforated screen. The perforated screen can be used in a simple manner in the discharge conduit of the reservoir generally configured as a pipe.

In a further convenient configuration of the invention, it is provided that the discharge duct has at least one overpressure valve, by means of which the discharge duct can be closed, and that at least one control device having a dc switch is provided. control, whose installation cooperates with the overpressure valve and with the pump installation for the generation of a negative pressure, in such a way that the pump is connected when the valve is open and disconnects when the valve is closed. This arrangement has the advantage that the device for separating the resulting vapor-gas mixture can also be used in tanks that can be completely closed for the storage of liquids, especially fuels for combustion engines. DESCRIPTION OF THE DRAWINGS The invention is explained in detail below with the help of the drawing. In this case: Figure 1 shows a service station with a device for carrying out the procedure according to the invention, and Figure 2 shows a service station with a device for carrying out the method according to the invention. in another embodiment. The embodiments shown in FIGS. 1 and 2 essentially coincide in their structure and differ mainly in the activation of the vacuum pump for the generation of the negative pressure on the permeate side of the separation membrane. Therefore, the elements and equal parts of the installation are provided with the same reference signs. The service station 1 shown schematically in the drawing has a reservoir 2 for storage of the fuel reserve 3. The reservoir 2 is in connection with an extraction device 4 for the liquid fuel. Furthermore, a ventilation installation 5 is provided, by means of which a compensation of the pressure of the tank 2 with the environment 6 can be realized. Furthermore, the tank 2 is provided with a filling device 7, through which the fuel can be filled in the tank 2. The extraction installation 4 has a spout column 8 known in general, in which the sprayer gun 9 is connected to refuel a car 10 by means of a connecting hose 11. In addition, the extraction installation 4 is provided with an active return system 12, not shown in detail in the drawing, of the vapor-gas mixture that is produced when the automobile is refueled. These return systems 12 are known in general and do not require any further explanation. The ventilation system 5 has a membrane installation 29 with a separation membrane 13. The side of the retained fraction 14 of the separation membrane 13 is connected, on the one hand, by means of a conduit 15 to the reservoir 2 and, on the other hand, with the discharge conduit 16, which empties into the environment 6. In particular, the provision is made that the conduit 15 opens into the upper zone 17 of the reservoir 2 above the level of the liquid 18 in the reservoir 2. A mixture of fuel vapor-air that flows from the reservoir 2, if necessary to compensate the pressure, can therefore only reach through the conduit 15 by means of the membrane installation 29 through the conduit. of discharge 16 to the environment 6. The permeate side 19 of the membrane installation 29 is connected to the negative pressure side of a vacuum pump 20 which, in turn, is in connection with the reservoir 2. Durant In the operation of the vacuum pump 20 there is a negative pressure on the permeate side 19 of the membrane installation 29, so that the fuel vapor of a vapor-air mixture charged in this way and circulating on the side of the retained fraction 14 through the membrane system can also pass through the separating membrane 13. The separation membrane 13 is in this case more conveniently configured as a semi-permeable gas separation membrane. The permeate enriched in this way with fuel vapor can be returned to the reservoir 2 via the vacuum pump 20. In the exemplary embodiment according to FIG. 1, an overpressure switch 21 is provided for the activation of the pump. empty 20, whose manometric recorder 22 is disposed in the upper zone 17 of the reservoir 2. This manometric recorder 22 cooperates with a switch 23 for the vacuum pump 20. In particular, the provision is taken that in the event that an overpressure is exceeded in the reservoir 2, the switch 23 reacts and the vacuum pump 20 is operated. The vapor-air mixture exiting by virtue of the overpressure that reigns inside the reservoir 2 circulates through the membrane installation 29, in which the fuel vapor is separated, by virtue of the existing overpressure, in the separation membrane 13 of the vapor-air mixture, so that the retained fraction exiting through the discharge conduit 16 is released. to a large extent of fuel vapor. In order to carry out a sufficient pressure rise for the reaction of the overpressure switch 21 inside the tank 2, the discharge conduit 16 has a throttle element 24 configured as a perforated disk 25. In the embodiment shown in FIG. 2, the discharge duct 16 has an overpressure valve 26, which opens when a liquid-gas vapor mixture emerges. In addition, a negative pressure valve 27 is provided, which opens when a negative pressure reigns inside the tank 2 when ambient air flows in. The overpressure valve 26 is provided with a control switch 28, which cooperates with the vacuum pump 20. In particular, provision is made in this case for the control switch 28 to react when the valve 26 is open, so both when the steam-gas mixture comes out and the vacuum pump 20 is put into operation. In this way, it is reliably guaranteed that when the steam-gas mixture is released, the separation process that takes place in the installation is carried out. of membrane 29. It is clear that with the embodiments shown in the drawing a reliable reduction of the emission in the area of the breathing duct of a reservoir of a service station can be realized. It can also be foreseen that the pumping installation 20 can be connected depending on the activation of the extraction valve of the extraction installation 4 or of the filling valve of the filling installation 7. Especially in the case of use of an active return system 12, in which the vapor-gas mixture produced during refueling is conducted back to tank 2, it can be ensured that these resulting vapor-gas mixtures are also separated from each other. the installation of membrane 12, which escape from the discharge conduit 16 without pressure formation or only with a formation of non-essential pressure inside the reservoir 2.

List of reference signs 1 Service station 2 Tank 3 Fuel reserve 4 Extraction installation Ventilation installation 6 Environment 7 Filling installation 8 Spout column 9 Spout gun 10 Automobile 11 Connecting duct 12 Active return system 13 Separation membrane 14 Side of retained fraction Conduit 16 Unloading conduit 17 Upper zone of reservoir 2 18 Liquid level 19 Permeate side 20 Vacuum pump 21 Overpressure switch 22 Manometric recorder 23 Switch 24 Throttle element Perforated screen Overpressure valve Negative pressure valve Control switch Membrane installation

Claims (9)

1. REVIVIPMENTS 1. Procedure for the separation of a vapor mixture of liquid / gas formed on a liquid that is in a tank (2), the mixture being discharged out of the tank (2) through a discharge duct (16) for compensation of the excess pressure, characterized in that the vapor-liquid-gas mixture is conducted from the tank (2) through at least one membrane installation (29) with at least one separation membrane (13), whose side of the permeate (19) a negative pressure is generated at least at intervals by means of at least one pumping installation (20) for the generation of a negative pressure and the permeate enriched with the vapor of the liquid is conducted back to the tank (2), and because the retained fraction depleted with the liquid vapor is discharged through the discharge conduit (16). Method according to claim 1, characterized in that the pumping device (20) is switched on as a function of the excess pressure in the tank (2) when a predetermined excess pressure is exceeded. Method according to claims 1 6 2, characterized in that the discharge conduit (16) can be closed by means of at least one overpressure valve (26) and the pumping installation (20) is switched on as a function of the Valve position (26) when the valve is open and disconnects when the valve is closed. Method according to one of the claims 1 to 3, characterized in that the pumping system (20) is switched on according to the position of an extraction valve and / or a reservoir liquid filling valve ( 2) when the valve is open. Device for separating a liquid / gas vapor mixture formed on a liquid (3) located in a tank (2), the mixture of which can be discharged out of the tank (2) through a discharge duct (16) for the compensation of excess pressure, especially for carrying out the process according to any of the preceding claims, characterized by at least one membrane installation (29) with at least one separation membrane (13), whose side of intake for the liquid-gas vapor mixture is connected to the reservoir (2) and whose side of the retained fraction (14) is connected to the discharge conduit (16), the permeate side (19) being connected to the return of the permeate enriched with the liquid vapor with the tank (2) through a pumping installation (20) for the generation of a negative pressure on the permeate side (19) of the separation membrane (13). 6. Device according to claim 5, characterized in that an excess pressure switch (21) is provided, whose manometric recorder (22) is connected to the interior (17) of the tank (2) and cooperates with the pump (20) for the generation of a negative pressure, in such a way that in case a predetermined pressure is exceeded, the pump is switched on. Device according to claim 5 or 6, characterized in that the discharge conduit (16) is provided with at least one throttle element (24). Device according to claim 7, characterized in that the throttle element (24) is designed as a perforated screen (25). Device according to one of claims 5 to 8, characterized in that the discharge conduit (16) has at least one overpressure valve (26), and because there is provided at least one control device having a control switch (28), whose installation cooperates with the overpressure valve (26) and the pump ( 20) for the generation of a negative pressure, and because the pump (20) is connected when the valve is open and disconnects when the valve is closed.