EP3359815A1 - Method and device for pumping a product by suction - Google Patents

Abstract

According to the present invention: the product (10) is sucked into a first transit vessel (2) placed under vacuum and, simultaneously, a second transit vessel (3) is emptied by flushing under pressure; and then, said product is sucked into said second transit vessel (3) placed under vacuum and, simultaneously, said first transit vessel (2) is emptied by flushing under pressure.

Description

 Method and device for pumping a product by suction

The present invention relates to a method and a device for pumping a product by vacuum suction. Although not exclusively, it is particularly suitable for use in pumping products that can produce an explosive atmosphere and / or emit volatile organic compounds.

 It is known that many industries, for example chemical, petrochemical, food processing, metallurgical, etc., generate sludge likely to produce an explosive atmosphere and / or emit volatile organic compounds. These sludges are generally stored in tanks, from which they must be pumped to be transported to specialized treatment and / or storage sites.

 Such pumping operations are also necessary to purge the industrial sewers, to recover the waste produced by the high-pressure cleaning of industrial installations, to extract the sludge from the purification plants, to dry the bottoms of the tanks so as to allow their inspection or maintenance, etc.

 These pumping operations present, for the safety and health of operators and residents, as well as for the protection of facilities and the environment, many risks that are related to the explosive nature of the pumped products and the emission of harmful gases like volatile organic compounds.

 To carry out such pumping operations, it is possible to use a vacuum pump to empty the tank containing the products to be pumped. A storage chamber is arranged between the vacuum pump and a suction pipe immersed permanently in the product to be pumped empty.

This technique has the advantages of allowing a stoppage of operation of the vacuum pump during the pumping operation, maintaining a suction capacity as the differential with respect to the atmospheric pressure exists. It allows to exhaust the tank to drain. In addition, it ensures the emptying of the pumping circuit. In addition, it allows the installation of the pump at great distances from the product to be pumped because of the suction force. It also avoids contact of the product with the pump with the exception of vapors or gases and limit the amount of pollutants released and to confined the hazardous area to the pumping area.

However, the main disadvantage of such a vacuum pumping technique is to promote the desorption of volatile products and therefore emission of explosive gases and volatile organic compounds.

 The object of the present invention is to improve the vacuum suction pumping technique in order to retain the advantages thereof and to eliminate the disadvantages thereof. To this end, according to the invention, the method for pumping a product by vacuum suction is remarkable in that, alternately: - the product is sucked into a first transit tank evacuated and simultaneously draining a second transit tank by pressurized flushing,

then, said product is sucked into said second transit tank evacuated and, simultaneously, said first transit tank is emptied by pressurized flushing.

Thus, in the process according to the present invention, the two transit tanks work simultaneously and alternately, one loading product by suction under vacuum and the other being drained under pressure of the previously aspirated product. Each transit tank is alternately loaded with product, then drained from it.

Although the evacuation and the pressurized flushing of said transit tanks can be obtained from any desired material, it is advantageous that, for the evacuation of said first and second tanks the suction vacuum of a vacuum pump, preferably a water-ring vacuum pump, is used, and for the pressure flushing of said first and second transit vessels the discharge pressure of said vacuum pump. The invention thus takes advantage of the fact that the use of the gases discharged by the vacuum pump as a pressure source does not modify the capacity of said pump to generate the vacuum.

 Very often, the industrial products to be pumped contain solid foreign bodies and must therefore be filtered at the time of pumping. However, such a filtration is very disadvantageous with regard to the pumping rate. To avoid such a disadvantage, in accordance with another feature of the present invention, said first and second transit vessels are used to remove solid foreign bodies present in said product to be pumped. To do this, said transit tanks may be cyclonic tanks.

The present invention further relates to a device for pumping a product by vacuum suction, said device comprising a vacuum source and a suction nozzle of said product and being remarkable in that it comprises:

- a source of pressure,

 two transit tanks for said product, and

 a set of controlled valves connecting, simultaneously and alternately, one of said transit tanks to said vacuum source and to said suction nozzle and the other of said transit tanks to said source of pressure and to a tank of receiving said product.

As mentioned above, the vacuum suction and the pressurization of said transit tanks can be obtained by a vacuum pump, preferably a water ring vacuum pump. In this case, said vacuum source and said pressure source are constituted respectively by the suction port and the discharge port of said vacuum pump. Such a pumping device can pump products whose flash point is less than 60 ° C.

 As previously indicated, in this pumping device according to the present invention, said transit tanks may be cyclonic tanks allowing the elimination of solid foreign bodies contained in the product to be pumped.

 It will be noted that said sources of vacuum and pressure (the vacuum pump), said suction nozzle, said transit tanks and said set of controlled valves form a vacuum pumping unit which, for safety reasons, must preferably be remote from said product receiving tank which is at atmospheric pressure or at a slightly higher pressure. For this purpose, the pumping device according to the present invention is connected to said receiving tank by a long pipe for moving said vacuum pumping unit away from said receiving tank of said product.

 The length of such a connecting pipe may be of the order of several tens of meters, for example at least 50 meters.

 In order to be able to drain different geographically distributed industrial sites of their products that can generate explosive atmospheres and / or volatile organic compounds, it is advantageous for the pumping device according to the present invention to be mobile, for example carried by a vehicle. automobile.

The figures of the appended drawing will make it clear how the invention can be realized. In these figures, identical references designate identical elements.

Figures 1 and 2 illustrate an exemplary embodiment of the pumping device according to the present invention in two different alternating phases of operation. The embodiment of the device according to the present invention shown diagrammatically in FIGS. 1 and 2 comprises:

 - A vacuum pump 1, for example a water ring pump, having a suction port 1 A and a discharge port 1 R;

a first transit tank 2, preferably a cyclonic tank, comprising a fluid inlet 2E, a product inlet 2P and a product outlet 2S;

 a second transit tank 3, preferably a cyclonic tank, comprising a fluid inlet 3E, a product inlet 3P and a product outlet 3S;

 a four-way valve 4, arranged between the suction and discharge openings 1A of the vacuum pump 1, on the one hand, and the fluidic inlets 2E and 3E of the first and second transit tanks 2 and 3, on the other hand;

 a product receiving tank 5, comprising a product inlet 5E; controlled drain valves 7 and 8 respectively connecting the outlets 2S and 3S of the transit tanks 2 and 3 to the product inlet 5E of the receiving tank 5 via a long pipe 6, a length at least 50 meters;

 - A suction nozzle 9 of a product 10 to be pumped, respectively connected to the product inlet 2P and 3P of the first and second transit tanks 2 and 3, through controlled filling valves 1 1 and 12; and

a control system 14 (only shown in FIGS. 1 and 2 by arrows) for controlling the valves 4, 7, 8, 11 and 12.

 In a first phase of operation of the device of the invention, shown in FIG. 1 and controlled by the control system 14, the four-way valve 4 connects the fluidic inlet 2E of the transit tank 2 to the orifice d suction 1 A of the vacuum pump 1 and the fluid inlet 3E of the transit vessel 3 to the discharge port 1 R of said pump. Moreover :

The drain valve 7, at the outlet 2S of the transit tank 2, is closed; the filling valve 1 1 at the product inlet 2P of the transit tank 2 is open;

 the filling valve 12, at the product inlet 3P of the transit tank 3, is closed; and

 the drain valve 8, at the outlet 3S of the transit tank 3, is open.

 Under these conditions, the transit tank 2 is evacuated by the pump 1 and the product 10, possibly accompanied by air, is sucked into said tank 2 via the suction nozzle 9, the 1 1 filling and 2P product inlet. The sucked product is retained in the transit tank 2, since the drain valve 7 is closed. Simultaneously, the transit tank 3 is pressurized by the discharge port 1 R of the pump 1 and the product previously sucked into said transit tank 3 is driven into the receiving tank 5 via the outlet 3S. , the drain valve 8 and the long pipe 6.

Conversely, in a second phase of operation of the device of the invention shown in Figure 2, and also controlled by the control system 14, the four-way valve 4 connects the fluid inlet 3F of the transit tank 3 to the suction port 1 A of the vacuum pump 1 and the fluid inlet 3E of the transit tank 2 to the discharge port 1 R of said pump. Moreover :

 the drain valve 8, at the outlet 3S of the transit tank 3, is closed;

 the filling valve 12, at the product inlet 3P of the transit tank 3, is open;

 the filling valve 1 1 at the product inlet 2P of the transit tank 2 is closed; and

the drain valve 7, at the outlet 2S of the transit tank 2, is open. Under these conditions, the transit tank 3 is evacuated by the pump 1 and the product 10, possibly accompanied by air, is sucked into said tank 3 via the suction nozzle 9, the filling 12 and product inlet 3P. The sucked product is retained in the container 3 since the drain valve 8 is closed. Simultaneously, the transit tank 2 is pressurized by the discharge port 1 R of the pump 1 and the product previously sucked into said transit tank 2 is driven into the receiving tank 5 via the outlet 2S. , the drain valve 7 and the long pipe 6.

 Thus, the alternation of said first and second phases controlled by the control system 14 makes it possible to pump the product 10 through the suction nozzle 9 to bring it into the receiving tank 5, by implementing not only the vacuum generated by the pump 1 at its suction port 1A, but also the pressure generated by said pump 1 at its discharge port 1 R.

 Although this is not shown in FIGS. 1 and 2, it will be readily understood:

 that the pumping device described above, consisting of the vacuum pump 1, the transit tanks 2 and 3, the valves 4, 7, 8, 11 and 12 and the control system 14 can be carried by a motor vehicle or a trailer to be mobile and to be able to move and pump products 10 in different places;

 that, similarly, the tank 5 for receiving the pumped product can be mobile; and

that the pipe 6 can be provided to be removably mounted on one side to the pumping device and on the other to the tank 5 for receiving the pumped product.

In addition, the pumping device has many additional advantages and features, and in particular: it makes it possible to limit as much as possible the lapse of time of evacuation of the liquid;

 it allows the liquid and the exhaust gases of the same vacuum pump to be discharged while continuing to pump;

 - The receiving tank is not a vacuum container, but a simple storage container;

 it can have short cycle times with reduced evacuation volumes; and

 - Pumping the product is alternated on the tanks, but without discontinuity.

 In addition, with the treatment on the two phases (liquid / gas) in small quantities imprisoned alternately in transit tanks, tanks which are arranged in parallel in the operating circuit, the alternation of the flushing cycles on the two tanks mounted in parallel allows to contain and repress the product in its entirety (gas phase included) to the storage tank, in steps. The phenomenon of desorption is reduced and treated by the phasing of alternating sequences depression-compression, on smaller volumes put in depression during short durations of exposure.

 Moreover, the capacity ratio between those of the transit tanks and that of the receiving tank is preferably of the order of 1/10.

Claims

1. Process for pumping a product (10) by vacuum suction, characterized in that, alternately:  the product is sucked into a first transit tank (2) which is evacuated and, simultaneously, a second transit tank (3) is emptied by flushing under pressure of the previously aspirated product, the previously sucked product being driven to a tank of reception (5),  - Then, said product is sucked into said second transit tank (3) evacuated and, simultaneously, said first transit tank (2) is emptied by flushing under pressure of the previously sucked product, the previously aspirated product being driven towards the receiving tank (5).  Pumping method according to claim 1, characterized in that, for evacuating said first and second transit vessels (2, 3), the suction vacuum of a vacuum pump (1) is used and in that for the pressure flushing of said first and second transit tanks (2, 3), the discharge pressure of said vacuum pump (1) is used.  3. A method of pumping according to one of claims 1 or 2, characterized in that said first and second transit tanks (2, 3) for removing solid foreign bodies present in said product.  4. Device for pumping a product (10) by vacuum suction, said device comprising a vacuum source and a suction nozzle (9) for said product, characterized in that it further comprises:  - a source of pressure,  two transit tanks (2, 3) for said product (10), and a set of controlled valves (4, 7, 8, 1 1, 12) connecting, simultaneously and alternately, one of said transit tanks to said vacuum source and to said suction nozzle (9) and the other of said transit tanks at said pressure source and a tank (5) for receiving said product.  Pumping device according to claim 4, characterized in that it comprises a vacuum pump (1) and in that said vacuum source and said pressure source are constituted respectively by the suction port (1 A) and the discharge port (1 R) of said vacuum pump (1).  Pumping device according to claim 5, characterized in that said vacuum pump (1) is of the water ring type.  7. Pumping device according to one of claims 4 to 6, characterized in that said transit tanks (2, 3) are cyclonic tanks.  8. A pumping device according to one of claims 4 to 7, characterized in that it is connected to said receiving tank (5) by a pipe (6) for moving said pumping device away from said tank (5). ) receiving said product.  Pumping device according to claim 8, characterized in that the length is at least 50 meters.  10. Pumping device according to one of claims 8 or 9, characterized in that it is movable.