EP1091812A1 - Method for cleaning an oil storage tank and device for implementing same - Google Patents

Method for cleaning an oil storage tank and device for implementing same

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Publication number
EP1091812A1
EP1091812A1 EP97952101A EP97952101A EP1091812A1 EP 1091812 A1 EP1091812 A1 EP 1091812A1 EP 97952101 A EP97952101 A EP 97952101A EP 97952101 A EP97952101 A EP 97952101A EP 1091812 A1 EP1091812 A1 EP 1091812A1
Authority
EP
European Patent Office
Prior art keywords
tank
lance
sediment
level
nozzle
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP97952101A
Other languages
German (de)
French (fr)
Other versions
EP1091812B1 (en
Inventor
Mike Wartel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Petrojet International SA
Original Assignee
Petrojet International SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Petrojet International SA filed Critical Petrojet International SA
Publication of EP1091812A1 publication Critical patent/EP1091812A1/en
Application granted granted Critical
Publication of EP1091812B1 publication Critical patent/EP1091812B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto 
    • B08B9/08—Cleaning containers, e.g. tanks
    • B08B9/093—Cleaning containers, e.g. tanks by the force of jets or sprays
    • B08B9/0933—Removing sludge or the like from tank bottoms

Definitions

  • the present invention relates to a method for cleaning a floating roof tank containing crude oil and to a device for carrying out said method.
  • crude oil storage tanks are generally cylindrical tanks with floating roofs.
  • the roof structure is therefore at a higher or lower level relative to the ground depending on the amount of crude oil that is in the tank.
  • the periphery of the floating roof has sealing members making it possible to prevent the oil from passing around the periphery of the roof. It has been found that in these storage tanks, a sediment is progressively deposited on the bottom of the tank, consisting largely of the heaviest fractions of the stored crude oil, in particular paraffinic compounds, and inorganic elements such as l water, sand, rust particles or the like.
  • This sediment is likely to constitute on the tank bottoms very thick layers of 1 or 2 meters or more and it is necessary to clean the tanks by removing this sediment. Indeed, if the sediment accumulates on the bottom of the tank and the floating roof descends towards the bottom as the tank is emptied, the risk is to have contact between the floating roof and a point on the deposit of sediment, which unbalances the roof and blocks it in an oblique position in the side wall of the tank; however, the weight of a floating roof being several hundred tonnes, it is understandable that the repair of such an incident involves considerable costs.
  • the invention is based on the fact that the sediment can be resuspended in the crude oil which overcomes it, provided that turbulence and / or vortices are generated in the entire volume of liquid oil which overcomes the sediment and to send jets of petroleum powerful enough on the sediment so that this one, gradually, is resuspended and maintained in this state by the turbulence imposed in the liquid crude oil.
  • the layer of sediment gradually disappears and is found inside the liquid crude oil, which revalorizes the sediment since there is no longer any sedimentary material to be evacuated from the tank to be destroyed.
  • the reinjection into the tank is carried out by rotary lances arranged vertically under the floating roof, these lances being equipped with nozzles which send jets of oil in the direction of the layer of sediment; the rotation of the lances generates vortices having for axis the axis of the lances and one makes so that these vortices interest the whole of the tank.
  • the crutches of the floating roof are replaced by the lances which ensure the reinjection of the crude oil, the bottom of the lances arriving in the vicinity of the mean plane of the upper face of the sediment layer.
  • the present invention therefore relates to a process for resuspending a sediment which has, by deposition, formed a layer on the bottom of a floating roof tank containing crude oil, said floating roof comprising a plurality crutch holes regularly distributed over its surface, said holes making it possible to secure crutches capable of supporting the roof by pressing on the bottom of the tank when the level of crude oil in the tank is less than the length of the crutches, characterized by the fact that :
  • the level of crude oil in the tank is brought to a distance L from the highest level of the sediment on the bottom of the tank, with L between 2 and 5 meters approximately,
  • the crude oil is drawn into the tank by at least one pump with an overall hourly flow rate equal to V / n, V being the volume remaining in the tank below the floating roof and n being a number between 8 and 15 approximately, - the pumped crude is reintroduced into the tank by injecting it using lances carried by the floating roof and put in place vertically in the tank above the sediment, each of said lances having, below the floating roof, a length less than L, being driven in rotation about its axis, being closed at its lower end and comprising at least one nozzle disposed above the sediment, nozzle whose jet is oriented towards the bottom of the tank, the outlet section of the nozzle (s) of the same lance being sufficiently small so that, with the flow rate delivered by the ( the) pump (s), the output pressure of the crude jet is sufficient for the vortex volume generated by a lance to intersect the vortex volumes relating to the adjacent lances,
  • the implementation of the process is continued until the density of the pumped crude oil is equal to a predetermined value which corresponds to an almost complete resuspension of the sediment.
  • n which defines the overall hourly flow aspirated and reintroduced into the tank is a function of the characteristics of the tank to be cleaned by resuspending the sediment, the physicochemical characteristics of the sediment itself and the immobilization time that we accept to proceed with cleaning the tank.
  • the lances are rotated at a speed of between 0.25 and 4 revolutions / minute.
  • the lances can be rotated about their axis by explosion-proof electric motors, one motor being assigned to each lance.
  • the present invention also relates to a device for implementing the method as defined above, this device being characterized in that the lances are arranged in the sleeves of the stand holes of the floating roof of the tank.
  • the essential advantage of installing the rotary lances in the crutch holes that is to say in the sleeves which usually hold the crutches integral with the floating roof, allows the installation of the cleaning device according to the invention, without any modification having to be made to the floating roof of the tank to be cleaned: it is enough to remove the crutches one by one and replace them progressively with rotating lances.
  • the crutch holes being sufficiently close together, the rotary jets from these lances cause the entire volume of crude oil remaining in the tank to be mixed, thus causing the erosion of the sediment fragments until they are completely resuspended.
  • each lance comprises a plurality of nozzles situated at different levels relative to the tank bottom, the jets of the nozzles of the lower level being directed towards the tank bottom while the jets nozzles of the upper level are directed towards the floating roof; advantageously, each lance has three nozzle levels, a nozzle of the median level generating a substantially horizontal jet while the nozzles of the two other levels generate jets whose axis is inclined by 50 to 70 ° relative to the axis of the lance that carries the nozzle. Provision can be made for each nozzle level to have two diametrically opposite nozzles.
  • the lower level nozzle (s) is (are) placed at a level between 20 and 50 cm above the average level of the sediment layer.
  • the pump (s), which sucks (s) the crude in the tank is (are) volumetric (s); it can be, for example, screw pumps.
  • This type of pump provides a given flow rate and the pressure obtained at the outlet of the nozzles is therefore a function of the outlet section of all the nozzles supplied by the pump.
  • the volume interested in the turbulence around a lance is obviously all the more important as the jet ejection pressure is higher.
  • these volumes which are substantially cylinders having for axis the axis of the lances, overlap with the volumes pertaining to the adjacent lances so that no part of the liquid petroleum contained in the tank remains outside the turbulence assembly created according to the invention.
  • the mixing of the sediment also causes the inorganic elements contained in the sediment to be resuspended.
  • a filter is therefore provided at the suction of the pumps to remove these inorganic elements, the parts which pass through the filter being, in any case, ground by the screws of the pump.
  • the operator of the tank empties the liquid content of the tank by transferring it to another tank containing a similar crude, this emptying being, of course, only carried out after having replaced the crutches of the floating roof at the place of the lances used for the implementation of the method according to the invention. After this mixing with the content of another tank has been carried out, the refining of the crude oil used for cleaning according to the invention can take place.
  • the device according to the invention comprises at least two pumps each preceded by at least one filter and each followed by a distributor, each outlet channel of which outputs on an enclosure which supplies p lances, p being the same integer for all the speakers of the device.
  • FIG. 1 schematically shows a device for implementing the method according to the invention
  • FIG. 2 shows schematically in section a crude oil tank with floating roof in which a lance has been put in place for the reinjection of the crude oil pumped as indicated in Figure 1, the other lances not being shown;
  • FIG. 3 shows a plan view of the floating roof of the tank according to Figure 2, this view showing the crutch sleeves provided on said floating roof and, in dotted lines, the circles delimiting the cylindrical volumes of turbulence generated by each of lances inserted in said crutch sleeves.
  • a crude oil storage tank has been designated by 1 as a whole; the tank 1 consists of a cylindrical side wall la, the base lb of which constitutes the bottom of the tank.
  • the tank is equipped with a floating roof 2, the periphery of which comprises sealing members, not shown.
  • the tank 1 is intended for the storage of crude oil, the roof 2 floating on the crude.
  • a tank can have a diameter of about 50 m and a height of 15 m.
  • the crude gradually settles and gives rise to a sediment 3 which constitutes a layer on the bottom of the tank 1b, a layer which can reach several meters in thickness; the diaper surface is relatively uneven.
  • the sediment is generally of a thyxotropic nature.
  • the tank is partially emptied; if we assume a layer of sediment with an average thickness of 1 m, we leave in the tank above the sediment about 3 m of crude oil, that is to say that the roof 2 is located about 4 m above the bottom of the tank.
  • the floating roof 2 is equipped with 72 crutches which pass through the roof by crutch sleeves designated by 4 in FIG. 3. These crutches have a length of between 1.8 and 2.2 m and come in support on the tank bottom when the floating roof descends sufficiently low.
  • each lance 5 is a tube which is pivotally placed in a crutch sleeve.
  • the lance 5 is driven in rotation about its axis by an explosion-proof electric motor 6 located at the head of the lance, above the floating roof 2.
  • the crude oil is supplied to the lance 5 by a pipe 7.
  • the lance 5 has on three levels of nozzles making it possible to evacuate the crude oil brought into the tube which constitutes the lance by the pipe 7. These nozzles orient the outlet jets. Each level has two diametrically opposite nozzles on the lance.
  • the two nozzles of the lower level provide jets 8a whose axes are 60 ° with the axis of the lance 5, these jets being oriented towards the bottom of the tank; the two upper level nozzles provide 8c jets. whose axes make with the axis of the lance 5 an angle of 60 °, these jets being oriented towards the floating roof 2; the two nozzles of the median level form jets 8b whose axes are substantially horizontal.
  • the nozzles on the lower level are approximately 30 cm above above the mean plane of the sediment layer 3; the median level nozzles are approximately 60 cm above those of the lower level and the upper level nozzles are also approximately 60 cm above those of the median level.
  • the base of the lances 5 is closed.
  • the motors 6 drive the lances 5 at two revolutions / minute.
  • the pumping in the tank 1 is carried out by means of two pumps 8; the pumps 8 are positive displacement pumps and which each flow 400 m 3 / h.
  • the pumps 8 are arranged in parallel and, upstream of each pump, there is a filter 9.
  • the two filters 9 are connected to the outlet of a 2000 liter tank 10, the inlet of which is connected by a pipe 11 to the lower part of the side wall 1a of the tank 1.
  • the filters 9 are intended to remove the inorganic elements which are present in the pumped oil.
  • Each of the two pumps 8 delivers on a distributor 12.
  • Each distributor 12 has three outlets, each of which delivers on a 200-liter enclosure 13; each enclosure 13 has six outputs fitted with a valve

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Cleaning In General (AREA)
  • Cleaning By Liquid Or Steam (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
  • Laser Beam Processing (AREA)
  • General Factory Administration (AREA)

Abstract

The invention concerns a method for cleaning an oil storage tank (1) with a floating cover containing crude oil, which consists in partially emptying the tank (1) above the sludge (3) contained therein; sucking up the crude oil and re-injecting it into the tank (1) using diffuser spray nozzles (5) borne by the floating cover (2), each spray nozzle being driven in rotation by a motor. The injection with the spray nozzles causes the oil volume to swirl and the sludge (3) to be suspended again in the oil. The invention also concerns a device for implementing said method.

Description

PROCEDE DE NETTOYAGE D'UNE CUVE DE PETROLE ET DISPOSITIF POUR LA MISE EN OEUVRE DUDIT PROCÉDÉMETHOD FOR CLEANING AN OIL TANK AND DEVICE FOR CARRYING OUT SAID METHOD
La présente invention a trait à un procédé de nettoyage d'une cuve à toit flottant renfermant du pétrole brut et a un dispositif pour la mise en oeuvre dudit procédé.The present invention relates to a method for cleaning a floating roof tank containing crude oil and to a device for carrying out said method.
On sait que les cuves de stockage de pétrole brut sont très généralement des cuves cylindriques à toit flottant. La structure de toit est donc à un niveau plus ou moins haut par rapport au sol selon la quantité de pétrole brut qui se trouve dans la cuve. Bien entendu, la périphérie du toit flottant comporte des organes d'étanchéité permettant d'éviter que le pétrole ne passe à la périphérie du toit. On a constaté que dans ces cuves de stockage, il se dépose progressivement sur le fond de cuve un sédiment constitué pour une large part des fractions les plus lourdes du pétrole brut stocké, notamment de composés paraffiniques, et d'éléments inorganiques tels que de l'eau, du sable, des particules de rouille ou analogues. Ce sédiment, appelé "sludge" en terminologie anglo-saxonne, est susceptible de constituer sur les fonds de cuve des couches très épaisses de 1 ou 2 mètres ou plus et il est nécessaire de nettoyer les cuves en enlevant ce sédiment. En effet, si le sédiment s'accumule sur le fond de cuve et que le toit flottant descend vers le fond au fur et à mesure du vidage de la cuve, le risque est d'avoir un contact entre le toit flottant et un point du dépôt du sédiment, ce qui déséquilibre le toit et le bloque en position oblique dans la paroi latérale de la cuve ; or, le poids d'un toit flottant étant de plusieurs centaines de tonnes, on conçoit que la réparation d'un tel incident entraîne des coûts considérables.It is known that crude oil storage tanks are generally cylindrical tanks with floating roofs. The roof structure is therefore at a higher or lower level relative to the ground depending on the amount of crude oil that is in the tank. Of course, the periphery of the floating roof has sealing members making it possible to prevent the oil from passing around the periphery of the roof. It has been found that in these storage tanks, a sediment is progressively deposited on the bottom of the tank, consisting largely of the heaviest fractions of the stored crude oil, in particular paraffinic compounds, and inorganic elements such as l water, sand, rust particles or the like. This sediment, called "sludge" in Anglo-Saxon terminology, is likely to constitute on the tank bottoms very thick layers of 1 or 2 meters or more and it is necessary to clean the tanks by removing this sediment. Indeed, if the sediment accumulates on the bottom of the tank and the floating roof descends towards the bottom as the tank is emptied, the risk is to have contact between the floating roof and a point on the deposit of sediment, which unbalances the roof and blocks it in an oblique position in the side wall of the tank; however, the weight of a floating roof being several hundred tonnes, it is understandable that the repair of such an incident involves considerable costs.
Pour permettre le vidage complet de la cuve sans que le toit flottant vienne en appui sur le fond de cuve, on prévoit dans le toit flottant des manchons dans lesquels on insère des béquilles de soutien. Lorsque le toit descend vers le fond, toutes les béquilles de soutien viennent simultanément poser sur le fond, ce qui maintient le toit à distance du fond et permet de vider totalement la cuve du pétrole brut liquide qu'elle contient. Pour extraire le sédiment lorsque la cuve est vidée de son pétrole liquide, on a déjà proposé d'effectuer un enlèvement manuel, le personnel entrant dans la cuve par les trous d'homme qu'elle comporte à la base de sa paroi latérale. Cette opération est longue, pénible et coûteuse et le sédiment, ainsi extrait d'une cuve, doit être évacué en évitant toute pollution ; il est alors généralement détruit par incinération. Une telle opération de nettoyage a un coût global prohibitif. On a déjà proposé également d'introduire par un trou d'homme, lorsque la cuve est vide, un agitateur central que l'on dispose à proximité de la couche de sédiment et qui peut tourner autour d'un axe vertical ; un tel agitateur utilise le caractère thixotropique du sédiment pour tenter de le remettre en suspension quand on a réintroduit du pétrole liquide dans la cuve, mais il n'a qu'une influence localisée dans la zone centrale du fond de cuve et, par ailleurs, la puissance, qui est nécessaire à sa mise en rotation à une vitesse efficace, entraîne la création d'une émulsion constituée de l'eau du sédiment et du pétrole brut, émulsion qui est hautement indésirable pour l'utilisation du pétrole brut stocké. Un tel dispositif de nettoyage ne donne donc pas satisfaction.To allow the complete emptying of the tank without the floating roof coming to bear on the tank bottom, there are provided in the floating roof sleeves in which support crutches are inserted. When the roof descends to the bottom, all the support crutches simultaneously come to rest on the bottom, which keeps the roof away from the bottom and allows the tank of liquid crude oil to be completely emptied. To extract the sediment when the tank is emptied of its liquid petroleum, it has already been proposed to carry out a manual removal, the personnel entering the tank through the manholes which it comprises at the base of its side wall. This operation is long, tedious and costly and the sediment, thus extracted from a tank, must be removed while avoiding any pollution; it is then generally destroyed by incineration. Such a cleaning operation has a prohibitive overall cost. It has also already been proposed to introduce through a manhole, when the tank is empty, a central agitator which is placed near the sediment layer and which can rotate around a vertical axis; such a stirrer uses the thixotropic nature of the sediment to try to resuspend it when liquid oil has been reintroduced into the tank, but it has only a localized influence in the central area of the tank bottom and, moreover, the power, which is necessary for it to rotate at an effective speed, leads to the creation of an emulsion consisting of sediment water and crude oil, an emulsion which is highly undesirable for the use of stored crude oil. Such a cleaning device is therefore not satisfactory.
On a également proposé de mettre en place à la base de la paroi latérale des cuves des hélico-agitateurs régulièrement répartis à la périphérie de la cuve ; ces hélico-agitateurs provoquent effectivement un mouvement du sédiment depuis la périphérie de la cuve vers la zone centrale de ladite cuve mais globalement le volume de la couche de sédiment n'est pas diminué de façon significative ; en revanche, la couche de sédiment a une épaisseur beaucoup plus irrégulière, d'où il résulte que le risque d'un incident à la descente du toit est loin d'être écarté. Enfin, la mise en oeuvre de ces hélico-agitateurs est extrêmement onéreuse vu l'énergie nécessaire à leur entraînement. Un tel procédé ne donne donc pas satisfaction.It has also been proposed to place at the base of the side wall of the tanks helical agitators regularly distributed around the periphery of the tank; these helico-agitators effectively cause movement of the sediment from the periphery of the tank towards the central zone of said tank, but overall the volume of the sediment layer is not significantly reduced; on the other hand, the layer of sediment has a much more irregular thickness, from which it follows that the risk of an incident on the descent of the roof is far from being ruled out. Finally, the implementation of these agitators is extremely expensive given the energy required for their training. Such a method is therefore not satisfactory.
L'invention est basée sur le fait que l'on peut remettre le sédiment en suspension dans le pétrole brut qui le surmonte, à condition de générer une turbulence et/ou des tourbillons dans l'ensemble du volume de pétrole liquide qui surmonte le sédiment et d'envoyer des jets de pétrole suffisamment puissants sur le sédiment pour que celui-ci, progressivement, soit remis en suspension et maintenu dans cet état par la turbulence imposée dans le pétrole brut liquide. De la sorte, la couche de sédiment disparaît petit à petit et se retrouve à l'intérieur du pétrole brut liquide, ce qui revalorise le sédiment puisqu'il n'y a plus aucune matière sédimentaire à évacuer hors de la cuve pour être détruite. Selon l'invention, on a donc proposé de vider partiellement la cuve sédimentée pour ne laisser subsister au- dessus du sédiment qu'une quantité restreinte de pétrole brut, quantité restreinte dans tout le volume de laquelle on va créer des turbulences ou tourbillons, en premier lieu, par une aspiration de pompage effectuée au niveau inférieur du pétrole brut liquide et, en deuxième lieu, par une réinjection dans la cuve du pétrole liquide pompé, le débit aspiré et réinjecté devant être suffisamment important par rapport au volume total subsistant sous le toit flottant au moment de l'opération de nettoyage. La réinjection dans la cuve s'effectue par des lances rotatives disposées verticalement sous le toit flottant, ces lances étant équipées de buses qui envoient des jets de pétrole en direction de la couche de sédiment ; la rotation des lances génère des tourbillons ayant pour axe l'axe des lances et l'on fait en sorte que ces tourbillons intéressent la totalité de la cuve. Pour ce faire, on remplace les béquilles du toit flottant par les lances qui assurent la réinjection du pétrole brut, le bas des lances arrivant au voisinage du plan moyen de la face supérieure de la couche de sédiment. La présente invention a, en conséquence, pour objet un procédé de remise en suspension d'un sédiment qui a, par dépôt, formé une couche sur le fond d'une cuve à toit flottant renfermant du pétrole brut, ledit toit flottant comportant une pluralité de trous de béquille régulièrement répartis sur sa surface, lesdits trous permettant de solidariser du toit des béquilles susceptibles de supporter le toit par appui sur le fond de cuve quand le niveau du pétrole brut dans la cuve est inférieur à la longueur des béquilles, caractérisé par le fait que :The invention is based on the fact that the sediment can be resuspended in the crude oil which overcomes it, provided that turbulence and / or vortices are generated in the entire volume of liquid oil which overcomes the sediment and to send jets of petroleum powerful enough on the sediment so that this one, gradually, is resuspended and maintained in this state by the turbulence imposed in the liquid crude oil. In this way, the layer of sediment gradually disappears and is found inside the liquid crude oil, which revalorizes the sediment since there is no longer any sedimentary material to be evacuated from the tank to be destroyed. According to the invention, it has therefore been proposed to partially empty the sedimented tank so as to leave only a limited quantity of crude oil above the sediment, a quantity which is limited throughout the volume of which turbulence or swirls are created, in first, by a pumping suction carried out at the lower level of the liquid crude oil and, secondly, by a reinjection into the tank of the pumped liquid oil, the flow aspirated and reinjected must be sufficiently large compared to the total volume remaining under the floating roof at the time of the cleaning operation. The reinjection into the tank is carried out by rotary lances arranged vertically under the floating roof, these lances being equipped with nozzles which send jets of oil in the direction of the layer of sediment; the rotation of the lances generates vortices having for axis the axis of the lances and one makes so that these vortices interest the whole of the tank. To do this, the crutches of the floating roof are replaced by the lances which ensure the reinjection of the crude oil, the bottom of the lances arriving in the vicinity of the mean plane of the upper face of the sediment layer. The present invention therefore relates to a process for resuspending a sediment which has, by deposition, formed a layer on the bottom of a floating roof tank containing crude oil, said floating roof comprising a plurality crutch holes regularly distributed over its surface, said holes making it possible to secure crutches capable of supporting the roof by pressing on the bottom of the tank when the level of crude oil in the tank is less than the length of the crutches, characterized by the fact that :
- on amène le niveau du brut dans la cuve à une distance L du niveau le plus élevé du sédiment sur le fond de cuve, avec L compris entre 2 et 5 mètres environ,- the level of crude oil in the tank is brought to a distance L from the highest level of the sediment on the bottom of the tank, with L between 2 and 5 meters approximately,
- on aspire le brut dans la cuve par au moins une pompe avec un débit horaire global égal à V/n, V étant le volume subsistant dans la cuve au-dessous du toit flottant et n étant un nombre compris entre 8 et 15 environ, - on réintroduit dans la cuve le brut pompé en l'injectant au moyen de lances portées par le toit flottant et mises en place verticalement dans la cuve au-dessus du sédiment, chacune desdites lances ayant, au-dessous du toit flottant, une longueur inférieure à L, étant entraînée en rotation autour de son axe, étant obturée à son extrémité inférieure et comportant au moins une buse disposée au- dessus du sédiment, buse dont le jet est orienté vers le fond de cuve, la section de sortie de la (ou des) buse (s) d'une même lance étant suffisamment faible pour que, avec le débit délivré par la (les) pompe (s), la pression de sortie du jet de brut soit suffisante pour que le volume tourbillonnaire généré par une lance recoupe les volumes tourbillonnaires afférents aux lances adjacentes,the crude oil is drawn into the tank by at least one pump with an overall hourly flow rate equal to V / n, V being the volume remaining in the tank below the floating roof and n being a number between 8 and 15 approximately, - the pumped crude is reintroduced into the tank by injecting it using lances carried by the floating roof and put in place vertically in the tank above the sediment, each of said lances having, below the floating roof, a length less than L, being driven in rotation about its axis, being closed at its lower end and comprising at least one nozzle disposed above the sediment, nozzle whose jet is oriented towards the bottom of the tank, the outlet section of the nozzle (s) of the same lance being sufficiently small so that, with the flow rate delivered by the ( the) pump (s), the output pressure of the crude jet is sufficient for the vortex volume generated by a lance to intersect the vortex volumes relating to the adjacent lances,
- on poursuit la mise en oeuvre du procédé jusqu'à ce que la densité du brut pompé soit égal à une valeur prédéterminée qui correspond à une remise en suspension quasi complète du sédiment.- the implementation of the process is continued until the density of the pumped crude oil is equal to a predetermined value which corresponds to an almost complete resuspension of the sediment.
Le choix du nombre n qui définit le débit horaire global aspiré et réintroduit dans la cuve est fonction des caractéristiques de la cuve à nettoyer par remise en suspension du sédiment, des caractéristiques physico-chimiques du sédiment lui-même et du temps d'immobilisation que l'on accepte pour procéder au nettoyage de la cuve.The choice of the number n which defines the overall hourly flow aspirated and reintroduced into the tank is a function of the characteristics of the tank to be cleaned by resuspending the sediment, the physicochemical characteristics of the sediment itself and the immobilization time that we accept to proceed with cleaning the tank.
Selon un mode de mise en oeuvre préféré du procédé selon l'invention, on dispose sur chaque lance une pluralité de buses réparties sur la longueur de la lance pour que le volume tourbillonnaire généré par la lance intéresse la totalité de la hauteur de la couche de brut liquide subsistant dans la cuve. De préférence, on entraîne les lances en rotation à une vitesse comprise entre 0, 25 et 4 tours/minute. Les lances peuvent être mises en rotation autour de leur axe par des moteurs électriques anti-déflagrants, un moteur étant affecté à chaque lance.According to a preferred embodiment of the method according to the invention, there is a plurality of nozzles distributed over the length of the lance on each lance so that the vortex volume generated by the lance concerns the entire height of the layer of crude liquid remaining in the tank. Preferably, the lances are rotated at a speed of between 0.25 and 4 revolutions / minute. The lances can be rotated about their axis by explosion-proof electric motors, one motor being assigned to each lance.
La présente invention a également pour objet un dispositif pour la mise en oeuvre du procédé tel que ci-dessus défini, ce dispositif étant caractérisé par le fait que les lances sont disposées dans les manchons des trous de béquille du toit flottant de la cuve. La mise en place des lances rotatives dans les trous de béquille, c'est-à-dire dans les manchons qui maintiennent habituellement les béquilles solidaires du toit flottant, a pour avantage essentiel de permettre de la mise en place du dispositif de nettoyage selon l'invention, sans qu'aucune modification n'ait à être apportée au toit flottant de la cuve à nettoyer : il suffit de retirer les béquilles une à une et de les remplacer au fur et à mesure par des lances rotatives. Les trous de béquille étant suffisamment rapprochés, les jets rotatifs issus de ces lances provoquent un brassage de la totalité du volume de pétrole brut qui subsiste dans la cuve, amenant ainsi l'érosion des fragments de sédiment jusqu'à leur complète remise en suspension.The present invention also relates to a device for implementing the method as defined above, this device being characterized in that the lances are arranged in the sleeves of the stand holes of the floating roof of the tank. The essential advantage of installing the rotary lances in the crutch holes, that is to say in the sleeves which usually hold the crutches integral with the floating roof, allows the installation of the cleaning device according to the invention, without any modification having to be made to the floating roof of the tank to be cleaned: it is enough to remove the crutches one by one and replace them progressively with rotating lances. The crutch holes being sufficiently close together, the rotary jets from these lances cause the entire volume of crude oil remaining in the tank to be mixed, thus causing the erosion of the sediment fragments until they are completely resuspended.
Selon un mode préféré de réalisation du dispositif selon l'invention, chaque lance comporte une pluralité de buses situées à des niveaux différents par rapport au fond de cuve, les jets des buses du niveau inférieur étant dirigés vers le fond de cuve alors que les jets des buses du niveau supérieur sont dirigés vers le toit flottant ; avantageusement, chaque lance comporte trois niveaux de buse, une buse du niveau médian générant un jet sensiblement horizontal alors que les buses des deux autres niveaux génèrent des jets dont l'axe est incliné de 50 à 70° par rapport à l'axe de la lance qui porte la buse. On peut prévoir que chaque niveau de buse comporte deux buses diamétralement opposées. De préférence, la (ou les) buse(s) de niveau inférieur est (sont) disposée(s) à un niveau compris entre 20 et 50 cm au-dessus du niveau moyen de la couche de sédiment. On peut avantageusement prévoir que la (ou les) pompe(s), qui aspire(nt) le brut dans la cuve est (sont) volumétrique(s) ; ce peut être, par exemple, des pompes à vis. Ce type de pompe fournit un débit donné et la pression que l'on obtient à la sortie des buses est, en conséquence, fonction de la section de sortie de l'ensemble des buses alimentées par la pompe. Le volume intéressé par la mise en turbulence autour d'une lance est évidemment d'autant plus important que la pression d'éjection du jet est plus élevée. On fait en sorte que ces volumes, qui sont sensiblement des cylindres ayant pour axe l'axe des lances, se recoupent avec les volumes afférents aux lances adjacentes pour qu'aucune partie du pétrole liquide contenu dans la cuve ne reste en dehors de la turbulence d'ensemble créée selon l'invention.According to a preferred embodiment of the device according to the invention, each lance comprises a plurality of nozzles situated at different levels relative to the tank bottom, the jets of the nozzles of the lower level being directed towards the tank bottom while the jets nozzles of the upper level are directed towards the floating roof; advantageously, each lance has three nozzle levels, a nozzle of the median level generating a substantially horizontal jet while the nozzles of the two other levels generate jets whose axis is inclined by 50 to 70 ° relative to the axis of the lance that carries the nozzle. Provision can be made for each nozzle level to have two diametrically opposite nozzles. Preferably, the lower level nozzle (s) is (are) placed at a level between 20 and 50 cm above the average level of the sediment layer. It is advantageously possible to provide that the pump (s), which sucks (s) the crude in the tank is (are) volumetric (s); it can be, for example, screw pumps. This type of pump provides a given flow rate and the pressure obtained at the outlet of the nozzles is therefore a function of the outlet section of all the nozzles supplied by the pump. The volume interested in the turbulence around a lance is obviously all the more important as the jet ejection pressure is higher. It is made so that these volumes, which are substantially cylinders having for axis the axis of the lances, overlap with the volumes pertaining to the adjacent lances so that no part of the liquid petroleum contained in the tank remains outside the turbulence assembly created according to the invention.
Bien entendu, le brassage du sédiment entraîne également la remise en suspension des éléments inorganiques contenus dans le sédiment. On prévoit donc un filtre à l'aspiration des pompes pour éliminer ces éléments inorganiques, les parties qui passent à travers le filtre étant, de toutes façons, broyés par les vis de la pompe. Lorsque l'opération de nettoyage selon l'invention est terminée, il y a dans la cuve, d'une part, un liquide homogène filtré qui est du pétrole brut directement disponible pour le pétrolier et, d'autre part, sur le fond de cuve une très faible couche constituée par les particules solides inorganiques les plus lourdes initialement contenues dans le sédiment. Généralement, l'exploitant de la cuve vidange le contenu liquide de la cuve en le transférant dans un autre réservoir contenant un brut semblable, cette vidange n'étant, bien entendu, effectuée qu'après avoir remis en place les béquilles du toit flottant à la place des lances utilisées pour la mise en oeuvre du procédé selon l'invention. Après que ce mélange avec le contenu d'une autre cuve ait été effectué, le raffinage du brut utilisé pour le nettoyage selon l'invention peut intervenir.Of course, the mixing of the sediment also causes the inorganic elements contained in the sediment to be resuspended. A filter is therefore provided at the suction of the pumps to remove these inorganic elements, the parts which pass through the filter being, in any case, ground by the screws of the pump. When the cleaning operation according to the invention is finished, there is in the tank, on the one hand, a homogeneous filtered liquid which is crude oil directly available for the tanker and, on the other hand, on the tank bottom a very weak layer consisting of the heaviest inorganic solid particles initially contained in the sediment. Generally, the operator of the tank empties the liquid content of the tank by transferring it to another tank containing a similar crude, this emptying being, of course, only carried out after having replaced the crutches of the floating roof at the place of the lances used for the implementation of the method according to the invention. After this mixing with the content of another tank has been carried out, the refining of the crude oil used for cleaning according to the invention can take place.
Selon un mode préféré de réalisation, le dispositif selon l'invention comporte au moins deux pompes précédées chacune par au moins un filtre et suivies chacune d'un répartiteur dont chaque voie de sortie débite sur une enceinte qui alimente p lances, p étant le même nombre entier pour toutes les enceintes du dispositif.According to a preferred embodiment, the device according to the invention comprises at least two pumps each preceded by at least one filter and each followed by a distributor, each outlet channel of which outputs on an enclosure which supplies p lances, p being the same integer for all the speakers of the device.
Pour mieux faire comprendre l'objet de l'invention, on va en décrire maintenant à titre d'exemple purement illustratif et non limitatif un mode de réalisation représenté sur le dessin annexé. Sur ce dessin :To better understand the object of the invention, there will now be described by way of purely illustrative and nonlimiting example an embodiment shown in the accompanying drawing. On this drawing :
- la figure 1 représente schématiquement un dispositif pour la mise en oeuvre du procédé selon l'invention ; - la figure 2 représente schématiquement en coupe une cuve de pétrole brut à toit flottant dans laquelle on a mis en place une lance pour la réinjection du pétrole brut pompé comme indiqué sur la figure 1, les autres lances n'étant pas figurées ;- Figure 1 schematically shows a device for implementing the method according to the invention; - Figure 2 shows schematically in section a crude oil tank with floating roof in which a lance has been put in place for the reinjection of the crude oil pumped as indicated in Figure 1, the other lances not being shown;
- la figure 3 représente une vue en plan du toit flottant de la cuve selon la figure 2, cette vue faisant apparaître les manchons de béquille prévus sur ledit toit flottant et, en pointillé, les cercles délimitant les volumes cylindriques de turbulence générés par chacune des lances insérée dans lesdits manchons de béquille.- Figure 3 shows a plan view of the floating roof of the tank according to Figure 2, this view showing the crutch sleeves provided on said floating roof and, in dotted lines, the circles delimiting the cylindrical volumes of turbulence generated by each of lances inserted in said crutch sleeves.
En se référant au dessin, on voit que l'on a désigné par 1 dans son ensemble une cuve de stockage de pétrole brut ; la cuve 1 est constituée d'une paroi latérale cylindrique la, dont la base lb constitue le fond de cuve. La cuve est équipée d'un toit flottant 2 dont la périphérie comporte des organes d'étanchéité non représentés. La cuve 1 est destinée au stockage de pétrole brut, le toit 2 flottant sur le brut. De façon classique, une telle cuve peut avoir un diamètre d'environ 50 m et une hauteur de 15 m. Dans une telle cuve, le brut décante progressivement et donne naissance à un sédiment 3 qui constitue une couche sur le fond de cuve lb, couche qui peut atteindre plusieurs mètres d'épaisseur ; la surface de la couche est relativement irrégulière. Le sédiment est généralement de nature thyxotropique. Pour nettoyer une cuve de ce type et enlever la couche de sédiment 3, on vide partiellement la cuve ; si l'on suppose une couche de sédiment d'une épaisseur moyenne de 1 m, on laisse subsister dans la cuve au-dessus du sédiment environ 3 m de pétrole brut, c'est-à-dire que le toit 2 se trouve à peu près à 4 m au-dessus du fond de cuve. Dans l'exemple décrit, le toit flottant 2 est équipé de 72 béquilles qui traversent le toit par des manchons de béquille désignés par 4 sur la figure 3. Ces béquilles ont une longueur comprise entre 1,8 et 2,2 m et viennent en appui sur le fond de cuve lorsque le toit flottant descend suffisamment bas. Lorsqu'on a amené le toit flottant 2 à 4 m au-dessus du fond de cuve, on retire une à une les béquilles et on les remplace par des lances 5 ; chaque lance 5 est un tube que l'on met en place à pivotement dans un manchon de béquille. La lance 5 est entraînée en rotation autour de son axe par un moteur électrique anti-déflagrant 6 situé en tête de lance, au-dessus du toit flottant 2. L'alimentation en pétrole brut de la lance 5 est effectuée par un tuyau 7. La lance 5 comporte sur trois niveaux de buses permettant d'évacuer le pétrole brut amené dans le tube qui constitue la lance par le tuyau 7. Ces buses orientent les jets de sortie. Chaque niveau comporte deux buses diamétralement opposées sur la lance. Les deux buses du niveau inférieur fournissent des jets 8a dont les axes font 60° avec l'axe de la lance 5, ces jets étant orientés vers le fond de cuve ; les deux buses du niveau supérieur fournissent des jets 8c. dont les axes font avec l'axe de la lance 5 un angle de 60°, ces jets étant orientés vers le toit flottant 2 ; les deux buses du niveau médian forment des jets 8b dont les axes sont sensiblement horizontaux. Les buses du niveau inférieur sont à peu près à 30 cm au- dessus du plan moyen de la couche de sédiment 3 ; les buses du niveau médian sont à peu près à 60 cm au dessus de celles du niveau inférieur et les buses du niveau supérieur sont également à environ 60 cm au dessus de celles du niveau médian. La base des lances 5 est obturée. Les moteurs 6 entraînent les lances 5 à deux tours/minute.Referring to the drawing, it can be seen that a crude oil storage tank has been designated by 1 as a whole; the tank 1 consists of a cylindrical side wall la, the base lb of which constitutes the bottom of the tank. The tank is equipped with a floating roof 2, the periphery of which comprises sealing members, not shown. The tank 1 is intended for the storage of crude oil, the roof 2 floating on the crude. Conventionally, such a tank can have a diameter of about 50 m and a height of 15 m. In such a tank, the crude gradually settles and gives rise to a sediment 3 which constitutes a layer on the bottom of the tank 1b, a layer which can reach several meters in thickness; the diaper surface is relatively uneven. The sediment is generally of a thyxotropic nature. To clean a tank of this type and remove the layer of sediment 3, the tank is partially emptied; if we assume a layer of sediment with an average thickness of 1 m, we leave in the tank above the sediment about 3 m of crude oil, that is to say that the roof 2 is located about 4 m above the bottom of the tank. In the example described, the floating roof 2 is equipped with 72 crutches which pass through the roof by crutch sleeves designated by 4 in FIG. 3. These crutches have a length of between 1.8 and 2.2 m and come in support on the tank bottom when the floating roof descends sufficiently low. When the floating roof has been brought 2 to 4 m above the bottom of the tank, the crutches are removed one by one and replaced with lances 5; each lance 5 is a tube which is pivotally placed in a crutch sleeve. The lance 5 is driven in rotation about its axis by an explosion-proof electric motor 6 located at the head of the lance, above the floating roof 2. The crude oil is supplied to the lance 5 by a pipe 7. The lance 5 has on three levels of nozzles making it possible to evacuate the crude oil brought into the tube which constitutes the lance by the pipe 7. These nozzles orient the outlet jets. Each level has two diametrically opposite nozzles on the lance. The two nozzles of the lower level provide jets 8a whose axes are 60 ° with the axis of the lance 5, these jets being oriented towards the bottom of the tank; the two upper level nozzles provide 8c jets. whose axes make with the axis of the lance 5 an angle of 60 °, these jets being oriented towards the floating roof 2; the two nozzles of the median level form jets 8b whose axes are substantially horizontal. The nozzles on the lower level are approximately 30 cm above above the mean plane of the sediment layer 3; the median level nozzles are approximately 60 cm above those of the lower level and the upper level nozzles are also approximately 60 cm above those of the median level. The base of the lances 5 is closed. The motors 6 drive the lances 5 at two revolutions / minute.
Le pompage dans la cuve 1 est effectué au moyen de deux pompes 8 ; les pompes 8 sont des pompes volumétriques à vis et qui débitent chacune 400 m3/h. Les pompes 8 sont disposées en parallèle et, en amont de chaque pompe, on a disposé un filtre 9. Les deux filtres 9 sont branchés sur la sortie d'un réservoir 10 de 2000 litres dont l'entrée est reliée par une canalisation 11 à la partie inférieure de la paroi latérale la de la cuve 1. Les filtres 9 sont destinés à éliminer les éléments inorganiques qui se trouvent dans le pétrole pompé. Chacune des deux pompes 8 débite sur un répartiteur 12. Chaque répartiteur 12 comporte trois sorties dont chacune débite sur une enceinte 13 de 200 litres ; chaque enceinte 13 comporte six sorties équipées d'une vanneThe pumping in the tank 1 is carried out by means of two pumps 8; the pumps 8 are positive displacement pumps and which each flow 400 m 3 / h. The pumps 8 are arranged in parallel and, upstream of each pump, there is a filter 9. The two filters 9 are connected to the outlet of a 2000 liter tank 10, the inlet of which is connected by a pipe 11 to the lower part of the side wall 1a of the tank 1. The filters 9 are intended to remove the inorganic elements which are present in the pumped oil. Each of the two pumps 8 delivers on a distributor 12. Each distributor 12 has three outlets, each of which delivers on a 200-liter enclosure 13; each enclosure 13 has six outputs fitted with a valve
14 et reliées chacune à un tuyau 7 pour l'alimentation de deux lances 5.14 and each connected to a pipe 7 for the supply of two lances 5.
Lorsque les pompes 8 aspirent le brut dans la cuve 1 et le refoulent dans les lances 5, il se crée autour de chaque lance un volume turbulent et tourbillonnaire, qui est approximativement délimité par les cercles dessinés en pointillé sur la figure 3. On choisit des sections de sortie de buses, qui soient suffisamment faibles pour que la pression d'éjection du jet soit suffisante pour que le rayon du volume tourbillonnaire créé autour de la lance permette à ce volume tourbillonnaire de venir recouper les volumes tourbillonnaires afférents aux lances adjacentes. De la sorte, l'ensemble du pétrole brut liquide qui surmonte le sédiment subit une mise en mouvement, les buses des niveaux inférieurs des lances 5 produisent des jets tournants qui viennent attaquer la surface supérieure du sédiment 3, lequel, étant thyxotropique, se remet lentement en suspension dans le pétrole brut qui le surmonte. Etant donné que ce pétrole brut est brassé dans tout son volume, le sédiment ne peut pas se redéposer et se répartit dans tout le volume du pétrole brut qui surmonte la couche de sédiment 3.When the pumps 8 draw the crude oil into the tank 1 and discharge it into the lances 5, there is created around each lance a turbulent and swirling volume, which is approximately delimited by the circles drawn in dotted lines in FIG. 3. nozzle outlet sections, which are small enough for the jet ejection pressure to be sufficient for the radius of the vortex volume created around the lance to allow this vortex volume to intersect the vortex volumes pertaining to the adjacent lances. In this way, all of the liquid crude oil which surmounts the sediment undergoes a movement, the nozzles of the lower levels of the lances 5 produce rotating jets which attack the upper surface of the sediment 3, which, being thyxotropic, recovers slowly suspended in the crude oil that overcomes it. Since this crude oil is brewed throughout its volume, the sediment cannot be redeposited and is distributed throughout the volume of crude oil which surmounts the layer of sediment 3.
On constate qu'après une période de fonctionnement comprise entre 5 et 7 jours, le sédiment a pratiquement disparu sur toute la surface du fond de cuve lb, seuls restant sur ledit fond des éléments inorganiques initialement contenus dans le sédiment. Pour repérer la fin de l'opération, on utilise généralement une mesure de densité du pétrole brut, le nettoyage étant arrêté lorsque la densité atteint la valeur que l'on a prédéterminée par le calcul à partir de prélèvements initiaux de brut et de sédiment et des volumes relatifs de sédiment et de pétrole brut maintenu dans la cuve pour l'opération de nettoyage. It can be seen that after an operating period of between 5 and 7 days, the sediment has practically disappeared over the entire surface of the bottom of the tank 1b, only remaining on the bottom of the elements inorganic initially contained in the sediment. To identify the end of the operation, a crude oil density measurement is generally used, the cleaning being stopped when the density reaches the value which has been predetermined by the calculation from initial crude and sediment samples and relative volumes of sediment and crude oil kept in the tank for the cleaning operation.

Claims

REVENDICATIONS
1. Procédé de remise en suspension d'un sédiment (3) qui a, par dépôt, formé une couche sur le fond d'une cuve (1) à toit flottant 2) renfermant du pétrole brut, ledit toit flottant (2) comportant une pluralité de trous de béquilles (4) régulièrement répartis sur sa surface, lesdits trous (4) permettant de solidariser du toit (2) des béquilles susceptibles de supporter le toit (2) par appui sur le fond de cuve (lb) quand le niveau du brut dans la cuve (1) est inférieur à la longueur (D) des béquilles, caractérisé par le fait que : - on amène le niveau de brut dans la cuve (1) à une distance (L) du niveau le plus élevé du sédiment (3) sur le fond de cuve (lb), avec L compris entre 2 et 5 mètres environ,1. Method for resuspending a sediment (3) which has, by deposition, formed a layer on the bottom of a tank (1) with a floating roof 2) containing crude oil, said floating roof (2) comprising a plurality of crutch holes (4) regularly distributed over its surface, said holes (4) making it possible to secure crutches capable of supporting the roof (2) by pressing on the tank bottom (lb) when the level of the crude in the tank (1) is less than the length (D) of the crutches, characterized in that: - the level of crude in the tank (1) is brought to a distance (L) from the highest level sediment (3) on the bottom of the tank (lb), with L of between 2 and 5 meters approximately,
- on aspire le brut dans la cuve (1) par au moins une pompe (8) avec un débit horaire global égal à V/n, V étant le volume subsistant dans la cuve (1) au-dessous du toit flottant (2) et n étant un nombre compris entre 8 et 15 environ,- the crude oil is drawn into the tank (1) by at least one pump (8) with an overall hourly flow rate equal to V / n, V being the volume remaining in the tank (1) below the floating roof (2) and n being a number between approximately 8 and 15,
- on réintroduit dans la cuve (1) le brut pompé en l'injectant au moyen de lances (5) portées par le toit flottant (2) et mises en place verticalement dans la cuve (1) au-dessus du sédiment (3), chacune desdites lances (5) ayant, au-dessous du toit flottant (2), une longueur inférieure à L, étant entraînée en rotation autour de son axe, étant obturée à son extrémité inférieure et comportant au moins une buse disposée au-dessus du sédiment (3), buse dont le jet (8a) est orienté vers le fond de cuve (la), la section de sortie de la (ou des) buse (s) d'une même lance (5) étant suffisamment faible pour que, avec le débit délivré par la (les) pompe (s) (8), la pression de sortie du jet de brut soit suffisante pour que le volume tourbillonnaire généré par une lance (5) recoupe les volumes tourbillonnaires afférents aux lances (5) adjacentes, - on poursuit la mise en oeuvre du procédé jusqu'à ce que la densité du brut pompé soit égal à une valeur prédéterminée qui correspond à une remise en suspension quasi complète du sédiment (3).- the pumped crude is reintroduced into the tank (1) by injecting it using lances (5) carried by the floating roof (2) and placed vertically in the tank (1) above the sediment (3) , each of said lances (5) having, below the floating roof (2), a length less than L, being driven in rotation about its axis, being closed at its lower end and comprising at least one nozzle disposed above sediment (3), nozzle whose jet (8a) is oriented towards the bottom of the tank (la), the outlet section of the nozzle (s) of the same lance (5) being sufficiently small to that, with the flow delivered by the pump (s) (8), the output pressure of the crude jet is sufficient for the vortex volume generated by a lance (5) to overlap the vortex volumes relating to the lances (5 ) adjacent, - the process is continued until the density of the crude pumped is equal to a predetermined value born which corresponds to an almost complete resuspension of the sediment (3).
2. Procédé selon la revendication 1, caractérisé par le fait que l'on dispose sur chaque lance (5) une pluralité de buses réparties sur la longueur de la lance, pour que le volume tourbillonnaire généré par une lance (5) intéresse la totalité de la hauteur de la couche de brut liquide subsistant dans la cuve (1).2. Method according to claim 1, characterized in that there is on each lance (5) a plurality of nozzles distributed over the length of the lance, so that the swirling volume generated by a lance (5) covers the entire height of the layer of liquid crude remaining in the tank (1).
3. Procédé selon l'une des revendication 1 ou 2, caractérisé par le fait que la vitesse de rotation des lances (5) est comprise entre 0, 25 et 4 tours/minute.3. Method according to one of claim 1 or 2, characterized in that the speed of rotation of the lances (5) is between 0, 25 and 4 revolutions / minute.
4. Dispositif pour la mise en oeuvre du procédé selon l'une des revendications 1 à 3, caractérisé par le fait que les lances (5) sont disposées à la place des béquilles, dans les manchons des trous de béquille (4) du toit flottant (2) de la cuve (1). 4. Device for implementing the method according to one of claims 1 to 3, characterized in that the lances (5) are arranged in place of the crutches, in the sleeves of the crutch holes (4) of the roof floating (2) of the tank (1).
5. Dispositif selon la revendication 4, caractérisé par le fait que chaque lance (5) comporte une pluralité de buses situées à des niveaux différents par rapport au fond de cuve (lb), les jets (8a) des buses du niveau inférieur étant dirigés vers le fond de cuve (lb), alors que les jets (8ç_) des buses du niveau supérieur sont dirigés vers le toit flottant (2).5. Device according to claim 4, characterized in that each lance (5) comprises a plurality of nozzles located at different levels relative to the tank bottom (lb), the jets (8a) of the nozzles of the lower level being directed towards the tank bottom (lb), while the jets (8ç_) of the upper level nozzles are directed towards the floating roof (2).
6. Dispositif selon la revendication 5, caractérisé par le fait que chaque lance (5) comporte trois niveaux de buse, une buse du niveau médian générant un jet (8b) sensiblement horizontal alors que les buses des deux autres niveaux génèrent des jets (8â, 8ç_), dont l'axe est incliné de 50 à 70° par rapport à l'axe de la lance (5), qui porte la buse.6. Device according to claim 5, characterized in that each lance (5) comprises three nozzle levels, a nozzle of the median level generating a jet (8b) substantially horizontal while the nozzles of the other two levels generate jets (8â , 8ç_), whose axis is inclined from 50 to 70 ° relative to the axis of the lance (5), which carries the nozzle.
7. Dispositif selon la revendication 6, caractérisé par le fait que chaque niveau de buse comporte deux buses diamétralement opposées.7. Device according to claim 6, characterized in that each nozzle level comprises two diametrically opposite nozzles.
8. Dispositif selon l'une des revendications 6 ou 7, caractérisé par le fait que la (ou les) buse(s) de niveau inférieur est (sont) disposée(s) à un niveau compris entre 20 et 50 cm au-dessus du niveau moyen de la couche de sédiment (3).8. Device according to one of claims 6 or 7, characterized in that the (or) nozzle (s) of lower level is (are) arranged (s) at a level between 20 and 50 cm above the average level of the sediment layer (3).
9. Dispositif selon l'une des revendications 4 à 8, caractérisé par le fait que la (ou les) pompe(s) (8), qui aspire(nt) le brut dans la cuve (1) est (sont) volumétrique(s). 10. Dispositif selon la revendication 9, caractérisé par le fait qu'il comporte au moins deux pompes (8) précédées chacune par au moins un filtre (9) et suivie chacune d'un répartiteur (12), dont chaque voie de sortie débite sur une enceinte (13), qui alimente p lances (5), p étant le même nombre entier pour toutes les enceintes (13) du dispositif. REVENDICATIONS MODIFIEES9. Device according to one of claims 4 to 8, characterized in that the (or) pump (s) (8), which sucks (s) the crude in the tank (1) is (are) volumetric ( s). 10. Device according to claim 9, characterized in that it comprises at least two pumps (8) each preceded by at least one filter (9) and each followed by a distributor (12), each output outlet of which outputs on an enclosure (13), which supplies p lances (5), p being the same integer for all the enclosures (13) of the device. AMENDED CLAIMS
[reçues par le Bureau International le 23 octobre 1998(23.10.98); revendications 1-10 remplacées par les revendications 1-9 modifιées(2 pages)][received by the International Bureau on October 23, 1998 (23.10.98); claims 1-10 replaced by amended claims 1-9 (2 pages)]
1. Procédé de remise en suspension d'un sédiment (3) qui a, par dépôt, formé une couche sur le fond d'une cuve (1) à toit flottant 2) renfermant du pétrole brut, ledit toit flottant (2) comportant une plur∑ilité de trous de béquilles (4) régulièrement répartis sur sa surface, lesdits trous (4) permettant de solidariser du toit (2) des béquilles susceptibles de supporter le toit (2) par appui sur le fond de cuve (lb) quand le niveau du brut dans la cuve (1) est inférieur à la longueur (D) des béquilles, dans lequel : - on amène le niveau de brut dans la cuve (1) à une distance (L) du niveau le plus élevé du sédiment (3) sur le fond de cuve (lb),1. Method for resuspending a sediment (3) which has, by deposition, formed a layer on the bottom of a tank (1) with a floating roof 2) containing crude oil, said floating roof (2) comprising a plurality of crutch holes (4) regularly distributed over its surface, said holes (4) making it possible to secure crutches capable of supporting the roof (2) by pressing on the tank bottom (2) when the level of crude in the tank (1) is less than the length (D) of the crutches, in which: - the level of crude in the tank (1) is brought to a distance (L) from the highest level of the sediment (3) on the bottom of the tank (lb),
- on aspire le brut dans la cuve (1) par au moins une pompe (8) avec un débit hor.aire glob.al égal à V/n, V étant le volume subsistant dans la cuve (1) au-dessous du toit flott.ant (2), - on réintroduit dans la cuve (1) le brut pompé en l'injectant au moyen de lances (5) portées par le toit flottant (2) et mises en place verticalement dans la cuve (1) au-dessus du sédiment (3), chacune desdites l.ances (5) ayant, au-dessous du toit flottant (2), une longueur inférieure à L, étant entraînée en rotation autour de son axe, étant obturée à son extrémité inférieure et comportant au moins une buse disposée au-dessus du sédiment (3), buse dont le jet (8a) est orienté vers le fond de cuve (la), la section de sortie de la (ou des) buse (s) d'une même lance (5) étant suffis.amment faible pour que, avec le débit délivré par la (les) pompe (s) (8), la pression de sortie du jet de brut soit suffisante pour que le volume tourbillonnaire généré par une lance (5) recoupe les volumes tourbillonnaires afférents aux lances (5) adjacentes,- the crude oil is sucked into the tank (1) by at least one pump (8) with a global hourly flow rate equal to V / n, V being the volume remaining in the tank (1) below the roof floating (2), - the crude pumped is reintroduced into the tank (1) by injecting it by means of lances (5) carried by the floating roof (2) and placed vertically in the tank (1) at above the sediment (3), each of said lances (5) having, below the floating roof (2), a length less than L, being driven in rotation about its axis, being closed at its lower end and comprising at least one nozzle disposed above the sediment (3), nozzle whose jet (8a) is oriented towards the bottom of the tank (la), the outlet section of the (or) nozzle (s) of a same lance (5) being sufficiently low so that, with the flow rate delivered by the pump (s) (8), the output pressure of the crude jet is sufficient for the swirling volume generated by a lance ( 5) intersects the swirling volumes relating to the adjacent lances (5),
- on poursuit la mise en oeuvre du procédé jusqu'à ce que la densité du brut pompé soit égal à une valeur prédéterminée qui correspond à une remise en suspension quasi complète du sédiment (3), caractérisé par le fait que l'on choisit la distance L comprise entre 2 et 5 mètres environ, le nombre n compris entre 8 et 15 environ et que les lances (5) sont entraînées en rotation à une vitesse comprise entre 0,25 et 4 tours/minute. 2. Procédé selon la revendication 1, caractérisé par le fait que la- the implementation of the process is continued until the density of the pumped crude oil is equal to a predetermined value which corresponds to an almost complete resuspension of the sediment (3), characterized in that the distance L comprised between 2 and 5 meters approximately, the number n comprised between 8 and 15 approximately and that the lances (5) are rotated at a speed comprised between 0.25 and 4 revolutions / minute. 2. Method according to claim 1, characterized in that the
(ou les) buse(s) de niveau inférieur de chaque lance est (sont) disposée(s) à un niveau compris entre 20 et 50 cm au-dessus du niveau moyen de la couche de sédiment (3).(or the) lower level nozzle (s) of each lance is (are) arranged at a level between 20 and 50 cm above the average level of the sediment layer (3).
3. Procédé selon l'une des revendications 1 ou 2, caractérisé par le fait que l'on dispose sur chaque lance (5) une pluralité de buses réparties sur la longueur de la lance, pour que le volume tourbillonnaire généré par une lance (5) intéresse la totalité de la hauteur de la couche de brut liquide subsistant dans la cuve (1).3. Method according to one of claims 1 or 2, characterized in that there is on each lance (5) a plurality of nozzles distributed over the length of the lance, so that the swirling volume generated by a lance ( 5) concerns the entire height of the layer of liquid crude remaining in the tank (1).
4. Dispositif pour la mise en oeuvre du procédé selon l'une des revendications 1 à 3, caractérisé par le fait que les lances (5) sont disposées à la place des béquilles, dans les manchons des trous de béquille (4) du toit flottant (2) de la cuve (1).4. Device for implementing the method according to one of claims 1 to 3, characterized in that the lances (5) are arranged in place of the crutches, in the sleeves of the crutch holes (4) of the roof floating (2) of the tank (1).
5. Dispositif selon la revendication 4, caractérisé par le fait que chaque lance (5) comporte une pluralité de buses situées à des niveaux différents par rapport au fond de cuve (lb), les jets (8a) des buses du niveau inférieur étant dirigés vers le fond de cuve (lb), alors que les jets (8ç) des buses du niveau supérieur sont dirigés vers le toit flottant5. Device according to claim 4, characterized in that each lance (5) comprises a plurality of nozzles located at different levels relative to the tank bottom (lb), the jets (8a) of the nozzles of the lower level being directed towards the tank bottom (lb), while the jets (8c) of the upper level nozzles are directed towards the floating roof
(2).(2).
6. Dispositif selon la revendication 5, caractérisé par le fait que chaque lance (5) comporte trois niveaux de buse, une buse du niveau médian générant un jet (8b) sensiblement horizontal alors que les buses des deux autres niveaux génèrent des jets (8a, 8ç), dont l'axe est incliné de 50 à 70° par rapport à l'axe de la lance (5), qui porte la buse.6. Device according to claim 5, characterized in that each lance (5) comprises three nozzle levels, a nozzle of the middle level generating a jet (8b) substantially horizontal while the nozzles of the other two levels generate jets (8a , 8c), whose axis is inclined from 50 to 70 ° relative to the axis of the lance (5), which carries the nozzle.
7. Dispositif selon la revendication 6, caractérisé par le fait que chaque niveau de buse comporte deux buses diamétralement opposées. 8. Dispositif selon l'une des revendications 4 à 7, caractérisé par le fait que la (ou les) pompe(s) (8), qui aspire(nt) le brut dans la cuve (1) est (sont) volumétrique(s).7. Device according to claim 6, characterized in that each nozzle level comprises two diametrically opposite nozzles. 8. Device according to one of claims 4 to 7, characterized in that the (or the) pump (s) (8), which sucks (s) the crude in the tank (1) is (are) volumetric ( s).
9. Dispositif selon la revendication 8, caractérisé par le fait qu'il comporte au moins deux pompes (8) précédées chacune par au moins un filtre (9) et suivie chacune d'un répartiteur (12), dont chaque voie de sortie débite sur une enceinte (13), qui alimente p lances (5), p étant le même nombre entier pour toutes les enceintes (13) du dispositif. 9. Device according to claim 8, characterized in that it comprises at least two pumps (8) each preceded by at least one filter (9) and each followed by a distributor (12), each output outlet of which delivers on an enclosure (13), which supplies p lances (5), p being the same integer for all the enclosures (13) of the device.
EP97952101A 1997-12-15 1997-12-18 Method for cleaning an oil storage tank and device for implementing same Expired - Lifetime EP1091812B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
LU90183A LU90183B1 (en) 1997-12-15 1997-12-15 Process for cleaning an oil tank and device for carrying out said process
PCT/FR1997/002347 WO1999032238A1 (en) 1997-12-15 1997-12-18 Method for cleaning an oil storage tank and device for implementing same

Publications (2)

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EP1091812A1 true EP1091812A1 (en) 2001-04-18
EP1091812B1 EP1091812B1 (en) 2007-08-22

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EP (1) EP1091812B1 (en)
AT (1) ATE370801T1 (en)
AU (1) AU5564598A (en)
BR (1) BR9714913A (en)
DE (1) DE69738052T2 (en)
DK (1) DK1091812T3 (en)
EA (1) EA003659B1 (en)
ES (1) ES2293666T3 (en)
HK (1) HK1035509A1 (en)
LU (1) LU90183B1 (en)
NO (1) NO322452B1 (en)
PT (2) PT1091812E (en)
UA (1) UA68367C2 (en)
WO (1) WO1999032238A1 (en)

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Publication number Priority date Publication date Assignee Title
KR100475172B1 (en) * 2001-02-20 2005-03-08 에스케이 주식회사 Method for Removing Sludges in A Crude Oil Tank and Recovering Oil Therefrom
GB0116579D0 (en) * 2001-07-06 2001-08-29 Mackrill David Cleaning apparatus and method
GB2397996B (en) * 2003-02-07 2005-01-19 Willacy Oil Services Ltd Sludge dispersal/inhibition in floating roof storage tanks
MX2008014610A (en) * 2006-05-15 2009-03-31 Petrojet Internat System for cleaning an oil tank and method of cleaning an oil tank.
US8931948B2 (en) 2008-10-01 2015-01-13 Bp Corporation North America Inc. Process and apparatus for mixing a fluid within a vessel
RU2443483C2 (en) * 2010-03-26 2012-02-27 Александр Фёдорович Луцык Method of washing out tank bottom sediment
BR102012015763A2 (en) * 2012-06-26 2014-12-02 Joel Ligiero Junior Vargas METHOD FOR CLEANING A STORAGE TANK USING SKIMMER AND USING SKIMMER.

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Publication number Priority date Publication date Assignee Title
EP0160805B1 (en) * 1984-03-13 1991-12-04 FIPROSA Holding Method and apparatus for the recovery of crude oil or refining products from their sludge
US4828625A (en) * 1987-03-09 1989-05-09 Nalco Chemical Company Apparatus and method for removal of sludge from tanks
DE4101184C2 (en) * 1991-01-17 1994-07-14 Sobinger Dietrich Process and installation for cleaning floating roof tanks for storing crude oil
US5087294A (en) * 1991-04-02 1992-02-11 Allen Rechtzigel Method and apparatus for cleaning a petroleum products storage tank
GB9508257D0 (en) * 1995-04-24 1995-06-14 British Nuclear Fuels Plc Removing liquids from tanks

Non-Patent Citations (1)

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Title
See references of WO9932238A1 *

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DE69738052T2 (en) 2008-05-15
PT975148E (en) 2007-02-28
NO20003169L (en) 2000-08-11
ATE370801T1 (en) 2007-09-15
WO1999032238A1 (en) 1999-07-01
ES2293666T3 (en) 2008-03-16
AU5564598A (en) 1999-07-12
HK1035509A1 (en) 2001-11-30
NO322452B1 (en) 2006-10-09
DE69738052D1 (en) 2007-10-04
EP1091812B1 (en) 2007-08-22
LU90183B1 (en) 1998-04-06
UA68367C2 (en) 2004-08-16
EA003659B1 (en) 2003-08-28
PT1091812E (en) 2007-12-03
BR9714913A (en) 2002-05-07
NO20003169D0 (en) 2000-06-19
EA200000668A1 (en) 2000-12-25
DK1091812T3 (en) 2008-01-28

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