AU683929B2 - Anti-sedimentation process - Google Patents

Abstract

A process and device are disclosed for preventing sediments from precipitating from mixtures of for example crude oil (4), refinery products and petrochemicals, which otherwise settle mainly at the bottom of cistern installations (T). Sediments have a precursor in the form of a thickening precipitation zone (4, 2). The precipitation of sediments is prevented by disturbing the formation of the precipitation zone (4, 2). This disturbance takes the form of global disturbance patterns (S) with local disturbance spots (L) and is applied according to the disturbance pattern (S) in a disturbance zone by means of disturbance devices (V) with disturbing means. The disturbance is hydrodynamically or mechanically applied by nozzles arranged in the disturbance zones through which crude oil flows out or by strings that may be made to vibrate as disturbing means (8, 12) excited by exciting elements (5) through pulling and pushing units (6) in the disturbance devices. The strings vibrate with fundamental and partial waves and deflect the components of the mixtures depending on the amplitude of said sonic waves.

Description

P0926A.PCT 22. Februar 1996 METHOD FOR AVOIDING SEDIMENTATION The invention relates to a method for avoiding a sedimentation from liquid phases or a thickening of liquid phases or liquid mixtures such as, oils, crude oil, refinery products and petrochemical products, which are successively mainly deposited on the bottom of scorage tanks, in which prior to the start of sedimentation in such tanks a precursor forms as a thickening sedimentation zone and as a result thickening is initiated and successively passes into sedimentation and/or thickening.

During the storage of liquid phases such as, oils, crude, refinery products and petrochemical products, undesired sedimentatic i and thickening often occurs, which will be discussed hereinafter in connection with the particular deposit-forming example of crude oil.

The liquid phase of crude oil is a mixture mainly consisting of hydrocarbons such as paraffins, aromatics and naphthenes, which are also accompanied by nonhydrocarbons or so-called impurities such as sludge, water, dissolved salts, sulphur compounds, sand, etc. In certain circumstances prior to processing in refineries, said crude undergoes rough refining processes for the separation of impurities. It is then generally conventional to store the crude to be processed I IL~I I P0926A.PCT -2and also the precleaned crude in large tanks. This involves holding times of varying lengths, which can be in the case of stockpiling long, whereas it is much less long with operationbased stored procedures.

In particular long holding times favour an undesired deposit formation from crude in tanks. These deposits can be of different types, being e.g. favoured by emulsions of water with hydrocarbon fractions, or can consist of segregates of heavy hydrocarbon fractions (hard waxes) or segregates of sludge or salts. This gives a type of oil sludge, which is compressed on the bottom of tanks and leads to high costs aind losses.

Costs and losses are caused because said oil sludge reduces the capacity of the tanks and also binds crude or largely consists of thickened crude. Thus, apart from the costly space loss in the tank, storage leads to a not inconsiderable substance loss. In addition, at least in the case of disposal the space loss cannot be removed again (storage of the sludge in closed systems, tanks made available for this purpose), or there is a final storage which is prejudicial to the environment (tipping out the sludge into open basins). In the case of large tanks with a diameter up to 1. 0 m, a height of 20 m and a corresponding capacity, sediment thicknesses of 1 to 2 m lead to a 5 to 10% capacity loss. In addition, the operation of the tanks is often disturbed, the oil sludge clogs the pumps, outflows from tanks have to be filtered, etc. Finally, downtimes are linked with the removal of the oil sludge. If the oil sludge is not removed, it accumulates further and finally leads to the abandonment of such sludged up storage containers and the construction of new tanks. Apart from these storage costs the unprocessed oil sludge also represents a loss, because despite its impurities it largely consists of utilizable hydrocarbons.

r P0926A.PCT -3- Several solutions are known for removing sediments from crude in tanks and two examples will now be given.

1) A first solution approach is proposed in US Patent 3436263 and French Patent 2211546, where cleaning substances are used for dissolving or removing bound form the oil sludge. A disadvantage of this method is that due to the introduced cleaning substances the dissolved oil sludge cannot be used and has to be disposed of on dumps or elsewhere. Such dumps are, old tanks or wasteland and constitute a serious pollution of the environment. The reprocessing of oil sludge is consequently not possible as a result of this method, so that instead of combating the damage it only combats the effect. However, it is still possible to clean and reuse tht tanks. The essential reason why the dissolved oil sludge cannot be processed is that the cleaning substances used represent impurities for processing in refineries, whose separation by standard cleaning methods involves a lot of effort and is expensive and bears no relationship to the recovered crude.

2) Another solution approach is proposed in European Patent 160805, where hydrokinetic energy is used in order to dissolve or suspend back into the liquid phase by means of turbulence sedimented residues in tanks. Thus, oil sludge dissolved by crude as the dissolving substance can be returned to the process and processed in the refinery following standard cleaning procedures.

This method is too expensive for the prevention of the formation of oil sludge and is intended for its elimination. For this purpose planned turbulence or eddy flows are generated, whose successive remote action is able to dissolve the deposits in an effective manner, even outside the direct injection zone.

However, this involves considerable material costs. Mechanically moving components within the tanks, such as, rotary liquefying lances, which hydrokinetically activate the oil sludge and dissolve it in crude, represent a not inconsiderable technical cost. Thus, although this method leads to a high oil sludge ~-~"11119 1 I C_ ~BIL i Pll P0926A.PCT recovery level, it is expensive. Under extreme environmental conditions, e.g., in sand or ice desert regions, this is undesired.

Moreover, from European Patent 202217 an agitating or stirring system is known by means of which it is possible to eliminate and also prevent sedimentations of oil sludge. It is a "swimming" agitating or stirring system which generates horizontal and vertical local flows by means of rotors, swims about in a storage tank, being remote-controlled, determines its position by means of ultrasound and signals its potition outwards. This solution has, among others, the disadvantage to make use of electric means, which is generally avoided in tanks for security reasons, and to develop an efficiency too poor for large-dimension tanks, because the effect is only local and it does not seem to be possible to bring into action simultaneously a plurality of such apparatuses in one common tank. In addition, the permanent use for the prevention of sedimentation is considered to be too expensive, and such high-complex apparatuses are scarcely suitable for this sort of duty.

The problem of the invention is to provide a method with the aid of which the deposition of sediments from liquid phases or thickening in liquids or liquid mixtures such as, oils, crude, refinery products and petrochemical products, can at least largely be avoided. This method must be simple and safe to carry out, because as a rule the storage units are either little or not monitored. This problem is solved by the invention defined in the claims.

The idea of the present invention is based on observations. Thus, it would appear that the sedimentation from liquid mixtures such as, from crude in tanks is a "precursor", a preliminary event, in the form of a deposition or thickening zone compressing in the bottom of the tank, which initiates oil I sp p l P0926A.PCT 4A sludge formation and causes successive sedimentation, and that the formation of this precursor can be influenced or prevented by a relatively small disturbar, perturbation, so that deposit formation is suppressed. This precursor of sedimentation from crude comprises crude thickening from a deposition zone, which so to speak "floats" in material-specific manner above a bottom surface, of the tank. Crude constituents coagulate and polymerize in this continuously thickening zone and are deposited in the form of sediments or the like and collect on the bottom of the tank as reutilizable oil sludge and therefore form a slowly rising bottom surface over which the precursor acts.

According to the invention the sedimentation from mixtures such as, e.g., crude, as well as other oils, is avoided by disturbing this precursor. As opposed to a per se sensible crude recovery from the sediment, this constitutes a type of prevention technology which reduces or prevents the formation of sludge. This approach differs to the solutions given hereinbefore, because there is no oil sludge disposal and instead the disadvantageous oil sludge formation is prevented.

P0926 PCT Most sludge formation is due to a type of gelling of the crude, which thickens and during thickening can be redissolved by stirring or agitating; during this phase no dilution by additional crude is required. However, in large tanks an effective agitating or stirring system can scarcely be obtained, so that it is necessary to find another form of planned disturbance appropriate for the enormous tanks.

According to the invention this can be achieved by the formation of energytransporting, travelling waves in the deposition zone, the precursor of the crude, e.g. by the supply and/or removal of crude.

Simple, maintenance-free disturbance means are brought about hydrodynamically by using perforated piping, pipe systems, nozzles, etc., so that flowing crude introduces the disturbance energy into the precursor of the deposition layer. Thus, no use is made of movable mechanical components in the tanks, sc that the method is maintenance-free, robust, mechanically simple and egy to control.

Further simple, maintenance-free disturbance means, vibrators, are advantageously obtained by using mechanical means such as "strings", "bell-shaped diaphragms" and the like, which are oscillated; in this way disturbance energy is introduced into the precursor of the sediment or deposit layer. Crossed strings, permit a good distribution of the energy-rich antinodes at points of strings where the deflection more and more decreases towards the fixing points. The same applies, for bell-shaped diaphragms. Their oscillations form sound figures, which can excite the liquid phase in the tanks. The excitation of the strings and the diaphragms takes place with corresponding s~aL~I P0926 PCT -6devices, which can be slowly moved backwards and forwards by means of a reciprocating drive (crank). Strings are, reoscillated by means of excitation elements at given intervals, in which they oscillate and transmit a disturbance. Diaphragms are restruck via striking elements at given time intervals, in which they oscillate and transmit a disturbance. Such devices are also substantially maintenance-free, robust, mechanically simple and easy to control.

In the method according to the invention this idea is put into effect in a highly advantageous manner, because the disturbance of the precursor and the prevention of sedimentation takes place with much smaller material and labour costs than recovery from existing sediment and it is possible to use particularly simple, proven and functionally robust equipment. A further advantage of this method is that the position and extension of the precursor, i.e. its location can be clearly defined and consequently disturbance means can be fitted in planned manner in said area, generally slightly above the tank bottom.

Details of the method according to the invention are described in greater detail hereinafter with respect to exemplified embodiments and with reference to the figures listed below.

Fig. 1 shows a diagrammatic longitudinal section through part of a tank with a deposition zone and sediment relief.

Fig. 2 shows a diagrammatic plan view of part of a tank.

Fig. 3 shows a first embodiment of a disturbance pattern in the form of a three-dimensionally arranged pattern of disturbance points.

I

P0926 PCT -7- Figs. 4a and 4b Fig. 5 Figs. 6a and 6b Fig. 7 show a further embodiment of a disturbance pattern in the form of a two-dimensionally arranged pattern of disturbance points.

shows the superimposing of the tank with the embodiment of a mechanically excited disturbance pattern according to Figs. 2 and 3.

show the superimposing of the tank with the embodiment of a mechanically or hydraulically excited disturbance pattern according to Figs. 2 and 4.

shows a diagrammatic plan view of part of the embodiment of a mechanically acting disturbance apparatus for the method according to the invention.

shows a diagrammatic side view of part of the embodiment of a disturbance apparatus for the method according to the invention, according to Fig. 7.

show diagrammatic plan views of part of the embodiment of a mechanically and hydraulically acting disturbance apparatus, respectively, for the method according to the invention.

shows a diagrammatic side view of part of the embodiment of a disturbance apparatus for the method according to the invention, according to Fig. 9b.

Fig. 8 Figs. 9a and 9b Fig. 10 s P0926 PCT -8- Fig. Ila shows a diagrammatic plan view of part of an embodiment of a drive for a push and pull unit in the form of a crank gear driving excitation elements.

Fig. lb shows a diagrammatic side view of part of an embodiment of a drive according to Fig. Ila.

Fig. 12a shows a diagrammatic view of part of a preferred embodiment of a disturbance means in the form of an oscillatory string system with a first embodiment of a stretching device.

Fig. 12b shows a diagrammatic view of how the oscillating string system and its stretching device according to Fig. 12a are stretched after contact with an excitation element, Fig. 12c shows a diagrammatic view of how the part of the oscillating string system and its stretching device according to Fig. 12a oscillate after excitation by an exciting element according to Fig. 12b.

Fig. 13 shows a diagrammatic view of part of another embodiment of a disturbing means in the form of an oscillatory, bell-shaped diaphragm.

Fig. 14 shows a diagrammatic plan view of part of a second embodiment of a stretching device for oscillatory string systems.

I L ~1 I P0926 PCT -9- Fig. 15 shows a diagrammatic plan view of part of a third embodiment of a stretching device for oscillatory string systems.

Fig. 16 shows a diagrammatic plan view of part of an embodiment of a hydrodynamically acting disturbance apparatus for the method according to the invention.

Fig. 17 shov ,a diagrammatic side view of part of the embodiment of a disturbance apparatus for the method according to the inv:cntion, according to Fig. 16.

Fig. 18 shows a diagrammatic plan view of part of a further embodiment of a hydraulically acting disturbance apparatus for the method according to the invention.

Fig. 19 shows a diagrammatic side view of part of the embodiment of a disturbance apparatus for the method according to the invention, according to Fig. 18.

Fig. 20 shows a diagrammatic side view of part of the embodiment of disturbance apparatus for the method according to the invention, according to Fig. 19.

Fig. 1 is a diagrammatic longitudinal section through a tank, having a diagrammatically represented deposition zone 4.2, namely the above-discussed precursor, over a sediment relief. The tank T has a cylindrical symmetry with an approximately planar bottom 1, a wall 2 and a floating roof 3. The capacity of such a tank T can be 100,000 m3 or more. The floating roof 3 is used for I sC P0926 PCT safety reasons, so as to permit the escape of volatile, flammable fractions of the stored crude 4 from the tank 2 and therefore prevent the formation of explosive mixtures within the tank T. When the tank T is wholly or partly filled the roof floats directly on the crude 4. However, the method according to the invention can obviously also be used for tanks having a firm roof.

Fig. 1 shows the sediments or deposits 4.1 and a compressing deposition ,!Jne 4.2 above them. The sediments 4.1 can e.g. comprise emulsions of water with hydrocarbon fractions, or segregates of heavy hydrocarbon fractions (hard waxes) or thickened crude or segregates of sludge, sand, salts or rust and form a firm deposit to a thick oil sludge or simply sludge, which is deposited on the bottom 1 of the tank T. These sediments 4.1 come from a sedimentation zone 4.2 thickening towards the bottom 1 of the tank T and which floats in material-specific manner above the bottom surface of the tank T, where it has a higher density than the crude 4 originally introduced into the tank T. Observations have shown that the thickness of the sedimentation zone 4.2 in such a tank T can be up to 1 m and is dependent on several difficultly determinable parameters, such as e.g. the composition of the crude 4, the ratio of the hydrocarbon fractions, e.g. subdivided into paraffins, aromatics and naphthenes, as well as the proportion and nature of the impurities, e.g. the quantity of water or sludge.

As stated, this thickening sedii.entation zone 4.2 is a type of precursor for the sedimentation from the crude 4. Thickening crude is a thixotropic mirYture, which, by mechanical activation, can change from the viscous to the less viscous liquid aggregate state. The thickening sedimentation zone 4.2 forms as soon as a specific minimum or critical quantity of crude in a tank T has found a specific, metastable equilibrium, considered over a period of time. The ~La P0926 PC, 11 critical crude quantity is e.g. that which permits the formation of a sedimentation zone 4.2. A metastable equilibriUn occurs, as a function of the nature and manner of the supply, the supply capacity and also the duration of the crude supply (with or without interruptions) in the tank T and this generally occurs after only a few weeks.

The ci 0d- 4 in the tank T can be influenced by external forces. One of these external forces, which cannot be suppressed, is gravity. Certain constituents of the crude 4, which thicken, coagulate and polymerize in a metastable sedimentation zone 4.2 undergo a specific density rise in time in such a way that under the action of gravity they are sedimented in the sedimentation zone 4.2 on the bottom surface of the tank T so as to form a bottom deposit 4.1. The possibilities of the coagulation, polymerization and sedimentation of crude components 4 are very varied in accordance with the very considerable variation range of a mixture and lead the same into a stable equilibrium in the form of sediments or deposits 4.1 or oil sludge. Similar mechanisms of sedimentatir- -iply to other substances forming liquid phases.

This interaction of the gravity with the sedimentation zone 4.2 is finely expressed. Thus, there is an expansion and spatial positioning of the sedimentation zone 4.2 relative to the bottom surface of the tank T, the zone 4.2 takes on the form of an eventual sediment relief. The statistically forming surface structure of the sediment 4.1 brings about corresponding strur.tures of the upper and lower surfaces of the sedimentation zone 4.2. The growth of the sediments 4.1 is accompanied by a more or less constant thickness of the sedimentation zone 4.2 (cf. Fig. 1).

L- ~LL~ ~LLI II

I

1P0926 PCT -12- According to the invention the sedimentation from mixtures such as, e.g., crude, refinery products and petrochemical products in tanks T is avoided, in that the metastable sedimenrtaiion zone 4.2 is disturbed by external forces, so as to prevent a coagulation and polymerization of components of the mixtures.

As a result of the known position discovered by methodical sounding of a sedimented formation and studying this formation and the extension or expansion of the precursor or sedimentation zone 4.2 restricted by the container, it is possible to apply to the tanks T disturbance means having a planned action thereon. Two groups of embodiments of distrubance apparatuses for the method include disturbances actuated hydrodynamically and mechanically, respectively. The disturbance is brought about hydrodynamically by the supply and removal of crude as the disturbing medium with respect to the sedimentation zone 4.2 of the tank T. Therefore the components of the crude are moving and the sedimentation zone 4.2 is subject to thorough mixing due to the incompressibility of the particles. The disturbance is brought about mechanically by generating running waves which transport energy; the waves are generated by vibrations or oscillations in the tank T and by exciting the components of the mixture in the sedimentation zone 4.2. Therefore these oscillating components are moving and the sedimentation zone 4.2 is subject to thorough mixing dLe to the incompressibility of the particles.

According to Fig. 2 the tank T is, as is usually the case, cylindrical and it has a circular diameter of e.g. 100 m and a height of 20 m. In such a container there is a disturbance zone of approximately 1 m depth, which according to the concept of the global disturbance pattern S, i.e. a disturbance model, comprises a plurality of local disturbance points L. This disturbance zone advantageously has a constant disturbance height of 1/2 metre with cm disturbance action above the bottom of the tank T. The dist-.rbance zone extends down to the bottom 1 of the tank T and may have a volume of a few e I pr P0926 PCT 13m 3 (surface area x extension of the disturbance action). According to the present invention, the disturbance of the sedimentation zone 4.2 is realized by hydrodynamic flow or by mechanical oscillations, whereby the latter are advantageously generated by strings or bell-shaped membranes inside the tank T. Thus the disturbance model is first outlined in the method; it links and optimizes the shape of the tank T with the shape of the propagation of oscillations or vibrations in mixtures. With increasing knowledge of the action specific disturbance models can be filed in the computer and can be modified and outputted as a function of the container, its capacity, shape and the environmental influences. According to the details of the optimized disturbance model the disturbance apparatuses are then selected and designed.

In a disturbance brought in by mechanical disturbance means according to Fig. 3 the disturbance pattern S has the form of a three-dimensional pattern of disturbance points L and constitutes a double-layer, symmetric arrangement of equidistant "disturbance ellipsoids". Both layers intersect in a right angle.

They are suited for long strings which are to be installed and excited inside the tank T, similar to two giant, crossed harps with thus optimally superimposed antinodes. They are designed as long strings which are excited by exciting elements and which oscillate in first and higher harmonics; thus the components of the crude 4 are forced to oscillate with an amplitude depending on that of the sound waves, and a disturbance or mixing effect is produced.

A different embodiment of a disturbance pattern S according to Figs. 4a and 4b is a two-dimensional pattern of disturbance points L, which are in the form of more or less equidistant equally large circular disturbance zones or of arbitrarily distributed disturbance zones. According to this pattern, jets are instal- P0926 PCT -14 led inside the tank T, or oscillatory strings are put into frame, or accordingly bell-shaped diaphragms are provided.

The disturbance points L are given an optimum reciprocal spacing corresponding to the disturbance model, so that they are not too close together or too far apart and in the disturbance zone between them no disturbance-free areas of the sedimentation zone 4.2 can form. Therefore the sizes of the disturbance ellipsoids and circles in Figs. 3 and 4, respectively, do not give the limits of the disturbance action of local disturbance points L and instead merely indicate that said disturbance point L is "active", operating. Tt must also be borne in mind that the oscillations subsequently to be produced are propagated in the medium and therefore have a certain working range, which is greater than the external design extension of said disturbance points L and is also greater than the physical extension of the subsequently produced disturbance nieans.

Disturbance must take place in a very volume-filling, homogeneous manner. Ic is made local by means of the disturbance points L and overall or global by means of the disturbance patterns S, with a view to preventing the formation of the sedimentation zone 4.2 by means of such a disturbance zone. It is possible to form several geometries of disturbance patterns S, e.g. three-dimensional structures, which have closely packed disturbance points L. The disturbance points L need not be of the same size and it is possible to combine weaker and stronger disturbance points L, which can be provided in regular or irregular intervals (long and short, Lhick and thin strings). Therefore it is possible in this way to overcome difficult geometry conditions in the tank T, such as round walls, which thus are disturbed calculatedly "with more power". In addition, the disturbance points L need not be symmetrical and can instead also P0926 PCT be randomly arranged disturbance points with individual disturbance capacities and geometries, which have a sufficiently long range to form interfering, overlapping disturbances, so that the action of these oscillations of the tank T as a resonator on the stored crude 4 is volume-filling and homogeneous. Even the symmetrical disturbances can vary widely. Thus, the disturbance points can be of a wide-range nature like flat disks, which are only uniform in one disturbance plane sinusoidal and circular) or non-uniform elliptical) and which here again act only in the predetermined disturbance height. This is advantageous, because the sedimentation zone 4.2 to be prevented is relatively flat or shallow. With the knowledge of the invention the expert is provided with numerous possibilities for the design of local disturbance points L and overall disturbance patterns S.

The design of the disturbance pattern S can be brought about with standardized disturbance points L in the form of a drawing board or on the computer as a disturbance model. An advantageous tool for this purpose is electronic data processing, where complete libraries of models can be built up, field experience can be stored and converted into sets of parameters. The distarbance patterns S and disturbance points L are then selected from a set of standardized, proven forms and, in accordance with the parameters to be fulfilled, are matched to the given geometry of the tank T or the nature of the crude 4. Figs. 5 and 6 show the way in which this is done.

In Figs. 5 and 6a/b the disturbance patterns S according to Figs. 3 and 4 are superimposed with the surface area of the tank T according to Fig. 2, so that most of the numerous disturbance points L within the disturbance zone within the tank T can be produced by means of disturbance apparatuses. The disturbance pattern S is projected onto the geometry of the tank T, there being no

I

P0926 PCT 16need to proceed in a categorical manner and instead projection can take place as a function of the type and extension of the disturbance points L.

Thus, in Fig. 5 the two layers of disturbance points L or disturbance parabolas are shortened with respect to their lengthwise extension in such a way as to "fit" into the tank T. However, in Figs. 6a/b certain of the disturbance points or circles L within the surface area of the tank T are subsequently not produced. Only those disturbance points L found to be necessary by comparison with th. geometry of the tank T are also created in disturbance apparatuses V.

The disturbance zone consists of a volume formed from the surface area of the tank T and a disturbance depth and which advantageously includes the sedimentation zone to be disturbed. For this purpose the disturbance points L are advantageously realized as disturbance apparatuses in the form of strings or bell-shaped diaphragms. Each string or bell-shaped diaphragm is an actual local disturbance point L with a local disturbance volume.

Figs. 7 and 8 diagrammatically show part of an exemplified embodiment of a disturbance apparatus V for performing the method according to the invention. Fig. 7 is a plan view and Fig. 8 a side view. The geometries of the disturbance apparatus V with its disturbance means 8 and the tank T are adapted to one another, so as to achieve an optimum, volume-filling, homogeneous disturbance. The disturbance apparatus has as actual disturbance points excitable disturbance means 8 in the form of strings. In the exemplified tank T with a cylindrical geometry and circular diameter, the disturbance means 8 are arranged as equidistant, differently long strings in two constant disturbance heights 9, 10 above the bottom 1 of the tank T, at a height of 40 cm (lower disturbance height 9) and a height of 60 cm (higher disturbance height 10). The disturbance zone covers the entire surface area of the tank T. In the I?0926 PCI' 17case of a disturbance action of 50 cm they extend down to the bottom 1 of the tank T and enclose the sedimentation zone 4.2 to be disturbed or prevented.

The stretched strings of this embodiment of the disturbance apparatus V are excitable by means of exciting elements 5 by means of two push and pull units 6. The strings are advantageously excited to oscillate or vibrate in the centre of their length. Such exciting elements S can be mandrels or springing-back striking means, which are fitted to the push and pull units 6. The stationary or slightly vibrating strings are excited by moving the exciting elements 5 backwards and forwards. The exciting elements 5 are moved up to the strings to be excited, uhich are deflected, stretched (by plucking), released, whereby the exciting element 5 moves away from the strings, so that the latter can vibrate in an undisturbed manner. The strings, their stretching devices and the push and pull unit 6 for the exciting elements 5 are advantageously fitted in several planes, so that the vibration of the strings and the moving backwards and forwards of the push and pull units 6 with the exciting elements 5 bring about no reciprocally hindering action.

As a function of their length, the strings can be stretched to a varying extent and can also be made of different thicknesses. They are made from stiff materials, wires made trom metals such as steel, copper, alloys and possibly plastic and metal-coated plastics. The prerequisite is that the materials are not attacked by the crude oil 4 and can be vibrated. Despite tension and lift long strings must not sag to such an extent that they are in contact with strings beneath them or the bottom 1 of the tank T. If necessary, great lengths must be subdivided into two or more strings, whereby accordingly more devices for the excitation of the strings must be provided, of course. More details concer- P0926 P'CT 18ning the strings, their excitation and the stretching device are provided in connection with Figs. 12, 14 and The push and pull units 6 have rigid members (rods, plungers) or movable members (chains which can be pushed/pulled), which run in sliding manner, in slotted, tubular guides and exciting element 5 for plucking or striking are fixed for the purpose of exciting the strings. In this first embodiment the push and pull units 6 are at right angles to one another and run linearly in two planes and are movable by means of, crank-operated, fluid-operated or gear-operated drives positioned outside the tank T. Details concerning an advantageous embodiment of such a drive are provided in the description of Fig 11. The push and pull units 6 are e.g. mounted by means of stands or similar devices connected to the slotted, tubular guides on the bottom 1 of the tank T and the rigid or movable members can be led to the outside through the floating roof 3 by means of passages 11 on the wall 2, in the bottom 1 or at the top on the tank T. For safety reasons said passage 11 must be tight, so that push and pull units 6 can be operated without any escape of liquid components of the mixtures to be processed, such as crude 4, from the tank T.

For the plucking or striking of the strings, compared with their length resulting from the size of the tank T, the push and pull units 6 only have to be moved backwards and forwards over relatively short distances of 10 cm to maximally 1 m. The force expenditure for driving the push and pull units 6 is also relatively small and they are mounted so as to slide in th guides without significant frictional losses and are lubricated by the crude JS. fhe parts of the push and pull units 6, such as the rigid or movable neenbers, the tubular guides and the exciting elements 5, are advantageously made from metals such as steel, bronze, etc., optionally plastic and metal-, ated plastic, so that they cannot be attacked by the surrounding media, sr that the drive for the strings is substantially maintenance-free. The disturuance means are mechanically P092(, PCT 19only slightly stressed. By material pairing they are planned in such a way that the strings are kept in use, whereas the exciting elements are exposed to wear and can easily be replaced in the case of inspections. They can, be detachably fixed to the push and pull units 6.

The strings produce sufficiently energy-rich vibrations (with an estimated power of 1 to 10 Watt) and have advantageously low (not audible) frequencies. With the knowledge of the present invention the expert has numerous possibilities for producing such disturbing apparatuses V.

Figs. 9b and 10 diagrammatically show part of a second embodiment of a disturbing apparatus V for the method according to the invention. Fig. 9 shows a plan view and Fig. 10 and side view along the section CC according to Fig. 9. The description of this second embodiment coincides with that of the first embodiment according to Figs. 7 and 8 and only the diverging points will be referred to hereinafter.

In the tank T having a cylindrical geometry and the same volume as described hereinbefore local disturbance points are formed as approximately equidistantly fitted disturbance means 12 in the form of bell-shaped diaphragms or short strings, which are at a constant disturbance height 13 of, 50 cm above the bottom 1 of the tank T, so that the disturbance zone formed by the entire surface area of the tank T with a disturbing action of 50 cm around the disturbance height 13 extends to the bottom 1 of the tank T and therefore covers the sedimentation zone 4.2. The disturbance means 12 can be excited by means of exciting elements 5 via a push and pull unit 6. The latter comprises movable members such as a chain and is therefore spatially flexible.

I, I P0926 PC7 It can, comprise chain links rotatable against one another and which are guided in slotted tubular guides. In this embodiment it is laid in a spiral plane in the interior of the tank T. It is fixed to the bottom I of the tank T and is led to the outside in the floating roof 3 by means of passages 11 at the top of the tank T. The exciting elements 5 can be small mandrels or sticks, which are fitted to the push and pull units 6. The stationary or slightly vibrating bellshaped diaphragms or strings are excited by the moving forwards and backwards of the exciting elements 5. Advantageous embodiments of such bellshaped diaphragms or strings are described relative to Figs. 12 to 15. The disturbance means 12 of the second embodiment are given smaller external dimensions than the disturbance means 8 of the first embodiment. The spatially flexible push and pull unit used can be laid in large lengths from a reel in accordance with a given disturbance pattern S or model.

Figure 9a diagrammatically shows, similarly as Fig. 9b, part of the hydrodynamic embodiment of a disturbing apparatus V for the method according to the invention. This disturbing apparatus V also consists of pipes 7 which are permanently installed inside the tank T and conduct the disturbance means; it makes possible the conveyance of crude 4 to and from the tank T by disturbance means 8 in the form of openings such as perforated piping, pipe systems, and nozzles, and thus prevents the formation of a sedimentation zone 4.2. Details of the hydrodynamic disturbance are discussed below.

Figs. 11a and 11b are a diagrammatic plan view and side view, respectively, of part of an embodiment of an exemplified drive for a push and pull unit 6 in the form of a crank gear driving exciting elements 5. This drive can be installed alongside the tank T or on its floating roof 3 and, comprises a hydraulic motor M with a power of a few kW. By means of a reduction gear U a u~ I P0926 iPCT -21slowly rotating flywheel 27 is driven at a speed of approximately 5 or 10 revolutions per minute. One end of a connecting rod E is mounted in rotary manlier on a fixed pin Z connected to the flywheel 27 and rotating thereon, whereas the other end of the connecting rod E is mounted in rotary manner with a piston 28 and the latter is fixed to the push and pull unit 6 to be driven. On rotating the flywheel 27 the piston 28 is moved linearly forwards and backwards and is guided by a guide 29. The length of the forward and backward movement of the push and pull unit 6 is twice the circular radius of the pin Z mounted on the flywheel 27 and can therefore be varied by modifying said radius in relatively simple manner in ranges of 10 cm and 1 m. The speed of the forward and backward movement of the push and pull unit can be easily and precisely set by varying the rotational speed of the motor M, e.g. by varying the reduction gear U. This is important, because the vibrating behaviour of disturbance apparatuses V in tanks T can in this way be externally regulated and controlled. It is also a very slowly running drive unit, which is suitable for permanent operation and scarcely requires any maintenance.

Figs. 12a-c show a diagrammatic view of part of a preferred embodiment of a disturbing means 8, 12 in the form of a vibratable multiple string 18 with "a first embodiment of a stretching device 16. Figs. 12a-c show how the said vibratory multiple string 18 and its stretching device 16 are stretched following contact with an exciting element 5 and how the two strings 15, 17 of the vibratory multiple string 18 vibrate following said excitation.

The vibratory multiple string 18 has two strings 15, 17. It can be fixed to the bottom 1 of the tank T together with its stretching device 16 and using the supports B, B' in accordance with the disturbance pattern S. This embodiment has the advantage that the stretching device 16 operates uith two flexible

I

110926 PCTI -22fastenings H, H' and that thus the strings 15, 17 fixed to said fastenings H, H' "reciprocally" stretch each other. The string tension is compensated in the same way as in a bow by the strings 15, 17 and the fastenings H, In this embodiment of a disturbing means 8, 12 the supports B, B' must be able to withstand relatively small string tensions and as a result installation expenditure for correspondingly powerfully designed supports and therefore costs are saved. Particularly in the case of thick steel strings with a diameter of, mm, which are tensioned with great forces, a stretching or tensioning device must be able to withstand considerable tensions, which is obviated by this "mutual" tensioning or stretching of the strings.

The tensioning or stretching device 16 can also fulfil other functions, such as the provision of tension via flexible fastenings H, The stringq i, 17 of the multiple string 18 are excitable simultaneously or in time-staggered manner, but only individual specific strings are excitable for vibration purposes. If, e.g., only one string 15 is deflected from its equilibrium position for vibration excitation, according to Fig. 12b after contact with an exciting element 5 and as a result of the movement of the push and pull unit 6 it is transversely tensioned in its longitudinal extension according to the arrow, so th the fastenings H, H' are deflected inwards and bend somewhat at the fixing points of the spring and are tensioned in much the same way as springs and the other string 17 is also tensioned and in this way the entire system stores energy. The exciting energy is therefore transferred into the strings 15, 17 and into the fastenings H, so that on releasing the contact with the exciting element 5 the system relaxes and starts to vibrate. According to Fig. 12c the strings 15, 16 vibrate through opposing excitation with different amplitudes. Therefore it is sufficient to excite vibration of one string 15 of a multiple string 18 by means of an exciting element 5 and as a result other strings 17 also vibrate and vice versa.

I _W P0926 PCT -23 Thcrefore the strings 15, 17 can be excited in fundamental or higher harmonics and emit sound waves. The sound pressure level which falls exponentially with time and the dying away of the amplitude of the vibrations due to frictional forces with the medium surrounding the same is delayed by the excitation of several strings 15, 17. Such a unison group as shown in Fig. 12 produces coupled oscillations or vibrations, which form a long, lingering sound due to phase shifts.

Fig. 13 shows part of a third embodiment of a disturbing means 12 in the form of an oscillatory bell-shaped diaphragm. Such a bell-shaped diaphragm can be excited to one or two natural vibrations or oscillations and therefore several partial oscillations or vibrations. It requires no stretching devices and by means of retaining means, a support, can be fixed with the disturbance pattern S on the bottom 1 of the tank T. It is excitable by means of an exciting element 5, which can, be firmly connected to the bell-shaped diaphragm by means of an elastic connection. Thus, an exciting element 5 in the form of a "striker-free, bell-shaped diaphragm" movable by means of the push and pull unit 6 can directly strike by moving forwards and backwards or, as in Fig. 13, can deflect by means of a contact arm A a striker K fitted in or on bell-shaped diaphragms. The striker K can be "pretensioned" in a relative equilibrium position with respect to the bell-shaped diaphragm by the inherent stiffness of the contact arm A and this pre ension is represented in stylized form by the spring F. By moving forwards or backwards the push and pull unit 6 in the direction of thc arrow an exciting element 5 is contacted in force-transferring manner by means of the contact arm A with the striker K, e.g., the exciting element 5 and the contacting part of the contact arm A according to Fig. 13 functions in such a way that during this movement a concave area of the exciting element 5 and a convex area of the contact arm A come into contact. Through further forward or backward movement in the same direc-

I

1'0926 PCT -24 tion of the push aud pull unit 6 Ihe striker K is deflected and the contact arm A is further tensioned and with a given deflection of the contact arm A the contact between the exciting element 5 and the arm A is interrupted and, eg., with a definable deflection the latter slips away over the exciting element the contact arm A is relaxed and the striker K strikes against the wall of the bell-shaped diaphragm. As soon as the striker K and contact arm A have again assumed a relative equilibrium position, the exciting element 5 is moved back in the opposite direction. The exciting element 5 and the contacting part of the contact arm A function in su ,h a way that during this return movement of the push and pull unit 6 there is no force-transferring contact between them, because two convex areas come into contact, which laterally slide past one another.

In Figs. 14 and 15 are shown diagrammatic plan views of part of a second and third embodiment of the stretching devices for vibrating multiple strings 18.

These stretching devices permit a simple fitting of strings 15, 17 to be stretched in the dis urbing apparatuses according to the invention and permit an easy correction of string tensions, also following the installation of the disturbing apparatus when the tank T is filled with crude 4. Thus. the tensional force of the said stretching devices can be adjusted. In the embodiment according to Fig. 14 the string tension is adjusted in single-acting manner by means of one of the two fastenings H, whereas in the embodiment according to Fig. 15 the string tension is adjusted in double-acting manner by means of both fastenings H, H'.

A guide rod 24 is mounted in rotary manner on a retaining mandrel B, which is in turn firmly anchored in the container, as is the fastening The second fastening I-I is fixed in rotary manner on the hinged support. Between the

I

l'0926) PCT same the strings 15 and 17 are stretched. On tightening the stretching unit 21 the hinged support moves and draws the fastening H with it, so that the strings are stretched, as is represented by the broken line position in the drawing.

For setting the string tension use is appropriately made of tensioning push or pull units 21 which have an identical or similar construction to the already described push and pull unit 6 for producing vibrations or oscillations cr can also be steel cables. These tensioning push and pull units 21 drive stretching elements 22 fixed thereto. In much the same way as the push and pull units 6 for producing vibrations, they can be laid in the tank T in accordance with a disturbalce pattern S and the resulting local position of the disturbance means 8, 12 and can be fixed on the bottom 1 of the tank T (cf. Figs. 6 to With the knowledge of the present invention the expert has numerous possibilities for producing such stretching or tensioning mechanisms.

According to Fig. 14 a stretching element 22 for multiple strings 18 comprises a mobile part 22.1 and a static part 22.2. According to Fig. 15 a stretching element 22 for multiple strings 18 comprises two, e.g. identical, mobile parts 22.1. The static part 22.2 is a fastening H with fixing points for the ends of the multiple string 18, which is installed in freely rotatable manner by means of a support B and in fixed manner on the bottom 1 of the tank T. The mobile part 22.1 has a similar fastening HI' with fixing points for the multiple string 18. For this purpose it is connected in freely rotary manner with a guide rod 24, which is in turn connected in freely otatable manner to a support B' and is rigidly connected to the tensioning push and pull unit 21. In the view according to Figs. 14 and 15 the supports B, B' are largely covered by the fastenings H, H'.

clLP P0926 PCT -26- Appropriately the changes to the string tension are effected in such a way that a movement of the tensioning means 21 in the direction of the long arrows brings about a rotation of the guide, rods 24 around the support B' (indicated by the curved arrows), which draws apart the fastenings H, H' relative to their original position and tensions the strings 15, 17. The guide rods 24, fastenings H, H' and strings 15, 17 are shown in broken line form in the new, tensioned positions. The fastenings H, H' of the ends of the multiple string 18 are mounted in freely rotatable manner, so that they are reciprocally oriented in accordance with the tension of the strings 15, 17.

In the embodiment according to Fig. 14 a rotation of the mobile part 22.1 and a securing of .he static part 22.2 of the stretching element 22 leads to a positional change of the multiple string 18 and in a certain angle it is "inclined" to the original position, which is not the case in the embodiment according to Fig. 15, where the two mobile parts 22.1 rotate and acquire the position of the multiple string 18.

The a.;-'mmetrical construction of the guide rods 24 leads to a leverage, a long movement of the push and pull units 21 with a relatively small force brings about a small deflection, but with a greater force on the fastenings H, Compared with the single-acting stretching device according to Fig. 14, the double-acting stretching device according to Fig. 15 can be tensioned with a greater force or for the same force a larger number of multiple strings 18 can be tensioned. These two tension-adjustable stretching devices permit a simple and rapid fitting or replacement of strings 15, 17. By relieving or relaxing the s'retching device (rearward movement of the tensioning push and pull unit 21 in opposition to the direction of the arrows) any tension strings 15, 17 are simultaneously relaxed and can then be loosely connected with the fastenings ill I~ I P0926 PCT -27- H, H' of the multiple strings 18 by means of snap closures, spring hooks, etc.), and the disturbing apparatus is made ready to operate by tensioning the stretching device.

Figs. 16, 17 and 18, 19 diagrammatically show parts of a first and a second embodiment of a disturbance apparatus V for performing the method according to the invention. Fig. 16 is a plan view and Fig. 17 a side view along the sectional plane CC of a first embodiment according to Fig. 16. Fig. 18 is a plan view and Fig. 19 a side view along the sectional plane DD of a second embodiment according to Fig. 18. The geometries of the disturbance apparatus V with the disturbance means 8 and the tank T are adapted to one another so as to achieve an optimum, a volume-filling, homogeneous disturbance. The disturbance apparatus ha- in the form of disturbance points disturbance means 8 in the form of nozzles through which can flow in and out the crude 4 with respect to the tank T. In the exemplary cylindrical tank T having a diameter of up to 100 m and a height of up to 20 m the disturbance means 8 are arranged in a chessboard geometry with a constant disturbance height 9 above the bottom 1 of the tank T, ''ith a 50 cm height 9. The disturbance zone covers the entire base area of the tank T. In the case of a disturbance action of 50 cm it extends down to the bottom 1 of the tank T and covers the deposition or sedimentation zone 4.2 to be disturbed, respectively prevented.

The disturbance apparatuses V for the disturbance points L according to Figs.

2 to 4 are realized and interconnected with pipe systems 7 at an adequate disturbance height 9 above the tank bottom 1. In the sedimentation zone 4.2 the pipe systems 7 supply/remove crude oil 4 with respect to the tank T, e.g., via passages 11 of the pipe systems 7. The supply and removal is effected by -I II P0926 PCT -28pumps P, which are connected at certain points of the pipe systems. In the embodiment according to Fig. 16 the disturbance means 8 are interconnected linearly, in an unbranched pipe system 7, whereas in the second embodiment according to Fig. 18 the disturbance means 8 are interconnected in a branched pipe system 7. Naturally it is also possible to have several, independently operable pipe systems 7. They can have independent passages 11 for the supply or removal of crude 4, but can also be operated in a dependent manner, so that the pipe systems 7 are, only suppliable via a supply or drain line.

Pipe systems 7 can be at the same disturbance height 9 or at different disturiO bance heights 9 over the bottom I of the tank T. They can have the same or different disturbance intervals or spacings 14 and this also applies with respect to the wall of the tank T.

Advantageously the geometry of the disturbance apparatuses V is adapted to that of the tank T, so as to ensure an optimum, i.e. volume-filling, homogeneous supply and removal of crude 4 with respect to the formation height of a sedimentation zone 4.2. The depth of this disturbance zone about the disturbance height 9 is referred to as the disturbance depth and covers the surface area of the tank T. In the first and second embodiments of a tank T with a cylindrical geometry and circular diameter of up to 100 m and a height of up to 20 m, there are numerous local disturbance means 8 in the form of openings, such as perforated pipe systems or nozzles and having a constant disturbance interval. They are fitted at a constant disturbance height 9 of, cm above the bottom of the tank T. The disturbance zone covers the entire surface area of the tank T. With a typical disturbance action of 50 cm, it extends down to the bottom 1 of the tank T and includes the sedimentation zone 4.2 to be disturbed or prevented.

I I I s P092( PCT -29 The disturbance means 8 of the disturbance apparatuses V are used for the supply or removal of crude 4 and are in the form of openings, such as perforated pipe components or nozzles, via which the crude 4 can flow in or out. In the present embodiment there are nozzles by means of which the crude is introduced into the disturbance zone. In the simplest case a volume-filling, homogeneous disturbance is achieved by identical disturbance sizes of these nozzles. The expert has available to him numerous known, proven methods, so as to permit a uniform outflow of crude 4 from these nozzles throughout the disturbance zone. As a function of the height of the crude column in the tank, in the disturbance height 9 there is an overpressure of 10, 20 or 30 atm. Thus, in the pipe systems 7, the crude 4 is pumped by pumps P with a sufficiently high pressure to all 76 nozzles, so that also at the end of the pipe systems 7, there is still a full dirturbance action at the final nozzle in the line. Such an adequate crude supplx ,an be obtained in a simple, controlled manner by the use of standardized, matched nozzles (nozzle cross-section). Advantageously the nozzles have large opening angles, so that, directed against the bottom 1 of the tank T, they supply the crude 4 in surface-covering manner thereto.

Generally the local crude quantity is determined by the pressure in the pipe systems 7 and the flow rate through the nozzles. For example the crude quantity flowing out of the individual nozzles is so small compared with the quantity of crude in the pipe systems 7, that in the latter, as a result of the outflow of crude 4 from the nozzles, no significant pressure drop occurs. Thus, for identical nozzles the same crude quantity can flow.

However, should there be a pressure drop, this can be corrected by the use of nozzles having different throughputs, in such a way that the ratio of the local I T- P0926 PCTI pressure at the rozzles in the pipe systems 7 to the throughput of the nozzles is kept constant. At the inlet of the pipe systems close to the passages 11, where the crude 4 has its highest pressure, are fitted the nozzles with the correspondingly small oil flow rate, whereas the nozzles at the end of the pipe systems 7 have a relatively large flow rate.

The hydrokinetically acting disturbance of the formation of the sedimentation zone 4.2 can also be prevented by a combined removal and supply of crude oil 4 from the disturbance zone by means of several pipe systems 7 as disturbance apparatuses V. In this case crude 4 would be fed in by means of pipe systems 7 via nozzles) and would simultaneously be removed by means of other pipe systems sucked out by openings in said systems 7).

The pipe systems 7 of the first and second embodiments can be constituted by standardized pipe components used in the crude-oil-processing industry, such as, rigid steel components, linear extension pieces, bends made with a given angle, T-pieces, which can be welded together and are permanently fixable to the bottom of the tank T. Such pipe components typically have circular diameters of 5 to 20 cm, and at the positions of the disturbance points L to be produced, they have openings or connecting means for the installation of the nozzles. Such connecting means can be welding sockets or standard flanges. These pipe systems 7 can, be installed by means of forked stands in the disturbance height 9 and fixed to the bottom 1 of the tank T.

Fig. 9a diagrammatically shows part of a further embodiment of a disturbance apparatus V for the method according to the invention. This disturbance apparatus V also comprises at least one pipe system 7 fixed in the interior of the

I

P0926 PCT -31tank T and which permits the supply and removal of crude 4 via disturbance means 8 in the form of openings, such as perforated pipe systems or nozzles in the tank T, so as to prevent the formation of a sedimentation zone 4.2.

The description of this embodiment of a disturbance apparatus V substantially coincides with that of the first and second embodiments according to Figs. 16 to 19. However, in this case the pipe system 7 is formed from flexible pipe components or reinforced, pressure-resistant hoses, which are, made from metal such as steel or steel alloys. Such hoses have typical circular diameters of 10 to 20 cm and can be laid from a reel in larger lengths, much as with the laying of cables, in accordance with a predetermined disturbanc_- pattern S.

These reinforced, pressure-resistant hoses have the advantage of a flexible laying. Such a flexibly layable pipe system 7 comprising one or more connected hoses and which in a tank T with a diameter of 100 m is laid with a fixed disturbance height 9 of 50 or 60 cm in accordance with a disturbance pattern S in the form of a spiral, for the production of the individual disturbance points as disturbance means 8 and the connection thereof requires no special manufacture of pipe components such as extension pieces and bends. Thus, as a result of the said laying the said pipe components need no longer be interconnected by means of flanges, which saves time and material. It is merely necessary to fit the openings or nozzles. This can take place during or after the laying operation by drilling openings, cutting threads and fitting standardized connecting means such as flanges, so that the nozzles can be connected to the pipe system 7.

r I P0926 PCT -32- A further advantage of the flexibly layable pipe system 7 is the simplification of the design of the disturbance pattern S and the bringing about of a particularly effective disturbance zone. As a result of the spatial flexibility of the flexibly layable pipe system 8, the shape of the disturbance pattern S and the shape of the pipe system 8 can be matched to one another. Unlike in the first and second embodiments, in the present third embodiment there is an interaction between the design of the disturbance pattern S and the laying of the pipe system 7.

Thus, with the knowledge of the length of the hose provisionally laid in spiral manner in the pipe system 7, it is virtually possible in situ to calculate the necessary number of nozzles required for an effective disturbance in a spiral disturbance pattern S. In this stage of the method rough details are obtained, a hose is laid but not fixed and a specific disturbance pattern S is calculated for the tank T the latter advantageously takes place by means of table or computer-based expert systems, by means of electronic data processing.

On the basis of these details both the flexibly layable pipe system 7 and the disturbance pattern S are matched to one another, the local positions of the hose can be easily modified and the local position, nature and size of the nozzles can be varied. Thus, the hose may, no longer have perfect spirals and instead it may locally have small structures in the form of waves or the like. These adaptations can take place on the basis of random, external circumstances, because otherwise there would not be optimum local disturbances in accordance with the disturbance pattern S. The obstacles which are to be taken into account in this fine matching, can, be turbulence and flows on the walls of the tank T. It is important to create the maximum freedom in the design of the disturbance pattern S. The disturbance pattern S does not requi-

I

P0926 PCT 33 re a predetermined chessboard configuration as in the first and second embodiments of Figs. 16 to 19 and instead the details are optimized. The latter are naturally freely selectable, so it is not important to lay the pipe system 7 in the form of a spiral, although this is practical and advantageous.

Following this optimization stage the flexibly layable hose is permanently fixed, on the bottom 1 of the tank T, openings are made in the hose at the calculated, optimized positions of the nozzles and the latter can be fitted by means of said openings and further connecting means such as cut threads or standardized flanges, so that the nozzles are connected in pressure-tight manner to the pipe system 7. The same observations as made concerning the first and second embodiments apply to the selection of the nozzles. The pressure in the pipe system 7 and the throughput or flow rate of the nozzles to be fitted must be so matched to one another that the crude oil 4 can be transported at a sufficiently high pressure to all the nozzles and consequently also has a full disturbance action on the final nozzle at the end of the pipe system 7.

Figure 20 diagrammatically shows a part of a further embodiment of a disturbance apparatus V for the method according to the invention.

Even though the fitting of stationary disturbance points in the precursor volume with disturbance apparatuses carried by the storage container bottom appears to be simple from the constructional standpoint, it is also possible to supply the disturbance from above, from the top of the container. For this purpose it is appropriate to have a "floating roof', whose top already has a lirge number of supports. During the storage, into the supports can be inserp, P0926 PCT -34 ted or installed lances, through which the disturbance flow can be introduced into the precursor.

Figure 20 shows a side view in section. This disturbance apparatus V comprises a plurality of lances 12 fixed in the floating roof 3 of the tank T and which permit the supply and removal of crude 4 via disturbance means 8 in the form of openings such as nozzles on the lances 12 in the tank T and consequently prevent the formation of a sedimentation zone 4.2 the supply network with the pumps not being shown.

Unlike in the first three embodiments according to Figs. 16 to 19, in this case lances 12 are fitted to passages 11 in the floating roof 3 of the tank T and extend down to a disturbance height 9, so as there to supply and/or suck off crude 4 by means of disturbance means 8 such as nozzles and in this way form the disturbance zones. The lances 12 can be made from standard pipe components used in the crude oil processing industry, such as rigid steel components, linear extension pieces, etc.

The disturbance points L in the tank T, in accordance with the disturbance pattern S of Figs. 4 and 6, are now realized as lances 12 and disturbance means 8, which are not fixed to the bottom 1 of the tank T, but instead to its floating roof 3. These lances 12 can be connected for the supply and removal of crude 4 by means of a common pipe system located outside the tank T, but can also be individually connected to other crude oil reservoirs for the supply and removal of crude 4. The disturbance zone covers the entire surface area of the tank T. With a typical disturbance action of 50 cm they extend down to the bottom 1 of the tank T and enclose the sedimentation zone 4.2 to P0926 PCTf be disturbed or prevented. As soon as the floating roof drops (on removal) or rises (on refilling), the lances are again "set to disturbance height". In this way it is possible without any reconstruction, new construction, etc. with respect to a storage container, to immediately arrive at the indicated preventative advantages, although this is somewhat more complicated, but definitely practicable for longer storage periods. Following the emptying of the storage container, it is then possible to pass to a preventatively acting apparatus in accordance with the above embodiments and reuse the released lances in other containers.

Claims (21)

1. Method for preventing sedimentation in liquid phases or a thickening of liquid phase or liquid mixtures such as oils, crude oil, refinery products and petrochemical products, which are successively deposited on the bottom of storage tank3 in which prior to the start of sedimentation in such tanks a precursor forms as a thickening sedimentation zone and as a result thickening is initiated and successively passes into sedimentation and/or thickening, characterized in that by means of a plurality of local disturbance points, an overall, three- 15 dimensional disturbance pattern which includes the sedimentation zone is formed, so that the sedimentation and/or thickening is suppressed or "prevented.

2. Method according to claim 1, characterized in that the disturbance of the formation of the sedimentation zone is designed in the form of an overall disturbance pattern with a plurality of local disturbance points so as 2s to convert the disturbance pattern in the form of all the disturbance points in volume- filling manner into disturbance zones, into which the disturbance is introduced into the disturbance zones within the storage container by means of disturbance apparatuses (V) having disturbance means 12).

3. Method according to claim 2, characterized in that disturbance zones are provided in disturbance heights 10, 13) above the bottom of a tank in such a manner that several disturbance zones with their respective \\MELB!\home$\Chelley\Keep\BJN\76134.94.doc 26/08/97 37 disturbance depths form a common volume which encloses the sedimentation zone Method according to one of the claims 1 to 3, characterized in that in the region of the sedimentation zone the disturbance is brought about by means of mechanical means. Method according to claim 4, characterized in that formation of the sedimentation zone (4.2) takes place by a plurality of disturbance points in the form of disturbance means 12) means which can be made to vibrate. 15 6. Method Pccording to one of the claims 1 to 3, characterized in that in the region of the sedimentation zone the disturbance is brought about by means of hydrodynamic means.

7. Method according to claim 6, characterized in that the disturbance of the formation of the sedimentation zone takes place by the supply of crude into the disturbance zone by means of pipe systems and that flowable means 25 are provided as disturbance means in the disturbance zones.

8. Apparatus for performing the method according to one of the claims 1 to 5, with a plurality of vibratory means which are arrangeable or arranged in a given disturbance zone pattern, in a storage container, and with vibration-exciting means 6) which are capable of individually or jointly exciting said vibratory means.

9. Apparatus according to claim 8, characterized in that the vibratory means are tensioned, oblong \\ELB \ho $\Chley\Keep\ N\76134.94.doc 26 B/97 38 means such as strings and excitable by exciting elements via push and pull units as disturbing apparatuses so that the excited strings vibrate in fundamental and partial vibrations and move the stored fluid according to the vibration amplitude. Apparatus according to claim 9, characterized in that the strings are arranged tensioned with a constant disturbance spacing, that they are excited to vibrate via exciting elements on the push and pull units positioned in each case in the centre of the length extension of the strings, the exciting elements in the form of 15 mandrels or striking parts being fitted to the push and pull unites and that strings which are stationary or only slightly vibrating are excited by the moving backwards and forwards of the plucking and striking elements

11. Apparatus according to claim 9 or characterized in that in each case more than one string (15, 17) are tensed between pivoting fastenings and in this way form a 25 mutually supported unit (18) with multiple strings, and that a plurality of units (18) with multiple strings are arranged so as to extend over one or more disturbance zones. \\MELBO1\homeS\Chelley\Keep\BJN\76134.94.doc 26/08/97 i l CI P0926 PCT 39 4. Januar 1996

12. Apparatus according to claim 11, characterized in that the unit (18) with multiple strings is fixed on at least one side to a guide rod (24), which is exerting a leverage and which is mounted in rotary manner on a fixed support so as to tense or relax the strings via said rod.

13. Apparatus according to claim 12, characterized in that the units (18) with multiple strings is fixed on both sides to guide rods (24) and that said guic rods (24) are movable via tension cables (21) so as to tense or relax the strings.

14. Apparatus according to claim 8, characterized in that for disturbing the formation of the sedimentation zone bell-shaped diaphragms excitable so as to vibrate are provided in disturbance zones as distur- bance means (12) and are excited by exciting elements via push and pull units in disturbing apparatuses so that the bell-sha- ped diaphragms vibrate in fundamental and partial vibrations, and move the stored fluid according to the vibration amplitude. Apparatus according to claim 14, characterized in that the bell-sha- ped diaphragms are made to vibrate by means of hammer elements (14) of the push and pull units, the hammer elements (14) in the form of small hammers being fixed to the push and pull units so that bell-shaped diaphragms which are stationary or only slightly vibrating are excited to vibrate by the moving backwards and for- wards of the hammer elements (14) and the hammering action of the latter on the bell-shaped diaphragms. yrC i I- P0926 PCT -40- 4. Januar 1996

16. Apparatus according to claim 15, characterized in that the bell-sha- ped diaphragms have elastic connections to the push and pull units, said connections having the form of strikers fitted in or on bell-sha- ped diaphragms, so that bell-shaped diaphragms in the stationary state or oscillating only slightly are excitable to oscillate by the for- ward and backward movement of the hammer elements (14) and by the hammering action of the hammer elements (14) on the bell-sha- ped diaphragms.

17. Apparatus according to one of the claims 8 to 16, characterized in that push and pull units are arranged with rigid or movable mem- bers in several planes, that they are fixed to the bottom of the tank and that their rigid or movable members are passed to the outside via passages (11) on the wall or in the floating roof so as to be driven by means of fluid-operated drives outside the tank

18. Apparatus according to claim 17, characterized in that spatially mova- ble push and pull means with movable members, which are made from metals such as steel, steel alloys, bronze or plastic or metal-- coated plastic and which are laid in long lengths from a reel corre- sponding to a given disturbance pattern are used as push and pull unit

19. Apparatus for performing the method according to one of the claims 1 to 3 and 6 to 7, characterized by a plurality of fluid-ejaculating means which are arranged in a given disturbance zone pattern and which are interconnected with fluid-conducting means i c; i P0926 PCT -41 4. Januar 1996 Apparatus according to claim 19, characterized in that for preventing the formation of a sedimentation zone a plurality of fluid-ejacu- lating means are interconnected by a pipe system and are admittable by a fluid by means of means for supplying and removing crude (4) into or from the disturbance zone via pipe systems as disturbance apparatuses

21. Apparatus according to claim 19, characterized in that for preventing the formation of a sedimentation zone hydrokinetically, a com- bined removal and supply of crude from and into the disturbance zone by means of nozzles and pipe systems in disturbance appara- tuses is provided.

22. Apparatus according to one of the claims 19 to 21, characterized in that pipe systems are constructed from standardized, rigid pipe components, that these rigid pipe components can be interconnected by means of connecting means such as flanges and that openings or nozzles are connected to the rigid pipe components by connecting means.

23. Apparatus according to one of the claims 19 to 21, characterized in that pipe systems are constructed from standardized, flexible pipe components, that the flexible pipe components can be interconnected by means of connecting means such as flanges and that openings or nozzles as disturbance points are connected to the flexible pipe components by connecting means. Il 1 P0926 PCT 42 4. Januar 1996

24. Apparatus according to claim 23, characterized in that the flexible pipe components are flexibly laid from a reel in the form of reinfor- ced, pressure-tight hoses, that nozzles as disturbance points are arranged on said hoses and that said hoses are permanently fixed to the bottom of the tank Apparatus according to claim 20 or 21, characterized in that the supply or removal of crude into and out of the disturbance zone is provided by means of nozzles, that the nozzles with standardized, different disturbance medium throughputs are fitted, so that the nozzles with different sizes prevent a disturbing pressure drop with respect to the disturbance medium in the pipe system by means of said different disturbance medium throughputs.

26. Apparatus according to claim 25, characterized in that by means of nozzles with different throughputs the ratio of the local pressure at the nozzles in the pipe system to the throughput of the nozzles is kept constant.

27. Apparatus according to one of the claims 19 to 21 and 25 to 26, characterized in that disturbance-causing means are passed from the top of the storage container into the sedimentation zone.

28. Apparatus according to claim 27, characterized in that the disturban- ce means are fluid-conducting lances, which are guidably arranged in supports in a floating roof or through a firm roof. -I P0926 PCT -43 ABSTRACT The invention relates to a method and an apparatus for avoiding the deposi- tion of sediments from mixtures such as e.g. from crude oil refinery pro- ducts and petrochemical products, which are mainly deposited on the bottom of tanks the sediments having a precursor in the form of a thickening sedimentation zone the deposition of sediments is prevented by the disturbance of the formation of the sedimentation zone the disturbance is designed in the form of overall disturbance patterns with local distur- bance points the disturbances brought about by providing disturbing ap- paratuses with disturbance means in accordance with the disturbance pattern in a disturbance zone, the disturbance taking place hydrodynami- cally or mechanically, with nozzles bringing up crude into the disturbance zones or with strings excitable to vibrate in the form of disturbance means (8, 12), which are excited by exciting elements via push and pull unils in disturbing apparatuses the strings vibrating in fundamental and partial vibrations and deflecting the components of the mixtures as a function of the amplitude of said sound waves. (Figs. 7 and 8)