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 
  • B08B9/02—Cleaning pipes or tubes or systems of pipes or tubes
  • B08B9/027—Cleaning the internal surfaces; Removal of blockages
  • B08B9/032—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing
  • B08B9/0321—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing using pressurised, pulsating or purging fluid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
  • F28F13/06—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media
  • F28F13/12—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media by creating turbulence, e.g. by stirring, by increasing the force of circulation
  • F28F13/125—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media by creating turbulence, e.g. by stirring, by increasing the force of circulation by stirring
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
  • F28F19/008—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using scrapers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28G—CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS
  • F28G1/00—Non-rotary, e.g. reciprocated, appliances
  • F28G1/06—Non-rotary, e.g. reciprocated, appliances having coiled wire tools, i.e. basket type

Definitions

• the present invention relates to a device for reducing fouling inside a tube in which a fluid circulates, of the type comprising a rotary element generating turbulence, in particular in the tubes constituting the heat exchangers.
• the present invention can particularly find application in industries, in particular the petroleum or petrochemical industry, which implement tubular heat exchangers in which fluids can circulate at high temperature and / or corrosive. Since approximately twenty years, devices have been installed rotatably inside heat exchanger tubes in order to prevent a possible fouling, for example due to impurities in suspension, to deposits. dissolved mineral salts in the fluid, coke forming in a thermal cracking process or sulfur species soluble in hydrocarbons.
• a movable element generally in the form of a helix consisting of several turns all having the same pitch orientation, attached to the upstream end of the tube in such a way that the movable element can freely rotate in the tube under the effect of the fluid flow.
• the dimensions of the movable element and the inside of the tube are such that the movable element does not continuously scrape the inner wall of the tube, in order to avoid any consequences. detrimental to the service life of the metal structure of said tube and / or mobile element.
• the reduction in fouling of the interior of the tubes is mainly due to the increase in fluid turbulence which decreases or even prevents the formation of hot spots and the formation of deposits. Without being bound by this theory, it is possible that this reduction of fouling is obtained through a thermal homogenization effect (rupture of the insulating thermal limit layer) and by a significant shear effect near the wall. This may make it possible to reduce or even avoid the formation of deposit (s), and / or to unhook, in whole or in part, any deposits weakly attached to the same wall before they start to grow in size and therefore become more resistant to tearing them away.
• the Applicant furthermore describes in Application EP 0 369 851, a movable element comprising, in all its transverse sections, at least one sharp edge shaped specifically to scrape the inner surface of the tube.
• the Applicant has continued its research to extend the operating time of said fouling reducing devices inside the tubes and in particular heat exchanger tubes used in petroleum refineries. Indeed, the longer this operating time is elongated, the less it will be necessary to provide for the replacement of said devices after a possible break at the fixed upstream element, that is to say that the operator will avoid the opening of the heat exchanger considered, will also de facto avoid the risk of a complete shutdown of the installation in which said exchanger is implemented, and thus ultimately, avoid human risks, expenses and loss of profits.
• the speed of the fluid inside the tube exceeds a limit value, for example greater than 1.5 m / s, the speed of rotation of the movable element can become very high (greater than 1500 rpm). ).
• a limit value for example greater than 1.5 m / s
• the speed of rotation of the movable element can become very high (greater than 1500 rpm). ).
• the use of such a mobile element is not recommended because the phenomena of wear at the fixed upstream element can become too great and result in premature failure of the fastener of the element. mobile at this fixed upstream part. This break can lead to an unsatisfactory operating time for most operators, for example limited to 4 years.
• the present invention relates to a device to remedy all or part of the problems mentioned above, in particular to have increased reliability and / or an increased range of use, while remaining simple to manufacture, inexpensive and / or easy to set.
• the subject of the invention is a device for reducing fouling of the inside of a tube traversed by a fluid, of the type comprising at least one turbulence-generating element, said device consisting of a rotary element.
• an upstream part forming a trunnion comprising a mechanical connection with the fixed element forming a bearing and allowing the free rotation of the movable element on itself around the axis of the tube;
• downstream portion in the form of a helix consisting of several turns and shaped so as to be rotated by the flow of the fluid in the tube, in which: the upstream and downstream parts of the mobile rotary element are connected to each other; to one another by a flexible elongate connector deformable over its entire length, and the downstream part contains at least one portion of turn whose pitch is inverted with respect to the pitch of the other turns.
• the invention relates to a device having a reduction in the speed of rotation of the movable part, associated with a fastening system, for example as described in FR 2 890 162, which comprises a flexible coupling connecting the trunnion of the movable member, positioned at the fixed upstream member, at the generally helical portion, formed of a plurality of turns, extending along a portion or the entire length of the tube and rotated by the flow of fluid flowing in said tube.
• a reduction in the rotational speed of the movable element may allow use for fluid speeds greater than 1.5 m / s while remaining in rotational speed ranges limited to 1500 rpm to limit the phenomena of wear.
• the subject of the invention is also a heat exchanger comprising a plurality of tubes traversed by a fluid, comprising at least one fouling reducing device according to the invention installed inside at least one of its tubes, in particular attached to the upstream end of at least one of these tubes.
• the flexible connector used in the present invention may be of any material provided that it has sufficient chemical and mechanical resistance under the operating conditions of the invention. device.
• the flexible connector is preferably made of metal, in particular steel, and especially stainless steel.
• the flexible connector may be, for example, a cable formed of braided or twisted strands preferably comprising a number of strands between 1 and 100, and more preferably between 1 and 50.
• a flexible connector having a length of between 1 cm and 5 cm, and preferably between 2 and 4 cm. Its diameter can range from 2 to 10 mm and preferably from 4 to 8 mm.
• This flexible coupling is fixed between the downstream end of the trunnion and the upstream end of the helically rotated portion.
• the attachment to these two parts can be done according to known techniques, for example by welding, crimping, screwing, or by gluing.
• the rotatably driven helical downstream portion may in principle have any suitable asymmetric shape allowing the fluid flowing through the tube to rotate it about the axis of said tube.
• the most effective form, creating maximum turbulence for minimal pressure drop, is the helix which is therefore used in almost all devices of the type described in the introduction and is also preferred for the present invention.
• This propeller must have an outer diameter less than the inside diameter of the tube to not scrape continuously the inner wall thereof.
• the outer diameter of the helix may however be sufficiently close to the inside diameter of the tube to create, in addition to turbulence, sufficient shear forces near the surface of the tube, for example to pick up deposits or particles weakly attached to the tube. wall. Satisfactory turbulence and shear effects are generally obtained for systems where the ratio of the outer diameter of the helix to the inside diameter of the tube is from 0.5 to 0.9, preferably from 0.6 to 0.8.
• Ratios between the above ranges have been found to be sufficient to avoid excessive frictional contact, or even to prevent frictional contact, between the tube and the propeller over almost the entire length of the propeller.
• the Applicant has found that for ratios of the outer diameter of the helix to the inside diameter of the tube included in the ranges indicated above, at least the first turn of the helix, and sometimes also the next two or three turns could show signs of chafing. Although this phenomenon is attenuated for flexible coupling fastening systems as described in this application, it may nevertheless persist under certain operating conditions of the device according to the invention.
• This problem can be solved in whole or in part through the use of a helix in which the outer diameter of the first turn, or first turns, is smaller than the outer diameter of the other turns of the helix. The first turn is the one closest to the tie.
• the number of "first" turns concerned by this decrease in diameter does not generally exceed 1 to 5% of the totality of the turns of the helix.
• the ratio of their outer diameter to the inside diameter of the tube may be between 0.1 and 0.6, preferably between 0.2 and 0.6.
• their outer diameter preferably increases progressively from upstream to downstream.
• the fixed bearing element intended to receive and support the trunnion, can have a great variety of shapes, insofar as it fulfills two functions which are on the one hand, to ensure the robustness of the fastener to the trunk. end of the exchanger tube, and secondly, to minimize restrictions on fluid flow. It preferably has the shape of a stirrup comprising a central portion pierced with an orifice intended to receive the trunnion of the movable element, and two branches, symmetrical to each other, having a shape enabling them to be fixed. on the upstream end of the tube.
• This caliper shape of the bearing part is known and is described for example in the applications EP 0 233 092, EP 0 282 406 and EP 0 369 851 of the Applicant. It may be for example a stirrup whose ends form a hollow cylinder intended to grip the end of the tube, as described in EP 0 233 092, or, preferably, a stirrup made of a rigid material but the ends of the two branches can be forcibly engaged in the upstream end of the tube for resiliently bearing against the inner wall thereof.
• the invention also includes any other system for rendering a bearing portion rigidly secured to the upstream end of the tube.
• the pin is retained in the bearing orifice by a first stop provided at its upstream end and secured thereto.
• a second abutment, tubular may be provided on the central part of the stirrup extending the orifice intended to receive the trunnion of the movable element.
• This second abutment, integral with the bearing may have a function of maintaining the journal in the axis of rotation of the movable element and is preferably relatively long.
• one or more wear washers are provided between the first stop and the second stop.
• This wear washer is free, that is to say integral solidarity of the movable element or the fixed element. It is preferably made of a different material or of different hardness, or even an anti-friction type with a very low coefficient of friction, which is generally softer than the materials of the first and second stops. Examples of such materials include steels, especially heat-treated steels, copper alloys, ceramics, and graphites.
• the known wear washers for example of EP 0 233 092, EP 2 637 659 and EP 0 282 406, have friction surfaces which are flat or complementary to the friction surface of the abutment. Preferably, it will be sought to reduce as much as possible the surfaces in contact by adopting shapes specific to wear washers and / or tubular abutments.
• the metal pin is replaced by an extension of the flexible coupling whose downstream end is secured to the stop.
• the mobile rotary element and more particularly its downstream portion in the form of a helix may consist of several turns and shaped so that said downstream portion is rotated by the flow of fluid in the tube.
• the rotational speed of the mobile element essentially depends on the flow rate of fluid passing through the tube, said flow rate being variable, for example in the heat exchanger tubes, from 0.5 m / s to 3 m / s, for a pressure that can change between 5 and 30 bar.
• This direction of rotation can be, according to the mounting of the turns constituting the downstream part of the movable element in the direction (not right) or inverse (not left) in the direction of rotation of the needles of a watch, without disturbing the efficiency of the reducing device of the fouling of the inside of a tube.
• the portion of turns having a pitch inverted with respect to that of the other turns is represented by a percentage of the length of the movable element.
• X for example 0.5%) of inverted pitch turns
• Y for example 6 m
• Z cm for example 3 cm
• Y x X cm in this case 3 cm
• Z cm for example 3 cm
• the speed of the minimum fluid passing through the tube, to set in motion a device of 6 m in length having a portion of inverted pitch, will be more important than the% of turns with reversed pitch is important.
• This minimum speed will always be greater than that of a standard device whose downstream part of the mobile element consists of a helix comprising only turns having a step in the same direction.
• This minimum speed can be around 1.5 to 2 m / s while it is usually 0.5 m / s for a standard device.
• the reduction of the rotational speed with respect to a standard device varies according to the speed of the fluid and the amount of inverted-pitch turns.
• the rotational speed reduction intervals of the movable element can range from 95% (fluid velocity 2.0 m / s) to 54% (fluid velocity 3.0 m / s) for 15% length of the movable element consisting of a coil having an inverted pitch.
• the reduction in rotational speed of the movable member can vary from 56% for a fluid velocity of 2.0 m / s to 16% for a fluid velocity of 3.0 m / s for 0.5% of inverted turns. Further data on the reduction of the rotational speed of the movable member is given in the example below.
• 15% of the total length of the movable element with a total length of 6 m can make it possible to use the device that is the subject of the present invention with a fluid speed of 2.85 m / s, whereas this speed is limited. at 1.5 m / s for a standard device.
• This rotational speed of 1500 rpm can also be achieved with 0.5% inverted turns for a fluid speed of 2.25 m / s (see fig 1).
• a target speed of rotation of the moving element of 1000 rpm obtained with fluid speeds ranging from 2.05 m / s to 2.55 m / s, with respectively lengths of turns having inverted steps from 0.5% to 15%.
• the speed of the permissible fluid with a standard device for a rotational speed of 1000 rpm is 1.45 m / s, without the possibility of going beyond without increasing the speed of rotation of the movable element.
• the total pressure drop (that is to say the sum of the losses due to the fixed upstream element as described in FR 2 890 162, the length of the tube and the device object of the present invention) may be greater than that of a tube of the same length equipped with a standard device.
• the increase in the pressure drop for a rotation speed of the movable element set at 1500 rpm can vary from 84% to 220% when the% of inverted pitch turns varies from 0.5% to 15%, 500 to 920 mbar and 500 to 1600 mbar respectively.
• the total pressure drop can vary from 93% to 206%, from 440 to 850 mbar and from 440 to 1380 mbar when the% inverted pitch turns varies by 0.5%. at 15%.
• FIG. 1 represents a device according to the invention
• FIG. 2 is a diagram representing the speed of rotation as a function of the speed of the fluid for different% of length of turns having an inverted pitch
• FIG. 3 is a diagram representing the% reduction in the speed of rotation of the device for different% of length of turns having a reversed pitch
• FIG. 4 represents the pressure drop in a tube as a function of the speed for different% of length of turns having an inverted pitch.
• Figure 1 is a longitudinal sectional view of a tube with a device for reducing fouling inside a tube, object of the present invention, attached to the upstream end of said tube.
• the device consists of a mobile part 2 and a fixed part 3 fixed at the upstream end of a tube 1.
• Downstream are defined with respect to the flow direction of the fluid that passes through the tube 1 represented by the arrow F.
• the fixed part 3 of the device has the shape of a stirrup consisting of a plate 9 pierced with a central orifice, and two branches 10, in principle symmetrical to each other with respect to the axis of the tube , the ends of which bear against the inner wall of the tube.
• the fixed portion further comprises a tubular abutment 1 1 secured to the plate 9.
• the channel of this abutment 1 1 is aligned with the orifice of the plate and forms with it a single long enough channel which serves mainly to maintain the trunnion 4 in the axis of rotation of the movable element 2.
• the movable element 2 In the fixed part 3 is mounted, free in rotation, the movable element 2.
• This movable element is constituted, starting from the upstream end thereof, an abutment 5, a journal 4 integral with the stop 5, a flexible connector 7 in stainless steel cable, and finally the helical portion 6 rotated in the direction of the arrow F by the flow of the fluid. Note that all the turns of the helix are not the same size but the first two have a smaller outer diameter than the next turns.
• a wear washer In addition, a wear washer
• the downstream element 6 of the movable element 2 consists of several turns having an identical pitch. Only the turn 8 in Figure 1 has, in accordance with the invention a step reversed to that of other turns.
• this turn (or of these turns) can be achieved by a simple inverted winding of the wire, for example stainless steel, constituting the downstream element in the form of a helix of the movable element, or can be attached to the downstream element by any means known in the art such as welding, crimping, screwing, gluing, etc.
• the Applicant has used a model that uses cold water circulating in a plexiglass tube 6 m long and allows measurements of water flow, loss of charge at different lengths and the rotational speed of the movable element of the device object of the present invention.
• test parameters are as follows:
• composition of the alloy constituting the wire 64.9% of nickel, 8.75% of molybdenum and 26.35% of iron, angle of turn: 55 °,
• the upstream portion of the movable member is constituted by a journal length of 8.0 cm and a diameter of 0.2 cm, according to the present invention, and is crimped to the flexible connector.
• the fixed upstream element is also constituted in accordance with FR 2 890 162.
• Figure 2 shows the ordinate speed of rotation (rpm) and abscissa the fluid velocity (m / s). These data were measured for moving elements 6 m in length, respectively (mark 1 in Figure 2) 0% reverse pitch turns, (2) 0.5% reverse pitch turns, (3) 2.0%, (4) 4.0%, (5)
• FIG. 2 shows that the more the number of turns having an inverted pitch increases, the greater the reduction in the speed of rotation of the movable element. This reduction also increases as the fluid velocity decreases.
• FIG. 3 represents in ordinate the% reduction in the speed of rotation of the device and in abscissa the% of length of inverted turns.
• FIG. 4 is the ordinate of the total pressure loss
• This pressure drop is the expression of the sum of the pressure losses corresponding to the fixed upstream element (fixing bracket), to the tube by itself and to the device object of the present invention.
• the operating time of the device described was less than 4 years.
• the lifetime of the device object of the present invention should reach 5 years or more, a period required by the operator of an oil refinery.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Rigid Pipes And Flexible Pipes (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=41010391

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (1)

Citations (7)

• 2008
  • 2008-12-19 FR FR0858848A patent/FR2940152B1/fr not_active Expired - Fee Related
• 2009
  • 2009-12-02 ES ES09801738T patent/ES2415908T3/es active Active
  • 2009-12-02 PL PL09801738T patent/PL2367642T3/pl unknown
  • 2009-12-02 EP EP09801738A patent/EP2367642B1/fr active Active
  • 2009-12-02 WO PCT/FR2009/052374 patent/WO2010076446A1/fr active Application Filing

Patent Citations (7)

Also Published As

Similar Documents

Legal Events