RU2046627C1 - Heat-and-mass transfer apparatus - Google Patents

Abstract

FIELD: oil refining industry, may be used for crystallization in mineral oil deparaffinizing unit and deoiling of oil gases. SUBSTANCE: heat-and-mass exchanging apparatus has heat-exchanging tubes incorporating shaft with spring-biased supporting members arranged in pairs one opposite the other and strip-shaped scrapers fixed in them for radial displacement, auxiliary supports, with scrapers being radially spaced with respect to contact surfaces of auxiliary supports. Auxiliary supports are formed as helical blades secured on shaft. Radial space is not in excess of 0,4(R_in-R_out), where R_in is inner radius of heat-exchanging tube, R_out is shaft outer radius. Contact surfaces of auxiliary supports may be formed as end webs of through slots made in blade bodies. Scrapers are positioned for displacement in slots. Auxiliary supports may be formed as helical centrators mounted between spring-loaded supporting members along shaft body or as single-threaded or multiple-thread augers positioned along shaft length. EFFECT: increased efficiency, simplified construction and enhanced reliability in operation. 4 cl, 5 dwg

Description

 The invention relates to equipment for oil refining, petrochemical and related industries, in particular, to devices for crystallization in plants for dewaxing of mineral oils and deoxidation of oil gas.

The prior art heat and mass transfer apparatus in the form of scraper crystallizers, containing several sections of the pipe-in-pipe type, interconnected by twins with screw scraper shafts mounted on supports inside the sections [1]
The main disadvantage of such crystallizers is the formation during operation of plugs from the deposited solid phase in the areas of the supports of the scraper shaft, because in these areas due to the annular protrusions formed by the supports on the scraper shaft there are no screw blades.

Also known is a heat and mass transfer apparatus in the form of a scraper mold, including a heat transfer tube, inside of which there is a shaft of elastic rings with strip scrapers mounted for radial movement [2]
However, due to the high rigidity of the elastic rings necessary to ensure the operability of the elastic shaft, an increased torque is required during its rotation due to the significant frictional forces between the strip scrapers and the surface of the heat exchange tube. This reduces the lifetime of the mold and increases operating costs.

The closest to the proposed device in terms of features is a heat and mass transfer apparatus in the form of a scraper crystallizer, including heat transfer pipes, each of which has a shaft with supports mounted in pairs protruded to each other by spring-loaded support elements in which strip scrapers are fixed [3]
The disadvantage of this mold is the low efficiency due to the formation of plugs from the deposits of the solid phase in the area of the supports of the scraper shaft. To remove these plugs, you must periodically stop and clean the device.

 The aim of the invention is to increase productivity and reduce hydraulic resistance due to the complete cleaning of the working volume of the apparatus.

This is achieved by the fact that in the heat and mass transfer apparatus, including heat exchange tubes, in each of which there is a shaft with spring-loaded supporting elements installed in pairs oppositely to each other and secured by radial movement of strip scrapers, according to the invention, the scrapers are installed along the entire length of the shaft with a radial the gap with respect to the contact surfaces of the additional supports made in the form of screw blades mounted on the shaft, while the radial clearance is not greater its 0,4 (R _a -R _n), wherein R _in the inner radius of the heat exchange tube;
R _{n is the} outer radius of the shaft.

 In addition, the contact surfaces of the additional supports can be made in the form of end bridges through the slots in the body of the blades, while the strip scrapers are installed with the possibility of movement in these slots. In embodiments, additional supports can be made either in the form of screw centralizers installed between the spring-loaded support elements along the entire length of the shaft, or in the form of a single or multiple feed screw located along the entire length of the shaft.

 The drawings show a heat and mass transfer apparatus, where: in FIG. 1 shows a longitudinal embodiment of a heat and mass transfer apparatus; in FIG. 2, section AA in FIG. 1; in FIG. 3 section BB in FIG. 1; in FIG. 4 is a general view of an embodiment of a heat and mass transfer apparatus (longitudinal section); in FIG. 5 section BB in FIG. 4.

 The heat and mass transfer apparatus comprises heat exchange tubes 1, inside of which there is a shaft 2 with spring-loaded support elements 3 arranged in pairs oppositely to each other, on which strip scrapers 4 are mounted with the possibility of radial movement in the radial direction along the entire length of the shaft 4. In addition, additional bearings are fixed to the shaft, made in the form of either screw centralizers 5 (see Figs. 1, 3), or in the form of a single or multiple feed screw 6 (see Figs. 4 and 5).

The scrapers are mounted on the spring-loaded support elements 3 (the design of which is similar to the design of these elements in the prototype) with a radial clearance b with respect to the contact surfaces 7 of the additional support elements. The gap b is not more than 0.4 (R _in -R _n ), where R _{in the} inner diameter of the heat exchange pipe 1;
R _{n the} outer diameter of the shaft 2.

 The contact surfaces 7 of the additional supports 5 or 6 are formed by end bridges of the through slots 8, made in the body of the blades. In addition, the outer surface of the additional supports 5 and 6 can be made with a radius smaller by b than the radius along which the lower edges of the scrapers 4 are located (not shown in the drawing). In this case, the contact surfaces of the additional support elements 5 and 6 are their outer surfaces. Screw centralizers 5 can be mounted on the shaft 2 with the help of clamps 9 and bolts 10.

 Heat and mass transfer apparatus operates as follows.

 Crude oil, from which paraffin hydrocarbons crystallize, enters the heat exchange pipe 1, filling its working volume. In the process of operation of the apparatus, the shaft 2 rotates. In this case, the spring-loaded scrapers 4 clean off the solid phase that crystallizes on the inner surface of the heat exchange pipe and is removed from the pipe due to the combined action of the energy of the liquid flow of oil feedstock and screw blades of additional supports 5 or 6. Due to that the scrapers 4 can radially move by a value of b, they rotate the shaft completely remove the solid phase from the surface of the pipe, compensating for the local misalignment of the heat exchange pipe and ala 2 arising from their distortions and inaccuracies of manufacture. The alignment of the shaft 2 and the pipe 1 is also provided by additional supports, the contact surfaces of which do not allow the scrapers to move to the center of the shaft beyond the set limit.

 The location of the scrapers 4 in the slots 8 allows you to transfer more force to the scrapers, as well as block the cross section of the pipe 1 with screw blades of additional supports, which allows you to more effectively use them as screw pumps. The strip scrapers 4 during rotation of the shaft also contribute to the twisting of the fluid flow, which ensures partial separation of lighter fractions (including paraffin fractions cleaned from the pipe walls) to the surface of the shaft 2.

 This significantly increases the heat transfer effect, as Directly at the surface of the heat exchanger tube, the layer of liquid petroleum feed is constantly updated, and low-heat-conducting paraffin fractions are effectively removed. After passing through the entire volume of the mold, the working mixture is removed from the apparatus.

 The technical result from the use of the invention is to increase productivity and efficiency while reducing material costs during the process of dewaxing of crude oil.

Claims (4)

1. HEAT AND MASS TRANSFER APPARATUS, including heat exchange tubes, in each of which there is a shaft with spring-loaded supporting elements installed in pairs oppositely mounted to each other and secured with the possibility of radial movement of strip scrapers, characterized in that it is equipped with additional bearings, scrapers are installed along the entire length of the shaft with a radial clearance in relation to the contact surfaces of the additional supports made in the form of screw blades mounted on the shaft, while the radial clearance was it is not more than 0.4 (R _in R _n ), where R _{is the} inner radius of the heat exchanger pipe, R _{n is the} outer radius of the shaft.  2. The apparatus according to claim 1, characterized in that the contact surfaces of the additional supports are made in the form of end bridges of through slots in the body of the blades, while the strip scrapers are installed with the possibility of movement in the slots.  3. The apparatus according to claims 1 and 2, characterized in that the additional bearings are made in the form of screw centralizers installed between the spring-loaded bearings elements along the entire length of the shaft.  4. The apparatus according to claims 1 and 2, characterized in that the additional supports are made in the form of a screw, continuous or multi-starting blades of which are placed along the entire length of the shaft.

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