RU2748169C1 - Tubular heater - Google Patents

Abstract

FIELD: heat engineering.

SUBSTANCE: invention relates to heat engineering and can be used in heating devices for fluids, namely in tubular heaters. A tubular heater consists of a heat exchange chamber, a burner device, a process coil, an internal process coil and tubular inlets and outlets of the process coils. The process coils are made of straight pipes and placed in the heat exchange chamber. The process coil is adjacent to the walls of the heat exchange chamber and the internal process coil is located symmetrically inside the process coil. The heat exchange chamber is made in the form of a rectangular parallelepiped with flat side, top, bottom, front and rear walls. The burner device is located on the front wall, to which the flue duct adjoins, the internal process coil is double-row and is placed with gaps relative to the front and rear walls of the heat exchange chamber, sheets of heat-resistant material are placed between the rows of pipes of the inner process coil, forming the walls of the gas channel.

EFFECT: simplified design, reduced metal consumption, increased efficiency and reliability of the tubular heater.

5 cl, 7 dwg

Description

The invention relates to heating devices for fluids, namely to tubular heaters, and can be used in the oil, chemical and other industries for thermal treatment of liquids that have technological and other restrictions on the maximum heating temperature. In particular, the tubular heater can be used in technologies for demulsification and stabilization of oils in oil fields and for heating oil during its transportation through pipelines.

Known tubular heaters with an intermediate heat carrier [1, 2], where the source of heat are the products of fuel combustion. These tubular heaters provide heating of oil without coke deposits on the inner surface of the product pipes. Their disadvantage is their high metal content, cumbersomeness and difficulty in controlling the process of heating the product due to the high thermal inertia of the intermediate heat carrier - water filling the heater body.

Known tubular furnaces, in which the products of fuel combustion transfer heat to the heated product in direct contact with the surface of the product pipes placed in the radiant and convection chambers of the furnace [3]. These furnaces are structurally complex and bulky. Their characteristic inhomogeneity of the heat flux density distribution over the heat transfer surface area and high local values of the wall temperature of product pipes lead to the formation of coke deposits on the pipe walls when heating media prone to thermal decomposition.

Also known is a block tubular heater for heating oil emulsions with increased corrosivity and a tendency to deposit salts and mechanical impurities [4]. The known heater consists of several prefabricated units and is transportable. Due to the internal circulation of fuel combustion products in the heat exchange chamber and a decrease in their maximum temperature at the same time, the rate of formation of coke deposits in the product pipes decreases. The disadvantage is the uneven distribution of the heat flux density over the heat transfer surface area, due to the presence of stagnant zones of heating gases in the corner regions of the heat exchange chamber. This leads to a low efficiency of using the heat transfer surface of the product coil, high metal content and dimensions of the device.

The closest to the proposed invention in technical essence is a device for heating fluids, containing a heat exchange chamber, a burner device made of straight pipes and placed in the heat exchange chamber, a product coil adjacent to the walls of the heat exchange chamber, and an internal product coil located symmetrically inside it, tubular inlets and outlets of product coils [5] - prototype.

In the known device [5], the flow of heating gases is swirled in the volume of the heat exchange chamber, which largely eliminates the corner stagnant zones of gases and contributes to the uniformity of the distribution of the heat flux density over the heat transfer surface area. Its disadvantage is the complexity of the design, manufacture and repair of the heater. In those parts of the pipes of the product coils, which are located in the zone of high temperatures of the heating products of fuel combustion with active radiative heat transfer, the deposition of coke on the walls inside the pipes is possible when heating oil and oil emulsion. The disadvantage is that the product coils of the device cannot be emptied by self-draining.

The technical problem to be solved by the present invention is to simplify the design, reduce the metal consumption, increase the efficiency and reliability of the tubular heater.

The essence of the invention lies in the fact that in a tubular heater containing a heat exchange chamber, a burner device made of straight pipes and placed in the heat exchange chamber, a product coil adjacent to the walls of the heat exchange chamber, and an internal product coil located symmetrically inside it, tubular inlets and outlets of product coils, the heat exchange chamber is made in the form of a rectangular parallelepiped with flat side, top, bottom, end front and rear walls, the burner device is located on the front wall, to which the flue duct adjoins, the internal product coil is made two-row and is placed with gaps relative to the front and rear walls heat exchange chamber, between the rows of pipes of the inner product coil there are sheets of heat-resistant material that form the walls of the gas channel, the product coil adjacent to the walls of the heat exchange chamber, and the inner product coil are made of of stud pipes, the open ends of which are interconnected by collector pipes with disc baffles in diametrical sections, on the outer surface of the stud pipes of the product coils there are discrete roughness elements, inside the stud pipes of a row of the inner product coil located in the gas channel there are twisted tapes, tubular inlets and outlets of product coils have gland seals with front and rear walls of the heat exchange chamber and threaded flanges at the ends.

In contrast to the known device, the execution of the heat exchange chamber in the form of a rectangular parallelepiped with flat side, top, bottom, end front and rear walls, the placement of the burner device on the front wall, to which the flue duct adjoins, the design of the internal product coil double-row and its placement with gaps with respect to the front and rear walls of the heat exchange chamber, the presence of sheets of heat-resistant material between the rows of pipes of the internal product coil, which form the walls of the gas channel, allows for organized recirculation of heating products of fuel combustion in the heat exchange chamber. At the same time, the maximum temperature of the heating combustion products is reduced to a value that excludes the active formation of coke deposits inside the product pipes when heating oil and oil emulsion. The efficiency and reliability of the tubular heater in the presence of organized recirculation of heating gases increases significantly.

The design of the product coil, adjacent to the walls of the heat exchange chamber, and the internal product coil of studded pipes, the open ends of which are interconnected by collector pipes with disc baffles in diametrical sections (patent RU No. 2382973), provides small dimensions of product coils, simplifies the design of the tubular heater and allows you to achieve high compactness.

The presence of discrete roughness elements on the outer surface of the pipe-hairpins of the product coils intensifies the heat transfer from the heating gases to the walls of the pipes-hairpins due to the turbulence of the near-wall layer of the gas flow, which makes it possible to reduce the surface area of the heat transfer of the product coils and contributes to a more compact tubular heater. Elements of discrete roughness represent a metal spiral bead applied by welding to the surface of stud pipes, or it can be a wire wound in a spiral with a certain diameter and pitch of winding.

Placing the twisted tapes inside the stud pipes of a row of the internal product coil located in the gas channel, where the highest temperature of the heating combustion products, intensifies the heat transfer from the walls of the stud pipes to the heated product. This leads to a decrease in the temperature of the walls of the stud pipes during the operation of the tubular heater, which, in turn, reduces the likelihood of coking of the heated product on the walls of the stud pipes and improves the efficiency and reliability of the tubular heater.

The use of stuffing box seals at the points of passage of tubular inlets and outlets of product coils through the front and rear walls of the heat exchange chamber and threaded flanges at the ends of tubular inlets and outlets simplifies the technologies for assembling and disassembling a tubular heater during manufacturing and repair.

Comparative analysis of the proposed technical solution with the prototype [5] shows that the proposed solution meets the criterion of "novelty".

Known technical solutions [3, 4], which implement direct heating of the product, do not provide intensified heat transfer. Their designs are cumbersome and difficult to manufacture. Product coils are susceptible to coking during operation.

All this allows us to conclude that the proposed technical solution meets the criterion of "significant differences".

FIG. 1 shows a schematic section of the proposed tubular heater; in fig. 2 is a left side view of FIG. one; fig. 3 is a section along AA in Fig. one; fig. 4 - remote element I in Fig. one; fig. 5 - remote element II in Fig. one; fig. 6 is a diagram of a product coil adjacent to the walls of the heat exchange chamber; fig. 7 - remote element III in Fig. 6.

The tubular heater contains a heat exchange chamber 1, bounded by flat side 2, top 3, bottom 4 and end front 5 and rear 6 walls. A burner device 7 is placed on the front wall 5. The flue duct 8 is adjacent to the front wall 5. The internal product coil 9 consists of two rows of stud pipes 10 and with gaps 11 relative to the front wall 5 and 12 relative to the rear wall 6 is located inside product coil 13, adjacent to the walls 2, 3, 4 and 6 of the heat exchange chamber 1. Between the rows of stud pipes 10 of the inner product coil 9, sheets 14 of heat-resistant material are placed, forming the walls of the gas channel 15. Open ends of the stud pipes 10 of the product coils 9 and 13 are interconnected by collector pipes 16 with disc baffles 17 in diametrical sections. On the outer surface of the stud pipes 10 of the product coils 9 and 13 there are elements of discrete roughness 18, and in the stud pipes 10 of the row of the internal product coil 9, located in the gas channel 15, there are additionally inserted twisted strips 19. Tubular inlets 20 and outlets 21 for product coils 9 and 13 have stuffing box seals 22 at the points of passage through the front 5 and rear 6 walls of the heat exchange chamber 1 and threaded flanges 23 at the ends.

The heater can be either single-flow or multi-flow for the heated product. In multi-stream movement, product coils 9 and 13 are divided into sections, the number of which is equal to the number of streams. FIG. 1, 2 and 6 show a variant of a six-flow tubular heater. The product coil 13 includes two sections, the first of which consists of flat panels formed by pipes-pins 10, adjacent to the upper 3 and lower 4 walls, and the second - of pipes adjacent to the side walls 2 and the rear wall 6 of the heat exchange chamber 1 Each of the two rows of stud pipes 10 of the inner product coil 9 also includes two sections, which consist of two adjacent horizontally and vertically aligned tubular panels connected in series along the heated product.

Tubular heater works as follows.

The heated product enters through the inlets 20 into the product coils 9 and 13, where it moves in the threaded pipes 10, which are connected in series with the collector pipes 16 and disks 17 located in them. Fuel and combustion air are fed into the burner 7, where they mix with each other. The fuel-air mixture exits at high speed from the nozzle of the burner device 7 into the space of the heat exchange chamber 1, bounded by sheets 14 of refractory material, forming a gas channel 15. At the outlet of the burner device 7, the fuel is ignited by means of an ignition device (not shown). The burning gas jet expands and fills the entire section of the gas channel 15. At the same time, the process of suction of cooled combustion products from the surrounding space of the heat exchange chamber 1 to the root of the expanding jet, due to the ejection effect of the high-speed jet, is taking place. The suction leads to a decrease in the temperature of the combustion products flowing around in the longitudinal direction of the pipe-studs 10 of the row of the internal product coil 9, located in the gas channel 15. In this case, the heat transfer from the combustion products through the wall of these pipes - studs to the heated product is not accompanied by active coke formation on the inner surface these pipes. The elimination of coke formation is also facilitated by swirling the flow of the heated product in the pipes using inserted twisted strips 19. At the same time, due to the intensification of heat transfer of the swirling flow, the temperature of the pipe wall decreases and, as a consequence, the rate of formation of the solid phase in the wall layer of the heated product decreases. When leaving the gas channel 15, the combustion products flow onto the pipes of the product coil 13, adjacent to the rear wall 6 of the heating chamber 1 and protecting the wall from the thermal effects of hot gases, pass through the gap 12 between the internal product coil 9 and the rear wall 6, and further , having turned, move to the front wall 5 in the space between the walls 14 of the gas channel 15 and the walls 2, 3 and 4 of the heat exchange chamber 1. In this movement, the combustion products flow in the longitudinal direction around the pipes of the product coils 9 and 13 and transfer heat to the walls of the pipes mainly convective mechanism. At the front wall 5, the flow of cooled combustion products bifurcates and is partially directed into the flue duct 8, and its other part through the gap 11 between the internal product coil 9 and the front wall 5 enters the root of the gas jet created by the burner 7. Thus, in the heat exchange chamber 1, an organized and regulated recirculation of combustion products is carried out, which makes it possible to intensify the heat transfer process and provides a "soft" temperature regime for heating the product. When the flow of combustion products flows around the pipes-hairpins 10 of the product coils 9 and 13, the discrete roughness elements 18 turbulize the flow, which intensifies the heat transfer of the flow and the heat transfer process as a whole.

The product heated in the product coils 9 and 13 is removed from the tubular heater through the outlets 21, which, like the inlets 20, have threaded flanges 23 at their ends for connection with the product transport lines. The use of threaded, rather than welded, flanges makes it relatively easy to assemble and disassemble the tubular heater. This is also facilitated by the use of stuffing box seals 22 at the points of passage of inlets 20 and outlets 21 through the front 5 and rear 6 walls of the heat exchange chamber 1. When the operation of the tubular heater stops, the product coils 9 and 13 are easily emptied by self-draining if necessary.

An example of the implementation of the proposed device. A tubular heater with a thermal power of 5 MW for heating oil emulsion from 10 ° C to 90 ° C has a cross-sectional area of the heat exchange chamber of 2.2 × 2.2 m and a length of 6.2 m. Product coils are made of pipes with a diameter of 159 × 5 mm. The fuel is petroleum gas. With equal amounts of fuel combustion products discharged for recirculation into the gas channel and into the flue gas duct for removal from the tubular heater, the maximum temperature of the heating gas flow is 1000 ° C. The temperature of gases leaving the tubular heater is 250 ° C, and its thermal efficiency is 88%. The specific volumetric index, defined as the ratio of the thermal power to the volume of the heater, is 0.17 MW / m. This indicator is significantly higher than that of similar known direct heating heaters. For example, for a tubular direct-fired heater PTB-10-160 [4] with a thermal power of 10 MW, it is 0.12 MW / m.

The advantages of the proposed tubular heater are:

- constructive simplicity;

- manufacturability and repair;

- low metal consumption and high compactness due to the intensification of heat exchange of the flow of heating gases and the use of collector-type product coils;

- "soft" temperature mode for heating products;

- increased reliability of the heater;

- high thermal efficiency.

Information sources

1. USSR author's certificate No. 1561612, M. class. F22B 7/00 dated 10/05/1987.

2. USSR author's certificate No. 1668827, M. class. F24P 1/14 dated 05/10/1989.

3. Skoblo A.I., Tregubova I.A., Molokanov Yu.K. Processes and apparatus of the oil refining and petrochemical industries. - 2nd ed., Rev. and add. M .: Chemistry, 1982. p. 450-458.

4. Medvedev V.F. Collection and preparation of oil and water. M .: Nedra, 1986. p. 181.

5. RF patent No. 20829225. M. class. F27B 5/00 dated 06/27/1997.

Claims (5)

1. A tubular heater containing a heat exchange chamber, a burner device made of straight pipes and a product coil located in the heat exchange chamber adjacent to the walls of the heat exchange chamber and an internal product coil located symmetrically inside it, tubular inlets and outlets of product coils, characterized in that the heat exchange chamber is made in the form of a rectangular parallelepiped with flat side, top, bottom, end front and rear walls, the burner device is located on the front wall, to which the flue duct adjoins, the internal product coil is double-row and is placed with gaps relative to the front and rear walls of the heat exchange chamber , sheets of heat-resistant material are placed between the rows of pipes of the inner product coil, forming the walls of the gas channel. 2. Tubular heater according to claim 1, characterized in that the product coil adjacent to the walls of the heat exchange chamber and the internal product coil are made of hairpin pipes, the open ends of which are interconnected by collector pipes with disk baffles in diametrical sections. 3. Tubular heater according to claim 1, characterized in that there are discrete roughness elements on the outer surface of the hairpin pipes of the product coils. 4. Tubular heater according to claim 1, characterized in that twisted ribbons are placed inside the stud pipes of the row of the internal product coil located in the gas channel. 5. Tubular heater according to claim 1, characterized in that the tubular inlets and outlets of the product coils have gland seals with front and rear walls of the heat exchange chamber and threaded flanges at the ends.

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