RU142878U1 - PIPE HEATING FURNACE - Google Patents

Abstract

1. A furnace for heating pipes, containing a working chamber with nozzles for supplying heated gases and a chimney located in the smoke channel, characterized in that it is equipped with an overhead conveyor for transporting pipes, a tool installed on the ends of the pipes and made to allow rotation of the pipe when moving the suspension conveyor, side and bottom duct, while the side nozzles for supplying heated gases are evenly installed in the side duct from one of the end faces of the working chamber of the furnace to direct the flow heated gases to the inner surface of the pipe and configured to control the angle of attack of the heated gas stream to ensure turbulent movement of the heated gas stream into them, the lower duct is made with louvres installed at the base of the furnace chamber to direct the heated gas flow to the outer surface of the pipe and made the ability to control the angle of attack of the heated gas stream to ensure turbulent movement of the heated gas stream, and the chimney to create the necessary draft full with a cross-sectional area greater than the sum of the cross-sectional areas of the lateral and lower ducts. 2. The furnace according to claim 1, characterized in that a deflector is installed at the outlet of the chimney to create additional traction.

Description

The utility model relates to the field of mechanical engineering, in particular to heating devices and can be used to heat pipes of steel and alloys in various technological processes.

The most common methods of heating furnaces for processing metal lengthy products are convective heating.

Known furnace for heating pipes, containing a housing covering the radiation and convective parts, burners placed in the radiation part, made in the form of a truncated cone, and a smoke exhauster with a channel equipped with a gate (link: http://ru-patent.info/20/ 40-44 / 2040749.html).

A disadvantage of the known device is its low efficiency due to the deteriorated heat transfer conditions in the convective part of the furnace.

The closest in technical essence to the proposed device is the "Method of heating a two-chamber furnace and a furnace for heating billets" (RF patent 2022035, application No. 5038258/02 of 02.25.1992, Bi No. 16, 1994, C21D 9/00). The billet heating furnace contains two working chambers in one unit. They are separated by a wall, equipped with vault burners and smoke channels. A smoke channel is made in the wall separating the chamber, located at the level of the hearth at the front end. The method is as follows. In chambers 1 and 2, they burn the gas burners and supply the air-fuel mixture (with an air flow coefficient α = 0.5-0.6, which protects the heated workpieces from oxidation and decarburization), heating both chambers of the furnace to a temperature of 750 ° C. After heating both chambers of the furnace, its heating is carried out by the proposed method, i.e. alternately burning the air-fuel mixture and afterburning it with secondary air. In one of the chambers, for example, the first chamber, the burners continue to operate, fed by the said mixture, closing the control valves of the fuel-air mixture supply system. The gate of the first chamber is closed, which directs the decomposition products of the mixture from the first chamber through the smoke channel into the second chamber for recovery. When the valve is closed, the valve of the afterburning system for incomplete combustion products opens to supply secondary air to the second chamber with the flow rate necessary for afterburning the products of incomplete combustion. The secondary air supplied with the indicated flow rate to the second chamber burns out products of incomplete combustion, which ensures an atmosphere that protects the metal from oxidation and decarburization, and the gases go through the flue channel with an open gate into the boron system of the workshop.

The disadvantages of this device include:

- uneven heating over the entire area of the heated product, due to the laminar motion of the heated gas stream, which reduces the quality of heating;

- low productivity due to the long wait for the product to reach the set temperature;

- inefficient use of the allocated stream of heated air, since heat transfer during heating of the product occurs during the laminar motion of the heated air flows, which also reduces the heating time, and overall productivity;

The proposed utility model is aimed at eliminating the disadvantages inherent in analogues and prototype.

The solved problem of the utility model is to improve the quality, speed of heating of the product and reduce energy consumption for heating.

The technical result from the use of the claimed utility model is the creation of a highly energy-efficient furnace with high-quality, fast heating over the entire area of the product, using the allocated stream of heated gas from an autonomous source.

The technical result is achieved by the fact that an overhead conveyor for transporting pipes, special accessories made with the possibility of rotation and installed on the ends of the pipes for movement along the overhead conveyor, a side and lower duct, side nozzles that are evenly installed on one of the end sides of the furnace chamber for directing the flow of heated gases to the inner surface of the pipes and are configured to I is the angle of attack of the heated gas flow to the inner surface of them, providing heat transfer during turbulent movement of the heated gas flow, and the lower louvres are installed at the base of the furnace chamber to direct the heated gas flow to the outer surface of the pipes and are configured to control the angle of attack of the heated gas flow to the outer their surface, providing heat exchange with turbulent movement of the heated gas stream, and to create the necessary traction, the cross-sectional area of the chimney is larger the sum of the cross-sectional areas of the lateral and lower ducts.

To create additional traction, a deflector is installed at the outlet of the chimney.

The novelty of this invention is the design of the furnace, which allows you to direct the flow of heated gases, both outside and on the inner surface of the product, while adjusting the angle of attack of the heated gas stream.

The technical essence of the method is illustrated in the drawing.

The device of the furnace for heating pipes is shown in FIG. 1, where:

1 - working chamber of the furnace;

2 - lateral duct;

3 - lower duct;

4 - side nozzles;

5 - lower louvres;

6 - steel pipe;

7 - chimney;

8 - special equipment;

9 - overhead conveyor;

10 - deflector

11 - gateway

The chamber of the furnace 1 is a room for heating the product (pipe 6).

The lateral duct 2 directs the heated gas stream of the gas turbine engine into the chamber of the furnace 1 through the lateral nozzle 4.

The lower duct 3 directs the heated gas stream of the gas turbine engine into the furnace chamber 1 through the lower louvre grilles 5.

A lateral nozzle 4 is mounted on one of the end sides of the chamber of the furnace 1 and directs the flow of heated gases to the inner surface of the pipe 6 and adjusts the angle of attack of the flow of heated gases to the inner surface of the pipe 6.

The lower louvre grilles 5 are installed at the base of the chamber of the furnace 1 and direct the flow of heated gases to the outer surface of the pipe 6 and adjusts the angle of attack of the flow of heated gases to the outer surface of the pipe 6.

Steel pipe 6 is a heated product.

The chimney 7 directs the flow of gases used to heat the product (pipe 6) into the smoke channel (not shown in FIG.).

Special equipment 8 is designed to betray the rotational movement of the pipe 6 and to save the outer surface of the pipe 6 from external contacts.

The overhead conveyor 9 is designed to transport the pipe 6.

The deflector 10 is designed to create additional (artificial) traction in the chamber of the furnace 1.

Gateway 11 is designed to open / close the entrance to the chamber of the furnace 1.

The operating mode of the furnace for heating pipes:

The steel pipe 6 is transported into the furnace chamber 1 on the overhead conveyor 9, using special equipment 8 installed on both ends of the steel pipe 6.

After the steel pipe 6 has been installed in the chamber of the furnace 6, the steel pipe 6 is subjected to rotation, using special equipment 8, betraying the steel pipe 6 rotational movement.

Then, through the lateral duct 2, the lateral nozzle 4, and the lower duct 3, the lower louvre grilles 5, the heated gas stream of the gas turbine engine is sent to the furnace chamber 1, where the steel pipe 6 is already installed and rotates.

The lateral nozzle 4 directs the heated gas stream from the lateral duct 2 to the inner surface of the steel pipe 6. At the same time, the angle of attack of the heated gas stream is adjusted to create a turbulent movement of the heated gas stream in the inner part of the steel pipe 6.

The lower louvre grilles 5 direct the flow of heated gases from the lower duct 3 to the outer surface of the steel pipe 6. At the same time, adjust the angle of attack of the heated gas stream to create a turbulent movement of the heated gas flow on the outer surface of the steel pipe 6.

The heat exchange carried out during the turbulent movement of the heated gas stream, using the side nozzle 4 and the louvre grilles 5, provides:

1. Reducing the heating time of the steel pipe 6, since the heat transfer coefficient in the turbulent mode is higher than in the laminar one;

2. High-quality heating of the steel pipe 6, which makes the heating more uniform, since there is a constant mixing of gases, which positively affects the temperature of the medium (ie, the temperature is the same throughout the volume of the furnace chamber 1).

The direction of the heated gas flow directly to the product (steel pipe 6), using the side nozzle 4, lower louvre grilles 5, provides:

1. Effective use of the heated gas stream, since the bulk of the heated gas will be used directly to heat the steel pipe 6, and not the furnace chamber 1;

2. Reduces the heating time of the steel pipe 6, since there is no need to wait for the heating of the furnace chamber 1 to a predetermined temperature.

During heating of the steel pipe 6, the flow of gases used to heat the product is utilized through the chimney 7 into the chimney, using a deflector 10.

To create the natural necessary traction in the chamber of the furnace 1, the cross-sectional area of the chimney must be greater than the sum of the cross-sectional areas of the side duct 2 and the bottom duct 3.

To create additional (artificial) traction in the chamber of the furnace 1 after the chimney 7, a deflector 10 is installed, which creates additional traction in the chamber of the furnace 1.

As an example, we took the technological process of the method of heating the steel pipe 6 before coating, where, one of the stages of the technological process involves heating the steel pipe 6 in the furnace to a temperature of 390-420 ° C and holding for about an hour.

This temperature range allows you to remove from the surface of the product (steel pipe 6) environment, reducing the adhesive strength, in particular oil inclusions. Also, at a given temperature range, the material of the product does not undergo structural changes.

Device operation:

Before starting work, special equipment 8, provided by this device, is installed on the ends of the steel pipe, betraying the steel pipe 6 to rotate during their heating.

In operating mode, the heated gas flows of the gas turbine engine are directed into the furnace chamber 1 through the lateral duct 2 and the lower duct 3, the lateral nozzle 4 and the lower louvre grilles 5. The lateral nozzle 4 controls the flow direction of the heated gases entering through the lateral duct 2 and adjusts the angle of attack the flow of heated gases to the inner surface of the steel pipe 6. The lower louvre grilles 5 control the flow of heated gases entering through the lower duct 5 and adjusts the angle of attack of the flow of heated gases to the outside the surface of the steel pipe 6.

During heating of the steel pipe 6, the stream of heated gases from an autonomous source, for example, a gas turbine engine, coming through the side nozzle 4 into the chamber of the furnace 1, is directed to the inner surface of the steel pipe 6, receiving a turbulent movement of the stream of heated gases in a spiral. This reduces the heating time of the steel pipe 6, helping to increase the productivity of the furnace and the efficient use of heat from the stream of heated gases.

During heating, the steel pipe 6 is betrayed by rotational movement with the help of special equipment 8 mounted on the ends of the steel pipe 6, which excludes the contact of the outer surface of the steel pipe 6 with other surfaces, which makes the heating of the steel pipe 6 better.

After the steel pipe 6 has been heated to a predetermined temperature, it is maintained at a predetermined temperature in the furnace chamber 1 for about an hour (“exposure”) to remove the adhesion strength from the surfaces of oil inclusions and other substances.

Calculation of pipe heating time

Heating metal in furnaces is a very important operation. It is desirable to heat the metal quickly, because in this case, its waste decreases, the furnace productivity increases and the specific fuel consumption for heating decreases. From these considerations, it is advisable to choose the optimal temperature regime of the furnace, which provides, on the one hand, fast heating of the metal, and on the other hand, which does not create excessive mechanical stresses in the heated metal, which can lead to cracking.

The duration of heating the metal to a predetermined temperature is an important parameter that determines the productivity of the furnace and its overall dimensions.

Given:

N (number of pipes) = 10 pcs.

Material - Steel 10; Steel 20

m _about (total weight) ≈8880 kg / GOST 20295-85 /

l (pipe length) = 12 m

C (pipe circumference) = 1,0205 m

d _nar. (outer diameter) = 0.325 m

V (volume of the first pipe) = 0.12246 m ³

S (pipe wall thickness) = 10 mm = 0.01 m

(average specific heat) = 512 J / (kg ° C) / at ; at /

(average specific heat) = 497 J / (kg ° C) / at ; at / ¹

ρ (density of the steel pipe) = 7800 kg / m ³

α is the heat transfer coefficient of convection, W / (m ² ∗ ° C) / for turbulent movement in pipes or between them is in the range - 12-115 W / (m ² ∗ ° C) /;

The calculation of metal heating begins with the determination of the Bi criterion.

The Bi criterion draws the line between “thin” and “massive” bodies.

Bi≤0.25 - the body is "thin"

Bi> 0.5 - the body is "massive"

Bi = α ∗ S / λ

where "S is the heated wall thickness of the pipe, m

S = 0.01 m

λ is the average coefficient of thermal conductivity, W / (m ∗ ° C)

λ ₂₀ = 51.9 W / (m ∗ ° C)

λ ₄₀₀ = 45 W / (m ∗ ° C)

λ _cp = (λ ₂₀ + λ ₄₀₀ ) / 2 = (51.9 + 45) / 2 = 48.45 W / (m ∗ ° C)

α is the heat transfer coefficient of convection, W / (m ² ∗ ° C) / for turbulent movement in pipes or between them is in the range - 12-115 W / (m ² ∗ ° C) /; take a value closer to the maximum ≈100 W / (m ² ∗ ° C).

Bi = 100 ∗ 0.01 / 48.45 = 0.02 - the body is “thin”

Calculation of heating of "thin" bodies in the furnace chamber 1:

When calculating the time of thin-walled pipes, use the formula -

where S is the heated wall thickness of the pipe, m;

d _nar. - outer diameter of the pipe, m;

K ′ is a coefficient that takes into account the method of laying pipes and depends on the relative distance between the centers of the pipes m / d _bunk. / where m is the distance between the centers of the pipes = 0.475 m, for one-sided heating at m / d _nar . constituting 1.0; 1.5; 2.0, the coefficient K ′ is 0.5, respectively; 0.8; 1.0 /;

m / d _nar = 0.475 / 0.325≈1.5⇒K ′ = 0.8

α is the heat transfer coefficient of convection, W / (m ² ∗ ° C) / for turbulent movement in pipes or between them is in the range - 12-115 W / (m ² ∗ ° C) /; take the value closer to the maximum - 100 W / (m ² ∗ ° C).

Since heating is performed on the outer and inner surfaces of the steel pipe, the time will decrease by about 1.5-2.0 times (average 1.75).

τ _fact. ≈τ / 1.75≈17 min

A table of heating times for the most commonly used steel pipe. No. Diameter
pipes
mm Pipe wall thickness, mm Heating time to 420 ° C, min (conventional oven) Heating time to 420 ° C, min (claimed for a utility model furnace for heating pipes) one 57 3,5 ≈14 ≈8.0 2 76 four ≈15 ≈8.6 3 89 5 ≈17.5 ≈10.0 four 114 6 ≈20 ≈11.4 5 159 7 ≈22 ≈12.8 6 219 8 ≈25 ≈14.2 7 273 9 ≈28 ≈15.6 8 325 10 ≈30 ≈17

The table shows that the performance of the inventive furnace for heating pipes will be higher by 45-75% relative to known analogues.

The advantages of the proposed utility model in comparison with well-known analogues.

The design of the proposed furnace for heating pipes in comparison with analogues:

1. Improves the quality of heating of the outer and inner surfaces of the steel pipe, due to:

1.1. Traditions of rotational movement of a steel pipe with special accessories;

1.2. Direction of heated gas flow to the outer and inner surfaces of the steel pipe using the side duct, side nozzle and lower louvres;

1.3. Exclusions of contact of the outer surface of the steel pipe with other surfaces with the help of special accessories that betray rotational movement;

2. Reduces the heating time of the steel pipe, due to:

2.1. Traditions of rotational movement of a steel pipe with special accessories;

2.2. Direction of heated gas flow to the outer and inner surfaces of the steel pipe using the side duct, side nozzle and lower louvres;

2.3. The turbulent movement of the heated gas stream in the furnace chamber, which generally increases the productivity of the furnace.

3. Increases the heating efficiency of the steel pipe by increasing the area of contact of the steel pipe with the heated gas stream, which is achieved by directing the lower louvre grilles of the heated gas stream directly to the outside and the lateral nozzle directing the heated gas stream to the inner surface of the steel pipe;

4. Increases efficiency by reducing the heating time of the steel pipe by directing the flow of heated gases from a stand-alone gas turbine engine, which eliminates the need to wait for the furnace chamber to reach a predetermined temperature.

All these structural components make it possible to obtain a highly energy-efficient inventive furnace for heating pipes.

Claims (2)

1. A furnace for heating pipes, containing a working chamber with nozzles for supplying heated gases and a chimney located in the smoke channel, characterized in that it is equipped with an overhead conveyor for transporting pipes, a tool installed on the ends of the pipes and made to allow rotation of the pipe when moving the suspension conveyor, side and bottom duct, while the side nozzles for supplying heated gases are evenly installed in the side duct from one of the end faces of the working chamber of the furnace to direct the flow heated gases to the inner surface of the pipe and configured to control the angle of attack of the heated gas stream to ensure turbulent movement of the heated gas stream into them, the lower duct is made with louvres installed at the base of the furnace chamber to direct the heated gas flow to the outer surface of the pipe and made the ability to control the angle of attack of the heated gas stream to ensure turbulent movement of the heated gas stream, and the chimney to create the necessary draft full with a cross-sectional area greater than the sum of the cross-sectional areas of the lateral and lower ducts. 2. The furnace according to claim 1, characterized in that a deflector is installed at the outlet of the chimney to create additional traction.