EP3252412B1 - Zinc coating furnace - Google Patents

Description

The invention relates to a method for operating a galvanizing furnace.

Such galvanizing furnaces are used in hot-dip galvanizing plants and are used to heat liquid zinc. The galvanizing furnace generally comprises a furnace housing with a galvanizing trough arranged therein. The furnace housing typically has a rectangular cross-section. The furnace housing has two opposite longitudinal side walls and two opposite front side walls, the longitudinal side walls being larger than the front side walls.

Burners, in particular gas burners, are typically used to heat the liquid zinc in the galvanizing tub. These burners heat the interior of the furnace between the walls of the furnace housing and the galvanizing tank through a flame tube. Electrically heated galvanizing furnaces are also known.

A widely used burner system for such galvanizing furnaces uses gas burners in the form of high-speed burners. These high speed burners are provided at diagonally opposite corners of the furnace body. The high-speed burners are each mounted in a front side wall of the furnace housing in such a way that the flame generated by the respective high-speed burner is guided into the space between a longitudinal side wall of the furnace housing and a wall of the galvanizing tub opposite this longitudinal side wall is. Depending on the size and capacity of the galvanizing furnace, several high-speed burners can be mounted one above the other in the diagonally opposite corners of the furnace housing.

To protect against the high flame temperatures of the high-speed burner, the corner areas of the galvanizing tub, which are directly opposite the flame outlets of the high-speed burners, are covered on their outside with flame guide plates and thus protected.

Wear effects occur during the operation of such galvanizing furnaces, which particularly affect the galvanizing tub. It has been shown that the wall thickness of the galvanizing tub is reduced in the course of operation of the galvanizing furnace. As wear progresses, the wall thickness of the galvanizing tub is reduced so much that the entire galvanizing tub has to be replaced, which requires considerable structural effort. In particular, it is disadvantageous that considerable downtimes of the galvanizing furnace are associated with this, that is to say the availability of the galvanizing furnace is undesirably low.

The US 2017 229 A relates to a galvanizing plant with a galvanizing tank. The contents of the galvanizing tank are heated by means of four ovens, one oven being provided in each corner of the rectangular galvanizing tank.

The U.S. 2,414,860 A relates to a galvanizing plant with a galvanizing tank that is laterally heated by means of burner units.

The invention is based on the object of providing a method for operating a galvanizing furnace which enables the availability of the galvanizing furnace to be increased with little structural effort.

The features of the independent claim are provided to solve this problem. Advantageous embodiments and expedient developments of the invention are described in the dependent claim 2.

The invention relates to a method for operating a galvanizing furnace with a galvanizing tub and a furnace housing which surrounds the galvanizing tub and which has a rectangular cross section. The furnace housing has two opposite longitudinal side walls and two opposite front side walls and with burners for heating liquid zinc in the galvanizing tub. At least one first receptacle for a burner is provided in each of the regions of two diagonally opposite corners of the furnace housing. A second receptacle for a burner is provided in each of the two other diagonally opposite corners of the furnace housing. Optionally, burners are arranged either in the first receptacles or in the second receptacles. Flames generated by the burners are guided in the area between a longitudinal side wall of the furnace housing and the opposite wall of the galvanizing tub. In the area of the flame outlet, the current wall thickness of the galvanizing tub is recorded for at least one burner. The burner is changed when the current wall thickness falls below a specified limit value.

With the method according to the invention, the availability of the galvanizing furnace according to the invention can be increased in a surprisingly simple manner.

The invention is based on the knowledge that the wear on the galvanizing tub is mainly caused by the high temperatures generated by the burners. It was found that in the area of the flame outlet on the respective burner, or, if a flame guide plate is arranged on the galvanizing tank, directly behind the flame outlet, the greatest wear of the galvanizing tank occurs, i.e. in this area the reduction in the wall thickness of the galvanizing tank is due to the Highest temperatures are highest, whereas with increasing distance to the respective burner, the wear, i.e. the reduction in the wall thickness of the galvanizing tub, continuously decreases.

In the galvanizing furnace which is used in the method according to the invention, this fact is taken into account in that first receptacles for the burners are not only provided in two diagonally opposite corner areas of the furnace housing. Rather, receptacles for the burners are also provided on the two further diagonally opposite corner regions, these second receptacles preferably being identical to the first receptacles.

In this way, the burners, which are preferably designed as high-speed burners, can be used either in the first receptacles or in the second receptacles.

According to the invention, the galvanizing furnace is then operated in such a way that the galvanizing furnace is initially operated with the burners in the first receptacles for a predetermined period of time. During this phase, in the area of the flame exits from the burner, that is to say in the area of the first receptacles, there is increased wear and tear on the galvanizing tub, that is, an increased reduction in wall thickness. This wear decreases continuously along the respective side wall of the galvanizing tub in the direction of the second receptacles.

After this first operating phase has expired, the burners are exchanged so that they are now stored in the second receptacles in the furnace housing. This exchange can be carried out quickly and easily, i.e. without long downtimes of the galvanizing furnace.

Due to the exchange of the burners, increased wear and tear occurs in the second phase in the areas of the galvanizing pan that adjoin the flame exit areas of the burners in the second receptacles. This means that the spatial wear profile in this second phase is complementary to the spatial wear profile in the first phase.

However, this means that by replacing the burners, overall uniform wear is obtained over the entire side walls of the galvanizing tub.

This considerably increases the service life of the galvanizing tub and thus the availability of the galvanizing furnace compared to conventional operation of the galvanizing furnace. In a conventional operation, the burners would only ever be stored in the first receptacles. This would lead to a spatially narrowly limited, strong reduction in the wall thickness of the galvanizing tub at certain points in the flame exit areas assigned to the first recordings, so that it must be replaced in a relatively short time.

By changing the installation locations of the burners according to the invention, the service life of the galvanizing tub can be increased significantly, so that the intervals in which the galvanizing tub has to be replaced by a new one can be considerably increased.

In principle, the time intervals in which the galvanizing furnace is operated with the burners stored in the first receptacles or in the second receptacles can be predetermined empirically.

According to a particularly advantageous embodiment of the invention, means are provided for location-dependent detection of the wear on the walls of the galvanizing tub. Depending on the determined wear values, the torches can be changed from the first receptacles to the second receptacles or vice versa.

In this case, the time intervals in which the galvanizing furnace is operated with the burners stored in the first or in the second receptacles can be specified as a function of the measured wear values and thus optimized.

The wall thickness of the galvanizing tub is particularly advantageously recorded as a measure of the wear on the walls.

In principle, the wall thicknesses over the entire side walls of the galvanizing tub along which the flames of the burners are guided can be measured using a corresponding number of measuring points.

The current wall thickness of the galvanizing tub is expediently recorded in the area of the flame outlet of at least one burner. The burner is changed when the current wall thickness falls below a specified limit value.

This measures the wall thickness of the galvanizing tub in the particularly critical areas. Since the areas of greatest wear limit the service life of the galvanizing pan, such a measurement is sufficient.

According to a particularly advantageous embodiment of the invention, an ultrasonic measuring head is provided for measuring the wall thickness of the galvanizing tub.

The wall thickness of the galvanizing tub can be measured with the ultrasonic measuring head while the galvanizing furnace is in operation.

To carry out these measurements, closable control openings are advantageously provided in the longitudinal side walls of the furnace housing. To measure the wall thickness, the ultrasonic measuring head is guided through a control opening to the outside of a wall of the galvanizing tub.

Using a suitable grid of control openings, the location-dependent course of the reduction in the wall thickness of the galvanizing tub can be precisely recorded.

The measurements can easily be carried out by just one person. For this, the respective person only needs to open the closure of the desired control opening in order to then guide the ultrasonic measuring head through the control opening into the furnace interior and then against the wall of the galvanizing tub.

The ultrasonic measuring head is advantageously designed as a so-called hot head, which is designed for use at high temperatures, such as those in the interior of the furnace exist, is suitable. Furthermore, the ultrasonic measuring head advantageously has a magnet with which the ultrasonic measuring head can adhere to the wall of the galvanizing tub. This guarantees an exact and reproducible measurement of the wall thickness with the ultrasonic measuring head.

According to an expedient embodiment, the receptacles for the burners are each arranged in a front side wall.

This ensures that the flames of the burners are guided in a simple manner in the space between a longitudinal side wall of the furnace housing and a wall of the galvanizing tub.

According to an advantageous development, a plurality of receptacles, in each of which a burner can be arranged, are provided in each corner area of the furnace housing.

This means that several burners can be installed in each corner area, which means that the performance of the galvanizing furnace, i.e. the throughput of liquid zinc per unit of time, can be increased.

All recordings are expediently designed identically.

This means that burners of the same design can be installed in any receptacles in the furnace housing.

It is also advantageous that the receptacles in which no burner is arranged are tightly closed with closure means.

This ensures that the furnace housing forms a unit that is encapsulated from the outside atmosphere.

According to an advantageous embodiment, the galvanizing tub has an essentially rectangular shape that is adapted to the cross section of the furnace housing Cross section on. In each corner area of the galvanizing tub, a flame guide plate is attached to the outer wall of the galvanizing tub.

Since the burners can optionally be stored in the first or second receptacles and can thus be arranged in every corner area of the furnace housing, it is accordingly useful to protect every corner area against flames from burners with flame guide plates.

Adapted to this, control openings are provided in the longitudinal side walls of the furnace housing in such a way that the ultrasonic measuring head guided through such a control opening is guided directly against a flame guide plate against a wall of the galvanizing tub.

This allows the ultrasonic measuring head to be guided to the wall of the galvanizing tub through the inspection opening immediately behind the flame guide plates, so that a measurement is possible at the most heavily loaded points of the galvanizing tub.

According to an advantageous development, first temperature sensors are integrated in rams which support a wall of the galvanizing tub against a longitudinal side wall of the furnace housing.

These temperature sensors can therefore be used to check whether the stamps are exposed to excessive temperature loads.

Second temperature sensors for measuring the temperature in the interior of the furnace housing are also advantageously provided.

The outputs of the burners are expediently set as a function of the measured values recorded with the first or second temperature sensors.

In this way, damage to components in the interior of the furnace housing can be avoided.

Figur 1:

Längsschnittdarstellung eines Ausführungsbeispiels des erfindungsgemäßen Verzinkungsofens.

Figur 2:

Querschnittdarstellung des Verzinkungsofens gemäß Figur 1.

The invention is explained below with reference to the drawings. Show it:

Figure 1:

Longitudinal sectional view of an embodiment of the galvanizing furnace according to the invention.

Figure 2:

Cross-sectional view of the galvanizing furnace according to Figure 1 .

The Figures 1 and 2 show an embodiment of the galvanizing furnace 1. The galvanizing furnace 1 has a furnace housing 2 with a base 3 having a rectangular contour and two longitudinal side walls 4 and end side walls 5 protruding vertically from the base 3, the two end side walls 5 being opposite and the longitudinal side walls 4 are arranged opposite one another. The furnace housing 2 thus has a rectangular cross section that is constant over its entire height.

In the interior of the furnace housing 2 there is a galvanizing tub 6 which is used to hold liquid zinc to be heated. The galvanizing tub 6 has a substantially rectangular cross section adapted to the cross section of the furnace housing 2, so that the side walls 7 of the galvanizing tub 6 are arranged at a constant distance from the longitudinal side walls 4 and the front side walls 5 of the furnace housing 2. The galvanizing tub 6 has a flat tub bottom 8 which rests on the bottom 3 of the furnace housing 2.

The upper edge of the galvanizing tub 6 is received in an edge segment 9 of the furnace housing 2 running on the upper sides of the longitudinal side walls 4 and the end side walls 5. The open top of the galvanizing tub 6 can be closed with a cover, not shown.

The galvanizing tub 6 is supported with punches 10 against the insides of the longitudinal side walls 4 of the furnace housing 2. The stamp 10 form thus a clamping frame for fixing the position of the galvanizing tub 6 in the furnace housing 2.

A flue gas outlet, which is designed in the form of a flange 11 with an exhaust flap 11a, opens out at an end-side side wall 5. The room pressure of the furnace atmosphere is regulated via the exhaust flap 11a in order to obtain an effective transition of the temperature to the galvanizing tub 6.

First temperature sensors 12 are provided in or on the stamps 10, with which the temperatures in the stamps 10 themselves can be measured. Overheating of the stamp 10 can thus be controlled.

Furthermore, in the area of the inner sides of the side walls 7, there are second temperature sensors 13 with which the temperature in the interior of the furnace housing 2 is measured.

The first and second temperature sensors 12, 13 are advantageously formed by thermocouples. The heating power of the galvanizing furnace 1 and thus the temperature in the interior of the furnace housing 2 can be controlled as a function of the measured values generated by the temperature sensors 12, 13.

The interior of the furnace housing 2 is heated by means of burners. The burners are designed as gas burners, in the present case as high-speed burners 14.

For mounting the high-speed burners 14, according to the invention, first receptacles 15 are incorporated into the respective end-face side wall 5 in two diagonally opposite corner regions of the furnace housing 2. Furthermore, in the two further diagonally opposite corner regions of the furnace housing 2, second receptacles 16 are incorporated into the respective end-face side wall 5.

The first and second receptacles 15, 16 are designed identically and are adapted to the size of the high-speed burners 14, so that the high-speed burners 14 can be optionally installed in first or second receptacles 15, 16.

Figure 2 shows a receptacle 15, 16 in each corner area. In general, several identical first receptacles 15 or second receptacles 16 can be arranged at a distance one above the other in each corner area, so that a high-speed burner 14 can be stored in each of these receptacles 15, 16 of a corner area.

According to the invention, the high-speed burners 14 are inserted either only into the first receptacles 15 or into the second receptacles 16 in order to heat the interior of the furnace housing 2.

Since the installation of high-speed burners 14 is possible in each corner area of the furnace housing 2, such as those Figures 1 and 2 show that the outer walls of the galvanizing tub 6 are clad with flame guide plates 17 at all corner areas in order to protect the walls of the galvanizing tub 6 against the flames occurring at the high-speed burners 14. The identically designed flame guide plates 17 extend over the entire height of the galvanizing tub 6.

In the in Figure 2 In the configuration shown, the high-speed burners 14 are arranged in the first receptacles 15. The second receptacles 16, in which there are no high-speed burners 14, are tightly closed with closure means 18 so that the furnace walls are tightly encapsulated. The closure means 18 can each be formed from furnace insulation material and a cover plate.

If the galvanizing furnace 1 with the burner configuration according to Figure 2 operated, the flames of the high-speed burner 14 are in each case in the interstices of a longitudinal side wall 4 of the furnace housing 2 and one wall of the galvanizing tub 6, whereby the liquid zinc in the tub is heated.

According to the type of installation of the high-speed burner 14 in the first receptacles 15, the flame temperature in the exit area of the high-speed burner 14 (in Figure 2 labeled A) and increases to the area at the other end of the furnace housing 2 (in Figure 2 denoted by B) continuously from.

Accordingly, during operation of the galvanizing furnace 1 with the burner configuration shown in FIG Figure 2 The greatest wear of the galvanizing tub 6 occurs in area A, the wear being a reduction in the wall thickness of the galvanizing tub 6. The reduction in wall thickness then decreases continuously from area A to area B.

The wear-related reduction in the wall thickness is recorded by measurement technology during operation of the galvanizing furnace 1, preferably within regular time intervals.

For this purpose, identical arrangements of control openings 19 are incorporated into the longitudinal side walls 4 of the furnace housing 2, which can be closed with covers not shown separately.

To carry out a contactless measurement of the wall thickness of the galvanizing tub 6 during operation of the galvanizing furnace 1, ultrasonic measuring heads (not shown) are provided. To carry out such a measurement, the cover is removed from a control opening 19 and then the ultrasound measuring head is guided through the control opening 19 to the wall of the galvanizing tub 6, where the ultrasound measuring head adheres to the wall of the galvanizing tub 6 in a defined measuring position, preferably by means of an integrated magnet.

How out Figure 1 As can be seen, four rows of inspection openings 19, each with three inspection openings 19 one above the other, are provided. The two outer rows are arranged immediately following the flame guide plates 17. Furthermore, two central rows of inspection openings 19 are provided.

By guiding ultrasonic measuring heads through the control openings 19, the wall thickness of the galvanizing tub 6 can be detected in a spatially resolved manner during operation of the galvanizing furnace 1. In particular, by guiding the ultrasonic measuring heads through the left row of control openings 19, the wall thickness of the galvanizing tub 6 can be measured in area A, where the greatest wear of the galvanizing tub 6 occurs.

In particular, if it is determined in this critical area A that the wall thickness of the galvanizing tub 6 has fallen below a critical value, the locations of the high-speed burners 14 are preferably replaced during the next maintenance period of the galvanizing furnace 1 in such a way that the high-speed burners 14 are removed from the first recordings 15 removed and now installed in the second recordings 16. The first receptacles 15 are then correspondingly closed with the closure means 18.

Since the high-speed burners 14 are now installed in the second receptacles 16 during the subsequent operation of the galvanizing furnace 1, the areas B are now subject to the greatest wear. On the other hand, areas A, which are still heavily stressed during the first operating phase, are spared since the flame temperatures of the high-speed burners 14 are now lower there. Thus, despite the severe wear and tear that occurred in the galvanizing tub 6 in areas A, the galvanizing furnace 1 can continue to be operated without the risk of damage, since in the second phase, with high-speed burners 14 in the second receptacles 16 in areas A, only there is little wear. With that, the The galvanizing furnace 1 can continue to be operated without the risk of damage to the galvanizing tub 6 until the wall thickness of the galvanizing tub 6 is reduced to the limit value in areas B as well. The wall thickness of the galvanizing tub 6 is checked again by measurements carried out with the ultrasonic measuring heads. The operating time of the galvanizing furnace 1 with the galvanizing tub 6 is thus significantly increased compared to an operation in which the high-speed burners 14 are permanently arranged only in the first receptacles 15.

List of reference symbols

(1)

Galvanizing furnace

(2)

Furnace housing

(3)

ground

(4)

long side wall

(5)

front side wall

(6)

Galvanizing tub

(7)

Side wall

(8th)

Tub bottom

(9)

Edge segment

(10)

stamp

(11)

Flange

(11a)

Exhaust flap

(12)

first temperature sensor

(13)

second temperature sensor

(14)

High speed burner

(15)

first shot

(16)

second shot

(17)

Flame deflector

(18)

Closure means

(19)

Control opening

Claims (2)

1. Method of operating a zinc coating furnace (1) with a zinc coating trough (6) and a furnace housing (2), which surrounds the zinc coating trough (6) and which has a rectangular cross-section, wherein the furnace housing (2) has two opposite longitudinal-side end walls (4) and two opposite end-side side walls (5), and with burners for heating liquid zinc in the zinc coating trough (6), wherein at least one respective first receptacle (15) for a burner is provided in the regions of two diagonally opposite corners of the furnace housing (2), wherein a respective second receptacle (16) for a burner is provided in the regions of the two other diagonally opposite corners of the furnace housing (2) and wherein burners are arranged selectably either in the first receptacles (15) or in the second receptacles (16), wherein flames produced by the burners are guided each time in the region between a longitudinal-side side wall (4) of the furnace housing (2) and the opposite wall of the zinc coating trough (6), characterised in that the current wall thickness of the zinc coating trough (6) is detected in the region of the flame outlet of at least one burner and that a change of the burner is carried out when the current wall thickness falls below a predetermined limit value.
2. Method according to claim 1, characterised in that the outputs of the burners are set in dependence on the measurement valuers detected by the first or second temperature sensors (12, 13).P

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