EP2119997B1 - Method for checking a knocking device - Google Patents

Abstract

The method involves determining a knocking device for cleaning an upper surface of a heat exchanging element (8) in an inner side (6) of a boiler housing (4) of a waste incineration plant. A knocking lifter (18) is moved in direction against the inner side and guided through walls (14) of the housing. The heat exchanging element is moved by the lifter from a resting position into a moving position. Force for moving the heat exchanging element is determined by a force sensor (34), and settling characteristics of the released heat exchanging element are determined. An independent claim is also included for a device for executing a method for checking a knocking device.

Description

The present invention relates to a method for checking a knocking device according to claim 1 and to a device for carrying out the method according to the preamble of claim 7.

Conventional waste incinerators usually have at least one boiler in which steam or hot water is generated, which can be used to generate electricity or to heat households. Depending on whether primarily steam or hot water is generated in the boiler, this is also referred to as a steam generator or hot water generator.

Steam or hot water production takes place by means of heat exchanger elements, which are arranged in the interior of the boiler housing. Said heat exchanger elements are in the so-called. Konvektionszügen usually in the form of tube bundles before (also known as "harps"), whose tubes are traversed by water or steam and discharge into a collector. Heat is transferred from the hot flue gas to the water or the steam at these tube bundles, which is thereby heated, evaporated or superheated. The heat transfer takes place in such tube bundles primarily by convection.

However, the surface of these heat exchanger elements is heavily contaminated by the deposition of flue gas entrained in the flue gas. This contamination or slag reduces the heat transfer to the water or the steam and leads thus in total to a reduced efficiency of the boiler.

In addition, due to the constriction of the flue gas cross section resulting from the deposits, the pressure loss increases and can lead to complete growth of the flue gas cross section. Furthermore, the required maintenance measures cause high costs and lost sales.

Overall, the pollution or slagging of the heat exchanger elements thus reduces the "travel time" of the boiler (ie the time in which the boiler can drive the highest assured load while maintaining all assured properties, without any maintenance is required) and thus the availability of Waste incineration plant (ie the ratio of the operating time of the plant plus the reserve time at nominal operating time).

This problem is taken into account in practice by the surface of the heat exchanger elements is cleaned during operation of the boiler. For this purpose, various methods come into question. For example, the surface of the heat exchanger elements can be cleaned by means of a sootblower, a water spray system, a ball rainwater system or a knocking device.

In horizontal boiler trains a waste incineration plant, the heat exchanger elements are usually designed as a hanging arranged tube bundle. For the cleaning of such hanging tube bundles in particular knocking devices are very suitable. The polluted tube bundles are set in vibration by a pulse, with the adhering to the surface Combustion residues fall off. The impulse is usually given by a knock ram, which is actuated by a mechanically driven hammer or by a pneumatic impact cylinder, depending on the situation. In general, the stroke of the knocking plunger is made on the collector of the tube bundle.

Examples of knocking devices are described in the prior art.

This is how the US-A-2007/0267175 a knocking device for reducing the fouling of heat exchangers used in refining processes in crude oil, comprising a base mounted on the heat exchanger and an impact surface and a shock body which generates vibration energy which is transmitted from the base to the heat exchanger. Force and displacement sensors are used on the heat exchanger element to optimize the cleaning process.

Next describes about the DE 27 10 153 the use of a designed as a knocking device with knocking cylinder vibrator for cleaning the heating surface of a steam generator.

Next describes DE 198 53 715 a knocking device for cleaning pipe coils of boiler systems.

The cleaning success of such knocking devices is dependent on a variety of factors. In addition to the impact energy and the impact frequency, in particular the vibration behavior and the suspension of the tube bundles are of crucial importance. Prior to commissioning of the boiler of the waste incineration plant is therefore checked in practice, whether the tappets of the tapping device impinge on the particular desired location and put the tube bundles in the desired manner in vibration.

However, the conditions before commissioning of the boiler from those during operation, especially in terms of operating temperature and the degree of contamination, very different. This results in practice in the problem that even with a check before commissioning the functional activity the knocking device, ie the application of the desired pulse to the heat exchanger element, is often not guaranteed during operation to the full extent. For this purpose, a variety of possible reasons come into question. For example, the lack of functional activity may be due to the fact that the tappet is severely worn or subjected to strong friction in the guide through the wall of the boiler housing. Further, it is conceivable that the heat exchanger element may jam during operation and thereby is no longer in its rest position before commissioning, whereby an optimal impact of the knocking ram is affected on the heat exchanger elements, etc.

So far, no suitable methods have been described for checking the knocking device during operation of the boiler. However, just a review of the knocking device during operation would be of great benefit, since only such a reliable information can be obtained to what extent the functioning of the knocking device is impaired during operation and where exactly maintenance should be performed.

The present invention is therefore based on the object to provide a simple method for checking a knocking device during operation of the boiler.

The object is achieved according to the invention by the method according to claim 1. Preferred embodiments are listed in the dependent claims.

1. A) die zur Auslenkung des Wärmetauscherelements benötigte Kraft bestimmt, in der Regel in Abhängigkeit zu dessen Weg.
   Nachdem das Wärmetauscherelement beim Erreichen der Auslenkposition freigegeben wurde, wird alternativ oder zusätzlich zur Bestimmung gemäss A
2. B) das Ausschwingverhalten des Wärmetauscherelements bestimmt, d.h. der Weg des Wärmetauscherelements in Abhängigkeit der Zeit.

According to the method of the present invention, the heat exchanger element by means of the knocking plunger from his Rest position deflected into a deflection position. It will

1. A) determines the force required for the deflection of the heat exchanger element, usually in dependence on its path.
   After the heat exchanger element has been released upon reaching the deflection position, is alternatively or additionally to the determination according to A
2. B) determines the decay behavior of the heat exchanger element, ie the path of the heat exchanger element as a function of time.

The determination according to A), i. the force required to deflect the heat exchanger element, for example, provides information regarding the arrangement of two or more heat exchanger elements to each other, such as whether the heat exchanger element abuts the deflection of one or more other heat exchanger elements and at what distance they are away from each other in the rest position. In addition, the force measurement allows conclusions to be drawn about the frictional resistance of the knocking plunger guided through the housing wall or its wear.

By way of the determination in accordance with B), it can be determined, for example, whether the deflection of the heat exchanger element is jammed or swung out. On the other hand, the damping constant determined via the decay behavior allows conclusions to be drawn about the mass of the soiled heat exchanger element and thus its degree of soiling.

The evaluation of the data obtained according to the invention can take place by subtraction with respect to reference data determined before the boiler is put into operation.

According to a preferred embodiment, both the force required for the deflection of the heat exchanger element according to A) and the decay behavior of the heat exchanger element according to B) are determined.

Moreover, it is preferred that the force required for the deflection of the heat exchanger element is determined by means of a force sensor.

The manner in which the movement of the knocking plunger has to take place in the direction of the deflection of the heat exchanger element is known to the person skilled in the art. It is conceivable, for example, that the knocking plunger is pushed by means of a plunger of a pneumatic lifting cylinder. In such an embodiment, alternatively or in addition to the force sensor, a pressure sensor may be provided which detects the pressure applied to the pressure piston.

In general, in said embodiment, the lifting cylinder moreover has switches which are intended to be actuated upon reaching a predetermined force or a predetermined pressure in such a way that the lifting cylinder is vented in the shortest time and thus relieved.

According to a particularly preferred embodiment of the method according to the invention, the movement of the knocking plunger is detected for determining the decay behavior of the heat exchanger element. In this case, the knocking plunger is generally held in constant contact with the heat exchanger element, in particular by means of a Feather. This is generally designed in the form of a pressure spring arranged on the tappet.

Preferably, the decay behavior of the heat exchanger element is determined by means of a displacement sensor. It is conceivable, for example, that the displacement sensor comprises an optical sensor, for example a laser rangefinder. In this case, the displacement sensor is usually arranged at a predetermined distance from the wall of the boiler housing and detects the movement of the knocking plunger directly or via a reflection element arranged on the knocking plunger. However, any other type of displacement sensor known to those skilled in the art, which is suitable for the corresponding purposes, is also conceivable.

In addition, the force sensor or the displacement sensor is generally associated with a data recording device in which the data obtained are recorded. Starting from the data recording device, the data can be fed to a computer for graphical representation or other evaluation.

The invention will be further explained with reference to the figures.

Fig. 1

rein schematisch einen Teil eines Kesselgehäuses mit zwei in dessen Innerem angeordneten Wärmetauscherelementen und eine ausserhalb des Kesselgehäuses angeordnete erfindungsgemässe Vorrichtung zur Überprüfung einer auf das Wärmetauscherelement wirkenden Klopfvorrichtung;

Fig. 2

rein schematisch einen Teil eines Kesselgehäuses mit zwei in dessen Innerem angeordneten Wärmetauscherelementen und eine graphische Darstellung der durch das erfindungsgemässe Verfahren bestimmten Daten; und

Figs. 3 bis 8

jeweils eine graphische Darstellung von durch das erfindungsgemässe Verfahren bestimmten Daten bei sechs unterschiedlichen Situationen.

Show it:

Fig. 1

purely schematically a part of a boiler housing with two arranged in its interior heat exchanger elements and arranged outside the boiler housing inventive device for checking a knocking device acting on the heat exchanger element;

Fig. 2

purely schematically a part of a boiler housing with two arranged in its interior heat exchanger elements and a graphical representation of the data determined by the inventive method; and

Figs. 3 to 8

in each case a graphic representation of data determined by the method according to the invention in six different situations.

According to Fig. 1 the boiler 2 of the waste incineration plant on a boiler housing 4, in the interior of which 6 heat exchanger elements 8 in the form of tube bundles 8a, 8b are arranged hanging, the tubes 10a, 10b at its lower end portion opposite the suspension in a manifold 12a and 12b (also referred to as "collectors") with a substantially horizontal longitudinal axis. In the schematic representation according to Fig. 1 two tube bundles 8a, 8b arranged in series are shown, which each comprise four tubes 10a or 10b opening into the collector 12a, 12b. It is also conceivable, however, any other suitable for the appropriate purpose number of tube bundles and covered by these pipes.

The wall 14 of the boiler housing 4 has on its side facing away from the interior 6 a sheath 16 of thermally insulating material. Through the wall 14 of the boiler housing 4, a knocking plunger 18 is passed, which is mounted in a sleeve 20 disposed outside the boiler housing 4 and movable in the direction against the interior 6, wherein in the schematic representation Fig. 1 the longitudinal axis and direction of movement of Knocking plunger 18 is substantially perpendicular to the wall 14 of the boiler housing 4.

The frontal region of the knocking plunger 18 forms the so-called arrowhead 19. This is in contact with the collector 12a of a first tube bundle 8a of the two tube bundles 8a, 8b. In this case, a spring 22 is associated with the knocking ram 18, which ensures that the arrowhead 19 is pressed against the baffle plate 13a of the collector 12a.

Outside the boiler housing 4, a device 24 is arranged according to the present invention. This has a drive in the form of a lifting cylinder 26 and a means of the lifting cylinder 26 in the direction of the knocking ram 18 movable plunger 28.

The lifting cylinder 26 is connected to the boiler housing 4 via a support plate 29 with spacers 30 arranged thereon, which on their side facing away from the support plate 29 are also mounted on a connecting plate 32 arranged on the wall 14 of the boiler housing 4.

The impact piston 28 is aligned so that its longitudinal axis defining the impact direction coincides with the longitudinal axis of the knocking ram 18. The ram 28 also has a force sensor 34 for continuously determining the force applied to the ram 18 force.

The in Fig. 1 shown lifting cylinder 26 is pneumatically operated and has for this purpose a compressed air supply line 36a for the forward movement of the plunger 28 and a compressed air return line 36b for the backward movement of the Shock piston 28 on. The forward or backward movement of the plunger 28 is controlled by a valve. The compressed air supply line 36a is further associated with a pressure sensor 40 for determining the pressure applied to the plunger 28 pressure.

The lifting cylinder 26 also has sensors 42a, 42b for determining the position of the plunger 28. The sensors 42a, 42b, a switch is assigned, which is actuated upon reaching a predetermined position of the plunger 28 to the effect that the lifting cylinder 26 is vented and the plunger 28 is moved back. Alternatively or additionally, a switch 43 may be provided, which is actuated upon reaching a predetermined pressure or a predetermined force for venting the lifting cylinder 26 or for returning the plunger 28.

Moreover, the device 24 has a displacement sensor 44. This is connected via a connecting element 46 with the support plate 29 and thus arranged at a constant distance from the boiler housing 4. The displacement sensor 44 is in communication with a planar reflection element 47, which is arranged in a region of the knocking plunger 18 located outside the boiler housing 4 and whose plane is in the in FIG Fig. 1 shown representation is substantially perpendicular to the longitudinal axis of the knocking ram 18.

Both the force sensor 34 and the pressure sensor 40 and the displacement sensor 44 are connected to a data recording device 48, via which the data are fed into a computer 50 in which they can be evaluated.

According to the in Fig. 1 As shown, the tube bundles 8a, 8b are in the rest position. For carrying out the method according to the invention, the plunger 28 is pushed over the lifting cylinder 26 in the direction of the knocking plunger 18, which is subsequently moved in the direction towards the interior 6 of the boiler housing 4. The movement of the plunger 28 and the knocking plunger 18 takes place at a speed of about 10 to 100 mm / second.

By the movement of the knocking rod 18, the first tube bundle 8a is deflected. After a certain stroke, the collector 12a of the first tube bundle 8a abuts against the collector 12b of the second tube bundle 8b, which is also deflected in the sequence until it abuts the wall 14 "of the boiler housing 4 opposite the wall 14 'which is penetrated by the knocking ram 18 ,

The force required to deflect the tube bundle 8a or 8b into the deflection position as a function of its travel is determined continuously by means of the force sensor 34 assigned to the push piston 28.

Once the deflection position is reached, the lifting cylinder 26 is immediately relieved or vented and the plunger 28 is retracted. As a result, the tube bundles 8a, 8b are released, which swing out in the sequence. The standing in contact with the first tube bundle 8a knocking ram 18 is pushed back by this up to a Rückschwingposition. The tappet 18 associated spring 22 ensures that this is held during the entire swinging out in contact with the first tube bundle 8a and its collector 12a.

Thus, it is possible to detect the decay behavior of the tube bundle 8a via the movement of the knocking plunger 18. For this purpose, the distance from the reflection element 47 over time is determined by means of the displacement sensor 44.

The data obtained are recorded by means of the data recording device 48 and fed to the computer 50 for evaluation.

A schematic representation of the arrangement of two tube bundles 8a, 8b in a vessel 2 with an idealized graphical representation of the force required to deflect the tube bundles 8a, 8b and the decay behavior of the tube bundle 8a in contact with a knocking ram 18 after its release is shown in FIG Fig. 2 shown.

How out Fig. 2 it can be seen, the force curve shown in dashed line on a step-increasing course. The curve section S1 corresponds to the stroke for the deflection of only the first tube bundle 8a of the two tube bundles 8a, 8b. At the point where the first tube bundle 8a abuts the second tube bundle 8b, the force to be applied increases. This point marks the beginning of the curve section S2, which corresponds to that stroke in which, in addition to the first tube bundle 8a, the second tube bundle 8b is also deflected. The stroke S2 ends at the point where the second tube bundle 8b abuts the wall 14 of the boiler housing 4. From this point, ie the so-called deflection position, the force curve rises sharply. Immediately after the detection of the deflection position, the tube bundles 8a, 8b are released and their decay behavior determined.

In the Fig. 2 a solid line curve corresponds to the damped oscillation of a pendulum and reflects a situation in the interior 6 of the boiler housing 4, in which the first tube bundle 8a and possibly also the second tube bundle 8b can swing freely without abutting or being blocked by further elements , From the vibration of the tube bundle, the damping constant can be determined, which allows conclusions about the mass of the contaminated tube bundle and thus its degree of contamination.

A graphical representation of the data determined according to the invention in another situation is in Fig. 3 shown. It is - as well as for the Fig.s 4 to 8 - The determined according to A of claim 1 power curve in a dashed line and the determined according to B of claim 1 way curve shown in a solid line.

How out Fig. 3 it can be seen, at the beginning of the deflection, the increase of the travel curve and the increase in the force curve substantially at the same time, which indicates that the tappet is subjected in the Klopfstösselführung only a small friction and at least the heat exchanger element in contact with the tappet is not jammed , In the Fig. 3 The path curve shown corresponds to a damped oscillation of a pendulum, which allows the conclusion that the heat exchanger element can swing freely, without being abut on other elements or blocked by them.

According to the in Fig. 4 shown graph is made at the beginning of the deflection of the increase in the path time-delayed with respect to the increase in the force curve. This indicates that the tappet and / or the heat exchanger element is subjected to strong friction. It is conceivable, for example, that the heat exchanger element is jammed in the wall guide. In addition, the fall of the path curve with respect to the fall of the force curve after the discharge of the lift cylinder is delayed, which supports the above interpretation.

According to the in Fig. 5 As shown, the rise of the path curve with respect to the increase in the force curve is strongly delayed, which in turn indicates that the tappet and / or the heat exchanger element is subjected to strong friction. With a substantially linear increase in the force, the path curve increases almost exponentially, which suggests a friction-induced bias of the knocking plunger or of the heat exchanger element at the beginning of the stroke. It is conceivable, for example, that the heat exchanger element is initially blocked and suddenly becomes free at a certain force. As in Fig. 4 also takes place in Fig. 5 the drop of the path curve with respect to the fall of the power curve after the discharge of the lift cylinder delayed. In addition, the heat exchanger element oscillates beyond its initial position during the return swing, which could indicate a jamming of the heat exchanger element at the beginning of the test period.

In Fig. 6 For a further situation, only the decay behavior of the heat exchanger element determined according to the invention is reproduced. According to Fig. 6 The first three troughs of the vibration curve are essentially the same depth, while the shaft tips according to a damped vibration decrease. This indicates that the heat exchanger element is located closer to the wall penetrated by the knocking plunger than the opposite wall and abuts the former when swinging out.

According to Fig. 7 At the beginning of the deflection, the increase in the force curve and the path curve takes place substantially simultaneously. After the relief of the lifting cylinder, the fall of the travel curve with respect to the fall in the power curve takes place with a time delay. Moreover, the heat exchanger element no longer reaches the rest position after unloading. This can be explained, for example, that the heat exchanger element jammed when deflecting.

According to Fig. 8 takes place - as well as according to the Fig. 4 and 5 - The increase of the path curve with respect to the increase of the force curve is strongly delayed. This in turn indicates that the tappet and / or the heat exchanger element is subjected to strong friction.

Claims (10)

1. A method for checking a rapping device which is intended for cleaning the surface of a heat exchanger element (8) arranged on the inside (6) of a boiler housing (4) of a waste incineration plant and which has a impact ram (18) guided through the wall (14) of the boiler housing (4) and movable in the direction toward the inside (6), the heat exchanger element (8) being deflected out of its position of rest into a deflection position by means of the impact ram (18), and

   A) the force required for deflecting the heat exchanger element (8) and/or

   B) the oscillatory behavior of the heat exchanger element (8) released after deflection being determined.
2. The method as claimed in claim 1, both the force required for deflecting the heat exchanger element (8), according to A), and the oscillatory behavior of the heat exchanger element, according to B), being determined.
3. The method as claimed in claim 1 or 2, the force required for deflecting the heat exchanger element (8) being determined by means of a force sensor (34).
4. The method as claimed in one of the preceding claims, the movement of the impact ram (18) being detected in order to determine the oscillatory behavior of the heat exchanger element (8).
5. The method as claimed in claim 4, the impact ram (18) being held in bearing contact against the heat exchanger element (8), in particular by means of a spring (22).
6. The method as claimed in one of the preceding claims, the oscillatory behavior of the heat exchanger element (8) being determined by means of a displacement sensor (44).
7. A device for carrying out the method as claimed in one of the preceding claims, with a drive (26) for moving the impact ram (18) in the direction toward the inside (6) of the boiler housing (4), defined by

   a) a force sensor (34) for determining the force required for deflecting the heat exchanger element (8) and/or

   b) means for releasing the heat exchanger element (8) when the deflection position is reached and a displacement sensor (44) for determining the oscillatory behavior of the released heat exchanger element (8).
8. The device as claimed in claim 7, defined by means for holding the impact ram (18) in bearing contact against the heat exchanger element (8), in particular a spring (22).
9. The device as claimed in claim 7 or 8, wherein the travel sensor (44) has an optical distance sensor, preferably a laser rangefinder.
10. The device as claimed in one of claims 7 to 9, wherein the force sensor (34) or the displacement sensor (44) is assigned a data recorder (48).

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