WO2001086206A1

WO2001086206A1 - Method for removing deposits in combustion chambers of thermal installations during operation

Info

Publication number: WO2001086206A1
Application number: PCT/DE2001/001623
Authority: WO
Inventors: Erik Riedel; Klaus Poppe; Werner Hammerschmidt; Winfried Wilke
Original assignee: Erik Riedel; Klaus Poppe; Werner Hammerschmidt; Winfried Wilke
Priority date: 2000-05-08
Filing date: 2001-04-27
Publication date: 2001-11-15
Also published as: AU6205301A; DE10022351A1

Abstract

The invention relates to a method for removing deposits or adhered matter in thermal energy installations during operation or during the cooling phase by invoking destructive mechanical stresses in the material bond of the deposits or adhered matter, whereby the mechanical stresses are produced by the increase in volume of vaporizing liquids.

Description

METHOD FOR REMOVAL OF DEPOSITS IN FIREPLACE THN THERMAL SYSTEMS DURING OPERATION

description

The invention relates to a method for removing deposits or buildup in plants which are operated with gaseous, liquid or solid fuels and in which thermal energy is released. In the following, these systems are referred to as thermal energy systems. These are, for example, boilers in power plants, boilers in heating plants, waste incineration plants, ovens, coal gasifiers, wood gasifiers, steel converters or reactors.

In thermal energy systems, deposits or buildup (e.g. ashes, slag, soot) often form on construction components (e.g. heat exchangers, boiler walls, pipe elbows, return chutes, ash funnels) during operation. These deposits or buildup (hereinafter called deposits) on the one hand deteriorate the heat transfer from the combustion site to the carrier medium of the heat to be dissipated in such a way that the efficiency of the thermal energy conversion drops after a relatively short operating time. On the other hand, these deposits can lead to the flow and pressure conditions for which the thermal energy system is designed being drastically deteriorated and the system's operability thus being restricted or no longer existing. For these reasons, the deposits must be removed at regular intervals. At the moment this is essentially done by a very labor-intensive and time-consuming manual cleaning during a multi-week shutdown of the system. This effort can be significantly reduced if hot deposits can be removed by liquid injection while the system is running or while the system is cooling down.

It is known that such deposits can be loosened using chemical explosives to generate pressure waves (Swanekamp, R .; Use of explosives for boiler deslagging gains acceptance; Power 140 (1996) 3, pp. 49-51). However, the transport, storage and use of these substances are characterized by the highest requirements for the protection of the general public, for the protection of the systems and for occupational safety, which make this process very complex (SprengG, 1. SprengV, 2. SprengV , SprengLR, GBefGG). For example, explosives without special approval may only use chemical explosives at temperatures below 70 ° C. Since the explosives cannot be introduced into the deposits in the plant during operation, the material deposits of the mostly mineral deposits build up in the Usually only compressive stresses, which can only destroy the material composite in comparison with tensile stresses with significantly larger energy inputs. Therefore, the use of chemical explosives in the ongoing operation of the plant is very limited and only possible with considerable effort.

It is also known that soot and ash deposits can be removed in boilers by means of so-called soot, steam or water blowers while the system is running. (Mayr, F. [Ed.]: Handbuch der Kesselbetriebstechnik, Graefeling, 6th ed. 1994). The basic idea of these processes is to “blow off” or “rinse” the deposits off the boiler internals by the external impulse effect of compressed air, steam or water jets. This process is characterized by the fact that the blowing medium has to travel a long distance, typically several meters, in the combustion chamber of the plant before it hits the ash or soot deposit. However, these blowing processes are not suitable for effectively removing solid deposits (e.g. slag) from construction components, since they can only build up relatively weak shear and compressive stresses in the material combination of the deposits, which as a rule cannot destroy the solid structure of the slag deposits , In addition, because of the large amounts of compressed air, steam or water that are introduced into the combustion chamber, this method leads to a severe impairment of the thermodynamic process, so that large losses in efficiency generally occur. Furthermore, due to the large spray angles, there is a danger with this method that the structural components of the thermal energy system to be cleaned are locally cooled down by the impact of the comparatively cold medium and are damaged by this thermal shock.

In particular in the areas of thermal energy systems without built-in heat exchangers, such as back-suction shafts, water jets are used to flake off deposits by means of thermal shocks. These processes correspond in their mode of operation to the blowing process (Hein, KRG: flue gas-related problems with the increase in the price of low-calorific coals, international VGB conference "slagging, contamination and corrosion in thermal power plants", Essen 29.02. - 02.03.84, p. 22 The method has the disadvantage that the components of the thermal energy systems are also subjected to high loads as a result of the thermal shocks and can therefore be easily damaged.

DE 19852217 describes a method with which deposits in thermal energy systems can in principle also be removed during operation. With electrical high-power pulses, this method uses a completely different physical principle than the invention and requires an electrical high-voltage source. DE 19723389 describes a method with which the interior of a fired boiler system on the flue gas side is cleaned by irradiation with solid particles. This process uses the abrasive effect of solids. The method has the disadvantage that the structural components of the thermal energy systems can be damaged by the abrasive effect and waste materials remain which have to be removed from the combustion chamber with a high level of technical complexity.

The invention is based on the object of specifying a method by means of which deposits in thermal energy systems of construction components can be removed by means of liquids while the system is running.

The object of the invention and solution to this problem is a method in which a liquid hits the surface of the hot deposit in a targeted manner with a high flow velocity, in particular during the ongoing operation of a thermal energy system, by means of a preferably automatic manipulator system and via material inhomogeneities in the material composite of the deposits is injected. On the one hand, there can be existing inhomogeneities in the deposition surface, for example cracks or cavities. On the other hand, the abrasive effect of rapid liquid flows known from the art of water jet cutting can produce the material inhomogeneity in the deposition surface, so that liquid can be injected into the material composite.

In the material compound of the hot deposit, the liquid then evaporates spontaneously with an extreme increase in volume, the inflowing liquid also preventing the steam from escaping through the material inhomogeneity and thus acting as insulation known from blasting technology. As a result, in addition to pressure surges and pressure waves, high mechanical tensile stresses are generated in the deposit, which destroy the material composite of the deposit with a relatively low energy input and thus remove the deposit from the structural components of the thermal energy systems.

The liquid can only penetrate into the deposit if it hits the surface of the deposit with a sufficiently high momentum. Since the impulse physically represents the mass / velocity product of the liquid mass particles, the mass particles must have a sufficiently high impact speed on the surface of the deposit and a sufficiently high concentration on a small surface segment of the deposit. The mass particles of the liquid can be accelerated to the required speed using two physically different effective principles:

a) A volume of liquid is pressurized and flows through a nozzle into the free atmosphere. Here, the liquid mass particles are accelerated to a high speed. On the one hand, a continuous high-speed liquid jet can be generated by means of a larger pressure accumulator and a valve. On the other hand, a partial liquid volume can also be displaced by means of volume displacement, e.g. B. by a piston or an expanding gas volume in front of the nozzle under the required pressure, so that a discontinuous high-speed jet is created.

b) A partial liquid volume is accelerated to the required speed in a hollow profile that is open on one side and closed on the circumference, preferably in a tube. This can be accomplished by means of volume displacement, for example by an explosively expanding gas volume or by a piston, by means of acceleration by an electric field or by means of acceleration by a magnetic field.

As an alternative to liquids, substances or mixtures of substances in the solid state can be injected into the deposits as ice by means of high impulses. In this case, the solid material acts as a projectile. For example, water, alcohols or carbon dioxide can be used. In the sufficiently hot deposits, these substances quickly take on the gaseous state of matter, so that the extreme increase in volume creates the tensions in the composite material of the deposits that are necessary to remove deposits. These solid substances can in a circumferentially closed hollow profile, for. B. a pipe can be accelerated to the required speed. This can be accomplished by means of volume displacement, for example by an explosively expanding gas volume or by a piston, by means of acceleration by an electric field or by means of acceleration by a magnetic field.

The mass concentration of the liquid flow impinging on the deposition surface required for the injection pulse can be achieved with different technical solutions:

1. The liquid stream is focused on a small surface segment of the deposition surface by means of a nozzle with a suitable geometry. 2. By means of a suitable spatial arrangement of several nozzles, several liquid flows are focused simultaneously on a small surface segment of the deposition surface.

3. The liquid flow or a substance in the solid state of aggregation is directed onto the deposition surface by means of a hollow profile.

4. By means of a suitable spatial arrangement of several hollow profiles, several liquid flows or projectiles made of substances in the solid aggregate state are simultaneously directed onto a small surface segment of the deposition surface.

The process objective of removing deposits with small amounts of liquid and the physical boundary conditions necessary for the injection of a high impulse of impingement of the liquid on the deposit surface can only be technically and with reasonable effort met under the condition that the liquid flow is as short as possible in the combustion chamber the thermal energy system must travel freely. Furthermore, in thermal energy systems, the mostly metallic construction components are very sensitive to sudden local cooling by liquids. It is therefore imperative to introduce the injections into the deposits in a controlled manner so that the injection device is brought as close as possible to the deposits and that no structural components are endangered by the injection liquid. This object can be achieved with known teleoperator, robot or manipulation systems, by means of which the deposits are preferably removed automatically and which are expediently equipped with sensor systems for on-line control of the cleaning process. Imaging systems are preferred for this on-line process control. The injection device and the manipulator system in the thermal energy system are supplied with the required amount of liquid, with energy and with signals from outside by means of a supply device. However, all of the devices mentioned must function reliably under extremely adverse environmental conditions in the combustion chamber of a thermal energy system in operation. The most important influences include the high temperature, the corrosive components of the atmosphere and the abrasive particles in the atmospheric flow within the thermal energy system. Consequently, the entire device for liquid injection with the manipulator system and the supply device for liquid, energy and signals must be isolated from the damaging influences.

The solution to this problem is protective insulation, which is based on the principle of evaporation and envelops the devices to be protected on all sides. Herewith a temperature is established on the inside of the insulation which corresponds to the temperature of the continuously supplied coolant. Water is preferably used as the cooling liquid. The cooling liquid evaporates on the outside of the insulation, thereby extracting heat from the insulation and also generating a continuous steam flow that flows away from the insulation. This keeps corrosive atmospheric components and most abrasive particles away from the insulation. In the areas of a thermal energy system in which high particle densities or high flow velocities of the particle-laden combustion gases prevail, such as in burners or return suction shafts, the area-specific volume flow of the cooling liquid that emerges from the insulation is increased in such a way that on the outside of the insulation forms a liquid film. This film slows down the particles and thus reinforces the protective effect of the insulation against abrasive particles. The insulation reliably protects the isolated components of the positioning systems, the supply device and the injection device from the adverse environmental conditions in the thermal energy system, so that they can be operated, for example, under the standard design conditions of the standard commercial components used.

In principle, the insulation consists of five layers, which together create the insulation effect in the combustion zone of thermal energy systems. In the technical configuration, a single device can take over the function of several layers. The insulation consists of the inner boundary layer, the water distribution layer, the throttle layer, the evaporation layer and the outer boundary layer, when viewed from the isolated space. The layers can be described as follows:

I) The inner boundary layer seals the insulation from the insulated interior and consists of a liquid-tight material. It protects the inside of the insulation from the effects of the cooling water and adopts its temperature. This layer also serves to mechanically stabilize the insulation system. Depending on the application, different materials are available for the inner boundary layer:

(1) In the case of mechanically rigid insulation, the inner boundary layer preferably consists of a metal sheet. (2) In the case of flexible insulation, the inner boundary layer preferably consists of foils which are good heat conductors for better temperature compensation.

II) The water distribution layer consists of a gap which is delimited on the one hand by the inner delimitation layer and on the other hand by the throttle layer. This layer is used to evenly distribute the cooling water over the entire insulation surface. The cooling water is pumped into this layer from outside with the necessary pressure.

III) The throttling layer consists of a liquid-tight material and is characterized in that it ensures a uniform metering of the cooling water by means of a suitable perforation over the entire surface of the insulation. In this throttling layer there is a location-dependent pressure loss which ensures that a uniform cooling water volume flow independent of the position of the cooling water feed enters the evaporation zone. This layer also serves to mechanically stabilize the insulation. Depending on the application, it is designed differently:

(1) In the case of mechanically rigid insulation, the throttle layer preferably consists of a perforated metal sheet or a rigid permeable membrane.

(2) In the case of flexible insulation, the throttle layer preferably consists of perforated foils, permeable membranes or of fabrics.

IV) The evaporation layer consists of temperature-resistant, highly porous material, which is characterized on the one hand by its absorbency and on the other hand by its specific surface. The absorbency determines the even distribution of the cooling water in the evaporation layer and thus ensures the even evaporation of the cooling water over the insulation surface. The specific surface of the porous material ensures that the cooling liquid evaporation takes place as surface evaporation and protects the material. The evaporation layer can be designed as a bed of small ceramic, glass, metallic or mineral bodies or as a fleece. Fibers made of glass, metal, carbon, minerals or ceramics can serve as the base material of the tile.

V) The outer boundary layer consists of thermally conductive material and represents the mechanical protection of the layers below from damage caused by external influences. This layer dissipates the heat when it comes into contact with the deposits and thus prevents damaging temperature increases. This layer also stabilizes the porous evaporation layer. Depending on the application, it is designed differently:

(1) In the case of mechanically rigid insulation, the outer boundary layer preferably consists of a perforated metal sheet.

(2) In the case of flexible insulation, the outer boundary layer preferably consists of fabrics or nets, for example of metal, carbon fibers, mineral fibers or ceramic fibers.

Claims

claims

1. Process for removing deposits or buildup in thermal energy systems during operation or during the cooling phase by destructive mechanical stresses in the material structure of the buildup or buildup, the mechanical stresses being generated by the volume increase of evaporating liquids.

2. The method of claim 1, wherein the liquid is injected in the liquid or solid state before evaporation in the material structure of the deposits or buildup.

3. The method according to claim 2, wherein the pulse necessary for injection is generated by a sufficiently high speed of the liquid upon impact.

4. The method of claim 3, wherein the sufficiently high speed of the liquid is generated by means of a nozzle through which liquid can flow out of a pressurized volume into the free atmosphere.

5. The method according to claim 4, wherein a continuous liquid jet is generated.

6. The method according to claim 4, wherein a discontinuous jet of liquid is generated.

7. The method according to claim 3, wherein the liquid is accelerated in a circumferentially closed hollow profile by means of volume displacement to the sufficiently high speed.

8. The method according to claim 3, wherein the liquid is accelerated in the solid state in a circumferentially closed hollow profile by means of volume displacement to the sufficiently high speed.

9. The method according to claim 3, wherein the liquid is accelerated in a circumferentially closed hollow profile by means of the force of one or more electric fields to the sufficiently high speed.

10. The method according to claim 3, wherein the liquid in the solid state in a circumferentially closed hollow profile by means of the force of one or several electric fields is accelerated to the sufficiently high speed.

11. The method according to claim 3, wherein the liquid is accelerated to the sufficiently high speed in a circumferentially closed hollow profile by means of the force effect of one or more magnetic fields.

12. The method according to claim 3, wherein the liquid is accelerated to the sufficiently high speed in the solid state in a circumferentially closed hollow profile by means of the force of one or more magnetic fields.

13. The method according to claim 2, wherein the pulse necessary for injection is generated by concentrating the liquid mass flow on a sufficiently small impact surface.

14. The method according to claim 13, wherein the liquid mass flow is concentrated by means of a nozzle on a sufficiently small area segment.

15. The method according to claim 13, wherein by means of a spatial arrangement of a plurality of nozzles, a plurality of liquid mass flows are concentrated simultaneously on a sufficiently small area segment.

16. The method according to claim 13, wherein the mass flow in the liquid or solid state of aggregate is directed to a sufficiently small area segment by means of a hollow profile.

17. The method according to claim 13, wherein by means of a spatial arrangement of a plurality of hollow profiles, a plurality of material mass flows in the liquid or solid state of aggregation are simultaneously directed to a sufficiently small surface segment.

18. The method according to claims 1 to 17, wherein the devices necessary for liquid injection are mounted on a system carrier which can be freely positioned by means of movement or manipulator systems in thermal energy systems during ongoing operation or during the cooling phase.

19. The method according to claim 18, wherein the devices necessary for liquid injection, the system carrier and the movement or manipulator system by means of a supply system within the thermal energy system of are supplied with energy, substances and signals on the outside and send signals to the outside.

20. The method according to claims 18 and 19, wherein all devices and systems by means of an insulation that between the surface of the devices and

Systems and the atmosphere inside the thermal energy system is protected from the effects of the combustion processes.

21. The method according to claim 20, wherein the thermal effect of the insulation is produced by means of evaporation of a liquid and the resulting vapor layer.

22. The method according to claim 20, wherein the protective effect of the insulation against abrasive particles is produced by means of a liquid film on the insulation surface.

23. The method according to claims 21 and 22, wherein the insulation has an inner liquid-tight boundary layer, which prevents the transfer of the cooling liquid into the interior of the insulation.

24. The method of claim 23, wherein the inner boundary layer is mechanically rigid.

25. The method of claim 23, wherein the inner boundary layer is mechanically flexible.

26. The method according to claims 21 and 22, wherein the insulation has a distribution and throttling layer, which serves for uniform distribution of the cooling liquid over the entire insulation surface and for an independent volume flow of the cooling liquid into the evaporation layer which is independent of the position of the cooling liquid feed ,

27. The method according to claim 26, wherein the distribution and throttle layer is mechanically rigid.

28. The method according to claim 26, wherein the distribution and throttle layer is mechanically flexible.

29. The method according to claims 26 to 28, wherein the distribution and throttle layer is divided into two different functional devices, one of which takes over the distribution and the other the throttle function.

30. The method according to claims 21 and 22, wherein the insulation has an evaporation layer in or on which the cooling liquid evaporates.

31. The method of claim 30, wherein the evaporation layer is characterized with an absorbent material with a high specific surface.

32. The method according to claim 31, wherein the evaporation layer is designed as a bed of small ceramic, metallic, mineral or glass bodies.

33. The method according to claim 31, wherein the evaporation layer is designed as a fleece of ceramic, metallic, mineral, glass or carbon fibers.

34. The method according to claim 31, wherein the evaporation layer is designed as a porous sintered body of ceramic, oxide, metallic, mineral or glass powder.

35. The method according to claims 32 to 34, wherein the evaporation layer is mechanically fixed to the insulation surface by means of fabrics or nets made of metallic, mineral, glass, ceramic or carbon fibers.

36. The method according to claims 21 and 22, wherein the insulation has an outer vapor and liquid permeable boundary layer, which protects the insulation from mechanical damage caused by contact with the deposits and buildup in the thermal energy system, and which protects the evaporation layer fixed on the insulation surface.

37. The method of claim 36, wherein the outer boundary layer is mechanically rigid.

38. The method of claim 36, wherein the outer boundary layer is mechanically flexible.