DE19607979A1 - Waste gas path of combustion apparatus for burning heavy oil - Google Patents

Abstract

Waste gas path is claimed for a combustion apparatus comprising a component (9,10,13) for utilising the waste gas energy of a combustion apparatus in which the path (12) is arranged.

Description

Technical field

The invention relates to the exhaust tract, in particular for Combustion of heavy oil usable combustion device and those in their exhaust tract to harness the exhaust gas gie the combustion device arranged components.

State of the art

As a result of burning natural, artificial or from Waste of existing fuels, but especially of Heavy oil, it comes to harnessing the exhaust gas energy serving and for this purpose in the exhaust tract of a corresponding Ver combustion device arranged components in addition to erosion and Corrosion phenomena also to contamination and Accumulation of combustion products. The disadvantages mentioned occur depending on the type of incinerator tion, the specific operating situation and the composition of the fuels used to different degrees.

The so-called "hot gas corrosion" is from gas turbine construction known. This condenses in the temperature range from 600 to 1000 ° C on the components of the gas turbine various sulfates (Na₂SO₄, CaSO₄) from the combustion gases. These sulfates we ken both on the base material of the turbine components also aggressive on the protective oxides. State of the Tech nik to prevent hot gas corrosion on components There are various protective layers in the hot turbine area  and corresponding methods for their application. Most are these protective layers also prevent erosion damage those provided by the impact of hard burns residues on the surface of the turbine components can stand.

For example, a method is known in which initially a silicon-enriched aluminum mixture on the respective Component is sprayed or painted. By subsequent Drying creates a hard coating, which in one further heat treatment between 870 and 1200 ° C partly in diffuses the base material and forms aluminides. Here it is the so-called Sermaloy J, an alumi nid-silicide compound with a silicon concentration of 9-15% in the outer layer envelope, which is down to 0% in the diff zone sinks (Technical information: STS SermaLoy J process, company name SermeTel, Germany, 08/1987).

Another example of a corrosion and erosion protection layer that is permanently heat-resistant up to 750 ° C is the so-called ALCOAT 400/100 (surface technology brochures a) ALCOAT 100 ceramic sealing layer and b) ALCOAT 400 metal ceramic, both from Böhler Schweißtechnik GmbH, Düsseldorf, 1992). This is a duplex layer consisting of a ceramic-bonded aluminum coating (ALCOAT 400 ) as the base layer and a ceramic seal (ALCOAT 100) based on chromium-phosphate as the cover layer, the cover layer closing the micropores of the base layer (see also DE-C1-38 30 848 and DE-A1-41 31 542).

In the exhaust gas turbine one with an internal combustion engine bound exhaust gas turbocharger are such protective layers Prevention of hot gas corrosion is not necessary because no correspondingly high temperatures can be reached there. In contrast, there is a risk of corrosion damage  due to the sulfur contained in the heavy oil at temperatures below 160 ° C, d. H. below the dew point of sulfur acid. However, so far there are no noteworthy ones in practice Corrosion problems due to the so-called "low-temperature cor rosion ". As a result, there is no need for turbines Corrosion protection measures for exhaust gas turbochargers.

After the lecture by R. Müller, BBC Brown Boveri & Cie., Ba den / Switzerland, on the subject of "exhaust gas turbochargers in heavy oil use", held at the SMM symposium in Hamburg in September 1984 leads the heavy oil operation with an exhaust gas turbocharger tied internal combustion engine to deposits on the components the exhaust gas turbine. But especially on the nozzle ring the turbine blades have a hard, predominantly from calcium sulfate and from sodium vanadium compounds standing dirt layer, resulting in a poorer turbo efficiency and thus to reduce the performance of the Internal combustion engine leads. It also happens in the combustion chamber an increase in exhaust gas temperatures and pressures where through the internal combustion engine and in particular its valves can be damaged or even destroyed. Therefore have to the nozzle rings according to the current state of the art regularly freed from the dirt adhering to them will.

Cleaning of the nozzle rings in disassembled condition is required the turbocharger is switched off for a long time space and is therefore not desirable. As a result Cleaning procedures in which the turbocharger in Operation can remain and does not have to be dismantled. As suitable procedures for removing nozzle ring contamination tongues are wet cleaning with water and drying known cleaning with a granulate. Especially when Heavy oil operation of the internal combustion engine is the effect these cleaning procedures are inadequate because the hard  Dirt layer of the nozzle ring is not completely removed that can. This means that despite cleaning, the be already described disadvantages, so that the exhaust gas bine ultimately has to be dismantled. In addition, by the use of cleaning granules the erosion effect the combustion exhaust gases to the corresponding turbine component le to be reinforced.

EP-A1-05 89 072 describes a turbocharger for heavy oil operation known to prevent erosion in partial erosion control layers on the exhaust gas turbine are brought, which contain carbide hard materials. As be a Chromkar is particularly resistant to erosion and temperature bid layer (Cr₃C₂) shown, which is a base material with relatively high ductility and long-term stability as well as with has good adhesion. Because of its rough surface, it can such a chrome carbide layer hardens the attachment Layers of dirt on the nozzle ring and the associated Do not prevent disadvantages. In addition, the uniform Ver Division of chrome carbide on the surface to be protected problematic because this material directly on the spray place sticks and does not run. Therefore, esp especially complicated surfaces in certain areas ne erosion protection layer.

After all, is from the field of kitchen, but also the Soil cultivation equipment the use of fluoropolymers such as B. PTFE and FEP (Teflon) as a non-stick coating knows. However, these organic materials are already at temperatures of 300 to 400 ° C and are therefore unstable not for the coating of in the exhaust tract of a cremation Component arranged device suitable.  

Presentation of the invention

The invention tries to avoid all these disadvantages. your the task is based, the accumulation of dirt layer ten in the exhaust tract, especially for the combustion of Heavy oil usable combustion device and to the Harnessing the exhaust energy of the combustion device to reduce components arranged in the exhaust tract.

According to the invention this is achieved in that at a Device according to the preamble of claim 1, on the Surface of the at least one, for harnessing the exhaust gas energy arranged in the exhaust tract or at least one of these components and / or one in the exhaust tract itself Non-stick coating is arranged.

The advantages of the invention lie in the fact that with With the help of the anti-stick coating an accumulation of hard Dirt builds up in the exhaust system of the respective device arranged components is reduced or even prevented. Any deposits can then be removed with a conventional Chen cleaning procedures relatively easy to eliminate. Thereby can increase the efficiency of the corresponding device will.

It is particularly useful if the anti-stick coating at least on the flow of exhaust gases through the exhaust gas tract limiting component is formed. In this way is an increasing blockage of the exhaust tract bends.

In an advantageous embodiment, the combustion device as one connected to an exhaust gas turbocharger Internal combustion engine trained. The exhaust gas turbocharger exists from a compressor and an exhaust gas turbine. The latter points  a turbine housing with a gas inlet and a gas outlet step housing, one arranged in the turbine housing, of one Shaft supported turbine impeller with turbine blades, one flow channel extending downstream of the turbine blades for the exhaust gases of the internal combustion engine and an upstream of the turbine impeller arranged nozzle ring. The exhaust gas wing of the internal combustion engine extends into the river exhaust duct. The non-stick coating is formed on the nozzle ring.

As a result, the nozzle rings of the exhaust gas turbines can also Heavy oil operation of those connected to the exhaust gas turbocharger Internal combustion engine before the superficial deposition of hard layers of dirt are protected. In combination with Training is one of the known cleaning methods such layers of dirt permanently prevented. A disassembly the exhaust gas turbine is therefore no longer required.

It is also advantageous if the turbine inspection is also carried out are coated with a non-stick coating. As The outer boundary of the flow channel is in the area of the turbos arranged a cover ring, which is also egg ne non-stick coating. Because of this additional Chen measures can also the corresponding components protected from the accumulation of hard layers of dirt the.

The material of the anti-stick coating is an aluminide-Si licide compound, with the following ge over the entire layer average chemical composition: Al 28-32%, Cr 8-12%, Si 8-10%, Co 7-9% and a residual Ni content. Especially The following chemical composition is advantageous: Al 30%, Cr 10%, Si 9%, Co 8% and a residual Ni content.  

Finally, there is advantageously a duplex layer from a ceramic-bonded aluminum base layer and from a ceramic top layer, each on Crom polyphosphate Ba sis, used as a non-stick coating. The base layer is advantageously composed as follows (details in Percent by weight): 65-75% Al, 3-5% Cr, 4-6% P, 0.3-0.5% Fe, 0.1-0.2% Si and a residual O. In contrast, there is the cover layer made of 12-15% P, 7-10% Cr, 5-8% Ti, 4-7% Mg, 1-2% Sb, 1-2% Si, 0.3-0.6% Al, 0.3-0.5% Fe and a residual content on O.

It is particularly advantageous that these have already been used for Prevention of corrosion and erosion damage known Materials now also targeted as non-stick coatings tion can be used.

Brief description of the drawing

In the drawing are two embodiments of the invention shown using the axial turbine of an exhaust gas turbocharger.

Show it:

Figure 1 is a partial longitudinal section of an exhaust gas turbocharger.

Figure 2 is a plan view of a nozzle ring with the inventive anti-stick coating, enlarged.

Fig. 3 shows a section through a nozzle ring blade accordingly Fig. 2, shown enlarged;

Fig. 4 is an illustration of the nozzle ring blade corresponding to Fig. 3, but in a second embodiment.

It is only essential for understanding the invention Chen elements shown. For example, is not shown the internal combustion engine.  

Way of carrying out the invention

Fig. 1 shows a turbocharger 1, consisting of a gas turbine from page 2 and page 3 of a compressor. Turbinensei tig 2 , a housing 4 is formed, which consists of a gas inlet and a gas outlet housing 5 , 6 . In the Tur binengehäuse 4 a turbine 7 supported by a shaft 7 turbine 8 with turbine blades 9 and upstream thereof a nozzle ring 10 are arranged. Compressor side 3 , a compression wheel 11 is arranged, which is connected via the shaft 7 to the turbine impeller 8 . In the turbine housing 4 , an exhaust tract 12 designed as a flow channel is arranged, which wel the exhaust gases of an unillustrated, connected to the exhaust gas bolader 1 and designed as a diesel engine and transmits to the turbine impeller 8 white. The flow channel 12 is limited in the region of the turbine impeller 8 by a cover ring 13 to the outside.

FIG. 2 shows a nozzle ring 10, shown on an enlarged scale, consisting of an outer and an inner ring 14 , 15 and between two on ordered nozzle ring blades 16 . An anti-adhesive coating 17 is applied to the inner surface of both the outer and inner rings 14 , 15 and on the nozzle ring blades 16 .

In a first exemplary embodiment, a slurry is first sprayed in several layers onto the inner surface of the nozzle ring 10 in order to produce this layer 17 . The slip has the following composition: 35 percent by weight aluminum powder, 6 percent by weight silicon powder, 12 percent by weight binder salts (dissolved in water) and 47 percent by weight water. Before applying each new layer, the previously sprayed-on layer is cured at about 350 ° C.

Depending on the base material, a final heat treatment is carried out for two hours at 850 to 1000 ° C. Elements diffuse from the base material into layer 17 and vice versa. Because of these diffusion processes, a layer structure results, the elements within the layers having different contents and thus a concentration gradient being present over the entire layer 17 .

The physical composition of the anti-adhesive coating 17 , ie its layer structure, becomes clear in the metallographic cut. There are four zones C to F, which are designed as follows:

• - Zone C is a silicon-rich surface zone, in which be both chromium silicides and other silicides are particularly concentrated. This zone can be patchy but also be completely absent. Your silicon content is 9 to 15 percent.
• - Zone D is below zone C and does not contain mutually penetrating layers of silicide and Aluminum phases. This zone is not always clear from distinguish the other areas.
• - Zone E is below zone D and contains mainly aluminides, but with varying fluctuations sharing of silicide deposits.
• - Zone F is below Zone E and represents one Interface diffusion zone in which due to Diffusion processes and reactions both in the Excretions as well as in the base material can kick.

The chemical components averaged over all zones of the anti-adhesive coating 17 are: aluminum (30 percent by weight), chromium (10 percent by weight), silicon (9 percent by weight), cobalt (8 percent by weight) and nickel (remaining portion). The proportion of chromium, cobalt and nickel as well come from the base material of the coated nozzle ring 10 .

An anti-adhesive coating 17 with a smooth (roughness of approx. 1.5 to 1.8 μm), erosion-resistant surface is thus formed on the nozzle ring 10 , due to the poor wettability of which dirt deposits are reduced. Fig. 3 shows a section through a provided with the non-stick coating 17 nozzle ring bucket 16.

In a second embodiment, a different material is used as the anti-adhesive coating 17 . This is a duplex layer composed of a base layer and a cover layer 18 , 19 . Both layers 18 , 19 are made of a ceramic-bonded material based on chromium-polyphosphate, the base layer 18 additionally containing aluminum powder as a filler. The latter consists of 65-75% Al, 3-5% Cr, 4-6% P, 0.3-0.5% Fe, 0.1-0.2% Si and a remainder containing O, while the Cover layer 19 made of 12-15% P, 7-10% Cr, 5-8% Ti, 4-7% Mg, 1-2% Sb, 1-2% Si, 0.3-0.6% Al, 0 , 3-0.5% Fe and a residual content of O (details in percent by weight). The base layer can optionally contain further additives, such as Ti or Mg.

In Fig. 4 a section through a nozzle ring blade 16 is shown, which is seen with such a, from the base and the top layer 18 , 19 existing non-stick coating 17 ver. To produce this non-stick coating 17 , an aqueous, acidic coating mixture with a pH of 1 to 4.5 is first sprayed onto the nozzle ring 10 . Of course, other application methods are also possible, such as. B. Diving and painting. The coating mixture has the composition shown in the following table:

The water contained in the applied base layer 18 is then expelled in an oven at 40 to 90 ° C. The dry substance contains 20 to 65 percent by weight of filler metal powder as a binder, 2.5 to 22 percent by weight of salts and 2.5 to 50 percent by weight of ceramic components. The dried base layer 18 is then annealed at 300 to 550 ° C for 30 min, the various particles growing together to form a continuous ceramic layer.

The cover layer 19 , which is the same except for the lack of metal powder additives in the base layer 18 , is applied analogously and is subjected to the same heat treatment as this. It is characterized by good penetration and closes the pores of the base layer 18th This creates a heat-resistant, smooth (roughness of about 0.8 microns) and dense non-stick coating 17 , which minimizes the adherence of a hard layer of dirt to the surface of the nozzle ring 10 .

Of course, such an anti-adhesive coating 17 can also be arranged on the turbine blades 9 and / or the cover ring 13 of the turbine rotor 8 . It is also possible to provide the entire flow channel 12 with such a layer 17 .

The use of a corresponding heat-resistant anti-stick coating 17 is of course not limited to use in exhaust gas turbochargers 1 . It can also be used in the exhaust tract of other combustion devices, for example in the waste heat boiler of a combination system, ie on the inner surfaces of the corresponding heat exchangers or on the turbine blades of a gas turbine (not shown).

Reference list

1 turbocharger
2 exhaust gas turbine, exhaust gas turbine side
3 compressors, compressor side
4 housing, turbine housing
5 gas inlet housing
6 gas outlet housing
7 wave
8 turbine impeller
9 turbine blade, component
10 nozzle ring, component
11 compressor wheel
12 Exhaust tract, flow channel
13 Cover ring, component
14 outer ring, from 10
15 inner ring, from 10
16 nozzle ring blade
17 Non-stick coating, layer
18 base layer, layer
19 surface layer, layer

Claims (10)

1. Exhaust tract of a combustion device which can be used in particular for the combustion of heavy oil, at least one component ( 9 , 10 , 13 ) for utilizing the exhaust gas energy of the combustion device being arranged in its exhaust tract ( 12 ), characterized in that on the surface of the at least one Component ( 9 , 10 , 13 ) or at least one of the components ( 9 , 10 , 13 ) and / or on the surface of the exhaust tract ( 12 ) itself an anti-adhesive coating ( 17 ) is arranged. 2. Exhaust tract according to claim 1, characterized in that the non-stick coating ( 17 ) is formed at least on the flow of exhaust gases through the exhaust tract ( 12 ) limiting component ( 10 ). 3. Exhaust tract of a combustion device according to claim 1 or 2, characterized in that

• a) the combustion device is formed as an internal combustion engine connected to a gas turbocharger ( 1 ),
• b) the exhaust-gas turbocharger (1) from a compressor (3) and an exhaust gas turbine (2), the latter a Turbi nengehäuse (4) with a Gaseintritt- and a gas outlet casing (5, 6), a) arranged in the turbine housing (4, from a shaft ( 7 ) supported turbine impeller ( 8 ) with turbine blades ( 9 ), from the gas inlet to the gas outlet housing ( 5 , 6 ) sufficient flow channel ( 12 ) for the exhaust gases of the internal combustion engine and an upstream of the turbine impeller ( 8 ) arranged nozzle ring ( 10 ),
• c) the exhaust tract of the internal combustion engine extends into the flow channel ( 12 ),
• d) the anti-stick coating ( 17 ) is formed on the nozzle ring ( 10 ).

4. Exhaust tract according to claim 3, characterized in that in addition the turbine blades ( 9 ) are provided with an anti-adhesive coating ( 17 ). 5. Exhaust tract according to claim 4, characterized in that the flow channel ( 12 ) in the region of the turbine blades ( 9 ) is limited to the outside by a cover ring ( 13 ) and an anti-adhesive coating ( 17 ) is also formed on the latter. 6. Exhaust tract according to one of claims 1 to 5, characterized in that the anti-adhesive coating ( 17 ) consists of egg ner aluminide silicide compound with the following chemical composition averaged over the entire layer ( 17 ): Al 28th -32%, Cr 8-12%, Si 8-10%, Co 7-9%, residual Ni. 7. Exhaust tract according to claim 6, characterized in that the anti-stick coating ( 17 ) has the following chemical composition: Al 30%, Cr 10%, Si 9%, Co 8%, the rest contains Ni. 8. Exhaust tract according to one of claims 1 to 5, characterized in that the anti-adhesive coating ( 17 ) is constructed as an egg ne consisting of a ceramic-bonded aluminum base layer ( 18 ) and a ceramic cover layer ( 19 ) existing duplex layer, both the base and the top layer ( 18 , 19 ) each have a chrome polyphosphate base. 9. Exhaust tract according to claim 8, characterized in that the base layer ( 18 ) made of 65-75% Al, 3-5% Cr, 4-6% P, 0.3-0.5% Fe, 0.1-0 , 2% Si and a residual content of O and the cover layer ( 19 ) consists of 12-15% P, 7-10% Cr, 5-8% Ti, 4-7% Mg, 1-2% Sb, 1-2 % Si, 0.3-0.6% Al, 0.3-0.5% Fe and a residual content of O is composed. 10. Exhaust tract according to claim 9, characterized in that the base layer ( 18 ) contains additions of Ti or Mg.