COMBUSTION CHAMBER HOT FACE REFRACTORY LINING

Abstract

The present application relates to a refractory lining in a combustion chamber operating in a reducing atmosphere, said lining comprising at least one or more Zirconia (Zr)-based refractory lining members comprising one or more Zr-based parts, wherein the Zr-based parts comprises at least 90 wt. %, preferably at least 95 wt. %, of monoclinic ZrO>.sub.2 and/or partially stabilized ZrO>.sub.2 and/or fully stabilized ZrO>.sub.2, wherein the total content of tetragonal and cubic ZrO>.sub.2 amounts to at least 20 wt. %, preferably more than 35 wt. % as well as Zr based refractory lining members and methods for manufacturing said Zr based refractory lining members.

Claims

1. Shaped and fired zirconia refractory material based on granular stabilized fused zirconia raw material low in silica for the inner lining of a combustion chamber in a vessel in which syngas comprising H.sub.2 and CO is produced under reducing conditions essentially of crystalline zirconia, wherein the fired refractory material comprises a total content of tetragonal and cubic ZrO.sub.2 measured by X-ray powder diffraction analysis of at least 20% by weight, wherein the Al.sub.2O.sub.3 content is 0.05-6% by weight, and wherein the SiO.sub.2 content of bonding phase of the material is below 1.5% by weight.

2. Shaped and fired refractory zirconia material according to claim 1, wherein the fused zirconia raw material is stabilized by Y.sub.2O.sub.3, MgO, CaO, CeO.sub.2 or mixtures thereof.

3. Shaped and fired zirconia refractory material according to the claim 1, wherein the zirconia refractory material is shaped in form of a coating layer on an Al.sub.2O.sub.3-based refractory material.

4. Shaped and fired zirconia refractory material according to claim 3, wherein the coating layer has a thickness of at least 100 m.

5. Shaped and fired zirconia refractory material according to claim 3, wherein the average grain size of the raw material is 2.5 m to 50 m.

6. Shaped and fired zirconia refractory material according to claim 1, wherein the refractory material is shaped in form of a brick.

7. Shaped and fired zirconia refractory material according to claim 6, wherein the brick has a bulk density of 3.80 g/cm.sup.3-5.40 g/cm.sup.3.

8. Use of the shaped and fired zirconia refractory material according to claim 1, for installing at least a part of an inner refractory lining of a combustion chamber of a vessel for producing H.sub.2 and CO rich syngas under reducing atmosphere at temperatures above 1000 C. and pressures above 20 bar, wherein the outlet temperature of the vessel is below 1100 C.

9. A combustion chamber operating in a reducing atmosphere comprising a refractory lining, wherein the refractory lining comprises a shaped and fired zirconia refractory material according to claim 1.

10. A combustion chamber operating in a reducing atmosphere according to claim 9, wherein the shaped and fired zirconia refractory material has a thickness of 100 m 250 mm.

11. A combustion chamber operating in a reducing atmosphere, according to claim 9, wherein the shaped and fired zirconia refractory material forms at least part of a combustion chamber refractory lining including at least part of the inner hot face wall lining and/or partition to downstream.

12-15. (canceled)

16. A method for manufacturing a shaped and fired zirconia refractory material comprising the steps of: shaping a mixture based on granular stabilized fused zirconia raw material low in silica into a shape, firing at temperature above 1400 C., thereby achieving a shaped and fired zirconia refractory material comprising a total content of tetragonal and cubic ZrO.sub.2 measured by X-ray powder diffraction analysis of at least 20% by weight, and wherein the Al.sub.2O.sub.3 content is 0.05-6% by weight, and the SiO.sub.2 content of bonding phase of the material is below 1.5% by weight.

17. (canceled)

18. A method for producing a shaped and fired zirconia refractory material shaped in form of coating layer on an alumina based refractory material, the method comprising the steps of: a) providing a shaped refractory of an Al.sub.2O.sub.3-based refractory material, optionally with a corresponding cleaning of the surface to be coated, b) applying a powder dispersion comprising granular stabilized fused ZrO.sub.2 raw material powder in form of a conditioned carrier fluid onto at least one surfaces of the shaped Al.sub.2O.sub.3 based refractory material, and c) drying the applied power dispersion followed by a thermal treatment at a temperature above 1200 C., thereby obtaining a bonded coating, the bonded coating layer comprises a total content of tetragonal and cubic ZrO.sub.2 measured by X-ray powder diffraction analysis of at least 20% by weight, and wherein the Al.sub.2O.sub.3 content is 0.05-6% by weight, and wherein the SiO.sub.2 content of bonding phase of the material is below 1.5% by weight.

19. (canceled)

20. A method for producing shaped and fired zirconia refractory material in form of coating layer according to claim 18, wherein the powder dispersion is applied by way of techniques within the group: spraying, painting, dipping and casting,

21. The method of claim 18, wherein the powder dispersion has a viscosity of 2000-6000 mPa's.

22. The method according to claim 18, wherein the powder dispersion comprising the stabilized fused ZrO2 raw material powder, presents an average grain size in the range of approximately 2.5 m to 50 m.

23-24. (canceled)

25. The method according to claim 9, wherein the powder dispersion is applied one or more times resulting in a bonded coating having a thickness of at least 100 m is obtained.

26. Process for in situ formation of a shaped and fired zirconia refractory material in form of coating layer supported on at least one base refractory material, wherein the fired refractory material comprises a total content of tetragonal and cubic ZrO.sub.2 measured by X-ray powder diffraction analysis of at least 20% by weight, wherein the Al.sub.2O.sub.3 content is 0.05-6% by weight and wherein the SiO.sub.2 content of bonding phase of the material is below 1.5% by weight, the method comprising the steps of, applying one or more layers of a powder or powder mixture dispersion comprising a powder or a powder mixture based on stabilized fused ZrO.sub.2, optionally admixed powdered Al.sub.2O.sub.3, wherein the mineralogical composition of the powder or a powder mixture based on stabilized fused ZrO.sub.2 is calculated in such a manner that, the mineralogical composition of the bonded coating is obtained after a thermal treatment, in a first heating step, heating to a first temperature, at a first pressure thereby forming a adhered coating, and in as second heating step, heating to a temperature above 1000 C. at a second pressure, thereby obtaining the bonded coating layer.

27. The process of claim 18, wherein the SiO.sub.2-content in the bonding phase of the coating layer is below 2.0 wt. %, and/or wherein the coating layer comprises 0.05-6 wt. % of Al.sub.2O.sub.3.

28. The process according to claim 18, wherein the at least one base refractory material comprises aluminum oxides and/or aluminum oxide based ceramic materials.

29. The process according to claim 18, wherein the first temperature is at least 200-300 C. and the first pressure is 1-20 bar.

30. The process according to claim 18, wherein the second pressure is at least 10 bar.

31. The process according to claim 18, wherein the atmosphere in the first heating step comprises an inert gas.

32. The process according to claim 18, wherein the atmosphere in the second heating step comprises hydrogen and carbon monoxide or a hydrocarbon containing gas or a hydrocarbon containing gas containing steam.

33. The process according to claim 18, wherein a refractory lining in a combustion chamber for producing H.sub.2 and CO containing syngas is formed.

Description

EXAMPLES AND FIGURES

[0059] The object of the invention is described in greater detail in the accompanying drawings and following examples without thereby limiting the object of the invention. Examples and figure are not to be construed as limiting to the invention.

Example 1

[0060] FIG. 1 is a cross-sectional electro microscopic image showing the structure of a zirconia based refractory lining member in form of a coating on a Al.sub.2O.sub.3 based refractory material according to the invention (89 times enlarged). The fine-grained crack-free coating is approximately 250 m to 300 m thick and firmly bonded to the coarse-grained alumina refractory.

[0061] A conditioned powder dispersion having a consistency similar to house-paints was applied in a layer of a thickness of approximately 500 m by way of spraying onto an untreated surface (approximately 230 mm114 mm) of an alumina refractory brick (Al.sub.2O.sub.3-content approximately 99.6 wt. %). The average grain size of the partially stabilized fused ZrO.sub.2-powder used was 11.75 m (laser diffraction), and the solids content of the powder dispersion was 68 wt. %. The coated and dried brick was thermal treated at a temperature well above 1200 C. Due to the drying and in particular the thermal treatment, the coating was compacted to a total thickness of approximately 250 m, which is in an advantageous matter accompanied with the formation of a very high strength, an excellent connection of the coating onto the alumina substrate.

[0062] Determined by X-ray powder diffraction, the macroscopic crack-free coating had a total content of tetragonal and cubic ZrO.sub.2 of 46 wt. %, the measured silica content was 0.20 wt. % and the alumina-content was 3.30 wt. %.

[0063] For further tests, coated specimens of approximately 65 mm45 mm20 mm were taken out of the sample, which represents 65 mm45 mm of the hot face surface. A specimen was heated to a temperature of approximately 950 C. and subsequently quenched in cold water. Even after four further cycles of rapid temperature changes (heating and water quenching), no macroscopically detectable formation of cracks was found. A second specimen was treated five times by thermal cycling within a temperature range from room temperature to approximately 1400 C. The heating and cooling rates were approximately 100 C./h, as above without detectable damages. No detachment of the coating was observed after repeated cycles of rapid temperature changes i.e. it was found that the coating was bonded to the substrate.

Examples 2 and 3

[0064] In preparing shaped Zr based refractory lining members two different prepared batch compositions were shaped to bricks having a thickness of about 100 mm and a weight of about 10-15 kg, whereby uniaxial pressing procedure was used (about 80 MPa pressing pressure). After appropriate drying, the bricks were then fired at 1720 C. The raw-material batch composition of example no. 2 was adjusted to reach a total content of tetragonal and cubic ZrO.sub.2 after firing of about 90 wt. %, whereby fully stabilized fused ZrO.sub.2 was used as raw-material basis. Accordingly, the composition of the Example No. 3 was calculated to reach a total content of tetragonal and cubic ZrO.sub.2 after firing of below 20 wt. % by using a blend of monoclinic and partially stabilized fused ZrO.sub.2. The grain size used in Example No. 2 and 3 was 0-2.5 mm, whereby the grading fraction of less than 63 m had an amount of approx. 25 wt.-%.

[0065] After firing, the properties of a brick of Example No. 2 were as follows: bulk density of 4.60 g/cm.sup.3, cold crushing strength of 70 MPa, SiO.sub.2-content of 0.10 wt. %, Al.sub.2O.sub.3-content of 0.31 wt. %, and 87 wt. % of total content of tetragonal and cubic ZrO.sub.2; no macroscopically detectable formation of cracks were found. A brick sample was also treated five times by thermal cycling within a temperature range from room to approximately 1400 C. without macroscopically detectable crack formation. The heating and cooling rates were about 100 C./h.

[0066] Bricks of Example no. 3 showed strong cracking already after the production-firing. The measured total content of tetragonal and cubic ZrO.sub.2 was 17 wt. % (SiO.sub.2-content of 0.40 wt. %, Al.sub.2O.sub.3-content of 0.20 wt. %).

[0067] The improved performance of Zirconia based refractory lining members according to the present invention, both the coated and the brick (shaped refractory) embodiment, were successfully demonstrated in the combustion chamber of a vessel for industrial production of syngas using the catalytic process. During demonstration the material was subjected to thermal cycling repeatedly. The demonstrated zirconia materials showed themselves to be superior to conventional alumina bricks. An up to 85% reduction of the material volatilization was found and the material retained its structural integrity and stability post operation.

[0068] FIGS. 2a and 2b show a combustion chamber in a gasification reactor which may form an integral part of the synthesis gas generation section of plants for production of chemicals such as methanol, ammonia and synthetic fuels. The feed is introduced at the top of the gasification unit through line (1) and converted to H.sub.2 and CO in the combustion chamber (b) by the burner (a) with air or oxygen introduced through line (2). The synthesis gas product leaves the reformer through an outlet channel line (3). The combustion chamber (b) is enclosed by combustion chamber lining comprising wall tiles (c) and a partitioning channel (d) and/or partitioning layer (d) to downstream sections. In FIG. 2b the partitioning to downstream section is in form of a permeable refractory material layer of a hold-down material (d) placed on the top of a fixed bed of catalyst pellets (e) separating the combustion chamber from the underneath situated catalyst bed. The uppermost surface of the partitioning (d) act as the bottom lining of the combustion chamber. The burner (a) can be a generic shower head burner, but often more complex burners including high degrees of swirl are used. Such burners generate high flow velocities, which can be high enough to move the catalyst pellets. Such movement leads to ball milling of the catalyst resulting in degradation of the catalyst pellets and fouling of the bed with the dust produced. Therefore, to prevent this, the top of the bed is covered with a layer of large pieces of a refractory hold-down material, typically manufactured from a high alumina material, either as a hydraulic presses or a castable refractory material. These materials are much larger than the catalyst pellets and are not affected by the gas movement.

[0069] FIGS. 3a and 3b show to embodiments of Zr based refractory members 4 according to the present invention. In FIG. 3a the Zr based refractory member consists of a single Zr based part 5 only. I.e. the Zr based refractory member is shaped refractory in form of a solid brick. In 3b the Zr based refractory member comprise a Zr based part 5 in form of a coating on a shaped refractory 7 such as an alumina based refractory. A refractory lining according to the present invention may comprise solid bricks (shaped refractories) as shown in 3a and/or coated bricks as shown in FIG. 3b.