WO2013032065A1 - Low cement corrosion-resistive unshaped refractories - Google Patents
Low cement corrosion-resistive unshaped refractories Download PDFInfo
- Publication number
- WO2013032065A1 WO2013032065A1 PCT/KR2011/008188 KR2011008188W WO2013032065A1 WO 2013032065 A1 WO2013032065 A1 WO 2013032065A1 KR 2011008188 W KR2011008188 W KR 2011008188W WO 2013032065 A1 WO2013032065 A1 WO 2013032065A1
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- WIPO (PCT)
- Prior art keywords
- alumina
- refractory
- cement
- zircon
- unshaped
- Prior art date
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- 239000004568 cement Substances 0.000 title claims abstract description 51
- 239000011819 refractory material Substances 0.000 title description 15
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 75
- 239000000203 mixture Substances 0.000 claims abstract description 38
- 229910052845 zircon Inorganic materials 0.000 claims abstract description 30
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000011230 binding agent Substances 0.000 claims abstract description 21
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 13
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052593 corundum Inorganic materials 0.000 claims abstract description 5
- 229910001845 yogo sapphire Inorganic materials 0.000 claims abstract 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 8
- 239000000395 magnesium oxide Substances 0.000 claims description 7
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 5
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 4
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 claims description 3
- 229910000449 hafnium oxide Inorganic materials 0.000 claims description 2
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 claims description 2
- 229910052596 spinel Inorganic materials 0.000 claims description 2
- 239000011029 spinel Substances 0.000 claims description 2
- 238000005260 corrosion Methods 0.000 abstract description 20
- 230000007797 corrosion Effects 0.000 abstract description 20
- 239000002893 slag Substances 0.000 abstract description 18
- 238000001035 drying Methods 0.000 abstract description 8
- 238000010438 heat treatment Methods 0.000 abstract description 5
- 239000000843 powder Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 238000005452 bending Methods 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 239000000654 additive Substances 0.000 description 6
- 239000002270 dispersing agent Substances 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 5
- 230000035515 penetration Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 2
- 239000011449 brick Substances 0.000 description 2
- XFWJKVMFIVXPKK-UHFFFAOYSA-N calcium;oxido(oxo)alumane Chemical compound [Ca+2].[O-][Al]=O.[O-][Al]=O XFWJKVMFIVXPKK-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 239000010431 corundum Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 108010025899 gelatin film Proteins 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- CJNBYAVZURUTKZ-UHFFFAOYSA-N hafnium(IV) oxide Inorganic materials O=[Hf]=O CJNBYAVZURUTKZ-UHFFFAOYSA-N 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000003317 industrial substance Substances 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000013001 point bending Methods 0.000 description 1
- 229920005646 polycarboxylate Polymers 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
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- C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
- C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
- C04B2235/6565—Cooling rate
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/74—Physical characteristics
- C04B2235/77—Density
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B2235/9669—Resistance against chemicals, e.g. against molten glass or molten salts
- C04B2235/9684—Oxidation resistance
Definitions
- the present invention relates to an unshaped refractory containing zircon, cement and an alumina binder that can be used in the lining of a gasifier.
- Unshaped refractories are preferred to refractory bricks having the problem of gaps between the bricks, and improvements are made in terms of lifespan, material and construction method.
- calcium aluminate cement has been predominantly used as inorganic binder, low-calcium aluminate cement is preferred as the operation environment becomes harsher (e.g., higher temperature and pressure).
- hydratable alumina with a trace amount of calcium is used in unshaped refractories in order to improve resistance to thermal wear and corrosion.
- this refractory has low strength (1.2-2.0 MPa) at 800-1200 oC where dehydration occurs and binding between ceramics disappear.
- a gasifier used in the integrated gasification combined cycle (IGCC) technology which is valued highly as an ecofriendly power generation system recently, is operated under harsh environments. Since a stainless steel pipe through which cooling water flows is attached to an unshaped refractory used in the lining of the gasifier, the unshaped refractory should allow good attachment of the stainless steel pipe, have good thermal conductivity, and allow easy formation of a slag layer initially.
- the unshaped refractory is made of oxide, carbide or a mixture thereof as a refractory as well as alumina cement as a binder.
- the as-pressed refractory has a low density and is difficult to handle and the control of drying time is difficult, although resistance to slag corrosion and penetration is improved. It is because calcium oxide (CaO) included in the cement reacts at high temperature with the slag, allowing the slag easily penetrate into the refractory by decreasing viscosity. Further, since evaporation of water from the cement occurs slowly, sufficient drying is necessary at room temperature.
- CaO calcium oxide
- phosphate-based unshaped refractories are used. For example, one using monoaluminum phosphate as a binder and magnesium oxide (MgO) as a hardening agent is used for a combustion furnace.
- hydratable alumina is used as an inorganic binder.
- Commercially available ones include AlphaBond 300 and 500 of Alcoa Industrial Chemicals.
- the refractory including the hydratable alumina binder requires a long mixing time.
- bending strength at room temperature is only 5-17 MPa.
- the unshaped refractory includes 7-10 wt% of ultrafine reactive alumina and at least 20 wt% of fine particulate powder including silica in addition to aggregate in order to improve flowability.
- the existing refractories are unsuited for use in the high-temperature, high-pressure environment of the gasifier because of the problems of adhesivity, thermal conductivity, drying time, corrosion resistance, etc. , as well as strength.
- the inventors of the present invention have studied for a refractory that can be used under the harsh environment of high temperature and pressure of a gasifier, and developed a refractory having superior adhesivity, strength, thermal conductivity and corrosion resistance.
- the present invention is directed to providing an unshaped refractory including a refractory mixture of alumina (Al 2 O 3 ) and silicon carbide (SiC) to which one or more of alumina cement, zircon and an alumina binder is added.
- alumina Al 2 O 3
- SiC silicon carbide
- the present invention provides an unshaped refractory including a refractory mixture of alumina (Al 2 O 3 ) and silicon carbide (SiC) to which one or more of alumina cement, zircon and an alumina binder is added.
- alumina Al 2 O 3
- SiC silicon carbide
- a small amount of the cement and alumina binder provides working flowability to the refractory mixture, and a small amount of the zircon significantly prevents corrosion by the calcium oxide (CaO) included in the cement in an amount of about 20%. Since the refractory of the present invention maintains shape after drying, has sufficient strength for handling, exhibits little shrinkage after heat treatment and shows low porosity, it is particularly suited for use in the gasifier.
- the alumina binder is mixed with the fine particulate alumina and coats the surface of the refractory like glue, improving contact between the refractories and facilitating evaporation of water as the sol transforms into gel.
- the alumina gel film formed from the small amount of alumina binder prevents cracking during drying even when the heating speed is fast and facilitates sintering of the fine particulate alumina powder, thereby proving high strength resulting from ceramic binding between the refractories.
- Fig. 1 shows a cross-sectional photographic image of a refractory sample of Comparative Example 1 comprising only an alumina binder after slag corrosion test.
- Fig. 2 shows a cross-sectional photographic image of a refractory sample of Example 6 comprising 2 wt% of zircon, 3 wt% of cement and an alumina binder after slag corrosion test.
- Fig. 3 shows a cross-sectional photographic image of a refractory sample of Comparative Example 2 comprising 3 wt% of alumina cement after slag corrosion test.
- the present invention provides an unshaped refractory comprising a refractory mixture of alumina (Al 2 O 3 ) and silicon carbide (SiC) to which alumina cement, zircon, an alumina binder or a mixture thereof is added.
- alumina Al 2 O 3
- SiC silicon carbide
- magnesium oxide, spinel, zirconia, chromia, hafnium oxide or a mixture thereof is further added to the refractory mixture of alumina (Al 2 O 3 ) and silicon carbide (SiC).
- the alumina binder is included in an amount of 0.5-4 parts by weight based on alumina per 100 parts by weight of the total unshaped refractory comprising alumina (Al 2 O 3 ) and silicon carbide (SiC).
- the alumina cement comprises 10-30 wt% of calcium oxide (CaO).
- the alumina cement is added in an amount of 0.5-5 wt% based on the total weight of the unshaped refractory.
- the zircon is added in an amount of 1-5 wt% based on the total weight of the unshaped refractory.
- a hydratable alumina binder is used for the refractory lining which cannot endure even a small amount of calcium oxide (CaO).
- Calcium oxide (CaO) is included in an amount less than 0.1 wt% in Alphabond 300 and in an amount of about 0.6 wt% in Alphabond 500, which are the products of Almatis. And, since it is included in an amount of about 3 wt% in castables, the calcium oxide (CaO) is present in the refractory as impurity levels.
- fine particulate dead-burned magnesia is used instead of calcium aluminate cement to improve resistance to slag corrosion.
- FIG. 1 shows a result of corrosion test for a refractory prepared by adding only an alumina binder to the refractory mixture composition D, using Usibelli slag with low viscosity under a reducing condition of 20% CO/N 2 at 1550 oC/4 hr. It can be seen that penetration hardly occurred. In contrast, complete penetration was observed for a refractory prepared by adding 3 wt% of alumina cement (Fig. 3). The penetration was about 2 mm for a refractory prepared by adding 3 wt% of alumina cement and 2 wt% of zircon (Fig. 2). This confirms that zircon greatly improves corrosion resistance.
- the fine particulate powder is added to improve the flowability of the unshaped refractory.
- the powder is sintered at heat treatment and thus improves strength.
- ultrafine particulate ⁇ -alumina powder is used in an amount of 10 wt%.
- the possibility of replacing the expensive ultrafine particulate alumina powder with cement was investigated.
- the refractory composition B to which a small amount (3 ⁇ 5 wt%) of cement was added without the ultrafine particulate powder showed strength of about 25 MPa and density.
- the composition M wherein only part of the ultrafine particulate powder was replaced with cement showed a high bending strength of about 40 MPa.
- the addition amount of cement is specifically 5 wt% or less, more specifically 3 wt%.
- PCE polycarboxylate ether
- BASF VP65
- alumina cement [3 wt% of cement comprising 0.6 wt% of calcium oxide (CaO)] can be used instead of the expensive ultrafine particulate alumina for a refractory which can endure a small amount of calcium oxide (CaO). And, it was also confirmed that, for a refractory which cannot endure even a small amount of calcium oxide (CaO), slag penetration can be greatly suppressed by adding a small amount of zircon.
- composition of a cement comprising about 80 wt% of alumina used according to the present invention is described in Table 1, and the compositions of refractory mixtures according to the present invention are described in Table 2.
- Composition (wt%) A B D M G Al 2 O 3 3-5 mm 7 7 0 0 15 SiC (average particle size) 0.3 ⁇ m 7.6 0 7.6 4 0 1.25 mm 38 38 45 40 30 750 ⁇ m 23 23 23 20 15 90 ⁇ m 3 3 3 10 7.4 20 ⁇ m 20 20 20 20 5 ⁇ m 1.4 1.4 1.4 6 5 Sum (%) 100 92.4 100 100 92.4 Boehmite (%) 0 0 3 3 3 3 3
- the refractory mixture composition A was mixed with cement and zircon with various amounts, put in a 120 x ( ⁇ 15) x 20 mm stainless steel mold, and formed into an unshaped refractory by tapping on an electric vibration table. After drying at room temperature followed by drying at 60 oC and then at 100 oC for over 6 hours, respectively, the refractory was heated in the air at 5 oC/min to 1350 oC, kept at that temperature for 3 hours, and then cooled down at a rate of 5 oC/min. The sample was subjected to 3-point bending strength measurement with an outer span of 35 mm. Density was measured by the Archimedes’ method in boiling water. The characteristics of the refractories depending on the additives are shown in Table 3.
- Table 3 shows the characteristics of the refractories prepared from the refractory mixture composition A.
- 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
- Table 4 shows the characteristics of the refractories prepared from the refractory mixture composition B in the same manner as in Example 1.
- 0Z0CA3B means 0 wt% zircon/0 wt% cement/3 wt% alumina sol (10wt%).
- Table 5 shows the characteristics of the refractories prepared from the refractory mixture composition D in the same manner as in Example 1.
- 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
- Table 6 shows the characteristics of the refractories prepared from the refractory mixture composition M in the same manner as in Example 1.
- 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
- Table 7 shows the characteristics of the refractories prepared from the refractory mixture composition G in the same manner as in Example 1.
- 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
- Slag corrosion test was performed using Usibelli slag under the condition of 20% CO/N 2 atmosphere at 1550 oC/4 hr.
- a castable comprising the refractory mixture composition D as well as 2 wt% of zircon and 3 wt% of cement was formed into a shape of a cup with an outer diameter of 60 mm and an inner diameter of 30 mm.
- heat treatment was performed as described in Example 1 to prepare a refractory sample D-4. After adding 35 g of slag powder over 2 hours while keeping temperature at 1550 oC and maintaining the temperature for additional 2 hours, the sample was furnace cooled and the cross-section of the sample was observed (Fig. 2).
- a refractory sample D-2 was prepared in the same manner as Example 7 by adding only alumina sol without addition of zircon or cement to the refractory mixture composition D. Slag corrosion test result is shown in Fig. 1.
- a refractory sample D-5 was prepared in the same manner as Example 7 by adding only 3 wt% of cement to the refractory mixture composition D. Slag corrosion test result is shown in Fig. 3.
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Abstract
Disclosed is an unshaped refractory containing a refractory mixture of alumina (Al2O3)<sub/>and silicon carbide (SiC) to which alumina cement, zircon and an alumina binder are added. The refractory exhibits high strength and density as well as significantly improved corrosion resistance, which is due to the reaction of zircon with calcium oxide (CaO), greatly suppressing corrosion by slag. Use of the alumina binder provides fast drying and strength sufficient for handling. Since shrinkage hardly occurs after heat treatment and low porosity and high strength can be obtained, the refractory is very suitable for use, in particular, a gasifier.
Description
The present invention relates to an unshaped refractory containing zircon, cement and an alumina binder that can be used in the lining of a gasifier.
Unshaped refractories are preferred to refractory bricks having the problem of gaps between the bricks, and improvements are made in terms of lifespan, material and construction method. Although calcium aluminate cement has been predominantly used as inorganic binder, low-calcium aluminate cement is preferred as the operation environment becomes harsher (e.g., higher temperature and pressure). Recently, hydratable alumina with a trace amount of calcium is used in unshaped refractories in order to improve resistance to thermal wear and corrosion. However, this refractory has low strength (1.2-2.0 MPa) at 800-1200 ºC where dehydration occurs and binding between ceramics disappear.
A gasifier used in the integrated gasification combined cycle (IGCC) technology, which is valued highly as an ecofriendly power generation system recently, is operated under harsh environments. Since a stainless steel pipe through which cooling water flows is attached to an unshaped refractory used in the lining of the gasifier, the unshaped refractory should allow good attachment of the stainless steel pipe, have good thermal conductivity, and allow easy formation of a slag layer initially. In general, the unshaped refractory is made of oxide, carbide or a mixture thereof as a refractory as well as alumina cement as a binder. When the cement is used in a small amount, the as-pressed refractory has a low density and is difficult to handle and the control of drying time is difficult, although resistance to slag corrosion and penetration is improved. It is because calcium oxide (CaO) included in the cement reacts at high temperature with the slag, allowing the slag easily penetrate into the refractory by decreasing viscosity. Further, since evaporation of water from the cement occurs slowly, sufficient drying is necessary at room temperature. As an alternative to the cement-based refractories, phosphate-based unshaped refractories are used. For example, one using monoaluminum phosphate as a binder and magnesium oxide (MgO) as a hardening agent is used for a combustion furnace. But, it is not suited for the gasifier where oxygen is insufficient. Since low melting point compounds are formed in the P2O5-MgO system and the water-soluble monoaluminum phosphate migrates to the surface, the strength may become nonuniform. Further, P2O5 evaporates under high-temperature reducing environment, resulting in decreased and nonuniform strength. Recently, hydratable alumina is used as an inorganic binder. Commercially available ones include AlphaBond 300 and 500 of Alcoa Industrial Chemicals. The refractory including the hydratable alumina binder requires a long mixing time. Also, although use of finely particulate silica and colloidal alumina with alumina cement is reported, bending strength at room temperature is only 5-17 MPa. Further, the unshaped refractory includes 7-10 wt% of ultrafine reactive alumina and at least 20 wt% of fine particulate powder including silica in addition to aggregate in order to improve flowability.
As described, the existing refractories are unsuited for use in the high-temperature, high-pressure environment of the gasifier because of the problems of adhesivity, thermal conductivity, drying time, corrosion resistance, etc. , as well as strength.
The inventors of the present invention have studied for a refractory that can be used under the harsh environment of high temperature and pressure of a gasifier, and developed a refractory having superior adhesivity, strength, thermal conductivity and corrosion resistance.
The present invention is directed to providing an unshaped refractory including a refractory mixture of alumina (Al2O3) and silicon carbide (SiC) to which one or more of alumina cement, zircon and an alumina binder is added.
In one general aspect, the present invention provides an unshaped refractory including a refractory mixture of alumina (Al2O3) and silicon carbide (SiC) to which one or more of alumina cement, zircon and an alumina binder is added.
Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.
In the refractory of the present invention, a small amount of the cement and alumina binder provides working flowability to the refractory mixture, and a small amount of the zircon significantly prevents corrosion by the calcium oxide (CaO) included in the cement in an amount of about 20%. Since the refractory of the present invention maintains shape after drying, has sufficient strength for handling, exhibits little shrinkage after heat treatment and shows low porosity, it is particularly suited for use in the gasifier. The alumina binder is mixed with the fine particulate alumina and coats the surface of the refractory like glue, improving contact between the refractories and facilitating evaporation of water as the sol transforms into gel. Further, the alumina gel film formed from the small amount of alumina binder prevents cracking during drying even when the heating speed is fast and facilitates sintering of the fine particulate alumina powder, thereby proving high strength resulting from ceramic binding between the refractories.
Fig. 1 shows a cross-sectional photographic image of a refractory sample of Comparative Example 1 comprising only an alumina binder after slag corrosion test.
Fig. 2 shows a cross-sectional photographic image of a refractory sample of Example 6 comprising 2 wt% of zircon, 3 wt% of cement and an alumina binder after slag corrosion test.
Fig. 3 shows a cross-sectional photographic image of a refractory sample of Comparative Example 2 comprising 3 wt% of alumina cement after slag corrosion test.
Hereinafter, the embodiments of the present invention will be described in detail with reference to accompanying drawings.
The present invention provides an unshaped refractory comprising a refractory mixture of alumina (Al2O3) and silicon carbide (SiC) to which alumina cement, zircon, an alumina binder or a mixture thereof is added.
In an exemplary embodiment of the present invention, magnesium oxide, spinel, zirconia, chromia, hafnium oxide or a mixture thereof is further added to the refractory mixture of alumina (Al2O3) and silicon carbide (SiC).
In an exemplary embodiment of the present invention, the alumina binder is included in an amount of 0.5-4 parts by weight based on alumina per 100 parts by weight of the total unshaped refractory comprising alumina (Al2O3) and silicon carbide (SiC).
In an exemplary embodiment of the present invention, the alumina cement comprises 10-30 wt% of calcium oxide (CaO).
In an exemplary embodiment of the present invention, the alumina cement is added in an amount of 0.5-5 wt% based on the total weight of the unshaped refractory.
In an exemplary embodiment of the present invention, the zircon is added in an amount of 1-5 wt% based on the total weight of the unshaped refractory.
Since cement is associated with severe slag corrosion, a hydratable alumina binder is used for the refractory lining which cannot endure even a small amount of calcium oxide (CaO). Calcium oxide (CaO) is included in an amount less than 0.1 wt% in Alphabond 300 and in an amount of about 0.6 wt% in Alphabond 500, which are the products of Almatis. And, since it is included in an amount of about 3 wt% in castables, the calcium oxide (CaO) is present in the refractory as impurity levels. In US Patent No. 5,972,102 (1999), fine particulate dead-burned magnesia is used instead of calcium aluminate cement to improve resistance to slag corrosion. By adding a compound that can improve corrosion resistance by reacting with calcium oxide (CaO), it will be possible to reduce the use amount of cement. In the pressurized pulverized coal combustion (PPCC) combined cycle, a flue gas is passed through a column packed with ceramic balls before entering the gas turbine and the steam cycle and a purification process of slag separation and removal of alkali metals follows. At present, chromium oxide (Cr2O3) ceramic, which is stable against slag by forming the (Cr,Al)2O3 corundum phases, is used. It is reported that HfO2 or ZrSiO4 (zircon) has superior corrosion resistance although inferior to the Cr2O3 ceramic (J. Eur. Ceram. Soc. 29 (2009) 2721-2725). By using a small amount of the zircon together with the alumina cement, resistance to slag corrosion could be improved. Fig. 1 shows a result of corrosion test for a refractory prepared by adding only an alumina binder to the refractory mixture composition D, using Usibelli slag with low viscosity under a reducing condition of 20% CO/N2 at 1550 ºC/4 hr. It can be seen that penetration hardly occurred. In contrast, complete penetration was observed for a refractory prepared by adding 3 wt% of alumina cement (Fig. 3). The penetration was about 2 mm for a refractory prepared by adding 3 wt% of alumina cement and 2 wt% of zircon (Fig. 2). This confirms that zircon greatly improves corrosion resistance.
The fine particulate powder is added to improve the flowability of the unshaped refractory. The powder is sintered at heat treatment and thus improves strength. In general, ultrafine particulate α-alumina powder is used in an amount of 10 wt%. The possibility of replacing the expensive ultrafine particulate alumina powder with cement was investigated. The refractory composition B to which a small amount (3~5 wt%) of cement was added without the ultrafine particulate powder showed strength of about 25 MPa and density. In contrast, the composition M wherein only part of the ultrafine particulate powder was replaced with cement showed a high bending strength of about 40 MPa.
The addition amount of cement is specifically 5 wt% or less, more specifically 3 wt%.
For the dispersing agent, polycarboxylate ether (PCE)-based SF60 and VP65 (BASF) were used.
It was confirmed that a small amount of alumina cement [3 wt% of cement comprising 0.6 wt% of calcium oxide (CaO)] can be used instead of the expensive ultrafine particulate alumina for a refractory which can endure a small amount of calcium oxide (CaO). And, it was also confirmed that, for a refractory which cannot endure even a small amount of calcium oxide (CaO), slag penetration can be greatly suppressed by adding a small amount of zircon.
The examples and experiments will now be described. The following examples and experiments are for illustrative purposes only and not intended to limit the scope of the present invention.
The composition of a cement comprising about 80 wt% of alumina used according to the present invention is described in Table 1, and the compositions of refractory mixtures according to the present invention are described in Table 2.
CaO | Al2O3 | SiO2 | TiO2 | Fe2O3 | Na2O | MgO | > 38 μm |
17-18.5 | 79-81 | 0.1-0.3 | - | 0.02-0.1 | 0.2-0.4 | 0.1-0.4 | 18-22 |
Composition (wt%) | A | B | D | M | G | |
Al2O3 | 3-5 mm | 7 | 7 | 0 | 0 | 15 |
SiC (average particle size) | 0.3 μm | 7.6 | 0 | 7.6 | 4 | 0 |
1.25 mm | 38 | 38 | 45 | 40 | 30 | |
750 μm | 23 | 23 | 23 | 20 | 15 | |
90 μm | 3 | 3 | 3 | 10 | 7.4 | |
20 μm | 20 | 20 | 20 | 20 | 20 | |
5 μm | 1.4 | 1.4 | 1.4 | 6 | 5 | |
Sum (%) | 100 | 92.4 | 100 | 100 | 92.4 | |
Boehmite (%) | 0 | 0 | 3 | 3 | 3 |
Example 1
The refractory mixture composition A was mixed with cement and zircon with various amounts, put in a 120 x (~15) x 20 mm stainless steel mold, and formed into an unshaped refractory by tapping on an electric vibration table. After drying at room temperature followed by drying at 60 ºC and then at 100 ºC for over 6 hours, respectively, the refractory was heated in the air at 5 ºC/min to 1350 ºC, kept at that temperature for 3 hours, and then cooled down at a rate of 5 ºC/min. The sample was subjected to 3-point bending strength measurement with an outer span of 35 mm. Density was measured by the Archimedes’ method in boiling water. The characteristics of the refractories depending on the additives are shown in Table 3.
Table 3 shows the characteristics of the refractories prepared from the refractory mixture composition A.
Sample | Additives (wt%; 10 wt% B)* | Dispersing agent (SF60, wt%) | Water (wt%) | Density (g/cm3) | Bending strength (MPa) |
A-1 | 0Z0CA3B | 0.3 | 5.4 | 2.61 | 22 |
A-2 | 0Z0CA6B | 0 | 0 | 2.63 | 32 |
A-3 | 0Z0CA8.3B | 0 | 0 | 2.64 | 33 |
A-4 | 0Z1CA1.8B | 0 | 4.3 | 2.64 | 28 |
A-5 | 1Z1CA5.3B | 0 | 3.6 | 2.63 | 29 |
A-6 | 3CA 0B | 0.2 | 6 | 2.76 | 17 |
A-7 | 3CA6.4B | 0 | 3.6 | 2.68 | 41 |
A-8 | 5Z3CA6.2B | 0 | 3.9 | 2.63 | 35 |
A-9 | 5Z10CA0B | VP0.2 | 7.3 | 2.67 | 24 |
* Z: zircon, CA: alumina cement, B: alumina sol (10 wt%)
For example, 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
Example 2
Table 4 shows the characteristics of the refractories prepared from the refractory mixture composition B in the same manner as in Example 1.
Sample | Additives (wt%; 10 wt% B)* | Dispersing agent (SF60, wt%) | Water (wt%) | Density (g/cm3) | Bending strength (MPa) |
B-1 | 0CA3.8B | 0 | 0 | 2.53 | 6 |
B-2 | 1CA1.8B | 0 | 6.3 | 2.51 | 14 |
B-3 | 3CA9.8B | 0 | 0 | 2.49 | 23 |
B-4 | 5CA9.8B | 0 | 0 | 2.52 | 27 |
* Z: zircon, CA: alumina cement, B: alumina sol (10 wt%)
For example, 0Z0CA3B means 0 wt% zircon/0 wt% cement/3 wt% alumina sol (10wt%).
Example 3
Table 5 shows the characteristics of the refractories prepared from the refractory mixture composition D in the same manner as in Example 1.
Sample | Additives (wt%; 10 wt% B)* | Dispersing agent (SF60, wt%) | Water (wt%) | Density (g/cm3) | Bending strength (MPa) |
D-1 | 0CA4.2B | 0 | 4.1 | 2.56 | 19 |
D-2 | 0CA7.6B | 0 | 0 | 2.54 | 38 |
D-2 | 1CA1.9B | 0 | 6.3 | 2.56 | 30 |
D-3 | 3CA1.9B | 0 | 6.7 | 2.54 | 35 |
D-4 | 2Z3CA | 0 | 7.5 | 2.56 | 37 |
D-5 | 3CA0B | 0 | 7.1 | 2.57 | 36 |
* Z: zircon, CA: alumina cement, B: alumina sol (10 wt%)
For example, 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
Example 4
Table 6 shows the characteristics of the refractories prepared from the refractory mixture composition M in the same manner as in Example 1.
Sample | Additives (wt%; 10 wt% B)* | Dispersing agent (SF60, wt%) | Water (wt%) | Density (g/cm3) | Bending strength (MPa) |
M-1 | 0CA0.85B | 0 | 7.8 | 2.50 | 27 |
M-2 | 1CA 0B | 0 | 9.0 | 2.45 | 41 |
M-3 | 1Z1CA0.8B | 0 | 8.5 | 2.43 | 40.5 |
M-4 | 3CA0B | 0 | 10.04 | 2.48 | 41.5 |
M-5 | 1Z2CA0.8B | 0 | 9.5 | 2.51 | 41.5 |
M-6 | 2Z1CA0.8B | 0 | 8.5 | 2.49 | 40 |
* Z: zircon, CA: alumina cement, B: alumina sol (10 wt%)
For example, 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
Example 5
Table 7 shows the characteristics of the refractories prepared from the refractory mixture composition G in the same manner as in Example 1.
Sample | Additives (wt%; 10 wt% B)* | Dispersing agent (SF60, wt%) | Water (wt%) | Density (g/cm3) | Bending strength (MPa) |
G-1 | 2Z1CA0B | 0.3 | 7.7 | 2.56 | 27.8 |
G-2 | 2Z1CA0B | 0.2 | 7.7 | 2.54 | 23.2 |
G-3 | 2Z1CA0.83B | 0.3 | 6.7 | 2.54 | 25.6 |
G-4 | 1CA0B | 0.2 | 8.6 | 2.59 | 23 |
G-5 | 3CA0B | 0.2 | 8.4 | 2.62 | 25 |
G-6 | 5CA0B | 0.2 | 8.1 | 2.59 | 32 |
G-7 | 5CA1.8B | 0 | 6.7 | 2.58 | 31 |
* Z: zircon, CA: alumina cement, B: alumina sol (10 wt%)
For example, 0Z0CA3B means 0 wt% of zircon/0 wt% of cement/3 wt% of alumina sol (10wt%).
Example 6
Slag corrosion test was performed using Usibelli slag under the condition of 20% CO/N2 atmosphere at 1550 ºC/4 hr. A castable comprising the refractory mixture composition D as well as 2 wt% of zircon and 3 wt% of cement was formed into a shape of a cup with an outer diameter of 60 mm and an inner diameter of 30 mm. Then, heat treatment was performed as described in Example 1 to prepare a refractory sample D-4. After adding 35 g of slag powder over 2 hours while keeping temperature at 1550 ºC and maintaining the temperature for additional 2 hours, the sample was furnace cooled and the cross-section of the sample was observed (Fig. 2).
Comparative Example 1
A refractory sample D-2 was prepared in the same manner as Example 7 by adding only alumina sol without addition of zircon or cement to the refractory mixture composition D. Slag corrosion test result is shown in Fig. 1.
Comparative Example 2
A refractory sample D-5 was prepared in the same manner as Example 7 by adding only 3 wt% of cement to the refractory mixture composition D. Slag corrosion test result is shown in Fig. 3.
The present application contains subject matter related to Korean Patent Application No. 10-2011-0088085, filed in the Korean Intellectual Property Office on August 31, 2011, the entire contents of which is incorporated herein by reference.
Those skilled in the art will appreciate that the conceptions and specific embodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims.
Claims (6)
- An unshaped refractory comprising a refractory mixture of alumina (Al2O3) and silicon carbide (SiC) to which alumina cement, zircon and an alumina binder are added.
- The unshaped refractory according to Claim 1, wherein magnesium oxide, spinel, zirconia, chromia, hafnium oxide or a mixture thereof is further added to the refractory mixture of alumina (Al2O3) and silicon carbide (SiC).
- The unshaped refractory according to Claim 1, wherein the alumina binder is included in an amount of 0.5-4 parts by weight based on alumina per 100 parts by weight of the total unshaped refractory comprising alumina (Al2O3) and silicon carbide (SiC).
- The unshaped refractory according to Claim 1, wherein the alumina cement comprises 10-30 wt% of calcium oxide (CaO).
- The unshaped refractory according to Claim 1, wherein the alumina cement is added in an amount of 0.5-5 wt% based on the total weight of the unshaped refractory.
- The unshaped refractory according to Claim 1, wherein the zircon is added in an amount of 1-5 wt% based on the total weight of the unshaped refractory.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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KR1020110088085A KR101262077B1 (en) | 2011-08-31 | 2011-08-31 | Low Cement Corrosion-Resistive Unshaped Refractories |
KR10-2011-0088085 | 2011-08-31 |
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WO2013032065A1 true WO2013032065A1 (en) | 2013-03-07 |
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PCT/KR2011/008188 WO2013032065A1 (en) | 2011-08-31 | 2011-10-31 | Low cement corrosion-resistive unshaped refractories |
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WO (1) | WO2013032065A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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DE212016000021U1 (en) | 2015-12-16 | 2017-06-07 | Calderys France | Castable refractory compositions comprising zeolite microstructures, and uses thereof |
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CN112851291A (en) * | 2021-03-05 | 2021-05-28 | 中冶武汉冶金建筑研究院有限公司 | Silicon carbide slurry utilizing waste silicon carbide shed plates and preparation method thereof |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2852401A (en) * | 1955-06-13 | 1958-09-16 | Harbison Walker Refractories | Unshaped high temperature refractory |
US5204298A (en) * | 1990-11-28 | 1993-04-20 | Harima Ceramic Co., Ltd. | Basic monolithic refractories |
US5972102A (en) * | 1996-10-29 | 1999-10-26 | North American Refractories Co. | Hydraulically-bonded monolithic refractories containing a calcium oxide-free binder comprised of a hydratable alumina source and magnesium oxide |
US20100093513A1 (en) * | 2008-03-28 | 2010-04-15 | Shigeru Nakama | Refractory composition, formed refractory article, and sintered refractory article |
-
2011
- 2011-08-31 KR KR1020110088085A patent/KR101262077B1/en not_active Expired - Fee Related
- 2011-10-31 WO PCT/KR2011/008188 patent/WO2013032065A1/en active Application Filing
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2852401A (en) * | 1955-06-13 | 1958-09-16 | Harbison Walker Refractories | Unshaped high temperature refractory |
US5204298A (en) * | 1990-11-28 | 1993-04-20 | Harima Ceramic Co., Ltd. | Basic monolithic refractories |
US5972102A (en) * | 1996-10-29 | 1999-10-26 | North American Refractories Co. | Hydraulically-bonded monolithic refractories containing a calcium oxide-free binder comprised of a hydratable alumina source and magnesium oxide |
US20100093513A1 (en) * | 2008-03-28 | 2010-04-15 | Shigeru Nakama | Refractory composition, formed refractory article, and sintered refractory article |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE212016000021U1 (en) | 2015-12-16 | 2017-06-07 | Calderys France | Castable refractory compositions comprising zeolite microstructures, and uses thereof |
DE212016000023U1 (en) | 2015-12-16 | 2017-06-08 | Calderys France | Castable refractory compositions comprising zeolite microstructures, and uses thereof |
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KR20130024562A (en) | 2013-03-08 |
KR101262077B1 (en) | 2013-05-08 |
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