PUMP USED IN GASIFICATION SYSTEM
BACKGROUND
[0001] The present invention relates, in general, to pumps used in a gasification
system, and, more specifically, to pumps with enhanced abrasion resistance.
[0002] Pumps used in a gasification system, such as a coal gasification system,
usually suffer severe abrasion and damage after a quite short period of use. These abrasion damages not only reduce the reliability of gasification, but also make the cost of gasification increase. Therefore it is a significant issue to enhance the abrasion resistance of pumps to prolong their working life and develop more reliable gasification system and process.
BRIEF DESCRIPTION
J0003] In one aspect, embodiments of the invention provide a pump used in a
gasification system. The pump comprises a housing having an inlet and an outlet, and a rotor supported within the housing. The rotor is configured with a hub and a plurality of disks spaced apart by sections of the hub and defining a plurality of transport channels for transporting solid carbonaceous feedstocks for the gasification system. The pump defines an interior feedstock facing surface adjacent to the solid carbonaceous feedstocks, and at least a portion of the interior feedstock facing surface is coated with a coating.
[0004] In another aspect, embodiments of the invention provide a method for
enhancing abrasion resistance of a pump used in a gasification system. The method comprises coating at least a portion of an interior feedstock facing surface of the pump with a coating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic view of cross-section of an exemplary pump, in
accordance with aspects of the present invention.
DETAILED DESCRIPTION
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[0006] Embodiments of the present disclosure will be described herein below with
reference to the accompanying drawings. In the subsequent description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail.
[0007] "Gasification system" or "gasification apparatus", as used herein, shall mean a
system for converting carbonaceous materials, such as coal, coke, biomass, bitumen, or carbon-containing waste into carbon monoxide and hydrogen by reacting the raw material at high temperatures with a controlled amount of oxygen and/or steam.
[0008] Referring to FIG.l, in the illustrated example, a pump 80 used in a gasification
apparatus for transporting solid carbonaceous feedstocks comprises a housing 82 having an inlet 84 for receiving carbonaceous material and an outlet 86 for discharging carbonaceous material, and a drive rotor 88 supported the housing 82 for rotation relative to the housing 82. The rotor 88 is configured with a hub 90 and a plurality of disks 92 spaced apart by sections of the hub 90, which define a plurality of transport channels 94 communicating with the inlet 84 and the outlet 86. When the pump 80 is used in a gasification apparatus, a solid carbonaceous feedstock, a feedstock comprising solid carbonaceous material, and optionally fiirther comprising other solids, liquids or gases, is fed into the pump 80 from the inlet 84, and by driving the rotor 88, the disks 92 act on the carbonaceous material in the transport channels 94 to cause them moving towards the outlet 86. The pump 80 comprises a feedstock facing interior surface adjacent to the solid carbonaceous feedstocks. In one embodiment, the feedstock facing interior surface comprises an internal surface 96 of the housing 82, a surface 98 defined by the disks 92 and hub sections between the disks 92, an internal surface 102 of the inlet 84 and internal surface 104 of the outlet 86. In certain embodiments, at least a portion of the feedstock facing interior surface is coated with a coating. The "coating", as used herein, may be a removable layer installed on an original surface, or a coating achieved by treating or modifying an original surface in a surface treatment or modification process, in which (1) a coating is applied to the surface, (2) chemical species are adsorbed onto the surface, (3) the chemical nature (e.g., electrostatic charge) of chemical groups on the surface are altered, and/or (4) the surface properties are otherwise modified. In one embodiment, the coating is a removable and replaceable wear-resistant layer installed on at least a portion of the feedstock facing interior surface. The wear-resistant layer can be installed using means including but not limited to fasteners, geometric features, welding, brazing, and/or adhesives.
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In an alternate embodiment, the coating is applied with a surface treatment process including ion implantation and penetration. In one embodiment, the whole feedstock facing interior surface is coated with the coating.
[0009] The pump can be made from metal or alloy. In certain embodiments, at least a
portion of the pump is made from a nickel, cobalt or iron based alloy.
[0010] In certain embodiments, the ion implantation is carried out by: placing the
pump in a processing chamber; supplying gas including argon into the processing chamber to create a vacuum about 0.002Pa; generating plasma by thermionic emission, radio frequency, or microwave excitation to make the pump immersed in the plasma; taking the pump as a negative pole, a member (such as a metal foil) made from the element(s) to be implanted into the pump as a positive pole; and imposing a single field pulse voltage in a range from approximately lOMeV to approximately 20MeV to urge electrons in the plasma to move fi-om the pump to the positive pole, positive ions to rush to the pump, which act as a negative pole. As the pump is immersed in the plasma, the positive ions are implanted to the surface of the pump from various directions. After the implantation, an implanted layer with a thickness of around lOnm to SO^m is formed. The element(s)/ions to be implanted can be W, V, Nb, Cr or their combination.
[0011] The pump is subsequently subjected to penetration, which might be
carburizing, nitriding, carbonitriding, or other diffusion treatments involving elemental additions to the surface. Taking carburizing as an example, in certain embodiments, it could be carried out by: annealing the pump after ion implantation in approximately 800°C for about an hour; preparing a carburizing furnace by heating the carburizing furnace to approximately 800°C, supplying a carburant or a cracking gas such as methanol into the carburizing furnace, and then further heating the carburizing furnace to a carburizing temperature in a range between approximately 920°C to approximately 940°C and maintaining the carburizing furnace at the carburizing temperature for about 1-2 hours till the carburant or gas in the furnace becomes regularly flowing; and placing the pump into the carburizing furnace for carburizing for about 1-2 hours under pressure of about 50-1 OOPa. During the carburizing, the carbon atoms that diffused into the pump to react with the implanted ions in the implanted layer to form a diffused layer comprising carbide of the implanted element(s), such as W, V, Nb, Cr. However, if penetration other than carburizing is
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applied, a diffused layer comprising other compound would be formed. For example, if the implanted component is subjected to a nitriding process, a diffused layer comprising nitride of W, V, Nb, Cr and/or etc would be formed. A thickness of the diffused layer may be below 2mm. In one embodiment, a thickness of the diffused layer is approximately 1mm.
[0012] In certain embodiments, the coating achieved by ion implantation and
penetration processes includes both the implanted layer formed by the ion implantation process and the diffused layer further formed by the penetration process.
[0013] Element distribution measured by an X-ray Photoelectron Spectroscopy (XPS)
shows that a concentration gradient is obtained in the coating, and the adhesion of the coating is much high than a deposited layer in which a concentration mutation may occur. A Vickers hardness of the coating may be above ISOOHv. In certain embodiments, a Vickers hardness of the coating is between approximately 2000Hv to approximately 3000Hv, and an abrasion resistance of the coating is about 2-3 times higher than that of surface without such a coating. Moreover, as a result of the coating, a certain compressional stress is generated in the surface of the component, therefore cracks on the component can be prevented, and anti-fatigue performance of the pump can be enhanced, and thereby the pump's working life under a fluctuating temperature environment can be significantly extended.
[0014] In certain embodiments, the coating on the feedstock facing interior surface
may be other coating materials applied with other processes. Other examples of coating materials that may be used for the pump interior surface include, but are not limited to, MCrAlY (chromium aluminum yttrium) coatings (where M = cobalt, nickel, or cobalt/nickel) and oxides of aluminum, silicon, magnesium, and calcium. Additionally, in certain embodiments, a portion of the feedstock facing interior surface, without the coating, or a surface of the pump, other than the feedstock facing interior surface may be coated by other processes, such as aluminizing.
[0015] The pumps with the coating on its feedstock facing surface are greatly
enhanced in hardness and abrasion resistance, and have been demonstrated very effective in increasing the working life in the industry for transporting solid carbonaceous materials under atmospheric pressure.
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[0016] While the disclosure has been illustrated and described in typical
embodiments, it is not intended to be limited to the details shown, since various modifications and substitutions can be made without departing in any way from the spirit of the present disclosure. As such, further modifications and equivalents of the disclosure herein disclosed may occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be within the spirit and scope of the disclosure as defined by the subsequent claims.
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WE CLAIM:
1. A pump used in a gasification system, comprising:
a housing having an inlet and an outlet;
a rotor supported within the housing for rotation relative to the housing and configured with a hub and a plurality of disks spaced apart by sections of the hub and defining a plurality of transport channels for transporting solid carbonaceous feedstocks for the gasification system; and
an interior feedstock facing surface adjacent to the solid carbonaceous feedstocks,
wherein at least a portion of the interior feedstock facing surface is coated with a coating.
2. The pump of claim 1, wherein the coating is applied with ion implantation and penetration.
3. The pump of claim 2, wherein a portion of the pump is made from a nickel, cobalt or iron-based alloy.
4. The pump of claim 2, wherein the ion comprises at least one of tungsten, vanadium, niobium and chromium.
5. The pump of claim 2, wherein the penetration comprises at least one of carburizing, nitriding and carbonitriding.
6. The pump of claim 2, wherein a thickness of the coating is between about 10 nanometers to about 50 micrometers.
7. The pump of claim 2, wherein a hardness of the coating is above about 1500 Hv.
8. The pump of claim 2, wherein said solid carbonaceous feedstocks comprises one or more of coal, coke, biomass, bitumen, and carbon-containing waste.
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9. The pump of claim 1, wherein the coating is a removable and replaceable wear-resistant layer installed on at least a portion of the interior feedstock facing surface.
10. The pump of claim 9, wherein the wear-resistant layer is installed using fasteners, geometric features, welding, brazing, and/or adhesives.
11. A method for enhancing abrasion resistance of a pump used in a gasification system, comprising coating at least a portion of an interior feedstock facing surface of the pump with a coating.
12. The method of claim 11, wherein the coating process comprising:
implanting ions into the pump; and
subjecting a portion of the pump to penetration.
13. The method of claim 12, wherein the implanting process
comprising:
immersing the pump in plasma; and
taking the pump as a negative pole, and an implanting member comprising an element to be implanted into the pump as a positive pole, and imposing a voltage to urge the ions of the element to move from the implanting member to the pump.
14. The method of claim 13, wherein the voltage is a pulse voltage
ranging from approximately l0MeV to approximately 20MeV.
15. The method of claim 12, wherein the ion to be implanted
comprises an ion of at least one of tungsten, vanadium, niobium and
chromium.
16. The method of claim 12, wherein a thickness of an implanted
layer is between about l0nm to about 50µm.

17. The method of claim 12, wherein the penetration is carburizing for about 1-2 hours under temperature of approximately 920~940°C and pressure of approximately 50-100Pa.
18. The method of claim 12, wherein a thickness of a penetrated layer is less than approximately 2mm.
19. The method of claim 12, further comprising annealing the pump between the ion implanting and the penetration.
20. The method of claim 11, wherein the coating is a removable and replaceable wear-resistant layer installed on at least a portion of the interior feedstock facing surface through fasteners, geometric features, welding, brazing, and/or adhesives.
21. A pump used in a gasification system, substantially as herein described with reference to accompanying drawings and example.