Thermal spray coatings applied in four pipe plant
Wall pulverized coal technology, such as the heating surface corrosion wear design
pulverized coal boiler because of its structural characteristics and design parameters due to its furnace water wall tubes and other parts of the heating surface, due to the extremely poor working conditions to run long suffered high temperatures High-speed high-temperature flue gas dust intense erosion corrosion and uneven wear, equipment can easily be wall corrosion, wear thinning, and even cause leaks and burst pipes. To ensure boiler safety, stability and economic operation, in order to achieve long-term operation purpose, take effective protective measures against the above equipment parts heating surface is essential. according to the plant protection cases across the country, combined with practical experience in the construction company engaged in the industry, each device specific furnace and boiler for your organization The design process parameters, by the careful analysis of company engineering and technical personnel, equipment wear and corrosion on the above techniques designed using this technology for protection can get good results, you can greatly extend the life of equipment.
a, failure analysis
1, the heating surface water wall tube furnace parts
main reason for the failure is part of the heating surface temperature flue gas temperature oxidation and hot corrosion, including corrosion, accompanied by loss of spray blowing gas flow and high-speed dust fumes uneven erosion wear.
Wall heating surface due to the effect of high temperature flue gas, resulting in high-temperature corrosion, including high temperature oxidation and sulfate and sulfur, sulfide hot corrosion, the parts of which the flue gas temperature is high, and Oxyfuel combustion is proved, at 300 ℃ above, pipe surface temperature increased by 50 ℃, the corrosion rate doubled. boiler wall surface temperature oxidation occurs first during operation, generate Fe2O3, and because the presence of sulfur, so the post-combustion flue gas contains some SO2, SO3, and a small amount of S2 and H2S, etc., on the wall of corrosion is extremely serious. SO2 in the flue gas reacts with O2 SO3, SO3, SO2 and fuel ash generated Na2O and K2O sulfate compounds and sulfite M2SO4 M2SO3, which captures the fly ash slagging and the formation of slag deposited on the flow surface of the metal pipe, when the flue gas SO3, SO2 and M2SO4, M2SO3 with wall Fe2O3 reaction to generate a composite sulfate on MFe (SO4) 2 or MFe (SO3) 2, the composite sulfate decomposition of the high temperature and loose like iron and sulphate and sulphite sediments, erosion susceptible ash flow away, the depth for the continued oxidation corrosion wall; Further, S2 elemental sulfur reacts with the wall of the low melting Fe FeS, which generates the metal eutectic Fe Fe effect • FeS, cause accelerated corrosion of Fe; H2S and wall Fe reaction FeS, and therefore had a strong corrosion wall while the wall is the amount of wear and airflow rate is closely related to the flue gas dust concentration, particle characteristics and flow channel geometry, etc. According to the Research data show that the amount of wear and airflow velocity 3.6 power is proportional to the burner tube surrounding the heating surface at great speed jet of gas streams containing high concentrations of dust, so its a very serious blow deteriorated in thin, and in the furnace flame near the corners and fold the corner there is a vortex effect, mainly due to the flue gas stream to split, the inertia of the dust particles, there is a serious erosion of uneven wear.
In these multiple factors working together, from the heating surface tubes the outside constantly being oxidation, corrosion and erosion wear make gradual thinning, when the local bear vapor pressure within the pipe leak that caused the explosion and failure.
Second, the coating design
For the above wall failure mechanism We design uses supersonic arc spraying technology, and use a combination of high strength, high temperature oxidation and hot corrosion resistance, good erosion excellent wear properties while cermet wire + high temperature composite coating produced special sealer for protection coating edge transition region, so that a smooth transition. using this technology for protection, to meet the protection requirements, greatly extending the life of the equipment.
1. thickness:0.5 mm around
2. bond strength:≥55Mpa
3. hardness:≥55HRC
4. high temperature oxidation resistance:+6.35mg/cm2（750℃ oxidation 250h)
5. porosity:≤0.9%
6. workpiece deformation: no distortion
7. coating surface treatment: special high-temperature sealing sealing agent
three boiler dedicated wire arc spray
is the main component of a dedicated wire:NiCr- Cr3C2, mo, al, RE, etc., with good resistance to high temperature oxidation resistance, high temperature corrosion and erosion wear performance, especially for pulverized coal and CFB boilers both strong erosion wear, there are more severe high-temperature oxidation, high temperature corrosion of parts produced scour a large area coating.
1. The main technical indicators:
(1) Vickers hardness:700—1000HV0.1；
(2) binding strength: 55MPa or more;
(3) Working temperature:1000℃ The following;
(4) relative wear resistance: Q235 steel more than 15 times, up to 18 times Q235 steel;
(5) can be sprayed thickness:2.0 mm the following;
(6) thermal shock resistance:700℃ 15 times the coating did not change the thermal shock
2. Recommended spray parameters:
(1) spray voltage:28—32V
(2) spray current:180—260A
(3) spraying distance:100—200mm
(4) atomization pressure:0.5—0.6MPa
CFB boiler heating surface abrasion and wear imbalance technical design
appears on the CFB boiler in operation wear imbalance, segmented analysis of wear and tear causes contention for wear resistance design program, you can achieve the desired The wear effect.
CFB boiler, cutting wear, imbalance, segmentation analysis, supersonic arc spraying, wire, arc welding wire, metal coating materials,
CFB boiler fired because of their adaptability Wide, high combustion efficiency, low cost and strong peaking capacity of desulfurization and other prominent characteristics favored in recent years has been the rapid development of the domestic, but its badly worn and extremely prominent imbalance problem.
General pulverized coal boiler heating surface using supersonic arc spraying, coating materials, the protection period of up to one to two overhaul (ie, four to eight years), but the CFB boiler heating surface wear to work but it is very difficult to make a CFB boiler heating surfaces in all Within a year is not due to wear and burst pipes, but it is very difficult. The difficulty lies in the very few wear parts leaving the imbalance problem is very prominent example: dense phase transition zone furnace wear like a cancer difficult to cure.
due to different wear mechanisms in different parts of the CFB boiler heating surface, and wear very uneven, so wear effectively address key CFB boiler is segmented analysis and remedy.
Non-heated surface of normal wear and tear abrasion and wear analysis program:
has been put into operation at CFB boiler, many local presence of a small number of regions of the furnace cutting mill
losses and other non-normal wear, the wear process should pay close attention.
dense phase transition zone furnace heating surface Wear and wear solutions:
CFB boiler from the country a lot of wear and tear has put into operation point of view, although many reasons causing dense phase transition zone furnace water wall and fins abnormal wear, However, the geometry of the problem is to bring their produce cutting most direct cause wear and tear. therefore, not yet installed CFB boiler, the proposed restructuring of the dense phase transition region, in order to avoid creating a vicious circle. has been put into operation on the CFB boiler, if the dense phase region Cutting badly worn, can actively get in touch with the original manufacturer and the design and installation of boiler units, as far as possible to improve the geometry if the geometry is difficult to improve, you can take comprehensive measures to wear, such as the use of supersonic arc spraying hot hardness and toughness The material is arranged with a hierarchical block material, the installation of trapezoidal wear tile, etc. According to many national plant protection point of view, these measures will help extend wear life cycle.
CFB boiler heating surface wear and imbalance Rash technical design
in the lower chamber protruding seam abrasion wear causes and solutions:
CFB boiler furnace water wall in the lower part protruding seam wear is also very serious, and some also have a cutting effect. circulating fluidized bed boiler installation or repair, welding must be fine, you can use the advanced welding, the weld formation does not protrude, even with projections, but also carefully polished smooth and flat as possible to reduce projections addition, welding the best use of the seam area near supersonic arc spraying, wear to achieve the desired effect.
power plant boiler corrosion and wear thermal spraying cold spray Wanted, part-time clerk and agency partners
each plant --- Boiler Plant Biotechnology Division Head of Plant Engineering Department Planning Department
Power Installation Company Electric Power Design Institute Power Engineering Company Boiler Group Company
each Polytechnic Institute of New Materials universities
China Nonferrous Metal Materials Corporation
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