Soot blower lance tube corrosion in recovery boilers (original) (raw)
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Analysis of failures in boiler tubes due to fireside corrosion in a waste heat recovery boiler
Engineering Failure Analysis, 2003
The failures of boiler tubes due to fireside corrosion in a waste heat recovery boiler utilizing the exhaust gas of a gas turbine fired with high-speed diesel has been analyzed. Deposits from the various zones of the boiler were collected and characterized by chemical analysis, scanning electron microscopy and X-ray diffraction. Thermodynamic modeling studies were carried out to study the interaction of the flue gas with the various components of the boiler. The high corrosion propensity and consequent failures in the low temperature sections of the boiler were found to be directly related to the formation of hydrated ferric sulfate in these regions. #
CORROSION AND CRACKING IN RECOVERY BOILERS
The different chemical environments in different parts of a recovery boiler cause many different types of corrosion. They can also aggravate thermal and mechanical cracking. This paper discusses how tubes corrode and crack in each environment. Implementing proven strategies developed to reduce corrosion rates and inhibit cracking reduces the risks of smelt-water explosions, extends the service life of a boiler and reduces its operating cost.
2007
Relative corrosion resistance and alloy suitability ………………………………… Conclusions And Recommendations ………………………………………………….. 72 FIELD STUDIES OF SUPERHEATER CORROSION ………………………………..… 73 Experimental Details Of Corrosion Probes …………… ...………………………….… Results …………………………………………………………………………………. Temperature measurements ……………………………..………………………… Mid-furnace area Superheater area MID-FURNACE CORROSION STUDIES Kraft recovery boilers experience localized accelerated corrosion in mid-furnace areas. Corrosion patterns may vary from one boiler to another depending on the operation parameters and general design of the boiler. Local gaseous environments were characterized in areas with corrosion and equivalent areas without accelerated corrosion in a selected boiler over the period of two years. Results from this study indicated that in the areas with accelerated corrosion there was a large variation in the local gas composition at the waterwall surface. Reducing and sulfidizing gases were found in the areas with accelerated corrosion, whereas the gas compositions were more oxidizing in the low corrosion areas. Observations during field tests at Weyerhaeuser's Flint River, Georgia and Columbus, Mississippi mills have indicated that the local waterwall temperature may also vary in the mid-furnace due to localized combustion and air flow patterns. Mid-furnace environments were simulated in the laboratory to evaluate the effect of gas composition and fluctuations on the corrosion kinetics of carbon steel tube material. Laboratory tests with SA-210 carbon steel samples with the gas composition cycling between an oxidizing and a reducing/sulfidizing condition led to an unstable scale formation on the surface. The extent of accelerated corrosion was found to depend upon the extreme partial pressure values of sulfur (S 2) and oxygen (O 2). Carbon steel samples were coated with chromized or aluminized diffusion coatings in the laboratory and were then tested under sulfidizing conditions. Both types of diffusion coatings had superior performance compared to the uncoated carbon steel samples under similar conditions. Mid-furnace corrosion can be controlled by making gaseous environments in the mid-furnace more stable. However, a more practical solution seems to be to use waterwall tubes with a protective outer layer. This may be done by using composite tubes (stainless steel outer layer), thermal spray coatings of resistant alloys or diffusion barrier coatings like a chromizing or an aluminizing treatment.
Paper on High Temperature Corrosion and Its Control in Coal Fired Boilers
2018
Recent research and development on high temperature corrosion problems, with the techniques available to control this problem, is reviewed and discussed in this paper. Boiler is an essential element of power generation plants. With increasing fuel and energy costs, maintaining the reliability and consistent performance of a boiler while minimizing energy costs is challenging for any industrial plant. Since boiler systems are constructed primarily of carbon steel, the potential for corrosion is high which can result in a forced shutdown of the boiler and the industrial process. The fireside corrosion in coal fired utility boilers is one of the main problems. Superheaters and reheaters suffer from steam oxidation on their inner surfaces and hot corrosion on the fireside. Fireside corrosion cannot be eliminated completely but it can be controlled. There are several techniques to control the high temperature corrosion problems in boilers which are Fuel blending, use of additives, replacing tubes with more corrosion resistant materials, thermal spray coating, thicker tube walls, adjustment of firing rate, amount of excess air, air temperature and amount of recirculating flue gas can be very effective in controlling the amount and composition of ash deposit, and effective boiler design and construction can also help in controlling ash deposition etc.
Journal of Engineering for Power, 1960
After burning 25 to 30 per cent Pana coal in 1957 (the same amount as during the first 18 months of operation), the corrosion rate remained low, 5 to 10 per cent, instead of returning to the higher rate of 50 per cent as might be expected if Pana coal were the major factor. The abrupt reduction in corrosion is more likely to have been due to the reduced metal and gas temperatures in the platens resulting from the installation of furnace-screen surface. Also, the use of higher excess air and the installation of 25-20 clad tubes have undoubtedly been beneficial in reducing corrosion. The use of additive and the shift of soot blowers seem to have been helpful, but the role they played was not decisive in the overall effort.
An overview of problems and solutions for components subjected to fireside of boilers
International Journal of Industrial Chemistry
In engineering applications, there are various types of boilers such as water tube boilers, fire tube boilers, packaged boiler, fluidized bed combustion boiler, pulverized fuel boiler and waste heat boilers. These boilers are used in different industries such as power plants, paper, and chemical. The present paper reports various problems (such as agglomeration, slagging, fouling, caustic embrittlement, fatigue failure and high temperature corrosion) related to boilers and their possible solutions. Some of the controlling parameters for high temperature corrosion has also been studied viz use of inhibitors, varying temperature and pressure, sol-gel coating and thermal spray coating. Thermal spraying has emerged as a main tool for improvement in surface. Problem of corrosion, wear resistance, electrical or thermal insulation can be altered using different coating techniques and materials. Deposition of ash in biomass-fired boilers also causes severe problems of agglomeration. The problem of agglomeration can be solved using kaolin or NH 3 in the bed of boilers. Some important processes such as pulse detonation wave technology, intelligent soot blower, chemical treatment technology can be used to minimize the effects of fouling.