Boiler Water Wall Tubes Research Articles

Detection of corrosion fatigue cracking in boiler waterwall tubes using constant potential x-rays: Edgley, J.S. Non-Destr. Test., Aust.26, (4), 96–102, July–Aug. 1989

Fabrication of p-type PbSe thin films on (1 1 1) and (1 0 0)-oriented silicon substrates by the pulsed laser deposition method is demonstrated. The PbSe films were investigated by X-ray diffraction method, spectroscopic ellipsometry, electrical, scanning electron microscopy and SIMS methods. The time-of-flight mass spectra of cold pressed powders of Pb and Se are also investigated and are reported for the first time.

The use of tafaloy 45CT, an Ni-Cr-Ti alloy, as an arc sprayed corrosion barrier in high temperature sulfurous environments

A high chromium content nickel alloy, Tafaloy 45CT, was developed to combat corrosion in high temperature sulfurous environments. The alloy is applied by arc thermal spraying at thickness of 15–20×10 -3 in (381– 508μm) onto surfaces such as water wall tubes in black liquor recovery boilers. The coating has a bond strength of 6500 lbf in -2 (44.82 MPa) and is well matched to the thermal expansion characteristics of steels used for boiler tube construction. Analysis of the coating indicates the presence of two solid solutions of chromium in nickel and two chromium oxides. The major component of the metallic phases is the high chromium (44%) bulk material. The other components are a small portion of the coating. Coatings in service for 18 months show surface sulfur concentrations amounting to only 1%. The sulfur is effectively blocked from more penetration by combining with the chromium and the formation of a self healing chromium oxide film on the coating's surface and within the pores with access to the atmosphere. The coating remains well bonded and protective. Coatings have been in service for over four years without failing.

Effects of Using a Four-Ribbed Tube on Improving Heat Transfer in Boiler Water Wall Tubes

In subcritical pressure, once-through boilers, suppressing the DNB phenomenon is one of the key problems in ensuring safe operation of boiler water wall tubes. A laboratory test project was conducted to determine the effectiveness of using a four-ribbed tube on improving the tube metal temperature conditions of a 300-MW power boiler operating at subcritical pressures. For the heating test section, a specially engineered heating apparatus was used to simulate a one-sided healing condition in the boiler furnace. In the pressure range 165-200 kg/cm2 (160-194 atm), the test results showed that nucleate boiling could be maintained to much higher steam qualities with a four-ribbed tube than with a smooth-bore tube. Field test data proved that this type of tube has satisfactory effectiveness and showed that the experimental correlation recommended in this paper provides a sufficient safety margin for boiler design.

Ash Fusion Study of West Virginia Coals: ABSTRACT

As more industries and utilities convert to coal, ash fusion information becomes more important for boiler design (waste disposal systems). For example, burning a low fusion temperature coal can cause slagging--the buildup of molten ash on boiler waterwall tubes. Not only is boiler efficiency lowered, but downtime is also increased. Recently, potential buyers of West Virginia coal have inquired frequently about ash fusion. However, the amount of information in the West Virginia Geological and Economic Survey's data base is limited to data from about 800 samples, 50% of which were collected in five counties. Thus, the survey is conducting a study of ash fusion temperatures for the state's coals, to increase available data and its geographic coverage. A Leco AF-500 automated ash fusion analyzer was used in this study, which addresses: (1) reliability of results from an automated analyzer, (2) comparison of automated data with conventional data, (3) techniques of sample preparation, high-temperature ashing, and cone preparation, (4) ash-fusion trends in the state, and (5) research developments. The research sought to develop for West Virginia coal a statistical correlation model relating ash-elemental data with fusion data, and to investigate the relationship between ash color and fusion temperature. (Light-colored ashes generally have higher fusion temperatures than darker ashes.) The ash fusion project adds vital information to our computer data base. With this addition, the survey can offer a more complete, unbiased source of information about West Virginia seams to prospective buyers of West Virginia coal. End_of_Article - Last_Page 1915------------

Acid Cleaning Operation for Scale Attacked WaterWall Tubes of a High Pressure Boiler

In this paper, a two stage acid etching (TSAE) technique has been developed and investigated to cleanup hard deposits on internal surfaces of boiler water wall tubes (WWTs) for a natural circulation highpressure drum boiler(fossil) unit: TIME-206-COB (Russia) at Ghorasal Thermal Power Station(GTPS), Bangladesh. TSAE technique was carried out very carefully by using a mixed solution of ammonium hydrogen fluoride, hydrochloric acid in presence of inhibitor urotropine and cleaning agent OP- 10(Russia).To attained maximum cleaning efficiency at each end of the cleaning stage compressed air 6kgfcm-2 was passed through the boiler WWTs by bottom headers very carefully. The overall close observations on the (TSAE)) cleaning operation revealed that not less than 90% of impurities were removed. The cleaning mechanism and the passivation on cleaned surface of boiler WWTs by 2.0% NaNO3 in presence of 0.5% NH4OH (pH 10.5) at 55°C were found to be satisfactory. Close macrostructural examinations (by SEM) of the tube materials after the TSAE operations reveled there is no remarkable corrosion or micro creaks on boiler WWTs materials. Key words: Boiler, Deposit, Passivation, Boiler water wall tubes (WWTs), Acid etching.DOI = 10.3329/bjsir.v43i3.1148Bangladesh J. Sci. Ind. Res. 43(3), 333-344, 2008