Contents Issue 10 (2000)

If you are interested in ordering back issues, please use this form

Wilfried Kelm, Hans-Dieter Kranz, and Detlef Vrhel

Boilout of Drum-Type Boilers with HELAMIN ®.(published under the heading of "Alternative Treatments").

Products based on polyamines and poly-acrylates have been used for on-line cleaning of boilers in operation, as well as for boilout of boilers during commis-sioning. The paper describes in detail the boilout of two drum-type steam generators (steaming capacity 640 t/h each, main steam pressure 90 bar and main steam temperature 502 °C) with Helamin ®, a proprietary mixture of polyamines and poly-acrylates. The following blowout led to the speedy reaching of the necessary boiler water and steam purity. Due to the significant reduction in the blowout time, savings in the fuel costs, faster commissioning, and an optimal condition of the heating surfaces were achieved. During the first commissioning following the boilout, a very low iron content was detected. Both units are still conditioned with the polyamine/polyacrylate mixture.

PowerPlant Chemistry 2000, 2(10)

Ivo Jiricek

Organics in Water/Steam Cycle - Three Case Studies

Based on the results of three case studies, the topical problem "Organics in the PlantCycle" is discussed. The first study describes the results of a survey on organics performed in eleven power stations in the Czech Republic. The authors give particular attention to the TOC (total organic carbon) actually measured in relation to the limits defined by turbine manufacturers and by utility organizations (VGB, EPRI). The second study concerns the content of organics in turbine blade deposits. The last study investigates the thermal decomposition and degradation of humic acids in plant cycles. The typical breakdown products as identified by gas chromatography analysis with mass spectrometry detection are listed.

PowerPlant Chemistry 2000, 2(10)

Tamara I. Petrova, Valery I. Kashinsky, Andrei A. Zonov, and Evgeny P. Trishin

Removal of Deposits from the Turbine Flowpath at Sakhalinskaya Power Plant Using a Filming Amine (published under the heading of "Alternative Treatments").

Extended laboratory experiments that have dealt with the possibility of washing out turbine deposits by means of octadecylamine emulsion cleaning were performed in the Moscow Power Institute. The following field trials (two 50 MW turbines at the Sakhalinskaya Power Plant, Sakhalin, Russia) demonstrated that the application of this emulsion may result in an almost complete removal of heavy turbine deposits, including silica. The use of octadecylamine is recommended for the cleaning of steam turbines, operating under conditions similar to those of the Sakhalinskaya Power Plant, particularly to remove deposits of silica compounds.

PowerPlant Chemistry 2000, 2(10)

V. Petr and M. Kolovratnik

Heterogeneous Effects in the Droplet Nucleation Process

Modeling of hetero-homogeneous droplet nucleation in the multistage LP steam turbine [1] suggests that further information on the heterogeneous effects occurring in condensing steam is necessaryWith the realization and evaluation of nozzle tests, this paper aim to contributeto the efforts in recognizing whether or not heterogeneous condensation exerts a strong influence on the liquid phase production in the LP turbine flow path.
Computational analysis of the laboratory nozzle tests has made it possible to recognize conditions under which dominant homogeneous, heterogeneous or hetero-homogeneous droplet nucleation can occur. These results can help to improve the analysis introduced in [1]. In principle the nozzle tests have made it possible to verify and improve to some extent the hetero-homogeneous computational model.
In the nozzle tests, variation of the light extinction (turbidity) was measured along the C/D nozzle axis. Parallel computation of the hetero-homogeneous steam condensation resulted in the corresponding computed turbidity data. This made it possible to compare the nucleation model with the experiment.
The homogeneous nucleation process was calculated using the classical theory of Becker and Dörring with the correction factor in the exponential term (to be predicted in the tests). The heterogeneous effects were considered in a simple way, i.e., existing chemical impurities in the inlet steam (probably hydrated heteromolecules that serve as condensation seeds) behave like water droplets. After reaching the critical size, they keep growing according to the droplet growth equation. The Gauss probability density function (with the width to be predicted) was used to define the initialdroplet size spectrum within the radius range 0,5 ¸ 2 nm, corresponding, e.g., to formation of the heteromolecules (m NaCl + n H2O) in the salt solution zone.

The matching process was then used to obtain the best fit with the measured variation of turbidity along the C/D nozzle axis. The method was applied to the test data from 2 C/D nozzles designed for high (4,5.103 s-1) and low (1.103 s-1) expansion rates. Reasonable results were obtained, suggesting, that homogeneous nucleation is the dominant process in the high expansion rate C/D nozzle. In contrast, almost completely heterogeneous condensation was observed in the low expansion rate C/D nozzle.
It can thus be concluded that even a simplified, but experimentally verified computational model of the hetero-homogeneous nucleation process will also give promising results in LP steam turbine applications.

[1] Petr, V.; Kolovratnik, M.: Contribution to the Nucleation Process in Steam Turbines. Steam, Water and Hydrothermal Systems: Physics and Chemistry Meeting the Needs of Industry - Proceedings of the 13th International Conference on the Properties of Water and Steam 1999 (Editors. P.G. Hill et. al), 2000. NRC Press, Ottawa, Canada.

Valil S. Sathyaseelan, S. Velmurugan, Appadurai L. Rufus, S.V. Narasimhan, Pratap K. Mathur, and Kamal Kishore

Analysis of Constituents of a Decontamination Formulation Containing Complexing Agents and Transition Metal Ions

Analysis of all the constituents of a chemical formulation containing several complexants and transition metal ions is difficult because of the interference by constituents other than the analyte. Formulations containing EDTA, ascorbic acid and citric acid (EAC) can be used for the chemical decontamination of primary heat transport systems of nuclear power reactors. During the process, frequent analysis of formulation constituents, dissolved metal ions and dissolved oxygen is essential to monitor the progress of the decontamination. Detailed studies on interference in the estimation of EDTA, ascorbic acid, citric acid, iron, Cu2+ and Ni2+ were carried out and feasible methods for their estimations were developed. A spectrophotometric method involving ion exchange pretreatment was developed for the determination of EDTA as Fe(III)EDTA. Estimation of EDTA could be carried out in the presence of Cu2+, Ni2+, ascorbic acid and citric acid. The citric acid in the formulation mixture was estimated by HPLC by injecting the sample as such. The kinetic study of Fe(II)-o-phenanthroline complex formation in EDTA and DTPA media showed that ascorbic acid was a better reductant than hydroxylamine hydrochloride, as complex formation with the former reductant is quite fast and it can function over a wide range of pH. Measurement of dissolved oxygen in the formulation mixture and the estimation of metal ions in heavy water medium are also discussed.

PowerPlant Chemistry 2000, 2(10)

D. A. Palmer, P. Bénézeth, D. J. Wesolowski, S. A. Wood, and C. Xiao

The Solubility of Metal Oxides and Hydroxides at High Temperatures: Results and Implications of Recent ORNL Measurements

The results of high temperature solubility studies at ORNL are presented in which mainly direct pH measurements were made of aqueous solutions in contact with the crystalline solid phases: Al(OH)3, AlO(OH), Fe3O4, Mg(OH)2, Nd(OH)3, and ZnO. Examples are highlighted of specific phenomena such as: the kinetics of gibbsite and boehmite dissolution and precipitation; the appearance of metastable equilibria in the dissolution of Fe3O4; the extremely rapid precipitation of crystalline brucite, Mg(OH)2; and anomalies in the apparent solubility profiles of AlO(OH) and ZnO. General trends associated with the effects of temperature and ionic strength are mentioned. Some of the potentiometric investigations were augmented by conventional batch {AlO(OH) and ZnO} and flow-through column {ZnO} experiments. In the additional case of ZnCr2O4, the extremely low solubility of this spinel permitted the application of only the latter techniques, these results are discussed interms of the measured chromium levels that resulted from incongruent dissolution.

PowerPlant Chemistry 2000, 2(10)

Albert Bursik

Chemistry in Cycles with Heat Recovery Steam Generators - A Problem and Challenge

The standard cycle chemistry guidelines, with few exceptions, do not consider the specific characteristics of an individual plant cycle sufficiently. The paper focuses on the most important design and operation peculiarities influencing the selection of the individual boiler water and feedwater treatments. The following items are discussed: t-ype or design of major cycle components, overall cycle design, cycle metallurgy, cooling system and cooling water composition, condensate polishing, and operation mode. The paper gives particular attention to combined cycles, industrial power generation, and cogeneration.

PowerPlant Chemistry 2000, 2(10)