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    • 专利摘要:
    A method relating to the transport of corrosion products in a power generation plant. The method is intended to test the resuspension characteristics of a chemical dispersant and comprises providing a test apparatus comprising: a solution containment vessel; a drive wheel system and a shaft, attaching a substrate coated with deposition material to the shaft; dipping the coated substrate in a solution contained in the vessel; using the drive wheel system to rotate the shaft and the coated substrate at a predetermined speed; and determining an amount of deposition material removed from the substrate.
    公开号:SE535137C2
    申请号:SE1150545
    申请日:2010-06-01
    公开日:2012-04-24
    发明作者:Keith Paul Fruzetti；Charles Marks
    申请人:Electric Power Res Inst；
    IPC主号:
    专利说明:

    535 137 maintains low concentrations of sulfur. In addition, prior art does not focus on growth or corrosion product transport to a reactor at a BWR plant.
    SUMMARY OF THE INVENTION The present invention relates to a method for testing resuspension characteristics of a chemical dispersant.
    Corrosion products present in recirculation paths, such as feed water and condensate systems, can be removed before starting by adding a dispersant during recirculation periods. This would promote the retention of iron oxides in suspension before they can be removed from the system by drainage pipes. condensate polishers, filter elements, etc., and would reduce the stock of corrosion products available for transport during operation.
    In addition, dispersants would provide a significant reduction in the time required to clean the secondary system before operation, a reduction in the stock of deposits in the secondary cycle (which can otherwise be transported during operation) and / or a significant reduction in the mass of corrosion product being transported. during operation early in the operating cycle (typical restart processes).
    In accordance with one aspect of the present invention, a method of testing resuspension characteristics of a chemical dispersant comprises the steps of providing a test apparatus having a solution containment vessel, a power transmission system and a shaft. The method further comprises the steps of attaching a substrate coated with a deposition material to the shaft; immersing the coated substrate in a solution contained in the vessel; using the power transmission system to rotate the shaft and the coated substrate at a predetermined speed; and determining an amount of deposition material removed from the substrate.
    BRIEF DESCRIPTION OF THE RELEASES The contents considered as the invention can best be understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: Figure 1 is a diagram of dispersant use in longitudinal recirculation; Figure 2 is a graph showing magnetite concentration versus% transmittance; Figure 3 is a graph showing Hematite concentration versus% transmittance; Figure 4 shows sedimentation behavior of Magnetite with 100 ppm PAA (2kD); Figure 5 shows sedimentation behavior of Magnetite with 10,000 ppm PAA (2kD); Figure 6 shows sedimentation behavior of Hematite with 10,000 ppm PAA (2kD); Figure 7 shows sedimentation behavior of Magnetite with 100 ppm PAA (5kD); Figure 8 shows sedimentation behavior of Magnetite with 10,000 PAA (5kD); Figure 9 shows sedimentation behavior of Hematite with 10,000 PAA (5kD); Figure 10 shows sedimentation behavior of Magnetite with 100 ppm PAA (high molecular weight); Figure 11 shows sedimentation behavior of Magnetite with 10,000 ppm PAA (high molecular weight); Figure 12 shows sedimentation behavior of Hematite with 10,000 ppm PAA (high molecular weight); Figure 13 shows sedimentation behavior of Magnetite with 100 ppm PMAA; Figure 14 shows sedimentation behavior of Magnetite with 10,000 ppm PMAA; Figure 15 shows sedimentation behavior of Hematite with 10,000 ppm PAA; Figure 16 shows sedimentation behavior of Magnetite with 100 ppm PMA: AA; Figure 17 shows sedimentation behavior of Magnetite with 10,000 ppm PMAIAA; Figure 18 shows sedimentation behavior of Hematite with 10,000 ppm PMA: AA; Figure 19 shows sedimentation behavior of Magnetite with 100 ppm PAAM; Figure 20 shows sedimentation behavior of Magnetite with 10,000 ppm PAAM; Figure 21 shows sedimentation behavior of Hematite with 10,000 ppm PAAM; Figure 22 shows sedimentation behavior of Magnetite with 100 ppm PAA: SA; Figure 23 shows sedimentation behavior of Magnetite with 10,000 ppm PAA: SA; Figure 24 shows sedimentation behavior of Hematite with 10,000 ppm PAA: SA; Figure 25 shows sedimentation behavior of Magnetite with 100 ppm PAA: SS: SA; Figure 26 shows sedimentation behavior of Magnetite with 10,000 ppm PAA: SS: SA; Figure 27 shows sedimentation behavior of Hematite with 10,000 ppm PAA: SS: SA; Figure 28 shows sedimentation behavior of Magnetite with 100 ppm PAA: AMPS; Figure 29 shows sedimentation behavior of Magnetite with 10,000 ppm PAA: AMPS; Figure 30 shows sedimentation behavior of Hematite with 10,000 ppm PAA: AMPS; Figure 31 shows sedimentation behavior of Magnetite with 100 ppm PAMPS; Figure 32 shows sedimentation behavior of Magnetite with 10,000 ppm PAMPS; Figure 33 shows sedimentation behavior of Hematite with 10,000 ppm PAMPS; Figure 34 shows sedimentation behavior of Magnetite with 100 ppm PMA: SS; Figure 35 shows sedimentation behavior of Magnetite with 10,000 ppm PMA: SS; 535 137 Figure 36 shows sedimentation behavior of Hematite with 10,000 ppm PMA: SS; Figure 37 shows the effects of dispersant candidate (10,000 ppm) on a solution of 10,000 ppm FeßO 2 (Magnetite); Figure 38 shows screening tests with dispersant alternatives - extended maturity; Figure 39 shows the effects of dispersant alternatives (100 ppm) on a solution with .000 ppm Fe 3 O 3, (Magnetite); Figure 40 shows screening tests with dispersant alternatives (100 ppm) - extended run time; Figure 41 shows the effects of dispersant alternative (10,000 ppm) on a solution of 10,000 ppm FezO 3 (Hematite); Figure 42 shows screening tests with dispersant alternatives (10,000 ppm) - extended maturity; Figure 43 shows a resuspension test apparatus according to an embodiment of the invention; Figure 44 shows the iron content of the test solutions at 1 ppm dispersant for magnetite 'Figure 45 shows the iron content of test solutions at 100 ppm dispersant for magnetite' Figure 46 shows the iron content of test solutions at 1 ppm dispersant for hematite; and Figure 47 shows the iron content of test solutions at 100 ppm dispersant for hematite.
    DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for testing resuspension characteristics of a chemical dispersant. A description of embodiments of this method 535 137 and resuspension tests is described in more detail below. Next comes a description of a method that relates to reducing corrosion transport in a power-producing plant and dispersant applications. This method is not covered by the invention according to the appended claims, but the method is described for a better understanding of the method according to the invention and applications thereof.
    While methods for removing corrosion products are discussed in relation to PWRs and long-distance recirculation, it should be understood that the methods are not limited to long-distance recirculation and PWRs and can be used in other power generating plants (such as a BWR) and with other recirculation paths. steam and drainage systems). PWRs and long-distance recirculation are used in this discussion for clarity and by way of example only.
    Dispersion application in nuclear power plants is currently only intended as a direct (on-line) application, in operation, to the feed water entering the secondary side of a nuclear steam generator with the aim of reducing the accumulation of metal oxide deposits within the nuclear steam generator, by blowing removal, during the continuous operation of the steam generator.
    In power-producing plants, long-distance recirculation is used to remove corrosion products (mainly iron oxides and / or oxyhydroxides) from the feed water and condensate systems before power production. This reduces the mass of corrosion products transported to the steam generator where corrosion products can be deposited, which exacerbates pipe corrosion and reduces thermal efficiency. Long and short-distance recirculation loops for a power-producing plant are generally shown in Figure 1 at reference numerals 10 and 11.
    With respect to long-distance recirculation, the process of injecting a dispersant into the long-distance recirculation cleaning process can be used as proposed for a feed train of a plant secondary system outside the core vapor generator, where the treatment water containing the dispersant would have no contact or limited contact (valve leakage) with core vapor leakage.
    Furthermore, cleaning of a plant's secondary system can take place outside the nuclear steam generator, and thus removal of metal oxides from the system before they can even enter the steam generator. In addition, the described method is applicable to plants with 535,137 recirculation steam generators, plants with single-flow type meadow generators (ie, independent of steam generator type) and BWRs with reactors.
    As described herein, the use of dispersants in long-distance recirculation increases the efficiency of corrosion product removal, either by reducing the mass finally transported to the steam generator or by reducing the time required for recirculation cleaning before power generation. Dispersant injection sites are generally shown in Figure 1 at reference numerals 12-14. Injection sites would be based on device-specific designs; thus, a site-specific inspection should be performed prior to injecting a dispersant.
    As shown, several sites can be used for injection. For example, a place may be just downstream of the cleaning equipment so that the entire system is exposed to the chemical. However, alternative locations can be used to provide significant cleaning benefits. In general, the cleaning process involves injecting a chemical, using chemical injectors 16-18 (such as metering pumps), specifically a polymer dispersant such as, but not limited to, polyacrylic acid (PAA), into feed water. the condensate system during a recirculation path cleaning. The injectors 16-18 may be existing injectors or new injectors installed for injecting the dispersant. The process involves injecting the chemical (which may be on a single or continuous basis); recirculation of the system (which can be started before injection); and cleaning the system (using existing equipment).
    The choice of a specific chemical is a non-trivial matter, and includes evaluation of efficiency as well as system compatibility. The rate and timing of chemical injection can be adjusted to the individual unit taking into account various factors such as estimated corrosion product loading, existing feedwater / condensate system configuration, and downtime / startup timetable.
    The dispersant works by effectively increasing the diameter of the corrosion product particles (i.e. by reducing their effective density). by reducing the tendency of these particles to settle and facilitate re-entrainment of deposited material. These effects are combined to increase the fraction of corrosion product circulating with the water in the system relative to the fraction retained on surfaces. The circulating corrosion product particles can be easily removed from the system with the hazardous equipment (for example, ion exchange resin beds, filters, etc.) or through system waste sites. As the chemical increases the fraction kept in suspension, its use increases the fraction that can be removed during cleaning, resulting in either removal of a larger mass, faster removal of the same mass, or both. In some cases, cleaning times are related to downtime schedules. Specifically, it is the time window during which recirculation can take place. At other units, cleaning is continued until a predetermined criterion (iron concentration, filter color, etc.) is reached. Chemical additives to increase suspended corrosion product concentrations would be beneficial in both of these cases.
    Dispersant efficiency is defined in part by the ability of the polymer to reduce the particle sedimentation rate. Particle sedimentation rate was determined from the specrophotometric data obtained from tests in which the solution transmittance was determined at different time intervals. The sedimentation rate of a particle in a given fluid is a function of its density and diameter, as well as the density and viscosity of the fluid.
    Two experiments without dispersant were therefore performed to characterize the sedimentation behavior of magnetite and hematite particles and to develop a conversion between the reported transmittance and the concentration of the deposition material in solution. This was done by measuring the percentage of light emitted by the solution at different time intervals and correlating these measurements with the theoretically calculated concentration of deposition material after the same time period.
    The concentration of deposition material in solution at each time period is determined as follows. The suspended particles (magnetite or hematite) can be modeled as approximately spherical particles that settle in an environment with low turbulence (low Reynolds number).
    Under these conditions, the sedimentation rate is described by Stokes' theorem: QQÉQÄQQJQI) z Vt 1 Su where Dp is the particle diameter; p, and p, are the density of the particle and the fluid, respectively, p is the viscosity of the fluid; g is the gravitational constant; and v, is the sedimentation rate. 535 137 A particle size distribution was previously determined (by laser particle size analysis) for magnetite and hematite deposition materials. Particle size measurements were taken before and after a short sonication period to ensure that the measurement was not affected by agglomerates. From the geometry of the spectrophotometer chamber, the sedimentation rate of the largest particle remaining in solution can be determined for any time interval.
    The transmittance measurement at each time point was plotted against the concentration of the relevant control, which was determined from size distribution data and Stokes model for particle sedimentation at low Reynolds numbers. A relationship between transmittance and concentration was obtained by adapting the resulting curve to a tan function. The point of zero transmittance predicted with this model was ~ 6500 ppm. These ranges correspond to transmittances between 67% and 90.7% (the transmittance of deionized water) for magnetite, and from 78% to 90.7% for hematite. In both areas, the curve can be described as a second order polynomial. The curves of the transmittance-concentration relationships for magnetite and hematite are shown in Figures 2 and 3, respectively.
    The purpose of dispersant additive is to reduce the sedimentation rate, which results in a visible change in particle diameter and density. Effective particle size S is used to describe this visible particle diameter and density and is defined as: S: Dzpß De "pf): Q where e with submerged position shows the" effective "or visible value, A parameter describing the difference ide visible and the actual particle sizes, which are proportional to the sedimentation rate, can then be generated for each time point by comparing the "effective" particle size with the particle size corresponding to the observed concentration by the following equation:% Change = Q; S_ C where C is the calculated the particle size is based on the observed transmittance in the absence of dispersant, and Pp and Pf are the known densities of the deposition material and deionized water.Parameter C is given by the following equation: 535 137 C z D2p.calc (p pmagnetite "pf)“% Change ”Therefore refers to the percentage decrease in sedimentation rate observed in the presence of a dispersant. The sedimentation rate was used to trigger “S”. "C" was then determined using the sedimentation rate of the control experiment at the current transmittance reading. The values of C and S were then used to determine the relative change in sedimentation rate (% Change ".
    Some general observations made during the test include: o At 100 ppm dispersant (a ratio of dispersant: magnetite of 1: 100), the effectiveness of polymeric dispersants with increasing particle size typically increases.
    At 10,000 ppm dispersant, the sedimentation rate of larger magnetite particles of high molecular weight dispersant was accelerated. High molecular weight dispersants can promote particle agglomeration at these concentrations. For low molecular weight dispersants, the dispersant was of the same order of effectiveness at both concentration / dispersant | s iron concentrations. ø All dispersant alternatives except PAAM promoted retention of hematitis in solution. o Sulfur-containing dispersants performed o not significantly better than the strict acrylic acid / methacrylic acid / maleic acid copolymers. Sulfur-containing dispersants should therefore be used in a restrictive manner due to material compatibility considerations. This would eliminate much of the risk associated with possible dispersant penetration into the steam generator in this application (through leaking isolation valves, human error, etc.).
    Examples of dispersants for use in recirculation paths and changes in effective particle diameter (and therefore sedimentation rate) in the presence of a polymer dispersant are summarized in Table 1. 535 137 12 Table 1 Dispersants Molecular Weight Performance Improvement (Dalton Dispersion 100 Ppm Dis 10,000 ring agent (1: 100) ring agent (1: 1) ppm Dispersant (111) PAA 2000 ~ 17% (<3 pm); ~ 18% -50% ~ 40% (larger particles) 5000 -10-20% 0-50% (Improvement ~ 50-70% decreases with increasing size) N.P. ~ 18-50% (Improvement Acceleration in sedi- ~ 100% increases with increasing size for play) particle diameters> 5pm PMAA 6500 ~ 19-50% (Improvement ~ 22-56% ~ 60% increases with increasing size) PMA: AA 3000 ~ 17% (<1 pm); ~ 30% ~ 20% (excluding particles ~ 70% (larger particles) <1 pm) PAAM 200,000 ~ 25-50% (<2.5 pm) Acceleration in sediment No segmentation rate for nitric particles> 4.5 pm . No change significant change for small particles PAA: SA <15,000 ~ 25-50% (Improvement <20%; decrease for 30-60% increases with increasing large- large (> 12 μm) particles play) PAA: SS: SA N.P. ~ 40% (> 5 pm); pre- ~ 40% (3-5 pm); 40-80% ring decreases with decreasing decreases with decreasing size decreases size (<3 pm) PAA: AMPS 5000 18-42% (Improvement ~ 30% 40-60%; increases with increasing size 80% (~ 2 play) pm) PAMPS 800,000 No significant effect Large acceleration in se- 70-90% sizing speed with increasing particle size (> 3.5 pm) PMA: SS 20,000 ~ 20-40% (Improvement ~ 20-40% (Improvement ~ 30-68% increases with increasing size) increases with increasing size) 535 137 13 The polyacrylic acid (PAA) effectively reduced the sedimentation rate of magnetite particles with a size of ~ 1-10 μm by ~ 20-50%. This polymer was also the most effective in dispersing hematite, which makes up a larger proportion of feedwater system deposits.
    Three PAA options were evaluated. All three PAA alternatives evaluated showed similar levels of efficacy in dispersing both magnetite and hematite. In particular, a low molecular weight polymer (2000 Daltons), a low molecular weight polymer (5000 Daltons), and a high molecular weight polymer were evaluated.
    The low molecular weight polymer performed moderately well to disperse both large and small particles. The dispersant was more effective in dispersing magnetite at the lower ratio (1: 100) of dispersant iron. Specifically, the following results were obtained: o At 100 ppm dispersant: The sedimentation rate was increased by ~ 40% for large particles and ~ 17% for smaller particles. The results of this test are shown in Figure 4. o At 10,000 ppm dispersant: The sedimentation rate increased by ~ 18% with the exception of two external points at larger particle sizes.
    The results of this test are shown in Figure 5. o Hematite dispersion: The dispersant increased the sedimentation time of hematite by ~ 50% over a wide range of particle sizes. The results of this test are shown in Figure 6.
    The low to moderate molecular weight polymer resulted in small improvements in an intermediate particle size range. but showed anomalous increases in sedimentation rate at the ends. Overall, this polymer appears to be less effective than the low molecular weight polymer. The following observations were made from these tests: o _ / id 100 ppm: The dispersant increased the sedimentation time by ~ 10-20% for some particle sizes, but showed significant decreases in performance at other points. The results of this test are shown in Figure 7. 535 137 14 o At 10,000 ppm: The dispersant increased the sedimentation time by up to ~ 50% for small particles, but had little effect on intermediate particle sizes.
    The sedimentation time of the largest particles decreased greatly. The results of this test are shown in Figure 8.
    Hematite dispersion: The low to moderate molecular weight polymer increased the hematite sedimentation time by 50-70%. The results of this test are shown in Figure 9.
    The high molecular weight polymer performed well at low concentrations (100 ppm), but was less effective at 10,000 ppm. o At 100 ppm: The sedimentation time increased by 18% to 50% with increasing particle size. The results of this test are plotted in Figure 10.
    ~ At 10,000 ppm: Sedimentation time increased slightly (up to about 20%) for smaller particles. For larger particles, however, the sedimentation time decreased by about 20%. The results of this test are plotted in Figure 11. o Hematite dispersion: The dispersant consistently increased the sedimentation time by almost 100% over the particle distribution tested. The results of this test are plotted in Figure 12.
    The generic Polymethacrylic Acid (PMAA) polymer similarly showed high efficiency at a concentration of 100 ppm. Unlike many of the dispersion alternatives, it did not increase the sedimentation rate or promote agglomeration; PMAA was equally effective at high concentration (10,000 ppm). The polymer was moderately effective in dispersing hematite and reduced the sedimentation rate by ~ 60%.
    PMAA has been tested for cooking applications with moderate levels of efficiency. The PMAA used in this test program had a molecular weight of ~ 6500 Daltons. The following observations were made.
    ~ At 100 ppm: Sedimentation time increased by 19 to 50% with increasing particle size. The results of this test are plotted in Figure 13. 535 13 At 10,000 ppm: Sedimentation time increased by 22 to 56%. A weak correlation was observed between the improvement in sedimentation rate and the particle size.
    The results of this test are shown in Figure 14.
    Hematite dispersion: Although few data points were available, the sedimentation rate increased by 6060% for all particle sizes. The results of this test are shown in Figure 15.
    Other polymers were also evaluated. Poly (acrylic acid: maleic acid) (PMA: AA) had a molecular weight of ~ 3000 Daltons and had the following characteristics: At 100 ppm: The presence of dispersants increased the sedimentation time by ~ 30% for moderate to low particle sizes, but decreased the sedimentation rate of particles of ~ 1 pm by almost 17%. The results of this test are shown in Figure 16.
    At 10,000 ppm: The sedimentation time was increased by ~ 20% with the exception of the smallest particles (~ 1 μm), which showed an extended sedimentation time. The results of this test are shown in Figure 17.
    Hematite dispersion: An increase of 7070% in sedimentation time was observed at all data points. The results of this test are shown in Figure 18.
    The poly (acrylic acid: acrylamide) (PAAM) copolymer had an average molecular weight of ~ 200,000 Daltons, making it significantly larger than most alternatives. PAAM was the only dispersant tested that did not disperse hematitis effectively.
    At 100 ppm: The dispersant increased the sedimentation time of small particles (diameter <2.5 μm) by 25-50%, but significantly reduced the sedimentation time of particles with a diameter larger than 10 μm. The results of this are shown in Figure 19.
    At 10,000 ppm: Larger increases in sedimentation rate were observed in particles with diameters> 4.5 μm. A small change in sedimentation rate was observed for smaller particles. The results of this test are shown in Figure 20. 535 137 16 o Hematite dispersion: No significant change in sedimentation behavior of hematite was observed in the presence of 10,000 ppm PAAM. The results of this test are shown in Figure 21.
    The poly (sulfonic acid: acrylic acid) (PAA: SA) copolymer had a molecular weight <15,000 Daltons.
    The following observations were made. o At 100 ppm: An improvement of 20-50% in sedimentation time was observed. The increase in sedimentation rate was greater for larger particles (~ 12 μm) and lower for smaller particles (2-3 μm). The results of this test are shown in Figure 22. o At 10,000 ppm: A small increase in sedimentation time (<20%) was observed for most particle sizes. Sedimentation time decreased for larger (~ 12 μm) particles. The results of this test are shown in Figure 23. o Hematite dispersion: An increase of 30-60% in sedimentation time was observed. The results of this test are shown in Figure 24.
    The po | y (acrylic | acid: sulfonic acid: sulfonated styrene) (PAA: SS: SA) polymer had the following characteristics. o At 100 ppm: The sedimentation time of magnetite increased by ~ 40% for particles with diameters> 5 μm. For smaller particles, a smaller increase in sedimentation rate was observed. The results of this test are shown in Figure 25. o At 10,000 ppm: The sedimentation time increased by ~ 40% for particles with a diameter of 3-5 μm. During 3 pm, the change in sedimentation time decreased with decreasing particle size. The result of this test is shown in Figure 26. o Hematite dispersion: An improvement of 40-80% ice sedimentation time was observed.
    The results of this test are shown in Figure 27.
    The Po | y (acrylic acid: 2 acrylamide-2 methylpropanesulfonic acid) (PAA: AMPS) copolymer had an average molecular weight of 5000 Daltons and resulted in the following observations. 535 137 17 o At 100 ppm: The sedimentation time increased by 18-42% with greater improvements in the dispersion of larger particles. The results of this test are shown in Figure 28. o At 10,000 ppm: The sedimentation time increased by ~ 30%, although a slight improvement was observed at the endpoints of the particle sizes examined.
    The results of this test are shown in Figure 29. o Hematite distribution: Sedimentation time generally increased by ~ 40-60%. ' A larger (80%) improvement in sedimentation time was observed at low particle sizes (~ 2 μm). The results of this test are shown in Figure 30.
    Poly (acrylamide-2-methylpropanesulfonic acid) (PAMPS) was the largest polymer tested with an average molecular weight of 800,000 Daltons. o At 100 ppm: Little to no improvement in sedimentation rate was observed.
    The results of this test are shown in Figure 31. o At 10,000 ppm: Sedimentation rate increased with increasing particle size At particle sizes above 3,53.5 μm, the sedimentation rate accelerated greatly. The results of this test are shown in Figure 32. o Hematite dispersion: With the exception of the anomalies observed at 88 μm, the sedimentation time increased by between 70 and 90%. The results of this test are shown in Figure 33.
    The poly (sulfonated styrene: maleic anhydride) (PMA: SS) copolymer had a molecular weight of ~ 20,000 Daltons. o At 100 ppm: The sedimentation time of particles> ~ 8 μm increased by ~ 40 ° / °.
    Smaller particles took ~ 20% more time to settle. The results of this test are shown in Figure 34. 535 137 18 ø At 10,000 ppm: Improvements in sedimentation time similar to that seen with 100 ppm were observed, with the improvement decreasing with decreasing particle size. The results of this test are shown in Figure 35. o Hematite dispersion: Sedimentation time of decreased by ~ 30-68%. The results of this test are shown in Figure 36. Recirculation procedures at three representative power-producing plants were reviewed to provide a baseline for evaluating dispersant application long-distance recirculation cleaning. The following parameters were typical of the long-distance recirculation for the three power-producing plants. ø Flow rates for the long-distance recirculation cleaning process range from 2000-4000 gpm. This shows that the cycle times for the long-distance recirculation cleaning application (i.e. the time required for all fluid to pass through the long-distance loop once) are of the order of ~ 1-2 hours depending on the fluid volume of the system. Consequently, the period of time that the corrosion products must remain suspended to be removed from the secondary system is limited to about 1-2 hours. o The recirculation cleaning period generally lasts 1-2 days and is not on a critical path. All three plants remain in long-distance recirculation for a sufficient period of time to achieve a steady state removal. Start-up procedures are generally initiated from the long-distance recirculation cleaning process, i.e. there are no further drains or flushes before power rise. Additional flushing may not be practical due to frequent downtime. The main part of the system remains at or around ambient temperature during the cleaning period.
    The duration of the dispersant alternative tests was originally set at minutes. This period is estimated to be representative of the recirculation time at Iangbanerengöring. In long-distance recirculation, the system volume typically rotates every 10 minutes to 1 hour (depending on the flow rate and system volume). Additional mixing can take place as the flow passes through bends. T-holders, width holders (eng. Expander) etc and increases the particle suspension. In some areas, the flow can be turbulent, which further increases the particle suspension. In the sedimentation experiments performed, iron oxide particles traveled a maximum distance of 2.17 cm to settle on the bottom of the cuvette; this distance is considerably smaller than the average radius of typical feedwater and condensate lines. A typical suspended particle would therefore have a greater distance to settle which reduces the probability of early particle deposition.
    Because the duration of a long-range recirculation application is much shorter (on the order of a few days), at lower temperatures (layup temperatures) and at less critical assets than the steam generators, the use of higher dispersant concentrations or more chemically active dispersions is pergents acceptable.
    Since one of the purposes of this dispersant application is to increase the time that iron oxide particles spend in suspension, a relatively high deposition concentration (10,000 ppm) was used. The experiments performed focus on the suspension of either magnetite (FesOt) or hematite (FezOß) at a concentration of 10,000 ppm. In the results, the degree of sedimentation has been measured by determining the light absorption of the suspension, i.e. the sedimentation rate is determined by the rate at which the clarity of the suspension increases. The list of dispersant alternatives and their properties are given in Table 2. Raw data from all experiments performed are included in Tables 3 to 7. Table 3 shows the results for the 1: 1 ratio Magnetite: Dispersant (10,000 ppm); Table 4 shows the results for the 1: 100 ratio Magnetite: Dispersants; Table 5 shows the results for the 1: 1000 ratio Magnetite: Dispersants; Table 6 shows the results for the 1: 1 ratio of Hematite: Dispersant (10,000 ppm); and Table 7 shows the results for the 1: 1 ratio Magnetite: Dispersant (100 ppm). 535 137 Table 2 Predicted Secondary Dispersant Pre. Molecular Efficiency System Commercial Substance Oxide Mate ': in than ii I Compazibiiiiei 9 9 9 dispersion 2,000 Polyacrylic acid PAA 5,000 Moderate Good Good N.P.
    Polymethacrylic acid PMAA 6,500 Moderate Good Good Poly (acrylic | acid: malic acid) PAA: MA 3,000 Moderate Good Good Poly (Acry | acid: acrylamide) PAAM 200,000 Moderate Good Good Poly (acrylic acid: 2 acrylic PAA: AMPS 5,000 High Poor (Black) Ownership amide-2 methylpropanesulfonyl) phonic acid) Po | y (acrylic acidzsulfonic acid: PAA: SA: SS NP High Poor (Black- Ownership sulfonated styrene) well) Poly (2-acrylamide-2 methyl PAMPS 800,000 High Poor (Black- Moderate propanesulfonic acid vel) Poly (sulfonic acid acrylic acid) PAA: SA <15,000 High Poor (Sva- Owned well) Poly (sislfonated sty- 'e "" "a' ° '" sy'aa "hyd" d) PMA: ss 20,000 High Dåiigisva- Owned velL 535 137 21 Table 3 Deposition Dispersion Time to% transmittance (seconds) Test Material Material Conc. Polymer Conc. 0.1% 1% 2% 5% 5 min 1 (ppm (ppm) (initial mm 'reading) 7 M 10,000 1 10,000 30 110 157 282 5.4 14 12 M 10,000 2 10,000 21 86 132 235> 5.1 15.8 22 M 10,000 4 10.00 114 192 243 354 3.4 16.4 47 M 10,000 9 10,000 65 143 188 266 6.1 18 42 M 10,000 8 10,000 86 151 199 277 5.6 19.5 27 M 10,000 5 10,000 61 118 157 254 6.7 22.1 37 M 10,000 7 10,000 86 99 135 225 8.9 23.2 57 M 10,000 11 10,000 151 189 280 6.1 23.5 17 M 10,000 3 10,000 0 O <10 <20 17.6 24.6 1 M 10,000 55 100 127 212 10.5 26.8 32 M 10,000 6 10,000 0 0 0 0 30.8 35.6 52 M 10,000 10 10,000 0 0 0 0 32.7 40 Table 4 Deposition Dispersion- Time to% transmittance (seconds) Test # medium Material Conc. Polymer Conc. 0.1% 1% 2% 5% 5 min. 1_0 (ppm) (ppm) (inmal mm 'reading) 33 M 10,000 6 100 25 105 159 282 5.4 14.2 43 M 10,000 8 100 103 181 219 294 5.2 16.3 18 M 10,000 3 100 106 182 216 333 4.4 17 38 M 10,000 7 100 114 183 215 308 4.4 17.6 23 M 10,000 4 100 114 170 216 314 4.9 19.2 48 M 10,000 9 100 104 169 200 313 4.4 20, 4 13 M 10,000 2 100 42 101 141 206 8.8 21.1 8 M 10,000 1 100 94 150 190 307 4.6 22 58 M 10,000 11 100 92 145 214 271 7.1 22.1 28 M 10,000 5 100 84 136 180 290 5.8 23.5 1 M 10,000 55 100 127 212 10.5 26.8 53 M 10,000 10 100 45 101 127 197 11 27.3 535 137 22 Table 5 Deposition Dispersion Time to% transmittance (seconds) Test # means Material Conc. Polymer Conc. 0.1% 1% 2% 5% 5 min. 1 (ppm) (ppm) (initial mm 'reading 14 M 10,000 2 10 86 152 194 271 5.2 19.9 29 M 10,000 5 10 95 161 199 262 6.4 19.9 44 M 10,000 8 10 104 162 210 312 4.8 20 39 M 10,000 7 10 88 156 198 276 6.4 21 49 M 10,000 9 10 86 152 200 291 5.5 21.6 24 M 10,000 4 10 86 140 188 275 6.4 22.6 9 M 10,000 1 10 84 164 182 262 6.7 22.9 19 M 10,000 3 10 74 126 177 261 7.3 23 59 M 10,000 11 10 66 124 163 <30O 8.8 23.1 34 M 10,000 6 10 59 109 151 244 7.6 24.3 1 M 10,000 55 100 127 212 10.5 26.8 54 M 10,000 10 10 43 82 112 187 13 29.2 Table 6 Deposition Dispersion Time to% transmittance (seconds) Thesis 1 # medium Material Conc Polymer Conc. 0.1% 1% 2% 5% 5 min. 1_0 (ppm) (ppm) (initial mm 'reading) 4 H 10,000 142 261 326 439 1.5 10.4 11 H 10,000 1 10,000 <474 531 597 734 0 2.0 16 H 10,000 2 10,000 502 660 727 876 0 0.5 21 H 10,000 3 10,000 1653 2871 3403> 3510 0 0 26 H 10,000 4 10,000 409 521 600> 60O O 5.0 31 H 10,000 5 10,000 526 612> 705> 705 0 0.8 36 H 10,000 6 10,000 0 14 688 4875 1.7 1.9 41 H 10.0 00 7 10,000 352 448 505 637 0 3.9 46 H 10,000 8 10,000 355 440 497 636 4.1 51 H 10,000 9 10,000 355 447 504 622 4.0 56 H 10,000 10 10,000 22 1665> 3090 <3780 0.2 0 , 3 61 H 10,000 11 10,000 424 530 580 686 0 2.6 535 137 23 Table 7 Time Transmittance (@ 458 nrn, blanked to a solution without magnetite) Check as Test Test Test Test Test Test Test Test Test Test Test Test 10 15 20 25 30 35 40 45 50 55 60 3a 3b (S) 87.2 87.2 76.4 56.9 77.8 82.9 79.8 69.5 69.3 95.4 71.2 81.3 78.1 89 .5 92.3 76.6 57.3 78.4 83.2 80.3 69.7 69.6 95.5 71.5 81.3 78.1 45 89.9 92.8 77.0 57.5 78 .4 83.7 80.6 70.0 70.0 95.6 71.7 81.5 78.3 60 90.2 93.0 77.0 57.8 78.6 83.7 80.9 70.3 70 .3 96.1 71.9 81.6 78.3 75 90.3 93.0 77.1 58.2 78.7 83.9 81.2 70.7 70.6 96.1 72.2 81.7 78 , 4 90 90.4 93.1 77.3 58.5 78.8 84.1 81.4 71.0 70.9 96.2 72.4 81.8 78.5 120 90.6 93.5 77.6 59, 1 79.1 84.5 82.0 71.5 71.1 96.2 72.8 82.0 78.7 150 90.5 93.5 77.7 59.6 79.4 84.7 82.5 71.8 71.5 96, 6 73.1 82.1 79.0 180 90.9 93.693.6 77.9 60.1 79.6 85.0 82.8 72.2 72.0 96.8 73.2 82.2 79.0 210 91.1 93.793.6 78.2 60.5 79.8 85.1 83.0 72.4 72.2 96.9 73, 4 82.4 79.2 240 91.2 93.893] 78.5 60.7 79.9 85.2 83.4 72.7 72.5 97.0 73.6 82.5 79.2 270 91.3 93.893.8 78 .6 61.3 79.9 85.2 83.6 72.9 72.7 97.0 73.8 82.6 79.3 300 91.6 93.8 78.6 61.6 80.0 85.3 83 .8 73.1 73.0 97.0 74.0 82.7 79.3 330 91.8 93.9 78.6 61.9 80.0 85.4 84.1 73.2 73.2 97.2 74.1 82.8 79.5 An initial 10,000 ppm dispersant concentration was selected to give a 1: 1 dispersant core oxide ratio. The results of these tests are shown in graphical form in Figure 37. Several tests were allowed to continue beyond the initial ten-minute interval. The results of these tests are shown in Figure 38.
    Since a dispersant concentration of 10,000 ppm may not be practical (due to concerns with material compatibility, cost, etc.), the effectiveness of the dispersant alternatives was also evaluated at dispersant concentrations of 100 ppm and 10 ppm (corresponding to dispersant ratios: 100 oxide of iron: 1 spectrum 121000). The results of the screen tests performed with 100 ppm dispersant are shown in Figure 39. Several tests were allowed to continue for an extended period of time; these results are shown in Figure 40.
    In some areas of the secondary system, in particular areas of the feedwater system that experience relatively low temperatures during normal operation, deposits are mainly composed of hematite (FezOs). The effectiveness of the polymer alternatives for dispersing hematite was therefore evaluated. The results of the dispersant screen tests performed with 10,000 535,137 24 ppm hematite are shown in Figure 41. As before, subsequent tests were continued for an extended period of time; the results of these tests are shown in Figure 42.
    Dispersant material compatibility was also evaluated to assess the feasibility of the dispersant application in a secondary system. The dispersants were tested with various materials such as nickel-based alloys, carbon and alloy steels, stainless steel, elastomers, ion exchange resins, copper alloys, titanium and titanium alloys and graphite materials.
    As a result, it was decided that the following guidance would be applied to an initial industrial plant trial.
    A dispersant concentration of 1 ppm is recommended as a starting point for an initial plant application. The concentration can be increased gradually within the time window for downtime or in subsequent applications as more data for the actual system response signal becomes available.
    It is recommended that the dispersant be fed through a metering pump to avoid overfeeding. The injection site should be: a) sufficiently far upstream of the condenser to allow adequate mixing, and b) downstream of the condensate grinders to maximize the contact time of the dispersant with corrosion products and prevent local areas of high dispersant concentration from coming into contact with the resins.
    For the proposed initial application at 1 ppm (for example), dispersant addition should be initiated ~ 36 hours after long-distance recirculation has been established. Data from three inspected plants show that the majority of the easily removable corrosion products will have been removed by this time.
    The exact timing of the addition of dispersant is somewhat flexible. If possible, the cleaning solution should be added before the dispersant injection to ensure that the iron concentration is <100 ppb before the dispersant injection. This injection schedule is based on maximizing the effectiveness of a limited dispersant injection. In future applications in which the concentration of dispersant is increased or is initially higher, injection could be done earlier. 535 137 If the long-distance recirculation cleaning period is predicted to be less than 36 hours, the dispersant injection should be initiated earlier and at least 8 hours before feed water is introduced into the steam generators. This will allow the i uid in the condenser hot water tanks to be reacted at least 4 times, which gives the dispersant plenty of time to act on any dispersant material and possibly be removed by the condenser grinders. o A plant-specific review of system compatibility should be performed before performing dispersant application in the long-distance recirculation cleaning process to ensure that the addition of dispersants will not have unintended or unplanned consequences. Specifically, the effect of significantly increased deposition load on the condensate grinders and the potential effect on flow measuring devices should be considered.
    Following the sedimentation tests, additional experiments were performed to evaluate dispersant performance under dynamic conditions. It was determined that in addition to increasing the retention of iron in solution, the addition of dispersants can promote the resuspension of iron oxides which have previously settled in the secondary system during the closure and storage periods. The experiments evaluated the ability of the dispersant alternatives to resuspend deposited material under dynamic conditions. Based on the results of the tests discussed above, three dispersant options were selected for further testing under dynamic (flow) conditions: PAA (high molecular weight), PMAA, and PAA (low molecular weight). The purpose of these experiments was to determine whether these dispersants would resuspend previously deposited material, and if so, qualitatively evaluate the differences in performance between the selected dispersant alternatives under dynamic conditions.
    An experimental apparatus 20, shown in Figure 43, was designed to simulate the flow stresses present in the long-distance recirculation cleaning process. The experimental inputs are described below.
    Samples 23 in stainless steel coated with a 10 thousandth (mile) thick layer of deposition material were used to simulate corrosion products deposited on pipe surfaces of secondary systems. These test pieces 23 were dipped in a test solution (deionized water, with or without dispersant) and rotated to generate a fluid shear stress characteristic similar to that experienced near the surface of the pipeline in the longitudinal recirculation cleaning process. The remainder of this paragraph describes the main components of the experimental apparatus.
    The simulated plant deposition materials used in these tests (synthetic magnetite and hematite) were identical to those used in the sedimentation tests. A mixture of the appropriate iron oxide and deionized water was applied to one surface of each stainless steel specimen 23. The excess was removed with the help of a calendar to create an even surface coating. Once the deposition material was applied, the specimens 23 were heated according to the following schedule: v 3 hours at 100 ° C ø 3 hours at 150 ° C v 3 hours at 225 ° C v 3 hours at 280 ° C Nitrogen was released over the specimens 23 completely the heating process to prevent oxidation. At the end of the heating cycle, the test pieces 23 were allowed to cool to room temperature before being loaded onto the experimental apparatus 20.
    The stainless steel specimens 23 used in this test measured 2.07 "in diameter and 0.03" in thickness. Prior to deposition application, a hole was drilled through the center of each specimen 23 and one side was etched with an identification number. The test pieces 23 were then prepared by cleaning and roughening the non-etched side with emery paper. The deposition material was then applied to this side as described above. At the start of each test, the pre-treated specimen 23 was attached to the end of the drive wheel shaft 22 and placed so that it was suspended in fluid contained in a vessel 24 (the deposited surface facing downward) within 0.25 inch of the vessel floor.
    The experimental apparatus 20 was assembled in an autoclave bay. This space is provided with a variable speed magnetic drive wheel and motor 21, which can be connected to the shaft 22 and rotated at a specified frequency. For each test, a stainless steel specimen 23 was attached to the end of the shaft 22 extending down from the magnetic drive wheel 21 via a hole drilled through the center of the specimen. The sample 23 was dipped in a solution of deionized water (with or without dispersant) at ambient temperature. The specimen 23 was attached to the shaft 22 in such a way that the surface coated with deposit material was directed downwards and suspended 1/4 "above the floor of the vessel 24 containing the test solution.
    The rotation of the sample piece 23 created a radial distribution of fluid velocities across the surface of the sample piece 23, which produced varying shear stresses. In order to approximate the forces present on previously deposited material present in the longitudinal recirculation loop, a characteristic fluid velocity was calculated based on a representative plant geometry.
    The average velocity of the fluid in the system, u, was calculated by dividing the known flow rate by the cross-sectional area of the flow path using the following information: ø The typical flow rate of a representative plant during the long-distance recirculation cleaning process is estimated at 4,000 gpm. o It is assumed that the flow is evenly distributed between the two heater trains, the total flow rate through the feedwater heater during long-distance recirculation is 4000 gpm / 2 = 2000 gpm (4,456 fta / s).
    ~ Heater tubes are specified to have an OD of 0.625 inches and a thickness of 0.035 inches from which it can be determined that the inside diameter is 0.625 inches - 0.035 inches = 0.59 inches, o Each heater contains a total of 1397 tubes.
    The total area of the flow path is therefore: 'f u). w-'I. x I 'j-: I-ü ii ~ <, -r 382 m; = 2_55 f 1397 pipes The average fluid velocity through the heater is then: _ »í '* ~" * 5 ° f * = 1_ss ft / s 2.05 il: 535 137 28 To ensure that the range of fluid velocities experienced by different points on the test piece 23 was similar to the range of surface velocities experienced by the pipe wall in a typical longitudinal web cleaning process, the speed of the motor 21 was set at 230 rpm, at which speed about half of the surface of the specimen 23 rotates at a speed greater than 1.68 ft / s and half of the surface rotates at a slower speed, Tests were performed over a 24-hour period measured from the time when rotation of the specimen 23 was initiated.A 5 ml sample of the test solution was collected at 0.5, 1, 2, 5, 10 and 24 hours for elemental analysis for Once the specimen 23 had begun to rotate, it continued to rotate at the same speed until after the 24-hour specimen had been collected (the specimens were collected from the fl destructive solution).
    Once the engine 21 was turned off, the vessel 24 containing the test solution was removed and the solution was transferred to a sealable bottle for analysis. The specimen 23 was then disconnected from the shaft 22 and dried at 30 ° C under an inert gas.
    When it was dry, the specimen was collected to determine the weight of the lost deposit material. The amount of resuspended deposition material was determined both from elemental analysis of samples from the test solution taken throughout the test (suspended iron) and from weight loss measurements at the beginning and end (gross particles). Elemental analysis of the samples was performed with an inductively coupled plasma spectrometer (ICP). The results of the ICP analysis performed at each sampling interval (0, 5; 1, 2, 5, 10 and 24 hours) for the resuspension tests performed are shown in Table 8. The results of Tests performed with magnetite (Tests 1-7) are shown graphically in Figure 44 (1 ppm dispersant) and Figure 45 (100 ppm dispersant). Figure 46 and Figure 47 show the results of Tests 8-14 in which hematite was used as a deposition material. Standard samples were run after each test to check that all measurements were within a tolerance of 10%. The standard samples were measured after the 1-hour and 2-hour samples for Test 10 (100 ppm high molecular weight PAA and hematite) fell below the acceptable range, that is, they indicated too low the actual iron concentration. It is therefore possible that the actual iron content of these solutions is 20% higher; however, since it is unclear when the change in instrument readings took place, this cannot be said with certainty. The measured values for all other standard samples were within the acceptable range. 535 137 00.0 00.0 00.0 00.0 00.0 00.0 00.0 00.0 00.0 00.0 00.0 00.0 00.0 00.0 000-00 00.0 00.0 00.0 00.0 00.0 0.0.0 00.0 00.0 00.0 00 00 00 00 00 00 00. 00.0 50-0 00.0 00.0 00.0 00.0. 00.0 00.0 00.0 00.0 00.0 00.0 0.0.0 0.0.0 00.0 00.0 .00-0 00.0 00.0 00.0. 00.0 00.0 00. 0 00.0 00.0 0 0.0 00.0 00.0 00.0 00.0 0 0.0 .E00 00.0 00.0 00.0 00.0 00.0 00.0 00.0 0.0.0 00.0 00.0 00.0 00.0 00.0 00.0 000-00 000000 000006005 000 0 000 0 000 0 <2 000 000 0 000 0 <2 .0000000000000 0 052.0 052.0 052% 9> 2I0 0520 0520 0052 :. 5> 2: 0 _0005 << 20 << 20 <5 ". SE << 0 << 0 0000. << 20 << 20 << 0 << 0 SE << 0 .00.0 -000000000000 Éïæmrc 000.00: 000, 00: 000000: 000.00: 000000: 00020: 000.0: 0000002 0000002 0000002 0000002 0000002 0000002 0000002 -000000 _> <0000090 0.0 .000 00 0000 00 030 00 .000 00 .000 0 .000 0 .000 0 0000 0 .00.0 0 _30 0 .000 0 .000 0 080 0 .000 000000 02.008 mm 535 137 The mass of each specimen 23 was noted before deposition loading, after deposition loading and at the conclusion of the test period to determine the amount of deposition material lost by specimen 23 during the test. The bulk of this material was released into the test solution as flakes or large particles, which rapidly settled to the bottom of the vessel (0.25 "below the surface of the specimen). Upon removal of the specimen 23, a small layer of deposit material about 1/2 inch in diameter was found to have accumulated at the center of the vessel floor, where flow rates were lowest.
    Since the large flakes are believed to have detached from the specimen 23 due to the shear force of the fluid and not by the action of the dispersant, the results of the ICP analysis are considered to best reflect the effectiveness of the dispersant (its ability to retain small particles in solution). Evidence of the flow patterns created by the rotation of the specimen 23 could be observed in the remaining deposition material on the specimens. In general, the measured iron content was higher in solutions containing 100 ppm dispersant. However, the relative improvements in performance observed at 100 ppm were significantly less than would have been expected for a factor of 100-fold increase, given that an increase in the amount of dispersant available would theoretically result in a proportional increase in iron suspension. In the tests to evaluate the resuspension of magnetite, the presence of 100 ppm dispersant resulted in iron concentrations which were on average 2 to 3 times higher than those observed with 1 ppm of the same dispersant. This corresponds to a factor of 2 to 3 times the increase in efficiency with a factor of one hundred times the increase in concentration. The relative increases in efficiency of solutions containing 100 ppm against 1 ppm dispersant are shown in Table 9.
    Table 9 Time Magnetite Suspension Hematite Suspension Period PAA (HMW) PAA (LMW) PMAA PAA (HMW) PAA (LMW) PMAA First -52% 159% 166% 55% 15% 249% 2 hours 2-24 hours 1318% 220% 24 % 107% 11% 168% Total 861% 199% 71% 90% 13% 195% Negative values show that the dispersant solution of 1 ppm was more effective than the dispersant solution of 100 ppm. Since the time required for the fluid to circulate throughout the flow path (and therefore the condensate grinders and / or filters) is in the order of 30 minutes to 2 hours, it is necessary for the dispersant to promote long-term particle suspension in order to be effective.
    The majority of the test results show that a dispersant concentration of 1 ppm is sufficient to significantly increase the iron oxide dispersion over a period of two hours. Since this is the estimated cycle time for a one-time run through the condensate grinders during the long-distance cleaning, the evaluation of the effect can be limited to this time frame.
    The percentage improvement in iron oxide suspension observed in each test containing dispersants is shown in Table 10 and Table 11 (for testing performed with magnetite and hematite deposition materials, respectively). Although all three dispersants significantly increased the suspension of iron oxides under dynamic conditions, the largest increase in magnetite concentration in the test solution containing 1 ppm of high molecular weight PAA polymer was observed at the time periods of interest (1- and 2-hour sampling points). These data show that the formulation of high molecular weight PAA will be most effective in dispersing corrosion products consisting of magnetite until they can be removed from the system.
    Table 1 0 Test no. Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Dispersion PAA (HMW) PAA (HMW) PAA (LMW) PAA (LMW) PMAA PMAA with Dispersion- 1 100 1 100 1 100 average conc. (ppm) 0.5 -tim. 160% 37% 12% 122% 9% 211% 1 -hours. 602% 202% 67% 434% 76% 332% Z-tirn. 121% 655% 65% 140% 145% 158% Table 1 1 Test Nr. Test 9 Test 10 Test 1 1 Test 12 Test 13 Test 14 Dispersion- PAA (H MW) PAA (HMW) PAA (LMW) PAA (LM Al) PMAA PMAA agent Dispersion- 1 100 1 100 1 100 agent conc. (ppm) 0.5-hr. 9% 69% 57% 143% 33% 384% 1-tim. -15% 30% 157% 96% 33% 346% Z-tim. -2% 36% 170% 133% 51% 399% 535 137 32 Unlike the results of the preliminary sedimentation tests, the high molecular weight PAA formulation performed less efficiently compared to the other two dispersant alternatives (and the control) in the resuspension tests with hematite. The iron oxide concentration of this test solution was slightly higher than that of the control solution.
    In summary, the resuspension tests gave the following results.
    A dispersant concentration of 1 ppm is sufficient to significantly increase the magnetite dispersion.
    Larger iron nut suspension was generally observed in tests with high dispersant concentrations (100 ppm) compared to those with 1 ppm dispersant. However, the increase in efficiency is not proportional, which could perhaps be predicted from theoretical considerations.
    The majority of the test results show that a dispersant concentration of 1 ppm is sufficient to significantly increase the iron oxide dispersion for a period of about 2 hours. Since the time required for the iden uid to circulate through the entire flow path (and therefore the condensate grinders and / or filters) is of the order of 30 minutes to 2 hours, this time period is sufficient for the dispersant to be effective (a suspension time greater than or equal to the cycle time ensures material will reach the condensate grinders before depositing in the system). Although all three dispersants significantly increased the suspension of iron oxides under dynamic conditions, the largest increase in magnetite concentration in the test solution containing 1 ppm of the high molecular weight PAA polymer was observed at the time periods of interest (1- and 2-hour sampling points).
    The high molecular weight PAA formulation did not perform as well as the other two dispersant alternatives in the hematitis resuspension tests.
    The foregoing has described a method for cleaning recirculation paths for a power-producing plant. Furthermore, embodiments of the invention relating to a method for testing resuspension characteristics and resuspension tests have been described. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications may be made therein without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are given for the purpose of illustration only and not for the purpose of limitation.
    权利要求:
    Claims (8)
    [1]
    A method of testing the resuspension characteristics of a chemical dispersant, comprising the steps of: (a) providing a test apparatus comprising: (i) a solution containment vessel; (ii) a drive wheel system; and (iii) a shaft; (b) attaching a substrate coated with deposit material to the shaft; (c) dipping the coated substrate in a solution contained in the vessel; (d) using the drive wheel system to rotate the shaft and the coated substrate at a predetermined speed; and (e) determining an amount of deposition material removed from the substrate.
    [2]
    The method of claim 1, further comprising the step of weighing the substrate prior to coating with the deposition material.
    [3]
    The method of claim 1, further comprising the step of weighing the substrate after coating with the deposition material.
    [4]
    The method of claim 1, further comprising the step of weighing the substrate after the substrate is removed from the solution.
    [5]
    The method of claim 1, further comprising the steps of collecting samples of the solution at predetermined time intervals during testing to determine an elemental content of the solution.
    [6]
    A method according to claim 1, wherein the amount of deposited material removed is determined by an amount of elemental content contained in the solution and a weight of deposition material removed from the substrate.
    [7]
    The method of claim 1, further comprising the step of coating the substrate with the deposition material. 535 13 35
    [8]
    The method of claim 7, wherein the step of coating the substrate comprises the steps of: (a) applying a predetermined amount of deposition material to the substrate; (b) removing excess deposition material from the substrate; (C) heating the coated substrate; (d) releasing nitrogen over the coated substrate during the heating step to prevent oxidation, and (e) cooling the coated substrate to room temperature. 10
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    同族专利:
    公开号 | 公开日
    JP5081950B2|2012-11-28|
    ZA201003750B|2011-03-30|
    FR2949261A1|2011-02-25|
    GB2488677A|2012-09-05|
    CA2706054A1|2010-12-02|
    JP5542164B2|2014-07-09|
    GB2480111B|2013-12-18|
    FR2945970A1|2010-12-03|
    ES2389218A1|2012-10-24|
    SE1150545A1|2011-06-16|
    GB2488677B|2013-12-18|
    JP2012163102A|2012-08-30|
    ES2389218B2|2013-07-04|
    FR2949201A1|2011-02-25|
    GB2480111A|2011-11-09|
    SE1050547A1|2010-12-03|
    GB201008501D0|2010-07-07|
    US20100300218A1|2010-12-02|
    GB201204892D0|2012-05-02|
    JP2011007179A|2011-01-13|
    SE534867C2|2012-01-24|
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    法律状态:
    2016-02-02| NUG| Patent has lapsed|
    优先权:
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    US18325209P| true| 2009-06-02|2009-06-02|
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