Author: anderthalbAdmin

Treating Make-up Water and Condensate by Reverse Osmosis in an LP Vinyl Records Pressing Plant

Pavel Hübner

At the Czech company GZ Media a.s., which produces vinyl records, the vinyl presses are heated by steam and after pressing, the steam is rinsed from the press by cooling water. The condensate therefore contains a high proportion of cooling water.

In the original system, the losses of steam and cooling water were replaced by filtrated and softened raw water. The polluted condensate was also treated by filtration and softening. The water used as make-up, which was originally considered drinking water, has been replaced for economic reasons by surface water with high salinity and alkalinity. Due to high operational costs and other considerations the original design was replaced with a new one in 2019.

The new system treats the mixture of raw water and cooled condensate by on-line coagulation followed by reverse osmosis. The hot condensate is cooled by heat exchange, which transfers the heat to the permeate as feedwater. The new system exhibits very low boiler blow-down, minimal consumption of chemicals and low operator attendance.

PPCHEM^® 2020, 22(3), 104–109

Calculations to Manage Phosphate and Caustic Treatment

Randy C. Turner

Phosphate and/or caustic (NaOH) treatment boiler water treatment is often employed to reduce the risk of corrosion.

This paper describes empirical calculations for proper control of phosphate and caustic treatment which could be incorporated into an Excel spreadsheet which includes several calculations, of which the most important are:

1. Boiler water ammonia corrected pH
2. Sodium to phosphate molar ratio
3. Free sodium hydroxide concentration
4. Amount of phosphate and/or caustic to dose for a specific concentration at the current operating pressure

This can also be used to calculate how much caustic must be added to an AVT treated boiler to achieve a desired pH-value.

PPCHEM^® 2020, 22(3), 112–117

The Impact of Low-Load Operation on Power Plant Chemistry

Frank Udo Leidich

Nowadays conventional power plants are more challenged in regard to load flexibility and especially frequent(very) low-load operation. While the so-called “dark doldrums” must be managed without de-stabilizing the grid,a bright sunny and windy day requires almost no conventional power generation. This kind of operation not onlystresses the plant components mechanically and thermally, leading to accelerated aging of the plant, but the physico-chemical operation also becomes more challenging. This paper highlights the most important aspects of theimpact of low-load operation on the chemical operation of a power plant. It is shown that it pays to operate the unitwith water and steam that is as clean as possible.

PPCHEM^® 2020, 22(3), 118–129

Corrosion Issues Caused by Changes in Pipe Cross-Sections

Andrés Rodríguez Pérez

Among the most detrimental corrosion phenomena observed in the power industry are those related to a sudden expansion of a fluid beyond the saturation point. The effects of such types of corrosion may be particularly aggressive due to a combination of physical factors and a variety of chemical mechanisms that could potentially be involved. Based on data collected from over one hundred inspections carried out in the power industry and refineries, this publication is aimed at building a stronger understanding of the issues to allow plant operators to predict areas of vulnerability, mitigate the risk of potential failures, and specify a correct chemical treatment program to operate their plant at its maximum level of performance and reliability.

PPCHEM^® 2020, 22(2), 66–72

Chloride Contamination of the Water/Steam Cycle in Power Plants: Part VII. Final Verdict on Vapor Ingress of Chlorinated Compounds via Weak Tube/Tubesheet Joints

Emmanuel K. Quagraine, Trever McNabb, Suzanne McNabb, Sheldon McNabb, Taneal Weiss, Gillian Bailey, Ashley Ponak, Brenna Janzen, and Janet Meyers

This paper concludes a series of publications on investigations at Shand Power Station (SaskPower) to understand selective chloride cycling in this plant. With naval brass tubesheet, dezincification was implicated as the corrosion mechanism at naval brass tube-to-tubesheet joints, which created vapor pathways for recirculating cooling water (RCW) chlorine compounds into the water/steam circuit, eventually forming chlorides. Replacing the tubesheet with Duplex 2507 SS, the expectation was that the chloride cycling would end. Yet it persisted. The paper provides evidence that even with new metallurgies, vapor ingress via weak tube-to-tubesheet joints has mainly been responsible for the persisting chloride cycling. Organochlorine compounds leaching from the tubesheet/shell interface gasket have also been shown to potentially contribute to the chloride cycling, to a major extent earlier on, but becoming less significant over time. Plugging of the leaking tubes at tube-to-tubesheet joints reduced the average daily increases in boiler chloride from 28.4µg⋅L^–1 to 2.7µg⋅L^–1, supporting the notion that the RCW was the principal source of the chloride contamination.

PPCHEM^® 2020, 22(2), 74–90

Dependence of the Corrosive Environment in BWRs on Operating Conditions

Yoichi Wada, Kazushige Ishida, Nobuyuki Ota, and Makoto Nagase

The effects of core management in a boiling water reactor (BWR) on radiolytic oxygen and hydrogen peroxide concentrations in the reactor water have been studied based on a radiolysis model. An increase in core flow promoted radiolysis of water in the core region since the amount of water present in the core region became larger and mass transfer from water to steam slowed down. Also, a decrease in core peripheral power at the end of the cycle reduced the effectiveness of hydrogen water chemistry (HWC) applied to reduce radiolytic oxygen and hydrogen peroxide and the subsequent electrochemical corrosion potential for mitigation of stress corrosion cracking since the downcomer dose rate became weaker with operation. These caused an increase in the sum of the oxygen and hydrogen peroxide concentrations at the same hydrogen injection rates and the effectiveness of HWC decreased. The effectiveness of noble metal chemical addition was not affected by changes in operating conditions at a 0.5 mg · kg^–1 hydrogen injection rate.

PPCHEM^® 2020, 22(1), 10–17

Water Chemistry Management for the Primary Circuit of the First EPR Unit during Hot Functional Testing

Zhu Wang, Zhi-Wei Ge, and Zi-Tao Liu

The paper describes in detail the water chemistry control during the hot functional testing (HFT) of the first European pressurized reactor (EPR) unit worldwide, and focuses on the water chemistry control during passivation treatment of the component surfaces in the primary circuit with hydrogen injection, higher pH_300°C and impurity control. Two identical surveillance coupons made of Inconel 690 TT steam generator (SG) tube samples were placed in the reactor pressure vessel (RPV) to evaluate the final passivation results. Water chemistry data and metallographic analysis results show that an excellent protective film was formed on the surface of the tubes, which reduces the corrosion rate of materials and the release of corrosion products, thereby also reducing radiation source terms during commercial operation of the unit. In addition, a brief comparison of the passivation film and passivation process between two types of the 3rd generation pressurized water reactors (PWRs), especially the hydrogen injection and zinc injection technologies, was made. The benefit of the passivation process during HFT for the dose rate is preliminary, and the dose rate reduction effectiveness also depends on the applied water chemistry control methods during future power operation of the unit.

PPCHEM^® 2020, 22(1), 20–29

2019’s Scientific and Technical Contributions

PPCHEM^® 2020, 22(1), 48–55