Introduction

A multinational energy company and global power and natural gas production giant discovered silica deposition issues in one of its power plants. Sediments damaged the turbine blades, leading to unplanned repairs. The company specializes in researching and utilizing innovative technologies, aiming to understand the root causes of power plant problems and find a sustainable solution to prevent future shutdowns and maintain optimal power generation efficiency.

Power plants determine their start-up and shutdown based on market demand and fuel costs. When the factory restarts, it is necessary to ensure steam purity in order to overcome temperature and pressure fluctuations during startup and shutdown.

problem

The operators of the power plant discovered a decrease in power generation and issues with turbine vibration. After they shut down and turned on the turbine, they saw obvious white deposits, which were various thicknesses of silica deposited at the edges of the turbine blades. After discovering this issue, operators and researchers had to evaluate the water quality and water treatment process.

In front of the boiler, the power plant uses a desalination system composed of cationic, anionic, and mixed resin layer units. The power plant has re evaluated the monitoring parameters for controlling desalination system regeneration and maintaining boiler feedwater purity. Reducing pollutants becomes particularly important when power plants are turned on and off, as pollutants may enter the steam and then the gas turbine during restart.

Previously, power plants used online silica analyzers to monitor silica and prevent it from entering steam and depositing in gas turbines. But when the silica analyzer reaches the alarm limit (10 ppb), it is often too late to stop the boiler feedwater and regenerate the mixed resin layer. Trace amounts of silica have leaked into the steam and entered the gas turbine.

Solution

In contrast to online silica analyzers, online boron analyzers are often used as zero pollution monitoring tools to control the leakage of silica from ion removal processes (such as ion exchange processes in mixed resin layers). Before other ions leak, the boron rate is eluted from the resin layer (see Figure 1). Online boron analysis can detect boron concentrations as low as 15 ppt (see Figure 2), so the boron analyzer can not only prevent silica from entering the boiler, but also prevent weak acids, weak bases, and other pollutants from the treatment process from entering the boiler. In addition to preventing silica leakage and managing resin depletion, power plants also use simple, internal methods to decide whether to accept or reject boiler feedwater. The Total Organic Carbon (TOC) analysis method can measure the total amount of organic compounds in both ionic and non-ionic forms in sample water. Non ionic organic matter can leak out of the treatment system and decompose into corrosive acid gas in high-temperature and high-pressure boilers. After the desalination system, the power plant uses TOC analysis to determine whether to allow water to flow into the boiler to generate steam that enters the gas turbine. The internal standard of the factory is TOC<40 ppb. At this point, most of the conductivity comes from TOC, so the redundant parameter is conductivity<0.4 μ S/cm.

Figure 2

　　(a) Sievers * online boron analyzer monitors boron in the flow path of samples 1, 2, 3, or 4 in ultrapure water, with a monitoring range of 15 ppt-20 ppb.

(b) Sievers * M500 online TOC analyzer measures TOC in ultrapure water, with a measurement range of 30 ppt-2.5 ppm.

(c) The dynamic TOC measurement range of Sievers * M9 online and (d) Sievers * M9 portable TOC analyzer is 30 ppt-50 ppm, with a wide measurement range and stable and accurate measurement results.

Conclusion

A large multinational power company uses online monitoring tools to protect equipment assets and control water treatment processes. Ensuring the purity of steam can greatly improve production efficiency, reduce downtime, and ensure the production, distribution, and sales of electricity and natural gas.

References

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2.Dennis,K.(Intel); Godec,R.(GE Analytical Instruments); Kosenka,P.(GE Analytical Instruments),“Progress Report on New On-Line Boron Analysis Research,”Executive Forum Proceedings,Watertech 2000 年

3.Sushma Malhotra(AMD),Otto Chan(AMD),Theresa Chu(Balazs Analytical),and AgotaFusko(Balazs Analytical),“Correlation of Boron Breakthrough versus Resistivity and Dissolved Silica in a RO/DI System,”Ultrapure Water,pp.22-26,Vol.13,No.4,1996 年

4.Wickham,R.(IDT),Godec,R.(GE Analytical Instruments),“Controlling Boron Levels in Semiconductor UPW using an Experimental OnLine Boron Analyzer,”Semiconductor Pure Water and Chemicals Conference,Proceedings,pp 15-33,2001 年

5.Johnson,E.(Micron),Somerville,K.(Micron),Godec,R.(GE Analytical Instruments),Dunn,R.(GE Analytical Instru-ments),“The Analysis of Boron,Colloidal Silica,and Reactive Silica Leakage from Primary and Secondary Regenerable Mixed Ion Exchange Beds in an UPW System,”Executive Fo-rum Proceedings,Watertech 2002 年, Portland,OR.

6.Dunn,R.,“New Analytical Technique Promotes Elimination of Silica in Feed,Steam and Condensate Systems,”Present-ed at International Water Conference,Pittsburgh,PA,2002 年10月

7.Godec,Richard,“Preventing the Release of Nano Materials from Depleting Ion-Exchange Beds by Using an Online Bo-ron,”Presented at ULTRAPURE WATER Conference,Port-land,OR,2011 年11月, Tall Oaks Publishing,Inc.