The cation conductivity is measured before as well as after degassing and cooling, so called 'degassed' cation conductivity. And if youre measuring multiple sample points, you may only get one analysis per point per hour. unsubscribe from these communications at any time. Conductivity is measured after this process and may also be measured at the analyzer inlet and ion exchange column outlet. In order to obtain a selective conductivity value for these saline-containing ions (with the maximum potential for corrosion), all remaining carbon dioxide must be removed from the sample in order to accurately determine the presence of corrosive ions. Cation Conductivity : Faster Startup Paper.pdf (5760kB). Cycle chemistry parameters may include specific conductivity, cation conductivity, degassed cation conductivity, calculated pH, pH by sensor, ORP, carbon dioxide, ammonia, dissolved oxygen and . 25 Minneakoning Road, Suite 101 The AMI Deltacon DG continuously ensures that boiler, condensate and steam samples are contamination-free by removing up to 95% of CO2 in the sample. Cation conductivity is the most common measurement in the steam/water cycle of a power plant. The measured electrode signal is compared to the reference electrode potential and translated into sodium ion concentration, which is displayed on a meter and supplied to a recording device. What passes through the resin unscathed are all the anions in the sample. What remains in the water sample are salt-like (acid-like) ions and organic components, as well as oxygen and nitrogen which do not form ions in aqueous media. Jun. According to the manufacturers, the instruments operate in a concentration range of 0.1 ppb to 100,000 ppm of sodium ion with a sensitivity of 0.1 ppb. Waltron Group Headquarters 1. Degas conductivity is used as an indicator of water quality in the water/steam cycle of power stations. Most of the combined cycles in the . Therefore, sodium detection in condensate, even at the 0.1 ppb level, becomes an excellent early warning system for condenser tube leaks or sodium leakage from water pretreatment systems. The removal of the carbon dioxide is carried out in an exchanger column according to the contraflow principle. I have 10 years of experience in the water treatment industry. Automatic shutoff of reboiler in the case of sample loss. For example, in a sample containing less than 1 ppm dissolved solids, specific conductance may be in the range of 1.0-2.0 S. With the addition of even a small amount of salt (say NaCl), conductivity shoots up drastically. Flame spectrophotometer testing is much more sensitive to quick changes in operating conditions and detects peaks in solids concentration. If a superheated steam sample is gradually cooled as it flows through the sample line, solids deposit on sample line surfaces. Locating and plugging the leaking condenser tube would have been easy and would have avoided the repair costs and millions of dollars in lost generation revenues. The DCC1000e is a degassed cation conductivity panel that provides the user with three measurements of conductivity: direct conductivity, cation conductivity and degassed . Scaled up. Because the ammonium ion is removed and exchanged for hydrogen, the pH of the water exiting the column is more acidic than it was entering. In typical operation, a regulated amount of an agent such as ammonium hydroxide is added to a regulated amount of condensed steam sample to raise pH and eliminate the possibility of hydrogen ion interference. The steams chloride concentration would have to rise to nearly 20 ppb before the resultant cation conductivity would exceed the generally accepted normal cation conductivity limit of 0.2 S/cm. Simultaneous measurement and display of conductivity (x 3), pH, alkalizing reagent. Chemical analysis of steam during startup and inspection of the turbine give a good indication of steam quality. When expanded it provides a list of search options that will switch the search inputs to match the current selection. In case (1), the cations replace Na ions and the outcome is HCl, the corresponding acid.In case (2), the cations replace NH4 ions and the result is water (H2O), i.e. This innovative on-line instrument is the complete solution for degassed cation conductivity monitoring requirements in cycling power stations. You may The degassed cation conductivity measurement uses the same ion exchange strategy as the cation conductivity measurement. This interference can be appreciable in a high-purity steam sample. All sample-wetted parts are either 316 SS or plastic Selection valve allows sample to be analyzed for either cation conductivity or degassed cation conductivity Versatile options include integral high purity conductivity analyzer; gas regulator; flow meter and flex hose; and isolation valve and flow meter Features Resources This ensures that no corrosive anions or other corrosive contaminants which can cause corrosion of turbine blades are present in steam. it is indirect measurement of anions present in water, mainly chloride & sulphate present in steam samples. 2. One reason for this is that superheated steam turbines have an extremely low tolerance for solids contamination in the steam. Ion chromatography analysis of a single sample for chloride, phosphate, and sulfate can take quite a few minutes. Steam & Water. The exact ratio of sodium to dissolved solids in the boiler water and consequently in the steam can be determined for each plant but is approximately 1:3 for most plants (i.e., for each 0.1 ppm of sodium in the steam there is approximately 0.3 ppm of dissolved solids present). A reservoir stores the conditioned sample and feeds it at a constant flow rate to the tip of the sodium ion electrode and then to a reference electrode. If you wish to view one of these items separately, click on the image or name. 1 Input One input for potential-free contact. Most turbine manufacturers call for the chloride level in the steam to be below 2 ppb under normal conditions. It ensures water purity with precise detection of corrosive contaminants. ,xpl`RbHkj8[ A regulated flow of technical grade nitrogen or helium gas is introduced into the bottom of the column and is diffused into the sample to create turbulence. EPRI also suggests the use of smart chemistry alarms to help aid in the determination alarm validity. See the graph showing relative CO2 concentration. Because some plant operators and chemists have had problems with degassed cation conductivity monitoring, they have looked for other ways to detect parts-per-billion levels of contamination in condensate. 1 Alarm relay One potential free contact for summary alarm indication for programmable alarm values and instrument faults. This would affect interpretation of test results. Is cation conductivity so important that high values justify taking a unit off-line? Another commonly used method for measuring steam purity is the sodium tracer technique. The flow cell is equipped with a manual flow adjustment valve and a digital sample flow meter. They also take advantage of the high conductance of solutions containing hydrogen ions. System cools re-boiled sample with incoming sample (no separate cooling system required). Get accurate and reliable cation conductivity measurements with Sentry Equipment. Figure 2 shows Hachs unit. Because sodium constitutes approximately one-third of the total solids in most boiler waters and can be accurately measured at extremely low concentrations, this method of steam purity testing has been very useful in a large number of plants. The DCC1000 System offers a new design for precise detection of degassed Cation Conductivity and Dissolved CO2. %PDF-1.5 % The most common complaint about reboiler-style degassed cation conductivity is unreliability. When the sampling procedures are not followed properly, the steam purity evaluation is of little or no value. All Rights Reserved. Isokinetic flow is established when steam velocity entering the sampling nozzle is equal to the velocity of the steam in the header. Dont operate your steam turbines and HRSGs without the tools to see whats coming down the road soon enough to steer away from problems. Growth in renewable (but unsteady) energy sources has placed greater burden on modern gas-fired electric plants to cycle on and off to maintain steady and reliable electric production between Renewables and Base Load. For that reason, M&M strongly recommends using both cation conductivity and sodium monitors not only on the main steam sample but also at the hotwell or condensate pump discharge (or, if there are condensate polishers, downstream of them). Rated load: 1A / 250 VAC 2 Signal outputs (3rd as option), 2 programmable signal outputs for measured values (freely scaleable, linear or bilinear) or as continuous control outputs (control parameters program-mable). 2023 Access Intelligence, LLC - All Rights Reserved, The operators of a new combined-cycle plant being run in two-shift mode (on 16 hours, off 8) had become used to the cation conductivity sample of the condensate pump discharge being in alarm for a while following each days start-up. The degassed cation conductivity value indicates whether this higher reading is caused by impurities or by the less problematic carbon dioxide. John Powalisz (JP): Cation conductivity is one of the best ways to monitor for contaminants within a steam or water sample. In contrast with a gas such as CO2, nitrogen and helium will dissolve in a sample but will not dissociate or react with the water. This measurement is typically done at startup when air intrusion is typical and can artificially raise the cation conductivity. Patented Slot-Lock system for easy sensor maintenance. JavaScript seems to be disabled in your browser. When a condenser tube springs a leak, chloride, sulfate, carbonate, and many other anions contaminate condensate and feedwater. Solids are usually dissolved in water droplets or are present as dust. This resin column removes ammonia, amines, and sodium hydroxide from the sample. Samples are gathered in special laboratory-prepared, polyethylene bottles, and care is taken to protect against contamination. Cation conductivity also responds to less aggressive bicarbonate ions from CO2, which could be considered interference. Of these, only silica contributes to the difficulties commonly associated with impure steam; the other constituents are of concern only where they interfere with the measurement of steam purity. Accurate sampling of superheated steam presents problems not encountered in saturated steam sampling. These ions replace the +ve ions of any salt /dissolved impurity as it dissociates in water. Degassed Cation Conductivity Description Features Specifications Benefits Applications Download A new design for conductivity measurement for power cycle chemistry monitoring. This has led some to use the term acid conductivity to describe cation conductivity. Though this sensitivity level is insufficient to detect contamination of feedwater, it has been used very successfully to continuously monitor chloride levels in boilers and HRSGs. Carbon dioxide is an impurity that enters the steam / water cycle mostly as air in-leakage or by decomposition of organic matter (impurities or added treatment chemicals). +31 85 065 45 50. The new parameter to be monitored and analyzed goes by the name of degassed cation conductivity. How low can you go? The degassed measurement incorporates a reboiler to remove volatile compounds (like ammonia, amine, volatile organics, and CO 2) from the steam to provide a more accurate indication of sulfate and chloride levels. Cation conductivity is also called acid conductivity or conductivity after cation exchange. It provides highly sensitive detection of corrosive anions such as chloride and sulfate, but it also responds to less aggressive bicarbonate ion from CO2 which could be considered an interference. Cation conductivity is sometimes improperly implemented by using oversized cation exchange cartridges in an attempt to lengthen their service life. For units that only experience high cation conductivity during start-ups, nitrogen sparging may be all that is required. Contact us at +1-262-567-7256, or complete our online contact form for more information. The DCCP is a complete panel that measures specific cation and degassed conductivity or any individual measurement needed. Called "degassed cation conductivity," it's often conducted at startup when air intrusion is common and can artificially raise the cation conductivity. NH4(+) + OH (-) =>. For this reason, a degassifier is sometimes used to further condition the sample by removing CO2. Faster Plant Startup After the sample has been cooled and the pressure controlled, it enters the sparger assembly. Resistivity / Specific Conductivity Monitoring AMI Rescon Why? Monitoring degassed cation conductivity provides valuable information to utilities that utility plants protect their assets from cycle chemistry contamination. Gases are dissolved in water in the ratio corresponding to the partial pressure of the gases in contact with it. Would you describe the material state of your application as bulk solids? Had the operators not ignored the high cation conductivity reading at the condensate pump discharge, they would have known they had a problem. Cation conductivity also responds to less aggressive bicarbonate ions from CO, Common Degassed Cation Conductivity Methods, Understanding the Challenges in HRSG Water and Steam Monitoring, The Advantages of Chlorine Dosing to Control Biofilm, Monitoring Cooling Water Systems to Improve Plant Performance. Please keep in mind that particular cation or anion is separately not present in water. Language links are at the top of the page across from the title. ABB can help you with solutions for power plants especially around analytical measurement needs. By precise heating of the process solution to near-boiling after a cation column, carbon dioxide and other low molecular organics are volatilised and removed. Programmable hold or remote off function. Swans Soditrace model claims the industrys lowest detection limit for sodium ion concentrations of 1 part per trillion (0.001 ppb). For this reason, a degassifier is sometimes used to further condition the sample by removing the CO2. Of course, if there is a large contribution from CO2 or organic acids, the problem may not be detected until it is too late. What cation conductivity is not is a reflection of a single parameter, as in the case of sodium or silica analysis. Neither method is suitable for continuous, unattended monitoring. Instructions for these nozzles can be found in ASTM Standard D 1066, "Standard Method of Sampling Steam" and ASME PTC 19.11. As explained above, the cation column removes effects of ammonia and other alkalising agents, but still dissolves gases like CO2 which contributes to the CACE value. The simplest, most reliable way to detect such contamination in real time has been cation conductivity. e.g. Like driving in the dark, the risks of operating a plant blind are far too great. Measurement of this increase provides a rapid and reasonably accurate method for determining steam purity. This white paper discusses how power plants can derive a calculated pH value and a calculated CO2 value from measurements of specific,cation and degassed cation conductivity. The conductivity increase is due to the conversion of CO2 in water to a weak acid (carbonic acid). It is also referred to as Conductivity after Ion Exchange (CACE), Acid Conductivity and After Exchange Conductivity. 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