Sampling Systems & Analytics

Transcription

1 Sampling Systems & Analytics THORNTON Leading Pure Water Analytics Matarvattenkonferensen Stockhom, 2013 Agenda METTLER THORNTON TOLE and METTLER Thornton TOLE background background Sampling System Measurement Recommendations Sampling System Tips for Analytics Trends 2 Page 1

2 Brief History of THORNTON Founded in 1964 by Dr. Richard Thornton to measure conductivity in semiconductor ultrapure water, joined MT in 2001 First coaxial conductivity sensor 1980s First microprocessor-based conductivity temperature compensation a major accuracy improvement 1990s First development of Smart Sensors and multiparameter analytical instrumentation 2000s First Total Organic Carbon (TOC) instrumentation using multi-parameter sensor concept 2010 Developed Intelligent Sensor Management, providing highest accuracy, widest range conductivity measurement with Uni sensors and advanced predictive maintenance with other parameters Always focused on pure water measurement & treatment. 3 Global Process Analytics Presence Urdorf: R&D Centre and Production Bedford: THORNTON R&D Centre and Production Shanghai: Production São Paolo: Production Representative Main Office Representative Branch Office Manufacturing 4 MO Main Office MO Branch Office Page 2

3 METTLER TOLE Thornton Industry Participation Present and exhibit at industry conferences - EPRI Chemistry Conferences - VGB Chemistry Conferences - Electric Utility Chemistry Workshop - International Water Conference - Southwest Chemistry Workshop - IAPWS - International Conf. of Nuclear Engineering Help develop and revise ASTM and TPRI standards Author technical papers and Advertise in - PowerPlant Chemistry - Ultrapure Water Journal - Combined Cycle Journal Distribute semi-annual power industry newsletter 5 MT PRO - Power Portfolio Overview MT & Thornton History/Brand Reputation on core technologies Quality, Service, Innovation Commitment to Power Uni w/ism Better Accuracy with Digital Expanded Measurement Range phure Best sensor for difficult application Better design and lower maintenance than competition for Power High Performance, Long Life and Optical in 2013 Easier and lower maintenance than competition TOC Co-gen applications Increasing interest in feed water testing Page 3

4 MT PRO - Power Portfolio Overview Thornton M800 THE ISM Transmitter Multi-parameter/Multi-Channel Touch Screen Interface Full range of Parameters Derived Values (Calculated ph) Complete solutions with flow measurements Thornton M300 Entry level ISM Transmitter Plug & Measure Multi-parameter/Multi-Channel Sodium & Silica New Parameters with Latest Technology Feature Rich/ Value for money Significant time savings vs. several Sodium competitors Lower cost of ownership for Silica vs. Competitors Completes the core Power Portfolio ISM for all Parameters True Innovation Making maintenance easier Measurement confidence Agenda METTLER TOLE background Sampling System Measurement Recommendations Sampling System Tips for Analytics Trends 8 Page 4

5 Sample Pts Drum Boilers with Phosphate Sample Pt. On-line Grab Freq Sample Pt. On-line Grab Freq Makeup Silica, Spec. Sulfate, TOC D, D, W Deaerator Outlet Sodium D Feedwater, Oxygen D, 3x Weekly, Storage Iron, Copper 3x Weekly Pump Discharge Polisher Deaerator Cation., Silica, Cation., Oxygen Scavenger or Economizer Scavenger, ph, Cation TOC W Boiler Water ph, Specific, Silica, Phosphate, Chloride Saturated Main / Scavenger Reheat Silica, Spec. Silica, Phosphate, Degassed C.C Sulfate, Sulfate TOC D All Daily D, W Source - Power Plant Water Chemistry : A Practical Guide by Brad Buecker 9 Sample Pts Utility Drum Boilers on AVT Sample Pt. On-line Grab Freq Sample Pt. On-line Grab Freq Makeup Silica, Spec. Sulfate, TOC D, D, W Deaerator Outlet Sodium D Feedwater, Oxygen Iron, Copper 3x Weekly, Storage 3x Weekly Pump Discharge Polisher Deaerator Cation., Silica, Cation., Oxygen Scavenger or Economizer Scavenger, ph, Cation TOC W Boiler Water ph, Specific, Cation, Silica, Chloride Saturated Main / Scavenger Reheat Silica Silica, Degassed C.C Sulfate, Sulfate TOC D All Daily D, W Source - Power Plant Water Chemistry : A Practical Guide by Brad Buecker 10 Page 5

6 Sample Pts Once Through Utility Boilers on AVT Sample Pt. On-line Grab Freq Sample Pt. On-line Grab Freq Makeup Silica, Spec. Sulfate, TOC D, D, W Deaerator Outlet Sodium D Feedwater, Oxygen Iron, Copper 3x Weekly, Storage 3x Weekly Pump Discharge Polisher Deaerator Cation., Silica, Cation., Oxygen Scavenger or Economizer Scavenger, ph, Cation, Ammonia TOC W Boiler Water ph, Specific, Cation, Silica, Chloride Main / Reheat Silica, Degassed C.C Sulfate, Sulfate, TOC D All Daily D, W Source - Power Plant Water Chemistry : A Practical Guide by Brad Buecker 11 Sample Pts Cogen Drum Boilers w/phosphate Sample Pt. On-line Grab Freq Sample Pt. On-line Grab Freq Makeup Silica, Spec. Feedwater or Economizer, Oxygen Scavenger, ph, Cation Iron, Copper Daily, 3x Weekly, 3x Weekly Return ph, Spec., TOC Boiler Water ph, Specific, Silica, Phosphate Chloride Sulfate, All Daily Pump Discharge Cation., TOC W Main / Reheat Silica, Degassed C.C Sulfate, TOC D, W Polisher Silica, Cation. Saturated Silica Source - Power Plant Water Chemistry : A Practical Guide by Brad Buecker 12 Page 6

7 Agenda METTLER TOLE background Sampling System Measurement Recommendations Sampling System Tips for Analytics Trends 13 Sampling Tips Sample source Where two-phase flow (steam/water droplet mixture) must be sampled, the sample should contain the same ratio of steam and water as the process line. A sample nozzle should be located near the center of the process pipe, facing into the flow. The sample flow velocity should be isokinetic with the same velocity inside the nozzle as in the surrounding process pipe. This will prevent pulling in excessive steam at too high sample velocity or accumulating too many water droplets at too low velocity. Sample reaction Where reducing agents such as hydrazine or reducing amines are used, the sample should be cooled as close to the sampling point as possible to prevent continued reaction with dissolved oxygen along the length of hot sample line. 14 Page 7

8 Sampling Tips Sample deposits Corrosion product particles that accumulate on sample tube walls create a large active surface area along the length that can adsorb and desorb materials in the sample. A sample line with a lot of deposits can act like an ion chromatograph and delay the passage of ions through the line much longer than a simple calculation from flowrate, diameter and length would predict. It has been found that a flow velocity of 2 m/s produces the least accumulation of particles in horizontal sample lines and is recommended wherever possible. This high velocity is only practical using very small diameter tubing for the long lengths of the sample line. The sample is then divided for measurement by multiple sensors, some of which require much lower flow rates. 15 Sampling Tips Sample flow The appropriate sample flowrate at the sensor depends on the particular measurement. For example, cation (acid) conductivity requires a high flowrate to obtain good ion exchange. ASTM standard D6504 cation conductivity recommends a flow velocity through the resin of at least 300 mm/min. Lower flow tends to reduce turbulence and allows channeling through the resin, resulting in incomplete exchange. On the other hand, ph measurement in low conductivity samples requires low flowrates to minimize electrostatic pickup and reference junctions potentials to yield a stable measurement. 16 Page 8

9 Sampling Tips Filtration Placing a filter in the sample line upstream of optical analyzers can protect them from particulate contaminants and errors. However, the filter elements must be changed frequently to prevent a thick accumulation of sediment that slows the response to real sample changes. Moving away from optical analyzers, electrochemical measurements such as conductivity, ph, ORP and dissolved oxygen are not directly affected by particles. Mettler-Toledo Thornton sensors for these parameters have flow housings designed with very small volume that encourages any particles to flow on through the housing and down the drain. In this way, the delays and maintenance of filters and the cleaning of bowl-shaped flow chambers are eliminated i and better overall measurements result. Of course, during initial startups when very high particulate concentrations are expected, all sample lines should be diverted to drain. Pressure regulators and flowmeters as well as sensors, with or without filters, should not be subjected to these heavy loads of corrosion products which could clog tubing and fittings. 17 Sampling Tips Air leaks Dissolved oxygen samples at ppb levels are especially vulnerable to air inleakage. Although samples are pressurized and flowing, it has been observed that a loose rotameter, valve or compression fitting seal that leaves a path through a thin film of water can allow a trace amount of oxygen to diffuse into the sample. At ppb levels no bubbles will be present but a significant change in readings can occur. A quick test for this is to increase the sample flowrate. If the dissolved oxygen reading goes lower, it is an indication there is a leak and the higher flow is diluting it. The readings should be fairly insensitive to flow. Air can also pass through polymer sample tubing and have the same effect as a leak. Stainless steel should be used for all dissolved oxygen samples. But if flexible tubing is needed, it should be as short as possible and be made of PVDF or Nylon which have especially low gas permeability. The same precautions should also be used for low conductivity measurements where CO 2 from the air can contaminate a sample and raise the conductivity due to increased bicarbonate and hydrogen ion concentrations. 18 Page 9

10 Sampling Tips Grab samples Off-line samples are inevitably subject to contamination from the air and the container. Whenever possible it is always preferable to take a portable instrument and sensor to the flowing sample rather than taking a grab sample to the laboratory. However, there are virtually no laboratory or portable instruments for conductivity and ph that have temperature compensation suitable for high purity measurement. They do not take into account the changing dissociation of water and ammonia or amines with temperature which is a major factor at low concentrations. ti Much better results are obtained by using on-line pure water instrumentation in a portable mode. Shown here is a two-wheeled portable Thornton based system that can be moved around the plant to confirm measurements of conductivity, ph, dissolved oxygen and TOC with the same capability and quality as on-line measurements. 19 Agenda METTLER TOLE background Sampling System Measurement Recommendations Sampling System Tips for Analytics Trends 20 Page 10

11 Outlook and Trends Increasing focus and importance being placed on Water & steam quality requirements as defined by international organizations : VGB, EPRI, IAPWS, TPRI and the Turbine & Boiler Manufacturers. Allowable levels l are being pushed downward d with increasing i priorities being placed on : - Continuous On-line measurements vs. lab/grab samples - Analog to Digital communication in Analytics - Multi-channel, Multi-parameters provides additional information and validation - Alternative Boiler Chemistry requires additional uctivity and measurements - Greater accuracy at lower levels of detection - Quality, reliability, low maintenance (minimum downtime) - Critical measurements that you MUST be able to trust 21 Oxygenated Treatment Trends The "home" for oxygenated treatment is Europe, growing in use for decades. Started in Germany where they don't use any copper alloys in the feedwater components. (Copper precludes use of oxygenated treatment due to its rapid corrosion with moderate amounts of oxygen.) - Also, the EU has banned the use of hydrazine as a carcinogen so that limits the possibilities for reducing chemistry, although there are reducing amines sometimes used. It finally came to the USA a few years ago for those plants that didn't use copper and that have very good quality water - must have very low cation conductivity for OT to maintain low corrosion rates. Reducing conditions are more forgiving of contaminants. Most recently in the USA, filming amines are being used to help reduce corrosion during startup and shutdown which occur much more frequently with all the intermittent "green" energy sources and to follow the fluctuating pricing of de-regulated power. Combined cycle plants take the brunt of the cycling but some coal plants are forced to do some of it and it takes quite a toll on them. 22 Page 11