Examining Density vs. Refractive Index Technologies For Inline Concentration Measurements

Transcription

1 Eric Gronowski Vice President Strategic Partnerships K-Patents, Inc. Examining Density vs. Refractive Index Technologies For Inline Concentration Measurements

2 Various Measurement Technologies Are similar to the tools in a toolbox 2

3 The World of Process Instrumentation Primary Function: to provide accurate and real-time information of the process Improves product quality Improves financial performance by optimizing (i.e. Raw Material Savings) Improves ecological and environmental performance Eliminates the need to interrupt processes Can prevent accidents & injuries from happening But which Instrument is the right tool for the job? Compare advantages and limitations for the task. Specifically, this presentation s focus is in the measurement of concentration. 3

4 What is Concentration: Concentration is the relative amount of a given substance contained within a solution in a particular volume of space. This is usually expressed in a percent by weight. For example: If one mixes 25 lbs of NaOh (Caustic) into 75 lbs of water, the result is a mixture equals 25% by weight in 100 lbs of solution. 25 lbs 75 lbs 100 lbs 4

5 Lab Density Measurement Hydrometer density works on the principle that a floating body displaces its own weight in a fluid. The hydrometer is floated in a fluid and the density (specific gravity) of the fluid is determined by the fluid level on the scale of the stem. This historical application of course would be to use density to determine the concentration of acid in a car battery, or the correct 50/50% glycol concentration. 5

6 Density Instrumentation This hydrometer idea also translates into industrial instrumentation measurements. If you have density from existing units in the field, you can arrive (or calculate) a concentration if you have a known material. 6

7 Coriolis Density Measurement Direct Measurement: The Coriolis density measurement works on the principle that the period of oscillation of the flow tubes is related to the density of the liquid in the flow tubes. Indirect Measurement: Calculating a concentration is a function of the specific gravity of the solution 7

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9 Manufacturers commonly use Coriolis Mass Flow Why? Multiple measurements can be made. Mass flow, density and temperature (the primary measured variables) can be used to derive other variables such as volume flow, total solids, concentrations 9

10 When an instrument is commonly used. There s Comfort in the Familiar. Engineers know what to expect from the measurement. Maintenance personnel know how to troubleshoot, re-calibrate, and maintain. Familiar is good, BUT the downfall is that you may miss out on something better. Or in this case, a tool specifically MADE for the task. 10

11 In Theory: Using Density for Conc % Density Concentration Conversion matches Density Standard Chemical Tables Conc% Density PR-43 Process Refractometer Theory: When calibrated perfectly, accuracy can reach +-0.1%

12 Practical (Real World) applications : Density for Concentration There s ALWAYS something Is it a accurate enough specifically for concentration measurements?

13 Air (Gas) Effects on inline, real time Density Technologies But What if the dark blue balls represent entrained air (gas)? In the case of homogeneously dispersed small bubbles, more power is required to vibrate the tubes. Separation of the gas phase from the liquid creates a damping effect on the tube vibration leading to measurement error. 13

14 ...Sometimes Accidental Air/Gas Entrainment for ONLINE applications Is Unavoidable. Free Falling Fluid Discharge. Vortexes from Agitators Suck Air In Cavitation Sudden Pressure Drops Pump and Valve seals Line Expansion Leaks in Piping 14

15 Particle Effects on inline, real time Density Technologies What if the orange balls represent suspended solids, such as pulp in juice, crystalized sugar, corn or even wood fibers (brown stock washing) or otherwise un-dissolved materials? How would this change the concentration reading? 15

16 Un-dissolved Liquid Bubbles on inline, real time Density Technologies What if the Yellow Balls represent varied Hydrocarbon liquid undissolved in spent Sulphuric acid, or even drops of oil in Hexane? How would this affect the calibration of mass density? 16

17 Specific Concentration Tool : Refractive Index nd Difference of speed of light in different process mediums n = c v n = refractive index c = speed of light in a vacuum v = speed of light in a particular medium 17

18 Why is Refractive Index (nd) the right tool for Concentration? Refractive index is the speed of light in a medium. When a ray of light passes from one medium into another, it is bent at an angle because of the change in the speed at which light travels in each medium. Solutions with different concentrations of a given solute will have different refractive indices. So, determining a solutions refractive index is direct measurement of its concentration. Important Note: nd is NOT influenced by bubbles or particles 18

19 Refractometer Technology: Lab and Inline Optical image Light source Process medium 19

20 Handheld nd Measurement Optical image High concentration Low concentration 20

21 Borderline Measurement Optical image CCD camera Digital image Refractive Index n D Conc% 21

22 No Measurement Errors Caused by: Crystals Particles Bubbles Color Light reflected from a bubble PR-43 Process Refractometer

23 A Video Test of This Theory - Note: Please install Apple Quick Time Installed in order to view Video 23

24 An Exclusive Advantage of K-Patents Digital and Direct Measuring Technology Bubbles (Entrained Air, Gas or Liquid), suspended solids, vibrations, flow, pressure and temperature changes do NOT Affect or otherwise interfere with K-Patents Concentration measurements. 24

25 Design Refractive Index n D and Temperature are measured Light source Fiber optics ma Ethernet Prism CCD-camera Pt-1000 Temp. sensor PR-43 Process Refractometer

26 Mounting Examples Large pipe Probe type Small pipe Compact type Pipe bend Vessel 2 or smaller 26

27 Prism Wash With Steam Refractometer Shut-off switch Multichannel user interface MI Power Air PR-43 Process Refractometer Steam Power Complete System: 1. Refractometer 2. Multichannel user interface MI (with wash relay) 3. Interconnecting cable 4. Wash nozzle -SN 5. Check valve 6. Shut-off valve with steam trap

28 Prism Wash With High Pressure Water Refractometer Power relay unit Multichannel user interface MI Power PR-43 Process Refractometer Warm water Power Complete System: 1. Refractometer 2. Multichannel user interface MI (with wash relay) 3. Wash nozzle -WP 4. Check valve 5. High pressure pump 6. Power relay unit

29 Exact Calibration Refractive Index n D and Concentration Conversion matches PR-43 Process Refractometer Standard Chemical Tables Conc% n D Practical: Accuracy +-0.1% even in less then perfect process conditions.

30 Instrument Verification nd calibration is traceable to international standards PR-43 Process Refractometer

31 Determining Suitable Technology What is the process? What is the process medium? What is the desired measurement? In short, know the P, the PM, & the PM 2 P = Process PM = Process Medium PM 2 = Process Medium Measurement 31

32 P Knowing the Process Understand the reason behind the concentration measurement Starch Sweeteners Process How is the measurement being used? Are multiple technologies able to provide MORE process information? Source: K-Patents Application Note Starch Sweeteners Process 32

33 REAL LIFE APPLICATON EXAMPLE: Sugar Crystallization BOTH Density and Refractive Index Technologies are needed. Crystallization is initiated by seeding the concentrated liquor (liquid) with starter crystals (solids). As the process continues, the liquid concentration % drops as more of the liquid sugar, becomes a solid sugar crystal. To optimize this process, keeping this liquid in a steady supersaturated state is the key! This is difficult to do when only looking at only total solids density. 33

34 TYPICAL CRYSTALLIZER TRENDS Solids, level and liquid concentration Point of Crystal Seeding Total Solids Level Liquid Concentration Having density as the only measurement, you can only see ONE variable in the process. SeedMaster SM-3

35 PM Knowing the Process Medium Liquid or Gas? Refractometer measures liquids Coriolis Liquids and Gases Suspended Solid? Is it desirable or undesirable to factor the suspended solid into the measurement? Harsh Chemical or Acid? Is a specialty material needed due to corrosive process environment? Know the Physical Properties of the Process Medium Look up R.I. and Density values of process medium 35

36 Real Life Case : Process Medium Physical Properties Liquid Hydrocarbon Identification: Chemical plants and refineries receive or deliver many different liquid hydrocarbons, including Natural gas Liquids (NGLs) which are transported via pipeline, railcar, tanker trucks and/or ship. Many of these products are very similar in properties and appearance, therefore, proper identification or interface detection of these hydrocarbons at transport locations that handle multiple products is important to ensure quality assurance from supplier, and correct product to correct vessel. 36

37 Real Life Case Continued: Process Medium Physical Properties Two typical products that require proper interface detection are n-butane and iso-butane. These are the two structural isomers of butane meaning they have the same molecular formula but a different arrangement of the chemical structural. Since they are isomers, the chemical properties of these products, in particular the density, is too similar to use Mass Flow Coriolis. However, the difference in refractive index (Repeatable to ) is wide enough to accurately and reliably distinguish between these two products. Chemical: Isobutane Formula: C 4 H 10 Molecular Weight: C: 0.56 g/cc Refractive Index: Chemical: n-butane Formula: C 4 H 10 Molecular Weight: C: 0.57 g/cc Refractive Index:

38 PM 2 Process Medium Measurement What is the goal of the measurement? Flow Measurement? Density Measurement? True Density Total Solids (including suspended solids) Liquid Density suspended solids (or un-dissolved liquid) and air are not desired in the measurement or truly a Concentration Measurement? What measurement techniques are currently used? In the process In the lab What is the acceptable accuracy range? Is good, good enough? OR is the goal, GREAT? 38

39 REAL LIFE APPLICATON NOTE: Process Medium Change = Density Change Corn Processing Density %DS Calibration 28 D.E. CORN SYRUP 36 D.E. CORN SYRUP HIGH MALTOSE - 34% MALTOSE HIGH MALTOSE - 43% MALTOSE 43 D.E. CORN SYRUP 43 D.E. ION EXCHANGED SYRUP 53 D.E. CORN SYRUP 63 D.E. CORN SYRUP 63 D.E. ION EXCHANGED CORN SYRUP 66 D.E. CORN SYRUP 95 D.E. CORN SYRUP 95 D.E. ION EXCHANGED CORN SYRUP 42% HIGH FRUCTOSE CORN SYRUP 55% HIGH FRUCTOSE CORN SYRUP Lab concentration technology in this case is often nd (Refractive Index) Same RI concentration curve to match lab, no mater which recipe is selected. Density to % Concentration is different. So a new density calibration is needed for each material. 39

40 Technology Review Refractometer 2* Measurement Readings: Refractive Index and temperature. *Multi app coming True dissolved solids measurement Pipe size does not affect cost Low maintenance (no moving parts) Easy calibration & on-site verification High measurement accuracy Coriolis Mass Flow Up to 4 Measurement Readings: mass flow, volumetric flow, temperature, and density Direct mass flow rate measurement, true density measurement Low Cost for Small Pipes High Cost for Large Pipes More maintenance (moving parts, flow tube forces) Recalibration needed; verification of measurement performed on test stand Good measurement accuracy 40

41 Technology Review Refractometer Measures dissolved material in liquids only Bubbles & entrained air, vibrations do not alter measurement Refractometers can be installed in various pipe sizes Coating/Build Up In-situ Prism Flush Digital device Can be used in tanks and vessels Coriolis Mass Flow Can perform measurements with liquids or gases Measurement Affected By: Bubbles & entrained air External vibrations Stress on piping Meters unique to pipe size Coating/Build-up Pipe Flush Mechanical device Cannot be used in tanks 41

42 Questions? And Thank You for Attending! Eric Gronowski President Tel. (630) ext.124 Mobile (630) Fax (630) K-Patents, Inc Centre Point Circle, Suite 106 Naperville, IL 60563, USA 42