MEASURING H2S IN CRUDE OIL FOR QUALITY CONTROL & TRANSPORTATION SAFETY Wesley Kimbell Analytical Systems Keco Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Why measure H2S in crude oil? Safety Industrial Process Control Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 2 Why measure H2S in crude oil? Safety • Personnel protection • Transportation (rail, roads, pipelines) Industrial Process Control Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 3 Why measure H2S in crude oil? Safety • Personnel protection • Transportation Industrial Process Control • Meet product specifications • Protect process equipment • Environmental concern Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 4 Why measure H2S in crude oil? •Safety Personnel protection 1. H2S gas is toxic and deadly 2. Even H2S dissolved in crude is deadly Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 5 H2S CHARACTERISTICS •Gas with rotten egg smell •Specific gravity: 1.1895 vs air •LEL 4.3%, UEL 46% •Highly corrosive •Toxic Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 6 Why measure H2S in crude oil? •Safety Personnel protection 1. H2S gas is toxic and deadly 2. Even H2S dissolved in crude is deadly Transportation 1. Prevent car derailments 2. Corrosion Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 7 Why measure H2S in crude oil? •Industrial Process Control 1.Meet product specifications Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 8 Why measure H2S in crude oil? •Industrial Process Control 1.Off-spec products 2. Protect process equipment Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 9 Why measure H2S in crude oil? •Industrial Process Control 1.Off-spec products 2.Industrial process control 3.Environmental concern Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 10 How do we measure H2S in crude oil? Direct optical measurement of crude oil is difficult: •Crude oil is opaque in nature •Complex compositional characteristics Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 11 How do we measure H2S in crude oil? Question: What is the best method to measure H2S in liquid samples like crude oil? Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 12 How do we measure H2S in crude oil? Answer: Measure the headspace • Upon saturation, the headspace concentration and the liquid sample concentration are proportional Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 13 How do we measure H2S in crude oil? Henry’s Law: "At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid." Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 14 Methods of sampling Headspace concentration function of: 1. Saturation time/volume 2. Temperature 3. Vapor pressure of analyte 4. Concentration of analyte Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 15 Methods of sampling Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 16 Methods of sampling H2 S Headspace H2 S H2S H2 S H2 S H2 S H2 S Proportional concentration H2 S Crude Oil H2 S H2 S H2 S H2 S H2 S H2 S Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 17 Methods of sampling Goal: Extract the ‘headspace’ vapor of the liquid sample for analysis in the gas phase Two methods: •‘Headspace’ stripping column •Sample Transfer Stripper™ with ASI Membrane Technologies (proprietary) Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 18 Methods of sampling Headspace stripping column Crude Oil In ~ 3 to 4 feet Stripping Column Stripped H2S to Detector Crude Oil to Drain Carrier / Stripping Gas In Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 19 Methods of sampling Headspace stripping column Crude Oil In ~ 3-4 feet Stripping Column Stripped H2S to Detector Crude Oil to Drain Drawbacks • Suffers from liquid “carry-over” • Cleaning requirements • Many moving parts = more maintenance Carrier / Stripping Gas In Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 20 Methods of sampling Membrane technology (proprietary) Sample Transfer Stripper™ with ASI Membrane Technologies by Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 21 Methods of sampling Membrane technology (proprietary) Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 22 Methods of sampling Membrane technology (proprietary) H2 S Headspace H2 S H2 S H2 S H2 S H2 S H2 S ASI Membrane Technology H2 S Crude Oil H2S H2S H2 S H2S H2 S Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 23 Methods of sampling Membrane technology (proprietary) • Membrane physically blocks mists from headspace vapor • Prevents fouling of detector • Prevents liquid “carry-over” • Radically reduced maintenance • Prevents in-gassing / out-gassing of H2S • Maintains compositional representation of the headspace vapor Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 24 Methods of sampling | Comparison Sampling Technology: Sample Transfer Stripper™ (STS) with exclusive ASI Membrane Technologies Principles incorporated Maintenance requirements Henry’s Law & proprietary methods LOW Moving parts Cost of ownership Accuracy Range Safety Headspace stripping column Henry’s Law X HIGH Plagued by frequent liquid “carry-overs”. No STS Membrane creates ultra-clean sample for physical block to prevent liquids from detector & physically blocks liquids from passing contaminating detector and gas sample lines. through to detector. Clean only one to two times User reported constant cleaning & upkeep per year typical NONE X HIGH No moving parts Complicated system using 85% more parts than STS Membrane Cost-Effective X HIGH Minimal maintenance means less cost Long term expense due to cleaning & over time maintenance requirements HIGH X LOW STS creates ultra-clean sample for analysis System fouls as liquids frequently pass through to detector and gas sample lines requiring frequent cleaning PPB, PPM and up to 100% ranges with high X Low ppm ranges not reliable precision SAFE X CAUTION User potentially exposed to residual H2S when Closed loop system for analysis and cleaning. No cleaning is required H2S exposure to user Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 25 Method of Analysis Difficulty of quantifying H2S in crude oil • Crude oil is compositionally complex • Many components interfere with H2S: Aromatics, SO2, ethyl-mercaptan, methyl-mercaptan and other sulfur compounds • Crude composition changes not uncommon • Low ppm especially a challenge Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 26 Method of Analysis Colorimetric-Rateometric Tape Detector Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 27 Colorimetric Rateometric Tape Detector Advantages Significant advantages with tape method • Only method inherently specific to H2S • No complicated chemometric modeling needed • No need to “trick” system to minimize interferences • Measures only H2S, no matter the compositional background • Inherently accurate—measure low ppb, ppm to 100% H2S without false positives even in crude oil headspace Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 28 Colorimetric Rateometric Tape Detector Improvements to design Significant technological advancements to Tape Method: • • • • • • Improved tape drive system 75% less parts 3-6 month tape life Reliable and rugged Remote diagnostics & troubleshooting Simplest detection & most straight forward method available Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 29 Method of analysis | Comparison Measurement Technology Specific to H2S only Accuracy Sensor Zero Drift Sample pressure requirements Range Calibration Stability Maintenance Consumables Colorimetric-Rateometric Tape Method UV-Absorbance Spectrophotometry TDL Absorbance Spectroscopy YES Innately and practically free of cross-interference. No false positives. X NO Problems with mercaptans (including naturally occurring mercaptans), hydrogen, ammonia, etc. giving false positives X NO Problems with moisture and other sulfur components giving false positives ± 2% of full scale typical NO zero drift (automatic self zero, no zero air required) Pressure between 5 to 2,000 PSI acceptable ±10% at 0-10ppm FS X YES 5% in 24 hours for low ppm ranges. Requires zero gas. Normally requires minimum of ~150 PSI X ± 4ppmv 0-10ppm FS X YES. Normally requires zero gas. PPB, PPM and up to 100% ranges with high accuracy X Low ppm ranges not reliable. PPB range not possible X Low ppm ranges not reliable. PPB range not possible X Unstable if process changes even slightly. Requires calibrations X Unstable if process changes even slightly. Requires calibrations X HIGH Optics / Flow cell require frequent cleaning Zero gas required. Light source and scrubber materials require replacement. Costly. Mirrors tend to fog or produce haze. Requires cleaning Long-term even in demanding environments and process changes LOW Tape change only 3 to 4 times per year Tape change every 3 to 6 months. ~$25 per tape reel Normally requires minimum of ~150 PSI Zero gas required. Scrubber (copper nanoparticle) replaced annually or more. Costly. NOTE: Data based on typical manufacturers published data Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 30 Method of Analysis Colorimetric-Rateometric Tape Analyzer Detection of H2S concentrations by the use of H2S sensing tape is achieved by exposing the film to an H2S sample through an aperture in the sample flow system, called the sample chamber. The reaction of photographic film to the light is analogous to the way that chemically saturated H2S sensing tape reacts to hydrogen sulfide Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 31 Method of Analysis Colorimetric-Rateometric Tape Detector The chemical formulation for reaction is as follows: H2 O Pb(OAc)2 + H2S →→→ PbS + 2HOAc White colored This reaction has three characteristics which allow it to be applied with unique analytical precision: 1. The reactants are colorless (white). 2. The product (PbS) is colored. 3. In more than a century of use, hydrogen sulfide is the only practical reactant found that produces a colored product on lead acetate (Pb(OAc)2 tape. Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 32 Method of Analysis Colorimetric-Rateometric Tape Detector The rate (r) of this reaction (forming PbS) is as follows: r = k Pb(OAc)2x H2S Where k, the proportionality factor, is called the rate constant. NOTE: The very large (more than 1000 times) concentration of Pb(OAc)2 on the H2S sensing tape simplifies the reaction as follows: [Pb(OAc)2]0 = [Pb(OAc)2]1 – PbS1 = K2 (<.1%) Therefore, rn = kk2(H2S - PbSn) For simplicity: kk2 = K rn = K(H2S = PbSn) Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 33 Method of Analysis Colorimetric-Rateometric Tape Detector By maintaining a constant H2S concentration, with continuous flow of the sample into the sample chamber, the rate of reaction equation is further reduced to: r = KH2S Therefore, by maintaining the control conditions of: 1. A large quantity of Pb(OAc)2 2. Constant H2S concentration. 3. Sufficient moisture. The rate of reaction (i.e. the rate of darkening) is linearly proportional H2S concentration. Measuring the rate of darkening is therefore directly equivalent to measuring the H2S concentration. Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 34 Method of Analysis Colorimetric-Rateometric Tape Detector The rate of reaction (i.e. the rate of darkening) is linearly proportional H2S concentration. Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 35 Method of Analysis Colorimetric-Rateometric Tape Detector In actual practice, the rate of darkening is determined by measuring the change in darkness from second to second. Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 36 Method of Analysis Colorimetric-Rateometric Tape Detector 80 PPM tape darkness Y 40 PPM b 0 0 X time The general equation for the lines of the graph above is: y = ax + b b is the zero drift or offset term in conventional equipment that is often adjusted to zero (zero drift) Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 37 Method of Analysis Colorimetric-Rateometric Tape Detector 80 PPM tape darkness Y 40 PPM b 0 0 X time Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 38 Case Study Measuring H2S for quality control Location: In-plant study in Middle East Participants: ASI Personnel, Customer Plant Manager, Customer Lab Manager Activity: Startup/commissioning and accuracy test Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 39 Case Study Measuring H2S for quality control Equipment: Model 205 H2S in Crude Oil Analyzer • Sample Transfer Stripper™ with ASI Membrane Technologies (proprietary) Colorimetric-Rateometric Tape Detector • Measuring Range: 0 to 80 ppm by wt. • Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 40 Case Study Verification of Calibration Method Volumetric Blending Process The calibration procedure calls for a known concentration of H2S, which is injected into the crude sample in a container. This will cause the concentration of H2S in the sample to read proportionally more based on the concentration of H2S injected. Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 41 Case Study Results The model 205 H2S in Crude Oil Analyzer measured continuously while two field samples were taken by lab personnel which were tested in the laboratory. The cross reference of the readings of the analyzer and the lab results can be seen below: SAMPLE #/ TIME Sample 1: 12:00 Sample 2: 15:00 ASI Prepared Standard 10 ppmw MODEL 205 5.201 ppm/w 15.02 ppm/w 10.07 ppm/w Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 LAB 4 ppm/w 14 ppm/w 14 ppm/w Slide 42 Case Study Conclusion The Model 205 H2S in Crude Oil Analyzer utilizing the membrane Sample Transfer Stripper™ and colorimetric-rateometric tape method of detection was tested by the plant laboratory specialists and found to be accurate. The Volumetric Blending method of calibration was also verified for accuracy. Both the plant engineers and Process Analyzer Engineer specialists along with ASI engineers were very pleased with the testing method and the accuracy of the model 205 H2S in Crude Oil Analyzer. The Sample Transfer Stripper combined with Tape detector results in an accurate and stable analyzer to measure H2S in crude oil: • The analyzer maintains calibration long term (no chemometric modeling required) • Field calibrations not required • Zero gas not required • Membrane stripper eliminates liquid carry over and cleanup • Advancements in tape technology results in low maintenance • Tape change required only 2-4 times annually Analytical Solutions by the Sea The 60th Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 26th – 30th April 2015 Slide 43