Process Gas Chromatographs

Tony Waters owns Analyzer Consulting Engineers, LLC in USA and is an Elected Fellow of International Society of Automation. Since 2000, he has been a Consultant in Process Analysis assisting refiners and chemical processors to achieve optimal use of process analyzers. He has twenty-five years' experience of working in the industry before setting up his own company, Measurementation, Inc. in 1986 to manufacture process analyzer systems.

• Preface xixContributors xxiAcknowledgments xxviiPart One PGC fundamentals 11 An introduction 3Chromatographic separation 3The gas chromatograph 4The basic instrument 4The process instrument 5The oven 7Temperature control 7Temperature programming 7The sample injection valve 8Laboratory and online practice 8Plug injection 8Gas sample injection 9Liquid sample injection 9The column 10The separating device 10It takes time 10Multiple columns 11SCI-FILE: On Column Types 12Introduction to SCI-FILEs 12Two kinds of column 12Packed columns 12Open-tubular columns 12The detector 13Making the measurements 13The chromatogram 14Knowledge Gained 18Did you get it? 19Self-assessment quiz: SAQ 01 19Student evaluation test: SET 01 20References 21Cited 21Figures 22New technical terms 222 Peakshape 25How columns work 25What happens inside the column 26How gas and liquid interact 26Troubleshooting tips 28How peaks form 28Forming an equilibrium 28The effect of movement 30A peak appears 31Effect of more equilibria 33Some conclusions 34Identical molecules – different behavior 34All peaks are symmetrical 35More equilibria – narrower peaks 35More equilibria – taller peaks 35Retention at the apex 36More equilibria – same retention time 36SCI-FILE: On Solubility 36Solubility 36Partition 36Distribution 37Limitations 37Knowledge Gained 37Did you get it? 38Self-assessment quiz: SAQ 02 38Student evaluation test: SET 02 38References 40Figures 40Equation 41Symbols 41New technical terms 413 Separation 43How peaks get separated 43A more realistic explanation 43A challenge question 46Significance of the air peak 47The answer 48Measurements from chromatograms 50A practical task 50Typical calculations 51Knowledge Gained 52Did you get it? 53Self-assessment quiz: SAQ 03 53Student evaluation test: SET 03 53References 55Figures 55Equations 55Symbols 55New technical terms 554 Peakpatterns 57Migration rate 57Predictable patterns in peak position 57Space or time 57Spatial or temporal separation 58Predictable patterns in peak width 59Distance or duration 59SCI-FILE: On Chemical Names 60Hydrocarbons 60Shorthand notation 61Predictable patterns in retention 61The doubling rule 61Challenge question 62A process of elimination 62Temperature programming 64Relative retention 66Separation and resolution 67Resolution 67Predictable patterns in resolution 69Knowledge Gained 71Did you get it? 72Self-assessment quiz: SAQ 04 72Student evaluation test: SET 04 72References 74Figures 74Equations 74Symbols 74New technical terms 74Part Two PGC analytics 775 Industrial gas chromatographs 79Process analyzers 79Introduction to process analysis 79The measurement of quality 80Process gas chromatographs 81Versatile and reliable 81PGC development 82The value of analysis 83Competing technologies 84Gas chromatograph or spectrophotometer? 84Speed of response 86The outlook 87The PGC analytics unit 87Introduction 87Carrier gas supply system 88Sample injection system 89Chromatographic valves 89Column system 89Detectors 89Temperature-controlled ovens 90Knowledge Gained 90Did you get it? 91Self-assessment quiz: SAQ 05 91Student evaluation test: SET 05 92References 93Cited 93Table 93Figures 93Symbol 94New technical terms 946 Carrier gas system 95Choice of carrier gas 95Carrier gas purpose 95Choice of carrier gas 95Mixed carrier gases 97Carrier gas purity 97Analytical effect of impurities 98Damaging effect of impurities 100Maintenance of gas cleaners 101Carrier gas supply system 101Carrier gas supply line 102Pressure regulation 103Mechanical pressure regulators 103Electronic pressure controllers 104Flow regulation 104Measuring the carrier gas flow rates 104Setting the flow rates 105Optimum flow rate 106Knowledge Gained 106Did you get it? 107Self-assessment quiz: SAQ 06 107Student evaluation test: SET 06 108References 109Cited 109Table 110Figures 110Symbols 110New technical terms 1117 Sample injection 113Introduction 113Injecting gas samples 114Gas sample volume 114Gas sample temperature 115Gas sample pressure 116Injecting liquid samples 118Less preferred 118Vaporizing a liquid sample 118Liquid sample volume 119Liquid sample temperature 120Liquid sample pressure 121Other techniques 122Sample splitting 122Remote sample injection 122Normalization 122SCI-FILE: On Analytic Units 123A fable 123Constant sample size 123Different ratio units 124Injected quantity 124Conversion of units 125Knowledge Gained 126Did you get it? 127Self-assessment quiz: SAQ 07 127Student evaluation test: SET 07 128References 130Cited 130Tables 130Figures 130Symbols 130New technical terms 1318 Chromatographic valves 133Valve technology 133Evolution 133The strange effect of competition 134Valve types 135Solenoid instrument valves 135Spool or piston valves 135Slide valves 136Rotary valves 139Diaphragm valves 141Plunger valves for liquid injection 143Other switching techniques 145Valve leaks 146About leaks 146Valve leak mitigation 148Knowledge Gained 149Did you get it? 151Self-assessment quiz: SAQ 08 151Student evaluation test: SET 08 151References 153Cited 153Table 154Figures 154New technical terms 1559 Column systems 157Two fundamental issues 157The general elution problem 157The temperature ramp solution 158The multiple column solution 159The choice 160Delayed injection 161Four types of column system 161Recognizing the functions performed 161Type A: A single column 162Type B: Multiple columns, single detector 163Type C: Multiple detectors, single injector 164Type D: Multiple sample injectors 166Elemental column systems 168Useful techniques 168Backflush column system 168Distribution column system 170Heartcut column system 171Trap-and-hold column system 173The real power 174Endnote 175Knowledge Gained 176Did you get it? 177Self-assessment quiz: SAQ 09 177Student evaluation test: SET 09 177References 180Cited 180Table 180Figures 180New technical terms 18110 Detectors 183Introduction 183Types of detector 183Two measured variables 183Concentration detectors 184Rate-of-arrival detectors 185Multiple detectors 186Signal capture 186SCI-FILE: On Detectors 187Signal noise 187Speed of response 187Sensitivity 188Thermal conductivity detector 189TCD application 189TCD basic function 190TCD detection principle 191TCD thermal elements 192TCD electrical arrangement 194TCD electrical improvements 194TCD performance enhancement 195Flame ionization detector 197FID application 197FID detection principle 198FID makeup gases 199FID sensitivity 199FID vent arrangements 200FID methanator 200Flame photometric detector 202FPD application 202FPD detection principle 202FPD concerns 203Other detectors 205Electron capture detector 205Helium ionization detector 206Photoionization detector 207Pulsed discharge detector 207Knowledge Gained 210Did you get it? 213Self-assessment quiz: SAQ 10 213Student evaluation test: SET 10 214References 216Cited 216Tables 217Figures 217Equations 217Symbols 218New technical terms 21811 Temperature control 221Need for stability 221Sample volume 221Retention times 221The air-bath oven 223Heating with air purging 223The airless oven 225Heating without air 225The 2008 ABB PGC1000 227The 2014 Rosemount Danalyzer 370XA PGC 227The 2009 Rosemount 700XA PGC 227The 2002 Maxum Edition II 228Direct column heating 228Resistive heating 228The ABB approach 229The Teledyne Falcon approach 230A few cautions 231Summary of heating methods 231PGC standardization 231Realities of the market 231The applications engineering conundrum 232MEMS technology 233The 2002 siemens MicroSAM 234A closing thought 234Knowledge Gained 235Did you get it? 236Self-assessment quiz: SAQ 11 236Student evaluation test: SET 11 237References 238Cited 238Table 239Figures 239New technical terms 240Part Three PGC control 24112 Event scheduling 243A sequence of actions 243Program timing 243Autozero 245Atmospheric referencing 245Sample injection 245Step stream 246Column switching 247Peak gating 247Initiate a calculation 248Data transmission 248Alarm notifications 248End-of-cycle 248Event markers 248Calendar events 248Timing mechanisms 249Mechanical programmers 249Electronic timers 249Microprocessor control 250The program or method 250Control of analyzer operation 250Temperature control 251Pressure control 251Peak identification 251Fixed-time gating 252Retention time tracking 253Knowledge Gained 254Did you get it? 256Self-assessment quiz: SAQ 12 256Student evaluation test: SET 12 256References 258Cited 258Figures 258New technical terms 25913 Data display techniques 261The chromatogram display 261Detector signal 261Digitized chromatograms 262Chromatogram autozero 263Peak height calibration 263Peak area calibration 264The bargraph display 265The paper saver 265The trend record 266Analog peak processing 266Digital signal processing 267The minicomputer story 267The ubiquitous microprocessor 268A regression perhaps? 269Central maintenance station 271Continuous analyzer controllers 271PGC function alarms 272Indicators 272Alarm notifications 272Knowledge Gained 273Did you get it? 274Self-assessment quiz: SAQ13 274Student evaluation questions: SET-13 275References 276Cited 276Table 277Figures 278New technical terms 27814 Peak area integration 279Digital chromatogram processing 279Pulse frequency digitization 279Signal noise measurement 281Signal noise reduction 281Quantifying the analyte peaks 283Forced integration 284Slope detection 285Errors from baseline disturbances 286Troubleshooting aids 287Measuring overlapping peaks 287Avoiding the problem 287Tackling the problem 288Perpendicular drop method 289Don’t integrate to a valley point 290Angular drop or allocated area 292Tangent skim method 292Effect of setup mistakes 293Knowledge Gained 294Did you get it? 296Self-assessment quiz: SAQ 14 296Student evaluation test: SET 14 296References 298Cited 298Figures 299New technical terms 29915 Calibration 301Measurement principles 301Terminology 301Random error 302Systematic error 302Uncertainty 302Accurate calibration 304Calibration and validation 304Calibration methods 307External standard method 307Normalization 308Calibrating a composite peak 309Grab sample calibration 310Internal standard method 310Area percentage method 311SCI-FILE: On Response Factors 312External standard 312Normalization 312Internal standard 312Area percentage 313Knowledge Gained 313Did you get it? 314Self-assessment quiz: SAQ 15 314Student evaluation test: SET 15 314References 317Cited 317Figure 317Equations 317Symbols 318New technical terms 318Answers to self-assessment questions 319Bibliography 329Glossary 331Index 367