Water Dew Point Measurement in Natural Gas and its ...

1 Water Dew Point Measurement in Natural Gas and its traceability Andrea Peruzzi - VSL. Water dew- Point Measurement in Natural gas and its traceability Andrea Peruzzi and Rien Bosma Pag. 2 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Outline The Measurement of the Water dew- Point of Natural gas: The Water dew- Point temperature of a moist gas The Natural gas chain The Measurement of the Water dew- Point of Natural gas along the chain Sensor technologies traceability of Water dew- Point measurements: Primary standard: high-pressure dew- Point generator o Principle of operation o Design o Construction o Use Investigation performances of Al2O3 sensors o Response time o Stability on time Pag.

2 3 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Water dew- Point of a moist gas Dew- Point (frost- Point ) temperature of a moist gas: the temperature at which a sample of a moist gas must be cooled, at constant pressure, for Water vapour to condense into Water (ice). Why does the Water vapour start condensing? Because, when cooling a moist gas, the Water vapour contained in it eventually reaches saturation with respect to liquid Water (ice). Dew Frost (In this case the moist gas is atmospheric air). Pag. 4 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Water dew- Point of Natural gas Given a sample of moist Natural gas: TDP = f(xW, P) (xW = mole fraction of Water in the sample, P = pressure).

3 Remove Water lower xW lower TDP. reduce P lower TDP (but same xW). TDP after pressure reduction (after expansion) requires the knowledge of the enhancement factor f(P, TDP): f ( P1 , TDP1 ) eW (TDP1 ) f ( P2 , TDP 2 ) eW (TDP 2 ). xW . P1 P2. Transforming TDP xW requires the knowledge of the pressure P and the enhancement factor f(P, TDP): f ( P, TDP ) eW (TDP ). xW . P. Pag. 5 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Natural gas chain Extraction Processing Transport Distribution Users Offshore or on-shore Gas processing plant: High-pressure Distribution to local - Power plants (35%). gas field dehydration and pipeline or LNG networks through - Large customers (10%). removal/separation of medium pressure - Retailers (25%).

4 Various components pipeline - Storage Pag. 6 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Natural gas chain Extraction/. Processing Transport Distribution Users Production Offshore or on-shore gas Gas plant: dehydration High-pressure pipeline or Distribution to local - Power plants (35%). field and removal/separation of LNG networks through medium - Retailers (25%). various components pressure pipeline - Large customers (10%). - Storage Pag. 7 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Natural gas processing plant Acid gases removal Mercury Nitrogen NGLs Dehydration (CO2 and H2S) removal rejection recovery Extracted gas is not suitable for high-pressure transmission and consumption Dehydration: H2O must be removed at a level below a specified contractual value Safety: remove H2O to avoid corrosion, condensation and hydrates formation in the pipeline lower TDP.

5 Removing H2O costs money (each C of TDP means M in plant operation costs). Find the optimal balance between satisfying contractual value and cost effective operation of the plant Accurate Measurement of TDP is crucial Pag. 8 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Measurement at gas processing plant: glycol dehydration Measurement Point : Glycol contactor Typical conditions: TDP < -30 C at 5 to 8 MPa Requirements: fast wet-up response protected against glycol or other liquid contaminants immune to chemical attack from H2S, mercaptans and other sulphides Accuracy: 1 C TDP (declared by manufacturer). Pag. 9 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Natural gas chain Extraction/.

6 Processing Transport Distribution Users Production Offshore or on-shore gas Gas plant: dehydration High-pressure pipeline or Distribution to local - Power plants (35%). field and removal/separation of LNG networks through medium - Retailers (25%). various components pressure pipeline - Large customers (10%). - Storage Pag. 10 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Long distance transportation of Natural gas? Pag. 11 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Natural gas transport Transport: High-pressure pipeline (80%). LNG (20%). In both cases: Pipeline custody transfer contractual requirements o Pipeline: TDP < -10 C at MPa EU (EASEE Madrid Forum: TDP < -8 C at 7 MPa).

7 LNG liquefaction plant: TDP < -80 C at 7 MPa Measurement requirement: Fast wet-up response Pag. 12 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Measurement of trace moisture before LNG liquefaction Measurement Point : molecular sieve columns Typical requirement: TDP < -80 C at 7 MPa ( ppmV). Sample Point : middle bed of each tower and outlet of each tower Pag. 13 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. LNG chain Pag. 14 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Measurement at re-gasification terminal Typical requirement: TDP < -10 C at 7 MPa (leakage indicator in heat-exchangers). Pag. EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015.

8 Sensor technologies Different Measurement principles: Impedance sensors: polymeric and metal oxyde sensors (Al2O3. (Easydew, Michell), P2O5 (Accupoint LP 2, Meeco), polymer (E+E)). Spectroscopic analyzers (Aurora, GE). Calibrated at atmospheric pressure and in nitrogen or air gas (conditions completely different from field conditions). Investigation of the performances of sensors and analyzers: Response time Stability on time (drift). Pressure dependence See: An investigation of the comparative performance of diverse humidity sensing techniques in Natural gas , Gallegos et al., Journal of Natural Gas Science and Engineering, 23 (2015) 407-416. Pag. 16 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015.

9 Primary dew- Point generator Source of traceability for Water dew- Point temperature Measurement : primary dew- Point generator Thermodynamically-based: A gas stream (air, N2, CH4, ) . is saturated with Water vapour . by flowing the gas over a plane surface of Water (or ice) . at known temperature TS and pressure PS. Dry gas Moist gas Water Saturator at {TS, PS}. If the gas is fully saturated in the saturator, the dew- Point temperature of the moist gas drawn from the saturator is: TDP TS. Pag. 17 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Saturator design Design criteria: Maximize turbulent flow Reduced tilt of Water surface Acceptable pressure drop Design features: Channel Segments and bends (180 each).

10 Dams and barriers Choice of design parameters: Depth of the channel: 30 mm Number of segments and bends: 20. Number of dams and barriers: 20. Water depth: 7 mm Pag. 18. HPDP generator construction Ethanol reservoir Ethanol bath Precooler Saturator Pag. 19 EUROPEAN FLOW Measurement WORKSHOP. Noordwijk, 18 March 2015. Validation of HPDP generator CMH. N2 Pressure Presat MBW. CH4 controller 973. Pressure Syringe pump SPRT. Precooler CMH. MBW. 373 HPX. Ethanol bath Saturator CMH. MBW. 373 LX. CMH Pressure Range Temperature range MBW 973 MPa -60 C to +20 C. MBW 373 HPX MPa to 10 MPa -80 C to +20 C. MBW 373 LX MPa to MPa -95 C to +20 C. Validation Monitor differential response of CMHs when: Pag. 20 changing saturator flow rate while keeping fixed flow rate at CMHs changing dew- Point of inlet gas Validation of HPDP generator (CH4, TDP = +15 C, P = 6 MPa).