Specification for use of pipeline fuel with admixtures for natural gas/bio-methane reference fuels. 02 Mar 2016 Dr P A Williams

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1 Specification for use of pipeline fuel with admixtures for natural gas/bio-methane reference fuels 02 Mar 2016 Dr P A Williams 1

2 Approach for natural gas fuel range Natural gas/bio-methane: Three different type approvals available 1. Type approval of engine for a wide range of fuel quality (adaptive fuelling) Engine for operation on both high calorific value and low calorific value natural gas (H-gas & L-gas) Emission test on minimum of two gaseous reference fuels (G R & G 25 ) 2. Type approval of an engine for operation on a specified restricted fuel range Engine for operation on a range of either H-gas or L-gas but not both; or engine for operation on one specific fuel composition at any given time (manual tuning) Emission test on minimum of two specified gaseous fuels (G R & G 23 or G 23 & G 25 ) 3. Type approval of an engine for operation on one specific fuel composition Available option for LNG engines intended for operation on fuel qualities close to that of a pure methane reference fuel Emission test on a single gaseous reference fuel (G 20 ) Need to determine how to sufficiently specify the required gas properties using pipeline gas plus admixtures of other gases 2

3 General principles for pipeline gas + admixture Pipeline fuel with admixture should be permitted alternative to bottled gas reference fuels Number of required tests independent of whether bottled gas or pipeline gas with admixture is used Pipeline fuel with admixture needs to be able to replicate bottle gas reference fuels to sufficient extent (to be defined) Pipeline gas + admixture solution should not impose requirement to operate engine at unacceptably low methane number compared with use of bottled gas Pipeline gas admixture systems are substantial capital investment and already exist at some manufacturers test sites. Solution should take into account existing systems to avoid need for expensive reengineering of test facilities. 3

4 Illustration Example of addition of Nitrogen or Propane ad-mixture to match specified reference fuel Illustration courtesy of Rolls Royce Power Systems 4

5 How to specify the fuel blend? 1. Specify what admixtures may be used in conjunction with the pipeline gas 2. Specify which property of the corresponding bottle-gas reference fuel to use (not possible to match all properties simultaneously especially as pipeline gas properties will vary geographically and temporally) 3. Specify range of the selected property within which blend should be maintained, recognising there will need to be a tolerance 4. Specify any additional parameters (such as a minimum Methane Number) 5. Specify how to verify that the blend was maintained during the test Need to address each item of above list 5

6 Proposed approach Manufacturers permitted to generate each reference fuel G R, G 20, G 23, and G 25 through blending of pipeline natural gas with admixtures of one following gases: Methane, ethane, and propane (commercial grade) CO 2 and N 2 The single parameter for fuel specification would be lambda shift The following lambda shift ranges are proposed which assume a blend control tolerance of ± 2.5% for each gas: G R : 0.87 to 0.95 G 20 : 0.97 to 1.03 G 23 : 1.05 to 1.10 G 25 : 1.12 to 1.20 A minimum Methane Number (MN) threshold of 70 shall apply for G R The manufacturer may adjust G R lambda shift as necessary until the MN threshold is achieved The manufacturer shall verify that the blend was maintained over the test Flow meter and gas analyzer (or supplier certificate of analysis for admixture) Open loop systems: Once before and once after the test Closed loop systems: Continuously during the test 6

7 Additional considerations What parameters should be included in test report? Admixture used Value of target fuel property achieved during test Methane number of fuel achieved during test Other? How to specify the necessary calculations on the fuel properties? Equations to be used for the calculations At what level of presence must the calculations include additional constituents e.g. Calculations that use an admixture of gas abc are based on the assumption of a pure gas except where the presence of other constituents exceeds [5]% Clear definitions of the properties to be used/calculated Lambda-shift, Methane number, and (if required) Wobbe Index and Lower Heating Value, etc to be clearly defined, including standard conditions (e.g C and 101.3kPa) 7

8 Next Steps A text proposal is being prepared by SWG 2 chairman based upon principles discussed in these slides Anticipate text to be ready for circulation by 18 March 8

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