Method For Measuring Mass Flow Of A Multi-Component Gas

Abstract

This invention relates to a method of measuring mass flow of a first gas component in a gas consisting of one or more known gas components. Typically such methods assume that certain parameters were constant, such as the gas composition, pressure and/or temperature, and likewise the heat capacity, density, etc., of the gas were presumed to be such that they could be determined to have a constant value. However, it has been found that the determination of the mass flow is associated with a comparatively high degree of measurement uncertainty, when it is assumed that the parameters are constant. The core of the invention relies on this discovery and on a method wherein all of the gas parameters that are used in the determination of the mass flow of the first gas component and that may vary considerably as a function of the gas composition, pressure and/or temperature are determined continually.

1 . A method of measuring mass flow of a first gas component in a gas consisting of one or more known gas components, which gas flows in a pipe in which one or more measurement devices ( 440 ,  450 ,  460 ,  461 ,  462 ,  465 ;  540 ,  550 ,  560 ,  561 ,  562 ,  565 ;  635 ,  640 ,  660 ,  661 ,  662 ,  665 ) is/are arranged in connection with the pipe, said method comprising the following steps: 
 determination of one or more gas parameters of the gas by means of the measurement device(s) ( 440 ,  450 ,  460 ,  461 ,  462 ,  465 ;  540 ,  550 ,  560 ,  561 ,  562 ,  565 ;  635 ,  640 ,  660 ,  661 ,  662 ,  665 ),    determination of the mass flow of the one gas component by means of the determination of the one or more gas parameters,    characterised in    that the determination of the one or more gas parameters comprises a continuous determination of all of those of the gas parameters that are used in the determination of the mass flow of the first gas component and which may vary considerable as a function of the gas composition, pressure and/or temperature.    
     
     
         2 . A method according to  claim 1 , characterised in that in connection with the pipe a tubular body ( 410 ;  510 ;  610 ) is incorporated, which is surrounded by an insulating material ( 430 ;  530 ;  630 ), and wherein the method further comprises the following steps: 
 supply of a given amount of energy E to the gas in the tubular body ( 410 ;  510 ;  610 ).    
     
     
         3 . A method according to  claim 2 , characterised in that the measurement device(s) ( 440 ,  450 ,  460 ,  461 ,  462 ,  465 ;  540 ,  550 ,  560 ,  561 ,  562 ,  565 ;  635 ,  640 ,  660 ,  661 ,  662 ,  665 ), that are used for determining the one or more gas parameters comprise a volume percentage measurement instrument ( 440 ;  540 ;  640 ) and two temperature measurement instruments ( 460 ,  465  ;  560 ,  565 ;  660 ,  665 ), wherein the volume percentage measurement instrument ( 440 ;  540 ;  640 ) is arranged in or in immediate vicinity of the tubular body ( 410 ;  510 ;  610 ) and wherein the one temperature measurement instrument ( 460 ;  560 ;  660 ) is arranged at the inlet of the tubular body ( 410 ;  510 ;  610 ) and the second temperature measurement instrument ( 465 ;  565 ;  665 ) is arranged at the outlet of the tubular body ( 410 ;  510 ;  610 ).  
     
     
         4 . A method according to claim , 2  characterised in that wherein the step of determination of one or more gas parameters by means of measurement devices comprise: 
 determination of the gas temperature T 1  at the inlet of the tubular body; and    determination of the gas temperature T 2  at the outlet of the tubular body.    
     
     
         5 . A method according to  claim 2 , characterised in that those of the gas parameters that are determined continuously and that partake in the determination of the mass flow consist of the gas composition and the gas temperature T 1 . at the inlet of the tubular body and the gas temperature T 2  at the outlet of the tubular body.  
     
     
         6 . A method according to  claim 1 , characterised in that the measurement devices comprise a pressure differential measuring instrument ( 450 ;  550 ;  640 ) and a volume percentage measurement instrument ( 440 ;  540 ;  640 ); and in that those of the gas parameters that are determined continuously and partake in the determination of the mass flow of the first gas component comprise pressure differential across a restriction and the volume percentage of the first gas component.  
     
     
         7 . A method according to  claim 6 , characterised in that the measurement devices moreover comprise a temperature measuring instrument ( 460 ,  461 ,  462 ,  465 ;  560 ,  561 ,  562 ,  565 ;  660 ,  661 ,  662 ,  665 ) and that those of the gas parameters that are determined continually and partake in the determination of the mass flow of the first gas component moreover comprise the gas temperature.  
     
     
         8 . A method according to  claim 6 , characterised in that those of the gas parameters that are determined continually and partake in the determination of the mass flow comprise the gas density.  
     
     
         9 . A method according to  claim 1 , characterised in that the measurement devices comprise a hotwire and a volume percentage measurement instrument.  
     
     
         10 . A method according to  claim 9 , characterised in that the measurement devices also comprise a temperature measurement instrument.  
     
     
         11 . A method according to  claim 9 , characterised in that those of the gas parameters that are determined continuously and partake in the determination of the mass flow comprise one or more of the following: the viscosity of the gas, the heat capacity of the gas, the heat conductivity of the gas, the density of the gas, and the temperature of the gas, the volume percentage of the first gas component.  
     
     
         12 . Use of the method according to any one of  claims 1  to  11  for the determination of the mass flow of a first gas component being in saturation state.  
     
     
         13 . Use of the method according to  claim 12 , wherein the first gas component being in saturation state is water vapour.  
     
     
         14 . Use of the method according to any one of  claims 1  to  11  for the determination of the mass flow of a first gas component in a biogas.  
     
     
         15 . A mass flow measurement device for measuring a first gas component in a gas consisting of one or more known gas components, wherein the mass flow measurement device performs the method according to any one of claims  1  through  11 .  
     
     
         16 . A mass flow measurement device according to  claim 15 , wherein the mass flow measurement device comprises a tubular body ( 410 ;  510 ;  610 ) surrounded by an insulating material ( 430 ;  530 ;  630 ), which tubular body ( 410 ;  510 ;  610 ) is configured for being connected to a pipe in which a gas flows, which tubular body ( 410 ;  510 ;  610 ) has an inlet ( 411 ;  511 ;  611 ) and an outlet ( 412 ;  512 ;  612 ) for the flowing gas; means ( 420 ;  520 ;  620 ) for supplying energy to gas in the tubular body ( 410 ;  510 ;  610 ), a temperature measurement instrument ( 460 ;  560 ;  660 ) at the inlet of the tubular body ( 411 ;  511 ;  611 ), a temperature measurement instrument ( 465 ;  565 ;  665 ) at the outlet of the tubular body ( 412 ;  512 ;  612 ) and a volume percentage measurement instrument ( 440 ;  540 ;  640 ).