NATURAL GAS HEAT COMBUSTION DETERMINATION ON MEASURING SYSTEMS WITH DUPLICATE GAS UNITS
Authors:   SE ", Petryshyn Igor ,   Ivano-Frankivskstandartmetrology", Bas Olexandr ,   SE "Ivano-Frankivskstandartmetrology"
Published: December 2020

The paper focuses on the need to determine the natural gas heat combustion in order to transition to gas metering in units of energy. The technical organization of gas transportation in the main and distribution pipelines on the territory of Ukraine is shown. A detailed analysis of regulatory and legal support, which regulates the definition and accounting of quantitative and qualitative characteristics of natural gas at gas metering units. The draft Rules for determining the natural gas volume are considered in detail. Specified variants of determining the weighted average value of combustion heat in the case of complex gas supply systems with the use of flow measuring means of gas combustion heat. The necessity and urgency of determining the natural gas heat combustion on measuring systems, which are equipped with duplicate metering units without the installation flow means measuring the heat combustion. Emphasis is placed on the fact that a large number of measuring systems are built on the method of variable pressure drop with the use of standard orifice devices. It is pointed out that this method, according to its physical principle, measures the mass gas flow rate. It is also stipulated that ultrasonic gas meters are often used to complete duplicate metering units. The advantages of ultrasonic meters are given. Attention is drawn to the availability of technical metrological support in Ukraine on the basis calibration prover, which includes two secondary standards gas volume and volume flow rate units. Methods and technical means for determining the natural gas heat combustion are analyzed. The calculation of the gas heat combustion and the Wobbe number based on the density values is shown. It is noted that the value of the gas mass flow rate is related to the value of the gas volume flow rate precisely the value of density. The nonlinear dependence of the gas mass heat combustion for the density, which is associated with a disproportionate change in the percentage of carbon atoms to hydrogen atoms, is shown. The structural scheme of the measuring system with the duplicating metering unit for gas density definition and gas heat combustion calculation is developed. The density calculation and natural gas heat combustion depending on the molar fraction of nitrogen and carbon dioxide in the gas from the minimum to the maximum value is carried out. The linear dependence of the change in the gas heat combustion for the molar fraction of nitrogen is established, on the basis of which the method of controlling the gas heat combustion for measuring systems with a duplicate metering unit is proposed. It is shown that the developed procedure for determining the natural gas heat combustion based on the value of density, which is obtained from the calculation of gas mass flow rate and gas volume flow rate consumption on measuring systems with duplicate metering units exactly satisfies class B and C according to DSTU OIML R 140.