天然气能量计量体系在中国的建设和发展

Construction and Development of Natural Gas Energy Measuring System in China

关键词:  天然气  能量计量体系  建设  发展

Key words:  natural gas  energy measuring system  construction  development

摘要:

天然气贸易交接中的计量方式通常有三种,即体积计量、质量计量和能量计量。由于能量计量反映的是天然气的热能,作为最能反映其燃料特点的一种合理和科学的计量方式,在天然气国际贸易中被广泛采用。然而,中国目前尚普遍采用以体积流量作为贸易结算的依据。2008年12月31日,中国国家标准化管理委员会发布GB/T 22723-2008《天然气能量的测定》国家标准,并于2009年8月1日起正式实施。依据GB/T 22723-2008在实施范围和对象、能量计量方法、标准参比条件和能量计量体系方面的要求,深入分析中国天然气能量计量体系在天然气能量计量标准体系、能量计量相关设备的配置和性能评价、体积流量和发热量量值溯源链、标准参比条件和结算单位等方面的建设现状,并通过3个天然气长输管道A级计量站天然气能量计量技术的应用实例,(该3个A级计量站发热量测定均达到了GB/T 18603-2001《天然气计量系统技术要求》对A级计量站0.5%的不确定度水平要求),表明中国已具备实施天然气能量计量的基础条件。为了进一步推动中国天然气能量计量体系的发展,本文还讨论了全面实施能量计量还存在的一些不足,提出当前最重要的是应尽快形成甲烷不确定度0.05%、其它少量组分不确定度0.5%的国家一级天然气分析用多组分(九元)气体标准物质,建立不确定度为0.25%的发热量直接测定装置,达到ISO 15971∶2008《天然气性质测定发热量和沃泊指数》规定的一级水平,完善天然气体积流量和发热量量值溯源链,制定天然气溯源标准和能量测定系统性能评价标准,促进天然气能量计量技术在中国的全面实施。

Abstract:

Volume measuring, mass measuring and energy measuring are three routine metering methods of the natural gas trade transaction. The energy metering is a reasonable and scientific metering method for natural gas because energy is the most important character of fuel. Thus, energy metering is widely acceptable in international trade. Currently, in China, it is general to use volume flow rate for trade settlement. On Dec. 31, 2008, the Standardization Administration of the People’s Republic of China published a national standard named GB/T 22723—2008 Energy Determination for Natural Gas and it became effective on Aug. 1, 2009. According to the requirements of GB/T 22723—2008, such as application scope and object, energy measuring method, standard reference conditions and energy measuring system, the current status of natural gas energy measuring system in China is analyzed deeply, including standard system of energy measuring, configuration and evaluation of energy measuring equipments, volume flow rate, traceability chain of calorific value, standard reference conditions and settlement unit. This article illustrates that China already has the basic requirements to implement natural gas energy measuring by three technology application examples of natural gas energy measuring in A—grade measuring stations of long distance pipelines. The uncertainties of calorific value measurements in all three measuring stations are lower than 0.5% and they have met the uncertainty requirement of GB/T 18603—2001 Technical Requirements of Measuring Systems For Natural Gas for A—grade measuring station. To further promote the development of natural gas energy measuring systems in China,this paper discussed some shortage for the overall implementation of energy measuring. It also proposed to develop national primary reference gas mixtures (nine components) with uncertainty 0.05% for methane and with uncertainty 0.5% for minor components, to establish a device for the direct measurement of calorific value with an uncertainty 0.25% to meet the first grade requirement of IS() 15971 so as to improve the traceability chain for natural gas volume and calorific value, to constitute traceability standards and the evaluation standards of energy measuring systems, and ultimately promote the comprehensive implementation of natural gas energy measuring techniques in China.