压缩天然气汽车燃料的推荐做法

[中文适用范围]： 压缩天然气 (CNG) 是一种实用的汽车燃料，与汽油相比有优点和缺点。北美蕴藏着大量天然气。它具有更高的辛烷值@产生的废气排放量低@无蒸发排放，并且在同等能源基础上比其他燃料成本更低。天然气通常从 20 684 kPa 压缩至 24 821 kPa（3000 至 3600 psig），以增加其能量密度，从而在给定的航程和有效载荷下减少其车载存储体积。 CNG 还可以通过提高液化天然气的压力并将其汽化为气体来制造。一旦转换，它就被称为 LCNG。天然气的性质受以下因素影响： (1) 供应来源，即气田成分或杂质； （二）生产和输送公司对天然气的加工； (3) 区域天然气供应@储存@和需求平衡，由分销公司经常与管道公司合作，以维持全年不间断的服务@例如@用丙烷空气调峰（参见美国矿业局出版物503）； (4)分配现场维护特性，即过滤和干燥。协调研究委员会 (CRC) 公布了全国压缩天然气汽车燃料调查的结果。有关分配系统天然气特性及其变异性的信息已包含在图 1@ 2@ 和 3@ 中，并且可以在 CRC 报告编号 PC-2-12 中找到。在该国某些地区的某些操作条件下，成分可能每小时都会发生变化。因此，数据通常应被视为代表所提到的区域，并适当考虑当地差异。在美国各地运输的天然气不受统一的国家标准的约束。根据涵盖州际天然气销售的联邦政府规定，美国联邦能源管理委员会 (FERC) 裁定关税@，对进入州际贸易的天然气提出经济和技术要求。 2006 年，@ FERC 发布了一份政策声明，建议利益相关者： 1. 只有 FERC 批准的天然气价格中包含的天然气质量和可互换性规范才能得到执行； 2. 管道费率对天然气质量和互换性的规定需要灵活，以允许管道平衡安全性和可靠性问题； 3.管道及其用户应根据技术要求制定气体质量和互换性规范； 4. 在谈判基于技术的解决方案时，强烈鼓励管道及其客户使用天然气理事会+ (NGC+) 临时指南——作为解决天然气质量和互换性问题的共同参考点； 5. 如果管道及其客户无法解决有关天然气质量和互换性的争议@，这些争议可以提交给 FERC，并根据具体情况进行解决？？1 NGC+ 临时指南要求天然气规范：包括： 1. 与当地历史平均气体@或@为服务区域@确定的调整或目标气体正负4%沃泊数变化的范围，但须满足：最大 Wobbe 数限制：1400 b．最大热值上限：1110 Btu/scf 2. 其他成分最大限值：最大丁烷+：1.5摩尔% b．最大总惰性物质：4 摩尔% 3. 例外：具有使用超过 Wobbe@ 较高热值和/或成分限制的供应品经验的服务区域可以继续使用符合此经验的供应品，只要它不会过度影响安全性和安全性。终端使用设备的利用问题。2虽然《临时指南》仅为设定天然气质量关税限制提供指导，但经验表明，在大多数情况下，州际关税中使用沃贝和更高热值限制。由于美国大部分天然气销售均受 FERC 管辖@，这意味着临时指南限制代表@在大多数情况下@适用于分配系统接收的天然气的限制。相比之下，州内天然气销售@不在 FERC 管辖范围内@，但包括出于实际目的@从州内和州际来源接收天然气的公用事业公司在内的客户通常会收到符合临时指南的天然气。 NGC+ 临时指南解决了与天然气相关的燃烧问题。另外@ FERC 考虑了可凝性碳氢化合物，以回应 NGC+ 的第二篇论文。3 FERC 没有建议具体行动来回应本报告中的 NGC+ 建议，@ 基本上建议将历史上可凝性碳氢化合物的经验转化为更一般的相图描述？ ?cricondentherm 碳氢化合物露点?? (CHDP) 高级烃混合物标准。 CHDP 标准有助于确保各种成分的天然气在所有操作压力和所有合理的环境温度下保持气态。天然气主要由甲烷组成（通常为88至96摩尔%），余量为比例递减的高级烃烷烃，例如乙烷、丙烷和丁烷。它还可能含有氮气@水@二氧化碳@氧气@硫化合物和微量润滑油。在零售店，天然气中可能含有警告剂@或气味剂@。天然气汽车的经验已显着增长。车队和持续使用的应用为表征气体成分因素奠定了基础，这将有助于了解气体质量对车辆和整体性能的影响，并可能导致天然气车辆 (NGV) 出现根本性的操作问题。水含量和其他腐蚀前体@较重的碳氢化合物@可能在燃料容器内凝结@颗粒物质@油@和能量含量都需要考虑。可凝性碳氢化合物（液态）也是天然气汽车设备退化的一个问题。目的 本 SAE 建议实践中包含的规定旨在提供在车站/车辆接口处测量的输送到车辆储存容器的压缩天然气燃料成分的最低要求。本文件介绍了压缩天然气车用燃料的重要物理和化学特性，并描述了定义或评估这些特性的相关测试方法。所包含的要求和指南旨在实现令人满意的车辆性能@操作和排放水平@并保护燃油系统组件免受与燃油相关的故障@以及过早恶化或故障。本文件旨在作为指南，可能会根据经验和技术进步进行更改。请参阅附录 A 了解发动机和车辆制造商的建议。有关液化天然气燃料成分的信息@请参阅推荐做法 SAE J2699@液化天然气汽车燃料。 [外文原描述]： Compressed Natural Gas (CNG) is a practical automotive fuel, with advantages and disadvantages when compared to gasoline. Large quantities of natural gas are available in North America. It has a higher octane number rating, produces low exhaust emissions, no evaporative emissions and can cost less on an equivalent energy basis than other fuels. Natural gas is normally compressed from 20 684 to 24 821 kPa (3000 to 3600 psig) to increase its energy density thereby reducing its on-board vehicle storage volume for a given range and payload. CNG can also be made from liquefied natural gas by elevating its pressure and vaporizing it to a gas. Once converted it is referred to LCNG.The properties of natural gas are influenced by: (1) source of supply i.e. field, composition or impurities; (2) the processing of natural gas by the production and transmission companies; (3) the regional gas supply, storage, and demand balancing done by distribution companies often in concert with pipeline companies to maintain uninterrupted service throughout the year, e.g., peak shaving with propane-air (see U.S. Bureau of Mines Publication 503); and (4) dispensing site maintenance characteristics i.e. filtration and drying.The Coordinating Research Council (CRC) has published the results of a national compressed natural gas vehicle fuel survey. Information on the properties of distribution system natural gas and its variability has been included in Figure 1 , 2 , and 3 , and can be found in CRC Report No. PC-2-12. Composition can vary hourly under certain operating conditions in certain areas of the country. Thus the data should generally be considered representative for the areas mentioned with due consideration for local variation.Natural gases transported throughout the U. S. are not subject to uniform national StandardDetails. Under federal government rules covering interstate sales of natural gas, the U. S. Federal Energy Regulatory Commission (FERC) adjudicates tariffs, placing economic and technical requirements upon natural gases entering interstate commerce. In 2006, FERC issued a policy statement advising stakeholders that:1Only natural gas quality and interchangeability specifications contained in FERC-approved gas tariffs can be enforced;2Pipeline tariff provisions on gas quality and interchangeability need to be flexible to allow pipelines to balance safety and reliability concerns;3Pipelines and their customers should develop gas quality and interchangeability specifications based on technical requirements;4In negotiating technically-based solutions, pipelines and their customers are strongly encouraged to use the Natural Gas Council Plus (NGC+) Interim Guidelines…as a common reference point for resolving gas quality and interchangeability issues; and5To the extent pipelines and their customers cannot resolve disputes over gas quality and interchangeability, those disputes can be brought before FERC to be resolved on a case-by-case basis… 2xThe NGC+ Interim Guidelines call for natural gas specifications that include:1A range of plus or minus 4% Wobbe number variation from local historical average gas, or alternatively, established adjustment or target gas for the service territory, subject to:aMaximum Wobbe number limit: 1400bMaximum higher heating value limit: 1110 Btu/scf2Additional composition maximum limits:aMaximum butanes+: 1.5 mole percentbMaximum total inerts: 4 mole percent3EXCEPTION: Service territories with demonstrated experience with supplies exceeding these Wobbe, higher heating value and/or compositional limits may continue to use supplies conforming to this experience as long as it does not unduly contribute to safety and utilization problems of end use equipment. 2xWhile the Interim Guidelines provide only guidance for the setting of tariff limits on gas quality, experience has shown that in most cases the Wobbe and higher heating value limits are used in interstate tariffs. Since the bulk of U. S. sales of natural gas fall under FERC jurisdiction, this means that the Interim Guideline limits represent, in most cases, the limits that apply to natural gases received by distribution systems. Intrastate natural gas sales, by contrast, are not within FERC jurisdiction, but customers including utilities receiving gases from both intrastate and interstate sources, for practical purposes, generally receive natural gas that meet s the Interim Guidelines.The NGC+ Interim Guidelines address combustion issues associated with natural gases. Separately, FERC considered condensable hydrocarbons in response to a second paper from NGC+. 2x No specific actions were recommended by FERC in response to the NGC+ recommendations from this report, which basically recommended translation of historical condensable hydrocarbon experience into more general phase diagram-depicted “cricondentherm hydrocarbon dew point” (CHDP) criteria for higher hydrocarbon mixtures. CHDP criteria help ensure that natural gases of various compositions remain in gaseous state at all operating pressures and all reasonable ambient temperatures.Natural gas is comprised chiefly of methane (generally 88 to 96 mole percent) with the balance being a decreasing proportion of proportion of higher hydrocarbon alkanes such as ethane, propane, and butane. It can also contain nitrogen, water, carbon dioxide, oxygen, sulfur compounds and trace amounts of lubricating oil. At the retail outlet a warning agent, or odorant, is likely present in natural gas.Experience with natural gas vehicles has grown considerably. Fleet and ongoing in-use applications provide a foundation for characterizing gas composition factors that will help to understand gas quality effects on vehicle and overall performance and may cause fundamental operational problems for natural gas vehicles (NGVs). Water content and other corrosion precursors, heavier hydrocarbons, which may condense within the fuel container, particulate matter, oil, and energy content all need to be considered. Condensable hydrocarbons (liquid state) are also of concern in NGV equipment degradation.Cross Reference: 902069,920593,ANSIAGA/NGV,ASTMD1142,ASTMD1945,ASTMD3588,ASTMD4084