Analysis of internally recurring unit processes in life cycle assessment
Analysis of internally recurring unit processes in life cycle assessment
复制标题
生命周期评价中内部重复单元过程分析
DOI：
10.1016/s0959-6526(02)00150-6
复制
发表时间：
2003
影响因子：
11.1
通讯作者：
Tak Hur
中科院分区：
文献类型：
--
作者：
J. Gwak;Mi;Tak Hur
在生命周期评估（LCA）研究中，单元过程或门到门模块的输入和输出的识别和量化是必不可少的。然而，通常，许多化学工业由具有内部重复单元过程的非常复杂的系统组成，其中单元过程的上游输入可以包括来自后面单元过程的下游输出。因此，为了生命周期清单分析的目的，很难分别确定和量化这些内部经常性单位流程的投入/产出。本文提出了几种适用于具有内循环单元过程的复杂系统的计算方法：（1）用联立方程确定与各单元过程相关的输入/输出。在这个建议中，任何与上游过程相关的参数都被视为“变量”，而其他参数集被视为“常量”。(2)根据累积总质量贡献，使用适当的截止标准确定输入/输出。(3)根据单个循环单元过程集的出现次数，使用适当的截止准则确定输入/输出。从这些方法的结果进行了分析，使用一个假设的例子和一个实际的情况下，从石化行业。这些方法提高了可靠性，并考虑到现场资料在经常性单位的过程。特别是，通过使用联立方程确定与每个单元过程相关的输入/输出，不增加关于截止标准选择的假设，并提供了节省时间、一致性和与现场考虑密切相关的优点。
In a life cycle assessment (LCA) study, the identification and quantification of the inputs and outputs of unit processes or gate-to-gate modules are essential. In general, however, many chemical industries are composed of very complex systems with internally recurring unit processes where the upstream input to a unit process may include the downstream output from a latter unit process. Therefore, it is rather difficult to identify and quantify the inputs/outputs for those internally recurring unit processes, respectively, for life cycle inventory analysis purposes. In this study, several calculation methods which are applicable to complex systems with internally recurring unit processes are proposed as follows: (1) Determination of the inputs/outputs associated with each unit process by using simultaneous equations. In this proposal, any parameter linked to an upstream process is treated as a ‘variable’ and the set of other parameters is considered to be a ‘constant’. (2) Determination of the inputs/outputs by using appropriate cut-off criteria based on the cumulative total mass contribution. (3) Determination of the inputs/outputs by using appropriate cut-off criteria based on the number of occurrences of an individual recurring set of unit processes. The results from these methodologies are analyzed using a hypothetical example and an actual case from the petrochemical industry. These methods enhance the reliability and consideration of on-site information in recurring unit processes. In particular, the determination of the inputs/outputs associated with each unit process by using simultaneous equations does not add assumptions regarding cut-off criteria selection and provides the advantages of time conservation, consistency and affinity to on-site consideration.