In the hydrogen network with the minimum hydrogen utility flow rate,the pinch appears at the point with zero hydrogen surplus,while the hydrogen surpluses of all the other points are positive.In the hydrogen purity profiles,the pinch can only lie at the sink-tie-line intersecting the source purity profile.According to the alternative distribution of the negative and positive regions,the effect of the purification to the hydrogen surplus is analyzed.The results show that when the purification is applied,the pinch point will appear neither above the purification feed nor between the initial pinch point and the purification feed,no matter the purification feed lies above or below the initial pinch point.This is validated by two case studies.
To explore the effect of removing different impurities to hydrogen networks, an MINLP model is proposed with all matching possibilities and the trade-off between operation cost and capital cost is considered. Furthermore,the impurity remover, hydrogen distribution, compressor and pipe setting are included in the model. Based on this model, the impurity and source(s) that are in higher priority for impurity removal, the optimal targeted concentration, and the hydrogen network with the minimum annual cost can be identified. The efficiency of the proposed model is verified by a case study.
