The deep seabed is known for its abundant reserves of various mineral resources.Notably,the Clarion Clipperton(C-C)mining area in the northeast Pacific Ocean,where China holds exploration rights,is particularly rich i...The deep seabed is known for its abundant reserves of various mineral resources.Notably,the Clarion Clipperton(C-C)mining area in the northeast Pacific Ocean,where China holds exploration rights,is particularly rich in deep-sea polymetallic nodules.These nodules,which are nodular and unevenly distributed in seafloor sediments,have significant industrial exploitation value.Over the decades,the deep-sea mining industry has increasingly adopted systems that combine rigid and flexible risers supported by large surface mining vessels.However,current systems face economic and structural stability challenges,hindering the development of deep-sea mining technology.This paper proposes a new structural design for a deep-sea mining system based on flexible risers,validated through numerical simulations and experimental research.The system composition,function and operational characteristics are comprehensively introduced.Detailed calculations determine the production capacity of the deep-sea mining system and the dimensions of the seabed mining subsystem.Finite element numerical simulations analyze the morphological changes of flexible risers and the stress conditions at key connection points under different ocean current incident angles.Experimental research verifies the feasibility of collaborative movement between two tethered underwater devices.The proposed deep-sea mining system,utilizing flexible risers,significantly advances the establishment of a commercial deep-sea mining system.The production calculations and parameter determinations provide essential references for the system’s future detailed design.Furthermore,the finite element simulation model established in this paper provides a research basis,and the method established in this paper offers a foundation for subsequent research under more complex ocean conditions.The control strategy for the collaborative movement between two tethered underwater devices provides an effective solution for deep-sea mining control systems.展开更多
Biomass,widespread and carbon-neutral energy,can provide electric energy and replace fossil fuel-derived production.Pyrolysis is the main way of converting biomass to different bioenergy products with the consumption ...Biomass,widespread and carbon-neutral energy,can provide electric energy and replace fossil fuel-derived production.Pyrolysis is the main way of converting biomass to different bioenergy products with the consumption of material and energy,which will cause environmental impacts.To confirm the actual environmental impact of biomass conversion,life cycle assessment(LCA)is used for analyzing the process.Due to choosing different LCA methods,the results for the same thing in different reports will show obvious fluctuation.This review is devoted to providing recommendations on how to handle methodological issues when analyzing LCA study,by which researchers can better realize the similarities and differences in biomass conversion system.In this review,multiple clarifications and methodological recommendations on the four steps of the LCA process(including goal and scope definition,life cycle inventory,life cycle impact assessment,and interpretation)are provided.Furthermore,the LCA results are discussed systematically,in which the global warming potential gets extra attention.Meanwhile,different biomass feedstocks are divided into agricultural residues,forest residues,and microalgae carefully.Finally,the current challenges and future framework of biomass conversion are expounded in detail from the perspective of LCA.展开更多
基金Supported by Finance Science and Technology Project of Hainan Province under Grant No.ZDKJ2021027the National Natural Science Foundation of China under Grant No.52231012.
文摘The deep seabed is known for its abundant reserves of various mineral resources.Notably,the Clarion Clipperton(C-C)mining area in the northeast Pacific Ocean,where China holds exploration rights,is particularly rich in deep-sea polymetallic nodules.These nodules,which are nodular and unevenly distributed in seafloor sediments,have significant industrial exploitation value.Over the decades,the deep-sea mining industry has increasingly adopted systems that combine rigid and flexible risers supported by large surface mining vessels.However,current systems face economic and structural stability challenges,hindering the development of deep-sea mining technology.This paper proposes a new structural design for a deep-sea mining system based on flexible risers,validated through numerical simulations and experimental research.The system composition,function and operational characteristics are comprehensively introduced.Detailed calculations determine the production capacity of the deep-sea mining system and the dimensions of the seabed mining subsystem.Finite element numerical simulations analyze the morphological changes of flexible risers and the stress conditions at key connection points under different ocean current incident angles.Experimental research verifies the feasibility of collaborative movement between two tethered underwater devices.The proposed deep-sea mining system,utilizing flexible risers,significantly advances the establishment of a commercial deep-sea mining system.The production calculations and parameter determinations provide essential references for the system’s future detailed design.Furthermore,the finite element simulation model established in this paper provides a research basis,and the method established in this paper offers a foundation for subsequent research under more complex ocean conditions.The control strategy for the collaborative movement between two tethered underwater devices provides an effective solution for deep-sea mining control systems.
基金supported by the National Natural Science Foundation of China(No.22108221)the Shaanxi Natural Science Foundation(2021JQ-028).
文摘Biomass,widespread and carbon-neutral energy,can provide electric energy and replace fossil fuel-derived production.Pyrolysis is the main way of converting biomass to different bioenergy products with the consumption of material and energy,which will cause environmental impacts.To confirm the actual environmental impact of biomass conversion,life cycle assessment(LCA)is used for analyzing the process.Due to choosing different LCA methods,the results for the same thing in different reports will show obvious fluctuation.This review is devoted to providing recommendations on how to handle methodological issues when analyzing LCA study,by which researchers can better realize the similarities and differences in biomass conversion system.In this review,multiple clarifications and methodological recommendations on the four steps of the LCA process(including goal and scope definition,life cycle inventory,life cycle impact assessment,and interpretation)are provided.Furthermore,the LCA results are discussed systematically,in which the global warming potential gets extra attention.Meanwhile,different biomass feedstocks are divided into agricultural residues,forest residues,and microalgae carefully.Finally,the current challenges and future framework of biomass conversion are expounded in detail from the perspective of LCA.
