Vol.5 No.2 2012

21/66

Research paper : Development of methane hydrate production method (J. Nagao)−95−Synthesiology - English edition Vol.5 No.2 (2012) comments, the author has added and revised the description in the text and the reference. However, the development of the production system depends not only on the production method, but also on the economic evaluation of methane production including the combination of machines in production tests at the sea bed conducted by JOGMEC. Thus, it is difficult to consider the validity of the production system based only on the tests with the large-scale apparatus. Therefore, the author has not described the development of the production system in this paper.2 The role of MHRCComment (Hiroshi Tateishi)In the latter half of “2. Overview” section, the goals of R&D issues in phase 2 at MHRC are explained. However, the description is sudden and difficult to understand for the readers since the relevance of phase 2 with phase 1 is not explained. Brief explanation for the following points is required: why MHRC is assigned for this part of R&D, what kind of results MHRC obtained in phase 1, and how the results obtained in phase 1 are connected to phase 2. Answer (Jiro Nagao)The author has added the following explanation. At the start of the program, the Methane Hydrate Research Laboratory of AIST (the present Methane Hydrate Research Center) participated in the MH21 Consortium as the research supervisor of R&D of production method & modeling in phase 1 since the laboratory had high level knowledge on methane hydrate engineering. The foregoing explanation has been connected to the subsequent description of implementation challenges and the research results. It has been found that depressurization is effective for the gas production method from the methane hydrate resource as a research result in phase 1. The finding is linked to the research purpose of phase 2 (technology advancement toward commercialization).3 Development of 1m-size test apparatusComment (Hioshi Tateishi )1. I can understand the logic that thermal decomposition is dominant in cm-size samples whereas mass transfer is dominant in the actual 100m-size bed, therefore a test filling the gap in between is required. Yet it is difficult to judge the adequateness of the specifications of the apparatus since no quantitative explanation is given on the scale boundary that separates the dominant factors. It seems difficult to set a strict boundary, but explanation is required such as, “Since critical scale is around this level because of such and such reasons, a 1m-size apparatus is adequate enough.” 2. Since the explanation of the specifications of the apparatus is simply listed, it is not clear where the focus is. For example, if the author arranges the explanation in the order of main items to test with the apparatus, technological issues and required functions to achieve the issues, the ways to clear the issues, the readers can understand the idea more easily. Especially, the manuscript lacks the explanation of originality of the MHRC.3. The author briefly explains the large-scale production apparatus LARS developed by the SUGAR Project in Germany. Since only the size is mentioned, it is difficult to understand the significance of the comparison. Please describe the purpose and design concept of the LARS and explain the difference of the two apparatuses, LARS and the apparatus of MHRC.Answer (Jiro Nagao)1. In order to design our apparatus, we have focused on solving the problem of predominant factors of hydrate dissociation. The sample size dependence of the rate-determining step has been investigated by using the production simulator, MH21-HYDRES. Another study shows that in the case of permeability of 10 mD order, the mass and heat transfers become comparable at the sample size of 0.5 m (Konno et al. Proc. Offshore Technology Conference 2010, 20591 (2010)). On the basis of the study and the analysis, we have judged that mass transfer dominates the dissociation process with an apparatus of over 1m-size. We have added the explanation in lines 3-8 on page 93 and reference No.15.2. On designing the apparatus, we have set the most important R&D issues to be investigating the dependence of productivity of the depressurization method on the permeability of the sample and finding the most suitable depressurization conditions, and analyzing quantitatively the impact of sand production, skin formation, and flow obstructions. The explanation of the functions prepared to clear the issues, their technological issues and the ways to clear the issues have been added to the manuscript.3. It was described in a paper that the objective of the SUGAR Project is to clarify the characteristics of CO2 geological storage and that the apparatus was introduced to carry out the methane hydrate decomposition using the reaction heat generated in the formation of CO2 hydrate. The explanation of the objective has been added to this manuscript. However, the author has not obtained the accurate information on the design concept of the apparatus and cannot explain it.

※このページを正しく表示するにはFlashPlayer9以上が必要です