Vol.2 No.1 2009

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Research paper : Innovation in distillation processes (M. Nakaiwa et al.)−63−Synthesiology - English edition Vol.2 No.1 (2009) Discussion with Reviewers1 Comparison with current processesQuestion and comment (Koichi Mizuno)I understand that HIDiC is superior to VRC and Petlyuk in terms of energy saving and operability. However, there are some problems in terms of manufacturing cost, performance, and so forth, as referred in the paper. For example, the cost of HIDiC manufacturing might be higher due to its complex structure. What do you think of this point? Also, what are the differences in distillation performance when this process is compared with the other processes?Answer (Masaru Nakaiwa)In general, a distillation column is entirely custom-made since the specifications of the apparatus are different according to the property of the solution to be separated, the level of product purity required, and the processing volume. Thus, the manufacturing cost depends on the specifications. For the pilot plant of HIDiC (at the Chiba plant of Maruzen Petrochemical Co., LTD.; fractional distillation of gasoline with 12 components at the commercial scale feed of 12,000 ton/year), the cost was 230 million yen. The amount of reduction in annual running cost via the energy saving of HIDiC is about 20 million yen when calculated at the crude oil price of 60 US dollar/barrel. While the manufacturing cost of an ordinary column at the same scale is uncertain, the response of Kimura Chemical Plants Co., Ltd. to user inquiries is: “It is about twice as much as a conventional type.” Applying this to the pilot plant, when the reduced annual running cost is subtracted from the cost difference between HIDiC and an ordinary column, the simple payback time is 5.75 years. I think the actual cost would be slightly different since the pilot plant has somewhat special specifications such as the use of temperature measurement system for investigations. The detailed descriptions are summarized in the Kagaku Kogaku Ronbunshu, 34(4), 444 (2008). For the distillation performance of HIDiC without the heat transfer, it is about the same as the ordinary process.2 Energy consumption in ideal state and “detuning” processQuestion and comment (Koichi Mizuno)Energy saving was achieved considerably in this study. Is it possible to quantitatively describe the difference in energy consumption between the ideal state and HIDiC?Answer (Masaru Nakaiwa)We have not done such a calculation since the amount of energy consumption depends on the several conditions. HIDiC is a “detuning” process from the reversible distillation operation that is ideal state, but an additional factor of the heat pump effect is involved. The total energy consumption in HIDiC is significantly influenced by the energy efficiency in the compression process. Here, the thermodynamically ideal state of this process is a reverse Carnot cycle, as described in the paper. The energy efficiency of a compression heat pump that is currently used in industries is at most 50 % of the reverse Carnot cycle. Therefore, there is a possibility of reducing the energy use by half at least. If we discuss the minimum energy consumption for the separation of mixture thermodynamically apart from HIDiC, it is possible to achieve a reduction of energy consumption of at least tenfold. Exergy analysis is useful to estimate the value of such a reduction quantitatively.3 Detuning from ideal stateQuestion and comment (Hiroshi Tateishi)I think Fig. 1 is easy to understand as a concept, yet the meanings of A, B, and C, respectively, are unclear. As I understand that an approximate operation is carried out under some conditions with “detuning” from the ideal state, can you include any explanations from such a viewpoint in the figure?Answer (Masaru Nakaiwa)We explain a general concept of “detuning” in Fig. 1. Petlyuk column and VRC process do not quantitatively correspond to B and C of Fig. 1. To clarify that Fig.1 illustrates a general concept, we added the explanation to the figure.4 Explaining key points of research on HIDiCQuestion and comment (Hiroshi Tateishi)I think the overall structure of paper where the R&D of HIDiC is overviewed from a higher stage of the innovation in distillation process is good. However, I think it is necessary to emphasize the significance of research on HIDiC at AIST using some specific examples. Can you give us more detailed explanation for how the theoretical analysis, numerical simulation and technological developments on HiDiC have been integrated at AIST?Answer (Masaru Nakaiwa)The description in chapter 6 was revised from the viewpoint of the contributions of AIST.

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