Vol.2 No.1 2009

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Research paper : Innovation in distillation processes (M. Nakaiwa et al.)−61−Synthesiology - English edition Vol.2 No.1 (2009) prototype column with diameter of about 300 mm and height of about 25 m was constructed in the Chiba Plant of Maruzen Petrochemical, and the continuous operation of over 100 hours was successfully achieved first in the world although it processed a small throughput of 300 kg/h with benzene/toluene system.In an effort to further develop this achievement, the Ministry of the Economy, Trade and Industry (METI) and the NEDO launched on September of 2002 the “Development of Energy Saving Distillation Technology through Internal Heat Exchange” project in the New Global Warming Prevention Technology Program [16]. One of the authors acted as a leader of this project. The companies participated are Kimura Chemical Plant Co., Ltd., Maruzen Petrochemical Co., Ltd., and Kansai Chemical Engineering Co., Ltd., the target of which is for the petrochemical industries; and two companies that aimed for the air separation market, namely Nippon Sanso Corporation (currently Taiyo Nippon Sanso Corporation) and Kobe Steel Ltd.. The project focused on a double-tube design, in which the stripping section was the outer tube; and the rectifying section was the inner tube with structured packings, as shown in Fig. 8a). At the end of FY 2003, the construction of a pilot plant (see Fig. 8b)) for 12-component mixture system was decided at the Chiba Plant of Maruzen Petrochemical. As illustrated in Fig. 8c), this plant consisted of 7 double-tubes bundled together. Several considerations to realize PI were carried out in the design of plant, such as the inner tubes with 3 settings for diameters according to the gas-liquid load.Construction of the pilot plant proceeded smoothly, and the first trial operation was conducted in FY 2005. Eventually, the continuous operation of 1000 h was achieved, and the operations under varied conditions and without external heat source were also carried out. In all the conditions, the stable operations demonstrated the energy reduction performance evaluated in the design stage. The amount of energy saving obtained during the experimental operations was 62 % in primary energy compared with the present distillation column. The reduction in required reboiler heat was 290 to 320 Mcal/h with an input electrical energy of about 30 Mcal/h into the condenser, and thus the ratio between the input electrical energy and the thermal energy gained (Coefficient of performance in heat pump) was approximately 10, which is quite high. After the completion of NEDO project, AIST and three companies in the petrochemical industries mentioned above with two new companies, namely Mitsubishi Chemical Corporation and Toyo Engineering Corporation, established a consortium to investigate on the commercialization of the process and prevailing the technology. The results were taken back to each company and Kimura Chemical Plant opened up the commercial activities on FY 2008. In foreign countries, the research and development of HIDiC has been started from the viewpoint of global environmental issues. Specifically, the research with the aim of commercializing the HIDiC process was begun on January of 2002 in the Netherlands, and currently it is in the second phase of research and development. Many prominent companies in Europe are participating in this project, with Delft University of Technology and Energy Research Centre of the Netherlands.Why was Japan able to launch commercialization first? The answer to this question is not clear, but we believe it is due to the difference in strategy of realizing the characteristics of HIDiC where the distillation and heat transfer are integrated. The goals of researches in the U.S.A. in the 1980s and Europe in the 1990s were mainly to increase the amount of heat transferred from the rectifying section to the stripping section. Therefore, the consideration of material transfer and distillation performance was presumably insufficient. For example, multiple heat pipes were proposed to use for the heat transfer between the rectifying and stripping sections in a patent submitted in the U.S.A. in 1980 [17] . This would achieve a sufficient heat transfer, but the realization of equipment would not be possible due to difficulty in c)b) a)Internal structure of pilot plant (7 double-tube unit)Outer tubePacking in stripping sectionInner tube (heat transfer surface)Packing in rectifying sectionView of the pilot plant (in the Chiba Plant of Maruzen Petrochemical Co., Ltd.)Basic flows of HIDiC (inner tube corresponds to the upper part of conventional column, and the outer annulus the lower part)Product from bottomCompressorProduct from topHeat flowLiquid flowSteam flowFeedFig. 8 Internal structure of HIDiC and pilot plant.

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