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Research paper : Innovation in distillation processes (M. Nakaiwa et al.)−56−Synthesiology - English edition Vol.2 No.1 (2009) processes in relation to PI, we would first like to explain the concept of “energy saving.” Descriptions like “Energy consumption was reduced by 20 % due to energy-saving efforts” are often encountered. Such statements are not so ambiguous and there is no problem as a daily expression. Thermodynamically, however, a closer inspection of them should be carried out, since according to the First Law of Thermodynamics, energy is something that is conserved, not something that can be consumed. If a person gets a 20 % improvement in rate of fuel consumption from purchasing a compact car, what is reduced is the amount of fuel like gasoline that would have been consumed by traveling a given distance, not the energy itself. In an automobile, the chemical energy of fuel is converted through heat into work that is used for moving with the engine (an Otto cycle heat engine for a gasoline vehicle). Except for electric and hybrid vehicles, the term fuel-efficient engine refers to one with high energy-conversion efficiency. The upper limit of the efficiency is theoretically determined with thermodynamics under the conditions such as temperature and so on. In other words, there exists a theoretical efficiency limit of converting fuel into moving for the gasoline engine. Improvement of engine efficiency is an important subject for enhancing the rate of fuel consumption in an automobile, but it is basically impossible to achieve the high efficiency that exceeds the limit determined with thermodynamics. As another example, a refrigerator with a compressor is a heat engine called a reverse Carnot cycle, and there is also a theoretical limit of its efficiency, which corresponds to the amount of heat that can be transferred and dissipated from the inside to outside using a given amount of electrical energy. Its limit is theoretically determined with the temperature inside the refrigerator and the outside (room) temperature. It cannot achieve energy saving exceeding the limit of reverse Carnot cycle.Energy saving can be defined as the reduction of amount of energy required to accomplish a given task. There is a theoretical limit in achievable energy saving, which differs for each task. In other words, energy saving is to realize a given function as close to the theoretical limit as possible. In this paper, we use the term “detuning” to refer to the changing the process from the ideal state to one that is feasible. The term “detuning” is generally used when the engine technology developed for the F1-race vehicles is modified for use of commercial car. Modifications usually include reduced cost, increased durability, and improved usability, while the engine performance is decreased. In the field of energy saving, the term “targeting” is often used. It suggests targeting a high-efficiency process with an energy-saving goal, by starting from a current process. In this paper, we take the opposite direction of strategy for the technology development. First, we determine the ideal state, from which no further energy saving is possible (due to requiring unrealistic initial costs and/or equipment setup), and then sacrifice a little energy efficiency to achieve the feasible process. To emphasize this point, we use in this paper the uncommon term “detuning” by intention.It should be noted that the path of “detuning” from an ideal state to a feasible condition is not one-dimensional. Fig. 1 shows a schematic diagram of the paths taken to enhance energy-saving performance in a certain process. Here, a conventional approach for energy saving with process improvement and refinement corresponds to slowly climbing up from the base of a mountain. On the other hand, the “detuning” process is like arriving first at the summit, then descending while considering energy efficiency as well as the other parameters like cost. In this approach, there are multiple paths that lead down the mountain, and therefore multiple possible destinations. Such an approach has two main characteristics. First, fundamentally unattainable goals are not derived, since the path descends from the theoretical upper limit. Second, when faced with various difficulties to a practical application, it is relatively easy to start again from the peak and seek another “detuning” path. One problem with “detuning” is the risk that a detuned process may become far from the current process. This means, however, that achieving PI that requires “rapid and discontinuous dynamic changes” would become possible.3 Strategy for energy saving in distillation process through “detuning”First, we examine the history of energy-saving efforts in the distillation process, while keeping previous discussions in mind. The distillation process is one of the oldest chemical processes: it was actually used to purify perfumes more than two thousand years ago. The principle of distillation is to separate solution components by evaporating them through heating and then condensing them through cooling. Solutions are separated with the difference in the boiling point (BP) of each solution components. The operation involved the heating of the source solution in a container for a given period of time to generate vapor, which was cooled, liquefied, and then collected. This process is known as simple distillation. Subsequently, distillation was used for many applications, CBAEnergy efficiencyCurrent processIdeal stateA, B, C: Processes obtained by “detuning” from ideal stateFig. 1 “Detuning” from ideal state.

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