成果報告書詳細
管理番号20100000001972
タイトル*平成21年度中間年報 新エネルギー技術研究開発 バイオマスエネルギー等高効率転換技術開発(転換要素技術開発) 自己熱再生方式による革新的バイオマス乾燥技術の研究開発
公開日2010/10/21
報告書年度2009 - 2009
委託先名国立大学法人東京大学 三菱重工業株式会社
プロジェクト番号P07015
部署名新エネルギー技術開発部
和文要約和文要約等以下本編抜粋:1. 共同研究の内容および成果等
1-1.事業概要
カーボンニュートラルであるバイオマス資源のエネルギー利用は、化石資源由来のエネルギーの代替につながることから、地球温暖化防止に有効であるとともに、持続可能な循環型社会の形成に向けて重要な役割を担うものであり、その積極的な導入促進が強く期待されている。しかし、バイオマスは含水率が50%以上と高い為、(1)輸送効率が低く輸送費用が高い、(2)腐敗する為、数日でも保管が困難、(3)ガス化や直接燃焼での発熱量が低い、などのデメリットがある。そこで、バイオマスの発生地点で「オンサイト乾燥」を行えば、前述のデメリットは改善し、更に発生地
点付近での分散型の保管も可能となる。そこで、本事業ではエタノール生産の事業化における重要な課題の一つとして、乾燥技術に着目する。このようなバイオマスの乾燥技術は、バイオエタノール生産に限らず、燃焼やガス化などの熱化学反応も含めて大変重要な技術である。
従来の乾燥技術では、水分の乾燥エネルギーに顕熱のみを利用しており、水分が蒸発する際に必要とする潜熱の回収・利用についてはほとんど行われていなかった。また、近年開発されている蒸気再圧縮法では潜熱の回収は行われているが、顕熱の回収については十分に行われていない。そこで、本開発事業では自己熱再生方式によるバイオマスの乾燥プロセスおよび乾燥装置を提案し、その実用化に向けた研究開発を行う。自己熱再生では圧縮操作を利用して、水分の潜熱および顕熱の両方を回収することにより、より高いエネルギー効率でのバイオマス乾燥が可能となる。
英文要約Title: New Energy Technology Development. Development of Technology for High-efficiency Conversion of Biomass and Other Energy (Development of Elemental Technology). R&D of Innovative Energy-Efficient Biomass Drying Process based on Self-Heat recuperation Technology (FY2008-FY2010) FY2009 Annual Report
Biomass, as carbon neutral, has a great potentiality to keep a balanced CO2 production and consumption alleviating global environmental problems caused by the use of fossil fuels. Unfortunately, the available biomass resources usually contain of large amount of moisture leading to higher transportation cost, debasement during storage, decrease of thermal efficiency in thermochemical conversion process, etc. Hence, it is necessary to develop a drying technology to establish an efficient and dependable biomass utilization system. Unfortunately, drying usually requires high energy input because of high latent heat of water evaporation and relatively low energy efficiency of the available driers. Recently, there are many drying technology utilizing a heat recovery system to improve energy efficiency, but most of them do not recover both sensible and latent heats during drying effectively.
In this work, an innovative drying process based on self-heat recuperation technology utilizing effectively both latent and sensible heat has been developed aiming for drying-energy saving. In this technology, water, which is contained in biomass, is heated up to its boiling point and subsequently the evaporated steam is superheated. The superheated steam is compressed by a compressor to provide a temperature difference enabling for heat exchange. The condensation heat of the compressed steam is exchanged with the evaporation heat of the water from biomass. On the other hand, the sensible heat of the compressed steam is utilized to raise the temperature of both evaporated steam and water contained in biomass. In addition, the sensible heat of the dried biomass is also recovered by air to improve overall energy efficiency.
Process simulation to determine the amount of required drying energy is conducted using a commercial process simulation tool (Invensys PROII) comparing to conventional drying process with heat recovery. The proposed drying process based on self-heat recuperation was found to drastically reduce the drying energy consumption. Numerically, it could reduce the drying energy from 250.9kW to 34.4kW per 1000kg of biomass drying from moisture content of 50% to 20%.
Based on the above simulation result, in the experimental stage, fluidized bed is selected as a dryer because of its characteristics on high heat and mass transfer and good solids contact between particles leading for effective drying. Inert material is inserted inside the bed to improve the fluidization performance of the biomass which is peculiar in shape and act as heat carrier enhancing the heat transfer across the bed. The fluidization performance, effect of the inlet mass ratio, gas flow rate, temperature, dust concentration, etc are investigated. Furthermore, to observe the heat transfer across the bed, heating elements simulated as compressed air and evaporated water are immersed inside the bed. The earned data are treated as design data for practical application of the developed system.
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