成果報告書詳細
管理番号20130000000977
タイトル *平成22年度中間年報 最先端PG(Mega-ton Water System) 浸透圧発電 正浸透膜の基礎特性評価
公開日2014/1/25
報告書年度2010 - 2010
委託先名国立大学法人山口大学
プロジェクト番号P09025
部署名環境部
和文要約和文要約等以下本編抜粋
(1)事業目的:環境に優しい再生可能エネルギーのひとつに浸透圧発電がある。このシステムは風力や太陽光などの自然エネルギーに特有な時間変動が殆どなく、また設備面積を抑えることが可能なため発電施設を都市部近郊にコンパクトな形で立地させることができ、電力損失の少ない安定した電力供給が可能である。本委託事業の目的は正味電力を安定に取り出せる浸透圧発電システムの構築である。
(2)事業概要:浸透圧発電システムにおいて発生する電力はタービンを回す水量と水圧の積に比例する。そのため高い発電量を得るために、浸透圧発電用の正浸透膜には(1)高い水透過性、(2)膜表面近傍での濃度分極によって引き起こされる浸透圧差の低下を抑えるための高い塩バリヤー性、(3)膜性能を長期間保持するために高い耐膜汚染性が必要となる。 本研究では、正浸透膜およびこの膜を用いたモジュールの基礎特性評価方法を確立することである。そしてその評価方法を用いて正浸透膜形成グループが作製した膜を種々の条件において水透過性、塩バリヤー性を測定し、その結果を正浸透膜形成グループにフィードバックすることで浸透圧発電の実用化に必要な正浸透膜の形成を行う。研究場所は山口大学大学院理工学研究科(山口県宇部市)で行った。
英文要約 Pressure retarded osmosis (PRO) can be a viable source of renewable energy. The membrane for forward osmosis (FO) in the PRO process is the key component. The requirements for a good FO membrane are high water permeability coefficient A, low salt permeability coefficient, B, and low structure parameter, S. The lower the structure parameter, the better the performance of the membrane under PRO conditions. The water flux and salt flux across a sample membrane was measured using RO test cell with 500 ppm NaCl solution to evaluate the A, and B values of a sample membrane. To assess the impact of S value on flux, FO mode measurements were conducted with a hand-made cross-flow test cell by having: (1) the dense selective layer of a sample membrane facing the draw solution; (2) deionized water as the feed solution; (3) the concentration of NaCl varied in the draw solution. A commercially-available NF membrane (Toray Industries, Inc.), RO membrane (Toray Industries, Inc.) and FO membrane (Hydration Technology Innovations, SS-2) were used as sample membranes. The A value of the NF and the RO membrane were about 7 and 3 times higher than that of the FO membrane, respectively. The B value of the NF membranes was about 30 times higher and that of the RO membrane about 1/6 times lower than the FO membrane. The water flux across the NF and the RO membrane in the FO mode were about 1/10 and 1/5 of that across the FO membrane. The calculated S values from the water flux of the NF and RO membranes were about 10 times higher than that of the FO membrane. These indicate that the internal concentration polarization due to the thick support layer of the NF and RO membrane reduced the water flux across the membranes. A FO/PRO/RO mode test system was built for evaluating the PRO performance of FO membrane module. The test system consists of (1) draw solution (DS) tank, (2) feed solution (FS) tank, (3) sample FO module, (4) RO module for DS regeneration, (5) high pressure pumps, (6) conductivity meters, (7) pressure gauges and (8) flow meters. Deionized water and NaCl solution were used as FS and DS of the system. Water flux across a hollow fiber type FO membrane module with 4 ports (Toyobo Co., LTD.) was measured as a function of pressure difference between the inlet and outlet of the module. Under the conditions that the draw solution, 0.8 mol/dm3 NaCl, the water flux across the sample FO module decreases with increasing pressure difference and became zero at 3.96 MPa, which is almost equal to the osmotic pressure difference in the module. Membrane power output of the PRO mode is calculated by multiplying the water flux and the hydrostatic pressure difference. The power output increases with pressure and had a maximum when the pressure was 2.0 MPa, which is almost equal to half of the osmotic pressure.
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