This paper describes analysis of performance of OTEC plant using an integrated hybrid cycle (I-H cycle). The integrated hybrid cycle is a combination of a closed cycle OTEC plant and a spray flash desalination plant. The optimization of using an integrated hybrid cycle is analyzed by the method of steepest descent. The total heat transfer area of heat exchanger per net power is used as an objective function. The numerical results are shown for a 10 MW integrated hybrid cycle with plate-type heat exchangers. Ammonia is used as a working fluid. The results are compared with that of a joint hybrid cycle (J-H cycle) system.
Using three types of low-pressure reverse osmosis membranes-NF-70 supplied from Film Tech, NTR-729HF from Nitto Denko Co., and SU-600 from Toray-reverse osmosis experiments were carried out under the operating pressure of 0.14, 0.34, and 0.49 MPa to separate aqueous solution of MgSO4 of which feed concentrations were 100,500, and 2,000 mg/l. The results were analyzed to obtain membrane constants based on the irreversible thermodynamics model proposed by Kedem & Katchalsky and modified by Ohya et al.; the agreements between the experimental data and that predicted by the models are excellent. The results of fluxes and salt passages were converted values at the standard conditions of 500 mg/l and 0.34 MPa with correction factor for pressure (PCF), for temperature (TCF), and for salt passage (SPCF) proposed by the American Society for Testing and Materials, ASTM D4516. PCFs estimated by ASTM and the model agree quite well with PCF obtained from the experimental results; SPCF and SP xperimentally obtained also agreed well with those by the model, but not with these by ASTM. The standardizing procedure proposed by ASTM particularly for salt passes may not be applied for the data obtained with low-pressure reverse osmosis method.
To develop potassium ion memorized inorganic ion-exchangers, potassium ions of specially selected synthetic potassium tungstate (K2W4O13) samples, which have tunnel crystal structures, have been ion-exchanged for sodium ions in molten sodium nitrate at 330°C or for protons in aqueous nitric acid solutions at 25°C. Proton-exchangedpotassium tungstates (for example, H0.25K1.75W4O13) were found to have the feasibility of the potassium memorized exchangers, but sodium-exchanged potassium tungstates (NaxK2-xW4O13) were not easily exchanged for potassium ions in aqueous solution at room temperature, because of stabilized sodium ions in the exchanged samples. The study in this paper is the first stage of the development of potassium ion memorized ionexchangers and details will be discussed in following papers.
The desorption properties of lithium ions from the ion-sieve manganes oxide [HMnO(2Mg)] were investigated using (NH4)2S2O8 as an eluent. The effects of temperature,(NH4) 2S2O8 concen tration, and solid-solution ratio on the Li+ ion desorptivity were examined. More than 97% of the adsorbed Li+ ions could be desorbed by the treatment of the adsorbent with a 0.5-M (NH4)2S2O8 solution at 30°C for 1 h. The adsorbent after the desorption showedthe lithium adsorptivity to be nearly equal to that on the original one.