| Popis: |
Major additions and modifications to a titanium loop system for conversion to the study of the formation of silica from simulated geothermal brine were completed. Preliminary pressure and temperature testing with water up to 1000 psig and 200/sup 0/C, respectively, indicated general operability of the system. A 0.5- to 1.5-gpm side-stream was monitored and cooled under controlled conditions from 190/sup 0/C to 50/sup 0/C in a five-section double-tube bypass heat exchanger, then reheated and recycled. Satisfactory performance of the saturator column in providing suitable silica containing brines was also demonstrated. An on-line programmable computer-based data acquisition system was connected to the loop system to read temperature and flow data; to estimate heat transfer coefficients; and to perform additional monitoring, such as limit control and safety functions. Studies with the Once-Through System showed that seeding by silica polymers formed during shutdowns has been the major factor in promoting scaling in the studies carried out thus far. In a run at pH 6 with 1 M NaCl, no deposits formed during 58 h of continuous operation without seeding, but substantial scale formed in 13 h of continued operation after a 17 h shutdown to allow seeding to take place. Such seeded scalesmore » show strong dependence of the amount and nature of the deposit on temperature of deposition. The rate of buildup is also substantially enhanced by raising the sodium chloride concentration from zero to one molar.« less |
