Abstract
A test module plant of multistage flash (MSF) evaporator to desalt sea water was constructed in Oita for the purpose to obtain sufficient data in designing a 100,000m3/day plant. The research and development had been conducted as an activity in the 2nd phase of the national project on the “SEA WATER DESALTING AND BY-PRODUCT RECOVERY” which was completed in March, 1977. The test module plant was operated not to produce water, but to acquire precise data. From this standpoint, the data acquisition system played a significant part in the project. In advance, we had already experienced the process to deal with an acquisition system in the 3,000m3/day MSF evaporator which had been tested for three years until 1973 in the 1st phase of the project, and found two problems to be practiced. One is the highly precise temperature measurement of flashing brine throughout a long-term operation and the other is the computer system capable of dealing with multijobs.
This paper describes the following valuable experiences with the system.
(1) The absolute precision of temperature measurement was better than about 10 ppm as far as independently regarding to the A/D-converter by calibrating with a standard resistance.
(2) Calibration of each platinum resistance for temperature measurement within an absolute precision of 0.01°C resulted in accomplishing temperature measurement at an absolute precision of better than 0.1°C even after two years.
(3) The secular change of resistance in platinum sensor brought about the greatest effect on the absolute precision of temperature measurement.
(4) The precisely measured temperature distribution in flashing brine provided an advanced idea for determining chamber geometry of the evaporator.
