Evaluation methods of energy conservation for an evaporation process to desalt sea water was studied to cope with the trend of soaring energy cost and the warning of resource crisis. By quoting a conceptual design of multistage flash (MSF) evaporator having a capacity of 35,520m3/d to desalt warm sea water wasted from a 700 MW power plant, the unit energy and the exergy balance were estimated for the purpose of evaluating the energy conservation. Estimation methods of unit energy were derived for a standard MSF evaporator (the maximum brine temperatureat 120°C) of both dual and single purpose. An exergy balance was also estimated for a standard MSF evaporator having a capacity of 50,000m3/d. Unit energy indicated by heavy oil consumption (liter) per one cubic meter of fresh water production was 1.82 for the waste heat utilizing type, 2.54 for the dual purpose MSF and 5.44 for thesingle purpose. Exergy input per cubic meter of fresh water as a measure of conservation was 29.3 kW for the waste heat utilizing type and 14.1 kW for the standard MSF. The inferior evaluation for the waste heat utilizing type could be attributed to the account of exergy in waste heat.
The purity of desalted water by a multistage flash (MSF) evaporator will not be warranted unlessthe entrained brine is sufficiently removed. For an investigation associating with this problem, an instrument to measure the mist concentration and the size distribution has been developed. A detector of the instrument was directly installed in the 20th flash chamber of a 39 stage MSF test plant having a capacity of 3,000m3/day and successfully offered following data. For one case, the concentration and the weight mean diameter were 0.72×10-4g/l and 70μm respectively, and for another case 2.2×10-4g/l and 120μm respectively. For both cases, the operational conditions were almost same except the brine flow rate in the chamber respectively 800 t/hr (1,300t/m·hr) and 1,000 t/hr (1,700t/m·hr). The 20% increase of evaporation rate resulted in increase of three times mist concentration and twice mist size. The fact indicates that the flash intensity is very sensitive to the mist formation.
The caking tendency of common grade salt and kitchen salt made by ion-exchange membrane method was compared with that made by salt-field method. And the effect of a palletized transportation system on the caking during transportation was concurrently examined. For these purposes, piling test of 30kg common grade salt and 5 kg kitchen salt made by three salt-manufacturing factories (Z, W and P) was made at six warehouses of various environmental conditions, where blocks of three pallets of salt-bags (30 and 36 piling steps for common grade and kitchen salt, respectively) were stored for three and six months. In this paper, the results of common grade salt are reported and later those of kitchen salt will be reported. And the following results were obtained; (1) The magnesium content of piled common grade salt of W was small and those of Z and P were average. And the mean particle sizes of Z and W were large and that of P was average. Variations of these values in three salt-manufacturing factories were large and must be controlled within smaller ranges. (2) The degree of caking in three warehouses of six was above 3kg/cm2 according to the combination of salt qualities (water content, magnesium ions and mean particle size) and environmental conditions (temperature and humidity), where some preventing procedure must be taken. (3) The water content of common grade salt of all piling warehouses decreased during three and six months' storage. (4) The piling blocks of 3 pallets of 30 kg common grade salt-bags about 3500 mm in height. sank 4-10% of their initial height in the manufacturing warehouses and 2.3-4.7% in the intermediate warehouses after transportation. Care must be taken of collapse of the piling blocks. (5) When the salt-bags of caked common grade salt of 0.8-4.2kg/cm2 fell down from 1 m height twice, more than 70% of the salt in a bag was normally crushed. No further effect was expected by more falling-down. (6) Generally common grade salt made by an ion-exchange membrane method showed more