Abstract
With regard to the static characteristics under the partial load condition of the saline water conversion plant operated by Multi-Stage Flash (MSF) type brine recirculating evaporator, a briefanalysis was executed by utilizing computer program for general process simulation. Prior to execute the calculation, we had set equations to decide the condensing capacity of an evaporator-condenser which would give much influence to the performance of MSF evaporator. It was shown in the equations that the operating conditions of various loads should be decided by the heat and material balance under the condition exactly corresponding to thecondensing capacity. The outline of this calculation program was described in the paper. A model plant for the calculation was assumedas below:
Capacity of distillate produced: 1000 T/D (24 hrs.)
Number of stage: 10 (Heat Rec. 8, Heat Rej. 2)
The result of analysis indicated that an operating range of MSF evaporator under the partialload was limited within a short range due to the restriction of brine-flowing condition in each, inrelation to brine levels and brine orifices mounted between stages of the evaporator. The extent of the range depended on the number of stages and the configuration of the flash chamber of the evaporator. In the case of the model, for instance, the operating range of the maximum brine temperature under 80 percent of production rate was between 110.0 to 111.5°C (1.5°C difference).
The result of analysis also showed that when the maximum temperature of brine was lower than the above condition, the levels of brine were over the maximum allowable one, and to the contrary when the temperature was higher, the levels were unsealed. In either case, these phenomena proved a hindrance to the operation of the plant. In addition to the above, the following results wereobtained from the analysis of the model:
(1) With a decrease in the load (distillate), most of such operating quantities as recirculating brine, heating steam supplied, maximum brine temperature, etc., showed a decrease respectively, but the quantity of raw sea water increased.
(2) Performance ratio (i. e. distillate (kg) vs. steam (kg)), increased in proportion so a decrease in the loading.
Furthermore, changes in operating quantities obtained when the orifices of brine were adjusted while the load was changed from full to partial, were mentioned for reference
