蒸発装置における結晶種添加法の解析

抄録

A theoretical treatment has been developed to determine the concentration of CaSO₄ in sea-water evaporators seeded with anhydrous CaSO₄ crystals to control the formation of hard scale of CaSO₄. Eq. (10) gives the transient behavior of the degree of supersaturation of the scaling material, in the evaporator liquor and Eq. (11) and Fig. 3, the behavior under the steady state. In the former the degree of supersaturation is found variable with c₀/c_s, c_F/c_sK, Kγ, and τ, and in the latter with two dimensionless parameters of c_F/c_sK and Kγ which cover entire operating variables of the seeded evaporators.
Published data on concentrated-sea-water evaporators seeded with anhydrous CaSO₄ crystals are analysed by using the correlation developed here, and summarized in Table 2 and Fig. 5, where the previous measurement of the growth rate of anhydrous CaSO₄ crystal is utilized to carry out the calculation. The correlation proves reasonable, since a good agreement is found between the calculated and measured concentration values as shown in Fig. 5 (a)5 (d). From this conclusion an evaporator design to give higher liquid retention is indicated equally effective with the increase of seed concentration in evaporator liquor to suppress the degree of supersaturation of scaling material, when the seed concentration is limited to a certain value to avoid operational difficulties due to denser suspension.