RU2186034C1 - Method of water or salt solution desalting by freezing and thawing - Google Patents

Abstract

FIELD: technology of water treatment. SUBSTANCE: invention relates to methods of water desalting in industry and in homes. Method of desalting water or salt solutions by freezing and thawing involves water freezing water or salts solution in a vessel in the ratio of vessel height to transverse section ≥ 2 being a vessel is fitted with a heater by is axis. After complete liquid freezing in a vessel a hole is made in vessel bottom center and ≥ 15% of ice is melted by means of axis heater obtaining a saline mother liquid and remained ice is melted in an arbitrary regime and purified water is prepared. For a single cycle 80 vol. % of liquid is obtained that is desalted by 30-40% and 20% of concentrate. Invention can be used for water treatment and desalting in homes, treatment of drinking water, industrial flows and concentration of waters and solutions. EFFECT: improved method of desalting. 2 cl, 7 dwg

Description

 The invention relates to a technology for purification and desalination of water, salt solutions in industry and at home, and can also be used to purify drinking water, industrial effluents.

 Freezing can be carried out in cone-shaped vessels, expanding upward, or in an oblique bulb that rotates around its axis. To obtain the phase of the concentrate and desalted liquid, the zone melting method is also used [Stadnik AS, Dedkov Yu.M. Freezing as a method of concentration of impurities in water. / Chemistry and technology of water. 1981. T. 3. 3. S. 227-233]. The author of the work [Puchko V.I. A new way to desalinate water by freezing. / Hydrotechnics and land reclamation. 1949. 3. P.46-55] recommends freezing ice piles, during subsequent melting of which receive desalinated water. Physico-chemical processes that occur during desalination by freezing and melting ice are described in [Mitin M.F. Desalination of water by natural freezing. / Hydrotechnics and land reclamation. 1963. 2. S. 20-27].

In the application [Method for producing melt water and a generator of melt water. Application 97100446/13. Russia. IPC ⁶ C 02 F 1/22 / Kuznetsov E.S., Soloviev E.F. Claim 01/14/97., Publ. November 10, 1998, Bull. 31] proposes a combined method, characterized in that the process of freezing water and thawing ice is carried out partially and alternately in two containers. The method is complicated in hardware and technological content.

 A simpler combined method closest to that proposed in this application is proposed in the patent [Method for improving the quality of drinking water by freezing / Pat. 2077160. Sosnovsky A.V., Ivlev S.A., Samoilov B.C., German V.V. Application 94011389/26. Claim 04/01/94, publ. 04/10/97 g]. This patent describes a method for improving the quality of drinking water by freezing, which consists in freezing, crushing and melting ice, characterized in that ice is frozen up to 70-90% of the water volume, ice melting is carried out by thermal insulation of its side and lower surfaces to form 30 -55% of the volume of ice melt runoff with its subsequent removal. The remaining pure ice is melted completely and 15-60% of pure water from its originally taken volume for desalination is obtained.

The disadvantages of the method:
1. It is necessary to control the degree of freezing, which is difficult under natural conditions (when air temperature and wind speed change).

 2. It is necessary to crush ice.

 3. It is necessary to control the degree of melting of ice in the conditions of its thermal insulation.

 4. Relatively low yield (15-60%) of pure water.

 A method for improving water quality that is free of these disadvantages is proposed. The method is based on the fact that when freezing water in a cylindrical vessel (heat was removed from the outside), the ice layer grows from the walls to the center of the vessel. In this case, at first clean water freezes, and the liquid remaining inside the ice zone gradually concentrates on the dissolved components of colloids and suspensions. As a result of this, the brine formed during gradual concentration is concentrated in the axial zone and freezes last. The concentration zone after complete freezing of the liquid is usually clearly visible to the naked eye: with colored impurities, a dendritic trunk in the form of a “carrot” is visible inside, and with unpainted impurities a milky-white trunk is formed. If the process of ice melting is carried out from the center to the periphery, then brine will flow out in the first portions of the liquid, and then pure ice will melt.

 To confirm the above, the following experiments were carried out. 1.3 l of tap water was poured into a standard plastic vessel with a capacity of 1.5 l and a tubular electric heater was immersed in water so that it was located along the entire height of the axis of the vessel.

 Schematically, the design of the device is shown in figure 1, which shows the power source of the heater 1, a vessel in the form of a bottle 2, an axial heater 3 and a place for a drain hole 4. The tubular electric heater (figure 2) was a quartz tube 1 sealed at one end with an external 8 mm in diameter, into which a tube 2 with a diameter of 4 mm was placed, on the outer surface of which a nichrome spiral 3 was wound as a heater.

 When freezing water, the vessel was motionless in an upright position. Thus, the heater turned out to be frozen in the axial zone of the ice boule. Then, a hole was cut in the center of the bottom of the vessel with a hot metal tube, it was fixed vertically, and a sampling vessel was installed under the hole in the bottom of the vessel. The heater was connected to an alternating voltage variator and, with a dark red heat of the spiral, thawing was performed, sequentially taking 50-70 ml portions of liquid. As a measure of the total salt content of portions of water, specific electrical conductivity was used. The dependence of the conductivity of melt water on the volume of the melted liquid is presented in figure 3. Figure 3 shows that when freezing the first portions of a liquid with a volume of 200-250 ml, the contaminated part of the ice is removed, the remaining ice is melted in any mode and 1150-200 ml of purified water is obtained. Thus, the yield of purified water is 82-86% of its originally taken volume. So, when freezing and thawing 1.4 L of tap water with a specific electrical conductivity of 297 μS / cm, 1200 ml of water with a specific electrical conductivity of 180 μS / cm was obtained. In this example, the degree of purification was 39.6%. It takes 20-25 minutes to melt the brine from a vessel with a capacity of 1.5 l, the melting rate of the remaining purified ice will depend on the melting temperature. It takes about 1.5 hours to completely melt ice from a vessel of the same capacity with the heater constantly on. We repeated the experiments several times and the above results were clearly reproduced.

The same patterns are observed during freezing and melting of salt solutions. Figures 4-7 show the axial melting curves of ice for KNO ₃ solutions with an initial specific conductivity of 1.13 mS / cm (Fig. 4), MgSO ₄ with an initial specific conductivity of 3.2 mS / cm (Fig. 5), BaCl ₂ with an initial specific conductivity of 1.8 mS / cm (FIG. 6) and FeCl ₃ with an initial specific conductivity of 133 μS / cm (FIG. 7). As can be seen from FIG. 4-7, all the curves are of the same type and are similar to the curve for tap water (figure 3). Thus, for salt solutions, after axial melting of 200-250 ml of liquid (with an initial frozen volume of 1300 ml), 1150-1200 ml of partially desalted solution are obtained.

 The proposed method can equally well be used for concentration of salt solutions, since axial melting of ice produces a concentrate and desalted liquid. To increase the degree of desalination or concentration, the process is repeated using a correspondingly partially desalted phase or concentrate.

 The above-described regularities of the distribution of salts during axial melting of ice are observed when the freezing of the liquid in the vessel goes from the periphery to the center. To ensure this, it is necessary that the ratio of the height of the vessel to its diameter be at least 2.2

Claims (2)

 1. The method of desalination of water or salt solutions by freezing and subsequent thawing, characterized in that before the freezing process, an axial heater is placed in the vessel, after which the water or salt solution is completely frozen, then a hole is made in the bottom of the vessel and the axial heater is not melted more than 15% of ice, receiving a concentrate, and the remaining ice is melted in a random mode, receiving purified water.  2. The method of desalination of water or salt solutions by freezing and subsequent thawing according to claim 1 is characterized in that the process is carried out mainly in a vessel with a ratio of the height of the vessel to the diameter of the cross section of ≥2.

Images