SU1735919A1 - Method and apparatus for producing ferromagnetic fluid - Google Patents

Abstract

The invention concerns a method for producing a ferromagnetic fluid and an installation for its implementation. The goal is to accelerate and stabilize the process of obtaining a ferromagnetic fluid. A 25% aqueous solution of ammonia with a volume of 7.5 liters and a 20% solution of sulfate and ferric chloride with a volume of 3 liters and 5.5 liters, respectively, are successively poured into an airtight container — an autoclave. Saturated steam is supplied under a pressure of 1.5 MPa with a temperature of 110 ° C. The mixture is stirred for 1 minute and warmed to 90 ° C. An electromagnet located under the tank is switched on for 1 min. After settling, under the influence of a magnetic field, the water separated from the magnet is drained. The steam, etc., is fed in again, the process is repeated three times. After rinsing and draining the void water, steam is supplied to the autoclave until the temperature rises to 80 ° C and the pressure is set to 0.12-0.15 MPa. The pressure is released and a thin stream of oleic acid (0.2 l) preheated to 30-40 ° C is fed into the autoclave for 0.2 min. The container is sealed and the contents are saturated with steam to the mode: 80 ° C and 0.12-0.15 MPa. An intensive process of peptization occurs - the formation of a layer of surfactant molecules on the surface of particles. Then a mixture of magnetite coated with a surfactant layer is dehydrated in a centrifuge. After sedimentation of magnetite paste on the walls, 0.1 kg of acetone is poured into it. It is necessary to equalize the concentration of water residues across the thickness of the formed layer of magnetite paste. After evaporation of the acetone from the surface of the paste, dispersing the paste in mineral oil is performed. The total time for obtaining a magnetic fluid is 25 minutes . The resulting magnetic fluid has a magnetization of 25 kA / m. The viscosity is kinematic at 50 ° C 40 -10 6 m2 / s, the density at 90 ° C 870 kg / m 2 s. and 1 з п ф-лы, 2 илл С-д, 00 01 ю ю

Description

This invention relates to a process for the production of ferromagnetic fluids used as magnetic liquid shaft seals, as well as for the purification of water from petroleum products.

A known method for producing ferrofluid by precipitating highly dispersed

magnetite from aqueous solutions of ferrous and ferric salts with an excess of alkali, washing the resulting precipitate with distilled water, a weak solution of hydrochloric acid, a polar solvent (for example, alcohol, acetone) and final washing with a non-polar solvent (for example, toluene), with further peptide - with oleic acid at 90-110 ° С with the addition of the necessary amount of non-polar solvent.

The disadvantage of this method is the complexity of the technological process due to its multi-stage nature, the use of large quantities of organic solvents (acetone, toluene, ethyl alcohol), which are fire hazardous and harmful to health.

Methods are known for producing ferrofluids by precipitating magnetite with an ammonia solution, followed by washing the precipitate, with water and peptizing in a solution of oleic acid in an organic solvent.

The closest in technical essence to the present invention is a method of obtaining a ferromagnetic fluid in a sealed container, including the precipitation of magnetite from a solution of ferrous and ferric iron salts with an aqueous solution of ammonia, washing with distilled water and peptization in a solution of oleic acid while stirring and heating the magnetite precipitate followed by centrifugation in a carrier fluid to the desired concentration.

A known apparatus for producing a ferromagnetic fluid contains a hermetic container of a given volume, means for heating and stirring the solution in the tank, and a device for dewatering.

The disadvantage of this method is the long duration of the ferromagnetic fluid production process due to the low deposition rate of magnetite from a solution of ferrous and ferric salts, as well as the instability of the process.

The purpose of the invention is to accelerate and stabilize the process of obtaining a ferromagnetic fluid.

The goal is achieved by the fact that in a known method of producing ferromagnetic liquid, which includes the process of precipitation of magnetite from a solution of ferrous and ferric iron salts with an excess of an aqueous solution of ammonia, peptization of the resulting precipitate in an oleic acid solution with simultaneous stirring and heating followed by centrifugation and dispersion in liquid carrier to the desired concentration, the deposition and peptization processes are carried out when the solution is exposed to saturated steam, while the process of precipitation nor are under the influence of a magnetic field.

The effect of saturated steam on a solution of ferrous and ferric salts and an aqueous solution of ammonia provides not only heating of the mixture, but also its mixing due to the kinetic energy of the supplied steam. Due to the heating of the mixture with its simultaneous stirring, the intermolecular bonds between the magnetite particles and other chemical components are weakened, which makes it possible to significantly accelerate the process of precipitation of magnetite from the solution when exposed to a magnetic field solution.

It is during the heating and stirring of the mixture by affecting the solution with saturated steam that the maximum effect of increasing the magnetite deposition rate is achieved by ensuring uniform heating of the mixture throughout the volume. At the same time, due to the presence of a large number of free magnetite particles throughout the volume of the mixture, the intensity of its precipitation under the influence of a magnetic field will increase sharply. In addition, due to the effect of saturated steam on the solution, the sticking of magnetite on the walls of the hermetic vessel is eliminated due to the formation of steam jacket on these walls.

PRI me R. A 25% aqueous solution of ammonia with a volume of 7.5 liters and a 20% solution of sulfate and ferric chloride with a volume of 3 and 5.5 liters, respectively, are successively poured into a sealed autoclave vessel. Saturated steam is supplied under a pressure of 1.5 MPa and with a temperature of 110 ° C. The mixture is stirred for 1 minute and heated to 90 ° C. Turn on the electromagnet for 1 min. After settling on the electromagnet, the water separated from the magnetite is drained. The steam is re-injected, etc. The process continues three times.

Upon completion of the washing and the last discharge of the water separation, steam is supplied to the autoclave until the temperature rises to 80 ° C and the pressure is set to 0.12-0.15 MPa. After that, the pressure is released and an oleic acid (0.2 l) preheated to 30–40 ° C is fed into the autoclave in a thin stream for 0.5 min. The vessel is sealed and the contents are adjusted with saturated steam to a mode of 80 ° C and 0.12-0.15 MPa. An intensive process of peptization occurs - a layer of surfactant molecules forms on the surface of particles. Then a mixture of magnetite coated with a surfactant layer is dehydrated in a centrifuge. After deposition on the walls of the magnetite paste, 0.1 kg of acetone is poured into it.

Such an operation is necessary to equalize the concentration of residual water throughout the thickness of the formed layer of magnetite paste. After evaporation of the acetone from the surface of the paste, the operation is carried out to disperse the paste in mineral oil. The total production time for the magnetite liquid is 25 minutes (in a known method, it is 30 minutes without a dispersing operation). The resulting magnetic fluid has a magnetization of 25 kA / m. The kinematic viscosity at 50 ° С is 40–10 m / s, the density at 90 ° С is 870 kg / m3.

Closest to the proposed installation by its technical nature is a hermetic apparatus that implements a method for producing a ferromagnetic fluid, which includes a sealed container of a given volume, means for heating and mixing the mixture, and a centrifuge.

A disadvantage of the known installation is the long duration of the ferromagnetic fluid production process and the process instability.

This goal is achieved by the fact that in a known installation for producing ferromagnetic fluid, which includes a sealed container of a given volume and a centrifuge, the hermetic container is additionally equipped with a device for supplying steam and an electromagnet mounted under the container. In addition, the centrifuge drum of the apparatus for producing ferromagnetic fluid is provided with a shoulder.

A sealed vessel fitted with a steam supply device acts as an autoclave. The presence of a magnet at the bottom under the container provides intensive precipitation from the magnetite solution. Sealed connection through the pipeline of the described containers allows the process to be carried out in a single, continuous cycle, which ensures the stability of the method and the acceleration of the process due to intensive mixing and precipitation.

In the proposed installation, the dewatering device is a centrifuge, the drum of which is made with a shoulder, selected depending on the mass of the ferrofluid obtained. Dehydration occurs as follows: under the influence of centrifugal forces, magnetite having the greatest density is pressed against the walls, water is displaced layer by layer and the volume calculated for its mass is filled.

The width of the collar is selected from the condition:

b

D-YD2-K

4M

where K is a coefficient equal to. . ,

ppl

D is the inner diameter of the centrifuge, mm;

m is the mass of the resulting liquid, kg;

o is the density of the magnetic fluid, kg / mg;

H is the height of the drum, m, with the centrifuge and the container being tightly connected to each other by a pipeline.

Thus, due to the presence of the bead, a magnetite layer with a uniform content of aqueous impurities is obtained which is uniform in thickness.

Fig. 1 is a schematic diagram of the installation; Fig. 2 is a schematic diagram of a centrifuge.

The plant for producing ferromagnetic fluid includes a sealed tank — reactor 1, equipped with a steam supply device 2, control devices 3, safety devices 4, drain hose 5 and electromagnet 6. Reactor 1 is tightly connected by pipeline 7 with centrifuge 8 equipped with drain hose 9. The drum 10 of the centrifuge is equipped with a collar 11.

The installation works as follows.

The production of magnetic fluid begins with the preparation of basic chemical components, which consists in bringing the iron salts to the desired concentration. To do this, hexafluoric ferric chloride-6H20 and ferric sulphate iron Resz 7N20 are loaded into a separate tank, mixed in the required amount with water and thoroughly mixed using a high-performance gear pump.

The masses of the initial components are taken from the calculation of a given reactor capacity, since an increase in the mass of the initial components leads to a loss of magnetite, and a decrease to a deterioration in properties due to poor distillation of water.

After the required amount of aqueous 25% ammonia is poured into reactor 1, iron salts are pumped (not shown) into reactor 1, where with steam at 110 ° C and pressure up to 0.15 MPa, they enter into a chemical reaction with the deposition of magnetite FeO-Re20z.

In order to accelerate the deposition process, an electromagnet 6 is used, which is an electric coil with a diameter of 1600 mm, wound from a copper strip, which is supplied with a direct current of 220 V. The magnet turns on for 12-15 minutes. After that, a column of water separated from above with the by-products dissolved in it is drained through a hose 5 into the sewer. The next step is washing the magnetite, which should be carried out at least three times.

The washing process is similar to the previous one: stirring magnetite with water, settling on an electromagnet, draining. After washing, the magnetite is heated with steam while stirring. Thus, the temperature in the autoclave rises to 85-90 ° C. Temperature control is carried out by electrocontact and mercury thermometers. After heating, the most responsible phase occurs - the magnetite penetration. It is carried out as follows: a mixture of oleic acid and mineral oil is added in a thin stream to the heated magnetite, steam is forcedly fed to the reactor to the specified pressure and after holding (1.5-2 min) the drain valve is opened, through which the mixture is discharged through line 7 in a centrifuge 8 with a separation factor of 8000 units, where water and water impurities are separated from magnetite coated with a surfactant layer.

After the magnetite, coated with a surfactant layer, is thus deposited, the drum stops and acetone in an amount of 10: 1 is applied to it in relation to the weight of the paste obtained. The centrifuge is restarted and, after complete evaporation of the acetone from the surface of the paste, it stops: this operation is necessary to equalize the concentration of residual water throughout the thickness of the formed layer of magnetite paste. The next step is to disperse the paste in mineral oil.

The mineral is poured into the drum a little and from a special frequency-controlled drive turns on

centrifuge. The rotation frequency is set depending on the amount of mineral oil embedded in the drum. Paste dispersion lasts 4 hours. Next

quality control of the magnetic fluid and transportation to storage is performed. The process of liquid production is discrete with a capacity of 1 l per hour. The application of the proposed method and

Production plant allows to obtain large quantities of magnetic fluid in a short time, reducing the duration and instability of the process, improving working conditions, and hence safety.

Claims (3)

Claim 1. Method for producing ferromagnetic fluid, comprising precipitating magnetite from a solution of divalent and trivalent iron salts with excess aqueous ammonia solution, peptizing the resulting precipitate in oleic acid solution while stirring and heating, followed by centrifuging and dispersing in a carrier fluid to the required concentration, characterized by the fact that, in order to accelerate and stabilize the process of obtaining ferromagnetic Liquids, sedimentation and peptization are performed when the solution is exposed to saturated steam, while the precipitation process is carried out under the influence of a magnetic field. 2. An apparatus for producing ferromagnetic fluid, containing a sealed container of a given volume and a centrifuge, characterized in that, in order to accelerate and stabilize the process of obtaining ferromagnetic fluid, it is equipped with a device for supplying steam into the container and an electromagnet installed under the container. 3. Installation according to claim 2, characterized in that the centrifuge drum is made with shoulder. Loyboy  R-1,2mPa 3 1