SU1196100A1 - Method and installation for preparing slurries - Google Patents

Description

The invention relates to foundry, and in particular to methods of preparing a suspension or binder and to mixing equipment, in particular to installations for the preparation of a binder, or suspension in the preparation of ceramic molds for investment casting and permanent models.

The purpose of the invention is to increase productivity and improve sanitary and hygienic working conditions, improving the quality of the ceramic slurry, reducing the consumption of components, slurry.

Cryo is prepared in a hermetic tank of the hydrolyzer. The mixing of the liquid and solid materials of the suspension is made by gas, while the sparging gas is mixed through the gas pipes ’with the help of a blower in a closed cycle.

The positive effect of the use of a closed cycle of the bubbling gas movement is as follows: the atmosphere of the workshop is not poisoned by harmful evaporations, there is no loss of the suspension components, as a result of which up to 20% of the liquid suspension components are saved, the composition of the ceramic suspension remains constant, because no evaporation of flammable substances.

Liquid slurry materials are fed into the sealed tank of the hydrolyzer through pipes, and solid materials are loaded into the gas stream supplied to the bubbling stirrer.

The loading of solid refractory components together with the bubbling gas has a number of advantages: fire resistant components are metered into different zones of the volume of the prepared suspension, thus achieving uniform distribution, completely eliminating dust from the surrounding atmosphere. At the same time, high accuracy and reliability of dosing is achieved, the process is easily automated.

Increasing the pressure during the hydrolytic polycondensation of ethyl silicate improves the solubility of the sparging gas in the binder solution, as a result of which the oxidation of the ethoxylic groups of ethyl silicate is accelerated and the time for the formation of silicon is shortened.

The xanic bond, and hence, in general, the duration of the preparation of the binder, in addition, decreases the evaporation of the volatile components of the suspension. The use of pulsating pressure helps to eliminate the settling of the refractory components and their more uniform distribution throughout the entire volume of the suspension, which

U significantly improves the quality of the prepared suspension.

The hydrolysis reaction proceeds with the evolution of heat and is accompanied by an increase in the temperature of the solution. The temperature of the solution is governed by the intensity of the cooling gas before it is supplied to the bubbling stirrer.

Cooling the bubbling gas to 0–20 ° C allows one to regulate the kinetics of the process of structure formation of the binder, to achieve the likely formation of a linear structure of polymer molecules, and, consequently, the maximum binding capacity of the hydrolyzed ethyl silicate solution.

Cold gas bubbles, rising upwards and contacting the withdrawn slurry reaction heat gidrolitiches Coy polikondonsatsii ₃₀ and carry it with them, giving it cooler and clear wa cooled gas is bubbled slurry. Solvent and ethyl silicate vapor condenses into smallest droplets and air while cooling the gas.

rotate with the gas in suspension. Consequently, the cooling of the bubbling gas allows one to control the kinetics of the hydrolytic polycondensation of ethyl silicate, to increase the binding capacity of the hydrolyzed ethyl silicate solution and to save the solvent and ethyl silicate.

For the operations of loading solid materials into the gas stream and cooling the gas, there are two parallel gas streams, of which water is cooled by the gas, and solid materials are charged in the other stream.

FIG. 1 shows an installation for the hydrolysis of ethyl silicate; in fig. 2 A general scheme of the installation for the preparation of a ceramic suspension with an amyclic circulating cycle of supplying bubbling gas.

The installation consists of a tank of 1 hydrolyser, a cover 2 with a gas outlet 3 '1196100

leading tubes_ 3. In tube 2, tubes 4 are inserted for supplying liquid materials for the suspension. To the cover 2 is attached at least one tapered circulation nozzle 5,, 5

tapering upwards. In the bottom. A curved shaped container is installed (a set of gas supplying tubes 6. In the center of the bottom of the tank 1 there is a pipe 7 to drain the finished suspension, in the side wall of the vessel there is a water glass 8. A pressure bypass valve 9 is installed in the gas outlet pipe 3.

The main functional purpose of the circulation nozzle 5 is to create an upward gas flow inside it, entraining the suspension volumes. Circulating pipe 5 is vertical but 20 is located in capacitance 1 such. the way that the upper end of the nozzle is below the level of the suspension, and the lower does not reach the bottom of the tank. The conical tapering upward shape 25 of the hollow circulation nozzle allows for a greater effect of seizing the suspension with gas bubbles, which further increases the intensity of mixing. Through the tubes of the building 4, the liquid components of the suspension are dispensed to the surface of the suspension and the binder or inside their volume into the downward flow of liquid by adjusting the immersion depth of the tubes. The dosage is made from a special measuring container or through rotameters.

Gas supply tubes 6 are designed for forcing gas into the tank

_ „40

hydrolyzer to create a bubbling mixing., The tubes are located under the end of the circulation nozzles so that the outgoing gas rises to the surface necessarily inside the nozzle. The gas contains the components of the suspension: water vapor, solvent, hydrogen chloride, the solid components of the suspension. The bottom of the tank has a curved shape to prevent the suspension from settling in the corners.

Through the drain pipe 7 is draining the finished suspension without any preliminary preparation of the tank. Gas outlet pipe 3 55

removes the bubbling gases saturated with the solvent vapor passing through the suspension volume. The gas exhaust pipe 3 is mounted a pressure relief valve 9, depending on the setting in which it is supported ^ζ bone hydrolyser and pressure regulated. Through gauge glass 8 is the visual observation of the amount of suspension in the tank.

The setup for preparing a ceramic suspension of a closed circulating cycle of supplying bubbling gas (Fig. 1) contains a tank 1 of a hydrolyzer, a gas outlet pipe 3 with a pressure relief valve 9, gas supply pipes 8, a drain pipe 7, a supercharger 10, a cooler 11, a tap-tee 12, in-person mixing device 13 for dispensing solid materials of a suspension consisting of a housing 14, a collecting funnel 15, a loading tray 16, a hermetically closing gate 17, a metal mesh with felt pad 18, a crane 19. The cooler 11 consists of a housing through which the refrigerant is pumped. Inside the case there are turns of spirally closed gas supply tubes,

The installation devices are interconnected by gas-conducting pipes.

The installation works as follows.

In the container · 1, hermetically sealed with a lid 2, liquid materials of the suspension are supplied through the pipes 4. When the container is filled above the upper end of the circulation nozzle 5, which is controlled through the water-metering glass 8, gas starts to flow through the gas supplying pipe 6. The gas rises inside the nozzle 5, carries away a liquid or suspension, with the result that the process of circulation mixing begins in the tank (shown in Fig. 1 with arrows). Solid materials are introduced into the tank along with the gas flow through the tubes 6. The sparging gas, passing through a volume of liquid, is saturated with solvent vapor and discharged through the gas outlet pipe 3. The pressure bypass valve 9 maintains the pressure in the tank within 1-2 MPa. At elevated pressure, physicochemical preparation of the binder proceeds faster.

At the end of the preparation of the suspension or binder, the gas supply is stopped and the finished product is discharged.

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through the outlet 7. If necessary, a quick release of the tank overlap the gas exhaust pipe 3 and the drain is made without stopping the gas supply. The gas is supplied to the tank 1 from the blower 10. At the first position (not shown) of the crane-tee 12, all gas passes through the cooling element 11 and then through the gas-supplying tubes 6 bubbled suspension in the tank 1, inside which a pressure of 1-2 atm is created, adjustable valve 9. Gas saturated with solvent vapors through the gas outlet pipe 3 and pressure valve 9 are again fed to the inlet of the supercharger 10. Thus, there is a constant circulating circulation of gases inside the system in a closed loop.

Due to the exothermicity of the hydrolytic polycondensation of ethyl silicate, the gases passing through the slurry get very hot, taking heat from the slurry. For carrying out the reaction in the desired direction, the bubbling gas is pre-cooled in the cooler 11.

If it is necessary to load solid materials into the tank of hydrolyzer 1, the valve 19 is opened, at which 25 50Х all gases are supplied through the device 13 to receive and dispense a fluidized suspension of refractory components. The gas, passing through the metal grid with felt pad 18, causes the solid components to fluidize. · Then quartz or other suspension through the collecting funnel 15 and the gas supply tubes 6 enters the container 1. The gases pass through the suspension, and the solid components remain in it volume, evenly distributed. The dosage of solid components in the device 13 is carried out from the loading tray 16 by opening the sealed gate 17. The dosage is performed when gas is not supplied to the device 13. After the end of the dosage of solid components in the device 13 sealed gate 17 closes. The release of the finished suspension through the drain pipe about to 7.

The composition of the suspension according to the proposed and known methods is the same, wt.%: Ethyl silicate brand 40 8.4;

100 6 • Acetone grade A 16.54; acidified water 0.06; quartz dust-like PK-2 | 75. The temperature of the purged gas is 15 C, the volume of the mixture is 15 liters.

Example 1. According to a known method, the solvent and acidified water are poured into the container of the mixer through the loading window in the lid and purged with oxygen-containing gas (compressed air) for 1-2 minutes. Then ethyl silicate is gradually poured into the tank, refractory components are charged, the operating pressure in the gas supply system is established, and the entire volume of the suspension is purged (stirred) with sparging gas until the suspension acquires the initial temperature (16 ° C). At the end of the preparation of the suspension, turn off the gas supply, lift the gas supply tubes and mix and use a special mechanism to turn the container to drain the prepared suspension. After draining the finished product, the container is returned to its original state, cleaned of any residual suspension, and proceed to the preparation of a new batch.

Example 2. Preparation of ceramic suspensions for the proposed method is as follows.

In the tank 1 hydrolyzer, hermetically sealed with a lid 2, through the tubes 4 serves as a well-known method liquid components. When the tank is filled above the upper end of the circulation nozzle 5, which is controlled through the gauge glass 8, from the supercharger 10, through the valve 12, the cooling element 11 and through the gas supply tubes 6 the gas is supplied to the tank for 1-2 minutes. The gas, rising inside the pipe 5, carries the liquid with it, as a result of which intensive circulation mixing takes place in the container. At this time, the valve 19 is fully closed.

Then, from the loading tray 16, using the gate 17, refractory components are metered into the device 13. After the solid components enter the device 13, the gate is hermetically closed and the valve 19 is opened, and the tee crane 12 is turned into the second position, in which <^ 35% of everything gas enters the device 13, Gas passing through

7 11

metal mesh and felt pad 18, causes the solid components in a fluidized state. The quartz suspension through the trapping funnel 15 and the gas supplying tube 6 enters the tank 1, where, due to the presence of circulation nozzles, the suspension is intensively stirred, and using the overflow valve 9 creates an overpressure within the required range of 1-2 atm. When the pressure is exceeded, the bypass valve 9 is activated, the pressure in the tank drops, and then begins to rise again to the specified limit. This continues until the temperature of the suspension reaches the initial temperature (16 ° C). When the valve 9 is triggered in the tank 1, there is a sharp drop in pressure and a surge in the suspension throughout the volume, which helps to eliminate the settling of refractory particles and their more uniform distribution throughout the entire batch volume.

Thus, during the preparation of the suspension according to the proposed method, the bubbling of the suspension, circulating and pulsating mixing takes place in the tank 1, which significantly speeds up the process of preparing the suspension and improves its quality. Gases saturated with vapors of the solvent and ethyl silicate, through the gas outlet pipe 3 again enter the tank of hydrolyzer 1, passing through the blower 10, the cooling element 11 and the gas supply pipes 6. Thus, a constant circulation of gases. At the end of the preparation of suspensions of the finished product is poured through the discharge pipe 7 into the transfer tanks.

In tab. 1 shows the comparative data of the Kinetics of a change in the temperature of a suspension in the process of its mixing depending on the pressure (an overpressure of 0 MPa corresponds to a known method).

From tab. 1 it follows that the optimal pressure in the tank of the hydrolyser when preparing the suspension is 1-2.0 MPa. When the pressure is lowered to 0.5 atm, the rate of hydrolytic polycondensation reaction noticeably decreases and differs little from the known method. With increasing pressure over 2.0 atm speed

100 th

the reaction practically does not change, and the creation of a large pressure requires the use of a powerful supercharger. In addition, the preparation time of the ceramic suspension using the proposed method is 22.5-25.0 minutes, versus 35 minutes according to the known, i.e. reduced by 1.4 - 1.5 times.

The more rapid course of physical and mechanical processes, in particular the hydrolytic polycondensation of ethyl silicate, according to the proposed method is due to the fact that increasing the pressure in the tank of the hydrolyzer improves the solubility of the sparging gas in the suspension. As a result, the oxidation of the ethoxyl groups of ethyl silicate is accelerated and the formation time of the silixane bond is shortened, which, along with circulation and pulsating mixing, is significantly reduced. reduces the duration of the preparation of the suspension and improves its quality.

Improving the quality of the prepared suspension leads to an increase in the mechanical characteristics of the samples.

In tab. 2 shows the bending strength of ceramic samples.

The strength of ceramic shells under static bending is determined by the standard method. The test is carried out after calcining at 900 ° C for 1 h of samples cooled to room temperature. The temperature of the purged gas is 15 ° C.

From tab. 2 it follows that the proposed method provides an increase in the strength of the ceramic shells in comparison with the known. The optimum pressure of the bubbling gas inside the tank is 1-2 MPa. The increase in pressure above 2.0 MPa is impractical, since the strength of the shells varies slightly. Reducing the pressure to 0-0.5 ati leads to a sharp decrease in strength.

The permeability of the samples according to the known and proposed methods practically does not change and is 5-7 conventional units.

In tab. 3 shows the strength of the shells obtained by stirring the suspension with a sparge gas cooled to different temperatures. Dav1196100

inside the tank is 1.5 ati, gas consumption is 0.25 m ³ / h per 15 l of suspension.

From tab. 3, it can be seen that the temperature of the bubbling gas, at which the strength of the shells is maintained at dos-5 at a sufficiently high level, is 0-20 ° C. In this temperature range, the strength of the shells of the proposed method is on average 1.3 times greater than the known.

Along with improving the quality of the prepared suspension, the use of a bubbling gas in a closed cycle completely eliminates the loss of solvent, ethyl silicate and 15 pulverized components of the suspension, as a result of which sanitary and hygienic working conditions are improved. it is. yield of the product. According to a known method, the loss of liquid and dustlike components is 1020% of the mixing capacity. The concentration in the working area of the installation for gases and vapors of the solvent and ethyl silicate is 1500 mg / m ^{3 of} air, and dusty-25 silica fractions when loading refractory components - 4-5 mg / m ³ (MPC is 1 mg / m ³ ).

The advantage of the proposed installation is that it does not disappear.

Turning capacity to drain the finished product and clean it from. residual suspension.

The economic effect of the present invention is to eliminate the loss of liquid and pulverized ingredients of the binder or suspension.

So, when preparing a suspension in a known manner, the losses amount to 10-20% of the mixing capacity. They are formed by evaporation of the solvent and ethyl silicate during the preparation of the slurry, the release of the refractory components into the atmosphere of the shop when they are loaded into the mixing tank, as well as the removal of the refractory filler remaining under the separator after the slurry has been drained.

. According to the proposed method, due to circulating use in a closed cycle of bubbling gas and eliminating the irretrievable losses of the refractory components, losses of liquid and pulverized ingredients are completely eliminated. At a cost of 1 ton of ceramic suspension 220 rubles, the economic effect is an average of 33 rubles. per 1 ton of cooked product.

Table 1

Purge time, min The temperature of the suspension, ° C, at a pressure of ATI 0 0.5 | 1.0 2.0 I ² · ⁵ 0 sixteen sixteen sixteen sixteen sixteen 2.5 sixteen 18 nineteen 20 21 5.0 sixteen 20 23 27 28 7.5 17 23 thirty 35 ³⁶ 10.0 18 25 ' 33 33 34 12.5. 18 27 31 thirty 32 15.0 nineteen 29 28 28 27 17.5. 20 thirty 24 23 21 20.0 21 28 20 nineteen sixteen 22.5 23 25 18 sixteen - 25.0 25 23 sixteen - - 27.5 25 ' nineteen - - - 20.0 23 17 - - 32.5 20 sixteen - - 35.0 sixteen - - -

eleven

1196100

table 2

———— Way cooking Strength on bending, kg / cm ² , with pressure in the vessel, pressure 0 Ί 0.5: | 1.0 | 2.0 | 2.5 Proposed 78.5 82.0 113.0 133.5 135.5 Famous 65.5 - - - Spreadsheets a 3 Way Flexural strength, kg / cm ² , at the temperature of the purged gas, ⁱⁿ C -five 0 10 | 15 | 20 | 25 Famous 51.5 69.0 78.5 90.1 95.4 97.0 62.5 Proposed 65.5 '97, 5. 105.0 115.0 130.5 127.0 70.7

φυ * .1

1 196100

Claims (2)

1. The method of preparation of the suspension used in the preparation of ceramic molds in investment casting, including the loading of solid and liquid materials in the tank ator hydrolysis, mixing materials using gas, the subsequent unloading of the finished suspension, characterized in that, in order to increase productivity, efficiency of the process and quality of the suspension, as well as improve sanitary and hygienic working conditions, before loading the liquid and solid materials, the capacity of the hydrolyzer is sealed, mixing is carried out under pulsating gas pressure from 1 to 2 atm, which they are forcibly transferred from the upper part of the hydrolyser to its lower part by two streams, in one of which the temperature of the gas is lowered to 0–20 ° C, and the other stream is loaded with solid materials and sent to the lower part of the hydrolyzer. 2. Installation for the preparation of suspensions used in the preparation of ceramic molds on investment casting, containing a tank of hydrolyser, a bubble stirrer and a gas supply system with gas supply tubes, characterized in that, in order to improve the performance, cost effectiveness of the process and the quality of the suspension, also improve sanitary and hygienic working conditions, it is equipped with a gas pump, a cooler and a loading and mixing device, interconnected by gas pipes, while the cooler and loading and mixing device for gas pipes are arranged parallel to each other between the supercharger and the capacitance hydrolyser and bubble agitator is mounted in the container hydrolyser vertically and is made in the form of several circulating pipes, each of which has the shape of a truncated cone, the ends of which are summed gas supplying tube. 8i, 1196100 1196100 one