RU2492251C2 - Method of heating reaction mix in production of metal salts and device to this end - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises heating the reaction mix in assembly consisting of two units composed of heaters and bubblers. Every of said unit is heated in turns to boil the solution and to direct live steam to bubbler of another unit. Proposed device represents the assembly consisting of two units composed of heaters and bubblers and integrated in a system by steam-gas pipelines. Note here that one pipeline is connected with bubblers while another one is connected with atmosphere. Shutoff valves and auxiliaries are fitted between units and pipelines. Proposed device may comprise shutoff valves automatic changer-over devices and their control unit.

EFFECT: maximum application of live steam heat, optimised thermal and hydrodynamic conditions, lower costs.

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Description

The invention relates to a method for heating the working mass in the process of producing metal compounds, as well as to a device for its implementation.

The preparation of metal compounds (salts, acids, basic salts) is usually carried out by chemical dissolution (etching) of metals in solutions of acids or salts. Chemical etching of metals in acids is carried out, for example:

- obtaining copper sulfate from copper and sulfuric acid;

- obtaining silver nitrate from silver and nitric acid;

- obtaining platinum chloride acid by dissolving platinum in aqua regia;

Basic salts in some cases are obtained by the interaction of metals with salt solutions. So, the production of aluminum oxychloride is carried out by the interaction of aluminum metal with a solution of aluminum chloride.

All these processes are characterized by a long duration (from several hours to several days), are accompanied by the release of gases and, as a rule, require heating to the maximum possible temperature in autoclave-free conditions - the boiling point of the solution. The economic and technological efficiency of the processes for producing metal compounds is largely determined by the method of heating the working mass.

As direct heat sources for heating solutions in processes and apparatuses of chemical technology, flue gases or electric energy are used. The most common heating by electrical resistance / Kasatkin A.G. The main processes and apparatuses of chemical technology M .: Alliance, 2009 ,, p.322 /. The disadvantage of using electric current for heating is the relative high cost of electricity.

To transfer heat to a heated medium, intermediate coolants are widely used - water vapor, hot water, high-temperature coolants (mineral oils, organic liquids, molten salts, etc.). The most widely used heating agent is water vapor. Heating with deaf steam, which transfers heat through the wall of a heat exchanger, is widespread / Kasatkin A.G. Basic processes and apparatuses of chemical technology M .: Alliance, 2009, p. 311 /. The disadvantage is the unproductive flow of steam associated with the departure of part of the steam with condensate (the so-called overflow steam).

A known method of heating solutions with hot steam, which is injected directly into a heated liquid / Kasatkin A.G. The main processes and apparatuses of chemical technology M .: Alliance, 2009, p.313 /. The input of sharp steam is carried out through bubblers - pipes located at the bottom of the apparatus. This method of heating allows you to better use the heat of steam, as the steam condensate is mixed with the heated liquid and their temperatures are equalized. The disadvantage is the dilution of the heated medium with steam condensate.

The closest analogue is a method of heating the reaction mixture in the process of obtaining metals by dissolving metals at a boiling point with the formation of sharp steam. (F. Khabashi, Fundamentals of Applied Metallurgy, vol. 2, M., Metallurgy, 1975, pp. 23-43). It is not possible to regulate the heating process, high energy consumption and loss of solution.

The objective of the invention is to develop a method of heating the working mass, ensuring maximum use of heat of hot steam without diluting the heated medium, and a device for its implementation.

The problem is solved by the proposed method of heating the reaction mixture in the process of obtaining metal compounds by dissolving metals to a boiling point with the formation of sharp steam, the difference of which is that the heating during dissolution is carried out in a system of two devices equipped with heaters and bubblers, each of two devices alternately heated with heaters to heat the reaction mixture, bring the solution to kiperium and the resulting sharp steam is sent to the bubbler of another apparatus that with the termination in it of heating the reaction mixture with a heater.

The exhaust steam is discharged from a device heated by hot steam.

Switching is periodically performed: in odd cycles, the first apparatus is heated by a heater, and the second by sharp steam coming from the first apparatus; in even cycles, on the contrary, the second apparatus is heated by a heater, and the first by hot steam.

Switching is carried out at predetermined intervals, either upon reaching a predetermined solution level in one of the apparatuses, or upon reaching a predetermined solution temperature. It is preferable to switch in automatic mode using a time relay or automatic controllers of the level or temperature of solutions.

A device is also proposed for heating the reaction mixture in the process of producing metal salts, including a device with a heater, the difference of which is that it contains two devices equipped with heaters and bubblers, while the devices are connected to the system by pipelines for hot steam and exhaust steam, moreover the pipeline for sharp steam is connected to the bubblers, the pipeline for exhaust steam is connected to the atmosphere, and shutoff valves are installed between the apparatus and pipelines to control the steam release.

Preferably, the device may comprise elements for automatically switching shutoff valves, as well as a control unit for automatically switching shutoff valves.

Any known method of heating apparatuses can be used - electric current, dead steam, etc.

Figure 1 presents a diagram of the operation of the device.

The device contains two apparatuses 1 and 2, equipped with heaters 3 and 4 and bubblers 5 and 6. The sharp steam pipe 7 with the valves 10 and 11 installed on it is connected to the bubblers, the exhaust steam pipe 8 with the valves 9 and 12 installed on it with the atmosphere .

The device operates as follows.

With closed valves 9 and 11 and open valves 10 and 12, heater 3 is turned on (heater 4 is turned off). Heat the solution in apparatus 1 to the boiling point. The sharp steam generated in the apparatus 1 through the pipeline 7 enters the bubbler 6 to heat the apparatus 2. The spent steam-gas mixture is discharged from the apparatus 2 through the pipeline 8.

Then make a switch. Turn off the heater 3, turn on the heater 4, open the valves 9 and 11, close the valves 10 and 12, heat the solution in the apparatus 2 to the boiling point. The sharp steam generated in the apparatus 2 through the pipeline 7 enters the bubbler 5 to heat the apparatus 1. The spent steam-gas mixture is discharged from the apparatus 1 through the pipeline 8.

This process is periodically (cyclically) repeated. In odd cycles, the sharp steam from the apparatus 1 enters the apparatus 2, in the even cycles the sharp steam from the apparatus 2 enters the apparatus 1. The vapor evaporates and condenses mainly inside the system from two apparatuses, moving from the apparatus to the apparatus and vice versa. The total amount of water circulating in the device remains almost unchanged. If necessary, steam produced in a small amount can be condensed and water can be returned to the apparatus.

Figure 2 shows a variant using steam heaters (heating with dead steam through the jacket of the apparatus), which provides for automatic control by transmitting signals from the level sensors of the reaction mixture to the valve control unit (signal lines from the control unit to the valve actuators are not indicated).

The list of positions in figure 2

1, 2 - devices,

3, 4 - bubblers,

5 - control unit

LI-1, LI-1 - level sensors,

XV-1 ... XV-10 - valves.

Control algorithm: when the level of the reaction mixture in apparatus 1 decreases to the limit value, the signal from the LI-1 sensor enters the control unit, from where the signal is transmitted to the valve actuators: valves XV-1, XV-5, XV-9, XV-4, XV-8 - close, XV-3, XV-7, XV-2, XV-6, XV-10 - open.

Similarly, when the level of the reaction mixture in apparatus 2 decreases to a limit value, a signal from the LI-2 sensor is sent to the control unit, after which a signal is transmitted to the valve actuators: valves XV-1, XV-5, XV-9, XV-4, XV-8 - open, XV-3, XV-7, XV-2, XV-6, XV-10 - close.

The invention is illustrated by the following examples.

Example 1

The implementation of the process of producing silver nitrate from silver metallic and nitric acid in the proposed system for heating the working mass.

Silver etching in nitric acid proceeds according to the reaction:

3Ag + 4HNO ₃ = 3AgNO ₃ + NO ↑ + 2H ₂ O

Silver etching is carried out in a system of two devices with a capacity of 160 liters. The devices are equipped with steam shirts, pressurized covers, bubblers and pipelines for the gas-vapor mixture. One of the pipelines (sharp steam pipeline) is connected to the bubblers, and the second (exhaust steam pipeline) is connected to the atmosphere. Between devices and pipelines installed shutoff valves.

One standard silver metal ingot according to GOST 28595 weighing (30 ± 2) kg is loaded into the apparatus, 25 l of distilled water and 25 l (35 kg) of nitric acid (chemical grade, density 1.4) are poured.

Initially, both apparatuses are heated with dead steam, while the exhaust steam is discharged. After reaching the boiling point, the steam supply to the shirt of the second apparatus is stopped, the sharp steam generated in the first apparatus is sent to the bubbler of the second apparatus and the silver etching process is carried out according to the proposed method.

Periodically (1 time in 30 minutes), the following is switched: in odd cycles, the first apparatus is heated with blank steam, and the second with hot steam coming from the first apparatus; in even cycles, on the contrary, the second apparatus is heated with blank steam, and the first with hot steam. Switching is carried out in automatic mode by means of shutoff valves.

The discharge of the spent steam-gas mixture is carried out from the apparatus heated by hot steam. The gas-vapor mixture for neutralizing the released nitrogen oxides is passed through an absorption column with a urea solution.

After the silver is completely dissolved, the resulting solution is diluted with distilled water and filtered on a vacuum filter. The filtrate was evaporated to a crystalline film and cooled. The precipitated crystals of silver nitrate are suctioned off on a vacuum filter, the mother liquor, together with the washings, is evaporated and crystallized as described above. Both fractions of the crystals are mixed and dried at 110 ° C in ovens. The finished product is packaged for shipment to consumers.

The main technological indicators of the etching process:

- duration - 4 hours

- nitric acid consumption - 35 kg

- loss of silver with ventilation emissions - 0.3 g

- nitrogen oxide emission into the atmosphere - 0.25 kg

Example 2 (comparative)

Implementation of the process of producing silver nitrate from silver metallic and nitric acid with traditional hardware design.

Silver etching is carried out in two bowls with a capacity of 160 l each, equipped with steam shirts, lids and exhaust ventilation.

One standard silver metal ingot according to GOST 28595 weighing (30 ± 2) kg is loaded into each bowl, 50 l of distilled water are poured, steam heating is turned on. Then, nitric acid is poured in - the first portion is 15 l, followed by 5 l (every 1.5 hours). A total of 40 L (56 kg) of nitric acid is charged. The process is conducted until silver is completely dissolved.

The process is conducted with a working local exhaust ventilation, which ensures the removal of nitrogen oxides. Ventilation emissions are passed through an absorption column with a urea solution.

After the silver is dissolved, the solution is filtered, the filtrate is returned to the cups and the product is crystallized and dried, as in Example 1.

Key process performance indicators:

- etching time - 9 h

- nitric acid consumption - 56 kg

- loss of silver with ventilation emissions - 1.5 g.

- emission of nitrogen oxides into the atmosphere - 3 kg.

Example 3

The implementation of the process of obtaining highly basic aluminum oxychloride from metal aluminum and a solution of aluminum chloride in the proposed system for heating the working mass.

The preparation of highly basic aluminum oxychloride from metallic aluminum and aluminum chloride solution is carried out according to the total reaction: 10Al + 2AlCl ₃ + 30H ₂ O = 6Al ₂ (OH) ₅ Cl + 15H ₂ ↑

The process is conducted in a system of two devices with a volume of 6 m ³ . The devices are equipped with steam shirts, bubblers and pipelines for the gas-vapor mixture. One of the pipelines (sharp steam pipeline) is connected to the bubblers, and the second (exhaust steam pipeline) is connected to the atmosphere. Between devices and pipelines installed shutoff valves.

In each technological cycle metal aluminum, aluminum chloride and water are loaded into both apparatuses in predetermined proportions. Aluminum is loaded in the form of standard ingots (ingots) of primary aluminum weighing (15 ± 1.5) kg according to GOST 11070-74.

Each device is loaded:

- metal aluminum - 180 kg (in the first cycle - 1800 kg);

- aluminum chloride solution (aluminum chloride - 82.7 kg; water - 1500 dm ³ ).

The amount of aluminum metal loaded into each device at the start of the technological process (in the first cycle) is 10 times greater than that required by the chemical reaction equation and amounts to 1800 kg. In each subsequent cycle, about 10% of aluminum (180 kg) is consumed, 90% of the metal remains in the apparatus as a carry-over. At the beginning of each cycle, ingots of aluminum metal in an amount corresponding to the mass of metal spent in the previous cycle are loaded into the apparatus. Thus, a constant amount of metal in the apparatus is maintained.

Initially, both apparatuses are heated with dead steam, while the exhaust steam is discharged. After reaching the boiling point, the steam supply to the shirt of the second apparatus is stopped, the sharp steam generated in the first apparatus is sent to the bubbler of the second apparatus and the etching process of aluminum is carried out by the proposed method.

Periodically (1 time in 60 min), the following is switched: in odd cycles, the first apparatus is heated with blank steam, and the second with hot steam coming from the first apparatus; in even cycles, on the contrary, the second apparatus is heated with blank steam, and the first with hot steam. Switching is carried out in automatic mode by means of shutoff valves.

The discharge of the spent steam-gas mixture is carried out from the apparatus heated by hot steam. The spent vapor-gas mixture is sent to the condensate tank through a heat exchanger cooled by circulating water. Steam condenses in the tank, hydrogen is discharged into the atmosphere through local exhaust ventilation. Condensate, as it accumulates, is returned by the pump to the apparatus.

Upon receipt of a product that meets the technical specifications, steam heating of the devices is turned off, after which the solution is pumped from the devices into the intermediate tank, cooled, filtered and pumped to the warehouse for subsequent shipment to consumers.

Metal aluminum and an aqueous solution of aluminum chloride are reloaded into the apparatus, and the next cycle for the production of highly basic aluminum oxychloride begins.

In each cycle, about 1743 kg of a solution of highly basic aluminum oxychloride of the following composition is formed: aluminum oxide (Al ₂ O ₃ ) - 22.8-24.0%, chlorine (Cl) - 7.9-8.4%, density 1.325 ... 1.345 g / cm ³ . Key process performance indicators:

Duration - 40 hours;

Steam consumption per 1 ton of product - 1.0 Gcal;

Recycled water consumption per 1 ton of product - 2.5 m ³ ;

Loss of aluminum with ventilation emissions - 0.2 kg per 1 ton of product.

Example 4 (comparative)

Implementation of the process for the production of highly basic aluminum oxychloride from metallic aluminum and a solution of aluminum chloride with traditional hardware design.

The process is carried out in two devices with a volume of 6 m ³ . The devices are equipped with steam shirts and pipelines to discharge the spent steam into the atmosphere.

In each technological cycle metal aluminum, aluminum chloride and water are loaded into both apparatuses. The number of reagents loaded is the same as in example 3.

Both devices are heated with dead steam, while the spent steam-gas mixture is sent to the condensate tank through a heat exchanger cooled by circulating water. Steam condenses in the tank, hydrogen is discharged into the atmosphere through local exhaust ventilation. Condensate, as it accumulates, is returned by the pump to the apparatus, while periodically replenishing the condensate with tap water.

The process requires systematic monitoring and regulation, since in case of violation of the water balance, the product can crystallize on the surface of aluminum ingots, which will lead to the termination of etching.

Upon receipt of a product that meets the technical specifications, steam heating of the apparatus is turned off, after which the solution is pumped from the apparatus into the intermediate tank, cooled, filtered and pumped to the warehouse. Metal aluminum and an aqueous solution of aluminum chloride are reloaded into the apparatus, and the next cycle for the production of highly basic aluminum oxychloride begins.

The result is about 1743 kg of product, the composition of which is similar to the composition of the product obtained in example 3 by the proposed method.

Key process performance indicators:

Duration - 50 hours;

Steam consumption per 1 ton of product - 2.0 Gcal;

Recycled water consumption per 1 ton of product - 5 m ³ ;

Additional consumption of tap water per 1 ton of product - 1 m ³ .;

Loss of aluminum with ventilation emissions - 0.5 kg per 1 ton of product.

The list of positions in figure 1

1, 2 - devices,

3, 4 - heaters,

5, 6 - bubblers,

7 - pipeline of sharp steam,

8 - exhaust pipe

9, 10, 11, 12 - shutoff valves

The proposed method for implementing such processes has a number of significant advantages. With the alternation of heating modes, the process acquires an oscillatory character, due to which it becomes adjustable.

1) Automatically maintained constant maximum temperature close to the boiling point. In the apparatus, which is currently heated by a heater, it slightly exceeds the boiling point of the solution at atmospheric pressure due to the fact that the pressure in this apparatus is higher than atmospheric by a height of a water column corresponding to the height of the bubbler; the temperature in the second apparatus is approximately equal to the vapor condensation temperature.

2) Energy costs are reduced, since the heat of evaporation of the solution in one device is automatically utilized by using the heat of condensation of steam in another device.

3) The losses of the solution are sharply reduced, since the vapor is not lost, but only passes from the apparatus to the apparatus and vice versa, the total amount of solution in the two apparatuses remains approximately constant. In contrast to the usual variant of heating with hot steam (in which the solution is highly diluted with condensate), as well as in contrast to ordinary boiling (in which the solution is evaporated), the process can be carried out for an arbitrarily long time, which is especially important when carrying out lengthy heterogeneous chemical processes.

4) The loss of the target product with ventilation emissions is minimized, which is very important when we are dealing with expensive raw materials - metals, including precious ones (platinum, gold, silver).

5) In some cases, reagents are used more fully. So, when precious metals (gold, platinum) are dissolved in aqua regia, the process proceeds through the stage of formation of gaseous chlorine, which is more fully “absorbed” in the cascade of two devices, i.e. dissolves more gold or platinum. Accordingly, less toxic gas enters the ventilation.

The hydrodynamic mode of the process improves: in one of the apparatuses, mixing occurs due to bubbles of the generated vapor (and gas released), in the other - by the stream of supplied steam (as well as gas coming from the first apparatus and released in the second apparatus). In this case, the alternation of modes provides optimal hydrodynamics.

Claims (4)

1. The method of heating the reaction mixture in the process of obtaining metal salts by dissolving metals to a boiling point with the formation of sharp steam, characterized in that the heating during dissolution is carried out in a system of two devices equipped with heaters and bubblers, each of the two devices being heated in turn by heaters for heating the reaction mixture, bring the solution to a boil and the resulting sharp steam is sent to the bubbler of another apparatus with the cessation of heating of the reaction mixture in it Lemma. 2. A device for heating the reaction mixture in the process of obtaining metal salts, characterized in that it is made in the form of a system of two devices equipped with heaters and bubblers, while the devices are connected to the system by piping for hot steam and exhaust steam, and the pipeline for sharp steam connected to the bubblers, and the exhaust steam pipeline - to the atmosphere, and between the devices and pipelines installed valves to control the release of steam. 3. The device according to claim 2, characterized in that it contains elements for automatically switching shutoff valves. 4. The device according to claim 2, characterized in that it comprises a control unit for automatically switching shutoff valves.

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