WO2007008115A1 - Method and device for producing hydroxides or aluminium and hydrogen oxides - Google Patents

Abstract

The invention relates to a method and device for producing hydroxides or aluminium oxides from metallic aluminium by oxidising in an aqueous medium, in particular for producing boehmite- and bayerite-shaped aluminium hydroxides. Said invention also relates to producing hydrogen by a chemical aluminium and water interaction. Contrary to known methods, the inventive method uses aluminium and water only, whose interreaction is carried out at the predetermined ratios of the fine aluminium powder to water in suspension supplied to a reactor, wherein the reactor operation is controlled by modifying the quantity of the aluminium powder-water suspension introducible into the reactor in unit time and by the aluminium powder quantity introducible into water within a defined limit in unit time, wherein the ratio between the aluminium powder and water in said suspension defines the shape a hydroxide or aluminium oxide obtainable at the output. An automated control system based on the CM 1820M KP2.14 controller is used for guaranteeing the determined reaction process conditions and obtaining the required-shaped product.

Description

 A method of producing hydroxides or oxides of aluminum and hydrogen and a device for its implementation

The invention relates to methods for producing aluminum hydroxides or oxides, and in particular to methods for producing aluminum oxides or hydroxides from aluminum metal by oxidation in an aqueous medium. Aluminum oxides and hydroxides are used in various industries as adsorbents, catalysts, etc. High purity hydroxides and oxides of aluminum are used in the electronic and optical industries in the form of a fine powder - as abrasive powders, in particular, for hard drives or magnetic heads. The invention relates, in particular, to methods for producing aluminum hydroxides of boehmite and bayerite form.

The method also relates to the production of hydrogen, namely, to methods for producing hydrogen by the chemical interaction of metals and water. Hydrogen can be used in various chemical processes as a reducing agent, as well as in certain conditions as a fuel.

Aluminum hydroxides exist in various crystalline forms - hydrargillite, bayerite, diaspora, boehmite, etc., oxides - in the form of alpha, gamma _; theta forms. The main difference between these forms is the location of aluminum ions and oxygen ions relative to each other. In this description, the term "aluminum hydroxide" also means hydrated aluminum oxides Al ₂ Oz.

The main method for the industrial production of aluminum hydroxides is the Bayer process, and their subsequent drying and calcination leads to the production of aluminum oxides [Chemical Encyclopedia, ed., Soviet Encyclopedia, M., 1988, tl, p.213-214]. However, conventional methods for producing aluminum hydroxides do not achieve high purity (and structural uniformity) of the product.

Known [US Patent 5,225,229, cl. 423/629, Аlumiшдm Сomrapu of АМериса, publ. 07/06/1993,] a method of producing aluminum hydroxide, in which there is a reaction of water in the liquid phase at a pH of about 12.4 with aluminum. At such pH gidrokisid alumina produced an acceptable rate as in the dispersion of the particles with a surface area of 75,000 mm ² / g and 50,000 mm ² / g. The reaction is also possible with values less than 50,000 mm ² / g, up to 20,000 mm ² / g. In accordance with another type of method, an organic substance, chlorin, is added to the catalyst as water. The disadvantage of the proposed method is the need to increase the pH, which is done by adding substances that provide such high

SUBSTITUTE SHEET (RULE 26) pH values. Therefore, this method does not provide the necessary purity of the products. In addition, the process proceeds with insufficient speed.

The prototype of the invention is a method for producing hydroxides or oxides of aluminum and hydrogen from aluminum and water [RF patent 2223221, cl. C 01 F 7/42, ZAO "Firm RIKOM SPb", op. 02/10/2004], in which a suspension of powdered aluminum in water is prepared from finely dispersed aluminum with a particle size of not more than 20 microns at a ratio of A1: H ₂ O = 1: 4-16 wt.h. The suspension is continuously fed into a high pressure reactor, where it is sprayed with a droplet diameter of not more than 100 μm into water. Steam gas is fed from the reactor to a condenser, where hydrogen is separated from water vapor. Aluminum hydroxide or aluminum oxide is fed to a hydroxide receiver. By changing the temperature and pressure ranges in the reactor, as well as the weight ratios of the aluminum and water involved in the reaction, the forms of aluminum hydroxides necessary for each specific case are obtained: boehmite, bayerite, as well as alpha-oxide, theta-oxide, gamma-aluminum oxide and a mixture of aluminum hydroxides boehmite and bayerite form. The implementation of the method takes place in an installation including a mixer, a high pressure reactor equipped with a nozzle that provides a spray of a suspension of powdered aluminum in water with a droplet diameter of not more than 100 μm, a receiving device for hydroxides, a condenser. Distilled water is used to produce high purity hydrogen. The method has a number of advantages: it is continuous, only water and aluminum take part in the reactions, which ensures the purity of the products obtained (hydroxides and oxides of aluminum, as well as hydrogen), changes in temperature and pressure conditions determine the type of products obtained. It should be noted that the necessary pressure and temperature ranges in the reactor with this method are supported by the continuous removal of steam and gas and a suspension of aluminum hydroxide. This support is a serious technical problem, since the ratio between the pressure, temperature, and mass of vented gas and a suspension of aluminum hydroxide is determined by a rather complex formula that takes into account the partial pressures of saturated water vapor and hydrogen, the mass of introduced aluminum, the temperature in the reactor, and the free volume of the reactor. The dynamic change of these factors makes it insufficient as a regulatory factor only to divert the reaction products from the reactor, and it does not provide the necessary accuracy of maintaining the regimes in

SUBSTITUTE SHEET (RULE 26) reactor in the absence of feedback between the processes occurring in the reactor and the source of the feed slurry. In addition, during the preliminary preparation of the suspension of finely dispersed powder of aluminum and water used in this method, it is not possible to change the composition of the suspension when the regime deviates from temperature and pressure in the reactor. When storing the prepared suspension, partial oxidation of the aluminum powder occurs, which leads to an actual change in the composition of the supplied suspension. At the same time, hydrogen is produced in the mixer, which affects the safety of the process. These disadvantages eliminates the proposed method.

The aim of the proposed method is to provide the necessary process parameters for guaranteed receipt of output products of specified types and purity. Such technical problems as increasing the reliability of the reactor and its stability are being solved.

The essence of the proposed method is to obtain hydroxides or oxides of aluminum and hydrogen from a suspension of finely divided aluminum powder in water, including preparing a suspension of finely divided aluminum powder in water, creating saturated water vapor pressure in the reactor, spraying the suspension into a high pressure reactor, and withdrawing a mixture of water vapor from the reactor and hydrogen, as well as the output from the reactor of aluminum hydroxide or aluminum oxide to the receiving device, measuring the temperature T in the reactor, measuring yes P Lenia gas mixture in the reactor. (The following are the distinguishing features of the method). The partial pressure of saturated water vapor PH ₂ O is determined. In the reactor, the partial pressure of hydrogen Рш is determined, and the

the free volume of the reactor V _cvι and adjust the pressure P and temperature

T in the reactor by changing the mass of aluminum introduced in the composition of the suspension JP ^ ι. In accordance with the formula

P = Pn ₂ o + PH ₂ = PH ₃ O + 0,55- R m _m T / V _cb , where

R is the universal gas constant (8.317-j / moltrad),

In addition, a method for producing hydroxides or oxides of aluminum and hydrogen from a suspension of finely divided powdered aluminum in water is proposed, in which the pressure and temperature in the reactor are adjusted,

SUBSTITUTE SHEET (RULE 26) by changing the ratio of AhHjO in the suspension, moreover, to obtain a bayerite form of hydroxide, the ratio Al: HgO = 1: 7-14 mass parts, to obtain a boehmite form of hydroxide, the ratio Al: H? O = 1: 5-12 mass parts, for preparing a mixture bayeritnoy hydroxide and boehmite forms ratio Al: H ₂ θ = l: 5- \ 4 phr, for the ratio of gamma alumina Al: H ₂ O = 1: 4-8 parts by weight, to obtain theta alumina ratio Al: H ₂ O = 1: 4-7 parts by weight, to obtain alpha alumina, the ratio A 1: H? O = 1: 3-5 parts by weight

The essence of the proposed device for producing hydroxides or oxides of aluminum and hydrogen is that it contains a source of suspension of fine powdered aluminum with water with a mixer, a reactor, a condenser, a receiving device, an adjustable valve to remove a mixture of water vapor and hydrogen, an adjustable valve to remove hydroxides or oxides aluminum, a temperature sensor in the reactor, a pressure sensor at the inlet of the slurry supply to the reactor, a pressure sensor at the outlet of the gas-vapor mixture, and a pressure sensor in front of the steam inlet call mixture into the capacitor. (The following are the distinguishing features of the proposed device), In addition, it contains an adjustable means of supplying a suspension to the reactor and a control controller with input and output, the source of the suspension containing an adjustable means of supplying water and an adjustable means of supplying aluminum powder, the input of the controller is connected to a temperature sensor in the reactor and the indicated pressure sensors, and the controller output is connected to a suspension source controlled by a means for supplying a suspension of finely divided aluminum powder with water into the reactor OP, an adjustable valve for discharging a mixture of water vapor and hydrogen and an adjustable valve for removing hydroxides or aluminum oxides.

In addition, a device is provided in which an adjustable means for supplying a suspension of finely divided aluminum powder in water comprises a high pressure pump and an adjustable valve.

In addition, a device is provided in which an adjustable means for supplying a suspension of finely divided aluminum powder in water comprises an adjustable high pressure pump.

The controller can be part of an automatic process control and management system and is connected to the top-level machine by an interface.

SUBSTITUTE SHEET (RULE 26) The proposed method and device for its implementation are illustrated by the following figures:

In FIG. 1 shows a block diagram of a device.

In FIG. 2 shows a functional diagram of the controller.

In FIG. 3 shows a functional diagram of a top-level machine.

List of accepted designations

1. An adjustable source of a suspension of fine powdered aluminum with water,

2. Adjustable aluminum powder feed means,

3. adjustable water supply

4. adjustable means for supplying the specified suspension in the reactor,

5. high pressure pump,

6. valve

7. controller

8. reactor

9. capacitor

10. receiving device

11. a pressure sensor at the inlet of the suspension to the reactor,

12. a pressure sensor at the outlet of the vapor-gas mixture,

13. a pressure sensor in front of the input of the gas mixture into the condenser,

14. An adjustable valve for removing a mixture of water vapor and hydrogen,

15. adjustable valve for the removal of hydroxides or aluminum oxides,

16. temperature sensor inside the reactor,

17. temperature sensor on the reactor shell,

18. controller input

19. controller output,

20. mixer

21. automatic control and management system (ASKU),

22. top-level machine (MVU),

23. discrete signal input modules,

24. analog input modules,

25. discrete signal output modules,

SUBSTITUTE SHEET (RULE 26) 26. analog output modules,

27. processor module of the controller,

28. controller network adapter,

29. network adapter MVU,

30. processor module MVU,

31. process control software module,

32. database of initial parameters,

33. software module for editing the database of source parameters.

In the block diagram of the device of FIG. 1 shows an installation comprising a source of a suspension of finely divided aluminum powder with water 1, a reactor 8, a receiver (suspension settler) 10, a condenser 9, an adjustable means for supplying the specified suspension to the reactor 4, a control controller 7. The source of the suspension 1 contains an adjustable means for feeding aluminum powder 2, which is a screw device with an adjustable drive; adjustable means of water supply 3 - a flow regulator of the company Вrkhophorst Hi-Tech BV, Aluminum powder and water are sent to the mixer 20 - a vessel made of stainless steel and equipped with a mixing device. Source mixture 1 is connected with adjustable means _^ slurry feed to reactor 4, which comprises a high pressure membrane type pump company URACA 5 and valve 6 firm LH Automation. The suspension of aluminum powder with water is fed into the reactor 8, which is a high-pressure apparatus equipped with a nozzle that atomizes a suspension of powdered aluminum in water to a droplet diameter of not more than 100 μm. The reactor is equipped with an internal temperature sensor 16, a temperature sensor 17 is installed on the reactor shell, a pressure sensor 11 is connected at the inlet of the suspension supply, a pressure sensor 12 is connected at the outlet of the gas-vapor mixture 12. From the upper part of the reactor, the mixture of water and hydrogen vapors is discharged through an adjustable valve 14 to the condenser 9 where the separation of water vapor from hydrogen takes place. A pressure sensor 13 is installed in front of the condenser entrance. Hydroxides and aluminum oxides are discharged from the lower part of the reactor through an adjustable valve 15 to the collection 10. Adjustable valves 14, 15 manufactured by LG Automation. Metran sensors are used to measure pressures and temperatures. Controller 7

SUBSTITUTE SHEET (RULE 26) has a control input 18 and a control output 19, in addition, it is connected to a upper level computer (hereinafter referred to as a machine), in FIG. 1 not shown.

In FIG. 2 shows a functional diagram of controller 7. The processor module of controller 27 is connected to input modules of discrete signals 23 and input modules of analog signals 24, which, in turn, are connected to the control input of controller 18. In addition, the processor module of controller 27 is connected to output modules of discrete signals 25 and output modules of analog signals 26, which, in turn, are connected to the control output of the controller 19. In addition, the processor module of the controller 27 is connected via network adapters 28 and 29 to the computer M WU 22 (see. Fig. 2 and 3). Controller 7, for example, type CM 1820M KP2.14 provides the input of 128 discrete signals of the “contact contact” type with the power of these contacts from an internal (12 V) power source, the output of 64 discrete signals via normally open relay contacts 10 A, 220 V AC 50 Hz, input of 64 analog 4 ÷ 20 mA signals and 4 analog output signals 4 ÷ 20 mA. Discrete signals are inputted by 4 discrete input modules 23 - MDB4.3 (32 channels per module) and 8 MKDB / B1.1 discrete I / O cross modules (16 channels per module), discrete signals are output by 2 modules 25 discrete output MDByw.4 and 4 modules cross relay MKRZ.l, input / output of analog signals is provided by 4 modules 26 MABl.8 and 4 modules cross analog input MKAB2.7. The processor module 27 MPZ.l has an integrated channel RS232 / 485 22 to provide communication with the machine 22 of the upper level at speeds up to 115200 bps.

In FIG. 3 shows a functional diagram of the machine of the upper level 22. The processor module 30 of the MVU is connected via the network adapter 29 of the MVU to the controller 7. In addition, the module 30 is connected to the software module for process control 31, which, in turn, is connected to the database of initial parameters 32. The source data database 32 is also connected to the software module for editing the source parameters database 33.

The implementation of the method

In order for the active interaction of powdered aluminum metal with water by reaction

2A1 + 4H ₂ 0 = 2AUOH + ЗH ₂ (gas) + β (kcal),

SUBSTITUTE SHEET (RULE 26) it is necessary to provide fine atomization of a suspension of aluminum powder with water into a reactor in which water and its vapors are present at a temperature of 250 - 400 C and a pressure of 10 - 20 MPa, and the ratio of the suspension fed to the reactor to water and its vapors in the reactor should be 1 : 50-100 parts by weight In this case, the size of the droplets of the injected suspension should be no more than 100 microns.

When implementing the method, water is preliminarily supplied to reactor 8, it is heated to create saturated water vapor to a temperature of 250 - 400 C and a pressure of 10 - 20 MPa. Upon reaching these values of the specified parameters from the source 1 of the preparation of the suspension using an adjustable feeding means 4, the suspension of finely dispersed aluminum powder with a given α-consumption and the ratio of Al and H ₂ O is fed into the reactor 8.

The resulting products are continuously withdrawn from the reactor. Hydrogen in the composition of combined-cycle gas (about 25 wt.% Hydrogen and about 75 wt.% Water) and aluminum hydroxides (oxides) in the form of an aqueous suspension (25-35 wt.% Hydroxides (oxides) are removed from the reactor to the separation stage.

Management of the installation process is as follows:

ASKU 21 introduces the set mass flow rates of the obtained hydroxides and hydrogen, the ratio of Al and H ₂ O in the suspension, which determines the type of hydroxides produced, and the calculated values of pressure and temperature in the reactor. The controller 7 provides the appropriate control signals to the means 2 and 3 of the supply of aluminum powder and distilled water, setting their nominal costs. Depending on the set values of the mass flow rate per unit time of the obtained hydroxides and hydrogen, control signals are supplied to the adjustable valves 14, 15 installed on the corresponding lines, determining their cross-section, control signals to the means for supplying the suspension 4 to the reactor (pump and adjustable valve). The presence of two adjustable elements is explained by the fact that the large flow rates of the suspension are more accurately set by adjusting the capacity of the pump 5, and the small ones by the adjustable valve 6. In stationary mode e of the process of oxidation of aluminum in the reactor, the pressure in it is determined by the sum of the partial pressures of saturated water vapor P _{n o} and hydrogen released as a result of the reaction: P = Pн # + PH ₁ 0)

SUBSTITUTE SHEET (RULE 26) for the temperature in the reactor T _p , (according to the readings of the sensor 16) P _HgQ is determined from the tabular values of the pressure of saturated water vapor from the temperature.

The partial pressure of hydrogen P _n is determined from the equation

m_н -масса выделившегося водорода в единицу времени, μ_Hi - молярная масса,Mendeleev, which is true in these conditions:

m _{n is the} mass of hydrogen released per unit time, μ _Hi is the molar mass,

R is the universal gas constant (8.317-J / moltrad), T ₁ , is the temperature in the reactor, V _aι is the free volume of the reactor.

The free volume of the reactor V _m is a part of the geometric volume of the reactor Vp, minus the volume that the water initially filled in (adjusted for expansion at a given temperature) V _{11 oιr} and the volume of suspension of aluminum powder with water that entered the reactor before stationary mode of hydrogen evolution V _cyaι

V _cll = V _p - V _th0ITr - V _cycп (3)

According to the reaction between aluminum and water, Igmol Al gives 1.5 gmol H ₂ , i.e. when completely oxidized, 9 g of Al gives Ir H ₂ .

Then equation (2) takes the following form:

/ ^> _ffi = 0.55 ^L (4), where:

m _Al is the mass of aluminum entering the reactor per unit time. Thus, in a stationary mode

P = P _{Hr () +} 0.55- ^ f ^ (5)

The calculated values are entered in the controller management program: x T w) * ¹ PH ₂ OI T ₁ ,,,, 'V' сι: ^•

SUBSTITUTE SHEET (RULE 26) Thus, the pressure in the reactor 8, and therefore the amount of hydrogen removed, can be adjusted by changing the mass of aluminum supplied to the reactor.

The controller compares the readings of the pressure sensor P 12 with the selected optimal value of P and, in the case of deviation of these values, generates control signals for the aluminum feed means according to formula (5), adjusting the mass of aluminum supplied to the reactor.

The temperature sensor on the reactor shell 17 serves to prevent accidents associated with overheating of the reactor.

. If it is necessary to obtain products of high purity, purified water is used, for example, distilled, but the method also allows the use of ordinary water.

Table 1.

The results of experimental studies of the modes of production of hydroxides and aluminum oxides

SUBSTITUTE SHEET (RULE 26)

The resulting method is characterized by non-waste, manufacturability and high productivity, as well as environmental safety. The installation was created mainly on the basis of commercially available elements; the reactor vessel with the necessary input and output lines of the processed products was specially manufactured. In addition, the corresponding software for automated control systems was developed.

SUBSTITUTE SHEET (RULE 26)

Claims

Claim 1. The method of producing hydroxides or oxides of aluminum and hydrogen, including preparing a suspension of finely divided aluminum powder in water, creating saturated water vapor in a reactor, spraying the suspension into a high pressure reactor, withdrawing a mixture of water and hydrogen vapors from the reactor, and also removing hydroxide from the reactor aluminum or aluminum oxide in the receiving device, measuring the temperature T in the reactor, measuring the pressure of the gas mixture P in the reactor, characterized in that the partial pressure of saturated in dyanogo pair P in the reactor is determined hydrogen partial pressure PH ₂ determine the free volume of the reactor V _CB, and changing the weight of the composition introduced into the slurry Shdι alumina according to the formula P = Pn ₂ o + PH ₂ = Pn ₂ o + 0, 55 R m _A iG / V _cb , where: ^• R - universal gas constant, adjust the pressure and temperature in the reactor. 2.- The method according to p. 1, characterized in that the pressure and temperature in the reactor are adjusted by changing the Al: HjO ratio in the suspension, and in order to obtain a Bayerite form of hydroxide, the ratio Al: H? O = 1: 7-14 mass.h ., to obtain a boehmite form of hydroxide, the ratio Al: HoO = 1: 5-12 mass parts, to obtain a mixture of the bayerite and boehmite forms of hydroxide, the ratio Al: H ₂ θ = l: 5-14 mass parts, to obtain gamma - alumina, the ratio of Al: H ₂ O = 1: 4-8 parts by weight, to obtain theta alumina, the ratio Al: H ₂ O = 1: 4-7 parts by weight, to obtain alpha-alumina Leningrad : H ^ O = 1: 3-5 parts by weight 3. A device for producing hydroxides or oxides of aluminum and hydrogen, containing a source of a suspension (1) of fine powdered aluminum with water with a mixer (20), a reactor (8), a condenser (9), a receiving device (10), an adjustable valve (14) a mixture of water and hydrogen vapors, an adjustable valve (15) for removing hydroxides or aluminum oxides, a temperature sensor (16) of the reactor, a pressure sensor (11) at the inlet of the suspension to the reactor, a pressure sensor (12) at the outlet of the gas-vapor mixture, and a pressure sensor (13) before entering the gas-vapor mixture in the conda nsator, characterized in that it contains an adjustable means (4) for feeding the suspension into a reactor, a control controller (7) with an input (18) and an output (19), and the suspension source (1) contains an adjustable means of supplying water (3) and an adjustable means of supplying aluminum powder (2), an input (18) of the controller (7) connected to a temperature sensor (16) in the reactor and pressure sensors (11,12,13), and the output (19) of the controller (7) is connected to a suspension source (1), controlled by means (4) for supplying a suspension of finely divided aluminum powder with water in reactor, adjustable valve (14) for discharging a mixture of water vapor and hydrogen and an adjustable valve (15) for discharging hydroxide s or alumina, 4. The device according to p. 3, characterized in that the adjustable means (4) for supplying a suspension of finely divided powdered aluminum in water contains a high pressure pump (5) with an adjustable valve (6). 5. The device according to p. 3, characterized in that the adjustable means (4) for supplying a suspension of finely powdered aluminum in water contains an adjustable high pressure pump.