Method of cooking soda solution supplied to the gas-cleaning installation of electrolysis aluminium

 

(57) Abstract:

The invention relates to the field of dust collection and gas cleaning in nonferrous metallurgy, in particular in the production of aluminum, and can be used in the process of cooking soda solution used for absorption of fluorine-containing gases of electrolysis. Method of cooking soda solution supplied to the gas-cleaning installation of electrolysis of aluminum, involves mixing the mother liquor of crystallization of cryolite, concentrated soda solution, technical water, naslovi water, clarified and unclarified saturated solutions, which maintain a constant concentration of soda ash and sodium sulfate in the soda solution by regulating the amounts of naslovi water, concentrated soda solution and water supply, as defined by the compiled equations. The claimed invention allows for the relative constancy of the concentrations of the major components in the gas cleaning solutions, zastabilizirovat their content in the soda solution supplied to the gas treatment. 1 PL.

The invention relates to the field of dust collection and gas cleaning in color Metallurgia, used for absorption of fluorine-containing gases of electrolysis.

Dust-gas mixture, being evacuated from buildings in aluminium electrolysis, contains carbon dioxide and carbon monoxide gases, hydrogen fluoride, sulfur dioxide, dust, resinous substance and has a temperature at the entrance to the gas-cleaning installation 90-180°C. during the wet purification of gases by water evaporation and Kaplunova, as well as with the output from the process is condensed sludge happen loss solution, resulting in the need to restore the water balance in the system.

Saturated solutions with gas cleaning equipment is recycled for regeneration cryolite in the fluorine-soda-bicarbonate scheme. Underlying the fluorine-soda-bicarbonate method, the regeneration of soda ash in the crystallization process of cryolite (reaction 1) determines the reuse of the mother liquor for cooking soda solution supplied to the gas-cleaning installation.

For cooking soda gas-cleaning solution to a stock solution of cooking cryolite containing soda ash, add the missing amount of working capital (technical) water, and to maintain the desired concentration of cal the config soda solution with content PA2CO3=100-300 g/DM3. The amount of soda solution and water added to the mother liquor, is the sum of the losses of fluids and is determined by the specific conditions of the plant.

The calculation of the concentration of ash in the feed gas purification is calculated by the formula:

where VMat.Vsod.Vtechnology.- accordingly, the volume of the mother liquor, concentrated soda solution and technical water supplied to stoperigaten;

WITHMat.WITHsod.accordingly, the content of ash in the mother solution and the concentrated soda solution (Typical instruction manual for the production of secondary cryolite developed Irkutsk branch YOU: TY 48-0141-40-01-87, pages 31-32).

The method has the following disadvantages. In the above method for the preparation of soda gas-cleaning solution using only three components: the mother solution, concentrated soda solution, technical (working) water. In addition, there are no recommendations for stabilization and regulation of the concentrations of the major components in the solution supplied to the gas treatment. The method is characterized by low efficiency ASS="ptx2">Almost all aluminum plants equipped with wet gas cleaning installations are operated more complex schemes adaptivemobile. These schemes include the use, in addition to the above in the formula (2), other components, in particular naslovi water, clarified and unclarified saturated gas treatment solutions. In this case, when calculating the concentration of sodium in the solution supplied to the gas cleaning, in the formula (2) is added to the volume and concentration of newly introduced components.

The closest to the technical nature of the claimed is a method of preparation of a solution for gas treatment, in which the mixed mother liquor of crystallization of cryolite, concentrated soda solution, circulating the solution from the gas purification (unclarified and clarified) and recycled water (Century, Terentyev and other aluminium Production, Novokuznetsk 2000, S. 270-273).

In accordance with the method adopted for the prototype, the concentration of soda ash in solution supplied to the gas-cleaning support-level 30-50 g/DM3the concentration of NaF is desirable to have no more than 15 g/DM3the concentration of sodium sulfate is not more than 70 g/DM3.

The prototype inherent fault is th solution supplied to the gas-cleaning only, it is recommended to maintain the concentration of soda ash in the concentration range of 30-50 g/DM3and the concentration of sodium sulfate is not more than 70 g/DM3without identifying specific ways to achieve the goal. The solution does not contain practical recommendations for stabilization and regulation of the concentration of soda ash PA2CO3and sodium sulfate Na2SO4in soda solution supplied to the gas treatment. The result is inefficient gas-cleaning installations, and unstable production technology is the recovery of cryolite from solutions.

The objective of the invention is to increase the efficiency of gas cleaning plants and further processing of saturated gas cleaning solutions on the regeneration cryolite by stabilizing the concentrations of the major components in the gas purification solutions. Maintaining a constant concentration of soda ash and sodium sulfate in the feed to the gas purification solution will provide stabilization of salt concentrations in the saturated solution. This in turn will increase the efficiency of the gas cleaning units and further processing rastia soda solution, supplied to the gas-cleaning installation of electrolysis of aluminum, by mixing the mother liquor of crystallization of cryolite, concentrated soda solution, service water, circulating cleaning solutions, according to the proposed method by mixing maintain a constant concentration of soda ash and sodium sulfate in the soda solution by regulating the amounts of naslovi water, concentrated soda solution and water supply, as defined by the following equations:

where VADSL- volume naslovi water supplied to stoperigaten, m3/h;

Vunder- the amount of soda solution supplied to the gas purification, m3/h;

the concentration of Na2SO4in the soda solution supplied to the gas purification, g/DM3;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

the concentration of Na2SO4in the mother solution, g/DM3;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

the concentration of Na2SO4in clarified saturated solution, g/DM3;

/h;

the concentration of PA2SO4in thick saturated solution, g/DM3;

the concentration of Na2SO4in naslovi water, g/DM3.

where Vsod- volume of concentrated soda solution on stoperigaten, m3/h;

Vunder- the amount of soda solution supplied to the gas purification, m3/h;

the concentration of Na2CO3in the soda solution supplied to the gas purification, g/DM3;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

the concentration of Na2CO3in the mother solution, g/DM3;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

the concentration of PA2CO3in clarified saturated solution, g/DM3;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

the concentration of Na2CO3in thick saturated solution, g/DM3;

VADSL- volume naslovi water supplied to stoperigaten, m3/h;

- Konzentrat the new soda solution, g/DM3.

,

where Vt- the volume of process water in stoperigaten, m3/h;

Vunder- the amount of soda solution supplied to the gas purification, m3/h;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

VADSL- volume naslovi water supplied to stoperigaten, m3/h;

Vsod- volume of concentrated soda solution on stoperigaten, m3/h;

Comparative analysis of the characteristics of the proposed solutions and features analog and prototype demonstrates compliance solutions to the criterion of “novelty”.

Efficient operation of the gas treatment plants as well as subsequent processing of saturated gas cleaning solutions on the regeneration cryolite is largely dependent on the stability of the concentrations of the major components in the gas purification solutions.

The proposed method of cooking soda rastvornyh solutions zastabilizirovat their content in the soda solution supplied to the gas treatment. Most important to maintain the constant concentration of soda ash Na2CO3and sodium sulfate Na2SO4. Stabilization of the concentration of the soda will provide a guaranteed recovery of hydrogen fluoride HF and sulfur dioxide (SO2a optimal residual concentration of soda in a saturated solution of the gas purification (5-12 g/DM3). Stabilization of the content of sodium sulfate in the solution supplied to the gas cleaning at the lowest possible level, will allow to avoid the loss of fluorine due to the local solution solutions and deposition of crystals of the double salt Na2SO4·NaF, as well as increase the efficiency of gas-cleaning equipment.

The proposed solution is illustrated a specific example of its implementation.

Consider the stabilization and regulation of volume and composition of the soda solution is fed to the gas-cleaning installation, the content of Na2CO3and Na2SO4. The calculation is made for the most complex technological scheme when preparing soda solution is fed six components of the solutions (mA is AMOVA water and process water).

Suppose that it is necessary to stabilize the concentration of Na2CO3in the solution supplied to the system, at the level of 20 g/DM3the concentration of Na2SO4at the level of 50 g/DM3when the flow rate of the gas treatment solution within 500± 50 m3/PM Task is to calculate the number naslovi water, concentrated soda solution and technical water that must be added to the existing volumes of mother liquor, clarified and unclarified saturated solutions, to provide the specified rate of gas-cleaning solution (500± 50 m3/h) required concentration PA2CO3=20 g/DM3and Na2SO4=50 g/DM3.

The basis of the algorithm put the balance calculation method (see table).

Calculation spend in 3 stages.

Step 1. Calculated volume naslovi water (VADSL) applied to stoperigaten, according to the formula:

where Vunder- the volume of solution, supplied to the gas purification, m3/h;

the concentration of Na2SO4in the solution supplied to the gas purification, g/DM3;

VMat- the volume of the mother liquor served n the;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

the concentration of Na2SO4in clarified saturated solution, g/DM3;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

the concentration of Na2SO4in thick saturated solution, g/DM3;

the concentration of Na2SO4in naslovi water, g/DM3.

Substituting from the table in equation (3) is known, we obtain:

Step 2. Calculated quantity of concentrated soda solution (Vsod) applied to stoperigaten, according to the formula:

where Vunder- the amount of soda solution supplied to the gas purification, m3/h;

the concentration of Na2CO3in the soda solution supplied to the gas purification, g/DM3;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

the concentration of Na2CO3in the mother solution, g/DM3;

VWWS- the volume of the clarified saturated solution supplied to stopright 3;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

the concentration of PA2CO3in thick saturated solution, g/DM3;

VADSL- volume naslovi water supplied to stoperigaten, m3/h;

the concentration of Na2CO3in naslovi water, g/DM3;

the concentration of Na2CO3in a concentrated soda solution, g/DM3.

Substituting in equation (4) are known values, we get:

Step 3. The volume of industrial water (Vt) applied to stoperigaten, is defined by the difference:

Vt- the volume of process water in stoperigaten, m3/h;

Vunder- the amount of soda solution supplied to the gas purification, m3/h;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

Vthe m concentrated soda solution, supplied to stoperigaten, m3/h;

In our example: Vtechnology.=500-150-180-30-71,6-10,62=57,78 m3/PM

When the number of components soda solution less than 6 to transform the diagram into a more simple will not present much difficulty. In this case, formulas (3-5) instead of the quantities and concentrations of missing components are substituted for null values.

The described method can be used to stabilize and regulate the composition and volume of the soda solution in both manual and automatic modes. For the implementation of the proposed technical solutions it is necessary that the apparatus-technological scheme of the Department or the Department of regeneration was equipped with monitoring and control (flow meters, electric locking bar, level sensors, dosing solutions, and so on) connected in a single system with automation.

Pilot testing of the proposed technical solutions confirmed possibility of implementing technology regulation and stabilization of the composition of the solution with high technical and economic indicators.

Method of cooking soda solution supplied to gazooks is the concentrated soda solution, service water and circulating cleaning solutions, characterized in that the mixing of the solutions maintain a constant concentration of soda ash and sodium sulfate in the soda solution by regulating the amounts of naslovi water, concentrated soda solution and water supply, as defined by the following equations:

where VADSL- volume naslovi water supplied to stoperigaten, m3/h;

Vunder- the amount of soda solution supplied to the gas purification, m3/h;

the concentration of Na2SO4in the soda solution supplied to the gas purification, g/DM3;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

the concentration of Na2SO4in the mother solution, g/DM3;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

the concentration of Na2SO4in clarified saturated solution, g/DM3;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

- K2SO4in naslovi water, g/DM3;

where Vsod- volume of concentrated soda solution on stoperigaten, m3/h;

Vunder- the amount of soda solution supplied to the gas purification, m3/h;

the concentration of Na2CO3in the soda solution supplied to the gas purification, g/DM3;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

the concentration of Na2CO3in the mother solution, g/DM3;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

the concentration of Na2CO3in clarified saturated solution, g/DM3;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

the concentration of Na2CO3in thick saturated solution, g/DM3;

VADSL- volume naslovi water supplied to stoperigaten, m3/h;

the concentration of PA2CO3in naslovi water, g/DM3;

the concentration of Na2CO3in a concentrated soda R is3/h;

Vunder- the amount of soda solution supplied to the gas purification, m3/h;

VMat- the volume of the mother liquor fed to stoperigaten, m3/h;

VWWS- the volume of the clarified saturated solution supplied to stoperigaten, m3/h;

VNeoV- thick volume of saturated solution supplied to stoperigaten, m3/h;

VADSL- volume naslovi water supplied to stoperigaten, m3/h;

Vsod- volume of concentrated soda solution on stoperigaten, m3/PM



 

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