Method of controlling salt solution dissolution

FIELD: process engineering.

SUBSTANCE: invention relates to production of synthetic carnallite. Proposed method comprises stabilising dissolution temperature, stabilising useful component concentration in varying stock consumption and determining useful component in flows entering the process. In varying said consumption relative to preset magnitude, useful component consumption is adjusted. Useful component comprises, apart from potassium chloride, magnesium chloride. Its concentration on feed stock flow is stabilised by evaporation of magnesium chloride initial solution. Additionally, content of magnesium chloride in evaporated solution is measured to calculate flow rate of evaporated solution by the following expression: where is flow rate of evaporated magnesium chloride solution, t; GKCl is potassium chloride flow rate per 100% of the product, t; is specified content of MgCl2 in evaporated solution, 35±0.5 %. Calculated magnitude is loaded in solution consumption control system as a setting point.

EFFECT: higher accuracy of control.

2 ex

 

The invention relates to techniques for managing the process of dissolution of potassium chloride in a concentrated solution of magnesium chloride and can be used in the process of obtaining synthetic carnallite in its synthesis and crystallization facilities vacuum crystallization.

A method of obtaining synthetic carnallite by reacting potassium chloride with magnesium chloride, followed by evaporation of the mixture at a temperature of 158-180°C to molecular ratio of components KCl MgCl2:H2O=1,0:1,0:3-5 - see A.S. USSR №448160, CL. C01F 5/30; C22D 3/08, 1974, bull. No. 40. Of the known method it is unclear what technical solutions manages the process of obtaining synthetic carnallite.

A method of obtaining synthetic carnallite, including mixing concentrated solutions of magnesium chloride to a suspension of potassium chloride at 75-80°C, followed by cooling the suspension crystallization, filtration of the product and refund of the uterine liquor to the step of mixing the raw materials, with a suspension of potassium chloride is heated to 75-85°C and fed to the mixture at a concentration of potassium chloride 7-8% - see A.S. USSR №582203, CL. C01F 5/30, 1977, bull. No. 44. In the known method is not technical solutions to manage the process of receiving carnallite.

The known method is automatic process control of dissolved salts prototype - see A.S. USSR №381374, CL. B01F 1/00, G05D 11/00, publ. 22.05.1973, bull. No. 22. The method includes stabilizing the temperature of the dissolution of salts and stabilizing the concentration of useful component in the solution by changing the flow rate of the raw material dissolution, determination of the useful component included in the process flow and changing the value of this flow relative to the setpoint adjustment expense useful component acting in the composition of raw materials.

The disadvantage of this method of automatic control is its low accuracy by dissolving potassium chloride in concentrated solutions of magnesium chloride, especially when you have a given ratio of KCl MgCl2in the suspension fed to the crystallization of synthetic carnallite.

The objective of the invention is to improve the accuracy of automatic control of the process of dissolution of potassium chloride in the solution of magnesium chloride to obtain a suspension with a given ratio of KCl MgCl2.

This object is achieved in that in contrast to the known method as a useful component, along with potassium chloride, entered magnesium chloride, the concentration of which in the input stream of raw stabilize the evaporation source of magnesium chloride, optionally measure the content of magnesium chloride in one stripped off the solution, calculate ashod one stripped off of the solution according to the following dependence:

,

where- one stripped off flow of a solution of magnesium chloride, t;

GKCl- consumption of potassium chloride in recalculation on 100% product t;

- routine maintenance MgCl2in one stripped off the solution, 35±0,5%,

and the calculated value serves as a job management system solution flow rate. When dissolved useful component (potassium chloride in a solution of magnesium chloride) part of it remains in suspension.

The essence of the method as a technical solution is as follows: in contrast to the known method, including stabilization of the temperature of dissolution, the stabilization of the concentration of the useful component in the solution by changing the flow rate of the raw material dissolution, determination of the useful component included in the process flow and changing the value of this flow relative to the setpoint adjustment expense useful component entering in the composition of the raw materials for the proposed method as a useful component, along with potassium chloride, entered magnesium chloride. In the production of synthetic carnallite from solutions of magnesium chloride and potassium chloride in contrast to the processing of carnallite ore is not formed large waste - halite blade and clay-salt slurry - see, for example, Salt is askie carnality, collection of scientific papers, 2007, S.-Pb, LICK, s-123.

Used in the production of potassium chloride, obtained from spent electrolyte magnesium plant, and the standard potassium chloride supplied to compensate for losses during electrolysis dehydrated carnallite and redistribution processing of the electrolyte.

Useful components of the chlorides of potassium and magnesium are relatively pure substances, and the flow of potassium chloride is variable. According to conducted studies of the dependence of consumption, one stripped off solution of magnesium chloride from the consumption of potassium chloride in the manufacture of synthetic carnallite is determined by dependence

,

where- one stripped off flow of a solution of magnesium chloride, t;

GKCl- consumption of potassium chloride in recalculation on 100% product t;

- routine maintenance MgCl2in one stripped off solution, %;

,

where Garticlethe consumption of standard potassium chloride, coming to replenish losses, t, in terms of 100% of the product;

Ge- consumption of potassium chloride, obtained from the electrolyte, t;

WithKCl- KCl content in the product obtained from the electrolyte.

amounted to -1,277 - multiplier with KCl on the anhydrous carnallite.

Loss of potassium chloride on the stages obasogie what I carnallite, its electrolysis and recycling of the electrolyte is determined by the specifics of production and are usually 10-20%, therefore, when entering a recovery factor of KCl on these conversions - α(0,8-0,9), we obtain the consumption of standard potassium chloride, depending on the consumption of potassium chloride, isolated from the electrolyte in the form of dependencies

in terms of 100% of the product

where- KCl content in a standard potassium chloride, %.

The total consumption of 100% potassium chloride will be

Consumption, one stripped off solution of magnesium chloride,will be

or

A necessary condition for obtaining the certified carnallite is the flow rate of the circulating liquor and the content of magnesium chloride in one stripped off the solution.

Usually scheduled value flow circulating circulating liquor stabilize calculation of ~2.7 tons per 1 ton of synthetic carnallite. Increased consumption leads to increased energy consumption for the heating and circulation, but reduces the amount of solid phase in suspension by dissolving potassium chloride. The decrease in consumption leads to contamination of synthetic carnallite by potassium chloride. Therefore, the optimum flow rate of the circulating solution is determined at the development of production and for replay as a routine indicator of the optimal circulation of the liquor - Ga circus..

When carrying out the process of dissolution of potassium chloride on the flushing of pipelines, equipment and other needs water. When the disturbance of the water balance of the process appear excessive working capital solutions, which must be removed from the process at the stage of evaporation of the source solution of magnesium chloride. The same effect will be obtained when there is insufficient Parke solution of magnesium chloride in relation to the scheduled value. When the concentration of MgCl2in one stripped off solution normalized over possible contamination of synthetic carnallite bischofite (MgCl2·6H2O), which will cause difficulties in further processing, was put on magnesium metal.

Therefore, it is also regulated by the concentration of one stripped off solution of chloride of magnesium is usually at 35±0,5% MgCl2.

The lack of circulating circulating solution, for example, during start-up of production in case of violations of the technological regime or repair of equipment, i.e. Gm<Ga circus.system contribute by supplying the necessary quantity of 27-30% solution of magnesium chloride, for example, with intermediate housings evaporator.

When the disturbance of the water balance of the process from the system to the residue output of the circulating mother liquor containing 28-30% of the chlorides of magnesium and calcium.

assaulta system water promotes the decomposition of carnallite and its contamination with potassium chloride. Therefore, it is necessary output MgCl2to compensate one stripped off with a solution of magnesium chloride with increased content of magnesium chloride. Adjustable concentration of magnesium chloride -- is determined by the following dependencies:

where Gwt.t - the amount of excess circulating liquor, defined by the equation Gwt.=Gm-Ga circus.;

Gm- consumption of uterine liquor obtained after the separation of suspensions of synthetic carnallite after vacuum crystallization, t;

Ga circus.- flow circulating circulating liquor entering the dissolution of potassium chloride is scheduled value t;

- concentration of MgCl2in the fallopian excessive liquor, %.

At steady state excess circulating liquor no - Gwt.=0;.

The calculated values of GArt.,, Gwt.andserved as the task management system flow one stripped off solution.

The dissolution of potassium chloride in the joint solution of magnesium chloride part KCl remains in a solid phase, however, upon further cooling, the suspension of the potassium chloride is dissolved in the solution with crystallization of sin is micheskogo carnallite.

An important factor in the stabilization process of dissolution is the temperature of the liquid phase, which is maintained in the range of 90-100°C by heating the circulating circulating liquor and selecting one stripped off solution of magnesium chloride from the last housing evaporator, where the solution has a maximum boiling point.

Thus, the task of improving the accuracy of automatic control of the process of dissolution of potassium chloride in the joint solution of magnesium chloride to obtain a suspension with a given ratio of KCl MgCl2while cooling which is formed of synthetic carnallite, quality all the requirements of the magnesium production.

The method is as follows. On stage dissolution serves potassium chloride, obtained from the electrolyte, potassium chloride standard to compensate for losses KCl, circulating circulating liquor from stage cooling, suspension and selection of synthetic carnallite heated to a temperature of ~100°C, and one stripped off the solution of magnesium chloride. The resulting suspension is intensively stirred and cooled to the crystallization of carnallite.

Measure:

- consumption of potassium chloride, obtained from the electrolyte, with the weight of the dispenser, for example, by "Technocon";

- mass fraction of potassium in the flow of potassium chloride with potassium meter, for example, the company "Berthold is LB 377-62;

the content of magnesium chloride in one stripped off solution - analytical method or the density of the solution is adjusted to a temperature of, for example, using a primary Converter MFS 2000 and signal Converter MFS 081;

- expenses of circulating uterine and one stripped off the liquor by means of an electromagnetic flow meter, for example, type Metran 370;

- the temperature of the suspension by dissolving using a thermal Converter with unified output signal, such as a Converter of TSMU Metran 274.

Are scheduled rate value of the circulating liquor, Ga circus.the degree of extraction of potassium chloride to magnesium plant and in the loop processing of the electrolyte, α, routine concentration value of one stripped off solution of magnesium chloride,for example Ga circus.=2.7 t/t carnallite; α=0,8;.

On the dependencies calculate

Gwt.=Gm-Ga circus.

The signals from the devices are received at the controller, where these dependencies are counting regulated concentration of magnesium chloride -consumption of one stripped off solutionconsumption of standard potassium chloride, and then the signals Postup who are the distributors of potassium chloride, one stripped off solution and system control the degree of evaporation of a solution of magnesium chloride, and optionally the system output excess fluids circulating liquor.

An example of the method

Example 1

Readings:

- consumption of potassium chloride, obtained after processing
electrolyte, Getfor 10.68
the content of potassium chloride in this thread, CKCl, %85,04
the content of potassium chloride in the standard chloride
potassium, WithKCl, %96,90
- consumption of the mother lye. Gmt122,57
the flow rate of the circulating liquor, Ga circus.t122,57

Asked scheduled value of the flow rate of the circulating liquor, Ga circus.equal to 2.7 t/t carnallite - 122,57 t, the degree of extraction of potassium chloride in magnesium and other productions, α=0.8, the maintenance and the concentration value of one stripped off solution of magnesium chloride,.

Depending on what we define consumption standard potassium chloride, calculated on 100% of the product

Determine the overall consumption of potassium chloride in recalculation on 100% of the product

Define consumption, one stripped off 34,5%-aqueous solution of magnesium chloride,.

We define the consumption of excess circulating liquor, Gwt.

Gwt.=Gm-Ga circus.=122,57-122,57=0.

Define regulated concentration of one stripped off solution of magnesium chloride

The calculation results filed in the system flow control standard potassium chloride, one stripped off solution of magnesium chloride and the degree of evaporation of a solution of magnesium chloride.

Example 2

The method was carried out in accordance with example 1, but the reading of the instrument determined the flow of the mother liquor (Gm=129,90 so

Consumption of excess circulating liquor Gwt.=Gm-Ga circus.=129,90-122,57=7,33 so

The indication contents of magnesium chloride in it.

Define regulated concentration of one stripped off solution of magnesium chloride,.

This value was applied in the control system of the degree of evaporation of a solution of magnesium chloride. Gradually the flow of excess fluids decreased to 0, the concentration of the one stripped off races the thief fell to and.

Method for automatic process control of dissolved salts, including stabilization of the temperature of dissolution, the stabilization of the concentration of the useful component in the solution by changing the flow rate of the raw material dissolution, determination of the useful component included in the process flow and changing the value of this flow relative to the given value, the adjustment of the flow of useful component acting in the composition of the raw material, characterized in that as a useful component along with potassium chloride introduced magnesium chloride, the concentration of which in the input stream of raw stabilize the evaporation source solution of magnesium chloride, optionally measure the content of magnesium chloride in one stripped off the solution, calculate the flow rate of one stripped off of the solution according to the following dependence:
,
where- one stripped off flow of a solution of magnesium chloride, t;
- consumption of potassium chloride in recalculation on 100% product t;
- routine maintenance MgCl2in one stripped off the solution, 35±0,5%,
and the calculated value serves as a job management system solution flow rate.



 

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