FR2702760A1 - Process and apparatus for the preparation of potassium carbonate - Google Patents

Abstract

It is proposed, in installations for manufacturing potassium carbonate in the form of a calcined product and / or hydrate, to add to the wet dewatering salt delivered after crystallization and separation of solid substance, dust and possibly ground material from the manufacture of the calcined product and mixing in a kneader. In addition, dust from the manufacture of the hydrate or ground material can be added to the dewatering salt. For this purpose, a mixer is provided, optionally comprising a device for recycling the mixture prepared between the separation of solid substance from the dewatering salt and the feed pipe for the installations for the production of calcined product and of hydrate.

Description

Potassium carbonate is, after crystallization

  tion, separated from the solution in a saturator, first in the state of dewatering salt, that is to say in the state of K 2 C 03 1.5 H 20 with additional contents up to at 3.0% by weight, most often up to 2% by weight of water. From this point it is possible, by moderate drying, to obtain hydrated potassium carbonate K 2 C 03 1.5 H 20 and , at higher drying temperatures, in

  beds of strongly agitated products, carbonate of potas-

  calcined sium K 2 C 03 As sales products, the two subsi-

  Depending on the requirements, granules of 0.1 to

3.0 and up to 1.5 mm.

  For the drying of the hydrated potassium carbonate and for the drying of the calcined product, use is made of separate drying facilities, each time followed by sieving or screening devices, milling and treatment, which are usually arranged next to one another By passing through a distributor, the spinning salt can be delivered to the drying plants for the calcined product or the hydrated product, or

  partial currents at both drying plants.

  Criticism of the state of the art:

  During drying, especially during calcification

  nation, for example when using tubular ovens

  In the case of a rotating bed or a fluidized-bed drying device, large quantities of dust which can not be used further and which have to be returned for subsequent hydrate burst or abrasion are formed.

  redissolution in the crystallization stage.

  Complementarily, large quantities of

  agglomerates, especially during calcination, since variable amounts of adherent mother liquor and

  variable particle size spectrum of the spin squeegee

  during drying, collages and incrustations

  such agglomerates are not broken by the movement of

  during drying and must therefore be separated

and again dissolved.

  Depending on the temperature and the procedure, the

  recycling and redissolving of dust and agglomerates

  mates reach up to 20% of the yield.

  This requires a high expense for separation and screening. By recycling, the capacity is reduced.

  facilities and increases energy expenditure.

  Particularly, during calcination, agglomerates and dusts lead to functional disturbances as a result of encrustations in the apparatus. To prepare potassium carbonate hydrate, it has been proposed according to DD 26 64 902 (Economic Patent of the former -DDR) to mix with the spinning salt the untreated product coming out of the

  This requires, however,

  is raised for the analysis of the variable contents of water of the spinning salt. Such a preparation of the hydrate modifies, but does not solve the problem of the large quantity of

  dust and agglomerates that form.

  The problem therefore existed during the preparation

  of calcined potassium carbonate in particular, but

  during the preparation of hydrogen potassium carbonate

  to reduce and even prevent the formation of

  and agglomerates and to shape them into

  According to the process according to the invention, it has been found that the dusts from the manufacture of calcined potassium carbonate can be mixed with the dewatering salt before the preparation of the potassium carbonate.

calcined and / or its hydrate.

  It has also been found that one can also

  change with the spinning salt the dust from

  the manufacture of hydrated potassium carbonate.

  All the dusts of the production are then

  If necessary, it is also possible to mix

  with the squeezing salt of crushed agglomerates

calcined and hydrated.

  The device, also planned for the implementation

  opens the process according to the invention, is essential

  characterized in that it comprises between the device for separating the dewatering salt and the feed of the drying plants for the calcined product and / or for the hydrate, there is provided a mixing device for mixing with the spinning salt, dust from the manufacture of calcined potassium carbonate and / or the manufacture of hydrated potassium carbonate. The mixture, with the dewatering salt, of the calcined product powder, which has predominantly

  particle sizes well below 0.1 mm, modifies all the

  the structure of the spin-drying salt and improves

  fluidity and behavior during drying, in particular

  particularly for calcined potassium carbonate.

  Dust covers the grain surface of the

  salt and prevents agglomeration After mixing

  age of the dust and the spinning salt, the mixture is

  consisting of grains of the spinning salt with a coating

  Many of the small grains of dust which have absorbed the dewatering salt have a fixed content of free water. In the case of the quantity of calcined product dust, it can be obtained that

  mixture of calcined product dust and salt of

  In this case, the grain still has the water content of the potassium carbonate hydrate, while a possibly excess quantity of calcined product dust

  remains virtually anhydrous, is separated and can be ex-

pleated by addition to the mixture.

  Dusting of the dust particles in the form of pellets can be prevented by partial recycling of the previously reacted mixture, dewatering salt and calcined product dust, varying amounts and also large amounts of dust which can be

absorbed from the mixture.

  To prepare the mixture of dust and salt

  in accordance with the invention a mala-

  (mixer A of the drawing) behind the centrifuge of

  soring to separate the solid substance In this mixer, the spinning salt, the calcined product dust and the hydrate dust are mixed intensively

with the spinning salt.

  It turned out that the product dust calcu-

  The separate oil reacts on the spinning salt in a particular time.

  In addition, the dust which originates from the preparation of the hydrated potassium carbonate and which is formed in a smaller quantity, leads to an improved fluidity of the spinning salt. If desired, it is also possible to add crushed agglomerates to the kneader A. , in particular

of calcined product.

  The mixer A may have a device for

  reference by which the dust and the mixture of

  and the spinning salt can be mixed in a separate kneader placed upstream of kneader A, or in the front part of kneader A, before mixing with the dewatering salt. Pellising of the dust grains can be prevented by return to the mixer A, and variable quantities, equally important of dust,

are absorbed.

  Preferably, the mixer A is made in the form of a mixing auger with a partial return mixture or as a mixing tank comprising, for example, rotary shearing arms and a displacement of the

mass mixed to the outlet.

  The product leaving the mixer A may optionally be delivered to the production of the calcined product or to the

  manufacture of the hydrated product or, in particular

  to be delivered to both installations through

of a dispatcher.

  The mixture according to the invention of the dusts, and possibly also of the ground material, in particular the mixture of the dusts resulting from the calcination, with the dewatering salt, provides the unexpected advantage that the quantities of agglomerates and dusts. inlays so far important are reduced to small fractions of this

  fact, the crushed material, in particular from agglomerates

  macerations and incrustations of calcination, does not play a significant role during calcination and possibly during

  of hydrate production, as soon as the two plants

  By recycling the dust in mixer A, they are in equilibrium, only residual amounts of dust are

  agglomerates Operating disturbances, imputa-

  in particular to incrustations, are prevented by the process according to the invention and by the device con-

form to the invention.

  It is particularly advantageous when

  manufacture of the hydrate, that when using quantities

  sufficient quantities of calcined product dust for the

  reaction with the dewatering salt, the continuous cost measurement

  moisture and subsequent evaluation of the report

  quantity of substance streams become super-

flues.

  Any excess of calum product dust

  in the mixer A is therefore

to the invention.

  In a particular embodiment of the procedure,

  Alternatively, some of the calcined product dust may be delivered directly to the hydrated potassium carbonate preparation and mixed with the spinning salt or

  with the mixture of dewatering salt and dust,

  ie the fraction of the product coming out of the mixer A, which

  is intended for the manufacture of potassium hydrogen carbonate

  DRATE. For this purpose, it is provided to choose, in the form

  particular embodiment of the device, a mixer (mala-

  drawing B), which is essentially done as the

  mixer A Behind mixer B, the dust that does not

  dhre not is removed by sieving and / or screening This

  Dust is mainly made up of the calcined product

  tion, only takes place in small quantities and is

  in the mixer A. The mixture forming in the mixer B is,

  after dust separation, surprisingly ex-

  hydrated potassium carbonate. The mixer B replaces the preparation

  the hydrate that was needed so far

  expensive, heated, drying process for the preparation of

  hydrate according to the state of the art is totally sup-

  winning. The plant for the production of hydrated potassium carbonate is therefore greatly simplified and is only constituted by a mixer, without adding

  The amount of dust is reduced and

crustations are prevented.

  In another particular embodiment of the method and the device, there is only one mixing phase for the manufacture of

  hydrated potassium, in the form of the kneader A of the

  tif. A drying plant for carbonate of

  hydrated potassium, as well as the B-kneader, are removed.

  A partial stream, or the overall product stream from the mixer A, is used to prepare the hydrated potassium carbonate, the water being completely bound to the state of K 2 C 3 O 1.5 H 2 O in the water. in this case, it is necessary to add in the mixer A an excess of

  calcined product dust, if necessary also

  potassium carbonate hydrate, that is to say an amount large enough that the grain certainly has the composition and the crystalline structure K 2 C 03 1.5 H 20 The excess of calcined product dust n does not adhere to the surface, does not react, remains separable as recyclable dust Directly behind the mixer A, accordingly, for manufacturing

  hydrated potassium carbonate, only one more

  positive screening and / or sieving.

  The grain consistency improved on the surface by

  the invention also clearly improves the fluidity and

  sability of all substance streams and products.

  Other features and advantages of the operating mode and devices for its implementation are illustrated by way of non-limiting example in the accompanying drawings. In these drawings, FIG. 1 is a flow diagram relating to the

  manufacture of potassium carbonate.

  FIG. 2 is a view of a kneader, FIGS. 3a to 3b illustrate the grain structures of FIG.

potassium carbonate.

  In Figure 1, the flow diagram shows schematically the crystallization and separation of solid substance from the spinning salt of the mother liquor of potassium carbonate and then the drying plant for the calcined product and the installation of mixing B for the preparation of the hydrate Au kneader A arranged,

  according to the invention between the separating device

  the feed devices of the calcined product and hydrate production plants are delivered with the spinning salt and, depending on the

  according to the invention, all the recycled quantities

  clues of product and dust from

  drying conditions for the calcined product and hydrates it

  along the path indicated by the arrows.

  In the flow diagram is maintained, for example, a stationary equilibrium of the amounts in% by weight, relative to the dewatering salt counted per 100, which is established by the subdivision chosen by way of example for the production of product. calcined for 84% and hydrate

  16% of the total amount of product dust

  cine is at most 8 to 9%, for example in the case of a highly agitated fludized bed drying device,

preferably from 6 to 7%.

  FIG. 2 represents, for example, a mixer A

  in which the product of possible mixing is delivered in 1

  recycled, in 2 of the dust, in 3 the spinning salt

  and o, at 4, the mixture can be subdivided into quantities

  for the calcining device and for the installation

hydrate preparation.

  FIG. 3a is a sectional view showing the particles in random distribution according to the state of the

technical.

  FIG. 3b shows the surface structure of the grain which originates according to the invention, with

  very small dust particles adhering to the surface.

Claims (10)

R E V E N D I C A T I 0 N S   1 Process for the preparation of potassium carbonate   calcined sium K 2 C 03 and / or hydrated potassium carbonate K 2 C 03 1.5 H 20, by drying from spin drying salt K 2 C 03 1.5 H 20 with contents up to 3 , 0% by weight of water, characterized in that the dusts   from the production of calcium carbonate   cine are mixed with the spinning salt and then delivered to the production of calcined potassium carbonate and / or hydrated potassium carbonate.   2 Process according to Claim 1, characterized in that, in addition to the dewatering salt, the dust originating from the manufacture of the hydrated potassium carbonate.   The process according to claim 1 or 2, wherein   the mixing of the dust mixture   salt and dewatering as a recycle with dust from the production of the calcined product,   before mixing with the spinning salt.   4 Process according to one of claims 1 to 3,   characterized by the fact that one delivers to the choice   hydrated potassium carbonate or the manufacturer   cation of calcined potassium carbonate, or   the two products, the blending salt mixture   age and calcined product dust with or without fraction   of hydrated potassium carbonate dust.   Method according to at least one of the claims   1 to 4, characterized by the fact that for the manufacture   hydrated potassium carbonate, mixed with dewatering salt or with a mixture of the dewatering salt and dust, dust from the manufacture of calcined potassium carbonate.   Process according to Claim 5, characterized in that, in order to produce hydrated potassium carbonate, the calcined product dust is delivered in   a single phase of mixing with the spin salt and separating   re and delivers at the same time an excess possibly present of calcined product dust.   7 Device for the manufacture of carbonate of   calcined potassium K 2 C 03 and / or hydrogenated potassium carbonate   Dried K 2 C 03 1.5 H 20 from formula wringing salt   K 2 C 03 1.5 H 20, with additional contents allo-   up to 3.0% by weight of water, characterized in that between the device for separating the dewatering salt and the feed of the drying plants for the calcined product and / or for the hydrate, a device is provided for   mixing to mix, with the spinning salt, the   from the manufacture of calcined potassium carbonate and / or the manufacture of hydrated potassium carbonate.   8 Device according to claim 7, characterized   rised by the fact that upstream or in the front part of the kneading device, there is provided a device for   mixture for mixing dust from the manufacturer   cation of calcined potassium carbonate, with the product leaving the mixing device.   9 Device according to one of claims 7 or   8, characterized in that the mixing device   is realized in the form of an endless mixing screw.   Device according to one of claims 7 to   9, characterized in that, behind the mixing device or the kneading devices, there is provided a   supply device of choice for   for the calcined product, or the preparation of the   drate, or a partial current splitter for both i nstal 1 ati ons.   11 Device according to one of claims 7 to   characterized in that it is provided as a potassium carbonate production plant   hydrated, a blender used to mix dust from   the production of calcined potassium carbonate with the spinning salt or with the spinning salt mixture   and dust from the product exiting the kneading.   Apparatus according to claim 11, characterized   rised by the fact that it is intended as an installation of   brication for hydrated potassium carbonate, as a single kneading device, the kneading device   disposed downstream of the screening and sieving facilities   hydrated potassium carbonate.