FR2543939A1 - PROCESS FOR PRODUCING ZEOLITE A AND PRODUCTS OBTAINED - Google Patents

Abstract

METHOD OF MANUFACTURING ZEOLITE A BY REACTION IN AQUEOUS MEDIUM OF SILICA AND ALUMINA AND CAUSTIC SODA IN AN ADEQUATE STOECHIOMETRIC RATIO. A SILICATE GEL PULP FROM THE TREATMENT OF HIGH-FURNACE MILK WITH RESIDUAL ACID IS USED, THIS PULP BEING BASED BY ADDITION OF CAUSTIC SODA AND SODIUM ALUMINATE FROM THE TREATMENT OF A GEL OF ' ALUMINA BY CAUSTIC SODA AND OR SODIUM ALUMINATE OBTAINED DURING THE SURFACE TREATMENT OF ALUMINUM, BY INCORPORATING ALUMINUM SILICA IN A PROPORTION DEFINED BY THE MOLAR RATIO OF SILICA TO ALUMIN, BETWEEN 60 AND 1, 2, PREFERRED BETWEEN 35 AND 1.7. ZEOLITE HAS OBTAINED ITS APPLICATION IN DETERGENT PREPARATIONS (WASHING POWDERS).

Description

PROCESS FOR PRODUCING ZEOLITE A AND PRODUCTS OBTAINED

  Zeolite A is a compound with ion exchange characteristics, which is incorporated in particular in the

washing powder formulations -

  It is well known to prepare zeolite A by

  reaction in a proper stoichiometric ratio of

  alumina and caustic soda This zeolite A

  must meet certain physical criteria among-

  for example, whiteness or reflectivity

  this, granulometry and sequestering power.

  For a production process to be profitable

  on an industrial scale, it is also necessary that

  operating meters, in particular the separability of the sub-

  sought-after products and products, are easily manageable. Zeolite A is currently produced by

  relatively expensive processes, starting from

  The present invention aims at producing a

  zeolite A of good quality, especially for common use

  rant, namely as an ingredient in washing powders.

  The method of the invention is based on the use

  less expensive reagents than those used

  on the one hand on the use of waste sulfuric acid, in particular as it is produced by the manufacture of titanium dioxide by the "sulphate" process, which is generally, until now, rejected by sea and secondly on the recovery of waste from

  aluminum, in particular products produced during the treatment of

face (anodizing) of aluminum.

  The main feature of the invention is the fact that the silicate gel pulp from the blast furnace slag treatment is used with residual acid, this pulp being made basic.

  by the addition of caustic soda and aluminum aluminate

  dium from a treatment of an alumina gel with caustic soda and / or sodium aluminate obtained during the surface treatment of aluminum; by incorporating

  the silica of the alumina in proportion defined by the ratio

  silica to alumina molar port of between 60 and 1.2,

preferably between 35 and 1.7.

  The Applicant has observed that the transposition in practice of the use of the indicated raw materials for the production of a zeolite A satisfies

  the industrial requirements made it necessary, however,

  using a series of specific techniques

  which will be described in more detail below and which

  as many inventive features.

  According to the invention, it is in particular intended to use a sequence of simple operations to put

  the aforementioned reagents, in order to arrive at the result

  desired state, namely a reduced cost price for a

zeolite A of good quality.

  It is known that granulated slag, obtained by rapidly cooling the molten slag during its

  out of the blast furnace, constitutes an interesting source

  of silica and aluminum There are also differences

  sources of residual sulfuric acid, in particular

  to link that resulting from the manufacture of

  tane or that containing residual sulfuric acid

  constituted for example by depleted etching acids.

  Residual acid compositions from

  of the manufacture of titanium dioxide depend in particular on

  composition of the leached titanium ore The average concentration of sulfuric acid varies between 10 and 20%, the major impurity being ferrous sulphate, the content of which can reach 20 gr of iron per liter. The acid contains other impurities. less important, such

that Al, Mg, Cr, V, Ti, Mn.

  The etching acid residues are characterized by

  also have a high iron content.

  Iron, however, is a particular pollutant

  particularly awful because it tends to finally color the

zeolite A produced.

  In some cases, it is advantageous to enrich the residual acid with aluminum; this aluminum can

  to be a waste of anodizing this metal.

  On the other hand, it has been found that the conditions

254393;

  Dissolving slag must be chosen to keep the silicic acid in a stable state with little polymerization.

  The reaction of the slag which is a basic reagent

  S that with acid proceeds according to the following equation

  (Ca O Si O 2 0.2A 123 0.35Mg O) + 1.95H 504 + 1.05H 20 -

  milk H 2 Si 03 + 0.2 A 12 (504) 3 + 0.6 Mg 504 + Ca 504 2 H 20 The neutralization of the slag is homogeneous, the dissolution of the various constituents taking place at the same speed The products of the reaction are soluble

  in water, except for the gypsum that precipitates the dissolu-

is exothermic.

  In practice, however, it can be seen that a separate

  Gypsum filtration is possible only if the granulometry of the treated slag is

  less than 0,4 mm, preferably 0,2 mm.

  operation of the process of the invention therefore consists of

  generally grind the granulated slag

indicated nullometry.

  The dissolution of the slag is carried out at a constant pH (1.5) while supplying the reactor simultaneously

  by a slag pulp (50% solid) and the acid

  The temperature of the dissolution medium can vary between 60 and 70 ° C. In order that the silicic acid be kept in a state of polymerization as low as possible, care should be taken to respect the following operating parameters: ## EQU1 ## of the reaction must be regulated so that the medium

  remains clearly acidic, the stability of the silicic acid

  that being maximum at p H 1.5; beyond p H 2, the silicon

it polymerizes quickly,

  the concentration of silicic acid is adjusted

  to be close to the optimal concentration

  25 g Si 02 per liter This may involve a dilution of the residual acid which is a function of the content of H 2504 In general, the dilution close to the ratio 1/1 in the case of concentrated concentrated waste acid production of Ti 02 and

  the polymerization rate of silicic acid increases

  Because of the fact that silica gel synthesis is carried out at 40 ° C, it is generally necessary to cool the dissolution medium.

  It is observed that the kinetic curve of dissolu-

  slag is characterized by a fast step and a slow step A near equilibrium is reached after 30

  minutes of contact and the yield of the dissolution cor-

  corresponds to 85% Advantageously, the retention time is set at 30 minutes and the dissolution system consists of two tanks, the material transiting 10 minutes in the first (fast stage) while it stays

  minutes in the second (slow step).

  The agitation of the tanks keeps the slag in suspension in order to achieve a high dissolution rate

  (> 85%) As will be indicated below, it is

  that gypsum suspensions obtained by floating

  during the separation of the gel-gypsum

  recycled at the level of dissolution, this recycling

  risking the formation of larger crystals and reducing

the number of filtrations.

  The dissolution slurry is filtered to separate the gypsum from the silicic acid solution; the

  Gypsum cake is washed to recover all the filtrate.

  The filterability of the gypsum is characterized by the value of S C F T (standard cake formation time); this parameter is defined as the time required for

  a 1 cm thick cake under a different pressure

  atmosphere of an atmosphere The value S C F T average

  of gypsum is 20 + 5 seconds, this diagnostic value

  that the very good filterability of gypsum.

  The gypsum cake is washed with a quantity of water corresponding to the filling of the pore volume and the total recovery of the filtrate is obtained. The gypsum produced is well suited to be recycled in a cement plant provided that it has a high dryness (85-90%). to achieve this objective, the separation of the gypsum can be carried out in two stages: the slurry being filtered on pressurized thickener filter and the cake of

  gypsum is then dewatered on a filter press.

  The silicic acid resulting from the dissolution of the slag, after separation by filtration of the gypsum formed during this dissolution, is then precipitated with concomitant precipitation of a new quantity of gypsum, with the aid of calcium carbonate. according to the equation:

  N Si (OH) 4 + A 13 + 1.5 SO 4 + 1.5 Ca COR -

  (HO) 3 Si O) n Al (OH) 2 + 1.5 Ca SO 4 2 H 20 + 1.5 C 02 + (n 3) H It appeared that obtaining a whiteness zeolite A is subject to the use of a calcium carbonate whose weight content of Fe 203 is less than 0,1% and preferably 0,02

% or less.

  In order to be able to easily filter the insoluble silica gel and gypsum, according to one characteristic of the invention, silica is incorporated with alumina in a proportion defined by the molar ratio of silica to alumina of between 60 and 1. , 2, preferably between 35

  and 1.7 and especially between 35 and 20 or 1.7 and 2 se-

  lon particular embodiments of the invention.

  The precipitation of the silicate gel is carried out

between 2.8 and 4.7.

  A first embodiment of the invention consists in precipitating a silica-rich silicate gel, the ratio of silica to alumina being at least equal to 20%.

  precipitation is preferably carried out at pH 3.2 by simultaneous additions

  The correct dosage of the incorporation of alumina into the silica is obtained by a careful adjustment of the precipitation pH. Below pH 2.8, the precipitation of the solution of the silicate gel and the calcium carbonate is obtained.

  silica is incomplete; the gel obtained is infiltrable.

  Above p H 4, too much alumina is incorporated into the silica. The gel is precipitated at 40 ° C.

  without heat input The silica sol must be

  cold because a reaction temperature above 400 C

  cause the precipitation of iron oxide.

  The precipitation of silica gel is very slow

  However, it is advantageous to maintain the reactions

  in the reactor for one hour to ensure complete dissolution of the calcium carbonate.

  The agitation system must allow the homogeneity

  the reaction medium to prevent sedimentation

  calcium carbonate in the bottom of the reactor.

  Under such conditions, the yield of the precipitation

silica reaches 100%.

  The gel-gypsum mixture is then separated from the mother liquor by vacuum filtration; the filtrate is

  preserved because it contains aluminum sulphate

  the recovery will be described below The cake

  is washed on the filter with water at pH 2 in order to

  The sequence of at least three washings is preferable, the volume of water of each wash corresponds to the pore volume of the cake.

  process, after purification and acidification, may be

for washing.

  Filterability of the cake of the mixture is observed

  gel-gypsum corresponding to a value S C F T of the

  40 seconds Because of the quality required of the

  vage, a (vacuum) band filter is appropriate.

  The separation of the two constituents of the mixture is then carried out by flotation of the gypsum This operation is carried out on a pulp whose solids content reaches 120 g / l and whose p H is between 3.0

and 3.5, preferably.

  The technique of separating gypsum and silica gel by flotation is an elegant way

  and effective to separate the components under conditions

  which, on their face, may seem to cause significant difficulties as a result of the presence of the

siliceous gel.

  The Applicant has observed in this respect that the

  use as a collector of dodecylamine (laurylamine) alone or mixed with other amines containing a fatty hydrocarbon chain (for example C 16) gives

  separation results that other compounds equally

  used in other circumstances as a collector

do not allow to get.

  By way of illustration, it may be mentioned that the use of a mixture of tallow and coconut amines can be provided as a gypsum collector, at a dosage which is a function of the amount of gypsum produced. Gypsum is excellent (99%)

  the loss of silica gel caused by gypsum is

  ble (8%) The dry matter content of the gel pulp

reaches 10% -

  At the operating level, the thickened pulp is kept as it is. The gypsum pulp is recycled into

the step of dissolving the slag.

  In the aforementioned working conditions, the

  silica gel synthesis solution contains aluminum

  recoverable minium at a content of the order of 6.3 g / l.

  This aluminum carried by the mother solution of

  silica gel is thus precipitated selectively by

  Calcium carbonate solution The overall precipitation reaction is represented by the equation v (Al <OH) 3 _n * 2 SO 4 _ + N Ca CO 3 (n + 1.5) H 2 O -Al (OH) 3 + 3-n 2 4 2 'n Ca SO 4 2 H 20 + N CO 2 2 So a precipitate of gypsum is formed at the same time

time as the alumina gel.

  It has appeared, according to a feature of the invention, that the subsequent separation of gypsum by

  flotation is facilitated if, prior to the precipitation

  of alumina, a certain amount of

  silicic acid soluble in the solution containing aluminum

  The addition of a small amount of soluble silicic acid corresponding approximately to the molar ratio SiO gives the gel surface properties which allow

  the separation of gypsum by flotation.

  Various techniques can be used to

  the precipitation of alumina in the gel state.

  Advantageously this precipitation is achieved

  in two stages. In a first stage, which takes place

  at a constant pH of about 3.9, the solution of aluminum and calcium carbonate is added simultaneously.

  (duration of the reaction of the order of 2 hours)

  with regard to the purity of carbonate of calcium

  used are less severe than when precipitating

  In particular, it has been found that a content of Fe 203 which can reach

  the order of 0.08% does not cause serious inconvenience.

  The precipitation is then completed (in thirty minutes) in a second stage at p H of the order of 4.6 by adding caustic soda contained in the stock solution of zeolite A. This technique ensures a good reactivity of the carbonate

  of calcium and serves to purge the crystallization circuit.

  zeolite A, the volume consumed of the stock solution

  solution A equals the purge required for balancing

  to break the material balance (water and impurities) of the system.

  It should be ensured that the pH of the second stage does not exceed 4.6, otherwise iron oxide precipitation will occur. Precipitation does not require a heat input; the temperature of the reaction medium reaches

  at most 40 ° C, the temperature of the mother-water of the gel of

  The agitation must be sufficient to maintain the

  solid phase in suspension The yield of the precipitate

  alumina reaches 100% under the conditions

indicated.

  The alumina-gypsum gel mixture is filtered and washed. The alumina gel pulp is characterized by a filterability having a SCFT value which can vary between 1 and 3 minutes. Pressure filtration on a thickening filter is suitable, given the low (5%) solids content of the suspension. The cake is washed to remove soluble salts, washing being

  performed on the pressure filter.

  The two are then separated

  components of the gypsum flotation mixture.

  ration is carried out on a pulp whose content in so-

  lide is fixed at 120 g / l and whose pH is between 4.5 and 5 The water of the process after purification is used for pulping The gypsum pulp, collected at the end of the flotation is preferably recycled at the level of

dissolution of the slag.

  Advantageously, the mixture of tallow amine and

  coconut is used as a gypsum collector

  which depends on the amount of gypsum produced.

  As a variant of the described technique, a second

  me mode of precipitation of alumina gel is possible.

  In order to do this, the metals of the residual solution are precipitated at a constant rate by means of aluminate.

  and then the aluminum is precipitated selectively

  nium at p H of about 4.3 constant by means of the suspension

  obtained in the previous step The gel obtained has

also good filterability.

  The second embodiment of the invention consists in precipitating a silicate gel rich in aluminum, the molar ratio of silica to alumina being between 20

  and 1.2 and preferably between 2 and 1.2 This high content

  aluminum is feasible if the waste acid is previously enriched in aluminum, for

  adding anodizing waste.

  The precipitation of silicate gel rich in aluminum

  minium is carried out between p H 4 and 4.7, preferably at p H

  4.2 by simultaneous additions of the silicic acid solution

that and calcium carbonate.

  The gel is precipitated at 40 ° C. without calorie

  The silica sol must be cooled because a reaction temperature greater than 40 OC would cause the precipitation of iron oxide The precipitation of the silicate gel is very rapid, however it is advantageous to keep the reagents in the reactor for one hour in order to ensure complete dissolution of the calcium carbonate.

  The agitation system must allow the homogeneity

  the reaction medium to prevent sedimentation

  calcium carbonate in the bottom of the reactor.

  Under such conditions, the yield of the precipitation

  silicate gel reaches 100%.

  The gel-gypsum mixture is then separated from the mother liquor by vacuum filtration. The cake is washed

  with water at p H 2 so as to reduce as much as possible

  iron neur Filterability of the gel-gypsum mixture is

  characterized by a S C F T of 22 seconds.

  The separation of the two constituents of the mixture

  is then carried out by flotation of the gypsum; the opera-

  It is carried out on a pulp whose solids content reaches 120 g / l and whose pH is preferably between 4.2 and 5.

  The separation efficiency of the gypsum is excellent

  slow (99%); the loss of silicate gel caused by the gypsum is low (8%) The silicate gel pulp (10% of dry matter) is preserved as it is while the

  gypsum pulp is recycled into the dissolution of the

  tier. The zeolite A is then synthesized in three steps: conditioning of the reagents; formation of the reaction mixture

  crystallization of zeolite A, filtration and

of it.

  The invention makes it possible to synthesize zeolite A in two ways depending on whether the reaction mixture is prepared either from silica and alumina gels.

  either from a silicate gel rich in aluminum.

  In a first mode of synthesis that is particular to the invention, the reaction mixture is formed from an alkaline suspension consisting of silica gel, sodium aluminate and caustic soda.

  of the mixture is fixed by the molecular ratios

  2 Si 2 Na 2 H 2 O O 1.7 2 = 1.8 and 2 33 2 3 Si 2 Na The addition sequence of the reactants in the formation of zeolite A was found to be important

in order to obtain good results.

  The conditioning of the reagents consists of

  trace the silica and alumina gels precipitated in acidic medium, with caustic soda and then to provoke a

attack in caustic soda.

  The silica and alumina pulps (100 g gel / l) obtained at the end of the flotation stages of the gypsum are first neutralized to pH 10, respectively to

  fresh brine of caustic soda and desiccants

  residual aluminate from the workshops of

* anodizing Neutralization is performed at room temperature

  room temperature up to p H = 10 Neutralization of the gel

  of alumina causes the precipitation of aluminum

  driven by residual aluminate solutions; the recap-

  This pulp is complete Neutral pulps are dewatered on a filter press to obtain a dryness of at least 35%. To balance the water balance, the volume of hydration of the cakes-filtration

  is replaced by an equivalent volume of syn-

thesis of zeolite A.

  The silica gel is attacked at ambient temperature

  The amount of sodium hydroxide used corresponds to the molar ratio Na 2 O = 0.8 SiO 2. The attack of the gel is rapid (3 minutes) but

  incomplete and an insoluble residue of silica remains.

  The alumina gel is dissolved at room temperature

  biante in a solution of caustic soda, consisting of the solution enriched with soda enrichment

  corresponds to the soda consumed by the purge

  The gel is made in 15 minutes.

2543939.

  silica associated with the alumina gel are very poorly soluble in alkaline medium; they form a precipitate polluting the

sodium aluminate solution.

  This residue is filtered under pressure and washed.

  yield of the dissolution is 90%; the composition of the solution obtained is characterized by the molar ratio Na 2 = 2

A 12 03

  The formation of the reaction mixture comprises the

  mixing reagents and predigestion.

  It appeared that two modes of addition of

reagents are possible.

  In the case of a batch process, it is

  useful that the addition sequence of the reagents of the

  mulation of zeolite A is: a sodium aluminate solution

b basic silica pulp.

  The reagent mixture can also be

  killed in steady state The alkaline pulp of silica and the

  sodium aluminate solution are fed simultaneously

  in this case, to the mixing tank and the flow rates of reagents are adjusted in order to achieve and maintain

  constant formulation of the mixture.

  In both cases, the agitation is adjusted so as to allow rapid homogenization of the reagents

  because the operation generates a thick gel.

  In a second particular mode of synthesis to the invention, the reaction mixture consists of an alkaline suspension consisting of silicate gel rich in alumina and caustic soda. The formulation of the mixture is fixed by the following molecular ratios Si 2 Na 2 O 2 1.7; = 1.8 and = 33 A 203 Si O 2 Na The conditioning of the silicate gel pulp rich in aluminum consists of neutralizing it with sodium hydroxide

  caustic up to p H 10 The mother-solution of the crystal -

  zeolite A can be used to advantage.

  for neutralization; this procedure allows

  eliminate the trace elements Chrome and Vanadium The pulp

  neutral pe is then filtered; the volume of hydration of the cake is replaced by an equivalent volume of synthetic solution of zeolite A in order to balance the

water balance.

  The silicate gel rich in aluminum is then etched at room temperature in a sodium hydroxide solution consisting of the mother-water of crystallization enriched with caustic soda. The amount of sodium hydroxide employed corresponds to the molar ratio Na.sub.20 = 1.8 i SiO.sub.2. According to the two methods of preparation described, the reaction mixture is directed to a digestion tank

  o It stays for 12 hours at room temperature.

  The zeolite A crystallization is finally caused by heating to 85 ° C. of the reaction mixture.

  during 2 hours; good agitation ensures homogeneity

  the environment whose solids content has

  tint 16% The yield of the crystallization is%. The crystalline solid is separated from the mother liquor by filtration, the filterability of the zeolite pulp

  being characterized by a value S C F T of 2 minutes.

  The solid is filtered and washed with deionized water until the p H of the pulp is 10.5 The humidity of the cake

  Vacuum filtered can reach 58%.

  The zeolite can be delivered in two different forms: either in suspension, a mixture of sodium polyacrylate (fluidization agent for atomization) and phosphate, preferably sodium polyphosphate, being added at a rate of 0.3% to the filtered pulp in order to obtain a fluid suspension at 40% dry matter, or in powder form, the zeolite paste being dried from

  to obtain a dispersed powder after drying.

  The invention will be described in more detail with reference to the accompanying examples which are intended to illustrate

  the invention, without limitation.

EXAMPLE 1

1 DISSOLUTION OF THE DAIRY.

  The granulated slag is dissolved in a waste acid from the manufacture of titanium dioxide; the composition of these two reagents is given below: Granulated slag Residue acid Component Proportion,% Constituent content, g / l If O 34.13 H 22504 184.4 Ai 2 12.63 Fe 2 + 19.16 2 3 Mg O 8.39 Ai 4.17 Ca O 34.86 Mg 5.13 Fe 2 O 0.96 Na 0.84 Mn O 0.54 V 0.96 K 1.37 Cr 0.26 Na 0.94 Ti 2 3.61 Ti 2 0.78

S 1.4

  Crushed slag pulp (0 <0.2 mm) is

  used while the waste acid is diluted

  to dissolve It is added to the slag pulp

  crushed gypsum suspensions obtained after separation

  silica and alumina gels.

  The dissolution is carried out at pH 1.5, in

  me continuously, in a system consisting of two reactors (15 and 28 liters) each equipped with 3 baffles and stirred

  in order to keep the solids in suspension.

  The reagents are introduced into the first tank by

peristaltic pumps.

  The supply of slag is constant while that of the acid is subjected to the measurement of the p H The contents of the first vat overflows in the second, the system

  the system is adjusted to achieve an average stay of 30 minutes in the reactors These conditions allow

  obtain a dissolution yield of 85%.

  The hourly consumption of the reagents is the following slag pulp comprising 6.65 kg of crushed slag, 4.38 kg of gypsum and 11.03 l of water, acid solution comprising: 31.8 l of acid and 28.33 1

dilution water.

  Hourly production of silicic acid pulp

  that is 77.16 1; the solids content is 5%. The acid pulp is filtered and washed on a vacuum filter (vacuum = 0.3 bar) at a rate of 1.3 l per m 2 and per second; under these conditions, the thickness

  of the cake measures 10.5 mm The composition of the acid

  separated from gypsum is shown below.

  Constituent Content, g / i Si 02 25 Ai 7.03 Fe 10.55 Mg 6.53 Ti-2 1.85 Cr 0, 14

V 0.49

Na 0.99

K 0.86

2 PRECIPITATION OF SILICA GEL,

  The precipitation of the silica gel is carried out

  at pH 3.2 by adding calcium carbonate to the solution

  silicic acid calcium carbonate is used

  as a 25% suspension; the particle size

  preferred range is less than 55 microns while the -

  iron oxide content does not exceed 0.02%.

  The precipitation plant consists of two tanks with a useful volume of 40 liters; they are internally equipped with 3 baffles and a heating resistor for carrying out the precipitation at 40 ° C. Stirring of the vats brings about the complete suspension of the solid phase. The reagents are introduced simultaneously into the first vat by pumps; the

  synthesis mixture then overflows into the second tank.

  The synthesis rates are set to maintain the

  gel for one hour in the synthesis medium A system

  electrode system measures the precipitation and

  mandates the servo regulating the flow of calcium carbonate.

  The hourly consumption of reagents is

  wind at 77.16 l silicic acid and 0.698 kg carbonate

  of calcium The pulp of silica gel and gypsum

  picking has a dry matter content of 5%.

  The inorganic mixture is filtered and washed with acidified water (p H 2) on a vacuum filter; washing is continued

  until complete elimination of iron.

  This solid-liquid separation is carried out at a rate of 0.37 l of pulp per m 2 and per second; the filter depression is 0.3 bar Under these conditions,

  the thickness of the cake is 11 mm.

  The flotation separation of silica gel and gypsum is carried out on a pulp containing 120 g of solid per liter, the separation requires roughing and

  finishing A mixture of tallow amine (C 16) and co-

  co (C 12) is used as a collector at the rate of 150 and 600 g respectively per tonne of product to be separated;

  pine oil is the foaming agent.

  Taking into account the efficiency of the separation,

  the hourly masses of the separated products are the following

: silica gel 2.33 kg,

gypsum 2.33 kg.

  The volume of stock solution, containing the alumina

nium is 77.16 1.

  The compositions of silica gel and water

  mother are given below: Silica gel Mother water Component Proportion,% Constituent g / 1 content Sio 2 78.1 Ai 6.3 Ai 203 3.81 Fe 2 + 10.55 Fire loss 8.7 Mg 6, 53 Cr 2 3 0.17 Mn 0.30 F 2 3

2 3 0.08 K 0.86

Ti 02 8.85 Na 0.99

V 2 05 0.34

3 PRECIPITATION OF ALUMINA GEL.

  Prior to the precipitation of the aluminum gel

  mine, a solution of silicic acid is added to the solution.

  aluminum containing mother, in order to achieve the molar ratio Si 02 = 0.1 Ai 2 O 3 Precipitation is carried out in two stages in an installation similar to that used for

precipitate the silica gel.

  In a first stage, the pH is raised to 3.9 by addition of a suspension of 25% calcium carbonate;

  the particle size of the carbonate is less than 55

  The residence time of the reagents in the reactors is two hours, the temperature reaches 400 ° C. In a second stage, the pH is raised to 4.6 by the addition of caustic soda from the synthetic water of zeolite A. The hourly consumption of reagents amounts to 77.16 l of aluminum solution to which 2.16 l of

  silicic acid solution (25 g / l), 1,247 kg of car-

  calcium bonate and 0.3 kg of caustic soda.

  The pulp of alumina gel and gypsum produced has a dry matter content of 5.2%; The mixture

  mineral is filtered and washed on a vacuum filter.

  The filtration which is followed by the washing is carried out at the rate of 0.53 l of pulp per m 2 and per second; the depression of the filter is 0.3 bar. In these conditions the thickness of the cake is 8 mm. The flotation separation of the gel of alumina and gypsum is carried out on a pulp containing 120 g of solid per liter; separation requires roughing

and two finishes.

  A Wedag machine, model MN 935/4, equipped with

  a 6-liter cell is used for flotation.

  A mixture of tallow amines and coconut is used.

  as a collector at the rate of 450 g of mixture per ton of solid to be separated; pine oil is the foaming agent. Taking into account the efficiency of the separation, the hourly masses of the separated products are as follows: 1.75 kg alumina gel

gypsum 2.14 kg.

  The volume of the residual solution amounts to 77.16. The composition of the alumina gel produced is given below: Component Proportion,% Al 2 03 57.71 Fe 2 O 3 2.45

SO 3 5.72

Loss on fire 30.65 Insoluble 1.54

4 SYNTHESIS OF ZEOLITE A.

1 Conditioning reagents.

Neutralization of gels.

  The pulp of silica and alumina (10% of

  dry matter) are neutralized to pH 10 by means of caustic soda. The neutralization is carried out under continuous conditions at room temperature.

  the neutralization reaction are shown below.

  gel If 2 gel A 1203 treated mass 2.33 kg 1.94 kg p H pulp before neutralization 3-3.5 4.5-5 neutralizing agent Na OH, brine NaOH aluminate 365.8 g / i waste ( 80 g NaOH / 1 and g A 1203/1 consumption, g / mole 6.77 40.8

  The neutralized gels are filtered, the improper water

  1 Sealing the cakes is exchanged by the zeolite A stock solution.

  The consumptions of mother water are respectively

  4.331, and 3.6 1 for silica gel and alumina.

b Attack of freezes.

  Neutralized gels are attacked in regime

  discontinuous at room temperature in caustic soda

  that according to the conditions listed below:

gel Si 2 -

  Brine Na OH, 365.8 g / 1 Consumption Composition solution

4.14 1

  Na 20 = 0.8 Si 2 gel A 1203 stock solution zeolite enriched NaOH, 33 1 + 514 g NaOH Na 20 = 2

A 12 3

  Clarification of the solution Reagent + The sodium aluminate solution is clarified to remove insoluble impurities (iron oxide and silica).

  2 Reagent mixing and predigestion.

  The two liquids obtained by attacking the gels

  are pumped simultaneously into a tank equipped with 3

  canes and stirred to achieve a homogeneous mixture of both currents The flow rates of reagents are balanced to maintain constant the formulation of the mixture which is represented by the molar ratios Si 02 Na 2 1 H 2 O = 1.7; = 1.8 and = 33

12 3 2 2

  The reaction mixture is matured one night at

room temperature.

3 Crystallization.

  The reaction mixture is heated to 85 WC

  2 hours; the reactor is agitated to maintain

the solid phase in suspension.

  The solid is separated from the mother liquor by filtration.

  under vacuum; the crystals are washed with deionized water

  until the p H of the dough is 10.5.

  The product obtained identified by X-ray diffraction is zeolite A; its chemical composition is given below: Constituent Proportion,% Si 02 32,31 Ai 2 03 31,05 Na O 18,03

H 12.90

  Ti 02 4.30 e 2 3 0.05 The main features are given below: Reflectance: 91 Hunter coordinates

Smell: without -

  Granulometry less than 10 p: 94%

6: 82%

50%

  p H (1% anhydrous in aqueous suspension): 10.4 weight loss after 50 minutes at 800 ° C.: 21% sequestering power at 25 ° C. per g of anhydrous zeolite after 15 minutes: 150 mg Ca O The zeolite A obtained is usable as a calcium sequestering agent in a washing powder formulation.

EXAMPLE 2

1 DISSOLUTION OF THE DAIRY.

  Granulated slag is dissolved in an acid

  waste from the manufacture of

  tane; the composition of these two reagents is given below.

  below: Granulated slag Residue acid Component Proportion,% Constituent Content, g / l Si 02 34.13 H 2 SO 4 205.4 A 12 03 12.63 Fe 2 + 19.6 Mg O 8.39 A 1 4.6 Ca 0 34.86 Mg 5.8 Fe 2 03 0.96 Na 0.84 Mn O 0.54 V 0.68 K 1.37 Cr 0.25 Na 0.94 Ti 02 2.9 Ti 02 0.78

S 1 4

  Before dissolution, the acid remains

  duaire is enriched in aluminum by addition of a waste resulting from the anodization of aluminum; this waste has

  the following composition: NaOH 102 g / l, A 1203 172 g / l.

  The enrichment is carried out in order to obtain a molar ratio SiO 2 molar 2 = 1.49 in the solution resulting from the

A 1203

  dissolution of the slag Practically, 0.1 liter of a solution containing 102 liters of residual acid is added per liter.

g / 1 NaOH and 172 g / l at 1203.

  The composition of the aluminum-enriched acid is as follows Aluminum-enriched residual acid Constituent Content, g / l

H 2 S 4 130.34

  Fe 2 + 17.64Ai 12.75Mg 5.22 Na 6.62

V 0.61

  Cr 0.22 Ti O 2 2.61 The dissolution of the slag is carried out in

  conditions similar to those described in Example 1.

  The hourly consumption of the reagents is as follows: slag pulp comprising: 5.75 kg of crushed slag, 9.18 kg of gypsum and 11.2 l of water; acid solution comprising: 40.5 l of acid and 10.29 l

dilution water.

  Hourly production of silicic acid pulp

  that is 70 1; the dry matter content is

21.8%.

  The acid pulp is filtered and washed on a vacuum filter (vacuum = 0.3 bar) at a rate of 1.0

  by m and per second; under these conditions, the thick

  cake size is 10.5 mm The composition of the acid

  silicic acid separated from the gypsum is shown below.

  Constituent Content, g / l Si 2 22.77 Ai 13.73 Fe 2 + 12.70 Mg 7.12 Ti 02 2.37 Cr 0.15

V 0.42

Na 5.09

K 0.97

2 PRECIPITATION OF SILICATE GEL

  The precipitation of the silicate gel is carried out at pH 4.2 by adding calcium carbonate to the silicic acid solution. The precipitation of the silicate gel is carried out under conditions similar to those described.

in example 1.

  The hourly consumption of reagents is

  wind at 70 l of silicic acid and 5.34 kg of calcium carbonate The silicate gel and gypsum pulp produced has a solids content of 20%. The mineral mixture is filtered and washed with acidified water ( p H 2) on a vacuum filter, washing is continued until

total elimination of iron.

  This solid-liquid separation is carried out at

  because of 2.0 1 of pulp per m 2 and per second; the-

  filter pressure is 0.3 bar. Under these conditions,

  the thickness of the cake is 11 mm.

  The flotation separation of silica gel and gypsum was carried out on a pulp containing 120 g of solid per liter, the separation requiring roughing and finishing. A mixture of tallow amine (C 16) and coconut (C 12) is used as a collector at a rate of 300 and 1200 g respectively per ton of oroduct to be separated,

  pine oil is the foaming agent.

  Taking into account the efficiency of the separation,

  the hourly masses of the separated products are the following

lowing

silica gel 4.67 kg.

gypsum 9.58 kg.

  The volume of stock solution is 70 l.

  The compositions of silica gel and water

  mother are given below: Silica gel Mother water Component Proportion,% Constituent content g / l Si 02 31.38 A 12 03 36,27 Fe 2 + 12,70 Loss on fire 24,37 Mg 7,32 Cr 2 03 0.14 Na 5.09 Fe 303 0.32 K 0.97 Tic 2.9

V 205 0.66

3 SYNTHESIS OF ZEOLITE A

1 Conditioning of the silicate gel

Neutralization of the silicate gel.

  Silicone gel pulp (10% of material

  dry matter) is neutralized to pH 10 by means of

  The mother of the crystallization The neutralization is carried out in continuous mode, at room temperature The characteristics of the reaction of neutralization are

indicated below.

  treated mass 4.67 kg p H of the pulp before neutralization 4.2-5 neutralizing agent Na OH, stock solution of crystallization at 97.3 g / l Consumption, g Na OH / mole 19.6 Si O 2) neutralized gel is filtered, the water impregnating the cake is exchanged by the mother solution of zeolite A.

  The consumption of mother liquor is 4.9 1.

* b Attack of silicate gel and predigestion.

  The neutralized gel is attacked in a discon-

  at room temperature in caustic soda under the conditions listed below Reagents: brine Na OH (365.8 g / l) crystallization stock solution (97.3 g / l) Consumption: sodium brine: 3, 96 1 mother solution of crystallization: 21.2 1

  Sodium brine is added to the silica gel

  you; after dispersion of the mixture, the mother solution of crystallization is added. The suspension obtained is

  stirred and matured for 12 hours.

2 Crystallization.

  The reaction mixture is heated to 85 ° C.

  2 hours; the reactor is agitated to maintain

the solid phase in suspension.

  The solid is separated from the mother liquor by filtration.

  under vacuum; the crystals are washed with deionized water

  until the H-weight of the dough is 10.5.

  The product obtained identified by X-ray diffraction is zeolite A; its chemical composition is

  identical to that given in example 1.

  The main characteristics are given below. 91 Hunter's co-ordinates Odor without particle size less than 10 Vi 95% 6 i 94% 4 j 90% p H (1% anhydrous in suspension): 10.4 weight loss after 50 minutes at 800 OC: 21% sequestering power at 25 OC per g of anhydrous zeolite after 15 minutes: 151 mg Ca O The zeolite A obtained can be used as a calcium sequestering agent in a powder formulation.

washing.

  In the attached drawing plates, there are shown block diagrams representing the

  operating phases according to the examples.

  FIGS. 1 and 2 refer to example 1 and represent, respectively, on the one hand the acid neutralization and the synthesis of gels and, on the other hand, the synthesis of zeolite A. FIGS. 2 and 3 refer to Example 2 and represent respectively the synthesis of the silico-aluminum compound and the synthesis of zeolite A.

Claims (19)

  A process for the manufacture of zeolite A by reaction in an aqueous medium of silica, alumina and caustic soda in a suitable stoichiometric ratio, characterized in that a silicate gel pulp from the blast furnace slag treatment is used. using residual acid, this pulp being made basic   by addition of caustic soda and sodium aluminate   dium from the treatment of an alumina gel with caustic soda and / or sodium aluminate obtained during the surface treatment of aluminum, incorporating   the silica of the alumina in proportion defined by the ratio   silica to alumina molar port of between 60 and   1.2, preferably between 35 and 1.7.   2 Process according to claim 1, characterized in that the crushed slag with a particle size of less than 0.4 mm and preferably less than 0.2 mm is dissolved at p H between 0 and 2, preferably of the order of 1 , And that the formed gypsum is separated by filtration of the solution.   3. Process according to claim 1 or 2,   terized in that it causes the precipitation of a gel   of silica by the addition of a calcium carbonate present   both a weight content of Fe 203 less than 0.1   % preferably of the order of 0.02% or less.   Process according to any of the claims   cations 1 to 3 characterized in that it incorporates   Alumina ratio in proportion defined by the ratio   silica to aluminum molar between 35 and 20.   A method according to any of the claims   cations 1 to 4 characterized in that the precipitation of the silica gel is carried out at a pH between 2.8 and 4, preferably of the order of 3.2.   Process according to any of the claims   cations 1 to 5 characterized in that the gypsum is separated from the mixture of silica gel and gypsum by flotation,   the gypsum being collected in the foam.   Process according to any one of the claims   cation 1 to 6 characterized by causing the precipitation   tation of the aluminum contained in the mother liquors of the silica gel synthesis, in the presence of a soluble silica content such as the molar ratio Si 2 If 02 is of the order of 0.1. Al 2 O A 2 3   Process according to Claim 7, characterized in that the separation of the mixture of alumina gel and   gypsum is carried out by flotation, the gypsum being picked in the moss.   Process according to claim 8, characterized in that the flotation separation operation of   gypsum of the mixture of alumina gel and gypsum is   killed on a pulp whose solid content is gold   dre of 120 g / l the p H is between 4.5 and 5.   Process according to claim 8 or 9   characterized in that the collector is   gypsum, dodecylamine, alone or in combination with other   very fatty hydrocarbon chain amines.   The process according to claim 10   rised by using a mixture of tallow amines and coconut.   The process according to claim 10 or 11   characterized in that the separated gypsum pulp is recycled   key to the dissolution of the slag.   Process according to any of the claims   1 to 12, characterized in that the precipitation of the alumina gel is carried out by adding carbonate of   calcium in two successive steps, the first   so, at constant P H of the order of 3.9 in the addition   multi-solution of aluminum and calcium carbonate and the second, taking place at a constant pH of 1 '   4.6 being carried out by addition of caustic soda.   tick from the parent solution of zeolite A.   Process according to any one of the claims   1 to 13, characterized in that the precipitation of the alumina gel is carried out by precipitating the metals of the residual solution with a solution of   caustic soda which may contain residual aluminate   then selectively precipitating the aluminum   nium at pH 4.3 with the suspension obtained in the first step;   Process according to any one of the   cations 1 to 14, characterized in that the solution   aluminate the basic silica pulp either batchwise according to the addition sequence a) sodium aluminate solution b) silica basic pulp or continuously mixing these two simultaneously reagents in the mixing tank.   Process according to any one of the claims   cations 1 to 15 characterized in that it incorporates   alumina in a proportion defined by a ratio   silica to alumina molar between 1.2 and 2.   Method according to claim 16, characterized   in that the corresponding alumina content is achieved   silica to alumina ratio of 1.2 to 2 per   reduction of the waste acid used for the treatment of   blast furnace slag by means of anodized waste aluminum.   Process according to any one of the claims   cations 6 to 17, characterized in that the separation operation   ration by flotation of the gypsum is carried out on a pulp   whose solids content reaches 120 mg / l and the pH is kill between 3.0 and 5.   19. A method according to any of the claims   cations 6 to 18, characterized in that gypsum or dodecylamine, alone or as a mixture with other amines containing a fatty hydrocarbon chain, is used as collector agent.   Process according to Claim 19, characterized   rised by using a mixture of tallow amines and coconut.   Method according to any of the claims   cations 5 to 20 characterized in that the separated gypsum pulp is recycled to the slag dissolution.   22 Products obtained by the process of a conque of claims 1 to 21.