INSTALLATION FOR THE PURIFICATION OF MINERALS, PIGMENTS AND/OR FILLERS AND/OR THE PREPARATION OF PRECIPITATED EARTH ALKALI CARBONATE

Abstract

The present invention relates to an installation for the purification of minerals, pigments and/or fillers and/or the preparation of precipitated earth alkali carbonate and/or mineralization of water and to the use of such an installation for the purification of minerals, pigments and/or fillers and/or mineralization of water and/or the preparation of precipitated earth alkali carbonate.

Claims

1. A process for the purification of minerals, pigments or fillers, the preparation of precipitated earth alkali carbonate, or the mineralization of water, comprising purifying minerals, pigments or fillers, preparing precipitated earth alkali carbonate, or mineralizing water using an installation comprising in fluid communication: a) at least one mixing unit provided with at least two inlets and at least one outlet, b) at least one dividing unit comprising dividing means, and c) at least one membrane filtration unit provided with at least one inlet and at least one outlet, wherein at least one outlet of the at least one mixing unit is connected to at least one inlet of the at least one membrane filtration unit and at least one outlet of the at least one membrane filtration unit is connected to at least one inlet of the at least one mixing unit.

2. The process according to claim 1, wherein the at least one mixing unit comprises a stirring device.

3. The process according to claim 1, wherein the at least one mixing unit comprises a heating device capable of heating the content of the at least one mixing unit to a temperature of between 5° C. and 90° C. or between 20° C. and 50° C.

4. The process according to claim 1, wherein the at least one dividing unit is at least one grinding device and/or at least one crushing device.

5. The process according to claim 1, wherein the at least one dividing unit is at least one vertical grinding device and/or at least one vertical crushing device or at least one horizontal grinding device and/or at least one horizontal crushing device.

6. The process according to claim 1, wherein the at least one dividing unit is a conical annular gap bead mill.

7. The process according to claim 1, wherein the at least one dividing unit comprises dividing means having a weight median particle diameter d.sub.50 value of from 0.01 mm to 100 mm, or from 0.1 mm to 75 mm, or from 0.5 mm to 5 mm.

8. The process according to claim 1, wherein the at least one dividing unit comprises moving beads as dividing means made of a material selected from the group comprising quartz sand, glass, porcelain, zirconium oxide, zirconium silicate and mixtures thereof, optionally comprising minor quantities of further minerals.

9. The process according to claim 1, wherein the dividing means of the at least one dividing unit are made of a mineral, pigment and/or filler material.

10. The process according to claim 1, wherein the dividing means and the minerals, pigments and/or fillers to be purified and/or to be prepared are of the same material.

11. The process according to claim 1, wherein the at least one membrane filtration unit is a cross flow membrane filtration device, a cross flow membrane microfiltration device and/or a cross flow membrane ultrafiltration device.

12. The process according to claim 11, wherein the at least one membrane filtration unit is a cross flow membrane filtration device comprising at least one tube filter membrane having an inner diameter of the tube from 0.01 mm to 25 mm, or from 0.1 mm to 10 mm.

13. The process according to claim 11, wherein the at least one membrane filtration unit comprises at least one membrane having a pore size of between 0.01 μm and 10 μm, or of between 0.05 μm and 5 μm, or of between 0.1 μm and 2 μm.

14. The process according to claim 13, wherein the membrane is made from a sintered material, a porous porcelain, a synthetic polymer, polyethylene, polypropylene, Teflon®, or any mixture thereof.

15. The process according to claim 11, wherein the at least one membrane filtration unit is a cross flow membrane filtration device having a speed of flow across its at least one membrane of between 0.1 m/s and 10 m/s, or between 0.5 m/s and 5 m/s, or between 1 m/s and 4 m/s, and/or an inlet pressure of between 0 bar and 30 bar, or between 0.2 bar and 10 bar, or between 0.5 and 5 bar.

16. The process according to claim 1, wherein the installation comprises at least three outlets, or at least four outlets, or at least five outlets and/or the installation comprises at least four inlets, at least five inlets, or at least six inlets.

17. The process according to claim 1, wherein the at least one mixing unit comprises at least two outlets and/or at least three inlets, or at least four inlets.

18. The process according to claim 1, wherein the installation comprises at least one gas inlet.

19. The process according to claim 18, wherein the gas inlet is a CO.sub.2 inlet.

20. The process according to claim 1, wherein the at least one mixing unit comprises at least two inlets being liquid inlets, or at least three liquid inlets, or at least four liquid inlets.

21. The process according to claim 1, wherein the installation comprises at least one control unit regulating the filling level of the at least one mixing unit, pump speed, pH, conductivity, calcium ion concentration optionally by ion sensitive electrode, and/or temperature.

22. The process according to claim 1, wherein the installation comprises at least one pump located between the at least one mixing unit and the at least one membrane filtration unit.

23. The process according to claim 1, wherein at least one outlet of the at least one mixing unit is connected to at least one inlet of the at least one dividing unit and at least one outlet of the at least one dividing unit is connected to at least one inlet of the at least one mixing unit.

24. The process according to claim 1, wherein the installation further comprises at least one pump located between the at least one mixing unit and the at least one dividing unit.

25. The process according to claim 24, wherein the pumping capacity of the at least one pump (in m.sup.3/h of the sum) feeding the at least one membrane filtration unit is 0.01 to 100 times the volume of the at least one mixing unit and/or the ratio of the pumping capacity of the at least one pump (in m.sup.3/h of the sum) feeding the at least one dividing unit to the pumping capacity of the at least one pump (in m.sup.3/h of the sum) feeding the at least membrane filtration unit is between 1:1 and 1:1000, or between 1:5 and 1:250.

26. The process according to claim 1, wherein the at least one dividing unit is integrated in the at least one mixing unit.

27. The process according to claim 1, wherein at least one inlet being a gas inlet is located between the at least one mixing unit and the at least one dividing unit, or between a feed pump of the at least one dividing unit and the at least one dividing unit, or at the inlet of the dividing unit.

28. The process according to claim 1, wherein at least one inlet being a gas inlet is a venturi injector that is located between the at least one mixing unit and the at least one dividing unit, or is located between the outlet of the at least one mixing unit and the inlet of the at least one dividing unit.

29. The process according to claim 2, wherein at least one inlet being a gas inlet is located at the top of a hollow shaft of the stirring device of the at least one mixing unit.

Description

FIGURES

[0213] FIG. 1 illustrates an installation as described in the prior art.

[0214] FIG. 2 illustrates an embodiment of the present installation comprising a mixing unit, a dividing unit and a membrane filtration unit, wherein at least one outlet of the at least one mixing unit is connected to at least one inlet of the at least one membrane filtration unit and at least one outlet of the at least one membrane filtration unit is connected to at least one inlet of the at least one mixing unit.

[0215] FIG. 3 illustrates an embodiment of the present installation comprising a dividing unit integrated in the mixing unit and a membrane filtration unit, wherein at least one outlet of the at least one mixing unit is connected to at least one inlet of the at least one membrane filtration unit and at least one outlet of the at least one membrane filtration unit is connected to at least one inlet of the at least one mixing unit.

[0216] FIG. 4 illustrates a venturi injector that can be used as gas inlet with the installation according to the present invention.

[0217] The scope and interest of the invention will be better understood based on the following examples which are intended to illustrate certain embodiments of the invention and are non-limitative.

EXAMPLES

Specific Surface Area (SSA) of a Material

[0218] The specific surface area (SSA) was measured using a Malvern Mastersizer 2000 (based on the Fraunhofer equation).

Particle Size Distribution (Mass % Particles with a Diameter <X) and Weight Median Diameter (d.sub.50) of a Particulate Material

[0219] Weight median grain diameter and grain diameter mass distribution of a particulate material were determined using a Malvern Mastersizer 2000 (based on the Fraunhofer equation).

pH of an Aqueous Suspension or Solution

[0220] The pH was measured using a Mettler-Toledo pH meter. The calibration of the pH electrode was performed using standards of pH values 4.01, 7.00 and 9.21.

Solids Content of an Aqueous Suspension

[0221] The suspension solids content (also known as “dry weight”) was determined using a Moisture Analyser HR73 from the company Mettler-Toledo, Switzerland, with the following settings: temperature of 120° C., automatic switch off 3, standard drying, 5 to 20 g of suspension.

Turbidity

[0222] The turbidity was measured with a Hach Lange 2100AN IS Laboratory Turbidimeter and the calibration was performed using StabCal turbidity standards (formazine standards) of <0.1, 20, 200, 1000, 4000 and 7500 NTU.

Determination of the Hardness (German Hardness; Expressed in “° dH”)

[0223] The hardness refers to the total amount of earth alkali ions in the aqueous suspension comprising the earth alkali hydrogen carbonate, and it is measured by complexometric titration using ethylene-diamine-tetra-actetic acid (EDTA; trade name Titriplex III) and Eriochrome T as equivalent point indicator.

[0224] EDTA (chelating agent) forms with the ions Ca.sup.2+ and Mg.sup.2+ soluble, stable chelate complexes. 2 ml of a 25% ammonia suspension, an ammonia/ammonium acetate buffer (pH 10) and Eriochrome black T indicator were added to 100 ml of a water sample to be tested. The indicator and the buffer is usually available as so-called “indicator-buffer tablet”. The indicator, when masked with a yellow dye, forms a red colored complex with the Ca.sup.2+ and Mg.sup.2+ ions. At the end of the titration, that is when all ions are bound by the chelating agent, the remaining Eriochrome black T indicator is in its free form which shows a green color. When the indicator is not masked, then the color changes from magenta to blue. The total hardness can be calculated from the amount of EDTA that has been used.

[0225] Table 1 below shows a conversion for the different units of the water hardness.

TABLE-US-00001 TABLE 1 Conversion for the different units of the water hardness.sup.[1] ° dH ° e ° fH ppm mval/l mmol/l German Hardness 1° dH = 1 1.253 1.78 17.8 0.357 0.1783 English Hardness 1° e = 0.798 1 1.43 14.3 0.285 0.142 French Hardness 1° fH = 0.560 0.702 1 10 0.2 0.1 ppm CaCO.sub.3 (USA) 1 ppm = 0.056 0.07 0.1 1 0.02 0.01 mval/l Earth alkali ions 1 mval/l = 2.8 3.51 5 50 1 0.50 mmol/l Earth alkali ions 1 mmol/l = 5.6 7.02 10.00 100.0 2.00 1 .sup.[1]In this regard the unit ppm is used in the meaning of 1 mg/l CaCO.sub.3.

Comparative Installation

[0226] A general process flow sheet of the installation used for the comparative example is shown in FIG. 1 (Device A). The installation comprises a feed tank having a feed tank volume of 50 l, which was fed with 45 l of suspension, as mixing unit including a stirrer and a crossflow membrane microfilter, wherein the suspension comprising minerals, pigments and/or fillers introduced into the mixing unit is withdrawn through an outlet locate at the mixing unit and directed and passed through the crossflow membrane microfilter. At least a part of the filtrate exiting the crossflow membrane microfilter is directed back to the mixing unit. The cross flow membrane microfilter has a total membrane area of 0.6 m.sup.2 (3 modules serial of 0.2 m.sup.2/module) and an inner tube diameter of 6 mm.

Inventive Installations

[0227] A general process flow sheet of one installation according to the present invention is shown in FIG. 2 (Device B). The installation comprises a feed tank having a feed tank volume of 50 l, which was fed with 45 l of suspension, as mixing unit including a stirrer and a crossflow membrane microfilter and a dividing unit which are installed in parallel. The suspension comprising minerals, pigments and/or fillers introduced into the mixing unit may thus be withdrawn simultaneously or independently through at least two outlets located at the mixing unit and directed and passed through the crossflow membrane microfilter and/or dividing unit. At least a part of the filtrate exiting the crossflow membrane microfilter and/or the suspension exiting the dividing unit is directed back to the mixing unit. The cross flow membrane microfilter has a total membrane area of 0.6 m.sup.2 (3 modules serial of 0.2 m.sup.2/module) and an inner tube diameter of 6 mm.

[0228] A general process flow sheet of another installation according to the present invention is shown in FIG. 3 (Device C). The installation comprises a mixing unit in which the dividing unit is integrated and equipped with a stirrer and grinding beads made of zirconium oxide. The installation further comprises a crossflow membrane microfilter such that the suspension comprising minerals, pigments and/or fillers introduced into the mixing/dividing unit is withdrawn through an outlet located at the mixing/dividing unit and directed and passed through the crossflow membrane microfilter. At least a part of the filtrate exiting the crossflow membrane microfilter is directed back to the mixing/dividing unit.

[0229] The feed water used in the inventive examples was obtained from an ion exchange equipment of Christ, Aesch, Switzerland Type Elite 1BTH, the feed water having the following water specification after the ion exchanger:

TABLE-US-00002 Sodium 169 mg/l Calcium  2 mg/l Magnesium .sup. <1 mg/l °dH 0.3

Example 1, Microdol A Extra (Dolomite)

[0230] In the present example, Microdol A extra a dolomite obtained from the Company Norwegian Talc, Knarrevik, was used as the at least one earth alkali carbonate.

[0231] The goal of the trials in Example 1 was to produce a suspension of earth alkali hydrogen carbonate of a pH of 7.2±0.1 out of dolomite at ambient temperature.

[0232] The dolomite feed material at the beginning of the trial had a d.sub.10 of 0.35 μm, a d.sub.50 of 2.75 μm and a d.sub.90 of 10.53 μm.

[0233] The reaction and operation conditions are given in Tables 2 and 3

Comparative:

[0234] Trial a) Device A, (tank temperature 23° C.)

[0235] Feed flow to the cross flow membrane microfilter: 2.0 m.sup.3/h

TABLE-US-00003 TABLE 2 Feed solids l/h of Membrane l/h/m.sup.2 d.sub.10 wt.-%/running CO.sub.2 ° dH l/h of Permeate pressure Permeate pH d.sub.50 time in minutes ml/min Permeate Permeate at 10° dH [bar] at 10° dH permeate d.sub.90 15 wt.-% 200 32.5 43 138 2 231 7.14 0.35 μm 2.68 μm 180 min 10.5 μm

Inventive:

[0236] Trial b) Device B, (tank temperature 25° C.)

[0237] Feed flow to the cross flow membrane microfilter: 2.0 m.sup.3/h

[0238] Feed flow to the dividing device: 0.20 m.sup.3/h

TABLE-US-00004 TABLE 3 Feed solids l/h of Membrane l/h/m.sup.2 d.sub.10 wt.-%/trial CO.sub.2 ° dH l/h Permeate pressure Permeate pH d.sub.50 running time ml/min Permeate Permeate at 10° dH [bar] at 10° dH permeate d.sub.90 15 wt.-% 250 50 40 209 2 349 7.3 0.28 μm 1.05 μm 165 min. 3.74 μm

[0239] From Table 3 (invention) it can be gathered that the capacity of permeate in l/h/m.sup.2 using the inventive equipment is increased by a factor of 1.5 compared to the capacity of permeate obtained in a prior art equipment as outlined in Table 2 (prior art). In particular, the medium particle diameter (d.sub.50) of particles in the suspension S obtained in the inventive equipment was determined as being 1.05 μm, while the medium diameter (d.sub.50) of particles in the suspension S using the prior art equipment stays nearly constant. Turbidity of the permeate sample obtained in the inventive equipment and taken after 165 min. was <0.3 NTU.

Example 2, Microdol A Extra (Dolomite)

[0240] In the present example, Microdol A extra a dolomite as described in Example 1 was used as the at least one earth alkali carbonate.

[0241] The goal of the trials in Example 2 was to produce a suspension of earth alkali hydrogen carbonate of a pH of 7.8±0.1 out of dolomite at an increased temperature of 40° C.

[0242] The Dolomite feed material at the beginning of the trial had a d.sub.10 of 0.35 μm, a d.sub.50 of 2.75 μm and a d.sub.90 of 10.53 μm.

[0243] The reaction and operation conditions are given in Table 4.

Inventive:

[0244] Trial c) Device B, (tank temperature 40° C.)

[0245] Feed flow to the cross flow membrane microfilter: 2.0 m.sup.3/h Feed flow to the dividing device: 0.20 m.sup.3/h

TABLE-US-00005 TABLE 4 Feed solids l/h of Membrane l/h/m.sup.2 d.sub.10 wt.-%/trial CO.sub.2 ° dH l/h Permeate pressure Permeate pH d.sub.50 running time ml/min Permeate Permeate at 10° dH [bar] at 10° dH permeate d.sub.90 8 wt.-% 100 38 74 280 1 467 7.7 0.32 μm 1.26 μm 165 min 3.72 μm

[0246] From Table 4 it can be gathered that the capacity of permeate in l/h/m.sup.2 using the inventive equipment at 40° C. is increased by a factor of 1.33 compared to the capacity of permeate obtained in the inventive equipment at 25° C. and compared to the prior art equipment as outlined in Table 2 (prior art) even by a factor of 2.0.

[0247] The Examples clearly show the improvement of efficiency of the inventive installations of Trial b) and c) versus Trial a).

Example 3, Raw Marble, Carinthia, Austria

[0248] In the present example, a raw marble from the region of Carinthia, Austria was used. The HCl insoluble content was 7.5 wt.-% (approx. 90 wt % mica and 10 wt.-% quartz, determined by XRD).

[0249] The Marble feed material at the beginning of the trial had a d.sub.10 of 1.0 μm, a d.sub.50 of 24.5 μm and a d.sub.90 of 104 μm. The specific surface area (SSA) was <0.1 m.sup.2/g.

[0250] The reaction and operation conditions of the installation can be gathered from Table 5.

Trial d), Device B, (mix tank temperature 24° C.)

[0251] Feed flow to the cross flow membrane microfilter: 2.0 m.sup.3/h Feed flow to the dividing device: 0.065 m.sup.3/h

TABLE-US-00006 TABLE 5 Feed solids l/h of Membrane l/h/m.sup.2 d.sub.10 wt.-%/trial CO.sub.2 ° dH l/h Permeate pressure Permeate pH d.sub.50 running time ml/min Permeate Permeate at 10° dH [bar] at 10° dH permeate d.sub.90 5 wt.-% 200 25 5.4 13.5 0 23 7.17 0.30 μm 1.18 μm 105 min 6.16 μm 3.07 m.sup.2/g 5 wt.-% 300 42.5 42.2 179 1 299 6.7 0.32 μm 1.2 μm 165 min 5.56 μm not determined 5 wt.-% 300 40.0 79.6 318 2 351 6.7 not determined 180 min

[0252] The total particle surface area (SSA.sub.total) of the suspension S obtained in the inventive equipment and taken after 105 min. represented 185000 m.sup.2/tonne of suspension S.

[0253] Turbidity of the permeate sample obtained in the inventive equipment taken after 165 min. was <0.3 NTU.

[0254] 2 liters of clear permeate obtained after 180 min were heated for 2 h at 70° C., and the resulting precipitate was collected by filtering using a laboratory membrane filter disc having a diameter of 50 mm and a pore size of 0.2 μm (produced by Millipore).

[0255] The XRD analysis of the resulting precipitate shows the following:

TABLE-US-00007 Aragonitic PCC 97.3 wt.-% Calcitic PCC  2.7 wt.-% Silica/Silicates (Mica) <0.1 wt.-% HCl insol. <0.1 wt.-%

[0256] Hence, the XRD results and the HCl insoluble content show that a very clean CaHCO.sub.3 solution as well as very pure precipitated calcium carbonate is obtained from a starting material that contains a HCl insoluble content (impurities) of 7.5 wt.-%.

[0257] This example clearly demonstrates that the inventive installation produces very pure extraction solutions as well as minerals, pigments and/or fillers out of impure starting material. This example shows the use of the inventive installation as a cost efficient alternative to processes where chemicals are used to separate the mineral, pigment and/or filler phases.

Example 4, Dolomite/Limestone Blend

Pilot Plant Trial

[0258] In the present example, one part Microdol A extra a dolomite as described in Example 1 was mixed with two parts of limestone of the region of Avignon, France, and was used as the blend of earth alkali carbonates.

[0259] The goal of the trial in Example 4 was to produce a solution of earth alkali hydrogen carbonate of a pH of 6.5 to 6.7 in pilot scale.

[0260] The blend of earth alkali carbonates had a d.sub.10 of 0.43 μm, a d.sub.50 of 2.43 μm and a d.sub.90 of 6.63 μm at the beginning of the trial.

[0261] The blend was fed as 50 wt.-% suspension in water.

[0262] The reaction and operation conditions of the installation can be gathered from Table 6.

Inventive:

[0263] Trial e) Device B, (tank temperature 18.5° C.)

[0264] The installation comprises a feed tank having a feed tank volume of 1,0001 as mixing unit including a stirrer and a crossflow polyethylene membrane microfilter as the crossflow membrane microfiltration unit and a dividing unit which are installed in parallel. The suspension comprising minerals, pigments and/or fillers introduced into the mixing unit may thus be withdrawn simultaneously or independently through at least two outlets located at the mixing unit and directed and passed through the crossflow membrane microfiltration unit and/or dividing unit. At least a part of the filtrate exiting the crossflow membrane microfiltration unit and/or the suspension exiting the dividing unit is directed back to the mixing unit. The cross flow polyethylene membrane microfilter has a total membrane area of 8 m.sup.2, an inner tube diameter of 5.5 mm and is 3 m long. Furthermore, the microfilter has a pore diameter of 1.0 μm and comprises 174 tubes in parallel (Seprodyn filter module SE 150 TP 1L/DF, Microdyn).

[0265] Feed water: deionized water obtained from an ion exchange equipment of Christ, Aesch, Switzerland, (<1 mg/l earth alkali carbonate).

Feed flow of suspension S to the cross flow membrane unit: 36 m.sup.3/h, speed across the membranes: 3 m/s.
Pressure at the cross flow membrane inlet: 1 bar
Pressure at the cross flow membrane outlet: 0.3 bar
Pressure at the solution outlet: 0.05 bar
Feed flow of suspension S to the dividing device: 0.40 m.sup.3/h
Pressure at the dividing unit inlet: 0.7 to 0.8 bar
Dose of CO.sub.2: 2.0 liter/min at a pressure of 1.5 to 1.6 bar.
Feed solids of suspension S: 15 wt.-%

[0266] Results are measured after 44 hours continuous running.

TABLE-US-00008 TABLE 6 d.sub.10 Earth alkali ion m.sup.3/h of l/h/m.sup.2 d.sub.50 ° dH m.sup.3/h concentration in Permeate Permeate pH d.sub.90 Permeate Permeate the permeate at 10° dH at 10° dH permeate SSA 33 0.5 Ca.sup.2+: 214 mg/l 1.65 0.21 6.7 0.34 μm Mg.sup.2+: 20 mg/l 1.47 μm 4.11 μm 2.72 m.sup.2/g

[0267] The specific particle surface of the suspension S obtained in the inventive installation and taken after 44 hours was 408,000 m.sup.2/tonne of suspension S.

[0268] A first quality of tap water comprising 45 mg/l earth alkali carbonate (sum of CaCO.sub.3/MgCO.sub.3) was produced by diluting the permeate of this trial with feed water. The resulting capacity of this trial corresponds to approximately 6.7 m.sup.3/h at a concentration of 45 mg/l earth alkali carbonate.

[0269] A second quality of tap water comprising 100 mg/l earth alkali carbonate 1(CaCO.sub.3) and 10-15 mg/l of earth alkali carbonate 2 (MgCO.sub.3) was produced by diluting the permeate of this trial with feed water. The resulting capacity of this trial corresponds to approximately 2.7 m.sup.3/h at a concentration of 100 mg/l CaCO.sub.3 and 10-15 mg/l MgCO.sub.3.

[0270] The total electrical power consumption of the inventive installation to obtain 1 m.sup.3 of the second quality of tap water was 0.07 to 0.12 kWh per m.sup.3 of tap water quality 2.

[0271] The electrical power consumption for the mill part of the inventive installation to obtain 1 m3 of the second quality of tap water was 0.06-0.09 kWh per m3 of tap water quality 2.