NZ510786A

NZ510786A - Method of formulating alkali metal salts

Info

Publication number: NZ510786A
Application number: NZ510786A
Authority: NZ
Inventors: Robin Phinney
Original assignee: Airborne Ind Minerals Inc
Priority date: 1998-10-13
Filing date: 1999-09-30
Publication date: 2002-05-31
Also published as: TR200100960T2; NO20011851L; HRP20000125A2; JP2002527330A; CZ20011176A3; HUP0104062A3; CN1515491A; CN1330612A; PL347098A1; ZA200001142B; CN1156397C; AU5845799A; SK5002001A3; EA200100340A1; EP1121327A1; KR20010088870A; UA73096C2; NO20011851D0; WO2000021887A1; HUP0104062A2

Abstract

A method of formulating potassium sulfate and food grade sodium bicarbonate is described. The method involves; a) providing a source of liquid sodium sulfate; b) providing a source of ammonium bicarbonate to precipitate sodium bicarbonate; c) contacting the sodium sulfate and the ammonium bicarbonate; d) precipitating sodium bicarbonate and forming a liquor; e) filtering the sodium bicarbonate; f) saturating liquor form step e) with sodium sulfate; g) contacting the liquor with ammonium carbonate ammonia gas or carbon dioxide to precipitate further sodium bicarbonate; h) filtering precipitated sodium bicarbonate from step g); i) combining sodium bicarbonate precipitate from step e) and h) and washing to form food grade sodium bicarbonate; j) cooling the liquor from step i) to 0oC to at least form a Glauber's salt precipitate; k) treating the liquor from step j) with sulfuric acid to convert carbonate minerals and release carbon dioxide gas; l) heating the liquor from step k) to between 30oC and 40oC; and m) precipitating potassium sulfate by contacting the liquor from step l) with potassium chloride.

Description

<div class="application article clearfix" id="description"> METHOD OF FORMULATING ALKALI METAL SALTS TECHNICAL FIELD The present invention relates to a method of formulating alkali metal salts and more particularly, the present invention relates to a method of generating food grade sodium bicarbonate and fertilizer grade potassium sulfate. BACKGROUND ART A significant amount of prior art has been promulgated with respect to the formulation of alkali metal salts. Sodium bicarbonate, as an example, has been prepared in as many different ways as it has been known. Despite this fact, previous unit operations for bicarbonate synthesis have been hampered by inefficient energy use which results directly in increased synthesis costs. As a further limitation, known processes do not make efficient use of the unit operations involved in the preparation of salts. Typically, a single high quality product is formulated with concomitant byproduct formation of a quality inadequate for commercial purposes or that would require too substantial an investment to render them commercially viable. Representative of the prior art is United States Patent No. 3,429,657,issued February 25,1969, to D'Arcy. The reference discusses a method for recovering and producing potassium salts. In the reference, a potassium bearing brine is reacted with sodium perchlorate to precipitate potassium perchlorate. The potassium is removed by ion exchange with sodium and the free potassium is then combined with chloride, sulfate, nitrate inter alia. INDUSTRIAL APPLICABILITY 30 The present invention has applicability in the fertilizer art. AMENDED SHEET IPEA/EP WO 00/21887 PCT/CA99/00905 DISCLOSURE OF THE INVENTION One object of one embodiment of the present invention is to provide a method of formulating food grade sodium bicarbonate and potassium sulfate, characterized in that the method comprises the steps of" a) providing a source of liquid sodium sulfate; b) providing a source of ammonium bicarbonate, c) contacting the sodium sulfate and the ammonium bicarbonate; d) precipitating sodium bicarbonate and forming a liquor, 10 e) precipitating sodium bicarbonate and forming a liquor by contacting the liquor from step d) with sodium sulfate; f) saturating the liquor from step e) with sodium sulfate, g) filtering solids from the liquor of step f); h) contacting the liquor from step g) with sulfuric acid to precipitate carbonates; i) cooling the liquor from step h) to 0°C to form Glauber's salt precipitate, j) heating the liquor from step i) to between 30° to 40°C; and k) precipitating potassium sulfate by contacting the liquor from step j) 20 with potassium chloride. A further object of one embodiment of the present invention is to provide a method of formulating food grade sodium bicarbonate and potassium sulfate, characterized in that the method comprises the steps of a) providing a source of liquid sodium sulfate; b) providing a source of ammonium bicarbonate; c) contacting the sodium sulfate and the ammonium bicarbonate, d) precipitating sodium bicarbonate and forming a liquor; e) precipitating sodium bicarbonate and forming a liquor by contacting 30 the liquor from step e) with sodium sulfate; f) saturating the liquor from step e) with anhydrous sodium sulfate; g) filtenng solids from the liquor of step f), WO 00/21887 PCT/CA99/00905 3 h) contacting the liquor from step g) with at least one of ammonium bicarbonate, ammonia gas or carbon dioxide to precipitate sodium bicarbonate; i) cooling the liquor from step h) to 0°C to a precipitate of sodium bicarbonate and sodium sulfate, and j) precipitating potassium sulfate by contacting the liquor from step i) with potassium chloride. It has been found that following the sodium bicarbonate formulation, significant success in cooling the liquor to 0°C is realized for removing sodium 10 sulfate as Glauber's salt and sodium bicarbonate Glauber's salt solubility in the system is contemplated by the ammonium sulfate-sodium sulfate phase diagram By increasing the sodium sulfate in the bicarbonate circuit with increased Glauber's salt recycle, there is a tendency to decrease the bicarbonate solubility and increase the process efficiency Regarding the conversion of the starting reagents to potassium sulfate, particular success has been encountered by maintaining a mole ratio of five (5) or greater for the potassium and ammonium ions This ratio ensures high conversion efficiency in the second stage of the process. 20 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a process flow diagram illustrating a first part of one process according to the present invention; Figure 1a illustrates a second part of the process illustrated in Figure 1; Figure 1 b illustrates a third part of the process illustrated in Figure 1; 30 Figure 2 is a is a process flow diagram illustrating a first part of a variation of the process according to the present invention, Figure 2a illustrates a second part of the process illustrated in Figure 2; and WO 00/21887 PCT/CA99/00905 4 Figure 2b illustrates a third part of the process illustrated in Figure 2 Similar numerals in the figures denote similar elements MODES FOR CARRYING OUT THE INVENTION Referring now to the drawings, Figures 1 through 1b illustrate the process according to a first embodiment 10 A source of liquid sodium sulfate 10 dissolved in fresh water and centrate water 12 discussed herein after. The solution is mixed in vessel 14 at 40°C to a specific gravity of 1.30 The solution is filtered in filter 16 which, as an example, may comprise a 5 micron filter The solids 18 are disposed of while the filtrate 20 is passed into a first sodium bicarbonate crystallization vessel 27 Feeds of water, ammonia and carbon dioxide all denoted by numeral 24 are reacted in vessel 22 in order to synthesize ammonium bicarbonate. Formulated ammonium bicarbonate is centrifuged in centrifuge 26, with the solid product being passed into crystallization vessel 27 A recycle loop 28 recirculates ammonium 20 bicarbonate solids and liquor into reaction vessel 29 The result of the combination in vessel 29 is the formulation of sodium bicarbonate The mixture is filtered by filter 30 and centrifuged The sodium bicarbonate is washed with water in vessel 32, centrifuged in centrifuge 34 and the solid retained as food grade sodium bicarbonate. The wash water is returned to vessel 14 The liquor from filter 30 has a specific gravity of 1 25 with the contents including approximately 10 4% sodium sulfate, 17 1% ammonium sulfate, 8% sodium bicarbonate and excess ammonium bicarbonate for reaction with the Glauber's salt (discussed herein after). The liquor is reacted in a vessel 36 at 40°C 30 with Glauber's salt formulated in the cooling phase of the process, which will be discussed later, to produce sodium bicarbonate from the excess of ammonium bicarbonate from crystallization vessel 29 Alternatively, the ammonium bicarbonate may be added to the second stage (vessel 36) as solid, slurry or solution. WO 00/21887 PCT/CA99/00905 5 To the liquor from vessel 36 is added to solid sodium sulfate from source 41 in vessel 40 to formulate a saturated liquor of sodium sulfate/ammonium sulfate. Sufficient ammonium bicarbonate may be present to complete the reaction is solution or some may be added to result in the liquor having a specific gravity of 1.285. The slurry from vessel 40 is filtered with filter 42. The sodium bicarbonate solids 48 are passed to vessel 32 and the liquor 44 is further processed with additional separation of sodium bicarbonate, which is returned to vessel 32 The liquor 44, is then passed to vessel 46 (Figure 1 A). Circuit volume from the sodium bicarbonate circuit can be controlled by evaporating the purified sodium sulfate in the 10 feed to produce solid sodium sulfate to ensure circuit saturation. Returning to Figure 1A, vessel 46 contains sulfuric acid to precipitate carbonate compounds. The so treated liquor is cooled to 0°C in chiller 48 to recover Glauber's salt and filtered in filter 50 The recovered Glauber's salt is returned to the sodium bicarbonate crystallization vessel 36 The filtrate contains 25.25% by weight ammonium sulfate and up to 11 % by weight sodium sulfate and is passed into a vessel 52 heated to between 30°C and 40°C and combined with solids 65 from filter 66. This solution is passed into vessel 20 54 where solid potassium chloride is reacted therewith to formulate a 20% by weight solution of ammonium chloride also containing, by weight approximately, 20 2% ammonium chloride, 6.7% potassium chloride, 4 9% sodium chloride, 2.3% as (x)2S04, where x = Na, K, and solid mixed crystals of potassium sulfate with 10% -20% ammonium sulfate The solution is filtered in filter 56, with the solid fraction containing approximately by weight, 5% potassium chloride, 80% - 85% potassium sulfate, 10% -15% ammonium sulfate. The solid fraction is combined in vessel 58 with water and potassium chloride brine from vessel 60 The potassium sulfate solid is centrifuged 30 and filtered in filter 62 and recrystallized with a solution of potassium chloride at 25°C. The remaining ammonium sulfate is converted to potassium sulfate. Grades of greater than 98% potassium sulfate are achievable WO 00/21887 PCT/CA99/00905 6 In further unit operations, the liquor or filtrate from the potassium sulfate operations and specifically from filter 56 is processed in accordance with the unit operations set forth in Figure 1 c The liquor is evaporated in evaporator in order to concentrate the ammonium chloride liquor such that upon cooling the potassium chloride and residual sulphates are minimized in solution The solution is filtered with filter 66 with the solid material 67 recycled to vessel 54. The filtrate containing approximately 22% to 30% ammonium chloride is reacted with lime in reactor 68 with liberated ammonia recycled The calcium chloride formed may be passed to a settler 70 or scrubber 72 depending on intended subsequent uses. Having set forth the process according to this first embodiment, reference will now be made to an example of the process 10 EXAMPLE 1 BICARBONATE KILL PRIOR TO POTASSIUM SULFATE PROCESS 20 Feed - 1 litre @ 1 3 S.G. 360 g/l Na2S04 1st STAGE Production of NaHC03 Brine Exit at reaction termination. 130g Na2S04 30 213.8g (NH4)2S04 10 4% Na2S04 17.1% (NH4)2S04 8.0% NaHC03 40°C 1.250 S.G. @0.951 100g NaHCOs 907g HoO 1350.8 solution This makes 172g NaHC03 solids consumes 55g NH3 142.5g COz SECOND STAGE ESTIMATE A) 25.07g NH3 + 64.9g C02 B)51.2g NH3 + 132.6g C02 40 WO 00/21887 PCT/CA99/00905 7 2nd STAGE 0 95 I of brine will dissolve the following ^) 1 Moles Ma2S0410H20 (332g) 272g Na2S04 16.2% Na2S04 213.8g (NH4)2S04 12.8% (NH4)2S04 100g NaHC03 5 9% NaHCO, 1087a H,0 65.1% HoO 3) 2 Moles Ma2S0410H20 [644g) 414g Na2S04 20.7% Na2S04 213.9g (NH4)2S04 10.7% (NH4)2S04 100g NaHC03 5.0% NaHCO, 1267a HoO 63 4%H,0 1672.8 1.275 S.G. and 1.313 I bnne l 1999 1.300 S G and 1 51 brine 2nd STAGE Final Solution Composition A) 167.3g Na2S04 311g (NH4)2S04 131 g NaHC03 1087a H.O 1644.5g Solution 10% Na2S04 18.9% (NH4)2S04 8% NaHC03 63 1% HzO Production of NaHC03 92 9g S.G 1.265 and makes 1 31 I brine 3) 200g Na2S04 412g (NH4)2S04 160g NaHC03 1267a H.O 10% Na2S04 20 2% (NH4)2S04 8% NaHC03 61.8% H,0 2039g Solution Production of 193.2g NaHC03 S.G. 1.285 and makes 1 6 I of Solution BICARB KILL 412g (NH4)2S04 200g NaS04 160g NaHC03 1267a H.O 40 2039g (16 1) 1.285 S.G This becomes- 412g (NH4)2S04 335g Na2S04 1267a H.O 2014g @ 1.265 = (1.61) 50 must add Na2S04 to Saturation of 1 30 S.G + 160 X 98 =93.3g H2S04 84(2) WO 00/21887 PCT/CA99/00905 8 1.61 x 1.30 = 2080 Therefore- 412g (NH4)2S04 400g Na2S04 1267a HoO 2079g total (1.61) Cooling 412g (NH4)2S04 28.7% 116g Na2S04 8.0% 907 HX> 63% 1435g Solution Feed to Evaporator NH4C1 330.8 g 21 9 KC1 130 g 8.6% NaC1 94.7 g 6.3% X-S04 50 3.3% H?0 907a 60.0 1512g @ 33% NH4CI then. - 2.8% KCI then- - 2 0% K2SQ4 Therefore- 330 8 = 1002 g .33 Evaporation Load = 907 - 623 = 284g 0.79t/t Na2S04 add 0.51 for washing 1.291 HzO /1 Na2S04 K-SO, Reaction a) K2S04 from (NH4)2S04 = 412 x 174 = 543g 132 b) K2S04 from Na2S04 = 116 x 174 = 142g 142 c) Losses of K2S04 = -43a TOTAL K2S04 642g WO 00/21887 PCT/CA99/00905 9 KCI Recovery a) KCI intermig reaction = 685 x 2 x 74 = 582g 174 b) KCI lost to tails = 50g c) Therefore. KCI need = 632g 10 K.SO, yield = 642 x 100 = 93.7% 685 KCI Conversion Efficiency = 582 x 100 = 92.1% 632 BASIS: One Tonne of Na2S04 feed 20 Inputs Product First Stage 0.153tNH3 0.396t C03 2 52t H,0 0.48t NaHCOs Second Stage 644g Na2S0410H20 0.142t NH3 0.368t CO, 0 53t NaHC03 Bicarb Kill + Na2S04 Saturation 0.26t H2S04 0.18t Na,SO„ Filter to Produce clear brine Cooler to 0°C -BTU's 1.8t Na,S0.10H,0 Cooler brine 1.14t (NH4)2S04 28.7% 0.32t Na2S04 8.0% 2.52qt HzO 63% 3 991 Total KC1 = 1.76t 1.78t K,SO„ Evaporation to 33% NH4CI 1.29t/t Na2S04 0.92t NH4CI brine 0.081 KCI SOLIDS 0 05t K2S04 0.28t KCI 1 73t H,0 0.08t K,SO< 2.78 Total 0.36t Recycle Lime Process @ 85% off 0.57t CaO 0 29t NH3 Brine. 0.955 CaCI2 0 08t KCI 0 05t K2S04 1 73t H20 2.815t @ 75 to 90°C WO 00/21887 PCT/CA99/00905 10 Turning to Figures 2 through 2b, an alternative processing scheme is schematically depicted In this reaction scheme, prior to the production of sodium bicarbonate, the liquors are saturated with anhydrite. In this embodiment, sodium bicarbonate is produced in crystallization unit 22 and undergoes generally similar steps as set forth for Figures 1 through 1B. The brine or filtrate is saturated with anhydrous sodium sulfate in vessel 36 and filtered with filter 38 to remove insolubles which are discarded The filtrate from this operation is reacted with ammonium bicarbonate in vessel 80. As an alternative, the filtrate could be reacted with ammonia or carbon dioxide to precipitate the sodium bicarbonate The solution is filtered with filter 82 and the sodium bicarbonate remains The latter is combined with the sodium bicarbonate from filter 30 and then washed, centrifuged and dried These steps are not shown The filtrate remaining has a composition of approximately, on a by weight basis, 10% sodium sulfate, 24% ammonium sulfate and 8% sodium bicarbonate. The solution has a specific gravity of 1.285 at 40°C. From this stage, the filtrate solution is cooled in a chiller 84 to approximately 0°C in order to produce a filtrate containing approximately, on a by weight basis 5% sodium sulfate, 28% ammonium sulfate and 6% sodium bicarbonate. The solution is filtered with filter 86 and precipitated sodium bicarbonate and sodium sulfate are recycled back to the bicarbonate crystallization vessel 32, while the filtrate is reacted with potassium chlonde in vessel 88 to synthesize first stage potassium sulfate in a purity range of about 75% to 90%. The solid potassium sulfate is repulped with potassium chloride brine from vessel 92 in vessel 94 This results in high quality, high grade potassium sulfate The product is washed with water in a conventional washing stage 96 with recycle to vessel 94 The solution from filter 90 is evaporated in evaporator 98 (Figure 2A) to concentrate ammonium chloride liquor whereby upon cooling the potassium chloride and sulfates are minimized The solution is filtered using filter 100 with the precipitated potassium chloride and (x)S04, where x = K, Na, recycled to vessel 88. WO 00/21887 PCT/CA99/00905 11 The filtrate from filter 100 containing ammonium chloride, potassium chloride and potassium sulfate is passed into evaporator 102 The sodium bicarbonate backs the reaction and as a result, ammonia and carbon dioxide are released. These gases are then scrubbed/handled using suitable techniques. The calcium chloride generated is then discarded or sold EXAMPLE 2 NO BICARBONATE KILL 10 Feed - 1 litre @1.3 S.G 360 g/l Na2S04 1st STAGE Production of NaHC03 Brine Exit at reaction termination. 20 130g Na2S04 10 4% Na2S04 213.8g (NH4)2S04 17 1 % (NH4)2S04 100 g NaHC03 8.0%NaHC03 907a H«Q 1350.8 This makes 172g NaHC03 solids consumes 55g NH3 142 5g C02 30 Resaturation with Na2S04- brine will hold 150g Na2S04 This brine is then filtered and fed to the second stage NaHC03 crystallizer 40°C 1.250 SG @0951 solution 40 FEED REACTION EXIT BRINE PRODUCT 280g Na2S04 35 9g NH3 130g Na2S04 177g NaHC03 213 8g (NH4)2S04 92.9g C02 353g (NH4)2S04 100g NaHC03 100g NaHCO, 907a HX> 907a H„0 1490.8g 1490g 1 151 @1.32 S.G 1.285 SG 1.151 23.7% (NHJ,SO. The exit brine is then cooled to 0°C. WO 00/21887 PCT/CA99/00905 12 Brine composition is • 5 0% Na2S04 which mean 60g Na2S04 precipitates as 136g of Na2S0410H20 precipitate and remove 76g of H20 Therefore: 907 - 76 = 831 g HzO. Brine composition @ 0°C and 1.26 S G 70g Na2S04 353g (NH4)2S04 10 100g NaHC03 831o HoO 13540 TOTAL About 1 litre brine KoSO, a) 70a Na.SO, x 174 = 85 8 142 20 b) 353a fNH,).SO, x 174 = 465 3a 132 EXIT BRINE 283g NH4CI 21.9% 57g NaCI 4.8% 119g (KNaHC03) 9.2% 831a H,0 1290 30 Boil up to 33.0% NH4CI. Release of NH3 and COz from evaporator but NH4CI salts out KCI and not the NaCI KCI is recovered same as in Example 1 BASIS One Tonne Na,SO, feed INPUTS PRODUCT First Stage 015tNH3 0.396t C02 2.52t H,0 0 48t NaHC03 Second Stage 0.10tNH3 0.26t C03 0 42t Na,SO, 0 49t NaHC03 Cooled to 0°C 0.4t of Na,SOJOH,0 Cooler Brine 0.19t Na2S04 5% 0.98t (NH4)2S04 26% 0.28t NaHCO, 7 4% 2.311 H.O 61 4% 3.76t Total WO 00/21887 PCT/CA99/00905 13 10 INPUT PRODUCT KCI 1.62t 1 8t K,SO, Evaporation to 33% NH4CI Circuit Control = 0.7t HzO Washing = 0.5t To evaporator 1,2t HzO/t Na2S04 Brine Solids 0.98t NH4CI 0.28t KCI 0.08t KCI 0.08t K.SO, 0.15t NaCI 0.36t 0.19t NaCI from C03 1.57t HzO 2.97t Lime Process @ 85% efficiency 0.611 CaO 1.01t CaCI2 0.08t KCI 0 34t NaCI 1.57t H20 3.0t @ 75 - 90°C EXAMPLE 3 - BICARBONATE KILL - NO EVAPORATION OF AMMONIUM CHLORIDE 20 Feed Solution- from#1 412 g (NH4)2S04 335 g Na2S04 1267 a HoO 2014 g @ 1 265 = 1.60 I Cooling to 0°C yields a filtered solution of. 412 g (NH4)2S04 28.7% 116 g Na2S04 8.0% 907 a HoO 1435 g solution 30 This bnne is then heated to 25°C where KCI solid is added to produce K2S04 The exit brine from the K2S04 circuit has the following composition: NH4CI 330 8 g 21.9% KCI 130 g 8.6 % NaCI 94.7 63% x-S04 50 g 3.3 % H,0 907o 60 1512 g WO 00/21887 PCT/CA99/00905 14 This brine is than heated and reacted with lime to recover the ammonia and bypass the evaporator The KCI reports to the CaCI2 brine rather than being recovered in the evaporator This represents a 15 to 20 % loss of K to the CaCI2 brine The KCI in the CaCI2 brine can be reduced to as low as 1.0% by adding solid Na2S04 to CaCI2/KCI brine The potassium is effectively collected as apprecipitated of syngenite (CaS04 • K2S04 • xHzO) at 0 to 100°C with preferred temperatures of 20 to 30°C so that S04 solubility is kept to minimum and the reaction occurs at a reasonable rate. 10 CaCI2 Brine composition 343.3 g CaCI2 22.5 % 130 g KCI 8.5% 94 7 g NaCI 6.3 % 50 g x S04 32 % (Na/K) 907 a H-Q 59 5% 1525 g 100% 140 g Na2S04 addition Exit Bnne Exit Cake 234.8gCaCl2 17.8% 20 15.25 g KCI 1.1% 310 g CaS04 • K2S04 209 g NaCI 15.9 % + 100 g ^ 50 g x S04 3.8 % 807 61 3 % The exit brine can be deep well disposed of and cake can be blended into the K2S04 product as binder or further processed to remove the CaS04. The cake can be reacted with (NH4)2HC03 from the NaHC03 process feed and the CaS04 reacts quickly to produce a brine of (NH4)2S04 and K2S04 and a filter 30 CaCI3 precipitate which is disposed of The (NHa)2S04/K2S04 brine is recycled to K2S04 first stage crystallizer WO 00/21887 PCTVCA99/00905 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> CLAIMS 15 / a Ufa

1. A method of formulating potassium sulfate and food grade sodium bicarbonate, characterized in that the method comprises of the steps of;

a) providing a source of liquid sodium sulfate;

b) providing a source of ammonium bicarbonate to precipitate sodium bicarbonate;

c) contacting said sodium sulfate and said ammonium bicarbonate;

d) precipitating sodium bicarbonate and forming a liquor;

e) filtering said sodium bicarbonate;

f) saturating liquor from step e) with sodium sulfate;

g) contacting said liquor with ammomium carbonate ammonia gas or carbon dioxide to precipitate further sodium bicarbonate;

h) filtering precipitated sodium bicarbonate from step g);

i) combining sodium bicarbonate precipitate from step e) and h) and washing to form food grade sodium bicarbonate;

j) cooling liquor from step i) to 0°C to at least form Glauber's salt precipitate;

k) treating liquor from step j) with sulfuric acid to convert carbonate minerals to sulfate minerals and release carbon dioxide gas,

I) heating liquor from step k) to between 30°C and 40°C; and m) precipitating potassium sulfate by contacting said liquor from step I) with potassium chloride.

2. The method as set forth in claim 1, characterized in that the method further includes the step of separating precipitated potassium sulfate and washing with potassium chloride.

3. The method as set forth in claim 2, characterized in that the method further includes the step of treating liquor from said step of separating precipitated potassium sulfate with lime to liberate ammonia gas.

INTELLECTUAL PROPERTY OFFICE OF N.Z.

- 5 FEB Ml received

WO 00/21887 5 10 78 0 PCr/GA99/00905

16 X

4. The method as set forth in claim 3, characterized in that the method further includes the step of recycling said ammonia gas to step g.

5' The method as set forth in claim 4, characterized in that the method further includes the step of evaporating filtrate from claim 4.

6. The method as set forth in claim 1, characterized in that said sodium sulfate has a specific gravity of between 1.30 and 1.34 at 40°C.

7. The method as set forth in claim 1, characterized in that said liquor from step d) has a specific gravity of 1.25 and contains, by weight, 10.4% sodium sulfate, 17.1% ammonium sulfate, between 8% to 12% sodium bicarbonate and an excess of ammonium bicarbonate.

8. The method as set forth in claim 1, characterized in that said sodium sulfate from step e) comprises Na2S04 • 10 HzO.

9. The method as set forth in claim 1, characterized in that said liquor from step f) has a specific gravity of 1.285 at 40°C.

10. The method as set forth in claim 1, characterized in that said liquor from step k) is a saturated liquor of sodium sulfate, ammonium sulfate and sodium bicarbonate.

11. The method as set forth in claim 1, characterized in that said potassium sulfate is generated in a yield of at least 80% with a purity of at least 98%.

12 A method of formulating potassium sulphate and food grade sodium bicarbonate, characterised in that the method comprises the steps of:

providing a source of liquid sodium sulfate;

providing a source of ammonium bicarbonate;

contacting said sodium sulfate and said ammonium bicarbonate; precipitating sodium bicarbonate and forming a liquor;

precipitating sodium bicarbonate and forming a liquor by contacting a)

b)

c)

d)

1 0 APR 2002 e) received

INTELLECTUAL PROPERTY OFFICE OF N.Z.

17

said liquor from step d) with sodium sulfate;

f) saturating said liquor from step d) with sodium sulfate;

g) filtering solids from said liquor of step e);

h) contacting said liquor from step f) with sulfonic acid to precipitate carbonates;

i) cooling said liquor from step h) to 0°C to form Glauber's salt precipitate;

j) heating said liquor from step I) to between 30°C to 40°C; and k) treating said liquor from step j) with potassium chloride to precipitate potassium sulfate;

I) evaporating liquor from step k) to recover potassium values for recycling to step k); and m) drying said potassium sulfate.

13. The method as set forth in claim 12, characterized in that the method further includes the step of treating liquor remaining from step I) with lime and ammonium chloride.

14. The method as set forth in claim 13, characterized in that ammonia gas is liberated and recycled.

15. The method as set forth in claim 12, characterized in that used potassium chloride solution is recycled to step k).

intellectual property

OFFICE OF N.Z.

- 5 FEB 2002 RECEIVED

AIRBORNE INDUSTRIAL MINERALS INC. by their authorised a|

JAMES & WEI

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