TECHNICAL FIELD

The present invention relates to processes for converting any bicarbonate, carbonate or mixtures of sodium carbonate and sodium bicarbonate, such as trona, into sodium into sodium bicarbonate or sodium carbonate.

BACKGROUND ART

Approximately 31% (12.2 million tons per year) of the world's production of soda ash is produced from natural trona deposits. Natural trona ore is a hydrated mixture of sodium carbonate and sodium bicarbonate along with various organic and inorganic impurities. Currently, soda ash is produced from trona by one of two processes (1) the monohydrate process or (2) the sesquicarbonate process.

In the monohydrate process, trona ore is first calcined in a rotary kiln at temperatures of 500 to 600OF. This serves to convert bicarbonate to carbonate. The calcining operation also destroys organic impurities present in the ore. Inorganic contaminants are removed from the calcined trona by dissolving the material in water and recrystallizing sodium carbonate from the filtered solution through the use of triple-effect evaporators. Soluble inorganic impurities, such as sodium carbonate and sodium sulfate remain in the mother liquor. Insoluble impurities, such as shale and calcium carbonate, are removed by filtration prior to crystallization. The resulting sodium carbonate crystals, in the monohydrate form, are separated by filtration or centrifugation.

The sesquicarbonate process utilizes basically the same unit operations as the monohydrate process. However, the arrangement of these unit operations differs. In the sesquicarbonate process, trona ore is first dissolved in hot water and the resulting solution filtered to remove insoluble impurities. Organic impurities are then removed by

adsorption of the organics on activated carbon. Pure trona (or sesquicarbonate) is then recrystallized from the purified solution by using triple-effect evaporators. To obtain the sesquicarbonate a solution of sodium carbonate, to maintain an excess of 10 to 25% excess carbonate, is recycled in the evaporators; otherwise since trona is an incongruently dissolving double salt, sesquicarbonate cannot be formed by cooling. This, once again, leaves soluble inorganic impurities in the mother liquor. The sesquicarbonate crystals are then calcined to produce sodium carbonate.

These processes are described in detail in various U.S. patents. For example, U.S. Patent No. 3,479,133, issued on November 18, 1969, to F.M. arzel describes the monohydrate process. U.S. Patent No. 3,119,655, issued in January of 1964, to Frint et al. describes the sesquicarbonate process. Similarly, U.S. Patent No. 3,260,567, issued on July of 1966, to Hellmers et al. and U.S. Patent No. 3,361,540, issued on January 2, 1968, to Peverly et al. teach these sesquicarbonate processes.

Both the monohydrate and sesquicarbonate processes produce sodium carbonate crystals having a density range of 0.95 to 1.25 g/cc. Some applications (those in which the sodium carbonate is to be used in solution form) prefer the use of low density crystals because these crystals dissolve faster than high density crystals. U.S. Patent No. 5,043,149, issued on August 27, 1991, to Frint et al., and assigned to the FMC Corporation, describes a process for the manufacture of such low density soda ash crystals. Sodium carbonate crystals obtained from all of the above process will vary greatly in size distribution. For example, FMC Grade 260 (dense sodium carbonate) and FMC Grade 100 (light sodium carbonate) crystals were analyzed and show the following size distribution:

TABLE I

Grade 260 Grade 100

850 microns and Greater = 0.16% 0.30% 600 to 850 microns = 0.54% 1.40% 425 to 600 microns = 14.41% 12.90% 212 to 425 microns = 65.54% 51.48% 106 to 212 microns = 17.66% 29.04% 63 to 106 microns = 1.25% 4.45% 38 to 63 microns = 0.25% 0.25% less than 38 microns = 0.17% 0.17%

This large size distribution can adversely affect dissolving rates and can produce undesirable dust (at less than about 60 microns). This is particularly a problem if the material is to be used in dry processes such as glass manufacturing. In addition, a wide particle size distribution, such as that illustrated above, can cause serious problems in the filtration or centrifugation processes used to separate crystals from the mother liquor. U.S. Patent No. 2,954,282 describes an additive which can be used to reduce crystal size variations in the sesquicarbonate process in order to enhance the centrifugation operation.

It is an object of the present invention to provide a method for the manufacture of sodium carbonate or bicarbonate that is cost effective.

It is another object of the present invention to provide a process for the manufacture of sodium carbonate or bicarbonate from trona or other bicarbonate and/or carbonate mineral or solutions that allows for the proper control of crystal size and density.

It is another object of the present invention to provide a process that can be used on any bicarbonate, carbonate or bicarbonate-carbonate mixture to produce either pure bicarbonate of carbonate.

It is still a further object of the present invention to provide a process that allows for the controlled production of bicarbonates and carbonates.

It is still a further object of the present invention to provide a process that can precipitate sesquicarbonate from a trona solution without excess carbonate.

These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.

SUMMARY OF THE INVENTION

The present invention is a method of producing sodium carbonate or bicarbonate from any solution or carbonate mineral, but especially from trona that comprises the steps of: (1) passing a solution containing trona to a precipitator; (2) adding an alcohol to the solution in the precipitator so as to precipitate bicarbonate and /or carbonate from the solution, (3) washing the precipitated bicarbonate, carbonate or mixture with an alcohol-containing solution, and (4) drying the washed precipitated crystals at low temperatures.

In the method of the present invention, if solid trona or another mineral is used initially, then the solid trona is passed to a crusher prior to precipitation. The solid trona is crushed into smaller particles. The smaller particles are then dissolved in water so as to form the solution containing trona or the other mineral. In this method, the step of dissolving includes the steps of heating the water to a temperature in excess of lOOop, and mixing the heated water with the crushed solid trona or mineral rock. Then the solution from the crushed solids or from a solution is filtered. Organics and suspended solids are filtered from some solutions, especially the solution containing trona prior to passing the solution to the precipitator. Alternatively, an organic inhibitor chemical can be added to a solution containing high TDS like tailing pond water prior to passing the solution to the precipitator. This allows for the prevention of the precipitation of sulfate. Another method of removal of high sulfate from the crystals in the precipitation step of this invention is via the precipitation step. The solution that contains trona has a concentration

of trona ranging between 50 grams per liter to saturation at 200OF at one atmosphere.

The step of adding the alcohol to the solution includes the step of adding methanol to the solution at a concentration ranging from approximately 10 volume percent to approximately 90 volume percent. This step of adding the methanol can further be utilized in a situation in which crystal size is controlled. In this process, the solution is passed to a first precipitator and to a second precipitator. A first concentration of methanol is added to the solution in the first precipitator. A second concentration of methanol is added to the solution in the second precipitator. Where different sizes of carbonate particles are being developed, the first concentration of methanol will have a different concentration than the second concentration of methanol.

After the step of precipitating, the alcohol is vacuum filtered from the precipitated carbonate prior to the step of washing.

The step of washing includes washing the precipitated crystals with methanol or another alocohol like ethanol, buryl or even acetone in a concentration of between 50 and 100 volume percent. In those processes in which the density of the crystal is to be controlled, the step of washing includes passing the precipitated crystals from the first precipitator to a first washer and passing the precipitated crystals from the second precipitator to a second washer. The precipitated carbonate from the first precipitator is washed with a third concentration of alcohol. The precipitated carbonate from the second precipitator is washed with a fourth concentration of alcohol. The third concentration of alcohol and the fourth concentration of alcohol can be varied depending upon the density of crystal that is desired.

The step of drying includes heating the washed precipitated crystals to a temperature of no less than 120OF. The step of drying can include passing the washed precipitated carbonate from the first washer to a first dryer and passing the washed precipitated carbonate from the second

washer to a second dryer. These dryers can have a different temperature or pressure applied therein. For example, if it is desired to make sodium bicarbonate, then the atmosphere within one of the dryers can have a carbon dioxide atmosphere.

In the present invention, the alcohol from the step of precipitating and from the step of washing is recycled through the system. In particular, this step of recycling includes the steps of: (1) passing the alcohol from the precipitation and washing steps to a distiller; (2) heating the passed alcohol in the distiller to a temperature of no less than 220OF, and (3) passing the distillates from the distiller for use in the system or for disposal.

In the present invention, the precipitator can be a multi-stage precipitator. In the event that the precipitator is a multi-stage precipitator, a fraction of the alcohol is added to each of the stages of the precipitator as the solution containing trona, other minerals or just bicarbonate or carbonate passes through these stages of the precipitator. The precipitated crystals is then removed from each of the stages of the precipitator. In the present invention, the step of adding alcohol and the step of washing is carried out at generally above ambient temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a block diagram showing the process of the present invention in its simplest form.

FIGURE 2 is a block diagram showing the process of the present invention in its preferred embodiment.

FIGURE 3 is a block diagram showing an alternative embodiment of the process of the present invention.

FIGURE 4 is a graph showing the solubility of trona in water.

FIGURE 5 is a graph showing the time versus temperature conversion rate of bicarbonate to carbonate in the drying section.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGURE 1, there is shown at 10 a block diagram showing the simplest form of the process of the present invention. The process 10 of the present invention initially involves the passing of a solution containing trona (indicated in FIGURE 1 as the "bicarbonate/carbonate solution") to a precipitator 12. As used herein, the term "trona" can also be applicable to solutions and minerals containing sodium carbonate, sodium bicarbonate or sesquicarbonate. The flow of the trona-containing solution will- pass along line 14. When the solution containing trona is in the precipitator 12, an alcohol is added to the solution in the precipitator 12 so as to precipitate carbonate from the solution. The alcohol enters the precipitator 12 along line 16. The precipitated carbonate and alcohol is passed along line 18 to the washer 20. The precipitated carbonate is washed in the washer 20 with an alcohol-containing solution. This alcohol-containing solution is passed along line 22 to the washer 20. The result of the washing process will cause the flow of the alcohol to pass outwardly of the washer 20 along line 16. Similarly, the remaining alcohol of the precipitation process is passed along line 24 through valve 26 and outwardly therefrom along line 28 to the distiller 30. The distiller 30 will recycle the alcohol by heating the alcohol to a temperature in which the distilates are separated. The alcohol distilate will pass along line 22, through valve 26, and to the washer 20.

When the carbonate crystals have been washed, the crystals are passed to a dryer 32. The dryer 32 will impart heat to the crystals so that the carbonate and with a carbon dioxide atmosphere bicarbonate crystals can be formed. These crystals are passed outwardly along line 34 for storage exterior of the system. The heating process in the dryer 32 will cause the evaporation and heating of the water within the crystals. This evaporated water is passed along line 36 for use as part of the steam stripper 38. The steam stripper 38 will facilitate the ability to recycle the water, along

line 40, back to the plant. Steam is introduced to the steam stripper 38 along line 42. The steam output of the steam stripper 38 is passed along line 44 for use in the distiller 30.

The process 10 of the present invention is proper for controlling the crystal size, crystal size distribution, and crystal density for the sodium carbonate crystals produced from the natural trona ores. The input of the bicarbonate/carbonate solution 14 can be natural trona that has been calcined prior to dissolving the ore (such as is used ^• in the monohydrate process) or on natural trona that is dissolved before calcining (such as used in the sesquicarbonate process). In the process 10 of the present invention, the addition of the alcohol 16 to the aqueous solution 14 of calcined of uncalcined trona ore serves to precipitate the carbonate crystals. The resulting crystals can be separated by filtration or centrifugation. The necessiate of an internal recycle of a carbonate solution to precipitate sesquicarbonate crystals is eliminated. The crystals are washed in the washer 20 in an alcohol solution. The crystals are then dried in the dryer 32. The alcohol 16 is recovered for reuse by passing through the distiller 30. In the process 10, the crystals size is controlled by the amount of alcohol 16 used in the crystalization and precipitation step. The crystal density can be controlled by the concentration of alcohol used in the washer 20. The crystals produced by this process show considerably less variation in size than crystals produced by the monohydrate, sesquicarbonate, or the FMC load density processes.

The process 10 of the present invention can be used on solutions of calcined or uncalcined trona over a concentration range of about 50 g/L to saturation at about 200OF and one atmosphere. Depending on the size of crystals desired, alcohol can be added over the concentration range of about 10 volume percent to about 90 volume percent. The average crystal size will vary as a function of the volume percent alcohol that is added. In the present invention, the preferable alcohol to use is methanol.

However, it is believed that other alcohols, such as ethanol, propanol, and the like can function properly. Methanol is the preferred alcohol in view of the low cost, quick evaporation, and ease of use.

Depending on the desired crystal density, the crystals can be washed in the washer 20 in alcohol solutions ranging from about 50 volume percent to 100 volume percent. The average crystal density will be a function of the volume percent of alcohol in the crystal wash solution entering the washer 20 through line 22.

In addition to the controlling of crystal size, crystal size distribution, and crystal density, the sesquicarbonate crystals generated by the process of the present invention can be converted at significantly lower temperatures than crystals generated by the sesquicarbonate process.

In the process 10 of the present invention, the steps of precipitating and washing are carried out at ambient temperatures. As such, the overall energy cost to the system is at a minimum. The dryer 32 serves to dry the washed precipitated carbonates. The dryer should apply temperatures of no less than 120OF to the washed precipitated carbonate therein. If it is desired to have a bicarbonate output of the dryer 30 when precipitating a pure bicarbonate solution, then the temperatures, which are applied, should be less than 150OF and the atmosphere within the dryer should be a vacuum or, at most, atmospheric pressure. Alternatively, if a bicarbonate crystal is desired from a mixture or pure carbonate then the atmosphere within the dryer 32 can be a carbon dioxide atmosphere.

In the process 10 of the present invention, the alcohol/water mixture is continually recycled throughout the system. As can be seen, after the alcohol is properly reacted with the trona containing solution in the precipitator 12, the used alcohol is passed to the distiller 30. The distiller 30 will then distill the impurities from the alcohol such that the alcohol can be recycled for use in the precipitation of the carbonate crystals. The mixture of water and alcohol can be controlled throughout the process 10

so as to control crystal density, crystal size, and crystal size distribution.

FIGURE 2 shows the simplified embodiment of the present invention for trona. In FIGURE 2, the initial trona-containing solution passes along line 50 to a first precipitator 52 and to a second precipitator 54. The trona-containing solution 50 can be the result of passing solid trona into a crusher 54. The crusher 54 will serve to crush the solid trona into solid particles. These particles then pass to a dissolver 56. The dissolver serves to dissolve the smaller particles in water so as to form the trona-containing solution. In order to properly dissolve the trona, the water within the dissolver 56 should be heated to a temperature in excess of lOOOF. As can be seen in FIGURE 4, the solubility of trona is dependent upon the temperature of water into which it is dissolved. The dissolver 56 serves to mix the heated water with the crushed solid trona. Any tailings from the dissolver 56 pass through line 58 to a tailings pond. A filter 60 is interposed between the dissolver 56 and the precipitators 52 and 54 so as to filter organics from the trona-containing solution.

In FIGURE 2, it can be seen that a trona-containing solution can pass from a tailing pond 62 through the valve 64 and into line 66. An organic inhibitor chemical 68 can be introduced to the flow of the trona-containing solution from the tailing pond 62 if required. The inhibitor chemical is, preferably, an amine which serves to prevent the precipitation of sulfate into the carbonate crystals. The trona-containing solution from the tailing pond 62 can pass along line 69 so as to be part of the water used in the dissolver 56 or can be valved so as to pass as part of the solid tailings 70. As can be seen in FIGURE 2, there are two precipitators 52 and 54. The trona-containing solution passes to both of the precipitators 52 and 54. The alcohol is then added to each of the precipitators 52 and 54. If it is desired to create large crystals from one precipitator 52 and small crystals from the other precipitator 54, then the concentration of alcohol passing into the precipitators 52

and 54 from line 72 can be properly controlled. In other words, the concentration of the alcohol entering precipitator 52 will be different than the concentration of alcohol entering the precipitator 54. As such, the arrangement of dual precipitators 52 and 54 can be used so as to "customize" crystal size. It can be seen that the output of the first precipitator 52 passes to the vacuum filter 74. Similarly, the output of the second precipitator 54 will pass to another vacuum filter 76. The vacuum filter will separate the remaining water and alcohol from the crystals. The output of the vacuum filter 74 passes to a first washer 78. Similarly, the output of the vacuum filter 76 passes to a second washer 80. When the crystals are in the separate washers 78 and 80, then different concentrations of alcohol can be used for the washing of the crystals. For example, if varying densities of crystals are desired, then one concentration of alcohol should be introduced into washer 78 and another concentration of alcohol should be introduced into washer 80. The control of the concentration of alcohol can be easily managed by the introduction of water into the flow of alcohol. In FIGURE 2, it can be seen that the output of the washers 78 and 80 passes as a single flow 82 back for use on the precipitators 52 and 54. The water and alcohol outputs of the vacuum filters 74 and 76 pass as a single flow 84 as reflux back to the distiller 86.

The output of the first washer 78 passes to a first dryer 88. Similarly, the crystal output of the second washer 80 passes to a second dryer 90. As stated previously, each of these dryers 88 and 90 can apply different temperatures and/or pressures to the washed carbonate crystals therein. For example, if it is desired to produce bicarbonate crystals, then heat can be applied to the crystals in accordance with the graphical representation of FIGURE 5. After the crystals are dried in the dryers 88 and 90, they can be passed for storage as heavy ash, light ash, or an intermediate size. The dual arrangement of precipitators, washers and dryers facilitates the ability to control the output of the system depending on the needs of the user.

The distiller 86 can be used to remove the water and impurities from the reflux passing from line 84. After the reflux has been distilled by the distiller 86, the alcohol passes through line 92 back for use in the system. This alcohol 92 can, for example, be used for the washing of the crystals in the washers 78 and 80. A vapor recovery line 94 is connected to the distiller 86 so as to recover any vapors that may pass as a result of the distillation process. The distillation process is carried out by the introduction of steam 96 into the distiller 86. The water output of the distillation process can pass as a flow outwardly of the system and/or into the drying units 88 and 90. The water output passes along line 98 to a steam stripping area 100. Steam is introduced at 102 to the steam stripping area. The heated water, containing the impurities of the previously- described process, will pass through the filter 104 for the removal of calcium and magnesium. The filtered water will then pass through the alumina 106. The alumina 106 will serve to remove silica from the filtered water. The alumina 106 combines with the filter 108 so as to properly remove this silica. The output of the filter 108 then passes back to the tailing pond 62 or for use throughout the system.

The tailing pond water has a high hardness and high silica and sulfate. These materials have been concentrated over the years from the blowdown from the processes. There is a natural inhibitor in the tailing pond water, an organic compound, which serves to prevent sulfates from being precipitated. The use of the steam stripping system 100, of the present invention, serves to reduce the contaminants passed through the system. Because of the high sulfate in the water, magnesium hydroxide does not aid in the removing of silica. As a result, hot water, after steam stripping, is passed over the alumina 106 prior to filtration 108 to remove silica. In this way, the hardness, some sulfate, and the silica, are reduced prior to reentry into the system or passage back to the tailing pond 62.

The process 10 of the present invention is a totally new concept with several applications. The process of the

present invention can be applied as a completely new trona plant which would be much more energy efficient than those in use today. It could also be used in a current plant so as to replace the evaporators. The method of the present invention causes the drying of precipitated carbonates so as to obtain the desired density of carbonate or ash. The drying allows for the formation of the ash. It has been found that this light ash has been even less dense than the FMC light ash and the crystals are smaller and more uniform in size so that the product dissolves in solution approximately twenty times faster than the FMC light ash.

FIGURE 3 shows an alternative embodiment of the process 120 of the present invention. In the process illustrated in FIGURE 3, the trona-containing solution can pass into the system directly through line 122, from a tailing pond 124, or from other sources 126. An inhibitor 128 is added to the tailing pond solution 124 prior to entry into the system. A filter 130 serves to remove organics from the flow streams 122 and 124. Similarly, a filter 132 serves to remove organics from the source 126. The flow from the filter 130 passes through line 132 to a precipitator 134, then to a washer 136, and then to a dryer 138. The water and alcohol mixture coming from the precipitator 134 passes through line 140 to the distiller 142. The distiller will serve to distill the water and alcohol mixture and pass the distilled mixture through line 146 for use as part of the washer 136. After washing, the alcohol passes through line 148 back for use with the precipitator 134.

Importantly, in the embodiment shown in FIGURE 3, a three stage precipitator 150 is provided for the filtering of the trona-containing solution passing from line 126. In the three stage precipitator 150, a fraction of the alcohol is added to each of the stages 152, 154, and 156 of the precipitator 150. The trona-containing solution will pass through the stages 152, 154, and 156 of the precipitator 150. The precipitated carbonate passes from each of the stages 152, 154, and 156 so as to pass along line 158 to the washer 136. A vacuum filter 160 acts on the precipitated

carbonate so as to separate the water from the precipitated carbonate. The three stage precipitator 150 finds particular application if the inhibitor 128 cannot be applied to the trona-containing solution. The multi-stage precipitator 150 allows alcohol to be added in small and controllable amounts. The multi-stage precipitator 150 reduces the time of reaction for the trona-containing solution, and its impurities, with the alcohol. As such, the undesirable salts will pass from the multi-stage precipitator 150 through line 164.

Tests of the present method have indicated superior results over prior systems. Examples of these test results are provided hereinafter.

EXAMPLE I

Simulated calcined trona solution containing 230 g/L of Na2C03 along with 100 volume percent methanol were pumped simultaneously into a stirred 500 ml E. flask using microprocessor driven Masterflex tubing pumps at rates of 20 ml/minute and 10 ml/minute respectively. The temperature in the E. flask was maintained at 50oc +/- 5θc. The system was run for about 15 minutes, then the resulting crystals were removed from the solution by vacuum filtration. The crystals were washed on the filter using two 75 ml portions of 100% methanol. The washed crystals were dried in an oven at 80OC for 30 minutes. Following drying the crystals were examined under a scanning electron microscope, the average crystal size measured, and a photomicrograph taken. The average crystal size was determined to be approximately 400 microns. The crystal size distribution was as follows:

TABLE II

850 microns and greater 0%

600 to 850 microns 2.50%

425 to 600 microns 49.22%

212 to 425 microns 30.63%

106 to 212 microns 16.70%

64 to 106 microns 0.87

38 to 64 microns 0.09% less than 38 microns 0%

EXAMPLE II

Simulated calcined trona solution containing 230 g/L of Na2C03 along with 100 volume percent methanol were pumped simultaneously into a stirred 500 ml E. flask using microprocessor driven Masterflex tubing pumps at rates of 20 ml/minute and 14 ml/minute respectively. The temperature in the E. flask was maintained at 50c ^* c +/- 50c The system was run for about 15 minutes, then the resulting crystals were removed from the solution by vacuum filtration. The crystals were washed on the filter using two 100 ml portions of 100% methanol. The washed crystals were dried in an oven at 80oc for 30 minutes. Following drying the crystals were examined under a scanning electron microscope, the average crystal size measured, and a photomicrograph taken. The average crystal size was determined to be approximately 250 microns. The crystal size distribution was as follows:

TABLE III

850 microns and greater 0%

600 to 850 microns 0%

425 to 600 microns 1.56%

212 to 425 microns 61.98%

106 to 212 microns 33.27%

64 to 106 microns 2.70

38 to 64 microns 0.48% less than 38 microns 0%

EXAMPLE III

Simulated calcined trona solution containing 230 g/L of Na2C03 along with 100 volume percent methanol were pumped simultaneously into a stirred 500 ml E. flask using microprocessor driven Masterflex tubing pumps at rates of 20 ml/minute and 20 ml/minute respectively. The temperature in the E. flask was maintained at 50oc +/- 5oc. The system was run for about 10 minutes, then the resulting crystals were removed from the solution by vacuum filtration. The crystals were washed on the filter using two 100 ml portions of 100% methanol. The washed crystals were dried in an oven at 80oc for 30 minutes. Following drying the crystals were examined under a scanning electron microscope, the average crystal size measured, and a photomicrograph taken. The average crystal size was determined to be approximately 150 microns. The crystal size distribution was as follows:

TABLE IV

850 microns and greater 0%

600 to 850 microns 0%

425 to 600 microns 0.14%

212 to 425 microns 35.37%

106 to 212 microns 60.12%

64 to 106 microns 3.76%

38 to 64 microns 0.50% less than 38 microns 0.10%

EXAMPLE IV

Simulated calcined trona solution containing 230 g/L of Na2C03 along with 100 volume percent methanol were pumped simultaneously into a stirred 500 ml E. flask using microprocessor driven Masterflex tubing pumps at rates of 20 ml/minute and 20 ml/minute respectively. The temperature in the E. flask was maintained at 50OC +/- 5θC. The system was run for about 8 minutes, then the resulting crystals were removed from the solution by vacuum filtration. The crystals were washed on the filter using two 120 ml portions of 100% methanol. The washed crystals were dried in an oven at

80°C for 30 minutes. Following drying the crystals were examined under a scanning electron microscope, the average crystal size measured, and a photomicrograph taken. The average crystal size was determined to be approximately 100 microns. The crystal size distribution was as follows:

TABLE V

850 microns and greater 0%

600 to 850 microns 0%

425 to 600 microns 0%

212 to 425 microns 7.68%

106 to 212 microns 48.25%

64 to 106 microns 39.01

38 to 64 microns 4.95% less than 38 microns 0.10%

EXAMPLE V

Crystals were prepared according to the method described in Example III except the crystals were washed with 100ml of 50 volume percent methanol. Following drying, the crystals were examined using a scanning electron microscope at l,000x magnification to observe the porosity of the crystals. The density of the crystals was determined by the weight of crystals that would fill a 10 ml graduated cylinder to the 10ml mark. The graduate was tapped sharply several times on a hard surface after each milliliter (approximately) of crystal addition. The density of the crystals determined by this method was 1.106 g/cc.

EXAMPLE VI

Crystals were prepared according to the method described in Example V except the crystals were washed with 100 ml of 70 volume percent methanol. Following drying, the crystals were examined using a scanning electron microscope at l,000x magnification to observe the porosity of the crystals. The density of the crystals was determined to be 1.050 g/cc.

EXAMPLE VII

Crystals were prepared according to the method described in Example V except the crystals were washed with 100 ml of 90 volume percent methanol. Following drying, the crystals were examined using a scanning electron microscope at l.OOOOx magnification to observe the porosity of the crystals. The density of the crystals was determined to be 0.793 g/cc.

EXAMPLE VIII

Crystals were prepared according to the method described in Example V except the crystals were washed with 100 ml of 90 volume percent methanol. Following drying, the crystals were examined using a scanning electron microscope at l,000x magnification to observe the porosity of the crystals. The density of the crystals was determined to be 0.793 g/cc.

EXAMPLE IX

Crystals were prepared according to the method describe in Example III except that a temperature of 70°C +/- 5oc was maintained in the E. flask. The crystals generated showed the same general characteristics as those in Example III.

EXAMPLE X

One-hundred milliliters of a solution of simulated calcined trona containing 230 g/L Na2C03 is heated to 50OC +/- 5θC and stirred continuously. Next 100 ml of methanol are added at the rate of about 10 ml/second. The solution is stirred for 5 minutes and the resulting crystals removed by filtration. The crystals were washed on the vacuum filter with two, 50 ml portions of methanol and dried in an oven at 80OC for 30 minutes. The crystals showed the following size distribution:

TABLE VI

850 microns and greater 0%

600 to 850 microns 0.76%

425 to 600 microns 1.48%

212 to 425 microns 2.73%

106 to 212 microns 21.53%

64 to 106 microns 56.61

38 to 64 microns 14.42% less than 38 microns 2.45%

EXAMPLE XI

171g of natural trona was dissolved in approximately 650 ml of DI water at 90oc. Following vacuum filtration, 667 ml of filtrate was collected and analyzed. The filtrate was found to contain 119.2 g/L of Na2C03, and 89.4 g/L Na2HC03. Methanol and the trona solution were pumped simultaneously into a 500 ml E. flask at rates of 5.4 and 6.2 ml/minute respectively. The system was run for about 20 minutes while maintaining a temperature of 50oc in the E. flask. The crystals were removed by vacuum filtration, washed on the vacuum filter with two 50 ml portions of 100% methanol and analyzed. The crystals were placed in a sealed plastic bottle and stored in a refrigerator at 5oc. Individual 2 gram (approximately) samples of the crystals were dried in a convection oven at 55, 75, 90, and lOOOC. The crystals were analyzed periodically to determine the rate at which bicarbonate was being converted to carbonate. The time required for 100% conversion of bicarbonate to carbonate at the respective temperatures shown on FIGURE 5.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the described method may be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.