Abstract:
A method of producing sodium carbonate from any solution or carbonate mineral, especially trona, that includes: removing calcium and magnesium compounds from an input solution; passing the input solution to a precipitator, adding methanol of 30% to 70% by volume to the solution in the precipitator so as to precipitate carbonate from the solution, washing the precipitated carbonate with a methanol-containing solution, and drying the washed precipitated crystals at low temperatures. The present invention provides a refined technique for reducing impurities and increasing efficiency of the process whereby sodium carbonate crystals can be formed of various sizes, shapes, densities and distributions by adjusting various parameters of the process. The sodium carbonate crystals produced from the process may originate from an input solution comprised of calcined-sodium carbonate solution, tailing pond water, waste pond water, sesquicarbonate or uncalcined trona solution, or from various mixtures of carbonates and bicarbonates.

Description:
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not applicable. 
     REFERENCE TO AN APPENDIX SUBMITTED ON COMPACT DISC 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to processes for manufacturing sodium carbonate and sodium bicarbonate crystals. More particularly, the present invention relates to methods and apparatus for forming sodium carbonate crystals of a desired size, shape and density. 
     2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98 
     Much of the world&#39;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 175 to 200° C./347 to 397° F. This serves to convert bicarbonate to carbonate. Calcining operations at temperatures between 350 to 400° C. also destroy 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 heat applied to the water. 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 monohydrate crystals are then dried and calcined to anhydrous sodium carbonate. 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. A solution of sodium carbonate (to maintain in excess of 10 to 25% excess carbonate) is recycled in the evaporators so as to obtain the sesquicarbonate. 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. Pat. No. 3,479,133, issued on Nov. 18, 1969, to F. M. Warzel describes the monohydrate process. U.S. Pat. No. 3,119,655, issued in January of 1964, to Frint et al. describes the sesquicarbonate process. Similarly, U.S. Pat. No. 3,260,567, issued on July of 1966, to Hellmers et al. and U.S. Pat. No. 3,361,540, issued on Jan. 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 lower density crystals or higher surface area crystals. U.S. Pat. No. 5,043,149, issued on Aug. 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. A large variety of commercial products are produced by the above-described processes. Each of the sodium carbonate crystals formed by these various processes were analyzed for the purpose of showing the size distribution of the crystals. The attached Table I shows the size distribution and shape of the various commercial products: 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Commercial Products 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                 General Chemical 
                 ITOCHU Chem 
               
               
                 Solution ID 
                 FMC 100 
                 FMC 160 
                 FMC 260 
                 RP Lite 
                 RP Dense 
                 Synthetic 
                 Fine Synthetic 
               
               
                   
               
               
                 MeOH Feed rate 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 RP feed rate 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 MeOH feed rate 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 Initial soln. volume 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 RPM 
               
               
                 Location of addition 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 Crystal Density (lb/ft3) 
                 49.4 
                 61.9 
                 65.31 
                 52 
                 61.4 
                 35 
                 60.2 
               
               
                 Size Distribution (%) 
               
               
                 1000 u 
                   
                   
                   
                   
                   
                   
                 0.2 
               
               
                  850 u 
                 0 
                 0 
                 0 
                 2.8 
                 0.3 
                 0 
                 3.6 
               
               
                  600 u 
                   
                   
                 0.03 
                   
                   
                   
                 8.5 
               
               
                  425 u 
                   
                   
                 0.98 
                   
                   
                   
                 21.1 
               
               
                  355 u 
                 15.5 
                 10.1 
                 11.38 
                 28.5 
                 54.7 
                 4.1 
               
               
                  300 u 
                   
                   
                   
                   
                   
                   
                 23.3 
               
               
                  250 u 
                 30.4 
                 35.8 
                 29.39 
                 31.7 
                 33.2 
                 4.3 
               
               
                  213 u 
                   
                   
                   
                   
                   
                   
                 24.5 
               
               
                  150 u 
                   
                   
                 29.48 
                   
                   
                   
                 13.5 
               
               
                  106 u 
                 46.4 
                 49.2 
                 17.21 
                 32.8 
                 31 
                 35.2 
                 3.1 
               
               
                  75 u 
                   
                   
                 7.55 
                   
                   
                 0.9 
               
               
                  63 u 
                 7.5 
                 4.6 
                 2.71 
                 4.1 
                 0.8 
                 33.1 
               
               
                  45 u 
                   
                   
                   
                   
                   
                   
                 1 
               
               
                  &lt;45 u 
                   
                   
                   
                   
                   
                   
                 0.3 
               
               
                  38 u 
                 0.1 
                 0.2 
                   
                 0.1 
                 0.3 
                 14.5 
               
               
                  &lt;38 u 
                 0 
                 0 
                   
                 0 
                 0 
                 8.5 
               
               
                 Screened 
                 x 
                 x 
                 x 
                 x 
                 x 
                 x 
                 x 
               
               
                 Not Screened 
                   
                   
                   
                   
                   
                   
                 x 
               
               
                 Detergency (%) 
               
               
                 Absorptivity (%) 
                 13.9 
                 12.5 
                   
                   
                   
                 25 
                 17.8 
               
               
                 Sulfate (ppm) 
                 300 
                 400 
                 700 
                 1000 
                 3000 
                 200 
                 600 
               
               
                 TOC (ppm) 
                 56 
                 2 
                   
                   
                   
                 8 
               
               
                 Crystal Morphology 
                 Large rods 
                 Small rods 
                 Blocky 
                 Mixed balls 
                 Mixed balls 
                 Small snowflakes 
                 Small Balls 
               
               
                 Date 
                 May 26, 1995 
                 Jun. 28, 1995 
                 Sep. 1, 1995 
                 Jun. 28, 1995 
                 Jun. 28, 1995 
                 Jun. 28, 1995 
                 November 1995 
               
               
                   
               
             
          
         
       
     
     The various sizes, shapes and distributions of crystals are applicable in various processes. For example, a large size distribution can adversely affect the dissolving rates of the sodium carbonate and also can produce undesirable dust (at less than about 60 microns). This poses a problem if the material is to be used in dry processes, such as glass manufacturing. In addition, a wide particle size distribution can cause serious problems in the filtration or centrifugation processes which are used to separate the crystals from the mother liquor. As such, it is desirable to form sodium carbonate crystals which have a size distribution, shape and density which mirrors that of commercial products while producing such products at a relatively low cost. 
     U.S. Pat. No. 4,584,077, issued on Apr. 22, 1986, to Chlanda et al. describes a process for recovering sodium carbonate from trona and other mixtures of sodium carbonate and sodium bicarbonate. This process includes the steps of: (1) forming an aqueous solution comprising sodium carbonate and sodium bicarbonate; (2) removing a portion of the sodium bicarbonate from the solution so as to form a mother liquor comprising sodium carbonate and a reduced amount of sodium bicarbonate; (3) subjecting the mother liquor to an electrodialytic water splitting by circulating the water liquor through an electrodialytic water splitter to produce a liquid reaction product comprising sodium carbonate substantially free of sodium bicarbonate; and (4) withdrawing the liquid reaction product comprising sodium carbonate substantially free of sodium bicarbonate from the electrodialytic water splitter. In this patent, it was described that the sodium carbonate solution product from the base compartment is fed to a primary absorber wherein a liquid loading substance is absorbed into the sodium carbonate solution. The “liquid loading substance” includes liquids such as ammonia, methanol, ethanol and the like. This is added to the sodium carbonate solution to cause the sodium carbonate to crystallize out as the decahydrate, monohydrate or mixtures thereof. As a reaction product, these can be readily separated from the crystallized sodium carbonate-containing material. 
     This Chlanda process is an extremely energy inefficient process for producing sodium carbonate from trona. A sodium carbonate solution is produced from an electrodialytic water splitter. Sodium bicarbonate is converted to sodium carbonate prior to reacting with the “liquid loading substance”. 
     U.S. Pat. No. 6,022,385, issued on Feb. 8, 2000, to the present inventor teaches 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 calcined trona, a solution of carbonate, or tailing pond water to a precipitator; (2) adding methanol of 30% to 70% by volume to the solution in the precipitator so as to precipitate carbonate from the solution, (3) washing the precipitated carbonate with an alcohol-containing solution, and (4) drying the washed precipitated crystals at low temperatures. Fundamentally, the process of the present invention provides a technique whereby sodium carbonate crystals can be formed of various sizes, shapes, densities and distributions by adjusting various parameters of the process. In particular, such sodium carbonate crystals can be produced from various inputs such as from a calcined-sodium carbonate solution, from tailing pond water, from sesquicarbonate or uncalcined trona, or from various mixtures of carbonates and bicarbonates. 
     Applications of the currently known processes for producing sodium carbonate crystals encounter problems when adjusting for the various types of sodium carbonate containing solutions. Such input solutions range from relatively pure bicarbonate solution, carbonate-bicarbonate solution, sesquicarbonate solution, calcined trona solution, uncalcined trona solution to tailing pond water. Each type of input solution contains various impurities and compounds which reduce the efficiency of the precipitation processes and affect the purity of the sodium carbonate crystals produced. 
     For example, when processing trona deposits from waste ponds and tailing ponds, the input solution from the ponds contain mostly carbonate and decahydrated carbonate with water impurities over 200,000 ppm and high levels of organics, hardness, silica and sulfates. In U.S. Pat. No. 6,022,385, issued on Feb. 8, 2000, to the present inventor, the amount of impurities may be minimized in sodium carbonate crystals by making large size crystals. The process disclosed in U.S. Pat. No. 6,022,385 also appears to convert the decahydrate carbonate to a lower hydrate and even to a monohydrate. Thus, when using the process of U.S. Pat. No. 6,022,385, additional heat to dehydrate the decahydrated carbonate is not required, unlike other disclosed processes. 
     Currently, the methods of precipitating sodium carbonate crystals from the various sources of sodium carbonate solutions requires finding means to reduce the amount of impurities from natural or less-refined sources. One method considered is to freeze the input solution in order to reduce the amount of impurities. For organic impurities, some methods include using organoclay to filter out organic impurities. For the hardness impurities, the removal involves steam stripping. For the silica impurities, alumina is used for the silica removal. Both the silica and hardness removal processes are disclosed in U.S. Pat. No. 6,022,385 to the present inventor. It is also known that hardness impurities may be removed by contacting with fresh water and the solid crystals in the precipitation process. These hardness impurities removed by this procedure include calcium and magnesium compounds. However, calcium and magnesium remain in the solution even after known means to attempt to purify the precipitated crystals. 
     It is an object of the present invention to provide a method for the manufacture of sodium carbonate or bicarbonate crystals that reduces scaling and impurity levels caused by hardness compounds, such as dolomite and trace shorite found in trona formations. 
     It is an object of the present invention to provide a method for the manufacture of sodium carbonate or bicarbonate crystals that reduces calcium and magnesium impurities from the input solution. 
     It is another object of the present invention to provide a method for the manufacture of sodium carbonate or bicarbonate crystals that washes excess methanol from the precipitated crystals so as to allow the use of direct fire dryers. 
     It is a further object of the present invention to provide a process that improves the overall heat balance. 
     It is still a further object of the present invention to provide a process for removing methanol from the precipitated crystals before drying. 
     These and other objects of the present invention will become apparent from a reading of the attached specification and appended claims. 
     BRIEF 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) removing calcium and magnesium compounds from an input solution; (2) passing the input solution to a precipitator, (3) adding methanol of 30% to 70% by volume to the solution in the precipitator so as to precipitate carbonate from the solution, (4) washing the precipitated carbonate with a methanol-containing solution, and (5) drying the washed precipitated crystals at low temperatures. The present invention involves removing bulk water and methanol from the crystals before the step of drying. Fundamentally, the process of the present invention provides a refined technique for reducing impurities and increasing efficiency of the process whereby sodium carbonate crystals can be formed of various sizes, shapes, densities and distributions by adjusting various parameters of the process. In the present invention, the sodium carbonate crystals produced from the process may originate from an input solution comprised of calcined-sodium carbonate solution, tailing pond water, waste pond water, sesquicarbonate or uncalcined trona solution, or from various mixtures of carbonates and bicarbonates. 
     In the method of the present invention, an input solution from trona has high concentrations of dolomite, shorite, and other calcium compounds. With both the tailing pond water and calcined trona input solutions, X-ray analyses may indicate a high concentration of three compounds in the tailing pond water. These were sulfate, hardness compounds and silica from the tailing pond. Hardness was not a scaling problem in the methanol process, and an exact hardness purity level was never discovered. However, for those trona formations with high dolomite (CaCO 3 .MgCO 3 ) concentration, it may be better to remove these calcium and magnesium-based impurities. The present invention uses methanol to concentrate these calcium and magnesium ions prior to reaching the methanol concentration level at which sodium carbonate begins to precipitate. 
     Most mines operate at about 50° C., 122° F., where the sodium carbonate solubility is about 477 g/1000 grams of water or 322 g/1000 grams saturated solubility. Most mines use about 300 g/1000 grams of sodium carbonate solution to go to the evaporators. About 15% volume methanol will initiate precipitation or exceed the saturation point of sodium carbonate, so the 15% by volume methanol would appear to concentrate the solution by about 37% to reach the 322 g/1000 grams of saturated solution (ignoring changes in volume of liter versus 1000 grams of saturated solution and decrease volume when adding methanol). Dolomite in the mined ore is about 5%. With a ratio of 1.65 for solution/ore the concentration in the solution is about 9%, assuming all dolomite goes into the solution. Thus, for 300 g/liter sodium carbonate concentration in an input solution, there would be approximately 30 g/liter dolomite. 
     To 300 g/l sodium carbonate, at 122° F., and 200, 1000, and 10,000 mg/liter of dolomite powder was added. Then a solution of 10% by volume methanol was added. The precipitate was about 98% dolomite and 2% calcite according to X-ray analyses. The removal was on average 90% of the dolomite added. Less than 1% sodium carbonate was precipitated in a few solutions, and this appeared to be due to cooling during filtration and would not be present in actual operations where the temperature would be maintained during filtration. 
     Therefore, most calcium and magnesium compounds should be precipitated from a solution of about 10% by volume methanol. Sodium carbonate from calcined trona did not precipitate until 15% by volume methanol. This result agrees with the solubility data for the dolomite and most other calcium and magnesium compounds reviewed. The data indicates less than 10% methanol could be added to concentrate most of the calcium and magnesium compounds at 122° F. 10% by volume was used to get maximum concentration and still be lower than the concentration required for sodium carbonate. 
     In the method of the present invention, the process also includes removal of excess methanol from the precipitated crystals prior to going to the dryer so that excess methanol would not be lost, and more efficient current direct fired dryers could be used. 
     It is known to take 15% by volume methanol density wast to precipitate a 300 g/l solution of sodium carbonate, so the excess methanol could be removed with the 300 g/l solution by washing the precipitated crystals as long as a 15% by volume methanol solution is not reached. The removal wash must be performed at less than 15% by volume to prevent further precipitation of crystals. 
     In the present invention, a vacuum filter was used to remove the bulk water and methanol after the density wash solution of 100% methanol. The density wash and the methanol removal wash were both performed at 0.2 gallons/pound of solids. Previous work had indicated a value from 0.15-0.2 gallons/pound of solids was required for the density wash. After the original precipitation of crystals by the density wash, the average methanol in the crystals was about 54,000 mg/1000 grams (about 17 gallons of methanol per ton of crystals). After the removal wash, the methanol in the crystals was below 20 mg/1000 grams. This removal wash on the crystals was performed on filter paper. With agitation in a large facility for the removal wash, the methanol in the crystals should be less than 5 mg/1000 grams. Therefore, a removal wash of the crystals should remove most of the remaining methanol on the crystals. 
     The removal wash may also be applied to precipitates of the calcium and magnesium compound. The simple mass and heat balance were made using precipitation of the dolomite and other calcium and magnesium impurities with a 90-100% methanol removal wash for lite density crystals and a 50-50% methanol removal wash for dense crystals. A triple effect distillation is used on the methanol for recycling. The precipitated dolomite and other impurities are also washed to remove excess methanol. 
     The removal of excess methanol allows for a more efficient heat balance to dry the crystals. It is indicated that about 1 mM Btu/ton of soda ash is required from steam latent heat at 366° F. for the distillation. However, about 1 mM Btu/ton of soda ash is available at 137° F. to condense part of the methanol. While the lower temperature heat is not the same entropy, the lesser heat can be used to heat the dissolving fluid for the calcined trona, to preheat the air to the dryer. Thus it has a use in the system and thus would appear to be a net cancellation of heat. The usual evaporators use 1 mM Btu/ton of soda ash. The condensed water from the steam for distillation was not used, but the water was left at that temperature so only the latent heat of evaporation had to be added. No thermal efficiencies were used in this simple heat balance for reusing the heat. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the process of the present invention in its simplest form. 
         FIG. 2  is a block diagram showing a preferred embodiment of the present invention for production of low density sodium carbonate crystals. 
         FIG. 3  is a block diagram showing a preferred embodiment of the present invention for production of high density sodium carbonate crystals. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 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 essentially involves the passing of an input solution at line  14  through a process to precipitate sodium carbonate crystals at line  34 . As used herein, the “input solution” can be comprised of calcined-sodium carbonate, tailing pond water, waste pond water, sesquicarbonate or uncalcined trona or various mixtures of carbonates and bicarbonates. The flow of the input solution will first pass along line  14 . 
     When the input solution passes to a crystallizer  48 , methanol is added to the input solution so as to precipitate impurities containing calcium and magnesium. In particularly, these impurities include dolomite, shorite and other calcium compounds. The amount of methanol is controlled so as to keep sodium carbonate in the liquid form, while other inorganic molecules are crystallized out of the input solution. Methanol enters the crystallizer  48  through line  46 , and the precipitated impurities are filtered as solids through the crystallizer  48  at line  58  as waste. The flow of the input solution, without the calcium and magnesium compounds, continues to pass along line  14  to a precipitator  12 . 
     When the input solution is in the precipitator  12 , methanol is added to the solution in the precipitator  12  so as to precipitate carbonate (the term “carbonate” is applicable to general sodium carbonate forms, like sodium bicarbonate, sodium carbonate, sodium sesquicarbonate and mixtures thereof), from the input solution. The methanol enters the precipitator  12  along line  16 . The precipitated carbonate and methanol is passed along line  18  to the filter and washer  20 . The precipitated carbonate is washed in the filter and washer  20  with a new methanol-containing solution. This methanol-containing solution is passed along line  22  to the filter and washer  20 . The result of the washing process will cause the excess methanol from the precipitator  12  to be removed from the precipitated carbonate crystals, and this methanol removal wash passes outwardly of washer  20  along line  16  to be recycled back into the system. The amount of methanol from the methanol removal wash is adjusted so as to prevent further precipitation of remaining sodium carbonate in the original input solution, if any. 
     The input solution is separated from the precipitated carbonate crystals in the filter, such that the remaining liquid, without sodium carbonate compounds, passes along line  34 A and line  36  to a steam stripper  38  for recycling. Also, any remaining methanol, cycled through line  16  of the precipitation process or received from the filter and wash  20 , is passed along line  24  through valve  26  and outwardly therefrom along line  28  to the distiller  30 . The distiller  30  will recycle the methanol by heating the methanol to a temperature in which the precipitated carbonate and methanol are separated. The distilled methanol passes along line  22 , through valve  26 , and to the filter and washer  20  for re-use in the process  10 . 
     When the precipitated carbonate crystals have been washed, the crystals are passed to a dryer  32  along line  34 . The dryer  32  will impart heat to the crystals so that either carbonate crystals or bicarbonate crystals (with a carbon dioxide atmosphere) can be formed. These crystals are further 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 and break hydrates in the crystals if an anhydrous form is desired. This evaporated water is combined into line  36  for use as part of the steam stripper  38 . Line  36  passes water and contains some alcohol. Line  34 A also passes water to 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 output steam of the steam stripper  30  can also serve to strip the carbon dioxide. 
     The input solution along original line  14  can originate from natural trona that has been calcined prior to dissolving the ore (such as is used in the monohydrate process) or natural trona that is dissolved before calcining (such as used in the sesquicarbonate process or in solution mining). In the process  10  of the present invention, the addition of the methanol  46  to the aqueous input solution  14  of calcined or uncalcined trona ore in the crystallizer  48  serves to crystallize and allow for separation of impurities before a different addition of methanol is used to precipitate the carbonate or carbonated bicarbonate crystals. The resulting impurity crystals can be separated by filtration, centrifugation or vibrating screen. The impurity crystals may also be washed in a filter/washer using a methanol-containing solution as a methanol removal wash, to remove excess methanol on the impurity crystals. The impurity crystals can also be dried in a dryer, and the methanol used to crystallize the impurities may be recovered for reuse by passing through the distiller. For efficiency, the crystallizer  48  may pass the impurity crystals and input solution into filter and wash  20  and drier  32  such that the impurity crystals are separated similar to the process of precipitating and washing the desired sodium carbonate crystals. 
     In the process  10 , the size, shape and distribution of the crystals can be controlled by the rate of addition of methanol as well as the volume percent of methanol  16  used in the precipitation step in the precipitator  12 . The crystal density also affects the required concentration of methanol used in the methanol removal wash of the filter and wash  20 . The crystals produced by this process  10  show considerably less variation in size than crystals produced by the current monohydrate or sesquicarbonate processes. 
     The process  10  can use trona to precipitate as sesquicarbonate without bicarbonate forming. With methanol the sesquicarbonate crystals are produced without additional alkalinity. X-ray diffraction analyses indicate only a small amount of sodium carbonate is present with the sesquicarbonate and no bicarbonate. The conversion of bicarbonate to carbonate in the original methanol precipitation depends upon the time of contact. The sesquicarbonate crystals are smaller crystals. In normal operation bicarbonate would be precipitated prior to getting a sesquicarbonate, without adding alkalinity. 
     The process  10  of the present invention can be used on solutions of sodium carbonate over a concentration range of about 120 grams/liter to saturation. Depending on the size of crystals desired, methanol can be added so as to produce a final solution concentration range (a resultant liquor) of about 15 volume percent to about 70 volume percent of methanol. The average crystal size will vary as a function of the volume percent methanol that is added plus the rate of methanol addition (residence time). In the present invention, the residence time can be between 10 and 100 minutes. The residence time of the methanol with the input solution in the precipitator will affect crystal size (to be described hereinafter). 
     Depending on the desired crystal density, the crystals can be washed in the filter/washer  20  in methanol-containing solutions ranging from about 50 volume percent to 100 volume percent. The average crystal density will be a function of the volume percent of methanol in the crystal wash solution entering the filter/washer  20  through line  22 . In the step of washing, other alcohols, such as ethanol, propanol, butanol and acetone, may be used; however, methanol is preferred because of the ease and efficiency of recycling the methanol throughout the process. 
     For sesquicarbonate crystals, when sesquicarbonate is washed with 50 to 100 volume percent methanol, sesquicarbonate converts to thermonatrite (monohydrate). This wash to precipitate the sesquicarbonate was performed at 0.15 gallons/pound crystals. After the completed process of washing and drying to form sesquicarbonate, the sesquicarbonate appears to form both anhydrous sodium carbonate and wegschiederite (Na 2 CO 3 .3NaHCO 3 ). By increasing the drying time or temperature, the wegschiederite may be expected to convert to anhydrous sodium carbonate. Process  10  of the present invention controls the need for conversion to anhydrous sodium carbonate. The methanol removal wash solution in the step prior to drying effects the density of the crystals to control the percentage of change from sesquicarbonate to anhydrous sodium carbonate and wegschiederite. For dense crystals a 50/50 volume percent methanol removal wash is used (See  FIG. 3 ), and for light density crystals or light ash, a 100 volume percent wash is used (See  FIG. 2 ). Once density is set, other washes do not appear to affect density. 
     Sesquicarbonate crystals generated by the process of the present invention can be converted to anhydrous crystals at significantly lower temperatures than crystals generated by the sesquicarbonate process. 
     For sodium carbonate crystals, the process  10  of the present invention may precipitate the trona into soda ash, also known as sodium carbonate. Depending upon the speed of addition of the methanol during the original precipitation, the size of the crystals can be controlled. In addition, the process  10 , when washing crystals in 100 volume percent methanol or 50/50 volume percent methanol in a methanol removal wash, may control the density of the crystals. Thus, tailor grade soda ash can be produced with controlled crystal size distribution and crystal density to some extent. 
     Furthermore, in the process  10  of the present invention, the precipitation step is carried out at considerably lower temperatures than the evaporation process. As such, the overall energy cost to the system is reduced. The dryer  32  serves to dry the washed precipitated carbonates. The dryer  32  should apply temperatures of no less than 120° F. to the washed precipitated carbonate therein. As pure bicarbonate passes to the dryer  32 , and if it is desired to have a bicarbonate output of the dryer  32  when precipitating a pure bicarbonate solution, then the temperatures, which are applied, should be less than 150° F. 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 of pure carbonate, then the atmosphere within the dryer  32  must be a carbon dioxide atmosphere. Sesquicarbonate can be formed directly from trona precipitation. Either bicarbonate or carbonate can be formed from the sesquicarbonate, depending upon the dryer process employed. For anhydrous carbonate, a drying temperature of 228° F./109° C. is required at one atmosphere of pressure. 
     Another aspect of the present invention shows that, in the process  10  of the present invention, the methanol/water mixture is continually recycled throughout the system. As can be seen, after the methanol is properly reacted with the input solution in the precipitator  12 , the used methanol is passed to the distiller  30 . The methanol used in the crystallizer  48  to remove the calcium and magnesium impurities is also recycled through line  46  and as line  14  continues through to the precipitator  12 . The methanol removal wash  22  recycles methanol through lines  16  and  24 . The distiller  30  will then distill the water from the methanol such that the methanol can be recycled for use in the other stages of the process, including the original precipitation of the crystals. The mixture of water and methanol can be controlled throughout the process  10  so as to control crystal density, crystal size, crystal size distribution and crystal morphology in the precipitator  12  and so as to adjust the volume percent of the methanol in the crystallizer  48  and methanol removal wash  22  for the desired crystallizing and washing effects. 
       FIG. 2  shows a preferred embodiment of the present invention for precipitation of low density crystals or lite ash through process  90 . Input solution, containing sodium carbonate, is first produced in dissolver  78 . As indicated in  FIG. 2 , solids are added into the dissolver  78  along with water. The solids may include uncalcined trona, calcined trona or other raw compounds containing sodium carbonate including sesquicarbonate. Additionally, the water is added into the dissolver and maintained at 122° F. as indicated in order to dissolve as much solids as possible. Water may also be added through line  61  from the triple affect distillation of the process  90 . In the dissolver  78 , the input solution becomes a liquid, and undissolved particles may be easily filtered out and removed from the dissolver  78  as indicated through line  91 . Input solution is then moved along line  62  to the organic wash station  79 . In the organic wash station  79 , a solvent is added in an attempt to separate organic impurities from the input solution. Known methods and solvent to remove dissolved organic impurities are used and isolated from the input solution through line  92 . 
     Along line  63 , the input solution proceeds to the crystallizer  80 . Methanol is added to the input solution to crystallize the calcium and magnesium impurities, such as dolomite, through line  68  in the crystallizer  80 . Line  68  supplies water and methanol from a triple effect distillation device  84 . By controlling the methanol concentration, only the calcium and magnesium impurities are crystallized out of the input solution. Such impurities are passed through a washing station  89  and proceed along line  69  as dolomite waste. The input solution, without the calcium and magnesium impurities, like dolomite, continue along line  70  towards a precipitator  81 . 
     Before reaching the crystallizer  80 , the input solution is set along line  64  to the washing station  89 . The input solution washes previously crystallized hardness impurities and returns to the crystallizer  80  on line  66 . From line  66  and the washing station  89 , the input solution has recycled residual methanol from the previous crystallization of dolomite. Also before reaching the crystallizer  80 , the input solution is set along line  65  to a centrifuge  83 . The input solution is passed through the centrifuge  83  and returned to the crystallizer  80  on line  67 . This step recycles residual methanol remaining in the centrifuge  83  from previous use. The preferred embodiment of the present invention in process  90  increases efficiency by reuse of materials throughout the system, as shown in the recycling streams through lines  64  and  66  and line  65  and  67 . 
     The input solution, without the calcium and magnesium impurities, enters the precipitator  81  to precipitate the desired sodium carbonate crystals. By controlling addition of methanol through lines  71  and  73  in the precipitator  81 , the sodium carbonate crystals will be precipitated according to the desired density and size as determined by the user. Water, in addition to methanol, may be supplied to the precipitator on line  71  from the triple effect distillation device  84 . The sodium carbonate crystals are formed in the precipitator  81 . To separate the solid carbonate crystals from the input solution, the mixture is transferred to hydrocyclone  82  and then to centrifuge  83  along line  74 . The input solution, now devoid of dissolved sodium carbonate, is filtered through the centrifuge  83  as recyclable water and methanol. The separated liquid is passed through line  75  to the triple effect distillation device  84 . 
     The sodium carbonate crystals in the centrifuge  83  have residual methanol. A methanol removal wash is performed by washing the crystals with 100 volume percent methanol for the low density crystals to become lite ash. The methanol enters the centrifuge  83  through line  72  and removes the excess methanol on the crystals. The methanol solution is now recycled back into the process of the present invention through line  73  for supplying methanol for a later precipitation in the precipitator  81 . Lines  72  and  73  represent another recycling stream for the efficiency of the present invention. 
     After the methanol removal wash, the precipitated and washed crystals are moved along line  76  to be sent to the dryer. The dryer may reduce the crystals into more anhydrous forms and fines  77  of lite soda ash. 
     In the triple affect distillation device  84 , the discarded input solution of water and methanol may be distilled into separate components for recycling back into the process  90  of the present invention. Methanol may be distilled and sent recycled back into the process via line  68  for the crystallization of the calcium and magnesium impurities in the crystallizer  80 . Alternatively, water and methanol may be heated to 137° F. so as to preheat the water to a dissolver. This process will only remove a portion of the methanol from the water. A controlled volume percent of methanol and water may be produced and sent via line  71  into the precipitator  81  for the precipitation of the sodium carbonate crystals. Still further, the triple affect distillation device  84  may heat the water to a point that steam is generated to steam generator  87 . At this point, the condensed water will be considered having less than one part per million of methanol, and this water may be re-used in the dissolver  78  via line  71  for the initial dissolving of trona and production of the original input solution. 
     In the present invention, various methods of reducing impurities has been applied. The input solution has been processed for solid impurities and organic impurities. The present invention offers the new means of reducing hardness impurities. The crystallizer  80  removes such calcium and magnesium compounds using previously disclosed techniques to crystallize the calcium and magnesium compounds from solution as solid crystals. Using a methanol solution of approximately 10 volume percent, the calcium and magnesium compounds are precipitated out of the input solution before the precipitation of the sodium carbonate crystals. As previously disclosed, the sodium carbonate precipitation requires a higher percentage of methanol in order to start a carbonate crystal formation. The present invention proposes the precipitation of different compounds using a lower concentration of methanol, which can be recycled and increase the efficiency of the process of the present invention. 
     Also in the present invention, the processes proposes a methanol removal wash in the centrifuge  83 . Using recycled methanol, at a lower concentration than precipitation, the sodium carbonate crystals are washed so as to remove excess methanol. The excess methanol originated from original precipitation of the crystals. Removing the excess methanol reduces the amount of heat necessary to dry the crystals. This inventive aspect increases the heat efficiency and overall efficiency of the production of sodium carbonate crystals. 
       FIG. 3  shows an alternative embodiment of the present invention for precipitation of high density crystals or heavy ash through process  130 . Similar to  FIG. 2 , the input solution, containing sodium carbonate, is first produced in dissolver  118 . The solids may include uncalcined trona, calcined trona or other raw compounds containing sodium carbonate including sesquicarbonate. Additionally, the water is added into the dissolver  118  and maintained at 122° F. as indicated in order to dissolve as much solids as possible. Water may also be added through line  101  from the triple effect distillation device  124  of the process  130 . In the dissolver  118 , the input solution becomes a liquid, and undissolved particles may be easily filtered out and removed from the dissolver  118  as solids. The input solution then moves along line  102  to the organic wash station  119 , where organic solvent is added to separate organic impurities from the input solution. Known methods and solvent to remove dissolved organic impurities are used and isolated from the input solution. 
     Along line  103 , the input solution proceeds to a crystallizer  120 . Methanol is added to the input solution to crystallize the calcium and magnesium impurities, such as dolomite, through line  108  in the crystallizer  120 . Line  108  supplies water and methanol from a triple effect distillation device  124 . By controlling the methanol concentration, only the calcium and magnesium impurities are crystallized out of the input solution. Such impurities are passed through a washing station and proceed along line  109  as dolomite waste. The input solution, without the calcium and magnesium impurities, continues along line  110  towards a precipitator  121 . 
     Before reaching the crystallizer  120 , the process  130  of  FIG. 3  incorporates the recycling as shown in  FIG. 2 . The input solution is set along line  104  to the washing station to wash previously crystallized hardness impurities and returns to the crystallizer  120  on line  106 . Also before reaching the crystallizer  120 , the input solution is set along line  105  to a centrifuge  123  and returned to the crystallizer  120  on line  107 . This step recycles residual methanol remaining in the centrifuge  123  from previous use. This alternative embodiment of the present invention in process  130  increases efficiency by reuse of materials throughout the system, as shown in the recycling streams through lines  104  and  106  and line  105  and  107 . 
     The input solution, without the calcium and magnesium impurities, enters the precipitator  121  to precipitate the desired sodium carbonate crystals. By controlling addition of methanol through lines  111  and  112  in the precipitator  121 , the sodium carbonate crystals will be precipitated according to the desired density and size as determined by the user. Water, in addition to methanol, may be supplied to the precipitator on line  111  from the triple effect distillation device  124 . The sodium carbonate crystals are formed in the precipitator  121 . To separate the solid carbonate crystals from the input solution, the mixture is transferred to hydrocyclone  122  and centrifuge  123  along line  114 . The input solution, now devoid of dissolved sodium carbonate, is filtered through the centrifuge  123  as recyclable water and methanol. The separated liquid is passed through line  115  to the triple effect distillation device  124 . 
     The sodium carbonate crystals in the centrifuge  123  have residual methanol. A methanol removal wash is performed by washing the crystals with 50 volume percent methanol for the high density crystals to become heavy soda ash. The methanol at 50 volume percent enters the centrifuge  123  through line  113  and removes the excess methanol on the crystals. The methanol solution is now recycled back into the process of the present invention through line  112  for supplying methanol for a later precipitation in the precipitator  121 . Importantly, the process  130  in  FIG. 3  differs in the recycling stream between lines  112  and  113 . The 50 volume percent mixture for the methanol removal wash starts from the precipitator  121 , unlike the 100 volume percent originating from the triple effect distillation device for low density crystals. However, the process  130  maintains efficiency by recycling the 50 volume percent methanol back to the precipitation of sodium carbonate crystals in the precipitator  121 . 
     After the methanol removal wash, the precipitated and washed crystals are moved along line  116  to be sent to the dryer and eventual processing into more anhydrous forms and fines  117  of heavy soda ash. 
     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.