Feb. 6, 1951 L. A. BACKMUN 2,540,648 PROCESS FOR RECOWERING SODIUM BICARBONATE AND SODIUM BORATE FROM A COMPLEX BRINE Filed Sept. 25, 1946

CA Reonation Tower

..a First crop NaHCO3 CRYstALs

Agitator-2 sul-2-

T- C - EN era. 22 - Second CreoP Ns HCO3 C2Ystals

NVENTOR, Ag//7/7 4. A5/sca/774 v?. 7 BY 4---- //. 6.-- agroaAYa Y Patented Feb. 6, 1951 2,540,648 UNITED STATES PATENT OFFICE 2,540,648 PROCESS FOR RECOVERING SOD. UM BI CARBONATE AND SODEUM BORATE FROW A COMPLEX. BRENE Lynn A. Blackmun, westend, Calif., assignor to West End Chemical Company, a corporation of California, Application September 25, 1946, Serial No. 699,283 1. Claims. (C. 23-59) 1. 2 This invention relates to a process for the present to make further purification of the borax treatment of a complex brine such as that which a necessity. I cannot say at present to what fac occurs naturally at Searles Lake, California, and tor this is attributable; Searles Lake has been which may contain various salts such as Sodium undergoing exploitation and utilization for many carbonate, sodium chloride, sodium Sulphate, years. The practice heretofore has been to pump potassium chloride and various Sodium Salts of the brine from only certain levels in the lake, boric acid. More particularly, this invention is usually at a depth of between 50 and 90 feet. concerned with a process for the recovery of Sodi With the brine continuously extracted from this um bicarbonate and borax from the brine. In region in the lake, the surface water running Patent 1756,122 of April 29, 1930, Hellmers dis 0. into the lake and the dilute brine present in the closed a process wherein a complex brine such as upper portion of the lake may be diluting the that derived from Searles Lake was carbonated lower brine body and altering its composition. to precipitate sodium bicarbonate. The Solution In any case, and irrespective of the explanation, remaining after removal of the sodium bicar whereas the borax produced heretofore has been bonate is saturated with respect to borax which Substantially Sodium bicarbonate free, Suficient crystallizes out when the solution is cooled. As Sodium bicarbonate now precipitates with the is indicated in the aforementioned patent, What borax during the cooling of the brine as to make occurs in the brine during carbonation may be borax refining essential. In any case, and ir represented by the following: respective of the explanation for the sodium 20 bicarbonate contamination of the borax, I have now discovered that by agitating the brine before cooling and after a first crop of sodium bicar The carbonation is carried on under pressure bonate Crystals have been deposited, a second until carbon dioxide is present in the brine in Crop of Sodium bicarbonate crystals can be re excess of that required to effect the precipitation covered So that thereafter the remaining brine of a substantial portion of the sodium carbonate can be cooled and the borax precipitated in a present as sodium bicarbonate. . In the aforemen relatively pure state. - tioned patent, it is indicated that this excess of This improvement I have been able to prac carbon dioxide probably served another useful tice Successfully on a commercial scale to produce purpose; e. g., carbonic acid is a stronger acid 30 the borax and sodium bicarbonate in relatively than boric acid and therefore an equilibrium is pure State, the borax being of such composition probably established in the brine undergoing car that recrystallization of the borax was made un bonation, in accordance with the following: necessary. It is in general the broad object of the present Na2B4O7--H2O--2CO2->4HaBO3-2NaHCO3 invention to provide a novel and improved pro As the process of Patent 1756,122 has been 35 ceSS for the treatment of a complex brine such as practiced commercially, the brine from Searles. that found in Searles Lake, California, to the end Lake is fed into a carbonation tower wherein it is that Sodium bicarboinate and borax can each be carbonated with carbon dioxide under a pressure recovered in a relatively pure state. of 35 to 40 pounds gauge. The sludge from the The invention includes other objects and fea carbonation towers is discharged into a classifier 40 tures of advantage, some of which, together with Where the sodium bicarbonate crystals rapidly the foregoing, will appear hereinafter wherein settle to the bottom and are removed by the clas the present preferred form of process of treating sifier rakes. The remaining brine is then cooled a complex brine is disclosed. S0 that SOdium borate decahydrate, 45 The drawing accompanying and forming a part hereof is a diagrammatic apparatus representa tion and a flow sheet. crystallizes out. In commercial operation when Referring to the drawing, the brine, as derived this process was first undertaken at Searles Lake, from Searles Take or from any other suitable Substantially all of the bicarbonate of soda con 50 Source 6 of a complex brine, is fed through line taminating the borax crystallized from the brine into a suitable carbonation tower or towers 8, could be removed by a simple washing operation preferably at the upper end thereof. Carbon On a Vacuum filter. I have now observed that dioxide is introduced from a suitable source 9 un the borax which precipitates is relatively im der a pressure of 40 to 45 pounds at the base of pure and that sufficient sodium bicarbonate is. 55. the tower to carbonate the brine and form sodium

2,540,648 3 4. bicarbonate from the sodium carbonate present. the first crop because it simplifies the operation The exit slurry from the carbonation tower is and the apparatus required. then run through line G into a classifier I claim: wherein, under atmospheric pressure, the sodium 1. A process for recovering sodium bicarbonate bicarbonate Crystals Settle to the bottom and are from a brine containing Sodium carbonate and taken off through line 2 as a first crop of sodium Sodiuin borate comprising carbonating the brine bicarbonate Crystals. until (a) carbon dioxide is present in Solution The brine from the classifier is taken off in excess of that required to convert substan through a line 4 to a first agitator 6 wherein tially all the Sodium carbonate present to sodium the brine is agitated as by means of paddles, 0. bicarbonate and (b) a first crop of sodium bi and by introducing air from line f8 So that the Carbonate Crystals precipitates in the brine, entire mass of brine in the agitator is subject to Separating the precipitated sodium bicarbonate agitation to the end that crystal formation of from the brine, then agitating and aerating Sodium bicarbonate occurs. The overflow brine the brine to form and to precipitate a second passes through line 9 into a second agitator 2 15 Crop of Sodium bicarbonate crystals in the brine, into which air is also introduced through a line Separating the Second crop of sodium bicarbon 22 and wherein the brine is further agitated as ate crystals from the brine, and then recovering by paddles 23 until crystallization of the Sodium the Sodium borate from the brine as substantially bicarbonate is substantially complete. The pure sodium borate decahydrate. Slurry from agitator 2 is taken off through a 20 2. A process for recovering sodium bicarbon line 24 into a thickenel 28, the underflow from ate from a brine containing sodium carbonate which, containing the second crop of sodium bi and Sodium borate comprising carbonating the carbonate crystals, is drawn off through line 27, brine until (a) carbon dioxide is present in solu and returned through line for feed to classi tion in excess of that required to convert Sub fier f . The remaining brine, constituting the 25 Stantially all the Sodium carbonate present to overflow from thickenel 26, is taken off through Sodium bicarbonate and (b) a first crop of line 29 and is cooled or is otherwise Suitably Sodium bicarbonate crystals: precipitates in the treated as at 3 to effect the precipitation of brine, Separating the precipitated sodium bi borax which is then removed through line 3 carbonate from the brine, then aerating and and recovered as at 32. 30 agitating the brine to form and to precipitate In previous operations, the brine removed a Second crop of Sodium bicarbonate crystals in from the classifier has been fed directly into the brine, Separating the second crop of sodium cooler 3 and the brine has not been Subject to bicarbonate Crystals from the brine, and then the agitation and retention provided by agi Cooling the brine to precipitate Substantially tato's 6 and 2. While this operation was con 35 pure borax therefrom. tinued successfully on a commercial basis for 3. A process for recovering sodium bicarbonate many years, it has now been found that the re from a brine containing sodium carbonate and Sulting borax, instead of being relatively pure, Sodium borate comprising carbonating the brine as has been the case in the past practice of the until (a) carbon dioxide is present in solution in process, is contaminated with sodium bicarbon 40 eXceSS of that required to convert substantially ate. By agitating the brine Suitably for an ade all the Sodium carbonate present to sodium bi quate period of time, a Second Crop of Sodium bi carbonate and (b) a first crop of sodium bi carbonate crystals can be derived, prior to the Carbonate Crystals precipitates in the brine, sepa borax recovery operation, so that Subsequently rating the precipitated sodium bicarbonate from the borax can be recovered in the Saale state of the brine, then slowly agitating the brine for a relative purity as was the case. When operation period of about eight hours to form and to pre of the Hellmers process was first undertaken. cipitate a second crop of sodium bicarbonate The extent and seriousiness of the borax con Crystals in the brine, Separating the second crop tamination will be more apparent when I point of Sodium bicarbonate crystals from the brine, out that the second crop of crystals amounts 50 and then recovering the sodium borate from the to as much as 20% of the total bicarbonate re brine as Substantially pure sodium borate dec covery. The first crop of bicarbonate. Crystals ahydrate. usually comprises 80% to 85% of the total bi 4. A process for recovering sodium bicarbon carbonate recovery, from 15% to 20% being re ate from a brine containing sodium carbonate covered as the Second CrOp. 55 and Sodium borate comprising carbonating the The extent of agitation and the an OUnt of air brine until (a) carbon dioxide is present in solu addition depends, in each case, upon the Vigo'- tion in excess of that required to convert sub ousness of the agitation, the temperature of the stantially, all the Sodium carbonate present to brine, the extent to Which the Sodium bicarbon Sodium bicarborate and (b) a first crop of ate has been previously precipitated and other 60 Sodium bicarbonate crystals precipitates in the factors. I have found that by agitating the brine, Separating the precipitated sodium bi brine slowly for a period of 8 to 9 hours total re carbonate from the brine, then slowly agitating tention in the two agitators, Sufficient of the the brine for a period of about eight hours to Sodium bicarbonate is removed as a second crop form and to precipitate a second crop of sodium 65 bicarbonate crystals in the brine, separating the of Crystals to ensure that the borax finally re Second crop of Sodium bicarbonate crystals from covered is of the desired and requisite purity. the brine, and then cooling the brine to precipi From the foregoing, it is believed to be ap F. Substantially bicarbonate free borax there parent that I have disclosed a novel and Worth 0. While improvement in the art of treating com 70 5. A process for recovering sodium bicarbon plex brine to recover sodium bicarbonate and ate from a brine containing sodium carbonate borax. It is not necessary that the first crop and Sodium borate comprising carbonating the of Sodium bicarbonate crystals be actually sepa brine until (a) carbon dioxide is present in solu rated from the brine prior to the agitation to tion in excess of that required to convert sub - bring down the second crop. I prefer to separate 75 stantially all of the sodium carbonate present

2,540,648 5 6 to SOdium bicarbonate and (b) a first crop Of 9. A process for recovering sodium bicarbon sodium bicarbonate Crystals precipitates in the ate from a brine containing sodium carbonate brine, Separating the precipitated Sodium bi and Sodium borate comprising carbonating the carbonate from the brine, then slowly agitating brine until (d) carbon dioxide is present in Soul the brine for a period of about eight hours While tion in exceSS of that required to convert Sub aerating the brine to form and to precipitate a stantially all the Sodium carbonate present to Second crop of Sodium bicarbonate crystals in Sodium bicarbonate and (b) a first crop of the brine, separating the Second crop of Sodium Sodium bicarbonate crystals precipitates in the bicarbonate crystals from the brine, and then brine, then agitating and aerating the brine to cooling the brine to precipitate Substantially bi 0. form and to precipitate a Second Crop of Sodium carbonate free borax therefrom. bicarbonate crystals in the brine, Separating the 6. A process for recovering sodium bicarbon sodium bicarbonate crystals from the brine, and ate from a brine containing Sodium carbonate then recovering the Sodium oorate from the and Sodium borate comprising carbonating the brine as Substantially pure Sodiuin borate deca brine under a super-atmospheric pressure until hydrate. (a) carbon dioxide is present in Solution in ex 10. A process for recovering Sodium bicarbon cess of that required to convert Substantially all ate from a brine containing Sodium carbonate the sodium carbonate present to Sodium bicar and sodium borate comprising carbonating the bonate and (b) a first crop of Sodium bicarbon brine until (a) carbon dioxide is present in Solu ate crystals precipitates in the brine amounting 20 tion in excess of that required to convert Sub to 80 to 85 per centum of the total carbonates stantially alli the Sodiunil carbonate present to present, separating the precipitated Sodium bi sodium bicarbonate and (b) a first crop of carbonate from the brine, then agitating the sodium bicarbonate crystals precipitates in the brine under atmospheric pressure without the brine, then agitating the brine in the presence addition of additional carbon dioxide to form 25 of the first crop of crystals to form and to pre and to precipitate a second crop of Sodium bi cipitate a second crop of Sodium bicarbonate carbonate crystals in the brine, separating the crystals in the brine, separating the first and the second crop of Sodium bicarbonate crystals from second crops of Sodium bicarbonate crystals from the brine, and then recovering the sodium borate the brine, and then recovering the Sodium borate from the brine as Substantially pure SOdium 30 from the brine as Substantially pure Sodiu borate decahydrate. borate decahydrate. 7. A process for recovering Sodium bicarbonate 11. A process for recovering Sodium bicarbon from a brine containing Sodium carbonate and ate from a brine containing Sodium carbonate sodium borate comprising carbonating the brine and sodium borate comprising carbonating the under a super-atmospheric preSSure until (d) 3 5 brine under a super-atmospheric pressure until carbon dioxide is present in Solution in exceSS (a) carbon dioxide is present in Solution in ex of that required to convert Substantially all the cess of that required to convert Substantially all sodium carbonate present to Sodium bicarborate the sodium carbonate present to Sodium bi and (b) a first crop of Sodium bicarbonate carbonate and (b) a first crop of Sodium bi crystals precipitates in the brine amounting to 40 carbonate crystals precipitates in the brine 80 to 85 percentum of the total carbonateS preS amounting to 80 to 85 percentum of the total ent, separating the precipitated Sodium bicar carbonates present, then slowly agitating the bonate from the brine, then agitating the brine brine under atmospheric pressure for a period under atmospheric pressure without the addi of about eight hours to form and to precipitate a tion of additional carbon dioxide to form and second crop of sodium bicarbonate crystals in to precipitate a second crop of Sodium bicarbon the brine, separating the Sodium bicarbonate ate crystals in the brine, Separating the Second crystals from the brine, and then recovering the crop of sodium bicarbonate Crystals from the sodium borate from the brine as Substantially brine, and then cooling the brine to precipitate pure sodium borate decahydrate. substantially pure borax therefrom. 50 8. A process for recovering sodium bicarbon LYNN A. BLACKMUN. ate from a brine containing Sodium carbonate and sodium borate comprising carbonating the REFERENCES CTED brine under a super-atmospheric pressure until (a) carbon dioxide is present in Solution in exceSS The following references are of record in the of that required to convert Substantially all the 55 file of this patent: sodium carbonate present to Sodium bicarbonate UNITED STATES PATENTS and (b) a first crop of sodium bicarbonate crystals Number Nairie Date precipitates in the brine amounting to 80 to 85 1,000,138 Wrinkle et al. ------Aug. 8, 1911 percentum of the total carbonates present, sepa 60 1,232,156 Wrinkle et al. ------July 3, 1917 rating the precipitated Sodium bicarbonate from 1,343,508 Hirschkind ------June 15, 920 the brine, then slowly agitating the brine under 1350,090 Wrinkle et al. ------Aug. 17, 1920 atmospheric pressure for a period of about eight 1756,122 Hellmers ------Apr. 29, 1930 hours to form and to precipitate a Second crop 1865,832 Chesny ------July 5, 1932 of sodium bicarbonate crystals in the brine, Sepa 65 1865,833 Chesny ------July 5, 1932 rating the second crop of Sodium bicarbonate crystals from the brine, and then recovering the 1911,794 Britton ------May 30, 1933 sodium borate from the brine as Substantially 2,105,109 Dolley ------Jan. 11, 1938 pure sodium borate decahydrate.