PROCESS FOR PRODUCING SODIUM BROMIDE

Abstract

The invention relates to chemical technology pertaining to mineral salts and can be used in the chemical industry. A process for producing sodium bromide from a bromide-containing polycomponent hydromineral feedstock includes: two-stage oxidation of bromide ions using gaseous chlorine during acidification of a brine: air desorption of elementary bromide: absorption of same using a cooled solution of sodium bromide: and reduction using ammonia in the presence of sodium hydroxide. The resulting concentrate of sodium bromide is evaporated until crystals are formed. The sodium bromide crystals are dried and a mother liquor is used to produce a solution of sodium bromide as a commercial product.

Claims

1. Method for producing sodium bromide from a bromide-containing polycomponent hydromineral feedstock of field brines of the chloride calcium-magnesium type of oil and gas producing enterprises, which consists of the following: the stream of field brine, purified from dissolved iron, petroleum products, and mechanical impurities, is subjected to preheating to 30-35 C., neutralization of alkalinity, and acidification to pH values in interval 2.5-3.5 using mineral acids to prevent hydrolysis of free bromine, then the oxidation of bromide ions with gaseous chlorine to elementary bromine is performed in two stages: in Stage I, the oxidation of bromide ions to elementary bromine is performed at 65%-70% of its initial content; wherein the air desorption of elementary bromine is performed in a countercurrent mode, and the absorption of elementary bromine from the bromine-air mixture is performed in a column-type mass transfer apparatus with a multidirectional screw nozzle operating in a countercurrent mode, then the absorption of elementary bromine is reduced in the form of complex bromide (Na[Br2]Br) to bromide ions in a circulation tank with ammonia, in the presence of a sodium hydroxide solution, then the resulting sodium bromide solution is purified from bromine and alkali impurities using formic acid, then the purified sodium bromide solution is evaporated in two stages: in Stage I, evaporation is performed to a concentration of sodium bromide of 50% in vacuum evaporators with water vapor recompression; in Stage II, evaporation is performed in evaporators equipped with steam jackets and anchor-type mixers, and evaporation is performed until a pulp containing sodium bromide crystals is obtained, with a ratio of sodium bromide to water of 3:1, the resulting pulp is cooled to 60-62 C. and subjected to centrifugation to separate crystalline sodium bromide from the mother liquor, then the separated crystals are dried in a screw dryer, and after Stage I of desorption, a bromide-containing polycomponent hydromineral feedstock is supplied for the oxidation of bromide ions to elementary bromine with chlorine gas up to 95% of its residual content in order to extract the residual amount of bromine.

2. Method according to claim 1, characterized in that the subsequent operations of air desorption of bromine, absorption of bromine-air mixture, recovery of absorbed elementary bromine, and purification of the resulting sodium bromide solution are similar to Stage I of oxidation.

3. Method according to claim 1, characterized in that the purified sodium bromide solution mixed with the mother liquor from the stage of obtaining crystalline sodium bromide is evaporated to the required density to produce the sodium bromide solution as a commercial product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 schematically shows the sequence of actions of the method for producing sodium bromide from a bromide-containing polycomponent hydromineral feedstock. The method includes acidification of the initial brine with mineral acids to prevent hydrolysis of free bromine, then the acidified brine enters Stage I of oxidation with gaseous chlorine to 65% of bromide ions from their initial content to elementary bromine, then the oxidized water enters Stage I of desorption of elementary bromine with atmospheric air that circulates in the system. The bromine-air mixture (BAM) is sent for the absorption of bromine by a solution of sodium bromide (absorbent). The absorbent saturated with bromine is periodically pumped into a collection tank, where the process of reducing bromine to sodium bromide (Stage I) occurs by dosing solutions of sodium hydroxide and ammonia water. The resulting solution of sodium bromide is used to produce crystalline sodium bromide. The air after bromine extraction, which contains some residual bromine, is used for desorption in Stage II. Waste water from Stage I of desorption enters Stage II of oxidation with chlorine gas, at which another 25% of bromide ions are oxidized from their initial content to elementary bromine. Next, water from Stage II of oxidation enters Stage II of air desorption of elementary bromine. Similar to Stage I, the bromine-air mixture is supplied for absorption by the same absorbent (solution of sodium bromide). The absorbent saturated with bromine is periodically pumped into a collection tank, where the process of reducing bromine to sodium bromide (Stage II) occurs by dosing solutions of sodium hydroxide and ammonia water. The resulting solution of sodium bromide is used to produce the commercial form of sodium bromide solution. Waste water is sent for neutralization to prepare it for further disposal.

EXAMPLES

[0013] Example 1. 10.65 m.sup.3 of brine with a density of 1,154 kg/m.sup.3, with a hydrogen index of 5.84 of the following composition: (Ca2+, Mg2+, Sr2+)=36.51 kg/m.sup.3; Fe.sub.total=0.0002 kg/m.sup.3; (K+, Na+, Li+)=25.40 kg/m.sup.3; Cl=142.92 kg/m.sup.3; HCO3=0.076 kg/m.sup.3; SO42=0.46 kg/m.sup.3; Br=2.94 kg/m.sup.3 was acidified with 30% hydrochloric acid to pH=2.5 and subjected to one stage of oxidation with gaseous (anodic) chlorine to a residual content of Br=1.05 kg/m.sup.3, which corresponds to the degree of oxidation=64.3%; elementary bromine was desorbed by atmospheric air and absorbed by a solution of sodium bromide with a concentration of 57.3 kg/m.sup.3 on a packed column; the absorbent saturated with elementary bromine was reduced with ammonia water in the presence of sodium hydroxide; the resulting concentrate of sodium bromide (density=1,373 kg/m.sup.3, bromide concentration=508 kg/m.sup.3) was evaporated on a gas burner until sodium bromide crystals precipitated; the resulting crystals were dried in a drying cabinet; the mother liquor was used to obtain sodium bromide solution as a product. As a result, 20.5 kg of crystalline sodium bromide with a content of the main substance in the dry product of 99.28% was obtained. After Stage I of oxidation and bromine extraction (Br=1.05 kg/m.sup.3), brine in a volume of 10.65 m.sup.3 entered Stage II of oxidation with gaseous (anodic) chlorine to a residual content of Br=0.30 kg/m.sup.3, which corresponds to the degree of oxidation for this stage=71.2%. The absorption of sodium bromide solution and the reduction of elementary bromine with ammonia water was performed similarly to Stage I. The resulting concentrate was mixed with the mother liquor after precipitation of sodium bromide crystals from Stage I and evaporated on a gas burner to the required density, and this solution was used as a product. The resulting liquid product was 15.3 dm.sup.3 with a density of 1,495 kg/m.sup.3 and sodium bromide content of 44.4%. The overall degree of bromine recovery from the brine was 89%.

[0014] Example 2. The composition of the initial brine differs from Example 1: 1,152 kg/m.sup.3, with a hydrogen index of 5.8 of the following composition: (Ca2+, Mg2+, Sr2+)=41.17 kg/m.sup.3; Fe.sub.total=0.0002 kg/m.sup.3; (K+, Na+, Li+)=31.92 kg/m.sup.3; Cl=151.12 kg/m.sup.3; HCO3=0.03 kg/m.sup.3; SO42=0.52 kg/m.sup.3; Br=2.32 kg/m.sup.3. The volume of brine was 10.5 m.sup.3. The degree of oxidation of bromine in Stage I was 75%, which corresponds to the residual concentration Br=0.58 kg/m.sup.3 in Stage II, the degree of oxidation was 74.1%, which corresponds to Br=0.15 kg/m.sup.3. The following was obtained: 19.2 kg of crystalline sodium bromide with main substance content of 98.51%; 16.6 dm.sup.3 of liquid product with a density of 1,470 kg/m.sup.3 and sodium bromide content of 44.1%. The overall degree of bromine recovery from the brine was 93.5%.

REFERENCES

[0015] 1. USSR Patent No. 8215, Class 12/J. H. Van der Meulen. 1929. [0016] 2. Pozin M. E. Technology Pertaining to Mineral Salts. 4.sup.th ed. Leningrad, Khimiya Publisher, 1974. Part 1. [0017] 3. Patent RU2135406C 1. Method for Producing Bromides of Alkali Metals, Calcium, and Ammonium/V. I. Kuzmin, V. N. Kuzmina; Institute of Chemistry and Chemical-Metallurgical Processes of the Siberian Branch of the Russian Academy of Sciences. No. 97108733/25; stated on 28 May 1997; published on 27 Aug. 1999. [0018] 4. USSR Inventor's Certificate No. 783229 Class 03 at 3/10/O. V. Lebedev Yu. F. Artamonov, 1980. [0019] 5. U.S. Pat. No. 3,145,084. 1964. [0020] 6. USSR Inventor's Certificate No. 138232 Class 01 at 9/04/V. I. Ksinzenko, E. A. Dianov, 1960.