PROCESS FOR PRODUCING AMMONIUM BROMIDE

Abstract

The invention relates to chemical technology pertaining to mineral salts and can be used in the chemical industry. A process for producing ammonium 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 ammonium bromide; and reduction using an ammonia solution. The resulting concentrate of ammonium bromide is evaporated until crystals are formed. The ammonium bromide crystals are dried and the mother liquor is used to produce a solution of ammonium bromide as a commercial product.

Claims

1. Method for producing ammonium bromide from a bromide-containing polycomponent hydromineral feedstock of commercial brines of the chloride calcium-magnesium type, which consists in the fact that the brine stream, purified from dissolved iron, manganese, and insoluble impurities, is subjected to preheating to 30-35? C., neutralization of alkalinity, and acidification to pH values of 2.5 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 73%-74% of the initial content in a flow chlorinator operating in a countercurrent mode; the air desorption of elementary bromine is performed in a countercurrent mode in a desorber; the absorption of elementary bromine from a bromine-air mixture is performed in a column-type mass transfer apparatus with a multidirectional screw nozzle operating in a countercurrent mode; a cooled ammonium bromide solution with a concentration of 400 g/dm.sup.3 is used as an absorbent; then the reduction of absorbed elementary bromine in the form of complex bromide (NH4 [Br2] Br) to bromide ions is performed in the reactor; the resulting ammonium bromide solution is purified from bromine impurities using formic acid, then the purified ammonium bromide solution is evaporated in two stages: in Stage I, evaporation is performed to a concentration of ammonium 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 ammonium bromide crystals is obtained, with a ratio of ammonium bromide to water of 3:1, the resulting pulp is cooled to 60-62? C. and subjected to centrifugation to separate crystalline ammonium 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 gaseous chlorine up to 88% 90% of its residual content in order to extract the residual amount of bromine.

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

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

Description

LIST OF FIGURES

[0015] FIG. 1 schematically shows the sequence of actions of the method for producing ammonium bromide from a bromide-containing polycomponent hydromineral feedstock. The method includes acidification of the initial brine using 31.5% hydrochloric acid to prevent hydrolysis of free bromine to pH=2.5, then the acidified brine enters Stage I of oxidation with gaseous chlorine to 73%-74% of bromide ions from their initial content to elementary bromine with control of the oxidation process by the redox potential of the platinum electrode, then the oxidized water enters Stage I of desorption of elementary bromine by atmospheric air, which circulates in the system (bromine desorption is 95%). The bromine-air mixture (BAM) is directed for the absorption of bromine by a solution of ammonium bromide (absorbent). The absorbent saturated with bromine is periodically pumped into the reactor, where the process of reducing bromine to ammonium bromide (Stage I) occurs by dosing a 25% ammonia solution. The resulting ammonium bromide solution is used to produce crystalline ammonium bromide. The air after bromine extraction, containing some residual bromine, is used for desorption in Stage II. Waste water from Stage I of desorption enters Stage II of oxidation with gaseous chlorine, at which 88%-90% of bromide ions are oxidized from their residual 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 ammonium bromide). The absorbent saturated with bromine is periodically pumped into the reactor, where the process of reducing bromine to ammonium bromide (Stage II) occurs by dosing a 25% ammonia solution. The resulting ammonium bromide solution is used to produce the commercial form of ammonium bromide solution.

[0016] Waste water is sent for neutralization to prepare it for further disposal.

IMPLEMENTATION OF THE INVENTION

[0017] Example 1. 2.43 m.sup.3 of brine with a density of ISO kg/m.sup.3, with a hydrogen index of 5.7 of the following composition: (Ca2+, Mg2+, Sr2+)=31.7 kg/m.sup.3; Fe.sub.total=0.002 kg/m.sup.3; Mg2+=0.003 kg/m.sup.3; (K+, Na+, Li+)=27.42 kg/m.sup.3; Cl=74.37 kg/m.sup.3; HCO3?=0.03 kg/m.sup.3; SO42?=0.73 kg/m.sup.3; Br=2.40 kg/m.sup.3 was acidified with 31.5% hydrochloric acid to pH=2.5 and subjected to Stage I of oxidation with gaseous (anodic) chlorine to a residual content of Br?=0.64 kg/m.sup.3, which corresponds to the degree of oxidation=73.3%; elementary bromine was desorbed by atmospheric air and absorbed with an ammonium bromide solution with a concentration of 395.5 kg/m.sup.3 on a packed column; the absorbent saturated with elementary bromine was reduced with a 25% ammonia solution; the resulting ammonium bromide concentrate was evaporated on a gas burner until ammonium bromide crystals precipitated; the resulting crystals were dried in a drying cabinet; the mother liquor was used to obtain a solution of ammonium bromide as a product. As a result, 4.84 kg of crystalline ammonium bromide with a content of the main substance in the dry product of 99.15% was obtained. After Stage I of oxidation and bromine extraction (Br?=0.64 kg/m.sup.3), brine entered Stage II of oxidation with gaseous (anodic) chlorine to a residual content of Br?=0.07 kg/m.sup.3, which corresponds to the degree of oxidation in this stage=89.0%. 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 ammonium 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 4.46 dm.sup.3 with a density of 1,233 kg/m.sup.3 and sodium bromide content of 32.7%. The overall degree of bromine recovery from the brine was 97.1%.

[0018] Example 2. The composition of the initial brine differs from Example 1:1, 195 kg/m.sup.3, with a hydrogen index of 5.3 of the following composition: (Ca2+, Mg2+, Sr2+)=49.55 kg/m.sup.3; Fe.sub.total=0.003 kg/m.sup.3; Mg2+=0.005 kg/m.sup.3; (K+, Na+, Li+)=25.98 kg/m.sup.3; Cl=166.8 kg/m.sup.3; HCO3?=0.024 kg/m.sup.3; SO42?=0.55 kg/m.sup.3; Br?=3.12 kg/m.sup.3. The volume of brine was 2.8 m.sup.3. The degree of bromine oxidation in Stage I was 73.4%, which corresponds to a residual concentration of Br=0.83 kg/m.sup.3; in Stage II, the degree of oxidation was 89.16%, which corresponds to Br?=0.09 kg/m.sup.3. The following was obtained: 5.7 kg of crystalline ammonium bromide with main substance content of 99.02%; 3.83 dm.sup.3 of liquid product with a density of 1,230 kg/m.sup.3 and sodium bromide content of 32.5%. The overall degree of bromine recovery from the brine was 97.12%.

[0019] Example 3. The composition of the initial brine differs from Example 1:1, 364 kg/m.sup.3, with a hydrogen index of 5.17 of the following composition: (Ca 2*, Mg 2+, Sr 2*)=162.25 kg/m.sup.3; Fe.sub.total=0.005 kg/m.sup.3; Mg 2*=0.005 kg/m.sup.3; (K*, Na*, Li*)=27.7 kg/m.sup.3; Cl=166.8 kg/m.sup.3; NCO3=0.8 kg/m 3; SO42?=0.003 kg/m.sup.3; Br?=8.25 kg/m.sup.3. The volume of brine was 2.0 m.sup.3. The degree of bromine oxidation in Stage I was 73.0%, which corresponds to a residual concentration of Br?=2.23 kg/m.sup.3; in Stage II, the degree of oxidation was 88.34%, which corresponds to Br?=0.26 kg/m.sup.3. The following was obtained: 14.0 kg of crystalline ammonium bromide with the content of the main substance of 99.2%; 9.8 dm.sup.3 of liquid product with a density of 1,231 kg/m.sup.3 and sodium bromide content of 32.6%. The overall degree of bromine recovery from the brine was 96.85%.

REFERENCES

[0020] 1. USSR Patent No. 8215, Class 12/J. H. Van der Meulen. 1929. [0021] 2. Pozin M. E. Technology Pertaining to Mineral Salts. 4th ed. Leningrad, Khimiya Publisher, 1974. Part 1. 233 pp. [0022] 3. RF U.S. Pat. No. 21,354,060, published on 27 Aug. 1999. [0023] 4. USSR Inventor's Certificate No. 783229, published on 30 Nov. 1980. [0024] 5. USSR Inventor's Certificate No. 138232, published on 1 Jan. 1961.