Alkaline process for bromine extraction by air blowing

Abstract

The utility model provides a kind of alkali method bromine extraction system for air blow-out method, through acidification oxidation-blow out-multistage absorption-absorption liquid cascade configuration circulation-distillation bromine extraction whole process cooperation, constructs the closed loop bromine extraction system of " bromine ion directional conversion→brim gas grading enrichment→absorption liquid gradient utilization→bromine precise purification". With at least two levels of series absorption tower to match independent absorption liquid pool, realize alkali liquid cascade configuration and absorption liquid reverse flow, adapt to different seawater bromine content and working condition, reduce alkali consumption and tail gas bromine loss;Each unit of whole process is accurately connected, both improve the conversion efficiency of bromine oxidation, absorption, distillation, also ensure the purity of bromine through multistage purification, solve the problem of low traditional bromine extraction yield, high energy consumption, poor adaptability, provide efficient, energy saving, quality controllable system scheme for large-scale seawater bromine extraction, achieve the collaborative optimization of bromine extraction efficiency, resource utilization, product quality.

Description

Technical Field

[0001] This utility model belongs to the field of marine resource utilization technology, specifically relating to an alkaline bromine extraction system for air blowing method. Background Technology

[0002] Air blowing is a widely used bromine extraction technology. Depending on the type of absorbent used in each absorption stage, it can be divided into acid absorption and alkaline absorption processes. The acid absorption process utilizes the reducing properties of sulfur dioxide to reduce free gaseous bromine into bromide ions, which are then enriched in the absorbent. The alkaline absorption process, on the other hand, is based on the principle of disproportionation of bromine in an alkaline solution, achieving the absorption and enrichment of free gaseous bromine. This process is widely used overseas, such as in Ethiopia and Laos. Currently, the mainstream air blowing and absorption tower setup adopts a "one-blow, three-absorption" configuration, where one blowing tower is paired with three absorption towers connected in series for three-stage absorption. The same concentration of alkaline solution is used in all three absorption towers to absorb bromine. Because bromine enters the absorption towers in a specific order, the first-stage absorption tower absorbs a larger amount of bromine, while the amount absorbed by the last-stage absorption towers decreases progressively. The absorbent liquid from the bottom of all the absorption towers is collected in the same circulation tank, mixed, and then circulated synchronously. This means that when the absorbent liquid reaches the required standard, it can only be transferred intermittently, making continuous operation impossible. Consequently, it affects the continuous production of absorbent liquid feeding and subsequent distillation, greatly reducing production efficiency and increasing the consumption of alkali solution. Utility Model Content

[0003] This invention provides an alkaline bromine extraction system for air blowing, which solves the problems of low efficiency and high consumption of alkali solution in the prior art.

[0004] This utility model provides an alkaline bromine extraction system for air blowing, including an acidification unit, an oxidation unit, a blowing tower, N-stage absorption towers connected in series, an alkaline solution storage tank, an alkaline preparation tank, N-stage absorption liquid tanks corresponding to the N-stage absorption towers, a distillation tower, a condensation unit, and a bromine water separation unit; wherein, N≥2;

[0005] The seawater inlet of the acidification unit is used to introduce seawater, the hydrochloric acid inlet of the acidification unit is used to introduce hydrochloric acid solution, and the outlet of the acidification unit is connected to the seawater inlet of the oxidation unit.

[0006] The chlorine inlet of the oxidation unit is used to introduce chlorine gas, the outlet of the oxidation unit is connected to the top liquid inlet of the blow-out tower, and the bottom outlet of the blow-out tower is used to output the bromine-blown seawater.

[0007] The circulating gas inlet of the blowout tower is used to introduce circulating gas, the top outlet of the blowout tower is connected to the air inlet of the first-stage absorption tower, and the exhaust port of the i-th-stage absorption tower is connected to the air inlet of the (i+1)-th-stage absorption tower; where 1≤i≤N-1.

[0008] The outlet of the alkali storage tank is connected to the inlet of the alkali mixing tank, and the outlet of the alkali mixing tank is connected to the inlet of the Nth stage absorption liquid tank.

[0009] The alkaline spray nozzle of the N-stage absorption tower is connected to the outlet of the N-stage absorption liquid tank, and the bottom outlet of the N-stage absorption tower is connected to the reflux port of the N-stage absorption liquid tank.

[0010] The transfer port of the Nth stage absorbent tank is connected to the inlet of the (N-1)th stage absorbent tank;

[0011] The transfer port of the j-th stage absorbent tank is connected to the inlet of the (j-1)-th stage absorbent tank; where 2≤j≤N-1;

[0012] The transfer port of the first-stage absorption liquid tank is connected to the inlet of the distillation column;

[0013] The hydrochloric acid inlet at the top of the distillation column is used to introduce hydrochloric acid solution, the steam inlet at the bottom of the distillation column is used to introduce steam, the tail liquid outlet at the bottom of the distillation column is used to output tail liquid, and the bromine outlet at the top of the distillation column is connected to the inlet of the condensation unit.

[0014] The outlet of the condensation unit is connected to the inlet of the bromine water separation unit, the bromine-containing water outlet of the bromine water separation unit is connected to the liquid inlet at the top of the distillation tower, and the bromine outlet of the bromine water separation unit is used to output industrial bromine.

[0015] Compared with existing technologies, the advantages of this invention are as follows: It constructs a closed-loop bromine extraction system through a coordinated process of acidification oxidation, blowing out, multi-stage absorption, cascaded configuration and circulation of absorbent liquid, and distillation for bromine extraction. This system achieves "directional conversion of bromide ions → graded enrichment of bromine-containing gas → gradient utilization of absorbent liquid → precise purification of bromine." At least two stages of absorption towers are connected in series with independent absorbent pools, enabling cascaded configuration of alkali liquid and counter-current flow of absorbent liquid. This adapts to different seawater bromine contents and operating conditions, reducing alkali consumption and bromine loss in tail gas. Precise connection between each unit throughout the process improves the conversion efficiency of bromine oxidation, absorption, and distillation, while multi-stage purification ensures bromine purity. This solves the problems of low yield, high energy consumption, and poor adaptability in traditional bromine extraction methods, providing a highly efficient, energy-saving, and quality-controllable system solution for large-scale seawater bromine extraction, achieving synergistic optimization of bromine extraction efficiency, resource utilization, and product quality.

[0016] Furthermore, N = 3.

[0017] Furthermore, it also includes a gas scrubbing tower;

[0018] The bromine-containing gas outlets of the condensation unit and the bromine water separation unit are connected to the gas inlet of the gas scrubbing tower, the transfer port of the first-stage absorption liquid tank is connected to the liquid inlet of the gas scrubbing tower, and the outlet of the gas scrubbing tower is connected to the liquid inlet of the distillation tower.

[0019] Furthermore, it also includes foam traps;

[0020] The exhaust port of the third-stage absorption tower is connected to the inlet of the demister tower, the gas phase outlet of the demister tower is connected to the circulating gas inlet of the blow-out tower, and the liquid phase outlet of the demister tower is connected to the liquid inlet of the gas scrubbing tower.

[0021] Furthermore, the air inlet of the first-stage absorption tower is located at the top of the tower body;

[0022] The air inlets of the second-stage and third-stage absorption towers are located above the liquid level at the bottom of their respective tower bodies and below the packing support frame.

[0023] Furthermore, a packing layer is installed inside the blowing tower.

[0024] Furthermore, the distillation column comprises 9 to 11 columns connected in series from top to bottom, with the absorption liquid inlet and hydrochloric acid inlet located in the first column, and the vapor distributor located in the bottom column. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the alkaline bromine extraction system in Embodiment 1 of this utility model;

[0026] Figure 2 This is a schematic diagram of the alkaline bromine extraction system in Embodiment 2 of this utility model.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Acidification unit; 2. Oxidation unit; 3. Blowout tower; 41. First-stage absorption tower; 42. Second-stage absorption tower; 43. Third-stage absorption tower; 51. Alkali storage tank; 52. Alkali mixing tank; 61. First-stage absorbent tank; 62. Second-stage absorbent tank; 63. Third-stage absorbent tank; 7. Gas scrubbing tower; 8. Distillation tower; 9. Condensation unit; 10. Bromine water separation unit; 11. Foam eliminator. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions in the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0030] The following is a detailed description of an alkaline bromine extraction system for air blowing provided by this utility model through specific embodiments.

[0031] Example 1

[0032] Please see Figure 1In this embodiment, seawater from a coastal power plant's DC cooling system is used as raw material (bromine content 55-60 g / m³). 3 (Water temperature 10-40℃) The alkaline bromine extraction system used in this embodiment includes an acidification unit 1, an oxidation unit 2, a blow-out tower 3, two-stage absorption towers connected in series, an alkaline storage tank 51, an alkaline preparation tank 52, a two-stage absorption liquid tank, a distillation tower 8, a condensation unit 9, and a bromine water separation unit 10. Specifically, it includes the following steps:

[0033] Seawater from the power plant's DC cooling system is introduced into the seawater inlet of acidification unit 1, along with a hydrochloric acid solution. This 30% hydrochloric acid treatment adjusts the pH to 3.5. After acidification, the seawater flows from the outlet of acidification unit 1 into the seawater inlet of oxidation unit 2. Chlorine gas is introduced through the chlorine inlet of oxidation unit 2, oxidizing bromide ions in the seawater to free bromine. The reaction equation is: Cl₂ + 2Br₂ - =Br2+2Cl - Chlorine gas is added at 120% of the molar amount of bromide ions to obtain bromine-containing seawater, which flows from the outlet of oxidation unit 2 to the top inlet of blow-out tower 3.

[0034] Bromine-containing seawater enters the top inlet of the blow-out tower 3 and is sprayed, flowing downwards through the tower's internal space. Circulating gas is introduced through the circulating gas inlet of the blow-out tower 3. Upon gas-liquid contact, bromine is desorbed and blown out, entering the inlet of the first-stage absorption tower 41 along with the circulating gas through the top outlet of the blow-out tower 3. After bromine removal, the seawater is discharged from the bottom outlet of the blow-out tower 3 and can be treated to meet standards before being discharged.

[0035] Alkali solution in alkali storage tank 51 flows into alkali mixing tank 52. The outlet of alkali mixing tank 52 is connected to the inlet of second-stage absorbent tank 62, where the alkali solution enters. The alkali spray nozzle of second-stage absorption tower 42 is connected to the outlet of second-stage absorbent tank 62, and the bottom outlet of absorption tower is connected to the reflux port of second-stage absorbent tank 62, achieving alkali solution circulation. The transfer port of second-stage absorbent tank 62 is connected to the inlet of first-stage absorbent tank 61, allowing for cascaded alkali solution flow. The alkali spray nozzle of first-stage absorption tower 41 is connected to the outlet of first-stage absorbent tank 61, and the bottom outlet is connected to the reflux port of first-stage absorbent tank 61. The transfer port of first-stage absorbent tank 61 is connected to the inlet of distillation tower 8.

[0036] Bromine-containing circulating gas enters the first-stage absorption tower 41, where alkaline solution is sprayed, causing a disproportionation reaction: 3Br2 + 6NaOH = 5NaBr + NaBrO3 + 3H2O. This enriches free bromine, yielding a primary absorption liquid (containing bromide ions, bromate ions, etc.). After primary absorption, the gas enters the inlet of the second-stage absorption tower 42 from the exhaust port of the first-stage absorption tower 41. Alkaline solution is also sprayed in the second-stage absorption tower 42, continuing bromine absorption and undergoing the same disproportionation reaction, yielding a secondary absorption liquid and secondary circulating gas. The secondary circulating gas can be introduced into the circulating gas inlet of the blow-out tower 3 for blow-out. The secondary absorption liquid is retained in the second-stage absorption liquid tank 62 and enters the first-stage absorption liquid tank 61 through the transfer port. Finally, the absorption liquid in the first-stage absorption liquid tank enters the inlet of the distillation tower 8 through the heat exchanger via the transfer port.

[0037] The absorbed liquid and hydrochloric acid (introduced from the hydrochloric acid inlet at the top of distillation column 8, concentration adjusted as needed, 30% optional) enter distillation column 8 through the liquid inlet. Steam (optional 0.4 MPa) is introduced through the steam inlet at the bottom of distillation column 8. Under acidic conditions, bromate ions and bromide ions undergo a disproportionation reaction: 6HCl + 5NaBr + NaBrO3 = 3Br2 + 6NaCl + 3H2O. The bromine-containing water vapor produced by distillation exits from the bromine outlet at the top of distillation column 8 and enters condensation unit 9. The tail liquid (mainly containing sodium ions, chloride ions, etc.) is discharged from the tail liquid outlet at the bottom of distillation column 8. After condensation in condensation unit 9, the bromine-containing water vapor enters bromine water separation unit 10. The separated bromine-containing water returns from the bromine water outlet to the liquid inlet at the top of distillation column 8 for further distillation; bromine is discharged from the bromine outlet, yielding industrial bromine.

[0038] Example 2

[0039] Please see Figure 2 In this embodiment, seawater from a coastal power plant's DC cooling system is used as raw material (bromine content 55-60 g / m³). 3 (Water temperature 10-40℃) The alkaline bromine extraction system used in this embodiment includes an acidification unit 1, an oxidation unit 2, a blowing tower 3, a three-stage series absorption tower, an alkaline solution storage tank 51, an alkaline preparation tank 52, a three-stage absorption liquid tank, a distillation tower 8, a condensation unit 9, a bromine water separation unit 10, a gas washing tower 7, and a mist eliminator 11. Specifically, it includes the following steps:

[0040] Seawater is introduced through the seawater inlet of acidification unit 1, and hydrochloric acid solution (30%) is introduced through the hydrochloric acid inlet, acidifying to pH 3.6. After acidification, the seawater flows into the seawater inlet of oxidation unit 2, and chlorine gas is introduced through the chlorine gas inlet (the amount added is 125% of the molar amount of bromide ions), resulting in the reaction Cl₂ + 2Br₂. - =Br2+2Cl - Bromine-containing seawater is generated and flows from the outlet of oxidation unit 2 to the top inlet of blowout tower 3.

[0041] Bromine-containing seawater enters the top inlet of blow-out tower 3 and is sprayed through the internal packing layer to enhance gas-liquid contact. Circulating gas is introduced from the circulating gas inlet of blow-out tower 3, where bromine is desorbed and blown out. The bromine then enters the inlet of the first-stage absorption tower 41 (located at the top of the tower) through the top outlet. After bromine removal, the seawater exits from the bottom outlet and is discharged after pH adjustment (e.g., by adding magnesium oxide slurry) to meet the required standards.

[0042] The alkali solution (sodium hydroxide solution) in the alkali storage tank 51 flows into the alkali mixing tank 52, and then enters the third-stage (final-stage) absorbent tank. The alkali spray port of the third-stage absorber 43 is connected to the outlet of the third-stage absorbent tank 63, and the bottom outlet is connected to the reflux port of the third-stage absorbent tank 63. The transfer port of the third-stage absorbent tank 63 is connected to the inlet of the second-stage absorbent tank 62. The alkali spray port and bottom outlet of the second-stage absorber 42 are connected to the outlet and reflux port of the second-stage absorbent tank 62, respectively. The transfer port of the second-stage absorbent tank 62 is connected to the inlet of the first-stage absorbent tank 61. The alkali spray port and bottom outlet of the first-stage absorber 41 are connected to the outlet and reflux port of the first-stage absorbent tank 61. The transfer port of the first-stage absorbent tank 61 is connected to the inlet of the distillation tower 8 (and simultaneously to the inlet of the gas scrubbing tower 7).

[0043] The bromine-containing circulating gas enters the first-stage absorption tower 41, where it is sprayed with alkaline solution, resulting in the reaction 3Br2 + 6NaOH = 5NaBr + NaBrO3 + 3H2O, yielding the first-stage absorption liquid and the first-stage circulating gas (containing a small amount of bromine). The first-stage circulating gas then enters the second-stage absorption tower 42, where it continues to be sprayed with alkaline solution for absorption, undergoing a disproportionation reaction to obtain the second-stage absorption liquid and the second-stage circulating gas. The second-stage circulating gas enters the third-stage absorption tower 43, where it absorbs bromine again, yielding the third-stage absorption liquid and the third-stage circulating gas. The third-stage circulating gas first enters the demisting tower 11. After demisting, the gas phase exits the demisting tower 11 from the gas phase outlet and is blown back out of the circulating gas inlet of tower 3, while the liquid phase enters the scrubbing tower 7 from the liquid phase outlet of the demisting tower 11. The first, second, and third-stage absorption liquids are retained in their respective absorption liquid pools. After transfer and circulation, the final absorption liquid in the first-stage absorption liquid pool (including those from multiple stages) enters the distillation tower 8 and the scrubbing tower 7 through the transfer port and heat exchange.

[0044] The bromine-containing gas outlets of condensation unit 9 and bromine water separation unit 10 are connected to the inlet of gas scrubbing tower 7, and the transfer port of the first-stage absorbent pool 61 is connected to the inlet of gas scrubbing tower 7. After the bromine-containing gas enters gas scrubbing tower 7, it contacts the absorbent to recover the bromine component. The washed liquid enters the inlet of distillation tower 8 from the outlet of gas scrubbing tower 7 to enhance bromine recovery.

[0045] The absorbed liquid (including the liquid from the gas scrubbing tower 7) and hydrochloric acid (introduced from the hydrochloric acid inlet at the top of distillation tower 8) enter distillation tower 8. Steam is introduced at the bottom, causing the disproportionation reaction 6HCl + 5NaBr + NaBrO3 = 3Br2 + 6NaCl + 3H2O. The bromine-containing water vapor exits from the top bromine outlet and enters the condensation unit 9, while the tail liquid is discharged from the bottom tail liquid outlet (sodium chloride, etc., can be recovered after treatment). After condensation, the bromine-containing water vapor enters the bromine water separation unit 10, and the bromine-containing water returns to distillation tower 8. Bromine is discharged from the bromine outlet, yielding industrial bromine.

[0046] The system of this invention allows for the continuous operation of the blowing absorption process, during which the prepared alkali absorbent is reused in multi-stage absorption towers, maximizing alkali utilization. There is no material stagnation within the absorption process system, enabling real-time monitoring of the alkali condition at different stages, providing more data for reference, facilitating remote operation and control of the alkali ratio and dosage, and reducing alkali consumption by approximately 30%.

[0047] The multi-stage absorbent no longer undergoes a unified, repeated circulation in a large recycling tank. Instead, it is sequentially pushed from the rear end to the front end for absorption, truly achieving one-time alkali preparation, multi-stage absorption, and graded concentration configuration. The absorbent flow in the system is uninterrupted, greatly improving the efficiency of feeding and discharging, and avoiding the problem of the system running dry during material transfer, which is common in unified large circulation systems.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. If these modifications and variations fall within the scope of the claims of this utility model and their equivalents, they should be considered to be within the protection scope of this utility model.

Claims

1. A system for alkaline bromine extraction using an air-blowing method, characterized in that, It includes an acidification unit, an oxidation unit, a blow-out tower, N-stage absorption towers connected in series, an alkali storage tank, an alkali mixing tank, N-stage absorption liquid tanks corresponding to the N-stage absorption towers, a distillation tower, a condensation unit, and a bromine water separation unit; wherein, N≥2; The seawater inlet of the acidification unit is used to introduce seawater, the hydrochloric acid inlet of the acidification unit is used to introduce hydrochloric acid solution, and the outlet of the acidification unit is connected to the seawater inlet of the oxidation unit. The chlorine inlet of the oxidation unit is used to introduce chlorine gas, the outlet of the oxidation unit is connected to the top liquid inlet of the blow-out tower, and the bottom outlet of the blow-out tower is used to output the bromine-blown seawater. The circulating gas inlet of the blowout tower is used to introduce circulating gas, the top outlet of the blowout tower is connected to the air inlet of the first-stage absorption tower, and the exhaust port of the i-th-stage absorption tower is connected to the air inlet of the (i+1)-th-stage absorption tower; where 1≤i≤N-1. The outlet of the alkali storage tank is connected to the inlet of the alkali mixing tank, and the outlet of the alkali mixing tank is connected to the inlet of the Nth stage absorption liquid tank. The alkaline spray nozzle of the N-stage absorption tower is connected to the outlet of the N-stage absorption liquid tank, and the bottom outlet of the N-stage absorption tower is connected to the reflux port of the N-stage absorption liquid tank. The transfer port of the Nth stage absorbent tank is connected to the inlet of the (N-1)th stage absorbent tank; The transfer port of the j-th stage absorbent tank is connected to the inlet of the (j-1)-th stage absorbent tank; where 2≤j≤N-1; The transfer port of the first-stage absorption liquid tank is connected to the inlet of the distillation column; The hydrochloric acid inlet at the top of the distillation column is used to introduce hydrochloric acid solution, the steam inlet at the bottom of the distillation column is used to introduce steam, the tail liquid outlet at the bottom of the distillation column is used to output tail liquid, and the bromine outlet at the top of the distillation column is connected to the inlet of the condensation unit. The outlet of the condensation unit is connected to the inlet of the bromine water separation unit, the bromine-containing water outlet of the bromine water separation unit is connected to the liquid inlet at the top of the distillation tower, and the bromine outlet of the bromine water separation unit is used to output industrial bromine.

2. The alkaline bromine extraction system for air blowing method according to claim 1, characterized in that, N=3。 3. The alkaline bromine extraction system for air blowing method according to claim 2, characterized in that, It also includes a gas scrubbing tower; The bromine-containing gas outlets of the condensation unit and the bromine water separation unit are connected to the gas inlet of the gas scrubbing tower, the transfer port of the first-stage absorption liquid tank is connected to the liquid inlet of the gas scrubbing tower, and the outlet of the gas scrubbing tower is connected to the liquid inlet of the distillation tower.

4. The alkaline bromine extraction system for air blowing method according to claim 3, characterized in that, It also includes foam traps; The exhaust port of the third-stage absorption tower is connected to the inlet of the demister tower, the gas phase outlet of the demister tower is connected to the circulating gas inlet of the blow-out tower, and the liquid phase outlet of the demister tower is connected to the liquid inlet of the gas scrubbing tower.

5. The alkaline bromine extraction system for air blowing method according to any one of claims 2-4, characterized in that, The air inlet of the first-stage absorption tower is located at the top of the tower body; The air inlets of the second-stage and third-stage absorption towers are located above the liquid level at the bottom of their respective tower bodies and below the packing support frame.

6. The alkaline bromine extraction system for air blowing method according to claim 5, characterized in that, The blow-out tower is equipped with a packing layer.

7. The alkaline bromine extraction system for air blowing method according to claim 5, characterized in that, The distillation column consists of 9 to 11 columns connected in series from top to bottom. The absorption liquid inlet and hydrochloric acid inlet are located in the first column, and the vapor distributor is located in the bottom column.

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