CN107930399A - The removal methods of foreign ion in a kind of organic amine desulfuration solution - Google Patents

Abstract

The invention belongs to the field of chemical industry, and in particular relates to a method for removing impurity ions in an organic amine desulfurization solution. The technical problem to be solved by the present invention is to provide a method for removing impurity ions in an organic amine desulfurization solution, comprising the following steps: the organic amine desulfurization rich solution absorbs Fe ³⁺ and Cu ²⁺ ions through a cationic resin exchange column of a chelating resin Afterwards, it enters the regeneration tower for SO ₂ regeneration and turns into lean liquid, which passes through the anion resin exchange column of macroporous weak base resin to remove Cl ^‑ , and then enters the freezing and crystallization system to remove SO ₄ ^2‑ . The method of the invention can purify the used organic amine desulfurizer, reduce poisoning of the desulfurizer, stabilize the desulfurization effect, reduce the desulfurization operation cost, and ensure the normal and stable operation of the desulfurization system.

Description

A method for removing impurity ions in organic amine desulfurization solution

technical field

The invention belongs to the field of chemical industry, and in particular relates to a method for removing impurity ions in an organic amine desulfurization solution. The invention relates to the technical field of purification of desulfurization solution in a wet flue gas desulfurization system.

Background technique

Panzhihua Iron and Steel No. 3 sintering flue gas desulfurization adopts organic amine technology. During the operation of the desulfurization system, the pH value of the desulfurization lean liquid is controlled at 5.0-5.5, and the pH value of the rich liquid after absorbing SO2 is controlled at _4.0-4.5 . , the oxidation of Fe ²⁺ , Cu ²⁺ , Cl ^- and SO ₂ entrained by the dust in the flue gas enters the desulfurization solution to increase the concentration of metal ions and acid radical ions, among which Fe ³⁺ and Cu ²⁺ will make the desulfurizer Failure, Cl ^- leads to system corrosion, and the increase of SO ₄ ^2- causes system blockage. These impurity ions not only seriously affect the sulfur absorption effect of the desulfurizer, reduce the desulfurization efficiency, but also increase the risk of unstable operation of the system, and the energy consumption increases sharply ,Increased costs. At present, the ion exchange resin desalination method is used in the field, which can only remove Cl ^- and SO ₄ ^2- ions to a certain extent, but there are still problems such as low removal effect of Cl ^- and waste lye treatment, and Fe ³⁺ , Cu ²⁺ Will deposit on the ion exchange resin, resulting in short resin life. Therefore, it is imminent to study a comprehensive process for removing impurity ions in organic amine desulfurization solution.

Contents of the invention

Aiming at the disadvantage of poor removal effect of impurity ions in desulfurization solution in existing sintering flue gas, especially organic amine desulfurization process, the invention provides a method for removing impurity ions in organic amine desulfurization solution. The process of the present invention adopts the combination of cation exchange bed, anion exchange bed and freezing crystallization system to remove Fe ³⁺ , Cu ²⁺ , Cl ^- and SO ₄ ^2- ions in the solution in sections; among them, chelating resin is selected It is used as a cation resin exchange bed to absorb Fe ³⁺ and Cu ²⁺ ions. After the adsorption, it enters the regeneration tower for SO ₂ regeneration to become a barren solution, and then uses a macroporous weak base resin as an anion resin exchange bed to remove Cl ^- , and finally enters The freezing and crystallization system removes SO ₄ ^2- , and the purified solution is returned to the desulfurization tower for adsorption and desulfurization again, thereby recycling.

The technical problem to be solved by the present invention is to provide a method for removing impurity ions in an organic amine desulfurization solution. The removal method comprises the following steps: after the organic amine desulfurization rich liquid absorbs Fe ³⁺ and Cu ²⁺ ions through a cation resin exchange column equipped with a chelating resin, it enters a regeneration tower for SO ₂ regeneration to become a lean liquid, and the lean liquid passes through The anion resin exchange column equipped with macroporous weak base resin removes Cl ^- , and then enters the freeze crystallization system to remove SO ₄ ^2- , and then the purified organic amine desulfurization liquid can be obtained.

Specifically, in the method for removing impurity ions in the above-mentioned organic amine desulfurization solution, the organic amine desulfurization rich liquid is a desulfurization solution obtained by desulfurizing sintered flue gas through an organic amine desulfurization agent (that is, absorbing sulfur dioxide); the temperature is 48-52 ° C, The pH is 4.7-5.0.

Preferably, in the above method for removing impurity ions in the organic amine desulfurization solution, before removing Fe ³⁺ and Cu ²⁺ ions, the step of adsorbing the rich organic amine desulfurization solution with activated carbon is also included.

Preferably, in the method for removing impurity ions in the organic amine desulfurization solution, the temperature of the solution after removal of Fe ³⁺ and Cu ²⁺ ions is controlled to be 45-50° C., and the pH is 4.0-4.3. That is, after the regeneration of the resin from which iron and copper ions have been removed, the residual acid gas condensate enters the rich liquid, so that the temperature of the system drops to 45-50°C, and the pH drops to 4.0-4.3 at the same time.

Preferably, in the method for removing impurity ions in the above-mentioned organic amine desulfurization solution, the chelating resin is a 5-aminosalicylic acid type chelating resin.

Preferably, in the method for removing impurity ions in the organic amine desulfurization solution, the macroporous weak base resin is a macroporous weak base styrene resin. Further, the macroporous weak base resin is selected from D301 and D301T.

Preferably, in the method for removing impurity ions in the above-mentioned organic amine desulfurization solution, before freezing and crystallization, a sodium hydroxide solution is used to adjust the pH of the solution to 9.5-10.0.

Preferably, in the above-mentioned method for removing impurity ions in the organic amine desulfurization solution, the mass concentration of the sodium hydroxide solution is 25-30%.

The method of the present invention can effectively remove various impurity ions in the desulfurization solution through proper process coordination, ensure the cleanness of the desulfurizer in the desulfurization system, further ensure the desulfurization effect, reduce regeneration energy consumption, and greatly save the desulfurization operation cost. When the desulfurization solution after impurity removal by this process is recycled again, the desulfurization effect equivalent to that of the unused desulfurization solution can be obtained. At the same time, this process method can effectively utilize the regenerated waste liquid, without secondary pollution, and also reduces sintering water and purchased CaCl ₂ solution.

Detailed ways

Panzhihua Iron and Steel's sintering flue gas has high sulfur content and complex components. The organic amine cycle desulfurization process is not only applicable to the existing sintering flue gas, but also can produce more than 20,000 tons of sulfuric acid per year. It has a good application prospect and is in line with the current green development. idea. However, during the operation of the organic amine desulfurization process, 100-200mg/ ^m3 dust enters the desulfurization system after the sintering flue gas is electrostatically precipitated, which contains HCl, SO ₃ gas and metal ions, etc., resulting in many impurity ions in the desulfurization solution. Only resin desalting is used to remove Cl ^- , and the effect is poor, only 30-50% removal rate.

Aiming at the situation that there are many impurity ions in the existing desulfurization solution, the invention provides a new method for purifying the impurity ions in the desulfurization solution. The temperature of the desulfurization-rich solution to be treated in the present invention is 48-52°C, and the pH is 4.7-5.0. Firstly, the chelating resin is used to remove metal ions Fe ³⁺ and Cu ²⁺ , thereby reducing the oxidation of SO ₃ ^2- in the solution. The loss of sulfur dioxide recovery is reduced; after iron removal, the solution temperature drops to 45-50°C, and the pH drops to 4.0-4.3; then the rich liquid is heat-exchanged to 80-90°C through the lean-rich liquid heat exchanger, and enters regeneration The tower uses steam to decompose sulfur dioxide at 104-108°C, and turns into lean liquid with a temperature of 104-108°C and pH of 5.2-5.5. After passing through the lean-rich liquid heat exchanger, the temperature of the lean liquid drops to 55-58°C, and enter Anion exchange bed removes Cl ^- , the removal effect is good by using special dechlorination resin, so that the concentration of Cl ^- in the solution is less than 1g/L; after dechlorination, it enters the freezing crystallization system, and the pH is 9.5-10, and the temperature drops to 4-7 °C, solid Na ₂ SO ₄ crystallizes out of the solution, and removes SO ₄ ^2- and Na ⁺ , so that the concentration of SO ₄ ^2- in the solution is lower than 30g/L (SO ₄ ^2- is beneficial to control the pH of the desulfurizer at 5.0-6.0 , to prevent the pH from being too high to volatilize), so as to ensure the stability of the solution for desulfurization. The regeneration step of the regeneration tower of the present invention is that after removing iron, the temperature of the solution is raised to regenerate and remove sulfur dioxide, and then the temperature of the solution is lowered to perform dechlorination.

The method for removing impurity ions from sintering flue gas with organic amine desulfurization and desulfurization agent comprises the following steps: after the sintering flue gas is absorbed by the organic amine desulfurization agent, the desulfurization rich liquid contains Fe ³⁺ , Cu ²⁺ , Cl ^- and SO ₄ ^{2 -Plasma} , after Fe ³⁺ and Cu ²⁺ ions are adsorbed by the cationic resin exchange column of chelating resin, it enters the regeneration tower for SO ₂ regeneration to become a poor solution, and then removes Cl through the anion resin exchange column of macroporous weak base resin ^- , into the freezing and crystallization system to remove SO ₄ ^2- return to the desulfurization tower for absorption, cycle operation.

Since activated carbon adsorption can remove large suspended solids in organic amine desulfurization rich liquid, it is preferable to include the step of using activated carbon adsorption to organic amine desulfurization rich liquid before removing Fe ³⁺ and Cu ²⁺ ions, and then pumping into a cation exchange resin column to remove Fe ³⁺ and Cu ²⁺ .

In the method of the present invention, after the steps of removing iron and copper, in order to recover the desulfurizer remaining in the adsorption column, the adsorption column will be washed with water, and the washing water will be mixed into the solution, and then the adsorbed iron will be removed by acid washing. , copper ions, and then empty the pickling liquid, and the adsorption column can be re-adsorbed and utilized, that is, the steps for the rich liquid to enter the exchange column are adsorption-washing-regeneration-emptying, and the adsorption adopts bottom-in and top-out, and the liquid intake is 20~ 25m ³ /h; water washing adopts top inlet and bottom outlet; pickling regeneration adopts top inlet and bottom outlet, and the SO ₂ acid gas condensate regenerated by desulfurization rich liquid through the regeneration tower has a pH of less than 1 and a flow rate of 12-15m ³ /h; null. The regenerated and emptied waste liquid enters the liquid separator, and the waste liquid after separating SO ₂ can be used as water distribution for sintering mixture, and SO ₂ gas enters the acid system. In this step, the temperature of the solution before dechlorination is finally controlled to be 45-50° C., and the pH is 4.0-4.3.

In the method of the present invention, the regeneration of the regeneration tower is to desorb the adsorbed sulfur dioxide. Since controlling the appropriate pH can facilitate the regeneration of SO ₂ , it is preferable to control the pH of the solution entering the regeneration tower to be 4.0 to 4.3. Desorb SO ₂ using conventional methods, such as steam desorption. After removing iron, the temperature of the solution drops to 45-50°C, and the pH drops to 4.0-4.3; then the rich liquid is heat-exchanged to 80-90°C through the lean-rich liquid heat exchanger, and enters the regeneration tower to use steam at 104-108 Decompose sulfur dioxide at ℃, turn into lean liquid, temperature is 104-108°C, pH is 5.2-5.5, after passing through lean-rich liquid heat exchanger, the temperature of lean liquid drops to 55-58°C, enters anion exchange bed to remove Cl ^- . The regeneration step of the present invention is that after removing iron, the solution is heated to regenerate and remove sulfur dioxide, and then the solution is cooled to perform dechlorination.

In the method of the present invention, macroporous weak base resin (such as D301, D301T, etc.) is used to process Cl ^- , and the steps of entering the barren liquid into the exchange column are adsorption-washing 1-washing 2-regeneration-washing 3-washing 4-emptying, adsorption It is top in and bottom out, and the liquid inflow is 25-30m ³ /h; water washing 1 is top in and bottom out, and the discharged waste liquid enters the desulfurization system; water washing 2 is bottom in and top out, and the discharged water is stored in the circulation tank for the next washing 1 is water; regeneration is bottom in and top out, using 2-4% NaOH solution for flushing, flow rate 12-15m ³ /h; water washing 3 is top in and bottom out, and the discharged waste water is mixed with waste lye to prepare CaCl ₂ solution for spraying and sintering Mine; washing 4 is up and down, and this waste water is used as the dilution water of 4% NaOH solution; finally emptying.

In the method of the present invention, conventional methods are used to remove SO ₄ ^2- in the system. The poor solution after removing Cl ^- is passed through the freeze crystallization system, using 25-30% NaOH solution to adjust the pH to 9.5-10.0, and the temperature is around 4-7°C to quickly produce Na ₂ SO ₄ solids to achieve the purpose of removing SO ₄ ^2- , The lean liquid after removal of impurity ions is returned to the system for cyclic absorption.

When the process of the present invention is in operation, the desulfurization solution absorbs SO ₂ and flows into the activated carbon adsorption tank by using the high head difference, pumps it into the bottom of the cation resin exchange column, and the purified solution flows out from the upper part, merges into the rich liquid and enters the regeneration tower, and desorbs SO through steam After ₂ , it becomes lean liquid, after heat exchange by the heat exchanger, the separated part enters the anion resin exchange column, and the effluent is transported to the freezing and crystallization system by the pump, and returns to the desulfurization system after removing impurities. Among them, the solution of the cationic resin exchange column adopts the bottom-in and top-out method, the treatment capacity is 20-25m ³ /h, and the time is 45min. After the adsorption, the resin is washed with 2m ³ soft water, and the acid gas condensate in the regeneration tower is regenerated, and the flow rate is 12-15m ³ /h, time 6min, and finally emptying; anion resin exchange column treatment solution adopts the method of top in and bottom out, the processing capacity is 25 ~ 30m ³ /h, time 4min, after adsorption, the resin is washed with water for 1 to remove the surface desulfurizer, and the lotion returns to desulfurization System, washing 2 and further flushing is used as water for washing 1. The regeneration adopts the bottom-in and top-out method, the flow rate is 12-15m ³ /h, and the time is 10min, so that the resin can be fully soaked and regenerated; after regeneration, wash 3 with water to wash away Na ⁺ and residual Cl ^- , wash with water 4 to fully wash away residual Na ⁺ as water with 2-4% NaOH, and finally empty. This process can effectively solve the chemical loss of the desulfurization agent and remove heat-stable salts, ensure the cleanness of the desulfurization agent in the desulfurization system, and then ensure the desulfurization effect, reduce the regeneration energy consumption, and greatly save the desulfurization operation cost. At the same time, this process method can effectively utilize the regenerated waste liquid, without secondary pollution, and also reduces sintering water and purchased CaCl ₂ solution.

Example

After the desulfurization solution absorbs _SO2 , it flows into the activated carbon adsorption tank by using the high potential difference, and pumps it into the bottom of the cation resin exchange column. After purification, the solution flows out from the upper part, merges into the rich liquid and enters the regeneration tower, and becomes a lean liquid after _desorbing SO2 by steam. After heat exchange by the heat exchanger, the separated part enters the anion resin exchange column, and the effluent is pumped to the freezing and crystallization system, and returns to the desulfurization system after removing impurities. Among them, the solution of cationic resin exchange column adopts bottom-in and top ^- out method, the processing capacity is 20-25m ³ /h, and the time is 45min. h, time 6min, and finally emptying; anion resin exchange column treatment solution adopts the method of top in and bottom out, the processing capacity is 25 ~ 30m ³ /h, time 4min, after adsorption, the resin is washed with water 1 to remove the surface desulfurization agent, and the lotion is returned to the desulfurization system , water washing 2 and further rinse as water for washing 1, the regeneration adopts the bottom-in and top-out method, the flow rate is 12-15m ³ /h, and the time is 10min, so that the resin can be fully soaked and regenerated; after regeneration, wash 3 with water to wash away Na ⁺ and residual Cl ^- , wash 4 with water to fully wash away residual Na ⁺ as water with 4% NaOH, and finally empty. Process cycle for desalination. When the desulfurization solution after impurity removal by this process is recycled again, the desulfurization effect equivalent to that of the unused desulfurization solution can be obtained.

Claims (8)

1. the removal methods of foreign ion in organic amine desulfuration solution, it is characterised in that：Comprise the following steps：Organic amine desulfurization is rich Liquid passes through the cation exchange resin column absorption Fe equipped with chelating resin³⁺、Cu²⁺After ion, SO is carried out into regenerator₂Regeneration is changed into Lean solution, lean solution pass through the resin anion (R.A.) exchange column equipped with macropore weak base type resin and remove Cl^-, removed subsequently into freezing and crystallizing system Remove SO₄ ^2-, you can the organic amine doctor solution after being purified.

2. the removal methods of foreign ion in organic amine desulfuration solution according to claim 1, it is characterised in that：It is described to have Machine amine sulfur removing pregnant solution is sintering flue gas through desulfuration solution obtained by organic amine desulfurizer desulfurization；Temperature is 48~52 DEG C, pH for 4.7~ 5.0。

3. the removal methods of foreign ion in organic amine desulfuration solution according to claim 1, it is characterised in that：Remove Fe^{3 +}、Cu²⁺The step of being further included organic amine sulfur removing pregnant solution before ion using activated carbon adsorption processing.

4. the removal methods of foreign ion in organic amine desulfuration solution according to claim 1, it is characterised in that：Control is de- Except Fe³⁺、Cu²⁺Solution temperature is 45~50 DEG C after ion, and pH is 4.0~4.3.

5. the removal methods of foreign ion in organic amine desulfuration solution according to claim 1, it is characterised in that：Described Chelating resin is 5-aminosalicylic acid type chelating resin.

6. the removal methods of foreign ion in organic amine desulfuration solution according to claim 1, it is characterised in that：Described Macropore weak base type resin is selected from D301, D301T.

7. the removal methods of foreign ion in organic amine desulfuration solution according to claim 1, it is characterised in that：Freezing knot Before crystalline substance, pH value of solution is adjusted to 9.5~10.0 using sodium hydroxide solution.

8. the removal methods of foreign ion in the organic amine desulfuration solution according to right wants 7, it is characterised in that：The hydrogen-oxygen The mass concentration for changing sodium solution is 25~30%.