Method for removing rare earth sulfate complex salt scale

Abstract

The application discloses a method for removing scale of rare earth sulfate complex salt, and relates to the field of scale removal. The method comprises the following steps: first, a container with rare earth sulfate complex salt on the inner wall is soaked with water, the water is drained after a period of soaking, high-humidity carbon dioxide gas is filled into the container and the container is pressurized, the pressure is released after the pressurization, warm water is added, the container is agitated, a wall vibrator is used to vibrate the container for a period of time, and then the water is drained, so that the scale is removed from the container with the water. The scale removal method is simple, low in cost, safe, non-toxic and harmless, and high in safety, and does not pollute the environment.

Description

Technical Field

[0001] This invention provides a method for removing rare earth sulfate complex salts, mainly relating to the field of descaling. Background Technology

[0002] The desulfurization sludge from catalytic cracking units is treated as hazardous waste because it contains spent catalytic cracking catalyst. One disposal method involves acid leaching to remove the metal elements, turning the solid sludge into general solid waste. The leached metal ions are then separated and purified using various methods. To ensure the removal rate of heavy metals, acid leaching must be carried out under specific temperature and pressure conditions. During this process, rare earth elements and other minerals contained in the sludge also dissolve. Because sodium hydroxide is used as the desulfurizing agent, the acid leaching solution also contains a large number of sodium ions. Rare earth elements and sodium react in a sulfate system to form sodium rare earth sulfate double salts. Under high temperature and pressure, these double salt precipitates adhere to the vessel walls, forming scale, which leads to low heat transfer efficiency and problems such as some scale sliding off and clogging the discharge port.

[0003] Therefore, it is necessary to develop a method to solve the scaling problem of rare earth sulfate double salts, improve the efficiency of removing rare earth sulfate double salt scales, increase the stability of equipment operation, and improve the energy saving and consumption reduction capabilities of the entire system. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing rare earth sulfate double salts, which mainly includes the following steps:

[0005] (1) Fill the container with rare earth sulfate double salt on the inner wall with water and soak it for 1 hour, then drain the water.

[0006] (2) Pour high humidity carbon dioxide gas into the container, control the internal pressure of the system to be 0.2~0.6Mpa, maintain it for more than 3 hours and then release the gas;

[0007] (3) Continue to add warm water at 30~50℃ to the container, stir the warm water and turn on the vibrator to make the loose solids enter the warm water with the stirring water flow, and then discharge it;

[0008] The water mentioned in step (1) is water in which polyvinylpyrrolidone is dissolved, and the concentration of polyvinylpyrrolidone is 0.1~0.5%, preferably 0.3~0.4%;

[0009] In step (2), the humidity is controlled at above 80%, and the carbon dioxide concentration in the remaining gas phase is >90%. Preferably, the humidity in the container is 90%~95%, and the carbon dioxide concentration in the remaining gas phase is 92%~95%.

[0010] The principle of this invention is as follows:

[0011] Rare earth sulfate double salts are bimetallic ionic salts. Although their solubility is low, they are still soluble in water. This invention uses water containing polyvinylpyrrolidone to soak the double salt scale. During the soaking process, polyvinylpyrrolidone binds with ions, which can prevent the deep binding of free rare earth ions, sodium ions and sulfate ions in the water. This allows the scale to slowly absorb the dissolved carbon dioxide and transform into rare earth carbonate during the subsequent introduction of carbon dioxide. Under certain pressure, the solubility of carbon dioxide in water increases, which increases the concentration of carbonate ions in the water and accelerates the reaction rate. During the transformation process, the original double salt scale is continuously destroyed and gradually transformed into new precipitates. Under the action of stirring warm water and vibration, the scale will not be adsorbed onto the container wall again and will be gradually carried away from the surface by the warm water solution.

[0012] Compared with the prior art, the advantages of the present invention are as follows:

[0013] There are no existing methods for treating rare earth sulfate double salts. For other types of scaling, physical intervention is generally used, which has drawbacks such as incomplete treatment and being time-consuming and labor-intensive. Alternatively, chemical methods, such as acid and alkali treatment, are used to dissolve the scale. However, such methods have requirements on the material of the container; steel cannot be treated with acid, and enamel cannot be treated with alkali. The scaling treatment method of this invention is particularly suitable for equipment that is not resistant to acids and alkalis. Detailed Implementation

[0014] Based on the key points of the present invention, the following specific embodiments illustrate the advantages of the present invention.

[0015] Example 1

[0016] In the desulfurization sludge treatment process, after the acid slurry in the reactor is unloaded, it is rinsed clean with water, the bottom valve is closed, water is added, the agitator is turned on, polyvinylpyrrolidone is added, the concentration is controlled at 0.3%, and the mixture is stirred and soaked for 1 hour. The bottom valve is then opened to drain the aqueous solution. Then, the container is filled with carbon dioxide gas containing water vapor, the humidity in the system is controlled at 90%, the carbon dioxide concentration in the remaining gas phase is 95%, and the system pressure is 0.4 MPa. After stabilizing for 3 hours, the system is vented. Then, warm water at 35°C is added to the container, the agitator and vibrator are turned on, and the system is run continuously for more than 3 hours to allow the precipitate to be discharged from the container along with the solution.

[0017] After the above treatment, the scale inside the container was almost completely removed, with a removal rate of 98% based on the container wall area.

[0018] Example 2

[0019] In the desulfurization sludge treatment process, after the acid slurry in the reactor is unloaded, it is rinsed clean with water, the bottom valve is closed, water is added, the agitator is turned on, polyvinylpyrrolidone is added, the concentration is controlled at 0.3%, and the mixture is stirred and soaked for 1 hour. The bottom valve is then opened to drain the aqueous solution. Then, the container is filled with carbon dioxide gas containing water vapor, the humidity in the system is controlled at 95%, the carbon dioxide concentration in the remaining gas phase is 93%, and the system pressure is 0.5 MPa. After stabilizing for 3 hours, the system is vented. Then, warm water at 35°C is added to the container, the agitator and vibrator are turned on, and the system is run continuously for more than 3 hours to allow the precipitate to be discharged from the container with the solution.

[0020] After the above treatment, the scale inside the container was almost completely removed, with a removal rate of 97% based on the container wall area.

[0021] Comparative Example

[0022] In the desulfurization sludge treatment process, after the acid slurry in the reactor is unloaded, it is rinsed clean with water, the bottom valve is closed, water is added, the agitator is turned on, and the mixture is stirred and soaked for 1 hour. The bottom valve is then opened to drain the aqueous solution. Then, the container is filled with carbon dioxide gas containing water vapor, the humidity in the system is controlled at 95%, the carbon dioxide concentration in the remaining gas phase is 93%, and the system pressure is 0.5 MPa. After stabilizing for 3 hours, the system is vented. Then, warm water at 35°C is added to the container, the agitator and vibrator are turned on, and the system is run continuously for more than 3 hours to allow the precipitate to be discharged from the container along with the solution.

[0023] After the above treatment, a significant amount of scale remained inside the container, and the removal rate was only 67% based on the container wall area.

Claims

1. A method for removing rare earth sulfate complex salt fouling, the main steps are as follows: (1) fill the container containing rare earth sulfate complex salt on the inner wall with water, soak for 1 hour, and then drain the water; (2) fill the container with carbon dioxide gas with high humidity, control the internal pressure to be 0.2-0.6 MPa, maintain for more than 3 hours, and then vent; (3) continue to add warm water at 30-50℃ to the container, stir the warm water and start the wall vibrator to vibrate, so that the loose solid enters the warm water with the stirred water flow, and then discharge; wherein the water in step (1) is water dissolved with polyvinylpyrrolidone, and the concentration of polyvinylpyrrolidone is 0.1-0.5%; the humidity in step (2) is controlled to be more than 80%, and the carbon dioxide gas concentration in the remaining gas phase is >90%. The rare earth sulfate complex salt includes one or a mixture of several of lanthanum sodium sulfate, cerium sodium sulfate, lanthanum potassium sulfate, and cerium potassium sulfate. The total metal ion concentration in the water used in step (1) is <20 ppm. The container includes enamel, carbon steel, and stainless steel materials. ​ ​ 2. The method of claim 1, wherein the method is characterized by, ​ 3. The method of claim 1, wherein the method is characterized by, ​ 4. The method of claim 1, wherein the method is characterized by, ​