Method for treating waste water containing silicon in the preparation of molecular sieves

Abstract

The present application relates to sewage treatment technical field, specifically to a kind of processing method of silicon-containing wastewater in molecular sieve preparation, comprising the following steps: (1) silicon-containing wastewater is passed into first reaction tank, A agent is added to first reaction tank, stirring is mixed, and standing is settled, and the pH value of mixed wastewater is controlled to be 11.0~13.0;(2) supernatant in first reaction tank overflow to second reaction tank, B agent and C agent are added to second reaction tank, stirring is mixed, and standing is settled, and the pH value of mixed wastewater is controlled to be 7.0~9.5;(3) supernatant in second reaction tank overflow to third reaction tank, D agent is added to third reaction tank, stirring is mixed, and standing is settled, and third reaction tank is overflowed to clarification tank after full tank.The present application does not introduce lime calcium and magnesium in sewage treatment system when removing silicon, reduces the amount of sludge, solves the technical problems of sewage treatment system blockage and scaling, saves soda for removing lime calcium, and the amount of lye is also greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a method for treating silicon-containing wastewater in the preparation of molecular sieves. Background Technology

[0002] During the production of catalytic cracking catalysts, the gel unit of the molecular sieve device generates wastewater with a high silicon content, ranging from 200 to 1200 mg / L. Before entering the wastewater membrane treatment system, the silicon content must be reduced to below 60 mg / L, the lower the better. Otherwise, dense silica scale will form on the surface of the permeate membrane, which will react with Al in the wastewater. 3+ The reaction forms silica-alumina gel. Both silica scale and silica-alumina gel can clog the permeation membrane channels, reduce membrane permeability, and severely affect the long-term operation of the permeation membrane. This will increase the operating pressure of the membrane column, and cleaning is necessary when a certain pressure is reached. The membrane cleaning water needs to be returned to the front system for retreatment. The increased number of cleaning times will increase the load on the wastewater system and increase treatment costs.

[0003] Currently, silicon in industrial wastewater is mainly removed through several methods, including coagulation desilication, electrocoagulation desilication, ion exchange desilication, air flotation for colloidal silicon removal, and ultrafiltration for colloidal silicon removal. The most common method is coagulation, which involves adding lime, magnesium, and flocculants to remove silicon from the wastewater. However, lime and magnesium introduce calcium and magnesium ions into the wastewater system. To remove calcium and magnesium from the lime, a high pH value must be adjusted using an alkaline solution before adding soda ash solution. For example, CN 105000642 A discloses a method for treating silicon-containing wastewater generated during molecular sieve preparation. This method involves adding a lime slurry with a solute concentration of 3%-10% to the silicon wastewater, stirring for a period of time, and then allowing it to stand for separation. The silicon content in the supernatant decreases, and the bottom sludge is discharged. This method effectively treats gel impurities in gel wastewater, and the turbidity of the treated wastewater is significantly reduced. Its technical drawbacks are: low silicon removal efficiency, only about 50%; lime is mainly composed of calcium oxide, and magnesium agent is mainly composed of magnesium oxide, which have low solubility, and the prepared solution is prone to sedimentation, which can easily clog the delivery pump and pipeline; calcium and magnesium are introduced into the sewage treatment system, which can easily form scale, clog pipelines, and adhere to the walls of the reaction vessel, stirring shaft, stirring blades, heat exchange fins of the downstream system heat exchanger, pump chamber and pump impeller, affecting the normal operation of the reactor, heat exchanger and pump, and requiring regular cleaning. Summary of the Invention

[0004] To address the technical problems of clogged and scaled wastewater treatment systems caused by lime-magnesium flocculant desiliconization, this invention provides a method for treating silicon-containing wastewater during molecular sieve preparation. This method avoids introducing lime-calcium and magnesium into the wastewater treatment system during desiliconization, reducing sludge volume and solving the technical problem of clogged and scaled wastewater treatment systems. It also saves on the soda ash used for removing lime-calcium and significantly reduces the amount of alkali used.

[0005] This invention provides a method for treating silicon-containing wastewater during molecular sieve preparation, comprising the following steps: (1) Silicon-containing wastewater is introduced into the first reaction tank. Agent A is added to the first reaction tank and stirred and mixed. The mixture is allowed to settle and the pH value of the mixed wastewater is controlled to be 11.0~13.0. Agent A includes Al2O3 and Na2O. (2) The supernatant in the first reaction tank overflows into the second reaction tank. Agent B and Agent C are added to the second reaction tank and stirred and mixed. The mixture is allowed to settle and the pH value of the mixed wastewater is controlled to be 7.0~9.5. Agent B is sulfuric acid and Agent C is polyferric sulfate. (3) The supernatant in the second reaction tank overflows into the third reaction tank. Agent D is added to the third reaction tank and stirred to mix. After settling, the third reaction tank overflows into the clarification tank. Agent D is polyacrylamide.

[0006] Furthermore, in step (1), the mass ratio of Al2O3 to Na2O is 3.5~11:13~29.

[0007] Furthermore, in step (1), every 1m 3 The volumetric dosage of agent A for silicon-containing wastewater is 2~29L.

[0008] Furthermore, in step (2), the concentration of sulfuric acid is 30%~98%.

[0009] Furthermore, in step (2), the amount of polyferric sulfate used is 20~80 mg / L, based on the maximum volume of mixed wastewater that can be stored in the second reaction tank.

[0010] Furthermore, in step (2), the amount of polyacrylamide used is 2~7 mg / L, based on the maximum volume of mixed wastewater that can be stored in the third reaction tank.

[0011] Furthermore, in step (3), the sludge settled at the bottom of the clarification tank is discharged to the sludge thickening tank by the sludge discharge pump. After further clarification, the supernatant overflows into the water collection tank, and the water in the water collection tank is returned to the third reaction tank for reuse.

[0012] Furthermore, the sludge concentrated in the sludge thickening tank is sent to a plate and frame filter press for filtration, and the filtered clear liquid is sent to a collection tank.

[0013] The beneficial effects of this invention are as follows: This invention abandons the traditional lime-magnesium flocculant-soda ash precipitation method. The silica-containing gel wastewater is first mixed with agent A in proportion and stirred evenly to adjust the pH value to 11.0~13.0. Then agents B and C are added, and the pH value is adjusted to 7.0~9.5 by acid adjustment. Flocculant is then added. After flocculation and clarification, the silica content in the wastewater is reduced from the original 200~800mg / L to below 40mg / L, and the turbidity is ≤60NTU. The amount of alkali used in wastewater treatment is greatly reduced, the amount of sludge in the system is reduced, and the amount of flocculant used is also greatly reduced. This solves the technical problem that lime-magnesium flocculant desilication easily causes blockage and scaling in the wastewater treatment system in the prior art. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0015] In the following embodiments, overflow in the reaction tank can be achieved through an overflow port or overflow pipe installed between two adjacent reaction tanks. The overflow port or overflow pipe can be opened or closed.

[0016] Example 1 A method for treating silicon-containing wastewater during molecular sieve preparation includes the following steps: (1) Silicon-containing wastewater is generated during the preparation of molecular sieve catalyst for catalytic cracking. The silicon content in the wastewater is 538 mg / L. The silicon-containing wastewater is introduced into the first reaction tank at the top of the tank. Agent A is added to the first reaction tank and stirred. Agent A includes Al2O3 and Na2O. The content of Al2O3 in Agent A is 99.7 g / L, the content of Na2O is 149.6 g / L, and the density of Agent A is 1.2~1.4 g / cm³. 3 per 1m 3 The volumetric dosage of agent A for the silicon-containing wastewater is 29L, the flow rate of agent A is 83L / h, and the mixture is allowed to settle to control the pH value of the mixed wastewater at 12.9.

[0017] (2) The supernatant in the first reaction tank overflows into the second reaction tank. Agent B and Agent C are added to the second reaction tank and stirred and mixed. The mixture is allowed to settle. Agent B is sulfuric acid with a concentration of 98% and Agent C is polyferric sulfate. The amount of polyferric sulfate is 50 mg / L based on the maximum volume of mixed wastewater that can be stored in the second reaction tank. The pH value of the mixed wastewater is controlled to be 7.5.

[0018] (3) The supernatant in the second reaction tank overflows into the third reaction tank. Agent D is added to the third reaction tank and stirred. Agent D is polyacrylamide (PAM). Based on the maximum volume of mixed wastewater that the third reaction tank can store, the amount of polyacrylamide is 4.5 mg / L and the flow rate of PAM added is 87 g / h. After settling, the supernatant overflows into the clarification tank.

[0019] (4) After the third reaction tank is full, the overflow enters the clarification tank. At the same time, the sludge scraper and sludge pump are turned on. The sludge scraper scrapes the sludge at the bottom of the clarification tank to the bottom of the inverted cone of the clarification tank. The sludge slurry is discharged to the sludge thickening tank by the sludge pump. After settling, it is pumped to the plate and frame filter press. The filter sludge is collected and transported off-site. The filtered water flows into the collection tank by gravity. After the clarification tank is full, the overflow enters the feed tank of the ammonia nitrogen removal device. At the same time, the supernatant of the sludge thickening tank flows into the collection tank by gravity through the valves of the overflow port at different liquid levels. The water in the collection tank is automatically controlled by the liquid level and the pump linkage. The wastewater in the collection tank is sent to the third reaction tank for reuse.

[0020] The silicon content, turbidity, and sludge discharge of the supernatant in each processing step of Example 1 were tested, and the data obtained are shown in Table 1.

[0021] Table 1 Wastewater treatment effect data for each treatment process Processing facilities Settling time, h Silicon content in supernatant, mg / L Turbidity of supernatant, NTU Sludge discharge volume First reaction tank 0.34 538 153.7 / Second reaction tank 0.34 174 261.3 / Third reaction tank 7 57 121.4 / Clarifying Pool 9 19.7 9.7 <![CDATA[12m 3 / h]]> sludge thickening tank 6 21.3 10.2 249t / h catch basin 0.8 20.6 12.3 / Example 2 A method for treating silicon-containing wastewater during molecular sieve preparation includes the following steps: (1) Silicon-containing wastewater is generated during the preparation of molecular sieve catalyst for catalytic cracking. The silicon content in the wastewater is 628 mg / L. The silicon-containing wastewater is introduced into the first reaction tank at the top of the tank. Agent A is added to the first reaction tank and stirred. Agent A includes Al2O3 and Na2O. The Al2O3 content in Agent A is 35.1 g / L, the Na2O content is 130.6 g / L, and the density of Agent A is 1.2~1.4 g / cm³. 3 per 1m 3 The volume of agent A used for the silicon-containing wastewater was 10L, the flow rate of agent A was 82L / h, and the mixture was allowed to settle to control the pH of the mixed wastewater at 11.0.

[0022] (2) The supernatant in the first reaction tank overflows into the second reaction tank. Agent B and Agent C are added to the second reaction tank and stirred and mixed. The mixture is allowed to settle. Agent B is sulfuric acid with a concentration of 70% and Agent C is polyferric sulfate. The amount of polyferric sulfate is 20 mg / L based on the maximum volume of mixed wastewater that can be stored in the second reaction tank. The pH value of the mixed wastewater is controlled to be 7.0.

[0023] (3) The supernatant in the second reaction tank overflows into the third reaction tank. Agent D is added to the third reaction tank and stirred. Agent D is polyacrylamide (PAM). Based on the maximum volume of mixed wastewater that can be stored in the third reaction tank, the amount of polyacrylamide is 2 mg / L and the flow rate of PAM added is 82 g / h. After settling, the supernatant overflows into the clarification tank.

[0024] (4) After the third reaction tank is full, the overflow enters the clarification tank. At the same time, the sludge scraper and sludge pump are turned on. The sludge scraper scrapes the sludge at the bottom of the clarification tank to the bottom of the inverted cone of the clarification tank. The sludge slurry is discharged to the sludge thickening tank by the sludge pump. After settling, it is pumped to the plate and frame filter press. The filter sludge is collected and transported off-site. The filtered water flows into the collection tank by gravity. After the clarification tank is full, the overflow enters the feed tank of the ammonia nitrogen removal device. At the same time, the supernatant of the sludge thickening tank flows into the collection tank by gravity through the valves of the overflow port at different liquid levels. The water in the collection tank is automatically controlled by the liquid level and the pump linkage. The wastewater in the collection tank is sent to the third reaction tank for reuse.

[0025] The silicon content, turbidity, and sludge discharge of the supernatant in each processing step of Example 2 were tested, and the data obtained are shown in Table 2.

[0026] Table 2 Wastewater treatment effect data for each treatment process Processing facilities Settling time, h Silicon content in supernatant, mg / L Turbidity of supernatant, NTU Sludge discharge volume First reaction tank 0.35 628 163.3 / Second reaction tank 0.33 221 272.3 / Third reaction tank 4 58 102.1 / Clarifying Pool 6 20.1 10.1 <![CDATA[11m 3 / h]]> sludge thickening tank 6 21.3 10.3 235t / h catch basin 0.8 21.0 11.9 / Example 3 A method for treating silicon-containing wastewater during molecular sieve preparation includes the following steps: (1) Silicon-containing wastewater is generated during the preparation of molecular sieve catalyst for catalytic cracking. The silicon content in the wastewater is 523 mg / L. The silicon-containing wastewater is introduced into the first reaction tank at the top of the tank. Agent A is added to the first reaction tank and stirred. Agent A includes Al2O3 and Na2O. The Al2O3 content in Agent A is 110.0 g / L, the Na2O content is 289.8 g / L, and the density of Agent A is 1.2~1.4 g / cm³. 3 per 1m 3 The volume of agent A used for the silicon-containing wastewater was 2L, and the flow rate of agent A added was 89L / h. After settling, the pH value of the mixed wastewater was controlled at 12.1.

[0027] (2) The supernatant in the first reaction tank overflows into the second reaction tank. Agent B and Agent C are added to the second reaction tank and stirred and mixed. The mixture is allowed to settle. Agent B is sulfuric acid with a concentration of 30% and Agent C is polyferric sulfate. Based on the maximum volume of mixed wastewater that can be stored in the second reaction tank, the amount of polyferric sulfate is 80 mg / L. The pH value of the mixed wastewater is controlled to be 9.5.

[0028] (3) The supernatant in the second reaction tank overflows into the third reaction tank. Agent D is added to the third reaction tank and stirred. Agent D is polyacrylamide (PAM). Based on the maximum volume of mixed wastewater that can be stored in the third reaction tank, the amount of polyacrylamide is 7 mg / L and the flow rate of PAM added is 83 g / h. After settling, the supernatant overflows into the clarification tank.

[0029] (4) After the third reaction tank is full, the overflow enters the clarification tank. At the same time, the sludge scraper and sludge pump are turned on. The sludge scraper scrapes the sludge at the bottom of the clarification tank to the bottom of the inverted cone of the clarification tank. The sludge slurry is discharged to the sludge thickening tank by the sludge pump. After settling, it is pumped to the plate and frame filter press. The filter sludge is collected and transported off-site. The filtered water flows into the collection tank by gravity. After the clarification tank is full, the overflow enters the feed tank of the ammonia nitrogen removal device. At the same time, the supernatant of the sludge thickening tank flows into the collection tank by gravity through the valves of the overflow port at different liquid levels. The water in the collection tank is automatically controlled by the liquid level and the pump linkage. The wastewater in the collection tank is sent to the third reaction tank for reuse.

[0030] The silicon content, turbidity, and sludge discharge of the supernatant in each processing step of Example 3 were tested, and the data obtained are shown in Table 3.

[0031] Table 3 Wastewater treatment effect data for each treatment process Processing facilities Settling time, h Silicon content in supernatant, mg / L Turbidity of supernatant, NTU Sludge discharge volume First reaction tank 0.33 523 159.8 / Second reaction tank 0.33 153 264.6 / Third reaction tank 10 59 127.3 / Clarifying Pool 12 21.3 10.1 <![CDATA[13.1m 3 / h]]> sludge thickening tank 6 20.9 10.3 234t / h catch basin 0.8 20.3 12.2 / Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for treating silicon-containing wastewater in molecular sieve preparation, characterized in that, Includes the following steps: (1) Silicon-containing wastewater is introduced into the first reaction tank. Agent A is added to the first reaction tank and stirred and mixed. The mixture is allowed to settle and the pH value of the mixed wastewater is controlled to be 11.0~13.

0. Agent A includes Al2O3 and Na2O. (2) The supernatant in the first reaction tank overflows into the second reaction tank. Agent B and Agent C are added to the second reaction tank and stirred and mixed. The mixture is allowed to settle and the pH value of the mixed wastewater is controlled to be 7.0~9.

5. Agent B is sulfuric acid and Agent C is polyferric sulfate. (3) The supernatant in the second reaction tank overflows into the third reaction tank. Agent D is added to the third reaction tank and stirred. After settling, the third reaction tank overflows into the clarification tank. Agent D is polyacrylamide. In step (1), every 1m 3 The volumetric dosage of agent A for silicon-containing wastewater is 2~29L; In step (2), the amount of polyferric sulfate used is 20~80 mg / L, based on the maximum volume of mixed wastewater that can be stored in the second reaction tank. In step (2), the amount of polyacrylamide used is 2~7 mg / L, based on the maximum volume of mixed wastewater that can be stored in the third reaction tank.

2. The method for treating silicon-containing wastewater in molecular sieve preparation as described in claim 1, characterized in that, In step (1), the mass ratio of Al2O3 to Na2O is 3.5~11:13~29.

3. The method for treating silicon-containing wastewater in molecular sieve preparation as described in claim 1, characterized in that, In step (2), the concentration of sulfuric acid is 30%~98%.

4. The method for treating silicon-containing wastewater in molecular sieve preparation as described in claim 1, characterized in that, In step (3), the sludge settled at the bottom of the clarification tank is discharged to the sludge thickening tank by the sludge discharge pump. After further clarification, the supernatant overflows into the water collection tank, and the water in the water collection tank is returned to the third reaction tank for reuse.

5. The method for treating silicon-containing wastewater in molecular sieve preparation as described in claim 4, characterized in that, The concentrated sludge in the sludge thickening tank is sent to a plate and frame filter press for filtration, and the filtered clear liquid is sent to a collection tank.