CN113020064A - Cleaning method of wet-process phosphoric acid extraction tower - Google Patents
Cleaning method of wet-process phosphoric acid extraction tower Download PDFInfo
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Abstract
The invention discloses a method for cleaning a wet-process phosphoric acid extraction tower, which comprises the following steps: performing high-pressure water physical cleaning on the interior of the extraction tower, and opening a scale inner channel; chemically cleaning the interior of the extraction tower by using cleaning liquid with the temperature of more than 70 ℃, and controlling the pressure of the cleaning liquid to be more than 0.05MPa in the chemical cleaning process so as to convert hard scales into soft scales; and (3) carrying out high-pressure water physical cleaning on the interior of the extraction tower to ensure that soft scales fall off and are discharged outwards, thereby completing the cleaning of the extraction tower. The cleaning method has the advantages of short cleaning period, low cleaning cost, high cleaning efficiency, good cleaning effect, safety, environmental protection and the like, can realize efficient and thorough cleaning of the wet-process phosphoric acid extraction tower, and has high use value and good application prospect.
Description
Technical Field
The invention relates to a cleaning method of a wet-process phosphoric acid extraction tower.
Background
The wet-process phosphoric acid process is to prepare phosphoric acid by reacting concentrated sulfuric acid with phosphate ore, and to remove calcium sulfate precipitate which is slightly soluble in water by filtering the reaction product of the concentrated sulfuric acid and the phosphate ore, so as to obtain filtrate, namely phosphoric acid solution. In order to further obtain high-quality phosphoric acid, it is necessary to continuously purify the phosphoric acid solution. In the purification process of phosphoric acid solution, the extraction tower is the key equipment of the purification process, and meanwhile, in order to improve the extraction rate, the extraction tower adopts a tower multi-stage plate-ring structure. However, in the extraction process, in the process of mutual dissolution of the extracting agent and phosphoric acid, a large amount of crystal salts are precipitated, and the crystal salts are accumulated together to form scale, so that gaps between plate rings are blocked, the space between extraction tower plates and rings is greatly reduced, the contact surface of the extracting agent and the phosphoric acid is reduced, and the extraction load of an extraction tower is finally reduced. Therefore, in the process of purifying phosphoric acid solution by using a phosphoric acid extraction tower to obtain high-quality phosphoric acid, scale generated in the purification process needs to be removed timely, efficiently and thoroughly. In addition, the extraction tower has large volume and complex structure; the extraction tower has complex scale forming components, hard texture and large scale amount; the field construction conditions are harsh, the extractant belongs to a flammable solvent, and the requirement on the explosion-proof grade is high, so that the existence of the factors puts higher requirements on the cleaning of the extraction tower.
The existing cleaning method for the extraction tower mainly comprises chemical cleaning and physical cleaning, however, the two methods still have the following defects, such as the defects of the chemical cleaning: (1) the cleaning time is long, and the cleaning time is about 30 days due to large scale amount and complex and hard scale quality; (2) the cleaning rate is low, and the cleaning rate cannot be ensured because the equipment structure is complex and dead corners cannot contact with the cleaning solution in the cleaning process; (3) the sewage discharge capacity is large, and the sewage discharge capacity is large and the post environmental-protection treatment cost is high because the acid and the alkali are alternated for many times in the cleaning process and are replaced by water; (4) the cleaning cost is high, and the consumption of chemicals, steam, electric energy and water is large during cleaning because the volume of the extraction tower is large. The disadvantages of physical cleaning are: (a) the scale is hard, the pressure of the adopted cleaning equipment is between 90 and 120MPa, and huge potential safety hazards exist on the damage of the equipment and operators and nearby workers; (b) the device has the advantages that the device has environmental protection problem, and the device releases heat when striking dirt in the physical cleaning process and releases methyl isobutyl ketone (MIBK) contained in the dirt, thereby not only polluting the environment, but also being harmful to human body; (c) the economic cost is high, the physical cleaning has high requirements on the pressure of equipment, the investment of the equipment and the investment of quick-wear parts of an actuating mechanism are large, the equipment is also greatly lost, and meanwhile, the high-pressure equipment has high requirements on the quality and the skill of operators and needs frequent hand changing, so the labor cost is high. Therefore, the cleaning method for the wet-process phosphoric acid extraction tower is short in cleaning period, low in cleaning cost, high in cleaning efficiency, good in cleaning effect, safe and environment-friendly, and has very important significance for obtaining low-cost and high-quality phosphoric acid.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a safe and environment-friendly method for cleaning a wet-process phosphoric acid extraction tower, which has the advantages of short cleaning period, low cleaning cost, high cleaning efficiency and good cleaning effect.
In order to solve the technical problems, the invention adopts the technical scheme that:
a cleaning method of a wet-process phosphoric acid extraction tower comprises the following steps:
s1, performing high-pressure water physical cleaning on the interior of the extraction tower, and opening a scale inner channel;
s2, chemically cleaning the interior of the extraction tower by adopting a cleaning solution with the temperature of more than 70 ℃, and controlling the pressure of the cleaning solution to be more than 0.05MPa in the chemical cleaning process to convert hard scales into soft scales;
and S3, performing high-pressure water physical cleaning on the interior of the extraction tower to enable soft scales to fall off and be discharged outwards, and finishing cleaning the extraction tower.
In the above cleaning method for the wet-process phosphoric acid extraction tower, in a further improvement, in step S2, the chemical cleaning is performed by any one of the following methods:
the first method is as follows: alkaline cleaning is carried out on the interior of the extraction tower by adopting alkaline cleaning liquid;
the second method comprises the following steps: acid cleaning is carried out on the interior of the extraction tower by adopting an acid cleaning solution;
the third method comprises the following steps: and (3) alternately performing alkali washing and acid washing on the interior of the extraction tower by adopting alkali washing cleaning liquid and acid cleaning liquid.
In the cleaning method of the wet-process phosphoric acid extraction tower, the alkaline cleaning solution is a sodium hydroxide solution or a mixed solution of sodium hydroxide and sodium carbonate; the mass percentage of the sodium hydroxide in the sodium hydroxide solution is 5-20%; the mixed solution of sodium hydroxide and sodium carbonate contains 8-15% of sodium hydroxide and 5-8% of sodium carbonate by mass.
In the cleaning method of the wet-process phosphoric acid extraction tower, the acid cleaning solution is a hydrochloric acid solution and/or a nitric acid solution; the mass concentration of the acidic cleaning solution is 5-20%.
In step S2, the chemical cleaning process further includes adding an auxiliary agent and/or a corrosion inhibitor into the extraction tower; the auxiliary agent is a penetrating agent, a surfactant and a defoaming agent; the addition amount of the penetrating agent is 0.1-0.3% of the total volume of the cleaning solution; the addition amount of the surfactant is 0.1-0.3% of the total volume of the cleaning solution; the addition amount of the defoaming agent is 0.1-0.3% of the total volume of the cleaning solution; the addition amount of the corrosion inhibitor is 0.1-0.3% of the total volume of the cleaning solution.
In the cleaning method of the wet-process phosphoric acid extraction tower, the penetrating agent is fatty alcohol-polyoxyethylene ether; the surfactant is sodium dodecyl benzene sulfonate and/or dodecyl ethoxy sulfobetaine; the defoaming agent is OP-10 and/or emulsified silicone oil; the corrosion inhibitor is LAN-826.
In step S1, before the high-pressure water physical cleaning, the method for cleaning the wet phosphoric acid extraction tower further comprises the following steps: introducing hot water with the temperature of 70-95 ℃ into an extraction tower for water transportation and cleaning; the pressure of hot water is controlled to be 0.05MPa to 0.08MPa in the water transportation cleaning process, and the flow is more than or equal to 50m3H, introducing the mixture into the extraction tower from the top and/or the side part of the extraction tower; the cleaning mode adopted in the water transportation cleaning process is mainly that washing is carried out from top to bottom, and circulation washing and positive backwashing are used as assistance; the time for water transportation cleaning is 16-24 h.
In the above cleaning method for the wet-process phosphoric acid extraction tower, the method further comprises the following steps after the water transportation cleaning is completed: discharging the product obtained after water transportation and cleaning from the bottom of the extraction tower, carrying out solid-liquid separation, and recovering the extraction agent and water.
In the above cleaning method for the wet-process phosphoric acid extraction tower, it is further improved that in step S1, the inside of the extraction tower is physically cleaned with high-pressure water; the pressure of the high-pressure water is 90MPa to 120 MPa; in the high-pressure water physical cleaning process, high-pressure water is introduced into the extraction tower from the top and/or the side part of the extraction tower; the cleaning mode adopted in the high-pressure water physical cleaning process is mainly that washing is carried out from top to bottom, and cyclic washing and forward backwashing are used as assistance; the time for physically cleaning the high-pressure water is 16-24 hours.
In the cleaning method of the wet-process phosphoric acid extraction tower, the following treatment is further included after the high-pressure water physical cleaning is completed: discharging the product obtained after the high-pressure water is cleaned from the bottom of the extraction tower, performing solid-liquid separation, and recovering water.
In step S2, the pressure of the cleaning solution is controlled to be 0.05MPa to 0.08MPa, and the temperature is controlled to be 70 ℃ to 95 ℃ during the chemical cleaning process.
In the above cleaning method for the wet-process phosphoric acid extraction tower, the cleaning liquid is introduced into the extraction tower from the top and/or the side of the extraction tower in the chemical cleaning process; the cleaning mode adopted in the chemical cleaning process is mainly that washing is carried out from top to bottom, and is assisted by circular washing and positive backwashing; the chemical cleaning time is 40-60 h.
In the above cleaning method for the wet-process phosphoric acid extraction tower, further improvement is that the following treatment is included after the chemical cleaning is completed: discharging the product obtained after chemical cleaning from the bottom of the extraction tower, performing solid-liquid separation, and recovering the cleaning solution.
In the above cleaning method for the wet-process phosphoric acid extraction tower, it is further improved that in step S3, the inside of the extraction tower is physically cleaned with high-pressure water; the pressure intensity of the high-pressure water is 30MPa-60 MPa; in the high-pressure water physical cleaning process, high-pressure water is introduced into the extraction tower from the top and/or the side part of the extraction tower; the cleaning mode adopted in the high-pressure water physical cleaning process is mainly that washing is carried out from top to bottom, and cyclic washing and forward backwashing are used as assistance; the time for physically cleaning the high-pressure water is 3 to 4 days; in the cleaning method of the wet-process phosphoric acid extraction tower, the following treatment is further included after the high-pressure water physical cleaning is completed: discharging the product obtained after the high-pressure water is cleaned from the bottom of the extraction tower, performing solid-liquid separation, and recovering water.
Compared with the prior art, the invention has the advantages that:
the invention provides a cleaning method of a wet-process phosphoric acid extraction tower, which comprises the steps of firstly carrying out high-pressure water physical cleaning on the interior of the extraction tower, and opening a chemical channel in scale in the extraction tower through high-pressure impact, so that subsequent cleaning liquid can be conveniently and fully contacted with the scale, and the cleaning efficiency and the cleaning effect of the subsequent chemical cleaning can be improved; and then carry on the chemical cleaning to the inside of the extraction column, through the reaction between detergent and dirt, make hard dirt soften and drop from column plate and support column of the extraction column, and the dirt piece after dropping flows to the bottom of the tower along with the cleaning solution, because a large amount of dirt is dissolved and brought out of the tower after the chemical cleaning, therefore can reduce the quantity of operating personnel and labour personnel, can also reduce the subsequent high-pressure water physical cleaning operating pressure and greatly relieve the working strength and fatigue strength of the operating personnel, high-strength, high-pressure operation more than 12 hours will not appear, both favorable to reducing the labour cost of manpower, also favorable to reducing the equipment, executive mechanism and operating personnel's operation safety risk and operating personnel's safe management cost, the detergent that is adopted in the chemical cleaning process can dissolve the extracting agent remaining in the tower at the same time, favorable to reducing the extracting agent that remains to the environment, The harm to operators can improve the cleaning safety and reduce the risk of secondary pollution; and finally, the softened scales obtained after the chemical cleaning in the extraction tower are continuously subjected to high-pressure water physical cleaning, the softened scales can be further knocked, loosened and smashed through high-pressure impact under the condition of lower pressure, so that more scales fall off from tower plates and supporting columns of the extraction tower, and flow to the bottom of the extraction tower from top to bottom by virtue of the high-pressure impact force in the high-pressure water physical cleaning process, and are discharged, so that the extraction tower is thoroughly and effectively cleaned. In addition, after the scale in the extraction tower is removed, the 6S management cost on site can be reduced, and meanwhile, the original acidity of the scale is changed into neutrality or alkalescence, so that the basic corrosion to the tower body and related equipment and facilities is avoided, and the service life of the tower body is prolonged. In addition, after the scale in the extraction tower is dissolved and taken away, the condition that manual cleaning leads to collapse is avoided, the operation safety risk is greatly reduced, and a toxic and harmful extracting agent (such as MIBK) in the extraction tower is effectively removed, so that the safety risk that an operator enters the operation in a limited space is greatly reduced. The cleaning method has the advantages of short cleaning period, low cleaning cost, high cleaning efficiency, good cleaning effect, safety, environmental protection and the like, can realize efficient and thorough cleaning of the wet-process phosphoric acid extraction tower, and has high use value and good application prospect.
Drawings
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
FIG. 1 is a flow chart of the cleaning process of the wet-process phosphoric acid extraction tower in the invention.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
The materials and equipment used in the following examples are commercially available. In this example, the fouling of the interior of the extraction column to be cleaned was substantially uniform.
Example 1
A cleaning method of a wet-process phosphoric acid extraction tower is shown in a process flow diagram in figure 1, and comprises the following steps:
and S1, introducing hot water at the temperature of 80 ℃ into the evacuated C200 extraction tower for water-borne cleaning for 1 day. In the step, the pressure of the hot water is controlled to be 0.05MPa to 0.08MPa, and the flow is more than or equal to 50m3H from extractionThe top and the lateral part of the tower are led into the extraction tower, the top-down scouring is taken as a main part, the interior of the extraction tower is cleaned by taking the circulating flushing and the forward backwashing as an auxiliary part, hot water is utilized to circularly clean the residual acid in the whole tower body in the cleaning process, so that the consumption of subsequent alkali cleaning agents is reduced, meanwhile, after the water transportation cleaning is finished, products obtained after the water transportation cleaning are discharged from the bottom of the extraction tower, the solid and liquid are separated, methyl isobutyl ketone (MIBK) and water are recovered, and the obtained recovered water is heated and then is continuously used for cleaning the extraction tower, so that the cost is saved.
S2, after the water transportation cleaning in the step S1 is finished, the interior of the extraction tower is subjected to high-pressure water physical cleaning, and an inner channel for scale opening is opened, specifically: and (3) circularly introducing high-pressure water with the pressure of 90MPa into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, and physically cleaning the interior of the extraction tower with the high-pressure water for 1 day by taking circular washing and forward backwashing as assistance. In the step, high-pressure water is utilized to impact the scale in the extraction tower in a circulating manner, a chemical cleaning channel is opened, the whole tower section fluid channel is smooth, and a larger contact surface with alkaline cleaning liquid is created for subsequent alkaline cleaning, so that an alkaline cleaning agent can be fully contacted with the scale, and the alkaline cleaning efficiency and the alkaline cleaning effect are ensured; and simultaneously, after the high-pressure water physical cleaning is finished, discharging a product obtained after the high-pressure water physical cleaning from the bottom of the extraction tower, carrying out solid-liquid separation, recovering water, and pressurizing the obtained recovered water for continuously cleaning and impacting scale in the extraction tower.
S3, after the high-pressure water physical cleaning in the step S2 is finished, alkaline cleaning liquid is adopted to carry out alkaline cleaning on the interior of the extraction tower, so that hard scales are converted into soft scales, and the method specifically comprises the following steps: dissolving sodium carbonate into water, adding sodium hydroxide to prepare a mixed solution of the sodium hydroxide and the sodium carbonate, namely an alkaline cleaning solution; adjusting the temperature of the alkaline cleaning solution to 90 ℃, starting a circulating pump, controlling the pressure of the alkaline cleaning solution to be 0.05-0.08 MPa, introducing the alkaline cleaning solution into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, and carrying out alkaline washing on the inside of the extraction tower with the assistance of circular washing and forward backwashing, wherein the alkaline washing time is 2 days. In the step, the alkaline cleaning agent can be fully contacted with the scale and react in the alkaline cleaning process, so that the hard scale is changed into soft scale, a prerequisite condition is provided for subsequent high-pressure water cleaning, meanwhile, methyl isobutyl ketone (MIBK) remained in the scale in the alkaline cleaning process is released and dissolved into the alkaline cleaning solution, and then the alkaline cleaning solution is discharged from the bottom of the extraction tower and taken out of the tower, and the residual MIBK in the tower is effectively removed, so that the safety risk and the injury of occupational diseases to personnel are reduced, and the efficiency of operators is improved. In the step, the inside of the extraction tower is subjected to alkaline washing mainly by top-down washing and assisted by circulating washing and forward backwashing, so that scale blocks with softened surfaces can flow to the bottom of the tower along with alkaline washing liquid, the pressure of subsequent high-pressure water washing operation and the fatigue strength of operators are greatly reduced, and the safety risk and the safety cost are also reduced.
In step S3, a mixed solution of sodium hydroxide and sodium carbonate is used as the alkaline cleaning solution, wherein the mixed solution of sodium hydroxide and sodium carbonate contains 10% by mass of sodium hydroxide and 5% by mass of sodium carbonate.
In the step S3, in the process of performing alkaline cleaning on the inside of the extraction tower with alkaline cleaning solution, an auxiliary agent and a corrosion inhibitor are added into the extraction tower, wherein the auxiliary agent is a penetrating agent, a surfactant and a defoaming agent, the penetrating agent is fatty alcohol-polyoxyethylene ether, and the addition amount is 0.1-0.3% of the total volume of the alkaline cleaning solution (in the actual treatment process, because the content and distribution of scale in the tower are different, the amounts of the auxiliary agent and the corrosion inhibitor can be adjusted according to the actual situation, and the addition amount is 0.1-0.3% of the total volume of the alkaline cleaning solution); the surfactant is sodium dodecyl benzene sulfonate, and the addition amount of the surfactant is 0.1-0.3 percent of the total volume of the alkaline cleaning solution; the defoaming agent is OP-10, and the addition amount is 0.1-0.3 percent of the total volume of the alkaline cleaning solution; the corrosion inhibitor is LAN-826, and the addition amount is 0.1-0.3% of the total volume of the alkaline cleaning solution. According to the invention, the penetrant and the surfactant are added, so that the cleaning liquid can be promoted to enter the scale, the effective reaction between the cleaning liquid and the scale can be promoted, the scale in the extraction tower can be softened, and more hard scales can be converted into soft scales; meanwhile, the added defoaming agent can effectively remove a large amount of foams generated in the cleaning process, and the addition of the corrosion inhibitor is favorable for reducing the corrosion of the cleaning solution to the extraction tower, so that the extraction tower can be effectively protected, and the adverse effect of the cleaning solution on the extraction tower is reduced.
S4, after the alkaline cleaning in the step S3 is finished, the interior of the extraction tower is subjected to high-pressure water physical cleaning, so that soft scales fall off and are discharged outwards, and the cleaning of the extraction tower is finished, specifically: introducing high-pressure water with the pressure of 60MPa into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, and physically cleaning the interior of the extraction tower with the high-pressure water by taking circulating washing and forward backwashing as assistance, wherein the time is 3 days. In the step, high-pressure water is used for impacting softened scales inside the extraction tower, all hardened material scales on the periphery of a tower plate of the extraction tower and on a support column are loosened and fall off, the falling scales are cleaned to the bottom of the extraction tower from top to bottom by the impact force of the high-pressure water, meanwhile, after the high-pressure water physical cleaning is completed, products obtained after the high-pressure water physical cleaning are discharged from the bottom of the extraction tower, solid-liquid separation is carried out, water is recycled, and the obtained recycled water is pressurized and then is continuously used for cleaning and impacting the scales inside the extraction tower.
In the present invention, the high-pressure water used in steps S2 and S4 is generally industrial water, including industrial water for general plant, and desalted water and fire water that may be used in the plant, but not limited thereto, and any water that can remove scale from the inside of the extraction tower can be used in this patent.
Table 1 cleaning effect of the cleaning method in example 1 on the extraction column
In table 1, the high-pressure water physical cleaning means cleaning the extraction tower only by using high-pressure water with a pressure of 90MPa to 120 MPa; the chemical cleaning is to alternately perform alkaline cleaning and acid cleaning by only adopting alkaline cleaning solution and acidic cleaning solution, wherein the alkaline cleaning solution adopted in the alkaline cleaning process is the same as that in the embodiment 1, the acidic cleaning solution adopted in the acid cleaning process is hydrochloric acid solution with the mass concentration of 15%, and the auxiliary agent and the corrosion inhibitor adopted in the chemical cleaning process are the same as those in the embodiment 1. As can be seen from table 1, before the alkaline cleaning, the inner passage of the scale in the extraction tower needs to be opened first, so the high-pressure water washing is a necessary process, because if the inner passage of the scale is opened without the high-pressure water washing, the alkaline cleaning solution adopted in the alkaline cleaning process is difficult to fully contact and react with the scale, so the hard scale in the extraction tower is difficult to be converted into soft scale, the expected effect cannot be achieved, and the hard scale cannot be completely converted into soft scale in the alkaline cleaning process, so the extraction tower after the alkaline cleaning needs to be further washed, the scale is further loosened and broken by the impact force of the high-pressure water, and is taken away with the cleaning solution, and meanwhile, after the second washing, the deep harmful substances and irritant gas are also taken away, so the scale is not hardened for the second time, and is beneficial to cleaning.
In example 1 of the present invention, on the premise that other conditions are the same, when a hydrochloric acid solution having a mass concentration of 15% is used as an acidic cleaning solution instead of an alkaline cleaning solution for pickling an extraction tower, the same cleaning effect as in example 1 can be achieved, but when a hydrochloric acid solution having a mass concentration of 15% is used as an acidic cleaning solution for pickling, there is a risk that equipment and facilities related to the extraction tower are easily corroded.
Example 2
A cleaning method of a wet-process phosphoric acid extraction tower comprises the following steps:
and S1, introducing hot water at the temperature of 80 ℃ into the evacuated C200 extraction tower for water-borne cleaning for 1 day. In the step, the pressure of the hot water is controlled to be 0.05MPa to 0.08MPa, and the flow is more than or equal to 50m3And h, introducing the water into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, washing the interior of the extraction tower with the aid of circulating washing and forward backwashing, effectively diluting the residual acid in the whole tower body by utilizing hot water for circulating washing in the washing process so as to reduce the consumption of subsequent alkali washing agents, and simultaneously after the water transportation washing is finished, conveying the product obtained after the water transportation washing from the extraction towerAnd discharging from the bottom, performing solid-liquid separation, recovering methyl isobutyl ketone (MIBK) and water, and heating the obtained recovered water for continuously cleaning the extraction tower, so that the cost is saved.
S2, after the water transportation cleaning in the step S1 is finished, the interior of the extraction tower is subjected to high-pressure water physical cleaning, and an inner channel for scale opening is opened, specifically: and (3) circularly introducing high-pressure water with the pressure of 90MPa into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, and physically cleaning the interior of the extraction tower with the high-pressure water for 1 day by taking circular washing and forward backwashing as assistance. In the step, high-pressure water is utilized to impact the scale in the extraction tower in a circulating manner, a chemical cleaning channel is opened, the whole tower section fluid channel is smooth, and a larger contact surface with alkaline cleaning liquid is created for subsequent alkaline cleaning, so that an alkaline cleaning agent can be fully contacted with the scale, and the alkaline cleaning efficiency and the alkaline cleaning effect are ensured; and simultaneously, after the high-pressure water physical cleaning is finished, discharging a product obtained after the high-pressure water physical cleaning from the bottom of the extraction tower, carrying out solid-liquid separation, recovering water, and pressurizing the obtained recovered water for continuously cleaning and impacting scale in the extraction tower.
S3, after the high-pressure water physical cleaning in the step S2 is finished, alkali cleaning is carried out on the interior of the extraction tower, so that hard scales are converted into soft scales, and the method specifically comprises the following steps: adjusting the temperature of the alkaline cleaning solution to 90 ℃, starting a circulating pump, controlling the pressure of the alkaline cleaning solution to be 0.05-0.08 MPa, introducing the alkaline cleaning solution into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, and carrying out alkaline washing on the inside of the extraction tower with the assistance of circular washing and forward backwashing, wherein the alkaline washing time is 2 days. In the step, the alkaline cleaning agent can be fully contacted with the scale and react in the alkaline cleaning process, so that the hard scale is changed into soft scale, a prerequisite condition is provided for subsequent high-pressure water cleaning, meanwhile, methyl isobutyl ketone (MIBK) remained in the scale in the alkaline cleaning process is released and dissolved into the alkaline cleaning solution, and then the alkaline cleaning solution is discharged from the bottom of the extraction tower and taken out of the tower, and the residual MIBK in the tower is effectively removed, so that the safety risk and the injury of occupational diseases to personnel are reduced, and the efficiency of operators is improved. In the step, the inside of the extraction tower is subjected to alkaline washing mainly by top-down washing and assisted by circulating washing and forward backwashing, so that scale blocks with softened surfaces can flow to the bottom of the tower along with alkaline washing liquid, the pressure of subsequent high-pressure water washing operation and the fatigue strength of operators are greatly reduced, and the safety risk and the safety cost are also reduced.
In step S3, the alkaline cleaning solution used is a sodium hydroxide solution or a mixed solution of sodium hydroxide and sodium carbonate, as shown in table 2.
Step S3, in the process of alkaline cleaning the inside of the extraction tower by using alkaline cleaning liquid, adding an auxiliary agent and a corrosion inhibitor into the extraction tower, wherein the auxiliary agent is a penetrating agent, a surfactant and a defoaming agent, the penetrating agent is fatty alcohol-polyoxyethylene ether, and the adding amount of the penetrating agent is 0.1-0.3% of the total volume of the alkaline cleaning liquid; the surfactant is sodium dodecyl benzene sulfonate, and the addition amount of the surfactant is 0.1-0.3 percent of the total volume of the alkaline cleaning solution; the defoaming agent is OP-10, and the addition amount is 0.1-0.3 percent of the total volume of the alkaline cleaning solution; the corrosion inhibitor is LAN-826, and the addition amount is 0.1-0.3% of the total volume of the alkaline cleaning solution. According to the invention, the penetrant and the surfactant are added, so that the cleaning liquid can be promoted to enter the scale, the effective reaction between the cleaning liquid and the scale can be promoted, the scale in the extraction tower can be softened, and more hard scales can be converted into soft scales; meanwhile, the added defoaming agent can effectively remove a large amount of foams generated in the cleaning process, and the addition of the corrosion inhibitor is favorable for reducing the corrosion of the cleaning solution to the extraction tower, so that the extraction tower can be effectively protected, and the adverse effect of the cleaning solution on the extraction tower is reduced.
S4, after the alkaline cleaning in the step S3 is finished, the interior of the extraction tower is subjected to high-pressure water physical cleaning, so that soft scales fall off and are discharged outwards, and the cleaning of the extraction tower is finished, specifically: high-pressure water with the pressure of 60MPa is introduced into the extraction tower from the top and the side of the extraction tower, the top-down flushing is mainly used, and the high-pressure water physical cleaning is carried out on the interior of the extraction tower with the aid of the circulating flushing and the forward backwashing, wherein the time is shown in Table 2. In the step, high-pressure water is used for impacting softened scales inside the extraction tower, all hardened material scales on the periphery of a tower plate of the extraction tower and on a support column are loosened and fall off, the falling scales are cleaned to the bottom of the extraction tower from top to bottom by the impact force of the high-pressure water, meanwhile, after the high-pressure water physical cleaning is completed, products obtained after the high-pressure water physical cleaning are discharged from the bottom of the extraction tower, solid-liquid separation is carried out, water is recycled, and the obtained recycled water is pressurized and then is continuously used for cleaning and impacting the scales inside the extraction tower.
Table 2 cleaning effect of different alkaline cleaning solutions on extraction column in example 2
Example 3
A cleaning method of a wet-process phosphoric acid extraction tower comprises the following steps:
s1, respectively introducing hot water with the temperature of 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃ and 100 ℃ into the evacuated C200 extraction tower for water transportation cleaning for 1 day. In the step, the pressure of the hot water is controlled to be 0.05MPa to 0.08MPa, and the flow is more than or equal to 50m3And h, introducing the water into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, washing the interior of the extraction tower with circulation washing and forward backwashing as assistance, effectively diluting the residual acid in the whole tower body by utilizing hot water in the washing process so as to reduce the consumption of a subsequent alkali washing agent, discharging a product obtained after water transportation washing from the bottom of the extraction tower after water transportation washing is finished, performing solid-liquid separation, recovering methyl isobutyl ketone (MIBK) and water, and heating the obtained recovered water and then continuously washing the extraction tower, thereby saving the cost.
S2, after the water transportation cleaning in the step S1 is finished, the interior of the extraction tower is subjected to high-pressure water physical cleaning, and an inner channel for scale opening is opened, specifically: and (3) circularly introducing high-pressure water with the pressure of 90MPa into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, and physically cleaning the interior of the extraction tower with the high-pressure water for 1 day by taking circular washing and forward backwashing as assistance. In the step, high-pressure water is utilized to impact the scale in the extraction tower in a circulating manner, a chemical cleaning channel is opened, the whole tower section fluid channel is smooth, and a larger contact surface with alkaline cleaning liquid is created for subsequent alkaline cleaning, so that an alkaline cleaning agent can be fully contacted with the scale, and the alkaline cleaning efficiency and the alkaline cleaning effect are ensured; and simultaneously, after the high-pressure water physical cleaning is finished, discharging a product obtained after the high-pressure water physical cleaning from the bottom of the extraction tower, carrying out solid-liquid separation, recovering water, and pressurizing the obtained recovered water for continuously cleaning and impacting scale in the extraction tower.
S3, after the high-pressure water physical cleaning in the step S2 is finished, alkali cleaning is carried out on the interior of the extraction tower, so that hard scales are converted into soft scales, and the method specifically comprises the following steps: dissolving sodium carbonate into water, adding sodium hydroxide to prepare a mixed solution of the sodium hydroxide and the sodium carbonate, namely an alkaline cleaning solution; respectively adjusting the temperature of the alkaline cleaning solution to 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃ and 100 ℃, starting a circulating pump, controlling the pressure of the alkaline cleaning solution to be 0.05-0.08 MPa, introducing the alkaline cleaning solution into the extraction tower from the top and the side of the extraction tower, mainly washing from top to bottom, and carrying out alkaline washing on the inside of the extraction tower with the assistance of circulating washing and forward backwashing, wherein the alkaline washing time is 2 days. In the step, the alkaline cleaning agent can be fully contacted with the scale and react in the alkaline cleaning process, so that the hard scale is changed into soft scale, a prerequisite condition is provided for subsequent high-pressure water cleaning, meanwhile, methyl isobutyl ketone (MIBK) remained in the scale in the alkaline cleaning process is released and dissolved into the alkaline cleaning solution, and then the alkaline cleaning solution is discharged from the bottom of the extraction tower and taken out of the tower, and the residual MIBK in the tower is effectively removed, so that the safety risk and the injury of occupational diseases to personnel are reduced, and the efficiency of operators is improved. In the step, the inside of the extraction tower is subjected to alkaline washing mainly by top-down washing and assisted by circulating washing and forward backwashing, so that scale blocks with softened surfaces can flow to the bottom of the tower along with alkaline washing liquid, the pressure of subsequent high-pressure water washing operation and the fatigue strength of operators are greatly reduced, and the safety risk and the safety cost are also reduced.
In step S3, a mixed solution of sodium hydroxide and sodium carbonate is used as the alkaline cleaning solution, wherein the mixed solution of sodium hydroxide and sodium carbonate contains 10% by mass of sodium hydroxide and 5% by mass of sodium carbonate.
Step S3, in the process of alkaline cleaning the inside of the extraction tower by using alkaline cleaning liquid, adding an auxiliary agent and a corrosion inhibitor into the extraction tower, wherein the auxiliary agent is a penetrating agent, a surfactant and a defoaming agent, the penetrating agent is fatty alcohol-polyoxyethylene ether, and the adding amount of the penetrating agent is 0.1-0.3% of the total volume of the alkaline cleaning liquid; the surfactant is sodium dodecyl benzene sulfonate, and the addition amount of the surfactant is 0.1-0.3 percent of the total volume of the alkaline cleaning solution; the defoaming agent is OP-10, and the addition amount is 0.1-0.3 percent of the total volume of the alkaline cleaning solution; the corrosion inhibitor is LAN-826, and the addition amount is 0.1-0.3% of the total volume of the alkaline cleaning solution. According to the invention, the penetrant and the surfactant are added, so that the cleaning liquid can be promoted to enter the scale, the effective reaction between the cleaning liquid and the scale can be promoted, the scale in the extraction tower can be softened, and more hard scales can be converted into soft scales; meanwhile, the added defoaming agent can effectively remove a large amount of foams generated in the cleaning process, and the addition of the corrosion inhibitor is favorable for reducing the corrosion of the cleaning solution to the extraction tower, so that the extraction tower can be effectively protected, and the adverse effect of the cleaning solution on the extraction tower is reduced.
S4, after the alkaline cleaning in the step S3 is finished, the interior of the extraction tower is subjected to high-pressure water physical cleaning, so that soft scales fall off and are discharged outwards, and the cleaning of the extraction tower is finished, specifically: high-pressure water with the pressure of 60MPa is introduced into the extraction tower from the top and the side of the extraction tower, the top-down flushing is mainly used, and the high-pressure water physical cleaning is carried out on the interior of the extraction tower with the assistance of the circulating flushing and the forward backwashing, and the time is shown in Table 3. In the step, high-pressure water is used for impacting softened scales inside the extraction tower, all hardened material scales on the periphery of a tower plate of the extraction tower and on a support column are loosened and fall off, the falling scales are cleaned to the bottom of the extraction tower from top to bottom by the impact force of the high-pressure water, meanwhile, after the high-pressure water physical cleaning is completed, products obtained after the high-pressure water physical cleaning are discharged from the bottom of the extraction tower, solid-liquid separation is carried out, water is recycled, and the obtained recycled water is pressurized and then is continuously used for cleaning and impacting the scales inside the extraction tower.
TABLE 3 cleaning effect of alkaline cleaning solution at different temperatures on extraction column in example 3
As can be seen from the results in tables 1 to 3, the cleaning technique of the present invention, which combines chemistry and high-pressure water jet, can further shorten the cleaning period, reduce the cleaning cost and safety risk, and simultaneously, does not pollute the surrounding environment and does not have the risk of secondary pollution on the premise of effectively removing the scale in the extraction tower. Compared with the conventional cleaning method, the cleaning method adopted by the invention has the following advantages: (1) the cleaning period is short, the cleaning period of the method is 5-7 days, and the conventional cleaning method is as long as 30 days; (2) the cleaning cost is low, the total cleaning cost of the method is 55 ten thousand per time, the total chemical cleaning cost is 70 ten thousand per time, and the total physical cleaning cost is 75 ten thousand per time; (3) the safety risk is low, the pressure grade in the method is 30MPa-60MPa, and the equipment operation pressure grade in the conventional method is 90MPa-130 MPa; (4) the method has the advantages of short cleaning period, low cleaning cost, high cleaning efficiency, good cleaning effect, safety, environmental protection and the like, can realize efficient and thorough cleaning of the wet-process phosphoric acid extraction tower, and has high use value and good application prospect. In addition, compared with an acid cleaning solution, when the alkaline cleaning solution is used for cleaning, the cleaning solution does not corrode the extraction tower, and is more suitable for cleaning a main stream extraction tower (made of stainless steel).
The above examples are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.
Claims (10)
1. The method for cleaning the wet-process phosphoric acid extraction tower is characterized by comprising the following steps of:
s1, performing high-pressure water physical cleaning on the interior of the extraction tower, and opening a scale inner channel;
s2, chemically cleaning the interior of the extraction tower by adopting a cleaning solution with the temperature of more than 70 ℃, and controlling the pressure of the cleaning solution to be more than 0.05MPa in the chemical cleaning process to convert hard scales into soft scales;
and S3, performing high-pressure water physical cleaning on the interior of the extraction tower to enable soft scales to fall off and be discharged outwards, and finishing cleaning the extraction tower.
2. The method for cleaning the wet phosphoric acid extraction tower according to claim 1, wherein in step S2, the chemical cleaning is performed by any one of the following methods:
the first method is as follows: alkaline cleaning is carried out on the interior of the extraction tower by adopting alkaline cleaning liquid;
the second method comprises the following steps: acid cleaning is carried out on the interior of the extraction tower by adopting an acid cleaning solution;
the third method comprises the following steps: and (3) alternately performing alkali washing and acid washing on the interior of the extraction tower by adopting alkali washing cleaning liquid and acid cleaning liquid.
3. The method for cleaning the wet-process phosphoric acid extraction tower according to claim 2, wherein the alkaline cleaning solution is a sodium hydroxide solution or a mixed solution of sodium hydroxide and sodium carbonate; the mass percentage of the sodium hydroxide in the sodium hydroxide solution is 5-20%; the mixed solution of sodium hydroxide and sodium carbonate contains 8-15% of sodium hydroxide and 5-8% of sodium carbonate by mass.
4. The cleaning method of the wet-process phosphoric acid extraction tower according to claim 2, characterized in that the acidic cleaning solution is a hydrochloric acid solution and/or a nitric acid solution; the mass concentration of the acidic cleaning solution is 5-20%.
5. The method for cleaning the wet phosphoric acid extraction tower according to any one of claims 1 to 4, wherein in the step S2, the chemical cleaning process further comprises adding an auxiliary agent and/or a corrosion inhibitor into the extraction tower; the auxiliary agent is a penetrating agent, a surfactant and a defoaming agent; the addition amount of the penetrating agent is 0.1-0.3% of the total volume of the cleaning solution; the addition amount of the surfactant is 0.1-0.3% of the total volume of the cleaning solution; the addition amount of the defoaming agent is 0.1-0.3% of the total volume of the cleaning solution; the addition amount of the corrosion inhibitor is 0.1-0.3% of the total volume of the cleaning solution.
6. The method for cleaning the wet-process phosphoric acid extraction tower according to claim 5, wherein the penetrating agent is fatty alcohol-polyoxyethylene ether; the surfactant is sodium dodecyl benzene sulfonate and/or dodecyl ethoxy sulfobetaine; the defoaming agent is OP-10 and/or emulsified silicone oil; the corrosion inhibitor is LAN-826.
7. The method for cleaning a wet phosphoric acid extraction tower according to any one of claims 1 to 4, wherein the step S1 further comprises the following steps before the step of physically cleaning the interior of the extraction tower with high pressure water: introducing hot water with the temperature of 70-95 ℃ into an extraction tower for water transportation and cleaning; the pressure of hot water is controlled to be 0.05MPa to 0.08MPa in the water transportation cleaning process, and the flow is more than or equal to 50m3H, introducing the mixture into the extraction tower from the top and/or the side part of the extraction tower; the cleaning mode adopted in the water transportation cleaning process is mainly that washing is carried out from top to bottom, and circulation washing and positive backwashing are used as assistance; the time for water transportation cleaning is 16-24 h; the water transportation cleaning method also comprises the following steps: discharging the product obtained after water transportation and cleaning from the bottom of the extraction tower, carrying out solid-liquid separation, and recovering the extraction agent and water.
8. The method for cleaning a wet phosphoric acid extraction tower according to any one of claims 1 to 4, wherein in step S1, the inside of the extraction tower is physically cleaned with high-pressure water; the pressure of the high-pressure water is 90MPa to 120 MPa; in the high-pressure water physical cleaning process, high-pressure water is introduced into the extraction tower from the top and/or the side part of the extraction tower; the cleaning mode adopted in the high-pressure water physical cleaning process is mainly that washing is carried out from top to bottom, and cyclic washing and forward backwashing are used as assistance; the time for physically cleaning the high-pressure water is 16-24 hours; the high-pressure water physical cleaning method also comprises the following steps of: discharging the product obtained after the high-pressure water is cleaned from the bottom of the extraction tower, performing solid-liquid separation, and recovering water.
9. The method for cleaning the wet phosphoric acid extraction tower according to any one of claims 1 to 4, wherein in the step S2, the pressure of the cleaning liquid is controlled to be 0.05MPa to 0.08MPa, and the temperature is controlled to be 70 ℃ to 95 ℃ in the chemical cleaning process; in the chemical cleaning process, cleaning liquid is introduced into the extraction tower from the top and/or the side of the extraction tower; the cleaning mode adopted in the chemical cleaning process is mainly that washing is carried out from top to bottom, and is assisted by circular washing and positive backwashing; the chemical cleaning time is 40-60 h; the chemical cleaning process also comprises the following steps: discharging the product obtained after chemical cleaning from the bottom of the extraction tower, performing solid-liquid separation, and recovering the cleaning solution.
10. The method for cleaning a wet phosphoric acid extraction tower according to any one of claims 1 to 4, wherein in step S3, the inside of the extraction tower is physically cleaned with high-pressure water; the pressure intensity of the high-pressure water is 30MPa-60 MPa; in the high-pressure water physical cleaning process, high-pressure water is introduced into the extraction tower from the top and/or the side part of the extraction tower; the cleaning mode adopted in the high-pressure water physical cleaning process is mainly that washing is carried out from top to bottom, and cyclic washing and forward backwashing are used as assistance; the time for physically cleaning the high-pressure water is 3 to 4 days; the high-pressure water physical cleaning method also comprises the following steps of: discharging the product obtained after the high-pressure water is cleaned from the bottom of the extraction tower, performing solid-liquid separation, and recovering water.
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