A method for breaking the limit neutralization of mother liquor water equilibrium

Abstract

The invention discloses a neutralization method for breaking the mother liquor water equilibrium limit. The method comprises the following steps: adding concentrated mother liquor into a neutralization kettle in a potassium dihydrogen phosphate production system; adding a phosphoric acid solution to carry out a first neutralization reaction to obtain a first neutralized liquid; heating the first neutralized liquid; adding a phosphoric acid solution to carry out a second neutralization reaction; measuring a pH value; naturally stirring, cooling and crystallizing; solid-liquid separation; feeding the sieved potassium dihydrogen phosphate crystals into a fluidized bed for drying, and recovering the neutralized mother liquor; feeding the potassium dihydrogen phosphate crystals dried in the fluidized bed to a double-layer vibrating screen for screening, and feeding the potassium dihydrogen phosphate crystals with a crystal particle size of less than φ0.2 mm to a baling machine through an elevator, thereby completing the neutralization method. The method solves the problem that, when producing potassium dihydrogen phosphate by the current neutralization method, the mother liquor water equilibrium space limit bottleneck hovers around 8 meters and cannot be lifted.

Description

Technical Field

[0001] The invention relates to the technical field of producing potassium dihydrogen phosphate by neutralization method, in particular to a neutralization method for breaking the mother liquor water equilibrium limit. Background Art

[0002] Potassium dihydrogen phosphate (KH2PO4) has the chemical formula KH2PO4 and appears as colorless tetragonal crystals or white crystalline powder. It deliquesces easily when exposed to air. There are many methods for producing potassium dihydrogen phosphate, including neutralization, extraction, ion exchange, double decomposition, direct production, crystallization, and electrolysis. Currently, the most widely used method is neutralization, with over 80% of companies using this method to produce potassium dihydrogen phosphate.

[0003] At present, the main raw materials used in the production of potassium dihydrogen phosphate by the neutralization method are KOH or K2CO3. Taking KOH as an example, when producing potassium dihydrogen phosphate by the neutralization method, KOH needs to be dissolved in water to generate a KOH solution. Then, by evaporating the water in the KOH solution, its specific gravity is controlled to 1.6~1.7 to obtain a concentrated mother liquor. The concentrated mother liquor is then reacted with a phosphoric acid solution to obtain KH2PO4, water, and the remaining KOH. The reaction formula is:

[0004] H3PO4+KOH=KH2PO4+H2O

[0005] Since the solution after the generation of KH2PO4 also contains KOH and P2O5, they need to be recovered. The traditional neutralization method involves heating the concentrated mother liquor to 100°C-110°C, then cutting off the heat source and starting acid neutralization. This results in a short neutralization reaction time and a small amount of water generated after the neutralization reaction and the evaporation of the original water. As a result, the solution after the neutralization reaction can only be concentrated using a multi-effect concentration method before being added to the neutralization kettle to maintain the mother liquor water balance in the neutralization kettle, that is, to maintain the specific gravity between KOH and water.

[0006] The invention patent with patent application number 201711139606.3 and publication number CN107804832B mentioned a method of obtaining potassium dihydrogen phosphate by heating and neutralizing concentrated mother liquor. In actual use of this invention, when producing potassium dihydrogen phosphate, there is a problem that the mother liquor water balance space limit bottleneck hovers around 8 meters and cannot be improved. Summary of the Invention

[0007] Based on this, in order to solve the above problems, the present invention proposes a neutralization method to break the mother liquor water balance limit, which solves the problem that when the current neutralization method is used to produce potassium dihydrogen phosphate, the mother liquor water balance space limit bottleneck hovers around 8 meters and cannot be improved.

[0008] The technical solution of the present invention is:

[0009] A method for breaking the mother liquor water equilibrium limit neutralization method comprises the following steps:

[0010] S1: adding the concentrated mother liquor to the neutralization kettle in the potassium dihydrogen phosphate production system;

[0011] S2: adding phosphoric acid solution to carry out a first neutralization reaction to obtain a first neutralized solution;

[0012] S3: heating the first neutralization solution;

[0013] S4: adding phosphoric acid solution to carry out a second neutralization reaction;

[0014] Turning on the stirring device in the neutralization kettle and starting stirring at a stirring frequency of 40 Hz, after the temperature of the first neutralized liquid rises to between 100 and 110° C., adding the phosphoric acid solution to the heated first neutralized liquid through the phosphoric acid pipe on the neutralization kettle, and then continuously heating the mixture of the first neutralized liquid and the phosphoric acid solution to a temperature greater than 115° C. by the heating device in the neutralization kettle, and then increasing the stirring frequency of the stirring device in the neutralization kettle to 50 Hz for stirring, while maintaining the mixture of the first neutralized liquid and the phosphoric acid solution in a high boiling state with a temperature greater than 115° C.;

[0015] S5: Measure pH value;

[0016] The pH value of the solution in the neutralization kettle is measured by the pH meter on the neutralization kettle. When the pH value reaches between 4.3 and 4.4, the second neutralization reaction is complete and the second neutralized solution is obtained;

[0017] S6: natural stirring, cooling and crystallization;

[0018] The stirring frequency of the stirring device in the neutralization kettle is reduced to 40 Hz and stirring is started. At the same time, the second neutralized liquid is cooled by the cooling device in the neutralization kettle. When the temperature drops to 95° C., potassium dihydrogen phosphate crystals and a neutralization mother liquor are obtained;

[0019] S7: solid-liquid separation;

[0020] The discharge temperature of the neutralization kettle is controlled at 90°C to 95°C, and the obtained potassium dihydrogen phosphate crystals and neutralization mother liquor are transported to a centrifuge for screening;

[0021] S8: The sieved potassium dihydrogen phosphate crystals are sent to a fluidized bed for drying and neutralization and mother liquor recovery;

[0022] S9: The potassium dihydrogen phosphate crystals after fluidized bed drying are transported to a double-layer vibrating screen for screening. The potassium dihydrogen phosphate crystals with a particle size of less than φ0.2mm are transported to a baler through an elevator, and the neutralization process is completed.

[0023] Preferably, in step S1, the concentrated mother liquor is a mixture of KOH and water, with a specific gravity of 1.65-1.68.

[0024] Preferably, in steps S2 and S4, the phosphoric acid solution is a mixed solution with a P2O5 content of 85% and a water content of 15%.

[0025] Preferably, step S2 is specifically:

[0026] The neutralization kettle is equipped with an acid regulating device and a stirring device. The phosphoric acid solution is added dropwise to the concentrated mother liquor in the neutralization kettle through the acid regulating device in the neutralization kettle. The stirring frequency of the stirring device in the neutralization kettle is set to 40 Hz and stirring is started to carry out the first neutralization reaction to obtain a neutral first neutralized liquid with a pH value of 7.

[0027] Preferably, step S3 is specifically:

[0028] A heating device is provided in the neutralization kettle, which continuously heats the first neutralization liquid. When the temperature of the first neutralization liquid rises to 100-110°C, the phosphoric acid solution is prepared for the second addition.

[0029] Preferably, in step S4, the flow rate of the phosphoric acid solution is controlled to be 2000-2500 kg / h, and the time for adding the phosphoric acid solution is controlled to be 105-110 minutes.

[0030] Preferably, in step S4, the phosphoric acid pipe is connected to a phosphoric acid solution storage tank.

[0031] Preferably, in step S8, the recovered neutralization mother liquor is a mixture of KOH and water, the specific gravity of which is between 1.64 and 1.67, and can be directly added to the neutralization kettle together with the concentrated mother liquor in step S1, and the ratio of the concentrated mother liquor to the neutralization mother liquor added in step S1 is controlled to be 2:1.

[0032] Preferably, in step S9, potassium dihydrogen phosphate crystals with a crystal particle size greater than φ0.2 mm are conveyed to a crusher by a screw conveyor, crushed, and then conveyed to a fluidized bed, and steps S8 and S9 are performed again.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] After adopting the method of the present invention, the mother liquor water balance limit bottleneck was gradually broken. Through 10 months of production operation from January to November 2023, the original system's mother liquor water balance limit bottleneck space increased from about 8 meters to 17.5 meters, an increase of 118%; the proportion of fine powder of the product under the 60-mesh sieve decreased from about 16.1% to below 9%, a year-on-year decrease of 43%; the single-shift single-kettle output increased from the original 13 tons per kettle to 15 tons per kettle, a year-on-year increase of 26%, which solved the problem that the mother liquor water balance space limit bottleneck hovered around 8 meters and could not be improved when producing potassium dihydrogen phosphate by the current neutralization method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the structure of the potassium dihydrogen phosphate production system described in an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the structure of the neutralization kettle described in an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the internal structure of the neutralization kettle described in an embodiment of the present invention;

[0038] Description of reference numerals:

[0039] 10-neutralization kettle, 100-acid adjustment device, 101-heating device, 102-stirring device, 103-cooling device, 104-liquid storage pipe, 105-dropper, 106-first solenoid valve, 107-motor, 108-rotating shaft, 109-stirring blade, 110-heating tube, 111-second solenoid valve, 112-steam generator, 113-condensing coil, 114-third solenoid valve, 115-condenser, 1 16- Reflux port, 117- First metering pump, 118- Phosphoric acid pipe, 119- Second metering pump, 120- Flue gas outlet, 121- pH value detection port, 122- Discharge port, 123- Solenoid valve, 124- Temperature detection port, 20- Centrifuge, 30- Fluidized bed, 40- Double-layer vibrating screen, 50- Elevator, 60- Screw conveyor, 70- Crusher, 80- Baler, 90- Phosphoric acid solution storage tank. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0041] Example 1:

[0042] like Figure 1 As shown, this embodiment discloses a method for breaking the mother liquor water equilibrium limit neutralization method, comprising the following steps:

[0043] S1: adding the concentrated mother liquor into the neutralization kettle 10 in the potassium dihydrogen phosphate production system;

[0044] S2: adding phosphoric acid solution to carry out a first neutralization reaction to obtain a first neutralized solution;

[0045] S3: heating the first neutralization solution;

[0046] S4: adding phosphoric acid solution to carry out a second neutralization reaction;

[0047] The stirring device 102 in the neutralization kettle 10 is turned on and stirring is started at a stirring frequency of 40 Hz. After the temperature of the first neutralized liquid rises to between 100 and 110° C., the phosphoric acid solution is added to the heated first neutralized liquid through the phosphoric acid pipe 118 on the neutralization kettle 10. Then, the mixture of the first neutralized liquid and the phosphoric acid solution is continuously heated to a temperature greater than 115° C. by the heating device 101 in the neutralization kettle 10. Then, the stirring frequency of the stirring device 102 in the neutralization kettle 10 is increased to 50 Hz, while the mixture of the first neutralized liquid and the phosphoric acid solution is kept in a high boiling state with a temperature greater than 115° C.

[0048] S5: Measure pH value;

[0049] Measure the pH value of the solution in the neutralization kettle 10. When the pH value reaches between 4.3 and 4.4, the second neutralization reaction is complete, and a second neutralized solution is obtained.

[0050] S6: natural stirring, cooling and crystallization;

[0051] The stirring frequency of the stirring device 102 in the neutralization kettle 10 is reduced to 40 Hz and stirring is started. At the same time, the second neutralized liquid is cooled by the cooling device 103 in the neutralization kettle 10. When the temperature drops to 95° C., potassium dihydrogen phosphate crystals and a neutralization mother liquor are obtained;

[0052] S7: solid-liquid separation;

[0053] The discharge temperature of the neutralization kettle 10 is controlled to be 90° C. to 95° C., and the obtained potassium dihydrogen phosphate crystals and the neutralization mother liquor are transported to the centrifuge 20 for screening;

[0054] S8: The sieved potassium dihydrogen phosphate crystals are sent to the fluidized bed 30 for drying and neutralization mother liquor recovery;

[0055] S9: The potassium dihydrogen phosphate crystals dried in the fluidized bed 30 are transported to the double-layer vibrating screen 40 for screening. The potassium dihydrogen phosphate crystals with a crystal particle size φ less than 0.2 mm are transported to the packing machine 80 through the elevator 50, and the neutralization process is completed.

[0056] In the present invention, the mixture of the first neutralization liquid and the phosphoric acid solution is continuously heated to a temperature greater than 115° C. by the heating device 101 in the neutralization kettle 10, and then the stirring frequency of the stirring device 102 in the neutralization kettle 10 is increased to 50 Hz for stirring to increase the crystallization burst rate. At the same time, the mixture of the first neutralization liquid and the phosphoric acid solution is kept in a high boiling state with a temperature greater than 115° C. to evaporate more water. Therefore, the water in the mixture of the first neutralization liquid and the phosphoric acid solution is continuously evaporated during the second neutralization reaction, thereby reducing the specific gravity of water in the second neutralization liquid after the second neutralization reaction, thereby increasing the specific gravity of KOH in the recovered neutralization mother liquor.

[0057] According to the online monitoring data of the flue gas discharged from the second neutralization reaction, the flue gas flow rate is about 30,000 m3 / h and the flue gas humidity is 11%. That is, while keeping the second neutralization liquid in a boiling state, one kettle of potassium dihydrogen phosphate product can evaporate more water in the second neutralization liquid by: 30,000*0.3h*11%=990 kg. This increases the proportion of KOH in the obtained neutralization mother liquor, breaking the bottleneck problem of the mother liquor water balance limit. After extending the neutralization time, the product appearance crystal quality is improved and the proportion of fine powder is reduced.

[0058] The invention solves the problem that when producing potassium dihydrogen phosphate by the current neutralization method, the mother liquor water balance space limit bottleneck is around 8 meters and cannot be improved.

[0059] In order to allow the concentrated mother liquor to fully react with the phosphoric acid solution, based on the above embodiment, this embodiment is further preferred in that, in step S1, the concentrated mother liquor is a mixture of KOH and water with a specific gravity of 1.65-1.68.

[0060] In order to produce less potassium dihydrogen phosphate crystal powder, based on the above embodiment, this embodiment is further preferred. Preferably, in steps S2 and S4, the phosphoric acid solution is a mixed solution with a P2O5 content of 85% and a water content of 15%.

[0061] In order to accelerate the first neutralization reaction, based on the above embodiment, this embodiment is further preferred, preferably, step S2 is specifically as follows:

[0062] The neutralization kettle 10 is provided with an acid adjustment device 100 and a stirring device 102. Phosphoric acid solution is added dropwise to the concentrated mother liquor in the neutralization kettle 10 through the acid adjustment device 100 in the neutralization kettle 10. The stirring frequency of the stirring device 102 in the neutralization kettle 10 is set to 40 Hz and stirring is started to carry out the first neutralization reaction, thereby obtaining a neutral first neutralized solution with a pH value of 7.

[0063] In order to improve the crystallization burst rate of the second neutralization reaction, this embodiment is further preferred on the basis of the above embodiment. Preferably, step S3 is specifically as follows:

[0064] A heating device 101 is provided in the neutralization kettle 10 , and the first neutralization solution is continuously heated by the heating device 101 in the neutralization kettle 10 . When the temperature of the first neutralization solution rises to 100-110° C., the phosphoric acid solution is prepared to be added for the second time.

[0065] Preferably, in step S4, the flow rate of the phosphoric acid solution is controlled to be 2000-2500 kg / h, and the time for adding the phosphoric acid solution is controlled to be 105-110 minutes.

[0066] In order to facilitate storage of the phosphoric acid solution, it is further preferred in this embodiment that, in step S4 , the phosphoric acid pipe 118 is connected to a phosphoric acid solution storage tank 90 .

[0067] Preferably, in step S8, the recovered neutralization mother liquor is a mixture of KOH and water, the specific gravity of which is between 1.64 and 1.67, and can be directly added to the neutralization kettle 10 together with the concentrated mother liquor in step S1, and the ratio of the concentrated mother liquor to the neutralization mother liquor added in step S1 is controlled to be 2:1.

[0068] In order to reduce the number of semi-finished product crystal heads in the finished product, this embodiment is further preferred on the basis of the above embodiment. In step S9, potassium dihydrogen phosphate crystals with a crystal particle size greater than φ0.2 mm are conveyed to the crusher 70 by the screw conveyor 60 for crushing and then conveyed to the fluidized bed 30, and steps S8 and S9 are performed again.

[0069] After adopting the method of the present invention, the mother liquor water balance limit bottleneck was gradually broken. Through 10 months of production operation from January to November 2023, the mother liquor water balance limit bottleneck space of the original system increased from about 8 meters to 17.5 meters, an increase of 118%; the proportion of fine powder of the product under the 60-mesh sieve decreased from about 16.1% to below 9%, a year-on-year decrease of 43%; the output of a single kettle in a single shift increased from the original 13 tons per kettle to 15 tons per kettle, a year-on-year increase in production capacity of 26%.

[0070] Example 2:

[0071] like Figures 1 to 3As shown, this embodiment discloses a potassium dihydrogen phosphate production system used in the above-mentioned neutralization method for breaking the mother liquor water equilibrium limit, including a neutralization kettle 10 for performing a neutralization reaction, a centrifuge 20 for separating the solid-liquid mixture from the reactor, a fluidized bed 30 for drying potassium dihydrogen phosphate, a double-layer vibrating screen 40 for screening potassium dihydrogen phosphate crystals that meet the crystal size requirements, an elevator 50 for conveying potassium dihydrogen phosphate crystals that meet the requirements to a baler 80, a screw conveyor 60 for returning potassium dihydrogen phosphate crystals that do not meet the requirements, a crusher 70 for crushing potassium dihydrogen phosphate crystals that do not meet the requirements to meet the requirements, a baler 80 for baling potassium dihydrogen phosphate crystals that meet the requirements, and a phosphoric acid solution storage tank 90 for storing phosphoric acid solution.

[0072] The fluidized bed 30, double-layer vibrating screen 40, elevator 50, screw conveyor 60, crusher 70 and baler 80 all adopt the fluidized bed 30, double-layer vibrating screen 40, elevator 50, screw conveyor 60, crusher 70 and baler 80 in the prior art that can realize the functions of the present invention.

[0073] Preferably, the neutralization kettle 10 is provided with an acid adjustment device 100 , a heating device 101 , a stirring device 102 and a cooling device 103 .

[0074] Preferably, the acid adjustment device 100 is arranged at the top of the neutralization kettle 10, and the acid adjustment device 100 includes a liquid storage pipe 104 and a dropper 105 arranged on the liquid storage pipe 104. The liquid storage pipe 104 is connected to the phosphoric acid solution storage tank 90 through a pipeline, and a first solenoid valve 106 is provided on the pipeline.

[0075] The dropper 105 is disposed on one side of the liquid storage tube 104 . When the phosphoric acid solution level in the liquid storage tube 104 is not full, the phosphoric acid solution cannot drip from the dropper 105 . When the phosphoric acid solution level in the liquid storage tube 104 is full, the phosphoric acid solution can drip from the dropper 105 by continuously injecting the phosphoric acid solution into the liquid storage tube 104 .

[0076] Preferably, the stirring device 102 includes a motor 107, a rotating shaft 108 and a stirring blade 109. The motor 107 is arranged at the top of the neutralization kettle 10, one end of the rotating shaft 108 is located in the neutralization kettle 10, and the other end is connected to the output shaft of the motor 107. The stirring blade 109 is arranged on the end of the rotating shaft 108 located in the neutralization kettle 10. The stirring frequency of the motor 107 can be controlled between 30Hz and 60Hz, and the motor 107 is used to drive the rotating shaft 108.

[0077] Preferably, the heating device 101 includes a plurality of heating tubes 110, which are arranged in the neutralization kettle 10. The heating tubes 110 surround the stirring blade 109 and are arranged in conjunction with the stirring blade 109. The ends of two heating tubes 110 can be respectively connected to the steam generator 112 through a pipeline with a second solenoid valve 111 to form a circulation.

[0078] The steam generator 112 adopts a steam generator 112 in the prior art that can realize the functions of the present invention. When in use, the steam generator 112 cooperates with the heating pipe 110 to realize steam circulation.

[0079] Preferably, the cooling device 103 is a condensing coil 113, which is arranged in the neutralization kettle 10 and is arranged in conjunction with the heating device 101 and the stirring device 102. The two ends of the condensing coil 113 can be connected to an external condenser 115 through a pipe with a third solenoid valve 114.

[0080] The condenser 115 adopts the condenser 115 in the prior art that can realize the function of the present invention. When in use, the condensation coil 113 and the condenser 115 cooperate to realize the circulation of condensed water.

[0081] Preferably, the neutralization kettle 10 is provided with a reflux port 116 , and the reflux port 116 is connected to the centrifuge 20 via a pipeline with a first metering pump 117 .

[0082] The centrifuge 20 is a centrifuge 20 in the prior art that can realize the functions of the present invention. When in use, the neutralization mother liquor separated by the centrifuge 20 enters the neutralization kettle 10 through the reflux port 116 .

[0083] Preferably, a phosphoric acid pipe 118 is provided on the neutralization kettle 10 , and the phosphoric acid pipe 118 is connected to the phosphoric acid solution storage tank 90 via a pipeline with a second metering pump 119 .

[0084] Preferably, the diameter of the phosphoric acid pipe 118 is set to 2.5 meters.

[0085] The phosphoric acid solution in the phosphoric acid solution storage tank 90 is injected into the neutralization kettle 10 through the phosphoric acid pipe 118 .

[0086] Preferably, the neutralization kettle 10 is provided with a flue gas outlet 120 , and the flue gas outlet 120 is connected to a flue gas online monitoring system.

[0087] The flue gas online monitoring system adopts the existing flue gas online monitoring system that can realize the function of the present invention. When in use, it can monitor the component content in the flue gas generated by the neutralization reaction online, mainly monitoring the water content in the flue gas.

[0088] According to the online monitoring data of the flue gas discharged from the second neutralization reaction, the flue gas flow rate is about 30,000 m3 / h, and the flue gas humidity is 11%. That is, while keeping the second neutralization liquid in a boiling state, the amount of water that can be evaporated from the second neutralization liquid by one kettle of potassium dihydrogen phosphate product is: 30,000*0.3h*11%=990KG.

[0089] Preferably, the neutralization kettle 10 is provided with a pH value detection port 121 , and the pH value detection port 121 is connected to a pH detector.

[0090] The pH value detector adopts a pH value detector in the prior art that can realize the function of the present invention. When in use, it can detect the pH value of the solution in the neutralization kettle 10, which is convenient for detecting the status of the neutralization reaction.

[0091] Preferably, a discharge port 122 is provided at the bottom of the neutralization kettle 10 , and the discharge port 122 is connected to the centrifuge 20 through a pipeline with an electromagnetic valve 123 .

[0092] The electromagnetic valve 123 adopts an electromagnetic valve in the prior art that can realize the function of the present invention, and when in use, it can control the discharge port 122 to discharge the material.

[0093] Preferably, the neutralization kettle 10 is provided with a temperature detection port 124 , and the temperature detection port 124 is connected to a temperature measuring instrument.

[0094] The temperature measuring instrument is a temperature measuring instrument in the prior art that can realize the function of the present invention, and when in use, it can detect the temperature of the solution in the neutralization kettle 10.

[0095] Preferably, the mesh size of the double-layer vibrating screen 40 is set to 0.2 mm.

[0096] The potassium dihydrogen phosphate below the screen is the finished product, which is transported by the elevator 50 to the baler 80 for packaging and storage; the potassium dihydrogen phosphate above the screen is the semi-finished product, which is transported by the screw conveyor 60 to the crusher 70 for crushing, and then re-enters the fluidized bed 30 for drying, and then is screened again by the double-layer vibrating screen 40.

[0097] During use, the neutralization kettle 10 discharges the material and conveys it to the centrifuge 20. The centrifuge 20 separates the potassium dihydrogen phosphate crystals discharged from the neutralization kettle 10 from the neutralization mother liquor, and the screened potassium dihydrogen phosphate crystals are sent to the fluidized bed 30 for drying. The neutralization mother liquor is recovered and conveyed to the neutralization kettle 10. The potassium dihydrogen phosphate crystals dried in the fluidized bed 30 are conveyed to the double-layer vibrating screen 40 for screening. The potassium dihydrogen phosphate crystals with a crystal particle size of less than φ0.2 mm are conveyed to the baler 80 via the elevator 50. The potassium dihydrogen phosphate crystals with a crystal particle size greater than φ0.2 mm are conveyed to the crusher 70 via the screw conveyor 60 for crushing, and then conveyed to the fluidized bed 30 for drying again, and then conveyed to the double-layer vibrating screen 40 for screening.

[0098] The present invention discloses a neutralization method for breaking the mother liquor water balance limit and a potassium dihydrogen phosphate production system. The present invention can effectively break the mother liquor water balance limit bottleneck generated when producing potassium dihydrogen phosphate by the current neutralization method, and the mother liquor water balance limit bottleneck is increased from about 8 meters to 17.5 meters, an increase of 118%; the proportion of fine powder in the product under the 60-mesh sieve is reduced from about 16.1% to below 9%, a year-on-year decrease of 43%; and the single-shift single-reactor output is increased from the original 13 tons per reactor to 15 tons per reactor, a year-on-year increase in production capacity of 26%.

[0099] The mixture of the first neutralization solution and the phosphoric acid solution is continuously heated to a temperature greater than 115° C. by the heating device 101 in the neutralization kettle 10, and then the stirring frequency of the stirring device 102 in the neutralization kettle 10 is increased to 50 Hz to increase the crystallization burst rate. At the same time, the mixture of the first neutralization solution and the phosphoric acid solution is kept in a high boiling state with a temperature greater than 115° C. to evaporate more water. Therefore, the water in the mixture of the first neutralization solution and the phosphoric acid solution is continuously evaporated during the second neutralization reaction, thereby reducing the specific gravity of water in the second neutralization solution after the second neutralization reaction, thereby increasing the specific gravity of KOH in the recovered neutralization mother liquor.

[0100] Principle of the invention:

[0101] In the present invention, the mixture of the first neutralization liquid and the phosphoric acid solution is continuously heated to a temperature greater than 115° C. by the heating device 101 in the neutralization kettle 10, and then the stirring frequency of the stirring device 102 in the neutralization kettle 10 is increased to 50 Hz to start stirring, so as to increase the crystallization burst rate. At the same time, the mixture of the first neutralization liquid and the phosphoric acid solution is kept in a high boiling state with a temperature greater than 115° C. to evaporate more water, so that the water in the mixture of the first neutralization liquid and the phosphoric acid solution is continuously evaporated during the second neutralization reaction, thereby reducing the specific gravity of water in the second neutralization liquid after the second neutralization reaction, thereby increasing the specific gravity of KOH in the recovered neutralization mother liquor, thereby breaking the bottleneck of the mother liquor water balance limit.

[0102] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for breaking the mother liquor water equilibrium limit neutralization method, characterized in that: The following steps are involved: S1: adding the concentrated mother liquor to the neutralization kettle (10) in the potassium dihydrogen phosphate production system; Among them, the concentrated mother liquor is a mixture of KOH and water with a specific gravity of 1.65-1.68; S2: adding phosphoric acid solution to carry out a first neutralization reaction to obtain a first neutralized solution; S3: heating the first neutralization solution; S4: adding phosphoric acid solution to carry out a second neutralization reaction; The stirring device (102) in the neutralization kettle (10) is turned on and stirring is started at a stirring frequency of 40 Hz. After the temperature of the first neutralization liquid rises to between 100 and 110° C., the phosphoric acid solution is added to the heated first neutralization liquid through the phosphoric acid tube (118) on the neutralization kettle (10). Then, the mixture of the first neutralization liquid and the phosphoric acid solution is continuously heated to a temperature greater than 115° C. through the heating device (101) in the neutralization kettle (10). Then, the stirring frequency of the stirring device (102) in the neutralization kettle (10) is increased to 50 Hz for stirring, while the mixture of the first neutralization liquid and the phosphoric acid solution is kept in a high boiling state with a temperature greater than 115° C.; S5: Measure pH value; The pH value of the solution in the neutralization kettle (10) is measured by a pH value measuring instrument on the neutralization kettle (10). When the pH value reaches between 4.3 and 4.4, the second neutralization reaction is complete, and a second neutralized solution is obtained; S6: natural stirring, cooling and crystallization; The stirring frequency of the stirring device (102) in the neutralization kettle (10) is reduced to 40 Hz and stirring is started. At the same time, the second neutralization liquid is cooled by the cooling device (103) in the neutralization kettle (10). When the temperature drops to 95° C., potassium dihydrogen phosphate crystals and a neutralization mother liquor are obtained; S7: solid-liquid separation; The discharge temperature of the neutralization kettle (10) is controlled to be 90°C to 95°C, and the obtained potassium dihydrogen phosphate crystals and the neutralization mother liquor are transported to a centrifuge (20) for screening; S8: The potassium dihydrogen phosphate crystals screened out are sent to a fluidized bed (30) for drying and neutralization, and the mother liquor is recovered; S9: The potassium dihydrogen phosphate crystals dried in the fluidized bed (30) are transported to a double-layer vibrating screen (40) for screening. The potassium dihydrogen phosphate crystals with a crystal size of less than φ0.2 mm are transported to a packing machine (80) via an elevator (50), and the neutralization process is completed.

2. A method for breaking the mother liquor water equilibrium limit neutralization according to claim 1, characterized in that: In steps S2 and S4, the phosphoric acid solution is a mixed solution with a P2O5 content of 85% and a water content of 15%.

3. The method for breaking the mother liquor water equilibrium limit neutralization according to claim 1, characterized in that: Step S2 is specifically as follows: An acid adjustment device (100) and a stirring device (102) are provided in the neutralization kettle (10). A phosphoric acid solution is added dropwise to the concentrated mother liquor in the neutralization kettle (10) through the acid adjustment device (100) in the neutralization kettle (10). The stirring frequency of the stirring device (102) in the neutralization kettle (10) is set to 40 Hz and stirring is started to carry out a first neutralization reaction, thereby obtaining a neutral first neutralized liquid with a pH value of 7.

4. The method for breaking the mother liquor water equilibrium limit neutralization according to claim 1, characterized in that: Step S3 is specifically as follows: A heating device (101) is provided in the neutralization kettle (10), and the first neutralization solution is continuously heated by the heating device (101) in the neutralization kettle (10). When the temperature of the first neutralization solution rises to 100-110° C., the phosphoric acid solution is prepared for the second addition.

5. The method for breaking the mother liquor water equilibrium limit neutralization according to claim 1, characterized in that: In step S4, the flow rate of the phosphoric acid solution is controlled to be 2000-2500 kg / h, and the time for adding the phosphoric acid solution is controlled to be 105-110 minutes.

6. The method for breaking the mother liquor water equilibrium limit neutralization according to claim 1, characterized in that: In step S4, the phosphoric acid pipe (118) is connected to the phosphoric acid solution storage tank (90).

7. The method for breaking the mother liquor water equilibrium limit neutralization according to claim 1, characterized in that: In step S8, the recovered neutralization mother liquor is a mixture of KOH and water, and its specific gravity is between 1.64 and 1.

67. It can be directly added to the neutralization kettle (10) together with the concentrated mother liquor in step S1, and the ratio of the concentrated mother liquor to the neutralization mother liquor added in step S1 is controlled to be 2:

1.

8. The method for breaking the mother liquor water equilibrium limit neutralization according to claim 1, characterized in that: In step S9, potassium dihydrogen phosphate crystals with a crystal particle size greater than φ0.2 mm are conveyed to a crusher (70) by a screw conveyor (60), crushed, and then conveyed to a fluidized bed (30), and steps S8 and S9 are performed again.

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