1. A recycling treatment device for aging mother liquor in the production of iron phosphate by a sodium method is characterized by comprising a pretreatment system and a phosphoric acid concentration system; the aging mother liquor produced in the sodium-method iron phosphate production is connected to a liquid inlet of a pretreatment system, a mud outlet of the pretreatment system sends out mud cakes, a liquid outlet of the pretreatment system sends out the effluent of the pretreatment system to a liquid inlet of a phosphoric acid concentration system, a No. 1 water outlet of the phosphoric acid concentration system sends out produced water, a liquid outlet of the phosphoric acid concentration system sends out concentrated phosphoric acid, and a No. 2 water outlet of the phosphoric acid concentration system sends out four-section reflux produced water to a water inlet of the pretreatment system; the sodium-method iron phosphate production aging mother liquor recycling device firstly utilizes a pretreatment system to filter aging mother liquor produced in sodium-method iron phosphate production, removes suspended matters and iron phosphate small crystals, and controls SS (suspended solid) of a pretreated effluent to be less than or equal to 0.1 mg/L; and concentrating by using a phosphoric acid concentration system, concentrating the concentration of phosphate radicals from 1-2% to 8-15% for recycling in the production process of the sodium-method iron phosphate, and recycling the produced water, thereby achieving the purpose of recycling the aging mother liquor in the production of the sodium-method iron phosphate.

2. The recycling device for aged mother liquor produced by sodium-method iron phosphate according to claim 1, which is characterized in that the structure of the pretreatment system comprises an aged mother liquor tank, an ultrafiltration device, an intermediate liquor tank, a backwash liquor collection tank, a filter press, a filtrate tank, a filter pump, a booster pump, a backwash pump, a sludge pump and a filtrate reflux pump; the system comprises an aging mother liquor tank, an intermediate liquor tank, a pretreatment system, a backwashing pump, a pressure filter, a pressure filtrate tank, a pressure filtrate return pump, a pressure filter, a pressure filtrate return pump, a pressure filter, a pressure filtrate return pump, a pressure filter and a pressure filter, wherein the aging mother liquor is connected to a liquid inlet of the aging mother liquor tank, a liquid outlet of the aging mother liquor tank is connected with a liquid inlet of the ultrafiltration device through the pressure filter, a liquid outlet of the ultrafiltration device is connected with a liquid inlet of the intermediate liquor tank through the pressure filter, a liquid outlet of the intermediate liquor tank is connected with a liquid inlet of the ultrafiltration device through the pressure filter, a liquid outlet of the intermediate liquor tank is connected with a pressure filtrate return pump, a liquid outlet of the pressure filter is connected with a liquid inlet of the pressure filter; through the pretreatment system, specifically, an acid-alkali-resistant PTFE ultrafiltration membrane is adopted to effectively filter SS and fine iron phosphate crystals in the aging mother liquor, suspended matters of pretreated effluent are controlled to be less than or equal to 0.1mg/L, the ultrafiltration device carries out backwashing once every 30-90 minutes to maintain the long-term stable operation of ultrafiltration, and backwashing discharge hydraulic pressure is used for filtering out mud cakes and transporting the mud cakes.

3. The recycling device for aged mother liquor in sodium ferric phosphate production according to claim 1, wherein the phosphoric acid concentration system structurally comprises a cartridge filter, a first-stage acid-resistant reverse osmosis system, a second-stage acid-resistant reverse osmosis system, a third-stage acid-resistant reverse osmosis system, a fourth-stage acid-resistant reverse osmosis system, a concentrated phosphoric acid tank, a water production tank, a high-pressure pump, a 1# interstage pump, a 2# interstage pump, a concentrated phosphoric acid delivery pump and a water production delivery pump; wherein the liquid outlet of the pretreatment system is connected to the liquid inlet of a cartridge filter, the liquid outlet of the cartridge filter is connected with a section of acid-resistant reverse osmosis liquid inlet through a high-pressure pump, the concentrated liquid outlet of a section of acid-resistant reverse osmosis is connected with a section of acid-resistant reverse osmosis liquid inlet through a No. 1 intersegmental pump, the concentrated liquid outlet of a section of acid-resistant reverse osmosis is connected with a section of acid-resistant reverse osmosis liquid inlet through a No. 2 intersegmental pump, the produced water outlet of a section of acid-resistant reverse osmosis and the produced water outlet of a section of acid-resistant reverse osmosis are connected to the water inlet of a produced water tank, the water outlet of the produced water tank sends produced water through a produced water delivery pump, the concentrated liquid outlet of the section of acid-resistant reverse osmosis is connected to a section of acid-resistant reverse osmosis liquid inlet of four sections of acid-resistant reverse osmosis, the four sections of acid-resistant reverse osmosis concentrated liquid outlet are connected to the liquid inlet of a concentrated phosphoric acid tank, a liquid outlet of the concentrated phosphoric acid box sends out concentrated phosphoric acid through a concentrated phosphoric acid conveying pump; through a phosphoric acid concentration system, specifically an acid-resistant reverse osmosis composite membrane formed by polyamide, polysulfone and a polyester supporting layer, the concentration of dilute phosphoric acid in the pretreated effluent is concentrated from 1-2% to 8-15%, and then the dilute phosphoric acid is reused in the production process of sodium-method ferric phosphate, the concentration of phosphoric acid in the acid-resistant reverse osmosis produced water is less than or equal to 0.02%, the phosphoric acid can be recycled, and the purpose of recycling the aging mother liquor in the sodium-method ferric phosphate production is achieved.

4. The resource treatment method for the aging mother liquor in the production of sodium-method iron phosphate according to claim 1, which is characterized by comprising the following steps:

1) filtering an aged mother solution generated in the production of the sodium-method iron phosphate by a pretreatment system to remove suspended matters and iron phosphate small crystals in the aged mother solution;

2) and (3) further concentrating the concentration of the dilute phosphoric acid in the pretreated effluent from 1-2% to 8-15% by a phosphoric acid concentration system.

5. The resource treatment method for the aged mother liquor in the production of iron phosphate by sodium method according to claim 4, characterized in that the SS and fine iron phosphate crystals in the aged mother liquor are effectively filtered by a pretreatment system in the step 1), specifically, an acid and alkali resistant PTFE ultrafiltration membrane is adopted to effectively filter the aged mother liquor, the suspended matters in the pretreated outlet liquor are controlled to be less than or equal to 0.1mg/L, a backwashing is performed by an ultrafiltration device every 30-90 minutes to maintain the long-term stable operation of ultrafiltration, and the backwashing is discharged to carry out the hydraulic filtration mud cake.

6. The recycling method of the aged mother liquor in the production of sodium ferric phosphate according to claim 4, characterized in that in the step 2), the concentration of dilute phosphoric acid in the pretreated effluent is concentrated from 1-2% to 8-15% by a phosphoric acid concentration system, specifically, an acid-resistant reverse osmosis composite membrane formed by polyamide, polysulfone and a polyester support layer, and then the dilute phosphoric acid is reused in the production process of sodium ferric phosphate, and the concentration of phosphoric acid in the acid-resistant reverse osmosis produced water is less than or equal to 0.02%, so that the recycling method can be used, and the purpose of recycling the aged mother liquor in the production of sodium ferric phosphate is achieved.

Background

The ferric phosphate is an ideal precursor of lithium iron phosphate which is a positive electrode material of the lithium ion battery. At present, two main production process paths of the iron phosphate exist. One is the ammonium method iron phosphate production technology, utilize ferrous sulfate to add hydrogen peroxide solution earlier and turn the ferrous iron into ferric iron, react with phosphoric acid again, control the pH value of reaction through throwing diammonium hydrogen phosphate or aqueous ammonia simultaneously, synthesize the iron phosphate, except a small amount of heavy metal in the production waste water that produces, mainly be ammonium ion, phosphate radical ion, sulfate radical ion. The other is a sodium method iron phosphate production process, namely ferrous sulfate and hydrogen peroxide are firstly utilized to oxidize ferrous iron into ferric iron, and then the ferric iron is reacted with phosphoric acid, except that sodium hydroxide is added to control the pH value of the reaction, the iron phosphate is synthesized, and the produced production wastewater mainly contains sodium ions, phosphate ions and sulfate ions except a small amount of heavy metals.

The wastewater produced by the sodium-method ferric phosphate can be divided into three types according to the production process and the wastewater quality. The first is oxidation mother liquor which mainly contains high-concentration sodium sulfate, a small amount of heavy metal ions and sodium phosphate, is phosphorus-containing high-salt wastewater and is seriously polluted. The second is aging mother liquor which mainly contains dilute phosphoric acid, a small amount of heavy metal ions and sodium sulfate and is a precious phosphoric acid resource. The third is washing water which mainly contains a small amount of heavy metal ions, sodium phosphate and sodium sulfate and is the salt-containing wastewater containing phosphorus and heavy metals. The patent mainly aims at the aging mother liquor generated in the production of sodium-method iron phosphate and provides a recycling treatment device and method for the aging mother liquor generated in the production of sodium-method iron phosphate.

Disclosure of Invention

The invention provides a resourceful treatment device and a resourceful treatment method for aging mother liquor in sodium-method iron phosphate production, aiming at the characteristic that the aging mother liquor in sodium-method iron phosphate production contains a large amount of dilute phosphoric acid, a small amount of heavy metal and sodium sulfate, and the typical aging mother liquor comprises the following components: PO (PO)₄ ^3-1-2% of (phosphate radical) and Na⁺160-490 mg/L, SO (sodium ion)₄ ^2-(sulfate radical) 340-1010 mg/L, Fe³⁺(iron ion) 10-30 mg/L, Mg²⁺(magnesium ion) 80-220 mg/L, Mn²⁺(manganese ion) 10-30 mg/L, Ca²⁺30-70 mg/L, Si (silicon) 5-15 mg/L, SS (suspended matter) 5-15 mg/L, pH 1.1.1-1.4 (calcium ion). Firstly, a pretreatment system is utilized for filtration, SS and fine iron phosphate crystals in aging mother liquor are effectively filtered by an ultrafiltration membrane, and SS of pretreated effluent is controlled to be less than or equal to 0.1 mg/L; then using acid-resistant reverse osmosis to make PO in the aged mother liquor₄ ^3-The concentration of the sodium iron phosphate is concentrated from 1-2% to 8-15%, and the sodium iron phosphate is recycled in the production process of sodium iron phosphate; acid-resistant reverse osmosis PO in produced water₄ ^3-The concentration of the catalyst is less than or equal to 0.02 percent, and the catalyst is recycled.

The ultrafiltration membrane is made of PTFE (polytetrafluoroethylene) and is a high polymer with a net structure formed by polymerizing tetrafluoroethylene, and the PTFE ultrafiltration membrane has the characteristics of high stability, acid and alkali resistance, corrosion resistance, long service life, high aperture ratio, large water flux, thorough flux recovery and the like, can resist 5% of sodium hydroxide and 30% of phosphoric acid, and has excellent filtration treatment effect for dilute phosphoric acid.

The acid-resistant reverse osmosis membrane is a composite membrane formed by polyamide, polysulfone and a polyester supporting layer, can maintain high flux in a strong acid environment and stably operate for more than 12 months; the pH range of the continuous work of the acid-resistant reverse osmosis is 0-12.0, the pH range of the chemical cleaning is 0-13.0, and when the acid-resistant reverse osmosis is used for purifying and concentrating dilute phosphoric acid, the concentration of phosphoric acid in a concentrated solution is less than or equal to 20%.

The technical solution of the invention is as follows: the sodium-method iron phosphate production aging mother liquor recycling treatment device structurally comprises a pretreatment system and a phosphoric acid concentration system; the aging mother liquor produced in the sodium-method iron phosphate production is connected to a liquid inlet of a pretreatment system, a mud outlet of the pretreatment system sends out mud cakes, a liquid outlet of the pretreatment system sends out the effluent of the pretreatment system to a liquid inlet of a phosphoric acid concentration system, a No. 1 water outlet of the phosphoric acid concentration system sends out produced water, a liquid outlet of the phosphoric acid concentration system sends out concentrated phosphoric acid, and a No. 2 water outlet of the phosphoric acid concentration system sends out four-section reflux produced water to a water inlet of the pretreatment system; the sodium-method iron phosphate production aging mother liquor recycling device firstly utilizes a pretreatment system to filter aging mother liquor produced in sodium-method iron phosphate production, removes suspended matters and iron phosphate small crystals, and controls SS (suspended solid) of a pretreated effluent to be less than or equal to 0.1 mg/L; and concentrating by using a phosphoric acid concentration system, concentrating the concentration of phosphate radicals from 1-2% to 8-15% for recycling in the production process of the sodium-method iron phosphate, and recycling the produced water, thereby achieving the purpose of recycling the aging mother liquor in the production of the sodium-method iron phosphate.

The device and the method for recycling the aging mother liquor in the production of the sodium-method iron phosphate aim at the characteristic that the aging mother liquor in the production of the sodium-method iron phosphate contains a large amount of dilute phosphoric acid, a small amount of heavy metals and sodium sulfate, firstly, a pretreatment system is utilized for filtration, suspended matters and fine iron phosphate crystals in the aging mother liquor are effectively filtered through an ultrafiltration membrane, and the concentration of the suspended matters in a pretreated effluent is controlled to be less than or equal to 0.1 mg/L; then, concentrating the phosphoric acid concentration in the aging mother liquor from 1-2% to 8-15% by utilizing acid-resistant reverse osmosis, and further reusing the phosphoric acid concentration in the sodium-method iron phosphate production process; the concentration of phosphoric acid in the acid-resistant reverse osmosis produced water is less than or equal to 0.02 percent and can be recycled; the purpose of recycling the aging mother liquor in the sodium-method ferric phosphate production is achieved.

Drawings

FIG. 1 is a schematic overall structure diagram of a resource treatment device for aging mother liquor in sodium-method iron phosphate production.

In the figure, AML represents aged mother liquor, SC represents mud cake, PW represents produced water, CPA represents concentrated phosphoric acid, BPW represents backflow four-stage produced water, PTO represents effluent of a pretreatment system, PTS represents a pretreatment system, and ACS phosphoric acid concentration system.

FIG. 2 is a schematic structural diagram of a pretreatment system of a recycling treatment device for aging mother liquor in the production of iron phosphate by a sodium method.

In the drawing, PTS represents a pretreatment system, AML represents aged mother liquor, SC represents mud cake, BPW represents return four-stage produced water, PTO represents effluent of the pretreatment system, MLT represents an aged mother liquor tank, UF represents an ultrafiltration device, MT represents an intermediate liquor tank, BWT represents a backwash liquor collection tank, PF represents a filter press, FLT represents a filtrate tank, P represents a filter press₁₁Denotes a filtration pump, P₁₂Showing a booster pump, P₁₃Indicating backwash pump, P₁₄Indicating a sludge pump, P₁₅The filtrate return pump is shown.

FIG. 3 is a schematic structural diagram of a phosphoric acid concentration system of a recycling treatment device for aging mother liquor in the production of iron phosphate by a sodium method.

In the figure, ACS represents phosphoric acid concentration system, PTO represents effluent of pretreatment system, PW represents produced water, BPW represents return four-stage produced water, CPA represents concentrated phosphoric acid, SAF represents cartridge filter, ARO₁Denotes a section of acid-resistant reverse osmosis, ARO₂To representTwo-stage acid-resistant reverse osmosis, ARO₃Denotes three-stage acid-resistant reverse osmosis, ARO₄Four stages of acid-resistant reverse osmosis, CPAT concentrated phosphoric acid tank, PWT produced water tank, P₂₁Indicating a high-pressure pump, P₂₂Denotes a 1# interstage Pump, P₂₃Denotes a 2# interstage Pump, P₂₄Denotes a concentrated phosphoric acid delivery pump, P₂₅Representing a water production delivery pump.

FIG. 4 is a process flow chart of an embodiment of recycling treatment of aged mother liquor in the production of iron phosphate by a sodium method.

FIG. 5 is a water quality and water quantity balance diagram of an embodiment of resource treatment of aged mother liquor in the production of iron phosphate by a sodium method.

Detailed Description

Referring to the attached figure 1, the sodium-method iron phosphate production aging mother liquor recycling device structurally comprises a pretreatment system PTS and a phosphoric acid concentration system ACS; wherein, an aging mother liquor AML generated in the production of the sodium-method ferric phosphate is connected to a liquid inlet of a pretreatment system PTS, a mud outlet of the pretreatment system PTS sends out a mud cake SC, a liquid outlet of the pretreatment system PTS sends out a pretreatment system liquid outlet PTO to a liquid inlet of a phosphoric acid concentration system ACS, a 1# water outlet of the phosphoric acid concentration system ACS sends out produced water PW, a liquid outlet of the phosphoric acid concentration system ACS sends out concentrated phosphoric acid CPA, and a 2# water outlet of the phosphoric acid concentration system ACS sends out four-section reflux produced water BPW to a water inlet of the pretreatment system PTS; the sodium-method iron phosphate production aging mother liquor recycling device firstly utilizes a pretreatment system to filter aging mother liquor produced in sodium-method iron phosphate production, removes suspended matters and iron phosphate small crystals, and controls SS (suspended solid) of a pretreated effluent to be less than or equal to 0.1 mg/L; and concentrating by using a phosphoric acid concentration system, concentrating the concentration of phosphate radicals from 1-2% to 8-15% for recycling in the production process of the sodium-method iron phosphate, and recycling the produced water, thereby achieving the purpose of recycling the aging mother liquor in the production of the sodium-method iron phosphate.

Referring to FIG. 2, the pretreatment system PTS comprises an aging mother liquor tank MLT, an ultrafiltration unit UF, an intermediate liquor tank MT, a backwash liquid collection tank BWT, a filter press PF, a filtrate tank FLT, and a filtration pump P₁₁And a booster pump P₁₂And a backwash pump P₁₃And a sludge pump P₁₄Filtrate return pump P₁₅(ii) a Wherein it is oldThe chemical mother liquor AML is connected to the liquid inlet of the aging mother liquor box MLT, and the liquid outlet of the aging mother liquor box MLT passes through a filter pump P₁₁Connected with the liquid inlet of the ultrafiltration device UF, the liquid outlet of the ultrafiltration device UF is connected with the liquid inlet of the intermediate liquid tank MT, and the No. 1 liquid outlet of the intermediate liquid tank MT passes through the booster pump P₁₂The liquid outlet PTO of the pre-treatment system is sent out, and the No. 2 liquid outlet of the intermediate liquid tank MT passes through a backwashing pump P₁₃Connected with a backwash liquid inlet of the ultrafiltration device UF, the backwash liquid outlet of the ultrafiltration device UF is connected with a liquid inlet of a backwash liquid collecting box BWT, and a liquid outlet of the backwash liquid collecting box BWT passes through a sludge pump P₁₄Connected with the liquid inlet of the filter press PF, the mud cake SC is sent out from the mud outlet of the filter press PF, the liquid outlet of the filter press PF is connected to the liquid inlet of the filtrate tank FLT, and the liquid outlet of the filtrate tank FLT passes through the filtrate reflux pump P₁₅The four-section backflow water production BPW is connected to a water inlet of the middle liquid tank MT; through the pretreatment system, specifically, an acid-alkali-resistant PTFE ultrafiltration membrane is adopted to effectively filter SS and fine iron phosphate crystals in the aging mother liquor, suspended matters of pretreated effluent are controlled to be less than or equal to 0.1mg/L, the ultrafiltration device carries out backwashing once every 30-90 minutes to maintain the long-term stable operation of ultrafiltration, and backwashing discharge hydraulic pressure is used for filtering out mud cakes and transporting the mud cakes.

Referring to FIG. 3, the phosphoric acid concentration system ACS comprises a cartridge filter SAF, a first stage acid-resistant reverse osmosis ARO₁Two-stage acid-resistant reverse osmosis ARO₂Three-stage acid-resistant reverse osmosis ARO₃Four-section acid-resistant reverse osmosis ARO₄CPAT, PWT and P₂₁1# intersegment Pump P₂₂2# intersegment Pump P₂₃Concentrated phosphoric acid delivery pump P₂₄Water producing delivery pump P₂₅(ii) a Wherein the liquid outlet PTO of the pretreatment system is connected to the liquid inlet of a security filter SAF, and the liquid outlet of the security filter SAF passes through a high-pressure pump P₂₁With a first stage acid-resistant reverse osmosis ARO₁Connected with the liquid inlet of the water purifier, and a section of acid-resistant reverse osmosis ARO₁The concentrated solution outlet of the pump passes through a No. 1 intersegmental pump P₂₂With two-stage acid-resistant reverse osmosis ARO₂The liquid inlet is connected with a two-section acid-resistant reverse osmosis ARO₂The concentrated solution outlet of the pump passes through a No. 2 intersegmental pump P₂₃And three-stage acid-resistant reverse osmosis ARO₃Connected with the liquid inlet of the water purifier, and a section of acid-resistant reverse osmosis ARO₁The produced water outlet and the two-stage acid-resistant reverse osmosis ARO₂Water outlet and three-section acid-resistant reverse osmosis ARO₃The water outlet of the produced water is connected to the water inlet of the produced water tank PWT, and the water outlet of the produced water tank PWT passes through the produced water delivery pump P₂₅Sending out produced water PW and three-stage acid-resistant reverse osmosis ARO₃The concentrated solution outlet is connected to four-section acid-resistant reverse osmosis ARO₄The four sections of the liquid inlet are acid-resistant reverse osmosis ARO₄The water-producing outlet sends back four-stage produced water BPW and four-stage acid-resistant reverse osmosis ARO₄The concentrated solution outlet of the concentrated phosphoric acid tank is connected to the liquid inlet of a CPAT of the concentrated phosphoric acid tank, and the liquid outlet of the CPAT of the concentrated phosphoric acid tank passes through a concentrated phosphoric acid delivery pump P₂₄Sending out concentrated phosphoric acid CPA; through a phosphoric acid concentration system, specifically an acid-resistant reverse osmosis composite membrane formed by polyamide, polysulfone and a polyester supporting layer, the concentration of dilute phosphoric acid in the pretreated effluent is concentrated from 1-2% to 8-15%, and then the dilute phosphoric acid is reused in the production process of sodium-method ferric phosphate, the concentration of phosphoric acid in the acid-resistant reverse osmosis produced water is less than or equal to 0.02%, the phosphoric acid can be recycled, and the purpose of recycling the aging mother liquor in the sodium-method ferric phosphate production is achieved.

The resource treatment method of the aging mother liquor in the production of iron phosphate by a sodium method comprises the following steps:

1) filtering an aged mother solution generated in the production of the sodium-method iron phosphate by a pretreatment system to remove suspended matters and iron phosphate small crystals in the aged mother solution;

2) and (3) further concentrating the concentration of the dilute phosphoric acid in the pretreated effluent from 1-2% to 8-15% by a phosphoric acid concentration system.

The method comprises the following steps that 1) through a pretreatment system, specifically, an acid-alkali-resistant PTFE ultrafiltration membrane is adopted to effectively filter SS and fine iron phosphate crystals in an aged mother liquor, suspended matters of pretreated effluent are controlled to be less than or equal to 0.1mg/L, backwashing is carried out on an ultrafiltration device every 30-90 minutes to maintain long-term stable operation of ultrafiltration, and backwashing discharge hydraulic pressure is carried out to filter out mud cakes to be transported.

And 2) concentrating the concentration of dilute phosphoric acid in the pretreated effluent from 1-2% to 8-15% by using a phosphoric acid concentration system, specifically adopting an acid-resistant reverse osmosis composite membrane consisting of polyamide, polysulfone and a polyester support layer, and further recycling the phosphoric acid in the acid-resistant reverse osmosis production water in the production process of sodium-method iron phosphate, wherein the concentration of the phosphoric acid in the acid-resistant reverse osmosis production water is less than or equal to 0.02%, and the phosphoric acid can be recycled, so that the purpose of recycling the aging mother liquor in the sodium-method iron phosphate production is achieved.

Examples

The iron phosphate is produced by 5 ten thousand tons in a certain group company annually, a sodium method process is adopted for producing the iron phosphate, ferrous sulfate and hydrogen peroxide are firstly utilized to oxidize ferrous iron into ferric iron, then the ferric iron is reacted with phosphoric acid, the pH value of the reaction is controlled by adding sodium hydroxide to synthesize the iron phosphate, and the iron phosphate is aged by the phosphoric acid. Three types of wastewater are generated in the production process of the iron phosphate, wherein one type of wastewater is an oxidation mother liquor containing a large amount of sodium sulfate, a small amount of heavy metal ions and phosphate radical ions, the other type of wastewater is an aging mother liquor containing a large amount of dilute phosphoric acid, a small amount of heavy metal ions, suspended matters and sodium sulfate, and the third type of wastewater is low-concentration washing water containing a large amount of heavy metal ions, phosphate radical ions and sodium sulfate. The embodiment designs a set of recycling treatment system for the aged mother liquor in the production of the sodium-method iron phosphate aiming at the characteristic that the aged mother liquor contains a large amount of diluted phosphoric acid, so that phosphoric acid and water in the aged mother liquor are effectively recycled, the pollution load is reduced, and the phosphoric acid is saved.

1. Design of aging mother liquor composition and waste liquor amount

The aging mother liquor for producing the ferric phosphate by the sodium method comprises the following components (wherein the pH value is not a unit):

components	pH	Na+	SO4 2-	PO4 3-	Fe3+
						Concentration (mg/L)	1.27	324	676	15000	20
Components	Mg2+	Mn2+	Ca2+	Si	SS
						Concentration (mg/L)	150	20	50	10	10

The waste liquid volume of the aging mother liquor in the sodium-method ferric phosphate production is 55T/H.

2. Process flow

2.1 Process flow

The process flow is shown in the attached figure 4, and the process flow chart of the recycling treatment embodiment of the aging mother liquor in the sodium method ferric phosphate production is shown.

2.2 flow sheet description

Aiming at the recycling requirement of the aging mother liquor in the production of sodium ferric phosphate, only phosphoric acid is concentrated and recycled, a small amount of heavy metal ions are not removed, in order to protect the normal operation of the acid-resistant reverse osmosis membrane device, the aging mother liquor is effectively filtered by an acid-and-alkali-resistant PTFE (polytetrafluoroethylene) ultrafiltration membrane, and then the phosphoric acid is concentrated by the acid-resistant reverse osmosis. The main process comprises the following steps: the method comprises the following steps that aged mother liquor generated in the production of sodium-method iron phosphate enters a mother liquor tank, the aged mother liquor is pumped into a PTFE (polytetrafluoroethylene) ultrafiltration device through a filter pump to filter out suspended matters and small iron phosphate crystals, filtrate enters an intermediate liquor tank, the PTFE ultrafiltration device is subjected to regular backwashing through a backwashing pump every 30-60 minutes, backwashing liquor drainage enters a backwashing liquor collection tank, the filtrate is pressurized by a sludge pump to a filter press to filter out mud cakes and is transported outwards, filter press liquor enters a filter press liquor tank, and the filter press liquor is sent to the mother liquor tank through a filter press reflux pump to; pressurizing the pretreated effluent by a booster pump, pumping the pretreated effluent into an acid-resistant reverse osmosis device through a cartridge filter and a high-pressure pump, concentrating and separating dilute phosphoric acid, wherein the content of phosphoric acid in the acid-resistant reverse osmosis produced water is less than or equal to 0.02%, pumping the acid-resistant reverse osmosis produced water out of a produced water tank and the produced water for reuse, the acid-resistant reverse osmosis 4-stage produced water has high acid content, returning the acid-resistant reverse osmosis produced water to an intermediate liquid tank for retreatment (not marked in a flow chart), the content of phosphoric acid in the acid-resistant reverse osmosis concentrated solution is more than or equal to 10%, and pumping the concentrated phosphoric acid out of a concentrated phosphoric acid tank and a concentrated phosphoric acid delivery pump to a production process.

3. Water quality and quantity balance

The water quality and water quantity balance of the aging mother liquor treatment system for producing the sodium ferric phosphate is shown in the attached figure 5, and the water quality and water quantity balance diagram of the resource treatment embodiment of the aging mother liquor for producing the sodium ferric phosphate is shown in the figure.

4. System main equipment