CN110272144B - Treatment method of iron phosphate production wastewater - Google Patents
Treatment method of iron phosphate production wastewater Download PDFInfo
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- C01C1/24—Sulfates of ammonium
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Abstract
The invention relates to the technical field of industrial production wastewater treatment, in particular to a treatment method of iron phosphate production wastewater, which comprises the following steps: a) Mixing iron phosphate production wastewater with calcium carbonate, carrying out precipitation reaction under the condition that the pH value is 2-4, and carrying out solid-liquid separation to obtain calcium sulfate and a first precipitation solution; b) Mixing the first precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 8-9.5, and carrying out solid-liquid separation to obtain calcium phosphate, calcium sulfate and a second precipitation solution; c) Mixing the second precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 10.5-11, and carrying out solid-liquid separation to obtain calcium sulfate and treated wastewater. The treatment method effectively removes sulfate radicals and phosphate radicals in the wastewater generated in the production of the iron phosphate. Meanwhile, the purity of the obtained calcium sulfate is high, and the precipitation slag obtained in the step B) can replace phosphorite and be recycled as a raw material for producing phosphoric acid.
Description
Technical Field
The invention relates to the technical field of industrial production wastewater treatment, in particular to a treatment method of iron phosphate production wastewater.
Background
The ferric phosphate is a positive electrode material of the lithium ion battery and is mainly prepared by a coprecipitation method. In the coprecipitation method, iron phosphate products are obtained by mixing and precipitating an iron source and a phosphorus source (such as monoammonium phosphate), but a large amount of Sulfate (SO) containing radicals with high concentration is generated 4 2- ) Phosphate radical (PO) 4 3- ) And ammonia Nitrogen (NH) 4 -N) acid waste water. At present, pollutants such as ammonia nitrogen, phosphate radical, sulfate radical, acid and the like in the iron phosphate wastewater are mainly removed by a chemical precipitation method, but residues generated by precipitation contain calcium phosphate and calcium sulfate, so that the recycling is difficult, and the problems of high operation cost, phosphorus and sulfur resource waste and the like are caused. From the viewpoint of environmental protection and resource recycling, it is necessary to develop a method which can recover phosphate and sulfate from wastewater from iron phosphate production and which is low in running cost.
The Chinese patent application CN108975469A proposes a method for removing phosphate radicals and sulfate radicals in iron phosphate wastewater step by step, but still has the problems of incomplete recovery of phosphate radicals and sulfate radicals, difficult iron phosphate precipitation recycling and the like.
Disclosure of Invention
In view of this, the technical problem to be solved by the present invention is to provide a method for treating wastewater from iron phosphate production, which can effectively recover sulfate and phosphate in wastewater from iron phosphate production.
The invention provides a method for treating wastewater from iron phosphate production, which comprises the following steps:
a) Mixing iron phosphate production wastewater with calcium carbonate, carrying out precipitation reaction under the condition that the pH value is 2-4, and carrying out solid-liquid separation to obtain calcium sulfate and a first precipitation solution;
b) Mixing the first precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 8-9.5, and carrying out solid-liquid separation to obtain calcium phosphate, calcium sulfate and a second precipitation solution;
c) Mixing the second precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 10.5-11, and carrying out solid-liquid separation to obtain calcium sulfate and treated wasteAnd (3) water.
Preferably, in the step A), in the wastewater from the production of iron phosphate, the concentration of phosphate radical is 1-10 g/L, the concentration of sulfate radical is 20-50 g/L, and the concentration of ammonia nitrogen is 4-8 g/L;
the pH value of the wastewater generated in the iron phosphate production is 0.8-1.2.
Preferably, in the step A), the precipitation reaction is carried out under the condition that the pH value is 2-3;
the time of the precipitation reaction is 0.5-1.5 h.
Preferably, in the step A), the dosage ratio of the calcium carbonate to the iron phosphate production wastewater is 18-48 g:1L of the total amount of the active ingredients.
Preferably, in step B), the precipitation reaction is carried out at a pH value of 8.8 to 9.2;
the time of the precipitation reaction is 0.5-1.5 h.
Preferably, ca (OH) in said step B) 2 The dosage ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 3-20 g:1L of the compound.
Preferably, in step C), the time of the precipitation reaction is 0.5-1.5 h.
Preferably, ca (OH) in said step C) 2 The dosage ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 5-10 g:1L of the compound.
Preferably, after the step C), the method further comprises the following steps:
d) Mixing the treated wastewater with a calcium remover, carrying out precipitation reaction under the condition that the pH value is 9.5-10.5, and carrying out solid-liquid separation to obtain calcium carbonate and a fourth precipitation solution;
e) Carrying out stripping absorption treatment on the fourth precipitation solution to obtain absorption mother liquor and stripping effluent; the absorbent adopted in the stripping absorption treatment is sulfuric acid solution;
f) And carrying out evaporation crystallization on the absorption mother liquor to obtain ammonium sulfate solid.
Preferably, the calcium remover is carbon dioxide and/or sodium carbonate solid;
the dosage ratio of the sodium carbonate solid to the iron phosphate production wastewater is 1-8 g:1L;
the volume ratio of the carbon dioxide gas to the iron phosphate production wastewater is (0.5-3): 1;
the mass concentration of the sulfuric acid solution is 25-35%.
The invention provides a method for treating wastewater from iron phosphate production, which comprises the following steps:
a) Mixing iron phosphate production wastewater with calcium carbonate, carrying out precipitation reaction under the condition that the pH value is 2-4, and carrying out solid-liquid separation to obtain calcium sulfate and a first precipitation solution;
b) Mixing the first precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 8-9.5, and carrying out solid-liquid separation to obtain calcium phosphate, calcium sulfate and a second precipitation solution;
c) Mixing the second precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 10.5-11, and carrying out solid-liquid separation to obtain calcium sulfate and treated wastewater.
The treatment method provided by the invention effectively removes sulfate radicals and phosphate radicals in the wastewater from the production of the iron phosphate. The purity of the calcium sulfate obtained in the step A) is high, the precipitation slag obtained in the step B) comprises calcium phosphate and calcium sulfate, the content of the calcium phosphate in the precipitation slag is higher than that of phosphorus in phosphorus ore, the requirement of the phosphorus ore grade in the chemical industry standard HG/T2673-95 of phosphate ore for acid method processing in the national chemical industry standard of the people's republic of China is met, and the calcium sulfate can replace the phosphorus ore and be recycled as a raw material for producing phosphoric acid. The purity of the calcium sulphate obtained in step C) is still high.
According to the invention, the treated wastewater is further subjected to precipitation treatment, stripping absorption and evaporative crystallization, so that ammonia nitrogen in the wastewater is effectively removed, ammonium sulfate solid is obtained, and the purity of the obtained ammonium sulfate solid is high. The ammonia nitrogen concentration, the sulfate radical concentration and the phosphate radical concentration in the blown-out water all meet the requirements in the national Integrated wastewater discharge Standard GB 8978-1996.
In addition, the treatment method provided by the invention has the advantages of simple overall process, low comprehensive operation cost, particularly low energy consumption of evaporation and crystallization, and effectively solves the problems of high cost, difficult recycling of sulfate radicals and sulfate radicals, difficult sales of recovered products and the like in the prior art.
The experimental result shows that the removal rate of sulfate radicals in the wastewater generated in the production of the iron phosphate is higher than 98.4%, and the removal rate of phosphate radicals is higher than 99.5%.
Drawings
FIG. 1 is a process flow diagram of the method for treating wastewater from iron phosphate production according to the present invention;
FIG. 2 is a process flow chart of a method for treating wastewater from iron phosphate production according to comparative example 5 of the present invention;
fig. 3 is a process flow chart of a method for treating iron phosphate production wastewater according to comparative example 6 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for treating wastewater from iron phosphate production, which comprises the following steps:
a) Mixing iron phosphate production wastewater with calcium carbonate, carrying out precipitation reaction under the condition that the pH value is 2-4, and carrying out solid-liquid separation to obtain calcium sulfate and a first precipitation solution;
b) Mixing the first precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 8-9.5, and carrying out solid-liquid separation to obtain calcium phosphate, calcium sulfate and a second precipitation solution;
c) Mixing the second precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 10.5-11, and carrying out solid-liquid separation to obtain calcium sulfate and treated wastewater.
In the invention, the iron phosphate production wastewater to be treated can be common iron phosphate production wastewater and mainly comprises sulfate radical (SO) 4 2- ) Phosphate radical (PO) 4 3- ) And ammonia Nitrogen (NH) 4 -N). In some embodiments of the invention, the iron phosphate production wastewaterThe concentration of sulfate radical is 20-50 g/L, the concentration of phosphate radical is 1-10 g/L, and the concentration of ammonia nitrogen is 4-8 g/L. In certain embodiments, the concentration of sulfate in the wastewater from the production of iron phosphate is 20g/L or 40g/L, the concentration of phosphate is 1g/L or 10g/L, and the concentration of ammonia nitrogen is 4g/L or 8g/L. In some embodiments of the present invention, the pH of the wastewater from iron phosphate production is 0.8 to 1.2. In certain embodiments, the pH of the wastewater from the iron phosphate production is 0.8 or 1.1.
In the step A), the iron phosphate production wastewater and calcium carbonate mainly react as shown in the formula (1):
CaCO 3 +SO 4 2- +2H + →CaSO 4 ↓+H 2 O+CO 2 × (1);
the main purpose of the step A) is to remove partial sulfate radicals in the wastewater generated in the production of the iron phosphate, and the obtained precipitation slag is mainly CaSO 4 The first precipitation solution mainly contains Ca 2+ 、PO 4 3- 、NH 4 + And SO 4 2- 。
In the step A), the pH value of the precipitation reaction is 2-4. In certain embodiments of the invention, the precipitation reaction has a pH of 2 to 3. In certain embodiments, the precipitation reaction has a pH of 3. If the pH of the precipitation reaction is higher than 4, caSO is caused 4 With Ca 3 (PO 4 ) 2 Simultaneously precipitating CaSO in the precipitation slag 4 The purity of (2) is reduced; if the pH value of the precipitation reaction is lower than 2, the recovery rate of sulfate radicals in the wastewater generated in the iron phosphate production is reduced.
In the step A), the precipitation reaction time is 0.5-1.5 h. In certain embodiments of the invention, the precipitation reaction time is 0.5h or 1.5h. The precipitation reaction is preferably a stirred reaction. The stirring method is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be used.
In the embodiment of the invention, the dosage ratio of the calcium carbonate to the iron phosphate production wastewater is 18-48 g:1L of the total amount of the active ingredients. In certain embodiments of the present invention, the ratio of the calcium carbonate to the iron phosphate production wastewater is 18g:1L of the compound.
In step a), in certain embodiments of the present invention, the method of solid-liquid separation is filtration. The method and parameters of the filtration are not particularly limited in the present invention, and those known to those skilled in the art can be used.
In the invention, the purity of the calcium sulfate obtained in the step A) is higher and is not lower than 99.9%.
In step B), the first precipitation solution is mixed with Ca (OH) 2 Reactions as shown in formula (2) and formula (3) mainly occur:
3Ca(OH) 2 +2PO 4 3- +3H + →Ca 3 (PO 4 ) 2 ↓+3H 2 o formula (2);
Ca(OH) 2 +SO 4 2- +2H + →CaSO 4 ↓+2H 2 o formula (3);
the main purpose of step B) is to fully recover phosphate ions in the first precipitation solution and to precipitate a part of the sulfate ions in the first precipitation solution. The obtained precipitation slag is Ca 3 (PO 4 ) 2 And CaSO 4 In which Ca is added 3 (PO 4 ) 2 Mainly comprises the following steps. The phosphorus content in the precipitation slag is higher than that of phosphate ore for phosphoric acid, and the precipitation slag can be used as a substitute of the phosphate ore for recycling. The second precipitation solution mainly contains Ca 2+ 、SO 4 2- And NH 4 + 。
In the step B), the pH value of the precipitation reaction is 8-9.5. In certain embodiments of the invention, the precipitation reaction has a pH of 8.8 to 9.2. In certain embodiments, the pH of the precipitation reaction is 9.2. If the pH value of the precipitation reaction is higher than 9.5, SO in the first precipitation solution 4 2- The removal efficiency is increased, which leads to CaSO in the precipitation slag 4 The mass percentage of the phosphorus is too large, and the phosphorus content is too low to be recycled; if the pH of the precipitation reaction is below 8, incomplete precipitation of phosphate will result and the phosphate will not be fully recovered.
In the step B), the precipitation reaction time is 0.5-1.5 h. In certain embodiments of the invention, the precipitation reaction time is 0.5h or 1.5h. The precipitation reaction is preferably a stirred reaction. The stirring method is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be used.
In an embodiment of the invention, ca (OH) in said step B) 2 The dosage ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 3-20 g:1L of the total amount of the active ingredients. In certain embodiments of the invention, ca (OH) in said step B) 2 The dosage ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 20g:1L of the compound.
In step B), in certain embodiments of the present invention, the method of solid-liquid separation is filtration. The method and parameters of the filtration are not particularly limited in the present invention, and those known to those skilled in the art can be used.
In the invention, the precipitation slag obtained in the step B) comprises calcium phosphate and calcium sulfate, the content of the calcium phosphate in the precipitation slag is higher than that of phosphorus in phosphate ore, the requirement of the first-class phosphorus ore in the chemical industry standard HG/T2673-95 of phosphate ore for acid method processing in the national chemical industry standard of people's republic of China is met, and the precipitation slag can replace the phosphate ore and be recycled as a raw material for producing phosphoric acid.
In step C), the second precipitate is mixed with Ca (OH) 2 The reaction shown in the formula (3) mainly occurs.
The main purpose of step C) is to remove the residual SO in the second precipitation solution 4 2- All are removed and treated with CaSO 4 Is recovered. The obtained precipitation slag is CaSO 4 The third precipitate (i.e., the treated wastewater) mainly contains Ca 2+ And NH 4 + 。
In the step C), the pH value of the precipitation reaction is 10.5-11. In certain embodiments, the precipitation reaction has a pH of 11. If the pH of the precipitation reaction is above 11, ca (OH) is caused 2 Excessive addition and waste; if the pH value of the precipitation reaction is lower than 10, the residual SO in the second precipitation solution 4 2- Can not be completely precipitated, and the sulfate radical can not be completely recovered.
In the step C), the precipitation reaction time is 0.5-1.5 h. In certain embodiments of the invention, the precipitation reaction time is 0.5h or 1.5h. The precipitation reaction is preferably a stirred reaction. The method of stirring is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be employed.
In an embodiment of the invention, ca (OH) in said step C) 2 The dosage ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 5-10 g:1L of the compound. In certain embodiments of the invention, ca (OH) in said step C) 2 The dosage ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 10g:1L of the total amount of the active ingredients.
In step C), in certain embodiments of the present invention, the method of solid-liquid separation is filtration. The method and parameters for the filtration are not particularly limited in the present invention, and the filtration method and parameters known to those skilled in the art can be used.
And C) after the precipitation reaction is finished, obtaining a third precipitation solution, namely the treated wastewater.
In the invention, the purity of the calcium sulfate obtained in the step C) is still higher and is not lower than 99.9%.
Through the treatment, sulfate radicals and phosphate radicals in the wastewater generated in the production of the iron phosphate are effectively removed. The experimental result shows that the removal rate of sulfate radicals in the wastewater generated in the production of the iron phosphate is higher than 98.4%, and the removal rate of phosphate radicals is higher than 99.5%.
In an embodiment of the present invention, after step C), the following steps are further included:
d) Mixing the treated wastewater with a calcium remover, carrying out precipitation reaction under the condition that the pH value is 9.5-10.5, and carrying out solid-liquid separation to obtain calcium carbonate and a fourth precipitation solution;
e) Carrying out stripping absorption treatment on the fourth precipitation solution to obtain absorption mother liquor and stripping effluent; the absorbent adopted in the stripping absorption treatment is sulfuric acid solution;
f) And carrying out evaporation crystallization on the absorption mother liquor to obtain ammonium sulfate solid.
In certain embodiments of the invention, the calcium removal agent is carbon dioxide and/or sodium carbonate solids.
In the step D), the treated wastewater and the calcium remover mainly react as shown in the formula (4):
Ca 2+ +CO 3 2- →CaCO 3 formula (4);
the main purpose of the step D) is to remove the residual Ca in the treated wastewater 2+ With CaCO 3 The scale in the tower in the subsequent stripping absorption process is avoided. The obtained precipitation slag is CaCO 3 And can therefore be recycled back for use in step a). The fourth precipitation solution mainly contains NH 4 + 。
In the step D), the pH value of the precipitation reaction is 9.5-10.5. In certain embodiments of the invention, the precipitation reaction has a pH of 9.5 to 10. In certain embodiments, the precipitation reaction has a pH of 10. CaCO if the pH of the precipitation reaction is below 9.5 3 Will be partially converted into Ca (HCO) 3 ) 2 Resulting in a decrease in the calcium removal efficiency.
In the step D), the time of the precipitation reaction is 0.5-1.5 h. In certain embodiments of the invention, the precipitation reaction time is 0.5h or 1.5h. The precipitation reaction is preferably a stirred reaction. The stirring method is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be used.
In the embodiment of the invention, the dosage ratio of the sodium carbonate solid to the iron phosphate production wastewater is 1-8 g:1L; the volume ratio of the carbon dioxide gas to the iron phosphate production wastewater is (0.5-3): 1. in certain embodiments of the present invention, the amount ratio of the sodium carbonate solid to the iron phosphate production wastewater is 1.33g:1L of the total amount of the active ingredients. In certain embodiments of the present invention, the volume ratio of the carbon dioxide gas to the iron phosphate production wastewater is 0.5:1.
in step D), in certain embodiments of the present invention, the method of solid-liquid separation is filtration. The method and parameters of the filtration are not particularly limited in the present invention, and those known to those skilled in the art can be used.
And carrying out stripping absorption treatment on the fourth precipitation solution to obtain absorption mother liquor and stripping effluent.
In the embodiment of the present invention, the air stripping absorption treatment is specifically air stripping + sulfuric acid absorption treatment. The absorbent adopted in the stripping absorption treatment is sulfuric acid solution. In certain embodiments, the sulfuric acid solution has a mass concentration of 25 to 35%. In certain embodiments, the sulfuric acid solution has a mass concentration of 35%.
And carrying out evaporation crystallization on the absorption mother liquor to obtain ammonium sulfate solid.
In certain embodiments of the invention, the temperature of the evaporative crystallization is from 100 to 110 ℃. In certain embodiments, the temperature of the evaporative crystallization is 105 ℃. In certain embodiments of the invention, the time for evaporative crystallization is 2 to 6 hours. In certain embodiments, the time for evaporative crystallization is 3 hours.
The invention effectively removes ammonia nitrogen in the wastewater by further precipitation treatment, stripping absorption and evaporative crystallization of the treated wastewater, obtains ammonium sulfate solid, and simultaneously obtains the ammonium sulfate solid with higher purity. The ammonia nitrogen concentration, the sulfate radical concentration and the phosphate radical concentration in the blown-out water all meet the requirements in the national Integrated wastewater discharge Standard GB 8978-1996.
The experimental result shows that the removal rate of ammonia nitrogen in the wastewater from the iron phosphate production is not lower than 99.8%. The purity of the obtained ammonium sulfate solid is not lower than 99.7%.
The process flow diagram of the method for treating the wastewater from the iron phosphate production provided by the invention is shown in detail in figure 1, the wastewater from the iron phosphate production and calcium carbonate are subjected to a first precipitation reaction to obtain a first precipitation slag (calcium sulfate) and a first precipitation solution, and the first precipitation solution and Ca (OH) 2 Mixing, performing a second precipitation reaction to obtain a second precipitation slag (calcium phosphate and calcium sulfate) and a second precipitation solution, and mixing the second precipitation solution with Ca (OH) 2 Mixing, carrying out a third precipitation reaction to obtain a third precipitation slag (calcium sulfate) and a third precipitation liquid (treated wastewater), mixing the treated wastewater with a calcium remover, carrying out a fourth precipitation reaction to obtain a fourth precipitation slag (calcium carbonate) and a fourth precipitation liquid, wherein the fourth precipitation slag can be reused for the first precipitation reaction, the fourth precipitation liquid is subjected to stripping absorption treatment to obtain an absorption mother liquid and stripping effluent, and the absorption mother liquid is subjected to evaporation crystallization to obtain an ammonium sulfate solid, thereby completing the waste iron phosphate productionAnd (4) treating the water.
In addition, the treatment method provided by the invention has the advantages of simple overall process, low comprehensive operation cost, particularly low energy consumption of evaporative crystallization, and effectively solves the problems of high cost, difficult recycling of sulfate radicals and sulfate radicals, difficult sales of recovered products and the like in the prior art.
In the present invention, the source of the raw material is not particularly limited, and may be generally commercially available.
In order to further illustrate the present invention, the following examples are provided to describe the method for treating wastewater from iron phosphate production in detail, but they should not be construed as limiting the scope of the present invention.
Example 1
In the wastewater from the production of the iron phosphate, the concentration of phosphate radical is 10g/L, the concentration of sulfate radical is 40g/L, the concentration of ammonia nitrogen is 8g/L, and the pH value of the wastewater from the production of the iron phosphate is 1.1.
(1) Adding 180g of calcium carbonate into 10L of iron phosphate mother liquor, carrying out a first precipitation reaction, controlling the pH value of the first precipitation reaction to be 3, stirring for reaction for 1.5h, and filtering to obtain first precipitation slag and first precipitation liquid;
(2) Adding 200g Ca (OH) into the first precipitation solution after the step (1) 2 Carrying out a second precipitation reaction, controlling the pH value of the second precipitation reaction to be 9.2, stirring for reaction for 1.5 hours, and filtering to obtain a second precipitation slag and a second precipitation solution;
(3) Adding 100g Ca (OH) into the second precipitation solution after the step (2) 2 Carrying out a third precipitation reaction, controlling the pH value of the third precipitation reaction to be 11, stirring for reaction for 1.5h, and filtering to obtain a third precipitation slag and a third precipitation liquid (namely, treated wastewater);
(4) Adding 13.3g of sodium carbonate into the third precipitation solution obtained in the step (3) to perform a fourth precipitation reaction, controlling the pH value of the fourth precipitation reaction to be 10, and stirring for reaction for 1.5 hours to obtain a fourth precipitation slag and a fourth precipitation solution; recycling the fourth precipitation slag in the first precipitation process in the step (1);
(5) Carrying out stripping absorption treatment on the fourth precipitation solution, and using 35% sulfuric acid as an absorbent of stripping tail gas to obtain absorption mother liquor and stripping effluent; the mass concentration of ammonium sulfate in the absorption mother liquor is 35 percent;
(6) The absorption mother liquor is evaporated and crystallized for 3h at 105 ℃ to obtain ammonium sulfate solid.
The detection shows that the dry weight of the first precipitation slag is 244.8g, and the purity of the calcium sulfate is 99.9%; the dry weight of the second precipitate was 235.0g, in terms of P, of the phosphorus content 2 O 5 Calculated) is 31.8 percent, and reaches the standard requirement of HG/T2673-95 phosphorite; the dry weight of the third precipitation slag is 88.4g, and the purity of the calcium sulfate is 99.9 percent; the dry weight of the fourth precipitation slag is 12.5g; the ammonium sulfate solids, 293.5g dry weight, had a purity of 99.5%. The concentration of sulfate radical in the blow-off water is 300mg/L, the concentration of phosphate radical is 6.6mg/L, and the concentration of ammonia nitrogen is 10mg/L.
The following results are obtained by calculation: the removal rate of sulfate radicals in the wastewater generated in the iron phosphate production is 99.25 percent, the removal rate of phosphate radicals is 99.93 percent, and the removal rate of ammonia nitrogen is 99.88 percent.
Example 2
The difference between the method for treating the wastewater generated in the iron phosphate production and the example 1 is that the pH value of the first precipitation reaction is controlled to be 2, and the stirring and mixing time is 0.5h; the pH value of the second precipitation reaction is 8, and the stirring and mixing time is 0.5h; the pH value of the third precipitation reaction is 10, and the stirring and mixing time is 0.5h; the pH value of the fourth precipitation reaction is 9.5, and the stirring and mixing time is 0.5h. The other conditions and parameters were the same as in example 1.
Through detection, the dry weight of the first precipitation slag is 206.5g, and the purity of the calcium sulfate is 99.9%; the dry weight of the second precipitation slag was 226.5g, the phosphorus content (in P) 2 O 5 Calculated) is 33.0 percent, and reaches the standard requirement of HG/T2673-95 phosphorite; the dry weight of the third precipitation slag is 129.8g, and the purity of the calcium sulfate is 99.9 percent; the dry weight of the fourth precipitation slag is 12.0g; the ammonium sulfate solids, 293.2g dry weight, had a purity of 99.5%. The sulfate radical concentration of the blow-off water is 320mg/L, the phosphate radical concentration is 8.3mg/L, and the ammonia nitrogen concentration is 14mg/L.
The following calculation results: the removal rate of sulfate radicals in the wastewater generated in the iron phosphate production is 99.2 percent, the removal rate of phosphate radicals is 99.92 percent, and the removal rate of ammonia nitrogen is 99.82 percent.
Example 3
In the wastewater from the production of the iron phosphate, the concentration of phosphate radical is 1g/L, the concentration of sulfate radical is 20g/L, the concentration of ammonia nitrogen is 4g/L, and the pH value of the wastewater from the production of the iron phosphate is 0.8.
The difference between the method for treating the wastewater from the production of iron phosphate and the method in example 1 is that the calcium remover is carbon dioxide (5L in volume) and the mass concentration of sulfuric acid is 25%.
The detection shows that the dry weight of the first precipitation slag is 122.7g, and the purity of the calcium sulfate is 99.9%; the dry weight of the second precipitate was 24.6g, with a phosphorus content (in P) 2 O 5 Calculated) is 30.6 percent, and reaches the standard requirement of HG/T2673-95 phosphorite; the dry weight of the third precipitation slag is 70.9g, and the purity of the calcium sulfate is 99.9 percent; the dry weight of the fourth precipitation slag is 12.4g; the dry weight of the ammonium sulfate solid is 146.6g, and the purity is 99.7%. The sulfate radical concentration of the blow-off water is 307mg/L, the phosphate radical concentration is 5.0mg/L, and the ammonia nitrogen concentration is 8mg/L.
The following calculation results: the removal rate of sulfate radicals in the wastewater generated in the iron phosphate production is 98.46 percent, the removal rate of the phosphate radicals is 99.5 percent, and the removal rate of ammonia nitrogen is 99.8 percent.
Comparative example 1
A method for treating wastewater from iron phosphate production, which is different from the method in example 1, wherein the pH value of the first precipitation reaction is controlled to be 5.
Detection shows that the purity of the calcium sulfate in the first precipitation slag is 80%, and the calcium sulfate cannot be recycled.
Comparative example 2
A method for treating wastewater from iron phosphate production, which is different from the method in example 1, wherein the pH value of the second precipitation reaction is controlled to be 10.
The detection shows that the phosphorus content of the second precipitation slag is 24 percent and is lower than the standard requirement of HG/T2673-95 phosphorite, and the second precipitation slag can not be recycled.
Comparative example 3
A method for treating wastewater from iron phosphate production, which is different from the method in example 1 in that the pH value of the third precipitation reaction is controlled to 10.
Through detection, the concentration of sulfate radicals in the third precipitation solution is 2000mg/L, the recovery rate of sulfate radicals in the mother solution is 89.2%, and the recovery rate of sulfate radicals is obviously reduced.
Comparative example 4
The difference between the method for treating the wastewater generated in the iron phosphate production and the example 1 is that the mass concentration of sulfuric acid is 20%, and the mass concentration of ammonium sulfate in absorption mother liquor is 20%.
In example 1, evaporation of 1t of the absorption mother liquor of the crystals required evaporation of 0.65t of water. In comparative example 4, evaporation of 1t of the absorption mother liquor of the crystals was required to evaporate 0.8t of water. The water mass required for evaporation in comparative example 4 is 1.23 times that in example 1, so the energy consumption and cost for evaporation are higher.
Comparative example 5
A method for treating wastewater from ferric phosphate production comprises adding Ca (OH) into 10L wastewater from ferric phosphate production, as shown in FIG. 2 2 Performing a first precipitation reaction, and adding Ca (OH) into the first precipitation solution 2 Carrying out a second precipitation reaction, then adding a calcium remover (calcium carbonate) into the second precipitation solution, and carrying out a third precipitation reaction;
carrying out stripping absorption treatment on the obtained third precipitation solution, and using 35% sulfuric acid by mass concentration as an absorbent of stripping tail gas to obtain absorption mother liquor and stripping effluent; the mass concentration of ammonium sulfate in the absorption mother liquor is 35 percent;
the absorption mother liquor is evaporated and crystallized for 3h at 105 ℃ to obtain ammonium sulfate solid.
And controlling the pH value of the first precipitation reaction to be 8 for 1.5h, the pH value of the second precipitation reaction to be 10 for 1.5h, and the pH value of the third precipitation reaction to be 9.5 for 1.5h to obtain first precipitation slag, second precipitation slag and third precipitation slag.
Through detection, the phosphorus content in the first precipitation slag is 15%, which is far lower than the standard requirement of HG/T2673-95 phosphorite, and the first precipitation slag can not be recycled.
Comparative example 6
A method for treating wastewater from ferric phosphate production comprises adding calcium carbonate and Ca (OH) into 10L ferric phosphate mother liquor step by step as shown in figure 3 2 And carrying out precipitation reaction with sodium carbonate, and controlling the pH value of the first precipitation to be 3, the pH value of the second precipitation reaction to be 11 and the pH value of the third precipitation reaction to be 10 to obtain first precipitation slag, second precipitation slag and third precipitation slag.
The detection shows that the phosphorus content of the second precipitation slag is 17 percent and is far lower than the standard requirement of HG/T2673-95 phosphorite, and the second precipitation slag can not be recycled.
As can be seen from example 1 and comparative examples 1 to 3, by controlling the conditions such as the precipitation reaction pH within the range of the present invention, the loss of phosphate radicals and phosphate radicals in the iron phosphate mother liquor can be avoided, and all of the phosphate radicals, sulfate radicals, and ammonium radicals can be recovered.
It is understood from the combination of example 1 and comparative example 4 that the mass of water in evaporative crystallization increases and the running cost increases without controlling the concentration of sulfuric acid as an absorbent used in the stripping absorption treatment.
By combining the example 1 and the comparative examples 5 to 6, it can be known that if the fractional precipitation process of the invention is not adopted, the phosphorus content in the obtained precipitation slag can not reach the standard requirement of HG/T2673-95 phosphorite, and the precipitation slag can not be recycled.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. The method for treating the wastewater generated in the iron phosphate production is characterized by comprising the following steps of:
a) Mixing iron phosphate production wastewater with calcium carbonate, carrying out precipitation reaction under the condition that the pH value is 2-3, and carrying out solid-liquid separation to obtain calcium sulfate and a first precipitation solution;
the dosage ratio of the calcium carbonate to the iron phosphate production wastewater is 18 to 48g: 1L;
in the iron phosphate production wastewater, the concentration of phosphate radical is 1-10 g/L, the concentration of sulfate radical is 20-50 g/L, and the concentration of ammonia nitrogen is 4-8 g/L;
the pH value of the wastewater generated in the iron phosphate production is 0.8 to 1.2;
b) Will be provided withThe first precipitation solution and Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 8.8-9.2, and carrying out solid-liquid separation to obtain calcium phosphate, calcium sulfate and a second precipitation solution;
ca (OH) in said step B) 2 The dosage ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 3 to 20g: 1L;
c) Mixing the second precipitation solution with Ca (OH) 2 Mixing, carrying out precipitation reaction under the condition that the pH value is 10.5 to 11, and carrying out solid-liquid separation to obtain calcium sulfate and treated wastewater;
ca (OH) in said step C) 2 The using amount ratio of the iron phosphate production wastewater to the iron phosphate production wastewater is 5 to 10g: 1L;
the purity of the calcium sulfate obtained in the step A) and the step C) is not lower than 99.9 percent, and the content of the calcium phosphate in the step B) is higher than the phosphorus content in the phosphorite, so that the calcium sulfate meets the requirement of first-class phosphorus ore in the chemical industry standard HG/T2673-95 of the people's republic of China for the standard of phosphorite for acid method processing;
d) Mixing the treated wastewater with a calcium remover, carrying out precipitation reaction under the condition that the pH value is 9.5 to 10.5, and carrying out solid-liquid separation to obtain calcium carbonate and a fourth precipitation solution;
the calcium remover is carbon dioxide and/or sodium carbonate solid;
the using amount ratio of the sodium carbonate solid to the iron phosphate production wastewater is 1 to 8g:1L;
the volume ratio of the carbon dioxide to the iron phosphate production wastewater is 0.5 to 3:1;
e) Carrying out stripping absorption treatment on the fourth precipitation solution to obtain absorption mother liquor and stripping effluent; the absorbent adopted in the stripping absorption treatment is sulfuric acid solution; the mass concentration of the sulfuric acid solution is 25 to 35 percent;
f) And carrying out evaporation crystallization on the absorption mother liquor to obtain ammonium sulfate solid.
2. The process according to claim 1, characterized in that in step A), the precipitation reaction time is from 0.5 to 1.5 hours.
3. The process according to claim 1, characterized in that in step B), the precipitation reaction time is from 0.5 to 1.5 hours.
4. The process according to claim 1, characterized in that in step C), the precipitation reaction time is from 0.5 to 1.5 hours.
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| CN115231840B (en) * | 2022-07-22 | 2024-02-02 | 湖南中金岭南康盟环保科技有限公司 | Method for recycling phosphogypsum from iron phosphate production wastewater |
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| CN115676790B (en) * | 2022-10-28 | 2024-04-02 | 贵州川恒化工股份有限公司 | Preparation method of high-tap-density spherical battery-grade ferric phosphate |
| CN115520995A (en) * | 2022-11-01 | 2022-12-27 | 湖北虹润高科新材料有限公司 | Method for utilizing sewage generated in iron phosphate production by calcium method and application of sewage |
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