A method for utilizing heavy residue removed from wet-process phosphoric acid

Abstract

The invention discloses a method for utilizing de-heavy residue from wet-process phosphoric acid, comprising the following steps: step 1), grinding and finely grinding low-grade phosphate ore; step 2), adding the powdered material in step 1), mixing and placing the mixture in a disc pelletizing machine for pelletizing; heating the dried pellets with conventional yellow phosphorus furnace charge, condensing volatilized arsenic sulfide and lead sulfide through a flue gas heat exchanger, and enriching them to obtain arsenic-lead dust; step 6), raising the furnace temperature in step 5) to 1300° C. to 1600° C., condensing P vapor and SiF4 gas generated by the high-temperature reaction through spraying water, and collecting them; step 7), performing solid-liquid separation of the solid yellow phosphorus collected in step 6) and liquid H2SiF6 to obtain a main product, yellow phosphorus, and a by-product, H2SiF6. The preparation of the pellets according to the invention does not require the addition of an additional binder or sintering, has low energy consumption, and has better effects; the invention can separate and enrich As and Pb elements in the de-heavy residue without causing phosphorus loss, and the arsenic-lead dust can be used as a raw material for lead smelting.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization of heavy residue removed, and in particular to a method for utilizing heavy residue removed from wet-process phosphoric acid. Background Art

[0002] Phosphoric acid is a crucial raw material for the phosphorus chemical industry, and phosphate products are widely used in industries such as petroleum, metallurgy, electronics, and pharmaceuticals. In my country, wet-process phosphoric acid is mostly produced by decomposing phosphate rock with sulfuric acid. This product contains numerous impurities and requires purification to meet production requirements. Arsenic and lead are the primary heavy metal impurities in wet-process phosphoric acid. Sulfides are typically added during the phosphoric acid purification process to remove these arsenic and lead as insoluble arsenic sulfides and lead sulfides. These insoluble sulfides mix with other solid precipitates in the phosphoric acid to form heavy metal removal residue. This heavy metal removal residue is a new waste product generated in recent years due to the depletion of phosphate rock and the increase in heavy metal content in the ore. Currently, there is no suitable treatment process, requiring it to be recycled back to the extraction tank. This heavy metal removal residue circulates and accumulates within the wet-process phosphoric acid system, leading to a continuous increase in the heavy metal content of the phosphoric acid, seriously threatening the quality of the phosphoric acid and subsequent products. Therefore, research on treatment processes for this heavy metal removal residue is imperative.

[0003] The key to treating de-heavy residue is to separate and enrich the arsenic in the residue and recover the valuable phosphorus resources. Currently, there are no research reports on the treatment of de-heavy residue from wet-process phosphoric acid. Domestic arsenic-containing waste residue mainly comes from smoke and waste residue generated by metallurgical processes. Its As2S3 content is generally 5-30%. The treatment methods include resource technology and stabilization and solidification technology. Ma Yanrong used sodium hydroxide to dissolve arsenic sulfide slag, and then reacted it with excess ferric sulfate solution to obtain elemental sulfur and filtrate. Sulfur dioxide gas was introduced into the filtrate to obtain arsenous acid solution. After distillation, concentration, and cooling, arsenous acid precipitate was obtained. After drying, arsenic trioxide product was obtained (A method for preparing arsenic trioxide from arsenic sulfide waste residue CN102115166A). Guo Boping et al. first treated the arsenic sulfide slag with high-pressure oxygen, and then reduced and extracted it to obtain refined arsenic white, copper sulfate and ammonium rhenate (A high-pressure oxygen continuous leaching resource utilization process for arsenic sulfide slag CN106086426A). Zhang Wenhui et al. added an inorganic flocculant to arsenic sulfide slag, stirred it evenly, then added a solid powdered adsorbent, and finally added asbestos wool. The treated arsenic sulfide slag can be directly landfilled (A method for treating arsenic sulfide slag, CN102151690A). Chen Xiaofeng et al. reacted arsenic sulfide slag with sodium sulfide, then added an oxidant to oxidize it, then added iron or aluminum salts, and finally solidified it with cement, reducing the toxicity of arsenic leaching and achieving the purpose of harmless treatment (A method for harmless treatment of arsenic sulfide slag, CN105963902A).

[0004] The above treatment methods can recover arsenic resources or solve the problem of arsenic-containing slag leaching toxicity standards, but these methods have complex process flows, high reagent costs, and large equipment investments. In addition, the existing arsenic sulfide slag treatment process is not suitable for treating the heavy slag produced in the wet phosphoric acid production process, mainly because: (1) the arsenic content in the heavy slag is tens to hundreds of ppm, which is much lower than the arsenic content of the above arsenic-containing slag, making it more difficult to utilize and the treatment cost higher; (2) in the process of treating the heavy slag, a large amount of strategic P and F resources need to be recovered to realize the resource utilization of the heavy slag. Therefore, it is urgent to develop a heavy slag treatment method that can not only recover strategic P and F resources but also separate and enrich As. Summary of the Invention

[0005] The invention provides a method for utilizing heavy residue removed from wet-process phosphoric acid.

[0006] The scheme of the present invention is:

[0007] A method for utilizing heavy residue removed from wet-process phosphoric acid comprises the following steps:

[0008] Step 1) grinding and finely grinding low-grade phosphate rock to obtain a powdery material of 60-400 mesh;

[0009] Step 2) adding a certain amount of de-weighted residue to the powdered material in step 1), mixing the mixture and placing it in a disc pelletizer for pelletizing, wherein the pellet size is 5 to 70 mm;

[0010] Step 3), placing the pellets obtained in step 2) into a rotary kiln and drying them using yellow phosphorus tail gas as a heat source to obtain dried pellets;

[0011] Step 4), the dried pellets obtained in step 3) are put into a furnace together with conventional yellow phosphorus charge;

[0012] Step 5) heating the dried pellets in step 4) with conventional yellow phosphorus charge, volatilizing arsenic sulfide and lead sulfide into the air duct, and cooling the high-temperature gas through a flue gas heat exchanger to obtain arsenic-lead dust;

[0013] Step 6) raising the furnace temperature of step 5) to 1300° C. to 1600° C., and collecting the P vapor and SiF4 gas generated by the high-temperature reaction by spraying water for condensation;

[0014] Step 7), solid-liquid separation of the solid yellow phosphorus collected in step 6) and the liquid H2SiF6 to obtain the main product yellow phosphorus and the by-product H2SiF6.

[0015] As a preferred technical solution, the P2O5 content of the low-grade phosphate rock in step 1) is 20% to 25%.

[0016] As a preferred technical solution, the deheavy residue in step 2) is a slurry that does not require solid-liquid separation; the P2O5 concentration in the deheavy residue is 30% to 45%, the F content is 0.5% to 8%, the As content is 0.001% to 0.08%, and the Pb content is 0.001% to 0.05%.

[0017] As a preferred technical solution, the amount of the deweighted slag added in step 2) is 10% to 40% of the mass of the phosphate rock.

[0018] As a preferred technical solution, the drying temperature in step 3) is 60-250° C., and the drying time is 30-240 minutes.

[0019] As a preferred technical solution, the heating temperature in step 5) is 800-1200° C. and the heating time is 30-400 min.

[0020] As a preferred technical solution, the temperature in step 6) is 1450-1500°C, the time is 30-400 min, and the P steam and SiF4 gas produced by the reaction are condensed and collected by spraying water.

[0021] Due to the adoption of the above technical solution, a method for utilizing the de-heavy residue of wet-process phosphoric acid comprises the following steps: step 1), grinding and finely grinding low-grade phosphate rock to obtain powdered phosphate rock with a mesh size of 60 to 400; step 2), adding the powdered phosphate rock in step 1) to the de-heavy residue, mixing and placing the mixture in a disc pelletizing machine for pelletizing, wherein the pellet size is 5 to 70 mm; the de-heavy residue has a P2O5 concentration of 30% to 45%, a F content of 0.5% to 8%, an As content of 0.001% to 0.08%, and a Pb content of 0.001% to 0.05%; and step 3), placing the pellets obtained in step 2) into a recycling machine. In the rotary kiln, yellow phosphorus tail gas is used as a heat source for drying to obtain dried pellets; in step 4), the dried pellets obtained in step 3) are fed into the kiln together with conventional yellow phosphorus charge; in step 5), the dried pellets in step 4) and the conventional yellow phosphorus charge are heated, and arsenic sulfide and lead sulfide are volatilized and enriched in the smoke; in step 6), the furnace temperature in step 5) is increased to 1300° C. to 1600° C., and P vapor and SiF4 gas generated by the high-temperature reaction are condensed and collected by spraying water; in step 7), the solid yellow phosphorus collected in step 6) is separated from liquid H2SiF6 to obtain the main product yellow phosphorus and the by-product H2SiF6.

[0022] Advantages of the present invention:

[0023] 1. One of the raw materials of the present invention is the heavy residue removed from wet-process phosphoric acid that does not require solid-liquid separation. The process is simple and can efficiently recover strategic P and F resources in the heavy residue removed, thereby making high-value use of phosphorus chemical waste residue.

[0024] 2. The present invention utilizes yellow phosphorus tail gas as a drying heat source and comprehensively utilizes phosphorus chemical waste gas;

[0025] 3. The present invention uses slurry-depleted slag as a binder, which can fully utilize low-grade powdered phosphate rock. Since the depleted slag contains 30-40% P2O5 resources, it can increase the P2O5 content of the pellets after mixing with the powdered ore. The present invention can accept low-grade phosphate rock with a grade as low as 20%;

[0026] 4. The present invention does not require the addition of additional binders or sintering to prepare pellets, resulting in low energy consumption and better results.

[0027] 5. The present invention can separate and enrich As and Pb elements in the deheaving slag without causing phosphorus loss, and the arsenic-lead dust can be used as a raw material for lead smelting. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a method for utilizing heavy residue removed from wet-process phosphoric acid to solve the problems in the above-mentioned background technology.

[0030] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific embodiments.

[0031] Example 1:

[0032] Low-grade phosphate rock is finely ground to a particle size of 160-200 mesh to obtain powdered phosphate rock; deweighted slag accounting for 33% of the weight of the powdered phosphate rock is mixed into the powdered phosphate rock, and the mixture is placed in a disc pelletizer for pelletizing to a particle size of 20-40 mm to obtain mixed pellets; the mixed pellets are placed in a rotary kiln and dried at 160°C for 120 minutes using yellow phosphorus tail gas as a heat source to obtain dried pellets; the dried pellets are placed in an electric furnace, the air duct is opened, and the furnace is kept at 1200°C for 60 minutes to volatilize gases containing As and Pb and enter a flue gas heat exchanger. The gases are cooled by heat exchange into a solid state and then collected to obtain arsenic-lead dust; the temperature is increased to 1450°C and reduced for 120 minutes. The P vapor and SiF4 gas are volatilized, purified by electrostatic dust removal, and then enter a spray condensation system. The gases are cooled by spray water into solid and liquid states and collected. After solid-liquid separation, solid yellow phosphorus as a main product and liquid H2SiF6 as a by-product are obtained.

[0033] Table 1 Chemical composition of low-grade phosphate rock used in this example

[0034]

[0035] Table 2 Chemical composition of the heavy-removed slag used in this embodiment

[0036]

[0037] Table 3 Chemical composition of the pellets in this embodiment

[0038]

[0039] Table 4 Physical and chemical properties of the pellets in this embodiment

[0040]

[0041] Table 5 Chemical composition of yellow phosphorus in this embodiment

[0042]

[0043] Table 6 Chemical composition of arsenic-lead dust in this example

[0044]

[0045] As shown in Tables 3 and 4, the P2O5 content of the pellets entering the furnace is 25.54%, exceeding 25%, and the compressive strength of the pellets is 287N, exceeding 180N, meeting the requirements for yellow phosphorus charge pellets (P2O5 content >25%, compressive strength >180N). The pellets entering the furnace do not pulverize during the reaction, causing arching in the furnace, and the reduction rate is above 95% at temperatures above 1400°C. The As and Pb contents in yellow phosphorus meet product requirements, and this technology can be used for yellow phosphorus production (see Table 5). The vast majority of the As and Pb heavy metals in the pellets are lost to dust, the chemical composition of which is shown in Table 6. The arsenic-lead powder, with its high lead content, can be used as a raw material for lead smelting. After arsenic is enriched in the lead metallurgical process, it can be used as a raw material for producing arsenic products, achieving comprehensive resource utilization.

[0046] Example 2:

[0047] Low-grade phosphate rock is finely ground to a particle size of 120-160 mesh to obtain powdered phosphate rock; deweighted slag accounting for 35% by weight of the powdered phosphate rock is mixed into the powdered phosphate rock, and the mixture is placed in a disc pelletizer for pelletizing to a particle size of 30-50 mm to obtain mixed pellets; the mixed pellets are placed in a rotary kiln and dried at 180°C for 45 minutes using yellow phosphorus tail gas as a heat source to obtain dried pellets; the dried pellets are placed in an electric furnace, the air duct is opened, and the temperature is kept at 1100°C for 120 minutes to volatilize gases containing As and Pb into a flue gas heat exchanger, where the gases are cooled to a solid state and then collected to obtain arsenic-lead powder; the temperature of the electric furnace is increased to 1400°C and reduced for 180 minutes, whereupon P vapor and SiF4 gas are volatilized, purified by electrostatic dust removal, and then enter a spray system where they are cooled by spray water into solid and liquid states and collected. After solid-liquid separation, solid yellow phosphorus as a main product and liquid H2SiF6 as a by-product are obtained.

[0048] Table 7 Chemical composition of low-grade phosphate rock used in this example

[0049]

[0050] Table 8 Chemical composition of the de-heavy slag used in this embodiment

[0051]

[0052] Table 9 Chemical composition of the pellets in this example.

[0053]

[0054]

[0055] Table 10 Physical and chemical properties of the pellets in this embodiment

[0056]

[0057] Table 11 Chemical composition of yellow phosphorus in this embodiment

[0058]

[0059] Table 12 Chemical composition of arsenic-containing powder in this example

[0060]

[0061] As shown in Tables 9 and 10, the P2O5 content of the pellets entering the furnace is greater than 25%, and the compressive strength of the pellets is greater than 180N, meeting the requirements for yellow phosphorus feed pellets. The pellets do not pulverize during the reaction, causing arching in the furnace, and the reduction rate is above 95% at temperatures above 1400°C. The As and Pb contents in yellow phosphorus meet product requirements, indicating that this technology can be used in yellow phosphorus production (see Table 11). The vast majority of the As and Pb heavy metals in the pellets are converted into arsenic-lead powder (see Table 8). Due to its high lead content, the arsenic-lead powder can be used as a raw material for lead smelting. After arsenic is enriched in the lead metallurgical process, it can be used as a raw material for producing arsenic products, achieving comprehensive resource utilization.

[0062] Example 3

[0063] Low-grade phosphate rock is finely ground to a particle size of 80-120 mesh to obtain powdered phosphate rock; deweighted slag accounting for 30% by weight of the powdered phosphate rock is mixed into the powdered phosphate rock and then placed in a disc pelletizer for pelletizing to a particle size of 20-40 mm to obtain mixed pellets; the mixed pellets are placed in a rotary kiln and dried at 250°C for 30 minutes using yellow phosphorus tail gas as a heat source to obtain dried pellets; the dried pellets are placed in an electric furnace, the air duct is opened, and the temperature is kept at 1000°C for 140 minutes to volatilize gases containing As and Pb into a flue gas heat exchanger, where the gases are cooled to a solid state and then collected to obtain arsenic-lead powder; the temperature of the electric furnace is increased to 1500°C and reduced for 45 minutes, whereupon P vapor and SiF4 gas are volatilized, purified by electrostatic dust removal, and then enter a spray system where they are cooled by spray water into solid and liquid states and collected. After solid-liquid separation, solid yellow phosphorus as a main product and liquid H2SiF6 as a by-product are obtained.

[0064] Table 13 Chemical composition of low-grade phosphate rock used in this example

[0065]

[0066] Table 14 Chemical composition of the de-heavy slag used in this embodiment

[0067]

[0068] Table 15 Chemical composition of the pellets in this embodiment

[0069]

[0070] Table 16 Physical and chemical properties of the pellets in this embodiment

[0071]

[0072] Table 17 Chemical composition of yellow phosphorus in this embodiment

[0073]

[0074] Table 18 Chemical composition of arsenic-containing dust in this example

[0075]

[0076] As shown in Tables 15 and 16, the P2O5 content of the pellets entering the furnace is greater than 25%, and the compressive strength of the pellets is greater than 180N, meeting the requirements for yellow phosphorus feed pellets. The pellets do not pulverize during the reaction, causing arching in the furnace, and the reduction rate is above 95% at temperatures above 1400°C. The As and Pb contents in yellow phosphorus meet product requirements, indicating that this technology can be used in yellow phosphorus production (see Table 11). The vast majority of the As and Pb heavy metals in the pellets are converted into arsenic-lead dust (see Table 18). The high lead content of the arsenic-lead dust can be used as a raw material for lead smelting. After arsenic is enriched in the lead metallurgical process, it can be used as a raw material for producing arsenic products, achieving comprehensive resource utilization.

[0077] Comparative Example 1

[0078] Low-grade phosphate rock is finely ground to a particle size of 80-120 mesh to obtain powdered phosphate rock; deweighted slag accounting for 33% by weight of the powdered phosphate rock is mixed into the powdered phosphate rock, and then placed in a disc pelletizer for pelletizing to a particle size of 20-40 mm to obtain mixed pellet 1; the mixture is prepared according to a ratio of powdered phosphate rock to coke of 100:15, and water of 5% by weight of the mixture is added, and then pelletized in a disc pelletizer to a particle size of 20-40 mm to obtain mixed pellet 2; mixed pellets 1 and 2 are placed in a rotary kiln, dried at 250°C for 30 minutes using yellow phosphorus tail gas as a heat source, to obtain dried pellets 1 and dried slag pellets 2; dried pellets 1 and 2 are respectively added to an electric furnace, the air guide pipe is opened, and the mixture is kept at 1000°C for 140 minutes; the temperature of the electric furnace is further increased to 1500°C, and reduced for 45 minutes.

[0079] Table 19 Chemical composition of low-grade phosphate rock used in this example

[0080]

[0081] Table 20 Chemical composition of the heavy-removed slag used in this embodiment

[0082]

[0083] Table 21 Chemical composition of coke used in this example

[0084]

[0085] Table 22 Comparison of properties of pellets used in this example

[0086]

[0087] Table 22 shows that when using deweighted slag as a binder, Pellet 1 achieves an average compressive strength of 289 N, higher than Pellet 2, which uses coke as a binder. It also exhibits a lower breakage rate after a 1.5-meter drop, making the pellets less susceptible to breakage during transport and charging. Furthermore, Pellet 1 exhibits a higher phosphorus reduction rate than Pellet 2. This is due to Pellet 1's higher strength, resulting in less powder formation during the high-temperature reduction process, allowing more material to remain in the high-temperature furnace for full reaction.

[0088] Comparative Example 2

[0089] Low-grade phosphate rock is finely ground to a particle size of 120-160 mesh to obtain powdered phosphate rock; deweighted slag accounting for 33% by weight of the powdered phosphate rock is mixed into the powdered phosphate rock, and the mixture is pelletized in a disc pelletizer to a particle size of 10-30 mm to obtain mixed pellet 1; the mixture is prepared according to a ratio of powdered phosphate rock to coke of 100:25, and water of 8% by weight of the mixture is added, and the mixture is pelletized in a disc pelletizer to a particle size of 10-30 mm to obtain mixed pellet 2; mixed pellets 1 and 2 are placed in a rotary kiln, dried at 180°C for 60 minutes using yellow phosphorus tail gas as a heat source, to obtain dried pellets 1 and dried slag pellets 2; dried pellets 1 and 2 are respectively added to an electric furnace, the air duct is opened, and the mixture is kept at 1100°C for 120 minutes; the temperature of the electric furnace is further increased to 1450°C, and reduced for 60 minutes.

[0090] Table 23 Chemical composition of low-grade phosphate rock used in this example

[0091]

[0092] Table 24 Chemical composition of the heavy-removed slag used in this example

[0093]

[0094] Table 25 Chemical composition of coke used in this example

[0095]

[0096] Table 26 Comparison of properties of pellets used in this example

[0097]

[0098] Table 22 shows that using deweighted slag as a binder results in higher compressive strength and a lower breakage rate after a 1.5-meter drop, making the pellets less susceptible to breakage during transport and charging. Furthermore, the phosphorus reduction rate of Pellet 1 is higher than that of Pellet 2 because Pellet 1 is stronger and produces less powder during the high-temperature reduction process, allowing more material to remain in the high-temperature furnace for full reaction.

[0099] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for utilizing wet-process phosphoric acid deheavy residue, characterized in that: The following steps are involved: Step 1) grinding and finely grinding low-grade phosphate rock to obtain a powdery material of 60-400 mesh; Step 2) adding the powdered material in step 1) to the de-weighted residue, mixing and placing in a disc pelletizer for pelletization, wherein the pellet size is 5 to 70 mm; Step 3), placing the pellets obtained in step 2) into a rotary kiln, using yellow phosphorus tail gas as a heat source, and drying to obtain dried pellets; Step 4), the dried pellets obtained in step 3) are put into a furnace together with conventional yellow phosphorus charge; Step 5) heating the dried pellets in step 4) with conventional yellow phosphorus charge, volatilizing arsenic sulfide and lead sulfide into the air duct, and cooling the high-temperature gas through a flue gas heat exchanger to obtain arsenic-lead dust; Step 6) The furnace temperature of step 5) is raised to 1300°C to 1600°C, and the P vapor and SiF4 gas generated by the high temperature reaction are electrostatically precipitated and then enter the spray water system for condensation and collection; Step 7), solid-liquid separation of the solid yellow phosphorus collected in step 6) and the liquid H2SiF6 to obtain the main product yellow phosphorus and the by-product H2SiF6.

2. The method for utilizing the heavy residue removed from wet-process phosphoric acid according to claim 1, wherein: The P2O5 content of the low-grade phosphate rock in step 1) is 20% to 25%.

3. The method for utilizing the heavy residue removed from wet-process phosphoric acid according to claim 1, wherein: The de-heavy residue in step 2) is a slurry that does not require solid-liquid separation; the P2O5 concentration in the de-heavy residue is 30% to 45%, the F content is 0.5% to 8%, the As content is 0.001% to 0.08%, and the Pb content is 0.001% to 0.05%.

4. The method for utilizing the heavy residue removed from wet-process phosphoric acid according to claim 1, wherein: The amount of the de-heavy slag added in step 2) is 10% to 40% of the mass of the phosphate rock.

5. The method for utilizing the heavy residue removed from wet-process phosphoric acid according to claim 1, wherein: The drying temperature in step 3) is 60-250° C., and the drying time is 30-240 minutes.

6. The method for utilizing the heavy residue removed from wet-process phosphoric acid according to claim 1, wherein: In step 5), the heating temperature is 800-1200° C. and the heating time is 30-400 min.

7. The method for utilizing the heavy residue removed from wet-process phosphoric acid according to claim 1, wherein: In step 6), the temperature is 1450-1500° C., the time is 30-400 min, and the P vapor and SiF 4 gas generated by the reaction are condensed and collected by spraying water.

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