Method for resource utilization of phosphorus spherulite sintering flue gas

Abstract

This invention discloses a method for the resource utilization of phosphate ore sintering flue gas that can efficiently recover fluorine and sulfur resources, reduce treatment costs, and create resource benefits. The method includes the following steps: sequentially subjecting the sintering flue gas to dust removal, denitrification, and heat exchange to obtain a first gas and dust; reacting the first gas with water to generate a first solid-liquid mixture containing fluorosilicic acid and silica gel, and a second gas; performing solid-liquid separation on the first solid-liquid mixture to obtain a first solid phase mainly composed of silica gel and a first liquid phase mainly composed of fluorosilicic acid; reacting the first liquid phase with sodium sulfate to generate a second solid-liquid mixture containing sulfuric acid and sodium fluorosilicate; and performing solid-liquid separation on the second solid-liquid mixture to obtain a second solid phase mainly composed of sodium fluorosilicate and a second liquid phase mainly composed of sulfuric acid.

Description

Technical Field

[0001] This invention relates to the technical field of producing yellow phosphorus from medium / low-grade phosphate rock, and more specifically, to a method for the resource utilization of flue gas from sintering phosphate spheroids. Background Technology

[0002] Based on the difference in the mass fraction of phosphorus pentoxide (P2O5), phosphate rock can be divided into high-grade phosphate rock (≥30wt%), medium-grade phosphate rock (20wt%~30wt%), and low-grade phosphate rock (10wt%~20wt%). Thermal yellow phosphorus refers to the production of elemental yellow phosphorus from phosphate rock, coke, and silica through high-temperature reduction in an electric furnace. It is an important basic phosphate chemical product. High-grade phosphate rock can be directly fed into the furnace, while medium / low-grade phosphate rock is usually in powder or fragmented form. Directly feeding it into the electric furnace can easily cause furnace blockage, making stable production difficult. To improve the utilization rate of medium / low-grade phosphate rock, it is usually mixed with binder and coke powder to form 10-20mm pellets, which are then sintered at 900-1200℃ to form phosphate pellets, which are then fed into the electric furnace to produce yellow phosphorus (i.e., deep processing).

[0003] The sintering flue gas produced from the deep processing of phosphate ore is rich in high concentrations of dust and NO. x Typical pollutants include SiF4 and SO2. Traditional treatment models treat SiF4 and SO2 simply as pollutants and adopt a step-by-step treatment of "defluorination + desulfurization", which has the following disadvantages: (1) High treatment cost: High concentration of pollutants causes a large amount of alkali to be consumed in the defluorination process, and the desulfurization adopts the limestone method to produce low-purity calcium sulfate with no market sales; (2) Secondary solid waste disposal pressure: By-product gypsum needs to be transported and stored, forming a negative cycle of "treatment-waste generation-re-disposal"; (3) Mismatch of resource utilization: The recoverable fluorine and sulfur resources in the flue gas are not effectively utilized. Fluorine is converted into fluorinated hazardous waste in the form of SiF4, and sulfur resources are solidified into low-value gypsum, resulting in resource loss. It can be seen that this kind of "input-type" end treatment model not only increases the comprehensive cost of phosphorus chemical production, but also contradicts the concept of circular economy development. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method and system for the resource utilization of phosphate ore sintering flue gas that can efficiently recover fluorine and sulfur resources, reduce treatment costs, and create resource benefits. The technical solution is as follows:

[0005] A method for resource utilization of flue gas from phosphate ore sintering includes the following steps:

[0006] The sintering flue gas is subjected to dust removal, denitrification and heat exchange treatment in sequence to obtain the first gas and dust.

[0007] The first gas is reacted with water to produce a first solid-liquid mixture containing fluorosilicic acid and silica gel, as well as a second gas.

[0008] The first solid-liquid mixture was subjected to solid-liquid separation treatment to obtain a first solid phase mainly composed of silica gel and a first liquid phase mainly composed of fluorosilicic acid;

[0009] The first liquid phase is reacted with sodium sulfate to produce a second solid-liquid mixture containing sulfuric acid and sodium fluorosilicate.

[0010] The second solid-liquid mixture was subjected to solid-liquid separation treatment to obtain a second solid phase mainly composed of sodium fluorosilicate and a second liquid phase mainly composed of sulfuric acid.

[0011] The resource utilization system for phosphate ore sintering flue gas includes:

[0012] The pretreatment unit is used to treat the sintering flue gas by dust removal, denitrification and heat exchange before outputting the first gas and dust; the pretreatment unit includes a dust removal device, a denitrification device and a heat exchanger connected in sequence.

[0013] A defluorination unit is used to react a first gas with water and output a first solid-liquid mixture containing fluorosilicic acid and silica gel, as well as a second gas; the defluorination unit includes a first reaction device, which has an air inlet and a water inlet, and the air inlet is connected to the heat medium outlet of a heat exchanger.

[0014] The first separation unit is used to perform solid-liquid separation treatment on the first solid-liquid mixture and output a first solid phase mainly composed of silica gel and a first liquid phase mainly composed of fluorosilicic acid; the first separation unit includes a settling tank and a first solid-liquid separation device connected in sequence, and the inlet of the settling tank is connected to the outlet of the first reaction device.

[0015] A fluorine recovery unit is used to react a first liquid phase with sodium sulfate and output a second solid-liquid mixture containing sulfuric acid and sodium fluorosilicate; the fluorine recovery unit includes a second reaction device, which has a liquid inlet and a sodium sulfate feed inlet, and the liquid inlet is connected to the drain outlet of the settling tank;

[0016] The second separation unit is used to perform solid-liquid separation treatment on the second solid-liquid mixture and output a second solid phase mainly composed of sodium fluorosilicate and a second liquid phase mainly composed of sulfuric acid; the second separation unit includes a second solid-liquid separation device connected to the discharge port of the second reaction device.

[0017] It can be seen that the resource utilization method and system of phosphate ore sintering flue gas of the present invention have the following advantages: (1) The pretreatment unit collaboratively completes multi-process pretreatment, which removes dust, NO xPollutants are also recovered from the waste heat of flue gas, which can be used for raw material drying, reducing the external energy consumption of the whole plant and realizing energy saving and consumption reduction. (2) The first gas reacts with water in the first reaction device to generate fluorosilicic acid and silica gel, and then is processed by the settling tank and the first solid-liquid separation device to obtain silica gel (first solid phase), fluorosilicic acid (first liquid phase) and acidic second gas respectively. Silica gel can be purified into white carbon black, and the second gas can be used to prepare sulfuric acid, realizing the high value of silicon and sulfur resources. (3) Fluorosilicic acid reacts with sodium sulfate in the second reaction device to generate sodium fluorosilicate and dilute sulfuric acid. After separation by the second solid-liquid separation device, high-purity sodium fluorosilicate product (second solid phase) and dilute sulfuric acid (second liquid phase) are obtained, so that fluorine and sulfur resources are converted into high value-added products or production reuse raw materials. (4) The entire process abandons the alkaline defluorination and limestone desulfurization process, does not require the consumption of a large amount of alkaline solution, does not produce low-purity gypsum and fluorinated hazardous waste, and achieves near-zero discharge of solid waste, eliminating the cost and environmental risks of transporting and storing solid waste. The various devices and units are seamlessly connected, and pollutant treatment and resource recovery are completed simultaneously, turning environmental protection investment into economic benefits and reducing the overall cost of phosphorus chemical industry.

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to aid in understanding the invention. The content provided in the drawings and their related descriptions can be used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 This is a schematic diagram of the resource utilization system for phosphate ore sintering flue gas of the present invention.

[0021] The relevant markings in the above figures are:

[0022] 110-Dust removal device, 120-Denitrification device, 130-Heat exchanger, 140-Backflush air manifold, 150-Compressed air buffer tank, 160-Ammonia water storage tank, 170-Ammonia water evaporator, 180-First blower, 210-Pipe scrubber, 220-Spray reaction tower, 310-Settling tank, 320-Clarification tank, 330-Filter press, 340-First liquid pump, 350-Second liquid pump, 400-Reaction tank, 500-Centrifuge, 610-Spray desulfurization tower, 620-Chimney, 630-Sulfuric acid storage tank, 711-First dehydration device, 712-Second dehydration device, 721-Second blower, 722-Third blower, 730-Granulator, 740-Sintering furnace. Detailed Implementation

[0023] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0024] The technical solutions and features provided in the various parts of this invention, including the following description, can be combined with each other without conflict.

[0025] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0026] Regarding the terminology and units used in this invention: The terms "comprising," "having," and any variations thereof in the specification, claims, and related parts of this invention are intended to cover non-exclusive inclusion.

[0027] Figure 1 This is a schematic diagram of the resource utilization system for phosphate ore sintering flue gas of the present invention.

[0028] like Figure 1 The resource utilization system for sintering flue gas of phosphate ore shown includes a pretreatment unit, a defluorination unit, a first separation unit, a fluorine recovery unit, a second separation unit, and an acid production unit.

[0029] The pretreatment unit is used to treat the sintering flue gas by dust removal, denitrification, and heat exchange before outputting the first gas and dust. The pretreatment unit includes a dust removal device 110, a denitrification device 120, and a heat exchanger 130 connected in sequence. The dust removal device 110 and the denitrification device 120 are integrated dust removal and denitrification devices 120 equipped with a backflush air manifold 140. The pretreatment unit also includes a compressed air buffer tank 150, an ammonia water storage tank 160, and an ammonia water evaporator 170. The outlet of the compressed air buffer tank 150 is... Simultaneously, it is connected to the air inlet of ammonia evaporator 170 and the air inlet of backflushing air manifold 140. The water inlet of ammonia evaporator 170 is connected to the liquid outlet of ammonia storage tank 160, and the exhaust port of ammonia evaporator 170 is connected to the sintering flue gas conveying pipeline. The air inlet of ammonia evaporator 170 is also connected to the air outlet of compressed air buffer tank 150 and the exhaust port of denitrification device 120. Thus, compressed air can dilute and atomize ammonia, while the partially returned high-temperature dust-free gas after dust removal and denitrification treatment and before heat exchange treatment can be used to evaporate ammonia. The cold air entering from the cold medium inlet of heat exchanger 130 is converted into hot air after heat exchange with the high-temperature dust-free gas. The hot air can be used to dry raw materials. Granulator 730 granulates dust and / or phosphate rock (medium / low grade) into pellets, which are then sintered into phosphate pellets in sintering furnace 740.

[0030] The defluorination unit is used to react a first gas with water and output a first solid-liquid mixture containing fluorosilicic acid and silica gel, as well as a second gas. The defluorination unit includes a first reaction device having an air inlet and a water inlet. The first reaction device includes a pipe scrubber 210 and a spray reaction tower 220 connected in sequence. The heat medium outlet of the heat exchanger 130 is connected to the air inlet of the pipe scrubber 210 via a first fan 180.

[0031] The first separation unit is used to separate the first solid-liquid mixture, outputting a first solid phase mainly composed of silica gel and a first liquid phase mainly composed of fluorosilicic acid. The first separation unit includes a settling tank 310, a clarifier 320, and a first solid-liquid separation device connected in sequence. The first solid-liquid separation device includes a filter press 330. The discharge port of the filter press 330 is connected to the inlet of the clarifier 320. The feed port of the settling tank 310 is connected to the discharge port of the spray reaction tower 220. The discharge port at the lower part of the settling tank 310 (discharging sediment) is connected to the feed port of the filter press 330, and the discharge port at the upper part of the settling tank 310 (discharging the first supernatant) is connected to the inlet of the clarifier 320. The discharge port at the lower part of the clarifier 320 (discharging the first liquid phase) is connected to the inlet of the second reaction device. The drain outlet at the top of the clarifier 320 (discharging aqueous reaction liquid) is connected to the inlet of the pipe scrubber 210 via the first liquid pump 340, and to the inlet of the spray reaction tower 220 via the second liquid pump 350.

[0032] The fluorine recovery unit is used to react the first liquid phase with sodium sulfate and output a second solid-liquid mixture containing sulfuric acid and sodium fluorosilicate. The fluorine recovery unit includes a second reaction device, which includes a reaction tank 400. The reaction tank 400 has a liquid inlet and a sodium sulfate feed inlet. The liquid inlet is connected to the discharge port at the bottom of the clarifier 320.

[0033] The second separation unit is used to perform solid-liquid separation treatment on the second solid-liquid mixture, outputting a second solid phase mainly composed of sodium fluorosilicate and a second liquid phase mainly composed of sulfuric acid. The second separation unit includes a second solid-liquid separation device connected to the discharge port of the reaction tank 400, and the second solid-liquid separation device includes a centrifuge 500.

[0034] The acid production unit is used to convert sulfur dioxide in the second gas into clean tail gas and a third liquid phase, mainly sulfuric acid. The acid production unit includes a spray desulfurization tower 610, which is equipped with an activated carbon packing layer. The inlet of the spray desulfurization tower 610 is connected to the outlet of the spray reaction tower 220 via a second gas delivery pipeline, and a humidifier is installed on the second gas delivery pipeline. The clean tail gas is discharged to the atmosphere through a chimney 620. The drain outlet of the centrifuge 500 (discharging the second liquid phase) and the drain outlet of the spray desulfurization tower 610 (discharging the third liquid phase) are connected to the inlet of the sulfuric acid storage tank 630.

[0035] The first solid phase discharged from the filter press 330 is dehydrated by the first dehydration device 711 to obtain silica, and the resulting dehydrated flue gas is drawn into the sintering flue gas conveying pipeline by the second fan 721. The second solid phase discharged from the centrifuge 500 is dehydrated by the second dehydration device 712 to obtain sodium fluorosilicate, and the resulting dehydrated flue gas is drawn into the sintering flue gas conveying pipeline by the third fan 722.

[0036] The resource utilization method for phosphate ore sintering flue gas of the present invention adopts the above-mentioned resource utilization system and specifically includes the following steps:

[0037] First, compressed air carrying ammonia is mixed with sintering flue gas (320-370℃), with the ammonia content in the mixture being 5-8 vol%. Then, the mixture of sintering flue gas, ammonia, and compressed air is sequentially subjected to dust removal, denitrification, and heat exchange treatments to obtain a first gas and dust. A portion of the high-temperature dust-free gas after dust removal and denitrification treatment and before heat exchange treatment can be recycled for ammonia evaporation. The dust content of the first gas is ≤10 mg / Nm³. 3 NO x Concentration ≤50 mg / Nm 3 The SiF4 concentration is 5000–15000 mg / Nm³. 3 SO2 concentration is 2000–4500 mg / Nm³ 3The temperature is 140–160℃. The dust is granulated and sintered to obtain phosphate spheroids.

[0038] The first gas undergoes a two-stage reaction with pure water and / or an aqueous reaction solution to produce a first solid-liquid mixture containing fluorosilicic acid and silica gel, and a second gas. The reaction equation is: 3SiF4 + (n + 2)H2O = 2H2SiF6 + SiO2·nH2O. The concentration of SiF4 in the resulting second gas is ≤9 mg / Nm³. 3 .

[0039] The second gas is subjected to catalytic oxidation to produce sulfuric acid, yielding a clean tail gas and a third liquid phase mainly composed of sulfuric acid. Specifically, activated carbon is used as both an adsorbent and a catalyst, allowing sulfur dioxide in the second gas to react with oxygen and water vapor on the activated carbon surface to produce sulfuric acid. The mass fraction of sulfuric acid in the third liquid phase is 5–12 wt%; the SO2 concentration in the clean tail gas is ≤35 mg / Nm³. 3 It can be discharged directly.

[0040] The first solid-liquid mixture is subjected to solid-liquid separation treatment to obtain a first solid phase mainly composed of silica gel and a first liquid phase mainly composed of fluorosilicic acid. Specifically, the first solid-liquid mixture is allowed to settle naturally to obtain a first supernatant and sediment. The sediment is then subjected to pressure filtration to obtain a first solid phase and a filtrate. The mixture of the first supernatant and the filtrate is allowed to settle naturally to obtain an upper aqueous reaction liquid and a lower first liquid phase. When the concentration of fluorosilicic acid in the first liquid phase reaches 8-12 wt%, it is then reacted with sodium sulfate.

[0041] The first liquid phase reacts with sodium sulfate to produce a second solid-liquid mixture containing sulfuric acid and sodium fluorosilicate; the reaction equation is: H2SiF6 + Na2SO4 = Na2SiF6 + H2SO4.

[0042] The second solid-liquid mixture was subjected to solid-liquid separation treatment to obtain a second solid phase mainly composed of sodium fluorosilicate and a second liquid phase mainly composed of sulfuric acid.

[0043] The first and second solid phases were dehydrated to obtain high-purity silica and sodium fluorosilicate, respectively. The dehydrated flue gas was then refluxed and mixed with the sintering flue gas for dust removal.

[0044] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the above description of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A method for the resource utilization of flue gas from phosphate ore sintering, characterized in that: Including the following steps: The sintering flue gas is subjected to dust removal, denitrification and heat exchange treatment in sequence to obtain the first gas and dust. The first gas is reacted with water to produce a first solid-liquid mixture containing fluorosilicic acid and silica gel, as well as a second gas. The first solid-liquid mixture was subjected to solid-liquid separation treatment to obtain a first solid phase mainly composed of silica gel and a first liquid phase mainly composed of fluorosilicic acid; The first liquid phase is reacted with sodium sulfate to produce a second solid-liquid mixture containing sulfuric acid and sodium fluorosilicate. The second solid-liquid mixture was subjected to solid-liquid separation treatment to obtain a second solid phase mainly composed of sodium fluorosilicate and a second liquid phase mainly composed of sulfuric acid.

2. The resource utilization method as described in claim 1, characterized in that: It also includes mixing compressed air carrying ammonia with sintering flue gas, with the ammonia gas fraction in the mixture being 5-8 vol%, and then subjecting the mixture to dust removal and SCR denitrification treatment.

3. The resource utilization method as described in claim 2, characterized in that: The dust content of the first gas is ≤10mg / Nm³. 3 NO x Concentration ≤50 mg / Nm 3 The SiF4 concentration is 5000–15000 mg / Nm³. 3 SO2 concentration is 2000–4500 mg / Nm³ 3 The temperature is 140–160℃.

4. The resource utilization method as described in claim 1, characterized in that: It also includes catalytic oxidation of the second gas to produce acid, resulting in clean tail gas and a third liquid phase mainly composed of sulfuric acid.

5. The resource utilization method as described in claim 4, characterized in that: Activated carbon is used as both an adsorbent and a catalyst to react sulfur dioxide in the second gas with oxygen and water vapor on the activated carbon surface to produce sulfuric acid. The sulfuric acid in the third liquid phase has a mass fraction of 5–12 wt%, and the SO2 concentration in the clean tail gas is ≤35 mg / Nm³. 3 .

6. The resource utilization method as described in claim 5, characterized in that: The first gas undergoes a two-stage reaction with pure water and / or an aqueous reaction solution, resulting in a second gas with a SiF4 concentration ≤ 9 mg / Nm³. 3 .

7. The resource utilization method as described in claim 1, characterized in that: The first solid-liquid mixture is allowed to settle naturally to obtain the first supernatant and sediment. The sediment is then subjected to pressure filtration to obtain the first solid phase and the filtrate. The mixture of the first supernatant and the filtrate is allowed to settle naturally to obtain the upper aqueous reaction liquid and the lower first liquid phase. When the concentration of fluorosilicic acid in the first liquid phase reaches 8-12 wt%, it is then reacted with sodium sulfate.

8. The resource utilization method as described in claim 1, characterized in that: It also includes dehydrating the first and second solid phases separately, and then recirculating the dehydrated flue gas to mix with the sintering flue gas for dust removal.

9. The resource utilization method as described in claim 1, characterized in that: It also includes obtaining phosphate spheroids after granulation and sintering of dust.

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