CN108383089A - A method of restoring ardealite and titanium dioxide waste residue green vitriol Sulphuric acid simultaneously using pyrite - Google Patents

Abstract

The invention discloses a method for simultaneously preparing sulfuric acid and calcium ferrite by using pyrite-titanium white waste slag green vitriol-phosphogypsum. The process includes: (1) finely grinding pyrite and phosphogypsum to a certain particle size Mix evenly with titanium dioxide waste slag green vitriol in a certain proportion; (2) After pressing the mixture into tablets or directly reacting the mixture at a certain temperature for a certain period of time, a solid reduction product and tail gas containing _SO2 are obtained; the obtained solid reduction product can be used as Pre-melted steelmaking slagging agent; (3) the SO2 _- containing tail gas obtained in step (2) is dedusted and purified, and then sent to a sulfuric acid system to prepare sulfuric acid finished products. This process uses pyrite to simultaneously reduce phosphogypsum and titanium white waste slag green vitriol to produce sulfuric acid, realizes solid waste treatment and recycling of phosphogypsum and titanium white waste slag green vitriol, and obtains sulfuric acid and steelmaking slagging agent calcium ferrite products. The decomposition rate of phosphogypsum in the invention can reach more than 98wt%, the concentration of _SO2 in the kiln gas can reach more than 15vol%, and the purity of the solid-phase product calcium ferrite can reach more than 90wt%. The invention has simple process, no discharge of three wastes, and remarkable advantages in environmental and economic benefits.

Description

A method of simultaneously reducing phosphogypsum and titanium white waste slag vitriol to produce sulfuric acid by using pyrite method

technical field

The invention belongs to the technical field of chemical metallurgy, and mainly relates to a method for simultaneously preparing sulfuric acid and calcium ferrite by utilizing pyrite, titanium white waste slag vitriol and phosphogypsum.

Background technique

Phosphogypsum is an industrial waste residue produced by the reaction of phosphate rock and sulfuric acid in the wet-process phosphoric acid production process. The main component is calcium sulfate, and it also contains iron, aluminum, phosphorus, silicon and other impurities. At present, phosphogypsum is mainly used for storage in the open air, except that it is partially used in the production of building materials. It is of great significance to increase the effective way to develop large-scale utilization of phosphogypsum to realize the sustainable development of the phosphate fertilizer industry, avoid excessive occupation of land resources and protect the environment.

The reduction of phosphogypsum to sulfuric acid can be coupled with the wet-process phosphoric acid production process, and the recycling of sulfur resources is a comprehensive utilization method with good application prospects that can realize large-scale consumption of phosphogypsum. The Chinese patent with the publication number CN 101041439 A proposes a method for preparing wollastonite and sulfuric acid by using waste phosphogypsum. It mixes phosphogypsum, carbon powder and quartz powder according to the stoichiometric ratio and puts them into a reactor, heats up to 1200°C and Insulate for 2.5h, cool to room temperature to obtain wollastonite, and the _SO2 produced during the calcination process is used in the subsequent sulfuric acid production section. The decomposition process of phosphogypsum in this invention is a coke reduction control step, which has problems such as high energy consumption, low _SO2 concentration in the kiln gas, and the generated _CO2 is not friendly to the environment. The Chinese patent with the publication number CN 1884048 A proposes a method for reducing and decomposing phosphogypsum with high-sulfur coal, which mixes the dried phosphogypsum and high-sulfur coal (sulfur content ≥ 3%) evenly and sends them into the reduction decomposition Furnace, the furnace temperature is controlled at 800~1350 ℃, and the reduction and decomposition reaction is carried out. The SO ₂ produced is used as the raw material gas for the sulfuric acid production process, and the CaO in the solid product is used as an ingredient for the production of cement. This invention still belongs to coke reducing and decomposing phosphogypsum in essence, and the energy consumption is still relatively high. The Chinese patent with the publication number CN 101708826 A proposes a method for reducing and decomposing phosphogypsum with sulfur. Firstly, the preheated phosphogypsum and gaseous sulfur are reacted at low temperature in an inert atmosphere for 1~2 hours; then the obtained calcium sulfide material is After the block is ground, it is evenly mixed with phosphogypsum, and fired in a non-oxidizing atmosphere at 1000-1400 °C for 0.5-3 hours. The CaO in the obtained solid slag is used as cement clinker for cement production, and the SO ₂ produced is the same as that produced in the first section. The tail gas is combined for sulfuric acid production. The process adopts two-stage processes, the process is not simple enough, and there are certain requirements for equipment corrosion.

Pyrite (FeS ₂ ) is the main source of sulfur resources in China, with rich reserves, and the proven resource reserves rank among the top in the world. At present, 40-50% of sulfuric acid production in China uses pyrite as raw material. The Chinese patent with the publication number CN 102530889 A proposes a method for producing sulfuric acid by reducing and decomposing gypsum from pyrite, which grinds gypsum and pyrite and mixes them evenly in proportion, and then adds the mixed material at a temperature of 800-1300 °C In the reactor, it is roasted for 0.1~4h in an inert, weakly oxidizing or reducing atmosphere, and the resulting SO ₂ tail gas is used to make sulfuric acid. This invention does not utilize the solid residue generated by it. The main reason is that the solid waste residue is a mixture of calcium oxide and calcium ferrite, and it is difficult to separate and utilize it; if it is piled up, it will inevitably waste land resources and increase maintenance costs. , and may cause secondary pollution.

Titanium dioxide waste slag Green vitriol is the by-product waste residue of sulfuric acid process titanium dioxide production, and every 1 t of titanium dioxide produced produces 3-4 t of ferrous sulfate. At present, there are not many effective utilization methods of titanium dioxide waste slag green vitriol, and stacking is still the main method, resulting in a huge waste of sulfur and iron resources and environmental pollution. The Chinese patent with the publication number CN 103539207 A proposes a method for preparing iron oxide red by reducing and decomposing ferric sulfate by ferrous disulfide. In this method, iron sulfate and ferrous disulfide are mixed in a certain molar ratio, and heated at 550-800 ° C. Roast for 0.5-3 hours to obtain sulfur dioxide and iron oxide red. The iron oxide red product obtained by the inventive method has a purity of more than 80 wt%, and is suitable for large-scale utilization of titanium white waste slag greenite.

The present invention uses pyrite to simultaneously reduce phosphogypsum and titanium white waste slag greenite to prepare sulfuric acid and calcium ferrite. SO ₂ , the concentration of SO ₂ in the kiln gas is high; CaO generated by the reaction of phosphogypsum is combined with Fe ₂ O ₃ generated by the reaction of green vitriol from titanium white waste slag through a reasonable ratio to form relatively pure calcium ferrite, which can be directly used as Pre-melted steelmaking slagging agent. This process couples the two processes of reducing and decomposing phosphogypsum with pyrite and reducing and decomposing green vitriol with pyrite, which can efficiently recycle and utilize the sulfur, iron and calcium resources in phosphogypsum and titanium white waste slag green vitriol without discharging the three wastes. A new method for the comprehensive utilization of phosphogypsum and titanium dioxide waste slag green vitriol solid waste has remarkable environmental and economic benefits.

Contents of the invention

The present invention utilizes pyrite to simultaneously reduce phosphogypsum and titanium white waste slag greenite to produce sulfuric acid and calcium ferrite. The process includes the following steps: (1) finely grinding pyrite, titanium white waste slag greenite, Phosphogypsum is uniformly mixed according to a certain proportion; (2) the mixture is put into a tablet press for tableting; (3) the tableted mixture is roasted at a certain temperature for a certain period of time to obtain a solid reduction product and tail gas containing SO2; (4) The solid reduction product obtained in step (3) can be used as a pre-melt steelmaking slagging agent after cooling; (5) the SO2-containing tail gas obtained in step (3) is dedusted and purified, and then sent to a sulfuric acid system to prepare sulfuric acid finished products. In above-mentioned method, the reaction that roasting process mainly takes place is as follows:

2 FeS ₂ + 11CaSO ₄ = Ca ₂ Fe ₂ O ₅ + 9CaO + 15SO ₂ ;

FeS ₂ + 11FeSO ₄ = 6Fe ₂ O ₃ + 13SO ₂ ;

2CaO _{+ Fe2O3 = Ca2Fe2O5 ;}

The overall response is:

FeS ₂ + 3FeSO ₄ + 4CaSO ₄ = 2Ca ₂ Fe ₂ O ₅ + 9SO ₂ .

Compared with the prior art, the present invention has the following advantages: (1) Compared with the traditional coke reduction of phosphogypsum, the reduction temperature of this process is reduced by about 200-300 °C, and the energy consumption is low; (2) This process uses pyrite to reduce Phosphogypsum and green vitriol have a high recovery rate of sulfur, and the concentration of SO ₂ tail gas is stable and high (greater than 15vol%), which can be directly used as raw material gas for sulfuric acid process; (3) CaO generated by decomposing phosphogypsum with titanium white waste green vitriol Converted to calcium ferrite, the solid product has simple components and can be directly used as a pre-melted steelmaking slagging agent. (4) The process of the present invention is simple, and the efficient recycling of sulfur, iron, and calcium resources in solid waste can be realized without discharge of the three wastes, and the environmental and economic benefits are remarkable.

Detailed ways

The present invention will be described in detail below in conjunction with the examples, but the protection scope of the present invention is not limited to the following examples. The composition of the titanium dioxide waste slag vitriol, pyrite and phosphogypsum used in the following examples is shown in the table below:

Table 1. Composition of titanium dioxide waste slag Element Fe S Mg mn Ti V Cr Al Si Contentwt. % 35.61 17.63 0.76 0.24 0.95 <0.1 <0.1 <0.1 <0.1

Table 2. Composition of pyrite Element Fe S Mg Ca Ti al Si Contentwt. % 39.54 32.15 1.62 2.21 0.35 0.65 3.29

Table 3. Chemical composition of phosphogypsum chemical components CaO SO ₃ P ₂ O ₅ SiO ₂ MgO Al ₂ O _{3 Fe2O3 _} f Contentwt. % 31.17 41.12 1.62 4.11 0.67 0.94 0.72 0.21

The specific implementation cases are as follows.

Embodiment one

(1) Mix finely ground pyrite below 500 μm, titanium white waste slag vitriol, and phosphogypsum, the active ingredient ferrous disulfide in pyrite, and the active ingredient ferrous sulfate in titanium white slag green vitriol The molar ratio of calcium sulfate, the active ingredient in phosphogypsum, is 1:3:4;

(2) The mixture is pressed into tablets and put into the rotary kiln;

(3) Roast the pellets at 1000 °C for 120 min under a nitrogen protective atmosphere to obtain SO ₂ tail gas and solid reduction products;

(4) send into sulfuric acid system to prepare sulfuric acid finished product after dedusting and purifying the tail gas containing _SO2 of step (3) gained, and solid reduction product is calcium ferrite, and purity is 74 wt%;

(5) In embodiment one, monitor the _SO2 concentration of tail gas with a flue gas analyzer, its volume percentage ≥ 15%, the calculated decomposition rate of phosphogypsum is 93%, the decomposition rate of pyrite is 98%, titanium The decomposition rate of white waste slag green vitriol is 96%.

Embodiment two

(1) Mix finely ground pyrite below 250 μm, titanium white waste slag greenite, and phosphogypsum, the active ingredient ferrous disulfide in pyrite, and the active ingredient in titanium white waste slag greenite ferrous sulfate The molar ratio of calcium sulfate, the active ingredient in phosphogypsum, is 1:2:3;

(2) The mixture is pressed into tablets and put into the rotary kiln;

(3) Roast the pellets at 1150 °C for 180 min under a nitrogen protective atmosphere to obtain SO ₂ tail gas and solid reduction products;

(4) send into sulfuric acid system to prepare sulfuric acid finished product after dedusting and purifying the tail gas containing _SO2 of step (3) gained, and solid reduction product is calcium ferrite, and purity is 87 wt%;

(5) In embodiment two, monitor the _SO2 concentration of tail gas with flue gas analyzer, its volume percent content≥15%, calculate the decomposition rate of phosphogypsum to be 95%, the decomposition rate of pyrite to be 99%, titanium The decomposition rate of white waste slag green vitriol is 98%.

Embodiment Three

Mix finely ground pyrite below 250 μm, titanium white waste slag green vitriol, and phosphogypsum. The active ingredient calcium sulfate molar ratio is 1:3:4;

(2) The mixture is pressed into tablets and put into the rotary kiln;

(3) Roast the pellets at 1200 °C for 120 min under a nitrogen protective atmosphere to obtain SO ₂ tail gas and solid reduction products;

(4) send into sulfuric acid system to prepare sulfuric acid finished product after dedusting and purifying the tail gas containing _SO2 of step (3) gained, and solid reduction product is calcium ferrite, and purity is 79 wt%;

(5) In embodiment three, monitor the _SO2 concentration of tail gas with flue gas analyzer, its volume percentage ≥ 15%, calculate the decomposition rate of phosphogypsum to be 90%, the decomposition rate of pyrite to be 98%, titanium The decomposition rate of white waste slag green vitriol is 98%.

Embodiment four

(1) Mix finely ground pyrite below 150 μm, titanium white waste slag vitriol, and phosphogypsum, the active ingredient ferrous disulfide in pyrite, the active ingredient ferrous sulfate in titanium white slag green vitriol The molar ratio of calcium sulfate, the active ingredient in phosphogypsum, is 1:2:3;

(2) The mixture is pressed into tablets and put into the rotary kiln;

(3) Roast the pellets at 800 °C for 120 min under a nitrogen protective atmosphere to obtain SO ₂ tail gas and solid reduction products;

(4) send into sulfuric acid system to prepare sulfuric acid finished product after dedusting and purifying the tail gas containing _SO2 of step (3) gained, and solid reduction product is calcium ferrite, and purity is 50 wt%;

(5) in embodiment four, monitor the _SO2 concentration of tail gas with flue gas analyzer, its volume percent content≥10%, calculate the decomposition rate of phosphogypsum to be 90%, the decomposition rate of pyrite to be 98%, titanium The decomposition rate of white waste slag green vitriol is 90%.

Embodiment five

(1) Mix finely ground pyrite below 250 μm, titanium white waste slag greenite, and phosphogypsum, the active ingredient ferrous disulfide in pyrite, the active ingredient in titanium white waste slag greenite ferrous sulfate The molar ratio of calcium sulfate, the active ingredient in phosphogypsum, is 1:2:3;

(2) The mixture is pressed into tablets and put into the rotary kiln;

(3) Roast the pellets at 1200 °C for 90 min under a nitrogen protective atmosphere to obtain SO ₂ tail gas and solid reduction products;

(4) send into sulfuric acid system to prepare sulfuric acid finished product after dedusting and purifying the tail gas containing _SO2 of step (3) gained, and solid reduction product is calcium ferrite, and purity is 81 wt%;

(5) In embodiment five, monitor the _SO2 concentration of tail gas with flue gas analyzer, its volume percent content≥15%, calculate the decomposition rate of phosphogypsum to be 95%, the decomposition rate of pyrite to be 99%, titanium The decomposition rate of white waste slag green vitriol is 97%.

Embodiment six

(1) Mix finely ground pyrite below 500 μm, titanium white waste slag vitriol, and phosphogypsum, the active ingredient ferrous disulfide in pyrite, and the active ingredient ferrous sulfate in titanium white slag green vitriol The molar ratio of calcium sulfate, the active ingredient in phosphogypsum, is 1:2:3;

(2) The mixture is pressed into tablets and put into the rotary kiln;

(3) Roast the pellets at 900 °C for 180 min under a nitrogen protective atmosphere to obtain SO ₂ tail gas and solid reduction products;

(4) send into sulfuric acid system to prepare sulfuric acid finished product after dedusting and purifying the tail gas containing _SO2 of step (3) gained, and solid reduction product is calcium ferrite, and purity is, and purity is 63 wt%;

(5) In embodiment six, use a _flue gas analyzer to monitor the SO concentration of the tail gas, and its volume percentage is ≥ 15%, and the calculated decomposition rate of phosphogypsum is 90%, and the decomposition rate of pyrite is 98%. The decomposition rate of white waste slag green vitriol is 96%.

Claims (6)

1. A method utilizing pyrite, titanium white waste slag greenite, phosphogypsum to prepare sulfuric acid and calcium ferrite simultaneously, is characterized in that, comprises the steps: (1) pyrite, titanium White waste slag green vitriol and phosphogypsum are evenly mixed in a certain proportion; (2) after the mixture is pressed into tablets or directly react the mixture at a certain temperature for a certain period of time to obtain a solid reduction product and tail gas containing _SO2 ; the obtained solid reduction product can be As a pre-melted steelmaking slagging agent; (3) the _SO2- containing tail gas obtained in step (2) is dedusted and purified, and then sent to a sulfuric acid system to prepare sulfuric acid finished products. 2. according to claim 1, utilize pyrite, titanium white waste slag vitriol, phosphogypsum to prepare simultaneously the method for sulfuric acid and calcium ferrite, it is characterized in that the certain granularity described in step 1 is 1～500 μ m. 3. according to claim 1, utilize pyrite, titanium white waste slag green vitriol, phosphogypsum to prepare the method for sulfuric acid and calcium ferrite simultaneously, it is characterized in that ferrous disulfide in the pyrite described in step 1: sulfuric acid in the green vitriol The molar ratio of ferrous iron:calcium sulfate in phosphogypsum is 1:1~4:1~5. 4. according to claim 1, utilize pyrite, titanium white waste slag green vitriol, phosphogypsum to prepare the method for sulfuric acid and calcium ferrite simultaneously, it is characterized in that the reaction equipment described in step 2 is fluidized bed, fixed bed, rotary kiln or One of the shaft kilns. 5. according to claim 1, utilize pyrite, titanium white waste slag vitriol, phosphogypsum to prepare the method for sulfuric acid and calcium ferrite simultaneously, it is characterized in that the non-oxidizing atmosphere described in step 3 is nitrogen, carbon monoxide, sulfur dioxide, carbon dioxide at least one. 6. According to claim 1, the method for preparing sulfuric acid and calcium ferrite simultaneously by using pyrite, titanium white waste slag vitriol, and phosphogypsum is characterized in that the roasting temperature described in step 3 is 800～1150 °C, and the heating rate is 3～ 10 ℃, the roasting time is 30-240 min.