CN1245334C - Production process of ferrous sulfate heptahydrate from magnetite - Google Patents

Abstract

The invention discloses a process for producing ferrous sulfate heptahydrate from magnetite. The process is to crush the magnetite, grind it into 80-100 mesh, and select the ore powder with T _Fe > 64%. , carry out the two-step process of acid dissolution and reduction, that is, leaching ore powder with sulfuric acid to generate ferric sulfate solution→reduction of eluate→low temperature crystallization of reducing solution→vacuum drying of ferrous sulfate heptahydrate to obtain heptahydrate with a content of 96%. Ferrous sulfate. The invention uses magnetite to produce ferrous sulfate heptahydrate, the raw material reserves are abundant, the price is cheap and easy to obtain, the production process has no environmental pollution, and is suitable for large-scale industrial production. Ferrous sulfate heptahydrate is widely used in medicine, pesticide, feed and sewage treatment and other industries. The product of the invention has reached the first-class product of the national standard GB10531-89 industrial water treatment agent, which broadens the new way for the application of magnetite in the chemical industry.

Description

Production process of ferrous sulfate heptahydrate from magnetite

technical field

The invention belongs to the field of inorganic salts, and relates to a production process of ferrous sulfate heptahydrate, in particular to a process for producing ferrous sulfate heptahydrate by using magnetite as a raw material and adopting an acid dissolution-reduction two-step method.

Background technique

The production method of ferrous sulfate heptahydrate used in industry has two kinds at present: the first kind is iron filings-sulfuric acid method to produce ferrous sulfate heptahydrate, and its production technology is sulfuric acid and iron filings reaction, through precipitation, crystallization, dehydration Get ferrous sulfate. Its chemical reaction is as follows:

The second is the production of ferrous sulfate heptahydrate by the titanium dioxide by-product method. The production process is to decompose ilmenite with sulfuric acid to generate FeSO ₄ and Fe ₂ (SO ₄ ) ₃ , in which the ferric iron is reduced with iron wire and frozen and crystallized. , the by-product FeSO ₄ ·7H ₂ O can be obtained, and its chemical reaction is as follows:

The problem that above-mentioned two kinds of production methods exist is: iron filings-sulfuric acid method produces ferrous sulfate heptahydrate, and its raw material iron filings price is higher, is subject to the fluctuation of steel price, and its source is limited, is not suitable for large-scale industrialized production; Titanium The production of ferrous sulfate heptahydrate by the white by-product method consumes a large amount of sulfuric acid, and the waste acid, waste water, waste residue and waste gas discharged during the production process seriously pollute the environment, and the impurity content of the product ferrous sulfate heptahydrate is relatively high, and the grade of the product lower.

Natural magnetite is mainly used in iron and steel smelting industry as a raw material for blast furnace refining pig iron. Ferrous sulfate heptahydrate, commonly known as green vitriol, is widely used in medicine, pesticide, feed and sewage treatment and other industries.

Contents of the invention

The present invention is mainly aimed at the high price and limited source of raw material iron filings in the existing production process of ferrous sulfate heptahydrate, which is not suitable for large-scale industrial production, and the product has high impurity content, low grade and waste water and waste gas discharged during production. , the problem of serious environmental pollution by waste residues, providing a process for producing ferrous sulfate heptahydrate from magnetite that is cheap and easy to get, suitable for large-scale industrial production, and has no environmental pollution.

The present invention solves the above-mentioned problems, and the technical solution to achieve the above-mentioned purpose is to mechanically crush the magnetite ore, grind it into 80-100 mesh, and select ore powder with T _Fe >64%; followed by adding industrial Sulfuric acid reacts with _Fe3O4 in mineral powder to produce ferric sulfate eluate, which is filtered and diluted with water; finally, ferric sulfate _in the diluted eluate is reduced to ferrous sulfate with iron filings, filtered and used at low temperature Ferrous sulfate heptahydrate crystals are precipitated from the reducing solution, and the crystals are separated and vacuum-dried to obtain ferrous sulfate heptahydrate.

Wherein, the raw material ratio of described acid-dissolving _reaction is that the molar ratio of industrial sulfuric acid and _Fe3O4 in mineral powder is 1:5; The optimal process condition of described acid-dissolving reaction is: sulfuric acid concentration is 40% , the reaction temperature is 100 DEG C, the reaction time is 1.5hr, and the stripping rate of magnetite is more than 96%; the acid-dissolution reaction generates ferric sulfate stripping solution, which is filtered and diluted with water to 23～24 ° Be ', and then carried out Reduction reaction; described reduction reaction operation condition is that when reaction temperature is 50 ℃～80 ℃, reaction time is 2.0hr, high iron is reduced to ferrous iron and can reach 100%; The temperature of described vacuum drying ferrous sulfate heptahydrate is ≤65℃, vacuum degree is 13.33KPa, drying time is 2.0hr.

The innovation of the present invention implementing the above-mentioned technical scheme is: replace iron filings with magnetite powder to produce ferrous sulfate heptahydrate, the raw material reserves are abundant, the price is low, and it is suitable for large-scale industrial production, and the proven reserves in 90 years have 50120Mt , of which industrial reserves account for 67.9% of the total reserves, ranking first in the world; while the output of iron filings from mechanical processing of parts is limited, which is not suitable for large-scale continuous production. The raw material cost of the invention is low, and the cost of the raw material is reduced by 45% based on the comparable price. The present invention proposes a two-step process of acid dissolution and reduction, which overcomes the serious pollution of the environment caused by a large amount of waste water, waste gas and waste residues existing in the titanium dioxide by-product process; and the ferrous sulfate heptahydrate produced by this process The product has high purity and low impurity content, and is a first-class industrial water treatment agent that meets the national standard GB10531-89. The technical quality indicators of the product are as follows in Table 1 and Table 2:

Table 1. Product quality technical indicators Element or compound name content(%) measured value National standard GB10531-89 For drinking water treatment For industrial water treatment Superior product First grade Qualified product Superior product First grade Qualified product Ferrous sulfate (FeSO ₄ 7H ₂ O) content, % ≥ 95.68 97.0 94.0 90.0 97.0 94.0 90.0 Titanium dioxide (TiO ₂ ) content, ≤ 0.0135 0.5 0.5 0.75 0.5 0.5 0.75 Water insoluble content, % ≤ 0.0000 0.2 0.5 0.75 0.2 0.5 0.75 Free acid (calculated as H ₂ SO ₄ ) ≤ 0.6350 0.35 1.0 2.0 - - - Arsenic (As), % ≤ 0.000012 0.0005 0.0005 0.0005 - - - Heavy metal (as Pb)% ≤ 0.00049 0.002 0.002 0.002 - - -

Table 2. Trace element content of products Unit: ug/g＝10 ^-6 (ppm)＝10 ^-4 % element Pb Zn Cu As mn Si Ca Mg content 4.9 8.2 17.5 0.12 31.6 8.4 12.7 0.8

Detailed ways

Below in conjunction with embodiment the present invention is described in further detail:

Get the magnetite produced in Ekou, Shanxi as the raw material for producing ferrous sulfate heptahydrate, through mechanical crushing, ore grinding, it will be 100 mesh, and be selected into 65% ore powder with methods such as magnetic separation or flotation, and use Sulfuric acid-phosphoric acid mixed acid decomposition method and potassium dichromate volumetric method were used to determine the content of total iron and ferrous iron in Table 1:

Table 1 Iron content of Shanxi Ekou magnetite powder mineral name Total Iron T _Fe % FeO% _{Fe2O3 %} Shanxi Ekou magnetite powder 63.56 27.79 59.99

Magnetite powder and industrial sulfuric acid are raw materials to carry out the following steps successively:

(1) acid soluble

According to the molar ratio of Fe in the magnetite powder O ₄ and industrial sulfuric acid is 1: 5, adding concentration is _the sulfuric acid of 40% in the magnetite powder, reacted 1.5 hours under reaction temperature 100 ℃, make the magnetite Iron oxides of various valence states can be dissociated in the solution, and the dissolution rate is over 96%. The chemical reaction in the acid dissolution process is:

(2) Restore

Heat the ferric sulfate solution that has been filtered and diluted to 23-24Bé (specific gravity: 1.1896-1.1995) to 50°C-80°C and put in excess reducing agent iron filings to perform the following reduction reaction:

The reduction reaction takes about 2.0 hr, and the reduction of ferrous Fe ³⁺ to ferrous Fe ²⁺ can reach 100% (red is not indicated by ammonium thiocyanate). The reduction process simultaneously carries out the following reactions:

(3) crystallization

The ferrous sulfate reducing solution crystallizes from the solution at about 0°C to precipitate ferrous sulfate heptahydrate crystals, that is, green vitriol:

The concentration of ferrous sulfate in the reducing solution is very high. When it reaches 2.3-2.6mol/l (35-40%), light green ferrous sulfate crystals can be crystallized at normal temperature. In order to increase the yield of ferrous sulfate, referring to the solubility data of ferrous sulfate in water, the method of freezing the reducing solution to 0°C is beneficial to the yield, not only can quickly crystallize ferrous sulfate heptahydrate, but the amount of mother liquor is small, and the mother liquor The residual amount of the product is also less. In this way, the crystallization mother liquor can be directly sent to the acid preparation section for diluting concentrated sulfuric acid. If natural crystallization is adopted, first, it takes a long time and occupies a large area of the crystallization pool; second, the summer temperature is high, the crystals precipitated are few, and the residual amount of the product in the mother liquor is high, so it is not suitable as a diluent for the pickling solution, and the mother liquor must be distilled twice. Concentration and crystallization.

(4) vacuum drying

The precipitated ferrous sulfate heptahydrate crystals contain residual mother liquor after liquid-solid separation. Because ferrous sulfate heptahydrate is easy to weather in dry air, it is easy to oxidize into brown basic ferric sulfate in humid air. When heated to 56.6°C, it changes from heptahydrate to tetrahydrate, and then turns into monohydrate at 64.4°C "It is known that ordinary drying at 100°C will result in monohydrate, so vacuum drying at a temperature lower than ≤65°C and a vacuum degree of 13.332Kpa for 2.0hr will yield ferrous sulfate heptahydrate.

Claims (6)

1. produce iron vitriol technology from magnetite, it is characterized in that with magnetic iron ore through Mechanical Crushing, ore grinding is processed as 80～100 orders, and selected to T _Fe＞64% breeze; Next is the Fe that adds in breeze in industrial sulphuric acid and the breeze ₃O ₄Carry out sour molten reaction and generate the ferric sulphate dissolution fluid, filter and dilute with water; Ferric sulphate in the dissolution fluid after will diluting with iron filings at last is reduced to ferrous sulfate, filters also to make reduced liquid separate out the iron vitriol crystallization at low temperatures, and fractional crystallization also carries out vacuum-drying, promptly gets iron vitriol.

2. according to claim 1 from magnetite production iron vitriol technology, the proportioning raw materials that it is characterized in that sour molten reaction is the Fe in industrial sulphuric acid and the breeze ₃O ₄Mol ratio be 1: 5.

3. according to claim 1ly produce iron vitriol technology from magnetite, it is characterized in that the optimum process condition of sour molten reaction is: sulfuric acid concentration is 40%, temperature of reaction is that 100 ℃, reaction times are 1.5hr, and the solubility rate of magnetite is more than 96%.

4. according to claim 1 from magnetite production iron vitriol technology, it is characterized in that sour molten reaction generates the ferric sulphate dissolution fluid, filter and be diluted with water to 23～24 ° of Be ', carry out reduction reaction again.

5. according to claim 1ly produce iron vitriol technology from magnetite, it is characterized in that the reduction reaction operational condition is: temperature of reaction is 50 ℃～80 ℃, reaction times when being 2.0hr, and high ferro is reduced to and ferrously reaches 100%.

6. according to claim 1ly produce iron vitriol technology from magnetite, it is characterized in that the temperature of vacuum-drying iron vitriol is≤65 ℃, vacuum tightness is that 13.33KPa, time of drying are 2.0hr.