CS258507B1 - Method of coagulating agent production - Google Patents

Abstract

Process for producing a coagulating agent

Description

The invention relates to a process for the production of a coagulating agent.

Coagulants based on iron are generally soluble trivalent iron salts and a mineral acid: e.g. FeClj ferric chloride, ferric sulphate Fe ₂ (SO _{4> 3-sulfate,} ferric chloride FeClSO-like.

The coagulating agent may also be an iron (II) salt, such as FeSO ₄ -7 H ₂ O ferrous sulfate heptahydrate, which is dosed simultaneously with the oxidizing agent, such as chlorine gas, when treating the water. Coagulating agents are most often produced by the action of an oxidizing agent

to the raw material containing iron. E.g. reactions 6 FeCl ₂ + 3 d ₂ = 6 FeCl ₃ (1) 6 Fed ₃ + 2 Fe = 6 FeCl ₂ (2) 2 Fe + 3 ^C1 2 = 2 F.eCl ₃ (3)

is produced by ferric chloride or by reaction

FeSO ₄ + Cl ₂ = 2 FeClSO ₄ (4) produces ferric sulfate. Ferric sulphate can also be produced by dissolving a suitable oxide or ferric hydroxide in sulfuric acid

Fe (OH) ₃ + 3 H ₂ SO ₄ = Fe ₂ (SO ₄ ) ₃ + 6 H ₂ O

Ferric oxides that are formed by thermal decomposition (e.g., the Ruthner process or thermal pigment production) are generally poorly soluble in acids and require high acid concentrations, long dissolution times, and high dissolution temperatures. In addition, the antisense iron oxide formed by the thermal decomposition of chlorides or sulphates is redissolved in the acid.

It is known that heaps with waste green vitriol, falling away! in the production of titanium dioxide, today they contain two basic solid materials, depending on the time of storage more or less oxidized green vitriol and waste, the so-called acidic systems, which is essentially FeSO ₄ .H ₂ O monohydrate containing 6 to 15% free sulfuric acid and solution in the lagoons of the landfill, containing! besides iron sulphates also a variable proportion of free sulfuric acid.

The natural process that takes place on the heap is essentially the oxidation of green vitriol by air oxygen 4 FeSO ₄ + O ₂ + 2 H ₂ O = 4 FeOHSO ₄ (6). The basic ferric sulphate can be according to the equation

Consider FeOHSO ₄ = Fe ₂ (SO ₄ ) ₃ + Fe (OH) ₃ (7) as a mixture of ferric sulphate and ferric hydroxide.

However, this iron (III) hydroxide is not formed by the thermal process and is therefore readily soluble at normal temperature even in dilute sulfuric acid. Thus, if iron (III) hydroxide is contacted with free sulfuric acid (eg from acidic systems or lagoon solutions), the above reaction (5) will result in additional ferric sulfate Fe ₂ (SG ₄ ) ₃ . However, a heap of green vitriol is an open system with waste green vitriol, acid waste systems and rainwater. Thus, the solutions formed on the heap still contain a higher concentration of divalent iron, a higher concentration of free sulfuric acid and a lower concentration of total iron than a conventional coagulation solution. Meanwhile, the resulting solutions are periodically drained at a neutralization station where they are neutralized with lime.

The solution to the production of a trivalent iron coagulating agent from the material contained in the open landfill of waste green vitriol and the acid systems of the titanium dioxide production according to the invention appears to be a method which consists in spraying the solid material of these landfills with the liquid phase in such proportions of components that the resulting solution contains at least 90% of the initially supplied iron, but not more than 10 g / l of free sulfuric acid, the liquid phase circulating in the closed system through the solid material until the total iron content in the circulating liquid phase increases 2+ above 150 g / l Fe and at the same time the content of Fe ions drops below 10 g / l. The coagulating agent can be produced in the presence of a culture of Thiobacillus ferrooxidans.

The process according to the invention does not require high investment costs and operating costs are reduced to the operator's wage and circulation pump drive.

The process according to the invention essentially consists in making the open system a closed system. This means that a suitable amount of waste green vitriol from the heap is introduced into a suitable device (eg a vessel equipped with a filter baffle) so that the ferric hydroxide formed by it or further oxidation by air oxygen roughly corresponds to the content of free sulfuric acid contained in simultaneously added acidic systems. and the solution from the lagoons, the oxidation of the ferrous sulphate contained in the acid systems and the solution from the lagoons should be similarly envisaged. The liquid phase is soaked through the solid phase layer on the filter partition and, after separation, the filter partition is collected at the bottom of the container. From there it is again pumped and sprayed onto the solid phase surface in the vessel. At the same time, oxidation by air oxygen occurs. The process is continued until the composition of the liquid phase is suitable for use as a coagulating agent. If the solids disappear in the system and the solution is not sufficiently concentrated or too acidic, either oxidized green vitriol or a mixture thereof with acidic systems shall be added. If there is enough solid phase left in the plant but the total iron concentration stops rising, which is accompanied by the disappearance of free sulfuric acid, acidic systems need to be added to the system. The solution was then further circulated.

The circulation of the solution can be adapted to occur automatically. It is preferred that the sprinkling of the entire surface is not always flooded, i.e. the total pumping rate is lower than the total filtration rate. The starting and stopping of the pump should preferably be controlled automatically according to the liquid phase content at the bottom of the pump container or reservoir. The whole station can thus work automatically without operator with occasional monitoring of pump operation, analytical control of solution composition and checking, eventually replenishment of solid phase content. In this way it is possible to process even the oldest heavily polluted parts of old heaps. The washed, sulphate and iron oxides substantially free of residues can then be deposited in a separate landfill. An acceleration of the oxidation process of up to two orders of magnitude is achieved in the process according to the invention by adding a suitable amount of a culture of Thiobacillus ferrooxidans to the system.

He did

We put 419 kg of material from an old heavily oxidized heap of green vitriol into an open container, eg nucha with the following composition:

FeSO. 18%

Fe ₂ (SO ₄ ) ₃ 20

TiOS, O ₄ 1%

MgSO ₄ 2%

Fe (OH) ₃ 13%

H ₂ O 46% in total and 161 kg of acidic systems with a composition of e.g.

FeSO ₄ 45 % Fe ₂ (SO ₄ ) '3 ¹ % tíoso ₄ 3 4 MgSO ₄ 7 4 H ₂ S ° ₄ 17 4 h ₂ o 27 Mar: % total 100 ALIGN! 4

Spray 411 kg of strongly acidic lagoon solution on the layer of this material, soak it through the material and circulate it again with the following composition:

FeSO ₄ 5 4

Fe ₂ (SO ₄ ) ₃ 5%

TiOSO. 2% '

MgSO ₄ 2%

H ₂ SO ₄ 25%

H ₂ 0 61 4 total 100%

After a period of circulation and uptake of 9 kg of air oxygen, 1000 kg of a coagulation solution of the following composition are produced:

^Fe 2 ^(SO 4> 3 43.0 % TÍOSO ₄ 1.7 4 MgSO ₄ 2.9 4 h ₂ ° 52.4 4 total 100.0 4

which contains 12% (180 g / l) Fe? ⁺ .

We do not consider solid impurities that do not participate in the reaction and remain on the filter screen and assume that the amount of water that evaporates during circulation is equal to the amount of water entering the system in the form of atmospheric precipitation.

Example 2

We put 557 kg of heap material (eg green vitriol) for a long time in an open container, eg nucha:

FeSO ₄ 47.3 % ^Fe 2 ^(SO 4> 3 0.7 4 tíoso ₄ 1,2 % MgSO ₄ 3.1 4 »2 ° 47.7 4

a total of 100.0% and 44 kg of acidic systems with the composition as in example 1. Spray 383 kg of medium acid lagoon solution on the layer of this material, soak the material and recirculate it, for example:

FeSO ₄ 7.8 4 ^Fe 2 ^<SO 4> 3 3.5 4 TiOSO ₄ 2,0 4 MgSO ₄ 2,0 4 ^H 2 ^SO 4 7.0 4 h ₂ o 77.7 4

After a certain solution with a circulation and uptake time of 16 kg of atmospheric oxygen, 1000 kg of coagulation is formed;

Fe ₂ (SO ₄ ) ₃ 43.0% TiOSO ^ 1.6% MgSO ₄ 2.8 »H ₂ 0 52.6» total 100.0 »under the same assumptions as in; Example 1.

Claims (2)

object of the invention 1. A process for producing a trivalent iron coagulating agent from a material contained in open dumps of waste green vitriol and acid systems from titanium dioxide production, characterized in that the solid material of such landfills is sprayed with the liquid phase of such landfills with air in such a proportion of individual components that the resulting solution contained at least 90% of the initially supplied iron but no more than 10 g / l of free sulfuric acid, the liquid phase circulating in the closed system through the solid material until the total 2+ iron content in the circulating liquid phase rises above 150 g / 1 Fe and the current Fe content drops below 10 g / l. 2. A method according to claim 1, characterized in that it is carried out in the presence of a culture of Thiobacillus ferrooxidans.