JPS63315523A - Method for purifying aqueous solution of iron chloride - Google Patents

Abstract

PURPOSE:To efficiently purify an aqueous solution of iron chloride, by thermally concentrating the aqueous solution of iron chloride generated in acid cleaning of steel with hydrochloric acid with a roasting gas produced in a roasting step, insolubilizing and separating Si, adding iron, precipitating and separating Al, Cr, Cu, P, etc. CONSTITUTION:An aqueous solution of iron chloride 6 generated in acid cleaning of steel with hydrochloric acid is introduced from a storage tank 1 into a contact column 2, brought into contact with a roasting gas 3 produced in a roasting step in the latter stage and thermally concentrated to insolubilize Si components in the aqueous solution of iron chloride 6 and the obtained insolubilized Si substance 14 is separated in a separator 4. The resultant concentrate is subsequently introduced into a regulation tank 7 and iron is added to consume free hydrochloric acid in the concentrate and insolubilize Al, Cr, Cu and P components in the solution. An insolubilized substance 13 is then separated in a separator 8 to provide a purified solution of iron chloride 9, which is subsequently roasted in a roasting furnace 5 to recover both high-purity iron oxide powder 10 from the generated hot gas 3 in an electric dust collector 11 and the hydrochloric acid in a hydrochloric acid recovering column 12.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for roasting an aqueous iron chloride solution generated during hydrochloric acid pickling of steel, recovering hydrochloric acid, and obtaining high-purity iron oxide powder. , a method for purifying an aqueous iron chloride solution, more specifically, purifying Si, AΩ, and Cr from an aqueous iron chloride solution.

This invention relates to a method for removing Cu and P. Since the purified iron chloride aqueous solution has a low content of Si, AM + Cr, Cu, and P, by roasting it, a highly purified iron oxide powder suitable for producing soft ferrite, for example, can be obtained.

[Prior Art] A method of manufacturing iron oxide powder by roasting an aqueous iron chloride solution generated during hydrochloric acid pickling of steel is widely practiced. For example, soft ferrite is produced by mixing this iron oxide powder with other metal oxide powders and sintering them.
It is desirable to have a small amount of impurities such as Q, Cr, Cu, and P in order to economically produce soft ferrite with good performance. By concentrating the solution and reacting the concentrate with a metal such as iron, or by adding carbonate to the concentrate,
Alternatively, a method is shown in which the concentrated solution is adjusted to a circle size of 13 to 6 with NH, O) I, etc., and then filtered. However, if the concentrated liquid is reacted with metals such as iron without special measures, or if the PI-1 of the concentrated liquid is adjusted to 3 to 6, a large amount of iron hydroxide will be generated in suspension in the concentrated liquid. However, since clogging occurs during filtration, the filtration process requires an extremely long time and is difficult to implement industrially. Also, JP-A-60-54907 and JP-A-60-65709 are methods of concentrating a metal chloride solution, adding a divalent metal, and then filtering.
Similar to No. 9-1.99505, these methods require an extremely long time for filtration and are difficult to implement on an industrial scale. Furthermore, these methods have the disadvantage that not only filtration is difficult, but also the yield of iron oxide powder itself is reduced due to fractionation of insolubilized iron hydroxide.

[Problems to be Solved by the Invention] The present invention solves the problem of removing impurity components Si, AQ + Cr, Cu, This is a method for removing P, and the separation is industrially efficient.
This invention relates to a method for producing a raw iron chloride aqueous solution that can be implemented.

[Means for solving the problems] The present invention provides (1) Steel salt N! In the process of roasting the iron chloride aqueous solution generated during pickling to recover hydrochloric acid and iron oxide powder, the iron chloride aqueous solution is brought into contact with the roasting gas generated in the process and concentrated by heating to form the iron chloride aqueous solution. The first purification step involves insolubilizing and fractionating the Si component of , and then iron is added to the fractionated concentrate to consume free hydrochloric acid and remove AQ, C in the solution.
A method for purifying an aqueous iron chloride solution comprising a second stage purification step of insolubilizing and fractionating r, Cu, and P components, and (2) the fractionation in the first stage purification step is a fractionation by adsorption separation. The iron chloride aqueous solution described in (1) above is
There are six methods made by M.

In this specification, "fractionation" refers to separating insolubilized substances from a solution by filtration using a filter paper, filter cloth, etc., adsorption separation, centrifugation, etc.

Figure 1 is a diagram showing an example of the process flow of the present invention.
6 is a raw iron chloride aqueous solution, and 1 is its storage tank.

2 is a contact tower, in which the raw iron chloride aqueous solution 6 is brought into contact with the hot gas 3 produced by roasting and concentrated by heating. The heated and concentrated liquid is Si
The solution is sent to a fractionating device (for example, an adsorption separation device) 4, where the Si insolubilized material 14 generated by heating and concentration is separated and removed from the solution. The above is the first stage purification step of the present invention. The solution after removing the Si insolubilized material is sent to the adjustment tank 7, where iron is added. 8 is a filtration device (for example, a filtration device using filter cloth)
So, AQ, Cr, Cu.

Insolubilized substances 13 such as P are separated by filtration. SL, AQ,
The purified iron chloride solution 9 from which the insolubilized substances of Cr and CupPTP have been removed is roasted in a roasting furnace 5 to produce hot gas 3 and Si,^
Q.Cr.

The resulting high-purity iron oxide powder 10 has extremely low contents of Cu and P. 11 is an electrostatic precipitator that collects high-purity iron oxide powder.
12 is a hydrochloric acid recovery tower for recovering hydrochloric acid from the hot gas 3.

[Operation, Examples] In the present invention, the raw iron chloride aqueous solution 6 is heated and concentrated in the contact tower 2, and most of the Si in the raw iron chloride aqueous solution becomes insolubilized by this heating and concentration. The Si insolubilized material produced at this time is a colloidal insolubilized material.

Although separation is possible by ordinary filtration using filter paper, filter cloth, etc., if there are many insolubilized substances, clogging is likely to occur. Since adsorption separation hardly causes clogging, colloidal Si insolubilized substances can be efficiently separated and removed from the solution. As the adsorption separation device, for example, an adsorption tank filled with a mesh plate made of polyethylene fiber as an adsorption substrate is suitable.

In the adjustment tank 7, iron is added to the solution from which the Si insolubilized substances have been removed. This is to adjust Pl+ by consuming free hydrochloric acid in the solution. The amount of iron to be added is preferably such that the pH becomes 1 to 3. When the pH becomes high, iron precipitates are formed, making it difficult to separate the insolubilized substances in the subsequent process.

It is desirable to adjust the pH to a low level. In this way, even if the circle is adjusted to a low value, AO, Cr, Cu, P in the solution
becomes insolubilized. The reason why A(1, Cr, Cu, and P collectively becomes an insolubilized substance) is as follows.

The raw iron chloride aqueous solution of the present invention is a raw iron chloride aqueous solution containing P. The heated and concentrated solution was heated and concentrated by contacting the hot gas 3 with a high hydrochloric acid gas concentration; therefore, it contains a large amount of free hydrochloric acid and has a low pH. In this state, P in the solution mainly exists as undissociated phosphoric acid or monophosphoric acid ions, but phosphoric acid and metal salts of monophosphoric acid are water-soluble. When iron is added to raise the circle, phosphoric acid and primary phosphate ions dissociate to form secondary and tertiary phosphate ions, but the metal salts of these ions are insoluble and cannot be dissolved in solution. It combines with ions such as A Q + Cr, Cu, etc. in it to become an insolubilized substance.

Since the raw iron chloride aqueous solution has a relatively low concentration of AQ, Cr, Cu, and P, the crystal growth of these insolubilized substances is insufficient immediately after neutralization, but it is possible to stir the solution or provide an aging period. By doing so, the crystal growth of the insolubilized substance can be promoted and the effect of fractionation such as filtration can be improved.

The present invention is characterized in that the pH can be lowered because AQ, Cr, Cu, and P are made into insoluble phosphates.
Since + is low, there are few extra precipitates such as iron hydroxide, and it is easy to separate insolubilized substances.

In the present invention, the solution after heating and concentration is subjected to the first stage of fractionation before adding iron.
Since the insolubilized material is colloidal, unlike the insolubilized material mainly composed of phosphate produced by the subsequent addition of iron, this method is suitable for fractionating the colloidal insolubilized material,
For example, by pre-fractionating by adsorption separation, and then separating the insolubilized substances due to iron addition in the second stage,
Equipment efficiency and work efficiency can be improved.

A specific method of adsorption separation is to heat and concentrate a solution,
Pass through an adsorption layer filled with an adsorption substrate with a large surface area,
This is done by separating the insolubilized colloidal silicon6.
Suitable adsorption substrates are inorganic or organic molded bodies having a complex three-dimensional structure, mesh plates made of fibers, or spherical packings. For example, molded bodies or fibers made of polyvinyl chloride, polyester, polyacrylonitrile, polypropylene, etc. are inexpensive and suitable adsorption substrates. Considering only adsorption, the larger the surface area of the adsorption substrate, the more effective it is, but in order to maintain an effective passage rate even when adsorption has progressed to a certain extent, a certain void or passage area is required. In other words, the molded body has a surface area of 150 m per 1 m3 of filling volume.
For an adsorption substrate made of fibers, it is appropriate that the porosity is 70-95% and the fiber diameter is 0.05-0.5 mm.Colloidal silicon insolubilized material is a fluffy material with many voids. Since the particles are FA aqueous, the inside and surface of the particles are covered with water molecules in water.
It is easily adsorbed and stabilized on hydrophilic solid surfaces (metals, metal oxides, polar organic substances, etc.). On the other hand, it is adsorbed on the surface of aqueous solids (for example, non-polar organic substances, etc.) due to the action of coexisting bicomponent compounds (surface-active substances, etc.). In other words, the hydrophobic surface is quickly made hydrophilic by the bicomponent compound, and colloidal Si insolubilized material is adsorbed thereon.

Table 1 shows examples of the present invention, including FeCQ of raw iron chloride aqueous solution.
This is an example where the 2eA degree is 26%. This raw iron chloride aqueous solution was brought into contact with roasting gas and concentrated by heating to a volume of 62% (heated concentrated liquid in Table 1). The heated concentrated solution is stirred for about 5 hours in order to sufficiently generate colloidal silicon insolubilized matter, and then the colloid is separated by adsorption and separation.
Front skewer 1 Fractionation by adsorption separation *2 Fractionation using analytical No. 5C filter paper The do-shaped insolubilized matter was fractionated.

In this first stage purification, the concentration of impurities in the solution after fractionation is as shown in the first stage purification tank in Table 1, although Si is significantly reduced, AQ, Cr, Cu, The concentration of P was not much different from before separation, and almost no P was removed.

Fe was added to the solution after the first stage purification to adjust the circle 1 of the solution, and the concentration of impurities in the solution after the generated insolubilized matter was filtered off is shown in the second stage purification tank in Table 1. .

The pH was adjusted to various levels ranging from 1.0 to 3.5. In the table, ripened pears are solutions in which insolubilized substances were filtered out within 1 hour after the adjustment of Yen 1, and ripened solutions are solutions in which insolubilized substances were filtered out after 5 hours after pH adjustment.

As shown in Table 1, in the present invention, the concentration of impurities in the filtrate can be significantly reduced by providing an aging period after adjusting the pH and then filtering off the insolubilized substances.

That is, in the example in Table 1, in the case of ripening ants, it is sufficient to adjust circle 1 to 2.5, and Al1. Cr.

The concentrations of Cu and P are both l/ of the concentration in the heated concentrate.
10 or less, and the Si concentration further decreases in the second stage of purification to 1710, which is the concentration in the heated concentrated liquid.

In addition, in a solution with P)I of 2.5, there is little precipitation of iron hydroxide and most of the Si is removed in the first stage purification, so it is easy to separate the insolubilized substances in the second stage purification. Materials can be filtered efficiently and efficiently using filter paper, filter cloth, etc.

[Effect of the invention] According to the present invention, Si and AQ in the hydrochloric acid pickling waste solution.

By efficiently removing Cr, Cu, and P, a highly pure iron chloride aqueous solution can be obtained. By roasting this high-purity iron chloride aqueous solution, high-purity iron oxide powder suitable for producing soft ferrite can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the process flow of the present invention.

Claims (2)

[Claims] (1) In the process of roasting the iron chloride aqueous solution generated during hydrochloric acid pickling of steel to recover hydrochloric acid and iron oxide powder, the iron chloride aqueous solution is brought into contact with the roasting gas generated in the process and concentrated by heating. The first purification step is to insolubilize and separate the Si component in the iron chloride aqueous solution, and then iron is added to the separated concentrate to consume free hydrochloric acid in the solution and remove the Al in the solution.
A method for purifying an aqueous iron chloride solution, comprising a second purification step of insolubilizing and fractionating Cr, Cu, and P components. (2) Claim 1, wherein the separation in the first-stage purification step is separation by adsorption separation, and the separation in the second-stage purification step is filtration using filter paper, filter cloth, etc. Method for purifying iron chloride aqueous solution