JPH07121808B2 - Purification method of hydrochloric acid pickling waste liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention purifies a hydrochloric acid pickling waste liquid for removing a small amount of Al, Cr, Cu, P, etc., which are impurities contained in a hydrochloric acid pickling waste liquid of steel. Is the way. When the hydrochloric acid pickling waste liquid after removing these impurities (hereinafter referred to as "refining waste liquid") is roasted or decalcified and then roasted, iron oxide powder with less impurities is obtained,
This iron oxide powder is a desirable raw material in terms of the performance of soft ferrite. Further, a high-purity iron chloride crystal can be produced from this purified waste liquid or a solution which has been further subjected to desiliconization through a crystallization step. Furthermore, the above-mentioned iron oxide powder containing a small amount of impurities is also used for producing high-purity iron powder by a method such as reducing the iron oxide powder in a high-temperature reducing atmosphere.

[Prior Art] For example, in order to produce high-purity iron oxide powder for soft ferrite, it is desirable to remove Al, Cr, Cu, P, etc. in the hydrochloric acid pickling waste liquid, but these impure elements should be removed at once. There is no conventional technique for reducing and removing.

[Problems to be Solved by the Invention] The present invention provides a simple method for Al, Cr, Cu, P in a hydrochloric acid pickling waste liquid.
The present invention relates to a method for purifying a hydrochloric acid pickling waste liquid, which collectively removes impure elements such as.

[Means and Actions for Solving Problems] The present invention is directed to the addition of iron to a hydrochloric acid pickling waste liquid generated in the descaling step of the steel by hydrochloric acid pickling, without adding heat to concentrate Al, This is a purification method of a hydrochloric acid pickling waste liquid, in which most of Cr, Cu, and P are collectively separated and removed as insolubilized products.

The hydrochloric acid pickling waste solution to which iron is added in the present invention is a solution which is received from a pickling factory or is a heat-retaining solution, and is, for example,
It is a solution with a free hydrochloric acid concentration of 1.5%, an iron chloride content of 26.5%, and a temperature of 80 ° C, which is described in the stock solution column of the table. When iron is added after heating or concentrating this hydrochloric acid pickling waste solution, the problems described below occur. To use.

Next, in the present invention, iron is added to this hydrochloric acid pickling waste liquid. Appropriate iron to be added is fine steel wire, thin steel plate, iron powder or the like.

Table 1 shows that Al in the purified waste liquid after the iron was dissolved in the hydrochloric acid pickling waste liquid having a FeCl ₂ concentration of 26.5% to adjust the PH and the insoluble matter was separated and removed by the No. 5C filter paper for analysis. , Cr, Cu, P, Si concentration.

The present invention is based on the discovery that when iron is added to a hydrochloric acid pickling waste liquid to deplete free hydrochloric acid and the pH of the liquid is appropriately raised, Al, Cr, Cu, and P collectively become insoluble substances. It is easily conceivable that Al, Cr, Cu, etc. will produce insoluble hydroxides when alkali is added to the hydrochloric acid pickling waste liquid to raise the pH to near neutrality. It becomes an oxide and becomes insoluble in large quantities. In the present invention, PH can be appropriately increased by adding iron, and P can be insolubilized together with Al, Cr, and Cu to be collectively removed. This is considered to be due to the following reasons. That is, since the pH of the hydrochloric acid pickling waste liquid is low, in the state of the hydrochloric acid pickling waste liquid, P in the solution is mainly undissociated phosphoric acid or primary phosphate ion, but phosphoric acid or primary phosphate metal salt is It is water soluble. When iron is added to raise the pH, dissociation of the first phosphate ion proceeds to produce the second phosphate ion and the third phosphate ion, but these metal salts are insoluble,
It can be removed as a precipitate.

In Table 1, the aging time 0 is an example in which iron was added to the hydrochloric acid pickling waste liquid to adjust the pH to a predetermined level, and then the insoluble matter in the solution was fractionated within 1 hour, and the aging time 2 was similarly treated. This is an example in which the insoluble matter in the solution was fractionated after 2 hours, and the aging time 6 was similarly fractionated after 6 hours. As shown in Table 1, Al, Cr, Cu, P in the refined waste liquid can be reduced by increasing the pH, and further reduced by increasing the aging time. it can. As shown in Table 1, Si cannot be removed sufficiently with PH of 3.5 or less, and if PH is further increased, a large amount of iron insoluble matter is generated and it takes a long time to separate the insoluble matter. In order to further reduce the amount of oxygen, a separate desiliconizing means as described later is used.

Next, as an application example of the present invention, a case where the present invention is applied to a known process of roasting a hydrochloric acid pickling waste liquid of steel to recover hydrochloric acid and iron oxide will be described.

FIG. 1 is a diagram showing an example of a known process of a method for recovering a hydrochloric acid pickling waste liquid. Reference numeral 1 is a hydrochloric acid pickling waste liquid, and 2 is a contact tower of the hydrochloric acid pickling waste liquid and the hot gas 3 produced by roasting. Since the hot gas 3 produced by roasting is a gas having a high HCl gas concentration, as will be described later, the hydrochloric acid pickling waste liquid has a high concentration of free hydrochloric acid in the contact tower 2 and is simultaneously heated and concentrated. The heat-concentrated liquid 4 is thermally decomposed in the roasting furnace 5 into the hot gas 3 containing the iron oxide powder 6 and having a high HCl gas concentration. Most of the iron oxide powder 6 is separated and recovered from the hot gas 3 by the dust collector 7, and the hot gas 3 is supplied to the contact tower 2. The hot gas 3 is introduced into the hydrochloric acid recovery tower 8 after coming into contact with the hydrochloric acid pickling waste liquid 1 in the contact tower,
HCl gas is recovered as hydrochloric acid 10 by water injection 9. 1
Reference numeral 12 is a hot-air stove that supplies hot air to the roasting furnace 5, and 12 is a fluidized bed as an example of the roasting process.

In this process, the purification method of the hydrochloric acid pickling waste liquid of the present invention is carried out at the step A in FIG. When producing iron oxide powder with low Si, since the removal of Si is insufficient in the refined waste liquid of the present invention,
Strongly heat and concentrate in the contact tower 2 to insolubilize Si, and then, as shown in FIG. 1B.
At the stage of, the insoluble matter is separated and removed. Table 2 shows the purified waste liquid 1 in which PH was adjusted to 2.5 at the stage of FIG. 1A to remove the insoluble matter, and the purified waste fluid 1 was further strongly heated and concentrated in the contact tower 2 to remove the insoluble matter and the purified waste fluid 2 was removed. It is an example of a component.

Although Si in the hydrochloric acid pickling waste liquid is not sufficiently removed by the present invention alone, it can be sufficiently removed by further performing fractional removal after the heat concentration which is usually performed in the operation. The inventors of the present invention tried to add iron to the solution 4 which had been heated and concentrated in the step B, without adding iron in the step A of FIG. 1, but the solution was heated and concentrated in the contact tower 2. At the same time, the concentration of free hydrochloric acid has increased due to contact with hot gas 3 having a high HCl concentration, so a large amount of iron needs to be added to adjust the PH, and a large amount of insoluble matter is also generated. It was found that the separation of products was inefficient and the efficiency of hydrochloric acid recovery was poor. Also, in the step A of FIG. 1, without adding iron,
It is also possible to separate or heat the hydrochloric acid pickling waste liquid in an atmosphere facility for oxygen or oxygen-containing gas that does not contain HCl gas separately provided, and add iron to this solution to form an insoluble matter and separate it. However, it is not economical in terms of thermal efficiency and equipment efficiency because it requires a separate heating or heating / concentrating device, which is not included in the normal hydrochloric acid pickling waste liquid recovery process.

[Effects of the Invention] According to the present invention, impurities such as Al, Cr, Cu and P in hydrochloric acid pickling waste liquid can be collectively removed by a simple method.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a process for recovering hydrochloric acid and iron oxide from a hydrochloric acid pickling waste liquid.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsunobu Okutani 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Teruo Mori 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Incorporated (56) Reference JP 60-54907 (JP, A) JP 60-65709 (JP, A) JP 61-44814 (JP, B2)

Claims (1)

[Claims] 1. A hydrochloric acid pickling waste liquid generated in a descaling step of hydrochloric acid pickling of iron and steel is added to this without being concentrated by heating, and most of Al, Cr, Cu, P contained is insolubilized. A method for purifying a hydrochloric acid pickling waste liquid that separates and removes all at once.