JPS59169902A - Improvement in procedures for waste acid purification - Google Patents

Abstract

PURPOSE:The waste acid, after iron-pickling, is heated by heat-exchange with the oxygen-containing waste gas to effect the concentration of the waste acid to near the saturation point of iron chloride, thus the soluble silicon is insolubilized, filtered off, then pyrolysis is effected to recover high-purity iron oxide and hydrochloric acid. CONSTITUTION:The iron-pickling waste acid resulting from passing iron plates through the hydrochloric acid bath for pickling oxidized surfaces is brought into contact in the heat exchanger with the high-temperature oxygen-containing waste gas from the roaster to raise its temperature up to 60 deg.C to the boiling point, further, waste is circulated under contact with the high temperature gas and effect the concentration of the solution until the content of iron chloride reaches 35% to the saturation point. Consequently, the soluble silicon precipitates. After filtration, the filtrate is heated up in the range from the decomposition point of iron chloride to 950 deg.C to recover iron oxide of less than 0.007 SiO2/Fe2O3 and 2.9-2.4 compression density as well as high-purity hydrochloric acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment method for purifying iron picrin liquid and recovering highly pure iron oxide and hydrochloric acid.

The medium-normal iron biculin solution is a waste solution obtained by dissolving the oxide film by running an iron plate coil through hydrochloric acid pickling dτ. This waste acid is 21
It is a simple waste liquid containing about 26% FeCl2, free acid, and other impurities.

k (about 10% of 01, about 25% of FeCl□, about 2% of Fe013 (sometimes as much as 12%), and the balance H and Q.

The main impurities are Mn, Si, AI, K, Na,
Oa.

These ions are SOI+, C1, etc. This waste liquid is concentrated in a heat exchange tower, thermally decomposed in a roaster, and recovered as hydrochloric acid and iron oxide. ~0.03' (0,03~0.
01)%N aLQ =, o, o+ 01- 0.5~0.1 (0,01)% (3a
□ o, o+ ) H2Q O, 3~0.4 Values within 0 are for different fR hammers.

The above-mentioned conventional recovered acids and recovered iron oxides are supplied as they are for the deer industry. However, when the impurities contained in the above-mentioned iron oxide are used in, for example, ferrite magnetic materials, it is not possible to obtain properties as high as 1, which exhibits general properties.

Therefore, in the present invention, this waste acid has been successfully purified to a high degree by simply adding a few purification steps to the conventional citric acid recovery apparatus.

This will be explained below.

First, the waste acid is brought into contact with the high humidity gas discharged from the roaster in a heat exchange tower to be condensed. In general concept, waste acid and!
Oil temperature υ1 Designed to ensure even contact with gas ■1
70' considering the efficiency of hydrochloric acid absorption and heat exchange.
It is sent to the hydrochloric acid absorption tower as a gas near C.

When concentrated by such uniform heat exchange, S+20
14 or 5iC14 etc. are partially oxidized or hydrolyzed to 5
i202 (OH) Like 01! It becomes a substance whose J shape is determined by fL. However, it is difficult to completely remove such molecularly dispersed linear hydroxide even by ultrafiltration.

From the above, the present invention has a two-stage heat exchange mechanism,
The aluminum salt and the aluminum salt are dehydrated or the degree of polymerization is increased to form a Si20°(01-1)2 form or a similar insolubilized product or to grow in a chain form.

Therefore, in the present invention, the concentrate in the heat exchange tower is raised to about 80'C, and the concentration is increased to 40 to 45%, preferably at the crystallization size im. When the product is discharged at this temperature, dihydrate crystals are formed, and the high lIJ liquid is injected into pentathermal gas in the form of droplets or spray for heat exchange. In this case, it is preferable that m of the injected liquid droplet is equal to -1U of the gas amount (calorie amount). When the liquid before crystallization τJ is sprayed into the gas in this manner, it is dehydrated to a hydrated salt or anhydrous salt.

It is important that the droplets or spray come into contact with the high-temperature gas stream, and may be on the y1 side where the dispersion node is scattered. That is, the droplets from the scattering node may be used for heat exchange, and the anhydrous powder may be prevented from being sent to the hydrochloric acid absorption tower.

In short, this is a treatment method that consists of bringing some of the droplets of the uniformly distributed liquid in the heat exchange tower into contact with the main stream of the high-temperature gas stream. In such a method, if the adjustment method is incorrect, the gas flow will naturally be greatly disturbed, and a part of the uniform distribution will be disturbed, resulting in local heat torrent (channeling), which will also affect the efficiency of hydrochloric acid absorption and heat exchange. A phenomenon occurs. But the P of the fountain! It can be treated without problems if the droplets, mist, knots of spray nodes, splashes, etc. are evenly contacted with the main stream of high-temperature gas and are heat-exchanged with the spray liquid so that they are in a dehydrated state such as anhydrous salt or the like.

The liquid concentrated under the above two precautions can be processed by the following methods.

1) Filter the concentrated liquid without crystallization.

2) Pour water into the concentrate to prevent crystallization and cool and filter.

3) Leave the concentrated solution for at least 14 hours, or about 1 week, and then pour water to dissolve the crystals and filter.

4) The concentrated solution is neutralized with Fe and filtered.

5) Add carbonate to the neutralized solution, stir, and filter.

When the liquid obtained by each method described above is thermally decomposed, the following products are obtained.

No, I No, '2 No, 3
No, 4 No, 5Fe20399.34 9
9.3 99.3+ 99.32 99.34
Mn0O, 290, 280, 300, 280,
27Si02 0.005 0. Oo3 o,
o02 0.0045 0.0032A10 0.
04 0.05+ 0.051 0.026
6 0.0+9401"-0,0560,0580,0
580,0590,0571-]2Q O,26
0,270,270,300,31X --
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Claims (1)

[Claims] /) Bringing oxygen-containing cloth gas into contact with iron picrin waste acid,
+C- Raise the temperature while below the boiling temperature and reduce the iron chloride content to 35%
~ the saturation point, circulating hot high acid, and concentrating while contacting with high temperature gas to insolubilize the soluble hexachloride, filter the concentrated liquid, and remove the residual liquid from iron oxide and A waste acid treatment method that recovers high-purity hydrochloric acid. 2) The treatment method according to claim 1, which comprises pouring nail pure water that can prevent crystallization into the concentrated liquid according to claim 1, cooling it, filtering and heating it for decomposition. 3) The treatment method according to claim 1, which comprises leaving the concentrated solution according to claim 1 for 24 hours or more, then pouring water to dissolve the crystals, filtering, and thermally decomposing the solution. ≠) A treatment method according to claim 1, in which the l1IIF4 liquid according to claim 1 is neutralized with Fe, filtered, and thermally decomposed. S) Adding one or more of iron carbonate, guanidine carbonate, zinc carbonate, and manganese carbonate to the neutralized liquid in claim 4, heating and stirring, filtering, and thermal decomposition. Processing method.