JPH03249984A - Method for regenerating used cr6+-containing basic brick - Google Patents

Abstract

PURPOSE:To obtain the method for regenerating the used Cr<6+>-contg. basic brick with which industrialization is easy by immersing the used Cr<6+>-contg. basic brick into water, warm water or hot water. CONSTITUTION:The used Cr<6+>-contg. basic brick is immersed into the water, warm water or hot water and is subjected to shaking, stirring, heating, etc. Not only the Cr<6+> compd. is eluted by this treatment but also sulfate, chloride, etc., such as K2SO4 and KCl, which are undesirable if included as regenerated raw materials and settled in the used brick are simultaneously eluted. The brick subjected to the elution treatment is subjected to draining an drying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for recycling basic bricks used in actual furnaces, particularly maguro bricks or chroma bricks.

[Prior Art] When maguro bricks or chroma bricks are used in a kiln in which alkaline or calcium components are present and the partial pressure of oxygen is high, the talomite Cr in the bricks is
ho, (Cr”) undergoes the following reaction to produce the harmful Cr” compound: 2 Cr 20! + 4 K 20 + 302 =
4 K 2 Cr O+2cr20z+ 4CaO+
302=4CaCrO.

These reactions are particularly likely to occur in cement kilns.

This is because clay, which is part of the raw material for cement, contains a few percent of alkali compounds, and the main raw material is CaO. In addition, maguro bricks are used in areas with high oxygen partial pressure, that is, in the firing zone of the rotary kiln. This is because it has been Hereinafter, this specification will be explained using an example of a cement rotary kiln.

Maguro bricks lined in a cement rotary kiln require only about 1/2 to 2/3 of the total thickness, leaving 1/2 to 1/3 of the original thickness (150 to 250 III m). It will be removed and replaced with a new brick. The removed Maguro brick, that is, the Maguro brick after use, is exposed to the presence of alkali and CaO, as described above, to produce hexavalent chromium compounds around the chromite.

The amount of Cr" produced varies depending on the conditions of use and is not certain, but it may reach 500 to 3000 ppm in some cases.

[Problem M to be Solved by the Invention] These used maguro bricks are used as a spray repair material or slag coating material for electric furnaces or converters for large-scale steelmaking. In this case, Cr in used Maguro bricks
Since "Cr" is diffused into the slag and the slag is solidified by cooling thereafter, there is virtually no actual damage caused by "Cr".

On the other hand, chromite (chromite), which is the main component of maguro bricks, is an extremely important raw material for refractories, and the recycling and utilization of used maguro bricks is an important issue from the perspective of resource conservation. Furthermore, if the supply and demand balance is disrupted and the amount of used maguro bricks becomes excessive as a spray repair material for steel, etc., depending on how they are handled, serious environmental pollution problems may occur.

[Means for Solving the Problems] That is, the present invention processes a Cr"-containing used basic brick by immersing it in water, warm water, or boiling water to elute other water-soluble substances of the Cr"-containing compound. The present invention relates to a method for recycling used basic bricks, which comprises draining and drying the treated bricks.

[Function] The present inventors used the above-mentioned K 2Cro , Ca Cr O *
Chromates such as chromates have high solubility in water (especially K 2
Focusing on CrO-), by immersing used Maguro bricks in water and applying shaking, stirring, heating, etc., Cr'' compounds are not only easily eluted, but also undesirable if they are included as recycled raw materials. Since sulfates and chlorides such as SO, K(l) deposited in used bricks can be eluted at the same time, a cleaner recycled raw material can be obtained.

By the way, 100 I of water at 0°C for these compounds? The solubility for K 2 Cr O 458, 0 g CaCrO < 22.0 IF K 2 S O 47, 35 Li KCl 27.6 g To increase the rate of these elutions, reduce the particle size by crushing the used bricks. It is effective to increase the surface area by increasing the particle size, but if the particle size is too small, the solid-liquid separability will decrease.

The particle size when reusing treated bricks is approximately 5II.
From I* to 11, it is not preferable to grind the particles to this particle size from the beginning due to the problems mentioned above, but since powdered particles are inevitably produced during the grinding process, are 50-5mm lumps or granules and 5I
It is best to divide it into powders of II*m or less.

The specific equipment for elution is generally a so-called solid extraction equipment, such as a discontinuous method (fixed type) such as a percolation tank method or a stirring tank method, and a continuous method such as a Rotocel.
Although there are methods such as the German method and the Kennedy method, this method is not limited here.

The used Maguro bricks that have been cleaned after the elution process are drained, dried, and recycled and used as a refractory raw material.
After adjusting the pH of the eluate containing r'' etc. according to a known method,
It is reduced to Cr″° by adding a reducing agent such as F e S O4, and then, when neutralized, it precipitates as Cr(OH)s, etc. After that, it is separated into a precipitate and a solution, and a flocculant is added. This facilitates separation from the solution.

In addition, any already established techniques can be used for the operations for pH adjustment, reduction treatment, neutralization treatment, separation of precipitates, and solution discharge in the treatment of eluate containing C60 etc. .

[Implementation example] The present invention will be further explained with reference to Examples below.

Examples include 202.08%, NazO0.25% and 11060
100 g of used Maguro bricks containing pp Cr'° were immersed in circulating warm water (50°C) 30 (H!) for 1 hour while being vibrated, drained, and dried to clean the Maguro bricks. .

When the Cr” of treated Maguro bricks was measured, it was found that Cr
@+ is 8pp3 K2O is 0.02%, and Na
20 saw a significant reduction of 0.005%. Although these values do not have any adverse effects on recycling, they can be further reduced by improving the treatment method, such as extending the immersion time and increasing the circulation speed of hot water.

[Effects of the Invention] As described above, the method of the present invention is extremely easy to industrialize, and can be said to be an extremely suitable and economical means for eluting water-soluble impurities such as Cr''-containing substances from used maguro bricks.

In addition, since impurities have been eluted and removed from treated bricks, they can not only be fully utilized as recycled raw materials, but also save resources and greatly contribute to environmental conservation.

Claims (1)

[Claims] A used basic brick containing Cr^6^+ is immersed in water, warm water, or boiling water to elute other water-soluble substances of compounds containing Cr^6^+, and the eluted brick is drained and dried. A method for recycling used basic bricks, characterized by: