Method for the production of iron oxide pigments

 

(57) Abstract:

The invention relates to the technology of production of iron oxide pigments used as colorants. The invention consists in the following: at the stage of separation and washing of red mud from alkali alumina production from the zone of deposition or seal the last washer select small fraction of red mud required size (for example, using a siphon) and then it is filtered. The precipitate collected on the filter, washed, dried, calcined and get finished products of iron oxide pigment. The method allows the use of as raw material, in contrast to the method known, not thickened red mud with its subsequent dilution with water for sustainable operation of hydrocyclones for selection of the required fraction of red mud, and the intermediate slurry zone of the last (tail) washer red mud, precluding the use of hydrocyclones in the scheme and the dilution of the sludge water. 1 Il.

The invention can be used to obtain the dyes of iron oxide pigments from red mud (waste from alumina production). A method of obtaining iron oxide pigment thermal JV is Lesny sulphate dehydrate prior to the formation of monohydride iron sulfate and then calcined at 700-825oC prior to the formation of iron oxide:

FeSO47H2O FeSO4H2O + 6H2O,

2FeSO4H2O ---> Fe2O3+ SO3+ SO2+ 2H2O

The disadvantage of this method is its complexity and high cost: first, dehydrating liquid sulphate is the sintering of particles, which reduces the quality of the pigment, so after dehydration, the product is subjected to grinding; secondly, the annealing of iron sulphate in rotary kilns is a long process (up to a residual content of iron sulfate in the product 5 - 10%), which increases the cost method.

As a prototype accept the method of obtaining iron oxide pigments (RF patent N 2047631, C 09 C 1/24, 1995 /2/) from red mud waste from alumina production. The method involves the separation of the red mud by class size in the hydrocyclone with a sampling fraction of particles not larger than 0.02 mm and calcination of this fraction at 290 - 850oC.

The disadvantage of this method is that, first, for the stable operation of hydrocyclones need thinning red mud water up to 6 m3water per 1 ton of sludge, i.e. the imbalance in water: second additional spending for the maintenance and operation of hydro determines the complexity of the method and reduces its effectiveness.

The purpose of the invention is improving the efficiency of the method.

The technical result - the possibility of selecting the necessary fraction of red mud for the production of iron oxide pigment without the use of hydrocyclones.

The technical result is achieved in that in the method of production of iron oxide pigments from red mud, including how and the way-prototype [2], the selection of the fraction of red mud required size, filtering the selected fraction and annealing, fractional sampling of the red sludge carried from the zone of deposition or seal the last washer on the stage of separation and washing of red mud from alumina production.

The drawing shows a diagram of the production of iron oxide pigment according to the proposed method.

The scheme includes the latest (usually 4th or 5th) washer 1 red mud from alumina production, for example, 5-tier washer, as shown in the drawing, the mixer with pump 3 with the direction of selected fractions by filtering, washing, drying and calcination.

The method is as follows. At the stage of separation and washing of red mud from the alkali in the alkaline method of production of alumina and is Prosti. Selection, in particular, can be carried out with the upper tier of the washer with a mark of mirror solution 1,0 - 1,25 m Selected fraction through the mixer 2 by the pump 3 is directed to filtering. Obtained filter cake is subjected to washing, drying and calcination, for example, in the crucible of the furnace, and receive the finished products of iron oxide pigment.

The selection of red mud is the last of the washer, as in this case provides better washing of the sludge from the alkali (compared with cuttings taken from the first or intermediate washer).

The fundamental difference between the proposed method from the prototype method in the following: use not waste alumina production - thickened red mud, and the intermediate slurry zone of the washer, so you do not need thinning red mud water in the process of selecting its fractions; eliminates the use of hydrocyclones.

The advantages of the proposed method, due to the presence of distinctive features: no additional equipment is hydrocyclones and, as a consequence, no additional costs for maintenance (release drain pipes from crusts); the absence of RA the Nations red mud, which faction + 0,063 mm does not exceed 0.2%, while the hydrocyclone she reaches 2.0%; on the other hand, you can obtain the fraction of red mud in other industries, for example, for the production of brick, concrete, varying the depth and the radius of the sampling point of the red sludge from the tail washer; proposed sampling scheme with red mud allows, in contrast to the prototype method, to obtain an almost unlimited number of iron oxide pigments (up to 600 thousand tons of pigments in the year).

Method for the production of iron oxide pigments from red mud, including the selection of the fraction of red mud required size, filtering the selected fraction and annealing, characterized in that the fractional selection of red sludge carried from the zone of deposition or seal the last washer red mud at the stage of separation and washing of red mud from alumina production.

 

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