DE19725018B4 - Process for the preparation of an inert, finely divided filler and its use - Google Patents

Abstract

method for producing an inert, finely divided filler whose particles are too at least 90% have a diameter of <90 μm have, for Asphalt mixed from the titanium dioxide in the production of incurred in the sulphate process in sulfuric acid digestion of titanium-containing raw materials insoluble Digestion residues, thereby characterized in that at the conclusion arising Sulfuric, titanyl sulfate-containing solution of the insoluble Digestion residues Filtration is separated, and the resulting in the filtration filter cake subsequently with dilute Sulfuric acid and / or Is washed water until the resulting filter cake a. sulphate content in the eluate (according to DEV S4) of <3.0 g / l, and optionally with air or heated air At least partially blown dry and then ground or deagglomerated.

Description

The The invention relates to a low-sulfation, inert, finely divided filler (SIFF) and a process for its preparation and its use as a filler in bituminous mixtures (minerals and bitumen).

at Titanium dioxide production by the sulphate process decreases the digestion of titaniferous raw materials with sulfuric acid the so-called titanylsulfathaltige Black solution which still contains a certain amount of undissolved constituents. These Solids must be separated before further processing of the black solution. This usually takes place by means of vacuum filters or filter presses frequently prior enrichment in thickeners (Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., Vol. A 20, p. 276-278).

The direct usability of the so-called digestion filter cake (I) obtained in this way is greatly limited on the one hand by its acidic character, on the other hand by its content of soluble sulphates. Therefore, the digestion filter cake for the purpose of recovery must usually be thermally pretreated and mixed with, for example, lime-like aggregates and used together. So will in SU 897 739 describes the use of the digestion filter cake as an iron-containing aggregate for the production of Portland cement clinker. In this use, the components contained in the digestion filter cake water, sulfuric acid and sulfate are thermally removed or split, which is associated with a considerable expenditure of energy. In SU 913,588 describes the use of digestion filter cake in addition to Portland cement clinker and gypsum for the production of a binder in the construction sector, the digestion filter cake must also be thermally pretreated here energy consuming.

In EP-A 611 740 describes that the digestion filter cake together with other ingredients as a titanium-containing aggregate to increase the durability of the refractory lining of a furnace used can be. The digestion filter cake in DE-A 4 419 816 is len together with various other Bestandtei as a titanium-containing aggregate to increase the durability of the refractory Brick lining and used as a slag former. The Necessary in the last two references Sintering of the digestion filter cake with the other ingredients for making briquettes, pellets or granules impaired However, the economics of the process considerably.

In DE-A 4 318 126 and EP-A 659 688, the digestion filter cake is re-digested together with fresh ore, whereby on the one hand the yield of TiO _{2 is} increased and on the other hand the amount of digestion filter cake is reduced. However, a great deal of effort must be made to obtain a relatively small amount of titanyl sulfate, so that this method is only economical if no other useful use is available for the digestion filter cake.

In DE 44 34 315 C1 describes a washing process of digestion residues from titanium dioxide production using at least 37%, preferably more than 50%, sulfuric acid.

The method described above for the utilization of the digestion filter cake are characterized either by a high technical effort or are economically less attractive. Partly the digestion filter cake also for the appropriate application to be conditioned, since it in the accruing Shape is not suitable. The effort for this can vary depending on the legal or industry-standard quality requirements be so high that it economically cheaper is, the digestion filter cake to deposit.

task It was therefore, a cost-effective, low energy, technically easy to perform Process for working up the compulsory decomposition filter cake to disposal which results in a product that is used sensibly or can be used again.

These Task could be solved with the method according to the invention.

It was surprising found that through Wash out the sulfate from the compulsorily resulting digestion cake (I) a product can be obtained which is then considered to be of high quality filler for asphalt mix can be used.

object The invention relates to a method for producing an inert, finely divided filler, whose particles have at least 90% of a diameter of <90 microns, for asphalt mix from those in the production of titanium dioxide by the sulphate process in sulfuric acid digestion of titanium-containing raw materials accumulating insoluble Digestion residues, which characterized in that the at the conclusion arising sulfuric acid, titanyl sulphate solution (black solution) of the insoluble Digestion residues Filtration is separated, and the resulting in the filtration Filter cake afterwards with dilute sulfuric acid and / or water until the resulting filter cake has a sulphate content in the eluate (according to DEV S4) of less than 3 g / l, preferably <1.2 g / l, most preferably <0.2 g / l, and optionally with air or heated Air blown dry and then ground or deagglomerated becomes. Preferably, the filter cake thus obtained has a sulfate content based on the solids content of <4.0 wt .-% to.

Preferably the resulting filter cake (I) with dilute sulfuric acid and / or Water in a known filtration unit, such as e.g. in a rotary vacuum filter or in a chamber or membrane filter press washed. The washed pulping filter cake obtained in this way (II) (inert, finely divided filler, SIFF) much less soluble Sulfates as the filter cake (I). To further reduce the sulfate content may preferably be re-filtered after prior redispersion of the digestion filter cake (II) in water.

Of the also obtained inert, finely divided filler may also partially or completely be neutralized, if desired. This may be preferred be done by the filler (SIFF) for the purpose of neutralization first redispersed in water and filtered again after the neutralization and optionally washed becomes. But it is also possible that the Neutralization of the filler (SIFF) without re-mashing directly in / on the filtration unit takes place by the filter cake with an aqueous solution of the neutralizing agent is washed. But it is also possible that the filler (II) for the purpose of Neutralization solid or liquid Alkalis are mixed or kneaded into the filler. Suitable neutralizing agents are all common alkaline compounds, in particular e.g. solid or dissolved Alkali or alkaline earth hydroxides.

alternative can the digestion filter cake (I) washed with water until neutral or nearly neutral reacts, so that the Addition of a neutralizing agent may be omitted in whole or in part.

Either with regard to the product properties of the process product as the economic viability of the process may also be advantageous if directly following the laundry in a filter press the filler (SIFF) with air or heated Air is wholly or partially blown dry.

Especially advantageous properties, the filler, if he after the Laundry or after neutralization by drying to a solids content of> 90% by weight, preferably> 95% by weight, dried and optionally simultaneously or subsequently again to a fine Powder is ground or deagglomerated. Due to the inertness of the filler (SIFF) can do the drying with any expert known method or unit, for example, in a Drying cabinet, with a belt dryer or a spinflash dryer.

It is possible, too, that neutralization and drying the filler (SIFF) in one step by adding a neutralizing agent to the filler to be dried (SIFF) is mixed. Particularly well suited for this purpose is a spinflash dryer, since this the product without subsequent Grinding or deagglomeration used directly as asphalt filler can be.

Of the inert, finely divided filler (SIFF) obtained in this way does not fulfill only in terms of its chemical properties (sparingly soluble Sulfate, preferably <3.0 g / l in the eluate (according to DEV S4), more preferably <1.2 g / l, most preferably <0.2 g / l; very little soluble Heavy metals) the requirements for a high quality filler, but surprisingly about that In addition, particularly favorable mechanical as well as very good granulometric and structural properties on, which allow use as a high-quality asphalt filler.

Of particular advantage is the low CaSO ₄ content of the SIFF, whereby a continuous, long-lasting leaching of Ca and SO ₄ ions is avoided.

Thus, in particular, the neutralized, dried and ground SIFF without further chemical or mechanical pretreatment can be used directly as asphalt filler and thus represents an exemplary case of raw material utilization, as in this way an energy-intensive grinding of natural substances such as calcite can be saved. Due to its relatively neutral light gray-green color, the SIFF is also suitable as a filler for colored asphalt mixes. The SIFF is particularly well suited as a filler for acid-resistant asphalt mix, otherwise basalt or other acid-resistant rock with particularly high energy expenditure must be ground for its production.

Of the SIFF can be used as a filler instead of ground limestone or basalt for asphalt mix be used or mixed with ground limestone or basalt, especially if this is below the limit for the Content of soluble Salting the filler or to optimize the structural properties of the on this Way prepared asphalt mix is necessary (see also example 1).

However, it is also possible to use the non-neutralized SIFF together with a quantity of ground lime (CaCO ₃ ) or quick lime (CaO) necessary for achieving a neutral pH of the mixture as a filler for bituminous mixture. In this way, the economy of the method according to the invention (neutralization falls away) can be further improved.

The Invention will be explained in more detail with reference to the following examples.

example 1

From a black solution obtained in the digestion of ground titanium raw materials with sulfuric acid, the undissolved constituents (insoluble digestion residue) are separated with a membrane filter press. Subsequently, the filter cake (I) is washed with twice the amount by weight of water (based on the solids-containing black solution used). The resulting filter cake (II) is redispersed in water in a mass ratio of 1: 1, neutralized with NaOH and filtered again. The neutral filter cake (III) obtained in this way is dried in a drying oven at 120 ° C and comminuted again by means of a pin mill. A neutralized and dried SIFF is obtained as a bright gray-green material with the following properties: Solids content (150 ° C, 16 h): 99.4% by weight PH value: 7.4 SO ₄ content (solids analysis): 2.9% by weight SO ₄ content (in the eluate according to DEV S4): 2.3 g / l Ca content (solids analysis): 1.7% by weight Eluate values (according to DEV S4): sb <0.001 mg / l ace <0.001 mg / l Ba 0.26 mg / l Be <0.002 mg / l pb <0.01 mg / l B 0.26 mg / l CD <0.001 mg / l Cr (ges.) <0.01 mg / l Cr (VI) not detectable Fe 0.15 mg / l Ca 6 mg / l Co <0.01 mg / l Cu 0.04 mg / l Mn 0.10 mg / l N / A 1300 mg / l Ni 0.05 mg / l hg <0.001 mg / l se <0.001 mg / l Ag <0.001 mg / l tl <0.001 mg / l V <0.05 mg / l Zn 0.04 mg / l sn not detectable F 0.13 mg / l Ammonia-N 0.70 mg / l Cl 19 mg / l Cyanide <0.01 mg / l nitrate 2.0 mg / l nitrite 0.10 mg / l phosphate 0.50 mg / l sulfate see above

Technological properties:

• (determined in accordance with Technical Delivery Conditions for Minerals in Road Construction, TL Min-StB 94, Road and Transportation Research Association, Cologne, 1994) Sieve analysis: proportions <90 μm: 99.4% density: 3.497 g / cm ³ Void content according to Rigden: 52.1% by volume Bitumen number (according to NEN 3977): 44 Stability Index: 67:33 weight% Erweichungspunkterhöhung: 21.5 ° C (with filler / bitumen ratio 65/35) water-soluble fractions: 3.36% by weight

The neutralized and dried SIFF was used in 1: 1 mixture with ground calcite (CaCO ₃ ) as asphalt filler:

Technological properties the mixture:

• (determined in accordance with Technical Delivery Conditions for Minerals in Road Construction, TL Min-StB 94, Road and Transportation Research Association, Cologne, 1994) Sieve analysis (proportions <90 μm): 97.5% by weight density: 3.077 g / cm ³ Void content according to Rigden: 41.9% by volume Bitumen number (according to NEN 3977): 35 Stability Index: 66:34 weight% Erweichungspunkterhöhung: 19.4 ° C (with filler / bitumen ratio 65/35) water-soluble fractions: 1.77% by weight

For the production of bituminous mixtures, bitumen and various minerals of different grain sizes are mixed at 150 to 160 ° C, the mixing can be done either continuously or discontinuously. The hot asphalt mix is then transported to the site of use (Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed., Vol. A3, p. 184). Depending on the quality and area of application of the bituminous mixture, certain requirements are set for the type and grain size distribution of minerals (Additional Technical Terms of Contract and Guidelines for the Construction of Road Tiles from Asphalt-ZTV Asphalt-StB 94, Federal Minister of Transport, Dept. Road Construction, Cologne, 1994) ). The mine The lowest-grade (<90 μm) fraction of the mineral is referred to as an asphalt filler and often consists of ground calcite (CaCO ₃ ).

Composition of asphalt mix as well as the results of asphalt tests for asphalt concrete 0/11 mm:

The technical exam of the asphalt made with neutralized and dried SIFF results in respect all the criteria tested gave a positive result. The investigations carried out show that the neutralized and dried SIFF 50% of ground calcite as asphalt filler can replace without problems.

Example 2

From a obtained in the digestion of ground titanium raw materials with sulfuric black Solution, the undissolved constituents (insoluble digestion residue) are separated with a membrane filter press. Subsequently, the filter cake (I) is redispersed with water in a ratio of 1: 1 and filtered with the aid of a band filter. The resulting filter cake (II) is redispersed with water in a ratio of 1: 1, neutralized with NaOH and filtered again. The neutral filter cake (III) obtained in this way is dried and comminuted by means of a pin mill. A neutralized and dried SIFF is obtained as a bright gray-green material with the following properties: Solids content (150 ° C, 16 h): 95.3% by weight SO ₄ content (solids analysis): 2.6% by weight (based on the solids content) SO ₄ content (in the eluate according to DEV S4): 2.04 g / l PH value: 7.7

The neutralized and dried SIFF thus obtained can be used, for example, as an asphalt filler in admixture with ground calcite (CaCO ₃ ).

Example 3

From a black solution obtained in the digestion of ground titanium raw materials with sulfuric acid, the undissolved constituents (undissolved pulping residue) are separated off with a membrane filter press. Subsequently, the filter cake (I) is first washed with the same amount (based on the solids-containing black solution) of dilute sulfuric acid and then with the same amount of water (based on the solids-containing black solution). Then air is blown through the filter cake (II) for a few minutes. A SIFF is obtained as a bright gray-green material with the following properties: Solids content (1000 ° C, 1 h): 74.1% by weight SO ₄ content (solids analysis): 1.42% by weight (based on the solids content) SO ₄ content (in the eluate according to DEV S4): 0.82 g / l PH value: 2.1

 Of the SIFF thus obtained may be mixed with other materials, e.g. CaO and / or ground calcite can be used as asphalt filler.

Example 4

From a black solution obtained in the digestion of ground titanium raw materials with sulfuric acid, the undissolved constituents (undissolved pulping residue) are separated off with a membrane filter press. Subsequently, the filter cake (I) is washed first with the same amount (based on the solids-containing black solution) of dilute sulfuric acid and then with twice the amount of water (based on the solids-containing black solution used). The resulting filter cake (II) is redispersed with half the amount of water, neutralized with the stoichiometric amount of sodium hydroxide solution and then filtered and washed with the same amount of water (based on filter cake (II)). A neutralized SIFF is obtained as a bright gray-green material with the following properties: Solids content (150 ° C, 16 h): 72% by weight SO ₄ content (solids analysis): 0.36 wt .-% (based on the solids content) SO ₄ content (in the eluate according to DEV S4): 0.012 g / l PH value: 7.1

 Of the neutralized SIFF thus obtained can be used either directly or in admixture with other materials, e.g. ground calcite, used as asphalt filler be or previously dried and ground analogously to Example 1 become.

Example 5

From a black solution which occurs in the digestion of ground titanium raw materials with sulfuric acid, the undissolved constituents (undissolved pulping residue) are separated with a membrane filter press. Subsequently, the filter cake (I) is washed with twice the amount of water (based on the solids-containing black solution used). The filter cake (II) thus obtained is with the stöchio Metric amount of sodium hydroxide solution and then washed with twice the amount of water (based on the solids-containing black solution used). A SIFF is obtained as a bright gray-green material with the following properties: Solids content (150 ° C, 16 h): 74% by weight SO ₄ content (solids analysis): 0.31% by weight (based on the solids content) SO ₄ content (in the eluate according to DEV S4): 0.048 g / l PH value: 9.8

Of the neutralized SIFF thus obtained can be used either directly or in admixture with other materials, e.g. ground calcite, used as asphalt filler be or previously dried and ground analogously to Example 1 become.

Claims (5)

Process for the preparation of an inert, finely divided filler whose particles have at least 90% of a diameter of <90 microns, for bituminous mixtures from the insoluble digestion residues obtained in the production of titanium dioxide by the sulfate process in the sulfuric acid digestion of titanium-containing raw materials, characterized in that the Dissolving sulfuric acid, titanylsulfathaltige solution is separated from the insoluble digestion residue by filtration, and the filter cake obtained in the filtration is then washed with dilute sulfuric acid and / or water until the filter cake obtained a. Sulphate content in the eluate (according to DEV S4) of <3.0 g / l, and optionally at least partially blown dry with air or heated air and then ground or deagglomerated. Method according to claim 1, characterized in that the with dilute Sulfuric acid and / or Water-washed filter cake has a sulfate content based on the Solid content of <4.0% by weight having. Inert, finely divided filler whose particles are too at least 90% a diameter of <90 microns can be produced by the method according to one of claims 1 or Second Use of the inert, finely divided filler according to claim 3 for the partial or complete substitution of ground Calcite as asphalt filler. Use of the inert, finely divided filler according to claim 3 for the partial or complete substitution of ground Basalt or other acid-resistant rock as an asphalt filler.