DD151735A1 - PROCESS FOR BINDER PREPARATION FOR RAW PHOSPHATAGGLOMERATION - Google Patents

Abstract

Fine-grained phosphates are processed in particular by built-up granulation with the aid of binders on granulation plates in a subsequent drying, hardening and firing process to form an agglomerate. The aim of the invention is the preparation of a binder of low viscosity, which is suitable for agglomerating finely ground raw phosphates, in particular apatite concentrates, and, when used, leads to sufficient granule stability. The object of the invention is to find a suitable binder composition which, with the simultaneous processing of electrostatic filter dust, permits the use of any pit-like clays which also have partially disturbed kaolinitic lattices, alternating layer minerals and / or three-layer silicates. It was found that oxidative thermal aftertreatment of the electrostatic precipitator dust destroys the carbon component which is primarily responsible for the binder thickenings. At the same time, this conversion effect achieves the conversion of alkali orthophosphates to corresponding polyphosphates which exert an additional leaching effect on the binder.

Description

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Binder preparation process for crude phosphate agglomeration

Field of application of the invention

The invention relates to a process for the preparation of a binder for the agglomeration of fine-grained phosphates. Fine-grained phosphates, eg. B. enriched by flotation Kolaapatitkonzentrat, are worked up in particular by built-up granulation with the aid of binders on Granuliertellern in a subsequent drying, curing and firing process to an agglomerate.

Characteristic of the known technical solutions

The optimum composition for the elementary phosphorus production process should have a particle size range of 15-20 mm for 80 % of the material. Strengths for the finished granules are reported to be 60 60 kp / gram, with a low content of undersize and minimum abrasion (DAS 1,300,911, 1,258,847). As binders for build-up granulation, aqueous mashes of clay, phosphate solutions and / or phosphate are used on sludges and electrostatic filter dust from electrothermal phosphorus recovery. The requirements for the binder include, inter alia, with a high proportion of clay, electrostatic precipitator dust (see Table 1) and phosphate additives to. to 35 - 45 %

and higher to ensure a sufficiently low viscosity.

Table 1:

approximately J - (7o It 15 - 40 % ! I 25 - 40 /, It 3 - 6 % tf 15 - 30 % ti 0.5 -3 % It 1 * · Ji / o ti 4 - 6 X

Chemical composition of Piesteritzer Elektro filter dust

Carbon SiO ₂

the latter is necessary in order to achieve good atomization of the binder on the granulating disc. From an economic and environmental point of view, there is a need for the elecric. filter dust, which is also referred to as Cottrellnilch in the form of its aqueous L'aischen, to recycle the phosphorus production process (DAS 1,667,567, DAS 1,258,847, DAS 1,300,911, DOS 1,567,611). As a fine dust component, it contributes to the solidification of green greens.

The simultaneous use of high amounts of clay and electrostatic precipitators causes considerable difficulties for most types of clay. This is due to an interaction process between the water-slurried clay component and the cottrell milk particles. It manifests itself in sometimes considerable increases in viscosity, so that the generally achievable liter weights do not exceed values of 1150-1200 r for electrostatic filter dust volumes of S 5 % , if the binder is still readily pumpable and sprayable

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pain should (DAS 1,667,567). Binders with such low levels of binding component lead to unstable granules with insufficient green strength, which is reflected in very high proportions of fine granules in the final granules »Well suited for the Rohphosphatagglomerierung low binder viscosity, the formation of a stable green granules as well as partly with respect to the requirements of the drying , Hardening and firing process are kaolinitische clays with high levels of kaolinite and / or halloysite and very low levels of alternating deposit minerals and / or three-layer silicates. Disturbed kaolinitic lattices (for example fire clay-type clays) again result in excessive binder viscosities (see Table 2). For schv.ergranuli available phosphates (eg the Kolaapatitkonzentrat) are suitable for a comparable with the Kolaapatitkonzentrat grain spectrum only carbonaceous kaolinitische clays (WP application C 01 B / 217 446) to achieve sufficient strength in the drying, curing and firing process ,

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Table 2

10-1 VJL 10-13 8th 8-10 10 ± 5 12 10 34 25-30 32 40

Mineralogical composition of clays and sensitivity compared to cottrellrailch

Clay kaolin Halloy illite / ml Hont quartz BL ¹ I-

nit sit Glim- moril- viscous

mer lonity

Hohenbocka 45 20 - - 12 +

Amsdorf 35-40 - 15 - - 45-50 + Haselbach 60-65 - 10-12 - - 20-22 ++

fireclaytyp

Brandis 65 Guttan 70 ± 7 Friedland 5 Rossbach 30-35

ra. 1. vVelixing plant minerals

BIvI binder

+ low BLI viscosity

++ too high BI, - viscosity

The interaction process of clay electrostatic precipitator dust takes place independently of the addition of the sequence of the components clay, electrostatic dust, phosphate components, irrespective of whether the clay is used in solid form or in the form of a ready-made slurry , sometimes quite significant viscosity reductions, fail in the presence of electrostatic precipitator dust.

Object of the invention

The aim of the invention is the preparation of a binder of low viscosity, which is used for agglomeration

finely ground raw phosphates (rock phosphate concentrates), in particular apatites, is suitable and, when used, leads to a sufficient granule stability in the drying, hardening and firing process.

Presentation of the Invention of the Invention

The object of the invention is to find a suitable binder composition which allows the use of any pit-fresh clays, which also have partially disturbed kaolinitische.-lattice and shares of Wechselzellermineralien and / or Dreischichtsilikate, with a simultaneous processing of electrostatic precipitator dust.

It has been found that by using an electrostatic precipitator prepared by thermal oxidative aftertreatment, clays of any composition, settlement, optionally with the addition of phosphate solutions and / or other phosphate components, are agglomerated in a manner known per se to give binders for the crude phosphate agglomeration the build-up granulation can be used with the help of granulating plates, can be used.

The thermal aftertreatment must take place in an oxidizing atmosphere in which, inter alia, most of the carbon contained in the electrostatic precipitator dust is oxidatively destroyed. One can achieve this by rapid cooling of approx .. 200 this technology in a very simple way and V / else - 300 ⁰ C hot dust is avoided at the discharge from the electrostatic precipitators of phosphorus furnaces. In a limited KaItIuftzufuhr causes the heat of combustion released further heating of the entire solid system (going to red hot), so that by further added air almost complete oxidation, especially the very surface-ac-

 fciven and thus very responsive carbon occurs. Appropriately, can be for this Ar-. Exhaust gases, as described e.g. in an amount sufficient in the firing process of Rohphosphatgranalien incurred in a rotary kiln, in a Lepolrost plant or other similar combustion devices, use advantageous.

The binder thickening in the system of clay electrostatic precipitator dust is effected above all by the interaction process clay - water-insoluble residue of the electrostatic precipitator dust

- the water-soluble component of the dust or

- the Cottrellmilch itself, or

- The water-insoluble component of the dust results in the same amount of clay used a strong increase in viscosity of the binder from the water-soluble fraction to the water-insoluble fraction. The primarily formed electrostatic filter dust and in particular the water-insoluble residue thereof are very surface-active. There is a direct correlation between the specific surface area of the dust and the viscosity of the binder, as shown in Table 3. The specific surface area was measured by the Blaine method (described in K. Schwabe, Physikalisch-chemische Keßverfahren, Part 1, Akadem. Verlagsgesellschaft Geest and Portig KG Leipzig 1973 p. 165 ff) and the binder viscosity was measured with a Rheo viscometer. The dust was collected under protective gas atmosphere and stored.

Table 3.

" Influence of the specific surface area on the binding properties of the specific surface (cm ² / g) 25500 17490 15500 10400 BEI viscosity (dyn at 196 15.7 130 71

100 cP)

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The electrostatic filter dust is also subject to a time-dependent aging process, see Table 4. _{% i}

Table 4 Influence of the aging of electrostatic filter dust on the Bindemittelvi.skosität

Sample viscosity of the BM viscosity of the BM

the ^a Eiek ro i -?! ^{S mixers} dust of 18-day-old tern) ^Dust

1 326 61

2 61 - 57

3 230 108

4 161 96

Due to its low bulk density as well as the very variable speed of the aging process of the dust, this phenomenon can not be used for the technology of BM production. Rather, a faster and better quality change of the dust must be achieved. This is possible because of the easy oxidizability of the carbon, which is considered to be the main component for binder thickening. The primary carbon formed in the warm state, to which the outlet temperature from the electrostatic precipitator suffices, has half-pyrophoric properties. When leaving such a dust sample in the air you can observe the formation of a glowing bed (red heat). The thin binder formed after dying out of the dusts, as well as strong increases in BM with the addition of carbon (eg small amounts finely powdered activated carbon), show in connection with the above statements that nonionic components, especially carbon, for the interaction process clay electrostatic precipitator dust are responsible.

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Thermal post-treatment of electrostatic precipitator dust not only destroys the main component responsible for binder thickening, but in the annealing process, a portion of the original alkali orthophosphates is converted to corresponding pyro- and polyphosphates which are added to the clay substances after destruction of the carbon constituents This means that high liter weights (- 1400 g) can be achieved without the additional use of liquids at low viscosity at the same time. "These binders provide good and rapid granulation of raw phosphates (eg colaapatite)." - reached) and the formed granules of sufficient and high strength.

Most of the occurring clays have shares :: r. disturbed kaolinite lattices or have shares in Y / echsellagennineralien and / or three-layer silicates. They are well applicable for the concerns of Rohphosphatagglomerierung when the procedure according to the invention 'is used. Inhomogeneities (for example, proportions of three-layer silicates which produce a particularly strong interaction process with the cottrell milk) hardly or not at all become noticeable in the clay, especially since the binder viscosities come to lie in a very low range due to the additional effect of the liquefying effect of the polyphosphate components. The advantageous use of this procedure is illustrated in Examples 1 b, 2b, 3b in comparison to Examples 1 a, 2 a, 3a.

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embodiments

Example 1 a

17.5 % Brandiser Fetton (see Table 2) and 17.5 % Brandiser Magerton, 1 % disodium hydrogen phosphate.

12 H ₂ O and 5.5 % electric filter dust, which was cooled to room temperature under Mp atmosphere and a

specific surface area of 20600 m / g, became a binder having a liter weight of 1345 g

and a viscosity of 224 dynes / cm at 100 cps.

Example 1 b

17.5 % Brandiser Fetton and 17.5 % Brandiser Magerton, 1 % disodium hydrogen phosphate. HPO 12 and 5.5% 'electrostatic precipitator dust in a storage vessel to temperatures of ~ 35O ⁰ C for a short time he ~ warmed, were exposed to air to form a binder with a liter

weight of 1350 g and a viscosity of 68 dyne / cm at 100 cP.

Example 2 a

32 % Brandiser Petton, 5 % disodium hydrogen phosphate • 12 HpO and 4 % electrostatic precipitator dust, which was immediately collected under water after it had left the electrostatic precipitator of the phosphorus furnace, gave after three hours of stirring a binder with one liter of

weight of 1336 g and a viscosity of 525 dyne / cm at 100 cP. The binder did not spray well, with. Kolaapatitkonzentrat formed a poorly formed green granules (can spherical granules with a size distribution 0 <10 mm 30 % _t 0 10 - 20 mm 30%, 0> 20 mm 40 %, even elliptically formed granules fraction 10 - 20 mm had low pestinessY / erte <500 p / granule.

Bei Piel 2 b

32 % Brandiser Fetton, 5% disodium hydrogen phosphate. 12 HpO and 4 % of the same electrostatic precipitator dust as in Example 3> which was annealed at 600 ° C for about 15 min, gave after three hours of stirring a binder with a liter weight of 1340 g and a Viskosi-. did 50 dynes / cm ² at 100 cps.

The binder was easily sprayed onto a granulating plate which had been charged with colaapatite concentrate. The well-spherical green granules had a composition of 95 V * for the fraction 0 10 - 20 mm. The strength values of the green granules were = -1000 p / granule. The up to a temperature of 1000 ⁰ C fired pellets exhibited strength values of 85 kp / granule.

Example 3 a

39 / j Haselbacher clay, 2 ^c / j disodium hydrogen phosphate. 12 H ₂ O, 6 % electrostatic filter dust was stirred into a binder having a liter weight of 1390 g and a viscosity of T = 950 dyn / cm at U = 100 cP. The binder was viscous, it could not be sprayed.

Example 3 b

39 / j Haselbacher clay, 2 % disodium hydrogen phosphate. 12 H ₂ O, 6 % electrostatic precipitator dust (same batch as in Example 2), which was heated at 600 ° C for 15 min, gave a binder with a liter weight of

ρ 1405 g and a viscosity of Γ = 35 dyne / cm at 100 cP. The very thin-bodied binder was well sprayed on a granulating plate, which was fed with Kolaapatitkonzentrat spray. The resulting green granules had a proportion> 98 % for the fraction ^> 10 mm; the fraction of 15-20 mm had a green strength of 1100 p / gr.

speeds of up to 100O ⁰ C fired granules were 125 kgf / granule.

Claims (4)

Brennenung sanspruch. 1. A process for the preparation of a binder for the agglomeration of fine-grained phosphates from clay, electrostatic precipitator dust from phosphorus production and optionally other phosphate components, characterized in that pit-fresh clays, which also shares in disturbed kaolinitischen grids and / or shares of V / echsellagermineralien and / or three-layer silicates may be mixed with electrostatic precipitator dust, which is subjected to a thermal aftertreatment under oxidizing conditions, to binders in a manner known per se. 2. A process for the preparation of a binder according to item 1, characterized in that the oxidative after-treatment of the electrostatic precipitator dust takes place immediately after its exit from the electrostatic precipitators. 3. A process for the preparation of a binder according to item 1 and 2, characterized in that the oxidative thermal treatment by the supply of fresh air is made so that the resulting heat of reaction is used for further heating of the dust and / or that the oxidative Hachbeliand-   with preheated air. 4. A process for the preparation of a binder according to item 1 to 3 », characterized in that the oxidative aftertreatment with exhaust gases, which occur in the phosphorus furnace process or during Rohphosphatagglomerierprozeß ·, is performed.