SK286462B6 - Method of drying of smectic clays - Google Patents

Abstract

Method of shock drying of initially moist smectic clays to a predetermined final moisture consists in that the removal of the moisture is carried out of during a short dwell time of less than 15 minutes in the drier at a material temperature of 85 °C or < 85 °C , wherein drying from the initial moisture of from 30 - 42 % is dried to the final moisture of from 7 - 12 % is carried out in a single stage drying and milling process and the drying process is carried out with an evaporation output of minimum 0.2 kg per kg bentonite and minute.

Description

Technical field

The present invention relates to a drying process for the production of clays.

The clay mineral powder is manufactured, for example, by Sudchemie, Munchen, or IBECO, Mannheim.

The importance of such a clay mineral powder lies primarily in its use for wall sealants. The essential properties of minerals, the course of the drying process, including grinding, and the formation of a mixture with excipients are decisive for achieving the stability properties in cement. At present, the achievement of stability in cement is associated with relatively expensive bentonite from certain sites.

Drying of the input mineral is carried out by known drying methods, for example in frying, tray or drum drying ovens, roller mills, ball mills, case mills, wheel mills are used for milling.

NBF bentonites, which are unstable in cement, practically do not provide stable suspensions of a certain viscosity, creep limit and filtration properties with the cement. The main properties of suspension-stable minerals, such as bentonites, are characterized by their morphology and charge distribution, and without further assignment of these properties directly to their chemical constituents, making the most reliable analysis an empirical procedure with testing in the system.

For the production of wall sealants, bentonite and cement, plus any additives such as stone meal or adsorbents, are conventionally stored dry and admixed for use with water (a multi-component mixture process, i.e. a one-step ESTV method). Alternatively, bentonite may be pre-dispersed in water before the cement is admixed (single component process into water or two-stage ZSTV process).

The ZBF bentonites used for the wall sealing structure exhibit a good, particularly site-appropriate, stated stability in the cement.

NBF bentonites, which are not stable in cement, mixed with different types of cement, as is known, do not provide a flawless process and are not yet used for sealing walls, independently of the generally admixable type of cement. The usual cement-stable ZBF bentonites are limited to mixing with certain suitable cements (F in NBF and ZBF stands for Fundstätte).

Today's cements differ significantly in the proportion of granulated blast furnace slag / blast furnace slag. Less suitable for wall sealants are cements with a low slag content (about 50 to 60%) and Portland clinker (about 30%). A suitable cement is one that contains more than 75% slag with a small, about 23%, clinker content. According to the cement manual, the most commonly produced cement is Portland cement (QA3), consisting of cement clinker. Slag cement (QA2), specially designed for underwater solidification, for example HOZ 35 L, contains above 60% blast furnace slag, in the case of standardized route cement the slag equivalent is replaced by route.

In small non-sold cement (QA1) with a slag content of 20-80% for single use and 30-60% for second use in a dry mixture with (cement stable) bentonite, according to DE 36 33 736 A1, it is used for the production of wall sealants in one-step ESTV. The cement according to DE 36 33 736 A1 as well as slag cement is suitable for said two-stage ZSTV process, but again only with known bentonite-stable cement. The Portland cement QA3 in the ESTV and ZSTV processes and the slag cement QA2 in the ESTV processes are unsuitable.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is an object of the present invention to provide a drying method so as to obtain microporous fine grits with defined material properties, which are stable in cement and form flawless wall sealants with different types of cement.

The invention therefore relates to a process for drying smectic clays with a starting moisture by shock to a predetermined final moisture content, characterized in that the removal of moisture takes place at a short residence time of less than 15 minutes in an oven at a material temperature of <85 ° C. The one-stage drying and milling process is dried from a starting humidity of 30 to 42% to a final humidity of 7 to 12% and wherein the drying process is conducted at an evaporation rate of at least 0.2 kg of water per kg of bentonite per minute.

Fields of application include cement-based wall sealants, cement-based materials for storing harmful substances, easily dispersible grouting bentonites shortening the swelling time, swelling bentonites with limited dustiness for on-site mixing applications (sealing of water reservoirs and depots), semi-finished products for highly dense bentonites, sealing panels.

With shock-dried, specially ground and thus microporous treated fine / finest ZBFM semolina from bentonite cement-stable ZBF, depending on the site, wall sealants made with cements may actually be unsuitable for them, e.g. QA3. The similar finest NBFM from cement-unstable bentonite NBF, depending on the site, changes to the quality initially exhibited by cement-stable bentonite ZBF, depending on the site. (M stands for microporosity.)

The obtained microporous fine semolina ZBFM, NBFM exhibits a storage stability in the dry cement mix, in which it can be used for at least seven days, and no significant quality changes also occur within about 30 days. The semolina is characterized in that the particle has a small surface accessible to disturbance by reactive cement, and an internal surface providing rapid dispersion due to the high micro-porosity.

As an advantage of fine semolina ZBFM, NBFM according to the invention, it appears that the cut ratios are relatively high, i. the semolina fraction achieves a high weight fraction but has a narrow distribution. The fine semolina also exhibits favorable properties in terms of swelling properties, dispersibility in terms of distribution of primary clay particles in water, flowability of the powder and storage stability.

For the grinding process:

an inlet particle size of about 5-20 mm, a particle size of grits after grinding of about 0.025 - 0.1 mm.

The density of semolina ZBFM, NBFM produced by the process of the invention is about 900 to 1200 kg / m ³ . The water content is in the range of 7-12%. The values of 0.5 - 3.5% are valid for the Na2O content. Said ranges are nominal values including all narrower ranges, and values within these limits, e.g. through technological measures.

The drying process is carried out with a high drying rate, comparable to a shock drying, with the following parameters to be respected: input moisture values during extraction or storage 30 - 42%, residual humidity 16-22%, evaporation intensity min. 0.2 kg water / kg bentonite per minute, with co-drying, inlet temperature of about 300 - 700 ° C (tumble dryer), with mill drying of about 40 to about 110 ° C with high air, with cross-flow drying of 100 - 300 ° C, the outlet temperature is less than or equal to 85 ° C.

Preferably, the internal temperature of the material should not exceed 60 ° C for an extended period of time to avoid irreversible changes in the morphology of the mineral.

The milling and drying may be carried out in a suitable mill, e.g. using an ultra fast rotary mill, using a combined grinding process. The residence time in the mill should be adjusted as short as possible to achieve the desired fineness (with a particle size of, for example, between 0.02 and 0.1 mm) without too long exposure to the particles, which implies a low circulation factor. Such fineness of the powder, which is of the order of magnitude of microporosity, should also be avoided because of the danger of drying out while at the same time disrupting the morphology. (All moisture values are given in accordance with DIN and refer to drying in an oven at 105 ° C to constant weight).

Usually, the milled material immediately after the mill is separated into sieves with the required fineness and still too coarse material to be returned. It is therefore in an indefinitely long circulation. In the drying process, the pre-grinding process, this circulating material is excessively dried, which in smectic clays results in that this dried fraction is not sufficiently dispersible / wettable in water and is not suitable in the most important areas of use.

When introduced into an ultrafast rotary mill, the material is split and the coarse, otherwise recirculated material becomes part of the usable fraction.

The number of revolutions, the number and design of the grinding bodies together with the grinding path determine the cut. The aim is to prevent the appearance of coarse particles that would require new grinding in the circulation.

The fine mineral powder ZBFM produced by the process according to the invention is capable of being used for wall sealants together with cement grades QA1, QA2 in a single-stage process (ESTV) as well as in a two-stage process, also applicable to Portland cement, cement type QA3 in a two-stage process . The fine mineral powder NBFM obtained from NBF due to the choice of a site unstable in cement is suitable as the prior art ZBF bentonite in cement stable for the construction of tight walls, as described in connection with the mixing method and types of cement of the prior art. The quality of NBF bentonite is thus increased to the degree of processability of ZBF in the form of ZBFM.

The described fine mineral powder ZBFM, NBFM is suitable for improving cement in screed and spray concrete.

The fine mineral powder ZBFM, NBFM exhibits the necessary increased storage stability in a dry mixture with a hydraulically setting binder, and is also readily dispersible due to its microporosity.

Overview of the figures in the drawing

The following is a description of the clay mineral powders obtained by the method according to the invention on the basis of the measurement results. The tables and drawings show:

tab. 1: indicators of cement stability of various samples, tab. 2: Time-dependent characteristics of suspension of samples dispersed in water, Tab. 3: indicators as in Tab. 2, but in relation to the drying method, FIG. 1: particle size distribution analysis of commercially available bentonite, FIG. 2: particle size distribution analysis of the bentonite according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In tab. 1 are in the rows labeled BI, respectively. B2 shows the measured values for the rheology of wall sealants produced immediately after dry mixing of cement and bentonite with water, as compared to dry mixtures that were stored dry for seven days prior to the production of the wall sealant. Line B1 relates to a two-stage bentonite J27, not formed according to the invention, B2 relates to the same output material J29, which was produced on the same device but in the usual manner. When comparing the values in the "Immediately" and "7d" columns, J27 shows almost unchanged values, indicating increased storage stability. J29 does not reach the required processing viscosity, see Marsh number and creep limit, and even loses its original viscosity level by storage.

Tab. 2 is constructed similarly to Tab. 1. However, it concerns the rheology of clay materials dispersed in cement-free water. Row C1 contains the values of clay materials in the conventional manner finely ground and shock dried, while row C2, on the other hand, contains the values of clay materials according to the invention, coarsely ground and shock dried. It is evident from the entire C2 line that the semolina fraction is microporous because the temporal evolution of the suspension rheology shows from "immediately" through "1 h" to "24 h" compared to the values in the C2 line the same, even slightly higher speed. In fact, it would be possible to expect a delayed course of rheology development in the material according to line C2.

Tab. 3 contains, as in Tab. 2 shows the development of suspension rheology over time, with line D1 referring to normally dried and ground material, and line D2 referring to material J27. Normally dried and ground material is understood to mean a material which has been pre-dried to 14% moisture and a milling drying in a roller bowl mill up to a residual moisture of 8%. It is apparent from row D1 that the material is not usable as a grouting bentonite on the walls, while the material according to row D2 exhibits excellent, very high theological values, which are only achievable with expensive selected bentonites or additives.

Fig. 1, 2 are constructed in the same way. They always refer to the list of XO / mym particle diameters tested against their Q3 fraction as a percentage of the total volume of all particles. This list is the basis for the integral curve of the volume distribution as well as the particle diameter distribution.

When comparing FIG. 1 and 2 it is evident that commercial bentonite, see FIG. 1 has a wider particle size distribution and contains a high proportion of fine particles, while the material according to the invention, see FIG. 2, has a narrow distribution substantially free of fines, with a maximum at 0.06 mm. From line A1 of the explanation to FIG. 1, case A2 of the explanation of FIG. 2 shows the specific surface area values relative to the particle volume. They exhibit different finenesses, see 0.63 m ² / cm ³ in line A1, compared to 0.36 m ² / cm ³ in line A2.

Table 1

Evaluation of stability in cement

indicators Rcológia Handle ^{: ω} 200 kg / m ⁴ Etchsofidur immediately 7d 30d Sample designation > 2 ABOUT in WITH 2 H and > l o H 1 OU and H s H 1 H P s á w 1 S 3 * aa i ^ε ϊ I H i s 2¾ e Ii S and 1 . s w '<0 u h a about Λ l J27 Mozer F; 23.7% JäckeflnqGrtesF9.7% H J 16.7 6.9 75 . 2 32.2 40 6 27.4 0.4 39 e 27.4 0.5 1,156 J29 Mczer F: 13.1% Jackering F. 4.7% Fein H J T 2.9 72.1 2 24.7 35 4 14 0.6 33 2 7.5 BD49 Binder Eing: 150'C 5 min H 8L 40.1 12.3 66 2 37 38 6 27.4 0.6 33 with 27.4 OJ 60 Hande S8M. Soda 5.S * 0M ⁺ Ex HD sputter BL 9.3 74 5 33 40 7 37.1 0.4 43 and 48 0.4 B47 M3 Babcock F: 21% Lab. Mahllrock H 0L 46.2 62 74.6 29 36 6 2 / .4 0.5 _ SoUwerte DYBS | I I 36 T / 1 38 7 JZA

Table 2

evaluation

R.Nr Sample designation I Adjustment j .2 WITH indicators rheology \ 'ásada50Wm ^J immediately 1 h 24 h m ct H * Water content M H . B V SS Ό * = Ii> c H * WITH M jh > '8 E C4 you 9 M y ä and jC n p g. H 'x. n Ξ ž & Sg i ~ s Ε · δ TH and tn P6 w ‘1 _, kjáá 2 a 's i M Zf % and 'ä w u s f-1 n «9 Έ p Í Dí and Z E 2 r- <th 2 WITH N o 3 Ϊ Ventŕtextrocknuna 73 10mm400 * C 2.0 min H BL0.3 E & 7.9 76.0 10.2 20.0 31 0 0 32 0 35 1 6.3 64 10 mm 400 * C 1.5 min H 010,3 7.1 8.5 78.5 17.6 21.0 32 1 6.3 36 2 8.3 41 5 1.7 ^ W 10mm400'C 1.5 min H SL0.5 39.5 10.0 75.0 17.8 20.0 33 1 6.3 36 4 15.4 40 5 21.7 65 10mm400'C 1 min H 010,3 10.0 7.2 7A, 4 21.1 25.0 34 2 6.3 39 4 15.1 48 6 30.2 65 10 mm 400'C 1 min H BL0.5 44.2 12.0 76.7 21.1 22.0 36 4 15.4 42 6 30.2 50 7 37.2 66 5 mm400 * C 1.5 min H BL0.3 0.1 7.2 75.4 10.3 17.0 31 0 0 33 0.3 37 3 12.3 67 5 mm4D0 ° C 2.0 min H BL0.3 8.3 3.8 72.8 2.8 17.0 29 0 0 31 0 0 30 0 0 68 10 mm 2 WC 2.0 min H 8L0.3 17.9 9.0 70.9 24.0 25.1 35 3 12 (s 41 5 53 0 30 (2 68 10 mm i0V * C 2.0 min H BLO.S «4 11.8 79.4 24 (0 25.0 69 10 mm 200C 3.0 min H BĽ0.3 8.3 8.1 19.5 28.0 33 1 8.3 38 4 15.4 48 6 30.2 70 10 mm 200'C 4.0 min H BL0.3 5.8 8.4 76.4 15.0 22.0 32 1 6.3 38 3 T5J 41 5 21.7 71 5 mm 200´C 2.5 min H BL0.3 10.0 6 (9 75, ¹ 16.8 21.0 33 1 6.3 38 3 12.3 43 they 30.2 71 5 mm 200´C 2.5 min H 810.5 40.0 ω 77.6 l6 _f Ô 21 (0 34 2 8.3 38 6 3U _t 2 46 6 30.2 72 5 mm 200'C 3.0 min H BL0,3 6.1 8.9 76.8 iš ,? 24.0 32 1 6.3 35 3 12.3 41 3 30.2 n 5 mm 200´C 3.0 min H 010.5 34.0 9.9 74.8 13.7 25.0 33 1 6.3 36 3 12.3 40 5 21 /

Table 3

evaluation

R.Nr Sample designation treatment indicators Reolóeia handle; 50 kg * d φ honors H immediately 1h 24 h and i A O H XJ 3 ä v 1 H 1 H IN 'WITH H It is> § CXr E ^ Λ £ & s ΐ » H n * Σ> <s • bC tg š 8 I M Z E s H B) XJ «£ ä ť ä • σ v C > y £ 8 From E »-> R ri Ή U. and £. «P £ H IN) £ U Ϊ Š 1 'No. "EI FROM mu P xJ f-r ΰ i Ϊ. 2 g pä 1 19 Rieter SBM10. Soda 3,5 + SR R bl 44 D, 7 64.5 23.6 100 34 2 8.3 38 4 15 (4 9.5 42 6 30.2 9 10 24 Rieter SBM1O. Soda 3,5 * SR6. Mo G À G0 0.4 6.8 76 25.6 w 33 6.3 36 3 12.3 10 44 5 21.7 9.5 9.9 1,026 56 Hflndle 6RSH, Soda 3,5 + M0VG6 hl BL 7.3 73 33 100 35 3 12.3 36 4 15.4 10 42 6 30.2 9 10 60 SBM Seals, Soda 5.5 + DM + SR10 HL BL 9.3 74 33 100 39 6 30.2 44 8 30.2 9 64 8 49 9 10.1 H48 Händle Nibra Mgdb nach SR H BL 8 65 30 100 34 3 12.3 38 4 15.4 10 45 6 30.2 9.5 10.1 1.025 34 Almonds Nibra Mgdb. SR * DM ♦ Extf. H BL 11.6 6 / 38 3 II.AO 44 6 30.2 10 61 you 30.2 9 9.9 N33 Mozer F: 14.2% Neuman 8 Esser F: 9% H NE 4.1 8.3 73.6 21 98 31 0 32 0 12 35 1 6.3 11 10 J27 MoxerF: 23.7% Jackering GrtesF.-9.7M H J 16.7 6.8 75 32.2 100 37 5 21.7 44 6 30.2 9.5 52 8 49 9.5 9.8 1.025 J26 Mozer F: 20.7% Jackering F: 9% H J 2 9.0 76.9 28.3 100 33 2 8.3 37 4 15.4 10 46 6 30.2 10 J29 Mozer F: 13.1% Jackering F: 4.7% Feinste H J 1 2.9 72.1 24.7 100 31 0 34 1 6.3 11 38 3 12.2 10 9.9 BĎ49 Bínder Einq .: 150'C 5 min H 8L 40.1 12.3 86 37 100 3 / 5 21I 40 6 30.2 9.5 47 8 49 10 10 R44 Babcock 12C'-80'C F: 10.5% H 8L 27.6 7.Θ 75.7 25 100 32 Q 33 1 6.3 10 3 / 3 12.3 10 9.8 1,027 845 M1 Babcock 120'-80 * C F: 22% H BL 48.9 Θ.4 76.4 33 100 34 2 8.3 38 4 15.4 10 45 7 37.9 w 9.6 1.027

Explanation of FIG. 1:

Particle size analysis of SYMPATEC HELOS

Measuring method = dry dispersant (RODOS) 10 Pressure = 1.5 bar

Transport speed =%

Focal length = 200 mm

Measurement time = 11 s

Cascade = no

Injector vacuum = max. mbar

Rotation speed = 5%

Density = 1.00 g / cm ³

Sample designation = 66805

XO / MYM Q3 /% 1 XO / mym Q3 /% 1 XO / MYM Q3 /% I. XO / MYM Q3 /% 1 6.20 14,62 1 25.00 43,32 l 102.00 90,14 1.80 4.89 1 7.40 17,14 1 30.00 46.73 I 122.00 94.75 2.20 6.11 1 8.60 19,44 1 36,00 54.35 I 146.00 57,97 2.60 7.19 Í 10,00 22.05 1 42,00 59,23 1 174.00 99.70 3.00 8.18 I 12,00 22,56 1 50.00 65,00 1 205.00 100.00 3.60 8.56 I 15,00 30,28 1 60,0Q 71.45 i 246.00 100.00 4.40 11.25 1 10,00 34.51 I 720Q 78,19 1 294.00 100.00 5.20 12.36 1 21,00 38.44 I 86,00 84,62 1 350.00 100.00 X10 = 3.81 mym x50 = 31.36 mym x90 = 101.58 mym x15 = 6,30 mym X85; ^: 87.09 mym x95 = 123.85 mym A1 Sv = = OJ 629 m ² / cm ³ C_opt = 4,0% RRSBx '= 41.33 mym 0: = 0.959 r = 0.9969

Explanation of FIG. 2:

Particle size analysis of SYMPATEC HELOS

Measuring method = dry dispersant (RODOS) Pressure = 1.5 bar

Transport speed =%

Focal length = 100 mm

Measurement time = 11 s

Cascade = no

Injector vacuum = max. mbar Rotation speed = 5%

Density = 2.38 g / cm ³

Sample designation = 16. 687S Bentonite

XO / MYM Q3 /% I XO / mym O3 /% t XO / mym Q3 /% 1 XO / mym Q3 /% (3.10 3.07 l 12:50 9.69 ¹ l 51.00 69.83 0.50 0.77 I 3.70 3.45 I 15,00 12,00 l 61,00 82.34 i.io 1.09 and 4.30 3.89 I 18,00 15:16 1 73.00 92.20 1.30 1.38 1 5.00 4,36 t 21,00 15.77 1 87.00 08.17 1.50 1.64 I 6.00 5.02 I 25.00 24.43 1,103.00 100.00 1.80 1.87 I 7,50 6.02 I 30.00 32.79 I 123,00 100.00 2.20 2.36 I 9.00 7.02 I 35.00 43.98 I 147,00 100.00 2.00 2.70 1 10.50 B, 05 I 43,00 56.92 {173,00 100.00 X10 - 12.83 mym x50 ’ 38,26 mym x90 = 70,32 mym X15 * 17.65 mym x85 e 64.23 mym x95 = 79,57 mym A2 Sv = 0.359 m ^a / cm ³ Sm « 1.507,17 cm '/ g cjjpt = 3,1% RRSBX ~ 54.73 mym n = 1,229 n = 0.9794

Fig. 1

0.9

0.8

0.7

0.6

0.5

0.6

0.3

0.2

o.l o

Volume distribution

10 ' ¹

W ³ · 10 ^_6 n

Fig. 2

Claims (6)

PATENT CLAIMS A method of drying smectic clays with a starting moisture by shock to a predetermined final humidity, characterized in that the removal of moisture is carried out with a short residence time of less than 15 minutes in an oven at a material temperature of <85 ° C, - in a one-stage drying and milling process, it dries from a starting humidity of 30 to 42% to a final humidity of 7 to 12%, and wherein the drying process is conducted at an evaporation rate of at least 0.2 kg water per kg bentonite per minute. Method according to claim 1, characterized in that a starting clay particle size in the range of 5 to 20 mm is used. Method according to claim 1 or 2, characterized in that the clay is dried by co-drying at an inlet temperature of 300 to 700 ° C and an outlet temperature of less than or equal to 85 ° C. Method according to claim 1 or 2, characterized in that the clay is dried by cross-flow drying at an inlet temperature of 100 to 300 ° C and an outlet temperature of less than or equal to 85 ° C. The method according to claim 1 or 2, characterized in that the clay is dried by means of a mill drying from 80 ° C at a high amount of air and an outlet temperature of less than or equal to 85 ° C. Method according to claim 1 or 2 and 5, characterized in that il is dried by means of a combined milling process in an ultrafast rotary mill which is set to a particle size range of 0.02 to 0.1 mm.