LU84164A1 - AQUEOUS COAL SUSPENSION - Google Patents

Description

NOT

'- Aqueous suspension of coal

The present invention relates to an aqueous suspension of carbon. More particularly, the invention relates to an extremely concentrated aqueous carbon suspension which can be used either to facilitate transport of the coal or directly as fuel.

The prior art suggests a large number of methods for preparing aqueous suspensions of carbon.

U.S. Patent No. 3,762,887 describes a suspension

H

10 carbon slon whose particle sizes correspond to Tyler sieves of module 4 to 325 (4.699 mm to 0.043 mm) in which the concentration of carbon reaches a maximum of 69 # by volume.

In the suspension of the US patent in question, most of the carbon particles have a size corresponding to Tyler sieves with a module of between 4 and 28 (between 4,649 mm and 0,589 mm) jet this means that sizes greater than 4 mm are reached .

The suspension of the above U.S. patent has substantially two disadvantages, namely, carbon particles which are most often of rather large size and a relatively low carbon concentration. These two drawbacks, and particularly the first, mean that the suspension can be used directly as a fuel only in special equipment such as cyclone burners and that, therefore, it cannot be used in conventional equipment. combustion.

4 It should also be noted that even with special combustion equipment, i.e. with an extended downtime of the type described hitherto, there is still the disadvantage of having to unload the coal. get in at the same time as smoke and / or ash if it malfunctions for any reason.

German patent application No. 2 823 568 35 describes an aqueous suspension of carbon having a particle size of less than 100 μπκ

The preparation of this suspension is however complicated by the fact that, when the said preparation is 1 * 2 * * carried out simultaneously with the separation of the inert products of carbon by the action of a polyelectrolyte which electrically charges the particles of carbon In a different way from inert particles, the carbon must be dls-5 persé in water at a concentration not exceeding 10 $ by weight, with the consequence that, after the separation of the inert products, the suspension of the carbon must be concentrated , with easily unimaginable drawbacks produced by the low efficiency of the filter due to the fine particles of carbon and by the relatively high costs of separation.

Surprisingly, the authors of the present invention have discovered that the disadvantages of the prior art described hitherto can be easily overcome by choosing the carbon particles in two suitable different dimensional ranges, and adding to the suspension a polyelectrolyte chosen from a class of compounds having a particular chemical structure.

According to the invention, the carbon suspension comprises particles of a first group having an average size of between 210 and 60 µm, the maximum size not exceeding 300 µm, and particles of a second group having an average size between 1/6 and 1/20 of the average particle size of the first group, the average particle size of any given group being that corresponding to 50 $ of the cumulative distribution of the mass of this given group.

The particles in the first group represent at least $ 40 by weight of the total, and preferably about 60% by weight of the total of the particles.

I As the cumulative granule-metric distribution curve represents the result of two fractions (i.e. two separate groups of carbon particles) it must show, when plotted on a bilogarithmic scale (log- log), a flat area between the values representing the average sizes of the eons-tltuantes fractions, flat area designating a part of the curve where 3 '- the derivative, when it is calculated on a loglog scale (log-log diagram) , is less than 0.4, preferably less than or equal to 0.1 and better still equal to zero.

The cumulative particle size distribution must therefore be such that there are always two particle sizes d ^ and dg located between the mean diameters of the two fractions, for which the numerical value of * the following expression: log (# CMl) - log (# CM2) 'in log dL - log dg is less than 0.4, preferably. Less than or equal to 0.1 and even better equal to zero.

(#CMl) and (# CM2) Indicate the total percentages ^ of the mass of the particles having a size Less than d ^ and dg respectively.

The numerical value of the expression is clearly independent of the unit of measurement (micrometer or mlll-meter) with which the particle sizes are expressed. 2q In addition to the coal having the sizes above, the carbon suspension according to the present invention contains a non-tenslo-actlf anionic polyelectrolyte, comprising in particular polynuclear aromatic groups substituted by alkyl radicals, and having a molecular weight greater than 500 and preferably between 800 and 3000.

<rb

In particular, the monovalent cationic salts of the polymerized alkylnaphthalenesulfonic acids * having a molecular weight of approximately 2000 can be mentioned, and among these, the chemical compounds known under the trade marks "DAXAD 15i! And" DAXAD lQ "from WR Grâce, and "REOPLAST 203" by Fratelli Lamberti SpA. The amount of polyelectrolyte in the suspensions is generally between 0.1 and 1% by weight, preferably between 0.3 and 0.5 # by weight and even better around 0 , 4 # by weight relative to the total suspension. It is important to note that the polyelectrolyte is preferably added in the form of a concentrated aqueous solution. The polyelectrolyte solution is added either to water before dispersion carbon particles of the 4 '- two groups, or to the aqueous suspension of the carbon particles of the second group, when the latter is prepared for example by wet grinding, before the addition of the particles of the first group.

5 The suspension according to the invention may also contain a stabilizer of the organic gel type preferably chosen from polysaccharides such as those known under the name of "ELZAN" from Kelco.

The stabilizer, in an amount of 0.01 to 0.03 # by weight of the total suspension and, preferably, in an amount of 0.02 # by weight, can be added at the same time as or after the polyelectrolyte .

The stabilizer is preferably used only when the carbon slurry is to be used after an extended period. This depends on the nature of the coal and, for example, this period can be of the order of 1 month. It is important to note that the aqueous suspension of carbon according to the present invention also includes any inert products accompanying the carbon. In this way, the pro-20 assigned to prepare the coal suspension according to the present invention differs from other processes which require a prior separation of the inert products, the coal-water suspensions being only prepared after this last operation. Consequently, inert products do not constitute an obstacle to the preparation of a fluid, stable, very concentrated suspension.

The concentration of the suspension can even reach very high values, for example 80% by weight, or more than carbon.

As regards the type of water to be used for preparing the carbon suspension according to the present invention, the inventors have discovered, quite surprisingly, that this water can be of any type, and thus of the normally soft water or demineralized water or even salt water containing up to 40 g / l, or more, of dissolved salts, and in particular mei water; can be used.

The process for the preparation of the coal suspension according to the present invention has been described in part hitherto, and comprises the following essential stages: 1) grinding the coal to two levels of particle size, said grinding being carried out either dry either by wet flies (that is to say in the presence of water) to obtain either added a ^ them groujje ^ of coal particles in the case of dry grinding / aqueous slurries of the two groups of particles of coal in the case of grinding by flies hu-v mlde, the grinding being however carried out preferably in the dry to obtain the larger tall particles, and by wet flies to obtain the particles of smaller sizes; the polyelectrolyte may be present during wet milling.

2) Mixing of the two groups of particles in the proportions described, a flask both prepared dry or both wet.

3) Addition of the polyelectrolyte either to water or, if only the particles of coal of smaller sizes are prepared by the wet process, to the suspension with which said particles of coal of smaller sizes.

4) Adding appropriate amounts of either the two mixed groups of carbon particles to the aqueous polyelectrolyte solution, or larger carbon particles to the aqueous suspension of the smaller carbon particles containing the polyelectro-25. lyte.

i _ 5) Optionally addition of the stabilizer either with the poly- j electrolyte, or after the addition of celul-cl, but before j. adding the particles of coal mixed together; larger groups or particles, one I 30 times that the two groups of carbon particles have already been introduced into the water.

The present invention is illustrated by the following descriptive and nonlimiting examples.

| Examples of Coal Substrates Prepared According to This | invention ί i t I -.- ,. "- * \

: J

6 Ü P »

CO

2 Ό <D ο. CD r (41 4

PS 2 '- · -v MD

ίτ * rH ”. CM CM VQ

£ MD CM H CM uS O

î->

"M

<T3

W £ Q

^ S §

m ^ O 0 r-i CM

„« Ό r-i H CA \ Q H

W ro ω o co ß

O CQ

rQ <H O VO

CO rj O CK CD O

XJ £ MD O r- | CM ri 0 Λ n v 0) Ό

W

S "

Tl “o S \ ^ CD

fi, „· o> · * A 1 — i o \ -v

O 5 MD O r-l CA L * O

£ O

^ H

O

CL,

1 — I

ω where that

* τ-i O O- CD

CO O v CM CA CM

£ MD “—I r-C CA VA o

O

1 — ΐ

O

P-, \ R.

U: G: g & C ί £ * -P> *.

L \ "3 5 co" îr. Ck • S o> * -t 0 J ^ J Uh

m '—O) tR 0} \ R

Ä -P φ o> H 0 * Ή 0) tu C Q) Μ Ό U Λ) o Pt / ο · -H «-H X! "In

I s ^ OECPPPJ

Γ'ΐ ri · PJ Φ CO CÖ O

^ P-i KO E O co I, 7 Ή Ο Ο Ο Ο siP * * Γ "* rH γΗ ^ Γ ° ν γΗ Ρ" Λ γΗ η rS £ * Λ η

COiH

Μ) • Ρ Ή § -> §§ <5 <<<<<<<. <Μ · <^ - <<: * <· <Ρΐ · <· <· <ϋοο (Τί "Η> 5 G 'ri η γη „ν c; ° ο ο ο α oooooooocTooooo Ά γΗ gg ο ο ο ~ ο ο ο ο ο ο οη ο ο ο θ '* ^ a" £ g5 Ç'ONCrvCNOCKO.OCKCS-vr ^ o ^ en ^ ο NvOVOVOvO ^ OvoOnO ^ ONNNN ρ. ^ 'A Ά ντ »ιπ \ ο ντν αο

5 »IIR? IS? I? IRÂÏÂ ^ ïS

SS ïssssssns ^ sss ο§ ïïssigssn'gâjs

I — i N

èS iAlA ^ 9900009ooirio 0v- ^ vrsu ^ '£,' OO'0N0 \ 0O-3-s0v0t <~ \\ 0 ρορ ^ οοοχπνποοοοο

• Ö Os NNNNNNNNNCNJ ^ f X) t-cO

w ”7T W

• jl'V °: O O Wt ΜΛ O O m 1Γ | N m ΆΟ O

dOvWNNHriNNHrl E NNNOvNlAiAO'O'ONNNw

^ ^ ^ r-J ^ fHr-ir-frnr-ii — l t— · r ~ î rS rH

* â B 2299 2 °° oo cvcooo ^ "iâsssaaas'saaa rH Cv

"> C W K

Ό G * H _ _ _ _ * H te

.Ω "J * - · - tos = = = <H

<U ï-t C P O ~ ~ ~ • Ck £ 0 ο ο c

i j >> x; H iH «H

Eh O O O JC

P- · P-, o

. ^ I I CSJ r ^ L ΙΑ νΛ K ΓΛ Λ Λ> Λ »rf \ -L

8 3t

"H

rH Ο Ο Τί ^ ^ Γ1 ί1 Η Η Η · ° \ \ \ \ \ \ V \ s. \ ^ Χ * ΧΧϊχϊ * ϊκϊκ * σι 2 8> a ^ - \ * - <^ R. Ν, η sy ° ° g ο οοοοοοοοοο * Γ \ 1-1 ^ R · ^ -4--4--4--4- ν \ - ^ · Π Ό 1 Xi ο ο ο ooö'o'od '.

äö

/-NOT

ë

. - £ pOOsCK ^ CMCMCNO

NS <0 \ û NNN \ oN

v- / C * - O- t> - vo Ό Ό î 5 ΐ1 ί σ \ σ \ σ \ οο 5 5-4-5 (Λ nc \ 4- 4 cm -—-> 'S ”. ΙΛΆΙΛΙΑΟΟΟΟΟ Ow 4 -4-44-555-44- 0 ^ \ Tvir) U- \ vr \ QQOOO Ον- 445555555 Ή

ΆΆ ^ νΛΟΟΟΟΟ Ow IC \ U ~ \ "f% U" \ vO VD vO vO vO

's CM4 OOOOOOOO Ά

- • d '-> - D-NNNNNNNN

* CMH O O ν \ Ά IT \ VT \ U ~ v U ~ \ r-l ^ ^ CM CM î i 1 1 1 i 1— ({—i r — i, - <H NNNNiniAiANi

<-S3 N N N N N N N M

’Ϋ́ r-irir-fr- {r-ir- (r- (r-i, -Ο _ O O O Q C \

r-jH O O O O r-! 1— (1 — i u'CO

θ3 iH H r-1 Ά CM CM CM r-i

-dO- CM CM CM iH

3 Ό a O fl)

^ C P

fl O cr _ ce <h = = _, - î “- * -, SÂT3 ^ T3 i ro e V13 1

r_ C <CO I

lc c - i

* - Ό CJ * C I

v · Û X! U \ vf 'N- <T5 ΓΚ fS _f Λ. fTN 1 »9

AT

• · legend dml: average particle size of the first group (pm) dm? : average particle size of the second group pm 5 Cwl - weight percentage of particles of the first group (relative to the dry matter;

Cw2: weight percentage of particles in the second group (relative to dry matter)

Cw: weight percentage of coal in the aqueous suspension 10 Cw "DAXAD 15m: weight percentage of" DAXAD "in the aqueous suspension! Cw" KELZAN: weight percentage -of "KELZAN" in the aqueous suspension

A / -: viscosity between 300 and 700 cP

15 B / -: viscosity greater than 700 and up to 1000 cP.

C / -: viscosity greater than 1000 cP

- / N: Newtonian or weak plastic behavior of

Blngham 20 - / B: plastic behavior of Blngham W / -: excellent stability X / -: good stability Y / -: acceptable stability - / 1: stability measured after 1 Day 25 - / 30: stability measured after 30 Days

Figures 1 and 2 show the possible shapes of the curve of cumulative percentages compared to the particle size plotted on a log-log scale.

The ordinate axis represents and the abscissa axis represents the diameters in μπι.

From Figure 1, we can see that the average straw of the particles of the first group is 83 pm, the average size of the particles of the second group is 11 pm, d- ^ is equal to 44 pm, is equal to 25 μπι, £ OKI is 40 and% CM2 is 40 35 (example 23).

From Figure 2 we can see that the average size of the particles in the first group is 82 pm, the average size of the particles in the second group is 7.2 pm, d · ^ is 50 pm,; * is 20 pm; % CMl is 69.6 and $ É CM2 is 63.6 (example 10). ^

Claims (5)

10 * - CLAIMS 1. Aqueous suspension of carbon, characterized in that it comprises particles of carbon in water which have a size not exceeding 300 μm and which are divided into two groups of different sizes, and that it also contains a polyelectrolyte and optionally a stabilizer. 2. Aqueous suspension of carbon according to claim 1, characterized in that the carbon particles of the first group have an average size of between 210 and 60 µm. 3. An aqueous suspension of carbon according to claims 1 or 2, characterized in that the particles of carbon of the second group have an average size of between 1/6 and 1/20 of the average size of the particles of the first group. 4. Aqueous suspension of carbon according to claims 1 or 2, characterized in that the particles of the first group represent at least k0% by weight of the totality of the particles. 5. An aqueous suspension of carbon according to claim 4, characterized in that the particles of the first group represent approximately 60 ^ by weight of the totality of the particles. 6. Aqueous suspension of charcoal according to any of the preceding claims, characterized in that the cumulative particle size distribution curve, * when it is plotted on a logarithmic scale, comprises a flat zone situated between the values representing the sizes means of the two groups of particles this different sizes. 7. Aqueous suspension of coal according to claim 6, characterized in that the cumulative particle size distribution curve is such that it comprises two values of particle sizes, d, and eu, located between the i- 2 mean diameters of the two groups of particles, for which the numerical value of the expression 11 "*. (a) log (# CM1) - log (# CM2) log to1 - log d? * is less than 0.4, expression in which #CMl and% CM2 indicate the total percentages of the mass of par-5 cells having sizes less than d ^ and d ^, respectively. 8. Aqueous suspension of carbon according to claim 7, characterized in that the numerical value of the expression (a) is less than or equal to 0.1. 9. Aqueous suspension of carbon according to claim 8, characterized in that the numerical value of expression (a) is zero. 10. Aqueous suspension of carbon according to claim 1, characterized in that the polyelectrolyte is anionic and non-surfactant. 11. Aqueous suspension of diarbon according to claim 10, characterized in that the nonionic surfactant anionic polyelectrolyte comprises polynuclear aromatic groups substituted by alkyl radicals. 12. Aqueous suspension of carbon according to claims 10 and 11, characterized in that the polyelectrolyte has a molecular weight exceeding 500 and, preferably, between 800 and 3000. 13. Aqueous suspension of carbon according to one. 25 as claimed in claims 1, 10, 11 and 12, characterized in that the polyelectrolyte is chosen from the monovalent cationic salts of polymerized alkylnaphthalene sulfonyl acids having a molecular weight of approximately 2000. 14. Aqueous suspension of sebn charcoal any of the claims 1, 10, 11 and 13, characterized by! the fact that the amount of polyelectrolyte is between 0.1 and 1%, and preferably between 0.3 and 0.5% by weight of the total suspension. 15. Aqueous suspension of carbon according to soumlca-35 tlon 14, characterized in that the quantity of polyelectrolyte is approximately 0.4% by weight of the total suspension. 16. Aqueous suspension of coal as claimed in 112 •. cation 1, characterized in that the stabilizer is present in an amount between 0.01 and 0.03 $ by weight of the total suspension. l7. Aqueous suspension of coal according to reven-5 dlcatlon 16, characterized in that the stabilizer is present in an amount of $ 0.02 by weight of the total suspension. 18. Aqueous suspension of coal according to one. any one of claims 1, 16 and 17, characterized in that the stabilizer is an organic gel, preferably a polysaccharide. I9. An aqueous suspension of carbon according to any one of the preceding claims, characterized in that the water is salt water. 20. Aqueous suspension of coal according to claim I9, characterized in that the salt water is sea water. 21. Process for the preparation of an aqueous suspension of coal according to any one of the preceding preceding claims, characterized in that it comprises: 1. the grinding of coal at two size levels; particulate, said grinding being carried out either dry or I wet (that is to say in the presence of water) to obtain either the two groups of carbon particles in the case of dry grinding, either aqueous slurries of the two groups of coal particles in the case of wet grinding, the grinding being preferably carried out dry to obtain the particles of larger sizes, and by wet method to obtain the particles of I 30 smaller sizes; polyelectrolyte may be present! during wet grinding. I 2) The mixing of the two groups of particles I in the proportions described a fols both prepared! dry or both wet. I 35 3) Addition of the polyelectrolyte either to water or, I if only the particles of carbon of smaller sizes I ε are prepared by the wet route, to the aqueous suspension! 'said particles of coal of smaller sizes. 13 '* 4) The addition in appropriate amounts of either the two mixed groups of carbon particles to the aqueous polyelectrolyte solution, or larger carbon particles to the aqueous suspension of the larger carbon particles containing the polyelectrolyte. 5. The optional addition of the stabilizer either with the polyelectrolyte, or after the addition of the polyelectrolyte, but before the addition of the mixed particles of carbon of the two groups or of particles of larger sizes, or after the two coal particle groups have - have already been Introduced into water. - * "Ht ^ / m ► i