Note: Descriptions are shown in the official language in which they were submitted.
1. 132873~ CASE 2260
"AQUEOUS SLURRY OF COAL AND RELATED PREPARATION
PROCESSES"
The present invention relates to an aqueous slurry
and to the related preparation processes.
Several processes are known for producing aqueous
slurries of coal.
In patent application DE-28 23 568, a process is
disclosed for the preparation of an aqueous coal slurry,
which comprises a grinding of coal to a size smaller than
100 ~m, a beneficiation of ground coal by using an
alkaline ammonium polycarboxylic salt endowed with the
property of charging the prevailingly organic portion of
coal with a higher charge than that of the inorganic
Portion~ a settling, so as to separate, according to as
:
stated in said patent application, said portions, and
finally a slurrying of coal, separated from the
inorganics, in water. The most striking disadvantages are
.;,
~` due both to the fact that coal must be ground to a very
fine size, and to the fact that the separation of coal
~I from the inorganic matter results very difficult, in~as
much as a sharp boundary line between the two phases does
20 not exist.
~, In BE-893,247 patent, an aqueous coal slurry is
, .
disclosed, which contains two separate groups of coal
; particles, wherein the particles of the first group have
an average size comprised within the range of from 210 to
,,
25 60 ~m, the maximum size being not greater than 300 ~m,
and the particles of the second group have a size
comprised within the range of from 1/6th to 1/20th of
those of the first group.
In this patent, the slurry is only obtained with
,, ~
- 2 - 132873~
non-beneficiated coals.
We have surprisingly found that overcoming the
drawbacks of the prior art is possible by using a heaby
liquid obtained from the distillation of pit-coal tar, or a
fuel oil deriving from mineral oil.
One of the advantages due to the use of either of
the two above-mentioned liquids consists in that the coal
surfaces are given a higher affinity for the dispersant
additive used for the formulation of the aqueous slurry,
with the efficaciousness of this latter being boasted, and
the amount thereof being considerably reduced.
A first object of the invention is to provide an
aqueous coal slurry containing from 60~ to 80% by weight of
coal particles having a granulometry not greater than 300
um, and a polyelectrolyte selected from the monovalent
cation salts of the polymerized naphthalenesulphonic acids
having a molecular weight comprised within the range of from
800 to 3,000, characterized in that said slurry also
-; contains a liquid obtained by the distillation of pit-coal
tar, or a fuel oil derived from mineral oil, said liquid
being present on the surface of the coal particles in an
amount ranging from 0.1% to 2% by weight relative to said
coal particles.
The presence of either of said liquids on coal
- 25 surface renders uniform the surface chemical-physical
~, characteristics of different coals, thus rendering
; efficacious the used dispersant towards coals of even
- diffrent origin.
The liquid obtaine from the distillation of pit-
- 30
' C
` 3. 132873~
coal tar is preferably selected from those having a
distiLlation range comprised within 200 and 400 C, more
- preferably between 250 and 350 C.
For example, creosote oil can be used.
Hereunder to informative purposes a typical
composition is reported for creosote oil, as relates to
some more characteristic components:
Naphthalene 10 % by weight
Methyl-naphthalene 5-7 % by weight
Dimethyl-naphthalene 5-7 % by we;ght
.,
Acenaphthene 8 X by weight
Diphenyl 1-2 X by weight
. .
. Diphenyl-oxide 4 % by weight
Fluorene 8 % by weight
.~ 15 Phenanthrene 15-20 % by ~eight
Anthracene 1 % by weight
Carbazole 2 % by weight
Nitrogenous bases 2-25 X by weight
Higher phenols 2-15 % by weight
The fuel oiL deriving from mineral oil is selected
from those having a viscosity at 50 preferably not lower
than 3 Engler (E), which corresponds to a 21.2 cSt viscosity.
. .,
Coal can be constituted by one single group of
` particles, or by two particle groups.
In case of two particle groups, the first group may
~- contain particles having an average granulometry
comprised within the range of from 210 to 60 ~m, the
maximum size being however not greater than 300 ~m; the
second group can contain particles having an average
granulometry comprised within the range of from 1/6th to
-~ 1/20th of the average granulometry of the particles of
~3
4 1 )~ ~73~
'
the first group, by "average granulometry of the
particles" the granulometry corresponding to 50% of the
cumulative mass distribution of that group being meant.
The particles of the first group should preferably
be at least 40% of total, more preferably at least 60% by
weight of total particles.
The cumulative particle distribution curve, by
resulting from two fractions (i.e., two distinct groups
of coal particles), should show, if reported on a bi-
;;
; 10 logarithmic scale (log-log chart), a flat zone comprised
` between the values of the average dimensions of component
fractions; wherein by "flat zone" a length of the curve
is meant, wherein the derivative, computed on a
bilogarithmic scale (log-log chart), is lower than 0.4,
and preferably lower than or equal to 0.1, and still more
preferably equals zero.
- The cumulative granulometric distribution should
- hence be such that always two particle size values d1
and d2, comprised between the average values of the
diameters of the two fractions exist, for which the
numeric value of the following expression
log(XCM1) - log(%CM2)
,, _____________________
-. log d1 - lo9 d2
".
is lower than 0.4, preferably lower than or equal to 0.1,
and, still more preferably, equals 0.
8y "(%CM1)" and "(%CM2)" the values are indicated of
the cumulative percentages of the mass of particLes,
respectively having a size lower than d1 and d2.
The numerical value of the expression is, obviously,
independent from the unit of measure (micrometres or
~" .
:,
1~?~73 J
millimetres) according to which the particle size ;s
expressed.
When preparing a slurry is desired, from a coal
; previously submitted to a beneficiation by agglomeration,
the addition of the liquid obtained by means of
distillation of pit-coal tar is carried out during the
`~ same beneficiation treatment, by performing such a
;
treatment in the presence of a light hydrocarbon of from
~` 4 to 8, preferably from 5 to 6, carbon atoms, said
hydrocarbon being flashed off after the agglomeration.
Among the preferred hydrocarbons, we ment;on here n-
pentane and n-hexane.
The light hydrocarbon is preferably present in a
percentage comprised within the range of from 5~to 30% by
weight relatively to coal.
A second object of the present invention is the
,. ..
process for preparation of the aqueous coal slurries.
In case coal must also be beneficiated, the process
, comprises a beneficiation by agglomeration in water of a
coaL having a granulometry not higher than 300 ~m with a
liquid obtained by means of the distillation of pit-coal
tar, or with a fuel oil deriving from mineral oil, in an
~ amount comprised within the range of from 0.21to 2X by
- weight relatively to coal, and a light hydrocarbon
comprising a number of carbon atoms comprised within the
range of from 4 to 8, in an amoung ranging from 5~.to 30%
by weight relatively to coal, the flashing of the light
hydrocarbon, after that the prevailingly organic portion
has agglomerated and separated from the aqueous solution
in which the inorganic components have remained suspended
or dissoLved, and, finally, the slurrying in an aqueous
'
.
132873~
solution comprising a polye~ectrolyt~, as the dispersant,
selected from the monovalent cation salts of polymerized
naphthalenesulphonic acids having a molecular weight of
from 800 to 3,000, preferably around 2,000, the percent
amount of the dispersant be;ng comprised within the range
of from 0.05 to 0.5% by ~e;ght relat;vely to the we;ght
of the slurry.
Among said polyelectrolytes there can be used, e.g.,
- the chemical compounds known under the tradename of DAXAD
15 and DAXAD 1~ ~y W.R. Grace, and Reoplast 203* by
Fratelli Lamberti S.p.A.
On the contrary, in case coal has not to be
beneficiated, the process comprises the slurrying of a
coal having a granulometry not greater than 300 pm, in a
solution containing a liquid obtained by means of the
; distilla~ion of pit-coal tar, or a fuel oil deriving from
mineral oil, in an amount comprised between 0,2~ and 2X
by weight relative to coal, and a light hydrocarbon
:~ liquid comprising a number of carbon atoms comprised
within the range of from 4 to 8, in an amount comprised
.
-` within the range of from 50% to 200% by weight relatively to coal,
; followed by the flashing of the light hydrocarbon and by the forma-
,:
; tion of an aqueous slurry by means of the addition of a dispersant
constituted by a polyelectrolite selected from the monovalent cation
salts of polymerized naphthalenesulphonic acids having a molecular
. weight of from 800 to 3,000, preferably around 2,000, the percent
amount of the dispersant being comprised within the range of from
0.05% to 0.5% by weight relatively to the weight of the slurry.
As relates to the preferred granulometries, the
- 30 preferred l;quids obtained from the dist;llation of pit-
coal tar, the preferred fuel o;ls der;ving from mineral
~ ,.
* trademarks
.' ~ ~
1~2873~
:.
:.
oil, the preferred light oils, and the preferred
polyelectrolytes, what above said for the aqueous
slurries holds true as well.
The following Examples are supplied to the purpose
:
of illustrating the invention, which however is not to be
, considered as being limited to them or by them.
" ameL 1-_
A American bituminous coal (Pittsburgh Nr. 8) was
dry-ground; it had the folLowing anaLytical
characteristics:
' I m m d i _ _ _Q _ a l y _ i _
Intrins;c Moisture % w 1.19
Volatile Matter % dry w37.10
Ashes % dry w7.56
Fixed C (by difference)% dry w 55.34
;. ED__Q__ly_i_
Carbon % dry w76~93
Hydrogen % dry w5.25
Nitrogen % dry w1.66
Sulphur % dry w1.63
Ashes % dry w7.56
Oxygen (by difference) % dry w 6.97
H_at_Val _
Gross Heat Value kcal/kg7,627
Net Heat Value kcaL/kg7,356
After the grinding, the end granulometry results to be
the following:
-, , Passl_g__h_QY9h %__f_C_m_Latlye_W_ight
150 ~m 99.3
74 ~m 87.0
; 53 ~m 61.9
8. 1328733
44 ~m 36.5
; The coal having this granulometry was used for
preparing the slurries after being coated with a creosote
oil film.
The coating by the creosote oil ~as achieved by
diluting this latter oil in n-hexane, subsequenty adding
coal, under stirring, and finally flashing off the
solvent.
The amount of creosote oil added to coal was 0.5% by
i,
;~ 10 weight based on dry coal, and the amount of n-hexane was
100% by weight.
W;th the used granulometry, samples were then
prepared and analysed of water-coal slurries, with a
solids concentration of 62% by weight, to which 0.~ 0.3
and 0.5% by weight of DAXAD 15, relatively to the
; suspension, was added.
The blend was characterized in terms of its
apparent viscosity at 50 sec
The results of these measurements are reported in
. -
Table 1.
x _m~ l_____8_ ( C ome r i _ o_ mP l_ S )
The same American coal (Pittsburgh Nr. 8), with the
- same granulometry as obta;ned in the foregoing Examples,
was used without any creosote oil for preparing slurry
samples to which respectiveLy 0.2~ (Example 5), 0.3
(Example 6), 0.4J (Example 7) and 0.5% (Example 8) of
DAXAD 15 by weight was added.
The results are reported in Table 1 as ~ell.
By comparing these results with the previous ones,
it can be see from Table 1 how considerable is the effect
of the treatment with creosote o;l on apparent viscosity
` ,: ' ' ,
9. 13.2~73~
;`
values.
;~^
Above all for low additive levels, the reduction in
viscosity is very evident (50-60% at DAXAD 15
concentrations of 0.2-0.3% by weight).
.~;,
The viscosity value observed at 0.2% of dispersant
additive for creosote-treated coal as such is even lower
!
than that obtained with non-treated coal with 0.5% of
additive.
Ex__el__9-11
A Polish coal, having the folLowing analytical
~ characteristics:
"' I m m _ _ i _ t . _9 _ l y _ i _
Intrinsic Moisture % w 1.60
Volatile Matter % dry w 32.80
Ashes % dry w 9.40
; Fixed C (by difference) % dry w 57.80
E___9__ly_i_
Carbon % dry w 73.80
Hydrogen % dry w 4.24
Nitrogen % dry w 1.44
Sulphur X dry w 0.86
Ashes X dry w 9.40
Oxygen (by difference) X dry w 10.26
__at_Valy
. .~
Gross Heat Value kcal/kg 7,167
Net Heat Value kcal/kg 6,948
was partly dry-ground to the following end granulometry:
,1' _aS_iDg_Thr_Y3h W_~ght_X
250 pm 98.8
150 ~m 82.0
125 ~m 52.2
.-
. .,
:
',,'~
.
10. 1328735
:~.
74 ~m 20.244 ~m 2.7
and the residual portion was micronized by wet-grinding
by a laboratory micronizer, to an end granulometric
distribution having an average value (d50) of 6.5 ~m.
With this granulometric distribution, obtain;ng a
66% concentration of coal in the slurry was possible.
,.~
The coal with the above described granulometry
,~
; underwent a beneficiation treatment by selective
;.:
agglomeration with n-pentane and creosote oil. Used
amount of creosote oil equalled 0.5% by weight relatively
to coal.
The beneficiation step was carried out on a batch
. .,
equipment having a capacity of 10 litres of slurry, on a
coal slurry in water at 20% of solids by weight, by using
a concentration of n-hexane of 20% relatively to dry
coal.
.,,
The results of the beneficiation treatment are
reported in Table 2.
At the end of the agglomeration treatment, n-pentane
was removed by drying under N2 in oven at 40 C.
With the beneficiated product, according to the
above disclosed modalities, samples were then prepared
and analysed of coal-water slurries with solids
concentration of 66X by weight and to which 0.2~ 0.3/.amd
0.5% of weight of DAXAD relatively to the suspension was
added.
The results of the rheological measurements are
reported in Table 3.
-xame~ 12-l4-(c-m~a-l-----xam~les)
The same Polish coal of Examples 9-11, with the same
.
'
:
11. 132~73~
,
bimodal granulometry was beneficiated with n-pentane
alone, without using any creosote oil, in the same
`~ equipment and w;th the same modalities as of the above Examples.
5The results of the beneficiation treatment are shown
in Table 2.
As it can be observed from Table 2, the presence of
creosote oil in the agglomeration step led to an increase
in yield, with the product quality being the same tfrom
1085.8% to 90.7% by weight), i.e., an increase of 5 percent
points in energy recovery (from 90.9% to 96.0%).
Furthermore, the induction times of the
agglomeration phenomenon, i.e., the times necessary for
agglomeration to begin, resulted sharply shorter: from
15the 15-minute time of the test with n-pentane only, a
decrease to the 8-minute time of the test with n-pentane
- :
pLus creosote oil as the agglomerating agent were
obtained, with obvious advantages from the viewpoint of
process economy.
20At the end of the agglomeration process, n-pentane
- was removed by oven-drying under N2 at 40 C.
~ith the beneficiated product, samples were then
prepared and analysed of coal-water slurr;es with a
- solids concentration of 66% by weight, and to which 0.2
25~Example 12), 0.3~(Example 13) and 0.4% (Example 14) by
. .
. weight of DAXAD 15, based on slurry was added.
The results of the rheological measurements are
reported in Table 3.
~;
It can be observed from Table 3 that the slurries
obtained with beneficiated coal plus pentane plus
creosote oil show a lower viscosity than those obtained
;'
,
x
12. 132873~
! ~
- from coal beneficiated with pentane only.
Exameles 15-17 (Comearison Exameles)
~, ____ ______________ ___________ ____
The same Polish coal as of ExampLe 9-11, with the
same bimodal granulometry, not beneficiated, and without
creosote oil, was used to prepare slurries to which 0.2
(Example 15), 0.3% (Example 16) and 0.5% by weight
tExample 17) of DAXAD had been added.
With 0.2% of DAXAD 15, no fluid slurry was obtained,
whilst with 0.3~ and 0.5% by weight of DAXAD 15 the
suspensions were obtained, the v;scosities of which are
reported in Table 3.
Always from Table 3, it can be observed that the
viscosities are considerably higher than the preceding
vaLues.
; 15 TABLE 1
_x_mele_ 1___ 2___ ____ 4___ ____ ____ 2 __ ____
; DAXAD % 0.2 0.30.4 0.5 0.2 0.3 0.4 0.5
- Viscosity
(cP) 996 710 745 740 2045 1754 1283 1174
~; 20 Coal % 62 62 62 62 62 62 62 62
TABLE 2
Yield,% by Ashes, % by Induction
,~ _X3mele W-i9bt-~ eight_____ tim_ _ __
9-11 90.7 5.0 8 minutes
12 85.8 5.0 15 minutes
~- TABLE 3
Examples 9 10 11 12 13 14 15 16 17
____ ___ ____ ____ ____ ____ ____ ____ ____ ____ ____
DAXAD % 0.2 0.3 0.5 0.2 0.3 0O5 0.2 0.3 0.5
Viscosity (cP) 569 496 412 905 713 532 - 1889 1336
Coal % 66 66 66 66 66 66 - 66 66
