PROCESS FOR THE PREPARATION OF A WATER-RESISTANT FUEL AGGLOMERATE

METHODE DE PREPARATION D'AGGLOMERE COMBUSTIBLE RESISTANT A L'EAU

English Abstract

PROCESS FOR THE PREPARATION OF A WATER-RESISTANT
FUEL AGGLOMERATE
ABSTRACT OF THE DISCLOSURE
Process for the preparation of a water-resistant
fuel agglomerate, characterized by the fact:
- that there are employed a finely divided fuel
material, an organic binder and an oxidizing agent,
- that the oxidizing agent is mixed with either the
fuel material, or the organic binder, or with one or
other of these products or their mixture,
- that the mixture so obtained is subjected to an
agglomeration treatment, and
- that the agglomerate obtained at the end of the
agglomeration treatment is subjected to a stoving
treatment.

Claims

-16-
CLAIMS
1. Process for the preparation of a water-
resistant fuel agglomerate, characterized by the fact
that:
- there are employed a finely divided fuel material,
an organic binder and an oxidizing agent,
- that the oxidizing agent is mixed with either the
fuel material, or the organic binder, or with one or
other of these products or their mixture,
- that the mixture so obtained is subjected to an
agglomeration treatment, and
- that the agglomerate obtained is subjected at the
end of the agglomeration treatment to a stoving
treatment.
2. Process according to claim 1, characterized
by the fact that the organic binder is selected from
the group comprising molasses, celluloses, hemi-
celluloses, flours, proteins, starches, derivatives of
these products and their mixtures, starches and the
derivatives of starch being preferred.
3. Process according to one of claims 1 and 2,
characterised by the fact that the oxidizing agent and
a water-soluble oxidizing agent selected from the
group comprising hypochlorides, perborates,
persulfates, percarbonates, bromates, peroxides and
their mixtures, persulfates being preferred, ammonium
persulfate being particularly preferred.
4. Process according to one of claims 1 to 3,
characterized by the fact that the agglomeration
technique used is selected from the group comprising
pelletization, pressure-compacting, extrusion and
molding.

-17-
5. Process according to one of claims 1 to 4,
characterized by the fact that the temperature
conditions inherent in the stoving treatment are generally
comprise between about 150°C and about 500°C,
preferably between 170°C and 300°C and, more
preferably still, between 190°C and 250°C.
6. Process according to claim 2, characterized by
the fact that the organic binder is
- either a native starch of any origin, natural or
hybrid derived for example from potato, manioc, corn,
waxy corn, corn with high amylose content, wheat and
granulometric fractions which may be made from, barley
and sorghum,
- or a starch derivative constituted by a physically
and/or chemically modified starch.
7. Process according to claim 6, characterized
by the fact that the organic binder is a native starch
possibly rendered soluble in cold water by physical
treatment of cooking-extrusion and/or of
gelatinization on a drum.
8. Process according to one of claims 1 to 7
characterized by the fact that, with respect to the
weight of finely divided fuel material, there are
employed:
- a proportion of 0.2 to 25% by weight of organic
binder, preferably from 1 to 15% by weight and, more
preferably still, from 2 to 7% by weight,
- a proportion of 0.01 to 10% by weight of oxidizing
agent preferably from 0.025 to 5% by weight and, more
preferably still, from 0.05 to 3% by weight.

-18-
9. Process according to one of claims 1 to 8,
characterized by the fact that at least one
organosilicic water-proofing agent is added to the
finely divided fuel material, to the organic binder,
to the oxidizing agent or to the mixture.
10. Process according to claim 9, characterized
by the fact that the organosilicic water-proofing
agent is a compound whose structural unit is
represented by the formula:
<IMG> (I)
in which R and R1, which may be identical or different
from one another, are organic radicals, said compound
being preferably selected from the group comprising
non-reactive silicone oils, silicone resins, reactive
silicone oils particularly hydroxylated, alkylated,
arylated, hydroalkylated, hydroarylated as well as
mixtures of these products and the emulsions which may
be prepared from these products,
or again a compound selected from the group of
siliconates of the general formula:
<IMG> (II)
in which
- R2 is and alkyl, alkenyl or aryl group,
- X is an alkali or alkaline earth metal atom
and
- 1 ? n ? 10
potassium siliconate being preferred.

Description

~1847~
PROCESS FOR THE PREPARATION OF A WATER-RESISTANT
FUEL AGGLOMERATE
BACKGROUND ~F THE INVENTION
The invention relates to a proce~s for the
preparation of a water resistant fuel agglomerate. It
i8 directed also to the composition of matter employed
in this process.
By the expres~ion ~fuel agglomeratesn, is meant
any physical presentation of finely divided fuel
materials which are easily handled and useful for
domestic or industrisl purposes. By way of example
may be mentioned nuts, briquets and pellets.
The finally divided fuel materials concerned by
the pre~ent invention may be any substances rich in
carbon, like for example coal fines or dusts, wood
fines, coal coke fines, fines of petroleum coke or a
mixture of these product~. The~e materials and in
particular coal fines and dusts are produced in large
amounts by modern methods of extraction and washing,
particularly of coal.
Among the value-enhancing uses of these
materials, may be mentioned more particularly their
use in the form of fuel agglomerates.
Different technique~ of agglomeration of the~e
fines or dusts, generally employing additives or
binders suitable for ensuring sufficient cohesion,
have already been propo~ed.
Among the~e additive~ or binders, the mo~t
employed currently are tar from coal, from wood or
from petroleum, lignosulfonate~, clays,

2018~7~
polysaccharlde~ among which in particular are starches
and starch derivative~.
The most used of theRe binder~ i~ incontestably
coal tar, but the exigencies as regards protection of
the environment becoming more and more strict, its use
today shows a certain recession.
In fact, its use makes it necessary to submit the
agglomerates 90 obtained to a heat treatment or fume
reduction treatment in order to lower the
concentration of phenolic compounds. Now this
treatment results in a non negligible atmo~pheric
pollution. Morecver, the fume reduction treatment not
being complete, the combustion of these agglomerates
at the time of their use causes a release of smoke
noxious to man.
The~e drawbacks have led certaln countries to
forbid their use.
The drawbacks inherent in the use of tar reoccur
during the use of bitumen as binder.
To overcome these drawbacks, it has been proposed
to resort, as binder, to lignosulfonates, in
particular that of ammonium.
The scientific literature relating to the use of
these products is extremely abundant and there may be
mentioned by way of example patents SU 983.147, SU
1.010.146 and su 1.137.103, patents EP 0 097 486 and
DE 3.277.395 or again patentq DD 224.331 and US
4.666.522.
It happens that the technique of agglomeration
with lignosulfonates is complex and its performance
requires considerable mastery. In particular, it is
necessary to dry the fines to a precise moisture
content 90 that the lignosulfonates-fines mixture may

20~8~7~
be agglomerated,an excess or a lack of moisture making
this operation impo~sible.
On the other hand, in the heat treatment, to
polymerise the lignosulfonates and thus to confer on
the agglomerates a good resistance to water, there is
produced a disengagement of noxious fumes rich in
sulfuric acid, a non negligible cause of atmospheric
pollution.
It has been propo~ed to resolve this pollution
problem by applying different arrangements to the
installations concerned, and particularly by providing
smoke condensing devices. But such devices have only
had the result of displacing the pollution problem to
a corrosion problem which it is known to have been
extremely difficult to control especially when it is a
matter of treatin8 condensates rich in sulfuric acid,
even by employing special steel as constituent
material of the agglomeration installations. In any
event and whatever the solutions envisaged, the
drawbacks associated with the use of lignosulfonates
make it a laborious technique.
Moreover, the agglomerate~ manufactured according
to this technique show the drawback of generating,
during their combustion, sulfurou~ residues which are
again found psrticularlr in the smoke.
Processes have been proposed not showing the
above mentioned drawbacks associated with pitch, with
tar and with the lignosulfonates, in which the binders
are replaced by clays particularly by bentonite (US
4.025.596 and DE 1.671.365). However, the
agglomerates obtained according to these techn~ques do
not all show the required physical properties; in
particular, their mechanical strength is insufficient

20~8475
and their behaviour with water mediocre. Consequently
these processes have not been developed in practice.
It has also been proposed to resort, a~ binder, to
starch which, used alone or in a mixture with other
binders, as taught, for example, by patents US
3,726,652 and DE 3.227.395 or again patent EP 0 097
486, shows numerous advantages.
A comparative study on pelletisation done in 1982
at the University of Berkeley (thesis of ~.V,S, SASTRY
and D.~. FUERSTENAU), showed that, with respect to an
asphalt emulsion, or to bentonite, starch led to
better results on the scores:
- of resistance to mechanical compression,
- of abrasion resistance,
- of lmpact resistance.
Moreover, starch may be used without limitation
in indu~trial plants initially designed in the use of
tar or bitumen which are the binder~ most used
currently, its employment hence not requiring an
additional investment; in addition, maintenance of
the plants is reduced.
Finally, combustion of agglomerates bound with
starch does not generate a toxic and/or polluting
smoke.
However, snd this constitutes a major drawback,
agglomerates based on starch, just as those based on
bentonite, show a very distinct sensitivity to water,
making their storage in the open air impossible.
It has been proposed, to overcome this drawback,
to associate starch with tar, with asphalt or with
bitumen or again to insolubilize the ~tarch with
resin~ of the urea-formol, phenol-formol, melamine-
formol, ketone-formol type or their admixture.

2018~75
None of the solutions is satisfactory since all
re~t on the problem of release of toxic and polluting
smoke during the combustion of the agglomerates 90
obtained.
It has also been proposed (~ee patent US
1.507.673), to render these fuel agglomerates based on
carbohydrates water resistant, to incorporate therein
a strong acid in proportions which are not negligible,
among which are in particular phosphoric acid,and to
treat said agglomerates at a temperature comprised at
a temperature comprised between 200 and 540C.
This solution is not satisfactory since, during
the treatment, there remains, as for the
lignosulfonates, the problem of release of corrosive
fumes. In addition, the handling of ~trong acid is
always a delicate and hence constraining operation.
It has also been proposed to coat the
agglomerates with a water-repellent sheet or film
obtained by the application of an emulsified wax.
Although original, such a solution i~ laborious
through the amount of wax employed and the protection
against moisture Yo conferred on the agglomerates may
be altered lf the~e agglomerates undergo, in the
course of their transportatlon, impacts resulting in a
deterioration of the protective sheet.
It ha~ lastly been proposed (see patent EP 89
400071) to prepare water resistant fuel agglomerates
comprising, distributed within their constituent mas~,
on the one hand, a carbohydrate as binder and, on the
other hand, an organosilicic agent as a water
repellent agent.
Such agglomerate~, although having suitable
resistance to bad weather have the dra~back of having

2018~7~
a relatively fragile surfsce condition when they are
moist. Such sensitivity i9 manifested by a well known
deterioration of their skin during their handling,
thus genersting dust in non negligible amount.
Consequently, none of the existing processes
enable the production, under economically and
ecologically acceptable conditions, of fuel
agglomerstes having simultaneously satisfactory
mechanical properties and behaviour to water.
GENERAL DESCRIPTION OF THE INVENTION
It i8 accordingly an object of the invention to
overcome the drawbacks of the prior art and to provide
a fuel sgglomerate responding better than those pre-
existing to the various exigencies or practice.
Applicants hsve had the merit of discovering that
thls objective was obtained by agglomerating a finely
divided fuel material with an organic binder and an
oxidizing agent and by subjecting the agglomerate thus
obtained to stoving treatment.
Accordingly, the process for preparing water-
resistant fuel agglomerates according to the
invention is characterized by the fact:
- that a finely divided fuel material,
an organic binder and an oxidizing agent are employed,
- that the oxidizing agent is mixed with either
the fuel material, or the organic binder, or with one
and other of these products or their mixture,
- that the mixture 90 obtained is subjected to
an agglomeration treatment,
- that the agglomerate obtained at the end of
the agglomeration treatment is subjected to a stoving

20~847~
--7 --
treatment.
According to an advantageous embodiment of the
proces~ according to the invention, the organic binder
i~ ~elected from the group comprising molasses,
celluloses, hemiculluloses, flours, proteins,
starches, derivatives of the~e products and their
mixtures, starches and derivatives of starch being
preferred.
According to another advantageous embodiment of
the proces~ according to the invention, the oxidizing
agent is a water-soluble oxidizing agent selected from
the group comprising hypochlorides, perborates,
persulfates, percarbonates, bromates, peroxides and
their mixtures, persulfates being preferred, ammonium
persulfate being particularly preferred.
It may be interesting to associate with the
action of these oxidizing agents that of duly selected
metal ions recognized for their catalytic power with
respect to oxidation reactions. May be mentioned by
way of example, copper, zinc, iron and other bivalent
metal ions.
When the organic binder entering into the
proces~ according to the invention is a starch or a
starch derivative, by these terms are meant,
- as regards the ~tarch, nstive starches of any
origin, natursl or hybrid starches derived, for
example, from potato, manioc, corn, waxy corn, maize
with a high amylose content, wheat and granulometric
fractions which may be made therefrom, barley and
90rghum~
- as regards the starch derivative, phyYically
andJor chemically modified starches.
Advantageou~ly, the organic binder iq a native

2018475
-- 8--
starch, possibly rendered ~oluble in cold water by the
physical treatment of cooking-extrusion and/or of
gelatinization on a drum.
With respect to the welghts of finely divided
fuel materials, there are employed in the process
according to the invention:
- 8 proportion of 0,2 to 25% by weight of
organic binder, preferably from l to 15% by weight
and, more preferably still, from 2 to 7% by weight,
- a proportion of O.Ol to 10% by weight of
oxidizing agent, preferably from 0,025 to 5~ by weight
and, more preferably still, from 0,05 to 3% by weight.
According to an advantageous embodiment of the
process according to the invention, the water-soluble
lS oxidizing agent may be added in powder form to the
finely divided fuel material and/or to the organic
binder and/or to the mixture of both.
According to another preferred embodiment, the
oxidizing agent may be added in aqueous solution to the
fuel material and/or to the mixture of said material
and the organic binder.
According to the process relating to the
invention, the agglomeration technique employed 19
selected from the group comprising pelletisatlon,
pressure-compacting, extrusion and molding; these
technlques are in themselves known and described in
the patent EP 097 486.
In addition, still according to the abovesaid
process, the agglomerate obtained at the end of the
agglomeration treatment is subjected to 8 stoving
treatment under temperature conditions generally
comprised between about 150c and 500C preferably,
between 170c and 300C and, still more preferably,

201847~
g
between 190c and 250 C .
According to another advantageous embodiment of
the process according the invention, at lea~t one
organosilicic water-proofing agent is added to the
finely divided fuel material, to the organic binder,
to the oxidizing agent or their mixtures in order to
limite possible risks of taking up water again by
csplllarity of the fuel agglomerates obtained
following the process according to the invention
during their exposure to bad weather.
Preferably, the organosilic water-proofing agent
is a compound whose structural unit i~ represented by
the formula:
R
- Si - O - (I)
I
Rl
in which R and R1, which may be identical or different
from one another, are organic radicals, said compound
being preferably selected from the group comprising
non-reactive silicone oils, silicone resins, reactive
silicone oils, particularly hydroxylated, alkylated,
arylated, hydroalkylated, hydroarylated as well as
mixtures of these products and the emulsions which may
be prepared from these products.
Or again, compounds selected from the group of
siliconates of the general formula:

201847~
--10--
~ 9i~ 0 - (II)
OX
in which
- R2 i8 a alkyl, alkenyl or aryl group,
- X i~ an alkali or alkaline-earth metal
and
- 1 ~ n ~ 10,
potassium siliconate being preferred.
The composition of matter employed in this
advantageous embodiment of the process according to
the invention constitutes, within the scope of this
particular application, a novel industrial product
under the same title as the fuel agglomerates 80
obtained.
According to another embodiment of the invention,
it i9 possible to include with the agglomerates other
constituents like, for example, carbonates, quick or
slaked lime, dolomite, slkaline silicates, clay~,
latex, borax, polyphosphates, pho~phates,
concentrated milk and/or whey, cement, polyvinyl
alcohol~ and thermo-setting resins. The proportion of
these constltuents may reach l5% by weight with
respect to the welght of finely divided materials; the
granulometric distribution of these constituents must
be preferably close to that of the finely material.
DESCRIPTION OF PREFERRED EMBODIMENTS
The invention will be better understood by means
of the examples which follow and which relate to
advantageous embodiments.

2018~75
--1 1--
EXAMPLE 1
Nuts based on charcoal dusts/Control
Into a mixer, are introduced, on one hand, 50 kg
of coal dusts having a granulometry less than 1 mm
and, on the other hsnd, 3 kg of native wheat starch.
This mixture is heated to 50 C and there i8 then
lntroduced therein 4.5 liters of water. The mixture 90
obtained i8 malaxated for a ~uarter of an hour with
heating raising the temperature to 90 C; the final
humidity measured by means of a moisture balance known
under the name CENCO is then 8.5%. The mixture is
agglomerated by pression-compacting on a press of the
SAHUT CONREUR type; among the parameters of the
treatment, the temperature of the mixture, which at
the time of agglomeration, is about 70 C, the
pressure of ad~ustment of the presses is 16.7 lO5
N/m linear, the speed of the rolls of the pre~s is
5 rpm and the power of the press is 6 kW.
In this manner coal nuts are obtained showing
sufficient cohesion when freshly prepared to be able
to withstand transportation.
The strength of these nuts, determined by means
of a counterweight compressiometer developed by the
SAHUT CONREUR Company, showed the following vatues:
- freshly prepared ......................... ..294.3 N
- after 24 hours drying
at ambiant temperature ................... 6~6.7 N
- after stoving for one
hour at 100 C followed by
stoving for one hour at
130 C ..... 1765.8 N.

201847~
-12-
These nuts are then immersed in cold water. It is
observed that they disintegrate very rapidly. After
some minute~, the agglomerate shows no cohesion.
The~e result~ illustrate the possibility, by
using only a binder of the starch type, of producing
agglomerates of coal dusts having good mechanical
properties but which do not withstand water.
EXAMPLE 2
Nuts of coal dusts according to the invention.
In a mixer, 50 kg of coal dust with
characteristics identical with those of the dust of
Example 1 and 2.5 kg of native wheat starch were
intimately mixed.
The mixture obtained was heated under kneading to
a temperature of 50 C. Then 25 grams of ammonium
persulfate diluted in 2.5 liters of water were added.
This mixture was kneaded for a quarter of an hour
bringing the temperature of the mixture to 90 C; the
final humidity was then 8%. The mixture was then
subjected to an agglomeration treatment by pressure-
compacting under the same conditions as in Example 1.
In this wa~, coal dust nuts are obtained having
sufficient cohesion when fresh to be able to undergo
tran~portion. The latter are then subjected to stoving
for a period of two hours at a temperature of 220 C.
The strength of these nuts, measured as in
Example 1, shows the following values:
- when fresh ...................... 200 N
- after stoving for two hours
at 220 C ....................... .1300 N
These nuts are then immersed in cold water. No
disagregation was observed even after several hours of

2018475
-13-
immersion.
The mechanical strength of the nuts remained
unchanged after their dwell in water and no
degradstion of their surface condition was observed
during their handling after immersion.
Thi~ example shows that the additlon of 5% of
native starch and 0.05% of ammonium persulfate by dry
weight with respect to the weight of fuel dust,
enables agglomerates to be obtained satisfying the
requirements of the technique from the point of view
of mechanical strength and behaviour to water.
EXAMPLE 3
Coal dust nuts according to the invention.
To a mixture of coal dust and starch identical
with that of Example 2 and this under the same
conditions, 50 g of sodium perborate was added. Then
the mixture was subjected to the same treatment as the
mixture of Example 2. The final humidity of the
mixture was identical with that of Example 2.
In this way coal dust fines were obtained having
sufficient cohesion when fresh to undergo
transport~on. These nuts were then sub~ected to
stoving for two hours at a temperature of 220C.
The strength of these nuts, measured as in
Example 1, showed the following values:
- when fresh ....350 N
- after stoving for two hours
at 220c ....1100 N.
These nuts were then immersed in cold water. No
disagregation was observed even sfter several month~'
immersion.
Their mechanical strength remained unchanged
after their dwell in water and after simple drainage.

2018~7~
-14-
No degradation of their ~urface condition was
observed.
This example shows that the addition of 5% of
native starch and 0.1% of sodium perborate by dry
weight with re~pect to the weight of fuel dust enables
agglomerates to be obtained satisfying the
requirements of the technique both from the point of
view of mechanical strength and behaviour to water.
EXAMPLE 4
Coal du~t nut~ according to the invention
To a mixture of coal dust, starch and ammonium
persulfate identical with that of Example 2 were added
100 g of water-proofing agent of the RHODORSIL
SILICONATE 51 T type (potassium siliconate marketed by
RHONE_POULENC with about 49% of dry matter).
The mixture was subjected to the same treatments
as the mixture of Example 2. In this way nuts of coal
dust were obtained hsving a sufficient cohesion when
fresh to undergo transportion. These nuts were then
subjected to stoving for two hours at a temperature of
230 C.
The strength of these nuts, measured as in
Example 1, had the following values:
- when fresh .... 200 N
- after stoving for two hours
at 230 C .... 1400 N.
The~e nuts were then immersed in cold water for
one hour. After this dwell, their take-up of water
again was only 1.6%.
The mechanical strength of the nuts remained
unchsnged after their dwell in water and no
degradation of their surface condition was observed
during their handling after immersion.

201847~
-15-
Thi~ example show~ that the addition of 5% of
native starch and 0.05% of ammonium persulfate and of
0.1% of potassium siliconate by dry weight with
respect to the weight of fuel du~t enabled
agglomerates to be obtained satisfying the
requirements of the technology from the point of view
of mechanical strength and behaviour to water, and
enabled also the retake-up of water of these
agglomerates to be considerably limited when the
latter is undesirable.