Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
METHOD AND DEVICE FOR SEPARATING MIXTURES
TECHNICAL FIELD
The present invention relates to a method and a device
for separating mixtures, such as for example the
separation of road asphalt surfacing breakup into
bitumen and the remaining components or also for the
separation of oil sand into oil and sand.
PRIOR ART
In the area of the reconstruction of asphalt roads, it
is prior art to carry out the road breakup with a
predetermined breaking value and to use the latter at
least partially as gravel substitute. The contained
bitumen does not perform any role. The remaining part
of the bitumen-containing surfacing material, on the
other hand, is added up to a maximum of 50% to the new
material in surfacing material processing plants. The
limitation to a maximum of 50% is based on the fact
that the composition of the breakup material is not
precisely defined.
However, in view of the fact that bitumen is a crude
oil derivative and cannot readily be otherwise
produced, the recovery or at least other reuse of the
bitumen becomes necessary for ecological and economic
reasons.
Furthermore, it is the case that the aforementioned use
of the old bitumen-containing surfacing material is
limited to the aforementioned 50%; correspondingly, it
is also of interest to reproduce the original gravel in
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a purified form, so that it can be used again
essentially without restriction.
The separation of oil sand involves separating the
crude oil contained therein from the stone or sand.
A method for separating mixtures, in particular for
recovering bitumen from road surfacing (asphalt)
breakup or for separating oil sand into oil and sand,
or stone, is known from WO 2008110486. The proposed
method is characterised in that a salt melt is used for
the separation, into which the breakup is introduced,
so that a part floats on the salt melt and a part sinks
in the salt melt. The bitumen-containing surfacing
breakup is thus separated into bitumen which floats on
the melt and stone material which sinks in the melt, or
oil sand is separated into oil which floats on the melt
and sand or stone which sinks in the salt melt. It is
proposed to adjust the temperature of the salt melt in
the range from 180 C-200 C.
A method for removing sulphur components from bitumen
slate clay and releasing kerogen components therefrom
has become known from US 4,545,891. Bitumen slate clay
first undergoes a treatment in a salt melt in a first
step, and sulphur components as well as kerogen
components are removed in this step. Kerogen is the
polymeric organic material from which hydrocarbons are
formed with increasing geological settling and heating.
It occurs in sedimentary rocks in the form of finely
distributed organic macerals and is by far the most
frequent form of organically bound carbon in the
earth's crust. It is insoluble in organic solvents,
non-oxidizing acids (HC1 and HF) and lyes. Kerogen
itself cannot be equated either with crude oil or with
bitumen nor can it be used in the sense of these
systems; it is a wholly different material, in
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particular a starting material for obtaining slate oil:
slate oil can be obtained from kerogen in a separate,
costly post-treatment step in a pyrolysis, a
hydrogenation or a thermal decomposition. The salt melt
mentioned in this document in connection with obtaining
kerogen comprises alkali hydroxides, wherein the latter
are held in the melt at high temperatures of 375 C and
it is only at such high temperatures that even brief
contact enables the separation of kerogen.
A method for the treatment of iron chloride waste, such
as arises for example in the chlorination of titanium,
is described in US 4,655,839. The iron chloride waste
is introduced into a molten calcium chloride hydrate
bath, a separation not then taking place in this bath,
but rather a reaction of the introduced iron chloride
into iron oxide.
DESCRIPTION OF THE INVENTION
Accordingly, it is, amongst other things, the problem
of the present invention to make available an improved,
i.e. in particular more efficient, safe and/or energy-
efficient separation method in the aforementioned
sense.
In other words, the present invention relates
specifically to a method and a device for the recovery
of bitumen from road surfacing (asphalt) breakup or for
separating oil sand into oil and sand, or stone,
wherein the bitumen-containing breakup or the oil sand
is introduced into a salt melt, wherein bitumen or oil
floats on the salt melt and after passage through the
salt melt is skimmed off or otherwise separated from
the salt melt, and wherein the stone material or the
sand/stone sinks in the salt melt and is carried away.
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It emerges as a result of extensive investigations
that, in view of the material properties of bitumen and
the adhesion of the bitumen to the stone material or
the oil to the sand/stone, such a process can only be
carried out efficiently, i.e. with a high degree of
separation efficiency and low energy consumption, but
also safely, i.e. protected against hazardous vapours
and flame formation, when on the one hand the
temperature of the salt melt is kept within a narrow
range, in particular it lies in the range from 200 C to
350 C, and at the same time the average dwell time of
the breakup in the salt melt is sufficiently long, in
particular it lies in the region of at least 5 minutes.
If the process is carried out in this way, bitumen
and/or stone material or oil and/or sand/stone can
again be put back to practical use. In particular, the
stone material for example can be put to any desired
use as good as new.
If a lower temperature is selected, a large part of the
bitumen remains adhering to the stone material and the
stone material accordingly cannot be put to any desired
use as good as new without a further purification step.
In addition, a subsequent purification step using water
must then take account of this high proportion of
bitumen and requires that account be taken of the
separation of bitumen and not only of the separation of
water and salt during the purification of the water.
Moreover, an excessively large proportion of salt is
removed from the salt melt at a lower temperature.
However, in order that the separation also takes place
for a sufficient length of time in the salt melt, the
average dwell time of the breakup in the salt melt must
lie in the aforementioned range.
If a higher temperature is selected, the risk of
spontaneous flame formation unexpectedly rises sharply,
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in particular with local temperature peaks due for
example to insufficient stirring; a high level of smoke
formation also occurs on account of the bitumen
floating at the top and it is no longer possible to
conduct the process safely.
Particularly efficient conducting of the process is
possible when the temperature of the salt melt lies in
the range from 250 C-300 C.
Furthermore, according to a further preferred
embodiment, the average dwell time of the breakup in
the salt melt lies in the range from 5-30 min.,
preferably in the range from 10-20 min.
A further preferred embodiment, which in particular
enables the energy requirement of the process to be
kept low, is characterised in that the salt melt is a
mixture of different salts, which has a melting point
of less than 200 C, preferably in the range from 80-
150 C, particularly preferably in the range from 100-
140 C.
It is preferably a eutectic mixture.
The salt melt can preferably be a binary or ternary
mixture, preferably of NaNO3/LiNO3/KNO3 (sodium
nitrate/lithium nitrate/potassium nitrate). If such
mixtures are selected, they can be adjusted to a
melting point in the range from 80-150 C by a suitable
adjustment of the proportions of the components, for
example in the vicinity of the eutectic. Particular
preference is given to a binary mixture of LiNO3/KNO3
(lithium nitrate/potassium nitrate) with a 50-70 mole
percent proportion of KNO3 and a melting temperature in
the range from 120-140 C.
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To express it in an alternative way, such mixtures are
preferably constituted such that, in the molten state,
potassium nitrate is present in a content of 55-80% by
weight and lithium nitrate in a content of 20-45% by
weight, and optionally calcium nitrate or sodium
nitrate in a proportion of 0-48% by weight. The
proportion of potassium nitrate in a binary mixture is
preferably in the range from 63-73% by weight, and the
proportion of lithium nitrate in the range from 27-37%
by weight.
It emerges that such mixtures precisely have an ideal
combination of low melting point and suitable viscosity
and density in the aforementioned temperature range in
the salt melt, so that the separation can be carried
out efficiently within the stated average window for
the dwell time of the breakup in the salt melt.
In this connection, use is preferably made of salt
mixtures which are prepared trickle-free as a starting
material. This can be provided for as a condition of
production, but can also be ensured in a suitable
processing step or by the addition of suitable
additives. For the aforementioned nitrate mixtures,
i.e. binary or ternary mixtures, based on LiNO3/KNO3 or
LiNO3/KNO3/NaNO3 (or instead NaNO3Ca(NO3)2), highly
dispersed, preferably hydrophobic and amorphous silicic
acids for example can be added, such additives
typically being present in the mixture in the range
from 0.04-0.1% by weight, preferably in the range from
0.06-0.07% by weight. If the individual components are
present individually, it is usually sufficient to add
such additives to the lithium nitrate, and in a
proportion of 0.1-0.3% by weight, typically in the
region of 0.2% by weight. For example, highly dispersed
silicic acids, particularly preferably with a high
specific (BET) surface area in the range from 120-140
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m2/g and/or an average particle size in the range from
14-18 nm, which are hydrophobised, are possible, for
example with DDS (dimethyldicholorosilane). For
example, systems of the type Aerosil , obtainable from
Evonik, for example the product Aerosil R 972, are
possible.
A further preferred embodiment of the proposed method
is characterised in that the removed stone material or
the sand/stone is washed using water, and that the salt
or salt mixture contained in the water used is
subsequently separated from the water and fed back at
least in part to the salt melt, this washing process
preferably being carried out at a water temperature
above room temperature, in particular in the range from
40-80 C, preferably in the range from 50-70 C. In other
words, the process is preferably carried out in as
closed a manner as possible, which has a bearing on the
use of the material for the salt melt. Typically, low-
melting salt mixtures are on the one hand expensive and
on the other hand not entirely harmless ecologically.
Accordingly, it is important to contain these salts as
far as possible in the process and to minimise the
discharge. This is possible if the salt unavoidably
carried out of the melt by the stone material conveyed
out of the salt melt due to adhesion of the salt to
said stone material is washed off and is then separated
again from the water and fed to the salt melt. Readily
soluble salts are accordingly advantageous, such as for
example the aforementioned specific mixture systems. It
emerges that the residual heat stored in the stone
precisely suffices to bring fresh water supplied at
room temperature or in the range between 5 C and room
temperature (in the minimally required quantity) to the
aforementioned preferred washing temperature.
Surprisingly, therefore, it emerges that the water
temperature can be adjusted to the optimum range
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without or essentially without further energy supply,
by the fact that the stone material removed from the
salt melt is fed directly to the washing process in the
warm state or hot state.
It is further preferable for the removed stone material
or the sand/stone to undergo the washing process while
still in the hot state, i.e. typically directly after
the salt melt, so that the heat stored in the stone
material or sand/stone is used at least partially,
preferably completely, to heat the washing water.
The separation of the salt solution into water and salt
or salt mixture preferably takes place at least
partially by precipitation/settling, optionally in
combination with centrifugation, and/or evaporation
and/or reverse osmosis.
For the purification of the stone material or the
removal of the salt adhering thereto, use may be made
of a multi-stage, preferably at least two-stage or at
least three-stage washing process, wherein washing
water and removed stone material or sand/stone are
preferably conveyed according to the counter-flow
principle, and wherein the separation of water and salt
or salt mixture is preferably carried out exclusively
with the washing water, which is carried away in the
first washing stage after the salt melt.
It is also possible, as is preferable, to carry out the
separation of water and salt or salt mixture in a
multi-stage, preferably at least in a two-stage or at
least in a three-stage manner, wherein a first
separation stage is preferably a precipitation stage or
a settling basin, optionally followed by or combined
with a centrifugation and the latter is preferably
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followed by a second separation stage using evaporation
and/or reverse osmosis.
The partially separated water can be fed back at least
partially into the washing process after the first
separation stage, preferably in a further washing stage
downstream of the first washing stage after the salt
melt.
The required process heat, in particular for ensuring
the temperature of the salt melt, and/or for purifying
washing water or separating the same from salt and
impurities, and/or for heating washing water, can be
made available at least partially or essentially
completely by combustion of the separated bitumen.
Thus, if the bitumen cannot be used or can be used only
to a limited extent, for example due to small sand
particles which cannot be separated from the bitumen in
the salt melt, or as a result of other chemical
properties that have been changed by the previous use
as road surfacing or by the processing in the salt melt
in a lasting manner or a manner that prevents further
use or renders this difficult, ecologically practical
and energy-efficient use is nonetheless possible in the
overall process. It emerges in calculations that the
calorific value of the bitumen is often precisely
sufficient to meet to the overall energy requirement of
the process.
The road surfacing breakup or oil sand is preferably
fed to the salt melt with a predetermined breaking
value, preferably up to max. 32 mm particle size.
According to a further preferred embodiment, it is
possible to feed the mixture (bitumen with fine sand or
oil with fine sand) floating on the salt melt, which
may not yet be sufficiently separated, to a further
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separation operation. Particularly in the case of the
separation of bitumen, for example, the bitumen
fraction can advantageously be further separated in
order to separate further fine stone material.
According to a very particularly preferred embodiment,
the separated bitumen fraction undergoes a grinding
process (e.g. cross-beater mill) down to a defined
particle size in a first step. Preferably, for example,
to a particle size less than or equal to 0.5 mm. This
mechanically size-reduced fraction can then be further
separated, either by renewed use of a salt melt as
described above or by using another separating process.
One such other separating process can for example be a
physical-chemical separating process for fine-grained
solids based on the different surface wettability of
the particles. With the use of the preferred flotation
process, for example, use can be made of the fact that
gas bubbles readily accumulate at hydrophobic surfaces,
i.e. difficultly wettable by water, here the bitumen,
and provide the particles with buoyancy, so that the
latter float. Under these conditions, the likewise
hydrophobic gas bubbles accumulate at the hydrophobic
particle surfaces. Preferably, therefore, use is made
of a process which is also known as a flotation
process, wherein substances dispersed or suspended in
water or another flotation means are transported by
adhering gas bubbles to the surface of the water and
are removed with a scraping device. For example, water
with a pH preferably of less than 8 or less than 7 can
be used with particular preference. So-called
collectors are preferably added to the water.
Collectors make the part of the mixture to be removed
in the foam, here the bitumen fraction with very small
particles, water-repelling (hydrophobic), whilst the
other components are intended to remain water-
attracting (hydrophilic). Air blown into the slurry
adheres only to the hydrophobic particles and carries
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them to the surface of the water, whereas the
hydrophilic particles remain in the turbid water.
Sulphur compounds such as xanthogenates,
dithiophosphates, mercaptanes, or also amines,
alkylsulfonates as well as a number of fatty acid salts
are suitable as collectors. Known anionic non-thio-
collectors are for example saturated and unsaturated
fatty acids, in particular tall oil fatty acids or
oleic acid, alkylsulfonates, in particular
alkylsulfonates derived from fatty alcohols or fatty
alcohol mixtures, alkylarylsulfonates,
alkylsulfosuccinates, alkyl-sulfosuccinamates and
acyllactylates. Known cationic non-thio-collectors are
for example primarily aliphatic amines, in particular
the fatty amines originating from the fatty acids of
vegetable and animal fats and oils, as well as certain
alkyl-substituted and hydroxyalkyl-substituted
alkylenediamines and the water-soluble acid addition
salts of these amines. Products of the type Alaphen or
Ekofol from EKOF FLOTATION GmbH are possible. On
account of their tenside character, many collectors
themselves develop a foam suitable for the flotation.
It may however also be necessary to generate the foam
by means of special foaming agents or to modify the
latter in a suitable way. Known foaming agents for the
flotation are alcohols with 4 to 10 carbon atoms,
polypropylene glycols, polyethylene glycol ethers or
polypropylene glycol ethers, terpene alcohols (pine
oils) and cresylic acids. Insofar as necessary,
modifying reagents should be added to the suspensions
(turbid waters) to be floated, for example regulators
for the pH value, activators for the mineral to be
obtained in the foam or deactivators for the minerals
not desired in the foam, and if need be also
dispersants. After mixing of the slurry at the adjusted
pH and, if need be, with the added collector, a foaming
agent can thus also be added in order to stabilise the
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air bubbles and air can be introduced. Foaming agents
split up the air blown into the suspension into as many
small bubbles as possible and stabilise the formed
foam. The foam with the bitumen can be skimmed off and
separated, e.g. by filtering, if need be in combination
with a washing step. The washing water can be reused in
the flotation process. The hydrophilic fraction can
also be separated for example by filtration, if need be
in combination with a washing step.
A sufficient separation was able to be guaranteed
within the scope of the experimental testing, so that
the separated stone material (fine sand, sinking
hydrophilic fraction) can still be reused at least as a
filler material. The floating foam fraction can be
filtered, the solid fraction being further enriched in
bitumen and containing only extremely fine particles.
As a result of this additional separation, it is
possible, if for example the bitumen can now only be
disposed of, to reduce the proportion of material to be
disposed of, or the bitumen can be increased by such
additional separation in terms of calorific value per
unit of mass or can even be made available for reuse.
Moreover, the present invention relates, as mentioned
at the outset, to a device for performing the method
described above. In particular, it relates to a device
for carrying out such a method for the recovery of
bitumen from road surfacing (asphalt) breakup, or for
the separation of oil and sand, or stone, from oil
sand. It is preferably characterised by
= at least one heatable, preferably groove-
shaped basin for the uptake and liquefaction
of a salt or salt mixture with a low melting
point, preferably a eutectic mixture of
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LiNO3/KNO3 (lithium nitrate/potassium
nitrate), for producing of a salt melt,
= with supply means upstream of the basin for
the road surfacing breakup or the oil sand
with a predetermined breaking value,
= with conveying means disposed in the basin
for transporting or moving the breakup or oil
sand through the salt melt and
= with scraping means disposed at the end of
the conveying path of the basin for skimming
off and further transporting the bitumen or
oil which has been separated from the stone
material of the breakup and is floating on
the salt melt,
= with removal means disposed at the end of the
conveying path of the basin for the bitumen-
free stone material, or the sand or the stone
of the oil sand, which has sunk in the salt
melt, as well as
at least one washing stage, in particular for
washing away the residues of the salt melt on
the stone material, or the sand or the stone
of the oil sand,
= at least one separation stage for separating
salt or salt mixture and washing water as
well as
= means for the at least partial feedback of
the separated salt or salt mixture into the
salt melt.
Further embodiments are given in the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are described
below with the aid of the drawings, which serve merely
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as illustration and are not to be interpreted as being
limiting. In the drawings:
fig. 1 shows a schematic flow diagram of the
separating and purification process;
fig. 2 shows a diagram of a washing process in the
counter-flow principle;
fig. 3 shows a diagram of a washing process with an
evaporator;
fig. 4 shows a diagram of a washing process with a
centrifuge; and
fig. 5 shows a diagram of a washing process with
reverse osmosis.
DESCRIPTION OF PREFERRED EMBODIMENTS
2.2 million tonnes of excavated asphalt is put either
into building rubble recycling or into dumps each year
in Switzerland. The recycling of asphalt surfacing is
admittedly widespread, but is severely limited by the
poor quality of this material. Instead of dumping the
road breakup or "diluting" it in an undefined (low-
quality) form into current asphalt production, the
latter is to be separated into its components of binder
(bitumen) and mineral grain (chippings) in a salt melt.
A mixture of KNO3 (potassium nitrate, 60 mol.-%) and
LiNO3 (lithium nitrate) is used, which produces a melt
with the density 2.0 g/cm3 above 130 C. Tests show that
the bitumen separates from the mineral grain and floats
on the melt, whereas the mineral grain sinks. The
mineral grain can then be recycled and the bitumen can
at best be used as mastic asphalt or be thermally
recycled.
In the area of phase 1, tests have been carried out in
a 10 litre salt bath. Samples of several kilograms of
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road breakup were processed in this bath, as a result
of which sufficient separated material was obtained in
order to carry out an assessment of the reusability of
the products (chippings, bitumen). Prior to the
project, the method was tested in trials in the test
tube. The results were able to be reproduced with the
tests in the 10 litre salt bath. It has also been shown
that the bitumen can be readily separated from the
mineral grain at temperatures of 250-300 C without the
addition of further chemicals. The employed pilot
reactor was equipped with a heating wire with a power
of 6.7 kW and was continuously adjustable from 0-500 C
by means of a setpoint sensor.
Phase 2 consisted in extensive test series, in which
the focus was put primarily on the separation of
bitumen from mineral grain. Primarily, the temperature,
the dwell time in the salt melt and the mechanical
loading due to the agitator were variable. Tests were
carried out at temperatures of 200-350 C and with dwell
times of the road breakup in the pilot reactor of 10-20
min. For the removal of the chipping fraction, the
qualitatively best results were achieved at
temperatures between 250-300 C. The test at above
300 C, in particular at 350 C, had to be terminated,
because the bitumen in the pilot reactor ignited. It
thus emerged that the reactor temperature must not be
higher than 300 C.
In this phase, 10 kg of asphalt was treated in the 100L
melt bath in such a way that 80% of the mineral
material was removed as purified chippings and not more
than 1% bitumen adheres to this mineral grain.
The required conditions with respect to separation were
met in the separating tests at a temperature of 300 C
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and a dwell time of the road breakup in the reactor of
and 20 min.
Phase 3 includes the recovery of the salt mixture
adhering to the chippings after the separation of the
bitumen. The profitability of the process depends on
the salt losses. Since this represents an essential
cost factor and an ecological aspect in the process,
the greatest possible recovery of the salt had to be
10 guaranteed with a suitable washing process.
Since the employed salt mixture is a very readily
water-soluble, a washing process for the products, in
particular for the mineral grain, was advisable. Since
the salt mixture can be removed again from the solution
only by evaporation of the water, and since the
evaporation of the water is costly in terms of energy,
washing must therefore take place with as little water
as possible.
10 kg of mineral product from phase 2 was washed in
such a way that it contains less than 0.1% of salt
mixture and that the washing water can be evaporated
with the energy content of the 500 g of bitumen
contained in 10 kg of asphalt.
Two tests were carried out for this purpose. In the
first test, the solubility of the salt mixture in water
was tested as a function of temperature. This test
showed that the solubility of salt mixture in water
increases linearly with the temperature. At a
temperature of 60 C, around 1 kg of salt mixture was
dissolved in a litre of water. When the temperature of
60 C was lowered to 20 C, around 2/3 of the dissolved
salt mixture is precipitated out. The whole of the
water does not therefore need to be evaporated, but
only part which was removed with the precipitated salt
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mixture. In the second test, a three-stage washing
process was carried out and a check was made to
establish what quantity of salt mixture is lost by the
washing process and what quantity of salt mixture still
adhered to the stone grains after the washing process.
This test showed that less than 1% of the salt mixture
is lost after the washing process and that less than
0.1% of salt mixture adheres to the mineral grain. The
evaporation of the water is described under phase 4.
Phase 4 was defined as follows: The results of the
large-scale test correspond to the specifications:
Recovery of 80% mineral grain with less than
1% bitumen adhesion and less than 0.1% salt
mixture
- The evaporation of the washing water does not
require more energy than is present in the
separated bitumen.
80% of the chippings introduced with the road breakup
into the reactor was recovered. A sample was analysed
in order to determine the bitumen adhesion to the
mineral grain. In addition, a sample of bitumen was
also analysed for quality testing and a sample of the
bitumen fraction was analysed to determine the
calorific value.
The analysis of the chippings showed that the
proportion of adhering bitumen to the material grain
amounts to less than around 0.3% and can thus be
reused.
The analysis of the bitumen showed that the bitumen is
in many cases too brittle for reuse. The analysis of
the calorific value showed that the latter amounted to
5 MJ/kg. This is around 1/8 of the calorific value of
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fresh bitumen. The energy content of the bitumen
fraction obtained from the process is sufficient to
evaporate the required quantity of washing water.
The loss of salt mixture can noticeably affect the
profitability of the process. It is therefore important
for the salt mixture to be retained as completely as
possible in the circuit. The losses must be reduced to
a minimum. These criteria are as follows: 10 kg of
mineral product was washed in such a way that it
contains less than 0.1% of salt mixture and that the
washing water can be evaporated with the energy content
of the 500 g of bitumen contained in the 10 kg of
asphalt.
For the washing process, it follows therefrom that as
little water as possible must dissolve as much salt
mixture as possible. Moreover, the evaporation of water
uses a very large amount of energy. A saving is
achieved by the fact that the temperature-dependent
solubility of salt mixture in the water is utilised by
the selection of suitable temperatures. Two series of
tests were carried out to determine the solubility. The
limit of the solubility thus known allows conclusions
to be drawn as to the required quantity of washing
water. Since the final process is intended to take
place continuously, the thermal energy in the chippings
after the salt melt bath can make a considerable
contribution to the energy efficiency of the plant. In
anticipation of this, the chippings are added to the
washing process at approx. 300 C. This temperature
makes a considerable contribution to heating up the
washing water to the required 60 C. The calculation of
the thermal energy thus held in the process is
represented below.
Thermal energy to heat 10 kg H2O from 20 C to 60 C:
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a 4 Liberated quantity of heat when 10 kg of chippings is
cooled from 300 to 60 C:
Q =~.crrr FS~ A _75 ) 1 k -(301-60) C==`"0'0 01=I:60 ki
On the basis of the calculations, no additional energy
needs to be expended in the washing process for heating
the water from 20 to 60 C, since the thermal energy
stored in the chippings is sufficient to heat the water
from 20 to 60 C. Energy has to be additionally supplied
solely to evaporate the water contained in the
precipitated salt mixture.
The calorific value analysis of the bitumen produced
the following result:
The calorific value of the removed bitumen amounts to:
H = 5'159 J/g = 5.159 MJ/kg.
Fresh bitumen has a calorific value which is comparable
with that of heating oil and amounts to approx. 40
MJ/kg. The recovered bitumen thus has a calorific value
reduced by a factor of 8.
Thermal energy of the bitumen fraction of 10 kg road
breakup:
F = = t.?6Ok& IS,~ 0~_ c. -- = 079' 40 = 9MJ
With the thermal energy of the bitumen fraction of 10
kg road breakup, the following quantity of water can be
evaporated:
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3 r
+ I ke __
Approx. 3.5 1 of water can thus be evaporated with the
bitumen fraction of 10 kg road breakup.
QBF thermal energy of the bitumen fraction J
CH2O specific thermal capacity of H2O 4182 J/(kg* C)
AT temperature difference C, K
mH2O mass H2O kg
m mass bitumen kg
H calorific value bitumen fraction J
rH2O specific heat of evaporation from water 2'257
kJ/kg
The results of the performed preliminary tests in the
10 1 reactor are entered in the following table:
total
introduced into after separation in the reactor
reactor
temperature chippings bitumen loss
,c dwell road breakup
time min kg kg % kg o kg %
180-190 10 1.5 1.315 87.7 0.030 2.0 0.155 10.3
200-220 10 1.5 1.345 89.7 0.050 3.3 0.105 7.0
200 20 0.663 0.606 91.5 0.026 3.9 0..031 4.6
250 20 0.663 0.488 73.6 0.167 25.1 0.008 1.3
300 20 0.673 0.454 68.5 0.219 31.5 0.000 0.0
300 10 1.5 1.130 75.3 0.235 15.7 0.135 9.0
300 10 1.5 1.185 79.0 0.310 20.6 0.005 0.4
250 30 1.5 1.255 83.7 0.175 11.6 0.070 4.7
250 20 1.5 1.315 87.7 0.110 7.3 0.075 5.0
The results of the tests carried out in the 10 1
reactor are entered in the following table (spontaneous
flame formation at 350 C in the test):
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total
introduced
into after separation in the
temperatu dwell road breakup reactor
re
'C time min k chippings bitumen fraction loss
fraction
blank experiment 1 250 10 10 chipping bitumen chippings bitumen chippi bitumen
s kg kg kg ngs kg
blank experiment 2 300 10 10 8.280 0.260 1.230 0.120 0.100 0.010
blank experiment 3 300 20 10 7.560 0.080 1.590 0.270 0.460 0.040
blank experiment 4 250 20 10 7.400 0.060 1.450 0.150 0.760 0.180
blank experiment 275 20 10 7.850 0.160 1.310 0.160 0.450 0.070
blank experiment 6 350 20 10 7.510 0.050 1.620 0.180 0.480 0.160
0 7.380 0.060 1.760 0.150 0.470 0.180
0
blank experiment 1 250 10 100 s %
blank experiment 2 300 10 100 o
blank experiment 3 300 20 100 86.2 66.7 12.8 30.8 1.0 2.5
blank experiment 4 250 20 100 78.7 20.5 16.5 69.2 4.7 10.3
blank experiment 5 275 20 100 77.0 15.3 15.1 38.5 7.9 46.2
blank experiment 6 350 20 100 81.7 41.0 13.6 41.0 4.7 18.0
78.1 12.8 16.9 46.2 5.0 41.0
76.8 15.3 18.3 38.5 4.9 46.2
The general process is summarised in figure 1. Road
breakup 1, typically after a preliminary treatment to
ensure a minimum fragment size, is introduced into a
salt melt 2. The salt required for salt melt 2 is made
available via a feedback via a path 3 or by a new
addition. The proportion of feedback should be as high
as possible. The purified stone material, which however
is still contaminated with salt mixture, is removed
from salt melt 2 via path 4. The bitumen is likewise
removed from salt melt 2 via path 5. After salt melt 2,
the stone material undergoes a washing process 6 and/or
a filtration. The employed washing water becomes salt
solution 7, which is subsequently fed to a water
treatment plant 8. The water is separated from the salt
mixture in the latter. The purified water can be fed
via path 9 back to washing process 6, the salt mixture
separated from the water being fed back to the salt
melt via path 3. Figure 2 shows a conveying process
with an evaporator. The stone material with adhering
salt mixture represented in figure 1 via path 4 is fed
to a purification stage in the form of a washing
cylinder 15. Housed in the latter is a transport
device, e.g. a transport spiral 16, which conveys the
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gravel from the bottom to the top, whilst the washing
water at a temperature of approx. 60 C is conveyed from
the top to the bottom in a counter-flow. The washing
water is brought up to this temperature by the residual
heat contained in gravel 4. The washing water can be
fed back by pumps 12 section by section via feedback 13
in order to optimise the washing process. Fresh water
11 is introduced at the upper end of cylinder 15,
purified gravel 10 being removed at the upper end. The
washing water accumulating at the lower end of cylinder
has the highest salt concentration and can be fed to
a separation operation. This takes place in a multi-
stage manner, first in a settling basin 17, in which
the water temperature typically amounts to approx.
C. The overlying water has a lower salt
concentration and can be fed back again to cylinder 15
by a pump 12 via feedback 14. The salt mixture
accumulating in settling basin 17 is in this case fed
to an evaporator 18, the evaporated water 19 being able
20 to be either released to the surroundings or condensed
and fed back to cylinder 15 or to the waste water.
Separated salt mixture 3 is then temporarily stored and
then fed back to salt melt 2 or is fed back directly to
salt melt 2.
Figure 3 also shows such a washing process, but the
latter is constituted here in a multi-stage manner. In
a first step, a pre-purification is carried out in a
washing drum 20 at a temperature of approx. 60 C. The
pre-purified stone material is then fed via path 26 to
washing drum 21, where essentially the same temperature
typically prevails. A final purification stage is then
carried out in a final purification basin 22, in which
the stone is fed via path 27 into basin 23. Purified
stone material 10 is then available for further use
essentially without restriction. The purification water
is conveyed in a counter-flow. Fresh water 11 is fed
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into basin 22 of the last purification stage where it
has a comparatively low salt concentration, then it is
fed via path 29 to washing drum 21, in which the salt
concentration is further increased somewhat, and the
washing water is then fed from drum 21 via path 28 for
pre-purification in unit 20, where the highest salt
concentration is then formed.
This washing water with the high salt concentration is
then fed via path 25 to settling basin 17. The
overlying water can then be fed via path 24 to drum 21.
The resulting moist salt mixture is fed via path 31 in
this case to an evaporator 18, the water is evaporated
and essentially dry salt mixture 3 is then available
for the feedback into salt melt 2.
Figure 4 shows an essentially analogous process to
figure 2, but here a centrifuge 23 is used instead of
an evaporator. The water resulting therefrom can be fed
via path 30 directly as fresh water 11 to basin 22,
since it is water with a fresh water quality,
Figure 5 shows an essentially analogous process to
figure 4, but here a unit with reverse osmosis 32 is
used instead of centrifuge 23.
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LIST OF REFERENCE NUMBERS
1 Road breakup 18 Evaporator
2 Separation in salt 19 Water vapor
melt
3 Salt, salt mixture 20 Washing drum for
4 Gravel after salt preliminary washing
melt
Bitumen 21 Washing drum
6 Washing/filtering 22 Washing basin
7 Salt solution 23 Centrifuge
8 Water treatment 24 Feedback water
9 Water 25 Transport of water from
10 Purified gravel 26-27 Transport of gravel with
salt between washing
11 Fresh water supply containers
12 Pump 28-29 Transport of water
13 Feedback between
washing containers
14 Feedback 30 Feedback fresh water
15 Washing cylinder 31 Settled salt solution
16 Transport spiral 32 Reverse osmosis unit
17 Settling basin
