CA2783053A1

CA2783053A1 - Method and device for separating mixtures

Info

Publication number: CA2783053A1
Application number: CA2783053A
Authority: CA
Inventors: Roger Reichmuth; Oskar Bloechlinger (Deceased)
Original assignee: AWESTRA AG
Current assignee: AWESTRA AG
Priority date: 2011-07-13
Filing date: 2012-07-13
Publication date: 2013-01-13
Also published as: EP2546003B1; EP2546003A1

Abstract

A method and a device are described for the recovery of bitumen from road surfacing (asphalt) breakup (1) or for separating oil sand into oil and sand, or stone, wherein the bitumen-containing breakup (1) or the oil sand is introduced into a salt melt (2), wherein bitumen (5) or oil floats on the salt melt (2) and after passage through the salt melt (2) is skimmed off from the salt melt (2), and wherein the stone material (3) or the sand/stone in the salt melt (2) sinks and is carried away. The proposed method is characterised in that the temperature of the salt melt (2) lies in the range from 200°C to 350°C and the average dwell time of the breakup (1) in the salt melt (2) lies in the region of at least 5 minutes.

Description

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

-2-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

-3-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.

-4-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,

-5-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.

-6-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

-7-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

-8-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

-9-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

- 10-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

-11-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

-12-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

-13-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

-14-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

-15-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

- 16-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

- 17-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

-18-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:

-19-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:

-20-3 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):

-21 -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 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

-22-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

-23-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.

-24-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

Claims

WHAT IS CLAIMED IS:

1. A method for the recovery of bitumen from road surfacing (asphalt) breakup (1) or for separating oil sand into oil and sand, or stone, wherein the bitumen-containing breakup (1) or the oil sand is introduced into a salt melt (2), wherein bitumen (5) or oil floats on the salt melt (2) and after passage through the salt melt (2) is skimmed off from the salt melt (2), and wherein the stone material (3) or the sand/stone in the salt melt (2) sinks and is carried away characterised in that the temperature of the salt melt (2) lies in the range from 200°C to 350°C and the average dwell time of the breakup (1) in the salt melt (2) lies in the region of at least 5 minutes.

2. The method according to claim 1, characterised in that the temperature of the salt melt (2) lies in the range from 250°C - 300°C.

3. The method according to any one of the preceding claims, characterised in that the average dwell time of the breakup (1) in the salt melt (2) lies in the range from 5-30 min., preferably in the range from 10-20 min.

4. The method according to any one of the preceding claims, characterised in that the salt melt (2) 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.

5. The method according to claim 4, characterised in that it involves a eutectic mixture, and/or a binary or ternary mixture of NaNO3/LiNO3/KNO3 (sodium nitrate/lithium nitrate/potassium nitrate), particularly preferably 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.

6. The method according to any one of the preceding claims, characterised in that the removed stone material (3) 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.

7. The method according to claim 6, characterised in that the removed stone material (3) or the sand/stone undergoes the washing process while still in the hot state after the salt melt, and that the heat stored in the stone material (3) or sand/stone is used at least partially, preferably completely, to heat the washing water.

8. The method according to any one of preceding claims 6-7, characterised in that the separation of the salt solution takes place at least partially by precipitation, optionally in combination with centrifugation, and/or evaporation and/or reverse osmosis.

9. The method according to any one of preceding claims 6-8, characterised in that use is made of a multi-stage, preferably at least two-stage or at least three-stage washing process, wherein washing water and removed stone material (3) or sand/stone are 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 (20) after the salt melt (2).

10. The method according to any one of preceding claims 6-9, characterised in that the separation of water and salt or salt mixture is carried out in a multi-stage, preferably at least in a two-stage or at least in a three-stage manner, wherein a first separation stage (17) is preferably a precipitation stage or a settling basin, optionally followed by or combined with a centrifugation (23) and the latter is preferably followed by a second separation stage using evaporation (18) and/or reverse osmosis (32).

11. The method according to claim 10, characterised in that the partially separated water is fed back at least partially into the washing process after the first separation stage (17), preferably in a further washing stage (21) downstream of the first washing stage (20) after the salt melt.

12. The method according to any one of the preceding claims, characterised in that 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, is made available at least partially or essentially completely by combustion of the separated bitumen (5).

13. The method according to any one of the preceding claims, characterised in that the road surfacing breakup (1) or oil sand is fed to the salt melt (2) with a predetermined breaking value, preferably up to max. 32 mm particle size.

14. The method according to any one of the preceding claims, characterised in that the bitumen (5) or oil floating on the salt melt (2) and after passage through the salt melt (2) skimmed off from the salt melt (2) is fed to a further separation operation, preferably by the fact that the separated fraction undergoes a grinding process down to a defined particle size in a first step, and in a second step this mechanically size-reduced fraction is further separated, either by renewed use of a salt melt or by using another separating process, preferably a physical-chemical separating process for fine-grained solids based on the different surface wettability of the particles, preferably a flotation process.

15. A device for carrying out the method according to any one of claims 1 to 14 for the recovery of bitumen from road surfacing (asphalt) breakup (1), or for the separation of oil and sand, or stone, from oil sand, 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 LiNO3/KNO3 (lithium nitrate/potassium nitrate), for producing of a salt melt (2), with supply means upstream of the basin (1) for the road surfacing breakup (1) or the oil sand with a predetermined breaking value, with conveying means disposed in the basin for transporting or moving the breakup (1) or oil sand through the salt melt (2) and with scraping means disposed at the end of the conveying path of the basin for skimming off and further transporting the bitumen (5) or oil which has been separated from the stone material of the breakup (1) and is floating on the salt melt (2), 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 (15, 16, 20, 21, 22) 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 (17, 18, 23, 32) 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 (2).