Note: Descriptions are shown in the official language in which they were submitted.
- 21 5Z78~
5 A method of proc~c.cin~ tar and similar products, the use of the resultino products~
and fuels obtainable bv the method.
This invention relates to a method of processing tar, tar products, distillation-, coke oven
plant- and oil residues and similar, liquid or viscous organic compounds consisting of
10 aromatics and other hydrocarbons or cont~ining the latter, to the use of the resulting
products, and to fuels obtainable by the method.
The term "tar" comprises liquid to semi-solid, brown to jet black decomposition products
which are formed during the thermal treatment of coal, wood, peat, oil and the like. A
15 distinction is made between tars from hard coal, lignite, wood, peat and oil. In addition,
viscous organic compounds which consist of aromatics and other hydrocarbons or which
contain the latter are formed during distillation processes and other industrial processes.
These compounds have properties similar to those of tar. The products which are to be
processed according to the invention are also to be understood to include residues from
~O accidents involving oil-transporting vehicles, which have a serious pollutant effect on the
environment.
If they are improperly handled, even the said products themselves constitute an
environmental hazard. Furthermore, they may contain other environmentally harmful
~S substances such as phenols, oils containing naphthenic acid, and heterocyclic compounds.
A common feature of the said materials is that they range from the highly viscous to the
fluid and sticky and they also have unpleasant odours. Due to their high viscosities they
cannot be pumped and are otherwise difficult to handle. They are difficult to load or
30 Iransport using dredgers or excavators or similar devices, for example.
2l52786
In the past, the said products have sometimes been improperly dumped. Waste dumps
of this type constitute a considerable environmental hazard, and their disposal is a
serious problem.
5 Attempts have sometimes been made in the past to dissolve the said products in organic
solvents to convert them into a handleable form. This is financially costly, however,
and is associated with further environmental hazards.
The object of the present invention is to provide a method of the type cited at the outset
10 which ensures that these products are disposed of or processed in an economical and
environmentally friendly manner. The aim of the method according to the invention is
to create products which can be handled, i.e. pumped or transported, and which can be
supplied for further utilisation if possible or can at least be dumped without problems.
15 It has surprisingly been found that the use of organic solvents can be dispensed with and
that the said tar products can be converted into easily handleable dispersions of low
viscosity or into solid materials which can be dumped, by using aqueous solutions or
slurries of inorganic alkaline compounds, wherein both the dispersions and the solids can
be employed as liquid and solid fuels, respectively.
~0
The present invention therefore relates to a method of processing tar, tar products~
distillation-, coke oven plant- and oil residues and similar organic compounds consisting
of aromatics and other hydrocarbons or containing the latter, which is characterised in
that the products to be processed are treated with one or more inorganic alkaline
~5 compounds.
For example, the products to be processed can be treated with aqueous solutions or
slurries of one or more inorganic alkaline compounds. In this manner it is possible in
particular to process viscous products and to convert them into liquid dispersions.
- 21~2786
However, it is also possible to treat the products to be processed with alkalinecompounds of alkaline earth metals and alkaline aluminium compounds. In this manner,
liquid products in particular can be treated and converted into a solid form.
A particularly preferred embodiment of the invention relates to a method of processing
tar, tar products, distiliation-, coke oven plant- and oil residues and similar, viscous
organic compounds consisting of aromatics and other hydrocarbons or cont~ining the
latter, which is characterised in that the products to be processed are converted into a
dispersion with the addition of aqueous solutions or slurries of one or more inorganic
alkaline compounds, and the dispersion obtained is optionally converted into a solid
form, even during the dispersion step or in a further process step, in the presence of
alkaline compounds of alkaline earth metals and alkaline aluminium compounds.
Within the scope of the invention it has been shown that the desired dispersion can be
effected using aqueous solutions or slurries of alkaline compounds. Alkali metalhydroxides, alkali metal oxides, ammonia, alkali metal aluminates, ammonium aluminate
or mixtures thereof can be used for this purpose, for example. Water-soluble ~Ik~line
compounds are preferred; however, it is also possible to use alkaline compounds which
can form a slurry in water. It has been shown that the method can also be carried out
~0 using alkaline earth metal hydroxides and oxides, optionally in admixture with alkali
metal hydroxides and oxides.
Examples of suitable alkali metal hydroxides include sodium hydroxide or potassium
hydroxide, calcium hydroxide and magnesium hydroxide are particularly suitable as
~5 alkaline earth metal hydroxides, and calcium oxide is particularly suitable as an alkaline
earth metal oxide.
The alkaline solutions or slurries for the method of processing according to the invention
preferably contain alkaline compounds in amounts of 1 to 60 weight %, most preferably
1 to 40 weighl %, at a water content of 99 to 40 weight %, preferably 99 to 60 weight
%.
- 215278~
Alkali aluminates such as sodium or potassium ahlmin~t~, alkaline earth ahlmin~tes such
as calcium aluminate, ammonium aluminate, or compounds cont~ining ahlmin~te suchas alumina or cements, or mixtures of two or more of the said substances, are
advantageously used as the water-soluble aluminates. The ahlmin~tes may also be
5 formed in situ, for example from freshly precipitated aluminium hydroxide by the
addition of alkali hydroxides such as sodium hydroxide, or of alkaline earth metal
hydroxides such as calcium hydroxide. For example, aluminium hydroxide can be
precipitated from a solution of an aluminium salt, such as aluminium chloride, with an
alkali, such as sodium hydroxide or calcium hydroxide, and dissolved to form the10 corresponding ahlmin~te.
The solidification of liquid products or dispersions may also be effected solely by the
addition of alkaline earth metal aluminates, instead of the mixture of an ahlmin~te and
an alkaline compound of an alkaline earth metal. In this respect, the alkaline earth metal
15 ahlmin~te may be used in aqueous form or also in anhydrous (dehydrated) form.
In order to speed up the dispersion of the products to be processed, mechanical energy
can be used according to the invention. This can advantageously be effected by stirring,
sparging, shaking or mixing. Stirring is generally preferred for practical reasons. In
~0 this connection, the usual stirrer or mixer units can be used, such as paddle mixers or
positive mixers, and also dissolvers and similar apparatuses known in the prior art. It
is essential that adequate shearing forces result in rapid dispersion.
In order to speed up or facilitate dispersion, it is also possible to heat the solutions or
25 dispersions used. The temperature to which they are heated may for example be up to
90C, preferably up to 50C.
Advantageously, 90 to 5 parts by weight of the said solutions or slurries of calcium
compounds and/or ahlmin~tes are used for 10 to 95 parts by weight of the product to be
30 processed; preferably, 50 to 25 parts by weight of the solutions or slurries are used for
50 to 75 parts by weight of the product to be processed, wherein the sum of the parts
by weight gives 100 parts by weight of dispersion. If a smaller amount of the solution
~1527~6
or slurry acting as the dispersing agent is used with respect lo the amount of product to
be processed, the dispersion step is generally not satisfactory. In fact larger amounts
result in a satisfactory dispersion step, but they unnecessarily dilute the dispersion
ob~ained and are therefore undesirable for economic reasons.
s
The surface of the products to be processed is advantageously covered before effecting
dispersion with a pasty slurry containing calcium compounds and aluminates, into which
carbon dioxide or air is introduced.
10 The underlying object of the invention is advantageously achieved by means of the
method described. The products to be processed are converted into an easily handled
dispersion, i.e. into a dispersion which can be pumped and transported, which can be
used as a fuel or can be fed to a further processing stage.
15 According to a further aspect of the invention, the dispersions obtained can be converted
into a solid form, even during the dispersion step but also in a second process step, by
the addition of alkali or alkaline earth aluminate and/or mixtures of calcium compounds
and ahlmin~tes, aluminium hydroxide and or aluminium oxide. The use of aluminiumhydroxide and/or aluminium oxide is particularly advantageous, since further waste
~0 materials can be used here. For example, aluminium oxide is formed in the so-called
anodising process; waste products of this type previously had ~o be deposited in waste
dumps. The compounds described above can be used as the alkali or alkaline earthaluminates .
~5 If the dispersion already contains alkaline earth compounds. it may be sufficient to treat
it with one or more alkaline aluminium compounds.
If. on the other hand, the dispersion already contains aluminate, it may be sufficient for
solidification to add one or more alkaline compounds of alkaline earth metals.
For solidification, the alkaline earth metal compounds as well as the aluminium
compounds may be used in dissolved or slurried aqueous form or in solid form without
21 S2786
water. Thus it is possible to use aluminates in hydrated and also in dehydrated form,
for example.
On the addition of alllmin~res to calcium compounds definite compounds are formed in
S the presence of water. These compounds may be obtained in situ during the
solidification, or they may be prepared previously and then added. They have a lamellar
structure comprising layers of cations and anions of the following formulae:
Cationic primary layer:
Ca4[AI7(0H)I7]2+
Anionic intermediate layer:
S [X7 aq]'~ or [Y . aq]~~,
where X is a monovalent anion such as OH-, Cl~ or NO3-, and Y is a divalent anion such
as S04'- or CO;'~,
~0 and where aq represents water.
The amount of water of crystallisation depends on the preparation conditions, particularly
on the temperature and pH; in practice it is of the order of 6 to 12 molecules of water
per anion.
'S
Compounds containing carbonate can also be used for the solidification according to the
invention. In particular, it has been shown that carbonate-containing modifications of
the absorption media described are particularly stable. These can be formed from the
above-mentioned compounds, for example, where X or Y are different from carbonate,
30 by the addition of carbonate ions or by working in the presence of carbon dioxide or of
a gas containing carbon dioxide. The X or Y anions are then replaced by carbonate
anions. The carbonates may also be produced directly if the absorption media are
21 5278C
produced from the outset in the presence of carbonate ions and/or carbon dioxide. The
carbonates are present as monocarbonate or semicarbonate, in which the cationic primary
layer is unchanged but the anionic intermediate layer has the following formulae:
5 semicarbonate:
[OH/O, SC03 . aq]2~
monocarbonate:
[C03 . aq]2~
Surprisingly, it has been shown within the scope of the invention that organic molecules
can be intercalated in the structures of the above-mentioned compounds. It can therefore
15 be assumed that organic compounds are incorporated in the intermediate layers of the
lamellar structures, replacing at least part of the water of hydralion there. Ions and
polar organic pollutants can also completely or partially replace the X or Y anion of the
intermediate layer.
~0 Tests with anthracene showed, for example, that absorption of anthracene occurred on
the monocarbonate, resulting in the following definite crystalline chemical compound:
[Ca4Al~-(OH)I2]2+ [C03 AC/H~0]2-
~5 where AC = anthracene.
Tests with anthracene carboxylic acid (ACC) resulted in the formation of the following
compound:
30 ICa4Al~(OH)I2]~+ [ACC nH20]~
(n depends on the temperature and atmospheric humidity).
- 21 5Z 786
The solutions or slurries containing calcium compounds and aluminates which can be
used according to the invention can be prepared in various ways. In principle, it is
sufficient to mix the calcium compound with the aluminate. Water may be added
previously or afterwards. If the corresponding monocarbonate or semicarbonate
S compound is prepared, carbonate and/or carbon dioxide must be present before, during
or after the reaction of the calcium compound with the alllmin~te.
For example, it is possible to mix the calcium compound, such as dry lime (CaO), with
dry alllmin~, such as sodium all1min~te, then to mix with water and optionally to add
10 carbonate ions and/or carbon dioxide.
A solution or slurry is advantageously used which has a content of 1 to 60 weight %,
preferably 10 to 40 weight %, of calcium compounds and/or 1 to 40 weight % of
aluminates, calculated as Al,03. Aqueous solutions or slurries which contain a total of
15 20 to 30 weight % of the said substances are particularly preferred.
Depending on the amount of alkali or alkaline earth aluminates used, crumb-like
products, ranging from moist to dry, are produced in the solidification step which can
optionally be carried out according to the invention. In contrast to the starting materials,
~0 these products are no longer semi-liquid, viscous and sticky, but can be conveyed and
transported in a simple manner. The solidified products can be used as solid fuel or
dumped in accordance with the regulations. In order to achieve solidification, which
may also be considered as a thickening or drying process, the alkali and/or alkaline
earth alllmin~t~s are preferably stirred into the dispersion produced by the method
~5 described at the outset in solid form or as a solution or slurry as in the first process step.
In this respect the amount is calculated so that the desired solidification is achieved. In
general, it is sufficient to use 1 to 50 weight %, preferably 10 to 30 weight %, of alkali
or alkaline earth aluminates with respect to the dispersion.
30 Aggregate materials which additionally assist solidification, such as fly ash, gypsum or
limestone, can advantageously be added to the dispersion. If fly ash is used, fly ash
from lignite is preferred, because this results in a particularly favourable solidification
- 21 5278~
due to its pozzolanic properties. The said aggregate materials not only improve
solidification, but also reduce the gross calorific value of the final product obtained.
This is advantageous inasmuch as the gross calorific value of the starting materials is too
high for many conventional combustion installations.
The present invention also relates to the use of the dispersions produced in the first
process step as a liquid fuel, to the use of the solids produced in the second process step
as a solid fuel, and to the liquid and solid fuels per se. The dispersions or solid fuels
are preferably not used as the only fuel, but are used as additional fuels in existing
10 combustion installations which generate heat energy by the combustion of coal, coke,
oil or gas and of combustible refuse.
If the starting materials to be processed are contaminated with heavy metals, a further
advantage arises in that completely insoluble heavy metal oxides are formed when the
15 final products produced according to the invention are heated. In particular. compounds
of the so-called spinel type are formed, which are particularly stable. In addition, the
basic properties obtained when calcium oxide or calcium hydroxide and alkali ah]min~te
and/or alkaline earth aluminate are used result in advantageous behaviour on combustion,
in a manner such that acidic gases formed on combustion, such as S07 or volatile~0 chlorides for example, are partially bound and their emission is reduced. These effects
comprise further aspects of the present invention which are advantageous from anenvironmental point of view.
On combustion, the basic components result in an advantageous reduction of emissions,
25 due to the bonding of acidic components.
The ash formed on the combustion of the liquid fuel or of the solid fuel acquires an
enhanced pozzolanic character due to its calcium and aluminium content. This favours
the suitability of the ash for being dumped.
The invention is described in more detail below by way of an example. The percentages
given are in weight %.
2152 78S
lo
Example 1
100 g of a 20 % sodium aluminate solution (20 weight % Al~03) are added to 1000 g
of tar residue and slowly stirred in. A dispersion with good handling properties is
5 obtained, which can be used as a liquid fuel.
Solidification is effected by the addition of 7500 g of 20 % milk of lime. The product
obtained is crumb-like, moist and easily handled, and can be used as a solid fuel.
