Note: Descriptions are shown in the official language in which they were submitted.
10~0~
The present invention relate~ to a mcthod and a ~ev[ce for the
recovery of acid tar, as it occurs in tlle re~ining of mLncral oil8 W~t1
acids.
It is the ob~ect o~ the present invention to create a method of
the kind mentioned and also a device for carrying it out which makes it
possible to undertake the recovery or elimination oE the said acid tar in
a manner which is economic, technically simple and above all
environmentally acceptable.
It is to be emphasised that in the case of the present invention,
insofar as both the method mentioned and also the equipment serving to
carry it out are concerned, it is a matter of a combination of defined
- procedural steps and design details respectively, which in their combined
effect as described below ensure the attainment of the desired effect.
Hitherto such great difficulties have been associated with the
eliminating of the acid tar that the refining with sulfuric acid and
oleum must in many cases even be discontinued for this reason, although
this form of refining would be technically more expedient or more
economical than other refining techniques for various products.
In some refineries the acid tar is still deposited in the open
and covered over with lime, despite the efforts for environmental
protection. This entails the danger that the oily residues present in
the acid tar will trickle down into the ground water and contaminate
thi3. Little by little these methods are no longer being permitted.
A neutralization with lime and dumping of the plaster-tar-oil sludge is
encumbered with the same disadvantages and is possible, if at all, only
on costly special dumps.
The simple burning of the acid tar only rearranges the problem.
Instead of the ground water being endangered, with this method S02 and S03
are discharged into the atmosphere in large quantities, and become a danger
to men and animals and the surrounding vegetation in the form of finely
-- 1 -- ~
bm ~
.
'
10~
distributed sulphuric all(l sulpllurous acids respectLvely. In order to
keep the emissions small, such installations are indeed permitted in
individual cases, but the chimney heights required involve considerable
expense. Also such permissions are constantly being granted less
frequently. The requirements for environmental protection consequently
make it necessary for the exhaust gases to be cleaned from S0~ and S03.
The acids so washed out of the exhaust gases must subsequently be
neutralised and either a plaster sludge deposited in a clay soil, or a
drain with a suitably heavy water flow is loaded with the resultant
soluble mineral salts. The advantage of the burning is that the residues
still remaining were liberated from the oil residues threatening the water,
the disadvantage, that the discharge of the sludge is a very costly matter
and the procurement of the exhaust-gas cleansing installation involves
very high investment costs constituting a charge upon the production cost.
The method in accordance with the invention avoids the
disadvantages outlined. It consists - disregarding initially the special
items of equipment which make it possible to carry out the method in the
- manner desired - according to its nature, in that the tar with oxides,
hydroxides or carbonates of the alkaline earths present in a dry form
or in the form of a possibly concentrated aqueous sludge is mixed with
lime for example, whereupon the semi-solid to solid reaction product being
formed is burnt for the oxidation of the organic components contained in
it, and possibly with the application of energy from an external source
and with the introduction of air, whereby other scrap products of any
desired provenance can also be burnt at the same time.
In accordance with one preferred form of embodiment of the
method in accordance with the invention the semi-solid to solid reaction
product is subjected, possibly after crushing, to a multi-stage,
preferably twD-stage heat treatment, consisting in a first stage of a
low-temperature carboni2ation treatment at from 350 to under
;
bm:
lO~Uf~
S00C, while in a sccoll~l stage the restJItLng gafieOUa carbon-
ization products are burnt, possibly aft:er intermixlng of a
starting fuel and preferably with a gain in energy, and finally
the solid carbonization residues are discharged from thc
carbonization plant.
The solid residues of the carbonization stage, substantially
consisting of gypsum, carbonization coke and perhaps a surplus
of the neutralization agent, are dumped or possibly applied to
a useful purpose, for example when valuable fe}tiliser is
made therefrom with the intermixing of other suitable activators.
A spiral mixer is preferably employed for the transport
of the mixing material from the collecting receptacle to a
discharge point, which in accordance with the invention is
characterized by the fact that is exhibits a cleaning device,
for instance a second worm, a sprocket chain or similar device
engaging in the track of the worm.
In one particular aspect the present invention provides
a method for the neutralization and combustion of acid tar,
characterized in that the tar is neutralized by admixture with -
an oxide, hydroxide or carbonate of an alkaline earth metal
and the mixture in the form of a semi solid or solid product
is subjected to a two-stage heat treatment in a carbonization
plant, consisting in a first stage of a low temperature
carbonization treatment at from 350 to under 500C, while in
a second stage the resulting gaseous carbonization products
are burnt in air, and finally the solid carbonization residues
are discharged from the carbonization plant.
The method in accordance with the invention and also the
devices serving for the putting of the method into effect will
now be described in more detail on the basis of the attached
drawings in its general operating cycle. The drawings show:
Figure 1 a flow diagram, and
-3-
L`~
iO~V~
Figures 2 to 6 details of the mixing devLce in accordance
with the invention,
Figure 2 being a section of a device operating with a
worm,
Figure 3 a plan view of the device as in Figure 2 with
the casing partly broken away,
Figure 4 a similar illustration to Figure 2 of a device
operating with corrugated wheels,
Figure 5 a section along the line IV-IV of Figure 4 and
Figure 6 a cross-section of a device operated with a
conveyor belt.
In Figure 1 a silo 21 serves to contain the neutralization
agent for the acid tar, thus perhaps for lime. 22 identifies
a container for the acid tar to be treated, and a further
container 31 is also provided for consumed fullers earth,
which can be added to the neutralization agent.
jl/ -3a-
c~
.~o~
The ~xing of the acid tar with the neutralizat~on agent and
also possibly with other components and the neutralization are effccted
in accordance with the invention in the mixer 23, the construction of
which likewise constitutes a part of the present invention, and the
design of which is described in detail below. The gaseous products
being formed by this neutralization process are, as shown, led to an
aqueous collector solution 30 and neutralized therein, after which the
neutralized gases are led away through the pipeline 33. If necessary,
the as already mentioned solid to semi-solid neutralization products
are then led to a crusher 24, and pass on from there into the first stage
of the heat treatment, which as explained is a low-temperature
carbonization process. The carbonization oven or similar device in
which this is carried out is identified with 25 in figure 1. In the case
of the carbonization process carried out at low temperatures of from 330
to under S00 C, gaseous products and a solid residue that is free from
sulphides under the conditions quoted result. The gaseous products are
led to a combustion chamber 26 in which, as has been said, a supporting
fuel introduced through the pipeline 29 and when starting a "starter fuel"
can also be burnt. The energy can sometimes be utilised. The combustion
exhaust gases pass into the chimney 27. The solid carbonization residue
is led through an extractor to a container 28, and the possible addition
of further substances to the (when calcined lime or limestone is used as
the neutralization agent) carbonization residue consisting essentially
of gypsum and carbonization coke for the production of fertilizer already
referred to can be undertaken in this container. Air can be introduced
through the pipeline 32.
It is mentioned above that the construction of the mixing device
generally identified with 3 in figure 1 likewise constitutes a part of
the present invention. This mixer, illustrated in figures 2 to 6 of the
drawings, comprises essentially a collecting vessel with a metering
-- 4 --
bm: -
10~
apparatus on tllc entry s~d~ for the fcedln~ o~ the acld tar and the
neutralization agent, such as lime and suchlike, and a mLxer at the
outlet side for the transport of the mixed material from the collection
vessel to a discharge point. Preferably a device is also provided in the
mixer for the positive guidance of the sulphuric acid vaporising to a
slight extent with the reaction steam through or over the mixed substances,
when the metering device delivers a surplus of previously mixed-in
neutralization agent, so that to a substantial extent a further
neutralization is attained.
It is also possible for a water bath 30 to be connected to the
mixer 23, perhaps across an exhauster, as illustrated, in which transported
acid vapours are diluted and then neutralized.
A collector vessel l, a delivery and mixer (neutralization) unit
2 and also a metering device 3 are common to all forms of embodiment of
the device. In the present cases the collector vessel l is made in the
form of a hopper. It is also possible to provide a bunker or a silo or
suchlike. The metering device 3 is located at the input side of the
collector vessel l and has the task of feeding the acid tar and the
alkaline earth products in the small quantities provided for. The
delivery unit 2 joins onto the bottom of the hopper 1 and has a delivery
duct 4 which runs horizontally and has at its one end an aperture 5 into
the collector vessel 1 and at the other end a discharge aperture 6. In
the case of the embodiment example of the device according to figures
2 and 3 the delivery duct 4 contains two worms 7, 8 running parallel,
the threads of which mesh with one another, so that besides the delivery
action they also fulfil a mutual cleaning effect. The two worms 7, 8
mix and fractionate the material they are feeding without any sticking
of the worm tracks taking place. The worm shafts 9, lO are supported in
the face walls 11, 12 of the delivery duct 4 and connected externally at
the hopper end to a transmission 13 that is connected to 2 driving source,
such as a motor.
bm:
lO~V~
In the case of the embodiment example of the devIce as ln
figures 4 and 5, corrugated wheels 14, 15 are provided instead of the worms
7, 8, which are disposed spaced out longitudinally and, viewed in the
vertical direction, offset from one another and driven in contra-rotation,
so that besides the processing of the material provided for, a feeding of
the same in the direction of the arrow A is also effected.
The device in accordance with figure 6 has an endless conveyor
belt 16 for the delivery of the material extending over the length of the
delivery duct 4, above which a mixer 17 is provided in the connection to
the aperture 5 mentioned above of the delivery duct 4.
It is possible to introduce another suitable device instead of
the second worm, for instance a sprocket chain, which engages in the track
of the first worm.
One advantage of the device lies in the small expenditure of
power for the mixing process. But besides this how~ver the device can be
so conceived that the acids being vaporized in small quantities with the
resulting steam can be led over or through the material mixture. If the
additions of alkaline agents (for example lime) are made beyond the extent
stochiometrically necessary, these gases also would wholly or in their
ma~ority be brought to a neutralization.
It was ini~ially mentioned that the progressive nature and
technical effectiveness of the present invention lie in the technical
simplicity and economical low-cost way in which the method in accordance
with the invention is carried out, but in particular in its environmental
acceptability. This is particularly illustrated by the experiments and
their results as described below:
In the manner in accordance with the invention, an acid-resin/
sulphuric acid mixture as it occurs in the refining of mineral oils with
sulphuric acid was neutralised in the mixer in accordance with the
invention, thereafter crushed and carbonized in a low-temperature
bm
10~
carbonization oven at carbonization temperatures of ~rom 380 to 400C.
In detail the experimental procedure was as follows:
The initial material was an acid tar (pitch) of the followi~_
composition:
500 parts by weight H2504
150 parts by weight H20
350 parts by wèight free oil and organic substances bonded to
sulphur.
1000 parts by weight
1) These 1000 parts by weight of pitch were then neutralized
with 700 parts by weight of CaC03, in accordance with the following
empirical reaction:
: H2so4 + CaC03 ~ CaS04 + C02 + H20 + H
(500 parts/wt.) (500 parts/wt. + ) (680 parts/wt.) (heat tone)
200 parts/wt in )
Stochiometric ) CaC03
surplus )- ~(200 parts/wt.)
(+ 350 parts/wt. organic substances ) orgànic substances
and suchlike
+ 150 parts/wt. H20 ) (350 parts/wt.)
H20
( 40 parts/wt.)
1700 parts by weight of pitch - ~ 1270 parts/wt. of Neutralized Product -
430 parts/wt. of gaseous losses.
The said 1270 parts by weight of neutralization product cannot
be deposited on normal dumps, because of the harmful subscances such as
oil and sulphonates and other organics which they contain.
- 2) In the case of the low-temperature carbonization process,
from the yield of the neutralization process
680 parts/wt. CaS04
+ 200 parts/wt. CaC03 surplus
also + about 70 parts/wt. Carbonization coke ( = about 20~
of the organic substances present,
namely 350 parts/wt.)
bm
iO8V~
there was obtained 950 parts/wt. of carbonization residues that can
be deposited on normal dumps.
These gaseous carbonization products were burnt in the manner
stated in the second stage of the heat treatment, and the solid residues
of carbonization were subjected to a series of tests, the execution and
results of which will now be described:
1) Carrying out the extraction of acid tar processed in accordance with
the invention (solid product of carbonization)
.
The extraction of the material was carried out in a standing
test, in which distilled water was used for the extraction. Various
quantities were added to the material to be extracted. A generally linear
behaviour was observed in the extraction.
The washing out of the material was carried out for three days
at a water temperature of 20 + 2C, with periodic agitation, in order to
ensure the thorough intermixing of the material.
- 2) Method of Examination
After the termination of the test the products of the washing
were filtered through blue tape. The analysis values as s~et out below
were determined in accordance with the German Uniform Method for the
Examination of Water, Waste Water and Sludge (DEV). The determination of
the COD ~as undertaken according to the method of W. Leithe (Die Analyse
der organ. Verunreinigungen in Trink-, Brauch-und Abwassern, p. 51 -
The Analysis of the Organic Impurities in Potable, Mains and Waste Water).
3) Examination Results
Extraction Ouantity 50 g/l25 g/l 12.5 g/l
pH Value 8.15 8.05 7.85
Electrical Conductivity (20)/u/cm 20501400 1015
Oxidisability mg/l KMnO4 90.0 51.534.0
COD mg/l 91.0 30.219.6
Sulphate mg/l S04 1250 650600
bm
,
1~)80~
Chloride mg/l Cl 6.4 5.7 5.0
Sulphide mg/l S N o t D e t e c t a b 1 e
Appearance All samples were clear, without
odour and without colour
4) Assessment of the Results
4.1 pH Value
The pH values lies in the mildly alkaline range. This residue
from the slight solubility of the materials (e.g. calcium carbonate) used
for the neutralization of the sulphuric acid.
4 2 Electrical ConductivitY
The electrical conductivity is conditioned by the lime salts
going into solution, in particular by calcium sulphate CIf formation of
- anhydrite is assumed during the low-temperature carbonization,
solubility will be 0.20 g/100 g of water, when the solubility decreases
somewhat with rising temperature)
4 3 Oxidizability and COD
Oxidizability and COD are roughly of the same order of magnitude
and show comparatively low values, which in some instances lie below the
extraction values of household refuse (oxidiza6ility).
4.4 Sulphate
The sulphate contents are typical for the extraction of gypsum or
; of anhydrite. Sulphides could not be detected, accordingly no reduction
of the sulphates to sulphides is yet taking place at the coking temperature
used.
The products occurring as the final result of the method in
accordance with the invention thus contain harmful substances in a quantity
that lies clearly below that of household refuse The sulphate content of
the products likewise lies in the order of magnitude which is also to be
found in many natural components of the soil, as perhaps in raw clay or
marl, loam, etc The residual solid products obtained in the case of the
treatment of the acid tar in accordance with the invention can be deposited
without more ado in approved dumps and stored with household refuse,
- bm:
-
construction scrap, earth and such].lke, and comply completely wLth thelegal requirements existing with regard to the protection of the
environment.
-- 10--
bm
