PROCESS AND APPARATUS FOR DRYING ORGANIC SOLID MATERIALS, PARTICULARLY BROWN COALS

METHODE ET INSTALLATION D'ASSECHEMENT DE SOLIDES ORGANIQUES, NOTAMMENT LA LIGNITE

English Abstract

Abstract:


Organic solid materials such as brown coals are dried by pre-
ferably continously passing the pre-heated organic solid ma-
terials through at least one drying stage and by subjecting
the organic solid materials within this drying stage to the
action of saturated steam under super atmospheric pressure
and at elevated temperature. Steam is used for pre-heating the
solid materials and the condensate formed is discharged prior
to introducing the solid materials into the drying stage ope-
rated with saturated steam. Saturated steam and preferably the
steam obtained during the drying process is used for pre-heating
purposes. Pre-heating itself can be effected under atmospheric
pressure thereby pressure-releasing the steam obtained in the
drying stage. Pre-heating is effected within a bunker (1) being
connected via a pressure lock (6) with an autoclave (7). Steam
is supplied via a conduit (2) to the solid materials to be pre-
heated.The condensed water is discharged from the bunker (1)
via a conduit (3). Additional conduits (5) can be connected to
the bunker (1) for discharging the condensate from different
cross-sectional planes.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:

1. Process for drying organic solid materials, particularly
brown coals, in which the preheated solid materials are,
preferably continuously, passed through at least one drying
stage within which the solid materials are subjected to the
action of saturated steam at super-atmospheric pressure and
at elevated temperature, characterized in that preheating
of the solid materials is effected by treatment with steam
and the condensate formed is discharged prior to introducing
the solid materials into the drying stage operated with
saturated steam.


2. Process as claimed in claim 1, characterized in that
the solid materials are preheated by treatment with saturated
steam.


3. Process as claimed in claim 1, characterized in that
steam obtained during the drying process is used for pre-
heating the solid materials.


4. Process as claimed in claim 1, 2 or 3, characterized
in that the steam formed on pressure-releasing the waste
water, being under high pressure, of the drying process is
used for preheating the solid materials.





5. Process as claimed in claim 1, 2 or 3, characterized
in that the solid materials to be preheated are under
atmospheric pressure.


6. Apparatus for drying organic solid materials,
particularly brown coals, characterized by a bunker for the
solid materials to be preheated, said bunker being in
connection with an autoclave via a pressure lock, a steam
supply conduit being connected to the hunker having connected
thereto at the lowermost portion a discharge conduit for the
condensed water.


7. Apparatus as claimed in claim 6, characterized in
that at least one additional conduit for removing the con-
densate is connected at an area of the bunker located at a
higher level.

Description

~,~51~
-- 2 --



The present invention refer~ to a process for drying
organic solid materials9 particularly brown coals,in which
the pre-heated solid materials are, preferably continuously1
passed through at least one drying stage and are there subjected
to the action o~ saturated steam a~ super-atmo~pheric pressure
and at elevated temperature. Particularly when drying brown coals
it is known that the frequently considerable humidity content
of the brown coal consi~ts of a major part of water absorbed
within the capillaries but also of chemically combined water
which can when immediately heating the coal only ba removed
with a high energy expenditure. It is already known that this
water can be expelled by means o~ steam but also by means of
hot water. There are also known processes which allow to a ~emi-
continuous drying process. Such known proces~e~ have ~requently
made a substantial better use of the energy supplied than the
original FleiBner-~ocess,but the problem of water removal was
only insuf~iciently solved by the known proces~es. The solid
materials to be supplied to the drying ~$age operated with sa-
turated steam must be pre-heated and with the known processes
o~ this kind pre-heating is e~fected by suspending and heating
the solid materials in water. A comparatively great water balla~t
is, however, introduced into the drying stage operated with
saturated ~team by this suspension and this water ballast must
be heated within the drying stage operated with saturated steam
for which purpose a comparatively great heat exp~nditure is re-
quired.


~S1864


~ he invention now aims at e~onomi~ing such a drying process
and to reduce the consumption of heat energy. The invention,
therefore,essentially consists in that pre-heating o~ the solid
material is e:~fected by treatme~t with steam and that the con-
densate formed is removed priorto introducing the solid material~
into the drying stage operated with saturated steam. In this
manner, the water ballast , with ~hich the solid materials are
introduced i~to the drying stage operated ~ith saturated steam,
is substantially reduced ~nd only the solid materials itsei~
must be further heated within the drying stage operated with
saturated steam. Thu~, also the amount of water is reduced which
has to be removed from the drying stage operated with saturatsd
steam. According to the invention, the solid materials are con-
veniently pre-heated by treatment with saturated steam. Satu
rated steam is produced during the drying process and according
to a pre~erred embodiment o~ the invention saturated ste~m o~-
tained during the drying process is used for pre-heating the
solid materials9 noting that also heated steam can be used if
such steam is generated during the dryin6 process Thus, energy
consumption can be reduced and the drying process can be made
more economic. For example, the steam ~ormed by pre~sure-relaa-
sing the was~b water, being under a high pressure9 from the
drying process can, according to the invention, be used ~or
pre-heating the solid materials.
The solid materials to be pre-heated are conveniently under
atmospheric pressure. Thus it is made possible to use a simple
bunker for receiving the solid materials to be pre-heated. Sub-
sequently, the solid ~aterials are in usual mannar introduced


~L51~369L


via a pressure lock into the auto~lave containing the atmos-
phere of saturated ~team~ The apparatus according to the in-
vention is thus es~entially characterized by a bunker for the
solid materials to be pre-héated, said bunker being in connec~
tion with an autoclave via a pressure lock and a ~team supply
conduit and a discharge conduit for condensed water bein~ connec-
tedtosa~ ~t~ethe discharge oonduit being connected to the
autoclave atrits lowermost area.
The condensate formed i~ thus immediately discharged end
can no more load the pre-heated solid material~. In this case
andaccording to the invention, at least one additional conduit
for discharging the condensate can be connected to the bunker
at a higher level. This is o~ advantage particularly if fine-
grained solid materials, a~ove all brown coals, having a par-
ticle size from 1 ~ m to 5mm are subjected to the dryi~g proee~s.
In such a case, it might oocurr that the condensed water for~
med is too slowly ~lowing through the charge containe~ withln
the pre-heating bunker and if one or more additional conduits
are connected to the bunker at a higher level the condensate~
formed can more rapidly be dischar~ed.
In the drawing the invention is further illustrated with
reference to a ~ow chart for treating of brown coal
The brown coal ls introduced into ~he pre ~eating bunker
1, which is open on top, either in lumpy form or in fine-grai~ed
form. Saturated steam is ~lown i~o the pre-heating bunker ~ia
a conduit ~ The condensate formed is, via a filter 4, removed
as waste water9 through a conduit 3 connected to the lower


1~5~864
-- 5 --



portion of the bunker. A second conduit 5 is connected to the
pre-heating bunker 1 at a higher level. From the pre-heating
bunker 1, the pre-heated coal, which is substantially dry or has
an only low water ballast, is introduced via a pressure lock 6
into an autoclave 7 within which the coal is downwardly ~liding
over cascades 8 of sieves~This autoclave is maintained under
super-atmospheric pressure and saturated s-team is introduced at
the lower end of the autoclave via a conduit 9. The~solid mate-
rials are subsequently discharged by means of a conveyor screw
10 and supplied9 i~ desired,to still ~urther drying stages. The
waste water is removed from the autoclave via oonduits 11 and
a collecting conduit 12 and is flowing into a pressure-relèase-
vessel 13, The saturated steam generated within the pressure-
release vessel is introduced into the pre-heating bun~er 1 ~ia
the conduit 2. The water is removed via a conduit 14 and can
be used ~or pre-heating purposes br lik~e purposes within the
drying process.




.