Note: Descriptions are shown in the official language in which they were submitted.
20~18~7
PROCESS F~R PRODUCING A POROUS CERAMIC GRANULAR MATERIAL F~R USE AS AN
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ADSORBENT AND/OR ABSORBENT, PARTICULARLY AS ANIMAL L m ER
The invention relates to a process for prcducing a pOI~US ceramic granular
material with pore sizes of ~ 1 mm, in which clay; calcite, quartz sand,
dolomite, fel~spar, chamotte, kieselguhr and/or sepiolite as additives;
water; deflocculant and surfactant are mixed and foamed in a per se known
dispersing unit under pressure (1 to 10 bar) by compressed air supply at a
te~perature between ambient temperature and 959C and optionally for produ-
cing a highly viscous~ thixotropic, naturally stable foam suspension agents
counteracting the effect of the deflocculant are added and subsequently the
~oam'ed mixture is optîonally shaped into shaped clay bodies, which are
dried at a temperature between ambient temperature and 200C, the dried
shaped clay bodies are optionally conminuted and, accompanied b~ the return
of the fines to the starting nixture, are scr~ened and subsequently the
shaped clay bodies and/or the comninuted shaped clay bodies with a
selected particle size range are baked at a pr3duct tempe~ature above 600C,
for use as adsorbents or absorbents, particularly as animal litter or bed-
ding, as well as to a product produced in this way.
~br the adsorption and/o,r absorption of liquids and gases and in particular
for use as animal litter, advantageously inter alia hi~herto a co~minuted,
porous ceramic material has been used, which is produced according tD a
process hnown fron Genman patent 34 14 965. miS material is in particul2r
inexpensive oorpaI~d wi~h o~her ædsorbents and/or abso~bents known from the
prior art and e.g. based on calciun silicate hydrate and has considerable
variation pcssibilities with re~pect to the product par~meters and in part-
i~ ~he appeaIance. Despite the advantageous chaxacteri~tics -of this
material, particularly rel~tive 13D it~ water abso~pti~n capaci~ d odc~ur
bindillg, a need was still felt to fur~e~ devel~p the c~mic mater~l
pm~ced according bD. ~he l~n pr~ess, particularly wi~ a view tiD it5
u~e' as animal l;tter or bedd~.
me pnDblem o~ ~e i~venti~n is ~erefore bD 80 fur~er devel~p ~e l~own
process ~ at a further l ~ vement bD l~he pDl:OUS strucl:ure o:E the ~ sorbing
and/or absorbing part~cle8 can be obtained, ~o as b~ impnove the water
absorption capa~i~y, odsur bin~ing, ebc. of the material.
2~807
According to the invention this problem is solved in that 25 to 45~ by
weight clay, 0 to 40% by weight calcite, quartz sand, dolomite, feldspar,
chamotte, kieselguhr and~or sepiolite, 20 to 50~ by weight water, 0.1 to
1.0~ by weight deflocculant and 0.1 to 1.0% by weight surfactant are used
and the shaped clay bcdies and/or the conninuted shaped clay bodies with a
residual moisture content of 5 to 25% are fed into a preheated kiln and
baked at a predetenmined product temperature in the r3nge 750 to 1050C.
Accordin~ to a preferred embcdi~ent of the invention an indirectly fired
rot~ry kiln is used for the baking pnocess.
It is particularly advantageous to directly transfer the baked product from
the kiln into a cooling drum into which water is directly s,orayed, in
parallel to the indirect cooling with air.
The invention also relates to an adsorbent and/or absorbentr particularly
animal litter, which can be prcduced according to the inventive process.
Surprisingly as a result of the inventively selected quantities o~ the
starting substances and the conditions during the baking of the shaped clay
bodies, their porous internal structure can be clearly further improved and
in particular nade more uniform, which qptimizes the water absorption cap-
acity, odour binding and other product characteristics associated therewith~
This has 13d to surprises for the oeramics Expert. Firstly it was not
hithert~ known that a ceramic material wi~h ~he i~dicated water content o
S bo 25% wou~d ~e able to withstand without any signific2nt deterioration
th~ thermal shock an introduction into tlhe pr~heated kiln, wh~6e temper-
ature at t ~ point is apprcximately 700 bo 800C. Secondly, particularly
as a result Oe the teaching of German p~tent 34 14 965, a prejudice exieted
~ha~ a treabment of the shapsd c ~ bodies at higher product temperatures
t~an 800C wou~d lead to an embrittle~ent of the material and to a redNc-
tion of ~he internal surface, which would hsve had a disadvanta~eous effect
on ~he desired characteri8tics of the product as an a~sorbent and/or
absorbent. It wa5 then2~0re co~pletely surprising that as a nesult o~ ~he
mea8ure8 accordiny to the inNention a much better and in p3rticular mu~h
.
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more uniform pore structure could be obtained, accompanied by the very
favourable economics of the process.
It was also surprising that under the indicated product conditions, it was
also possible to positively thermochemically influence the colour of the
ceranic baked material. m e iron contained in the clay nonmally leads
through oxidation to a reddish product and then, by reduction to whitish
colours the~ein. Hcwever, as in ceramic baXing processes generally direct
firing takes place, the in each case desired kiln atmosphere is a~justed
via the kiln burners. In the caæe of indirect firing, which is used in
preferrel manner accor~ing to the invention, and the air quantity no~mally
present in the kiln chamber of 5 to 10 m3/tonne of baXing material, an at
least partial cxidation, i.e. a reddish colouring of the product would have
been eKpected. However, under the given pr~duction conditions, contrary to
expectations, the iron contained in the clay is reduced, as is made clear
by the whitish colour of the end product. The reasons for this reductio,n
have not as yet been completely clarified. However, it is assumed that
there is an interplay of several factors, namely th`e relatively ~hort
baking time, st~am andtor hydrogen formation in ~he pores with local inert
gas/reaction gas fo D tion and a steam and/or hydrogen formation throughout
the klln ch~n~er, which largely neutralizes the oxidation action of the
oxygen.
m e ~udden cooling by the direct spraying of water into the ooo ~ drum
and which advantageously directly follows ~he baking of the shqped clay
bodies and in which the product is cooled withln a f~w minute~ ~ m m
approximately 1000C to 60C,~must also be considered e~treme for such a
ceranic material, ~o that itwRs ~urprising that ~uch a rapid oooling, which
1~ naturally of great interest for econamic reasons, 13d to no negative
infiuence~ an the pro~uct characteristics.
E~a~ple
400 kg o~ Westerwald clay with 10~ residual humiaity are fsd together with
200 k~ of water and 460 kg of feldspar with 5% residual humidity and 2 kg
of sodi~n polyph~x~ohate and 4.5 kg of sodium dodecyl su1phonate into a
205~7
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mixer, ~ollcwed by vigorous stirring for approximately 5 minutes and the
transfer of the resulting highly thixotropic clay suspension into a shaping
unit and feeding in 1 cm diameter strands into a drying apparatus. On
reaching the desired residuaI m~isture content the foamed clay material is
passed into a roller crusher, where it is comminuted. The comminuted
foamed clay particles are subsequently subdivided in a screening plant into
a size fraction of between 1.0 and 5.0 mm, which is passed to the kiln, and
a size fraction below 1.0 mm and which is returned to the starting mixture.
m e foamed clay particles transferred to the kiln are intrnduced into a
continuously operating kiln preheated to 750 to 1050~C. The baked ceranic
product is directly transferred from the kiln into a cooling drum into
which water is directly sprayed in parallel with the indirect air cooling.
After a few minutes the product can be transferred to the packing plant.
The ~hus produced materials are characterized ~y the follcwing parameters:
p~-value: 7.3 to 7.5
water absorption c~pacity: 150 to 190~ by weight
internal surface: 100 to 200 m2/g
pore diameter: ~ 0.8 mm~
m e features of ~he invention disclosed in the description and the claims
can be ~portant bo the reali3ation of the varlous embodiments of the inven-
tion, both singly ana in randam c~mbinations.
