Note: Descriptions are shown in the official language in which they were submitted.
'9~ 3 l7: ;~c EYER~LINiER P~T ~ 17~ REIEI~H 2 0 2 9 8 8 7 P. ~ i7
MULTILAYER PELLETS
BACKGROU~I~ OF TH~: lNVENTIOrl
The prPsent invention concerns pelletizad mate~ial6
for use in chemical conversion processes of industry or
agriculture, for example in the purifi~ation o ~omm~nal,
in~ust~ial and private sewa~e, or the f~rtilizing or
deacidifica~ion o~ soil utilized i~ agriculture or forestry,
and a pro¢e~# for their preparation.
Qne of the essential problems of chemi~al conversion
proce~ses conæiætæ of the con~rol of the rea~tion rate an~ in
particular the regulation of the ~uantity of reagents
introduced. Thi6 is partic~larly true in conversion ~rocesses
in which water soluble materials are used as rea~ents, the
reaction mat~rial i9 p~eæent in an aqueOus solution and
ext0nded contact times between the reagents and the solution
cannot ~e avoided, This is the case for esample in the
deacidification of ~oils in agriculture and forestry and in
numerou~ ~h~mical conv~rgion processes, for eYample sewage
purification. Materials ~pread to improve soils are
conti~uouxly e~posed to di~s41ution by ~he humidity of the
soil, which ~articularly in ~ainy weather leads to the
excessive dissolution of the soil improvement materialæ. The
excessive su~ly of these materials themselves can lsad to
damage to the soil, and there is a risk that the materials will
be introduced into the ground wat~r. The same is true for
chemical conversion proces~es, for example, in sewage
purification processes. In order to obtain adequate conversion
of the harmful su~stances, reagents are used in great excess on
the one h~nd, and on the other, long retention times are
2029887
required agai~ posin~ the danger of an excessive uptake of the
reagents with harm~ul conseguences for the dispo~al o sewage
waters .
~ his pro~lem in chemical conversion procos~e~ is
es~ecially prevalent in the purification of acidic waste waters
wherein acidic sewage waters are defined as all typeæ of sewage
with a low pH value, including the ~lue ga~ condensates
originating in th~ chimneys of househo~ds and industrial
heating installations which are of particular importance.
These condensates have estraordinarily low pH values, and -- as
revealèd ~y recent investigations -- Carry apprscia~le
proportions of heavy metal~ from the chimney linings in the
form of abrasion products or ~olution~ by ~he drippin~ or
~unning condensatos. The neutralization of such sewage waters
represents a considerable environmental problem a~ their
introduction into public outfalls leads to considerable damage
to biological puriication in~tallation~ and subsequently to
the environment itself. I~ is therefore increasingly nece~gary
in order to prevent such damage, ~o develop chemical ~ewage
t~eatment proCe~ses wher~in purification is achiev~d by
chemical or phy~iochemical reactions, as a supplement or
alternative to biolo~ical purification methodg wherein
purification effects are obtained by bac~erial, enzymatically
catalyzed metabolic ~eactions.
~ iological processes are limited relative to each
other by that only substances that fit into the metabolism of
the bacteria are affected and which are taken up during the
retention time in the biological system ~activation basin,
percolation filter) and reacted, i.e. decomposed. In view of
tho increasin~ly complex compo~ition of communal and
particularly industrial sewage waters, the ~iologicall~
unreacted residual loads remaining in the biological treatment
process will increase in volume, For this reason alone
chemical sewaqe treatment methods are particularlY important
relativ~ to the future safetY of the aquatic ~art of our
ecosystem.
- 2 -
6360K
3-l1-Z3 17:Z4 E`l'Ei~iLII15ER ~i~T S~ 72 ~ EIEI'~H 2029887 F~4~17
It is known to u~e so-called neutralization ~oxes for
the neutra}ization of acid sewage waters; the bos is filled
with a basic filler material and the acid solution is drippea
into it, thereby reactin~ during the more or less extenxive
retention time with t~e reaction mate~ial within the bo~. The
known processes have seve~al disadvantages. The one
disadvantage is the high consumption rate of neutralizing
material due to the complete æaturation o the condensates.
Anothe~ disadvantage is that large proportions of the
neutralizing material~ are dissolved in the box during the
retention time, leading to eYcessive loa~ing. Finally, there
is no ~limination of the heavy metals contained in the wa~te
water.
~IEF p~a~IPTION O~ INVENTION
It i8 the o~ject o the present invenSion to provide
initial materials for u5e in chemical conversion processes, the
consumption of which i8 r~gulated as a function o~ the reactiOn
vclocity desired, and a process for thei~ preparation.
Tho P~esent invention utilize~ materi~l ~ w; th varied
~olubility products which are Çormed into layers, preferably
with materials of higher solubility on the in~ide of the
yellet~ an~ mate~ials o~ ~ower solu~ y on the out~ide of the
pellets. Pelletization and the controlled g~anulation
desiqnated ~mi~rocoated buildup-agglomoration~ is performed in
a nuclei formation step by the initial formation of pelletizing
nuclei fol~owed by ~urther pelletization.
In the initial pellet ~ormation st~p, a minimal amount
of pelletizing water is used, to allow nucleation of primary
m~torials of higher solubility. Upon contact with the solution
containing the reactive substances, the pellets of the present
invention react in a controlled and quasi-buf~e~ed manner so
that the more readily soluble materials are protected against
premature dissolution, thereby preventing the e~cessive
636~K
3~ 3 17:25 E`lER~LINSER P~T ~-6~37Z ~REIElCH 2029887 P . 5/17
accumulation of materials o~ low or very low solu~ility. The
pellets of the present invention insure that the solution
containing the reactive su~st~nces i6 expos~d to large contact
surface area, thereby insuring direct contact of the r~acti~e
substance usually present in a high dilution, with the reagent
and thus it~ convsrsion. In this manne~ it is insured -- for
e~ample in the deacidification of sewage waters -- that even in
the case of a simple flow of the xewage water through a pile o
the pellets prepared according to t~e present in~ention, the
quantity o~ reactive material necessary for neutrali~ation is
always available to the sewage. Additionally, a Nslow release
effect~ is obtained whereby the materials with extremely low
solubility ~roducts are concentrated in the outer layers of the
nuclei and ~ellets, and a controlled buffer action is obtained
preventing eYcessive dissolution ana neutralization whi~h iæ as
harmful to the environment as excessi~e acidification. Another
siqni~icant advantage of the invention is the complete
elimination of heavy metal~ simultaneously with the
neutralization of the sewage waters, said metal~ precipitating
during the gradual transition of the waters from the acid phase
into the baeic ~hase in particle sizes such that they are
initially bon~ed phy~ically to the surface ef the pellets an~
may be collected in a special filte~ layer upon being washea
out from the ~ellet pile.
nE~AILED ~ R~pTION 5~E_E~E PREFERR~ aoDIM~
In practising the present invention, the ~tructure of
the nuclei and matri~ ~aterials with dif~erent solubility
products, and the choice of tho initial material~ is of
doci~ive importance in obtaining the aforementioned efects.
Tho metered addition of pellotizing water i9 the controlling
factor in the preparation process. Buildup a~glomeration is
the result of the strongly reduced su~ply o pelletiz~n~ water
in the nucleation phase. Initially a dissolution of the
surface layers of the more rea~ily soluble material particles
- 4 -
6360K
Z3 17: :~6 E'('ER~LI NSE~ Pf~T ~-~J37~ rjREIE IC:H 2 0 2 9 8 8 7 P . 6 ' 17
takes place, which therefore aq~lomerate preferentially with
the bonding of slight proPortions of the less soluble
materials. The di~solution of the surfaces of the pa~ticles of
the less soluble material takes place a~ a ~i~nificantly later
time, so that this material i~ located, following comPletion OT'.
the pelletizing process, mainly in the outer layers of the
re~ulting pellets, thus encapsulating the nuclei and residual
guantiti~s of not prenucleated material with a higher
solubilitY product.
The neutralization of garden, agricultural and forest
soils is an example of an especially advsntageous ap~lication
of pelletized material~ prepared according to the present
invention. ~his application, for e~ample, can be administered
usin~ pellets with 40 to 65, pref0ra~1y 45-55~ by weight
dolomite, 10 to 25, p~eferabl~ 15-20$ by weight calcium
carbonate, 2.5 to 7.5, preferably 4-5~ by weight
disodium-monohydrogen-phosphate, 2.5 to 7.7, preerably 4-5~ by
weight calcium-hydrogen-phosphate, 10 to 15, preferably 6.5-7~
by weight calcium hydro~ide, 2.5 to 7.5~ preferabl~ 4.5-5.0% 4y
w~ight bentonite, 1.5 to 3.0, preferably 2.5-3.0~ by weight
feldspar, 1,5 to 5.0, preferably 2.5-3,0~ by weight potassium
silicate and 1~5 to 5.0, prefe~ably 3.5~ by weight magnesium
oxide. The pelletizing is advantageously carried out in a
polydispersod manner, i.e, with hiqhly different sizes, with a
proportion of small grain inversely propo~tional to the pH
value of the soil to be treated. The effective period of time
an~ the action rato, , the time during which a soil with
pH value of for ~ample 2 may be b~ought to a pH value of
between 6 and 7 and maintained at this value, may be
determined. This action rate is controlled by increasing the
small grain size proportion in the case of low pH values and
with the controlled selection of the initial materials as a
function of their ~olubility pro~ucts. In this Tnanner, for
example, the pelletizing of dolomite (calcium-magnesium
carbonate) with a ~olubilit~ product Of 2 . 6 ~ 10 5 for
-- 5 --
63 ~OK
' ~12J-11 -2S 17: 27 E~'ER~LII ISE~ P~T ~ 72 Il~E IE I I~H 2 0 2 9 8 8 ~ P . 7/17
magnesiu~ carbonate and 4.7 x 10 7 for aalcium carbonat~, may
be buffered ~y use of aalci~m hydro~ide (solubility product ~.9
~ 10 6) magnesium hydroxide (1.5 x 10 12~ aluminum
hydroxide (1.9 x 1~ 31) or iron hydro~i~e (5.0 Y lo 38),
thereby obtaining in a controlled manner a more or less strong
4uffering of the active material, whereby the dissolution of
the material (in this e~ample the dolomite) is corresPondingly
delayed.
Further activ~ substanceæ may be added to the initial
material, æ~ch as for eY~mple activated ~entonite or
sodium-sulfate-d~cahydrate to regulate the water content of the
soil. Activated bentonite i~ capable of storing water in a
quantity of 30 times of its wei~ht, while
sodium-sulfate-decahydrate cleaves off its wat~r of
~ry~allization congruently at temperatu~e~ ov~r 30C. In a
similar manner, an active sub~tance m~y be added to the
~ellets, where~y the ozone taken up by the plant as the result
of the action of s~n light on the loaves may be eliminated,
tog~ther with it~ ha~mful effe~ts. This may con~ist either of
a ~uffer causinq a mildly al~aline reaction -- pHC7 -- the sap
o the plant, o~ an agrotechnically acceptable metalizer, or
exa~pl~ manganese sulfate (MnS04), which decomposes the
ozone, whe~ein the rate of decompo~ition decrea6es with the
inCrea~in~ alkalinity o the solution (plant sap).
A~other em~odiment is a process for making ~ollets for
the eliminatio~ of nitrogen impurities, and in combination with
it, of phosphorus impurities, possibly together with the
removal of heavy metals. This ombodiment contains hydroyen
phosphate salts of a cation of the second principal and
secondary groups of the Periodic Syste~, p~eferably
magnesium-hydrogen-phosphate ~MgHP04) and/or phosphate salts,
in par~icular the ortho-phos~hate salt~ of a cation of the
second principal (Be, Mg, Ca, Sr, Ba and Ra) and secondary (Zn,
6360K
'ge~ 3 l7:c~ EYEf~LINSER G~T ~ EIr2 ~ EIEII::H 2~29887 P.~/17
. .
.,.
Cd and Hg) groups of the Periodic System, preerably
tri-magnesi~m-di-phosphate. Optionally, the ~hosphate salt, in
particular the ortho-phosphate ~onstituting one o~ the active
substancec, may be ~ynt~e~i~ed in the fir~t pelletizing stage
in a manner such that initiallg a partial ~uantity of the m~tal
oxide i8 reacted with phoæphoric acid in a guantitY necessary
for conversion, after which more maqnesium o~ide i~ added,
whereupon followinq the comPlete con~ersion, pelletizing takes
place usin~ the magnesium hydroxi~e formed in the seeond
rea~tion step a~ the binder, in combina~ion with the excess
re~ction water formed in the ~irst reaction ~tep. In this
manner, the control of the addition of p~lletizing wat~r is
made po~æible in the fir~t pelletizing stage in a particularly
#imple manner, since in the reaction of magnesium oxide with
pho~phoric acid an ~xaes~ ~uantity of reac~ion water i~
released suffi~ient for the hydrating of the sub~e~uently added
magnesium o~ide, A metere4, ~light quantity o~ water i~
required for the formation o~ t~e nuclei preferably ~ro~ the
more soluble active materials. The less ~oluble materials ~ake
part later only in the agglomeration and encapsulate a~ the
matrix material in a mix~ure the the ~ore soluble nucl~i.
The present invention may be applied with great
advantage in the preparation of pellets for the neutralization
of a~ids, with the ~imultaneous elimination of heavy metals.
In ~his case pHlletizing is carried out ~onveniently in a
manner such that initially nuclei are formed with a core
consisting essentially of bases of the second principal group
o~ the periodic sy~tem, in particular magnesium hydroxide, an~
an encapsulation by iron-III h~droxide, The nuclei are
subsequently pelletized in a matrix, wherein pellets of
different composition, i~Çl in ~axticular pellet~ with a
different magnesium hydroxide/iron-III hydro~ide ratio, may ~e
formed. The pellets c~ntaining a high proportion of magnesium
hydroxide are used for the rapid neutralization of the acids
~ contained in the liquid being treated, while the pellets
,.~
-- 7 --
6360K
,
', r9QI-11-2:~ 17:29 E`'EI~LIN5ER F'~T ll-S13,2 DREIEICH 202988~ P.~'17
containing a higher proportion of iron-III hydro~ide pro~iae a
stronger encapsulation of the magnesium hydroxide, with the
effect of reducing to about 7.5 the pH value which had been
increased to over 9 in the neutralization phase with the
purpose o precipitating the heavy metals. This lowered pH of
about 7. 5 is more compatible with the environment.
The iron hydroxide is present in the form of a
trivalent hydrated iron ion which Convert~ gradually from
Fe(H20~63 to Fe(~20)2(OH)4, The hydrogen ions
thus produced re~ult in a slightly acidic ~roperty of the iron
hydro~ide. In addition to this advantageous effect of the
regulation o~ the pN value, the pellets prepared in this manner
have the ~urther advantage that in the phase of the increa~ed
pH val~e (~9~ the heavy metals conta~nea in the ~ol~tion are
precipitated and the precipitate is absorbed on the iron
hydroxi~e pre~ent in the colloidal form.
T~e invention will become more apparent ~rom the
~ollowing esam~les:
~XAMPLE 1s
15 kg dolomite 18~23, 5 kg calcium carbonate, 0.5 kg
each of di~odium-mon~hydrogon-~hosphate and
calcium-hydrogen-phosphate, ~.5 kg calcium hydroxide, 1.5 kg
~1dspar, 1.0 potassium silicat~, 3.0 kg active bentonite and 1
kg mangane~e sulfate, i8 placed into a ~elletizing mixer.
The mi~ture is homogenized intensively. Subg~quently,
2.5 k~ water, 2.5 kg magnesium oxide and 5.0 kg white li~e are
added and mi~ed intensively. Following the completion of the
e~oth~rmic reac~ion of lime ~laking, the ~i~ture is pelletized
with the addition of 4.5 kg ~elletizing water to the nucleation
#tage~ whereupon ~inal pelletizin~ takes ~lace with the
a~dition o another 0.5 to 0.6 kg water, until the microcoated,
nuclei-based pellet~ desired are obtained with a grain size
distributio~ between 3 and 6 mm, T~ey contain water in
- 8 -
6360K
.. : .
.
2~ 17:S~l EYER~.LIN-,ER Pf~T D~ REIEICH 2~2 98 ~7 P. 1~17
quantitie~ of abou~ 2.0 to 2.2 kg, have a deactivating effect
on o~on~ sol~tions and have a pH val~es of approximately 11.6
in water and in acidic water -- initial v~lue 3.8 -- ~ buf~ered
value of 7.35.
EXAMPLE 2:
100 kg magne~ium o~ide with a degree of purity in
e~ceæs of 98~ and a calcium ion content o l~s~ than 0.5~ by
weight ~re weighted into the pellstizer, together with 10 kg
iron oxide -- again of a purit~ in e~esæ of 98%. A~ter
intensive mi~ing for about lO min, 48.4 kg deionized ~softened
di~tilled water) are addea, which is ~ufficient for the
conversion of the oYides to hydroxides, ~n excess Of about
0.5% to 1% by weignt should not be increased further. The
reaction i8 carried ou~ under intensive cooling to remove the
reaction heat so that the rea~tion t~mperature o~ 35~ is n~
e~ceeded. Following the completion of the intensive reaction
phase, the misture is allowed to a~e fo~ between 30 and 120 min.
More pelletizing water i8 then added in three ste~s to
the cool~d rea~tion ma~s with continuou~ pelletizing, i.e.
initial}y a quantit~ of about 2.75 kg, then after lO min
another 1.35 kg. After a ~elletizing time of another lO min,
pellet nucl~i have been ormed, whi~h followin~ the addition of
another 1.35 kg water are pelletized into final pellets with
dim~nsio~s between 3 and 6 mm. ~he wet pellets are ~owdered
with abo~t 2.5 kg magnesium o~ido and dried in air for 12 h.
~XAMPLE 3:
lO0 k~ iron oxide with lO kg ma~nesium ox~de, are
~rocessed wit~ the addition o~ 34.0 kg hydratin~ water and
-- in three part~ -- of 2.0 ~ 0.95 + 0.95 kg pelleti~ing water,
into pellets suita~le or pH value adj~stments. ~h~ pellets
are prepared in the manner described in the foregoing exarnples,
un~er the ~ame conditions.
_ g _
6360K
