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Патент USA US2368042

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Patented lien. 23', 1945 ‘
- T 2,368,042
um'rso STATES '- PATENT
0mm
2,368,042
PROCESS FOR PRODUCING NEUTRAL
CALCIUM HYPOCHLQBITE
_ ‘
- Homer Louis Robson, Lewiston, N. Y., assignor to V
The Mathieson Alkali Works, Inc., New York,
vN. Y., a corporation of Virginia
No Drawing. Application January 21, 1942, ‘
Serial No. 427,589
, 11 Claim.
This invention relates, to the production of
neutral calcium hypochlorlte and provides an ;
improved method of preparing slurries thereof
‘
‘
(on. 23-86) f
of the neutral compound formed by the procedure
just outlined is the tendency of the slurry to,
becomesupersaturated and then to form many j
very small crystals of the neutral hypochlorlte
The general method of producing calcium hy~ 5. which cannot vbe grown to satisfactory size ‘for
?ltering during the completion of the chlorina
pochlorites consists essentiallyv of chlorinating
tion. To reduce this tendency, it has been pro
lime slurries whereby the lime is converted to
posed to form the neutral compound in the pres
hypochlorite which crystallizes to form slurries
ence of previously formed crystalsof the neutral '
oi’ hypochlorite crystals. The hypochlorite crys
this are customarily recovered from the mother 10 compound. Following this procedure, it has been
found necessary to employ very large amounts
liquor by ?ltration; or centrifuging. ' Though this
of seed crystals in order to avoid the formation‘
method has long been known, its practical ap
of small crystals due to spontaneous crystalliza
plication to the production of neutral calcium
tion. Amounts of seed crystals exceeding the ‘
hypochlorite has presented many difficulties.
For example, it has been known that milk of is expected yield have been suggested.
It has further been suggested that better crys
lime can be chlorinated at ordinary tempera
tals of the neutral hypochlorite may be obtained
However. under such
conditions, basic '
tures.
’
by thinning the slurry in which the precipitation,
hypochlorite compounds are formed which have
oi the neutral compound is to occur, as by dilut
been found objectionably to thicken the slurry
so that chlorination could not be carried on 20 ing it with ?ltrate obtained from the ?ltering 0!
a previous portion of the slurry. Because of the
satisfactorily. The usual procedure is to con
solubility relations, thinning the slurry with water
duct the ?rst stage of the chlorination at an
is uneconomical due to solution of the neutral
elevated temperature, for example 30 to 45° C.,
compound and its-loss in the increased amount
at which temperature the dlbasic calcium hy
pochlorite compound, Ca(OCl2.2Ca(OH)2, is 25 of ?ltrate. The use of‘several volumes of ?ltrate
per volume of chlorinated milk of lime slurry
formed. The dibasic compound crystallizes in
has been suggested. Such procedure calls for
hexagonal plates and does not objectionably
a considerable increase in tank capacity and in
thicken the slurry.
volves the-handling of large amounts of ?ltrate
If the chlorination is carried further toward ‘
completion at such elevated temperatures, a pre so which is corrosive to pipes and pumps.
One di?lculty of operating in the above de
cipitation oi’ the hemibasic hypochlorit'e com
scribed manner is the small proportion of the
pound occurs. This compoundhas been vari
chlorinating time during‘ which the neutral com
ously termed “monobasic,” "two thirds basic,”
pound is being crystallized. If the slurry formed
etc. However, I have found the composition of
this compound ~to be in accordancev with the 35 by chlorinating the milk of lime until the lime
has been substantially converted to the dibasic
formula, 2Ca(OCl)z.Ca(0H)2. This hemibasic
compound is cooled to 15 to 25° C., and further
compound forms in pointed lath-like crystals and
‘chlorinated to form the neutral compound, so
these interfere with the growth 0! crystals oi the
lution of the‘ di-basic compound takes place'ior a
neutral calcium hypochlorite, Ca(OCl)2.2(H2O>),
40
considerable period. For a brief interval the so- .
upon iurther chlorination.
lution then becomes saturated, and subsequently
m some operations the chlorination is stopped
supersaturated with rapect to the neutral com
while the solids present in the slurry are pre
pound, and spontaneous crystallization of many
dominantly the hemibasic compound which has
?ne crystals will occur unless a large amount oi’
been found to be generallymore ?lterable than
having advantageous ?lterability characteristics.
the neutral compound resulting from further 46 neutral hypochlorite seed crystals is present.
Then follows a period during which growth of
chlorination oi the hemibasic slurry. By other
the crystals of the neutral compound'takes place.
procedures the partly chlorinated slurry in which
the solids present are predominantly the dibasic , This period is but a small portionwoi the entire
compound, is cooled to 15 to 25° C. and the
chlorination period. For example, ‘it the milk of
chlorination continued toward completion. While so lime slurry is made up or 1 part ‘lime to 2.6 parts
a slurry of the neutral compound may be ob- ‘
tamed by this latter procedure, the neutral com
water, less than one-?fth oi the chlorine will be
I added during the period of growth of the neutral
compound crystals. Consequently, the neutral
crystals do not have su?lcientv timet'o grow.
talc and the slurry thereofv is diincult to ?lter.
One reason tor the small size 01' the crystals, “ Poorly'?lterable slurries are objectionable be
pound thus produced is in the form of ?ne crys- ~
2
2,388,042
cause they formcakes containing large amounts
of mother liquor. This mother liquor is rich in
calcium chloride. Because of its hygroscopic
properties, calcium chloride resists drying and
causes considerable loss of hypochlorite by de->
the dibasic slurry used should not exceed 47'
Twaddell and‘ preferably should be between 40
and 44° Twaddell. The free lime content of the
composite slurry is advantageously maintained at
a value below 1.5%, byv weight, throughout its
composition during the drying operation. When
' chlorination.
the milk of lime is chlorinated, equimolecular
portions of calcium chloride and calcium hypo
l the calcium hydroxide present in the dibasic slur
In this chlorination, the chlorine reacts with
chlorite are formed in the solution. One-half or
ry as indicated by the equation
more of the calcium hypochlorite formed is usu 10
ally precipitated as the neutral compound while
Ca( 001) z.2Ca( OH) =+2Clz—>2Ca(OCi) z+CaCh
all of the calcium chloride stays in solution. The ' In other words, two moles of chlorine are required
amount of calcium chloride remaining in the cake
to react with each mole of the dibasic hypochlo
decreases as ?lterability increases.
rite. one mole of chlorine being required to react
To reduce the calcium chloride content, it has
with each mole of Ca(OH):, to form the neutral
been proposed to prepare crystals of the dibasic
calcium hypochlorite. Reference herein and in
compound and to separate these as by centrifug
the appended claims to equivalent quantities of
ing or ?ltration. The separated crystals of the
chlorine and dibasic hypochlorite slurry will be
dibasic compound may then be suspended in wa
understood to have reference to this reaction. I
ter and the chlorination continued until neutral 20
The process of the present invention has the
calcium hypochlorite is formed. By this sepa
distinct advantage of being adapted to continu
ration of the dibasic compound crystals from
ous operation. For example, a supply of the di
the mother liquor in which they are formed, a
basic slurry may be maintained and a portion of
considerable proportion of the calcium chloride
this slurry constantly supplied to and admixed
is vremoved and therefore the ?nal slurry of neu 25 with the neutral slurry with simultaneous chlori
tral calcium hypochlorite contains a smaller pro
nation. However, if desired, the addition of the
portion of calcium chloride. Consequently, for
dibasic slurry to the neutral slurry may be in
the same size of crystals and equal ?lterability,
termittent.
the amount of calcium chloride in the ?ltercake
In the continuous operation of this process a
will be less so that drying thereof is simplified. 30 quantity of the neutral slurry is maintained in
It has also been claimed that larger crystals of
the mixing and chlorinating chamber. In the
the neutral compound can be crystallized from ,
batch type of operation a quantity of the neutral
solutions of lower calcium chloride content than
slurry from a previous run may be used. For ex
would be obtained by ordinary chlorination.
ample, a portion of the neutral slurry from a
Separation and resuspension of the dibasic com 35 previous run may be allowedto remain in the
pound crystals are, however, objectionable as a
mixing and chlorinating chamber for use in start
plant procedure because of the greatly increased
ing the following run. In either type of opera
tank capacity required and because of the in
tion the neutral slurry for the initial run may
creased losses of calcium hypochlorite in the ?l
be prepared in a conventional manner, for in
trates. Also, the ?ltrate resulting from ?ltra
stance by the chlorination of a lime slurry or of
tion of the neutral compound slurry is higher in
a slurry of the dibasic compound, advantageously
calcium hypochlorite content than that obtained
to a point where its free lime content is below
by ordinary chlorination. To make such opera
1.5% by weight and usually about 0.5% by weight.
tion economical, it is necessary to treat this ?l
depending upon the operating conditions to be
trate with lime to effect the recovery of basic 45 employed.
'
hypochlorite therefrom which can be ?ltered oil!
The dibasic compound slurry used in accord
and returned to the process. If this recovery step
' ance with the present invention may be prepared,
is practiced with both the ordinary and with the
for instance, by chlorinating a milk of lime slurry
basic compound separation and resuspension type
until the clear liquor, on separation from the slur
of chlorination, the loss of calcium hypochlorite 51 ry, shows the desired gravity. It is not neces
is greater in the latter-case due to the larger
sary to ?lter or centrifuge the dibasic compound
volume of ?ltrate from the recovered basic hypo
~ and resuspend it, as has been previously sug
chlorites. Further, since water enters the second
gested, though such procedure may be followed if
stage of such chlorination processes with the
desired. Likewise, a portion of the mother liquor
separated dibasic compound, less water may be 55 from the dibasic slurry may be removed by set
added' to the lime in preparing the initial milk.
tling and drawing of! part of the clear super
of lime slurry, if an excessive amount of ?ltrate is
natant' liquor at a favorable stage in the chlori
' to be avoided, and this would necessitate the
nation. Such variations may be advantageous.
handling of objectionably thick milk of lime
particularly if the ?ltrate from the neutral com-.
slurries.
Oil pound is treated with lime to recover basic hypo
In accordance with my improved process, slur
chlorite compounds which are addedto the milk
ries of neutral calcium hypochlorite of excellent
of lime slurry prior to or during its chlorination,
?lterability may be prepared while avoiding the
so as to avoid the accumulation of calcium chlo
above-mentioned di?iculties of the previously pro
ride in the system.
posed methods.
One satisfactory method of preparing the di
'05
Brie?y, I have discovered that slurries of neu
basic compound slurry is as follows: A milk of
tral calcium hypochlorite crystals of excellent
lime slurry is chlorinated until substantially all
?lterability may be prepared by adding, prefer
the calcium hydroxide has been converted to the
ably at a uniform rate, a slurry of dibasic calcium
dibasic compound. At this point, if desired, the
hypochlorite to a previously prepared slurry of 70 chlorination may be stopped, the slurry settled
neutral calcium hypochlorite with simultaneous
and a portion of the supernatant liquid discard
chlorination by injecting chlorine into the com
posite slurry at a rate approximately equivalent,
chemically, to the rate at which the disbasic slurs
ry is added. The gravity of the liquid phase of
ed. The remaining 'slurry is then chlorinated
until the ‘clear liquor on separation .from the
slurry shows a gravity of 40 to 44' Twaddell. The
chlorination of the milk of lime may be started
2,388,042
at ordinary room temperature and the tempera
ture allowed to rise to 35 to 45° C. and held there
during continued chlorination until the .clear
liquor separated from the slurry reaches the de
sired gravity.
My present invention is not dependent upon the
use of any particular method of preparing the di
3
in the size or shape of the crystals of the dibasic
compound. Likewise, I have found‘ that the slurry
of neutral calcium hypochlorite may be stored
without alteration providing the free lime content
is not over 0.5%. For short periods such as one
hour, the neutral slurry having higher lime con
tents, for instance up to 1%, may be stored with.
out change, and for still shorter periods the lime
basic slurry used in accordance therewith. How
content may be up to 1.5%. Slurries of the di
ever, best results have been obtained where the
crystals of the dibaslc slurry were relatively larg 10 basic compound, the solutions of which are of
more than 47° Tw. gravity, should not be stored,
and ‘well formed.
‘
as they may alter, the dibasic compound changing
In experimental runs I have found it possible
into the hemibasic compound. Similarly, a slurry
and advantageous to continue the chlorination
of the neutral compound containing more than
of the dibasic slurry until the clear liquor sepa
rated from the slurry-shows a gravity of 47° Twad 15 1.5% freelime should not be stored at any tem
perature, as fine crystals of the hemibasic com
dell. As precipitation of the hemibasic compound
pound may form and seriously impair the ?lter
may occur at slightly higher gravities, We pre
ability. These ?ne crystals could be partly re
fer to stop the chlorination at 44° Tw. or pref
moved by slow, careful chlorination of the mixed
erably to proceed to this point, stop the chlorina
tion and continue stirring for a short period. The 20 slurry but the ?nal slurry of the neutral com
pound would be less ?lterable than one formed
gravity of the liquid 7 phase will fall slightly as
without such storage period.
equilibrium with respect to the dibasic compound
By reason of the fact that these slurries of suit
is established. If the gravity should fall below
able gravity and free lime content may be stored
40° Tw., for instance, the slurry‘ may be further
chlorinated to bring the gravity above 40° Tw.
25 without change in the size or character of their
In preparing the neutral hypochlorite slurry ~ solid constituents, a supply of the dibasic slurry
may be maintained for the operation of the proc
in accordance with my present method, the pres
ess and interruption of the process by failure of
vlously prepared dibasic slurry is passed, pref-_
the chlorine supply or of the pumps or cooling
erably at a constant rate, into a chamber or tank
equipmentdoes not result in poorer ?lterability of
partly ?lled with a previously prepared slurry of
the ?nal neutral slurry. Partly chlorinated milk
neutral calcium hypochlorite, the free lime con
of lime slurries, the solution phase of which has a
tent of which is advantageously less than 1.5%
gravity of less than 30° Tw., should not be stored,
and preferably about 0.5% by weight. Simul
due to the formation of undesirable basic com
taneously, chlorine is added to the slurry in the
pounds which become serious at temperatures be
mixing and chlorinating chamber, which for con
_ low about 23° C. and may result in complete block
venience is herein sometimes referred to as the
age of tanks and lines.
composite slurry, at a rate dependent upon the
In accordance with my invention, I have found
composition of the dibasic slurry and the rate at
it particularly advantageous to use dibasic slur
which the dlbasic slurry isiadded, and such that
the alkalinity of the composite slurry is main
tained substantially constant. During the chlori
' nation and addition of the dibasic slurry. the com
posite slurry is cooled and preferably kept at a
. temperature between 15 and 20° C. A tempera
ture as high as 25° C. may be maintained provid
ries which consist of crystals of the dibasic com- _
pound and liquid solutions of 40 to 47° Tw. gravity.
However, my improved process has been suc
cessfully operated using dibasic slurries, the grav
ity of the liquid solution of which was as low as
34-“ Tw. The use of such low gravity slurries in
troduces difficulties and ordinarily the slurry of
the neutral compound obtained by their use is not
as ?lterable as that obtained by use of dibasic
tendency of the slurry to foam and foaming in
slurries having a liquid phase of 40° to 47° Tw.
terferes with the circulation and hence the growth
of the crystals of the neutral compound. Simi 50 gravity. Dibasic slurries, the liquid phase of
which has gravities as lowas 30° Tw., may be
larly, I have found that temperatures as low as
used with advantage but the ,dibasic crystals pres
10° C. may be employed but that at lower tem
ent in dibasic slurries, having a liquid phase of
peratures the solution tends to become super
35° Tw. gravity or less, have sharp edges which
saturated to an undesirable degree with the neu
tral compound so that unsatisfactory slurries may 55 may provide nuclei for undesirable small crystals
or the neutral compound during the subsequent
result unless the rate of chlorination is quite slow.
chlorination. When the liquid phase of the di
In the‘ batch-type of operation, when the mixe
basic slurry has a gravity of 40° to 47° ‘Tw., and
ing and chlorinating chamber is substantially
particularly if the gravity is above 44° Tw., these
filled, the addition of the dibasic slurry.is dis;
edges have been dulled by solution of part of the
continued and the neutral slurry therein may-be
dibasic crystals during the chlorination required
further chlorinated, for instance, to a lime con
to attain such gravity.
tent of 0.1 to 0.2%, at which point a portion of
There is a further advantage in employing
the neutral slurry may be transferred to storage,
slurries of the dibasic-compound, the liquid phase
leaving in the chamber sumcient neutral slurry
for the resumption of the operation. The opera 85 of which is of 40° to 47° Tw. gravity. This is the
advantage of easier mixing of such dibasic slur
tion is resumed by the addition of further dibasic
ries with the neutral slurry and a more uniform
slurry with simultaneous chlorination, as just
concentration in the mixing and chlorinating
described, until the chamber is again ?lled or un
chamber. Precipitation of the neutral compound 7
til the desired quantity of neutral slurry has been
prepared.
'
70 may be effected, for example, from solutions of
50 to 55° Tw. gravity. The addition of a dibaslc
1 have found that a dibasic slurry, the clear
slurry having a gravity of 80 to 35° Tw. to such
liquid of which upon separation from the slurry
neutral slurry may cause serious dilution locally,
has a gravity of 40 to 47° Tw., may be stored at
ordinary temperatures without formation of un
so that the concentration of dissolved ‘salts may
desirable basic compounds or appreciable change 75 vary seriously throughout the mixing and chlori
ing the alkalinity is kept above 0.5% but such
higher temperatures are inadvisable as there is a
4
escapes
nating chamber. By the addition of a dibasic
slurry of 40 to 44° Tw. gravity, this dilution prob‘
_to be advantageous for commercial operation;
With this throughput the capacity of the system
lem is lessened to a point where it is no longer
troublesome. The dilution problem is more di?i
cult because of the fact that crystals of the neu
tral compound are relatively thin and fragile and
~ per unit of tank volume is considerably in excess
suflicient to maintain the gravity of the liquid
prepared neutral calcium hypochlorite slurry hav
ing a calcium hydroxide content of approximately
0.1% by weight. The free lime content of the
neutral slurry was allowed vto increase to 0.5%
of that obtainable with processes which involve
the separation of the dibasic compound and its
resuspension in water. This is an important ad
violent stirring cannot be employed during their
vantage of my improved process, particularly so
precipitation as such stirring would tend to break
since all equipment must be constructed of cor
the crystals into small fragmentsand seriously
rosive-resistant material and is consequently
reduce the ?lterability of the ?nal neutral slurry. 10 quite expensive.
Vigorous stirring would also tend to introduce
The following speci?c example is given as a de
foam into the slurry which would seriously im
tailed illustration of the improved process of my
pair the ?lterability.
.
present invention as applied to the discontinuous
or batch-type of operation. 3500 pounds of lime
Instead of preparing the dibasic slurry in ad
vance and storing it for subsequent use, the prep
of 95% Ca(OH)z content and 8900 pounds of
aration oi the dibasic slurry, and its subsequent
water were made into a milk of lime slurry and
use in preparing the neutral slurry, may with
charged to a 1500 gallon tank equipped with a
slow speed turbine type agitator. 2230 pounds of
advantage be combined in a unitary continuous
operation. For example, I have found that such
chlorine was added, the temperature being al
continuous operation may advantageously be car 20 lowed to rise to 37° C. and held thereby circu
lating cooling water through coils located within
ried on in four tanks constructed of corrosion
resistant materials. Milk of lime and chlorine
the tank. When all the chlorine had been added,
are fed continuously to the ?rst tank, the amount ‘ the solution was stirred for ten minutes and the
of chlorine being sufficient to maintain the grav
clear liquor was found to have a gravity of 44° Tw.
ity of the solution therein between 22 and 26° Tw.
This dibasic slurry was then pumped at the rate
The slurry from this tank, which is normally
of 8 gallons per minute into a mixing and chlo
fairly thin, then ?ows or is pumped to the second
rinating tank also having a capacity of 1500 gal
tank to which chlorine is also admitted at a rate
ions and which was half-?lled with previously
phase of the dibasic slurry at 40 to 47° Tw. In -
the ?rst tank the temperature is allowed to rise
to about 30' to 40° C., and in the second tank it is
preferably held between 35 and 40° C. by suitable
cooling. The division of this chlorinating opera
tion into two stages tends to equalize the chlori
and at this point the introduction of chlorine into
the tank was started at a rate equal to approxi
mately. 300 pounds per hour. The chlorine was
natlng load and to facilitate proper temperature
added in the liquid form, being passed through
a rotormeter tube calibrated at 50 to 1500 pounds
per hour and then through a needle valve into the
slurry. The rate at which the chlorine was added
ing the neutral slurry previously described, 40 was adjusted so as to hold the free lime content
of the slurry at 0.5%.
I
wherein it is chlorinated at a rate sufficient to
keep the free lime content of the composite slurry
At the end of 90 minutes half of the dibasl-c
control.
v
.
The dibasic slurry from said second tank may‘
be passed continuously to the third tank contain
under 1.5% and preferably between 0.5 and 1.0%
by weight. The neutral slurry may be passed
continuously from the third tank to the ?nal tank
to which a slow stream of chlorine is admitted
which reduces the remaining lime to the desired
residual which may be from, say, 0.05 to 0.25%
by weight.
slurry and 450 pounds of chlorine had been added.
‘ At this point addition of the dibosic slurry was
stopped and the addition of chlorine continued
for about 10 minutes at a slightly reduced rate so
as to reduce the alkalinity of the resultant neutrtl
slurry to 0.1%, expressed as calcium hydroxide.
v‘720 gallons of the resulting neutral slurry were
In the third tank the temperature is advan 50 then discharged to storage and the cycle repeated,
tageously kept between 15 and 25° C., and prefer
converting the remaining 720 gallons of dlbasic
ably between 15 and 18° C., by suitable cooling.
slurry to neutral slurry. The temperature of the
The temperature maintained in the ?nal tank
neutral slurry was maintained between 15 and 17°
will depend upon the intendeddisposition of the
C. during addition of the chlorine by circulatin¢
low alkalinity neutral slurry therein. If this 55 brine through cooling coils positioned therein.
slurry is to be used promptly, as by continuous \ The resulting slurry of the neutral compound was
?ltration or centrifuging,‘ the temperature may i found to be of good ?lterability.
with advantage be from 15 to 25° C. If, however,
The following is a specific illustration of my
the slurry from this fourth tank is to be stored
improved method of preparing slurries of neutral
for an extended period of time, it should be cooled 80 calcium hypochlorite as applied to the continuous
type of operation. A dlbasic slurry, the liquid
While the above-mentioned temperatures have
phaseof which had a gravity of 43 to 44° Tw.,
been found. particularly suitable for this type of
prepared by chlorinating a slurry of 3500 pounds
‘operation of my improved process, other tempera
of lime of 95% Ca.(OH)z content and 8900 pounds'
tures may be used. However, the use of tempera 66 of water, as previously described, was charged at
tures other than those within the speci?ed range
the rate of 8 gallons per minute into a mixing and
- down, for instance, to 0° C. prior to storage.
' is apt to lead to reduced capacity of the opera
tion and to poorer fllterability of the ?nal slurry .
chlorinatlng tank of 1500 gallons capacity half
?lled with a previously prepared slurry of neutral
calcium hypochlorite having a‘ lime content of.
In continuous operation such- as described 70 0.5% to 1.0% by weight. Simultaneously there
above, the throughput may be varied widely ac
with chlorine was added at the rate of approxi
cording to the chlorine supply available and the
mately 300 pounds per hour. The temperature of
desired .?lterability of the ?nal slurry. A
the neutral slurry was held down to 15 to 17° C.,
throughput of one-half of one per cent of the
by circulating refrigerated brine through cooling
volume of each tank per minute has been found 76 coils submerged therein. Samples of the neutral
' of neutral compound.
9,368,042
slurry were taken from time to time and tested
for free lime content and the rate of chlorine ad- '
5 .
Twaddell and simultaneously chlorinating the
composite slurry by adding chlorine thereto at
dition adjusted to keep the lime content of the
neutral slurry between 0.5% and 1.0%. It was
, a rate such‘as to maintain the free lime content
found that the alkalinity could be kept within this
5. A continuous process for the production of
readily filterable slurries of neutral calcium hypo
chlorite crystals comprising adding to a previ
ously prepared slurry of neutral calcium hypo
range with infrequent adjustment of the chlorine
?ow, for instance one adjustment per hour.
of the composite slurry substantially constant.
As the operation continued, the neutral slurry
chlorite at a uniform rate a slurry of dibasic
was permitted to over?ow from the mixing and
chlorinating tank into a second tank. Gaseous 10 calcium hypochlorite, the liquid phase of the lat
,ter having a gravity within the range of 30° to 47°
chlorine under approximately 20 pounds pressure
was supplied to this second tank at an average
rate of about 20 pounds per hour to complete the
chlorination of the neutral slurry, the lime con
tent being reduced to approximately 0.1% by
weight. In this second tank the slurry was cooled
to 0°-+5° C. and from this tank the ?nal slurry
was drawn o? to storage.
Twaddell, while chlorinating the composite slurry
by passing chlorine thereto at a rate substantially
equivalent, chemically, to that at which the di
basic calcium hypochlorite slurry is added so as
to maintain substantially constant the free
, C8.(OH)2 content of the composite slurry.
6. A continuous process for the production of
readily ?lterable slurries of neutral calcium hypo
as above described, over a period of 10 hours a 20 chlorite crystals comprising maintaining a quan
tity of neutral calcium hypochlorite slurry in a
portion of the ?nal slurry was withdrawn from
mixing and chlorinating chamber, continuously
storage and was found to be of good ?lterability.
passing thereto a slurry of dibasic calcium hypo
A portion thereof was ?ltered through a rotary
chlorite, the liquid phase of the latter having a
vacuum ?lter and without using the water spray
the resultant cake had the following analysis:
25 gravity within the range of 30° to 47° Twaddell,
while chlorinating the composite slurry by con
Per cent
tinuously passing chlorine thereto at a rate sub
After the continuous operation of this process,
Ca<OCDz _____________________________ __-_ 53.6
stantially equivalent, chemically, to that at
_________ __ _____________________ __
1.0
which the dibasic calcium hypochlorite slurry is
Ca(Ol-I)2 ______________________________ __
0.4
added, continuously withdrawing neutral calcium
CaCl-z _________________________________ .._
7.0
CaCOa
hypochlorite slurry from the chlorinating and
mixing chamber to a second chamber and fur
ther chlorinating the withdrawn‘ neutral slurry.
By using alight spray of wash water during the
in the said second chamber.
?ltration the calcium chlorine content of the cake
7. A process for the production of readily ?l
was reduced to 3-496.
35
I claim:
terable slurries of neutral calcium hypochlorite
crystals which comprises simultaneously adding
1. A process for the production of readily ill
to a previously prepared slurry of neutral calcium
terable slurries of neutral calcium hypochlorite
crystals comprising adding to a previously preé
hypochlorite chlorine and a slurry of dibasic cal
pared slurry of neutral calcium hypochlorite a 40 cium hypochlorite, the liquid phase of the latter
slurry of dibasic calcium hypochlorite,'the liquid
having a gravity within the range of 30° to 47°
phase of the latter having a gravity within the
Twaddell, the chlorine being added at a rate sub
stantially equivalent, chemically, to the rate at
range or‘ 30° to d7“ Twaddell, while chlorinat
ing the composite slurry at a rate such as to
which the slurry of dibasic calcium hypochlorite
Water __________________________________ __ 38.0
maintain the free lime content thereof below
1.5% by weight.
is added.
8. A process for the production of readily fil
2. A process for the production of readily ?l
terable slurries of neutral calcium hypochlorite
crystals comprising adding to a previously pre~
terable slurries of neutral calcium hypochlorite
crystals which comprises simultaneously adding
to a previously prepared slurry of neutral cal
. pared slurry of neutral calcium hypochlorite a 50 cium hypochlorite chlorine and a slurry of dibasic
slurry of dibasic calcium hypochlorite prepared
calcium hypochlorite, the liquid phase of the la‘
by chlorinating milk of lime and composed of a
ter having. a gravity within the range of 40° to
solid phase consisting essentially of dibasic cal
47° Twaddell, the chlorine being added at a rate
cium hypochlorite and a liquid phase having a
substantially equivalent, chemically, to the rate
gravity within the range of 30° to 47° Twaddell, - at which the slurry of dibasic calcium hypo
while chlorinating the composite slurry at a rate
chlorite is added.
such as to maintain the free lime content thereof
9. A process for the production of readily ?l
below 1.5% by-weight.
terable slurries of neutral calcium hypochlorite
3. A process for the production of readily ill
crystals which comprises simultaneously adding
terable slurries of neutral calcium hypochlorite 60 to a previously prepared slurry of neutral cal—
crystals comprising admixing with a slurry of
cium hypochlorite chlorine and a slurry of di
neutral calcium hypochlorite a slurry of dibasic
basic calcium hypochlorite, the liquid phase of
calcium hypochlorite, the liquid phase of which
the latter having a gravity within the range of
has a gravity within the range of 30° to d7°
30° to 47° Twaddell, the chlorine being added at
Twaddell and simultaneously chlorinating the 65 a rate substantially equivalent, chemically, to the
composite slurry by adding chlorine thereto at a
rate at which the slurry of dibasic calcium hypo
rate such as to maintain the free lime content
chlorite is added, and maintainingv the com
of the composite slurry substantially constant.
posite slurry at a temperature of between about
4. A process for the production of readily fil
10° to 25° C. while the chlorine and slurry of di
terable slurries of neutral calcium hypochlorite 70 basic calcium hypochlorite are being added
crystals comprising admixing with a slurry of
thereto.
neutral calcium hypochlorite having a free lime
10. A process for the production of readily ?l
terable slurries or’ neutral calcium hypochlorite
crystals which comprises simultaneously adding
has a gravity within the range of 30 to 47° 75 to a previously prepared slurry of neutral cal
content below 1.5%, by weight, a slurry of dibasic '
calcium hypochlorite, the liquid'phase of which
6
ohm hypcchlorite chlorine and a slurry of di
cium hypochlorite chlorine and a slurry oi’ dibasic
basic calcium hypochlorite prepared by chlorinat
ing milk of lime and composed of a solid phase
consisting essentially of dibasic calcium hypo
calcium hypochlorite, the liquid phase of the lat
chlorite and a liquid phase having a gravity with
in the range of 30° to 47° Twaddell, the chlorine
being added at a rate substantially equivalent,
substantially equivalent, chemically, to the rate
ter having a gravity within the range of 30' to
47° Twaddell, the chlorine being added at a rate
at which the slurry of dibaslc calcium hypo
chlorite is added, and thereafter discontinuing
ehemicall , to the rate to which the slurry of
the addition of the slurry of dlbasic calcium hy
dibasic calcium hypochlorite is added.
pochlorite while continuing the chlorination fur
"11. it process for the production of readily ?l 10 ther to reduce the calcium Mdroxide content of
terable siurries of neutral calcium hypochlorite
the resultant neutral slurry
crystals which comprises simultaneously adding
to a previously prepared slurry of neutral cal
LUEJZEE ROBSON.
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