Field of the Invention:
The present invention relates to an in situ process for preparing near micron size particles of
alkaline earth metal carbonate.
Background of the Invention:
For the industrial production of barium carbonate, the barium sulfide is pumped to barium
carbonate generation towers in which carbon dioxide is bubbled through the barium sulfide
solution to precipitate insoluble barium carbonate.
BaS + C02 + H20 • BaC03 + H2S (1)
The carbon-dioxide gas may be supplied in pure form or may be obtained from the combustion
gases of barium sulfide reduction kilns.
Barium carbonate is also manufactured by the reaction of barium-sulphide solution with sodium
carbonate, either dissolved or in solid form (soda ash method).
BaS + Na2C03 • BaC03 + Na2S (2)
The usual operating temperature is 60-70 °C. The resulting slurry is filtered and the barium
carbonate is washed, dried, ground, and packaged.
The choice between the carbon dioxide method and the soda ash method depends on the end
use of barium carbonate. In the first method, the C02 is available from smoke stacks of
furnaces. The method produces free flowing barium carbonate. The second method requires
large investment due to the cost of separation of Na2S from BaC03. It produces barium
carbonate with low sulphur content.
Some of the very important uses of barium carbonate are listed below.
• As a raw material for production of other barium compounds
• Glass industry
• Manufacturing brick and clay products
• Production of photographic papers
• Oil-well drilling industry
Several attempts have been made to prepare small sized particles of the alkaline earth metal
carbonates.
JP2004059372 is directed to the method of manufacturing fine particle barium carbonate and
method of manufacturing barium titanate. Said method of manufacturing fine particle barium
carbonate is performed by bringing a soluble barium salt-containing solution, carbon dioxide or
a soluble carbonate-containing solution, and a granular medium into contact with each other
and while fluidizing the granular medium at high speed. The method of manufacturing the fine
particle barium carbonate is performed by fluidizing the mixture of barium carbonate slurry and
the granular medium while fluidizing the granular medium at high speed.
%
CN1152548 is directed to preparation process for barium carbonate used in electronic
ceramic. Said invention mainly uses the refined barium chloride and sodium carbonate as raw
material, and respectively makes them into the saturated solutions, then the saturated solutions
are mixed and reacted under the condition of a certain temperature, and then the obtained
reaction product is washed and dried so as to obtain the invented product. Said invention is
simple in process, low in cost and high in yield, and its particle size is uniform, generally is 0.8-
1.0 micron.
GB1132767 teaches production of barium carbonate particles rod-shaped particles of barium
carbonate are prepared by reacting barium sulphide solution with carbon dioxide for a time
sufficient to precipitate up to 50% of the soluble barium values as barium carbonate seed
crystals. Seed crystals are first formed when a barium sulphide solution at a temperature below
40 oC is contacted for less than 60 seconds (preferably 0.01 to 10 seconds) with C02. This
solution is then continuously carbonated for several hours with more C02 until nearly all the
barium values have been precipitated and Na2C03 is then added to complete the precipitation
at pH 6.
JP7025611 is directed to fine barium carbonate and production thereof. A soluble barium salt
is reacted with a soluble carbonate salt or C02 to produce BaC03. Therein, the reaction is
performed in a state in which the soluble barium salt is excessive. The carboxylic acid is added
to the reaction system at any time in a period ranging from the time before the reaction to the
time after the reaction. The added carboxylic acid is reacted with the excessive barium salt in
the reaction to form a barium salt. The formed barium salt reacts with the carbonate salt or
C02, and the produced product deposits on the surface of the BaC03 to prevent the abnormal
growth of the particles.
US2006035266 is directed to particle size variable reactor. Said reactor comprises a granular
substrate and a capturing unit fixed onto the surface of the granular substrate. The capturing
unit comprises a rod-shaped body having a length of 810 nm or less, a configuration variable
element which may be structurally transformed when stimulation is applied, and a capturing
structured body which specifically captures an object to be captured. The particle size variable
reactor is highly biodegradable and environmentally friendly, and can specifically act on and
thus selectively capture its target alone. The reactor may preferably be used in various fields
including medical and industrial fields.
CA2292862 and US2001006611 are directed to modular reactor system allowing control of
particle size during chemical precipitation. The reactor assembly comprising a substantially
elongate tubular housing, at least one reactant inlet, at least one reaction mixture outlet
disposed above the at least one reactant inlet, and agitator disposed in a region near the at
least one reactant inlet and a perforated member disposed in tubular housing between the
agitator and the reaction mixture outlet.
CN1301590 is directed to the method and equipment for synthesizing nanometer particle by
film reactor. Separating film is utilized for constituting the film reactor. The liquid or gaseous
reactants are on two sides of the film separately. By utilizing the pressure difference and/or
concentration difference, the reactant on one side may produce reaction with the reactant on
the other side to nanometer particle homogeneously in small amount via micro-pores in the
3
film. The method and equipment of the present invention may be used in preparing nanometer
particle as well as micron level or submicron level particles.
CN1380255 is directed to the method and equipment for preparing basic carbonate nanoparticle
by means of spray pyrolysis of ammonia complex liquor. The present invention utilizes
amino-complex liquor and hot air and special-purpose complete set of equipment, and adopting
a series of suitable technological processes and method, to prepare basic carbonate nanoparticles.
Its special-purpose equipment is formed from centrifugal spray dryer and cyclone
separator. The complete set of equipment can integrate several processes of mixing, reaction,
drying and separation into one step, so that it's technological process is short and its product
quality is raised.
CN1344679 is directed to direct carbon dioxide precipitation process of strontium carbonate or
barium carbonate from neutral strontium or barium salt solution. Said invention utilizes C02 to
deposit strontium carbonate or barium carbonate directly from neutral strontium and barium
chloride, strontium and barium nitrate or other strontium and barium salt solution obtained by
decomposing celestite, strontianite, barite or witherite. In the same time, extracting process is
used to extract produced hydrochloric acid, nitric acid or other acid from water solution to
organic phase so as to complete the reaction. The present invention can reduce the
consumption of chemical material ammonium bicarbonate and ammonium nitrate, eliminate the
need of distilling ammonium carbonate, and results in lowered consumption and raised
economic efficiency.
Fabien Salvatoria ef a/in "Determination of nucleation and crystal growth kinetics of
barium carbonate"; Powder technology 128 (2002) 114-123 provides a compact
apparatus of specific construction is used for nucleation measurements in accordance with
Nielsen's method. Experiments are realized by varying the super-saturation ratio from 35 to 280
and temperature from 10 to 50°C. Barium carbonate is precipitated by mixing equal volumes of
sodium carbonate and barium hydroxide solutions. The experimental data have shown that the
nucleation rate of barium carbonate in the super-saturation range cited above is characterized
by the primary heterogeneous mechanism. An original method, using a high seed charge in a
batch crystallizer, is developed for the determination of crystal growth kinetics in a large range
of super-saturation variation.
Clifford Y. Tai et al in "Synthesis of submicron barium carbonate using a highgravity
technique"; Chemical Engineering Science 61 (2006), 7479-7486 teaches the
purpose of this study was to build a platform for producing fine particles by applying a highgravity
(higee) technique to achieve reactive precipitation. Barium carbonate was chosen as a
model compound and was produced in a spinning disk reactor (SDR), which is one type of higee
equipment, via a carbonation route and a once-through mode. For size measurement, a suitable
dispersion method was developed to obtain reproducible particle size data, using a laser-light
analyzer. Several factors that affected the particle size of barium carbonate, including the C02
flow rate, the feed rate of Ba(OH)2 slurry, the rotation speed, and the solid-content of feed
slurry, were investigated. A high rotating speed and low feeding rate of slurry yielded small
particles. The optimum solid-content of feeding slurry for obtaining small particles was also
determined. However, the effect of the C02 flow rate on the particle size of the product was
not significant.
«i
Noriaki Kubota et a/in "Precipitation of BaC03 in a semi-batch reactor with doubletube
gas injection nozzle"; Journal of Crystal Growth 102 (1990) 434-440, teaches
BaC03 crystals produced in a semi-batch reactor adding C02 gas continuously to the agitated
BaS aqueous solution through a double-tube gas injection nozzle. Larger crystals were obtained
in comparison with the case where the gas was directly dispersed in the whole reactor as
usually done. The gas bubbles, around which the higher supersaturation regions are thought to
be localized, were made to contact only with the solution inside the outer tube of the nozzle.
The gas was absorbed there and the adsorbed gas was transferred into the agitated bulk
solution through the lower opening of the nozzle and then it reacted with Ba2+ ions in the bulk
solution. The larger crystals were thought to be obtained because of lower nucleation rate
caused by the limited bubbling region. In addition, the lower pH of the solution in the nozzle
was thought to help in lowering the nucleation rate.
Ivan Sondi et al in "Homogeneous precipitation by enzyme-catalyzed reactions
Strontium and barium carbonates"; Chemistry of Materials 15 (2003) 1322-1326
teaches catalytic decomposition of urea by an enzyme in aqueous strontium and barium
chloride solutions was used to rapidly precipitate witherite (BaC03) and strontianite (SrC03)
particles at room temperature. At the early stages of the process, uniform spheroidal particles
were generated, which were shown to consist of nanosized subunits. On continuous aging of
the same systems the additionally precipitated alkali earth carbonates grow as whiskers onto
original core particles, which eventually fully transform into crystalline rod-like clusters.
H. Yagi et al in "Semibatch precipitation accompanying gas-liquid reaction";
Chemical Engineering Communications 65 (1988) 109-119 utilized a carbonation route
for preparing BaC03 in a batch precipitator under a controlled pH. The obtained BaC03 appeared
in the form of floes with sizes ranging from 10 to 30 urn.
Pao-chi Chen et aim "Nucleation and morphology of barium carbonate crystals in a
semi-batch crystallizer"; Journal of Crystal Growth 226 (2001) 458-472 provided a
double-jet feed, semi-batch crystallization system was used to explore the nucleation kinetics,
growth kinetics, and morphology of barium carbonate crystals under a constant pH value. The
results showed that the pH and initial concentration of the solution play an important role on
the morphology of barium carbonate crystals. The crystal forms are floe, candy-like, olivary with
end dendrite, olivary-like and needle-like, depending on the operating conditions. At high to
moderate concentrations the floe precipitates are the major products in the pH range of 9.0-
10.0. At moderate to low concentrations the candy-like and olivary with end dendrite crystals
become the major products. At low concentrations and low pH values the crystal forms are
olivary-like and needle-like precipitates.
Thus, none of the prior art process, provides barium carbonate in near micron size. Thus there
is an urgent need to develop a process for preparing solid particles of barium carbonate in near
micron size.
Object of the Invention:
Thus, in order to obviate the drawbacks of the prior art, the object present invention provides
cited prior art and its drawback of present invention is to develop one step process for the
production of near-micron size solid particles of alkaline earth metal carbonates.
r
It is still another object of the present invention to provide a foam bed reactor for preparing
alkaline earth metal carbonate.
Yet another object of the present invention is to provide a cost effective process for preparing
near micron size particles.
Summary of the Invention:
In order to achieve the aforesaid objectives, present invention provides an in situ process for
preparing near micron size alkaline earth metal carbonate particles comprising:
• preparing alkaline earth metal sulphide reactant solution by leaching said compound
with distilled water and thereby adding surfactant to the clear solution,
• introducing said reactant mixture in the foam bed reactor with the gas mixture,
• treating the known volume of said reactant solution with the gas mixture in foam bed
reactor,
• said gas mixture is optionally dehydrated before introducing it in the foam bed reactor,
• removing the slurry from the reactor and decanting the same to obtain near micron size
barium carbonate particles.
The present invention further provides a foam bed reactor for preparing alkaline earth metal
carbonate , wherein the reactor comprises of:
• a glass column, having plurality of tappings at various heights of said column to
measure the liquid hold up in the foam,;
• a distributor plate assembly placed between the cylindrical part and conical section of
the foam-bed reactor;
• an inlet port above the distributor plate for reactant solution;
• a outlet port above the distributor plate for collection of samples for chemical analysis;
• a sieve plate suspended from the top of the reactor to break the foam and maintain
constant foam height.
The alkaline earth metal is selected form barium and calcium.
Description of the Drawings:
Figure 1: diagrammatic illustration of a typical semi-batch foam-bed reactor in accordance
with the present invention.
Figure 2: diagrammatic illustration of liquid film with associated gas pockets.
Figure 3: diagrammatic illustration of a stirred cell used for the preparation of aqueous bariumsulfide
solution.
Figure 4: diagrammatic illustration of the experimental set-up in accordance with the present
invention.
(
Figure 5: diagrammatic illustration of the correlation for the determination of particle diameter
in a foam-bed reactor.
Figure 6: diagrammatic illustration of particle size distribution for reaction product barium
carbonate.
Figure 7: diagrammatic illustration of photograph and SEM of the barium carbonate produced in
accordance with the present invention.
Figure 8: diagrammatic illustration of particle size distribution for reaction product calcium
carbonate.
Figure 9: diagrammatic illustration of the process flow diagram for the production of barium
carbonate from carbon dioxide route.
Detailed Description of the Invention:
The present provides a new process produces in-situ, near-micron sized solid product by
carrying out the precipitation reaction in a foam-bed reactor. The cost of grinding the particles
(which is an energy intensive process) is thus saved.
Precipitation reaction is carried out in a foam-bed reactor to produce near-micron-sized (~ 5
urn) solid product.
A foam-bed reactor is a novel gas-liquid contactor and offers large interfacial areas, low liquid
holdups, and long contact times at the cost of moderate pressure drops when compared to
conventional gas-liquid contactors. Gas bubbles are continuously generated at a distributor
plate submerged in liquid in the storage section. Liquid stream continually flows across the
storage section or can be added in batch. This liquid is presumed to contain a dissolved reactive
solute and a surfactant. Presence of surfactant ensures formation of stable films around the gas
bubbles, which emerge at the top of the storage section and become a part of foam matrix. As
the foam bubbles move up, the gas-phase reactant diffuses into the flat liquid foam films. It
reacts with the dissolved reactive solute to produce the solid product. As the reaction takes
place in the films which are limited in thickness (typically less than 150 urn), the solid product
formed can also be limited to sizes of the order of microns. By optimizing the different
physicochemical and hydrodynamic parameters which govern the performance of a foam-bed
reactor, near-micron sized solid particles (~ 5 urn) can be produced in-situ. The solid product
formed is oven-dried and stored in a closed container. Even after storing the product for more
than a year, the average particle size increases only by a few microns (to ~ 6 urn) due to the
surface coating of the particles by thin surfactant layer which prevents agglomeration of the
particles. In the absence of surfactant and foams, the average particle size obtained is almost
twenty times larger (~ 107 urn).
Preparation of reactant solution
Commercial grade barium sulfide (nearly 60% BaS) was used as the reactant for the study.
Distilled water used for preparing the solutions was first boiled to remove any dissolved gases,
like oxygen and carbon dioxide. Barium-sulfide powder was added to the carbon dioxide free
distilled water and the resulting slurry mixed thoroughly in an air-tight stirred cell for leaching of
1
barium sulfide. Fresh solutions, filtered to clarity, were always used for experimentation,
knowing that barium-sulfide solution undergoes a slow oxidation in air, forming elemental
sulphur and a family of oxidized sulphur species including sulfite, thiosulfate, polythionates, and
sulfate. A known amount of surfactant (Triton X-100 or CTAB) was added to the barium-sulfide
solution and mixed to uniformity, before carrying out the gas-liquid reaction.
Set-up
The regulator of carbon-dioxide gas cylinder is heated using two infra-red lamps to avoid
formation of dry ice and consequent plugging of the supply line. Calibrated rotameters are
provided to measure the flow rates of the diluent and reactant gases. A saturator saturates the
diluent nitrogen gas with water vapor. A packed bed, containing glass Raschig rings, is used to
mix the saturated diluent gas with reactant gas and also to trap any entrained water droplets,
before the gas mixture enters the foam-bed reactor.
The foam-bed reactor comprises of a glass column and a distributor plate assembly. The glass
column is provided with four tappings at various heights (0.065, 0.375, 0.69, and 1.03 m) to
measure the liquid hold-up in the foam. The tappings are connected to inclined-tube
manometers using rubber tubings. These manometers are filled with water and used for
measuring the hydrostatic head exerted by foam. The head indicated by the manometer divided
by the foam height above the tapping directly gives the average liquid hold-up in foam above
that point. The inlet for reactant solution is provided at a height of 0.03 m above the gasdistributor
plate. The outlet for the reaction mixture, provided just above the distributor plate, is
used to collect samples for chemical analysis. The distributor plate made of glass is placed
between the cylindrical part and the conical section of the foam-bed reactor. The conical section
ensures a uniform distribution of the stabilized flow of gaseous mixture through the distributor
holes. Table 1 shows the dimensions of the reactor and details of the distributor plate.
Table 1. Dimensions of the foam-bed reactor.
Experimental procedure
At the beginning of an experimental run, the glass column was thoroughly rinsed with distilled
water. Flow rates of nitrogen (diluent gas) and carbon dioxide (gas-phase reactant) were
measured separately, using calibrated rotameters. Nitrogen gas was first saturated with water
vapor by bubbling it through a packed saturator. The saturated nitrogen gas was then mixed
with a small stream of carbon-dioxide gas in a packed bed, which also helped in removing any
entrained water droplets. The gas mixture was then introduced into the foam-bed reactor. A
batch of known volume of barium-sulfide solution, with known concentrations of sulfide and
surfactant, was poured into the column through the inlet port after ensuring that the gas
mixture passing continuously through the reactor had already attained a steady flow rate. The
barium-sulfide solution started foaming and the foam began rising through the cylindrical
reactor column. A direct contact with a layer of 1-butanol applied on to a sieve plate suspended
from the top was effectively employed to break and maintain the foam at a definite height. The
parameters affecting the performance of foam-bed reactor are shown in table 2 along with their
ranges used in this study.
Table 2. Parameters affecting the performance of a foam-bed reactor.
Particle size measurement
The particle sizes of the final reaction product barium carbonate were measured using a particle
size analyzer (0.5 ^m to 1000 |im range). After each experimental run was over, the slurry
inside the reactor was collected and subjected to decantation for about an hour to settle all
solid barium carbonate particles formed during the reaction. The top liquid was removed and
the remaining liquid was kept in an oven at 100 °C for 12 hours. The dried barium carbonate
thus obtained was used in determining the particle size. The barium carbonate particle size was
measured as a function of foam height, initial concentration of aqueous barium-sulfide solution,
initial concentration of gas-phase reactant carbon dioxide, initial concentration of surfactant,
gas-flow rate, nature of surfactant, and volume of liquid-phase reactant charged into the
reactor. Buckingham-Pi theorem was used to find out a correlation which will predict the
particle diameter as a function of these parameters.
Parameters: H, CBS, Q, CAg0, V, dP, Qr
Dimensions: M, L, T
Functions:
1
COMMERCIAL POTENTIAL
1. Cost saving due to absence of primary filter and size reduction equipment.
2. Minor modifications in the bubble reactors to convert them into foam-bed reactors.
3. Granular BaC03 cost = 240 $/MT [DP > 850 mm]
Particle BaC03 cost = 400 $/MT [1 mm < DP < 150 mm]
4. Because of reduced agglomeration, the products can be stored for a longer time.
5. Other solid products which can be manufactured using the same technology: (even
liquid-liquid reactions)
• CuS, ZnS, CdS
• Ti02, Si02, SrC03
• BaTi03, BaS04
• In(OH)3, ln203, InSb
• Ni/Cu/Zn/AI/Ce/Pt/Rh based catalysts
The solids were precipitated using a foam-bed reactor. The ranges of parameters studied are
given in table 2. The particle sizes were measured using a CILAS Particle Size Analyzer.
[•*
The invention will now be explained with the help of following examples. However, the scope of
the invention should not be limited to these examples as the person skilled in the art can easily
make variations.
//
EXAMPLE 1
For the lean-gas absorption experiments, the glass column was thoroughly rinsed at the
beginning with distilled water. Flow rates of nitrogen (diluent gas) and carbon dioxide (gasphase
reactant) were measured separately, using calibrated rotameters. Nitrogen gas was first
saturated with water vapor by bubbling it through a packed saturator. The saturated nitrogen
gas was then mixed with a small stream of carbon-dioxide gas in a packed bed, which also
helped in removing any entrained water droplets. The gas mixture was then introduced into the
foam-bed reactor at flow rate of 4.17 x 10-5 m3/s and at C02 concentration of 1.0 x 10 -2 k
mol/m3. A batch of barium-sulfide solution (0.6 x 10-4 m3), with known concentrations of
barium sulfide (0.65 k mol/m3) and surfactant (triton x-100, 1000 ppm), was poured into the
column through the inlet port after ensuring that the gas mixture passing continuously through
the reactor had already attained a steady flow rate. The barium-sulfide solution started foaming
at once and the foam began rising through the cylindrical reactor column. A direct contact with
a layer of n-butanol coated on to a sieve plate suspended from the top was effectively
employed to break and maintain the foam at a definite height of 0.7 m. Samples of the reaction
mixture were withdrawn from the storage section of the reactor through the sampling port at
different time intervals till the reaction was complete. These samples were analyzed
iodometrically to determine the concentration of unreacted barium sulfide. After each
experimental run was over, the slurry inside the reactor was collected and allowed to stand for
about 15 minutes to settle all solid barium-carbonate particles formed during the reaction. The
top clear liquid was decanted and the remaining slurry was kept in an oven at 100 oC. The
dried barium carbonate thus obtained was used in determining the particle size.
For calcium carbonate production, similar procedure was followed and the corresponding
parameter values were: foam height = 0.5 m, calcium hydroxide concentration = 40 kg/m3,
gas-flow rate = 6.67 x 10-5 m3/s, C02 concentration = 1.5 x 10-2 k mol/m3, volume of calcium
hydroxide = 10-4 m3, concentration of triton x-100 surfactant = 500 ppm.
EXAMPLE 2
In one study, the particle size distribution of freshly prepared barium carbonate (not subjected
to drying) was monitored for the following cases:
i. No surfactant added to the liquid-phase reactant,
ii. Surfactant (Triton X-100, CTAB) present in the liquid-phase reactant but no foam
allowed to form,
iii. Surfactant (Triton X-100, CTAB) present in the liquid-phase reactant and foam allowed
to form up to a height of 0.4 m, and
iv. Barium carbonate from (iii) dried and stored for more than a year in closed conditions.
The aim of doing this study was to see the effect of presence of surfactant and foam on the
particle size of barium carbonate and also to check the agglomeration characteristics of barium
carbonate. After the reaction was over, the samples were analyzed for particle sizes.
EXAMPLE 3
An experiment was performed for the carbonation of calcium hydroxide to produce precipitate
of calcium carbonate. The aim was to see if other reactions also produce near-micron sized
particles or not. The particle size of calcium carbonate obtained was ~ 10 |im indicating that
II
any gas-liquid reaction or even liquid-liquid reaction can be carried out in similar fashion to
produce near-micron sized solid particles.

We Claim:
1. An in situ process for preparing near micron size alkaline earth metal carbonate particles
comprising :
• preparing alkaline earth metal sulphide reactant solution by leaching said compound
with distilled water and thereby adding surfactant to the clear solution,
• introducing said reactant mixture in the foam bed reactor with the gas mixture,
• treating the known volume of said reactant solution with the gas mixture in foam
bed reactor,
• said gas mixture is prepared by optionally mixing the nitrogen gas saturated with
water followed by mixing with carbon dioxide gas,
• said gas mixture is optionally dehydrated before introducing it in the foam bed
reactor,
• removing the slurry from the reactor and decanting the same to obtain near micron
size carbonate particles after drying.
2. The process as claimed in claim 1, wherein concentration of said alkaline earth metal
sulphide reactant solution is 0.16-0.66 k mol/m3.
3. The process as claimed in claim 1, wherein said initial concentration of gas phase
reactant is 25-62.5% v/v.
4. The process as claimed in claim 1, wherein said volume of alkaline earth metal sulphide
reactant solution is 60x 10 (-6) to 260 x 10 (-6) m3.
5. The process as claimed in claim 1, wherein boiled distilled water is used for leaching.
6. The process as claimed in claim 1, wherein said surfactant is non- ionic or cationic in
nature, preferably Triton X-100 or (TAB or their mixture.
7. The process as claimed in claim 1, wherein concentration of the said surfactant is
preferably [500-10000 ppm].
8. The process as claimed in claim 1, wherein said dehydration of gas mixture is carried
out in a packed bed.
9. The process as claimed in claim 8, wherein said packed bed comprises glass Rashchig
rings.
10. The process as claimed in claim 1, wherein said alkaline earth metal is selected form
barium and calcium.
iH
11. The process as claimed in claim 1, wherein said reactant solution is introduced in reactor
once the gas mixture attains a steady flow rate in the reactor column.
12. The process as claimed in claim 1, wherein the maximum size of the solid particles
produced in-situ is limited by the thickness of the liquid film in the foam.
13. A foam bed reactor for preparing barium carbonate as claimed in claim 1, wherein the
reactor comprises of:
• a glass column, having plurality of tappings at various heights of said column to
measure the liquid hold up in the foam,;
• a glass column, having plurality of ports at various heights of said column to
monitor the liquid and foam temperatures;
• a distributor plate assembly placed between the cylindrical part and conical
section of the foam-bed reactor;
• an inlet port above the distributor plate for reactant solution;
• a outlet port above the distributor plate for collection of samples for chemical
analysis;
• a sieve plate suspended from the top of the reactor to break the foam and to
maintain a constant foam height.
14. The reactor as claimed in claim 13, wherein said glass column is preferably provided
with four taps and ports at heights of 0.065, 0.375, 0.69and 1.03 m.
15. The reactor as claimed in claim 13, wherein said distributor plate assembly is made of
glass.
16. The reactor as claimed in claim 13, wherein said inlet port is at a height of 0.03m above
the said gas distributor plate.
17. The reactor as claimed in claim 13, wherein said distributor plate has a diameter of
0.057m and a thickness of 0.003m.
18. The reactor as claimed in claim 13, wherein said column has a diameter of 0.057m and
height of 1.1m.
19. The reactor as claimed in claim 13, wherein said sieve plate is coated with a layer of 1-
butanol.
20. The reactor as claimed in claim 13, wherein height (H) of said foam is in the range of
0.1-0.7m.