Title of Invention	PROCESS FOR PREPARATION OF ULTRA FINE, LOW BULK DENSITY ALUMINA TRI HYDRATE
Abstract	The invention relates to the ultra fine, low bulk density alumina tri hydrate and process for preparation thereof having packed bulk density 0.15-0.35 g/cc, with median diameter size from 0.2 to 1.0 micron through special precipitation method. Precipitation test has been carried out using sodium aluminate liquor is treated with NaHCO3 at 8 to 9 pH with aging time from 8 to 16 hours. Precipitation was carried out at 35 to 55 deg. C, for 24 to 48 hours using 8 to 12 gpl to gel as seed. Passing of CO2 at 70 deg.C. for 4-6 hours is optionally employed as per the precipitation requirement. The resulted precipitated slurry is then filtered, washed and dried. The dried alumina tri hydrate with bulk density of 0.15 to 0.35 g/cc with median diameter (d50)= 0.2 to 10 micron was achieved in this process under optimum conditions.

Title of Invention

PROCESS FOR PREPARATION OF ULTRA FINE, LOW BULK DENSITY ALUMINA TRI HYDRATE

Abstract

The invention relates to the ultra fine, low bulk density alumina tri hydrate and process for preparation thereof having packed bulk density 0.15-0.35 g/cc, with median diameter size from 0.2 to 1.0 micron through special precipitation method. Precipitation test has been carried out using sodium aluminate liquor is treated with NaHCO3 at 8 to 9 pH with aging time from 8 to 16 hours. Precipitation was carried out at 35 to 55 deg. C, for 24 to 48 hours using 8 to 12 gpl to gel as seed. Passing of CO2 at 70 deg.C. for 4-6 hours is optionally employed as per the precipitation requirement. The resulted precipitated slurry is then filtered, washed and dried. The dried alumina tri hydrate with bulk density of 0.15 to 0.35 g/cc with median diameter (d50)= 0.2 to 10 micron was achieved in this process under optimum conditions.

Full Text	FIELD OF INVENTION: This invention relates to ultra fine, low bulk density alumina tri hydrate and process for preparation thereof. BACKGROUND OF THE INVENTION: Coarse grade alumina tri hydrate is mainly used for metal making and is produced industrially by Bayer's process. Alumina tri hydrate used for non- metallurgical applications such as fire retardant filler in cable, paper, paint, printing ink etc. are finer in particle size (ultra fine), having median diameter(d50) of about 0.2 to 10.0 micron. In some applications like cable, paint, inks etc. the property like low bulk density (light) is important for its flow-ability characteristics. Normally alumina tri hydrates has a bulk density of about 0.50 to 1.2 g/cc. In the present invention, efforts have been made to develop a process for preparation of ultra fine, light alumina tri hydrate through precipitation technique, using sodium aluminate liquor and specially prepared barite seed and/or by passing CO2 to increase productivity in a manner which can be industrially feasibly to produce alumina tri hydrate of fineness as low as 0.5 micron or less and packed bulk density as low as 0.15 g/cc. OBJECTS OF THE INVENTION: An object of this invention is to propose a process for the preparation of ultra fine, low bulk density alumina tri hydrate; Another object of this invention is to propose a process for the preparation of light (low bulk density) alumina tri hydrate of superior purity. BRIEF DESCRIPTION OF THE INVENTION: According to this invention there is provided a process for preparation of ultra fine, low bulk density alumina tri hydrate comprising: preparing alumina tri hydrate (barite) gel using saturated sodium aluminate liquor and NaHCO3 at pH between 8 to 9 and aging for 8-16 hours; subjecting the said alumina tri hydrate (barite) as seed and/or by passing CO2 to the step of precipitation of aluminate liquor to produce ultra fine light alumina tri hydrate; filtering and washing the said product till the soda is reduced to 0.005 to 0.020%; subjecting the washed product to the step of spray drying or simple drying. DETAILED DESCRIPTION OF THE INVENTION: This invention relates to a process for the preparation of ultra fine, light alumina tri hydrate which comprises the preparation of alumina tri hydrate (barite) gel using sodium aluminate liquor and sodium bi-carbonate and aging for a period of 8-16 hrs and then precipitation of ultra fine, light alumina tri hydrate from saturated sodium aluminate liquor at 35 to 55 deg. C using the barite gel as seed and/or by passing CO2 for 4-6 hours at 70 deg.C, followed by filtration, washing, cake separation and drying or spray drying. In accordance with the above method, sodium alumina liquor of 125 to 145 gpl Na20 (caustic), 125 to 161.25 gpl AI203 has been taken as the main raw material along with required amount of commercial grade NaHCO3 to maintain pH of the liquor between 8 to 9 to prepare alumina tri hydrate gel. The gel was aged under stirring for a period of 8-16 hrs to convert it into barite phase. The settled thick gel was again used as the seeding reagent in precipitating ultra fine, light alumina tri hydrate from the fresh sodium aluminate liquor under slow stirring for 24 to 48 hrs at 35 to 55 deg. C temperature. Passing of CO2 at 70 deg. C. for 4-6 hours is optionally employed as per the precipitation requirement. The precipitated product was filtered, washed and dried or spray dried and analysed for particle size, bulk density and whiteness. Ultra fine particle size of median diameter (d50) as fine as 0.2 to 1.0 micron with packed bulk density as low as 0.15 to 0.35 g/cc and whiteness 98 to 100% was achieved. Particle size could be attained up to 10 micron median size with adjusting the precipitation parameters. To achieve ultra fine, light alumina tri hydrate the following process parameters were studied: a) Preparation of stable alumina tri hydrate gel using sodium aluminate liquor and NaHCO3 at 8 to 9.0 pH and aging for 8-16 hrs under slow stirring to convert to barite phase. b) Precipitation of ultra fine, light alumina tri hydrate using different quantity of barite gel as seed and or by passing CO2 with saturated sodium aluminate liquor for 24 to 48 hours at 35 to 70 deg.C temperature. c) Filtration and hot water washing of alumina tri hydrate till the washable soda in cake reduced to 0.005 to 0.020%. d) Drying or spray drying of alumina tri hydrate cake at 110+/-10 deg.C for 1 to 2 hours. The typical characteristics of base raw material sodium aluminate liquor with the specification of final product prepared in this method has been reported in Table 1 and 2 respectively. Commercial grade NaHCO3 has been used for the preparation of barite gel. Water used in this invention is tap water. Table-1 Table-2 Specification of Final Product (Ultra fine, light alumina tri hydrate) Specification of Sodium Aluminate liquor (Source: Nalco Alumina Refinery, Orissa) EXAMPLES: 10 gm of alumina tri hydrate gel was prepared using 67 ml of sodium aluminate liquor (with typical characteristics as reported in Table 1) and required amount of NaHCO3 (commercial grade) to bring the pH of liquor to 8. Resulted slurry was aged under slow agitation for 10 hours to convert to barite phase (confirmed from X-ray diffraction analysis). Then the prepared gel (10 gpl) was taken for seeding of 1 litre of fresh sodium aluminate liquor in a thermostatic container at 35 deg. C for 24 hours with constant, slow stirring. The resulted precipitated slurry was then filtered, washed, dried or spray dried. The product prepared as above has been analysed to have Na2O=0.425 %, Fe2O3=0.002%, SiO2=0.003%, d50=0.44 micron, bulk density = 0.18 g/cc and whiteness = 100%. EXAMPLES: 10 gm of alumina tri hydrate gel was prepared using 67 ml of sodium aluminate liquor (with typical characteristics as reported in Table-1) and required amount of NaHCO3 (commercial grade) to bring the pH of liquor to 8.5. Resulted slurry was aged under slow agitation for 12 hours to convert to barite phase (confirmed from X-ray diffraction analysis). Then the prepared gel (10 gpl) was taken for seeding of 1 litre of fresh sodium aluminate liquor in a thermostatic container at 40 deg.C for 30 hours followed by passing CO2 at 70 deg.C for 4 hours with constant, slow stirring. The resulted precipitated slurry was then filtered, washed, dried or spray dried. The product prepared as above has been analysed to have Na2O=0.420%, Fe2O3=0.0025%, SiO2=0.002%, d50=0.25 micron, bulk density = 0.22 g/cc and whiteness =100%. EXAMPLE 10 gm of alumina tri hydrate gel was prepared using 67 ml of sodium aluminate liquor (with typical characteristics as reported in Table 1) and required amount of NaHCO3 (commercial grade) to bring the pH of liquor to 9. Resulted slurry was aged under slow agitation for 16 hours to convert to barite phase (confirmed from X-ray diffraction analysis). Then the prepared gel (8 gpl) was taken for seeding of 1 litre of fresh sodium aluminate liquor in a thermostatic container at 50 deg.C for 40 hours with constant, slow stirring. The resulted precipitated slurry was then filtered washed, dried or spray dried. The product prepared as above has been analysed to have Na2O=0.386%, Fe2O3=0.002%, SiO2=0.002%, d50=0.65 micron, bulk density = 0.28 g/cc and whiteness = 99%. WE CLAIM: 1. A process for preparation of ultra fine, low bulk density alumina tri hydrate comprising: preparing alumina tri hydrate (barite phase) using saturated sodium aluminate liquor and NaHCO3 at pH between 8 to 9 followed by aging for 8-16 hours; subjecting the said alumina tri hydrate as seed and/or by passing CO2 to the step of precipitation of aluminate liquor to produce ultra fine light alumina tri hydrate; filtering and washing the said product till the soda is reduced to 0.005 to 0.020%; subjecting the washed product to the step of drying or spray drying. 2. The process as claimed in claim 1, wherein the pH of slurry is maintained between 8 to 9 for preparation of alumina tri hydrate gel. 3. The process as claimed in claim 1, wherein the saturated sodium aluminate liquor & NaHCO3 is aged for a period of 8 to 16 hours for preparation of gel with barite phase. 4. The process as claimed in claim 1, wherein the precipitation period is maintained between 24 to 48 hours and temperature of precipitation between 35 to 55 deg.C. 5. The process as claimed in claim 1, wherein alumina tri hydrate gel seed quantity is varied between 8 to 12 gpl of sodium aluminate liquor. 6. The process as claimed in claim 1, wherein precipitation is carried out using barite seed and or by passing C02. 7. The process as claimed in claim 1, wherein precipitation is carried out by passing C02 at 70 deg.C for 4-6 hours. 8. The process as claimed in claim 1, wherein ultra fine, light alumina tri hydrate of median particle size as low as 0.2 micron, packed bulk density as low as 0.15 to 0.35 g/cc is obtained. 9. The process as claimed in claim 1, wherein the said product is dried at 100- 110 deg.C for 1 to 2 hours. The invention relates to the ultra fine, low bulk density alumina tri hydrate and process for preparation thereof having packed bulk density 0.15-0.35 g/cc, with median diameter size from 0.2 to 1.0 micron through special precipitation method. Precipitation test has been carried out using sodium aluminate liquor is treated with NaHCO3 at 8 to 9 pH with aging time from 8 to 16 hours. Precipitation was carried out at 35 to 55 deg. C, for 24 to 48 hours using 8 to 12 gpl to gel as seed. Passing of CO2 at 70 deg.C. for 4-6 hours is optionally employed as per the precipitation requirement. The resulted precipitated slurry is then filtered, washed and dried. The dried alumina tri hydrate with bulk density of 0.15 to 0.35 g/cc with median diameter (d50)= 0.2 to 10 micron was achieved in this process under optimum conditions.

Full Text

FIELD OF INVENTION:
This invention relates to ultra fine, low bulk density alumina tri hydrate and
process for preparation thereof.
BACKGROUND OF THE INVENTION:
Coarse grade alumina tri hydrate is mainly used for metal making and is
produced industrially by Bayer's process. Alumina tri hydrate used for non-
metallurgical applications such as fire retardant filler in cable, paper, paint,
printing ink etc. are finer in particle size (ultra fine), having median diameter(d50)
of about 0.2 to 10.0 micron. In some applications like cable, paint, inks etc. the
property like low bulk density (light) is important for its flow-ability characteristics.
Normally alumina tri hydrates has a bulk density of about 0.50 to 1.2 g/cc. In the
present invention, efforts have been made to develop a process for preparation
of ultra fine, light alumina tri hydrate through precipitation technique, using
sodium aluminate liquor and specially prepared barite seed and/or by passing
CO2 to increase productivity in a manner which can be industrially feasibly to
produce alumina tri hydrate of fineness as low as 0.5 micron or less and packed
bulk density as low as 0.15 g/cc.
OBJECTS OF THE INVENTION:
An object of this invention is to propose a process for the preparation of ultra fine,
low bulk density alumina tri hydrate;
Another object of this invention is to propose a process for the preparation of light
(low bulk density) alumina tri hydrate of superior purity.

BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a process for preparation of ultra
fine, low bulk density alumina tri hydrate comprising:
preparing alumina tri hydrate (barite) gel using saturated sodium aluminate liquor
and NaHCO3 at pH between 8 to 9 and aging for 8-16 hours;
subjecting the said alumina tri hydrate (barite) as seed and/or by passing CO2 to
the step of precipitation of aluminate liquor to produce ultra fine light alumina tri
hydrate;
filtering and washing the said product till the soda is reduced to 0.005 to 0.020%;
subjecting the washed product to the step of spray drying or simple drying.
DETAILED DESCRIPTION OF THE INVENTION:
This invention relates to a process for the preparation of ultra fine, light alumina
tri hydrate which comprises the preparation of alumina tri hydrate (barite) gel
using sodium aluminate liquor and sodium bi-carbonate and aging for a period of
8-16 hrs and then precipitation of ultra fine, light alumina tri hydrate from
saturated sodium aluminate liquor at 35 to 55 deg. C using the barite gel as seed
and/or by passing CO2 for 4-6 hours at 70 deg.C, followed by filtration, washing,
cake separation and drying or spray drying.

In accordance with the above method, sodium alumina liquor of 125 to 145 gpl
Na20 (caustic), 125 to 161.25 gpl AI203 has been taken as the main raw
material along with required amount of commercial grade NaHCO3 to maintain
pH of the liquor between 8 to 9 to prepare alumina tri hydrate gel. The gel was
aged under stirring for a period of 8-16 hrs to convert it into barite phase. The
settled thick gel was again used as the seeding reagent in precipitating ultra fine,
light alumina tri hydrate from the fresh sodium aluminate liquor under slow
stirring for 24 to 48 hrs at 35 to 55 deg. C temperature. Passing of CO2 at 70
deg. C. for 4-6 hours is optionally employed as per the precipitation requirement.
The precipitated product was filtered, washed and dried or spray dried and
analysed for particle size, bulk density and whiteness. Ultra fine particle size of
median diameter (d50) as fine as 0.2 to 1.0 micron with packed bulk density as
low as 0.15 to 0.35 g/cc and whiteness 98 to 100% was achieved. Particle size
could be attained up to 10 micron median size with adjusting the precipitation
parameters.
To achieve ultra fine, light alumina tri hydrate the following process parameters
were studied:
a) Preparation of stable alumina tri hydrate gel using sodium aluminate liquor
and NaHCO3 at 8 to 9.0 pH and aging for 8-16 hrs under slow stirring to
convert to barite phase.
b) Precipitation of ultra fine, light alumina tri hydrate using different quantity
of barite gel as seed and or by passing CO2 with saturated sodium
aluminate liquor for 24 to 48 hours at 35 to 70 deg.C temperature.
c) Filtration and hot water washing of alumina tri hydrate till the washable
soda in cake reduced to 0.005 to 0.020%.
d) Drying or spray drying of alumina tri hydrate cake at 110+/-10 deg.C for 1
to 2 hours.

The typical characteristics of base raw material sodium aluminate liquor with the
specification of final product prepared in this method has been reported in Table
1 and 2 respectively. Commercial grade NaHCO3 has been used for the
preparation of barite gel. Water used in this invention is tap water.
Table-1
Table-2
Specification of Final Product
(Ultra fine, light alumina tri hydrate)
Specification of Sodium Aluminate liquor
(Source: Nalco Alumina Refinery, Orissa)

EXAMPLES:
10 gm of alumina tri hydrate gel was prepared using 67 ml of sodium aluminate
liquor (with typical characteristics as reported in Table 1) and required amount of
NaHCO3 (commercial grade) to bring the pH of liquor to 8. Resulted slurry was
aged under slow agitation for 10 hours to convert to barite phase (confirmed from
X-ray diffraction analysis). Then the prepared gel (10 gpl) was taken for seeding
of 1 litre of fresh sodium aluminate liquor in a thermostatic container at 35 deg. C
for 24 hours with constant, slow stirring. The resulted precipitated slurry was then
filtered, washed, dried or spray dried. The product prepared as above has been
analysed to have Na2O=0.425 %, Fe2O3=0.002%, SiO2=0.003%, d50=0.44
micron, bulk density = 0.18 g/cc and whiteness = 100%.
EXAMPLES:
10 gm of alumina tri hydrate gel was prepared using 67 ml of sodium aluminate
liquor (with typical characteristics as reported in Table-1) and required amount of
NaHCO3 (commercial grade) to bring the pH of liquor to 8.5. Resulted slurry was
aged under slow agitation for 12 hours to convert to barite phase (confirmed from
X-ray diffraction analysis). Then the prepared gel (10 gpl) was taken for seeding
of 1 litre of fresh sodium aluminate liquor in a thermostatic container at 40 deg.C
for 30 hours followed by passing CO2 at 70 deg.C for 4 hours with constant, slow
stirring. The resulted precipitated slurry was then filtered, washed, dried or spray
dried. The product prepared as above has been analysed to have
Na2O=0.420%, Fe2O3=0.0025%, SiO2=0.002%, d50=0.25 micron, bulk density
= 0.22 g/cc and whiteness =100%.

EXAMPLE
10 gm of alumina tri hydrate gel was prepared using 67 ml of sodium aluminate
liquor (with typical characteristics as reported in Table 1) and required amount of
NaHCO3 (commercial grade) to bring the pH of liquor to 9. Resulted slurry was
aged under slow agitation for 16 hours to convert to barite phase (confirmed from
X-ray diffraction analysis). Then the prepared gel (8 gpl) was taken for seeding of
1 litre of fresh sodium aluminate liquor in a thermostatic container at 50 deg.C for
40 hours with constant, slow stirring. The resulted precipitated slurry was then
filtered washed, dried or spray dried. The product prepared as above has been
analysed to have Na2O=0.386%, Fe2O3=0.002%, SiO2=0.002%, d50=0.65
micron, bulk density = 0.28 g/cc and whiteness = 99%.

WE CLAIM:
1. A process for preparation of ultra fine, low bulk density alumina tri hydrate
comprising:
preparing alumina tri hydrate (barite phase) using saturated sodium aluminate
liquor and NaHCO3 at pH between 8 to 9 followed by aging for 8-16 hours;
subjecting the said alumina tri hydrate as seed and/or by passing CO2 to the
step of precipitation of aluminate liquor to produce ultra fine light alumina tri
hydrate;
filtering and washing the said product till the soda is reduced to 0.005 to 0.020%;
subjecting the washed product to the step of drying or spray drying.
2. The process as claimed in claim 1, wherein the pH of slurry is maintained
between 8 to 9 for preparation of alumina tri hydrate gel.
3. The process as claimed in claim 1, wherein the saturated sodium aluminate
liquor & NaHCO3 is aged for a period of 8 to 16 hours for preparation of gel with
barite phase.
4. The process as claimed in claim 1, wherein the precipitation period is
maintained between 24 to 48 hours and temperature of precipitation between 35
to 55 deg.C.

5. The process as claimed in claim 1, wherein alumina tri hydrate gel seed
quantity is varied between 8 to 12 gpl of sodium aluminate liquor.
6. The process as claimed in claim 1, wherein precipitation is carried out using
barite seed and or by passing C02.
7. The process as claimed in claim 1, wherein precipitation is carried out by
passing C02 at 70 deg.C for 4-6 hours.
8. The process as claimed in claim 1, wherein ultra fine, light alumina tri hydrate
of median particle size as low as 0.2 micron, packed bulk density as low as 0.15
to 0.35 g/cc is obtained.
9. The process as claimed in claim 1, wherein the said product is dried at 100-
110 deg.C for 1 to 2 hours.

The invention relates to the ultra fine, low bulk density alumina tri hydrate and
process for preparation thereof having packed bulk density 0.15-0.35 g/cc, with
median diameter size from 0.2 to 1.0 micron through special precipitation
method. Precipitation test has been carried out using sodium aluminate liquor is
treated with NaHCO3 at 8 to 9 pH with aging time from 8 to 16 hours.
Precipitation was carried out at 35 to 55 deg. C, for 24 to 48 hours using 8 to 12
gpl to gel as seed. Passing of CO2 at 70 deg.C. for 4-6 hours is optionally
employed as per the precipitation requirement. The resulted precipitated slurry is
then filtered, washed and dried. The dried alumina tri hydrate with bulk density of
0.15 to 0.35 g/cc with median diameter (d50)= 0.2 to 10 micron was achieved in
this process under optimum conditions.

Documents:

205-KOL-2009-(05-09-2012)-ABSTRACT.pdf

205-KOL-2009-(05-09-2012)-AMANDED CLAIMS.pdf

205-KOL-2009-(05-09-2012)-DESCRIPTION (COMPLETE).pdf

205-KOL-2009-(05-09-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

205-KOL-2009-(05-09-2012)-FORM-1.pdf

205-KOL-2009-(05-09-2012)-FORM-2.pdf

205-KOL-2009-(05-09-2012)-FORM-5.pdf

205-KOL-2009-(05-09-2012)-OTHERS.pdf

205-kol-2009-abstract.pdf

205-kol-2009-claims.pdf

205-KOL-2009-CORRESPONDENCE-1.1.pdf

205-KOL-2009-CORRESPONDENCE-1.2.pdf

205-kol-2009-CORRESPONDENCE-1.3.pdf

205-kol-2009-correspondence.pdf

205-kol-2009-description (complete).pdf

205-KOL-2009-FORM 1-1.1.pdf

205-kol-2009-form 1.pdf

205-kol-2009-form 18.pdf

205-kol-2009-form 2.pdf

205-kol-2009-form 3.pdf

205-KOL-2009-FORM 9.pdf

205-kol-2009-PRIORITY DOCUMENT.pdf

205-kol-2009-specification.pdf

« Previous Patent

Next Patent »

Patent Number

255308

Indian Patent Application Number

205/KOL/2009

PG Journal Number

07/2013

Publication Date

15-Feb-2013

Grant Date

11-Feb-2013

Date of Filing

05-Feb-2009

Name of Patentee

NATIONAL ALUMINIUM COMPANY LIMITED

Applicant Address

NALCO BHAWAN, NAYAPALLI, BHUBANESWAR

Inventors:

#	Inventor's Name	Inventor's Address
1	B. K. SATPATHY	C/O NATIONAL ALUMINIUM COMPANY LIMITED NALCO BHAWAN, PLOT NO. P/1, NAYAPALLI, BHUBANESWAR
2	S. K. PATNAIK	C/O NATIONAL ALUMINIUM COMPANY LIMITED NALCO BHAWAN, PLOT NO. P/1, NAYAPALLI, BHUBANESWAR
3	S. C. PATNAIK	C/O NATIONAL ALUMINIUM COMPANY LIMITED NALCO BHAWAN, PLOT NO. P/1, NAYAPALLI, BHUBANESWAR

PCT International Classification Number

B41M5/00; B01J20/08

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA