Title of Invention

"A PROCESS FOR THE PREPARATION OF COLLOIDAL-GRAPHITE FROM WASTE CATHODE BLOCKS GENERATED BY ALUMINIUM INDUDSTRIES"

Abstract The present invention relates to a process for the preparation of colloidal - graphite from waste cathode blocks generated by aluminum industries. Colloidal graphites are used as lubricants for high temperature applications like ball bearings. In the process, the spent cathode blocks are decontaminated and they absorb the toxic elements in dilute alkali for safe disposal. The process essentially involves only two steps chemical and physical treatment of the raw material to generate the final product. The product is neutral and free flowing in nature, with narrow band of particle size distribution.
Full Text The present invention relates to a process for the preparation of colloidal-graphite from waste cathode blocks generated by aluminum industries.
Colloidal graphites are generally used as lubricants for high temperature applications. One such example is in the ball bearings where large heat may generate due to friction. Graphites as such are stable upto a very high temperature and provide lubrication facility due to its unique planar molecular configuration.
A very large volume of spent cathode blocks are being discarded by electrolytic aluminum extraction plant every year, and storage as well as ultimate disposal of these wastes possess a big problem for the plants. In the long run, waste materials stored in this manner possess environment risks as it can easily contaminate underground potable water through seepage of the harmful contaminants. Storage of such wastes in large dug out trenches with various absorbing layers and concrete lining costs large sum of money to the plant as well. Accordingly, this invention provides a means for safe disposal of these wastes and simultaneously the treated waste provides a high value saleable product. An internet search on the above key words indicates colloidal graphite of above nature has not been attempted so far form spent cathode blocks of aluminum industry'.
The main objective of this invention is to provide a process for the preparation of colloidal graphite from waste cathode blocks generated by aluminum industries.
Yet another objective of the invention is to decontaminate these spent cathode block and absorb the toxic elements in dilute alkali for safe disposal.
Accordingly the present invention provides a process for the preparation of colloidal graphite from waste cathode blocks generated by aluminum industries, the said process comprising the steps of
a) grinding the waste cathode blocks to 2 mm down to dust size.
b) reacting the ground materials with chromic acid for 20-90 minutes.
c) washing the reacted product with distilled water till it gel neutralized from extraneous elements followed by drying at 100°C in an oven.
d) subjecting the above treated cathode powder to thermal shock for 2-5 minutes at a temperature ranging from 900 to 1000°C in order to transform the said product to a free-flowing fine graphite powder with average particle size of 20 micro-meter,
e) suspending the above said processed graphite powder in silicone-oils with wide viscosity differences and loading rate of 15-20 w% to obtain the desired colloidal graphite.
In an embodiment of the present invention the colloidal graphite obtained is useful for the high temperature lubrication applications.
The spent/waste cathode blocks were collected from NALCO, Angul. aluminum smelting plant, and ground to various sizes from ½ inch to -125 micron size. These crushed samples were taken into a 500 ml flask and the flask was provided with a stirrer and a thermometer. This assembly was placed inside a small fume cupboard, exhaust of which was passed through a dilute sodium-hydroxide solution.
The said crushed waste cathode powder was then reacted with small amount of chromic acid which in turn was produced by reaction of sodium-dichromate with concentrated (98%) sulfuric acid and cooled to room temperature. Addition of chromic acid was controlled along with stirring the said sample in such a way that reaction temperature do not exceed 140°C but do not fall below 130°C. The reaction is vigorous and when reaction is over, the resulting mixture was diluted with distilled water and allowed to settle for some time. The supernatant liquid was filtered through a sintered gouche funnel. The said mixture was again washed with distilled water and filtered through same sintered gouche crucible untill a neutral filtrate emerged after filtration.
The said treated sample was then dried in an oven at 80-100°C for 2 hours, and thermally shock treated by inserting in a preheated oven at about 950UC for 2-3 minutes.
The said treatment generates a fine free flowing graphite powder of average cruystallite size of about 20 micro-meter as determined by MALVERN particle size analyzer. It was observed the size of the said graphite crystallite was same irrespective of the size of the said starting material although rate of the reaction and time of completion of the reaction depends upon the size of the said starting material. The resultant graphite can also be deashed by standard procedure.
The said graphite powder was then suspended in wide range of viscosities of different silicone-oil to generate the colloidal-graphite solution. For a wide viscosity range of these silicone oils, the loading rate of graphite was found to be 15-20 wt.%. The process brings down F" and CN" concentration from 15 to 0.3% to nil after above treatment.
The following examples are given by the way of illustration and should not be construed to limit the scope of the invention.
EXAMPLE 1 50 gm of the said waste cathode material of size 2-3 mm was reacted with 50 ml of chromic acid in about 20 minutes time and washed with distilled water untill neutral and then dried in an oven at 100°C for 2 hours and then inserted into a heated furnace at 950°C to generate free flowing graphite crystallite with average particle size of 20 micro¬meter. The resultant graphite powder was suspended in silicone oil as shown in Table-1 below with as mentioned loading rate to obtain a satisfactory colloidal-graphite solution :
TABLE-1 Loading rate of processed graphite from 2-3 mm waste cathode powder with wide ranging silicone oil.

(Table Removed)
EXAMPLE 2 100 gm of the said cathode material of size 1/2 inch was reacted with about 100 ml of chromic acid in about 1 hour time and the treated mateiral was washed with distilled water until neutral and then dried in an oven at 100°C, and then was inserted into a preheated furnace at 1000°C for 3 minute to generate a free flowing graphite powder with graphite crystallite size on average being 20 micro-meter (as determined by MALVERN particle size analyzer).
The said graphite crystallites were then suspended in wide ranging viscosities of silicone oils with following loading rates to obtain satisfactory colloidal graphite solution.
TABLE-2 Loading rate of processed graphite from 1/2 inch size waste cathode material with wide viscosity ranging silicone oil at room temperature

(Table Removed)
The main advantages of the present invention are:
1. The process essentially involves only two steps (chemical and physical treatment) of the raw material to generate the final product. Thus, it is fast and easy to carry out.
2. The product is neutral and free flowing in nature, with narrow band of particle size distribution.
3. The process provides a means for safely disposing off waste cathode materials while simultaneously producing a high value product, without causing any environmental pollution.
4. The resultant product is suitable for high temperature lubrication applications.
5. The initial concentration of fluoride in the cathode block was 15% and that of cyanide 0.3%, which after above chemical treatment came down to nil.






We Claim:
1. A process for the preparation of colloidal graphite from waste cathode blocks
generated by aluminum industries, the said process comprising the steps of
a) grinding the waste cathode blocks to 2 mm down to dust size,
b) reacting the ground materials with chromic acid for 20-90 minutes,
c) washing the reacted product with distilled water till it get neutralized from extraneous elements followed by drying at 100°C in an oven.
d) subjecting the above treated cathode powder to thermal shock for 2-5 minutes at a temperature ranging from 900 to 1000°C in order to transform the said product to a free-flowing fine graphite powder with average particle size of 20 micro-meter,
e) suspending the above said processed graphite powder in silicone-oils with wide viscosity differences and loading rate of 15-20 w% to obtain the desired colloidal graphite.

2. A process as claimed in claim 1, wherein the colloidal graphite obtained is useful for the high temperature lubrication applications,
3. A process for the preparation of colloidal graphite from waste cathode blocks generated by aluminum industries substantially as herein described with reference to the examples.

Documents:

999-del-2001-abstract.pdf

999-del-2001-claims.pdf

999-del-2001-complete specification(granted).pdf

999-del-2001-correspondence-others.pdf

999-del-2001-correspondence-po.pdf

999-del-2001-description (complete).pdf

999-del-2001-form-1.pdf

999-del-2001-form-18.pdf

999-del-2001-form-2.pdf

999-del-2001-form-3.pdf


Patent Number 242323
Indian Patent Application Number 999/DEL/2001
PG Journal Number 35/2010
Publication Date 27-Aug-2010
Grant Date 24-Aug-2010
Date of Filing 27-Sep-2001
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 BIMANRANJAN MAZUMDAR SCIENTIST , REGIONAL RESEARCH LABORATORY, BHUBNESHWAR
PCT International Classification Number C01B 31/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA