Title of Invention	"A PROCESS FOR PRODUCING MAGNESIA DUST AND CRYSTALS OF SODIUM SULPHATE AND CHROMIC ACID FROM WASTE MAG-CHROME BRICK BATS"
Abstract	The invention provides a process for producing chromic acid along with sodium sulphate and magnesis dust as by-products from waste mag-chrome brick bats, comprising the steps: (i) crushing and grinding mag-chrome brick bats separated from slag and metal parts into sizes below 3 cm in a crushing machine; (ii) milling crushed and ground brick bats in a dry ball mill in presence of equal weight of balls to produce fines of mesh size (-) 325; (iii) mi.jd.ng the fines with alkali, such as sudium hydroxide or sodium carbonate or a mixture of sodium carbonate and calcium carbonate, in the ratio of 1:0.5 to 1:2 by weight; (iv) calcining the mix in an electrically operated canthol furnace at a temperature upto 950°C for 3-7 hours to produce a mass containing sodium chromate and magnesia dust; (v) cooling the mass for 15-20 hours in natural air; (vi) leaching out the cooled mass with hot v/ater at a temperature of 50-80°C for a period required to make the mass free from its colouring materials; (vii) drying the leached out mass in ovens at 50-80 G to obtain magnesia dust as a by-product; (viii) adding concentrated sulphuric acid to the leached out solution in an amount required to make pH of the latter to be below 7.0, and to convert the sodium chromate contained in the solution into chromic acid, and obtanining sodium sulphate as a by-product; (ix) concentrating the solution to the specific gravity of 1.4-1.6 by heating the solution on electrically operated heaters; (x) separating the sodium sulphate crystals from the solution by decantation in shallow enamelled trays till the solution cools to room temperature; and (xi) drying the supernatant solution separated by decantation in ovens at a temperature of 50-60°C, to obtain dried chromic acid crystals as the main product.

Title of Invention

"A PROCESS FOR PRODUCING MAGNESIA DUST AND CRYSTALS OF SODIUM SULPHATE AND CHROMIC ACID FROM WASTE MAG-CHROME BRICK BATS"

Abstract

The invention provides a process for producing chromic acid along with sodium sulphate and magnesis dust as by-products from waste mag-chrome brick bats, comprising the steps: (i) crushing and grinding mag-chrome brick bats separated from slag and metal parts into sizes below 3 cm in a crushing machine; (ii) milling crushed and ground brick bats in a dry ball mill in presence of equal weight of balls to produce fines of mesh size (-) 325; (iii) mi.jd.ng the fines with alkali, such as sudium hydroxide or sodium carbonate or a mixture of sodium carbonate and calcium carbonate, in the ratio of 1:0.5 to 1:2 by weight; (iv) calcining the mix in an electrically operated canthol furnace at a temperature upto 950°C for 3-7 hours to produce a mass containing sodium chromate and magnesia dust; (v) cooling the mass for 15-20 hours in natural air; (vi) leaching out the cooled mass with hot v/ater at a temperature of 50-80°C for a period required to make the mass free from its colouring materials; (vii) drying the leached out mass in ovens at 50-80 G to obtain magnesia dust as a by-product; (viii) adding concentrated sulphuric acid to the leached out solution in an amount required to make pH of the latter to be below 7.0, and to convert the sodium chromate contained in the solution into chromic acid, and obtanining sodium sulphate as a by-product; (ix) concentrating the solution to the specific gravity of 1.4-1.6 by heating the solution on electrically operated heaters; (x) separating the sodium sulphate crystals from the solution by decantation in shallow enamelled trays till the solution cools to room temperature; and (xi) drying the supernatant solution separated by decantation in ovens at a temperature of 50-60°C, to obtain dried chromic acid crystals as the main product.

Full Text	The present invention relates to a process for producing magnesia dust and crystals of sodium sulphate and chromic acid from waste mag-chrome brick bats. The invention relates more particularly to treating readily available waste mag-chrome bricks bats with alkali like sodium hydroxide solution to produce sodium chromate and magnesia dust, treating the sodium chromate produced with sulphuric acid to produce chromic acid and sodium sulphate. The existing process for producing chromic acid is based on the use of chrome ores containing sodium dichromate as the raw materials. The supply of said chrome ores at present is decreasing with consequent increase in the cost of chromic acid produced in the existing process, which comprises the steps :- (a) Dehydrated sodium dichromate from the ores is mixed with sulphuric acid (Specific gravity 1.84) in a heavy walled steel or cast-iron reactor heated externally and provided with a sweep agitator to produce chromic acid, sodium bisulphate and water. Water is driven off and the hydrous sodium bisulphate melts at about 1600C. As the temperature is gradually increased, the molten sodium bisulphate provides a heat transfer medium for melting the chromic acid at 197°C without appreciable decomposition; (b) As soon as the chromic acid melts, the agitator is stopped and the mixture separates into a heavy layer of molten chromic acid and a light layer of molten sodium bisulphate; (c) The chromic acid is trapped and flaked on water-cooled rolls to produce it in its commercial form; and (d) The sodium bisulphate containing dissolved CrO3 and soluble and insoluble chromic sulphates is subjected to the treating operation for purification. The object of the invention is to provide a process for producing sodium sulphate and magnesia dust and chromic acid at a reduced cost from waste mag-chrome brick bats available readily. The invented process comprises the following steps in sequence :- (a) collecting mag-chrome brick bats separated from slag and metal parts; (b) crushing and grinding the brick bats in a crushing machine to reduce the size of the same to be less than 3 cm; (c) milling the crushed brick bats in a dry ball mill, charging brick bats and the balls in the ratio of 1 : 1 by weight to produce brick bat fines of size 325 mesh; (d) mixing brick bat fines with alkali such as sodium hydroxide or sodium carbonate or mixture of sodium carbonate and calcium carbonate, in the ratio of 1:0.5 to 1:2 by weight; (e) calcining the mix to red heat in an electrically operated canthol furnace at a temperature upto 950°C, preferably at 700-800°C, for 3-7 hours to produce a mass containing sodium chromate and magnesia dust; (f) cooling the calcined mass for 15 to 20 hours in natural air; (g) leaching out the cooled mass with hot water at a temperature of 50-80°C in plastic enamelled wares for 2-5 hours till the leached mass becomes free from its colouring materials; (h) drying the leached out mass in ovens at 50-80°C to obtain magnesia dust; (i) adding concentrated sulphuric acid to the leached out solution to make the pH of the latter to be below 7.0, preferably 6.0-6.5, and convert the sodium chromate in the solution into chromic acid and sodium sulphate; (j) concentrating the solution to be of specific gravity 1.4-1.6 by heating the same on electrically operated heaters; (k) separating sodium sulphate crystals from the concentrated solution by decantation in shallow enamelled trays till the solution cools to room temperature; and (1) drying the supernatant solution separated by decantation in ovens at a low temperature, preferably, 50-60°C to obtain dried chromic acid crystals. The invented process has been found to be economical compared with the existing process of producing chromic acid from chrome ores because of using readily available waste mag-chrome brick bats as the raw material and production of sodium sulphate and magnesia dust as valuable products and chromic acid in its nascent form which can be stored without any degradation. We Claim :- 1. A process for producing magnesia dust and crystals of sodium sulphate and chromic acid from waste mag-chrome brick bats, characterised in that the said process comprises the following steps in sequence : (i) mag-chrome brick bats separated from slag and metal parts are crushed and ground into sizes below 3 cm in a crushing machine; (ii) crushed and ground brick bats are milled in a dry ball mill in presence of equal weight of balls to produce fines of mesh size 325; (iii) the fines are mixed with sodium hydroxide or sodium carbonate or a mixture of sodium carbonate and calcium carbonate in the ratio of 1:0.5 to 1:2 by weight; (iv) the mix is calcined in an electrically operated canthol furnace at a temperature upto 950°C for 3-7 hours to produce a mass containing sodium chromate and magnesia dust; (v) cooling the mass for 15-20 hours in natural air; (vi) leaching out the cooled mass with hot water at a temperature of 50-80°C in plastic enamelled wares for 2-3 hours to make the mass free from its colouring materials; (vii) the leached out mass is dried in ovens at 50-80°C to obtain dry magnesia dust; (viii) concentrated sulphuric acid is added to the leached out solution in an amount required to make pH of the latter to be 6,0-6.5, and to convert the sodium chromate contained in the solution into chromic acid, and sodium sulphate; (ix) the solution is concentrated to the specific gravity of 1.4-1.6 by heating the solution on electrically operated heaters; (x) sodium sulphate crystals are separated from the solution by decantation in shallow enamelled trays till the solution cools to room temperature; and (xi) the supernatent solution separated by decantation is dried in ovens at a temperature of 50-60°C, to obtain dried chromic acid crystals. 2. The process as claimed in claim 1, wherein the mix of brick bat fines and alkali is calcined at 700-800°C.

Full Text

The present invention relates to a process for producing magnesia dust and crystals of sodium sulphate and chromic acid from waste mag-chrome brick bats.
The invention relates more particularly to treating readily available waste mag-chrome bricks bats with alkali like sodium hydroxide solution to produce sodium chromate and magnesia dust, treating the sodium chromate produced with sulphuric acid to produce chromic acid and sodium sulphate.
The existing process for producing chromic acid is based on the use of chrome ores containing sodium dichromate as the raw materials. The supply of said chrome ores at present is decreasing with consequent increase in the cost of chromic acid produced in the existing process, which comprises the steps :-
(a) Dehydrated sodium dichromate from the ores is mixed with sulphuric acid (Specific gravity 1.84) in a heavy
walled steel or cast-iron reactor heated externally and provided
with a sweep agitator to produce chromic acid, sodium bisulphate
and water. Water is driven off and the hydrous sodium bisulphate melts at about 1600C. As the temperature is gradually increased, the molten sodium bisulphate provides a heat transfer medium for melting the chromic acid at 197°C without appreciable decomposition; (b) As soon as the chromic acid melts, the agitator is stopped and the mixture separates into a heavy layer of molten chromic acid and a light layer of molten sodium bisulphate; (c) The chromic acid is trapped and flaked on water-cooled rolls to produce it in its commercial form; and (d) The sodium bisulphate containing dissolved CrO3 and soluble and

insoluble chromic sulphates is subjected to the treating operation for purification.
The object of the invention is to provide a process for producing sodium sulphate and magnesia dust and chromic acid at a reduced cost from waste mag-chrome brick bats available readily.
The invented process comprises the following steps in sequence :-
(a) collecting mag-chrome brick bats separated from slag
and metal parts;
(b) crushing and grinding the brick bats in a crushing
machine to reduce the size of the same to be less than 3 cm;
(c) milling the crushed brick bats in a dry ball mill,
charging brick bats and the balls in the ratio of 1 : 1 by weight
to produce brick bat fines of size 325 mesh;
(d) mixing brick bat fines with alkali such as sodium
hydroxide or sodium carbonate or mixture of sodium carbonate
and calcium carbonate, in the ratio of 1:0.5 to 1:2 by weight;
(e) calcining the mix to red heat in an electrically
operated canthol furnace at a temperature upto 950°C, preferably
at 700-800°C, for 3-7 hours to produce a mass containing sodium
chromate and magnesia dust;
(f) cooling the calcined mass for 15 to 20 hours in natural
air;
(g) leaching out the cooled mass with hot water at a
temperature of 50-80°C in plastic enamelled wares for 2-5 hours
till the leached mass becomes free from its colouring materials;
(h) drying the leached out mass in ovens at 50-80°C to obtain magnesia dust;

(i) adding concentrated sulphuric acid to the leached out solution to make the pH of the latter to be below 7.0, preferably 6.0-6.5, and convert the sodium chromate in the solution into chromic acid and sodium sulphate;
(j) concentrating the solution to be of specific gravity 1.4-1.6 by heating the same on electrically operated heaters;
(k) separating sodium sulphate crystals from the concentrated solution by decantation in shallow enamelled trays till the solution cools to room temperature; and
(1) drying the supernatant solution separated by decantation in ovens at a low temperature, preferably, 50-60°C to obtain dried chromic acid crystals.
The invented process has been found to be economical compared with the existing process of producing chromic acid from chrome ores because of using readily available waste mag-chrome brick bats as the raw material and production of sodium sulphate and magnesia dust as valuable products and chromic acid in its nascent form which can be stored without any degradation.

We Claim :-
1. A process for producing magnesia dust and crystals of sodium sulphate and chromic acid from waste mag-chrome brick bats, characterised in that the said process comprises the following steps in sequence : (i) mag-chrome brick bats separated from slag and metal parts are crushed and ground into sizes below 3 cm in a crushing machine; (ii) crushed and ground brick bats are milled
in a dry ball mill in presence of equal weight of balls to produce
fines of mesh size 325; (iii) the fines are mixed with sodium hydroxide
or sodium carbonate or a mixture of sodium carbonate and calcium carbonate in the ratio of 1:0.5 to 1:2 by weight; (iv) the mix is calcined in an electrically operated canthol furnace at a temperature upto 950°C for 3-7 hours to produce a mass containing sodium chromate and magnesia dust; (v) cooling the mass for 15-20 hours in natural air; (vi) leaching out the cooled mass with hot water at a temperature of 50-80°C in plastic enamelled wares for 2-3 hours to make the mass free from its colouring materials; (vii) the leached out mass is dried in ovens at 50-80°C to obtain dry magnesia dust; (viii) concentrated sulphuric acid is added to the leached out solution in an amount required to make pH of the latter to be 6,0-6.5, and to convert the sodium chromate contained in the solution into chromic acid, and sodium sulphate; (ix) the solution is concentrated to the specific gravity of 1.4-1.6 by heating the solution on electrically operated heaters; (x) sodium sulphate crystals are separated from the solution by decantation in shallow enamelled trays till the solution cools to room temperature; and (xi) the

supernatent solution separated by decantation is dried in ovens at a temperature of 50-60°C, to obtain dried chromic acid crystals.
2. The process as claimed in claim 1, wherein the mix of brick bat fines and alkali is calcined at 700-800°C.

Documents:

122-del-1999-abstract.pdf

122-del-1999-claims.pdf

122-del-1999-correspondence-others.pdf

122-del-1999-correspondence-po.pdf

122-del-1999-description (complete).pdf

122-del-1999-form-1.pdf

122-del-1999-form-19.pdf

122-del-1999-form-2.pdf

122-del-1999-form-4.pdf

122-del-1999-gpa.pdf

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Patent Number

230915

Indian Patent Application Number

122/DEL/1999

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

28-Feb-2009

Date of Filing

20-Jan-1999

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

ISPAT BHAWAN, LODI ROAD, NEW DELHI – 110003.

Inventors:

#	Inventor's Name	Inventor's Address
1	SUBRATA BHATTACHARYA	RDCIS/SAIL, DORANDA, RANCHI-834002, INDIA.
2	HARI DUTTA PANDEY	RDCIS/SAIL, DORANDA, RANCHI-834002, INDIA.
3	PRANAB DAS	RDCIS/SALL, DORANDA, RANCHI-834002, INDIA.

PCT International Classification Number

B22F 8/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA