Title of Invention	"AN IMPROVED PROCESS FOR PRODUCING LOW-CYANIDE CONTENT DRINKABLE WATER FROM HIGH-CYANIDE CONTAINING WASTE WATER DISCHARGED FROM COKE OVEN PLANTS"
Abstract	The invention provides an improved process for producing low cyanide content drinkable water from high cyanide containing waste water discharged from coke oven plants, comprising the following steps in sequence '• (i) magnesia-chrome brick bats separated from slag and metal parts are collected and crushed into sizes smaller than 3 cm in a crushing machine; (ii) the crushed pieces are dry-milled in a ball mill into fines of mesh size 325; (iii) the fines are mixed with alkali such as sodium hydroxide, sodium carbonate, and mixture of sodium carbonate and calcium carbonate at a weight ratio of fines to alkali of 180.5 - 1:2,0; (iv) the mix is calcined at a temperature upto 950°C, preferably at 700-800°C, for 3 to 5 hours; (v) the calcined mix containing sodium chromate formed by reaction between the fines and alkali is cooled in natural air for 15 to 20 hours; (vi) the cooled mix is leached out with hot water at 50-80°C; characterised in that (a) the leached out dilute solution of sodium chromate in water is. concentrated by heating at 50-80°C to increase the concentration of sodium chromate in the solution to 8-10 mg/1; (b) 1 part by volume of concentrated solution of sodium chromate in water and 1 part by volume of sulphuric acid of strength 97-99% are added separately to 500 parts by volume of waste water containing 1 mg/1 cyanide, discharged from coke oven plants; and (c) the mixture is agitated thoroughly for 1 to 3 hours till the cyanide content of the waste water reduces to 0.2 mg/1.

Title of Invention

"AN IMPROVED PROCESS FOR PRODUCING LOW-CYANIDE CONTENT DRINKABLE WATER FROM HIGH-CYANIDE CONTAINING WASTE WATER DISCHARGED FROM COKE OVEN PLANTS"

Abstract

The invention provides an improved process for producing low cyanide content drinkable water from high cyanide containing waste water discharged from coke oven plants, comprising the following steps in sequence '• (i) magnesia-chrome brick bats separated from slag and metal parts are collected and crushed into sizes smaller than 3 cm in a crushing machine; (ii) the crushed pieces are dry-milled in a ball mill into fines of mesh size 325; (iii) the fines are mixed with alkali such as sodium hydroxide, sodium carbonate, and mixture of sodium carbonate and calcium carbonate at a weight ratio of fines to alkali of 180.5 - 1:2,0; (iv) the mix is calcined at a temperature upto 950°C, preferably at 700-800°C, for 3 to 5 hours; (v) the calcined mix containing sodium chromate formed by reaction between the fines and alkali is cooled in natural air for 15 to 20 hours; (vi) the cooled mix is leached out with hot water at 50-80°C; characterised in that (a) the leached out dilute solution of sodium chromate in water is. concentrated by heating at 50-80°C to increase the concentration of sodium chromate in the solution to 8-10 mg/1; (b) 1 part by volume of concentrated solution of sodium chromate in water and 1 part by volume of sulphuric acid of strength 97-99% are added separately to 500 parts by volume of waste water containing 1 mg/1 cyanide, discharged from coke oven plants; and (c) the mixture is agitated thoroughly for 1 to 3 hours till the cyanide content of the waste water reduces to 0.2 mg/1.

Full Text	The present invention relates to an improved process for producing low-cyanide content drinkable water from high-cyanide containing waste water discharged from coke oven plants. The invention relates more particularly to a process in which the waste water discharged from coke oven plants, containing cyanide in excess of the permissible limit of 0.3 mg/1 is brought within limit with nascent chromic acid addition which is prepared from magnesia-chrome brick bats available in plenty as waste material in the form of worn-out magnesia-chrome bricks used for lining furnaces in steel plants and hence at a much reduced cost. In the existing process sodium hypochlorite is used for treating the waste water discharged from coke oven plants. The drawbacks of the existing process are : (a) cost of sodium hypochlorite being relatively high (around Rs.9000/- per ton), the process is expensive; and (b) the storage life of sodium hypochlorite being relatively short (2 weeks maximum), a recurring cost is incurred for its continuous supply. The object of the invention is to provide a relatively low cost process for reducing the cyanide content of waste water discharged from coke oven plants to a level below the permissible level of 0.3 mg/1 to make the water amenable for municipal water supply system. The other object is to find a useful application of the waste magnesia-chrome brick bats which are available in plenty in steel plants. Yet another object is to prevent pollution of natural water sources like rivers, dams and lakes with high if at times cyanide content waste waters discharged from coke oven plants. The invented process comprises the following steps in sequence :- (a) collecting waste magnesia-chrome brick bats separated from slag and metal parts; (b) crushing and grinding of the brick bats to sizes below 3 cm in a crushing machine; (c) milling the brick bats in a ball mill with equal weight of balls to produce magnesia chrome brick bat fines of mesh size 325; (d) mixing the magnesia-chrome brick bat fines with alkali such as sodium hydroxide, sodium carbonate and mixture of sodium carbonate and calcium carbonate, at a weight ratio of the fines to alkali of 1:0.5-1:2.0; (e) calcining the mix at a temperature upto 950°C, preferably at 700 to 800°C, for 3 to 5 hours to produce sodium chromate by chemical reaction between the alkali and the magnesia-chrome brick bat fines; (f) cooling the mix containing sodium chromate formed in natural air for 15 to 20 hours; (g) leaching the cooled mix with hot water at 50-80°C till the mix is free of its colouring materials to produce a dilute solution of sodium chromate in water; (h) concentrating the dilute solution of sodium chrornate in water by heating at a temperature of 50-80°C till the concentration of sodium chromate increases to 8 - 10 mg/1; (i) adding separately 1 part by volume the concentrated solution of sodium chromate in water and 1 part by volume of sulphuric acid of 97-9956, preferably 98%,strength to 500 parts by volume of waste water from coke oven plants, containing around 1 mg/1 of cyanide,discharged; and (J) agitating the mixture thoroughly for 1 to 3 hours till the cyanide content of the waste water reduces to a level around 0.2 mg/1 by oxidation of cyanide into water insoluble solid form by the nascent chromic acid produced by chemical reaction between sodium chromate and sulphuric acid in step (i). Because of the use of waste magnesia-chrome brick bats as the raw material for producing nascent chromic acid to oxidise the cyanide in waste water, the cost of the invented process is significantly lower in comparison with the existing process in which appreciably expensive sodium hypochlorite is used for reducing the cyanide content in waste water. Besides providing a useful application of the waste magnesia-chrome brick bats, the invented process prevents also pollution of natural water sources for municipal water supply like rivers, dams and lakes by high cyanide containing waste even if water discharged from coke oven plants. We Claim :- 1. An improved process for producing low-cyanide content drinkable water from high-cyanide containing waste water discharged from coke oven plants, the said process comprises the following steps in sequence : (i) magnesia-chrome brick bats separated from slag and metal parts are collected and crushed into sizes smaller than 3 cm in a crushing machine; (ii) the crushed pieces are dry-milled in a ball mill into fines of mesh size 325; (iii) the fines are mixed v/ith alkali such as sodium hydroxide, sodium carbonate, and mixture of sodium carbonate and calcium carbonate at a weight ratio of fines to alkali of 1:0.5 - 1:2.0; (iv) the mix is calcined at a temperature up to 950°C, preferably at 700-800°C, for 3 to 5 hours; (v) the calcined mix containing sodium chromate formed by reaction between the fines and alkali is cooled in natural air for 15 to 20 hours; (vi) the cooled mix is leached out v/ith hot water at 50-80°C; (vii) the leached out dilute solution of sodium chromate in water is concentrated by heating at 50-80°C to increase the concentration of sodium chromate in the solution to 8-10 mg/1; characterised in that 1 part by volume of concentrated solution of sodium chromate in water and 1 part by volume of sulphuric acid of strength 97-99% are added separately to 500 parts by volume of waste water containing 1 mg/1 cyanide, discharged from coke oven plants; and the mixture is agitated thoroughly for 1 to 3 hours till the cyanide content of the waste water reduces to 0.2 mg/1 by oxidation of cyanide into water insoluble solid form by the nascent chromic acid produced by chemical reaction between sodium chromate and sulphuric acid. 2. The process as claimed in claim 1, wherein the concentration of sodium chromate in the solution is 9 mg/1. 3. The process as claimed in claim 1 or 2, wherein the sulphuric acid is of strength

Full Text

The present invention relates to an improved process for producing low-cyanide content drinkable water from high-cyanide containing waste water discharged from coke oven plants.
The invention relates more particularly to a process in which the waste water discharged from coke oven plants, containing cyanide in excess of the permissible limit of 0.3 mg/1 is brought within limit with nascent chromic acid addition which is prepared from magnesia-chrome brick bats available in plenty as waste material in the form of worn-out magnesia-chrome bricks used for lining furnaces in steel plants and hence at a much reduced cost.
In the existing process sodium hypochlorite is used for treating the waste water discharged from coke oven plants. The drawbacks of the existing process are : (a) cost of sodium hypochlorite being relatively high (around Rs.9000/- per ton), the process is expensive; and (b) the storage life of sodium hypochlorite being relatively short (2 weeks maximum), a recurring cost is incurred for its continuous supply.
The object of the invention is to provide a relatively low cost process for reducing the cyanide content of waste water discharged from coke oven plants to a level below the permissible level of 0.3 mg/1 to make the water amenable for municipal water supply system.
The other object is to find a useful application of the waste magnesia-chrome brick bats which are available in plenty in steel plants.
Yet another object is to prevent pollution of
natural water sources like rivers, dams and lakes with high
if at times cyanide content waste waters discharged from coke oven plants.
The invented process comprises the following steps in sequence :-
(a) collecting waste magnesia-chrome brick bats separated
from slag and metal parts;
(b) crushing and grinding of the brick bats to sizes
below 3 cm in a crushing machine;
(c) milling the brick bats in a ball mill with equal
weight of balls to produce magnesia chrome brick bat fines
of mesh size 325;
(d) mixing the magnesia-chrome brick bat fines with
alkali such as sodium hydroxide, sodium carbonate and mixture
of sodium carbonate and calcium carbonate, at a weight ratio
of the fines to alkali of 1:0.5-1:2.0;
(e) calcining the mix at a temperature upto 950°C,
preferably at 700 to 800°C, for 3 to 5 hours to produce
sodium chromate by chemical reaction between the alkali and
the magnesia-chrome brick bat fines;
(f) cooling the mix containing sodium chromate formed
in natural air for 15 to 20 hours;
(g) leaching the cooled mix with hot water at 50-80°C till the mix is free of its colouring materials to produce a dilute solution of sodium chromate in water;
(h) concentrating the dilute solution of sodium chrornate in water by heating at a temperature of 50-80°C till the concentration of sodium chromate increases to 8 - 10 mg/1;
(i) adding separately 1 part by volume the concentrated solution of sodium chromate in water and 1 part by volume of sulphuric acid of 97-9956, preferably 98%,strength to 500 parts by volume of waste water from coke oven plants, containing around 1 mg/1 of cyanide,discharged; and
(J) agitating the mixture thoroughly for 1 to 3 hours till the cyanide content of the waste water reduces to a level around 0.2 mg/1 by oxidation of cyanide into water insoluble solid form by the nascent chromic acid produced by chemical reaction between sodium chromate and sulphuric acid in step (i).
Because of the use of waste magnesia-chrome brick bats as the raw material for producing nascent chromic acid to oxidise the cyanide in waste water, the cost of the invented process is significantly lower in comparison with the existing process in which appreciably expensive sodium hypochlorite is used for reducing the cyanide content in waste water.
Besides providing a useful application of the waste magnesia-chrome brick bats, the invented process prevents also pollution of natural water sources for municipal water supply
like rivers, dams and lakes by high cyanide containing waste
even if water discharged from coke oven plants.

We Claim :-
1. An improved process for producing low-cyanide content drinkable water from high-cyanide containing waste water discharged from coke oven plants, the said process comprises the following steps in sequence : (i) magnesia-chrome brick bats separated from slag and metal parts are collected and crushed into sizes smaller than 3 cm in a crushing machine; (ii) the crushed pieces are dry-milled in a ball mill into fines of mesh size 325; (iii) the fines are mixed v/ith alkali such as sodium hydroxide, sodium carbonate, and mixture of sodium carbonate and calcium carbonate at a weight ratio of fines to alkali of 1:0.5 - 1:2.0; (iv) the mix is calcined at a temperature up to 950°C, preferably at 700-800°C, for 3 to 5 hours; (v) the calcined mix containing sodium chromate formed by reaction between the fines and alkali is cooled in natural air for 15 to 20 hours; (vi) the cooled mix is leached out v/ith hot water at 50-80°C; (vii) the leached out dilute solution of sodium chromate in water is concentrated by heating at 50-80°C to increase the concentration of sodium chromate in the solution to 8-10 mg/1; characterised in that 1 part by volume of concentrated solution of sodium chromate in water and 1 part by volume of sulphuric acid of strength 97-99% are added separately to 500 parts by volume of waste water containing 1 mg/1 cyanide, discharged from coke oven plants; and the mixture is agitated thoroughly for 1 to 3 hours till the cyanide content of the waste water reduces to 0.2 mg/1 by oxidation of cyanide into water insoluble solid form by the nascent chromic acid produced by chemical reaction between sodium chromate and sulphuric acid.
2. The process as claimed in claim 1, wherein the concentration of sodium chromate in the solution is 9 mg/1.
3. The process as claimed in claim 1 or 2, wherein the sulphuric acid is of strength

Documents:

250-del-1999-abstract.pdf

250-del-1999-claims.pdf

250-del-1999-correspondence-others.pdf

250-del-1999-correspondence-po.pdf

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

250-del-1999-form-1.pdf

250-del-1999-form-19.pdf

250-del-1999-form-2.pdf

250-del-1999-form-4.pdf

250-del-1999-gpa.pdf

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Patent Number

231004

Indian Patent Application Number

250/DEL/1999

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

28-Feb-2009

Date of Filing

15-Feb-1999

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, A.GOVT.OF INDIA ENTERPRISE,HAVING ITS REGISTERED OFFICE AT ISPAT BHAWAN,LODHI ROAD, NEW DELHI-110003.

Inventors:

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

PCT International Classification Number

C02F 5/06

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA