Title of Invention	AN IMPROVED PROCESS FOR THE TREATMENT OF PAPER MILL BLACK LIQUOR TO PRODUCE CLEAN WATER
Abstract	An improved process for treatment of paper mill black waste liquor to produce clean water which comprises pre-conditioning the black liquor by known method, adding coagulating agents and cationic magnofloc in the range of 50 mg to 150mg/l and mixing well, allowing to settle for a period ranging from 60 to 180 minutes, separating the liquid from residue and then bleaching the solution with chlorine for a period ranging from 60-180 minutes to get environmentally acceptable clean water.

Title of Invention

AN IMPROVED PROCESS FOR THE TREATMENT OF PAPER MILL BLACK LIQUOR TO PRODUCE CLEAN WATER

Abstract

An improved process for treatment of paper mill black waste liquor to produce clean water which comprises pre-conditioning the black liquor by known method, adding coagulating agents and cationic magnofloc in the range of 50 mg to 150mg/l and mixing well, allowing to settle for a period ranging from 60 to 180 minutes, separating the liquid from residue and then bleaching the solution with chlorine for a period ranging from 60-180 minutes to get environmentally acceptable clean water.

Full Text	This invention relates to an improved process for treatment of paper mill black liquor to produce enviornmontally accoptable clean water The black liquor discharged from paper mills during processing is highly polluting in nature. The large quantities of the odorous waste are a serious environmental problem having high Biochemical Oxygen Demand (B.O.D) and Chemical Oxygen demand (C.O.D), lots of fibre particles and colour. Its high B.O.D and C.O.D values are threat to aquatic life by depleting oxygen, contaminating ground water,polluting environment and also destroy soil structure. Other problem for recycling black liquor is the presence of silica, which affects the evaporator operation. In large mills integrated with recovery system, the liquor is concentrated to about 65% solid and burnt in the recovery boiler to recover NaOH and energy. In small mills, due to high silica and high capital cost involved in regeneration/treatment, the liquor generated is discharged as effluent. Dissolved organic materials from paper mill waste water was separated by coagulation using alum, Fe2 (SO4)3 and bentonite. The efficiency of removal depends on the concentration of organics in the waste water, pH , and residual Al and Fe salts. Silica (Eur. Pat Appl EP 249,545) is separated from black liquor with a CO2 containing gas to lower its pH , passing the liquor through ≥1 cyclone separators, seeding the separated liquor to give a clarified liquor and a silica sediment. The alkaline ( pH -10) straw pulp black liquor discharged by the Chinese paper making industry was coagulated with alum. The resultant sulphate ion in the filtrate being precipitated as calcium sulphate by the addition of calcium oxide. The CaS04 is reacted with ammonium carbonate to form a liquid fertilizer. The COD of the resultant filtrate reduced to 600 mg/l. But each of them have certain disadvantages associated with concentration of organic matter in waste water, pH , raw material and chemical treatment of pulp. This invention relates to the chemical treatment of black liquor generated from paper mills using particularly the one bamboo/ straw/ grass/ bagasse as raw materials to bring down B.O.D to environmentally acceptable limits by removing organic matter. The residue obtained from the liquor contain more than 50% organic matter. The organic material has high calorific value and can be utilised to recover energy. The process of the present invention brings down B.O.D to around 30 ppm by treating with settling agent and flocculant followed by bleaching. The aim of the process invention is to remove silica and organic matter followed by bleaching,in order to bring down B.O.D to approximately 30 ppm and also liquor environmentally acceptable. The main finding of the process of this invention is to reduce the B.O.D load of the black liquor from around 3000ppm to approximately 30ppm through clariflocculation using ferric alum and cationic magnofloc (Mag floe 352/Zetag 32) followed by bleaching with chlorine gas. Accordingly, the present invention provides an improved process for treatment of paper mill black waste liquor to produce clean water which comprises ; i) preconditioning the black liquor, having about 2800 to 3000 ppm Biochemical Oxygen Demand (BOD), to a pH ranging from 3.0 to 7.0 by known method; ii) adding 0.2 to 0.6 g% w/v coagulating agents selected from alum, ferric alum or mixture thereof and cationic magnofloc in the range of 50 mg to 150mg/l and mixing well; iii) allowing to settle for a period ranging from 60 to 180 minutes; iv) separating the liquid from residue by conventional methods, then bleaching the solution with chlorine with concentration ranging from 5-30 g/1 for a period ranging from 60-180 minutes to get environmentally acceptable clean water. The mixing may be effected by bubbling air. The settling may be carried out for 30 to 180 minutes. The separation of r esidue and liquid may be conducted by conventional methods such as sedimentation. The bleaching may be effected by passing chlorine gas in a known manner. The process is further illustrated by the following examples: Example :1 10 litrs. Black liquor having B.O.D. level 2800 ppm, 2.8gm/l, suspended solids, gm/1 silica, is pre-conditioned in a settling tank at pH-5, the pre- conditioned solution is dosed with 0.4% ferric alum and 0.005% cationic magnofloc. The solution is mixed throughly by bubbling air and allowed to settle for 60 min. The residue is separated . The liquor is analysed for B.O.D and it is found to be 350 ppm. The B.O.D is further brought down to 30 ppm by bleaching the solution with 5 g/l of chlorine for 60 minutes. The final water obtained is within the environmentally acceptable limits. EXAMPLE: II 10 litrs. black liquor having B.O.D level 2800 ppm, 2.8gm/l, suspended solids, 5 gm/l silica, is pre-conditioned in a settling tank at pH 5, the preconditioned solution is dosed with 0.2% ferric alum and 0.01% cationic magnofloc. The solution is mixed throughly by bubbling air and allowed to settle for 180 min. The residue is separated . The liquor is analysed for B.O.D and it is found to be 300 ppm. The B.O.D is further brought down to 32 ppm by bleaching the solution with 5 g/l of chlorine for 180 minutes. The final water obtained is within the environmentally acceptable limits. EXAMPLE: III 10 litrs. black liquor having B.O.D level 2800 ppm, 2.8gm/l, suspended solids, 4.7 gm/l silica, is pre-conditioned in a settling tank at pH 5, the preconditioned solution is dosed with 0.6% ferric alum and 0.0015% cationic magnofloc. The solution is mixed throughly by bubbling air and allowed to settle for 30 min. The residue is separated . The liquor is analysed for B.O.D and it is found to be 300 ppm. The B.O.D is further brought down to 30 ppm by bleaching the solution with 30 g/l of chlorine for 60 minutes. The final solution obtained is within the environmentally acceptable limits. The advantages of the process are:- 1. The process wherein the black liquors generated using different raw materials like bamboo/straw/grass/bagasse can be treated. 2. The process wherein the pre-conditioning of the liquor is carried out at a near neutral pH. 3. The process wherein the settling is faster using flocculant. The process wherein the equipment used is a simple settling tank and can be easily fabricated. 4. The process wherein the reagents used are in ppm and hence the process can be easily commercialised. 5. The residue obtained from the liquor contain more than 50% organic matter. The organic material has high calorific value and can be utilised to recover energy. We Claim: 1. An improved process for treatment of paper mill black waste liquor to produce clean water which comprises ; i) pre-conditioning the black liquor, having about 2800 to 3000 ppm Biochemical Oxygen Demand (BOD), to a pH ranging from 3.0 to 7.0 by known method ii) adding 0.2 to 0.6 g% w/v coagulating agents selected from alum, ferric alum or mixture thereof and cationic magnofloc in the range of 50 mg to 150mg/l and mixing well, iii) allowing to settle for a period ranging from 60 to 180 minutes, iv) separating the liquid from residue by conventional methods, then bleaching the solution with chlorine with concentration ranging from 5-30 g/1 for a period ranging from 60-180 minutes to get environmentally acceptable clean water. 2. An improved process for treatment of paper mill black waste liquor to produce clean water substantially as here in described with reference to the examples.

Full Text

This invention relates to an improved process for treatment of paper mill black liquor to produce enviornmontally accoptable clean water
The black liquor discharged from paper mills during processing is highly polluting in nature. The large quantities of the odorous waste are a serious environmental problem having high Biochemical Oxygen Demand (B.O.D) and Chemical Oxygen demand (C.O.D), lots of fibre particles and colour. Its high B.O.D and C.O.D values are threat to aquatic life by depleting oxygen, contaminating ground water,polluting environment and also destroy soil structure. Other problem for recycling black liquor is the presence of silica, which affects the evaporator operation. In large mills integrated with recovery system, the liquor is concentrated to about 65% solid and burnt in the recovery boiler to recover NaOH and energy. In small mills, due to high silica and high capital cost involved in regeneration/treatment, the liquor generated is discharged as effluent. Dissolved organic materials from paper mill waste water was separated by coagulation using alum, Fe2 (SO4)3 and bentonite. The efficiency of removal depends on the concentration of organics in the waste water, pH , and residual Al and Fe salts. Silica (Eur. Pat Appl EP 249,545) is separated from black liquor with a CO2 containing gas to lower its pH , passing the liquor through ≥1 cyclone separators, seeding the separated liquor to give a clarified liquor and a silica sediment.
The alkaline ( pH -10) straw pulp black liquor discharged by the Chinese paper making industry was coagulated with alum. The resultant sulphate ion in the filtrate being precipitated as calcium sulphate by the addition of calcium oxide. The CaS04 is reacted with ammonium carbonate to form a liquid fertilizer. The COD of the resultant filtrate reduced to 600 mg/l. But each of them have certain disadvantages associated with concentration of organic matter in waste water, pH , raw material and chemical treatment of pulp.
This invention relates to the chemical treatment of black liquor generated from paper mills using particularly the one bamboo/ straw/ grass/ bagasse as raw materials to bring down B.O.D to environmentally acceptable limits by removing organic matter. The residue obtained from the liquor contain more than 50% organic matter. The organic material has high calorific value and can be utilised to recover energy.
The process of the present invention brings down B.O.D to around 30 ppm by treating with settling agent and flocculant followed by bleaching. The aim of the process invention is to remove silica and organic matter followed by bleaching,in order to bring down B.O.D to approximately 30 ppm and also liquor environmentally acceptable.
The main finding of the process of this invention is to reduce the B.O.D load of the black liquor from around 3000ppm to approximately 30ppm
through clariflocculation using ferric alum and cationic magnofloc (Mag floe 352/Zetag 32) followed by bleaching with chlorine gas.
Accordingly, the present invention provides an improved process for treatment of paper mill black waste liquor to produce clean water which comprises ; i) preconditioning the black liquor, having about 2800 to 3000 ppm Biochemical Oxygen Demand (BOD), to a pH ranging from 3.0 to 7.0 by known method; ii) adding 0.2 to 0.6 g% w/v coagulating agents selected from alum, ferric alum or mixture thereof and cationic magnofloc in the range of 50 mg to 150mg/l and mixing well; iii) allowing to settle for a period ranging from 60 to 180 minutes; iv) separating the liquid from residue by conventional methods, then bleaching the solution with chlorine with concentration ranging from 5-30 g/1 for a period ranging from 60-180 minutes to get environmentally acceptable clean water.
The mixing may be effected by bubbling air.
The settling may be carried out for 30 to 180 minutes.
The separation of r esidue and liquid may be conducted by conventional methods such as sedimentation.
The bleaching may be effected by passing chlorine gas in a known manner.
The process is further illustrated by the following examples: Example :1
10 litrs. Black liquor having B.O.D. level 2800 ppm, 2.8gm/l, suspended solids, gm/1 silica, is pre-conditioned in a settling tank at pH-5, the pre-
conditioned solution is dosed with 0.4% ferric alum and 0.005% cationic magnofloc. The solution is mixed throughly by bubbling air and allowed to settle for 60 min. The residue is separated . The liquor is analysed for B.O.D and it is found to be 350 ppm. The B.O.D is further brought down to 30 ppm by bleaching the solution with 5 g/l of chlorine for 60 minutes. The final water obtained is within the environmentally acceptable limits.
EXAMPLE: II
10 litrs. black liquor having B.O.D level 2800 ppm, 2.8gm/l, suspended solids, 5 gm/l silica, is pre-conditioned in a settling tank at pH 5, the preconditioned solution is dosed with 0.2% ferric alum and 0.01% cationic magnofloc. The solution is mixed throughly by bubbling air and allowed to settle for 180 min. The residue is separated . The liquor is analysed for B.O.D and it is found to be 300 ppm. The B.O.D is further brought down to 32 ppm by bleaching the solution with 5 g/l of chlorine for 180 minutes. The final water obtained is within the environmentally acceptable limits.
EXAMPLE: III
10 litrs. black liquor having B.O.D level 2800 ppm, 2.8gm/l, suspended solids, 4.7 gm/l silica, is pre-conditioned in a settling tank at pH 5, the preconditioned solution is dosed with 0.6% ferric alum and 0.0015% cationic magnofloc. The solution is mixed throughly by bubbling air and allowed to settle for 30 min. The residue is separated . The liquor is analysed for B.O.D and it is found to be 300 ppm. The B.O.D is further brought down to 30 ppm
by bleaching the solution with 30 g/l of chlorine for 60 minutes. The final solution obtained is within the environmentally acceptable limits.
The advantages of the process are:-
1. The process wherein the black liquors generated using different raw
materials like bamboo/straw/grass/bagasse can be treated.
2. The process wherein the pre-conditioning of the liquor is carried out at a
near neutral pH.
3. The process wherein the settling is faster using flocculant. The process
wherein the equipment used is a simple settling tank and can be easily
fabricated.
4. The process wherein the reagents used are in ppm and hence the
process can be easily commercialised.
5. The residue obtained from the liquor contain more than 50% organic
matter. The organic material has high calorific value and can be utilised to
recover energy.

We Claim:
1. An improved process for treatment of paper mill black waste liquor to produce
clean water which comprises ; i) pre-conditioning the black liquor, having about
2800 to 3000 ppm Biochemical Oxygen Demand (BOD), to a pH ranging from
3.0 to 7.0 by known method ii) adding 0.2 to 0.6 g% w/v coagulating agents
selected from alum, ferric alum or mixture thereof and cationic magnofloc in the
range of 50 mg to 150mg/l and mixing well, iii) allowing to settle for a period
ranging from 60 to 180 minutes, iv) separating the liquid from residue by
conventional methods, then bleaching the solution with chlorine with
concentration ranging from 5-30 g/1 for a period ranging from 60-180 minutes to
get environmentally acceptable clean water.
2. An improved process for treatment of paper mill black waste liquor to produce
clean water substantially as here in described with reference to the examples.

Documents:

3694-del-1998-abstract.pdf

3694-del-1998-claims.pdf

3694-del-1998-correspondence-others.pdf

3694-del-1998-correspondence-po.pdf

3694-del-1998-description (complete).pdf

3694-del-1998-form-1.pdf

3694-del-1998-form-19.pdf

3694-del-1998-form-2.pdf

« Previous Patent

Next Patent »

Patent Number

242687

Indian Patent Application Number

3694/DEL/1998

PG Journal Number

37/2010

Publication Date

10-Sep-2010

Grant Date

04-Sep-2010

Date of Filing

09-Dec-1998

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	JITENDRA NATH MOHANTY	REGIONAL RESEARCH LABORATORY, BHUBANESWAR-751013, ORISSA
2	BHASKARA VENKATA RAMANA MURTHY	REGIONAL RESEARCH LABORATORY, BHUBANESWAR-751013, ORISSA
3	HEMANTA KUMAR TRIPATHY	REGIONAL RESEARCH LABORATORY, BHUBANESWAR-751013, ORISSA
4	ANIL KANTA TRIPATHY	REGIONAL RESEARCH LABORATORY, BHUBANESWAR-751013, ORISSA
5	YERRAMSELTE VENKATA SWAMY	REGIONAL RESEARCH LABORATORY, BHUBANESWAR-751013, ORISSA

PCT International Classification Number

D21C 11/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA