Title of Invention	"PROCESS FOR THE RECOVERY OF INORGANIC SODIUM COMPOUNDS FROM KRAFT BLACK LIQUOR"
Abstract	This invention relates to an improved process for the A process for the recovery of inorganic sodium compounds from the Kraft Black Liquor which comprises the following steps : (i) Pressure Carbonation of Kraft Black Liquor by treatment with carbon dioxide, (ii) The resultant solution is treated by an open Ultrafiltration (UF) membrane in cross flow geometry at a low pressure to separate higher molecular weight fractions of Lignin in the Kraft Black Liquor, (iii) The permeate of the UF is then subjected to Nanofiltration (NF) which rejects almost all the organic molecules and passes water along with inorganic compounds which are mainly sodium carbonate salt.

Title of Invention

"PROCESS FOR THE RECOVERY OF INORGANIC SODIUM COMPOUNDS FROM KRAFT BLACK LIQUOR"

Abstract

This invention relates to an improved process for the A process for the recovery of inorganic sodium compounds from the Kraft Black Liquor which comprises the following steps : (i) Pressure Carbonation of Kraft Black Liquor by treatment with carbon dioxide, (ii) The resultant solution is treated by an open Ultrafiltration (UF) membrane in cross flow geometry at a low pressure to separate higher molecular weight fractions of Lignin in the Kraft Black Liquor, (iii) The permeate of the UF is then subjected to Nanofiltration (NF) which rejects almost all the organic molecules and passes water along with inorganic compounds which are mainly sodium carbonate salt.

Full Text	The present invention relates to a process for the recovery of inorganic sodium compounds from Kraft Black Liquor. The Black Liquor obtained from Kraft pulping process contains valuable inorganic compounds. The inorganic constituents of Black Liquor are basically sodium compounds such as sodium hydroxide, sodium sulphide, sodium carbonate, sodium sulphate. In the Black Liquor, some of these compounds are present in the free form but most of the sodium is bound with the phenolic hydroxy! group of colloidal alkali lignin. Recovery of these valuable inorganic compounds from the Black Liquor is an important aspect of the Kraft pulping process affecting its commercial and economic feasibility and viability. According to the conventional process, the inorganic compounds present in the Black Liquor are recovered by concentrating by the use of multiple effect evaporators, the Black Liquor having 3 160-160 Kg/m total dissolved solids to 600-650 Kg/m3 and then is incinerated. The molten inorganic compounds are then causticized to recover around 85 % of sodium hydroxide. The main handicaps of the conventional process are : (i) That it involves the use of costly multiple effect evaporators and leads to great loss of water during the concentration step. (ii) The organic compounds present in the Black Liquor get burnt during incineration step leading to loss of the organic compounds and also causing enviormental pollution. (iii) The equipment for the process involves high capital investment and also high energy costs. In case of small-scale paper industries using Kraft pulping 3 process, the Black Liquor obtained contains 10 to 80 Kg/m total dissolved solids. At times, this Black Liquor is processed according to the said conventional process to recover the valuable inorganic compounds present therein and at times, instead of processing, the Black Liquor is discarded as it is, resulting in more pollution problems, lower efficiency and higher capital investment owing to the loss of valuable inorganic compounds present in the Black Liquor. The object of the present invention is to provide a process for better recovery of inorganic compounds from Kraft Black Liquor obtained from Kraft pulping process. Accordingly the present invention provides a process for the recovery of inorganic sodium compounds from the Kraft Black Liquor which comprises the following steps : (i) Pressure carbonation of Kraft Black Liquor by treatment with carbon dioxide, (ii) The resultant solution is treated by an open Ultrafiltration (UF) membrane in cross flow geometry at a low pressure to separate higher molecular weight fractions' of lignin in the Kraft Black Liquor, (iii) The permeate of the UF is then subjected to Nanofil-tration (NF) which rejects almost all the organic molecules and passes water along with inorganic compounds which are mainly sodium carbonate salt. According to the present invention, the Black Liquor is first subjected to pressure carbonation by treatment with carbon dioxide. During carbonation of the Black Liquor, as carbon dioxide passes through the Black Liquor, pH of the solution decreases and -O-Na bonds break, Lignins get precipitated and sodium ions go into solution. After sufficient treatment with carbon dioxide, almost all the sodium compounds get converted into sodium carbonate and Lignin gets settled in the fragmented form. The treatment of Black Liquor with carbon dioxide is also advantageous for subsequent UF and NF membrane separation. The cellulose acetate membranes used for the UF and NF separation are amenable to degradation at high alkalinity of pH more than 12 or high acidity of pH less than two. The Black Liquor which has not been treated with carbon dioxide has a pH of about 11.5 and at this pH it would shorten the membrane life. After carbon at ion, the carbonated Black Liquor has a pH of about 7.5, which causes lass damage to the membrane during subsquent UF and NF membrane separation. The carbonated Black Liquor is then passed through a UF membrane in cress flow geometry at a low pressure to separate higher molovular weight fractions of Lignin present in Black Liquor. The cress flow through UF membrane improves the permeate flux and reduces concentration polarization. The peraeate of UF membrane separation contains almost total sodium conpeunds and lower molecular weight fractions of Lignin. This perawate is subjected to NF membrane separation. The inorganic compounds pre sent in the Block Liquer srerecovered nainly as sediua carbonate. The recovery of the inorganic compounds is higher for higher food concentration of the Black Liquor and the yield of the inorganic compounds re coved is higher than that recovered by the conventional process. The precise advantages of the present invention are : 1. The recovery of inorganic compounds from the Black Liquor is higher as compared to the conventional process. 2. The organic compounds present in the Black Liquor are not destroyed, 3. This process avoids the expensive equipments used in the conventienal process thereby avoiding high capital investments. 4. This process does not create any environmental pollution. Since many apparently different embodiments of the present invention could be made without departing from the spirit and scope of the present invention. it is intended that the descri-ption of the invention heroin be interpret ted as being illus-trative only and not Uniting in any manner whatsoever. We Claim : 1. A process for the recovery of inorganic sodium compounds from the Kraft Black Liquor which comprises the following steps : (i) Pressure carbonation of Kraft Black Liquor by treatment with carbon dioxide, (ii) The resultant solution is treated by an open Ultrafiltration (UF) membrane in cross flow geometry at a low pressure to separate higher molecular weight fractions of Lignin in the Kraft Black Liquor, (iii) The permeate of the UF is then subjected to Nanofiltration (NF) which rejects almost all the organic molecules and passes water along with inorganic compounds which are mainly sodium carbonate salt. 2. A process for the recovery of inorganic sodium compounds from the Kraft Black Liquor substantially as herein described.

Full Text

The present invention relates to a process for the recovery of inorganic sodium compounds from Kraft Black Liquor.
The Black Liquor obtained from Kraft pulping process contains valuable inorganic compounds. The inorganic constituents of Black Liquor are basically sodium compounds such as sodium hydroxide, sodium sulphide, sodium carbonate, sodium sulphate. In the Black Liquor, some of these compounds are present in the free form but most of the sodium is bound with the phenolic hydroxy! group of colloidal alkali lignin. Recovery of these valuable inorganic compounds from the Black Liquor is an important aspect of the Kraft pulping process affecting its commercial and economic feasibility and viability.
According to the conventional process, the inorganic compounds present in the Black Liquor are recovered by concentrating by the use of multiple effect evaporators, the Black Liquor having
3
160-160 Kg/m total dissolved solids to 600-650 Kg/m3 and then
is incinerated. The molten inorganic compounds are then
causticized to recover around 85 % of sodium hydroxide.
The main handicaps of the conventional process are :
(i) That it involves the use of costly multiple effect evaporators and leads to great loss of water during the concentration step.
(ii) The organic compounds present in the Black Liquor get burnt during incineration step leading to loss of the organic compounds and also causing enviormental pollution.
(iii) The equipment for the process involves high capital investment and also high energy costs.
In case of small-scale paper industries using Kraft pulping
3 process, the Black Liquor obtained contains 10 to 80 Kg/m total dissolved solids. At times, this Black Liquor is processed according to the said conventional process to recover the valuable inorganic compounds present therein and at times,
instead of processing, the Black Liquor is discarded as it is,
resulting in more pollution problems, lower efficiency and higher
capital investment owing to the loss of valuable inorganic
compounds present in the Black Liquor.
The object of the present invention is to provide a process for better recovery of inorganic compounds from Kraft Black Liquor obtained from Kraft pulping process.
Accordingly the present invention provides a process for the recovery of inorganic sodium compounds from the Kraft Black Liquor which comprises the following steps :
(i) Pressure carbonation of Kraft Black Liquor by treatment with carbon dioxide,
(ii) The resultant solution is treated by an open Ultrafiltration (UF) membrane in cross flow geometry at a low pressure to separate higher molecular weight fractions' of lignin in the Kraft Black Liquor,
(iii) The permeate of the UF is then subjected to Nanofil-tration (NF) which rejects almost all the organic molecules and passes water along with inorganic compounds which are mainly sodium carbonate salt.
According to the present invention, the Black Liquor is first subjected to pressure carbonation by treatment with carbon dioxide. During carbonation of the Black Liquor, as carbon dioxide passes through the Black Liquor, pH of the solution decreases and -O-Na bonds break, Lignins get precipitated and sodium ions go into solution. After sufficient treatment with carbon dioxide, almost all the sodium compounds get converted into sodium carbonate and Lignin gets settled in the fragmented form. The treatment of Black Liquor with carbon dioxide is also advantageous for subsequent UF and NF membrane separation. The cellulose acetate membranes used for the UF and NF separation are amenable to degradation at high alkalinity of pH more than 12 or high acidity of pH less than two. The Black Liquor which has not been treated with carbon dioxide has a pH of about 11.5 and at this pH it would shorten
the membrane life. After carbon at ion, the carbonated Black Liquor has a pH of about 7.5, which causes lass damage to the membrane during subsquent UF and NF membrane separation.
The carbonated Black Liquor is then passed through a UF membrane in cress flow geometry at a low pressure to separate higher molovular weight fractions of Lignin present in Black Liquor. The cress flow through UF membrane improves the permeate flux and reduces concentration polarization.
The peraeate of UF membrane separation contains almost total sodium conpeunds and lower molecular weight fractions of Lignin. This perawate is subjected to NF membrane separation. The inorganic compounds pre sent in the Block Liquer srerecovered nainly as sediua carbonate. The recovery of the inorganic compounds is higher for higher food concentration of the Black Liquor and the yield of the inorganic compounds re coved is higher than that recovered by the conventional process.
The precise advantages of the present invention are :
1. The recovery of inorganic compounds from the Black Liquor is higher as compared to the conventional process.
2. The organic compounds present in the Black Liquor are not destroyed,
3. This process avoids the expensive equipments used in the conventienal process thereby avoiding high capital investments.
4. This process does not create any environmental pollution.
Since many apparently different embodiments of the present invention could be made without departing from the spirit and scope of the present invention. it is intended that the descri-ption of the invention heroin be interpret ted as being illus-trative only and not Uniting in any manner whatsoever.

We Claim :
1. A process for the recovery of inorganic sodium compounds from
the Kraft Black Liquor which comprises the following steps :
(i) Pressure carbonation of Kraft Black Liquor by treatment with carbon dioxide,
(ii) The resultant solution is treated by an open Ultrafiltration (UF) membrane in cross flow geometry at a low pressure to separate higher molecular weight fractions of Lignin in the Kraft Black Liquor,
(iii) The permeate of the UF is then subjected to
Nanofiltration (NF) which rejects almost all
the organic molecules and passes water along
with inorganic compounds which are mainly
sodium carbonate salt.
2. A process for the recovery of inorganic sodium compounds
from the Kraft Black Liquor substantially as herein
described.

Documents:

814-del-1995-abstract.pdf

814-del-1995-claims.pdf

814-DEL-1995-Correspondence-Others-(18-02-2010).pdf

814-del-1995-correspondence-others.pdf

814-del-1995-correspondence-po.pdf

814-del-1995-description (complete).pdf

814-del-1995-form-1.pdf

814-del-1995-form-13.pdf

814-del-1995-form-2.pdf

814-del-1995-form-5.pdf

814-del-1995-form-6.pdf

814-del-1995-form-9.pdf

814-del-1995-pa.pdf

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Patent Number

189310

Indian Patent Application Number

814/DEL/1995

PG Journal Number

15/2010

Publication Date

09-Apr-2010

Grant Date

05-May-2005

Date of Filing

03-May-1995

Name of Patentee

THE DIRECTOR, INDIAN INSTITUTE OF TECHNOLOGY

Applicant Address

INDIAN INSTITUTE OF TECHNOLOGY , KANPUR, 208016

Inventors:

#	Inventor's Name	Inventor's Address
1	PRASHANT KUMAR BHATTACHARYA	PROFESSIOR CHEMICAL ENGINEERING, IIT KANPUR, U.P.
2	SIRSHENDU DE	RESEARCH SCHOLOR CHEMICAL ENGINEERING, INDIAN INSTITUTE OF TECHNOLOGY, KANPUR

PCT International Classification Number

C01D 7/32

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA