US4297164A
Expired / Lapsed
US
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Process for displacement washing of porous media
Assignee: Weyerhaeuser Co
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Filing: 1980-03-10
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Granted: 1981-10-27
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Expires: 2000-03-10
Abstract
Abstract An improved displacement washing process for recovering processing chemicals from a porous medium, particularly wood pulp, is described. The effective mobility of a displacing solution, typically a more dilute solution of the chemical sought to be recovered, is reduced such that it is less than the mobility of the solution to be recovered. In a pulp mill washing system, consumption of wash water may be reduced 0.6 tons of water per ton of pulp produced without reducing chemical recovery. Conversely, chemical effluent from the washer could be reduced by 50% without increasing wash water requirement. Mobility is proportional to the permeability of the porous medium with respect to the solution of interest and inversely proportional to the viscosity of that solution. Mobility of the wash solution relative to the solution to be displaced is preferrably reduced by the addition of a soluble, high molecular weight polymer, greater than 10 6 , until the ratio of the mobility of the wash solution to that of the chemical rich solution is in the range of 0.05-2.0, preferably within the range of 0.2-1. As examples, copolymers of acrylamide and acrylic acid, carboxypolymethylene, polyacrylic acid and deacetylated chitin have been found to be effective in reducing mobility. The presence of 6-10 ppm of a copolymer of acrylamide and acrylic acid of MW greater than 10 6 in the wash solution of a brownstock washer can double the efficiency of the washer.
Inventors
- 👤 Peter F. Lee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 03:03
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/02
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
161 words
In a process for separating a liquid from an insoluble material which includes the steps of thickening said insoluble material by draining excess liquid therefrom while retaining the material in a porous formation on a porous support means and displacing a substantial portion of the liquid remaining in the insoluble porous material after thickening from said material by injecting a wash liquid into said material, without substantially disturbing said porous formation of the retained material, the improvement, comprising: reducing the mobility of said wash liquid in the porous formation of the insoluble material with respect to the mobility of said liquid originally retained in the porous insoluble material, wherein the mobility of a liquid with respect to a porous formation is proportional to the permeability of the porous formation to a liquid and inversely proportional to the viscosity of said liquid, such that the ratio of wash liquid mobility to the mobility of the liquid to be displaced is about 0.05-2.0.
Claim 2
Dependent Claim
161 words
In a process for separating a liquid from an insoluble material which includes the steps of thickening said insoluble material by draining excess liquid therefrom while retaining the material in a porous formation on a porous support means and displacing a substantial portion of the liquid remaining in the insoluble porous material after thickening from said material by injecting a wash liquid into said material, without substantially disturbing said porous formation of the retained material, the improvement, comprising: reducing the mobility of said wash liquid in the porous formation of the insoluble material with respect to the mobility of said liquid originally retained in the porous insoluble material, wherein the mobility of a liquid with respect to a porous formation is proportional to the permeability of the porous formation to a liquid and inversely proportional to the viscosity of said liquid, such that the ratio of wash liquid mobility to the mobility of the liquid to be displaced is about 0.05-2.0.
Claim 3
Dependent Claim
26 words
The process of claim 1, wherein: reducing the mobility of said wash liquid is accomplished by increasing its viscosity relative to said liquid to be displaced.
Claim 4
Dependent Claim
36 words
The process of claim 2, wherein: the viscosity of said wash liquid is increased by reducing the temperature of said wash liquid below ambient temperature, thereby reducing its mobility relative to said liquid to be displaced.
Claim 5
Dependent Claim
35 words
The process of claim 2, wherein: the viscosity of said wash liquid is increased by adding starch to said solution, thereby reducing the mobility of said wash liquid relative to said liquid to be displaced.
Claim 6
Dependent Claim
44 words
The process of claim 1, wherein: reducing the mobility of said wash liquid is accomplished by reducing the effective permeability of said liquid with respect to the porous formation of insoluble material by adding a polymer to said liquid to form a wash solution.
Claim 7
Dependent Claim
31 words
The process of claim 1, wherein: reducing the mobility of said wash liquid is accomplished by adding liquid-soluble polymers thereto, said polymers characterized by their hydrating ability at very low concentrations.
Claim 8
Dependent Claim
41 words
The process of claim 6, wherein: the mobility of the wash solution is adjusted by adding said polymer in an amount such that the ratio of wash solution mobility to the mobility of the solution to be displaced is about 0.05-2.0.
Claim 9
Dependent Claim
28 words
The process of claim 6, wherein: the mobility of wash solution is adjusted by adding said polymer in an amount such that the mobility ratio is about 0.2-1.0.
Claim 10
Dependent Claim
48 words
The process of claim 6, wherein: said mobility reducing polymers are one or more homo or copolymers of ethylene oxide, acrylamide, vinyl pyprolidone, acrylic acid, methacrylic acid, the Na, K, Li and amine salts of carboxymethyl cellulose, maleic acid, Na, K, Li and amine salts of alginic acid.
Claim 11
Dependent Claim
26 words
The process of claim 9, wherein: the mobility of the wash solution is adjusted by said polymer having a molecular weight of greater than 1 million.
Claim 12
Dependent Claim
25 words
The process of claim 6, wherein: said mobility reducing polymers are one or more homo or copolymers of acrylamide, acrylic acid, carboxymethylene or deacetylated chitin.
Claim 13
Dependent Claim
134 words
An improved process for displacement washing of pulp substantially free of soluble contaminants, wherein said pulp is first thickened and retained on a porous supporting means, comprising: preparing a wash solution, in which the fiber is insoluble and having a concentration therein of said contaminants to be removed less than that of the pulp to be washed; adjusting the apparent, effective mobility of said wash solution such that the ratio of wash solution mobility to the mobility of the solution to be recovered is about 0.05 to 2.0, wherein the mobility of each solution is proportional to the permeability of the pulp with respect to that solution and inversely proportional to the viscosity of said solution; and injecting the pulp with said wash solution, wherein the solution containing the dissolved solids is preferentially displaced.
Claim 14
Dependent Claim
134 words
An improved process for displacement washing of pulp substantially free of soluble contaminants, wherein said pulp is first thickened and retained on a porous supporting means, comprising: preparing a wash solution, in which the fiber is insoluble and having a concentration therein of said contaminants to be removed less than that of the pulp to be washed; adjusting the apparent, effective mobility of said wash solution such that the ratio of wash solution mobility to the mobility of the solution to be recovered is about 0.05 to 2.0, wherein the mobility of each solution is proportional to the permeability of the pulp with respect to that solution and inversely proportional to the viscosity of said solution; and injecting the pulp with said wash solution, wherein the solution containing the dissolved solids is preferentially displaced.
Claim 15
Dependent Claim
19 words
The process of claim 12 wherein the solution to be displaced is spent cooking liquor from a pulping process.
Claim 16
Dependent Claim
23 words
The process of claim 12 wherein the soluble contaminants of the solution to be displaced are dissolved solids from the bleaching of pulp.
Claim 17
Dependent Claim
29 words
The process of claim 12 wherein the mobility of the wash solution is adjusted by adding a high molecular weight polymer that is soluble in the wash solution solvent.
Claim 18
Dependent Claim
35 words
The process of claim 15 wherein said polymers are one or more homo or copolymers of ethylene oxide, acrylamide, vinyl pyprolidone, acrylic acid, methacrylic acid, or Na, K, Li and amine salts of carboxymethyl cellulose.
Claim 19
Dependent Claim
19 words
The process of claim 16 wherein the high molecular weight polymer has a molecular weight greater than 1 million.
Claim 20
Dependent Claim
26 words
The process of claim 12 wherein the ratio of the mobility of the wash solution to that of the solution to be displaced is about 0.2-1.0.
Claim 21
Dependent Claim
20 words
The process of claim 12 wherein said polymer is added in an amount of 2-50 ppm to the wash solution.
Claim 22
Dependent Claim
14 words
The process of claim 19 wherein said polymer is polyacrylamide, carboxypolymethylene, or deacetylated chitin.
Claim 23
Dependent Claim
152 words
An improved process for recovering processing chemicals from wood pulp retained in solution with the pulp after the pulp has been thickened, by displacement washing of said pulp, the improvement, comprising: preparing a wash solution, said solution having a lower concentration of the chemicals to be displaced than that initially retained with said pulp; adding to said solution a polymer having a molecular weight greater than 1 million, wherein said polymer is polyacrylamide, carboxypolymethylene, or deacetylated chitin, in an amount of about 2-50 ppm such that the apparent, effective ratio of wash solution mobility to the mobility of the chemical solution to be recovered is about 0.05 to 2.0 wherein the mobility of each solution is proportional to the permeability of the pulp with respect to that solution and inversely proportional to the viscosity of said solution; injecting into said pulp said wash solution; and recovering said wash solution containing said chemicals.
Claim 24
Dependent Claim
152 words
An improved process for recovering processing chemicals from wood pulp retained in solution with the pulp after the pulp has been thickened, by displacement washing of said pulp, the improvement, comprising: preparing a wash solution, said solution having a lower concentration of the chemicals to be displaced than that initially retained with said pulp; adding to said solution a polymer having a molecular weight greater than 1 million, wherein said polymer is polyacrylamide, carboxypolymethylene, or deacetylated chitin, in an amount of about 2-50 ppm such that the apparent, effective ratio of wash solution mobility to the mobility of the chemical solution to be recovered is about 0.05 to 2.0 wherein the mobility of each solution is proportional to the permeability of the pulp with respect to that solution and inversely proportional to the viscosity of said solution; injecting into said pulp said wash solution; and recovering said wash solution containing said chemicals.
Claim 25
Dependent Claim
17 words
The process of claim 21 wherein said displacement wash solution is employed on rotary cylinder vacuum washers.
Claim 26
Dependent Claim
17 words
The process of claim 21 wherein said displacement wash solutions is employed in a ring diffuser washer.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-10-26 | 1985-04-27 | 1985-10-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-26 | 1989-04-27 | 1989-10-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-26 | 1993-04-27 | 1993-10-27 | $7700.00 | Window Closed / Lapsed |