US4670150A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cross-flow microfiltration lime softener
Assignee: CPC ENGINEERING COMPANY A MA CORP
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Filing: 1985-10-24
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Granted: 1987-06-02
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Expires: 2005-10-24
Abstract
Abstract A method for softening a fluid containing hardness constituents, comprising the steps of: (a) mixing the fluid with sufficient amounts of a softening agent, and previously precipitated hardness constituents in a reactor to establish a softening reaction in the reactor for precipitating a substantial portion of the hardness constituents contained in the fluid; (b) removing a portion of the fluid and precipitated hardness constituents from the reactor as a slurry and filtering the slurry through a cross-flow microfiltration module containing at least one elongated filtration tube, whereby substantially all of the precipitated hardness constituents are removed from the portion of the fluid exiting from the module as filtrate; and (c) returning at least a portion of the filtered out precipitated hardness constiuents exiting from the module to the reactor as the previously precipitated hardness constituents.
Inventors
- 👤 Andrew K. Hsiung
- 👤 Daniel L. Comstock
- 👤 Robert D. Hagen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:35
CPC Classifications
C; C02; C02F; C02F5/00; C02F5/02; B; B01; B01D; B01D61/00; B01D61/14; B01D61/147; B01D63/00; B01D63/06; B01D63/062; B01D2315/00; B01D2315/10; B01D2317/00; B01D2317/04
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
205 words
A method for softening an aqueous fluid containing harness constituents, comprising the steps of: (a) mixing the fluid with sufficient amounts of a lime-containing softening agent and previously precipitated hardness constituents including, calcium carbonate in a reactor to establish a lime softening reaction in the reactor for precipitating a substantial portion of the hardness constituents including calcium carbonate contained in the fluid; (b) prior to any substantial settling of the precipitated harness constituents, removing a portion of the fluid and precipitated hardness constituents from the reactor as a slurry having a concentration of at least about 1%, by weight, of said precipitated hardness constituents, and filtering the slurry through at least one cross-flow microfiltration module containing at least one elongated microporous thermoplastic filtration tube, said tube having a pore size of from about 1 micron to about 10 microns and a filter cake of said precipitated hardness constituents at the inner wall thereof, whereby substantially all of the precipitated hardness constituents are removed from the portion of the fluid exiting from the module as filtrate; and (c) returning at least a portion of the filtered out precipitated hardness constituents exiting from the module as a slurry to the reactor as the previously precipitated hardness constituents.
Claim 2
Independent Claim
205 words
A method for softening an aqueous fluid containing harness constituents, comprising the steps of: (a) mixing the fluid with sufficient amounts of a lime-containing softening agent and previously precipitated hardness constituents including, calcium carbonate in a reactor to establish a lime softening reaction in the reactor for precipitating a substantial portion of the hardness constituents including calcium carbonate contained in the fluid; (b) prior to any substantial settling of the precipitated harness constituents, removing a portion of the fluid and precipitated hardness constituents from the reactor as a slurry having a concentration of at least about 1%, by weight, of said precipitated hardness constituents, and filtering the slurry through at least one cross-flow microfiltration module containing at least one elongated microporous thermoplastic filtration tube, said tube having a pore size of from about 1 micron to about 10 microns and a filter cake of said precipitated hardness constituents at the inner wall thereof, whereby substantially all of the precipitated hardness constituents are removed from the portion of the fluid exiting from the module as filtrate; and (c) returning at least a portion of the filtered out precipitated hardness constituents exiting from the module as a slurry to the reactor as the previously precipitated hardness constituents.
Claim 3
Dependent Claim
18 words
A method as claimed in claim 1, wherein the microfiltration module contains a plurality of elongated filtration tubes.
Claim 4
Dependent Claim
23 words
A method as claimed in claim 1 wherein the slurry is filtered through a plurality of cross-flow microfiltration modules piped together in series.
Claim 5
Dependent Claim
37 words
A method as claimed in claim 1, wherein the concentration of precipitated hardness constituents and previously precipitated hardness constituents in the reactor is constantly maintained within the range of from about 1% to about 4%, by weight.
Claim 6
Dependent Claim
30 words
A method as claimed in claim 1, wherein the concentration of precipitated hardness constituents and previously precipitated hardness constituents in the reactor is constantly maintained at about 2%, by weight.
Claim 7
Dependent Claim
22 words
A method as claimed in claim 1, wherein the average mixing time of the fluid in the reactor is about 4 minutes.
Claim 8
Dependent Claim
50 words
A method as claimed in claim 1, wherein the filtration flux through the microfiltration module is maintained at a constant value during the filtration run, said value being within the range of from about 1050 to about 1500 gallons per day per sq. ft. of active filtration tube surface area.
Claim 9
Dependent Claim
25 words
A method as claimed in claim 1, wherein the fluid velocity measured at the slurry exit end of the microfiltration module is about 4 ft./sec.
Claim 10
Dependent Claim
22 words
A method as claimed in claim 1, further comprising the step of adding an organic polymer to the mixture in the reactor.
Claim 11
Dependent Claim
37 words
A method as claimed in claim 1, further comprising the step of continually recycling a portion of the filtered out precipitated hardness constituents exiting from the microfiltration module to the feed end of the module during filtration.
Claim 12
Dependent Claim
112 words
A method as claimed in claim 1, wherein the fluid flows transversely through the filtration tube wall by establishing a pressure differential across the wall, and further comprising the step of maintaining the filtration flux rate through the tube at a preselected substantially constant value during the entire filtration run by applying a variable throttling pressure on the filtrate side of the tube and reducing said throttling pressure during the run to control the instantaneous value of said pressure differential as required to maintain said preselected flux rate, said flux rate being greater than the equilibrium flux rate, whereby the time-averaged filtration flux over the period of the filtration run is increased.
Claim 13
Dependent Claim
43 words
A method as claimed in claim 11, wherein the filtrate which is permeated through the filtration tube wall is collected in a closed jacket surrounding said tube, and wherein said variable throttling pressure is applied to a product line exiting from said jacket.
Claim 14
Dependent Claim
55 words
A method as claimed in claim 12, further comprising the step of cleaning the interior surface of the filtration tube prior to commencement of the filtration run by flowing a cleaning solution laterally over said tube surface while simultaneously temporarily eliminating said pressure differential across the filtration tube by blocking all flow from said jacket.
Claim 15
Dependent Claim
46 words
A method as claimed in claim 11, further comprising the step of cleaning the surface of the filtration tube prior to commencement of the filtration run by flowing a cleaning solution laterally over said surface while simultaneously temporarily eliminating said pressure differential across the filtration tube
Claim 16
Dependent Claim
36 words
A method as claimed in claim 11, further comprising the step of periodically backflushing a liquid transversely through the filtration tube wall by reversing the direction of said pressure differential, thereby physically cleaning the filtration tube.
Claim 17
Dependent Claim
43 words
A method as claimed in claim 15, wherein said backflushed liquid includes said filtrate and the duration of each backflushing period is about 2 seconds and the interval between backflushings is within the range of from about 1 minute to about 2 minutes.
Claim 18
Dependent Claim
34 words
A method as claimed in claim 11, further comprising the of periodically increasing the circulation velocity of the slurry flowing laterally along the interior surface of the filtration tube, thereby physically cleaning said surface.
Claim 19
Dependent Claim
65 words
A method as claimed in claim 17, wherein the duration of each such periodic increase in circulation velocity is within the range of from about 5 seconds to about 60 seconds, the interval between such periodic increases does not exceed about 20 minutes, and the circulation velocity is increased to a value within the range of from about 10 to about 20 ft. per sec.
Claim 20
Dependent Claim
63 words
A method as claimed in claim 1, further comprising the step of commencing the filtration run by gradually increasing the flow rate of the filtrate from essentially zero to the desired operational flow rate over a sufficiently extended period of time to substantially prevent the deleterious intrusion of the precipitated hardness constituents filtered out of the fluid into the filtration tube wall matrix.
Claim 21
Dependent Claim
26 words
A method as claimed in claim 19, wherein said extended period of time is within the range of from about 15 seconds to about 45 seconds.
Claim 22
Dependent Claim
48 words
A method as claimed in claim 19, further comprising the step of cleaning the interior surface of the filtration tube prior to commencement of the filtration run by flowing a cleaning solution laterally over said tube surface while simultaneously temporarily eliminating said pressure differential across the filtration tube.
Claim 23
Dependent Claim
62 words
A method as claimed in claim 1, wherein the fluid flows transversely through the filtration tube wall by establishing a pressure differential across the wall, and further comprising the step of maintaining the filtration flux rate transversely through the filtration tube wall at substantially the same value along the entire length of the tube during filtration, whereby the filtration flux is increased.
Claim 24
Dependent Claim
118 words
A method as claimed in claim 22, wherein the portion of the slurry exiting from the downstream end of the filtration tube is recycled back to the feed end of the tube via a return line having a recycle pump operatively connected thereto, and wherein the filtration flux rate is maintained at substantially the same value along the entire length of the filtration tube by pumping the slurry to be filtered into said return line at a point between the downstream end of the filtration tube and said recycle pump connection, whereby the pressure drop measured between a point immediately upstream of said feed end and a point immediately following said downstream end is approximately zero during filtration.
Claim 25
Dependent Claim
30 words
A method as claimed in claim 23, wherein the flow rate of said slurry is selected to equal the flow rate of the filtrate permeated, through the filtration tube wall.
Claim 26
Dependent Claim
39 words
A method as claimed in claim 22, further comprising the step of periodically backflushing a liquid transversely through the filtration tube wall from the filtrate side by reversing the direction of said pressure differential, thereby physically cleaning the tube.
Claim 27
Dependent Claim
29 words
A method as claimed in claim 22, wherein the pressure immediately downstream of the filtration tube and the pressure immediately upstream of the tube are maintained at equal values.
Claim 28
Dependent Claim
45 words
A method as claimed in claim 1, further comprising the of periodically backflushing a portion of the filtrate transversely through the filtration tube wall from the filtrate side, said backflushing flow comprising about 0.5 gallons per minute per sq. ft. of active filtration tube surface.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-06-01 | 1990-12-01 | 1991-06-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-01 | 1994-12-01 | 1995-06-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-01 | 1998-12-01 | 1999-06-02 | $7700.00 | Window Closed / Lapsed |