Feedback control scheme for optimizing dewatering processes

• US 7,993,526 B2
• Filed: 03/17/2009
• Issued: 08/09/2011
• Est. Priority Date: 04/11/2008
• Status: Expired due to Fees

• Current Assignee: James M. Dunbar
• Original Assignee: James M. Dunbar
• Inventors: Dunbar, James M.
• Primary Examiner(s): Hruskoci; Peter A
• Application Number:
  US12/405,658
• Publication Number:
  US 20090255876A1
• Time in Patent Office: 875 Days
• Field of Search: 210/709
• US Class Current: 210/705
• CPC Class Codes: C02F 1/008 Control or steering systems not provided for elsewhere in subclass C02F
• CPC Class Codes: C02F 1/24 by flotation C02F1/465 takes precedence
• CPC Class Codes: C02F 1/5209 Regulation methods for flocculation or precipitation
• CPC Class Codes: C02F 1/56 Macromolecular compounds
• CPC Class Codes: C02F 11/121 by mechanical de-watering
• CPC Class Codes: C02F 11/147 using organic substances C02F11/148 takes precedence
• CPC Class Codes: C02F 2103/002 Grey water, e.g. from clothes washers, showers or dishwashers
• CPC Class Codes: C02F 2209/001 Upstream control, i.e. monitoring for predictive control
• CPC Class Codes: C02F 2209/003 Downstream control, i.e. outlet monitoring, e.g. to check the treating agents, such as halogens or ozone, leaving the process
• CPC Class Codes: C02F 2209/006 comprising a software program or a logic diagram
• CPC Class Codes: C02F 2209/11 Turbidity
• CPC Class Codes: C02F 2209/40 Liquid flow rate
• CPC Class Codes: D21C 9/18 De-watering de-watering in general F26B; Elimination of cooking or pulp-treating liquors from the pulpD21C9/002, D21C9/02 take precedence; paper-making machines D21F; strainers in digesters D21C7/00; presses in general B30B
• CPC Class Codes: D21H 21/10 Retention agents or drainage improvers
• CPC Class Codes: Y10S 210/928 Paper mill waste, e.g. white water, black liquor treated

Abstract

A method and apparatus for dewatering of effluents through the use of automated optimization using feedback control. The method and apparatus for feedback control optimizes dewatering processes for any water cleansing process that uses retention and/or flocculation aids (e.g., polymers) to impact endpoint water clarity. Disclosed implementations include processing using dissolved air flotation (DAF) and sludge cake formation. The methodology includes real-time monitoring of turbidity and incremental control of polymer to manage changes to turbidity/suspended solids due to operating parameters such as temperature, chemical variations, and mechanical influences.

Claims

1. A method for optimizing a dewatering process producing dewatered sludge and clarified water from a flocculated effluent, said method comprising the steps:

a) determining clarity of an output of said clarified water;

b) automatically adjusting flocculant supplied to said flocculated effluent, said automatically adjusting flocculant step having an increase loop and a decrease loop which, respectively, increase and decrease said flocculant supplied to said effluent based upon said clarity, and said increase loop includes increasing said flocculant in accordance with predetermined levels which vary in accordance with changes detected in said clarity, said increase loop and said decrease loop including delays which are provided to allow for the flocculant adjustment to take effect in said flocculated effluent;

c) re-determining said clarity of said clarified water; and

d) repeating steps b) and c) continuously during dewatering of said flocculated effluent to produce said dewatered sludge so as to maintain said clarity within a predetermined range.

2. The method as claimed in claim 1 wherein said determining and re-determining are embodied in determining logic and said increase loop and said decrease loop are embodied in command logic.

3. The method as claimed in claim 2 wherein said determining logic and said command logic are implemented within a computer readable medium.

4. The method as claimed in claim 2 wherein said determining logic and said command logic are implemented within programmable hardware.

5. The method as claimed in claim 2 wherein said output is obtained from a dissolved air flotation device outlet.

6. The method as claimed in claim 2 wherein said output is obtained from a sludge filtrate outlet.

7. The method as claimed in claim 6, said method further including

increasing a counter incrementally when said adjusting is operating within said increase loop,

reversing said adjusting to operate within said decrease loop upon reaching a predetermined value within said counter, and

resetting said counter.

8. The method as claimed in claim 6, said method further including

monitoring a sludge level of said dewatered sludge within a sludge press chute and

adjusting a chute controller set point in response to a press amperage controller signal

wherein any increase in press amperage results in a corresponding decrease in said chute controller set point.

9. The method as claimed in claim 2 wherein said flocculant is an anionic polymer.

10. The method as claimed in claim 2 wherein said flocculant is a cationic polymer.

11. A method for optimizing a dewatering process, said method comprising the steps:

a) determining turbidity of clarified water obtained from a dissolved air flotation (DAF) device outlet producing dewatered sludge and said clarified water from a flocculated effluent;

b) automatically adjusting flocculant supplied to said DAF, said automatically adjusting flocculant step having an increase loop and a decrease loop which, respectively, increase and decrease said flocculant supplied to said DAF based upon said turbidity, and said increase loop includes increasing said flocculant in accordance with predetermined levels which vary in accordance with changes detected in said turbidity, said increase loop and said decrease loop including delays which are provided to allow for the flocculant adjustment to take effect in said flocculated effluent;

c) re-determining said turbidity of said clarified water; and

d) repeating steps b) and c) continuously during dewatering of said flocculated output to produce clarified water and dewatered sludge so as to maintain said turbidity within a predetermined range.

12. The method as claimed in claim 11 wherein said determining and re-determining are embodied in determining logic and said increase loop and said decrease loop are embodied in command logic.

13. The method as claimed in claim 12 wherein said determining logic and said command logic are implemented within a computer readable medium.

14. The method as claimed in claim 12 wherein said determining logic and said command logic are implemented within programmable hardware.

15. The method as claimed in claim 12 wherein said flocculant is an anionic polymer.

16. The method as claimed in claim 12 wherein said flocculant is a cationic polymer.