Operation of Louisiana Low Turbulence (LLT) Clarifiers

8/12/2019 Operation of Louisiana Low Turbulence (LLT) Clarifiers

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Operation of Louisiana Low Turbulence (LLT)Clarifiers

Vadim Kochergin

Audubon Sugar Institute

Presented at the

Jamaica Association of Sugar Technologists

Annual Conference,

November 4, 2011, Ocho Rios, Jamaica


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Rapidorr 444

CFD Modeling

Chetty and Davis, 2001

Large Scale Turbulent Eddies in an Industrial

Clarifier


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Design Concepts

Large scale turbulent eddies created by juiceintroduction need to be reduced.

Velocity in the feed channels should remain

relatively high to eliminate plugging/scaling. Uniform distribution of feed inlets and outlets

in order to have uniform vertical juice

velocities to make full use of the cross-

sectional area of the clarifier.

Minimize any non-vertical flows within a

clarifier.


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Proof of Concept- 25 m3/hr flow


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Proof of Concept


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Basic TRD Layout

Side View

Top View


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Industrial Trials 2009 Grinding Season

Turbidity, suspended solids, and flocculant usage

were monitored for the three clarifiers at Westfield

Sugar Mill.

a 20 ft. diameter Graver

a 20 ft. diameter Graver retrofitted with the new design

a 30 foot diameter Dorr, with two mud boots

* High mud levels -200-300 Lbs per ton of cane was notuncommon


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Turbidity- Comparison 2009 season

20

30

40

50

60

70

80

90

100

110

10/7/2009 10/27/2009 11/16/2009 12/6/2009 12/26/2009 1/15/2010

Turbidity(N

TU)

Date

GraverModified

Dorr

Poly. (Graver)

Poly. (Modified)

Poly. (Dorr)


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Results


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Observations

Season 2009/2010

Clarifier showed better performance compared toGraver and Dorr at the same mill

Bagacillo in clear juice was observed due to air

entrainment in the pre-distributor


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Turbulence Reduction Device


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Updated clarifer design 2010

Sterling, LA

Residence time 30-40 minutes

Redesigned feed distributor

Material of construction- Cromgard Steel

(American Utility Metals)


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Clarifier Retrofit


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Water test Sterling, Summer 2010


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Sterling Clarifier Turbidity Comparison


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Controlled Tests

Two separate tests were conducted in which the

flowrate to the LLT was increased from 750 to

1000-1100 GPM to test the limits of the clarifierthroughput


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Controlled Tests Summary

No air entrainment at 1100 GPM ( 50 % increasecompared to the standard operating flowrate of 750GPM)

No mud flocs / bagacillo in clear juice

No significant change in turbidity

Using the same amount of flocculant as at 750 GPM

Mud consistency remained constant during second test. Flocculant was increased with increased flowrate.


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Conclusions

Air entrainment problem has been resolved withimproved pre-distribution

No air entrainment was observed even at 50 % increase

compared to nominal throughput

LLT design showed on average 20 % better performancethan SRT design at lower residence time (35 min vs 45

min)

Slightly more flocculant was used as compared to the

SRT. Flocculant use optimization has not beenperformed

Capital cost of LLT design was estimated at about 30-40

% of SRT design


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Acknowledgements

American Sugar Cane League for providing partial

funding for the project

Personnel of Sterling, Lula, Westfield and EnterpriseSugar Mills

Documents

Operation of Louisiana Low Turbulence (LLT) Clarifiers