improvements in cane sugar refining at ssm

IMPROVEMENTS IN CANE SUGAR REFINING ATSANGHAR SUGAR MILLS LTD., SANGHAR, PAKISTAN

HAYAT-UR-RAHIM KHAN*[email protected]@gmail.com

Abstract

In order to improve the sugar quality, high performance adsorbent of CarboUA FRS-W2 was used in Sanghar Sugar Mills Ltd., for most part of the cane crushing campaign 2012-13. With the use of FRS-W2 , the color of raw melt liquor reduced by 15.4 %, color of fine liquor reduced by 28.5 %, color of white refined sugar reduced by 27.5 % (average) and cost of chemical consumption reduced by 8.5 %. Additional benefits were, reduced hot water washing at refine centrifugals, reduction in re-circulation of sugars at pans and reduced steam consumption.Key words: Phosphatation, refined sugar, high performance absorbents, centrifugals.

IntroductionSanghar Sugar Mills ltd. (SSML) was established in 1987-88. It has a cane crushing capacity of +5500 tons per day (tcd) and white sugar production of 500-600 tons per day. It follows defecation- remelt - phosphatation (Talofloc) process for manufacture of white sugar of 99.8° polarization and 45-95 ICUMSA Color. The brief description of the process is given hereunder in Figure - 1. (Naqvi-2006).

*Process Advisor, Sanghar Sugar Mills and Vice President, Pakistan Society of Sugar Technologists. Pakistan.

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The Boiling Scheme (Raw Side)Four batch pans to prepare A, A1, B and C-grain and four continuous pans to boil A, B and C-massecuite are installed at raw pan station. A four massecuite boiling system is adopted at SSML to boil A, A1, B and C-massecuites. Syrup received from evaporators is used to boil A-grain in a batch pan. This A-grain along with the syrup is fed continuously to A-continuous pan to boil A-massecuite. The A-massecuite is purged in A-continuous centrifugals to obtain A-heavy molasses and A-sugar. The A-sugar is remelted in sugar melter and then pumped to Phosphatation Station for further processing. The A-heavy molasses is fed to B-massecuite continuous pan. The B-grain is made with the help of A-heavy and C-seed in batch pan and used in B-massecuite continuous pan. From B-massecuite B-heavy molasses and B-sugar is produced, B-heavy is fed to C-massecuite pan and B-sugar is used as nucleus for A-grain.

The A-heavy and a little quantity of syrup is taken as footing in a batch pan to prepare C-grain which is to be fed to C-massecuite continuous pan. Slurry seeding is used to develop grain in C-massecuite. The C-massecuite is centrifuged twice, at first stage C-single cured sugar of lower purity (78-80°) and final molasses obtained. The final molasses is disposed off from the factory to final molasses pond. Whereas C-single cured sugar is magmatized and purged again in C after worker machines to yield C-sugar of purity (92-94°) and light molasses (C-light). The C-light molasses is again fed to C-massecuite and C-sugar is used as nucleus for B-grain.

A1-massecuite is boiled with the help of RO3 molasses; B/C-sugar is used as nucleus for the same massecuite. Sugar obtained from A1-massecuite is melted with A-sugar and sent to Talo Clarifier Station, the molasses is mixed with the syrup to boil A-massecuite. (Hayat-2000).

(No system exists to weigh raw sugar and 3rd run off)

The Boiling Scheme (Refinery Side) Three batch pans are installed at refinery pan station.

A three massecuites boiling system (R1, R2, & R3) is employed, at refinery pan station. R1-massecuite is boiled with fine liquor received from Phosphatation Station. Sugar dust grain separated from sugar grader is used as seed to boil all refine massecuites. Sugar gained from refine centrifugals from R1-

massecuite is sent to sugar dryer, grader, and then to bagging house for filling of sugar bags, the molasses (RO1) so obtained is fed in R2-massecuite and so on. RO3-molasses is pumped to raw pan side to be used as footing for A1-massecuite boiling. (Equipment is not available to boil R4-massecuites).

Working ParametersConsidering the local market requirements about the improved quality of sugar and also export of sugar from Pakistan for the last two years, more emphasis was laid upon in the SSML to improve and maintain quality of sugar with not much capital or operational expenses. Therefore, initially it was decided to test high performance adsorbents CarboUA FRS-W2 for extra color removal of raw melt liquor from raw A-sugar in addition to the existing phosphatation process during the cane crushing season 2012-13.

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FRS-W2 is an orthophosphate with proprietary sulphonic group activation. It has an acidic odour, appearance of a crystalline powder and a specific gravity 1.2-1.6. ph 4 – 6. It decomposes at > 300 C°. (Sarir-2011).

The cane crushing season of SSML started on Nov. 3, 2012 and continued up to March, 2013. The use of high adsorbent FRS-W2 was started from Dec. 3, 2012 on a trial basis initially for two weeks. But noting its superior performance, it was decided to continue for the remaining part of the season.

The application of FRS-W2 is quite simple i.e. 300 ppm FRS-W2 was added in the raw melt liquor and at the same time dosing of decolorizer and phosphoric acid was reduced as per color requirement. However, it took about a week to make the final adjustment of the dosage, etc. Brief description of the refining process with the use of FRS-W2 is shown in figure – 2.

Results & DiscussionTable –1 , 2 & 3 below gives the comparative results of color of melt liquor, fine liquor, R 1, R2, R3

sugars, chemical consumption, cost of chemicals per ton of white sugar, lime consumption and steam consumption.

Table 1: Comparative results of SSML refining process with and without FRS-W2.

S. No. DescriptionMelt liquor

(IU)Fine liquor

(IU)R1

(IU)R2

(IU)R3

(IU)

01 Previous process 860-890 400-425 45-60 60-75 75-95

02Modified Process

with CarboUAFRS-W2

700-780 280-310 28-32 44-58 60-75

03Extra Color

reduction % due to FRS-W2

15.4 28.5 42.8 24.4 20.5

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Table 2: Chemical cost comparison of SSML refining process with and without FRS-W2.

Previous Process(Phosphatation /Talofloc)

Modified Process(Phosphatation and CarboUA FRS-W2)

ChemicalsDosage Kg/tonsugar

ChemicalCost/

ton sugar*PKR

Dosage Kg/tonsugar

ChemicalCost/

ton sugar*PKR

Decolorizer 0.410 155.80 0.138 52.44

Phosphoric acid 0.426 44.73 0.190 19.95

FRS –W2 ------- ------- 0.300 111.00

Total 200.53 183.39

Lime % Cane

Cane Crushing Season 2008 to 2012 (Avg)

Cane Crushing Season2012-13

0.079 0.070

* PKR = Pakistan Rupees = 98 = US$ 1.0

Table 3: Brix of run off molasses and steam % cane from 2008-09 to 2012-13.

Season 2008-09 2009-10 2010-11 2011-12 2012-13

Brix of run off molasses

RO1 RO2 RO3 RO1 RO2 RO3 RO1 RO2 RO3 RO1 RO2 RO3 RO1 RO2 RO3

75.20 76.30 77.10 75.35 76.40 77.93 74.01 76.43 77.45 75.30 76.41 77.32 78.10 78.80 78.90

Steam % cane

61.5 60.6 59.8 59.7 57.8

From the Tables 1, 2 & 3, it will be noted that with the use adsorbent FRS-W2, there was:

1. Reduction in Colora) A reduction of 15.4 % color in the melt liquor.b) 28.5 % reduction in the color of fine liquor.c) 42.8 % color reduction in R1 sugar, 24.4 % color reduction in R2 sugar and 20.5 % color

reduction in R3 sugar.

2. Reduction in consumption of chemicala) With the extra use of the adsorbent FRS-W2, the consumption of phosphoric acid reduced by

55 %, and decolorizer reduced by 66 %.b) There was also, reduction of 0.009 % on cane in the consumption of lime as compared to last

five cane crushing seasons average figures.

3. Reduction in Costa) The overall cost of use of chemicals reduced by more than 8.5 %. (Cost of lime not included).b) An amount of US$ 3500 also saved during season 2012-13 due to reduction in lime

consumption.

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4. Reduction in consumption of steama) There was a reduction in the use of wash water at refined centrifugals, which ultimately

increased the Brix° of run off, reduced re-circulation of sugar at raw and refine pans and 2 % on cane reduction in consumption of steam.

b) No extra fuel (Furnace Oil) was used at steam boilers during cane crushing season 2012-13.

5. Improvement in the Quality of Refined Sugar Improved quality (99.85 pol) and low color sugar (27-75 IU) was produced.

ConclusionThe removal of color is probably the most important unit operation in a sugar refinery. Good color removal has many benefits as stated above. The use of high performance absorbents have proven to give very low color feed syrup (fine liquor) to the refine crystallization station, thereby improving the energy consumption and the sugar quality. This was achieved without any capital investment and has improved the over-all profitability of the refinery. It has been decided to continue the use of FRS-W2 for whole of the next cane crushing season 2013-14 also.

Acknowledgement

Grateful acknowledgement is extended to Mr. Mohammad Hashim Rajar, Dy. Managing Director and General Manager for his support and keen interest towards improving the quality of sugar.

Thanks are also due to Mr. Muhammad Waseem for composing, proof reading of the manuscript.

References

1. Khan Hayat-ur-Rahim. 2000. Fabrication Practices of Boiling House of A-sugar Factory. Karachi. Pakistan. 56 p

2. Naqvi, H.A. 2006. Brief description of cane sugar manufacturing process in Pakistan sugar industry. Pakistan Sugar Book – 2005. Pakistan Society of Sugar Technologists, 1st ed., pp121-22.

3. Naqvi, H.A. 2013. Studies in Cane Sugar Industries. Fine Book Printers, Lahore, Pakistan.377p4. Sarir, E.M., C.A. Donado and L. Jaramillo. 2011. Enhanced Carbonation and phosphatation

Clarification performance for improved production efficiency and product quality in A-sugar refining. International Sugar Journal, England, U.K. vol.113, pp50-54.

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