Component Analysis of The Sugar Cane Molasses Stillage Sediment

Hong-xiang ZHU1 , Rui-feng MAO1*, Shuang-Fei WANG1，Yan-yan QIN1,

Ying-hui WANG2,* 1Institute of Light Industry and Foodstuff Engineering, Guangxi University Nanning, China, 530004

2School of Environment, Guangxi University, Nanning, China, 530004

Corresponding author * gnmf@163.com, *wyh@gxu.edu.cn

Keywords: molasses stillage, sediment, distillation, X-ray diffraction , Scanning electron microscopy.

Abstract. With the development of the sugar industry, the molasses composition of sugar cane has

changed greatly. Sugar cane molasses purity decreased, while the colloid and ash increased. In

recent years, the deposits from the sugar cane molassesas hindered the operation in the alcohol

distillation tower, and sometimes even blocked the whole process, leading to stop the distillation

flow. This paper researched the components analysis of the sugar cane molasses stillage sediment in

the alcohol production scale factors. It is helpful to illustrate the formation mechanism of the

deposits from the sugar molassesas stillage. By the test of X-ray diffraction, scanning electron

microscopy with EDX and chemical analysis，we conclude that the main components of the

deposits of molassesas is calcium sulfate, it also contains a small amount of magnesium sulfate,

potassium sulfate, silica and calcium carbonate et cetera.

Introduction

Molasses, the by-product of sugar industry, is sometimes used as ethanol production [1]

. It provided

a solution to the environmental issue arising from the disposal of molasses，and the fuel ethanol

production can also help stabilizing the agricultural sector in the sugar producing countries[2]

. Due

to the oil crisis the last 30 years, research conducted in the scientific area of alcoholic fermentation,

has been focusing mainly on the increase of ethanol productivity of bioprocesses and reduction of

energy demands [3]

. Fermentation of molasses continues to pay as regards ethanol productivity [4，5]

.

To increase ethanol productivity, sugar molassesas operation in the alcohol distillation tower with

molassesas as raw materials for ethanol production has been extensively studied and reviewed [6]

.

The Frequent downtime in distillation tower，not only affects productivity, but also brings about

very negative impact on the fermentation, which restrained the

yeast activity and promoted susceptible bacteria fermentation by-products. In this situation it is

difficult to guarantee product quality and complete production tasks. In order to solve the alcohol

distillation equipment sediment hinder problem, many methods are applied to adjust the Process

Parameters. Yin Guo provided comprehensive control measures which including the process from

the raw materials preparation to the ethanol industry technology [7]

. Li Jianjun isolated sugar

molasses serum with alcohol practical experience in the operation of evaporation on the causes of

forming molasses stillage deposits , summarized the evaporator scale prevention for the molasses

stillage deposits and elimination of layers of molasses stillage deposits [8]

. Fu Qijun get the

conclusion from the production practice, which about the scaling of molasses stillage deposits is due

to water hardness, high ash content of molasses, molasses lower in quality and the decrease of purity.

The measures taken are: use the raw water as dilution water, choose a better quality of molasses,

molasses stillage fermentation brix and lower dosage of sulfuric acid [9]

.

From the current research view, the main work about the reduce the sediment of molasses in the

process of alcohol production is about the method of reduce the mount of the sediment，there are

few work have been done about the formation mechanism of molasses sediment. The composition

Advanced Materials Research Vols. 455-456 (2012) pp 1267-1272Online available since 2012/Jan/24 at www.scientific.net© (2012) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.455-456.1267

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of sediment molasses is the basis data for the formation mechanism of molasses sediment. So it has

become the first priority work to analysis the composition of alcohol distillation equipment

sediment. It can tell us more about the process of sediment formation in the molasses industry [10]

.

Materials and Methods

Experimental materials. The test sediment samples take from the alcohol evaporation tower in the

sugar cane molasses alcohol plant of Nanning Sugar Co.

Experimental methods

1) X-ray diffraction analysis

To employ Holland PANalytical company XcPert PRO X-ray diffraction. Analytical conditions:

Cu target KA-ray, voltage 40 kV, current 20 mA, scan range (2H) 5b-60b, scanning speed 015 (b)

Pmin.

2) Sample measurement conditions

Sediment samples were dried in vacuum at 65 ℃ and grounded into powder with agate mortar，

200-300 mesh particle size. Then take the samples 0.5g for X-ray diffraction analysis. Parameters of

test were: tube voltage: 30 kV, tube current: 30 mA, target type: Cu, glancing angle scan range: 10°-

70°, step length: 0.02, integration time: 0.1s, scanning speed: 12°• min-1.

3) Analyzing composition by SEM

Analyze crystal shape and composition of sediment from molasses by Scanning electron

microscopy with energy dispersive. Model JSM5610LV (SEM) (Japan Electronics), the sample was

sprayed with gold after vacuum drying.

Experimental results and discussion

X-ray diffraction patterns . In the process of the fermentation with sugar cane molasses, there is

sediment which looks like soft fouling with a flocculation state in the bottom of fermentation tank.

These deposits are the aging part of fermentation yeast, fermentation metabolites and colloid. After

the sugar cane molasses liquid flow into the preheater, under the condition of the higher temperature

and a certain concentration of ethanol, the molasses fermentation hydrocolloids was destroyed and

rapidly flocculated. With the increase of the temperature and the accumulated of reaction time, the

inlet of molasses distillation tower was filled by the loose block of sediment. In the alcohol

distillation process, insoluble solids will be gradually deposited on the tower board, which mainly

composed of three substances: inorganic salts, colloids, suspended solids.

Inorganic salt content includes about 90% calcium sulphate, for the rest part, it may be sulfite,

calcium phosphate, silica, etc., in which Calcium ion, sulfite, phosphate ions, colloid, suspension

comes mainly from Lees initial molasses, and sulfate ion mainly is from the acidification process in

the molasses stillage alcohol fermentation production. The colloid has a good solubility in water but

little can soluble in alcohol. In the upper part of the Evaporation tower the content of alcohol is

more than 30% (V/V), this situation will cause rapid colloidal precipitation and sediment, and the

colloid will absorb salts and Fragments of yeast suspension，which will form some hard texture of

sediments under high temperature.

It was found that the sediment has different colors and hardness in the different layer of molasses

distillation tower. The thickness of sediment molasses in distillation column are different with it

appearing at different layers. Taking the sediment samples from molasses distillation tower, using

X-ray diffraction analysis, the pattern was shown in Fig. 1.

1268 Future Material Research and Industry Application

10 20 30 40 50 60 70

2-Theta(°

0

250

500

750

1000

Intensity(C

ounts)

[2.raw] 2

Fig.1 The X-ray diffraction pattern of Scale from topping still

The molasses distillation tower tends to generate a large number of sediment. From the fig. 1, we

can see that there are three spectrums graphs in the larger peak intensity. With the Analysis of

patterns by Software of MID Jade 5.0, Composition of sediment were detected in the distillation

tower，which is composed primarily of Calcium sulfate dihydrate, also some other small amount of

Hydrated iron oxide, silicon dioxide, Magnesium sulfate heptahydrate and Dicalcium phosphate

dihydrate.

Analysis of crystal shape and composition. Using scanning electron microscopy，the type of

crystal and distribution can be clearly observed in sediments. With the analyzing of energy

dispersive distribution on the surface of the sediment，the atomic composition in the sediment

appeared on the Figure below. Scannogram of sediment from different parts of molasses distillation

tower shows that：The sediment of crystals has different forms when it was took from different

positions in distillation tower，but all of these crystals can be attributed to four kinds of typical

shape, shown in Fig.2, Fig.3, Fig.4 and Fig.5.

Fig.2 The first crystal form and its energy spectrum

The first crystal form was larger with smooth surface. Through the date of elements and atomic

ratio provided by the spectrum analysis software，we can see the details in Tab. 1.

Tab. 1 Main elements and the atomic ratio in the first crystal

Element O S Ca O/S S/Ca

Atomic ratio（%） 70.29 15.91 13.79 4.42 1.15

The major components of crystalline sediments are of calcium, sulfur and oxygen elements, in

which the main compound is calcium sulfate with a certain amount of crystal water.

The second is the spherical crystal with smaller size. Calculated by energy spectrum analysis, it

was found that the crystal contains a large amount of carbon (see Tab. 2).

Advanced Materials Research Vols. 455-456 1269

Fig.3 The second crystal form and its energy spectrum

Tab. 2 Main elements and the atomic ratio in the second crystal

element C O S Ca Mg Si K O/S S/Ca

atomic ratio（%） 69.13 23.47 3.49 3.01 0.38 0.42 0.14 6.78 1.15

High content of carbon and low content of metal elements indicated that there is a great amount

of sediment organic matter, which might be the yeast metabolite and yeast debris. Inorganic

components are primarily calcium sulfate; possibly be a small amount of magnesium sulfate, silica,

potassium sulfate and other salts.

Fig.4 The third crystal form and its energy spectrum

The third crystal is some of irregular crystal with flocculation form. Calculated by energy

spectrum analysis, we found that the crystal contains a large amount of carbon (see Tab. 3).

Tab. 3 Main elements and the atomic ratio in the third crystal

element C O S Ca Mg Si K Al

atomic ratio（%） 55.88 35.58 1.79 1.20 0.68 4.50 0.21 0.16

High content of carbon and low content of metal elements indicated that there is a great amount

of sediment organic matter. Divided the carbon element from the energy spectrum，the other part of

crystal has silicon element for about 70%. This shows that the main inorganic component is silica.

In addition to above components，the crystal may also contain a certain proportion of calcium

sulfate, magnesium sulfate, calcium carbonate, magnesium carbonate, along with a small amount of

potassium and aluminium.

1270 Future Material Research and Industry Application

Fig.5 The fourth crystal form and its energy spectrum

The fourth sediment is a needle-like crystal. Through energy spectrum analysis and calculations

(see Tab. 4), the element consists of oxygen, sulfur, calcium, potassium, in which oxygen, sulfur,

calcium accounted for the majority. The main component is calcium sulfate, as well as a small

amount of potassium sulfate

Tab. 4 Main elements and the atomic ratio in the fourth crystal

element O S Ca K O/S S/Ca

atomic ratio（%） 68.82 15.76 14.02 1.39 4.37 1.12

Conclusions

Analysis about the chemical composition of molasses sediment is a very complex, trivial work with

high-demanding technical operations. In traditional testing methods, some components may not be

analyzed while some may have been lost in the ignition and some might be damaged in sample

processing. Through X-ray diffraction analysis of sediment components, the major components of

sediment was calcium sulphate, with 20% of organic material and other fractions of Calcium sulfate,

magnesium sulfate, calcium carbonate, magnesium carbonate, etc. It was concluded that the main

influential factors to the sediment is Calcium ion, sulfate and the organic components in the sugar

solution. Analysis of composition of sediment from molasses by scanning electron microscopy with

energy dispersive proved that calcium sulphate dihydrate was the main component.

Acknowledgements

This work was supported by Foundation item: National High Technology Research and

Development Program — 863 Program - 2009AA06A416 ， Projects of research

2010GXNSFE013006 ， National Water special research 2008ZX07317-02-03A2 ， Guangxi

Science Foundation for the Youth, Contract No. 0832005.

Advanced Materials Research Vols. 455-456 1271

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