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By-Products
FILTER MUD CAKE AS A FUEL FOR STEAM GENERATION IN EGYPT
A.A. Elkader* and A.A. Yassin**
* Sugar & Distil lation Company, Egypt
* * Department of Chemistry, University of Cairo, Egypt
Key words: Filter mud, bagasse, fuel, steam generation
ABSTRACT
Disposal of filter mud cake constitues a nuisance and a significant expense for sugar mills. It may pollute the environment when dumped in natural water courses or burnt in the fields. A trial was conducted to use muds as fuel in steam generating plants. It was concluded that a mixture with bagasse in the ratio of 1:12 provided a useful, eco- nomic, safe and easy means of disposal. Moreover, this procedure allowed the ash to be removed easily from the boilers by mechanical means.
INTRODUCTION
In the sugar industry the filter mud cake contains much of the colloidal organic matter originally dispersed in the juices together with inorganic and organic anions that precipi- tate during clarification. Certain other nonsugars present in the iuice are usually oc- cluded in these precipitates. The amount of filter mud and its composition vary greatly with the locality, variety of cane, milling efficiency and method of clarification. Various uses have been proposed for filter mud. The most useful that have proved feasible on a laboratory scale, but still requere feasibility studies for commercial application, are in cement, distemper paints, foaming agents, activated carbon, filter aids, protein and compost industries (~a tu rau~) . The extraction of wax from the filter mud has been successfully undertaken in a num- ber of countries. However, the problem of disposing of the filter mud as a whole is not solved by this process. The problems caused by disposing of the filter muds are not only related to the volume to be handled, but also to its polluting effects and an increase in insect pollution such as house flies. There are two common methods for disposing of muds, either by burning or throwing into water courses. For burning the muds are carried to nearby fields where they are left to dry and then burned, either alone or together with the bagasse. This incomplete combustion produces a great amount of soot in the surrounding atmosphere, affecting the quality of the air. When muds are diluted and incorporated into irrigation systems, the consequences are limited, but when this slurry is dumped into natural water courses of low volume, or during the drought season, the solids settle to form a layer that covers the bottom, des- troying both flora and fauna. This biodegradable organic material has a high oxygen demand, thus impovershing the physico-chemical quality of the water, which conse- quently affects the plankton and use of the water (Fors'). In Egypt, where more than eight million tons of sugarcane are crushed annually, clarifi- cation of the cane iuice is carried out either by the sulphitation or the phosphatation processes. The muds are treated with milk of lime to pH 8.3, bagacillo is added as a filter aid, filtration is carried out on rotary vacuum filters, and about 230 thousand tons of filter muds are discharged in the form of cake. The muds were formerly discharged to water courses. Nowadays pollution is controlled by strict state laws, hence in recent years muds have been transported to the fields by dump-trucks, which is an ex'pensive system. Furthermore the muds are unloaded in heaps which still have to be distributed throughout the fields.
MATERIALS AND SAMPLING
Samples of filter mud from-different factories were collected throughout the crushing
season of 1987. Samples from Armant sugar factory were analysed for moisture, sugar, wax, fat, organic matter and ash contents. The samples under investigation were 601-
lected every hour from the working filters of the factory and were analysed once every hour. The mean values for the whole season were calculated.
Representative samples of bagasse from different factories were similarly collected and
mixed with representative samples of filter mud cake in a ratio of 12 bagsse to 1 mud
by weight. A 100 g sample of the mixture was burned completely at 5006C and the flue gases were collected in 500 cc of distilled water. The solution was analyzed for pH and
SO, content. The same experiment was repeated by collecting the gases in an H,O, so- lution for determining SO,. A similar analysis was carried out for bagasse samples
alone.
The ash contents of filter mud and bagasse were analysed and the compositions were
compared. Different representative samples of filter mud cake and bagasse were ana-
lysed for C & S using the universal apparatus for the rapid determination of C & S. The calorific value of representative samples of bagasse and filter mud cake were under-
taken separately by the bomb calorimeter method.
METHODS OF ANALYSIS
Determination of ash in bagasse and muds: A platinum dlsh conta~ning the bagasse
or mud sample was steadily heated in a sufficient stream of air using an electric muffle
furnace at 550°C. After one hour the temperature was raised to lOOOOC and heating
was continued to constant weight.
Determination of sugar in filter mud: The mud was analysed by polarizing 25 g of the
mud, according to official methods of sugar factory control in Mauritius. Silica was determined by the alkaline fusion method (Voge14). Combined oxides were
determined by precipitation as hydroxides (Voge14). Calcium oxide was determined by
precipitation as calcium oxalate (Voge14). Magnesium oxide was determined gravimetri-
cally by precipitation as magnesium pyrophosphate (Voge14). SO, was determined by
the Monier-Williams method and SO, was determined gravimetrically by the barium chloride method (Voge14). Phosphates were determined calorimetrically by the ammo-
nium molybdate and ascorbic acid method. Sodium and potassium in ash were deter-
mined by using the flame photometer. C and S analysis of bagasse and muds was con-
ducted by using the universal apparatus for rapid determination of C and S. Fats and wax were determined by extraction with petroleum ether at 200C and then at 600C us-
ing soxhlet apparatus.
RESULTS
The filter mud from Armant sugar factory during the 1986187 crushing season was ana-
lysed for moisture, sugar, wax, fat, ash and organic matter contents. The results are shown in Table 1. In order to evaluate the possibility of using the filter mud cake as a fuel
in the steam generating plant, two important points had to be taken Into consideration: (i) the chemical composition of the mud ash and its effect on the sintering and melting
points of the ash
(ii) the carbon and sulphur contents and the calorific value of the mud. Since the composition of the ash of any fuel material has a direct effect on the differ- ence between the sintering and fusion points of the ash, full analyses for the ash of
both bagasse and filter mud cake were carried out (see Tables 2 and 3).
BY-PRODUCTS
Table 1 - Analysis of filter muds from Armant sugar factory 1986/87 season
Ash Wax Fats
N 0
1 77.7 1.96 5.61 2 77.8 1.83 4.93 3 77.6 2.00 4.94 4 77.8 2.00 4.35 5 77.6 2.04 4.31 6 77.8 1.98 4.43 7 77.6 2.28 4.09 8 77.6 2.05 4.66 9 77.5 1.89 4.43
10 77.7 1.88 4.37 1 1 77.7 1.87 4.32 12 77.7 2.00 4.27 13 77.6 2.03 3.28 14 77.7 2.15 4.46
Means 77.7 2.00 4.52
Organic non sugar
Yo
The decrease in the melting point of the ash due to the presence of some metals was
lculated by the Van Nieuwen Burg equation (Honig2). crease in melting point: = - 0:25 a + (0.03 b - 0.8) c
b = SiO,% c = 1 0 0 - a - b
From Tables 2 and 3 it is clear that the bagasse ash had much higher percentages of Na20 and K 2 0 than those of filter mud ash, and this difference reached its maximum
in Armant samples.
From Tables 4 and 5 it is also clear that the factor (F), which is the decrease in the melt- ing point of the ash, has a positive sign in the case of bagasse ash while it has a nega-
tive sign in case of filter mud ash, which means that it has a high melting point. Fur- thermore, the sintering and melting points of filter mud ash were much wider apart
than were those of bagasse ash.
Melting point measurements
The melting points for bagasse ash and filter mud ash from Armant sugar factory were
determined by thermogravimetric analysis using the TGD instrument type 300. Sample weight: about 40 mg Chart spread: 150 mm/hr
Heating rate: 100C/min Full scale: DTA f 50 uv
type 20 mv
Table 2 - Chemical analysis of bagasse ash from different sugar factories
Analysis Factory
Carbon Si02 Fe203 CaO MgO K2O Na20 so3 p205
Abou korkas 0.39 78.66 6.61 4.61 3.37 4.20 0.8823 0.1 667 0.30 0.71 Nagaharnadi 1.04 73.12 6.29 4.26 6.70 1.97 2.0877 0.2952 2.92 Dishna 1.12 73.70 6.43 4.55 4.38 4.93 2.0946 0.3465 0.75 1.64 Kous 0.97 72.65 7.07 4.04 5.41 3.78 2.4524 0.3966 1.20 1.14 Arrnant 1.17 60.45 9.04 6.58 5.54 2.60 7.842 1 1.2510 4.26 1.01 Edfou 0.98 65.17 10.14 6.57 5.16 2.65 4.2583 0.4986 2.30 1.89 Kornornbo 1.15 69.87 6.13 3.69 4.90 3.22 3.9647 0.6440 4.24 2.1 1
Means 0.74 70.52 7.39 4.90 5.07 3.34 3.3689 0.5141 1.86 1.63
Table 3 - Chemical composition of ash of filter mud during the 1986/87 crushing season at Armant sugar factory
BY-PRODUCTS
Table 4 - Bectease in the melting point of bagasse ash of different sugar factaries, factor (F)
-- - --
Factory A1,03 SiO, 100 - a - b Decrease in M.F!
a b c F
Aboukorkas 6.61 78,66 Nagahamadi 6.29 73.12 Dishna 6.43 73.70 Kous 7.07 72.65 Armant 9.04 59.47 Edfou 10.14 65.17 Komombo 6.13 69,87
Table 5 - Dectease in the melting point of the ash of filter mud cake of.Armbnt sugdr fact6ry during the 1986/87 crushing season, factor (F)
- -
Decade A1,03 SiOz 100 - a - b Decrease in M. P. N o a b c F
1 9.78 21.030 69.190 - 14.145 2 8.67 21.890 69.440 - 11.118 3 15.90 17.050 67.050 - 23.318 4 14.80 20.740 64.460 - 15.160 5 9.76 19.410 70.030 - 14.685 6 6.24 19.690 74.070 - 17.062 7 9.00 20.020 70.980 - 16.403 8 7.23 17.910 74.860 - 21.473 9 4.59 20.580 74.830 - 14.811
10 4.00 21.110 74.890 - 13.484
Means 9.00 19.940 71 060 - 16.589
Ash of filter mud Ash of bagasse
Melting point about 1100 - 13000C about 970°C
sintered state at s~ntered state at llOOOC and completely 9200C and completely
melted at 1300°C melted at 1070°C
These important results imply that a great advantage is gained due to the increase in
the melting point, and consequently the prevention of the adhesion of the ash to the boiler tubes.
Carbon and sulphur content of filter mud cake
Analyses for carbon and sulphur were undertaken using the universal apparatus for de- termination of carbon and sulphur. Table 6 shows the percentage of carbon and sulphur
on dry basis in representative samples of filter mud cake, and its comparison with com-
posite samples of both bagasse and mazote used as fuel in the steam generating plants.
A.A. ELKADER AND A.A. YASSIN
From the table it is clear that although the percentage of combustible sulphur present
in filter muds is higher than that of bagasse, it is far below the percentage of sulphur
present in mazote, which is used in the steam generating plants in Egypt.
Table 6 - Carbon and sulphur analyses in filter mud, bagasse, and mazote
Samples Carbon % on
dry basis
Filter mud cake of
Aboukorkas Nagahamadi Dishna
Kous
Armant
Edfou Komombo
Bagasse samples
(composite sample from)
(different factories) Mazote sample
Combustible sulphur
% on dry basis
0.37 0.25 0.29 0.38 0.38 0.35 0.11
The calorific value of representative samples of bagasse and filter mud were found to
be 4340 cal/g and 3675 cal/g respectively (on dry basis). Comparative analyses of the flue gases arising from the burning of bagasse alone and
its mixture with filter mud cake in a 12:l ratio, are given in Table 7. It is clear that there
is no detectable difference between the SO, and SO, contents in the flue gases aris- ing from burning bagasse alone or its mixture with filter mud ~n ratio of 12:l.
Table 7 - Comparative analysis of the flue gases (SO, + SO,) arising from burning bagasse alone and its mixture with filter mud cake (12:l)
Moisture % Analysis of flue gases
arising from burning
pH SO, mg/g'
SO, mg/g Ash mg/g
Bagasse
Mixture of bagasse
& filter mud cake in 12:l
CONCLUSION
Mixing filter mud cake with bagasse in a ratio 1:12 for use as fuel in the steam generat-
ing plants can constitute an economic and easy way to dispose of the filter mud cake, thus avoiding further pollution of the surrounding atmosphere. An additional advan-
tage from their use as a fuel is that they increase the melting point temperature of the
ash, and therefore the difference between the sintering and melting points of the ash, which permits its easy mechanical removal from the boilers.
REFERENCES
1. Fors, AA (1986). Proc Inter Amer Sug Cane seminar: energy and by products from sugar- cane p 230.
2. Honrg, P (1963). Vol I, Elsevier Publishing Co, London, p 360. 3. Paturau, MJ (1969). By-products of the sugarcane industry. Elsevier Publishing Co, New
York p 119. 4. Vogel, Al (1968). 3rd edition, Lowe and Birypone, London.
ETUDES SUR LA POSSIBILITE D'UTILIZAPION DES POURTEAUX DES FILTWES SOMME COMBUSTIBLE POUR LA GENERATION BE VAPEUR
DANS L'INDUSTRIE SUCRI~RE EN EGYPTE
A. A. Elkader* et A.A. Yassin** I "Sugar & Distil lation Company, Egypt
**Department of Chemistry, University of Cairo, Egypt
EXTRAIT I L'elirnination des tourteaux des filtres est une activite nuisante et de coirt eleve duns les sucreries. Jetes sur les rivieres ou brirles sur les champs ils sont cause de pollution de I'arnbiance. Ce travail propose I'utilisation des tourteaux comme combustible pour la generation de vapeur. Les rbsultats ont montre que le melange de tourteau et de bagasse dans la proportion de 1:12 est un combustible convenable pour les chaudieres et son usage facilite la remotion des cendres des fours.
US8 DE TORTAS DE FIUWO COMO COMBUSTIBLE PARA GENERACION BE VAPOR NO EGlTO
A.A. Elkader* y A.A. Yassin**
'Sugar & Distil lation Company, Egito
**Department of Chemistry, Universidad del Cairo, Egito
RESUMEN I I La eliminaci6n de las tortas de filtro es laboriosa y costosa. Ellas impurifican el am- biente cuando despejadas en cursos naturales de agua o cuando son quernadas en el campo. Por un experiment0 de quema de tortas en generadores de vapor se verific6 que una mescla de torta y bagazo de cafia en la proporci6n de 1:12 result6 en un rne- dio irtil, econ6mic0, seguro y facil de disposici6n. En adici6n este proceso facilita la remoci6n de la ceniza de las calderas por rnedios mec6nicos.
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