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Oil seeds industry emissions: A case study
Oil Seeds Industry Emissions: A Case Study PAOLO BATTISTONI* GABRIELE FAVA** Istituto di Scienza dei Materiali, Universitd di A n c o n a , Via della Montagnola, 3 0 - 6 0 1 0 0 A n c o n a , Italy
SUMMARY This study assessed the contribution o f an oil seed industry to the organic loadings o f an urban atmosphere, so that more realistic strategies can be developed to control such pollution. Emission measurements suggest that fatty acMs, aldehydes and solvent related hydrocarbons are emitted in amounts comparable to or even exceeding anthropogenic organics. Technological options for controlling emissions in the context of the local situation with the data presented are discussed.
INTRODUCTION Notwithstanding the number of air pollution studies concerning mineral oil processing plants there is a lack of papers referring to extraction, solvent evaporation and refining of vegetable oils. Dust, obnoxious odors, solvents and other organic compounds (Finelt, 1979) are typical emissions of oil seed industry; in particular in the extraction and refining of soybean oil high losses of hexane require an air pollution control through adsorption on activated carbon or thermal incineration (Becker, 1972). Characteristic odors of oil seed processing plants have been attributed to compounds such as low molecular weight fatty acids, ketones with 7,8,9 carbon atoms, and aldehydes also widely diffused in the manufacture of fatty acid (Heinz, 1978), and found even in tomato seed oil fac-
*Paolo Battistoni was born in Ancona, Italy in 1951 and received a degree in chemistry in 1974 at Bologna University. He started his activity at A n c o n a University where he is a p e r m a n e n t professor o f waste water treatments. His research interests have centered on monitoring of organics in ambient air and waste streams and m e t h o d developments in these areas. **Gabriele L. Fava was born near Bologna, Italy in 1945 and received his degree in chemistry from the University of Bologna in 1972. He started his research activity at A n c o n a University where he is a p e r m a n e n t professor of pollution and environmental control. He has spent research terms at the Iowa State University, USA in 1976 and 1979. His main interest is in the environmental behaviour o f toxic substances through physicochemical profiles. 0251-1088/83/$3.00
tories (Volpi and Casagrande, 1978). A sufficient system of seeds stocking has been recently suggested to prevent fermentation and consequent deleterious effect on the emissions from the processing plants (Volpi and Casagrande, 1978). The aim of the present work is to devise a strategy of air pollution control through measurement of the emissions extent associated with the major unit operations of a medium-sized oil seed processing plant which utilizes soybean, sunflower and castorbean. In particular the contribution to the air quality of classes of compounds characterized by higher toxicity than that of hexane, and the differences related to the various seeds processed have been evaluated. The factory under investigation, I.C.I.C.s.p.a., is situated in the harbour zone of Ancona not far from downtown (Fig. 1) and produces vegetable food oils such as sunflower oil (2000 q/d seed manufactured) soybean oil (3500 q/d) and castor oil (600 q/d) (Battistoni and Fava, 1983). All the seeds are manufactured in a continuous process, through a combination of pressing and solvent extraction, which includes three distinct phases: (a) Seed preparation: includes cleaning operations on the stored seeds and mechanical pretreatment to arrange the seed for maximum oil recovery; only for sunflower seed and castorbean is the major part of the oil obtained by mechanical expression. (b) Solvent extraction: the prepared seed is extracted with warm solvent; the enriched solvent is then sent for solvent recovery and oil separation. The seed residue on leaving the extractor is treated with steam to remove hexane and retained oil, following which it is dried and cooled. (c) Meal production: after all mechanical treatments and solvent extraction the seed is dried, cooled and sized to produce a residue meal suitable as animal feed. Figure 2 indicates the emissions associated with the various process operations; the large number
The Environmentalist, 3 (1983) 2 1 3 - 2 1 8
@Elsevier Sequoia/Printed in The Netherlands
Fig. 1. Map of Ancona showing the location of factory under investigation.
of emission sources is reducible, either on the basis of concentration values of the total organic carbon (T.O.C. mg/Nma), or, on the basis of the location of the point emissions connected with the unit operation. T.O.C. values indicate that the emissions fall into two major groups (Fig. 3): H i g h - M e d i u m concentration emissions (T.O.C./> 100 mg/Nm 3) These sources are characterized by physicochemical modifications that take place on the seed during heating, meal desolventing and drying. L o w - n i l concentration emissions (T.O.C. ~< 40 mg/Nma). Mechanical cleaning of the seeds (T.O.C. traces) and meal manufacturing (Fig. 3) are typical examples. These last sources have been neglected since their low T.O.C. value ( 3 0 - 4 0 mg/Nm 3) can be attributed mainly to solvent losses, which diminishes the emission of corn214
pounds of higher toxicity. On the contrary the soybean heater emission has been considered in spite of the low T.O.C. value, because in this in stance the compounds arise as the result of thermal treatment. For this reason the investigation has been limited only to the more meaningful sources (Table 1).
EXPERIMENTAL The volumetric flow rate of the gaseous stream to be sampled is obtained by means of velocity traverses performed through a pilot tube, the sampling ports having been located far from any disturbance. For the determination of the moisture content, condensation and adsorption techniques were used. (In both cases the flow rate has been adjusted to 10 1/min). The Environmen talist
\
TABLE 1. Emission data of the vent streams selected for class compound analyses Vent
Temperature Q (flow) Water T.O.C. °C Nm3/h content CH4 mg/Nma g/Nm3
Soybean (,) la 2a 2b
40 57 50
20000 7000 7000
trace 200 trace
Castorbean (,) 2a 57
600
150
572 800 900 1000
180 1200 600 80
Sunflower (A) la 2a 2b 3a
68 88 75 35
m
trace 300-760 70-100 >1600 230-312 >1950 580-950 70-100
2a •
Chemical Analysis T h e isokinetic sampling was p e r f o r m e d b y passing the gas in a c o n d e n s e r k e p t at 0 °C in a t h e r m o s t a t c o n t r o l l e d b a t h and t h e n bubbling in the a d s o r p t i o n solution. Chemical analyses have been carried o u t b o t h on the dried gas and o n the collected c o n d e n s a t e . A d s o r b e n t solutions and m e t h o d s used are i n d i c a t e d below. Determination A l d e h y d e s (Sawicki et al., 1961) F a t t y Acids ( D y u z h e v a , 1960). Acrolein ( C o h e n and Altshuller, 1961 ) Oxidants ( S a l t z m a n and Gilbert, 1959) Reactive h y d r o c a r b o n s (Kubel m e t h o d ) , ~&Sunflower
, • Castorbean • Soybean
Oil 9 • ,0
Mechanical p r e P ! l
la
ration and pre- ~
Ib
pressing.
Heaters Cyclones •Sunfiower
la
Heaters
Ib
Cyclones
• Soybean HexaDe Extraction
2a
Meal desolventizer
2b
Dryer - cooler
Oil~ ~eal desolventizer
•Sunflower 2a
Drver
2b
Cooler
preparation
Dryer • Castorbean
2a
1 Meal
Meal desolventizer
~
Cyclones Cyclones
• Sunflower
3a
Cooler
3b
Cyclones
Fig. 2. Block flow diagram for emission of soybean (m),sunflower (A), and castorbean (o), oil seed industry. Vol. 3, No. 3 (]983)
D
3a
3b
la
[]
ab
z~ ~,3b
•AAA
la~
a~b []
Fig. 3. Point emissions for manufacturing cycles: soybean (m, ~); sunflower (A, z~);castorbean(e, o). Closedsymbols = high-medium concentration (T.O.C. > 100 gm/Nm3); open symbols = low-nil concentration (T.O.C. ~<40 mg/Nm3).
Adsorbent solution 3 - M e t h y l - 2 - b e n z o t h i a z o l i n o n e h y d r a z o n e (alc.) Methanol 4-Aryl-resorcinol (alc.) KI ( a q u e o u s ) KMnO4 ( a q u e o u s ) All c o n d e n s a t e s were c o n t r o l l e d b y U.V. s p e c t r o s c o p y d i r e c t l y o n the solution using a Perkin E l m e r 554 s p e c t r o p h o t o m e t e r , while the c a r b o n t e t r a c h l o r i d e e x t r a c t s were c h e c k e d t h r o u g h I.R. s p e c t r o s c o p y using a P e r k i n - E l m e r 298 infrared s p e c t r o p h o t o m e t e r c o u p l e d with a C.D.S. d a t a station. T h e t o t a l organic c a r b o n c o n t e n t s were determ i n e d on the dried gas using a Carlo Erba THM 4 7 0 gas c h r o m a t o g r a p h while the C.O.D. o f the c o n d e n s a t e s were evaluated chemically b y the bichromate method. T h e t o t a l a m o u n t e m i t t e d at the source has been evaluated b y c o m b i n i n g d r y gas and condensate d e t e r m i n a t i o n s o n the basis o f m o i s t u r e content.
Dryer - cooler • Soybean
3a 3b
c-~
--7
[]
• Soybean
~
RESULTS T h e gas c h r o m a t o g r a p h i c analyses on the dried emissions show the presence o f a n u m b e r o f organic c o m p o u n d s with d i f f e r e n t r e t e n t i o n times, some o f t h e m c h a r a c t e r i z e d b y low p o l a r i t y like h y d r o c a r b o n s , and others with m u c h 215
higher polarity. The examination of the U.V. and I.R. spectra reveals the presence of saturated aldehydes and fatty acids while excluding other functional groups. In addition, repeated analyses specifically addressed to the search of acrolein, oxidants like ozone and PAN, were performed on the soybean and sunflower vents and gave systematically negative results. Attention has, therefore, mainly been focused on the determination of aldehydes and fatty acids completing the analyses with the determination of the total organic carbon as comprehensive organic pollution index. In this way it has been possible to relate the emissions to the type and the phase of the manufacturing cycle. The emission concentrations show the higher content of both aldehydes (Fig. 4(a) and (b)) and
3 mg/Nm
Sunflower italian
foreign
soybean 1981
castorbean
fatty acids (Fig. 5(a) and (b)) in the sunflower seed cycle compared to the ones of soybean and castorbean. Under comparable conditions the highest values obtained during the processing of all types of seeds are found in the desolventizer zone. This may be explained with the higher degree of the seed thermal exposure. Emission factors given in Table 2 indicate clearly the contribution of each type of seed processed. For instance there is an equal contribution of aldehydes and fatty acids in the castor bean processing cycle, and a substantial contribution of fatty acids in the soybean cycle (fatty acids-aldehydes ratio equal to 2.2-2.3), while, on the contrary in the sunflower oil process, the ratio is reversed (fatty acids-aldehydes ratio equal to 0.98-0.56).
mg/Nm3
1981
300
300
200
200
100
(a)
Sunflower italian foreign
soybean 1981
castorbean 1981
IO0
IN
,ll
(a)
mg/Nm 3 , 5OO
3 mg/Nm
400
400
300
300
200
200
loo
10° 11 nH
!il
l tn
,I,
I I o
Co)
(b)
Fig. 4. Aldehydes vent concentration expressed as mg/Nm 3 o f formaldehyde. (a) Dried gas, (b) undried gas.
Fig. 5. Fatty acids vent concentration expressed as mg/Nrn 3 of acetic acid. (a) Dried gas, (b) undried gas.
216
The Environmentalist
TABLE 2. Emissions factors for sunflower,soybean and castorbean cycle. Aldehydes, fatty acids and total organic carbon are evaluated as grams for q of seed processed. Vent
Aldehydes Fatty acids Total organic HCHO g/q CH3COOHg/q carbon CH4 g/q
Italian sunflower
8.60 1.30 5.00 1.50 0.80
7.10 1.70 3.20 1.80 0.40
>34.80 3.50 > 19.00 11.00 1.30
9.00 1.00 4.20 3.00 0.80
4.80 1.10 2.20 1.10 0.40
30.80 3.00 > 19.00 7.50 1.30
6.00 6.00 -
4.00 6.30 3.00
Heater Desolventizer Dryer Cooler Foreign sunflowers
Heater Desolventizer Dryer Cooler Soybean 1981
Heater Desolventizer Cooler Castorbean
4.20
13.30
4.30
6.6
4.7
33.00
"I 4 .(9
-
31.50 1.50
Soybean
~s~:~i£;~ ~ ~ Castorbean
ij!!ij!!ji!i i!i !!ii !i i!i i!¸i i!i i Sunflower
(a)
33.00
It is also possible to ascertain a decreasing cont r i b u t i o n o f chemical emission, viz. s u n f l o w e r > s o y b e a n > c a s t o r b e a n for the a l d e h y d e s , and s o y b e a n > s u n f l o w e r > c a s t o r b e a n for f a t t y acids. T h e emission factors based o n T.O.C. values are a n y w a y n o t very m e a n i n g f u l because o f interference due to losses o f the e x t r a c t i o n solvent. H o w e v e r c o m p a r i n g the a l d e h y d e s and f a t t y acids c o n t r i b u t i o n to the value o f t o t a l organic c a r b o n (T.O.C.) according to a f a c t o r o f 1.26, as f o u n d for the s u n f l o w e r h e a t e r unit, it is possible to estimate the solvent losses, e.g., expressed as m e t h a n e , in 0.12 kg/t for the s o y b e a n cycle and 0.18 kg/t for the s u n f l o w e r cycle. This is m u c h l o w e r t h a n t h a t o f 1.2 kg/t, f o u n d b y Finelt ( 1 9 7 9 ) b u t justified on the basis o f the partiality o f emission sources c o n t r o l l e d . This indicates that the vegetable oil seed i n d u s t r y , besides the n e e d to r e d u c e the losses o f the solvent, the p r o b l e m o f organic substances does exist in spite o f r e d u c t i o n o f solvent losses t h r o u g h t e c h n o l o g ical i m p r o v e m e n t in the processing plants.
4.3
4.1
24.6
I
SoVb ean
~l~!{:!,~i~!~[# C as t o r b e a n
:
S u n f 1 .....
Co)
57.
I0.0
3.0
DISCUSSION A c c o r d i n g to the results o b t a i n e d f r o m this investigation on the m e d i u m - s i z e d oil seed processing plant, the mass balance on the emissions (Fig. 6(a)(b) and (c)) stresses the i m p o r t a n c e o f s o y b e a n m a n u f a c t u r e which, in this c o n t e x t , a c c o u n t s f o r 80% o f the f a t t y acids and 50% o f the a l d e h y d e s released. Since a substantial emission o f pollutants, in addition to the e x p e c t e d loss o f solvent, has been shown, the t r e a t m e n t o p t i o n s usually selected Vol. 3, No. 3 (1983)
0.8
I (c)
Soybean
6.5
~ ,~!~~i C a s t o r b e a n !~:!::#~[{#~ ~'N### I}~,~'
)::L,..'{<}S u n f l o w e r
:.: . ...
Fig. 6. Relative contribution to the total emissions assigned to each circle. (a) Total aldehydes, (b) total fatty acids, (c) total organic carbon. 217
may not result in satisfactory ambient air quality. Following Becker (1972), the intervention policy is recommended to be based on incinerators, or on carbon adsorption for the solvent recovery optimization, but, in the latter case, the adsorption capacities for aldehydes and fatty acids differ by at least one order from that o f hexane. It seems, therefore, reasonable, in order either to prevent environmental pollution or to minimize the cost o f the pollution control, to define the best treatment conditions for such classes of compounds. In any specific case consideration must be given to the large number o f emissions sources and leaks and, as a general principle, the difficulty o f treating large volumes of air. It seems reasonable, in agreement with Heinz (1978), to suggest that an approach involving the treatment o f the emissions should be characterized by a T.O.C. of 100 mg/Nm 3 (Fig. 6(a)(b) and (c)). The comparison between the analytical data relative to the dried and undried gas furthermore, points out the possibility of lowering the pollution load. Considering the variation o f fatty acids concentration (Fig. 5(a) and (b)), it is possible to observe a higher abatement in the case o f high water content (Table 1). Abatement yields o f up to 86% can be foreseen which would be in good agreement with the 90% reported utilizing scrubbers in similar plants of tomato seed extraction (Volpi and Casagrande, 1978). For the low water content emissions (soybean and castorbean, see Table 1) the abatement yield turns out to be drastically lowered. As far as aldehydes are concerned a similar trend is found (see data of Fig. 4(a) and (b)), even with an abatement yield of 45% (desolventizer, Italian sunflower seeds). This is probably due to the lower water solubility of these compounds.
218
These considerations in relation to the factory under examination show the following balance (Fig. 6(a)(b) and (c)), dashed area): - treatment of 52% o f the fatty acids with a 90% efficiency treatment o f 90% o f the total aldehydes with a 45% efficiency. The suggested emissions treatment becomes more valuable if examined in the light o f reactive hydrocarbons before and after drying (Table 3). The results observed suggest that the improvement obtainable may be higher than that foreshown only on the basis o f the total abatement data.
TABLE3. Reactivehydrocarbons(KMnO4index) Vent
Emissionsas 02 meq/m3
Dried gas 02 meq/m3
182-150 90-70 67-50
trace trace trace
90-83
trace
Sunflower (A)
Heater la Desolventizer 2a Drying2b Soybean (m)
Desolventizer2a
REFERENCES
Battistoni, P. and Fava, G. (1983) J. Air Poll. Cont. Ass., in press. Becker, K. W. (1972) J. Am. Oil Chemists Soc., 49, p. 40. Cohen, I. R. and Altshuller, A. P. (1961)Anal Chem., 33, p. 726. Dyuzheva, Y. V. (1960) Inst. San. Igieny, 17-49; Chemical Abstracts, 56, 6319a. Finelt, S. (1979) J. AirPoll. ControlAss., 29, p. 1192. Heinz, H. J. (1978) Rev. Fr. Corps Gras, 25, p. 123. Saltzman, B. E. and Gilbert, N. (1959) Anal. Chem., 31, p. 1914. Sawicki, E., Havser, T. R., Stanley,T. W. and Elbert, W. (1961) Anal, Chem., 33, p. 93. Volpi, E. and Casagrande, G. (1978) Riv. Ital. Sontanze Grasse, 55, p. 329.
The Environmentalist
SUMMARY This study assessed the contribution o f an oil seed industry to the organic loadings o f an urban atmosphere, so that more realistic strategies can be developed to control such pollution. Emission measurements suggest that fatty acMs, aldehydes and solvent related hydrocarbons are emitted in amounts comparable to or even exceeding anthropogenic organics. Technological options for controlling emissions in the context of the local situation with the data presented are discussed.
INTRODUCTION Notwithstanding the number of air pollution studies concerning mineral oil processing plants there is a lack of papers referring to extraction, solvent evaporation and refining of vegetable oils. Dust, obnoxious odors, solvents and other organic compounds (Finelt, 1979) are typical emissions of oil seed industry; in particular in the extraction and refining of soybean oil high losses of hexane require an air pollution control through adsorption on activated carbon or thermal incineration (Becker, 1972). Characteristic odors of oil seed processing plants have been attributed to compounds such as low molecular weight fatty acids, ketones with 7,8,9 carbon atoms, and aldehydes also widely diffused in the manufacture of fatty acid (Heinz, 1978), and found even in tomato seed oil fac-
*Paolo Battistoni was born in Ancona, Italy in 1951 and received a degree in chemistry in 1974 at Bologna University. He started his activity at A n c o n a University where he is a p e r m a n e n t professor o f waste water treatments. His research interests have centered on monitoring of organics in ambient air and waste streams and m e t h o d developments in these areas. **Gabriele L. Fava was born near Bologna, Italy in 1945 and received his degree in chemistry from the University of Bologna in 1972. He started his research activity at A n c o n a University where he is a p e r m a n e n t professor of pollution and environmental control. He has spent research terms at the Iowa State University, USA in 1976 and 1979. His main interest is in the environmental behaviour o f toxic substances through physicochemical profiles. 0251-1088/83/$3.00
tories (Volpi and Casagrande, 1978). A sufficient system of seeds stocking has been recently suggested to prevent fermentation and consequent deleterious effect on the emissions from the processing plants (Volpi and Casagrande, 1978). The aim of the present work is to devise a strategy of air pollution control through measurement of the emissions extent associated with the major unit operations of a medium-sized oil seed processing plant which utilizes soybean, sunflower and castorbean. In particular the contribution to the air quality of classes of compounds characterized by higher toxicity than that of hexane, and the differences related to the various seeds processed have been evaluated. The factory under investigation, I.C.I.C.s.p.a., is situated in the harbour zone of Ancona not far from downtown (Fig. 1) and produces vegetable food oils such as sunflower oil (2000 q/d seed manufactured) soybean oil (3500 q/d) and castor oil (600 q/d) (Battistoni and Fava, 1983). All the seeds are manufactured in a continuous process, through a combination of pressing and solvent extraction, which includes three distinct phases: (a) Seed preparation: includes cleaning operations on the stored seeds and mechanical pretreatment to arrange the seed for maximum oil recovery; only for sunflower seed and castorbean is the major part of the oil obtained by mechanical expression. (b) Solvent extraction: the prepared seed is extracted with warm solvent; the enriched solvent is then sent for solvent recovery and oil separation. The seed residue on leaving the extractor is treated with steam to remove hexane and retained oil, following which it is dried and cooled. (c) Meal production: after all mechanical treatments and solvent extraction the seed is dried, cooled and sized to produce a residue meal suitable as animal feed. Figure 2 indicates the emissions associated with the various process operations; the large number
The Environmentalist, 3 (1983) 2 1 3 - 2 1 8
@Elsevier Sequoia/Printed in The Netherlands
Fig. 1. Map of Ancona showing the location of factory under investigation.
of emission sources is reducible, either on the basis of concentration values of the total organic carbon (T.O.C. mg/Nma), or, on the basis of the location of the point emissions connected with the unit operation. T.O.C. values indicate that the emissions fall into two major groups (Fig. 3): H i g h - M e d i u m concentration emissions (T.O.C./> 100 mg/Nm 3) These sources are characterized by physicochemical modifications that take place on the seed during heating, meal desolventing and drying. L o w - n i l concentration emissions (T.O.C. ~< 40 mg/Nma). Mechanical cleaning of the seeds (T.O.C. traces) and meal manufacturing (Fig. 3) are typical examples. These last sources have been neglected since their low T.O.C. value ( 3 0 - 4 0 mg/Nm 3) can be attributed mainly to solvent losses, which diminishes the emission of corn214
pounds of higher toxicity. On the contrary the soybean heater emission has been considered in spite of the low T.O.C. value, because in this in stance the compounds arise as the result of thermal treatment. For this reason the investigation has been limited only to the more meaningful sources (Table 1).
EXPERIMENTAL The volumetric flow rate of the gaseous stream to be sampled is obtained by means of velocity traverses performed through a pilot tube, the sampling ports having been located far from any disturbance. For the determination of the moisture content, condensation and adsorption techniques were used. (In both cases the flow rate has been adjusted to 10 1/min). The Environmen talist
\
TABLE 1. Emission data of the vent streams selected for class compound analyses Vent
Temperature Q (flow) Water T.O.C. °C Nm3/h content CH4 mg/Nma g/Nm3
Soybean (,) la 2a 2b
40 57 50
20000 7000 7000
trace 200 trace
Castorbean (,) 2a 57
600
150
572 800 900 1000
180 1200 600 80
Sunflower (A) la 2a 2b 3a
68 88 75 35
m
trace 300-760 70-100 >1600 230-312 >1950 580-950 70-100
2a •
Chemical Analysis T h e isokinetic sampling was p e r f o r m e d b y passing the gas in a c o n d e n s e r k e p t at 0 °C in a t h e r m o s t a t c o n t r o l l e d b a t h and t h e n bubbling in the a d s o r p t i o n solution. Chemical analyses have been carried o u t b o t h on the dried gas and o n the collected c o n d e n s a t e . A d s o r b e n t solutions and m e t h o d s used are i n d i c a t e d below. Determination A l d e h y d e s (Sawicki et al., 1961) F a t t y Acids ( D y u z h e v a , 1960). Acrolein ( C o h e n and Altshuller, 1961 ) Oxidants ( S a l t z m a n and Gilbert, 1959) Reactive h y d r o c a r b o n s (Kubel m e t h o d ) , ~&Sunflower
, • Castorbean • Soybean
Oil 9 • ,0
Mechanical p r e P ! l
la
ration and pre- ~
Ib
pressing.
Heaters Cyclones •Sunfiower
la
Heaters
Ib
Cyclones
• Soybean HexaDe Extraction
2a
Meal desolventizer
2b
Dryer - cooler
Oil~ ~eal desolventizer
•Sunflower 2a
Drver
2b
Cooler
preparation
Dryer • Castorbean
2a
1 Meal
Meal desolventizer
~
Cyclones Cyclones
• Sunflower
3a
Cooler
3b
Cyclones
Fig. 2. Block flow diagram for emission of soybean (m),sunflower (A), and castorbean (o), oil seed industry. Vol. 3, No. 3 (]983)
D
3a
3b
la
[]
ab
z~ ~,3b
•AAA
la~
a~b []
Fig. 3. Point emissions for manufacturing cycles: soybean (m, ~); sunflower (A, z~);castorbean(e, o). Closedsymbols = high-medium concentration (T.O.C. > 100 gm/Nm3); open symbols = low-nil concentration (T.O.C. ~<40 mg/Nm3).
Adsorbent solution 3 - M e t h y l - 2 - b e n z o t h i a z o l i n o n e h y d r a z o n e (alc.) Methanol 4-Aryl-resorcinol (alc.) KI ( a q u e o u s ) KMnO4 ( a q u e o u s ) All c o n d e n s a t e s were c o n t r o l l e d b y U.V. s p e c t r o s c o p y d i r e c t l y o n the solution using a Perkin E l m e r 554 s p e c t r o p h o t o m e t e r , while the c a r b o n t e t r a c h l o r i d e e x t r a c t s were c h e c k e d t h r o u g h I.R. s p e c t r o s c o p y using a P e r k i n - E l m e r 298 infrared s p e c t r o p h o t o m e t e r c o u p l e d with a C.D.S. d a t a station. T h e t o t a l organic c a r b o n c o n t e n t s were determ i n e d on the dried gas using a Carlo Erba THM 4 7 0 gas c h r o m a t o g r a p h while the C.O.D. o f the c o n d e n s a t e s were evaluated chemically b y the bichromate method. T h e t o t a l a m o u n t e m i t t e d at the source has been evaluated b y c o m b i n i n g d r y gas and condensate d e t e r m i n a t i o n s o n the basis o f m o i s t u r e content.
Dryer - cooler • Soybean
3a 3b
c-~
--7
[]
• Soybean
~
RESULTS T h e gas c h r o m a t o g r a p h i c analyses on the dried emissions show the presence o f a n u m b e r o f organic c o m p o u n d s with d i f f e r e n t r e t e n t i o n times, some o f t h e m c h a r a c t e r i z e d b y low p o l a r i t y like h y d r o c a r b o n s , and others with m u c h 215
higher polarity. The examination of the U.V. and I.R. spectra reveals the presence of saturated aldehydes and fatty acids while excluding other functional groups. In addition, repeated analyses specifically addressed to the search of acrolein, oxidants like ozone and PAN, were performed on the soybean and sunflower vents and gave systematically negative results. Attention has, therefore, mainly been focused on the determination of aldehydes and fatty acids completing the analyses with the determination of the total organic carbon as comprehensive organic pollution index. In this way it has been possible to relate the emissions to the type and the phase of the manufacturing cycle. The emission concentrations show the higher content of both aldehydes (Fig. 4(a) and (b)) and
3 mg/Nm
Sunflower italian
foreign
soybean 1981
castorbean
fatty acids (Fig. 5(a) and (b)) in the sunflower seed cycle compared to the ones of soybean and castorbean. Under comparable conditions the highest values obtained during the processing of all types of seeds are found in the desolventizer zone. This may be explained with the higher degree of the seed thermal exposure. Emission factors given in Table 2 indicate clearly the contribution of each type of seed processed. For instance there is an equal contribution of aldehydes and fatty acids in the castor bean processing cycle, and a substantial contribution of fatty acids in the soybean cycle (fatty acids-aldehydes ratio equal to 2.2-2.3), while, on the contrary in the sunflower oil process, the ratio is reversed (fatty acids-aldehydes ratio equal to 0.98-0.56).
mg/Nm3
1981
300
300
200
200
100
(a)
Sunflower italian foreign
soybean 1981
castorbean 1981
IO0
IN
,ll
(a)
mg/Nm 3 , 5OO
3 mg/Nm
400
400
300
300
200
200
loo
10° 11 nH
!il
l tn
,I,
I I o
Co)
(b)
Fig. 4. Aldehydes vent concentration expressed as mg/Nm 3 o f formaldehyde. (a) Dried gas, (b) undried gas.
Fig. 5. Fatty acids vent concentration expressed as mg/Nrn 3 of acetic acid. (a) Dried gas, (b) undried gas.
216
The Environmentalist
TABLE 2. Emissions factors for sunflower,soybean and castorbean cycle. Aldehydes, fatty acids and total organic carbon are evaluated as grams for q of seed processed. Vent
Aldehydes Fatty acids Total organic HCHO g/q CH3COOHg/q carbon CH4 g/q
Italian sunflower
8.60 1.30 5.00 1.50 0.80
7.10 1.70 3.20 1.80 0.40
>34.80 3.50 > 19.00 11.00 1.30
9.00 1.00 4.20 3.00 0.80
4.80 1.10 2.20 1.10 0.40
30.80 3.00 > 19.00 7.50 1.30
6.00 6.00 -
4.00 6.30 3.00
Heater Desolventizer Dryer Cooler Foreign sunflowers
Heater Desolventizer Dryer Cooler Soybean 1981
Heater Desolventizer Cooler Castorbean
4.20
13.30
4.30
6.6
4.7
33.00
"I 4 .(9
-
31.50 1.50
Soybean
~s~:~i£;~ ~ ~ Castorbean
ij!!ij!!ji!i i!i !!ii !i i!i i!¸i i!i i Sunflower
(a)
33.00
It is also possible to ascertain a decreasing cont r i b u t i o n o f chemical emission, viz. s u n f l o w e r > s o y b e a n > c a s t o r b e a n for the a l d e h y d e s , and s o y b e a n > s u n f l o w e r > c a s t o r b e a n for f a t t y acids. T h e emission factors based o n T.O.C. values are a n y w a y n o t very m e a n i n g f u l because o f interference due to losses o f the e x t r a c t i o n solvent. H o w e v e r c o m p a r i n g the a l d e h y d e s and f a t t y acids c o n t r i b u t i o n to the value o f t o t a l organic c a r b o n (T.O.C.) according to a f a c t o r o f 1.26, as f o u n d for the s u n f l o w e r h e a t e r unit, it is possible to estimate the solvent losses, e.g., expressed as m e t h a n e , in 0.12 kg/t for the s o y b e a n cycle and 0.18 kg/t for the s u n f l o w e r cycle. This is m u c h l o w e r t h a n t h a t o f 1.2 kg/t, f o u n d b y Finelt ( 1 9 7 9 ) b u t justified on the basis o f the partiality o f emission sources c o n t r o l l e d . This indicates that the vegetable oil seed i n d u s t r y , besides the n e e d to r e d u c e the losses o f the solvent, the p r o b l e m o f organic substances does exist in spite o f r e d u c t i o n o f solvent losses t h r o u g h t e c h n o l o g ical i m p r o v e m e n t in the processing plants.
4.3
4.1
24.6
I
SoVb ean
~l~!{:!,~i~!~[# C as t o r b e a n
:
S u n f 1 .....
Co)
57.
I0.0
3.0
DISCUSSION A c c o r d i n g to the results o b t a i n e d f r o m this investigation on the m e d i u m - s i z e d oil seed processing plant, the mass balance on the emissions (Fig. 6(a)(b) and (c)) stresses the i m p o r t a n c e o f s o y b e a n m a n u f a c t u r e which, in this c o n t e x t , a c c o u n t s f o r 80% o f the f a t t y acids and 50% o f the a l d e h y d e s released. Since a substantial emission o f pollutants, in addition to the e x p e c t e d loss o f solvent, has been shown, the t r e a t m e n t o p t i o n s usually selected Vol. 3, No. 3 (1983)
0.8
I (c)
Soybean
6.5
~ ,~!~~i C a s t o r b e a n !~:!::#~[{#~ ~'N### I}~,~'
)::L,..'{<}S u n f l o w e r
:.: . ...
Fig. 6. Relative contribution to the total emissions assigned to each circle. (a) Total aldehydes, (b) total fatty acids, (c) total organic carbon. 217
may not result in satisfactory ambient air quality. Following Becker (1972), the intervention policy is recommended to be based on incinerators, or on carbon adsorption for the solvent recovery optimization, but, in the latter case, the adsorption capacities for aldehydes and fatty acids differ by at least one order from that o f hexane. It seems, therefore, reasonable, in order either to prevent environmental pollution or to minimize the cost o f the pollution control, to define the best treatment conditions for such classes of compounds. In any specific case consideration must be given to the large number o f emissions sources and leaks and, as a general principle, the difficulty o f treating large volumes of air. It seems reasonable, in agreement with Heinz (1978), to suggest that an approach involving the treatment o f the emissions should be characterized by a T.O.C. of 100 mg/Nm 3 (Fig. 6(a)(b) and (c)). The comparison between the analytical data relative to the dried and undried gas furthermore, points out the possibility of lowering the pollution load. Considering the variation o f fatty acids concentration (Fig. 5(a) and (b)), it is possible to observe a higher abatement in the case o f high water content (Table 1). Abatement yields o f up to 86% can be foreseen which would be in good agreement with the 90% reported utilizing scrubbers in similar plants of tomato seed extraction (Volpi and Casagrande, 1978). For the low water content emissions (soybean and castorbean, see Table 1) the abatement yield turns out to be drastically lowered. As far as aldehydes are concerned a similar trend is found (see data of Fig. 4(a) and (b)), even with an abatement yield of 45% (desolventizer, Italian sunflower seeds). This is probably due to the lower water solubility of these compounds.
218
These considerations in relation to the factory under examination show the following balance (Fig. 6(a)(b) and (c)), dashed area): - treatment of 52% o f the fatty acids with a 90% efficiency treatment o f 90% o f the total aldehydes with a 45% efficiency. The suggested emissions treatment becomes more valuable if examined in the light o f reactive hydrocarbons before and after drying (Table 3). The results observed suggest that the improvement obtainable may be higher than that foreshown only on the basis o f the total abatement data.
TABLE3. Reactivehydrocarbons(KMnO4index) Vent
Emissionsas 02 meq/m3
Dried gas 02 meq/m3
182-150 90-70 67-50
trace trace trace
90-83
trace
Sunflower (A)
Heater la Desolventizer 2a Drying2b Soybean (m)
Desolventizer2a
REFERENCES
Battistoni, P. and Fava, G. (1983) J. Air Poll. Cont. Ass., in press. Becker, K. W. (1972) J. Am. Oil Chemists Soc., 49, p. 40. Cohen, I. R. and Altshuller, A. P. (1961)Anal Chem., 33, p. 726. Dyuzheva, Y. V. (1960) Inst. San. Igieny, 17-49; Chemical Abstracts, 56, 6319a. Finelt, S. (1979) J. AirPoll. ControlAss., 29, p. 1192. Heinz, H. J. (1978) Rev. Fr. Corps Gras, 25, p. 123. Saltzman, B. E. and Gilbert, N. (1959) Anal. Chem., 31, p. 1914. Sawicki, E., Havser, T. R., Stanley,T. W. and Elbert, W. (1961) Anal, Chem., 33, p. 93. Volpi, E. and Casagrande, G. (1978) Riv. Ital. Sontanze Grasse, 55, p. 329.
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