Recovery solvents methods and performances

1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 8, August (2014), pp. 56-61 © IAEME
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH
IN ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 5, Issue 8, August (2014), pp. 56-61
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IJARET
© I A E M E
RECOVERY SOLVENTS: METHODS AND PERFORMANCES
Adel OUESLATI(1), Mohamed JEMAIEL(2), Rihab YAHYAOUI(2), Leila DRIDI(2)
(1)Higher Institute of Technological Studies Zaghouan-Tunisia
(2)North African Chemical manufacturing, ZI Benarous-Tunisia
ABSTRACT
Organic solvents such as acetone, alcohols, acetates, toluene, etc..are heavily used in the
manufacturing industries of paint, inks and semiconductors. They are not only harmful and
dangerous to human health and the environment, but are also expensive. They are released as liquid
mixtures. Their recovery is a requirement for economic and environmental order. They are recovered
in the form of mixtures, usually, colorless processes by simple distillation or flash, by rotary
evaporator under vacuum. A novel method of solvent recovery in mixtures, using sodium chloride as
an additive, was tested. The results are very important viewpoint of energy saving, the time and ease
of implementation.
Keywords: Solvents, recovery, NaCl
1- INTRODUCTION
A solvent is a substance which is liquid at its operating temperature, which has the property
to dissolve, dilute or remove other substances without chemically modifying itself without change.
Solvents are used in very diverse sectors such as degreasing, paints, inks, detergents, organic
synthesis, and represent considerable amounts in terms of raw material and release [1]. Acetone,
butanols, acetates, cyclohexane, alcohols and water are found in large quantities in industrial
discharges of paint and semiconductors [2, 3, 4, 5]. Their number in liquid discharges may exceed
40. They are toxic and harmful to health and the environment. Handling can result in serious
accidents risk [5, 6]. Solvent regeneration uses simple distillation, fractional distillation column and /
or distillation by steam distillation to separate the different components of spent solvents. After
distillation, the solvents were dried. The residual water is removed by attachment to a support
which does not react chemically with the solvent [4, 7, 8].
The performance of these processing techniques, waste, are limited by the complexity of
mixtures of solvents. Indeed these solvents have boiling temperatures neighboring moreover they are

2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 8, August (2014), pp. 56-61 © IAEME
not totally immiscible azeotropic and mixtures thereof are [9, 10, 11]. Hence their separation by
distillation and extraction proves not beneficial.
Other attempts at separation of a ternary heteroazeotropic mixture was conducted by Stathis Skouras
Skogestad and Sigurd. This attempt uses a hybrid extraction-distillation column wherein there is a
decanter [12]. This method is beneficial for a ternary mixture, but it is still inadequate for mixtures
containing more than three solvents.
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On an industrial scale, solvent recovery is effected using a recycling apparatus comprising an
enclosure in which the crude mixture is heated by an electric heater. The generated vapors are
conducted to a heat exchanger cooled by a condenser-air fan [13].
Sodium chloride was used as an additive for water-containing solvent mixtures, toluene and acetone.
The solvent recovery is affected by the evaporation condensation method [14].
In this article, we performed tests recovering solvents using sodium chloride as an additive.
The tests are carried out on a rotary evaporator under vacuum. The generated vapors are condensed
on the outer walls of a coil. We seek to study the influence of sodium chloride on the amount of
solvent recovered as condensate.
2- THEORETICAL BASES
The addition of sodium chloride to a ternary mixture can reduce the boiling point. It can
optionally change the relative volatility and the azeotropic composition of solvent mixtures.
Furthermore, the salt is used to reduce energy consumption inthe a distillation process [14].
The effect of sodium chloride on the boiling point of a mixture of iso-propyl alcohol toluene-water
was confirmed. Indeed the boiling point decreases with increasing concentration of sodium
chloride [15]. The same findings were found with a ternary mixture acetone-toluene-water [16].
Sodium chloride is the intermolecular bonds in the solution to make it more fragile. Therefore
the boiling temperature and the latent heat of evaporation will be reduced.
Figure-1: Temperature of pure water and water containing NaCl as a function of time [17]

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 8, August (2014), pp. 56-61 © IAEME
58
3- EXPERIMENTAL PROCEDURE
Figure 2 shows the diagram of the vacuum rotary evaporator. It is used in the chemical
industry is to quickly distill solvents, either partially concentrating a solution. The apparatus consists
of a balloon to the crude mixture, another balloon for condensate, a glass coil whose inclination is
adjustable, a hot water bath where the temperature is controlled by a temperature controller, a system
vacuum, a water cooler and the condenser used in a control panel. The positions of the balloons as
well as the condenser can be adjusted.
The principle of this device is based on the discontinuous distillation in vacuo. The flask
containing the crude mixture is immersed in the hot water bath. It is rotated at a selected rate. he
vapors generated are led to the condenser where it condenses on the walls and fall into the coil
condensate flask. The cooling water, circulating inside the coil tube, to absorb calories and it moves
towards the cooler. Its temperature is controlled by an instruction. The system is evacuated by a
vacuum pump.
We will study the effects of the bath temperature, the rotational speed, the initial volume of
the crude mixture in the evaporator, the temperature of the cooling water flow rate of the condensate.
Concerning the effect of the chemical composition of the crude mixture on the flow of the
condensate was examined by comparison with pure water.
Figure-2: Schematic of the rotary vacuum evaporator used in solvent recovery
4- RESULTS AND DISCUSSION
Figure 3 is a graphical representation of volume of condensate according to the initial volume
of the crude mixture. We observe that the quantities of condensate, obtained from crude mixtures
containing sodium chloride, mix 1s, 2s mix and mix-3s are higher than those obtained from crude
mixtures without sodium chloride, mix 1 mix -2 and mix 3. Crude mixtures containing high levels of
volatile solvents and in addition containing sodium chloride produce high amounts of condensate.
The addition of sodium chloride to the crude mixture allows an improvement of 20% of the amount
of solvent recovered. This is in agreement with the theoretical results claimed by Koller [18].

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 8, August (2014), pp. 56-61 © IAEME
59
Figure-3: Volume of condensate according to the initial volume of the crude mixture in the
evaporator
Figure-4: Volume of the condenser temperature as a function of the hot water bath
The effect of the temperature of hot water bath on the amount of recovered solvent is
illustrated in Figure 4. Crude mixtures for mix 1 mix 2 and mix 3 without sodium chloride, the
amount of solvent recovered is below 0.4 liters for bath temperatures between 85 ° C and 100 ° C.

5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 8, August (2014), pp. 56-61 © IAEME
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To the mix-1w mixtures, mix-2s and 3s each mix containing 10 g of sodium chloride, then
the amounts of recovered solvent as condensate than 0.4 and can reach 0.9 Liter
The effect of the rotational speed of the evaporator on the amount of recovered solvent is
shown in Figure 5. For mixtures mix 1 mix 2 and mix 3 without sodium chloride, the amounts of
recovered solvent is improved with increasing the speed of rotation of the evaporator. But when
adding sodium chloride to the crude mixtures to be distilled, the amounts of recovered solvent is
improved at least 16%.
Figure-5 : Volume de condensat en fonction de la vitesse de rotation de l’évaporateur
5- CONCLUSIONS
Recovery of solvents in liquid discharges from factories painting by conventional methods
such as distillation, liquid-liquid extraction and absorption is very difficult and expensive. Using a
rotary evaporator condenser vacuum to reclaim solvents as condensate is cost effective as long as
you choose the operating conditions.
The effects of Initial volume and temperature of crude mixture in the evaporator, rotation speed of
the evaporator are studied.
Use of NaCl as an additive in the crude mixture to be separated, allows to increase significantly, the
flow of condensate. It also saves the energy required for evaporation.
ACKNOWLEDGMENTS
We thank the directors and officers of the Company Manufacturing NORTH AFRICAN
CHEMICAL support and availability.

6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 8, August (2014), pp. 56-61 © IAEME
61
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