EMULSION PRODUCTION FROM PO
Production of emulsions at laboratory scale
Two different Pyrolysis Oils were studied during the first 18 months
of the project. The first one was a saw dust (spruce) flash pyrolysis
oil produced by FORTUM (presently Neste Oil), while the second one
was a Forestry Residue (spruce, pine, birch, bark, needles) Oil produced
Both the oils were characterized in terms of their composition and
physical-chemical properties. Similar analyses were already performed
by VTT and FORTUM (presently Neste Oil), but they were repeated in
order to check if changes occurred during the transportation from
the production facility to our laboratories.
Composition and physical-chemical properties of oils are extremely
important in the formulation of a stable emulsion.
Spruce Saw Dust
(FORTUM-presently Neste Oil)
| H2O content (% w/w)a
| Viscosity at 40°C
|| 17 cSt
|| 25 cSt
| Insoluble Solid Contentb (%w/w)
| Ash Weigth (%w/w)
| Density at 20°C
|| 1.12 kg/dm3
|| 1.22 kg/dm3
| Carbon content (% w/w)
| Nitrogen content (% w/w)
| Hydrogen content (% w/w)
| Oxygen content (% w/w)c
Alkali/Ash (mg g–1)
Spruce oil (FORTUM-presently Neste Oil) showed higher values for
viscosity and density, while the ash content is about a third with
respect to the forestry residue oil (VTT). It is well known that these
oils change their composition upon ageing, forming big aggregates
that after long storage times (1 or 2 years) eventually settle down.
The higher viscosity value of spruce oil (FORTUM-presently Neste Oil)
agrees with the higher stability experienced. While the forestry residue
oil (VTT) showed a higher tendency to separate in a lighter top phase
and a darker bottom phase, that can be hardly dispersed by vigorous
agitation during the first storage months and can’t be dispersed
anymore at about 6 months.
The low ash content of the spruce oil (FORTUM-presently Neste Oil)
is due to the fact that they filter the oil as fresh.
Elemental analysis results reflected the difference in the feedstocks
used by VTT and FORTUM (presently Neste Oil) and it was interesting
to note a big difference in terms of alkali content.
No final conclusions on the quality of spruce and forestry residue
oils can be made due to the limited number of samples.
Six different PO/Diesel oil emulsions were prepared: 30/70, 25/75,
20/80, 15/85, 10/90, 5/95 expressed as % by weight. In this way we
tried to clarify the role of PO for emulsion stability: in fact emulsions
constituted by a higher amount of oil are more stable than low oil
In order to finally formulate a stable emulsion, several trial and
error tests were performed. For structures as complex as PO made of
a mixture of several organic products and water, the choice of the
proper surfactant was not an easy task, being dependent on the molecular
structure (especially the hydrophilic and lipophilic tendency). Approximately
one hundred different surfactants, cationic, anionic, zwitterionic,
polymeric and non-ionic, with different values of HLB (Hydrophilic-Liphophilic
Balance) were tested. Additives containing sulphur or nitrogen have
been neglected in order to avoid an increase in NOx and SOx emissions
The stability of emulsions was checked both leaving the emulsion
at room temperature and in oven at 65°C in order to accelerate
the aging process.
Preliminary tests were performed simply by dissolving the surfactant
in the PO or in the Diesel oil, depending on its solubility. The amount
of surfactant used at this stage was 1.5% wt/wt of emulsion. PO and
Diesel were then mixed with a magnetic stirrer at room temperature.
No stable emulsions were obtained.
Two methods were then tried: inverse phase emulsification and high
energy dispersion. In the former case the surfactant was dissolved
in PO. The Diesel oil was then added drop wise to this mixture, always
mixing it gently with a magnetic stirrer. The PO phase initially represented
the continuous phase. By increasing the Diesel amount, the emulsion
went trough a bicontinuous emulsion (when PO and Diesel contents are
similar) and finally formed an inverse phase emulsion, where Diesel
represented the continuous phase and PO was dispersed as micro-dimensioned
droplets. The effect of temperature on the stability of emulsions
obtained by means of this methodology was investigated. A temperature
of about 70ºC represented the optimal choice for stability. This
effect was probably due to the presence of big aggregates in the PO
that could be dissolved by increasing the temperature.
With regards to the high energy dispersion methodology a Ika Ultra-Turrax
disperser was used. The high shear energy transferred by the disperser
to the mixture was sufficient to produce droplets as small as a few
The emulsion stability was strongly influenced by the methodology
used to obtain it.
Also for high energy dispersion technology 70°C represented the
optimal temperature to obtain stable emulsions.
The most stable emulsions were obtained by using the Ultra-Turrax
disperser adding a non-ionic block copolymer surfactant.
From several experiments carried out, some of them also in oven at
65°C, the observed emulsion instability observed even just in
few weeks was interpreted as a sedimentation phenomenon due to the
highest density of PO with respect to the Diesel oil.
In order to investigate stability the variation of viscosity in time
was measured and the droplet size distribution of the dispersed phase
was studied by means of light scattering measurements and optical
Measurements were performed both on freshly prepared samples and
room temperature aged ones.
In the case of spruce oil (FORTUM-presently Neste Oil) the fresh
emulsion and the shaken aged emulsion showed identical droplets size,
confirming our hypothesis regarding the density depending sedimentation.
While for emulsions prepared with forestry residue oil (VTT) two different
destabilisation processes were identified: sedimentation due to density
mismatching (effective also in the case of Fortum Oil) and growing
of droplets (present only in the forestry residue oil case). However,
these results have to be evaluated taking into account that the surfactant
was developed for white wood oils and not for forestry residues oils.
A summary of the mean diameters as obtained by FOQELS (light scattering)
and microscopy for both the oils is reported:
Average of diameters for emulsions with 30% PO, 70% Diesel oil, 1.0%
surfactant wt respect to PO.
| Spruce oil (FORTUM) fresh
|| 1.87 [µm]
|| 3.90 [µm]
| Spruce oil (FORTUM) aged
|| 2.26 [µm]
|| 3.15 [µm]
| Forestry residue oil (VTT) fresh
|| 1.64 [µm]
|| 2.87 [µm]
| Forestry residue oil (VTT) aged
|| 1.99 [µm]
|| 7.90 [µm]
A summarizing conclusion is that emulsions containing forestry residue
oil (VTT) are less stable than the ones prepared with spruce oil (FORTUM-presently
Neste Oil), due to a higher tendency of forestry residue oil to separate
in different phases.
In May 2005 further samples of pyrolysis oil were sent by VTT to
1. Whole Forestry Residue (FR)
2. Fresh bottom phase of FR
3. Fresh top phase of FR
4. Emulsion 1 prepared by VTT using the whole FR + 2% ethanol
5. Emulsion 2 prepared by VTT using the bottom FR phase
6. Concentrated bottom phase
The emulsions produced were 30 wt% pyrolysis oil from samples 2,
3 and 6 and from samples 2 and 3 after aging process.
The aging process of samples 2 and 3 was obtained leaving the oils
at 65° for 7 days.
All samples and the prepared emulsions were characterized by means
of FOQELS and Optical Microscopy in the CSGI laboratories.
All the emulsions and the aged samples 2 and 3 were prepared and sent
to IM for combustion tests.
Due to differences in composition the three oils showed different
results for the emulsification process. Huge differences in viscosity
between the emulsion prepared with the concentrated bottom phase and
the fresh one were observed. These differences were found also in
the droplets dimension, as it is shown by the results of FOQELS measurements.
The most important difference is the droplet size between the emulsion
obtained with concentrated bottom phase and the fresh bottom phase.
By means of optical microscopy it was possible to notice that the
sample prepared with aged oil presented bigger droplets.
The emulsification plant
The plant is divided into three different skids, in order to keep
small and light every single part and allow for easy handling and
transport to the VTT facility where the in-line pyrolysation test
will be performed.
Fuel storage tanks and pumping system are installed in the first
skid, the heat exchangers, the dispersing motor and all the regulations
are in the second and at the exit of the dispersing device the separator
The plant is a continuous LFO/PO emulsification system, with a production
capacity of at least 50 l/h and a range between 5 and 50% of PO (w/w).
PO Pump |
Additive Pump |