Page 203 - Biofuels Refining and Performance

186 Chapter Six

Ali et al. [61] have observed that engine performance with diesel
fuel—methyl soyate blends did not differ to a great extent up to a
70–30% (v/v) from that of diesel-fueled engine performance. There was
a slight increase in NO emissions with increasing methyl soyate con-
x
tent in the blends at higher speeds but at lower speeds there was a
quadratic trend with diesel fuel content.
Carbon monoxide emissions were very similar for blends up to 70–30%
(v/v) diesel fuel—methyl soyate blends at any speed. Visible smoke
decreased with increasing speed and methyl soyate content. More smoke
was produced with neat diesel fuel at full load.

6.3 Engine Performance with Esters
of Tallow and Frying Oil
The estimated amount of good quality and nutritive-value oils and fats
used for frying around the world is around 20 million metric tons (MT).
In frying, the hot oil serves as a heat exchange medium by which heat
is transferred to the material being fried. As a result of frying, the oil
darkens from the formation of polar materials such as minor phenolic
components; elevated FFA; high total polar materials; compounds
having high foaming property, low smoke point, low iodine value, and
increased viscosity; and color compounds.
Sims [62] reported has conversion of tallow, a by-product of the meat
industry, into esters. The fuel properties of methyl, ethyl, and butyl
esters of tallow were similar to diesel fuel, particularly ME, which were
remarkably similar except for the higher liquidification temperature of
tallow esters. Short-term engine performance tests with methyl, ethyl,
and butyl esters gave comparable results as diesel fuel, but at higher
BSFC. Blends with diesel in 50–50% proportion by volume gave inter-
mediate results between esters and neat diesel fuel.
Richardson et al. [63] have tested an engine with ME of tallow.
Preliminary engine tests indicated that the use of 10% and 20% blends
(volume basis) performed similar to diesel fuel. However, lubricant qual-
ity aspects were not studied and an endurance test was not conducted.
The ignition quality of the blend was significantly better than that of
diesel. Overall, it was concluded that tallow ME on 10% (volume basis)
can be successfully used as diesel fuel where large amounts of tallow are
produced and temperatures below 10 C are not encountered. The fuel
consumption of ME of used frying oil has been measured by Mittelbach
and Tritthard [64]. The ester fuel showed slightly lower hydrocarbon and
carbon monoxide emissions but increased oxides of nitrogen, compared
with that of diesel fuel. The particulate emissions, however, were sig-
nificantly lower for used frying oil. But, they suggest long-term engine
testing to prove the quality of this fuel.