BLENDING: RAISING THE BAR
The proliferation of biofuel
blending
requirements over
recent years has driven
forward the need for ever
more sophisticated solutions
for petroleum terminal and
distribution operations. As
seen with many fuel recipe
solutions over the years, the
transition from experimental
to mainstream is a rapid one,
and requires proactive
development of systems to be
able to exceed the demands
of operators. The drive
towards increased operational
flexibility has led to an exodus
of blending equipment from
the tank farm to the loading
rack, as operators demand
multi-arm, multi-ratio
capability.
The Enraf MicroBlender™
has played a key part in the
evolutionary cycle of ethanol
and bio-diesel blending.
Instigating revolutionary
techniques such as 'Side
Stream Blending' to take
advantage of the variable
endothermic and exothermic
growth phenomenon
experienced during ethanol
blending, and utilising
dedicated hydraulic power
systems to stabilise control of
actuator valves, facilitating
smooth linear control across
the blend range. Likewise, the
development of the new
MicroBlender V2, sees the
introduction of yet more
innovation and enhancements,
in search of 'The Perfect
Blend'.
The accuracy and control of
bio-fuel blend systems are of
paramount importance, and
has created some of the
toughest challenges, in the
form of profiling the handling
characteristics of the plethora
of new products being
introduced into the petroleum
distribution network. As has
been said many times, “all
bio-fuels are not made equal”.
Although standards for
ethanol and bio-diesel are set
out by standards such as
ASTM D4806 (ethanol) and
ASTM D6751 (bio-diesel), the
multitude of base feed-stocks
used in producing these
products, creates numerous
product characteristic and
compatibility traits. To assuage
some of the problems this has
created, the actuator for the
slotted V ball control valve on
the MicroBlender V2 has been
further developed. The new
actuator now incorporates just
a single piston and is fitted
with PTFE dynamic and static
seals. This has radically
reduced the number of seals
in the actuator and enhanced
further its reliability and
performance. The addition of
PTFE seals allows for a
common specification across
both ethanol and bio-diesel
blend applications, thus
simplifying maintenance and
spares procedures. An added
benefit of the unique actuator
porting arrangement is the
balanced pressurising
conditions it generates across
the piston, negating the
previous issues of fluctuating
control pressure from the
loading arm. This eliminates
the requirement for separate
closed loop hydraulic control
pressure, and therefore
eliminates the requirement for
a hydraulic power-pak,
previously required on a Multi-
Stream Blender. With the
slotted V ball valve sized to
create a precisely calculated
pressure drop across the
valve, the system generates
its own motive power to
control the actuator.
Furthermore the actuator now
also incorporates a valve
positional indicator site glass
and multiple bleed points.
These small but often
overlooked features facilitate
both improved system
commissioning and simpler
maintenance procedures.
To further improve this
aspect of the MicroBlender V2
system, Enraf has utilised
integrated manifold
technology, previously
developed so successfully for
their family of additive
injection systems. This has
been used to condense the
actuator control pipe-work
and control solenoid
assemblies into one compact
manifold block which is
mounted directly onto the
actuator. This again
introduces multiple design
benefits. Most obviously, it
reduces the size of this
section of the system, by
eliminating much of the
previously extensive control
pipe-work which is seen on
most load rack control valves.
Removal of this pipe-work
also drastically reduces the
number of possible leak
paths, cutting them down the
number of original fittings
from the 27 to merely 5. It is
also acknowledged that the
higher cold flow properties of
bio-diesel presents operators
with the challenge of ensuring
that the bio-diesel
temperatures are maintained
above the manufacturers
specified operating limits.
