Up until now refineries have been unable to provide
a cost effective solution to burning volatile gases
at the flare.
Currently, compressors have been used to recover
some or all of these gases to use as fuel for the
boilers to raise steam within the process. In some
cases it has been possible to sell the remaining product
as low grade LPG for local communities. However, this
is usually uneconomical. A far more effective and
profitable solution would be to introduce WF to prevent
the need to flare in the first place.
It is important to note that the flare stack will
still remain on site in operating condition for safety
In general refinery vapour gases that occur throughout
the process are usually collected and re-refined in
the gas refinery. The gas refinery process is only
approximately 85% efficient. Thus 15% of these gases
are either sent to the flare stack or compressed and
used as low-grade fuel for the refinery boilers.
(A complete case study explaining refinery vapour
gas can be viewed
In order to prevent the need to flare WF enhances
the process at the source of the problem - the refinery
condensers. It is here where inefficient heat exchange
leads to volatile gases occurring.
WF chills the refinery process water so that heat
exchange in the condensers is increased from 85% -
98%. This increased efficiency means relatively small
amounts of gas need to be flared and more gas is processed
as butane or propane. Of course the added volume of
product has a market value. It is possible to suggest
that in most cases this increased efficiency has a
payback of 12 months. When considering the plant has
a 25-year lifetime this is extremely attractive as
an economically viable package.
The remaining flare gas, which is minimal at this
point (approximately 80-90% less than the original
volume of the flare) can be either burnt at the torch
or compressed using an auxiliary WF apparatus. This
auxiliary system uses a combination of WF ejectors
and hydrocylones to compress the flare gas so that
it can be containerized or sent to the next stage
of refining. This system is subject to a feasibility
study as it may not be economically viable to do this
and flaring would be the cheapest option.
Simplified Flow Sketch
of a WF Refinery Installation