View of a distance piece of
one of the two Mannesmann
Demag, four-throw compressors, C-24101 A/B type
23B4G3/17, in the Petrobras oil
shale plant in São Mateus do
Sul. These compressors were
instrumented with a Prognost
NT monitoring system.
CONDITION MONITORING OF RECIPROCATING COMPRESSORS IN AN OIL SHALE PLANT
Prognost-NT System Monitors Compressors Installed
in Petrobras’ Oil Shale Plant in São Mateus do Sul
By Roberto Chellini
Often, reciprocating compressors
are used to handle very dirty and corrosive gases that have a negative impact on the life of their components
and can affect plant productivity. In
such cases, installation of a condition
monitoring system that enables operating the compressor safely by warning the operator in advance that maintenance is necessary, will increase the
whole plant efficiency. This is why
Petrobras (Petróleo Brasileiro S.A.)
asked Prognost to install its Prognost-NT system on two Mannesmann
Demag reciprocating compressors.
These compressors were installed in
1987 in its oil shale plant in São
Mateus do Sul to compress hydrogen
sulfide. With the increase of energy
prices, the use of oil shale to produce
liquid fuels and hydrocarbon gases is
becoming more popular.
Oil shale is a fine-grained sedimentary rock with significant amounts of
kerogen, and is found around the
world. This material can be burned
directly as a low-grade fuel for power
generation and heating purposes, or
can be used as a raw material in the
chemical and construction industries.
As of 2008, industry uses oil shale
in Brazil, China, Estonia and to some
extent in Germany, Israel and Russia.
Several additional countries started assessing their reserves or had built experimental production plants, while
others had phased out their oil shale
industry. Petrobras’ oil shale processing activities started as early as 1953
by developing Petrosix technology,
extracting oil from oil shale. Now
Petrobras operates two retorts, the
largest of which processes 250
tons/hour of oil shale.
Owned and operated by Petrobras,
Petrosix, Shale-Industrialization
Business Unit, is operator of the
world’s largest surface oil shale pyrolysis retort with a 36 ft. ( 11 m) diameter vertical shaft kiln. It is located in
São Mateus do Sul, some 75 mi. (120
km) from Curitiba and 119 mi. (180
km) from the Atlantic Ocean. Juliano
Alexandre Lampert, machine maintenance engineer at São Mateus do Sul,
and Carlos Roberto Chaves, automation engineer, explained how the
whole process works. Petrosix developed its own process, which is one of
five technologies commercially used
for oil shale extraction. This is an externally generated hot gas technology
for extracting oil from oil shale.
After mining, the shale is transported to a crusher, where it is reduced to particles, so-called lump
shale. These fragments are then transported on a belt to the retort, a vertical cylindrical reactor, to be heated for
pyrolysis up to about 932°F (500°C).
This reaction produces the kerogen,
an organic complex that decomposes
when exposed to heat, and produces
oil and gas. After pyrolysis, the oil is
cooled to condense the vapor, and
shale gases undergo another cleaning
process for light oil extraction. The
rest is then sent to the gas treatment
unit, where fuel and liquefied petroleum gas (LPG) are produced and sulfur recovered. Part of the cooled retort gas is used as fuel in a tubular
heater; part is heated in the heater
pipes and circulated back to the middle of the retort as hot gas carrier for
heating the oil shale feed. Part is circulated and enters into the bottom of
the retort, where it cools down the
hot shale coke. This part takes on
heat and ascends into the pyrolysis
