METHODE DE NETTOYAGE DE FILTRE A TAMIS MULTICOUCHES

METHOD OF CLEANING CONTAMINANTS FROM A MULTI-LAYERED MESH FILTER

Abrégé français

Une méthode de nettoyage de contaminants d'un filtre à mailles à couches multiples. Une première étape consiste à immerger le filtre dans un bac de prétrempage chimique contenant un agent de nettoyage chimique efficace avec les contaminants. Le bac de prétrempage chimique est maintenu à une température d'au moins 160 degrés Fahrenheit et pas plus de 180 degrés Fahrenheit. Le filtre est maintenu dans le bac de prétrempage pendant une durée de temps suffisante pour ramollir les contaminants sans faire en sorte que les contaminants se décomposent en couches d'éléments constitutifs, tout en élevant la température du filtre en préparation pour le nettoyage. Une deuxième étape consiste à immerger le filtre dans une cuve de nettoyage contenant de l'eau chaude maintenue à une température d'au moins 160 degrés Fahrenheit et pas plus de 180 degrés Fahrenheit et soumettant l'eau chaude dans le réservoir de nettoyage à des ondes d'ultrasons à une fréquence d'au moins 80 mégahertz et pas plus de 120 mégahertz.

Abrégé anglais

A method of cleaning contaminants from a multi-layered mesh filter. A first step involves immersing the filter in a chemical presoak tank containing a chemical cleaning agent effective with the contaminants. The chemical presoak tank is maintained at a temperature of not less than 160 degrees fahrenheit and not more than 180 degrees fahrenheit. The filter is maintained in the presoak tank for a time duration sufficient to soften the contaminants without causing the contaminants to break down into layers of constituent elements, while raising the temperature of the filter in preparation for cleaning. A second step involves immersing the filter in a cleaning tank containing hot water maintained at a temperature of not less than 160 degrees fahrenheit and not more than 180 degrees fahrenheit and subjecting the hot water in the cleaning tank to ultrasonic waves at a frequency of not less than 80 megahertz and not more than 120 megahertz.

Revendications

7
1. A method of cleaning bitumen from a multi-layered mesh filter, comprising
the steps of:
immersing the filter in a chemical presoak tank containing a chemical cleaning
agent
effective with the bitumen maintained at a temperature of not less than 160
degrees
fahrenheit and not more than 180 degrees fahrenheit for a time duration
sufficient to soften
the bitumen without causing the bitumen to break down into layers of
constituent elements,
while raising the temperature of the filter in preparation for cleaning; and
immersing the filter in a cleaning tank containing hot water maintained at a
temperature of not less than 160 degrees fahrenheit and not more than 180
degrees
fahrenheit and subjecting the hot water in the cleaning tank to ultrasonic
waves of not less
than 80 megahertz and not more than 120 megahertz while varying the amplitude
of the
ultrasonic waves.
2. The method as defined in Claim 2, including the further step of rinsing the
filter.

Description

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TITLE OF THE INVENTION:
Method Of Cleaning Contaminants From A Multi-layered Mesh
Filter
FIELD OF THE INVENTION
The present invention relates to a method of cleaning
contaminants from a mufti-layered mesh filter and, in
particular, bitumen.
BACKGROUND OF THE INVENTION
Steel mesh filters are used in the Alberta oil sands to
remove contaminants from synthetically produced crude oil.
These steel filters consist of multiple layers of steel mesh.
The mesh can be arranged in various braided wire patterns . Over
time these steel mesh filters become clogged with contaminants
and must be cleaned. In this application the contaminants are
bitumen.
Attempts to clean these filters with steam or high
pressure water blasting have proven unsuccessful. The steam
and high pressure water cleaned surface layers but was
incapable of penetrating to the core of the filter. In
addition, the high pressure water tended to translocate the
bitumen; it moved the bitumen around the filter without
removing it. There were also pressure control problems
experienced. If there was insufficient pressure, the high
pressure water did not clean effectively. If the pressure was
too great, the high pressure water would destroy the filter.
Soaking in chemical degreasers has also proven
unsuccessful. Although the chemical degreasers are capable of
penetrating the core of the filter, leaving the filter in a
bath of chemical degreaser merely resulted in the bitumen
breaking down into its constituent layers. Instead of cleaning
the filter, soaking in chemical degreasers results in the
substitution of a cleaning problem involving bitumen for a
cleaning problem involving one or more of the constituents of

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bitumen. With caustic cleaning agents that need to be
neutralized, problems were experienced with removing cleaning
agent residues. These cleaning agent residues would eat away
at the filters destroying them from the inside.
SUMMARY OF THE INVENTION
What is required is a more effective method of cleaning
contaminants from a multi-layered mesh filter.
According to the present invention there is provided a
method of cleaning contaminants from a multi-layered mesh
filter. A first step involves immersing the filter in a
chemical presoak tank containing a chemical cleaning agent
effective with the contaminants. The chemical presoak tank is
maintained at a temperature of not less than 160 degrees
fahrenheit and not more than 180 degrees fahrenheit. The
filter is maintained in the presoak tank for a time duration
sufficient to soften the contaminants without causing the
contaminants to break down into layers of constituent elements,
while raising the temperature of the filter in preparation for
cleaning. A second step involves immersing the filter in a
cleaning tank containing hot wager maintained at a temperature
of not less than 160 degrees fahrenheit and not more than 180
degrees fahrenheit and subjecting the hot water in the cleaning
tank to ultrasonic waves at a frequency of not less than 80
megahertz and not more than 120 megahertz.
The method, as described above, represents the culmination
of great deal of research into what works and what does not
work. Ultrasonic cleaning will not be effective, unless the
filter is presoaked in a chemical cleaning agent to soften the
contaminants. The filter must be at the same temperature as
the temperature range at which the ultrasonic cleaning takes
place. A further purpose of the presoak is, therefore, to
raise the temperate of the filter to at or near the desired
temperature range. It was found that the ultrasonic cleaning
was not effective at temperatures less than 160 degrees

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fahrenheit. However, when the temperature exceeded 180 degrees
fahrenheit the heat began to become detrimental to the process
and, in some instances, damaged the filters. At frequencies
of less than 80 megahertz the ultrasonic cleaning wa.s not
effective. However, at frequencies in excess of 120 megahertz
too much cavitation took place, tending to destroy the
amplitude of the waves.
Although beneficial results may be obtained through use
of the method, as described above, an even greater improvement
in the cleaning was achieved by varying the amplitude of the
ultrasonic waves. Ultrasonic cleaning is a product of
frequency and amplitude. By varying the amplitude,
contaminants that would not release from the filter at one
amplitude tended to release at another amplitude.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more
apparent from the following description in which reference is
made to the appended drawings, the drawings are for the purpose
of illustration only and are not intended to in any way limit
the scope of the invention to the particular embodiment or
embodiments shown, wherein:
FIGURE 1 is a side elevation view, in section,
illustrating pre-soak step of the method in accordance with the
teachings of the present invention.
FIGURE 2 is a side elevation view, in section,
illustrating a rinsing step of the method in accordance with
the teachings of the present invention.
FIGURE 3 is a side elevation view, in section,
illustrating a ultrasonic cleaning step of the method in
accordance with the teachings of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred method of cleaning contaminants from a
multi-layered mesh filter will now be described with reference
to FIGURES 1 through 3. Bitumen will be used as a specific

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example of a contaminant that can be effectively removed in
accordance with the teachings of this method.
Referring to FIGURES 1 through 3, there is provided a
method of cleaning bitumen from a multi-layered mesh filter
that includes several steps . Referring to FIGURE 1, a pre-soak
step involves immersing filter 10 in a chemical presoak tank
12 that, contains a chemical cleaning agent 14 effective with
bitumen. Chemical cleaning agent 14 is maintained at a
temperature of not less than 160 degrees fahrenheit: and not
more than 180 degrees fahrenheit. In the illustrated
embodiment, chemical presoak tank 12 is equipped with a heater
16 with a temperature controller 18 for heating chemical
cleaning agent 14 to the appropriate temperature, however other
means are available for maintaining the temperature of presoak
tank 12. Ultrasonic cleaning will not be effective, unless
filter 10 is presoaked in chemical cleaning agent 14 to soften
the contaminants. Filter 10 is maintained in presoak tank 12
for a time duration sufficient to soften bitumen without
causing bitumen to break down into layers of its constituent
elements, while raising the temperature of filter 10 in
preparation for cleaning. Filter 10 must be at the same
temperature as the temperature range at which the ultrasonic
cleaning takes place for ultrasonic cleaning to be effective.
A period of approximately 20 minutes of soaking filter 10 in
tank 12 is usually sufficient. There are a variety of chemical
cleaning agents 14 commercially available which are known to
be effective in the removal of bitumen. Chemical cleaning
agents 14 will, therefore, not be further described.
Referring to FIGURE 2, a rinsing step involves immersing
filter 10 in a cleaning tank 20 containing hot water 22 that
is maintained at a temperature of not less than 160 degrees
fahrenheit and not more than 180 degrees fahrenheit. In the
illustrated embodiment, cleaning tank 20 is equipped with a
heater 24 and temperature controller 26 for heating hot water
to the appropriate temperature, although other means can be
used to maintain the temperature in cleaning tank 20.

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Ultrasonic cleaning is not effective at temperatures less than
160 degrees fahrenheit, while temperatures that exceed 180
degrees fahrenheit, become detrimental to the process and, in
some instances, can damage filter 10.
5 Referring to FIGURE 3, hot. water 22 in cleaning tank 20
is then subjected to ultrasonic waves 28 of not less than 80
megahertz and not more than 120 megahertz while varying the
amplitude of ultrasonic waves 28. At frequencies of less than
80 megahertz, ultrasonic cleaning is not effective and at
frequencies in excess of 120 megahertz too much cavitation
takes place which tends to destroy the amplitude of ultrasonic
waves 28. In the illustrated embodiment, an ultrasonic
generator 30 is provided for supplying ultrasonic waves 28.
A controller 32 is provided on ultrasonic generator 30 for
varying the amplitude of ultrasonic waves 28. By varying the
amplitude, contaminants that would not release from filter 10
at one amplitude tend to release at another amplitude.
Exposure of filter 10 and hot water 22 to ultrasonic waves 28
. for a period of approximately 30 minutes has been found to be
sufficient. Care must be taken not to over expose filter 10,
as excessive exposure to ultrasonic waves 28 will cause bitumen
to breakdown into constituent elements.
A further step includes rinsing filter 10. Rinsing of
filter 10 aids in removing bitumen particles that were freed
from filter 10 during cleaning. If desired a rinse can also
take place between the presoak and the ultrasonic cleaning
stages to remove any large bitumen particles that have become
sufficient softened during the presoak that they can be readily
removed without ultrasonics. If desired, a hot water presoak
can be used in combination with the chemical presoak. The hot
water presoak enables longer dwell times without the bitumen
separating into constituent elements. The method as described
above is a more effective method of cleaning contaminants from
mesh filter 10.
In this patent document, the word "comprising" is used in
its non-limiting sense to mean that items following the word

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are included, but items not specifically mentioned are not
excluded. A reference to an element by the indefinite article
"a" does not exclude the possibility that more than one of the
element is present, unless the context clearly requires that
there be one and only one of the elements.
It will be apparent to one skilled in the art that
modifications may be made to the illustrated embodiment without
departing from the spirit and scope of the invention as
hereinafter defined in the Claims.

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