Note: Descriptions are shown in the official language in which they were submitted.
CA 02866470 2014-09-30
Attorney Docket No. 1222P001CA01
DUAL SENSOR ANALYZER
TECHNICAL FIELD
The present invention relates to testing equipment. More
specifically, the present invention relates to equipment for
testing for concentrations of specific substances.
BACKGROUND OF THE INVENTION
The presence of hydrogen sulfide in natural gas, liquid
petroleum gas (LPG), and even in crude petroleum has led to a
need to determine hydrogen sulfide concentrations in different
samples. H2S detection that is fast and reliable is the
cornerstone of many industrialized processes that cannot
tolerate H2S in their gas due to fatal consequences for humans
and degradation of physical assets such as pipelines.
To determine hydrogen sulfide concentrations, the chemical
reaction
H2S + Pb(CH 3C00), ________________ H2 > PbS +2CH3COOH
is used. This reaction is implemented by using paper tape
impregnated or covered with lead acetate. The paper tape is
immersed in a liquid bath with lead acetate, thereby leaving the
paper capable of detecting H2S. Instead of hydrogen sulfide
concentration, the same reaction can be used to determine total
sulfur concentration by mixing the sample gas with hydrogen then
heating the resulting gas to approximately 900 C where all
sulphurs are changed into H2S.
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The above processes are well-known and are detailed in US
Patents 4,127,780 and 5,206,519.
The issue with current testing equipment is that, currently,
only one side of the testing tape is used. This leads to waste
and inefficiencies as each sensing tape is only used once and is
then discarded. As well, due to the cost of a single analyzer
of the above type, most users that require analysis on more than
one stream of gas will utilize a stream switching technique on a
single analyzer rather than purchasing multiple analyzers.
Stream switching implies that the stream(s) currently not being
analyzed can encounter a rise in the H25 concentration to
unacceptable levels and this rise in H25 concentration may be
undetected.
SUMMARY OF INVENTION
The present invention provides systems, methods, and devices for
testing gaseous samples for concentrations of specific
chemicals. An apparatus has two sensing assemblies for testing
for hydrogen sulfide concentrations in gaseous samples. A first
assembly is disposed to expose a first side of a sensing tape to
a first stream of a gaseous sample. A second assembly is
disposed to expose a second side of the same sensing tape to a
second stream of another gaseous sample. Both assemblies detect
and analyze the hydrogen sulfide concentrations of their
respective gaseous samples by way of their respective sides of
the sensing tape.
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Date Recue/Date Received 2021-04-30
CA 02866470 2014-09-30
Attorney Docket No. 1222P001CA01
In a first aspect, the present invention provides a system for
analyzing gaseous samples, the system comprising:
- a sensing tape having a first side and a second side,
said first side being exposed to a first stream of a first
gaseous sample and said second side being exposed to a
second stream of a second gaseous sample;
- a first sensing assembly for sensing a concentration of a
first substance from said first stream from said first side
of said sensing tape, said first sensing assembly including
a first sensor;
- a second sensing assembly for sensing a concentration of
a second substance from said second stream from said second
side of said sensing tape, said second sensing assembly
including a second sensor;
wherein
- said first side of said sensing tape passes by said first
sensor such that said first sensor senses a quality of said
first side after said first side has been exposed to said
first stream;
- said second side of said sensing tape passes by said
second sensor such that said second sensor senses a quality
of said second side after said second side has been exposed
to said second stream.
In a second aspect, the present invention provides a system for
analyzing samples, the system comprising:
- a sensing tape having a first side and a second side,
said first side being exposed to a sample of a first
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substance and said second side being exposed to a sample of
a second substance;
- a first sensing assembly for analyzing a first specific
chemical of said first stream from said first side of said
sensing tape, said first sensing assembly including a first
sensor;
- a second sensing assembly for analyzing a second specific
chemical of said second stream from said second side of
said sensing tape, said second sensing assembly including a
second sensor;
wherein
- said first side of said sensing tape passes by said first
sensor such that said first sensor senses a quality of said
first side after said first side has been exposed to said
first sample of said first substance;
- said second side of said sensing tape passes by said
second sensor such that said second sensor senses a quality
of said second side after said second side has been exposed
to said second sample of said second substance.
BRIEF DESCRIPTION OF THE DRAWINGS
The embodiments of the present invention will now be described
by reference to the following figures, in which identical
reference numerals in different figures indicate identical
elements and in which:
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FIGURE I is a block diagram of a system according to one aspect
of the invention;
FIGURE 2 is a variant of the system illustrated in Figure 1;
FIGURE 3 is a diagram illustrating a sensing assembly according
to one aspect of the invention;
FIGURE 4 is a diagram illustrating the gas flow and the
components of a sensing assembly; and
FIGURE 5 is a diagram illustrating the components of an eductor.
DETAILED DESCRIPTION
Referring to Figure 1, a block diagram of one aspect of the
invention is illustrated. As can be seen, the system 10 has two
sensing assemblies 20A, 20E, each of which is adjacent a sensing
tape 30. Each of the two sides of the sensing tape 30 is
exposed, independently, to a separate stream of a gaseous
sample. Each sensing assembly 20A, 203 is able to sense and
detect the hydrogen sulfide concentration of its respective
gaseous sample from its respective side of the sensing tape 30.
Thus, a first side of the sensing tape is exposed to a first
stream of a first gaseous sample and this first side is analyzed
and detected by a first sensing assembly 20A. Similarly, a
second side of the sensing tape is exposed to a second stream of
a second gaseous sample and this second side is analyzed and
detected by a second sensing assembly 203. The sensing tape 30
is illustrated has having a coating on each of its two sides.
The configuration of the system may depend on the implementation
but a sample configuration is provided in Figure 2. In this
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configuration, one side of the sensing tape passes by a first
sample chamber 40A and that side of the sensing tape is exposed
to a first stream of a first gaseous sample. The first sample
chamber has an input pipe 50A through which the first gaseous
sample enters the chamber 40A. The sample chamber also has a
venting pipe 60A through which the gaseous sample exits the
sample chamber 40A. The sensing tape then passes by the first
sensing assembly so that the side exposed to the first gaseous
sample can be analyzed by the first sensing assembly. After
passing by the first sensing assembly, the sensing tape then
passes by a second sample chamber 40B which exposes the other
side of the sensing tape to a second stream of a second gaseous
sample. The second sample chamber 40B has an input pipe 50B
through which the second gaseous sample enters the chamber 403.
The second sample chamber 40B also has a venting pipe 60B
through which the gaseous sample exits the sample chamber 40B.
After being exposed to this second stream, the sensing tape then
passes by the second sensing assembly so that the second exposed
side can be analyzed by the second sensing assembly.
The various components of the system can be arranged vertically
such that each sample chamber is stacked above its corresponding
sensing assembly. Alternatively, the system can be arranged
horizontally such that each sample chamber is adjacent or oeside
its corresponding sensing assembly.
Each sensing assembly can be configured to be equipped with
optical means to detect staining on its side of the sensing tape
with the staining being caused by a gaseous sample. In one
embodiment of the invention, useful for determining hydrogen
sulfide or for determining total sulfur, the sensing assembly
may be configured as illustrated in Figure 3.
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Referring to Figure 3, the sensing assembly uses a light
emitting diode (LED) to illuminate a portion of one side of the
sensing tape which has been exposed to the gaseous sample. For
this implementation, the gaseous sample stains the portion of
sensing tape it comes into contact with. The amount of staining
on the exposed sensing tape is indicative of the concentration
of hydrogen sulfide in the gaseous sample. The LED illuminates
the exposed section and, based on how much of this illumination
is reflected back, a reading of the hydrogen sulfide
concentration can be derived. To detect the amount of light
reflected back, the sensing assembly uses a light detector as
illustrated in Figure 3.
As can also be seen in Figure 3, the gaseous sample enters the
system and passes through a water bath or humidifier before
being used to stain one side of the sensing tape. The gaseous
sample is then vented out.
To better illustrate the configuration of the sensing assembly
and its use of a sample chamber, Figure 4 is provided. Figure 4
illustrates the flow of the gaseous sample as it passes by a
sample chamber equipped with a window through which the sensing
tape is exposed to the sample. Once the gaseous sample has
passed by the sample chamber, the sample may be vented by way of
an eductor. A configuration for such an eductor is illustrated
in Figure 5.
To explain the need and/or necessity for an eductor, the reading
made by a sensing assembly can be affected by positive or
negative pressure on the sample vent line. This can be caused by
strong winds blowing across or directly into the vent or by
mechanical venting caused by external sources such as an exhaust
fan. An eductor eliminates external influences on the sensing
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assembly reading. In cold climates, since the system is venting
a moist sample, freezing can occur. The eductor will help
prevent freezing problems in the vent line due to the increased
velocity and drying effect of the sweep gas.
As can be seen from Figure 5, gas from the system is sent to a
vent chamber (labelled as sample vent in the Figure). A
positive pressure Is provided to the sample by way of the supply
from the right of the figure. A vacuum is provided by way o the
connection to the bottom of the figure. It should be noted that
the eductor is not necessary for the system to work. However,
it has been found that the use of an eductor may help improve
system performance.
In one implementation, the sensing tape is a paper tape which
has been impregnated or covered with lead acetate. For this
implementation, the sensors in the sensing assemblies detect
variant levels of light intensity due to a color change on the
sensing tape impregnated with lead acetate and which has been
exposed to H2S. The concentration of H2S can be determined
relative to the rate at which the paper tape changes color or
varies the light intensity. The sensing tape is non-permeable
to the lead acetate nor to the H2S. This allows for the amount
of chemical reaction available for the color change to not be
affected by exposing the opposite side of the paper tape to H2S.
It should be noted that while the above implementation refers to
H2S and/or sulfur concentrations in the gaseous samples, the
system may be used to determine concentrations of other
chemicals or substances. Other chemicals which react with other
substances and which stains a sensing tape may be used. For
these implementations, the coating on the sensing tape as well
as the various substances and chemicals used would need to be
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adjusted and/or replaced. As well, it should be noted that
while the above implementation details a gaseous sample, other
non-gaseous samples may be used. Any stream (perhaps run
through a mechanism which turns the liquid or solid into an
aerosol) may be used. Similarly, a mechanism which allows for
contact between the sensing tape and a solid, liquid, or gaseous
sample may also be used.
For other implementations, the sensing tape may be made from
substances other than paper. Preferably, the substrate used for
the sensing tape is capable of being rolled into rolls as this
method of packaging is convenient and easy to use. If packaged
into rolls, as in the hydrogen sulfide implementation, the
sensing tape can be easily mounted on to reels and can be easily
replaced within the system. As well, passing the sensing tape
by the different sample chambers and sensing assemblies would be
easier as the reels would simple need to be rotated to move the
sensing tape past these system components. It is also
preferable that the substrate be impermeable to the coating or
the substance used on the sensing tape as well as to the
substances the sensing tape is exposed to. By rendering the
substrate impermeable to these substances, one test and analysis
can be done on one side of the sensing tape without
contamination or interference from the tests being conducted on
the other side. Of course, it is preferable that the substance
used to coat the sensing tape is reactive in some visible manner
to a component or chemical in the sample substance to which the
sensing tape is exposed to. Such a visible reaction would allow
for the optical sensor to be used as in the hydrogen sulfide
example. Other ways by which the coating substance on the
sensing tape reacts to the substances to which the sensing tape
is exposed to may, of course, also be used.
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It should further be noted that, when using the two sensing
assemblies, these sensing assemblies need not be configured to
detect and analyze for the same substance. One sensing assembly
may be configured to detect H2S concentration using one sample
stream while the other sensing assembly may be used to detect
and analyze for another substance using the other sample stream.
Conversely, the two sensing assemblies may be configured to
detect and analyze for similar substances. As an example, one
sensing assembly may be configured to detect and analyze for H2S
concentration in one sample stream. The other sensing assembly
may then be configured to detect and analyze for total sulfur
concentration using another sample stream. Of course, the two
sample streams may be from different sources or they may be from
the same source.
A person understanding this invention may now conceive of
alternative structures and embodiments or variations of the
above all of which are intended to fall within the scope of the
invention as defined in the claims that fellow.
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