Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory...
Reexamination Certificate
1999-07-12
2002-09-24
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
C422S051000, C436S147000, C073S023200, C073S023250, C073S025010
Reexamination Certificate
active
06455000
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a thermomechanical method and apparatus for measuring the concentration of a gas and in particular a reactive gas (i.e. gasses that may be reacted to produce by-products and which produce heat or remove heat from a system as a result of the reaction). Examples of such gasses include ozone, oxygen, nitrogen or oxides of nitrogen, and the like. The method and apparatus may function independent of the temperature of a gas mixture containing the reactive gas.
BACKGROUND OF THE INVENTION
There are instruments available that measure ozone concentration in a gas mixture. One such instrument is disclosed in U.S. Pat. No. 5,167,927, Karlson. This Pat. discloses an apparatus that measures heat energy released when a reactive gas is catalytically converted to a different gas, for example using a catalyst to convert ozone to oxygen. In particular, Karlson discloses an apparatus that directs a stream of a gas mixture containing ozone against thermally conducting heat sinked plates on opposite sides of an axis of the stream with the plates extending upstream at an acute angle to the axis. One plate carries on its upstream facing a coating including a catalyst for ozone, while the other plate includes no catalyst on its upstream facing. A sensor is provided for measuring the temperatures of the respective plates. A separate chamber is provided having a similar arrangement of plates. The ozone concentration of the gas is electronically measured as the resistance difference of the two plates in each chamber.
One disadvantage of Karlson is that the flow of the gas mixture stream in Karlson is important to the instruments sensitivity, and is electronically controlled to be constant for each sample of gas mixture measured. A further disadvantage is that the instrument's sensitivity and time constant is dependant on the velocity of the sample flow through the instrument, its electronic time constant and its thermal time constant.
There is also a need for an inexpensive, durable and easily calibrated apparatus for determining the concentration of reactive gasses such as ozone.
SUMMARY OF THE INVENTION
In accordance with the instant invention a thermochemical means is used to produce movement of a member which is drivingly connected to an indicator. In a preferred embodiment, the indicator is associated with an analog scale to thereby provide a readout of the concentration of a gas without the use of any electronic monitoring means. In this way a simple mechanical sensor for reactive gasses such as ozone and NO
X
can be produced.
In accordance with the instant invention, there is provided a method of measuring a change in heat produced during conversion of a reactive gas by a catalyst to produce a by-product, the method comprising the steps of:
(a) using a first temperature sensor which undergoes movement with changes in temperature to which it is exposed to produce. a first measurement representing the initial temperature of the gas mixture;
(b) exposing at least a portion of the gas mixture to the catalyst to produce a change in heat;
(c) using a second temperature sensor which undergoes movement with changes in temperature to which it is exposed to produce a second measurement representing the change in heat due to the portion of the gas stream being exposed to the catalyst; and,
(d) combining the first measurement and the second measurement to determine a differential measurement representing a measurement of the heat change during conversion of the reactive gas by the catalyst.
In one embodiment, the method further comprises the step of calibrating the first and second temperature sensors so that when there is no reactive gas within the gas mixture the first measurement and the second measurement produce a differential measurement which is a fixed measurement and is preferably zero.
In another embodiment, the differential measurement is calibrated to represent the concentration of the reactive gas within the gas mixture and the method further comprises the step of reading the concentration of the reactive gas from a display of the differential measurement.
In another embodiment, the first temperature sensor is positioned in a first chamber and the second temperature sensor is positioned in a second chamber and the method further comprises dividing the gas stream into two portions and introducing a portion into each chamber.
In another embodiment, the first temperature sensor is positioned in a first chamber and the second temperature sensor is positioned in a second chamber and the method further comprises sequentially passing the gas stream through the first chamber and then the second chamber.
In another embodiment, the method further comprises first converting. a specific gas in a gas stream to produce the reactive gas. Thus, the method may be used to measure the concentration of a non-reactive gas (eg. oxygen or nitrogen).
In another embodiment, the first measurement and the second measurement are signals produced by the temperature sensors and the method further comprises reading the first and second measurements prior to combining them to determine a differential measurement.
In another embodiment, the first measurement and the second measurement are opposed forces which are exerted on a member and the net movement of the member produces the differential measurement and the method further comprises reading the differential measurement.
In accordance with another aspect of the instant invention, there is also provided a method of measuring a change in heat produced during conversion of a reactive gas by a catalyst to a by-product, the method comprising the steps of:
(a) exposing the gas mixture to the catalyst to generate heat; and,
(b) using a temperature sensor which undergoes movement with changes in temperature to which it is exposed to produce a measurement representing the change in heat due to the gas stream being exposed to the catalyst.
In one embodiment, the method further comprises the step of calibrating the temperature sensor so that at ambient conditions when there is no reactive gas within the gas mixture the measurement is constant and preferably is zero. The measurement may be calibrated to represent the concentration of the reactive gas within the gas mixture and the method further comprises the step of reading the concentration of the reactive gas from a display of the measurement.
In another embodiment, the method further comprises first converting a specific gas in a gas stream to produce the reactive gas.
In another embodiment, the measurement is a force which is exerted on a member and the movement of the member produces a corresponding measurement and the method further comprises reading the corresponding measurement.
In accordance with another aspect of the instant invention, there is also provided an apparatus comprising:
(a) a catalyst positioned in an air flow path of a gas mixture containing a reactive gas, the reactive gas undergoing a reaction to produce a by-product and a change in heat upon exposure to the catalyst; and,
(b) a reacted gas temperature sensor which undergoes movement with changes in temperature to which it is exposed to produce a reacted gas measurement representing the change in heat produced by the reaction of the reactive gas.
In one embodiment, the measurement is calibrated to represent the concentration of the reactive gas within the gas mixture.
In another embodiment, the temperature sensor includes an indicator, the apparatus further comprises an analog display which is calibrated to represent the concentration of the reactive gas within the gas mixture, and the measurement comprises the movement of the indicator due to the change in temperature of the temperature sensor. Alternately, the measurement may be an electronic signal. However in this alternate embodiment, the sensing means still uses a thermomechanical member. The difference resides in the type of signal which is produced.
In another embodiment, the gas mixture comprises a specific gas and the apparatus further comprise
Conrad Helmut Gerhard
Conrad Wayne Ernest
Szylowiec Ted
Bereskin & Parr
Fantom Technologies Inc.
Mendes da Costa Philip C.
Sines Brian
Warden Jill
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