WO1998036815A1

WO1998036815A1 - Analytical gas instrument recycle system and method

Info

Publication number: WO1998036815A1
Application number: PCT/US1998/003241
Authority: WO
Inventors: Kenneth A. Perrotta; Barbara Marshik-Geurts; Karen Girard
Original assignee: Whatman Inc.
Priority date: 1997-02-24
Filing date: 1998-02-23
Publication date: 1998-08-27
Also published as: AU6331298A

Abstract

A carrier gas recycle system and method for carrier gases like helium or argon, used with instruments like gas chromatographs (12), normally vented to the atmosphere. The system collects, purifies, compresses, and optionally employs make-up carrier gas, and recycles the carrier gas for use in the instrument. The system includes means to collect the carrier gas (13) along with contaminants as discharged from the instrument; a purifier means (18, 28) in the system to remove contaminants from the collected carrier gas; a compressor means (20) to compress the collected, purified carrier gas to a selected pressure; a source of make-up carrier gas (26); a regulator (24) to regulate and control the quantity of compressed, purified, collected carrier gas as a recycled carrier gas; and a means (30) to receive the recycled carrier gas and to introduce the recycled carrier gas into the analytical instrument (12).

Description

Description ANALYTICAL GAS INSTRUMENT RECYCLE SYSTEM AND METHOD

Reference to Prior Applications This application claims the benefit of and incorporates by 5 reference U.S. Provisional Patent Application Serial No. 60/038,252, filed February 24, 1997,

Background of the Invention

Various gases may be employed in analytical gas instruments, such as helium, which is commonly used as a 0 carrier gas in gas chroraatographic instruments and their application, which helium gas is a most expensive consumable carrier gas. Often the gases employed in analytical gas instruments are employed as a carrier or for other use, and then a substantial portion of the gas is discharged to the 5 atmosphere. Where the gas is expensive, such as the use of helium in gas chromatographic instruments, where the consumption rate of high purity helium (for example, 99.99% or greater) in a laboratory with a plurality of gas chromatographic instruments may be high, such as, for example, 0 one A-size, compressed helium gas cylinder per week, typically,

80% or more of the helium carrier gas is vented into the atmosphere .

It is desirable, therefore, to provide for a gas consuming or using analytical instrument with a gas recycle or recovery Fj system and method, whereby gas which is vented into the atmosphere or normally unused in an analytical gas instrument, particularly expensive gas, such as helium, is recycled for use to prevent waste in a simple, efficient, recycle system and method. 0 finτfiιτrfaτ-y of the Invention

The invention relates to an analytical or other gas instrument recycle system and method whereby gas is recycled for reuse. In particular, the invention involves a system and method which recovers and recycles helium from a gas h> chromatograph, typically a plurality of gas chromatographic instruments, and repurifies, recompresses and recycles the helium, together, optionally as required, with make-up helium, back to the gas chromatographic apparatus or system for reuse as a helium carrier gas. The invention comprises a gas instrument recycle system, which comprises an instrument which employs a gas, like a carrier gas, which is typically discharged to the atmosphere, but which is desired to be recovered for reuse; and a means to collect the carrier gas along with contaminants as discharged from the instrument; a purifier means in the system to remove contaminants from the collected carrier gas, or recycle gas or both; a compressor means to compress the collected, purified, carrier gas to a selected pressure; a source of make-up carrier gas to provide make-up carrier gas; a regulator means to regulate and control the quantity of make-up carrier gas from said source and the quantity of compressed, purified, collected, carrier gas as a recycled carrier gas; and a means to receive the recycled carrier gas and to introduce the recycled carrier gas into the analytical instrument. The method of recycling carrier gas from one or more carrier gas-using instruments is comprised of collecting the carrier gas with contaminates after discharge from the instrument; purifying the carrier gas with contaminants to remove the contaminants; compressing (e.g., 25 to 250 psig) the purified carrier gas to a selected pressure; providing a source of compressed make-up carrier gas; regulating and controlling the quantity of the make-up carrier gas and the purified, compressed carrier gas as a recycled carrier gas; and introducing the recycled carrier gas to the analytical instrument for reuse.

The system and method of the invention comprises at least one, but typically a plurality of, gas employing-gas vented analytical devices; such as, but not limited to, gas chromatographs , for example, using helium, argon, nitrogen, or other gases, or a mixture thereof as a carrier gas for a sample; and in which the carrier gas is normally wasted and vented into the atmosphere, and particularly where a large portion of the carrier gas comprises expensive helium or argon which is vented into the atmosphere, for example, over 80 to 90 percent .

The gas recycle system is applicable to a single gas-using instrument, but for reasons of economy, is particularly useful where a plurality of instruments are in use, and the normally vented gas is collected by a gas manifold for recycle purposes. Gas chromatographs, as one form of instruments useful in the recycle system and method, are used to detect volatile compounds, to determine physical properties and the distribution of compounds and to isolate or separate compounds or forms thereof. The gas chromatograph usually has a sample inlet, a carrier gas inlet, optionally, a sample vaporizer, a separating column in a column over or with a heater, a detector and a recorder device. The detector in each gas chromatograph is used to detect or analyze the sample in the carrier gas. The recycle system, optionally and preferably, employs a separate detector for the carrier gas normally vented, or as collected in the carrier gas manifold, for the purposes of determining if the carrier gas to be recycled is heavily contaminated with contaminants which would interfere with the recycle system, place too great a purification burden on the system, can not be adequately purified or handled by the recycle system, or would be undesirable or expensive to recycle or any combination thereof. In such cases, the detector would detect the carrier gas normally vented and not duplicate the detection function of the usual detector of the sample-carrier gas. The recycle system is designed to recycle and process only the carrier gas uncontaminated by the sample used.

The detector may comprise a variety of detectors alone, or in combination, such as, thermocouple detector (TCD) , flame ionization detector (FID), electrochemical cell, infrared, ultraviolet, geiger counter, or other detector devices. The detector is employed in combination with a vent, so that when a heavily contaminated carrier gas is detected, the heavily contaminated carrier gas may be removed from the recycle system, such as by venting to the atmosphere, as mainly done, or directed to another process or system. A heavily contaminated carrier gas may include a carrier gas with large amounts of organic, e.g., hydrocarbon compounds or mixtures, water vapor, and very minor amounts of radioisotopes or toxic materials. The detector-vent may include a detector which sends an electrical signal to a solenoid-type vent valve. The detector-vent device may be used with each separate instrument and with the gas collecting manifold.

Optionally, the system would include a gas delivery manifold means to introduce the selected gas or gas mixture into the analytical devices. The system optionally also would include a gas-receiving manifold to receive the vented gas discharged from the instruments; and to provide a vented, collected gas stream, typically, the gas stream contaminated with the sample, water vapor, and various other chemicals or combinations; such as organic compounds, like light and heavy hydrocarbons, sulfur, phosphorous, nitrogen; and halogens such as chlorine, and various combinations thereof, developed by and during the use of the instrument or associated with the sample and the sample being detected. The system may include a flow stabilizer to receive the manifold vented gas and to prevent the development of gas back pressure on the gas receiving manifold, and on the analytical instruments, which might interfere with the operation of the analytical instruments. The flow stabilizer may comprise a variety of devices, for example, a bellows-type apparatus together with a pressure limit switch, which limit switch on the operation of the bellows, by excess pressure, activates the subsequent gas compression if the gas back pressure increases beyond a desirable amount. Optionally, a flow stabilizer may also be usefully employed after the gas compressor in the system.

The system would include a gas purifier means which may comprise one or a plurality of serially aligned, selected modules to remove contaminants from the flow stabilized, vented gas for introduction into the gas compressor. Typically, a multiple stage purifying module would have the capability of removing high amounts, for example 99% or greater of trace amounts of most chemical analytes, for example, to absorb water vapor and would include a final purifying module for the vented, flow stabilized gas stream. Purifying modules would include means for scrubbing out oxygen and removing organic matter related to the sample, or carbon adsorption, or molecular sieve adsorption for water vapor, employment of membranes, e.g., hollow fiber membranes, to separate contaminants or the use of catalytic oxidation or other catalytic or cryogenic, absorption or adsorption purifying processes and techniques to provide for a gas stream of selected purity. Other purifying modules useful to remove specific gas phase contaminants would include; but not be limited to, pressure swing adsorption and filters, such as glass fiber resin impregnated tublular filters of 0.01 to 10 microns capture, and membranes to remove particulate matter from the collected, contaminated carrier gas. The purifying modules may be used alone or in any combination to provide a collected carrier gas or recycle gas of selected purity for reuse.

The system includes a gas compressor to receive the flow stabilized, purified, vented gas stream and to compress the gas stream, such as helium, to the desired pressure for reuse in the analytical instrument(s) . For example, the gas compressor for use with helium would include a helium tight sealed- containment compression-type device providing for a compressed hydrogen or helium. The system may optionally also include a flow stabilizer after the gas compressor module for pressure control purposes.

The system includes a switch-over regulator and modulator, typically an automatic switch-over regulator module, which is connected to a separate or independent source of the gas or gas mixture to be employed in the analytical instrument, such as, for example, a compressed helium gas tank. The compressed gas tank would supply make-up gas, which is make-up helium gas, into the close-loop recycle system as described. This system would capture and recycle not all of the gas introduced into the instrument, so make-up gas would be required from time to time. Generally, the regulator module would comprise a gas reservoir, with the gas pressure of the reservoir monitored and integrated to an automatic changeover gas regulator assembly, including a separate source , such as a tank of gas for make-up purposes, which is a compressed helium cylinder connected to changeover regulator. The automatic switch-over regulator modulator means would control the carrier gas supply source for the analytical instrument in the recycled system. Generally, it would operate automatically depending on carrier gas demands .

Optionally, the recycled, purified, compressed gas from the gas compressor module , and/or the tank gas , make-up gas may be recycled through another purifying module as required, and then delivered to the gas delivery manifold, thus providing for a close-loop recycle system and method, by which previously vented gas from an analytical gas-type instrument may be collected, flow stabilized, purified, compressed and automatically redelivered with make-up gas as required back into the instrument.

The recycle system and method as described and illustrated is suitable for employment with single or multiple devices, such as, single or multiple gas chromatographic applications.

The recycle system and method may be employed usefully with other instruments used for the detection, analysis. separation or other process where high amounts of carrier gas are vented and are desired to be recovered for reuse in a closed-loop recycle system. An instrument employing argon as a carrier gas would include an inductively coupled plasma (an atomic absorption device) . The term carrier gas is not limited to a gas which only carries or transports a sample, but rather, generically to refer to all types of inert gases desired to be recovered, usually having economic value, but normally discharged at high flow rates or larger quantities to the atmosphere. The carrier gas in a gas chromatograph would not include the carrier gas employed with the actual sample to be analyzed, due to contamination and the small amount of carrier gas involved.

The system is particularly suitable for a gas chromatograph (GC) with capillary column and split injection or with packed columns and non-FID detectors, since the system will take the helium both from the split and purge ports. The contaminated helium carrier gas for sample injection will pass through a multiple stage purifying module and through the system, remove contaminants to be recompressed, and repurify the helium gas made up with additional helium gas, and reintroduce it into the system. The system is particularly useful for either ordinary gas chromatography or in all of the gases employed as a carrier gas to a detector, or more particularly to a split-flow gas chromatograph pulling a higher flow of carrier gas to transport the sample; but with only a small portion of the carrier gas with a sample diverted to the detector, while a large percentage, 80 to 90 percent, of the carrier transport gas is then vented into the atmosphere. In the present system and method, the vented gas may then be collected and recycled for reuse at a considerable savings.

In one embodiment, the system and method comprises a plurality of gas chromatographs employing helium as a carrier gas, and wherein a substantial portion of the helium carrier gas is normally vented to the atmosphere. The system includes a flow stabilizer means to receive the vented gas and to prevent back pressure of the gas from interfering with the operation of the gas chromatograph; a purifying means to purify contaminants from the flow stabilized carrier gas; a helium compression, means to compress the helium to the desired pressure for reuse in the gas chromatograph; and optionally, a flow stabilizer means to then stabilize the compressed helium gas ; an automatic switch-over regulator module means regulating the supply of the recompressed, recycled helium carrier gas, together with a source of a helium make-up tank to provide a selected amount of recycled and make-up helium gas back into the gas chromatograph; and optionally, employing a purifying module means to further purify the gas before introducing it as the carrier gas into the gas chromatograph. The invention will be described for the purpose of illustration only in connection with certain illustrated embodiments; however, it is recognized that various changes, modifications, additions and improvements may be made in the illustrative embodiments without departing from the spirit and scope of the invention.

Brief Description of the Drawing The drawing comprises a schematic illustration of a helium recovery, recycle system of the invention.

Brief Description of the Kmhodiments A system is illustrated in the schematic illustration of the drawing which is a recycle system 10, which includes a plurality of gas chromatographs (GC) as gas analyzing instruments 12, a purity detector and vent 13 for each GC, a gas receiving manifold 14 to collect the 80 to 90 percent or greater of the helium carrier gas normally vented to atmosphere, and to transport the gas to a flow stabilizer I 16 to prevent back pressure from the collected gas from interfering with the instruments 12. The system includes a purifying module I 18, which removes contaminants and water vapor from the flow-stabilized helium carrier gas, with the gas then sent to a helium compression pump 20 for compression to the desired pressure level. The compressed helium is then optionally sent to a further flow stabilizer II 22, and then to an automatic switch-over regulator module 24 which controls the amount of recycled and make-up gas from make-up helium tank 26, wherein the recycled gas, the make-up gas, and the recycled recompressed gas is optionally then sent through a further purifying module II 28, and then delivered to a gas delivery manifold 30 where it is sent to the selected instruments 12. In the illustrated embodiment, purifying module I and II are shown; however, it is recognized that the collected carrier gas, or the mixture of the recycled carrier gas, may be purified either before or after the compression, or as illustrated, both before and after the compression of the carrier gas, or anywhere in the system.

The recycle system as described is particularly useful where large amounts of gas are not to be used or to be vented to the atmosphere, particularly where the gas employed is expensive and not easily resupplied, such as in the case of hydrogen, helium, argon, neon, or other gases or mixture thereof, in particular, helium or argon gases, when used in sample detection or gas-using systems.

Claims

ClaimsWhat is claimed is:

Claim 1. A gas instrument recycle system which comprises: a) an instrument which employs a carrier gas which is desired to be recovered for reuse and typically discharged to the atmosphere; b) means to collect the carrier gas, along with contaminants, as discharged from the instrument; c) compressor means to compress the collected carrier gas to a selected pressure; d) a source of make-up carrier gas to provide make- up carrier gas; e) regulator means to regulate and control the quantity of make-up carrier gas from said source and the quantity of compressed, collected carrier gas as a recycled carrier gas; f) purifier means in the system to remove contaminants from the collected carrier gas or recycled carrier gas ; and g) means to receive the recycle carrier gas and to introduce the recycle carrier gas into the instrument.

Claim 2- The system of claim 1 wherein the carrier gas comprises helium or argon.

Claim 3. The system of claim 1 wherein the instrument comprises a plurality of gas chromatograph instruments.

Claim 4. The system of claim 1 wherein the purifier means removes water vapor and organic contaminants from the collected carrier gas or recycled carrier gas or both.

Claim 5. The system of claim 1 which includes a first gas flow stabilizer means to prevent back pressure from the collected carrier gas from interference with the operation of the instruments .

Claim 6. The system of claim 1 which includes a second gas flow stabilizer means to prevent back pressure from the collected, pumped, compressed carrier gas.

Claim 7. The system of claim 5 wherein the stabilizer means includes a bellow and a pressure limit switch, wherein the bellow, by collected carrier gas, activates the pressure switch to maintain a selected back carrier gas pressure.

Claim 8. The system of claim 1 wherein the carrier gas comprises helium or argon, and the source of make-up carrier gas comprises compressed helium or argon.

Claim 9. The system of claim 1 wherein: a) the instrument comprises a plurality of helium carrier gas-using gas chromatographs; b) the means to collect comprises a helium gas collecting manifold to collect the helium carrier gas not used for sample analysis; c) the source of make-up carrier gas comprises a compressed helium gas cylinder; and d) the means to receive and introduce comprises a helium gas receiving manifold to distribute the recycle carrier gas to the gas chromatograph.

Claim 10. The system of claim 1 which includes a detector and vent means to detect heavily contaminated, collected carrier gas and to vent the heavily contaminated gas from use in the recycle system.

Claim 11. A method of recycling carrier gas from one or more carrier gas-using instruments, which method comprises: a) collecting the carrier gas with contaminants after discharge from the instrument; b) compressing the carrier gas to a selected pressure; c) providing a source of compressed make-up carrier gas ; d) regulating and controlling the quantity of the mixture of make-up carrier gas and the compressed carrier gas as a recycle carrier gas; e) purifying the carrier gas or recycle carrier gas with contaminants to remove the contaminants; and f ) introducing the purified, recycle carrier gas to the instrument for reuse .